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On thermodynamical evolution of Kerr black holes in active galactic nuclei

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Chinese Science Bulletin 1998年第2期43卷 104-107页

作者： yongjian zhang Yaoquan Chu Univ Sci & Technol China Ctr Astrophys Hefei 230026 Peoples R China

The effect of Blandford_Znajek process on the thermodynamical evolution of Kerr black holes in active galactic nuclei is discussed. It is demonstrated that a black hole does not evolve into an extreme Kerr state provi... 详细信息

关键词： black hole thermodynamical evolution Blandford_Znajek effect.

Unequal error protection scheme for layered sources transmission over MIMO systems using spatial diversity and multiplexing technology

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The Journal of China Universities of Posts and Telecommunications 2015年第3期22卷 56-63页

作者： zhang yongjian zhang Kexin Kang Yanmei Yang Dacheng School of Telecommunication Engineering Beijing University of Posts and Telecommunications University of International Relations Academic office Beijing University of Posts and Telecommunications

This paper proposes a hybrid scheme of the Alamouti coding and vertical bell labs layered space-time （V-BLAST） with the zero-forcing （ZF） receiver, which can achieve the unequal error protection （UEP） transmission in terms of the differences of importance in the layered sources. We analyze the tradeoff between spatial diversity and multiplexing in a mathematical manner, and prove the monotonic behavior of the crosspoint. Based on this scheme, we adopt V-BLAST to provide high data rates for the enhancement layer （EL） bitstreams, and adopt Alamouti coding to guarantee high reliability for the base layer （BL） bitstreams. Meanwhile, to improve the transmission reliability for the layered sources under the multiple-input multiple-output （MIMO） system with the limited-bandwidth and the total limited power, and to raise the frequency bandwidth efficiency, we take the power allocation considered in this proposed scheme. The simulation results show that the hybrid scheme has the average 1.9 dB and 1.3 dB gain in video peak signal-to-noise ratio （PSNR）, compared with the pure spatial diversity and pure spatial multiplexing scheme, respectively.

关键词： unequal error protection spatial diversity and multiplexing outage probability multiple-input multiple-output (MIMO) powerallocation

Omnidirectional Antenna Diversity System for High-Speed Onboard Communication

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Engineering 2022年第4期8卷 72-79页

作者： yongjian zhang Yue Li Weiquan zhang Zhijun zhang Zhenghe Feng Department of Electronic Engineering Tsinghua UniversityBeijing 100084China Beijing National Research Center for Information Science and Technology Tsinghua UniversityBeijing 100084China

In this article,an omnidirectional dual-polarized antenna with synergetic electromagnetic and aerodynamic properties is propounded for high-speed diversity *** propounded antenna comprises a probe-fed cavity for horizontally polarized radiation and a microstrip-fed slot for vertical ***-layer metasurfaces are properly designed as artificial magnetic conductor boundaries with direct metal-mountable onboard installation and compact *** attached wedge-shaped block is utilized for windage reduction in *** propounded antenna is fabricated for design verification,and the experimental results agree well with the simulated *** vertical polarization,the operating bandwidth is in the range of 2.37–2.55 GHz,and the realized gain variation in the azimuthal radiation pattern is 3.67 decibels(dB).While an impedance bandwidth in the range of 2.45–2.47 GHz and a gain variation of 3.71 dB are also achieved for horizontal polarization.A port isolation more than 33 dB is obtained in a compact volume of 0.247λ_(0)×0.345λ_(0)×0.074λ_(0),whereλ_(0)represents the wavelength in vacuum at the center frequency,wherein the wedge-shaped block is *** propounded diversity antenna has electromagnetic and aerodynamic merits,and exhibits an excellent potential for high-speed onboard communication.

