Asymptotic solution of a weak nonlinear model for the mid-latitude stationary wind field of a two-layer barotropic ocean

A weak nonlinear model of a two-layer barotropic ocean with Rayleigh dissipation is built.The analytic asymptotic solution is derived in the mid-latitude stationary wind field,and the physical meaning of the corresponding problem is discussed.

A Novel Two-Layer Model for Overall Quality Assessment of Multichannel Audio

With the development of multichannel audio systems, corresponding audio quality assessment techniques, especially the objective prediction models, have received increasing attention. Existing methods, such as PEAQ(Perceptual Evaluation of Audio Quality) recommended by ITU, usually lead to poor results when assessing multichannel audio, which have little correlation with subjective scores. In this paper, a novel two-layer model based on Multiple Linear Regression(MLR) and Neural Network(NN) is proposed. Through the first layer, two indicators of multichannel audio, Audio Quality Score(AQS) and Spatial Perception Score(SPS) are derived, and through the second layer the overall score is output. The final results show that this model can not only improve the correlation with the subjective test score by 30.7% and decrease the Root Mean Square Error(RMSE) by 44.6%, but also add two new indicators: AQS and SPS, which can help reflect the multichannel audio quality more clearly.

Two-Layer Non-Hydrostatic Model for Generation and Propagation of Interfacial Waves

When pycnocline thickness of ocean density is relatively small, density stratification can be well represented as a two-layer system. In this article, a depth integrated model of the two-layer fluid with constant density is considered,and a variant of the edge-based non-hydrostatic numerical scheme is formulated. The resulting scheme is very efficient since it resolves the vertical fluid depth only in two layers. Despite using just two layers, the numerical dispersion is shown to agree with the analytical dispersion curves over a wide range of kd, where k is the wave number and d the water depth. The scheme was tested by simulating an interfacial solitary wave propagating over a flat bottom, as well as over a bottom step. On a laboratory scale, the formation of an interfacial wave is simulated,which also shows the interaction of wave with a triangular bathymetry. Then, a case study using the Lombok Strait topography is discussed, and the results show the development of an interfacial wave due to a strong current passing through a sill.

Two-way coupling model for shock-induced laminar boundary-layer flows of a dusty gas

The present paper describes a numerical two-way coupling model for shock-induced laminar boundary-layer flows of a dust-laden gas and studies the transverse migration of fine particles under the action of Saffman lift force. The governing equations are formulated in the dilute twophase continuum framework with consideration of the finiteness of the particle Reynolds and Knudsen numbers. The full Lagrangian method is explored for calculating the dispersedphase flow fields （including the number density of particles） in the regions of intersecting particle trajectories. The computation results show a significant reaction of the particles on the two-phase boundary-layer structure when the mass loading ratio of particles takes finite values.

A rapid and accurate two-point ray tracing method in horizontally layered velocity model

A rapid and accurate method for two-point ray tracing in horizontally layered velocity model is presented in this paper. Numerical experiments show that this method provides stable and rapid convergence with high accuracies, regardless of various 1-D velocity structures, takeoff angles and epicentral distances. This two-point ray tracing method is compared with the pseudobending technique and the method advanced by Kim and Baag (2002). It turns out that the method in this paper is much more efficient and accurate than the pseudobending technique, but is only applicable to 1-D velocity model. Kim's method is equivalent to ours for cases without large takeoff angles, but it fails to work when the takeoff angle is close to 90°. On the other hand, the method presented in this paper is applicable to cases with any takeoff angles with rapid and accurate convergence. Therefore, this method is a good choice for two-point ray tracing problems in horizontally layered velocity model and is efficient enough to be applied to a wide range of seismic problems.

Comparison of Isobaric and Non-isobaric Operations on a Two-Phase Dynamic Model for PEFC Cathode Gas Diffusion Layer

Key words,： Two 1-D dynamical and isothermal models of cathode gas diffusion layer（GDL） with isobaric and non-isobaric operations for polymer electrolyte fuel cells（PEFCs） were developed and implemented in COMSOL Multiphysics v3.5.The artificial diffusion coefficient was introduced as well to make the numerical computation be stable.In the non-isobaric model,the pressure of gas mixture was obtained by summing up the governing equations of gaseous components,instead of Navier-Stoks equation.Comparison of the two models were carried out with the steady-states and dynamical simulations under given conditions.The corresponding analysis based on the simulated results was also given simultaneously.This paper is contributed to finding the differences between the isobaric and non-isobaric operation in the two-phase model of cathode GDL.

