检索结果-南通市图书馆

Influences of Ag and Au Additions on Structure and Tensile Strength of Sn-5Sb Lead Free Solder Alloy

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2008年第6期24卷 921-925页

作者： A.A.el-Daly y.Swilem A.E.Hammad Physics Department Faculty of ScienceZagazig UniversityZagazigEgypt

It is important, for electronic application, to decrease the melting point of Sn-5Sb solder alloy because it is relatively high as compared with the most popular eutectic Pb-Sn solder alloy. Adding Au or Ag can decrease the onset melting temperature （233℃） of this alloy to 203,5℃ and 216℃, respectively. The results indicate that the Sn-5Sb-i.5Au alloy has very good ultimate tensile strength （UTS）, ductility, and fusion heat, which are better than both those of the *** and Sn-5Sb alloys. The formation of intermetallic compounds （IMCs） AuSn4 and Ag3Sn enhanced the SbSn precipitates in the solidification microstructure microstructure stability, while retained the formation of thus significantly improved the strength and ductility For all alloys, both UTS and yield stress （σy） increase with increasing strain rate and decrease with increasing temperature in tensile tests, but changes of ductility are generally small with inconsistent trends.

关键词： Sn-Sb solder Lead-free solder Melting temperature Tensile strength

Characterization of low-purity clays for geopolymer binder formulation

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2014年第6期21卷 609-619页

作者： Nasser y.Mostafa Q.Mohsen A.el-maghraby Materials and Corrosion Lab (MCL) Department of Chemistry Faculty of Science Taif University Department of Chemistry Faculty of Science Suez Canal University Refractory & Ceramics Department National Research CenterDokki 12622 Cairo Egypt

The production of geopolymer binders from low-purity clays was investigated. Three low-purity clays were calcined at 750℃ for 4 h. The calcined clays were chemically activated by the alkaline solutions of NaOH and Na2SiO3. The compressive strength was measured as a function of curing time at room temperature and 85℃. The results were compared with those of a pure kaolin sample. An amorphous aluminosilicate polymer was formed in all binders at both processing temperatures. The results show that, the mechanical properties depend on the type and amount of active aluminum silicates in the starting clay material, the impurities, and the processing temperature.

关键词： geopolymers microstructure X-ray diffraction compressive strength clay

Stem cell transplantation in cerebrovascular accidents:A global bibliometric analysis(2000-2023)

在线全文

学校读者我要写书评

暂无评论

World Journal of Stem Cells 2024年第9期16卷 832-841页

作者： Jad el masri Ahmad Afyouni Maya Ghazi Karim Hamideh Israe Moubayed Abdo Jurjus Hanine Haidar Ruzanna Petrosyan Pascale Salameh Hassan Hosseini École Doctorale Sciences de la Vie et de la Santé UniversitéParis-Est CréteilCréteil 94010France INSERM U955-E01 Institut Mondor de Recherche BiomédicaleUniversitéParis-Est CréteilCréteil 94000France Faculty of Medical Sciences Lebanese UniversityBeirut 1533Lebanon Department of Anatomy Cell Biology and Physiological SciencesFaculty of MedicineAmerican University of BeirutBeirut 1107Lebanon Department of Neurology Faculty of MedicineLebanese American UniversityBeirut 1102Lebanon Department of Pathology Faculty of MedicineLebanese American UniversityBeirut 1102Lebanon Faculty of Pharmacy Lebanese UniversityBeirut 1102Lebanon Faculty of Medicine Lebanese American UniversityBeirut 1102Lebanon Department of Primary Care and Population Health University of Nicosia Medical SchoolNicosia 2408Cyprus Institut National de SantéPublique d'Épidémiologie Clinique et de Toxicologie-Liban Beirut 1103Lebanon Department of Neurology Henri Mondor HospitalAP-HPCréteil 94000France

BACKGROUND Cerebrovascular accident(CVA)is a major global contributor to death and *** part of its medical management,researchers have recognized the importance of promising neuroprotective strategies,where stem cell transplantation(SCT)is thought to confer advantages via trophic and neuroprotective *** To evaluate the current state of research on SCT in patients with CVA,assess key trends and highlight literature *** PubMed was screened for SCT in CVA-related articles in October 2023,for each country during the period between 2000 and *** the World Bank data,total population and gross domestic product were collected for ***_1.6.19 was used to create the VOS figure using the results of the same *** and tables were obtained using Microsoft Office *** A total of 6923 studies were identified on SCT in CVA,making 0.03%of all published studies ***,68%were conducted in high-income countries,with a significant focus on mesenchymal stem *** journal“Stroke”featured the largest share of these articles,with mesenchymal SCT having the highest rate of inclusion,followed by hematopoietic *** time,there has been a noticeable shift from in vitro studies,which assess stem cell proliferation and neurogenesis,to in vivo studies aimed at evaluating efficacy and ***,the number of reviews increased along this *** This bibliometric analysis provides a comprehensive guide for physicians and researchers in the field through an objective overview of research activity,and highlights both current trends and *** a potential therapeutic role in CVA,more research is needed in the future to focus on different aspects of SCT,aiming to reach a better treatment strategy and improve life quality in patients.

