Implicit stochastic Runge-Kutta methods for stochastic differential equations

In this paper we construct implicit stochastic Runge-Kutta (SRK) methods for solving stochastic differential equations of Stratonovich type. Instead of using the increment of a Wiener process, modified random variables are used. We give convergence conditions of the SRK methods with these modified random variables. In particular, the truncated random variable is used. We present a two-stage stiffly accurate diagonal implicit SRK (SADISRK2) method with strong order 1.0 which has better numerical behaviour than extant methods. We also construct a five-stage diagonal implicit SRK method and a six-stage stiffly accurate diagonal implicit SRK method with strong order 1.5. The mean-square and asymptotic stability properties of the trapezoidal method and the SADISRK2 method are analysed and compared with an explicit method and a semi-implicit method. Numerical results are reported for confirming convergence properties and for comparing the numerical behaviour of these methods.

A simulation model of cereal-legume intercropping systems for semi-arid regions I. Model development

Cereal-legume intercropping plays an important role in subsistence food production in developing countries, especially in situations of limited water resources. Crop simulation can be used to assess risk for intercrop productivity over time and space. In this study, a simple model for intercropping was developed for cereal and legume growth and yield, under semi-arid conditions. The model is based on radiation interception and use, and incorporates a water stress factor. Total dry matter and yield are functions of photosynthetically active radiation (PAR), the fraction of radiation intercepted and radiation use efficiency (RUE). One of two PAR sub-models was used to estimate PAR from solar radiation; either PAR is 50% of solar radiation or the ratio of PAR to solar radiation (PAR/SR) is a function of the clearness index (K-T). The fraction of radiation intercepted was calculated either based on Beer's Law with crop extinction coefficients (K) from field experiments or from previous reports. RUE was calculated as a function of available soil water to a depth of 900 mm (ASW). Either the soil water balance method or the decay curve approach was used to determine ASW. Thus, two alternatives for each of three factors, i.e., PAR/SR, K and ASW, were considered, giving eight possible models (2 methods x 3 factors). The model calibration and validation were carried out with maize-bean intercropping systems using data collected in a semi-arid region (Bloemfontein, Free State, South Africa) during seven growing seasons (1996/1997-2002/2003). The combination of PAR estimated from the clearness index, a crop extinction coefficient from the field experiment and the decay curve model gave the most reasonable and acceptable result. The intercrop model developed in this study is simple, so this modelling approach can be employed to develop other cereal-legume intercrop models for semi-arid regions. (c) 2004 Elsevier B.V. All rights reserved.

The empirical basis of substance use disorders diagnosis: research recommendations for the Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-V)

Aims This paper presents the recommendations, developed from a 3-year consultation process, for a program of research to underpin the development of diagnostic concepts and criteria in the Substance Use Disorders section of the Diagnostic and Statistical Manual of Mental Disorders (DSM) and potentially the relevant section of the next revision of the International Classification of Diseases (ICD). Methods A preliminary list of research topics was developed at the DSM-V Launch Conference in 2004. This led to the presentation of articles on these topics at a specific Substance Use Disorders Conference in February 2005, at the end of which a preliminary list of research questions was developed. This was further refined through an iterative process involving conference participants over the following year. Results Research questions have been placed into four categories: (1) questions that could be addressed immediately through secondary analyses of existing data sets; (2) items likely to require position papers to propose criteria or more focused questions with a view to subsequent analyses of existing data sets; (3) issues that could be proposed for literature reviews, but with a lower probability that these might progress to a data analytic phase; and (4) suggestions or comments that might not require immediate action, but that could be considered by the DSM-V and ICD 11 revision committees as part of their deliberations. Conclusions A broadly based research agenda for the development of diagnostic concepts and criteria for substance use disorders is presented.

The status and relevance of Vietnamese journalism education: An empirical analysis

Based primarily on data from indepth interviews with senior journalists and journalism educators as well as a content analysis of journalism curricula, this paper sets out to provide an overview of the demand, overall provision structure, teaching materials and methods of Vietnamese journalism education. It first shows that with a fast expansion in both size and substance, the Vietnamese media system is beginning to feel the urgent need for formal journalism education. However, the country's major journalism programs have been criticised for producing hundreds of unqualified journalism graduates a year. In general, the most deplorable aspects of Vietnamese journalism education include its body of outdated and awkward teaching material, its undue focus on theories and politics at the expense of practical training, its lack of qualified teaching staff and its inadequate teaching resources.

