• Safety and Health at Work
• /
• 제2권3호
• /
• pp.260-272
• /
• 2011

Objectives: The promotion of health and safety (H&S) awareness among hospital staff can be applied through various methods. The aim of this study was to assess the risk level of physical hazards in the hospital sector by combining workers' perception, experts' evaluation and objective measurements. Methods: A cross-sectional study was designed using multiple triangulation. Hospital staff (n = 447) filled in an H&S questionnaire in a general hospital in Athens and an oncology one in Thessaloniki. Experts observed and filled in a checklist on H&S in the various departments of the two hospitals. Lighting, noise and microclimate measurements were performed. Results: The staff's perception of risk was higher than that of the experts in many cases. The measured risk levels were low to medium. In cases of high-risk noise and lighting, staff and experts agreed. Staff's perception of risk was influenced by hospital's department, hospital's service, years of working experience and level of education. Therefore, these factors should be taken into account in future studies aimed at increasing the participation of hospital workers. Conclusion: This study confirmed the usefulness of staff participation in the risk assessment process, despite the tendency for staff to overestimate the risk level of physical hazards. The combination of combining staff perception, experts' evaluation and objective measures in the risk assessment process increases the efficiency of risk management in the hospital environment and the enforcement of relevant legislation.

• 한국지구과학회지
• /
• 제36권5호
• /
• pp.476-483
• /
• 2015

The high-order Laplacian-type filter, which is capable of providing isotropic and sharp cut-off filtering on the spherical domain, is essential in processing geophysical data. In this study, a spherical high-order filter was designed by combining the Fourier method with finite difference-method in the longitude and latitude, respectively. The regular grid system was employed in the filter, which has uniform angular spacing including the poles. The singularity at poles was eliminated by incorporating variable transforms and continuity-matching boundary conditions across poles. The high-order filter was assessed using the Rossby-Haurwitz wave, the observed geopotential, and observed wind field. The performance of the filter was found comparable to the filter based on the Galerkin procedure. The filter, employing the finite difference method, can be designed to give any target order of accuracy, which is an important advantage being unavailable in other methods. The computational complexity is represented with 2n-1 diagonal matrices solver with n being the target order of accuracy. Along with the availability of arbitrary target-order, it is also advantageous that the filter can adopt the reduced grid to increase computational efficiency.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2002년도 추계종합학술대회
• /
• pp.163-166
• /
• 2002

4세대 통신에서는 고속 통신을 위해 OFDM이 사용되기로 되어 있다. OFDM은 스펙트럼 효율이 좋고 페이딩 채널에 강인하기 때문에 주로 DAB, DVB, IMT2000 그리고 고속 유무선 통신 등에 주로 사용되고 있다. 그러나 OFDM송신 신호는 매우 큰 PAR를 가지고 있기 때문에 상호 변조를 유발 할 수 있다. 따라서 본 논문에서는 PAR를 억제하는 기존 기술인 PTS와 SLM을 비교분석 하였으며 PAR를 더욱 경감하기 위해 PTS와 SLM을 결합한 혼합형 PAR 제거법을 제안하였고 시뮬레이션 결과 기존의 방법보다 성능이 향상됨을 확인할 수 있었다.

• 한국전자파학회논문지
• /
• 제22권12호
• /
• pp.1139-1147
• /
• 2011

본 논문에서는 S대역 400 MHz 대역폭을 갖는 능동 배열 위상레이더 시스템에 적용 가능한 GaN 반도체 전력 증폭기의 설계 및 제작 측정에 관해 소개하였다. GaN 팔레트 증폭 소자를 ${\lambda}$/4 입출력 차이를 둔 결합기를 이용하여 고출력 증폭기를 구현하였고, Suspended 형태의 고출력용 저손실 결합기와 개구면을 이용한 스트립라인 간의 커플러를 사용하여 자동 이득 제어(ALC) 기능을 가지는 고출력, 고효율의 반도체 전력증폭기를 구현하였다. 제작된 반도체 전력증폭기는 자동 이득 제어 미적용 시 최대 출력 5 kW, 효율 27.8 %, 이득 67 dB 특성을 가지며, 자동 이득 제어 적용 시 출력 4 kW, 효율 25.5 %와 duty 10 %, 최장 펄스 200 us에서 droop 0.1 dB 특성을 갖는다.

• Korean Journal of Acupuncture
• /
• 제36권3호
• /
• pp.139-149
• /
• 2019

Objectives : A dermal needle is one of the therapeutic method by stimulating or tapping on the certain points of skin. Recently, roller or stamp-needle have been applied to various diseases in combination with microneedle technology. In this study, we analyzed the trend of roller and stamp-needle in Korean patent. Methods : Electronic search for Korean patent of roller or stamp needle was performed in Korea Intellectual Property Right Information Service database to April, 2019. Results : Sixty seven patents (51, roller-needle; 15, stamp-needle; 1, both types of needle) met the inclusion criteria. According to patent details, 34 of 67 patents were skin stimulation, 14 patents were intended to increase the efficiency of drug delivery through skin stimulation, 16 patents combined skin stimulation with technologies such as electrode or high frequency, and three patents applied both electrode or high frequency stimulation, and drug application as well as physical skin stimulation. Each of these patents aims to increase the efficiency of the needle manufacturing process (n=24), to facilitate the use of tools or to increase the efficiency of the technology (n=61), or to increase the technical skill of the needle itself (n=23). Conclusions : This study confirms that technological advances were being made by combining various types of stimuli to dermal needle and there have been attempts to expand the scope of drug delivery in terms of application of dermal needle. In the future, more research and development is needed in order to apply the dermal needle to modern technology.

