期刊文献+
共找到59篇文章
< 1 2 3 >
每页显示 20 50 100
田间土壤钾素有效性影响因素及其评估 被引量:37
1
作者 王筝 鲁剑巍 +1 位作者 张文君 李小坤 《土壤》 CAS CSCD 北大核心 2012年第6期898-904,共7页
在全球性人口和资源的双重压力下,充分利用土壤有效钾素和科学地施用钾肥,对提高作物产量和保障农业生产可持续发展的意义重大。本文参考已有研究成果并结合自己最近的研究结果,综述了影响农田土壤钾素有效性及其正确评估的若干因素。... 在全球性人口和资源的双重压力下,充分利用土壤有效钾素和科学地施用钾肥,对提高作物产量和保障农业生产可持续发展的意义重大。本文参考已有研究成果并结合自己最近的研究结果,综述了影响农田土壤钾素有效性及其正确评估的若干因素。在影响土壤钾素有效化的众多因素中,土壤黏土矿物类型、黏粒含量及气候水热条件是影响土壤钾素有效性评估的主要因素;耕作措施改变了自然条件下土壤钾库有效钾的数量和土壤钾素的有效转化;土壤有效钾的测定也是客观评价土壤供钾能力的重要环节,进而影响着农田钾素养分管理策略,这一因素在实践中常被忽视。文章最后还提出了今后该领域研究需要开展的主要内容和一些重要方向。 展开更多
关键词 土壤有效钾 自然因 耕作方式 采样时间 测钾方法 评估
下载PDF
基于误差扩展与像素容量评估的图像水印算法 被引量:9
2
作者 李红日 方逵 《西南大学学报(自然科学版)》 CAS CSCD 北大核心 2017年第10期109-118,共10页
为了解决当前图像水印算法无法准确预测相邻像素间的误差值,不能根据像素的局部纹理特征差异来自适应确定其嵌入容量,导致复原水印信息存在较大失真以及水印容量较小的问题,本文提出了基于误差扩展与像素容量评估的无损图像水印算法.首... 为了解决当前图像水印算法无法准确预测相邻像素间的误差值,不能根据像素的局部纹理特征差异来自适应确定其嵌入容量,导致复原水印信息存在较大失真以及水印容量较小的问题,本文提出了基于误差扩展与像素容量评估的无损图像水印算法.首先,设计动态混淆方法,对水印信息完成加密;再考虑3个相邻像素,引入边缘像素预测机制,准确预测载体图像的每个像素值,获取其对应的误差值;随后,利用载体图像中的任意3个相邻像素的方差,设计像素容量评估方法,对其水印容量完成评估;借助误差扩展技术,设计水印信息嵌入机制,根据像素容量评估结果,将不同容量的水印数据植入到载体图像的不同像素中,获取水印图像;最后,建立水印提取方法,结合解密密钥,准确复原水印信息.实验数据表明:与当前图像水印技术相比,所提算法具有更高的水印质量与水印容量. 展开更多
关键词 图像水印 误差扩展 值预测 容量评估 水印嵌入 动态加密 水印提取
下载PDF
基于像素评估与运动补偿预测误差扩展的视频水印算法 被引量:1
3
作者 李思广 郑逢斌 《包装工程》 CAS 北大核心 2018年第19期204-211,共8页
目的为了解决当前视频水印技术因忽略了视频像素特性与时间的相关性,从而出现嵌入失真和水印容量较低等不足,设计一种基于像素评估和运动补偿预测误差扩展的自适应视频水印算法。方法首先,引入运动补偿预测误差扩展方法,预估每个视频帧... 目的为了解决当前视频水印技术因忽略了视频像素特性与时间的相关性,从而出现嵌入失真和水印容量较低等不足,设计一种基于像素评估和运动补偿预测误差扩展的自适应视频水印算法。方法首先,引入运动补偿预测误差扩展方法,预估每个视频帧的像素灰度值,从而获取其对应的运动补偿预测误差。再依据预测误差,计算像素的运动补偿局部标准差,将整个视频分割为平滑和非平滑子块。依据运动补偿局部标准差,结合像素选择阈值,从平滑块中选择出合适的像素用于嵌入水印。依据评估的水印容量与选择的视频像素,针对不同的像素,设计不同的水印嵌入机制,将水印信息隐藏到视频特定的像素中,通过完成边信息的嵌入,从而输出水印视频。最后,构建水印提取方法,从水印图像中检测出初始水印。结果测试数据显示,与当前视频水印方法相比,所提算法具有更高的水印容量和更低的失真度,其最大水印容量为2 bits,提取水印信息的PSNR值在40 dB以上。结论所提算法具有良好的不可感知性与较低的失真,在版权保护、信息防伪等领域具有一定的应用价值。 展开更多
关键词 视频水印 评估 运动补偿预测误差扩展 分类 选择阈值 水印嵌入 水印提取
下载PDF
对幼儿园游戏评估的思考
4
作者 彭兵 《学前教育研究》 CSSCI 北大核心 2000年第4期33-34,共2页
关键词 幼儿园 游戏活动 评估 评估标准 定位 评估素 游戏环境 游戏目标 游戏指导 幼儿游戏水平
下载PDF
NEW METHOD FOR SAFETY ASSESSMENT OF PARALLEL ROUTES 被引量:1
5
作者 隋东 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2009年第1期36-43,共8页
A new safety assessment method for parallel routes is presented. From the aspects of safety guard system of air traffic control(ATC) and considering the flight conflict as causing event of air collision accidents, t... A new safety assessment method for parallel routes is presented. From the aspects of safety guard system of air traffic control(ATC) and considering the flight conflict as causing event of air collision accidents, this paper fosters a four-layer safety guard of controller command, short-term conflict alerts (STCAs), pilot visual avoidance, and traffic alert collision avoidance system(TCAS). Then, the problem of parallel routes collision risk is divided into two parts:the calculation of potential flight conflict and the analysis of failure probability of the four-layer safety guard. A calculation model for controller interference times is induced. By using cognitive reliability and error analysis method(CREAM),the calculation problem to failure probability of controller sequencing flight conflicts is solved and a fault tree model of guard failure of STCA and TCAS is established. Finally, the Beijing-Shanghai parallel routes are taken as an example to be calculated and the collision risk of the parallel routes is obtained under the condition of radar control. Results show that the parallel routes can satisfy the safety demands. 展开更多
关键词 air traffic control human factors safety assessment short-term conflict alerts traffic alert collision avoidance system
下载PDF
Construction and application of an assessment index system for evalu ating the eco-community’s sustainability 被引量:1
6
作者 韩英 代力民 +2 位作者 赵小汎 于大炮 吴胜男 《Journal of Forestry Research》 SCIE CAS CSCD 2008年第2期154-158,共5页
