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Discrete elem.nt sim.lation of cylindrical particles using super-ellipsoids

Particuology 2019年第5期17卷 55-66页

作者： Yongzhi Zhao Lei Xu Paul B. Um.anhowar richard m. lueptow Institute of Process Equipm.nt College of Energy Engineering Zhejiang University Hangzhou 310027 China Departm.nt of m.chanical Engineering Northwestern University Evanston Illinois 60208 USA Departm.nt of Chem.cal and Biological Engineering Northwestern University Evanston. Illinois 60208 USA The Northwestern Institute on Com.lex System. (NICO) Northwestern University Evanston Illinois 60208 USA

A discrete elem.nt m.del based on super-ellipsoids was used to sim.late cylindrical particle flow. The m.del can describe a cylindrical particle accurately provided the shape indices of the super-ellipsoids are set to appropriate values. To achieve m.re rapid calculations, we im.lem.nted an "oriented bounding box algorithm.(OBBA) for the initial contact detection of cylindrical particles. Several types of Sim.lations were perform.d to validate the super-ellipsoid m.del and the contact-detection algorithm. First, the effect of shape index of the super-ellipsoids on m.del accuracy was investigated through three sim.lations: im.act of a cylindrical particle on a flat wall, flow of cylindrical particles in a rotating tum.ler, and segregation of cylindrical particles of different length flowing down a bounded heap. The sim.lation results show that the super-ellipsoids describe cylindrical particles accurately when the shape index that specifies the sharpness of the cylinder edges is sufficiently large. The efficiency of the OBBA is m.asured by sim.lations in which a box is filled with cylindrical particles and a tum.ler that contains cylindrical particles is rotated. The sim.lation results show that the OBBA can accelerate the calculations significantly. The effect of particle shape (such as aspect ratio and shape index) on the calculation speed was obtained. The sim.lation of rod-like particles tended to take m.re calculation tim. than that of disk-like particles, and the sim.lation tim. increased with an increasing particle-shape index.

关键词： Discrete elem.nt m.thod Super-ellipsoid Super-quadric Cylindrical particle Non-spherical particle Granular m.terial

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Seism.c perform.nce of steel m.F building with nonlinear viscous dam.ers

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Frontiers of Structural and Civil Engineering 2016年第3期10卷 254-271页

作者： Baiping DONG Jam.s m. RICLES richard SAUSE ATLSS Engineering Research Center Department of Civil and Environmental Engineering Lehigh University Bethlehem PA 18015 USA

This paper presents an experim.ntal study of the seism.c response of a 0.6-scale three-story seism.cresistant building structure consisting of a m.m.nt resisting fram. （m.F） with reduced beam.sections （RBS）, and a fram. with nonlinear viscous dam.ers and associated bracing （called the DBF）. The em.hasis is on assessing the seism.c perform.nce for the design basis earthquake （DBE） and m.xim.m.considered earthquake （m.E）. Three m.F designs were studied, with the m.F designed for 100%, 75%, and 60%, respectively, of the required base shear design strength determ.ned according to ASCE 7-10. The DBF with nonlinear viscous dam.ers was designed to control the lateral drift dem.nds. Earthquake sim.lations using ensem.les of DBE and m.E ground m.tions were conducted using the real-tim. hybrid sim.lation m.thod. The results show the drift dem.nd and dam.ge that occurs in the m.F under seism.c loading. Overall, the results show that a high level of seism.c perform.nce can be achieved under DBE and m.E ground m.tions, even for a building structure designed for as little as 60% of the base shear design strength required by ASCE 7-10 for a structure without dam.ers.

关键词： seism.c response steel m.F nonlinear viscous dam.er design basis earthquake real-tim. hybrid sim.lation

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Behavioral differences within and am.ng populations of an African cichlid found in divergent and extrem. environm.nts

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Current Zoology 2019年第1期65卷 33-42页

作者： richard C. Oldham.Lauren m. Pintor Suzanne m. Gray School of Environm.nt and Natural Resources The Ohio State University Columbus OH 43210 USA

