期刊文献+
共找到1,049篇文章
< 1 2 53 >
每页显示 20 50 100
喷砂工艺对Y-TZP力学性能和表面粗糙度的影响
1
作者 林信平 陈戈 +1 位作者 杨清平 李和祯 《中国锰业》 2024年第1期72-76,共5页
为了评估不同喷砂工艺对氧化锆陶瓷力学性能和表面粗糙度的影响,采用不同的喷砂处理工艺对样品进行喷砂处理。研究表明氧化锆陶瓷经过喷砂处理后表层单斜相含量明显增加。喷砂原料的颗粒尺寸越大,相变越多。喷砂后表面粗糙度增加,在相... 为了评估不同喷砂工艺对氧化锆陶瓷力学性能和表面粗糙度的影响,采用不同的喷砂处理工艺对样品进行喷砂处理。研究表明氧化锆陶瓷经过喷砂处理后表层单斜相含量明显增加。喷砂原料的颗粒尺寸越大,相变越多。喷砂后表面粗糙度增加,在相同的喷砂条件下,经球形Al_(2)O_(3)处理的样品表面粗糙度Sa远小于经SiC颗粒处理的。在喷砂原料粒径为100μm、喷砂时间为20 s、压力为0.2 MPa的情况下,四点弯曲强度分别提高了27%(SiC)与21%(Al_(2)O_(3))。因此,具有球形颗粒形貌的Al_(2)O_(3)颗粒更适合用作表面喷砂处理。 展开更多
关键词 四方多晶氧化锆 喷砂 相转变 弯曲强度 表面粗糙度
下载PDF
Fuzzy Fruit Fly Optimized Node Quality-Based Clustering Algorithm for Network Load Balancing
2
作者 P.Rahul N.Kanthimathi +1 位作者 B.Kaarthick M.Leeban Moses 《Computer Systems Science & Engineering》 SCIE EI 2023年第2期1583-1600,共18页
Recently,the fundamental problem with Hybrid Mobile Ad-hoc Net-works(H-MANETs)is tofind a suitable and secure way of balancing the load through Internet gateways.Moreover,the selection of the gateway and overload of th... Recently,the fundamental problem with Hybrid Mobile Ad-hoc Net-works(H-MANETs)is tofind a suitable and secure way of balancing the load through Internet gateways.Moreover,the selection of the gateway and overload of the network results in packet loss and Delay(DL).For optimal performance,it is important to load balance between different gateways.As a result,a stable load balancing procedure is implemented,which selects gateways based on Fuzzy Logic(FL)and increases the efficiency of the network.In this case,since gate-ways are selected based on the number of nodes,the Energy Consumption(EC)was high.This paper presents a novel Node Quality-based Clustering Algo-rithm(NQCA)based on Fuzzy-Genetic for Cluster Head and Gateway Selection(FGCHGS).This algorithm combines NQCA with the Improved Weighted Clus-tering Algorithm(IWCA).The NQCA algorithm divides the network into clusters based upon node priority,transmission range,and neighbourfidelity.In addition,the simulation results tend to evaluate the performance effectiveness of the FFFCHGS algorithm in terms of EC,packet loss rate(PLR),etc. 展开更多
关键词 Ad-hoc load balancing H-MANET fuzzy logic system genetic algorithm node quality-based clustering algorithm improved weighted clustering fruitfly optimization
下载PDF
中国少年女子足球运动员功能性动作能力与下肢爆发力、Y-平衡的关系探究
3
作者 崔健华 张俊杰 叶俊 《四川体育科学》 2024年第1期35-41,共7页
目的:分析中国少年女子足球运动员(以下简称国少女足)功能性动作筛查评分结果与下肢爆发力、Y-平衡存在的内在联系,为提高国少女足运动员运动表现提供参考。方法:选取24名国少女足运动员进行功能性动作筛查测试、20m冲刺、立定跳远、下... 目的:分析中国少年女子足球运动员(以下简称国少女足)功能性动作筛查评分结果与下肢爆发力、Y-平衡存在的内在联系,为提高国少女足运动员运动表现提供参考。方法:选取24名国少女足运动员进行功能性动作筛查测试、20m冲刺、立定跳远、下蹲跳、Y-平衡测试,并对结果进行分析。位置间采用单因素方差分析,相关性研究采用Person分析。结果:(1)国少女足运动员功能性动作筛查测试平均分为16.20,最佳截断点为14.5分;(2)跨栏步、主动直膝抬腿与20m分段冲刺速度存在显著负相关(r=-0.466,P<0.05;r=-0.367,P<0.05),过顶深蹲动作模式与立定跳远存在显著正相关(r=0.181,P<0.05),Y-平衡临界值在各个位置之间存在统计学意义(P<0.01);(3)FMS总分对准确预测国少女足球员非接触性损伤具有较高的诊断价值,曲线下面积为0.903。结论:(1)我国优秀国少女足运动员髋关节主动灵活性和臀大肌-髂胫束联合等肌群的主动柔韧性较好,但存在膝关节、髋关节稳定性差、躯干核心区肌群控制能力不足等问题,训练应着重加强臀部肌群的激活与练习、核心区稳定与核心区力量训练。(2)FMS得分与20m分段冲刺速度存在显著负相关,与立定跳远存在显著正相关,与下蹲跳能力存在正相关,与Y-平衡得分存在负相关,FMS测试得分并不能全面反映球员下肢爆发力、Y-平衡能力的高低,测试评估与训练需要考虑球员个体差异性,强调针对性帮助球员提高运动表现,降低损伤风险。 展开更多