What does the community think about lifespan extension technologies? The need for an empirical base for ethical and policy debates

Objectives: This paper examines public understandings of possibilities for increasing life expectancy, interest in taking up lifespan-extending interventions, and motivations influencing these intentions. Methods: Structured interviews were conducted with 31 adults, aged 50 and over. Results: Participants believed that technological advances would increase life expectancy but questioned the value of quantity over quality of life. Life in itself was not considered valuable without the ability to put it to good use. Participants would not use technologies to extend their own lifespan unless the result would also enhance their health. Conclusions: These findings may not be generalisable to the general public but they provide the first empirical evidence on the plausibility of common assumptions about public interest in 'anti-ageing' interventions. Surveys of the views of representative samples of the population are needed to inform the development of a research agenda on the ethical, legal and social implications of lifespan extension.

Statistical racing techniques for improved empirical evaluation of evolutionary algorithms

In empirical studies of Evolutionary Algorithms, it is usually desirable to evaluate and compare algorithms using as many different parameter settings and test problems as possible, in border to have a clear and detailed picture of their performance. Unfortunately, the total number of experiments required may be very large, which often makes such research work computationally prohibitive. In this paper, the application of a statistical method called racing is proposed as a general-purpose tool to reduce the computational requirements of large-scale experimental studies in evolutionary algorithms. Experimental results are presented that show that racing typically requires only a small fraction of the cost of an exhaustive experimental study.

DO VIRTUAL AO REAL: COMUNICAÇÃO, SEXO E INTERNET

Este trabalho é um estudo exploratório sobre o Ambiente Comunicacional Internet que investiga tanto a possibilidade da influência de suas ferramentas de interação/comunicação sobre o comportamento sexual e de risco quanto o desenvolvimento de comportamento compulsivo no uso destas ferramentas na busca de parceiros sexuais. A metodologia adotada é, além da pesquisa bibliográfica, a da pesquisa exploratória, um levantamento e análise de dados quantitativos e pode ser considerada como pertencente ao paradigma tradicional empírico, pois a coleta de dados foi baseada em respostas a questionários semi-estruturados, aplicados a um grupo de informação composto por 428 estudantes universitários dos cursos ligados à área de Computação e Informática de uma instituição particular de Ensino Superior do município de São Paulo SP, Brasil. Para isso, obedece à Resolução do Conselho Nacional de Saúde CNS 196/96 e conta com o TCLE. Os resultados indicam que as práticas sexuais, a exposição a DST e vírus HIV e, particularmente, a tendência ao desenvolvimento do Transtorno de Adicção à Internet se distinguem de modo irrefutável. Os participantes que alegaram buscar parceiros sexuais reais na Internet são diretos nos seus objetivos, pois quando encontram esse parceiro concretizam o ato sexual, em ambientes impessoais, como por exemplo, o motel, e muitas vezes de modo arriscado no que toca à prevenção e à segurança no contato com outro. Destaca-se, ainda, que a compulsão não é reconhecida pelo grupo e que a procura de parceiros por intermédio das mídias digitais, para esse grupo, não está relacionada a itens negativos quanto a sua qualidade de vida o que suscita o estudo e a discussão mais aprofundada sobre a interação comunicação, sexo e Internet .(AU)

GESTÃO DEMOCRÁTICA: O PERFIL IDEOLÓGICO DOS PAIS MEMBROS DO CONSELHO DE ESCOLA

O presente trabalho enfoca a participação e atuação dos pais no Conselho de Escola. Tal participação passou a ser possível após a Constituição de 1988 e a Lei de Diretrizes e Bases da Educação Nacional nº. 9394/96 LDBEN. O estudo tem por objetivo identificar a concepção de participação dos pais membros do Conselho de Escola, e traçar os possíveis perfis ideológicos dos mesmos quanto à gestão escolar. A pesquisa é de natureza empírica, todavia ela se apóia em perfis ideológicos, construídos a partir de análises propiciadas pela Sociologia da Educação e pela Ciência Política. Como referencial teórico apropriamo-nos de Luis Pereira, Juan Bordenave, Maurício Tragtenberg, Edmundo Campos e de C.B. Macpherson. A pesquisa concentrou-se em uma das escolas da Rede Estadual no Município de São Bernardo do Campo SP. Utilizamos métodos de pesquisa de campo e bibliográfica. Além da pesquisa de campo, que teve como base entrevista qualitativa e semi-aberta, realizamos análises das Legislações Federal e Estadual com o objetivo de verificarmos as lacunas existentes na legislação, assim como os limites por ela impostos à participação dos pais na gestão escolar.(AU)

