Prediction of vacuum circuit breakers' insulating characteristics based on the examination of pre-breakdown phenomena

U ovom radu se razmatra uticaj sklopnih operacija na izolacione karakteristike vakuumskih sklopnih elemenata. Razmatraju se sledeće sklopne operacije: uklop bez struje – isklop bez struje, uklop bez struje - uklop sa nominalnom strujom, uklop bez struje - isklop sa strujom kratkog spoja. Pri tome se ovaj uticaj ispituje na slučajne veličine ac probojni napon, impulsni probojni napon i na pretprobojne parametre V-4,V-5 i V-6 (dc naponi pri kojima je pretprobojna struja 10-4 A, 10-5 A i 10-6 A). Dobijeni efekti promene karakteristika nakon sklopnih operacija se porede sa odgovarajućim rezultatima dobijenim sa istim skopnim elementima kondicioniranih kontakata. Tako dobijeni rezultati se tumače preko mehanizma elektičnog pražnjenja u vakuumu. Osnovni rezultat, a ujedno i cilj rada, je ispitivanje relacija korelacije i regresije između eksperimentalno dobijenim statističkim uzorcima slučajne veličine ac i impulsni probojni napon i njima odgovarajućih statističkih uzoraka slučajnih veličina predprobojnih parametara V-4,V-5 i V-6. Ispitivanje se vrši na komercijalnim vakuumskim sklopnim elementima sa CuCr i CuBi kontaktima.This work considers the influence of switching operations on the insulating characteristics of vacuum circuit breakers. The following operations, all with circuit-making without current, have been taken into account: circuit-breaking without current, circuit-breaking with nominal current and circuit-breaking with short-circuit current. The influence of switching operations is examined for the random variables breakdown voltage (ac and pulse) and the prebreakdown parameters V-4, V-5, and V-6. Parameters V-4, V-5, and V-6 represent the dc voltage at which the pre-breakdown current takes values of 10-4, 10-5, and 10-6 A, respectively. Switching element characteristics after the switching operations are compared with the corresponding results obtained for switching element with conditioned contacts. Obtained results are analyzed through mechanisms of electrical discharges in vacuum. The main result is an examination of the correlation and regression between the experimentally obtained breakdown voltage (ac and pulse) random variable and its corresponding pre-breakdown parameters V-4, V-5, and V-6, respectively. Statistical samples created by using this method do not require the repetition of switching operations and therefore the dielectric strength of the vacuum insulation is kept in its initial state. The examination is carried out on commercial vacuum switching elements with CuCr and CuBi contacts

The influence of magnetic field shape on dielectric characteristics of vacuum switches

Cilj ovog rada je ispitivanje uticaja oblika magnetnog polja u međukontaktnom prostoru u smislu degradacije kontakata tokom sklopnih operacija isklopa pod opterećenjem. U tom smislu statistički su analizirani rezultati merenja naizmeničnog probojnog napona i impulsnog probojnog napona. Eksperimenti su sprovedeni na komercijalnim prekidačima sa CuCr kontaktima. Parametri u eksperimentu bili su vrednost napona prilikom prekidanja struje i međukontaktno rastojanje. Ustanovljeno je da prekidači sa radijalnim magnetnim poljem u međukontaktnom prostoru trpe manje ireverzibilne promene tokom prekidanja nominalne struje i nominalne struje kratkog spoja.The aim of this paper is to examine the influence of the magnetic field shape in the inter-contact space in the context of contact degradation during the switching operation of circuit-breaking with current. The results of measuring the AC breakdown voltage and pulse breakdown voltage are statistically analyzed for that purpose. The experiments are carried out on the commercial switching elements with CuCr contact. The experiment parameters are the current breaking voltage value and inter-electrode distance. Results showed that switches with radial magnetic field suffer less irreversible changes during the breaking operation such as circuit-breaking with nominal current and circuit-breaking with short-circuit current

