The Experts below are selected from a list of 9375 Experts worldwide ranked by ideXlab platform
Haoxun Chen - One of the best experts on this subject based on the ideXlab platform.
-
Model and Algorithm for the Vendor-Warehouse Transportation and Inventory Problem in a Three-Level Distribution System
IFAC Proceedings Volumes, 2016Co-Authors: Jianxiang Li, Haoxun ChenAbstract:Abstract We consider the inventory-routing problem in a three-Level Distribution system with a single vendor, a single warehouse and many geographically dispersed retailers. In this problem, each retailer faces a demand at a deterministic, retailer-specific rate. The demand of each retailer is replenished either from the warehouse by a small vehicle or from the vendor bypassing the warehouse by a big vehicle. Inventories are kept not only at the retailers but also at the warehouse. The objective is to find a combined inventory policy and routing pattern minimizing a long-run average system-wide cost while meeting the demand of each retailer without shortage. We present an efficient solution approach based on a fixed partition policy where the retailers are partitioned into disjoint and collectively exhaustive sets and each set of retailers is served on a separate route. Given a fixed partition, the original problem is decomposed into three subproblems. In this paper, we focus on the modelling and resolution of the vendor-warehouse transportation and inventory subproblem. We demonstrate that the subproblem can be reduced to a C/C/C/Z capacitated dynamic lot sizing problem and there exists an algorithm to solve the reduced problem to optimality in O( T 2 ) time.
-
Optimization of (R;Q) policies for two-Level Distribution inventory systems with operating flexibility
2015 IEEE 12th International Conference on Networking Sensing and Control, 2015Co-Authors: Peng Li, Haoxun ChenAbstract:Guaranteed-Service Approach (GSA) was used to set safety stocks for multi-echelon inventory systems. This approach assumes that each stock can use operating flexibility measures such as expediting and overtime to fulfill excessive customer demand superior to a bound as a supplement to its safety stock. In this paper, we consider a two-Level Distribution inventory system with Poisson final demand and fixed costs at each stock controlled by a (R, Q) policy. We use the GSA to optimize the policy with the consideration of operating flexibility costs and fixed order costs. A deterministic mathematical programming model is established for the problem. This model is solved by a line search for finding the optimal target cycle service Level to customer and an iterative procedure for solving the model. Numerical experiments on randomly generated instances demonstrate the efficiency of the procedure.
-
ICNSC - Optimization of (R;Q) policies for two-Level Distribution inventory systems with operating flexibility
2015 IEEE 12th International Conference on Networking Sensing and Control, 2015Co-Authors: Peng Li, Haoxun ChenAbstract:Guaranteed-Service Approach (GSA) was used to set safety stocks for multi-echelon inventory systems. This approach assumes that each stock can use operating flexibility measures such as expediting and overtime to fulfill excessive customer demand superior to a bound as a supplement to its safety stock. In this paper, we consider a two-Level Distribution inventory system with Poisson final demand and fixed costs at each stock controlled by a (R;Q) policy. We use the GSA to optimize the policy with the consideration of operating flexibility costs and fixed order costs. A deterministic mathematical programming model is established for the problem. This model is solved by a line search for finding the optimal target cycle service Level to customer and an iterative procedure for solving the model. Numerical experiments on randomly generated instances demonstrate the efficiency of the procedure.
-
A solution to the inventory routing problem in a three-Level Distribution system
European Journal of Operational Research, 2011Co-Authors: Jianxiang Li, Haoxun ChenAbstract:We consider the infinite horizon inventory routing problem in a three-Level Distribution system with a vendor, a warehouse and multiple geographically dispersed retailers. In this problem, each retailer faces a demand at a deterministic, retailer-specific rate for a single product. The demand of each retailer is replenished either from the vendor through the warehouse or directly from the vendor. Inventories are kept at both the retailers and the warehouse. The objective is to determine a combined transportation (routing) and inventory strategy minimizing a long-run average system-wide cost while meeting the demand of each retailer without shortage. We present a decomposition solution approach based on a fixed partition policy where the retailers are partitioned into disjoint and collectively exhaustive sets and each set of retailers is served on a separate route. Given a fixed partition, the original problem is decomposed into three sub-problems. Efficient algorithms are developed for the sub-problems by exploring important properties of their optimal solutions. A genetic algorithm is proposed to find a near-optimal fixed partition for the problem. Computational results show the performance of the solution approach. 2010 Elsevier B.V. All rights reserved.
