疏勒河流域泥沙分布规律及水沙关系研究

泥沙是影响河流健康和水环境的重要因素之一,受气候变化和人类活动的影响,流域水文要素和下垫面条件发生了较大变化,尤其是实施大规模的水土保持措施后,部分河流的泥沙含量大幅减少,但在河西内陆河流域发源于祁连山西端的疏勒河流域,受降水条件和人类活动的影响,河流泥沙呈增加趋势。本文应用疏勒河流域实测长系列水文资料,采用水文统计法、差积曲线法、趋势检验法、突变检验法、非线性复相关模型法等方法,分析了流域泥沙时空分布规律及水沙关系,结果表明：疏勒河干流昌马堡站年输沙量为333.5×104 t,至下游潘家庄站减少到223.5×104 t;党河党城湾站年输沙量为76.56×104 t,至下游沙枣园站增加到121.3×104 t;疏勒河干流输沙量主要集中在汛期7～8月,占全年的81.9 %～84.0 %,党河流域输沙量主要集中在4-8月,占全年的92.3 %;流域泥沙变化总体呈增加趋势,突变点1998年以后,年输沙量增加了86.3 %～148.2 %。建立了潘家庄站降水～泥沙、径流～泥沙以及年输沙量～年径流量～年最大洪峰流量关系模型,相关关系较好,相关系数达到0.717～0.858。流域出山口以上对泥沙的影响因素主要是降水,出山口以下主要是修建水库、水电站、引水工程、河道采砂等人类活动影响。随着国家对内陆河流域祁连山和河西走廊的日益关注,以及全国河长制的推行,河流生态健康已经提上日程,研究疏勒河流域泥沙分布规律及水沙关系,对国家实施西部生态安全战略、区域生态环境修复治理、水资源可持续利用等具有重要意义。     

中国西部区域GRACE卫星重力变化

针对研究中国西部长期重力变化的问题,该文利用GRACE月重力场模型,基于Slepian变换构建中国西部区域局部重力场,并采用GIA和GLDAS等模型扣除相应误差,通过时间序列分析方法得到该区域2003—2013年卫星重力变化。结果表明,东天山呈现负重力变化,可能由区域冰川消融引起的;西天山的正重力变化,应与冰川小幅增加和构造运动引起的壳幔物质积累有关;青藏高原内陆正重力变化可能由区域地壳抬升、粘弹性地壳的构造应变以及壳幔物质的质量迁移与积累引起;青藏高原边界区域的负重力变化,应与冰川加速消融以及地下水抽取有关。Slepian方法较好地克服了滤波平滑处理带来的重力变化信号压制及细节平滑,可为中国西部的地壳运动、地震活动和气候变化等研究提供数据支撑。     

论山东省矿山地质环境现状及存在问题

山东省是矿产资源大省,资源储量丰富,开采历史悠久,开发强度较大。矿产资源的开发在保障经济社会发展的同时,也引发了较多的矿山地质环境问题,破坏了局部生态环境,影响了人民生产生活。为推进生态山东、美丽山东建设步伐,谋划一个时期内的矿山地质环境保护与治理工作,根据国土资源部等五部局的统一部署,2017年山东省率先在全国开展了山东省矿山地质环境详细调查工作,共完成高精度遥感解译157 900km~2,矿山地质环境调查34 290km~2,调查矿山9 672座,水土样测试各200余件,取得了大量翔实的矿山地质环境调查数据。该文在深入分析调查成果的基础上,高度概括了由于矿产资源开采引发的地形地貌景观破坏、采煤塌陷、非煤矿山采空区及废弃矿井、占压土地资源等主要矿山地质环境问题的分布、规模、危害和治理工作开展等情况;客观剖析了山东省地质环境保护与治理存在的主要问题;科学预测了矿山地质环境保护与治理工作发展趋势,并针对性地提出了对策建议。     

Experimental study on the cyclic behavior of loose calcareous sand under linear stress paths

