A marine propeller as a hydrokinetic turbine - CFD analysis of energy characteristics

It is sometimes economically unreasonable to develop specific turbines, but rather to use a well-known concept of a pump in the turbine mode - PAT (Pump As Turbine). Inspired by PAT, the scope of this paper covers the assessments of the possibility to use marine propellers as runners for the hydrokinetic turbines. Numerical analyses are conducted for selected propeller geometry with the aim of evaluating its energy characteristics in the turbine regime. The chosen propeller belongs to the conventional, thoroughly experimentally tested, Wageningen B -screw series. The experimental data were used for validation of the numerical results in propeller regimes. Based on the obtained results, the researched non-optimized turbine in its optimum regime achieves a satisfactory power coefficient which is close to the value of other types of contemporary hydrokinetic turbines efficiencies

Development of methods for polymer networks and hybrid materials synthesis

U ovom radu vršena su istraživanja u cilju razvoja novih postupaka sinteze za nekoliko vrsta polimernih mreža i hibridnih biopolimernih materijala za specijalne primene. Cilj je bio da se razvije novi postupak sinteze rotaksana na bazi poli(etilen glikola) i β-ciklodekstrina kaoprekursora mreža. Dobijeni prekursori mreža iskorišćeni su za sintezu topoloških gelova koji su umreženi preko hidroksilnih grupa ciklodekstrinskih prstena. Analiziran je i uticaj količine umreživača, odnosno gustine umreženja, na svojstva bubrenja. Proučavan je i uticaj nanopunila na svojstva modelnih epoksi mreža na bazi bisfenola A i poli(oksi propilen) diamina. Kao punila korišćene su nanočestice nemodifikovanog i površinski modifikovanog titanijum(IV)oksida (TiO2). Dinamičko-mehaničkom analizom potvrđen je ojačavajući efekat punila. Razvijen je postupak sinteze poli(D,L-laktida) u mikrotalasnom polju, čime je drastično smanjeno vreme polimerizacije (sa 150 sati na 15 minuta) u odnosu na klasičnu termosintezu. Sintezom poli(laktida) kao i kopolimera poli(laktida) sa biorazgradivim monomerima (na osnovu obnovljivih sirovina) dobijeni su materijali izuzetnih ekoloških svojstava. Poli(laktid) se odlikuje veoma dobrim mehaničkim svojstvima i biorazgradivošću, dok je blok-kopolimerizacijom sa drugim biorazgradivim monomerima vršena sinteza termoplastičnih poliestara. Variranje dužine segmenata je ostvareno sintezom adekvatnih oligomera kao prekursora za kopolimerizaciju. Vršeno je projektovanje sirovinskog sastava segmentiranih elastomera kod kojih postojanje mekih i tvrdih segmenata ima za posledicu mikrofaznu separaciju faza što u toku eksploatacije utiče na mehanička svojstva i mogućnost III razgradnje. Na taj način dobijeni su elastomerni materijali željenih svojstava. Metodama FTIC i 1H NMR spektroskopijom potvrđena je pretpostavljena struktura segmenata i finalnih termoplastičnih poliestara. Analizom molskih masa poliestara metodama gel propusne hromatografije, viskozimetrije i osmometrije napona pare, potvrđena je izuzetna kontrola reakcija polimerizacije i uspešnost primenjenih metoda sinteze. Analiza toplotnih svojstava blok poliestara diferencijalno skenirajućom kalorimetrijom je pokazala da zbog nemešljivosti faza, tvrdih i mekih segmenata, finalni blok poliestri mogu da pokažu razlike u temperaturama faznih transformacija u zavisnosti od dužine i udela segmenata. Termogravimetrijskom