Characteristics.

Common behaviors.

Common stuttering behaviors are observable signs of speech disfluencies, for example: repeating sounds, syllables, words or phrases, silent blocks and prolongation of sounds. These differ from the normal disfluencies found in all speakers

Variability.

The severity of a stutter is often not constant even for people who severely stutter. People who stutter commonly report dramatically increased fluency when talking in unison with

Feelings and attitudes.

Stuttering could have a significant negative cognitive and affective impact on the person who stutters. It has been described in terms of the analogy to an iceberg, with the immediately visible and audible symptoms of stuttering above the waterline and a broader set of symptoms such as negative emotions hidden below the surface. Feelings of embarrassment, shame, frustration, fear, anger, and guilt are frequent in people who stutter, and may actually increase tension

Fluency and disfluency.

Linguistic tasks can invoke speech disfluency. People who stutter may experience varying disfluency. Tasks that trigger disfluency usually require a controlled-language processing, which involves linguistic planning. In stuttering, it is seen that many individuals do not demonstrate disfluencies when it comes to tasks that allow for automatic processing without substantial planning.

Causes.

No single, exclusive cause of developmental stuttering is known. A variety of hypotheses and theories suggests multiple factors contributing to stuttering. Among these is the strong evidence that stuttering has a genetic basis. Children who have first-degree relatives who stutter are three times as likely to develop a stutter. However, twin and adoption studies suggest that genetic factors interact with environmental factors for stuttering to occur, and many people who stutter have no family history of the disorder. There is evidence that stuttering is more common in children who also have concurrent speech, language, learning or motor difficulties. Robert West, a pioneer of genetic studies in stuttering, has suggested that the presence of stuttering is connected to the fact that articulated speech is the last major acquisition in human evolution.  Another view is that a stutter or stammer is a complex tic. This view is held for the following reasons. It always arises from repetition of sounds or words. Young children like repetition and the more tense they are feeling, the more they like this outlet for their tension – an understandable and quite normal reaction. They are capable of repeating all types of behaviour. The more tension that is felt, the less one likes change. The more change, the greater can be the repetition. So, when a 3 year old finds he has a new baby brother or sister he may start repeating sounds. The repetitions can become conditioned and automatic and ensuing struggles against the repetitions result in prolongations and blocks in his speech. More boys stammer than girls, in the ratio of 3–4 boys : 1 girl. This is because the male Hypothalamic-Pituitary-Adrenal (HPA) Axis is more active. Whilst they are pumping out more cortisol than females under the same provocation, they can be tense

Mechanism.

Physiology.

Though neuroimaging studies have not yet found specific neural correlates, there is much evidence that the brains of adults who stutter differ from the brains of adults who do not stutter. Several neuroimaging studies have emerged to identify areas associated with stuttering. In general, during stuttering, cerebral activities change dramatically in comparison to silent rest or fluent speech between people who stutter and people who do not stutter. There is evidence that people who stutter activate motor programs before the articulatory or linguistic processing is initiated. Brain imaging studies have primarily been focused on adults. However, the neurological abnormalities found in adults does not determine whether childhood stuttering caused these abnormalities or whether the abnormalities cause stuttering.  Studies utilizing positron emission tomography (PET) have found during tasks that invoke disfluent speech, people who stutter show

Abnormal lateralization.

Much evidence from neuroimaging techniques has supported the theory that the right hemisphere of people who stutter interferes with left-hemisphere speech production.  Adults who stutter have anatomical differences in gyri within the perisylvian frontotemporal areas. A large amount of white matter is found in the right hemisphere of the brain, including the region of the superior temporal gyrus. This was discovered using voxel-based morphometry (VBM). On the other hand, lesser amounts of white matter are found in the left inferior arcuate fasciculus connecting the temporal and frontal areas in stuttering adults.  Results have shown that there is less coordination between the speech motor and planning regions in

Other anatomical differences.

The corpus callosum transfers information between the left and right cerebral hemispheres. The corpus callosum, rostrum, and the anterior mid-body sections are larger in adults who stutter as compared to normally fluent adults. This

Dopamine.

Recent studies have found that adults who stutter have elevated levels of the neurotransmitter dopamine, and have thus found dopamine antagonists that reduce stuttering (see anti-stuttering medication below). Overactivity of the midbrain has been found

Diagnosis.

Some characteristics of stuttered speech are not as easy for listeners to detect. As a result, diagnosing stuttering requires the skills of a certified speech-language pathologist (SLP). Diagnosis of stuttering employs information both from direct observation of the individual and information about the individual's background, through a case history. Information from both sources should consider things such as age, the various times it has occurred, and other impediments. The SLP may collect a case history on the individual through a detailed interview or conversation with the parents (if client is a child). They may also observe parent-child interactions and observe the speech patterns of the child's parents. The overall goal of assessment for the SLP will be (1) to determine whether a speech disfluency exists, and (2) assess if its severity warrants concern for further treatment.  During direct observation of the client, the SLP will observe various aspects of the individual's speech behaviors. In particular, the therapist might test for factors including the types of disfluencies present (using a test such as the Disfluency Type Index (DTI)), their frequency and duration (number of iterations, percentage of syllables stuttered (%SS)), and speaking rate (syllables per minute (SPM), words per minute (WPM)). They may also test for naturalness and fluency in speaking (naturalness rating scale (NAT), test of childhood stuttering (TOCS)) and physical concomitants during speech ("Riley’s Stuttering Severity Instrument Fourth Edition (SSI-4)"). They might also employ a test to evaluate the severity of the stuttering and predictions for its course. One such test includes the stuttering prediction instrument for young children (SPI), which analyzes the child's case history, part-word repetitions and prolongations, and stuttering frequency in order to determine the severity of the disfluency and its prognosis for chronicity for the future.  Stuttering is a multifaceted, complex disorder that can impact an individual's life in a variety of ways. Children and adults are monitored and evaluated for evidence of possible social, psychological or emotional signs of stress related to their disorder. Some common assessments of this type measure factors including: anxiety (Endler multidimensional anxiety scales (EMAS)), attitudes (personal report of communication apprehension (PRCA)), perceptions of self (stutterers’ self-rating of reactions to speech situations (SSRSS)), quality of life (overall assessment of the speaker's experience of stuttering (OASES)), behaviors (older adult self-report (OASR)), and mental health (composite international diagnostic interview (CIDI)).  The SLP will then attempt to combine the information garnered from the client's case study along with the information acquired from the assessments in order to make a final decision regarding the existence of a fluency disorder and determine the best course of treatment for the client.  Stuttering can also diagnosed per the DSM-5 diagnostic codes by clinical psychologists with adequate expertise. The most recent version of the DSM-5 describes this speech disorder as "Childhood-Onset Fluency Disorder (Stuttering)" for developmental stuttering, and "Adult-onset Fluency Disorder". However, the specific rationale for this change from the DSM-IV is ill-documented in the APA's published literature, and is felt by some to promote confusion between the very different terms "fluency" and "disfluency".

Treatment.

Before beginning treatment, an assessment is needed, as diagnosing stuttering requires the skills of a certified speech-language pathologist (SLP). While there is no complete cure for stuttering, several treatment options exist that help individuals to better control their speech. Many of the available treatments focus on learning strategies to minimize stuttering through speed reduction, breathing regulation, and gradual progression from single-syllable responses to longer words, and eventually more complex sentences. Furthermore, some stuttering therapies help to address the anxiety that is often caused by stuttering, and consequently worsens stuttering symptoms. This method of treatment is referred to as a comprehensive approach, in which the main emphasis of treatment is directed toward improving the speaker's attitudes toward communication and minimizing the negative impact stuttering can have on the speaker's life. Treatment from a qualified S-LP can benefit people who stutter of any age.  Speech language pathologists teach people who stutter to control and monitor the rate at which they speak. In addition, people may learn to start saying words in a slightly slower and less physically tense manner. They may also learn to control or monitor their breathing. When learning to control speech rate, people often begin by practising smooth, fluent speech at rates that are much slower than typical speech, using short phrases and sentences. Over time, people learn to produce smooth speech at faster rates, in longer sentences, and in more challenging situations until speech sounds both fluent and natural. When treating stuttering in children, some researchers recommend that an evaluation be conducted every three months in order to determine whether or not the selected treatment option is working effectively. "Follow-up" or "maintenance" sessions are often necessary after completion of formal intervention to prevent relapse.

Fluency shaping therapy.

Fluency shaping therapy, also known as "speak more fluently", "prolonged speech", or "connected speech", trains people who stutter to speak less disfluently by controlling their breathing, phonation, and articulation (lips, jaw, and tongue). It is based on operant conditioning techniques.  People who stutter are trained to reduce their speaking rate by stretching vowels and consonants, and using other disfluency-reducing techniques such as continuous airflow and

Modification therapy.

The goal of stuttering modification therapy is not to eliminate stuttering but to modify it so that stuttering is easier and less effortful. The rationale is that since fear and anxiety

Electronic fluency device.

Altered auditory feedback, so that people who stutter hear their voice differently, has been used for over 50 years in the treatment of stuttering. Altered auditory feedback effect can be produced by speaking in chorus with another person, by blocking out the person who stutters' voice while talking (masking), by delaying slightly

Mobile applications.

There are specialized mobile applications and PC programs for stutter treatment. The goal pursued by the applications of this kind is speech cycle restoration – I say –>I hear –>I build a phrase –>I say

Medications.