关键词 国少女足 功能动作筛查 下肢爆发力 y-平衡 ROC曲线
下载PDF
Auto-Bcklund transformation and exact solutions of Wick-type stochastic Burgers equation 被引量:1
4
作者 陈彬 《Journal of Southeast University(English Edition)》 EI CAS 2005年第4期513-516,共4页
Burgers equation in random environment is studied. In order to give the exact solutions of random Burgers equation, we only consider the Wick-type stochastic Burgers equation which is the perturbation of the Burgers e... Burgers equation in random environment is studied. In order to give the exact solutions of random Burgers equation, we only consider the Wick-type stochastic Burgers equation which is the perturbation of the Burgers equation with variable coefficients by white noise W(t)=Bt, where Bt is a Brown motion. The auto-Baecklund transformation and stochastic soliton solutions of the Wick-type stochastic Burgers equation are shown by the homogeneous balance and Hermite transform. The generalization of the Wick-type stochastic Burgers equation is also studied. 展开更多
关键词 Wick-type stochastic Burgers equation auto-Baecklund transformation stochastic soliton solution white noise Hermite transform homogeneous balance principle
下载PDF
Hf含量对Ti_(49-X)Ni_(44)Cu_(6)Y_(1)Hf_(X)形状记忆合金的组织与超弹性的影响
5
作者 赵光伟 李达 +4 位作者 陈健 方东 黄才华 石增敏 叶永盛 《材料导报》 EI CAS CSCD 北大核心 2023年第9期154-159,共6页
Ti-Ni-Cu基形状记忆合金具有相变滞后小、可回复应变大、热稳定性好等优良性能。本工作采用非自耗真空电弧熔炼制备了Ti_(49-X)Ni_(44)Cu_(6)Y_(1)Hf_(X)(X=0,2,6,10)形状记忆合金,并研究了Hf含量对其组织、相变行为与超弹性等的影响。... Ti-Ni-Cu基形状记忆合金具有相变滞后小、可回复应变大、热稳定性好等优良性能。本工作采用非自耗真空电弧熔炼制备了Ti_(49-X)Ni_(44)Cu_(6)Y_(1)Hf_(X)(X=0,2,6,10)形状记忆合金,并研究了Hf含量对其组织、相变行为与超弹性等的影响。结果表明,合金在室温下的主要组织为B2奥氏体与少量化合物相,加载与卸载过程中发生了B2B19′马氏体相变。随Hf含量增加,Ti_(49-X)Ni_(44)Cu_(6)Y_(1)Hf_(X)合金的马氏体相变温度降低,合金的压缩强度和断裂应变均有所降低,应力诱发马氏体的临界应力增加。在压缩应变为3%~11%的应力递增压缩循环过程中,合金出现加工硬化现象,并且可回复应力随着预应力的增加而增加。Hf含量为10%的合金在压缩应变为11%时具有最大的可回复应变7.9%,其中超弹性应变为5.2%。在压缩应变固定为7%的循环压缩过程中,10%Hf的样品循环稳定性较好,可以完全回复。 展开更多
关键词 形状记忆合金 Ti-Ni-Cu-y-Hf合金 马氏体相变 超弹性
下载PDF
Y形与Δ形电阻网络等效变换公式的推理记忆法
6
作者 黄晓艳 王野 +1 位作者 樊楼英 蒋伟丽 《丽水学院学报》 2023年第2期112-115,共4页
提出了电阻Y形网络和Δ形网络相互等效变换式的推理记忆法。具体推理步骤有量纲推理、电路结构类比推理和公平原则推理三个方面。特别在电路结构类比推理中指出电阻Y形网络和Δ形网络与简单电阻串联网络和并联网络具有对应相似性,有助... 提出了电阻Y形网络和Δ形网络相互等效变换式的推理记忆法。具体推理步骤有量纲推理、电路结构类比推理和公平原则推理三个方面。特别在电路结构类比推理中指出电阻Y形网络和Δ形网络与简单电阻串联网络和并联网络具有对应相似性,有助于学生联想记忆。 展开更多
关键词 y形网络 Δ形网络 等效变换 推理记忆法
下载PDF
Modelling Wave Transmission and Overtopping Based on Energy Balance Equation 被引量:2
7
作者 JI Qiaoling DONG Sheng 《Journal of Ocean University of China》 SCIE CAS CSCD 2018年第5期1033-1043,共11页
