Estimation of snow and glacier melt contribution to Liddar stream in a mountainous catchment,western Himalaya: an isotopic approach

Snow- and glacier-dominated catchments in the Himalayas are important sources of fresh water to more than one billion people. However, the contribution of snowmelt and glacier melt to stream flow remains largely unquantified in most parts of the Himalayas. We used environmental isotopes and geochemical tracers to determine the source water and flow paths of stream flow draining the snow- and glacier-dominated mountainous catchment of the western Himalaya. The study suggested that the stream flow in the spring season is dominated by the snowmelt released from low altitudes and becomes isotopically depleted as the melt season progressed. The tracer-based mixing models suggested that snowmelt contributed a significant proportion (5–66?%) to stream flow throughout the year with the maximum contribution in spring and summer seasons (from March to July). In 2013 a large and persistent snowpack contributed significantly (～51?%) to stream flow in autumn (September and October) as well. The average annual contribution of glacier melt to stream flow is little (5?%). However, the monthly contribution of glacier melt to stream flow reaches up to 19?% in September during years of less persistent snow pack.     

基于正交拟群的流密码算法

利用正交拟群的特点, 克服Edon80的弱点, 设计了称为Double40的二进制加法同步流密码算法. 它基于一对8阶相互正交的自正交拟群, 使得Johansson和Hell的密钥恢复攻击对Double40无法奏效.     

基于Pareto优化理论的多目标超椭梯度线圈设计

磁共振系统梯度线圈设计是一个多目标优化问题,在设计时需要综合考虑能耗、磁场能、线性度等设计要求.这些设计要求通常难以同时获得极小解,因此在设计梯度线圈时需要权衡线圈的各方面的设计需求.本文基于柱面可展性和流函数设计方法,结合Pareto优化方法实现了在超椭圆柱设计表面上梯度线圈的多目标设计.分别分析了磁场能、能耗目标对梯度线圈线性度、线圈构型的影响;并在Pareto解空间中分析各目标的相互变化关系,通过数值算例验证了该方法在超椭梯度线圈设计时的有效性与灵活性.优化结果显示,在满足线性度误差小于5%,能耗与磁场能分别小于用户设定值的设计约束下,梯度线圈的多目标设计存在多个局部优化解.该方法可以直观地比较相同目标函数值的情况下各单目标的具体表现,有利于实现不同的设计要求下梯度线圈的最终定型设计.     

Turbulent flow and loading on a tidal stream turbine by LES and RANS

This paper presents results from numerical simulations of a 3-bladed horizontal axis tidal stream turbine. Initially, Reynolds Averaged Navier Stokes (RANS) k–ω Shear Stress Transport eddy-viscosity and Launder–Reece–Rodi models were used for code validation and testing of a newly implemented sliding mesh technique for an unstructured finite volume code. Wall- and blade-resolved large-eddy simulations (LES) were then performed to study the complete geometry at various tip speed ratios (TSR). Thrust and power coefficients were compared to published experimental measurements obtained from a towing tank for a range of TSR (4, 5, 6, 7, 8, 9 and 10) at a fixed hub pitch angle. A strong meandering is observed downstream of the supporting tower due to interaction between the detached tip vortices and vortex shedding from the support structure. The wake profiles and rate of recovery of velocity deficit show high sensitivity to the upstream turbulence intensities. However, the mean thrust and power coefficients were found to be less sensitive to the upstream turbulence. Comparisons between RANS and LES are also presented for the mean sectional blade pressures and mean wake velocity profiles. The paper also presents an overview of modelling and numerical issues relating to simulations for such rotating geometries.     

不同底质、饵料种类和日投饵量对管角螺幼螺生长的影响

通过单因子试验,研究了不同底质、饵料种类和日投饵量对管角螺生长的影响.结果表明:不同底质对幼螺存活率无显著影响(P>0.05),但对其生长影响显著,有底质比无底质效果佳,尤以粗沙底质组为宜;4种饵料对幼螺的存活率和生长率均有影响,以投喂缢蛏和冰鲜杂鱼存活率最大(96.67%);生长效果以特定生长率作为指标进行比较,依次为:缢蛏组(0.54%)>冰鲜杂鱼(0.34%)>软饵(0.18%)>硬饵(0.07%)>不投饵(0.06%);日投饵量对幼螺存活率无显著性差异(P>0.05),但对其生长影响显著,日投饵量以体重的4%效果最佳.     

