無 / We derive the MacLaurin series for the moments of the idle time with respect to the parameters in the service time and interarrival time distributions for a GI/G/I queue. The light traffic derivatives are obtained to investigate the quality of a well-known MacLaurin series. The coefficients in these series are expressed in terms of the derivatives of the interarrival time density function evaluated at zero and the moments of the service time distribution, which can be easily calculated through a simple recursive procedure. The result for the idle period is easily taken as input to the calculation of other performance measures of the system, e.g., interdeparture time distributions. Numerical examples are given to illustrate these results.

Idle time is a common phenomenon that prevents employees from performing their core job tasks, with detrimental effects on employee well-being and performance. Drawing on affective events theory, the job demands-resources model, and action regulation theory, this dissertation addresses three main questions: First, how idle time affects employee well-being and performance; second, the mechanisms behind these effects, namely appraisals and affective reactions; and third, the conditions under which idle time may be beneficial for employees. Study 1 (N = 338) showed indirect negative effects of objective idle time on employee well-being through the subjective experience of being idle. Age was negatively and boredom proneness positively associated with subjective idle time. Two experiments in Study 2 (N2a = 445, N2b = 597) demonstrated the detrimental effects of regulation problems on employee well-being and performance, mediated by objective and subjective idle time. Recovery activities buffered the detrimental effects of idle time. In Study 3, a 12-month, five-wave longitudinal study (N = 1,036), the associations of idle time with lower job satisfaction, higher turnover intentions, and higher counterproductive work behavior were mediated by higher boredom. Finally, the results of Study 4, based on the same data as Study 3, showed that the effects of idle time on employee exhaustion and engagement depended on boundary conditions, namely workload and autonomy. For high workload employees, idle time was positively associated with engagement, whereas when autonomy was high, idle time was associated with lower exhaustion and lower engagement. During idle time, relaxation was beneficial, whereas detachment was detrimental regarding employee exhaustion and engagement. Idle time is detrimental to employee well-being and performance, mediated by subjective idle time, boredom, and lack of recovery, respectively. Certain conditions, like high workload or using idle time for relaxation, can make it beneficial for employees. The results provide insights for research, particular in the areas of waiting, interruptions, recovery, and well-being.:Acknowledgments i English Abstract ii German Abstract iii Table of Contents iv List of Tables ix List of Figures x 1 General Introduction 1 2 Study 1: Effects of Idle Time on Well-Being – An Experimental Study 6 2.1 Abstract 6 2.2 Introduction 7 2.3 Idle Time as an Affective Event at Work 9 2.4 Method 11 2.4.1 Open Science 11 2.4.2 Study Design 11 2.4.3 Participants 12 2.4.4 Materials 13 2.4.5 Data Analysis 14 2.5 Results 15 2.5.1 Descriptive Statistics 15 2.5.2 Confirmatory Factor Analysis 15 2.5.3 Manipulation Check 15 2.5.4 Hypothesis Tests 15 2.5.5 Exploratory Results 16 2.6 Discussion 17 2.6.1 Theoretical and Practical Implications 17 2.6.2 Limitations and Future Research 19 2.7 Conclusion 21 2.8 Open Data and Electronic Supplementary Materials (ESM 1) 21 3 Study 2: Idle Time, Recovery, and Work Outcomes: Results of Two Experimental Studies 26 3.1 Abstract 26 3.2 Introduction 27 3.3 Idle Time at Work 29 3.3.1 Antecedents of Idle Time 29 3.3.2 The Consequences of Idle Time 30 3.3.3 The Mechanisms Underlying Effects of Idle Time 31 3.4 Study 1 33 3.4.1 Method 33 3.4.2 Results 36 3.4.3 Discussion 37 3.5 Study 2 37 3.5.1 Method 37 3.5.2 Results 40 3.5.3 Discussion 43 3.6 General Discussion 43 3.6.1 Theoretical and Practical Implications 44 3.6.2 Limitations and Future Research 46 3.7 Conclusion 47 4 Study 3: Is it Bad Because it is Boring? Effects of Idle Time on Employee Outcomes 58 4.1 Abstract 58 4.2 Introduction 59 4.3 The Effects of Idle Time 62 4.3.1 Idle Time and Boredom 63 4.3.2 Boredom and Employee Outcomes 64 4.3.3 Idle Time and Employee Outcomes 65 4.4 Method 66 4.4.1 Participants and Procedure 66 4.4.2 Measures 68 4.4.3 Statistical Analysis 70 4.5 Results 71 4.5.1 Hypothesis Tests 71 4.5.2 Additional Analyses 73 4.6 Discussion 75 4.6.1 Theoretical and Practical Implications 75 4.6.2 Limitations and Future Research 77 4.7 Conclusion 79 5 Study 4: Can Idle Time Serve as a Resource? A Job Demands-Resources Approach 88 5.1 Abstract 88 5.2 Introduction 89 5.3 Theoretical Background and Hypotheses Development 91 5.3.1 The Downsides of Idle