• Journal of the Korean Solar Energy Society
• /
• v.30 no.3
• /
• pp.124-130
• /
• 2010

Ocean Thermal Energy Conversion(OTEC) power plants have been examined as a viable option for supplying clean energy. This paper evaluated the thermodynamic performance of the OTEC Power system for the production of electric power and desalinated water. The results show that newly developed fluids such as R32, R125, R143a, and R410A that do not cause stratospheric ozone layer depletion perform as well as R22 and ammonia. Overall cycle efficiency of open cycle is the lowest value of 3.01% because about 10% of the gross power is used for pumping out non-condensable gas. Also, the hybrid cycle is an attempt to combine the best features and avoid the worst features of the open and closed cycles. The overall cycle efficiency of hybrid cycle is 3.44% and the amount of desalinated water is 0.0619 kg/s.

• Journal of the Korean Society of Earth Science Education
• /
• v.4 no.2
• /
• pp.126-133
• /
• 2011

This study explored different concepts by handing out the questionnaires asking the 6 students of the second year of junior high school who had no lesson on cycle "which words related to cycle are suggested?" In regard to the stimulation of the word 'cycle', students relate it to different fields that they learn at school such as biology, environmentology, and earth science. The analyzed results from the answers by students are as follows. First, it resulted in from analysis on the questionnaire and the half-structured interviews that students were unable to expand the concept of cycle to the scientific concept, and perceived it fragmentarily. Secondly, their understanding on the system of the earth was low and they understood the concept of cycle with a unilinear thought rather than a systematic thought. Therefore, we need to synthesize the students' unilinear thoughts on cycle shown through this study and an effective educational strategy for their continuous, systematic thoughts, is essential.

• The KSFM Journal of Fluid Machinery
• /
• v.16 no.3
• /
• pp.10-17
• /
• 2013

The organic Rankine cycle has been widely used to convert the renewable energy such as the solar energy, the geothermal energy, or the waste energy etc., to the electric power. Some previous studies focused to find what kind of refrigerant would be a best working fluid for the organic Rankine cycle. In this study, R245fa was chosen to the working fluid, and the cycle analysis was conducted for the output power of 30kW or less. In addition, properties (temperature, pressure, entropy, and enthalpy etc.) of the working fluid on the cycle were predicted when the turbine output power was controlled by adjusting the mass flowrate. The configuration of the turbine was a radial-type and the supersonic nozzles were applied as the stator. So, the turbine was operated in partial admission. The turbine efficiency and the optimum velocity ratio were considered in the cycle analysis for the low partial admission rate. The computed results show that the system efficiency is affected by the partial admission rate more than the temperature of the evaporator.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.7
• /
• pp.2289-2297
• /
• 1996

Flows in the combustion chamber near the spark plug are measured using LDv.A single cylinder DOHC S.I. engine of compression ratio 9.5:1 with a transparent quartz window piston is used. Combustion chamber shape is semi-wedge type. Measured data are analyzed using the ensemble averaged analysis and the cycle resolved analysis which uses FFT Filtering. Turbulent intensity and mean velocity are studied in the main flow direction and the normal to main flow direction as a function of engine speeds. The results shows that the turbulent intensity obtained by the ensemble averaged analysis is greater than that calculated by the cycle resolved analysis. Especially, the ensemble averaged analysis shows increase in turbulence at the end of compression stroke although the cycle resolved analysis shows increase only in the cycle-by-cycle variation with no noticeable increase in turbulence. The mean velocity in the main flow direction increase as engine speed increase. But the mean velocity normal to the main flow does not show such increase. Turbulent intensity in both direction increase in proportion to engine speeds. The magnitude of turbulent intensity is about 0.3 ~ 0.4 times the mean piston speeds at the end of the compression stroke.

• International Journal of Quality Innovation
• /
• v.9 no.3
• /
• pp.71-91
• /
• 2008

The definition of cycle time is the time from the wafer start to the wafer output. It usually takes one or two months to get the product since customer decides to produce it. The cycle time is a critical factor for customer satisfaction because it represents the response time to the market. Long cycle time reflects the ineffective investment for the capital. The cycle time is very important for foundry because long cycle time will cause customer unsatisfied and the order loss. Consequently, all of the foundries put lots of human source in the cycle time improvement. Usually, we make decisions based on the experience in the cycle time management. We have no mechanism or theory for cycle time management. We do work-in-process (WIP) management based on turn rate and standard WIP (STD WIP) set by experiences. But the experience didn't mean the optimal solution, when the situation changed, the cycle time or the standard WIP will also be changed. The experience will not always be applicable. If we only have the experience and no mechanism, management will not be work out. After interview several foundry fab managers, all of the fab can't reflect the situation. That is, all of them will have an impact period after product mix or utilization varied. In this study, we want to develop a formula for standard WIP and use statistical process control (SPC) concept to set WIP upper/lower limit level. When WIP exceed the limit level, it will trigger action plans to compensate WIP Profile. If WIP Profile balances, we don't need too much WIP. So WIP level could be reduced and cycle time also could be reduced.

