Ett-p Rdjournal Â€ " a Hewlett-packard Journal Contents: April 1983 Volume 34 Â€¢ Number 4 Noise Figure Meter Sets Records for Accuracy, Repeatability, and Convenience, a New Microcomputer-controlled Laser Dimensional Measurement and Analysis System Dimensional Metrology Software Eases Calibration S
A New and Laser Dimensional Measurement and Analysis System, by Robert C. Quenelle and Lawrence J. Wuerz It's more compact, more powerful, and less expensive than previous systems. Dimensional Metrology Software Eases Calibration, by Lawrence J. Wuerz and Chris topher time An HP-85 Computer automates complex laser calibrations to save time and reduce errors. Automatic Compensation, by Deane A. Gardner Sensors help the laser measurement system compensate for atmospheric conditions and material temperature. Laser Optical Components for Machine Tool and Other Calibrations, by Richard R. Bald component Larry E. Truhe, and David C. Woodruff Each optical component is designed to mea sure a particular degree of freedom of a machine tool. Manufacturing the Laser Tube, by Richard H. Grote Custom-designed machines auto mate the process to control quality at every step. Mechanical Design Features of the Laser Head, by Charles R. Steinmetz Low manu facturing cost and ease of repair are designed in. Measurements that used to be tedious or inaccurate or both are now neither. Laboratory Notebook â€ " Mass Storage Unit Exerciser The problem was how to provide built-in diagnostics for a flexible disc drive that didn't come with them. In this Issue: In this surface, world of ours, there's no such thing as a straight edge, a flat surface, or parallel lines. Those who inhabit the world of precision machining are constantly reminded of these newest as designers demand tolerances just a little tighter than the newest and best Â» machine a can deliver. In this environment, it's essential to know just how imperfect a machine tool is. Many machine tools are computer controlled and can be programmed to compensate for errors if accurate calibration data is available. Because today's machine tools are very, very precise, it takes a super-precise measuring tool 22, Laser them. The subject of the articles on page 3 to 22, the HP 5528A Laser Measurement System, is such a tool. The LMS consists of a laser head, precision optical components, and a microcomputer-based measurement and display unit, optionally augmented with an HP-85 Computer. The cover photo shows it doing its job. The LMS is used periodically or as needed to check a machine's accuracy, to provide data for computer error compensation, to detect wear, and to diagnose problems. Back described as 1 970, HP's first laser measurement system was described in these pages as "a two-hundred-foot LMS with graduations every microinch." The …
Noise of a Self‐Sustaining Avalanche Discharge in Silicon: Studies at Microwave Frequencies
The studies of avalanche noise reported by Haitz are extended to frequencies up to and above the avalanche frequency ωa. It is found that the open‐circuit spectral voltage density is flat within ±5% from less than 100 Hz up to frequencies approaching ωa. Near ωa the open‐circuit spectral voltage density increases with frequency, goes through a maximum at ωa and then decreases rapidly. The spectral power density is similarly flat but fails to exhibit an expected maximum at ωa. For ω≫ωa the spectral power density decreases with ω−4. The experimental results are in good agreement with Hines' theory of avalanche noise for ω≪ωa and ω≫ωa. The discrepancies observed near ωa are thought to be caused by an oversimplification in Hines' theory which neglects internal diode losses. Compared with conventional noise sources such as temperature‐limited diodes or gas discharge tubes, avalanche diodes have several advantages: larger noise output, larger bandwidth, lower 1/f noise, low power consumption, small size, and lo...
Analysis of the stress wave effect during coal breakage by a high-pressure abrasive air jet
In view of the defects of borehole collapse, inhibition of gas desorption and migration of gas existing in hydraulic fracturing and other hydraulic permeability–increasing measures for soft coal seams with low-permeability technology is proposed for coal breakage by a high-pressure abrasive gas jet for relieving pressure and increasing permeability. The comparative analysis of gas jet flow field structure between convergent nozzle and Laval nozzle has been given by numerical simulation. For Laval nozzle, the expansion wave and compression wave alternate and move forward steadily in gas jet and vanish when potential core length reaches maximum. So, the Laval nozzle can form more stable flow filed structure of gas jet and avoid shock wave in gas jet. Furthermore, a high-speed camera is adopted to analyze the jet structure and verify the conclusion of numerical simulation. Based on thermodynamic theory, this article calculates and analyzes the critical local sound velocity and pressure generated from the stress wave during the process of coal breakage by the gas jet. Furthermore, experimental coal breakage by a high-pressure abrasive gas jet is carried out. The high-pressure abrasive gas jet impacts the coal body as a quasi-static load and a dynamic load and forms corrosion pits on the surface of the coal body. Penetrating cracks are formed within the coal in the pattern of the loaded stress wave which leads to coal breakage. The effects of porosity and permeability on the propagation of the stress wave in coal are analyzed by establishing the dispersion equation for the spread of the stress wave in coal. The results show that porosity has a significant effect on wave velocity and that the attenuation of the stress wave is intensified with an increase in porosity. Moreover, the stress wave attenuation is more obvious at high frequency. The effect of permeability on the wave velocity is not significant at low frequencies. In contrast, at high frequency and relatively low permeability, the wave velocity increases with the permeability, and the attenuation of the wave velocity initially increases and then decreases. When the permeability is greater than 10−11 m2, the wave velocity is not affected by the permeability. However, the stress wave is not attenuated.