• 한국산업보건학회지
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• 제18권3호
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• pp.177-184
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• 2008

The purpose of this study was to compare the performance characteristics of Andersen and total suspended particulate (TSP) samplers in terms of particle size distribution (PSD) and mass sampling efficiency. In the present study, two Andersen and four TSP samplers were selected and tested to quantitatively estimate human exposure to fly ash representing industrial particulate matter (PM) in a carefully controlled chamber. The PSD characteristics, a mass median aerodynamic diameter and a geometric standard deviation, were found from the sampled PM of airborne samplers in the chamber. An Andersen sampler was compared with a TSP sampler quantified by a coulter counter multisizer, as a reference sampler, to describe the correlation of mass sampling efficiencies between two types of samplers. Overall results indicate that Andersen samplers overestimated small PM due to particle bounce phenomena between impaction stages. There was reasonably good correlation ($R^2$ = 0.89 and 0.91) between the mass sampling efficiencies of Andersen and TSP samplers during the two tests. However, the lower values of slope (0.71 and 0.72) in two tests showed that the Andersen sampler underestimated PM (> AD $10.1\;{\mu}m$) with sufficient inertia due to a relatively lower Andersen inlet velocity at 0.8 m/s comparing with the operating air velocity at 2.1 m/s in the sampling zone of a chamber.

• Structural Engineering and Mechanics
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• 제6권6호
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• pp.659-671
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• 1998

Exercise of complete control on all aspects of any manufacturing / fabrication process is very difficult, leading to uncertainties in the material properties and geometric dimensions of structural components. This is especially true for laminated composites because of the large number of parameters associated with its fabrication. When the basic parameters like elastic modulus, density and Poisson's ratio are random, the derived response characteristics such as deflections, natural frequencies, buckling loads, stresses and strains are also random, being functions of the basic random system parameters. In this study the basic elastic properties of a composite lamina are assumed to be independent random variables. Perturbation formulation is used to model the random parameters assuming the dispersions small compared to the mean values. The system equations are analyzed to obtain the mean and the variance of the plate natural frequencies. Several application problems of free vibration analysis of composite plates, employing the proposed method are discussed. The analysis indicates that, at times it may be important to include the effect of randomness in material properties of composite laminates.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.532-537
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• 2000

The purpose of this study is to determine the performance of a commercial air cleaner in removing tobacco smoke indoors. Following injection of tobacco smoke in a room, decay rates for particle concentrations were obtained far mass concentration at each point. The size distribution of the tobacco smoke particles was approximately $1.266{\mu}m$ in mass median diameter with a geometric standard deviation of 1.313. The air cleaner consisted of an electrostatic filtration unit and a fan operated at a flow rate of 5.98 CMM. The collection efficiency for $>1\;{\mu}m$ was more than 99%. Without air cleaner operation, tobacco smoke concentration ratio in room decreased to 30% of initial values within 30 minutes and with air cleaner operation, decreased to 90% of initial values in the test chamber, volume $51.27\;m^3$. Without air cleaner operation, tobacco smoke concentration ratio in room decreased to 10% of initial values within 30 minutes and with air cleaner operation, decreased to 30-70% of initial values in the test chamber, volume $149.2\;m^3$.

• 대한토목학회논문집
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• 제14권6호
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• pp.1349-1356
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• 1994

본 연구에서는 3가지 교각형상에 대하여 국부적 정지상세굴에 대한 실험결과를 분석하였다. 실험결과에 의하면 교각의 세굴은 $V/V_c=0.4{\sim}0.5$, $Fr_p{\fallingdotseq}0.2$일 때 시작되었고 상대세굴심은 유속비와 교각푸르드수와의 관계에서 선형적으로 증가하였다. 또한 상대세굴심은 ${\tau}_r$ < $10^{-4}$일 때는 선형적으로 증가하지만 ${\tau}_r$ > $10^{-4}$이 되면 일정해지는 경향을 가지며 모래의 기하표준편차(${\sigma}_g$)와 교각형상과도 깊은 관계가 있었다.

• 한국항공우주학회지
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• 제41권5호
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• pp.350-356
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• 2013

먼거리에서 접촉하지 않고 측정할 수 있다는 장점으로 인해 사진계측은 항공분야에서도 널리 활용되고 있다. 본 연구에서는 한 대의 카메라로 6자유도 해석을 수행하는 사진계측에서 발생할 수 있는 오차를 분석하였다. 사진계측의 오차 분석 프로그램을 개발하였으며, 사진계측 문제를 공선조건에 기반한 기하학적 문제로 변환하여 프로그램을 검증하였다. 각 좌표계간 6자유도 해석을 위해 필요한 카메라 포즈에 대한 통계량은 정규분포한다는 것을 수치실험을 통해 유추할 수 있었으며, 모표준편차를 이용하여 사진계측의 오차를 정량화하였다.

