입자의 전기전도도에 따른 하전 입자의 응집 성장 특성 해석

박형호(Hyungho Park),김상수(Sangsoo Kim),장혁상(Hyuksang Chang) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.9

The effect of electric conductivity of particles was studied for the aggregation process of charged particles with a Brownian dynamic simulation in the free molecular regime. A periodic boundary condition was used for calculation of the aggregation process in each cell with 500 primary particles of 16 ㎚ in diameter. We considered two extreme cases, a perfect conductor and a perfect nonconductor. The electrostatic force on a particle in the simulation cell was considered as a sum of electrostatic forces from other particles in the original cell and its replicate cells. We assumed that aggregates were only charged with pre-charged primary particles. The morphological shape of aggregates was described in terms of the fractal dimension. The fractal dimension for the uncharged aggregate was D<SUB>f</SUB> = 1.761. However, in case of centered charge, the fractal dimension decreased from 1.750 to 1.537 with the increase of the average number of charges on the particles from 0.1 to 0.3 in initial states. This tendency does not vary for the case of a conductor or nonconductor.

대류난방시 가습연동에 의한 실내환경변화 및 쾌적성 검증

박동률(Dongryul Park),권서현(Suhhyun Kwon),박형호(Hyungho Park),이윤희(Yoonhee Lee),한지은(Jieun Han),전정윤(Chungyoon Chun) 대한설비공학회 2019 대한설비공학회 학술발표대회논문집 Vol.2019 No.-

Convective heating can lead to high temperature and low humidity conditions, which can cause to discomfort. The heat pump air conditioner equipped with a heating type humidifier was used to evaluate the change of the room temperature and humidity condition according to the presence or absence of the humidification operation during heating. The subjective evaluation and the skin wetness were measured through the experiment of the subjects and the improvement effect of the dry feeling and the discomfort. The tendency of the room temperature was similar, and the relative humidity was increased by about 10% in the heating and humidifying condition compared to the single heating condition. By comparing of behavior on psychrometric chart with comfort zone, the effect of the humidification operation can be verified. The subjective evaluation and skin moisture were measured physiologically. The results of the subjective response evaluation under the advanced experimental conditions did not distinguish between the two conditions. The skin measurement showed higher stratum corneum hydration(SCH) and lower transepidermal water loss(TEWL) in humidification heating mode.

환기가동 조건에서 가습공기청정기의 공기청정 및 가습성능 검증

박동률(Dongryul Park),김용민(Yongmin Kim),박형호(Hyungho Park),허덕(Deok Huh) 대한설비공학회 2018 대한설비공학회 학술발표대회논문집 Vol.2018 No.6

While most air purifiers and humidifiers are meant for domestic use, few are available for public and commercial environments. In the present study, we performed tests to verify air purifying and humidifying performance of air purifiers with mechanical ventilation. Our results suggest that, when air purifier is operated with a ventilator (clean air supply), reduction of PM2.5 is more effective and humidification is sufficient to maintain comfort humidity.

초음속 유동에서 코로나 방전을 이용한 금속 나노 입자의 생성

정재희(Jaehee Jung),박형호(Hyungho Park),김상수(Sangsoo Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

The effects of additive ions on the generation of metallic nanoparticles were evaluated using a corona induced supersonic nozzle. Applying the corona discharge to the nanoparticle generator, a tungsten needle and the supersonic nozzle are used as an anode electrode and a cathode electrode respectively. The corona ions act as nuclei for the silver vapor condensation. The ion density was controlled precisely as varying the applied voltage between electrode and nozzle. The mean diameter of the silver particle decreases as the ion density increases. However, the number concentration of the silver particle tended to increase with the ion density. The size distribution is more uniform as the ion density increases.

다중노즐을 이용한 정전분무 특성 연구

강영진(Youngjin Kang),박형호(Hyungho Park),김상수(Sangsoo Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

The purpose of the paper is to evaluate the electrospray characteristics of multi-nozzle system. The droplet size, droplet velocity, spray angle and spray current were selected as the main characteristics of electrospray. In addition, the performance of coating with PSL (200㎚ in diameter) using electrospray was evaluated by counting number of particles on the substrate. The electrospray was operated in the cone-jet mode, and there were no differences in the generated droplet size distribution between the single- and multi- nozzle electrospray with a guard plate which made the spray angle became smaller. The droplet velocity increased with the increase of voltage applied to the guard plate. Using the electrospray, the coating of PSL nanoparticles on the slide glass was successfully employed, and the multi-nozzle electrospray could cover wider area of substrate than the single-nozzle electrospray.

