Career.

Haynes was born in the Roxbury section of Boston, Massachusetts. His younger brother, Michael E. Haynes, would go on to become an important leader in the black community of Massachusetts, working with Martin Luther King Jr. during the civil rights movement, representing Roxbury in the Massachusetts House of Representatives, and for forty years serving as pastor of the Twelfth Baptist Church, where King had been a member while he pursued his doctoral degree at Boston University. Haynes made his professional debut in 1944 in his native Boston and began his full-time professional career in 1945. From 1947 to 1949 he worked with saxophonist Lester Young, and from 1949 to 1952 was a member of saxophonist Charlie Parker's quintet. He also recorded at the time with pianist Bud Powell and saxophonists Wardell Gray and Stan Getz. From 1953 to 1958 he toured with singer Sarah Vaughan and also recorded with her.  A tribute song was recorded by Jim Keltner and Charlie Watts of the Rolling Stones, and he appeared on stage with the Allman Brothers Band in 2006 and Page McConnell of Phish in 2008.  On June 25, 2019, "The New York Times Magazine" listed Roy Haynes among hundreds of artists whose material was destroyed in the 2008 Universal fire.

Technique.

Haynes extracted the rhythmic qualities from melodies and created unique new drum and cymbal patterns in an idiosyncratic, now instantly recognizable style. Rather than using cymbals strictly for effect, Haynes brought them to the forefront of his unique rhythmic approach. He also established a distinctively crisp and rapid-fire sound on the snare; this was the inspiration for his nickname, "Snap Crackle".

Awards and honors.

"A Life in Time - The Roy Haynes Story" was named by "The New Yorker" magazine as one of the Best Boxed Sets of 2007 and was nominated for an award by the Jazz Journalist's Association. WKCR-FM, New York, surveyed Haynes's career in 301 hours of programming, January 11–23, 2009.  "Esquire" named Roy Haynes one of the Best Dressed Men in America in 1960, along with Fred Astaire, Miles Davis, Clark Gable, and Cary Grant.  In 1994, he was awarded the Danish Jazzpar prize, and in 1996 the French government knighted him with the Chevalier de l'Ordre des Arts et des Lettres" France's top literary and artistic honor. Haynes received honorary doctorates from the Berklee College of Music (1991), and the New England Conservatory (2004), as well as a Peabody Medal, the highest honor bestowed by the Peabody Institute of The Johns Hopkins University, in 2012. He was inducted into the "Down Beat" magazine Hall of Fame in 2004. On October 9, 2010, he was awarded the Mid Atlantic Arts Foundation's BNY Mellon Jazz Living Legacy Award at the Kennedy Center for the Performing Arts in Washington, DC. On December 22, 2010, he was named a recipient of a Grammy Lifetime Achievement Award by the National Academy of Recording Arts and Sciences. Haynes received the award at the Special Merit Awards Ceremony & Nominees Reception of the 53rd Annual Grammy Awards on February 12, 2011. In 2019, Haynes was given the Lifetime Achievement Award by the Jazz Foundation of America at the 28th Annual Loft Party.

Roy Owen Haynes (born March 13, 1925) is an American jazz drummer. He is among the most recorded drummers in jazz. In a career lasting over 70 years he has played swing, bebop, jazz fusion, and avant-garde jazz. "Snap Crackle" was a nickname given to him in the 1950s.

Roy Haynes (* 13. března 1925, Boston, USA) je americký jazzový bubeník a leader několika jazzových ansámblů. Je jedním z nejnahrávanějších jazzových bubeníků, během své více než šedesátilété kariéry hrál celou řadu jazzových stylů: od swingu přes bebop až k fusion a avantgardnímu jazzu.


History.

While the method of adding particles or objects to a fluid in order to observe its flow is likely to have been used from time to time through the ages no sustained application of the method is known. The first to use particles to study fluids in a more systematic manner was Ludwig Prandtl, in the early 20th century.  Laser Doppler Velocimetry predates PIV as a laser-digital analysis system to become widespread for research and industrial use. Able to obtain all of a fluid's velocity measurements at a specific point, it can be considered the 2-dimensional PIV's immediate predecessor. PIV itself found its roots in Laser speckle velocimetry, a technique that several groups began experimenting with in the late 1970s. In the early 1980s it was found that it was advantageous to decrease the particle concentration down to levels where individual particles could be observed. At these particle densities it was further noticed that it was easier to study the flows if they were split into many very small 'interrogation' areas, that could be analyzed individually to generate one velocity for each area. The images were usually recorded using analog cameras and needed immense amount of computing power to be analyzed.  With the increasing power of computers and widespread use of CCD cameras, digital PIV has become increasingly common, to the point that it is the primary technique today.

Equipment and apparatus.

Seeding particles.

The seeding particles are an inherently critical component of the PIV system. Depending on the fluid under investigation, the particles must be able to match the fluid properties reasonably well. Otherwise they will not follow the flow satisfactorily enough for the PIV analysis to be considered accurate. Ideal particles will have the same density as the fluid system being used, and are spherical (these particles are called microspheres). While the actual particle choice is dependent on the nature of the fluid, generally for macro PIV investigations they are glass beads, polystyrene, polyethylene, aluminum flakes or oil droplets (if the fluid under investigation is a gas). Refractive index for the seeding particles should be different from the fluid which they are seeding, so that the laser sheet incident on the fluid flow will reflect off of the particles and be scattered towards the camera.  The particles are typically of a diameter in the order of 10 to 100 micrometers. As for sizing, the particles should be small enough so that response time of the particles to the motion of the fluid is reasonably short to accurately follow the flow, yet large enough to scatter a significant quantity of the incident laser light. For some experiments involving combustion, seeding particle size may be smaller, in the order of 1 micrometer, to avoid the quenching effect that the inert particles may have on flames. Due to the small size of the particles, the particles motion is dominated by stokes drag and settling or rising affects. In a model where particles are modeled as spherical (microspheres) at a very low Reynolds number, the ability of the particles to follow the fluid's flow is inversely proportional to the difference in density between the particles and the fluid, and also inversely proportional to the square of their diameter. The scattered light from the particles is dominated by Mie scattering and so is also proportional to the square of the particles' diameters. Thus the particle size needs to be balanced to scatter enough light to accurately visualize all particles within the laser sheet plane, but small enough to accurately follow the flow.  The seeding mechanism needs to also be designed so as to seed the flow to a sufficient degree without overly disturbing the flow.

Camera.

To perform PIV analysis on the flow, two exposures of laser light are required upon the camera from the flow. Originally, with the inability of cameras to capture multiple frames at high speeds, both exposures were captured on the same frame and this single frame was used to determine the flow. A process called autocorrelation was used for this analysis. However, as a result of autocorrelation the direction of the flow becomes unclear, as it is not clear which particle spots are from the first pulse and which are from the second pulse. Faster digital cameras using CCD or CMOS chips were developed since then that can capture two frames at high speed with a few hundred ns difference between the frames. This has allowed each exposure to be isolated on its own frame for more accurate cross-correlation analysis. The limitation of typical cameras is that this fast speed is limited to a pair of shots. This is because each pair of shots must be transferred to the computer before another pair of shots can be taken. Typical cameras can only take a pair of shots at a much slower speed. High speed CCD or CMOS cameras are available but are much more expensive.

Laser and optics.

For macro PIV setups, lasers are predominant due to their ability to produce high-power light beams with short pulse durations. This yields short exposure times for each frame. s, commonly used in PIV setups, emit primarily at 1064 nm wavelength and its harmonics (532, 266, etc.) For safety reasons, the laser emission is typically bandpass filtered to isolate the 532 nm harmonics (this is green light, the only harmonic able to be seen by the naked eye). A fiber optic cable or liquid light guide might be used to direct the laser light to the experimental setup.  The optics consist of a spherical lens and cylindrical lens combination. The cylindrical lens expands the laser into a plane while the spherical lens compresses the plane into a thin sheet. This is critical as the PIV technique cannot generally measure motion normal to the laser sheet and so ideally this is eliminated by maintaining an entirely 2-dimensional laser sheet. The spherical lens cannot compress the laser sheet into an actual 2-dimensional plane. The minimum thickness is on the order of the wavelength of the laser light and occurs at a finite distance from the optics setup (the focal point of the spherical lens). This is the ideal location to place the analysis area of the experiment.  The correct lens for the camera should also be selected to properly focus on and visualize the particles within the investigation area.

Synchronizer.

The synchronizer acts as an external trigger for both the camera(s) and the laser. While analogue systems in the form of a photosensor, rotating aperture and a light source have been used in the past, most systems in use today are digital. Controlled by a computer, the synchronizer can dictate the timing of each frame of the CCD camera's sequence in conjunction with the firing of the laser to within 1 ns precision. Thus the time between each pulse of the laser and the placement of the laser shot in reference to the camera's timing can be accurately controlled. Knowledge of this timing is critical as it is needed to determine the velocity of the fluid in the PIV analysis. Stand-alone electronic synchronizers, called digital delay generators, offer variable resolution timing from as low as 250 ps to as high as several ms. With up to eight channels of synchronized timing, they offer the means to control several flash lamps and Q-switches as well as provide for multiple camera exposures.

Analysis.

