The rapid development and continuous updating of the mega satellite constellation(MSC)have brought new visions for the future 6G coverage extension, where the global seamless signal coverage can realize ubiquitous ser...The rapid development and continuous updating of the mega satellite constellation(MSC)have brought new visions for the future 6G coverage extension, where the global seamless signal coverage can realize ubiquitous services for user terminals. However, global traffic demands present nonuniform characteristics. Therefore, how to ensure the on-demand service coverage for the specific traffic demand, i.e., the ratio of traffic density to service requirement per unit area, is the core issue of 6G wireless coverage extension exploiting the MSC. To this regard, this paper first discusses the open challenges to reveal the future direction of 6G wireless coverage extension from the perspective of key factors affecting service coverage performance, i.e., the network access capacity, space segment capacity and their matchingrelationship. Furthermore, we elaborate on the key factors affecting effective matchings of the aforementioned aspects, thereby improving service coverage capability.展开更多
With the massive increase of digital resource based on the network,it becomes very important that how to help readers acquire the information needed according to the individualized requirement and interest in an accur...With the massive increase of digital resource based on the network,it becomes very important that how to help readers acquire the information needed according to the individualized requirement and interest in an accurate,convenient and prompt method. Therefore,it is very urgent to investigate individualized information service of library. In this paper,based on the development of the individualized information service for the reader in the college library,the individualized information service is clarified by using three perspectives,including establishment of individualized information demand model,integration of internal and external resource and protection of the reader privacy. Finally,the corresponding strategy and related measure are presented.展开更多
背景近十年来,随着医疗保健生态学模型(ecology of medical care model)应用价值的突显,该模型得到了学者们的高度关注。医疗保健生态学理论模型构建的差异与变化在一定程度上可以反映医疗模式的转变,为了解我国人群健康需求和卫生服务...背景近十年来,随着医疗保健生态学模型(ecology of medical care model)应用价值的突显,该模型得到了学者们的高度关注。医疗保健生态学理论模型构建的差异与变化在一定程度上可以反映医疗模式的转变,为了解我国人群健康需求和卫生服务利用情况提供证据基础。目的对运用医疗保健生态学模型的研究进行整合和对比,以描述使用医疗保健生态学模型建立的研究现状、对比研究方法和主要发现。方法于2022年6月,在PubMed、Ovid Medline、Web of Science、EmBase、中国生物医学文献服务系统、中国知网、万方数据知识服务平台中根据关键词、不限制语种开展检索,检索时限为1961-2022年。在Joanna Briggs Institute(JBI)概况性评价方法学手册的指导下,对文献进行筛选、信息提取,并开展描述性分析。结果共纳入符合要求的文献28篇,其中22篇(78.6%)发表于2010年以后。多数研究运用医疗保健生态学模型重点关注人群的健康需求、医疗资源利用模式,聚焦就医行为模式、疾病转诊等问题。在研究人群方面,多数研究覆盖全年龄段人群(11篇,39.3%),针对特定人群开展的研究有7篇(25.0%)。有4项研究在中国开展,均针对城市地区。相较于发达国家(地区),发展中国家(地区)研究中较少关注患者自我寻求帮助(非处方药、按摩等)情况,已有的医疗保健生态学模型反映出发展中国家(地区)具有较低的患者自报有健康问题(症状)比例,但具有更高的医院门诊就诊和急诊就诊比例。结论医疗保健生态学模型及其研究方法在过去20年间不断演进,仍然是帮助研究者和政策制定者了解医疗保健需求和医疗资源供需关系的重要工具。目前,中国对医疗保健生态学框架的应用程度不高,未来可更多地运用该模型反映卫生服务不平等和健康需求未被满足情况,并可开展群医学等领域的研究,为提高我国人群健康资源合理分配提供证据基础。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
基金supported in part by the National Key R&D Program of China under Grant 2020YFB1806100in part by the Natural Science Foundation of China under Grants U19B2025, 62121001, 62001347, and 61801361。
文摘The rapid development and continuous updating of the mega satellite constellation(MSC)have brought new visions for the future 6G coverage extension, where the global seamless signal coverage can realize ubiquitous services for user terminals. However, global traffic demands present nonuniform characteristics. Therefore, how to ensure the on-demand service coverage for the specific traffic demand, i.e., the ratio of traffic density to service requirement per unit area, is the core issue of 6G wireless coverage extension exploiting the MSC. To this regard, this paper first discusses the open challenges to reveal the future direction of 6G wireless coverage extension from the perspective of key factors affecting service coverage performance, i.e., the network access capacity, space segment capacity and their matchingrelationship. Furthermore, we elaborate on the key factors affecting effective matchings of the aforementioned aspects, thereby improving service coverage capability.
文摘With the massive increase of digital resource based on the network,it becomes very important that how to help readers acquire the information needed according to the individualized requirement and interest in an accurate,convenient and prompt method. Therefore,it is very urgent to investigate individualized information service of library. In this paper,based on the development of the individualized information service for the reader in the college library,the individualized information service is clarified by using three perspectives,including establishment of individualized information demand model,integration of internal and external resource and protection of the reader privacy. Finally,the corresponding strategy and related measure are presented.
文摘背景近十年来,随着医疗保健生态学模型(ecology of medical care model)应用价值的突显,该模型得到了学者们的高度关注。医疗保健生态学理论模型构建的差异与变化在一定程度上可以反映医疗模式的转变,为了解我国人群健康需求和卫生服务利用情况提供证据基础。目的对运用医疗保健生态学模型的研究进行整合和对比,以描述使用医疗保健生态学模型建立的研究现状、对比研究方法和主要发现。方法于2022年6月,在PubMed、Ovid Medline、Web of Science、EmBase、中国生物医学文献服务系统、中国知网、万方数据知识服务平台中根据关键词、不限制语种开展检索,检索时限为1961-2022年。在Joanna Briggs Institute(JBI)概况性评价方法学手册的指导下,对文献进行筛选、信息提取,并开展描述性分析。结果共纳入符合要求的文献28篇,其中22篇(78.6%)发表于2010年以后。多数研究运用医疗保健生态学模型重点关注人群的健康需求、医疗资源利用模式,聚焦就医行为模式、疾病转诊等问题。在研究人群方面,多数研究覆盖全年龄段人群(11篇,39.3%),针对特定人群开展的研究有7篇(25.0%)。有4项研究在中国开展,均针对城市地区。相较于发达国家(地区),发展中国家(地区)研究中较少关注患者自我寻求帮助(非处方药、按摩等)情况,已有的医疗保健生态学模型反映出发展中国家(地区)具有较低的患者自报有健康问题(症状)比例,但具有更高的医院门诊就诊和急诊就诊比例。结论医疗保健生态学模型及其研究方法在过去20年间不断演进,仍然是帮助研究者和政策制定者了解医疗保健需求和医疗资源供需关系的重要工具。目前,中国对医疗保健生态学框架的应用程度不高,未来可更多地运用该模型反映卫生服务不平等和健康需求未被满足情况,并可开展群医学等领域的研究,为提高我国人群健康资源合理分配提供证据基础。
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.
