检索结果-南通市图书馆

Tribological performance of iron- and nickel-base self-lubricating claddings containing metal sulfides at high temperature

引用

Friction 2022年第12期10卷 2069-2085页

作者： Hector torres Tugce CAYKARA Jens HARDELL Janne NURmINEN Braham PRAKASH manel RODRIGUEZ RIPOLL AC2T research GmbH Viktor-Kaplan-Straße 2/CWiener Neustadt 2700Austria Department of Applied Physics and mechanical Engineering LuleåUniversity of TechnologyLuleå97187Sweden Castolin Eutectic GmbH Gutenbergstraße 10Kriftel 65830Germany Department of mechanical Engineering Tsinghua UniversityBeijing 100084China

Iron-based coatings with the incorporation of solid lubricants have been prepared by means of laser cladding,in an effort to control friction and decrease tool wear at high temperatures during metal forming applications.The choice of a Fe-based powder has been considered advantageous,as it can lead to decreased costs compared to nickel-based claddings previously studied by the authors,in addition to having a lower environmental impact.In particular,the incorporation of transition metal dichalcogenides such as moS_(2) as precursors leads to the encapsulation of silver in Fe-based self-lubricating claddings,resulting in a uniform distribution of the soft metal across the thickness of the coating.Subsequent tribological evaluation of the claddings at high temperatures shows that the addition of lubricious compounds leads to lower friction at room temperature and significantly decreased wear up to 600℃ compared to the unmodified iron-based reference alloy,although higher than similar self-lubricating Ni-based claddings.In order to cast light into these observed differences,the corresponding microstructures,phase composition,and self-lubricating mechanisms have been studied and compared for Fe-and Ni-based claddings having both of them the addition of silver and moS_(2).The results suggest a key role of the formation of protective tribolayers on the counter body during high temperature sliding contact.Additional simulation of the phase evolution during solidification reveals that the formation of different chromium-and nickel-based metal sulfides in Fe-and Ni-claddings during laser cladding by the decomposition of moS_(2) plays a key role in determining their tribological behaviour at high temperatures.

关键词： high temperature laser cladding self-lubrication metal forming chromium sulphide moS_(2)

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

Electrospinning Polylactic Acid Polymer membranes as Biological Sieve for Yeast and Bacteria

引用

materials Sciences and Applications 2022年第6期13卷 389-400页

作者： Ernesto Suaste-Gómez Grissel Rodríguez-Roldán Ilian Pérez-Solis Ana Laura torres-Huerta Carlos cruz-cruz José Tapia-Ramírez Department of Electrical Engineering Section of Bioelectronics Center for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV) Mexico City Mexico National Laboratory of Experimental Services (LaNSE) CINVESTAV Mexico City Mexico Department of Genetics and molecular Biology CINVESTAV Mexico City Mexico

Vaginal infections are suffered by millions of women of reproductive age. Recent research has shown that timely diagnosis of these infections avoids complications in the patient’s health. Since the symptoms of infections caused by yeast and bacteria are similar, the patient is not always treated properly. membranes with three different thicknesses (66 μm, 83 μm, 128 μm) were produced by electrospinning of polylactic polymer (PLA) and were used as a biological sieve to detect microorganisms present in vaginal infections, bacteria or yeasts. Electrospinning technique is a technique that allows the generation of membranes from nanofibers of material polymeric and therefore, obtaining porous structures. The size of the fibers was observed as well as the morphology and the size of the pores, using the scanning electron microscopy (SEm). The effectiveness of these membranes was proven by the cultivation of the bacteria that passed through the polymeric membrane and the yeasts retained by it. The membranes allowed the retention of yeasts of Candida albicans type with dimensions of 7 μm, which allowed the separation of Brevibacterium ravens purgense bacteria with dimensions of 1.4 μm, thus demonstrating their effectiveness as biological sieve.

关键词： Biological Sieve Electrospinning Polylactic Acid Vaginal Infections

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

Variational Calculus With Conformable Fractional Derivatives

引用

IEEE/CAA Journal of Automatica Sinica 2017年第2期4卷 340-352页

作者： matheus J.Lazo Delfim F.m.torres Instituto de matemática Estatística e Física-FURG Center for Research and Development in mathematics and Applications (CIDmA) Department of MathematicsUniversity of Aveiro

Invariant conditions for conformable fractional problems of the calculus of variations under the presence of external forces in the dynamics are studied. Depending on the type of transformations considered, different necessary conditions of invariance are obtained. As particular cases, we prove fractional versions of Noether's symmetry theorem. Invariant conditions for fractional optimal control problems, using the Hamiltonian formalism, are also investigated. As an example of potential application in Physics, we show that with conformable derivatives it is possible to formulate an Action Principle for particles under frictional forces that is far simpler than the one obtained with classical fractional derivatives.

