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Conceptual design of an experiment to study dust destruction by astrophysical shock waves

High Power Laser Science and Engineering 2018年第3期6卷 9-14页

作者： m. j.-E. manuel T. Temim E. Dwek A. m. Angulo E X. Belancourt R. E Drake C. C. Kuranz m. j. macDonald B. A. Remington General Atomics 3550 General Atomics Court San Diego CA 92121 USA Space Telescope Science Institute 3700 San Martin Drive Baltimore MD 21218 USA Observational Cosmology Lab Code 665 NASA Goddard Space Flight Center Greenbelt MD 20771 USA Climate and Space Science and Engineering University of Michigan Ann Arbor M148109 USA Department of Physics University of California Berkeley CA 94720 USA Lawrence Livermore National Laboratory Livermore CA 94450 USA

A novel laboratory experimental design is described that will investigate the processing of dust grains in astrophysical shocks. Dust is a ubiquitous ingredient in the interstellar medium(ISm) of galaxies; however, its evolutionary cycle is still poorly understood. Especially shrouded in mystery is the efficiency of grain destruction by astrophysical shocks generated by expanding supernova remnants. While the evolution of these remnants is fairly well understood, the grain destruction efficiency in these shocks is largely unknown. The experiments described herein will fill this knowledge gap by studying the dust destruction efficiencies for shock velocities in the range ～10–30 km/s(μm/ns), at which most of the grain destruction and processing in the ISm takes place. The experiments focus on the study of grain–grain collisions by accelerating small(～1 μm) dust particles into a large(～5–10 μm diameter) population; this simulates the astrophysical system well in that the more numerous, small grains impact and collide with the large population. Facilities that combine the versatility of high-power optical lasers with the diagnostic capabilities of X-ray free-electron lasers, e.g., the matter in Extreme Conditions instrument at the SLAC National Accelerator Laboratory, provide an ideal laboratory environment to create and diagnose dust destruction by astrophysically relevant shocks at the micron scale.

关键词： laboratory astrophysics shock waves dust destruction

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Effects of various parameters on the attrition of bed material in a recirculating fluidized bed with a draft tube

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Particuology 2018年第3期16卷 61-70页

作者： Shivali Chourasia Babu j. Alappat Department of Civil Engineering Indian Institute of Technology Delhi Hauz Khas New Delhi 110016 India

We performed an experimental study to investigate the effects of various parameters on the attrition of bed material and its size distribution with increasing operation time in a recirculating fluidized bed （RCFB）. The studied parameters included superficial velocity of fluidizing air, bed inventory, and spacing between the j.t top and draft tube bottom （spacer height）. The bed material was prepared from Indian Standard （IS） Grade I sand from sieves with a size range of 2.20-1.00 mm. Experiments were performed at ambient conditions, with the superficial air velocity ranging from 7.13-9.16 m/s, a bed inventory of 7-10 kg, spacing of 0.085 and 0.045 m between the j.t top and draft tube bottom, and an operating time of 40 h. We investigated the influence of these parameters in terms of changes in the size distribution of particles, changes in the %-weight of particles of different size ranges, generation of particles with smaller diameters, the decrease of the downcomer bed height, variations in the coefficient of uniformity and coefficient of curvature, and material loss from entrainment of fines with increasing operation time. The mode of attrition was abrasion in all experiments. We found that with increasing operation time and other parameters （bed inventory, superficial air velocity, and spacer height） attrition of the bed material also increased. Generation and elutriation of fines were more pronounced at higher superficial air velocity, bed inventory, and spacer height.

