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Now showing items 17 - 32 of 34

  • A vendor managed inventory supply chain with deteriorating raw materials and products

    Yu, Yugang   Wang, Zheng   Liang, Liang  

    Fast deteriorating raw materials such as raw milk, fruit and vegetables are commonly used to produce slowly deteriorating finished products such as milk powders, cheeses, and pastas. This paper studies a Vendor Managed Inventory (VMI) type supply chain where the manufacturing vendor decides how to manage the system-wide inventories of its fast deteriorating raw material and its slowly deteriorating product. The decision variables are a common replenishment cycle of the product and the replenishment frequency of the raw material. We assume the deteriorating rates are known constants and every retailer's demand is deterministic. We develop an integrated model to calculate the total inventory and deterioration cost for such a system. We prove the convexity of the cost functions, and based on this a golden search algorithm is developed to find the optimal solution of the model. Our numerical results show that the deteriorating rate of the product may increase the total cost by more than 40% compared to the zero-deteriorating rate, while the deteriorating raw material has less impact on the total cost (commonly less than 5% in our numerical examples). This indicates that more attention should be paid to the product than the raw material. Further, an increase in the number of retailers can make the replenishment frequency of the raw material increase significantly but the common replenishment cycle of the product decreases a little. This indicates that adding a new retailer would not be felt strongly by the other retailers but would be felt by the supplier of the raw material. (C) 2011 Elsevier B.V. All rights reserved.
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  • Stackelberg game-theoretic model for optimizing advertising, pricing and inventory policies in vendor managed inventory (VMI) production supply chains RID B-4711-2010

    Yu, Yugang   Huang, George Q.   Liang, Liang  

    This paper discusses how a manufacturer and its retailers interact with each other in order to optimize their individual net profits by adjusting product marketing (advertising and pricing) and inventory policies in an information-asymmetric VMI (vendor managed inventory) supply chain. The manufacturer produces and supplies a single product at the same wholesale price to multiple retailers who then sell the product in dispersed and independent markets at retail prices. The demand rate in each market is an increasing and concave function of the advertising investments of both local retailers and the manufacturer, but a decreasing and convex function of the retail prices. The manufacturer determines its wholesale price, its advertising investment, replenishment cycles for the raw materials and finished product, and backorder quantity to maximize its profit. Retailers in turn consider the replenishment policies and the manufacturer's promotion policies and determine the optimal retail prices and advertisement investments to maximize their profits. This problem is modeled as a Stackelberg game where the manufacturer is the leader and retailers are followers. An algorithm has been proposed to search the Stackelberg equilibrium. A numerical study has been conducted to demonstrate how the algorithm works and to understand the influences of decision variables and/or parameters. Several research questions are examined, including under what circumstances the retailers and manufacturer should increase their advertising expenditures and/or reduce the retail prices and what actions should be taken if the prices of raw materials or their holding costs increase. (C) 2008 Elsevier Ltd. All rights reserved.
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  • Do confucianism and political connections affect stock price crash risk:evidence from Chinese economy?

    Bashir, Usman   Yu, Yugang  

    Utilizing a large dataset on Chinese A-Share listed firms comprising 18763 firm-year observation for the period of 2001-2015, we examined whether Confucianism and political connections lessen the stock price crash risk of firms by using geographical-proximity-based Confucianism variables. Our findings point towards the evidence that firms situated in China with higher levels of Confucianism reveal low levels of stock price crash risk and this relationship is incrementally significant for politically connected firms while controlling for a battery of control variables. Our results are robust by using alternate proxies.
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  • Consumer’s intention to purchase green furniture: Do health consciousness and environmental awareness matter?

