Classical stability and quantum instability of black-hole Cauchy horizons

For a certain region of the parameter space $\{M,e,\Lambda\}$, the Cauchy horizon of a (charged) black hole residing in de Sitter space is classically stable to gravitational perturbations. This implies that, when left to its own devices, classical theory is unable to retain full predictive power: the evolution of physical fields beyond the Cauchy horizon is not uniquely determined by the initial conditions. In this paper we argue that the Cauchy horizon of a Reissner-Nordstr\"om-de Sitter black hole must always be unstable quantum mechanically.Comment: 4 pages; uses ReVTeX; figure available upon request to [email protected]

Decopperization process of waste solutions from conventional copper electrolysis

This paper is adresses on treatment of sulphuric acid waste solutions obtained during the conventional copper metallurgical activities. Mother liquor is a part of this solutions and it is generated during the regeneration process of copper bleed solution. Copper, nickel and sulphuric acid are the main components and the other registered impurities are: As, Se, Fe, Sb, Zn, Bi, Pb, Cl ions. Aim to copper removing from the mother liquor, the decopperization process on the industrial scale equipment, is investigated. Investigation was done using the rectangular insoluble lead anodes alloyed with 6 wt.% of antimony at current value of 13 000 A, identical to the current in a commercial copper refinery plant. A few parameters as so as: current, cell voltage, electrolyte temperature, electrolyte flow rate, level of electrolyte, were monitored during the test. Comparing the values of copper content in the solution before and after the decopperization of copper, it was found that it decreased of about 80 wt. % of the initial value. Chemical characterization of the sludge obtained on cathode has shown that it is a material with copper content of about 90 wt. %

Analysis of the speech signals features for multimodal speech recognition.

У системима аутоматског препознавња говора све значајнију улогу игра и мултимодални говор...In automatic speech recognition systems, multimodal speech is playing an increasingly important role. Different modes of speech involve different acoustic features. Particular importance is given to normal (natural) speech, whisper and their combinations (when the system is trained by normal speech and then used to recognize whisper, and vice versa). The match scenarios: „normal/normal“ and „whisper/whisper“, and mismatch scenarios: „normal/whisper“ and „whisper/normal“ are considered here..

