Subwavelength triangular random gratings

A subwavelength triangular diffractive element, whose local periods are not regular as an ordinary grating but has random values within a certain range, is proposed as a substitute for a common subwavelength antireflection grating. Its diffraction properties are electromagnetically analysed by the finite-difference time-domain method. Such a random grating shows some interesting properties, including suppression of higher diffraction orders. This improves the signal-to-noise ratio of a signal wave. Also, it is found possible for a random grating to retain a diffraction effciency comparable with that of a regular grating, even when some local periods violate the subwavelength condition, provided that the random local period range is properly chosen. This is another advantage of a random grating over the regular grating in the fabrication process, because upper limitation on feature sizes is partially relieved. In addition, application to general random scattering problems is discussed.     

Invar36合金搅拌摩擦焊焊缝的低温韧性

为了研究Invar36合金搅拌摩擦焊焊缝的低温韧性,采用小冲杆试验方法（small punch test）对焊接速度2mm／s,搅拌头旋转频率200一1000r／min的Invar36合金焊缝进行低温（77K）和室温（298K）韧性测试．298K下,所有焊接工艺的焊缝小冲杆试验能均高于母材,焊缝韧性随搅拌头旋转频率的提...     

An Electricity Price Forecasting Model with Fuzzy Clustering Preconditioned ANN

In this paper, a hybrid model of fuzzy clustering and ANN (Artificial Neural Network) is proposed for electricity price forecasting. Due to the complicated behavior of electricity price in power markets, market players are interested in maximizing profits while minimizing risks. As a result, more accurate models are required to deal with electricity price forecasting. This paper proposes a new method that makes use of fuzzy clustering preconditioned GRBFN (Generalized Radial Basis Function Network) to provide more accurate predicted prices. Fuzzy clustering plays a key role to prevent the number of learning data from decreasing at each cluster. GRBFN is one of efficient ANNs to approximate nonlinear systems. Furthermore, a modified GRBFN model is developed to improve the performance of GRBFN with the use of DA (Deterministic Annealing) clustering for the parameters initialization and EPSO (Evolutionary Particle Swarm Optimization) for optimizing the parameters of GRBFN. The proposed method is successfully applied to real data of ISO New England, USA.     

THE EFFECT OF A NON-UNIFORM SURFACE TEMPERATURE ON LAMINAR NATURAL CONVECTION IN A RECTANGULAR ENCLOSURE

Three dimensional solutions were developed for natural convection in a 2 × 1 × 1 rectangular enclosure by finite-difference calculations. Sawtooth temperature distributions with different amplitudes and orientations were imposed on the lower (2×1) surface to simulate the effect of cooling coils or jackets on the collector plate of a flat-plate solar heater. The shorter dimension of the enclosure was progressively inclined.

The circulation patterns were not changed significantly by the surface temperature distributions. The variation of the Nusselt number with inclination was not changed significantly but the magnitude increased with the amplitude of the surface temperature variations for inclinations of less than 90 degrees.

It is concluded that the collecting plate of a solar collector should be maintained as nearly isothermal as possible to minimize heat losses by natural convection through the air gap.     

INTRAPARTICLE MASS TRANSFER IN THERMALLY REGENERABLE ION EXCHANGER

An intraparticle mass transfer model was developed for a thermally regenerable ion exchanger which is coagulated by weak acidic and basic microspheres. It was assumed that salt diffuses (hrough macropore and microspheres in the radial direction of a resin particle. Uptake curves were measured not only in [R_aCOOH + R_bN] + NaCl ) [R_aCOONa + R_bNHCl] system but also in [R_aCOO²²Na⁺ + R_aN] + Na⁺ )[R_aCOONa⁺ + R_bN] + ²²Na⁺ and [R_aCOOH + R_aN] + HCl ) [R_aCOOH + R_bNHCl] systems. Macropore diffusivity D_p.Na, tortuosity factor τ_p and diffusivity through weak acidic microspheres D_a,Na were obtained from the isotopic ion exchange. The uptake curves of HC1 gave diffusivity through weak basic microspheres.D_b,Hcl The experimental uptake and desorption curves of NaCl agreed fairly well with the theoretical values. Diffusions through both macropore and microspheres were significant. The diffusivity through microspheres D_b,Nacl NaCI are smaller than D_a,Na. and can be estimated by D_bHcl approximately.     

Heuristics free group method of data handling algorithm of generating optimal partial polynomials with application to air pollution prediction†

In this paper a revised GMDH (Group Method of Data Handling) algorithm is developed in which heuristicsare not required such as dividing the available date. into training data and checking data, predetermining the structure of the partial polynomials, or predetermining the number of intermediate variables. In this algorithm the prediction error criterion, such as PSS (Prediction Sum of Squares) or AIC (Akaike's Information Criterion) evaluated from all the available data, in used as a criterion for generating optimal partial polynomials, for selecting intermediate variables and for stopping the multilayered iterative computation. This heuristics freeGMDH algorithm is applied to non-linear modelling for short-term prediction of air pollution concentration. By using the time series data of SO₂, concentration, the wind velocity and the wind direction in Tokushima; Japan, a suitable model for predicting SO₂concentration at a few hours in advance is developed. The predicted results obtained by the revised GMDH model are compared with the results obtained by a linear regression model, a linear autoregressive model and a. basic GMDH model.     

Enthalpy of Denaturation and Surface Functional Properties of Heated Egg White Proteins in the Dry State

The enthalpy of denaturation (ΔH) and surface properties of proteins were related to elucidate the mechanisms of foaming and emulsifying properties by using various heated egg white proteins in the dry state. Foaming and emulsifying properties of all sample proteins were greatly increased with a decrease in the enthalpy of denaturation as determined by differential scanning calorimetry analysis. In plots, foaming and emulsifying properties correlated linearly with ΔH values for various dry-heated egg white proteins. Thus, the enthalpy of denaturation of proteins seemed to be a significant structural factor governing surface functional properties.     

Molecular Dynamics Simulation of the Structure of Borate Glasses

The structures of borate glasses have been simulated by use of molecular dynamics. A new type of potential calculated by means of the intermediate neglect of differential overlap (INDO) method and a three-body potential were introduced into the molecular dynamics simulation. Boroxyl rings and diborate groups have been successfully reproduced in the structure models obtained from the present molecular dynamics simulation. Calculated radial distribution functions agreed well with the observed one obtained from X-ray diffraction data. The distribution of O–B–O and B–O–B bond angles is also given.     

Running Torque of Ball Bearings with Polymer Lubricant (Effect of the Enclosure Form of Polymer Lubricant)

This article deals with the running torque of ball bearings with polymer lubricant (solid composite material composed of plastic impregnated with a large amount of oil or grease). The results of the experiment showed that the measured running torque of ball bearings with polymer lubricant was affected by the enclosure form of the polymer lubricant. With regard to ball bearings with different enclosure forms of the polymer lubricant, the measured running torque difference was not affected significantly by the rotational speeds or the axial loads. The analytical results showed that the running torque difference was caused mainly by the friction (depending on the enclosure form of the polymer lubricant) between the balls and the polymer lubricant (or cage).