In order to let the supplier make more reasonable supply decisions,an integrated continuous replenishment policy for the vendor-managed inventory system is presented,which considers the quantity-based shipment consoli...In order to let the supplier make more reasonable supply decisions,an integrated continuous replenishment policy for the vendor-managed inventory system is presented,which considers the quantity-based shipment consolidation and stock replenishment with lead time.Then the system cost is analyzed and a mathematical model is built.Since the model is rather complex,the bounds of the optimal policy are first attained,then the problem is solved by a heuristic algorithm.Through experiments the relationship between the order lead time and the corresponding integrated policy is discussed,and the influence on the system cost is also analyzed.The results reveal that the lead time's influence on the system is more serious with the increase of the order lead time,the integrated policy with the order lead time is more reasonable and the optimal policy can minimize the total system cost.Finally,the parameter sensitivity of the model is analyzed.展开更多
This article analyzes a continuous-review inventory system with random supply interruptions and random lead time which may be interrupted by a random number of supplier’s OFF periods. The inventory with constant dema...This article analyzes a continuous-review inventory system with random supply interruptions and random lead time which may be interrupted by a random number of supplier’s OFF periods. The inventory with constant demand rate is managed by a （r; q1, q2, · · · , qm） policy and supplies from an unreliable sole supplier. By renewal theory and matrix Geometric method, the long-run average cost function is obtained and some important properties of the function are proved. Furthermore, performance of the inventory is derived.展开更多
In recent times, mathematical models have been developed to describe various scenarios obtainable in the management of inventories. These models usually have as objective the minimizing of inventory costs. In this res...In recent times, mathematical models have been developed to describe various scenarios obtainable in the management of inventories. These models usually have as objective the minimizing of inventory costs. In this research work we propose a mathematical model of an inventory system with time-dependent three-parameter Weibull deterioration and a stochastic type demand in the form of a negative exponential distribution. Explicit expressions for the optimal values of the decision variables are obtained. Numerical examples are provided to illustrate the theoretical development.展开更多
China was one of the earliest countries to set up a system to continuously inventory natural forest resources. From the beginning of the 1970s until today, seven forest resource inventories have been carried out. This...China was one of the earliest countries to set up a system to continuously inventory natural forest resources. From the beginning of the 1970s until today, seven forest resource inventories have been carried out. This research summarizes the progress of forest continuous inventories and analyzes the existing deficiencies ofChina’s forest continuous inventory system and forest management plan inventory. As stated above, this research offers corresponding countermeasures and suggestions: establishing a sample plot system for comprehensive national forest inventory and monitoring with each province’s continuous forest inventory based on the foundation of the national sample plot system, able to develop the province as a subset of the overall province-level forest resource inventory according to the actual conditions in each province. Through annual multi-resource/multi-benefit surveying of the forests, the monitoring of forest amounts, quality, functions and benefits will be assisted in its entirety. The further integration of the forest continuous inventory and the forest management plan inventory is also discussed. This research also proposes the varied probability sampling method with sub-compartments as the basic sampling unit (or combinations of sub-compartments). This will also satisfy the requirements of ecological inventory by region.展开更多
Geological heritage inventory procedures and templates have been principally emerged from European countries. Each of these countries has developed its proper method of inventory based on its natural heritage, recogni...Geological heritage inventory procedures and templates have been principally emerged from European countries. Each of these countries has developed its proper method of inventory based on its natural heritage, recognized on local and/or regional scales. Natural sites were mainly identified and characterized in a particular geological context, which is usually very unique, valuable and impressive;resulting in the protection of the sites. Madagascar is known internationally as a beautifully landscaped island, but the impressive sites were not cataloged. We carried out a series of field inventory of potential geological sites within the Isalo National Park in southern Madagascar. We invented several inventory sheets in order to record the most detailed information about the sites identified within the park. This is to aid in organizing the park and to establish a sustainable base for the creation of a geopark, and also they help us to build a database for geosites and their classifications. This article suggests a prototype model for inventorying intangible geosites, paleosites and geomorphosites. Our inventory sheets help to identify and to promote geological importance of any sites, not only for academia but also for other sectors such as tourism and conservation.展开更多