关键词： Antenna diversity system Aerodynamics Electromagnetics Omnidirectional radiation High-speed onboard communication

Wideband Microstrip Antenna in Small Volume Without Using Fundamental Mode

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Electromagnetic Science 2023年第2期1卷 71-76页

作者： yongjian zhang Yue Li Department of Electronic Engineering Tsinghua UniversityBeijing 100084China Beijing National Research Center for Information Science and Technology Tsinghua UniversityBeijing 10084China

Microstrip antennas are of significant interest and extensively utilized in communication systems because of their unique low ***,the general difficulty in microstrip antenna design lies in its wideband electromagnetic radiation within a low-profile *** enhance the bandwidth,superposing the fundamental mode and other high-order modes is the most common method,but this occupies a larger footprint than regular narrow-band ***,as a counterintuitive way to broaden the bandwidth,a wideband miniaturized microstrip antenna is proposed by using two high-order *** avoidance of the fundamental mode allows for footprint miniaturization without decreasing the bandwidth,providing a different but feasible design strategy for wideband microstrip *** with other microstrip antennas at the same profile,the proposed antenna achieves wider bandwidth and a smaller *** experimental result shows a bandwidth of 4.81–6.01 GHz is achieved with a volume of 0.47×0.47×0.043 λ_(0)^(3),whereλ0 represents the in-vacuum wavelength at the center ***,the proposed design provides an effective solution to the intrinsic contradiction between wideband electromagnetic radiation and compact antenna dimensions,not only in a low profile but in a small footprint,contributing to the fundamental development of microstrip antennas.

关键词： Microstrip antennas Wideband antennas High-order modes Low profile Small footprint.

Pattern transition and sluggish cracking of colloidal droplet deposition with polymer additives

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Science China(Physics,Mechanics & Astronomy) 2013年第9期56卷 1712-1718页

作者： zhang yongjian LIU ZhengTang ZANG DuYang QIAN YiMeng LIN KeJun State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical University Key Laboratory of Space Applied Physics and Chemistry(Ministry of Education) School of ScienceNorthwestern Polytechnical University

Drying of colloidal droplets often develops versatile *** study the drying deposition of both colloidal droplets containing silica nanoparticles and the silica colloidal droplets with polyethylene oxide(PEO) *** focus on the effect of polymer additives on the deposition formation and the cracking dynamics by using in-situ microscope *** PEO additives,a transition from ring-like deposition to uniform deposition is observed,and the cracking dynamics is greatly *** PEO additives enhance the adsorption of particles at the air-water interface,thus forming the network structure at the interface which blocks the outward capillary *** contributes to the uniform ***,the multi-distribution of the aggregates size enhances the non-homogeneity of the drying film and consequently results in multi-nucleation of *** reduces the stress accumulation that drives the crack propagation and may be responsible for the sluggish cracking dynamics.

关键词： sessile droplet drying crack pattern coffee effect

Reinforcement size effect on thermal conductivity in Cu-B/diamond composite

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Journal of Materials Science & Technology 2021年第32期91卷 1-4页

作者： yongjian zhang Guangzhu Bai Xiaoyan Liu Jingjie Dai Xitao Wang Hailong zhang State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China School of Mechanical and Electronic Engineering Qingdao Binhai UniversityQingdao 266555China XI'AN Rare Metal Materials Institute Co.Ltd Xi'an 710016China Shandong Provincial Key Laboratory for High Strength Lightweight Metallic Materials Advanced Materials InstituteQilu University of Technology(Shandong Academy of Sciences)Jinan 250014China Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China

With the miniaturization and integration of microelectronic components,power density of electronic devices such as integrated circuits,light emitting diodes(LEDs),and semiconductor lasers increases dramatically[1].Traditional thermal management materials are difficult to maintain the safety and reliability of the highpower devices.

关键词： thermal conductivity effect

Effect of Cooling Rate and Vanadium Content on the Microstructure and Hardness of Medium Carbon Forging Steel

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Journal of Materials Science & Technology 2016年第6期32卷 545-551页

作者： Weijun Hui yongjian zhang Chengwei Shao Silian Chen Xiaoli Zhao Han Dong School of Mechanical.Electronic and Control Engineering.Beijing Jiaotong University Beijing 100044.China Center Iron and Steel Research Institute Beijing 100081China

This paper reports the effect of cooling rate on the microstructure and hardness of a kind of medium carbon steel microalloyed with two levels of V content （0.15% and 0.28%） after hot deformation by using single compression tests on a Gleeble-3800 thermal simulator. The results show that cooling rate has a significant effect on the microstructure and hardness of the tested steels. Both the fraction of pearlite and hardness increase with increasing cooling rate, whereas a further increase of the cooling rate above a critical value promotes the formation of acicular ferrite （AF）, and thus leads to a decrease of hardness mainly owing to the decrease of pearlite fraction and replacing it by AF and the less effective precipita- tion strengthening. Increasing V content results in a significant increase of hardness, and this tendency enhances with increasing cooling rate until the formation of AF. Furthermore, increasing V content also significantly enhances the formation of AF structure at a lower cooling rate. The results also suggest that by controlling microstructure, especially the precipitation of fine V（C,N） particles through adjusting post- forging cooling, the strengthening and gradient function in one hot-forging part could be obtained.