Gender differences in victims of war torture: Types of torture and psychological consequences

Uvod/Cilj. Tortura, kao poseban vid političkog nasilja, predstavlja ekstremnu primenu nasilnog ponašanja u interpersonalnim odnosima, koji za posledicu mogu imati ne samo akutne psihijatrijske poremećaje, već, veoma često snažne i dalekosežne negativne posledice po ukupno psihosocijalno funkcionisanje žrtve. Cilj ovog rada bio je ustanovljavanje međupolnih razlika kod osoba koje su pretrpele ratnu torturu, s obzirom na vrste pretrpljenog mučenja i karakteristike psihičkih posledica. Metode. Ispitanike (410 osoba muškog i 76 ženskog pola) činili su korisnici 'Centra za rehabilitaciju žrtava torture' - IAN, koji su pretrpeli mučenje u zatvorima i koncentracionim logorima za vreme građanskih ratova u bivšoj Jugoslaviji 1991-1995. i 1999. godine. Za evidentiranje vrsta mučenja korišćen je Upitnik o vrstama mučenja sa 81 stavkom. Za procenu karaktera i intenziteta psiholoških tegoba korišćena je skala provere simptoma-revidirana verzija (SCL-90-R), a za procenu posttraumatske simptomatologije korišćena je Skala uticaja (traumatskog) događaja - IES. Rezultati. Ustanovljena je međupolna razlika prema tipu pretrpljenog mučenja kod 33 vrste torture; 28 su bili češće zastupljeni kod osoba muškog pola, a 5 kod osoba ženskog pola. Faktorska analiza pokazala je postojanje tri faktora koja objašnjavaju 29% ukupne varijanse i protumačeni su kao 'obična tortura', 'sadistička tortura' i 'seksualna tortura'. Diskriminativna analiza ukazala je na značajno razlikovanje među polovima s obzirom na dobijene faktore: kod muškaraca bili su značajno češće prisutni 'obična tortura' i 'sadistička tortura', a kod žena 'seksualna tortura'. Analizom SCL-90-R ustanovljeno je da su aktuelne psihološke tegobe značajno veće kod osoba ženskog pola u dimenzijama somatizacije, depresivnosti, anksioznosti, opsesivnosti i interpersonalne senzitivnosti. Generalni skor na IES i skor na supskalama 'nametanja' traumatskih događaja i 'izbegavanja' socijalnih interakcija bio je značajno veći kod žena nego kod muškaraca. Zaključak. Žene izložene ratnoj torturi bile su kraće i ređe izložene mučenju nego muškarci, ali imaju značajnije izražene posttraumatske tegobe i druge psihičke smetnje. Ustanovljene međupolne razlike u odnosu na različite forme torture, pri čemu su žene značajno češće bile izložene 'seksualnoj torturi', a muškarci 'sadističkoj' i 'običnoj' torturi, ne mogu u potpunosti objasniti češću pojavu posttraumatskih psiholoških posledica kod žena.Background/Aim. Torture for political reasons is an extreme violence in interpersonal relations resulting in not only acute psychiatric disorders but also very often in very severe and far reaching negative consequences for the overall psychosocial functioning of a victim. The aim of this study was to investigate gender differences in types of torture and psychological consequences in subjects who experienced war torture. Methods. A sample (410 men and 76 women) included clients of 'Centre for rehabilitation of torture victims - IAN, Belgrade' who experienced torture in prisons and concentration camps during civil wars in ex-Yugoslavia 1991-1995 and 1999. Types of Torture Questionnaire with 81 items was used for collecting data about forms of torture. Symptom Checklist 90-Revised (SCL-90- R) was used for assessing type and intensity of psychological symptoms, and Impact of Event Scale (IES) was used to estimate posttraumatic complaints. Results. A gender difference was found for 33 types of torture: 28 more frequent in men, and 5 in women. Factor analysis of torture types revealed three factors explaining 29% of variance: 'common torture', 'sadistic torture', and 'sexual torture'. Discriminant analysis revealed significant gender difference concerning the factors. 'Common torture' and 'sadistic torture' were more prominent in men, and 'sexual torture' was more present in women. Higher scores on depression, anxiety, somatization, interpersonal sensitivity and obsessive-compulsive dimensions on SCL-90-R were found in women. General score and scores of subscales (intrusion and avoidance) on IES were significantly higher in women. Conclusion. Women exposed to war torture experienced less torture techniques and shorter imprisonment than men, but had more frequent and severe symptoms of posttraumatic stress disorder and other psychological symptoms. Gender differences in posttraumatic symptomatology can not be explained exclusively by gender differences in types of torture found in this study

