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Optimization of flow control devices in a tenstrand billet caster tundish

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China Foundry 2016年第6期13卷 414-421页

作者： shu-guo zheng Miao-yong Zhu School of Metallurgy Northeastern University

The physical model of a ten-strand billet caster tundish was established to study the effects of various flow control devices on the melt flow. Before and after the optimization of the melt flow, the inclusion removal in the tundish was evaluated by plant trials. The physical modeling results show that when combined with a baffle, the turbulence inhibitor, instead of the impact pad, can significantly improve the melt flow. A turbulence inhibitor with a longer length of inner cavity and without an extending lip at the top of the sidewall seems to be efficient in the improvement of the melt flow. Various types and designs of baffles all influence the flow characteristics significantly. The "V" type baffles are better than the straight baffles for flow control. The "V" type baffle with four inclined holes at the sidewall away from the stopper rods is better in melt flow control than the one with one inclined hole at each sidewall. The combination of a well-designed turbulence inhibitor and an appropriate baffle shows high efficiency on improving the melt flow and an optimal proposal was presented. Plant trials indicate that, compared with the original tundish configuration in prototype, the inclusions reduce by 42% and the inclusion distribution of individual strands is more similar with the optimal one. The optimal tundish configuration effectively improves the melt flow in the ten-strand billet caster tundish.

关键词： billet continuous casting ten-strand caster tundish flow control device physical modeling plant trials

Flow Characteristics and Inclusion Removal in a Ten-strand Continuous Casting Tundish:Physical Modelling and Industrial Trials

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Journal of Iron and Steel Research(International) 2016年第2期23卷 92-97页

作者： shu-guo zheng Miao-yong ZHU Ye-lian ZHOU Wang SU School of Metallurgy Northeastern University

The flow characteristics and inclusion removal in a ten-strand continuous casting tundish were investigated with physical modelling and industrial trials. The results show that, among the strands, the strand with the mini mum dimensionless time of the first appearance of tracer at the tundish exit appears to be the worst one for inclusion removal, while the strand with the maximum dimensionless mean residence time shows the best inclusion removal efficiency. The inclusion number decreases with increasing inclusion size for all strands. The inclusion number distri bution among strands is the same for all inclusion sizes and the descending order of inclusion number is basically con sistent with the ascending order of dimensionless mean residence time among individual strands. However, when the strand with the minimum dimensionless time of the first appearance of tracer at the tundish exit is not the same one with the minimum dimensionless mean residence time, the former seems to be inferior to the latter for inclusion re moval.

关键词： multistrand continuous casting tundish flow characteristics inclusion removal physical modelling in-dustrial trial

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高原城市拉萨典型VOCs排放源成分谱特征

环境科学 2024年第4期45卷 2011-2018页

作者：郭淑政叶春翔林伟立陈熠曾立民尹晴晴刘雪莉民族地区生态环境国家民委重点实验室(中央民族大学) 北京100081 北京大学环境科学与工程学院北京100871

高海拔地区低的气压和含氧量会影响燃烧和溶剂挥发过程,进而影响挥发性有机物(VOCs)的排放特征.然而,人们对海拔3 000 m以上的燃烧源或挥发源的VOCs排放特征的认识有限.拉萨市正在经历快速的经济发展和城市化进程,VOCs排放源日趋复杂.... 详细信息

高海拔地区低的气压和含氧量会影响燃烧和溶剂挥发过程,进而影响挥发性有机物(VOCs)的排放特征.然而,人们对海拔3 000 m以上的燃烧源或挥发源的VOCs排放特征的认识有限.拉萨市正在经历快速的经济发展和城市化进程,VOCs排放源日趋复杂.采集拉萨市机动车尾气、汽油挥发、柴油挥发、液化石油气和燃香等排放源VOCs样品进行分析,研究成分谱特征,并与平原地区的相比较.发现液化石油气VOCs排放谱以丙烷和丁烷为主,与平原地区的一致;汽油挥发中1,2,4-三甲苯占比最高,而汽油车尾气中异戊烷、正丁烷和丙烷占比高,1,2,4-三甲苯占比较低,这不同于平原地区的结果;柴油挥发比汽油及汽油车排放具有更高占比的C7以上高碳化合物;柴油车排放中含氧挥发性有机物(OVOC)占比最高,而平原地区则是丙烯和C7以上烷烃占比高;燃香排放中OVOC占比最高,特征示踪物是乙腈,且有不容忽视的异戊二烯排放.从甲苯与苯的比值上看,汽油车及柴油车排放与平原地区的结果基本一致,但两地区柴油挥发和燃香排放则不同.从苯、甲苯和乙苯比例三元图上看,柴油挥发落在工业及溶剂排放区内,有别于平原地区的结果 .与其它城市一样,烯烃和芳香烃化合物也是高原城市中具有高反应活性VOCs组分,二者分别对臭氧和二次有机气溶胶的生成有重要的贡献.初步研究结果表明,高原城市地区不同VOCs源的组分特征与平原地区有所差异,需要进一步深入研究,以应对潜在的环境和健康风险.

