This thesis is focused on a simulation modelling approach to address the inventory inaccuracy problems in a warehouse operation. The main motivation which led to this research was a desire to investigate the inventory inaccuracy issues that have been highlighted by a logistics company. Previous and current research into inventory inaccuracy issues is largely related to the development of RFID technology as a possible solution to inventory problems. Since the inventory inaccuracy related to RFID technology is focused on the overall measurement of inventory management and retail business, there are differences between this existing research and the research presented in this thesis which is focused on issues of inventory inaccuracy in a warehouse operation. In this thesis, warehouse operation is studied as a detailed sequence of processes that are involved in the flow of items physically in parallel with related information being stored in the computer system. In these processes there are many places where errors can occur in counting or recording details of inventory, or in physically moving, storing or picking items incorrectly. These details of a warehouse operation are used to develop a conceptual model of inventory inaccuracy in warehouse operations. The study also found that typically a product needs to be considered differently at different stages of its progress through a warehouse (and therefore within different sections of the conceptual model). This is because initially batches of a product are likely to be delivered from a supplier, therefore if errors occur soon after the product is delivered to the warehouse, the error might involve the whole batch (for example the batch may be misplaced and put in an incorrect storage location), or the error might involve just part of the batch (for example poor transportation by forklift truck may damage the packaging carton and some of the items within the carton). When the product is stored ready for meeting customer orders, it needs to be considered as individual items (and errors can occur in counting of individual items or individual items may be misplaced or stolen). Finally, when a customer order is received, the product will be picked and grouped to meet the requirements of the order (for example, one order may require 10 of the product whilst another order may require 20 of the product). Errors might again occur to the whole group or to just part of the group. (Continued ...)

This study identifies the concepts of reliability, cost of downtime, cost of spare parts, and procurement lead time as the four key moderators of spare parts availability. These concepts are used to establish a model to manage spare parts inventories. Reliability was assessed in terms of developing failure predictions for major component categories. Cost of downtime was evaluated by identifying various methods for determining costs associated with downtime. Cost of spare parts was examined to find correlations with economic indicators. These correlations were used to predict future price movements. Yearly changes in lead time were identified and correlated with economic indexes to develop movement predictability.