Wave transmission and overtopping around nearshore breakwaters can have significant influence on the transmitted wave parameters,which affects wave conditions and sediment transportation and becomes the focus of desig... Wave transmission and overtopping around nearshore breakwaters can have significant influence on the transmitted wave parameters,which affects wave conditions and sediment transportation and becomes the focus of design in engineering.The objective of this paper is to present a simplified model to estimate these important wave parameters.This paper describes the incorporation of wave transmission and overtopping module into a wave model for multi-directional random wave transformation based on energy balance equation with the consideration of wave shoaling,refraction,diffraction,reflection and breaking.Wen's frequency spectrum and non-linear dispersion relation are also included in this model.The influence of wave parameters of transmitted waves through a smooth submerged breakwater has been considered in this model with an improved description of the transmitted wave spectrum of van der Meer et al.(2000) by Carevic et al.(2013).This improved wave model has been validated through available laboratory experiments.Then the verified model is applied to investigate the effect of wave transmission and overtopping on wave heights behind low-crested breakwaters in a project for nearshore area.Numerical calculations are carried out with and without consideration of the wave transmission and overtopping,and comparison of them indicates that there is a considerable difference in wave height and thus it is important to include wave transmission and overtopping in modelling nearshore wave field with the presence of low-crested breakwaters.Therefore,this model can provide a general estimate of the desired wave field parameters,which is adequate for engineers at the preliminary design stage of low-crested breakwaters. 展开更多
关键词 random wave transformation energy balance equation numerical modelling Wen's spectrum DIFFRACTION transmission OVERTOPPING
下载PDF
Bcklund Transformation and Localized Coherent Structure for the (2+1)-Dimensional Asymmetric Nizhnik-Novikov-Veselov Equation 被引量:1
8
作者 张解放 刘宇陆 《Journal of Shanghai University(English Edition)》 CAS 2002年第3期191-195,共5页
This article is concerned with the extended homogeneous balance method for studying the abundant localized solution structure of the (2+1) dimensional asymmetric Nizhnik Novikov Veselov equation. A B a¨... This article is concerned with the extended homogeneous balance method for studying the abundant localized solution structure of the (2+1) dimensional asymmetric Nizhnik Novikov Veselov equation. A B a¨ cklund transformation was first obtained, and then the richness of the localized coherent structures was found, which was caused by the entrance of two variable separated arbitrary functions, in the model. For some special choices of the arbitrary functions, it is shown that the localized structures of the model may be dromions, lumps, and ring solitons. 展开更多
关键词 homogeneous balance method coherent soliton structures asymmetric Nizhnik Novikov veselov equation (ANNV equation) B cklund transformation.