GESTÃO DO CONHECIMENTO TÁCITO: ESTUDO DE CASOS MÚLTIPLOS NA ÁREA DE DESENVOLVIMENTO DE PRODUTOS DE EMPRESAS DO SETOR AUTOMOBILÍSTICO DO ABC PAULISTA.

O presente estudo buscou a compreensão dos motivos que levam as empresas pesquisadas do setor automobilístico a gerir o conhecimento tácito, mediados pela gestão do conhecimento, na área de gestão de desenvolvimento de produtos. As questões de pesquisa que este estudo objetivou responder foram: Como empresas estudadas utilizam o conhecimento tácito para se tornarem mais eficientes e eficazes nas atividades/ operações? De que forma o conhecimento tácito é percebido na organização por parte dos funcionários e gestores? Para responder a estas perguntas houve a investigação de duas empresas do setor automobilístico, na área de desenvolvimento de produtos. Como base teórica para o desenvolvimento do presente estudo autores como Davenport e Prusak (1998), Nonaka e Takeuchi (1997) e Choo (2006) orientam esta pesquisa. A pesquisa abrange duas empresas do ramo automobilístico na região do ABC Paulista, com equivalência no número de funcionários e porte. Dentre os entrevistados há funcionários e gestores de áreas de gestão de projetos e produtos. A metodologia aplicada ao estudo foi de caráter qualitativo por meio de pesquisa exploratória-descritiva, sendo que o método de coleta de dados se deu a partir de entrevistas semiestruturadas. O estudo investigou quais as práticas usadas para a conversão do conhecimento, fatores facilitadores e fatores dificultadores para a conversão do conhecimento e as principais contribuições da aplicação das práticas e iniciativas voltadas gerir o conhecimento tácito, sob a ótica dos gestores e funcionários. Através do presente estudo pode-se verificar que existe a preocupação com a gestão do conhecimento nas empresas estudadas e que há práticas diversas relativas ao conhecimento tácito e que as formas de disseminação deste conhecimento são distintas. Algumas das práticas são os cursos de especialização, brainstorming e lesson learned e conversas informais. Nos fatores facilitadores há a troca de informação entre os pares, reuniões semanais, equipes multidisciplinares/ multifuncionais. Nos fatores dificultadores há a indicação de questões comportamentais, acúmulo de funções e tempo para partilhar informações.

Stereotypes of salespeople in Taiwan:an empirical examination and research agenda

Stereotypes of salespeople are common currency in US media outlets, and research suggests that these stereotypes are uniformly negative. However there is no reason to expect that stereotypes will be consistent across cultures. The present paper provides the first empirical examination of salesperson stereotypes in an Asian country, specifically Taiwan. Using accepted psychological methods, Taiwanese salesperson stereotypes are found to be twofold, with a negative stereotype being quite congruent with existing US stereotypes, but also a positive stereotype, which may be related to the specific culture of Taiwan.

The valuation of travel time savings in least developed countries:theoretical and empirical challenges and results from a field study

In developed countries travel time savings can account for as much as 80% of the overall benefits arising from transport infrastructure and service improvements. In developing countries they are generally ignored in transport project appraisals, notwithstanding their importance. One of the reasons for ignoring these benefits in the developing countries is that there is insufficient empirical evidence to support the conventional models for valuing travel time where work patterns, particularly of the poor, are diverse and it is difficult to distinguish between work and non-work activities. The exclusion of time saving benefits may lead to a bias against investment decisions that benefit the poor and understate the poverty reduction potential of transport investments in Least Developed Countries (LDCs). This is because the poor undertake most travel and transport by walking and headloading on local roads, tracks and paths and improvements of local infrastructure and services bring large time saving benefits for them through modal shifts. The paper reports on an empirical study to develop a methodology for valuing rural travel time savings in the LDCs. Apart from identifying the theoretical and empirical issues in valuing travel time savings in the LDCs, the paper presents and discusses the results of an analysis of data from Bangladesh. Some of the study findings challenge the conventional wisdom concerning the time saving values. The Bangladesh study suggests that the western concept of dividing travel time savings into working and non-working time savings is broadly valid in the developing country context. The study validates the use of preference methods in valuing non-working time saving values. However, stated preference (SP) method is more appropriate than revealed preference (RP) method.

