• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.793-795
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• 2005

지식 시스템(knowledge system)을 구축한다는 것은 구조적인 지식(structured knowledge)과 추론 모델(reasoning model)을 개발하기 위한 활동을 모델링하는 것을 말한다. 특별히 모델을 재사용한다는 것은 새로운 응용(application)을 만드는 데 있어서 비용과 시간을 감소시켜 준다. 서로 다른 응용과 영역(domain)에서 지식 구성요소를 재사용 한다는 것은 전문가 지식의 습득과 추론 과정을 정확하게 기술하는데 도움을 주게 된다. 본 연구에서는 문제해결방법 재사용에 대한 기존의 몇 가지 방법들을 함께 사용함에 의해서 급성복통과 관련된 질환 진단 태스크를 모델링할 수 있는 진단시스템을 제안하여 기존 시스템과 비교했을 때 지식 획득율을 향상시키게 되었다.

• Proceedings of the Membrane Society of Korea Conference
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• 1995.04a
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• pp.62-63
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• 1995

혐기성 소화는 고농도의 유기폐수를 최종적으로 메탄으로 전환하여 에너지원을 회수할 수 있는 효율적인 생물학적 폐수처리 공정 중의 하나이다. 그런데 이러한 혐기성 소화 공정에서 가장 큰 장애요인으로 작용하고 있는 요소 중의 하나가 매생물의 침강성 저하로 인한 고액분리의 문제이다. 이로인해 현재 고전적인 중력침강법, 부상법 대신에 분리막을 이용한 막결합형 혐기성 소화 공정이 대두되고 있으며 완전한 고액분리, 반응조내의 고농도 미생물 보유, 양질의 최종 유출수 획득 등 많은 장점들이 제시되고 있다. 그러나 이러한 장점에도 불구하고 시간에 따른 막오염 현상, 분리막 표면에서의 케이크층 형성 등으로 인한 막투과 유속 (flux)의 감소는 분리막의 응용에 있어 경제성을 저하시키는 주요한 부정적 요인으로 지적되고 있다. 그리고 막분리 성능은 분리막의 특성, 유체역학적 조건, 그리고 혐기성 소화 상태 등에 의해 영향을 받을 수 있다. 본 연구에서는 막결합형 혐기성 소화 공정의 십자흐름 (crossflow) 막분리 공정에서 유체역학적 조건 및 혐기성 소화조의 상태와 관련된 요인들이 어떻게 막투과도 및 배제율 등에 영향을 미치는 지 살펴보고자 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04a
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• pp.737-740
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• 2002

본 논문에서는 영상에서 연속적인 얼굴 표정 변화 인식 방법에 대하여 제안하였다. 제안된 방법은 가중 결합으로 정합 된 분류 그래프를 이용한 얼굴 특징점 추적과 특징 궤도와 표정 변화 모델의 비교에 의한 얼굴표정 인식의 두 가지 부분으로 구성된다. 표정 변화 모델은 얼굴 특징 동작과 표정의 변화사이의 연관 관계를 표현한 B-spline 곡선을 이용하여 구성된다. 유형뿐만 아니라 표정의 변화 단계까지 인식 할 수 있다. 더욱이 획득된 표정 정보는 다음 프레임의 추적의 지침으로 피드백 됨에 따라 추적의 검색 시간을 감소시킴으로서 교점 확산 구간을 최소화 할 수 있다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2016.11a
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• pp.4-5
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• 2016

최근 현실 세계의 기반 위에 가상의 정보를 증강하여 사용자와 상호작용하며 즐기는 증강 현실 컨텐츠가 대중들에게 많은 인기를 얻고 있다. 이러한 증강 현실 콘텐츠는 현실 세계를 기반으로 한다는 점에서 실제의 3차원 공간을 정확하게 복원하는 것이 중요하다. 초기의 3차원 복원 방법으로 RGB-D 카메라를 이용한 KinectFusion 방법이 제안되었고 많은 연구자들에 의해 다루어지고 있다. 하지만 기존의 방법은 시간이 흐름에 따라 누적되는 오차에 의해 3차원 모델이 정확하게 복원되지 않는 객체 표류 문제가 발생한다. 이러한 문제는 깊이 카메라 센서의 잡음 때문에 정확하지 않은 표면 법선 벡터가 계산되는 것에 기인한다. 본 논문에서는 이러한 문제를 해결하기 위해 잡음에 강건한 표면 법선 벡터를 계산하는 방법을 제안한다. 실험결과에서는 기존의 방법과 비교하여 제안하는 방법이 절대 궤적 오차 (absolute trajectory error)가 감소하는 것을 확인 했고 카메라 궤적이 정확하게 예측되는 것을 확인할 수 있었다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.300-304
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• 2020

