970 resultados para Practical problems


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The aim of this project was to develop the education work of an environmental pressure group. The research devised and implemented a project to produce multi-media teaching packs on the urban environment. Whilst this involved understanding environmental education it was necessary to research beyond this to include the various structural and dynamic constraints on change in the field. This presented a number of methodological difficulties; from the resolution of which a model of the research process involved in this project has been developed. It is argued that research oriented towards practical change requires the insights of an experienced practitioner to be combined with the rigours of controlled systematic enquiry. Together these function as a model-building process encompassing intuition, induction and deduction. Model testing is carried out through repeated intervention in the field; thus an interplay between researcher and client ensues such that the project develops in a mutually acceptable direction. In practice, this development will be both unpredictable and erratic. Although the conclusions reached here are based on a single case study they address general methodological issues likely to be encountered in different field settings concerned with different practical problems.

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In order to study the structure and function of a protein, it is generally required that the protein in question is purified away from all others. For soluble proteins, this process is greatly aided by the lack of any restriction on the free and independent diffusion of individual protein particles in three dimensions. This is not the case for membrane proteins, as the membrane itself forms a continuum that joins the proteins within the membrane with one another. It is therefore essential that the membrane is disrupted in order to allow separation and hence purification of membrane proteins. In the present review, we examine recent advances in the methods employed to separate membrane proteins before purification. These approaches move away from solubilization methods based on the use of small surfactants, which have been shown to suffer from significant practical problems. Instead, the present review focuses on methods that stem from the field of nanotechnology and use a range of reagents that fragment the membrane into nanometre-scale particles containing the protein complete with the local membrane environment. In particular, we examine a method employing the amphipathic polymer poly(styrene-co-maleic acid), which is able to reversibly encapsulate the membrane protein in a 10 nm disc-like structure ideally suited to purification and further biochemical study.

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Pavement analysis and design for fatigue cracking involves a number of practical problems like material assessment/screening and performance prediction. A mechanics-aided method can answer these questions with satisfactory accuracy in a convenient way when it is appropriately implemented. This paper presents two techniques to implement the pseudo J-integral based Paris’ law to evaluate and predict fatigue cracking in asphalt mixtures and pavements. The first technique, quasi-elastic simulation, provides a rational and appropriate reference modulus for the pseudo analysis (i.e., viscoelastic to elastic conversion) by making use of the widely used material property: dynamic modulus. The physical significance of the quasi-elastic simulation is clarified. Introduction of this technique facilitates the implementation of the fracture mechanics models as well as continuum damage mechanics models to characterize fatigue cracking in asphalt pavements. The second technique about modeling fracture coefficients of the pseudo J-integral based Paris’ law simplifies the prediction of fatigue cracking without performing fatigue tests. The developed prediction models for the fracture coefficients rely on readily available mixture design properties that directly affect the fatigue performance, including the relaxation modulus, air void content, asphalt binder content, and aggregate gradation. Sufficient data are collected to develop such prediction models and the R2 values are around 0.9. The presented case studies serve as examples to illustrate how the pseudo J-integral based Paris’ law predicts fatigue resistance of asphalt mixtures and assesses fatigue performance of asphalt pavements. Future applications include the estimation of fatigue life of asphalt mixtures/pavements through a distinct criterion that defines fatigue failure by its physical significance.