D. Litt. et Phil. / Factor analytic techniques were used to investigate the psychometric properties of three measuring instruments, namely the Adult Career Concerns Inventory (Super, Thompson & Lindeman, 1988), the Career Attitudes and Strategies Inventory (Holland & Gottfredson, 1994), and the Career Resilience Questionnaire (Fourie & Van Vuuren, 1998). The analyses served the purpose of elucidating the conceptual meanings of the constructs of career concerns, career status and career resilience in adult vocational adjustment. In an exploratory factor analysis of the Adult Career Concerns Inventory theoretical considerations suggested the extraction of four factors which explained 74% of the variance in the correlation matrix. The communalities of the variables were determined by means of squared multiple correlations of the subscales. On oblique rotation by means of Promax, a four factor solution was supported, reflecting the underlying dimensions of Exploration, Establishment, Maintenance and Disengagement. High correlations among the factors suggested the presence of a general factor, which may be termed career concerns. A factor extension analysis indicated the high quality of the test items, and a high level of correspondence between the Maintenance and Establishment factors. Maximum likelihood confirmatory factor analyses of the Adult Career Concerns Inventory were subsequently performed to test four and three factor measurement models. The estimated standardised factor pattern coefficients of both the models were found to be statistically significant. High correlations between the Maintenance and Establishment factors from the four factor model however favoured the three factor model, which allows for the merging of these two latent dimensions. In an exploratory factor analysis of the Career Attitudes and Strategies Inventory use were made of constructed item parcels. Theoretical considerations suggested the extraction of nine factors, which accounted for 54% of the variance in the correlation matrix. The squared multiple correlations of the Career Attitudes and Strategies Inventory item parcels were used to determine the initial communalities, and the nine factors were obliquely rotated by means of Promax. With the exception of two of the parcels, the factor pattern coefficients indicated that all the item parcels could be explained by nine factors that correspond with the Career Attitudes and Strategies Inventory subscales, namely Job Satisfaction, Career Worries, Family Commitment, Interpersonal Abuse, Skill Development, Geographical Barriers, Risk-taking Style, Work Involvement, and Dominant Style. The relative independence of these factors were inferred from the interfactor correlation matrix. A factor extension analysis indicated the overall high quality of the test items. A maximum likelihood confirmatory factor analysis of the Career Attitudes and Strategies Inventory at item parcel-level was based on a measurement model in accordance with the nine factors mentioned above. This analysis supported the nine factor model and revealed interesting relations among the dimensions of the Career Attitudes and Strategies Inventory. An exploratory factor analysis of the Career Resilience Questionnaire at item-level was also performed. Although the Kaiser criterion suggested the extraction of as many as 15 factors, and the MAP values suggested six factors, the initial communalities based on the squared multiple correlations were also considered. The initial communalities were reiterated twice, and the residual four factors accounted for 27% of the variance. An oblique rotation of the factors by means of Promax resulted in the tentative labelling of four latent dimensions, namely Leadership, Sense of Security in One’s Career, Acceptance of Uncertainty, and Values. These factors had satisfactory reliability coefficients, but no significant intercorrelations. Due to the theoretical inadequacies of this analysis, an oblique multiple groups factor analysis of the Career Resilience Questionnaire was performed in an attempt to cross-validate the factor solution reported by Fourie and Van Vuuren (1998). Low reliability coefficients of the factors were however obtained, an the postulated measurement model could not be supported. In an interbattery factor analysis of the Adult Career Concerns Inventory and the Career Attitudes and Strategies Inventory both theory and reliability coefficients of various factor solutions were considered, which resulted in the extraction of six factors. The factors were rotated obliquely by means of Direct Quartimin. The resultant factor solution met theoretical expectations by indicating several shared dimensions of the two instruments. Implementation, Advancing, Holding and Updating were grouped with Career Worries and Risk-taking Style. Job Satisfaction related negatively in a shared dimension with Crystallisation, Specification, Implementation, Retirement Planning and Retirement Living. Innovation was associated with Work Involvement, Skill Development and Dominant Style. Stabilisation, Risk-Taking Style and Geographical Barriers formed a shared dimension. Deceleration and Interpersonal Abuse were likewise associated. Lastly, Family Commitment and Updating shared a negative relation within another dimension. In essence, these factor analyses support the construct validity, theoretical generalisability, and usefulness of both the Adult Career Concerns Inventory and the Career Attitudes and Strategies Inventory, but fails to support the construct validity of the Career Resilience Questionnaire. Moreover, a foundation has been laid for the theoretical integration of the constructs of career concerns and career status.