下载PDF
Homogenous Balance Method and Exact Analytical Solutions for Whitham-Broer-Kaup Equations in Shallow Water 被引量:1
9
作者 XIAZhi 《Chinese Quarterly Journal of Mathematics》 CSCD 2004年第3期240-246,共7页
Based on the homogenous balance method and with the help of mathematica, the Backlund transformation and the transfer heat equation are derived. Analyzing the heat-transfer equation, the multiple soliton solutions and... Based on the homogenous balance method and with the help of mathematica, the Backlund transformation and the transfer heat equation are derived. Analyzing the heat-transfer equation, the multiple soliton solutions and other exact analytical solution for Whitham-Broer-Kaup equations(WBK) are derived. These solutions contain Fan's, Xie's and Yan's results and other new types of analytical solutions, such as rational function solutions and periodic solutions. The method can also be applied to solve more nonlinear differential equations. 展开更多
关键词 improved homogenous balance method Backlund transformation solitary wave solution multiple solution exact analytical solution rational solution
下载PDF
Interference of Y-27632 on the signal transduction of transforming growth factor beta type 1 in ocular Tenon capsule fibroblasts 被引量:7
10
作者 Xiao-Hui Zhang, Jian-Ming Wang 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2012年第5期576-581,共6页
AIM: To investigate the interfering effect of Y-27632, a ROCK-I selective inhibitor, on the signal transduction pathway of transforming growth factor-beta 1 (TGF-beta 1) in ocular Tenon capsule fibroblasts (OTFS) in v... AIM: To investigate the interfering effect of Y-27632, a ROCK-I selective inhibitor, on the signal transduction pathway of transforming growth factor-beta 1 (TGF-beta 1) in ocular Tenon capsule fibroblasts (OTFS) in vitro. METHODS: After OTFS from passages 4 to 6 47 vitro were induced by TGF-beta 1 and then treated by Y-27632, the changes of the OTFS cell cycles were analyzed via flow cytometry, and the proteins expression of the alpha -smooth muscular actin (alpha -SMA), connective tissue growth factor (CTGF), collagen I were calculated by Western blot. After OTFS treated by the different concentrations of Y-27632, the expression levels of the alpha -SMA, CTGF and collagen I mRNA were assayed by RT-PCR. RESULTS: Y-27632 had no markedly effect on the OTFS cell cycles. After treated by TGF-beta 1, OTFS in G1 period significantly increased. The cell cycles distribution by both TGF-beta 1 and Y-27632 had no remarkable difference from that in control group. Y-27632 significantly inhibited the proteins expressions of both alpha -SMA and CTGF, while to some extent inhibited that of collagen I. TGF-beta 1 significantly promoted the proteins expressions of alpha -SMA, CTGF and collagen I. After OTFS treated by both TGF-beta 1 and Y-27632, of alpha -SMA, the protein expression was similar with that in control group (P=0.066>0.05), but the protein expression of CTGF or collagen I, respectively, was significantly different from that in control group (P=0.000<0.01). The differences of expressions of the alpha -SMA, CTGF and collagen I mRNA in 30, 150, 750 mu mol/L Y-27632 group were statistically significant, compared with those in control group, respectively (alpha -SMA, P=0.002, 0.000, 0.000; CTGF, P=0.014, 0.002, 0.001; collagen I,P=0.003, 0.002, 0.000). CONCLUSION: Blocking the Rho/ROCK signaling pathway by using of Y-27632 could inhibit the cellular proliferation and the expression of both CTGF and alpha -SMA whatever OTFS induced by TGF-beta 1 or not. Y-27632 suppressed the expression of collagen I mRNA without induction. 展开更多
关键词 y-27632 ocular Tenon's capsule fibroblasts transforming growth factor beta type 1 α-smooth muscular actin connective tissue growth factor collagen I
下载PDF
Adaptive IIR filtering based on balanced-realization
11
作者 Yongfeng Zhi Panguo Fan Jun Zhang 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2013年第1期19-25,共7页
Due to low parameter sensitivity for balanced realiza- tions, balanced structure becomes a good candidate for an statespace adaptive infinite impluse response (IIR) filter. Here, using coefficients of the transfer f... Due to low parameter sensitivity for balanced realiza- tions, balanced structure becomes a good candidate for an statespace adaptive infinite impluse response (IIR) filter. Here, using coefficients of the transfer function as the adaptive filtering parameters, a balanced adaptive IIR filtering algorithm is proposed for output-error minimization. The algorithm in the internally balanced realization guarantees that the adaptive IIR filter always minimizes the ratio of maximum-to-minimum eigenvalue of the Grammian matrices at the each iteration. Simulation results are provided to corroborate the proposed algorithm. 展开更多
关键词 balanced realization adaptive infinite impluse response filtering state-space transformation.
