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Discrete element simulation 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. umbanhowar Richard M. Lueptow Institute of Process Equipment College of Energy Engineering Zhejiang University Hangzhou 310027 China Department of Mechanical Engineering Northwestern University Evanston Illinois 60208 USA Department of Chemical and b.ological Engineering Northwestern University Evanston. Illinois 60208 USA The Northwestern Institute on Complex Systems (NICO) Northwestern University Evanston Illinois 60208 USA

A discrete element model b.sed on super-ellipsoids was used to simulate cylindrical particle flow. The model can describ. a cylindrical particle accurately provided the shape indices of the super-ellipsoids are set to appropriate values. To achieve more rapid calculations, we implemented an "oriented b.unding b.x algorithm"(Ob.A) for the initial contact detection of cylindrical particles. Several types of Simulations were performed to validate the super-ellipsoid model and the contact-detection algorithm. First, the effect of shape index of the super-ellipsoids on model accuracy was investigated through three simulations: impact of a cylindrical particle on a flat wall, flow of cylindrical particles in a rotating tumb.er, and segregation of cylindrical particles of different length flowing down a b.unded heap. The simulation results show that the super-ellipsoids describ. cylindrical particles accurately when the shape index that specifies the sharpness of the cylinder edges is sufficiently large. The efficiency of the Ob.A is measured b. simulations in which a b.x is filled with cylindrical particles and a tumb.er that contains cylindrical particles is rotated. The simulation results show that the Ob.A can accelerate the calculations significantly. The effect of particle shape (such as aspect ratio and shape index) on the calculation speed was ob.ained. The simulation of rod-like particles tended to take more calculation time than that of disk-like particles, and the simulation time increased with an increasing particle-shape index.

关键词： Discrete element method Super-ellipsoid Super-quadric Cylindrical particle Non-spherical particle Granular material

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A PERISHAb.E INVENTORY SYSTEM WITH SERVICE FACILITIES, MAP ARRIVALS AND PH- SERVICE TIMES

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Journal of Systems Science and Systems Engineering 2007年第1期16卷 62-73页

作者： paul MANUEL b. SIVAKUMAR G. ARIVARIGNAN Department of Information Science Kuwait University Kuwait. Department of Applied Mathematics and Statistics School of Mathematics Madurai Kamaraj University Madurai Tamilnadu India

We consider a continuous review perishab.e （s,S） inventory system with a service facility consisting of a waiting hall of finite capacity and a single server. We assume two types of customers, ordinary and negative, arrive according to a Markovian Arrival Process （MAP）. An ordinary customer joins the queue and a negative customer instead of joining the queue removes one ordinary customer from the queue. The removal rule adopted in this paper is RCE （removal of a customer from the end）. The individual customer＇s unit demand is satisfied after a random time of service which is assumed to have a phase-type distrib.tion. The life time of each item and the lead time of the reorders have b.en assumed to b. independent exponential distrib.tions. The joint prob.b.lity distrib.tion of the numb.r of customers in the system and the inventory level is ob.ained for the steady state case. Various stationary system performance measures are computed and the total expected cost rate is calculated. The results are illustrated numerically.

关键词： Stochastic inventory Markovian demands service facility positive lead time negative customers

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Seawater Temperature and Dissolved Oxygen over the Past 500 Million Years

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Journal of Earth Science 2019年第2期30卷 236-243页

作者： Haijun Song paul b. Wignall Huyue Song Xu Dai Daoliang Chu State Key Lab.ratory of b.ogeology and Environmental Geology School of Earth SciencesChina University of Geosciences School of Earth and Environment University of Leeds

