음향심리분석을 이용한 고소음 작업장 소음의 규제기준 설정

장희라,정아영,김재수 한국환경기술학회 2017 한국환경기술학회지 Vol.18 No.6

Industrial development has led to invention of diverse types of working machinery, reducing labor force and time. However, the machinery generates high noises according to its use and materials and exerts physically and mentally adverse effects on workers and long-term exposure to high noises can cause hearing impairments, such as hearing loss. So workers at high-noise workshops have gradually required a calm working environment and constantly complained that the national standard for noises in working environments, 90 dB(A) is too high. From this perspective, this study aimed to conduct psycho-acoustic experiment in noises of 31 machines generating high noises and present a model for grading noises as well as the lowest level of noises in a working environment, which is appropriate for the national condition. The physical assessment indexes for noises, such as dB(A), PSIL, NR, Mean, were most strongly correlated with loudness among the assessment terminology and the gap of 5dB was most appropriate between grades. It was most desirable to set the lowest level of working machinery noises at the seventh stage for some in which negative responses started in the 13-stage semantic differential(SD) scale. Therefore, the lowest level for noises in a working environment appropriate for the national condition most favorably involved 85dB(A), PSIL-75, NR-85, Mean-75dB. 산업화의 발달로 인해 다양한 작업기계가 발명되면서 노동력과 시간을 줄일 수 있었다. 그러나 이러한 작업기계는 사용 목적 및 제원에 따라 고소음을 발생시켜 작업자들에게 신체적, 정신적 악영향을 미치고 있으며, 이러한 고소음에 장시간 노출될 경우 난청과 같은 청력장애를 유발할 수도 있다. 따라서 고소음 작업장에서 근무하는 작업자들은 점차 정온한 작업환경을 요구하고 있으며 국내 작업환경 소음기준인 90dB(A)가 너무 높다는 불만이 지속적으로 제기되고 있다. 이러한 관점에서 본 연구에서는 고소음을 유발하는 31개의 작업기계 소음을 대상으로 청감실험을 실시하여 국내 실정에 적합한 작업환경 소음의 최저기준 및 등급화 모델을 제시하고자 한다. 연구결과 소음의 물리적 평가지수인 dB(A), PSIL, NR, 산술평균 등은 “크다”의 평가어휘와 가장 상관성이 높았으며, 평가등급간의 차이는 5dB 간격이 가장 적당하였다. 또한 작업기계 소음의 최저기준은 13단계 SD척도 중 부정적으로 반응하기 시작하는 “약간”에 해당하는 7단계에서 최저기준을 설정하는 것이 가장 바람직하였다. 따라서 국내 실정에 적합한 작업환경 소음의 최저기준은 85dB(A), PSIL-75, NR-85, 산술평균-75dB이 가장 적절하였다.

수소주택 연료전지실 내 수소 누출 및 환기 특성에 관한 실험적 연구

장희라,황인주,이홍철,지현욱 국제차세대융합기술학회 2022 차세대융합기술학회논문지 Vol.6 No.8

Hydrogen houses supply electricity and heat necessary for residential use using fuel cells that use hydrogen as an energy source. In a hydrogen house, hydrogen fuel cells can be installed outside or inside the house according to the floor plan of the house. When installing a hydrogen fuel cell inside a house, it is necessary to plan a separate dedicated space to minimize the safety impact of hydrogen leakage. Therefore, in this study, an experiment was performed to evaluate the hydrogen leakage and diffusion characteristics and the exhaust effect to maintain the lower explosion limit of 2 vol% in a dedicated room where a hydrogen fuel cell was installed. When natural ventilation was applied, the hydrogen concentration inside the dedicated room reached the lower explosive limit in 7 seconds when the leakage was the largest. In addition, the hydrogen concentration increased at the top of the dedicated room. However, when a 1 vol% shutoff valve and forced ventilation were applied, it was possible to stably control the hydrogen concentration to the lower explosive limit. When planning a space dedicated to hydrogen fuel cells, it is very important to manage the hydrogen concentration as the lower explosive limit in the space, and for this, it is necessary to establish standards for hydrogen shutoff valves, vents, and forced ventilation. 수소주택은 주거용도에 필요한 전기와 열을 수소를 에너지원으로 하는 연료전지를 이용하여 공급한다. 수 소주택에서 수소연료전지는 주택의 평면계획에 따라 주택의 외부 또는 내부에 설치할 수 있다. 주택의 내부에 수 소연료전지를 설치할 경우에, 별도의 전용공간을 계획하여 수소 누출에 의한 안전 영향을 최소화하는 방안이 필요 하다. 이에 본 연구에서는 수소연료전지를 설치한 전용실에서 수소 누출 및 확산 특성과 폭발하한 2 vol%를 유지 하기 위한 배기 효과 등을 평가하기 위한 실험을 수행하였다. 자연환기를 적용했을 때, 수소 누출 시 전용실 내부 의 수소 농도는 누출량이 가장 클 때 7초 만에 폭발하한에 도달하였다. 또한 전용실 상단에서 수소농도가 증가하 는 현상을 보였다. 그러나 1 vol% 차단밸브와 강제환기를 적용한 경우에 수소 농도가 폭발하한으로 안정적인 조 절이 가능했다. 수소연료전지 전용공간을 계획할 경우에 공간 내 폭발하한으로 수소농도 관리가 매우 중요하며, 이를 위한 수소차단밸브, 통기구 및 강제환기 등에 관한 기준 확립이 필요하다.