关键词： Cooling rate Microalloyed steel Vanadium Microstructure Hardness Acicular ferrite

The Ultrafast and Accurate Mapping Algorithm FANSe3:Mapping a Human Whole-Genome Sequencing Dataset Within 30 Minutes

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Phenomics 2021年第1期1卷 22-30页

作者： Gong zhang yongjian zhang Jingjie Jin MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes Institute of Life and Health EngineeringCollege of Life Science and TechnologyJinan UniversityGuangzhou 510632China Chi-Biotech Co.Ltd. Shenzhen 518000China

Aligning billions of reads generated by the next-generation sequencing(NGS)to reference sequences,termed“mapping”,is the time-consuming and computationally-intensive process in most NGS applications.A Fast,accurate and robust mapping algorithm is highly ***,we developed the FANSe3 mapping algorithm,which can map a 30×human wholegenome sequencing(WGS)dataset within 30 min,a 50×human whole exome sequencing(WES)dataset within 30 s,and a typical mRNA-seq dataset within seconds in a single-server node without the need for any hardware acceleration *** its predecessor FANSe2,the error rate of FANSe3 can be kept as low as 10-9 in most cases,this is more robust than the Burrows-Wheeler transform-based *** allowance hardly affected the identification of a driver somatic mutation in clinically relevant WGS data and provided robust gene expression profiles regardless of the parameter settings and sequencer *** novel algorithm,designed for high-performance cloud-computing after infrastructures,will break the bottleneck of speed and accuracy in NGS data analysis and promote NGS applications in various *** FANSe3 algorithm can be downloaded from the website:http://***-biote ***/fanse 3/.

关键词： Next-generation sequencing Mapping Speed Robustness

Design spherical particles of potassium peroxymonosulfate compound salt with high stability and good powder properties via an agglomeration-dissolution mechanism

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Particuology 2023年第9期80卷 157-169页

作者： Shanshan Feng Changyou Yu Shilin Guo Jinbo Ouyang Fei Yin Xiaodong zhang yongjian zhang Mingyang Chen Dandan Han Junbo Gong Jingkang Wang State Key Laboratory of Chemical Engineering School of Chemical Engineering and TechnologyTianjin UniversityTianjin300072China Haihe Laboratory of Sustainable Chemical Transformations Tianjin300192China Institute of Shaoxing Tianjin UniversityZhejiang312300China School of Chemistry Biology and Materials ScienceEast China University of TechnologyNanchang330013China Zhejiang Jinke Daily Chemical Materials Co. Ltd.Zhejiang312300China

With the outbreak of COVID-19,disinfection protection has become a necessary measure to prevent *** a new type of disinfectant,potassium peroxymonosulfate compound salt(PMS)has the advantages of good bactericidal effect,non-toxicity,high safety and ***,the current PMS products with irregular particle shapes lead to poor flowability,high hygroscopicity,poor stability of reactive oxygen species(ROS)and serious caking *** this work,an agglomeration-dissolution mechanism was designed to prepare spherical PMS particles with large size(>300μm)and high sphericity(up to 90%),effectively addressing the above ***(dissolution and abrasion)is the key to improving sphericity,which is mainly controlled by the design of the heating mode,residence time and stirring *** with the irregular PMS particles,the large spherical particles present better flowability(angle of repose decreased by 35.80%,Carr's index decreased by 64.29%,Hausner's ratio decreased by 19.14%),lower hygroscopicity(decreased by 38.0%),lower caking ratio(decreased by 84.50%),and higher stability(the monthly loss of ROS was reduced by 61.68%).The agglomeration-dissolution mechanism demonstrates the crystallization,agglomeration,dissolution and abrasion process of inorganic salt crystals,providing an opportunity to prepare high-end inorganic crystal materials with high-quality morphologies.

关键词： Potassium peroxymonosulfate compound salt Spherical crystallization Agglomeration Dissolution Disinfection protection