• 한국대기환경학회지
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• 제34권2호
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• pp.223-232
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• 2018

As the Seoul metropolitan city has the largest numbers of population and vehicles, the citizens can be exposed to hazardous air pollutants(HAPs) mainly from the vehicular exhaust and human activities. In this study, we proposed a systematic method for the selection of priority monitoring areas for HAPs using Geographic Information System (GIS). First, emission parameters(emission data, vehicle registration, monitoring data, and so on) and population parameters (population and population density) were plotted using the inverse distance weighted (IDW) interpolation. Then, the interpolation data for individual parameters, which were normalized between 1 and 5 points, were compiled for 270 grids with a resolution of $2km{\times}2km$. The total score of each grid was calculated using weights(1~5) for the individual parameters. The final ranking of each grid was assigned by four scenarios with varying fractions of the emission and population parameters from 50 : 50 to 80 : 20. Consequently, nine grids were suggested as priority monitoring areas, and all of them are located in the southwestern part of Seoul.

• 한국통신학회논문지
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• 제30권5B호
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• pp.274-286
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• 2005

본 논문에서는 이동 에드 혹 네트워크에서 효율적인 전력 사용 및 신뢰성 있는 데이터 전송을 보장하는 연결형 dominating set 기반의 라우팅 프로토콜을 제안하였다. 연결형 dominating set 기반의 라우팅 알고리즘에서 잦은 dominating set의 재구성은 루트 손실로 인한 전송 에러를 발생시키기 때문에, 노드의 잔여 전력량과 이동성을 고려하여 게이트웨이 노드를 선택하여야 한다. 또한 같은 지역에 노드가 집중되어 있다면 매체를 공유하는 무선네트워크의 특성상 병목으로 인한 충돌 및 지연 등을 야기 시킬 가능성이 크다. 따라서 본 논문에서는 노드의 잔여전력량 및 이동성, 이웃 노드수의 가중 가산 값에 비례하여 이웃 구성 통보 메시지 (neighbor set advertisement message)의 브로드캐스팅을 지연시키는 방법을 통해 연결형 dominating set의 재구성을 최소화 하면서도 신뢰성 있고 효율적인 데이터 전송을 보장하는 새로운 연결형 dominating set 구성 방법을 제안하고 다양한 상황에서의 실험을 통해 그 성능을 비교 평가하였다.

• Imaging Science in Dentistry
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• 제36권4호
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• pp.199-206
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• 2006

Purpose: The purpose of this study was to evaluate comparison of static MRI and pseudo-dynamic (cine) MRI in temporomandibular joint (TMJ) disorder patients. Materials and Methods: In this investigation, 33 patients with TMJ disorders were examined using both conventional static MRI and pseudo-dynamic MRI. Multiple spoiled gradient recalled acquisition in the steady state (SPGR) images were obtained when mouth opened and closed. Proton density weighted images were obtained at the closed and open mouth position in static MRI. Two oral and maxillofacial radiologists evaluated location of the articular disk, movement of condyle and bony change respectively and the posterior boundary of articular disk was obtained. Results: No statistically significant difference was found in the observation of articular disk position, mandibular condylar movement and posterior boundary of articular disk using static MRI and pseudo-dynamic MRI (P<0.05). Statistically significant difference was noted in bony changes of condyle using static MRI and pseudo-dynamic MRI (P<0.05). Conclusion: This study showed that pseudo-dynamic MRI didn't make a difference in diagnosing internal derangement of TMJ in comparison with static MRI. But it was considered as an additional method to be supplemented in observing bony change.