An assessment index system including environment, socio-culture, economy and technology was established for evaluating environmental construction level of community (objective construction), and questionnaire was de... An assessment index system including environment, socio-culture, economy and technology was established for evaluating environmental construction level of community (objective construction), and questionnaire was designed according to paper review for evaluating residential satisfaction (subjective satisfaction). The index system was divided into four layers: system (A), subsystems (B), categories (C), and indicators (D), and in total of 38 indicators was established. The Xihe community, affiliated to Nanfen district, Benxi City, Liaoning Province, China was selected as a case study. Results indicated that the community sustainability index related to objective environmental construction was 0.4355 and was classified as class Ⅲ (moderate); the community sustainability index related to the residential satisfaction was 0.4255, belonging to class Ⅲ. In conclusion, the sustainability of Xihe community was moderate and needed to be improved. Residential satisfaction was lower than objective environmental construction. The assessment index system established in this study is able to reflect the comprehensive sustainability of community and can be used to evaluate other similar communities' sustainability. 展开更多
关键词 community sustainability assessment index system objective environmental construction residential satisfaction Xihe community
下载PDF
Mining Weights of Land Evaluation Factors Based on Cloud Model and Correlation Analysis 被引量:17
7
作者 HU Shiyuan LI Deren +1 位作者 LIU Yaolin LI Deyi 《Geo-Spatial Information Science》 2007年第3期218-222,共5页
The veracity of land evaluation is tightly related to the reasonable weights of land evaluation fac- tors. By mapping qualitative linguistic words into a fine-changeable cloud drops and translating the uncertain facto... The veracity of land evaluation is tightly related to the reasonable weights of land evaluation fac- tors. By mapping qualitative linguistic words into a fine-changeable cloud drops and translating the uncertain factor conditions into quantitative values with the uncertain illation based on cloud model, and then, inte- grating correlation analysis, a new way of figuring out the weight of land evaluation factors is proposed. It may solve the limitations of the conventional ways. 展开更多
关键词 cloud models correlation analysis land evaluation factor weight data mining
下载PDF
Prediction of risk of cardiovascular events in patients with mild to moderate coronary artery lesions using naive Bayesian networks 被引量:2
8
作者 Wei WANG Xian-Tao SONG +7 位作者 Yun-Dai CHEN Xing-Sheng YANG Feng XU Min ZHANG Kai TAN Fei YUAN Dong LI Shu-Zheng LYU 《Journal of Geriatric Cardiology》 SCIE CAS CSCD 2016年第11期899-905,共7页
Background This prospective study integrated multiple clinical indexes and inflammatory markers associated with coronary atherosclerotic vulnerable plaque to establish a risk prediction model that can evaluate a patie... Background This prospective study integrated multiple clinical indexes and inflammatory markers associated with coronary atherosclerotic vulnerable plaque to establish a risk prediction model that can evaluate a patient with certain risk factors for the likelihood of the occurrence of a coronary heart disease event within one year. Methods This study enrolled in 2686 patients with mild to moderate coronary artery lesions. Eighty-five indexes were recorded, included baseline clinical data, laboratory studies, and procedural characteristics. During the 1-year follow-up, 233 events occurred, five patients died, four patients suffered a nonfatal myocardial infarction, four patients underwent revascularization, and 220 patients were readmitted for angina pectoris. The Risk Estimation Model and the Simplified Model were conducted using Bayesian networks and compared with the Single Factor Models. Results The area under the curve was 0.88 for the Bayesian Model and 0.85 for the Simplified Model, while the Single Factor Model had a maximum area under the curve of 0.65. Conclusion The new models can be used to assess the short-term risk of individual coronary heart disease events and may assist in guiding preventive care. 展开更多
关键词 Bayesian networks Cardiovascular events PREDICTION
下载PDF
Assessment and Comparison of in vitro Immunoregulatory Activity of Three Astaxanthin Stereoisomers 被引量:9
