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An Empirical Analysis of the Impact of Fund Manager's Personal Characteristics on Fund Performance
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作者 Lingze Meng 《经济管理学刊(中英文版)》 2019年第2期126-143,共18页
A great deal of research found that fund performance is related to a series of personal characteristics of fund managers,but how these personal characteristics affect fund performance is still unknown.China is the mos... A great deal of research found that fund performance is related to a series of personal characteristics of fund managers,but how these personal characteristics affect fund performance is still unknown.China is the most important emerging country and the second largest economy in the world.The development of China's capital market is different from that of most developed countries.Therefore,empirical evidence on the performance of funds in developed countries often cannot be extended to the Chinese market.In addition,there is evidence that many successful fund managers in developed countries may not achieve good performance in China.Therefore,it is particularly meaningful to examine the determinants of fund performance in the Chinese market.This paper establishes a three-level framework model to study this connection.Considering return and risk,the two basic factors that affect fund performance,this paper chooses nine proxy variables:Sharpe ratio,Jensen index,Treynor index,abnormal return(α),total risk(β),non-systemic risk,standard deviation of return,stock choosing ability and time picking ability as the criteria to measure the comprehensive performance.This paper investigates China's open-end funds to fill the gap in literature on the relationship between fund managers'personal characteristics and fund performance in emerging capital markets.The results of this paper found that age,gender,fund manager years,number of funds under management,master's or doctor’s degree,MBA degree,business background and fund managers have better stock choosing ability,higher abnormal return and better overall performance has a significant positive relationship.The results of further decomposition indicate that the abnormal return is the main influencing factor of the fund's comprehensive performance;the abnormal return is also affected by the fund manager's ability of stock choosing and time picking.In addition,stock choosing ability is the main factor affecting abnormal return.Therefore,the education background of the fund manager’s personal characteristics will affect the abnormal return and ultimately affect the comprehensive performance of the fund.This paper also finds that gender and majors affect fund managers'risk control behavior.The research results in this paper have great practical significance.Firstly,it introduces a framework that can explain how the individual characteristics of fund managers affect the performance mechanism of funds.Secondly,the findings in China's stock market supplement the empirical evidence in the mature markets of developed countries.Since China is already the largest emerging economy in the world,the results of this study are of great significance not only to Chinese researchers,but also to international scholars who want to study China's capital market.Thirdly,the empirical study is of great practical significance to test the ability of fund managers to divide abnormal earnings into stock choosing ability and time picking ability. 展开更多
关键词 Fund manager characteristics Fund Performance Panel Data Threshold Panel
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Manager’s Characteristics, Debt Financing and Firm Value
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作者 He Ying Zhang Dawei 《China Economist》 2019年第5期96-110,共15页