Time 91 5.3.2 The Benefits of Idle Time 92 5.4 Method 94 5.4.1 Participants and Procedure 94 5.4.2 Measures 95 5.4.3 Data Analysis 97 5.5 Results 97 5.5.1 Hypothesis Tests 97 5.5.2 Additional Analyses 99 5.6 Discussion 99 5.6.1 Theoretical and Practical Implications 100 5.6.2 Limitations and Future Directions 102 5.7 Conclusion 103 6 General Discussion 109 6.1 Summary 109 6.2 Theoretical Contributions 110 6.2.1 The Consequences of Idle Time 110 6.2.2 The Mechanisms Underlying Idle Time 111 6.2.3 Recovery and Boundary Conditions 112 6.3 Practical Contributions 113 6.4 Limitations and Future Directions 114 6.4.1 Affective Events Theory 114 6.4.2 Event System Theory 115 6.4.3 Action Regulation Theory 116 6.5 Conclusion 117 References 118 Appendix I Theses I Idle Time at Work I Study 1: Effects of Idle Time on Well-Being – An Experimental Study II Study 2: Idle Time, Recovery, and Work Outcomes: Results of Two Experimental Studies II Study 3: Is it Bad Because it is Boring? Effects of Idle Time on Employee Outcomes II Study 4: Can Idle Time Serve as a Resource? A Job Demands-Resources Approach III Conclusion IV References IV Thesen VI Leerlaufzeiten bei der Arbeit VI Studie 1: Auswirkungen von Leerlaufzeiten auf das Wohlbefinden – eine Experiment VII Studie 2: Leerlaufzeit, Erholung und Arbeitsergebnisse: Ergebnisse von zwei experimentellen Studien VII Studie 3: Sind sie schlecht, weil sie langweilig sind? Auswirkungen von Leerlaufzeiten auf Beschäftigte VII Studie 4: Kann Leerlaufzeit als Ressource dienen? Ein Arbeitsanforderungen-Ressourcen-Ansatz VIII Schlussfolgerungen IX Literaturverzeichnis IX Curriculum Vitae XI Publication List XII Selbstständigkeitserklärung XIV Nachweise über die Anteile der Co-Autorschaft: Studie 1 XV Nachweise über die Anteile der Co-Autorschaft: Studie 2 XVI Nachweise über die Anteile der Co-Autorschaft: Studie 3 XVII Nachweise über die Anteile der Co-Autorschaft: Studie 4 XVIII

Computer based simulation models have often been used to study the multimodal freight transportation system. But these studies have not been able to dynamically couple the various modes into one model; therefore, they are limited in their ability to inform on dynamic system level interactions. This research thesis is motivated by the need to dynamically couple the multimodal freight transportation system to operate at multiple spatial and temporal scales. It is part of a larger research program to develop a systems modeling framework applicable to freight transportation. This larger research program attempts to dynamically couple railroad, seaport, and highway freight transportation models. The focus of this thesis is the development of the coupled railroad and seaport models. A separate volume (Wall 2010) on the development of the highway model has been completed. The model railroad and seaport was developed using Arena® simulation software and it comprises of the Ports of Savannah, GA, Charleston, NC, Jacksonville, FL, their adjacent CSX rail terminal, and connecting CSX railroads in the southeastern U.S. However, only the simulation outputs for the Port of Savannah are discussed in this paper. It should be mentioned that the modeled port layout is only conceptual; therefore, any inferences drawn from the model's outputs do not represent actual port performance. The model was run for 26 continuous simulation days, generating 141 containership calls, 147 highway truck deliveries of containers, 900 trains, and a throughput of 28,738 containers at the Port of Savannah, GA. An analysis of each train's trajectory from origin to destination shows that trains spend between 24 - 67 percent of their travel time idle on the tracks waiting for permission to move. Train parking demand analysis on the adjacent shunting area at the multimodal terminal seems to indicate that there aren't enough containers coming from the port because the demand is due to only trains waiting to load. The simulation also shows that on average it takes containerships calling at the Port of Savannah about 3.2 days to find an available dock to berth and unload containers. The observed mean turnaround time for containerships was 4.5 days. This experiment also shows that container residence time within the port and adjacent multimodal rail terminal varies widely. Residence times within the port range from about 0.2 hours to 9 hours with a mean of 1 hour. The average residence time inside the rail terminal is about 20 minutes but observations varied from as little as 2 minutes to a high of 2.5 hours. In addition, about 85 percent of container residence time in the port is spent idle. This research thesis demonstrates that it is possible to dynamically couple the different sub-models of the multimodal freight transportation system. However, there are challenges that need to be addressed by future research. The principal challenge is the development of a more efficient train movement algorithm that can incorporate the actual Direct Traffic Control (DTC) and / or Automatic Block Signal (ABS) track segmentation. Such an algorithm would likely improve the capacity estimates of the railroad network. In addition, future research should seek to reduce the high computational cost imposed by a discrete process modeling methodology and the adoption of single container resolution level for terminal operations. A methodology combining both discrete and continuous process modeling as proposed in this study could lessen computational costs and lower computer system requirements at a cost of some of the feedback capabilities of the model This tradeoff must be carefully examined.