关键词： Attrition Recirculating fluidized bed (RCFB) Fluidization Elutriation Fines

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Greenhouse gas emissions during co-composting of cattle feedlot manure with construction and demolition （C＆D） waste

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Frontiers of Environmental Science & Engineering 2017年第3期11卷 141-152页

作者： Xiying Hao Francis j. Larney Agriculture and Agri-Food Canada Lethbridge Research and Development Centre Lethbridge Alberta T1J 4B1 Canada

manure management strategies should reflect current animal feeding practices and encourage recycling of organic waste to help protect our environment. This research investigated greenhouse gas （GHG） emissions during cattle manure stockpiling or composting with and without construction and demolition （C＆D） waste. manure was collected from cattle fed a typical finishing diet （CK manure） and from cattle on diets which included 30% dried distillers grains with solubles （DG manure）. The CK and DG manures were co-composted with （4：1） C＆D waste （treatments： CK CD, DG CD）, composted alone （treatments： CK and DG） in 13 m3 bins or stockpiled without C＆D ~vaste （treatments： CK ST and DGST） for 99 days. manure type （CK vs. DG manure） had no effect on GHG emissions-over the 99 day manure composting or stockpiling. Composting with C＆D waste 2 produced similar CO2 emissions, about double that from manure stockpthng （7.9 kgC.m^-2）. In contrast, CH4 emissions were reduced by the inclusion of C＆D waste （64 gC.m^-1 with C＆D vs. 244 gC.m 2 without C＆D） while the manure stockpile emitted the greatest amount of CH4 （464 gC. m 2）. Additionally, only 0.48% of C was emitted in CH4 form with C＆D waste, compared to 1.68% when composting without C＆D waste and 7.00% when cattle manure was stockpiled. The N2O emissions （12.4 to 18.0 gN.m ） were similar across all treatments. The lower CH4 emissions with C＆D waste are beneficial in reducing overall GHG emissions from manure composting, while reducing the amount of material entering landfills.

关键词： Livestock manuregreenhouse gas fluxstraw bale compost binN2O CH4 CO2

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The total cross sections of the ^(11)B(α,n)^(14N) and the ^(10)B(α,n)^(13)N reactions between 2 and 6 meV

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Nuclear Science and Techniques 2017年第8期28卷 111-116页

作者： R. m. Prior m. C. Spraker R. H. France S. Stave m. W. Ahmed H. j. Karwowski j. m. mueller L. S. myers H. R. Weller University of North Georgia Dahlonega GA 30597 USA Georgia College & State University MilledgevilleGA 31061 USA Duke University Durham NC 27708 USA Triangle Universities Nuclear Laboratory DurhamNC 27708 USA University of North Carolina Chapel Hill NC 27599 USA Present Address: Bluffton University Bluffton OH 45817USA

There is considerable interest in potential aneutronic fusion reactors. One possible reaction is^(11)B(p,a)***, the emitted alpha particles are energetic enough to generate neutrons by interacting with boron inside the reactor through the ^(11)B(α,n)^(14N) and ^(10)B(α,n)^(13)N *** aid in evaluating neutron production within this potential aneutronic reactor, the total cross sections were measured for the ^(11)B(α,n)^(14N) reaction between 2 and 6 meV and for the ^(10)B(α,n)^(13)N reaction between 2 and 4.8 meV. The results are presented and compared with previously reported results.

关键词：聚变反应堆 meV 总截面核反应堆中子反应器 α粒子电子

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Performance Prediction of a multi-Stage Wind Tower for Indoor Cooling

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j.urnal of Thermal Science 2012年第4期21卷 327-335页

作者： Roy j. Issa Byungik Chang Department of Engineering and Computer Science West Texas A&M University Canyon

A theoretical model is developed to establish an indepth understanding of the performance of a three-stage wind tower with a bypass system for indoor cooling in rural dry and hot climates. model simulations are presented for a wide range of ambient conditions that include inlet wind speed, inlet temperature and relative humidity. Simulation results provide an insight into the desirable water flow rates and air-to-water loadings for comfort zone tem-peratures and relative humidity levels at the exit of the wind tower. Simulations show wind towers with variable cross-sections provide an increase in the cooling power for the same inlet wind speed, inlet air temperature and relative humidity when compared to wind towers with a constant cross-section. The study shall lead to a better understanding to designing wind towers that are both environmentally friendly and energy efficient.

