Simulation of the ocean surface mixed layer under the wave breaking

A one-dimensional mixed-layer model, including a Mellor-Yamada level 2.5 turbulence closure scheme, was implemented to investigate the dynamical and thermal structures of the ocean surface mixed layer in the northern South China Sea. The turbulent kinetic energy released through wave breaking was incorporated into the model as a source of energy at the ocean surface, and the influence of the breaking waves on the mixed layer was studied. The numerical simulations show that the simulated SST is overestimated in summer without the breaking waves. However, the cooler SST is simulated when the effect of the breaking waves is considered, the corresponding discrepancy with the observed data decreases up to 20% and the MLD calculated averagely deepens 3.8 m. Owing to the wave-enhanced turbulence mixing in the summertime, the stratification at the bottom of the mixed layer was modified and the temperature gradient spread throughout the whole thermocline compared with the concentrated distribution without wave breaking.

An exact solution for the three-phase piezoelectric cylinder model under antiplane shear and its applications to piezoelectric composites

A three-phase piezoelectric cylinder model is proposed and an exact solution is obtained for the model under a farfield antiplane mechanical load and a far-field inplane electrical load. The three-phase model can serve as a fiber/interphase layer/matrix model, in terms of which a lot of interesting mechanical and electrical coupling phenomena induced by the interphase layer are revealed. It is found that much more serious stress and electrical field concentrations occur in the model with the interphase layer than those without any interphase layer. The three-phase model can also serve as a fiber/matrix/composite model, in terms of which a generalized self-consistent approach is developed for predicting the effective electroelastic moduli of piezoelectric composites. Numerical examples are given and discussed in detail.

The development of an inhomogeneous damage field in an elastic-plastic model

By making use of the evolution equation of the damage field as derived from the statistical mesoscopic damage theory, we have preliminarily examined the inhomogeneous damage field in an elastic-plastic model under constant-velocity tension. Three types of deformation and damage field evolution are presented. The influence of the plastic matrix is examined. It seems that matrix plasticity may defer the failure due to damage evolution. A criterion for damage localization is consistent with the numerical results.

Numerical Analysis of the Effects of Free-Stream Thermo-Chemical State on the Test Model Flow Field in High-Enthalpy Tunnel

The effects of the free-stream thermo-chemical state on the test model flow field in the high-enthalpy tunnel are studied numerically. The properties of the free-stream, which is in thermo-chemical non-equilibrium, are determined by calculating the nozzle flow field. A free-stream with total enthalpy equal to the real one in the tunnel while in thermo-chemical equilibrium is constructed artificially to simulate the natural atmosphere condition. The flow fields over the test models (blunt cone and Apollo command capsule model) under both the non-equilibrium and the virtual equilibrium free-stream conditions are calculated. By comparing the properties including pressure, temperature, species concentration and radiation distributions of these two types of flow fields, the effects of the non-equilibrium state of the free-stream in the high-enthalpy shock tunnel are analyzed.

BRST invariant theory of a generalized 1+1 Dimensional nonlinear sigma model with topological term

We give a generalized Lagrangian density of 1 + 1 Dimensional O( 3) nonlinear sigma model with subsidiary constraints, different Lagrange multiplier fields and topological term, find a lost intrinsic constraint condition, convert the subsidiary constraints into inner constraints in the nonlinear sigma model, give the example of not introducing the lost constraint. N = 0, by comparing the example with the case of introducing the lost constraint, we obtain that when not introducing the lost constraint, one has to obtain a lot of various non-intrinsic constraints. We further deduce the gauge generator, give general BRST transformation of the model under the general conditions. It is discovered that there exists a gauge parameter beta originating from the freedom degree of BRST transformation in a general O( 3) nonlinear sigma model, and we gain the general commutation relations of ghost field.

Valence stability and change of Eu(II)in oxides

Valence stability and change of Eu(II) in oxides have been studied by luminescence spect a. The results show that the valence stability and change of Eu(II)in oxides is closely related to the radius and electric charge of positive ions substituted by Eu(II) and crystal structure of the host such as Al2O3 which can form alpha-Al2O3 single phase and alpha-Al2O3 and gamma-Al2O3 mixed phases under different reaction temperatures. A, fairly good explanation is made by the proposed relation between energy coefficient and crystal structure for the first time to the observed experiment results. if the energy coefficients of substitution ions is more than that of Eu(II), the lattice substitution of Eu(II)for these ions is not occured generally and valence stare of Eu(II)is not stable and be easily changed into Eu(III). The lattice of gamma-Al2O3 can stablize the valence state of Eu(II)within certain coped concentration and in alpha-Al2O3 crystal lattice Eu(II)can be easily changed into Eu(III).

Controlling electric field distribution by graded spherical core-shell metamaterials

This paper investigates analytically the electric field distribution of graded spherical core-shell metamaterials, whose permittivity is given by the graded Drude model. Under the illumination of a uniform incident optical field, the obtained results show that the electrical field distribution in the shell region is controllable and the electric field peak's position inside the spherical shell can be confined in a desired position by varying the frequency of the optical field as well as the parameters of the graded dielectric profiles. It has also offered an intuitive explanation for controlling the local electric field by graded metamaterials.

