• Title/Summary/Keyword: 반송비

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In-Band Full-Duplex Wireless Communication Using USRP (USRP 장치를 이용한 동일대역 전이중 무선통신 연구)

  • Park, Haeun;Yoon, Jiyong;Kim, Youngsik
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.30 no.3
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    • pp.229-235
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    • 2019
  • The implementation of an in-band full-duplex wireless communication system is demonstrated in this study. In the analog/RF domain, the self-interference(SI) signal is reduced using a separate antenna for the transmitter and receiver paths, and most of the SI signal is canceled in the digital domain. A software defined radio(SDR) is used to implement the in-band full-duplex wireless communication system. The USRP X310 device uses transmitting and receiving antennas. By adjusting the gain of the transmitting and receiving ends of the SDR device, the magnitude of the SI signal entering the receiving antenna, and the size of the received signal from the outside, are both set to -64 dB. To verify the in-band full-duplex wireless communication performance, the source data is image and orthogonal frequency-division multiplexing is used for modulation. A WiFi standard frame with a carrier frequency of 2.67 GHz and bandwidth of 20 MHz is used. In the received signal, the SI signal is canceled by digital signal processing and the SI signal is attenuated by up to 34 dB. OFDM demodulation was impossible when the SI signal was not removed. However, the bit error rate is reduced to $2.63{\times}10^{-5}$ when the SI signal is attenuated by 34 dB, and no error is detected in the 100 Mbit data output as a result of passing through the Viterbi decoder.

Status of Health and Safety Management in Occupational Hygiene Laboratories in Korea

  • Yang, Hyukseung;Choi, Jaewook;Yoon, Seokjoon;FARR, Terry
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.17 no.1
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    • pp.53-62
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    • 2007
  • 목적: 1990년대 초반부터 시작된 우리나라의 산업 보건에 대한 사회적 관심의 증대와 시장의 요구에 따라 산업위생기관의 양적인 팽창이 이루어지긴 하였으나 실험실 관련 안전보건규정이 미비한 상태에서 추진되어 산업위생 실험실에서 다양한 유해 위험성 인자를 취급함에도 불구하고 사용되는 량이 소규모로 인해 안전보건과 관련된 사항은 대부분 간과하고 있으며, 산업위생 실험실의 안전보건관리 실태는 선진외국에 비해 상당히 낙후되어 있는 실정이다. 따라서 본 연구는 우리나라 산업위생 실험실과 관련한 안전보건관리 실태를 평가함으로써 향후 실험실의 안전보건관리 수준을 향상 시키는데 효과적인 자료로 활용하는데 기여하고자 한다. 방법: 산업위생실험실의 안전보건 실태를 파악하기 위해 설문조사를 수행하였으며, 설문은 실험실의 전반적인 안전보건, 화학물질 저장 및 용기, 가연성 및 인화성 화학물질, 가스 실린더, 의사전달, 응급처치 및 비상사태 장비, 정리정돈, 소방안전, 전기안전, 개인보호구, 흄후드 및 환기, 및 이황화탄소 취급 사례로서 12개 영역으로 구성되었다. 연구대상은 2001년 한국산업안전공단 정도관리프로그램에 참여한 기관으로서 총 대상은 119개 기관이었다. 연구기간은 2002년 7월 01일부터 8월 30일까지 약 60일 이었다. 설문은 반송봉투에 넣어 설문완성 후 연구자에게 보낼 수 있도록 배려하였으며, 1차 설문을 보낸 후 2주 후에 설문 참여를 독려하기 위해 엽서를 발송하였고, 다시 2주 후에 각 산업위생기관에 개별 전화 연락을 취하였다. 그 결과 63% (75개 기관)의 완성된 설문을 얻을 수 있었다. 설문의 총 조사항목은 79문항으로 구성되어 있으며, 산업위생실험실의 안전보건 수준을 정량적으로 평가하기 위해 안전보건 매뉴얼, 교육훈련프로그램 및 한국산업안전공단 실험실 지침서를 보유한 기관과 그렇지 않은 기관간의 차이는 선별된 67문항에 대해 각 문항에 합당하거나 적절할 경우 1점을 부여하는 방식으로 점수화하였다. 이들의 관련성을 파악하기 위하여 Microsoft-Excel 2000 프로그램을 이용하여 two-tailed t-test 분석을 실시하였다. 결과 1. 산업위생실험실 운영과 관련한 67개 항목(항목별로 각 1점 부여)에 대한 안전보건 성과지수화 (100점으로 점수 환산) 결과 안전보건 매뉴얼을 보유한 기관은 $42.98{\pm}13.36$(p<0.001)점, 교육훈련프로그램을 보유한 기관은 $50.75{\pm}14.12$(p<0.01)점, 한국산업안전공단 실험실 지침서를 보유한 기관은 $43.58{\pm}11.92$(p<0.01)점으로 그렇지 않은 기관에 비해 통계적으로 유의하게 높은 점수분포를 보였다. 2. 화학물질 보관 캐비닛이 있는 기관 중 64.8%의 기관은 화학물질을 알파벳 순으로, 27.8%는 분류 기준에 따라, 그리고 7.4%는 무작위로 보관하고 있었다. 3. 단지 8.0% (6개)의 기관만이 실험실내에 눈세정 분수(2 개), 샤워기(3개) 및 눈세정물병(3개, 2개 중복 응답 기관)과 같은 응급처치 장치 및 물품을 갖추고 있었다. 4. 89.0%의 기관이 흄후드내에 화학물질을 보관하고 있었다. 5. 물질안전보건자료, 흄후드 기록지, 비상사태 절차서 및 한국산업안전공단 실험실 지침서와 같은 문서관리는 부적절하게 관리 및 기록되고 있었다. 6. 대부분의 산업위생 실험실은 응급처치 장비, 화학물질 또는 가스용기 보관실과 같은 실험실 안전설비가 부족할 뿐만 아니라 정리정돈, 화학물질 저장 캐비닛, 안전보호구 및 흄후드와 같은 관리가 미비하였다. 결론: 이상의 결과에 근거하여 기관장은 실험실의 안전보건관리를 위하여 문서관리체계를 제공하고, 모든 실험실 종사자가 적절한 개인보호구를 착용할 수 있도록 하며, 비상 장비를 설치하고, 실험실과 관련한 적절한 규정을 제정하며, 교육훈련 프로그램을 제공하여야 한다. 또한 실험실 종사자는 실험 중 적절한 개인보호구의 착용하고, 비상장비 이용에 대한 교육훈련에 참여하며, 적절한 실험실 운영관리에 대한 책임감을 가져야 한다. 위의 권고사항 이행을 위해서 KOSHA는 KQCP 프로그램에 실험실 안전보건관리 항목을 삽입하여 주기적인 평가를 수행할 필요가 있다. 우리나라 실험실의 특성을 고려할 때 본 연구결과는 일반 실험실에도 적용될 수 있을 것으로 생각된다.

