Visible light-induced charge storage, on-demand release and self-photorechargeability of WO3 film

Tungsten oxide (WO(3)) electrodes subjected to a positive bias are self-photorecharged with alkali cations in the electrolyte during visible light illumination. Upon photoexcitation, part of the photogenerated charges generated by WO(3) is stabilized by the cations and stored in situ within the WO(3) framework. This light-induced storage of charges is subsequently utilized in dark conditions in an on-demand manner and is able to be recharged in the successive illumination cycles. The amount of charges stored is shown to be dependent on the cation ionic radii and the presence of these intercalated cations is verified by X-ray diffraction (XRD) and inductively coupled plasma mass spectroscopy (ICP-MS). This self-photorecharge and on-demand charge-release phenomena demonstrate the ability of WO(3) to supply photoexcited charges under dark condition in a photoelectrochemical reaction with greater flexibility.     

Size-selective concentration and label-free characterization of protein aggregates using a Raman active nanofluidic device

Trace detection and physicochemical characterization of protein aggregates have a large impact in understanding and diagnosing many diseases, such as ageing-related neurodegeneration and systemic amyloidosis, for which the formation of protein aggregates is one of the pathological hallmarks. Here we demonstrate an innovative label-free method for detecting and characterizing small amounts of early stage protein aggregates using a Raman active nanofluidic device. Sub-micrometre channels formed by a novel elastomeric collapse technique enable the separation and concentration of matured protein aggregates from small protein molecules. The Raman enhancement by gold nanoparticle clusters fixed below a micro/nanofluidic junction allows characterization of intrinsic properties of protein aggregates at concentration levels (～fM) much lower than can be done with traditional analytical tools. With our device we show for the first time the concentration dependence of protein aggregation over these low concentration ranges. We expect that our method could facilitate definitive diagnosis and possible therapeutics of diseases at early stages.     

Nonlocal instability analysis of FCC bulk and (1 0 0) surfaces under uniaxial stretching

The objective of this paper is to examine the instability characteristics of both a bulk FCC crystal and a (1 0 0) surface of an FCC crystal under uniaxial stretching along a 〈1 0 0〉 direction using an atomistic-based nonlocal instability criterion. By comparison to benchmark atomistic simulations, we demonstrate that for both the FCC bulk and (1 0 0) surface, about 5000–10,000 atoms are required in order to obtain an accurate converged value for the instability strain and a converged instability mode. The instability modes are fundamentally different at the surface as compared to the bulk, but in both cases a strong dependence of the instability mode on the number of atoms that are allowed to participate in the instability process is observed. In addition, the nonlocal instability criterion enables us to determine the total number of atoms, and thus the total volume occupied by these atoms, that participate in the defect nucleation process for both cases. We find that this defect participation volume converges as the number of atoms increases for both the bulk and surface, and that the defect participation volume of the surface is smaller than that of the bulk. Overall, the present results demonstrate both the necessity and utility of nonlocal instability criteria in predicting instability and subsequent failure of both bulk and surface-dominated nanomaterials.     

Two-phase annular flow and evaporative heat transfer in a microchannel

A physical and mathematical model has been developed to predict the two-phase flow and heat transfer in a microchannel with evaporative heat transfer. Sample solutions to the model were obtained for both constant wall temperature and constant wall heat flux conditions. Results are provided for evaporation rate, liquid film thickness, liquid and vapor phase pressure and temperature distributions. In addition to the sample calculations that were used to illustrate the transport characteristics, computations based on the current model were performed to generate results for comparisons with the experimental results of Qu and Mudawar (2004) where two different mass flow rates of the working fluid were used in the experiment. The comparisons of total pressure drops with the experimental data of Qu and Mudawar (2004) cover the wall heat flux range of 142.71-240 W/cm² with a total channel mass flux of 400.1 kg/m² s and also the wall heat flu range of 99.54-204.39 W/cm² with total channel mass flux of 401.9 kg/m² s. The calculated results from the current model match closely with those of Qu and Mudawar (2004).     

