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Journal of Iron and Steel Research International 2024年第3期31卷 767-777页

作者： hong-bin dai jian Miao Jia-xin Lin School of Materials Science and Engineering Harbin University of Science and TechnologyHarbin 150040HeilongjiangChina

The welding arc,as a carrier for the conversion of electrical energy to thermal energy,has a direct impact on the quality of welding by its properties and *** the tungsten inert gas(TIG)welding process under the condition of Ar-He alternating gas supply,the arc is alternately converted between Ar arc and He arc with an alternating gas supply cycle,which has obvious arc change *** FLUENT software was used to numerically simulate the characteristics of the TIG arc under the condition of alternating gas supply,and the arc temperature field,arc pressure,electric potential and current density distribution under the condition of alternating gas supply were *** with the real-time data of arc pressure measured by the water-cooled copper plate with holes,it is proved that the TIG arc has obvious dynamic characteristics under the condition of Ar-He alternating gas *** unique dynamic TIG arc acts on the 5A06 aluminum alloy weld,causing the molten pool to stir,resulting in uniform microstructure and grain refinement at the weld,and thereby improving the mechanical properties of the welded joint.

关键词： Alternating gas supply Grain refinement Numerical simulation Tungsten argon arc morphology Microstructure Mechanical property

Strong evidence for latitudinal diversity gradient in mosses across the world

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Plant Diversity 2024年第4期46卷 537-541页

作者： hong Qian Zun dai jian Wang Research and Collections Center Illinois State Museum1011 East Ash StreetSpringfieldIL 62703USA Bryology Laboratory School of Life SciencesEast China Normal UniversityShanghai 200241China Shanghai Institute of Eco-Chongming(SIEC) 3663 Northern Zhongshan RoadShanghai 200062China

Species richness generally decreases with increasing latitude,a biodiversity gradient that has long been considered as one of the few laws in *** latitudinal diversity gradient has been observed in many major groups of *** plants,the latitudinal diversity gradient has been observed in vascular plants,angiosperms,ferns,and ***,a conspicuous latitudinal diversity gradient in mosses at a global or continental scale has not been observed until ***,we analyze a comprehensive data set including moss species in each band of 20° in latitude *** results show that moss species richness decreases strongly with increasing latitude,regardless of whether the globe is considered as a whole or different longitudinal segments(e.g.,Old World versus New World) are considered *** result holds when variation in area size among latitudinal bands is taken into ***'s correlation coefficient between latitude and species richness is-0.99 for both the Northern and Southern *** bryophytes are an extant lineage of early land plants and because mosses not only include most of extant species of bryophytes but also are important constituents of most terrestrial ecosystems,understanding geographic patterns of mosses is particularly important The finding of our study fills a critical knowledge gap.

关键词： Bryophyte Latitudinal diversity gradient Moss Species density Species diversity

Optically Detected Magnetic Resonance of Diamond Nitrogen-Vacancy Centers under Megabar Pressures

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Chinese Physics Letters 2022年第11期39卷 63-67页

作者： jian-hong dai Yan-Xing Shang Yong-hong Yu Yue Xu Hui Yu Fang hong Xiao-Hui Yu Xin-Yu Pan Gang-Qin Liu Beijing National Research Center for Condensed Matter Physics and Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Songshan Lake Materials Laboratory Dongguan 523808China CAS Center of Excellence in Topological Quantum Computation Beijing 100190China

Megabar pressures are of crucial importance for cutting-edge studies of condensed matter physics and *** the development of diamond anvil cell(DAC),laboratory studies of high pressure have entered the megabar era for ***,it is still challenging to implement in situ magnetic sensing under ultrahigh *** this work,we demonstrate optically detected magnetic resonance and coherent quantum control of diamond nitrogen-vacancy(NV)center,a promising quantum sensor inside the DAC,up to 1.4 *** pressure dependence of optical and spin properties of NV centers in diamond are quantified,and the evolution of an external magnetic field has been successfully tracked at about 80 *** results shed new light on our understanding of diamond NV centers and pave the way for quantum sensing under extreme conditions.