The frames are split into a large number of interrogation areas, or windows. It is then possible to calculate a displacement vector for each window with help of signal processing and autocorrelation or cross-correlation techniques. This is converted to a velocity using the time between laser shots and the physical size of each pixel on the camera. The size of the interrogation window should be chosen to have at least 6 particles per window on average. A visual example of PIV Analysis can be seen here.  The synchronizer controls the timing between image exposures and also permits image pairs to be acquired at various times along the flow. For accurate PIV analysis, it is ideal that the region of the flow that is of interest should display an average particle displacement of about 8 pixels. This is a compromise between a longer time spacing which would allow the particles to travel further between frames, making it harder to identify which interrogation window traveled to which point, and a shorter time spacing, which could make it overly difficult to identify any displacement within the flow.  The scattered light from each particle should be in the region of 2 to 4 pixels across on the image. If too large an area is recorded, particle image size drops and peak locking might occur with loss of sub pixel precision. There are methods to overcome the peak locking effect, but they require some additional work. If there is in house PIV expertise and time to develop a system, even though it is not trivial, it is possible to build a custom PIV system. Research grade PIV systems do, however, have high power lasers and high end camera specifications for being able to take measurements with the broadest spectrum of experiments required in research.  An example of PIV analysis without installation  PIV is closely related to digital image correlation, an optical displacement measurement technique that uses correlation techniques to study the deformation of solid materials.

Pros/cons.

Advantages.

The method is, to a large degree, nonintrusive. The added tracers (if they are properly chosen) generally cause negligible distortion of the fluid flow.  Optical measurement avoids the need for Pitot tubes, hotwire anemometers or other intrusive Flow measurement probes. The method is capable of measuring an entire two-dimensional cross section (geometry) of the flow field simultaneously.  High speed data processing allows the generation of large numbers of image pairs which, on a personal computer may be analysed in real time or at a later time, and a high quantity of near-continuous information may be gained.  Sub pixel displacement values allow a high degree of accuracy, since each vector is the statistical average for many particles within a particular tile. Displacement can typically be accurate down to 10% of one pixel on the image plane.

Drawbacks.

In some cases the particles will, due to their higher density, not perfectly follow the motion of the fluid (gas/liquid). If experiments are done in water, for instance, it is easily possible to find very cheap particles (e.g. plastic powder with a diameter of ~60 μm) with the same density as water. If the density still does not fit, the density of the fluid can be tuned by increasing/ decreasing its temperature. This leads to slight changes in the Reynolds number, so the fluid velocity or the size of the experimental object has to be changed to account for this.  Particle image velocimetry methods will in general not be able to measure components along the z-axis (towards to/away from the camera). These components might not only be missed, they might also introduce an interference in the data for the x/y-components caused by parallax. These problems do not exist in Stereoscopic PIV, which uses two cameras to measure all three velocity components.  Since the resulting velocity vectors are based on cross-correlating the intensity distributions over small areas of the flow, the resulting velocity field is a spatially averaged representation of the actual velocity field. This obviously has consequences for the accuracy of spatial derivatives of the velocity field, vorticity, and spatial correlation functions that are often derived from PIV velocity fields.  PIV systems used in research often use class IV lasers and high-resolution, high-speed cameras, which bring cost and safety constraints.

More complex PIV setups.

Stereoscopic PIV.

Stereoscopic PIV utilises two cameras with separate viewing angles to extract the z-axis displacement. Both cameras must be focused on the same spot in the flow and must be properly calibrated to have the same point in focus.  In fundamental fluid mechanics, displacement within a unit time in the X, Y and Z directions are commonly defined by the variables U, V and W. As was previously described, basic PIV extracts the U and V displacements as functions of the in-plane X and Y directions. This enables calculations of the formula_1, formula_2, formula_3 and formula_4 velocity gradients. However, the other 5 terms of the velocity gradient tensor are unable to be found from this information. The stereoscopic PIV analysis also grants the Z-axis displacement component, W, within that plane. Not only does this grant the Z-axis velocity of the fluid at the plane of interest, but two more velocity gradient terms can be determined: formula_5 and formula_6. The velocity gradient components formula_7, formula_8, and formula_9 can not be determined. The velocity gradient components form the tensor:

Dual plane stereoscopic PIV.

This is an expansion of stereoscopic PIV by adding a second plane of investigation directly offset from the first one. Four cameras are required for this analysis. The two planes of laser light are created by splitting the laser emission with a beam splitter into two beams. Each beam is then polarized orthogonally with respect to one another. Next, they are transmitted through a set of optics and used to illuminate one of the two planes simultaneously.  The four cameras are paired into groups of two. Each pair focuses on one of the laser sheets in the same manner as single-plane stereoscopic PIV. Each of the four cameras has a polarizing filter designed to only let pass the polarized scattered light from the respective planes of interest. This essentially creates a system by which two separate stereoscopic PIV analysis setups are run simultaneously with only a minimal separation distance between the planes of interest.  This technique allows the determination of the three velocity gradient components single-plane stereoscopic PIV could not calculate: formula_7, formula_8, and formula_9. With this technique, the entire velocity gradient tensor of the fluid at the 2-dimensional plane of interest can be quantified. A difficulty arises in that the laser sheets should be maintained close enough together so as to approximate a two-dimensional plane, yet offset enough that meaningful velocity gradients can be found in the z-direction.

Multi-plane stereoscopic PIV.

There are several extensions of the dual-plane stereoscopic PIV idea available. There is an option to create several parallel laser sheets using a set of beamsplitters and quarter-wave plates, providing three or more planes, using a single laser unit and stereoscopic PIV setup, called XPIV

Micro PIV.

With the use of an epifluorescent microscope, microscopic flows can be analyzed. MicroPIV makes use of fluorescing particles that excite at a specific wavelength and emit at another wavelength. Laser light is reflected through a dichroic mirror, travels through an objective lens that focuses on the point of interest, and illuminates a regional volume. The emission from the particles, along with reflected laser light, shines back through the objective, the dichroic mirror and through an emission filter that blocks the laser light. Where PIV draws its 2-dimensional analysis properties from the planar nature of the laser sheet, microPIV utilizes the ability of the objective lens to focus on only one plane at a time, thus creating a 2-dimensional plane of viewable particles.  MicroPIV particles are on the order of several hundred nm in diameter, meaning they are extremely susceptible to Brownian motion. Thus, a special ensemble averaging analysis technique must be utilized for this technique. The cross-correlation of a series of basic PIV analyses are averaged together to determine the actual velocity field. Thus, only steady flows can be investigated. Special preprocessing techniques must also be utilized since the images tend to have a zero-displacement bias from background noise and low signal-noise ratios. Usually, high numerical aperture objectives are also used to capture the maximum emission light possible. Optic choice is also critical for the same reasons.

Holographic PIV.

Holographic PIV (HPIV) encompasses a variety of experimental techniques which use the interference of coherent light scattered by a particle and a reference beam to encode information of the amplitude and phase of the scattered light incident on a sensor plane. This encoded information, known as a hologram, can then be used to reconstruct the original intensity field by illuminating the hologram with the original reference beam via optical methods or digital approximations. The intensity field is interrogated using 3-D cross-correlation techniques to yield a velocity field.  Off-axis HPIV uses separate beams to provide the object and reference waves. This setup is used to avoid speckle noise form being generated from interference of the two waves within the scattering medium, which would occur if they were both propagated through the medium. An off-axis experiment is a highly complex optical system comprising numerous optical elements, and the reader is referred to an example schematic in Sheng et al. for a more complete presentation.  In-line holography is another approach that provides some unique advantages for particle imaging. Perhaps the largest of these is the use of forward scattered light, which is orders of magnitude brighter than scattering oriented normal to the beam direction. Additionally, the optical setup of such systems is much simpler because the residual light does not need to be separated and recombined at a different location. The in-line configuration also provides a relatively easy extension to apply CCD sensors, creating a separate class of experiments known as digital in-line holography. The complexity of such setups shifts from the optical setup to image post-processing, which involves the use of simulated reference beams. Further discussion of these topics is beyond the scope of this article and is treated in Arroyo and Hinsch  A variety of issues degrade the quality of HPIV results. The first class of issues involves the reconstruction itself. In holography, the object wave of a particle is typically assumed to be spherical; however, due to Mie scattering theory, this wave is a complex shape which can distort the reconstructed particle. Another issue is the presence of substantial speckle noise which lowers the overall signal-to-noise ratio of particle images. This effect is of greater concern for in-line holographic systems because the reference beam is propagated through the volume along with the scattered object beam. Noise can also be introduced through impurities in the scattering medium, such as temperature variations and window blemishes. Because holography requires coherent imaging, these effects are much more severe than traditional imaging conditions. The combination of these factors increases the complexity of the correlation process. In particular, the speckle noise in an HPIV recording often prevents traditional image-based correlation methods from being used. Instead, single particle identification and correlation are implemented, which set limits on particle number density. A more comprehensive outline of these error sources is given in Meng et al.  In light of these issues, it may seem that HPIV is too complicated and error-prone to be used for flow measurements. However, many impressive results have been obtained with all holographic approaches. Svizher and Cohen used a hybrid HPIV system to study the physics of hairpin vortices. Tao et al. investigated the alignment of vorticity and strain rate tensors in high Reynolds number turbulence. As a final example, Sheng et al. used holographic microscopy to perform near-wall measurements of turbulent shear stress and velocity in turbulent boundary layers.

Scanning PIV.

