• 제목/요약/키워드: Exposure limiting times

검색결과 12건 처리시간 0.027초

저온 작업환경이 인간의 생리적 반응 및 작업 수행도에 미치는 영향 (An Effect of Cold Environment on Human's Physiological Responses and Task Performances)

  • 구학근;곽효연
    • Journal of Advanced Marine Engineering and Technology
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    • 제31권5호
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    • pp.622-629
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    • 2007
  • Some worker is occupationally exposed to cold and freezing environment. The cold stimuli in the working environment impose physiological and psychological loads on workers to decrease the task performance. The purpose of this study is to investigate the cold stimuli of cold and freezing stores widely used in Busan can make an effect on human's physiological responses and task performance, experimentally and analytically. In the experiment, 5 workers are selected as subjects, and then their skin temperatures of hand and ear, heart rates, blood pressure, and ring test performances in cold($3^{\circ}C$) and freezing($-22^{\circ}C$) stores were measured for 21 minutes and analyzed by using statistical method. It is observed that a physiological variation and the task performance are significantly influenced by an exposure time as well as a strength of cold stimuli. Also, it is suggested the exposure limiting times for the useful manual work and the performance predict model of the ring tasks. The result of this study will be useful for a fundamental data of which design the standard task time of manual tasks and solve the job placement problem of worker selection and placement in cold environment.

Effects of polymer support fluid on shaft resistance of offshore bored piles

  • Chungsik Yoo;Chun-Won Shin
    • Geomechanics and Engineering
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    • 제33권5호
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    • pp.519-528
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    • 2023
  • In this paper, we present the results of an experimental study on the effect of polymer support fluid on shaft resistance of offshore bored piles. A series of pullout tests were performed on bored piles installed under various boundary conditions considering different types of grounds and support fluids, and a range of support fluid exposure times. Contrary to previous studies concerning onshore bored piles, a time dependent effect of polymer fluid on shaft resistance was observed in all ground types. The adverse effect of polymer support fluid on the shaft resistance, however, was considerably less than bentonite support fluid for a given exposure time. No significant reduction in shaft resistance was evident when limiting the exposure time of the polymer support fluid to the side wall of the borehole within 2-3 hours. The degree to which the polymer fluid affects shaft resistance seemed to vary with the ground type. A proper consideration should be given to the time dependent effect of polymer fluid on shaft resistance of bored piles installed in offshore construction environment to limit its adverse effect on the pile performance. The practical implications of the findings are discussed.

Computed Radiography의 영상특성에 관한 연구 (Study of Image Properties for Computed Radiography)

  • 류기현;정재은
    • 대한디지털의료영상학회논문지
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    • 제10권2호
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    • pp.23-31
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    • 2008
  • Computed radiography(CR) has been widely used in the field of diagnostic radiography since digital X-ray image was introduced. The imaging performance of CR system was studied by analyzing the digital image data of the CR images which are the outcomes of the whole imaging system composed of image plate(IP), laser digitizer, analoge-digital convertor, and a given image processing unit. In this study, we used a conventional CR system made by Agfa. From the flat field image of 150$\times$150 image pixels, signal-to-noise ratio(SNR) was calculated. SNR of the CR image increases in proportion to logarithm value of the X-ray exposure irradiated on the IP. SNR is less than about 6 at the exposure below 0.2mR and is more than 10 at the exposure above 0.54mR. In our study, most of images obtained by the smaller exposures less than 2.0mR can not be readable. In general, the minimum value of the SNR ranges from 3 to 5. We obtained modulation transfer function(MTF) by analyzing the bar pattern image which was made under conditions as follows: X-ray tube potential was 55kVp, the IP exposure was 0.54 mR, and the distance between X-ray source to IP was 2m, where bar pattern was located on the IP. MTF is 23% at 2.5lp/mm spatial frequency. Provided that the MTF of noise equivalent modulation is 10%, the CR system has the limiting spatial resolution of 3.2lp/mm. If the image sharpness is evaluated by the spatial frequency where MTF is 50%. the corresponding spatial frequency is 0.5$\sim$0.75lp/mm. MTFA(Modulation Transfer Function Area) is 1.0lp/mm. Compared with the Fuji CR whose MTFA is 1.1lp/mm, Agfa CR in this study shows almost same MTFA performance.

