检索结果-南通市图书馆

Chinese Journal of Chemistry 2020年第2期38卷 220-221页

作者： xiang zhao Lei Cai Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation School of PharmacyHuazhong University of Science and Technology13 Hangkong RoadWuhanHubei 430030China

Developing efficient glycosylation methods and strategies is always a top priority and endless pursuit for carbohydrate chemists to acquire complex glycosidic *** most glycosylation reactions are step-wise,that is,installation of the leaving group at the anomeric position first followed by activation and coupling with acceptors(Scheme 1a),dehydrative glycosylation is obviously more straightforward.[1]In this strategy,C1-hemiacetals are directly activated to couple with acceptors,thus obviating additional C1 modification steps(Scheme 1b).Unfortunately,the intrinsic stability of C1-hemiacetals impedes their applications.

关键词： straight steps pursuit

Deriving average delay of traffic flow around intersections from vehicle trajectory data

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Earth Science 2013年第1期7卷 28-33页

作者： Minyue zhao xiang LI Shanghai Key Labortatory for Urban Ecology and Sustainability East China Normal University Shanghai 200062 China Key Labortatory of Geographical Information Science (Ministry of Education) East China Normal University Shanghai 200062 China

Advances of positioning and wireless commu- nication technologies make it possible to collect a large number of trajectory data of moving vehicles in a fast and convenient fashion. The data can be applied to various fields such as traffic study. In derive average delay of traffic and verify the results with this paper, we attempt to flow arotmd intersections changes of time. The intersection zone is delineated first. Positioning points geographically located within this zone are selected, and then outliers are removed. Turn trips are extracted from selected trajectory data. Each trip, physically consisting of time-series positioning points, is identified with entry road segment and turning direction, i.e. target road segment. Turn trips are grouped into different categories according to their time attributes. Then, delay of each trip during a turn is calculated with its recorded speed. Delays of all trips in the same period of time are plotted to observe the change pattern of traffic conditions. Compared to conven- tional approaches, the proposed method can be applied to those intersections without fixed data collection devices such as loop detectors since a large number of trajectory data can always provide a more complete spatio-temporal picture of a road network. With respect to data availability, taxi trajectory data and an intersection in Shanghai are employed to test the proposed methodology. Results demonstrate its applicability.

关键词： trajectory data traffic flow information intersection

Research on the measurement of the price change of telecom services in China

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2006年第3期13卷 110-113页

作者： zhao Hui-juan Management Department Xi'an University of Posts and TelecommunicationsXi'an 710061 China

It is difficult to measure the total change of the telecom service price （TSP） in China due to the complexity of TSP and the diversity of telecom service. This article analyzes the relation between telecom service revenue and traffic volumes of telecom service and deduces the method of measuring the total change in tendency of telecom price, which is based on the consumer＇s actual payment for telecom services. After describing the changing trend of TSP with the time series data from 1949 to 2000, the TSP showed a continuous declining tendency during 1949～1975. In contrast, the TSP showed a rising tendency from 1976 to 1991 and a sharp declining trend after 1992. Empirical tests and actual background of telecom reform support the results.

关键词： price telecom service price revenue traffic volumes of telecom service

Systematic comparison of the effectiveness of radial artery and saphenous vein or right internal thoracic artery coronary bypass grafts in non-left anterior descending coronary arteries

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2011年第4期12卷 273-279页

作者： xiang HU Qiang zhao Department of Cardiac Surgery Ruijin Hospital School of Medicine Shanghai Jiao Tong University Shanghai 200025 China

Coronary artery bypass grafting surgery is increasingly being carried out on patients with multi-vessel coronary artery disease,but the best grafting candidate for non-left anterior descending coronary arteries is *** research sought to systematically compare the efficacies and safeties of coronary bypass with radial artery and other available grafts.A systematic literature retrieval was performed for all clinical trials comparing the outcomes of coronary artery bypass surgery with radial artery and other grafts in PubMed,EMBASE,and the Cochrane *** eligible clinical studies,comparing radial artery and great saphenous vein grafts,were found between 1966 and 2010:one prospective non-randomized and six prospective randomized *** pooling analysis obtained a relative risk of 0.507 (P<0.05) of graft occlusion in radial arteries compared with great saphenous *** was a significantly lower infection rate in arms (i.e.,harvest sites for radial arteries) relative to legs (harvest sites for veins),with a pooled relative risk of 0.140 (P<0.05).From the reports on mortality after follow-up ranging from one year to six years,there was no significant difference in mortality between the two graft types (P=0.927).In addition,four cohort controlled trials for radial and right internal thoracic artery grafts were *** radial graft was associated with less cardiac related events relative to the right internal thoracic artery graft (P=0.014),but with comparable mortality and comparable rates of repeat percutaneous transluminal coronary *** with radial arteries seemed to have a lower occlusion rate and a lower graft harvest site infection rate than those with great saphenous *** there were fewer cardiac related events with radial arteries relative to the right internal thoracic artery *** studies are needed to confirm these findings concerning the favorable outcomes of coronary artery bypass grafting with radia