Anim.ls are increasingly faced with hum.n?induced stressors that vary in space and tim., thus we can expect populati on-level diverge nee in behaviors that help anim.ls to cope with en vironm. ntal change. However, em.irical evidenee of behavioral trait divergence across environm.ntal extrem.s is lacking. We tested for variation in behavioral traits am.ng 2 populations of an African cichlid fish (Pseudocrenilabrus m.lticolor victoriae Seegers, 1990) that experience extrem.s of dissolved oxygen (DO) and turbidity and are known to vary in a num.er of physiological and life history traits associated with these stressors. Using a com. on garden reari ng experim. nt, F1 progeny from.wild-caught parents originating from.a swam. (low DO, clear) and a river (high DO, turbid) were reared in high DO, clear water. Predator sim.lation assays were conducted to test for (1) variation in boldness, general activity, and foraging activity between populations,(2) differences in correlations betwee n behaviors with in and across populati ons, and (3) repeatability of behaviors. There was strong evide nee for diverge nee betwee n populati ons, with swam. fish being m.re bold (i.e.z leaving refuge sooner after a sim.lated predator attack) and active (i.e., spent m.re tim. out of refuge) than river fish. Across populations there were positive correlations between foraging activity and both boldness and general activity;however, within populations, there was only a strong positive relationship between foraging activity and boldness in the river population. Here, we have dem.nstrated that populations that originate from.drastically different environm.nts can produce proge ny that exhibit m.asurable differences in behaviors and their correlated relati on ships eve n whe n reared un der com. on conditions.

关键词： behavioral correlation behavioral syndrom. boldness hypoxia pace of life turbidity

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Wild dogm.： An exam.nation of recent ＂evidence＂ for dingo regulation of invasive m.sopredator release in Australia

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Current Zoology 2011年第5期57卷 568-583页

作者： Benjam.n L. ALLEN richard m. ENGEm.N Lee R. ALLEN The University of Queensland School of Animal Studies Warrego Highway Gatton QLD 4343 National Wildlife Research Centre 4101 LaPorte Avenue Fort Collins CO 80521-2154 USA （Richard.M.Engeman@aphis.usda.gov） Biosecurity Queensland Robert Wicks Pest Animal Research Centre Tor Street Toowoomba QLD 4350 （Lee.Allen@deedi.qld.gov.au）

There is growing interest in the role that apex predators play in shaping terrestrial ecosystem. and m.intaining tro- phic cascades. In line with the m.sopredator release hypothesis, Australian dingoes （Canis lupus dingo and hybrids） are assum.d by m.ny to regulate the abundance of invasive m.sopredators, such as red foxes Vulpes vulpes and feral cats Fells catus, thereby providing indirect benefits to various threatened vertebrates. Several recent papers have claim.d to provide evidence for the bio- diversity benefits of dingoes in this way. Nevertheless, in this paper we highlight several critical weaknesses in the m.thodologi- cal approaches used in m.ny of these reports, including lack of consideration for seasonal and habitat differences in activity, the com.lication of sim.le track-based indices by incorporating difficult-to-m.et assum.tions, and a reduction in sensitivity for as-sessing populations by using binary m.asures rather than potentially continuous m.asures. Of the 20 studies reviewed, 15 of them.（75%） contained serious m.thodological flaws, which m.y partly explain the inconclusive nature of the literature investigating interactions between invasive Australian predators. We therefore assert that m.st of the ＂growing body of evidence＂ for m.so- predator release is m.rely an inconclusive growing body of literature only. We encourage those interested in studying the eco- logical roles of dingoes relative to invasive m.sopredators and native prey species to account for the factors we identify, and cau- tion the value of studies that have not done so [Current Zoology 57 （5）： 568-583, 2011].

关键词： Activity index Apex predator Canis lupus dingo Experim.ntal design m.sopredator release Sam.ling

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Sperm.ne induced reversible collapse of deoxyribonucleic acid-bridged nanoparticle-based assem.lies

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Nano Research 2018年第1期11卷 383-396页

作者： Kristian L. Goeken richard B. m. Schasfoort Vinod Subram.niam.Ron Gill m.RA Institute for Biom.dical Technology and Technical m.dicine University of Twente Dfienerlolaan 5 7522 NB Enschede the Netherlands Vrije UniversiteitAm.terdam De Boelelaan 1105 1081 HVAmsterdam the Netherlands Saxion University of Applied Sciences M. H. Tromplaan 28 7513 A8 Enschede the Netherlands

DNA-linked 2D and 3D nano-assem.lies find use in a diverse set of applications, ranging from.DNA-origam. in drug delivery and m.dical im.ging, to DNA-linked nanoparticle structures for use in plasm.nics and （bio）sensing. However, once these structures have been fully assem.led, few options are available to m.dulate structure geom.try. Here, we investigated the use of the polycation sperm.ne to induce DNA collapse in sm.ll oligonucleotide-linked （54 bp） gold nanoparticle structures by m.nitoring shifts in the localized surface plasm.n resonance （LSPR） peak and by com.aring the data with finite-difference tim.-dom.in （FDTD） sim.lations. Our data shows that low concentrations of sperm.ne can be applied to induce large changes in DNA conform.tion, leading to a significant reduction in interparticle distance （from.- 25 to - 3 nm. and enhanced plasm.nic coupling. The DNA collapse is near-instantaneous and reversible, and its application at low and high DNA densities is dem.nstrated with surface plasm.n resonance im.ging （SPRi）, showing the potential of sperm.ne to dynam.cally m.dulate distances and geom.try in DNA-based nano-assem.lies.

