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Friction 2024年第4期12卷 796-811页

作者： Samuel BOND robert L.jackson German MILLS Department of Chemistry and Biochemistry Auburn UniversityAuburn 36849-5412USA Department of Mechanical Engineering Auburn UniversityAuburn 36849-5412USA

Leakage currents accelerate surface degradation of metal contacts via small scale arcing across lubricating films,but recent observations suggest that metallic nanoparticle additives in lubricants may be useful to improve contact *** findings prompted a study that examined electrically induced surface pitting of steel contacts in the presence of several lubricating greases including some containing nanometer-sized colloidal silver(Ag)*** rolling sphere-on-disk experiments were conducted under electro-tribological loads employing polyurea greases derived from mineral and synthetic base oils with and without *** forces and electrical resistance were monitored continuously during the tests;surface changes were characterized by means of optical spectroscopy,stylus profilometry,and scanning electron microscopy(SEM)including compositional analysis using energy dispersive spectroscopy(EDS).The observations demonstrate that surface pitting induced by arcing occurs mainly at the points were the rolling motion changes direction and that eroded metal is deposited along the wear ***-sized pits are formed which contain carbon and oxygen indicating that arcing causes decomposition of the hydrocarbon *** findings indicate a significant inhibition of pitting is induced by the Ag nanoparticles;some greases containing other additives exhibit a similar,although less pronounced,effect.

关键词： electric motor bearings wheel bearings electric vehicles arcing electrically induced bearing damage pitting leakage current stray current

Boundary element method (BEM) applied to the rough surface contact vs. BEM in computational mechanics

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Friction 2019年第4期7卷 359-371页

作者： Yang XU robert L.jackson Mechanical Engineering Department Auburn University

In the numerical study of rough surfaces in contact problem, the flexible body beneath the roughness is commonly assumed as a half-space or a half-plane. The surface displacement on the boundary, the displacement components and state of stress inside the half-space can be determined through the convolution of the traction and the corresponding influence function in a closed-form. The influence function is often represented by the Boussinesq-Cerruti solution and the Flamant solution for three-dimensional elasticity and plane strain/stress, respectively. In this study, we rigorously show that any numerical model using the above mentioned half-space solution is a special form of the boundary element method(BEM). The boundary integral equations(BIEs) in the BEM is simplified to the Flamant solution when the domain is strictly a half-plane for the plane strain/stress condition. Similarly, the BIE is degraded to the Boussinesq-Cerruti solution if the domain is strictly a half-space. Therefore, the numerical models utilizing these closed-form influence functions are the special BEM where the domain is a half-space(or a half-plane). This analytical work sheds some light on how to accurately simulate the non-half-space contact problem using the BEM.

关键词： boundary element method rough surface contact half-space half-plane Flamant solution Boussinesq-Cerruti solution

How spiders practice aggressive and Batesian mimicry

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Current Zoology 2012年第4期58卷 620-629页

作者： Ximena J. NELSON robert R. jackson School of Biological Sciences University of Canterbury Private Bag 4800 Christchurch New Zealand International Centre of Insect Physiology and Ecology Thomas Odhiambo Campus EO. Box 30 Mbita Point Kenya

To understand communication, the interests of the sender and the receiver/s of signals should be considered sepa-rately. When our goal is to understand the adaptive significance of specific responses to specific signals by the receiver, questions about signal information are useful. However, when our goal is to understand the adaptive significance to the sender of generating a signal, it may be better to envisage the receiver＇s response to signals as part of the sender＇s extended phenotype. By making signals, a sender interfaces with the receiver＇s model of the world and indirectly manipulates its behaviour. This is especially clear in cases of mimicry, where animals use deceptive signals that indirectly manipulate the behaviour of receivers. Many animals adopt Batesian mimicry to deceive their predators, or aggressive mimicry to deceive their prey. We review examples from the lite-rature on spiders to illustrate how these phenomena, traditionally thought of as distinct, can become entangled in a web of lies .

