• 한국항만경제학회지
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• 제18권1호
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• pp.3-26
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• 2002

The purpose of this paper is to Investigate the productive efficiency and competitive strength of world container ports using the DEA, Super-efficiency, and FDH methods with the raw data from previous research by Jun et al.(1993). The super-efficiency measure examines the maximal radial change In input, outputs for an observation to remain efficient. Therefore, it provides a means of distinguishing between efficient observations, which would otherwise seem identical. FDH provides a good test mechanism for examining the practical implications of the choice available among alternative efficiency measures and orientations, because of the lack of convexity of its production possibility set. Both methods are complementary to DEA. This paper follows the traditional productivity analysis method overcoming the limitation of previous studies by using the DEA, FDH and Super-efficiency methods, and proposing in measure the relative competitive strength of worldwide container ports. The main empirical results of this paper are as follows: Firstly the ports of Singapore, Hongkong, Kilrung, Busan, Tokyo. and Longbeach were found to be efficient In the CCR model. The ports of Felixstowe, Bangkok, Singapore, Hongkong, Kilung, Busan, Tokyo, and Longbeach were found to be efficient in the BCC model. Secondly, super. efficiency rankings under CRS and input-oriented model are as follows: Longbeach, Keelung, Singapore, Busan, Tokyo, and Honkong. However, it was difficult In differenciate the rankings under the VRS and input-oriented model. due to major difficulties posed by the ports of Singapore, Hongkong, and Longbeach. Thirdly, the FDH method shows that the inefficient ports are Bremerhaven, Antwerp, Le Havre, Kobe, Seattle, New York The policy Implications of this study are as follows: Firstly, when port authorities want to measure the international competitive strength of container ports and enhance their productive efficiency, they should consider the traditional method as well as introducing the Super-efficiency and FDH methods. Secondly, according to the analysis results of the super-efficiency and FDH methods, poll authorities should recommend benchmarks ports and dominated ports as reference ports in order to enhance the productive efficiency of their container ports that have an efficiency rating of less than 1. Efficient ports whose efficiency ratings are over 1 in the Input-oriented Super-efficiency model should also consider the usage of input and output elements used by more efficient ports.

• Radiation Oncology Journal
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• 제37권1호
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• pp.22-29
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• 2019

Purpose: The aim of this study is to evaluate the efficacy and feasibility of four-field box whole brain radiotherapy (FB-WBRT) with tilting baseplate by comparing bilateral WBRT (B-WBRT). Methods and Materials: Between March 2016 and September 2018, 20 patients with brain metastases underwent WBRT using the four-field box technique. WBRT is performed with a dose of 30 Gy in 10 fractions daily. Two computed tomography simulations per person were performed. One was in the traditional supine position for B-WBRT and the other by applying the tilting acrylic supine baseplate to elevate the head by 40° for FB-WBRT. The B-WBRT used the field-in-field technique, which is the most commonly used method in our institution. The FB-WBRT comprised anterior, posterior, and bilateral beams. A wedge was applied in anterior and posterior fields to compensate for skull convexity. Results: The average of Dmean of both parotid glands was 10.2 Gy (range, 3.8 to 17.8 Gy) in B-WBRT and 5.4 Gy (range, 2.0 to 11.7 Gy) in FB-WBRT (p < 0.05). Compared to B-WBRT, FB-WBRT reduced the mean dose of the right and left parotid glands from 10.1 Gy to 4.9 Gy and from 10.4 Gy to 5.8 Gy, respectively (p < 0.05). Further, V₅, V₁₀, V₁₅, V₂₀, and V₂₅ for the parotid gland decreased significantly in FB-WBRT (p < 0.05). The Dmax and Dmean of lens decreased according to the dose-volume histogram. Conclusion: Compared to B-WBRT, FB-WBRT with a tilting baseplate is a simple and effective method that takes feature of noncoplanar beam to protect the parotid gland.

• 소성∙가공
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• 제20권5호
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• pp.369-376
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• 2011

본 연구를 통하여 비이차 비등방 항복 응력 포텐셜들의 근접 짝되는 변형률 속도 포텐셜들에 대해서 정리하고 Yld2000-2d의 근접 짝되는 Srp2003-2d에 대해서 상세 설명하였다. 제안된 비이차 비등방 변형률 속도 포텐셜 Srp2003-2d 식 형태가 소개 되었고, 볼록성이 증명되었다. 아울러 이방성 상수를 구하는 방법이 제시되었다. Srp2003-2d의 소성 거동을 살펴보기 위하여 자동차 용 알루미늄 합금 판재 AA6022-T4와 항공재료용 알루미늄 합금 AA2090-T3에 응용되었다. Srp2003-2d는 항복 응력 포텐셜 Yld2000-2d와 거의 흡사한 짝됨을 보여 주었으며, 알루미늄 판재의 비등방성을 적절히 묘사하였다. Srp2003-2d는 알루미늄 판재의 성형 공정의 모사를 위하여 이상 공정 이론을 비롯한 강소성체 재료에 대한 정식화에 적절히 응용될 수 있을 것이다.