La gestion des stocks et la maîtrise de la distribution sont les deux activités importantes dans le management de la chaîne logistique. L’optimisation simultanée de ces deux activités est connue sous l’intitulé du problème de gestion de stock et de tournée de livraison (Inventory Routing Problem, IRP). L’IRP traditionnelle est confronté aux différents problèmes, causé principalement par le manque d'informations complètes et/ou temps réel, tels que les changements de la demande, l’embouteillage soudain causé par un accident, etc. Le partage et la mise à jour d'information logistique peut améliorer l'efficacité d’IRP. De plus, en raison de la spécificité de l'IRP dans la logistique urbaine, il est important de considérer d'autres critères comme les critères sociaux, environnementaux et le niveau de service qui pourraient être en conflictuel. L’objectif principal de cette thèse est de développer des modèles et des méthodes des IRP avec la prise en compte des incertitudes, du niveau de service et de l’impact environnemental, social en finalement les informations du temps réel (IRP dynamique). Dans cette thèse, trois modèles mathématiques sont proposés. Le premier modèle multi-objectif est pour identifier un compromis entre le niveau de service, les critères environnementaux et économiques. Pour gérer des paramètres incertains, on applique une approche floue. Dans le deuxième modèle, nous avons étudié l'impact des critères sociaux sur les IRPs en proposant un modèle mathématique bi-objectif. Une approche stochastique basée sur des scénarios est développée pour faire face à l'incertitude dans le modèle. Enfin, le troisième model concerne l'impact de l'utilisation d'informations du temps réel dans les IRP. Il est à noter que, selon la durée de vie du produit tant sur le plan financier que sur le plan écologique, les produits périssables sont considérés dans les trois modèles proposés. Les résultats montrent une gestion dynamique est beaucoup plus efficace que la statique. / The inventory management and transportation are two main activities of supply chain management. The joint optimization of these two activities is known as Inventory Routing Problem (IRP). The main objective of IRP is to determine the set of retailers to be delivered to in each period, the delivery sequence for each vehicle, and the quantities of goods delivered to each retailer for each period of a planning horizon. The traditional IRPs are faced different problems, caused mainly by lack of complete and/or timely information such as shifts in demand, traffic caused by a sudden vehicles accident, etc. sharing of updated and reliable logistics information can meaningful improve the efficiency of IRP. Moreover, because of the specificity of IRP in urban logistic, it is important to tack into account other criteria as social, environmental criteria and service level that could be in conflict. The main objective of this thesis is to (i) choose appropriate social, environmental and service level criteria, (ii) integrate them in mathematical models, and (iii) study the impact of these criteria on dynamic optimization of IRPs for perishable products under uncertain parameters. For this purpose, three mathematical models are proposed. The first model is multi-objective mathematical model in order to make a trade-off between service level, environmental criteria and economic. To decrease quantity of expired products, a nonlinear step function as holding cost function is integrated in the model. Moreover, to solve the problem a fuzzy possibilistic approach is applied to handle uncertain parameters. In the second model, a bi-objective mathematical model is proposed to study impact of social issues on the IRPs. In the proposed model, first objective function concerns economic criteria while the second one social issues. A scenario-based stochastic approach is developed to cope with uncertainty in the model. Finally, the third model concerns impact of using real-time information in efficiency of IRPs. It is noteworthy that, according significant role of perishable products in the both financially and ecology sides of IRPs, perishable products are considered in all three proposed model while even proposed models are appropriate to nonperishable ones as well. The results show that a dynamic management is more efficient than the static one.

Application of multisource feedback (MSF) increased dramatically and became widespread globally in the past two decades, but there was little conceptual work regarding self-other agreement and few empirical studies investigated self-other agreement in other cultural settings. This study developed a new conceptual framework of self-other agreement and used three samples to illustrate how national culture affected self-other agreement. These three samples included 428 participants from China, 818 participants from the US, and 871 participants from globally dispersed teams (GDTs). An EQS procedure and a polynomial regression procedure were used to examine whether the covariance matrices were equal across samples and whether the relationships between self-other agreement and performance would be different across cultures, respectively. The results indicated MSF could be applied to China and GDTs, but the pattern of relationships between self-other agreement and performance was different across samples, suggesting that the results found in the U.S. sample were the exception rather than rule. Demographics also affected self-other agreement disparately across perspectives and cultures, indicating self-concept was susceptible to cultural influences. The proposed framework only received partial support but showed great promise to guide future studies. This study contributed to the literature by: (a) developing a new framework of self-other agreement that could be used to study various contextual factors; (b) examining the relationship between self-other agreement and performance in three vastly different samples; (c) providing some important insights about consensus between raters and self-other agreement; (d) offering some practical guidelines regarding how to apply MSF to other cultures more effectively.

