NUMERICAL MODEL OF THERMAL TRANSIENT EFFECT IN FIBER OPTIC GYRO

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不同冷冻方法对兔颈总动脉形态结构及活性的影响

目的玻璃化法和慢速冷冻法深低温保存兔颈总动脉,比较两种保存方法对血管活性及形态结构的影响。方法无菌条件下切取兔颈总动脉,采用玻璃化法和慢速冷冻法在-196℃液氮中深低温保存2周,37℃水浴复温。新鲜血管作为对照,分别观察血管的大体、组织学、超微结构;同时对冷冻复温的血管采用组织块法培养并鉴定细胞,通过细胞计数描述细胞生长曲线,观察培养后血管的活性、细胞的再生及增殖能力。结果玻璃化组和慢速冷冻组动脉出现部分内皮细胞脱落,平滑肌细胞和成纤维细胞轻度肿胀、变性,前者损伤程度轻于后者。体外培养两组动脉的细胞分别于第6、7天自组织块内长出,细胞形态结构、生物学特性与新鲜组相似。生长曲线显示玻璃化组细胞的生长增殖状态优于慢速冷冻组,两组均差于新鲜动脉。将培养后的细胞分别进行免疫组织化学染色,经鉴定为平滑肌细胞。结论玻璃化法能较好地保持血管的形态结构和组织活性,保存效果优于慢速冷冻法。     

Conceptualizing Social Outcomes of Large Marine Protected Areas

There has been an assumption that because many large marine protected areas (LMPAs) are designated in areas with relatively few direct uses, they therefore have few stakeholders and negligible social outcomes. This article challenges this assumption with diverse examples of social outcomes that are distinctive in LMPAs. We define social outcomes as inclusive of both social change processes and social impacts, where “social” includes all perceptual or material human dimensions. We draw on five in-depth case studies to report social outcomes resulting from proposed or designated LMPAs in Bermuda, Rapa Nui (Easter Island), Kiribati, Palau, and the Commonwealth of the Northern Mariana Islands & Guam. We conclude: (1) social outcomes arise even in remote LMPAs; (2) LMPA efforts generate social outcomes at all stages of development; (3) LMPAs have the potential to produce outcomes at a higher level of social organization, which can change the scope and type of affected populations and, in some cases, the nature and stakes of the outcomes themselves; (4) the potential for LMPAs to impart distinctive social outcomes results from their unique geographies and/or intersection with high-level politics and policy processes; and (5) social outcomes of LMPAs may emerge in the form of social change processes and/or social impacts.     

基于组合预测模型的世界海运周转量预测分析

世界海运周转量是衡量未来航运市场运力需求的直接体现,在确定航运市场和船舶市场的发展趋势方面具有关键作用。针对世界海运周转量受到众多复杂因素影响的现实,基于传统的单个预测方法,分别采用时间序列、灰色系统、神经网络方法对世界海运周转量进行预测,然后再对单个预测方法进行加权组合,建立组合预测模型进行海运周转量的预测,预测结果表明:组合预测模型能够得到更加可靠的结果。     

Effects of small-scale turbulence on the growth of two diatoms of different size in a phosphorus-limited medium

The effect of turbulence on the nutrient flux towards osmotrophic cells is predicted to be size dependent. This should translate into growth. We experimentally followed and modelled the growth of two marine diatoms of different size (Thalassiosira pseudonana, 6 μm in diameter and Coscinodiscus sp., ca. 109 μm in diameter) under still water and turbulent conditions, using a shaker table. Experiments were done with phosphorus-limited cultures and lasted for ca. 5 days. Turbulence enhanced the growth of Coscinodiscus sp. in agreement with theory but not the growth of T. pseudonana, which was actually slightly lower under turbulence. At the end of the experiments there were about 1.7 times as many Coscinodiscus sp. cells in the turbulent treatment than in the still treatment, while for T. pseudonana almost the same cell concentration was found in both conditions. In addition, the Coscinodiscus sp. cells growing under still conditions presented a higher specific alkaline phosphatase activity than those growing in turbulence which indicates a higher need for phosphorus in the still cultures. A simple dynamic model, based on Michaelis–Menten nutrient uptake kinetics, needed nearly no optimisation other than using observed initial conditions of phosphate and cell concentrations. The model showed how an increased nutrient flux towards the cells translates non-linearly into cell growth, most likely by affecting the half-saturation constant (K_M). However, since Coscinodiscus sp. experienced significant mortality and cells partially settled to the bottom of the containers, unequivocal support for the size-dependent effect of turbulence on nutrient uptake will require further experiments and more sophisticated modelling. The mechanisms to connect an increased nutrient flux towards cells with population growth and whether this process is size dependent are important in parameterizing the effects of turbulence on marine plankton in coupled physical–biological models.     

