A COMPARATIVE STUDY OF THE INVENTORY SYSTEM WITH SERVICE FACILITY AND POSTPONED DEMANDS

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.

A Stochastic Inventory System with Postponed Demands and Infinite Pool in Discrete-Time Setup

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.

PARADISE POSTPONED DALI'S LAKE NOW INFAMOUS FOR POLLUTION

Up to 1,000 guesthouses and restaurants adjacent to Dali’s Erhai Lake have all put up closure signs.The once-bubbly town of Shuanglang is now devoid of tourists,but full of workers laying sewage pipes.It’s a bittersweet victory for those who have long decried the tourist-led gentrification of this idyllic Yunnan community.

Underlying slip/twinning activities of Mg-xGd alloys investigated by modified lattice rotation analysis

The inconsistencies regarding the fundamental correlation between Gd content and slip(twinning)activities of Mg alloys appeal further investigations.However,the traditional slip dislocations analysis by TEM is time-consuming,and that by SEM/EBSD cannot recognize the partial slip modes.These urge a more efficient and comprehensive approach to easily distinguish all potential slip modes occurred concurrently in alloy matrix.Here we report a modified lattice rotation analysis that can distinguish all slip systems and provide statistical results for slip activities in Mg alloy matrix.Using this method,the high ductility of Mg-Gd alloy ascribed to the enhanced non-basal slips,cross-slip,and postponed twinning activities by Gd addition is quantitatively clarified.

Factors Determining the Postponement of Schedule Gyneaco-Obstetric Surgery at CHUMEFJE in Libreville (Gabon)

The study aimed to identify factors causing delays in scheduled gynaeco-obstetric surgeries at CHUMEFJE in Libreville from January 2019 to July 2020. Through a 16-month observational survey, it was found that out of 346 scheduled procedures, 128 (36.4%) were postponed. Organizational issues in the operating theatre were responsible for 80.3% of these delays, with 95.3% being preventable. To enhance efficiency, improvements in operating theatre organization are recommended.

Effects of Postponing N Application on Metabolism,Absorption and Utilization of Nitrogen of Summer Maize in SuperHigh Yield Region

[Objective] The aim was to explore effects of application postponing of N fertilizer and the mechanism of yield increase in order to provide references for N fertilizer application in a rational way. [Method] In a super-high yielded region of summer maize, field experiment was conducted to research effects of N fertilizer postponing on key enzymes of N metabolism, yield of maize and N fertilizer use. [Result] After application of N fertilizer was postponed, NR, SPS and GS activities of ear-leaf of summer maize increased by 11.99%-34.87%, 8.25%-10.64% and 10.00%- 16.81% on the 28^th d of silking; content of soluble sugar in leaves enhanced signifi- cantly and accumulated nitrogen increased by 5.00%-9.74% in mature stage. The postponing fertilization of ＂30% of fertilizer in seedling stage＋30% of fertilizer in flare- opening stage＋40% of fertilizer in silking stage meets N demands of summer maize in late growth period. Compared with conventional fertilization, the maize yield, agro- nomic efficiency and use of N fertilizer all improved by 5.05%, 1.75 kg/kg and 6.87%, respectively, after application postponed. [Conclusion] Application postponing of N fertilizer maintains activity of NR, GS and SPS higher and coordinates metabolism of C and N in late growth period, to further improve yield of maize.

Nonautonomous solitons in the continuous wave background of the variable-coefficient higher-order nonlinear Schrodinger equation

We reduce the variable-coefficient higher-order nonlinear Schrodinger equation （VCHNLSE） into the constantcoefficient （CC） one. Based on the reduction transformation and solutions of CCHNLSE, we obtain analytical soliton solutions embedded in the continuous wave background for the VCHNLSE. Then the excitation in advancement and sustainment of soliton arrays, and postponed disappearance and sustainment of the bright soliton embedded in the background are discussed in an exponential system.