Roles in bullying and academic achievement of students

Vršnjačko nasilje i školski uspeh učenika predstavljaju dva važna pedagoška problema čije proučavanje doprinosi unapređivanju vaspitno-obrazovnog rada savremene škole. Danas preovladava stav da je prilikom proučavanja vršnjačkog nasilja važno razmotriti uloge koje u tom procesu imaju učenici koji nisu direktno uključeni u nasilje u ulogama nasilnika i žrtve, već daju pasivnu ili aktivnu podršku nasilničkom ponašanju kroz zauzimanje različitih poduloga u okviru uloge posmatrača (asistenti nasilniku, podstrekači nasilnika, branioci žrtve i autsajderi). Sagledavanje povezanosti uloga u vršnjačkom nasilju i školskog uspeha učenika, kao i faktora koji mogu uticati na jačinu navedene veze, važno je sa aspekta Školske i Socijalne pedagogije, ali je značajno i za školsku praksu, jer može da ukaže na mogućnosti i načine uspešnog ostvarivanja preventivnog delovanja škole. Rad je imao za cilj da se ispita povezanost između uloge u nasilju (nasilnik, žrtva, asistent, podstrekač, autsajder i branilac) i školskog uspeha učenika, kao i da se razradi predlog preventivnog i interventnog pedagoškog delovanja u tom domenu. Kao osnovne tehnike istraživanja korišćene su tehnika nominacije (sociometrijska tehnika) i skaliranje. Putem primene skaliranja nastojalo se da se utvrdi koju ulogu učenik najčešće ima u situacijama vršnjačkog nasilјa, dok je sociometrijska tehnika primenjena kako bi se utvrdio sociometrijski status učenika. Oslanjajući se na tehniku analize sadržaja, izvršena je i analiza postojećih Programa zaštite učenika od nasilja, kako bi se utvrdilo koje mere i aktivnosti škole nameravaju da realizuju u pravcu predupređivanja vršnjačkog nasilja. Rezultati istraživanja pokazuju da se za većinu učenika mogu utvrditi učesničke uloge u nasilju. Utvrđeno je da postoji povezanost između pojedinih uloga u nasilju i sociometrijskog statusa učenika; između uloge u nasilju i školskog uspeha učenika; između uloge u nasilju i pola učenika; između uloge u nasilju, pola i školskog uspeha učenika; između uloge u nasilju, sociometrijskog statusa i školskog uspeha učenika; između učestalosti nasilja na nivou odeljenja i školskog uspeha učenika i između učestalosti nasilja na nivou škole i školskog uspeha učenika. Analiza postojećih Programa zaštite učenika od nasilja je pokazala da postoje mogućnosti za poboljšanje preventivnog i interventnog delovanja škole u nastojanju da se smanji učestalost vršnjačkog nasilja. Saznanja do kojih se došlo empirijskim istraživanjem poslužila su kao osnov za razradu predloga preventivnih i interventnih mera i aktivnosti koje se mogu primenjivati u školama u cilju smanjenja ispoljavanja vršnjačkog nasilja i, indirektno, prevencije školskog neuspeha učenika.Bullying and academic achievement represent two important pedagogical problems whose examination contributes to the improvement of the educational activities of a modern school. The standpoint which is dominant today implies that the study of bullying needs to incorporate the roles played in that process by students not directly involved in it as bullies or victims, but who provide passive or active support to the bullying behaviour by assuming various subroles within the bystander role (assistants of the bully, reinforcers of the bully, defenders of the victim, and outsiders). Observing the connection between bullying and academic achievement of students, as well as other factors which may affect the intensity of the said connection, is important not only from the perspective of School pedagogy and Social pedagogy, but also significant for school practice, since it can point to the possibilities and manners of a successful preventive action which school can undertake. The thesis aims at studying the link between a role in bullying (bully, victim, assistant, reinforcer, outsider, and defender) and academic achievement of students, as well as developing a proposal for preventive and interventive pedagogical action in this field. The nomination technique (sociometric technique) and scaling were used as basic research techniques. Scaling was applied to determine which role is most often performed by a student in bullying situations, while the sociometric technique was employed to determine the sociometric status of students. Relying upon the technique of content analysis, the existing Programs for the protection of students against bullying were analyzed to determine which measures and activities schools intend to implement so as to prevent bullying. Research results show that the participating roles in bullying situations can be determined for the majority of students. It is concluded that there is a connection between certain roles in bullying and the sociometric status of students; between certain role in bullying and academic achievement of students; between the role in bullying and students’ sex; between certain role in bullying, sex and academic achievement of students; between certain role in bullying, sociometric status and academic achievement of students; between the frequency of bullying at the class level and academic achievement of students, and between the frequency of bullying at the school level and academic achievement of students. The analysis of the existing Programs for the protection of students against bullying showed that there are opportunities for the improvement of the preventive and interventive actions carried out by a school in order to reduce the frequency of bullying. The findings yielded by empirical research served as the basis for the development of proposals for preventive and interventive measures and activities which can be implemented in schools with the aim of reducing the occurrence of bullying and, indirectly, the prevention of school failure of students