关键词： nanoparticles sperm.ne deoxyribonucleic acid localized surface plasm.nresonance surface plasm.n resonanceim.ging

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Single-particle photolum.nescence connects therm.l processing with heterogeneity in the trap distribution of cesium.lead brom.de nanocrystals

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NANO RESEARCH 2024年第12期17卷 10363-10375页

作者： Wang, Dong Chen, Jie Zhang, Dongyan Niedzwiedzki, Dariusz m. Loom.s, richard A. Sadtler, Bryce Washington Univ Dept Chem St Louis MO 63130 USA Washington Univ Ctr Solar Energy & Energy Storage St Louis MO 63130 USA Washington Univ Dept Energy Environm & Chem Engn St Louis MO 63130 USA Washington Univ Inst Mat Sci & Engn St Louis MO 63130 USA

Understanding the m.chanism. of degradation in lead halide perovskite nanocrystals is critical for their future application in optoelectronic devices. We report single-particle m.asurem.nts of the photolum.nescence from.cesium.lead brom.de nanocrystals coated with a silica shell (CsPbBr3@SiO2). Through correlative im.ging, we quantified changes in the fluorescence intensity trajectories of the sam. nanocrystals before and after annealing them.at different tem.eratures. We observe that nearly equal num.ers of CsPbBr3@SiO2 nanocrystals exhibit an increase versus decrease in the am.unt of tim. they spend in an em.ssive state after annealing at tem.eratures of 70 and 100 degrees C. On the other hand, annealing at 120 degrees C produces a decrease in the on-fraction for m.st nanocrystals and, correspondingly, a substantial decrease in the photolum.nescence intensity for a thin film.annealed at this tem.erature. We attribute the differences in behavior am.ng individual nanocrystals to heterogeneity in the distribution of trap states that are initially present. X-ray photoelectron, tim.-resolved photolum.nescence, and transient absorption spectroscopies perform.d on thin film. of CsPbBr3@SiO2 nanocrystals indicate that therm.l annealing heals electron traps by passivating surface Pb ions and sim.ltaneously creates hole traps through the form.tion of Pb and Cs vacancies. The relative rates of these parallel processes depend on the annealing tem.erature, which are im.ortant to account for when developing passivation strategies for lead halide perovskite nanocrystals in optoelectronic devices that will operate at elevated tem.eratures.

关键词： single-particle m.croscopy photolum.nescence nanocrystals cesium.lead brom.de therm.l annealing

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Wild dogm. II： The role and im.lications of wild dogm. for wild dog m.nagem.nt in Australia

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Current Zoology 2011年第6期57卷 737-740页

作者： Benjam.n L. ALLEN richard m. ENGEm.N Lee R. ALLEN The University of Queensland School of Animal Studies Warrego Highway Gatton QLD 4343 National Wildlife Research Centre 4101 l_aPorte Avenue Fort Collins CO 80521-2154 USA. Richard.M.Engeman@aphis.usda.gov Biosecurity Queensland Robert Wicks Pest Animal Research Centre Tor Street Toowoomba QLD 4350. Lee.Allen@ deedi.qld.gov.au

The studies of Allen （2011） and Allen et al. （2011） recently exam.ned the m.thodology underpinning claim. that dingoes provide net benefits to biodiversity by suppressing foxes and cats. They found m.st studies to have design flaws and/or observational m.thods that preclude valid interpretations from.the data, describing m.st of the current literature as ＇wild dogm.＇. In this short supplem.nt, we briefly highlight the roles and im.lications of wild dogm. for wild dog m.nagem.nt in Australia. We discuss nom.nclature, and the influence that unreliable science can have on policy and practice changes related to apex predator m.nagem.nt

关键词： Apex predator Canis lupus dingo Practice change Public perceptions Wild dog m.nagem.nt

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Understanding Science Through the Com.utational Lens

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Journal of Com.uter Science & Technology 2011年第4期26卷 569-577页

作者： richard m.Karp Departm.nt of Electrical Engineering and Com.uter Sciences University of California

This article explores the changing nature of the interaction between com.uter science and the natural and social sciences. After briefly tracing the history of scientific com.utation, the article presents the concept of com.utational lens, a m.taphor for a new relationship that is em.rging between the world of com.utation and the world of the sciences. Our m.in thesis is that, in m.ny scientific fields, the processes being studied can be viewed as com.utational in nature, in the sense that the processes perform.dynam.c transform.tions on inform.tion represented as digital data. Viewing natural or engineered system. through the lens of their com.utational requirem.nts or capabilities provides new insights and ways of thinking. A num.er of exam.les are discussed in support of this thesis. The exam.les are from.various fields, including quantum.com.uting, statistical physics, the World Wide Web and the Internet, m.them.tics, and com.utational m.lecular biology.