关键词： Mimicry Communication Spider Deception Signal Search image

The Utilization of the Generating Function Technique in the Discovery of Solutions for the Three-Dimensional Navier-Stokes Equation System

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Open Journal of Fluid Dynamics 2022年第1期12卷 86-95页

作者： robert Lloyd jackson Independent Researcher Stilwell KS USA

The derivation of solutions to the Navier-Stokes (system of) equations (NSEs), in three spatial dimensions, has been an enigma as time can tell. This study wishes to show how to eradicate this problem via the usage of a recently proposed method for solving partial differential equations called the Generating Function Technique, or GFT for short. The paper will first quickly define the NSEs with and without an external force, then provide a quick synopsis of the GFT. Next, the study will derive solutions to these two major problems and give an analysis of the data concerning a specific set of criteria established by the Clay Mathematics Institute to determine the smoothness and existence of solutions. Results via GFT will show one can easily prove the existence of solutions to the NSEs with or without the presence of an external force. However, only the solutions to the NSEs will be globally bound.

关键词： Physics and Mathematics Fluid Mechanics Partial Differential Equations

Mitigation of spectral leakage for single carrier, block-processing cognitive radio receivers

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Digital Communications and Networks 2018年第2期4卷 106-110页

作者： Adam C. Polak Mark Wagner Marco F. Duarte robert W. jackson Dennis L. Goeckel Electrical and Computer Engineering Department University of Massachusetts Amherst United States

Cognitive Radio （CR） is a multiuser, wireless communication concept that allows for a dynamic and adaptive assignment of spectral resources. The coexistence of multiple users, often transmitting at significantly different power levels, makes CR receivers vulnerable to spectral leakage caused by components＇ nonlinearities and timetruncation of the processed signal records. In this work we propose a method for mitigating the latter with an adaptive choice of the length of the processing block size. With simulations we show that a significant leakage reduction that leads to receiver dynamic range improvement of around 10 dB can be achieved with the proposed method.

关键词： Spectral leakage Dynamic range Single carrier block transmission Interference White space Cognitive radio

Data-driven estimates of global nitrous oxide emissions from croplands

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National Science Review 2020年第2期7卷 441-452页

作者： Qihui Wang Feng Zhou Ziyin Shang Philippe Ciais Wilfried Winiwarter robert B.jackson Francesco N.Tubiello Greet Janssens-Maenhout Hanqin Tian Xiaoqing Cui Josep G.Canadell Shilong Piao Shu Tao Sino-France Institute of Earth Systems Science Laboratory for Earth Surface Processes College of Urban and Environmental Sciences Peking University European Commission Joint Research Centre International Institute for Applied Systems Analysis (IIASA) The Institute of Environmental Engineering University of Zielona Góra Global Carbon Project CSIRO Oceans and Atmosphere Department of Earth System Science Stanford University Statistics Division Food and Agricultural Organization of the United Nations Via Terme di Caracalla International Center for Climate and Global Change Research School of Forestry and Wildlife Sciences Auburn University Laboratoire des Sciences du Climat et de l'Environnement LSCE CEA CNRS UVSQ

Croplands are the single largest anthropogenic source of nitrous oxide(NO) globally, yet their estimates remain difficult to verify when using Tier 1 and 3 methods of the Intergovernmental Panel on Climate Change(IPCC). Here, we re-evaluate global cropland-NO emissions in 1961–2014, using N-rate-dependent emission factors(EFs) upscaled from 1206 field observations in 180 global distributed sites and high-resolution N inputs disaggregated from sub-national surveys covering 15593 administrative units. Our results confirm IPCC Tier 1 default EFs for upland crops in 1990–2014, but give a ～15% lower EF in 1961–1989 and a ～67% larger EF for paddy rice over the full period. Associated emissions(0.82 ±0.34 Tg N yr) are probably one-quarter lower than IPCC Tier 1 global inventories but close to Tier 3 estimates. The use of survey-based gridded N-input data contributes 58% of this emission reduction, the rest being explained by the use of observation-based non-linear EFs. We conclude that upscaling NO emissions from site-level observations to global croplands provides a new benchmark for constraining IPCC Tier 1 and 3 methods. The detailed spatial distribution of emission data is expected to inform advancement towards more realistic and effective mitigation pathways.

