一种改进的不规则三角网格曲面切割算法

三角网切割是实现三维地质建模和模型分析的关键算法, 它的效率直接决定了建模算法的效率.通过建立三角网的方向包围盒(oriented bounding box, OBB) 树实现曲面间的碰撞检测, 然后对发生相交的三角形对统一计算交点, 通过对顶点坐标归一化完成曲面切割后的快速重构, 并针对不同的曲面类型采用不同的切割分类方法进行2侧切割结果的划分.阐述了算法的实现过程并展示了切割后的图形效果.      

Analysis of Safe Span Length and Fatigue Life of Submarine Pipelines

Owing to the complex environmental conditions, suspension could induce complicated forces on submarine pipelines and even cause vortex-induced vibration, resulting in fatigue damage of pipelines. Through aiming at the 28-inch submarine pipeline in the East China Sea, the pipeline was segmented according to the similarity, considering the factors of pipe assembly, typhoon, current, wave and seabed topography. The effects of span length on natural frequency in each section of submarine pipeline were analyzed by finite element model. The maximum safe span length allowed by each pipeline section was verified by fatigue cumulative damage theory, and the fatigue life of each pipeline section were predicted. The results showed that each order natural frequency of the pipeline decreased with the increase of span length. The calculated results of empirical formulas were much smaller than those of the FEM analysis. The increase of the gap between the suspended pipeline and the seabed was beneficial to enhance the fatigue life of the suspended pipeline.     

1970—2016年阿尔金山冰川长度变化

长度是冰川的重要几何参数,对于认识冰川动态特征和模拟冰川厚度具有重要价值.基于阿尔金山第一次和第二次冰川编目数据及Landsat OLI遥感影像,利用冰川中流线方法提取了阿尔金山1970年、2010年和2016年的冰川长度数据,并结合气象资料分析了冰川长度对气候变化的响应.结果表明:2016年阿尔金山共有冰川507条,...     

不同法截面子午线椭球衔接的研究及应用

为了满足高速铁路线路控制网的投影长度变形值不大于10 mm／km的要求,将长线工程线路分成多段并建立各自的法截面子午线椭球．针对相邻法截面子午线椭球的衔接问题,提出交点法线重合的方法,实现椭球变换之后交点位置的一致性,解决线路的衔接问题,从而大大加强法截面子午线椭球理论在工程线路弯曲性、复杂性及长度的适用性．      

CMIP5气候模式下淡水通量变化

基于全球降水气候态计划(GPCP)的降水资料和美国伍兹霍尔海洋研究所(WHOI)的客观分析海气通量(OAFlux)的蒸发数据,对CMIP5的13个耦合模式的淡水通量历史模拟结果进行评估。结果表明:模式能够模拟出淡水通量的气候态空间分布,但普遍存在双热带辐合带(ITCZ)现象,热带海域是模式模拟不确定性最大的区域。模式能较好模拟出纬向平均的淡水通量的分布特征,但量值较实测偏小,且由于模式对1月10°S附近淡水通量的模拟过低,导致年平均的赤道和10°S之间的淡水通量模拟存在明显的偏差。季节尺度上,模式对北半球淡水通量的变化特征有很好的模拟能力,但对南半球的模拟能力不足。年际尺度上,模式普遍能够刻画ENSO引起的淡水通量在太平洋中部同西太平洋以及印尼贯通流反相变化的空间分布特征,但是时间特征模拟很差。从各个方面评估模式的历史模拟结果,多模式集合的结果都要优于单个模式的结果。全球变暖背景下,未来淡水通量变化最显著的区域位于热带和亚热带区域。原本蒸发(降水)占主导的海域,蒸发(降水)更强。不同气候情景下,淡水通量变化的空间形态没有显著变化,但RCP8.5气候情景下模拟的淡水通量变化幅度及模式间变化的一致性均强于RCP4.5的结果。     

大菱鲆体重和主要体型比率性状的遗传动态分析

The objective of this study was to estimate genetic parameters of body width(BW)to body length(BL)ratio(BW/BL)and of body weight traits(BWT)in turbot,and to elucidate the genetic mechanism of the two traits during ontogeny by dynamic genetic analysis.From 3 to 27 months,BW,BL and BWT of each communally stocked fish were measured every 3 months.The BW/BL ratio was measured at different sampling ages.A twotrait animal model was used for genetic evaluation of traits.The results showed that the heritability values of BW/BL ratio ranged from 0.2168 to 0.3148,corresponding to moderate heritability.The BWT heritability values ranged from 0.2702 to 0.3479 corresponding to moderate heritability.The heritability of BW/BL ratio was lower than that of BWT,except at 3 months of age.Genetic correlation between BW/BL ratio and BWT decreased throughout the measurement period.Genetic correlations were higher than the phenotypic correlations.The current results for estimating genetic parameters demonstrate that the BW/BL ratio could be used as a phenotypic marker of fast-growing turbot,and the BW/BL ratio and BWT could be improved simultaneously through selective breeding.     

