Optimal detection and error exponents for hidden semi-Markov models

We study detection of random signals corrupted by noise that over time switch their values (states) between a finite set of possible values, where the switchings occur at unknown points in time. We model such signals as hidden semi-Markov signals (HSMS), which generalize classical Markov chains by introducing explicit (possibly non-geometric) distribution for the time spent in each state. Assuming two possible signal states and Gaussian noise, we derive optimal likelihood ratio test and show that it has a computationally tractable form of a matrix product, with the number of matrices involved in the product being the number of process observations. The product matrices are independent and identically distributed, constructed by a simple measurement modulation of the sparse semi-Markov model transition matrix that we define in the paper. Using this result, we show that the Neyman-Pearson error exponent is equal to the top Lyapunov exponent for the corresponding random matrices. Using theory of large deviations, we derive a lower bound on the error exponent. Finally, we show that this bound is tight by means of numerical simulations

Teorijski pristupi liderstvu u obrazovanju

In the paper we take into consideration a short review and the analysis of the major theoretical approaches to leadership with the special attention to modern thining about leadership in education. It is determined which approaches represent good basis for planning the activities with the purpose of promoting leadership in schools. The main conclusion of the analysis is that the shown theoretical approaches shed light to different aspects of leadership and that in the theoretical researches and practical considerations it is the integrative approach very often in need. The integrated leadership gives very pragmatic and operative frame for action in the direction of leadership.Polazeći od toga da su u domaćoj literaturi malobrojni pregledni radovi o liderstvu u obrazovanju, u ovom radu napravili smo kratak prikaz i analizu glavnih teorijskih pristupa liderstvu, sa posebnim osvrtom na savremena razmišlja- nja o liderstvu u obrazovanju, kako bismo utvrdili koji pristupi predstavljaju dobru osnovu za planiranje aktivnosti u cilju unapređivanja liderstva u školama. Jednim delom, reč je o pristupima koji se odnose na liderstvo “uopšte”, dok su drugi pristupi (poput transformativnog, pedagoškog i integrisanog liderstva) čvrsto zasnovani na nalazima istraživanja u obrazovanju. Glavni zaključak analize je da prikazani teorijski pristupi osvetljavaju različite aspekte liderstva i da je u teorijskim, istraživačkim i praktičnim razmatranjima često nužno imati integrativni pristup. Upravo zato se u radu posebno ističe značaj integrisanog liderstva kao savremenog pristupa koji, pored toga što je teorijski i empirijski dobro zasnovan, pruža veoma pragmatičan i operativan okvir za delovanje u pravcu razvoja liderstva u školama

