Factors driving riverbed scouring and sedimentation in the Bayangaole to Toudaoguai reaches of the Upper Yellow River

The Inner Mongolia reaches of the Yellow River face problems of severe sedimentation caused by a variety of complex factors. The sedimentation process in those reaches has been characterized using the sediment balance method, and the key factors affecting the process have been analyzed using the correlation analysis method. The results show that during the period 1952–2012 the Bayangaole (Bayan Gol) to Toudaoguai reaches in Inner Mongolia have undergone successive processes of accumulative sedimentation, then relative balance, and then accumulative sedimentation once again. The total annual sedimentation is 12.0341×10⁸ m³, of which accumulations from July to October account for 95.1% and the reaches from Sanhuhekou to Toudaoguai account for 98.5%. The main factor affecting scouring and sedimentation of the Bayangaole to Sanhuhekou reaches is the combined water and sediment condition. The critical conditions for equilibrium are an incoming sediment coefficient < 0.007 kg·s·m^–6 and a flow discharge > 700 m³·s^–1. The main factor affecting scouring and sedimentation of the Sanhuhekou to Toudaoguai reaches is the incoming sediment from the tributaries on the south bank and the combined water and sediment condition of the main stream. The critical conditions of the main stream for maintaining equilibrium status are a flow discharge of the main stream exceeding 800 m³·s^–1 and a comprehensive incoming sediment coefficient < 0.005 kg·s·m^–6. The incoming sediment from the tributaries has little impact on the main stream when the annual sediment load is less than 0.1×10⁸ t. The incoming sediment coefficient of the main stream and the incoming sediment from the tributaries both play vital roles in the riverbed evolution of the Inner Mongolia reaches, but the latter contributes the most.     

Effect of stocking density on water quality and (Growth,Body Composition and Plasma Cortisol Content) performance of pen-reared rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>)

The goal of the study was to examine the effect of stocking density on the water quality of culture area, as well as the growth, body composition and cortisol content of rainbow trout（Oncorhynchus mykiss）. Pen-reared trout were stocked in densities of 40, 60, 80 fish individuals m^-3(4.6, 6.6, 8.6 kg m^-3, SD1, SD2 and SD3 groups, respectively) for 300 days. Compared to the water from SD1 and SD2, that from SD3 exhibited significantly higher NH₄⁺-N content and COD（chemical-oxygen-demand）, and a significant reduction of dissolved oxygen in day 180(40.6 kg m^-3). Stocking density was significantly associated with body weight, standard length, VSI（viscerosomatic index）, CF（condition factor） and FC（food coefficient） in group SD3, particularly in day 240 and day 300(45 or 49.3 kg m^-3). Increased crude fat and decreased crude protein were displayed in high density group when the density reached to 36 kg m^-3. As a cumulative effect of density-related stress, VSI, CF, FC, moisture, and crude protein content varied over time in each density group（SD1, SD2, and SD3）. In summary, trout exhibited a better growth performance in low density(26.3 kg m^-3) than those reared in high densities(36 and 45 kg m^-3). The results indicate that rainbow trout（114.44 g ± 6.21 g, 19.69 cm ± 0.31 cm） initially stocked in 6.6 or 8.6 kg m^-3 should be lightened to less than 36 kg m^-3 after an intensive rearing for 240 days.     

The modeled atmospheric and oceanic response to the South China Sea SST anomaly

The sensitivity of the global atmospheric and oceanic response to sea surface temperature anomaly (SSTA) throughout the South China Sea (SCS) is investigated using the Fast Ocean-Atmosphere Model (FOAM). Forced by a warming SST, the experiment explicitly demonstrates that the responses of surface air temperature (SAT) and SST exhibit positive anomalous center over SCS and negative anomalous center over the Northern Pacific Ocean (NPO). The atmospheric response to the warm SST anomalies is characterized by a barotropical anomaly in middle-latitude, leading to a weak subtropical high in summer and a weak Aleutian low in winter. Accordingly, Indian monsoon and eastern Asian monsoon strengthen in summer but weaken in winter as a result of wind convergence owing to the warm SST. It is worth noting that the abnormal signals propagate poleward and eastward away in the form of Rossby Waves from the forcing region, which induces high pressure anomaly. Owing to action of the wind-driven circulation, an anomalous anti-cyclonic circulation is induced with a primary southward current in the upper ocean. An obvious cooling appears over the North Pacific, which can be explained by anomalous meridional cold advection and mixing as shown in the analysises of heat budget and other factors that affect SST.     

西藏改则县多不扎地区上侏罗统对望山组的建立及意义

对望山组是发育在羌南板块南缘的一套岩石组合,以安山岩、流纹岩、玄武质凝灰岩为主,有少量的玄武安山岩夹层,具有明显的岩浆喷出相和沉积相韵律分布的特点。利用LA-ICP-MS同位素定年技术对对望山组安山岩中的锆石进行了U-Pb同位素测年,获得锆石的~(206)Pb/~(238)U年龄加权平均值为150.5±0.6Ma,表明对望山组的形成时代为晚侏罗世中晚期,在详细剖面测制和区域对比的基础上建立了对望山组。对望山组的建立对完善班公湖-怒江缝合带的地层系统、探讨班公湖-怒江洋的晚侏罗世构造演化具有重要的地质意义。     

Numerical Analysis of Gravity Coring Using Coupled Eulerian-Lagrangian Method and a New Corer

The shortcomings of gravity corers in sampling marine sediments have been observed extensively in various field tests. In order to optimize the coring, this article provides an alternative numerical way to model the gravity coring and analyze the sampling effect. Based on this analysis, a new hydraulic hammer corer is devised. A coupled Eulerian-Lagrangian method with capability of simulating the problem involving extreme deformation, penetration is used to simulate the coring process. The results show that the hydrostatic pressure and deviator stress increase and reach their peak when the pile tip is slightly above or at the level of the observation point and then drop rapidly when the pile tip slides below the observation point. In addition, the stress path indicates that the soil element sustains plastic compression before yielding and then expands until recovering to the original state. The obvious “under-sampling” phenomenon is also well-captured by the finite element model.     

