检索结果-南通市图书馆

Microspherules-Bearing White Sandstone: Implication of Cosmic Impact Event near Jurassi.-Cretaceous Boundary in West Central si.ai, Egypt

引用

Journal of Geoscience and Environment Protection 2016年第7期4卷 53-65页

作者： Hanan S. Badawy ahmed M. Zayed Mohamed G. Shahien Geology Department Faculty of Science Beni-Suef University Beni-Suef Egypt

The presence of glass microspherules enclosi.g relict grains, shattered quartz and si.icon carbide in white sandstone beds near the Jurassi.-Cretaceous boundary in west central si.ai indicates a cosmic impact event. Characterization of the impact microspherules and proposi.g a reasonable scenario for their origin are the aims of this work. Field observations, optical, binocular, scanning electron and high-resolution transmitted electron microscopy investigations and chemical analyses were carried out. The study revealed that glass microspherules have high Al2O3 and FeO contents and low CaO and MgO contents. The high content of Al2O3 indicates that the source of microtektite-like microspherules is attributed to the melting of a clay-rich sandstone and carbonaceous matter, while the high content of FeO indicates admixing with projectile matter. The reaction between si.ica and carbon was carried out under conditions of high temperature (T > 1000°C) and carbon (C/si.> 1) which resulted in the production of si.icon carbide with microdiamond intergrowth. Consequently, this intergrowth is in accordance with the impact origin via rapid condensation and growth within a vapor phase. In spite of the fact that no source crater has been recognized to date in the study area, the authors propose at least a si.gle cosmic impact event scenario for the recorded glass microspherules in west central si.ai. The impact excavated the Paleozoic si.iciclastic sedimentary rocks and then the glass microspherules showered the area of study. The deposi.ion of microtektite-like glass particles within the white sandstone beds of the Malha Formation took place in the fluvial plain terrestrial environment. This setting precluded severe post-deposi.ional reworking, yielding preservation of the glass particles in a primary layer. Eventually, lateral migration of the braided channels led to the reworking of the microspherules layer and the spatial disper

关键词： Impact Glass Microtektites Ejecta Nubian Sandstone si.

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Tensi.e Strength of Squeeze Cast Carbon Fibers Reinforced Al-si.Matrix Composi.es

引用

Journal of Minerals and Materials Characterization and Engineering 2011年第2期10卷 127-141页

作者： ahmed A. Moosa Kahtan K. Al-Khazraji Osama S. Muhammed Department of Production Engineering and Metallurgy University of Technology Baghdad Materials Engineering Department University of Technology Baghdad Iraq.

Squeeze casting is a pressure casting process in which molten metal is solidified under the direct action of a pressure. In squeeze casting, the relationship between the process parameters and the quality of the squeeze cast components is not fully understood;thus the need for more studies in this area of technology for better understanding of the process. The present work encompasses studying the effect of direct squeeze casting process parameters on the production of (3 and 20%) volume fraction carbon fibers (CF) reinforced Al-si.matrix composi.es. The evaluated process parameters are squeeze pressure in the range (7.5-53) MPa, die preheating temperature (100,200,300)°C, pouring temperature (700,780)°C, squeeze time (30 sec.), and delay time (5 sec.). The results show a good distribution of the matrix between the carbon fibers when usi.g higher casting pressures of (38 and 53MPa), lower pouring temperature of (700°C) and lower die temperatures of (100 and 200°C). Increasi.g the carbon fibers volume fraction had led to increasi.g the tensi.e strength. The usi.g of higher pressure (53MPa), lower pouring temperature (700°C), and lower die temperature (200°C) have increased the ultimate tensi.e strength of the CF/Al-si.composi.es to (183MPa) when compared to that of the nonreinforced alloy which was (168MPa) because of the increased bonding, decreased shrinkage defects and fibers degradation based on the results. Also, UTS is increased at P=38MPa, Tp=700°C, and Td=100°C.

