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Chinese Physics B 2024年第4期33卷 339-343页

作者：郑煜臻熊康林冯加贵杨辉 School of Nano-Tech and Nano-Bionics University of Science and Technology of ChinaHefei 230026China Suzhou Institute of Nano-Tech and Nano-Bionics Chinese Academy of SciencesSuzhou 215123China

A Josephson traveling wave parametric amplifier(JTWPA),which is a quantum-limited amplifier with high gain and large bandwidth,is the core device of large-scale measurement and control systems for quantum computing.A typical JTWPA consists of thousands of Josephson junctions connected in series to form a transmission line and hundreds of shunt LC resonators periodically loaded along the line for phase matching.Because the variation of these capacitors and inductors can be detrimental to their high-frequency characteristics,the fabrication of a JTWPA typically necessitates precise processing equipment.To guide the fabrication process and further improve the design for manufacturability,it is necessary to understand how each electronic component affects the amplifier.In this paper,we use the harmonic balance method to conduct a comprehensive study on the impact of nonuniformity and fabrication yield of the electronic components on the performance of a JTWPA.The results provide insightful and scientific guidance for device design and fabrication processes.

关键词： Josephson traveling wave parametric amplifier(JTWPA) harmonic balance method yields uniformity

Assessing mixing uniformity in microreactors via in-line spectroscopy

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Chinese Journal of Chemical Engineering 2024年第2期66卷 119-124页

作者： Shusaku Asano Shinji Kudo Taisuke Maki Yosuke Muranaka Kazuhiro Mae Jun-ichiro Hayashi Institute for Materials Chemistry and Engineering Kyushu UniversityKasuga 816-8580Japan Department of Chemical Engineering Graduate School of EngineeringKyoto UniversityJapan

Mixing behavior is critical for enhancing the selectivity of fast chemical reactions in microreactors.A high Reynolds number(Re)improves the mixing rate and selectivity of the reactions,but some exceptions of increasing side product yield with the higher Re have been reported.This study investigated the mixing uniformity in microreactors with in-line UV-vis spectroscopy to clarify the relationship between reaction selectivity and chaotic mixing with the higher Re.A colorization experiment of thymolphthalein in an acidic solution was conducted with an excess acid amount to the base to indicate a non-uniformly mixed region.Non-uniformity significantly increased with Re.At the same time,the degree of mixing,which was measured by a usual decolorization experiment,showed that the mixing rate increased with Re.The in-line analysis of the Villermaux-Dushman reaction during the mixing clarified that side product yield significantly increased with Re at around 300 and then decreased at around 1100.These results suggest the compensation effect between the mixing uniformity and mixing rate on the selectivity of the mixing-sensitive reactions.Faster mixing,characterized by a larger Re,can disturb mixing uniformity and,in some cases,decrease reaction selectivity.

关键词： Microreactor Villermaux-Dushman reaction In-line analysis Mixing Mass transfer uniformity

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Effects of baffle position in serpentine flow channel on the performance of proton exchange membrane fuel cells

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Chinese Journal of Chemical Engineering 2024年第5期69卷 250-262页

作者： Guodong Xia Xiaoya Zhang Dandan Ma MOE Key Laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy ConversionBeijing University of TechnologyBeijing 100124China

This study used a three-dimensional numerical model of a proton exchange membrane fuel cell with five types of channels:a smooth channel(Case 1);eight rectangular baffles were arranged in the upstream(Case 2),midstream(Case 3),downstream(Case 4),and the entire cathode flow channel(Case 5)to study the effects of baffle position on mass transport,power density,net power,etc.Moreover,the effects of back pressure and humidity on the voltage were investigated.Results showed that compared to smooth channels,the oxygen and water transport facilitation at the diffusion layer-channel interface were added 11.53%-20.60%and 7.81%-9.80%at 1.68 A·cm^(-2)by adding baffles.The closer the baffles were to upstream,the higher the total oxygen flux,but the lower the flux uniformity the worse the water removal.The oxygen flux of upstream baffles was 8.14%higher than that of downstream baffles,but oxygen flux uniformity decreased by 18.96%at 1.68 A·cm^(-2).The order of water removal and voltage improvement was Case 4>Case 5>Case 3>Case 2>Case *** power of Case 4 was 9.87%higher than that of the smooth channel.To the Case 4,when the cell worked under low back pressure or high humidity,the voltage increments were higher.The potential increment for the back pressure of 0 atm was 0.9%higher than that of 2 atm(1 atm=101.325 kPa).The potential increment for the humidity of 100%was 7.89%higher than that of 50%.

关键词： Proton exchange membrane fuel cell Baffle position Mass transfer Net power uniformity Voltage increment

What makes for uniformity for non-contrastive self-supervised learning?