analizom je potvrđen uticaj dužine segmenata i faznog razdvajanja na toplotna svojstva termoplastičnih poliestara. Očekuje se da će sintetisani materijali biti podesni za primene u inženjerstvu tkiva, a posebno kao materijali za kontrolisano otpuštanje lekova.The primary goal of the work described in this thesis was to develop new methods for the synthesis of polymer networks and hybrid biopolymers for special applications. The purpose was a development of synthesis procedure for the preparation of rotaxane based on poly(ethylene glycol) and β-cyclodextrin, as network precursors. These network precursors were then cross-linked through hydroxy groups on cyclodextrine rings. Polyrotaxanes are intermediary products in the synthesis of topological gels and they are formed by the insertion of the linear polymer chains of poly(ethylene oxide) into the β-CD cavities. In this work polyrotaxanes from acetylated-β-CD and poly(ethylene oxide) were synthesized. The influence of crosslinker contents, and crosslink density on swelling properties was investigated. The influence of synthesis parameters and filler modification on reactions and final properties of organic-inorganic hybrid materials based on epoxy resin and an organically modified titanium(IV)oxide (TiO2) was investigated. Dynamic-mechanical analysis was used to determine reinforcement effect of nanofiller on the epoxy resin properties. The aim of this work was the investigation of microwave irradiation on the polymerization of D,L-lactide. It was found that if heating is carried out in the microwave field polymerization time of D,Llactide rapidly decreases from 150 hours to 15 minutes. Environmentally friendly materials were obtained from poly(lactide) and copolymers of poly(lactide) and monomers based on renewable resources. Poly(lactide) is biocompatible and biodegradable polymer with high stretching and low extension capacities. It has been used for the production of orthopedic fraction fixators and sutures surgery. Poly(lactide) was used for thermoplastic polyester (TPE) synthesis. Most thermoplastic polyesters derive their properties from segmented or block structures which are achieved by alternating hard and soft segments. FT-IR and 1H NMR spectroscopy were confirmed the assumed structure of segments and final thermoplastic polyesters. Since the properties of these materials strongly depend on the degree of phase separation, the influence of the lenghts of soft and hard segment on final properties of obtained TPEs was studied. Analysis of molecular mass of these polyesters by gel permeation chromatography, vapor pressure osmometry and viscozimetric analysis confirmed that good control of polymerization was achieved and that synthesis methods were successful. Thermal properties were characterized by means of differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Phase separation had strong influences on thermal properties of obtained TPEs. DCS measurements showed that due to poor mixability of hard and soft segments, final block polyesters could have different temperatures of phase transitions depending on the length of the segments. Thermal degradation and the influence of phase separation on thermal stability of segmented thermoplastic polyesters were confirmed by nonisothermal analysis, using thermogravimetric analysis. It is expected that synthesized materials will be suitable for tissue engineering and as drug carriers