본 논문에서는 원격 탐사 영상 정합에서 정확도는 유지하면서 특징점 매칭 (Matching) 복잡도를 줄이기 위해 입력 영상을 전처리하는 구조물 검출 네트워크를 이용한 원격 탐사 영상 정합 방법을 제안한다. 영상 정합의 기존 방법은 입력 영상에서 특징점을 추출하고 설명자 (Descriptor)를 생성한다. 본 논문에서 제안하는 방법은 입력 영상에서 특징점 매칭에 영향을 미치는 구조물만 추출하여 새로운 영상을 만들어 특징점을 추출한다. 추출된 특징점은 필터링 (Filtering)을 거쳐 원본 영상에 매핑 (Mapping)되어 설명자를 생성하여 특징점 매칭 속도를 향상시킨다. 또한 구조물 검출 네트워크에서 학습 영상과 시험 영상의 특성의 차이로 생기는 성능 저하 문제를 개선하기 위해 히스토그램 매핑 기법을 이용한다. 아리랑 3 호가 획득한 원격 탐사 영상에 대한 실험을 통해 제안하는 방법은 정확도를 유지하면서 계산 시간을 SURF 보다 87.5%, SIFT 보다 92.6% 감소시킬 수 있다.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.227-232
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• 2019

MRI examination for patients with metal objects has in poor image quality. Metallic implants can result in poor image because magnetic susceptibility causes signal loss and distortion and makes poor imaging, which is called magnetic susceptibility artifact or metal artifact. There are several approaches to reduce metal artifacts. In this study, we study the reduction of metal artifact by VAT and SEMAC techniques. A metal implant used for orthopedic surgery was attached to the phatom and the distortion caused by the artifact was measured under T1WI and T2WI protocols. Several techniques of VAT only and VAT and SEMAC for the reduction of metal artifact were compared. The metal artifact showed a reduction of at least 8% to a maximum of 26% in the VAT-SEMAC. The VAT-SEMAC technique can be applied to patients with orthopedic implants to improve image quality. If scan time and image quality are simultaneously considered in VAT-SEMAC technique, metal artifact will be reduced in clinical practice.

• Journal of Chest Surgery
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• v.30 no.10
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• pp.949-960
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• 1997

Background. Limited ischemic tolerance of the lung has remained one of the factors that limits the expansion of pulmonary transplantation as a treatment for end-stage pulmonary disease. Numerous studies on safe long term preservation for lung transplantation has been performed for the purpose of developing ideal preservation solution with extracellular type or intracellular type solutions. In this. study, we examined the efficacy of L DG solution in lung preservation longer than 20 hours by comparison with modified Euro-Collins solution. Iwethods. Thirty-(our adult mongrel dogs were divided into two groups. Donor lungs were flushed with LPDG solution(n=9) or modified Euro-Collins(MEC) solution(n=8) and stored for 24 hours at 1$0^{\circ}C$. All donor lungs were perfused through the pulmonary arteries with solutions containing prostaglandin El and verapamil. Left canine lung allotransplantations wereperformed. Assessment(hemodynamic indices and arterial blood gas analysis) of left implanted lung was made by occluding the right pulmonary artery for ten minutes using pulmonary artery Cuff. Assessment was repeated at the interval of 30 minutes, one hour, and two hours later after reperfusion and then chest X-ray, computed tomogram and lung perfusion scan were obtained. In survival dogs follow-up studies were done with assessment with chest X-ray, computed tomogram of the chest and lung perfusion scan on 7th day postoperatively. After preservation above 20 hours, pathological examinations for ultrastructural findings on right lung were performed in each group. Results. With respect to arterial oxygen tension, LPDG group was superior to MEC but there was no statistical significance for 2 hours after reperfusion. Mean pulmonary artery pressure was less increased(p < 0.05) and cardiac output higher(p <0.05) than MEC group until 2 hours after reperfusion. After 2 hours of reperfusion, both groups showed transplanted lung function deteriorated gradually. Perfusion scan of the transplanted lung in LPDG group showed better perfusion rate in immediate post-reperfusion, 3 days and 7 days later respectively but there was no statistical significance and corelation with PaO2 and computed tomoRravhic views. In scanning electron microscopy of pulmonary artery after preservation, LPDG group relatively shows less irregular protrusion of the inner surface of endothelial cell of poulmonary artery than MEC group. Conclusions, e concluded that LPDG solution can offer safe lung preservation above 20 hours with adequate immunosuppressive therapy and prevention of the infection.