Zwicker 파라미터를 이용한 MRI 소음의 음질평가

장희라,조한희,김재수 한국생활환경학회 2019 한국생활환경학회지 Vol.26 No.3

As a technique of using a magnetic field to change body signals into digital information, Magnetic Resonance Imaging(MRI) has recently been highly preferred because it produces accurate results and does no harm to a human body. However, MRI generates very serious noises from the process of coil movement to create a magnetic field and causes anxiety among patients having an examination, and the psychological factors make the results less accurate. For this reason, although it is urgent to take measures to reduce MRI operating noises, almost no research has been conducted on this issue in South Korea. In addition, while damage from noises has been rated simply on the basis of a weighted sound level (dB(A)), which is loudness of noises, sound quality should be taken into account in case of MRI noises having physical and psychological effects on patients directly. From this perspective, this study measured noises from four MRI devices, which differed in intensity of magnetic field, and used Zwicker parameters, which are to evaluate sound quality related to human beings’ psychological responses, to analyze the noises in terms of loudness, sharpness, fluctuation strength, unbiased annoyance, tonality, roughness, and so on. The correlation between six Zwicker parameters and such physical quantities of noises as SPLdB(A), SPLO.A., PSIL, and NR was also analyzed. MRI operating noises were perceived as loud, annoying, and rough sounds in human psychology. In particular, louder MRI noises were gradually perceived as ‘Loud and Annoying sounds’ but were less likely to draw the perception of ‘Roughness.’ Therefore, if MRI noises were evaluated not only in terms of the physical size of sound but also in terms of loudness, unbiased annoyance, and roughness, which are closely correlated with the physical size, it would be possible to determine the characteristics and effects of MRI noises more accurately.

생산단계 참나물의 Carbendazim 잔류특성에 따른 노출평가 및 농약 잔류허용기준 개선

장희라,곽혜민,Chang, Hee-Ra,Gwak, Hye-Min 한국환경농학회 2022 한국환경농학회지 Vol.41 No.3

BACKGROUND: The residue dissipation pattern of pesticides for agricultural products during the pre-harvest period after the final application is important to prevent the maximum residue limit (MRL) violations in domestic and export markets. The MRL violations of carbendazim are observed more often in chamnamul by pesticide residue management surveys by the Ministry of Food and Drug Safety. The residue level at the pre-harvest interval (PHI) and the residue dissipation constant from the critical good agricultural practice (cGAP) trials could be estimated to meet the MRL and pose a health risk to consumers. METHODS AND RESULTS: Chamnamuls were harvested at 0, 1, 3, 5, 7, 10, and 14 days after application of carbendazim in accordance with critical GAP. The residue analysis in chamnanul was performed by HPLC-DAD with the C₁₈ column. The limit of quantitation of carbendazim was 0.04 mg/kg, and the recoveries were 74.4 - 95.8% at the two spiked levels (LOQ and 10LOQ) of carbendazim. The dissipation rates in chamnamul were calculated from the residues at the sampling days by statistical method at a 95% confidence level. The biological half-lives of residual carbendazim in the field trials 1 and 2 were 4.9 and 4.4 days, respectively. CONCLUSION(S): In this dissipation study, the residue concentrations at the recommended PHI were higher than the established MRL in Korea. Therefore, the MRL is proposed based on the residue data sets from the trials conducted at the same cGAP and the dietary exposure assessment.