Although no medication is FDA approved for stuttering, several studies have shown certain medications to have beneficial effects on reducing the severity of stuttering symptoms. Although different classes of medications have been investigated, those with dopamine blocking activity have been shown in numerous trials to have positive effects on stuttering. These medications are FDA approved in the United States and hold similar approval in most countries for other conditions and their safety profiles are well established in these disorders.  The best studied medication in stuttering is olanzapine whose effectiveness has been established in replicated trials. Olanzapine acts as a dopamine antagonist to D2 receptors in the mesolimbic pathway, and works similarly on serotonin 5HT2A receptors in the frontal cortex. At doses between 2.5–5 mg, olanzapine has been shown to be more effective than placebo at reducing stuttering symptoms, and may serve as a first-line pharmacological treatment for stuttering based on the preponderance of its efficacy data. However, other medications are generally better tolerated

Support.

With existing behavioral and prosthetic treatments providing limited relief and pharmacologic treatments in need of FDA approval for widespread use, support groups and the self-help movement continue to gain popularity and support from professionals and people who stutter. Self-help groups provide people who stutter a shared forum within which they can access

Psychological approach.

Cognitive behavior therapy has been used to treat stuttering. Also

Diaphragmatic breathing.

Several treatment initiatives, for example the McGuire programme, and the Starfish

Prognosis.

Among preschoolers with stuttering, the prognosis for recovery is good. Based on research, about 65% to 87.5% of preschoolers who stutter recover spontaneously by 7 years of age or within the first 2 years of stuttering, and about 74% recover by their early teens. In particular, girls seem to recover well. For others, early intervention is effective in helping the child overcome disfluency.  Once stuttering has become established, and the child has developed secondary behaviors, the prognosis is more guarded, and only 18% of children who stutter after five years recover spontaneously. Stuttering that persists

Epidemiology.

The lifetime prevalence, or the proportion of individuals expected to stutter at one time in their lives, is about 5%, and overall males are affected two to five times more often than females. However, there is not much information known about the underlying cause for such a skewed sex ratio. Most stuttering begins in early childhood, and studies suggest that 2.5% of children under the age of 5 stutter. As seen in children who have just begun stuttering, there is an equivalent number of boys and girls who stutter. Still, the sex ratio appears to widen as children grow: among preschoolers, boys who stutter outnumber girls who stutter by about a two to one ratio, or less. This ratio widens to three to one during first grade, and five to one during fifth grade, as girls have higher recovery rates. Due to high (approximately 65–75%) rates of early recovery, the overall prevalence of stuttering is generally considered to be approximately 1%.  Cross-cultural studies of stuttering prevalence were very active in early and mid-20th century, particularly under the influence of the works of Wendell Johnson, who claimed that the onset of stuttering was connected to the cultural expectations and the pressure put on young children by anxious parents. Johnson claimed there were cultures where stuttering, and even the word "stutterer", were

History.

Because of the unusual-sounding speech that is produced and the behaviors and attitudes that accompany a stutter, it has long been a subject of scientific interest and speculation as well as discrimination and ridicule. People who stutter can be traced back centuries to the likes of Demosthenes, who tried to control his disfluency by speaking with pebbles in his mouth. The Talmud interprets Bible passages to indicate Moses was also a person who stuttered, and that placing a burning coal in his mouth had caused him to be "slow and hesitant of speech" (Exodus 4, v.10).  Galen's humoral theories were influential in Europe in the Middle Ages for centuries afterward. In this theory, stuttering was attributed to imbalances of the four bodily humors—yellow bile, blood, black bile, and phlegm. Hieronymus Mercurialis, writing in the sixteenth century, proposed methods to redress the imbalance including changes in diet, reduced libido (in men only), and purging. Believing that fear aggravated stuttering, he suggested techniques to overcome this. Humoral manipulation continued to be a dominant treatment for stuttering until the eighteenth century. Partly due to a perceived lack of intelligence because of his stutter, the man who became the Roman emperor Claudius was initially shunned from the public eye and excluded from public office.  In and around eighteenth and nineteenth century Europe, surgical interventions for stuttering were recommended, including cutting the tongue with scissors, removing a triangular wedge from the posterior tongue, and cutting nerves, or neck and lip muscles. Others recommended shortening the uvula or removing the tonsils. All were abandoned due to the high danger of bleeding to death and their failure to stop stuttering. Less drastically, Jean Marc Gaspard Itard placed a small forked golden plate under the tongue in order to support "weak" muscles. Italian pathologist Giovanni Morgagni attributed stuttering to deviations in the hyoid bone, a conclusion he came to via autopsy. Blessed Notker of St. Gall (c.

Society and culture.

Bilingual stuttering.

Identification.

Bilingualism is the ability to speak two languages. Many bilingual people have been exposed to more than one language since birth and throughout childhood. Since language and culture are relatively fluid factors in a person's understanding and production of language, bilingualism may

Research.

Much research is being conducted to look at the prevalence of stuttering in bilingual populations and the differences between languages. For instance, one study concluded that bilingual children who spoke English and another language had an increased risk of stuttering and a lower chance of recovery from stuttering than monolingual speakers and speakers who spoke solely a language other than English. Another study, though methodologically weak, showed relatively indistinguishable percentages of monolingual and bilingual stutterers. Due to so much conflicting data, the relationship between bilingualism and stuttering has been called enigmatic, which can demonstrate the intricacies of the topic and encourages more research to be conducted in order to sway the belief of impact the relationship between bilingualism and stuttering has.

Stuttering in popular culture.

Jazz and Eurodance musician Scatman John wrote the song "Scatman (Ski Ba Bop Ba Dop Bop)" to help children

Stuttering, also known as stammering and dysphemia, is a speech disorder in which the flow of speech is disrupted by involuntary repetitions and prolongations of sounds, syllables, words or phrases as well as involuntary silent pauses or blocks in which the person who stutters is unable to produce sounds. The term "stuttering" is most commonly associated with involuntary sound repetition, but it also encompasses the abnormal hesitation or pausing before speech, referred to by people who stutter as "blocks", and the prolongation of certain sounds, usually vowels or semivowels. According to Watkins et al., stuttering is a disorder of "selection, initiation, and execution of motor sequences necessary for fluent speech production". For many people who stutter, repetition is the main problem. The term "stuttering" covers a wide range of severity, encompassing barely perceptible impediments that are largely cosmetic to severe symptoms that effectively prevent oral communication. In the world, approximately four times as many men as women stutter, encompassing 70 million people worldwide, or about 1% of the world's population.

Koktavost (též zejména odborně balbutismus, balbuties) je řečová porucha, při které je plynulost řeči neúmyslně přerušována opakováním jednotlivých slabik či částí slov nebo jejich nechtěným prodlužováním. Řeč je v některých případech proložena neúmyslnými pauzami, kdy koktavý člověk není schopen vydat žádný zvuk (tzv. řečové bloky).Lidé, kteří koktají, vědí, co chtějí říct. Mohli by to říct třeba stokrát, ba tisíckrát, kdyby nekoktali. Přesto navzdory všemu svému úsilí nejsou schopni plynule a bez námahy promluvit. Všeobecně vžitá představa, že koktavost se vyznačuje pouze rychlým opakováním několika slabik, není tedy pravdivá. Lidé trpící touto poruchou bývají označováni jako balbutici. Věda, která se koktavostí zabývá se nazývá balbutologie.


Background.

In a traditional solid-state semiconductor such as silicon, a solar cell is made from two doped crystals, one an n-type semiconductor, which has extra free electrons, and the other a p-type semiconductor, which is lacking free electrons, referred to as "holes." When initially placed in contact with each other, some of the electrons in the n-type portion will flow into the p-type to "fill in" the missing electrons. Eventually enough will flow across the boundary to equalize the Fermi levels of the two materials. The result is a region at the interface, the p-n junction, where charge carriers are depleted on each side of the interface. In silicon, this transfer of electrons produces a potential barrier of about 0.6 V to 0.7 V.  When the material is placed in the sun, photons from the sunlight can be absorbed in the p-type side of the semiconductor, causing electrons in the valence band to be promoted in energy to the conduction band. This process is known as photoexcitation. As the name implies, electrons in the conduction band are free to move about the semiconductor. When a load is placed across the cell as a whole, these electrons will flow from the p-type side into the n-type side, lose energy while moving through the external circuit, and then go back into the p-type material where they can re-combine with the valence-band holes they left behind. In this way, sunlight creates an electric current.

The limit.

The Shockley–Queisser limit is calculated by examining the amount of electrical energy that is extracted per photon of incoming sunlight. There are several considerations:

Blackbody radiation.

Any material, that is not at absolute zero (0 Kelvin), emits electromagnetic radiation through the black-body radiation effect. In a cell at room temperature, this represents approximately 7% of all the energy falling on the cell.  Any energy lost in a cell is turned into heat, so any inefficiency in the cell increases the cell temperature when it is placed in sunlight. As the temperature of the cell increases, the outgoing radiation and heat loss through conduction and convection also increase, until an equilibrium is reached. In practice, this equilibrium is normally reached at temperatures as high as 360 Kelvin, and consequently, cells normally operate at lower efficiencies than their room-temperature rating. Module datasheets normally list this temperature dependency as (NOCT - Nominal Operating Cell Temperature).  For a "blackbody" at normal temperatures, a very small part of this radiation (the number per unit time and per unit area given by, "c" for "cell") is photons having energy greater than the band gap (wavelength less than about 1.1 microns for silicon), and part of these photons (Shockley and Queisser use the factor "t") are generated by recombination of electrons and holes, which decreases the amount of current that could be generated otherwise. This is a very small effect, but Shockley and Queisser assume that the total rate of recombination (see below) when the voltage across the cell is zero (short circuit or no light) is proportional to the blackbody radiation. This rate of recombination plays a negative role in the efficiency. Shockley and Queisser calculate to be 1700 photons per second per square centimetre for silicon at 300K.