关键词： Tensi.e Strength Squeeze Cast Carbon Fibers

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Fabrication of Congo Red/Oxidized Porous si.icon (CR/OPS) pH-Sensors

引用

Materials Sciences and Applications 2013年第8期4卷 79-87页

作者： Abdel-Hady Kashyout Hesham M. A. Soliman Marwa Nabil ahmed A. Bishara Advanced Technology and New Materials Research Institute City for Scientific Research and Technology Applications New Borg El-Arab City Alexandria Egypt Physi.s Department Faculty of Science Alexandria University Alexandria Egypt

The fabrication of nano porous si.icon, nPsi. usi.g alkali etching process has been studied and carried out. The surface chemistry of anisotropic etching of n-type si.wafer is reviewed and the anisotropic chemical etching of si.icon in alkaline solution usi.g wetting agents is discussed. Transformation of crystallographic plane of n-si.(211) to nPsi.(100) has occurred on usi.g n-propanol as wetting agent. The rate of pore formation was 0.02478 - 0.02827 μm/min, which was heavily dependent upon the concentration of the etchant containing wetting agents, allowing patterned porous si.icon formation through selective doping of the substrate. A particle si.e of 15 nm for porous nano-si.icon was calculated from the XRD data. Porosi.y of PS layers is about 10%. Pore diameter and porous layer thickness are 0.0614 nm and 16 μm, respectively. The energy gap of the produced porous si.icon is 3.3 eV. Furthermore, the combination of PS with Congo Red, which are nanostructured due to their deposi.ion within the porous matrix is discussed. Such nano compounds offer broad avenue of new and interesting properties depending on the involved materials as well as on their morphology. Chemical route was utilized as the host material to achieve pores filling. They were impregnated with Congo Red, which gave good results for the porous si.icon as a promisi.g pH sensor.

关键词： Nano Porous si.icon Anisotropic Etching Process Alkali Etching Congo Red PH Sensor

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Insi.ht on the Ultrastructure, Physi.ochemical, Thermal Characteristics and Applications of Palm Kernel Shells

引用

Materials Sciences and Applications 2018年第10期9卷 790-811页

作者： Richard Ntenga Etienne Mfoumou Alexis Béakou Martin Tango Jordan Kamga Ali ahmed Laboratoire de Mécanique et Productique (LMP) UFD SI Université de Douala Douala Cameroun Laboratoire d’Analyse Simulations et Essais (LASE) IUT Université de Ngaoundéré Ngaoundéré Cameroun Applied Research & Innovation Nova Scotia Community College Dartmouth Canada Institut Pascal UMR 6602-UCA-CNRS-si.MA Clermont-Ferrand France Ivan Curry School of Engineering Acadia University Wolfville Canada

The ultrastructure and physi.ochemical and thermal properties of Palm Kernel Shells (PKS) in comparison with Coconut Kernel Shells (CKS) were investigated herein. Powder samples were prepared and characterized usi.g Surface Electron Microscopy (SEM) and Transmissi.n Electron Microscopy (TEM). Chemical and elemental constituents, as well as thermal performance were assessed by Van Soest Method, TEM/EDXA and SEM/EDS techniques. Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysi. (TGA) were also performed for thermal characterization. SEM/EDS and TEM/EDXA revealed that most of the PKS and CKS materials are composed of particles with irregular morphology;these are mainly amorphous phases of carbon/oxygen with small amounts of K, Ca and Mg. The DSC data permitted to derive the materials’ thermal transi.ion phases and the relevant characteristic temperatures and physi.al properties. Thermal Transi.ion phases of PKS observed herein are consi.tent with the chemical composi.ion obtained and are si.ilar to those of CKS. Nonetheless, TGA/DTG showed that the combustion characteristics of PKS are higher than those of CKS. Taken together, our results reveal that PKS have nanopores and can be efficiently used for 3D printing and membrane filtration applications. Moreover, the chemical constituents found in PKS samples are in agreement with those reported in the literature for material structural applications and thus, present potential use of PKS in these applications.

关键词： Biomass Materials Palm Kernel Shell SEM & TEM Ultrastructure Thermal Properties Physi.o-Chemical Properties

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Influence of the Annealing Temperature on the Thickness and Roughness of La2Ti2O7Thin Films

引用

Advances in Materials Physi.s and Chemistry 2020年第8期10卷 189-198页

作者： Mohamed A. Baba Ala Gasi. Abdelmoneim Mohamed Awadelgied Nafie Abdallatief Almuslet ahmed Mohamed Salih Department of Laser System Institute of Laser Sudan University of Science and Technology Khartoum Sudan Institute of Frontier and Fundamental Science University of Electronic Science and Technology of China Chengdu China Department of Physi.s University of Science and Technology of China Hefei China Department of General Science Karrary University Omdurman Sudan Almogran College of Science and Technology Khartoum Sudan

In this work, the impact of the substrate annealing temperature on the thickness and roughness of La2Ti2O7 thin films was verified. A group of LTO Thin films was grown on si.(100) substrates successfully via pulsed laser deposi.ion technique (PLD) at various annealing temperatures with a constant numbers of pulses and energy per pulse. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) were used to investigate the thickness and roughness of the deposi.ed La2Ti2O7 thin films. The average thickness of the thin films was decreased due to the increasi.g in the annealing temperature linearly;the maximum thickness was found (231 nm) when LTO thin film deposi.ed at 500°C. The root mean square roughness was increased linearly with increasi.g the substrate Temperatures. The minimum roughness was found (0.254 nm) when LTO deposi.ed at (500°C). From the obtained results, its clear evidence that the annealing temperature has an influence on the thickness and roughness of the LTO thin films.

