• The Journal of the Korea Contents Association
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• v.6 no.2
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• pp.117-126
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• 2006

Although the Java bytecode has numerous advantages, there are also shortcomings such as slow execution speed and difficulty in analysis. In order to overcome such disadvantages, bytecode analysis and optimization must be performed. First control flow of the bytecode should be analyzed, after which information is required regarding where the variables are defined and used to conduct data flow analysis and optimization. There may be cases where variables with an identical name contain different values at a different location during the execution according to the value assigned to a variable in each location. Therefore, in order to statically determine the value and type, the variables must be separated according to allocation. In order to do so, the variables can be expressed using a static single assignment form. After the transformation into a static single assignment form, the type information of each node expressed by each variable and expression must be configured to perform static analysis and optimization. Based on the basic type information, this paper proposes a method for finding related equivalent nodes, setting the nodes with strongly connection components and efficiently assigning each node the type.

• Journal of Advanced Navigation Technology
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• v.22 no.3
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• pp.220-227
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• 2018

The most widely used method for constructing an inertial navigation system (INS)/global navigation satellite system (GNSS) coupling system is to construct an integrated navigation system using a Kalman filter. However, depending on the trajectory, non-observable state variables may be generated. In this case, the state variables are not estimated. To solve this problem, a integrated navigation system is constructed and then an observability analysis is performed. In this paper, a 24th order position-matched Kalman filter is defined to design an INS/GNSS integrated navigation system for vehicles moving with a large pitch angle change. To verify the appropriateness of the error state variables applied to the Kalman filter, an observability analysis was performed. The trajectory was divided into five segments, and the piece-wise constant system (PWCS) was assumed for each segment, and the results were analytically analyzed. The analytical results and the simulation results confirm that the error state parameters of the Kalman filter are well-designed to the estimation side.

• Journal of Korea Water Resources Association
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• v.51 no.8
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• pp.677-686
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• 2018

There remain numerous ungauged watersheds in Korea owing to limited spatial and temporal streamflow data with which to estimate hydrological model parameters. To deal with this problem, various regionalization approaches have been proposed over the last several decades. However, the results of the regionalization models differ according to climatic conditions and regional physical characteristics, and the results of the regionalization models in previous studies are generally inconclusive. Thus, to improve the performance of the regionalization methods, this study attaches hydrological model parameters obtained using a spatial proximity model to the explanatory variables of a regional regression model and defines it as a hybrid regionalization model (hybrid model). The performance results of the hybrid model are compared with those of existing methods for 37 test watersheds in South Korea. The GR4J model parameters in the gauged watersheds are estimated using a shuffled complex evolution algorithm. The variation inflation factor is used to consider the multicollinearity of watershed characteristics, and then stepwise regression is performed to select the optimum explanatory variables for the regression model. Analysis of the results reveals that the highest modeling accuracy is achieved using the hybrid model on RMSE overall the test watersheds. Consequently, it can be concluded that the hybrid model can be used as an alternative approach for modeling ungauged watersheds.

• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.4
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• pp.1.1-11
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• 1974

A general and systematic method of organizing two-dimensional flexible cellular array which is capable of reclizing arbitrary combinational switching function is developed. A set of n functions of n variables is transformed to revalued functions of one variable. This set of functions form a semigroup under the normal operation which is defined in this paper. A systematic method of generating any functions using three base functions is presented. Three basic networks which are capable of realizing three base functions are designed using only one one-dimensional array. The algorithm is presented for lealizing arbitrary combinational switching functions by organizing this basic array in two.dimensional cellular array and by appropriately setting the parameters or the edge of the array.

• Transactions of the Korean Society of Mechanical Engineers
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• v.1 no.3
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• pp.156-163
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• 1977

길이방향의 열전도효과가 비교적 큰유체- 고체 열교환계내에 일정한 조ㅍ은 온도를 가진 유체가 유입될 때 이에 따른 비정상 온도분포가 해석되었다. 이러한 계를 기술하는 연립편미분 방정식의 수치해가 유한차분법에 의해 구해졌으며, 열전도가 무시된 경우에 대한 해석적 해를 구하여 위의 결과를 검증하였다. 한편 이상화된 모델에 대한 실험을 행하고 이 결과를 앞서 구한 수치해와 비교 검토하였다. 여기서 구해진 온도분포를 이용하여 축열효율${\eta}_A$및 ${\eta}_B$를 ${\eta}_A$는 시간 t에서의 축열량과 정상상태에 도달했을 때의 축열량의 비로 , 그리고 ${\eta}_B$는 시간 t 동안의 축열된 양과 공급된 열량의 비고 정의하여 온도분포와 효율들에 애하여 시간변수 .tau., 위치변수 .xi.와 무차원 열확산율 .betha.가 미치는 영향을 조사하였다. 이에 따르면 온도는 .betha. 가 적어짐에 따라 점점 가파르게 분포되고 한편 ${\eta}_A$는 .tau.가 점점 커지거나, .xi.가 작아질수록 좋아지는 것을 알 수 있다. 또한 ${\eta}_B$는${\eta}_A$와는 정반대의 경향을 보여주어 축열계의 최적상태가 존재함을 알 수 있다.

• Tunnel and Underground Space
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• v.14 no.3
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• pp.229-240
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• 2004

Coastal aquifers may serve as major sources fur freshwater. In many coastal aquifers, intrusion of seawater has become one of the major constraints imposed on groundwater utilization. The management of groundwater in coastal acquifers means making decision as to the pumping rate and the spatial distribution of wells. Several numerical techniques for flow and solute transport simulation can provide the means to achieve this goal. As a basic study to predict the intrusion of seawater in coastal phreatic aquifers, the coupled flow and solute transport analysis was conducted by use of the 3-D finite element code, SWICHA. In order to understand how the location and the shape of freshwater-seawater transition zone were affected by the boundary conditions and hydrogeologic variables, parametric study was carried out.

• Journal of Digital Convergence
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• v.9 no.1
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• pp.201-212
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• 2011

This study is to carry out meta-analysis on doctoral dissertations which had been written after 2004 when the empirical analysis about digital politics had begun. This study aims to identify tendency of recent analysis. For this purpose, it classifies the research trends of digital politics as political participation, political process, political advertising and election campaigns, and examines the researcher's definition, framework of empirical analysis, and all the results. Moreover, the study systematically summarizes the research model, analysis unit, concept and its components in order to ensure availablity so that the information could be available for the further research.

• Journal of Digital Convergence
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• v.16 no.7
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• pp.123-129
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• 2018

This study aims m-learning based on UTAUT and learners' satisfaction For empirical analysis, a survey was conducted on 289 university students and SPSS 22.0, AMOS 21.0 were used. The result of structual equation modeling analysis are as follows: First, performance expectancy was influenced by security, diversity, economics. Second, performance expectancy, effort expectancy affect learners' satisfaction. This research provide practical guidance in m-learning based on UTAUT amd the limltation of this research and future study are discussed. In the future, variables of m-learning based on UTAUT including the general public besides university students will be complement to analyze.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2C
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• pp.41-48
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• 2005

In this paper, we present a low complexity modified Gaussian model based pre-processing filter to improve the performance of H.264 compressed video. Video sequence captured by general imaging system represents the degraded version due to the additive noise which decreases coding efficiency and results in unpleasant coding artifacts due to higher frequency components. By incorporating local statistics and quantization parameter into filtering process, the spurious noise is significantly attenuated and coding efficiency is improved for given quantization step size. In addition, in order to reduce the complexity of the pre-processing filter, the simplified local statistics and quantization parameter are introduced. The simulation results show the capability of the proposed algorithm.

• Geophysics and Geophysical Exploration
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• v.25 no.4
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• pp.242-251
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• 2022

Automatic differentiation automatically calculates the derivatives of a function using the chain rule once the forward operation of a function is defined. Given the recent development of computing libraries that support automatic differentiation, many researchers have adopted automatic differentiation techniques to solve geophysical inverse problems. We analyzed the advantages, disadvantages, and performances of automatic differentiation techniques using the gradient calculations of seismic full waveform inversion objective functions. The gradients of objective functions can be expressed as multiplications of the derivatives of the model parameters, wavefields, and objective functions using the chain rule. Using numerical examples, we demonstrated the speed of analytic differentiation and the convenience of complex gradient calculations for automatic differentiation. We calculated derivatives of model parameters and objective functions using automatic differentiation and derivatives of wavefields using analytic differentiation.