Impacts of Surface Exchange Coefficients on Simulations of Super Typhoon Megi(2010)Using a Coupled Ocean-Atmosphere-Wave Model

In this study,the effects of surface exchange coefficients on simulations of Super Typhoon Megi(2010)are investigated using a fully coupled ocean-atmosphere-wave model.Several experiments are conducted using different parameterization schemes for the drag(C_(D))and enthalpy exchange(C_(K))coefficients.For the selected case,considering only the leveling-off of C_(D)at high wind speeds does not effectively improve the simulated typhoon track,intensity,or size.We found that increasing C_(K)monotonically with wind speed(Komori et al.,2018)yields stronger winds and deeper pressures by enhancing latent and sensible heat fluxes,but typhoon intensity remains underestimated.We propose a new higher C_(K)than that from Komori et al.(2018)based on the theory of Emanuel(1995).This approach produces a greater modeled typhoon intensity that is in good agreement with the best track data and effectively improves the track error for the simulation.Improved accuracy for modeled typhoon intensity is achieved with the new coefficient because C_(K)/C_(D)reaches the threshold of about 0.75 predicted by Emanuel(1995).The new proposed C_(K)also results in a reasonably accurate modeled sea surface temperature.However,typhoon size and surface wave height are overestimated.This finding implies that more numerical tests for tropical cyclones of different nature(such as strong,weak,dissipating,rapidly intensifying,or weakening tropical cyclones)should be studied,and more physical processes should be explored in future coupled models.

STUDY ON THE DIFFUSION OF Cu^(2+)-H^+ COUPLE IN A CATION EXCHANGE MEMBRANE——A RAPID METHOD TO DETERMINE SELF-DIFFUSION COEFFICIENTS OF COUNTER-IONS WITH UNEQUAL VALENCE

1 INTRODUCTIONKnowledge of the basic transport phenomena of ions in an ion exchange membrane isimportant for the application of such a membrane.Various studies on the developmentof mathematical models for predicting and correlating membrane transport rate havebeen published in recent years.More exact estimation of the diffusion coefficientshas been the subject of chief concern in many of these papers.For a bi-ionic systemwith the same valence,Sato et al.gave a method for estimating diffusion coefficients

Impact of Surface Exchange Coefficients and Sea Surface Cooling on Tropical Cyclone Simulation

The surface flux exchange associated with the exchange coefficients and upper ocean conditions is essential to the development of tropical cyclones(TCs).Using the Weather Research and Forecasting(WRF)model,the present study has investigated the impact of exchange coefficients and ocean coupling during Super Typhoon Saomai(2006).Firstly,two experiments with different formula of roughness are conducted.The experiment with the Donelan formula for drag coefficient(C_(d))and ramped formula for enthalpy coefficient(C_(k))can simulate stronger intensity compared to other experiments due to the increased surface wind and enthalpy fluxes.That is because the new formulas allows for a smaller C_(d)and larger C_(k)in the high wind regime than the former formulas did.Moreover,two coupled simulations between WRF and a one-dimensional ocean model are conducted to examine the feedback of sea surface cooling to the TC.In the experiments with a horizontal uniform mixed layer depth of 70 m,the sea surface cooling is too weak to change the evolution of TC.While in the experiment with an input mixed layer calculated using the Hybrid Coordinate Ocean Model(HYCOM)data,the significant sea surface cooling induces obvious impact on TC intensity and structure.Under the negative feedback of sea surface cooling,the sensible and latent heat fluxes decreases,especially in the right part of Saomai(2006).The negative feedback with coupled ocean model plays a vital role in simulating the intensity and structure of TC.

A RAPID METHOD TO DETERMINE DIFFUSION COEFFICIENTS OF COUNTER-IONS IN AN ION-EXCHANGE MEMBRANE

1 INTRODUCTIONRapid and precise methods to obtain the diffusion coefficients of counter-ions are im-portant for the characterization of ion exchange membranes.Many theoreticaldescriptions of ion transport in ion exchange membranes have been developed by usingthe principles of irreversible thermodynamics,or the Nernst-Planck equations.Fick’s law can also be used for the description of the transport of ions with equaldiffusivity.However,for counter-ions of different diffusivities,Nerst-Planck

