• 대한전자공학회논문지TC
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• 제49권7호
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• pp.32-38
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• 2012

다중경로 전파에 의한 수신 신호의 심벌간 간섭을 제거하기 위해, 두 오차 추정 함수를 사용하는 병렬 등화(parallel equalization) 알고리즘을 제안한다. 제안 알고리즘에서는 다치레벨 이차원 신호를 등가 이진 신호로 간주하고, 등화 초기에 효과적인 시그모이드 함수와 정상상태 성능이 우수한 임계 함수를 사용하여 각각 오차를 추정한다. 이때 두 오차 추정의 상대적 정확도에 따라 두 오차를 가중 처리하여 두 필터를 서로 다르게 갱신하도록 하였다. 결과적으로 결합된 두 필터의 출력이 최적한 값이 되도록 하였으며, 두 동작 모드를 완만하게 결합하는 효과로 등화 초기의 빠른 수렴과 정상상태에서의 낮은 오차 레벨을 동시에 달성하였다. 제안 알고리즘의 유용성을 모의실험을 통해 기존 방식과 비교, 검증하였다.

• 한국연초학회지
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• 제16권1호
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• pp.26-33
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• 1994

A tobacco ripeness grading meter was designed and constructed using the color sensor, its performance was evaluated. A degree of ripeness grading of a leaf is very closely related to the measured tobacco leaf color. Measuring the small amount of the reflectance precisely depends on the apparatus including color sensor, light source, detector sensitivity, and geometric characteristics of appratus. To analyze and minimize the variational effects, experiments to select the proper condition were performed. Because of the combined effect mentioned above, the system has some variation on its response. Basis on the results of the experiments, prototype was developed and interfaced to a computer system. The main components of prototype included a tungsten lamp as a light source, Amorphous full color sensor with three filters, regulated D.C. power supply, OP - AMP(741 TC) for amplification, AR - B3001 board for interfacing to a computer with analog to digital conversion, and a compatible IBM PC XT computer. The experimental results of the developed ripeness tobacco leaf measurement system are summarized as following: [1] The output readings of ripeness grade meter for tobacco leaf, which is based on harvesting time, showed the apparent difference in variety of different quality. It was considered suitable that three filters(red, green, blue) in Amorphous full color sensor could be used in four different ripeness degree measurement of tobacco leaf. [2] The output readings of ripeness grade meter for tobacco leaf, which is based on government procurement, showed apparent difference in variety of different quality. Tobacco leaf varieties to stalk position are divided into tips, leaf, cutters, and primings, It is considered suitable that only red filter in the sensor could be used to classify the grade of tobacco leaf within the same kind tobacco stalk. However, the ripeness grade meter was not adequate to classify all the tobacco grades in the four different tobacco leaves.

• Journal of Forest and Environmental Science
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• 제28권3호
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• pp.158-169
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• 2012

Sabah has experienced a rapid decline in the extent of forest cover. The precise impact of habitat loss on the conservation status of the plants of Sabah is uncertain. In this study we use the niche modelling algorithm MAXENT to construct preliminary, revised and final ecological niche models for Dipterocarpus lamellatus and Dipterocarpus ochraceus and combined these models with data on current land-use to derive conservation assessments for each species. Preliminary models were based on herbarium data alone. Ground surveys were conducted to evaluate the performance of these preliminary models, and a revised niche model was generated from the combined herbarium and ground survey data. The final model was obtained by constraining the predictions of the revised models by filters. The range overlap between the preliminary and revised models was 0.47 for D. lamellatus and 0.39 for D. ochraceus, suggesting poor agreement between them. There was substantial variation in estimates of habitat loss for D. ochraceus, among the preliminary, revised and constrained models, and this has the potential to lead to incorrect threat assessments. From these estimates of habitat loss, the historic distribution and estimates of population size we determine that both species should be classified as Critically Endangered under IUCN Red List guidelines. Our results suggest that ground-truthing of ecological niche models is essential, especially if the models are being used for conservation decision making.