关键词： Wind tower Cooling power Cooling effectiveness Relative humidity

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Effect of Noisy Fitness in Real-Time Strategy Games Player Behaviour Optimisation Using Evolutionary Algorithms

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j.urnal of Computer Science & Technology 2012年第5期27卷 1007-1023页

作者： Antonio m. mora Antonio Fernndez-Ares j.an j. merelo Pablo García-Snchez Carlos m. Fernandes Computer Architecture and Technology Department University of Granada Institute for Systems and Robotics Technical University of Lisbon

This paper investigates the performance and the results of an evolutionary algorithm （EA） specifically designed for evolving the decision engine of a program （which, in this context, is called bot） that plays Planet Wars. This game, which was chosen for the Google Artificial Intelligence Challenge in 2010, requires the bot to deal with multiple target planets, while achieving a certain degree of adaptability in order to defeat different opponents in different scenarios. The decision engine of the bot is initially based on a set of rules that have been defined after an empirical study, and a genetic algorithm （GA） is used for tuning the set of constants, weights and probabilities that those rules include, and therefore, the general behaviour of the bot. Then, the bot is supplied with the evolved decision engine and the results obtained when competing with other bots （a bot offered by Google as a sparring partner, and a scripted bot with a pre-established behaviour） are thoroughly analysed. The evaluation of the candidate solutions is based on the result of non-deterministic battles （and environmental interactions） against other bots, whose outcome depends on random draws as well as on the opponents＇ actions. Therefore, the proposed GA is dealing with a noisy fitness function. After analysing the effects of the noisy fitness, we conclude that tackling randomness via repeated combats and reevaluations reduces this effect and makes the GA a highly valuable approach for solving this problem.

关键词： real-time strategy game genetic algorithm noisy fitness player behaviour optimisation parameter adaptation

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microstructure and magnetic properties of Fe-Co-Nd-Y-B alloys obtained by suction casting method

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j.urnal of Rare Earths 2009年第4期27卷 680-683页

作者： j.Olszewski j.Zbroszczyk m.Hasiak j.Kaleta m.Nabiaek P.Bragiel K.Sobczyk W.Ciurzyńska j.wierczek A.Lukiewska Institute of Physics Cz■stochowa University of Technology Al.Armii Krajowej 19 42-200 Cz■stochowa Poland Institute of materials Science and Applied mechanics Wroctaw University of Technology ul.Smoluchowskiego 25 50-370 Wroctaw Poland j.n Dtugosz University Al.Armii Krajowej 13/15 42-200 Cz■stochowa Poland

The phase composition, magnetic properties i.e. coercivity and the magnetic polarization at room temperature for the bulk Fe67Co5Nd3Y6B19 and Fe64Co5Nd6Y6B19 alloys were studied. The bulk amorphous Fe67CosNd3Y6B19 alloy, inhomogeneous in the as-quenched state, crystallized after annealing at 948 K for 0.5 h and consisted of Nd2Fe14B-type, Fe2B and paramagnetic phases. The rapidly solidified Fe64Co5Nd6Y6B19 alloy contained the Nd2Fel4B-type and paramagnetic phases. The annealing of the bulk Fe67CosNd3Y6B19 alloy at 948 K for 0.5 h led to hard magnetic properties. However, the bulk Fe64Co5Nd6Y6B19 alloy exhibited good hard magnetic properties directly after preparation.

关键词： moessbauer spectroscopy bulk alloys rare earth hard magnetic materials

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Numerical simulation of self-similar thermal convection from a spinning cone in anisotropic porous medium

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j.urnal of Hydrodynamics 2016年第2期28卷 184-194页

作者： O. Anwar BEG m. j. UDDIN T. BEG R. Reddy GORLA Spray Research Group Petroleum and Gas Engineering Division Room G77 Newton Building School of Computing Science and Engineering (CSE) University of Salford M54WT UK Department of mathematics American International University-Bangladesh Dhaka Bangladesh Engineering mechanics Associates Dickenson Road Manchester M 16 England UK Department mechanical Engineering Cleveland State University Cleveland Ohio USA