关键词： quantum centers extreme

Interfacial reaction between AZ91D magnesium alloy melt and mild steel under high temperature

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China Foundry 2024年第2期21卷 159-167页

作者： Jia-hong dai jian-yue Zhang Bin jiang Xiang-jun Xu Zhong-tao jiang hong-mei Xie Qing-shan Yang Guo-qing Zhang College of Materials Science and Engineering Yangtze Normal UniversityChongqing 408100China National Engineering Research Center for Magnesium Alloys College of Materials Science and EngineeringChongqing UniversityChongqing 400044China Chongqing Jiulongyuan High-tech Industry Group Co. Ltd.Chongqing 400080China Loncin Industry Co. Ltd.Chongqing 400080China Department of Materials Science and Engineering The Ohio State UniversityColumbusOH 43210USA Chongqing Key Laboratory of Materials Surface&Interface Science Chongqing University of Arts and SciencesChongqing 402160China School of Metallurgy and Material Engineering Chongqing University of Science and TechnologyChongqing 401331China

The metallurgical quality control of magnesium(Mg)and Mg alloys in melting process is required to ensure a satisfied mechanical and corrosion performance,while the typical used steel crucible introduces impurities and interfacial interaction during melting ***,a systematic study about impurities diffusion and interfacial interaction between molten Mg and steel is *** the present study,the interfacial reaction between molten AZ91D Mg alloy and mild steel during melting process was investigated with the melting temperatures of 700℃,750℃ and 800℃.The results show that Al(Fe,Mn)intermetallic layer is the intermetallic primarily formed at the interfaces of AZ91D melt and mild ***,Al_(8)(Mn,Fe)5is indexed between Al(Fe,Mn)and ***_(3)C appears between the mild steel and Al(Fe,Mn)at 700℃ and 750℃,but absent at 800℃ due to the increased solubility of carbon in Mg *** is found that the growth of the intermetallic layer is controlled by diffusion mechanism,and Al and Mn are the dominant diffusing species in the whole interfacial reaction *** measuring the thickness of different layers,the growth constant was *** increases from 1.89(±0.03)×10^(-12)m^(2)·s^(-1)at 700℃ to 3.05(±0.05)×10^(-12)m^(2)·s^(-1)at 750℃,and 5.18(±0.05)×10^(-12)m^(2)·s^(-1)at 800℃.Meanwhile,the content of Fe is linearly increased in AZ91D with the increase of holding time at 700℃ and 750℃,while it shows a significantly increment after holding for 8 h at 800℃,indicating holding temperature is more crucial to determine the Fe content of AZ91D than holding time.

关键词： AZ91D mild steel interface reaction intermetallic growth kinetics

Magnetic Sensing inside a Diamond Anvil Cell via Nitrogen-Vacancy Center Spins

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Chinese Physics Letters 2019年第8期36卷 74-79页

作者： Yan-Xing Shang Fang hong jian-hong dai Hui-Yu Ya-Nan Lu En-Ke Liu Xiao-Hui Yu Gang-Qin Liu Xin-Yu Pan Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190 School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049 Songshan Lake Materials Laboratory Dongguan 523808 CAS Center of Excellence in Topological Quantum Computation Beijing 100190

The diamond anvil cell-based high-pressure technique is a unique tool for creating new states of matter and for understanding the physics underlying some exotic *** situ sensing of spin and charge properties under high pressure is crucially important but remains technically *** the nitrogen-vacancy(NV)center in diamond is a promising quantum sensor under extreme conditions,its spin dynamics and the quantum control of its spin states under high pressure remain *** this study,we demonstrate coherent control,spin relaxation,and spin dephasing measurements for ensemble NV centers up to 32.8 *** this in situ quantum sensor,we investigate the pressure-induced magnetic phase transition of a micron-size permanent magnet Nd2Fe14B sample in a diamond anvil cell,with a spatial resolution of ~2μm,and sensitivity of ~20 μT/Hz1/2. This scheme could be generalized to measure other parameters such as temperature,pressure and their gradients under extreme *** will be beneficial for frontier research of condensed matter physics and geophysics.