Implicitne pedagogije nastavnika i njihova inicijativa za saradnju s roditeljima

The article presents an analysis of the results of the research aimed at examining the relatedness of the teachers' implicit pedagogies and their initiatives for cooperation with students' parents. The starting hypothesis was that the acceptance of modern pedagogical ideas (new pedagogic paradigm) leads towards more successful initiative of the teachers for the cooperation with their students' parents. The sample included 118 subject teachers and 78 class teachers from elementary schools in Serbia. The procedure included a correlation chart and special assessment scales were construed for examining implicit pedagogies and teacher's readiness for cooperation with parents. The results indicate the lack of the initiative of both groups of teachers for enhanced cooperation with parents as it should be in modern school. The research showed the implicit pedagogies of the teachers are still somewhere between traditional and modern pedagogic ideas. Subject teachers showed lower levels of initiative for cooperation with parents, as well as lower levels of acceptance of the 'new pedagogic paradigm' in comparison with class teachers. Among the latter the relatedness of their implicit pedagogies and initiatives for cooperation with parents was established, while it was not evident among subject teachers. In order to enhance the cooperation between school and family the existing personal pedagogic ideas of the teachers should change and come closer to the 'new pedagogic paradigm' which might be achieved through pre-service and in-service teacher training and provision of more support by school and educational system.U radu su analizirani rezultati istraživanja koje je imalo za cilj ispitivanje povezanosti implicitnih pedagogija nastavnika i njihove inicijative za saradnju s roditeljima. Polazi se od pretpostavke da prihvatanje savremenih pedagoških ideja (nova pedagoška paradigma) doprinosi većoj inicijativi nastavnika za saradnju s roditeljima. U istraživanju je učestvovalo 118 nastavnika predmetne nastave i 78 nastavnika razredne nastave iz osnovnih škola u Srbiji. Primenjen je korelacioni nacrt, a za ispitivanje implicitnih pedagogija i inicijative nastavnika za saradnju s roditeljima kreirane su skale procene. Rezultati ukazuju na nedostatak inicijative učitelja i nastavnika za produbljeniju saradnju s roditeljima, kakva bi u savremenoj školi trebalo da se odvija. Istraživanje je pokazalo da su implicitne pedagogije nastavnika još uvek između tradicionalnih i savremenih pedagoških ideja. Rezultati našeg istraživanja ukazuju na manju inicijativu nastavnika predmetne nastave za saradnju s roditeljima, kao i na njihovo manje prihvatanje 'nove pedagoške paradigme', u poređenju s učiteljima. Kod nastavnika razredne nastave je utvrđena povezanost između njihovih implicitnih pedagogija i inicijative za saradnju s roditeljima, dok ta povezanost nije uočena kod predmetnih nastavnika. Za poboljšanje saradnje škole i porodice neophodno je da se postojeća lična pedagoška uverenja nastavnika promene i približe 'novoj pedagoškoj paradigmi', putem inicijalnog obrazovanja i daljeg stručnog usavršavanja nastavnika, kao i kroz obezbeđivanje veće podrške na nivou škole i obrazovnog sistema

Strategic Management and its Effects on Serbian Wood Industry

According to the available data on economic trends in Serbia, it is noticeable that companies in wood in-dustry do not use their capacities to the maximum. Furthermore, a significant number of newly founded small en-terprises, shortly after their establishment, go bankrupt or go into liquidation. Research works that have beenconducted so far have indicated that, most commonly, company deterioration is caused by a lack of strategic ap-proach in business management and company development. The aim of this paper is to gain an insight into the ex-tent to which wood industry enterprises apply strategic approach (their vision, mission and development strategies)when making business decisions, as well as the effects of such approach. This will be achieved by analyzing col-lected questionnaires and interviews with competent experts from wood industry monitoring institutions. Besides,SWOT and PESTLE analyses of the surveyed companies will be conducted. Furthermore, possible solutions forovercoming weaknesses and threats emerging in Serbian wood industry development will be indicated. Likewise,the possibilities for encouraging industry development and increasing its competitiveness level will be presented

On some verbal short-term and working memory properties in patients suffering from clinical depression

