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Chinese Journal of Aeronautics 2024年第3期37卷 391-403页

作者： Wei HAO andrews larbi Hongkang DONG Dongyun WANG Shenghu LI Zhejiang Provincial Key Laboratory of Urban Rail Transit Intelligent Operation and Maintenance Technology and Equipment Zhejiang Normal UniversityJinhua 321004China College of Engineering Zhejiang Normal UniversityJinhua 321004China Hangzhou Lilong Hydraulic Co. LtdHangzhou 311200China

The cylinder block/valve plate interface is one of the most critical frictional interfaces of the swashplate-type axial piston ***,the poor lubrication interface caused rapid wear and high friction loss in an elastohydrodynamic lubrication system,decreasing the pump *** resistant bronze coatings were fabricated on 38CrMoAl substrate by Physical Vapor Deposition(PVD)and Chemical Vapor Deposition(CVD),***-on-disc wear tests were performed to comparatively investigate the wear behaviors of the coatings and bulk ductile iron *** can be found that the PVD-bronze coating exhibited better wear resistance than the other two *** enhanced wear resistance was attributed to the unique composite microstructure and desired mechanical strength,which could resist to mechanical shear and spallation,decreasing friction *** appropriate hardness of(1.33±0.07)GPa could be beneficial for enhancing its wear *** PVD-bronze coating possessed a much lower and stable coefficient of friction(about 0.1)and wear rate(about 6000μm3.N-1.m-1)under the loading forces of about 100 N after 20 *** wear mechanism was the abrasive wear.

关键词： Aircraft hydraulic pump Bronze Coatings Wear resistance Mechanisms

基于表面形貌优化的轴向柱塞泵缸体/配流盘界面性能仿真与实验验证

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基于表面形貌优化的轴向柱塞泵缸体/配流盘界面性能仿真与实验验证

作者：安迪（larbi andrews）浙江师范大学

学位级别：硕士

斜盘式轴向柱塞泵在航空、航天,船舶及工程机械等领域具有广泛应用。因为它们能够在高压和高速下运行,同时保持高效率。缸体-配流盘摩擦副(配流副)是其最关键的摩擦副组件,而优异的承载能力、耐磨性能和密封性能是其在极端工况下长寿命... 详细信息

斜盘式轴向柱塞泵在航空、航天,船舶及工程机械等领域具有广泛应用。因为它们能够在高压和高速下运行,同时保持高效率。缸体-配流盘摩擦副(配流副)是其最关键的摩擦副组件,而优异的承载能力、耐磨性能和密封性能是其在极端工况下长寿命工作的保障。在泵低速运行时,摩擦副界面润滑不良导致配流副磨损加剧,甚至降低泵体的寿命。可见,配流副界面油膜不仅需要承受外部载荷,而且在界面上起润滑作用,可以保持缸体-配流盘摩擦副的润滑特性,保证泵的高效运行。油膜无法在高压下维持外部负载,摩擦热耗散的表面处理不良,导致界面磨损。针对以上问题,前期研究者们采用表面耐磨涂层技术提高配流副表面的耐磨性能,但是耐磨涂层织构化引入表面起伏,这样会破坏摩擦副表面原有结构,增加其表面局部的变形,对配流副的耐磨性能极其不利。为了解决上述问题,本论文首先通过理论建模和数值仿真对配流副组件进行动态特性分析,揭示了表面粗糙度参数对其泄漏流量的影响,及容积效率损失的主要原因,从而为配流副表面结构优化提供理论指导;其次,设计制备了不同微观结构的铜基耐磨涂层,对上述仿真模拟理论进行验证。具体研究内容如下:(1)为了优化配流副界面设计提高其耐磨性能,建立数值模型来预测配流盘上的微凹坑半径,更好地了解其界面磨损和弹性变形机理。还研究了不同工况下温度对油液运动粘度和表面变形的影响。使用三种不同材料的配流盘,即38Cr Mo Al基底的青铜涂层(P1)、38Cr Mo Al基底的PVD青铜涂层(P2)、和氮化体球铁(P3)。结果表明,增加表面粗糙度值会影响泄漏流量和摩擦界面上的压力积聚。由于材料微观结构、所需韧性和硬度之间的最佳相关性,配流盘的铅青铜PVD涂层显示出更好的摩擦学性能,可能具有耐磨性。(2)为了验证仿真结果,本论文设计制备了三种不同的配流副表面涂层材料(经过不同表面处理的配流盘、相同材料的缸体对磨件),即青铜涂层-38Cr Mo Al基体(P1)、PVD涂层-38Cr Mo Al基体(P2)、氮化处理后的球墨铸铁-38Cr Mo Al基体(P3),采用油液环境摩擦磨损实验研究了不同载荷下上述涂层材料的耐磨性能。结果表明,界面的表面粗糙度影响配流盘材料的摩擦系数和磨损率。因此,当配流盘表面被纹理化时,需要一个合适的Ra值～0.4μm以获得最佳的摩擦界面性能。此外,阀板的铅青铜PVD涂层(P2)表现出优异的摩擦学性能,其适当的相组成和微观结构被认为是更好的摩擦学性能的原因,这与仿真结果一致。分析了不同涂层组成、微观结构对轴向柱塞泵缸体/配流盘涂层耐磨性能的影响。结合涂层硬度的表征,揭示了表面涂层磨损失效机理。本文可为斜盘轴向柱塞泵缸体/配流盘摩擦副的优化设计提供指导。