关键词： nitrous oxide agricultural soils flux upscaling emission factor emission inventories temporal trend

Panicle-Cloud:An Open and Al-Powered Cloud Computing Platform for Quantifying Rice Panicles from Drone-Collected Imagery to Enable the Classification of Yield Production in Rice

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Plant Phenomics 2023年第4期5卷 905-916页

作者： Zixuan Teng Jiawei Chen Jian Wang Shuixiu Wu Riqing Chen Yaohai Lin Liyan Shen robert jackson Ji Zhou Changcai Yang Digital Fujian Research Institute of Big Data for Agriculture and Forestry College of Computer and Information SciencesFujian Agriculture and Forestry UniversityFuzhou 350002China State Key Laboratory of Crop Genetics&Germplasm Enhancement academy for Advanced Interdisciplinary StudiesNanjing Agricultural UniversityNanjing 210095China Ningxia Academy of Agriculture and Forestry Sciences Yinchuan 750002China College of Mechanical and Electrical Engineering Fujian Agriculture and Forestry UniversityFuzhou 350002China Cambridge Crop Research National Institute of Agricultural Botany(NIAB)Cambridge CB3 OLEUK Key Laboratory of Smart Agriculture and Forestry(Fujian Agriculture and Forestry University) Fujian Province UniversityFuzhou 350002China Center for Agroforestry Mega Data Science School of Future TechnologyFujian Agriculture and Forestry UniversityFuzhou 350002China

Rice(Oryza sativa)is an essential stable food for many rice consumption nations in the world and,thus,the importance to improve its yield production under global climate *** evaluate different rice varieties'yield performance,key yield-related traits such as panicle number per unit area(PNpM^(2))are key indicators,which have attracted much attention by many plant research ***,it is still challenging to conduct large-scale screening of rice panicles to quantify the PNpM^(2)trait due to complex field conditions,a large variation of rice cultivars,and their panicle morphological ***,we present Panicle-Cloud,an open and artificial intelligence(AI)-powered cloud computing platform that is capable of quantifying rice panicles from drone-collected *** facilitate the development of Al-powered detection models,we first established an open diverse rice panicle detection dataset that was annotated by a group of rice specialists;then,we integrated several state-of-the-art deep learning models(including a preferred model called Panicle-AI)into the Panicle-Cloud platform,so that nonexpert users could select a pretrained model to detect rice panicles from their own aerial *** trialed the Al models with images collected at different attitudes and growth stages,through which the right timing and preferred image resolutions for phenotyping rice panicles in the field were ***,we applied the platform in a 2-season rice breeding trial to valid its biological relevance and classified yield production using the platform-derived PNpM^(2)trait from hundreds of rice *** correlation analysis between computational analysis and manual scoring,we found that the platform could quantify the PNpM^(2)trait reliably,based on which yield production was classified with high ***,we trust that our work demonstrates a valuable advance in phenotyping the PNpM^(2)trait in rice,which provides a useful toolkit to enable rice br

关键词： breeding cultivar hundreds

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回首往事

回首往事

1000年

作者： robert G.jackson

来源：汇雅图书（南通市图书馆... 评论

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多尺度粗糙度对接触面真实接触面积的影响

润滑与密封 2015年第6期40卷 76-80页

作者：张晓寒 robert L.jackson 孟文俊太原科技大学机械工程学院山西太原030024 Mechanical Engineering Auburn Universityauburnusa36849

当两个粗糙面在力的作用下相互接触时,只有表面上的微凸体相互接触。这些微凸体的接触影响着接触面的摩擦、磨损并且决定着两接触面之间的导电性和热传递功能。这些微凸体存在于各个不同的尺度下,并且形状也不相同。运用堆叠式多尺度接... 详细信息

当两个粗糙面在力的作用下相互接触时,只有表面上的微凸体相互接触。这些微凸体的接触影响着接触面的摩擦、磨损并且决定着两接触面之间的导电性和热传递功能。这些微凸体存在于各个不同的尺度下,并且形状也不相同。运用堆叠式多尺度接触模型对典型的加工表面进行分析,研究多尺度粗糙度对接触面真实接触面积的影响。结果表明,在塑性接触和弹塑性接触情况下,接触表面的多尺度粗糙度对于真实的接触面积和接触力均都有着很大的影响,不同表面之间的接触面积和平均接触压力以一个数量级的大小变化。研究结果表明某些加工工艺得到的表面或许更适合于作为设备中相互接触的表面。

关键词：粗糙表面接触表面凸起多尺度接触模型

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