13 February 2017, Volume 35 Issue 3

    

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  Top advances of science, technology and engineering from China in 2016

  CHEN Guangren, LIU Zhiyuan, TIAN Tian, ZHU Yehua

  Science & Technology Review. 2017, 35(3): 13-28. https://doi.org/10.3981/j.issn.1000-7857.2017.03.001

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  Based on the event every year for selecting the annual top advances in science, technology and engineering held by Editorial Department of Science & Technology Review, top 10 scientific achievements, top 10 technological achievements and top 10 engineering achievements from China in 2016 during January 1 to December 31, are selected respectively from a lot of scientific researches published in influential academic journals and scientific newspapers. The selection procedure involved screening and recommending candidate internally, followed by appraisal from experts including editorial board members and external reviewers. These achievements are introduced as the time sequence of publishing.
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  Advancing in study of the blown sand physics and its application in desertification control

  LIU Shizeng, XU Xianying, ZHAN Kejie

  Science & Technology Review. 2017, 35(3): 29-36. https://doi.org/10.3981/j.issn.1000-7857.2017.03.002

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  Due to its serious obstacle and threat to human survival and society sustainable development, desertification has received much attention from the world. The movement of sand and dust particles on the land surface and in the air driven by air flow is the main form of desertification occurrence and development process, it is also one of the core contents of desert science and desertification control engineering. The interaction mechanism among wind,surface and dust particles is the key to analysising of land desertification process or the establishment of disaster prevention project. This paper presents the development course of the physics of wind-blown sand, and an extensive review of the structure of the wind-sand field, physicas of aeolian dust emission, collision mechanism of the sand dust, electrification of wind-blown sand, modelling and experiment of the sand flow, formation and development of sand ripples and dunes, and the application of research work on mechanism of wind-blown sand to the desertification control. At last the direction for future study was put forward.
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  Field observations on wind-blown sand/dust storm and high Reynolds wall turbulence

  WANG Ping

  Science & Technology Review. 2017, 35(3): 37-42. https://doi.org/10.3981/j.issn.1000-7857.2017.03.003

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  Wind-blown sand and dust storm are typical gas-solid two phase flow occur in high Reynolds atmospheric boundary layer turbulence. Better understanding, accurate prediction and effective controlling of wind-blown sand and dust storm all rely on knowledges of sand/dust particle movement, and therefore on the research results on high Reynolds wall turbulence:The driving force of particle movement. After a briefly review on high Reynolds wall turbulence and sand/dust storm researches, the Qingtu Lake Observation Array (QLOA) established in Minqin county was introduced in detail. Preliminary results achieved in the light of observed data and outlook were described.
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  Review of optical measurement of near-surface aeolian sand transport in wind tunnel experiment

  ZHOU Xiaosi, ZHANG Yang, WANG Yuan, LI Min

  Science & Technology Review. 2017, 35(3): 43-50. https://doi.org/10.3981/j.issn.1000-7857.2017.03.004

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  Near-surface aeolian sand transport is a very complex process which involves the problems of multiple scales, nonlinearity and randomness, so it has always been a focus of the study in wind-blown sand physics. This paper reviews the recent development of optical measurement techniques in wind tunnel experiments, including laser velocity measurement, high-speed photography, and other novel systems. Their properties and applicabilities are briefly analyzed. Finally, some existing problems and future issues in wind tunnel experiment of aeolian sand transport based on the optical measurement are discussed.
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  Large eddy simulation of flow over urban vegetated regions

  YAN Chao, CUI Guixiang, ZHANG Zhaoshun

  Science & Technology Review. 2017, 35(3): 51-56. https://doi.org/10.3981/j.issn.1000-7857.2017.03.005

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  Vegetation exerts notable influences on urban microenvironment through biophysical processes. Studying the flow over urban vegetated region requires a proper treatment of the vegetation canopy. A large eddy simulation (LES) method is developed in the present work, which can well simulate the canopy flow. Using LES the turbulent flow over a model vegetation canopy is investigated under the neutral atmospheric condition. Each vegetation element consisting of a sphere-shaped tree crown and a cylindrical trunk is fully resolved. The resulting turbulence statistics and the drag force on vegetation agree well with the measurements from the corresponding wind-tunnel experiment. Two other numerical representations of vegetation canopies, referred to as drag element approach and drag crown approach, have also been developed to assess their performances. The drag crown approach yields better agreement between numerical results and experimental measurements than the traditional drag element approach, thus providing a promising numerical model for simulating canopy turbulence.
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  Development of surface water quality modeling: From survival to quality of life

  YIN Hailong, LI Xiao, Steven C. Chapra, WANG Daozeng

  Science & Technology Review. 2017, 35(3): 57-65. https://doi.org/10.3981/j.issn.1000-7857.2017.03.006

