期刊文献+
共找到80,703篇文章
< 1 2 250 >
每页显示 20 50 100
Improvements in methodology to determine feedback reactivity coefficients 预览
1
作者 Faisal Qayyum Muhammad Rizwan Ali +1 位作者 Awais Zahur R. Khan 《核技术:英文版》 SCIE CAS CSCD 2019年第4期91-104,共14页
The reactivity of a nuclear reactor is the most important safety and operating parameter. Due to short reactor period, the Light Water Reactor (LWR) designs require the compensations of rapid unfavorable reactivity in... The reactivity of a nuclear reactor is the most important safety and operating parameter. Due to short reactor period, the Light Water Reactor (LWR) designs require the compensations of rapid unfavorable reactivity increases. The increase in fuel or moderator temperature leads to compensate the reactivity jumps as inherent safety characteristics. The safe and reliable reactor operation requires the accurate assessment of these reactivity changes. This paper highlights the improvements in the methodology to determine the feedback reactivity changes in IAEA MTR benchmark. This method incorporates the reactivity effects of fuel temperature in moderator regions and vice versa. For this purpose, a detailed 3D model of the IAEA 10 MW MTR benchmark reactor is developed employing OpenMC computer code. OpenMC is a probabilistic computer code for neutronic calculations. This work uses temperature-dependent JEFF 3.2 cross-sectional library. The model is validated against the reference results of eigenvalues for control rods (inserted and in fully withdrawn position), control rod reactivity worth, averaged thermal flux in the central flux trap, and power fraction for each fuel element at beginning of life. The validated model is applied to simulate the feedback reactivity coefficients against the conventional reference results. In order to improve the methodology, the effect of the moderator temperature and void on fuel is incorporated to obtain a more realistic value of the fuel temperature coefficient.Similarly, the moderator temperature coefficient and void coefficient are improved by incorporating the coupling effects of fuel temperature on moderator. This methodology can be applied to improve the LWR designs. 展开更多
关键词 OpenMC MTR benchmark REACTIVITY FEEDBACK coefficients Fuel TEMPERATURE COEFFICIENT MODERATOR TEMPERATURE COEFFICIENT Void COEFFICIENT of REACTIVITY
在线阅读 下载PDF
采用有限差分方法模拟穿孔式防波堤规则波中水动力性能研究 预览
2
作者 Javad Mohammadbagheri Fouad Salimi Maryam Rahbani 《船舶与海洋工程学报:英文版》 CSCD 2019年第3期314-324,共11页
Using a discretized finite difference method, a numerical model was developed to study the interaction of regular waves with a perforated breakwater. Considering a non-viscous, non-rotational fluid, the governing equa... Using a discretized finite difference method, a numerical model was developed to study the interaction of regular waves with a perforated breakwater. Considering a non-viscous, non-rotational fluid, the governing equations of Laplacian velocity potential were developed, and specific conditions for every single boundary were defined. The final developed model was evaluated based on an existing experimental result. The evaluated model was used to simulate the condition for various wave periods from 0.6 to 2 s. The reflection coefficient and transmission coefficient of waves were examined with different breakwater porosities, wave steepnesses, and angular frequencies. The results show that the developed model can suitably present the effect of the structural and hydraulic parameters on the reflection and transmission coefficients. It was also found that with the increase in wave steepness, the reflection coefficient increased logarithmically, while the transmission coefficient decreased logarithmically. 展开更多
关键词 Perforated BREAKWATER Transmission COEFFICIENT Reflection COEFFICIENT Numerical model Finite difference method REGULAR WAVES
在线阅读 下载PDF
On Boeing 737– 300 Wing Aerodynamics Calculations Based on VLM Theory 预览
3
作者 Jacob Nagler 《机电工程前沿》 2019年第1期94-100,共7页
In this paper,aerodynamics coefficients of Boeing 737-300 are calculated using VLM(vortex lattice method)theory.The wing was divided into N panels of the size:6X6.The wing was assumed to be planar and the panels are i... In this paper,aerodynamics coefficients of Boeing 737-300 are calculated using VLM(vortex lattice method)theory.The wing was divided into N panels of the size:6X6.The wing was assumed to be planar and the panels are in the trapezoid shape.Aerodynamics lifting and moment coefficients were calculated.Also,center of pressure location was found using data from VLM and wing geometry.Comparisons between literature,finite wing theory and VLM theory were done.It was found that maximum lifting coefficient error between literature and VLM is about 4.0%.Moreover,the maximum lifting coefficient error between finite wing theory and VLM is about 2.2%.Center of pressure location error between finite wing theory and VLM is about 0.5%. 展开更多