Today's commercial rapid prototyping systems (i.e., solid freeform fabrication, layered manufacturing) rely on human intervention to load and unload build jobs. Hence, jobs are processed subject to both the machine's and the operator's schedules. In particular, first-in-first-out (FIFO) queuing of such systems will result in machine idle time whenever a build job has been completed and an operator is not available to unload that build job and start up the next one. These machine idle times can significantly affect the system throughput, and, hence, the effective cost rate. This thesis addresses this problem by rearranging the job queue to minimizing the machine idle time, subject to the machine's and operator's schedules. This is achieved by employing a general branch-and-bound search method, that, for efficiency, reduces the search space by identifying contiguous sequences and avoiding reshuffling of those sequences during the branching procedure. The effectiveness of this job scheduling optimization has been demonstrated using a sequence of 30 jobs extracted from the usage log for the FDM 1600 rapid prototyping system in the Department of Mechanical Engineering at Virginia Tech. / Master of Science

Este trabalho apresenta procedimentos que podem ser utilizados na programação da produção em um ambiente JIT. Esses procedimentos deveriam ser utilizados em sistemas clássicos de programação, onde a utilização do sistema kanban é inviável. O caso estudado se baseia em uma única máquina, com datas de entrega múltiplas e com penalidades distintas de adiantamento e de atraso para cada ordem. O objetivo a ser alcançado é a minimização do custo total. Para isso, é utilizado um procedimento de busca denominado beam search, para gerar as seqüências, e um algoritmo de inserção de ociosidade, para definir os programas. O algoritmo utilizado é uma generalização do algoritmo de GAREY et al. (1988) onde as penalidades são distintas para adiantamento e para atraso. O procedimento e o algoritmo são testados em várias condições sendo comparados com regras de despacho e com a função EXP-ET. Quando a função EXP-ET é utilizada com a possibilidade de inserção de ociosidade, o período de ociosidade ótimo é determinado. Assume-se que a dificuldade de solução do problema é dependente de dois parâmetros clássicos: fator de atraso médio e amplitude relativa das datas de entrega. Testes empíricos comparativos são realizados através de simulação computacional, onde se mede o tempo de solução e o valor alcançado pela função objetivo. Os resultados indicam que o desempenho dos vários procedimentos testados é altamente dependente dos dois parâmetros, mostrando que para a escolha de um procedimento apropriado, deve-se primeiramente conhecer o valor dos parâmetros. São fornecidos os resultados encontrados e os códigos computacionais utilizados no estudo. / This work presents some procedures which can be used in production scheduling problems in JIT environments. These procedures may be used in cases of classical production scheduling where the use of the kanban system is infeasible. The case studied is based on a single machine, with multiple due dates, and distinct earliness and tardiness penalties for each job. The objective function is to minimize total cost. A heuristic search procedure known as beam search is used to construct sequences of jobs, and an idleness insertion algorithm is used to obtain schedules. The algorithm used is a generalization of the GAREY et al. (1988) algorithm, where penalties are distinct for earliness and tardiness. The procedure and algorithm are tested in many conditions involving comparisons with dispatching rules and the EXP-ET function. When EXP-ET function is applied with possibility of idleness insertion, the optimal idleness period is provided. It was assumed that problem hardness is dependent on two classical parameters: average tardiness factor and relative range of due dates. Empirical comparative tests are conducted with computational simulation, where computational solution time and objective function value are evaluated. Results indicate that procedures performance is highly dependent on both parameters, showing that is necessary to know parameters values before choosing an appropriate procedure. The detailed results and computational code used in this study are also provided.