关键词：轴向柱塞泵缸体-配流盘界面动力学仿真模拟弹性变形耐磨性能失效机理

Molecular regulation of calcium-sensing receptor(CaSR)-mediated signaling

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Chronic Diseases and Translational Medicine 2024年第3期10卷 167-194页

作者： Li Tian Corey andrews Qiuyun Yan Jenny J.Yang Department of Chemistry Center for Diagnostics and TherapeuticsAdvanced Translational Imaging FacilityGeorgia State UniversityAtlantaGeorgiaUSA

Calcium-sensing receptor(CaSR),a family C G-protein-coupled receptor,plays a crucial role in regulating calcium homeostasis by sensing small concentration changes of extracellular Ca^(2+),Mg^(2+),amino acids(e.g.,L-Trp and L-Phe),small peptides,anions(e.g.,HCO_(3)^(-)and PO_(4)^(3-)),and ***-mediated intracellular Ca^(2+)signaling regulates a diverse set of cellular processes including gene transcription,cell proliferation,differentiation,apoptosis,muscle contraction,and neuronal *** of CaSR with mutations results in diseases such as autosomal dominant hypocalcemia,familial hypocalciuric hypercalcemia,and neonatal severe *** also influences calciotropic disorders,such as osteoporosis,and noncalciotropic disorders,such as cancer,Alzheimer's disease,and pulmonary arterial *** study first reviews recent advances in biochemical and structural determination of the framework of CaSR and its interaction sites with natural ligands,as well as exogenous positive allosteric modulators and negative allosteric *** establishment of the first CaSR protein-protein interactome network revealed 94 novel players involved in protein processing in endoplasmic reticulum,trafficking,cell surface expression,endocytosis,degradation,and signaling *** roles of these proteins in Ca^(2+)-dependent cellular physiological processes and in CaSR-dependent cellular signaling provide new insights into the molecular basis of diseases caused by CaSR mutations and dysregulated CaSR activity caused by its protein interactors and facilitate the design of therapeutic agents that target CaSR and other family C G-protein-coupled receptors.

关键词： calcium signaling calcium-sensing receptor G-protein-coupled receptors structure trafficking

Considerations for the use of porcine organ donation models in preclinical organ donor intervention research

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Animal Models and Experimental Medicine 2024年第3期7卷 283-296页

作者： Frazer I.Heinis Shaheed Merani Nicholas W.Markin Kim F.Duncan Michael J.Moulton Lance Fristoe William E.Thorell Raechel A.Sherrick Tami R.Wells Matthew T.andrews Marian Urban School of Natural Resources Institute of Agriculture and Natural ResourcesUniversity of Nebraska-LincolnLincolnNebraskaUSA Division of Transplantation and Vascular Surgery Department of SurgeryUniversity of Nebraska Medical CenterOmahaNebraskaUSA Department of Anesthesiology University of Nebraska Medical CenterOmahaNebraskaUSA Division of Cardiothoracic Surgery Department of SurgeryUniversity of Nebraska Medical CenterOmahaNebraskaUSA Clinical Perfusion Nebraska Medicine-Nebraska Medical CenterOmahaNebraskaUSA Department of Neurosurgery University of Nebraska Medical CenterOmahaNebraskaUSA Nutrition and Health Sciences College of Education and Human SciencesUniversity of Nebraska-LincolnLincolnNebraskaUSA Department of Comparative Medicine University of Nebraska Medical CenterOmahaNebraskaUSA

Use of animal models in preclinical transplant research is essential to the optimization of human allografts for clinical *** models of organ donation and preservation help to advance and improve technical elements of solid organ recovery and facilitate research of ischemia-reperfusion injury,organ preservation strategies,and future donor-based *** considerations include cost,public opinion regarding the conduct of animal research,translational value,and relevance of the animal model for clinical *** present an overview of two porcine models of organ donation:donation following brain death(DBD)and donation following circulatory death(DCD).The cardiovascular anatomy and physiology of pigs closely resembles those of humans,making this species the most appropriate for pre-clinical *** are also considered a potential source of organs for human heart and kidney *** is imperative to minimize animal loss during procedures that are surgically *** present our experience with these models and describe in detail the use cases,procedural approach,challenges,alternatives,and limitations of each model.

