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A NEW EXPRESSION OF FATIGUE SIZE FACTOR
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作者 Yao Weixing(Department of Aircraft Engineering ,NUAA 29 Yudao Street,Nanjing 210016,P.R.China) 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 1994年第2期229-233,共5页
An expression describing the size effect on fatigue strength is presented, which is deduced based on the fatigue design approach of stress field intensity. The fatigue size factors under rotating-bending or reversed t... An expression describing the size effect on fatigue strength is presented, which is deduced based on the fatigue design approach of stress field intensity. The fatigue size factors under rotating-bending or reversed torsion for smooth specimen and under rotating-bending for notched specimen are estimated, and the main effects on the fatigue size factor are discussed. Some experimental data are analysed and it is shown that the description of fatigue size factor developed in this paper is satisfactory. 展开更多
关键词 FATIGUE size factor FATIGUE mechanism stress field intensity rotating-bending reversed TORSION notched SPECIMEN
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An algorithm of adaptive step size factor in adaptive filtering
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作者 CHEN Geng(State Key Laboratory of AcousticesJnslilule of Acoustics, Academia Sinica, Beijing 100080) 《Chinese Journal of Acoustics》 1992年第4期289-297,共9页
In this paper a model of transversal filter is presented to study the adaptive match of the time variant channel. The least mean square error filtering method is used to obtain the weighting coefficients of the filter... In this paper a model of transversal filter is presented to study the adaptive match of the time variant channel. The least mean square error filtering method is used to obtain the weighting coefficients of the filter. With the purpose of speeding up the convergence of the iteration equation of adaptive filtering, an adaptive factor of the iteration step size μa is derived in this paper. The result of computer simulation shows that in the case of using adaptive μa, the convergence speed of the iteration equation is increased 2 times approximately in comparison with constant μ1. The study suggests that the adaptive filter with adaptive μa have the performance to follow the change of time-variant characteristics of the channel. 展开更多
关键词 An algorithm of adaptive step size factor in adaptive filtering
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Study on Factors Influencing the Reliability of the Organization Management Chain of the Large and Medium-Sized Project in the Construction Period
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作者 Jingchun Feng Yao Qian +1 位作者 Zhanjun Liu Haiyang Li 《Journal of Water Resource and Protection》 2011年第2期131-139,共9页
On the basis of analyzing the reliability of the organization’ management chain of the large and medium- sized project in the construction period, the paper studies the factors influencing the reliability of the orga... On the basis of analyzing the reliability of the organization’ management chain of the large and medium- sized project in the construction period, the paper studies the factors influencing the reliability of the organi-zation management chain, which, corresponding to four elements of management chain – “Management Loop”, “Management Link”, “Management Chain”, and “Management Network”, can be summarized as project main body, interface management, connection sequence and management model. The paper then re-searches on the specific influencing factors from the above-mentioned four aspects. 展开更多
