• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 심포지엄 논문집 정보 및 제어부문
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• pp.59-61
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• 2004

Researches about scheduling distributed real-time systems have some weak points, not scheduling both sporadic and periodic tasks and messages or being unable to guaranteeing the end-to-end constraints due to omitting precedence relations between sporadic tasks. This paper describes the application model of sporadic tasks with precedence constraints in a distributed real-time system. It is shown that existing scheduling methods such as Rate Monotonic scheduling are not proper to be applied to the system having sporadic tasks with precedence constraints. So this paper proposes an end-to-end laxity-based priority assignment algorithm which considers the practical laxity of a task and allocates a proper priority to a task.

• 전력전자학회논문지
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• 제23권6호
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• pp.381-388
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• 2018

A novel and simple algorithm for accurate calculation of RMS voltage is proposed in a digitally controlled grid-tie inverter system. Given that the actual frequency of grid voltage is continuously changing, the constant sampling frequency cannot be a multiple number of the fundamental frequency. Therefore, the RMS of grid voltage contains periodic oscillations due to the differences in the phase angle of sampled data during calculation. The proposed algorithm precisely calculates and updates the initial phase angle of the first sampled voltage in a half-cycle period using phase-locked loop, which is commonly utilized for phase angle detection in grid-tie inverter systems. The accuracy and dynamic performance of the proposed algorithm are compared with those of other algorithms through various simulations and experiments.

• 대한수학회논문집
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• 제34권3호
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• pp.967-979
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• 2019

Chaotic dynamical systems, preferably on a Cantor-like space with some arithmetic operations are considered as good pseudo-random number generators. There are many definitions of chaos, of which Devaney-chaos and pos itive topological entropy seem to be the strongest. Let $A=\{0,1,{\dots},p-1\}$. We define a continuous map on $A^{\mathbb{Z}}$ using addition with a carry, in combination with the shift map. We show that this map gives rise to a dynamical system with positive entropy, which is also Devaney-chaotic: i.e., it is transitive, sensitive and has a dense set of periodic points.

• 대한수학회보
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• 제61권1호
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• pp.247-262
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• 2024

In this paper we introduce and study the notions of topological sensitivity and its stronger forms on semiflows and on product semiflows. We give a relationship between multi-topological sensitivity and thick topological sensitivity on semiflows. We prove that for a Urysohn space X, a syndetically transitive semiflow (T, X, 𝜋) having a point of proper compact orbit is syndetic topologically sensitive. Moreover, it is proved that for a T₃ space X, a transitive, nonminimal semiflow (T, X, 𝜋) having a dense set of almost periodic points is syndetic topologically sensitive. Also, wherever necessary examples/counterexamples are given.

• 한국정보처리학회논문지
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• 제5권10호
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• pp.2725-2736
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• 1998

본 논문은 WRLS-VFF-VT 알고리듬을 이용한 새로운 피치 검색 방법론을 제안하도록 한다. 제안된 알고리듬에서는 VFF(가변 망각 인자)를 사용하여 유성음에서의 주 여기 펄스 시점과 관련된 성문 폐쇄 점을 확인한다. 또한 본 논문은 VFF 기반 알고리듬과 함께 기존의 EGG 와 LP-Error 방법을 이용한 피치 검색 알고리듬에서 가변 한계 값을 이용 수정된 알고리듬을 제안한다. 제안된 알고리듬들은 주기와 주기 근간에서 강인한 피치 측정 능력과 준 주기 및 비 주기성 음성 신호에서도 우수한 피치 검색 기능을 가지고 있음을 알 수 있다. 제안된 알고리듬의 우수성을 입증하기 위해 실제 사람의 자연스러운 음성 및 사람의 비정상 상태 음성에서 준 주기 및 비 주기성 음성 진동 패턴을 확인하고 검출하는 성능 측정을 통하여 표준 SIFT 알고리듬과 비교 평가하였다.

• 한국수학사학회지
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• 제25권4호
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• pp.53-67
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• 2012

오늘날, 우주비행궤도의 정밀계산은 매우 실용적인 학문이 되었다. 프엥카레의 천체역학의 주요 키워드는 적분불변, 주기해, 점근해, 특성지수, 단일값을 갖는 새로운 적분의 불가능성등으로 볼 수 있다. 적분불변은 모든 시간에 걸쳐서 일정한 적분 값을 유지하는 것을 말한다. 곡선의 호상에서 취한 적분은 2, 3차원으로 확장하였다. 고유치는 궤적의 형식에 따라서 분류되는 바 매듭, 초점들, 말 안장점, 중심과 같은 것이다. 주기해에서는 고유값에 해당하는 특성지수에 따라서 주기해를 갖는다고 하였다. 주기해의 안정성은 특성지수의 성질을 조사하는 것과 동일한 것이다. 분지라고 불리는 천체궤도의 카오스적 존재 가능성을 프엥카레는 예외적 궤도의 존재로 주장하였고, 이는 아다마르의 견해대로 우연에 의한 확률적 궤도의 존재를 말하는 것이다. 호모크리닉점의 존재는 삼체문제의 이중 점근해를 말하고, 이것은 궤적이 카오적임을 말해주는 것이다. 주어진 조건에 따라서 엑스포넨셜 함수의 고유값인 특성지수가 계속 변함으로, 매우 작은 간격에서도 분지들은 얻게 되고, 원래의 주기와는 다소 멀어지는 것이다. 주기해의 안정성문제는 특성지수를 연구하는 것과 같다. 프엥카레는 궤적의 거동이 선형변환의 고유값 성질에 의존하고 이 고유값들과 서로 다른 특이점들 사이에 매우 밀접한 관련이 있음을 발견하였다. 뷔른스, 질덴, 순드만, 힐, 다윈, 벌코프, 하이테커, 아다마르등의 이론전개는 프엥카레의 이론과 불가분의 관계를 갖는다.

