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Nanophononic metamaterials induced proximity effect in heat flux regulation

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Frontiers of physics 2024年第2期19卷 149-156页

作者： Jian zhang Haochun zhang Gang zhang School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150001China Institute of High Performance Computing Agency for ScienceTechnology and Research(A*STAR)Singapore 138632Singapore

Recent studies have shown that the construction of nanophononic metamaterials can reduce thermal conductivity without affecting electrical properties,making them promising in many fields of application,such as energy conversion and thermal ***,although extensive studies have been carried out on thermal conductivity reduction in nanophononic metamaterials,the local heat flux characteristic is still *** this work,we construct a heat flux regulator which includes a silicon nanofilm with silicon *** regulator has remarkable heat flux regulation ability,and various impacts on the regulation ability are ***,even in the region without nanopillars,the local heat current is still lower than that in pristine silicon nanofilms,reduced by the neighboring nanopillars through the thermal proximity *** combine the analysis of the phonon participation ratio with the intensity of localized phonon modes to provide a clear *** findings not only provide insights into the mechanisms of heat flux regulation by nanophononic metamaterials,but also will open up new research directions to control local heat flux for a broad range of applications,including heat management,thermoelectric energy conversion,thermal cloak,and thermal concentrator.

关键词： nanophononic metamaterials proximity effect

Optimising multi-vent module-based adaptive ventilation using a novel parameter for improved indoor air quality and health protection

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Building Simulation 2024年第1期17卷 113-130页

作者： Haotian zhang Xiaoxiao Ding Weirong zhang Weijia zhang Yingli Xuan Key Laboratory of Green Built Environment and Energy Efficient Technology Beijing University of TechnologyBeijing 100124China Department ofArchitecture TokyoPolytechnic UniversityTokyoJapan

As infectious respiratory diseases are highly transmissible through the air,researchers have improved traditional total volume air distribution systems to reduce infection ***-vent module-based adaptive ventilation(MAV)is a novel ventilation type that facilitates the switching of inlets and outlets to suit different indoor scenarios without changing ductwork ***,little research has evaluated MAV module sizing and air velocity selection,both related to MAV system efficiency in removing contaminants and the corresponding level of protection for occupants in the ventilated ***,the module-source offset ratio(MSOR)is proposed,based on the MAV module size and its distance from an infected occupant,to inform selection of optimal MAV module *** fluid dynamics simulations illustrated contaminant distribution in a two-person MAV equipped *** phase particles modelled respiratory contaminants from the infected occupant,and contaminant concentration distributions were compared under four MAV air distribution layouts,three air velocities,and three module sizes considered using the *** indicate that lower air velocities favour rising contaminant levels,provided the ventilation rate is *** contaminant discharge can be achieved when the line of outlets is located directly above the infected *** this parameter to guide MAV system design,85.7% of contaminants may be rendered harmless to the human body within 120 s using the default air vent layout.A more appropriate supply air velocity and air vent layout increases this value to 91.4%.These results are expected to inform the deployment of MAV systems to reduce airborne infection risk.

关键词： multi-vent module-based adaptive ventilation computational fluid dynamics indoor air quality infection control

Non-isothermal kinetics and characteristics of calcium carbide nitridation reaction with calcium-based additives

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Frontiers of Chemical Science and Engineering 2024年第4期18卷 49-61页

作者： Zhihan zhang Mengxiao Yu Xiaoyu zhang Jinli zhang You Han School of Chemical Engineering and Technology Tianjin UniversityTianjin 300350China Haihe Laboratory of Sustainable Chemical Transformations Tianjin 300192China

The nitridation reaction of calcium carbide and N_(2) at high temperatures is the key step in the production of ***,the challenges faced by this process,such as high energy consumption and poor product quality,are mainly attributed to the lack of profound understanding of the *** study aimed to improve this process by investigating the non-isothermal kinetics and reaction characteristics of calcium carbide nitridation reaction at different heating rates(10,15,20,and 30℃·min^(-1))using thermogravimetric *** kinetic equation for the nitridation reaction of additive-free calcium carbide sample was obtained by combining model-free methods and model-fitting *** effect of different calcium-based additives(CaCl_(2) and CaF_(2))on the reaction was also *** results showed that the calcium-based additives significantly reduced reaction temperature and activation energy E_(a) by about 40% with CaF_(2) and by 55%-60% with CaCl_(2).The reaction model f(α)was also changed from contracting volume(R3)to 3-D diffusion models with D3 for CaCl_(2) and D4 for CaF_(2).This study provides valuable information on the mechanism and kinetics of calcium carbide nitridation reaction and new insights into the improvement of the lime-nitrogen process using calcium-based additives.