藏北羌塘南部埃迪卡拉系达布热组的建立及其地质意义

羌塘位于青藏高原腹地,构造上处于冈瓦纳大陆北缘。因其特殊的构造位置,羌塘地体的起源及构造演化对于探讨青藏高原的早期形成演化、冈瓦纳大陆裂解,以及特提斯洋演化等关键科学问题至关重要。最近,在羌塘南部达布热地区发现一套碎屑岩夹玄武岩的岩石组合,碎屑岩具有低成分成熟度的特点,虽然岩石发生了低绿片岩相变质,但仍然保留了原岩类复理石沉积的特点。根据碎屑锆石定年结果,该套地层中碎屑锆石的最年轻年龄为550Ma左右。此外,该套地层中玄武岩夹层的测年结果表明,该套地层形成于埃迪卡拉纪(约550Ma)。结合地层剖面及区域地层对比,建立了埃迪卡拉纪达布热组。达布热组是羌塘地区首次发现的埃迪卡拉纪地层,该组地层的建立为探讨冈瓦纳大陆北缘构造演化提供了重要线索。     

藏北羌塘中部日湾茶卡地区晚三叠世安山岩与闪长质包体岩石成因及地质意义

龙木错-双湖-澜沧江缝合带将羌塘板块划分为南、北2个次级板块,在缝合带两侧大规模发育晚三叠世岩浆作用,并伴随大量的高压超高压变质岩。在缝合带以南的日湾茶卡地区识别出一套安山岩,其中发育大量的暗色闪长质捕虏体,锆石U-Pb测年结果在安山岩中获得了364.7±1.9Ma和223.9±1.3Ma两组年龄信息,锆石原位Hf同位素测试结果εHf(t)分别为+7.22~+8.69和-5.94~-4.14。结合羌塘中部已有的研究成果,认为闪长质捕虏体形成于晚泥盆世洋壳俯冲背景,是地幔楔部分熔融底侵至地壳的产物;而安山岩形成于晚三叠世碰撞后伸展背景,是深部板片断离机制下深俯冲陆壳边缘一侧熔体混染晚泥盆世新生地壳的产物。安山岩中闪长质捕虏体的发现支持了俯冲带作为大陆生长的重要场所的观点。     

The Derivation and Validation of TBM Disc Cutter Wear Prediction Model

The problem of disc cutter wear is inevitable when shield or TBM excavating hard rock for a long distance, thus, the study of disc cutter wear model has an important project value on predicting its service life and replacement opportunity. It is put forward by analyzing disc cutter wear mechanism that the main wear form is abrasive wear, which is based on plastic removal mechanism. Then, disc cutter wear rate and linear wear rate prediction models are obtained by approximate calculation and mathematical deduction, which are based on Rabinowicz equation and CSM model. At last, the two models are verified through field test data from three projects, and the results show that the prediction model can accurately reflect the real wear situation of disc cutter.     

Geochemical Characteristics and Tectonic Significance of Aoyougou Group Basalts in Western North Qilian

The North Qilian orogenic belt is a typical plate suture zone, which is studded with numerous different sizes of fragments of micro-continental crust consisting of pre-Sinian metamorphic rocks and the North Qilian orogenic belt provides important study carrier for studying the pre-orogenic tectonic process of the North Qilian. The relatively complete volcanic-clastic-carbonate rocks formation of Zhulongguan Group, Changchengian System, Mesoproterozoic are distributed in the Kawa-Qiqing area, Western North Qilian orogenic belt. Geochemical characteristics of the Aoyougou Group basalts in the North Qilian indicated that the contents of major element were relatively stable, high K₂O contents(4.27%~6.07%), TFe₂O₃(10.49%~13.01%),TiO₂(1.96%~2.90%)and middle MgO(5.37%~6.71%,Mg^# 48~51), CaO(2.57%~5.51%)content. Thus, the Aoyougou Group basalts belong to potassium alkaline basalt. The contents of Cr and Ni of the basalts decreased with the decreasing of Mg^#, and there was a positive correlation between CaO and CaO/Al₂O₃, Furthermore, the Eu anomaly of samples was slightly negative, high contents of high field strength elements (HFSE, Nb, Ta, Ti), and the ratios of Gd/Yb(2.5~3.0), Zr/Y(8.6~10.2), Ta/Yb(0.96~1.23), Ti/Yb(5 074~6 021), Zr/Yb(81~97), Ce/Nb(1.87), Zr/Nb(6.41)indicated that the Aoyougou Group basalts had obvious OIB-type magmatic affinity. In combination with the regional geological background, the study results showed that Aoyougou Group alkaline basalt generated from deep enrichment mantle similar to the source of OIB, with fractional crystallization of olivine and monoclinic pyroxene and a certain degree of contamination of continental crust in the process of magmatism, formed in the background of continental rift, might response to the Proterozoic Columbia supercontinent rifting, which further provides important petrological evidences for the relationship between North China Craton rifting events and Columbia supercontinent rifting during Proterozoic.