The aim of this thesis is to develop a tractable method for approximating the steady-state behavior of continuous-review base-stock controlled assembly systems with Poisson demand arrivals and manufacturing and assembly facilities modeled as Jackson networks. One class of systems studied is to produce a single type of finished product assembling a number of components and another class is to produce two types of finished products allowing component commonality. The performance measures evaluated are the expected backorders, fill rate and the stockout probability for finished product(s). A partially aggregated but exact model is approximated assuming that the state-dependent transition rates arising as a result of the partial aggregation are constant. This approximation leads to the derivation of a closed-form steady-state probability distribution, which is of product-form. Adequacy of the proposed model in approximating the steady-state performance measures is tested against simulation experiments over a large range of parameters and the approximation turns out to be quite accurate with absolute errors of 10% at most for fill rate and stockout probability, and of less than 1.37 (&amp / #8776 / 2) requests for expected backorders. A greedy heuristic which is proposed to be employed using approximate steady-state probabilities is devised to optimize base-stock levels while aiming at an overall service level for finished product(s).

In this thesis, an approximation is proposed to evaluate the steady-state performance of kanban controlled assembly systems. The approximation is developed for the systems with two components making up an assembly. Then, it is extended to systems with more than two components. A continuous-time Markov model is aggregated keeping the model exact, and this aggregate model is approximated replacing some state-dependent transition rates with constant rates. Decomposition of the approximate aggregate model into submodels guarantees product-form steady-state distribution for each subsystem. Finally, submodels are combined in such a way that the size of the problem becomes independent of the number of kanbans. This brings about the computational advantage in solving the combined model using numerical matrix-geometric solution algorithms. Based on the numerical comparisons with simulation, the exact model, an approximate aggregate model and another approximation in a previous study in the literature, the approximation is observed to be good in terms of accuracy with respect to computational burden and has the potential to be a building block for the analysis of systems that are more complex but closer to real-life applications.

nÃo hà / O trabalho tem como objetivo propor um modelo diagnÃstico que permita avaliar o alinhamento entre os indicadores de resultados organizacionais e os indicadores de desempenho das pessoas. O pressuposto à de que a concepÃÃo de um modelo dessa natureza à factÃvel, desde que se consiga representar quantitativamente e de uma maneira simplificada essa relaÃÃo. A princÃpio, foi feita revisÃo bibliogrÃfica sobre os fundamentos da gestÃo estratÃgica, avaliaÃÃo de desempenho organizacional e de pessoas, sistemas e mÃtodos de avaliaÃÃo de desempenho. ApÃs a revisÃo bibliogrÃfica e com base nas premissas dos sistemas e modelos pesquisados, elaborou-se o modelo diagnÃstico organizacional para o cargo de gerente de unidade, tendo sido empreendida pesquisa de campo, com o objetivo de testar o modelo em trÃs instituiÃÃes financeiras pÃblicas da cidade de Fortaleza. O modelo à composto por cinco nÃveis, denominados dimensÃes, perspectivas, subdimensÃes, itens de verificaÃÃo e desdobramentos. Percebeu-se que a ferramenta à sensÃvel Ãs trÃs dimensÃes do modelo proposto, alÃm de constatar-se a sua viabilidade e utilidade para o processo decisÃrio. Observou-se a necessidade de se adaptar os itens de verificaÃÃo aos cargos em anÃlise, conforme as caracterÃsticas de cada espaÃo ocupacional, sendo essa condiÃÃo primordial para que o modelo proposto traduza a realidade das empresas e facilite o processo decisÃrio. A relevÃncia do sistema de pesos tambÃm foi abordada, com sugestÃes de modificaÃÃo do sistema em consonÃncia com as estratÃgias de cada organizaÃÃo que vier a adotar o modelo proposto.

System of performance evaluation is an essential part of performance management and a major source of organizational control. Discussion about motivational/demotivational power of the formal and informal systems of performance evaluation for different personality types of employees opens a new page in the studies of human resource management. The following research question reflects the core of this thesis “To what extent the informal system of performance evaluation exists beside the formal system of performance evaluation and how do they operate as work motivators/demotivators for civil servants of different psychological types?”. The formal and informal systems of performance evaluation in the Office of the Prime Minister of Lithuania (OPML) are analysed using the theoretical research framework based on three different perspectives: sociology of law, human resource management and psychology. An ethnographic research, supplemented by the psychometric instrument HEXACO PI-R, is conducted to unfold the informal system of performance evaluation and to investigate its motivational/demotivation impact on two different personality types of OPML advisers (ORGANIZED and FLEXIBLE). The formal system is found to be a motivator for the ORGANIZED civil servants and demotivator for the FLEXIBLE advisers, while the informal system served as demotivator for all of the advisers who admitted its existence. In-depth interpretations of the doctoral dissertation research results are provided... [to full text] / Veiklos vertinimo sistema yra neatskiriama veiklos valdymo dalis ir svarbus organizacinės kontrolės įrankis. Diskusijos apie formalios ir neformalios vertinimo sistemų motyvavimo / demotyvavimo galią skirtingų asmenybės tipų darbuotojams atveria naujas perspektyvas žmogiškųjų išteklių valdymo tyrimuose. Šios disertacijos esmę atspindi tyrimo klausimas „Kiek neformali veiklos vertinimo sistema egzistuoja šalia formalios veiklos vertinimo sistemos, ir kaip jos, kaip darbo motyvatoriai / demotyvatoriai, veikia skirtingų asmenybės tipų viešojo sektoriaus darbuotojus?“. Formali ir neformali veiklos vertinimo sistemos Lietuvos Respublikos Ministro Pirmininko tarnyboje (MPT) analizuojamos pasitelkiant teorinį tyrimo pagrindą, kuris yra paremtas trimis skirtingomis perspektyvomis: teisės sociologija, žmogiškųjų išteklių valdymu ir psichologija. Etnografinis tyrimas, kurį papildo psichometrinis įrankis HEXACO PI-R, atliktas siekiant identifikuoti neformalią veiklos vertinimo sistemą ir ištirti jos motyvacinį / demotyvacinį poveikį dviejų skirtingų asmenybės tipų(ORGANIZUOTIESIEMS ir LANKSTIESIEMS) MPT patarėjams. Nustatyta, kad formali sistema veikia kaip motyvatorius ORGANIZUOTIESIEMS patarėjams ir kaip demotyvatorius LANKSTIESIEMS valstybės tarnautojams, o neformali sistema demotyvuoja visus patarėjus, kurie pripažino, kad tokia sistema egzistuoja. Darbe analizuojami atlikto tyrimo rezultatai ir pateikiamos išvados.