We study the stochastic inventory problem with optimal （s,S） policies.In a finite horizon model with lost sales,we establish new lower and upper bounds of s and S.These bounds have structural implications for the op...We study the stochastic inventory problem with optimal （s,S） policies.In a finite horizon model with lost sales,we establish new lower and upper bounds of s and S.These bounds have structural implications for the optimal solutions.Consequently,when demand has a generalized phase type distribution,there are no more than a pre-determined number of minima.Similar bounds can also be found for the system where unsatisfied demand is backordered instead of lost sales.展开更多
We analyze a continuous review lost sales inventory system with two types of orders—regular and emergency. The regular order has a stochastic lead time and is placed with the cheapest acceptable supplier. The emergen...We analyze a continuous review lost sales inventory system with two types of orders—regular and emergency. The regular order has a stochastic lead time and is placed with the cheapest acceptable supplier. The emergency order has a deterministic lead time is placed with a local supplier who has a higher price. The emergency order is not always filled since the supplier may not have the ability to provide the order on an emergency basis at all times. This emergency order has a higher cost per item and has a known probability of being filled. The total costs for this system are compared to a system without emergency placement of orders. This paper provides managers with a tool to assess when dual sourcing is cost optimal by comparing the single sourcing and dual sourcing models.展开更多
In this research work we propose a mathematical model of an inventory system with time dependent three-parameter Weibull deterioration and <span style="font-family:Verdana;">price-</span><span...In this research work we propose a mathematical model of an inventory system with time dependent three-parameter Weibull deterioration and <span style="font-family:Verdana;">price-</span><span style="font-family:Verdana;">dependent demand rate. The model incorporates shortages and deteriorating items are considered in which inventory is depleted not only by demand but also by decay, such as, direct spoilage as in fruits, vegetables and food products, or deterioration as in obsolete electronic components. Furthermore, the rate of deterioration is taken to be time-proportional, and a power law form of the price dependence of demand is considered. This price-dependence of the demand function is nonlinear, and is such that when price of a commodity increases, demand decreases and when price of a commodity decreases, demand increases. The objective of the model is to minimize the total inventory costs. From the numerical example presented to illustrate the solution procedure of the model, we obtain meaningful results. We then proceed to perform sensitivity analysis of our model. The sensitivity analysis illustrates the extent to which the optimal solution of the model is affected by slight changes or errors in its input parameter values.</span>展开更多
As fresh agricultural products are perishable and vulnerable,reducing inventory cost is a strategic target for supply chain enterprises.How to design a reliable multi-echelon inventory control policy is still a great ...As fresh agricultural products are perishable and vulnerable,reducing inventory cost is a strategic target for supply chain enterprises.How to design a reliable multi-echelon inventory control policy is still a great challenge.Therefore,the inventory cost of a three-level fresh agricultural products inventory system was firstly mathematically analyzed.Then,the simulation-based optimization model of the multi-echelon inventory system for fresh agricultural products was proposed by using the Flexsim simulation software and the improved particle swarm optimization algorithm.Finally,the multi-echelon inventory system is simulated based on a large number of survey data.Simulation results demonstrate that the proposed simulation-based optimization model of multi-echelon inventory system for fresh agricultural products can provide decision-making and technical support for the formulation of inventory control policy,and also it shows that the modeling of system simulation is an effective method to solve the problem of complex system.展开更多