• Journal of the Institute of Convergence Signal Processing
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• v.2 no.3
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• pp.39-44
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• 2001

In frequency hopping spread spectrum(FHSS) communication systems, exact frequency synchronization is required due to the random hopping of carrier frequencies between transmitter and receiver even under harsh channel conditions. For synchronization of FHSS communications, multi-frequency hopping synchronization(MFHS) method has been used in which a small set of frequencies are repeatedly sent several times for long duration. But this long duration resulted in being easily detected by the unauthorized users as well as long duration of acquisition time. In this paper, motivated by these problems, an adaptive synchronization method(ASM) is proposed. ASM is technics to reduce the synchronization time where the number of synchronization frequencies and repetition numbers is adaptively changed (increased or decreased) according to the channel conditions. The performance analysis showed that the time duration of synchronization was reduced to 0.2sec, and the influence of jamming or interference was decreased to 46% in ASM.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.10 no.3
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• pp.237-242
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• 2016

The major advantage of slip-ring technology in Spiral CT is that it facilitates continuous rotation of the x-ray tube, so that volume data can be acquired from a patient quickly. Not only for such a fast scan, but also for the dose reduction purpose, high signal-to-noise ratio and fast data acquisition system is required. In this study, we have built a multi-channel photodetector and multi-channel data acquisition system for CT application. The detector module consisted of CdWO4 crystal and Si photodiode in 16 channels. For the performance test of the preamplifier stage, both the transimpedance and switched integrator types are optimized for the photodetector modules. Switched integrator showed better noise performance in the limited bandwidth which is suitable for the current CT application. The control sequence for data acquisition and 20 bit ADC is designed with VHDL(Very High Speed Integrated Circuit Hardware Description Language) and implemented on FPGA(Field Programmable Gate Array) chip. Our Si photodiode detector module coupled to CdWO4 crystal showed comparable signal with other commercially available photodiode for CT. Switched integrator type showed higher SNR but narrower bandwidth compared to transimpedance preamplifier. Digital hardware is designed by FPGA, so that the control signal could be redesigned without hardware alteration.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.2
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• pp.122-127
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• 2010

Purpose: The Xpress3.$cardiac^{TM}$ which is a kind of wide beam reconstruction (WBR) method developed by UltraSPECT (Haifa, Israel) enables the acquisition of at quarter time while maintaining image quality. The purpose of this study is to investigate the usefulness of WBR method for decreasing scan times and to compare to it with filtered back projection (FBP), which is the method routinely used. Materials and Methods: Phantom and clinical studies were performed. The anthropomorphic torso phantom was made on an equality with counts from patient's body. The Tl-201 concentrations in the compartments were 74 kBq (2 ${\mu}Ci$)/cc in myocardium, 11.1 kBq (0.3 ${\mu}Ci$)/cc in soft tissue, and 2.59 kBq (0.07 ${\mu}Ci$)/cc in lung. The non-gated Tl-201 myocardial perfusion SPECT data were acquired with the phantom. The former study was scanned for 50 seconds per frame with FBP method, and the latter study was acquired for 13 seconds per frame with WBR method. Using the Xeleris ver. 2.0551, full width at half maximum (FWHM) and average image contrast were compared. In clinical studies, we analyzed the 30 patients who were examined by Tl-201 gated myocardial perfusion SPECT in department of nuclear medicine at Asan Medical Center from January to April 2010. The patients were imaged at full time (50 second per frame) with FBP algorithm and again quarter-time (13 second per frame) with the WBR algorithm. Using the 4D MSPECT (4DM), Quantitative Perfusion SPECT (QPS), and Quantitative Gated SPECT (QGS) software, the summed stress score (SSS), summed rest score (SRS), summed difference score, end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) were analyzed for their correlations and statistical comparison by paired t-test. Results: As a result of the phantom study, the WBR method improved FWHM more than about 30% compared with FBP method (WBR data 5.47 mm, FBP data 7.07 mm). And the WBR method's average image contrast was also higher than FBP method's. However, in result of quantitative indices, SSS, SDS, SRS, EDV, ESV, EF, there were statistically significant differences from WBR and FBP(p<0.01). In the correlation of SSS, SDS, SRS, there were significant differences for WBR and FBP (0.18, 0.34, 0.08). But EDV, ESV, EF showed good correlation with WBR and FBP (0.88, 0.89, 0.71). Conclusion: From phantom study results, we confirmed that the WBR method reduces an acquisition time while improving an image quality compared with FBP method. However, we should consider significant differences in quantitative indices. And it needs to take an evaluation test to apply clinical study to find a cause of differences out between phantom and clinical results.