On the car sequencing problem: analysis and solution methods

This work deals with the car sequencing (CS) problem, a combinatorial optimization problem for sequencing mixed-model assembly lines. The aim is to find a production sequence for different variants of a common base product, such that work overload of the respective line operators is avoided or minimized. The variants are distinguished by certain options (e.g., sun roof yes/no) and, therefore, require different processing times at the stations of the line. CS introduces a so-called sequencing rule H:N for each option, which restricts the occurrence of this option to at most H in any N consecutive variants. It seeks for a sequence that leads to no or a minimum number of sequencing rule violations. In this work, CS’ suitability for workload-oriented sequencing is analyzed. Therefore, its solution quality is compared in experiments to the related mixed-model sequencing problem. A new sequencing rule generation approach as well as a new lower bound for the problem are presented. Different exact and heuristic solution methods for CS are developed and their efficiency is shown in experiments. Furthermore, CS is adjusted and applied to a resequencing problem with pull-off tables.

On arc-routing problems

Das Basisproblem von Arc-Routing Problemen mit mehreren Fahrzeugen ist das Capacitated Arc-Routing Problem (CARP). Praktische Anwendungen des CARP sind z.B. in den Bereichen Müllabfuhr und Briefzustellung zu finden. Das Ziel ist es, einen kostenminimalen Tourenplan zu berechnen, bei dem alle erforderlichen Kanten bedient werden und gleichzeitig die Fahrzeugkapazität eingehalten wird. In der vorliegenden Arbeit wird ein Cut-First Branch-and-Price Second Verfahren entwickelt. In der ersten Phase werden Schnittebenen generiert, die dem Master Problem in der zweiten Phase hinzugefügt werden. Das Subproblem ist ein kürzeste Wege Problem mit Ressourcen und wird gelöst um neue Spalten für das Master Problem zu liefern. Ganzzahlige CARP Lösungen werden durch ein neues hierarchisches Branching-Schema garantiert. Umfassende Rechenstudien zeigen die Effektivität dieses Algorithmus. Kombinierte Standort- und Arc-Routing Probleme ermöglichen eine realistischere Modellierung von Zustellvarianten bei der Briefzustellung. In dieser Arbeit werden jeweils zwei mathematische Modelle für Park and Loop und Park and Loop with Curbline vorgestellt. Die Modelle für das jeweilige Problem unterscheiden sich darin, wie zulässige Transfer Routen modelliert werden. Während der erste Modelltyp Subtour-Eliminationsbedingungen verwendet, werden bei dem zweiten Modelltyp Flussvariablen und Flusserhaltungsbedingungen eingesetzt. Die Rechenstudie zeigt, dass ein MIP-Solver den zweiten Modelltyp oft in kürzerer Rechenzeit lösen kann oder bei Erreichen des Zeitlimits bessere Zielfunktionswerte liefert.

Population-based analysis of 4113 patients with acute cholecystitis: defining the optimal time-point for laparoscopic cholecystectomy

Objective: To compare clinical outcomes after laparoscopic cholecystectomy (LC) for acute cholecystitis performed at various time-points after hospital admission. Background: Symptomatic gallstones represent an important public health problem with LC the treatment of choice. LC is increasingly offered for acute cholecystitis, however, the optimal time-point for LC in this setting remains a matter of debate. Methods: Analysis was based on the prospective database of the Swiss Association of Laparoscopic and Thoracoscopic Surgery and included patients undergoing emergency LC for acute cholecystitis between 1995 and 2006, grouped according to the time-points of LC since hospital admission (admission day (d0), d1, d2, d3, d4/5, d ≥6). Linear and generalized linear regression models assessed the effect of timing of LC on intra- or postoperative complications, conversion and reoperation rates and length of postoperative hospital stay. Results: Of 4113 patients, 52.8% were female, median age was 59.8 years. Delaying LC resulted in significantly higher conversion rates (from 11.9% at d0 to 27.9% at d ≥6 days after admission, P < 0.001), surgical postoperative complications (5.7% to 13%, P < 0.001) and re-operation rates (0.9% to 3%, P = 0.007), with a significantly longer postoperative hospital stay (P < 0.001). Conclusions: Delaying LC for acute cholecystitis has no advantages, resulting in significantly increased conversion/re-operation rate, postoperative complications and longer postoperative hospital stay. This investigation—one of the largest in the literature—provides compelling evidence that acute cholecystitis merits surgery within 48 hours of hospital admission if impact on the patient and health care system is to be minimized.

