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Variability of the deep South China Sea circulation derived from HYCOM reanalysis data

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Acta Oceanologica Sinica 2022年第7期41卷 54-64页

作者： yaohua zhu Guojiao Cao Yonggang Wang Shujiang Li Tengfei Xu Dingqi Wang Fei Teng Zexun Wei First Institute of Oceanography and Key Laboratory of Marine Science and Numerical ModelingMinistry of Natural ResourcesQingdao266061China Laboratory for Regional Oceanography and Numerical Modeling Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao266237China Shandong Key Laboratory of Marine Science and Numerical Modeling Qingdao266061China Navigation College Jiangsu Maritime InstituteNanjing211100China College of Oceanic and Atmospheric Sciences Ocean University of ChinaQingdao266100China

This study aims to investigate variability of the deep South China Sea(SCS)circulation using the Hybrid Coordinate Ocean Model(HYCOM)global reanalysis product.The results reveal that annual cycle is a dominant component in the deep SCS circulation.Meanwhile,the boundary circulation strength is the weakest in January and peaks between June and September.The eastern and southern boundary currents strengthen/weaken one to three months earlier than that in the western and northern boundaries.Vector Empirical Orthogonal Functions(VEOF)analysis results reveal that semiannual and intraseasonal fluctuations are significant components,of which the spatial patterns are mainly confined in the northern and western boundary areas as well as the southwestern sub-basin.Wavelet analysis results show the strength of significant fluctuation varies year to year.Trend analysis results indicate a decadal weakening in the deep SCS circulation.An anomalous anticyclonic circulation,50–70 km apart from the slope break,tends to weaken the cyclonic boundary circulation in the western and northern boundaries as well as the southwestern sub-basin.This trend is similar to the observed decadal weakening in the North Atlantic deep circulation.Thus,the findings of this study reveal that the variation of the deep SCS circulation has a remarkable response to the climate change.The mechanisms responsible for the variation are worth pursuing if more observations are available.

关键词： South China Sea variability of deep circulation HYCOM data VEOF analysis wavelet analysis

Effect of Electropulsing on Recrystallization and Mechanical Properties of Silicon Steel Strips

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Journal of Materials Science & Technology 2011年第11期27卷 1034-1038页

作者： Guoliang Hu yaohua zhu Guoyi Tang Chanhung Shek Iianan Liu Materials Department and Advanced Materials Institute Tsinghua University Shenzhen 518055 China Department of Industrial and Systems Engineering Hong Kong Polytechnic University Kowloon Hong Kong China Department of Physics and Materials Science City University of Hong Kong 83 Tat Chee Avenue Kowloon Tong Honk Kong China

Electropulsing-induced recrystallization and its effect on mechanical properties of oriented silicon steel strips （Fe-3.0%Si） were studied by optical microscopy, scanning electron microscopy and electron back-scatter diffraction. The results indicated that electropulsing accelerated recrystallization, and decreased the temperature of recrystallization. Electropulsing favors refinement of the grain structure of the alloy. Effects of electropulsing on strength and elongation of the alloy were discussed from the point view of dislocation dynamics, microstructural changes, and electropulsing kinetics.

关键词： Recrystallization Electropulsing Oriented silicon steel strip

Effects of Electropulsing Induced Microstructural Changes on THz-Reflection and Electrical Conductivity of Al-Doped ZnO Thin-Films

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Journal of Surface Engineered Materials and Advanced Technology 2016年第3期6卷 106-117页

作者： yaohua zhu Weien Lai Department of Industrial and Systems Engineering Hong Kong Polytechnic University Hong Kong China Faculty of Physics and Materials Sciences Center Philipps-University Marburg Marburg Germany

Electropulsing induced phase transformation and crystal orientation change and their effects on electrical conductivity, THz reflection and surface roughness of thin-films of Al2O3 (2 wt%) doped ZnO were studied using XRD, SEM, AFM and Thz spectroscopy techniques. AZO-2 thin-films showed an effective response in THz spectroscopy under electropulsing. Electropulsing induced circular preferred crystal orientation changes and phase transformations were observed. The preferred crystal orientation changes accompanying decrease in stress and the secondary phase precipitation favored enhancing conductivity and THz reflection of the AZO-2 thin-films. After adequate electropulsing, both THz reflection and electrical conductivity of the thin-films were enhanced by 22.8% and 6.8%, respectively;meanwhile surface roughness reduced. The property responses of electropulsing are discussed from point view of microstructural change and dislocation dynamics.