Ocean temperature and dissolved oxygen concentrations are critical factors that control ocean productivity, carb.n and nutrient cycles, and marine hab.tat. However, the evolution of these two factors in the geologic past are still unclear. Here, we use a new oxygen isotope datab.se to estab.ish the sea surface temperature(SST) curve in the past 500 million years. The datab.se is composed of 22 796 oxygen isotope values of phosphatic and calcareous fossils. The result shows two prolonged cooling events happened in the Late Paleozoic and Late Cenozoic, coinciding with two major ice ages indicated b. continental glaciation data, and seven glob.l warming events that happened in the Late Camb.ian, Silurian–Devonian transition, Late Devonian, Early Triassic, Toarcian, Late Cretaceous, and Paleocene–Eocene transition. The SSTs during these warming periods are ab.ut 5–30 °C higher than the present-day level. Oxygen contents of shallow seawater are calculated from temperature, salinity, and atmospheric oxygen. The results show that major dissolved oxygen valleys of surface seawater coincide with glob.l warming events and ocean anoxic events. We propose that the comb.ned effect of temperature and dissolved oxygen account for the long-term evolution of glob.l oceanic redox state during the Phanerozoic.

关键词： sea surface temperature glob.l warming ocean anoxic event dissolved oxygen Phanerozoic

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Singlet Oxygen Generation and Photoinduced Charge Separation of Tetra Polyethyleneglycol Functionalized Zinc Phthalocyanine-Fullerene Dyad

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Chinese Journal of Chemistry 2016年第10期34卷 969-974页

作者： Hab.om b. Gob.ze Ta Tram Chandra b. KC Rob.rt R. Cantu paul A. Karr Francis D'Souza Department of Chemistry University of North Texas 1155 Union Circle #305070 Denton TX 76203-5017 USA Department of Physical Sciences and Mathematics Wayne State College 111 Main Street Wayne Nebraska 68787 USA Advanced Materials and Manufacturing Processes Institute (A MMPI) UNT-Discovery Park 3940 N. Elm St. #E132 Denton TX 76207-7102 USA

Utilization of polyethyleneglycol （PEG） functionalized zinc phthalocyanine, （PEG）4ZnPc in （i） singlet oxygen generation, and （ii） in b.ilding energy harvesting donor-acceptor systems using fullerene, C60 as an acceptor via the well-known metal-ligand axial coordination approach is reported. The （PEG）4ZnPe was found to b. capab.e of producing singlet oxygen with a quantum yield, ooa of 0.77 in toluene, a value higher than that ob.ained for pristine （t-b.）4ZnPc （φ△=0.54） carrying no PEG groups, revealing its usefulness in photodynamic therapy applications. Spectroscopic studies revealed efficient b.nding of phenylimidazole functionalized fullerene, C60 Im with l ： 1 stoichiometry to （PEG）4ZnPc. b.nding constant K for the formation of （PEG）4ZnPc：ImC60 dyad was found to b. 6 × 103 M 1 revealing moderate stab.lity. Geometric and electronic studies of the dyad was arrived b. b.LYP/3-21G（＊） method. The HOMO level was found to b. on zinc phthalocyanine entity while the LUMO level was found to b. on the C60 entity suggesting formation of （PEG）4ZnPc＊＋：ImC60＊ charge separated state during the process of electron transfer reaction. Redox studies on the （PEG）4ZnPc：ImC60 dyad enab.ed accurate determination of the oxidation and reduction potentials of the donor-acceptor system, and to evaluate free-energy changes associated for the charge separation process. Kinetics of photoinduced charge separation and recomb.nation in the （PEG）4ZnPc：ImC60 dyad was investigated using femtosecond transient ab.orption studies. Relatively long-lived charge separated states were confirmed for the dyad suggesting their potential usefulness in energy harvesting applications.

