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Surface heat Budget and Solar Radiation Allocation at a Melt Pond During Summer in the Central Arctic Ocean

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Journal of Ocean University of China 2014年第1期13卷 45-50页

作者： ZHANG Shugang ZHAO Jinping SHI Jiuxin JIAO yutian College of Physical and Environmental Oceanography Ocean University of China

The heat budget of a melt pond surface and the solar radiation allocation at the melt pond are studied using the 2010 Chinese National Arctic Research Expedition data collected in the central Arctic. Temperature at a melt pond surface is proportional to the air temperature above it. However, the linear relationship between the two varies, depending on whether the air temperature is higher or lower than 0℃. The melt pond surface temperature is strongly influenced by the air temperature when the latter is lower than 0℃. Both net longwave radiation and turbulent heat flux can cause energy loss in a melt pond, but the loss by the latter is larger than that by the former. The turbulent heat flux is more than twice the net longwave radiation when the air temperature is lower than 0℃. More than 50% of the radiation energy entering the pond surface is absorbed by pond water. Very thin ice sheet on the pond surface(black ice) appears when the air temperature is lower than 0℃; on the other hand, only a small percentage(5.5%) of net longwave in the solar radiation is absorbed by such a thin ice sheet.

关键词： heat budget melt pond solar radiation Arctic

4-methylumbelliferone (4-MU) enhances drought tolerance of apple by regulating rhizosphere microbial diversity and root architecture

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Horticulture Research 2023年第7期10卷 53-68页

作者： Dehui Zhang Jieqiang he Pengda Cheng yutian Zhang Abid Khan Shicong Wang Zhongxing Li Shuang Zhao Xiangqiang Zhan Fengwang Ma Xuewei Li Qingmei Guan State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple College of HorticultureNorthwest A&F UniversityYangling 712100China College of Life Science Northwest A&F UniversityYangling 712100China Department of Horticulture The University of HaripurHaripur 22620Pakistan

The dwarfing rootstocks-mediated high-density apple orchard is becoming the main practice ***,dwarfing rootstocks are widely used worldwide,but their shallow root system and drought sensitivity necessitate high irrigation ***,the root transcriptome and metabolome of dwarfing(M9-T337,a drought-sensitive rootstock)and vigorous rootstocks(Malus sieversii,a drought-tolerant species,is commonly used as a rootstock)showed that a coumarin derivative,4-Methylumbelliferon(4-MU),was found to accumulate significantly in the roots of vigorous rootstock under drought *** exogenous 4-MU was applied to the roots of dwarfing rootstock under drought treatment,the plants displayed increased root biomass,higher root-to-shoot ratio,greater photosynthesis,and elevated water use *** addition,diversity and structure analysis of the rhizosphere soil microbial community demonstrated that 4-MU treatment increased the relative abundance of putatively beneficial bacteria and *** these,Pseudomonas,Bacillus,Streptomyces,and Chryseolinea bacterial strains and Acremonium,Trichoderma,and Phoma fungal strains known for root growth,or systemic resistance against drought stress,were significantly accumulated in the roots of dwarfing rootstock after 4-MU treatment under drought stress *** together,we identified a promising compound—4-MU,as a useful tool,to strengthen the drought tolerance of apple dwarfing rootstock.

关键词： drought dwarf roots

An approximation algorithm for lower-bounded k-median with constant factor

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Science China(Information Sciences) 2022年第4期65卷 93-101页

作者： Xiaoliang WU Feng SHI yutian GUO Zhen ZHANG Junyu HUANG Jianxin WANG School of Computer Science and Engineering Central South University Hunan Provincial Key Lab on Bioinformatics Central South University School of Frontier Crossover Studies Hunan University of Technology and Business

The lower-bounded k-median problem plays a key role in many applications related to privacy protection, which requires that the amount of assigned client to each facility should not be less than the requirement. Unfortunately, the lower-bounded clustering problem remains elusive under the widely studied k-median objective. Within this paper, we convert this problem to the capacitated facility location problem and successfully give a(516+ε)-approximation for this problem.