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Seoul National University Camera II (SNUCAM-II) : The New SED Camera for Lee Sang Gak Telescope (LSGT)

  • Choi, Changsu;Im, Myungshin
    • 천문학회보
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    • 제42권1호
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    • pp.35.1-35.1
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    • 2017
  • We present the characteristics and the performance of the new CCD camera system, SNUCAM-II (Seoul National University CAMera system II) that was installed on the Lee Sang Gak Telescope (LSGT) at the Siding Spring Observatory Australia in 2016. SNUCAM-II consists of a deep depletion chip covering a wide wavelength from $0.3{\mu}m$ to $1.1{\mu}m$ with high sensitivity (QE at 90%). It is equipped with SDSS ugriz filters and 13 medium band width (50nm) filters. On LSGT, SNUCAM-II covers $15.7{\times}15.7arcmin$ FOV at pixel scale of 0.92 arcsec and a limiting magnitude of g = 19.91 AB mag at $5{\sigma}$ with 180s exposure time. SNUCAM-II will enable us to study Spectral Energy Distributions (SEDs) of diverse objects from extragalactic sources to solar objects in the southern hemisphere for research and education activities.

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자기제한적 표면반응에 의한 ZnO 박막성장 및 기판온도에 따른 박막특성 (Self-Limiting Growth of ZnO Thin Films and Substrate-Temperature Effects on Film Properties)

  • 이두형;권새롬;이석관;노승정
    • 한국진공학회지
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    • 제18권4호
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    • pp.296-301
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    • 2009
  • ZnO에 대한 박막증착 연구를 위하여 유도결합 플라즈마 원자층박막증착(inductively coupled plasma assisted atomic layer deposition: ICP-ALD) 장치를 제작하고, 장치에 대한 기본 공정조건을 설정하기 위하여 플라즈마를 유도하지 않은 상태에서 p-type Si(100) 기판 위에 ZnO 박막을 증착하는 다양한 실험을 수행하였다. Zn 전구체(precursor)로는 Diethyl zinc [$Zn(C_2H_5)_2$, DEZn]를, 반응가스(reaction gas)로는 $H_2O$를, 캐리어(carrier) 및 퍼지가스(purge gas)로는 Ar을 사용하였다. 기판온도 $150^{\circ}C$에서 DEZn, $H_2O$, Ar의 공급시간을 변화시켜가면서 자기제한적 표면반응(self-limiting surface reaction)에 의한 박막성장조건을 성공적으로 유도하였다. 기판온도를 변화시켜가면서($90{\sim}210^{\circ}C$) 증착실험을 반복하여, 본 장치에 대한 ALD 공정온도(thermal ALD process window)를 확립하고 성장된 ZnO박막에 대한 증착특성, 결정성, 불순물 및 내부조성비등을 조사하였다. ALD 공정온도는 기판온도 $110{\sim}190^{\circ}C$로써 이 구간에서의 박막 평균증착률은 0.29 nm/cycle로 일정하게 나타났다. 기판온도가 높아질수록 결정성이 향상되어 ZnO(002) 피크가 우세하였다. 모든 ALD 공정온도에서 Zn와 O로만 구성된 고순도의 ZnO 박막을 실현하였는데, 온도가 높아질수록 Zn와 O의 비가 1에 근접하며 안정된 hexagonal wurtzite ZnO 구조의 박막이 성장되었다.