关键词： Electropulsing Precipitation Preferred Crystal Orientation THz Reflection Electrical Conductivity AZO Thin-Films

Dynamic Electropulsing Induced Phase Transformations and Their Effects on Single Point Diamond Turning of AZ91 Alloy

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Journal of Surface Engineered Materials and Advanced Technology 2012年第1期2卷 16-21页

作者： Duo Zhang S. To yaohua zhu Hao Wang Guoyi Tang 不详

The effects of dynamic electropulsing on microstructure changes and phase transformations of a rolled Mg-9Al-1Zn alloy were studied by using optical microscopy, X-ray diffraction, back-scattered scanning microscopy and transmission electron microscopy techniques. The decomposition of β phase was accelerated under dynamic electropulsing, compared with the conventional thermal processes. Dynamic electropulsing was less effective in affecting the phase transformations, but more effective in reducing residual stress than the static electropulsing. Dynamic electropulsing improved machinability of single point diamond turning, the mechanism of which is discussed from the point of view of dislocation dynamics.

关键词： Electropulsing Phase Transformations Dislocation Twins Magnesium Alloy

A Loss-model-based Efficiency Optimization Control Method for Induction Traction System of High-speed Train under Emergency Self-propelled Mode

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CES Transactions on Electrical Machines and Systems 2024年第2期8卷 227-239页

作者： Yutong zhu yaohua Li Institute of Electrical Engineering Chinese Academy of Sciences Beijing 100190China University of Chinese Academy of Sciences Beijing 100190China China Academy of Railway Sciences Corporation Limited(Beijing Zongheng Electromechanical Technology Co.Ltd Beijing 100081 China IEEE

Increasing attention has been paid to the efficiency improvement of the induction traction system of high-speed trains due to the high demand for energy saving. In emergency self-propelled mode, however, the dc-link voltage and the traction power of the motor are significantly reduced, resulting in decreased traction efficiency due to the low load and low speed operations. Aiming to tackle this problem, a novel efficiency improved control method is introduced to the emergency mode of high-speed train traction system in this paper. In the proposed method, a total loss model of induction motor considering the behaviors of both iron and copper loss is established. An improved iterative algorithm with decreased computational burden is then introduced, resulting in a fast solving of the optimal flux reference for loss minimization at each control period. In addition, considering the parameter variation problem due to the low load and low speed operations, a parameter estimation method is integrated to improve the controller's robustness. The effectiveness of the proposed method on efficiency improvement at low voltage and low load conditions is demonstrated by simulated and experimental results.

关键词： Efficiency optimization Induction motor Loss model control Motor drives Traction system

Interbasin exchanges and their roles in global ocean circulation:A study based on 1 400 years' spin up of MOM4p1

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Acta Oceanologica Sinica 2014年第1期33卷 11-23页

作者： zhu yaohua WEI Zexun FANG Guohong WANG Yonggang GUAN Yuping Key Laboratory of Marine Science and Numerical Modeling First Institute of Oceanography State Oceanic Administration State Key Laboratory of Tropical Oceanography South China Sea Institute of Oceanology Chinese Academy of Sciences

A global prognostic model based on MOM4p1,which is a primitive equation nonBoussinesq numerical model,has been integrated with 1 400 years from the state of rest based on the realistic topography to study the long-term pattern of combined wind-driven and thermodynamically-driven general circulation.The model is driven by monthly climatological mean forces and includes 192×189 horizontal grids and 31 pressure-based vertical levels.The main objective is to investigate the mass and heat transports at interbasin passages and their compensations and roles in the global ocean circulation under equilibrium state of long-term spin up.The kinetic energy analysis divides the spin up process into three stages：the quasi-stable state of wind driven current,the growing phase of thermodynamical circulation and the equilibrium state of thermohaline circulation.It is essential to spin up over a thousand years in order to reach the thermohaline equilibrium state from a state of rest.The Arctic Throughflow from the Bering Strait to the Greenland Sea and the Indonesian Throughflow（ITF） are captured and examined with their compensations and existing data.Analysis reveals that the slope structures of sea surface height are the dynamical driving mechanism of the Pacific-Arctic-Atlantic throughflow and ITF.The analysis denotes,in spite of O（1.4×106m3/s） of the southward volume transport in the northern Atlantic,that there is still O（1 PW） of heat transported northward since the northward currents in the upper layer carry much higher temperature water than the southward flowing northern Atlantic deep water（NADW）.Meridional volume and heat transports are focused on the contributions to NADW renewals and Atlantic meridional overturning circulation（AMOC）.Quantitative descriptions of the interbasin exchanges are explained by meridional compensations and supported by previous observations and numerical modeling results.Analysis indicates that the volume and heat exchanges on the interbasin passages proposed in this article manifest their hub

