南海西沙海域永乐海底峡谷形成演化过程分析

远海孤立碳酸盐台地周缘发育了碳酸盐岩峡谷,对其开展研究有助于深刻理解碳酸盐碎屑沉积物的“源-汇”体系及深水油气成藏等方面。文章利用多波束测深、高分辨率二维多道地震等数据,精细刻画南海西沙海域永乐海底峡谷的地貌形态及内部充填特征,揭示该峡谷沉积演化过程,分析峡谷成因控制因素及稳定性。永乐海底峡谷形成演化可分为萌芽、汇聚和拓展3个阶段,随着演化过程的发展,峡谷规模及对沉积物输运作用增加。永乐海底峡谷形成及演化主要受古地貌隆起形成的负地形和沉积物重力流侵蚀作用影响。峡谷在第四纪以后仍有较明显的活动迹象。分析显示永乐海底峡谷是西北次海盆的重要物质输送通道,其沉积演化过程及稳定性对研究碳酸盐台地沉积物输运等深水沉积过程及岛礁工程建设具有一定参考意义。     

中国北方砂栖纤毛虫的空间分布及其驱动因素

为深入了解不同地理尺度因素对驱动微型生物群落空间结构的相对影响,本研究于2020年10月调查了中国北方14个砂质潮间带的砂栖纤毛虫群落。研究结果如下：（1）检获纤毛虫105种,隶属26目65属,按丰度优势依次为帆口目、小胸目和环毛目;（2）黄海、渤海两区域的环境因子存在显著差异,但纤毛虫群落组成趋于相似;（3）偏Mental分析显示,环境条件较空间距离在纤毛虫群落组成的驱动中更为重要,其中盐度、粒度和海滩坡度是解释纤毛虫空间分布的最优环境因子组合,而潮差和溶解无机氮含量是次要影响因子;（4）沿海区域微型生物的强扩散效应在一定程度上掩盖了环境异质性影响。综上,由于沿海生态系统中微型生物受到更少扩散限制,在空间分布格局的形成上,环境条件的影响比空间距离更重要。本研究为海洋微型生物地理学提供了基础数据,有助于在全球变化背景下制定沙滩管理和保护规划。     

Homotopy Method for Inverse Design of the Bulbous Bow of A Container Ship

The homotopy method is utilized in the present inverse hull design problem to minimize the wave-making coefficient of a 1300 TEU container ship with a bulbous bow. Moreover, in order to improve the computational efficiency of the algorithm, a properly smooth function is employed to update the homotopy parameter during iteration. Numerical results show that the homotopy method has been successfully applied in the inverse design of the ship hull. This method has an advantage of high performance on convergence and it is credible and valuable for engineering practice.     

Analyses of the long-term salinity variability in the Bohai Sea and the northern Huanghai(Yellow) Sea

Based on the comprehensive collection of the field observed salinity of the Bohai Sea (BHS) and the northern Huanghai Sea (NHS) from the 1950s to the present,the patterns of 10-years-averaged salinity at the different layers in the recent five decades (the 1950s,the 1960s,the 1970s,the 1980s and the 1990s) are obtained by the spatial-temporal interpolation technique with the scrupulous data quality control in this study.Then,by combining the spatial-temporal interpolation technique with successive correction method,the annual distributions of salinity both in the BHS and in the NHS are obtained as well.The data analyses indicate that the overall salinity in the BHS and the NHS increases from the 1960s till the present,with the increase of annual mean salinity of 0.04 psu from the 1950s,and the maximum increase rate of salinity is about 0.14 psu/a in the Bohai Bay.The high salinity tongue extended significantly from the NHS into the BHS.The intensified eastern wind field is related to the western intrusion of the NHS warm current,which probably leads to the moving forward of the high salinity water mass into the BHS.However,it is rather different from the salinity distribution characteristics between the 1950s and the 1960s.The extensive precipitation in the 1960s could lead to an increase in the discharge of the Huanghe River,which might result in the decrease of salinity in the BHS.But the salinity isoline of 32 in the NHS still extended significantly into the BHS in the 1960s.Since the 1980s,the patterns of salinity distribution have changed thoroughly.The salinity in the central area of the BHS was low,while the salinity in the Bohai Bay and the Liaodong Bay was higher than the other regions with its horizontal salinity gradient decreasing in the 1980s.The Empirical Orthogonal Function Analysis (EOF) is also conducted to study the interannual salinity variability of the BHS and the NHS.The correlation coefficient between the time coefficient series of the main mode and the Huanghe River discharge can reach -64.57%.It can be concluded that salinity variation of the BHS and the NHS has strong negative correlation with the Huanghe River discharge.     

Seasonal changes in nitrogen and phosphorus transport in the lower Changjiang River before the construction of the Three Gorges Dam

Water and sediment samples were collected at Datong from June 1998 to March 1999 to examine seasonal changes in the transports of nitrogen (N) and phosphorus (P) from the Changjiang River (Yangtze River) to the East China Sea (ECS). Dissolved inorganic nitrogen (DIN; dominated by nitrate) concentration exhibited small seasonality, and DIN flux was largely controlled by water discharge. Dissolved inorganic phosphorus (DIP) concentration was inversely correlated with water discharge, and DIP was evenly delivered throughout a year. The transports of DIN and DIP from the Changjiang River were consistent with seasonal changes in nutrient distributions and P limitation in the Changjiang Estuary and the adjacent ECS. Dissolved organic and particulate N (DON and PN) and P (DOP and PP) varied parallel to water discharge, and were dominantly transported during a summer flood. The fluxes of DOP and particulate bioavailable P (PBAP) were 2.5 and 4 times that of DIP during this period, respectively. PBAP accounted for 12–16% of total particulate P (PP), and was positively correlated with the summation of adsorbed P, Al–P and Fe–P. Ca–P, the major fraction of PP, increased with increasing percent of CaCO₃. The remobilization of riverine DOP and PBAP likely accounted for the summer elevated primary production in DIP-depleted waters in the Changjiang Estuary and the adjacent ECS. The Changjiang River delivered approximately 6% of DIN (1459 × 10⁶ kg), 1% of DIP (12 × 10⁶ kg), and 2% of dissolved organic and particulate N and P to the totals of global rivers. The construction of the Three Gorges Dam might have substantially reduced the particulate nutrient loads, thereby augmenting P limitation in the Changjiang Estuary and ECS.     