In this article, we present a continuous review （s,S） inventory system with a service facility consisting of finite buffer （capacity N ） and a single server. The customers arrive according to a Poisson process. Th...In this article, we present a continuous review （s,S） inventory system with a service facility consisting of finite buffer （capacity N ） and a single server. The customers arrive according to a Poisson process. The individual customer＇s unit demand is satisfied after a random time of service, which is assumed to be exponential. When the inventory level drops to s＇an order for Q（= S-s） items is placed. The lead time of reorder is assumed to be exponential distribution. An arriving customer, who finds the buffer is full, enters into the pool of infinite size or leaves the system according to a Bernolli trial. At the time of service completion, if the buffer size drops to a preassigned level L （1 〈 L 〈 N） or below and the inventory level is above s, we select the customers from the pool according to two different policy ： in first policy, with probability p （0 〈 p 〈 1） we select the customer from the head of the pool and we place the customer at the end of the buffer; in the second policy, with p （0 〈 p 〈 1） the customer from the pool is transferred to the buffer for immediate service and after completion of his service we provide service to the customer who is in the buffer with probability one. If at a service completion epoch the buffer turns out to be empty, there is at least one customer in the pool and the inventory level is positive, then the one ahead of all waiting in the pool gets transferred to the buffer, and his service starts immediately. The joint probability distribution of the number of customers in the pool, number of customers in the buffer and the inventory level is obtained in the steady-state case. Various stationary system performance measures are computed and total expected cost rate is calculated. A comparative result of two models is illustrate numerically.展开更多
The multi echelon inventory system theory (MEIST) ,which is an important branch of inventory theory, is applied mainly in solving the problem of a multi echelon inventory and supply system. In this paper, a brief re...The multi echelon inventory system theory (MEIST) ,which is an important branch of inventory theory, is applied mainly in solving the problem of a multi echelon inventory and supply system. In this paper, a brief review of MEIST is given and its main points are summarized. An application is made to the decision of spares stock levels in maintenance management. The result shows that it can reduce costs of spares by using MEIST in the case of a multi echelon maintenance system.展开更多
In this article,we consider a discrete-time inventory model in which demands arrive according to a discrete Markovian arrival process.The inventory is replenished according to an es;ST policy,and the lead time is assu...In this article,we consider a discrete-time inventory model in which demands arrive according to a discrete Markovian arrival process.The inventory is replenished according to an es;ST policy,and the lead time is assumed to follow a discrete phase-type distribution.The demands that occur during stock-out periods either enter a pool which has an infinite capacity or leave the system with a predefined probability.The demands in the pool are selected one by one,if the on-hand inventory level is above s t 1;and the interval time between any two successive selections is assumed to have a discrete phase-type distribution.The joint probability distribution of the number of customers in the pool and the inventory level is obtained in the steady-state case.We derive the system performance measures under steady state and using these measures,the total expected cost rate of the system is calculated.The impacts of arrival rate on the performance measures are graphically illustrated.Finally,we study the impact of cost on the optimal values of the total expected cost rate,inventory level and the reorder point.展开更多
Because of the importance of discrete event systems, much attention is being paid by more and more people to the ( s,S ) type of random inventory systems. In this paper, the simulation aim, evaluation criterion and...Because of the importance of discrete event systems, much attention is being paid by more and more people to the ( s,S ) type of random inventory systems. In this paper, the simulation aim, evaluation criterion and the general strategy are studied by employing SIMAN. And they are explained with a case at last.展开更多
