• 대한간호학회지
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• 제38권4호
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• pp.612-619
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• 2008

Purpose: The purpose of this study was to examine health problems and to estimate economic impact based on health problems of workers. Methods: The subjects of this study consisted of 301 workers who received a group occupational health service. Data was collected from February 1 to March 30, 2006. The questionnaire contained questions based on general characteristics and the Stanford Presenteeism Scale. Data was analyzed with descriptive statistics, t-test using SPSS program. Results: The primary health conditions as reported by workers were ranked in order as stomach or bowel disorders, back or neck disorders, or liver function disorders. The reason of absenteeism per worker was ranked in order as asthma, or a breathing disorder. The reason of presenteeism was ranked in order as asthma, insomnia or a sleep disorder. The cost of the total economic impact on the workplace in this study was 8,851,838 won. The cost of absenteeism per worker was 8,390 won. The cost of presenteeism per worker was 941,732 won. Conclusion: Presenteeism had a strong correlation to health conditions of the workers. Therefore, improving the work conditions of the workers is very important. If employers improve the health condition of workers, they will benefit from improved productivity in their business.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.62-68
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• 2004

A comprehensive numerical analysis has been carried out for both non-reacting and reacting flows in a scramjet engine combustor with and without a cavity. The theoretical formulation treats the complete conservation equations of chemically reacting flows with finite-rate chemistry of hydrogen-air. Turbulence closure is achieved by means of a k-$\omega$ two-equation model. The governing equations are discretized using a MUSCL-type TVD scheme, and temporally integrated by a second-order accurate implicit scheme. Transverse injection of hydrogen is considered over a broad range of injection pressure. The corresponding equivalence ratio of the overall fuel/air mixture ranges from 0.167 to 0.50. The work features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the previous studies. In particular, the oscillatory flow characteristics are captured at a scale sufficient to identify the .underlying physical mechanisms. Much of the flow unsteadiness is related not only to the cavity, but also to the intrinsic unsteadiness in the flow-field. The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The roles of the cavity, injection pressure, and heat release in determining the flow dynamics are examined systematically.

• 한국가시화정보학회지
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• 제9권3호
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• pp.65-70
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• 2011

Three major physiological functions of nose can be described as air-conditioning, filtering and smelling. Detailed knowledge of airflow characteristics in nasal cavities is essential to understanding of the physiological and pathological aspects of nasal breathing. In our laboratory, a series of experimental investigations have been conducted on the airflows in normal and abnormal nasal cavity models by means of PIV under both constant and periodic flow conditions. In this work, more specifically experimental and numerical results on the surgically modified inferior turbinate model were presented. With the high resolution CT data and a careful treatment of the model surface under the ENT doctor's advice yielded quite sophisticated cavity models for the PIV experiment. Physiological nature of the airflow was discussed in terms of velocity distribution and vortical structure for constant inspirational flow. Since the inferior and middle turbinate are key determinants of nasal airflow, the turbinectomy obviously altered the main stream direction. This phenomenon may cause local changes in physiological function and the flow resistance.

• Tuberculosis and Respiratory Diseases
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• 제68권3호
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• pp.125-139
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• 2010

Patients with chronic obstructive pulmonary disease (COPD) frequently complain of dyspnea on exertion and reduced exercise capacity, which has been attributed to an increase in the work of breathing and in impaired of gas exchange. Although COPD primarily affects the pulmonary system, patients with COPD exhibit significant systemic manifestations of disease progression. These manifestations include weight loss, nutritional abnormalities, skeletal muscle dysfunction (SMD), cardiovascular problems, and psychosocial complications. It has been documented that SMD significantly contributes to a reduced exercise capacity in patients with COPD. Ventilatory and limb muscle in these patients show structural and functional alteration, which are influenced by several factors, including physical inactivity, hypoxia, smoking, aging, corticosteroid, malnutrition, systemic inflammation, oxidative stress, apoptosis, and ubiquitin-proteasome pathway activation. This article summarizes briefly the evidence and the clinical consequences of SMD in patients with COPD. In addition, it reviews contributing factors and therapeutic strategies.

