• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.917-930
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• 2018

A quantitative risk assessment method for quantitatively evaluating the fire risk in designing a road tunnel disaster prevention facilities has been introduced to evaluate the appropriateness of a disaster prevention facility in a large tunnel through which all vehicle types pass. However, since the quantitative risk assessment method of the developed can be applied only to the large sectional area tunnels (large tunnels), it is necessary to develop a quantitative risk assessment method for road tunnels passing only small cars which has recently been constructed or planned. In this study, fire accidents scenarios and quantitative risk assesment method for small road tunnels through small cars only which is based on the methods for existing road tunnels (large tunnels). And the risk according to the distance between cross passage is evaluated. As a result, in order to satisfy the societal risk assessment criteria, the distance of the appropriate distance between cross passages was estimated to be 200 m, and the effect of the ventilation system of the large port exhaust ventilation system was quantitatively analyzed by comparing the longitudinal ventilation system.

• Journal of Aerospace System Engineering
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• v.16 no.3
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• pp.23-34
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• 2022

Cities around the world are increasing their demand for Urban Air Mobility (UAM) aircraft due to traffic congestion with population concentration. Aircraft with various shapes depending on fixed-wing and propulsion systems, are being prepared for commercialization. Airworthiness certification is required as it is a manned transportation vehicle that flies in the city center and transports people on board. UAM aircraft are vulnerable to lightning and HIRF environments due to the increasing use of composite materials, the use of electric motors, and use of electronic equipment. Currently, the development of certification technology, guidelines, and requirements in lightning and HIRF environments for UAM aircraft is incomplete. In this study, the certification procedures for lightning and HIRF indirect impacts of rotorcraft shown in AC 20-136B and AC 20-158A issued by the Federal Aviation Administration (FAA), were verified and applied to the computerized simulation of UAM aircraft. The impact of lightning and HIRF on ducted fan UAM aircraft was analyzed through computerized simulation, and the basis for establishing practical guidelines for certification of UAM aircraft to be operated in the future is presented.

• Membrane Journal
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• v.33 no.6
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• pp.398-408
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• 2023

This work developed a hood and filter for antibacterial protective clothing for medical powered air purifying respirators (PAPR) that can be used in medical settings and quarantine against infectious diseases such as Zika virus, Middle East respiratory syndrome (MERS), and coronavirus disease-19 (COVID-19). The hood material of the protective clothing was made of polypropylene spunlace nonwoven fabric (SFS) was used for withstand wind pressure and external physcial pressure. Forthermore, in order to reduce the user's risk of infection, phytoncide-based materials were used on the outer-surface of the hood to achieve a 99.9% antibacterial effect, and the inner-surface were treated with hydro-philic materials to improve absorbency by 25%. In addition to evaluating the artificial blood penetration resistance, dry mi-croorganism penetration resistance, wet bacteria penetration resistance, and bacteriophage penetration resistance required for medical protective clothing hoods, it received a passing evaluation of levels 2-6. Meanwhile, as a result of evaluating the performance of the antibacterial treated spunlace high efficiency particulate air (HEPA) filter, excellent antibacterial properties, dust removal rate, and differential pressure effect were confirmed. All performance evaluations were conducted by an accredited certification body in accordance with the medical PAPR certification standards.

• Journal of Bio-Environment Control
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• v.28 no.1
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• pp.78-85
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• 2019