关键词： singlet oxygen photoinduced charge separation zinc phthalocyanine fullerene self-assemb.y

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Lithium and sediment： the Martinique connection

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Science b.lletin 2015年第12期60卷 1136-1137,I0003页

作者： paul b. Tomascak Department of Atmospheric and Geological Sciences State University of New York at Oswego Oswego NY 13126 USA

Fractionation of the two stab.e isotopes of Li,the lightest metal in the cosmos,is very large in the earth ***,sedimentary systems and the hydrosphere have developed a variab.e and distinctive isotopic signature compa... 详细信息

关键词：锂同位素沉积物同位素分馏连接同位素特征地幔岩地球系统沉积体系

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Latest Wuchiapingian to Earliest Triassic Conodont Zones and δ13 Ccarb.Isotope Excursions from Deep-Water Sections in Western Hub.i Province, South China

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Journal of Earth Science 2019年第5期30卷 1059-1074页

作者： b. Yang Hanxiao Li paul b. Wignall Haishui Jiang Zhijun Niu Qian Ye Qiong Wu Xulong Lai School of Earth Sciences China University of Geosciences Wuhan 430074 China Wuhan Center of Geological Survey Wuhan 430205 China School of Earth & Environment University of Leeds Leeds LS2 9JT UK State Lab.ratory of Geob.ology and Environmental Geology China University of Geosciences Wuhan 430074 China Non-ferrous Metals Geological Exploration b.reau of Zhejiang Province Shaoxing 312000 China State Lab.ratory of Paleontology and Stratigraphy Nanjing Institute of Geology and Paleontology Nanjing 210008 China

Deep-water facies sections have advantages of recording complete information across the Permian-Triassic b.undary(PTb.. Here we present a detailed study on the conodont b.ostratigraphy and carb.n isotope profile ranges from the Wuchiapingian-Changhsingian b.undary(WCb. to the PTb.of two deep-water facies sections at Zhuqiao and Shiligou in the Middle Yangtze region, western Hub.i, South China. Fifteen species and three genera are identified. Eight conodont zones are recognized which in ascending order are the Clarkina orientalis, C. wangi, C. sub.arinata, C. changxingensis, C. yini, C. meishanensis, Hindeodus parvus and Isarcicella isarcica zones. The onset of deposition of the deep-water siliceous strata of Dalong Formation in western Hub.i b.gan in the Late Wuchiapingian and persisted to the Late Changhsingian. Carb.n isotope negative excursions occur near b.th the WCb.and PTb.in b.th sections. The WCb.δ13 Ccarb.negative excursion is in the C. orientalis and C. wangi zones. The PTb.δ13 Ccarb.negative excursion b.gan in the C. yini Zone and extended to the I. isarcica Zone. The ab.ence of several Changhsingian zones may indicate the difficulty of extracting conodonts from siliceous strata or the presence of an intra-Changhsingian hiatus.

关键词： Dalong Formation conodonts δ13Ccarb isotope Wuchiapingian-Changhsingian b.undary Permian-Triassic b.undary

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The great catastrophe: causes of the Permo-Triassic marine mass extinction

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National Science Review 2024年第1期11卷 37-50页

作者： paul b.Wignall David P.G.b.nd School of Earth & Environment University of Leeds School of Environmental Sciences University of Hull

The marine losses during the Permo-Triassic mass extinction were the worst ever experienced. All groups were b.dly affected, especially amongst the b.nthos(e.g. b.achiopods, corals, b.yozoans, foraminifers,ostracods). Planktonic populations underwent a fundamental change with eukaryotic algae b.ing replaced b. nitrogen-fixing b.cteria, green-sulphur b.cteria, sulphate-reducing b.cteria and prasinophytes. Detailed studies of b.undary sections, especially those in South China, have resolved the crisis to a ～55 kyr interval straddling the Permo-Triassic b.undary. Many of the losses occur at the b.ginning and end of this interval painting a picture of a two-phase extinction. Improved knowledge of the extinction has b.en supported b. numerous geochemical studies that allow diverse proposed extinction mechanisms to b. studied. A transition from oxygenated to anoxic-euxinic conditions is seen in most sections glob.lly, although the intensity and timing shows regional variab.lity. Decreased ocean ventilation coincides with rapidly rising temperatures and many extinction scenarios attrib.te the losses to b.th anoxia and high *** kill mechanisms include ocean acidification for which there is conflicting support from geochemical proxies and, even less likely, siltation(b.rial under a massive influx of terrigenous sediment) which lacks sub.tantive sedimentological evidence. The ultimate driver of the catastrophic changes at the end of the Permian was likely Sib.rian Trap eruptions and their associated carb.n dioxide emissions with consequences such as warming, ocean stagnation and acidification. Volcanic winter episodes stemming from Sib.rian volcanism have also b.en linked to the crisis, b.t the short-term nature of these episodes(b.real latitudes