下载PDF
Y染色体平衡易位与精液质量的相关性研究
12
作者 刘钰君 陈琪琪 +4 位作者 孙希雅 邵敏杰 袁人培 姜辉 智旭 《中国生育健康杂志》 2023年第1期56-59,89,共5页
目的分析Y染色体平衡易位与男性精液质量的相关性。方法回顾性分析2019年1月—2021年12月北京大学第三医院生殖医学中心就诊的男性病例资料,筛选出14例染色体核型分析为Y染色体平衡易位病例,以及同期185例染色体核型结果正常(46,XY)的... 目的分析Y染色体平衡易位与男性精液质量的相关性。方法回顾性分析2019年1月—2021年12月北京大学第三医院生殖医学中心就诊的男性病例资料,筛选出14例染色体核型分析为Y染色体平衡易位病例,以及同期185例染色体核型结果正常(46,XY)的男性作对照。通过比较两组间精液常规质量,包括精子的数量、活率以及形态学检测,分析Y染色体与常染色体间平衡易位与男性精液质量的相关性。结果除精液量外,Y染色体平衡易位患者的精液密度、精子总数、精子活率、前向运动精子百分率以及正常形态精子百分率均显著低于对照男性组。14例患者中有7例为无精子症,7例为严重少弱畸形精子症。q12(14例)、q11.23(4例)是Y染色体平衡易位断裂点高发区域。结论Y染色体平衡易位对于精子数量、活力及形态具有显著影响,严重时可导致少弱畸形精子症或无精症,影响患者的生育能力。 展开更多
关键词 y染色体 平衡易位 男性不育 精液质量
下载PDF
POLARIZATION-SENSITIVE OPTICAL COHERENCE TOMOGRAPHY USING A MODIFIED BALANCE DETECTOR
13
作者 LI-PING YU JIAN-CHEN GUO +4 位作者 LI-DEK CHOU TE-LUN MA JHENG-SYONG WU JIANN-DER LEE CHIEN CHOU 《Journal of Innovative Optical Health Sciences》 SCIE EI CAS 2012年第4期18-23,共6页
In conventional polarization sensitive optical coherence tomography(PS-OCT),phase retar-dation is obtained by the amplitude of P and S polarization only,and the fast axis angle is obtained by the phase difference in P... In conventional polarization sensitive optical coherence tomography(PS-OCT),phase retar-dation is obtained by the amplitude of P and S polarization only,and the fast axis angle is obtained by the phase difference in P and S polarizations via Hilbert transformation.In this paper,we proposed a modifed PS OCT setup in which the phase retardation and fast axis angle are simply expressed as the function of the amplitude ofP and S polarization and their differential signal.Due to the common-path feature between the two channels ofP and S polarization,the fuctuation in the measurement of phase retardation and fast axis angle caused by excess noise and phase noise from the laser source can be reduced by the differential signal of P and S polarization via a modified balance detector.Thus,the signal of phase retardation and fast angle axis in the deep layer of a porcine sample can be improved. 展开更多
关键词 PS OCT modifed balanced detector Hilbert transformation
下载PDF
Acidity Evaluation of Industrially Dealuminated Y Zeolite via Methylcyclohexane Transformation
14
作者 Hou Kaige Qin Bo +3 位作者 Han Junjie Du Yanze Ma Jinghong Li Ruifeng 《China Petroleum Processing & Petrochemical Technology》 SCIE CAS 2021年第3期50-57,共8页
