• 한국지능시스템학회논문지
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• 제25권1호
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• pp.78-84
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• 2015

로봇 비전, 3차원 형상 모델링 그리고 모션 제어를 하기 위해 3차원 깊이 추정이 필요하다. 기존에 제안 되었던 깊이 추정 방법은 렌즈와 물체사이의 거리를 변화시켜 가면서 취득된, 일련의 전체영상에 대해서 초점값을 계산하는 방법에 기초하고 있다. 그러나 이러한 방법은 전체 영상에 대해서 초점값 계산을 위한 마스크 연산을 하기에 수행 시간이 오래 걸리는 단점이 있다. 이에 반해서 본 논문에서 제안하는 방법은 물체간의 깊이를 추정하는 시간을 개선하기 위하여 전체 영상을 고려하지 않고, 물체간의 경계면과 경계면 부근의 영상 정보만을 이용하여 깊이를 추정한다. 특히 직선과 원으로 구성된 물체의 경계면을 검출하기 위해서 허프 변환을 이용하였으며, 깊이 추정은 초점 정보를 이용하였다. PCB 영상을 이용하여 실험을 수행한 결과, 이전에 비해서 더욱 효과적인 깊이 추정이 가능함을 알 수 있었다.

• 벤처창업연구
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• 제16권6호
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• pp.119-130
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• 2021

본 연구는 팬데믹한 불확실성하에서 창업동기에 영향을 미치는 조절초점과 기업가정신에 관한 연구이다. 특히 국내의 선행연구에서 유의성이 관측되지 않은 방어초점과 위험감수성, 경제적 창업동기 사이의 실증분석에서 한계점으로 제언하고 있는 표본의 다양성에 집중하여 보완적으로 검증하고자하였다. 또한 코로나19로 불확실성이 심화되고 경제상황이 큰 타격을 받고 있는 특수한 외부환경 아래에서 창업동기에 영향을 미칠 수 있는 선천적 성향의 개인특성인 조절초점과 위험감수성을 회귀분석하고, 조절초점과 창업동기 사이에서 위험감수성의 매개효과를 실증하였다. 실증결과, 방어초점과 위험감수성, 경제적 창업동기에 유의미한 영향을 미치는 것으로 나타났으며, 방어초점과 경제적 창업동기 사이에서 위험감수성이 매개효과를 가지는 것으로 나타냈다. 이러한 결과는 기존의 선행연구에서는 관측되지 않은 결과로써 의미가 있으며, 선천적 성향이 큰 개인특성인 조절초점이 후천적 성향의 위험감수성과 상호작용하여 창업동기에 영향을 주는 것으로 판단된다. 이러한 연구결과는 갈수록 심화되는 외부환경의 불확실성 속에서 창업을 꿈꾸거나 창업하려는 창업가에게 기업가정신 또는 창업교육 프로그램을 할 때 조절초점과 위험감수성을 이해하고 집중함으로써 실질적 도움을 줄 수 있을 것이다. 반면, 선행연구와 다른 이러한 결과들이 표본의 다양성 효과인지 아니면, 코로나19같은 외부환경의 영향인지 확인할 필요가 있으며, 추후 추가연구를 통하여 재검증이 필요하다.

• International Journal of Computer Science & Network Security
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• 제22권3호
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• pp.382-388
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• 2022

Satellite communication for high altitude platform stations (HAPS) and low earth orbit (LEO) systems suffer from dust and sand (DU&SA) storms in the desert regions such as Saudi Arabia. These attenuations have a distorting effect on signal fidelity at high frequency of operations. This results signal to noise ratio (SNR) to dramatically decreasing and leads to wireless transmission error. The main focus in this paper is to propose common relations between HAPS and LEO for the atmospheric impairments affecting the satellite communication networks operating above Ku-band crossing the propagation path. A double phase three dimensional relationship for HAPS and LEO systems is then presented. The comparison model present the analysis of atmospheric attenuation with specific focus on sand and dust based on particular size, visibility, adding gaseous effects for different frequency, and propagation angle to provide system operations with a predicted vision of satellite parameters' values. Skillful decision and control system (SD&CS) is proposed to control applied parameters that lead to improve satellite network performance and to get the ultimate receiving wireless signal under bad weather condition.

• 한국엔터테인먼트산업학회논문지
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• 제13권4호
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• pp.321-329
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• 2019

본 연구는 일상생활에 중점을 둔 가상현실 훈련이 뇌졸중 환자의 상지기능과 일상생활활동에 미치는 효과를 알고자 하였다. 만성 뇌졸중 환자 20명이 본 연구에 참여하였다. 모든 대상자는 실험군 10명과 대조군 10명으로 배정되었다. 두 군은 하루 30분, 주 5회, 4주 동안 보편적인 재활치료를 받았다. 실험군은 일상생활에 중점을 둔 가상현실 훈련을 각 회기마다 30분 추가로 받았으며, 대조군은 일반적인 가상현실 훈련을 30분 받았다. 상지기능을 측정하기 위해 Fugl-Meyer 평가를 수행하였고, 일상생활활동 능력을 알아보기 위하여 기능적 독립척도를 수행하였다. 연구 결과, 두 군은 중재 전과 후로 상지기능과 일상생활활동에서 유의한 향상을 보였다(p<.05). 두 군의 중재 전과 후의 변화량을 비교한 결과, 실험군은 대조군보다 Fugl-Meyer 평가 하위항목 중 손목과 기능적 독립척도 총점과 자기관리, 대·소변 관리에서 유의하게 더 큰 향상이 있었다(p<.05). 본 연구의 결과는 일상생활에 중점을 둔 가상현실 훈련이 일반적인 가상현실 훈련보다 뇌졸중 환자의 손목 기능과 일상생활활동에 더 나은 효과가 있음을 제안한다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.280-284
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• 1997