Investment decision optimization for delayed product differentiation based on queuing theory

To balance inventory cost with diverse demand,an optimal investment decision on necessary process improvement for delayed product differentiation is studied. A two-stage flexible manufacturing system is modeled as a continuous time Markov chain. The first production stage manufactures semifinished products based on a make-to-stock policy. The second production stage customizes semi-finished products from the first production stage on a make-to-order policy. Various performance measures for this flexible manufacturing system are evaluated by using matrix geometric methods. An optimization model to determine the level of investment on process improvement that minimizes the manufacturer ’s total cost is established. The results show that,a higher investment level can reduce both the expected customer order fulfillment delay and the expected semi-finished products inventory. When the initial order penetration point is 0. 4,the manufacturer ’s total cost is reduced by 15. 89% through process investment. In addition, the optimal investment level increases with the increase in the unit time cost of customer order fulfillment delay,and decreases with the increase in the product value and the initial order penetration point.

Low N apparent surplus with higher rice yield under long-term fertilizer postponing in the rice-wheat cropping system

Nitrogen(N)fertilization increases rice yield,but inappropriate N fertilizer application increases N loss and the risk of environmental pollution.Short-term fertilizer postponing(FP)generally reduces N apparent surplus and increases rice yields,but the effects of long-term FP on N surplus and rice yields remain unknown.Our study was the first to investigate the impacts of long-term FP(11 years)on N apparent surplus and rice yields.FP effects in the short term(≤6 years)did not affect rice yields,whereas FP effects in the long term(>6 years)increased rice yields by 13.9%compared with conventional fertilization(CF).FP did not affect panicles per unit area,1000-kernel weight,and filled-kernel rate,but spikelets per panicle increased over time due to spikelet formation stimulation.FP also reduced the N apparent surplus over time more strongly than CF owing to higher N accumulation and N utilization efficiency.FP effects in the long term also significantly increased soil organic matter,total N,and NH4_(+)^(-)N content.Our results were supported by a pot experiment,showing that rice yields in soils with a history of FP were significantly higher than those for soils without a history of FP,indicating that FP increased rice yields more strongly in later years mainly because of soil quality improvement.Our findings suggest that longterm FP can reduce N loss while increasing rice yields by improving soil quality.

Effect of Postponing Nitrogen Application on Growth and Yield of Different Wheat Cultivars

[Objective] The aim was to study whether there are differences in top- dressing period for wheat cultivars. [Method] With three representative wheat culti- vats selected, effects of different N topdressing period on wheat tiller dynamics and yield components were studied. [Result] Appropriately postponing N topdressing time improved the yield of wheat. Appropriate N topdressing time tended to be volatile upon wheat cultivar. Jointing stage was appropriate for topdresSing for most wheat cultivars such as Jimai 22 and Linmai No. 4 and flowering stage was appropriate for the cultivar featured by early-senescence such as LN66. [Conclusion]It is neces- sary to select the optimal topdressing time according to wheat characteristics.

POSTPONING RETIREMENT AND ECONOMIC GROWTH

This paper investigates the effects of postponing retirement on economic growth in an aging society by using the infinite overlapping generations model constructed by Blanchard (1985) in a simple endogenous growth framework.It shows that postponing retirement may decelerate economic growth.

Quantitative Analysis on Postponement Strategies of Decoupling Points in Mass Customization

The key to mass customizing effectively is postponing the deco upling point of customer order in the supply network. This paper focused on quantitative analysis on postponement strategies of multiple decoupling points in mass customization to improve operating efficiency and quickly meet customer demands with a minimum amount of inventory.

Postponement in Mass Customization: A Literature Review

Mass customization (MC) is emerging as a competitive advantage of firms with the intensified competition and economic globalization.As a key feature of MC,postponement strategy postpones activities in the supply chain until customer orders are received.This article provides a review of the literature on postponement from perspectives of research content and methodology.Taking postponement as a supply chain concept,this article specifically reclassifies the postponement applications according to the positioning of the customer order decoupling point (CODP) in the supply chain.Future directions for postponement research are also suggested in this article.

Raising Retirement Age,TFP and Elderly Welfare in China

The fact that China is facing the challenge of aging population has led to debates about whether the government should raise the retirement age.The current pension system in China is characterized by the collection of contributions on payment and adopts the defined benefit(DB)plan.Considering the welfare effects of intergenerational support,this paper develops a dynamic general equilibrium model to investigate how postponing retirement would affect the TFP and the welfare of the elderly.Utilizing realistic parameters,our simulation finds that raising the retirement age will benefit the welfare of the elderly.This conclusion remains robust after a sensitivity analysis with respect to core parameters,the average age of the working population,and the pension system.However,opinion polls have found that most people oppose delaying retirement.This stems from the absence of pension transfer payments and pension system inequalities.The policy implications of this paper are twofold:Firstly,the government should convince the public about the benefits of delaying retirement;secondly,it is necessary to introduce supportive policies facilitating the implementation of delayed retirement(e.g.increasing the replacement rate of pensions or implementing a healthy aging strategy),and the retirement policy should be differentiated for people from various socio-economic backgrounds.