关键词： Conformable fractional derivative fractional calculus of variations fractional optimal control invariant variational conditions Noether’s theorem

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

Constrained Fractional Variational Problems of Variable Order

引用

IEEE/CAA Journal of Automatica Sinica 2017年第1期4卷 80-88页

作者： Dina Tavares Ricardo Almeida Delfim F.m.torres Department of mathematics Polytechnic Institute of Leiria Department of mathematics University of Aveiro

Isoperimetric problems consist in minimizing or maximizing a cost functional subject to an integral constraint.In this work, we present two fractional isoperimetric problems where the Lagrangian depends on a combined Caputo derivative of variable fractional order and we present a new variational problem subject to a holonomic constraint. We establish necessary optimality conditions in order to determine the minimizers of the fractional problems. The terminal point in the cost integral,as well as the terminal state, are considered to be free, and we obtain corresponding natural boundary conditions.

关键词： Fractional calculus fractional calculus of variations holonomic constraints isoperimetric constraints optimization variable fractional order

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

Influence of fire on woody vegetation of savanna and forest formations in the Cerrado biome

引用

林业研究:英文版 2023年第5期34卷 1207-1216页

作者： Aline das Gracas Costa Fillipe Tamiozzo Pereira torres Gumercindo Souza Lima Fabiano Rodrigues de melo Carlos moreira miquelino Eleto torres Bruno Leao Said Schettini Vicente Paulo Santana Neto AndréLuiz Lopes de Faria Department of Forest Engineering Federal University of VicosaUFVVicosaMG 36570-900Brazil Department of Geography Federal University of VicosaUFVVicosaMG 36570-900Brazil

Wildfires have environmental,economic,and social impacts,and can shape the landscape and benefit ecosystems such as the Cerrado.This study evaluated the diversity,similarity,and floristic and structural differences of woody savanna and forest formations of the Cerrado,when affected and not affected by fire.Twenty-eight 25-400m2 plots were randomly allocated and divided into Burnt Cerrado and Unburnt Cerrado,Burnt Forest,and Unburnt Forest,and divided into three levels of inclusion according to diameter class(smaller than 2 cm,2-5 cm and larger than5 cm).Species were identified,DBH and height measured,and phyto sociological parameters such as volume,diversity,and floristic similarity evaluated.Burnt Cerrado had lower diversity,density,and dominance at all inclusion levels compared to the Unburnt Cerrado,and showed similarities between treatments at the inclusion levels.Burnt Forest had smaller differences in diversity,density,and dominance than Unburnt Forest.Forest formation was similar at level 1 of inclusion and in the total area.However,it was dissimilar at lower levels.The lower density and diversity of species at the lowest levels of inclusion was associated with mortality from fire.

关键词： Biodiversity Brazil Burning Floristic Phytosociology

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

Obesity is associated with the Arg389Gly ADRB1 but not with the Trp64Arg ADRB3 polymorphism in children from San Luis Potosí and León,méxico

引用

The Journal of Biomedical Research 2017年第1期31卷 40-46页

作者： Celia Aradillas-García miguel cruz Elva Perez-Luque maria E.Garay-Sevilla Juan m.malacara Aduna R Jesús Peralta Ana Burguete-García Jorge A.Alegría-torres Faculty of medicine of the Autonomous University of San Luis Potosi MéxicoCIACYT-Facuity of MedicineC.P. 78210 San Luis Potosi S.L.P. México medical Research Unit in Biochemistry Hospital de EspecialidadesCentro Medico Nacional Siglo XXI del Instituto Mexicano del Seguro SocialMexico City C.P 06720 Mexico Department of medical Sciences Campus LeónUniversity of Guanajuato.LeónC.P.37320.México Chronic Infection and Cancer Division Research Center on Infectious DiseasesInstituto Nacional de Salud PublicaC.P.62100CuernavacaMorelosMéxico Department of Pharmacy Campus GuanajuatoUniversity of GuanajuatoNoria Alta C.P.36050GuanajuatoMéxico

This research was designed to analyze the possible associations of Arg389 Gly ADRB1 and Trp64 Arg ADRB3polymorphisms in children with obesity.A cross-sectional study included 1,046 school-age mexican participants（6-12 years old） from the cities of San Luis Potosi and Leon.Children were classified as non-obese or obese according to their body mass index（BmI） percentile;obese children had a BmI≥95th percentile for sex and age.Biochemical data were collected.Polymorphisms were detected using Taqman qPCR assay.A logistic regression analysis was used to calculate the risk of obesity based on genotypes.Differences were found between groups where obese children had a significant increase in systolic and diastolic blood pressure,fasting plasma glucose,insulin,HOmAIR,LDL-cholesterol,triglycerides,and lower HDL-cholesterol compared with the normal weight group（P 〈 0.05）.The distribution of allele frequency in the population was Arg = 87.4 and Gly = 12.6（Hardy Weinberg equilibrium x^2= 3.16,P = 0.07）;Trp = 81.5 and Arg= 18.5（Hardy Weinberg equilibrium x^2 = 2.2,P = 0.14） for ADRB1 and ADRB3,respectively.Even though no different frequencies of Arg389 Gly polymoiphism between groups were found（P = 0.08）,children carriers of one Gly389,ADRB1 allele had a risk for obesity of OR = 1.40（95%CI,1.03-1.90,P =0.03） after adjustment for age and gender.No other association was found for Trp64 Arg ADRB3 polymorphism.Only the Arg389 Gly ADRB1 polymorphism was associated with risk for obesity in mexican children.