Glacial lakes are not only the important refresh water resources in alpine region, but also act as a trigger of many glacial hazards such as glacial lake outburst flood （GLOF） and debris flow. Therefore, glacial lak...Glacial lakes are not only the important refresh water resources in alpine region, but also act as a trigger of many glacial hazards such as glacial lake outburst flood （GLOF） and debris flow. Therefore, glacial lakes play an important role on the cryosphere, climate change and alpine hazards. In this paper, the issues of glacial lake were systematically discussed, then from the view of glacial lake inventory and glacial lake hazards study, the glacial lake was defined as natural water mainly supplied by modern glacial meltwater or formed in glacier moraine＇s depression. Furthermore, a complete classification system of glacial lake was proposed based on its formation mechanism, topographic feature and geographical position. Glacial lakes were classified as 6 classes and 8 subclasses, i.e., glacial erosion lake （including cirque lake, gla- cial valley lake and other glacial erosion lake）, moraine-dammed lake （including end mo- raine-dammed lake, lateral moraine-dammed lake and moraine thaw lake）, ice-blocked lake （including advancing glacier-blocked lake and other glacier-blocked lake）, supraglacial lake, subglacial lake and other glacial lake. Meanwhile, some corresponding features exhibiting on remote sensing image and quantitative indices for identifying different glacial lake types were proposed in order to build a universal and operational classification system of glacial lake.展开更多
In this paper, we consider a production inventory system with service time and production vacations. Customers arrive in the system according to a Poisson process requiring service from a single server. The single pro...In this paper, we consider a production inventory system with service time and production vacations. Customers arrive in the system according to a Poisson process requiring service from a single server. The single production facility produces items according to an (s, S) policy, and 让 takes a vacation of random duration once the inventory level becomes S. It is assumed that all arriving customers are lost during the stock out period. We first derive the stationary joint distribution of the queue length and the on-hand inventory level in product form. Then, we compute explicitly some performance measures, and develop a cost function based on these performance measures. Finally;some numerical results are presented.展开更多
We discuss a single-period inventory system with a general S-shaped utility function and exponential demand. It is shown that there exists a state-dependent order-up-to policy to be optimal. Behaviors of optimal polic...We discuss a single-period inventory system with a general S-shaped utility function and exponential demand. It is shown that there exists a state-dependent order-up-to policy to be optimal. Behaviors of optimal policy are illustrated by a numerical example.展开更多
In this paper, we consider the inventory system with a bounded emergency order, using a probability criterion. It is shown that there exist two critical numbers x and x such that the optimal emergency order policy is ...In this paper, we consider the inventory system with a bounded emergency order, using a probability criterion. It is shown that there exist two critical numbers x and x such that the optimal emergency order policy is order-up-to-x with a bound and the optimal regular order policy is order-up-to-x.展开更多
We consider a continuous review perishable （s,S） inventory system with a service facility consisting of a waiting hall of finite capacity and a single server. We assume two types of customers, ordinary and negative,...We consider a continuous review perishable （s,S） inventory system with a service facility consisting of a waiting hall of finite capacity and a single server. We assume two types of customers, ordinary and negative, arrive according to a Markovian Arrival Process （MAP）. An ordinary customer joins the queue and a negative customer instead of joining the queue removes one ordinary customer from the queue. The removal rule adopted in this paper is RCE （removal of a customer from the end）. The individual customer＇s unit demand is satisfied after a random time of service which is assumed to have a phase-type distribution. The life time of each item and the lead time of the reorders have been assumed to be independent exponential distributions. The joint probability distribution of the number of customers in the system and the inventory level is obtained for the steady state case. Various stationary system performance measures are computed and the total expected cost rate is calculated. The results are illustrated numerically.展开更多
This paper considers a production inventory system with service time and product returns, dependent on the characteristics of online shopping beliaviors. The customers arrive according to a Poisson process, in which t...This paper considers a production inventory system with service time and product returns, dependent on the characteristics of online shopping beliaviors. The customers arrive according to a Poisson process, in which the arriving customer requires an item in the inventory, as well as a server service that the service time is exponentially distributed. Moreover, there is one production facility to produce items according to (s, S) policy, and the production time also follows an exponential (listribution. In the beginning, the stationary joint distribution is obtained in the product form for the queue length and the on-hand inventory level. Additionally, the resulting distribution is applied to derive some performance measures, which can be adopted to numerically calculate the optimal (s, S) policy. Finally, numerical analyses are processed to investigate the effects of some system parameters on the performance measures. The numerical results clearly indicate that the product return rate has a significantly monotonic effect on the optimal policy and optimal cost.展开更多
