Prediction of Flow Duration Curves for Ungauged Basins with Quasi-Newton Method

Prediction of flow-duration-curves (FDC) is an important task for water resources planning, management and hydraulic energy production. Classification of the basins as carstic and non-carstic may be used to estimate parameters of the FDC with predictive tools for catchments with/without observed stream flow. There is a need for obtaining FDC for ungauged stations for efficient water resource planning. Thus, study proposes a quite new approach, called the EREFDC model, for estimating the parameters of the FDC for which the parameters of the FDC are obtained with quasi-Newton method. Estimation are made for using the bv gauged stations at first than the FDC parameters are estimated for ungauged stations based on drainage area, annual mean precipitation, mean permeability, mean slope, latitude, longitude, and elevation from the mean sea level are used. The EREFDC model consists of various type of linear- and nonlinear mathematical equations, is able to predict a wide range of the FDC parameters for gauged and ungauged basins. The method is applied to 72 unimpaired catchments studied are about for 50 years average daily measured stream flow. Results showed that the EREFDC model may be used for estimating. FDC parameters for ungauged hydrological basins in order to find FDC for ungauged stations. Results also showed that the EREFDC model performs better in carstic regions than non-carstic regions. In addition, parameters of FDC for tributaries at the basins with insufficient flow data or without flow data may be determined by using basin characteristics.

Therapeutic effects of different durations of acupuncture on rats with middle cerebral artery occlusion

Acupuncture is regarded as an effective therapy for cerebral ischemia. Different acupuncture ma- nipulations and durations may result in different therapeutic effects. In the present study, the Neig uan （PC6） acupoint of rats with occluded middle cerebral arteries was needled at a fixed frequency （3 Hz） with different durations, i.e., 5, 60 and 180 seconds under a twisting-rotating acupuncture method. Results showed that different durations of acupuncture had different therapeutic effects, with 60 seconds yielding a better therapeutic effect than the other two groups. This duration of treatment demonstrated rapid cerebral blood flow, encouraging recovery of neurological function, and small cerebral infarct volume. Experimental findings indicated that under 3 Hz frequency, the treatment of needling Neiguan for 60 seconds is effective for ischemic stroke.

Energy analysis of rock plug thickness in karst tunnels based on non-associated flow rule and nonlinear failure criterion

The geological hazards, such as water inrush and mud outburst, are easily induced by the high water pressure caverns ahead of a karst tunnel face. Therefore, it is a pivotal issue to determine the reserved thickness of rock plug during the construction of tunnels. The limit analysis principle is employed to analyze the safe thickness from the point of energy dissipation, and the nonlinear and non-associated characteristics of geotechnical materials are both considered. On the basis of a plane failure pattern of rock plug, the expressions of detaching curve and rock plug thickness are derived. The effect of each parameter on the safe thickness of rock plug is discussed in detail, which interprets the corresponding failure scope of rock plug. The obtained results indicate that the thickness of rock plug is highly influenced by the nonlinear dilatancy coefficient and the nonlinear coefficient. The proposed method is validated by a comparison of the calculated results with those of the engineering project of the "526 karst cavern" of Yunwushan tunnel. This proposed method can provide reference basis for the design and excavation of karst tunnels in the future.

A Rainfall Intensity-Duration Threshold for Mass Movement in Badulla, Sri Lanka

Mass movement in Sri Lanka is mainly triggered by heavy rainfall. International literature is rich of works defining rainfall intensity-duration models to identify the rainfall threshold for various types of Mass movement. However, studies have not focused to establish a relationship between intensity and duration of rainfall in Sri Lanka. Therefore, this study focused to establish rainfall intensity-duration models to identify the rainfall threshold for mass movements in Badulla district in Sri Lanka, where forty four (44) rainfall events that resulted in same number of landslides during the last three decades were considered. Results indicate the rainfall threshold relationship fits to the log linear model of the exponential function, I = α&#183D-β. The constructed I-D curve revealed that short duration (54 mm/h) in rainfall events can potentially trigger the landslide. However, long-duration (>8 h) and low-intensity (<25 mm/h) in rainfall events may also trigger mass movements in Badulla. As per the results, most mass movements occur during northeast monsoons and inter-monsoons. In general, higher mean rainfall intensities trigger the debris flows, while long-duration rainfall events can trigger both landslides and debris flow. When compared to Sri Lankan mass movements triggering threshold intensities are fairly higher than the global threshold values. It confirms that within Badulla, mass movements are triggered by very high intense and/or long duration rainfalls events only. Further, time series analysis of the rainfall events shows an upward trend of extreme rainfall events, which increased landslide occurring frequency in last six (6) years.