关键词： childhood obesity β-adrenergic receptor（ADRB） gene polymorphisms mexican children

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

Expression and function of renal and hepatic organic anion transporters in extrahepatic cholestasis

引用

World Journal of Gastroenterology 2012年第44期18卷 6387-6397页

作者： Anabel Brandoni maría Herminia Hazelhoff Romina Paula Bulacio Adriana mónica torres Pharmacology Unit Department of Physiological SciencesFaculty of Biochemical and Pharmaceutical SciencesNational University of Rosariothe National Scientific and Technical Research Council2000 RosarioArgentine

Obstructive jaundice occurs in patients suffering from cholelithiasis and from neoplasms affecting the pancreas and the common bile duct.The absorption,distribution and elimination of drugs are impaired during this pathology.Prolonged cholestasis may alter both liver and kidney function.Lactam antibiotics,diuretics,non-steroidal anti-inflammatory drugs,several antiviral drugs as well as endogenous compounds are classified as organic anions.The hepatic and renal organic anion transport pathways play a key role in the pharmacokinetics of these compounds.It has been demonstrated that acute extrahepatic cholestasis is associated with increased renal elimination of organic anions.The present work describes the molecular mechanisms involved in the regulation of the expression and function of the renal and hepatic organic anion transporters in extrahepatic cholestasis,such as multidrug resistanceassociated protein 2,organic anion transporting polypeptide 1,organic anion transporter 3,bilitranslocase,bromosulfophthalein/bilirubin binding protein,organic anion transporter 1 and sodium dependent bile salt transporter.The modulation in the expression of renal organic anion transporters constitutes a compensatory mechanism to overcome the hepatic dysfunction in the elimination of organic anions.

关键词：有机阴离子转运蛋白胆汁盐肝脏肾脏淤积非甾体类抗炎药抗病毒药物

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

Electrochemical Corrosion Study in H₂SO₄ of NiAl with Cu Additions, microstructure and micro-Hardness at Room Temperature

引用

Journal of minerals and materials Characterization and Engineering 2022年第3期10卷 225-241页

作者： Jesús m. Colín de la cruz Sergio A. Serna Barquera Alvaro torres-Islas Arturo molina-Ocampo Edgar Valenzuela José G. González Rodríguez Universidad Autónoma del Estado de morelos Facultad de Ciencias Químicas e Ingeniería UAEM-FCQeI. Av. Universidad 1001Colonia Chamilpa Cuernavaca Morelos México Universidad Autónoma del Estado de morelos Centro de Investigación en Ingeniería y Ciencias Aplicadas UAEM-CIICAp Cuernavaca Morelos México UABC Baja California Sur México

For many years, intermetallic materials promise applications in a wide variety of technology areas. NiAl intermetallic compound is material that exhibits important characteristics such as high corrosion resistance and low density besides its ability to retain strength and stiffness at elevated temperatures. However NiAl intermetallic is too hard, brittle and exhibits very low ductility at room temperature being the reason because this material is not yet available for structural applications. In order to increase the ductility of the NiAl intermetallic compound, the addition of a third alloying element has been proved, nevertheless it is important to determine if such additions decrease or increase the hardness and the corrosion resistance of the alloy. So, the present investigation reports the corrosion performance of the NiAl intermetallic compound modified with Cu, emphasizing the EIS analysis and the relation between physical parameters and the modelling equations used in the Equivalent Electric Circuit. It was found that the addition of Cu promotes the formation of the γ’-Ni3Al phase in Cu contents greater than 15 at. %, in addition to a decrease in micro hardness and an increment in the Icorr values. In this way, the electrochemical characterization evidenced a high corrosion resistance of these intermetallic alloys.