Based on the behavioral finance theory and the upper echelons theory, this paper employs the data of China's A-share listed companies from 2008 to 2013 as research samples, and empirically tests the effects of man... Based on the behavioral finance theory and the upper echelons theory, this paper employs the data of China's A-share listed companies from 2008 to 2013 as research samples, and empirically tests the effects of managers with different characteristics on debt financing and firm value for enterprises of different ownership nature. Results of this study indicate that the debt financing of the listed companies in China can reduce the agency cost with a positive governance effect that promotes firm value. Male, better educated, short-tenured, and financially experienced managers are more likely to be overconfident and prefer debt financing. Specifically, the manager's age, level of education, and work experience can significantly promote the effect of debt financing on firm value. Compared with SOEs, private enterprises can improve their firm value more significantly through debt financing;the education and work experience of the managers of private enterprises are more positively correlated with debt financing and can more significantly improve firm value through debt financing. This paper's findings suggest that the manager's characteristics and firm ownership nature must be taken into account to reach valid conclusions on the governance effects of debt financing on firm value. Meanwhile, these conclusions help unravel the mechanism and economic implications of debt financing, and contribute to the improvement of the capital structure decisions and human resources management practices of China's listed companies. This study not only enriches the literature and empirical evidence on the correlation between managers' characteristics and firm financing, but indicate that managers' characteristics and firm ownership are important considerations for investigating the governance effects of debt financing on firm value and have a vital impact on the formulation and implementation of firm financing decisions. 展开更多
关键词 manager's characteristics DEBT FINANCING FIRM value FIRM OWNERsHIP nature
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Ibrutinib and atrial fibrillation:An in-depth review of clinical implications and management strategies
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作者 Moiud Mohyeldin Shitij Shrivastava Sai Vishnu Vardhan Allu 《World Journal of Cardiology》 2024年第5期269-273,共5页
Ibrutinib,a targeted therapy for B-cell malignancies,has shown remarkable efficacy in treating various hematologic cancers.However,its clinical use has raised concerns regarding cardiovascular complications,notably at... Ibrutinib,a targeted therapy for B-cell malignancies,has shown remarkable efficacy in treating various hematologic cancers.However,its clinical use has raised concerns regarding cardiovascular complications,notably atrial fibrillation(AF).This comprehensive review critically evaluates the association between ibrutinib and AF by examining incidence,risk factors,mechanistic links,and management strategies.Through an extensive analysis of original research articles,this review elucidates the complex interplay between ibrutinib’s therapeutic benefits and cardiovascular risks.Moreover,it highlights the need for personalized treatment approaches,vigilant monitoring,and interdisciplinary collaboration to optimize patient outcomes and safety in the context of ibrutinib therapy.The review provides a valuable resource for healthcare professionals aiming to navigate the intricacies of ibrutinib’s therapeutic landscape while prioritizing patient well-being. 展开更多
