• Korea-Australia Rheology Journal
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• 제21권1호
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• pp.71-79
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• 2009

The incomplete saturation and the void formation during the resin infiltration into fibrous porous media in the resin transfer molding process cause failure in the final product during its service. In order to better understand flow behavior during the filling process, a finite-element scheme for transient flow simulation across the micro-structured fibrous media is developed in the present work. A volume-of- fluid (VOF) method has been incorporated in the Eulerian frame to capture the evolution of flow front and the vertical periodic boundary condition has been combined to avoid unwanted wall effect. In the microscale simulation, we investigated the transient filling process in various fiber structures and discussed the mechanism leading to the flow fingering in the case of random fiber distribution. Effects of the filling pressure, the shear-thinning behavior of fluid and the volume fraction on the flow front have been investigated for both intra-tow and the inter-tow flows in dual-scale fiber tow models.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2299-2301
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• 2001

광 디스크의 용량을 증가시기키 위해선, 레이저 다이오드의 단파장화와 렌즈의 개구수 증가가 수년 동안 시도되어왔다. 불행히도 이러한 노력들은 디스크 틸트(tilt)로 인해 야기되는 코마(coma) 수차로 인한 부작용을 유발하였다. 이런 문제를 해결하기 위해, 램(random access memory, RAM) 디스크의 경우 몇 가지 검출과 보상 방법이 제안되었다. 그러나, 롬(read only memory, ROM) 디스크의 경우 아직까지 뚜렷한 해결책이 제시되지 않고 있다. 본 논문에서는 8분할 광 검출기에 의해 생성되는 차동 위상 검출(differential phase detection, DPD) 신호를 이용한 고밀도 롬 디스크에서 래디얼(radial) 틸트를 검출하는 방법을 제안한다. 3축 렌즈 구동형 액츄에이터(actuator)를 이용하여 개발한 래디얼 틸트 서보로 검출된 래디얼 틸트를 보상한다. 액츄에이터의 회전이 트래킹(tracking) 서보(servo)에 미치는 영향을 소개한다. 끝으로 제안된 방법의 유용성을 고밀도 롬 드라이브에 대한 실험을 통해 검증한다.

• 한국멀티미디어학회논문지
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• 제25권1호
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• pp.61-71
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• 2022

When communication such as light, radio wave, or magnetic field is used underwater, the communication distance is very short, so sound waves are mainly used. However, by combining the strengths of each medium and communicating, stable communication may be possible. Underwater multi-media communication requires a protocol stack that supports it, which is very complex. To this end, this paper proposes a standard protocol stack and modeling technique to enable easy protocol stack modeling for the purpose. In fact, in this paper, a random model was created and analyzed through the proposal of modeling elements and similarity measurement methods, and as a result, it was analyzed that it was very helpful in creating a new model based on a standard model.

• The Journal of Asian Finance, Economics and Business
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• 제7권12호
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• pp.283-292
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• 2020

The implementation of physical or social distancing during the Covid-19 pandemic has an implication on the shifting of conventional to online business activities. This study aims to explore how financial support, perceived benefits, external pressure determine social media marketing as well as understanding the role of internet and e-business technology (IEBT) that occurs in this relationship. This study adopted a quantitative study with Structural Equation Modeling (SEM)-based variance Partial Least Square (PLS), which aims to enhance understanding of the relationship between variables. The surveyed population of this study came from 123 small- and medium-sized enterprise (SME) owners in East Java of Indonesia, using an online survey and selected with the convenience random sampling method. The findings of this study indicated that the perceived benefits and external pressure have a positive effect on the adoption of IEBT. However, financial support failed in explaining SMEs' adoption of IEBT. This study confirmed that the adoption of IEBT has successfully mediated the influence of financial support, perceived benefits, and external pressure on social media marketing. Despite the samples solely collected from East Java, this study is the first step in research related to the social media marketing in SMEs in Indonesia.