Abstract

Hollow cylinder torsional shear tests on loose isotropically and anisotropically consolidated calcareous sand were conducted to investigate the cyclic behavior under three different linear stress paths, including horizontal line, oblique line, and vertical line stress paths, in a coordinate system of the normal stress difference and the horizontal shear stress. The dominant strain components of the isotropically consolidated specimens are affected by the stress paths. With increasing consolidation stress ratio, axial strain gradually becomes the dominant strain component under the three different stress paths. The cyclic strength of the isotropically consolidated specimens under the three different stress paths are almost the same, while for the anisotropically consolidated specimens, the cyclic strengths are strongly affected by the stress paths. These results indicate that conventional cyclic triaxial tests may overestimate cyclic strength in some cases. Irrespective of the stress paths and cyclic stress ratios, the terminal residual excess pore pressure ratio decreases with increasing consolidation stress ratio. Moreover, an empirical equation is proposed to describe the relationship between the normalized shear work and the normalized residual excess pore pressure ratio. The comparative study reveals that the relationship proposed for silica sand is not suitable for the dynamic analyses of calcareous sand.     

Aspects of the measurement of the acoustic transfer function in a cavitation tunnel

Model scale experiments represent one of the most effective, and probably the most commonly used, approaches for the study of cavitating propeller noise. Despite this, the acquirement of consistent data of propeller noise from tests in model scale facilities is still a challenging task. Data collected with such an approach are usually affected by several scale effects and facility related issues which make such experiments still very complex. Among others, the effect of the facility itself as acoustical surrounding must be carefully addressed in order to properly estimate propeller source levels in ideal free field conditions. This is currently carried out, when possible, by measuring facility transfer functions and applying such functions as a correction to measured noise spectra. The development of robust procedures for the measurement of these transfer functions is thus very important. In the present work, this problem is addressed by discussing in details techniques, merits and possible problems related to this topic.     

国内外赤潮的发展趋势与研究热点

本文以最近10多年的赤潮典型事件、研究进展为主要依据,综合论述了国内外赤潮发生的新特点。分别从组学技术、食品安全与公共健康、赤潮生物学、赤潮监测与预测预报、赤潮应急处置等几方面,介绍了目前国际上该领域的研究热点。本文还回顾了我国赤潮研究的主要发展历程,结合科技部2017年启动的国家重点研发计划"我国近海致灾赤潮形成机理、监测预测及评估防治技术"项目,展望了我国赤潮研究的未来发展趋势。     

Characterizing the Spatio-temporal Dynamics and Variability in Climate Extremes over the Tibetan Plateau during 1960-2012

Extreme climate events play an important role in studies of long-term climate change. As the Earth’s Third Pole, the Tibetan Plateau (TP) is sensitive to climate change and variation. In this study on the TP, the spatiotemporal changes in climate extreme indices (CEIs) are analyzed based on daily maximum and minimum surface air temperatures and precipitation at 98 meteorological stations, most with elevations of at least 4000 m above sea level, during 1960-2012. Fifteen temperature extreme indices (TEIs) and eight precipitation extreme indices (PEIs) were calculated. Then, their long-term change patterns, from spatial and temporal perspectives, were determined at regional, eco-regional and station levels. The entire TP region exhibits a significant warming trend, as reflected by the TEIs. The regional cold days and nights show decreasing trends at rates of -8.9 d (10 yr)^-1 (days per decade) and -17.3 d (10 yr)^-1, respectively. The corresponding warm days and nights have increased by 7.6 d (10 yr)^-1 and 12.5 d (10 yr)^-1, respectively. At the station level, the majority of stations indicate statistically significant trends for all TEIs, but they show spatial heterogeneity. The eco-regional TEIs show patterns that are consistent with the entire TP. The growing season has become longer at a rate of 5.3 d (10 yr)^-1. The abrupt change points for CEIs were examined, and they were mainly distributed during the 1980s and 1990s. The PEIs on the TP exhibit clear fluctuations and increasing trends with small magnitudes. The annual total precipitation has increased by 2.8 mm (10 yr)^-1 (not statistically significant). Most of the CEIs will maintain a persistent trend, as indicated by their Hurst exponents. The developing trends of the CEIs do not show a corresponding change with increasing altitude. In general, the warming trends demonstrate an asymmetric pattern reflected by the rapid increase in the warming trends of the cold TEIs, which are of greater magnitudes than those of the warm TEIs. This finding indicates a positive shift in the distribution of the daily minimum temperatures throughout the TP. Most of the PEIs show weak increasing trends, which are not statistically significant. This work aims to delineate a comprehensive picture of the extreme climate conditions over the TP that can enhance our understanding of its changing climate.     