关键词： animal model brain death circulatory death organ transplantation

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混动飞机飞向蓝天

科技纵览 2024年第2期 30-36,4页

作者： Amy Jankovsky Christine andrews Bill Rogers 不详

NASA、通用电气航空公司和波音公司正在合作开发一款混合动力客机。商业航空联结了现代世界。国际民用航空组织(ICAO)的数据表明,在全球新冠疫情之前,每天平均有1200万人乘坐约10万次商业航班。这些数字现在已经大幅回升:预计2023年行... 详细信息

NASA、通用电气航空公司和波音公司正在合作开发一款混合动力客机。商业航空联结了现代世界。国际民用航空组织(ICAO)的数据表明,在全球新冠疫情之前,每天平均有1200万人乘坐约10万次商业航班。这些数字现在已经大幅回升:预计2023年行业收入将达到8030亿美元,比2022年增长9.7%,接近2019年疫情前的峰值。

关键词：商业航空混合动力通用电气合作开发数据表波音公司航空公司疫情

Underground mine stream crossing assessment:A multi-disciplinary approach

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International Journal of Mining Science and Technology 2021年第1期31卷 59-65页

作者： Kevin andrews Steve Keim Marshall Miller&Associates BluefieldVA 24605USA

Underground mine designs typically try to avoid extraction beneath streams and rivers of any significant size,especially when the overburden rock thickness between the stream bed and the mine is *** issues with mining beneath streams include excessive groundwater inflow to the mine,weak ground(roof,floor,and pillar)conditions,horizontal stress effects,as well as stream loss and other potential adverse environmental ***,there are times when crossing beneath a stream or river is necessary to move into a new area of mineral reserve without creating additional mine access points from the ground ***,stream crossings are completed without thorough assessment,potentially resulting in increased costs,decreased safety,and,in some cases,failure to advance the *** of the most favorable location(s)to cross the stream must account for numerous factors and the associated assessment often requires a multi-disciplinary *** crossing investigations often require geological,hydrogeological,geotechnical,and geophysical *** of stream crossing investigations include desktop evaluation of maps and aerial photography,stream bed observations,drilling,detailed rock core logging,downhole geophysical surveying,hydraulic conductivity testing(packer testing),geotechnical laboratory testing,assessment,and *** deliverables from a stream crossing assessment typically include geological,geotechnical,and hydrogeological characterization of potential stream crossing locations,classification of favorable and unfavorable crossing locations,recommendations for entry design and pillar sizing,and recommendations for if,and how,to conduct pre-grouting *** of technical aspects of data collection and assessment are provided based on decades of industry experience conducting stream crossing assessments in various underground mining scenarios.

关键词： Underground mining Geotechnical Stream-crossing Hydrogeology Characterization

Partitions with Initial Repetitions

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Acta Mathematica Sinica,English Series 2009年第9期25卷 1437-1442页

作者： George E.andrews The Pennsylvania State University University Park

A variety of interesting connections with modular forms, mock theta functions and Rogers- Ramanujan type identities arise in consideration of partitions in which the smaller integers are repeated as summands more often than the larger summands. In particular, this concept leads to new interpretations of the Rogers Selberg identities and Bailey＇s modulus 9 identities.