关键词 The LARGE and MEDIUM sized PROJECT The Reliability of the Organizaton Management CHAIN In-fluencing factor
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Fama-French-factor model,size and book-to-market effect:An empirical investigation of the Chinese stock market
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作者 宋晨 《China Economist》 2010年第5期109-118,共10页
In this study, we use Chinese A-share stock market data from 1995 to 2005 to test the persistence of the size and valueeffect and the robustness of the Fama-French three-factor model in explaining the variation in sto... In this study, we use Chinese A-share stock market data from 1995 to 2005 to test the persistence of the size and valueeffect and the robustness of the Fama-French three-factor model in explaining the variation in stock returns.Wefind that the three-factor model can explain the common variation in stock returns well.However, it is mis-specifiedfor the Chinese stock market.We demonstrate that the size effect and the book-to-market effect are significant andpersistent over our sample period.Interestingly, the book-to-market effect for China is much stronger than the averageones in mature markets and other emerging markets documented by Fama and French (1998).Moreover, we find noevidence to support the argument that seasonal effects can explain the results of the multifactor model.Last, our mixedobservations on firm-specific fundamentals suggest that the risk-based explanation proposed by Fama and French(1995) cannot shed light on the size and BM effect for China.In view of the features of the Chinese stock market, weinstead argue that China’s size and book-to-market effect may be attributed to syndicate speculators’ manipulation andmispricing caused by irrational investor behavior. 展开更多
关键词 ASSET pricing three-factor model A-share market size EFFECT BOOK-TO-MARKET EFFECT risk
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Size Distributions and Elemental Compositions of Particulate Matter on Clear,Hazy and Foggy days in Beijing,China 被引量:13
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作者 杨勇杰 王跃思 +3 位作者 黄蔚薇 胡波 温天雪 赵亚南 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2010年第3期663-675,共13页
Total suspended particulates (TSP) samples were collected using low pressure impactors (Andersen Series 20-800, USA) on typical clear, hazy and foggy days in Beijing in order to investigate the characteristics of ... Total suspended particulates (TSP) samples were collected using low pressure impactors (Andersen Series 20-800, USA) on typical clear, hazy and foggy days in Beijing in order to investigate the characteristics of size distributions and elemental compositions of particulate matter (PM) in different weather conditions. The concentrations of sixteen elements, including Na, Mg, Al, K, Ca, Mn, Fe, Ni, Cu, Zn, As, Se, Cd, Ba, T1 and Pb were detected using inductively coupled plasma mass spectrometry (ICP-MS). The results showed that Ca, A1, Fe, Mg and Ba on foggy days were 2.0 2.6 times higher than on clear days, and 2.3-2.9 times higher than on hazy days. Concentrations of Cu, Zn, As, Se and Pb on foggy days were 163.5, 1186.7, 65.9, 32.0 and 708.2 ng m-3, respectively, in fine particles, and 68.1, 289.5, 19.8, 1.6 and 103.8 ng m-3, respectively, in coarse particles. This was 1.0~8.4 times higher and 1.4-7.4 times higher than on clear and hazy days, respectively. It is then shown that Mg, A1, Fe, Ca and Ba were mainly associated with coarse particles, peaking at 4.7~5.8 μm; that Cd, Se, Zn, As, T1 and Pb were most dominant in fine particles, peaking at 0.43-1.1 μm; and that Na, K, Ni, Cu and Mn had a multi-mode distribution, with peaks at 0.43-1.1 μm and 4.7-5.8 μm. The enrichment factors indicated that coal combustion along with vehicle and industry emissions may be the main sources of pollution elements. 展开更多
