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老年人惯常活动规律和北京老年旅游市场发展趋势研究 被引量:2
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作者 王琦 《时代经贸》 2019年第28期24-30,共7页
随着人口老龄化程度的提速,老年旅游市场需求不断扩大,适老旅游产品的开发和老年旅游公共服务体系的建设具有十分重要的意义。本文基于老年惯常活动规律的调查研究,分析老年旅游市场供需双方对于老年旅游市场的认知结论,得出对于北京老... 随着人口老龄化程度的提速,老年旅游市场需求不断扩大,适老旅游产品的开发和老年旅游公共服务体系的建设具有十分重要的意义。本文基于老年惯常活动规律的调查研究,分析老年旅游市场供需双方对于老年旅游市场的认知结论,得出对于北京老年旅游市场的趋势研究和发展建议。 展开更多
关键词 活动规律 老年旅游市场 均服务
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常规镀铬液中SO_4^(2-)测定方法的改进
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作者 高萍 何志邦 《材料保护》 CAS CSCD 北大核心 1990年第11期23-24,共2页
镀铬液中SO_4^(2-)的测定,往往先用乙醇、乙酸与盐酸混合来还原六价铬,在进行这一步骤的操作时,我们认为存在以下弊端: 1.所用混合液成本高; 2.在加热煮沸还原过程中,很易发生突然暴沸现象,试液喷溅出来,不得不重新取样; 3.乙醇的混合... 镀铬液中SO_4^(2-)的测定,往往先用乙醇、乙酸与盐酸混合来还原六价铬,在进行这一步骤的操作时,我们认为存在以下弊端: 1.所用混合液成本高; 2.在加热煮沸还原过程中,很易发生突然暴沸现象,试液喷溅出来,不得不重新取样; 3.乙醇的混合液煮沸时易燃,显然这对实验室存在不安全因素。针对上述问题,我们在用蔗糖、草酸……等物质代替上述醇酸混合液进行还原试验时,发现将镀铬液与浓盐酸一起加热时,马上能嗅到带刺激性的典型氯气味道,而且溶液颜色很快由黄转绿,由此可见,在强酸性介质并加热条件下,Cl^-是可以完全还原CrO_3的,其反应式为: 展开更多
关键词 常规律 镀铬 镀液 测定法 硫酸根
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Analysis of Small Earthquake Activities before Medium-strong Earthquakes in Northeast China
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作者 Li Yongzhen Jiang Jinzheng Liang Yongduo 《Earthquake Research in China》 2013年第3期382-390,共9页
13 earthquakes with M 〉 5.0 have been recorded in the northeast region of China since 1970, among which eight medium-strong earthquakes are independent in space and time. Studies of seismicity before these eight medi... 13 earthquakes with M 〉 5.0 have been recorded in the northeast region of China since 1970, among which eight medium-strong earthquakes are independent in space and time. Studies of seismicity before these eight medium-strong earthquakes show that small earthquake activity was enhanced before the occurrences. Though seismicity increase is a common phenomenon in the northeast China region, we have difficulty in predicting the medium-strong earthquakes by this phenomenon alone. In order to predict medium-strong earthquakes through se|smicity increase, this paper tries to propose a new method that calculates small earthquake frequency through the changing pattern of small earthquake activities based on the characteristics of small earthquake activity in the northeast China region. The results show that we can get the obvious anomaly frequency of small earthquakes before medium-strong earthquakes through the new method, and can obtain a medium to short term anomaly index for the northeast China region. 展开更多
关键词 Medium-strong earthquake Northeast China region Small earthquakeactivity Medium to short term anomaly
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A General Law of Precise Asymptotics for the Complete Moment Convergence 被引量:17
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作者 Yong ZHANG Xiaoyun YANG Zhishan DONG 《Chinese Annals of Mathematics,Series B》 SCIE CSCD 2009年第1期77-90,共14页
The authors achieve a general law of precise asymptotics for a new kind of complete moment convergence of i.i.d. random variables, which includes complete con- vergence as a special case. It can describe the relations... The authors achieve a general law of precise asymptotics for a new kind of complete moment convergence of i.i.d. random variables, which includes complete con- vergence as a special case. It can describe the relations among the boundary function, weighted function, convergence rate and limit value in studies of complete convergence. This extends and generalizes the corresponding results of Liu and Lin in 2006. 展开更多
关键词 Complete moment convergence General law Precise asymptotics
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Variational Formulation of 1-D Unsteady Compressible Flow in a Deforming Tube 被引量:2
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作者 Gaolian Liu Yi Tao Yingxue LiuShanghai University, 200072 Shanghai, China 《Journal of Thermal Science》 SCIE EI CAS CSCD 2003年第2期114-117,共4页
The variational principles for 1-D unsteady compressible flow in a deforming tube derived in a previous paper are improved essentially by reconstructing the initial/final-integral terms according to a new method sugge... The variational principles for 1-D unsteady compressible flow in a deforming tube derived in a previous paper are improved essentially by reconstructing the initial/final-integral terms according to a new method suggested in a recent paper. As a result, the inherent shortcoming of variational principles of being unable to admit physically rational initial/final-value conditions in initial/boundary-value problems is successfully eliminated. Thus, a new theoretical basis for the time-space finite-element analysis is provided. 展开更多
关键词 variational principle time boundary condition 1-D unsteady flow.
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