BOUNDARY LAYER STRUCTURE IN TYPHOON SAOMAI(2006):UNDERSTANDING THE EFFECTS OF EXCHANGE COEFFICIENT

Recent studies have shown that surface fluxes and exchange coefficients are particularly important to models attempting to simulate the evolution and maintenance of hurricanes or typhoons.By using an advanced research version of the Weather Research and Forecasting(ARW)modeling system,this work aims to study the impact of modified exchange coefficient on the intensity and structures of typhoon Saomai(2006)over the western North Pacific.Numerical experiments with the modified and unmodified exchange coefficients are used to investigate the intensity and structure of the storm,especially the structures of the boundary layer within the storm.Results show that,compared to the unmodified experiment,the simulated typhoon in the modified experiment has a bigger deepening rate after 30-h and is the same as the observation in the last 12-h.The roughness is leveled off when wind speed is greater than 30 m/s.The momentum exchange coefficient(CD)and enthalpy exchange coefficient(CK)are leveled off too,and CD is decreased more than CK when wind speed is greater than 30 m/s.More sensible heat flux and less latent heat flux are produced.In the lower level,the modified experiment has slightly stronger outflow,stronger vertical gradient of equivalent potential temperature and substantially higher maximum tangential winds than the unmodified experiment has.The modified experiment generates larger wind speed and water vapor tendencies and transports more air of high equivalent potential temperature to the eyewall in the boundary layer.It induces more and strong convection in the eyewall,thereby leading to a stronger storm.

Vertical Distribution of Momentum Exchange Coefficient and Sediment Concentration in Estuarine and Coastal Waters

Vertical structures of momentum exchange coefficient and sediment concentration are the keys in the research on es- tuarine and coastal suspended sediment transport. Based on the parabolic mixing length distribution pattern, the distribu- tion pattern of vertical momentum exchange coefficient which is suitable for estuarine and coastal waters is constructed. A compari^n with steady flow and measured momentum exchange coefficient during one tidal cycle in the Menai Strait of England shows that the result of this pattern is closer to the measured values than those of commonly used Rouse＇ s and van Rijn＇s patterns, and the pattern is also suitable for estuarine and coastal waters. Successively, based on the precon- dition that momentum exchange coefficient is equivalent to sediment turbulent diffusion coefficient, and combining with the Diffusion Theory, we obtain the exponential vertical distribution pattern of sediment concentration, which is also suitable for estuafine and coastal waters, Thereby, using measured vertical stratified sediment concentration data of the South and the North Passages of the Yangtze Estuary and Zhoushan archipelago waters for fitting calculation, and comparing the results with those from Rouse＇s （1938） and Zhang et al. ＇s （1989） formulas, the results show that the exponential vertical distribution pattern of sediment concentration obtained in the present study not only overcomes the defect of Rouse＇s formula that the surface sediment concentration will be 0, but also has a holistic higher precision along the vertical lines than those of Rouse＇s and Zhang et al. ＇s formulas.

Relation between stabilization energy, crystal field coefficient and the magnetic exchange interaction for Tb^(3+) ion

Based on a single ion model, Hamiltonian of the simplest form about magnetocrystalline anisotropy for Tb3+ ion was solved by using the numerical method. The relation between the stabilization energy, crystal field coefficient B20 and the magnetic exchange interaction was studied as temperature approaches to 0 K. The results show that the stabilization energy contributed by Tb3+ is linear with crystal field coefficient B20 approximately, but it is insensitive to the change of magnetic exchange interaction for the strong magnetic substances such as TbCo5, Tb2Co17 and Tb2Fe14B compounds.

Laminar Heat Transfer Modeling and Investigation of Thermal Dispersion in a Flat Plate Heat Exchanger： Estimating Heat Transfer Coefficient, Heat Flux and Nusselt Number

PHEs （plate heat exchangers） are among the most common thermal equipments in diverse industries particularly in oil and gas companies. This wide usage is obviously due to significant benefits of these heat exchangers over other types. In this article, a behavioral analysis of heat transfer in fiat plates of these heat exchangers in laminar flow situation through CFD （computational fluid dynamics） simulation using FLUENT 6.3.26 software is done. The study reveals results graphically based on fluid＇s behavior in co-current and counter current flows and discusses thermal indexes consisting of heat transfer coefficient, Nusslet and total heat flux in both conditions. Eventually, a comparison via the graphical results is presented between the two types of flow directions.

Two-Dimensional Modeling of the NAPL Dissolution in Porous Media: Heterogeneities Effects on the Large Scale Permeabilities and Mass Exchange Coefficient

In this paper, we are interested by the dissolution of NAPL (Non-Aqueous Phase Liquid) contaminants in heterogeneous soils or aquifers. The volume averaging technique is applied to 2D systems with Darcy-scale heterogeneities. A large-scale model is derived from a Darcy-scale dissolution model in the case of small and large Damkholer numbers, i.e., for smooth or sharp dissolution fronts. The resulting models in both cases have the mathematical structure of a non-equilibrium dissolution model. It is shown how to calculate the resulting mass exchange and relative permeability terms from the Darcy-scale heterogeneities and other fluid properties. One of the important finding is that the obtained values have a very different behavior compared to the Darcy-scale usual correlations. The large scale correlations are also very different between the two limit cases. The resulting large-scale models are compared favorably to Darcy-scale direct simulations.

