期刊文献+
共找到9,057篇文章
< 1 2 250 >
每页显示 20 50 100
Antimalarial activities of butanol and ethylacetate fractions of Combretum nigricans leaf
1
作者 Enegide Chinedu Peter A.Akah +3 位作者 Dabum L.Jacob Ifeoma A.Onah Chimere Y.Ukegbu Chukwuma K.Chukwuemeka 《亚太热带生物医学杂志:英文版》 CAS 2019年第4期176-180,共5页
Objective: To evaluate the antimalarial activity of the ethylacetate and butanol fractions of Combretum nigricans(C. nigricans) leaf extract in mice. Methods: C. nigricans solvent(butanol and ethylacetate) fractions w... Objective: To evaluate the antimalarial activity of the ethylacetate and butanol fractions of Combretum nigricans(C. nigricans) leaf extract in mice. Methods: C. nigricans solvent(butanol and ethylacetate) fractions were screened for their phytochemical constituents using standard procedures illustrated by Harborne and Evans. The Peters’ 4-day suppressive test against early malaria infection, Rane’s curative test against established malaria and prophylactic test for residual activity were employed for evaluating the antimalarial potential in mice. Results: The phytochemical screening revealed the presence of alkaloids, terpenoids, saponins, and flavonoids in both fractions at different intensity. Both fractions exhibited significant antimalarial activity in all test models(P<0.05). The ethylacetate fraction of C. nigricans had better chemosuppressive and curative effects compared to the butanol fraction, which however, elicited a better chemoprophylactic effect. The chemosuppressive effect of C. nigricans ethylacetate fraction(200-800 mg/kg) was 77.6%, 69.1% and 86.1%;curative effect was 62.3%, 71.3% and 72.4%;while the chemoprophylactic activity was 32.1%, 48.6% and 61.2% respectively. C. nigricans butanol fraction(200-800 mg/kg) had 40.3%, 54.1% and 69.1% chemosuppression;26.2%, 36.9% and 34.5% curative effect;and 48.4%, 70.0% and 87.4% chemoprophylaxis. Conclusions: Both solvent fractions of C. nigricans possess antimalarial activity, and may be useful at different stages of malaria therapy. 展开更多
关键词 ANTIMALARIAL COMBRETUM nigricans BUTANOL FRACTION Ethylacetate FRACTION In vivo
核桃蛋白组分的营养价值、功能特性及抗氧化性研究 预览
2
作者 韩海涛 宴正明 +3 位作者 张润光 戚登斐 杨涛 张有林 《中国油脂》 CAS CSCD 北大核心 2019年第4期29-34,共6页
以'清香'核桃为原料,经液压榨油机冷榨取油后得到核桃饼,将其粉碎,再用石油醚对核桃饼进行脱脂处理得到脱脂核桃粕,从中提取清蛋白、球蛋白、醇溶蛋白、谷蛋白-1、谷蛋白-2 5种蛋白质,并测定5种蛋白质的营养价值、功能特性及抗... 以'清香'核桃为原料,经液压榨油机冷榨取油后得到核桃饼,将其粉碎,再用石油醚对核桃饼进行脱脂处理得到脱脂核桃粕,从中提取清蛋白、球蛋白、醇溶蛋白、谷蛋白-1、谷蛋白-2 5种蛋白质,并测定5种蛋白质的营养价值、功能特性及抗氧化性。结果表明:5种蛋白质氨基酸组成中,谷氨酸含量最高,精氨酸次之,5种蛋白质均具有良好的乳化性、乳化稳定性;谷蛋白-1必需氨基酸含量最高,占37. 14%,谷蛋白-2的乳化性、起泡性和泡沫稳定性最佳,分别为278. 66 m2/g、50. 03%、60. 01%;球蛋白乳化稳定性最高,为75. 27%;清蛋白对DPPH自由基清除能力最高,清除率为97. 15%。 展开更多
关键词 核桃蛋白 组分 营养价值 功能特性 抗氧化性
在线阅读 下载PDF
Experimental determination of distributions of soot particle diameter and number density by emission and scattering techniques
3
作者 柳华蔚 郑树 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第1期400-405,共6页
A diagnostics method was presented that uses emission and scattering techniques to simultaneously determine the distributions of soot particle diameter and number density in hydrocarbon flames. Two manta G-504 C camer... A diagnostics method was presented that uses emission and scattering techniques to simultaneously determine the distributions of soot particle diameter and number density in hydrocarbon flames. Two manta G-504 C cameras were utilized for the scattering measurement, with consideration of the attenuation effect in the flames according to corresponding absorption coefficients. Distributions of soot particle diameter and number density were simultaneously determined using the measured scattering coefficients and absorption coefficients under multiple wavelengths already measured with a SOC701 V hyper-spectral imaging device, according to the Mie scattering theory. A flame was produced using an axisymmetric laminar diffusion flame burner with 194 mL/min ethylene and 284 L/min air, and distributions of particle diameter and number density for the flame were presented. Consequently, the distributions of soot volume fraction were calculated using these two parameters as well, which were in good agreement with the results calculated according to the Rayleigh approximation,demonstrating that the proposed diagnostic method is capable of simultaneous determination of the distributions of soot particle diameter and number density. 展开更多