A marine propeller as a hydrokinetic turbine - CFD analysis of energy characteristics

It is sometimes economically unreasonable to develop specific turbines, but rather to use a well-known concept of a pump in the turbine mode - PAT (Pump As Turbine). Inspired by PAT, the scope of this paper covers the assessments of the possibility to use marine propellers as runners for the hydrokinetic turbines. Numerical analyses are conducted for selected propeller geometry with the aim of evaluating its energy characteristics in the turbine regime. The chosen propeller belongs to the conventional, thoroughly experimentally tested, Wageningen B -screw series. The experimental data were used for validation of the numerical results in propeller regimes. Based on the obtained results, the researched non-optimized turbine in its optimum regime achieves a satisfactory power coefficient which is close to the value of other types of contemporary hydrokinetic turbines efficiencies

Bogdan Bogdanović

Bogdan Bogdanović (geboren 1922) zählte zu den herausragendsten Denkmalarchitekten und Architekturtheoretikern im ehemaligen Jugoslawien. Im Jahr 2005 brachte er seinen Vorlass in die Sammlung des Architekturzentrums Wien ein, wodurch mehr als 12.500 Skizzen, Pläne und Architekturfantasien auf Papier sowie eine umfangreiche Fotodokumentation einem breiten Kreis der Forscherinnen zugänglich wurden. Auch bot sich durch diese großzügige Schenkung die Möglichkeit, im Frühling 2009 im der Alten Halle des Architekturzentrums die bislang umfangreichste Retrospektive des Architekten zu präsentieren. In der Ausstellung galt das Augenmerk vor allem Memorialarchitekturen – den Langzeitexperimenten, in welchen die Linearchronologien, ja fallweise auch die Realisierungen selbst eine untergeordnete Rolle spielten. Denn Bogdanović zeichnete das jeweilige Objekt auch nach dessen Realisierung und ließ dadurch, wie er es treffend formuliert, grafische Romane entstehen; nicht anders verhielt sich dies mit seinen teils utopischen Wohnbauprojekten. Dabei ist zu bedenken, dass es nach Titos Bruch mit Stalin (1948) in Jugoslawien zu einer gesellschaftlichen Liberalisierung und einer Annäherung an den Westen kam. Um sich vom Ostblock abzuheben, begab sich der junge sozialistische Staat auf die Suche nach einer eigenen visuellen Identität. In welcher Form sollte man nun der Gefallenen im Zweiten Weltkrieg und der Opfer des Faschismus gedenken? Es bedurfte mehr als eines sozialistischen Realismus oder einer abstrakten Bildhauerei, deren Stunde nun auch in den Staaten des Warschauer Paktes geschlagen hatte. Bogdan Bogdanović entschied sich für eine eigene ideologiefreie, zivilisationenübergreifende Architektursprache. Bis Anfang der 1980er Jahre entstanden neunzehn Gedenkstätten, die nahezu über das gesamte Gebiet Ex-Jugoslawiens verstreut liegen. Für jeden Denkmalort entwickelte der unermüdliche Zeichner jeweils neue Formen im Dialog mit den lokalen Gegebenheiten. Es liegt vor allem am Besucher, an Bogdanovićs Kenotaphen, Tumuli, Toren und Stadtabbreviaturen Geschichten abzulesen. Der vom Surrealismus geprägte Architekt interpretierte diese Orte, die zum Verweilen und Nachdenken einladen, selten selbst. Ein jeder ist Exeget, jedermanns Erinnerung ist gleich viel wert. Die beiden realisierten Wohnbauprojekte in der Nähe von Belgrad – eine Wohnsiedlung (1953) und der Umbau einer Villa (1961) – belegen Bogdanovićs Suche nach einer eigenen Formel in der Zeit der modernistischen Rezidive in den Bauformen. Sowohl im Rückgriff auf althergebrachte, scheinbar obsolet gewordene Baumaterialien als auch in seiner Vorliebe für das Ornament erinnern seine Grundsätze an diejenigen von Jože Plečnik. Bogdanović machte keinen Hehl aus seiner Bewunderung für den slowenischen Architekten. Vom Leitgedanken geprägt, wonach die älteste architektonische Niederschrift konzeptueller und nicht physischer Natur ist, führte Bogdanović 1973 als Professor der Architektonischen Fakultät in Belgrad den Kurs „Symbolische Formen“ ein. Es ging dabei nicht darum, einen Kanon der Symbole, also Kataloge leerer Insignien zu schaffen. Vielmehr wurden die Studierenden dazu angehalten, eigene bildliche Vorstellungen zu entwickeln, welche sich zwangsläufig mit Urformen aus einem allgemeinmenschlichen Bewusstsein decken würden. Bogdanovićs erstes Buch Der kleine Urbanismus ging aus einer Zeitungskolumne hervor. Ähnlich wie in Gordon Cullens Townscapes setzte er sich darin für die Perspektive des Einzelnen als Maß aller urbanistischen Eingriffe ein. Auch und vor allem tat sich Bogdanović aber als surrealistischer Exeget des