SEOUL NATIONAL UNIVERSITY CAMERA II (SNUCAM-II): THE NEW SED CAMERA FOR THE LEE SANG GAK TELESCOPE (LSGT)

  • Choi, Changsu;Im, Myungshin
    • 천문학회지
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    • 제50권3호
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    • pp.71-78
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    • 2017
  • We present the characteristics and the performance of the new CCD camera system, SNUCAM-II (Seoul National University CAMera system II) that was installed on the Lee Sang Gak Telescope (LSGT) at the Siding Spring Observatory in 2016. SNUCAM-II consists of a deep depletion chip covering a wide wavelength from $0.3{\mu}m$ to $1.1{\mu}m$ with high sensitivity (QE at > 80% over 0.4 to $0.9{\mu}m$). It is equipped with the SDSS ugriz filters and 13 medium band width (50 nm) filters, enabling us to study spectral energy distributions (SEDs) of diverse objects from extragalactic sources to solar system objects. On LSGT, SNUCAM-II offers $15.7{\times}15.7$ arcmin field-of-view (FOV) at a pixel scale of 0.92 arcsec and a limiting magnitude of g = 19.91 AB mag and z=18.20 AB mag at $5{\sigma}$ with 180 sec exposure time for point source detection.

보행 환자에서의 위볼기동맥천공지뒤집기피판을 이용한 허리엉치 부위 연부조직 결손의 치료 (Superior Gluteal Artery Perforator Turn-Over Flap Coverage for Lumboscaral Soft Tissue Defect in Ambulatory Patient)

  • 문석호;김동석;오득영;이중호;이종원;서제원;안상태
    • Archives of Plastic Surgery
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    • 제37권5호
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    • pp.712-716
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    • 2010
  • Purpose: Extensive lumbosacral defects after removal of spinal tumors have a high risk of wound healing problems. Therefore it is an effective reconstructive strategy to provide preemptive soft tissue coverage at the time of initial spinal surgery, especially when there is an instrument exposure. For soft tissue reconstruction of a lumbosacral defect, a variation of the gluteal flap is the first-line choice. However, the musculocutaneous flap or muscle flap that is conventionally used, has many disadvantages. It damages gluteus muscle and causes functional disturbance in ambulation, has a short pedicle which limits areas of coverage, and can damage perforators, limiting further surgery that is usually necessary in spinal tumor patients. In this article, we present the superior gluteal artery perforator turn-over flap that reconstructs complex lumbosacral defects successfully, especially one that has instrument exposure, without damaging the ambulatory function of the patient. Methods: A 67 year old man presented with sacral sarcoma. Sacralectomy with L5 corpectomy was performed and resulted in a $15{\times}8\;cm$ sized complex soft tissue defect in the lumbosacral area. There was no defect in the skin. Sacral stabilization with alloplastic fibular bone graft and reconstruction plate was done and the instruments were exposed through the wound. A $18{\times}8\;cm$ sized superior gluteal artery perforator flap was designed based on the superior gluteal artery perforator and deepithelized. It was turned over 180 degrees into the lumbosacral dead space. Soft tissue from both sides of the wound was approximated over the flap and this provided in double padding over the instrument. Results: No complications such as hematoma, flap necrosis, or infection occurred. Until three months after the resection, functional disturbances in walking were not observed. The postoperative magnetic resonance imaging scan shows the flap volume was well maintained over the instrument. Conclusion: This superior gluteal artery perforator turn-over flap, a modification of the conventional superior gluteal artery perforator flap, is a simple method that enabled the successful reconstruction of a lumbosacral defect with instrument exposure without affecting ambulatory function.