• 한국전자통신학회논문지
• /
• 제7권5호
• /
• pp.983-989
• /
• 2012

IEEE 802.3az LPI 메커니즘은 전송할 데이터가 없을 경우 취침 모드로 천이하여 다수의 컴포넌트들을 저전력 상태를 유지하게 함으로써 에너지 효율성을 향상시킨다. LPI는 소량의 데이터가 주기적으로 전송되는 상황에서는 잦은 전송 모드 변환에 따른 오버헤드 때문에 에너지 효율이 크게 개선되지 못하는 문제점이 있다. 본 논문에서는 전송계층 트래픽 특성 및 네트워크 상태에 따라 LPI 모드 상태 천이를 적응적으로 수행하는 개선된 LPI 메커니즘을 제안한다. 시뮬레이션 방법에 의한 성능 분석을 통해 제안한 메커니즘이 다양한 트래픽 부하에 대해서 기존 방법보다 에너지 효율성을 향상시키는 것으로 나타났다.

• 한국통신학회논문지
• /
• 제29권6A호
• /
• pp.677-682
• /
• 2004

본 논문에서는 C-band의 중심 주파수인 6 GHz 대역을 중심으로 광대역 공간 전력 합성기를 설계, 제작하여 그 특성을 고찰하였다. 제안된 공간 전력 합성기는 광대역 특성을 갖는 입ㆍ출력 안테나에 평면형 다이폴 안테나를 사용함으로서 기존의 공간 전력 합성기의 대역폭의 제한을 극복하였고 입ㆍ출력 안테나의 편파를 교차편파가 되도록 사용하였기 때문에 입력단과 출력단의 격러도를 높여서 공간 전력 합성기의 안정성을 향상 시켰다. 설계된 입력부와 출력부 안테나의 대역폭은 각각 24.8%와 23%의 대역폭을 얻었다. 제작한 4${\times}$l 공간 전력 합성기는 6 GHz에서 24.04 dB의 유효 등방성 이득(EIPG), 17% 이상의 이득 대역폭, 68.69%의 전력 합성 효율을 얻었다.

• 대한기계학회논문집A
• /
• 제27권4호
• /
• pp.551-558
• /
• 2003

An efficient and reliable subspace iteration algorithm using the block algorithm is proposed. The block algorithm is the method dividing eigenpairs into several blocks when a lot of eigenpairs are required. One of the key for the faster convergence is carefully selected initial vectors. As the initial vectors, the proposed method uses the modified Ritz vectors for guaranteering all the required eigenpairs and the quasi-static Ritz vectors for accelerating convergency of high frequency eigenvectors. Applying the quasi-static Ritz vectors, a shift is always required, and the proper shift based on the geometric average is proposed. To maximize efficiency, this paper estimates the proper number of blocks based on the theoretical amount of calculation in the subspace iteration. And it also considers the problems generated in the process of combining various algorithms and the solutions to the problems. Several numerical experiments show that the proposed subspace iteration algorithm is very efficient, reliable ,and accurate.

• Journal of Welding and Joining
• /
• 제31권2호
• /
• pp.4-15
• /
• 2013

The laser/arc hybrid welding process is a new process combining the laser beam and the arc as welding heat source. The laser beam and arc influence and assist one another. By application of hybrid welding, synergistic effects are achievable, and disadvantage of the respective processes can be compensated. The laser-arc hybrid welding process has good potential to extend the field of applications of laser technology, and provide significant improvements in weld quality and process efficiency in manufacturing applications. This review analyses the recent advances in the fundamental understanding of hybrid welding processes using the works of the data base of Web of Science (SCI-Expanded) since the 2000 year. The research activity on the hybrid welding has been become more actively since 2006, especially in China, presenting the most research papers in the world. Since the hybrid welding process was adopted in manufacturing of the automobile in Europe in the early of 2000's, its adopting is widely expanded in the field of manufacturing of automobile, ship building, steel construction and the other various industry. The hybrid welding process is expected to advance toward higher productivity, higher precision, higher reliability through the mixing of high power and flexible fiber laser or disk laser and digitalized pulsed arc source.

• Journal of Magnetics
• /
• 제22권1호
• /
• pp.104-108
• /
• 2017

Induction motors have wide applicability in many fields, both in industrial sectors and households, for their advantages of a high efficiency and robust structure. The introduction of power-source-containing harmonics into the induction motor winding lowers its efficiency and increases its temperature, greatly affecting its operation characteristics. In this study, we performed an electromagnetic field analysis using the time-difference finite-element method with the purpose of analyzing the steady-state current characteristics of an induction motor. Additionally, we calculated the steady-state current with a method combining an electromagnetic field equation and a circuit equation. In the electromagnetic field analysis, the nonlinearity was taken into account using the Newton-Raphson method, and a backward time-difference method was employed for the time derivative term. Then, we compared the steady-state current of the induction motor obtained by calculation with the experimentally measured values, thus validating the proposed algorithm. Furthermore, we analyzed the impacts of the shape and material of the rotor conductor bar of the induction motor on the steady-state current of the main winding.