关键词 particulate matter size distribution enrichment factor
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Mechanics criterion and factors affecting overburden stability in solid dense filling mining 被引量:6
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作者 Sun Jian 《International Journal of Mining Science and Technology》 SCIE EI CSCD 2017年第3期407-413,共7页
The effect of controlling strata movement in solid filling mining depends on the filling rate of the goal. However, the mechanical property of the overburden in the backfill stope and the designed size of the backfill... The effect of controlling strata movement in solid filling mining depends on the filling rate of the goal. However, the mechanical property of the overburden in the backfill stope and the designed size of the backfill mining workface should also be considered. In this study, we established a main roof strata model with loads in accordance with the theory of key strata to investigate the stability of the overburden in solid dense filling mining. We analyzed the stress distribution law of the main roof strata based on elastic thin plate theory. The results show that the position of the long side midpoint of the main roof strata failed more easily because of tensile yield, indicating that this position is the area where failure is likely to occur more easily. We also deduced the stability mechanics criterion of the main roof strata based on tensile yield criterion. The factors affecting the stability of the overburden in solid dense filling mining were also analyzed, including the thickness and elasticity modulus of the main roof strata, overlying strata loads, advanced distance and length of workface, and elastic foundation coefficient of backfill body. The research achievements can provide an important theoretical basis for determining the designed size of the solid dense filling mining workface. 展开更多
关键词 Filling mining Strata movement Stability control Influencing factors size design
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Observation of Resistive Switching Memory by Reducing Device Size in a New Cr/CrO_x/TiO_x/TiN Structure 被引量:2
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作者 Debanjan Jana Subhranu Samanta +2 位作者 Sourav Roy Yu Feng Lin Siddheswar Maikap 《Nano-Micro Letters》 SCIE EI CAS 2015年第4期392-399,共8页
The resistive switching memory characteristics of 100 randomly measured devices were observed by reducing device size in a Cr/Cr Ox/Ti Ox/Ti N structure for the first time.Transmission electron microscope image confir... The resistive switching memory characteristics of 100 randomly measured devices were observed by reducing device size in a Cr/Cr Ox/Ti Ox/Ti N structure for the first time.Transmission electron microscope image confirmed a viahole size of 0.4 lm.A 3-nm-thick amorphous Ti Oxwith 4-nm-thick polycrystalline Cr Oxlayer was observed.A small 0.4-lm device shows reversible resistive switching at a current compliance of 300 l A as compared to other larger size devices(1–8 lm)owing to reduction of leakage current through the Ti Oxlayer.Good device-to-device uniformity with a yield of[85%has been clarified by weibull distribution owing to higher slope/shape factor.The switching mechanism is based on oxygen vacancy migration from the Cr Oxlayer and filament formation/rupture in the Ti Oxlayer.Long read pulse endurance of[105cycles,good data retention of 6 h,and a program/erase speed of 1 ls pulse width have been obtained. 展开更多