Recombination.

Absorption of a photon creates an electron-hole pair, which could potentially contribute to the current. However, the reverse process must also be possible, according to the principle of detailed balance: an electron and a hole can meet and recombine, emitting a photon. This process reduces the efficiency of the cell. Other recombination processes may also exist (see "Other considerations" below), but this one is absolutely required.  In the Shockley–Queisser model, the recombination rate depends on the voltage across the cell but is the same whether or not there is light falling on the cell. A factor "f" gives the ratio of recombination that produces radiation to total recombination, so the rate of recombination per unit area when "V" = 0 is "2tQ"/"f" and thus depends on "Q", the flux of blackbody photons above the band-gap energy. The factor of 2 was included on the assumption that radiation emitted by the cell goes in both directions. (This is actually debatable if a reflective surface is used on the shady side.) When the voltage is non-zero, the concentrations of charge carriers (electrons and holes) change (see Shockley diode equation), and according to the authors the rate of recombination changes by a factor of exp("V"/"V"), where "V" is the voltage equivalent of the temperature of the cell, or "thermal voltage", namely  ("q" being the charge of an electron). Thus the rate of recombination, in this model, is proportional to exp("V"/"V") times the blackbody radiation above the band-gap energy:  (This is actually an approximation, correct so long as the cell is thick enough to act as a black body, to the more accurate expression  The difference in maximum theoretical efficiency however is negligibly small, except for tiny bandgaps below 200meV.)  The rate of "generation" of electron-hole pairs "not" due to incoming sunlight stays the same, so recombination minus spontaneous generation is  formula_4  where formula_5  The rate of generation of electron-hole pairs due to sunlight is  where formula_7 is the number of photons above the band-gap energy falling on the cell per unit area, and "t" is the fraction of these that generate an electron-hole pair. This rate of generation is called "I" because it is the "short circuit" current (per unit area). When there is a load, then "V" will not be zero and we have a current equal to the rate of generation of pairs due to the sunlight minus the difference between recombination and spontaneous generation:  The open-circuit voltage is therefore given (assuming "f" does not depend on voltage) by  The product of the short-circuit current "I" and the open-circuit voltage "V" Shockley and Queisser call the "nominal power". It is not actually possible to get this amount of power out of the cell, but we can get close (see "Impedance matching" below).  The ratio of the open-circuit voltage to the band-gap voltage Shockley and Queisser call "V". Under open-circuit conditions, we have  Asymptotically, this gives  or  where is the voltage equivalent of the temperature of the sun. As the ratio goes to zero, the open-circuit voltage goes to the band-gap voltage, and as it goes to one, the open-circuit voltage goes to zero. This is why the efficiency falls if the cell heats up. In fact this expression represents the thermodynamic upper limit of the amount of work that can be obtained from a heat source at the temperature of the sun and a heat sink at the temperature of the cell.

Spectrum losses.

Since the act of moving an electron from the valence band to the conduction band requires energy, only photons with more than that amount of energy will produce an electron-hole pair. In silicon the conduction band is about 1.1 eV away from the valence band, this corresponds to infrared light with a wavelength of about 1.1 microns. In other words, photons of red, yellow and blue light and some near-infrared will contribute to power production, whereas radio waves, microwaves, and most infrared photons will not. This places an immediate limit on the amount of energy that can be extracted from the sun. Of the 1,000 W/m2 in AM1.5 sunlight, about 19% of that has less than 1.1 eV of energy, and will not produce power in a silicon cell.  Another important contributor to losses is that any energy above and beyond the bandgap energy is lost. While blue light has roughly twice the energy of red light, that energy is not captured by devices with a single p-n junction. The electron is ejected with higher energy when struck by a blue photon, but it loses this extra energy as it travels toward the p-n junction (the energy is converted into heat). This accounts for about 33% of the incident sunlight, meaning that, for silicon, from spectrum losses alone there is a theoretical conversion efficiency limit of about 48%, ignoring all other factors.  There is a trade-off in the selection of a bandgap. If the band gap is large, not as many photons create pairs, whereas if the band gap is small, the electron-hole pairs do not contain as much energy.  Shockley and Queisser call the efficiency factor associated with spectrum losses, for "ultimate efficiency function". Shockley and Queisser calculated that the best band gap for sunlight happens to be 1.1 eV, the value for silicon, and gives a of 44%. They used blackbody radiation of 6000K for sunlight, and found that the optimum band gap would then have an energy of 2.2 "kT". (At that value, 22% of the blackbody radiation energy would be below the band gap.) Using a more accurate spectrum may give a slightly different optimum. A blackbody at 6000 K puts out 7348 W per square centimetre, so a value for of 44% and a value of photons per joule (corresponding to a band gap of 1.09 V, the value used by Shockley and Queisser) gives equal to photons per second per square centimetre.

Impedance matching.

If the resistance of the load is too high, the current will be very low, while if the load resistance is too low, the voltage drop across it will be very low. There is an optimal load resistance that will draw the most power from the solar cell at a given illumination level. Shockley and Queisser call the ratio of power extracted to the impedance matching factor,. (It is also called the fill factor.) The optimum depends on the shape of the versus curve. For very low illumination, the curve is more or less a diagonal line, and will be 1/4. But for high illumination, approaches 1. Shockley and Queisser give a graph showing as a function of the ratio of the open-circuit voltage to the thermal voltage. According to the authors, this ratio is well approximated by, where is the combination of factors, in which is the solid angle of the sun divided by π. The maximum value of without light concentration (with reflectors for example) is just, or, according to the authors. Using the above mentioned values of and, this gives a ratio of open-circuit voltage to thermal voltage of 32.4 ( equal to 77% of the band gap). The authors derive the equation  which can be solved to find, the ratio of optimal voltage to thermal voltage. For a of 32.4, we find equal to 29.0. One can then use the formula  to find the impedance matching factor. For a of 32.4, this comes to 86.5%.

All together.

Considering the spectrum losses alone, a solar cell has a peak theoretical efficiency of 48% (or 44% according to Shockley and Queisser – their "ultimate efficiency factor"). Thus the spectrum losses represent the vast majority of lost power. Including the effects of recombination and the "I" versus "V" curve, the efficiency is described by the following equation:  with  where,, and are respectively the ultimate efficiency factor, the ratio of open-circuit voltage to band-gap voltage, and the impedance matching factor (all discussed above). Letting be 1, and using the values mentioned above of 44%, 77%, and 86.5% for the three factors gives about 29% overall efficiency. Shockley and Queisser say 30% in their abstract, but do not give a detailed calculation. A more recent reference gives, for a single-junction cell, a theoretical peak performance of about 33.7%, or about 337 W/m2 in AM1.5.  When the amount of sunlight is increased using reflectors or lenses, the factor (and therefore ) will be higher. This raises both and. Shockley and Queisser include a graph showing the overall efficiency as a function of band gap for various values of. For a value of 1, the graph shows a maximum efficiency of just over 40%, getting close to the ultimate efficiency (by their calculation) of 44%.

Other considerations.

Shockley and Queisser's work considered the most basic physics only; there are a number of other factors that further reduce the theoretical power.

Limited mobility.

When an electron is ejected through photoexcitation, the atom it was formerly bound to is left with a net positive charge. Under normal conditions, the atom will pull off an electron from a surrounding atom in order to neutralize itself. That atom will then attempt to remove an electron from another atom, and so forth, producing an ionization chain reaction that moves through the cell. Since these can be viewed as the motion of a positive charge, it is useful to refer to them as "holes", a sort of virtual positive electron.  Like electrons, holes move around the material, and will be attracted towards a source of electrons. Normally these are provided through an electrode on the back surface of the cell. Meanwhile, the conduction-band electrons are moving forward towards the electrodes on the front surface. For a variety of reasons, holes in silicon move much more slowly than electrons. This means that during the finite time while the electron is moving forward towards the p-n junction, it may meet a slowly moving hole left behind by a previous photoexcitation. When this occurs, the electron recombines at that atom, and the energy is lost (normally through the emission of a photon of that energy, but there are a variety of possible processes).  Recombination places an upper limit on the "rate" of production; past a certain rate there are so many holes in motion that new electrons will never make it to the p-n junction. In silicon this reduces the theoretical performance under normal operating conditions by another 10% over and above the thermal losses noted above. Materials with higher electron (or hole) mobility can improve on silicon's performance; gallium arsenide (GaAs) cells gain about 5% in real-world examples due to this effect alone. In brighter light, when it is concentrated by mirrors or lenses for example, this effect is magnified. Normal silicon cells quickly saturate, while GaAs continue to improve at concentrations as high as 1500 times.

Non-radiative recombination.

Recombination between electrons and holes is detrimental in a solar cell, so designers try to minimize it. However, radiative recombination—when an electron and hole recombine to create a photon that exits the cell into the air—is inevitable, because it is the time-reversed process of light absorption. Therefore, the Shockley–Queisser calculation takes radiative recombination into account; but it assumes (optimistically) that there is no other source of recombination. More realistic limits, which are lower than the Shockley–Queisser limit, can be calculated by taking into account other causes of recombination. These include recombination at defects and grain boundaries.  In crystalline silicon, even if there are no crystalline defects, there is still Auger recombination, which occurs much more often than radiative recombination. By taking this into account, the theoretical efficiency of crystalline silicon solar cells was calculated to be 29.4%.

Exceeding the limit.

It is important to note that the analysis of Shockley and Queisser was based on the following assumptions:  None of these assumptions is necessarily true, and a number of different approaches have been used to significantly surpass the basic limit.