Experimental investigation of blade and propeller loads: Steady turning motion

This paper is the continuation of the work described in [14], dedicated to the presentation of the results of propeller performance in behind-hull during straight ahead motion obtained by a novel experimental set-up for the measurements of single blade loads. In the present case, the study shows and discusses the single blade and propeller loads developed during steady turning conditions, that were simulated by means of free running, self propelled maneuvering tests for a twin screw configuration. Maneuvering conditions are critical for the ship propulsion system, because the performance of the propeller and the side effects related to its functioning (propeller–hull induced pressure and vibrations, noise) are completely different with respect to the design condition in straight ahead motion. Thrust and torque and generation of in-plane loads (force and moments), developed by the blade during the period, evolve differently for the two propellers, due to different propeller–wake interactions. The understanding and the accurate quantification of propeller loads, in these realistic operative scenarios, are pivotal to design low emission and comfortable ships, fulfilling the requirements of safety and continuity of operations at sea. The analysis is carried out revisiting the investigation in [14] for three different speeds (F_N = 0.26, 0.34 and 0.40) and a large set of rudder angles that span moderate and tight maneuvers.     

Trends of sea surface temperature and sea surface temperature fronts in the South China Sea during 2003–2017

The trends of the sea surface temperature(SST) and SST fronts in the South China Sea(SCS) are analyzed during2003–2017 using high-resolution satellite data. The linear trend of the basin averaged SST is 0.31°C per decade,with the strongest warming identified in southeastern Vietnam. Although the rate of warming is comparable in summer and winter for the entire basin, the corresponding spatial patterns of the linear trend are substantially different between them. The SST trend to the west of the Luzon Strait is characterized by rapid warming in summer, exceeding approximately 0.6°C per decade, but the trend is insignificant in winter. The strongest warming trend occurs in the southeast of Vietnam in winter, with much less pronounced warming in summer. A positive trend of SST fronts is identified for the coast of China and is associated with increasing wind stress. The increasing trend of SST fronts is also found in the east of Vietnam. Large-scale circulation, such as El Ni?o, can influence the trends of the SST and SST fronts. A significant correlation is found between the SST anomaly and Ni?o3.4 index, and the ENSO signal leads by eight months. The basin averaged SST linear trends increase after the El Ni?o event(2009–2010), which is, at least, due to the rapid warming rate causing by the enhanced northeasterly wind. Peaks of positive anomalous SST and negatively anomalous SST fronts are found to co-occur with the strong El Ni?o events.     

丁字湾近岸海域表层沉积物粒度特征及沉积动力环境

根据丁字湾近岸海域126个表层沉积物样品粒度分析结果,对沉积物类型和粒度参数分布进行了总结。在此基础上,利用粒径趋势分析模型(GSTA)和沉积动力判别图解,探讨了表层沉积物的运移趋势及沉积水动力规律。结果表明,丁字湾近岸海域表层沉积物类型共有8种,其中砂、砂质粉砂和粉砂分布最广泛;平均粒径具有从岸向海逐渐变细的特征,分选性、偏度和峰度分别具有较差—差、正偏—极正偏、中等的特征;粒度运移趋势分析反映出湾口海岸附近泥沙由两侧向湾口中心运移,远离海岸泥沙由北西向南东偏东方向运移;沉积动力判别图解揭示出丁字湾海域沉积水动力具有整体较强,由岸向海方向逐渐减弱的特征。