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Koopmans gyakorlati problémák megoldása során szerzett tapasztalatait általánosítva fogott hozzá a lineáris tevékenységelemzési modell kidolgozásához. Meglepődve tapasztalta, hogy a korabeli közgazdaságtan nem rendelkezett egységes, kellően egzakt termeléselmélettel és fogalomrendszerrel. Úttörő dolgozatában ezért - mintegy a lineáris tevékenységelemzési modell elméleti kereteként - lerakta a technológiai halmazok fogalmán nyugvó axiomatikus termeléselmélet alapjait is. Nevéhez fűződik a termelési hatékonyság és a hatékonysági árak fogalmának egzakt definíciója, s az egymást kölcsönösen feltételező viszonyuk igazolása a lineáris tevékenységelemzési modell keretében. A hatékonyság manapság használatos, pusztán műszaki szempontból értelmezett definícióját Koopmans csak sajátos esetként tárgyalta, célja a gazdasági hatékonyság fogalmának a bevezetése és elemzése volt. Dolgozatunkban a lineáris programozás dualitási tételei segítségével rekonstruáljuk ez utóbbira vonatkozó eredményeit. Megmutatjuk, hogy egyrészt bizonyításai egyenértékűek a lineáris programozás dualitási tételeinek igazolásával, másrészt a gazdasági hatékonysági árak voltaképpen a mai értelemben vett árnyékárak. Rámutatunk arra is, hogy a gazdasági hatékonyság értelmezéséhez megfogalmazott modellje az Arrow-Debreu-McKenzie-féle általános egyensúlyelméleti modellek közvetlen előzményének tekinthető, tartalmazta azok szinte minden lényeges elemét és fogalmát - az egyensúlyi árak nem mások, mint a Koopmans-féle hatékonysági árak. Végezetül újraértelmezzük Koopmans modelljét a vállalati technológiai mikroökonómiai leírásának lehetséges eszközeként. Journal of Economic Literature (JEL) kód: B23, B41, C61, D20, D50. /===/ Generalizing from his experience in solving practical problems, Koopmans set about devising a linear model for analysing activity. Surprisingly, he found that economics at that time possessed no uniform, sufficiently exact theory of production or system of concepts for it. He set out in a pioneering study to provide a theoretical framework for a linear model for analysing activity by expressing first the axiomatic bases of production theory, which rest on the concept of technological sets. He is associated with exact definition of the concept of production efficiency and efficiency prices, and confirmation of their relation as mutual postulates within the linear model of activity analysis. Koopmans saw the present, purely technical definition of efficiency as a special case; he aimed to introduce and analyse the concept of economic efficiency. The study uses the duality precepts of linear programming to reconstruct the results for the latter. It is shown first that evidence confirming the duality precepts of linear programming is equal in value, and secondly that efficiency prices are really shadow prices in today's sense. Furthermore, the model for the interpretation of economic efficiency can be seen as a direct predecessor of the Arrow–Debreu–McKenzie models of general equilibrium theory, as it contained almost every essential element and concept of them—equilibrium prices are nothing other than Koopmans' efficiency prices. Finally Koopmans' model is reinterpreted as a necessary tool for microeconomic description of enterprise technology.

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Az alábbi írás Kornai János életműsorozata közeljövőben megjelenő harmadik kötetének bevezetője alapján készült. (A sorozat első kötete, A hiány és második kötete, A szocialista rendszer 2012-ben jelent meg.) Ritkán fordul elő, hogy életművét rendszerezve, egy szerző maga veszi tételesen sorra írásait, tárja fel az írások megszületésének körülményeit, és elemzi őket több évtized távlatából. Kornai János életműsorozatának összeállításakor erre a rendkívüli feladatra vállalkozott. A kötetben megjelenő 22 íráshoz fűzött gondolatainak közlésekor mai szemmel veszi górcső alá az egy kivételével a rendszerváltás előtt írt cikkeit, valamint 1956-ban írott első könyvét, A túlzott központosítást. Az írásokat rendszerező bevezető a központosításra és a piaci reformra összpontosítja a figyelmet - e témakörről bebizonyosodott, hogy korai még csupán a közgazdaságtani elmélettörténet fejezeteként számon tartani. A kötetben megjelenő írások egy része közvetlenül kapcsolódik a magyar gazdaság tapasztalataihoz, másik része pedig elméleti jellegű. Ennek megfelelően az itt közölt bevezetés is foglalkozik mind a magyar gazdaságtörténet máig is figyelemre méltó és tanulságos gyakorlati problémáival, mind pedig a szocializmust és a kapitalizmust, a centralizált és decentralizált formákat összehasonlító általános elméletekkel. ______ This piece forms the introduction to the forthcoming third volume of János Kor-nai s life s work series reissued in Hungarian. (The first and second volumes, Economics of Shortage and The Political Economy of the Socialist System, ap-peared in 2012.) It is rare for an author to arrange his own life s work, taking his writings item by item, presenting the circumstances in which they arose, and ana-lysing them decades later. His thoughts on the twenty-two writings in the volume, at the time of republication, involve scrutinizing with present-day eyes articles written, with one exception, before the change of system, along with his first book, Overcentralization, written in 1956. The introduction that systematizes these fo-cuses on centralization and on market reform - events show it is still too soon to see these subjects simply as a chapter in the theoretical history of economics. Some of the articles draw directly on experiences with the Hungarian economy, while others have a theoretical nature. So the introduction also deals both with practical problems of Hungarian economic history that remain notable and instructive, and with comparative general theories of socialism and capitalism and centralized and decentralized forms.

