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A Population Dynamics Approach to the Distribution of Space Debris in Low Earth Orbit

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Communications on Applied Mathematics and Computation 2024年第1期6卷 340-353页

作者： John Jurkiewicz peter Hinow Department of Mathematical Sciences University of Wisconsin-MilwaukeeMilwaukeeWI53201USA

The presence of the debris in the Earth’s orbit poses a significant risk to human activity in outer *** debris population continues to grow due to ground launches,the loss of external parts from space ships,and uncontrollable collisions between objects.A computationally feasible continuum model for the growth of the debris population and its spatial distribution is therefore *** we propose a diffusion-collision model for the evolution of the debris density in the low-Earth orbit and its dependence on the ground-launch *** parametrize this model and test it against data from publicly available object catalogs to examine timescales for the uncontrolled ***,we consider sensible launch policies and cleanup strategies and how they reduce the future risk of collisions with active satellites or space ships.

关键词： Population dynamics Space debris kessler syndrome Diffusion Low-Earth orbit

Effect of age on the standardized ileal amino acid digestibility of soybean meal and canola meal in broilers

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Animal Nutrition 2024年第1期16卷 11-22页

作者： Mukti Barua M.Reza Abdollahi Faegheh Zaefarian Timothy J.Wester Channarayapatna k.Girish peter V.Chrystal Velmurugu Ravindran Monogastric Research Center School of Agriculture and EnvironmentMassey UniversityPalmerston North 4442New Zealand Department of Animal Science and Nutrition Faculty of Veterinary MedicineChattogram Veterinary and Animal Sciences UniversityKhulshiChattogram 4225Bangladesh Nutrition and Care Animal NutritionEvonik(SEA)Pte.Ltd609927 Singapore Complete Feed Solutions Howick 2145AucklandNew Zealand

Standardized ileal digestibility coefficients(SIDC)of nitrogen(N)and amino acids(AA)in two protein sources(soybean meal[SBM]and canola meal[CM])were investigated at six broiler ages(d 7,14,21,28,35,and 42).Two assay diets were formulated to contain either SBM(413 g/kg)or CM(553 g/kg)as the sole dietary AA *** dioxide(5 g/kg)was added as an indigestible marker.A total of 696 male broilers at 1 d old were allotted to 12 replicate cages per age *** assay diet was offered to birds for 4 d prior to the ileal digesta collection on d 7(14 birds/cage),14(12 birds/cage),21(10 birds/cage),28(8 birds/cage),35(8 birds/cage)and 42(6 birds/cage),*** apparent digestibility coefficients were standardized using age-specific basal endogenous AA *** the SBM group,though the SIDC of N tended to be influenced(quadratic;P=0.075)by age,no linear or quadratic response of age effect was observed on the average SIDC of indispensable(IAA)and total AA(TAA).An age effect(quadratic;P<0.05)was observed on the average SIDC of dispensable AA(DAA)in SBM with the highest value recorded at d 7,followed by a decrease from d 14 to 28,which increased beyond d *** SIDC of some individual AA(Arg,Thr,Trp,Cys,Pro)were affected(P<0.05 or P<0.001)in a quadratic manner by *** the CM,the SIDC of N,average SIDC of IAA,DAA and TAA were influenced(quadratic;P<0.05 or P<0.001)by *** SIDC of N and average SIDC of DAA and TAA were higher from d 7 to 14,declined at d 21,and then increased beyond d *** average SIDC of IAA was low between d 7 and 28 and increased *** SIDC of individual AA were affected(linear or quadratic;P<0.05 or P<0.001)by different magnitudes by *** age influence on the SIDC AA was variable,depending on the protein source and *** results demonstrate that age-specific SIDC AA data might need consideration in broiler feed formulations.