Lights, camera and acoustics: Assessing macrobenthic communities at a dredged material disposal site off the North East coast of the UK

This study presents the results of a trial assessment based on a combination of sampling techniques at a dredged material disposal site located off the North East coast of the UK, over 2001 to 2004. The site was surveyed with a high-resolution sidescan sonar system producing a mosaic with 100% coverage of the survey area. Benthic communities and sediments were ground-truthed using a Hamon grab with a video camera. Additionally, the area was also sampled in 2003 with a Sediment Profile Imaging (SPI) camera, which complemented other techniques by providing in situ information on sediment quality, and biogenic activities. An assessment is made of the benefits of combining the results from conventional methods, principally using grab samples, with those from acoustic techniques and optical imaging devices to determine seafloor and macrobenthic conditions. This information has the potential to contribute to the enhancement of routine monitoring programmes within UK waters.     

海底管线的地球物理探测技术探讨

从应用原理、工程实例、应用效果等方面分析了目前国内外常用的海底管线探测的技术方法,并且探讨了各种方法的优缺点及适用条件,总结了海底管线探测现状及发展趋势.     

大直径PHC桩竖向承载力分布的试验研究

结合某跨海大桥桩基试验项目,对4组大直径PHC桩进行了竖向承载力静载试验,并通过桩身预埋的应变式钢筋计测试桩身轴力分布.试验结果表明,随着桩端土层刚度的提高,单桩极限承载力也将进一步增大,因此对于大直径PHC桩,也应选择较好土层作为持力层;随着桩顶荷载的不断增大,桩端阻力分担荷载所占的比例也逐渐增大,表明大直径PHC桩呈端承摩擦桩的承载性状;对于桩端持力层较好,而上覆软弱土层较厚的大直径PHC桩,尚应考虑上部土层侧摩阻力软化现象的影响;尽管大直径PHC桩桩身刚度较大,但在设计工作荷载下,此次试验的桩顶实测沉降主要由桩身压缩引起.     

Marine Shoreline Management—A 35-Year Evaluation of Outcomes in San Juan County,Washington, US

In 1976, Washington became the first state to implement the federal Coastal Zone Management Act (CZMA) primarily through the 1971 WA Shoreline Management Act (SMA). However, there has been little effort in Washington to evaluate outcomes of shoreline protection programs post SMA. In 2006–2008, we characterized shoreline conditions in San Juan County over three time periods spanning pre and post SMA and engaged community members to improve effectiveness of shoreline protection. We found modest improvements in forest retention on marine shorelines between pre and post 1977, but few other improvements through time. While we could not measure shoreline construction rates, construction practices for shore armor and overwater structures (docks) have changed very little, despite the increased regulatory standards. The vast majority of shore armor constructed post SMA occurred without mandatory county or state permits likely due to: widespread perception that permits were unnecessary and that permit standards were arbitrary and inconsistently applied; poor understanding of shoreline ecology by community members; lack of county or state enforcement authority and shoreline monitoring programs; and poor permit tracking systems.     

PIV study of the effect of piston position on the in-cylinder swirling flow during the scavenging process in large two-stroke marine diesel engines

A simplified model of a low speed large two-stroke marine diesel engine cylinder is developed. The effect of piston position on the in-cylinder swirling flow during the scavenging process is studied using the stereoscopic particle image velocimetry technique. The measurements are conducted at different cross-sectional planes along the cylinder length and at piston positions covering the air intake port by 0, 25, 50 and 75 %. When the intake port is fully open, the tangential velocity profile is similar to a Burgers vortex, whereas the axial velocity has a wake-like profile. Due to internal wall friction, the swirl decays downstream, and the size of the vortex core increases. For increasing port closures, the tangential velocity profile changes from a Burgers vortex to a forced vortex, and the axial velocity changes correspondingly from a wake-like profile to a jet-like profile. For piston position with 75 % intake port closure, the jet-like axial velocity profile at a cross-sectional plane close to the intake port changes back to a wake-like profile at the adjacent downstream cross-sectional plane. This is characteristic of a vortex breakdown. The non-dimensional velocity profiles show no significant variation with the variation in Reynolds number.