检索结果-南通市图书馆

Cu, Mn, Fe, and Zn Levels in soils of shika Area, Nigeria

Biomedical and Environmental sciences 2004年第4期17卷 426-431页

作者： s.A.MAsHI s.A.YARO A.s.HAIBA DepartmentofGeography UniversityofAbujaP.M.B.117AbujaNIGERIA DepartmentofMetallurgicalEngineering AhmaduBelloUniversityZariaNigeria DepartmentofGeography AhmaduBelloUniversityZariaNigeria

Objective Heavy metals presented in toxic amounts can become injurious to human health. In areas where there is a high level of human activities on soils (such as agriculture and grazing) studies are therefore required from time to time to monitor levels of such metals in the soils in order to identify the point in time when toxicity problems become real. The objective of this paper is to determine the concentrations of some trace metals (Cu, Mn, Fe, and Zn) in soils under cultivation and grazing practices in shika, a rural area of Kaduna state of Nigeria. Method In this study, soil samples collected from three different categories of locations (cultivated, grazed, and uncultivated/non- grazed serving as a control) across shika area, Nigeria, were analysed for some trace metal levels (Cu, Mn, Fe, and Zn) using atomic absorption spectrophotometry. For each category, multiple sites were chosen to accommodate all possible intra-category variations, especially in terms of land use and management history and topographic characteristics. Topsoil (0-15 cm) and subsoil (20-30 cm) samples were collected from every site and analysed for the above metals. Averaged values of the metals for the three categories revealed that Zn is the most abundant metal, followed by Fe, then Mn and Cu the least. Results The results obtained indicate that the cultivation practices, and to a lesser extent grazing, in the area result in higher levels of all the metals than in the control, suggesting that crop immobilization of the metals from soils of the area is low, and that their systematic accumulation is taking place in cultivated soils of the area. Prospects of having elevated soil levels of the metals due to cultivation practices in the area therefore seem quite high. Conclusion On the basis of the results obtained, it was concluded that grazing and cultivation practices have in general caused some significant elevations in the bioavailable (i.e the plant available forms) levels of Z

关键词： Trace Metals soil Contamination Cultivation Grazing Control Nigeria

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

The internal propagation of fusion flame with the strong shock of a laser driven plasma block for advanced nuclear fuel ignition

引用

Chinese Physics B 2013年第5期22卷 369-374页

作者： B. Malekynia s. s. Razavipour Department of Physics Gachsaran BranchIslamic Azad University

An accelerated skin layer may be used to ignite solid state fuels. Detailed analyses were clarified by solving the hydrodynamic equations for nonlinear force driven plasma block ignition. In this paper, the complementary mechanisms are included for the advanced fuel ignition： external factors such as lasers, compression, shock waves, and sparks. The other category is created within the plasma fusion as reheating of an alpha particle, the Bremsstrahlung absorption, expansion, conduction, and shock waves generated by explosions. With the new condition for the control of shock waves, the spherical deuterium-tritium fuel density should be increased to 75 times that of the solid state. The threshold ignition energy flux density for advanced fuel ignition may be obtained using temperature equations, including the ones for the density profile obtained through the continuity equation and the expansion velocity for the r≠ 0 layers. These thresholds are significantly reduced in comparison with the ignition thresholds at x = 0 for solid advanced fuels. The quantum correction for the collision frequency is applied in the case of the delay in ion heating. Under the shock wave condition, the spherical proton- boron and proton-lithium fuel densities should be increased to densities 120 and 180 times that of the solid state. These plasma compressions are achieved through a longer duration laser pulse or X-ray.

关键词： block ignition advanced fuel quantum correction shock wave

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Daily variation of radon gas and its short-lived progeny concentration near ground level and estimation of aerosol residence time

引用

Chinese Physics B 2016年第5期25卷 111-118页

作者： M Mohery A M Abdallah A Ali s s Baz Physics Department Faculty of Science University of Jeddah Physics Department Faculty of Science Sohag University Astronomy Department Faculty of Science King Abdulaziz University Astronomy Department Faculty of Science Cairo University Physics Department Girls Faculty of Science King Abdulaziz University