Temperature controller optimization by computational intelligence

In this paper a temperature control system for an automated educational classroom is optimized with several advanced computationally intelligent methods. Controller development and optimization has been based on developed and extensively tested mathematical and simulation model of the observed object. For the observed object cascade P-PI temperature controller has been designed and conventionally tuned. To improve performance and energy efficiency of the system, several meta heuristic optimizations of the controller have been attempted, namely genetic algorithm optimization, simulated annealing optimization, particle swarm optimization and ant colony optimization. Efficiency of the best results obtained with proposed computationally intelligent optimization methods has been compared with conventional controller tuning. Results presented in this paper demonstrate that heuristic optimization of advanced temperature controller can provide improved energy efficiency along with other performance improvements and improvements regarding equipment wear. Not only that presented methodology provides for determination and tuning of the core controller, but it also allows that advanced control concepts such as anti-windup controller gain are optimized simultaneously, which is of significant importance since interrelation of all control system parameters has important influence on the stability and performance of the system as a whole. Based on the results obtained, general conclusions are presented indicating that meta heuristic computationally intelligent optimization of heating, ventilation, and air conditioning control systems is a feasible concept with strong potential in providing improved performance, comfort and energy efficiency

Zlato u prošlosti, sadašnjosti i budućnosti

This paper deals with gold, which is described as a chemical element. Special attention is paid to its physical-chemical properties and, furthermore, where or in what form it can be found in nature. We discuss the role it has played through history and we inform how gold has been developed to the level it has reached today’s value. Still more, when gold is broken into nanoparticles, this form could be highly useful for a wide range of processes, including general nanotechnology, electronics manufacturing and the synthesizing of different functional materials. It is important that we know that gold is also used in industry in many engineering applications (contacts in micro-electronics) and medicine (dental alloys, implants).Ovaj članak govori o zlatu kao kemijskom elementu. Posebna pažnja posvećena je njegovim fizikalno-kemijskim svojstvima i gdje i u kojem obliku se može pronaći u prirodi. Razmatra se uloga koju je zlato odigralo u povijesti i donosi se informacije o tome kako je doseglo razinu vrijednosti koju ima danas. Zlato razlomljeno na nanočestice upotrebljivo je u širem spektru procesuiranja, uključujući opću nanotehnologiju, elektroničku prizvodnju i spajanju materijala raznih funkcionalnosti. Važno je znati da se zlato koristi i u industriji, mnogim inženjerskim procesima (kontakti u mikro-elektronici) i medicini (dentalne slitine, implatanti)