波浪破碎散射模式的研究及应用

海面反射、散射或自发辐射的各个波段的电磁波携带着海表面温度、海平面高度、海表面粗糙度以及海水所含各种物质浓度的信息。波浪破碎是海洋的一种重要现象，波浪破碎支撑着海－气之间的热通量和气体通量的交换，这些通量对于天气和气候都有深远影响。同时，波浪破碎使得海表的粗糙度增加，这对于海表散射电磁波有极大的影响，因此在处理雷达散射问题时，考虑波浪破碎的影响十分必要。 本文分析了雷达散射的两种模式，并阐述了波浪破碎在海表电磁波散射过程中的重要性。论文的创新点在于利用Kudryavtsev03模式，反演得到了波浪破碎率与风速的两种新关系式，同时得到了较高精度的风速反演的隐含模式。针对波浪破碎微波散射模式问题，论文主要研究结果如下： 1.在Kudryavtsev03模式的基础上，以黄兴忠的白冠覆盖率公式替代破碎率，利用ERS-1散射计数据，对Bragg散射模式和Kudryavtsev03模式的结果进行了比较。结果表明：在相同条件下，考虑波浪破碎的Kudryavtsev03模式明显优于纯Bragg散射模式。 2 对Kudryavtsev03模式进行了修正。通过与实测ERS-1散射计数据比较，表明修正后，入射角在18-35°范围内，模式的结果具有较高的精度。 3 利用修正后的模式及散射计数据，在入射角为30-35°范围内，反演破碎率，并对反演结果进行了拟合，得到了两个新的破碎率与风速的关系式。 4 利用修正后的模式及新的破碎率公式，在入射角为30-35°范围内，反演风速，具有较高精度。 5 利用反演的风速，根据经验关系式，推算了各种海洋物理量。

混流汽车总装配线上的零部件优化配送方案研究

配送车每次配送的利用率大小是提高配送效率的主要因素,因此设计一种启发式算法使配送车一次装载的标准塑料周转箱尽可能多,提高配送车空间利用率。最后的仿真实验验证了上述配送方法的实用性,提出的零部件配送管理方法,只需使用较少的配送工人,同时降低了线旁库存,能为企业节省人力,降低生产成本。

汽车混流总装线投产排序优化研究

汽车混流总装线上交替装配不同型号的汽车产品,不同型号的汽车在同一装配工位上装配的零部件可能不同,如果不对车型的投产顺序加以优化排序,连续投入一种相同的车型,会使同一个工位的零部件消耗率严重不均衡。为了使各装配工位的零部件消耗率达到均匀化和平准化,本文采用模拟退火优化算法,对车型上线序列进行优化,最后的实例验证表明算法是可行的。

基于RFID的混流装配汽车生产线物料动态配送研究

针对混流装配的汽车自动化生产线提出了基于RFID的车辆追踪和基于条码的无线物料库存管理实现方法。在此基础上,设计了装配生产线的物料动态配送调度业务流程,给出了物料动态配送的规划依据,并进行了实例计算。

混流汽车装配线物料配送优化策略研究

随着世界经济的迅速发展和科学技术的不断进步，物流对经济贸易活动的影响与日俱增，受到越来越多人们的关注。在中国，越来越多的人们已经意识到物流对企业发展的重要性，因为物流业的发展必然降低物流成本在GDP中的比重；加快企业流动资金周转速度；还必然带动固定资产投资，降低企业的物流成本，提高市场竞争力。汽车生产物流系统是制造业界公认的最复杂，组织难度最大，物流管理任务最繁重的系统，对企业内部来说，生产的全过程更多的转化为生产物料的配送与装配，而不是过去的原材料的加工生产。据统计在装配线的实际运行过程中，由于物料配送不及时或错误导致输送链停止的情况占有很大的比例，优化装配线上的物料配送管理系统就显得非常重要。 本文结合当地某汽车总装厂的生产物流现状，研究设计一种高效的物流配送管理系统。汽车混流装配线上多种型号的汽车共线生产，一个好的物料配送系统应保证将正确数量的合格零部件在准确的时间配送到需要的工位旁边。在分析混流装配线上物料流的基础上，我们提出了针对系统的几个优化目标，首先以使各工位的零部件使用速率均衡化为目标，采用模拟退火算法，来得到车身上线的最优投产排序序列，在此基础上，我们设计物流配送系统的体系结构，包括库房条形码管理系统和线上物料配送管理系统，然后根据配送管理系统中存在的一系列问题，文中研究提出了一种插入启发式优化算法，来实现零部件从库房到生产线旁的动态配送，最后我们采用数字化工厂仿真软件Em-plant建立一套物流配送管理系统的仿真模型，仿真结果验证了该系统的高效性，并对汽车制造业的企业管理者作决策起到一定的参考意义。

Equivalent Model Of Expansion Of Cement Mortar Under Sulphate Erosion

The expansion property of cement mortar under the attack of sulfate ions is studied by experimental and theoretical methods. First, cement mortars are fabricated with the ratio of water to cement of 0.4, 0.6, and 0.8. Secondly, the expansion of specimen immerged in sulphate solution is measured at different times. Thirdly, a theoretical model of expansion of cement mortar under sulphate erosion is suggested by virtue of represent volume element method. In this model, the damage evolution due to the interaction between delayed ettringite and cement mortar is taken into account. Finally, the numerical calculation is performed. The numerical and experimental results indicate that the model perfectly describes the expansion of the cement mortar.

An Electrowetting Model For Rough Surfaces Under Low Voltage

Electrowetting is one of the most effective methods to enhance wettability. A significant change of contact angle for the liquid droplet can result from the surface microstructures and the external electric field, without altering the chemical composition of the system. During the electrowetting process on a rough surface, the droplet exhibits a sharp transition from the Cassie-Baxter to the Wenzel regime at a low critical voltage. In this paper, a theoretical model for electrowetting is put forth to describe the dynamic electrical control of the wetting behavior at the low voltage, considering the surface topography. The theoretical results are found to be in good agreement with the existing experimental results. (c) Koninklijke Brill NV, Leiden, 2008.