• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1564-1570
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• 2007

There are normally two types of the energy absorbers used in the crashworthiness of trains. The first is a structure type, which mainly used in not only the primary structures of the train but also the crash energy absorbers at the accident. The second is a module type, which just absorbs the crash energy independent of the primary structures and attached to the structures of the train. The expansion and inversion tube are widely used as the module type crash energy absorbers, especially in the train. The tubes should not be buckled under the load acting on the end of the tube in longitudinal direction during absorbing the crash energy. The buckling stability of the tubes is affected by the boundary conditions, thickness and length of tube. In this study, the effects of the length and thickness of the tubes on the buckling load are studied by using the ABAQUS, a commercial finite element analysis program, and then presents the guideline to design the tube. The analysis processes to compute the buckling load consist of a linear buckling analysis and a nonlinear post-buckling analysis. The buckling modes are evaluated by the linear buckling analysis, as using these modes, the buckling loads are computed by the nonlinear post-buckling analysis.

• Carbon letters
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• v.16 no.4
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• pp.241-246
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• 2015

Rapid industrial development in recent times has increased the demand for light-weight materials with high strength and structural integrity. In this context, carbon fiber-reinforced plastic (CFRP) composite materials are being extensively used. However, laminated CFRPs develop faults during impact because CFRPs are composed of mixed carbon fiber and epoxy. Moreover, their fracturing behavior is very complicated and difficult to interpret. In this paper, the effect of the direction of lamination in CFRP on the absorbed impact energy and impact strength were evaluated, including symmetric ply (0°/0°, −15°/+15°, −30°/+30°, −45°/+45°, and −90°/+90°) and asymmetric ply (0°/15°, 0°/30°, 0°/45°, and 0°/90°), through drop-weight impact tests. Further, the thermal properties of the specimens were measured using an infrared camera. Correlations between the absorbed impact energy, impact strength, and thermal properties as determined by the drop-weight impact tests were analyzed. These analyses revealed that the absorbed impact energy of the specimens with asymmetric laminated angles was greater than that of the specimens with symmetric laminated angles. In addition, the asymmetry ply absorbed more impact energy than the symmetric ply. Finally, the absorbed impact energy was inversely proportional to the thermal characteristics of the specimens.

• KIEAE Journal
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• v.13 no.2
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• pp.53-60
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• 2013

This study examined the building envelope structure used in small housings near urban area which have not good energy source in relation to the application of passive design for energy saving of small-sized architectural design firms in local cities and aimed to provide the basic materials of future design direction of designers and housing owners by analyzing economy of a project in order to know the amount of energy saving and additional expenses depending on the building envelope pattern. As a result of comparing and examining the energy saving cost from the period of use compared to investment by the thickness of insulating materials based on building envelope pattern for energy saving, it was found that the thicker the insulating materials are, the more energy saving amount is. While the current bead-type insulating materials have short payback period due to low initial investment, extruded insulating materials show the difference of five years compared to bead-type insulation because of its high initial investment.

• Proceedings of the Korea Technology Innovation Society Conference
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• 2003.11a
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• pp.359-368
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• 2003

In the early stage of 21th century, international nuclear society was on the active look out for new direction, and had a common recognition on the necessity of innovative reactor system. To achieve this purpose effectively, several international projects have been initiated for development of new nuclear energy systems that secure stable energy supply and have improved public acceptance, safety, and cost-effectiveness. In this study, status of international projects on future innovative nuclear energy systems and technology goals of future nuclear energy systems were surveyed, and the technological features of Generation IV nuclear energy system were described.

• Journal of the Korean Wood Science and Technology
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• v.26 no.1
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• pp.38-50
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• 1998

Laser cutting tests were conducted to investigate the laser cutting characteristics of solid woods such as 25mm-thick white oak(Quercus acutissima) and maple(Acer mono), and wood-based panels such as 15mm-thick medium density fiberboard and particleboard. Test variables were laser power, cutting speed, grain direction, and moisture content. Specific cutting energy was measured and the qualities of cut surface were estimated in constant laser power. Specific cutting energy of white oak was larger than that of maple, and specific cutting energy of medium density fiberboard was smaller than that of particleboard. For both white oak and maple, specific cutting energy of green wood was smaller than that of air-dried wood because weight loss of moisture evaporation in green wood was larger than that in air-dried wood. In laser-cut surface, wood cells were not deformed and damaged, but in circular saw-cut surface fibers were pushed out and cut, and wood cells were deformed severely. However, mechanical surface roughness of saw-cut surface was smoother than that of laser-cut surface because of the existence of undeformed cell cavity in laser-cut surface.

• Journal of the Korean Solar Energy Society
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• v.24 no.3
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• pp.19-25
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• 2004

The measured solar radiation incident on tilted surfaces by all directions has been widely used as important solar radiation data in installing photovoltaic modules. To maximize the incident beam radiation, the slope, which is the angle between the plane of the surface in question and the horizontal, an4 the solar azimuth angles are needed for these solar photovoltaic systems. This is because the performance of the solar photovoltaic systems is much affected by angle and direction of incident rays. Recognizing those factors mentioned above are of importance, actual experiment has been performed in this research to obtain the an91e of inclination with which the maximum incident rays can be absorbed. The results obtained in this research could be used in installing optimal photovoltaic modules.

