• International Journal of Computer Science & Network Security
• /
• v.23 no.10
• /
• pp.67-72
• /
• 2023

This paper portrays the design and optimization of a wideband four element triangular dielectric resonator antenna (TDRA) using PSO. The proposed antenna's radiation characteristics were extracted using Ansoft HFSS software. At a resonant frequency of 5-7 GHz, the four element antenna provides nearly 21 percent bandwidth and the optimized gives 5.82 dBi peak gain. The radiation patterns symmetry and uniformity are maintained throughout the operating bandwidth. for WLAN (IEEE 802.16) and WiMAX applications, the proposed antenna exhibits a consistent symmetric monopole type radiation pattern with low cross polarisation. The proposed antenna's performance was compared to that of other dielectric resonator antenna (DRA) shapes, and it was discovered that the TDRA uses a lot less radiation area to provide better performance than other DRA shapes and PSO optimized antenna increases the gain of the antenna

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.8
• /
• pp.739-745
• /
• 2009

This paper presents a design for trapezoidal planar UWB(Ultra Wide-band) antenna using symmetry meander line to realize broad bandwidth at low frequency region. The size of proposed design antenna is $15.5{\times}21{\times}1.6mm^3$ and dielectric substrate considered in design has 4.4 of relative permittivity. The calculated bandwidth is from 1.31 GHz to 10.83 GHz and the measured return loss is 1.5 GHz to 10.6 GHz at -10 dB below, and satisfies with the UWB antenna's bandwidth. The simulated and measured radiation patterns show fine agreement with each other at each frequency.

• Aerospace Engineering and Technology
• /
• v.8 no.1
• /
• pp.117-131
• /
• 2009

In this study, a detail design was conducted for KSLV-1 1st stage Rear Fuselage Upper Compartment assembly. A basic structural sizing was done by the aircraft fuselage sizing in-house program. The frame structural design and the interface check were conducted by the FE and the CAD program. The structural margin of safety was conformed by FE analysis for the normal section model and duct cut-out section models which are the weakest parts of the rear fuselage. The shear stress analysis was performed for a fastener design of the skin-stringer which is most affected by the shear stress induced by the shear load.

• Journal of computational fluids engineering
• /
• v.4 no.2
• /
• pp.57-66
• /
• 1999

Numerical Analysis has been done for the supersonic off-design jet flow due to the pressure difference between the jet and the ambient fluid. The difference of pressure generates an oblique shock or an expansion wave at the nozzle exit. The waves reflect repeatedly on the center axis and the sonic surface in the shear layer. The pressure difference is resolved across these reflected waves. In this paper, the axi-symmetric Navier-Stokes equation has been used with the κ-ε turbulence model. The second order TVD scheme with flux limiters, based on the flux vector split with the smooth eigenvalue split, has been used to capture internal shocks and other discontinuities. Numerical calculations have been done to analyze the off-design jet flow due to the pressure difference. The variation of pressure along the flow axis is compared with an experimental result and other numerical result. The characteristics of the interaction between the shock cell and the turbulence mixing layer have been analyzed.

• Korean Journal of Computational Design and Engineering
• /
• v.5 no.3
• /
• pp.255-262
• /
• 2000

A computer-aided process planning (CAPP) system for rotationally symmetric deep drawing products has been developed. The application for non-axisymmetric components, however, has not been reported yet. Therefore, this study investigates process sequence design in deep drawing process and constructs an expert system of process planning for non-axisymmetric motor frame products with elliptical shape. The system developed consists of four modules. The first one is recognition of shape module to recognize the products. The second one is a 3-D modeling module to calculate surface area for non-axisymmetric products. The third one is a blank design module that creates an oval-shaped blank with the identical surface area. The forth one is a process planning module based on production rules that play the best important role in an expert system for manufacturing. The production rules are generated and upgraded by interviewing with field engineers. The constructed system using AutoLISP language under the AutoCAD environment is baled on the knowledge base system which is involved a lot of expert's technology. Results of this system will be provide effective aids to the designer and engineer in this field.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.11 no.5
• /
• pp.340-348
• /
• 1986