• Journal of Korean Neurosurgical Society
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• 제30권sup2호
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• pp.211-215
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• 2001

Objective : The present study was performed to analyze treatment results for 22 cases of arachnoid cyst and to have appropriate surgical method in our department. Material and Methods : We performed a retrospective study in 22 cases in 11 years between 1989 to 2000 that could be followed up. The analysis was based on the results of patients age, sex distribution, developed area, clinical symptom, treatment method, and complication. Results : The age range of cyst development was between 7 months to 60 years with the average age of 21 years. As for sex distribution, 20 were male and 2 were female, with significantly more cyst development in males than females. Thirteen cases were developed in the sylvian fissure, 3 cases in the posterior fossa, 4 cases in the cerebral convexity of the supratentorial area, 1 case in the suprasella and 1 case in interhemiphere. Those cases with the sylvian fissure involvement included 6 cases of Type I, 4 cases of Type II, and 3 cases of Type III. As for the distribution according to hemisphere, more arachnoidal cysts were seen in the right hemisphere. The most common clinical symptom was headache, followed by seizure and speech disturbance. As for the treatment method in 22 cases, surgery was performed in 17 cases and conservative treatment in 5 cases. Fenestration was performed in 14 cases. 13 cases of them showed good outcome, and 1 case with delayed development showed no improvement. Cyst-peritoneal shunt was done in 2 cases. Both fenestration and cyst-peritoneal shunt were done in 1 case. Conclusion : Patients who perforemed fenestration were showed good outcome with few complication. We concluded that fenestration is the most appropriate surgical method for arachnoid cyst.

• Journal of Korean Neurosurgical Society
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• 제37권5호
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• pp.329-335
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• 2005

Objective: Acute spontaneous subdural hematoma(SDH) secondary to a ruptured intracranial aneurysm is a rare event. The authors present nine cases with aneurysmal SDH. Methods: We analyzed nine cases of aneurysmal SDH from 337 patients who underwent treatment for a ruptured aneurysm between January 1998 and May 2004. Clinical and radiological characteristics and postoperative course were evaluated by reviewing medical records, surgical charts and intraoperative videos. Results: The nine patients comprised four males and five females with a mean age of 53years (range 15-67years). The World Federation of Neurosurgical Societies grades on admission were I in one patient, II in two patients, III in five patients and V in one patient. With respect to location, there were four internal carotid-posterior communicating artery(ICA-Pcom) aneurysms, one distal anterior cerebral artery(DACA) aneurysm, one anterior communicating artery and three middle cerebral artery aneurysms. CT scans obtained from the four patients with ICA-Pcom aneurysms revealed SDH over the convexity and along the tentorium, and two of these patients presented with pure SDH without subarachnoid hemorrhage(SAH). In three patients with ICA-Pcom aneurysm, the ruptured aneurysm domes adhered to the petroclinoid fold. In the patient with the DACA aneurysm, the domes adhered tightiy to the pia mater and the falx. Conclusion: Ruptured intracranial aneurysm may cause SDH with or without SAH. In the absence of trauma, the possibility of aneurysmal SDH should be considered.

• 한국컴퓨터그래픽스학회논문지
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• 제25권3호
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• pp.93-103
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• 2019

3차원상의 자유곡면에 대한 효율적인 기하 연산을 지원하기 위한 새로운 공간자료구조로서 토러스 패치 기반 정밀 근사를 이용한 자유곡면의 기하학적 처리 기법을 소개한다. 토러스는 곡률이 양이나 음인 경우뿐만 아니라, 0인 부분도 있으므로 자유곡면의 볼록, 오목 여부에 상관없이 곡면을 정밀하게 근사할 수 있다. 전통적인 기법과 달리 토러스 패치는 자유곡면의 법벡터 방향까지 쉽게 모델링할 수 있고, 토러스의 오프셋은 다시 토러스가 되므로 다양한 기하 연산의 가속화를 지원할 수 있다. 자유곡면과 이를 근사하는 토러스 패치 집합 사이의 양방향 하우스도르프 거 리의 상한을 계산하여 토러스 패치를 이용하여 자유곡면을 높은 정밀도로 근사할 수 있음을 보였다. 이 기법을 이용하여 두 자유곡면의 교차곡선 계산과 자유곡면의 오프셋 곡면 생성을 쉽게 처리할 수 있음을 보였다.