关键词 SOOT PARTICLE DIAMETER SOOT PARTICLE NUMBER density SOOT volume FRACTION SCATTERING measurement
Neodymium-catalyzed Polymerization of C5 Fraction:Efficient Synthesis of 1,3-Pentadiene-isoprene Copolymer Rubbers
4
作者 Jin-Yan Hou Fang Guo +2 位作者 Qian Hu Yang Li Zhao-Min Hou 《高分子科学:英文版》 SCIE CAS CSCD 2019年第7期674-680,共7页
The polymerization of C5 fraction without separation and concentration by using a commercial available Nd(P204)3/ AliBu3/AlEt2Cl has afforded for the first time a new kind of 1,3-pentadiene-isoprene random copolymers ... The polymerization of C5 fraction without separation and concentration by using a commercial available Nd(P204)3/ AliBu3/AlEt2Cl has afforded for the first time a new kind of 1,3-pentadiene-isoprene random copolymers as rubber materials. Isoprene (IP) and E-1,3-pentadiene (EPD) acted as polymerization monomers, cyclopentadiene acted as poison, and other substances like alkanes, monoolefins, Z-1,3-pentadiene acted as solvents in this multicomponent C5 fraction polymerization system. The data of kinetic experiments, NMR, and DSC indicated that the polymerization of C5 fraction by Nd(P204)3/AliBu3/AlEt2Cl afforded the IP-EPD random copolymers. By controlling polymerization conditions such as [Al]/[Nd]/[Cl] molar ratio and polymerization temperature, the random EPD-IP copolymers containing high cis-1,4-poly(IP)(with selectivity 96%) and moderate cis-1,4-poly(EPD)(with selectivity 60%) units with a low glass transition temperature (about 60 ℃), controllable molecular weight (Mn = 3.8 × 10^4-14.3 × 104), and moderate molecular weight distribution (Mw/Mn = 2.17-2.78) were obtained in a high yield. 展开更多
关键词 C5 FRACTION NEODYMIUM ISOPRENE 1 3-Pentadiene COPOLYMERIZATION
Modeling and Software Development of the Interfacial Transition Zone of Ellipsoidal Aggregate in Cement-Based Composites
5
作者 张建建 ZHANG Lijuan +1 位作者 孙国文 WANG Caihui 《武汉理工大学学报:材料科学英文版》 SCIE EI CAS 2019年第3期648-655,共8页
The interfacial transition zone (ITZ) between the aggregates and the bulk paste is the weakest zone of ordinary concrete, which largely determines its mechanical and transporting properties. However, a complete unders... The interfacial transition zone (ITZ) between the aggregates and the bulk paste is the weakest zone of ordinary concrete, which largely determines its mechanical and transporting properties. However, a complete understanding and a quantitative modeling of ITZ are still lacking. Consequently, an integrated modeling and experimental study were conducted. First, the theoretical calculation model of the ITZ volume fraction about the rotary ellipsoidal aggregate particles was established based on the nearest surface function formula. Its calculation programs were written based on Visual Basic 6.0 language and achieved visualization and functionalization. Then, the influencing factors of ITZ volume fraction of the ellipsoidal aggregate particles and the overlapping degree between the ITZ were systematically analyzed. Finally, the calculation models of ITZ volume fraction on actual ellipsoidal aggregate were given, based on cobblestones or pebbles particles with naturally ellipsoidal shape. The results indicate that the calculation model proposed is highly reliable. 展开更多
关键词 INTERFACIAL transition zone (ITZ) CEMENT-BASED composites ellipsoidal AGGREGATE volume FRACTION VISUALIZATION software development
高模量聚丙烯管材料的结构与性能
6
作者 杜斌 陈商涛 +3 位作者 王宇杰 彭占录 张凤波 王艳芳 《化工新型材料》 CAS CSCD 北大核心 2019年第6期240-243,共4页
采用升温淋洗分级(TREF)方法对高模量聚丙烯管材料进行了分级,并应用凝胶渗透色谱(GPC)、傅立叶变换红外光谱(FT-IR)、结晶淋洗分级(CEF)和差示扫描量热(DSC)等方法研究了其组成、序列结构与相对分子质量及分布。结果表明:材料由高规整... 采用升温淋洗分级(TREF)方法对高模量聚丙烯管材料进行了分级,并应用凝胶渗透色谱(GPC)、傅立叶变换红外光谱(FT-IR)、结晶淋洗分级(CEF)和差示扫描量热(DSC)等方法研究了其组成、序列结构与相对分子质量及分布。结果表明:材料由高规整度的均聚聚丙烯、含有少量乙烯链段的聚丙烯、含乙烯和丙烯长链段的乙丙共聚物和乙丙无规共聚物组成。均聚聚丙烯相含量最高,为材料的主要组成部分,提供了材料的刚性;乙丙无规共聚物组分分子量较大且分布较宽,构成了材料的橡胶相,保证了材料的抗冲强度;含乙烯和丙烯长链段的共聚物含量较低,但对材料性能的提高起到了重要作用。 展开更多
关键词 高模量聚丙烯管材料 抗冲性能 分级 均聚聚丙烯 乙丙共聚物
Cavitation performance of high-speed centrifugal pump with annular jet and inducer at different temperatures and void fractions 预览
7
作者 Jin Jiang Yan-hui Li +4 位作者 Chong-yan Pei Lin-lin Li You Fu Hong-gui Cheng Qiang-qiang Sun 《水动力学研究与进展:英文版》 SCIE EI CSCD 2019年第1期93-101,共9页