• 대한한방내과학회지
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• 제21권4호
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• pp.575-581
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• 2000

Objective : Asthma is a lung disorder characterized by periodic attacks of wheezing alternating with periods of relatively normal breathing. And quality of life in asthmatic patients shows a tendency to decrease. So we had a clinical study whether if oriental medical treatment could improve their quality of life or not. Methods : The 15 cases were new patients that visited at division of respiratory system, department of internal medicine in Kyunghee medical center from the 1 st of July, 2000 to the 1 st of August. All of them were diagnosed as asthma and treated by western medical therapy. We used a Quality of Life Questionnaire for adult Korean Asthmatics(QLQAKA) and evaluated the results after two times answers, at an interval of two weeks. Results : The mean of the first answer was 2.84 marks and 3.36 ones after two weeks. If there is a difference of over 0.5 points between the two, we can admit significant effect. After the asthmatic patients treated by oriental medical therapy, they gained a difference of 0.52 points, 10.4%. Conclusions : We suggest that oriental medical therapy can improve the quality of life of asthmatic patients arid we can alternate side effects of western medical therapy with oriental one. if they carry out two different treatments at the same time.

• Journal of Astronomy and Space Sciences
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• 제5권2호
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• pp.111-122
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• 1988

지구의 비대칭 중력장 $J_2$와 $J_3$가 원궤도에 가까운 인공위성의 궤도요소에 미치는 장, 단주기 섭동과 영년섭동을 해석적 방법으로 구하였다. 이 때 궤도의 이심률이 작은 경우에 섭동방정식에서 발생하는 특이점은 Taff(1985)가 제시한 방법중 궤도요소 e, $\omega$, M을 $e_s$=$esin\omega$, $e_c=e\;cos\;\omega$, $\ell=\omega+M$으로 치환하는 방법을 사용하여 제거시켰다. Walter(1967)의 방법을 이용하여 기상위성 NOAA-10호의 평균궤도요소를 결정하였고 이를 NASA의 Brouwer 평균 궤도요소와 비교하였다. 평균 궤도요소 a, i, $\Omega$는 TBUS의 결과와 거의 일치하나 평균 궤도요소 e, $\omega$, M은 약간의 차이를 보였다. 그리고 특이점을 제거하기 위한 Taff의 방법 중 e, $\omega$, M 대신에 $e_s=e\;sin(\Omega+\omega)$, $e_c=e\;cos(\Omega+\omega)$, $L=\Omega+\omega+M$으로 치환하는 방법이 극궤도위성에는 부적합한 것으로 나타났다.

• 한국산업보건학회지
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• 제28권3호
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• pp.304-311
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• 2018

Objectives: The purpose of this study was to compare the self-reported symptoms of occupational asthma, occupational rhinitis, and respiratory symptoms between a direct exposure to flour dust group and a non-exposure group from the bakery industry. Methods: The participants were 62 workers directly exposed to flour dust and 30 non-exposed workers. The survey was composed of questions related to general characteristics. Korean self-reported respiratory symptoms(SNU-93), occupational asthma, and occupational rhinitis data was collected from April to July 2017. Results: The smoking rate among the direct exposure to flour dust workers was 67.7% and the mean of working hours(11-12) was 96.8%. The SNU-93 questionnaire revealed that respiratory symptoms in the chest and wheezing or whistling were significantly higher among the direct-exposure group than non-exposure group. The response for occupational asthma symptoms was significantly higher in the direct exposure group(2.4 points) than in the non-exposure group(1.6 points). Conclusion: In order to decrease the symptoms of these respiratory diseases among bakery workers exposed to flour dust, it is necessary to reduce working hours and the smoking rate. The performance of periodic medical examinations is needed to find abnormal respiratory diseases. In addition, workers who have been diagnosed with asthma and rhinitis should consider switching to a process that is not exposed to flour dust.

• 대한족부족관절학회지
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• 제18권3호
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• pp.108-114
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• 2014

Purpose: Ligament reattachment technique using a suture anchor appears to show satisfactory functional outcomes and mechanical stability compared with conventional bone tunnel technique. This study was prospectively conducted in order to evaluate functional outcomes of modified Brostrom procedures using the suture bridge technique for chronic ankle instability in athletes. Materials and Methods: Twenty eight athletes under 30 years of age were followed for more than two years after undergoing the modified Brostrom procedure using the suture bridge technique. Functional evaluation consisted of the foot and ankle outcome score (FAOS), foot and ankle ability measure (FAAM) score. Range of motion and time to return to exercise were evaluated using a periodic questionnaire. Talar tilt angle and anterior talar translation were measured through stress radiographs for evaluation of mechanical stability. Results: FAOS improved significantly from preoperative mean 59.4 points to 91.4 points (p<0.001). Daily living and sport activity scores of FAAM improved significantly from preoperative mean 50.5, 32.5 points to 94.8, 87.3 points, respectively (p<0.001). Talar tilt angle and anterior talar translation improved significantly from preoperative mean $16.8^{\circ}$, 13.5 mm to $4.2^{\circ}$, 4.1 mm at final follow-up (p<0.001). Times to return to exercise were as follows: mean 10.2 weeks in jogging, 15.4 weeks in spurt running, 13.1 weeks in jumping, 11.5 weeks in walking on uneven ground, 9.1 weeks in standing on one leg, 7.2 weeks in tip-toeing gait, 8.4 weeks in squatting, and 10.6 weeks in descending stairs. Conclusion: Modified Brostrom procedure using the suture bridge technique showed satisfactory functional outcomes for chronic ankle instability in athletes. Optimal indication and cost-effectiveness of the suture bridge technique will be studied in the future.