• 대한기계학회논문집B
• /
• 제26권12호
• /
• pp.1729-1737
• /
• 2002

A mathematical model for the prediction of carbon-dioxide absorption rate during the transient state of rotary type absorber is developed. The rotary type absorber operates using a fast rotating porous structure and clean water. The model for the transient state rotary type absorbers is based on the steady state model of packed tower absorber. The paper manipulates the operating data of an arbitrary quasi-steady state condition of rotary type absorber for the determination of the coefficients involved in the model developed. The prediction accuracy is evaluated from the measured data of rotary type absorber operated under fast transient state. The measured data include the mole fraction of carbon dioxide in mixed gas and the pressure of absorber. The relative error in carbon dioxide prediction is estimated to be 20% at maximum. The model is successfully applied for the prediction of the behavior of a closed cycle diesel engine.

• 복식
• /
• 제63권8호
• /
• pp.156-170
• /
• 2013

The purpose of this research is to scrutinize the cyclist's consumer behavior by analyzing the eWOM information search behavior of cycle-wear according to benefits sought and involvement. The research was conducted through an online survey and the respondents were 291 men who wore cycle-wear and searched information via online. The results of this research are as following. First, the benefits sought from wearing cycle apparel are composed of five sub-factors such as, ideal body figure, brand ostentation, comfort ease, personality, and economic feasibility. In addition, the cycle-wear involvement consisted of two sub-factors: cycling involvement and fashion involvement. Second, the eWOM information search behavior of cyclists was different depending on the benefits sought by the cyclists. When the cyclists pursued ideal body figure they searched more information of design and color, while cyclists put more weight on the information of design, color, and brand when they sought brand ostentation. Moreover, the valence and the type of the information were dissimilar depending on the benefits sought. Third, the sub-factors of eWOM information search behavior affected the eWOM effect distinctively. The price information was the only factor that influenced the eWOM effect among the contents of the information. The valence of the information influenced the eWOM effect, and the effect of positive information was stronger than negative information. Additionally, the subjective information also affected the eWOM effect. Lastly, the effect of the benefits sought influencing the eWOM information search behavior varied by the difference of the cycle-wear involvement. For example, when they are both high in the involvement there were various benefits sought affecting the eWOM information search behavior. However, when only the cycling involvement was high, and they pursued personality, the price information was not important to them.

• 디지털콘텐츠학회 논문지
• /
• 제19권7호
• /
• pp.1297-1302
• /
• 2018

이 연구의 목적은 실제 장애인 선수들을 대상으로 시중에 판매되고 있는 High-end급 핸드 사이클과 새로 개발한 핸드사이클의 크랭킹을 비교 분석 하고자 한다. 현재 대한장애인사이클 연맹에 선수로 등록되어 있는 선수중 동일한 지체유형을 가지고 있는 남자선수 10명을 대상으로 하였다. 대상자들의 운동학적 데이터 획득을 위해 12대의 적외선카메라(Oqus-500)를 사용하였다. 자료 획득을 위해 30초 자료 중 15초 전 후의 크랭킹 3회를 분석하였다. 통계적 검정은 SPSS 16을 이용하여 대응표본 t-test를 이용하여 RX와 시제품의 운동역학적 변인의 차이를 검정하였으며, 이때의 유의 수준은 ${\alpha}=.05$로 하였다. 크랭킹 시 근발현이 가장 높게 나타나는 180~195도 구간에 대한 선수들의 근 피로도 감소를 위해 핸드사이클 크랭크를 곡선으로 제작하여 적용할 필요가 있으며, 향후 연구에서는 핸드사이클의 크랭킹이 경기력 향상의 주요변인인 만큼 구조를 변형시킨 크랭크와 기존데이터를 비교 분석할 필요가 있다.