关键词 CrOx TiOx Resistive switching memory Slope/shape factor Device size
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老年急性脑梗死患者血清Del-1和IL-17水平变化及与梗死面积和预后的关系 被引量:3
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作者 郑德泉 江华 +4 位作者 韩玉惠 杨青平 吴义森 欧阳林 李清金 《中国实用神经疾病杂志》 2024年第1期26-30,共5页
目的 探究老年急性脑梗死(ACI)患者血清内皮发育调节基因-1(Del-1)、白细胞介素-17(IL-17)水平与脑梗死面积、病情严重程度及预后的关系。方法 回顾性收集2019-01-2021-12厦门大学附属东南医院收治的126例老年ACI患者(病例组)及105名健... 目的 探究老年急性脑梗死(ACI)患者血清内皮发育调节基因-1(Del-1)、白细胞介素-17(IL-17)水平与脑梗死面积、病情严重程度及预后的关系。方法 回顾性收集2019-01-2021-12厦门大学附属东南医院收治的126例老年ACI患者(病例组)及105名健康体检者(对照组)的临床资料,根据脑梗死面积将病例组患者分为大面积梗死组(梗死最大直径>5 cm,n=14)、中面积梗死组(梗死最大直径3~5 cm,n=53)和小面积梗死组(梗死最大直径<3 cm,n=59);根据NIHSS评分分为重症组(NIHSS评分≥16分,n=13)、中症组(5分<NIHSS评分<15分,n=58)和轻症组(NIHSS评分≤5分,n=55);根据m RS评分分为预后良好组(mRS评分≤2分,n=81)和预后不良组(mRS评分>2分,n=45)。采用荧光免疫法检测血清Del-1、IL-17水平,受试者工作特征(ROC)曲线评估血清Del-1、IL-17水平预测老年ACI患者预后的价值。结果 病例组吸烟史比例、收缩压、舒张压、糖化血红蛋白、血清IL-17水平均高于对照组,血清Del-1水平低于对照组(P<0.05)。不同脑梗死面积患者血清Del-1水平比较,小面积梗死组>中面积梗死组>大面积梗死组;血清IL-17水平比较,小面积梗死组<中面积梗死组<大面积梗死组(P<0.05)。轻症组血清Del-1水平高于中症组、重症组(P<0.05),不同病情严重程度患者血清IL-17水平比较,重症组>中症组>轻症组(P<0.05)。预后良好组患者血清Del-1水平高于预后不良组,血清IL-17水平低于预后不良组(P<0.05)。ROC曲线分析显示,血清Del-1、IL-17预测ACI患者预后的AUC值分别为0.763、0.747(P<0.05)。结论 老年ACI患者血清Del-1水平较低,IL-17水平较高,二者与患者脑梗死面积、病情严重程度和预后关系密切,可作为预测老年ACI患者预后的可靠指标。 展开更多
关键词 急性脑梗死 内皮发育调节基因-1 白细胞介素-17 梗死面积 预后 危险因素 血清
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SEMI-ELLIPTIC SURFACE CRACK IN AN ELASTIC SOLID WITH FINITE SIZE UNDER IMPACT LOADING 被引量:1
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作者 Guo Ruiping Liu Guanting Fan Tianyou 《Acta Mechanica Solida Sinica》 SCIE EI 2006年第2期122-127,共6页
In this paper a semi-elliptic surface crack problem in an elastic solid of finite size under impact loading is investigated. An analysis is performed by means of fracture dynamics and the finite element method, and a ... In this paper a semi-elliptic surface crack problem in an elastic solid of finite size under impact loading is investigated. An analysis is performed by means of fracture dynamics and the finite element method, and a three-dimensional finite element program is developed to compute the dynamic stress intensity factor. The results reveal that the effects of the solid's boundary surface, crack surface, material inertia and stress wave interactions play significant roles in dynamic fracture. 展开更多
关键词 surface crack solid of finite size impact loading dynamic stress intensity factor finite element method
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The grain-size distribution of the suspended particulate matter in the Huanghe Estuary and its adjacent sea area in winter 被引量:1
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作者 ZENG Ming FAN Dejiang +2 位作者 SUN Xiaogong WANG Shuai YANG Zuosheng 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2011年第2期75-83,共9页
The grain-size of suspended particulate matter (SPM) in the Huanghe Estuary and its adjacent sea area was investigated with an in situ laser particle size analyzer (LISST-100) in November 2006.The spatial distribu... The grain-size of suspended particulate matter (SPM) in the Huanghe Estuary and its adjacent sea area was investigated with an in situ laser particle size analyzer (LISST-100) in November 2006.The spatial distribution of the grain-size parameters was very complicated.The results show that (1) the mean particle size of SPM ranged from 3.00Φ to 6.41Φ,with an average value of 4.66Φ;(2) the frequency distribution patterns of the SPM grain-size showed three different types,which were mono-mode,dual-mode and tri-mode,respectively;(3) C-M chart suggested that the transportation-processes of the SPM not only included suspended mode,but also the bed load transportation mode.The bed load transportation mode mainly occurred at the bottom layer.The characteristics and space distribution of SPM grain-size might be mainly controlled by sediment discharge of the Huanghe River,hydrodynamics condition,surface sediment types,and biological process within the study area. 展开更多