关键词 VLM FINITE WING Theory LIFTING COEFFICIENT MOMENT COEFFICIENT Center of Pressure
在线阅读 下载PDF
浅谈室内固结法计算地基基床系数 预览
4
作者 刘盖 沈亚兰 汤娜娜 《价值工程》 2019年第23期171-172,共2页
基床系数是地质勘查的重要参数。本文引用已有的基床系数的研究成果的取值现状的计算值与规范给出的经验值做对比,经过试验分析研究,对室内固结试验方法基床系数的取值相关问题进行对比,以供同仁参考。
关键词 室内固结法 地基 基床 计算 系数
在线阅读 下载PDF
Concentration and Characterization of Colored Dissolved Organic Matter in the Surface Microlayer and Subsurface Water of the Yellow Sea and the East China Sea 预览
5
作者 ZHANG Jing ZHAO Junjie +1 位作者 YANG Guipeng LIU Weifeng 《中国海洋大学学报:英文版》 SCIE CAS CSCD 2019年第2期383-393,共11页
The distribution and chemical properties of colored dissolved organic matter(CDOM)in the Yellow Sea and the East China Sea during December 2011-January 2012 were investigated.The input of freshwater and biological act... The distribution and chemical properties of colored dissolved organic matter(CDOM)in the Yellow Sea and the East China Sea during December 2011-January 2012 were investigated.The input of freshwater and biological activities had an evident influence on the CDOM levels(characterized by the light absorption coefficient at the wavelength of 355 nm a355)in the study area.The spatial distribution of CDOM levels displayed a gradually decreasing trend from the coastal waters(0.37m^-1)to the open sea(0.18m^-1).The spectral slope ratio(the slope ratio SR defined as S275-295:S350-400)during the cruise was correlated with salinity,and exhibited a large variation from inshore(average of 2.515)to offshore sites(average of 5.327)compared with the distribution of a355.The values of SR were related to CDOM molecular weight(MW).The a355,SR,and chlorophyll a in 37 samples collected from the surface microlayer were significantly correlated with those in the corresponding subsurface water samples,implying a strong exchange action between the microlayer and bulk water.The a355 and SR of CDOM exhibited significant microlayer enrichment,with mean enrichment factors(EFs)of 1.72 and 1.62,respectively. 展开更多
关键词 COLORED dissolved organic matter(CDOM) absorption coefficient spectral SLOPE ratio YELLOW SEA East China SEA
在线阅读 下载PDF
Experimental study on the velocity-dependent dispersion of the solute transport in different porous media 预览
6
作者 YAN Xiao-san QIAN Jia-zhong MA Lei 《地下水科学与工程:英文版》 2019年第2期106-114,共9页
The hydrodynamic dispersion is an important factor influencing the reactive solute transport in the porous media, and many previous studies assumed that it linearly varied with the average velocity of the groundwater ... The hydrodynamic dispersion is an important factor influencing the reactive solute transport in the porous media, and many previous studies assumed that it linearly varied with the average velocity of the groundwater flow. Actually, such linear relationship has been challenged by more and more experimental observations, even in homogeneous media. In this study, we aim to investigate the relationship between hydrodynamics dispersion and the flow velocity in different types of porous media through a laboratory-controlled experiment. The results indicate that (1) the dispersion coefficient should not be a linear function of the flow velocity when the relationship between the flow velocity and the hydraulic gradient can be described by Darcy's law satisfactorily;(2) Power function works well in describing the dispersion coefficient changing with the flow velocity for different types of porous media, and the power value is between 1.0-2.0 for different particle sizes. 展开更多
关键词 SOLUTE transport POROUS media Flow VELOCITY DISPERSION COEFFICIENT
在线阅读 下载PDF
Fekete-Szego Inequality for a Subclass of Bi-univalent Functions Associated with Hohlov Operator and Quasi-subordination 预览
7
作者 Guo Dong Tang Huo +1 位作者 Ao En Xiong Liang-peng 《数学研究通讯:英文版》 CSCD 2019年第3期235-246,共12页
In this paper, we introduce a new subclass of bi-univalent functions defined by quasi-subordination and Hohlov operator and obtain the coefficient estimates and Fekete-Szego inequality for function in this new subclas... In this paper, we introduce a new subclass of bi-univalent functions defined by quasi-subordination and Hohlov operator and obtain the coefficient estimates and Fekete-Szego inequality for function in this new subclass. The results presented in this paper improve or generalize the recent works of other authors. 展开更多
