检索结果-南通市图书馆

Defence Technology（防务技术） 2018年第5期14卷 408-411页

作者： s.W.Maseko A.P.i.Popoola O.s.i.Fayomi Department of Chemical Metallurgicaland Materials EngineeringTshwane University of TechnologyPretoriaSouth Africa Department of Mechanical Engineering Covenant UniversityOtaNigeria

Titanium has found extensive use in various engineering applications due to its attractive physical,mechanical, and chemical characteristics. However, titanium has relatively low hardness for use as an armour material. ZrB2 was incorporated to the Ti matrix to form a Ti-based binary composites. in this study, powder metallurgy techniques were employed to disperse the ceramic particulates throughout the matrix material then consolidated through spark plasma sintering. The composites were densified at1300 ℃, pressure of 50 MPa, and holding time of 5 min. The microstructure and phase analysis of the sintered composites was carried out using sEM and XRD, while the hardness was determined using Vickers' microhardness tester. The sEM and XRD results confirmed the presence of the TiB whiskers which renowned with the improving the hardness of titanium. The hardness of the composite with 10 wt% ZrB_2 showed the highest hardness compared to that obtained for the 5 and 15 wt% ZrB_2 composites which was 495 and 571 Hv respectively.

关键词： sPs TiB whiskers Hardness Titanium matrix composites Reinforcement

Targeting harmful effects of non-excitatory amino acids as an alternative therapeutic strategy to reduce ischemic damage

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第9期20卷 2454-2463页

作者： Victoria Jiménez Carretero irisÁlvarez-Merz Jorge Hernández-Campano sergei A.Kirov Jesús M.Hernández-Guijo Department of Pharmacology and Therapeutic School of MedicineUniv.Autónoma de MadridMadridSpain Ramón y Cajal institute for Health Research(iRYCis) Neurobiology-Research ServiceHospital Ramón y CajalMadridSpain institute of Neurobiology Faculty of Mathematics and Natural SciencesHeinrich Heine University DüsseldorfDüsseldorfGermany Department of Neuroscience and Regenerative Medicine&Department of Neurosurgery Medical College of Georgia at Augusta UniversityAugustaGAUSA

The involvement of the excitatory amino acids glutamate and aspartate in ce rebral ischemia and excitotoxicity is ***,the role of non-excitatory amino acids in brain damage following a stroke or brain trauma remains largely *** release of amino acids by necrotic cells in the ischemic core may contribute to the expansion of the *** findings indicated that the reversible loss of field excitato ry postsynaptic potentials caused by transient hypoxia became irreversible when exposed to a mixture of just four non-excitatory amino acids(L-alanine,glycine,L-glutamine,and L-serine)at their plasma *** amino acids induce swelling in the somas of neurons and astrocytes during hypoxia,along with permanent dendritic damage mediated by N-methyl-D-aspartate *** N-methyl-D-aspartate receptors prevented neuronal damage in the presence of these amino acids during *** is likely that astroglial swelling caused by the accumulation of these amino acids via the alanine-serine-cysteine transporter 2 exchanger and system N transporters activates volume-regulated anion channels,leading to the release of excitotoxins and subsequent neuronal damage through N-methyl-D-aspartate receptor ***,previously unrecognized mechanisms involving non-excitatory amino acids may contribute to the progression and expansion of brain injury in neurological emergencies such as stroke and traumatic brain *** these pathways co uld highlight new therapeutic targets to mitigate brain injury.

关键词： cell swelling N-methyl-D-aspartate receptor non-excitatory amino acids stroke synaptic transmission

Response of plasma turbulence against externally-controlled perturbations

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2012年第9期21卷 385-395页

作者： s. i. itoh K. itoh Research institute for Applied Mechanics Kyushu University itoh Research Center for Plasma Turbulence Kyushu University National institute for Fusion science

A theory of the dynamic response of the turbulent plasma against the externally-controlled perturbations is reported. Based on Mori＇s method [Prog. Theor. Phys. 33 423 （1965）], the nonlinear force is assmned to be separated into the memory function and the nonlinear fluctuating force. The former corresponds to the damping term, and the latter is categorized into the noise term. The response of the turbulent plasma against the externally-controlled source is formulated. The response kernel, which connects the externally-controlled source and the response of the turbulent field, is shown to have both the nonlocal property （in space） and the non-Markovian response （in time）. A discussion is made on the nonlocal and non-Markovian response, including the case of disparate-scale interactions. A new method is proposed to observe experimentally the nonlocal interaction in the drift wave turbulence via the zonal flows.