-
a solution approach to the inventory routing problem in a three Level Distribution system
European Journal of Operational Research, 2011Co-Authors: Jianxiang Li, Haoxun ChenAbstract:We consider the infinite horizon inventory routing problem in a three-Level Distribution system with a vendor, a warehouse and multiple geographically dispersed retailers. In this problem, each retailer faces a demand at a deterministic, retailer-specific rate for a single product. The demand of each retailer is replenished either from the vendor through the warehouse or directly from the vendor. Inventories are kept at both the retailers and the warehouse. The objective is to determine a combined transportation (routing) and inventory strategy minimizing a long-run average system-wide cost while meeting the demand of each retailer without shortage. We present a decomposition solution approach based on a fixed partition policy where the retailers are partitioned into disjoint and collectively exhaustive sets and each set of retailers is served on a separate route. Given a fixed partition, the original problem is decomposed into three sub-problems. Efficient algorithms are developed for the sub-problems by exploring important properties of their optimal solutions. A genetic algorithm is proposed to find a near-optimal fixed partition for the problem. Computational results show the performance of the solution approach.
Jianxiang Li - One of the best experts on this subject based on the ideXlab platform.
-
Model and Algorithm for the Vendor-Warehouse Transportation and Inventory Problem in a Three-Level Distribution System
IFAC Proceedings Volumes, 2016Co-Authors: Jianxiang Li, Haoxun ChenAbstract:Abstract We consider the inventory-routing problem in a three-Level Distribution system with a single vendor, a single warehouse and many geographically dispersed retailers. In this problem, each retailer faces a demand at a deterministic, retailer-specific rate. The demand of each retailer is replenished either from the warehouse by a small vehicle or from the vendor bypassing the warehouse by a big vehicle. Inventories are kept not only at the retailers but also at the warehouse. The objective is to find a combined inventory policy and routing pattern minimizing a long-run average system-wide cost while meeting the demand of each retailer without shortage. We present an efficient solution approach based on a fixed partition policy where the retailers are partitioned into disjoint and collectively exhaustive sets and each set of retailers is served on a separate route. Given a fixed partition, the original problem is decomposed into three subproblems. In this paper, we focus on the modelling and resolution of the vendor-warehouse transportation and inventory subproblem. We demonstrate that the subproblem can be reduced to a C/C/C/Z capacitated dynamic lot sizing problem and there exists an algorithm to solve the reduced problem to optimality in O( T 2 ) time.
-
A solution to the inventory routing problem in a three-Level Distribution system
European Journal of Operational Research, 2011Co-Authors: Jianxiang Li, Haoxun ChenAbstract:We consider the infinite horizon inventory routing problem in a three-Level Distribution system with a vendor, a warehouse and multiple geographically dispersed retailers. In this problem, each retailer faces a demand at a deterministic, retailer-specific rate for a single product. The demand of each retailer is replenished either from the vendor through the warehouse or directly from the vendor. Inventories are kept at both the retailers and the warehouse. The objective is to determine a combined transportation (routing) and inventory strategy minimizing a long-run average system-wide cost while meeting the demand of each retailer without shortage. We present a decomposition solution approach based on a fixed partition policy where the retailers are partitioned into disjoint and collectively exhaustive sets and each set of retailers is served on a separate route. Given a fixed partition, the original problem is decomposed into three sub-problems. Efficient algorithms are developed for the sub-problems by exploring important properties of their optimal solutions. A genetic algorithm is proposed to find a near-optimal fixed partition for the problem. Computational results show the performance of the solution approach. 2010 Elsevier B.V. All rights reserved.
-
a solution approach to the inventory routing problem in a three Level Distribution system
European Journal of Operational Research, 2011Co-Authors: Jianxiang Li, Haoxun ChenAbstract:We consider the infinite horizon inventory routing problem in a three-Level Distribution system with a vendor, a warehouse and multiple geographically dispersed retailers. In this problem, each retailer faces a demand at a deterministic, retailer-specific rate for a single product. The demand of each retailer is replenished either from the vendor through the warehouse or directly from the vendor. Inventories are kept at both the retailers and the warehouse. The objective is to determine a combined transportation (routing) and inventory strategy minimizing a long-run average system-wide cost while meeting the demand of each retailer without shortage. We present a decomposition solution approach based on a fixed partition policy where the retailers are partitioned into disjoint and collectively exhaustive sets and each set of retailers is served on a separate route. Given a fixed partition, the original problem is decomposed into three sub-problems. Efficient algorithms are developed for the sub-problems by exploring important properties of their optimal solutions. A genetic algorithm is proposed to find a near-optimal fixed partition for the problem. Computational results show the performance of the solution approach.