Esta tese apresenta análises de dois problemas de máquina única relacionados à programação da produção com seqüência predefinida. Para ambos os problemas são sugeridas modelagens via programação matemática e algoritmos que encontram a solução ótima em tempo polinomial e pseudo-polinomial. O primeiro problema é o de inserção de espera no problema com função-objetivo que considera s soma de funções convexas do horário de término independentes para cada ordem. O segundo considera custos distintos de adiantamento e atraso para cada ordem e custos de utilização de capacidade adicional ponderados distintamente para cada período de capacidade adicional que possa ser utilizado. Sugere-se adicionalmente um procedimento onde o mesmo avalia a melhor opção entre se utilizar tempo de espera, horas-extras e criar ou eliminar turnos de trabalho. São feitas análises e algumas generalizações como a utilização de diversos intervalos de tempo com diferentes custos concatenados e uma sugestão para a utilização dos procedimentos num ambiente de múltiplas máquinas / This thesis analyses two cases of one-machine problem regarding to production scheduling with fixed sequence. In both problems, modeling with mathematical programming, and (pseudo)polynomial-time algorithms are suggested. The first problem deals with idle time insertion in the problem where the objective function (represented by a sum of costs) considers that each job has costs described as any convex function of its completion time. The second problem considers earliness and tardiness with distinct costs for each job considering the possible use of additional capacity. For the additional capacity we assume that there are distinct costs for each time period where jobs can be processed. A procedure dealing with options of either to change the number of shifts or to utilize overtime considering total costs is suggested. Analysis and generalizations based on the utilization of several contiguous time periods with distinct costs and a heuristic extension for the multiple-machine case are also presented

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The present study was developed with the objective of evaluate if the frequency of roughage and supplement supply and/or animal category affect performance and behavior of feedlot cattle. Sixteen heifers and sixteen cows were used, with average initial age of 20 and 66 months and average initial weight of 338 and 462 kg, respectively. The frequencies of roughage and supplement supply were: 2 V/C roughage and supplement 2 times per day; 1 V/C roughage and supplement 1 time per day; 1 V/2 C roughage 1 time per day and supplement 2 times per day; 1 V/3 C roughage 1 time per day and supplement 3 times per day. Each food supply was offered to cows and heifers. The supplied diet was composed by 60% of maize silage and 40% of concentrate, on dry matter base (DM). The process of obtaining performance parameters was by animal weighting and attribution of body condition, weighting of the supplied food and it s respective orts, chemical analysis of diet ingredients and orts. Behavior parameters were obtained by register of animal activities at each 5 minutes, beyond counting chews per ruminated bolus and it s duration. The complete randomized experimental design was used, with a 4 x 2 factorial arrangement. No significant interaction was observed (P>.05) between supply frequencies and animal category for performance variables. For ingestive behavior, was observed interaction between supply and animal category for rumination (RT) and idle (IDT) times, efficiencies of dry matter rumination (EDMR) and neutral detergent fiber rumination (ENDFR), number of daily bolus and daily time of chews (DTC). Supply frequencies did not influence (P>.05) average daily weight gain (ADWG). Dry matter intake (DMI) per animal was superior for animal of 1 V/2 C or 1 V/3 C treatments. The DMI and digestible energy intake per animal and per metabolic size were higher for cows, however ADWG was