By using a rotating mirror, a high-speed camera and correcting for geometric changes, PIV can be performed nearly instantly on a set of planes throughout the flow field. Fluid properties between the planes can then be interpolated. Thus, a quasi-volumetric analysis can be performed on a target volume. Scanning PIV can be performed in conjunction with the other 2-dimensional PIV methods described to approximate a 3-dimensional volumetric analysis.

Tomographic PIV.

Tomographic PIV is based on the illumination, recording, and reconstruction of tracer particles within a 3-D measurement volume. The technique uses several cameras to record simultaneous views of the illuminated volume, which is then reconstructed to yield a discretized 3-D intensity field. A pair of intensity fields are analyzed using 3-D cross-correlation algorithms to calculate the 3-D, 3-C velocity field within the volume. The technique was originally developed by Elsinga et al. in 2006.  The reconstruction procedure is a complex under-determined inverse problem. The primary complication is that a single set of views can result from a large number of 3-D volumes. Procedures to properly determine the unique volume from a set of views are the foundation for the field of tomography. In most Tomo-PIV experiments, the multiplicative algebraic reconstruction technique (MART) is used. The advantage of this pixel-by-pixel reconstruction technique is that it avoids the need to identify individual particles. Reconstructing the discretized 3-D intensity field is computationally intensive and, beyond MART, several developments have sought to significantly reduce this computational expense, for example the multiple line-of-sight simultaneous multiplicative algebraic reconstruction technique (MLOS-SMART) which takes advantage of the sparsity of the 3-D intensity field to reduce memory storage and calculation requirements.  As a rule of thumb, at least four cameras are needed for acceptable reconstruction accuracy, and best results are obtained when the cameras are placed at approximately 30 degrees normal to the measurement volume. Many additional factors are necessary to consider for a successful experiment.  Tomo-PIV has been applied to a broad range of flows. Examples include the structure of a turbulent boundary layer/shock wave interaction, the vorticity of a cylinder wake or pitching airfoil, rod-airfoil aeroacoustic experiments, and to measure small-scale, micro flows.. More recently, Tomo-PIV has been used together with 3-D particle tracking velocimetry to understand predator-prey interactions, and portable version of Tomo-PIV has been used to study unique swimming organisms in Antarctica.

Thermographic PIV.

Thermographic PIV is based on the use of thermographic phosphors as seeding particles. The use of these thermographic phosphors permits simultaneous measurement of velocity and temperature in a flow.  Thermographic phosphors consist of ceramic host materials doped with rare-earth or transition metal ions, which exhibit phosphorescence when they are illuminated with UV-light. The decay time and the spectra of this phosphorescence are temperature sensitive and offer two different methods to measure temperature. The decay time method consists on the fitting of the phosphorescence decay to an exponential function and is normally used in point measurements, although it has been demonstrated in surface measurements. The intensity ratio between two different spectral lines of the phosphorescence emission, tracked using spectral filters, is also temperature-dependent and can be employed for surface measurements.  The micrometre-sized phosphor particles used in thermographic PIV are seeded into the flow as a tracer and, after illumination with a thin laser light sheet, the temperature of the particles can be measured from the phosphorescence, normally using an intensity ratio technique. It is important that the particles are of small size so that not only they follow the flow satisfactorily but also they rapidly assume its temperature. For a diameter of 2 μm, the thermal slip between particle and gas is as small as the velocity slip.  Illumination of the phosphor is achieved using UV light. Most thermographic phosphors absorb light in a broad band in the UV and therefore can be excited using a YAG:Nd laser. Theoretically, the same light can be used both for PIV and temperature measurements, but this would mean that UV-sensitive cameras are needed. In practice, two different beams originated in separate lasers are overlapped. While one of the beams is used for velocity measurements, the other is used to measure the temperature.  The use of thermographic phosphors offers some advantageous features including ability to survive in reactive and high temperature environments, chemical stability and insensitivity of their phosphorescence emission to pressure and gas composition. In addition, thermographic phosphors emit light at different wavelengths, allowing spectral discrimination against excitation light and background.  Thermographic PIV has been demonstrated for time averaged  and single shot  measurements. Recently, also time-resolved high speed (3 kHz) measurements  have been successfully performed.

Real time processing and applications of PIV.

With the advance of digital technologies, real time processing and applications of PIV became possible. For instance, GPUs can be used to speed up substantially the direct of Fourier transform based correlations of single interrogation windows. Similarly multi-processing, parallel or multi-threading processes on several CPUs or multi-core CPUs are beneficial for the distributed processing of multiple interrogation windows or multiple images. Some of the applications use real time image processing methods, such as FPGA based on-the-fly image compression or image processing. More recently, the PIV real time measurement and processing capabilities are implemented for the future use in active flow control with the flow based feedback.

Applications.

PIV has been applied to a wide range of flow problems, varying from the flow over an aircraft wing in a wind tunnel to vortex formation in prosthetic heart valves. 3-Dimensional techniques have been sought to analyze turbulent flow and jets.  Rudimentary PIV algorithms based on cross-correlation can be implemented in a matter of hours, while more sophisticated algorithms may require a significant investment of time. Several open source implementations are available. Application of PIV in the US education system has been limited due to high price and safety concerns of industrial research grade PIV systems.

Granular PIV: velocity measurement in granular flows and avalanches.

PIV can also be used to measure the velocity field of the free surface and basal boundary in a granular flows such as those in shaken containers, tumblers and avalanches. This analysis is particularly well-suited for nontransparent media such as sand, gravel, quartz, or other granular materials that are common in geophysics. This PIV approach is called “granular PIV.” The set-up for granular PIV differs from the usual PIV setup in that the optical surface structure which is produced by illumination of the surface of the granular flow is already sufficient to detect the motion. This means one does not need to add tracer particles in the bulk material.

External links.

PIV research at the Laboratory for Experimental Fluid Dynamics (J. Katz lab)

Particle image velocimetry (PIV) is an optical method of flow visualization used in education and research. It is used to obtain instantaneous velocity measurements and related properties in fluids. The fluid is seeded with tracer particles which, for sufficiently small particles, are assumed to faithfully follow the flow dynamics (the degree to which the particles faithfully follow the flow is represented by the Stokes number). The fluid with entrained particles is illuminated so that particles are visible. The motion of the seeding particles is used to calculate speed and direction (the velocity field) of the flow being studied.

Integrální laserová anemometrie (: "Particle image velocimetry", zkráceně PIV), je moderní metoda používaná k měření rychlostního pole v proudící tekutině.


History.

In the middle of the 19th century, an industrial boom, supported by small and medium-sized enterprises, began in the Müglitz valley, which coincided with the beginning of the manufacture of watches in Glashütte (1845). In addition, a number of smaller production facilities in the wood and paper industry were built after Friedrich Gottlob Keller invented a method for making paper from wood pulp in 1843. Along the Müglitz numerous small paper and paper industries were established, including large paper factories such as the Peschelmühle near Burkhardswalde and the Pappenfabrik Glashütte (1886). Also metalworking plants such as the Schlottwitz machine factory and iron foundry in Glashütte (1874). The upturn in the industrial economy was closely linked to the growing industries in the Dresden Basin, which depended on supplies from the surrounding area. The transport systems were not able to cope with the increased requirements (access to raw materials, transport of finished products), so that between 1846 and 1864, the Müglitz valley road was extended and rebuilt.  In the medium term, however, the valley road was hardly able to cope with ever-increasing quantities of goods, especially as the demand for cheap lignite (brown coal) rose for the operation of steam boilers. Since horse-drawn carts were unable to match the capacity, speed and costs of the railway, manufacturers, merchants, trade associations and representatives of the cities demanded the construction of a railway line from 1865. It would connect the municipalities in the Müglitz valley to the Dresden–Bodenbach line and the lignite deposits of the North Bohemian Basin via the Ore Mountains (Erzgebirge). In December 1887, the Saxon Landtag (parliament) agreed to the construction of the railway, as the competitiveness of the companies in the valley diminished markedly in the 1880s due to poor accessibility. Plans, which provided, among other things, for lines via Lockwitz–Kreischa–Schlottwitz or Pirna–Zehista–Liebstadt–Schlottwitz could not be realised and the factories in the lower Müitz valley were not connected. The permit was therefore given for the construction of a complete valley railway from Mügeln bei Pirna (now a district of Heidenau) to Geising. It was designed as a 750 mm gauge railway to make it easier to follow the curves of the valley and to provide numerous connections. A continuation to Bohemia did not occur because the transit traffic was considered to be insufficient and would have been difficult to finance the technically complex route through Bohemia that would have been required by the steep descent following the crossing of the Ore Mountains.

The narrow-gauge railway from 1890 to 1939.