关键词： Age Amino acid Broiler Digestibility Protein source

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Achieving strength-ductility synergy in novel paramagnetic Fe-based medium-entropy alloys through deep cryogenic deformation

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Rare Metals 2024年第9期43卷 4493-4507页

作者： Hu-Wen Ma Yan-Chun Zhao Li Feng Tian-Zeng Liu Zhi-Qi Yu Bo Jin Wang-Chun Duan peter k.Liaw Dong Ma State key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals Lanzhou University of TechnologyLanzhou 730050China Wenzhou Pump and Valve Engineering Research Institute Lanzhou University of TechnologyWenzhou 325105China Iron and Steel Research Institute Jiuquan Iron and Steel CorporationJiayuguan 735100China Lanzhou Resources and Environment Voc-Tech University Lanzhou 730123China Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN 37996-2200USA Neutron Science Center Songshan Lake Materials LaboratoryDongguan 523808China

Cryogenic pre-deformation treatment has been widely used to effectively improve the comprehensive mechanical properties of steels and novel ***,the dislocation evolution and phase transformation induced by different degrees of deep cryogenic deformation are not yet fully *** this study,the effects of multiple cryogenic pre-treatments on the mechanical properties and deformation mechanisms of a paramagnetic Fe_(63.3)Mn_(14-)Si_(9.1)Cr_(9.8)C_(3.8)medium-entropy alloy(MEA)were investigated,leading to the discovery of a pretreated MEA that exhibits exceptional mechanical properties,including a fracture strength of 3.0 GPa,plastic strain of 26.1%and work-hardening index of *** addition,X-ray diffraction(XRD)and transmission electron microscopy(TEM)analyses revealed that multiple cryogenic pre-deformation treatments significantly increased the dislocation density of the MEA(from 9×10^(15)to 4×10^(16)m^(-2)after three pretreatments),along with a transition in the dislocation type from predominantly edge dislocations to mixed dislocations(including screw-and edge-type dislocations).Notably,this pretreated MEA retained its paramagnetic properties(μ_(r)king fault energy of the MEA by a factor of approximately four(i.e.,from 9.7 to2.6 m J·m^(-2)),thereby activating the synergistic effects of transformation-induced plasticity,twinning-induced plasticity and dislocation strengthening *** synergistic effects lead to simultaneous strength and ductility enhancement of the MEA.

关键词： Deep cryogenic transformation Iron-based medium-entropy alloys Dislocation evolution Phase transformation Stacking fault energy

Optimization of product characteristics of porous carbon agglomerates using a design of experiments in fluidized bed agglomeration

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Particuology 2024年第6期89卷 258-269页

作者： Martin Oelofse Robert Rack Marcelle Hilden peter Langguth Department of Pharmaceutical Technology and Biopharmaceutics Johannes Gutenberg UniversityMainzGermany Carbon Advanced Solutions GmbH HeuchelheimGermany

Spraying parameters during particle agglomeration processes can affect the agglomeration kinetics and particle *** study was conducted to better understand the influence of the spraying parameters in a fluidized bed wet agglomeration process,and the influence on the stability characteristics of carbon tablets.A formulation based on fine carbon and peroxide powder,as well as carboxymethyl cellulose as a binder,was used to produce agglomerates in a first production *** in a second production step carbon tablets with a high porosity were molded for the customer goods *** optimization of the compressive strength of these carbon tablets was the goal of the *** agglomerates were produced with a laboratory scale granulator called“ProCell”and were compressed with a five-cavity mechanical *** screening of the agglomeration process parameters and their influence on the agglomerates quality,as well as the performance characteristics of the carbon tablets,were investigated using a multilevel factorial *** experimental runs were done by varying atomized air pressure and feed rate of the *** was determined by the design *** findings of the statistical trials showed that low atomized air pressure and a low feed rate lead to a higher tablet compressive strength.

关键词： Wet agglomeration Fluidized bed Design of experiments Carbon agglomerates and tablets

Chinese Medicine,Acupuncture and Science

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Chinese Medicine and Culture 2024年第1期7卷 77-85页

作者： peter Eckman Private practitioner San Francisco 94131USA

Ever since the introduction of Western biomedicine into China, there has been friction between proponents of this new approach, and proponents of the traditional medical practices that had evolved over thousands of years in China. For the most part, this friction has been couched in the unexamined assumption that Western medicine is based on science, while Chinese medicine is not. This article will examine that assumption, which in this author’s opinion is unjustified and incorrect. Having practiced acupuncture for the past 50 years, after receiving my doctoral degrees in medicine and physiology, my thinking on this topic has also evolved over time. I will begin this article with some historical information that bears on the topic under discussion, followed by my personal ideas about how to resolve the confiicts that have arisen.

