禁止底拖网作业对珠江口香港海域底层鱼类的影响

【目的】研究禁止底拖网作业对珠江口香港海域底层鱼类的影响。【方法】根据2007-2009年及2014-2016年在珠江口香港海域进行的定点底拖网调查数据,分析该海域在禁止底拖网捕捞实施前后鱼类种类组成及生物量和生态多样性指数,评估5种典型底层鱼类资源的变化。【结果与结论】该海域捕获鱼类种类数在禁止底拖网作业后明显增加,鱼类种类数量从44种升至73种。种类丰富度指数D变化范围为:2007至2009年,4.937～5.711,2014至2016年,6.559～7.074;多样性指数H’变化范围为:2007至2009年,1.945～2.841,2014至2016年,2.220～2.381;均匀度指数J变化范围为:2007至2009年,0.539～0.776,2014至2016年,0.557～0.600。卵鳎Solea ovata、韦式羊舌鮃Arnoglossus waitei、尖嘴魟Dasyatis zugei这3种底层鱼类禁止底拖网实施后在数量(number)和生物量(biomass)上都增幅明显。不同站位数量和生物量的数值在“禁拖令”实施后也都有所增加,其中以站位2(大屿山以北,较靠近香..

底拖网作业对珠江口香港海域底层鱼类的影响

【目的】研究底拖网作业对珠江口香港海域底层鱼类的影响。【方法】根据2007-2009年及2014-2016年在珠江口香港海域进行的定点底拖网调查数据,分析该海域在禁止底拖网捕捞实施前后鱼类种类组成及生物量和生态多样性指数,评估5种典型底层鱼类资源的变化。【结果与结论】该海域捕获鱼类种类数在禁止底拖网作业后明显增加,鱼类种类数量从44种升至73种。种类丰富度指数D变化范围为:2007至2009年,4.937～5.711,2014至2016年,6.559～7.074;多样性指数H’变化范围为:2007至2009年,1.945～2.841,2014至2016年,2.220～2.381;均匀度指数J变化范围为:2007至2009年,0.539～0.776,2014至2016年,0.557～0.600。卵鳎Solea ovata、韦式羊舌鮃Arnoglossus waitei、尖嘴魟Dasyatis zugei这3种底层鱼类禁止底拖网实施后在数量(number)和生物量(biomass)上都增幅明显。不同站位数量和生物量的数值在"禁拖令"实施后也都有所增加,其中以站位2(大屿山以北,较靠近香港国际机场海域)增加最为显著

Electric-field-induced selective catalysis of single-molecule reaction

随着单分子电学检测技术的迅速发展，分子电子学的研究不再局限于分子电子学器件的构筑及其电学性质的测量，而且扩展到单分子尺度化学反应过程的探索。然而目前相关的研究仍然局限于理论计算方面，在单分子尺度上实时监测和调控化学反应的活性和选择性是化学领域的长期目标和挑战。针对这一挑战，洪文晶教授课题组与程俊教授课题组合作，自主研发了精密科学仪器，将单个有机分子定向连接在两个末端尺寸为原子级的电极之间，解决了化学反应中分子取向控制的问题.理论计算结果证实了定向电场可以有效地稳定化学反应的过渡态，从而降低反应能垒。该研究工作在化学化工学院洪文晶教授、程俊教授、能源材料化学协同创新中心（iChEM）刘俊扬副研究员的共同指导下完成，由硕士研究生黄晓艳、iChEM博士研究生唐淳、博士研究生李洁琼以及兰州大学的陈力川博士作为共同第一作者，化学化工学院师佳副教授、陈招斌高级工程师、夏海平教授和田中群教授，萨本栋微纳研究院杨扬副教授、环境与生态学院白敏冬教授以及兰州大学张浩力教授参与了研究工作的讨论并给予指导，博士后乐家波、博士研究生郑珏婷、张佩（已毕业）、李瑞豪、李晓慧也参与了研究工作。Oriented external electric fields (OEEFs) offer a unique chance to tune catalytic selectivity by orienting the alignment of the electric field along the axis of the activated bond for a specific chemical reaction; however, they remain a key experimental challenge. Here, we experimentally and theoretically investigated the OEEF-induced selective catalysis in a two-step cascade reaction of the Diels-Alder addition followed by an aromatization process. Characterized by the mechanically controllable break junction (MCBJ) technique in the nanogap and confirmed by nuclear magnetic resonance (NMR) in bottles, OEEFs are found to selectively catalyze the aromatization reaction by one order of magnitude owing to the alignment of the electric field on the reaction axis. Meanwhile, the Diels-Alder reaction remained unchanged since its reaction axis is orthogonal to the electric fields. This orientation-selective catalytic effect of OEEFs reveals that chemical reactions can be selectively manipulated through the elegant alignment between the electric fields and the reaction axis.This work was supported by the National Key R&D Program of China (2017YFA0204902), the National Natural Science Foundation of China (21722305, 21703188, 21673195, 21621091, 51733004, 51525303, and 91745103), the China Postdoctoral Science Foundation (2017M622060), and the Young Thousand Talents Project of China. 该工作得到国家自然科学基金委（21722305、21703188、21673195、51733004、51525303、91745103），国家重点研发计划课题（2017YFA0204902），中国博士后面上基金（2017M622060）的资助，以及固体表面物理化学国家重点实验室、醇醚酯化工清洁生产国家工程实验室、能源材料化学协同创新中心的支持