关键词： turbulent transport nonlocal and non-Markovian response

stability of triple diffusive convection in a viscoelastic fluid-saturated porous layer

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2018年第10期39卷 1385-1410页

作者： K.R.RAGHUNATHA i.s.sHiVAKUMARA Department of Mathematics Bangalore University

The triple diffusive convection in an Oldroyd-B fluid-saturated porous layer is investigated by performing linear and weakly nonlinear stability analyses. The condition for the onset of stationary and oscillatory is derived analytically. Contrary to the observed phenomenon in Newtonian fluids, the presence of viscoelasticity of the fluid is to degenerate the quasiperiodic bifurcation from the steady quiescent state. Under certain conditions, it is found that disconnected closed convex oscillatory neutral curves occur, indicating the requirement of three critical values of the thermal Darcy-Rayleigh number to identify the linear instability criteria instead of the usual single value, which is a novel result enunciated from the present study for an Oldroyd-B fluid saturating a porous medium. The similarities and differences of linear instability characteristics of Oldroyd-B, Maxwell, and Newtonian fluids are also highlighted. The stability of oscillatory finite amplitude convection is discussed by deriving a cubic Landau equation,and the convective heat and mass transfer are analyzed for different values of physical parameters.

关键词： Oldroyd-B fluid bifurcation instability perturbation method nonlinear stability heat and mass transfer

Optimizing the defensive characteristics of mild steel via the electrodeposition of Zn-si3N4 reinforcing particles

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2019年第4期15卷 526-532页

作者： i.G. Akande O.O. Oluwole O.s.i. Fayomi Department of Mechanical Engineering University of Ibadan Ibadan Oyo state Nigeria Department of Mechanical Engineering Covenant University ota ogun state Nigeria Department of Chemical Metallurgical and Materials Engineering Tshwane University of Technology Pretoria South Africa

The effect of Zn-si3 N4 deposition prepared via direct electrolytic co-deposition on mild steel was studied as a result its inherent vulnerability to corrosion in an aggressive environment and failure on the application of *** experiment was conducted varying the mass concentration of silicon nitride(si3 N4)between 7 and 13 gat cell voltage of 0.3 and 0.5 V,at constant temperature of 45℃.The morphologies of the coated surfaces were characterized using high resolution Nikon Optical Microscope and scanning Electron Microscope(sEM)revealing that the particles of the Zn-si3 N4 were homogeneously *** corrosion behaviour was studied using potentiodynamic polarization technique in 3.65%NaCl solution and the microhardness was examined using Brinell hardness testing *** result of the corrosion experiment confirmed an improved corrosion resistance with a reduction in corrosion rate from 9.7425 mm/year to 0.10847 mm/year,maximum coating efficiency of 98.9%,maximum polarization resistance of 1555.3 Ω and a very low current density of 9.33 × 10-6A/*** negative shift in the Ecorr revealed the cathodic protective nature of the *** microhardness was also found to have increased from 137.9 HBN for the unmodified steel to a maximum value of 263.3 HBN for the0.5 Zn-13 si3 N4 coated steel representing 90.9% increment in hardness as a result of the matrix grain refining and dispersion-strengthening ability of the incorporated si3 N4 particles.

关键词： Polarization Corrosion Microhardness Coating Composite Matrix

Flow-Field of an Axisymmetric Lobed Mixer

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal science 2004年第1期13卷 40-45页

作者： i.Yimer s.Manipurath i.Campbell W.E.Carscallen Gas Turbine Environmental Research Centre Aerodynamics LabInstitute for Aerospace ResearchNational Research Council Canada1200 Montreal RoadOttawaOntarioCanadaK1A 0R6

The flow-field of a fuel/air mixing system with an axisymmetric lobed mixer was numerically investigated. Large-scale streamwise vortices are formed immediately downstream of the mixer trailing edge, stretched further downstream, and finally broken into fragments where more intense mixing occurs. Both numerical and experimental results indicate that the length required for streamwise vortices breakdown in the confined flow-field of an axisymmetric lobed mixer is much shorter than that in the case of planar lobed mixers subject to parallel freestreams. For the conditions studied, the streamwise vortices start to breakdown at three wavelengths downstream of the mixer trailing edge.

关键词： axisymmetric lobed mixer confined flow fuel/air mixing

A simple semiempirical model for the static polarizability of electronically excited atoms and molecules

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2023年第4期32卷 290-301页

作者： Alexander s sharipov Alexey V Pelevkin Boris i Loukhovitski Central institute of Aviation Motors Aviamotornaya 2Moscow 111116Russia

We present a semiempirical analytical model for the static polarizability of electronically excited atoms and molecules,which requires very few readily accessible input data,including the ground-state polarizability,elemental composition,ionization potential,and spin multiplicities of excited and ground *** very simple model formulated in a semiclassical framework is based on a number of observed trends in polarizability of electronically excited *** adjust the model,both accurate theoretical predictions and reliable measurements previously reported elsewhere for a broad range of multielectron species in the gas phase are *** some representative compounds of general concern that have not yet attracted sufficient research interest,the results of our multireference second-order perturbation theory calculations are additionally *** show that the model we developed has reasonable(given the considerable uncertainties in the reference data)accuracy in predicting the static polarizability of electronically excited species of arbitrary size and excitation *** findings can be useful for many applications,where there is a need for inexpensive and quick assessments of the static gas-phase polarizability of excited electronic states,in particular,when building the complex nonequilibrium kinetic models to describe the observed optical refractivity(dielectric permittivity)of nonthermal reacting gas flows.