9
作者 SUN Weihong XING Lihong +3 位作者 LIN Hong LENG Kailiang ZHAI Yuxiu LIU Xiaofang 《Journal of Ocean University of China》 SCIE CAS 2016年第2期283-287,共5页
In recent years,the immune-modulatory role of all-trans astaxanthin from different pigment sources has been studied.It was reported that all-trans astaxanthin might exist as three stereoisomers,and the composition of ... In recent years,the immune-modulatory role of all-trans astaxanthin from different pigment sources has been studied.It was reported that all-trans astaxanthin might exist as three stereoisomers,and the composition of all-trans stereoisomers in natural materials differs from that of synthetic products.However,the different biological effects of various all-trans stereoisomers still remain unclear.In the present study,we evaluated the bioactivity of three astaxanthin stereoisomers,(3S,3'S)-trans-,(3R,3'R)-transand meso-trans-astaxanthin,in regulating cell-mediated immune response using mice lymphocytes and peritoneal exudates cells(PECs) systems.After the treatment with three astaxanthin stereoisomers(20 μmol L-1),the lymphocyte proliferation capacity,neutral red phagocytosis of PECs and natural killer(NK) cell cytotoxic activity were comparatively assessed.The results showed that all three astaxanthin stereoisomers significantly promoted lymphocyte proliferation,phagocytic capacity of PECs,and cytotoxic activity of NK cells.Moreover,the(3S,3'S)-trans-astaxanthin exhibited a much higher response than others. 展开更多
关键词 all-trans-astaxanthin STEREOISOMER IMMUNITY
下载PDF
Coronary heart disease incidence and competing risks: an important issue 被引量:3
10
作者 Paolo Emilio Puddu Peter Louis Amaduzzi Beatrice Ricci 《Journal of Geriatric Cardiology》 SCIE CAS CSCD 2017年第7期425-429,共5页
The estimation of lifetime morbid events is not a rare presentation of relatively old and of more recent epidemi- ological investigations, accompanied by evaluating rates, risks and predictors (more in general determ... The estimation of lifetime morbid events is not a rare presentation of relatively old and of more recent epidemi- ological investigations, accompanied by evaluating rates, risks and predictors (more in general determinants or risk factors). However, when the follow-up period is very long and Kaplan-Meier survival curves are adopted, or Kaplan- Meier-based more complex models such as Cox's analysis are used, clinical (or epidemiological) reality may well be distorted since by these survival methods risks tend to be overestimated, whereas survival tends to be reduced. 展开更多
关键词 Coronary heart disease Competing risks The elderly
下载PDF
How to select elderly colorectal cancer patients for surgery: a pilot study in an Italian academic medical center 被引量:4
11
作者 Giampaolo Ugolini Francesco Pasini +4 位作者 Federico Ghignone Davide Zattoni Maria Letizia Bacchi Reggiani Daniele Parlanti Isacco Montroni 《Cancer Biology & Medicine》 SCIE CAS CSCD 2015年第4期302-307,共6页
Objective: Cancer is one of the most common diagnoses in elderly patients. Of all types of abdominal cancer, colorectal cancer(CRC) is undoubtedly the most frequent. Median age at diagnosis is approximately 70 years o... Objective: Cancer is one of the most common diagnoses in elderly patients. Of all types of abdominal cancer, colorectal cancer(CRC) is undoubtedly the most frequent. Median age at diagnosis is approximately 70 years old worldwide. Due to the multiple comorbidities affecting elderly people, frailty evaluation is very important in order to avoid over- or undertreatment. This pilot study was designed to investigate the variables capable of predicting the long-term risk of mortality and living situation after surgery for CRC.Methods: Patients with 70 years old and older undergoing elective surgery for CRC were prospectively enrolled in the study. The patients were preoperatively screened using 11 internationally-validated-frailty-assessment tests. The endpoints of the study were long-term mortality and living situation. The data were analyzed using univariate Cox proportional-hazard regression analysis to verify the predictive