The performance of a chirped waveguide grating as a wavelength demultiplexer has been investigated. Considerations include TE-TE, TE-TM and TM-TM mode coupling for different incident angles and ...waveguide parameters. The spectral response of the chirped sinusoidal surface relief grating in the optical waveguide has been studied by means of Local Normal Mode Expansion (LNME) theory to account for the varying thickness of a corrugated waveguide. A matrix technique has been applied to account for the varying grating period, the grating being divided into segments with constant periods and coupling coefficients. A nonslanted first-order diffraction grating is considered and contradirectional coupling between guided modes in phase synchronism at arbitrary incident angles. We show the effect of geometry and waveguide parameters on the performance of the chirped grating as a wavelength demultiplexer. Also, we demonstrate how the bandwidth of the filtering and demultiplexing characteristics and the spectral shift between different polarization modes can be controlled.
The reliance of Iran's handmade carpet traders and producers on the traditional business practices and their distrust of the internet and e-commerce is an important cause to blame for the recent ...decline in the share of the Iranian carpet export in the world market. The paper briefly discusses the importance of e-commerce, outlines its advantages and disadvantages and emphasizes its effects on Persian handmade carpet as one of the main industries of Iran. The research method is based on investigating inter-organizational strengths and weaknesses, and external-organizational opportunities and threats. According to conducted studies, launching business information networks in order to increase carpet exporters awareness of the new e-business practices, motivating carpet producers and exporters through increasing government supports to the carpet industry, reducing custom clearance processes for buyers through Iran membership in WTO, application of advanced technology to enhance the quality of products, using information technology in marketing and internet advertisement, are the most important factors that impact Iranian carpet industry's success in e-commerce.
Recently, a design of model matching and adaptive control systems under the presence of measurement noise is reported by employing a non-minimal order state observer. But this method can be only used ...for the single-input, single-output plant which is stably invertible. In this paper, it will be shown that the idea is also applicable to the multivariable plant which may not have a stable inverse. Since the proposed method can be implemented by simple calculation, it is adequate for an adaptive control in which the controllers must be calculated on line.
The paper uses an LMI-based iterative nonlinear optimization algorithm to establish a method of designing state-feedback controllers for power systems with a time-varying delay. This method is based ...on the delay-dependent stabilization conditions obtained by free weighting matrix approach. In the stabilization conditions, the upper bound of wide-area signal's transmission delays is taken into consideration. Combining theories of state observer, the adeptive supervisory controller (ASC) is designed and time-delay output feedback robust controller is realized for power system. The ASC uses the input information from wide-area measurement systems (WAMS) and dispatches supplementary control signals to the available local controllers. Simulation study in the New England test power system confirm that the proposed ASCs can dampen power oscillation effectively and is robust to time-varying delay condition.
The optical rectification coefficient in electric-field biased hyperbolic quantum wells was studied. The analytic expression of optical rectification coefficient of this system is derived by means of ...density matrix approach and the iterative method. Finally, the numerical results were presented for a typical GaAs electric-field biased hyperbolic quantum wells. The results show that the optical rectification coefficient in this system is larger than that in bulk GaAs material and it will change, with the change of the parameter a of the quantum well and the applied electric field F.
The effective nonlinear response of the random mixtures of coated granular cylinders is studied by means of the field-dependent T-matrix approach. The composite considered here is composed of ...nonlinear cylindrical grains with linear concentric shells randomly distributed in a linear host. Exact expressions of effective dielectric function and the higher-order susceptibilities in the low field are given. The influence of interfacial shells to the effective third-order nonlinear response of the mixture system are discussed in detail.
This paper presents an approach to elimination or reduction of steady-state output errors in regulatory control of continuous-time LTI MIMO systems with a number of inputs not less than a number of ...outputs. Classical modal and LQR/LQG feedback controllers are effectively supplemented with a feedforward path from a reference vector to a plant's input vector. Conditions for full elimination of the steady-state error are given and the ability for only reduction of the error is discussed. Various simulation examples illustrate the usefulness of the methodology.
Based on the transfer matrix method, a standing wave-duct system with a four-microphone configuration for acoustical property measurement of soundproof materials is developed in this study. The ...transfer matrices of sample materials are calculated by using an approach combined by the two-cavity and two-load methods. Three steps, i.e., hardware architecture, code programming, and accuracy verification, are followed in the system development. Based on the developed system, furthermore, the absorption ratio and transmission loss of the soundproof materials are measured and verified. The results suggest that the newly designed system is accurate for measuring acoustical properties, which may be applied as a substitution tool for acoustical material research and development in engineering.
PDF