关键词 the Huanghe Estuary grain-size of suspended particulate matter spatial distribution influence factor
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Construction of hepatocyte growth factor gene recombinant adenovirus vector and its expression in rat bone marrow mesenchymal stem cells
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作者 Yue Yu Feng Zhang Ling Lü Ye Fan Guoqiang Li Xuehao Wang 《Journal of Nanjing Medical University》 2008年第2期81-86,共6页
Objective:To construct the adenoviral expression vector system containing human hepatocyte growth factor (hHGF) cDNA, and to further study the transduction efficiency and the expression of HGF in mesenchymal stem c... Objective:To construct the adenoviral expression vector system containing human hepatocyte growth factor (hHGF) cDNA, and to further study the transduction efficiency and the expression of HGF in mesenchymal stem cells (MSCs). Methods:The HGF cDNA was amplificated from the expression plasmid pCMV-HGF, and was subcloned into the adenovirus shuttle plasmid pDC316-IRESEGFP vector containing a green fluorescence protein (GFP) reporter gene. Virus Ad-HGF was produced by homologous recombination in HEK293 package cells. Bone marrow derived MSCs were harvested and cultured, and then were transduced with Ad-HGF. The efficiency of Ad-HGF transduction was assessed by FACS analysis using GFP gene expression. And HGF/MSCs were generated. The HGF concentrations in supernatants of HGF/MSCs were determined by ELISA using anti-human HGF monoclonal antibody. Results: The recombinant, named pDC316-HGF-IRES-eGFP, was digested with restriction enzyme, and the DNA sequencing of HGF was identical to the report in Genebank and did not reveal any mutation. GFP expression could be observed on the second day after packing of the linearized pAd-HGF in HEK293 cells and 7.15 × 10^10pfu/ml titer of Ad-HGF was obtained. Forty-eight hours after transduction, 96.89% of HGF/MSCs were GFP positive. Peak concentration levels of hHGF(103ng/mL) in the cultured supernatants were detected on day 2 post-transduction, and the adenovirus-mediated expression of HGF by MSCs was maintained for at least 2 weeks in vivo. Conclusion:Our data demonstrated that the adenovirus expression'vector system pDC316-HGF-IRES-EGFP has been constructed successfully, and their effective expressions also have been obtained in MSCs. This will provide material basis for the next study on liver regeneration after small-for-size liver transplantation. 展开更多
关键词 liver transplantation mesenchymal stem cells hepatocyte growth factor small-for-size graft REGENERATION
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A Situational Assessment of Socioeconomic Factors Affecting Solid Waste Generation and Composition in Freetown, Sierra Leone
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作者 Foday Pinka Sankoh Xiangbin Yan Alhaji Mohamed Hamza Conteh 《Journal of Environmental Protection》 2012年第7期563-568,共6页