Background: Ménières disease is a complex neurological disease that varies greatly from individual to individual with symptoms such as dizziness and tinnitus. There are few studies that examines the differences regarding balance and dizziness related perception of disabilitiy between men and women with Ménière’s disease. Purpose: Investigate self-assessed perception of disability and balance of people with Ménières disease. The study also aimed to investigate whether there were any differences between men and women regarding the above mentioned variables. Method: Retrospective study with quantitative, correlative and comparative design. 41 subjects, 21 women, 20 men were included in the study. Results: No significant difference between men and women regarding scores on DHI-S or result on Romberg’s test could be shown in this study. Neither could any significant connection between self-assessed perception of disability and balance measured with DHI-S and Romberg’s respectively could be made. Conclusion: No relation between self-assessed disability and balance was detected between men and women. The study also did not find any differences between the sexes on how they perform on balance measurement or rate their disability. More studies are needed to further investigate and map this area. / Bakgrund: Ménières sjukdom är en neurologisk sjukdom med symtom som yrsel och tinnitus. I dagsläget finns få studier som undersöker skillnader gällande balans och yrsel relaterad upplevelse av funktionsnedsättning mellan män respektive kvinnor med Ménières sjukdom. Syfte: Syftet med studien var att undersöka eventuella samband mellan självskattad funktionsnedsättning och balans samt skillnader mellan män och kvinnor. Metod: Retrospektiv studie med kvantitativ, korrelerande och komparativ design. 41 antal försökspersoner, 21 kvinnor, 20 män inkluderades i studien. Resultat: Ingen skillnad mellan män och kvinnors värde på DHI-S kunde påvisas. Det förelåg ingen signifikant skillnad mellan män och kvinnor gällande resultat på Rombergs test. Inget samband mellan upplevelse av funktionsnedsättning och balans mätt med DHI-S respektive Rombergs test för kvinnor och män gick att påvisa. Konklusion: Inget samband mellan självskattad funktionsnedsättning och balans kunde påvisas hos män och kvinnor. Studien fann inte heller några skillnader mellan könen gällande hur de presterar på balansmätning eller skattar sin funktionsnedsättning. Vidare studier behövs för att kunna ytterligare undersöka och kartlägga detta område.

This diploma thesis focuces on a analysis of business process, which controls storage and on solution suggestions which is written down in the analysis part. This thesis was made in a medium-sized business in which this draft will help for better control over storage prcess and inventory.

The thesis focuses on the analysis of various extensions of the classical multi-period single-item stochastic inventory problem. Specifically, we investigate two particular approaches of modeling risk in the context of inventory management: risk-averse models and robust formulations. We analyze the classical newsvendor problem utilizing a coherent risk measure as the objective function. Properties of coherent risk measures allow us to offer a unifying treatment of risk averse and min-max type formulations. We show that the structure of the optimal policy of the risk-averse model is similar to that of the classical expected value problem for both single and multi-period cases. The result carries over even when there is a fixed ordering cost. We expand our analysis to robust formulations of multi-period inventory problems. We consider both independent and dependent uncertainty sets and prove the optimality of base-stock policies for the general problem formulation. We focus on budget of uncertainty approach and develop a heuristic that can also be employed for a class of parametric dependency structures. We compare our proposed heuristic against alternative solution techniques.

This dissertation consists of three independent sections: In the first part, focusing on the auto industry we look at the challenges and solution strategies of employing build-to-order (BTO) with global supply. We consider some familiar tools for managing domestic supply and exploit them for managing international supply, and propose new methods. We study frequency of supply as a way to improve performance. We study the impact of forecast accuracy, and conclude that improvements there alone may not be sufficient to obtain desired savings. Within this perspective we look at a new shipping policy, 'Ship-to-Average", which prescribes sending a fixed quantity, based on the long term average forecast, with each shipment and making adjustments only if the inventory strays outside a prescribed range. In the second part we look at a Brownian control problem. When a manufacturer places repeated orders with a supplier to meet changing production requirements, he faces the challenge of finding the right balance between holding costs and the operational costs involved in adjusting the shipment sizes. Consider a storage system whose content fluctuates as a Brownian motion in the absence of control. A linear holding cost is incurred continuously. Inventory level can be adjusted by any quantity at a fixed plus proportional cost. We show control band policies are optimal for the average cost problem and calculate the optimal policy parameters. This form of policy is described by three parameters q, Q, S. When the inventory falls to 0 (rises to S), the controller expedites (curtails) shipments to return it to q (Q). Developing techniques based on Lagrangian relaxation we show that this type of policy is optimal even with constraints on the size of adjustments and on the maximum inventory level. The Brownian Control problem can be viewed as an idealization --without delivery delays, of the problem of supplying BTO operations, and provides some theoretical explanation for the Ship-to-Average policies. In fact, Ship-to-Average policies are a practical implementation of Control Band policies in the setting with delivery delays. Finally, we explore the power and applicability of the Lagrangian approach developed in the second part.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 240-259). Available also in a digital version from Dissertation Abstracts.