The design of two-dimensional zero-phase FIR digital filters by transformations is a popular and well-developed technique, but is suffers from the disadvantage that in its current form the filters with only four quadrant symmetry can not be designed exactly circular symmetry at frequencies far from the origin. it is shown how symmetry requirement for the filters with any number of dimensions can be fulfilled with arbbitrary percision by adapting transformation with the appropriate series expansions. this transformation has been known generally as the McClellan transformation. In this paper, a simple method for ensuring exelent circular symmetry at frequencies far from the origin is presented. This method which employs the Modified Mcclellan trnsformation for the design of 2-D FIR filter form 1-D FIR filters is quite useful for the design of 2-D FIR filters with multiple cutoff boundaries such as band-pass filters.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.7 no.3
• /
• pp.72-80
• /
• 1997

A new design method for Takagi-Sugeno (T-S in short) fuzzy controller which guarantees global asymptotic stability and satisfies a desired performance is proposed in this paper. The method uses LMI(Linear Matrix Inequality) approach to find the common symmetric positive definite matrix P and feedback fains K/sub i/, i= 1, 2,..., r, numerically. The LMIs for stability criterion which treats P and K'/sub i/s as matrix variables is derived from Wang et al.'s stability criterion. Wang et al.'s stability criterion is nonlinear MIs since P and K'/sub i/s are coupled together. The desired performance is represented as $ LMIs which place the closed-loop poles of $ local subsystems within the desired region in s-plane. By solving the stability LMIs and pole placement constraint LMIs simultaneously, the feedback gains K'/sub i/s which gurarntee global asymptotic stability and satisfy the desired performance are determined. The design method is verified by designing a T-S fuzzy controller for an inverted pendulum with a cart using the proposed method.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.48 no.11
• /
• pp.1382-1387
• /
• 1999

This paper presents an optimal fuzzy power system stabilizer to damp out low frequency oscillation. So far fuzzy controllers have been applied to power system stabilizing controllers due to its excellent properties on the nonlinear systems. But the design process of fuzzy logic power system stabilizer requires empirical and heuristic knowledge of human experts as well as many trial-and-errors in general. This paper presents and optimal design method of the fuzzy logic stabilizer using the genetic algorithm. Non-symmetric membership functions are optimally tuned over an evaluation function. The present inputs of fuzzy stabilizer are torque angle error and the change of torque angle error without loss of generality. The coding method used in this paper is concatenated binary mapping. Each linguistic fuzzy variable, defined as the peak of a membership function, is assigned by the mapping from a minimum value to a maximum value using eight bits. The tournament selection and the elitism are used to keep the worthy individuals in the next generation. The proposed system is applied to the one-machine infinite-bus model of a power system, and the results showed a promising possibility.

• Transactions on Electrical and Electronic Materials
• /
• v.18 no.4
• /
• pp.229-236
• /
• 2017

This paper deals with the design and implementation of an efficient topology for cascaded multilevel inverters with reduced part counts. In the proposed design, a well-established basic unit is first developed. The series extension of this unit results in the formation of the proposed multilevel inverter. The proposed design minimizes the number of power electronic components including insulated-gate bipolar transistors and gate driver circuits, which in turn cuts down the size of the inverter assembly and reduces the operating power losses. An explicit control strategy with enhanced device efficiency is also acquired. Thus, the part count reductions enhance not only the economical merits but also the technical features of the entire system. In order to accomplish the desired operational aspects, three algorithms are considered to determine the magnitudes of the dc voltage sources effectively. The proposed topology is compared with the conventional cascaded H-bridge multilevel inverter topology, to reflect the merits of the presented structure. In continue, both the analytical and experimental results of a cascaded 31-level structure are analyzed. The obtained results are discussed in depth, and the exemplary performance of the proposed structure is corroborated.

• Journal of Korean Association for Spatial Structures
• /
• v.24 no.2
• /
• pp.65-73
• /
• 2024

In this study, we propose an optimal design method by applying the Prefabricated Buckling Restrained Brace (PF-BRB) to structures with asymmetrically rigidity plan. As a result of the PF-BRB optimal design of a structure with an asymmetrically rigidity plan, it can be seen that the reduction effect of dynamic response is greater in the case of arrangement considering the asymmetric distribution of stiffness (Asym) than in the case of arrangement in the form of a symmetric distribution (Sym), especially It was confirmed that at an eccentricity rate of 20%, the total amount of reinforced PF-BRBs was also small. As a result of analyzing the dynamic response characteristics according to the change in eccentricity of the asymmetrically rigidity plan, the distribution of the reinforced PF-BRB showed that the larger the eccentricity, the greater the amount of damper distribution around the eccentric position. Additionally, when comparing the analysis models with an eccentricity rate of 20% and an eccentricity rate of 12%, the response reduction ratio of the 20% eccentricity rate was found to be large.