After two years of construction, with up to 1100 workers per month, the line was put into operation on 17 November 1890. It was 36.1 km long and overcame a difference in height of 470 m. The narrow and winding valley made considerable demands on the route selection. Of the total length, 86% was uphill (31 km) and 40% was in curvy sections (14.5 km). The Geising Viaduct was at 65 m long, the longest of the 57 bridges built. For the time being, Altenberg did not have a connection to the railway, as there was insufficient finance and no suitable locomotives available for the steep Geising–Altenberg section. Geising station was officially given the double name of "Geising-Altenberg", although the hill town hardly gained any benefit, since it was about 3 km away from and 160 metres in altitude above Geising. Despite this small "flaw", the railway was greeted by the valley inhabitants with festivals, fireworks and gun salutes. The first timetable provided for four daily train pairs; the travel time for the entire route was 150 minutes, a one-way trip in second class cost 2.30 Marks. The total of 3.6 million Marks spent on the railway contributed significantly to the economic boom of the neighbouring communities. As early as 1895, 14 industrial plants were connected by branches. In addition to the finished products, lignite, wood pulp, straw, paper, wood and bricks have been transported. From the 1920s, ice blocks were carried in winter from the Große Galgenteich lake near Altenberg to the Dresden cold stores. Passenger traffic was also significant. Numerous hikers took advantage of the railway to travel from Dresden and the Dresden Basin into the Ore Mountain area, which developed into a summer resort. The snow safety of the upper levels has also given the railway significant winter sport traffic since the turn of the century]]. As a result, it developed into one of the most economic routes in the Saxonian narrow-gauge railway network. Because of the heavy freight traffic, there were even proposals in 1914 for the operational separation of goods and passenger traffic on the Mügeln–Weesenstein section by the construction of a second railway. However, these plans were not implemented due to the post-war economic crisis. Instead, the extension of the line to Altenberg became the focus of interest. The town repeatedly proposed an extension of the railway. Various plans would have seen a continuation from Geising via Altenberg to Moldava, Hermsdorf, Kipsdorf or Frauenstein.  The government did not support these projects because of high construction costs and the low revenues expected. The 1914 proposal for an extension to Altenberg failed at the beginning of the First World War, but was then started as an emergency project in 1919. Within four years the 5.5 km-long roundabout line from Geising via the Geisingberg to Altenberg was opened on 10 November 1923. Large sections of the railway line were destroyed during a devastating flood on 8 July 1927.

Conversion to standard gauge.

Because of the steadily increasing transport demand after the Great Depression, Deutsche Reichsbahn decided to rebuild the line as standard gauge in 1934. This project was implemented between 1935 and December 1938. The Heidenau-Lauenstein section was completely redesigned; on the rest of the section to Altenberg, only the radius of the curve was enlarged. As a result, the line was approximately 3 km shorter. With the commencement of services on the standard gauge track in 1938, the number of road and track crossings and thus the danger of accidents were markedly reduced despite the increasing road traffic, but the Niederschlottwitz–Glashütte section was not accessible until April 1939. The flood risk also declined due to the raising of the line, although not on all sections of the line. However, the creation of a profitable basis for freight transport and improvements in passenger services were more important. For Deutsche Reichsbahn, the railway was the "new gateway to the eastern Ore Mountains", which made the Altenberg winter sport region "a sports ground at the gates of the national capital". The travel time for passenger services was shortened significantly, Altenberg was approximately 70 minutes from Dresden, about 160 minutes from Leipzig and about 180 minutes from Berlin.

During the Second World War.

The outbreak of the Second World War strongly restricted tourism. Because of the lack of coal, only three to five pairs of passenger trains operated every day, but the number of railcars from regions affected by air warfare was increasing. At the end of the Second World War there were fighting in the Müglitz Valley between Soviet and German troops. In April 1945, the railway installations in Glashütte, Bärenhecke-Johnsbach and Altenberg were damaged by strafing. In the last days of the war in May 1945 further damage occurred during air raids on Altenberg and Glashütte. Parts of the 10th SS Panzer Division Frundsberg used the Müglitz Valley as a retreat to northern Bohemia and planned the demolition of the Weesenstein tunnel. The derailment of a military train at Bärenstein on 7 May, as well as the rapid Soviet advance, prevented the planned destruction of the operationally important railway.

After the Second World War.

Although the Müglitz Valley Railway survived the Second World War largely intact apart from isolated damage in some railway stations, the enterprise was difficult in the early post-war years. On the other hand, there was an acute shortage of rollingstock as on all other lines. Class 84 locomotives were used for the transport of uranium in the Western Ore Mountains and passenger cars of the "Altenberg" class were used for express services. On the other hand, the track of the line had been built between 1935 and 1938 out of reused materials due to the scarcity of raw materials, and the material shortage of the immediate post-war years made the urgently necessary renewal difficult. From 1949/50, it was possible to speak of an initial normalisation of traffic, which included, among other things, the reinstatement of the first winter sports traffic. In the passenger and freight transport sector of the early 1950s, the operations of the uranium ore mining operation of the "SDAG Wismut" company near Bärenhecke played an important role between 1948 and 1954. All in all, rail traffic reached considerable proportions again. In the mid-1960s, at least 14 plants were connected to nine freight lines, including metal, chemical and paper processing companies in Dohna ("VEB Druckguss Heidenau" and "VEB Chemiewerke Dohna"). In passenger transport, it was used by hikers as well as increasingly by commuters to the Dresden Basin.  Since the beginning of the 1960s, Deutsche Reichsbahn has been trying to increase the transport performance and profitability of the railways by the use of railcars, double-deck wagons and diesel locomotives. While the operation of the former succeeded only to a limited extent, the diesel traction increasingly took over operations from the mid-1960s onwards with the class 110. This locomotive class took over operations on the Müglitz Valley Railway from 1967. At the same time, there were considerations of abandoning operations, in particular freight, on part or even all of the line. This was an issue particularly after the flooding in October 1966 of Geising station with a wave carrying sludge and gravel, which had escaped after the failure of the drainage system of "VEB Zinnerz Altenberg". In addition, the railway was affected by increased the competition from private cars. This, however, was probably the reason for a shift in transport services to the already heavily-used streets, especially in the winter months on the Dresden–Altenberg and Heidenau–Altenberg routes. Nevertheless, freight traffic declined in the following decades and focused on the section between Heidenau and Köttewitz. The route was maintained as a route for excursion traffic. In the winter months numerous special trains were used, connecting Altenberg directly with Dresden, Cottbus, Halle (Saale), Leipzig, Riesa and Hoyerswerda.  In the mid-1970s there were serious plans to electrify the line. The electrification was to be carried out by Czechoslovak State Railways (ČSD) in May 1976 after completion of work on the Elbe Valley Railway between Dresden and Schöna. Technically, it would have been easy to carry out, since all the tunnels have the rail profile necessary for the catenary installation. The project was not implemented for unknown reasons.

Decline and refurbishment to 1990.

In July 1990, the Müglitz Valley Railway celebrated the 100th anniversary of the opening of its route. The economic upheaval that began as a result of German reunification put the continuation of operations on the line into question again. A number of industrial enterprises were closed between Heidenau and Altenberg at the beginning of the 1990s. In 1991 the VEB Zinnerz Altenberg factory was closed. Other companies were able to continue their production only to a much lesser extent. As a result, the railways lost a large part of the freight volume within a few years. The decline in traffic volume was exacerbated by the sudden increase in competition between road and rail fieight transport as well as rail passenger transport. This negative development led to the closure of the freight operations south of Köttewitz (where there is a siding to the Fluorchemie factory) in 1995. Due to the uncertain future of the route, Deutsche Bahn failed to carry out necessary investments and only remediated wear and tear. As a result of this and the further decline in passenger numbers, the decommissioning of the entire line for safety reasons was considered in 1997. Also, the timetable introduced in that year was operationally unstable during the peak hours and its regular-interval timetable of services every two hours was unattractive.  It was only when the Verkehrsverbund Oberelbe, the local public transport utility, took over the line and awarded a contract to DB for the operation of train services for 15 years that a general restoration took place in 1998/99. The expenditure of €15 to 20 million enabled a thorough renewal of the railways and thus the elimination of numerous speed restrictions. In addition, DB used modern Siemens Desiro sets. With a reduction of travel times of60 minutes, services running every to 60 or 90 minutes and the use of new technology, there was a considerable increase in passenger numbers. The rehabilitated railway achieved patronage of about 1,200 to 2,000 passengers a day and thus proved its profitability. It was not only important for tourists, but also for student and commuter traffic.  As early as 1897, during the floods in the Eastern Ore Mountains of 1927 as well as in 1954, 1957, 1958 and 1966, serious flood damage occurred along the line, but this was by no means as great as the 2002 floods. Between 12 and 14 August 2002 enormous masses of water were discharged above the crest of the Eastern Ore Mountains. In Zinnwald-Georgenfeld, 406 mm of rain fell in this time, almost half of the annual average precipitation. The torrential rain turned the Müglitz into a torrential stream, devastating almost the entire valley. The situation was exacerbated by the break-up of the only flood retention basin in the Brießnitz valley, which is located above Glashütte. For the third time after 1897 and 1927, the line was largely destroyed. The dams and bridges were submerged and heavily devastated by parts of structures that had broken away. The resulting total loss amounted to approximately €50 million.  On 11 December 2002, after the construction of 1888/90, the flood of 1927, the standardisation in 1934/39 and the rehabilitation in 1998/99, the fifth period of major works on the railway began, which was finished by 20 December 2003. The resumption of operations was celebrated with popular festivals; Altenberg alone welcomed around 2,000 people on the first train. Its journey was preceded by the construction of two bridges and the repair of a further 13 bridges and five railway stations. Within a very short time, the railway reached patronage levels similar than before the flood with about 1,000 passengers each day and thus proved its importance as a transport route through the Eastern Ore Mountains. At the end of December 2010, Regionalbahn RB72 (Heidenau–Kurort Altenberg) services were running on the line; there were additional Regional-Express RE19 (Dresden Hbf–Kurort Altenberg) services run on the weekends of the winter half year. A special feature of the route is that these additional trains are only run if the conditions are appropriate for winter sports. It is announced in the traditional media on Thursdays whether they are running. The 2008 timetable included a total of 14 pairs of regional railway train running between Heidenau and Altenberg. Apart from a few gaps in the morning, a regular-interval hourly service was offered on working days. On the weekends, services ran every two hours.