• Annals of Occupational and Environmental Medicine
• /
• 제35권
• /
• pp.30.1-30.13
• /
• 2023

Background: Dysmenorrhea and menstrual cycle changes occur in women working shifts. Circadian rhythm disruption and sleep disturbances associated with shift work leads to health problems. We identified chronotypes and the occurrence of insomnia among newly employed university hospital nurses and investigated the association of these factors with menstrual problems. Methods: We conducted pre-placement health examinations for shift workers using self-reported questionnaires between 2018 and 2020. A total of 463 nurses were included in the study. Sociodemographic data, shift work experience, and information on insomnia were collected from health examination data. In addition, details regarding chronotype, dysmenorrhea, irregular and abnormal menstrual cycles, amenorrhea, and contraceptive use were obtained from the questionnaire. Multiple logistic regression analysis was performed to study the association between chronotype, insomnia, and menstrual problems after controlling for age, body mass index, contraceptive use, amenorrhea, and prior shift work. Results: The prevalence rates of dysmenorrhea, irregular menstrual cycles, and longer menstrual cycles were 23.8%, 14.9%, and 4.1%, respectively. The risk of dysmenorrhea increased in the evening-type (odds ratio [OR]: 3.209; 95% confidence interval [CI]: 1.685-6.113) and those with insomnia (OR: 1.871; 95% CI: 1.074-3.261). Additionally, the risk of an irregular menstrual cycle (OR: 2.698; 95% CI: 1.167-6.237) increased in the evening-type, and the risk of a longer menstrual cycle (OR: 4.008; 95% CI: 1.354-11.864) increased in individuals with insomnia. Conclusions: Our findings suggest that dysmenorrhea is promoted in the evening-type and insomnia individuals. There may be an increased risk of irregular menstrual cycles among evening-type nurses and an increased risk of longer menstrual cycles among those with insomnia. Therefore, factors such as evening-type and insomnia should be considered for the prevention of menstrual problems in women performing shift work.

• 한국수소및신에너지학회논문집
• /
• 제10권2호
• /
• pp.141-149
• /
• 1999

현재 수소저장 합금을 이용하여 2차전지의 음극으로 개발되고 있는 $AB_5$ type의 $(LM)Ni_{4.49}Co_{0.1}Mn_{0.205}Al_{0.205}$ 조성의 수소저장합금과 $AB_2$ type의 $Ti_{0.6}Zr_{0.4}V_{0.6}Ni_{1.4}$ 조성의 수소저장합금에 Pd를 0, 0.5, 1, 2 wt% 첨가한 조성을 진공 중에서 arc 용해를 하였다. 용해된 합금의 조직과 결정구조를 SEM, XRD로 조사하였다. Pd 가 첨가되었음에도 조직이나 결정구조의 변화는 보이지 않았다. 미세한 구리분말을 합금분말 대비 3:1로 첨가하여 pellet형태의 전극을 제조하여 전극특성을 조사한 결과 Pd 첨가에 따른 초기 활성화와 급속 충방전 특성은 크게 변하지 않았다. 그러나 싸이클 수명에 있어서는 Pd를 첨가한 전극들이 Pd를 첨가하지 않는 전극에 비해 우수하였다. $AB_5$ type 조성의 합금에서는 Pd를 2wt% 첨가한 전극, 그리고 $AB_2$ type 조성의 합금에서는 Pd를 0.5wt% 첨가한 전극에서 싸이클 특성이 가장 우수하게 나타났다.

• 한국추진공학회지
• /
• 제3권2호
• /
• pp.48-55
• /
• 1999

50㎾급 터보제너레이터 가스터빈 엔진에 리쿠퍼레이터가 부착되는 경우 성능 변화를 조사하였다. 리쿠퍼레이터는 군사 및 소형 자동차용 엔진에 경제적 연비와 배기가스 저감의 목적으로 많이 적용되어 왔다. 열역학적 관점에서 볼 때 재생사이클은 압축비 10이하 및 비교적 낮은 터빈 입구온도에서 사이클의 효율 상승에 기여하는 바가 큰 것으로 나타난다. 1축단순사이클 터보제너레이터 가스터빈 엔진에 리쿠퍼레이터를 부착하는 경우 리쿠퍼레이터 효율 $\varepsilon$ = 0.5에서 엔진의 효율은 상대적으로 약 30% 증가하는 것으로 나타났고 이때 열교환기내의 압력 손실은 5.2%로 설계하였다. 용이한 제작, 구조적 견고성, 최소의 누출 둥의 장점으로 튜브형의 열교환 시스템이 본 가스터빈 엔진에 적합한 것으로 판단되었다.

