Stochastic H∞ finite-time control for linear neutral semi-Markovian jumping systems under event-triggering scheme     

Yuanyuan Ju  Guifang Cheng  Zhishuai Ding 《Journal of The Franklin Institute》2021,358(2):1529-1552

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电子商务及单供应商模式下的购买费用分析     

郑江波  赵黎明 《预测》2003,22(6):78-80

本文对电子商务交易模式下的用户定货过程和供应商交货服务进行了数学假设，在原有的（S，Q）模型基础上提出了在单一供应商情况下进行电子商务交易的购买费用模型，并详细分析了其求解方案，为进一步的研究奠定了基础。  相似文献   

大鼠帕金森氏病动物模型的建立   总被引：2，自引：0，他引：2  

郑杰胜  郑树森  詹仁雅  周永庆  许德华  张家兴 《科技通报》2001,17(6):80-83

采用SD大鼠30只，25只为试验组，5只为对照组。在三维立体定向仪上用微量注射器将6－OHDA32μg分两点注射入右侧纹状体，每周检测动物的旋转行为，第1周动物没有出现旋转行为，第2周动物出现明显的旋转行为，随后缓慢上升；至术后5周才升至较高的水平并保持平稳。其中有15只动物达到或超过了7r/min这一通常采用的标准，模型成功率达60％。酪氨酸羟化酶免疫组化显示：术后第1周至第5周右侧黑质TH免疫反应细胞逐渐砬少，各个时期的右侧黑质TH免疫反应细胞较对侧明显减少。采用此方法建立的大鼠帕金森氏病模型更加符合临床PD病人的病程进展并明显提高成功率。  相似文献   

企业知识管理水平的测评   总被引：2，自引：1，他引：2  

李刚  程国平 《科技管理研究》2005,25(6):98-100

从管理者对知识管理的重视程度，知识管理基础设施的建设水平，人力资源管理知识化水平，组织结构和企业文化的适宜度，知识的检测、评估和利用水平，外部关系整合的知识化水平等六个方面建立了企业知识管理水平的测度指标体系，并进行了综合评价。  相似文献   

两种绿篱植物对作物养分吸收的影响     

丁树文  王峰  蔡崇法  史志华  彭业轩  姜成  张光远 《资源科学》2004,26(Z1):156-160

种植等高绿篱是丘陵山区实现农业可持续发展较为理想的经营措施,是防治坡耕地的水土流失和土地退化的有效手段.由于绿篱植物的引入,存在着绿篱植物与作物之间的抑制或促进作用,尤其是两者之间在养分、光、水和气方面的竞争作用,又成为植物篱推广应用的限制因子.本研究选用豆科紫穗槐和禾木科香根草为绿篱植物,间作小麦、大豆,设置单作、板隔、网隔和无隔4个处理.借助同位素示踪技术,测定绿篱和作物养分含量及吸收量.研究结果表明:香根草、紫穗槐对小麦N吸收影响不大,香根草不利于大豆N吸收,紫穗槐对大豆N的吸收有利;香根草抑制小麦P的吸收,促进大豆对P的吸收,紫穗槐对小麦、大豆P吸收都有利;香根草、紫穗槐对小麦、大豆K吸收起促进作用;香根草对N的竞争和对P、K的吸收能力均强于紫穗槐,而对N的吸收能力弱于紫穗槐;两种绿篱对小麦影响弱于小麦个体间的影响,对大豆的影响强于大豆个体的相互影响.这些揭示了紫穗槐和香根草对小麦、大豆之间的养分促进与竞争特点,为丘陵山区植物篱技术的推广应用提供理论依据.  相似文献   

茭白孕茭前后植株叶片和叶鞘器官中游离氨基酸和总糖含量的变化   总被引：4，自引：0，他引：4  

郑许松  陈法军  陈建明  陈列忠  张钰锋  俞晓平 《科技通报》2006,22(4):467-470

试验比较了“河姆渡”双季茭在孕茭前和膨大期植株叶片和叶鞘中营养成分的变化。结果表明：(1)膨大期茭白叶鞘和叶片内的总糖含量分别比孕茭前显著增加99．07%和123．79%(P＜0．05)；(2)膨大期,叶鞘内总糖的含量显著大于叶片中总糖的含量,增加达18．1%(P＜0．05)；(3)孕茭前和膨大期相比．茭白叶片内游离氨基酸的组成和含量无显著差异；但叶鞘内游离氨基酸的组成和含量却差异显著(P＜0．05),氨基酸总量提高了127．8%；(4)膨大期与孕茭前相比,叶鞘中有6种氨基酸的含量增幅最大,依次是：谷氨酸(Glu；610．0%)＞甘氨酸(Gly；303．6%)＞丙氨酸(Ala；228．7%)＞赖氨酸(Lys；207．2%)＞丝氨酸(Ser；203．7%)＞天门冬氨酸(Asp；172．0%)；其中,丝氨酸含量最高,孕茭前和膨大期分别占氨基酸总量的34．81%和46．42%；(5)膨大期与孕茭前相比,叶片和叶鞘中脯氨酸(Pro)、精氨酸(Arg)和亮氨酸(Leu)含量均有明显降低。  相似文献   

