A rational approach to seepage flow effects on bottom friction beneath random waves

The bottom friction beneath random waves is predicted taking into account the effect of seepage flow. This is achieved by using wave friction factors for rough turbulent, smooth turbulent and laminar flow valid for regular waves together with a modified Shields parameter which includes the effect of seepage flow. Examples using data typical to field conditions are included to illustrate the approach. The analytical results can be used to make assessment of seepage effects on the bottom friction based on available wave statistics. Generally, it is recommended that a stochastic approach should be used rather than using the rms values in an otherwise deterministic approach.     

海底双相随机介质声反射的SVM神经网络分类识别研究

考虑海底沉积介质为双相介质,为了更好地模拟实际海底底质的不均匀性,将随机介质理论引入双相介质理论。首先,通过基于随机-双相介质理论的高阶有限差分数值技术模拟计算海底底质分别为泥质砂、泥、泥质砾时的地震反射波信号。然后利用小波变换分别求取不同底质的一次反射波的包络作为其特征向量,最后利用基于粒子群智能算法优化的支持向量机神经网络对这些反射波信号进行分类识别。为了进一步考察所用方法的抗噪能力,对正演得到的海底底质反射波信号分别加入10%、30%、50%的高斯白噪音之后再进行分类,支持向量机仍然取得了较好的分类预测效果。基于上述正演模拟及分类识别方法的论证,提出了一套行之有效的微机软件模拟海底沉积物分类识别的一般化流程,这将有利于开展海底沉积物反射特征的进一步研究。     

琼东南盆地深水区构造热演化特征及其影响因素分析

To reveal the tectonic thermal evolution and influence factors on the present heat flow distribution, based on 154 heat flow data, the present heat flow distribution features of the main tectonic units are first analyzed in detail, then the tectonic thermal evolution histories of 20 profiles are reestablished crossing the main deep-water sags with a structural, thermal and sedimentary coupled numerical model. On the basis of the present geothermal features, the Qiongdongnan Basin could be divided into three regions: the northern shelf and upper slope region with a heat flow of 50–70 m W/m2, most of the central depression zone of 70–85 m W/m2, and a NE trending high heat flow zone of 85–105 m W/m2 lying in the eastern basin. Numerical modeling shows that during the syn-rift phase, the heat flow increases generally with time, and is higher in basement high area than in its adjacent sags. At the end of the syn-rift phase, the heat flow in the deepwater sags was in a range of 60–85 m W/m2, while in the basement high area, it was in a range of 75–100 m W/m2. During the post-rift phase, the heat flow decreased gradually, and tended to be more uniform in the basement highs and sags. However, an extensive magmatism, which equivalently happened at around 5 Ma, has greatly increased the heat flow values, and the relict heat still contributes about 10–25 m W/m2 to the present surface heat flow in the central depression zone and the southern uplift zone. Further analyses suggested that the present high heat flow in the deep-water Qiongdongnan Basin is a combined result of the thermal anomaly in the upper mantle, highly thinning of the lithosphere, and the recent extensive magmatism. Other secondary factors might have affected the heat flow distribution features in some local regions. These factors include basement and seafloor topography, sediment heat generation, thermal blanketing, local magmatic injecting and hydrothermal activities related to faulting and overpressure.     

Nonlinear optimization method of ship floating condition calculation in wave based on vector

Ship floating condition in regular waves is calculated. New equations controlling any ship＇s floating condition are proposed by use of the vector operation. This form is a nonlinear optimization problem which can be solved using the penalty function method with constant coefficients. And the solving process is accelerated by dichotomy. During the solving process, the ship＇s displacement and buoyant centre have been calculated by the integration of the ship surface according to the waterline. The ship surface is described using an accumulative chord length theory in order to determine the displacement, the buoyancy center and the waterline. The draught forming the waterline at each station can be found out by calculating the intersection of the ship surface and the wave surface. The results of an example indicate that this method is exact and efficient. It can calculate the ship floating condition in regular waves as well as simplify the calculation and improve the computational efficiency and the precision of results.     