关键词： approximation algorithm k-median lower-bounded k-median

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Progress of d^0 magnetism in SiC

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Journal of Semiconductors 2017年第3期38卷 100-109页

作者： yutian Wang Chenguang Liu Yuming Zhang School of Microelectronics Xidian University and Key Laboratory of Wide Band-Gap Semiconductor Materials and DevicesXi'an 710071 China

The properties of defect-induced ferromagnetism（d^0magnetism） in SiC belong to carbon-based material which has been systematically investigated after *** this paper,we reviewed our research progress about d^0 magnetism in two aspects,i.e.,magnetic source and magnetic coupling *** V_（Si）V_C divacancies have been evidenced as the probable source of d^0 magnetism in *** trace the ferromagnetic source in microscopic and electronic view,the p electrons of the nearest-neighbor carbon atoms,which are around the V_（Si）V_C divacancies,are *** magnetic coupling mechanism,a higher divacancy concentration leads to stronger paramagnetic interaction but not stronger ferromagnetic *** the d^0 magnetism can probably be explained as a local effect which is incapable of scaling up with the volume.

关键词： SiC d0 magnetism graphite

Deep waters warming in the Nordic seas from 1972 to 2013

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Acta Oceanologica Sinica 2015年第3期34卷 18-24页

作者： WANG Xiaoyu ZHAO Jinping LI Tao ZHONG Wenli JIAO yutian Key Laboratory of Physical Oceanography Ocean University of China

The warming of deep waters in the Nordic seas is identified based on observations during Chinese 5th Arctic Expedition in 2012 and historical hydrographic data. The most obvious and earliest warming occurrs in the Greenland Basin （GB） and shows a coincident accelerated trend between depths 2000 and 3500 m. The ob-servations at a depth of 3000 m in the GB reveal that the potential temperature had increased from ？1.30°C in the early 1970s to ？0.93°C in 2013, with an increase of about 0.37°C （the maximum spatial deviation is 0.06°C） in the past more than 40 years. This remarkable change results in that deep waters in the center of the Lofton Basin （LB） has been colder than that in the GB since the year 2007. As for the Norwegian Basin （NB）, only a slight trend of warming have been shown at a depth around 2000 m since the early 1980s, and the warming amplitude at deeper waters is just slightly above the maximum spatial deviation, implying no obvious trend of warming near the bottom. The water exchange rate of the Greenland Basin is estimated to be 86% for the period from 1982 to 2013, meaning that the residence time of the Greenland Sea deep water （GSDW） is about 35 years. As the weakening of deep-reaching convection is going on, the abyssal Nordic seas are playing a role of heat reservoir in the subarctic region and this may cause a positive feedback on the deep-sea warming in both the Arctic Ocean and the Nordic seas.

关键词： Nordic seas Greenland Basin deep waters temperature variation

Effect of helium implantation on mechanical properties of niobium doped tungsten

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Science China(Physics,Mechanics & Astronomy) 2013年第7期56卷 1396-1400页

作者： MA yutian ZHANG Ying LU GuangHong ZHU KaiGui Department of Physics Beihang University

helium atoms were implanted into niobium-doped tungsten and pure tungsten via ion implantation, and the effect of helium implantation on mechanical properties of two types of sample was studied by X-ray photoelectron spectroscopy, scanning electron microscope and nano-hardness tester. The results clearly show that the surface hardness and elastic modulus of tungsten are improved by implanted niobium ions, and the degradation of mechanical properties is mitigated comparing to pure tungsten under identical helium implantation fluence. It can be concluded that the defects induced by niobium implantation improved the mechanical properties of tungsten by obstructing the slip of dislocation.