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Science China(Technological Sciences) 2022年第10期65卷 2399-2408页

作者： WANG YinQuan ZHANG XiaoPeng TIAN Qi Lü JinHu Key Laboratory of Systems and Control Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100049China Huawei Inc. Shenzhen 518128China School of Automation Science and Electrical Engineering State Key Laboratory of Software Development EnvironmentBeihang UniversityBeijing 100191China

Recent advances in self-supervised learning(SSL) have made remarkable progress, especially for contrastive methods that target pulling two augmented views of one image together and pushing the views of all other images away. In this setting, negative pairs play a key role in avoiding collapsed representation. Recent studies, such as those on bootstrap your own latent(BYOL)and SimSiam, have surprisingly achieved a comparable performance even without contrasting negative samples. However, a basic theoretical issue for SSL arises: how can different SSL methods avoid collapsed representation, and is there a common design principle? In this study, we look deep into current non-contrastive SSL methods and analyze the key factors that avoid collapses.To achieve this goal, we present a new indicator of uniformity metric and study the local dynamics of the indicator to diagnose collapses in different scenarios. Moreover, we present some principles for choosing a good predictor, such that we can explicitly control the optimization process. Our theoretical analysis result is validated on some widely used benchmarks spanning differentscale datasets. We also compare recent SSL methods and analyze their commonalities in avoiding collapses and some ideas for future algorithm designs.

关键词： contrastive learning self-supervised learning representation uniformity dynamics

uniformity of TiN Films Fabricated by Hollow Cathode Discharge

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Plasma Science and Technology 2010年第2期12卷 212-217页

作者：姜海富巩春志田修波杨士勤 R.K.Y.FU P.K.CHU State Key Lab.of Advanced Welding Production & Technology School of Material Science and Engineering Harbin Institute of Technology Department of Physics and Materials Science City University of Hong Kong

Titanium nitride （TIN） films were deposited on AISI 304 stainless steel substrates using hollow cathode plasma physical vapor deposition （HC-PVD）. Titanium was introduced by eroding the Ti cathode nozzle and TiN was formed in the presence of a nitrogen plasma excited by radio frequency （RF）. The substrate bias voltage was varied from 0 to -300 V and the uniformity in film thickness, surface roughness, crystal size, microhardness and wear resistance for the film with a diameter of 20 mm was evaluated. Although the central zone of the plasma had the highest ion density, the film thickness did not vary appreciably across the sample. The results from atomic force microscopy （AFM） revealed a low surface roughness dominated by an island-like morphology with a similar crystal size on the entire surface. Higher microhardness was measured at the central zone of the sample. The sample treated at -200 V had excellent tribological properties and uniformity.

关键词： hollow cathode TiN film uniformity

Cold compression deformation method for reducing residual stress and uniformizing micro-property in ferrite steel

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Journal of Iron and Steel Research(International) 2022年第3期29卷 503-511页

作者： Bo Ning Hui-bin Wu Gang Niu Xin-pan Yu Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing100083China Beijing Laboratory of Metallic Materials and Processing for Modern Transportation University of Science and Technology BeijingBeijing100083China

To reduce internal residual stress and homogenize micro-property of hot-rolled ferrite steel,the cold compression deformation method with small reduction rate has been performed in the hot-rolled samples,and X-ray diffraction and nanoindentation test have been used to detect the residual stress and micro-property.The samples with deformation rate of 0-5.59%or annealing at 550℃ are analyzed.The results show that,due to the coupling effect of thermal expansion and cold contraction and the volume expansion of microstructural transformation from austenite to ferrite,compressive residual stress was found inside the hot-rolled samples.With the increase in cold compression deformation,the dislocation density increased and the microhardness increased gradually,and there is no obvious rule for the change of mean nano-hardness in micro-zone for the center of samples.However,the uniformity of nano-hardness in the micro-zone increased first and then decreased,and the value of residual stress has obvious corresponding relationship with the uniformity of micro-zone property.The cold compression deformation with appropriate reduction rate can reduce residual stress and improve nano-hardness uniformity of the hot-rolled samples,but more deformation(such as reduction rateε=5.59%)makes residual stress increase and makes uniformity of nano-hardness deteriorate.

关键词： Ferrite Cold compression deformation Residual stress Nano-hardness uniformity Dislocation density

Reference device for calibration of radon exhalation rate measuring instruments and its performance

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Nuclear Science and Techniques 2023年第8期34卷 131-141页

作者： Wei-Gang Li De-Tao Xiao Zheng-Zhong He Xiang-Yuan Deng Shou-Kang Qiu School of Nuclear Science and Technology Hunan Provincial Key Laboratory of RadonUniversity of South ChinaHengyang 421001China

Environmental radon emanates from the exhalation and release of soil,rocks,and building materials.Environmental radon contamination tracing and radon pollution prevention and control require the measurement of the radon exhalation rate on media surfaces.Reliable measurements of the radon exhalation rate cannot be achieved without regular calibration of the measuring instrument with a high-performance reference device.In this study,a reference device for the calibration of radon exhalation rate measuring instruments was developed using a diffusion solid radon source with a high and stable radon emanation coefficient,an integrated diffusion component composed of a plasterboard and a high-density wooden board,an air pressure balance device,a radon accumulation chamber,and a support structure.The uniformity and stability of the reference device were evaluated using the activated carbon-γspectrum and open-loop method,respectively,to measure the radon exhalation rate.The reference device achieved different radon exhalation rates by using different activities of diffusion solid radon sources.Nineteen measurement points were regularly selected on the radon exhalation surface of the reference device,and the uniformity of the radon exhalation rate exceeded 5%.The short-term stability of the reference device was better than 5%under different environmental conditions and was almost unaffected by the ambient air pressure,environmental temperature,and relative humidity.