The cavitation is very common in a centrifugal pump,especially when the speed is very high,and it seriously influences the centrifugal pump performance.In this investigation,the RNG k-ε turbulence model and the cavit... The cavitation is very common in a centrifugal pump,especially when the speed is very high,and it seriously influences the centrifugal pump performance.In this investigation,the RNG k-ε turbulence model and the cavitation model with consideration of the mass transferring are first used to simulate the cavitation performance of the high-speed centrifugal pump without taking any measure for improving the pump cavitation performance.The calculation results reveal that a number of bubbles appear in the centrifugal pump flow channel,and the head as well as the flow rate of the high-speed centrifugal pump are far from its design condition.The cavitation performance can be improved effectively by arranging a variable pitch inducer and adopting an annular nozzle scheme.The flow field analysis of the pump is conducted to obtain the suitable working temperature distribution at different void fractions.On one hand,with the same void fraction,the head of the centrifugal pump drops slowly with the increase of temperature.However,when the temperature exceeds 90°C,the head of the pump drops rapidly.On the other hand,at the constant temperature,the higher the void fraction,the worse the cavitation performance.This research conducted under different temperatures and void fractions provides some guidance for designing an effective high-speed centrifugal pump. 展开更多
关键词 High-speed CENTRIFUGAL pump CAVITATION performance INDUCER ANNULAR NOZZLE VOID fraction
在线阅读 下载PDF
Removal of polycyclic aromatic hydrocarbons from different soil fractions by persulfate oxidation
8
作者 Xiaoyong Liao Qiongzhi Liu +2 位作者 You Li Xuegang Gong Hongying Cao 《环境科学学报:英文版》 SCIE EI CAS CSCD 2019年第4期239-246,共8页
Removal of polycyclic aromatic hydrocarbons(PAHs) from different soil fractions of contaminated soil was investigated by using activated persulfate oxidation remediation in our research. The results showed that the li... Removal of polycyclic aromatic hydrocarbons(PAHs) from different soil fractions of contaminated soil was investigated by using activated persulfate oxidation remediation in our research. The results showed that the light fraction, which accounted for only 10% of the soil, contained 30% of the PAHs at a concentration of 4352 mg/kg. The heavy fraction contained more high-molecular-weight PAHs, and the total PAH concentration was 625 mg/kg. After being oxidized, the removal rate of PAHs was 39% in the light fraction and nearly 90% in the heavy fraction. Among the different fractions of the heavy fraction,humic acid contained the highest concentration of PAHs, and consequently, the highest removal efficiency of PAHs was also in humic acid. Compared with the light fraction, the heavy fraction has more aromatic compounds and those compounds were broken down during the oxidation process, which may be the removal mechanism involved in the oxidation of high-ring PAHs. Similarly, the enhancement of C= C bonds after oxidation can also explain the poor removal of high-ring PAHs in the light fraction. These results imply that different fractions of soil vary in composition and structure, leading to differences in the distribution and oxidation efficiencies of PAHs. 展开更多
关键词 Soil FRACTION PERSULFATE OXIDATION PAHs Organic MATTER BOND
Heart failure with preserved ejection fraction in the elderly:pathophysiology,diagnostic and therapeutic approach 预览
9
作者 Ernesto Ruiz Duque Alexandros Briasoulis Paulino A Alvarez 《老年心脏病学杂志:英文版》 SCIE CAS CSCD 2019年第5期421-428,共8页