Experimental Investigation on Heat Exchange and Separation Performance of an Annular Structured Internal Heat-integrated Distillation Column

In this paper heat exchange coefficient and separation efficiency of an annular structured internal heat-integrated distillation column(HIDi C) were experimentally measured. About 50% heat of the inner column could be transferred to the outer column. The overall heat exchange coefficient decreased with an increase in pressure ratio of the inner column and the outer column, but was little affected by the F-factor. The increase of the pressure ratio decreased obviously the separation efficiency of the outer column but had little effect on that of the inner column.

Identification and analysis based on genetic algorithm for proton exchange membrane fuel cell stack

The temperature of proton exchange membrane fuel cell stack and the stoichiometric oxygen in cathode have relationship with the performance and life span of fuel cells closely. The thermal coefficients were taken as important factors affecting the temperature distribution of fuel cells and components. According to the experimental analysis, when the stoichiometric oxygen in cathode is greater than or equal to 1.8, the stack voltage loss is the least. A novel genetic algorithm was developed to identify and optimize the variables in dynamic thermal model of proton exchange membrane fuel cell stack, making the outputs of temperature model approximate to the actual temperature, and ensuring that the maximal error is less than 1 ℃. At the same time, the optimum region of stoichiometric oxygen is obtained, which is in the range of 1.8-2.2 and accords with the experimental analysis results. The simulation and experimental results show the effectiveness of the proposed algorithm.

Behaviour of radioactive iodide and bromide ions from aqueous solution on ion exchange resins Amberlite IRA-400

The ion exchange resin Amberlite IRA-400 in iodide and bromide form where equilibrated separately with the respective labeled iodide and bromide ion solution of different concen-trations varying from 0.005M to 0.100M in the temperature range of 32.0 oC to 48.0 oC. The dis-tribution coefficient Kd values calculated for iodide and bromide ion exchange increases with rise in ionic concentration of the external solution, however with rise in temperature the Kd values calculated where found to decrease. Also the Kd values calculated where higher for iodide exchange than bromide exchange. Among the different alternative techniques available for obtaining the Kd values, the radio-active tracer technique used in the present ex-perimental work offers high detection sensitivity. It is expected that the distribution coefficient data obtained from such experimental work will significant in environmental impact assessment on the disposal of radioactive waste.

Discussion of Exchange Rate Fluctcation Using IS-LM Model

This paper analyses the essential cause of exchange market fluctuation by using IS－LM model: excessive investment causes goods overstocking in goods market, which brings about supply exceeding demand:financial market loses equilibrium as well, resulting imbalance of money demand and money supply, which causes interest rate to drop. This Paper gives the relationship between interest rate and exchange rate: as a result of interest rate dropping, exchange rate is in great turbulence,whose fluctuation range relates to some coefficients.

A more precise method to evaluate kinetic leakage of anion exchange resin used in condensate polishing of power plant

Sulfate mass transfer coefficient(MTC) is a sensitive parameter to evaluate the kinetic leakage of anion exchange resin used in condensate polishing system of thermal and nuclear power plant.However,a sufficiently precise determination method has not been well established.In this paper,the final expression of sulfate MTC derived based on plug flow reactor model is the same as Harries' model,which is widely acknowledged in this field.In the determining system we constructed,in-situ calibration of the concentration of sulfate and its cation conductivity was conducted and sulfate MTCs of four typical strongly basic anion exchange resin samples were determined.The systematic error is 8.26% and the calibrated curve used for quantifying sulfate is obtained.The repeatability and reproducibility standard deviation are 0.05×10^(-4) m·s^(-1) and 0.07×10^(-4) m·s^(-1) respectively,which are lower than previous works.By controlling test condition accurately,this study has developed a more precise sulfate MTC determining method.This method provides a basis for further research.