Lexical database enrichment through semi-automated morphological analysis

Derivational morphology proposes meaningful connections between words and is largely unrepresented in lexical databases. This thesis presents a project to enrich a lexical database with morphological links and to evaluate their contribution to disambiguation. A lexical database with sense distinctions was required. WordNet was chosen because of its free availability and widespread use. Its suitability was assessed through critical evaluation with respect to specifications and criticisms, using a transparent, extensible model. The identification of serious shortcomings suggested a portable enrichment methodology, applicable to alternative resources. Although 40% of the most frequent words are prepositions, they have been largely ignored by computational linguists, so addition of prepositions was also required. The preferred approach to morphological enrichment was to infer relations from phenomena discovered algorithmically. Both existing databases and existing algorithms can capture regular morphological relations, but cannot capture exceptions correctly; neither of them provide any semantic information. Some morphological analysis algorithms are subject to the fallacy that morphological analysis can be performed simply by segmentation. Morphological rules, grounded in observation and etymology, govern associations between and attachment of suffixes and contribute to defining the meaning of morphological relationships. Specifying character substitutions circumvents the segmentation fallacy. Morphological rules are prone to undergeneration, minimised through a variable lexical validity requirement, and overgeneration, minimised by rule reformulation and restricting monosyllabic output. Rules take into account the morphology of ancestor languages through co-occurrences of morphological patterns. Multiple rules applicable to an input suffix need their precedence established. The resistance of prefixations to segmentation has been addressed by identifying linking vowel exceptions and irregular prefixes. The automatic affix discovery algorithm applies heuristics to identify meaningful affixes and is combined with morphological rules into a hybrid model, fed only with empirical data, collected without supervision. Further algorithms apply the rules optimally to automatically pre-identified suffixes and break words into their component morphemes. To handle exceptions, stoplists were created in response to initial errors and fed back into the model through iterative development, leading to 100% precision, contestable only on lexicographic criteria. Stoplist length is minimised by special treatment of monosyllables and reformulation of rules. 96% of words and phrases are analysed. 218,802 directed derivational links have been encoded in the lexicon rather than the wordnet component of the model because the lexicon provides the optimal clustering of word senses. Both links and analyser are portable to an alternative lexicon. The evaluation uses the extended gloss overlaps disambiguation algorithm. The enriched model outperformed WordNet in terms of recall without loss of precision. Failure of all experiments to outperform disambiguation by frequency reflects on WordNet sense distinctions.

A semi-oriented radial measure for measuring the efficiency of decision making units with negative data, using DEA

Data Envelopment Analysis (DEA) is a nonparametric method for measuring the efficiency of a set of decision making units such as firms or public sector agencies, first introduced into the operational research and management science literature by Charnes, Cooper, and Rhodes (CCR) [Charnes, A., Cooper, W.W., Rhodes, E., 1978. Measuring the efficiency of decision making units. European Journal of Operational Research 2, 429–444]. The original DEA models were applicable only to technologies characterized by positive inputs/outputs. In subsequent literature there have been various approaches to enable DEA to deal with negative data. In this paper, we propose a semi-oriented radial measure, which permits the presence of variables which can take both negative and positive values. The model is applied to data on a notional effluent processing system to compare the results with those yielded by two alternative methods for dealing with negative data in DEA: The modified slacks-based model suggested by Sharp et al. [Sharp, J.A., Liu, W.B., Meng, W., 2006. A modified slacks-based measure model for data envelopment analysis with ‘natural’ negative outputs and inputs. Journal of Operational Research Society 57 (11) 1–6] and the range directional model developed by Portela et al. [Portela, M.C.A.S., Thanassoulis, E., Simpson, G., 2004. A directional distance approach to deal with negative data in DEA: An application to bank branches. Journal of Operational Research Society 55 (10) 1111–1121]. A further example explores the advantages of using the new model.