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  Practices of water pollution control at home and abroad indicate that obvious water quality improvement depends on systematic planning and integrated water environment rehabilitation on a catchment or even watershed scale. Surface water quality modeling is the key technical approach to optimize the set of water pollution control schemes. This paper introduces the four stages of surface water quality modeling development, from emphasizing the elimination of black and odorous water to restoring aquatic ecological system. Furthermore, the prospects for the development of surface water quality modeling are discussed, from the perspective of social-economical and technical drive. In the future, the trade-off between model complexity and reliability is anticipated to be overcome, thus quality modeling will play a more effective role in the realization of high quality water environment during the shift from people survival to quality of life.
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  Distribution characteristics of phosphorus in the water of Lake Fuxian and its influencing factors

  YAO Bo, LIU Qingquan, HU Chunming, XI Beidou, WU Xianhua

  Science & Technology Review. 2017, 35(3): 66-71. https://doi.org/10.3981/j.issn.1000-7857.2017.03.007

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  Deep lakes usually have long water exchange period, high pollutant retention rate, and vertical thermal stratification,therefore large spatiotemporal variability may exist in the water body. Based on the two field surveys in May and July 2009 to investigate the horizontal and vertical variations of phosphorus in Lake Fuxian, the influences of main polluting sources and hydrodynamic conditions are analyzed and the distributions of phosphorus in the lake are studied. Results show that the distribution of TP in the surface water agrees with the wind-induced surface flow and the distribution of main polluting sources. The concentrations of TP in the surface water in July are obviously larger than those in May, which is mainly caused by pollutants in runoff in the rainy season. However, the water below 100 m and more is less affected by the runoff pollutions. Besides, TP concentration has an increasing trend along the water depth. The accumulation of phosphorus in deep water is heavy and the situation is getting more serious. The existence of "a phosphorus pool" at the bottom is a big potential threat to the whole water body, which needs more attention.
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  Analysis of ice load on ship and offshore structure in polar region with discrete element method

  JI Shunying, WANG Shuailin, LIU Lu

  Science & Technology Review. 2017, 35(3): 72-80. https://doi.org/10.3981/j.issn.1000-7857.2017.03.008

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  The ice load is an important factor for vibration and fatigue of ship and offshore structure in polar region. For analyzing the ice load on different type offshore structures, the bonding-breaking effect between bonded spherical elements, the expansion disk element, and the polyhedron element based on the Minkowski sum theory are respectively adopted to construct the discrete element model of sea ice. Additionally, the ice-induced vibration of the jacket platform is calculated by using the coupled discrete element-finite element numerical method. And IceDEM, a software tool for sea ice DEM simulation based on GPU is developed to improve the computational efficiency. The present study can not only promote the development of discrete element method in polar marine engineering but also assist the design of ship and offshore structure in ice-covered fields.
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  Simulation study on hydrothermal plume transport in a stratified background

  YI Weilong, LIU Huan, YE Feng, BAO Yun

  Science & Technology Review. 2017, 35(3): 81-85. https://doi.org/10.3981/j.issn.1000-7857.2017.03.009

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  The seafloor hydrothermal system plays an important role in exchanging both thermal energy and chemical components between the ocean and earth crust. The hydrothermal system in a temperature stratified background is simulated using an axisymmetric model, and the influences of spout temperature, spout radius, spout flow velocity are discussed. The results show that the temperature decreases because the plume continues to entrain fluid, the plume overshoots to the maximum plume rise height in the stratified environment eventually. Over time, a laterally spreading intrusion develops above the plume and the plume's transport range at the bottom still remains unchanged. The spout temperature and spout radius have positive correlations with the rise height and lateral range of the hydrothermal plume.
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  Mechanisms and variations of arsenic accumulation in different ecotypes of Pteris vittata L.

  XU Feifei, MA Xiaona, LUO Wanqing, WU Fuyong

  Science & Technology Review. 2017, 35(3): 86-91. https://doi.org/10.3981/j.issn.1000-7857.2017.03.010

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  Arsenic (As) contamination has become a global environmental issue for years, with the most severe problem occurring in Southeast Asia and China. There has been a particular research interest since the first As-hyperaccumulator, Pteris vittata L., was identified. The mechanism of accumulation and metabolism of As in P. vittata can contribute to the optimization of phytoremediation. P. vittata has developed different ecotypes during its long-term evolution process. It is shown that there are significant differences in As accumulation and tolerance among the ecotypes of P. vittata. Based on a systematic analysis of characteristic and mechanism of As accumulation in P. vittata, the present work reviews the latest progress in the effects of different ecotypes on As accumulation in P. vittata. The preliminary result shows that the nonmetallicolous ecotypes possess more effective As accumulation than the metallicolous ecotypes, suggesting that the efficiency of phytoextration can be greatly enhanced by judicious selection of appropriate ecotypes of P. vittata. However, it is still not fully clear how molecular mechanisms are related to accumulation and tolerance of As in different ecotypes of P. vittata. Further studies should concentrate on key functional genes and the process involved in As hyperaccumulation in P. vittata.