Heart failure with preserved ejection fraction(HFpEF)is a clinical syndrome characterized by symptoms and sings of heart failure with elevated left ventricular filling pressures at rest or during exercise.It is the mo... Heart failure with preserved ejection fraction(HFpEF)is a clinical syndrome characterized by symptoms and sings of heart failure with elevated left ventricular filling pressures at rest or during exercise.It is the most common type of heart failure in the elderly and its prevalence increases with age and is higher in females at any given age.HFpEF is frequently accompanied of comorbid conditions such as diabetes mellitus,obesity,atrial fibrillation and renal dysfunction.The diagnosis relies in the integration of clinical information,laboratory data and interpretation of cardiac imaging and hemodynamic findings at rest and during exercise.Conditions that have a specific treatment such as coronary artery disease,valvular disease,cardiac amyloidosis and constrictive pericarditis should be considered and evaluated as appropriate.Aggressive management of comorbidities,optimization of blood pressure control and volume status using diuretics as needed are among the current treatment recommendations.There are no specific therapies that have shown to decrease mortality in HFpEF.In symptomatic patients with history of hospital admission for decompensated heart failure,the implantation of a wireless pulmonary artery pressure monitor should be considered.Finally,given the high mortality of this condition,goals of care discussion should be initiated early and involvement of palliative care medicine should be considered. 展开更多
关键词 ECHOCARDIOGRAPHY EJECTION fraction Heart failure PHARMACOLOGY The elderly
在线阅读 下载PDF
Water incubation-induced fluctuating release of heavy metals in two smelter-contaminated soils
10
作者 Bin Yang Yunzhe Cao +3 位作者 Jie Ren Mei Wang Huilong Luo Fasheng Li 《环境科学学报:英文版》 SCIE EI CAS CSCD 2019年第8期14-23,共10页
The soil moisture regime can affect the release of heavy metals in soil. In the previous studies, slightly polluted soils or artificially contaminated soil samples were considered to investigate the effect of soil moi... The soil moisture regime can affect the release of heavy metals in soil. In the previous studies, slightly polluted soils or artificially contaminated soil samples were considered to investigate the effect of soil moisture. We used highly smelter-contaminated and aged soils to study the release of typical heavy metals(Cu, Zn, Cd and Pb) induced by water incubation in batch experiments with characterization via speciation and X-ray diffraction analyses(XRD). The results show that the leachable concentrations of the heavy metals increased slightly in the first 30 days, decreased drastically between 30 and 90 days, and immobilized relatively constant thereafter. The fluctuation was ascribed to the changes of soil Eh and pH, the reductive dissolution of crystalline iron oxides, the formation of new amorphous iron oxides, the absorption of dissolved organic matter and the precipitation of metal sulfide. Speciation analysis indicated that a proportion of the soil heavy metals was transformed from an exchangeable fraction to a less labile fraction after water incubation. And the presence of a lead iron oxide phase and the peak increasing of zinc sulfide were observed via XRD analyses. Finally, water incubation restrained the release of heavy metals after 180 days of incubation, and reduced the leachability of Cu, Zn, Cd and Pb by as much as 1.61%–7.21% for soil A and 0.43%–3.36% for soil B, respectively. The study findings have implications for the formulation of risk control and management strategies for heavy metals in smelter-contaminated soils. 展开更多
关键词 Smelter-contaminated soil Heavy metals WATER INCUBATION RELEASE FRACTION
Directional Analysis of Urban Expansion Based on Sub-pixel and Regional Scale: A Case Study of Main Districts in Guangzhou, China 预览
11
作者 ZHAO Yi ZHONG Kaiwen +2 位作者 XU Jianhui SUN Caige WANG Yunpeng 《中国地理科学:英文版》 SCIE CSCD 2019年第4期652-666,共15页
Multi-scale data have had a wide-ranging level of performance in the area of urban change monitoring. Herein we investigate the correlation between the impervious surface fraction(ISF) and the Defense Meteorological S... Multi-scale data have had a wide-ranging level of performance in the area of urban change monitoring. Herein we investigate the correlation between the impervious surface fraction(ISF) and the Defense Meteorological Satellite Program/Operational Linescan System(DMSP/OLS) nighttime stable light(NTL) data with respect to the urban expansion in the main districts of Guangzhou. Landsat 5 Thematic Mapper and Landsat 8 Operational Land Image(OLI) data from 1988 to 2015 were used to extract the ISF using the linear spectral mixture analysis model and normal difference build-up index at the sub-pixel