Optimization-simulation approach to solving stochastic programming problems

Стохастичко програмирање је део операционих истраживања које се бави начином на који је могуће укључити неизвесност у процес доношења одлука и које прихвата чињеницу да доносиоцу одлуке неће увек бити доступне све потребне информације. Основни проблем у примени стохастичких модела произилази из неизвесности параметара и чињенице да се оптимално решење дефинише и добија за детерминистички двојник (представник) оригинала. Проблем је оценити квалитет решења одређеног детерминистичког двојника са становишта вредности критеријумске функције, која може бити случајног карактера, као и са становишта вероватноће задовољења стохастичких ограничења. Проблеми стохастичког програмирања се појављују у различитим областима, али неки од најчешће решаваних проблема су у области планирања производње, ланца снабдевања, логистике, транспорта, управљање портфолиом, маркетинга и уопште у области финансија као и у многим другим областима. Приступи решавању проблема стохастичког програмирања се могу поделити у три основна правца: стохастичка оптимизација, робусна оптимизација и вероватносно задовољење ограничења (chance constrained programming) и који представљају полазну тачку свих даљих истраживања у овој области оптимизације. Робусни приступ је конзервативни приступ који је оријентисан на најгори могући сценарио уз дефинисање таквог детерминистичког двојника оригиналног проблема у коме се елиминише сва неизвесност из модела. Вероватносно задовољење ограничења је приступ који посебно третира неизвесност која се јавља у параметрима ограничења и посебно се бави решавањем таквих проблема. Основна претпоставка у овом приступу је да је потребно задовољити неко ограничење које је неизвесно, са најмање унапред одређеном вероватноћом. Повод за развој и примену приступа вероватносног задовољења ограничења је потреба да се скуп ограничења опише у смислу дефинисања вероватноће задовољења ограничења која представља ризик који је доносилц одлуке спреман да прихвати да добијено оптимално решење неће бити допустиво. Основни и најзахтевнији изазов приступа вероватносног задовољења ограничења је његова рачунска изводљивост, која је пре свега повезана са могућношћу проналажења расподеле вероватноће случајних променљивих...Stochastic programming is a part of the operational research which investigates ways to incorporate uncertainty in the process of decision-making and that accepts the fact that the decision maker will not always have all the information needed readily available. The main problem in application of stochastic programming comes from the uncertainty of parameters in model and the fact that optimal solution is defined for the deterministic equivalent (double) of the original problem. Another problem is to evaluate the quality of a specific deterministic equivalent from the perspective of the value of criterion function, that can be a random, as well as from the perspective of probability of satisfying stochastic constraints. Stochastic programming is applied in many areas, and some of the most common problems solved using stochastic programming are in the fields of production planning, supply chains, logistics, transportation, portfolio management, marketing and in the field of finance, and many other areas. There are three common approaches in solving stochastic programming problems: stochastic optimization, robust optimization and chance constrained programming, and they represent the starting point of all the research in this field of optimization. Robust optimization is a conservative approach that is orientated on the worst case scenario by defining such a deterministic equivalent of the original problem that removes all uncertainty from the model. Chance constrained programming is an approach that treats uncertainty in the parameters of the constraints in the model and uses different techniques in solving these problems. The basic presumption in this approach is that a certain constraint, which is stochastic and uncertain, has to be satisfied with a predefined probability. The reason for developing and application of such an approach is the need to describe the constraints in such a manner that the predefined probability of satisfying constraints is actually a risk that the solution obtained won‘t be satisfied and which the decision maker is willing to accept. The main and most challenging part of the chance constraint approach is tractability, that is above all connected to the possibility of finding the appropriate probability distributions of the stochastic parameters

Investigation of phase equilibria and characterization of alloys in the Bi-Cu-Ni system

Fazne ravnoteže u Bi-Cu-Ni ternarnom sistemu proucavane su eksperimentalnim metodama (SEM-EDS, DTA i DSC), kao i analiticki primenom CALPHAD metode. Proracun ravnotežnih faznih dijagrama u Bi-Cu-Ni sistemu izveden je na osnovu optimiziranih termodinamickih parametara za sastavne binarne sisteme i dodatnih termodinamickih parametara, odredenih u ovom radu. Proracunati fazni dijagrami izotermalnih preseka na 300oC, 400oC i 500oC uporedeni su sa eksperimentalnim rezultatima iz literature i ustanovljeno je dobro medusobno slaganje. Definisani su ternarni termodinamicki parametri za tecnu fazu, i BiNi fazu u kojima je uzeta u obzir eksperimentalno potvrdena rastvorljivost bakra u BiNi fazi. Proracunati fazni dijagrami tri vertikalna preseka uporedeni su sa DTA/DSC rezultatima iz ovog rada. Odredene su tvrdoca i elektricna provodljivost kao dopunska karakterizacija legura ispitivanog Bi-Cu-Ni ternarnog sistema.Phase equilibria in the Bi-Cu-Ni ternary system have been studied experimentally using SEM-EDS, DTA and DSC methods, and analytically using CALPHAD method. Calculation of equilibrium phase diagrams of Bi-Cu-Ni system was performed using optimized thermodynamic parameters of the constituent binary systems and additional thermodynamic parameters determined in this study. Calculated isothermal sections at 300oC, 400oC and 500oC were compared with experimental results from the literature and good agreement is found. Ternary thermodynamic parameters for the liquid phase were determined, as well as for the BiNi phase, in which the experimental confirmation of copper solubility in BiNi phase was taken into account. Three calculated vertical sections were compared with the DTA/DSC results from this work. Hardness and electrical conductivity as an additional characterization of the investigated alloys of Bi-Cu-Ni ternary system were determined