value of score indices in order to identify possible risk factors.Results: Forty-six patients were studied. The median follow-up time after surgery was 4.6 years(range, 2.9-5.7 years) and no patients were lost to follow-up. The overall mortality rate was 39%. Four of the patients who survived(4/28, 14%) lost their functional autonomy. The preoperative impaired Timed Up and Go(TUG), Eastern Cooperative Group Performance Status(ECOG PS), Instrumental Activities of Daily Living(IADLs), Vulnerable Elders Survey(VES-13) scoring systems were significantly associated with increased long term mortality risk.Conclusion: Simplified frailty-assessing tools should be routinely used in elderly cancer patients before treatment in order to stratify patient risk. The TUG, ECOG-PS, IADLs and VES-13 scoring systems are potentially able to predict long-term mortality and disability. Additional studies will be needed to confirm the preliminary data in order to improve management strategies for oncogeriatric surgical patients. 展开更多
关键词 Elderly geriatric assessment surgical oncology risk assessment screening tools colorectal cancer(CRC)
下载PDF
Risk Assessment of Unmanned Aerial Vehicle Flight Based on Kmeans Clustering Algorithm 被引量:4
12
作者 BU Jian ZHANG Honghai +1 位作者 HU Minghua LIU Hao 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2020年第2期263-273,共11页
To quantify unmanned aerial vehicle(UAV)flight risks in low-altitude airspace,we analyze the factors of UAV flight risks from three aspects:flight conflict,flight environment,and traffic characteristics.The aerial ris... To quantify unmanned aerial vehicle(UAV)flight risks in low-altitude airspace,we analyze the factors of UAV flight risks from three aspects:flight conflict,flight environment,and traffic characteristics.The aerial risk index and ground risk index of the UAV are constructed,the index screening model and the UAV flight risk assessment model are established,and a UAV flight risk assessment model based on K-means clustering has been proposed.Meanwhile,numerical simulations show the proposed method can not only evaluate the UAV flight risks effectively,but also provide technical support for UAV risk management and control. 展开更多
关键词 unmanned aerial vehicle(UAV) risk factor risk index assessment model K-means clustering
下载PDF
Risk for gastric neoplasias in patients with chronic atrophic gastritis:A critical reappraisal 被引量:76
13
作者 Lucy Vannella Edith Lahner Bruno Annibale 《World Journal of Gastroenterology》 SCIE CAS CSCD 2012年第12期1279-1285,共7页
Chronic atrophic gastritis (CAG) is an inflammatory condition characterized by the loss of gastric glandular structures which are replaced by connective tissue (non-metaplastic atrophy) or by glandular structures ... Chronic atrophic gastritis (CAG) is an inflammatory condition characterized by the loss of gastric glandular structures which are replaced by connective tissue (non-metaplastic atrophy) or by glandular structures inappropriate for location (metaplastic atrophy). Epidemiological data suggest that CAG is associated with two different types of tumors: Intestinal-type gastric cancer (GC) and type I gastric carcinoid (T I GC). The pathophysiological mechanisms which lead to the development of these gastric tumors are different, It is accepted that a multistep process initiating from Helico- bacterpylori-related chronic inflammation of the gastric mucosa progresses to CAG, intestinal metaplasia, dysplasia and, finally, leads to the development of GC. The T I GC is a gastrin-dependent tumor and the chronic elevation of gastrin, which is associated with CAG, stimulates the growth of enterochromaffin-like cells with their hyperplasia leading to the development of T I GC. Thus, several events occur in the gastric mucosa before the development of intestinatype GC and/ or T I GC and these take several years. Knowledge ofCAG incidence from superficial gastritis, its prevalence in different clinical settings and possible risk factors as- sociated with the progression of this condition to gastric neoplasias are important issues. This editorial intends to provide a brief review of the main studies regarding incidence and prevalence of CAG and risk factors for the development of gastric neoplasias. 展开更多