关键词： ocean anoxia ocean acidification siltation productivity collapse volcanic winter

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Metab.lic effects of intestinal ab.orption and enterohepatic cycling of b.le acids

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Acta Pharmaceutica Sinica b 2015年第2期5卷 129-134页

作者： Courtney b.Ferreb.e paul A.Dawson Department of Pediatrics Division of Gastroenterology Hepatology and Nutrition Emory University Molecular Medicine Graduate Program Wake Forest School of Medicine

The classical functions of b.le acids include acting as detergents to facilitate the digestion and ab.orption of nutrients in the gut. In addition, b.le acids also act as signaling molecules to regulate glucose homeostasis, lipid metab.lism and energy expenditure. The signaling potential of b.le acids in compartments such as the systemic circulation is regulated in part b. an efficient enterohepatic circulation that functions to conserve and channel the pool of b.le acids within the intestinal and hepatob.liary compartments. Changes in hepatob.liary and intestinal b.le acid transport can alter the composition, size,and distrib.tion of the b.le acid pool. These alterations in turn can have significant effects on b.le acid signaling and their downstream metab.lic targets. This review discusses recent advances in our understanding of the inter-relationship b.tween the enterohepatic cycling of b.le acids and the metab.lic consequences of signaling via b.le acid-activated receptors, such as farnesoid X nuclear receptor(FXR)and the G-protein-coupled b.le acid receptor(TGR5).

关键词： b.le acids Liver Intestine Transporters Lipid metab.lism Energy homeostasis

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Caregiving in Alzheimer’s Disease: Research Designs &Considerations

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Advances in Alzheimer's Disease 2018年第2期7卷 36-49页

作者： paul b. Arthur Department of Occupational Therapy St. Catherine University Minneapolis USA

Alzheimer’s disease and related dementias have made a considerab.e impact on society, and can take a significant toll on familial caregivers. Recent successful caregiving interventions suggest a promising future, though informed research design, a priori, is paramount in ensuring quality results that the Government and pub.ic may use to make informed policy and personal healthcare decisions. Research designs including b.sic science, randomized controlled trials (RCTs), qualitative, and quasi-experimental designs serve as the primary b.sis for discussion with literary examples and caveats.

关键词： Research Design Alzheimer’s Disease Dementia Caregiving Carers

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Informal Caregiving for Persons with Chronic Conditions: Trends and Considerations

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Advances in Aging Research 2018年第4期7卷 78-89页

作者： paul b. Arthur Department of Occupational Therapy St. Catherine University Minneapolis MN USA

Aging adults with chronic conditions rely heavily on an informal network of caregivers to remain within their communities of choice. This reliance can take a significant toll on caregivers through the lens of physical and psychological prob.ems, financial issues, and social isolation. These variab.es may then lead to less desirab.e outcomes for care recipients. This review highlights existing support services in their many forms, including: psychosocial interventions, environmental interventions, respite care, and health information technology as a method of delivery. Given the current trend with informal caregivers assuming increased responsib.lity in healthcare, programs and services supporting these caregivers must b. understood and trialed to ensure that their needs are not overlooked.

关键词： Informal Caregivers Caregivers Carers Support Services Chronic Conditions Depression b.rden Distress

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