关键词 Ibrutinib Bruton’s tyrosine kinase inhibitor Atrial fibrillation Cardiovascular risk management strategies
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Site Management Strategy in Highway Project Management
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作者 Huan Deng 《Journal of Architectural Research and Development》 2024年第3期75-79,共5页
Highway project management involves overseeing the on-site construction of a highway project,taking into account the specific circumstances and conditions of the site.This type of management requires a high level of e... Highway project management involves overseeing the on-site construction of a highway project,taking into account the specific circumstances and conditions of the site.This type of management requires a high level of expertise and is characterized by its dynamic and systematic approach.Effective on-site management can ensure the quality,cost-saving,smooth progress,and safety of highway construction.However,there are still some problems in the implementation of site management in some highway projects,which seriously affect the improvement of site management.This paper analyzes the characteristics and existing problems of highway engineering management,and puts forward the effective strategies of site management,hoping that this study will help to improve highway engineering site management. 展开更多
关键词 Highway engineering characteristics PROBLEMs site management
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Do Land Characteristics Affect Farmers' Soil Fertility Management? 被引量:6
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作者 TAN Shu-hao 《Journal of Integrative Agriculture》 SCIE CAS CSCD 2014年第11期2546-2557,共12页
Soil fertility management (SFM) has important implications for sustaining agricultural development and food self-sufifciency. Better understanding the determinants of farmers’ SFM can be a great help to the adoptio... Soil fertility management (SFM) has important implications for sustaining agricultural development and food self-sufifciency. Better understanding the determinants of farmers’ SFM can be a great help to the adoption of effective SFM practices. Based on a dataset of 315 plots collected from a typical rice growing area of South China, this study applied statistical method and econometric models to examine the impacts of land characteristics on farmers’ SFM practices at plot scale. Main results showed that in general land characteristics affected SFM behaviors. Securer land tenure arrangements facilitated effective practices of SFM through more diversiifed and more soil-friendly cropping pattern choices. Plot size signiifcantly reduced the intensities of phosphorus and potassium fertilizer application. Given other factors, 1 ha increase in plot size might reduce 3.0 kg ha-1 P2O5 and 1.8 kg ha-1 K2O. Plots far from the homestead were paid less attention in terms of both chemical fertilizers and manure applications. Besides, plots with better quality were put more efforts on management by applying more nitrogen and manure, and by planting green manure crops. Signiifcant differences existed in SFM practices between the surveyed villages with different socio-economic conditions. The ifndings are expected to provide important references to the policy-making incentive for improving soil quality and crop productivity. 展开更多
关键词 land characteristics soil fertility management farm household rice cropping south China
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The Communication Analysis Among Stakeholders in Management of Children Education by the Poor Scholarship as Human Capital to Grow Quality Characteristics of Educational Basics