Vertical two-dimensional non-hydrostatic pressure model with single layer

The vertical two-dimensional non-hydrostatic pressure models with multiple layers can make prediction more accurate than those obtained by the hydrostatic pres- sure assumption. However, they are time-consuming and unstable, which makes them unsuitable for wider application. In this study, an efficient model with a single layer is developed. Decomposing the pressure into the hydrostatic and dynamic components and integrating the x-momentum equation from the bottom to the free surface can yield a horizontal momentum equation, in which the terms relevant to the dynamic pressure are discretized semi-implicitly. The convective terms in the vertical momentum equation are ignored, and the rest of the equation is approximated with the Keller-box scheme. The velocities expressed as the unknown dynamic pressure are substituted into the continuity equation, resulting in a tri-diagonal linear system solved by the Thomas algorithm. The validation of solitary and sinusoidal waves indicates that the present model can provide comparable results to the models with multiple layers but at much lower computation cost.

Research in Moisture Transport through One and Two-layered Porous Composites

Research into the moisture transport processes in porous materials is primarily important for theoretical modelling and industrial applications in the design of energy saving buildings and living environments, etc. Based on experimental investigation, we propose new models which describe one-dimensional transport through one-layered uniform materials and dissimilar two-layered composites. Diffusivity as a function of moisture content is obtained through a Boltzman transformation, master curves, and combined numerical and regression techniques. Transport processes in one and two-layered composites are simulated on the basis of extended unsaturated Darcy’s Law using the finite element method (FEM). Simulation results show significantly different transport patterns of moisture profile when moisture migrates in different directions, and high agreement with experimental moisture profiles. Keywords Porous materials - moisture transport - two-layered composites - modelling and simulation Qingguo Wang graduated from Hebei Normal University, China, in 1985. He received the M.Sc. degree from Beijing Petroleum University in 1988 and the Ph.D. degree from the University of Luton, UK, in 2005. He is currently a Research Associate in the Department of Electrical Engineering and Electronics at the University of Liverpool, UK and an Associate Professor of Shijiazhuang Mechanical Engineering College, China. His research interests include measurement and control, mass and heat transportation, EMC, etc.Kemal Ahmet graduated in physics from the University of Leeds. Following the completion of his masters degree, he completed his Ph.D. at the University of London in the area of nuclear instrumentation in 1992. Until recently, he was a Principal Lecturer at the University of Luton, leading a research group in moisture instrumentation, measurement and monitoring. In 2004 he joined Medtronic, world leader in medical technology, and is currently working in the Neurologic Technologies division as a specialist in powered surgical instrumentation.Young Yue is a Principal Lecturer at the University of Luton, UK. He holds a B.Sc. in mechanical engineering from the Northeastern University, China, and a Ph.D. from Heriot-Watt University, UK. He is a chartered engineer and a member of the Institution of Mechanical Engineers, UK. Dr. Yue has been working in academia for 15 years following his 8 years of industrial experience. His main research interests are CAD/CAM, geometric modelling, virtual reality, and pattern recognition. He has over 70 publications in refereed books, journals and conferences.

Numerical solutions of rotational normal modes of a triaxial two-layered anelastic Earth

The Earth's rotational normal modes depend on Earth model used, including the layer structures,principal inertia moments of different layers and the compliances. This study focuses on providing numerical solution of the rotational normal modes of a triaxial two-layered anelastic Earth model without external forces but with considering the complex forms of compliances and the electromagnetic coupling between the core and mantle. Based on the present knowledge of the Chandler wobble(CW) and Free Core Nutation(FCN), we provide a set of complete compliances which could be used for reference in further investigations. There are eight rotational normal mode solutions, four of which might exist in nature. However, in reality only two of these four solutions correspond to the present motion status of the prograde CW and the retrograde FCN. On one hand, our numerical calculations show that the periods and quality factors(Qs) of CW and FCN are respectively 434.90 and 429.86 mean solar days(d) and 76.56 and 23988.47 under frequency-dependent assumption, and the triaxiality prolongs CW about 0.01 d and has hardly effect on FCN. On the other hand, we analyze the sensibility of compliances and electromagnetic coupling parameter on the periods and Qs of CW and FCN and find the sensitive parameters with respect to them.

