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라병소,신경자,신준식,서동엽 한국수학교육학회 2002 수학교육 Vol.41 No.3
We investigated on the primary school children's abilities of formal reasoning. Seventy students in grade 5 participated in the study. They responsed their best reactions on the problems constituted of three parts requiring the informal or formal reasoning and generalization. Their reactions are classified by some criteria depending the level of reasoning. About 10 students showed that they constructed a kind of scheme for solving the problems, similar to formal reasoning and beyond naive informal reasoning. And about 30 students did so partially. We concluded that the teaching and learning of reasoning by the progressive increasing the degree of rigor from grade 5 is possible.
Transmission Through an Annular Aperture Surrounded With Corrugations in a PEC Plane
Dong Yeop Na,Kyung-Young Jung,Yong Bae Park IEEE 2015 IEEE antennas and wireless propagation letters Vol.14 No.-
<P>Electromagnetic transmission through an annular aperture surrounded with corrugations in a PEC plane is investigated based on the mode-matching method. The eigenfunction expansion and Hankel transform are utilized to represent the scattered field in the discrete and continuous modes. We demonstrate that a new type of extraordinary electromagnetic transmission can occur due to the strong excitation of TM11 mode even if the corrugation is wide, as well as finding the optimal dimensions based on the three-dimensional parametric study.</P>
모드 탐색 알고리즘을 이용한 측정치 기반의 전파 환경 시각화 기법
나동엽(Dong Yeop Na),구형일(Hyung Il Koo),박용배(Yong Bae Park),이경훈(Kyoung Hoon Lee),이재기(Jae Ki Lee),황인호(In Ho Hwang) 한국전자파학회 2014 한국전자파학회논문지 Vol.25 No.3
본 논문에서는 제한된 위치에서 측정된 수신 신호 세기(RSSI) 값과 3차원 지리 정보를 기반으로 주변의 전파 환경을 추정하고, 시각화할 수 있는 알고리즘을 제안한다. RSSI가 동일한 수신점은 송신점으로부터 같은 거리에 위치한다는 가정 하에서 삼각형의 외심을 이용하여 송신점의 위치를 추정하고, 전파 모델을 이용해 전파 손실을 고려하여 전파환경을 시각화한다. 영상 신호 처리에서 사용되는 모드 탐색 알고리즘인 mean-shift clustering 방법을 사용하여 피크 값을 탐색하고, 여러 개의 추정점들의 무게 중심을 사용하여 오차를 감소시킬 수 있는 방법을 제안한다. 본 논문에서 제시한 모드탐색 알고리즘을 이용한 전파 환경 시각화 기법은 전파 자원의 효율적인 이용을 위한 전파 감시 시스템에 활용될 수 있을 것으로 기대된다. In this paper, we propose an algorithm to visualize radio wave environment based on the measured Received Signal Strength Indication(RSSI) and 3D geographic information. We estimate the source position using the circumcenter of the triangle and visualize the radio wave environment using the empirical propagation models. A mode seeking algorithm(mean-shift clustering) is used to seek the peak points and the center of gravity is utilized to reduce the estimation errors. Our approach finds its applications in the radio wave monitoring systems for the efficient utilization of radio resources.
Imaging-Based Management of Acute Ischemic Stroke Patients: Current Neuroradiological Perspectives
Na, Dong Gyu,Sohn, Chul-Ho,Kim, Eung Yeop The Korean Society of Radiology 2015 KOREAN JOURNAL OF RADIOLOGY Vol.16 No.2
<P>Advances in imaging-based management of acute ischemic stroke now provide crucial information such as infarct core, ischemic penumbra/degree of collaterals, vessel occlusion, and thrombus that helps in the selection of the best candidates for reperfusion therapy. It also predicts thrombolytic efficacy and benefit or potential hazards from therapy. Thus, radiologists should be familiar with various imaging studies for patients with acute ischemic stroke and the applicability to clinical trials. This helps radiologists to obtain optimal rapid imaging as well as its accurate interpretation. This review is focused on imaging studies for acute ischemic stroke, including their roles in recent clinical trials and some guidelines to optimal interpretation.</P>