• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1171-1177
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• 2011

A high power laser beam focused on a small area accelerates a thin material that flies and hits other target material in which a shock wave may be induced. This laser induced shock experimental method is more repeatable and cheaper but worse than other experimental method using gas gun or other apparatus. An optical system including a phase zone plate reduces the interference and also makes the focused-beam-intensity distribution uniform. We wrote a computer code that calculates light ray traces. Using the code we designed and fabricated an optical system including a phase zone plate and improved the laser-beam uniformity. We introduce preliminary experimental results of laser induced shock of the samples such as aluminum and other materials.

• Journal of Information Processing Systems
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• v.13 no.1
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• pp.114-127
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• 2017

This paper proposes a color image coding algorithm based on shape-adaptive all phase biorthogonal transform (SA-APBT). This algorithm is implemented through four procedures: color space conversion, image segmentation, shape coding, and texture coding. Region-of-interest (ROI) and background area are obtained by image segmentation. Shape coding uses chain code. The texture coding of the ROI is prior to the background area. SA-APBT and uniform quantization are adopted in texture coding. Compared with the color image coding algorithm based on shape-adaptive discrete cosine transform (SA-DCT) at the same bit rates, experimental results on test color images reveal that the objective quality and subjective effects of the reconstructed images using the proposed algorithm are better, especially at low bit rates. Moreover, the complexity of the proposed algorithm is reduced because of uniform quantization.

• Journal of the Korean Society of Visualization
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• v.15 no.3
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• pp.20-26
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• 2017

The two-fluid equations are widely used to simulate two-phase flows in a nuclear reactor. For the two-fluid momentum equation, the wall and interfacial drag terms play an important role in predicting a two-phase flow behavior. Since the bubble density is much smaller than the water density, the bubble accelerates faster than the liquid in a nozzle. As a result, the bubble phase becomes faster than the liquid phase in the nozzle. In contrast, the opposite phenomena occur in the diffuser. The purpose of our study is to experimentally show these behaviors in an area-varying channel such as nozzle and diffuser. Experiments were made of turbulent bubbly flows in an area-varying horizontal channel. The velocities of the bubble and liquid phases were measured by the PIV technique. It was shown that the two-phase velocities were no longer close to each other in the area-varying regions. The bubble was faster than the liquid in the nozzle; in contrast, the bubble was slower than the liquid in the diffuser. Code simulations were also performed using the MARS code. By replacing the original wall drag model in the MARS code with Kim (1)'s wall drag partition model, we obtained the simulation results being consistent with experimental observations.

• Nuclear Engineering and Technology
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• v.31 no.3
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• pp.314-327
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• 1999

A subchannel analysis code MATRA applicable to PWRs and ALWRs has been developed to be run on an IBM PC or HP WS based on the existing CDC CYBER mainframe version of COBRA-Rf-1. This MATRA code is a thermal-hydraulic analysis code based on the subchannel approach for calculating the enthalpy and How distribution in fuel assemblies and reactor cores for both steady-state and transient conditions. HATRA has been provided with an improved structure, various functions, and models to give more convenient user environment and to enhance the code accuracy. Among them, the pressure drop model has been improved to be applied to non-square-lattice rod arrays, and the models for the lateral transport between adjacent subchannels have been improved to enhance the accuracy in predicting two-phase flow phenomena. The predictions of MATRA were compared with the experimental data on the flow and enthalpy distribution in some sample rod-bundle cases to evaluate the performance of MATRA. All the results revealed that the predictions of MATRA were better than those of COBRA-IV-I.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.1
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• pp.1-14
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• 2018

The Global Positioning System (GPS) provides more accurate positioning estimation performance by processing L1 and L2 signals simultaneously through dual frequency signal processing technology at the L-band rather than using only L1 signal. However, if anti-spoofing (AS) mode is run at the GPS, the precision (P) code in L2 signal is encrypted to Y code (or P(Y) code). Thus, dual frequency signal processing can be done only when the effect of P(Y) code is eliminated through the L2 signal processing technology. To do this, a codeless technique or semi-codeless technique that can acquire phase measurement information of L2 signal without information about W code should be employed. In this regard, this paper implements L2 signal processing technology where two typical codeless techniques and four typical semi-codeless techniques of previous studies are applied and compares their performances to discuss the optimal technique selection according to implementation environments and constraints.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.3
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• pp.506-514
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• 1997