• Journal of the Korean Solar Energy Society
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• v.32 no.1
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• pp.1-7
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• 2012

Predictions of wind speed for six different near-shore sites were made using the NCAR (National Center for Atmospheric Research) wind data. The distances between the NCAR sites and prediction sites were varied between 40km and 150km. A well-known wind energy prediction program, WindPRO, was used. The prediction results were compared with the measured data from the AWS(Automated Weather Stations). Although the NCAR wind data were located far away from the AWS sites, the prediction errors were within 9% for all the cases. In terms of sector-wise wind energy distributions, the predictions were fairly close to the measurements, and the error in predicting main wind direction was less than $30^{\circ}$. This proves that the NCAR wind data are very useful in roughly estimating wind energy in offshore or near-shore sites where offshore wind farm might be constructed in Korea.

• Journal of Drive and Control
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• v.12 no.3
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• pp.25-35
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• 2015

The hydraulic power-take-off mechanism (HPTO) is one of the most popular methods in wave energy converters (WECs). However, the conventional HPTO with only one direction motion has a number of drawbacks that limit its power capture capability. This paper proposes an adjustable moving angle wave energy converter (AMAWEC) and investigates the effect of the moving angle on the performance of the wave energy converter to find the optimal moving angle in order to increase the power capture capability as well as energy efficiency. A mathematical model of components from a floating buoy to a hydraulic motor was modeled. A small scale WEC test rig was fabricated to verify the power capture capability and efficiency of the proposed system through experiments.

• Journal of Radiation Industry
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• v.17 no.3
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• pp.299-307
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• 2023

Given that toxic substances are diffused by the various movements of the atmosphere, it is very important to evaluate the risks associated with this phenomenon. When analyzing the behavioral characteristics of these atmospheric diffusion models, the main input data are the wind speed and wind direction among the meteorological data. In particular, it is known that a certain wind direction occurs in summer and winter in Korea under the influence of westerlies and monsoons. In this study, synoptic meteorological observation data provided by the Korea Meteorological Administration were analyzed from January 1, 2012 to the end of August of 2022 to understand the regional wind characteristics of nuclear power plants and surrounding areas. The selected target areas consisted of 16 weather stations around the Hanbit, Kori, Wolsong, Hanul, and Saeul nuclear power plants that are currently in operation. The analysis was based on the temperature, wind direction, and wind speed data at those locations. Average, maximum, minimum, median, and mode values were analyzed using long-term annual temperature, wind speed, and wind direction data. Correlation coefficient values were also analyzed to determine the linear relationships among the temperature, wind direction, and wind speed. Among the 16 districts, Uljin had the highest wind speed. The median wind speed values for each region were lower than the average wind speed values. For regions where the average wind speed exceeds the median wind speed, Yeongju, Gochang, Gyeongju, Yeonggwang, and Gimhae were calculated as 0.69 m s^-1, 0.54m s^-1, 0.45m s^-1, 0.4m s^-1, and 0.36m s^-1, respectively. The average temperature in the 16 regions was 13.52 degrees Celsius; the median temperature was 14.31 degrees and the mode temperature was 20.69 degrees. The average regional temperature standard deviation was calculated and found to be 9.83 degrees. The maximum summer temperatures were 39.7, 39.5, and 39.3 in Yeongdeok, Pohang, and Yeongcheon, respectively. The wind directions and speeds in the 16 regions were plotted as a wind rose graph, and the characteristics of the wind direction and speed of each region were investigated. It was found that there is a dominant wind direction correlated with the topographical characteristics in each region. However, the linear relationship between the wind speed and direction by region varied from 0.53 to 0.07. Through this study, by evaluating meteorological observation data on a long-term synoptic scale of ten years, regional characteristics were found.

• Journal of Agricultural Extension & Community Development
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• v.11 no.2
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• pp.251-265
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• 2004

The agricultural sector's economic structure in Korea is regarded to encounter major barriers on the way toward revitalizing its economic prosperity. Among many, the energy-related problem is one of prime nuclei embedded in the country's agricultural sector. The ought-to-come structural changes in the country's agricultural energy system hinge upon the central government's policy direction as well as efforts of local governments and local farming community members. The indirect aids via 'cross subsidy' of electricity tariff rate and 'tax-exempt price' of oil fuels are two notable causes of the unsustainable energy consumption pattern in the country's agricultural sector. As measures, demand-side management(DSM) and energy-efficiency promotions are regarded to be the most attractive methods for energy conservation and economic productivity as well. Development of renewable energy sources are also receiving a great deal of attention for the long-term alternatives to the country's existing oil-based agricultural production mode. This study examines the contributive potential of DSM approaches and renewables-based technologies. With the critical evaluation on the concurrent adversities of the country's agricultural energy system, various sources of renewable energy-solar power, wind power, biomass, etc.-are examined for the purpose of technological and economical viability. As sufficient potentials of renewable energy sources are being estimated, both the system production cost and the installation cost for the county's rural areas are expected to lower in the long term. DSM options are also evaluated to be fruitful even in the short term. Both the public and civil arenas must galvanise each side's effort in order to promote these policy options and community potentials.