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作者 Abubakar Iskandar Maria Fitriah +1 位作者 R.Akhmad Munjin Ike Atikah Ratnamulyani 《Management Studies》 2019年第1期70-85,共16页
The economic crisis in 1997-1998 increased poverty to 49.5 million,but in 2005 decreased to 35.10 million,then in 2006 increased 39.05 million.The worst communities were workers,dependent families,small farmers and fi... The economic crisis in 1997-1998 increased poverty to 49.5 million,but in 2005 decreased to 35.10 million,then in 2006 increased 39.05 million.The worst communities were workers,dependent families,small farmers and fishermen,informal sector workers,low-level civil servants,and people affected by natural disasters.The research design was cross sectional;the research was in Pangkal Pinang City in January 2016.The data were summarized by interview,observation,documentation,and Focus Group Discussion.Data analyses were flow model,product moment,and Likert scale.The result of the research shows the correlation between how to obtain the poor scholarship and the criteria of obtaining the poor scholarship that is very tight which is 0.453.The relation between the criteria of obtaining the poor scholarship and the determination of the poor scholarship is quite close which is 0.218.The relationship between the determination of the scholarship for poor students and obtaining the poor scholarship is 0.395.The correlation between how to get the poor scholarship and the poor scholarship receiver is quite close that is 0.190.The relationship between the determination of the poor scholarship and the impact of the poor scholarship is quite close that is 0.171.The relationship between using of the poor scholarship and the poor scholarship receiver is very close that is 0.297.The relation between the poor receiver and the impact of poor the scholarship is 0.270. 展开更多
关键词 managEMENT education students POOR human capital characteristics quality
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From social management to social governance: Evolution, characteristics and innovation
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作者 DONG Liang-feng LIU Yuan 《Ecological Economy》 2017年第4期358-362,共5页
The Third Plenary Session of the 18th Central Committee of the CPC firstly required innovative social governance in 2013. This is the CPC's focus on safeguarding the fundamental interests of the majority of the pe... The Third Plenary Session of the 18th Central Committee of the CPC firstly required innovative social governance in 2013. This is the CPC's focus on safeguarding the fundamental interests of the majority of the people, to maximize social harmony, and to enhance the vitality of social development. The differences between governance and management are embodied in such as the governance system, legality, resource management, and comprehensive measures, etc. Compared with the way of social management, in which the government was used to controlling and ordering all social affairs, social governance pays more attention to the process of co-operations among different parties, to more emphasis on parties' co-operations and co-governance, with a continuous and interactive process of coordinated negotiations among multiple stakeholders. Social governance pays more emphasis on respect to social and political rights of members in the society, trying to stimulate the potential of social members, so that members of the community, in the process of social governance, have rights to speak, to choose and to influence; it pays more emphasis not only on maximizing autonomy of the social organizations and community, but also emphasizes the comprehensive use of a variety of means. The constructions of social governance system should mainly consist of four aspects: first, it is to improve the quality of social grassroots governance; second, it is to stimulate the vitality of social organizations; third, it tries to become an innovative and effective system to prevent and resolve social conflicts; fourth, it is to improve the public security system. To innovate the social management system, it is not only to achieve the transformation of the idea from control to service, but also to change the governance way from inflexible to flexible, thus, to finally form the social governance structure of Party leadership, government responsibility, social coordination,and public 展开更多