关键词： polarizability electronic excitation semiempirical model quantum chemistry

Low cycle fatigue properties and cyclic deformation behavior of as-extruded AZ31 magnesium alloy

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous Metals society of China 2010年第B07期20卷 533-539页

作者： s.KWON K.sONG K.s.sHiN s.i.KWUN Department of Materials science and Engineering Korea University school of Materials science and Engineering Seoul National University

The low cycle fatigue(LCF)properties of as-extruded AZ31 Mg alloy were investigated under total strain amplitudes in the range of 0.4%-1.2%with strain rate of 1×10- 2s -*** to the twinning effect in compression during loading and the detwinning effect during unloading,the alloy showed an asymmetric hysteresis *** cyclic stress response exhibited cyclic hardening at high total strain *** cyclic deformation behaviors were discussed using the Coffin-Manson plot,which divided the plastic strain amplitudes into the tension side and the compression *** the LCF tests that were started from either tension or compression under a total strain amplitude of 1.0%,the interaction between the twinning effect and dislocation was *** twinning effect during the LCF test and the variation of the dislocation density were investigated using optical microscopy and transmission electron microscopy,respectively.

关键词： AZ31 magnesium alloy low cycle fatigue twinning dislocation

Magnetic properties of sn-substituted Ni-Zn ferrites synthesized from nano-sized powders of NiO, ZnO, Fe2O3, and snO2

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2017年第7期26卷 377-382页

作者： M A Ali M M Uddin M N i Khan F U Z Chowdhury s M Hoque s i Liba Department of Physics Chittagong University of Engineering and Technology (CUET) Materials science Division Atomic Energy Center

A series of Ni0.6-x/2Zn0.4-x/2snxFe2O4(x = 0.0, 0.05, 0.1, 0.15, 0.2, and 0.3)(NZsFO) ferrite composities have been synthesized from nano powders using a standard solid state reaction technique. The spinel cubic structure of the investigated samples has been confirmed by x-ray diffraction(XRD). The magnetic properties such as saturation magnetization(Ms),remanent magnetization(Mr), coercive field(Hc), and Bohr magneton(μ) are calculated from the hysteresis loops. The value of Msis found to decrease with increasing sn content in the samples. This change is successfully explained by the variation of A-B interaction strength due to sn substitution in different sites. The compositional stability and quality of the prepared ferrite composites have also been endorsed by the fairly constant initial permeability(μ’) over a wide range of frequency. The decreasing trend of μ’ with increasing sn content has been observed. Curie temperature TChas been found to increase with the increase in sn content. A wide spread frequency utility zone indicates that the NZsFO can be considered as a good candidate for use in broadband pulse transformers and wide band read-write heads for video recording. The composition of x = 0.05 shows unusual results and the possible reason is also mentioned with the established formalism.

关键词： magnetic properties saturation magnetization permeability Curie temperature

Prevalence and Associated Factors of Eating Disorders in Weight Management Centers in Tanta, Egypt

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Medical Journal 2018年第1期131卷 50-55页

作者： Noha Eladawi Randah Helal Nermeen A Niazy sherehan abdelsalam Department of Public Health and Community Medicine Faculty of Medicine Mansoura University Mansoura 35516 Egypt

Background： Eating disorders （EDs） are serious illnesses associated with medical complications and have been increased, especially among societies with an excessive concern about weight, shape, or appearance. This study aimed to investigate the prevalence of EDs among the individuals attending weight management centers and its associated factors. Methods： A cross-sectional study was carried out among individuals attending four weight management centers in Tanta, Gharbia Governorate, Egypt during the period from July to December 2016. Precoded interview questionnaires were used to identify the following data： sociodemographic characteristics and medical history of depression or psychological disorders and the Eating Attitude Test （EAT-40） was used to assess the attitudes, behavior, and traits associated with the EDs. Results： A total of 400 participants （i 12 males and 288 females） were included in the study. According to EAT-40 questionnaires, the prevalence of positive and negative EDs was 65.0% （n = 260） and 35.0% （n = 140）, respectively. EDs were more likely reported by females, married singles, rural residents, those with higher education, and nonworking or part-time working patients, those who were overweight or obese, and who were suffering from depression or any psychological problems. Logistic regression analysis revealed that the independent predictors of EDs were age （adjusted odds ratio [OR]： 1.06）, nonworking （adjusted OR： 2.32） or part-time working （adjusted OR： 2,18）, increased body weight （adjusted OR： 2.66 for overweight and adjusted OR： 1.24 for obese）, and having a history of depression or any psychological problem （adjusted OR： 2.76）. Factor analysis of EAT-40 revealed four factors （eating behavior, diet-related lifestyle, weight concern, and food preoccupation） that were responsible for 33.2% of the total variance. Conclusions： EDs are prevalent among individuals attending the weight management centers in a northern city in Egypt. specific manage

关键词： Eating Disorders: Egypt: Weight Management Centers