Securities: Its Conception and Protection of Interests of its Holders

Theoretical studies of the problems of the securities markets in the Russian Federation incline to one or other of the two traditional approaches. The first consists of comparing the definition of "valuable paper" set forth in the current legislation of the Russian Federation, with the theoretical model of "Wertpapiere" elaborated by German scholars more than 90 years ago. The problem with this approach is, in Mr. Pentsov's opinion, that any new features of the definition of "security" that do not coincide with the theoretical model of "Wertpapiere" (such as valuable papers existing in non-material, electronic form) are claimed to be incorrect and removed from the current legislation of the Russian Federation. The second approach works on the basis of the differentiation between the Common Law concept of "security" and the Civil Law concept of "valuable paper". Mr. Pentsov's research, presented in an article written in English, uses both methodological tools and involves, firstly, a historical study of the origin and development of certain legal phenomena (securities) as they evolved in different countries, and secondly, a comparative, synchronic study of equivalent legal phenomena as they exist in different countries today. Employing the first method, Mr. Pentsov divided the historical development of the conception of "valuable paper" in Russia into five major stages. He found that, despite the existence of a relatively wide circulation of valuable papers, especially in the second half of the 19th century, Russian legislation before 1917 (the first stage) did not have a unified definition of valuable paper. The term was used, in both theoretical studies and legislation, but it covered a broad range of financial instruments such as stocks, bonds, government bonds, promissory notes, bills of exchange, etc. During the second stage, also, the legislation of the USSR did not have a unified definition of "valuable paper". After the end of the "new economic policy" (1922 - 1930) the stock exchanges and the securities markets in the USSR, with a very few exceptions, were abolished. And thus during the third stage (up to 1985), the use of valuable papers in practice was reduced to foreign economic relations (bills of exchange, stocks in enterprises outside the USSR) and to state bonds. Not surprisingly, there was still no unified definition of "valuable paper". After the beginning of Gorbachev's perestroika, a securities market began to re-appear in the USSR. However, the successful development of securities markets in the USSR was retarded by the absence of an appropriate regulatory framework. The first effort to improve the situation was the adoption of the Regulations on Valuable Papers, approved by resolution No. 590 of the Council of Ministers of the USSR, dated June 19, 1990. Section 1 of the Regulation contained the first statutory definition of "valuable paper" in the history of Russia. At the very beginning of the period of transition to a market economy, a number of acts contained different definitions of "valuable paper". This diversity clearly undermined the stability of the Russian securities market and did not achieve the goal of protecting the investor. The lack of unified criteria for the consideration of such non-standard financial instruments as "valuable papers" significantly contributed to the appearance of numerous fraudulent "pyramid" schemes that were outside of the regulatory scheme of Russia legislation. The situation was substantially improved by the adoption of the new Civil Code of the Russian Federation. According to Section 1 of Article 142 of the Civil Code, a valuable paper is a document that confirms, in compliance with an established form and mandatory requisites, certain material rights whose realisation or transfer are possible only in the process of its presentation. Finally, the recent Federal law No. 39 - FZ "On the Valuable Papers Market", dated April 22 1996, has also introduced the term "emission valuable papers". According to Article 2 of this Law, an "emission valuable paper" is any valuable paper, including non-documentary, that simultaneously has the following features: it fixes the composition of material and non-material rights that are subject to confirmation, cession and unconditional realisation in compliance with the form and procedure established by this federal law; it is placed by issues; and it has equal amount and time of realisation of rights within the same issue regardless of when the valuable paper was purchased. Thus the introduction of the conception of "emission valuable paper" became the starting point in the Russian federation's legislation for the differentiation between the legal regimes of "commercial papers" and "investment papers" similar to the Common Law approach. Moving now to the synchronic, comparative method of research, Mr. Pentsov notes that there are currently three major conceptions of "security" and, correspondingly, three approaches to its legal definition: the Common Law concept, the continental law concept, and the concept employed by Japanese Law. Mr. Pentsov proceeds to analyse the differences and similarities of all three, concluding that though the concept of "security" in the Common Law system substantially differs from that of "valuable paper" in the Continental Law system, nevertheless the two concepts are developing in similar directions. He predicts that in the foreseeable future the existing differences between these two concepts will become less and less significant. On the basis of his research, Mr. Pentsov arrived at the conclusion that the concept of "security" (and its equivalents) is not a static one. On the contrary, it is in the process of permanent evolution that reflects the introduction of new financial instruments onto the capital markets. He believes that the scope of the statutory definition of "security" plays an extremely important role in the protection of investors. While passing the Securities Act of 1933, the United States Congress determined that the best way to achieve the goal of protecting investors was to define the term "security" in sufficiently broad and general terms so as to include within the definition the many types of instruments that in the commercial world fall within the ordinary concept of "security' and to cover the countless and various devices used by those who seek to use the money of others on the promise of profits. On the other hand, the very limited scope of the current definition of "emission valuable paper" in the Federal Law of the Russian Federation entitled "On the Valuable Papers Market" does not allow the anti-fraud provisions of this law to be implemented in an efficient way. Consequently, there is no basis for the protection of investors. Mr. Pentsov proposes amendments which he believes would enable the Russian markets to become more efficient and attractive for both foreign and domestic investors.