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The span of control is the most discussed single concept in classical and modern management theory. In specifying conditions for organizational effectiveness, the span of control has generally been regarded as a critical factor. Existing research work has focused mainly on qualitative methods to analyze this concept, for example heuristic rules based on experiences and/or intuition. This research takes a quantitative approach to this problem and formulates it as a binary integer model, which is used as a tool to study the organizational design issue. This model considers a range of requirements affecting management and supervision of a given set of jobs in a company. These decision variables include allocation of jobs to workers, considering complexity and compatibility of each job with respect to workers, and the requirement of management for planning, execution, training, and control activities in a hierarchical organization. The objective of the model is minimal operations cost, which is the sum of supervision costs at each level of the hierarchy, and the costs of workers assigned to jobs. The model is intended for application in the make-to-order industries as a design tool. It could also be applied to make-to-stock companies as an evaluation tool, to assess the optimality of their current organizational structure. Extensive experiments were conducted to validate the model, to study its behavior, and to evaluate the impact of changing parameters with practical problems. This research proposes a meta-heuristic approach to solving large-size problems, based on the concept of greedy algorithms and the Meta-RaPS algorithm. The proposed heuristic was evaluated with two measures of performance: solution quality and computational speed. The quality is assessed by comparing the obtained objective function value to the one achieved by the optimal solution. The computational efficiency is assessed by comparing the computer time used by the proposed heuristic to the time taken by a commercial software system. Test results show the proposed heuristic procedure generates good solutions in a time-efficient manner.

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This paper examines variations in suicide in the eight Health Boards of the Republic of Ireland for the years 1976 to 1995. It is found that while all have experienced a rise in male suicide, it has been much less pronounced in the Eastern Health Board which is somewhat surprising when one considers Dublin’s much-publicised problems with homelessness and hard drug misuse. Since the mid-eighties, female rates have been somewhat higher in the southern half of the country, comprising the Southern, Mid-Western and South-Eastern Health Boards. This variation may reflect a difficulty with contacting services for psychological distress in rural areas, either because of stigma or simple practical problems associated with transport. The development of appropriate services, especially in rural areas, should be at the top of the agenda of any Resource Officer to be appointed subsequent to the Final Report of the Task Force.

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Research on the mechanisms and processes underlying navigation has traditionally been limited by the practical problems of setting up and controlling navigation in a real-world setting. Thanks to advances in technology, a growing number of researchers are making use of computer-based virtual environments to draw inferences about real-world navigation. However, little research has been done on factors affecting human–computer interactions in navigation tasks. In this study female students completed a virtual route learning task and filled out a battery of questionnaires, which determined levels of computer experience, wayfinding anxiety, neuroticism, extraversion, psychoticism and immersive tendencies as well as their preference for a route or survey strategy. Scores on personality traits and individual differences were then correlated with the time taken to complete the navigation task, the length of path travelled,the velocity of the virtual walk and the number of errors. Navigation performance was significantly influenced by wayfinding anxiety, psychoticism, involvement and overall immersive tendencies and was improved in those participants who adopted a survey strategy. In other words, navigation in virtual environments is effected not only by navigational strategy, but also an individual’s personality, and other factors such as their level of experience with computers. An understanding of these differences is crucial before performance in virtual environments can be generalised to real-world navigational performance.