中国翻译理论史研究:“一体双层”模式建构

当理论研究发展到一定阶段,就需要进行必要的学术史梳理,以便回望来路,展望去路。近年来,中国翻译理论史研究正成为国内译学界研究的热点之一,以应对翻译学学科进一步发展的诉求。但与当前欣欣向荣的翻译史研究相比,国内的翻译理论史研究还较为薄弱。本研究聚焦中国翻译理论史研究模式的元思考,尝试以翻译理论史的4个要素——译论、翻译实践、译论者和社会为构成性的“一体”,从内层——心理层和外层——社会层以及相对应的两个跨学科视角——发生认识论和知识社会学作为阐释性的“双层”,建构一个研究和撰写中国翻译理论史的“一体双层”模式,并对该模式进行宏观与微观相结合的理论阐发和举例论证,最后对中国翻译理论史研究提出几点建议,特别是提出建立一个译学分支学科——“译论思想史”的设想。本研究希望能为中国翻译理论史的研究和撰写提供研究模式方面的可能途径,助力中国翻译理论史研究向纵深发展。

多园区综合能源系统接入主动配电网双层优化调度研究

随着园区综合能源系统的不断发展与普及,其与上级大电网并网实现交互已成为大势所趋。文中构建了通过联络线相耦合的多园区综合能源系统接入主动配电网的双层优化调度模型。在主动配电网层面,以最小运行成本为目标,充分考虑了联络线功率、分布式电源、储能设备、柔性负荷、电动汽车等可调度资源;在园区层面,以多园区总运行成本最小为目标,考虑了相互联结的多类型园区的并网情况。利用目标级联法对双层模型进行求解。通过算例验证,文中所构建模型具有良好的经济特性与削峰填谷效果,充分证明了文中所提模型的经济性与有效性。

复杂地形对风速廓线的影响

随着风电利用的发展,越来越多的风电场建立在复杂地形的山区,为了更好地进行风能评估和风电预报,就需要了解复杂地形对风速廓线的影响。本文基于薄翼理论和湍流边界层扰动的线性化理论,采用两层模型对坡度较小的山地在其二维横截面上的风廓线进行了预测,该模型能够较为准确地预报地形、压力、稳定度对风速增速的影响,但对于三维地形或其他因素产生的风速的复杂变化,需要进一步将其扩展至三维,并结合数值模拟进行研究。

多因素影响下无人机编队任务可靠性模型构建研究

针对多因素影响下无人机(unmanned aerial vehicle,UAV)编队任务可靠性问题,提出了无人机编队任务可靠性双层模型。首先,基于故障树分析方法,构建了无人机编队任务可靠性下层模型,描述无人机编队的故障状态;其次,基于Markov模型构建无人机编队任务可靠性上层模型,描述无人机编队任务过程中,阶段及状态的转换;最后,建立任务可靠度求解的双层模型对无人机编队任务可靠度进行仿真模拟。设定应用场景仿真验证,仿真结果表明:在起飞/爬升阶段和巡航阶段,本文方法与传统故障树法所计算的任务可靠度结果一致;在侦察阶段,本文方法比传统故障树法的任务可靠度计算结果高0.012 5,给定显著性水平,本文算法的可靠度结果均落在置信区间内,验证了计算结果的可信性。

中央空调负荷精细化调控双层优化技术研究

针对当前中央空调系统粗放式调节不能准确释放调控潜力的问题,深入分析中央空调各子系统工作原理与调控方式,提出基于双层优化的中央空调负荷精细化调控技术方案。首先,面向实际工程实践需求建立建筑湿热标度模型;然后,建立以舒适度和经济性优化目标函数为主的上层调控模型,采用Shapley值法对温湿设定值的进行分配;接着,建立以各子系统优化组合能耗最低为优化目标函数的下层调控模型,采用蚁群算法对优化目标函数进行求解;之后,通过求解双层模型,制定包括末端风机、冷冻水泵以及冷水机组等组件的精细化调控策略;最后,通过多个算例验证所提中央空调负荷精细化调控技术方案的正确性与有效性。

基于高精度热泵模型的电热协同独立微网设备优化配置

为实现含丰富工业余热、数据中心余热、生活污水余热等低品位热源的区域协同供能,以及提高区域清洁能源利用效率,针对区域独立微网供能系统的设备优化配置策略进行研究。基于多类型低品位热源的不同温度品位特征,提出用于提升热源温度品位的关键电热泵设备多参数拟合模型,并生成热泵拟合模型的误差不确定性场景;考虑微网在实际运行不确定性场景下产生的供热舒适度补偿、切负荷与切光伏风险,提出基于多条件风险价值(CVaR)理论的独立微网设备容量优化配置双层模型,上层模型基于全寿命周期成本费用年值与年CVaR值优化设备配置方案,下层模型基于场景分析法优化运行成本;采用遗传算法对双层模型进行求解。算例结果证明:考虑热泵拟合模型误差有效降低了系统运行风险,且低品位热源的回收利用具有较大经济性潜力。