This study was designed to examine the performance of an aspirated radiation shield(ARS), which was made at the investigator's lab and characterized by relatively easier making and lower costs based on survey data and reports on errors in its measurements of temperature and relative humidity. The findings were summarized as follows: the ARS and the Jinju weather station made measurements and recorded the range of maximum, average, and minimum temperature at $2.0{\sim}34.1^{\circ}C$, $-6.1{\sim}22.2^{\circ}C$, $-14.0{\sim}15.1^{\circ}C$ and $0.4{\sim}31.5^{\circ}C$, $-5.8{\sim}22.0^{\circ}C$, $-14.1{\sim}16.3^{\circ}C$, respectively. There were no big differences in temperature measurements between the two institutions except that the lowest and highest point of maximum temperature was higher on the campus by $1.6^{\circ}C$ and $2.6^{\circ}C$, respectively. The measurements of ARS were tested against those of a standard thermometer. The results show that the temperature measured by ARS was lower by $-2.0^{\circ}C$ or higher by $1.8^{\circ}C$ than the temperature measured by a standard thermometer. The analysis results of its correlations with a standard thermometer reveal that the coefficient of determination was 0.99. Temperature was compared between fans and no fans, and the results show that maximum, average, and minimum temperature was higher overall with no fans by $0.5{\sim}7.6^{\circ}C$, $0.3{\sim}4.6^{\circ}C$ and $0.5{\sim}3.9^{\circ}C$, respectively. The daily average relative humidity measurements were compared between ARS and the weather station of Jinju, and the results show that the measurements of ARS were a little bit higher than those of the Jinju weather station. The measurements on June 27, July 26 and 29, and August 20 were relatively higher by 5.7%, 5.2%, 9.1%, and 5.8%, respectively, but differences in the monthly average between the two institutions were trivial at 2.0~3.0%. Relative humidity was in the range of -3.98~+7.78% overall based on measurements with ARS and Assman's psychometer. The study analyzed correlations in relative humidity between the measurements of the Jinju weather station and those of Assman's psychometer and found high correlations between them with the coefficient of determination at 0.94 and 0.97, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.5 s.108
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• pp.461-475
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• 2006

In this paper, it is described about the tri-band mobile antenna system design to provide broadband multimedia and direct broadcasting services using goo-stationary Koreasat 3, simultaneously operated in Ka/K/Ku band. The radiating part of the antenna system with a fan beam characteristic in the elevation plane is composed of the quasi-offset dual shaped reflector and the tri-band feeder. The tri-band feeder is also composed of the Ka/K dual band feeder with the protruding dielectric rod, the circular polarizer, the ortho-mode transducer and the circular-polarized Ku band feed array. Especially, the Ka/K dual band circular polarizer was realized firstly using the comb-type structure. For fast satellite-tracking on the movement, the Ku band feed array has the structure of the $2{\times}2$ active phased array which can make electrical beams. And, the circular-polarized characteristic in the feed array was improved by $90^{\circ}$ rotating arrangement of four radiating elements polarized circularly by a $90^{\circ}$ hybrid coupler, respectively. Four beam forming channels to make electrical beams at Ku band are divided into the main beam channel and the tracking beam channel in the output, and noise temperature characteristics of each channel were analyzed on the basis of the contributions of internal sub_units. From the fabricated antenna system, the output power at $P_{1dBc}$ of Ka_Tx channel was measured more than 34.1 dBm and the measured noise figures of K/Ku_Rx channels were less than 2.4 dB and 1.5 dB, respectively, over the operating band. The radiation patterns with co- and cross-polarization in the tri-band were measured using a near-field measurement in the anechoic chamber. Especially, Ku radiation patterns were measured after correcting each initial phase of active channels with partial radiation patterns obtained from the independent excitation of each channel. The antenna gains measured in Ka/K/Ku band of the antenna system were more than 39.6 dBi, 37.5 dBi, 29.6 dBi, respectively. And, the antenna system showed good system performances such as Ka_Tx EIRP more than 43.7 dBW and K/Ku_Rx G/T more than 13.2 dB/K and 7.12 dB/K, respectively.

• Journal of Biosystems Engineering
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• v.8 no.1
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• pp.47-60
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• 1983

