On Long-range Dependence of SMS Traffic in Wireless Cellular Networks

Jun Ha,Woo Cheol Shin,Jin Kyung Park,Cheon Won Choi 대한전자공학회 2005 ITC-CSCC :International Technical Conference on Ci Vol.2005 No.2

Robust Extrinsic Calibration for Arbitrarily Configured Dual 3D Lidars using a Single Planar Board

Junha Kim,Changhyeon Kim,H. Jin Kim 제어로봇시스템학회 2020 제어로봇시스템학회 국제학술대회 논문집 Vol.2020 No.10

Many robotic and mobile vehicles have widely used multiple lidars to perceive surrounding circumstances. In such systems, a precise extrinsic calibration is essential to seamlessly utilize all data from different sensors. Most of the studies on the multi-lidar calibration use a target with known dimensions, need additional sensors, and rely on tailored initialization steps by users. Furthermore, because some of their studies assume that two lidars are located on parallel planes, those methods are hard to be generalized for rotated and complex sensor configurations. In this paper, we propose a dual lidar extrinsic calibration algorithm that is accurate and robust to arbitrary configurations using a single planar board with reflective tapes. By sensing three different postures of the target, the proposed algorithm geometrically calculates the transformation of dual lidars. Due to no need for accurate dimensions of the target and user-intervention for the target, the proposed method is more practically feasible than the previous methods. To evaluate the proposed method, we set three different configurations and obtain a dataset using two 16-channel 3D lidar sensors. Experiments with real data are demonstrated that the proposed method is accurate and robust.

Functional Connectivity of the Striatum as a Neural Correlate of Symptom Severity in Patient with Obsessive-Compulsive Disorder

Junha Park,Taekwan Kim,김민아,이태영,Jun Soo Kwon 대한신경정신의학회 2020 PSYCHIATRY INVESTIGATION Vol.17 No.2

Objective It is well established that the cortico-striato-thalamo-cortical (CSTC) circuit is implicated in the pathophysiology of obsessive- compulsive disorder (OCD). However, reports on corticostriatal functional connectivity (FC) in OCD have been inconsistent due to the structural and functional heterogeneity of the striatum. Therefore, in the present study, we investigated corticostriatal FC using a fine 12-seed striatal parcellation to overcome this heterogeneity and discover the neural correlates of symptoms in OCD patients. Methods We recruited 23 OCD patients and 23 healthy controls (HCs). Whole-brain FC based on striatal seeds was examined using resting-state functional magnetic resonance imaging data and compared across OCD patients and HCs. We conducted correlation analysis between FCs of striatal subregions with significant group differences and symptom severity scores on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), Hamilton Rating Scale for Depression, and Hamilton Rating Scale for Anxiety (HAM-A). Results Compared to HCs, patients demonstrated increased FC of the dorsal caudal putamen and ventral rostral putamen (VRP) with several cortical regions, such as the intracalcarine cortex, inferior frontal gyrus, supramarginal/angular gyrus (SMG/AG), and postcentral gyrus (PCG). Furthermore, FC between the VRP and SMG/AG and between the VRP and PCG was negatively correlated with scores on the Y-BOCS compulsive subscale and the HAM-A, respectively. Conclusion These findings suggest that striatal subregions have strengthened FC with extensive cortical regions, which may reflect neural correlates of compulsive and anxious symptoms in OCD patients. These results contribute to an improved understanding of OCD pathophysiology by complementing the current evidence regarding striatal FC.