What’s the Problem? Precarious Youth: Marginalisation, Criminalisation and Racialisation.

Since the nineteenth century invention of adolescence, young people have been consistently identified as social problems in western societies. Their contemporary status as a focus of fear and anxiety is, in that sense, nothing new. In this paper, I try to combine this sense of historical recurrence about the youth problem with some questions about what is different about the present – asking what is distinctive about the shape of the youth problem now? This is a difficult balance to strike, and what I have to say will probably lean more towards an emphasis on the historical conditions and routes of the youth problem. That balance reflects my own orientations and knowledge (I am not expert on the contemporary conditions of being young). But it also arises from my belief that much contemporary social science is profoundly forgetful. An enthusiasm for stressing the newness, or novelty, of the present connects many varieties of contemporary scholarship. One result is the construction of what Janet Fink and I have referred to as ‘sociological time’ in which

A Column-Generation Approach for a Short-Term Production Planning Problem in Closed-Loop Supply Chains

We present a new model formulation for a multi-product lot-sizing problem with product returns and remanufacturing subject to a capacity constraint. The given external demand of the products has to be satisfied by remanufactured or newly produced goods. The objective is to determine a feasible production plan, which minimizes production, holding, and setup costs. As the LP relaxation of a model formulation based on the well-known CLSP leads to very poor lower bounds, we propose a column-generation approach to determine tighter bounds. The lower bound obtained by column generation can be easily transferred into a feasible solution by a truncated branch-and-bound approach using CPLEX. The results of an extensive numerical study show the high solution quality of the proposed solution approach.

The Acceleration of Stock Options in Anticipation of FAS 123 (R)

The Financial Accounting Standards Board (FASB) mandated the expensing of stock options with FAS 123 (R). As of March 2006, 749 companies had accelerated the vesting of their employee stock options and avoided a reduction in their reported profits that otherwise would have occurred under the new standard. There are many different motives for the acceleration strategy, and the focus of this study is to determine whether shareholders viewed these motives as either positive or negative. A favorable return subsequent to an acceleration announcement would signify that shareholder's viewed management's motives as positive. An unfavorable return subsequent to an acceleration announcement would signify that shareholder's viewed management's motives as negative. The evidence from this study suggests that shareholders reacted favorably, on average, to acceleration announcements. However, these results lack statistical significance and are based on a small sample, thus, they should be interpreted with caution.

Asset Pricing with Heterogeneous Agents, Incomplete Markets and Trading Constraints

The consumption capital asset pricing model is the standard economic model used to capture stock market behavior. However, empirical tests have pointed out to its inability to account quantitatively for the high average rate of return and volatility of stocks over time for plausible parameter values. Recent research has suggested that the consumption of stockholders is more strongly correlated with the performance of the stock market than the consumption of non-stockholders. We model two types of agents, non-stockholders with standard preferences and stock holders with preferences that incorporate elements of the prospect theory developed by Kahneman and Tversky (1979). In addition to consumption, stockholders consider fluctuations in their financial wealth explicitly when making decisions. Data from the Panel Study of Income Dynamics are used to calibrate the labor income processes of the two types of agents. Each agent faces idiosyncratic shocks to his labor income as well as aggregate shocks to the per-share dividend but markets are incomplete and agents cannot hedge consumption risks completely. In addition, consumers face both borrowing and short-sale constraints. Our results show that in equilibrium, agents hold different portfolios. Our model is able to generate a time-varying risk premium of about 5.5% while maintaining a low risk free rate, thus suggesting a plausible explanation for the equity premium puzzle reported by Mehra and Prescott (1985).