关键词： numerical modeling global ocean interbasin exchange meridional transport meridional over-turning circulation

The annual mean sketches and climatological variability of the volume and heat transports through the inter-basin passages:A study based on 1 400-year spin up of MOM4p1

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Acta Oceanologica Sinica 2014年第9期33卷 12-24页

作者： zhu yaohua WEI Zexun WANG Yonggang GUAN Yuping WANG Xinyi Key Laboratory of Marine Science and Numerical Modeling First Institute of Oceanography State Oceanic Administration State Key Laboratory of Tropical Oceanography South China Sea Institute of Oceanology Chinese Academy of Sciences

The annual mean volume and heat transport sketches through the inter-basin passages and transoceanic sections have been constructed based on 1400-year spin up results of the MOM4p 1. The spin up starts from a state of rest, driven by the monthly climatological mean force from the NOAAWorld Ocean Atlas （1994）. The volume transport sketch reveals the northward transport throughout the Pacific and southward transport at all latitudes in the Atlantic. The annual mean strength of the Pacific-Arctic-Atlantic through flow is 0.63x106 m3/s in the Bering Strait. The majority of the northward volume transport in the southern Pacific turns into the Indonesian through flow （ITF） and joins the Indian Ocean equatorial current, which subse- quently flows out southward from the Mozambique Channel, with its majority superimposed on the Ant- arctic Circumpolar Current （ACC）. This anti-cyclonic circulation around Australia has a strength of 11 x 106 ms /s according to the model-produced result. The atmospheric fresh water transport, known as P-E^R （pre- cipitation minus evaporation plus runoff）, constructs a complement to the horizontal volume transport of the ocean. The annual mean heat transport sketch exhibits a northward heat transport in the Atlantic and poleward heat transport in the global ocean. The surface heat flux acts as a complement to the horizontal heat transport of the ocean. The climatological volume transports describe the most important features through the inter-basin passages and in the associated basins, including： the positive P-E＋R in the Arctic substantially strengthening the East Greenland Current in summer; semiannual variability of the volume transport in the Drake Passage and the southern Atlantic-Indian Ocean passage; and annual transport vari- ability of the ITF intensifying in the boreal summer. The climatological heat transports show heat storage in July and heat deficit in January in the Arctic; heat storage in January and heat deficit in July in the Antarctic circumpolar current regime （ACCR）; and

关键词： volume transport heat transport global ocean circulation inter-basin passages climatologicalvariability

A fresh look at the deepwater overflow in the Luzon Strait

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Acta Oceanologica Sinica 2017年第5期36卷 1-8页

作者： zhu yaohua SUN Junchuan WEI Zexun WANG Yonggang FANG Guohong QU Tangdong Key Laboratory of Marine Science and Numerical Modeling The First Institute of OceanographyState Oceanic Administration Laboratory for Regional Oceanography and Numerical Modeling Qingdao National Laboratory for Marine Science and Technology Joint Institute for Regional Earth System Science and Engineering University of California

On the basis of the latest version of a U.S. Navy generalized digital environment model （GDEM-V3.0） and World Ocean Atlas （WOA13）, the hydraulic theory is revisited and applied to the Luzon Strait, providing a fresh look at the deepwater overflow there. The result reveals that：（1） the persistent density difference between two sides of the Luzon Strait sustains an all year round deepwater overflow from the western Pacific to the South China Sea （SCS）; （2） the seasonal variability of the deepwater overflow is influenced not only by changes in the density difference between two sides of the Luzon Strait, but also by changes in its upstream layer thickness; （3） the deepwater overflow in the Luzon Strait shows a weak semiannual variability; （4） the seasonal mean circulation pattern in the SCS deep basin does not synchronously respond to the seasonality of the deepwater overflow in the Luzon Strait. Moreover, the deepwater overflow reaches its seasonal maximum in December （based on GDEM-V3.0） or in fall （October-December, based on the WOA13）, accompanied by the lowest temperature of the year on the Pacific side of the Luzon Strait. The seasonal variability of the deepwater overflow is consistent with the existing longest （3.5 a） continuous observation along the major deepwater passage of the Luzon Strait.

关键词： Luzon Strait deepwater overflow seasonal variability South China Sea

The Crystal Structure of Immunoglobulin Like Transcript 7 Domain 1

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The Crystal Structure of Immunoglobulin Like Transcript 7 Do...