scale. DMSP/OLS NTL data from 1992 to 2013 were calibrated to illustrate the urban nighttime light conditions at the regional scale. Urban expansion directions were identified by statistics and kernel density analysis for the ISF study area at the sub-pixel scale. In addition, the correlation between the ISF and DMSP/OLS NTL data were illustrated by linear regression analysis. Furthermore, Profile Graph in ArcGIS was employed to illustrate the urban expansion from the differences in correlation in different directions. The conclusions are as follows: 1) The impervious surface(IS)in the study area has expanded to the northeast and the east, starting with the old urban zones, and the high-density IS area has increased by321.14 km~2. 2) The linear regression analysis reveals a positive correlation between the ISF and the DMSP/OLS NTL data. The multi-scale data changes are consistent with the actual urban planning of Guangzhou. 3) The DMSP/OLS NTL data overestimate the urban extent because of its saturation and blooming effects, causing its correlation with ISF to decrease. The pattern of urban expansion influences the saturation and blooming effects of the DMSP/OLS NTL data. 展开更多
关键词 impervious surface FRACTION linear spectral mixture ANALYSIS NIGHTTIME light kernel density profile graph
在线阅读 下载PDF
Step distribution of Yb filling fraction during microstructural evolution in skutterudites
12
作者 Jing MEI Zheng YAO +5 位作者 Shuya ZHU Dongli HU Ying JIANG Juanjuan XING Hui GU Lidong CHEN 《先进陶瓷(英文版)》 CSCD 2019年第1期62-71,共10页
To achieve a better material for thermoelectric power generation device, filled skutterudite Yb0.3 Co4 Sb12 samples were fabricated by melting-quenching-annealing-spark plasma sintering(SPS)method. Two sets of samples... To achieve a better material for thermoelectric power generation device, filled skutterudite Yb0.3 Co4 Sb12 samples were fabricated by melting-quenching-annealing-spark plasma sintering(SPS)method. Two sets of samples, before and after SPS, were investigated. In both the two sets of samples,the average grain size of the samples increases monotonously with the increase of annealing time,while Yb filling fraction firstly increases and then decreases. Yb not filling into the skutterudite remains at the grain boundaries in the form of Yb2 O3 after SPS, which could be quantified by the spatially difference method of energy dispersive spectra. Step distribution of Yb filling fraction was observed in the samples annealed for 1 h, which was caused by the microstructural evolution from the peritectic phases to the skutterudite phase. The sample annealed for 3 days and SPS sintered possesses the maximum value of Yb filling fraction 0.249 and the maximum ZT value of 1.24 at 850 K. These results are helpful to better understand the microstructural evolution and Yb filling behavior in skutterudite materials. 展开更多
关键词 SKUTTERUDITE ytterbium FILLING FRACTION microstructure STEP DISTRIBUTION
MODIS observed snow cover variations in the Aksu River Basin,Northwest China 预览
13
作者 Jing Li ShiYin Liu Qiao Liu 《寒旱区科学:英文版》 CSCD 2019年第3期208-217,共10页
A major proportion of discharge in the Aksu River is contributed from snow-and glacier-melt water.It is therefore essential to understand the cryospheric dynamics in this area for water resource management.The MODIS M... A major proportion of discharge in the Aksu River is contributed from snow-and glacier-melt water.It is therefore essential to understand the cryospheric dynamics in this area for water resource management.The MODIS MOD10A2 remotesensing database from March 2000 to December 2012 was selected to analyze snow cover changes.Snow cover varied significantly on a temporal and spatial scale for the basin.The difference of the maximum and minimum Snow Cover Fraction(SCF)in winter exceeded 70%.On average for annual cycle,the characteristic of SCF is that it reached the highest value of 53.2%in January and lowest value of 14.7%in July and the distributions of SCF along with elevation is an obvious difference between the range of 3,000 m below and 3,000 m above.The fluctuation of annual average snow cover is strong which shows that the spring snow cover was on the trend of increasing because of decreasing temperatures for the period of 2000-2012.However,temperature in April increased significantly which lead to more snowmelt and a decrease of snow cover.Thus,more attention is needed for flooding in this region due to strong melting of snow. 展开更多