考虑共享储能容量配置的多虚拟电厂优化运行方法

由于分布式能源具有间歇性和波动性的特点,其大规模接入电网会对系统稳定性产生一定的影响。为了减少用户侧用电成本以及提高新能源的消纳能力,在多虚拟电厂背景下提出共享储能系统促进风光消纳的规划和运行双层决策博弈模型。上层模型对共享储能电站投资运行成本进行等年值转换分析,以共享储能总成本最低且使用寿命尽可能的长为目标函数建立模型;下层模型以虚拟电厂运行成本最低及弃风弃光最小为目标函数建立运行优化模型。采用鲸鱼算法与CPLEX商业求解器结合的形式对共享储能电站的容量配置、充放电行为以及虚拟电厂运行状态进行求解,并通过设置3个场景算例对所提方案进行验证,结果表明,所提方法可以优化共享储能电站容量最优配置和充放电策略,提高可再生能源的消纳能力和虚拟电厂系统运行效率,兼顾供给侧与需求侧的利益,使电能分配更加公平合理。

配电网负荷预测中信号分解和预测模型组合的双层优化策略

负荷时间序列的波动性和非线性特征的加剧对负荷预测方法提出了更高的要求,而常规组合预测方法针对海量负荷数据存在应用局限性问题。为此,提出了配电网负荷预测中时序分解方法和预测模型组合的双层优化策略。首先针对某一负荷预测数据,在时序信号分解层配置权重,以负荷均方根误差最小寻优各分解方法的权重系数,进而获得各时序信号分解方法的最优组合;在此基础上,在预测模型层进行组合方案寻优,通过配置权重系数以获得各预测模型的最优组合,进一步提升负荷预测的精度。仿真结果表明,所提策略可根据预测对象的特征优化组合各信号分解方法和预测模型,降低了配电网负荷序列的非平稳性对预测精度的影响。

水火风光多能互补系统联合调度问题两层优化建模方法研究

为解决水火风光多能互补发电系统联合优化复杂问题,提出了一种水火风光多能互补系统联合调度问题两层优化建模和求解方法,上层以余荷均方差和期望均值最小为目标函数对水风光清洁能源打捆进行联合优化,下层以成本经济指标最小为目标函数对火电适配余荷进行优化。以江西省典型春秋季、夏季和冬季江西省的电网负荷以及风电、光电的出力过程为研究对象进行实例分析,采用研究团队提出的DPSA-POA和智能算法混合优化方法进行模型求解,验证了本文所提两层优化建模和求解方法的有效性。并发现了风光可弃情境相比风光完全消纳情景虽然在火电出力上有所提高,但在整体运行费用上有所降低。在以春秋季江西省的电网负荷和风电、光电的出力过程为研究对象进行的实例分析结果显示,火电出力总和提升了5.79%,多能互补系统整体运行费用减少了4.97%;在以夏季江西省的电网负荷和风电、光电的出力过程为研究对象进行的实例分析结果显示,火电出力总和提升了0.32%,多能互补系统整体运行费用减少了1.95%;在以冬季江西省的电网负荷和风电、光电的出力过程为研究对象进行的实例分析结果显示,火电出力总和提升了10.70%,多能互补系统整体运行费用减少了6.78%。该方法为求解水火风光多能互补联合优化复杂问题提供了一种新的思路。

考虑气水打捆外送的气水协调双层优化模型

针对水电“丰多枯少”资源特性给电力系统调峰、输电通道利用率造成的挑战,提出一种考虑气水打捆外送的气水协调双层优化方法。首先,分析川渝地区气水融合发展策略,提出气水打捆外送模式;其次,建立考虑气水打捆外送的气水协调发电双层优化模型。上层模型以考虑气电投资成本的系统年总利润最大化为目标,实现气水协调的容量优化配置,下层模型以年运营收益最大化为目标,实现气水协调优化运行;然后,采用混沌粒子群算法结合CPLEX求解器对模型进行求解,利用Shapley值法实现气水打捆外送的利润分配;最后,以某区域电力系统为例进行算例分析,结果表明所提模型可优化配置气电装机容量,实现气水协调优化运行,缓解水电季节性矛盾造成的调峰困境,提升外送通道利用率。

考虑电力系统灵活性供需平衡的混合储能联合规划

风电、光伏等可再生能源出力具有强波动性和随机性,增加了电力系统的灵活性需求。文章提出了兼顾经济性和灵活性的电力系统混合储能联合规划方法。首先,针对源荷两端灵活性需求,从电力电量平衡角度对系统灵活性进行了评估;其次,以火电机组灵活性改造、全钒液流电池、抽水蓄能3类灵活性资源为规划对象,构建火电机组灵活性改造和混合储能协调的双层规划模型;利用上、下层模型对方案不断进行迭代优化,得到兼顾经济性和灵活性的最优混合储能配置方案;再次,采用基于反向学习的改进型白鲸算法对规划模型进行优化,并通过仿真验证了模型的正确性;最后,以蒙东某地区历史数据进行算例分析,验证所提方法的有效性。