Application of lean scheduling and production control in non-repetitive manufacturing systems using intelligent agent decision support

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Lean Manufacturing (LM) is widely accepted as a world-class manufacturing paradigm, its currency and superiority are manifested in numerous recent success stories. Most lean tools including Just-in-Time (JIT) were designed for repetitive serial production systems. This resulted in a substantial stream of research which dismissed a priori the suitability of LM for non-repetitive non-serial job-shops. The extension of LM into non-repetitive production systems is opposed on the basis of the sheer complexity of applying JIT pull production control in non-repetitive systems fabricating a high variety of products. However, the application of LM in job-shops is not unexplored. Studies proposing the extension of leanness into non-repetitive production systems have promoted the modification of pull control mechanisms or reconfiguration of job-shops into cellular manufacturing systems. This thesis sought to address the shortcomings of the aforementioned approaches. The contribution of this thesis to knowledge in the field of production and operations management is threefold: Firstly, a Multi-Agent System (MAS) is designed to directly apply pull production control to a good approximation of a real-life job-shop. The scale and complexity of the developed MAS prove that the application of pull production control in non-repetitive manufacturing systems is challenging, perplex and laborious. Secondly, the thesis examines three pull production control mechanisms namely, Kanban, Base Stock and Constant Work-in-Process (CONWIP) which it enhances so as to prevent system deadlocks, an issue largely unaddressed in the relevant literature. Having successfully tested the transferability of pull production control to non-repetitive manufacturing, the third contribution of this thesis is that it uses experimental and empirical data to examine the impact of pull production control on job-shop performance. The thesis identifies issues resulting from the application of pull control in job-shops which have implications for industry practice and concludes by outlining further research that can be undertaken in this direction

Capacity expansion under a service level constraint for uncertain demand with lead times

For a service provider, stochastic demand growth along with expansion lead times and economies of scale may complicate a capacity planning problem. We consider a service provider who has to maintain certain minimum level of service and is interested in knowing the optimal timings and sizes of the future capacity expansions. This service level is defined in terms of unsatisfied demand over an expansion cycle. Under this service level constraint, the service provider wants to minimize the infinite time horizon cost of expansion. We assume a stationary policy where the timing and the sizes of the expansions are determined as fixed proportions of the capacity position, where the capacity position is the capacity that will be available when the current expansion is completed. We assume that the demand for the capacity follows a geometric Brownian motion (GBM) process. We discuss a method to check the GBM process fit for any data series representing the demand values and find that the data for electric utility consumption in the US, and the airline passenger enplanement data over a period of 15 years satisfy the assumptions of a GBM process. Using properties of the demand process, we can use financial option pricing theory to express the service level in terms of the decision variables. Particularly, we use the Up-and-Out partial barrier call option price expression to formulate the service level constraint. We use cutting plane algorithm to solve the optimization problem. Numerical optimization shows that it could be optimal to accumulate initial shortage before initiating the next capacity expansions for a low growth, low volatility demand and also when the expansion lead times are shorter. However, when the demand grows at a high rate or is more volatile, it is optimal to start the next expansion project before the demand reaches the current capacity position

Proceedings of the 2004 Coal Operators\u27 Conference

Proceedings of the 2004 Coal Operators\u27 Conference. All papers in these proceedings are peer reviewed in accordance with The AUSIMM publication standard