关键词：挥发性有机物(VOCs) 源谱成分谱排放特征羟基消耗速率(L_(·OH)) 臭氧生成潜势(OFP)

Physical modeling of gas-liquid interfacial fluctuation in a thick slab continuous casting mold with argon blowing

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International Journal of Minerals,Metallurgy and Materials 2010年第6期17卷 704-708页

作者： shu-guo zheng Miao-yong Zhu School of Materials and Metallurgy Northeastern University Shenyang 110004 China

Combining with the physical model of level fluctuation in a thick slab continuous casting mold with the cross-section of 1500 mm×280 mm and argon blowing, the rationalities of estimating the level fluctuation by three traditional quantitative approaches were discussed, and the effects of gas flowrate, casting speed, and the immersion depth of submerged entry nozzle （SEN） on the level fluctuation were also investigated. As a result, it seems that three traditional quantitative approaches are not very suitable for estimating the level fluctuation in a mold with argon blowing, so a new approach for estimating level fluctuation in the mold with argon blowing was presented. The experimental results show that the level fluctuation is mainly in the region around the nozzle wall. When the casting speeds are larger than a certain value, there is the escape of large bubbles near the nozzle wall, which causes an obvious increase of level fluctuation. Furthermore, optimal process parameters, viz., the gas flowrate of 6 NL/min, the casting speed of 1.1 m/min, and the immersion depth of 170 mm, are presented to restrain the level fluctuation by a physical model.

关键词： slabs continuous casting molds level fluctuation modelling

Emergent symmetry in quantum phase transition:From deconfined quantum critical point to gapless quantum spin liquid

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Science Bulletin 2024年第2期69卷 190-196页

作者： Wen-Yuan Liu Shou-shu Gong Wei-Qiang Chen zheng-Cheng Gu Department of Physics The Chinese University of Hong KongHong KongChina Division of Chemistry and Chemical Engineering California Institute of TechnologyPasadena CA 91125USA School of Physical Sciences Great Bay UniversityDongguan 523000China Great Bay Institute for Advanced Study Dongguan 523000China Department of Physics and Shenzhen Institute for Quantum Science and Engineering Southern University of Science and TechnologyShenzhen 518055China Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices Southern University of Science and TechnologyShenzhen 518055China

The emergence of exotic quantum phenomena in frustrated magnets is rapidly driving the development of quantum many-body physics,raising fundamental questions on the nature of quantum phase transitions.Here we unveil the behaviour of emergent symmetry involving two extraordinarily representative phenomena,i.e.,the deconfined quantum critical point(DQCP)and the quantum spin liquid(QSL)state.Via large-scale tensor network simulations,we study a spatially anisotropic spin-1/2 square-lattice frustrated antiferromagnetic(AFM)model,namely the J1x-J1y-J2 model,which contains anisotropic nearestneighbor couplings J1x,J1y and the next nearest neighbor coupling J2.For small J1y/J1x,by tuning J2,a direct continuous transition between the AFM and valence bond solid phase is observed.With growing J1y/J1x,a gapless QSL phase gradually emerges between the AFM and VBS phases.We observe an emergent O(4)symmetry along the AFM–VBS transition line,which is consistent with the prediction of DQCP theory.Most surprisingly,we find that such an emergent O(4)symmetry holds for the whole QSL–VBS transition line as well.These findings reveal the intrinsic relationship between the QSL and DQCP from categorical symmetry point of view,and strongly constrain the quantum field theory description of the QSL phase.The phase diagram and critical exponents presented in this paper are of direct relevance to future experiments on frustrated magnets and cold atom systems.

关键词： Tensor network Quantum phase transition Emergent symmetry Quantum spin liquid Deconfined quantum critical point Anisotropic

Mechanism Design for Ancillary Service Market Considering Social Welfare and Fairness

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CSEE Journal of Power and Energy Systems 2024年第3期10卷 1000-1010页

作者： Zhi Wu Yuanxi Wu Wei Gu zheng Xu shu zheng Jingtao Zhao School of Electrical Engineering Southeast UniversityNanjing 210096China NARI Technology Co. Ltd.Nanjing 211106China IEEE CSEE

Increasing penetration of distributed energy resources in the distribution network(DN)is threatening safe operation of the DN,which necessitates setup of the ancillary service market in the DN.In the ancillary service market,distribution system operator(DSO)is responsible for safety of the DN by procuring available capacities of aggregators.Unlike existing studies,this paper proposes a novel market mechanism composed of two parts:choice rule and payment rule.The proposed choice rule simultaneously considers social welfare and fairness,encouraging risk-averse aggregators to participate in the ancillary service market.It is then formulated as a linear programming problem,and a distributed solution using the multi-cut Benders decomposition is presented.Moreover,successful implementation of the choice rule depends on each aggregator’s truthful adoption of private parameters.Therefore,a payment rule is also designed,which is proved to possess two properties:incentive compatibility and individual rationality.Simulation results demonstrate effectiveness of the proposed choice rule on improving fairness and verify properties of the payment rule.

