• Proceedings of the Korean Society of Computer Information Conference
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• 2024.01a
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• pp.109-111
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• 2024

군사 목적으로 개발된 드론은 최근 다양한 산업 및 민간 분야로 확대되고 있으며, 이러한 확대에 따라, 드론이 급격하게 발전하여, 농업이나 무인 드론 택배와 같은 산업 전반적으로 긍정적인 효과를 창출하는 추세이다. 그러나 이러한 발전에 반하여, 드론에 장착된 카메라를 통한 사생활 침해나 테러 목적으로 활용하는 것과 같은 부정적인 측면이 드러나기 시작하였다. 특히, 드론의 위치와 밀접한 연관이 있는 GPS와 관련하여, 무인 이동체의 특성상, GPS 신호에 의존하여 사용자에게 드론의 위치를 전달하지만, 이러한 GPS 신호를 송신하는 위성은 거리가 매우 멀리 위치하고, 이에 따라, 신호 세기가 비교적 약한 문제점을 가진다. 이와 같은 문제점을 악용하는 GPS 스푸핑 공격이 등장하였으며, 이 공격은 만약 공격자가 GPS 신호를 조작하여 송신한다면, 드론에 장착된 GPS 수신기는 조작된 GPS 위치를 수신하며, 이에 따라, 드론의 제어권을 탈취하거나 충돌 유발, 비정상적인 비행 경로 유도와 같은 문제점이 발생한다. 본 논문에서는 최신의 상용화된 드론을 대상으로, GPS 스푸핑 공격의 취약점을 분석하고 실증한다. 이를 위하여, 공격자가 비행 금지 구역에 해당하는 GPS 신호를 조작하는 것으로 공격을 시도하고, 이에 따른 드론에서 준비된 동작인 강제 착륙과 같은 비정상적인 행위를 유발하여, 드론의 임무 수행 능력을 제한하는 취약점을 분석하고 실험을 통하여 실증한다. 본 논문의 결과를 토대로, 최신 드론에서 발생 가능한 보안 위협을 도출함으로써, 드론의 안전성을 향상시키기 위한 자료로 활용될 수 있을 것으로 사료된다.

• Maritime Security
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• v.7 no.1
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• pp.61-96
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• 2023

Amidst the ongoing instability and military tensions between North and South Korea, it is essential for us to comprehend and assess North Korea's military capabilities, while preparing for potential contingencies through military reinforcement. However, to conduct a comprehensive analysis of the military balance on the Korean Peninsula, it is imperative to move beyond simplistic quantitative comparisons of combat capabilities and embrace a broader perspective, which includes qualitative comparisons of military strength, operational capabilities, and a nation's ability to wage war. To address this need, this study employs the method of "Net Assessment" to evaluate the relative combat power of South and North Korean conventional naval forces, with a particular focus on surface combatants. This evaluation involves both quantitative and qualitative comparisons of military assets (personnel and equipment) and intangible factors (naval strategies, geography, etc.). By conducting a holistic assessment, the research aims to identify and analyze strategic asymmetries that may exist between the two navies.

• Journal of the Korean Arthroscopy Society
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• v.5 no.2
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• pp.63-68
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• 2001

Purpose : To propose the diagnosis, 'hypertrophy of the anterior cruciate ligament(ACL)', and its clinical, radiological and pathological characteristics. Materials & Method : Since Dec. 1995, we have experienced 10 patients(12 knees) with hypertrophy of the ACL. There were 2 males and 8 females, and the age of the patients ranged from 35 to 67 years. Characteristics of clinical, radiological and pathological findings were analysed. Results : The chief complaint was insidious onset of dull pain on the knee which became worse with activity. The constant physical finding was painful limitation of full extension of the knee. Sagittal MR images showed diffuse swelling of the ACL, similar finding that could be seen in acute ACL tear. Arthroscopically, noted was a marked enlargement of the ACL causing notch impingement. Biopsies of the hypertrophied ACL showed increased collagenous tissue with variable degree of myxoid degeneration. With partial excision of the hypertrophied ACL with or without notchplasty, the symptoms improved in all. Conclusion : Hypertrophy of the ACL, a newly proposed diagnosis, should be considered be determining the cause of the painful knee, and further study should be done about its pathogenesis.