-
A solution approach to the inventory routing problem in a three-Level Distribution system
European Journal of Operational Research, 2011Co-Authors: Jianxiang Li, Feng Chu, Haoxun ChenAbstract:We consider the infinite horizon inventory routing problem in a three-Level Distribution system with a vendor, a warehouse and multiple geographically dispersed retailers. In this problem, each retailer faces a demand at a deterministic, retailer-specific rate for a single product. The demand of each retailer is replenished either from the vendor through the warehouse or directly from the vendor. Inventories are kept at both the retailers and the warehouse. The objective is to determine a combined transportation (routing) and inventory strategy minimizing a long-run average system-wide cost while meeting the demand of each retailer without shortage. We present a decomposition solution approach based on a fixed partition policy where the retailers are partitioned into disjoint and collectively exhaustive sets and each set of retailers is served on a separate route. Given a fixed partition, the original problem is decomposed into three sub-problems. Efficient algorithms are developed for the sub-problems by exploring important properties of their optimal solutions. A genetic algorithm is proposed to find a near-optimal fixed partition for the problem. Computational results show the performance of the solution approach. © 2010 Elsevier B.V. All rights reserved.
-
To construct 100%-asymptotic optimal inventory routing strategies
2008 Chinese Control and Decision Conference, 2008Co-Authors: Jianxiang Li, Huijiang WuAbstract:Inventory routing problem (IRP) has become a hotspot of researches on supply chain management. This paper considers infinite horizon deterministic inventory routing problems for both a two-Level Distribution system and a three-Level Distribution system. A simple region partitioning policy is designed. Based on the region partitioning policy, 100%-asymptotic optimal inventory routing strategies in the Phi strategies are constructed for the two Distribution systems, respectively. The strategies proposed are better than the asymptotical sub-optimal policies suggested in the literature.
Kottaismy Karthikeyan - One of the best experts on this subject based on the ideXlab platform.
-
Multi-Level Distribution STATCOM for reducing the effect of voltage sag and swell
Power System Technology 2004. PowerCon 2004. 2004 International Conference on, 2004Co-Authors: C. Sharmeela, G. Uma, M. R. Mohan, Kottaismy KarthikeyanAbstract:Multi-Level power conversion has been receiving increasing attention in the past few years for high power applications. The unique structure of the multi-Level voltage source converter (VSC) allows it to reach high voltages with low harmonics without the use of transformers or series-connected, synchronised switching devices. The diode clamped multi-Level VSC with simple configuration and control structure finds application as Distribution-STATCOM in custom power conditioners. This inverter has emerged as a solution for high power applications. The main purpose of the proposed diode clamped D-STATCOM is that it injects reactive power in shunt with a Distribution feeder. It reduces the short-term voltage sags, swells and momentary interruptions. This paper presents the multi-Level D-STATCOM configuration consisting of a five Level voltage source converter, a DC energy storage device, a coupling transformer and associated control circuits. The control is based on sinusoidal PWM and only requires the measurement of the RMS voltage at the load point PSCAD/EMTDC simulation tool is used for modeling and simulation. Extensive simulation results are presented to verify the dynamic performance of multi-Level D-STATCOM with two Level D-STATCOM.
C. Sharmeela - One of the best experts on this subject based on the ideXlab platform.
-
Multi-Level Distribution STATCOM for voltage sag and swell reduction
IEEE Power Engineering Society General Meeting 2005, 2005Co-Authors: C. SharmeelaAbstract:Multi-Level power conversion has been receiving increasing attention in the past few years for high power applications. The unique structure of the multi-Level voltage source converter (VSC) allows it to reach high voltages with low harmonics without the use of transformers or series-connected, synchronised switching devices. The diode clamped multi-Level VSC with its simple configuration and control structure finds application as Distribution STATCOM (D-STATCOM) in custom power conditioners. This inverter has emerged as a solution for high power applications. The main purpose of the proposed diode clamped D-STATCOM is that it injects reactive power in shunt with a Distribution feeder. It reduces the effect of short-term voltage sags, swells and momentary interruptions in the Distribution system. This paper presents the multi-Level D-STATCOM configuration consisting of a three Level voltage source converter, a DC energy storage device, a coupling transformer and associated control circuits. The control is based on sinusoidal PWM and only requires the measurement of the RMS voltage at the load point. PSCAD/EMTDC simulation tool is used for modeling and simulation. Extensive simulation results are presented to verify the superiority of multi-Level D-STATCOM with two Level D-STATCOM.