In this paper, Nonlinear VSS control based on bang-bang control concept is derived under the assumption that the control input is bounded. We try to derive control algorithm which has almost same performance as the time optimal control. We focus this control scheme on the real implementation of DC motor position controller of flexible link, i.e. we obtain the switching curves from the real data of DC motor system operating under the full maximum and minimum applied voltages. State space is separated into several regions and we set different switching surfaces in each region to reduce chattering problem. The efficiency of the proposed controller is compared with PID controller and it is shown that the controller converges fast than PID controller without chattering. The hybrid controller scheme is also proposed not only to control the position of hub but also to reduce the vibration of end tip of flexible link.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.108-108
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• 2000

This application study presents a solution to control a Permanent Magnet Synchronous Motor without sensors. The use of this system yields enhanced operations, fewer system components, lower system cost, energy efficient control system design and increased efficiency. The control method presented is field oriented control (FOC). The sinusoidal voltage waveforms are generated by the power module using the space vector modulation technique. A practical solution is described and results are given in this application Study. The performance of a Sensorless architecture allows an intelligent approach to reduce the complete system costs of digital motion control applications using cheaper electrical motors without sensors. This paper deals with an overview of sensorless solutions in digital motor control applications whereby the focus will be the new Controller without sensors and its applications.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 전력전자학술대회 논문집
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• pp.423-427
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• 1998

A new single-switch, three-phase, high power factor, multi-resonant, ZCS buck rectifier that operates in the continuous conduction mode has been reported. Basically, pulse frequency modulation method should be adopted to suitably control the system. This paper puts main focus on the methods how the pulse frequency modulation can be implemented and a comprehensive investigation on the corresponding control loops is coducted.

• Asian Pacific Journal of Cancer Prevention
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• 제15권16호
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• pp.6609-6612
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• 2014

Opisthorchis viverrini is an ongoing public health problem in Northeast Thailand. Despite continuous efforts for decades by healthcare organizations to overcome this problem, infection rates remain high. To enable related personnel to identify and address the various issues effectively, a cross-sectional study was performed to investigate prevalence and risk factors for opisthorchiasis. The target group was 3,916 Thai residents of Northeast Thailand who were 15 or over. Participants were recruited using the 30 clusters sampling technique. The data were gathered through questionnaires, focus group discussions, in-depth interviews, and stool examinations for parasite eggs (using the Modified Kato Katz method). The data were analyzed using descriptive and inference statistics; in order to ascertain the risk factors and test them using the odds ratio and multiple logistic regressions. The prevalence of opisthorchiasis was 22.7% (95%CI: 0.26 to 0.24). The province with the highest prevalence was Nakhorn Phanom (40.9%; female to male ratio =1:1.2). The age group with the highest prevalence was 40-49 year olds. All age groups had a prevalence >20%. Four of seven provinces had a prevalence >20%. The factors related to opisthorchiasis were (a) sex, (b) age (especially > 50), (c) proximity and duration living near a water body, and (d) eating raw and/or fermented fish. In order to reduce the prevalence of opisthorchiasis, the focus in populations living in upper Northeast Thailand should be changing their eating behaviors as appropriate to their tradition and context.

• Asian Pacific Journal of Cancer Prevention
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• 제15권2호
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• pp.589-594
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• 2014

Few studies have examined reasons why those with low socioeconomic status do not adequately receive cancer screening. We therefore conducted a qualitative study to assess the barriers to cancer screening in people with low socioeconomic status, and to examine the reasons why Medical Aid Program (MAP) recipients do not participate in the National Cancer Screening Program (NCSP). A focus group methodology was used. Participants included MAP recipients (men aged 45-79 years, women aged 35-79 years) who had been invited to cancer screening at least twice based on the NCSP protocol, but had not been screened for any cancer from 2009-2012. We recruited participants living in the cities of Goyang and Paju. A total of 23 MAP recipients participated in four focus group discussions, including 12 men and 11 women. In this qualitative study, we identified six barriers to screening: lack of trust in the NCSP and cancer screening units; fear of being diagnosed with cancer; discomfort or pain from the screening procedure; lack of time, lack of knowledge about cancer screening or lack of awareness of the existence of the NCSP; physical disability or underlying disease; and logistic barriers. Interventions such as individualized counseling, letters and reminders, or other individually-targeted strategies, especially for those with lower socioeconomic status are required to increase participation and reduce disparities in cancer screening.

• 제어로봇시스템학회논문지
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• 제10권2호
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• pp.103-111
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• 2004

In this survey paper, we attempt to introduce the subjects of fuzzy logic and neural network technology for flight control systems based on completed and ongoing research programs other developed countries. Also, it is prepared with intention of providing the reader with an overview of related topics and a basic concepts of fuzzy logic and neural network control. The focus is on relatively practical control schemes realistically applicable in the area of flight control system design that could find its usage in the near future in our country. It is hoped that this paper will serve as a useful reference and even concepts provide solutions far current problems and future designs.