A self-optimizing inverse analysis method for estimation of cyclic elasto-plasticity model parameters

In this paper, a novel inverse analysis methodology call a Self-Optimizing Inverse Method (Self-OPTIM) has been presented, which inversely estimates cyclic elasto-plastic constitutive model parameters using global forces and displacement on the same partial boundaries and full-(or partial-) field displacement data. A novelty of the methodology is that it automatically self-estimates material parameters by updating “full-field” reference stresses and strains through two parallel nonlinear finite element simulations. Although a well-known classical cyclic plasticity model is chosen in this paper, it must be emphasized that the proposed Self-OPTIM method is a model-independent method, which means that any advanced model can be naturally integrated with the proposed methodology. Thus, using numerically generated test data of low-carbon steel specimens (AISI 1010), the proposed Self-OPTIM method has been verified showing its successful performance to estimate nonlinear isotropic and kinematic hardening parameters, yield stress, Young’s modulus and Poisson ratio. The effects of experimental noises from CCD camera and measurement errors of the boundary forces are also investigated for the Self-OPTIM method.     

重大工程引起的珠江河口潮波逆向不稳定传播现象

采用模式ccost-2d对50年前白藤堵海工程及10年之后泥湾门区域的水动力特征变化进行了模拟和分析.结果可见,堵海工程造成泥湾门水道白蕉站潮差变小,高低潮时刻滞后2h以上,低潮水位抬升超过0.5m,引起严重的内涝问题.通过数值解对整个河网区的流动过程分析发现,由于堵海工程堵塞了泥湾门水道直接通向大海的通道,仅留的鸡啼...     

Validation of EMMS-based drag model using lattice Boltzmann simulations on GPUs

Interphase momentum transport in heterogeneous gas–solid systems with multi-scale structure is of great importance in process engineering. In this article, lattice Boltzmann simulations are performed on graphics processing units (GPUs), the computational power of which exceeds that of CPUs by more than one order of magnitude, to investigate incompressible Newtonian flow in idealized multi-scale particle–fluid systems. The structure consists of a periodic array of clusters, each constructed by a bundle of cylinders. Fixed pressure boundary condition is implemented by applying a constant body force to the flow through the medium. The bounce-back scheme is adopted on the fluid–solid interfaces, which ensures the no-slip boundary condition. The structure is studied under a wide range of particle diameters and packing fractions, and the drag coefficient of the structure is found to be a function of voidages and fractions of the clusters, besides the traditional Reynolds number and the solid volume fractions. Parameters reflecting multi-scale characters are, therefore, demonstrated to be necessary in quantifying the drag force of heterogeneous gas–solid system. The numerical results in the range 0.1 ≤ Re ≤ 10 and 0 < ? < 0.25 are compared with Wen and Yu's correlation, Gibilaro equation, EMMS-based drag model, the Beetstra correlation and the Benyahia correlation, and good agreement is found between the simulations and the EMMS-based drag model for heterogeneous systems.     

Representations of efficient score for coarse data problems based on Neumann series expansion

We derive new representations of the efficient score for the coarse data problems based on Neumann series expansion. The representations can be applied to both ignorable and nonignorable coarse data. Approximations to the new representations may be used for computing locally efficient scores in such problems. We show that many of the successive approximation approaches to the computation of the locally efficient score proposed in the literature for such problems can be derived as special cases of the representations. In addition, the representations lead to new algorithms for computing the locally efficient scores for the coarse data problems.     

Ellipsoidal BGK model for polyatomic molecules near Maxwellians: A dichotomy in the dissipation estimate

We consider the global existence and asymptotic behavior of classical solutions to the ellipsoidal BGK model for polyatomic molecules when the initial data starts sufficiently close to a global polyatomic Maxwellian. We observe that the linearized relaxation operator is decomposed into a truly polyatomic part and an essentially monatomic part, leading to a dichotomy in the dissipative property in the sense that the degeneracy of the dissipation shows an abrupt jump as the relaxation parameter θ reaches zero. Accordingly, we employ two different sets of micro–macro system to derive the full coercivity and close the energy estimate.