• 응용통계연구
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• 제35권4호
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• pp.469-484
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• 2022

텍스트 데이터는 일반적으로 많은 단어로 이루어져 있으므로 변수의 수가 매우 많은 고차원 데이터에 해당된다. 이러한 고차원 데이터에서는 계산 효율성과 통계분석의 정확성을 높이기 위해 많은 변수 중 중요한 변수를 선택하기 위한 절차를 거치는 경우가 많다. 텍스트 데이터에서도 많은 단어 중 중요한 단어를 선택하기 위해 여러가지 방법들이 사용되고 있다. 이 연구에서는 단어 선택을 위한 대표적인 필터링 방법인 카이제곱통계량과 정보이득의 공통점과 차이점을 살펴보고 실제 텍스트 데이터에서 이 단어선택 방법들의 성질을 확인해보았다. 카이제곱통계량과 정보이득은 비음성, 볼록성 등의 성질을 공유하지만 불균형 텍스트 데이터에서 카이제곱통계량이 양변수 위주로 단어를 선택하는 반면, 정보이득은 음변수도 상대적으로 많이 선택하는 경향이 있음을 확인하였다.

• 한국지형학회지
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• 제17권1호
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• pp.1-14
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• 2010

본 논문은 비접근지역인 DMZ에서 동해안의 원산만에 이르는 추가령 열곡에 대해 GIS를 이용하여 지형면을 분류하고 그 분포의 특징과 형성과정에 미친 영향을 분석한 것이다. 분석 방법으로 수치고도모델(DEM)과 Landsat 위성영상을 이용하였다. 지형면 분류는 고도, 경사도, 기복량 등을 이용하여 지형 표면의 요철 정도를 지수로 산출하는 TPI(Topographical Position Index)를 이용하였다. 연구지역의 지형면은 깊은 계곡, 얕은 계곡, 산지유로, 평탄곡지, 평탄지(단구, 평야, 대지), 산록사면, 산복사면, 소구릉, 완사능선, 산정능선 등 10가지 유형으로 분류하였다. 이들 지형면의 지형형성과정의 평균적인 특성을 파악하기 위하여 기반암과 기복량, 지형면과 기복량, 지형면과 식생활력도 등의 관계에 대한 구역 평균(Zonal Statistics)을 실시하였다. 이러한 분석을 통하여 비접근 지역인 추가령열곡 DMZ의 용암대지 개석과정과 분수계 발달과정 등을 파악할 수 있었다.

• 로봇학회논문지
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• 제18권1호
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• pp.1-9
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• 2023

This paper presents an optimal path planning strategy for aerial searching and surveying of a user-designated area using multiple Unmanned Aerial Vehicles (UAVs). The method is designed to deal with a single unseparated polygonal area, regardless of polygonal convexity. By defining the search area into a set of grids, the algorithm enables UAVs to completely search without leaving unsearched space. The presented strategy consists of two main algorithmic steps: cellular decomposition and path planning stages. The cellular decomposition method divides the area to designate a conflict-free subsearch-space to an individual UAV, while accounting the assigned flight velocity, take-off and landing positions. Then, the path planning strategy forms paths based on every point located in end of each grid row. The first waypoint is chosen as the closest point from the vehicle-starting position, and it recursively updates the nearest endpoint set to generate the shortest path. The path planning policy produces four path candidates by alternating the starting point (left or right edge), and the travel direction (vertical or horizontal). The optimal-selection policy is enforced to maximize the search efficiency, which is time dependent; the policy imposes the total path-length and turning number criteria per candidate. The results demonstrate that the proposed cellular decomposition method improves the search-time efficiency. In addition, the candidate selection enhances the algorithmic efficacy toward further mission time-duration reduction. The method shows robustness against both convex and non-convex shaped search area.

• 한국정보통신학회논문지
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• 제26권11호
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• pp.1679-1685
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• 2022

본 논문에서는 무선전력 통신 네트워크에서 소스에서 목적지 노드까지 종단간 데이터 전송률을 최대화하기 위한 최적의 멀티홉 전송 방식을 제안한다. 에너지 하베스팅을 하면서 멀티홉 전송을 위한 프레임 구조를 제시하고, 노드간 서로 다른 에너지 수확량과 링크 품질을 고려하여 종단간 전송률을 최대화하는 각 노드의 전송 시간을 수학적 분석을 통하여 도출한다. 아울러, 고려하는 무선전력기반 멀티홉 전송의 시스템 모델링을 통하여 최적화 문제를 도출하고, 이 최적화 문제가 convex 함을 보임으로써 전역 최적해가 존재함을 증명한다. 이를 통하여 최적화 문제를 계산 가능한 형태로 변형하여 손쉽게 최적해를 찾는다. 제안한 최적 멀티홉 전송 방식은 모든 링크의 전송률이 같아지도록 노드별 전송 시간을 최적으로 할당함으로써 종단간 전송률을 최대화한다.