• Journal of Radiation Protection and Research
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• 제38권2호
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• pp.78-90
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• 2013

최근 방사선 피폭에 대한 관심이 높아지고 있다. 유방촬영용장치의 방사선 피폭은 일반 X선 촬영에 비해 비교적 흡수선량이 높기 때문에 화질은 개선하되 불필요한 피폭을 줄여야 노력을 할 필요가 있다. 최근 국제방사선방어위원회(ICRP)나 우리나라의 한국의료영상품질관리원(KIAMI)에서 권고하는 평균유선선량은 3 mGy이하이지만 이는 유방의 두께에 따라 다르므로 모든 경우에 권고수치가 넘지 않는다고 해서 적다고 말할 수는 없다. 일반적으로 방사선 촬영에 사용되는 선질은 영상의 화질과 피폭선량을 결정하는 중요한 인자로 촬영 관전압과 부가필터에 영향을 받는다. 일반적으로 유방촬영용장치에서 방출되는 X선 에너지는 연속 스펙트럼(spectrum)으로서 영상의 화질에 미치는 영향이 적은 저 에너지부터 이미지상의 대조도(contrast)를 저해하는 고 에너지 성분까지 포함하고 있다[1,3]. 현재 유방촬영용장치에 많이 사용되고 있는 부가필터는 몰리브덴(molybdenum, Mo), 로듐(rhodium, Rh)등이 있으며, 이는 사용되어지는 X선질의 에너지 영역에 따라 구분하여 사용되고 있다. 현재 유방촬영용장치에 가장 많이 사용되어지고 있는 부가필터의 물질인 몰리브덴(Molybdenum, Mo), 로듐(rhodium, Rh)외에 원자번호와 K-흡수단 영역이 비슷한 니오븀(niobium, Nb)이나 지르코늄(zirconium, Zr)재질의 부가여과판을 사용 하였을때 화질과 선량의 개선된 변화를 알아보고, X선의 저에너지를 흡수할 수 있는 알루미늄(aluminum, Al)재질을 복합으로 사용하였을 때 유방촬영용장치의 화질에 손실없이 알루미늄(aluminum, Al)두께에 따른 조사선량의 경감 정도를 확인하려 한다. 본 실험에서는 몰리브덴(molybdenum, Mo), 니오븀(niobium, Nb), 지르코늄(zirconium, Zr)등의 부가필터를 종류별로 단일필터로 사용할 경우와 이들 단일필터에 알루미늄(aluminum, Al)필터를 복합으로 사용한다. 이 경우 상기 부가필터의 종류에 따른 화질의 개선이 될 것으로 판단되고, 알루미늄(aluminum, Al)필터를 복합으로 사용함으로 인해 저 에너지의 불필요한 X선이 흡수되므로 동일한 농도가 되었을 때 화질에 큰 영향없이 선량이 감소될 것으로 기대된다.

• 한국자동차공학회논문집
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• 제17권2호
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• pp.10-19
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• 2009

The working of diesel particulate filters(DPF) needs to periodically burn soot that has been accumulated during loading of the DPF. The prediction of the relation between an uniformity of gas velocity and soot regeneration efficiency with simulations helps to make design decisions and to shorten the development process. This work presents a comprehensive combined 'DOC+CDPF' model approach. All relevant behaviors of flow fluid are studied in a 3D model. The obtained flow fields in the front of DPF is used for 1D simulation for the prediction of the thermal behavior and regeneration efficiency of CDPF. Validation of the present simulation are performed for the axial and radial direction temperature profile and shows goods agreement with experimental data. The coupled simulation of 3D and 1D shows their impact on the overall regeneration efficiency. It is found that the flow non-uniformity may cause severe radial temperature gradient, resulting in degrading regeneration efficiency.

• 한국항행학회논문지
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• 제16권6호
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• pp.900-909
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• 2012

저궤도 위성에 탑재하는 위성항법 수신기는 관측된 신호를 필터링하고 신호중단 시 궤도예측을 수행하는 항법필터를 장착하는데, 사용하는 위성동역학 모델이 필터성능을 주로 결정하게 된다. 본 연구에서는 항법필터에 필요한 정밀위성동역학 알고리듬을 연구하고 이를 계산하는 프로그램을 개발하였다. 정밀 중력가속도, 정밀좌표변환, 3체 중력, 대기저항, 태양복사압 모델을 결합하였으며, 해외 정밀궤도결정 프로그램을 이용하여 정확도를 검증하였다. 시뮬레이션과 실제 궤도 데이터를 사용하여 초기위치 정확도에 따른 궤도예측정확도를 분석 하였다. 개발된 모델은 위성탑재용 실시간 항법필터에 적용되는 동역학모델로는 충분한 정확도를 가지는 것을 확인하였다.