Prediction of vacuum circuit breakers' insulating characteristics based on the examination of pre-breakdown phenomena

U ovom radu se razmatra uticaj sklopnih operacija na izolacione karakteristike vakuumskih sklopnih elemenata. Razmatraju se sledeće sklopne operacije: uklop bez struje – isklop bez struje, uklop bez struje - uklop sa nominalnom strujom, uklop bez struje - isklop sa strujom kratkog spoja. Pri tome se ovaj uticaj ispituje na slučajne veličine ac probojni napon, impulsni probojni napon i na pretprobojne parametre V-4,V-5 i V-6 (dc naponi pri kojima je pretprobojna struja 10-4 A, 10-5 A i 10-6 A). Dobijeni efekti promene karakteristika nakon sklopnih operacija se porede sa odgovarajućim rezultatima dobijenim sa istim skopnim elementima kondicioniranih kontakata. Tako dobijeni rezultati se tumače preko mehanizma elektičnog pražnjenja u vakuumu. Osnovni rezultat, a ujedno i cilj rada, je ispitivanje relacija korelacije i regresije između eksperimentalno dobijenim statističkim uzorcima slučajne veličine ac i impulsni probojni napon i njima odgovarajućih statističkih uzoraka slučajnih veličina predprobojnih parametara V-4,V-5 i V-6. Ispitivanje se vrši na komercijalnim vakuumskim sklopnim elementima sa CuCr i CuBi kontaktima.This work considers the influence of switching operations on the insulating characteristics of vacuum circuit breakers. The following operations, all with circuit-making without current, have been taken into account: circuit-breaking without current, circuit-breaking with nominal current and circuit-breaking with short-circuit current. The influence of switching operations is examined for the random variables breakdown voltage (ac and pulse) and the prebreakdown parameters V-4, V-5, and V-6. Parameters V-4, V-5, and V-6 represent the dc voltage at which the pre-breakdown current takes values of 10-4, 10-5, and 10-6 A, respectively. Switching element characteristics after the switching operations are compared with the corresponding results obtained for switching element with conditioned contacts. Obtained results are analyzed through mechanisms of electrical discharges in vacuum. The main result is an examination of the correlation and regression between the experimentally obtained breakdown voltage (ac and pulse) random variable and its corresponding pre-breakdown parameters V-4, V-5, and V-6, respectively. Statistical samples created by using this method do not require the repetition of switching operations and therefore the dielectric strength of the vacuum insulation is kept in its initial state. The examination is carried out on commercial vacuum switching elements with CuCr and CuBi contacts

Prediction of vacuum circuit breakers' insulating characteristics based on the examination of pre-breakdown phenomena