토양대사시험을 이용한 중ㆍ장기시험에 대한 환경 위해성 평가체제 확립

장희라,이용주,김정칠,유정림,김균,김용화 환경독성보건학회 2004 한국독성학회 심포지움 및 학술발표회 Vol.- No.-

시설재배 딸기의 생산단계에서 살충제 잔류량에 따른 반감기 및 감소상수 산출에 의한 안전성 평가

장희라,유정선,반선우 한국환경농학회 2020 한국환경농학회지 Vol.39 No.2

BACKGROUND: Dissipation patterns of insecticides (acequinocyl, clothianidin, diflubenzuron, thiacloprid, and thiamethoxam) on strawberry grown in plastic-covered greenhouse were evaluated at 7 intervals including the pre- harvest interval after application. This study was performed to determine the residue concentrations, half-lives and dissipation rates in strawberry for the harvest periods. METHODS AND RESULTS: Acequinocyl, clothianidin, diflubenzuron, thiacloprid, and thiamethoxam were applied in accordance with critical good agricultural practices for strawberry. Strawberry samples were collected at 0, 1, 2, 3, 5, 7 and 10 days after application. Quantitaion was performed by HPLC/DAD and HPLC-MSMS system with C18 column. The limit of quantitation (LOQ) values varied between were 0.00025~0.05 mg/kg on strawberry. The recoveries of acequinocyl, clothianidin, diflubenzuron, thiacloprid and thiamethoxam at two concentrations ranged from 70.9~ 104.9% on strawberry. The half-lives of pesticide dissipation on strawberry for two fields ranged from 1.3~8.2 days. The dissipation rates were evaluated according to the statistics method with a 95% confidence. CONCLUSION: The residue levels of insecticides (acequinocyl, clothianidin, diflubenzuron, thiacloprid, and thiamethoxam) on strawberry at 0-day after application were below the specified values by Korean MRL. To estimate dissipation rate constant of pesticides on crop for harvest periods, it is important to set the pre-harvest residue limit for human health and consumer protection in Korea. .

가청화 기법을 이용한 터빈소음이 발생하는 수차 발전기실의 음성정보전달 개선

장희라,김재수 한국기계기술학회 2022 한국기계기술학회지 Vol.24 No.2

The waterpower generation of the dam generates electricity by revolving the turbine through a water pipe using the difference of high/low of water, the revolving turbine makes an occurrence a terribly loud noise. Accordingly, in the water turbine generator room located on such hydroelectric generator, since a mutual communication is not establish properly when working, they are suffering many difficulties, and it is real state that such noise damages even to those workers in the office of power plant. Since the most of dam water turbine generator room built in domestic country had used the finishing materials of a huge volume and a high reflexibility, it is carrying more amplifying function with the turbine noise arising when generates the electricity. Therefore, there is not only a difficulty for mutual communication among those workers in the workplace, but also it becomes an obstruction factor for working even to the workers in the adjacent office, and because they are suffering the mental and physical damages, it is actual state that a noise-reduction measure is urgently needed. As a result of the study, on the object with the dam hydraulic turbine dynamo room in which an acoustic defect is being occurring, this Study has conducted the Psycho-Acoustics Experiment about the Delivery of Voice Information using Auralization Technique that can experience the Virtual Acoustic Field. It is considering that such study result could be used usefully for improvement of the Voice Definition when construction the dam hydraulic turbine dynamo room, in the future.

Environmental Risk Assessment of Polyhexamethyleneguanidine Phosphate by Soil Adsorption/Desorption Coefficient

장희라,김용화,양경욱 한국환경농학회 2006 한국환경농학회지 Vol.25 No.4

This study was performed to determine the adsorption-desorption characteristics of polyhexamethyleneguanidine phosphate in three different soil types of textural classification. Adsorption and desorption studies is important for prediction their fate and generating essential information on the mobility of chemicals and their distribution in the soil, water and air of our biosphere. The detection limit of the test substance quantified by a spectroscopic method using Eosin indicator was 0.25 μg/mL. The reproducibility of analytical method was confirmed by the preliminary test. The concentrations of polyhexamethyleneguanidine phosphate in aqueous solution were 1.36 ± 0.09, 2.45 ± 0.01, and 4.25 ± 0.05 μg/mL by a spectroscopic method using Eosin indicator. The adsorption percents of polyhexamethylenequanidine phosphate in soil were greater than 95.2% for all three test soils. The desorption percents from the adsorbed soil were less than 4.5, 4.7 and 4.7%. Therefore, the adsorption coefficients (K) were greater than 110, 111 and 116. The adsorption coefficient calculated as a function of the organic carbon content (Koc) of the test soils were greater than 9,181, 11,100, and 8,942, respectively. Therefore, the test substance, polyhexamethylenequanidine phosphate could be concluded as medium or high adsorption (>25%) and poorly desorption (<75%) in soil media. Therefore, this chemical is likely to be retained in soil media and may not pose a risk in the aquatic environment.