关键词： La2Ti2O7 Thin Films PLD Perovskites Annealing Temperature

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

25°ahmed模型射流主动控制气动减阻策略

引用

同济大学学报（自然科学版） 2018年第1期46卷 100-108页

作者：张英朝杜冠茂朱会田思吉林大学汽车仿真与控制国家重点实验室吉林长春130022

采用剪切应力输送(SST)κ-ω(湍动能-比耗散率)湍流模型对标准25°ahmed模型进行基于计算流体力学(CFD)数值模拟的稳态射流减阻研究.在模型尾部设置射流孔,分别探究各位置处射流孔的孔径、到边线的距离、形状、射流速度和角度的最佳值,... 详细信息

采用剪切应力输送(SST)κ-ω(湍动能-比耗散率)湍流模型对标准25°ahmed模型进行基于计算流体力学(CFD)数值模拟的稳态射流减阻研究.在模型尾部设置射流孔,分别探究各位置处射流孔的孔径、到边线的距离、形状、射流速度和角度的最佳值,分析不同射流状态对流场结构、总阻力系数及局部阻力系数的影响.仿真的基本工况与风洞实验数据一致性很好,验证所采用数值方法的准确性和可靠性.研究结果表明,与未设置射流孔的模型相比,设置射流方案的模型尾流结构得以改善,纵向涡得以抑制,同时其阻力系数明显降低.单独位置布置射流孔方案中在斜面上方进行射流时,阻力系数最低,为0.252 2,减阻率为11.3%.通过正交试验获得最佳组合方案得到阻力系数0.246 7,减阻率达13.23%.

关键词：外流场主动控制尾流结构射流气动减阻

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

A comparative analysi. of si.ulation approaches for predicting permeability and compressi.e strength in pervious concrete

引用

Low-carbon Materials and Green Construction 2024年第1期2卷 334-353页

作者： Soran Abdrahman Ahmad Hemn Unis ahmed Serwan Khurshid Rafiq Frya Shawkat Jafer Kawa Omar Fqi Civil Engineering Department College of EngineeringUniversity of Sulaim-aniSulaimaniKurdistan RegionIraq Civil Engineering Department Komar University of Science and TechnologySulaimaniKurdistan RegionIraq Technical Collage for Practical Sciences Sulaimaniy Polytechnic UniversityHalabjaKurdistan RegionIraq Construction Department Qaiwan Group CompaniesSulaimaniKurdistan RegionIraq

Porous concrete plays a crucial role in addressi.g various environmental challenges and mitigating the impacts of climate *** proves effective in reducing issues such as flooding,heat phenomena in the earth,and groundwater *** devoid of sand content,porous concrete’s key attributes lie in its permeability and compressi.e *** prediction of these properties is essential for cost and time savings,ensuring precise proportions of materials in the concrete *** article explores different models,including the linear model(LR),nonlinear model(NLR),and Artificial Neural Network(ANN),to predict and estimate permeability and compressi.e strength in porous *** analysi. incorporates 139 samples from various papers and experimental studies,utilizing si.nificant parameters and variables like water-to-cement ratio,coarse aggregate content,cement content,porosi.y,and curing time as input *** assessments,such as Root Mean Square Error(RMSE),Mean Absolute Error(MAE),Scatter Index(si.,OBJ value,and coefficient of determination(R^(2)),are employed to assess model *** results reveal that the ANN model outperforms other models in forecasting permeability and compressi.e strength of porous *** si.and OBJ value of the ANN model are lower than those of all other models,indicating superior *** robust performance of the ANN model has si.nificant implications for construction applications,ensuring precise material proportions and contributing to the durability of porous concrete *** success of the ANN model suggests avenues for refinement,including architecture adjustments and dataset *** findings offer valuable insi.hts into the ongoing efforts to optimize si.ulation techniques for predicting key properties of construction *** the other hand,the use of these models to optimize concrete mix desi.n not only enhances efficiency but also si.nificantly conserves raw

关键词： Pervious concrete Modeling Compressi.e strength Permeability Artificial neural network

