Thesis (M. Sc.)--University of Hong Kong, 1979.

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 252-300).

published_or_final_version / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy

The procurement of commodity materials for production is an important issue in supply chain management. Effective procurement should consider both uncertain customer demand and fluctuating commodity price which, when act together, give rise to the procurement risk. To protect the bottom line, a manufacturer has to plan its procurement activities with special attention given to such procurement risk. Existing research has studied the use of exchange market-traded commodities in mitigating procurement risk. This study addresses the case of a manufacturer with long-term procurement commitments who wishes to hedge against the risk exposure by using long-dated futures contracts. In the commodities markets, however, long-dated futures are often illiquid or even unavailable, thus making the hedge ineffective. Alternatively, in a stack-and-roll hedge, the hedging positions are rolled forward in actively traded short-dated futures contracts of equal maturity until the procurement is executed. This in effect replicates the long-term futures contract in performing a hedge. This study therefore aims at developing a dynamic stack-and-roll approach that can effectively manage the long maturity procurement risk. The proposed dynamic stack-and-roll approach is inherently a discrete-time hedging strategy that divides the procurement planning horizon into multiple decision stages. The nearby futures are adopted as the short-dated futures as they are typically liquid. The hedging positions are adjusted periodically in response to the commodity price behaviour and updated information about the forward customer demand. For a manufacturer who wishes to mitigate the procurement risk as well as maximise the terminal revenue after the procurement, the mean-variance objective function is employed to model the manufacturer’s risk aversion behaviour. Then, a dynamic program formulation of the approach is presented for determining a closed-form expression of the optimal hedging positions. Notice that the hedging policy is a time-consistent mean-variance policy in discrete-time, in contrast to the existing discrete hedging approaches that employ minimum-variance policies. In this study, the commodity prices are modelled by a fractal nonlinear regression process that employs a recurrent wavelet neural network as the nonlinear function. The purpose of this arrangement is to incorporate the fractal properties discovered in commodity prices series. In the wavelet transform domain, fractal self-similarity and self-affinity information of the price series over a certain time scale can be extracted. The Extended Kalman Filter (EKF) algorithm is applied to train the neural network for its lower training error comparing with classical gradient descent algorithms. Monthly returns and volatility of commodity prices are estimated by daily returns data in order to increase the estimation accuracy and facilitate effective hedging. The demand information is updated stage by stage using Bayesian inference. The updating process are defined and adapted to a filtration, which can be regarded as the information received at the beginning of each decision stage. Numerical experiments are carried out to evaluate the performance of the proposed stack-and-roll approach. The results show that the proposed approach robustly outperforms other hedging strategies that employ minimum-variance or naïve policies, and effectively mitigate the procurement risk. / published_or_final_version / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy

Transportation procurement problem (TPP) is the problem of setting transportation service prices, delivery timing and quantity, and controlling costs and capacity to reduce empty movements and improve market efficiency. The purchase of transportation service is traditionally achieved using a request for proposal and long-term contracts. However, as business relationships become ever more flexible and dynamic, there has been an increasing need to hedge the risks of traditional transportation procurement such as entrance of new carriers and sudden drop in fuel price. This thesis proposes a holistic aution-based solution for the TPP. Four typical scenarios are investigated. The first scenario incorporates bilateral bidding into auction mechanism design for multi-unit TPP. This scenario considers one-sided Vickrey-Clarke-Groves (O-VCG) combinatorial auctions for a complex transportation marketplace with multiple lanes. This scenario then designs three alternative multi-unit trade reduction (MTR) mechanisms for the bilateral exchange transportation marketplace where all the lanes are partitioned into distinct markets. Proposed mechanisms ensure incentive compatibility, individual rationality, budget balance and asymptotical efficiency. The second scenario presents a double auction model for the TPP in a dynamic single-lane transportation environment. This scenario first addresses the TPP in a transportation spot market with stochastic but balanced or “symmetric” demand and supply. A periodic sealed double auction (PSDA) is proposed. This scenario then devises a modified PSDA (M-PSDA) to address the TPP with “asymmetric” demand and supply. The auctioneer is likely to gain higher profits from setting a relatively short auction length. However, it is optimal to run the auction (either PSDA or MPSDA) with a relatively large auction length, when maximizing either the social welfare or the utility of shippers and carriers (agents). When the degree of supply-demand imbalance is low, the auctioneer’s myopic optimal expected profit under supply-demand imbalance is larger than that under symmetric demand and supply. This third scenario presents an auction-based model for the TPP in make-toorder systems. The optimality of dynamic base-stock type (S(x)-like policy) is established. The optimal allocation can be achieved by running an O-VCG auction or a first-price auction with closed-form reserve prices. By mild technical modifications, the results derived in the infinite horizon case can all be extended to the finite horizon case. The fourth scenario proposes allocatively efficient auction mechanisms for the distributed transportation procurement problem (DTPP), which is generally the problem of matching demands and supplies over a transportation network. This scenario constructs an O-VCG combinatorial auction for the DTPP where carriers are allowed to bid on bundles of lanes. To simplify the execution of auction, this scenario next proposes a primal-dual Vickrey (PDV) auction based on insights from the known Ausubel auctions and the primal-dual algorithm. The PDV auction realizes VCG payments and truthful bidding under the condition of seller-submodularity, which implies that the effect of each individual carrier is decreasing when the coalition increases. / published_or_final_version / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy

Questa tesi mette in evidenza e studi una possibile trade-off tra stabilità e l'efficienza economica che un ente governativo può affrontare quando si cerca di costruire un progetto di valore sociale in un paese in via di sviluppo instabile. Nel primo capitolo, i rivedere l'attuale stato di avanzamento in materia di appalti in cui espongo le sfide con i processi di approvvigionamento attuali nei paesi in via di sviluppo. La revisione dimostra infatti che l'assunzione di acquiescenza militare è una grande svista nel tentativo di ottenere un sistema di appalti solido ed efficace in un paese in via di sviluppo. Come espone Laffont che nella letteratura di appalto la necessità per le spese di revisione è stata presa in considerazione con attenzione all'impegno imperfetta delle procedure di controllo e della corruzione dei revisori dei conti. Questo contributo esamina le varie situazioni di sviluppo e di appalti all'interno di un paese in via di sviluppo e gli effetti dello stato attraverso il suo esercito. Particolare esposizione è data per selezionare gli stati africani. / This thesis highlights and studies a possible trade-off between stability and economic efficiency that a government agency may face when trying to build a socially valuable project in a unstable developing country. In the first chapter, i review the current progress made in procurement where I expose the challenges with the current procurement processes in developing countries. The review indeed shows that the assumption of military acquiescence is a big oversight in the endeavor to obtain a solid and effective procurement system in a developing country. As Laffont exposes that in the procurement literature the need for auditing costs was taken into account with attention given to imperfect commitment of auditing procedures and to the corruption of auditors. This contribution surveys the various situations of development and procurement within a developing country and the effect of the state through its military. Particular exposition is given to select African states.

This research project specifically investigates the use of information processing strategies by organizational buyers in the first stage of the supplier selection process, the selection of an evoked set of qualified suppliers. In this selection process it is hypothesized that the buyer's use of evaluation functions or information processing strategies is influenced by the task faced by the buyer. The varying levels of risk, familiarity and informational requirements of the buying situation should impact the use of the information processing strategies. Structured protocols--written descriptions of compensatory and noncompensatory information processing strategies--were used to determine the evaluation function which organizational buyers use to qualify suppliers into an evoked set. The data was collected in a field study of 135 organizational buyers from 76 different organizations. The subjects were interviewed about purchases they were presently working on in which suppliers had been selected but the final purchase decision was still pending. Identification of the buying task, new task, modified rebuy, and straight rebuy also utilized the structured protocol technique. Written descriptions, based on the constitutive definitions of Robinson and Farris (1967), were used to address the following research question: Is there a difference in the decision rules or information processing strategies utilized by organizational buyers in the development of an evoked set of qualified suppliers when the buyer is qualifying suppliers for a new task, modified rebuy, or straight rebuy buying task? In addition to the information gathered via the structured protocols, information was gathered about the level of risk, familiarity and information requirements of the purchasing task. This was done to gain a better understanding of the use of information-processing strategies by organizational buyers. Analysis of the data indicates that the buying task is related to the choice of an information-processing strategy. The data also support the contention that the organizational buyer will utilize any of the information-processing strategies in the selection of an evoked set of suppliers. Although the buying task was found to significantly influence the use of the information-processing strategies, the study shows that all of the strategies were reported as being used for each of the buying tasks. In addition to finding that the buying task influences the choice of an information-processing strategy, the data support the model of information processing presented. The model addressed the impact that risk, familiarity, and information load had on the use of the evaluation functions. The risk node of the model was supported by two of the five risk variables included in the study: product homogeneity and supplier homogeneity. At the familiarity nodes of the model, the subjective measures of familiarity which support the model are supplier familiarity and frequency of product purchase. Supplier familiarity was found to be significantly different between the weighted and unweighted compensatory strategies. The significant difference in the level of familiarity found in the use of the conjunctive and disjunctive information processing strategies is associated with the frequency of product purchase. The final nodal section of the information-processing model which was supported is the comparison of the conjunctive and lexicographic strategies. The lexicographic strategy was found to be used when there was a higher perceived number of suppliers capable of supplying the needed product. In general this study has shown that the situation in which suppliers are selected impacts the use of an information-processing strategy. The findings are consistent with the research and hypothesizing associated with the use of information-processing strategies by consumers.

Focusing on a rural community in Colchester County, Nova Scotia, this research examines the Atlantic Canadian context for farm-to-school programs, gauging interest and attitudes and examining current barriers which prevent more locally grown food from being served in the school cafeteria. A major component of this research is a comparative case study using a successful American farm-to-school program in Hancock County, Maine. By way of comparative study, this research examines how stronger farm-school partnerships can be developed in Atlantic Canada. Results in Nova Scotia indicate financial and structural barriers, as well as a number of community assets, including a strong belief on the part of relevant stakeholders that farm-to-school programs have the potential to increase student health and foster economic well being for farmers. This paper puts forth recommendations and strategies for expanding farm-to-school programs in Nova Scotia based on results from the comparative case study.

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