klassischen Lehrgutes hervor. Zu seinen anregendsten Textschöpfungen zählt Der Kreis mit vier Ecken, eine „neopythagoräische“ Abhandlung, sowie Das Buch der Kapitelle, das durch eine gehörige Portion an Neologismen und seine Illustrationen besticht. Ego-Dokumente dieser Art, Archivalien sowie die vom Verfasser durchgeführte Gespräche mit dem Architekten machten die Zusammenstellung des ersten Werkverzeichnisses der Architektur- und Buchprojekte möglich, welches nun auch in der vorliegenden Dissertation enthalten ist.Bogdan Bogdanović (born 1922) is one of the most distinguished architects of memorials and architecture theoreticians in Ex-Yugoslavia. In 2005 he brought his papers to the collection of the Architekturzentrum Wien. In doing so, he made a living donation of over 12,500 sketches, plans and architectural fantasies on paper as well as extensive photographic documentation accessible to a broad circle of researchers. This generous gift has also provided an opportunity to host the most extensive retrospective by the architect held to date in the spring of 2009 in Architekturzentrum’s “Alte Halle”. The key focus in the exhibition was on the memorial architecture: long-term experiments where linear chronologies, sometimes even the execution itself, played a subordinate role. For Bogdanović also made drawings of the relevant building after its completion, creating, as he aptly put it, graphic novels; a similar approach is taken in his housing developments, some of which were utopian in character. One should bear in mind the fact that following Tito's break with Stalin (in 1948) Yugoslavian society became increasingly liberal and advancements were made towards the West. To separate itself from the Eastern Bloc, the young socialist state was searching for a new visual identity. What form should the commemoration take of those who fell in World War II and the victims of fascism? There was a need for more than a Socialist realist approach or abstract sculpture, whose last hour had also come in the states of the Warsaw Pact. Bogdan Bogdanović decided on a transcivilisational architectural language free of ideology. By the beginning of the 1980s nineteen commemorative sites had been completed, scattered throughout the former Yugoslavia. The untiring draughtsman developed new formal solutions for each of these locations in a dialogue with the local specifics. Seeing himself as an architect of the Old School, he placed great value on the interaction with the stonemasons. It is, above all, up to the visitors to read the histories in Bogdanović's cenotaphs, tumuli, gateways and iconic urban representations. Being imprinted by the surrealism, the architect himself seldom interpreted these locations, which are inviting places to linger and for contemplation. Everybody provides their own exegesis, everybody's memories are equally valid. Both of the realised housing projects at the outskirts of Belgrade – a housing estate (1953) and an adaptation of a Villa (1961) – bear testimony to Bogdanović's search for a formula of his own in the period of a modernist recidivism in the architecture sector. Both in the recourse to traditional, apparently obsolete building materials as well as in his preference for the ornament, his approach is reminiscent of that of Jože Plečnik. Bogdanović made no secret of his admiration for the Slovenian architect. Led by the notion that the oldest architectural writings are of a conceptual and not a physical nature, in 1973 Bogdanović launched in his function as professor of the Architecture Faculty in Belgrade a course on 'symbolic forms'. The aim was not to create a canon of the symbols, i.e. a catalogue of empty insignia, students were encouraged to engage in developing independent imagery of their own that would clearly correspond with archetypes from a shared human consciousness. Bogdanović’s first book, Small Urbanism, was compiled from a newspaper column. Like Gordon Cullen in Townscapes, he promoted the perspective of the individual as the scale for all urban interventions. Also, and above all, Bogdanović excelled as a surrealist exegete of the classical curriculum. Among his most stimulating texts are The Circle with Four Corners, a neo-Pythagorean treatise, and The Book of Capitals — the latter being captivating, with its considerable portion of neologisms and its illustrations. The ego-documents of this kind, records as well as the interviews with the architect enabled the autor to compile the first catalogue raisonné of Bogdanović’s architectural and illustration projects also included in the present dissertation