This paper deals with a periodic review inventory system serving multiple demand classes that are differentiated by the treatment for shortages.Shortages of some classes were treated according to lost-sales,while thos...This paper deals with a periodic review inventory system serving multiple demand classes that are differentiated by the treatment for shortages.Shortages of some classes were treated according to lost-sales,while those of the others were backlogged.In each period,both replenishment decisions of inventory and allocation for all classes were made by a setup cost for each replenishment.By using the approach of stochastic dynamic programming formulation,the optimal replenishment policy is a state-dependent（s,S） policy,and the optimal allocation decision follows a state-dependent prioritization policy.展开更多
基金The National Key Technology R&D Program of China during the 11 th Five-Year Plan Period(No.2006BAH02A06)
文摘In order to let the supplier make more reasonable supply decisions,an integrated continuous replenishment policy for the vendor-managed inventory system is presented,which considers the quantity-based shipment consolidation and stock replenishment with lead time.Then the system cost is analyzed and a mathematical model is built.Since the model is rather complex,the bounds of the optimal policy are first attained,then the problem is solved by a heuristic algorithm.Through experiments the relationship between the order lead time and the corresponding integrated policy is discussed,and the influence on the system cost is also analyzed.The results reveal that the lead time's influence on the system is more serious with the increase of the order lead time,the integrated policy with the order lead time is more reasonable and the optimal policy can minimize the total system cost.Finally,the parameter sensitivity of the model is analyzed.
基金supported by the National Natural Science Foundation of China (71071134 and 71001073)funds by Hebei Science and Technology Research and Development Program (10457202D-3)2010 Social Development of Research Subject of Hebei Province(201005006)
文摘This article analyzes a continuous-review inventory system with random supply interruptions and random lead time which may be interrupted by a random number of supplier’s OFF periods. The inventory with constant demand rate is managed by a （r; q1, q2, · · · , qm） policy and supplies from an unreliable sole supplier. By renewal theory and matrix Geometric method, the long-run average cost function is obtained and some important properties of the function are proved. Furthermore, performance of the inventory is derived.
文摘In recent times, mathematical models have been developed to describe various scenarios obtainable in the management of inventories. These models usually have as objective the minimizing of inventory costs. In this research work we propose a mathematical model of an inventory system with time-dependent three-parameter Weibull deterioration and a stochastic type demand in the form of a negative exponential distribution. Explicit expressions for the optimal values of the decision variables are obtained. Numerical examples are provided to illustrate the theoretical development.
文摘China was one of the earliest countries to set up a system to continuously inventory natural forest resources. From the beginning of the 1970s until today, seven forest resource inventories have been carried out. This research summarizes the progress of forest continuous inventories and analyzes the existing deficiencies ofChina’s forest continuous inventory system and forest management plan inventory. As stated above, this research offers corresponding countermeasures and suggestions: establishing a sample plot system for comprehensive national forest inventory and monitoring with each province’s continuous forest inventory based on the foundation of the national sample plot system, able to develop the province as a subset of the overall province-level forest resource inventory according to the actual conditions in each province. Through annual multi-resource/multi-benefit surveying of the forests, the monitoring of forest amounts, quality, functions and benefits will be assisted in its entirety. The further integration of the forest continuous inventory and the forest management plan inventory is also discussed. This research also proposes the varied probability sampling method with sub-compartments as the basic sampling unit (or combinations of sub-compartments). This will also satisfy the requirements of ecological inventory by region.
