• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.6 no.1
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• pp.47-52
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• 2002

In this paper we propose a simple decoding algorithm for the 4-ary lexicographic codes (or lexicodes) of length 10 with minimum distance 4, write $S_{10,4}$. It is based on the syndrome decoding method. That is, using a syndrome vector we detect an error and it will be corrected an error from the four parity check equations.

• Journal of radiological science and technology
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• v.30 no.2
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• pp.153-159
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• 2007

Digital medical image commenced with an introduction of PACS has become more popular today in the radiation diagnosis and radiation treatment and made great progress, in particular, for medical testing field, whereas it has made slow progress for radiation treatment field. In order to accommodate the current trend of digital from analog, a spherical mechanical check device(SMCD) that is the form of spherical differing from the existing form of flat or cube has been designed and tested its practicability to replace the part in mechanical check with digital image from QA operation. If the distance maintains constance between source(target) and image detector with constant distance to the center of spherical mechanical check device(SMCD), the size will be shown as a constant image at all times regardless of its direction exposed. For the test, two accurate hemispheres are made and put together which results in a sphere of the equilateral circle. It enables a variety of implementation of the existing mechanical check using digital image as follows: congruity level of radiation field and light field, size accuracy of radiation field and collimation field, gantry rotation isocenter check, collimation rotation isocenter check, room laser accuracy check, collimation rotation angle check, couch rotation angle check, and more. In addition, it has proved its practicability in checking isocenter congruity level as real time at the time of simultaneous rotation between gantry and couch that is applied to the non-coplanar field, which had been hard to apply as a device formed of existing flat or cube.

• The Journal of Korean Society for Radiation Therapy
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• v.19 no.1
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• pp.55-62
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• 2007

Purpose: Digital medical image commenced with an introduction of PACS has become more popular today in the radiation diagnosis and medical treatment and made great progress, in particular, for medical testing field, whereas it has made slow progress for radiation therapy area. In order to accommodate the current trend of digital from analog, a spherical type mechanical check device (SMCD) that is form of spherical differing from the existing form of flat or cube has been designed and tested its practicability to replace the part in mechanical check with digital image from QA operation. Materials and Methods: If the distance maintains constant between source(target) and image detector with constant distance to the center of spherical type mechanical check device(SMCD), the size will be shown as a constant image at all times regardless of its direction exposed. For the test, two accurate hemispheres are made and put together which results in a sphere of the equilateral circle. Results: It enables a variety of implementation of the existing mechanical check using digital image as follows: congruity level of radiation field and light field, size accuracy of radiation field and collimation field, gantry rotation isocenter check, collimation rotation isocenter check, room laser accuracy check, collimation rotation angle check, couch rotation angle check, and more. Conclusion: It has proved its practicability in checking isocenter congruity level as real time at the time of simultaneous rotation between gantry and couch that is applied to the non-coplanar field, which had been hard to apply as a device formed of existing flat or cube.

• The KSFM Journal of Fluid Machinery
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• v.10 no.1 s.40
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• pp.41-48
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• 2007

The effect of the upstream flow conditions on the disc stability of the swing check valves was investigated at various upstream flow disturbance sources and distances from the tested check valves. The experimental loop was designed and installed to measure the disc positions, disc back stop load, and differential pressure at flow velocities lot 3 inch and 6 inch swing check valves. The selected disturbance sources are elbow and globe valve. The effect of the disc fluctuation is different depending on the type of disturbance and the distance between the disturbance and the check valve. Disturbances generated by elbow and globe valve located upstream from check valve create greater and more violent disc motion than uniform flow.

• Transactions of the Society of Information Storage Systems
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• v.3 no.3
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• pp.126-128
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• 2007

일반적으로 주어진 하나의 H matrix 로 다수의 코드율을 가지는 코드화가 가능하다. 하지만 Low Density Parity Check(LDPC) 코드의 H matrix는 H matrix 내의 1의 개수와 위치에 따라 그 성능이 달라짐으로 해서 하나의 H matrix로 다수의 코드율을 대응하기 위한 설계 방법이 요구된다. H matrix 의 성능은 일반적으로 girth나 minimum distance에 의해 좌우되고 H matrix의 1의 위치에 따라 달라진다. 본 논문에서는 H matrix의 girth 와 minimum distance에 입각한 다수 개의 코드율이 대응 가능한 LDPC code의 H matrix 설계 방법을 제시하고자 한다. 이렇게 함으로써 하나의 H matrix로 다수의 코드율에 따른 각각의 성능을 일정 수준 이상 유지하는 multi-rate LDPC code가 가능하다.

• Journal of Communications and Networks
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• v.10 no.1
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• pp.5-9
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• 2008

Researchers have investigated many upper bound techniques applicable to error probabilities on the maximum likelihood (ML) decoding performance of turbo-like codes and low density parity check (LDPC) codes in recent years for a long codeword block size. This is because it is trivial for a short codeword block size. Previous research efforts, such as the simple bound technique [20] recently proposed, developed upper bounds for LDPC codes and turbo-like codes using ensemble codes or the uniformly interleaved assumption. This assumption bounds the performance averaged over all ensemble codes or all interleavers. Another previous research effort [21] obtained the upper bound of turbo-like code with a particular interleaver using a truncated union bound which requires information of the minimum Hamming distance and the number of codewords with the minimum Hamming distance. However, it gives the reliable bound only in the region of the error floor where the minimum Hamming distance is dominant, i.e., in the region of high signal-to-noise ratios. Therefore, currently an upper bound on ML decoding performance for turbo-like code with a particular interleaver and LDPC code with a particular parity check matrix cannot be calculated because of heavy complexity so that only average bounds for ensemble codes can be obtained using a uniform interleaver assumption. In this paper, we propose a new bound technique on ML decoding performance for turbo-like code with a particular interleaver and LDPC code with a particular parity check matrix using ML estimated weight distributions and we also show that the practical iterative decoding performance is approximately suboptimal in ML sense because the simulation performance of iterative decoding is worse than the proposed upper bound and no wonder, even worse than ML decoding performance. In order to show this point, we compare the simulation results with the proposed upper bound and previous bounds. The proposed bound technique is based on the simple bound with an approximate weight distribution including several exact smallest distance terms, not with the ensemble distribution or the uniform interleaver assumption. This technique also shows a tighter upper bound than any other previous bound techniques for turbo-like code with a particular interleaver and LDPC code with a particular parity check matrix.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.309-314
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• 2004

The experimental loop was designed and installed to measure the disc positions, disc back stop load and differential pressure with flow velocity for 3 inch and 6 inch swing check valves. The tests were performed at various conditions of upstream flow disturbance source and distance from the tested check valves to investigate the effect of the upstream flow conditions on the disc stability of the swing check valves. The selected disturbance sources were elbow, globe valve, and orifice. The experimental results are presented herein.

• Journal of The Korean Association of Information Education
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• v.16 no.3
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• pp.283-289
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• 2012

A distance learning is diffusing rapidly in society. It is more difficult to confirm a learner's identity and learning processing in a distance learning. Distance learning has a checking attendance system because a teacher and student do not meet face to face. There are some checking attendance systems such as login check, SMS authenticating system, unexpected quiz, and so on. However, existing checking attendance system has some problems to check learner's attendance in a whole lesson. Therefore, this study designed and developed learner's attendance system based on PC camera's shot of certification in a whole lesson. This attendance checking system can judge real attendance of learners in a distance learning and distance evaluation. The system is expected to make trust of a distance learning higher.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10C
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• pp.1363-1369
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• 2004

LDPC(Low Density Parity Check) codes are described by bipartite graphs with bit nodes and parity-check nodes. Tanner derived minimum distance bounds of the regular LDPC code in terms of the eigenvalues of the associated adjacency matrix. In this paper we generalize the Tanner's results. We derive minimum distance bounds applicable to both regular and blockwise-irregular LDPC codes. The first bound considers the relation between bit nodes in a minimum-weight codeword, and the second one considers the connectivity between parity nodes adjacent to a minimum-weight codeword. The derived bounds make it possible to describe the distance property of the code in terms of the eigenvalues of the associated matrix.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.157-158
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• 2004

To investigate the effects of the upstream flow conditions on the opening performance of the swing check valve, the tests were performed at various conditions of the disturbance type and distance from the tested check valves. The results show that the upstream flow disturbances due to elbow and globe valve at $2{\sim}10$ diameters upstream of the check valve produced minor effects on the check valve performance compared to the uniform flow condition. However, more detail analysis and additional testing with the other disturbance source, such as orifice with a large number of holes, are needed to refine and confirm the present results.