• Communications for Statistical Applications and Methods
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• v.7 no.2
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• pp.513-523
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• 2000

The X-12-ARIMA program was utilized on the analysis of the time series trend on 76 Korean industrial activities data in order to ensure that the trading day effect adjustment as well as the seasonal effect adjustment is needed to extract the fundamental trend-cycle factors from various economic time series data. The trading day effect is strongly correlated with the activity of production and shipping but not with the activity of inventory. Furthermore, the industrial activities were classified with respect to the sensitivity on the tranding day effect.

• Journal of the Korean earth science society
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• v.40 no.5
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• pp.487-501
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• 2019

In this study, steric height variability in the East Asian Seas (EAS) has been analyzed by using ocean reanalysis intercomparison project (ORA-IP) data. Results show that there are significant correlations between ocean reanalysis and satellite data except the phase of annual cycle and interannual signals of the Yellow Sea. Reanalysis ensemble derived from 15-different assimilation systems depicts higher correlation (0.706) than objective analysis ensemble (0.296) in the EAS. This correlation coefficient is also much higher than that of the global ocean (0.441). For the long-term variability of the thermosteric sea level during 1993-2010, a significant warming trend is found in the East/Japan Sea, while cooling trend is shown around the Kuroshio extension area. For the halosteric sea level, a dominant freshening trend is found in the EAS. However, below 300 m depth around this area, the signal-to-noise ratio of the linear trend is generally less than one, which is related to the low density of observation data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.6
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• pp.753-762
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• 1998

A domestic refrigerator is composed of many components such as a compressor, evaporator, capillary tube, and the cabinet which plays a great role on the cycle performance, even if it is not the basic component part in the cycle. Recently, the restriction policy on the energy-saving and environmentally friendly refrigerator is reinforced in our nation as well as developed countries. Therefore, in this paper, cycle simulations and experiments were carried out ito understand the characteristics of the cycle performance using CFC 12, HFC 134a, and HC 600a and to know how changes in UA(overall heat transfer coefficients$\times$ heat transfer area) of evaporator, the position displacement of compressor, and the rpm of fan in the freezing room which has influence on the cycle performance. The result shows that the quantitative values of simulation and experiment are not coincident, but their trend is similar. When HFC 134a and HC 600a were used without the change of design in refrigerator used CFC 12, the performance of system in HC 600a is 30% lower, and the case of HFC 134a is 10% lower than that of CFC 12 on freezing temperature.

• The KSFM Journal of Fluid Machinery
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• v.18 no.5
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• pp.33-41
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• 2015

Organic Rankine cycle (ORC) has been used to generate electrical or mechanical power from low-grade thermal energy. Usually, this thermal energy is not supplied continuously at the constant thermal energy level. In order to optimally utilize fluctuating thermal energy, an axial-type turbine was applied to the expander of ORC and two supersonic nozzle were used to control the mass flow rate. Experiment was conducted with various turbine inlet temperatures (TIT) with the partial admission rate of 16.7 %. The tip diameter of rotor was to be 80 mm. In the cycle analysis, the output power of ORC was predicted with considering the load dissipating the output power produced from the ORC as well as the turbine efficiency. The predicted results showed the same trend as the experimental results, and the experimental results showed that the system efficiency of 2 % was obtained at the TIT of $100^{\circ}C$.

• Journal of the Korea Society for Simulation
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• v.21 no.1
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• pp.1-8
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• 2012

In recent days, global shipbuilding companies have been showing great interest in eco-friendly ship products and trying to reduce environmental pollution - harmful gas and dust in shipbuilding process. Following this trend, Life Cycle Assessment (LCA) was carried out to an application of shipyards layout. LCA is a technique used to assess environmental impacts during the life cycle of products and systems. Until now, LCA has been used through ISO 14040 in somewhat limited industries, such as Building Life Cycle Assessment. Thus, this study analyzes the shipyard layout planning framework and builds life cycle inventory along with the simulation model structure to evaluate environmental impacts.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.1
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• pp.39-52
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• 2021