The generation of solid waste has become an increasing environmental and public health problem, especially in developing countries. These problems associated with the generation of solid waste are part of social chang... The generation of solid waste has become an increasing environmental and public health problem, especially in developing countries. These problems associated with the generation of solid waste are part of social changes where households play an important role. Invariably, these social changes influence the size, structure and characteristics of given households. This paper presents the findings of a study carried out in Freetown municipal area in Sierra Leone to assess socioeconomic factors affecting household solid waste generation and composition in Freetown, Sierra Leone. Structured questionnaires were administered with respect to these socioeconomic factors in four (4) selected constituencies of the city. These are the most populated constituencies that generated 70% of the total quantity of solid waste in the city. Therefore, they are suitable samples of the study area. The rate of waste generation was determined by using door- to-door approach in five (5) selected households from each constituency through sorting and weighing of solid wastes respectively. The dependent variables were solid waste generation and composition, and the independent variables were family size, education, income levels among others. The data obtained were subjected to statistical analysis to determine relationships between independent variables and dependent variables through correlation. The results showed that the solid waste generation and composition in Freetown was significantly affected by average family size, employment status, monthly income, and number of room(s) occupied by households. In general, the paper adequately suggests new insights concerning the role of socioeconomic factors in affecting the generation and composition of household solid waste. 展开更多
关键词 SOCIOECONOMIC factorS SOLID WASTE Generation Freetown FAMILY size
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Distribution and exploration direction of medium-and large-sized marine carbonate gas fields in Sichuan Basin, SW China 被引量:9
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作者 MA Xinhua YANG Yu +1 位作者 WEN Long LUO Bing 《Petroleum Exploration and Development》 2019年第1期1-15,共15页
Based on the analysis of the basic characteristics of medium-and large-sized marine gas fields in Sichuan Basin, combined with the division of major reservoir forming geological units in the marine craton stage and th... Based on the analysis of the basic characteristics of medium-and large-sized marine gas fields in Sichuan Basin, combined with the division of major reservoir forming geological units in the marine craton stage and their control on key hydrocarbon accumulation factors, the distribution law of medium-and large-sized marine carbonate gas fields in the basin was examined and the exploration direction was pointed out. Through the analysis of the periodic stretching-uplifting background, it is concluded that five large scale paleo-rifts, three large scale paleo-uplifts, five large scale paleo erosion surfaces were formed in the marine craton stage of Sichuan Basin, and these geological units control the key reservoir forming factors of medium and large sized gas fields:(1) Large-scale paleo-rifts control the distribution of high-quality hydrocarbon generation centers.(2) The margin of large-scale paleo-rifts, high position of paleo-uplifts and paleo erosion surfaces control the distribution of high-quality reservoirs.(3) Large-scale paleo-rifts, paleo-uplifts, paleo erosion surfaces and present tectonic setting jointly control the formation of many types of large and medium-sized traps.