文摘Geological heritage inventory procedures and templates have been principally emerged from European countries. Each of these countries has developed its proper method of inventory based on its natural heritage, recognized on local and/or regional scales. Natural sites were mainly identified and characterized in a particular geological context, which is usually very unique, valuable and impressive;resulting in the protection of the sites. Madagascar is known internationally as a beautifully landscaped island, but the impressive sites were not cataloged. We carried out a series of field inventory of potential geological sites within the Isalo National Park in southern Madagascar. We invented several inventory sheets in order to record the most detailed information about the sites identified within the park. This is to aid in organizing the park and to establish a sustainable base for the creation of a geopark, and also they help us to build a database for geosites and their classifications. This article suggests a prototype model for inventorying intangible geosites, paleosites and geomorphosites. Our inventory sheets help to identify and to promote geological importance of any sites, not only for academia but also for other sectors such as tourism and conservation.
基金supported by the Shanghai Excellent Junior Faculty Foundation
文摘We study the stochastic inventory problem with optimal （s,S） policies.In a finite horizon model with lost sales,we establish new lower and upper bounds of s and S.These bounds have structural implications for the optimal solutions.Consequently,when demand has a generalized phase type distribution,there are no more than a pre-determined number of minima.Similar bounds can also be found for the system where unsatisfied demand is backordered instead of lost sales.
文摘We analyze a continuous review lost sales inventory system with two types of orders—regular and emergency. The regular order has a stochastic lead time and is placed with the cheapest acceptable supplier. The emergency order has a deterministic lead time is placed with a local supplier who has a higher price. The emergency order is not always filled since the supplier may not have the ability to provide the order on an emergency basis at all times. This emergency order has a higher cost per item and has a known probability of being filled. The total costs for this system are compared to a system without emergency placement of orders. This paper provides managers with a tool to assess when dual sourcing is cost optimal by comparing the single sourcing and dual sourcing models.
文摘In this research work we propose a mathematical model of an inventory system with time dependent three-parameter Weibull deterioration and <span style="font-family:Verdana;">price-</span><span style="font-family:Verdana;">dependent demand rate. The model incorporates shortages and deteriorating items are considered in which inventory is depleted not only by demand but also by decay, such as, direct spoilage as in fruits, vegetables and food products, or deterioration as in obsolete electronic components. Furthermore, the rate of deterioration is taken to be time-proportional, and a power law form of the price dependence of demand is considered. This price-dependence of the demand function is nonlinear, and is such that when price of a commodity increases, demand decreases and when price of a commodity decreases, demand increases. The objective of the model is to minimize the total inventory costs. From the numerical example presented to illustrate the solution procedure of the model, we obtain meaningful results. We then proceed to perform sensitivity analysis of our model. The sensitivity analysis illustrates the extent to which the optimal solution of the model is affected by slight changes or errors in its input parameter values.</span>
基金We acknowledge that this work was supported by the science and technology innovation fund of Henan Agricultural University,No.KJCX2016A04Henan province institution of higher learning youth backbone teachers training program,No.2016GGJS-036Henan Provincial Department of Science and Technology Research Project under Grant 192102110205.
文摘As fresh agricultural products are perishable and vulnerable,reducing inventory cost is a strategic target for supply chain enterprises.How to design a reliable multi-echelon inventory control policy is still a great challenge.Therefore,the inventory cost of a three-level fresh agricultural products inventory system was firstly mathematically analyzed.Then,the simulation-based optimization model of the multi-echelon inventory system for fresh agricultural products was proposed by using the Flexsim simulation software and the improved particle swarm optimization algorithm.Finally,the multi-echelon inventory system is simulated based on a large number of survey data.Simulation results demonstrate that the proposed simulation-based optimization model of multi-echelon inventory system for fresh agricultural products can provide decision-making and technical support for the formulation of inventory control policy,and also it shows that the modeling of system simulation is an effective method to solve the problem of complex system.