U ovom radu se razmatra uticaj sklopnih operacija na izolacione karakteristike vakuumskih sklopnih elemenata. Razmatraju se sledeće sklopne operacije: uklop bez struje – isklop bez struje, uklop bez struje - uklop sa nominalnom strujom, uklop bez struje - isklop sa strujom kratkog spoja. Pri tome se ovaj uticaj ispituje na slučajne veličine ac probojni napon, impulsni probojni napon i na pretprobojne parametre V-4,V-5 i V-6 (dc naponi pri kojima je pretprobojna struja 10-4 A, 10-5 A i 10-6 A). Dobijeni efekti promene karakteristika nakon sklopnih operacija se porede sa odgovarajućim rezultatima dobijenim sa istim skopnim elementima kondicioniranih kontakata. Tako dobijeni rezultati se tumače preko mehanizma elektičnog pražnjenja u vakuumu. Osnovni rezultat, a ujedno i cilj rada, je ispitivanje relacija korelacije i regresije između eksperimentalno dobijenim statističkim uzorcima slučajne veličine ac i impulsni probojni napon i njima odgovarajućih statističkih uzoraka slučajnih veličina predprobojnih parametara V-4,V-5 i V-6. Ispitivanje se vrši na komercijalnim vakuumskim sklopnim elementima sa CuCr i CuBi kontaktima.This work considers the influence of switching operations on the insulating characteristics of vacuum circuit breakers. The following operations, all with circuit-making without current, have been taken into account: circuit-breaking without current, circuit-breaking with nominal current and circuit-breaking with short-circuit current. The influence of switching operations is examined for the random variables breakdown voltage (ac and pulse) and the prebreakdown parameters V-4, V-5, and V-6. Parameters V-4, V-5, and V-6 represent the dc voltage at which the pre-breakdown current takes values of 10-4, 10-5, and 10-6 A, respectively. Switching element characteristics after the switching operations are compared with the corresponding results obtained for switching element with conditioned contacts. Obtained results are analyzed through mechanisms of electrical discharges in vacuum. The main result is an examination of the correlation and regression between the experimentally obtained breakdown voltage (ac and pulse) random variable and its corresponding pre-breakdown parameters V-4, V-5, and V-6, respectively. Statistical samples created by using this method do not require the repetition of switching operations and therefore the dielectric strength of the vacuum insulation is kept in its initial state. The examination is carried out on commercial vacuum switching elements with CuCr and CuBi contacts

Correlation and regression between the breakdown voltage and pre-breakdown parameters of vacuum switching elements

This paper considers the influence of switching operations on the characteristics of vacuum switching elements. The following operations, all with circuit-making without current, have been taken into account: circuit-breaking without current, circuit-breaking with nominal current and circuit-breaking with short-circuit current. The influence of switching operations is examined for the random variables breakdown voltage (ac and pulse) and the pre-breakdown parameters V-4, V-5, and V-6. Parameters V-4, V-5, and V-6 represent the dc voltage at which the pre-breakdown current takes values of 10(-4), 10(-5), and 10(-6) A, respectively. Switching element characteristics after the switching operations are compared with the corresponding results obtained for switching element with conditioned contacts. The main result is an examination of the correlation and regression between the experimentally obtained breakdown voltage (ac and pulse) random variable and its corresponding pre-breakdown parameters V-4, V-5, and V-6, respectively. Statistical samples created by using this method do not require the repetition of switching operations and therefore the dielectric strength of the vacuum insulation is kept in its initial state. The examination is carried out on commercial vacuum switching elements with CuCr and CuBi contacts

Correlation and regression between the breakdown voltage and pre-breakdown parameters of vacuum switching elements

This paper considers the influence of switching operations on the characteristics of vacuum switching elements. The following operations, all with circuit-making without current, have been taken into account: circuit-breaking without current, circuit-breaking with nominal current and circuit-breaking with short-circuit current. The influence of switching operations is examined for the random variables breakdown voltage (ac and pulse) and the pre-breakdown parameters V-4, V-5, and V-6. Parameters V-4, V-5, and V-6 represent the dc voltage at which the pre-breakdown current takes values of 10(-4), 10(-5), and 10(-6) A, respectively. Switching element characteristics after the switching operations are compared with the corresponding results obtained for switching element with conditioned contacts. The main result is an examination of the correlation and regression between the experimentally obtained breakdown voltage (ac and pulse) random variable and its corresponding pre-breakdown parameters V-4, V-5, and V-6, respectively. Statistical samples created by using this method do not require the repetition of switching operations and therefore the dielectric strength of the vacuum insulation is kept in its initial state. The examination is carried out on commercial vacuum switching elements with CuCr and CuBi contacts