关键词： Coronary artery bypass grafting (CABG) Arterial grafts Meta-analysis

Complex patterns of precipitation and extreme events during 1951-2011 in Sichuan Basin, Southwestern China

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2018年第2期15卷 340-356页

作者： ZHOU xiang-yang LEI Wen-juan Guizhou Provincial Key Laboratory of Public Big Data Guizhou University State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University College of Architecture & Environment Sichuan University

Sichuan Basin is located in southwestern China and affected by a complex water vapor （WV） sources. Here, the spatial and temporal patterns of precipitation and extreme events are investigated by six indices of World Meteorology Organization Commission, including annual precipitation total （AP）, maximum daily precipitation （Maxld）, intensity of rainfall over 1 mm/d （IR1）, maximum and mean consecutive dry days （Max CDD, Mean CDD） and coefficient of variance. Based on 24 daily precipitation time series from 1951 to 2o11, Mann-Kendall test is employed to quantify the significant level of these indices, from which the classification of precipitation change and its spatial patterns are obtained. Meanwhile, the probability distributions of these indices are identified by L-moment analysis and the Goodness-of-fit test, and the corresponding values are calculated by theoretical model at different return periods. The results reveal that the western basin displays normal drought： less AP and precipitation intensity while longer drought. The southern basin shows normal increase： larger AP and precipitation intensity but shorter CDD. However, in hilly region of the central basin and the transition zone between basin and mountains, precipitation changes abnormally： increasing both drought （one or both of Mean CDD and MaxCDD） and precipitation intensity （one or both of Maxld and trend of AP is. Probability IR1） no matter what the distribution models also demonstrate the complex patterns： a negative correlation between Maxld and Max CDD in the west （R2≥0.61） while a positive correlation in the east （R2≥0.41） at all return periods. These patterns are induced by the changes in WV sources and the layout of local terrain. The increase of WV in summer and decrease in spring leads to the heavier rainfall and longer drought respectively. The large heat island effect of the basin contributes to a lower temperature in transition zones and more precipitation in the downwind area. These resul

关键词： Extreme precipitation events Climatechange Sichuan Basin Trend analysis Probability distribution

Entropy of Vaidya-deSitter Spacetime

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2001年第3期18卷 463-465页

作者： LI xiang zhao Zheng Department of Physics Beijing Normal UniversityBeijing 100875

As a statistical model of black hole entropy,the brick-wall method based on the thermal equilibrium in a large scale cannot be applied to the cases out of equilibrium,such as the non-static hole or the case with two ***,the leading term of hole entropy called the Bekenstein-Hawking entropy comes from the contribution of the field near the *** to this idea,the entropy of Vaidya-deSitter spacetime is calculated,A difference from the static case is that the result proportional to the area of horizon relies on a time-dependent *** condition of local equilibrium near the horizon is used as a working postulate.

关键词： horizon entropy equilibrium

Periodic dividends and capital injections for a spectrally negative Lévy risk process under absolute ruin

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Applied Mathematics(A Journal of Chinese Universities) 2020年第3期35卷 349-358页

作者： DONG Hua zhao xiang-hua School of Statistics Qufu Normal UniversityQufu 273165China

The spectrally negative Lévy risk model with random observation times is considered in this paper,in which both dividends and capital injections are made at some independent Poisson observation *** the absolute ruin,the expected discounted dividends and the expected discounted capital injections are *** also study the joint Laplace transforms including the absolute ruin time and the total dividends or the total capital *** the results are expressed in scale functions.