Current operation.

The responsible authority for the provision of transport services in regional traffic is the Verkehrsverbund Oberelbe (VVO). After all transport services were retendered, they have been provided by the Städtebahn Sachsen since 12 December 2010. The services have been operated as SB72 and SE19 since then. It has a full-day regular-interval hourly service with trains crossing in Glashütte. On the weekends, the timetable remains unchanged with a two-hour cycle. In order to connect with the S-Bahn in Heidenau, the timetable has an unusual symmetry minute, which is approximately at 14 minute past the hour. Köttewitz, Weesenstein, Burkhardswalde-Maxen, Mühlbach (b Pirna), Oberschlottwitz, Bärenhecke-Johnsbach, Bärenstein (b Glashütte/Sachs) and Hartmannmühle stations are request stops. As in the past, additional direct trains are still operated between Dresden Hbf and Kurort Altenberg, only stopping at selected stations.  From 10 December 2011 to 14 December 2014, the little used request stops of Köttewitz and Burkhardswalde-Maxen were not served. The reason for this was the construction of the S-Bahn tracks between Dresden-Neustadt and Coswig, which led to timetable changes. In order to speed up the trains and ensure connections in Heidenau, the VVO decided to drop the stops temporarily.  On 2 June 2013, train operations had to be stopped again due to floods. In contrast to the flood in 2002, however, there was only minor damage, and the trains were able to return to schedule as of noon on 4 June.

Buildings.

During the reconstruction of the line in the 1930s, a great deal of importance was attached to the connection of the station buildings to the landscape. The goal was to create a smooth transition between the rural structures of the Dresden Basin and those of the eastern Ore Mountains. Even smaller halts were given individually designed wooden service buildings.  At the same time, a new slate-covered steep roof and the use of wood as a building material for all attachments, such as freight sheds and waiting rooms, are common to all the newly-built station buildings. The red-painted window frames are also typical of the landscape. Some of the buildings–as in Burkhardswalde-Maxen and Lauenstein–are decorated with Sgraffito elements on the facades.  During the floods of August 2002, some of the station buildings of the line were badly affected.

Route description.

The route turns from Heidenau station southwards into the Müglitz valley and crosses the four-lane state road 172. Just before Dohna, it crosses Autobahn 17 and climbs the first significant slope before Köttewitz station. After the station, the Müglitz is crossed for the first time, followed immediately by the first and, at 198 metres, the longest of a total of four tunnels through spurs. Just after Weesenstein station, the route is shortened again by a second tunnel, 240 metres long. After Burkhardswalde-Maxen, the valley narrows for a short time and at 15.0 km between Niederschwottwitz and Oberschwottwitz, the line runs past the rock of the Schlottwitz agate lode. Again, the valley is shortened before Glashütte with the 292 metre-long Brückenmühle tunnel. After the station is the longest tunnel of the line, 539 metres long, and a two-lane concrete bridge, which is untypical of the Müglitz Valley Railway, is traversed at Bärenhecke-Johnsbach. From Lauenstein, the line leaves the Müglitz valley and follows the Roten Wasser (part of the Greifenbach) valley to the southwest towards Geising. The town itself is reached to the north through a 235-metre-long curving tunnel and a 76-metre-long bridge so that the line changes direction completely from running south to running north. The last section leaves the valley on the western slope and rounds the Geisingberg. Starting from kilometre 36.6, the steepest section begins with a gradient of 1:37.6.

Stations.

Heidenau ()  The Müglitz Valley Railway begins in "Heidenau station" on the Děčín–Dresden-Neustadt railway. There is a connection to the Dresden S-Bahn line S1 (Meissen-Triebischtal – Schöna) and S2 (Dresden Flughafen – Pirna).  Dohna (Sachs) ()  "Dohna (Sachs)" station still has the entrance building from the narrow gauge period. Because of its great importance for passenger traffic, Dohna was integrated into the Dresden S-Bahn fare zone before German reunification. At times, the station, which is located in the Dohna lower town, was also planned as the terminus of an S-Bahn service, but this was not implemented.  Dohna Fluorchemie siding ()  The "Dohna Fluorchemie" siding is located beyond Dohna station just before Köttewitz station. The siding leading to a chemical plant in Dohna is the only one on the line still used for freight traffic.  Köttewitz ()  "Köttewitz" halt (German: "Haltepunkt", that is a station without any points) is located just outside the town. Köttewitz is only a request stop because of the extremely low volume of passengers. From 10 December 2011 to 14 December 2013, Köttewitz was not served to save time in order to improve connections in Heidenau to the trains on line S1. Instead, a special bus served this halt from Heidenau or Mühlbach. The halt is beyond the approach signal to Dohna station and is thus operationally part of Dohna station.  Weesenstein ()  "Weesenstein" halt is now only a demand stop. The small service building is owned by Deutsche Bahn AG. The entrance building dates back to 1938.  Burkhardswalde-Maxen ()  "Burkhardswalde-Maxen" halt is located just outside the villages of Burkhardswalde and Maxen. Today it has little traffic. Directly on the slope above the station are the formerly well-known Margon mineral water ("Margonwasser") springs and the attached "Schloss Gesundbrunnen" ("healthy spring palace"). In the course of the restoration the line in 1998/99, the former station was restored as a halt.  The station building, which is heritage listed, is mainly known for its sgraffito decorations on its gable. These have their background in some events of the Seven Years' War that took place nearby. After the Battle of Maxen on 20 November 1759, the Prussian General von Finck surrendered and was captured by the Austrians, who were allied with Saxony, together with 14,000 men. Pictured are a Saxon grenadier and a Prussian Freikorps knight and above is the inscription "Anno 1759". In 2002, the flood waters of the Müglitz destroyed the station building’s rear wooden freight platform. The structure was then demolished and not rebuilt.  Deutsche Bahn has offered the station building for sale for a few years, but so far without success. The building is empty and decaying.  Mühlbach (b Pirna) () The current "Mühlbach (b Pirna)" halt is in an almost identical position to the station on the narrow gauge line. It was originally called "Häselich" after the neighbouring small village and was later called "Häselich-Mühlbach". Since 15 May 1938, it has borne the present name.  The layout originally consisted of a continuous railway track with a platform and a loading track, which was connected at both ends, which was not included in the standardisation. The originally wooden waiting room was replaced in 1938 by a more formal, significantly enlarged building in the Heimatstil (“homeland style”, a German revivalist style), which is now used for residential purposes. During 1998/99, the separate passenger tracks were moved a few metres towards Heidenau and are no longer connected to the line.  Niederschlottwitz ()  The former "Niederschlottwitz" station, now classified as a halt was built in 1938 on the site of the narrow-gauge station. The entrance building is almost the same as in Burkhardswalde and Bärenstein. The sgraffito on the gable represents a peasant couple that was typical for the area. The signal box was built in a contemporary style.  Niederschlottwitz was reclassified in 1999 after the extension of the second station track as a halt with block post. The elevated signal box served until the 2002 flood to protect the signal block and the neighbouring level crossing. The block post was not re-established after the flood and an automatic system is now used to secure the line.  Oberschlottwitz ()  "Oberschwottwitz" halt was established in 1938 on the slope before the Müglitz Viaduct and is sited approximately on the location of the former narrow gauge station. The small, massive entrance building is built in the Heimatstil and is now unused.  Glashütte (Sachs) ()  "Glashütte (Sachs)" station is now the only station on the line with a passing loop. When the new building was built in 1938, the entire station area was raised above flood level. A new entrance building was built; it now serves as Nomos Glashütte’s headquarters and production site.  Bärenhecke-Johnsbach ()  "Bärenhecke-Johnsbach" halt is located near the village of Bärenhecke, on the opposite side of the Müglitz, but has a very limited passenger traffic because of its great distance from the much larger village of Johnsbach. At the end of the 1990s, the entrance to the Bärenhecke mill and bakery was located at the stop.  Bärenstein (b Glashütte/Sachs) () The "Förderverein für die Müglitztalbahn eV" (“supporting association for the Müglitz Valley Railway”, which developed the station precincts into a museum with several buildings, had its headquarters in the "Bärenstein" station. After the insolvency of the association, the entrance building is now privately owned. Officially, the station is connected to an industrial spur, so that regular use by museum trains is possible. It is notable for having a waterhouse (for supplying water for steam trains) from the narrow-gauge era, which is the oldest in Saxony and which is still operational. A similar building exists in all of Saxony only at Burkhardswalde-Maxen halt and on the Pressnitz Valley Railway in Steinbach.  Lauenstein (Sachs) ()  The current "Lauenstein (Sachs)" halt was classified as a station until 1998/99, before it was an important passing point on the upper part of the line.  Hartmannmühle ()  It is still possible to find the wooden waiting room from the narrow-gauge era at "Hartmannmühle" halt. The "Wildpark Osterzgebirge" tourist attraction now lies opposite the stop. Because of the low traffic, Hartmannmühle is now only a request stop.  Geising ()  The current "Geising" halt was the terminus of the narrow-gauge line until 1923 and called Geising-Altenberg station. In October 1966, Geising station was flooded with a mud and boulder wave that had escaped due to a damage to the drainage system of the washing plant of VEB Zinnerz Altenberg. The station was then returned to the station and the signal box was left open. The entrance building dates back to the narrow-gauge period. The only change with standardisation of the line in 1938 was the addition of a spacious waiting room. Today it is used for commercial purposes.  Geisingberg-Sprungschanze  The "Geisingberg-Sprungschanze" halt was only open between 1933 and 1941. It was only served at sporting events on the ski jumping hill on the Geisingberg.  Kurort Altenberg (Erzgeb) ()  "Kurort Altenberg" station is the terminus of the Müglitz Valley Railway. It was built in 1938 at the same place as the old narrow-gauge station, however with a change in the angle of the tracks. Originally there were four platforms for winter sports, which were reduced to three after the 1999 rehabilitation of the track. The station has a covered structure that directly links to the suburban bus stop, which can also be used as a conference hall. The entrance building, which was destroyed in 1945 and later rebuilt, now belongs to the town of Altenberg, which uses it as a centre for tourist information and the operation of a cross-country ski trail.  Platform 1 was developed in 2013 with the federal funds from the "Schienenwegeausbaugesetz" (“railways extension act). It was raised to a platform height of 55 centimetres above the top edge of the rail and a given guidance system for the blind. The cost was over €240,000.