关键词： tungsten niobium doped helium implantation mechanical property

Water mass of the northward throughflow in the Bering Strait in the summer of 2003

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Acta Oceanologica Sinica 2006年第2期25卷 25-32页

作者： ZHAO Jinping SHI Jiuxin GAO Guoping JIAO yutian ZHANG Hongxin Key Laboratory of Physical Oceanography of Ministry of Education Ocean University of China Qingdao 266003 China North China Sea Branch of the State Oceanic Administration Qingdao 266000 China

The temperature and salinity data obtained by the Chinese national arctic research expedition （CHINARE2003） are used to study the water structure in the Bering Strait and ambient regions. Four water masses appeared in the research region： the intermediate Bering Sea water mass （IBWM）, the Alaska coastal water （ACW）, the Anadyr water （AW） and the Bering shelf water （BSW）. The AW originates from the IBWM, but the upper layer water has been greatly altered. In the cruise on 28/29 July 2003, there were only the BSW and ACW in a section across the Bering Strait （BS section）, but in the September 12/13 cruise, the AW, BSW and ACW flowed parallelly into the Bering Strait. The upper waters of these water masses were all altered due to ice melting, runoff, solar radiation, and wind mixing. The waters in the central and northern parts of Bering Strait stratified by two uniform layers,were expressed as the typical feature of the water masses originating from the pacific. A two-layer structure also dominated the vertical stratification in most part of the Chukchi Sea. An obvious subseasonal variation was observed in the BS section, which caused varying transportation of fresh water, heat, and substance, and produced a long-term and extensive impact on the Arctic Ocean.

关键词： Bering Strait water mass Pacific water Arctic Ocean CHINARE2003

Design and development of a five-axis machine tool with high accuracy,stiffness and efficiency for aero-engine casing manufacturing

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Chinese Journal of Aeronautics 2022年第4期35卷 485-496页

作者： yutian WANG Dong WANG Shizhen ZHANG Zihan TANG Liping WANG Yanmin LIU State Key Laboratory of Tribology and Institute of Manufacturing Engineering Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China Beijing Key Lab of Precision Ultraprecision Manufacturing Equipment and Control Beijing 100084China Beijing Precision Machinery&Engineering Research Co.LTD Beijing 101312China Beijing Institute of Control Engineering Beijing 100094China

In order to satisfy the machining requirements of aero-engine casing in modern aviation industry, this paper investigates three main issues during the design and development process of a five-axis machine tool with high accuracy, stiffness and efficiency, including whole structure design,key components design, and supporting stiffness design. First, an appropriate structure of five-axis machine tool is determined considering the processing characteristics of aero-engine casing. Then, a dual drive swing head and a compact motorized spindle are designed with enough drive capability and stiffness, and related structure, assembly method, cooling technology, and performance simulation are given in detail. Next, a design method of supporting stiffness of guide is proposed through the deformation prediction of the spindle end. Based on above work, a prototype of machine tool is developed, and some experiments are carried out, including performance tests of swing head and motorized spindle, and machining of a simulated workpiece of aero-engine casing. All experimental results show that the machine tool has satisfactory accuracy, stiffness and efficiency, which meets the machining requirements of aero-engine casing. The main work can be used as references for engineers and technicians, which are meaningful in practice.

关键词： Aero-engine casing manufacturing Compact motorized spindle Dual drive swing head Five-axis machine tool Supporting stiffness

Regional characteristics of sea ice thickness in Canadian shelf and Arctic Archipelago measured by Ground Penetrating Radar

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Acta Oceanologica Sinica 2015年第5期34卷 110-116页

作者： LI Tao ZHAO Jinping JIAO yutian HOU Jiaqiang MU Longjiang Ocean University of China Physical Oceanography Laboratory Ocean University of China

Ground Penetrating Radar （GPR） measurements of sea ice thickness including undeformed ice and ridged ice were carried out in the central north Canadian Archipelago in spring 2010. Results have shown a significant spatial heterogeneity of sea ice thickness across the shelf. The undeformed multi-year fast ice of （2.05±0.09） m thick was investigated southern inshore zone of Borden island located at middle of the observational section, which was the observed maximum thickness in the field work. The less thick sea ice was sampled across a flaw lead with the thicknesses of （1.05±0.11） m for the pack ice and （1.24±0.13） m for the fast ice. At the northernmost spot of the section, the undeformed multi-year pack ice was （1.54±0.22） m thick with a ridged ice of 2.5 to 3 m, comparing to the multi-year fast ice with the thickness of （1.67±0.16） m at the southernmost station in the Prince Gustaf Adolf Sea.

关键词： Arctic sea ice thickness Canadian Archipelago Ground Penetrating Radar