• 한국전자파학회논문지
• /
• 제13권5호
• /
• pp.407-415
• /
• 2002

본 논문에서는 무인항공기에 탑재된 서로 다른 주파수에서 동작하는 안테나간의 상호결합을 계산하여 안테나의 효율적인 배치방법을 제안한다. FDTD 기법을 이용하여 계산하였다. 시뮬레이션 파라미터는 안테나간의 거리, 안테나간의 높이차, 접지구조 등으로 제한하였다. 시뮬레이션 결과의 정확도를 검증하기 위해 다른 수치 해석 기법을 이용한 해석결과와 비교하였다. 안테나간의 상대적인 높이차가 안테나 상호결합에 가장 큰 영향을 주는 요인으로 나타났다.

• 한국자동차공학회논문집
• /
• 제3권6호
• /
• pp.78-86
• /
• 1995

The structure of premixed turbulent flames in a constant-volume vessel was investigated using a microprobe method. The flame potential signal having one to eight peaks was detected in the case of turbulent flames, each of them being regarded as a flamelet existing in the flame zone. Based on this consideration, the flame propagation speed, the thickness of the flame zone, the number of flamelets and the separation distance between adjacent flamelets in the flame zone were measured. The experimental resuits of this work suggest the existence of "reactant islands" behind the flame front when the turbulence was intensified to some extent. The critical(lowest) ratio of turbulence intensity to the laminar burning velocity being found to be about 0.7 for the formation of reactant islands in this experiment.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제17권10호
• /
• pp.2809-2821
• /
• 2023

Effective recommendation of similar business groups is a critical factor in obtaining market information for companies. In this study, we propose a novel method for enhancing similar business group recommendation by incorporating derivative criteria and web crawling. We use employment announcements, employment incentives, and corporate vocational training information to derive additional criteria for similar business group selection. Web crawling is employed to collect data related to the derived criteria from 'credit jobs' and 'worknet' sites. We compare the efficiency of different datasets and machine learning methods, including XGBoost, LGBM, Adaboost, Linear Regression, K-NN, and SVM. The proposed model extracts derivatives that reflect the financial and scale characteristics of the company, which are then incorporated into a new set of recommendation criteria. Similar business groups are selected using a Euclidean distance-based model. Our experimental results show that the proposed method improves the accuracy of similar business group recommendation. Overall, this study demonstrates the potential of incorporating derivative criteria and web crawling to enhance similar business group recommendation and obtain market information more efficiently.

• 한국가시화정보학회지
• /
• 제21권3호
• /
• pp.15-22
• /
• 2023

This research introduces an innovative approach for fabricating microstructure surfaces using spray-coating deposition. The resulting surface, referred to as Magnetically Responsive Microstructures (MRM), exhibits hierarchically structured micro-pillar arrays with remarkably high aspect ratios. The fabrication process involves precisely mixing PDMS and hexane with Carbonyl iron powders, followed by ultrasonication and spray-coating on the top of a PDMS substrate placed on the neodymium magnet. The MRM surface shows hydrophobic properties, characterized by a contact angle surpassing 150° and an aspect ratio exceeding 10. Through a comprehensive exploration of critical parameters, including spray amount, magnet-substrate distance, and solution ratio enhanced dynamic tunability and exceptional hydrophobic characteristics are attained. This novel approach holds significant potential for diverse applications in the realm of dynamically tunable microstructures and magnetically responsive surfaces.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1997년도 하계학술대회 논문집 D
• /
• pp.1078-1082
• /
• 1997

The distance in load parameter space to the closest voltage collapse point provides the worst case power margin and the left eigenvector identifies the most effective direction to steer the system to maximize voltage stability under contingency. This paper presents the results of the comparative performance study of the algorithms, which are applicable to a large scale power system, for computing the closest saddle node bifurcation (CSNB) point. Dobson's iterative method converges with robustness. However the slow process of updating the load increasing direction makes the algorithm less efficient. The direct method converges very quickly. But it diverges if the initial guess is not very close to CSNB. Zeng's method of estimating the approximate critical point in the pre-determined direction is attractive in the sense that it uses only using load flow equations. However, the method is found to be less efficient than Dobson's iterative method. It may be concluded from the above observation that the direct method with the initial values obtained by carrying out the iterative method twice is most efficient at this time and more efficient algorithms are needed for on-line application.

• 대한전기학회논문지:전력기술부문A
• /
• 제48권8호
• /
• pp.951-957
• /
• 1999

The saddle node bifurcation (SNB) and the distance voltage instability are valuable information in power system planning and operation. This paper presents a new efficient, robust and unified strategy to compute the SNB by the combined use of the continuation power flow (CPF), Point of Collapse (PoC) method, and the method of a pair of multiple load flow solutions (PMLFS) with Lagrange interpolation utilizing only their advantages: the approximate nose curves and critical loading are determined fast by Lagrange-interpolating two stable and two unstable solutions obtained by using the robust CPF and PMLFS; the exact SNB is computed by the quadratically converging PoC method. The proposed method has been tested on Klos-Kerner 11-bus, New England 30-bus, IEEE 118-bus and KEPCO 791-bus systems. The method is found to be so efficient that computation time for determining the SNB of the KEPCO 791-bus system is 17.82 sec by a notebook PC with 300 MHz Pentium processor.