The Heidenau–Kurort Altenberg railway, also known in German as the "Müglitztalbahn" ("Müglitz Valley Railway") is a German railway in Saxony. Branching off the Elbe Valley Railway, it connects the town of Heidenau near Dresden with the towns of Glashütte and Altenberg in Erzgebirge (Ore Mountains), where it terminates. The total length is 38 km, with a total incline of 634 meters. The scenic track follows primarily the Müglitz river, passing the towns of Dohna, Glashütte and Geising.

Železniční trať Heidenau–Altenberg, známá též jako Müglitztalbahn ("Mohelnická dráha"), je vedlejší trať stoupající z Heidenau (dříve "Mügeln") údolím Mohelnice ("Müglitz") do města Altenberg v Krušných horách. Odbočuje z hlavní trati Děčín – Drážďany v údolí Labe a na 38 kilometrech délky překoná převýšení 637 metrů. 17. listopadu 1890 byl otevřen úsek do města Geising, vybudovaný jako úzkorozchodná trať. Zbývající úsek do Altenbergu byl otevřen až o desítky let později. Na konci 30. let dvacátého století byla trať přebudována na normální rozchod. Trať byla několikrát poškozena povodněmi, naposledy v roce 2002.


Types.

Containment systems for nuclear power reactors are distinguished by size, shape, materials used, and suppression systems. The kind of containment used is determined by the type of reactor, generation of the reactor, and the specific plant needs.  Suppression systems are critical to safety analysis and greatly affect the size of containment. Suppression refers to condensing the steam after a major break has released it from the cooling system. Because decay heat does not go away quickly, there must be some long term method of suppression, but this may simply be heat exchange with the ambient air on the surface of containment. There are several common designs, but for safety-analysis purposes containments are categorized as either "large-dry", "sub-atmospheric", or "ice-condenser".

Pressurized water reactors.

For a pressurized water reactor, the containment also encloses the steam generators and the pressurizer, and is the entire reactor building. The missile shield around it is typically a tall cylindrical or domed building. PWR containments are typically large (up to 7 times larger than a BWR) because the containment strategy during the leakage design basis accident entails providing adequate volume for the steam/air mixture that results from a loss-of-coolant-accident to expand into, limiting the ultimate pressure (driving force for leakage) reached in the containment building.  Early designs including Siemens, Westinghouse, and Combustion Engineering had a mostly can-like shape built with reinforced concrete. As concrete has a very good compression strength compared to tensile, this is a logical design for the building materials since the extremely heavy top part of containment exerts a large downward force that prevents some tensile stress if containment pressure were to suddenly go up. As reactor designs have evolved, many nearly spherical containment designs for PWRs have also been constructed. Depending on the material used, this is the most apparently logical design because a sphere is the best structure for simply containing a large pressure. Most current PWR designs involve some combination of the two, with a cylindrical lower part and a half-spherical top.  The spent fuel pool is outside of the containment building in most PWR designs except the german.  Modern designs have also shifted more towards using steel containment structures. In some cases steel is used to line the inside of the concrete, which contributes strength from both materials in the hypothetical case that containment becomes highly pressurized. Yet other newer designs call for both a steel and concrete containment - which is in decades long use in the current German PWR-designs - notably the AP1000 and the European Pressurized Reactor plan to use both; which gives missile protection by the outer concrete and pressurizing ability by the inner steel structure. The AP1000 has planned vents at the bottom of the concrete structure surrounding the steel structure under the logic that it would help move air over the steel structure and cool containment in the event of a major accident (in a similar way to how a cooling tower works).  The Russian VVER-1000 design is mostly the same as other modern PWRs in regards to containment, as it is a PWR itself. However, the VVER-440-type has a significant more vulnerable containment, in form of a so-called "bubble condensor" with relatively low design pressure.

Light water graphite reactors.

Light water graphite reactors were built only in the USSR. RBMK designs used secondary containment-like structures, but the reactor's top plate was a part of the protective structure. During the Chernobyl accident in 1986 the plate suffered a pressure beyond the predicted limits and lifted up.

Boiling water reactors.

In a BWR, the containment strategy is a bit different. A BWR's containment consists of a drywell, where the reactor and associated cooling equipment is located, and a wetwell. The drywell is much smaller than a PWR containment and plays a larger role. During the theoretical leakage design basis accident the reactor coolant flashes to steam in the drywell, pressurizing it rapidly. Vent pipes or tubes from the drywell direct the steam below the water level maintained in the wetwell (also known as a torus or suppression pool), condensing the steam, limiting the pressure ultimately reached. Both the drywell and the wetwell are enclosed by a secondary containment building, maintained at a slight sub-atmospheric or negative pressure during normal operation and refueling operations.  Common containment designs are referred to by the names Mark I, Mark II, and Mark III. The Mark I is the oldest, distinguished by a drywell which resembles an inverted lightbulb above the wetwell which is a steel torus containing water. The Mark II was used with late BWR-4 and BWR-5 reactors. It is called an "over-under" configuration with the drywell forming a truncated cone on a concrete slab. Below is a cylindrical suppression chamber made of concrete rather than just sheet metal. Both use a lightweight steel or concrete "secondary containment" over the top floor which is kept at a slight negative pressure so that air can be filtered. The top level is a large open space with an overhead crane suspended between the two long walls for moving heavy fuel caskets from the ground floor, and removing / replacing hardware from the reactor and reactor well. The reactor well can be flooded and is straddled by pools separated by gates on either side for storing reactor hardware normally placed above the fuel rods, and for fuel storage. A refueling platform has a specialized telescoping mast for lifting and lowering fuel rod assemblies with precision through the "cattle chute" to the reactor core area. The Mark III uses a concrete dome, somewhat like PWRs, and has a separate building for storing used fuel rods on a different floor level. All three types also use the large body of water in the suppression pools to quench steam released from the reactor system during transients.  The Mark I containment was used in those reactors at the Fukushima I Nuclear Power Plant which were involved in the Fukushima I nuclear accidents. The site suffered from a combination of two beyond design-basis events, a powerful earthquake, which may have damaged reactor plumbing and structures, and 15 meter tsunami, which destroyed fuel tanks, generators and wiring, causing back up generators to fail, and battery-powered pumps also eventually failed. Insufficient cooling and failure of pumps needed to restore water lost to boiling off led to partial or possible complete meltdowns of fuel rods which were completely uncovered by water. This led to releases of significant amounts of radioactive material to the air and sea, and hydrogen explosions. The thin secondary containments were not designed to withstand hydrogen explosions, and suffered blown out or destroyed roofs and walls, and destruction of all equipment on the refueling floor including cranes and refueling platform. Unit 3 suffered a particularly spectacular explosion which created a plume of debris over 300 m high which resulted in a collapse of the north end of the top floor, and buckled concrete columns on its west side as can be seen by aerial photographs. Although they were fitted with modified hardened vent systems to vent hydrogen into exhaust stacks, they may have not been effective without power. Even before the Fukushima incident, Mark I containment had been criticized as being more likely to fail during a blackout.  From a distance, the BWR design looks very different from PWR designs because usually a square building is used for the secondary containment. Also, because there is only one loop through the turbines and reactor, and the steam going through the turbines is also radioactive, the turbine building has to be considerably shielded as well. This leads to two buildings of similar construction, with the higher one housing the reactor and the long one housing the turbine hall and supporting structures.

CANDU plants.

CANDU power stations, named after Canadian-invented Deuterium-Uranium design, make use of a wider variety of containment designs and suppression systems than other plant designs. Due to the nature of the core design, the size of containment for the same power rating is often larger than for a typical PWR, but many innovations have reduced this requirement.  Many multiunit CANDU stations utilize a water spray equipped vacuum building. All individual CANDU units on site are connected to this vacuum building by a large pressure relief duct which is also part of containment. The vacuum building rapidly draws in and condenses any steam from a postulated break, allowing the reactor building pressure to return to subatmospheric conditions. This minimizes any possible fission product release to the environment.  Additionally, there have been similar designs that use double containment, in which containment from two units are connected allowing a larger containment volume in the case of any major incident. This has been pioneered by one Indian HWR design where a double unit and suppression pool was implemented.  The most recent CANDU designs, however, call for a single conventional dry containment for each unit.

Design and testing requirements.

