• 한국항공우주학회지
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• 제48권7호
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• pp.523-528
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• 2020

스프링-메스 시스템의 원리를 이용하여 수평 구동형 MEMS 관성 스위치를 설계하였다. 본 MEMS 스위치는 외부에서 발생하는 가속도를 감지하여 점화안전장치를 장전시키는 역할을 한다. 성능 모델링을 통하여 다양한 가속도 조건에서의 구동 양상을 분석하였다. 시뮬레이션 결과 가속도의 기울기가 10g/msec 이하인 경우에 MEMS 스위치는 10g에서 잘 작동하는 것으로 나타났다. 반면에, 설계 변수들의 공차를 10%로 고려한 시뮬레이션 결과 스프링 폭과 길이에 의해 임계 동작 가속도가 규격(10±2g)을 벗어났다. 제작 공정상 10% 이하의 공차 관리가 어려운 스프링 폭을 두 배로 늘렸을 때 규격을 만족하는 것을 확인하고 설계보완을 제안하였다.

• 대한의용생체공학회:의공학회지
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• 제38권1호
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• pp.49-55
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• 2017

The prevalence of obesity has noticeably increased worldwide over several decades with various complication. Even though anti-obesity drug treatments have been spotlighted by resulting in effective mean weight losses, its adverse effects cannot be overlooked. Thus, this study aimed to evaluate the effects of multi-frequency whole body vibration, one of the mechanical stimulus, as a countermeasure against obesity. Thirty-two-6-week-old C57BL/6J male mice were equally assigned to four groups: the Control group (CON, n = 8), the Sham group (Sham, n = 8), the sham with single frequency whole body vibration (S+V, n = 8), and the sham with multi frequency whole body vibration (S+MV, n = 8). After 4 weeks, morphologic changes in the adipose tissue were evaluated from three-dimensional images using in vivo micro-computed tomography. At 4 weeks, the volume of the abdominal adipose tissue, which had the highest value in Sham group, noticeably reduced in S+MV group compared to it in S+V group. These results implied that the accumulation of abdominal adipose tissue can be effectively reduced through applying multi-frequency whole body vibration.

• Asian Pacific Journal of Cancer Prevention
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• 제16권6호
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• pp.2317-2322
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• 2015

Background: Despite the increasing number of screening examinations performed for cervical cancer utilizing the Papanicolaou smear test (Pap test), few studies have examined whether this strategy is cost-effective in Korea. Objective: This study was conducted to evaluate the cost-effectiveness of cervical cancer screening strategies incorporating the Pap test based on age at the start and end of screening as well as screening interval. Materials and Methods: We designed four alternative screening strategies based on patient age when screening was started (20 or 30 years) and discontinued (lifetime, 79 years). Each strategy was assessed at screening intervals of 1, 2, 3, or 5 years. A Markov model was developed to determine the cost-effectiveness of the 16 possible cervical cancer screening strategies, and this was evaluated from a societal perspective. The main outcome measures were average lifetime cost, incremental quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratio (ICER). Results: Compared with various strategies comprising younger starting age, discontinuation age, and longer screening intervals, strategies employing annual screening for cervical cancer starting at a target age of 30 years and above were the most cost-effective, with an ICER of 21,012.98 dollars per QALY gained (with a Korean threshold of 30,000,000 KRW or US$27,272). Conclusions: We found that annual screening for cervical cancer beginning at a target age of 30 years and above is most cost-effective screening strategy. Considering the potential economic advantages, more intense screening policies for cervical cancer might be favorable among countries with high rates of cervical cancer and relatively low screening costs.

• Asian Pacific Journal of Cancer Prevention
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• 제13권6호
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• pp.2721-2728
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• 2012

Background: There are limited data evaluating the cost-effectiveness of gastric cancer screening using endoscopy or upper gastrointestinal x-ray in the general population. Objective: To evaluate the cost-effectiveness of population-based screening for gastric cancer in South Korea by decision analysis. Methods: A time-dependent Markov model for gastric cancer was constructed for healthy adults 30 years of age and older, and a deterministic sensitivity analysis was performed. Cost-utility analysis with multiple strategies was conducted to compare the costs and effects of 13 different screening alternatives with respect to the following eligibility criteria: age at the beginning of screening, screening interval, and screening method. The main outcome measurement was the incremental cost-effectiveness ratio. Results: The results revealed that annual endoscopic screening from ages 50-80 was the most cost-effective for the male population. In the females, biennial endoscopy screening from ages 50-80 was calculated as the most cost-effective strategy among the 12 screening alternatives. The most cost-effective screening strategy may be adjustable according to the screening costs and the distribution of cancer stage at screening. The limitation was that effectiveness data were obtained from published sources. Conclusions: Using the threshold of $19,162 per quality-adjusted life year on the basis of the Korean gross domestic product (2008), as suggested by the World Health Organization, endoscopic gastric cancer screening starting at the age of 50 years was highly cost-effective in the Korean population. The national recommendation for gastric cancer screening should consider the starting age of screening, the screening interval, and the screening modality.