Irreversible changes of vacuum circuit breakers' dielectric strength as a result of current breaking operation

In the vacuum switching element, current breaking operations cause the changes of the electrodes' surface by means of the following mechanism: 1 - cathode erosion (during the movement of electric arc's cathode spot); 2 - the explosion of the conducting metal bridge during the arc stretching; 3 - condensation of neutral metal vapor on the contacts, and 4 - the emission of micro-particles of the melted electrode surface regions the first three mechanisms are dominant in the case of diffuse arc (there are more parallel arcs of the small current, up to 100 A, which do not have consolidated the cathode spot) the fourth mechanism is dominant for the constricted arc (cathode spot is consolidated) the diffusion arc has the arc voltage typical value of 30 V, while in case of the consolidated arc, the arc voltage may increase more than 100 V the transition between the diffusion arc and consolidated arc does not occur instantaneously, but rather, there are some transitional shapes the mentioned contact topography changes of the vacuum circuit breakers lead to irreversible changes of vacuum insulation through the braking operations the aim of this paper is to determine the irreversibility rate of the vacuum insulation caused by circuit braking operations thereby evaluating the possible number of these switching operations in the course of the life cycle of one such element the results of measuring the AC breakdown voltage, pulse breakdown voltage and the voltage whose corresponding prebreaking current equals 10-4 A and 10-5 A will be statistically analyzed for that purpose the experiments will be carried out on the commercial switching elements with CuCr and CuBi contacts the experiment parameters will be the current breaking value and interelectrode distance, respectively

Sucrose effects on in vitro fruiting and seed production of Centaurium pulchellum

The effect of sucrose on fruiting, seed production, and seed germination of lesser centaury [Centaurium pulchellum (Sw.) Druce] was examined using explants of flowers and flower buds. Sucrose concentrations in the culture medium ranged from 0.003 to 0.3 M. It has been shown that the number of auxiliary buds, capsules dimension, number of viable seeds per capsule and seed dimensions increased with the increase of sucrose concentrations. The highest values were recorded at sucrose concentrations higher than 0.03 M, except for seeds size, which were larger at sucrose concentration ranging from 0.003 to 0.1 M. The germination of in vitro produced seeds was affected by previous culture history: a higher germination percentage was obtained in seeds that were raised from explants originally grown on medium with sucrose concentrations higher than 0.003 M.nul

Effect of nitric oxide - releasing compounds on phytochrome - controlled germination of Empress tree seeds

Using different nitric oxide releasing compounds and appropriate controls we have obtained data strongly suggesting the involvement of nitric oxide in the phytochrome controlled germination of Paulownia tomentosa seeds. Direct detection of nitric oxide, under various experimental conditions, was performed by a spin-trapping technique combined with electron paramagnetic resonance (EPR) spectroscopy. The addition of methylene blue prevented light-induced and NO donors-potentiated germination of P. tomentosa seeds. This inhibition could be completely overcome by addition of gibberellin. The promotive effect of nitrite was pH dependent, maximally pronounced at the pH range where nitrite undergoes dismutation and liberates nitric oxide. Under these conditions, nitrite exerted its efficacy at the same concentrations at which nitric oxide releasing compounds such as sodium nitroprusside (SNP), S-nitroso acetylpenicillamine (SNAP), and 3-morpholinosydnonimine (SIN-1), were the most effective. Likewise, the potentiation of P. tomentosa seed germination could be achieved by chemical reduction of nitrite with Na2S2O4 during which liberation of nitric oxide could be detected.nul