关键词： lime-nitrogen calcium carbide calciumbased additive thermogravimetric analysis nonisothermal kinetics

Estimating the yield stress of soft materials via laser-induced breakdown spectroscopy

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Chinese Physics B 2024年第3期33卷 428-432页

作者：龚书航李亚举钱东斌叶晋瑞赵扣曾强陈良文张少锋杨磊马新文 Advanced Energy Science and Technology Guangdong LaboratoryHuizhou 516000China Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China

Taking three typical soft samples prepared respectively by loose packings of 77-,95-,and 109-μm copper grains as examples,we perform an experiment to investigate the energy-dependent laser-induced breakdown spectroscopy(LIBS)of soft *** discovered a reversal phenomenon in the trend of energy dependence of plasma emission intensity:increasing initially and then decreasing separated by a well-defined critical *** trend reversal is attributed to the laser-induced recoil pressure at the critical energy just matching the sample's yield *** a result,a one-to-one correspondence can be well established between the samples'yield stress and the critical energy that is easily obtainable from LIBS *** allows us to propose an innovative method for estimating the yield stress of soft materials via LIBS with attractive advantages including in-situ remote detection,real-time data collection,and minimal destructive to sample.

关键词： laser-induced breakdown spectroscopy soft materials yield stress

Particle size spatial distribution in landslide dams

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Journal of Mountain Science 2024年第6期21卷 1886-1903页

作者： zhang Jingyi zhang Jianmin State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan UniversityChengdu 610064China

The particle composition and spatial distribution of landslide-induced dam bodies are critical geotechnical parameters for studying the hazards of dam-break ***,current research often neglects the influence of the initial particle composition and spatial distribution of the landslide on the particle composition and spatial distribution of the landslide *** study investigated the impact of initial particle size distribution,volume,and sliding length on the energy and velocity changes of characteristic particles during the sliding process and the spatial distribution of particle sizes in the landslide dam *** simulations and physical models were employed to examine the effects of sequential gradient arrangements(where particle sizes decrease from top to bottom)and four other different initial particle arrangements on the energy and velocity changes of particles and the spatial distribution of particle sizes in the dam *** study reveals the characteristics of translational and rotational energy of different particles and the laws of mechanical energy conversion,obtaining the spatial distribution patterns of particle sizes in landslide-induced *** results show that under the sequential gradient arrangement,the energy dissipation of the landslide movement is lower,with larger particles mainly distributed at the distal end and smaller particles at the proximal end of the landslide *** contrast,under the reverse gradient arrangement,the energy dissipation of the landslide movement is higher,and the distribution pattern of the dam particles is opposite to that of the sequential gradient *** the other arrangement modes,the spatial distribution of dam particles falls between the aforementioned *** is a positive correlation between particle size and translational kinetic energy within the particle flow during the landslide process,and rotational motion increases energy *** constant slope conditions,sliding

关键词： Particle size distribution Landslide Numerical simulation Discrete element method

Unveiling the protective role of biofilm formation on the photoaging of microplastics

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Science China Technological Sciences 2024年第10期67卷 3067-3078页

作者： zhang HaiYu LIU Peng zhang JiaYu DAI JiaMin zhang XinRui zhang ZiXuan JIA HanZhong Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China Ministry of AgricultureCollege of Natural Resources and EnvironmentNorthwest A&F University Key Laboratory of Organic Compound Pollution Control Engineering School of Environmental and Chemical EngineeringShanghai University

In natural water, microplastics（MPs） inevitably undergo microbial colonization to form biofilm, while the effect of biofilm formation on the photoaging of MPs remains unknown. This study systematically investigated the photoaging behavior of disposable box-derived polypropylene（PPMPs） and polystyrene（PSMPs） mediated by formed biofilm in water. After incubating in Weihe water samples for 105 d, the biofilm was validated to form in PPMPs and PSMPs, with higher formation in PSMPs. In particular, biofilm formation inhibited the photoaging of PPMPs and PSMPs, with an 11.1% and 50.6% decrease in photooxidation compared to their virgin counterparts after 20 d of ultraviolet（UV） irradiation. Moreover, the photoaging route of MPs such as the reaction priority of functional groups（e.g., C–H, C=O, and benzene ring） was altered, indicating the important role of biofilm formation in the photoaging process of MPs. The protective effect of the biofilm was mainly caused by the role of optical light filters that absorbed UV energy by sacrificing themselves. Also, as the main attacker on MPs, the production of reactive oxygen species（ROS, mainly1O2and ·OH） was inhibited by biofilm, which was mainly responsible for the decreased photoaging of MPs. This study revealed the important role of biofilm in the photoaging process of MPs and suggested a higher resistance of（micro）plastics in natural water than that in the laboratory using pure MPs, which contributed to a deeper understanding of the environmental fate and pollution of MPs.

