주변 셀을 고려한 LTE-Femtocell Power Control 알고리즘

정재환,손인수 한국통신학회 2009 한국통신학회 학술대회논문집 Vol.2009 No.11

현재 가장 주목받는 기술 중 하나인 Femtocell은 Macrocell 내에 설치한다는 점에서 Macrocell에 필연적으로 간섭과 원치않는 Handover을 일으키게 된다. 따라서 일반적으로 Femtocell의 Tx Power를 조절하여 이러한 확률을 낮추기 위한 많은 연구가 진행되었다. 그러나 기존의 논문을 살펴보면 Handover 확률을 줄이기 위해 Tx Power를 너무 낮춘 결과 통신 용량의 저하가 나타나게 된다. 본 논문에서는 주변 셀들의 간섭을 고려하여 Power Control을 하는 기법을 제안하였다. 그 결과 기존의 논문에 비해 Handover 확률은 유지하며 Throughput 성능은 높은 결과를 얻었다.

시작은 동시상영이었다

정재환 민족21 2012 민족21 Vol.- No.-

선박평형수 처리용 UV 살균기의 성능평가를 위한 열유동 해석

정재환,윤현식,전호환,이영우,배상범 한국해양환경·에너지학회 2012 한국해양환경·에너지학회 학술대회논문집 Vol.2012 No.5

BIM 기반 협업에서의 상호운용성 향상을 위한 설계정보의 확장방안에 대한 기초적 연구

정재환,김진만,김성아,Jung, Jae-Hwan,Kim, Jim-Man,Kim, Sung-Ah 한국BIM학회 2015 KIBIM Magazine Vol.5 No.1

In the initial step of BIM based architectural design process, workloads are increased and the decision making process becomes more complex than those of the conventional design process. Technologies regarding distribution, exchange, classification, verification of BIM data are fundamental elements of construct environment for information sharing based on BIM. Interoperability of BIM model data is another issue to integrate BIM model. To improve interoperability in BIM-based collaboration, a model for utilizing formal&unformal design informations is suggested. Futhermore, Prototyping the model and practical test is conducted for advancement of data exchange making design data richen.

Facile Synthesis of Metal Nanocrystals Embedded Hydrogel Beads and Their Application

정재환,김문호 한국고분자학회 2020 한국고분자학회 학술대회 연구논문 초록집 Vol.45 No.2

오픈폼을 활용한 자유진동하는 라이저 주위 유동의 LES 해석

정재환,정광열,길재흥,정동호 한국해양공학회 2019 한국해양공학회지 Vol.33 No.5

In this study, the free motion of a riser due to vortex shedding was numerically simulated with Large Eddy Simulation (LES) and Detached Eddy Simulation (DES) turbulence models. A numerical simulation program was developed by applying the Rhie-Chow interpolation method to the pressure correction of the OpenFOAM standard solver pimpleDyMFoam. To verify the developed program, the vortex shedding around the fixed riser at Re = 3900 was calculated, and the results were compared with the existing experimental and numerical data. Moreover, the vortex-induced vibration of a riser supported by a linear spring was numerically simulated while varying the spring constant. The results are compared with published direct numerical simulation (DNS) results. The present calculation results show that the numerical method is appropriate for simulating the vortex-induced motion of a riser, including lock-in phenomena.