• 한국수소및신에너지학회논문집
• /
• 제26권1호
• /
• pp.64-70
• /
• 2015

Organic Rankine cycle (ORC) is an useful cycle for power generation system with low temperature heat sources ($80{\sim}400^{\circ}C$). Since the boiling point of operating fluid is low, the system is used to recover the low temperature heat source of waste heat energy. In this study, a ORC with R134a is applied to recover the waste energy of condenser of coal fired power plant. A system model is developed via Thermolib$^{(R)}$ under Simulink/MATLAB environment. The model is composed of a refrigerant heat exchanger for heat recovery from coal fired condenser, a drum, turbine, heat exchanger for ORC heat rejection, storage tank, water recirculation pump and water drip pump. System analysis parameters were heat recovery capacity, type of refrigerants, and types of turbines. The simulation model is used to analyze the heat recovery capacity of ORC power system. As a result, increasing the overall heat transfer coefficient to become the largest of turbine power is the most economical.

• 한국자동차공학회논문집
• /
• 제5권1호
• /
• pp.129-135
• /
• 1997

Previous studies has shown that the curve of low-cycle fatigue life was not expressed with the single line subjected to Manson-Coffin's law type and bent to short life in low ${\Delta}{\varepsilon}_p$ region. The main cause of this phenomenon has been considered that the localization of plastic strain in the crack initiation process fosters the crack initiation. In this study, the low-cycle fatigue life was investigated for each specimens omitted crack initiation process and it was found that fatigue life curve in log(${\Delta}{\varepsilon}_p$)-log($N_f$)was bent in low ${\Delta}{\varepsilon}_p$ region as ever. Therefore, the main cause of appearance of knee point in fatigue life curve is not found in the crack initiation process but in the crack propagation process. In the crack propagation process, the localization of the plastic strain in the vicinity of crack tip and the influence of test environment on the crack propagation rate were observed and these inclinations were more remarkable in low ${\Delta}{\varepsilon}_p$ region. Hence, it was concluded that these two phenomena in the crack propagation process were proved to the main cause which accelerates the crack propagation in low ${\Delta}{\varepsilon}_p$ region and bent the fatigue life curve in result.

• 한국태양에너지학회 논문집
• /
• 제37권5호
• /
• pp.27-37
• /
• 2017

In this study, an artificial solar simulator composed of a 2.5 kW Xe-Arc lamp and mirror reflector was used to carry out the solar thermal two step thermochemical water decomposition cycle which can produce high efficiency continuous hydrogen production. Through various operating conditions, the change of hydrogen production due to the possibility of a dual-zone reactor and heat recovery were experimentally analyzed. Based on the reaction temperature of Thermal-Reduction step and Water-Decomposition step at $1,400^{\circ}C$ and $1,000^{\circ}C$ respectively, the hydrogen production decreased by 23.2% under the power off condition, and as a result of experiments using heat recovery technology, the hydrogen production increased by 33.8%. Therefore, when a thermochemical two-step water decomposition cycle is conducted using a dual-zone reactor with heat recovery, it is expected that the cycle can be operated twice over a certain period of time and the hydrogen production amount is increased by at least 53.5% compared to a single reactor.

• 상하수도학회지
• /
• 제36권2호
• /
• pp.97-106
• /
• 2022

Recently microplastic (MP) biofilm is being attracted as an important environmental issue because it can act as a pollutant carrier in aqueous system. Therefore, this study investigated the MP biofilm communities originated from freshwater. The results showed the bacterial community structure of MP biofilm was distinctively different from the freshwater regardless of biofilm-forming condition and MP type. For MP biofilm communities exposed to raw freshwater, Solimonas variicoloris-like microbe, Frigidibacter albus-like microbe, Nitrospirillum amazonense-like microbe, and Pseudochroococcus couteii-like microbe became abundant, while Acinetobacter johnsonii, Macellibacteroides fermentans, and Sedimentibacter acidaminivorans-like microbe were found as major bacteria for MP biofilm communities exposed to organic rich condition. The results of this study suggest that the unique freshwater biofilm community could be formed on the MP surface.