• 지능정보연구
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• 제15권4호
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• pp.53-64
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• 2009

본 논문에서는 실루엣 동영상으로부터 보행 분석에 사용되는 형태 기술자의 성능을 평가하였다. 형태 기술자는 모멘트기술자(MD), 푸리에기술자(FD), 저나이크기술자(ZD)를 사용하였다. 먼저 성능 평가 지수인 비대칭 지수 AI와 주기지수 PI를 정의하였다. 이 지수는 보행은 주기적으로 주어지며, 이를 표현한 형태 기술자도 같은 보행 주기를 가져야 하는 것을 기반으로 한다. 또한 지수는 형태의 특성을 정확하게 나타내는 인식 성능보다는 형태 기술자들에 의해 얼마나 잘 표현되었는가를 평가하는 것이다, 성능평가결과, ZD가AI = 1.09, PI = 2.21로 대체로 무난한 성능으로 나타났으며, FD가 MD보다 AI = 0.93로 하나의 주기내에서의 성능이 우수하였다. 반면 MD는 FD보다 PI = 2.37로 반복적인 특징이 높게 나타났다. 또한 형태 기술자는 5~10개 정도의 파라미터 개수를 사용하는 것이 좋은 성능을 가짐을 보였다.

• 전자공학회논문지
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• 제50권7호
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• pp.34-42
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• 2013

본 논문에서는 웨이블릿 OFDM (Orthogonal Frequency Division Multiplexing) 및 FD-OFDM(Frequency Diversity OFDM) 시스템과 일반 OFDM 시스템의 성능을 비교 분석 한다. 푸리에 변환에 기반하는 일반 OFDM방식과는 달리 웨이블릿 OFDM 방식은 웨이블릿 변환을 사용하며, CDM (Code Division Multiplexing)과 OFDM의 중간적인 특성을 통해 심볼간 간섭을 효과적으로 제거할 수 있으며 채널간 간섭 역시 최소화 할 수 있다. FD-OFDM 방식의 경우, 각 병렬 브랜치에 입력된 심볼들이 직교 시퀀스로 곱해진 뒤 모든 부반송파에 분배되고, 각 부반송파는 주어진 프레임에서 각 병렬 브랜치의 심볼 조각들의 합의형태로 이루어진 정보를 전달한다. FD-OFDM의 한 부반송파 내에 포함된 모든 심볼들은 직교 시퀀스에 의해 구별되며, 간섭에 강하며 주파수 다이버시티 특성을 가진다는 장점을 지닌다. 협대역 간섭과 하모닉 잡음 환경에서 BER (Bit Error Rate) 성능을 통해 시스템 간 성능 비교 분석을 진행하였으며, 이를 통해 웨이블릿 OFDM과 FD-OFDM의 성능이 일반 OFDM보다 간섭에 대해 강건하고 특히 하모닉 노이즈 환경에서는 웨이블릿 OFDM이 가장 강건한 특성을 보이는 것을 알 수 있다.

• Imaging Science in Dentistry
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• 제42권4호
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• pp.231-235
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• 2012

Purpose: This study was performed to evaluate the trabecular pattern on panoramic radiographs to predict age-related osteoporosis in postmenopausal women. Materials and Methods: Thirty-one postmenopausal osteoporotic women and 25 postmenopausal healthy women between the ages of 50 and 88 were enrolled in this study. The bone mineral density (BMD) of the lumbar vertebrae and femur were calculated using dual-energy X-ray absorptiometry (DXA), and panoramic radiographs were obtained. Fractal dimension (FD) was measured using the box counting method from 560 regions of interest ($51{\times}51$ pixels) in 6 sites on the panoramic radiographs. The relationships between age and BMD and between FD and BMD were assessed, and the intraobserver agreement was determined. Results: There was a significant difference in the FD values between the osteoporotic and normal groups (p<0.05). There was a significant difference in the FD values at three sites in the jaws (p<0.05). Age was significantly correlated with the BMD measurements, with an odds ratio of 1.25. However, the FD values were not significantly correlated with the BMD measurements, with an odds ratio of 0.000. The intraobserver agreement showed relatively higher correlation coefficients at the upper premolar, lower premolar, and lower anterior regions than the other sites. Conclusion: Age was an important risk factor for predicting the presence of osteoporosis in postmenopausal women. The lower premolar region was the most appropriate site for evaluating the FD value on panoramic radiographs. However, further investigation might be needed to predict osteoporosis using an FD value on panoramic radiographs.