Investigation project: Representations about the professional role of recently graduated from the psychology career, state University of La Plata : Its relation with job insertion and performance

In this paper we present a research that took place between 2010 and 2012 included in an investigation scholarship awarded by the State University of la Plata. It is about the problem with the transition between college and professional work. It is a part of the produced studies on the importance of social representations as factors that impact on the performance of specific activities. In this case it's about finding out the relations given among the representations about graduated professional role of the Psychology career and its job insertion and performance. The theoretical framework corresponds to Social Psychology and Guidance theories. Methodologically this is an exploratory and descriptive study, based on the 'triangulation' conception, of multiple type, that allows combining in the same investigation, different strategies, theoretical perspectives and sources; however qualitative techniques were prioritized to analyze data. Finally there are some considerations about the social representations concerning to the professional performance, mainly in the clinical field associated to education, and also to the problems of both situations over other fields

Investigation project: Representations about the professional role of recently graduated from the psychology career, state University of La Plata : Its relation with job insertion and performance

In this paper we present a research that took place between 2010 and 2012 included in an investigation scholarship awarded by the State University of la Plata. It is about the problem with the transition between college and professional work. It is a part of the produced studies on the importance of social representations as factors that impact on the performance of specific activities. In this case it's about finding out the relations given among the representations about graduated professional role of the Psychology career and its job insertion and performance. The theoretical framework corresponds to Social Psychology and Guidance theories. Methodologically this is an exploratory and descriptive study, based on the 'triangulation' conception, of multiple type, that allows combining in the same investigation, different strategies, theoretical perspectives and sources; however qualitative techniques were prioritized to analyze data. Finally there are some considerations about the social representations concerning to the professional performance, mainly in the clinical field associated to education, and also to the problems of both situations over other fields

Investigation project: Representations about the professional role of recently graduated from the psychology career, state University of La Plata : Its relation with job insertion and performance

In this paper we present a research that took place between 2010 and 2012 included in an investigation scholarship awarded by the State University of la Plata. It is about the problem with the transition between college and professional work. It is a part of the produced studies on the importance of social representations as factors that impact on the performance of specific activities. In this case it's about finding out the relations given among the representations about graduated professional role of the Psychology career and its job insertion and performance. The theoretical framework corresponds to Social Psychology and Guidance theories. Methodologically this is an exploratory and descriptive study, based on the 'triangulation' conception, of multiple type, that allows combining in the same investigation, different strategies, theoretical perspectives and sources; however qualitative techniques were prioritized to analyze data. Finally there are some considerations about the social representations concerning to the professional performance, mainly in the clinical field associated to education, and also to the problems of both situations over other fields

Logic-Based Outer Approximation for the Design of Discrete-Continuous Dynamic Systems with Implicit Discontinuities

We address the optimization of discrete-continuous dynamic optimization problems using a disjunctive multistage modeling framework, with implicit discontinuities, which increases the problem complexity since the number of continuous phases and discrete events is not known a-priori. After setting a fixed alternative sequence of modes, we convert the infinite-dimensional continuous mixed-logic dynamic (MLDO) problem into a finite dimensional discretized GDP problem by orthogonal collocation on finite elements. We use the Logic-based Outer Approximation algorithm to fully exploit the structure of the GDP representation of the problem. This modelling framework is illustrated with an optimization problem with implicit discontinuities (diver problem).

Comparative study of RPSALG algorithm for convex semi-infinite programming

The Remez penalty and smoothing algorithm (RPSALG) is a unified framework for penalty and smoothing methods for solving min-max convex semi-infinite programing problems, whose convergence was analyzed in a previous paper of three of the authors. In this paper we consider a partial implementation of RPSALG for solving ordinary convex semi-infinite programming problems. Each iteration of RPSALG involves two types of auxiliary optimization problems: the first one consists of obtaining an approximate solution of some discretized convex problem, while the second one requires to solve a non-convex optimization problem involving the parametric constraints as objective function with the parameter as variable. In this paper we tackle the latter problem with a variant of the cutting angle method called ECAM, a global optimization procedure for solving Lipschitz programming problems. We implement different variants of RPSALG which are compared with the unique publicly available SIP solver, NSIPS, on a battery of test problems.

Ukraine's cooperation with the IMF - unfulfilled hopes for deeper reforms. OSW Commentary No. 52, 2011-06-15

