A comparison between backscattering coefficients using Gaussian and non-Gaussian surface statistics

This communication provides a comparison between the backscattering coefficients computed using Gaussian versus non-Gaussian surface statistics. The computations are performed for a class of surface height distributions and surface correlation functions. Results indicate that the coherent component of the scattering coefficient is strongly dependent upon the surface height distribution. The noncoherent component also depends on the surface height distribution and the surface root mean square (rms) slope when the rms surface height is large relative to the incident wavelength. On the other hand, when the surface rms height is moderate or small, the noncoherent component is sensitive mainly to the surface height correlation function.     

Effects of a Rough Boundary Surface on Polarization of the Scattered Field from an Inhomogeneous Medium

The effect of surface roughness on the polarization of the scattered field is studied by combining the standard Kirchhoff method for rough surface scattering with the radiative transfer method for volume scattering using the Rayleigh phase function. Corresponding cases of pure surface scattering from a homogeneous layer and volume scattering from a plane inhomogeneous layer are also computed to serve as points of reference. In each case the degree of polarization DP, polarization ratio PR, locations on the Poincaré sphere of copolarization nulls CN, and cross-polarization nulls XN are computed. It is found that for pure surface scattering PR between 0-20° incidence angles is quite sensitive to change in surface roughness. However, when both surface and volume scattering are present, CN by colatitude or DP between 0-15° incidence angles and CN or XN by longitude at large incidence angles (>60°) are better indicators of change in surface roughness. Since XN changes insignificantly in pure surface scattering, it appears that a significant change in it can serve as an indicator for the presence of volume scattering. Also, in pure surface or volume scattering, the variations of DP and CN by colatitude are monotone with the incidence angle, while in the combined surface and volume scattering DP has a minimum and CN by colatitude has a maximum. This character offers the possibility of separating combined surface and volume scattering from pure surface or volume scattering.     

Simulation and experimental investigation of two hybrid solar domestic water heaters with drain water heat recovery

In this paper, the performance of two solar domestic hot waters (SDHW) with drain water heat recovery (DWHR) units is investigated. Both SDHW systems are recently installed at the Archetype Sustainable Twin Houses at Kortright Center, Vaughan, Ontario. The first SDWH system in House A consists of a flat plate solar thermal collector in combination with a gas boiler and a DWHR unit. The second SDHW system in House B includes an evacuated tube solar collector, an electric tank, and a DWHR unit. Both systems are modeled in TRNSYS, and the models are validated by experimental data. The addition of the DWHR and the flat‐plate solar thermal collector would result in 1831 kWh of annual energy saving in House A. While the addition of the DWHR and the evacuated tube collector in House B would result in an annual energy saving of 1771 kWh. Subsequently, the models are used to investigate the performance of similar systems for five major Canadian cities of Halifax, Montreal, Toronto, Edmonton, and Vancouver. The conjunctions of solar thermal collectors with DWHR units are found most beneficial in Edmonton. It is also noted from experimental and simulated results that flat‐plate solar collector‐based water heater produced more thermal energy than the system based on the evacuated tube solar collector for all major Canadian cities. Copyright © 2015 John Wiley & Sons, Ltd.     

The synthesis and characterization of the Sm0.5Sr0.5Co1−xCuxO3−δ cathode by the glycine-nitrate process

In this study, a new oxygen-deficient cathode material, Sm_0.5Sr_0.5Co_1−xCu_xO_3−δ (SSCCu) was developed. It is expected to enhance the efficiency of intermediate-temperature solid oxide fuel cells (IT-SOFCs). The structure, conductivity and electrochemical performance of SSCCu were examined as a function of copper content. The structure of Sm_0.5Sr_0.5Co_0.9Cu_0.1O_3−δ and Sm_0.5Sr_0.5Co_0.8Cu_0.2O_3−δ samples was a single orthorhombic perovskite phase. Second phase SrCoO_2.8, however, formed in the Sm_0.5Sr_0.5Co_0.7Cu_0.3O_3−δ and Sm_0.5Sr_0.5Co_0.6Cu_0.4O_3−δ samples. The conductivity of the Sm_0.5Sr_0.5Co_0.7Cu_0.3O_3−δ cathode was higher than that of other samples. However, the Sm_0.5Sr_0.5Co_0.8Cu_0.2O_3−δ electrode exhibited the lowest overpotential of 25 mV at 400 mA cm⁻² and the lowest area special resistance of 0.2 Ω cm² at 700 °C.     