关键词 social management social governance characteristics INNOVATION
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Characteristics of management of reproductive endocrine problems in female patients
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作者 Ge Qinsheng(葛秦生) 《生殖医学杂志》 CAS 2002年第z1期2-6,共5页
  In 1956, my former Head and Professor of the Department of Obstetrics and Gynecology KT LIM, asked me to take the initiative to establish a reproductive endocrinology unit. As China is a developing country, we wer...   In 1956, my former Head and Professor of the Department of Obstetrics and Gynecology KT LIM, asked me to take the initiative to establish a reproductive endocrinology unit. As China is a developing country, we were then short of diagnostic facilities and therapeutic agents. We can learn basic knowledge and clinical experiences from the literature, but hormonal preparations were expensive and generally most of our patients were poor. We needed to find simpler, inexpensive and yet effective ways to treat our patients. In a word, we had to develop our own way.…… 展开更多
关键词 characteristics of management of reproductive endocrine problems in female patients
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The characteristics of blood station management after the blood donation art came into practice
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《中国输血杂志》 CAS CSCD 2001年第S1期355-,共1页
关键词 The characteristics of blood station management after the blood donation art came into practice
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Intersection capacity based on driver's visual characteristics 被引量:5
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作者 陆建 陈伟伟 范红静 《Journal of Southeast University(English Edition)》 EI CAS 2009年第1期117-122,共6页
In order to reflect the influence of the drivers' characteristic differences on intersection capacity under a mixed traffic flow, a driver correction coefficient for the intersection capacity calculation according to... In order to reflect the influence of the drivers' characteristic differences on intersection capacity under a mixed traffic flow, a driver correction coefficient for the intersection capacity calculation according to the driver's visual characteristics is proposed. First, the parameters of the driver's visual characteristics at some real roads, including gaze fixation distribution, mean fixation duration, visual angle distribution and some other parameters at intersections, are collected. Then, the relationship between the traffic flow rate at intersections and the parameters of driver eye movements are established. The analytical results indicate that when the traffic flow is unsaturated, the parameters of driver eye movements change relatively little; however, when the traffic flow is saturated, the parameters of driver eye movements change drastically. Finally, the saturation-flow-rate model is modified according to the parameters of driver eye movements; thus, a capacity model of intersections considering the driver's visual characteristics is obtained. 展开更多
关键词 INTERsECTION driver's visual characteristics saturation-flow-rate capacity compensation factor