Lattice-preferred orientation of amphibole in amphibolites in Jenner and Ring Mt., California and implications for seismic anisotropy

Junha Kim,Haemyeong Jung 대한지질학회 2015 대한지질학회 학술대회 Vol.2015 No.10

Object Pose Estimation via Viewpoint Matching of 3D Models

Junha Lee,Sanghoon Ji,Sujeong You 제어로봇시스템학회 2021 제어로봇시스템학회 국제학술대회 논문집 Vol.2021 No.10

Object recognition in a static or dynamic environment provides important information in semantic SLAM. In this paper, we provide a system that can detect objects that are not registered in advance and build a data set that can automatically learn pose information from a recognition network using a CAD model. In general, object recognition and SLAM algorithms operate independently but complementary. When recognizing an object only with an image, it is difficult to grasp the exact posture or properties required by the SLAM algorithm. However, in order to build a 3d object recognition network, preparations such as modeling and labeling are required in advance, so it is difficult to apply to SLAM. In this paper, the CAD model can be applied to the SLAM algorithm by making artificial images rendered from various directions, reducing the effort of additional model or labeling work.

An Integer Programming-based Local Search for the Set Partitioning Problem

Junha Hwang 한국컴퓨터정보학회 2015 韓國컴퓨터情報學會論文誌 Vol.20 No.9

The set partitioning problem is a well-known NP-hard combinatorial optimization problem, and it is formulated as an integer programming model. This paper proposes an Integer Programming-based Local Search for solving the set partitioning problem. The key point is to solve the set partitioning problem as the set covering problem. First, an initial solution is generated by a simple heuristic for the set covering problem, and then the solution is set as the current solution. Next, the following process is repeated. The original set covering problem is reduced based on the current solution, and the reduced problem is solved by Integer Programming which includes a specific element in the objective function to derive the solution for the set partitioning problem. Experimental results on a set of OR-Library instances show that the proposed algorithm outperforms pure integer programming as well as the existing heuristic algorithms both in solution quality and time.

Relative Pose Estimator based on Semi-Dense Homography for UAV Landing on Moving Target using Monocular Camera

Junha Kim,Changhyeon Kim,H. Jin Kim 제어로봇시스템학회 2019 제어로봇시스템학회 국제학술대회 논문집 Vol.2019 No.10

Autonomous landing has been studied on various types of landing targets. In particular, relative pose estimation between a moving landing target and a UAV is important for stable landing in various environments. Most of the studies on UAV landing for a moving landing target used templates given in advance and feature-based methods to estimate the relative pose between the UAV and the landing target. However, the feature-based methods are vulnerable to ambiguity due to the symmetric shape of the helipad or camera noise. In this paper, we propose the algorithm that accurately estimates pose by applying the direct method. The algorithm does not need to use a given template image, which enables landing in various environments. Since the algorithm does not use the feature-based method, there is no concern about the ambiguity. To evaluate the proposed algorithm, we collect our dataset and confirm that the proposed algorithm is more accurate than the feature-based method.

Designing new honey bee hive with multiple sensory system for urban beekeeping

Junha Park,Eujin Kim,Jinho Seo,Sewook Lee,Sungwon Shin,Aiden Choi,Susie Cho 한국응용곤충학회 2023 한국응용곤충학회 학술대회논문집 Vol.2023 No.10

꿀벌에 대한 중요성이 인식되고 도시양봉의 수요가 증가하는 가운데 도시양봉에 최적화된 벌통을 제작하였 다. 꿀벌과 도시양봉에 대한 설문를 진행한 결과, 분봉으로 인한 민원이 도시양봉을 하는 데 가장 큰 저해요소로 꼽혔다. 이에 분봉을 방지하여 시민과 어우러질 수 있으며 친환경적인 벌통을 제작하는 데 초점을 맞췄다. 분봉을 방지하기 위해서는 여왕벌의 이탈을 감지하는 자성 센서와 벌들이 분봉을 하고자 하는 욕구인 분봉열을 감지하 는 온도 센서를 설치하여 효율을 파악하였다. 더불어 최근 이상기후로 인한 잦은 폭우와 고열을 견디기 위하여 밀랍을 이용한 벌통 코팅을 진행하였다. 벌통의 바닥에는 트레이를 서랍처럼 분리 설치할 수 있도록 함으로써 무더운 기온에서는 손쉽게 트레이를 빼서 환기에 중점을 두고, 그 외의 조건에서는 트레이를 끼워둠으로써 바닥 에 떨어진 꿀벌의 사체를 주기적으로 수거하여 유전자 분석을 함으로써 꿀벌의 건강 상태를 점검할 수 있도록 하였다. 꿀벌이 해당 벌통으로 인하여 스트레스를 받는지 꿀벌의 주요 스트레스 마커 유전자의 상대적 발현량을 조사한 결과, 일반적인 벌통에서의 발현량 수준과 큰 차이가 없는 것을 확인할 수 있었다. 이처럼 새로이 디자인된 벌통을 이용한다면 이상기후에서도 도시양봉을 하는 데 기여할 수 있을 것으로 기대된다.