关键词 MODIS SNOW data Aksu River SNOW cover FRACTION climate change
在线阅读 下载PDF
Clay mineralogy affects the efficiency of sewage sludge in reducing lead retention of soils
14
作者 Giovana Clarice Poggere Vander Freitas Melo +4 位作者 Beatriz Monte Serrat Antunio Salvio Mangrich Amanda Araújo Franca Rodrigo Stuart Corrêa Julierme Zimmer Barbosa 《环境科学学报:英文版》 SCIE EI CAS CSCD 2019年第6期45-57,共13页
Recent studies have shown the feasibility of using of sewage sludge for the remediation of heavy metal-contaminated soils. However, there are no researches to check the influence of clay mineralogy on the efficiency o... Recent studies have shown the feasibility of using of sewage sludge for the remediation of heavy metal-contaminated soils. However, there are no researches to check the influence of clay mineralogy on the efficiency of the sewage sludge to remediation of contaminated soils with heavy metals. For this purpose, we use two contrasting soils:Oxisol rich in hematite and gibbsite and Inceptisol rich in kaolinite. Thermal-treated sludge was applied to Pb-contaminated soil samples and incubated for 40 days. The soil samples were submitted to seven sequential extractions: soluble-Pb, exchangeable-Pb,precipitated-Pb, organic matter-Pb, Fe and Mn oxide-Pb, gibbsite and kaolinite-Pb, and residual-Pb. The reduction of soluble Pb forms by thermal sludge application was more pronounced in the Oxisol than in the Inceptisol because of the conversion of soluble-Pb into more stable forms, such as precipitated-Pb and oxides-Pb. For Inceptisol was necessary to apply high rates of thermal sludge to reach a significant reduction in soluble-Pb contents. The addition of humic fractions in the form of thermal sludge increased the concentration of organic matter-Pb. In confined area, the use of sewage sludge to reduce the heavy metals levels in soils must be better considered, mainly in more weathered soils. 展开更多
关键词 Sequential extraction HUMIC fraction Fe OXIDES GIBBSITE KAOLINITE
Human neural stem cell transplants to address multiple pathologies associated with traumatic brain injury 预览
15
作者 Helene Clervius Mirza Baig +1 位作者 Anil Mahavadi Shyam Gajavelli 《中国神经再生研究:英文版》 SCIE CAS CSCD 2019年第10期1699-1700,共2页
Traumatic brain injury (TBI), an unmet need: TBI is an alteration in brain function caused by an external force with evidence of brain pathology. It could be from a bump, blow, blast or jolt to the head including pene... Traumatic brain injury (TBI), an unmet need: TBI is an alteration in brain function caused by an external force with evidence of brain pathology. It could be from a bump, blow, blast or jolt to the head including penetrating the cranium. TBI is a public health concern worldwide due to its economic impact. Most TBIs are survivable, do not need hospitalization but may influence productivity. A smaller percentage of TBI due to falls or penetrating TBI (PTBI) needs hospitalization and accounts for largest fraction of TBI care costs. 展开更多
关键词 TRAUMATIC brain injury(TBI) function caused by an external largest fraction of TBI care COSTS
在线阅读 下载PDF
Environmental factors influencing snowfall and snowfall prediction in the Tianshan Mountains, Northwest China
16
作者 ZHANG Xueting LI Xuemei +2 位作者 LI Lanhai ZHANG Shan QIN Qirui 《干旱区科学:英文版》 SCIE CSCD 2019年第1期15-28,共14页
Snowfall is one of the dominant water resources in the mountainous regions and is closely related to the development of the local ecosystem and economy. Snowfall predication plays a critical role in understanding hydr... Snowfall is one of the dominant water resources in the mountainous regions and is closely related to the development of the local ecosystem and economy. Snowfall predication plays a critical role in understanding hydrological processes and forecasting natural disasters in the Tianshan Mountains, where meteorological stations are limited. Based on climatic, geographical and topographic variables at 27 meteorological stations during the cold season(October to April) from 1980 to 2015 in the Tianshan Mountains located in Xinjiang of Northwest China, we explored