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Influences of Family Ranches Management Mode on Plant Community Characteristic in Hulunber Meadow Steppe 被引量:1
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作者 闫瑞瑞 卫智军 +5 位作者 杨桂霞 韩国栋 辛晓平 卢志红 斯琴毕力格 吴宏军 《Agricultural Science & Technology》 CAS 2013年第11期1664-1669,共6页
[Objective] The aim was to explore the management mode on optimal re-sources al ocation of family ranch in meadow steppe. [Method] Three double repre-sentative family ranches were selected in meadow steppe of Hulunber... [Objective] The aim was to explore the management mode on optimal re-sources al ocation of family ranch in meadow steppe. [Method] Three double repre-sentative family ranches were selected in meadow steppe of Hulunber Old Barag Banner, and the study was carried out with the baseline survey. Three family ranches were selected as the demonstrative households for the corporation study, while other three family ranches with the similar conditions were looked as the non-demonstrative households for the comparison. Demonstrative households of the fami-ly ranches reduced the stocking rate, optimized the flock structure and took a winter feeding and other means to explore the different management models on plant com-munity characteristic of family ranch. [Result] The seasonal dynamic of community characteristic in family ranches showed the single-peaks curves. The seasonal dy-namics of community coverage, height and biomass in the demonstrative households showed higher compared with the non-demonstrative households, and community density in the experiment households was lower than that of the control experiment households. Community coverage, height and biomass of degraded grassland in family ranch have a great improve after optimization of management. Community coverage, height , density and biomass were increasing in fencing plot, but decreas-ing in free grazing area. Enclosure improved grassland coverage, vegetation height, density and forage yield. Leymus chinensis played an important role in plant com-munity. The important values of Leymus chinensis, Stipa baicalensis, Cleistogenes squarrosa, and Carex duriuscula were high. Leymus chinensis important value in the demonstrative households of optimal management was higher than that in the non-demonstrative households, and Carex duriuscula important value of the non-demon-strative households was significantly higher than that of the demonstrative house-holds. The indexes of Margalef richnes,Shannon-Wiener diversity, Simpson diversity and Pielou uniformity showed that the demonstrative households were higher than the non-demonstrative households. [Conclusion] The research provides theoretical ref-erences for sustainable development of pastures dominated by family ranch. 展开更多
关键词 Family ranches management mode Hulunber meadow steppe Community characteristic
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International Comparison,Regional Characteristics and Regulatory Management of Structural Rise in the Prices of Chinese Industrial and Agricultural Products
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作者 Ming ZHANG Hong TAN +1 位作者 Ran AN Zhibo ZHOU 《Asian Agricultural Research》 2014年第4期1-4,9,共5页