关键词 Chronic atrophic gastritis Gastric neoplasia Intestinal-type gastric cancer Type I gastric carcinoid PREVALENCE INCIDENCE Risk factors
下载PDF
Safety assessment of Bifidobacterium longum JDM301 based on complete genome sequences 被引量:5
14
作者 Yan-Xia Wei Zhuo-Yang Zhang +2 位作者 Chang Liu Pradeep K Malakar Xiao-Kui Guo 《World Journal of Gastroenterology》 SCIE CAS CSCD 2012年第5期479-488,共10页
AIM: To assess the safety of Bifidobacterium/ongum (B. longum) JDM301 based on complete genome sequences. METHODS: The complete genome sequences of JDM301 were determined using the GS 20 system. Putative virulence... AIM: To assess the safety of Bifidobacterium/ongum (B. longum) JDM301 based on complete genome sequences. METHODS: The complete genome sequences of JDM301 were determined using the GS 20 system. Putative virulence factors, putative antibiotic resis- tance genes and genes encoding enzymes respon- sible for harmful metabolites were identified by blast with virulence factors database, antibiotic resistance genes database and genes associated with harmful metabolites in previous reports. Minimum inhibitory concentration of 16 common antimicrobial agents was evaluated by E-test RESULTS: JDM301 was shown to contain 36 genes as- sociated with antibiotic resistance, 5 enzymes related to harmful metabolites and 162 nonspecific virulence fac- tors mainly associated with transcriptional regulation, adhesion, sugar and amino acid transport. B. longum JDM301 was intrinsically resistant to ciprofloxacin, ami- kacin, gentamicin and streptomycin and susceptible to vancomycin, amoxicillin, cephalothin, chloramphenicol, erythromycin, ampicillin, cefotaxime, rifampicin, imi- penem and trimethoprim-sulphamethoxazol. JDM301 was moderately resistant to bacitracin, while an earlier study showed that bifidobacteria were susceptible to this antibiotic. A tetracycline resistance gene with the risk of transfer was found in JDM301, which needs to be experimentally validated. CONCLUSION: The safety assessment of JDM301 using information derived from complete bacterial ge- nome will contribute to a wider and deeper insight into the safety of probiotic bacteria. 展开更多
关键词 Bifidobacterium longum Safety assess-ment GENOME Antibiotic resistance Harmful metabo-lite Virulence factor
下载PDF
Eight-Regularity of Types of Crop Capacity Structure of Winter Wheat
15
作者 N. N. Petrova 《Journal of Agricultural Science and Technology(B)》 2011年第2期285-296,共12页
The elements of crop capacity structure of 13 summer characteristics in 33 winter wheat varieties, qualitative three-regularity and quantitative eight-regularity are investigated through the application of systematic ... The elements of crop capacity structure of 13 summer characteristics in 33 winter wheat varieties, qualitative three-regularity and quantitative eight-regularity are investigated through the application of systematic approach. The principle of triadness applied in a language, in a genetic code and other codes is used, i.e. the logic homology is employed. The purpose are (1) to show the use of a systematic approach to the analysis of elements of crop capacity structure of winter wheat; (2) to analyze efficiency, the years of harvests and winter hardiness; (3) to find the way of selection and varieties assessment in terms of the elements efficiency. The quantitative compatibility as the highest with the sign "+" and the lowest with the sign "-" in terms of elements efficiency gives eight types of crop capacities. The type of crop capacity structure "+++" can serve as a full (higher) measure of a variety adaptableness and optimality of technologies. The triad of three characteristics as a type-"+++" in which the first sign is the quantity of ears (QE); the second is a quantity of grains (QG); the third is the weight of grains (WG) creates the highest level of crop capacity. 展开更多
关键词 Category of triadness eight-regularity crop capacity efficiency quantity of ears in 1 m^2 (QE) quantity of grains in anear (QG) weight of 1 000 grains (WG) winter wheat.
