• Transactions of the Korean hydrogen and new energy society
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• v.23 no.6
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• pp.604-611
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• 2012

For the commercialization of fuel cell powered vehicle, it is highly important to improve the performance and efficiency of an automotive polymer electrolyte membrane fuel cell (PEMFC) system. The performance and efficiency of PEMFC systems are significantly influenced by their operating conditions. Among these conditions, the system operating pressure is considered as the one of the main factors. In this study, to investigate the effects of operating pressure on the performance and efficiency of automotive PEMFC systems, two types of high-pressure operating PEMFC systems adopting two different compressors (i. e. different performance maps) are modeled by using MATLAB/Simulink environment. The PEMFC system efficiency and parasitic compressor power are mainly analyzed and compared for the two types of high-pressure operating PEMFC systems under the same system net power conditions. It is expected that this kind of study can contribute to provide basic insight into the operating strategies of high-pressure operating PEMFC systems for automotive use.

• Journal of Mechanical Science and Technology
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• v.19 no.4
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• pp.1018-1026
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• 2005

The proton exchange membrane (PEM) fuel cell system consisting of stack and balance of plant (BOP) was modeled in a MATLAB/Simulink environment. High-pressure operating (compressor type) and low-pressure operating (air blower type) fuel cell systems were con­sidered. The effects of two main operating parameters (humidity and the pressure of the supplied gas) on the power distribution characteristics of BOP and the net system efficiency of the two systems mentioned above were compared and discussed. The simulation determines an optimum condition regarding parameters such as the cathode air pressure and the relative humidity for maximum net system efficiency for the operating fuel cell systems. This study contributes to get a basic insight into the fuel cell stack and BOP component sizing. Further research using muli­object variable optimization packages and the approach developed by this study can effectively contribute to an operating strategy for the practical use of fuel cell systems for vehicles.

• The Journal of the Korea Contents Association
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• v.22 no.3
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• pp.296-308
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• 2022

In the COVID-19 crisis, the elderly over 60 have various psychological health problems such as depression, anxiety, and fear, and the community has become the only space for senior activities. To this end, this study presented a therapeutic aging-friendly community environmental design evaluation system using theoretical review, FGI interview, and hierarchical analysis AHP. The evaluation system is a three-dimensional space, with 10 upper layers and 68 lower layers. In addition, the weight of each index of the evaluation system was distributed through expert survey and SPSS program analysis. First, the material space environment design must satisfy the comfort and health of the elderly when they are active in a common space for their daily life. Second, the design of social space environment is designed to promote exchange and social connection among the elderly. Third, the operating space environment design considers the operating system of the community operating company as important. Through this, it is expected to improve the psychological health of the elderly by providing systematic technical basis and action guidelines for the development of the residential environment of the elderly.

• Journal of Climate Change Research
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• v.7 no.1
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• pp.19-29
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• 2016

In this study, the emission intensity calculation method of GHGs was developed by considering the characteristics of the models and time series. The telematics device was installed on the car (OBD-II) to collect information on the operation conditions from each sample vehicle of public authorities. Based on emission intensity of GHGs, it presented a methodology of quantitative comparison of GHGs emission by vehicles. Collected driving information of vehicle was used for operating characteristics analysis of the target vehicle, and it was confirmed different operating characteristics through comparison of the results and previous study. GHGs emission intensity were analyzed considering characteristics of vehicle type by passenger car, van, cargo, and considering characteristics of the time series by summer, winter, and intermediate. From the analysis result, it was calculated GHGs emission intensity based on mileage ($g\;CO_2\;eq./km$) and operating time ($g\;CO_2\;eq./sec$).

• The KIPS Transactions:PartD
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• v.10D no.5
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• pp.773-780
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• 2003

SecuROS(Secure & Reliable Operating System) prevents and blocks possible system cracking by implementing additional security functions in FreeBSD 4.3 operating system (OS) kernel, including access control, user authentication, audit trail, encryption file system and trusted channel. This paper describes access control technique, which is one of core technologies of SecuROS, introduces the implementations of DAC, MAC and RBAC, all of which are corresponding access control policies, and show security and results of performance measurement on the basis of application of access control policies. Finally, security and performance between conventional OS environment and environment adopting access control policy is described.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.3
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• pp.240-245
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• 2015