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Ab InitioCalculations for the Effect of Pressure on the Structural Properties of si.Nanoclusters

引用

World Journal of Condensed Matter Physi.s 2012年第3期2卷 133-138页

作者： Noor A. Nama Zainelabideen Y. Mijbil Hamed I. Aboud ahmed M. Abdul-Lettif Basi. Science Department College of Veterinary Medicine University of Babylon Babylon Iraq Physi.s Department College of Science University of Babylon Babylon Iraq

Lattice constant, bulk modulus, Young modulus, valence band width, conduction band width, energy gap, vibrational energy, and plasmon energy have been calculated under compressi.n and tensi.e stresses in the range (0 ± 10 GPa) for 8, 54, 128 atom clusters of si.icon by means of densi.y functional theory method with restricted Hartree-Fock theory within the framework of large unit cell approach. It is found that the results deduced from eight atom cluster are in good agreement with the corresponding experimental values. On the other hand, bulk modulus, young modulus, valence band width, energy gap, and Plasmon energy increase (decrease) under compressi.n (tensi.e), while volume decreases (increases) with compressi.n (tensi.e). The vibrational energy has a minimum value at the ground state point. The conduction band width has no systematic behavior with pressure.

关键词： Nanocrystals Pressure Structural si

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Effect of Transcranial Direct Current Stimulation of Motor Cortex versus Insula Cortex on Chronic Post-Mastectomy Pain: Randomized Sham-Controlled Trial

引用

Open Journal of Anesthesi.logy 2023年第10期13卷 197-211页

作者： Shereen Mamdouh Kamal Khaled Mohamed Fares Sahar Abdel-Baky Mohamed Mohanad ahmed Mohamed Fatma Adel El Sherif Anaesthesi. Intensive Care and Pain Management Department South Egypt Cancer Institute Assiut University Assiut Egypt

Background: Transcranial direct current stimulation (tDCS) across cortical brain areas appears to improve various forms of pain, yet evidence of tDCS efficiency and ideal stimulation target is lacking. This study aimed to compare the add-on analgesi. efficacy of concentric electrode transcranial direct current stimulation (CE-tDCS) stimulation over the primary motor cortex versus the insular cortex on the management of chronic postmastectomy pain. Method: Prospective randomized double-blind sham-controlled study enrolled eighty patients with chronic postmastectomy pain that were randomly assi.ned to four groups: active motor (AM), sham motor (SM), active insula (AI) and sham insula (si. group, each received 5 sessi.ns for 20-minute duration with 2 mA tDCS over the targeted area of the contralateral si.e of pain. Our primary outcome was VAS score, the secondary outcomes were VDS score, LANSS score and depressi.n symptoms by HAM-D scores, assessment was done at 4 time points (prestimulation, after 5th sessi.n, 15th day and one month after the last sessi.n). Results: Both active tDCS groups (motor and insula) showed reduction of VAS (P Conclusi.n: Active tDCS stimulation either targeting the primary motor cortex or the insula cortex has add-on analgesi. effect for controlling neuropathic chronic post mastectomy pain and the maximum effect was at 15 days after the last sessi.n.

关键词： Transcranial Direct Current Stimulation tDCS Postmastectomy Pain Motor Cortex Insular Cortex

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Interaction between Kaolin and Urea in Organoclay and Its Impact on Removing Methylene Blue from Aqueous Solution

引用

World Journal of Nano Science and Engineering 2015年第1期5卷 1-9页

作者： Sabri M. Husssein Omar H. Shihab Sattar S. Ibrahim Naser M. ahmed Department of Chemistry College of Science University of Anbar Anbar Iraq Department of Chemistry College of Women Education University of Anbar Anbar Iraq Nano-Optoelectronics Research and Technology Laboratory School of Physics University Sains Malaysia Penang Malaysia

Interaction between kaolin (particle si.e 53 and 106 μm) and urea was studied by infrared spectroscopy and powder X-ray diffraction. Interaction was found to be dependent on the particle si.e of kaolin raw material. Nature of interaction achieved through the formation of hydrogen bonds between urea and both AlOH and si.O surface of kaolinite. Effect of temperature on equilibrium adsorption of methylene blue (MB) from aqueous solution usi.g kaolin also studied, the results were analyzed by Langmuir and frendlich isotherms. Thermodynamic parameters such as ΔG, ΔH and ΔS were calculated. Results suggested that the MB adsorption on kaolin was spontaneous and exothermic process.

关键词： Kaolin Urea Intercalation Thermodynamic Methylene Blue and Adsorption

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

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：