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Operations and Supply Chain Management Commons™

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Singapore Management University

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Articles 271 - 300 of 409

Full-Text Articles in Operations and Supply Chain Management

Cellular Bucket Brigades On U-Lines With Discrete Work Stations, Yun Fong Lim, Yue Wu Jul 2014

Cellular Bucket Brigades On U-Lines With Discrete Work Stations, Yun Fong Lim, Yue Wu

Research Collection Lee Kong Chian School Of Business

It is challenging to maximize and maintain productivity of a U-line with discrete stations under the impact of variability. This is because maximizing productivity requires assigning workers to suitable tasks and maintaining productivity requires sufficient flexibility in task assignment to absorb the impact of variability. To achieve this goal, we propose an operating protocol to coordinate workers on the U-line. Under the protocol the system can be configured such that its productivity is maximized. Workers are allowed to dynamically share work so that the system can effectively absorb the impact of variability. Analysis based on a deterministic model shows that …

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Modeling Queues With Simulation Versus M/M/C Models, Kum Khiong Yang, Joyce M. W. Low, Cayirli Tugba Jun 2014

Modeling Queues With Simulation Versus M/M/C Models, Kum Khiong Yang, Joyce M. W. Low, Cayirli Tugba

Research Collection Lee Kong Chian School Of Business

This paper examines the performance of single-queue service systems using a combination of computer simulation and M/M/C queuing models. Our results show that the accuracy of M/M/C models is significantly affected by the assumptions supporting the models. Managers should therefore exercise caution in using the M/M/C models for designing queuing systems when the models’ assumptions are violated. Our results show that cost-centric and servicecentric firms should manage their queues differently. While cost-centric firms should target higher arrival load, single service session, and front-loaded arrival pattern for higher efficiency, service-centric firms should strive for lower arrival load, multiple short sessions and …

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Robust Two-Stage Stochastic Linear Programs With Moment Constraints, Sarah Yini Gao, Lingchen Kong, Jie Sun Jun 2014

Robust Two-Stage Stochastic Linear Programs With Moment Constraints, Sarah Yini Gao, Lingchen Kong, Jie Sun

Research Collection Lee Kong Chian School Of Business

We consider the two-stage stochastic linear programming model, in which the recourse function is a worst case expected value over a set of probabilistic distributions. These distributions share the same first- and second-order moments. By using duality of semi-infinite programming and assuming knowledge on extreme points of the dual polyhedron of the constraints, we show that a deterministic equivalence of the two-stage problem is a second-order cone optimization problem. Numerical examples are presented to show non-conservativeness and computational advantage of this approach.

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Service Systems With Finite And Heterogeneous Customer Arrivals, Rowan Wang, Oualid Jouini, Saif Benjaafar Jun 2014

Service Systems With Finite And Heterogeneous Customer Arrivals, Rowan Wang, Oualid Jouini, Saif Benjaafar

Research Collection Lee Kong Chian School Of Business

We consider service systems with a finite number of customer arrivals, where customer interarrival times and service times are both stochastic and heterogeneous. Applications of such systems are numerous and include systems where arrivals are driven by events or service completions in serial processes as well as systems where servers are subject to learning or fatigue. Using an embedded Markov chain approach, we characterize the waiting time distribution for each customer, from which we obtain various performance measures of interest, including the expected waiting time of a specific customer, the expected waiting time of an arbitrary customer, and the expected …

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Sourcing Hub, Anupam Agrawal, Luk N. Van Wassenhove, Arnoud De Meyer May 2014

Sourcing Hub, Anupam Agrawal, Luk N. Van Wassenhove, Arnoud De Meyer

Asian Management Insights

Managing the suppliers of your suppliers may be a lot of work, but there is plenty of value in unlocking the supply chain.