The catalytic transformation of methylcyclohexane as an accepted probe reaction to evaluate zeolitic acidity(concentration,strength,and accessibility)is employed to study the acidity and the reactivity of three commer... The catalytic transformation of methylcyclohexane as an accepted probe reaction to evaluate zeolitic acidity(concentration,strength,and accessibility)is employed to study the acidity and the reactivity of three commercial dealuminated Y zeolites(DAY)with different Si/Al ratios and meso/microporosities,with their properties analyzed by N_(2) adsorption/desorption,pyridine-IR,and hydroxyl-IR spectroscopy technologies.The global activity(conversion)is largely dependent on the concentration of the acid sites,and the activity of the protonic sites in terms of turnover frequency(TOF)reflects the accessibility of acid sites.The products of aromatics and isomers,and the yield of cracking products increase with the increase of concentration of strong protonic sites in zeolite micropores.Moreover,the decrease of aromatics with the reduction of the concentration of acid sites and the diffusion length within DAY zeolites are observed due to the decrease of the secondary reaction.For the same reason,it results in the increasing of C_(7)products and alkenes/alkanes ratios in the cracking products.The high i-C_(4)product selectivity is a unique reflection of the high percentage of very strong acid sites,which is characterized by the hydroxyl-IR band at 3600 cm^(-1). 展开更多
关键词 methylcyclohexane catalytic transformation industrially modified y zeolite zeolitic acidity strong protonic sites spectroscopic technology
下载PDF
利用FMS-LE和YBT-LQ预测足球运动员下肢损伤率的研究
15
作者 侯明岳 李春满 +1 位作者 朴顺哲 宋英哲 《体育科技文献通报》 2023年第5期257-261,共5页
目的:探讨高校男子足球运动员FMS-LE下肢功能动作筛查测试、YBT-LQ下肢Y平衡测试与运动损伤发生率的关系。方法:对43名高校男子足球运动员进行FMS-LE和YBT-LQ测试,跟踪并记录运动员在训练和比赛中的损伤情况,分析两个测试得分与运动损... 目的:探讨高校男子足球运动员FMS-LE下肢功能动作筛查测试、YBT-LQ下肢Y平衡测试与运动损伤发生率的关系。方法:对43名高校男子足球运动员进行FMS-LE和YBT-LQ测试,跟踪并记录运动员在训练和比赛中的损伤情况,分析两个测试得分与运动损伤率之间的关系。研究发现:将FMS-LE<6.5作为阈值时,预测的准确率为53.84%;将YBT-LQ的X/Y/Z>4cm和前侧伸够标准值<54.4%作为阈值时,预测准确率为76.92%;将FMS-LE<6.5与YBT-LQ前侧伸够标准值<54.4%和X/Y/Z>4cm作为阈值时,预测成功率为92.30%。单一使用FMS-LE或YBT-LQ对损伤概率的预测均有一定的准确性,但将两者结合对损伤预测的准确性更高。 展开更多
关键词 足球 高校运动员 功能性动作筛查 y平衡测试 运动损伤
下载PDF
城市轨道交通Y形线路信号系统拆分改造方案 被引量:1
16
作者 裴立原 《铁路通信信号工程技术》 2023年第11期85-91,共7页