A Study of Ultrafast Ablation on ITO Thin Films with Wavelengths of 513 and 1026 nm for High Resolution Patterning

Junha Choi,Sung Hak Cho 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.11

Indium tin oxide (ITO) exhibits transparency and high electrical conductivity in the visible and near-IR wavelength ranges. Therefore, ITO is used in liquid crystal displays, organic light-emitting diodes, photovoltaics, and solar cells. However, ITO must be partially ablated before employing it in applications. High-resolution patterning technology is required to obtain the desired ITO morphology, and accordingly, various technologies have been developed. Recently, ultrafast lasers have been widely used for controlled ablation because of their non-thermal properties caused by short pulse widths. This study analyzes the changes in ablation characteristics as a function of various parameters such as pulse energy, pulse duration, number of pulses, and wavelength. We show that the optimized ablation characteristics could lead to the efficient formation of the desired morphology of ITO.

Neighbor Generation Strategies of Local Search for Permutation-based Combinatorial Optimization

Junha Hwang(황준하) 한국컴퓨터정보학회 2021 韓國컴퓨터情報學會論文誌 Vol.26 No.10

지역 탐색은 다양한 조합 최적화 문제들을 해결하기 위해 활용되어 왔다. 지역 탐색에 있어서 가장 중요한 요소 중 하나가 이웃해를 생성하는 방법이다. 본 논문에서는 순열 기반 조합 최적화를 위한 지역 탐색의 이웃해 생성 전략들을 제안하고, 순회 외판원 문제를 대상으로 각 전략들의 성능을 비교한다. 본 논문에서는 총 10가지 이웃해 생성 전략을 제안한다. 기본적으로 기존에 많이 사용했던 Swap 등 4가지 전략 이외에 Rotation 등 4가지 기법을 새롭게 제안한다. 이외에 기본 이웃해 생성 전략들을 결합하여 만든 Combined1과 Combined2가 있다. 실험은 기본적인 지역 탐색을 적용하되 이웃해 생성 전략만 변경하여 수행하였다. 실험 결과, 이웃해 생성 전략에 따라 성능차이가 큰 것을 확인하였으며 아울러 Combined2의 성능이 가장 좋음을 확인하였다. 뿐만 아니라 Combined2는 기존의 지역 탐색 기법들보다 더 좋은 성능을 발휘함을 확인하였다. Local search has been used to solve various combinatorial optimization problems. One of the most important factors in local search is the method of generating a neighbor solution. In this paper, we propose neighbor generation strategies of local search for permutation-based combinatorial optimization, and compare the performance of each strategies targeting the traveling salesman problem. In this paper, we propose a total of 10 neighbor generation strategies. Basically, we propose 4 new strategies such as Rotation in addition to the 4 strategies such as Swap which have been widely used in the past. In addition, there are Combined1 and Combined2, which are made by combining basic neighbor generation strategies. The experiment was performed by applying the basic local search, but changing only the neighbor generation strategy. As a result of the experiment, it was confirmed that the performance difference is large according to the neighbor generation strategy, and also confirmed that the performance of Combined2 is the best. In addition, it was confirmed that Combined2 shows better performance than the existing local search methods.