Sharks caught in the KwaZulu-Natal bather protection programme,South Africa. 14. The smooth hammerhead shark Sphyrna zygaena (Linnaeus)

The current study provides long-term catch-rate, biological and feeding data for smooth hammerhead sharks, Sphyrna zygaena, caught in South Africa’s KwaZulu-Natal bather protection programme. In total, 2 512 S. zygaena were caught in net installations between 1978 and 2014, and 72 S. zygaena were caught on drumlines between 2007 and 2014. There was no significant log-linear year trend in the net catch rate over time (slope = 0.0054, t = 1.808, p = 0.07). However, there was a significant temporal increase in mean size of the captured sharks (slope = 0.0012, t = 3.502, p < 0.001). A quasi-Poisson generalised additive mixed model showed that increasing latitude, winter months, colder sea temperatures and the deployment of drumlines all had a significant positive effect on the catch rate of sharks in nets. The size frequency of the catch was unimodal, with significantly more females caught in the nets and more males on the drumlines. The majority (93.1%) of all sharks caught were immature and measured between 80 and 120 cm precaudal length. Teleosts and cephalopods dominated the sharks’ diet in terms of all dietary indices. The prey species consumed indicate that immature S. zygaena are feeding primarily within the pelagic zone of shallow coastal habitats.     

海冰爬坡和堆积行为的试验研究

对于浅海区采油平台等设施常采用斜坡式人工岛形式,虽然在一定程度上起到降低海冰对平台的作用,但是海冰沿着斜坡上爬至平台并形成堆积,同样也会对平台设施造成破坏,因此有必要对海冰堆积爬坡的关键参数进行研究。通过在冰排前进方向放置混凝土实体结构物模拟海冰堆积和爬坡过程,分析了模型冰爬坡和下滑角度、最大堆积高度等关键参数以及模型冰断裂长度的统计特性及其与变形模量的关系,试验结果表明水位越高,冰排越容易发生堆积爬坡。破碎的模型冰在结构物前堆积后,形成爬坡角和下滑角。爬坡角随着堆积体的增大而增大,下滑角则逐渐减小。堆积冰高度一定时,高度不再增加,在来冰方向会形成新的堆积。这种现象为浅海区海上结构物的防冰减灾提供了新思路。     

Latitudinal and local variations of the life history characteristics of the thalassinidean decapod, Upogebia yokoyai: A hypothesis based on trophic conditions

Mean total length of the eldest cohort (MTLe) of the thalassinidean decapod, Upogebia yokoyai sampled at 16 sites showed a latitudinal variation from south-west islands of the Ryukyu Archipelago (24° N) to the Seto-Inland Sea of Japan (34° N). Local variations were however also found from sites in the same latitudes. The level of the organic content in each habitat showed a positive correlation with MTLe. We hypothesized that MTLe is strongly affected by the trophic condition, resulting in the local variations. To test this hypothesis, two estuaries with different organic content were compared; Kodono River (Kochi Prefecture, 33° N) which was relatively oligotrophic and Sakata River (Hiroshima Prefecture, 34° N) which was highly eutrophicated. The Kodono River population showed slow growth after settlement, and growth stopped in May to June. This population survived for only one or two years, resulting in small MTLe. On the other hand, the Sakata River population showed fast growth from August to December. This population survived for three years, resulting in large MTLe. Maturation was estimated to occur two years after settlement in both populations. Low salinities may partially affect MTLe. Habitats in the Seto-Inland Sea (33.5–34.8° N) were eutrophicated, but many habitats in the subtropical islands (24–31° N) were relatively oligotrophic. Latitudinal variation of MTLe was reflected by the geographical difference in trophic condition. A negative relationship between population density and growth was found, which was explained in terms of reduced survival of recruits in the eutrophicated habitats.     

基于低成本单频u-blox接收机的GPS/BDS定向性能分析

针对高精度GNSS定向应用场景,通过实验对比对低成本单频u-blox接收机的数据质量和解算精度。结果表明,u-blox接收机GPS、BDS观测值的信噪比略低于测量型接收机;伪距精度分别为0.91 m、0.56 m,相位精度分别为1.35 cm、1.20 cm。在静态观测环境下,u-blox的定向精度可以达到航向0.2°/m和俯仰0.4°/m;动态环境下解算结果稍差,但也可以达到航向0.3°/m和俯仰0.6°/m,略低于高成本测量型接收机单频数据的实时动态定向精度。