(4) Natural gas accumulation is controlled by the inheritance evolution of traps in large geological units. Based on the comparative analysis of the distribution characteristics of medium-and large-sized gas fields and large geological units, it is proposed that the superimposition relationship between single or multiple geological units and the present structure controls the distribution of medium-and large-sized gas fields, and the "three paleo" superimposed area is the most advantageous. According to the above rules, the main exploration fields and directions of medium-and large-sized marine carbonate gas fields in Sichuan Basin include periphery of Deyang-Anyue paleo-rift, eastern margin of Longmenshan paleo-rift, margins of Kaijiang-Liangping oceanic trough and Chengkou-western Hubei oceanic trough, the high part of the subaqueous paleo-uplifts around Central Sichuan, paleo erosion surfaces of the top boundary of Maokou Formation in eastern and southern Sichuan Basin, paleo erosion surfaces of the top boundary of the Leikoupo Formation in central and western Sichuan Basin. 展开更多
关键词 Sichuan Basin marine CARBONATES medium-and large-sized gas fields GEOLOGIC unit reservoir forming factors paleo-rifts paleo-uplifts paleo erosion surfaces
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柔性机械爪力控的变步长自适应滤波算法
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作者 包天悦 王永咏 +2 位作者 祁祥瑞 赵佳鑫 蔡存 《信息技术》 2024年第7期40-45,共6页
机械爪工作中,由于电源和机械震动会导致电流有波动,将测得的电流数据通过滤波,减少电流的波动,从而让力控的准确度更高。传统的自适应算法无法满足在快速收敛的同时,实现较高鲁棒性和较小稳态误差的要求。针对上述问题,文中提出一种新... 机械爪工作中,由于电源和机械震动会导致电流有波动,将测得的电流数据通过滤波,减少电流的波动,从而让力控的准确度更高。传统的自适应算法无法满足在快速收敛的同时,实现较高鲁棒性和较小稳态误差的要求。针对上述问题,文中提出一种新的自适应滤波算法。首先,建立基于双曲正切函数的变步长模型,实现更新步长因子的动态变值,其次,将滤波器权向量差及可变因子引入更新权值迭代算法中,以达到快速收敛和减少稳态误差的目的。通过实验证明,文中算法实现了快速收敛,并具有较小的稳态误差,提高了系统的鲁棒性。 展开更多
关键词 自适应算法 变步长 双曲正切 可变因子 柔性机械爪
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融合三维螺旋运动和混合反向学习策略的改进鹈鹕优化算法
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作者 李彦苍 李一凡 +1 位作者 王钊 王育德 《科学技术与工程》 北大核心 2024年第11期4607-4617,共11页
针对鹈鹕优化算法收敛速度较慢、初始化过程随机产生初始种群导致种群多样性差,在后期易陷入局部最优等问题,提出了一种融合三维螺旋飞行和混合反向学习策略的鹈鹕优化算法。首先使用Gauss映射初始化种群,提高种群多样性;其次利用三维... 针对鹈鹕优化算法收敛速度较慢、初始化过程随机产生初始种群导致种群多样性差,在后期易陷入局部最优等问题,提出了一种融合三维螺旋飞行和混合反向学习策略的鹈鹕优化算法。首先使用Gauss映射初始化种群,提高种群多样性;其次利用三维螺旋飞行和混合最优最差反向学习策略,加强算法跳出局部最优的能力;最后,引入自适应平衡因子与自适应步长,提出鹈鹕坠落策略,以模拟捕食过程中群体的微小变化。最后,通过12个基准函数和实际案例对IPOA(improved pelican optimization algorithm)进行测试,并与8个仿生算法进行对比,测试结果与Wilcoxon符号秩和检验结果均表明IPOA收敛精度与稳定性等各项性能都有所提升,具有明显优势。 展开更多
关键词 鹈鹕优化算法 GAUSS映射 三维螺旋运动策略 反向学习 自适应平衡因子 自适应步长
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Variations in vascular endothelial growth factor levels during ovarian superovulation and reduction of ovarian hyperstimulation incidence in young women: A prospective study 被引量:1
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作者 Eliahu Levitas M. Huleihal +3 位作者 E. Lunenfeld R. Gakman M. Friger G. Potashnik 《Open Journal of Obstetrics and Gynecology》 2013年第2期296-300,共5页
Variations in Vascular Endothelial Growth Factor (VEGF) levels were prospectively evaluated in 18 young women undergoing in vitro fertilization treatments according to the “Long Protocol” and a typical pattern of VE... Variations in Vascular Endothelial Growth Factor (VEGF) levels were prospectively evaluated in 18 young women undergoing in vitro fertilization treatments according to the “Long Protocol” and a typical pattern of VEGF levels was recorded. A significant increase in VEGF concentrations was observed only when the follicles reached a mean diameter of 15.3 mm in concurrence with mature oocyte retrieval. Since an increase in VEGF levels is related to follicular vascularity and oocyte developpment, our study supports the approach that oocyte retrieval may be performed when follicles > 15 mm in diameter appear. Anticipating egg retrieval in young patients with an optimal ovarian reserve may decrease the incidence of severe ovarian hyperstimulation, without compromising the treatment results. 展开更多