In this paper, we implement digital circuit of despreading delay lock loop for GPS receiver. The designed system consists of Epoch signal generator, two 13bit correlators which correlates the received C/A code and the locally generated C/A code in the receiver, the C/A code generator which generates C/A code of selected satellite, and the direct digital clock synthesizer which generates the clock of the C/A code generator to control the phase and clock rate, the clock controller, and the clock divider. The designed circuit has the function of the acquisition and tracking by the autocorrelation characteristics of Gold code. The controller generates each other control signals according to the correlation value. The designed circuit is simulated to verify the logic functional performance. By using the simulator STR-2770 that generates the virtual GPS signal, the deigned FPGA chip is verified the circuit performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9C
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• pp.820-825
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• 2007

Super-orthogonal space-time trellis code (SOTTC) uses the expanded set of the orthogonal space-time block code to obtain coding gain and diversity gain without loss of transmit rate. In SOSTTCs, signal set expansions are performed by rotating the first column of the code matrix. The rotating phases used previously were selected to avoid the signal constellation expansion rather than the performance improvement. In this paper, we make a design criterion to select the proper rotating phase to improve the performance of SOSTTCs for fast Rayleigh fading channels. In addition, we design improved SOSTTCs by using the proper rotating phase. Simulation results are also provided to confirm our SOSTTCs are superior to the previous SOSTTCs in the view of BER performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11C
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• pp.1059-1065
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• 2007

In this paper, we propose a class of polyphase signature sequences, whose general odd correlation properties are useful for M-ary phase signaling systems. The maximum magnitude of the general odd correlation functions of the proposed sequences are investigated and compared with those of FZC (Frank-Zadoff-Chu) sequences and those of EOE (equivalent odd and even correlation) sequences. The performance of the asynchronous M-ary phase signaling systems using the proposed sequences is simulated and compared with that using FZC sequences in direct sequence code division multiple access (DS/CDMA) systems. The performance of the system using the proposed sequence is shown to be better than that using FZC sequences when the multipath fading is in existence.

• Journal of computational fluids engineering
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• v.14 no.4
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• pp.13-22
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• 2009

A two-phase (gas and liquid) flow analysis solver, named CUPID, has been developed for a realistic simulation of transient two-phase flows in light water nuclear reactor components. In the CUPID solver, a two-fluid three-field model is adopted and the governing equations are solved on unstructured grids for flow analyses in complicated geometries. For the numerical solution scheme, the semi-implicit method of the RELAP5 code, which has been proved to be very stable and accurate for most practical applications of nuclear thermal hydraulics, was used with some modifications for an application to unstructured non-staggered grids. This paper is concerned with the effects of interpolation schemes on the simulation of two-phase flows. In order to stabilize a numerical solution and assure a high numerical accuracy, the second-order upwind scheme is implemented into the CUPID code in the present paper. Some numerical tests have been performed with the implemented scheme and the comparison results between the second-order and first-order upwind schemes are introduced in the present paper. The comparison results among the two interpolation schemes and either the exact solutions or the mesh convergence studies showed the reduced numerical diffusion with the second-order scheme.

• Journal of IKEEE
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• v.19 no.2
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• pp.186-192
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• 2015

This paper proposes an automatic generation technology of test case based on API in source code for software's quality improvement. The proposed technology is comprised of four processes which are analyzing source code by using the Doxygen open source tool, defining API specification by using analyzed results, creating test design, generating a test case by adapting Pairwise test technology. Analyzing source code by using the Doxygen open source tool is the phase in which API information in source code such as the API name, input parameter and return parameter are extracted. Defined API specification by using analyzed results is the phase where API informations, which is needed to generate test case, are defined as a form of database by SQLite database on the basis of extracted API information. Creating test design is the phase in which the scenario is designed in order to be composed as database by defining threshold of input and return parameters and setting limitations based on the defined API. Generating a test case by adapting Pairwise test technique is the phase where real test cases are created and changed into database by adapting Pairwise technique on the base of test design information. To evaluate the efficiency of proposed technology, the research was conducted by begin compared to specification based test case creation. The result shows wider test coverage which means the more cases were created in the similar duration of time. The reduction of manpower and time for developing products is expected by changing the process of quality improving in software developing from man-powered handwork system into automatic test case generation based on API of source code.