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671.
采用低盐度(4、6、8、10、12、14、16)和高盐度(40、45、50、55、60、65、70)在40%~50%受精卵出现第一极体时处理10和15min,进行长牡蛎三倍体的诱导。在低盐度诱导三倍体实验中,随着盐度降低,D型幼虫孵化率逐渐降低,处理10和15min的卵裂率差异显著(P0.05),孵化率差异不显著(P0.05)。当盐度为8时,处理受精卵10与15min,三倍体诱导率最高分别可达84.4%和91.0%,两处理组三倍体诱导率差异显著(P0.05)。在高盐度诱导三倍体实验中,随着盐度升高,D型幼虫孵化率逐渐降低,处理10和15min的卵裂率和孵化率均差异显著(P0.05)。当盐度为55时,处理受精卵10min,三倍体诱导率最高为80.3%;当盐度为60时,处理受精卵15min,三倍体诱导率最高为97.1%,两处理组三倍体诱导率差异显著(P0.05)。研究发现,在盐度为8和60条件下,40%~50%的受精卵出现第一极体时,处理15min,长牡蛎三倍体诱导率最高。 相似文献
672.
Experimental Study on Response Performance of VIV of A Flexible Riser
with Helical Strakes 总被引:1,自引:1,他引:0
Laboratory tests were conducted on a flexible riser with and without helical strakes. The aim of the present work is to further understand the response performance of the vortex induced vibration (VIV) for a riser with helical strakes. The experiment was accomplished in the towing tank and the relative current was simulated by towing a flexible riser in one direction. Based on the modal analysis method, the displacement responses can be obtained by the measured strain. The strakes with different heights are analyzed here, and the response parameters like strain response and displacement response are studied. The experimental results show that the in-line (IL) response is as important as the cross-flow (CF) response, however, many industrial analysis methods usually ignore the IL response due to VIV. The results also indicate that the response characteristics of a bare riser can be quite distinct from that of a riser with helical strakes, and the response performance depends on the geometry on the helical strakes closely. The fatigue damage is further discussed and the results show that the fatigue damage in the CF direction is of the same order as that in the IL direction for the bare riser. However, for the riser with helical strakes, the fatigue damage in the CF direction is much smaller than that in the IL direction. 相似文献
673.
A set of generalized solutions are proposed for estimating ultimate load capacity of pipeline with arbitrary corrosion shapes subjected to combined internal pressure, axial force and bending moment. Isotropic and anisotropic material characteristics in longitudinal and circumferential direction of pipeline are also considered in the proposed equations. Simplified numerical method is used to solve the generalized expressions. The comparisons of numerical results based generalized solutions and full-scale experimental results are carried out. The predicted results agree reasonably well with the experiment results. Meanwhile, the effects of corrosion shapes and locations on the ultimate load capacity are studied. 相似文献
674.
文章采用基于特殊处理数据的叠后谱反演方法对南海北部陆坡神狐海域的含水合物沉积层厚度进行预测。正演模拟结果表明,谱反演技术可以精细识别异常地质体,获取高分辨率的反射系数剖面。结合研究区高信噪比地震资料,基于频谱分析,发现在频率剖面上含水合物沉积层主要表现为低频高能、高频低能或高频盲区之上的低频低能、高频高能或高频低能区,含水合物沉积层顶底界面均存在频率异常,且含水合物沉积层底界衰减最为强烈,通过谱反演,发现获取的反射系数剖面比原始地震数据分辨率更高,且与实际测井结果可对比,通过定义?90?相位旋转后谱反演结果上振幅为零值的点之间的距离为地层厚度,计算的过井含水合物沉积层厚度与测井估算结果吻合度高。研究表明,该方法可以获取精度较高的含水合物沉积层厚度信息,实现精度较高的水合物储量估算。 相似文献
675.
??RINEX HO???????GPS?????λ?????е???(?????????)????????????????????GPS???????е??????????(ΔIH)p,qi,g??????????(ΔIH)p,qi,g????γ?????????????????????????????????????????????????????£???Bernese 5.0???????????????????????????????δ???и????????????????????л????????????????????????????????ΔbH???????????ΔbH???????С????????????????????Δ??b??H??????????????????????????????????????????ε??С??ΔbH????????? 相似文献
676.
677.
A Comparative Study of Fish Assemblages Near Aquaculture,Artificial and Natural Habitats 总被引:1,自引:0,他引:1
Habitat plays a critical role in regulating fish community structure. Using the data collected from a monthly trammel net survey in Ma’an archipelago off the east coast of China, we evaluated impacts of five different habitats(artificial reefs, mussel farms, cage aquaculture, rocky reefs and soft bottom) on fish assemblages. This study suggests that artificial reefs(AR) have significantly higher species richness, abundance and diversity than mussel farms(MF) or soft bottom(SB) habitats during most seasons, and that fish taxa in the AR habitats are similar to those in the rocky reef(RR) habitats. Two different fish assemblage patterns were revealed in the study area using non-metric multidimensional scaling ordination: an assemblage dominated by reef fishes(especially by Scorpaenidae species) in AR, RR and cage aquaculture(CA) habitats and an assemblage dominated by Sciaenidae species in MF and SB habitats. We suggest that reef fishes play a key role in differentiating fish community structures in the study area. Although few differences in fish abundance and diversity were found between the CA and SB habitats, a more diverse age structure was observed in the CA habitats. A much more complex fish assemblage and enhanced population of local species were established as a result of the presence of both floating and fixed artificial structures, probably through improved survival rates. 相似文献
678.
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