用Moldflow设计汽车后保险杠支架注塑模具

介绍了一种汽车后保险杠左右支架塑料件的模具设计,首先分析了汽车后保险杠左右支架的形状结构和成型工艺难点问题,而后运用Moldflow进行了浇注系统有效性验证分析;CAE分析结果中,针对性地分析了充填时间、压力、平均温度、熔接痕、气穴位置等与注塑生产难点问题直接相关的结果,并给出了最终的注塑机试模参数,为模具结构设计提供了精确的设计依据;最后着重阐述了基于UG–HB_Mould6.6外挂的模具整体结构设计。此设计方法综合运用模具CAD/CAE技术,将生产经验和有限元分析技术有机结合,将模具试模前的潜在技术难题集中在设计阶段解决,提高了模具的生产效率。

基于OpenFlow协议的流表超时机制研究

软件定义网络技术为网络的控制管理带来了更加丰富和高效的手段,但在复杂网络环境中应用软件定义网络技术还面临着一系列问题,而流表超时机制是其中之一。真实网络环境中的业务流持续时间差异巨大,且包含大量单包或持续时间极短的业务流,而不恰当的超时机制可能造成网络资源和计算资源的浪费。因此,针对真实网络环境中的业务流持续时间模型,分析现有超时机制的缺陷,提出了基于Open Flow协议的流表超时机制的改进方案,并通过仿真试验验证了改进效果。

Poly-Acrylic Acid Derivatives as Diesel Flow Improver for Paraffin-Based Daqing Diesel

Since the diesel products from paraffin-based Daqing crude oil showed low sensitivity to certain commercial diesel pour point depressant （PPDs） that resulted from the high content of paraffin, certain poly-acrylic acid derivatives （PADE） with-COOR, -COOH,-CONHR, and -COO-NH3^＋R groups by molecular design on the mechanics of diesel; PPDs were synthesized and evaluated as cold flow improver for Daqing 0^# diesel in this paper. The pure PADE was superior to the commercial PPDs and displayed a substantial ability of wax crystals dispersion. There was a synergistic effect among the PADE and T1804 and secondary amine. The synergism clearly improved the low temperature performance of Daqing diesel products and could reduce the cold filter plugging point of 0^# diesel by 6-7 ℃.

A new alternating copolymerized derivative as a cold flow improver for diesel fuel

Synthesis of a cold flow improver （MAVA-a） for diesel fuel and its effect on solidifying point （SP） and cold filter plugging point （CFPP） of diesel fuels were investigated, The cold flow improver was prepared by using maleic anhydride （MA） and vinyl acetate （VA） as raw materials, toluene as solvent, dibenzoyl peroxide （BPO） as initiator, through alternating polymerization under nitrogen to obtain a binary-polymer and then through aminolysis by using a higher carbon amine as aminating agent at a temperature of 80 ℃. A cold flow improver was designed and prepared for No. 0 diesel fuel from Zhang Jia-Gang Petrochemical Company according to the contents of n-paraffin and its carbon number distribution in the No. 0 diesel fuel. It was also used together with two kinds of ethene-vinyl acetate copolymer improvers （EVA） separately. The test result showed that the CFPP of the No. 0 diesel fuel could be lowered by 3-5 ℃ when the improver MAVA-a was used. The CFPP was lowered by 8℃ when the improver MAVA-a was used together with EVA-2.

Analysis of Bingham fluid radial flow in smooth fractures

Solutions for radial flow of a Bingham fluid are analyzed in this paper.It aims to eliminate confusions in the literature concerning the plug flow region in different solutions for analysis and design of grouting in rock fractures.The analyses based on the force balance equation reveal that the plug flow region in Bingham radial flow is independent of the fracture radius,and is not a growth function adapted from the solution of one-dimensional(1D)slit flow according to‘similarity’.Based on the shear stress distribution,we analytically proposed that a non-uniform plug flow region cannot exist.The Bingham fluid(grout)penetration and flowrate evolution as functions of grouting time are given using the correct expression for the plug flow region.The radius-independent plug flow region and the presented flowrate evolution equation are also verified numerically.For radial flow,the relative penetration length is equal to the relative width of plug flow region,which is the same as that for 1D channel flow.Discrepancies in analytical solutions for grout penetration and flowrate evolution were also illustrated.The clarification of the plug flow region and evaluation of discrepancies in analytical solutions presented in this work could simplify modeling and design of grouting in rock engineering applications.