关键词 analytic FUNCTION UNIVALENT FUNCTION bi-univalent FUNCTION coefficient estimate FEKETE-SZEGO INEQUALITY Hohlov operator quasi-subordination
在线阅读 下载PDF
Actual evapotranspiration of subalpine meadows in the Qilian Mountains,Northwest China
8
作者 GAO Yunfei ZHAO Chuanyan +6 位作者 Muhammad W ASHIQ WANG Qingtao RONG Zhanlei LIU Junjie MAO Yahua GUO Zhaoxia WANG Wenbin 《干旱区科学:英文版》 SCIE CSCD 2019年第3期371-384,共14页
As a main component in water balance,evapotranspiration(ET)is of great importance for water saving,especially in arid and semi-arid areas.In this study,the FAO(Food and Agriculture Organization)Penman-Monteith model w... As a main component in water balance,evapotranspiration(ET)is of great importance for water saving,especially in arid and semi-arid areas.In this study,the FAO(Food and Agriculture Organization)Penman-Monteith model was used to estimate the magnitude and temporal dynamics of reference evapotranspiration(ET0)in 2014 in subalpine meadows of the Qilian Mountains,Northwest China.Meanwhile,actual ET(ETc)was also investigated by the eddy covariance(EC)system.Results indicated that ETc estimated by the EC System was 583 mm,lower than ET0(923 mm)estimated by the FAO Penman-Monteith model in 2014.Moreover,ET0 began to increase in March and reached the peak value in August and then declined in September,however,ETc began to increase from April and reached the peak value in July,and then declined in August.Total ETc and ET0 values during the growing season(from May to September)were 441 and 666 mm,respectively,which accounted for 75.73%of annual cumulative ETc and 72.34%of annual cumulative ET0,respectively.A crop coefficient(kc)was also estimated for calculating the ETc,and average value of kc during the growing season was 0.81(ranging from 0.45 to 1.16).Air temperature(Ta),wind speed(u),net radiation(Rn)and soil temperature(Ts)at the depth of 5 cm and aboveground biomass were critical factors for affecting kc,furthermore,a daily empirical kc equation including these main driving factors was developed.Our result demonstrated that the ETc value estimated by the data of kc and ET0 was validated and consistent with the growing season data in 2015 and 2016. 展开更多
关键词 actual EVAPOTRANSPIRATION reference EVAPOTRANSPIRATION CROP coefficient METEOROLOGICAL FACTORS biotic FACTORS
Causes of geothermal fields and characteristics of ground temperature fields in China 预览
9
作者 MAO Xiao-ping LI Ke-wen WANG Xin-wei 《地下水科学与工程:英文版》 2019年第1期15-28,共14页
There are many arguments on energy sources and main controlling factors of geothermal fields, so a systematic study on the distribution of ground temperature fields shall be necessary. In this paper the thermal conduc... There are many arguments on energy sources and main controlling factors of geothermal fields, so a systematic study on the distribution of ground temperature fields shall be necessary. In this paper the thermal conduction forward method of geothermal field is used to simulate cooling rate of abnormal heat sources and heat transfer of the paleo-uplift model. Combined with a large number of geothermal field exploration cases and oil exploration well temperature curves of domestic and foreign, the following conclusions are drawn:(1) According to the magmatic activity time, the magmatism activities are divided into two categories: Magma active areas (activity time < 500 000 years) and weak/magma inactive areas (activity time > 500 000 years). The latter has a fast cooling rate (the cooling time of the magma pocket buried around 10 km is less than 200 000 years) after it has intruded into the shallow layer and it has no direct contribution to modern geothermal fields;(2) China belongs to a weak/magma inactive area such as Tengchong region and Qinghai-Tibet region because the chronological data of these regions show that its magma activity time is more than 500 000 years;(3) The temperature of most geothermal fields can be obviously divided into three segments in the vertical direction: A high geothermal gradient segment (Segment H) at the surface, then a low geothermal gradient segment (Segment L) at a secondary depth, and finally a lower temperature segment (Segment D) at a deeper depth. The temperature isoline presents a mirror reflection relation on the temperature profile, indicating that geothermal field is dominated by heat conduction, rather than having an abnormally high temperature “heat source” to provide heat;(4) Near-surface (0-5 km) materials’ lateral heterogeneity caused by tectonic movement shall probably be the main controlling factor of ground temperature fields. 展开更多