水-冰相变凝固换热与热泵耦合供热系统实验研究

针对河北山区农村水源不足、地源钻井成本高、太阳能不稳定、造价高、没有合适的热泵低温热源等问题,研发了水-冰相变换热器;利用水的相变潜热作为热泵的低温热源,设计了水-冰相变凝固换热与热泵耦合供热系统,搭建了实验平台,经测试平台运行稳定可靠。通过对实验数据进行分析计算,得到系统性能系数在2.87~3.42之间。研究结果可为解决河北山区农村供暖问题提供参考。

二维材料复合质子膜的制备及其氕氚分离性能研究

采用溶液浇铸法分别制备了Graphene-Nafion和hBN-Nafion 2种二维纳米复合质子交换膜,利用XRD､ATR-FT-IR和SEM对复合膜的结构及微观形貌进行表征,并对复合膜的离子交换容量､质子电导率､机械性能和热稳定性进行测试,结果表明,Graphene和hBN纳米片均匀地分散于Nafion基体内部。相较于重铸Nafion膜(空白对照样品),复合膜的离子交换容量､质子电导率以及机械性能均有不同程度的提升,特别是在掺入质量分数为0.50%时,Graphene-Nafion和hBN-Nafion复合膜的质子传导性能约为重铸Nafion膜的1.25倍和1.14倍。通过对比Graphene-Nafion和hBN-Nafion 2种复合膜的氕氚分离性能发现,在初始氚水比活度为3.51×10^(7)Bq/L时,持续电解超过60 h,2种复合膜的氕氚分离系数分别为5.73和8.46,氚回收率分别为78.53%和85.35%,表明hBN-Nafion复合膜具有更好的氕氚分离性能。

渗透系数非均质场对沙丘尺度潜流交换的影响研究

为了研究河床介质渗透系数非均质性对潜流交换的影响,应用随机一阶分析工具,分析潜流交换通量与河床不同空间位置渗透系数的互相关关系以及渗流流速方差的空间分布。结果表明:潜流交换通量与渗透系数之间成正相关关系,且正相关关系最强的区域位于沙丘表面附近;忽略河床非均质性将导致河床浅层位置的流速具有较大不确定性,野外应重点监测河床浅层位置的渗透系数以减小潜流交换的不确定性。

磺酸型阳离子树脂的元素分配行为及高精度同位素分析应用

不同元素在离子交换树脂的分配系数是元素纯化和分离的基础,不同酸中各元素分配系数差异可用于设计高效的元素提纯流程,从而被广泛应用于现代高精度同位素分析。本文以AG®50W-X8阳离子树脂为研究对象,以分配系数(Kd)作为量化指标,通过系统实验研究不同元素在该树脂中的分配行为。在前人研究基础上,本实验增加了元素数量和酸的种类,涵盖了金属、类金属、非金属和稀土元素。结果表明:在盐酸和硝酸介质中,几乎所有元素的Kd都与酸度呈负相关,当酸度达到6mol/L时,除Th和Ca以外的所有元素都会被酸洗脱。稀土元素(REEs)和高场强元素在0.1~0.5mol/L稀硝酸和稀盐酸中强烈吸附在树脂上;而一些过渡金属、类金属和非金属元素(如Mo、W、Re、Ir、Sb、Ge、As、Se、Te等)在酸溶液中会形成含氧阴离子,不与阳离子树脂发生吸附。Al、Fe、Se、Pd、Cd、In等元素在盐酸中易与氯离子形成配位化合物或离子团,导致这些离子在盐酸中的分配系数显著降低。在硝酸和盐酸与氢氟酸的混合酸中,除稀土元素外,绝大部分元素随酸度增加Kd迅速降低。稀土元素在盐酸-氢氟酸混合介质中,随着盐酸的浓度增加(从0.1mol/L盐酸-0.2mol/L氢氟酸至6mol/L盐酸-0.2mol/L氢氟酸),稀土元素分配系数(KdREE)具有先增加后降低的趋势。氢氟酸的加入可显著降低Be、Al、Sc、Fe、Sn、Th、U、Ti、Zr、Hf等元素在稀盐酸和稀硝酸中的分配系数,使这些元素几乎不与树脂发生吸附。本研究揭示了不同酸介质中各类元素在阳离子交换树脂上的分配行为存在差异,尤其是氢氟酸的加入可显著改变高场强元素、部分过渡金属和稀土元素的分配系数,为应用该树脂开发和优化适用于高精度金属稳定同位素分析的元素提纯流程(如Li、Mg、K、Sr、Ce、U等)提供了数据支撑,并可有效地减少后续实验设计的工作量。

冷凝器面积对空气源热泵制热性能的影响研究

目的研究低温条件下空气源热泵的烘干性能。方法论文主要采用焓差法研究在换热面积和室外温度(温度为7、−12、−20℃,相对湿度为65%)不同时,空气源热泵的制热量、输入功率、能效等性能。结果在7℃环境中,增加室内侧换热器面积,热泵的制热量提高了19%,系统能效提升了14%,但输入功率增加了5%;在−12~−20℃环境中,增加室内侧换热器面积,热泵的制热量提升了5%,系统能效提升明显,最大可提升27%,输入功率最大降低为17%。结论增加室内侧换热器面积,系统焓差降低,但是能提高系统在低温下的循环风量,制热性能更加优异。