Tandem cells.

The most widely explored path to higher efficiency solar cells has been multijunction photovoltaic cells, also known as "tandem cells". These cells use multiple p-n junctions, each one tuned to a particular frequency of the spectrum. This reduces the problem discussed above, that a material with a single given bandgap cannot absorb sunlight below the bandgap, and cannot take full advantage of sunlight far above the bandgap. In the most common design, a high-bandgap solar cell sits on top, absorbing high-energy, shorter-wavelength light, and transmitting the rest. Beneath it is a lower-bandgap solar cell which absorbs some of the lower-energy, longer-wavelength light. There may be yet another cell beneath that one, with as many as four layers in total.  The calculation of the fundamental efficiency limits of these multijunction cells works in a fashion similar to those for single-junction cells, with the caveat that some of the light will be converted to other frequencies and re-emitted within the structure. Using methods similar to the original Shockley–Queisser analysis with these considerations in mind produces similar results; a two-layer cell can reach 42% efficiency, three-layer cells 49%, and a theoretical infinity-layer cell 68% in non-concentrated sunlight.  The majority of tandem cells that have been produced to date use three layers, tuned to blue (on top), yellow (middle) and red (bottom). These cells require the use of semiconductors that can be tuned to specific frequencies, which has led to most of them being made of gallium arsenide (GaAs) compounds, often germanium for red, GaAs for yellow, and GaInP for blue. They are very expensive to produce, using techniques similar to microprocessor construction but with "chip" sizes on the scale of several centimeters. In cases where outright performance is the only consideration, these cells have become common; they are widely used in satellite applications for instance, where the power-to-weight ratio overwhelms practically every other consideration. They also can be used in concentrated photovoltaic applications (see below), where a relatively small solar cell can serve a large area.  Tandem cells are not restricted to high-performance applications; they are also used to make moderate-efficiency photovoltaics out of cheap but low-efficiency materials. One example is amorphous silicon solar cells, where triple-junction tandem cells are commercially available from Uni-Solar and other companies.

Light concentration.

Sunlight can be concentrated with lenses or mirrors to much higher intensity. The sunlight intensity is a parameter in the Shockley–Queisser calculation, and with more concentration, the theoretical efficiency limit increases somewhat. If, however, the intense light heats up the cell, which often occurs in practice, the theoretical efficiency limit may go down all things considered.  In practice, the choice of whether or not to use light concentration is based primarily on other factors besides the small change in solar cell efficiency. These factors include the relative cost per area of solar cells versus focusing optics like lenses or mirrors, the cost of sunlight-tracking systems, the proportion of light successfully focused onto the solar cell, and so on.  A wide variety of optical systems can be used to concentrate sunlight, including ordinary lenses and curved mirrors, fresnel lenses, arrays of small flat mirrors, and luminescent solar concentrators. Another proposal suggests spreading out an array of microscopic solar cells on a surface, and focusing light onto them via microlens arrays, while yet another proposal suggests designing a semiconductor nanowire array in such a way that light is concentrated in the nanowires.

Intermediate band photovoltaics.

There has been some work on producing mid-energy states within single crystal structures. These cells would combine some of the advantages of the multi-junction cell with the simplicity of existing silicon designs. A detailed limit calculation for these cells with infinite bands suggests a maximum efficiency of 77.2% To date, no commercial cell using this technique has been produced.

Photon upconversion.

As discussed above, photons with energy below the bandgap are wasted in ordinary single-junction solar cells. One way to reduce this waste is to use photon upconversion, i.e. incorporating into the module a molecule or material that can absorb two or more below-bandgap photons and then emit one above-bandgap photon. Another possibility is to use two-photon absorption, but this can only work at extremely high light concentration.

Thermal photon upconversion.

Thermal upconversion is based on the absorption of photons with low energies in the upconverter, which heats up and re-emits photons with higher energies. The upconversion efficiency can be improved by controlling the optical density of states of the absorber and also by tuning the angularly-selective emission characteristics. For example, a planar thermal upconverting platform can have a front surface that absorbs low-energy photons incident within a narrow angular range, and a back surface that efficiently emits only high-energy photons. A hybrid thermophotovoltaic platform exploiting thermal upconversion was theoretically predicted to demonstrate maximum conversion efficiency of 73% under illumination by non-concentrated sunlight. A detailed analysis of non-ideal hybrid platforms that allows for up to 15% of absorption/re-emission losses yielded limiting efficiency value of 45% for Si PV cells.

Hot electron capture.

One of the main loss mechanisms is due to the loss of excess carrier energy above the bandgap. It should be no surprise that there has been a considerable amount of research into ways to capture the energy of the carriers before they can lose it in the crystal structure. One system under investigation for this is quantum dots.

Multiple exciton generation.

A related concept is to use semiconductors that generate more than one excited electron per absorbed photon, instead of a single electron at the band edge. Quantum dots have been extensively investigated for this effect, and they have been shown to work for solar-relevant wavelengths in prototype solar cells.  Another, more straightforward way to utilise multiple exciton generation is a process called singlet fission (or singlet exciton fission) by which a singlet exciton is converted into two triplet excitons of lower energy. This allows for higher theoretical efficiencies when coupled to a low bandgap semiconductor and quantum efficiencies exceeding 100% have been reported.  Also in materials where the (excited) electrons interact strongly with the remaining electrons such as Mott insulators multiple excitons can be generated.

Fluorescent downconversion/downshifting.

Another possibility for increased efficiency is to convert the frequency of light down towards the bandgap energy with a fluorescent material. In particular, to exceed the Shockley–Queisser limit, it is necessary for the fluorescent material to convert a single high-energy photon into several lower-energy ones (quantum efficiency > 1). For example, one photon with more than double the bandgap energy can become two photons above the bandgap energy. In practice, however, this conversion process tends to be relatively inefficient. If a very efficient system were found, such a material could be painted on the front surface of an otherwise standard cell, boosting its efficiency for little cost. In contrast, considerable progress has been made in the exploration of fluorescent downshifting, which converts high-energy light (e. g., UV light) to low-energy light (e. g., red light) with a quantum efficiency smaller than 1. The cell may be more sensitive to these lower-energy photons. Dyes, rare-earth phosphors and quantum dots are actively investigated for fluorescent downshifting. For example, silicon quantum dots enabled downshifting has led to the efficiency enhancement of the state-of-the-art silicon solar cells.

Thermophotovoltaic downconversion.

Thermophotovoltaic cells are similar to phosphorescent systems, but use a plate to act as the downconvertor. Solar energy falling on the plate, typically black-painted metal, is re-emitted as lower-energy IR, which can then be captured in an IR cell. This relies on a practical IR cell being available, but the theoretical conversion efficiency can be calculated. For a converter with a bandgap of 0.92 eV, efficiency is limited to 54% with a single-junction cell, and 85% for concentrated light shining on ideal components with no optical losses and only radiative recombination.

In physics, the Shockley–Queisser limit (also known as the detailed balance limit, Shockley Queisser Efficiency Limit or SQ Limit, or in physical terms the radiative efficiency limit) refers to the maximum theoretical efficiency of a solar cell using a single p-n junction to collect power from the cell where the only loss mechanism is radiative recombination in the solar cell. It was first calculated by William Shockley and Hans-Joachim Queisser at Shockley Semiconductor in 1961, giving a maximum efficiency of 30% at 1.1 eV. This first calculation used the 6000K black-body spectrum as an approximation to the solar spectrum. Subsequent calculations have used measured global solar spectra (AM1.5G) and included a back surface mirror which increases the maximum efficiency to 33.7% for a solar cell with a bandgap of 1.34 eV. The limit is one of the most fundamental to solar energy production with photovoltaic cells, and is considered to be one of the most important contributions in the field.

Ve fyzice určuje Shockleyův–Queisserův limit teoretickou maximální účinnost přeměny slunečního záření na elektřinu pro fotovoltaický článek s jedním p-n přechodem. Byl vypočítán v roce 1961 Williamem Shockleyem a Hansem Queisserem ze společnosti Shockley Semiconductor. Jedná se o jeden z nejdůležitějších limitujících faktorů při návrhu fotovoltaických článků.


Biography.

Early years.

Brébeuf was born 25 March 1593 in Condé-sur-Vire, Normandy, France. (He was the uncle of poet Georges de Brébeuf). He joined the Society of Jesus in 1617 at the age of 24, spending the next two years under the direction of Lancelot Marin. Between 1619 and 1621, he was a teacher at the college of Rouen. Brébeuf was nearly expelled from the Society when he contracted tuberculosis in 1620—a severe and usually fatal illness that prevented his studying and teaching for the traditional periods.  His record as a student was not particularly distinguished, but Brébeuf was already beginning to show an aptitude for languages. Later in New France, he would teach Native American languages to missionaries and French traders. Brébeuf was ordained as a priest at Pontoise Cathedral in February 1622.

Missionary.