• 한국콘텐츠학회논문지
• /
• 제13권4호
• /
• pp.427-439
• /
• 2013

복잡계 과학의 발달에 따라 많은 사회 네트워크들이 분석되고 있다. 사회 네트워크는 현재 인문, 경제, 웹 사이언스 등 다양한 분야에 응용되고 있다. 최근, 소설의 등장인물을 이용한 네트워크와 실제 사회 네트워크의 특성을 비교하는 다양한 연구가 진행되고 있다. 그러나 기존의 등장인물 네트워크는 대부분 미리 정리된 인명사전을 이용하므로 주요한 몇몇 인물들 사이의 연관성은 밝힐 수 있으나, 한번 이상 등장한 모든 인물의 전체적인 사회적 구조는 설명하지 못하고 있다. 본 연구에서는 소설로부터 등장인물을 직접 추출하고, 등장인물 사이의 거리를 사용하여 상관관계를 설정하여 네트워크를 구축한다. 제안방법은 소설 텍스트로부터 등장인물의 출현빈도와 등장인물들 사이의 연관성의 발생 빈도를 이용하여 연관성 가중치를 구할 수 있으며, 이 연관성 가중치를 사용하여 노드의 수를 조절하여 K-critical 네트워크를 구성한다. 제시한 K-critical 네트워크는 분석대상 소설에 등장하는 인물들끼리 얼마나 긴밀하게 연관되어 있는지를 정량적으로 파악하는 매우 중요한 정보를 줄 수 있음을 실험을 통하여 제시할 수 있었다.

• 한국지반공학회논문집
• /
• 제35권2호
• /
• pp.37-51
• /
• 2019

본 연구는 사질토 지반에서 수행되는 콘관입시험의 수치적 모사에 초점을 맞추고 있다. 지반은 한계상태 토질역학을 바탕으로 수정된 한계상태 Mohr Coulomb 소성 모델로 모사하였다. 한계상태 Mohr Coulomb 모델에서 팽창각은 상수가 아닌 현재상태와 한계상태 사이의 위상차의 함수로 표현된다. 수치적으로 콘관입시험은 대변위 해석을 요구하며, 이를 Lagrangian 유한요소법으로 해석하기 위해 관입 유도체 개념을 적용한 축대칭 조건 유한요소법을 이용하였다. 캘리브레이션 챔버에서 수행된 콘관입시험을 한계상태 Mohr Coulomb 모델을 이용하여 본 논문에서 제안된 유한 해석 기법을 적용한 결과, 실험 결과와 유사한 결과를 얻을 수 있었다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
• /
• pp.3-5
• /
• 2004

Cleft lip is one of the most common congenital deformities in craniofacial region. Despite the many reports on the outcome of various surgical techniques from individual medical centers, the evaluation of the outcome is based on the subjective observation because of lack of the objective evaluation system. Therefore, a new technique of objective and scientific evaluation for the nasal deformity of secondary cleft lip and nose deformity is critical to improve the management of the cleft patients including the decision of optimal age of operation and surgical technique as veil as evaluation of the outcome. In this study, a new method was proposed to evaluate the nasal deformity using nostril angle, distance, and area of patient images. The images were also evaluated by three expert plastic surgeons, and put into scale of 5 percentile. Measurement results were compared between the each category and the surgeon's evaluation, and coefficients of each category were statistically tested. As a result, The normalized overlap area of right and left nostrils and distance ratio between two centers of nostrils showed high coefficient with evaluations of plastic surgeons.

• Journal of Electrical Engineering and Technology
• /
• 제6권6호
• /
• pp.867-873
• /
• 2011

A navigation mesh (NavMesh) is a suitable tool for the representation of a three-dimensional game world. A NavMesh consists of convex polygons covering free space, so the path can be found reliably without detecting collision with obstacles. The main disadvantage of a NavMesh is the huge state space. When the $A^*$ algorithm is applied to polygonal meshes for detailed terrain representation, the pathfinding can be inefficient due to the many states to be searched. In this paper, we propose a method to reduce the number of states searched by using visibility tests to achieve fast searching even on a detailed terrain with a large number of polygons. Our algorithm finds the visible vertices of the obstacles from the critical states and uses the heuristic function of $A^*$, defined as the distance to the goal through such visible vertices. The results show that the number of searched states can be substantially reduced compared to the $A^*$ search with a straight-line distance heuristic.