关键词： Magnetic Diamond Center

The Rate of Convergence of Augmented Lagrangian Method for Minimax Optimization Problems with Equality Constraints

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Journal of the Operations Research Society of China 2024年第2期12卷 265-297页

作者： Yu-hong dai Li-Wei Zhang LSEC ICMSECAMSSChinese Academy of SciencesBeijing 100190China Institute of Operations Research and Control Theory School of Mathematical SciencesDalian University of TechnologyDalian 116024China

The augmented Lagrangian function and the corresponding augmented Lagrangian method are constructed for solving a class of minimax optimization problems with equality *** prove that,under the linear independence constraint qualification and the second-order sufficiency optimality condition for the lower level problem and the second-order sufficiency optimality condition for the minimax problem,for a given multiplier vectorμ,the rate of convergence of the augmented Lagrangian method is linear with respect to||μu-μ^(*)||and the ratio constant is proportional to 1/c when the ratio|μ-μ^(*)||/c is small enough,where c is the penalty parameter that exceeds a threshold c_(*)>O andμ^(*)is the multiplier corresponding to a local ***,we prove that the sequence of multiplier vectors generated by the augmented Lagrangian method has at least Q-linear convergence if the sequence of penalty parameters(ck)is bounded and the convergence rate is superlinear if(ck)is increasing to ***,we use a direct way to establish the rate of convergence of the augmented Lagrangian method for the minimax problem with a quadratic objective function and linear equality constraints.

关键词： Minimax optimization Augmented Lagrangian method.Rate of convergence Second-order sufficiency optimality

Metagenomics reveals the microbial community and functional metabolism variation in the partial nitritation-anammox process:From collapse to recovery

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Journal of Environmental Sciences 2024年第1期135卷 210-221页

作者： hong Wang Hui Gong Xiaohu dai Min Yang State Key Laboratory of Pollution Control and Resource Reuse College of Environmental Science and EngineeringTongji UniversityShanghai 200092China BIOMATH Department of Data Analysis and Mathematical ModellingGhent UniversityGhent 9000Belgium

Mainstream partial nitritation-anammox(PNA)process easily suffers from performance instability and even reactor collapse in ***,it is of great significance to unveil the characteristic of performance recovery,understand the intrinsic mechanism and then propose operational *** this study,we combined long-term reactor operation,batch tests,and metagenomics to reveal the succession of microbial community and functional metabolism variation from system collapse to *** aeration control(0.10-0.25mg O_(2)/L)was critical for performance *** was also found that Candidatus Brocadia became the dominant flora and its abundance increased from 3.5%to 11.0%.Significant enhancements in carbon metabolism and phospholipid biosynthesis were observed during system recovery,and the genes abundance related to signal transduction was dramatically *** up-regulation of sdh and suc genes showed the processes of succinate dehydrogenation and succinyl-CoA synthesis might stimulate the production of amino acids and the synthesis of proteins,thereby possibly improving the activity and abundance of AnAOB,which was conducive to the performance ***,the increase in abundance of hzs and hdh genes suggested the enhancement of the anammox *** in the abundance of key genes involved in nitrogen metabolism indicated that nitrogen removal pathway was more diverse after system *** achievement of performance recovery was driven by anammox,nitrification and denitrification coupled with dissimilatory nitrate reduction to *** results provide deeper insights into the recovery mechanism of PNA system and also provide a potential regulation strategy for the stable operation of the mainstream PNA process.

关键词： Partial nitritation-anammox Metagenomics Microbial community Functional metabolism Recovery

Cognitive interference decision method for air defense missile fuze based on reinforcement learning

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Defence Technology（防务技术） 2024年第2期32卷 393-404页

作者： Dingkun Huang Xiaopeng Yan jian dai Xinwei Wang Yangtian Liu Science and Technology on Electromechanical Dynamic Control Laboratory School of Mechatronical EngineeringBeijing Institute of TechnologyBeijing 100081China

To solve the problem of the low interference success rate of air defense missile radio fuzes due to the unified interference form of the traditional fuze interference system,an interference decision method based Q-learning algorithm is ***,dividing the distance between the missile and the target into multiple states to increase the quantity of state ***,a multidimensional motion space is utilized,and the search range of which changes with the distance of the projectile,to select parameters and minimize the amount of ineffective interference *** interference effect is determined by detecting whether the fuze signal ***,a weighted reward function is used to determine the reward value based on the range state,output power,and parameter quantity information of the interference *** effectiveness of the proposed method in selecting the range of motion space parameters and designing the discrimination degree of the reward function has been verified through offline experiments involving full-range missile *** optimal interference form for each distance state has been *** with the single-interference decision method,the proposed decision method can effectively improve the success rate of interference.