After three years as Steward at the College of Rouen, Brébeuf was chosen by the Provincial of France, Father Pierre Coton, to embark on the missions to New France.  In June 1625, Brébeuf arrived in Québec with Fathers Charles Lalemant and Énemond Massé, together with the lay brothers Francois Charton and Gilbert Burel. He worked at the Sainte-Marie among the Hurons. For about five months Brébeuf lived with a tribe of Montagnais, who spoke an Algonquian language. He was later assigned in 1626 to the Huron with Father Anne Nouée. From then on Brébeuf worked mostly as a missionary to the Huron, who spoke an Iroquoian language. Brébeuf briefly took up residence with the Bear Tribe at Toanché, but met with no success in trying to convert them to Catholicism. He was summoned to Québec because of the danger to which the entire colony was then exposed by the English. He reached Québec on 17 July 1628 after an absence of two years. On 19 July 1629, Samuel de Champlain surrendered, and the missionaries returned to France.  In Rouen, Brébeuf served as a preacher and confessor, taking his final Jesuit vows in 1630. Between 1631 and 1633, Brébeuf worked at the College of Eu, Seine-Maritime in northern France as a steward, minister and confessor. He returned to New France in 1633, where he lived and worked for the rest of his life.  Along with Antoine Daniel and Ambroise Davost, Brébeuf chose "Ihonatiria" (Saint-Joseph I) as the centre for missionary activity with the Huron. At the time, the Huron suffered epidemics of new Eurasian diseases contracted from the Europeans. Their death rates were high, as they had no immunity to the diseases long endemic in Europe. They, with our hindsight rightly, blamed the Europeans for the deaths, with none of the parties understanding the causes.  Called "Échon" by the Hurons, Brébeuf was personally involved with teaching. His lengthy conversations with Huron friends left him with a good knowledge of their culture and spirituality. He learned their language and taught it to other missionaries and colonists. Fellow Jesuits such as Paul Ragueneau describe his ease and adaptability to the Huron way of life.  His efforts to develop a complete ethnographic record of the Huron has been described as "the longest and most ambitious piece of ethnographic description in all "The Jesuit Relations"". Brébeuf tried to find parallels between the Huron religion and Christianity, so as to facilitate conversion of the Huron to the European religion. Brébeuf was known by the Huron for his apparent shamanistic skills, especially in rainmaking. Despite his efforts to learn their ways, he considered Huron spiritual beliefs to be undeveloped and "foolish delusions"; he was determined to convert them to Christianity. Brébeuf did not enjoy universal popularity with the Huron, as many believed he was a sorcerer. By 1640, nearly half the Huron had died of smallpox and the losses disrupted their society. Many children and elders died. With their loved ones dying before their eyes, many Huron began to listen to the words of Jesuit missionaries who, unaffected by the disease, appeared to be men of great power.  Brébeuf's progress as a missionary in achieving conversions was slow. Not until 1635 did some Huron agree to be baptized as Christians. He claimed to have made 14 converts as of 1635 and, by the next year, he claimed 86. He wrote a detailed account in 1636 of The Huron Feast of the Dead, a mass reburial of remains of loved ones after a community moved the location of its village. It was accompanied by elaborate ritual and gift-giving. In the 1940s, an archeological excavation was made at the site Brébeuf had described, confirming many of his observations.  In 1638, Brébeuf turned over direction of the mission at Saint-Joseph I to Jérôme Lalemant; he was called to become Superior at his newly founded Saint-Joseph II. In 1640, after an unsuccessful mission into Neutral Nation territory, Brébeuf broke his collarbone. He was sent to Québec to recover, and worked there as a mission procurator. He taught the Huron, acting as confessor and advisor to the Ursulines and religious Hospitallers. On Sundays and feast days, he preached to French colonists.

Linguistic work.

The educational rigor of the Jesuit seminaries prepared missionaries to acquire native languages. But, as they had learned the classical and Romance languages, they likely had difficulty with the very different conventions of the New World indigenous languages. Brébeuf's study of the languages was also shaped by his religious training. Current Catholic theology tried to reconcile knowledge of world languages with accounts in the Bible of the tower of Babel, as this was the basis of European history. This influence can be seen in his discussion of language in his accounts collected in "The Jesuit Relations."  Jean de Brébeuf's remarkable facility with language was one of the reasons he was chosen for the Huron mission in 1626. He is distinguished for his commitment to learning the Huron (Wyandot) language. People with a strong positive attitude towards the language often learn the language much more easily. Brébeuf was widely acknowledged to have best mastered the Native oratory style, which used metaphor, circumlocution and repetition. Learning the language was still onerous, and he wrote to warn other missionaries of the difficulties.  To explain the low number of converts, Brébeuf noted that missionaries first had to master the Huron language. His commitment to this work demonstrates he understood that mutual intelligibility was vital for communicating complex and abstract religious ideas. He believed learning native languages was imperative for the Jesuit missions, but noted that it was so difficult a task that it consumed most of the priest's time. Brébeuf felt his primary goal in his early years in New France was to learn the language.  With increasing proficiency in the Wyandot language, Brébeuf became optimistic about advancing his missionary goals. By understanding Huron religious beliefs and communicating Christian fundamentals, he could secure converts to Christianity. He realized the people would not give up all their traditional beliefs.  Brébeuf worked tirelessly to record his findings for the benefit of other missionaries. He built on the work of Recollects priests but significantly advanced the study, particularly in his representations of sounds. He discovered and reported the feature of compound words in Huron, which may have been his major linguistic contribution. This breakthrough had enormous consequences for further study, becoming the foundation for all subsequent Jesuit linguistic work.  He translated Ledesma's catechism from French into Huron, and arranged to have it printed. It was the first printed text in that language (with French orthography). He also compiled a dictionary of Huron words, emphasizing translation of religious phrases such as from prayers and the Bible.  Brébeuf is credited with composing the "Huron Carol", Canada's oldest Christmas song, written around 1642. He wrote the lyrics in the native language of the Huron/Wendat people. The song's melody is based on a traditional French folk song, "Une Jeune Pucelle" (A Young Maid).

Death.

Brébeuf was killed at St. Ignace in Huronia on 16 March 1649. He had been taken captive with Gabriel Lalemant when the Iroquois destroyed the Huron mission village at Saint-Louis. The Iroquois took the priests to the occupied village of Taenhatenteron (also known as St. Ignace), where they subjected the missionaries and native converts to ritual torture before killing them.  Three priests had been killed in Mohawk country at Ossernenon in 1642 and 1646. Antoine Daniel had been killed in a similar Iroquois raid in 1648. Charles Garnier was killed by Iroquois in December 1649 in a Petun (Tobacco People) village, and Noel Chabanel was also martyred that year in the conflict between the Mohawk and other tribes. The Jesuits considered the priests' martyrdom as proof that the mission to the Native Americans was blessed by God and would be successful.  Throughout the torture, Brébeuf was reported to have been more concerned for the fate of the other Jesuits and of the captive Native converts than for himself. As part of the ritual, the Iroquois drank his blood and ate his heart, as they wanted to absorb Brébeuf's courage in enduring the pain. The Iroquois mocked baptism by pouring boiling water over his head. The Jesuits Christophe Regnault and Paul Ragueneau provided the two accounts of the deaths of Jean de Brébeuf and Gabriel Lalement. According to Regnault, they learned of the tortures and deaths from Huron refugee witnesses who had escaped from Saint-Ignace. Regnault went to see the bodies to verify the accounts, and his superior Rageuneau's account was based on his report. The main accounts of Brébeuf's death come from "The Jesuit Relations." Jesuit accounts of his torture emphasize his stoic nature and acceptance, claiming that he suffered silently without complaining.  Potential martyrdom was a central component of the Jesuit missionary identity. Missionaries going to Canada knew they were at risk from harsh conditions, as well as from confronting alien cultures. They expected to die in the name of God; they believed the missionary life and its risks were a chance to save converts and be saved.

Relics, beatification and canonization.

Fathers Brébeuf and Lalement were recovered and buried together in a Sainte Marie cemetery. Brébeuf's relics later became important religious objects within Catholic New France. Historian Allan Greer notes that "his death seemed to fit the profile of a perfect martyr's end" and was preceded by what were considered religious signs pointing to correspondences with the Passion of Christ, which added to the significance of Brébeuf. On 21 March 1649, Jesuit inspectors found the bodies of Brébeuf and Lalement. In the late spring of 1649, Christophe Regnault prepared the skeletal remains of Brébeuf and Lalemant for transportation to Québec for safekeeping. Regnault boiled away the remaining flesh and reburied it in the mission church, scraped the bones and dried them in an oven, wrapped each relic in separate silk, deposited them in two small chests, and sent them to Québec.  Brébeuf's family later donated his skull in a silver reliquary to the Catholic church orders in Québec. It was held by the women of the Hôtel-Dieu de Québec and the Ursuline convent from 1650 until 1925, when the relics were moved to the Québec Seminary for a ceremony to celebrate Brébeuf's beatification. According to Catholic belief, these relics provide physical access to the influence of the saint of whom they are a part.  In 1652 Paul Raguenau went through the "Relations" and pulled out material relating to the martyrs of New France. He formalized this material in a document, to be used as the foundation of canonization proceedings, entitled "Memoires touchant la mort et les vertus (des Pères Jesuits)," or the "Manuscript of 1652." The religious communities in New France considered the Jesuit martyrs as imitators of previous saints in the Catholic Church. In this sense, Brébeuf in particular, and others like him, reinforced the notion that "...Canada was a land of saints".  Catherine de Saint-Augustin said that Brébeuf appeared to her in a vision at the Québec Hôtel-Dieu while she was in a state of "mystical ecstasy," and he acted as her spiritual advisor. According to one account, Catherine de Saint-Augustin ground up part of Brébeuf's relic bone and gave it in a drink to a heretical and mortally ill man. It is said that the man was cured of his disease. In another instance, in 1660–61, a possessed woman was exorcised by the aid of one of Brébeuf's ribs, again while under the care of Catherine de Saint-Augustin. The exact circumstances of this event are disputed. Brébeuf's relics were also used by nuns who were treating wounded Huguenot (Protestant) soldiers, and they "reported that his assistance [bone slivers put in soldiers' drinks] helped rescue these patients from heresy".  Jean de Brébeuf was canonized by Pope Pius XI on 29 June 1930, and proclaimed one of the patron saints of Canada by Pope Pius XII on 16 October 1940. A contemporary newspaper account of the canonization declares: "Brébeuf, the 'Ajax of the mission', stands out among them [others made saints with him] because of his giant frame, a man of noble birth, of vigorous passions tamed by religion," describing both the man and his defining drive according to formal terms of hagiography.