杭州地铁1号线作为Y形线路,计划将1号线临平支线拆分划归到9号线控制。为安全、高效地保障临平支线信号系统拆分改造,从拆分改造目标、倒切方案、关键技术等方面进行研究分析。创新地提出倒切柜搭配接续分线柜的新旧系统倒切方案,为后... 杭州地铁1号线作为Y形线路,计划将1号线临平支线拆分划归到9号线控制。为安全、高效地保障临平支线信号系统拆分改造,从拆分改造目标、倒切方案、关键技术等方面进行研究分析。创新地提出倒切柜搭配接续分线柜的新旧系统倒切方案,为后续有计划开展拆分改造的轨道交通线路提供思路,具有一定的参考价值。 展开更多
关键词 城市轨道交通 信号系统 拆分改造 y形线路
下载PDF
脂肪酸平衡在反刍动物上的研究进展
17
作者 张永根 白海鑫 《饲料工业》 CAS 北大核心 2024年第3期1-7,共7页
脂肪酸平衡是继蛋白质和氨基酸平衡后的又一新概念。脂肪酸平衡主要包括3个方面:短、中、长链脂肪酸平衡,饱和与不饱和脂肪酸平衡,ω_(3)和ω_(6)脂肪酸平衡。随着研究的深入,脂肪不再单一地被认为只发挥能量效应,更多个体脂肪酸或脂肪... 脂肪酸平衡是继蛋白质和氨基酸平衡后的又一新概念。脂肪酸平衡主要包括3个方面:短、中、长链脂肪酸平衡,饱和与不饱和脂肪酸平衡,ω_(3)和ω_(6)脂肪酸平衡。随着研究的深入,脂肪不再单一地被认为只发挥能量效应,更多个体脂肪酸或脂肪酸间组合的生物活性效应被陆续挖掘。文章主要综述了长链脂肪酸平衡在反刍动物上的最新研究进展。 展开更多
关键词 脂肪酸平衡 消化吸收 转化沉积 生产性能 反刍动物
下载PDF
股权结构对制造业企业绿色创新的影响研究
18
作者 程晓多 张立彤 杨博文 《管理现代化》 北大核心 2024年第2期136-146,共11页
以2007-2022年A股制造业上市公司数据,实证检验了股权结构对企业绿色创新的影响及其机制。研究结果表明,股权集中度与企业绿色创新负相关,而股权制衡度与企业绿色创新正相关。机制分析表明,股权集中度以降低数字化转型水平阻滞企业绿色... 以2007-2022年A股制造业上市公司数据,实证检验了股权结构对企业绿色创新的影响及其机制。研究结果表明,股权集中度与企业绿色创新负相关,而股权制衡度与企业绿色创新正相关。机制分析表明,股权集中度以降低数字化转型水平阻滞企业绿色创新,融资约束在股权集中度与企业绿色创新之间发挥了遮掩效应;股权制衡度通过缓解企业融资约束、提高数字化转型程度促进企业绿色创新。另外,异质性分析发现,股权集中度与企业绿色创新的负相关性在国有企业和非重污染企业中更强;股权制衡度与企业绿色创新的正相关性在非国有企业、中小型企业和非重污染企业中更为显著。 展开更多
关键词 股权集中度 股权制衡度 融资约束 数字化转型 绿色创新
下载PDF
单相PET级联整流SVPWM均压边界及拓展方法 被引量:1
19
作者 王顺 马兰 +3 位作者 朱磊磊 杨帆 谢锡锋 舒泽亮 《高电压技术》 EI CAS CSCD 北大核心 2024年第3期1235-1243,共9页
电力电子变压器(power electronic transformer,PET)是交直流配电系统互联的重要接口设备,然而后级等效负载不平衡将造成前级整流器各模块的电压偏移。针对单相级联H桥整流器空间矢量调制均压失效问题,推导出基于最优矢量选择均压策略... 电力电子变压器(power electronic transformer,PET)是交直流配电系统互联的重要接口设备,然而后级等效负载不平衡将造成前级整流器各模块的电压偏移。针对单相级联H桥整流器空间矢量调制均压失效问题,推导出基于最优矢量选择均压策略的边界计算方法。根据计算所得的负载不平衡度限制边界与级联模块数、调制度以及功率因数的关系,提出了变调制度和功率因数的控制策略以增加均压能力。该策略通过改变直流电压或降低功率因数来重建更宽的均压工作范围,确保原不平衡度均压极限的系统稳定运行。最后,通过三模块级联整流器的仿真与实验验证了该均压边界的正确性,以及所提均压拓展方法保障极端不平衡负载条件下均压的有效性。 展开更多
关键词 电力电子变压器 单相级联H桥整流器 直流电压均衡 均压边界 负载不平衡限制边界
下载PDF
Y/>/平衡变压器运行特性分析与模型试验 被引量:15
20
作者 蒋寿生 周有庆 +1 位作者 刘光晔 罗信芝 《中国电机工程学报》 EI CSCD 北大核心 2003年第4期102-106,共5页
该文分析了Y/>/平衡变压器的接线原理,论证了该变压器在不同运行工况时两侧电流的映射关系,在此基础上对该变压器的模型进行了全面的试验验证。试验结果表明:该变压器的理论分析正确,模型的参数和结构设计合理,工艺易于实现;当负... 该文分析了Y/>/平衡变压器的接线原理,论证了该变压器在不同运行工况时两侧电流的映射关系,在此基础上对该变压器的模型进行了全面的试验验证。试验结果表明:该变压器的理论分析正确,模型的参数和结构设计合理,工艺易于实现;当负荷大范围变化时,原方三相系统的对称性好,副方任一相的输出电压几乎不受另一相负荷变化的影响,抑制负序分量的能力强。应用于电气化铁道做牵引供电变压器时,不仅能较好抑制负序电流对电力系统的影响,而且能提高牵引网的电压水平,有利于电力机车的安全稳定运行。 展开更多
关键词 牵引变压器 平衡变压器 运行特性 分析 模型试验
下载PDF
上一页 1 2 53 下一页 到第
使用帮助 返回顶部