The Party of Regions took power in early 2010, after Ukraine had been plunged deep in economic crisis. Over the next year, with the external markets recovering, the country’s economic situation started to improve gradually. Ukraine’s economic stabilisation was also strengthened by its resumed cooperation with the International Monetary Fund, which provided for a loan worth $15.1 billion. The issuing of successive tranches of the loan was made dependent on the implementation of a comprehensive reform programme. The cooperation went quite smoothly at first; however, as the economic situation in Ukraine improved, the reformist zeal of the Ukrainian government started to fade, and obstacles began piling up. As a result, Ukraine was refused the third tranche, scheduled for this March, and for the moment the credit line remains frozen. Even though the IMF has numerous reservations about the Ukrainian government’s economic policy, the fundamental condition for resuming cooperation is reform of the pension system, which the parliament should adopt. The difficulties with fulfilling the obligations made to the IMF reflect the wider problem with implementing reforms in Ukraine, as the Party of Regions promised after taking power. Changes which do not affect the interests of influential lobbies are quite easy to carry out. Often, however, these changes are not conducive to the economy’s liberalisation; moreover, the influential lobbies are successful in blocking reforms that could harm their businesses. Another impediment to the changes is that some reforms are likely to bring about painful social consequences, and that can affect public support for the ruling group. Even though theoretically possible, it does not seem likely that Ukraine’s cooperation with the IMF will be terminated. But even if this cooperation is continued, deeper reforms in Ukraine are likely to be postponed until after the parliamentary elections in autumn 2012.

Evolução da perceção parental da imagem corporal da criança : análise retrospetiva de dois estudos

Introdução: A obesidade é reconhecida pela OMS como um importante problema de saúde pública, que afeta adultos, crianças e adolescentes e que tem tomado proporções epidémicas em todo o mundo. Os estudos revelam que os pais, mas sobretudo as mães se mostram preocupadas e concordam com a adoção de hábitos alimentares saudáveis, no entanto a perceção que estas têm do estado nutricional dos filhos nem sempre é adequada e frequentemente a imagem corporal é distorcida, percebendo-se contudo que esta distorção tem vindo a diminuir. Foi neste âmbito que emergiu como objetivo geral deste estudo, explorar a evolução da perceção parental da imagem corporal da criança em dois estudos, estudo A (Graça Aparício) e estudo B (Graça Aparício, Madalena Cunha, João Duarte; Anabela Pereira, Jorge Bonito, Carlos Albuquerque), publicados respetivamente, em 2012 e 2013 e relacioná-la com o comportamento alimentar da criança do estudo B. Material e métodos: Este estudo de carácter retrospetivo e transversal, foi realizado com as crianças que participaram no estudo A e no estudo B, num total de 2216 crianças em idade pré-escolar, média idade= 4.51 anos (±0.97Dp), residentes as crianças do estudo A na região de Viseu e Dão e as do estudo B, nas regiões Viseu, Lamego, Vila Real, Évora e Leiria, tendo sido efetuada pelos autores originais, uma avaliação antropométrica e classificação nutricional das crianças com base no referencial NCHS (CDC, 2000). Para a recolha de dados os autores originais, utilizaram um Questionário de Caracterização Sociodemográfica das Crianças e dos Progenitores; o Questionário de Avaliação da Perceção Parental da Imagem Corporal da criança (Collins, 1991) e o Questionário de Caracterização do Comportamento Alimentar Infantil (CEBQ), traduzido e validado para a população portuguesa por Viana & Sinde (2008). Resultados: Comparativamente ao estudo A, no estudo B os pais revelaram-se significativamente mais preocupados com o estado nutricional dos seus filhos (p= 0,000). Ainda no estudo B uma maior percentagem de pais assinala as imagens representativas de pré-obesidade (27,5%) e obesidade (0,6%), comparativamente ao estudo A, onde se verifica o oposto; uma maior sinalização das crianças no grupo da normalidade e baixo-peso (56,3% e 20,4% respetivamente). Apurou-se uma diferença de médias significativa da perceção parental da imagem corporal da criança entre o estudo A e o estudo B, evidenciando a perceção dos pais, a uma maior aproximação com os valores mais elevados de IMC dos filhos, ou seja, os pais têm uma perceção menos distorcida da imagem corporal dos filhos, quando estes apresentam valores de IMC mais elevados. Relativamente ao comportamento alimentar, apesar dos comportamentos de “atração pela comida” se associarem a uma perceção parental de imagem corporal maior, e de alguns dos comportamentos de “evitamento da comida” se associarem a uma perceção parental de imagem corporal menor, a relação entre o comportamento alimentar e a perceção parental da imagem corporal criança não se revelou significativa. Conclusões: Os resultados indicam uma maior acurácia da perceção da imagem corporal dos pais ao real estado nutricional dos filhos, podendo este facto ser o primeiro passo para o seu reconhecimento do excesso de peso dos seus filhos e facilitar a adequação a um estilo de vida mais saudável entre as crianças em idade pré-escolar, e maior sensibilização da família para o controlo do excesso de peso na infância. Palavras-chave: Perceção parental, imagem corporal, Obesidade infantil.