• 한국화재소방학회논문지
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• 제21권2호
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• pp.64-73
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• 2007

호흡기 내에서 유해물질의 체내흡수 및 방어특성은 영역별로 다르며 흡입연기의 장 단기 인체 유해성은 연기의 호흡기 내 침착위치 및 침착밀도와 밀접한 관계를 가지고 있다. 이 연구에서는 미소부피 위치 추적법을 이용한 입자침착율 계산 기법을 사용하여 휴식 및 가벼운 운동에 해당하는 호흡조건별로 또한 구강 및 비강 호흡별로 각 입자크기에 대하여 호흡기 각 영역별로 단위 면적당 침착분율 등 침착 특성을 구하였다. 이 결과는 연기에 흡착된 유해물질의 체내 흡수량 산정 등에 이용되어 연기의 인체 유해성 판정에 도움을 줄 수 있을 것으로 판단된다.

• International Journal of Aerospace System Engineering
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• 제2권2호
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• pp.58-61
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• 2015

Combustion instability in solid rocket motors is a long-term open problem since the first rockets were used. Based on the numerous previous studies, it is known that the limit cycle amplitude is one of the key characteristics of the nonlinear combustion instability in solid rocket motors. Flandro's extended energy balance corollary, aims to predict the limit cycle amplitude of complex, nonlinear pressure oscillations for rockets or air-breathing engines, and leads to a precise assessment of nonlinear combustion instability in solid rocket motors. However, based on the comparison with experimental data, it is revealed that the Flandro's method cannot accurately describe such a complex oscillatory pressure. Thus in this work we make modifications of the nonlinear term in the nonlinear wave equations which represents the interaction of different modes. Through this modified method, a numerical simulation of the cylindrical solid rocket has been carried out, and the simulated result consists well with the experimental data. It means that the added coefficient makes the nonlinear wave growth equations describe the experimental data better.

• Physical Therapy Rehabilitation Science
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• 제10권3호
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• pp.289-296
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• 2021

Objective: The purpose of this study was to changes in respiratory function due to differences in mask blocking grade, and effects on cardiovascular function during aerobic exercise. Design: Comparative study using paired t-test and analysis of variance measures. Methods: Male and female subjects were randomly divided into 4 groups according to mask blocking grade and measured respiratory functions before and after wearing the mask using spirometers, and their cardiovascular capabilities were measured using pulse oxygen meters and blood pressure meters before and after running for 10 minutes wearing mask. Used paired t-test, one-way ANOVA and Bonferroni post-test to compare the differences according to the mask blocking grade. Results: The experimental results verified that three groups except for the Non-mask group had a significant reduction in all values of FVC, FEV1, MVV, and PEF after wearing a mask compared to those before wearing a mask(p<0.05). Also a significant difference in cardiovascular functions was also observed after aerobic exercises wearing mask in all groups and there was a significant difference between all four groups(p<0.05). Conclusions: Lung patients with poor breathing, elderly and children with poor lung function, and professional groups who need to wear masks and take high-intensity work or aerobic movements are encouraged to take frequent breaks in advance, wear masks and social distancing at moderate and low levels.

• 재활복지공학회논문지
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• 제1권1호
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• pp.1-6
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• 2007

자이로센서기술을 적용하여, 헤드마우스는 웹에 접근하기위한 마우스의 좌 클릭, 우 클릭, 더블 클릭, 드래그와 드롭, 휠 기능까지 시현할 수 있도록 개발되었다. 이 기기는 USB케이블을 사용하여 PC와 매킨토시 환경에서 동작할 수 있도록 설계되었다. 이 장비를 처음 사용할 때, 손을 자유롭게 사용하지 못하는 사람에게 이 장비가 얼마나 큰 자유를 줄 수 있는지 알게 될 것이다. 컴퓨터에 얽매이는 것 대신, 음파센서에 공기를 부는 것 같은 간단한 조작은 휠 기능까지 포함한 일반 마우스의 모든 기능들을 수행할 수 있다. 또한 매크로인터페이스(macro-interface) 도 개발되었다. 반복적 작업을 메모리에 저장함으로써, 버튼 한번 클릭하는 것만으로 반복되는 작업들을 수행할 수 있다.