• Journal of the Korean Arthroscopy Society
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• v.6 no.2
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• pp.136-141
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• 2002

Purpose : The role of biceps pulley is stabilizing sling for the long head of the biceps tendon against anterior shearing stress in the rotator interval. The purpose of this study was to classify arthroscopic findings of biceps pulley and to evaluate the relationship with shoulder pathology. Materials and Methods : From January 2002 through July 2002, we observed biceps pulley in 49 cases of shoulder pathology treated with arthroscopically. There were 22 cases of anterior instability, 12 cases of rotator cuff tear, 5 of impingement syndrome, 6 of frozen shoulder, 2 of superior labral injury and 1 of each scapulothoracic bursitis and biceps dislocation. We classified biceps pulley as four types according to the arthroscopic appearance. Type I its stretched type. type II as sling type, type III at detached sling type, and type IV as concealed type. Results : We observed stretched type in 24 cases $(49\%)$, sling type in 5 cases $(10\%)$, detached sling type in 2 cases, concealed type in 1 case, and unidentified cases in 17 cases $(35\%)$. Conclusion : Development and variation of biceps pulley may have symptomatic correlation according to the degree of shoulder motion or pathologic status.

• The Journal of Korean Orthopaedic Ultrasound Society
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• v.1 no.1
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• pp.23-26
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• 2008

Ultrasonography (USG) is widely accepted diagnostic method for the rotator cuff tear. The availability, low cost, easy to access is main factors that favor USG as a primary diagnostic modality for various cuff disorders. We experienced a case of discrepancy between USG, MR arthrography (MRA) and arthroscopic examination. Seventy four year old female patient complained of right shoulder pain. USG depicted rotator cuff tear with the size of 1cm, and MRA demonstrated about 3cm sized tear. Complex massive tear with delamination of degenerated rotator cuff was identified in the arthroscopic examination. When we encounter a patient who has loss of rotator cuff power or severe symptom than findings of USG, MRA or repeat USG is warranted. We report a case of discrepancy between examination modalities with brief review of the literature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.7
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• pp.655-663
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• 2017

With the development of ICT technology, the indoor utilization of robots is increasing. Research on transportation, cleaning, guidance robots, etc., that can be used now or increase the scope of future use will be advanced. To facilitate the use of mobile robots in indoor spaces, the problem of self-location recognition is an important research area to be addressed. If an unexpected collision occurs during the motion of a mobile robot, the position of the mobile robot deviates from the initially planned navigation path. In this case, the mobile robot needs a robust controller that enables the mobile robot to accurately navigate toward the goal. This research tries to address the issues related to self-location of the mobile robot. A robust position recognition system was implemented; the system estimates the position of the mobile robot using a combination of encoder information of the mobile robot and the absolute space coordinate transformation information obtained from external video sources such as a large number of CCTVs installed in the room. Furthermore, vector field histogram method of the pass traveling algorithm of the mobile robot system was applied, and the results of the research were confirmed after conducting experiments.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.1
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• pp.36-41
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• 2011

Configuration space(C-space) including configuration obstacle(C-obstacle) is one of the most important concepts in mobile robot path planning. Using C-space and C-obstacles, the robot with different shapes and moving mechanisms can be considered as a point in the C-space. And, as a result, the collision-free path for the robot can be easily achieved. To make C-space including C-obstacle, many researchers used circular approximation method for the efficient caluculation time. This method can help us to save our time by approximating the shape of a robot as the minimum sized circle which can cover all the area of robot. But, by using the circle larger than the robot, more space are considered as the part of robot and, as a result, some obstacles which are very near each other may be considered as a combined one obstacle. To solve this problem, multi-level configuration space is proposed by this paper. This multi-level method also use the circular approximation method as the initial step. But, after finding the initial path, it will check how many obstacles are combined. And then, for each combined obstacle, more accurate C-space generation will be continued. To check the efficiency of the proposed algorithm, time for c-space generation are compared with the well-known accurate C-space generation method using various types of robot shape.

• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.554-561
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• 2022

Technology development related to maritime autonomous surface ships (MASS) is actively progressing around the world. However, since there are still many technically unresolved problems such as communication, cybersecurity, and emergency response capabilities, it is expected that it will take a lot of time for MASS to be commercialized. In this study, we proposed a ship group navigation system in which one leader ship and several follower ship are grouped into one group. In this system, when the leader ship begins to navigate, the follower ship autonomously follows the path of the leader ship. For path following, PD (proportional-derivative) control is applied. In addition, each ship navigates in a straight line shape while maintaining a safe distance to prevent collisions. Speed control was implemented to maintain a safe distance between ships. Simulations were performed to verify the ship group navigation system. The ship used in the simulation is the L-7 model of KVLCC2, which has related data disclosed. And the MMG (Maneuvering Modeling Group) standard method proposed by the Japan Society of Naval Architects and Ocean Engineering (JASNAOE) was used as a model of ship maneuvering motion. As a result of the simulation, the leader ship navigated along a predetermined route, and the follower ship navigated along the leader ship's path. During the simulation, it was found that the three ships maintained a straight line shape and a safe distance between them. The ship group navigation system is expected to be used as a navigation system to solve the problems of MASS.