关键词 Ground temperature FIELD BASEMENT HEAT flow GEOTHERMAL FIELD MAGMA pocket Coefficient of HEAT conduction Palaeouplifth MAGNETOTELLURIC
在线阅读 下载PDF
不同蔗糖溶液浓度对表面张力影响的实验研究 预览
10
作者 段晓丽 《山西大同大学学报:自然科学版》 2019年第2期13-14,73共3页
利用拉脱法测定了不同浓度的红糖溶液和白糖溶液表面张力系数,结果表明两种溶液的表面张力系数与纯水相比要低,同一浓度下表面张力系数不同。
关键词 表面张力 系数 拉脱法 蔗糖 浓度
在线阅读 免费下载
Influence of alumina/MWCNT hybrid nanoparticle additives on tribological properties of lubricants in turning operations
11
作者 Anuj Kumar SHARMA Jitendra Kumar KATIYAR +1 位作者 Shubrajit BHAUMIK Sandipan ROY 《摩擦(英文版)》 CSCD 2019年第2期153-168,共16页
A hybrid lubricant with improved thermal and tribological properties was developed by blending multiwalled carbon nanotubes(MWCNTs) with alumina-based nanoparticles into cutting fluid at fixed volumetric proportions(1... A hybrid lubricant with improved thermal and tribological properties was developed by blending multiwalled carbon nanotubes(MWCNTs) with alumina-based nanoparticles into cutting fluid at fixed volumetric proportions(10:90).The hybrid cutting fluid was prepared in different volumetric concentrations(0.25,0.75,and 1.25 vol%),and the tribological properties and contact angles were measured using pin-on-disc tribometry and goniometry,respectively.The study showed a reduction in wear and friction coefficient with increasing nanoparticle concentration.The cutting fluid performance was investigated using minimum quantity lubrication(MQL) in the turning of AISI 304 stainless steel.Regression models were developed for measuring the temperature and tool flank wear in terms of cutting speed,feed,depth of the cut,and nanoparticle concentration using response surface methodology.The developed hybrid nanolubricants significantly reduced the tool flank wear and nodal temperature by 11% and 27.36%,respectively,as compared to alumina-based lubricants. 展开更多
关键词 HYBRIDS nanolubricants MQL MWCNT tool wear friction coefficient
Influence of Fiber Types on Strengthening Effect and Variability of Compressive Strength and Flexural Toughness of Concrete 预览
12
作者 Xuehai Yang 《智能建筑研究》 2019年第1期73-89,共17页
In order to study the influence of steel fiber, polypropylene fiber and cellulose fiber on the compressive strength and flexural toughness of mixed concrete, the compressive strength and flexural toughness of concrete... In order to study the influence of steel fiber, polypropylene fiber and cellulose fiber on the compressive strength and flexural toughness of mixed concrete, the compressive strength and flexural toughness of concrete blocks were tested under different volume contents, and the results of the tests were analyzed by variation. The test results show that the compressive strength of three kinds of fiber concrete is increased by 26.5% on average compared with plain concrete. 7%、 6.1% and 11.1%;the retention rate of secondary compressive strength reached 77. 9% respectively. 0%、45.7% and 58.0%;the maximum bending bearing capacity was increased by31.6%、3.5% and 14.0%;the bending toughness index I20, the new Kumar index pcsm and the toughness ratio rx calculated based on the load-deflection curve, the new Kumar method and the bending-tension strain curve respectively are 4.2、3.1、2. Six times, 19.9、9.8、6. Nine times and four times. 0、3.4、2. Seven times. Variability analysis results show that the variability of compressive strength of concrete mixed with fiber is less than flexural toughness. At the same time, the bending toughness index variation coefficient calculated based on the New Kumar method and the stress-strain curve method is smaller than the bending line method under load. Overall, the compressive strength and flexural toughness of steel fiber reinforced concrete are the most significant, and the number of variation systems is the smallest. The compressive strength of fiber-reinforced concrete and the flexural toughness of polypropylene fiber reinforced concrete are relatively significant. 展开更多
关键词 Fiber CONCRETE Retention rate of secondary compressive strength Curved LINE of DEFLECTION under load The bending tension should be changed to curve LINE FLEXURAL TOUGHNESS Coefficient of variation
在线阅读 下载PDF
Alteration of functional connectivity in patients with Alzheimer’s disease revealed by resting-state functional magnetic resonance imaging 预览
13
作者 Jie Zhao Yu-Hang Du +2 位作者 Xue-Tong Ding Xue-Hu Wang Guo-Zun Men 《中国神经再生研究:英文版》 SCIE CAS CSCD 2020年第2期285-292,共8页