In this study, experiments were performed using a model of a very large crude oil carrier (VLCC), which is a typical blunt ship, in a wave-making towing tank. The aim of the experiments was to determine the effect of added resistance in waves on the various operating conditions of a VLCC. An analysis of the results was conducted to determine the characteristics of resistance performance in waves. In addition, the characteristics of added resistance on a tanker were analyzed under irregular waves based upon the above result. The experimental results showed that added resistance was the highest around ${\lambda}/L=1.0$, and the added resistance increased with the increase of the ship speed. Furthermore, under even keel conditions, the added resistance was higher than that under the trim changes, and the smallest added resistance was measured at the trim by the stern. Based on the experimental results, this study proposes effective operating conditions by analyzing the characteristics of the mean added resistance and the expected extreme response in irregular waves.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.3
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• pp.302-308
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• 2021

Developers generally use test standards suggested by military standards such as MIL-STD-810G when performing vibration tests in the materiel development. However, according to MIL-STD-810G, it is recommended to test by tailoring the test standard suitable for the developed materiel, and it is specified to apply the suggested test standard only when there is difficulty in tailoring. In addition, the test standards presented by MIL-STD-810G are standards created under operating conditions different from the actual operating environment of each developed materiel, so the test according to this standard may be excessive or understated. Therefore, the developer must create an appropriate vibration test standard for the developed materiel as similar to the operating conditions as possible. In this paper, the procedure for creating the functional test standard and durability test standard suitable for the operating environment of the equipment to be mounted on the propeller aircraft under development is described, and the created standard is introduced.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2097-2100
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• 2003

Many studies have been done on secure operating system using secure kernel that has various access control policies for system security. Secure kernel can protect user or system data from unauthorized and/or illegal accesses by applying various access control policies like DAC(Discretionary Access Control), MAC(Mandatory Access Control), RBAC(Role Based Access Control), and so on. But, even if secure operating system is running under various access control policies, network traffic among these secure operating systems can be captured and exposed easily by network monitoring tools like packet sniffer if there is no protection policy for network traffic among secure operating systems. For this reason, protection for data within network traffic is as important as protection for data within local system. In this paper, we propose a secure operating system trusted channel, SOSTC, as a prototype of a simple secure network protocol that can protect network traffic among secure operating systems and can transfer security information of the subject. It is significant that SOSTC can be used to extend a security range of secure operating system to the network environment.

• Journal of Korean Academy of Nursing Administration
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• v.22 no.5
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• pp.471-479
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• 2016

Purpose: This study was conducted to evaluate the level of safety climate, fatigue, and safety performance and to identify the impact of safety climate and fatigue on the safety performance of operating room nurses. Methods: The study design was a descriptive survey. Participants were 174 operating room nurses from two general hospitals and two university hospitals in S and D cities. Three structurally designed questionnaires were used to evaluate their safety climate, fatigue, and safety performance. Collected data were analyzed using descriptive analysis, t-tests, ANOVAs, Pearson correlation coefficient, and stepwise multiple regression. Results: Safety performance of operating room nurses had a mean of 3.26 on a 5-point scale. 'Current department career'(${\beta}=.17$, p=.006) and 'safety climate (work-unit contribution) (${\beta}=.63$, p<.001) accounted for 39% of the variance in operating room nurses' safety performance. Conclusion: Findings indicate that work-unit contribution towards safety climate is an important factor in increasing operating room nurses' safety performance. Therefore, it is essential to find motivational properties consistent with the characteristics of the operating room environment.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.389-396
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• 2006

A quantitative survey of the protozoa microfauna at two advanced wastewater treatment plants has been carried out on a weekly basis. The abundance of the protozoa were compared with operating parameters and effluent quality using statistical procedures. The protozoa distribution indicated it seemed the composition of the influent wastewater and operating conditions of plant influenced the structure of protozoa in the plant. In statistical analysis, the distribution of protozoa showed the present operating condition of plant and predicted near-future effluent qualify. Enough data concerning protozoa, operating parameters and effluent has been gathered, the operator has a valuable tool for predicting plant performance and near-future data of effluent based on microscopic examination. Perhaps more importantly it can be used to actually control the plant to adjust the operating conditions to obtain the protozoal populations that have been shown to provide the best effluent quality.