Polarimetry of solar system small bodies using the Seoul National University 61cm telescope and TRIPOL

  • Jin, Sunho;Ishiguro, Masateru;Kwon, Yuna Grace;Geem, Jooyeon;Bach, Yoonsoo P.;Seo, Jinguk;Sasago, Hiroshi;Sato, Shuji
    • 천문학회보
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    • 제44권1호
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    • pp.64.2-64.2
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    • 2019
  • It is known that lights scattered by comets and asteroids are partially polarized. From polarimetric observations of those objects, we can investigate physical properties, such as albedos, sizes of cometary dust particles and regolith of asteroids. Since the polarization degrees of those objects highly depend on their phase angles (Sun-object-observer's angles), long-term monitoring observations are required. Moreover, comets show unforeseeable activations (i.e., outbursts) which need follow-up observations to understand the mechanism. In order to realize such monitoring and transient observations, we installed the Triple-Range Imager and POLarimeter (TRIPOL) on the 61cm telescope of Seoul National University (Hereafter, SNU) Gwanak campus. With this combination, we can obtain g', r', i' bands photopolarimetric images simultaneously with $8.0^{\prime}{\times}8.0^{\prime}$ field of view and pixel resolution of 0.94" pixel-1. Here, we make a presentation regarding the photometric and polarimetric performances of TRIPOL on the SNU 61cm telescope. In addition, we introduce initial polarimetric results of asteroid and comets with the instruments. First, we determine the limiting magnitudes (defined as magnitudes for S/N=5) of $15.17{\pm}0.06$ (g'-band), $15.68{\pm}0.01$ (r'-band), $16.24{\pm}0.03$ (I'-band), respectively, with total 240-seconds exposure (four 60-seconds exposure images, each was taken at different rotation angle for the half-wave plate). Second, we found that the instrumental polarization is negligibly small, ($-0.32{\pm}0.04%$ in the g', $-0.36{\pm}0.05%$ in the r' and $-0.21{\pm}0.04%$ in the i'-bands), while the polarization efficiencies are large enough to maximize the performance (i.e., $97.52{\pm}0.03%$ in the g', $98.83{\pm}0.02%$ in the r' and $99.15{\pm}0.02%$ in the i'-bands). With the instruments, we made observations of three Jupiter-family comets, 21P/Giacobini-Zinner, 38P/Stephan-Oterma, and 46P/Wirtanen and plan to observe one near-Earth asteroid, (433) Eros, on a trial basis. Especially for comets, we discriminate signals from dust and gas to eliminate gas contamination, which are known to change observed degree of linear polarization, using multi-band images. We confirm that the phase angle dependency of these comets are consistent with previous observations, probably because polarimetric property of Jupiter-family comets are broadly homogeneous unlike asteroids. We will also describe future observation plans using TRIPOL and SNU 61cm telescope.

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3차원 시각노출도를 이용한 전주 풍남문 역사문화환경보존지역의 경관 관리 효과 분석 (An Effectiveness Analysis of Landscape Management for the Historic and Cultural Environment Preservation Area of the Pungnammun Gate, Jeonju, by Applying 3D Visual Exposure)

  • 이재용
    • 한국전통조경학회지
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    • 제36권2호
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    • pp.30-37
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    • 2018
  • 문화재의 경관을 보호하기 위해 설정된 개인 소유의 건축물에 대한 일괄적인 높이 규제 기준은 토지 소유자의 개발을 제한함으로써 심각한 사회적 갈등의 원인이 되고 있다. 이러한 갈등을 해소하고 도시 개발과 문화재의 경관 관리를 동시에 충족시킬 수 있는 건축물의 높이 규제 기준을 평가할 수 있는 지표의 도입이 절실히 요구되고 있는 상황이다. 이에 본 연구는 건조물 문화재가 도시의 상징적 경관을 형성하고 있는 전주 풍남문(보물 제308호)과 그 주변 지역을 대상으로 문화재보호법과 국토의 계획 및 이용에 관한 법률에 따른 경관 변화를 시뮬레이션하고, 3차원 시각노출도라는 지표를 적용함으로써 경관의 정량적 평가를 시도하였다. 그 결과, 풍남문의 조망 기회와 조망 부위는 관련 법규에 따른 경관 변화가 발생하더라도 큰 영향을 받지 않는 것으로 나타났다. 다만 개발 용량이 가장 큰 국토의 계획 및 이용에 관한 법률에 의한 건축물의 높이 변화는 배경 건물의 3차원 시각노출도를 현황 보다 2배 이상 증가시킴으로써 풍남문의 식별을 약화시킬 수 있는 가능성이 확인되었다. 또한 풍남문의 스카이라인은 국토의 계획 및 이용에 관한 법률에 따른 개발 시 확연히 침해되는 현상이 나타났으나 문화재보호법에 의한 규제에 있어서는 현황과 유사하게 유지되는 것으로 확인되었다. 이와 같이 본 연구는 3차원 시각노출도의 적용을 통해 건축물의 높이 변화에 따른 문화재로의 조망 기회와 조망 부위의 변화, 스카이라인의 침해 여부 등을 정량적으로 평가하기 위한 프로그램을 개발하고, 도심 지역에 위치한 문화재의 경관 평가 지표로서 3차원 시각노출도의 활용 가능성을 보여주었다는 점에서 의의가 있다.