similar (1.330 vs. 1.378, respectively), resulting on worst food conversion for cows in relation to heifers (9.4 vs. 7.4 kg, respectively). Heifers showed higher (P<.05) IDT and DTC when compared with cows that received food once in a day. Time of food intake (TFI) did not vary (P>.05) with supply frequencies. Ingestion rate (IR) was higher (P<.05) for animals that received 1 V/3 C, and did not differ from the ones that received 1 V/2 C in relation to 1 V/C and 2 V/C supply frequencies (2.89; 2.72; 2.43 and 2.48 kg of DM/hour of intake, respectively). Cows were higher for TFI and IR in relation to heifers (4.38 vs. 4.09 hours, 2.91 vs. 2.35 kg of DM/hour of intake, respectively). The frequencies supply of one, two or three times per day stimulates animals to intensify ingestion on the moment of the supply, but this don t alter time of food intake during the day and animals weight gain. / O presente estudo foi desenvolvido com o objetivo de avaliar se a freqüência do fornecimento do volumoso e concentrado e/ou a categoria animal afetam o desempenho e o comportamento de bovinos confinados. Foram utilizadas 16 novilhas e 16 vacas, com idade média inicial de 20 e 66 meses e peso médio inicial de 338 e 432 kg, respectivamente. As freqüências do fornecimento do volumoso e concentrado foram as seguintes: 2 V/C volumoso e concentrado 2 vezes ao dia; 1 V/C volumoso e concentrado 1 vez ao dia; 1 V/2 C volumoso 1 vez ao dia e o concentrado 2 vezes ao dia; 1 V/3 C volumoso 1 vez ao dia e o concentrado 3 vezes ao dia. Cada fornecimento alimentar foi ofertado nas categorias vaca e novilha. A dieta fornecida aos animais foi composta de 60% de silagem de milho e 40% de concentrado com base na matéria seca (MS). A obtenção das variáveis de desempenho ocorreu pela pesagem e atribuição de escore corporal aos animais, pesagem do alimento fornecido e respectivas sobras, análise bromatológica dos ingredientes da dieta e das sobras. As variáveis de comportamento foram avaliadas através do registro de atividades dos animais a cada 5 minutos, além da contagem de mastigações por bolo ruminado e sua duração. O delineamento experimental adotado foi inteiramente casualizado em arranjo fatorial 4 x 2 (fornecimentos x categoria animal). Não houve interação significativa (P>0,05) entre freqüência de fornecimento e categoria animal para as variáveis de desempenho. Para o comportamento ingestivo, foi observada interação entre o fornecimento e a categoria animal para o tempo de ruminação (TR) e ócio (TO), eficiência de ruminação da matéria seca (ERMS) e da fibra detergente neutro (ERFDN), número de bolos diário e tempo de mastigação diário (TMD). As freqüências do fornecimento não influenciaram (P>0,05) o ganho de peso médio diário (GMD). O consumo de matéria seca (CMS) por animal foi superior para os animais alimentados 1 V/2 C ou 1 V/3 C. O CMS e o consumo de energia digestível por animal e por tamanho metabólico foram superiores para as vacas em relação às novilhas, porém, o GMD foi semelhante (1,330 vs 1,378 kg, respectivamente), resultando em pior conversão alimentar (9,4 vs 7,4 kg, respectivamente). As novilhas apresentaram maiores (P<0,05) TO e TMD em relação às vacas quando receberam a alimentação uma vez ao dia. O tempo de consumo de alimento (TCA) não teve variação (P>0,05) conforme a freqüência do fornecimento da dieta. A taxa de ingestão (TI) foi superior (P<0,05) para os animais que receberam 1 V/3 C, e esta não diferiu dos que receberam 1 V/2 C em relação aos fornecimentos de 1 V/C e 2 V/C (2,89; 2,72; 2,43 e 2,48 kg de MS/hora de consumo, respectivamente). As vacas permaneceram mais TCA e apresentaram maiores TI em comparação às novilhas (4,38 vs 4,09 horas; 2,91 vs 2,35 kg de MS/hora de consumo, respectivamente). A freqüência do fornecimento do alimento aos animais em uma, duas ou três vezes ao dia estimula estes a intensificar a ingestão no momento do fornecimento, mas isso não altera o tempo de ingestão do alimento ao longo do dia e o ganho de peso dos animais.