Controllable synthesis of bilayer graphene on Cu foils

提出采用改进的化学气相沉积（chenmical vaper deposition,CVD）方法,利用甲烷为碳源在展平的Cu箔表面直接制备双层石墨烯薄膜。通过细致研究甲烷气体流量、生长时间等参数对双层石墨烯成核密度的影响,进一步探讨双层石墨烯生长的机理和条件。研究利用扫描电子显微镜（scanning electron microscope,SEM）、光学显微镜、Raman光谱对石墨烯的表面形貌、结构和堆叠方式进行了表征,提出双层石墨烯的“高效生长时间”为双层石墨烯成核完成后到第1层石墨烯完全覆盖Cu箔之间的时间段。通过优化生长条件,制备出高成核密度（双层与单层石墨烯成核密度比接近0.95）和高覆盖度的双层石墨烯（其中AB堆叠双层石墨烯比例高达82.7%）,实现展平Cu薄基底上高覆盖度双层石墨烯的可控制备。To make bilayer graphene grown directly on Cu foils, improved chemical vapor deposition （CVD） method was applied by using methane as precursor. The impacts of the methane flow rates,growth time on the bilayer graphene nuclei were evaluated to understand the growth mechanism and the key factor to the bilayer graphene synthesis. Scanning electron microscope （SEM）, optical microscopy, and Raman spectroscopy were applied to characterize the morphology and the stacking order of the bilayer graphene. We proposed that the ＂highly effective growth time＂ for bilayer grpahene was between the complete nuclei of the bilay-er graphene and the time that the Cu foil was fully covered by the monolayer graphene. On the basis of these results, bilayer gra-phene with high nucleation density （nuclei density ration of the first and bilayer graphene is about 0. 95） as well as high coverage （bilayer graphene with Bernal stacking ratio up to 82. 7% ） were successfully achieved over the Cu foil.高等学校博士学科点专项科研基金资助项目（20130121120017）;国家自然科学基金资助项目（51302233）;福建省自然科学基金资助项目（2015J06016

超高转速齿轮箱轴承-转子系统性能分析及优化设计研究

以可倾瓦轴承-转子系统为基础，仿真计算分析了轴承跨距、轴径及轴承相关参数对轴承-转子系统临界转速的影响，为高速齿轮箱轴承-转子的优化设计提供依据。研究表明，跨距的影响与转速关系密切；轴径超过54 mm后，影响可忽略；间隙比、支点偏移及预负荷系数对1阶、2阶临界转速的影响趋势基本相同，关系曲线分别为线性、对数和指数形式。根据分析结果，设计了60 000 r/min齿轮箱，轴承-转子系统通过空载试验，齿轮箱整体性能满足要求

高速转子用非接触式迷宫密封的密封性能影响因素研究

为了提高高速齿轮箱密封装置的密封性能，对常用于石油、化工等领域中的高速齿轮传动装置的非接触式迷宫密封进行了分析。通过建立（Computational fluid dynamics，CFD）数值计算模型，分析了该密封装置的密封齿数量、密封压差、油气混合物浓度、甩油环位置等因素对各密封腔回油口回油量及漏油口泄漏量的影响。研究对高速齿轮箱用非接触式迷宫密封的设计具有指导意义

大连极紫外相干光源

先进光源的发展在前沿科学研究中发挥的作用越来越重要。近十年来,飞速发展的自由电子激光技术为科学家们提供了探索未知世界、发现新科学规律和实现技术变革的重要工具。建成的大连极紫外(EUV)相干光源的运行波段为50~150nm,单脉冲能量大于100μJ,且可提供10-12 s和10-13 s量级的超快激光脉冲,是我国第一台自由电子激光用户装置,并且是国际上唯一运行在极紫外波段的自由电子激光用户装置,在世界范围内为用户提供具有高峰值亮度和超短脉冲的极紫外激光。大连EUV相干光源是由国家自然科学基金委资助、由中国科学院大连化学物理研究所和上海应用物理研究所共同承担的重大科学仪器研制项目,目标是打造一个以先进极紫外光源为核心、主要用于能源基础科学研究的光子科学平台

Shell Evolution Study for New Magic Number N =32 via Isochronous Mass Spectrometry

<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Recent results and progress of mass measurements of neutron-rich nuclei utilizing Isochronous Mass Spectrometry (IMS) based on the HIRFL-CSR complex at Lanzhou are reported. The nuclei of interest were produced through projectile fragmentation of primary 86Kr ions at a realistic energy of 460.65 MeV/u. After in-flight separation by the fragment separator RIBLL2, the fragments were injected and stored in the experimental storage ring CSRe, and their masses were determined from measurements of their revolution times. The re-determined masses were compared and evaluated with other mass measurements, and the impact of these evaluated masses on the shell evolution study is discussed.</span

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel