• Geophysics and Geophysical Exploration
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• v.11 no.2
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• pp.85-92
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• 2008

Magnetotelluric (MT) methods are widely applied as an effective exploration technique to geothermal surveys. Two-dimensional (2-D) analysis is frequently used to investigate a complicated subsurface structure in a geothermal region. A 2-D finite-element method (FEM) is usually applied to the MT analysis, but we must pay attention to the accuracy of so-called auxiliary fields. Rodi (1976) proposed an algorithm of improving the accuracy of auxiliary fields, and named it as the MOM method. Because it introduces zeros into the diagonal elements of coefficient matrix of the FEM total equation, a pivoting procedure applied to the symmetrical band matrix makes the numerical solution far less efficient. The MOM method was devised mainly for the inversion analysis, in which partial derivatives of both electric and magnetic fields with respect to model parameters are required. In the case of forward modeling, however, we do not have to resort to the MOM method; there is no need of modifying the coefficient matrix, and the auxiliary fields can be elicited from the regular FEM solution. The computational efficiency of the MOM method, however, can be greatly improved through a sophisticated rearrangement of the total equation.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.1
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• pp.45-53
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• 1991

The nonlinear forward diffraction of a modulated wave train by a thin wedge has been studied analytically. Since the physical variables involved in the problem have vastly different scales, the multiple scale expansion method has been used to obtain an approximate solution. To simplify the problem. the wedge is assumed to be thin and the parabolic approximation is utilized. The wave evolution can be described by a kind of the cubic Schrodinger equation. which consists of the linear time evolution. the lateral dispersion and the nonlinearity. Numerical results indicate that the nonlinearity. which it defined by the ratio of the ratio of the incident wave to the wedge angle. governs the amplitude and the stability of diffracted waves. The instability of dirffracted waves becomes more pronounced as the nonlinearity increases and the modulation ratio decreases. It is also found that the stem waves. initially developed along the wedge. can not sustain for a long time.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.9
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• pp.88-93
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• 2003

This Paper described the simulation program development for helicopter. In the design of flight control system to accomplish some special missions like UAV, it is important to minimize the execution time obtaining a linear model from nonlinear model that is used for design of controller. The first step for this kind of purpose is to complete a nonlinear model that contains full dynamic characteristics. The second step is to get the trim values that are obtained from the nonlinear model by solving an algebraic equation. And then stability and control derivatives are derived through hovering to forward flight by numerical perturbation that will be used for linear model for a specified flight condition. The software program(HeliSim) is developed by using MATLAB GUI and will provide easy modeling procedure. The suggested method in this paper is much more simpler than any other method like a fully scale helicopter model. The advantage of our suggested method will reduce the computational time due to simple formula to extract a linear model from nonlinear model that will be beneficially used for flight control system of unmanned helicopter by some reduction of computational load.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.3
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• pp.211-221
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• 2020

This study aims to analyze the effect of structural Person-Organization Fit and organizational justice on organizational commitment, job satisfaction, Organizational Citizenship Behavior and employee performance. This study is based on a quantitative approach by collecting data using a survey conducted on three SOE's companies in Indonesia that operate in Makassar City, namely Pelindo. Ltd (Port Company), PLN. Ltd (Electric Company) and Pertamina. Ltd (Oil and Gas Company), with a sample of 90 employees. The study population was all non-managerial permanent employees. Data analysis using Structural Equation Modeling. In structural relations, out of the nine direct tests, there were two insignificant relationships, and in all three hypotheses there was one not-supported hypothesis. When compared between person-organization Fit and Organizational Justice, it is found that organizational justice has a more critical role in building Human Resource performance compared to Person-Organization Fit, because organizational justice is better able to provide job satisfaction and make organizational commitment and OCB as a prerequisite for its formation to better Human Resources performance. With organizational justice, employees will feel more satisfied working, committed to the work and organization, and behaves as a supportive organizational citizen for the realization of the best performance for the interests of the organization going forward.

• Journal of Korea Port Economic Association
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• v.29 no.4
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• pp.223-246
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• 2013

The purpose of our study is to investigate the relationships among business performance, information technology capacity, partnering, and strategy orientation within China's manufacturing industry. Based on theoretical observations and precedent studies, we forward a hypothesis and conduct an empirical analysis through a structural equation model using AMOS statistical package. Our questionnaire survey targets senior managers of domestic Chinese manufacturing companies. The results of our study are as follows: First, strategy orientation has a significant positive effect on information technology capacity and partnering. Second, information technology capacity has a significant positive effect on business performance of Chinese manufacturers. Third, partnering has a significant positive effect on the business performance of Chinese manufacturers. Our results imply that information technology capacity, partnering, and strategy orientation are critical factors in determining successful business performance of Chinese manufacturing companies when they employ third party logistics.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.3
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• pp.3885-3893
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• 1975

This work was intended to study the cutting graph and vibratory phenomina of a newly developed mower which may be suitable for mowing agricultural product having large and hard stems like corn and sugar beet. The system consists of cutter-bar having Curvilinear-translation motion, which attached to drag-crank mechanism. The motion of equation developed for experimental vibratory system which equipped with the cutter-bar system was established and the parameters defining the system's vibratory motion were experimentally determined. The optimum balancing weight for the cutter-bar am vibratory characteristics of the cutter-bar for various counterweight were analyzed to provide the design and operational conditions. The results of the study are summarized as follows; (1) The cutting graph by the new cutter-bar system depends upon the magnitude of ratio of forward travel(Vm) to crank speed (R$\omega$); The cutting pitch for Vm/R$\omega$ 1 (whole cycle cutting) and Vm/R$\omega$=2/$\pi$ (a half cycle cutting) are 2$\pi$ Vm and 4R, respectively. (2) The experimental vibratory system had been proved to function adequately so that it can be used in determining the required counterweight to minimize the vibratory motion of cutter-bar. (3) Experimentally determined counterweight to give the least vibratory motion was a little greater than the theoretically determined one. With the optimum counterweight it was possible to reduce up to about 87% of the amplitude without counterweight, which may be considered to be within safe operational region. (4) To avoid the actual operation of the cutter-bar at resonance which occured in low frequency ratio, it was considered that the rotational speed of the crank for a specific design of mower should be determined separately in connection with the desired cutting graph.

• Nuclear Engineering and Technology
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• v.52 no.3
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• pp.575-580
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• 2020

We have developed a position-sensitive Parallel Plate Avalanche Counter (PPAC) to detect the fission fragments and reconstruct the fission reaction plane in the experiment of studying nuclear equation of state (nEOS) by means of heavy ion collision (HIC). This experiment put forward high requirements for the performances of PPAC, such as the time resolution, efficiency and position resolution. According to these requirements we designed the PPAC with an active area of 240 mm × 280 mm working at low gas pressure. The results show that time resolution could be less than 300 ps. Position resolution is consistent with the theoretical calculation about 1.35 mm. Detection efficiency could be approaching 100% gradually with the voltage increasing in different gas pressures. The performances of PPAC have also been verified in beam experiment. Each set of anode wires can be accurately separated in the position spectrum. In the beam experiment, we also got the back-to-back correlation of fission fragments which is one of the direct signals characterizing binary decay.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.3 s.108
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• pp.291-297
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• 2006

The BVI(blade vortex interaction) noise Prediction has been one of the most challenging acoustic analyses in helicopter aeromechanical Phenomenon. It is well known high resolution airloads data with accurate tip vortex positions are necessary for the accurate prediction of this phenomenon. The truly unsteady time-marching free-wake method, which is able to capture the tip vortices instability in hover and axial flights, is expanded with the rotor flapping motion and trim routine to predict unsteady airloads in forward and descent flights. And Farassat formulation 1-A based on the FW-H equation is applied for the noise prediction considering the blade flapping motion. Main objective of this study is to validate the newly developed prediction code. To achieve the objective, the descent flight condition of AH-1 OLS(operational loads survey) configuration is analyzed using present code. The predicted sectional thrust distribution and sectional airloads time histories show the present scheme is able to capture well the unsteady airloads caused by a parallel BVI. Finally, the predicted noise data, observed in two different positions where are 3.44 times of rotor radius far from the hub center, are quite reasonable agreements with the experimental data compared to the other analysis results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.2
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• pp.207-213
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• 2013

This study describes an omega-K algorithm for focusing bistatic synthetic aperture radar(SAR) data using bistatic-to-monostatic conversion. Bistatic SAR system considered in this study consists of a transmitting antenna and a physical array of several receiving antennas. The length of the physical array is identical to the SAR synthetic aperture. Unlike the monostatic case, an omega-K algorithm for the bistatic case is difficult to obtain the exact equation in the 2D wavenumber domain. The key of the proposed algorithm is converting the bistatic data into a monostatic one. The effectiveness of the proposed algorithm is proved by simulation and real measurement data.

• Korean Membrane Journal
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• v.7 no.1
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• pp.1-18
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• 2005

The permeate flux decline due to membrane fouling can be addressed using a variety of theoretical stand-points. Judicious selection of an appropriate theory is a key toward successful prediction of the permeate flux. The essential criterion f3r such a decision appears to be a detailed characterization of the feed solution and membrane properties. Modem theories are capable of accurately predicting several properties of colloidal systems that are important in membrane separation processes from fundamental information pertaining to the particle size, charge, and solution ionic strength. Based on such information, it is relatively straight-forward to determine the properties of the concentrated colloidal dispersion in a polarized layer or the cake layer properties. Incorporation of such information in the framework of the standard theories of membrane filtration, namely, the convective diffusion equation coupled with an appropriate permeate transport model, can lead to reasonably accurate prediction of the permeate flux due to colloidal fouling. The schematic of the essential approach has been delineated in Figure 5. The modern approaches based on appropriate cell models appear to predict the permeate flux behavior in crossflow membrane filtration processes quite accurately without invoking novel theoretical descriptions of particle back transport mechanisms or depending on adjust-able parameters. Such agreements have been observed for a wide range of particle size ranging from small proteins like BSA (diameter ${\~}$6 nm) to latex suspensions (diameter ${\~}1\;{\mu}m$). There we, however, several areas that need further exploration. Some of these include: 1) A clear mechanistic description of the cake formation mechanisms that clearly identifies the disorder to order transition point in different colloidal systems. 2) Determining the structure of a cake layer based on the interparticle and hydrodynamic interactions instead of assuming a fixed geometrical structure on the basis of cell models. 3) Performing well controlled experiments where the cake deposition mechanism can be observed for small colloidal particles (< $1\;{\mu}m$). 4) A clear mechanistic description of the critical operating conditions (for instance, critical pressure) which can minimize the propensity of colloidal membrane fluting. 5) Developing theoretical approaches to account for polydisperse systems that can render the models capable of handing realistic feed solutions typically encountered in diverse applications of membrane filtration.