The main symptom of patients with Alzheimer’s disease is cognitive dysfunction. Alzheimer’s disease is mainly diagnosed based on changes in brain structure. Functional connectivity reflects the synchrony of function... The main symptom of patients with Alzheimer’s disease is cognitive dysfunction. Alzheimer’s disease is mainly diagnosed based on changes in brain structure. Functional connectivity reflects the synchrony of functional activities between non-adjacent brain regions, and changes in functional connectivity appear earlier than those in brain structure. In this study, we detected resting-state functional connectivity changes in patients with Alzheimer’s disease to provide reference evidence for disease prediction. Functional magnetic resonance imaging data from patients with Alzheimer’s disease were used to show whether particular white and gray matter areas had certain functional connectivity patterns and if these patterns changed with disease severity. In nine white and corresponding gray matter regions, correlations of normal cognition, early mild cognitive impairment, and late mild cognitive impairment with blood oxygen level-dependent signal time series were detected. Average correlation coefficient analysis indicated functional connectivity patterns between white and gray matter in the resting state of patients with Alzheimer’s disease. Functional connectivity pattern variation correlated with disease severity, with some regions having relatively strong or weak correlations. We found that the correlation coefficients of five regions were 0.3–0.5 in patients with normal cognition and 0–0.2 in those developing Alzheimer’s disease. Moreover, in the other four regions, the range increased to 0.45–0.7 with increasing cognitive impairment. In some white and gray matter areas, there were specific connectivity patterns. Changes in regional white and gray matter connectivity patterns may be used to predict Alzheimer’s disease;however, detailed information on specific connectivity patterns is needed. All study data were obtained from the Alzheimer’s Disease Neuroimaging Initiative Library of the Image and Data Archive Database. 展开更多
关键词 Alzheimer's disease blood oxygen level-dependent signal correlation coefficient FUNCTIONAL connectivity pattern FUNCTIONAL magnetic resonance imaging gray MATTER RESTING state white MATTER
在线阅读 下载PDF
Friction predication on pin-to-plate interface of PTFE material and steel
14
作者 Zhuming BI Donald W.MUELLER 《摩擦(英文版)》 CSCD 2019年第3期268-281,共14页
In this paper,the friction behavior at a pin-to-plate interface is investigated.The pin and plate are made of Polytetrafluoroethylene(PTFE) and steel,respectively,and there is a reciprocating motion at the interface.G... In this paper,the friction behavior at a pin-to-plate interface is investigated.The pin and plate are made of Polytetrafluoroethylene(PTFE) and steel,respectively,and there is a reciprocating motion at the interface.Governing mathematical models for the relations of design variables and frictions are investigated,and a general procedure is proposed to solve the developed models and predict the friction forces at the interface subjected to given test conditions.Novel models have been developed to represent intrigued friction behaviors affected by various factors such as pin geometrics and finishes,lubrication conditions,and reciprocating speed.The test data from experiments is used to verify the effectiveness of the proposed models. 展开更多
关键词 pin-to-plate FRICTION wear coefficient of FRICTIONS PTFE sealing finite element analysis
基于区域划分方法的中国人口分布格局及变化研究——从1953年到2010年
15
作者 刘翠玲 许亚平 王法辉 《地理学报:英文版》 SCIE CSCD 2019年第11期1908-1922,共15页
This study uses six censuses (1953,1964,1982,1990,2000,and 2010) at the county level since the foundation of the People’s Republic of China to examine the changes of population density pattern in mainland China over ... This study uses six censuses (1953,1964,1982,1990,2000,and 2010) at the county level since the foundation of the People’s Republic of China to examine the changes of population density pattern in mainland China over time.Based on the Gini coefficient,the change of disparity in population density followed a “U-shaped” trend,i.e.,decreasing during 1953–1982 and increasing during 1982–2010.The shrinking disparity in the pre-reform periods was largely attributable to various ill-conceived political movements,and the enlarging gap in population growth rates in the post-reform era reflected a natural outcome of urbanization,which will continue in the foreseeable future.In addition,this research employs a GIS-automated regionalization method,REDCAP,to uncover a natural demarcation line like the classic “Hu Line” that divides China into two regions of similar area sizes but a strong contrast in population.The results show that the regionalization-derived lines were largely consistent with the Hu Line over time.Therefore,the disparity between the high-density southeast and low-density northwest regions is likely due to differing physical environments that form a natural barrier.Any public policy to overcome this barrier at a large scale is destined to be a vain attempt. 展开更多