Disaster Risk Reduction Based on a GIS Case Study of the Čađavica River Watershed

Background and Purpose: Although natural hazards cannot be prevented, a better understanding of the processes and scientific methodologies for their prediction can help mitigate their impact. Torrential floods, as one of the consequential forms of the existing erosion processes in synergy with extremely high precipitation, are the most frequent natural hazard at the regional level, which was confirmed by the catastrophic events in May 2014 when huge territories of Serbia, Bosnia and Herzegovina and Croatia were flood-struck. The basic input data for the design of protective structures in torrential beds and watershed slopes are the values of the maximal discharge, area sediment yields, and sediment transport. The calculation of these values requires a careful approach in accordance with the characteristics of torrential watersheds, such as the steepness of slopes and beds in torrential watersheds, intensive erosion processes, favorable conditions for fast runoff formation and the transport of huge quantities of sediment. Materials and Methods: The calculations of maximal discharges, area sediment yields, and sediment transport in the experimental watershed of the Čađavica River were based on using two different spatial resolutions of digital elevations models (DEMs) – 20 m resolution DEM, with land use determined from aerial photo images, and the 90 m resolution DEM, with land use determined on the basis of the CORINE database. The computation of maximal discharges was performed by applying a method that combined synthetic unit hydrograph (maximum ordinate of unit runoff qmax) and Soil Conservation Service methodologies (deriving effective rainfall Pe from total precipitation Pb). The computation was performed for AMC III (Antecedent Moisture Conditions III – high content of water in the soil and significantly reduced infiltration capacity). The computations of maximal discharges were done taking into account the regional analysis of lag time, internal daily distribution of precipitation and classification of soil hydrologic groups (for CN – runoff curve number determination). Area sediment yields and the intensity of erosion processes were estimated on the basis of the “Erosion Potential Method”. Results and Conclusions: The selected methodology was performed using different input data related to the DEM resolution. The results were illustrated using cartographic and numerical data. Information on relief conditions is a vital parameter for calculating the elements of the environmental conditions through the elements of maximal discharge, area sediment yields and sediment transport. The higher precision of input data of DEM provides a more precise spatial identification and a quantitative estimation of the endangered sites