• The Journal of the Petrological Society of Korea
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• v.21 no.2
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• pp.151-171
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• 2012

The Permo-Triassic Songrim orogeny in the Korean peninsula was a major tectonic event involving complicated continental collisions at the eastern margin of Eurasia. Based on the previous studies on the metamorphic and deformations features of the Songrim orogeny, this paper presents metamorphic and structural characteristics and timing of the Songrim orogeny in the Taebaeksan basin, and discuss about correlation of the tectono-metamorphic evolution of the Taebaeksan basin with the Okcheon basin and the Imjingang belt with a combined analysis of bulk crustal shortening direction, metamorphic P-T and T-t (time) paths. The metapelites in the Pyeongan Supergroup in the northeastern margin of the Taebaeksan basin have experienced lower-temperature/medium-pressure (LT/MP) regional metamorphism followed by high-temperature contact metamorphism due to the Jurassic granite intrusion. The earlier LT/MP regional metamorphism produced two loops of clockwise P-T-d (deformation) paths combined with four deformation events ($D_1-D_4$). The first loop concomitant with $D_1$ and $D_2$ occurred at $400-500^{\circ}C$, 1.5-3.0 kbar, and related with growth of syn-$D_1$ chloritoid and andalusite, post-$D_1$ margarite, Ca-rich syn-$D_2$ or post-$D_2$ plagioclase. The second loop accompanying $D_3$ and $D_4$ occurred at $520-580^{\circ}C$, 2.0-6.0 kbar, and associated with the growth of syn-$D_3$ garnet and staurolite, and syn-$D_4$ and/or post-$D_4$ andalusite porphyroblasts. Furthermore the syn-$D_1$ chloritoid and andalusite porphyroblasts grew during E-W bulk crustal shortening, whereas the syn-$D_3$ garnet and staurolite, and the syn-$D_4$ and/or post-$D_4$ andalusite porphyroblasts have grown under N-S bulk crustal shortening. The similarity in the characteristics and timing of the metamorphism and bulk crustal shortening directions between the Okcheon and Imjingang belts suggest that the peak metamorphic conditions tend to increase toward the western part (Imjingang belt and southwestern part of the Gyeonggi Massif) from the eastern part (Taebaeksan basin). The E-W bulk crustal shortening influenced the eastern part of the Okcheon belt, whereas the N-S bulk crustal shortening resulted in strong deformation in the Imjingang and Okcheon belts. Consequently, the Permo-Triassic Songrim orogeny in the Korean peninsula is probably not only related to collision of the North and South China blocks, but also to the amalgamation of terrane fragments at the eastern Eurasia margin (e.g., collision of the Sino-Korean continent and the Hida-Oki terrane).

• Journal of the Korean Arthroscopy Society
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• v.11 no.1
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• pp.39-44
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• 2007

Purpose: To evaluate the results of subtalar arthroscopy and to define the indications for the procedure. Materials and Methods: Fifty-four patients were followed up for more than 1 year after subtalar arthroscopy. The mean age was 40 years, and the mean follow-up period was 18 months. Preoperative diagnoses included sinus tarsi syndrome in 19 cases, degenerative arthritis in 13 cases, calcaneal fracture in 10 cases, arthrofibrosis in 5 cases, os trigonum syndrome in 3 cases, talar fracture in 3 cases, talocalcaneal coalition in 3 cases and calcaneal tumor in 1 case. Clinically AOFAS ankle-hindfoot scale and satisfaction of the patients were evaluated. Results: There were 23 synovectomies, 13 subtalar fusions, 11 diagnostic arthroscopies, 5 adhesiolyses, 4 loose body removals, 3 excisions of os trigonum and 1 arthroscopic reduction of fracture. Twenty-five ankle arthroscopies and 11 modified Brostrom's operations were performed for the accompaning 17 ankle impingment syndromes, 11 chronic ankle instabilities and 7 osteochondral lesions of talus. AOFAS ankle-hindfoot scale was increased from 33 points preoperatively to 77 points postoperatively in subtalar fusion group, and was increased from 69 points preoperatively to 89 points postoperatively in other-than-fusion group. Ninety one percent of patients were satisfied with the procedures. There were no serious complications related to the subtalar arthroscopy. Conclusion: Subtalar arthroscopy appears to be safe and highly accurate procedure for subtalar pathology, although it requires technical expertise.