关键词： com.utational process com.uter science and other sciences com.utational lens

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m.tam.rphic consequences of secular changes in oceanic crust com.osition and im.lications for uniform.tarianism.in the geological record

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Geoscience Frontiers 2018年第4期9卷 1009-1019页

作者： richard m.Palin Brendan Dyck Departm.nt of Geology and Geological Engineering Colorado School of Mines Departm.nt of Earth Sciences Simon Fraser University

Cooling of the Earth＇s m.ntle since the m.so-Archean is predicted by therm.l and petrological m.dels to have induced a secular change in the com.osition of prim.ry m.ntle-derived m.gm.s-and thus bulk oceanic crust; in particular, suggesting a decrease in m.ficity over tim.. This hypothesis underpins several recent studies that have addressed key geological questions concerning evolving plate tectonic styles, the rates and tim.ng of continental crust form.tion, com.arative planetology, and the em.rgence of com.lex life on Earth. m.jor, m.nor, and trace elem.nt geochem.cal analyses of（m.ta）m.fic rocks preserved in the geological record allows exploration of this theory, although no consensus currently exists about the m.gnitude of this change and what com.ositions-if anything-constitute representative exam.les of Paleo-, m.so-, or Neo-Archean prim.tive oceanic crust. In this work, we review the current state of understanding of this issue, and use phase equilibria to exam.ne the different m.neral assem.lages and rock types that would form.during m.tam.rphism.of basalt of varying m.ficity in subduction zone environm.nts. The presence（or absence） of such m.tam.rphic products in the geological record is often used as evidence for（or against） the operation of m.dern-day subductiondriven plate tectonics on Earth at particular tim. periods; however, the control that secular changes in com.osition have on the stability of m.neral assem.lages diagnostic of subduction-zone m.tam.rphism.weakens such uniform.tarianistic approaches. Geodynam.c interpretations of the Archean m.tam.rphic rock record m.st therefore em.loy a different set of petrological criteria for determ.ning tectonotherm.l histories than those applied to Proterozoic or Phanerozoic equivalents.

关键词： Archean m.ntle cooling Oceanic crust Basalt m.tam.rphism Uniform.tarianism

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What we have learned from.random.zed trials of prostate cancer screening

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Asian Journal of Andrology 2011年第3期13卷 369-373,510页

作者： richard m.Hoffm.n Anthony Y Sm.th m.dicine Service New Mexico VA Health Care System Albuquerque NM 87108 USA Departm.nt of m.dicine University of New Mexico School of Medicine Albuquerque NM 87108 USA Departm.nt of Surgery University of New Mexico School of Medicine Albuquerque NM 87108 USA

The introduction of prostate-specific antigen （PSA） for prostate cancer screening in the late 1980s led to an epidem.c of prostate cancer, particularly in developed countries. However, the first valid reports from.random.zed controlled trials on the efficacy of screening were not published until 2009. m.n in the screening group in the European Random.zed Study of Screening for Prostate Cancer were 20% less likely than those in the control group to die from.prostate cancer. The absolute difference was only 0.7/1000, im.lying that over 1400 m.n needed to be screened to prevent one prostate cancer death. Screening was also associated with a 70% increased risk for being diagnosed with prostate cancer. The Am.rican Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial found no survival benefit for screening. Results were not conclusive because a substantial proportion of study subjects had previously undergone PSA testing, over half of the control group had PSA testing, follow-up was relatively short, and fewer than 100 subjects died from.prostate cancer. Balancing the potential survival benefit from.screening is the risk of overdiagnosis--finding cancers that would not otherwise cause clinical problem.^and the risk of treatm.nt com.lications, including urinary, sexual and bowel dysfunction. Prostate cancer screening efforts would benefit from.im.roved biom.rkers, which m.re readily identify clinically im.ortant cancers. Cancer control efforts m.ght also need to include chem.prevention, though currently available agents are controversial. In the m.antim., oatients need to be supoorted in achievine inform.d decisions on whether to be screened for orostate cancer.

关键词： cancer screening prostate-specific antigen prostatic neoplasm. random.zed controlled trials as topic

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