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The Sourcing Hub And Upstream Supplier Networks, Anupam Agrawal, Luk N. Van Wassenhove, Arnoud De Meyer Mar 2014

The Sourcing Hub And Upstream Supplier Networks, Anupam Agrawal, Luk N. Van Wassenhove, Arnoud De Meyer

Research Collection Lee Kong Chian School Of Business

In this paper, we explore how firms can better manage their sourcing by developing relationships not only with their suppliers but also with their suppliers' suppliers. We detail an empirical case study explaining how the firm developed relationships with its suppliers and raw material suppliers via a collaborative center, the sourcing hub. We then analytically model the scenarios encountered in our empirical work and examine two facets of upstream sourcing under uncertain demand scenarios: (a) firms can supply raw material directly to their suppliers, and this may be beneficial for the firm and its suppliers; and (b) firms can bring …

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Joint Product Improvement By Client And Customer Support Center: The Role Of Gain-Share Contracts In Coordination, Shantanu Bhattacharya, Alok Gupta, Sameer Hasija Mar 2014

Joint Product Improvement By Client And Customer Support Center: The Role Of Gain-Share Contracts In Coordination, Shantanu Bhattacharya, Alok Gupta, Sameer Hasija

Research Collection Lee Kong Chian School Of Business

We study the role of different contract types in coordinating the joint product improvement effort of a client and a customer support center. The customer support center's costly efforts at joint product improvement include transcribing and analyzing customer feedback, analyzing market trends, and investing in product design. Yet this cooperative role must be adequately incentivized by the client, since it could lead to fewer service requests and hence lower revenues for the customer support center. We model this problem as a sequential game with double-sided moral hazard in a principal-agent framework (in which the client is the principal). We follow …

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Distributionally Robust Mixed Integer Linear Programs: Persistency Models With Applications, Xiaobo Li, Karthik Natarajan, Chung-Piaw Teo, Zhichao Zheng Mar 2014

Distributionally Robust Mixed Integer Linear Programs: Persistency Models With Applications, Xiaobo Li, Karthik Natarajan, Chung-Piaw Teo, Zhichao Zheng

Research Collection Lee Kong Chian School Of Business

In this paper, we review recent advances in the distributional analysis of mixed integer linear programs with random objective coefficients. Suppose that the probability distribution of the objective coefficients is incompletely specified and characterized through partial moment information. Conic programming methods have been recently used to find distributionally robust bounds for the expected optimal value of mixed integer linear programs over the set of all distributions with the given moment information. These methods also provide additional information on the probability that a binary variable attains a value of 1 in the optimal solution for 0–1 integer linear programs. This probability …

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New Bounds For The Price Of Anarchy Under Nonlinear And Asymmetric Cost, Deren Han, Jie Sun, Marcus Ang Feb 2014

New Bounds For The Price Of Anarchy Under Nonlinear And Asymmetric Cost, Deren Han, Jie Sun, Marcus Ang

Research Collection Lee Kong Chian School Of Business

We derive new bounds for the price of anarchy under nonlinear and asymmetric costs. The bounds depend on an additional factor called the intrinsic cost of the system and therefore tend to be more accurate than the current bounds that are dependent only on the degree of asymmetry of the Jacobian and the degree of the nonlinearity of the cost function.

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Comparison As Incentive: Newsvendor Decisions In A Social Context, Buket Avci, Zeina Loutfi, Jurgen Mihm, Elena Belavina, Steffen Keck Feb 2014

Comparison As Incentive: Newsvendor Decisions In A Social Context, Buket Avci, Zeina Loutfi, Jurgen Mihm, Elena Belavina, Steffen Keck

Research Collection Lee Kong Chian School Of Business

Explicit formal mechanisms dominate the discussion about incentives in Operations Management, yet many other mechanisms exist. Social comparison between peers may provide strong implicit incentives for individuals. Social comparison arises naturally in all social settings and may thus be unintended; however, many companies deliberately use it to motivate employees. In this study, we model a social context in which purchasers evaluate their performance relative to their peers; a feeling of inferiority results in a negative contribution to utility, whereas a feeling of superiority results in a positive contribution. We find that social comparison induces characteristic deviations from the newsvendor optimum …