In the United States, Title 10 of the Code of Federal Regulations, Part 50, Appendix A, General Design Criteria (GDC 54-57) or some other design basis provides the basic design criteria for isolation of lines penetrating the containment wall. Each large pipe penetrating the containment, such as the steam lines, has isolation valves on it, configured as allowed by Appendix A; generally two valves. For smaller lines, one on the inside and one on the outside. For large, high-pressure lines, space for relief valves and maintenance considerations cause the designers to install the isolation valves near to where the lines exit containment. In the event of a leak in the high-pressure piping that carries the reactor coolant, these valves rapidly close to prevent radioactivity from escaping the containment. Valves on lines for standby systems penetrating containment are normally closed. The containment isolation valves may also close on a variety of other signals such as the containment high pressure experienced during a high-energy line break (e.g. main steam or feedwater lines). The containment building serves to contain the steam/resultant pressure, but there is typically no radiological consequences associated with such a break at a pressurized water reactor.  During normal operation, the containment is air-tight and access is only through marine style airlocks. High air temperature and radiation from the core limit the time, measured in minutes, people can spend inside containment while the plant is operating at full power. In the event of a worst-case emergency, called a "design basis accident" in NRC regulations, the containment is designed to seal off and contain a meltdown. Redundant systems are installed to prevent a meltdown, but as a matter of policy, one is assumed to occur and thus the requirement for a containment building. For design purposes, the reactor vessel's piping is assumed to be breached, causing a "LOCA" (loss Of coolant accident) where the water in the reactor vessel is released to the atmosphere inside the containment and flashes into steam. The resulting pressure increase inside the containment, which is designed to withstand the pressure, triggers containment sprays ("dousing sprays") to turn on to condense the steam and thus reduce the pressure. A SCRAM ("neutronic trip") initiates very shortly after the break occurs. The safety systems close non-essential lines into the air-tight containment by shutting the isolation valves. Emergency Core Cooling Systems are quickly turned on to cool the fuel and prevent it from melting. The exact sequence of events depends on the reactor design.  Containment buildings in the U.S. are subjected to mandatory testing of the containment and containment isolation provisions under 10 CFR Part 50, Appendix J. Containment Integrated Leakage Rate Tests (Type "A" tests or CILRTs) are performed on a 15-year basis. Local Leakage Rate Tests (Type B or Type C testing, or LLRTs) are performed much more frequently, both to identify the possible leakage in an accident and to locate and fix leakage paths. LLRTs are performed on containment isolation valves, hatches and other appurtenances penetrating the containment. A nuclear plant is required by its operating license to prove containment integrity prior to restarting the reactor after each shutdown. The requirement can be met with satisfactory local or integrated test results (or a combination of both when an ILRT is performed).  In 1988, Sandia National Laboratories conducted a test of slamming a jet fighter into a large concrete block at. The airplane left only a gouge in the concrete. Although the block was not constructed like a containment building missile shield, it was not anchored, etc., the results were considered indicative. A subsequent study by EPRI, the Electric Power Research Institute, concluded that commercial airliners did not pose a danger.  The Turkey Point Nuclear Generating Station was hit directly by Hurricane Andrew in 1992. Turkey Point has two fossil fuel units and two nuclear units. Over $90 million of damage was done, largely to a water tank and to a smokestack of one of the fossil-fueled units on-site, but the containment buildings were undamaged.

A containment building, in its most common usage, is a reinforced steel or lead structure enclosing a nuclear reactor. It is designed, in any emergency, to contain the escape of radioactive steam or gas to a maximum pressure in the range of. The containment is the fourth and final barrier to radioactive release (part of a nuclear reactor's defence in depth strategy), the first being the fuel ceramic itself, the second being the metal fuel cladding tubes, the third being the reactor vessel and coolant system.

Kontejnment je ochranná obálka (či budova) jaderného reaktoru v jaderné elektrárně, vystavěná z oceli a betonu. Spojuje funkci hermetického prostoru pro ochranu před únikem nebezpečných látek do vnějšího prostředí a mechanické ochrany proti vnějším vlivům.


History.

The Catalan derives its name from Catalonia, after tournament organisers at the 1929 Barcelona tournament asked Savielly Tartakower to create a new variation in homage to the area's chess history. It had been played a few times before Tartakower's usage in the tournament, however: Réti–Leonhardt, Berlin 1928, for instance, transposed into an Open Catalan.  The Catalan came to prominence at the top level when both Garry Kasparov and Viktor Korchnoi played it in their Candidates Semifinal match in London in 1983: five games of the eleven-game match were Catalans.  In 2004, Ruben Felgaer won a tournament celebrating the 75th anniversary of Barcelona 1929 and the birth of the Catalan Opening, ahead of Grandmasters (GMs) Viktor Korchnoi, Mihail Marin, Lluis Comas and Viktor Moskalenko and International Master Manel Granados. Each game in the tournament, which was also held in Barcelona, began with the moves 1.d4 d5 2.c4 e6 3.g3 Nf6.  With its use by Vladimir Kramnik, the Catalan has gained a good deal of attention by high-level GMs in recent times. Kramnik played the opening three times in the World Chess Championship 2006. The Catalan was also played four times by Viswanathan Anand in the World Chess Championship 2010; in both instances the opponent was Veselin Topalov, and in each instance White scored two more points than Black.

Open Catalan, Classical Line.

The Open Catalan, Classical Line begins 1.d4 Nf6 2.c4 e6 3.g3 d5 4.Bg2 dxc4 5.Nf3 Be7. White trades the pawn for a lead in. Without the d5-pawn, White's bishop hinders Black's development. The Open Catalan line has been a favorite of Anatoly Karpov and Efim Geller as Black and Oleg Romanishin with the white pieces. Usually, White will recover the pawn with Qc2 and a4, Ne5, or Qa4. In order to hold the pawn, Black will have to seriously weaken the queenside with...a6 and...b5. The "ECO" code is E05.

The Catalan is a chess opening where White adopts a combination of the Queen's Gambit and Réti Opening: White plays d4 and c4 and fianchettoes the white bishop on g2. A common opening sequence is 1.d4 Nf6 2.c4 e6 3.g3, although the opening can arise from various move orders (see transposition). "Encyclopaedia of Chess Openings" ("ECO") codes E01–E09 are for lines with 1.d4 Nf6 2.c4 e6 3.g3 d5 4.Bg2, and others are part of E00.

Katalánský systém (ECO E00-E09) je šachové zahájení zavřených her charakterizované tahy 1. d4 Jf6 2. c4 e6 3. g3 1. d4 Jf6 2. c4 e6 3. g3


Design.

The diesel engine may be located above the frame in an engine bay or under the floor. Driving controls can be at both ends, on one end, or in a separate car.

Types by transmission.

DMUs are usually classified by the method of transmitting motive power to their wheels.

Diesel–mechanical.

In a diesel–mechanical multiple unit (DMMU), the rotating energy of the engine is transmitted via a gearbox and driveshaft directly to the wheels of the train, like a car. The transmissions can be shifted manually by the driver, as in the great majority of first-generation British Rail DMUs, but in most applications, gears are changed automatically.

Diesel–hydraulic.

In a diesel–hydraulic multiple unit (DHMU), a hydraulic torque converter, a type of fluid coupling, acts as the transmission medium for the motive power of the diesel engine to turn the wheels. Some units feature a hybrid mix of hydraulic and mechanical transmissions, usually reverting to the latter at higher operating speeds as this decreases engine RPM and noise.

Diesel–electric.

In a diesel–electric multiple unit (DEMU), a diesel engine drives an electrical generator or an alternator which produces electrical energy. The generated current is then fed to electric traction motors on the wheels or bogies in the same way as a conventional diesel–electric locomotive.  On some DEMUs, such as the Bombardier Voyager family, each car is entirely self-contained and has its own engine, generator and electric motors. In other designs, such as the British Rail Class 207 or the Stadler GTW and Stadler Flirt DMU, some cars within the consist may be entirely unpowered or only feature electric motors, obtaining electric current from other cars in the consist which have a generator and engine.  With diesel–electric transmission, some DMU can be no other than an EMU without pantograph, which "is substituted" by one or more on-board diesel generators; this kind of DEMU can be potentially upgraded to electro-diesel multiple unit "EDMU", becoming a bi-mode multiple units train (BMU), just adding one or two pantographs (with opportune converters, if necessary) and related modifications on the electric system.

Advantages and disadvantages.

A train composed of DMU cars scales well, as it allows extra passenger capacity to be added at the same time as motive power. It also permits passenger capacity to be matched to demand, and for trains to be split and joined en route. It is not necessary to match the power available to the size and weight of the train, as each unit is capable of moving itself. As units are added, the power available to move the train increases by the necessary amount. DMUs may have better acceleration capabilities, with more power-driven axles, making them more suitable for routes with frequent closely spaced stops, as compared with conventional locomotive and unpowered carriage setups.  Distribution of the propulsion among the cars also results in a system that is less vulnerable to single-point-of-failure outages. Many classes of DMU are capable of operating with faulty units still in the consist. Because of the self-contained nature of diesel engines, there is no need to run overhead electric lines or electrified track, which can result in lower system construction costs.  Such advantages must be weighed against the underfloor noise and vibration that may be an issue with this type of train.  Generally diesel traction has several downsides compared to electric traction, namely higher fuel costs, more noise and exhaust as well as worse acceleration and top speed performance. The power to weight ratio also tends to be worse.  DMUs have further disadvantages compared to diesel locomotives in that they cannot be swapped out when approaching or passing onto an electrified line, necessitating either passengers to change trains or Diesel operation on electrified lines. Similarly the lost investment once electrification reduces the demand for diesel rolling stock is higher than with locomotive hauled trains where only the locomotive has to be replaced. Finally, incremental maintenance costs for DMUs are significantly higher than with electric (EMUs), because of the added fueling, lubrication, replacement and maintenance of engine parts and systems in every car.