Modern era.

It is said that the modern name of the Native North American sport of lacrosse was first coined by Brébeuf who thought that the sticks used in the game reminded him of a bishop's crosier ("crosse" in French, and with the feminine definite article, "la crosse").  He is buried in the Church of St. Joseph at the reconstructed Jesuit mission of Sainte-Marie among the Hurons across Highway 12 from the Martyrs' Shrine Catholic Church near Midland, Ontario. A plaque near the grave of Jean de Brébeuf and Gabriel Lalemant was unearthed during excavations at Ste Marie in 1954. The letters read "P. Jean de Brébeuf /brusle par les Iroquois /le 17 de mars l'an/1649" (Father Jean de Brébeuf, burned by the Iroquois, 17 March 1652).  In September 1984, Pope John Paul II prayed over Brébeuf's skull before fully joining in an outdoor ecumenical service on the grounds of the nearby Martyrs' Shrine. The service was attended by an estimated 75,000 and mixed pre-Christian first-nation ritual with Catholic liturgy.  Many Jesuit schools are named after him, such as Collège Jean-de-Brébeuf in Montreal, Brébeuf College School in Toronto and Brebeuf Jesuit Preparatory School in Indianapolis, Indiana.  St. John Brebeuf Regional Secondary School in Abbotsford, British Columbia, Canada and St. Jean de Brebeuf Catholic High School in Hamilton, Ontario, Canada are also named in his honour.  There is a high school St-Jean de Brebeuf Catholic High School in Vaughan, Ontario, Canada. There is also Eglise St-Jean de Brebeuf in Sudbury, Ontario. There is also an elementary school in Brampton, Ontario, Canada named after him; called St. Jean Brebeuf Roman Catholic Elementary School as well as one in Winnipeg, Manitoba, Canada called St. John Brebeuf Catholic School which is part of the St. John Brebeuf Catholic Parish. Also one French elementary school in Gatineau, Québec, called École Jean-de-Brébeuf. Also included is St. Jean Brebeuf Junior High School, located in Calgary, Alberta. The school closest to his burial site in Midland is St. Jean de Brébeuf Catholic Elementary School in Bradford, Ontario. St. John Brebeuf Catholic School in Erin, ON, is part of St. John Brebeuf Catholic Parish, part of the Roman Catholic Diocese in Hamilton, ON. There is also a St. John Brebeuf Catholic Parish in Niles, Illinois, USA.  There is also a unit at Camp Ondessonk in the Shawnee National Forest named after Jean de Brébeuf. The Catholic camp is named for all of the North American Martyrs and those who helped them.  The parish municipality of Brébeuf, Quebec, is named after him, as is rue de Brébeuf on the Plateau Mont-Royal in Montreal.  The character of Christophe in "The Orenda", a 2013 novel by Joseph Boyden, is based on Jean de Brebeuf. The novel won the 2014 Canada Reads competition, a reality show with elimination-style voting on CBC Radio.  Jean de Brébeuf is the subject of "Brébeuf and his Brethren", a blank-verse epic poem by the Canadian poet E. J. Pratt, FRSC, for which Pratt was awarded one of his three Governor General's Awards for Poetry in 1940.

Jean de Brébeuf () (25 March 1593 16 March 1649) was a French Jesuit missionary who travelled to New France (Canada) in 1625. There he worked primarily with the Huron (Wyandot people) for the rest of his life, except for a few years in France from 1629 to 1633. He learned their language and culture, writing extensively about each to aid other missionaries.

Svatý Jean de Brébeuf (zvaný též Apoštol Huronů, samotnými Huróny nazývaný Echon - Léčivý strom; 25. březen 1593 – 16. březen 1649) byl jezuitským misionářem, který strávil téměř čtvrt století v Nové Francii (Kanada). Působil především u kmenového svazu Huronů a svou mučednickou smrtí si vysloužil kanonizaci. Je také jedním se svatých patronů Kanady.


History.

The oldest human inhabitant archaeological findings in the region were unearthed in Anyer (the western coast of Java) with evidence of bronze and iron metallurgical culture dating to the first millennium AD. The prehistoric Buni culture (near present-day Bekasi) clay pottery were later developed with evidence found in Anyer to Cirebon. Artefacts (dated from 400 BC — AD 100), such as food and drink containers, were found mostly as burial gifts. There is also archaeological evidence in Batujaya Archaeological Site dating from the 2nd century and, according to Dr Tony Djubiantono, the head of Bandung Archaeology Agency, Jiwa Temple in Batujaya, Karawang, West Java was also built around this time.  One of the earliest known recorded history in Indonesia is from the former Tarumanagara kingdom, where seven fourth century stones are inscribed in Wengi letters (used in the Pallava period) and in Sanskrit describing the kings of the kingdom Tarumanagara. Records of Tarumanegara's administration lasted until the sixth century, which coincides with the attack of Srivijaya, as stated in the Kota Kapur inscription (AD 686).  The Sunda Kingdom subsequently became the ruling power of the region, as recorded on the Kebon Kopi II inscription (AD 932).  An Ulama, Sunan Gunung Jati, settled in Cirebon, with the intention of spreading the word of Islam in the pagan town. In the meantime, the Sultanate of Demak in central Java grew to an immediate threat against the Sunda kingdom. To defend against the threat, Prabu Surawisesa Jayaperkosa signed a treaty (known as the Luso-Sundanese Treaty) with the Portuguese in 1512. In return, the Portuguese were granted an accession to build fortresses and warehouses in the area, as well as form trading agreements with the kingdom. This first international treaty of West Java with the Europeans was commemorated by the placement of the Padrao stone monument at the bank of the Ciliwung River in 1522.  Although the treaty with the Portuguese had been established, it could not come to realization. Sunda Kalapa harbour fell under the alliance of the Sultanate of Demak and the Sultanate of Cirebon (former vassal state of Sunda kingdom) in 1524, after their troops under Paletehan alias Fadillah Khan had conquered the city. In 1524/1525, their troops under Sunan Gunung Jati also seized the port of Banten and established the Sultanate of Banten which was affiliating with the Sultanate of Demak. The war between the Sunda kingdom with Demak and Cirebon sultanates then continued for five years until a peace treaty was made in 1531 between King Surawisesa and Sunan Gunung Jati. From 1567 to 1579, under the last king Raja Mulya, alias Prabu Surya Kencana, the Sunda kingdom declined, essentially under the pressure from Sultanate of Banten. After 1576, the kingdom could not maintain its capital at Pakuan Pajajaran (the present-day Bogor) and gradually the Sultanate of Banten took over the former Sunda kingdom's region. The Mataram Sultanate from central Java also seized the Priangan region, the southeastern part of the kingdom.  In the sixteenth century, the Dutch and the British trading companies established their trading ships in West Java after the falldown of Sultanate of Banten. For the next three hundred years, West Java fell under the Dutch East Indies' administration. West Java was officially declared as a province of Indonesia in 1950, referring to a statement from Staatblad number 378. On 17 October 2000, as part of nationwide political decentralisation, Banten was separated from West Java and made into a new province. There have been recent proposals to rename the province Pasundan ("Land of the Sundanese") after the historical name for West Java.

Administrative divisions.

Since the creation of West Bandung Regency in 2008, the Province of West Java has been subdivided into 9 cities () and 17 regencies (). These 26 cities and regencies are divided into 620 districts (), which comprise 1,576 urban villages () and 4,301 rural villages (). An 18th regency was formed in October 2012 - Pangandaran Regency - from the southern half of Ciamis Regency; and on 25 October 2013, the Indonesian House of Representatives (DPR) began reviewing draft laws on the establishment of 57 prospective regencies (and 8 new provinces), including a further three regencies in West Java - South Garut (Garut Selatan), North Sukabumi (Sukabumi Utara) and West Bogor (Bogor Barat) - but none of these three new regencies are shown separately on the map below, nor in the following table.

Geography.

West Java borders Jakarta and Banten province to the west, and Central Java to the east. To the north is the Java Sea. To the south is the Indian Ocean. Unlike most other provinces in Indonesia which have their capitals in coastal areas, the provincial capital, Bandung, is located in the mountainous area in the centre of the province. Banten Province was formerly part of West Java Province but was created a separate province in 2000. West Java, in the densely populated western third of Java, is home to almost 1 out of every 5 Indonesians.  West Java and Banten provinces, as a part of the Pacific Ring of Fire, have more mountains and volcanoes than any of the other provinces in Indonesia. The vast volcanic mountainous region of inland West Java is traditionally known as Parahyangan (also known as Priangan or Preanger) which means "The abode of hyangs (gods)". It is considered as the heartland of the Sundanese people. The highest point of West Java is the stratovolcano Mount Cereme (3,078 meters) bordering Kuningan and Majalengka Regencies. West Java has rich and fertile volcanic soil. Agriculture, especially traditional dry rice cultivation (known as "ladang" or "huma"), has become the main way of life of traditional Sundanese people. Since the colonial VOC and Dutch East Indies era, West Java has been known as a productive plantation area for coffee, tea, quinine, and many other cash crops. The mountainous region of West Java is also a major producer of vegetables and decorative flowering plants. The landscape of the province is one of volcanic mountains, steep terrain, forest, mountains, rivers, fertile agricultural land, and natural sea harbours.  Flowing through Bandung Basin to the northeast is Citarum River, the longest and most important river in the province. This 300-km long river is the site of 3 dams, namely Cirata Dam, Saguling Dam, and Jatiluhur Dam. The river is heavily polluted by industrial and household sewage to the point that it has been called as 'the world's dirtiest river' by some.