• 의학교육논단
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• 제25권1호
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• pp.17-34
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• 2023

This study aimed to investigate the current status of faculty development (FD) programs operated by medical colleges and institutions in Korea, and to suggest future-oriented directions for FD. A survey was conducted targeting medical colleges and medical education institutions that operate FD programs. We investigated the reasons for selecting topics, program themes, program operation methods, longitudinal program status, program improvement and quality control methods, the evaluation of the program effects, the outcomes and problems of the programs, and opinions on the latest trends. Twenty-nine out of 40 medical colleges and three out of six institutions responded. Topics were selected based on an analysis of medical education trends and the educational environment in both groups. The most common program themes were assessments in medical colleges, and teaching/learning and curriculum themes in institutions. FD was perceived to induce professors' and administrators' interest in medical education and improve the quality of medical education. The most common program method was workshops. Three medical colleges and one institution had longitudinal programs. Participant surveys constituted the most common method of evaluating programs' effects. Difficulties in publicizing programs and inducing voluntary participation were the most common problems in both groups. New attempts for FD were perceived as the role of external institutions. Based on the results, it is necessary to develop a framework and quality improvement indications for FD programs in the future, and FD programs are expected to be developed through new initiatives, such as longitudinal programs and those focusing on the community of practice.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제48권1호
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• pp.41-49
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• 2022

Objectives: We compared changes in fractal dimension (FD) and grayscale value (GSV) of peri-implant alveolar bone on digital panoramic radiography (DPR) and cone-beam computed tomography (CBCT) immediately after implant surgery and 12 months postoperative. Materials and Methods: In this retrospective study, 16 patients who received posterior mandibular area dental implants with CBCT scans taken about 2 weeks after implantation and one year after implantation were analyzed. A region of interest was selected for each patient. FDs and GSVs were evaluated immediately after implant surgery and at 12-month follow-up to examine the functional loading of the implants. Results: There were no significant differences between DPR and CBCT measurements of FD values (P>0.05). No significant differences were observed between FD values and GSVs calculated after implant surgery and at the 12-month follow-up (P>0.05). GSVs were not correlated with FD values (P>0.05). Conclusion: The DPR and reconstructed panoramic CBCT images exhibit similar image quality for the assessment of FD. There were no changes in FD values or GSVs of the peri-implant trabecular bone structure at the 12-month postoperative evaluation of the functional loading of the implant in comparison to values immediately after implantation. GSVs representing bone mass do not align with FD values that predict bone microstructural parameters. Therefore, GSVs and FDs should be considered different parameters for assessing bone quality.

• 한국광학회지
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• 제14권4호
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• pp.399-405
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• 2003

FD10 유리를 이용한 클램프형 광전류 센서를 제작하였다. 대칭형 구조로 이루어진 2조각의 FD10유리를 이용하여 제작하였으며, 센서헤드 내부에서 반사시에 위상차가 발생하는 것을 방지하기 위해 정확히 임계각으로 광이 진행하도록 구조를 설계하였다. 제작한 광-전류 변류기 헤드를 이용하여, 0-1,000 AT 까지의 전류를 측정하고, 빛의 입사각에 따른 광의 손실, 입사광의 편광회전에 따른 광출력변화, 온도에 따른 출력의 변화 및 장시간 전류 측정 등에 대한 실험결과를 제시하고 이에 대한 분석을 통해 제작된 광전류 변류기 헤드의 전류계로서의 가능성을 입증하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.3908-3920
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• 2015

In this paper, performance analysis of full-duplex (FD) relay selection under decode-and-forward (DF) relaying mode is carried out by taking into account several critical factors, including the distributions of the received signal-to-noise ratio (SNR) and the outage probability of wireless links. The tradeoff between the FD and half-duplex (HD) modes for relay selection techniques is also analyzed, where the former suffers from the impact of residual self-interference, but the latter requires more channel resources than the former (i.e., two orthogonal channels are required). Furthermore, the impact of optimal power allocation (OPA) on the proposed relay-selection scheme is analyzed. Particularly, the exact closed-form expressions for outage probability of the proposed scheme over Rayleigh fading channels are derived, followed by validating the proposed analysis using simulation. Numerical results show that the proposed FD based scheme outperforms the HD based scheme by more than 4 dB in terms of coding gain, provided that the residual self-interference level in the FD mode can be substantially suppressed to the level that is below the noise power.