상온통풍(常溫通風)을 이용(利用)한 In-bin drying에 대(對)한 많은 실험결과(實驗結果)에 의(依)하면 우리나라 10월(月)의 기상조건(氣象條件)은 저온건조(低溫乾燥) system에 적합(適合)한 건조능력(乾燥能力)을 가지고 있는 것으로 나타났다. 최근(最近) Computer를 이용(利用)한 Simulation model이 개발(開發)되어 건조현상(乾操現象)에 관(關)한 경제적(經濟的)이고 효율적(效率的)인 분석(分析)이 가능(可能)하게 되었다. 이러한 분석결과(分析結果)에 의(依)하면 초기함수율(初期含水率)이 높은 벼를 Full-bin을 이용(利用)한 상온통풍건조(常溫通風乾操)를 할 경우(境遇) 건조기간(乾燥期間)이 길어지며 bin내(內)의 상층부(上層部) 곡물(穀物)이 변질(變質)되는 문제점(問題點)이 발생(發生)하였다. 또한 벼의 수확작업체계(收穫作業體系)가 관행(慣行) 및 Binder작업체계(作業體系)에서 점차(漸次) Combine작업체계(作業體系)로 전환(轉換)되어감에 따라 포장(圃場)에서의 건조(乾燥)가 어려우며 예취(刈取), 탈곡작업과정(脫穀作業過程)에서의 기계적(機械的)인 곡물(穀物) 손실(損失)을 줄이기 위(爲)하여 함수율(含水率)이 비교적(比較的) 높은 벼를 수확(收穫)하여야 한다. 본(本) 연구(硏究)의 목적(目的)은 상온통풍건조(常溫通風乾燥)에 있어서 건조능력(乾燥能力)을 증가(增加)시키기 위(爲)하여 곡물(穀物)을 일정기간(一定期間) 나누어서 bin에 넣고 건조(乾燥)를 하는 Layer drying의 Simulation model을 개발(開發)하고 이 Model에 수원지방(水原地方)의 7년간(年間) 평균(平均) 기상자료(氣象資料)를 입력(入力)시켜 곡물(穀物)의 초기함수율(初期含水率), 투입량(投入量), 투입기간(投入期間)의 변화(變化)에 따른 Layer drying현상(現象)을 규명(糾明)하는데 있다. Simulation에 사용(使用)된 bin의 크기는 직경(直徑) 2m, 깊이 1.5m이며 송풍(送風)팬의 용량(容量)은 0.5HP이었다. Simulation분석(分析) 결과(結果)를 요약(要約)하면 다음과 같다. (1) Layer drying의 Simulation model을 개발(開發)하였으며 이 Model은 벼의 상온통풍건조(常溫通風乾燥) 실험(實驗)에서 함수량(含水量) 변화(變化)의 이론치(理論値)와 실제실험치(實際實驗値)가 잘 일치(一致)하였다. (2) 곡물투입기간(穀物投入期間) 1일(日)을 Full-bin drying으로 간주(看做)할 때 Layer drying의 건조성능(乾燥性能)은 Full-bin보다 높은 것으로 나타났다. (3) 연속송풍(連續送風)(24시간(時間))을 할 경우(境遇) 곡물투입기간(穀物投入期間)이 증가(增加)함에 따라 건조기간(乾燥期間)의 감소경향(減少傾向)은 단속송풍(斷續送風)인 경우(境遇)보다 적었지만 건조기간(乾燥期間)은 단축(短縮)되었다. 그러나 건조(乾燥)에너지의 소모(消耗)는 단속송풍(斷續送風)일 때보다 크게 나타났다. (4) 단속송풍(斷續送風)(9 : 00AM~6 : 00PM)일 경우(境遇) 곡물투입기간(穀物投入期間)을 증가(增加)시키면 건조기간(乾燥期間)이 크게 줄어 들었다. (5) 곡물(穀物)의 초기함수율(初期含水率)이 21% 이하(以下)일 경우(境遇) 연속(連續) 및 단속송풍(斷續送風)에서 건조기간(乾燥期間)의 차이(差異)가 별로 없었다. (6) 곡물(穀物)의 초기함수율(初期含水率)이 높으면 Full-bin drying에서는 상부층(上部層)에 곡물(穀物)이 변질(變質)될 우려(憂慮)가 있으나 Layer drying에서는 곡물투입량(穀物投入量)을 조절(調節)하면 이것을 방지(防止)할 수 있었다. (7) 건조(乾燥)가 완료(完了)된 후(後) 층별(層別) 최종곡물(最終穀物) 함수율(含水率)은 모든 건조조건(乾燥條件)에서 동일(同一)하였으나 bin의 하부층(下部層)은 과건조(過乾燥) 물상(物象)을 일으켰다.