• 디지털산업정보학회논문지
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• 제8권2호
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• pp.95-104
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• 2012

In this paper, an estimation of person height and 3D location of a moving person by using the pan/tilt-embedded stereo tracking system is suggested and implemented. In the proposed system, face coordinates of a target person is detected from the sequential input stereo image pairs by using the YCbCr color model and phase-type correlation methods and then, using this data as well as the geometric information of the stereo tracking system, distance to the target from the stereo camera and 3-dimensional location information of a target person are extracted. Basing on these extracted data the pan/tilt system embedded in the stereo camera is controlled to adaptively track a moving person and as a result, moving trajectory of a target person can be obtained. From some experiments using 780 frames of the sequential stereo image pairs, it is analyzed that standard deviation of the position displacement of the target in the horizontal and vertical directions after tracking is kept to be very low value of 1.5, 0.42 for 780 frames on average, and error ratio between the measured and computed 3D coordinate values of the target is also kept to be very low value of 0.5% on average. These good experimental results suggest a possibility of implementation of a new stereo target tracking system having a high degree of accuracy and a very fast response time with this proposed algorithm.

• 한국대기환경학회지
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• 제8권4호
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• pp.269-276
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• 1992

인체에 영향을 미치는 중금속은 대개 환경중에서 음식물, 공기, 먼지 및 음료수를 통하여 축적된다. 본 연구는 중금속중 납이 인체에 미치는 유해정도를 평가하기 위하여 서울과 여주등 대기중 납농도가 차이가 나는 지역주민들의 혈액중 납농도를 측정하여 Bio kinetic Model을 이용 납에 대한 인체의 위해성 정도를 알아보았으며 그 결과는 다음과 같다. - 지역별로는 혈액중 납농도가 별다른 차이를 보이지 않았으나 나이와 성별에 따라서는 다소 차이가 나고 있다. - 또한 혈액중 납농도는 log normal 분포를 나타내고 있음. - 기하표준편차는 1.2 $\sim$ 1.3 정도의 값으로 미국 EPA에서 추정한 1.31 $\sim$ 1.41의 값보다 약간 적은 값을 나타냈다.

• 한국측량학회지
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• 제18권4호
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• pp.359-367
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• 2000

이 논문은 지구중력포텐셜에 대한 포텐셜계수모델이 표고이상을 계산하는데 사용될 수 있다는 것과, 지오 이드 계산에 있어서 표고이상을 고려하였을 때 보다 정밀한 지오이드고를 산출할 수 있다는 것을 보여 주고 있다. 연구를 위해 EGM96의 계수와 수정계수가 사용되었고 한반도 일원의 수치지형모델인 KODEM33이 사용되었다. 연구 결과 나타난 표고이상의 크기는 최대 0.025 m, 평균 -0.015 m의 크기를 보여주었다. 본 연구에서 계산된 중력지오이드 모델의 평가를 위하여 GPS/Leveling데이터로부터 기하학적 지오이드를 산출하였으며, 비교 결과 교차의 평균값과 표준편차는 0.0114 m와 0.2817 m를 나타내 개선된 결과를 보여 주었다.

• 지식경영연구
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• 제20권3호
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• pp.39-47
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• 2019

Response surface methodology (RSM) is a group of statistical modeling and optimization methods to improve the quality of design systematically in the quality engineering field. Its final goal is to identify the optimal setting of input variables optimizing a response. RSM is a kind of knowledge management tool since it studies a manufacturing or service process and extracts an important knowledge about it. In a real problem of RSM, it is a quite frequent situation that considers multiple responses simultaneously. To date, many approaches are proposed for solving (i.e., optimizing) a multi-response problem: process capability function approach, desirability function approach, loss function approach, and so on. The process capability function approach first estimates the mean and standard deviation models of each response. Then, it derives an individual process capability function for each response. The overall process capability function is obtained by aggregating the individual process capability function. The optimal setting is given by maximizing the overall process capability function. The existing process capability function methods usually use the arithmetic mean or geometric mean as an aggregation operator. However, these operators do not guarantee the Pareto optimality of their solution. Moreover, they may bring out an unacceptable result in terms of individual process capability function values. In this paper, we propose a maximin-based process capability function method which uses a maximin criterion as an aggregation operator. The proposed method is illustrated through a well-known multiresponse problem.

• 한국음향학회지
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• 제41권6호
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• pp.637-646
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• 2022

임의의 곡면 배열에서 단위 빔 형성에 사용되는 부배열은 조향 방위마다 기하학적 형상이 다르다. 이 때문에 조향 방위 별 부배열의 빔 패턴은 항상 균일하지 않다. 본 논문에서는 볼록 최적화를 이용한 빔 형성 기법을 곡면 배열에 적용하고, 조향 방위별 빔 성능의 균일성이 향상되는 것을 보였다. 시뮬레이션은 절단 구면 형상의 곡면 배열에 대해 수행되었다. 고각 3 dB 빔 폭의 표준 편차가 크게 감소하였으나 반대급부로 지향 지수도 감소하는 것을 관찰했다. 이를 완화시키기 위한 하나의 방법으로 쉐이딩 함수를 이용한 최적화 기법을 제안한다.