Development of methods for polymer networks and hybrid materials synthesis

U ovom radu vršena su istraživanja u cilju razvoja novih postupaka sinteze za nekoliko vrsta polimernih mreža i hibridnih biopolimernih materijala za specijalne primene. Cilj je bio da se razvije novi postupak sinteze rotaksana na bazi poli(etilen glikola) i β-ciklodekstrina kaoprekursora mreža. Dobijeni prekursori mreža iskorišćeni su za sintezu topoloških gelova koji su umreženi preko hidroksilnih grupa ciklodekstrinskih prstena. Analiziran je i uticaj količine umreživača, odnosno gustine umreženja, na svojstva bubrenja. Proučavan je i uticaj nanopunila na svojstva modelnih epoksi mreža na bazi bisfenola A i poli(oksi propilen) diamina. Kao punila korišćene su nanočestice nemodifikovanog i površinski modifikovanog titanijum(IV)oksida (TiO2). Dinamičko-mehaničkom analizom potvrđen je ojačavajući efekat punila. Razvijen je postupak sinteze poli(D,L-laktida) u mikrotalasnom polju, čime je drastično smanjeno vreme polimerizacije (sa 150 sati na 15 minuta) u odnosu na klasičnu termosintezu. Sintezom poli(laktida) kao i kopolimera poli(laktida) sa biorazgradivim monomerima (na osnovu obnovljivih sirovina) dobijeni su materijali izuzetnih ekoloških svojstava. Poli(laktid) se odlikuje veoma dobrim mehaničkim svojstvima i biorazgradivošću, dok je blok-kopolimerizacijom sa drugim biorazgradivim monomerima vršena sinteza termoplastičnih poliestara. Variranje dužine segmenata je ostvareno sintezom adekvatnih oligomera kao prekursora za kopolimerizaciju. Vršeno je projektovanje sirovinskog sastava segmentiranih elastomera kod kojih postojanje mekih i tvrdih segmenata ima za posledicu mikrofaznu separaciju faza što u toku eksploatacije utiče na mehanička svojstva i mogućnost III razgradnje. Na taj način dobijeni su elastomerni materijali željenih svojstava. Metodama FTIC i 1H NMR spektroskopijom potvrđena je pretpostavljena struktura segmenata i finalnih termoplastičnih poliestara. Analizom molskih masa poliestara metodama gel propusne hromatografije, viskozimetrije i osmometrije napona pare, potvrđena je izuzetna kontrola reakcija polimerizacije i uspešnost primenjenih metoda sinteze. Analiza toplotnih svojstava blok poliestara diferencijalno skenirajućom kalorimetrijom je pokazala da zbog nemešljivosti faza, tvrdih i mekih segmenata, finalni blok poliestri mogu da pokažu razlike u temperaturama faznih transformacija u zavisnosti od dužine i udela segmenata. Termogravimetrijskom analizom je potvrđen uticaj dužine segmenata i faznog razdvajanja na toplotna svojstva termoplastičnih poliestara. Očekuje se da će sintetisani materijali biti podesni za primene u inženjerstvu tkiva, a posebno kao materijali za kontrolisano otpuštanje lekova.The primary goal of the work described in this thesis was to develop new methods for the synthesis of polymer networks and hybrid biopolymers for special applications. The purpose was a development of synthesis procedure for the preparation of rotaxane based on poly(ethylene glycol) and β-cyclodextrin, as network precursors. These network precursors were then cross-linked through hydroxy groups on cyclodextrine rings. Polyrotaxanes are intermediary products in the synthesis of topological gels and they are formed by the insertion of the linear polymer chains of poly(ethylene oxide) into the β-CD cavities. In this work polyrotaxanes from acetylated-β-CD and poly(ethylene oxide) were synthesized. The influence of crosslinker contents, and crosslink density on swelling properties was investigated. The influence of synthesis parameters and filler modification on reactions and final properties of organic-inorganic hybrid materials based on epoxy resin and an organically modified titanium(IV)oxide (TiO2) was investigated. Dynamic-mechanical analysis was used to determine reinforcement effect of nanofiller on the epoxy resin properties. The aim of this work was the investigation of microwave irradiation on the polymerization of D,L-lactide. It was found that if heating is carried out in the microwave field polymerization time of D,Llactide rapidly decreases from 150 hours to 15 minutes. Environmentally friendly materials were obtained from poly(lactide) and copolymers of poly(lactide) and monomers based on renewable resources. Poly(lactide) is biocompatible and biodegradable polymer with high stretching and low extension capacities. It has been used for the production of orthopedic fraction fixators and sutures surgery. Poly(lactide) was used for thermoplastic polyester (TPE) synthesis. Most thermoplastic polyesters derive their properties from segmented or block structures which are achieved by alternating hard and soft segments. FT-IR and 1H NMR spectroscopy were confirmed the assumed structure of segments and final thermoplastic polyesters. Since the properties of these materials strongly depend on the degree of phase separation, the influence of the lenghts of soft and hard segment on final properties of obtained TPEs was studied. Analysis of molecular mass of these polyesters by gel permeation chromatography, vapor pressure osmometry and viscozimetric analysis confirmed that good control of polymerization was achieved and that synthesis methods were successful. Thermal properties were characterized by means of differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Phase separation had strong influences on thermal properties of obtained TPEs. DCS measurements showed that due to poor mixability of hard and soft segments, final block polyesters could have different temperatures of phase transitions depending on the length of the segments. Thermal degradation and the influence of phase separation on thermal stability of segmented thermoplastic polyesters were confirmed by nonisothermal analysis, using thermogravimetric analysis. It is expected that synthesized materials will be suitable for tissue engineering and as drug carriers

Bulgaria in the politics of the Kingdom of Serbs, Croats and Slovenes:(1919-1929)