China's price fluctuations increasingly exhibit significant structural characteristics,and since 2003,there have been several rounds of significant structural price rise.The degree of structural rise in the prices... China's price fluctuations increasingly exhibit significant structural characteristics,and since 2003,there have been several rounds of significant structural price rise.The degree of structural rise in the prices of industrial and agricultural products in China is not only higher than in the general developed countries and developing countries,but also more prominent than in other transition economies.And the structural rise in the prices of Chinese industrial and agricultural products exhibits significant economic zone differences:the structural fluctuations are the greatest in the central and western regions,significantly higher than in the eastern regions as well as the national average.From the perspective of causes of structural rise in the prices of Chinese industrial and agricultural products,the government must aim to coordinate the industrial and agricultural investments and bridge the gap in the industrial and agricultural technologies and supply capacity. 展开更多
关键词 The PRICEs of INDUsTRIAL and agricultural products
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甘肃积石山 M_(s)6.2级地震的震害特征与启示 被引量:5
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作者 王丽丽 王兰民 +5 位作者 卢育霞 许世阳 夏晓雨 盖海龙 池佩红 郭梅 《世界地震工程》 北大核心 2024年第1期58-71,共14页
2023年12月18日,甘肃省临夏回族自治州积石山保安族东乡族撒拉族自治县(35.70°N,102.79°E)发生了6.2级地震,震中烈度为VIII度。地震发生后,通过实地烈度评估与科学考察,对震区VI~VIII度区不同建(构)筑物与生命线工程的震害特... 2023年12月18日,甘肃省临夏回族自治州积石山保安族东乡族撒拉族自治县(35.70°N,102.79°E)发生了6.2级地震,震中烈度为VIII度。地震发生后,通过实地烈度评估与科学考察,对震区VI~VIII度区不同建(构)筑物与生命线工程的震害特点进行了统计分析;从抗震设计与施工管理、场地放大效应与地震次生灾害对建筑结构抗震性能的影响等角度,提出了此次地震的震害启示。结果表明:1)严重破坏和毁坏的建筑结构主要集中在老旧的土木结构、砖木结构和无设防或设防不规范的砖混结构。2)造成建筑结构破坏的主要原因是少量自建房抗震设计和施工的不规范、场地放大效应和地震次生灾害。3)优化和改良生土砌筑材料,改进纵横墙间的拉结措施,强化结构整体性是提高土木结构抗震的有效方法;普及“上下圈梁与构造柱”等基本抗震设防措施,规范水泥砂浆强度,提升农村工匠的施工水平,可有效提高砌体结构的整体性,避免房屋出现整体性垮塌;室内洗手间的墙体应该与房顶、纵横墙间建立有效联接,提高结构的抗震性能。4)孤突斜坡、河流高阶地与岸边为抗震不利地带。当建造用地极为匮乏,不得不选址在这些场地之上时,应该综合考虑场地的地形地貌特征、岩土体物理力学特性、水文地质条件、抗震设防目标、建筑结构类型等影响因素,做好地震灾害风险评估,根据评估结果进行科学设防。灾后重建过程中,应由政府统一规划选址、统一设计,规范施工。 展开更多
关键词 积石山6.2级地震 震害调查 场地放大效应 黄土液化流滑 震害特征
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基于数值模拟的高速公路S型曲线积水规律分析
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作者 吴文亮 曾威凯 +1 位作者 李智 王晓飞 《华南理工大学学报(自然科学版)》 EI CAS CSCD 北大核心 2024年第8期56-64,共9页
S型曲线由于特殊的线型几何特征形成了易积水的路面区域,对于积水规律的掌握有利于在设计和建造阶段提前预防和处理积水路段的危害。该文基于计算流体力学软件Fluent,结合计算流体力学分析中基于欧拉-拉格朗日方法的欧拉液膜模型EWF(Eul... S型曲线由于特殊的线型几何特征形成了易积水的路面区域,对于积水规律的掌握有利于在设计和建造阶段提前预防和处理积水路段的危害。该文基于计算流体力学软件Fluent,结合计算流体力学分析中基于欧拉-拉格朗日方法的欧拉液膜模型EWF(Eulerian Wall Film),针对精细化处理的典型S型曲线双向多车道道路模型进行模拟计算。模拟包含了几何特征与降雨量等不同变量因素,得出了积水的水膜厚度以及流速分布规律。模拟结果表明:在降雨阶段,S型曲线横坡坡度0%~1%路段为积水路段,横坡坡度1%~2%路段为易积水路段,横坡坡度大于2%的路段积水情况受到降雨强度影响;在排水阶段,S型曲线横坡坡度0%~1%路段为排水困难路段,横坡坡度1%~2%路段为排水不畅路段,横坡坡度大于2%的路段排水顺畅,在排水时间结束时,路面在不同的几何条件和降雨条件下均能将积水排除至水膜厚度小于2 cm,横坡的大小与渐变影响了积水的横向分布与纵向分布,横向呈现中间高两边低、横断面上标高大的位置水膜厚度小和标高小的位置水膜厚度大的水膜厚度分布规律,总体呈现S型的分布规律;水膜流速在积水阶段呈现纵向上中间低两边高、水膜厚度大则水膜流速大的水膜厚度分布规律,在排水阶段则为纵向上中间高两边低的水膜流速分布规律。道路宽度影响了降雨落到路面的积水总量,进而对积水水膜厚度产生了影响;超高缓和率则主要使得积水路段、易积水路段增长,从而影响了积水分布的范围。 展开更多
关键词 计算流体力学 s型曲线 路面积水 积水规律
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K-S变换及其电网超谐波时频分析应用
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作者 滕召胜 梁成斌 +2 位作者 唐求 张雷鹏 成达 《湖南大学学报(自然科学版)》 EI CAS CSCD 北大核心 2024年第6期128-136,共9页
依据FFT→优化窗→IFFT思路,突破线性时频变换的窗函数积分性能桎梏,实现高性能优化窗函数的线性时频变换应用,建立新型时频变换算法——K-S变换.对信号x(t)的FFT频谱向量进行频移处理后,与该频移点下Kaiser优化窗的频谱向量进行Hadamar... 依据FFT→优化窗→IFFT思路,突破线性时频变换的窗函数积分性能桎梏,实现高性能优化窗函数的线性时频变换应用,建立新型时频变换算法——K-S变换.对信号x(t)的FFT频谱向量进行频移处理后,与该频移点下Kaiser优化窗的频谱向量进行Hadamard乘积,再将乘积结果进行FFT逆变换(IFFT),构造出K-S变换复时频矩阵,由此获得x(t)的时间-频率-幅值、时间-频率-相位三维信息;给出逆变换的数学推导与局部性质、线性性质和变分辨率特性;0~150 kHz电网的稳态与时变超谐波信号仿真实验表明,K-S变换的时域、频域分辨能力均优于流行的短时傅里叶变换、S变换,具有优良的变分辨率性能;0~40 kHz超谐波信号的实测证明,基于K-S变换的超谐波电压幅值测量绝对误差均小于0.032 3 V. 展开更多
关键词 K-s变换 时频分析 Kaiser优化窗 变分辨率特性 电网超谐波
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改变导叶翼型对水泵水轮机“S”特性的影响
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作者 李琪飞 谢耕达 +1 位作者 韩天丁 李正贵 《排灌机械工程学报》 CSCD 北大核心 2024年第1期1-7,共7页