• 한국산업보건학회지
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• 제28권2호
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• pp.200-210
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• 2018

Objectives: The purpose of this study is to assess the exposure to ozone and total volatile organic compounds(TVOCs) generated during welding work at a shipyard and recommend respiratory protective equipment(RPE) adequate against these hazards. Method: Ozone was collected for about 30 minutes at two-minutes intervals using a direct reading instrument, specifically an ozone analyzer(Serinus 10, Ecotech, Australia). TVOCs were collected for about 30 minutes at three-minute intervals using a portable GC (Alpha 115, Synspec BV, the Netherlands), and were determined simultaneously by area sampling at the welding plume closest to the welder's breathing zone. The total measurements were 162 for ozone($CO_2$ welding 47, TIG 60, stick 55), and 136 for TVOCs($CO_2$ 65, TIG 50, stick 21). Based on these measurements, a literature survey was conducted to assess the adequacy of RPE. Results: Relative to Korean OEL, measurements above STEL 0.2 ppm were 23.4% for $CO_2$, 63.3% for TIG and 14.5% for stick welding. There were significant differences(p=<0.0001) among welding types. Compared with ACGIH peak exposure of 0.4 ppm for ozone, which is not applied in Korea, $CO_2$ welding exceeded it by 10.6%, TIG by 40.0% and stick by 7.3%. Although it was not feasible to compare them directly since there are no Korean OEL, TVOCs had very high levels similar to the concentrations before moving into a new apartment and about 10-20 times the indoor air quality recommendations for some individual measurements. Conclusions: As ozone removal RPE has been recommended in welding environments for a long time(Lunau, 1967), this fact was demonstrated based on the results of the on-site work environment measurements(ozone and TVOCs). In conclusion, for all welding at a shipyard, gas/vapor and particulate combination RPE are recommended. If this is not possible, it should at least be present for TIG welding.

• Tuberculosis and Respiratory Diseases
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• 제45권4호
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• pp.813-822
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• 1998

연구배경: 압력보조환기로 이탈시 발판 시기는 최소보조압력수준에서 시행하는 것이 추천되고 있다. 그러나 임상에서는 압력보조환기법에 의한 이탈시 기관내 관의 발관을 최소압력보조법에 도달하였다고 판단되는 경우에서도 기관내 관의 재삽관 가능성을 줄이기 위하여 때로는 T-piece 시도를 1 시간 더한 뒤 기관내 관을 제거하는 방법도 시행되고 있다. 이는 환자의 호흡예비력을 좀더 확실하게 검증할 수 있는 장점이 있는 반면, 기관내 관 자체가 높은 기도 저항을 유발하므로 환자의 호흡 일이 증대되어 오히려 이탈이 지연될 가능성도 있다. 본 저자들은 최소압력보조치에서 1 시간 T-piece 추가가 이탈에 어떤 영향을 미치는지 알아보고자하였다. 연구방법: 1997년 5월부터 1998년 3월까지 서울중앙병원 내과계 중환자실에서 이탈을 시도한 44명을 대상으로 무작위 전향적 연구를 시행하였다. 이탈 대상이 되는 환자는 모두 압력보조환기방법으로 이탈을 진행하고 압력보조수준이 최소압력보조치에 이르면 환자를 무작위로 실험군 (1시간 T-piece 시도)과 대조군(즉시 발관)으로 나누었다. 연구결과: 전체 42회 이탈의 최소압력보조치는 7.6 [${\pm}1.9$, (4-13)] cm $H_2O$였다. 1. 환자들의 기저 상태 : 두 군간 환자들의 총 기계환기 시간, APACHE III 접수, 영양지표, 분당 호흡수, 얕은 숨지수, 호흡, 일 등에서 차이가 없었다. 2. 두 군간 성공률 및 호흡역학의 차이 : 실험군이 55%, 대조군이 70%로 즉시 발관한 군이 성공률이 높으나 통계학적 차이는 없었다 (p>0.05). 재삽관률도 실험군이 18%, 대조군이 20%로 두 군간 차이가 없었다. 실험군에서 1시간 T-piece 시도후 일회호흡 용적, 분당 호흡수, 얕은 숨지수, 호흡 일에서 악화된 소견을 보였으며(P<0.05), 특히 실험군내의 실패군에서는 일회호흡용적, 호흡 일, 압력시간곱의 악화가 심하였다 (P<0.05). 3. 성공군과 실패군 분석 : 전체 성공군에서 총 기계환기 시간이 유의있게 낮았고 ($246{\pm}195$ 시간 대 $407{\pm}248$ 시간, P<0.05), 일회호흡용적은 유의하게 높았다 ($0.43{\pm}0.11$ L 대 $0.35{\pm}0.10$ L). 결 론: 이상의 결과로서 최소압력보조치에서 1 시간 T-piece 추가는 환자의 호흡 일을 증가시키며 이탈 성공률에 있어 최소압력보조치에서 즉시 발관하는 방법에 비하여 차이가 없으므로 압력보조환기 양식으로 이탈을 시도할 때는 최소압력보조치에서 즉시 발관하는 것이 나을 것으로 사료된다.