A multiagent supply chain planning and coordination architecture

A supply chain is a worldwide network of suppliers, manufactures, warehouses, distribution centers and retailers through which raw materials are acquired, transformed and delivered to customers. In recent years, a new system approach for managing the supply chain at the tactical and operational levels has emerged. It views a supply chain as composed of a set of intelligent (software) agents, who are responsible for one or more activities and interacting with other related agents in planning and executing their responsibilities. This paper presents a multiagent architecture of supply chain integration. Agents coordination using extended contract net protocol is discussed. Two types of bidding approaches, i.e., the customizing-type and webbing-type are introduced into the multiagent supply chain system. Finally, a heuristics and two programming models for the planning and coordination of demand-driven supply chains are suggested.     

Field measurement of the air flow characteristics of big mechanically ventilated spaces

Air speeds induced by mechanical ventilation systems in the occupied zone are studied experimentally in seven railway stations in Hong Kong. Values of air speed at different positions are measured. From these values, air speed contours and turbulence intensities are calculated. Macroscopic numbers describing airflow in a space including the Reynolds number and the jet momentum number are estimated and their potential uses are discussed.     

Variable structure tracking control of a single‐link flexible arm using time‐varying sliding surface

In this article, a novel variable structure controller has been developed for the trajectory tracking of a one‐link flexible arm. The controller consists of two sliding surfaces: namely, a three‐term time invariant surface for the hub angle and a two‐term time varying surface for the first vibration mode of the arm. Switching control laws are obtained analytically so as to guarantee the global stability as well as the attractiveness toward the two sliding surfaces. The lowest allowable sampling frequency for digital implementation is also derived. Experiments are performed on a one‐link flexible arm and results demonstrate the effectiveness of the proposed controller. ©1999 John Wiley & Sons, Inc.     

Thin Film Deposition of Semiconducting Ni-Co Oxide Spinel with Adequate Electrical and Optical Properties for Energy Application

Nickel-cobalt oxide with spinel structure was successfully fabricated using a wet chemical route followed by calcinations at 300 °C. In nickel-cobalt spinel oxide, Ni²⁺ ions occupy the octahedral sites and Co³⁺ ions are distributed over both octahedral and tetrahedral sites. Very interestingly, nickel-cobalt spinel oxide does not only show a p-type semi-conducting behavior material but also exhibits desired transparency in infrared wavelengths. Electrical and optical properties of the deposited films were investigated as a function of different processing conditions. The sputtering target is fabricated by homogeneously mixing oxide powders and followed by sintering at 1,500 °C. The nickel-cobalt oxide film showed a resistivity as low as 10^?2 Ω-cm by radio frequency (RF) magnetron sputtering in a pure oxygen atmosphere. The sputter-deposited nickel-cobalt oxide films also showed more than 70% transmittance in the infrared range.     

GENERALISED TRANSFER FUNCTIONS OF NEURAL NETWORKS

When artificial neural networks are used to model non-linear dynamical systems, the system structure which can be extremely useful for analysis and design, is buried within the network architecture. In this paper, explicit expressions for the frequency response or generalised transfer functions of both feedforward and recurrent neural networks are derived in terms of the network weights. The derivation of the algorithm is established on the basis of the Taylor series expansion of the activation functions used in a particular neural network. This leads to a representation which is equivalent to the non-linear recursive polynomial model and enables the derivation of the transfer functions to be based on the harmonic expansion method. By mapping the neural network into the frequency domain information about the structure of the underlying non-linear system can be recovered. Numerical examples are included to demonstrate the application of the new algorithm. These examples show that the frequency response functions appear to be highly sensitive to the network topology and training, and that the time domain properties fail to reveal deficiencies in the trained network structure.