Transport of Wetting and Nonwetting Liquid Plugs in a T-shaped Microchannel

The transport of liquid plugs in microchannels is very important for many applications such as in medical treatments in airways and in extraction of oil from porous rocks.A plug of wetting and non-wetting liquids driven by a constant pressure difference through a T-shaped microchannel is studied numerically with lattice Boltzmann(LB) method.A two-phase flow LB model based on field mediators is built.Three typical flow patterns(blocking,rupture and splitting flow) of plug flow are obtained with different driving pressures.It is found that it becomes difficult for a plug with short initial plug length to leave the microchannel;the flow pattern of plug transport varies with the contact angle,especially from wetting to nonwetting;with the increase of interfacial tension,the front interface of plug moves faster;the front and rear interfaces of the plug with small viscosity ratio move faster in the microchannel than those of the plug with large viscosity ratio.The study is helpful to provide theoretical data for the design and scale-up of liquid-liquid reactors and separators.

Effect of Stagnation Temperature on the Supersonic Two-Dimensional Plug Nozzle Conception. Application for Air

When the stagnation temperature of a perfect gas increases, the specific heats and their ratio do not remain constant any more and start to vary with this temperature. The gas remains perfect, its state equation remains always valid, except it will name in more calorically imperfect gas or gas at High Temperature. The goal of this research is to trace the profiles of the supersonic plug nozzle when this stagnation temperature is taken into account, lower than the threshold of dissociation of the molecules, by using the new formula of the Prandtl Meyer function, and to have for each exit Mach number, several nozzles shapes by changing the value of this temperature. A study on the error given by the PG （perfect gas） model compared to our model at high temperature is presented. The comparison is made with the case of a calorically perfect gas aiming to give a limit of application of this model. The application is for the air.

NUMERICAL ANALYSIS OF SOIL PLUG INSIDE SUCTION FOUNDATIONS DURING SUCTION PENETRATION BY DISCRETE ELEMENT METHOD

The phenomenon of the soil plug usually rising inside the suction foundations during suction penetration was quantitatively described and predicted. The formation process of the soil plug was simulated and calculated by DEM （discrete element method） model. The seepage flow, the self-weight of soil, the friction on the chamber wall as well as the suction inside the chamber are considered as the main external forces in the process. The results are compared with a set of laboratory model tests performed by using three soil types （sand, silty clay and clay） in the Bohai Sea area. The heights of soil plug from numerical estimations are lower than those from model test results, mainly because the suction pressure and friction resistance are applied in an ideal way under the numerical simulation.

Gravel Accumulation in Deposits of Viscous Debris Flows with Hyper-concentration

According to the observational data of viscous debris flows with hyper-concentration, debris flows can be classified into three types:high-viscous, viscous, and sub-viscous debris flows.Distinct formation mechanism of different graded bedding structures in deposits of viscous debris flows was analyzed in this paper by using their yield-stress ratio and flow plug ratio.This paper specially analyzed the effect of Weissenberg which the gravels in squirm condition of hyper-concentration viscous flows would tend to move vertically, and the formation mechanism of the gravels accumulated at surface was also studied.The analysis in this paper can establish a foundation for the studies on differentiation of bedding structures of debris flow deposits and studies on dynamic parameters of debris flows.

Flow mixing model of liquid phase in an internal airlift loop reactor

Residence time distribution (RTD) analysis of liquid phase was conducted in an internal airlift loop reactor (AL) and a bubble column (BC) with the tracer response technique. These data were simulated and compared through several flow mixing models. The modeling results of two-parameter model indicated that there were higher ratio of full mixing zones and lower ratio of bypass flow in AL than in BC. Then a completely mixed-plug flow parallel combined (four-parameter) model was established. Modeling results show that it is more precise and more obvious than two-parameter model.

Study on Dibehenyl Fumarate-Vinyl Acetate Copolymer for Lowering Cold Filter Plugging Point of Diesel Fuel

In the practice of petroleum industry, adding cold flow improver （CFI） to lower the fuel＇s cold filter plugging point （CFPP） is an effective and economic way for improving the cold flow performance of diesel fuel. This paper described the synthesis and evaluation of the performance of dibehenyl fumarate-vinyl acetate （FV） copolymer for improving the cold flow performance of the tested diesel fuels. The carbon distribution in n-alkanes of the tested diesel samples were analyzed by gas phase chromatography. The structure of the copolymer was confirmed by the 1H NMR spectroscopy. The wax crystals morphologies with and without adding the FV additive were investigated by means of polarizing microscope. The test results indicated that the FV additive could depress CFPP of the tested diesel samples by 2℃ and 4℃, respectively, when dosage of the additive was 0.08 m%. The additive can modify the size and shape of the wax crystals and inhibit the formation of larger wax crystal lattices.