UWB 센서를 탑재한 스마트 디퓨저의 공기질 서비스 시나리오 개발 사전 연구

장희라,황인주,이홍철 국제차세대융합기술학회 2022 차세대융합기술학회논문지 Vol.6 No.7

최근 독거노인과 1 인 가구 증가 등 주거 형태 변화 및 미디어 업종의 증가, 전염병 등은 업무형태를 크게 변화시키고 있다. 이로 인해 현대인들의 실내 거주 시간이 늘어나며 실내 공기질 확보에 대한 관심이 늘어나고 있다. 이러한 실내 공기 환경은 외부 요인뿐 아니라 거주자의 생활 패턴의 영향을 크게 받는다. 이에 본 연구에서는 거주 자의 활동 유형을 분석하였으며, 실내 공기질 관리를 위한 최적의 시나리오를 제안하고자 하였다. 이러한 시나리오 계획을 위해 리빙랩에서 생활 활동에 대해 실내 공기질과 생체 활동 신호 분석을 실시하였다. 실험결과를 토대로 가 정 내에서 일어나는 생활 활동을 공기오염도 및 재실자 활동량에 따라 ‘ 미활동, 비활동, 활동, 주의활동’ 으로 분류하 였다. 따라서 이러한 활동분류로 예측 환기를 진행할 때 실내 공기질의 쾌적함을 관리 할 수 있을 것으로 보인다. Recent changes in housing types, such as the increase in the elderly living alone and single- person households, as well as an increase in the media industry, and infectious diseases have significantly changed work patterns. As a result, modern people spend more time indoors, and interest in securing I AQ is increasing. T his indoor air environment is greatly influenced b y the living patterns of residents as well as ex ternal factors. T herefore, this study analyz ed the types of residents' activities and attempted to propose an optimal scenario for indoor air q uality management. I n order to plan these scenarios, I AQ and b iological activity signal analysis were performed on living activities in the L iving L ab . Based on the ex perimental results, living activities occurring in the home were classified into ‘ activity, less activity, proper activity, and caution activity’ according to the air pollution level and the amount of activity. Therefore, it seems that the comfort of indoor air quality can b e managed when predictive ventilation is carried out with this activity classification.

전산유체역학을 활용한 연료전지실 내 수소 환기 특성 분석을 통한 안전설계 계획 최적화

장희라,황인주 국제차세대융합기술학회 2024 차세대융합기술학회논문지 Vol.8 No.2

최근 전세계적으로 탄소중립 목표달성을 위해 수소경제로의 전환을 시도하고 있다. 우리나라에서는 수소 경제 전환의 일환으로 수소도시개발을 추진하고 있다. 수소도시 중 주거 영역인 주택의 경우 수소를 에너지원으로 활용해 탄소발생을 줄이고 에너지 자립률을 높이고자 한다. 이를 위해 주택내 연료전지 전용실을 계획하나 밀폐공 간에서의 수소 누출시 폭발위험성이 있어 안전에 대한 고려가 필수적이다. 그러나 현재 수소 연료전지 전용실에 적합한 기준 및 안전을 고려한 설계 가이드도 미비한 상황이다. 따라서 본 연구에서는 전산유체역학을 활용해 연 료전지 전용실에서 수소 누출시 내부 안전 설계 조건 변경을 통해 최적의 수소 환기 조건을 갖는 안전설계 계획 을 검토해보고자 한다. Recently, there have been efforts worldwide to transition to a hydrogen economy to achieve carbon neutrality. In South Korea, as part of the transition to a hydrogen economy, efforts are being made to develop hydrogen cities. In the residential areas of these hydrogen cities, particularly in houses, there is a desire to utilize hydrogen as an energy source to reduce carbon emissions and increase energy self-sufficiency. For this purpose, plans are being made for dedicated fuel cell rooms within homes. However, due to the potential explosion risks associated with hydrogen leakage in enclosed spaces, safety considerations are essential. Currently, there is a lack of adequate standards and design guidelines that prioritize safety for fuel cell rooms. Therefore, this study aims to utilize computational fluid dynamics(CFD) to review the safety design plans by altering the internal safety conditions when hydrogen leaks in fuel cell rooms, with the objective of establishing optimal hydrogen ventilation conditions for a safe design.