关键词： partitions without gaps initial k-repetitions Glaisher's theorem Rogers-Selberg identities Bailey's modulus 9 identities

Soil carbon stock and emission: estimates from three land-use systems in Ghana

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Ecological Processes 2021年第1期10卷 157-169页

作者： Joseph Anokye Vincent Logah andrews Opoku Department of Crop and Soil Sciences Kwame Nkrumah University of Science and Technology(KNUST)KumasiGhana

Background:Land-use systems that sequester carbon and reduce CO_(2) emissions are key in the global mitigation strategies of climate *** gas emission from agro-ecosystems in sub-Saharan Africa is little ***,we quantified soil carbon stock(SCS)and CO_(2) emissions from three land-use systems *** land,oil palm plantation and forestland in the semi-deciduous forest zone of ***:Soil organic carbon concentration at the 0–15 cm layer in the forestland was 62 and 23%greater than that in the arable land and palm plantation,*** SCS along the 1.0-m profile was 108.2,99.0 and 73.5 Mg ha^(−1) in the forestland,palm plantation and arable land,*** land emitted 30–46%more CO_(2) than palm plantation and *** the dry season,CO_(2) emissions were respectively 0.93,0.63 and 0.5 kg ha^(−1) h−1 from the arable land,palm plantation and *** relationships were observed between CO_(2) emissions and SCS,soil temperature,and *** SCS greatly influenced CO_(2) emission in the dry season more than in the wet season in the relatively higher carbon-input systems(forestland and palm plantation).Soil temperature accounted for more than 55%of CO_(2) emissions in both seasons,which has implications in the era of rising global ***:The study provides relevant information on carbon storage abilities of the three land-use types in tropical climate and calls for drastic climate change actions to reduce degradation of forest cover and soil disturbance in agro-ecosystems in sub-Saharan Africa.

关键词： Arable land Carbon dioxide emission Climate change Soil moisture Soil temperature Sub-Saharan Africa

Kinetics of hydrogen peroxide quenching following UV/H_(2)O_(2)advanced oxidation by thiosulfate,bisulfite,and chlorine in drinking water treatment

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Frontiers of Environmental Science & Engineering 2023年第12期17卷 59-69页

作者： Tianyi Chen Lizbeth Taylor-Edmonds Susan andrews Ron Hofmann Department of Civil and Mineral Engineering University of TorontoTorontoOntario M5S 1A4Canada

Residual H_(2)O_(2)from UV/H_(2)O_(2)treatment can be quenched by thiosulfate,bisulfite,and chlorine,but the kinetics of these reactions have not been reported under the full range of practical *** this study,the rates of H_(2)O_(2)quenching by these compounds were compared in different water matrices,temperatures,pH,and when using different forms of bisulfite and *** general,it was confirmed that thiosulfate would be too slow to serve as a quenching agent in most practical *** pH 7-8.5,chlorine tends to quench H_(2)O_(2)more than 20 times faster than bisulfite in the various conditions *** important observation was that in lightly-buffered water(e.g.,alkalinity of 20 mg/L as CaCO_(3)),the form of chlorine can have a large impact on quenching rate,with gaseous chlorine slowing the reaction due to its lowering of the pH,and hypochlorite having the opposite *** impacts will become less significant when water buffer capacity(i.e.,alkalinity)increases(e.g.,to 80 mg/L as CaCO_(3)).In addition,water temperature should be considered as the time required to quench H_(2)O_(2)by chlorine at 4℃is up to 3 times longer than at 20℃.

关键词： UV/H_(2)O_(2) H_(2)O_(2) quenching Chlorine type Water alkalinity Temperature

Comparison of three-dimensional fluorescence analysis methods for predicting formation of trihalomethanes and haloacetic acids

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Journal of Environmental Sciences 2015年第1期27卷 159-167页

作者： Nicolás M.Peleato Robert C.andrews Department of Civil Engineering University of Toronto

This work investigated the application of several fluorescence excitation–emission matrix analysis methods as natural organic matter（NOM） indicators for use in predicting the formation of trihalomethanes（THMs） and haloacetic acids（HAAs）. Waters from four different sources（two rivers and two lakes） were subjected to jar testing followed by 24 hr disinfection by-product formation tests using chlorine. NOM was quantified using three common measures： dissolved organic carbon, ultraviolet absorbance at 254 nm, and specific ultraviolet absorbance as well as by principal component analysis, peak picking,and parallel factor analysis of fluorescence spectra. Based on multi-linear modeling of THMs and HAAs, principle component（PC） scores resulted in the lowest mean squared prediction error of cross-folded test sets（THMs： 43.7（μg/L）^2, HAAs： 233.3（μg/L）^2）. Inclusion of principle components representative of protein-like material significantly decreased prediction error for both THMs and HAAs. Parallel factor analysis did not identify a protein-like component and resulted in prediction errors similar to traditional NOM surrogates as well as fluorescence peak picking. These results support the value of fluorescence excitation–emission matrix–principal component analysis as a suitable NOM indicator in predicting the formation of THMs and HAAs for the water sources studied.

关键词： Natural organic matter Fluorescence Principal component analysis PARAFAC Disinfection byproducts Drinking water