关键词： Spectrally negative Lévy risk model Randomized observation Barrier dividend Capital injection Absolute ruin

Improved Operation Characteristics for Nonvolatile Charge-Trapping Memory Capacitors with High-κ Dielectrics and SiGe Epitaxial Substrates

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2017年第9期34卷 95-99页

作者： zhao-zhao Hou Gui-Lei Wang Jin-juan xiang Jia-Xin Yao Zhen-Hua Wu Qing-Zhu Zhang Hua-xiang Yin Key Laboratory of Microelectronics Devices&Integrated Technology Institute of MicroelectronicsChinese Academy of SciencesBeijing 100029 University of Chinese Academy of Sciences Beijing 100049

A novel high-κ~ A1203/HfO2/AI203 nanolaminate charge trapping memory capacitor structure based on SiGe substrates with low interface densities is successfully fabricated and investigated. The memory capacitor exhibits excellent program-erasable characteristics. A large memory window of ~4 V, a small leakage current density of ~2 ×10-6 Acre-2 at a gate voltage of 7V, a high charge trapping density of 1.42 × 1013 cm-2 at a working vo]tage of 4-10 V and good retention characteristics are observed. Furthermore, the programming （△ VFB = 2.8 V at 10 V for 10μs） and erasing speeds （△VFB =-1.7 V at -10 V for 10μs） of the fabricated capacitor based on SiGe substrates are significantly improved as compared with counterparts reported earlier. It is concluded that the high-κ Al2O3/HfO2/Al2O3 nanolaminate charge trapping capacitor structure based on SiGe substrates is a promising candidate for future nano-scaled nonvolatile flash memory applications.

关键词： Dielectrics and SiGe Epitaxial Substrates Improved Operation Characteristics for Nonvolatile Charge-Trapping Memory Capacitors with High

基于模糊层次综合分析的残损状态纯木结构安全评估方法

在线全文

学校读者我要写书评

暂无评论

土木与环境工程学报（中英文） 2025年第1期47卷 110-117页

作者：杨庆山赵剑波刘纲王娟重庆大学土木工程学院重庆400045 北京交通大学土木建筑工程学院北京100044

现存古建筑大多带伤服役,体内残损状态复杂多样,且对古建筑进行的加固维修与原有残损对结构本体的安全性能影响截然相反。为实现对古建筑的预防性保护,需要量化古建筑纯木结构中的残损状态及修缮措施对其安全状态的影响。基于山西万荣... 详细信息

现存古建筑大多带伤服役,体内残损状态复杂多样,且对古建筑进行的加固维修与原有残损对结构本体的安全性能影响截然相反。为实现对古建筑的预防性保护,需要量化古建筑纯木结构中的残损状态及修缮措施对其安全状态的影响。基于山西万荣飞云楼各构件残损状态普查统计数据,结合现有规范及工程经验对构件残损状态等级详细划分,建立4级模糊层次分析模型,确定结构体中承重构件及构件残损类型的权重值及判断矩阵,通过模糊层次分析方法对飞云楼进行安全状态评估。结果表明,建立的模糊层次安全评价模型能反映残损状态及修缮措施对飞云楼安全状态的影响,有效将结构评价与构件评价联系起来,验证了修缮措施能有效增强古建筑结构本体的安全性及稳定性,该模型及方法可以应用到多层古建木结构的安全等级评价中。

关键词：飞云楼纯木结构残损状态修缮加固模糊层次分析方法安全评估

维普期刊数据库博看期刊

Sun's total irradiance reconstruction based on multiple solar indices

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2012年第1期55卷 179-186页

作者： zhao juan HAN YanBen Department of Astronomy Beijing Normal University Beijing 100875 China National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

In order to uncover a possible influence on the Earth's climate, we need a much longer time series, i.e., the total solar irradiance (TSI) which is also an interesting issue in its own right in solar physics. By comparing different solar indices associated with TSI during the period 1979 to 2009, several empirical models in the TSI are presented. We verify that the reconstruction model based on the three variables: sunspot number, sunspot area, and solar 10.7 cm radio flux, is the best one. As demonstrated by model calculations, the history of TSI was reconstructed back to 1947 based on 3-indices and to 1874 based on 2-indices, respectively. The reason that the reduced irradiance on the trough during 2006 to 2009 lasts long may be due to the about 85-year cycle of solar activity, which modulates the intensity of the 11-year cycle (Schwabe cycles), possesses a considerable potential to produce an effective reducing, and holds on a steadily lower level of irradiance.

关键词： solar total irradiance sunspot number sunspot area solar 10.7 cm radio flux reconstruction