Sang-Won Nam

Dispersed generation planning using improved Hereford ranch algorithm

This paper presents a new approach to dispersed generation planning based on Hereford ranch algorithm (HRA) in a subtransmission system. Dispersed generations could be photovoltaic cells, wind generation, battery storage, fuel cell, etc. A method to optimally locate such generation in a meshed network for maximizing the potential benefits is outlined using HRA and its improvement in this paper. The benefit expressed as a performance index is minimization of losses. The proposed method was tested for several sample power systems with 6, 14 and 30 bus types. Also, to show its effectiveness, the results of suggested algorithm are compared with those of classical genetic algorithm and conventional second-order method.

Application of higher order spectral analysis to cubically nonlinear system identification

In this study, digital higher-order spectral analysis and frequency-domain Volterra system models are utilized to yield a practical methodology for the identification of weakly nonlinear time-invariant systems up to third order. The primary focus is on consideration of random excitation of nonlinear systems and, thus, the approach makes extensive use of higher-order spectral analysis to determine the frequency-domain Volterra kernels, which correspond to linear, quadratic, and cubic transfer functions. Although the Volterra model is nonlinear in terms of its input, it is linear in terms of its unknown transfer functions. Thus, a least squares approach is used to determine the optimal (in a least squares sense) set of linear, quadratic, and cubic transfer functions. Of particular practical note, is the fact that the approach of this paper is valid for non-Gaussian, as well as Gaussian, random excitation. It may also be utilized for multitone inputs. The complexity of the problem addressed in this paper arises from two principal causes: (1) the necessity to work in a 3D frequency space to describe cubically nonlinear systems, and (2) the necessity to characterize the non-Gaussian random excitation by computing higher-order spectral moments up to sixth order. A detailed description of the approach used to determine the nonlinear transfer functions, including considerations necessary for digital implementation, is presented. >

On the identification of a third-order Volterra nonlinear system using a frequency-domain block RLS adaptive algorithm

A frequency-domain block recursive least-square adaptive algorithm is presented for the identification of nonlinear systems which can be modeled by a third-order Volterra series. The identification algorithm is based on the application of the Volterra theory and adaptive signal-processing techniques. The approach does not assume any particular statistics of the input. Moreover, the adaptive algorithm can be used, with a little modification, for the identification of a second-order Volterra system driven by stationary random inputs.<<ETX>>

Utilization of digital polyspectral analysis to estimate transfer functions of cubically nonlinear systems with nonGaussian inputs

Spectral estimation of the nonlinear transfer functions (linear, quadratic, and cubic) of a nonlinear system with stationary nonGaussian inputs, which can be modeled by single-input/single-output third-order Volterra functionals is presented. This method is general in the sense that it does not depend on the input statistics. The practicality and the feasibility of the digital implementation of the method are tested by analyzing simulated input-output data of known cubically nonlinear systems. In addition, the notion of coherency is extended to cubically nonlinear systems and generalized for nonGaussian inputs.<<ETX>>

Volterra series representation of time-frequency distributions

This paper addresses a Volterra series representation of bilinear (or quadratic) time-frequency distributions that belong to Cohens class, whereby the analogy of the bilinear class with a second-order double Volterra series is utilized. In addition, a different viewpoint for the bilinear kernel and a complementary interpretation concerning the quadratic time-frequency distributions are provided.

A new blood pressure measurement using dual-cuffs

Most automatic sphygmomanometers use oscillometric method with a blood pressure cuff. Conventional oscillometric sphygmomanometer is simple to use and it needs no peripheral device. However, the method provides no guarantee of accuracy in all circumstance, because it is based on statistics. In this paper, we propose a new oscillometric method with two cuffs. A cuff is placed on upper arm as usual and another cuff is added on forearm. By adding one more blood pressure cuff, there are two different waveforms are shown and the different characteristics between both cuffs can be compared. The results of our experiments show that it is possible to measure blood pressure using dual-cuff oscillometric method.

Discovery of Novel DUSP16 Phosphatase Inhibitors through Virtual Screening with Homology Modeled Protein Structure

Recently, dual-specificity phosphatase 16 (DUSP16) emerged as a promising therapeutic target protein for the development of anti-atherosclerosis and anticancer medicines. The present study was undertaken to identify the novel inhibitors of DUSP16 based on the structure-based virtual screening. We have been able to find seven novel inhibitors of DUSP16 through the drug design protocol involving homology modeling of the target protein, docking simulations between DUSP16 and its putative inhibitors with the modified scoring function, and in vitro enzyme assay. These inhibitors revealed good potency, with IC50 values ranging from 1 to 22 µM, and they were also screened computationally for having desirable physicochemical properties as drug candidates. Therefore, they deserve consideration for further development by structure-activity relationship studies to optimize the inhibitory activity against DUSP16. Structural features relevant to the stabilization of the newly identified inhibitors in the active site of DUSP16 are addressed in detail.

On the selective counting of third-order products

A practical and efficient method is presented for the counting of third-order products generated by an arbitrary number of carriers with arbitrary power spectral shapes. In particular, three selective counting procedures (i.e. sorting by position, sorting by position and group, and sorting by position, group, and kind) are introduced in a systemic way, based upon a discrete third-order Volterra model. The advantage of the counting algorithm is that (1) the algorithm provides the exact counting of third-order products of all eleven possible groups; (2) the counting process requires only two multiplications for the selective counting of third-order products at each position, and the algorithm, which is thus efficient, can be easily implemented. >

Nonlinear echo cancellation using a correlation LMS adaptation scheme

A robust nonlinear echo cancellation is proposed, where a third-order adaptive Volterra filtering is employed along with a correlation LMS adaptation scheme. In particular, the adaptive Volterra filtering technique is employed to compensate for the nonlinear distortion in the echo path (e.g., the DAC of the hybrid network). Finally, the robustness in the echo cancellation of the proposed approach is demonstrated using computer simulations, where high attenuation of echo signals is achieved even in the double-talk situation.

Notch filter design using theα-scaled sampling kernel and its application to power line noise removal from ECG signals

A new design approach is proposed for sharp notch FIR filters, whereby a modified alpha- scaled sampling kernel is utilized. In particular, the proposed approach provides closed-form formulae for filter coefficients, leading to an effective design procedure for sharp notch filters with given specifications. Simulation results demonstrate that the proposed design method yields high performance in removing the power line interference from ECG signals.