The global water shortage is getting more attention by global climate change. And water demand rapidly increases due to industrialization and population growth. Desalination technology is being expected as an alternative water supply method. Desalination technology requires low energy or maintenance costs, making it a competible next generation technology, with examples such as forward osmosis (FO), membrane distillation (MD), capacitive deionization (CDI), and electrodialysis (ED) to compete with reverse osmosis (RO). In order to identify recent research trends in desalination technologies (FO, MD, RO, CDI, and ED) between 2000-2020, a bibliometric analysis was conducted in the current study. The number of published papers in desalination technology have increased in Desalination and Journal of Membrane Science mainly. Moreover, it was found that FO, MD, RO, CDI, and ED technologies have been applied in various research areas including electrochemical, food processing and carbon-based material synthesis. Recent research topics according to the desalination technologies were also identified.

• Economic Analysis
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• v.26 no.2
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• pp.43-71
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• 2020

This paper aims to derive macroeconomic implications by analyzing the business cycle characteristics of the youth unemployment. The results of empirical analysis seem to show that youth unemployment appears to be relatively less correlated with business cycle compared to other age groups, and thus it is difficult to explain the recent steady increase in the potential labor force as a result of the business cycle fluctuation alone. Moreover, the alternative unemployment measures of the youth group showing upward trend were estimated to be co-integrated with output measures. This co-integrated trend increase suggests that unlike other age groups, youth may be influenced by structural factors inherent in Korea's economic growth path. The fact that the wage difference based on firm size has widened steadily since the Asian financial crisis and that the proportion of large companies that provide relatively high-quality jobs compared to major industrialized countries is significantly lower may be the evidence of the structural changes in Korean youth labor market. The results of above analysis may explain why the job search periods for youth has lengthened amid these structural changes.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.67.1-67.1
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• 2016

We examined the relations between CME speed and properties of magnetic helicity in the source region such as helicity injection rate and total unsigned magnetic flux, which reflect the magnetic energy in the active region. For this, we selected 22 CMEs occurred during the increasing phase of solar cycle 24, which shows extremely low activities and classified them into two groups according to evolution pattern of helicity injection rate. We then compared the relations with those from previous study based on the events in solar cycle 23. As the results, we found several properties as follows: (1) Both of CME speed and helicity parameters have very small values since we only considered increasing phase; (2) among 22 CMEs, only 6 events (27%) are classified as group B, which show sign reversal of helicity injection and they follow behind of appearance of group A events. This fact is well coincide with the trend of solar cycle 23 that only group A events was observed in the first 3 years of the period; (3) as the solar activity is increasing, the CME speed and helicity parameters are also increasing. Based on the observations of solar cycle 23, the helicity parameters was still increasing in spite of decreasing solar activity after maximum period.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.178-183
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• 2004

For developing fatigue design curve of cast stainless steels that would be used in piping material of domestic nuclear power plants, a low-cycle fatigue test rig was built. It is capable of performing tests in pressurized high temperature water environment of PWR. Cylindrical specimens of CF8M were used for the strain-controlled environmental fatigue tests. Fatigue life was measured in terms of the number of cycles with the variation of strain amplitude at 0.04%/s strain rates. The disparity between target length and measured length of specimens was corrected by using finite element method. The corrected test results showed similar fatigue life trend with another previous results.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.681-688
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• 2004

For use of the thermal cycle of the biochemical fluid sample, the isothermal temperature source with a large surface area was designed, fabricated and its thermal characterization was experimentally evaluated. The comprehensive overview of the technology trend on the temperature control devices was detailed. The large surface area isothermal temperature source was realized by using the vapor chamber heat spreader. The cost-effectiveness and simple manufacturing process were achieved by using the metal-etched wick structure. The temperature distribution was quantitatively investigated by using IR temperature imaging system at equivalent temperatures to the PCR thermal cycle. The standard deviation was measured to be within 0.7$^{\circ}C$ for each temperature cycle. This concludes that the presented isothermal temperature source enables no temperature gradient inside bio-sample fluid. Furthermore it can be applied to the cooling of the electronic devices due to its slimness and low thermal spreading resistance.