关键词： Bibliometric analysis PubMed Stem cell transplantation Cerebrovascular accidents Stroke

Unlocking the power of blockchain in education:An overview of innovations and outcomes

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Blockchain(Research and Applications) 2023年第4期4卷 99-117页

作者： Amr el Koshiry Entesar eliwa Tarek Abd el-Hafeez Mahmoud y.Shams Department of Curricula and Teaching Methods College of EducationKing Faisal UniversityAl-Ahsa31982Saudi Arabia Faculty of Specific Education Minia UniversityMinia61519Egypt Department of Mathematics and Statistics College of ScienceKing Faisal UniversityAl-Ahsa31982Saudi Arabia Department of Computer Science Faculty of ScienceMinia UniversityMinia61519Egypt Computer Science Unit Deraya UniversityMinia UniversityMinia61519Egypt Faculty of Artificial Intelligence Kafrelsheikh UniversityKafrelsheikh33516Egypt

Blockchain is a revolutionary technology that has the potential to revolutionize various industries,including finance,supply chain management,healthcare,and *** decentralized,secure,and transparent nature makes it ideal for use in industries where trust,security,and efficiency are of paramount *** integration of blockchain technology into the education system has the potential to greatly improve the efficiency,security,and credibility of the educational *** creating secure and transparent platforms for tracking and verifying students’academic achievements,blockchain technology can help to create a more accessible and trustworthy education system,making it easier for students to showcase their skills and knowledge to potential *** the potential benefits of blockchain in education are significant,there are also several challenges that must be addressed in order to fully realize the potential of this technology in the educational *** of the major challenges include adoption,technical knowledge,interoperability,regulation,cost,data privacy and security,scalability,and *** necessary equipment for the implementation of blockchain technology in education is diverse and critical to the success of this innovative *** should carefully consider this equipment when planning their implementation of blockchain technology in education to ensure the efficient and secure transfer of educational data and transactions within the blockchain *** technology has the potential to play a significant role in promoting sustainability education and advancing the sustainability goals of both individuals and *** should consider incorporating blockchain technology into their sustainability education programs,in order to enhance the transparency,verifiability,and efficiency of their sustainability-related *** the use of blockchain technology in education is still i

关键词： Blockchain Education Sustainability Internet of things Machine learning Credential verification

Position and Velocity Time Delay for Suppression Vibrations of a Hybrid Rayleigh-Van der Pol-Duffing Oscillator

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Sound & Vibration 2020年第3期54卷 149-161页

作者： y.A.Amer A.T.el-Sayed M.N.Abd el-Salam Mathematics Department Science FacultyZagazig UniversityZagazigEgypt Basic Sciences Department Modern Academy for Engineering and TechnologyCairoEgypt Basic Sciences Department Higher Technological Institute10th of Ramadan CityEgypt

In this paper,we used time delay feedback to minimize the vibrations of a hybrid Rayleigh–van der Pol–Duffing *** system is a one-degree-offreedom containing the cubic and fifth nonlinear terms and an external *** applied the multiple scales method to get the solution from first *** and numerically,we studied the system before and after adding time delay feedback at the primary resonance case(ffi!).We used MATLAB program to simulate the efficacy of different parameters and the time delay on the main system.

关键词： Position time delay feedback velocity time delay feedback multiple scales method resonance cases

A Suitable Active Control for Suppression the Vibrations of a Cantilever Beam

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Sound & Vibration 2022年第2期56卷 89-104页

In our consideration,a comparison between four different types of controllers for suppression the vibrations of the cantilever beam excited by an external force is carried *** four types are the linear velocity feedback control,the cubic velocity feedback control,the non-linear saturation controller(NSC)and the positive position feedback(PPF)*** suitable type is the PPF controller for suppression the vibrations of the cantilever *** approximate solution obtained up to the first approximation by using the multiple scale *** PPF controller effectiveness is studied on the *** used frequency-response equations to investigate the stability of a cantilever *** notified that,there is a good agreement between the analytical solution and the numerical solution.

关键词： Cantilever beam cubic velocity feedback control linear velocity feedback control non-linear saturation controller(NSC) positive position feedback(PPF)controller

Vibration suppression in multi-tool ultrasonic machining to multi-external and parametric excitations

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2009年第3期25卷 403-415页

作者： M.M.Kamel W.A.A.el-Ganaini y.S.Hamed Department of Engineering Mathematics Faculty of Electronic EngineeringMenoufiya University

Ultrasonic machining （USM） is of particular interest for the machining of non-conductive, brittle materials such as engineering ceramics. In this paper, a multi-tool technique is used in USM to reduce the vibration in the tool holder and have reasonable amplitude for the tools. This can be done via dynamic absorbers. The coupling of four nonlinear oscillators of the tool holder and tools representing ultrasonic cutting process are investigated. This leads to a four-degree-of-freedom system subjected to multi-external and multi-parametric excitation forces. The aim of this work is to control the tool holder behavior at simultaneous primary, sub-harmonic and internal resonance condition. Multiple scale perturbation method is used to obtain the solution up to the second order approximations. The different resonance cases are reported and studied numerically. The stability of the system is investigated by using both phase-plane and frequency response techniques. The effects of the different parameters of the tools on the system behavior are studied numerically. Comparison with the available published work is reported.