• 한국항행학회논문지
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• 제15권6호
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• pp.1034-1041
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• 2011

일반적으로 분산 형 구조의 게임서버시스템 하에서 게임 배경처리는 일정크기로 나누어진 여러 개의 부분 배경들을 다수의 게임서버가 나누어서 처리한다. 그런데 분할된 게임 배경에 대한 게임 사용자들의 선호도가 사용자의 특성에 따라 다르게 나타나기 때문에 모든 게임 배경 내 사용자들의 분포를 일률적으로 만들기는 매우 어렵다. 이 때문에 캐릭터들이 한 장소에 급격히 집중되어 게임이 진행되는 경우, 서버가 처리할 수 있는 한계를 넘어 시스템이 일시적으로 다운되는 문제가 발생 할 수 있으며, 그 반대의 경우 수행할 캐릭터가 없는 상황에서도 배경처리를 계속 수행해야 하므로 게임서버의 효율이 상당히 떨어지게 된다. 이를 해결하기 위하여 본 논문에서는 Map 밸런스 서버를 이용하여 사용자 처리를 위한 부하를 비교적 균등화 시킬 수 있는 Map 관리 방법을 제안 하였다. 제안한 모델 하에서는 사용자가 활동하지 않는 게임 내 공간 처리를 일시 중지시키는 방법으로 게임 서버의 부하를 감소시킬 수 있으며, 서버 간 처리하는 배경을 새로 할당하여 부하를 재분배함으로써 서버들의 효율을 극대화할 수 있다.

• 한국항행학회논문지
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• 제12권2호
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• pp.146-153
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• 2008

UWB(Ultra Wide-Band)통신 기술은 매우 짧은 펄스를 사용하기에 정밀한 동기 획득 제어가 필요하다. 고속 W-PAN 응용이나 저속 무선측위 응용 모두를 위해 정확한 UWB 신호의 동기 획득(Signal Acquisition)은 매우 중요하다. 본 논문에서는 UWB 다중경로 채널 환경에서 동기 획득을 위해 두 단계 신호 탐색기법을 이용하여 동기 획득 알고리즘을 제안한다. 첫 번째 단계는 수신된 신호전체 시간을 두고 탐색 구간을 절반으로 나눠 각각 나눠진 창의 전력 값의 합을 비교하여 더 큰 전력 값을 가지는 구간을 다음 탐색 창으로 잡는다. 이러한 과정을 반복하여 다음 탐색 창을 구한다. 비교된 값이 임계값을 넘을 때까지 탐색을 반복한다. 두 번째 단계에서는 첫 번째 단계에서의 구해진 탐색 창을 Fine Search 하기 위하여 Linear 탐색 알고리즘을 적용하여 검색한다. 이 제안 알고리즘을 UWB 다중경로 채널 환경에서 모의실험 결과 병렬 탐색 알고리즘에 비해 고속 동기 획득이 가능하고 SNR의 변화가 심한 환경에 적합한 특성을 확인하였다.

• Computers and Concrete
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• 제10권2호
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• pp.135-147
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• 2012

At mesoscale, concrete is considered as a three-phase composite material consisting of the aggregate particles, the cement matrix and the interfacial transition zone (ITZ). The reconstruction of the internal structures for concrete composites requires the identification of the boundary of the aggregate particles and the cement matrix using digital imaging technology followed by post-processing through MATLAB. A parameter study covers the subsection transformation, median filter, and open and close operation of the digital image sample to obtain the optimal parameter for performing the image processing technology. The subsection transformation is performed using a grey histogram of the digital image samples with a threshold value of [120, 210] followed by median filtering with a $16{\times}16$ square module based on the dimensions of the aggregate particles and their internal impurity. We then select a "disk" tectonic structure with a specific radius, which performs open and close operations on the images. The edges of the aggregate particles (similar to the original digital images) are obtained using the canny edge detection method. The finite element model at mesoscale can be established using the proposed image processing technology. The location of the crack determined through the numerical method is identical to the experimental result, and the load-displacement curve determined through the numerical method is in close agreement with the experimental results. Comparisons of the numerical and experimental results show that the proposed image processing technology is highly effective in reconstructing the internal structures of concrete composites.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2007년도 학술대회 1부
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• pp.667-674
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• 2007