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The purpose of this research is to investigate potential methods to produce an ion-exchange membrane that can be integrated directly into a polydimethylsiloxane Lab-on-a-Chip or Micro-Total-Analysis-System. The majority of microfluidic membranes are based on creating microporous structures, because it allows flexibility in the choice of material such that it can match the material of the microfluidic chip. This cohesion between the material of the microfluidic chip and membrane is an important feature to prevent bonding difficulties which can lead to leaking and other practical problems. However, of the materials commonly used to manufacture microfluidic chips, there are none that provide the ion-exchange capability. The DuPont product Nafion{TM} is chosen as the ion-exchange membrane, a copolymer with high conductivity and selectivity to cations and suitable for many applications such as electrolysis of water and the chlor-alkali process. The use of such an ion-exchange membrane in microfluidics could have multiple advantages, but there is no reversible/irreversible bonding that occurs between PDMS and Nafion{TM}. In this project multiple methods of physical entrapment of the ion-exchange material inside a film of PDMS are attempted. Through the use of the inherent properties of PDMS, very inexpensive sugar granulate can be used to make an inexpensive membrane mould which does not interfere with the PDMS crosslinking process. After dissolving away this sacrificial mould material, Nafion{TM} is solidified in the irregular granulate holes. Nafion{TM} in this membrane is confined in the irregular shape of the PDMS openings. The outer structure of the membrane is all PDMS and can be attached easily and securely to any PDMS-based microfluidic device through reversible or irreversible PDMS/PDMS bonding. Through impedance measurement, the effectiveness of these integrated membranes are compared against plain Nafion{TM} films in simple sodium chloride solutions.

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Denna studie syftar till att undersöka hur en stor organisation arbetar med förvaltning av information genom att undersöka dess nuvarande informationsförvaltning, samt undersöka eventuella förslag till framtida informationsförvaltning. Vidare syftar studien också till att undersöka hur en stor organisation kan etablera en tydlig styrning, samverkan, hantering och ansvars- och rollfördelning kring informationsförvaltning. Denna studie är kvalitativ, där datainsamlingen sker genom dokumentstudier och intervjuer. Studien bedrivs med abduktion och är en normativ fallstudie då studiens mål är att ge vägledning och föreslå åtgärder till det fall som uppdragsgivaren har bett mig att studera. Fallet i denna studie är ett typiskt fall, då studiens resultat kan vara i intresse för fler än studiens uppdragsgivare, exempelvis organisationer med liknande informationsmiljö. För att samla teori till studien så har jag genomfört litteraturstudier om ämnen som är relevanta för studiens syfte: Informationsförvaltning, Business Intelligence, Data Warehouse och dess arkitektur, samt Business Intelligence Competency Center. Denna studie bidrar med praktiskt kunskapsbidrag, då studien ger svar på praktiska problem. Uppdragsgivaren har haft praktiska problem i och med en icke fungerade informationsförvaltning, och denna studie har bidragit med förslag på framtida informationsförvaltning. Förslaget på framtida informationsförvaltning involverar ett centraliserat Data Warehouse, samt utvecklingen utav en verksamhet som hanterar informationsförvaltning och styrningen kring informationsförvaltningen inom hela organisationen.

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[ES] To actively protect sea turtles on their nesting beaches, it is essential to obtain knowledge about trends in abundance. The way sea turtles live makes it extremely difficult to identify how many individuals there are in a population at any point in time. Due to practical problems, given their entirely marine life with limited visibility and great oceanic dispersal, counting males or juveniles is currently quite difficult and imprecise. Counting females and nests on beaches during the nesting season is the best feasible but still imperfect method, since only an unknown portion of adult females nest every season. It is impossible to know the real number of females in the population by merely counting females and nests in a given year.