Comparison of Co-Current and Counter-Current Flow Fields on Extraction Performance in Micro-Channels

Several applications such as liquid-liquid extraction in micro-fluidic devices are concerned with the flow of two immiscible liquid phases. The commonly observed flow regimes in these systems are slug-flow and stratified flow. The latter regime in micro-channels has the inherent advantage that separation of the two liquids at the exit is efficient. Recently extraction in a stratified counter-current flow has been studied experimentally and it has been shown to be more efficient than co-current flow. An analytical as well as a numerical method to determine the steady-state solution of the corresponding convection-diffusion equation for the two flow-fields is presented. It is shown that the counter-current process is superior to the co-current process for the same set of parameters and operating conditions. A simplified model is proposed to analyse the process when diffusion in the transverse direction is not rate limiting. Different approaches to determining mass transfer coefficient are compared. The concept of log mean temperature difference used in design of heat exchangers is extended to describe mass transfer in the system.

单裂隙内浆液基本流动规律的理论、试验、模拟对比分析

工程中广泛使用的水泥浆液是一种非牛顿流体,在裂隙内扩散时表现出复杂的宏观非线性渗流特征,在细观流场上也因屈服应力的作用呈现出柱塞流等特殊流动现象。配制符合Herschel-Bulkley(H-B)模型的模拟浆液,利用粒子图像测速(particle image velocity,PIV)技术开展平直裂隙内的可视化渗流试验,同时求解H-B-P(H-B-Papanastasiou)方程开展浆液渗流有限元数值模拟。基于平直裂隙中单相屈服幂律流体渗流解析解,从理论、试验、模拟相结合的角度分析了平直裂隙内注浆压力与流速的非线性关系;通过对流速剖面图的对比,分析了H-B流体的柱塞流特征;通过与Bingham模型的对比证明了H-B流体更符合实际浆液流动规律。通过原创的可视化测试手段验证了理论和数值模型,提出了参数取值依据,对提升复杂工程岩体中的注浆工艺具有参考价值。

段塞流分相流量的多传感器信息融合测量

气液两相流广泛存在于能源化工领域,由于两相流流动特性复杂多变,为流量准确测量带来了极大困难。为了建立准确的气液两相流量测量模型,针对气液两相段塞流分相流量测量,充分利用声发射传感器捕获气液两相流动噪声的功能和近红外吸收会因介质类别产生较大差异的特性,设计了一种新型测量传感器。在文丘里管的喉管和延伸段分别安装两组声发射探头,并在文丘里管的喉管处安装两组近红外光电探测器。设计了声发射与近红外同步采集系统,以水平管段塞流为实验对象,在河北大学高精度气液两相循环装置上完成了54组段塞流试验的数据采集,并进行融合处理,得到气液两相流特征参数。引入时域分析方法,提取声发射与近红外测量数据的标准差与偏斜度。结合参数拟合方法,建立两相流流量预测模型并进行误差分析。经验证,92.6%的流量预测值的相对偏差在±20%以内。结果表明,基于声发射传感器与近红外传感器的多传感器信息融合方案为气液两相流流动特征参数研究提供了一种新的思路。

绿色创新如何影响隐含权益久期?——来自工业企业的证据

基于2008—2019年中国A股上市工业企业数据,运用多元线性回归模型探讨绿色创新对隐含权益久期的影响及其作用机制。研究发现:绿色创新的实施增加了企业的隐含权益久期。机制分析表明,绿色创新在短期内抑制企业的增长,长期内则提高了企业的成长潜力,因此实施绿色创新的企业的现金流将较少集中在近期。此外,国有企业可以更快突破绿色创新短期内的抑制作用,从而减小绿色创新对隐含权益久期的影响。鉴于此,决策部门应充分关注绿色创新的双重外部性,明晰其长短期经济效益差异,助力企业绿色创新。

全产业链贯通布局下钒液流电池长时储能发展思考

清洁能源的发展和“双碳”目标的实施推动了能源结构调整和电网系统升级,这必将催生巨大的万亿长时储能需求,麦肯锡预测2030年全球可再生能源占比将升至60%~70%,长时储能比2025年增加5~10倍(预计2025年30~40 GW)。全钒液流电池相比其他电化学储能具有安全长寿、灵活可靠、资源丰富等优点,2018~2023年国家和地方发布了多项清洁能源储能配置标准的政策性文件,在此背景下钒储能电池行业企业持续高速增长,行业集中度提升,宏观领域表现为我国钒储能产业正处在加速发展期。目前,钒储能电池总体成本较高,主要原因是钒原料价格高,降低成本的核心环节是钒资源提取成本和电解液生产制造成本。中国恩菲研发的短流程制备钒电解液技术相对于传统钒电解液制备技术具有流程短、钒利用率高的特点,制造成本降低了30%~50%,后期随着钒资源开发和新工艺的研发成功,钒储能产业降本优势将愈发突出。在国家政策支持下,钒液流电池储能系统有望在短期内实现规模化、商业化应用,成为储能领域的重要选择。未来,钒液流电池储能系统仍需从多方面进行优化,如重视技术创新和研发、健全回收利用体系等,以实现钒液流电池长时储能产业的可持续发展。