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761.
采用微机、光电脉冲技术并通过中断工作方式实现对旋转平台在低转速下转速均匀度相位分布的精密测量.为估计转台对旋转流体实验造成的误差提供数据,实现转台的转速精密测量,转速补偿和转速控制等方面的智能化  相似文献   
762.
The Tsunami of December 26, 2004, in the Indian Ocean arrived on the coast of Kerala in southwest India some three hours after the tsunami was generated. The tsunami activity persisted throughout that day and, in some locations, even into the early morning of the next day. Based on interviews with eye witnesses, arrival times of tsunami waves are presented here followed by some preliminary analysis of the results.  相似文献   
763.
The mackerel scad Decapterus macarellus is of great social and economic importance to Cabo Verde citizens; however, in recent years catches have shown an unexplained decline. The harvest is regulated by way of a minimum legal size and a seasonal closure, with both measures based on the results of reproductive studies that did not consider the microscopic characteristics of the gonads. This study aimed to analyse the gonads microscopically in order to classify the sexual development stage of individuals and to estimate the size at first maturity and the reproductive season. This information was then used to analyse the match between the reproductive parameters and the management measures. The samples comprised 284 females (20–36 cm fork length [FL]) and 85 males (21–35 cm FL). The annual variation in gonadosomatic index and the monthly frequencies of mature phases suggest that the reproductive season occurs from March to October, with two spawning peaks, one in March and another from July to October. The current seasonal closure (from July to September) covers the main reproductive period. However, the species has a long spawning period and the timing of peaks can vary between years; hence, a reassessment of this management measure is recommended. The sizes at first maturity were estimated at 24.1 cm FL for females, and 26.6 cm FL for males. These values are higher than the minimum legal size (20 cm FL) currently established for management of the species at Cabo Verde; thus, we strongly recommend an increase in the minimum legal size in an attempt to reduce catches of immature individuals.  相似文献   
764.
1.IntroductionVertical breakwaters are widely used for harbor and coastline protection in coastal engineering.Recently,perforated breakwaters have been often used in practice as they can effectively reduce thewaveforces actingon,the wave reflectionfromand…  相似文献   
765.
本文进一步考虑了具有正弦鉴相特性的锁相环路,我们提供了不同于文[2]的锁定参数,且求出周期解的界和渐近稳定域。  相似文献   
766.
提出采用相转移催化法,一步合成了抗癌新药ASF。工艺条件达到最简。利用正交实验法确定了最佳反应条件,通过一系列分析手段确定产物结构。  相似文献   
767.
潍河下游地区浅埋古河道沉积与第四系地层划分   总被引:3,自引:0,他引:3  
浅埋古河道带以冲洪积扇体为核心向北呈指掌状分布,古河道沉积具有明显的阶段性,早期沉积以中、细砂为主,粒度变化比较大,晚期沉积物以粉砂为主。在垂向上,古河道自下而上分为5段,其粒径呈愈向上愈细的趋势。钻孔剖面分析表明,潍河古河道沉积在横向上摆动幅度不大,沉积物自浅埋古河道主流带向两侧逐渐变细,沉积物粒度也随水动力强弱变化而变化,从上游到下游粒度变细,分选性增强。潍河下游地区晚更新世以来共发育5期古河道,与冰期-间冰期气候变化相对应。其中Ⅰ、Ⅱ期古河道厚度大,颗粒组,纵向上连续性好,为优良的含水层,其埋藏层位与古卤水埋藏层位基本一致,相互贯通,古河道成为卤水入侵的良好通道。晚期古河道沉积厚度大,沉积物粒度小,是早期主要的淡水取水层,但人类开采地下水的活动使其已成为海水入侵的主要通道。  相似文献   
768.
Influence of wave-current interactions on fluid force on a single cylinder and on two cylinders in tandem is examined. Quantities obtained are spectra of fluid force on elements, total fluid force and its statical moment. Comparisons are made of the cases in which wave-current interactions are considered and ignored. It is shown that interactions affect spectra of element force and statical moment more than do total force spectrum. For two cylinders in tandem, for cylinder spacings, current conditions and frequency range of practical interest, the effect of interactions is slightly reduced.  相似文献   
769.
舰载浅水激光测深系统研究   总被引:1,自引:0,他引:1  
本文提出了近海浅水区域水深测量的激光双频相位法测量方案,采用声光调制1064nm和532nm光波分别测量水面和水底距离。在实验室进行了该系统的模拟实验,证实了该方案的可行性。  相似文献   
770.
The recent identification of multiple strike‐parallel discontinuities within the exhumed Himalayan metamorphic core has helped revise the understanding of convergence accommodation processes within the former mid‐crust exposed in the Himalaya. Whilst the significance of these discontinuities to the overall development of the mountain belt is still being investigated, their identification and characterization has become important for potential correlations across regions, and for constraining the kinematic framework of the mid‐crust. The result of new phase equilibria modelling, trace element analysis and high‐precision Lu–Hf garnet dating of the metapelites from the Likhu Khola region in east central Nepal, combined with the previously published monazite petrochronology data confirms the presence of one of such cryptic thrust‐sense tectonometamorphic discontinuities within the lower portion of the exhumed metamorphic core and provides new constraints on the P–T estimates for that region. The location of the discontinuity is marked by an abrupt change in the nature of P–T–t paths of the rocks across it. The rocks in the footwall are characterized by a prograde burial P–T path with peak metamorphic conditions of ~660°C and ~9.5 kbar likely in the mid‐to‐late Miocene, which are overlain by the hanging wall rocks, that preserve retrograde P–T paths with P–T conditions of >700°C and ~7 kbar in the early Miocene. The occurrence of this thrust‐sense structure that separates rock units with unique metamorphic histories is compatible with orogenic models that identify a spatial and temporal transition from early midcrustal deformation and metamorphism in the deeper hinterland to later deformation and metamorphism towards the shallower foreland of the orogen. Moreover, these observations are comparable with those made across other discontinuities at similar structural levels along the Himalaya, confirming their importance as important orogen‐scale structures.  相似文献   
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