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A Nonparametric Method For Pricing And Hedging American Options, Guiyun Feng, Guangwu Liu, Lihua Sun Dec 2013

A Nonparametric Method For Pricing And Hedging American Options, Guiyun Feng, Guangwu Liu, Lihua Sun

Research Collection Lee Kong Chian School Of Business

In this paper, we study the problem of estimating the price of an American option and its price sensitivities via Monte Carlo simulation. Compared to estimating the option price which satisfies a backward recursion, estimating the price sensitivities is more challenging. With the readily-computable pathwise derivatives in a simulation run, we derive a backward recursion for the price sensitivities. We then propose nonparametric estimators, the k-nearest neighbor estimators, to estimate conditional expectations involved in the backward recursion, leading to estimates of the option price and its sensitivities in the same simulation run. Numerical experiments indicate that the proposed method works …

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Social Media For Supply Chain Risk Management, Xiuju Fu, Rick S. M. Goh, J. C. Tong, Loganathan Ponnanbalam, Xiaofeng Yin, Zhaoxia Wang, H. Y. Xu, Sifei Lu Dec 2013

Social Media For Supply Chain Risk Management, Xiuju Fu, Rick S. M. Goh, J. C. Tong, Loganathan Ponnanbalam, Xiaofeng Yin, Zhaoxia Wang, H. Y. Xu, Sifei Lu

Research Collection School Of Computing and Information Systems

With the rapid increase of online social network users worldwide, social media feeds have become a rich and valuable information resource and attract great attention across diversified domains. In social media data, there are abundant contents of two-way and interactive communication about products, demand, customer services and supply. This makes social media a valuable channel for listening to the voices from the market and measuring supply chain risks and new market trends for companies. In this study, we surveyed the potential value of social media in supply chain risk management (SCRM) and examined how they can be applied to SCRM …

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Decision Trees To Model The Impact Of Disruption And Recovery In Supply Chain Networks, Loganathan Ponnanbalam, L. Wenbin, Xiuju Fu, Xiaofeng Yin, Zhaoxia Wang, Rick S. M. Goh Dec 2013

Decision Trees To Model The Impact Of Disruption And Recovery In Supply Chain Networks, Loganathan Ponnanbalam, L. Wenbin, Xiuju Fu, Xiaofeng Yin, Zhaoxia Wang, Rick S. M. Goh

Research Collection School Of Computing and Information Systems

Increase in the frequency of disruptions in the recent times and their impact have increased the attention in supply chain disruption management research. The objective of this paper is to understand as to how a disruption might affect the supply chain network - depending upon the network structure, the node that is disrupted, the disruption in production capacity of the disrupted node and the period of the disruption - via decision trees. To this end, we first developed a 5-tier agent-based supply chain model and then simulated it for various what-if disruptive scenarios for 3 different network structures (80 trials …

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The Principles Of The Dry Bulk Ffa Market, Ron Wilson Oct 2013

The Principles Of The Dry Bulk Ffa Market, Ron Wilson

Research Collection Lee Kong Chian School Of Business

No abstract provided.

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On The Allocation Of Exclusive-Use Counters For Airport Check-In Queues: Static Vs. Dynamic Policies, Mahmut Parlar, Brian Rodrigues, Sharafali Moosa Sep 2013

On The Allocation Of Exclusive-Use Counters For Airport Check-In Queues: Static Vs. Dynamic Policies, Mahmut Parlar, Brian Rodrigues, Sharafali Moosa

Research Collection Lee Kong Chian School Of Business

In this paper we propose a static policy for the optimal allocation of a fixed number of exclusive-use check-in counters dedicated to a single flight. We first provide the motivation for considering the static policy by showing that the dynamic policy already available in the literature suffers from the curse of dimensionality. The objective is to minimize the (expected) total cost of waiting, counter operation, and passenger delay costs which we show to be convex in the number of counters allocated. In those cases where the passenger delay cost is difficult to estimate, we propose an alternative formulation and minimize …

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Corporate Myths: Sourcing And Vendor Management In Asia Pacific, Patrick Thng Sep 2013

Corporate Myths: Sourcing And Vendor Management In Asia Pacific, Patrick Thng

Research Collection School Of Computing and Information Systems

There exists many mistaken beliefs about Sourcing and Vendor Management. Consequently the function is often mismanaged resulting in errors and frauds. Equipping the function with the needed skills and knowledge is critical for competent management of this key function which every organisation has to have.