Self-similar steady natural convection thermal boundary layer flow from a rotating vertical cone to anisotropic Darcian porous medium is investigated theoretically and numerically. The transformed non-dimensional two-point boundary value problem is reduced to a system of coupled, highly nonlinear ordinary differential equations, which are solved subj.ct to robust surface and free stream boundary conditions with the mAPLE 17 numerical quadrature software. Validation with earlier non-rotating studies is included, and also further verification of rotating solutions is achieved with a variational finite element method （FEm）. The rotational （spin） parameter emerges as an inverse function of the Grashof number. The influence of this parameter, primary Darey number, secondary Darcy number and Prandtl number on tangential velocity and swirl velocity, temperature and heat transfer rate are studied in detail. It is found that the dimensionless tangential velocity increases whilst the dimensionless swirl velocity and temperature decrease with the swirl Darcy number, tangential Darcy number and the rotational parameters. The model finds applications in chemical engineering filtration processing, liquid coating and spinning cone distillation columns.

关键词： self-similarity spinning cone finite element method (FEm) anisotropic porous medium heat transfer mAPLE FEm

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;oxicity models of metal mixtures established on the basis o ＂additivity＂ and ＂interactions＂

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Frontiers of Environmental Science & Engineering 2017年第2期11卷 11-23页

作者： Yang Liu martina G. Vij.er Bo Pan Willie j. G. m. Peij.enburg Faculty of Environmental Science and Engineering Kunming University of Science and Technology Kunming 650500 China Institute of Environmental Sciences (CmL) Leiden University Leiden 2300 RA The Netherlands National Institute of Public Health and the Environment (RIVm) Center for Safety of Substances and Products Bilthoven 3720 BA The Netherlands

Observed effects of metal mixtures on animals and plants often differ from the estimates, which are commonly calculated by adding up the biological responses of individual metals. This difference from additivity is commonly referred to as being a consequence of specific interactions between metals. The science of how to quantify metal interactions and whether to include them in risk assessment models is in its infancy. This review summarizes the existing predictive tools for evaluating the combined toxicity of metals present in mixtures and indicates the advantages and disadvantages of each method. We intend to provide eco-toxicologists with background information on how to make good use of the tools and how to advance the methods for assessing toxicity of metal mixtures, It is concluded that statistically significant deviations from additivity are not necessarily biologically relevant. Incorporation of interactions between metals in a model does not on forehand mean that the model is more accurate than a model developed based on additivity only. It is recommended to first use a relatively simple method for effect prediction of uninvestigated metal mixtures. To improve the reliability of toxicity modeling for metal mixtures, further efforts should focus on balancing the relationship between the significance of statistics and the biological meaning, and unraveling the toxicity mechanisms of metals and their mixtures.

关键词： metal mixtures Toxicity Additivity modeling Interactions

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X-ray multiple Diffraction Topographic Imaging Technique For Growth History Study of Habit modifying Impurity Doped Crystals

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Chemical Research in Chinese Universities 2004年第4期20卷 411-416页

作者： LAI X. mA C. K. j. Robert m. C. miller Institute of Particle Science and Engineering Department of Chemical Engineering University of LeedsInstitute of Particle Science and Engineering Department of Chemical Engineering University of LeedsInstitute of Particle Science and Engineering Department of Chemical Engineering University of LeedsCCLRC Daresbury Laboratory Daresbury Leeds LS2 9JT UKLeeds LS2 9JT UKLeeds LS2 9JT UKWarrington Cheshire WA4 4AD UK

A novel crystal characterization instrument has been built up in which a combination of X-ray multiple diffraction and X-ray topography is applied to enabling the cross-correlation between micro-crystallographic symmetry and its spatial dependence in relation to lattice defects. This facility is used to examine, in a self-consistent manner, growth sector-dependant changes to both the crystallographic structure and the lattice defects associated with the action of habit-modifying additives in a number of representative crystal growth systems. In addition, the new instrument can be used to probe micro-crystallographic aspects(such as distortion to crystal symmetry) and relate these in a spatially resolved manner to the crystal defect structure in crystals doped with known habit modifiers.

关键词： X-ray diffraction X-ray multiple diffraction X-ray topography Habit modification Crystal growth Growth defects

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