the potential influence of these variables on snowfall and predicted snowfall using two methods: multiple linear regression(MLR) model(a conventional measuring method) and random forest(RF) model(a non-parametric and non-linear machine learning algorithm). We identified the primary influencing factors of snowfall by ranking the importance of eight selected predictor variables based on the relative contribution of each variable in the two models. Model simulations were compared using different performance indices and the results showed that the RF model performed better than the MLR model, with a much higher R~2 value(R~2=0.74;R~2, coefficient of determination) and a lower bias error(RSR=0.51;RSR, the ratio of root mean square error to standard deviation of observed dataset). This indicates that the non-linear trend is more applicable for explaining the relationship between the selected predictor variables and snowfall. Relative humidity, temperature and longitude were identified as three of the most important variables influencing snowfall and snowfall prediction in both models, while elevation, aspect and latitude were of secondary importance, followed by slope and wind speed. These results will be beneficial to understand hydrological modeling and improve management and prediction of water resources in the Tianshan Mountains. 展开更多
关键词 SNOWFALL PREDICTION SNOWFALL fraction random forest multiple linear regression PREDICTOR variables TIANSHAN Mountains
Numerical simulation on centrifugal pump compressible flow field with different gas volume fractions 预览
17
作者 WANG Like LIAO Weili +4 位作者 LU Jinling LUO Xingqi RUAN Hui ZHAO Yaping WANG Jing 《排灌机械工程学报》 CSCD 北大核心 2019年第2期106-111,129共7页
In order to study the influence of gas-liquid two-phase flow on the performance and internal flow field of a centrifugal pump,the steady three-dimensional flow with different gas volume fractions was simulated by appl... In order to study the influence of gas-liquid two-phase flow on the performance and internal flow field of a centrifugal pump,the steady three-dimensional flow with different gas volume fractions was simulated by applying the Reynolds-average N-S equation and mixture gas-liquid two-phase flow model,and the compressibility of gas was taken into consideration in the simulation.Then the centrifugal pump characteristic and the gas distribution law in different gas volume fractions were analyzed.The computational results show that gas volume fraction has a certain influence on the performance of the centrifugal pump,and the efficiency and head of the pump are on the decline with the increase of it.Static pressure in the impeller increases in the radial direction,but the pressure gradient in the flow direction is different under the different gas volume fractions.The gas volume is distributed mainly in the ipsilateral direction of impeller back shroud in the flow channel of the volute.On the suction side of the blade inlet there is an obvious low-pressure area,which causes bubbles agglutination and higher gas volume fraction.With the gas entering passage flow,gas volume fraction in the suction decreases and the pressure surface rises gradually.Higher gas volume fraction causes air blocking phenomenon in the flow passage and the discharge capacity reduces.The increase of gas volume makes the turbulent motion within the impeller more and more intense,which leads to more and more energy loss. 展开更多
关键词 centrifugal pump Mixture model GAS-LIQUID TWO-PHASE flow gas volume fraction COMPRESSIBILITY
在线阅读 下载PDF
Kinetics of Ligand-Controlled Release of Zinc in Acid Sulfate Paddy Soils
18
作者 Worachart WISAWAPIPAT Aksarapak PONGPOM 《土壤圈:英文版》 SCIE CAS CSCD 2019年第2期216-223,共8页