关键词： Science Chinese medicine Western medicine Resonance Constitution

When to repair a retinal detachment?

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International Journal of Ophthalmology(English edition) 2024年第4期17卷 607-609页

作者： peter Wiedemann Medical Faculty Leipzig UniversityLeipzig 04103Germany

Rhegmatogenous retinal detachment(RRD)is the most common retinal emergency,threatening visual acuity,with an incidence of 1/10000[1].The number of RRDs is increasing[2-3].I recently had to prepare two expert reports a... 详细信息

关键词： RRD visual reports

Relationship between the unique microstructures and behaviors of high-entropy alloys

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International Journal of Minerals,Metallurgy and Materials 2024年第6期31卷 1350-1363页

作者： Yaqi Wu peter kLiaw Ruixuan Li Weiran Zhang Guihong Geng Xuehui Yan Guiqun Liu Yong Zhang State key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN 37996USA Xi’an Rare Metal Materials Institute Co.Ltd. Xi’an 710016China School of Materials Science and Engineering North Minzu UniversityYinchuan 750030China GRIMAT Engineering Institute Co. Ltd.Beijing 101407China

High-entropy alloys(HEAs),which were introduced as a pioneering concept in 2004,have captured the keen interest of nu-merous ***,in this context,can be perceived as representing disorder and *** contrast,elemental composi-tions within alloy systems occupy specific structural sites in space,a concept referred to as *** accordance with Shannon entropy,structure is analogous to ***,the arrangement of atoms within a material,termed its structure,plays a pivotal role in dictating its *** addition to expanding the array of options for alloy composites,HEAs afford ample opportunities for diverse structural *** profound influence of distinct structural features on the exceptional behaviors of alloys is underscored by numer-ous *** features include remarkably high fracture strength with excellent ductility,antiballistic capability,exceptional radi-ation resistance,and corrosion *** this paper,we delve into various unique material structures and properties while elucidating the intricate relationship between structure and performance.

关键词： high-entropy alloys unique microstructure special properties alloy design

Thin-Shell Wormholes Admitting Conformal Motions in Spacetimes of Embedding Class One

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International Journal of Astronomy and Astrophysics 2024年第3期14卷 162-171页

作者： peter k. F. kuhfittig Department of Mathematics Milwaukee School of Engineering Milwaukee USA

This paper discusses the feasibility of thin-shell wormholes in spacetimes of embedding class one admitting a one-parameter group of conformal motions. It is shown that the surface energy density σis positive, while the surface pressure is negative, resulting in , thereby signaling a violation of the null energy condition, a necessary condition for holding a wormhole open. For a Morris-Thorne wormhole, matter that violates the null energy condition is referred to as “exotic”. For the thin-shell wormholes in this paper, however, the violation has a physical explanation since it is a direct consequence of the embedding theory in conjunction with the assumption of conformal symmetry. These properties avoid the need to hypothesize the existence of the highly problematical exotic matter.

关键词： Thin-Shell Wormholes Conformal Symmetry Embedding Class One Exotic Matter

Macroscopic Traversable Wormholes: Minimum Requirements

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International Journal of Astronomy and Astrophysics 2024年第3期14卷 230-243页

作者： peter k. F. kuhfittig Department of Mathematics Milwaukee School of Engineering Milwaukee USA

While wormholes are just as good a prediction of Einstein’s theory as black holes, they are subject to severe restrictions from quantum field theory. To allow for the possibility of interstellar travel, a macroscopic wormhole would need to maintain sufficiently low radial tidal forces. It is proposed in this paper that the assumption of zero tidal forces, i.e., the limiting case, is sufficient for overcoming the restrictions from quantum field theory. The feasibility of this approach is subsequently discussed by 1) introducing the additional conditions needed to ensure that the radial tidal forces can indeed be sufficiently low and 2) by viewing traversable wormholes as emergent phenomena, thereby increasing the likelihood of their existence.

关键词： Morris-Thorne Wormholes Traversability Minimum Requirements Stability Compatibility with Quantum Field Theory