Around the world.

Europe.

Belgium.

NMBS/SNCB uses its NMBS/SNCB Class 41 DMU's on the few remaining unelectrified lines. As electrification progresses, the DMU's become less and less important.

Croatia.

Diesel multiple units cover large number of passenger lines in Croatia which are operated by the national operator Croatian Railways. On Croatian Railways, DMU's have important role since they cover local, regional and distant lines all across the country. Country's two largest towns, Zagreb and Split, are connected with an Inter City service that is provided by DMU tilting trains "RegioSwinger" (Croatian series 7123) since 2004. Those trains may also cover other lines in the country depending on need and availability.  Luxury DMU series 7021, built in France, started to operate for Yugoslav Railways in 1972 and after 1991 stil remained in service of Croatian Railways until 2005. Units 7121 and 7122 (which came as a replacement for 7221 units), together with the newest series 7022 and 7023 built in 2010's Croatia, cover many of the country's local and regional services on unelectrified or partly electrified lines.

Estonia.

Elron has since 2015 a Stadler Flirt fleet, with 20 trains DEMU version.

Ireland.

In the Republic of Ireland the Córas Iompair Éireann (CIÉ), which controlled the republic's railways between 1945 and 1986, introduced DMUs in the mid-1950s and they were the first diesel trains on many main lines.

Romania.

DMUs are used mostly on shorter and less frequently travelled routes in remote and often poorer areas like Banat and Bukovina. The national railway company CFR uses Malaxa class 77 and 78 DMUs locally built between the 1920s and 50s and refurbished in the 70s. It also uses a smaller number of other newer DMUs. Main DMU in use is the Class 96 Siemens Desiro aka Săgeata Albastră (Blue Arrow).

United Kingdom.

The first significant use of DMUs in the United Kingdom was by the Great Western Railway, which introduced its small but successful series of diesel–mechanical GWR railcars in 1934. The London and North Eastern Railway and London, Midland and Scottish Railway also experimented with DMUs in the 1930s, the LMS both on its own system, and on that of its Northern Irish subsidiary, but development was curtailed by World War II.  After nationalisation, British Railways (BR) revived the concept in the early 1950s. At that time there was an urgent need to move away from expensive steam traction which led to many experimental designs using diesel propulsion and multiple units. The early DMUs proved successful, and under BR's 1955 Modernisation Plan the building of a large fleet was authorised. These BR "First Generation" DMUs were built between 1956 and 1963.  BR required that contracts for the design and manufacture of new locomotives and rolling stock be split between numerous private firms as well as BR's own workshops, while different BR Regions laid down different specifications. The result was a multitude of different types, one of which was:  In 1960, British Railways introduced its Blue Pullman high-speed DEMUs. These were few in number and relatively short-lived, but they paved the way for the very successful InterCity 125 or High Speed Train (HST) units, which were built between 1975 and 1982 to take over most principal express services on non-electrified routes. These trains run with a streamlined power car at each end and (typically) 7 to 9 intermediate trailer cars. Although originally classified as DEMUs, the trailer cars are very similar to loco-hauled stock, and the power cars were later reclassified as locomotives under Class 43. They remain in widespread use.  By the early 1980s, many of the surviving First Generation units were reaching the end of their design life, leading to spiralling maintenance costs, poor reliability and a poor public image for the railway. A stopgap solution was to convert some services back to locomotive haulage, as spare locomotives and hauled coaching stock were available, but this also increased operating costs. Commencing in the mid '80s, British Rail embarked upon its so called "Sprinterisation" programme, to replace most of the first generation DMUs and many locomotive-hauled trains with three new families of DMU:  Following the impact of the privatisation of British Rail in the late 1990s, several other diesel–hydraulic DMU families have been introduced:  In 2018 the first bi and tri-mode electro-diesel multiple units were introduced:

North America.

Canada.

Canada generally follows similar buffer strength requirements to the US, but new services are evaluated on a case-by-case basis. As a result, several types of lightweight DMUs have been used:

Costa Rica.

Costa Rica has purchased several Apolo 2400 series DMU railcars from the former narrow gauge operator in Spain, which are run in commuter service.

United States.

A type of diesel multiple units in the U.S. was the Budd Rail Diesel Car (RDC). The RDC was a single passenger car with two diesel engines and two sets of controls.  In the United States only FRA-compliant DMU systems are permitted on freight rail corridors. This is due to the Federal Railway Administration setting higher coupling strength requirements than European regulators, effectively prohibiting the use of lighter weight European-style inter-city rail DMUs on U.S. main line railways without timesharing with freight operations or special waivers from the FRA. This has greatly restricted the development of DMUs within the U.S. as no other country requires the much heavier FRA compliant vehicles, and no export market for them exists.  Operations using FRA-compliant vehicles:  Operations using non FRA-compliant vehicles:  Proposed operations:

Asia/Australasia.

Australia.

DMUs were first introduced to Australia in the late mid-20th century for use on quiet branch lines that could not justify a locomotive hauled service. Today, DMUs are widely used throughout Australia's southern states:  In Queensland, heritage DMUs are used on the Savannahlander and Gulflander tourist trains.

Bangladesh.

Chinese manufactured (CNR Tangshan) DEMU was introduced in Bangladesh from May 25, 2013. DEMU is the country's first-ever commuter train service starting its journey on the Chittagong–Fouzdarhat line. These DEMUs also operate on the Chittagong Circular Railway and on the Bangladesh Railway's service between Dhaka and Narayanganj.

India.

DMUs (DEMUs) are widely used in India. DEMUs in India are used in both the 8 coach format and the 4 coach format. These trains replaced many (up to 10 car) trains with a WDM-2 or WDM-3A locomotive in the middle. These old trains had the loco controls duplicated in the Driving Trailer coach and all the actuation information reaching the locomotive through thin communication lines. This was called 'push-pull train'. The longest running such push-pull service operated between Diva - Bhiwandi Road and Vasai Road and was recently converted into an MEMU train service in 2018.  First generation DMU: Rated power was 700 HP and had 3 or 6 coaches, made first by ICF. Transmission was Voith-hydraulic. Max speed 100 kmph. Second generation DMU: Rated power is 1400 HP and have 8 coaches. Max speed is 105 kmph. Transmission is DC electric. Made at HCF and RCF. Third generation DMU: Rated power is 1600 HP and have 10 coaches. Max speed is 110 kmph. Transmission is AC electric. Made at ICF.

Indonesia.

State-owned company PT.INKA builds several type of DMU, some of which operate in urban and suburban areas:

Japan.

In Japan, where gasoline-driven railbuses (on small private lines) and railmotors (Kihani 5000 of the national railways) had been built since the 1920s, the first two streamlined DMUs came in service in 1937, class Kiha 43000 (キハ43000系).  The service of several hundreds (in sum even thousands) of diesel railcars and DMUs started in 1950s following the improvement of fuel supply that was critical during World War II.

Philippines.

The Southrail or the South Main Line of the Philippine National Railways which travels South of the Luzon island is one of the oldest rail lines in Asia and in the world. The Southrail of Philippine National Railways uses Hyundai Rotem DMUs together with second-hand DMUs from East Japan Railway Company or JR East and Kanto Railway. These are Kiha 52, Kiha 59 which is also known as the "Kogane" and Kiha 350. Trains such as the Hyundai Rotem DMUs Kiha 350 and Kiha 52 are often used for Metro Commuter Line services, while Kiha 59 is mostly used for Bicol interprovincial services and sometimes also for the Metro Commuter services.

South Korea.

Korail operates many DMUs. The DHC (Diesel Hydraulic Car), which made its debut for the 1988 Seoul Olympics, can reach speeds up to and serves Saemaul-ho trains.

Sri Lanka.

DMUs were first introduced to Sri Lanka in 1940. The aim of this was connecting minor railway stations and stops on the main line where most express trains don't have a halt.

Taiwan.

The DMUs are now usually used on the Taiwan Railway Administration Hualien–Taitung Line, North-Link Line, South-Link Line. DMUs in Taiwan are classified as Class DR.

Manufacturers.

DMU manufacturers include:

A diesel multiple unit or DMU is a multiple-unit train powered by on-board diesel engines. A DMU requires no separate locomotive, as the engines are incorporated into one or more of the carriages. Diesel-powered single-unit railcars are also generally classed as DMUs. Diesel-powered units may be further classified by their transmission type: diesel–mechanical "DMMU", diesel–hydraulic "DHMU", or diesel–electric "DEMU".

Motorová jednotka je železniční dopravní prostředek používaný v regionální i dálkové dopravě. Jednotka je složena z několika vozů (motorových, řídicích, vložených), které jsou navzájem pevně spojeny. V běžném provozu tak není možné jednotku rozdělit na jednotlivé vozy jako běžnou soupravu. Výhodou jednotek oproti soupravám motorových a přípojných vozů je průchodnost jednotek (pomocí krytých mezivozových přechodů) či větší kapacita.