关键词： NiAl-Cu Corrosion Behavior Electrochemical Impedance Spectrum Vickers micro Hardness microstructure

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

A novel and stretchable carbon-nanotube/Ni@TiO_(2):W photocatalytic composite for the complete removal of diclofenac drug from the drinking water

引用

Journal of Environmental Sciences 2023年第4期126卷 575-589页

作者： Ernesto Valadez-Renteria Rafael Perez-Gonzalez Christian Gomez-Solis Luis Armando Diaz-torres Armando Encinas Jorge Oliva Vicente Rodriguez-Gonzalez Consejo Nacional de Ciencia y Tecnología-División de materiales Avanzados Instituto Potosino de Investigación Científica y TecnológicaSan Luis Potosí78216México División de Ciencias e Ingenierías Universidad de GuanajuatoLeón 37150México Grupo de Espectroscopia de materiales Avanzados y Nanoestructurados(GEmANA) Centro de Investigaciones enópticaA.C.Lomas Del CampestreLeón 37150México

We present the structural,morphological and photocatalytic properties of stretchable composites made with carbon nanotubes (CNTs),silicon rubber and Ni@TiO_(2):W nanoparticles(TiWNi NPs) with average size of 37±2 nm.microscopy images showed that the TiWNi NPs decorated the surface of the CNT fibers,which are oriented in a preferential direction.TiWNi NPs presented a mixture of anatase/rutile phases with cubic structure.The performance of the TiWNi powders and stretchable composites was evaluated for the photocatalytic degradation of diclofenac (DCF) anti-inflammatory drug under ultraviolet-visible light.The results revealed that the maximum DCF degradation percentages were 34.6%,91.9%,97.1%,98.5%and 100%for the CNT composite (stretched at 0%),TiWNi powders,CNT+TiWNi(stretched at 0%),CNT+TiWNi (stretched at 50%) and CNT+TiWNi (stretched at 100%),respectively.Thus,stretching the CNT+TiWNi composites was a good strategy to enhance the DCF degradation percentage from 97.1%to 100%,since stretching created additional defects (oxygen vacancies) that acted as electron sink,delaying the electron-hole recombination,and favors the DCF degradation.Raman/absorbance measurements confirmed the presence of such defects.moreover,the reactive oxygen species (ROS) were determined by the scavenger’s experiments and found that the main ROS were the·OH and O_(2)-radicals,which attacked the DCF molecules,causing their degradation.The results of this investigation confirmed that the stretchable CNT/TiWNi-based composites are a viable alternative to remove pharmaceutical contaminants from water and can be manually separated from the decontaminated water,which is unviable using photocatalytic powders.

关键词： Diclofenac Pharmaceutical contaminant TiO_(2) Carbon nanotubes Stretchable composite Photocatalysis

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

Effect of heat treatment on the mechanical and biocorrosion behaviour of two mg-Zn-Ca alloys

引用

Journal of magnesium and Alloys 2022年第2期10卷 581-595页

作者： N.Pulido-González P.Hidalgo-manrique S.García-Rodríguez B.torres J.Rams Departamento de matemática Aplicada Ciencia e Ingeniería de Materiales y Tecnología ElectrónicaESCETUniversidad Rey Juan CarlosC/Tulipán s/nMóstolesMadrid28933Spain

The effect of heat treatment on the mechanical and biocorrosion behaviour of the mg-1 wt.%Zn-1 wt.%Ca(ZX11)and mg-3 wt.%Zn-0.4 wt.%Ca(ZX30)alloys was evaluated.For this purpose,three-point bending tests as well as electrochemical and immersion tests in Hank’s solution were performed on both alloys in four different thermal conditions:as-cast,solution-treated,peak-aged and over-aged.microstructural examinations revealed that the as-cast ZX11 and ZX30 alloys exhibit a microstructure composed ofα-mg grains separated by large mg_(2)Ca and Ca_(2)mg_(6)Zn_(3) particles and by large Ca_(2)mg_(6)Zn_(3) particles,respectively.During solution treatment,the Ca_(2)mg_(6)Zn_(3) precipitates at the grain boundaries(GBs)are fully dissolved in the ZX11 alloy,but mainly redistributed to form a more connected configuration in the ZX30 alloy,showing a poor age-hardening response.Consequently,after solution-treatment,galvanic corrosion and corrosion rate decreases in the former,but increases in the latter.The peak-aged condition displays the highest corrosion rate for both alloys,maybe due to an excessive number density of fine Ca_(2)mg_(6)Zn_(3) particles acting as cathodic sites.However,the over-aged condition shows the lowest corrosion rate for the ZX11 alloy and a very similar one to that of the as-cast sample for the ZX30 alloy.The ZX11 alloy shows generally better biocorrosion behaviour than the ZX30 alloy to its lower content in the Ca_(2)mg_(6)Zn_(3) phase and thus reduced galvanic corrosion.The mg_(2)Ca phase present in the studied ZX11 alloy has been proved to exhibit an increased corrosion potential,which has been related to an observed enrichment with Zn.

关键词： magnesium alloys Biodegradable implants Heat treatment microstructure mechanical properties Corrosion

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：