동계 Plastic house내 고추(Capsicum annuum L.) 육묘시 온도와 광도가 생장에 미치는 영향 I. 다중피복 고추육묘 시설내의 온도 및 광환경 영향 (Effects of Temperature and Light Intensity on the Growth of Red Pepper(Capsicum annuum L.) in Plastic House During Winter. I. Fluctuations of Temperature and Light Environment in the Multilayered Plastic House Grown Red Pepper)

  • 정순주;이범선;권용웅
    • 생물환경조절학회지
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    • 제3권2호
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    • pp.106-118
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    • 1994
  • 동계 무가온 다중피복 plastic house내 고추육묘의 생장에 영향을 미치는 온도, 광도 및 지온의 변화를 노지와 시설내 피복별로 조사 분석하여 고추의 적정 육묘생장 환경과 실제 무가온 다중피복 plastic house내의 환경요인과의 관련성을 파악코자 수행한 결과는 다음과 같다. 1. 12월 20일부터 2월 25일 까지 P. E.필름으로 4중피복된 턴널내에서도 최저온도는 대부분 5$^{\circ}C$를 보여 고추의 냉해온도에 대한 노출을 피할 수 없었고 이 기간에 최고온도는 대부분 33$^{\circ}C$를 보였으며 극값은 42$^{\circ}C$를 보여 다소간 환기의 필요도 인정되었다. 2. 피복이 증가할수록 온도 일교차가 크게 나타나 노지는 5-1$0^{\circ}C$를 보인 반면 피복내에는 16-38$^{\circ}C$의 일교차를 보였다. 3. 저온기에 다중피복에 의한 보온효과는 뚜렷하였으나 4중피복하에서도 12$^{\circ}C$이하의 온도출현이 많아서 고추 시설내 육묘시 냉해피해 가능성이 상존하며, 3$0^{\circ}C$이상의 고온출현회수도 200회 이상이었다. 4. 광도에 있어서도 피복이 증가할수록 광도는 감소하였고 온도증가는 크게 광의존성이었으며, 최저광도는 피복에 관계없이 고추의 광보상점 이하를 보여주었다. 5. 12월 20일부터 2월 중순까지 기온은 오전 10시 이후에야 고추의 생육한계온도인 10-12$^{\circ}C$이상이 되었고, 오후 4시 이후에는 기온은 12$^{\circ}C$이상이 되어도 광도가 급격히 낮아 고추유묘의 광합성 및 생장에 제한적일 것으로 사료되었다. 6. 시설내 최저지온은 동계 4중피복내에서도 1$0^{\circ}C$내외로서 고추생장에는 생리적 피해온도 범위에 속하였다. 7. 광주지방에 45년간 온도자료를 보면 노지 최저온도의 극값은 1월 5일에 -19.4$^{\circ}C$를 기록하였으며 대부분 장기자료로부터 얻은 평균에서 $\pm$5$^{\circ}C$의 편차를 보였다.

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