Economy.

Initially, the economy of the Sundanese people in West Java relied heavily on rice cultivation. Ancient kingdoms established in West Java such as the Tarumanagara and Sunda Kingdom are known to have relied on rice taxes and agriculture revenues. The cycle of life of the ancient Sundanese people revolved around the rice crop cycle. Traditional rice harvest festivals such as the Seren Taun were important. The ancient goddess of rice, Nyai Pohaci Sanghyang Asri, is revered in Sundanese culture. Traditionally, Sundanese people often used dry rice cultivation ("ladang"). After the Mataram expanded to the Priangan area in the early 17th century following the Sultan Agung campaign against Dutch Batavia, "sawah" (wet rice cultivation) began to be adopted in the northern lowlands of West Java. Regencies such as Indramayu, Cirebon, Subang, Karawang and Bekasi are now well known as key rice producing areas. The mountainous region of West Java supplies vegetables, flower and many horticultural produce to Jakarta and Bandung. Animal farms in West Java produce dairy products and meats.

Colonial period.

During the Dutch East India Company (VOC) and Dutch East Indies era, West Java fell under Dutch administration centered in Batavia. The Dutch colonial government introduced cash crops such as tea, coffee, and quinine. Since the 18th century, West Java (known as "De Preanger") was known as a productive plantation area, and became integrated with global trade and economy. Services such as transportation and banking were provided to cater for wealthy Dutch plantation owners. West Java is known as one of the earliest developed regions in the Indonesian archipelago. In the early 20th century, the Dutch colonial government developed infrastructures for economic purposes, especially to support Dutch plantations in the region. Roads and railways were constructed to connect inland plantations area with urban centers such as Bandung and port of Batavia.

Post independence.

After Indonesian independence in 1945, West Java became a supporting region for Jakarta, the Indonesian capital. Jakarta remained as the business and political center of Indonesia. Several regencies and cities in West Java such as Bogor, Bekasi and Depok were developed as supporting areas for Jakarta and came to form the Greater Jakarta area or "Jabodetabek" (JAkarta, BOgor, DEpok, TAngerang and BEKasi). The northern area of West Java has become a major industrial area. Areas such as Bekasi, Cikarang and Karawang are sprawling with factories and industries. The area in and around Bandung also developed as industrial area.

Natural resources.

Based on the data from Indonesia State Secretary, the total area of rice fields in West Java Province in 2006 was 9,488,623 km which produced 9,418,882 tons of paddy in 2006, consisting of 9,103,800 tons rice field paddy and 315,082 tons farmland paddy. Palawija (non-rice food) production, reached 2,044,674 tons with productivity 179.28 quintal per ha. Nevertheless, the widest plant's width is for corn commodity which reaches 148,505 ha, West Java also produce horticulture consists of 2,938,624 tons vegetables, 3,193,744 tons fruits, and 159,871 tons medicines plants/ bio pharmacology.  Forest in West Java covers 764,387.59 ha or 20.62% from total size of the province. It consists of productive forest 362,980.40 ha (9.79%), protected forest 228,727.11 ha (6.17%), and conservation forest 172,680 ha (4.63%). Mangrove forest reaches 40,129.89 ha, and spread in 10 regencies where coasts are available. Besides, there is also another protected forest of about 32,313.59 ha organized by Perum Perhutani Unit III West Java and Banten.  From the productive forest, in 2006 West Java harvested crop of about 200,675 m3 wood, although the need of wood in this province every year is about 4 million m3. Until 2006, populace forest's width 214,892 ha with wood production is about 893,851.75 m3. West Java also produce non-forest's crop which is potential enough to be developed as forestry work, such as silk, mushroom, pine, dammar, maleleuca, rattan, bamboo, and swallow bird's nest.  In fishery sector, commodities include goldfish, nila fish, milkfish, freshwater catfish, windu shrimp, green mussel, gouramy, patin, seaweed and vaname shrimp. In 2006, this province harvested 560,000 tons fish from fishery cultivation crop and brackish or 63.63% from fishery production total in West Java.  In the poultry field, dairy cow, domestic poultry, and ducks are common commodities in West Java. 2006 data stated that there are 96,796 dairy cows (25% of the national population), 4,249,670 sheep, 28,652,493 domestic poultries, and 5,596,882 ducks (16% of the national population). Now there are only 245,994 beef cattle in West Java (3% national population), whereas the need every year is about 300,000 beef cattle.  This province has many plantation crops, such as tea, cloves, coconut, rubber, cacao, tobacco, coffee, sugar, palm and akar wangi (Chrysopogon zizanioides). From all those commodities, cloves, coconut, rubber, cocoa, tobacco, and coffee are common in West Java. From area side, the best productivity, that is plan area's width equals with plant's width that produces tobacco and sugar palm commodities. From production side, the highest productivity is oil palm (6.5 tons per ha) and sugar palm (5.5 tons per ha).  West Java also has a number of mining operations. In 2006, it contributed 5,284 tons zeolite, 47,978 tons bentonite, iron sand, pozzolan cement, feldspar, and jewel barn/ gemstone. Precious stone mining potential generally are found in Garut, Tasikmalaya, Kuningan, and Sukabumi Regency areas.  As consequences of has many volcanoes, West Java is potential of Geothermal energy. There are 11 points of geothermal energy and 3 points, i.e. Papandayan, Ceremai and Gede Pangrango have conducted pre-exploration.  Raw natural resources include chalk, several offshore oilfields in the Java Sea, and lumber. Most of the province is very fertile, with a mix of small farms and larger plantations. There are several hydropower dams, including Jatiluhur, Saguling, Cirata, and Jatigede.

Tourism.

Tourism is an important industry in West Java, and the Bandung and Puncak areas have long been known as popular weekend destinations for Jakartans. Today Bandung has developed into a shopping destination, popular not only among local Indonesian especially Jakartans, but also with neighboring Malaysian and Singaporean visitors. The history-rich coastal city of Cirebon is also a cultural tourism destination since the city has several kratons and historical sites such as Gua Sunyaragi. Other tourist destinations include the Bogor Botanical Garden, Safari Park of Indonesia, Tangkuban Perahu crater, Pelabuhanratu Bay, Ciater hot springs, Kawah Putih crater to the south of Bandung, Pangandaran beach, and various mountain resorts in Cianjur, Garut, Tasikmalaya, and Kuningan.

Demographics.

The population of West Java was put at 43,054,000 in mid-2010 making it the most populous province of Indonesia, home to 18% of the national total on 1.8% of the national land. Aside from the special district of Jakarta, it is the most densely populated province in the country with an average of 1,394 people per km2 (2019 data). The population growth rate recorded in the ten years to 2010 was 1.9%,

Ethnic and linguistic composition.

West Java is the native homeland of Sundanese people which forms the largest ethnic group in West Java, followed by Javanese who migrated to the province centuries ago. Since Jakarta and the surrounding area, including West Java, is the business and political center of Indonesia, the province has attracted various people from throughout Indonesia. Other Native Indonesian ethnic groups such as Minangkabau, Batak, Malay, Madurese, Balinese, Ambonese and many other Indonesians who migrated to and settled in West Java cities can also be easily found. West Java urban areas also have a significant population of Chinese Indonesians.  In addition to Indonesian, the official national language, the other widely spoken language in the province is Sundanese. In some areas near the southern borders with Central Java, Javanese is also spoken. The main language spoken in Cirebon and nearby areas (Majalengka, Indramayu, Sumber) is Cirebonese, a dialect of Javanese with Sundanese influence.  Indonesian is widely spoken as a second language.

Culture.

The Sundanese share Java island with the Javanese people and primarily live in West Java. Although the Sundanese live in the same island as the Javanese, their culture is distinct and they likewise consider themselves to live in a separate cultural area called "Pasundan" or "Tatar Sunda". Someone moving from West Java Province to Central or East Java Provinces is literally said to be moving from Sunda to Java worlds. Bandung, the capital city of West Java, is considered as the cultural heartland of Sundanese people. Many indigenous Sundanese artforms were developed in this city. The nearby province of Banten, which was formerly part of West Java before it became its own province, is similar in this regard and is also considered to be part of "Pasundan" as well.

Music.

Gamelan orchestra.

The musical arts of Sunda, which is an expression of the emotions of Sundanese culture, express politeness and grace of Sundanese. Degung orchestra consists of Sundanese gamelan.  In addition to the Sundanese forms of Gamelan in Parahyangan, the region of Cirebon retains its own distinct musical traditions. Amongst Cirebons' varying Gamelan ensembles the two most frequently heard are Gamelan Pelog (a non-equidistant heptatonic tuning system) and Gamelan Prawa (a semi-equidistant pentatonic tuning system). Gamelan Pelog is traditionally reserved for Tayuban, Wayang Cepak, and for listening and dance music of the Kratons in Cirebon. Whereas Gamelan Prawa is traditionally reserved for Wayang Purwa.  Cirebon also retains specialized Gamelan ensembles including: Sekaten, which is played in the Kratons to mark important times in the Islamic calendar. Denggung, also a Kraton ensemble which is believed to have a number of "supernatural powers". And Renteng, an ensemble found in both Cirebon and Parahyangan that is known for its loud and energetic playing style.

Zither ensembles.