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Riskvis: Supply Chain Visualization With Risk Management And Real-Time Monitoring, Rick S. M. Goh, Zhaoxia Wang, Xiaofeng Yin, Xiuju Fu, Loganathan Ponnanbalam, Sifei Lu, Xiaorong Li Aug 2013

Riskvis: Supply Chain Visualization With Risk Management And Real-Time Monitoring, Rick S. M. Goh, Zhaoxia Wang, Xiaofeng Yin, Xiuju Fu, Loganathan Ponnanbalam, Sifei Lu, Xiaorong Li

Research Collection School Of Computing and Information Systems

With increased complexity, supply chain networks (SCNs) of modern era face higher risks and lower efficiency due to limited visibility. Hence, there is an immediate need to provide end-to-end supply chain visibility for efficient management of complex supply chains. This paper proposes a visualization scheme based on multi-hierarchical modular design and develops a supply chain visualization platform with risk management and real-time monitoring, named RiskVis, for realizing better Supply Chain Risk Management (SCRM). A Supply Chain Visualizer (SCV) with a graphical visualization platform is mounted as a part of a SCRM management decision-making dashboard and it provides senior management a …

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On Properties Of Discrete (R,Q) And (S,T) Inventory Systems, Marcus Ang, Jing-Sheng Song, Mingzheng Wang, Hanqin Zhang Aug 2013

On Properties Of Discrete (R,Q) And (S,T) Inventory Systems, Marcus Ang, Jing-Sheng Song, Mingzheng Wang, Hanqin Zhang

Research Collection Lee Kong Chian School Of Business

We consider single-item (r, q) and (s, T) inventory systems with integer-valued demand processes. While most of the inventory literature studies continuous approximations of these models and establishes joint convexity properties of the policy parameters in the continuous space, we show that these properties no longer hold in the discrete space, in the sense of linear interpolation extension and L♮-convexity. This nonconvexity can lead to failure of optimization techniques based on local optimality to obtain the optimal inventory policies. It can also make certain comparative properties established previously using continuous variables invalid. We revise these properties in the discrete space.

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Plant Networks For Processing Recyclable Materials, Lieven Demeester, Mei Qi, Luk N. Van Wassenhove Aug 2013

Plant Networks For Processing Recyclable Materials, Lieven Demeester, Mei Qi, Luk N. Van Wassenhove

Research Collection Lee Kong Chian School Of Business

We use a modified optimal market area model to examine how links between material recycling and other aspects of operations strategy can shape plant networks for the processing of recyclable materials. We characterize the complementarity of the recyclate ratio, defined as the maximum recycled content, with material versatility and miniscaling of recycling plants. We also observe that it is beneficial to coordinate investments in recycling- and production-related competencies because colocated recycling and production plants (minimills) eliminate recyclate transport. We therefore consider versatile miniplants, defined as a competency that factors in both material versatility and coordinated miniscaling of recycling and production …

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Dark, Semi-Sweet And Full-Bodied, Singapore Management University Jul 2013

Dark, Semi-Sweet And Full-Bodied, Singapore Management University

Perspectives@SMU

Cadbury grows up in India

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Evaluations Of Port Performances From A Seaborne Cargo Supply Chain Perspective, Joyce M. W. Low, Shao Wei Lam, Loon Ching Tang, Zhang Lan Jul 2013