• Journal of Information Processing Systems
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• 제13권3호
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• pp.464-475
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• 2017

In this paper, we present a new texture image retrieval method which combines color and texture features extracted from images by a set of multi-resolution multi-direction (MRMD) filters. The MRMD filter set chosen is simple and can be separable to low and high frequency information, and provides efficient multi-resolution and multi-direction analysis. The color space used is HSV color space separable to hue, saturation, and value components, which are easily analyzed as showing characteristics similar to the human visual system. This experiment is conducted by comparing precision vs. recall of retrieval and feature vector dimensions. Images for experiments include Corel DB and VisTex DB; Corel_MR DB and VisTex_MR DB, which are transformed from the aforementioned two DBs to have multi-resolution images; and Corel_MD DB and VisTex_MD DB, transformed from the two DBs to have multi-direction images. According to the experimental results, the proposed method improves upon the existing methods in aspects of precision and recall of retrieval, and also reduces feature vector dimensions.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2008년도 학술대회 1부
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• pp.510-516
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• 2008

In ubiquitous environment, there are no limits to utilize networks whenever and wherever you are. That pervasive networks are combined with the information devices and then create various services such as car navigation of LBS(location based service) and DMB(Digital Multimedia Broadcasting). As these kinds of services are getting more various, the complexity is also getting higher and ultimately the convergence will make people feel frustrated. One of the solutions is Context-Awareness[1] technology. User interface with context-awareness filters unnecessary information and prevents users from being blocked due to the massive information. In this paper, we describe the seamless service system based on location-awareness, which is a type of context-awareness. We developed the system based on UPnP AV Framework. This system provides the automatic terminal device selection for the nomadic user. The system establishes new connections for the ongoing streaming playback session with the new AV devices without substantial loss of playback so that the user can enjoy the seamless service. The AV device selection based on the user's location needs no user's intervention or notification so it achieves the improvement of usability and complexity.

• 환경위생공학
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• 제17권2호
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• pp.11-17
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• 2002

Diesel particulate matter (DPM) is known to be one of the major harmful emissions produced by diesel engines. The majority of diesel particles are in the range of smaller than $I{\mu}\textrm{m}$. Because of their tiny volume, ultrafine diesel particles contribute very little to the total mass concentration which is currently regulated for automobile emissions. Diesel particles are known to have deleterious effects upon human health because they penetrate human respiratory tract and have negative effects on the health. The measurement of the number distribution of nanometer size particles (nanoparticles) in the diesel exhaust emission is important in order to evaluate their environmental and health impact, and to develop new types of diesel particulate filters. In this study, we directly sampled particulate matters emitted from a diesel truck mounted on the chassis dynamometer by a flow separator and dilution system, and measured the nanoparticles using two types of differential mobility analyzers combined with a Faraday cup electrometer (FCE) and a condensation particle counter (CPC). The particle size distributions were analyzed by changing engine operation condition, i.e. ratio of engine loading. The total number concentration of particles were increased with the engine loading ratio and the nanoparticles (less than 50nm) were affected by hydrocarbon (HC) concentration in the diesel exhaust.

• 한국전자파학회논문지
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• 제16권10호
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• pp.982-988
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• 2005

본 논문에서는 모드 변환기나 필터, 매칭 구조가 모두 연결되어 있는 개구면 안테나의 특성을 예측을 위해 급전 부분에 전이 구조가 붙어 있는 원형 개구면 안테나의 해석적인 산란 해를 제시한다. 개구면의 모양이 원형이기 때문에 길이가 짧고 반지름이 다른 원형 도파관이 연결되어 있는 구조로 모델링하여 안테나를 해석했다. 안테나의 해석에서 급전 도파관과 개구면 사이의 영역은 일반화된 산란 행렬을 이용하여 전기장과 자기장을 나타냈고, 개구면에서 복사되는 전기장과 자기장은 적분 변환을 이용하여 나타내어 전체 구조를 해석했다. 여기서 필요한 산란 행렬과 적분 변환은 모두 해석적으로 계산 가능하고, 엄밀한 해이므로 안테나의 반사 특성, 복사 특성 등을 정확하게 예측 가능하다.