• Journal of the Korean Society of Systems Engineering
• /
• v.11 no.2
• /
• pp.1-11
• /
• 2015

During the industrial plant system life cycle, required technologies are developed and assessed to analyze their performance, risks and costs. The assessment is called technology readiness assessment (TRA) and the measure of readiness is called technology readiness level (TRL). The TRL consists of 9 levels and through the TRL assessment, the technology to be developed and its components are assigned to their appropriate TRL. TRL assessment should be performed in each life cycle stages to monitor the technology readiness and analyze the potential risks and costs. However, even though the concept of TRL has been largely adopted by numerous organizations and industry, direct and clear assignment of target TRL for each life cycle stage has been overlooked. Direct mapping/assignment of target TRL for each life cycle has benefits as follow: (1) the technical risks condition of each life cycle stage can be better understood, (2) cost incurred if the technology development is failed can be analyzed in each life cycle stage, and (3) more effective decision making because the technology readiness achievement for each life cycle stages is agreed beforehand. In this paper, we propose a steel-making plant system life cycle and TRL assignment to each of the system life cycle stage. By directly assigning target TRL for each life cycle stages, we look forward to a more coordinated (in terms of exit criteria) and highly effective (in terms of technical risks identification and eventually prevent project failure) technology development and assessment processes.

• Journal of Society of Preventive Korean Medicine
• /
• v.24 no.3
• /
• pp.57-67
• /
• 2020

Background : The Life cycle Health Promotion Programs using Traditional Korean Medicine (the Life cycle HaPPs-TKM) are the on-going 3rd stage projects that have centered on the development and dissemination of the standard life cycle HaPPs-TKM in the local community. The purpose of the study was to introduce the development background of the standard life cycle HaPPs-TKM and to suggest its activation plan. Methods : Academic and government research reports on the life cycle HaPPs-TKM were analyzed to introduce the development process, development backgrounds and the details of KM-HPP for each life cycle, such as infants and toddlers, adolescents, pregnant women, adults and the elderly. Results : We reviewed the development process of the standard life cycle HaPP-TKM consisted of a series of diagnosis on community members' health problems, establishment of project purpose, research on the involvement of KM intervention in a project, and final development of the project model. And we rediscovered that in the development backgrounds of KM-HPP, there were beneficial goals to manage and promote public health conditions for each life cycle. Conclusion : To activate life cycle HaPPs-TKM, we would recommend that activation plan should include six factors through systematic analysis of research reports. These factors consist of diversified goals for each life-cycle, competency reinforcement of local project manager, diversified Korean Medicinal modalities to enhance Sasang Constitution and Qigong, development of standard Outcome Index, periodical holding of performance contest, and improved guidance of government and associated entities through whole process of HaPP-TKM.

• Journal of The Korean Astronomical Society
• /
• v.50 no.2
• /
• pp.21-27
• /
• 2017

The autoregressive method provides a univariate procedure to predict the future sunspot number (SSN) based on past record. The strength of this method lies in the possibility that from past data it yields the SSN in the future as a function of time. On the other hand, its major limitation comes from the intrinsic complexity of solar magnetic activity that may deviate from the linear stationary process assumption that is the basis of the autoregressive model. By analyzing the residual errors produced by the method, we have obtained the following conclusions: (1) the optimal duration of the past time for the forecast is found to be 8.5 years; (2) the standard error increases with prediction horizon and the errors are mostly systematic ones resulting from the incompleteness of the autoregressive model; (3) there is a tendency that the predicted value is underestimated in the activity rising phase, while it is overestimated in the declining phase; (5) the model prediction of a new Solar Cycle is fairly good when it is similar to the previous one, but is bad when the new cycle is much different from the previous one; (6) a reasonably good prediction of a new cycle can be made using the AR model 1.5 years after the start of the cycle. In addition, we predict the next cycle (Solar Cycle 25) will reach the peak in 2024 at the activity level similar to the current cycle.

• Journal of ILASS-Korea
• /
• v.18 no.3
• /
• pp.132-139
• /
• 2013

Smoke emissions from light duty diesel vehicles were measured using light extinction method with the free acceleration test mode. The smoke emissions for each measurement cycle of the free acceleration method showed large variations according to driver's pedal pushing pattern. The smoke values for each measurement cycle initially increased and reach a peak value. Integration of the smoke emissions with time for each measurement cycle was performed to get a representative smoke value which was obtained by averaging the integrated results. Two kinds of integration time range were used. One is range over the whole measurement cycle of the free acceleration method. The other is only the acceleration range in the measurement cycle. Overall, variation of the representative smoke values obtained by the integration method was reduced comparing to the traditional representative smoke value which was obtained from a peak smoke value over the measurement cycle. Ten vehicles of the same model with 2.5 liter diesel engines, and seven vehicles of the same model with 2.7 liter diesel engines, were tested using the free acceleration test method.

• Plant Journal
• /
• v.15 no.2
• /
• pp.46-55
• /
• 2019

This paper presents a LNG Liquefaction cycle configuration using two stages of methane expansion (i.e. spliting into two stages as warm & cold to generate an additional inflection point within a cold composite curve) and a single stage of nitrogen expansion to improve the efficiency of the conventional Methane & Nitrogen Expansion Cycle. In comparison with Double Nitrogen Expansion Cycel and Methane & Nitrogen Expansion Cycle, the cycle efficiency has increased approximately from 13.92 and 13.13 to 12.08 kW/ton/day (8~15% efficiency increase). A Life Cycle Cost (LCC) analysis based on Net Present Value (NPV) also show an improvement in therms of project NPV, against a minor increment of a CAPEX.