1321号台风“蝴蝶”强度变化特征和影响因素分析

利用NCEP/NCAR全球再分析格点资料（空间分辨率1°×1°）、台风实况资料及海南省气象台站观测资料,选取1321号台风＂蝴蝶＂为研究个例,从天气学原理高低空形势及动力、热力学物理量等多角度分析了＂蝴蝶＂强度演变特征及影响因素.研究结果表明,副热带高压与高空西风槽是影响此次台风的主要大尺度天气系统,弱冷空气南侵、南海海温偏高及越赤道气流强盛是＂蝴蝶＂迅速加强的重要原因.西风槽引导弱冷空气南侵使得台风外围环流气压梯度增加,斜压不稳定状态加剧;南海海温达到29℃,海温偏高使台风区域大气层结降低,深热对流发展;105°E越赤道气流强盛为台风提供了充沛水汽和能量.三者共同作用促使台风强度突然增强.另外,低层涡度、高层散度、湿位涡及水汽通量等物理量能够较好地表征＂蝴蝶＂强度变化特征.低层辐合流入、高层辐散流出为台风的加强提供了动力条件;湿位涡下负上正表明大气热力层结不稳定;水汽通量增加表明水汽条件充足.良好的动力条件、热力条件与水汽条件共同作用,使得＂蝴蝶＂在短时间内迅速加强为强台风.     

新疆克拉玛依强下坡风暴的机理研究

利用美国中尺度数值模式 WRF 对2013年3月7—8日克拉玛依强风进行了模拟,对下坡风发生、发展和结束3个阶段的三维结构特征进行了分析,并由此提出克拉玛依强下坡风的形成机制模型：上游地区出现中高层西南风、低层西北风并伴有强冷平流的配置,当风速不断增大时,气流能够翻越加依尔山在背风坡侧形成重力波,重力波相位向气流上游方向倾斜产生非线性效应,促进了波不稳定区域的形成并导致波破碎,形成湍流活跃层,不断把上层的能量向下传播;克拉玛依中低层形成三层夹心的大气层结稳定度分布,出现明显的过渡气流带从而导致强下坡风的形成;南北风分量在低层和中层符号相反,形成了临界层,不断吸收上层波能量并向地面传送,强下坡风暴不断维持发展。最后利用2006—2012年克拉玛依33个强下坡风过程中的探空观测资料对提出的形成机制进行了验证。     

结合地形因子与分层策略的喀斯特地区无人机影像分类

西南喀斯特山区地形起伏较大,地物分布较为破碎,致使传统的光谱特征一次分类方法的精度较低。本文基于高分辨率无人机正射影像和地形指标,充分利用无人机遥感影像空间特征、光谱特征、纹理特征及地形特征,采取面向对象CART决策树算法与分层策略提取了研究区土地覆盖类型。研究表明,结合空间地形因子和分层策略的方法减少了破碎区地物间的相干扰,故具有较高的分类精度,总体分类精度达91.2%,Kappa系数为0.87,较传统一次分类精度提高了9.8%,Kappa系数提高了0.13。该方法对西南喀斯特地区土地覆盖解译精度较好,可为土地利用监测提供参考。     

北京门头沟区涧沟泥石流危险性调查评价

涧沟泥石流位于北京市门头沟区潭柘寺镇西北,本文分析了涧沟泥石流的基本特征和形成条件,预测了不同暴雨频率下的泥石流流量,结合泥石流的易发程度及可能造成的损失,评价了泥石流隐患的危险性,并提出了防治建议。     

自然泥石流与矿渣泥石流复合效应与防治对策

石棉县后沟是一条典型的自然泥石流和矿渣泥石流并存的泥石流沟。本文以石棉后沟为例,结合早期自然泥石流、矿产开采以来矿渣泥石流、以及2013年7 4复合型泥石流,总结了自然泥石流和矿渣泥石流的复合效应,包括泥石流物源补给的多元效应、泥石流发展演化的逆转效应、泥石流起动发生的复杂效应、泥石流动力沿程的放大效应、泥石流致灾破坏的链式效应。对照泥石流对已建防治工程的破坏,提出了自然泥石流和矿渣泥石流复合型泥石流沟防治对策,建议充分利用起动位置和物源集中补给位置的差异,加强对中上游及支沟自然泥石流起动和运动的拦挡防治,最大限度减小自然泥石流对下游矿渣防护工程的基底侵蚀和冲击破坏,从而保障综合防治工程的有效性。     

江苏平原地区(淮河流域)潜水碘含量控制因素探讨

本文通过工作区潜水碘含量的分布特点,与所处土壤、水文地质条件、地形地貌等一起进行综合分析,对地下水中碘的控制因素有了一个全新的认识:与前人认为地下水中碘的含量与有机质成正比的观点不同的是,本文认为地下水中碘的含量与有机质含量无固定关系,但有机质有助于促进水溶性碘的增加,相似水文地质条件下成正比;地下水径流条件对潜水碘含量影响重大,径流条件较好的丘陵、岗地往往较低,地势低平、径流条件较差的洼地和泛滥沉积区往往为高碘地区;相同水文地质条件下,地下水中的碘含量与土壤中的含量成正比;碘的另一重要特征是在地下水中的浓度较为稳定,随时间、开采而变化不大。