-
Multi-Level Distribution STATCOM for reducing the effect of voltage sag and swell
Power System Technology 2004. PowerCon 2004. 2004 International Conference on, 2004Co-Authors: C. Sharmeela, G. Uma, M. R. Mohan, Kottaismy KarthikeyanAbstract:Multi-Level power conversion has been receiving increasing attention in the past few years for high power applications. The unique structure of the multi-Level voltage source converter (VSC) allows it to reach high voltages with low harmonics without the use of transformers or series-connected, synchronised switching devices. The diode clamped multi-Level VSC with simple configuration and control structure finds application as Distribution-STATCOM in custom power conditioners. This inverter has emerged as a solution for high power applications. The main purpose of the proposed diode clamped D-STATCOM is that it injects reactive power in shunt with a Distribution feeder. It reduces the short-term voltage sags, swells and momentary interruptions. This paper presents the multi-Level D-STATCOM configuration consisting of a five Level voltage source converter, a DC energy storage device, a coupling transformer and associated control circuits. The control is based on sinusoidal PWM and only requires the measurement of the RMS voltage at the load point PSCAD/EMTDC simulation tool is used for modeling and simulation. Extensive simulation results are presented to verify the dynamic performance of multi-Level D-STATCOM with two Level D-STATCOM.
Sevgi O Aral - One of the best experts on this subject based on the ideXlab platform.
-
Changes in the state-Level Distribution of primary and secondary syphilis in the USA, 1985-2007.
Sexually transmitted infections, 2010Co-Authors: Harrell W Chesson, Maya Sternberg, Jami S Leichliter, Sevgi O AralAbstract:To examine changes over time in the Distribution of primary and secondary syphilis cases across states, using Lorenz curves and Gini coefficients. For each year from 1985 to 2007, the Gini coefficient for the state-Level Distribution of male and female syphilis cases was calculated. The Gini coefficient can range from 0 (indicating equality in syphilis rates across states) to 1 (indicating complete inequality such that all syphilis cases occur in one state). The Gini coefficients for men are notably lower (indicating more equality in the Distribution of syphilis across states) in recent years (in which men who have sex with men (MSM) account for most syphilis cases) than in the heterosexual epidemic of the late 1980s and early 1990s. Although syphilis rates in men were similar in 1995 and 2007 (6.7 and 6.6 per 100,000, respectively), the Gini coefficient for male syphilis decreased from 0.523 in 1995 to 0.333 in 2007. For syphilis in women, Gini coefficients have not shown the same degree of decline. The spread of MSM syphilis cases to urban areas across the nation is likely to be a main cause of the decreased concentration of male syphilis cases across states from 1995 to 2007.
-
Changes in the state-Level Distribution of primary and secondary syphilis in the USA, 1985–2007
Sexually Transmitted Infections, 2010Co-Authors: Harrell W Chesson, Jami S Leichliter, Maya R. Sternberg, Sevgi O AralAbstract:Objectives To examine changes over time in the Distribution of primary and secondary syphilis cases across states, using Lorenz curves and Gini coefficients. Methods For each year from 1985 to 2007, the Gini coefficient for the state-Level Distribution of male and female syphilis cases was calculated. The Gini coefficient can range from 0 (indicating equality in syphilis rates across states) to 1 (indicating complete inequality such that all syphilis cases occur in one state). Results The Gini coefficients for men are notably lower (indicating more equality in the Distribution of syphilis across states) in recent years (in which men who have sex with men (MSM) account for most syphilis cases) than in the heterosexual epidemic of the late 1980s and early 1990s. Although syphilis rates in men were similar in 1995 and 2007 (6.7 and 6.6 per 100 000, respectively), the Gini coefficient for male syphilis decreased from 0.523 in 1995 to 0.333 in 2007. For syphilis in women, Gini coefficients have not shown the same degree of decline. Conclusions The spread of MSM syphilis cases to urban areas across the nation is likely to be a main cause of the decreased concentration of male syphilis cases across states from 1995 to 2007.