关键词： Cognitive radio Interference decision Radio fuze Reinforcement learning Interference strategy optimization

Ultralow-phase-noise and broadband frequency-hopping coupled optoelectronic oscillator under quiet point operation

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Photonics Research 2024年第08期12卷 1785-1793页

作者： HUI LIU MINGYANG GUO TIAN ZHANG jian dai KUN XU State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications School of Electronic Engineering Beijing University of Posts and Telecommunications

Advancements in microwave photonics have yielded novel approaches for generating high-purity microwave sources. Among these, optoelectronic oscillators（OEOs） and coupled optoelectronic oscillators（COEOs） have demonstrated the capability to generate frequency-independent microwaves with exceptionally low phase ***, the tunability of the oscillators is rather limited due to the necessity for narrowband electronic bandpass filters, presenting challenges in achieving both wide and rapid tuning capabilities. Here, we present a COEO featuring ultralow phase noise, flexible tuning capability, and high robustness. This is achieved through a quiet point（QP）-operated harmonic mode-locked fiber laser, which effectively mitigates optical amplifier noise and supermode competition, thus significantly diminishing the necessity for ultra-narrow electronic filters. Due to the liberated tuning ability, we present an oscillator that can be tuned from 2 GHz to 18 GHz, with phase noise as low as-140 d Bc/Hz at 10 k Hz under the QP operation. We then illustrate the practical application of the proposed oscillator in generating frequency-hopping signals with consistent spurious modes less than-85 d Bc,absolute phase noise below-135 d Bc/Hz at 10 k Hz, hopping resolution of 1.25 MHz, and fractional frequency stability below 6.1 × 10-12at 1 s averaging time when locked to a reference. The presented COEO structure emerges as a compelling solution for agile and low-noise microwave sources in advanced wireless communication and radar systems.

关键词： Bandpass filters Beam splitters Microwave photonics Mode-locked fiber lasers Optical amplifiers Phase noise

Automatic modulation recognition of radio fuzes using a DR2D-based adaptive denoising method and textural feature extraction

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Defence Technology（防务技术） 2024年第4期34卷 328-338页

作者： Yangtian Liu Xiaopeng Yan Qiang Liu Tai An jian dai Science and Technology on Electromechanical Dynamic Control Laboratory School of Mechatronical EngineeringBeijing Institute of TechnologyBeijing 100081China China Research and Development Academy of Machinery Equipment Beijing 100089China

The identification of intercepted radio fuze modulation types is a prerequisite for decision-making in interference ***,the electromagnetic environment of modern battlefields is complex,and the signal-to-noise ratio(SNR)of such environments is usually low,which makes it difficult to implement accurate recognition of radio *** solve the above problem,a radio fuze automatic modulation recognition(AMR)method for low-SNR environments is ***,an adaptive denoising algorithm based on data rearrangement and the two-dimensional(2D)fast Fourier transform(FFT)(DR2D)is used to reduce the noise of the intercepted radio fuze intermediate frequency(IF)***,the textural features of the denoised IF signal rearranged data matrix are extracted from the statistical indicator vectors of gray-level cooccurrence matrices(GLCMs),and support vector machines(SVMs)are used for *** DR2D-based adaptive denoising algorithm achieves an average correlation coefficient of more than 0.76 for ten fuze types under SNRs of-10 d B and above,which is higher than that of other typical *** trained SVM classification model achieves an average recognition accuracy of more than 96%on seven modulation types and recognition accuracies of more than 94%on each modulation type under SNRs of-12 d B and above,which represents a good AMR performance of radio fuzes under low SNRs.

关键词： Automatic modulation recognition Adaptive denoising Data rearrangement and the 2D FFT(DR2D) Radio fuze