有限区域求解流函数和速度势的迭代调整方法及其收敛性分析

全球区域求解流函数和速度势的解是唯一的,但有限区域内,由于受区域边界条件限制,流函数和速度势的计算以及风场的分解不是唯一的,减小或消除边界不确定对结果的影响是有限区域求解流函数和速度势以及分解风场最重要的问题．该文在Endlich迭代调整思想上,提出了能准确求解有限区域流函数和速度势且对边界条件要求较低的迭代调整方法．该方法也能准确地分解和重建风场,且风场重建的误差非常小．对该迭代方法的收敛性进行分析,发现其收敛性与不同方向网格的格距和调整系数有关．最后将该方法应用到Arakawa A-D网格和不规则区域,验证了该方法的可靠性．     

油-气两相流管线系统振动分析及减振控制

针对油-气主管线系统的油-气两相流振动问题,建立了管线系统的动力学模型.分析计算油-气两相流在管道内的动力学特性,判断其流型;根据动量定理得到了管线各处受力的时间历程,从而确定管道系统受到的实际动载荷并求出其振动时间历程响应;分析管线系统的模态和影响振动模态的关键因素,采用合理加强原有支撑刚度和在恰当部位增加新支撑等措施,使管道系统的振动得到控制.分析结果与现场实测数据对比,验证了此振动分析方法的有效性.     

太平洋多金属结核区深海沉积物细菌多样性分析

从太平洋多金属结核区东区两个站点沉积物中直接提取环境总基因组,通过PCR及TA克隆分别构建了16S rRNA基因文库．经序列分析结果表明,2个文库共93个克隆分属13个类群,包括α变形菌纲、β变形菌纲、γ变形菌纲、δ变形菌纲、浮霉菌门、酸杆菌门、噬纤维菌-黄杆菌-拟杆菌群、硝化螺旋菌门、放线菌门、绿弯菌门、厚壁菌门、异常球菌-栖热菌门和OP11类群．其中,γ变形菌纲的细菌在2个站点沉积物中都是优势种群,变形菌纲、浮霉菌门、放线菌门、噬纤维菌-黄杆菌-拟杆菌群、硝化螺旋菌门是2个站点共有的细菌类群．DOTUR和LIBSHUFF数据分析结果表明,两个站点的沉积物均具有丰富的细菌多样性,并且物种组成具有显著性差异．     

Ablation of CdTe with 100 µs Nd:YAG laser pulses: dependence on target preparation method

The results of experimental studies of the ablation of CdTe with a pulsed Nd:YAG laser (wavelength 1064 nm) performed with 100 µs pulses and repetition time of 35 Hz are presented for the pulse energy range from 0.13 to 0.25 J. The main goal is to elucidate the dependence of the ablation process on the target preparation method. The investigation of the vapour stream intensity and chemical composition and their evolution with time are performed with a quadrupole mass spectrometer synchronized with the laser pulses. These studies are performed for three kinds of targets: a target made of CdTe bulk crystal (BC target), a target made of CdTe fine powder pressed under the pressure of 700 atm (PP target), and a target made of loose CdTe powder (N‐PP target). The applicability of these targets for obtaining high quality CdTe thin films is determined. The best chemical composition of the vapour stream can be obtained with the BC target. A major drawback of this target is the energetic threshold for ablation with Nd:YAG laser and resulting delay in the ablation process above the threshold. The advantage of powder targets over BC target is the lack of any ablation threshold or delay. Weaker angular dependence of the particle emission (associated with the surface roughness), if confirmed in further experiments, can be the most important advantage of PP and N‐PP targets. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hodograph method of flow on two-dimensional manifold

For some special flows, especially the potential flow in a plane, using the hodograph method has obvious advantages. Realistic flows have a stream surface, namely, a two-dimensional manifold, on which the velocity vector of the flow lies on its tangent space. By introducing a stream function and a potential function, we establish the hodo- graph method for potential flows on a surface using the tensor analysis. For the derived hodograph equation, we obtain a characteristic equation and its characteristic roots, from which we can classify the type of the second-order hodograph equation. Moreover, we give some examples for special surfaces.