关键词： Aggregator ancillary service market distributed mechanism fairness mechanism design

Fluorogenic sensing of amorphous aggregates,amyloid fibers,and chaperone activity via a near-infrared aggregation-induced emission-active probe

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Aggregate

Aggregate 2024年第1期5卷 309-320页

作者： Wei He Yuanyuan Yang Yuhui Qian Zhuoyi Chen Yongxin zheng Wenping Zhao Chenxu Yan Zhiqian guo shu Quan State Key Laboratory of Bioreactor Engineering Shanghai Collaborative Innovation Center for Biomanufacturing(SCICB)East China University of Science and TechnologyShanghaiChina Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular Engineering Shanghai Key Laboratory of Functional Materials ChemistryFrontiers Science Center for Materiobiology and Dynamic ChemistryInstitute of Fine ChemicalsSchool of Chemistry and Molecular EngineeringEast China University of Science and TechnologyShanghaiChina Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism East China University of Science and TechnologyShanghaiChina

The presence of protein aggregates in numerous human diseases underscores the significance of detecting these aggregates to comprehend disease mechanisms and develop novel therapeutic approaches for combating these disorders.Despite the development of various biosensors and fluorescent probes that selectively target amyloid fibers or amorphous aggregates,there is still a lack of tools capable of simultaneously detecting both types of aggregates.Herein,we demonstrate the quantitative discernment of amorphous aggregates by QM-FN-SO3,an aggregationinduced emission(AIE)probe initially designed for detecting amyloid fibers.This probe easily penetrates the membranes of the widely-used prokaryotic model organism Escherichia coli,enabling the visualization of both amorphous aggregates and amyloid fibers through near-infrared fluorescence.Notably,the probe exhibits sensitivity in distinguishing the varying aggregation propensities of proteins,regardless of whether they form amorphous aggregates or amyloid fibers in vivo.These properties contribute to the successful application of the QM-FN-SO3 probe in the subsequent investigation of the antiaggregation activities of two outer membrane protein(OMP)chaperones,both in vitro and in their physiological environment.Overall,our work introduces a near-infrared fluorescent chemical probe that can quantitatively detect amyloid fibers and amorphous aggregates with high sensitivity in vitro and in vivo.Furthermore,it demonstrates the applicability of the probe in chaperone biology and its potential as a high-throughput screening tool for protein aggregation inhibitors and folding factors.

关键词： aggregation-induced emission fluorescence molecular chaperone protein aggregation

Differentially private SGD with random features

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Applied Mathematics(A Journal of Chinese Universities) 2024年第1期39卷 1-23页

作者： WANG Yi-guang guo zheng-chu Polytechnic Institute of Zhejiang University Zhejiang UniversityHangzhou 310015China School of Mathematical Sciences Zhejiang UniversityHangzhou 310058China

In the realm of large-scale machine learning,it is crucial to explore methods for reducing computational complexity and memory demands while maintaining generalization performance.Additionally,since the collected data may contain some sensitive information,it is also of great significance to study privacy-preserving machine learning algorithms.This paper focuses on the performance of the differentially private stochastic gradient descent(SGD)algorithm based on random features.To begin,the algorithm maps the original data into a lowdimensional space,thereby avoiding the traditional kernel method for large-scale data storage requirement.Subsequently,the algorithm iteratively optimizes parameters using the stochastic gradient descent approach.Lastly,the output perturbation mechanism is employed to introduce random noise,ensuring algorithmic privacy.We prove that the proposed algorithm satisfies the differential privacy while achieving fast convergence rates under some mild conditions.

关键词： learning theory differential privacy stochastic gradient descent random features reproducing kernel Hilbert spaces

Strong anisotropy of thermal transport in the monolayer of a new puckered phase of PdSe

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Frontiers of physics 2024年第3期19卷 143-151页

作者： zheng shu Huifang Xu Hejin Yan Yongqing Cai Joint Key Laboratory of the Ministry of Education Institute of Applied Physics and Materials EngineeringUniversity of MacaoTaipaMacao 999078China

We examine the electronic and transport properties of a new phase PdSe monolayer with a puckered structure calculated by first-principles and Boltzmann transport equation.The spin−orbit coupling is found to play a negligible effect on the electronic properties of PdSe monolayer.The lattice thermal conductivity of PdSe monolayer exhibits remarkable anisotropic characteristic due to anisotropic phonon group velocity along different directions and its intrinsic structure anisotropy.The compromised electronic mobility despite a relatively low thermal conduction results in a moderate ZT value but significantly anisotropic thermoelectric performance in single-layer PdSe.The present work suggests that the remarkable thermal transport anisotropy of PdSe monolayer can be used for thermal management,and enhance the scope of possibilities for heat flow manipulation in PdSe based devices.The sizeable puckered cages and wiggling lattice implies it an ideal platform for ionic and molecular engineering for thermoelectronic applications.

关键词： 2D materials first-principles calculations phonon