关键词： microplastics biofilm photoaging physical shielding reactive oxygen species

Periodic Variation Studies of the Two Short Period W UMa-type Eclipsing Binaries: LX Lyn and V0853 Aur

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Research in Astronomy and Astrophysics 2024年第1期24卷 273-284页

作者： Xu zhang Bin zhang School of Physics and Electronic Science Guizhou Normal UniversityGuiyang 550001China Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing Guizhou Normal UniversityGuiyang 550025China

In this paper,new light curves(LCs) of contact eclipsing binary(CEB) systems LX Lyn and V0853 Aur are presented and analyzed by using the 2015 version of the Wilson-Devinney(W-D) *** order to explain their asymmetric LCs,cool starspots on the components were *** is suggested that their fill-out degrees are f=12.0%(LX Lyn) and f=26.3%(V0853 Aur).At the same time,we found that LX Lyn is a W-type eclipsing binary(EB) with an orbital inclination of i=84°.88 and a mass ratio of q=2.31.V0853 Aur is also a W-type CEB with a mass ratio of q=2.77 and an orbital inclination of i= 79°.*** on all available times of light minimum,their orbital period changes are studied by using the O-C *** O-C diagram of LX Lyn reveals a cyclic oscillation with a period of about 14.84 yr and an amplitude of 0.0019 days,which can be explained by the light-travel time effect(LTTE) due to the presence of a third body with a minimum mass of0.06M_⊙.For V0853 Aur,it is discovered that the O-C diagram of the system also shows a cyclic oscillation with a period of 9.64 yr and an amplitude of 0.03365 *** cyclic oscillation of V0853 Aur can be attributed to the LTTE by means of a third body with a mass no less than 3.77M_⊙.The third body may play an important role in the formation and evolution of these systems.

关键词： stars:activity (stars:)binaries(including multiple):close (stars:)binaries:eclipsing (stars:)brown dwarfs stars:evolution stars:formation

Higher-order properties and extensions for indirect MRAC and APPC of linear systems

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Science China(Information Sciences) 2024年第4期67卷 218-238页

作者： Yanjun zhang Zhipeng zhang Jian SUN Lei WANG Kangkang zhang National Key Lab of Autonomous Intelligent Unmanned Systems Beijing Institute of Technology Beijing Institute of Technology Chongqing Innovation Center College of Control Science and Engineering Zhejiang University Department of Electrical and Electronic Engineering Imperial College London KIOS Research and Innovation Center of Excellence University of Cyprus

Recently, a reference derived some new higher-order output tracking properties for direct model reference adaptive control(MRAC) of linear time-invariant(LTI) systems: limt→∞ e~((i))(t) = 0, i = 1,..., n~*-1, where n~* and e~((i))(t) denote the relative degree of the system and the i-th derivative of the output tracking error, respectively. However, a naturally arising question involves whether indirect adaptive control(including indirect MRAC and indirect adaptive pole placement control) of LTI systems still has higher-order tracking properties. Such properties have not been reported in the literature. Therefore, this paper provides an affirmative answer to this question. Such higher-order tracking properties are new discoveries since they hold without any additional design conditions and, in particular, without the persistent excitation condition. Given the higher-order properties, a new adaptive control system is developed with stronger tracking features.(1) It can track a reference signal with any order derivatives being unknown.(2) It has higher-order exponential or practical output tracking properties.(3) Finally, it is different from the usual MRAC system, whose reference signal’s derivatives up to the n~* order are assumed to be known. Finally, two simulation examples are provided to verify the theoretical results obtained in this paper.

关键词： higher-order tracking indirect adaptive control model reference adaptive control adaptive pole placement control

Shells in the cabinet:four new species of Tellinidae(Mollusca:Bivalvia:Tellinoidea)identified from existing South China Sea collections

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Journal of Oceanology and Limnology 2024年第2期42卷 627-639页

作者： Yuyan zhang Junlong zhang School of Life Sciences Qingdao Agricultural UniversityQingdao 266109China Laboratory of Marine Organism Taxonomy and Phylogeny Qingdao Key Laboratory of Marine Biodiversity and ConservationInstitute of OceanologyChinese Academy of SciencesQingdao 266071China Marine Biological Museum Chinese Academy of SciencesQingdao 266071China University of Chinese Academy of Sciences Beijing 100049China

Four species new to science were identified in the Tellinidae museum collections in the Marine Biological Museum of Chinese Academy of *** triquetra ***.,collected in 1981,has not previously been described or *** differs from other Pinguitellina species by its trigonal shape,rose-colored valve interior,and deep and wide pallial sinus,which is confluent with the pallial *** protuberangla *** a broad and deep dorsal corner,short and straight posterodorsal margin,comparatively large adductor scars,depressed and fragile shells,and deep socket at the anterior edge of the right *** minuta *** previously misidentified as Arcopella casta in *** is a new species based on its unique characteristics,which include small,fragile,inflated,translucent,and triangularly ovate-shaped shells with acuminated and convex *** the first species described in China within the genus Abranda Iredale,1924,Abranda xui *** internal ligaments and thin,fragile,and translucent elliptical shells with fine radials on the *** this study,we reorganized the species currently contained in the two genera Pinguitellina and Abranda and created keys to the known *** believe that numerous collected bivalve specimens have been overlooked in the South China Sea,and to date,mollusk has not been adequately ***,further exploration and analysis are required to understand species diversity in this area.

关键词： Abranda morphology Pinguitellina species diversity taxonomy Tellinidae