The elevated solubility of zinc(Zn) in acid sulfate paddy soils can limit rice production and pose a risk of environmental pollution.However, little attention has been paid to the ligand-controlled release of Zn in th... The elevated solubility of zinc(Zn) in acid sulfate paddy soils can limit rice production and pose a risk of environmental pollution.However, little attention has been paid to the ligand-controlled release of Zn in these soils. Here we quantified the rate of ligandcontrolled Zn release in Thai acid sulfate paddy soils, using ethylenediaminetetraacetic acid as the extractant. Sequential extractions were performed to obtain quantitative information on Zn fractions contributing to the ligand-controlled mechanisms. The amount of Zn released within 192 h varied significantly(8–43 mg kg-1), which corresponded to 12%–40% of the total soil Zn, indicating that Zn solubility in most soils was relatively low and that Zn mainly occurred as residual phases. The kinetics of Zn release was well described by the power function model(r = 0.65–0.99, median = 0.87). The magnitude of initial Zn release(coefficient a) was significantly(P < 0.05) related to the aqua regia-soluble Zn. Easily mobile Zn, organically bound Zn, and Zn associated with Fe and Mn oxides also contributed to the ligand-controlled release mechanisms to various degrees. Our results provide a systematic understanding of Zn fractions and release from acid sulfate paddy soils, the dynamics of which have a significant influence on the availability, phytoextraction, and mobility of Zn in terrestrial and engineered environments. 展开更多
关键词 ethylenediaminetetraacetic ACID kinetic release LIGAND exchange sequential extraction ZINC FRACTION ZINC SOLUBILITY
TRISO fuel volume fraction and homogeneity: a nondestructive characterization 预览
19
作者 K. V. Vrinda Devi J. N. Dubey +1 位作者 Jyoti Gupta I. H. Shaikh 《核技术:英文版》 SCIE CAS CSCD 2019年第3期46-52,共7页
A new nondestructive method to estimate the volume fraction and homogeneity of tristructural isotropic (TRISO)-coated fuel particles in fuel compacts designed for high-temperature reactors has been developed using ima... A new nondestructive method to estimate the volume fraction and homogeneity of tristructural isotropic (TRISO)-coated fuel particles in fuel compacts designed for high-temperature reactors has been developed using image analysis of conventional X-radiographs. The method is demonstrated on surrogate fuel compacts containing TRISO-coated particles with kernels made of zirconium dioxide. The methodology incorporates a correction for superimposed images of TRISO particles such that a single X-ray image obtained in any one random orientation is sufficient to characterize the fuel compact in terms of volume fraction and homogeneity. The method is based on the virtual segregation of images of each particle inside the compact with the aid of a calibration standard. 展开更多
关键词 TRISO VOLUME FRACTION HOMOGENEITY RADIOGRAPHY
在线阅读 下载PDF
Radiological characterization of building materials used in Malaysia and assessment of external and internal doses 预览
20
作者 Shittu Abdullahi Aznan Fazli Ismail Supian Samat 《核技术:英文版》 SCIE CAS CSCD 2019年第3期82-96,共15页
In this study, the activity concentrations of ^226Ra,^232Th,^222Rn, and 40K, emanation fractions (P), equilibrium equivalent concentration (EEC), and mass exhalation rates (Em) of radon released from building material... In this study, the activity concentrations of ^226Ra,^232Th,^222Rn, and 40K, emanation fractions (P), equilibrium equivalent concentration (EEC), and mass exhalation rates (Em) of radon released from building materials used in Malaysia were studied using gamma-ray spectrometer with HPGe detector. Radiological parameters [activity concentration index (ACI), indoor air-absorbed dose rate (Din), annual effective dose (AEDin) from external and internal (ERn), soft tissues (HST) and lung (HL), and effective dose equivalent (Heff)] were estimated to evaluate radiological hazards due to the use of these building materials: sand, cement, gravel, bricks, tiles, fly ash, white cement, and ceramic raw materials. The measured P, EEC, and Em vary from 10 to 30%, 0.9 to 22 Bq m-3, and 33 to 674 mBq h^-1 kg^-1, respectively, while the calculated ACI and AEDin vary from 0.1 ± 0.01 to 2.1 ± 0.1 and 0.1 ± 0.01 to 2.4 ± 0.6 mSv y^-1, respectively. On the other hand, the internal annual effective dose ranges from 0.1 to 1.4 mSv y^-1. The estimated radiological risk parameters were below the recommended maximum values, and radiological hazards associated with building materials under investigation are therefore negligible. 展开更多
关键词 Indoor radon EMANATION fraction Equilibrium EQUIVALENT concentration Mass EXHALATION rate Annual EFFECTIVE DOSE EFFECTIVE DOSE EQUIVALENT
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