한반도 토양수분 상태 모니터링을 위한 천리안 정지궤도 위성 기반 건조 지수 산정

정재환,백종진,최민하 한국수자원학회 2018 한국수자원학회논문집 Vol.51 No.2

Satellite data have attracted attention on research such as natural disaster and climate changes because satellite data is very advantageous for observing a wide range of variability. However, there are still limited spatial and temporal resolutions in satellite data. To overcome these limitations, fusion of various sensors and combination of primary products are used. In this study, surface temperature data of 500 m spatial resolution was produced by fusion of GOCI and MI data of COMS. Also these LST are used with NDVI for estimating TVDI. Soil moisture condition of the Korean peninsula was evaluated by these TVDI and it was compared with SSMI derived from ASCAT surface soil moisture data. As a result, COMS TVDI and ASCAT SSMI showed similar spatial distribution and suggested the possibility of observing the soil moisture using COMS. Therefore, the TVDI estimations can be used as a basis for estimating the high resolution soil moisture, and the application of the COMS can be expanded for various studies. 위성자료는 광범위한 지역의 변동성을 관측하기에 매우 유리하다는 특성 때문에 최근 기후변화로 인한 자연재해 등의 연구에서 각광받고 있다. 하지만 위성자료에도 여전히 시 ․ 공간적인 해상도의 한계가 있으며, 이를 극복하기 위해 다양한 센서의 융합이나 1차 산출물들을 조합하는 방법을 사용한다. 본 연구에서는 천리안 위성의 GOCI와 MI에서 관측되는 자료를 융합함으로써 500 m 공간 해상도의 지표면 온도 자료를 생산하였고, 정규 식생지수와 함께 사용하여 TVDI를 산정하였다. 산정된 TVDI를 통해 한반도의 토양수분 상태를 모니터링 하고자 하였으며, 이를 비교하기 위해 ASCAT 지표 토양수분 자료를 통해 산정된 SSMI와 비교하였다. 그 결과 천리안 TVDI와 SSMI가 대한민국 전역에서 비슷한 공간 분포를 나타냈으며, 천리안 위성을 활용하여 토양수분을 관측할 수 있는 가능성을 제시하였다. 따라서 본 연구에서 산정 된 한반도의 TVDI가 고해상도의 토양수분을 산정하는 기반이 될 수 있고, 이를 통해 천리안 위성의 활용 범위가 보다 확장되어 다양한 연구의 기반이 될 수 있을 것으로 보인다.

굽은 형상을 가지는 라이저 주위 유동 특성에 관한 연구

정재환,오승훈,남보우,박병원,권용주,정동호 한국해양공학회 2019 한국해양공학회지 Vol.33 No.2

The flow around a curved riser exposed to the current in various directions was investigated at a Reynolds number of 100 using a numerical simulation. The present study found that the flow features of the curved riser were distinct from those of a straight riser as a result of its large radius of curvature. Namely, there were various wake patterns according to the flow’s incident angle. As the incident angle increased from 0° to 90°, a two-row street of vortices that developed along the centerline of the curved riser became more apparent. However, when the incident angle approached 180° from 90°, these vortices were completely suppressed by the interaction between the wake and an axial flow induced by the curvature of the riser. To identify this feature, the sectional force coefficients were also considered, and it was found that the force coefficients could be different from those found in a sectional analysis based on the strip theory when investigating vortex-induced vibration. As a result, this kind of study would be important to realistically estimate the riser VIV (vortex-induced vibration) and fatigue life, and a new force coefficient database that includes the three-dimensional effect should be established.

접경지역 최적 주민철수 계획수립을 위한 모형 연구

정재환,윤호영,정창순,김경섭,Jung, Jae Hwan,Yun, Ho Yeong,Jeong, Chang Soon,Kim, Kyung Sup 한국재난정보학회 2018 한국재난정보학회 논문집 Vol.14 No.2

Purpose: This research proposes an optimization model for effective evacuation routing and scheduling of civilians near the border area when full-scale war threats heighten. Method: To reflect the reality, administrative unit network is created using Kruscal's Algorithm, Harmony Search, CCRP based on the geographical features, population, and traffic data of real cities, and then, optimal civilian evacuation routes are found. Results: Optimal evacuation routes and schedules are computed by repetitive experiments, and it is found that the scenario that minimizes the average civilian evacuation time is effective for the civilian evacuation plan. Conclusion: By using the civilian evacuation plan this research proposes, at the time of establishing the actual civilian evacuation plan, quantitative analysis is used for the effective plan making rather than only depending.

A Strategic-Constructivist Analysis of Korea’s Economic Restructuring after the 1997 Financial Crisis

정재환 한국정치학회 2017 한국정치학회보 Vol.51 No.3

This article aims to explain the process of Korea’s economic restructuring after the 1997 financial crisis from the perspective of constructivist political economy. In particular, it seek to interpret Korea’s economic restructuring as a strategic-constructivist process of institutional change in which the strategic use of discourse plays an important role by combining strategic constructivism with discursive institutionalism. Discursive strategies are political acts seeking to provide people with the linguistic description of critical events from a particular perspective, thereby affecting the way people understand the world surrounding them. Political actors employ discursive strategies to spur a collective mobilisation and thus to enhance their political legitimacy and power. After the 1997 financial crisis, the Kim Dae Jung government succeeded in localising the crony capitalism argument, especially by associating it with democratisation in the name of “the parallel development of democracy and the market economy,” thereby enhancing the policy legitimacy of regulatory-liberal economic restructuring, which in turn strengthened its power to impose its will on recalcitrant actors.