Evaluations Of Port Performances From A Seaborne Cargo Supply Chain Perspective, Joyce M. W. Low, Shao Wei Lam, Loon Ching Tang, Zhang Lan

Research Collection Lee Kong Chian School Of Business

Previous research on port efficiency focuses primarily on the provider’s perspective and assumes that maximizing the output is always desirable. This paper recognizes that maximizing the final output does not necessarily guarantee an efficient system and the notion of port efficiency and service effectiveness needs to be considered from the perspectives of both the provider and the consumer of the port service. The paper proposes a network-DEA model to evaluate the performances of 30 seaports worldwide. The concurrent consideration of efficiency scores from the network-DEA model and the traditional DEA-CCR model will offer valuable insights to port operators on how …

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Multi-Item Production Planning With Carbon Cap And Trade Mechanism, Bin Zhang, Liang Xu Jul 2013

Multi-Item Production Planning With Carbon Cap And Trade Mechanism, Bin Zhang, Liang Xu

Research Collection Lee Kong Chian School Of Business

Carbon emission control becomes a challenge in recent years, and carbon emission trading is an effective way to curb carbon emission. This paper investigates the multi-item production planning problem with carbon cap and trade mechanism, in which a firm uses a common capacity and carbon emission quota to produce multiple products for fulfilling independent stochastic demands, and the firm can buy or sell the right to emit carbon on a trading market of carbon emission. A profit-maximization model is proposed to characterize the optimization problem. The optimal policy of production and carbon trading decisions is analyzed, and an efficient solution …

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Scheduling Arrivals To A Stochastic Service Delivery System Using Copositive Cones, Qingxia Kong, Chung-Yee Lee, Chung-Piaw Teo, Zhichao Zheng May 2013

Scheduling Arrivals To A Stochastic Service Delivery System Using Copositive Cones, Qingxia Kong, Chung-Yee Lee, Chung-Piaw Teo, Zhichao Zheng

Research Collection Lee Kong Chian School Of Business

In this paper we investigate a stochastic appointment-scheduling problem in an outpatient clinic with a single doctor. The number of patients and their sequence of arrivals are fixed, and the scheduling problem is to determine an appointment time for each patient. The service durations of the patients are stochastic, and only the mean and covariance estimates are known. We do not assume any exact distributional form of the service durations, and we solve for distributionally robust schedules that minimize the expectation of the weighted sum of patients' waiting time and the doctor's overtime. We formulate this scheduling problem as a …

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The Future Of International Trade: Sustainability Is Key, Singapore Management University Apr 2013

The Future Of International Trade: Sustainability Is Key, Singapore Management University

Perspectives@SMU

What can multinational companies do to ensure that international trade flourishes in years to come? Gerry Craggs, the Far East managing director of steel trading company Stemcor, says that companies like his need to focus on developing sustainable trading policies rather than immediate gain. "Sustainable trading is not driven by short term profit but by providing optimal medium and long-term supply chain solutions that benefit all participants," he told Perspectives@SMU on the sidelines of the 5th anniversary celebration of the university’s International Trade Institute (ITI). Craggs is also Chair of the International Trading Concentration Sub-Committee at the institute that consists …

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Decision Support For Lead Time And Demand Variability Reduction, Xin Fang, Cheng Zhang, David J. Robb, Joseph D. Blackburn Apr 2013

Decision Support For Lead Time And Demand Variability Reduction, Xin Fang, Cheng Zhang, David J. Robb, Joseph D. Blackburn

Research Collection Lee Kong Chian School Of Business

Companies undertaking operations improvement in supply chains face many alternatives. This work seeks to assist practitioners to prioritize improvement actions by developing analytical expressions for the marginal values of three parameters – (i) lead time mean, (ii) lead time variance, and (iii) demand variance – which measure the marginal cost of an incremental change in a parameter. The relative effectiveness of reducing lead time mean versus lead time variance is captured by the ratio of the marginal value of lead time mean to that of lead time variance. We find that this ratio strongly depends on whether the lead time …