Atmospheric concentrations of radon（^（222）Rn） gas and its short-lived progenies^（218）Po,^（214）Pb, and^（214）Po were continuously monitored every four hours at the ground level in Jeddah city, Kingdom of saudi Arabia. The measurements were performed three times every week, starting from November 2014 to October 2015. A method of electrostatic precipitation of positively charged^（218）Po and ^（214）Po by a positive voltage was applied for determining^（222）Rn gas concentration. The short-lived^（222）Rn progeny concentration was determined by using a filter holder connected with the alpha-spectrometric technique. The meteorological parameters（relative air humidity, air temperature, and wind speed） were determined during the measurements of^（222）Rn and its progeny concentrations.^（222）Rn gas as well as its short-lived progeny concentration display a daily and seasonal variation with high values in the night and early morning hours as compared to low values at noon and in the afternoon. The observed monthly atmospheric concentrations showed a seasonal trend with the highest values in the autumn/winter season and the lowest values in the spring/summer season. Moreover, and in parallel with alphaspectrometric measurements, a single filter-holder was used to collect air samples. The deposited activities of^（214）Pb and the long-lived^（222）Rn daughter ^（210）Pb on the filter were measured with the gamma spectrometric technique. The measured activity concentrations of^（214）Pb by both techniques were found to be relatively equal largely. The highest mean seasonally activity concentrations of ^（210）Pb were observed in the autumn/winter season while the lowest mean were observed in the spring/summer season. The mean residence time（MRT） of aerosol particles in the atmospheric air could be estimated from the activity ratios of ^（210）Pb/^（214）Pb.

关键词： daily variation radon progeny concentration meteorological variables

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Effects of the partial replacement of La by M(M=Ce,Ca and sr) in La_(2-x)M_xCuO_4 perovskites on catalysis of the water-gas shift reaction

引用

Journal of Natural Gas Chemistry 2010年第6期19卷 567-574页

作者： s.s.Maluf E.M.Assaf Institute de Química de so Carlos Universidade de So PauloAv.Trabalhador Socarlense400 So CarlosSP 13560-970Brazil

The performance of La2-x M x CuO4 perovskites （where M=Ce,Ca or sr） as catalysts for the water-gas shift reaction was investigated at 290℃ and 360℃.The catalysts were characterized by EDs,XRD,N2 adsorption-desorption,XPs and *** XRD results showed that all the perovskites exhibited a single phase （the presence of perovskite structure）,suggesting the incorporation of metals in the perovskite *** XPs and XANEs results showed the presence of Cu2＋ on the *** perovskites that exhibited the best catalytic performance were La 2 x Ce x CuO 4 perovskites,with CO conversions of 85% 90%.Moreover,these perovskites have higher surface areas and larger amounts of Cu on the *** Ce has a higher filled energy level than the other metals,increasing the energy of the valence band of Ce and providing more electrons for the ***,the La1.80Ca0.20CuO4 perovskite showed a good catalytic performance.

关键词： perovskites water-gas shift reaction lanthanum copper calcium cerium strontium

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

The influence of stimulated temperature-dependent emission cross section on intracavity optical parametric oscillator

引用

Chinese Physics B 2017年第2期26卷 238-241页

作者： s samimi A Keshavarz Department of Physics Shiraz University of Technology Shiraz Ira

In this paper, the influence of temperature on the intracavity optical parametric oscillator（IOPO） is investigated by using the stimulated temperature-dependent emission cross section of laser crystal. The rate equations under plane wave approximation have been used for simulation of signal output pulse. Results show that the signal output pulse width is decreased by increasing the laser crystal temperature. Also, the signal output energy is increased by the increasing of the laser crystal temperature. The simulation results for IOPO based on Nd：YAG and Nd：YVO_4, show that the signal pulse energies are increased by 3.2 and 5.6 times respectively when the laser crystal temperature increased from 15℃ to 300℃. The presented model indicates that the temperature sensitivity of Nd：YVO_4-based IOPOs is more than that of Nd：YAG-based IOPOs which is expected from a physical point of view.

关键词： nonlinear optic two-wave mixing parametric oscillators and amplifiers

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

First evidence for chiral wobbling of triaxial nuclei

引用

Nuclear science and Techniques 2024年第7期35卷 4-7页

作者： s.Frauendorf Department of Physics and Astronomy University of Notre DameNotre DameIN 46556USA

Chirality(Greek“handiness”)is a property of many com-plex *** molecules exist in two forms,one being the mirror image of the *** for our hands,it is impossible to make the images identical by a suitable *** two forms are called left-handed and *** have the same binding energy,because the electro-magnetic interaction,which holds the molecule together,does not change under a *** properties that are insensitive to the geometry are also the *** different geometry is the reason why the left-handed form turns the polarization plane of transmitted light in one direction by some angle while the right-handed form turns it in the oppo-site direction by the same ***,the geometrical differences between the two species may have other *** two species of the carvon molecule shown in Fig.1 taste quite differently.