关键词 regional population distribution TEMPORAL change DISPARITY GINI COEFFICIENT REGIONALIZATION GIS HU Line China
Extinction coefficients of surface atmospheric aerosol above LHAASO
16
作者 皮文萱 黄敏 +5 位作者 祝凤荣 何钰 谢宁 张勇 陈起辉 贾焕玉 《中国物理C:英文版》 SCIE CAS CSCD 2019年第8期117-123,共7页
We investigate the extinction coefficients of the surface atmospheric aerosol over the Large High Altitude Air Shower Observatory (LHAASO), located at the Haizi Mountain, Daocheng County, China. To this end, we utiliz... We investigate the extinction coefficients of the surface atmospheric aerosol over the Large High Altitude Air Shower Observatory (LHAASO), located at the Haizi Mountain, Daocheng County, China. To this end, we utilize the Longtin model, Mie scattering theory, and experimental data obtained by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). Our theoretical calculations show that the total extinction coefficients of the atmospheric aerosol at the wavelength of 200–500 nm are inversely proportional to the laser wavelength, and influenced by the wind speed. From July 2015 to October 2016, the extinction coefficient of the surface atmospheric aerosols at 532 nm wavelength reached 0.04 km^-1 with no wind, while it increased to 0.1 km^-1 with gusts. In this period, the extinction coefficients of the surface atmospheric aerosol at 532 nm wavelength, obtained by the CALIPSO, change from 0.01 to 0.07 km^-1, which is less than the values obtained the theoretical calculation and larger than the average of Tibetan Plateau in 2006-2016. These calculations and experimental evidence provide important arguments to the model of atmospheric aerosol to be applied in the calibration of LHAASO. Our results suggest that the extinction coefficients over LHAASO require further study, including research on the size distribution, shape, concentration of aerosols particles, wind dependence, relative humidity dependence, etc. 展开更多
关键词 LHAASO EXTINCTION COEFFICIENT ATMOSPHERIC AEROSOL
Consistency check of degradation mechanism between natural storage and enhancement test for missile servo system 预览
17
作者 Wang Xu Sun Quan 《系统工程与电子技术:英文版》 SCIE EI CSCD 2019年第2期415-424,共10页
Reliability enhancement testing(RET) is an accelerated testing which hastens the performance degradation process to surface its inherent defects of design and manufacture. It is an important hypothesis that the degrad... Reliability enhancement testing(RET) is an accelerated testing which hastens the performance degradation process to surface its inherent defects of design and manufacture. It is an important hypothesis that the degradation mechanism of the RET is the same as the one of the normal stress condition. In order to check the consistency of two mechanisms, we conduct two enhancement tests with a missile servo system as an object of the study, and preprocess two sets of test data to establish the accelerated degradation models regarding the temperature change rate that is assumed to be the main applied stress of the servo system during the natural storage. Based on the accelerated degradation models and natural storage profile of the servo system, we provide and demonstrate a procedure to check the consistency of two mechanisms by checking the correlation and difference of two sets of degradation data. The results indicate that the two degradation mechanisms are significantly consistent with each other. 展开更多
关键词 reliability ENHANCEMENT testing (RET) degradation model ACCELERATED equation CONSISTENCY CHECK Pearson correlation coefficient
在线阅读 下载PDF
Main Regulations of CAPM Model and Its Modern Modification 预览
18
作者 Lamara Qoqiauri Nino Qoqiauri 《管理研究:英文版》 2019年第1期15-32,共18页