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Este trabalho, desenvolvido por uma professora de educação especial no contexto onde exerce funções, resultou da vontade de aprofundar o conhecimento sobre as dinâmicas de trabalho entre os professores do Ensino Regular e entre estes e o professor de Educação Especial. Desta forma elaborámos um projeto de investigação com o propósito de aprofundar o conhecimento sobre estas dinâmicas, no âmbito de uma oficina de formação, dinamizada pela investigadora, realizada no contexto de trabalho dos participantes. Neste âmbito, foi proporcionado um conjunto de experiências vivenciadas em conjunto, procurando contribuir para novas perspetivas teóricas sobre o conhecimento, bem como o envolvimento dos participantes em situações empíricas que lhes permitissem aplicar esses conhecimentos na resolução de problemas concretos emergentes no seu contexto de trabalho. A estratégia formativa baseou-se na colaboração como factor de desenvolvimento e de aprendizagem, surgindo como relevante e necessário o envolvimento dos formandos em processos de investigação da própria prática. A formação, na modalidade de Oficina, foi promovida através do Centro de Formação da Instituição onde a escola, um estabelecimento de ensino particular e cooperativo, se integra. Neste âmbito foi acreditada pelo Conselho Científico-Pedagógico da Formação Contínua e envolveu dezasseis professores do 1.º, 2.º e 3.º ciclos do ensino básico. A formação desenvolveuse em duas fases - a primeira fase, constituída por 4 sessões, teve lugar entre maio e julho de 2011, e a segunda fase, igualmente constituída por 4 sessões, teve lugar de setembro a novembro de 2011, num total de 25 horas presenciais e 25 horas não presenciais. Trata-se de um estudo com uma dupla intencionalidade – formativa e investigativa – no qual se procura compreender (i) a relação entre as estratégias de formação e supervisão promovidas pela professora de educação especial e o desenvolvimento de dinâmicas de trabalho colaborativo entre os participantes (ii) e o impacto dessas dinâmicas no desenvolvimento profissional e nas suas práticas, tendo em vista a promoção de uma educação inclusiva. Configura-se como estudo de caso, na variante de multicaso apresentando, ainda, algumas características de investigação-ação. No âmbito deste estudo, utilizámos um conjunto diverso e complementar de procedimentos investigativos, nomeadamente, o inquérito por questionário aplicado a todos os participantes no início e no fim da oficina de formação; o inquérito por questionário de avaliação das sessões, tendo por base os objetivos do estudo; a entrevista semi-estruturada, realizada a quatro docentes do 1º CEB que constituem os subcasos e o portfolio reflexivo individual dos mesmos, os quais se constituem como estratégia de formação e de investigação. Recorreu-se, ainda, como fontes de informação secundária, ao Teaching portfolio do investigador, às videogravações das sessões de formação, aos registos em vídeo de alguns episódios relativos à intervenção dos formandos em sala de aula e aos projetos de investigação-ação, bem como aos dados recolhidos na entrevista dirigida ao Diretor do estabelecimento de educação e ensino, depois de concluído o programa de formação. Os resultados da análise parecem evidenciar a existência de dinâmicas colaborativas e um clima de inter-ajuda que caraterizou a interação ocorrida na formação, em torno de casos concretos, os quais tiveram um impacto significativo sobre o pensamento e a prática dos participantes. Todo o processo desenvolvido parece ter dado lugar à partilha de saberes e à procura conjunta de soluções para os problemas, tendo contribuído para que os professores passassem a ser mais interventivos, evidenciando novas aprendizagens e uma maior consciencialização do conceito de educação para todos e do que esta implica. Os resultados parecem ainda revelar o desenvolvimento de uma parceria estratégica entre os professores do ensino regular e a professora de educação especial, a qual passou a ser aceite como uma pessoa que pode ajudar a encontrar soluções para os problemas que surgem na sala de aula, de forma a garantir a inclusão de todos os alunos e não apenas dos que têm necessidades educativas especiais.