Facial expressions provide significant clues about one's emotional state; however, it always has been a great challenge for machine to recognize facial expressions effectively and reliably. In this paper, we report a method of feature-based adaptive motion energy analysis for recognizing facial expression. Our method optimizes the information gain heuristics of ID3 tree and introduces new approaches on (1) facial feature representation, (2) facial feature extraction, and (3) facial feature classification. We use minimal reasonable facial features, suggested by the information gain heuristics of ID3 tree, to represent the geometric face model. For the feature extraction, our method proceeds as follows. Features are first detected and then carefully "selected." Feature "selection" is finding the features with high variability for differentiating features with high variability from the ones with low variability, to effectively estimate the feature's motion pattern. For each facial feature, motion analysis is performed adaptively. That is, each facial feature's motion pattern (from the neutral face to the expressed face) is estimated based on its variability. After the feature extraction is done, the facial expression is classified using the ID3 tree (which is built from the 1728 possible facial expressions) and the test images from the JAFFE database. The proposed method excels and overcomes the problems aroused by previous methods. First of all, it is simple but effective. Our method effectively and reliably estimates the expressive facial features by differentiating features with high variability from the ones with low variability. Second, it is fast by avoiding complicated or time-consuming computations. Rather, it exploits few selected expressive features' motion energy values (acquired from intensity-based threshold). Lastly, our method gives reliable recognition rates with overall recognition rate of 77%. The effectiveness of the proposed method will be demonstrated from the experimental results.

• Journal of Information Technology Applications and Management
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• 제15권3호
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• pp.79-90
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• 2008

With the corporate environment nowadays being surrounded by plenty of information, the sharing of information among businesses through mutual cooperation tops the list of hot issues. Predictions of demands from the customer, business, or consumer by sharing information can affect the inventory and order production system. However, notwithstanding the importance of sharing information, empirical studies on quantitative use of information still remain insufficient in spite of many a discussion now being made on the sharing of information. This paper proposes to examine the ways meteorological information may affect the rises in the achievements of supply chains in distributive businesses, the kind of information that noticeably affects the consumer behavioral patterns in the distributive businesses but rarely perceived as a form of information shared by businesses. This study is based on a model in which meteorological information has been added as the one used to predict demands, after the beer distribution game has been modified to fit the current status, and simulations under an assumptive situation, where decisions are made on a daily basis, were conducted 50 times for a period of 1000 days for the generalization of the results, while at the same time a Duncan Test was conducted to determine the threshold to use the meteorological information that will be most profitable to the retailer, wholesaler, supplier and the supply chain as a whole. Our findings indicate that corporations have thresholds that vary from business to business depending upon the ratio of backlog costs to inventory costs. At the same time, our findings also show that there existed effective thresholds depending upon the ratio of backlog costs to inventory costs for the performance of the overall supply chain.

• 한국지능시스템학회논문지
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• 제11권5호
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• pp.379-387
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• 2001

본 논문은 그레이 명암도 변화와 HSl 컬러 모형의 Hue 정보를 함께 이용한 번호판 영역 추출 방법을 제안한다. 차량 이미지에서 차량 번호판 추출은 명암도 변화를 이용하여 번호판 후보 영역을 추출하고 후보 영역에 대해 HSI 컬러 모형의 Hue 정보를 이용하여 실제 번호판 영역을 결정한다. 추출된 번호판 영역으로부터 문자를 포함하는 특징 영역 추출은 각 문자들에 대한 히스토그램을 이용하여 추출한다. 그리고 Yager의 합접속 연산자를 이용하여 경계 변수 값을 동적으로 변화시키는 개선된 ART2 알고리즘을 제안하고 번호판의 개별 문자 인식에 적용한다. 또한 개선된 ART2와 지도 학습 방법을 통합한 SOSL 알고리즘을 제안한다. 100개의 실제 차량 이미지를 이용한 실험 결과를 통해 제안된 번호판 영역 추출 방법이 단일 컬러 모형을 적용한 기존 추출 방법보다 추출률이 향상되었고, 개선된 알고리즘들이 기존의 ART2 알고리즘과 오류 역전파 알고리즘 보다 더 높은 인식률을 보임을 알 수 있었다.