关键词： turns Chiral mirror

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

substrate Evolution to Microstructural and Optoelectrical Properties of Evaporated Cds Thin Films Correlated with Elemental Composition

引用

Acta Metallurgica sinica(English Letters) 2021年第9期34卷 1307-1316页

作者： Anuradha Purohit Himanshu s.L.Patel s.Chander M.s.Dhaka Department of Physics Mohanlal Sukhadia UniversityUdaipur 313001India Department of Chemical sciences Indian Institute of Science Education and Research.Mohali 140306India Centre for Advanced study in Physics Department of PhysicsPanjab UniversityChandigarh 160014India

A typical high-e fficiency solar cell device needs the best lattice matching between different constituent layers to mitigate the open-circuit voltage loss. In the present work, the physical properties of Cds thin films are investigated where films with 100 nm thickness were fabricated on the different types of substrates viz. soda–lime glass, indium-doped tin oxide(ITO)-and fl uorine-doped tin oxide(FTO)-coated glass substrates, and silicon wafer using electron beam evaporation. The X-ray diffraction patterns confirmed that deposited thin films showed cubic phase and had(111) as predominant orientation where the structural parameters were observed to be varied with nature of substrates. The ohmic behaviour of the Cds films was disclosed by current–voltage characteristics, whereas the scanning electron microscopy micrograph revealed the uniform deposition of the Cds films with the presence of round-shaped grains. The elemental analysis confirmed the Cds films deposition where the Cd/s weight percentage ratio was changed with nature of substrates. The direct energy band gap was observed in the 1.63–2.50 eV range for the films grown on different substrates. The investigated properties of thin Cds layers demonstrated that the selection of substrate(in terms of nature) during device fabrication plays a crucial role.

关键词： Cds thin films substrate evolution E-beam evaporation Microstructural properties Optoelectrical properties

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Intergrain contact density indices for granular mixes——Ⅱ: Liquefaction resistance

引用

Earthquake Engineering and Engineering Vibration 2007年第2期6卷 135-146页

作者： s. Thevanayagam Dept. of Civil Struct. & Env. Eng. State Univ. of New York Buffalo NY 14260 USA

Whether the presence of non-plastic silt in a granular mix soil impact its liquefaction potential and how to evaluate liquefaction resistance of sand containing different amounts of silt contents are both controversial issues. This paper presents the results of an experimental evaluation to address these issues. Two parameters, namely, equivalent intergranular void ratio （ec）eq and equivalent interfine void ratio （ef）eq, proposed in a companion paper （Thevanayagam, 2007） as indices of active grain contacts in a granular mix, are used to characterize liquefaction resistance of sands and silty sands. Results indicate that, at the same global void ratio （e）, liquefaction resistance of silty sand decreases with an increase in fines content （Cv） up to a threshold value （Crth）. This is due to a reduction in intergrain contact density between the coarse grains. Beyond Crth, with further addition of fines, the interfine contacts become significant while the inter-coarse grain contacts diminish and coarse grains become dispersed. At the same e, the liquefaction resistance increases and the soil becomes stronger with a fttrther increase in silt content. Beyond a limiting fines content （CrL）, the liquefaction resistance is controlled by interfine contacts only. When Cr〈Crth, at the same （e）eq, the liquefaction resistance of silty sand is comparable to that of the host clean sand at a void ratio equal to （ec）eq. When CF〉CFth, at the same （ef）eq, the cyclic strength of a sandy silt is comparable to the host silt at a void ratio equal to （ef）eq.

关键词： sand silt fines silty sand liquefaction cyclic strength

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Rock joint coefficients and their computerized classification

引用

International Journal of Mining science and Technology 2019年第5期29卷 701-709页

作者： Tomás Ficker Faculty of Civil Engineering Brno University of Technology60200 BrnoCzech Republic

A computerized method for determining rock joint coefficients is *** relative similarity indicators are introduced to classify surface morphology of rock *** classification enables to compare investigated and database rock *** a comparison aims at finding the couple of surfaces that are distinguished by the highest dynamical *** first absolute indicator results from the Fourier matrix and evaluates wavy shapes of *** second absolute indicator quantifies the heights of surface reliefs and is defined as the root mean square height of the surface *** reliability of these indicators is tested within the surface analysis of a series of limestone *** the computerized assessment,25 people have performed visual assessment of these limestone *** results of visual assessments have been statistically processed and compared to the results received from the computerized *** newly introduced absolute indicators have proved to be prospective numerical tools for evaluating joint rock coefficients.

关键词： Rock joints shear strength Joint rock coefficients Numerical indicators Computerized assessment

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Fibre optic distributed scattering sensing system:perspectives and challenges for high performance applications

引用

仪器仪表学报 2007年第8期28卷 1345-1352页

作者： Marc Niklès Omnisens sA Riond-Bosson 3CH-1110 MorgesSwitzerland

As fiber optic distributed scattering sensing systems are providing innovative solutions for the monitoring of large structures,the comparison of different techniques and solutions is difficult because of the lack of standardized specifications and the difficulty associated to the characterization of such *** article presents a tentative definition of performance specifications and qualification procedures applicable to fiber optic distributed sensing systems aiming at providing clear guidelines for their design,specifications,qualification,application and selection.

关键词：纤维光学传感器分布式散射传感系统发展前景应用布里渊散射空间分辨率温度

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：