Postponement in New Product Introduction

Agility has now been a main research topic in the l it erature. There is much written on agility mainly focusing on manufacturing p rocess and strategic processes. However, we argue that new product introduction should call for agility as well due to uncertainty about technological advances and customers’ demand. A technological superiority alone may not guarantee succe ss for new product introduction. We focus on the role of postponement for two ma in processes in new product introduction: new product development and new produc t launch. Postponement enables designers to incorporate the most current technol ogical advances and user needs as these co-evolve with the development process. Postponement can also significantly reduce risk associated with new product lau nch. It thus can be expected that postponement will be increasingly employed in new product introduction.

Will Postponing Retirement Age Affect Youth Employment?--A Perspective Differentiating Workforce Education Levels

This paper calculates the employment substitutability between young workforce and ageing workforce using Welch index. The result shows that the employment substitutability between these two groups of people is rather poor. Furthermore, the result of our dynamic panel regression analysis indicates that an increase in the share of ageing workforce is conducive to youth employment. Such a positive effect mainly derives from more educated ageing workforce, while the increase of less educated ageing workforce has little effect on youth employment.

Factors for Postponement or Cancellation of Operating Programs Set in the Orthopedics-Traumatology Department of Yalgado Ouédraogo University Teaching Hospital in Ouagadougou (Burkina Faso)

Objective: The purpose of this work was to study the factors of cancellations or postponement of regulated operating programs of the Orthopedic-Traumatology unit of Yalgado Ouédraogo University Teaching Hospital. Materials and Methods: This was a prospective descriptive study over a period of six months. All interventions postponed or canceled during the study period were included. Patients who died or were lost to follow-up before surgery were not included. Results and Comments: the postponement/ cancellation rate was 24.5%. Out of 83 operations cancelled, 72.3% of patients were under 50 years old [extreme 15 and 88 years old]. ASA classes I and II were dominant with 57% and 37% of patients canceled, respectively. There were more postponed interventions (67.5%) than definitive cancellations (32.5%). The causes found were avoidable in 68.7% of cases. The most common was the unavailability of labile blood products (57%), the lack of financial means (36%) and the absence of the patient (28%). The results of our study show that 53% of the causes of cancellations were related to the organization of the hospital. Conclusion: the cancellation rate of orthopedic surgeries remains high at Yalgado Ouédraogo University Teaching Hospital. Most of the causes of cancellations are potentially preventable and the vast majority of them are related to the organization of the hospital. Financial accessibility to care plays an important role in cancellations.

Influencing Factors of Personal Retirement Decision： Perspective of Research Summary

Because the policy of delay retirement is facing demand differences widely, research workers retirement needs and the basic law from the micro perspective will become increasingly important. Based on the demographic characteristics, family relationships, social and economic factors and professional environment, such as in four dimensions, the article has reviewed the individual retirement decisions affecting factors and its mechanism of action, and summed up the consensus theory and some controversy. In future research, we need to strengthen the cross disciplines and integration, to explore more available research variables, provide a new starting point for further theoretical research and policy making.

Production Planning and Control of the Pipeline Assembly Enterprise under SCM

It is vital for pipeline assembly enterprise to respond to changing market needs quickly and keep its cost advantage. A production planning and control （PPC） model under supply chain management combining with operation characteristics of pipeline assembly enterprise was proposed. The present model can realize synchroni- zation in real-time response in production by establishing a win-win corporate model, classified regulation be- tween strategic parts and non-strategic parts, postponing the production of special modules and guaranteeing pro- duction at the bottleneck.

Can postponing school starting age solve China’s “Boy Crisis?”

Education has always been a deeply emotional topic for Chinese parents. A recent proposal calling for postponing boys＇ school starting age by one year has led to even more heated discussions on the topic.