下载PDF
Evaluating the risk of coal bursts in underground coal mines 被引量:16
16
作者 Mark Christopher Gauna Michael 《International Journal of Mining Science and Technology》 SCIE EI CSCD 2016年第1期47-52,共6页
Coal bursts involve the sudden,violent ejection of coal or rock into the mine workings. They are almost always accompanied by a loud noise,like an explosion,and ground vibration. Bursts are a particular hazard for min... Coal bursts involve the sudden,violent ejection of coal or rock into the mine workings. They are almost always accompanied by a loud noise,like an explosion,and ground vibration. Bursts are a particular hazard for miners because they typically occur without warning. Despite decades of research,the sources and mechanics of these events are not well understood,and therefore they are difficult to predict and control. Experience has shown,however,that certain geologic and mining factors are associated with an increased likelihood of a coal burst. A coal burst risk assessment consists of evaluating the degree to which these risk factors are present,and then identifying appropriate control measures to mitigate the hazard. This paper summarizes the U.S. and international experience with coal bursts,and describes the known risk factors in detail. It includes a framework that can be used to guide the risk assessment process. 展开更多
关键词 Underground miningCoalCoal burstMine safetyGround control
下载PDF
Radium isotopes assess water mixing processes and its application in the Zhujiang River estuary
17
作者 郭肖伊 许博超 +6 位作者 于志刚 李秀芹 南海明 简慧敏 江雪艳 刁少波 高茂生 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2017年第5期1108-1116,共9页
Radium (Ra) isotopes are useful for tracing water mass transport and examining estuarine hydrological dynamics. In this study, several hydrological parameters, nutrients, ehlorophyll-a (ehl-a), suspended particula... Radium (Ra) isotopes are useful for tracing water mass transport and examining estuarine hydrological dynamics. In this study, several hydrological parameters, nutrients, ehlorophyll-a (ehl-a), suspended particulate matter (SPM) and Ra isotopes (223Ra, 224Ra and 226Ra) of surface waters of the Zhujiang (Pearl) River estuary (ZRE) were measured. This was done for both winter (December) and summer (July) seasons, to quantitatively understand the seasonal characteristics of river plume flow rate and trajectories, as well as the ecological response. The results show that Ra concentrations in summer were higher than in winter, especially Z24Ra (about 2-5 times higher). The spatial distribution of three Ra isotopes and relative Ra water ages indicated that river water mainly flushed out of ZRE through the western side in winter, where the water transport was about 5 days faster than in the eastern zone. In summer, diluted river water expended to the east side, resulting in fairly similar water ages for both sides of the river mouth. Although nutrients were higher during the summer season, lower chl-a concentrations indicated that reduced primary production might be caused by high SPM (low light penetration). The results obtained from this study will provide knowledge needed for effectively developing and managing the ZRE. 展开更多
关键词 Zhujiang River estuary radium isotopes water ages NUTRIENTS
下载PDF
Angiographic evaluation and management of acute gastrointestinal hemorrhage 被引量:25
18
作者 T Gregory Walker Gloria M Salazar Arthur C Waltman 《World Journal of Gastroenterology》 SCIE CAS CSCD 2012年第11期1191-1201,共11页
Although most cases of acute nonvariceal gastrointestinal hemorrhage either spontaneously resolve or respond to medical management or endoscopic treatment,there are still a significant number of patients who require e... Although most cases of acute nonvariceal gastrointestinal hemorrhage either spontaneously resolve or respond to medical management or endoscopic treatment,there are still a significant number of patients who require emergency angiography and transcatheter treatment.Evaluation with noninvasive imaging such as nuclear scintigraphy or computed tomography may localize the bleeding source and/or confirm active hemorrhage prior to angiography.Any angiographic evaluation should begin with selective catheterization of the artery supplying the most likely site of bleeding,as determined by the available clinical,endoscopic and imaging data.If a hemorrhage source is identified,superselective catheterization followed by transcatheter microcoil embolization is usually the most effective means of successfully controlling hemorrhage while minimizing potential complications.This is now wellrecognized as a viable and safe alternative to emergency surgery.In selected situations transcatheter intra-arterial infusion of vasopressin may also be useful in controlling acute gastrointestinal bleeding.One must be aware of the various side effects and potential complications associated with this treatment,however,and recognize the high re-bleeding rate.In this article we review the current role of angiography,transcatheter arterial embolization and infusion therapy in the evaluation and management of nonvariceal gastrointestinal hemorrhage. 展开更多