Este trabalho apresenta procedimentos que podem ser utilizados na programação da produção em um ambiente JIT. Esses procedimentos deveriam ser utilizados em sistemas clássicos de programação, onde a utilização do sistema kanban é inviável. O caso estudado se baseia em uma única máquina, com datas de entrega múltiplas e com penalidades distintas de adiantamento e de atraso para cada ordem. O objetivo a ser alcançado é a minimização do custo total. Para isso, é utilizado um procedimento de busca denominado beam search, para gerar as seqüências, e um algoritmo de inserção de ociosidade, para definir os programas. O algoritmo utilizado é uma generalização do algoritmo de GAREY et al. (1988) onde as penalidades são distintas para adiantamento e para atraso. O procedimento e o algoritmo são testados em várias condições sendo comparados com regras de despacho e com a função EXP-ET. Quando a função EXP-ET é utilizada com a possibilidade de inserção de ociosidade, o período de ociosidade ótimo é determinado. Assume-se que a dificuldade de solução do problema é dependente de dois parâmetros clássicos: fator de atraso médio e amplitude relativa das datas de entrega. Testes empíricos comparativos são realizados através de simulação computacional, onde se mede o tempo de solução e o valor alcançado pela função objetivo. Os resultados indicam que o desempenho dos vários procedimentos testados é altamente dependente dos dois parâmetros, mostrando que para a escolha de um procedimento apropriado, deve-se primeiramente conhecer o valor dos parâmetros. São fornecidos os resultados encontrados e os códigos computacionais utilizados no estudo. / This work presents some procedures which can be used in production scheduling problems in JIT environments. These procedures may be used in cases of classical production scheduling where the use of the kanban system is infeasible. The case studied is based on a single machine, with multiple due dates, and distinct earliness and tardiness penalties for each job. The objective function is to minimize total cost. A heuristic search procedure known as beam search is used to construct sequences of jobs, and an idleness insertion algorithm is used to obtain schedules. The algorithm used is a generalization of the GAREY et al. (1988) algorithm, where penalties are distinct for earliness and tardiness. The procedure and algorithm are tested in many conditions involving comparisons with dispatching rules and the EXP-ET function. When EXP-ET function is applied with possibility of idleness insertion, the optimal idleness period is provided. It was assumed that problem hardness is dependent on two classical parameters: average tardiness factor and relative range of due dates. Empirical comparative tests are conducted with computational simulation, where computational solution time and objective function value are evaluated. Results indicate that procedures performance is highly dependent on both parameters, showing that is necessary to know parameters values before choosing an appropriate procedure. The detailed results and computational code used in this study are also provided.

Esta tese apresenta análises de dois problemas de máquina única relacionados à programação da produção com seqüência predefinida. Para ambos os problemas são sugeridas modelagens via programação matemática e algoritmos que encontram a solução ótima em tempo polinomial e pseudo-polinomial. O primeiro problema é o de inserção de espera no problema com função-objetivo que considera s soma de funções convexas do horário de término independentes para cada ordem. O segundo considera custos distintos de adiantamento e atraso para cada ordem e custos de utilização de capacidade adicional ponderados distintamente para cada período de capacidade adicional que possa ser utilizado. Sugere-se adicionalmente um procedimento onde o mesmo avalia a melhor opção entre se utilizar tempo de espera, horas-extras e criar ou eliminar turnos de trabalho. São feitas análises e algumas generalizações como a utilização de diversos intervalos de tempo com diferentes custos concatenados e uma sugestão para a utilização dos procedimentos num ambiente de múltiplas máquinas / This thesis analyses two cases of one-machine problem regarding to production scheduling with fixed sequence. In both problems, modeling with mathematical programming, and (pseudo)polynomial-time algorithms are suggested. The first problem deals with idle time insertion in the problem where the objective function (represented by a sum of costs) considers that each job has costs described as any convex function of its completion time. The second problem considers earliness and tardiness with distinct costs for each job considering the possible use of additional capacity. For the additional capacity we assume that there are distinct costs for each time period where jobs can be processed. A procedure dealing with options of either to change the number of shifts or to utilize overtime considering total costs is suggested. Analysis and generalizations based on the utilization of several contiguous time periods with distinct costs and a heuristic extension for the multiple-machine case are also presented