关键词 Vascular Endothelial Growth factor (VEGF) In VITRO Fertilization GONADOTROPIN Stimulation Follicle size Prevention of OVARIAN HYPERSTIMULATION
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气溶胶粒径吸湿增长因子的机器学习模型 被引量:2
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作者 米家媛 李娜 +1 位作者 佟景哲 倪长健 《中国环境科学》 EI CAS CSCD 北大核心 2024年第2期638-645,共8页
利用成都市2017年10~12月浊度计、黑碳仪和GRIMM180环境颗粒物分析仪的逐时观测数据,结合该时段同时次大气能见度(V)、相对湿度(RH)和二氧化氮(NO_(2))监测资料,基于Mie散射理论和免疫进化算法反演气溶胶粒径吸湿增长因子.首先,以RH、C_... 利用成都市2017年10~12月浊度计、黑碳仪和GRIMM180环境颗粒物分析仪的逐时观测数据,结合该时段同时次大气能见度(V)、相对湿度(RH)和二氧化氮(NO_(2))监测资料,基于Mie散射理论和免疫进化算法反演气溶胶粒径吸湿增长因子.首先,以RH、C_(BC)、C_(BC)/C_(PM1)、C_(PM1)/C_(PM2.5)以及C_(PM2.5)/C_(PM10)作为解释变量集,构建了3种气溶胶粒径吸湿增长因子的机器学习模型(XGBoost模型、CatBoost模型和LightGBM模型),对应的决定系数(R 2)分别为0.869、0.893和0.898,均方根误差(RMSE)分别为0.108、0.097和0.090,平均绝对误差(MAE)分别为0.061、0.054和0.052.通过3种模型进行测试表明,气溶胶粒径吸湿增长的机器学习模型显著降低了传统单变量气溶胶粒径吸湿增长模型在高湿条件下的模拟偏差,也提升了气溶胶粒径吸湿增长多变量GAM模型的计算精度.最后,分析了不同解释变量对机器学习模型模拟效果的影响,确认了黑碳是气溶胶吸湿增长模型的主控变量.研究进一步阐明了气溶胶粒径吸湿增长因子多因素影响的复杂性,并为其模型的科学表征提供了新途径. 展开更多
关键词 气溶胶 粒径吸湿增长因子 机器学习 解释变量集 成都
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黄河流域中小河流水质评价的比较研究 被引量:2
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作者 史陈雪 刘庆庆 +3 位作者 杨艳霞 安东妹 刘玥 祖国峰 《河南师范大学学报(自然科学版)》 CAS 北大核心 2024年第1期16-27,I0004,共13页
我国中小河流众多,流域面积覆盖了全国85%的城镇及广大农村地区,是区域生产生活用水的主要来源和污染负荷排放的接纳者.开展中小河流水质综合评价对于客观、准确地评价水环境质量状况,制订水污染防治整体规划具有重要意义.以黄河流域河... 我国中小河流众多,流域面积覆盖了全国85%的城镇及广大农村地区,是区域生产生活用水的主要来源和污染负荷排放的接纳者.开展中小河流水质综合评价对于客观、准确地评价水环境质量状况,制订水污染防治整体规划具有重要意义.以黄河流域河南省2条典型中小河流为研究对象,在识别河流水污染状况的基础上,采用单因子评价法、综合污染指数法、水质标识指数法和模糊综合评价4种方法对水质现状进行了综合评价,探讨了不同方法在中小河流水质评价中的适用性.结果表明:2条中小河流主要污染指标为NH_(3)-N、挥发酚及TP;水质标识指数法的评价结果与可靠性分析中的水质评价结果一致性最高,该方法得到的水质类别结果更加可靠. 展开更多
关键词 中小河流 单因子评价法 综合污染指数法 水质标识法 模糊综合评价
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含椭圆孔有限大二十面体准晶板平面弹性问题的边界元分析 被引量:1
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作者 王会苹 王桂霞 陈德财 《应用数学和力学》 CSCD 北大核心 2024年第4期400-415,共16页
基于扩展的Stroh方法,对含椭圆孔有限大二十面体准晶板平面弹性问题进行边界元分析.首先利用扩展的Stroh方法,研究了二十面体准晶的Green函数,得到了含椭圆孔无限大二十面体准晶平面弹性问题位移和应力的基本解.利用该基本解,通过加权... 基于扩展的Stroh方法,对含椭圆孔有限大二十面体准晶板平面弹性问题进行边界元分析.首先利用扩展的Stroh方法,研究了二十面体准晶的Green函数,得到了含椭圆孔无限大二十面体准晶平面弹性问题位移和应力的基本解.利用该基本解,通过加权余量法建立了区域内积分方程和边界积分方程,并采用线性插值函数及Gauss积分对含未知量的边界积分方程和区域内积分方程分别进行离散,得到了离散格式.进一步,对椭圆孔的孔边应力进行了数值求解,并将有限大板的数值结果与无限大板的解析解进行了对比验证,说明当板与椭圆孔尺寸之比小于某下限值时,不能用无限大板的解析解对有限大板进行分析.最后,分析了在垂向拉伸作用下,板的大小、孔口尺寸及倾斜角度对孔边应力的影响.结果表明:板的尺寸沿垂直拉伸方向变化对孔边应力的影响更明显;随着椭圆孔尺寸的增加,孔边应力集中现象越明显;若长轴垂直拉伸方向,椭圆孔倾斜会减缓孔边应力集中程度. 展开更多
关键词 二十面体准晶 Stroh方法 椭圆孔 有限尺寸 应力集中系数
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扶正化浊汤联合甲状腺片治疗对甲状腺结节大小及疗效的影响 被引量:1
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作者 韩娟 张立文 +4 位作者 宋金岭 董进 李海华 赵辉 左艳敏 《贵州医科大学学报》 CAS 2024年第3期463-468,共6页
目的探讨扶正化浊汤治疗甲状腺结节(TN)对结节大小的影响。方法TN患者106例,随机均分为观察组和对照组,对照组给予左甲状腺素钠片常规治疗,观察组在对照组基础上同时增加扶正化浊汤治疗;于治疗前、治疗3个月时,对2组患者进行中医主症评... 目的探讨扶正化浊汤治疗甲状腺结节(TN)对结节大小的影响。方法TN患者106例,随机均分为观察组和对照组,对照组给予左甲状腺素钠片常规治疗,观察组在对照组基础上同时增加扶正化浊汤治疗;于治疗前、治疗3个月时,对2组患者进行中医主症评分,采用彩色多普勒超声仪记录2组患者结节数目、最大直径、结节体积、血流阻力指数(RI)及搏动指数(PI),同时采集患者外周静脉血4 mL,检测促甲状腺激素(TSH)、游离三碘甲状腺原氨酸(FT3)、游离四碘甲腺原氨酸(FT4)及血管内皮生长因子(VEGF)水平,治疗3个月后评估2组患者的西医疗效,记录2组治疗期间恶心、呕吐、皮疹及口干等不良反应发生情况。结果治疗后3个月,2组中医主症评分均较治疗前下降,且观察组低于对照组(P<0.05);与对照组比较,2组TN患者治疗3个月后结节数目减少、结节最大直径和结节体积均降低,且观察组低于对照组,差异有统计学意义(P<0.05);治疗后3个月,观察组TSH低于对照组,FT 3、FT 4高于对照组(P<0.05);治疗3个月后,观察组VEGF、RI、PI低于对照组(P<0.05);观察组西医疗效和中医证候疗效中的临床痊愈和总有效率均高于对照组,差异有统计学意义(P<0.05);比较观察组与对照组不良反应发生率比较,差异无统计学意义(P>0.05)。结论扶正化浊汤治疗TN疗效显著,可有效减轻患者症状,减小结节数目及大小,调节甲状腺功能,改善血流状况,降低VEGF表达,且安全性高。 展开更多
关键词 甲状腺结节 扶正化浊汤 疗效 结节大小 甲状腺功能 血管内皮生长因子水平
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