Tembang Sunda is a genre of Sundanese vocal music accompanied by a core ensemble of two kacapi (zither) and a suling (bamboo flute). Tembang means song or poem and Sunda is a geographical, historical, and cultural construct which signifies home for the Sundanese people of Indonesia. The music and poetry of tembang Sunda are closely associated with the Parahyangan (literally the abode of the gods), the highland plateau that transverses the central and southern parts of Sunda. The natural environment of Priangan, an agricultural region surrounded by mountains and volcanoes, is reflected in some songs of the tembang Sunda.  Kacapi suling is tembang Sunda minus vocal.  Tarawangsa is a genuine popular art is performed on ensemble consists of tarawangsa (a violin with an end pin) and the jentreng (a kind of seven-stringed zither). It is accompanied by a secret dance called Jentreng. The dance is a part of a ritual celebrating the goddess of paddy Dewi Sri. Its ceremonial significance is associated with a ritual of thanksgiving associated with the rice harvest. Tarawangsa can also be played for healing or even purely for entertainment.

Bamboo ensembles.

The three main types of Sundanese bamboo ensembles are angklung, calung, and arumba. The exact features of each ensemble vary according to context, related instruments, and relative popularity.  Angklung is a generic term for sets of tuned, shaken bamboo rattles. Angklung consists of a frame upon which hang several different lengths of hollow bamboo. Angklungs are played like handbells, with each instrument played to a different note. Angklung rattles are played in interlocking patterns, usually with only one or two instruments played per person. The ensemble is used in Sundanese processions, sometimes with trance or acrobatics. Performed at life-cycle rituals and feasts (hajat), angklung is believed to maintain balance and harmony in the village. In its most modern incarnation, angklung is performed in schools as an aid to learning about music.  The Angklung got more international attention when Daeng Soetigna, from Bandung, West Java, expanded the angklung notations not only to play traditional pélog or sléndro scales, but also diatonic scale in 1938. Since then, angklung is often played together with other western music instruments in an orchestra. One of the first well-known performances of angklung in an orchestra was during the Bandung Conference in 1955.  Like those in angklung, the instruments of the calung ensemble are of bamboo, but each consists of several differently tuned tubes fixed onto a piece of bamboo; the player holds the instrument in his left hand and strikes it with a beater held in his right. The highest-pitched calung has the greatest number of tubes and the densest musical activity; the lowest-pitched, with two tubes, has the least. Calung is nearly always associated with earthy humor, and is played by men.  Arumba refers to a set of diatonically tuned bamboo xylophones, often played by women. It is frequently joined by modern instruments, including a drum set, electric guitar, bass, and keyboards.

Puppetry.

"Wayang golek" is a traditional form of puppetry from Sunda. Unlike the better-known leather shadow puppets ("wayang kulit") found in the rest of Java and Bali, "wayang golek" puppets are made from wood and are three-dimensional, rather than two. They use a banana palm in which the puppets stand, behind which one puppeteer ("dalang") is accompanied by his "gamelan" orchestra with up to 20 musicians. The "gamelan" uses a five-note scale as opposed to the seven-note western scale. The musicians are guided by the drummer, who in turn is guided by signals from the puppet master dalang gives to change the mood or pace required. "Wayang golek" are used by the Sundanese to tell the epic play "Mahabarata" and various other morality type plays.

Dance.

Sundanese dance shows the influence of the many groups that have traded and settled in the area over the centuries, and includes variations from graceful to dynamic syncopated drumming patterns, quick wrist flicks, sensual hip movements, and fast shoulder and torso isolations. "Jaipongan" is probably the most popular traditional social dance of Sundanese people. It can be performed in solo, in group, or in pair. The "Tari Merak" (Peafowl Dance) is a female dance inspired by the movements of a peafowl and its feathers blended with the classical movements of Sundanese dance.

Folktales and legend stories.

There are stories and folktales transcribed from Pantun Sunda stories. Among the most well known folktale and stories are:

Literature.

Old Sundanese literature, among others, are:

Human Development Index.

Cities and Regencies in West Java range high to medium Human Development Index (HDI).

Transportation.

Toll roads.

Due to its proximity to the capital city and its growing population and industry, West Java has the longest tolled highway road of any provinces. As of April 2015, there are several toll roads in West Java In addition to completed highways there are some highways that are being built, one of them is Cileunyi–Sumedang–Dawuan (Cisumdawu) with length 60.1 kilometres.  Several other proposed toll roads are Bandung Intra-Urban Toll Road, Cileunyi–Tasikmalaya, and Jakarta Outer Ring Road 2 (a section of this road has been built).

Railways.

Most cities and towns in West Java are served with narrow-gauge (mainly 1067mm) lines and connected to other provinces on Java Island. Jakarta's KRL Commuterline electric suburban trains run into the province to Bogor and Cikarang.  A high-speed railway, connecting Jakarta and Bandung, is now under construction.

Air.

Bandung Husein Sastranegara International Airport serves direct domestic flights to Batam, Pekanbaru, Medan, Bandar Lampung, Surabaya, Yogyakarta, Denpasar, Semarang, Banjarmasin, Makassar, and also international services to/from Kuala Lumpur and Singapore. The Kertajati International Airport in Majalengka Regency is built to replace the Husein Sastranegara Airport and to ease air traffic at Soekarno–Hatta International Airport in Jakarta.

Education.

West Java is one of the most popular destinations for higher education in Indonesia. It has many well-known universities joined by many students from the entire country. Some of which are:

West Java (; is a province of Indonesia on the western part of the island of Java, with its provincial capital in Bandung. West Java is bordered by the province of Banten and the country's capital region of Jakarta to the west, the Java Sea to the north, the province of Central Java to the east and the Indian Ocean to the south. The province is the homeland of the Sundanese people, the second-largest ethnic group in Indonesia after the Javanese.

Západní Jáva () je jedna z provincií Indonésie. Zabírá většinu západní části ostrova Jáva. Jde o nejlidnatější a nejhustěji zalidněnou provincii v celé zemi s vysokým přírůstkem populace. Z více než 40 milionů obyvatel tvoří zhruba tři čtvrtiny Sundánci; většina příslušníků tohoto etnika žije právě v této provincii.


Types.

Transfer cases used on "part-time" four-wheel-drive off-road vehicles such as trucks, truggies, rock-crawling vehicles, and some military vehicles generally allow the driver to select 2WD or 4WD, as well as high or low gear ranges. Those used in sports cars and performance sedans are usually "transparent" to the driver; there is no shifter or select lever.

Drive type.

Gear-driven.

There are two different types of internal power-transfer mechanism found in most transfer cases. Gear-driven transfer cases use sets of gears to drive either the front or both the front and rear driveshafts. These are generally strong, heavy units that are used in large trucks, but there are currently several gear drive cases in production for passenger cars.

Chain-driven.

Chain-driven transfer cases use a chain to drive most often only one axle, but can drive both axles. Chain-driven transfer cases are quieter and lighter than gear-driven ones. They are used in vehicles such as compact trucks, full size trucks, Jeeps and SUVs. Some off-road driving enthusiasts modify their vehicles to use gear-driven transfer cases, accepting the additional weight and noise to gain the extra strength they generally provide.

Housing type.

Married.

Transfer cases are also classified as either "divorced"/independent or "married". Married transfer cases are bolted directly to the transmission, usually between the transmission's output shaft and the rear or main driveshaft. Sometimes a married transfer case is an integral part of the transmission and the two components share the same housing or "case", as is commonly found on recent Subaru products and some other all-wheel-drive cars.

Divorced/independent.

A divorced or independent transfer case is completely separate from the transmission. It is located further down the driveline than a married transfer case and connected to the transmission output shaft by a short driveshaft. Independent transfer cases are used on very long wheelbase vehicles, such as commercial trucks or military trucks.

Transfer case shift type.

M.S.O.F..

Manual Shift On-the-Fly transfer cases have a selector lever on the driver's side floor transmission hump and may also have either two sealed automatic front axle locking hubs or two manual front axle hub selectors of "LOCK" and "UNLOCK" or "FREE". To engage the four-wheel-drive system the vehicle must be moving at a low speed. The speed at which 4x4 can be engaged depends on the vehicle. This is only for the four-wheel-drive high setting. To engage the four-wheel-drive low setting, the vehicle must be stopped and the transmission must be shifted to neutral, then the four-wheel-drive low can be selected.

E.S.O.F..

Electronic Shift On-the-Fly (ESOF) transfer cases have a dash-mounted selector switch or buttons with front sealed automatic locking axle hubs or drive flanges. Unlike the manual transfer case, this system has a transfer case motor. To engage the four-wheel-drive system the vehicle must be moving at a lower speeds. The speed at which 4x4 can be engaged depends on the vehicle. This is only for the four-wheel-drive high setting. To engage the four-wheel-drive low setting, the vehicle must be stopped and the transmission must be shifted to neutral, then the four-wheel-drive low can be selected.

A transfer case is a part of the drivetrain of four-wheel-drive, all-wheel-drive, and other multiple powered axle vehicles. The transfer case transfers power from the transmission to the front and rear axles by means of drive shafts. It also synchronizes the difference between the rotation of the front and rear wheels, and may contain one or more sets of low range gears for off-road use.

Rozvodovka je převodová skříň sloužící většinou k rozdělení točivého momentu vstupní hřídele na dvě a více hřídelí výstupních, obvykle s jinou úhlovou rychlostí a točivým momentem než vstupní. Rozvodovka je součástí mnoha strojů – nejčastěji se s ní setkáme v motorových vozidlech. Obvyklé typy automobilových rozvodovek obsahují stálý převod hnací nápravy a diferenciál který umožňuje přenos rozdílného poměru otáček (diference otáček) na výstupních hřídelích (polonápravách).