关键词 ANGIODYSPLASIA ANEURYSM Digital subtrac-tion angiography Contrast media HEMORRHAGE Radio-nuclide angiography Therapeutic embolization
下载PDF
Risk based security assessment of power system using generalized regression neural network with feature extraction 被引量:2
19
作者 M. Marsadek A. Mohamed 《Journal of Central South University》 SCIE EI CAS 2013年第2期466-479,共14页
A comprehensive risk based security assessment which includes low voltage, line overload and voltage collapse was presented using a relatively new neural network technique called as the generalized regression neural n... A comprehensive risk based security assessment which includes low voltage, line overload and voltage collapse was presented using a relatively new neural network technique called as the generalized regression neural network (GRNN) with incorporation of feature extraction method using principle component analysis. In the risk based security assessment formulation, the failure rate associated to weather condition of each line was used to compute the probability of line outage for a given weather condition and the extent of security violation was represented by a severity function. For low voltage and line overload, continuous severity function was considered due to its ability to zoom in into the effect of near violating contingency. New severity function for voltage collapse using the voltage collapse prediction index was proposed. To reduce the computational burden, a new contingency screening method was proposed using the risk factor so as to select the critical line outages. The risk based security assessment method using GRNN was implemented on a large scale 87-bus power system and the results show that the risk prediction results obtained using GRNN with the incorporation of principal component analysis give better performance in terms of accuracy. 展开更多
关键词 generalized regression neural network line overload low voltage principle component analysis risk index voltagecollapse
下载PDF
Non-coordination in China′s Urbanization: Assessment and Affecting Factors 被引量:26
20
作者 SUN Pingjun SONG Wei +1 位作者 XIU Chunliang LIANG Zhenming 《Chinese Geographical Science》 SCIE CSCD 2013年第6期729-739,共11页
Urbanization is a comprehensive concept, a trinity process that population urbanization, economic urbanization and space urbanization, is based on the interactions and mutual influences among the in which, people are ... Urbanization is a comprehensive concept, a trinity process that population urbanization, economic urbanization and space urbanization, is based on the interactions and mutual influences among the in which, people are the central and leading players in this process, while economic activities serve as the driving force and space is the carrier-the physical or material setting as well as the product. So the coordination among these processes is crucial for a country or region's sustainable development. China is experiencing rapid growth of cities and a surge in urban population, with the basic national condition of many people and little land, which calls for a systematic study of the issue of coordinated urbanization from theoretical, methodological and practical perspectives. Based on the concept of urbanization and non-coordination of urbanization, this article built a quantitative method to identify and evaluate the urbanization and non-coordination of urbanization, and made an empirical analysis in China between 2000 and 2008. The results show that the non-coordination overall level of China's urbanization declined during the study period, because population urbanization, economic urbanization, and space urbanization exhibited different trajectories of change. This study also reveals that performance assessment system, household registration system, and urban land expropriation system, etc., are the main affecting factors. At the end, we put forward some suggestions to achieve sustainable development of China's urbanization from the aspects of improving the local government's obiective function, imolementing the urban plalming svstem, enforcing public particination asnects and so on. 展开更多
关键词 non-coordination of urbanization coordinated development degree China
下载PDF
上一页 1 2 3 下一页 到第
使用帮助 返回顶部