• 대한핵의학회지
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• 제38권3호
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• pp.268-271
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• 2004

A 43-year-old man was presented with persistent headache for two weeks. 72 weighted MR imaging showed high signal intensity with surrounding edema in the left frontal lobe. These findings were considered with intracranial tumor such as glioma or metastasis. Tc-99m tetrofosmin SPECT showed focal radiotracer accumulation in the left frontal lobe. The operative specimen contained cerebral infarction with organizing leptomeningeal hematoma by pathologist. Another 73-year-old man was hospitalized for chronic headache. Initial CT showed ill-defined hypodensity with mass effect in the right parietal lobe. Tc-99m tetrofosmin SPECT showed focal radiotracer uptake in the right parietal lobe. These findings were considered with low-grade glioma or infarction. Follow-up CT after 5 months showed slightly decreased in size of low density in the right parietal lobe, and cerebral infarction is more likely than others. Tc-99m tetrofosmin has been proposed as a cardiotracer of myocardial perfusion imaging and an oncotropic radiotracer. Tc-99m tetrofosmin SPECT image provides a better attractive alternative agent than T1-201 as a tumor-imaging agent, with characteristics such as high-energy flux, short half-life, favorable biodistribution, dosimetry and lower background radioactivity. We have keep in mind on the analysis of Tc-99m tetrofomin imaging when cerebral infarction is being differentiated from brain tumor.

• 수산해양기술연구
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• 제40권4호
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• pp.351-359
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• 2004

본 연구에서는 실선에 적용된 알루미늄 하니콤 샌드위치 판 (AHSP)을 저자가 제안한 심재의 형상이 피라미드인 알루미늄 샌드위치 판의 구조적 특성 및 진동특성을 검토해 보았다. 알루미늄 피라미드 샌드위치 판(APSP)의 기초 자료로 쓰일 수 있게 심재의 각도변화, 높이변화 및 면재와 심재의 두께변화에 따른 구조적 특성을 검토한 결과 APSP가 강도 및 강성에서 우수함을 보였으며, 질량대비 큰 강성 때문에 고유진동수도 다소 크게 평가되었다.

• 대한기계학회논문집B
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• 제25권11호
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• pp.1594-1605
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• 2001

In this study, a numerical simulation was developed which was capable of predicting the characteristics of NO formation in pilot scale combustor adopting the air-staged burner flame. The numerical calculation was constructed by means of establishing the mathematical models fur turbulence, turbulent combustion, radiation and turbulent nitric oxide chemistry. Turbulence was solved with standard k-$\xi$ model and the turbulent combustion model was incorporated using a two step reaction scheme together with an eddy dissipation model. The radiative transfer equation was calculated by means of the discrete ordinates method with the weighted sum of gray gases model for CO$_2$and H$_2$O. In the NO chemistry model, the chemical reaction rates for thermal and prompt NO were statistically averaged using the $\beta$ probability density function. The results were validated by comparison with measurements. For the experiment, a 0.2 MW pilot multi-air staged burner has been designed and fabricated. Only when the radiation was taken into account, the predicted gas temperature was in good agreement with the experimental one, which meant that the inclusion of radiation was indispensable for modeling multi-air staged gas flame. This was also true of the prediction of the NO formation, since it heavily depended on temperature. Subsequently, it was found that the multi-air staged combustion technique might be used as a practical tool in reducing the NO formation by controlling the peak flame temperature.

• 제어로봇시스템학회논문지
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• 제8권1호
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• pp.21-27
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• 2002

Inspection and shape measurement of three-dimensional objects are widely needed in industries for quality monitoring and control. A number of visual or optical technologies have been successfully applied to measure three-dimensional surfaces. However, those conventional visual or optical methods have inherent shortcomings such as occlusion and variant surface reflection. X-ray vision system can be a good solution to these conventional problems, since we can extract the volume information including both the surface geometry and the inner structure of any objects. In the x-ray system, the surface condition of an object, whether it is lambertian or specular, does not affect the inherent characteristics of its x-ray images. In this paper, we propose a three-dimensional x-ray imaging method to reconstruct a three dimensional structure of an object out of two dimensional x-ray image sets. To achieve this by the proposed method, two or more x-ray images projected from different views are needed. Once these images are acquired, the simultaneous algebraic reconstruction technique(SART) is usually utilized. Since the existing SART algorithms have several shortcomings such as low performance in convergence and different convergence within the reconstruction volume of interest, an advanced SART algorithm named as USART(uniform SART) is proposed to avoid such shortcomings and improve the reconstruction performance. Because, each voxel within the volume is equally weighted to update instantaneous value of its internal density, it can achieve uniform convergence property of the reconstructed volume. The algorithm is simulated on various shapes of objects such as a pyramid, a hemisphere and a BGA model. Based on simulation results the performance of the proposed method is compared with that of the conventional SART method.