关键词： Radon exhalation rate Stability uniformity High-density wooden board Plasterboard

Uniform, fast, and reliable CMOS compatible resistive switching memory

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Journal of Semiconductors 2022年第5期43卷 109-115页

作者： Yunxia Hao Ying Zhang Zuheng Wu Xumeng Zhang Tuo Shi Yongzhou Wang Jiaxue Zhu Rui Wang Yan Wang Qi Liu Key Laboratory of Microelectronic Devices&Integrated Technology Institute of MicroelectronicsChinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100049China School of Integrated Circuits Anhui UniversityHefei 230601China Frontier Institute of Chip and System Fudan UniversityShanghai 200433China

Resistive switching random access memory(RRAM) is considered as one of the potential candidates for next-generation memory. However, obtaining an RRAM device with comprehensively excellent performance, such as high retention and endurance, low variations, as well as CMOS compatibility, etc., is still an open question. In this work, we introduce an insert TaO_(x) layer into HfO_(x)-based RRAM to optimize the device performance. Attributing to robust filament formed in the TaO_(x) layer by a forming operation, the local-field and thermal enhanced effect and interface modulation has been implemented simultaneously. Consequently, the RRAM device features large windows(> 10^(3)), fast switching speed(-10 ns), steady retention(> 72h), high endurance(> 10^(8) cycles), and excellent uniformity of both cycle-to-cycle and device-to-device. These results indicate that inserting the TaO_(x) layer can significantly improve HfO_(x)-based device performance, providing a constructive approach for the practical application of RRAM.

关键词： uniformity resistance switching field enhance layer thermal enhance layer and interface modulation

Optimization of flow uniformity control device for six-stream continuous casting tundish

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Journal of Iron and Steel Research(International) 2020年第9期27卷 1035-1044页

作者： Xin-gang Ai Dong Han Sheng-li Li Hong-bo Zeng Hui-ya Li Key Laboratory of Chemical Metallurgy Engineering Liaoning Province University of Science and Technology LiaoningAnshan 114051LiaoningChina

For a multistream tundish,the uniformity among the streams plays a significant role in the quality of molten steel.How to analyze the uniformity quantitatively and optimize structures of a multistream tundish is an important research content for a multistream tundish.A new approach was proposed to quantify the uniformity among the streams.And a physical study and a numerical study were carried out to optimize the structure of the diversion hole based on the prototype of a six-stream tundish in a steel plant.On the basis of average residence time,the uniformity of each flow was considered fully and then the optimal structure of the diversion hole was obtained by means of the comprehensive analysis of temperature field and velocity field.The results show that the optimum structural parameters adopted for diversion holes are height of 20 mm,angle of 15°and diameter of 80 mm.

关键词： Multistream tundish uniformity Diversion hole Physical simulation Numerical simulation

Experimental and numerical investigation on the uniformity of nanosecond pulsed dielectric barrier discharge influenced by pulse parameters

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Plasma Science and Technology 2023年第11期25卷 31-41页

作者：张东璇余俊贤李梦遥潘杰刘峰方志 College of Electrical Engineering and Control Science Nanjing Tech UniversityNanjing 211816People’s Republic of China School of Electric Power South China University of TechnologyGuangzhou 510641People’s Republic of China School of Physics and Electronics Shandong Normal UniversityJinan 250014People’s Republic of China

Nanosecond(ns)pulsed dielectric barrier discharge(DBD)is considered as a promising method to produce controllable large-volume and high activity low-temperature plasma at atmospheric pressure,which makes it suitable for wide applications.In this work,the ns pulse power supply is used to excite Ar DBD and the influences of the pulse parameters(voltage amplitude,pulse width,pulse rise and fall times)on the DBD uniformity are investigated.The gas gap voltage(Ug)and conduct current(Ig)are separated from the measured voltage and current waveforms to analyze the influence of electrical parameters.The spectral line intensity ratio of two Ar excited species is used as an indicator of the electron temperature(Te).The time resolved discharge processes are recorded by an intensified charge-coupled device camera and a one-dimensional fluid model is employed to simulate the spatial and temporal distributions of electrons,ions,metastable argon atoms and Te.Combining the experimental and numerical results,the mechanism of the pulse parameters influencing on the discharge uniformity is discussed.It is shown that the space electric field intensity and the space particles'densities are mainly responsible for the variation of discharge uniformity.With the increase of voltage and pulse width,the electric field intensity and the density of space particles increased,which results in the discharge mode transition from non-uniform to uniform,and then non-uniform.Furthermore,the extension of pulse rise and fall times leads to the discharge transition from uniform to nonuniform.The results are helpful to reveal the mechanism of ns pulsed DBD mode transition and to realize controllable and uniform plasma sources at atmospheric pressure.

关键词： nanosecond pulse dielectric barrier discharge electrical characteristics active particle uniformity