• Nuclear Engineering and Technology
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• 제47권5호
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• pp.546-558
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• 2015

Chord length sampling method in Monte Carlo simulations is a method used to model spherical particles with random sampling technique in a stochastic media. It has received attention due to the high calculation efficiency as well as user convenience; however, a technical issue regarding boundary effect has been noted. In this study, after analyzing the distribution characteristics of spherical particles using an explicit method, an alternative chord length sampling method is proposed. In addition, for modeling in finite media, a correction method of the boundary effect is proposed. Using the proposed method, sample probability distributions and relative errors were estimated and compared with those calculated by the explicit method. The results show that the reconstruction ability and modeling accuracy of the particle probability distribution with the proposed method were considerably high. Also, from the local packing fraction results, the proposed method can successfully solve the boundary effect problem. It is expected that the proposed method can contribute to the increasing of the modeling accuracy in stochastic media.

• 한국임상약학회지
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• 제26권1호
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• pp.40-45
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• 2016

Objective: The increasing use of imaging examinations such as computed tomography (CT) results in increased contrast media use, which increases contrast media-induced adverse reactions (AR). This study investigated the risk factors of ARs to nonionic iodinated contrast media. Methods: This study evaluated patients who were administered iodinated contrast media during CT scanning in Yeouido St. Mary's Hospital in Seoul, Korea in 2012. Among the subjects, those with contrast media-induced ARs were classified as the AR group. The control group included individuals without ARs who were selected through simple random sampling. The effects of sex, age, contrast media type and dose, CT region, previous contrast media administration, allergy history, and comorbidity were analyzed in the AR and control groups. Results: Multivariate logistic regression analyses were performed to evaluate the identified AR risk factors in 103 subjects in the AR group and 412 subjects in the control group. The results confirmed that the risk of developing ARs was significantly higher in females [odds ratio (OR): 2.206; 95% confidence interval (CI): 1.353-3.598], in individuals administered Iohexol (OR: 9.981; 95% CI: 2.361-42.193), in individuals with an allergy history (OR: 3.982; 95% CI: 1.742-9.101), and in individuals with comorbid asthma (OR: 6.619; 95% CI: 1.377-31.826). Most of the ARs were mild and immediate. Conclusion: In patients who were administered contrast media during CT scans, female gender, Iohexol use, allergy history, and asthma were risk factors for ARs. Therefore, special care is required for patients with such risk factors to prevent ARs.

• 대한간호학회지
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• 제30권1호
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• pp.148-159
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• 2000

The purpose of this study was to test the theoretical model designed to explain juvenile delinquency by media violence. Data were collected through questionnaire survey over a period of 3 months. Subjects served for this study consisted of 537 adolescents including 217 delinquent adolescents and 320 student adolescents in Korea, sampled from Korean student population and delinquent adolescent population confined in juvenile correctional institutions, using proportional stratified random sampling method. In this study, exogeneous variable was family dynamic environment and endogeneous variables were character of adolescent including need satisfaction/ frustration, sociability, antisocial personality tendency, complaints of psychosomatic symptoms and depressive trend, juvenile delinquent behavior and media violence themes including the extent of interest in and exposure and modelling impulsiveness and modelling to media violence themes. A total of 18 instruments were used to operationalized concepts in this model. A validation study indicated that internal consistencies for the 18 instruments which the researcher used were reliable. The one month test-retest correlation for these instruments ranged from 0.54 to 0.88. Statistical methods employed were descriptive statistics and covariance structural modelling. In summarized conclusion, it was found that media violence served as the most contributor to juvenile delinquency by direct effect of 0.64(t=10.18). That is, as the adolescents have to be the higher extent of interest in and exposure and modelling impulsiveness and modelling to media violence themes, they will show the more frequency of delinquent behavior. The single most powerful contributor by total effect of 0.73(t=7.90) (direct effect=0.19, indirect effect=0.54) to the development of delinquent behavior identified in this study was a construct defining family dynamic environment. That is, as the adolescents had to be more unstable family dynamic environment, they became more frustrated to their psychological need, and revealed the more maladaptive personality pattern, consequently they behaved the higher misconducts such as juvenile delinquency through media violence.

