• Journal of Power System Engineering
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• v.9 no.4
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• pp.83-89
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• 2005

Molding shrinkage is one of the problems to be solved in conventional injection molding. Despite many trying-out has been to solve it, intrinsic cause of shrinkage such as orientation and thermal exchange between melt and mold has not been solved yet. For reducing shrinkage and residual stress on molding, injection compression molding process was invented. In this study, experiments about effects of injection compression molding's parameters on shrinkage of PMMA molding were conducted and compared with conventional injection molding's shrinkage. Before the injection compression molding experiment, molding shrinkage rate was predicted by analyzing pvT diagram and was compared with the results of experiment. The shrinkage rate of injection compression molding was lower than convention injection molding's one which was different from the predicted shrinkage. The reason was observed that the experimental mold was not a proper type for injection compression, flowing backward of melt into nozzle and unreasonable mechanism of injection molding machine.

• Journal of Power System Engineering
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• v.6 no.2
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• pp.68-72
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• 2002

Design of experiment was applied to analyze the shrinkage characteristics of the bobbin molded by injection molding. Among lots of design and processing conditions, the thickness of a bobbin and cooling conditions of a mold were considered. The temperature difference between top and bottom parts of the bobbin was considered as the objective to minimize the shrinkage of a bobbin. Optimal thickness of a bobbin was 2.0mm at the part of body and 1.5mm at the part of wing, respectively. Optimal cooling conditions such as cooling time and coolant inlet temperature were 12 second and $12^{\circ}C$, respectively.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1993.04a
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• pp.164-164
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• 1993

Nicorandil의 심근허혈 감소효과를 평가하고운동부하 201-Thallium 심근허혈 감소효과의 임상적 판정에 적용 가능성 여부를 알아보고자 하였다. 대상 및 방법: 위약투여 후 시행한운동부하 201-thallium-SPECT 상에서 가역적 thallium 결손을 보였던 49명의 노작성 협심증 환자들을 대상으로 하여 7일후 nicorandil을 10mg (group 1:n=19)혹은 20mg (group 2: n=20) 1회 경구투여한후 다시 운동부하201- thallium-SPECT를 시행하여 비교 분석하였다. 다답차운동 부하의 최대 운동량에 도달시 201-thallium을 정주하여 1분간 운동을 지속시킨후 부하영상을 얻고 안정 4시간후 재촬영하여 thallium결손 범위를 비교하여 심근허혈 범위를 정하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.219-221
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• 2012

본 논문은 무손실 데이터 은닉 기법중 주변 화소의 통계적 특성을 이용하여 어떠한 추가적인 맵 정보 없이 키 파라미터로써 원본 영상과 삽입한 데이터를 정확히 분리해 내는 기법이다. 오버/언더 플로우에 더 강한 데이터 은닉을 위해, 데이터 삽입에 대한 변수로 작용할 수 있는 주변 화소값들의 범위 뿐만 아니라 주변 화소값들의 표준 편차와 평균값을 모두 키 파라미터의 인자로 사용하여 화소값이 낮은, 즉 영상의 밝기가 어두운 부분에 더 많은 데이터를 삽입할 수 있는 기법을 제안하였고, 실험을 통하여 기존 기법 대비 평균 2배 이상의 삽입 용량이 증진된 것을 확인하였다.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.111-114
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• 2008

The Injection molding is used more than 70% of total production in plastic products. The injection molding process has 4 processes such as filling, packing, cooling and ejecting. It spends most of times in the cooling process. Therefore, it is important to control the mold temperature in producing plastic products. The cooling system and time affect the product's quality and productivity. Especially, cooling time has about 60% of total injection cycle time. Therefore, we can improve a productivity by shortening cooling time. In this study, the rapid cooling system was developed and performed a efficiency test. This system could refrigerate coolant to $1^{\circ}C$ and had to need 10 minutes for normal operating. However, if response time of temperature controller and sensor will be increased, the performance of this system will increase.

• Journal of Biomedical Engineering Research
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• v.21 no.2
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• pp.145-156
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• 2000

본 논문에서는 중앙시상 두뇌 자기공명영상 분할결과를 이용한 3차원 시상 두뇌 자기공명영상의 자동분할기법을 제안한다. 제안된 알고리즘에서는 먼저 3차원 시상 두뇌 자기공명영상의 중앙영상을 분할하고, 분할된 중앙두뇌 자기공명영상을 인접하는 영상에 마스크로 적용한다. 이 때 마스크 적용으로 인하여 인접하는 영상이 절단되는 문제가 발생할 수 있다. 이러한 문제를 해결하기 위하여 절단 영역의 경계점을 검출한 후, 절단 영역에 대한 경로 재설정을 통해 절단 영역을 복원한다. 이러한 경로 재설정을 위해 connectivity-based threshold segmentation algorithm을 사용하였다. 실험결과 제안된 알고리즘의 유용성을 확인할 수 있었다.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.8
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• pp.369-374
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• 2006

Due to development of internet network environments and data compression techniques, the size and amount of multimedia data has greatly increased. They are compressed before transmission or storage. Dealing with these compressed data such as video retrieval or indexing requires decompression procedure in most cases. This causes additional computations and increases the processing time. In various applications a histogram is one of the most frequently used tools. Efficiency of extracting such histograms will drop down if decompression is involved. We propose a novel scheme for extracting histograms from images that are transformed into the compressed domain by 8x8 DCT(Discrete Cosine Transform). In this scheme an averaged version of original image is obtained by a simple linear combination of DCT coefficients with the sets of coefficients we designed.

• Proceedings of the IEEK Conference
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• 2002.06d
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• pp.29-32
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• 2002

In typical block-based video coding, the objective of RC(Rate Control) is to select the quantization parameters so that the encoder produces bits at the rate of the channel and the overall distortion is minimized. To reduce the huge amount of computations required for offline RC, there have been significant efforts to speed up the process of video encoders. Those efforts have been mainly focused on the modes for bit rate and distortion in types of coders, in terms of the quantization parameters. Because previous works related to model based online RC are based on statistics of previous frame, it occurs the problem such that allocates bits unequally without regard to current frame statistics. In this thesis, an equal bit allocation scheme using current frame statistics is proposed.

• Proceedings of the IEEK Conference
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• 2002.06d
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• pp.77-80
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• 2002

In this paper, We have studied for guaranteeing the clear display of MPEG-2 video sequence when conduct splicing of MPEG-2 system streams. we focus on the PES domain splicing considering video sequence. And we wish to make a base on the TS or PS domain splicing considering video sequence. For that, first, we compared and analyzed problems that is raised when different two PES streams are spliced and effects that affect the video sequence. And based on this analysis, we have searched for methods that resolve the cause of problems that can be happened in the display of video sequence directly in PES domain.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.291-292
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• 2006

This paper presents rate-distortion optimization that is considered sequence statistics(complexity) to choose the best macroblock mode decision in H.264. In previous work, Lagrange multiplier is derived by the function of constant value 0.85 and QP so that is not the proper Lagrange multilplier for any image sequence. The proposed algorithm solves the problem by changing constant value 0.85 into adaptive value which is influenced by image complexity, and by reducing the encoder complexity to estimate the image statistics with the multiplication of transformed, quantized rate and distortion. Proposed algorithm is achieved the bit-rate saving up to 5% better than previous method.