• 응용통계연구
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• 제16권1호
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• pp.101-115
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• 2003

본 논문에서는 Chen, Dey와 Shao(1999), Branco와 Dey(2001)가 제안한 왜도가 있는 두터운 꼬리를 가지는 오차 분포와 디리슈레 과정 사전분포를 이용한 베이지안 메타분석 (meta-analysis)을 하고자 한다. 베이지안 메타분석을 위하여 가중함수를 고려한 계층적 선택 모형을 이용한다. 이때의 오차항은 왜도가 있는 비정규 분포로 가정한다. 이를 위하여 우선 왜도 타원형 분포의 일반적인 족을 소개한다 이 분포족중 왜도 정규분포와 왜도 t 분포를 오차항 분포로 이용한 베이지안 계층적 선택 모형을 고려하며, 이 때 발생하는 복잡한 베이지안 계산은 MCMC 방법으로 해결한다. 마지막으로, 실제 자료(Johnson, 1993)인 두 가지의 충치예방약의 효과에 대한 차이를 비교하기 위해 얻어진 12개의 연구 자료를 이용하여 본 연구에서 제시된 베이지안 방법을 이용하여 메타분석을 한다.

• 환경위생공학
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• 제9권2호
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• pp.1-7
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• 1994

Rainwater was collected in Seoul area from January 1991 to December 1993 (over 3years) and by the analysis of the chemical components contained in rainwater, investigated the components that effect on rainwater pH Through the above studies the following conclusions were obtained. 1) Method for Averaging pH Volume weighted method is considered to be acceptable providing that precipitation is measured at the same time when the samples are taken, without precipitation data a simple averaging method should be the next choice. 2) Annual average rainwater pH was 4.98 in 1991, 4.80 in 1992, 4.67 in 1993, measurement range was 3.6-8.1. 3) In the relationship between rainwater pH and rainfall amounts rainwater pH for light rain(<15mm rainfall) was existent in the wide range(pH 4-7), but for heavy rain was corresponded to the annual average values. 4) Annual frequency of pH was Birrndat the frequency($\gamma $) between the density of the [$H^{+}$] and pH in the rainwater(over 3years ), $NO_{3}^{-}$ was excellent and the obtained results was 0.62 in 1992. Also In the correlation coefficient($\gamma $) according to the pH range $SO_{4}^{2-}, NO_{3}^{-}$, were 0.85 ,0.68 at 3.6 $Cl^-$ was 0.99(1993). At 4.1$NO_{3}^{-}(\gamma=0.48)$ in 1992, SO_4^{2-}($\gamma$=0.54), $NO_{3}^{-}(\gamma$=0.72), $Cl^- (\gamma$=0.49) in 1993. 6) pH values gradually increased with increase in $Ca^{2+}/SO_{4}^{2-}$.

• Radiation Oncology Journal
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• 제26권2호
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• pp.126-130
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• 2008

대퇴골두 무혈성괴사는 혈류장애로 인해 대퇴골두의 골세포 괴사가 나타나는 것으로 여러 원인 중 방사선치료도 하나의 원인으로 알려져 있으나 발병률에 대해서는 보고된 바 없는 상태이다. 저자들은 삼성서울병원에서 전골반 방사선치료를 받은 자궁암환자 577명 중 2명의 환자에서 대퇴골두 무혈성괴사를 경험하였다. 2예 모두 전형적인 방사선학적 소견을 보였다. 골반 방사선치료 후 발생하는 대퇴골두 무혈성괴사는 매우 드물게 나타나지만 방사선 조사 범위에 국한된 특징적인 영상의학적 소견을 보이므로 진단에 유념해야 하겠다.