Veza depresije i kratkoročnog verbalnog pamćenja nije jednoznačno rasvetljena. Deficiti kratkoročnog pamćenja (KP) depresivnih pacijenata doslednije se ispoljavaju u zadacima koji iziskuju efikasnost radne memorije (RM) i s njom skopčanu izvršnu pažnju no što je to slučaj sa zadacima isključivo pasivnog skladištenja jezičkog materijala u kratkoročnu memoriju (KM). Cilj istraživanja. Primarni cilj bio je pribavljanje nalaza o verbalnom KP kod pacijenata na lečenju od depresije u domaćim ustanovama. Proverili smo dodatno upotrebljivost subtestova RM skale WAIS IV za procenu problema KP kod depresivnih pacijenata. Metod. Uporedili smo uzorak pacijenata na lečenju od depresije s paralelnom grupom zdravih ispitanika u pogledu učinka na subtestovima 'Aritmetika', 'Ponavljanje brojeva' i 'Slova pa brojevi', kao i na zadacima slobodnog prisećanja lista reči i semantičke fluentnosti bez promene kategorije i s promenom kategorije. Rezultati. Mere učinka u zadacima RM, sa izuzetkom 'Ponavljanja brojeva unazad', razlikuju grupe depresivnih pacijenata i kontrolnih ispitanika. Zadaci pasivnog pohranjivanja verbalnog materijala u KM, sa izuzetkom KP lista reči, ne pružaju tu mogućnost. Za pomenute izuzetke ponudili smo objašnjenje u terminima efikasnosti RM. Od subtestova WAIS IV, 'Aritmetika', 'Ponavljanje brojeva rastućim redosledom' i 'Slova pa brojevi' diskriminišu depresivne pacijente i kontrolne ispitanike. Učinak u zadacima KP nalazi se u srednjoj do visokoj negativnoj korelaciji sa intenzitetom depresije. Zaključak. Problemi KP pacijenata sa depresijom pre se mogu očekivati u zadacima koji iziskuju izvršnu pažnju i efikasnost RM nego u uobičajenim zadacima procene opsega verbalne KM. Deficiti verbalnog KP u negativnoj su vezi sa intenzitetom depresije.Clinical depression with verbal short-term memory relation research does not yield unequivocal results. While short-term memory (STM) deficits in depressed patients are consistently displayed in working memory (WM) and executive attention tasks, for STM passive memorizing tasks this holds less correct. Objective. Primary goal was to collect initial data on depressed patients treated in Serbian institutions WM/ STM. In addition, we estimated the power of WAIS IV WM subtests to discriminate depressed patients from normal subjects. Method. Depressed patients' sample was contrasted with the parallel group in WAIS' IV Arithmetic, Digit Span, and Letter- Number Sequencing; free word recall task, semantic fluency task, without and with category switching. Results. All the WM measures, with the exception of Digit Span Backward score, discriminate depressed from no depressed subjects. On the other hand, STM tasks, with the exception of short-term word free recall, fail to do the same. We suggest explanation for both the exceptions in terms of WM efficiency. WAIS IV Arithmetic, Digit Span Sequencing and Letter-Number Sequencing can be used to discriminate depressed from control subjects. Performance in STM/WM tasks is in moderate to strong negative correlation with depression severity as assessed with the Hamilton scale. Conclusion. STM deficits in the depressed are likely to be observed in tasks requiring executive attention and WM efficiency rather than in standard STM span tasks. The deficits are inertly related to depression severity

Some implications of an experimental reading comprehension task

Standardizovani testovi sposobnosti čitanja sa razumevanjem (TČR) predstavljaju nezamenljivi instrument za procenu jezičkih sposobnosti. Uprkos tome, mi ne raspolažemo takvim instrumentom na srpskom jeziku. U ovom radu izneli smo i pokušali da proverimo održivost koncepcije TČR za koju se zalažemo. Predlažemo TČR u kojem će se materijal za čitanje sastojati od većeg broja kratkih novinskih tekstova, čija bi se shvaćenost proveravala po jednim pitanjem tipa višestrukog izbora, a tekst i odgovarajuće pitanje bi se izlagali sukcesivno, ne jednovremeno. TČR sačinjen od stavki ovakvog sadržaja i oblika uz predloženi oblik zadavanja trebalo bi da, po našoj proceni, pored određenih praktičnih pogodnosti, poseduje jednaku ili bolju hipotetičku valjanost od dobropoznatih TČR na stranim jezicima. Naše postavke operacionalizovali smo eksperimentalnim zadatkom čitanja sa razumevanjem (EZČR), koji je na uzorku studenata izveden pomoću računara, primenom opisanog materijala i postupka. Rezultati pokazuju da EZČR poseduje dobru diskriminativnost i pouzdanost nešto slabiju od optimalne. Analiza strukture i intenzitet veza skorova u EZČR sa skorovima na ostalim testovima inteligencije ukazuju na to da ovaj zadatak pripada prostoru koji definišu dobropoznati jezički testovi. Različite strategije rešavanja EZČR nisu imale uticaja na glavnu meru učinka, a to je broj tačnih odgovora. Nalazi do kojih smo došli primenom EZČR podržavaju koncepciju TČR koju predlažemo. Stoga smo predložili i moguća dalja istraživanja u pravcu konstrukcije standardnog TČR na srpskom jeziku.Standardized reading comprehension tests (RCTs) are indispensable instruments in language abilities assessment. Nevertheless, we do not have such an instrument in Serbian. In the present paper, we attempted to verify the basic assumptions of the RCT conception we proposed: the reading material consisting of a relatively large selection of short newspaper articles followed by a single multiplechoice question each, displayed in temporal succession, not simultaneously. We argued that RCT consisting of such item form and content, as well as the administration procedure, should be of equal or even better construct validity than well-known RTCs in foreign languages, also possessing some other practical advantages. These assumptions were implemented in a computer-ran experimental reading comprehension task (ERCT), in a student sample. ERCT psychometric properties analyses showed good discriminability and somewhat less than preferable reliability. The structure and strength of ERCT x other intelligence tests correlations suggest ERCT belonging to the core of verbal abilities tests. Different strategies subjects employed showed no impact on major performance measure number correct answers. Our findings obtained by ERCT implementation support the RCT conception we propose. We therefore suggest possible further research towards the construction of standardized RCT in Serbian