阶变折射率轴棱锥产生局域空心光束

提出利用折射率成阶跃性变化的轴棱锥产生局域空心光束(bottle beam).讨论了折射率沿径向成阶跃式减小或增加两种模型,从几何光学角度分析了它们产生bottle beam的原理,利用衍射积分理论数值模拟两种轴棱锥光传输的光场分布和不同距离处的二维光斑图,研究结果表明折射率沿径向阶跃减小的轴棱锥产生单个bottle beam,而折射率沿径向阶跃增加的轴棱锥产生具有周期再现的bottle beams.bottle beam在原子引导和囚禁、光学俘获及光镊等方面有广泛的应用, 因此本文的研究对bottle     

非稳腔主动式直接获取纳秒近似无衍射贝塞尔绿光

通过对基于轴棱锥的贝塞尔谐振腔和贝塞尔-高斯谐振腔的研究,设计了一台腔内倍频Nd:YAG纳秒近似无衍射贝塞尔绿光激光器. 非稳激光器谐振腔由轴棱锥和凸面镜组成. 实验采用单灯脉冲抽运激光增益介质Nd:YAG晶体,倍频晶体选用KTP. 当抽运电压为350 V时,由主动式直接产生纳秒近似零阶贝塞尔绿光,其脉冲宽度为55.1 ns,波长为532 nm,线宽为0.8 nm,近似无衍射零阶贝塞尔绿光的中心光斑直径为192 μm. 利用Fresnel-Kirchhoff 衍射积分和Fox-Li迭代法,通过数值计算得出     

中西太平洋金枪鱼围网鲣鱼起水鱼群种群结构分析

根据2006年10月—2007年2月及2007年10月—2008年1月在中西太平洋海域测定的1343尾由金枪鱼围网捕获的起水鱼群的鲣鱼生物学数据,应用统计与回归的分析方法对鲣鱼的叉长组成、叉长和体重关系、性比、性腺成熟度等基本生物学特性进行了分析。结果表明:(1)起水鱼群鲣鱼的叉长范围为243～746 mm,优势叉长组为401～600 mm,占到88.24%,其中雌、雄个体叉长组成呈显著性差异(x2=843.7,P0.01);(2)起水鱼群鲣鱼的叉长(FL)与体重(W)的关系为W=6.3905×10-6FL3.1938(R2=0.9443),且叉长与体重的关系并不因性别而存在显著性差异(ANCOVA,F=0.549,P0.05);(3)起水鱼群鲣鱼的平均雌雄性比约为1∶0.95,但在501～550 mm(x2=4.00,P0.05)和651～700 mm(x2=4.17,P0.05)2个体长组中,雌雄性别比例不符合"1∶1"的理论期望;(4)起水鱼群鲣鱼的性成熟度以Ⅳ期(28.93%)和Ⅴ期(43.67%)为主,计算得出的雌鱼和雄鱼的首次性成熟叉长分别为473.15 mm和440.78 mm,均大于实际观测到的达到性成熟的鲣鱼的最小叉长。本次调查研究得出了"在调查水域鲣鱼的起水鱼群是以性成熟的成鱼为主的群体"的初步结论。     

东海陆扰海域铜、铅、锌、镉重金属排海通量及海洋环境容量估算

汇总并分析了20世纪80年代初以来东海陆扰海域重金属排海通量年变化规律及主要来源,应用多介质海洋环境中重金属迁移-转化模型,估算了东海陆扰海域重金属海洋环境容量。20世纪80年代初以来,东海陆扰海域铜、铅、锌、镉排海总量整体上呈不对称的倒"U"形变化趋势,基本符合"环境库兹涅茨曲线",20世纪90年代达到最大值,当前排海总量仍高于20世纪80年代初期的水平。东海陆扰海域铜、铅、锌、镉污染物主要来源于以河流为主的陆源排放,其中88.0%左右来源于河流排放,7.5%左右来源于排污口,只有4.5%左右来源于大气沉降。长江流域排海通量占东海陆扰海域排海总量的比例最大,平均为92.4%左右,钱塘江流域平均只有3.9%左右,闽江流域平均只有3.7%左右。东海陆扰海域铜、铅、锌、镉污染物海洋环境容量分别约为17.0,4.7,113.1,0.71 kt/a。当前铅、锌、镉污染物排海总量没有超过东海陆扰海域海洋环境容量,但铜的排海总量超过其海洋环境容量大约8%。     

Probabilistic Approach of Coastal Defense Against Typhoon Attacks for Nuclear Power Plant

With the global wanning and sea level rising, it is widely recognized that there is an increasing tendency of typhoon occurrence frequency and intensity. The defenses code against typhoon attacks for nuclear power plant should be calibrated because of the increasing threat of typhoon disaster and severe consequences. This paper discusses the probabilistic approach of definitions about "probable maximum typhoon" and "probable maximum storm surge" in nuclear safety regulations of China and has made some design code calibrations by use of a newly proposed Double Layer Nested Multi-objective Probability Model (DLNMPM).