    Xu, Xiaoping   Wang, Shanyong   Yu, Yugang  

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  • Controlled Homoepitaxial Growth of Hybrid Perovskites

    Lei, Yusheng   Chen, Yimu   Gu, Yue   Wang, Chunfeng   Huang, Zhenlong   Qian, Haoliang   Nie, Jiuyuan   Hollett, Geoff   Choi, Woojin   Yu, Yugang   Kim, NamHeon   Wang, Chonghe   Zhang, Tianjiao   Hu, Hongjie   Zhang, Yunxi   Li, Xiaoshi   Li, Yang   Shi, Wanjun   Liu, Zhaowei   Sailor, Michael J.   Dong, Lin   Lo, Yu-Hwa   Luo, Jian   Xu, Sheng  

    Organic-inorganic hybrid perovskites have demonstrated tremendous potential for the next-generation electronic and optoelectronic devices due to their remarkable carrier dynamics. Current studies are focusing on polycrystals, since controlled growth of device compatible single crystals is extremely challenging. Here, the first chemical epitaxial growth of single crystal CH3NH3PbBr3 with controlled locations, morphologies, and orientations, using combined strategies of advanced microfabrication, homoepitaxy, and low temperature solution method is reported. The growth is found to follow a layer-by-layer model. A light emitting diode array, with each CH3NH3PbBr3 crystal as a single pixel, with enhanced quantum efficiencies than its polycrystalline counterparts is demonstrated.
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  • Approaching the Quantum Limit of Photodetection in Solid-State Photodetectors

    Hall, David   Liu, Yu-Hsin   Yan, Lujiang   Yu, Yugang   Lo, Yu-Hwa  

    Many aspects of life involve sensitive photodetection, which is now widely implemented in solid-state devices made from semiconductor materials due to their relatively low cost, high scalability, and better compatibility with the existing CMOS technology. State-of-the-art Geiger-mode avalanche detectors and the challenges they faced in single-photon detection efficiency and timing resolution are covered. Emerging classes of solid-state detectors are then reviewed, including bandgap engineering and the use of a heavily doped emitter. A novel class of detector is introduced exhibiting monolithic incorporation of impact ionization and bipolar gain in a single device structure by using bandgap engineering. Finally, we discuss a recent detector concept which involves using disorder in solid-state material to substantially increase the probability of carrier excitation and reduce noise. The recent breakthroughs in solid-state photodetection can significantly impact areas of quantum information processing, optic communications, and imaging.
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  • Plasmonically Enhanced Amorphous Silicon Photodetector With Internal Gain

    Yu, Yugang   Xu, Zihan   Li, Shilong   Zhang, Alex Ce   Yan, Lujiang   Liu, Zhaowei   Lo, Yu-Hwa  

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  • Dual-channel decision in a shopping complex when considering consumer channel preference

    Yu, Yugang   Sun, Libo   Guo, Xiaolong  

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  • Do confucianism and political connections affect stock price crash risk: evidence from Chinese economy?

    Bashir, Usman   Yu, Yugang  

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  • Frequency- and Power-Dependent Photoresponse of a Perovskite Photodetector Down to the Single-Photon Level

    Xu, Zihan   Yu, Yugang   Arya, Shaurya   Niaz, Iftikhar Ahmad   Chen, Yimu   Lei, Yusheng   Miah, Mohammad Abu Raihan   Zhou, Jiayun   Zhang, Alex Ce   Yan, Lujiang   Xu, Sheng   Nomura, Kenji   Lo, Yu-Hwa  

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  • Response time analysis of a live-cube compact storage system with two storage classes

    Zaerpour, Nima   Yu, Yugang   de Kosterc, Rene B. M.  

    We study a next generation of storage systems: live-cube compact storage systems. These systems are becoming increasingly popular, due to their small physical and environmental footprint paired with a large storage space. At each level of a live-cube system, multiple shuttles take care of the movement of unit loads in the x and y directions. When multiple empty locations are available, the shuttles can cooperate to create a virtual aisle for the retrieval of a desired unit load. A lift takes care of the movement across different levels in the z-direction. Two-class-based storage, in which high turnover unit loads are stored at storage locations closer to the Input/Output point, can result in a short response time. We study two-class-based storage for a live-cube system and derive closed-form formulas for the expected retrieval time. Although the system needs to be decomposed into several cases and sub-cases, we eventually obtain simple-to-use closed-form formulas to evaluate the performance of systems with any configuration and first zone boundary. Continuous-space closed-form formulas are shown to be very close to the results obtained for discrete-space live-cube systems. The numerical results show that two-class-based storage can reduce the average response time of a live-cube system by up to 55% compared with random storage for the instances tested.
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  • Dual-channel decision in a shopping complex when considering consumer channel preference

    Yu, Yugang   Sun, Libo   Guo, Xiaolong  

    In practice, dual-channel structures are commonly adopted by manufacturers to reach a wider range of customers. This paper investigates a manufacturer's dual-channel ("direct" + "indirect") decision in a shopping complex, considering consumer channel preference between the direct and indirect channels, with the choices for the indirect channel being reselling and agency selling. We develop an analytical framework to study this problem. Our result demonstrates that the dual-channel structures should be adopted when there exists a significant channel preference gap between channels, which in turn could help the manufacturer reduce the substitution effect between channels. Besides, our analysis discloses that consumer channel preference plays a significant role when the manufacturer leverages different indirect selling formats. In the case of reselling, the manufacturer should adopt a dual-channel structure if consumers show a much higher preference for the direct channel. In the case of agency selling, a dual-channel structure should be adopted when consumers significantly prefer either the direct channel or the indirect (agency) platform. Finally, exact conditions are provided in this paper to help manufacturers make optimal dual-channel decisions in shopping complexes.
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  • Designing an optimal turnover-based storage rack for a 3D compact automated storage and retrieval system RID B-4711-2010

    Yu, Yugang   de Koster, M. B. M.  

    Compact, multi-deep (3D) automated storage and retrieval systems (AS/RS) are becoming increasingly popular for storing products. We study such a system where a storage and retrieval (S/R) machine takes care of movements in the horizontal and vertical directions of the rack, and an orthogonal conveying mechanism takes care of the depth movement. An important question is how to layout such systems under different storage policies to minimize the expected cycle time. We derive the expected single-command cycle time under the full-turnover-based storage policy and propose a model to determine the optimal rack dimensions by minimizing this cycle time. We simplify the model, and analytically determine optimal rack dimensions for any given rack capacity and ABC curve skewness. A significant cycle time reduction can be obtained compared with the random storage policy. We illustrate the findings of the study by applying them in a practical example.
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  • Optimal two-class-based storage in a live-cube compact storage system

    Zaerpour, Nima   Yu, Yugang   de Koster, Rene B. M.  

    Live-cube compact storage systems realize high storage space utilization and high throughput, due to full automation and independent movements of unit loads in three-dimensional space. Applying an optimal two-class-based storage policy where high-turnover products are stored at locations closer to the Input/Output point significantly reduces the response time. Live-cube systems are used in various sectors, such as warehouses and distribution centers, parking systems, and container yards. The system stores unit loads, such as pallets, cars, or containers, multi-deep at multiple levels of storage grids. Each unit load is located on its own shuttle. Shuttles move unit loads at each level in the x and y directions, with a lift taking care of themovement in the z-direction. Movement of a requested unit load to the lift location is comparable to solving a Sam Loyd's puzzle game where 15 numbered tiles move in a 4 x 4 grid. However, with multiple empty locations, a virtual aisle can be created to shorten the retrieval time for a requested unit load. In this article, we optimize the dimensions and zone boundary of a two-class live-cube compact storage system leading to a minimum response time. We propose a mixed-integer nonlinear model that consists of 36 sub-cases, each representing a specific configuration and first zone boundary. Properties of the optimal system are used to simplify the model without losing any optimality. The overall optimal solutions are then obtained by solving the remaining sub-cases. Although the solution procedure is tedious, we eventually obtain two sets of closed-form expressions for the optimal system dimensions and first zone boundary for any desired system size. In addition, we propose an algorithm to obtain the optimal first zone boundary for situations where the optimal system dimensions cannot be achieved. To test the effectiveness of optimal system dimensions and first zone boundary on the performance of a two-class-based live-cube system, we perform a sensitivity analysis by varying the ABC curve, system size, first zone size, and shape factor. The results show that for most cases an optimal two-class-based storage outperforms random storage, with up to 45% shorter expected retrieval time.
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  • Pricing Strategies and Mechanism Choice in Reward-based Crowdfunding

    Du, Shaofu   Peng, Jing   Nie, Tengfei   Yu, Yugang  

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  • Editorial: Online-to-offline ecommerce operations management (EOM)

    Huang, George Q.   de Koster, René   Yu, Yugang  

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