节理峰值后归一化位移软化模型

切向荷载作用下贯通节理岩体峰值强度后的剪切应力、位移变形规律一般呈双曲线形式发展,即峰值后强度衰减速率逐步变小而趋于0,到达残余强度。直剪试验表明,非贯通节理岩体峰值后剪切应力、位移呈“S”型趋势发展,即强度衰减速率先是逐步增大,到达一定程度后逐步减少,最后趋于稳定达到残余强度值。贯通节理岩体峰值强度后的本构关系并不适合于描述该特征。提出一个新的非线性归一化位移软化本构模型,通过归一化剪切应力R与归一化剪切位移D的指数函数关系体现峰值后剪切应力、位移的发展趋势,即模型采用无量纲表达式。归一化剪切应力R是峰值后强度降? p-? 与峰值强度、残余强度差值? p-? r的比值;归一化位移D是峰值后剪切位移、峰值位移差值? -? p与残余位移、峰值位移差值? r -? p的比值。对含不同起伏角的非贯通节理岩体在常法向荷载条件下的直剪试验数据进行拟合分析,模型预测结果与实测值具有相当高的吻合度,验证了模型的正确性     

湖北省夏季不同阶段强降水及其大气低频特征

利用1961-2014年湖北省68站逐日降水资料和美国国家海洋和大气管理局环流资料,对比分析了湖北省夏季梅雨期和盛夏期低频强降水事件的基本特征、大气环流形势和低频信号传播特征。结果表明:(1)湖北省夏季降水存在显著的准双周低频周期。(2)相较于盛夏期,梅雨期低频强降水事件次数多,强度强。(3)梅雨期和盛夏期低频强降水事件发生期间的环流形势有着显著的差异。梅雨期,对流层中层东亚沿岸为南北向的波列分布,低层受强索马里越赤道气流和副热带高压外围西南气流共同影响,水汽条件好,东亚存在鞍型场,流场变形,利于形成中尺度气旋系统;盛夏期,对流层中层为欧亚波列分布,低层索马里越赤道气流弱,主要受副热带高压外围水汽输送的影响,日本海以西地区有一异常气旋,其西侧的偏北气流与暖湿气流在30°N附近交汇维持。(4)在强降水事件发生前后,对流层低层的低频正涡度传播特征有较大差异,在梅雨期表现为驻波特征,盛夏期传播更为明显,表现为向西、向南向北传播。     

徕卡RTC360三维激光扫描仪在竣工测量中的应用

徕卡RTC360不仅操作简单、扫描速度快,而且非常智能。可以实时跟踪计算两个连续站点间的相对位置,点云实时预拼接。后期搭配Register360智能拼接软件,点云智能拼接处理,无需人工干预,简单高效。     

AEKF在星敏感器低频误差补偿中的应用

高分辨率对地观测卫星需要精确的姿态信息来满足后续对地定位等工作,因此姿态确定精度十分重要。星敏感器的低频误差是影响卫星姿态确定精度的重要因素之一,主要是由空间周期性的热环境变化引起的。为进一步提高卫星姿态确定精度,对星敏感器的低频误差产生机理即星敏感器主光轴做周期性扰动进行了分析,设计了星敏感器低频误差补偿方案,建立了考虑星敏感器低频误差在内的组合定姿模型,利用拓维卡尔曼滤波(AEKF)对低频误差进行补偿,并引入RTS平滑滤波进一步提高姿态确定精度。仿真实验表明,设计的星敏感器低频误差补偿方案能有效对其进行补偿,提高卫星姿态确定精度。     

泡沫泥浆钻进工艺及护壁堵漏机理研究

介绍了所研制的ＤＦ－１型泡沫剂组分及性能；对泡沫泥浆钻进的配方进行了研究，得出的最优配方应用于现场，取得了较好的效果，并对泡沫泥浆的护壁机理进行了研究。     

Optimisation of underwater visual census and controlled angling methods for monitoring subtidal temperate reef fish communities

Standardised sampling protocols for monitoring fish stocks are essential to assess changes in stock status and provide a means to evaluate the effectiveness of fisheries management measures, such as marine protected areas (MPAs). This study aimed to optimise two standard sampling methods, namely underwater visual census (UVC) and controlled angling, for assessing subtidal reef fish communities. In terms of efficiency, variability and bias, UVC transects were found to be superior to point counts. For controlled angling, an effort of two angler-hours per fishing station provided low catch variability, high catch per unit effort and a representative catch. Whereas UVC provided less variable estimates of relative density, controlled angling provided greater sampling efficiency. It is thus recommended that the two methods be used in conjunction. The optimal sampling protocols identified are suitable for rapid assessments or long-term monitoring of subtidal, temperate reef fish communities.     

Fishermen responses on marine protected areas in the Baltic cod fishery

Much of the research that concerns the impacts of management measures in the eastern Baltic cod fishery has focused on fish stock rather than understanding fishermen's attitudes towards regulations. Hence, there is little information available on fishermen's responses although they are the ones whom the regulations affect most profoundly. This study analyses the views of fishermen towards management measures with an emphasis on fishing closures (marine protected areas, MPAs). Swedish log-book data from 1996 to 2005 were used to describe MPA induced fishing effort displacements. Fishermen argued that MPAs have been inefficient in conservation of cod stock. The enlargement of Bornholm MPA in 2005 caused substantial effort displacement towards areas dominated by smaller sized fish. This contributed to the increased discarding of juvenile cod. Enlarged MPAs also intensified competition between different fleet segments and reallocated fishing areas. To reduce fishing mortality, fishermen suggested days-at-sea (effort) regulation and an effective landings control system for all fleets that exploit cod stocks in the Baltic Sea Main Basin. These measures would better motivate fishermen for mutual rule compliance, which is a prerequisite for a sustainable cod fishery.     

Adhesion of foulings on surface energy of silicone rubber coatings

INTRODUCTIONBiologicalfoulingonthehullsofshipsandothersubmergedmarinestructurescausesgreatha~s.Inadditiontodecreasingship'sspeed,andincreasingitsfuelconsumption,biologicalfoulingalsoincreasestheweightofnavigationalbuoys,interfereswithoperatingequipmentandsounddevices,clogsseawaterpipingsystems,adverselyaffectsheat-exchangerperformance,andpromotescorrosionofmetalsurface(HuangandCat,1984).UPtothepresent,antifoulingpaintshaveachievedtheireffectivenessbyreleasingattheirsurfacebiocides,allcom…     

Field Study on the Behavior of Destructive and Non-Destructive Piles Under Compression

This paper presents a series of full-scale load tests on long bored piles instrumented with strain gauges along the shafts, including eight field tests of piles loaded to failure and one non-destructive pile load test. The load-displacement response, skin friction, end resistance, and the threshold of the pile-soil relative displacement for fully mobilizing skin resistance were discussed. A simple softening model was proposed to describe the degradation behavior of the skin friction along the pile-soil interface and the load-displacement relationship developed at the pile base. It is found that the shaft resistance degradation investigated in the non-destructive load test only occurs at a shallow depth, and the skin friction of deeper soil is not fully developed. However, unlike the results of the non-destructive load tests, the softening is accompanied by a reduction in skin friction and observed to be along the whole pile depth. The thresholds of pile-soil relative displacement for fully mobilizing skin resistances in different soils have been found to be in the range 0.6% to 2.4% of the pile diameter. Moreover, in practical applications, a bilinear model is assumed to be feasible in analyzing the load-settlement relationship developed at the end of non-destructive pile, whereas the load transmission curve of the soils below the pile base corresponds to a softening model in the field tests of piles loaded to failure.