스파크 방전을 이용한 은 나노입자 생성 특성 연구

오현철(Hyuncheol Oh),박형호(Hyungho Park),김상수(Sangsoo Kim),지준호(Junho Ji) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

A spark discharge aerosol generator using air as a carrier gas has successfully been applied to silver nanoparticle production in connection with an evaluation of by-product gases such as ozone. The spark discharge between two silver electrodes, which was periodically obtained by discharging the capacitor, produced sufficient high temperatures to evaporate a small fraction of the silver electrodes. The silver vapor was subsequently condensed to silver nanoparticles of about 20 ㎚ size in diameter. The morphology and chemical composition of the generated particles were observed by TEM/EDS, and the particle size distribution was measured using a SMPS system. A stable operation of the spark discharge generator has been achieved, and the size and concentration of the particles can be easily controlled by altering the repetition frequency, capacitance, gap distance and flow rate of the spark discharge system.

광압을 이용한 입자빔 집속

김상복(Sangbok Kim),박형호(Hyungho Park),김상수(Sangsoo Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

A novel technique for fine particle beam focusing under the atmospheric pressure is introduced using a radiation pressure assisted aerodynamic lens. To introduce the radiation pressure in the aerodynamic focusing system, a 25 ㎜ plano-convex lens having 2.5 ㎜ hole at its center is used as an orifice. The particle beam width is measured for various laser power, particle size, and flow velocity. In addition, the effect of the laser characteristics on the beam focusing is evaluated comparing an Ar-Ion continuous wave laser and a pulsed Nd-YAG laser. For the pure aerodynamic focusing system, the particle beam width was decreased as increasing particle size and Reynolds number. For the particle diameter of 0.5 ㎛, the particle beam was broken due to the secondary flow at Reynolds number of 694. Using the Ar-Ion CW laser, the particle beam width becomes smaller than that of the pure aerodynamic focusing system about 16 %, 11.4 % and 9.6 % for PSL particle size of 2.5 ㎛, 1.0 ㎛, and 0.5 ㎛ respectively at the Reynolds number of 320. Particle beam width was minimized around the laser power of 0.2 W. However, as increasing the laser power higher than 0.4 W, the particle beam width was increased a little and it approached almost a constant value which is still smaller than that of the pure aerodynamic focusing system. The radiation pressure effect on the particle beam width is intensified as Reynolds number decreases or particle size increases relatively. On the other hand, using 30 ㎐ pulsed Nd-YAG laser, the effect of the radiation pressure on the particle beam width was not distinct unlike Ar-Ion CW laser.

듀얼베인 적용 천장형 1way 에어컨 기류의 사용자 생산성 평가에 대한 연구

이정훈(Jeong Hoon Lee),이주연(Juyoen Lee),서기원(Ki Won Seo),박형호(Hyungho Park) 대한설비공학회 2022 대한설비공학회 학술발표대회논문집 Vol.2022 No.6

In recent years, research on improving work productivity has been attracting attention, and many studies are being conducted to improve work productivity through a pleasant air flow. Subjects work productivity under various airflow mode was evaluated by EEG and NASA-TLX. As a result of using the work productivity airflow mode, concentration-related brain waves (beta waves) increased by 3.44%. The work productivity airflow mode also achieved 68.8% of performance category of NASA-TLX, 6.3% higher than the standard cooling mode. Airflow control affects arousal and work productivity, so it is expected to be used in schools and offices.

전자식 마스크 착용 편의성 평가방법 연구

이지언(Jieon Lee),이강현(Kanghyun Lee),김용민(Yongmin Kim),박형호(Hyungho Park),신관섭(Gwanseob Shin) 대한인간공학회 2021 대한인간공학회 학술대회논문집 Vol.2021 No.11

Objective: 본 연구는 전자식 마스크 장시간 사용 시 유발되는 사용자의 불편함을 평가할 수 있는 정성적, 정량적 평가지표 도출 및 평가법 개발에 목적을 두고 있다. Background: 전자식 마스크는 충전식의 휴대용 공기청정기의 역할을 하는 웨어러블 기기로 기존 일회용 마스크의 단점을 개선하고 이를 대체할 수 있는 수단으로써 개발되었다. 그러나 기존 마스크와 달리 전자식 마스크는 그 무게로 인해 사용자 불편함을 유발할 수 있으며 이는 장시간 착용을 방해하는 요인이 된다. 따라서 사용자 불편함에 대한 이해는 적절한 전자식 마스크 평가 및 설계에 중요하지만, 아직 이를 평가할 수 있는 수단은 표준화되지 않았다. 이 연구는 전자식 마스크의 착용으로 인한 사용자의 불편함을 정성적, 정량적으로 평가할 수 있는 지표와 평가법을 제시한다. Method: 우선적으로, 불편함의 종류와 특성 파악을 위한 설문조사가 실시되었다. 건강한 20대 4명이 10일 간 일상생활에서 전자식 마스크 사용 후 인터뷰와 불편도 정성평가에 참여하였다. 주요 불편 발생 부위는 귀와 얼굴의 접촉 부위로, 귀 불편함은 이어밴드의 당김, 이물감, 얼굴 불편함은 습도, 압박감, 흘러내림이 주요 요인임을 확인하였다. 이를 토대로 마스크 착용의 불편함을 결정하는 중요한 변수로 이어 밴드의 장력 및 얼굴에 가해지는 압력을 선정하였다. 이후 평가 지표의 도출 및 분석을 위해, 이를 정량적으로 평가할 수 있는 다양한 지표들이 테스트되었다. 이어밴드로 인한 불편함과 장력과의 비례관계를 파악하였으며, 마스크 페이스가드의 형상에 따라 얼굴의 압박감과 착용 안정성이 변화함을 확인함으로써 평가지표로 이어밴드의 장력과 얼굴의 접촉 압력 분포, 마스크와 얼굴의 상대적 회전 각도를 선정하였다. 평가시 피험자가 수행할 과제의 경우 사용자 관찰을 통해 다양한 마스크 사용 환경을 고려하여 결정되었다. 파일럿 테스트를 통해 수정 및 보완된 최종 평가법은 전자식 마스크 기존안과 개선안의 비교 평가에 적용되었다. Results: 본 연구에서는 전자식 마스크의 착용 편의성을 평가하기 위한 방법을 제안하고, 이를 검증하기 위한 소규모 비교 평가를 진행하였다. 비교 결과, 초기 제품에 비해서 후속 제품의 정성적 불편함이 개선되었으며, 이러한 개선 효과는 정량적 지표의 결과로도 확인되었다. Conclusion: 전자식 마스크의 착용 편의성을 정량적 평가지표를 이용하여 평가할 수 있는 방법을 제안하였다. 이러한 정량적 평가법은 제품의 개발과 개선 연구에 활용하여 사용자의 편의성을 향상시키는데 기여할 수 있을 것이다. Application: 본 연구의 결과는 제품 평가 및 개발의 참고자료로 이용될 수 있으며 전자식 마스크 장시간 착용에 대한 사용자 경험을 개선하고 제품 활용성을 높일 수 있다. 또한 본 연구에서 제시된 마스크 평가법은 유사한 타 제품의 평가에도 적용되어 활용될 수 있다.

귀농인 정착의 장애요인과 대응전략 : 경북 영천과 충남 청양 귀농인을 중심으로

정진화(Jin Hwa Jung),노재선(Jae-Sun Roh),박형호(Hyungho Park),임동근(DongGeun Lim),김다울(Dawool Kim) 한국농식품정책학회 2015 농업경영정책연구 Vol.42 No.4

Returning farmers mostly go through an arduous course of settlement in terms of re-adapting themselves to farming activities and rural environment. The obstacles encountered in settlement may differ according to the diverse types of returning farmers. This paper classifies returning farmers by years after migration, income level, and crop type to investigate the obstacles and countermeasures in the settlement process by the features of returning farmers. The survey data of 207 returning farmers and in-depth interviews with seven returning farmer households are analyzed. With low income as a common hindrance, clear differences are established with regard to major obstacles for different types of returning farmers. Recommended strategies to overcome such obstacles include active but prudent investment, enhancement of returning farmers’ farming capability, participation in producers’ cooperatives, and securement of nonfarm income activities.