The value of modified DASH questionnaire for evaluation of elbow function after supracondylar fractures in children

Background/Aim. The Disabilities of the Arm, Shoulder and Hand (DASH) Outcome Questionnaire represents a region- specific instrument for functional outcome measurement of hand function. The aim of the study was to analyze the correlation between the values of modified DASH questionnaire and change of elbow function after supracondylar fracture (SCF) of humerus and to analyze the effects of early rehabilitation. Methods. The study included 35 schoolaged children with flexion of SCF of humerus without lesion of nerves. The patients were divided into two groups: group A in which rehabilitation started up to 14 days after the removal of fixation (20 children), and group B in which rehabilitation started after 15 days and more (15 children). The effects of the applied rehabilitation procedures were analyzed by measuring the range of motion of elbow and using modified DASH questionnaire. Testing was performed during the first examination, on the first day of rehabilitation (retest) and after the rehabilitation. Pearson's coefficient of liner correlation was applied. Results. Statistically significant negative correlation of DASH score and extension was verified in all three measurements. The values for the first test and for the final test were highly significant (p < 0.001), as well as negative correlation of DASH score and flexion on the first test and retest (p < 0.01), and at the end of rehabilitation (p < 0.001) in the group B. For all three tests in the group A negative correlation without significant differences for DASH score and flexion was found. Conclusion. A modified DASH questionnaire correlates with objective parameters of final status of elbow after SCF in children and it is applicable to small series of patients. A positive effect of early rehabilitation of children with SCF was found

EDITORIAL

We would like to thank, first of all, authors of the articles published in this Issue of the Journal. At the same time, we feel grateful to all the referees for their valuable help in selecting the papers and improving their quality

Approximation of Electric Field in Biological Tissue

This paper presents the method of homogenization of several different biological tissues in order to simplify the numerical calculation of the electric field distribution in certain biological structures of interest. For this purpose, a 3D model was used with blocks that have the same electromagnetic characteristics as their corresponding biological tissues of the human head. The results obtained in the case of homogenized block model were compared with the ones obtained by using the original heterogeneous model containing the following tissues: skin, fat, muscle, bone, and brain. Homogenization of the model has been caried out only for the layers that precede the layer in which the analysis of electric field distribution was performed. A smart phone was used as the source of electromagnetic radiation at a frequency of 0,9 GHz. A comparative analysis of the electric field intensity in the layer of interest indicates good matches for the heterogeneous and homogenized models. Based on the obtained results, deviations in the electric field intensity can be observed for both models. These deviations range from 3,7% to 5,2% for different layer thicknesses.The proposed homogenization method significantly simplifies the modelling and also reduces the simulation time required to obtain appropriate results