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W artykule autorzy podejmują się dokonania analizy zagadnienia dotyczącego możliwości naruszenia umowy spółki lub statutu przez członków zarządu oraz wpływu takiego naruszenia na ważność podjętej czynności prawnej. Zagadnienie to wywołuje liczne problemy praktyczne, chociażby z uwagi na obowiązek każdorazowej weryfikacji przed zawarciem umowy listy czynności, na dokonanie których statut lub umowa spółki zastrzega sobie taki wymóg. Nie ma tu znaczenia dobra czy zła wiara kontrahenta, który ma świadomość o istnieniu takiego zapisu dla ważności danej czynności prawnej. Zgoła odmienna jest sytuacja członka zarządu, dla którego uzyskanie takiej zgody jest ważne, z uwagi na naruszenia umowy spółki albo statutu, a w konsekwencji jego odpowiedzialność odszkodowawczą do dochodzenia ewentualnego odszkodowania za szkodę wyrządzoną działaniem lub zaniechaniem. Pamiętać jednak należy, że do istnienia odpowiedzialności niezbędne jest wykazanie szkody. Jednakże biorąc pod uwagę uwarunkowania biznesowe niekiedy trudno uzyskać zgodę rady nadzorczej lub walnego zgromadzenia wspólników na taką zgodę. Powstaje wtedy pytanie, czy można ją uzyskać następczo. Autorzy w artykule dokonują analizy stawiając tezę, iż możliwe jest następcze wyrażenie zgody na dokonaną bez uprzedniej zgody czynność prawną. Dokonując wnioskowania a maiori ad minus można w ocenie autorów dopuścić potwierdzenie takiej czynności następczo i to nie tylko w wymaganym dwumiesięcznym terminie, ale nawet późniejszym, co może mieć wpływ na ich ewentualne wyłączenie odpowiedzialności z tytułu naruszenia postanowień umowy spółki (statutu). Całość rozważań ściśle oscyluje wokół praktycznych problemów pojawiających się funkcjonowaniu spółki.

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As a typical NP-complete problem, 0/1 Knapsack Problem (KP), has been widely applied in many domains for solving practical problems. Although ant colony optimization (ACO) algorithms can obtain approximate solutions to 0/1 KP, there exist some shortcomings such as the low convergence rate, premature convergence and weak robustness. In order to get rid of the above-mentioned shortcomings, this paper proposes a new kind of Physarum-based hybrid optimization algorithm, denoted as PM-ACO, based on the critical paths reserved by Physarum-inspired mathematical (PM) model. By releasing additional pheromone to items that are on the important pipelines of PM model, PM-ACO algorithms can enhance item pheromone matrix and realize a positive feedback process of updating item pheromone. The experimental results in two different datasets show that PM-ACO algorithms have a stronger robustness and a higher convergence rate compared with traditional ACO algorithms.

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The K-means algorithm is one of the most popular clustering algorithms in current use as it is relatively fast yet simple to understand and deploy in practice. Nevertheless, its use entails certain restrictive assumptions about the data, the negative consequences of which are not always immediately apparent, as we demonstrate. While more flexible algorithms have been developed, their widespread use has been hindered by their computational and technical complexity. Motivated by these considerations, we present a flexible alternative to K-means that relaxes most of the assumptions, whilst remaining almost as fast and simple. This novel algorithm which we call MAP-DP (maximum a-posteriori Dirichlet process mixtures), is statistically rigorous as it is based on nonparametric Bayesian Dirichlet process mixture modeling. This approach allows us to overcome most of the limitations imposed by K-means. The number of clusters K is estimated from the data instead of being fixed a-priori as in K-means. In addition, while K-means is restricted to continuous data, the MAP-DP framework can be applied to many kinds of data, for example, binary, count or ordinal data. Also, it can efficiently separate outliers from the data. This additional flexibility does not incur a significant computational overhead compared to K-means with MAP-DP convergence typically achieved in the order of seconds for many practical problems. Finally, in contrast to K-means, since the algorithm is based on an underlying statistical model, the MAP-DP framework can deal with missing data and enables model testing such as cross validation in a principled way. We demonstrate the simplicity and effectiveness of this algorithm on the health informatics problem of clinical sub-typing in a cluster of diseases known as parkinsonism.