基金supported by the INSPIRE fellowship,New Delhi,research award No.DST/INSPIRE fellowship/2010/[168],Reg.No.IF1020supported by the Council of Scientific and Industrial Research(CSIR)-India for their financial support(no.25(0813)/10/EMR-II)
文摘In this article, we present a continuous review （s,S） inventory system with a service facility consisting of finite buffer （capacity N ） and a single server. The customers arrive according to a Poisson process. The individual customer＇s unit demand is satisfied after a random time of service, which is assumed to be exponential. When the inventory level drops to s＇an order for Q（= S-s） items is placed. The lead time of reorder is assumed to be exponential distribution. An arriving customer, who finds the buffer is full, enters into the pool of infinite size or leaves the system according to a Bernolli trial. At the time of service completion, if the buffer size drops to a preassigned level L （1 〈 L 〈 N） or below and the inventory level is above s, we select the customers from the pool according to two different policy ： in first policy, with probability p （0 〈 p 〈 1） we select the customer from the head of the pool and we place the customer at the end of the buffer; in the second policy, with p （0 〈 p 〈 1） the customer from the pool is transferred to the buffer for immediate service and after completion of his service we provide service to the customer who is in the buffer with probability one. If at a service completion epoch the buffer turns out to be empty, there is at least one customer in the pool and the inventory level is positive, then the one ahead of all waiting in the pool gets transferred to the buffer, and his service starts immediately. The joint probability distribution of the number of customers in the pool, number of customers in the buffer and the inventory level is obtained in the steady-state case. Various stationary system performance measures are computed and total expected cost rate is calculated. A comparative result of two models is illustrate numerically.
文摘The multi echelon inventory system theory (MEIST) ,which is an important branch of inventory theory, is applied mainly in solving the problem of a multi echelon inventory and supply system. In this paper, a brief review of MEIST is given and its main points are summarized. An application is made to the decision of spares stock levels in maintenance management. The result shows that it can reduce costs of spares by using MEIST in the case of a multi echelon maintenance system.
基金supported by Council of Scientific and Industrial Research,India,research award(No.25(0183)/10/EMR-II).
文摘In this article,we consider a discrete-time inventory model in which demands arrive according to a discrete Markovian arrival process.The inventory is replenished according to an es;ST policy,and the lead time is assumed to follow a discrete phase-type distribution.The demands that occur during stock-out periods either enter a pool which has an infinite capacity or leave the system with a predefined probability.The demands in the pool are selected one by one,if the on-hand inventory level is above s t 1;and the interval time between any two successive selections is assumed to have a discrete phase-type distribution.The joint probability distribution of the number of customers in the pool and the inventory level is obtained in the steady-state case.We derive the system performance measures under steady state and using these measures,the total expected cost rate of the system is calculated.The impacts of arrival rate on the performance measures are graphically illustrated.Finally,we study the impact of cost on the optimal values of the total expected cost rate,inventory level and the reorder point.
文摘Because of the importance of discrete event systems, much attention is being paid by more and more people to the ( s,S ) type of random inventory systems. In this paper, the simulation aim, evaluation criterion and the general strategy are studied by employing SIMAN. And they are explained with a case at last.
基金National Natural Science Foundation of China,No.41261016,No.41561016Opening Foundation Projection of State Key Laboratory of Cryosphere Sciences,CAS,No.SKLCS-OP-2016-10+1 种基金Youth Scholar Scientific Capability Promoting Project of Northwest Normal University,No.NWNU-LKQN-14-4Geological Survey Project of China Geological Survey,No.DD2016034206
文摘Glacial lakes are not only the important refresh water resources in alpine region, but also act as a trigger of many glacial hazards such as glacial lake outburst flood （GLOF） and debris flow. Therefore, glacial lakes play an important role on the cryosphere, climate change and alpine hazards. In this paper, the issues of glacial lake were systematically discussed, then from the view of glacial lake inventory and glacial lake hazards study, the glacial lake was defined as natural water mainly supplied by modern glacial meltwater or formed in glacier moraine＇s depression. Furthermore, a complete classification system of glacial lake was proposed based on its formation mechanism, topographic feature and geographical position. Glacial lakes were classified as 6 classes and 8 subclasses, i.e., glacial erosion lake （including cirque lake, gla- cial valley lake and other glacial erosion lake）, moraine-dammed lake （including end mo- raine-dammed lake, lateral moraine-dammed lake and moraine thaw lake）, ice-blocked lake （including advancing glacier-blocked lake and other glacier-blocked lake）, supraglacial lake, subglacial lake and other glacial lake. Meanwhile, some corresponding features exhibiting on remote sensing image and quantitative indices for identifying different glacial lake types were proposed in order to build a universal and operational classification system of glacial lake.