• 한국해양공학회지
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• 제38권2호
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• pp.53-63
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• 2024

Submerged breakwaters can be installed underneath floating structures to reduce the external wave loads acting on the structure. The objective of this study was to establish an optimization analysis framework to determine the corresponding shape and position of the submerged breakwater that can minimize or maximize the external forces acting on the floating structure. A two-dimensional frequency-domain boundary element method (FD-BEM) based on the linear potential theory was developed to perform the hydrodynamic analysis. A metaheuristic algorithm, the advanced particle swarm optimization, was newly coupled to the FD-BEM to perform the optimization analysis. The optimization analysis process was performed by calling FD-BEM for each generation, performing a numerical analysis of the design variables of each particle, and updating the design variables using the collected results. The results of the optimization analysis showed that the height of the submerged breakwater has a significant effect on the surface piercing body and that there is a specific area and position with an optimal value. In this study, the optimal values of the shape and position of a single submerged breakwater were determined and analyzed so that the external force acting on a surface piercing body was minimum or maximum.

• 대한한방내과학회지
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• 제42권4호
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• pp.488-509
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• 2021

Purpose: Functional dyspepsia (FD) is a chronic syndrome accompanied by repetitive digestive symptoms that appear in the upper gastrointestinal tract and are not caused by specific diseases. Psychological symptoms like anxiety, depression, insomnia, and somatization are frequently observed in FD. The purpose of this study was to review the effect of herbal medicine on the psychological symptoms that accompany FD. Methods: Database search (PubMed, EMBASE, KISS, Kmbase, KoreanMed, NDSL, OASIS, CNKI) was performed on February 24, 2021; a total of 1825 studies were searched. After the screening, 22 studies were included. Results: The studies were assessed by Cochrane RoB 2 and sorted into a table according to psychological symptoms. Meta-analysis was performed to estimate the effect of herbal medicine. Twenty of the twenty-two studies reported that herbal medicine was significantly more effective than the control group. Only three of the studies did not have a high risk of bias. Conclusion: Herbal medicine was significantly effective with or without Western medicine and had fewer adverse effects. Severe adverse effect was not reported. Psychological symptoms in FD affect onset and duration of FD, and some FD patients want to be treated for their anxiety before other symptoms. Reliable information about treatment for the psychological symptoms of FD is lacking. We reviewed the effect of herbal medicine treatment in this study, the results of which could be selected for primary or secondary treatment for FD.

• Journal of Neurogastroenterology and Motility
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• 제24권4호
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• pp.603-613
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• 2018

Background/Aims Functional dyspepsia (FD) is one of the most common gastrointestinal disorders, and FD imposes social and economic burden worldwide. The aim of this study is to identify the prevalence and risk factors of FD in health check-up population in tertiary centers in Korea. Methods A nationwide multicenter prospective study was performed at 9 tertiary healthcare centers in Korea between September 2016 and June 2017. A total of 2525 subjects were investigated based on endoscopic findings and questionnaires with the Rome III criteria, and Helicobacter pylori serology (IgG). Results A total of 1714 subjects without organic disease were enrolled. The mean (${\pm}SD$) age was 51.5 (${\pm}12.7$) years, and 917 patients (53.5%) were female. The proportion of H. pylori seropositivity was 51.0% (874/1714). The prevalence of FD was 10.3% (176/1714), and the subtypes of postprandial distress syndrome alone, epigastric pain syndrome alone, and postprandial distress syndromeepigastric pain syndrome overlap were 4.8%, 3.0%, and 2.5%, respectively. Multivariate analysis showed that female gender (OR, 1.58; 95% CI, 1.14-2.21) and education below college level (OR, 1.45; 95% CI, 1.01-2.07) were related to FD. Multivariate analysis based on age 60 showed female gender as a significant (OR, 2.90; 95% CI, 1.06-7.94) factor in the group ${\geq}60$ years. Conclusions The prevalence of FD was 10.3% in the health check-up population in Korea. Female sex and education below college level were risk factors for FD. Female sex is a risk factor for FD in old age, underscoring the need for close attention in this age group.