氢经济社会发展前瞻及我国的对策     

张志强  郑军卫 《科学对社会的影响》2006,(3):21-25

能源是国家发展的重大战略问题．能源安全是国家安全的重要组成部分。在人类能源利用历史中．世界各国的能源结构大致经历了两次重大转变．一是从19世纪中叶前的以生物质燃料为主转变为19世纪末到20世纪初的以煤为主．二是从20世纪中叶以来石油天然气代替煤成为人类的主要能源。伴随人类主要能源形式的重大转变而形成的“煤经济”、“石油经济”．有力地促进了人类经济社会的大发展。然而，化石能源终究是要枯竭的．以当前最重要的石油资源为例，最新预测结果是储采比为40年。  相似文献   

信息检索策略研究     

王征清  成全 《情报探索》2007,(4):61-64

分析影响信息检索效率的要素,并从各个要素层面提出了相应的信息检索策略,以期指导用户的信息检索行为。  相似文献   

西藏高原植物区系中特有属的研究     

Ni Zhi-Cheng  Cheng Shu-Zhi 《中国科学院研究生院学报》1987,25(6):417-429

The Xizang (Tibetan) flora with numerous endemics is of importance in Chi- nese flora.   According to recent statistics there are in Xizang 27 genera of  spermatophytes endemic to China, being only 2.25% percent of the total number of genera in the Xizang flora. Four of them are regarded as palaeoendemics (14.81%) and the others as neoendemics (85.19%). These endemic genera, of 30 species and 3 varieties, belong to 17 families, of which, Umbelli- ferae contains 6 genera, 7 species and 3 varieties; Compositae has 6 genera and 7 species, and Gentianaceae 1 genus and 2 species.  All the other families each comprises one genus with a single species.       The cosmopolitan families together comprising 14 genera with 15 species have the highest perecentage (52.92%) and the tropical ones (5 families, 5 genera with 5 species) come to the next (29.42%), followed by the temperate ones (3 families, 10 genera with 10 species) (17.66%). It shows that these endemic genera are obviously related to the tropical flora and temperate one in essence.        According to the number of species, the genera endemic to China and occurring in Xi- zang flora may be grouped as fallows. Monotypic endemic ones 14 (51.85%) Ditypic endemic ones 6 (22.22%) Oligotypic endemic ones 4 (14.81%) Small endemic ones 3 (11.11%)        The formation of the endemic genera is correlated with the topography, climate and en- vironmental conditions, and they may have resulted from the diversification in geography and climatic influence for a long time.  The southeastern part of Xizang Plateau is of very diverse ecological conditions, with the adequate precipitation, which may explain the concentration of these endemic genera in this region.        The largest similarity coefficient (38.30%) of the genera endemic to China and occurring in Xizang is with those in Qinghai Plateau, next, with those in Yunnan and in Sichuan pro- vinces (both 27.60%), which shows that these endemic genera are related to the floras of the regions mentioned above.        The difference in the horizontal distribution of these endemic genera is obviously between the southern and northern parts of Xizang Plateau.  The vertical distribution of the genera is also rather obvious, from 800 m to 5200 m above sea level, but concentrated in the zone of 3000 m to 4500 mm.  Therefore their occurrence in Xizang is not only affected by the historical environmental conditions but also controlled by the horizontal and vertical distribution.      The origin and evolution of some endemic genera, such as Psammosilene, Parateropyrum, Sphaerotylos, Salweenia, Ajaniopsis, Xizangia, Sinoleontopodium, are discussed in this paper.      Parateropyrum, a monotypic palaeotropic endemic, belongs to the tribe Atraphaxideae in- cluding Atraphaxis, Calligonum and Pteropyrum.  It may be a comparatively advanced group in the tribe, and is closely related to the genus Pteropyrum  which is  distributed in western Asia.  The genus Parapteropyrum has possibly survived as a palaetropic-tertiary  relic in this region.      Sphaerotylos, a member of the subtribe Sphaerotylinae, the tribe Boehmerieae in the family Urticaceae, is a comparatively primitive genus in the tribe Boehmerieae so far known.  As the other subtribes, such as Boehmerinae, Sarconchlamydinae, Orecnidinae and Maoutinae, are dis- tributed in the tropics, rarely in the subtropics, the genus is no doubt a palaetropic -tertiary relic.      Sinoleontopodium, belonging to the tribe lnuleae in Compositae, is also related to the ge- nus Leontopodium.  It is probable that the genus Sinoleontopodium arised later than the other.       We come to the conclusion that the southern part of Xizang Plateau is also one of thecentres of the origin and differentiation of genera endemic to China.  相似文献   

基于QoS的Web服务发现模型研究   总被引：10，自引：0，他引：10  

郑晓霞  王建仁 《情报科学》2007,25(2):249-253

Web服务的大量涌现对服务的发现提出了挑战,UDDI基于关键词和简单分类的服务发现机制已经不能很好地满足需求。服务发现需要基于服务质量QoS来对服务进行选择和排序。本文在分析现有相关研究的基础上,首先分析了影响服务发现的三类质量因素:静态因素、动态因素和统计因素,并采用“基于约束的需求规范语言”的语法和语义来描述质量因素的约束。其次,扩展了现有的WSDL,全面地描述Web服务的质量。最后提出了基于QoS的Web服务发现模型,该模型不需要改变UDDI的内部实现,能够直接在现有的UDDI服务上进行扩展。  相似文献