基金the Natural Science Foundation of Hebei Province, China (No.A2017203078).
文摘In this paper, we consider a production inventory system with service time and production vacations. Customers arrive in the system according to a Poisson process requiring service from a single server. The single production facility produces items according to an (s, S) policy, and 让 takes a vacation of random duration once the inventory level becomes S. It is assumed that all arriving customers are lost during the stock out period. We first derive the stationary joint distribution of the queue length and the on-hand inventory level in product form. Then, we compute explicitly some performance measures, and develop a cost function based on these performance measures. Finally;some numerical results are presented.
基金supported in part by NSF of China under grants 70971072 and 70871066
文摘We discuss a single-period inventory system with a general S-shaped utility function and exponential demand. It is shown that there exists a state-dependent order-up-to policy to be optimal. Behaviors of optimal policy are illustrated by a numerical example.
文摘In this paper, we consider the inventory system with a bounded emergency order, using a probability criterion. It is shown that there exist two critical numbers x and x such that the optimal emergency order policy is order-up-to-x with a bound and the optimal regular order policy is order-up-to-x.
文摘We consider a continuous review perishable （s,S） inventory system with a service facility consisting of a waiting hall of finite capacity and a single server. We assume two types of customers, ordinary and negative, arrive according to a Markovian Arrival Process （MAP）. An ordinary customer joins the queue and a negative customer instead of joining the queue removes one ordinary customer from the queue. The removal rule adopted in this paper is RCE （removal of a customer from the end）. The individual customer＇s unit demand is satisfied after a random time of service which is assumed to have a phase-type distribution. The life time of each item and the lead time of the reorders have been assumed to be independent exponential distributions. The joint probability distribution of the number of customers in the system and the inventory level is obtained for the steady state case. Various stationary system performance measures are computed and the total expected cost rate is calculated. The results are illustrated numerically.
基金supported by in part by the Natural Science Foundation of Hebei Province,China under Grant No.A2017203078the Basic Research Project of Yanshan University,China under Grant No.16LGB017
文摘This paper considers a production inventory system with service time and product returns, dependent on the characteristics of online shopping beliaviors. The customers arrive according to a Poisson process, in which the arriving customer requires an item in the inventory, as well as a server service that the service time is exponentially distributed. Moreover, there is one production facility to produce items according to (s, S) policy, and the production time also follows an exponential (listribution. In the beginning, the stationary joint distribution is obtained in the product form for the queue length and the on-hand inventory level. Additionally, the resulting distribution is applied to derive some performance measures, which can be adopted to numerically calculate the optimal (s, S) policy. Finally, numerical analyses are processed to investigate the effects of some system parameters on the performance measures. The numerical results clearly indicate that the product return rate has a significantly monotonic effect on the optimal policy and optimal cost.
基金Supported by the National Natural Science Foundation of China(No 70871066)
文摘This paper deals with a periodic review inventory system serving multiple demand classes that are differentiated by the treatment for shortages.Shortages of some classes were treated according to lost-sales,while those of the others were backlogged.In each period,both replenishment decisions of inventory and allocation for all classes were made by a setup cost for each replenishment.By using the approach of stochastic dynamic programming formulation,the optimal replenishment policy is a state-dependent（s,S） policy,and the optimal allocation decision follows a state-dependent prioritization policy.