The article gives readers the main regulations of elaboration of capital actives evaluating model(CAPM)theory,topics of its practical usage,common ways of definition of investments(securities)optimal portfolio and on ... The article gives readers the main regulations of elaboration of capital actives evaluating model(CAPM)theory,topics of its practical usage,common ways of definition of investments(securities)optimal portfolio and on the basis of CAPM theory it is discussed evaluating methods of investing business,and it is highlighted two criteria of portfolio chosen by an investor—profit and risk.Besides,it is discussed modern modification of the mentioned model on the point of time horizon,a problem of time factor measurement while evaluating risk and profit,also evaluation of investing effectivity by using sharp coefficient.The work presents and evaluates possible income of securities and possibilities of risks in a modern way,which is characteristic only for CAPM model and it is considered to be its positive side. 展开更多
关键词 SECURITIES risk INCOME CAPM model stock MARKET bond MARKET optimal PORTFOLIO investments market sharp coefficient
在线阅读 下载PDF
Photon attenuation parameters for some tissues from Geant4 simulation, theoretical calculations and experimental data: a comparative study 预览
19
作者 Halil Arslan 《核技术:英文版》 SCIE CAS CSCD 2019年第6期78-87,共10页
Mass attenuation coefficients, effective atomic numbers, effective electron densities and Kerma relative to air for adipose, muscle and bone tissues have been investigated in the photon energy region from 20 keV up to... Mass attenuation coefficients, effective atomic numbers, effective electron densities and Kerma relative to air for adipose, muscle and bone tissues have been investigated in the photon energy region from 20 keV up to 50 MeV with Geant4 simulation package and theoretical calculations. Based on Geant4 results of the mass attenuation coefficients, the effective atomic numbers for the tissue models have been calculated. The calculation results have been compared with the values of the Auto-Zeff program and with other studies available in the literature. Moreover, Kerma of studied tissues relative to air has been determined and found to be dependent on the absorption edges of the tissue constituent elements. 展开更多
关键词 ATTENUATION COEFFICIENT Effective ATOMIC number GEANT4 SIMULATION Tissue model
在线阅读 下载PDF
Spreading fully at the ice-water interface is required for high ice recrystallization inhibition activity
20
作者 Shenglin Jin Lingkang Yin +7 位作者 Bin Kong Shuwang Wu Zhiyuan He Han Xue Zhang Liu Qi Cheng Xin Zhou Jianjun Wang 《中国科学:化学英文版》 SCIE EI CAS CSCD 2019年第7期909-915,共7页
Although materials for ice recrystallization inhibition(IRI) are essential for the cryopreservation of cells and tissues, there exists no guiding mechanism for the design of such materials. Therefore, the construction... Although materials for ice recrystallization inhibition(IRI) are essential for the cryopreservation of cells and tissues, there exists no guiding mechanism for the design of such materials. Therefore, the construction of materials for IRI relies on the try-and-error strategy. Herein, through changing the tacticity of hydroxyl groups on poly(vinyl alcohol)(PVA) backbones with the affinities of PVAs to ice unchanged, we experimentally find IRI activity decreases significantly for isotactic PVA in comparison to that of atactic PVA. Molecular dynamics simulation shows atactic PVA spreads fully at the ice-water interface due to its much stronger interaction with water. This indicates atactic PVA can cover more ice surface and possess a higher IRI activity when the same amount of PVAs are used, which is consistent with the results that PVA can cover the same amount of ice surface more efficiently through experimentally measuring the adsorption of PVAs on the ice surface. A guiding mechanism of high active IRI materials can be obtained: only having affinity to ice is not enough to obtain high IRI activity(i.e., only small amount of materials is required to reduce the size of ice crystals to ca.(35±10)μm), IRI agents must also have high affinity to water, i.e., low interfacial energies, to both ice and water. The former is to guarantee the adsorption of the IRI agent on the ice surface, and the latter is required for the IRI agent to spread sufficiently at the ice-water interface. Therefore, each IRI molecule can effectively block the diffusion of water onto the ice surface, and consequently inhibits the growth of ice. A spreading coefficient of IRI agents is therefore introduced to quantitatively assess the capability of IRI agents to spread at the ice-water interface. 展开更多
关键词 TACTICITY poly(vinyl alcohol) cryopreservative agents SPREADING coefficient INTERFACIAL energy
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