Тема рада је југословенска политика према Бугарској од 1919. до 1929. године. Обрадили смо различите аспекте односа (политички, трговински, саобраћајни, културни), мада су у средишту пажње били дипломатски, односно политички односи. Циљ рада је да укажемо на значајно место Бугарске у спољној политици Краљевине Срба, Хрвата и Словенаца (СХС), као и на различите нивое југословенске политике према Бугарској. Посебно смо обрадили ставове и улогу кључних политичких фактора у југословенској држави (краљ, војска, политичке странке) према Бугарској, као и однос јавности према Бугарима, Бугарској и југословенско-бугарским односима. У оквиру анализе ставова јавности, обрадили смо широк дијапазон тема, као што су стереотипи о Бугарима, место ратова, историјских конфликата и страдања у колективном памћењу итд.The paper discusses the Yugoslav policy towards Bulgaria from 1919 to 1929. We have processed various aspects of relations (political, trade, transport, cultural), though the spotlight was diplomatic, and political relations. The aim is to point out the important role of Bulgaria in the foreign policy of the Kingdom of Serbs, Croats and Slovenes (S.C.S.), as well as the different levels of the Yugoslav policy towards Bulgaria. In particular, we have covered the views and the role of key political factors in the Yugoslav state (King, Army, Political Parties) towards Bulgaria, as well as the public attitudes towards the Bulgarians, Bulgaria and the Yugoslav-Bulgarian relations. In the analysis of public attitudes, we dealt with a wide range of topics, such as stereotypes about Bulgarians, the role of wars, historical conflicts and peoples suffering in the collective memory, etc..

Uticaj kompjuterskog trening programa i standardnih metoda na kvalitet određivanja boje zuba pri različitim izvorima svetlosti

Accurate and predictable shade matching for dental restorations can be a challenge for dentists and dental technicians. Visual color matching using shade guides is still the most commonly used method, but this method remained a skill acquired through clinical experience. The seemingly simple method of comparing and matching the color of shade tabs with the color of teeth often leads to mistakes that range from minor to severe mismatches. The main goal of this study was to evaluate the shade matching ability of dental students as they progress through their education. Dental students (N=174), divided into experimental and control groups, matched the color of eight shade tabs colors under standardized lighting conditions, using viewing booth, and hand-held shade matching unit. The experimental group attended the lecture on color and appearance in dentistry and completed Dental Color Matcher, an online education and training program. The control group did not have any additional information in between two shade matching sessions. The score for the best match (the match with the smallest color difference) was 10 points, the 2nd best match 9 points and so on up to 1 point if the 10th best match was selected. Means and standard deviations were calculated using two CIE color difference formulae, CIELAB and CIEDE2000. Differences were analyzed using the Student t-test, ANOVA and ANCOVA test. The experimental group achieved a statistically significant improvement in the after shade matching session on overall results, on different shade tabs and on all colors separately. The control group (with no color education and training) did not improve shade matching scores in the second session. No significant differences were found between genders in this study. The main conclusion was that education has crucial role in improvement of shade matching skills

RESOLVING DATABASE CONSTRAINT COLLISIONS USING IIS*CASE TOOL

Integrated Information Systems*Case (IIS*Case) R.6.21 is a CASE tool that we developed to support automated database (db) schema design, based on a methodology of gradual integration of independently designed subschemas into a database schema. It provides complete intelligent support for developing db schemas and enables designers to work together and cooperate reaching the most appropriate solutions. The process of independent design of subschemas may lead to collisions in expressing the real world constraints and business rules. IIS*Case uses specialized algorithms for checking the consistency of constraints embedded in the database schema and the subschemas. IIS*Case supports designers in reviewing and validating results obtained after each step of the design process. The paper outlines the process of resolving collisions. A case study based on an imaginary production system is used to illustrate the application of IIS*Case. Different outcomes and their consequences are presented