• 방송공학회논문지
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• 제23권1호
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• pp.154-161
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• 2018

최근 스마트폰 사용자가 늘어남에 따라 실내 위치인식 서비스에 대한 연구의 중요성이 증가하고 있다. 실내 위치인식에는 주로 WiFi, Bluetooth 등이 연구되고 있으나, 본 연구에서는 대부분의 실내 공간에 설치되어 있고 스마트폰에 WiFi 기능이 탑재되어 있어 접근성이 좋은 WiFi를 사용한다. 본 연구에서는 수집된 WiFi의 수신신호세기를 이용하는 핑거프린트 기술과 다변량 분류법 중 Ensemble learning method인 랜덤포레스트 알고리즘을 사용한다. 핑거프린트의 데이터로는 수신신호세기와 더불어 Mac주소를 사용해 총 4개의 라디오 맵을 만들어 사용하였다. 실험은 제한된 실내공간에서 진행하였고 실험분석을 위해 본 연구에서 제안하는 방법과 유사한 기존의 랜덤포레스트를 사용하는 실내 위치인식 시스템과 비교 분석하였다. 실험 결과 기존의 랜덤포레스트를 사용하는 실내 위치인식 시스템보다 본 연구에서 제안하는 시스템의 위치인식 정확도가 약 5.8% 높고 학습 데이터 개수에 상관없이 위치인식 속도가 일정하게 유지 되며 기존 방식 보다 더 빠름을 입증하였다.

• 방송공학회논문지
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• 제20권6호
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• pp.938-949
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• 2015

본 논문에서는 외부압력에 의한 외형 손상이나 빛의 방향에 따른 색상 대비변화 등에 견고한 영상기반 속도 제한 표지판 인식 시스템 설계를 제안한다. 속도 제한 표지판 인식을 위해서 최근 패턴 인식 분야에서 뛰어한 성능을 보여주고 있는　CNN (Convolutional neural network)을 사용한다. 하지만 기존의 CNN은 특징 추출을 위해 다수의 은닉층이 사용되고 추출된 결과에 대해 MLP(Multi-layer perceptron) 등과의 완전 연결(fully-connected) 방식을 사용함으로 학습과 테스트 시간이 많이 걸리는 단점이 있다. 본 논문에서는 이러한 단점을 줄이기 위해 2계층의 CNN을 구성하고 패턴 분류를 위해 랜덤 포레스트(Random forest)를 결합하여 완전 연결이 아닌 랜덤 연결 방식을 적용하였다. GTSRB(German Traffic Sign Recognition Benchmark)데이터의 교통안전표지판 중에서 8개 속도 제한 표지판 데이터를 사용하여 제안하는 방식이 SVM (Support Vector Machine)이나 MLP 분류기를 적용할 때 보다 성능이 우수함을 입증하였다.

• 디지털콘텐츠학회 논문지
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• 제16권5호
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• pp.805-813
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• 2015

Compressive sensing 및 희소 복원 문제(sparse recovery problem)는 기존 디지털 기술의 한계를 극복할 수 있는 새로운 이론으로 많은 관심을 받고 있다. 그러나 신호 재구성에서 l1 norm 최적화 문제 해결에 많은 연산이 수행되며 따라서 병렬 처리 기법이 필요하다. 이 과정에서 무작위 행렬과 벡터 연산을 통한 변환 연산이 전체 과정 중에서 많은 부분을 차지하는데, 특히 원본 신호의 크기로 인해 이 과정에서 필요한 무작위 행렬을 메모리에 저장하기 곤란하며 계산 시 무작위 행렬의 절차적(procedural) 처리 방식이 필수적이다. 본 논문에서는 이 문제에 대한 해결책으로 단일 명령 다중 스레드(SIMT) 병렬 플랫폼 상에서 무작위 부분적 Haar 웨이블릿 변환을 절차적으로 계산할 수 있는 새로운 병렬 알고리듬을 제안한다.