关键词： Control Stability Ultrasonic machining (USM)

Geochemical constraints and uranium potential of the younger granitic rocks in el Maghrbia area, Central Eastern Desert, Egypt

在线全文

学校读者我要写书评

暂无评论

Acta Geochimica 2021年第4期40卷 623-639页

作者： A.E.el-Kammar A.H.el-Afandy T.Nasr M.Coltorti F.Casetta Department of Geology Faculty of ScienceCairo UniversityCairoEgypt Nuclear Materials Authority El MaadiCairoEgypt Department of Physics and Earth Sciences University of FerraraFerraraItaly

The present work deals with the mineralogy,geochemical behavior and uranium potentiality of the monzogranites of el Maghrbia area,which comprise *** Maghrbia and *** Eredyia and situated in the central Eastern Desert of ***-Erediya monzogranites represents a promising area for uranium *** granites have shear zone filled with red and black silica veins containing many radioactive anomalies with visible yellow secondary uranium *** shear zone is highly affected by different degrees of alterations such as silicification,kaolinitization,sassuritization and *** of el-Erediya area possess higher values of their radioactivity than in el Maghrbia monzogranites in which eU and eTh,reaches up to 792.3 and 66.81 ppm,whilst average content of eU and eTh in el Maghrabia granites are 3.86 and 8.55 ppm,respectively owing to the presence of radioactive minerals such as uraninite,uranothorite,uranophane,kasolite,betafite,zircon and *** geochemical analyses indicated that,the studied monzogranites are distinctly anomalous in U,where the average U is more than 620-fold the Upper Continental Crust(UCC),marked enrichment(> tenfold) of the elements Cd,Mo,Pb,Bi,Nb and *** Th/U ratio decreases from 2.8,as a chondritic value,to 0.0023 for the studied granites,proposing extreme fractionation towards an extensive secondary migration-in of *** Zr and Hf are depleted in the studied granites relative to the UCC,whereas Nb and Ta are strongly *** content of y is about sixfold enriched which reflects relative enhancement of the HREE during the alteration *** correlates with Fe_(2)O_(3),suggesting a possible association between uranium and ***,the occurrences of uranium are epigenetic by remobilization from the host rock to the sheared zones,probably through metasomatic process where U-Fe-Mg replaced the feldspars in an oxidized *** high levels of radioactivity in the rocks

关键词： Potentiality Uranium Geochemistry el Maghrabia el Erediya Egypt

Thermal oil recovery factors from sandpacks of variable mineralogy

在线全文

学校读者我要写书评

暂无评论

Petroleum Research 2023年第4期8卷 481-489页

作者： Viacheslau y.Kudrashou Hisham A.Nasr-el-Din Slippery Rock University United States Texas A&M University United States

S Steam injection is commonly used for production of viscous crude *** rock often contains clay *** nature of steam and clay minerals may lead to formation *** work in-vestigates oil recovery and changes in petrophysical properties as a function of the ***-packs with quartz,calcite,feldspar,kaolinite,smectite,and illite were prepared for steam injection *** of the steamed sandpacks was determined using coreflood *** composition of the produced aqueous samples was determined using ICP-OES(inductively coupled plasma-optical emission spectroscopy).Morphology of the rock samples was studied using SEM-EDs(scanning electron microscope-energy dispersive X-ray spectroscopy).Mineralogy and elemental content of the solid samples were determined using XRD(X-ray diffraction)analysis and XRF(X-ray fluorescence)*** was found that aqueous phase samples produced from clay-rich sandpacks tend to have higher pH than samples produced from samples without clay *** recovery factors for 100%quartz case was determined to be 65 wt%.Calcite-and feldspar-rich sandpacks produced 56 and 61 wt%of oil *** with clay fractions have shown the lowest oil recovery-39,29,and 28 wt%for kaolinite-,smectite-,and illite-rich samples *** dissolution and pre-cipitation were the dominant damaging mechanism for quartz and calcite ***-rich sandpack demonstrated signs of structural destruction of the mineral and fines ***'s effect on oil recovery was found to be associated with fines *** hydration and swelling in presence of steam was the dominant formation damage effect on the oil *** interaction with illite-rich sandpack caused formation of amorphous *** paper presents oil recovery factors as a function of injected pore volume(PV)of steam for sandpacks of different *** results characterize petroph

关键词： Steam injection Oilrecovery Kaolinite Smectite Ilite Sandpack