针对水泵水轮机“S”特性区域的不稳定性问题,提出使用改型活动导叶翼型进行性能提升.以某水泵水轮机模型为研究对象,采用SST k-ω湍流模型对水泵水轮机全流道进行三维数值计算,通过对活动导叶翼型的改型设计,得出流量-转速模拟曲线,分... 针对水泵水轮机“S”特性区域的不稳定性问题,提出使用改型活动导叶翼型进行性能提升.以某水泵水轮机模型为研究对象,采用SST k-ω湍流模型对水泵水轮机全流道进行三维数值计算,通过对活动导叶翼型的改型设计,得出流量-转速模拟曲线,分析水泵水轮机组“S”特性改善情况.将计算与试验结果进行对比,并对改型活动导叶翼型前后机组的无叶区进行压力脉动分析.结果表明:在保证整体效率依然保持在92%附近的前提下,新的活动导叶翼型对机组的“S”特性依旧具有改善效果;无叶区压力脉动主要是受到活动导叶叶栅区域的分流在此重新聚集影响,并且与转轮叶片的动静相互扰动引起的;改型后的活动导叶降低了无叶区的压力脉动幅值,提升了水泵水轮机运行中的并网稳定性. 展开更多
关键词 水泵水轮机 s”特性曲线 活动导叶 翼型设计 数值计算
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基于哨兵函数和S变换的风力机叶片材料损伤特性研究
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作者 廖力达 舒王咏 +3 位作者 张芝铭 刘亮 冯飞 陈为强 《太阳能学报》 EI CAS CSCD 北大核心 2024年第7期656-663,共8页
利用声发射检测技术研究玻璃纤维增强环氧树脂复合材料的损伤特性,在此过程中,采用哨兵函数来表征该材料的损伤程度,并通过S变换和模糊C均值(FCM)聚类来分析声发射信号,从而获得材料的损伤特征。三点弯曲实验结束后对试件断口进行扫描... 利用声发射检测技术研究玻璃纤维增强环氧树脂复合材料的损伤特性,在此过程中,采用哨兵函数来表征该材料的损伤程度,并通过S变换和模糊C均值(FCM)聚类来分析声发射信号,从而获得材料的损伤特征。三点弯曲实验结束后对试件断口进行扫描电子显微镜(SEM)拍照来验证,可得:通过对SEM照片的分析得到基体开裂、纤维脱粘、分层破坏、纤维断裂4种损伤模式;对整个声发射事件进行哨兵函数分析,观察到试件在弯曲过程中哨兵函数曲线呈明显下降趋势;对依据哨兵函数划分的不同阶段的信号进行VMD降噪处理,然后采用S变换进行时频分析得到不同损伤的特征频率,最后采用FCM聚类进行验证。结果表明:哨兵函数值的突变可作为材料断裂的预警信号,材料损伤类型的识别可依据S变换的频率分布结果进行确定。 展开更多
关键词 风力机叶片 复合材料 声发射 损伤特性 哨兵函数 s变换
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湿气环境中CO_(2)-H_(2)S在α-Fe(110)密排面上吸附与点蚀机理研究
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作者 李金灵 马文骏 +2 位作者 朱世东 屈撑囤 付安庆 《表面技术》 EI CAS CSCD 北大核心 2024年第20期82-93,共12页
目的从微观尺度探究CO_(2)-H_(2)S(CO_(2)和H_(2)S共存)在湿气管道顶部的吸附特性,进而揭示点蚀机理。方法基于密度泛函理论的第一性原理,利用Materials Studio构建CO_(2)、H_(2)S和CO_(2)-H_(2)S在α-Fe(110)密排面的吸附模型,对CO_(2)... 目的从微观尺度探究CO_(2)-H_(2)S(CO_(2)和H_(2)S共存)在湿气管道顶部的吸附特性,进而揭示点蚀机理。方法基于密度泛函理论的第一性原理,利用Materials Studio构建CO_(2)、H_(2)S和CO_(2)-H_(2)S在α-Fe(110)密排面的吸附模型,对CO_(2)、H_(2)S和CO_(2)-H_(2)S在α-Fe(110)面的吸附能、局域态密度、分波态密度和差分电荷密度进行仿真;利用高温高压釜模拟CO_(2)-H_(2)S-Cl^(-)腐蚀环境,分析L360钢在湿气环境中的腐蚀行为;最后,揭示含Cl^(-)湿气管道顶部CO_(2)-H_(2)S吸附机制与点蚀机理。结果CO_(2)、H_(2)S、CO_(2)-H_(2)S及CO_(2)-H_(2)S-Cl^(-)在最稳定位置时的吸附能分别为-4.065、-3.961、-8.538、-12.775e V,表明相较于CO_(2)与H_(2)S单独吸附,CO_(2)-H_(2)S在α-Fe(110)面的吸附能更负,Cl^(-)会进一步降低CO_(2)-H_(2)S的吸附能;且CO_(2)在与H_(2)S竞争环境电子中占优势;Cl^(-)会使CO_(2)-H_(2)S的局域态密度峰值降低,转移趋势为失去电子,基体和腐蚀介质的电子向着低能级跃迁释放出更多能量,进而加强了Fe与CO_(2)-H_(2)S间的化学键强度;Cl^(-)的2p轨道与Fe的3d轨道在-6.8 eV和-5.7 eV发生重叠,Cl^(-)被吸附到Fe表面并与Fe形成化学键生成氯化物,进而改变腐蚀产物膜的组分与结构,削弱产物膜的致密性和稳定性,减弱腐蚀阻抗力。在含Cl^(-)湿气的CO_(2)-H_(2)S环境中,液相中的Cl^(-)浓度升高,使L360钢的气相平均腐蚀速率逐渐增大,最高达2.935mm/a,点蚀越发严重。结论CO_(2)与H_(2)S在α-Fe(110)面吸附存在一定的协同和竞争作用,协同促进金属的腐蚀,FeCO3会优先沉积成膜,但H_(2)S会抑制FeCO3的生长,腐蚀产物以FeS为主;Cl^(-)会增强CO_(2)-H_(2)S与α-Fe(110)面间的作用力,弱化腐蚀产物膜层的保护性,进一步加速金属腐蚀、尤其是点蚀。 展开更多
关键词 CO_(2)-H_(2)s Cl^(-) 第一性原理 α-Fe(110)密排面 吸附特征 腐蚀机理
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电液3-UPS/S并联稳定平台参数振动特性分析
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作者 袁晓明 王维锜 +1 位作者 庞浩东 张立杰 《振动与冲击》 EI CSCD 北大核心 2024年第5期52-61,共10页
针对电液3-UPS/S并联稳定平台驱动液压缸的压力脉动所产生的参数振动,建立了稳定平台的参数振动方程并利用多尺度法求解了主共振响应与组合共振响应的一次近似解;分析了主共振与组合共振响应特性以及振动幅值在初始工作空间内的变化规律... 针对电液3-UPS/S并联稳定平台驱动液压缸的压力脉动所产生的参数振动,建立了稳定平台的参数振动方程并利用多尺度法求解了主共振响应与组合共振响应的一次近似解;分析了主共振与组合共振响应特性以及振动幅值在初始工作空间内的变化规律,最后采用四阶龙格库塔法与模态试验对参数振动模型进行验证。结果表明:数值解与理论解之间的最大误差为4.20%,固有频率理论值与试验值之间的最大误差为4.66%,可验证参数振动模型的正确性。 展开更多
关键词 电液3-UPs/s并联稳定平台 压力脉动 参数振动 多尺度法 振动特性
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基于C/S架构和物联网技术的可移动医疗设备共享调配系统的设计与应用
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作者 王杰 薛博宇 +2 位作者 徐云华 张琛 顾伟 《中国医疗设备》 2024年第1期85-91,共7页
目的 设计一个可移动医疗设备高效管理与临床科室共享调配相结合的医疗设备共享管理平台,实现可移动医疗设备使用的全过程管理。方法 基于C/S架构,利用物联网技术优化整合现有医疗设备大数据资源,结合医院需求,构建可移动医疗设备共享... 目的 设计一个可移动医疗设备高效管理与临床科室共享调配相结合的医疗设备共享管理平台,实现可移动医疗设备使用的全过程管理。方法 基于C/S架构,利用物联网技术优化整合现有医疗设备大数据资源,结合医院需求,构建可移动医疗设备共享调配系统,实现医疗设备共享管理、预约借用、统计分析等核心功能。通过比较系统上线前后呼吸机调配次数、平均调配时间、呼吸机使用率、单台呼吸机日均收入4个指标,分析系统应用效果。结果 系统上线后,呼吸机调配次数明显增加、平均调配时间明显降低,呼吸机使用率、单台呼吸机日均收入明显升高,且差异均有统计学意义(P﹤0.05),表明系统对提高呼吸机调配效率与使用效率有促进作用。结论 可移动医疗设备共享调配系统优化了医院设备管理流程,实现了医疗资源的统一调配,有效满足临床紧急抢救时医疗设备调配使用的相关需求,提高了医疗设备周转率以及设备管理人员的工作效率,有助于医院节约人员成本、降低采购费用,为医院管理者制定相关决策提供数据支撑。 展开更多
关键词 可移动医疗设备 物联网 C/s架构 设备共享 管理系统
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