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Institutional Voids: Black Hole Or Opportunities?, Singapore Management University Feb 2013

Institutional Voids: Black Hole Or Opportunities?, Singapore Management University

Perspectives@SMU

Emerging markets and their institutional voids offer great growth potential for corporates and organisations seeking an exit strategy from the gloomy European market, says Harvard professor Tarun Khanna. ‘Institutional voids’, a phrase coined by Khanna in his book "Winning in Emerging Markets, refers to the absence of intermediaries like market research firms and credit card systems to efficiently connect buyers and sellers. This creates daunting obstacles for companies trying to operate in emerging markets. According to Khanna, understanding these voids – and learning how to work with them in specific markets – is the key to success

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Step By Step: The Benefits Of Stage-Based R&D Licensing Contracts, Pascale Crama, Bert De Reyck, Zeger Degraeve Feb 2013

Step By Step: The Benefits Of Stage-Based R&D Licensing Contracts, Pascale Crama, Bert De Reyck, Zeger Degraeve

Research Collection Lee Kong Chian School Of Business

We examine how a licensor can optimally design licensing contracts for multi-phase R&D projects when he does not know the licensee’s project valuation, leading to adverse selection, and cannot enforce the licensee’s effort level, resulting in moral hazard. We focus on the effect of the phased nature typical of such projects, and compare single-phase and multi-phase contracts. We determine the optimal values for the upfront payment, milestone payments and royalties, and the optimal timing for outlicensing. Including multiple milestones and accompanying payments can be an effective way of discriminating between licensees holding different valuations, without having to manipulate the royalty …

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Robust Storage Assignment In Unit-Load Warehouses, Marcus Ang, Yun Fong Lim, Melvyn Sim Nov 2012

Robust Storage Assignment In Unit-Load Warehouses, Marcus Ang, Yun Fong Lim, Melvyn Sim

Research Collection Lee Kong Chian School Of Business

Assigning products to and retrieving them from proper storage locations are crucial in minimizing the operating cost of a unit-load warehouse. The problem becomes intractable when the warehouse faces variable supply and uncertain demand in a multi-period setting. We assume a factor-based demand model in which demand for each product in each period is affinely dependent on some uncertain factors. The distributions of these factors are only partially characterized. We introduce a robust optimization model that minimizes the worst-case expected total travel in the warehouse with distributional ambiguity of demand. Under a linear decision rule, we obtain a storage and …

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Ecosystem Advantage: How To Successfully Harness The Power Of Partners, Peter James Williamson, Arnoud De Meyer Oct 2012

Ecosystem Advantage: How To Successfully Harness The Power Of Partners, Peter James Williamson, Arnoud De Meyer

Research Collection Lee Kong Chian School Of Business

Changes in the global environment are generating opportunities for companies to build advantage by creating loosely coupled networks or ecosystems. Ecosystems are larger, more diverse, and more fluid than a traditional set of bilateral partnerships or complementors. By leveraging ecosystems, companies can deliver complex solutions while maintaining corporate focus. This article describes six keys to unlock ecosystem advantage: pinpointing where value is created, defining an architecture of differentiated partner roles, stimulating complementary partner investments, reducing the transaction costs, facilitating joint learning across the network, and engineering effective ways to capture profit.

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Transit Deserts: The Gap Between Demand And Supply, Junfeng Jiao, Maxwell Dillivan Oct 2012

Transit Deserts: The Gap Between Demand And Supply, Junfeng Jiao, Maxwell Dillivan

Research Collection College of Integrative Studies

The term “transit desert” is a new concept that looks at the gap between level of transit service (supply) and needs of a particular population (demand). These populations are often referred to as “transit dependent,” people that are too young, too old, or too poor or who are physically unable to drive. “Transit deserts” in this case are defined as areas that lack adequate public transit service given areas containing populations that are deemed transit-dependent. This study aims to analyze and establish a clear method for calculating and quantifying gaps between transit demand and supply using Geographic Information Systems (GIS). …

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