Nutrient Recovery from Sludge Fermentation Effluent in Upflow Phosphate Crystallization Process (상향류 인 결정화공정을 이용한 슬러지 발효 유출수로 부터의 영양소 회수)

  • Ahn, Young-Ho
    • Journal of Korean Society of Environmental Engineers
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    • v.28 no.8
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    • pp.866-871
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    • 2006
  • The nutrient recovery in phosphate crystallization process was investigated by using laboratory scale uptlow reactors, adopting sequencing batch type configuration. The industrial waste lime was used as potential cation source with magnesium salt($MgCl_2$) as control. The research was focused on its successful application in a novel integrated sludge treatment process, which is comprised of a high performance fermenter followed by a crystallization reactor. In the struvite precipitation test using synthetic wastewater first, which has the similar characteristics with the real fermentation effluent, the considerable nutrient removal(about 60%) in both ammonia and phosphate was observed within $0.5{\sim}1$ hr of retention time. The results also revealed that a minor amount(<5%) of ammonia stripping naturally occurred due to the alkaline(pH 9) characteristic in feed substrate. Stripping of $CO_2$ by air did not increase the struvite precipitation rate but it led to increased ammonia removal. In the second experiment using the fermentation effluent, the optimal dosage of magnesium salt for struvite precipitation was 0.86 g Mg $g^{-1}$ P, similar to the mass ratio of the struvite. The optimal dosage of waste lime was 0.3 g $L^{-1}$, resulting in 80% of $NH_4-N$ and 41% of $PO_4-P$ removal, at about 3 hrs of retention time. In the microscopic analysis, amorphous crystals were mainly observed in the settled solids with waste lime but prism-like crystals were observed with magnesium salt. Based on mass balance analysis for an integrated sludge treatment process(fermenter followed by crystallization reactor) for full-scale application(treatment capacity Q=158,880 $m^3\;d^{-1}$), nutrient recycle loading from the crystallization reactor effluent to the main liquid stream would be significantly reduced(0.13 g N and 0.19 g P per $m^3$ of wastewater, respectively). The results of the experiment reveal therefore that the reuse of waste lime, already an industrial waste, in a nutrient recovery system has various advantages such as higher economical benefits and sustainable treatment of the industrial waste.