Modelling and analysis of pull production systems

Ankara : Industrial Engineering and the Institute of Engineering and Science of Bilkent Univ., 1995.Thesis (Ph.D.) -- Bilkent University, 1995.Includes bibliographical references.A variety of production systems appearing in the literature are reviewed in order to develop a classification scheme for production systems. A number of pull production systems appearing in the classification are found to be equivalent to a tandem queue so that accurate tandem queue decomposition methods can be used to find the performance of such systems. The primary concern of this dissertation is to model and analyze non-tandem queue equivalent periodic pull production systems. In this research, an exact performance evaluation model is developed for a singleitem periodic pull production system. The processing and demand interarrival times are assumed to be Markovian. For large systems, which are difficult to evaluate exactly because of large state spaces involved, an approximate decomposition method is proposed. A typical approximate decomposition procedure takes individual stages or pairs of stages in isolation to analyze the system and then it aggregates the results to obtain an approximate performance for the whole system. An experiment is designed in order to investigate the general behavior of the decomposition. The results are worth attention. A second aspect of this study is to investigate an allocation methodology to achieve the maximum throughput rate with providing two sets of allocation parameters regarding the number of kanbans and the workload at each stage of the system. Together with some structural properties, the experimental results provide some insight into the behavior of pull production systems and also provide a basis for the proposed allocation methodology. Finally, we conclude our findings together with some directions for future research.Kırkavak, NureddinPh.D

Capital Flows and Implication for Central Bank Policies in The SEACEN Countries

The SEACEN economies have liberalised their external accounts and domestic financial markets. The current account is fully convertible in all the countries in the SEACEN region while the capital account is by and large fully convertible in the majority of these countries. Since early 1990s, net capital flow to the SEACEN countries increased steadily until 1996 due to the massive increase in total capital inflows. However, after the financial crisis of 1997, total capital outflows have outweighed total capital inflows resulting in a negative net capital flow. Both domestic factors such as attractive economic growth, attractive interest rates and large current account deficits and external factors such as low world interest rates are responsible for the increased capital inflows in the region. However, determinants of short-term capital inflows vary from that of the total capital inflows. Notably, short-term capital inflows are found to be inversely associated with domestic economic growth. The effects of push and pull factors on capital flows vary across the countries. Recent experiences of SEACEN countries indicate that the US sub-prime mortgage crisis has led to slower capital inflows in the region while domestic political climate, further liberalisation in overseas investment; and, encouragement to invest abroad have accelerated capital outflows. The SEACEN region has benefited significantly from the increased capital inflows mainly in terms of increased investment, higher economic growth, favourable external accounts and developed financial markets. However, capital flows have also led to challenges for monetary and financial stability. The recent experience of SEACEN countries shows that capital flows can create asset price bubbles and induce sharp increases in bank credit while outflow of capital results in lower equity prices and depreciation of exchange rates. Short-term capital inflows are highly volatile and prone to sudden reversals. After 2003, the share of short-term inflow started to become increasingly dominant in the total inflow in the SEACEN region, resembling the pattern of capital flows before the 1997 crisis. Due to the larger share of highly volatile shortterm foreign capital, SEACEN economies are again, facing the risk of massive capital reversals. In order to prevent a repetition of the same problems in the future, SEACEN countries need to encourage more long-term capital inflows rather than short-term ones. To safeguard the financial system and the economy from speculative attacks, authorities need to implement more prudent regulations and cautiously monitor potential areas of such attacks. In order to maintain a conducive monetary stability environment, central banks need to sterilise inflows with appropriate intervention measures. Freer exchange rates allow for more capital flows in and out of the country. However, in the time of distress, the countries that have a free floating exchange rate regime may suffer from larger capital reversals. Therefore, a managed floating exchange regime may be more advantageous during a crisis. The financial markets and economies of the SEACEN countries are currently affected by the global financial crisis, due mainly to external factors. In order to minimise further negative impacts of the crisis on various sectors of the economy including capital flows, to speed up the recovery process, and also to explore the possibility of inventing new economic drivers within the region, coordinated policy measures need to be implemented at the national as well as regional levels.

Labour Migration From EaP Countries to the EU - Assessment of Costs and Benefits and Proposals for Better Labour Market Matching

It is reasonable to expect steady migratory flows from Eastern Parntership nations in the future, and that migration would be a desirable phenomenon (based on the so-far advantageous migratory flows from EaP nations). They cause no negative wage effects on native workers