Treatment of Garbage Leachate with Two-phase Anaerobic Digestion Coupled with Ultra Filtration (막결합형 2상 혐기성 소화 공정을 이용한 음식물 탈리액 처리)

  • Lee, Eun-Young;Kim, Hyung-Kuk;Giang, Luu Thi Thuy;Bae, Jae-Ho;Bae, Young-Shin;Won, Jong-Choul;Lee, Jae-Hoon;Park, Seung-Kyun;Cho, Yong-Wan
    • Journal of Korean Society of Environmental Engineers
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    • v.31 no.11
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    • pp.997-1006
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    • 2009
  • Organic removal efficiency and methane production rate, a feasibility of power generation from biogas, and the optimum conditions for membrane operation were evaluated for the pilot scale (5 tons/day) two-phase anaerobic digestion coupled with ultra filtration (TPADUF) system fed with garbage leachate. The TPADUF system is consisted of a thermophilic acidogenic reactor, a mesophilic methanogenic reactor, and an UF membrane. When garbage leachate with 150 g/L of TCOD was fed to the TPADUF up to organic loading rate (OLR) of 11.1 g COD/L/d, the effluent TCOD was lower than 6 g/L and the average removal efficiencies of TCOD and SCOD were higher than 95%. The methane composition of the gas was 65%, and the methane yield was 39 $m^3/m^3$ garbage leachatefed, 260 $m^3$/tons $COD_{added}$, or 270 $m^3$/tons $COD_{removed}$, even there was some gas leak. The power production per consumed gas was 0.96 kWh/$m^3$ gas or 1.49 kWh/$m^3$ methane. This lower power production efficiency mainly due to the small capacity of gas engine (15 kW class). The membrane was operated at the average flux of 10 L/$m^2$/hr. When the flux decreased, washing with water and chemical (NaOCl) was conducted to restore the flux. In the TPADUF system, optimum pH could be maintained without alkali addition by recycling the membrane concentrate or mixed liquor of the methanogenic digester to the acidogenic reactor. Also, partial production of methane in the acidogenic reactor had a positive effect on lowering the OLR of the methanogenic reactor.

The Design of Wireless Underwater Telephone -Analysis of Underwater Background Noise for Wireless Underwater Telephone Design - (수중 무선 전화기의 설계 - 수중무선전화기 설계를 위한 수중소음분석을 중심으로-)

  • 박문갑;윤갑동;김석제;윤종락
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.37 no.4
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    • pp.302-307
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    • 2001
  • The underwater background noise measured in Geoje and Tongyoung diving fishing ground from May to December, 2000 and analyzed to get optimum carrier frequency and transmitter power level for underwater wireless telephone design. The results obtained are summarized as follows: 1. At the Geoje and Tongyoung diving fishing ground, the lowest ambient noise band was 25~30kHz with 57dB and 52dB re 1$\mu$Pa, respectively. 2. At the Geoje and Tongyoung diving fishing ground, the lowest noise band during fishing activity was 67dB and 62dB re 1$\mu$Pa, respectively. 3. At the Geoje diving fishing ground, the noise of water jetter which is a digging machine for subbottom shells was 102dB re 1$\mu$Pa. 4. Considering the design parameters of underwater wireless telephone, it is found that the optimum carrier frequency band is around 30kHz and the transmitter source level should be at least 131dB re 1$\mu$Pa for 500m range telephone.

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Survey on Quality of Hospice.Palliative Care Programs in Korea (한국 호스피스.완화의료기관 실태 조사)

  • Yun, Young-Ho;Choi, Eun-Sook;Lee, In-Jeong;Rhee, Young-Sun;Lee, Jung-Suk;You, Chang-Hoon;Kim, Hyun-Sook;Paek, Yu-Jin
    • Journal of Hospice and Palliative Care
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    • v.5 no.1
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    • pp.31-42
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    • 2002
  • Purpose : The purpose of this study was to evaluate the present status of hospice palliative care programs in Korea as a basic database for standardization of hospice palliative care. Method : The data was collected from July to October, 2001. The instrument used for this study was the questionnaires which was consisted of the general characteristics of organization, recipient of service, manpower, contents of service, financial conditions and facilities. Sixty-four hospice palliative care programs answered the questionnaires, confirmed by telephone. Results : They were 40 hospital-based hospice palliative care programs and 24 nonmedical hospice palliative care programs. 11 Hospital-based hospice palliative programs have isolated unit or hospital affiliated free standing hospice. 6 Non-hospital hospice palliative programs have a free standing hospice. Major subjects of hospice palliative program were terminal cancer patients but patients with non-terminal illness were also included. Only 24 of 64 hospice palliative programs had all of the essential professionals : physicians, nurses, social workers, and clergies. Home hospice palliative care programs have a referral system in hospital based (89.7%) and nonmedical programs (73.7%). 24hr hospice are were provided in 26 hospital-based (65.0%) and 9nonmedical programs (37.5%). There were rooms for family in half of hospital-based programs. 73.9% of hospice palliative care programs have financial problems. 62.0% of Hospice palliative care programs need financial support from government. Conclusion : 64 Hospice palliative care programs provided hospice palliative services but had many problems in manpower, quality of care and facility. For improving the quality of terminal patients' life and promoting the cost effectiveness of health care resources, it is necessary to consider the standardization and institutionalization of hospice palliative care.

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