• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.9
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• pp.409-415
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• 2014

Ground-source heat pump (GSHP) systems have become an efficient alternative to conventional cooling and heating methods due to their higher energy efficiency. These systems use the ground as a heat source and the heat sink for cooling mode operation. The purpose of this simulation study is to evaluate the performance of a hypothetical GSHP system in an office building and to assess the energy saving effect against the existing HVAC systems (boiler and turbo chiller). We collected monthly energy consumption data from an actual office building ($32,488m^2$) in Seoul, and created a model to calculate the hourly building loads with EnergyPlus. In addition, we used GLD (Ground Loop Design) V8.0, a GSHP system design and simulation software tool, to evaluate hourly and monthly performance of the GSHP system. The energy consumption for the GSHP system based on the hourly simulation results were estimated to be 582.6 MWh/year for cooling and 593.2 MWh/year for heating, while those for the existing HVAC systems were found to be 674.5 MWh/year and 2,496.4 MWh/year, respectively. The seasonal performance factor (SPF) of the GSHP system was also calculated to be in the range of 3.37~4.28.

• Journal of Environmental Science International
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• v.16 no.12
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• pp.1345-1353
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• 2007

The effect of salicylic acid(SA) on antioxidant system and protective mechanisms against UV-B induced oxidative stress was investigated in cucumber(Cucumis sativus L.) leaves. UV-B radiation and SA were applied separately or in combination to first leaves of cucumber seedlings, and dry matter accumulation, lipid peroxidation and activities of antioxidant enzymes were measured in both dose and time-dependant manner. UV-B exposure showed reduced levels of fresh weight and dry matter production, whereas SA treatment significantly increased them. SA noticeably recovered the UV-B induced inhibition of biomass production. UV-B stress also affected lipid peroxidation and antioxidant enzyme defense system. Malondialdehyde(MDA), a product of lipid peroxidation, was greatly increased under UV-B stress, showing a significant enhancement of a secondary metabolites, which may have antioxidative properties in cucumber leaves exposed to UV-B radiation. Combined application of UV-B and SA caused a moderate increase in lipid peroxidation. These results suggest that SA may mediate protection against oxidative stress. UV-B exposure significantly increased SOD, APX, and GR activity compared with untreated control plants. Those plants treated with 1.0 mM SA showed a similar pattern of changes in activities of antioxidant enzymes. SA-mediated induction of antioxidant enzyme activity may involve a protective accumulation of $H_2O_2$ against UV-B stress. Moreover, their activities were stimulated with a greater increase by UV-B+SA treatment. The UV-B+SA plants always presented higher values than UV-B and SA plants, considering the adverse effects of UV-B on the antioxidant cell system. ABA and JA, second messengers in signaling in response to stresses, showed similar mode of action in UV-B stress, supporting that they may be important in acquired stress tolerance. Based on these results, it can be suggested that SA may participates in the induction of protective mechanisms involved in tolerance to UV-B induced oxidative stress.

• Journal of the Korea Concrete Institute
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• v.21 no.1
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• pp.21-27
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• 2009

In this study, experimental findings on the resistance to magnesium sulfate attack of portland cement mortar and paste specimens incorporating metakaolin (MK) are presented. Specimens with four replacement levels of metakaolin (0, 5, 10 and 15% of cement by mass) were exposed to solutions with concentrations of 0.424% and 4.24% as $MgSO_4$ at ambient temperature. The resistance of mortar specimens was evaluated through visual examination and linear expansion measurements. Additionally, in order to identify the products formed by magnesium sulfate attack, microstructural analyses such as XRD, DSC and SEM/EDS were also performed on the paste samples incorporating metakaolin. Results confirmed that mortar specimens with a high replacement level of metakaolin exhibited lower resistance to a higher concentration of magnesium sulfate solution. It was found that the negative effect of metakaolin on the magnesium sulfate attack is partially attributed to the formation of gypsum and thaumasite. Conclusively, it is necessary to pay a special attention when using metakaolin in concrete structures, particularly under highly concentrated magnesium sulfate environment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.189-196
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• 2011

Recently, research and development of a hybrid system for passenger cars as well as for heavy-duty vehicles has become more intensive. An electric powertrain system using an electric motor can replace conventional gasoline and diesel engines. The electric motor has a higher efficiency, better acceleration performance, and is more comfortable than conventional powertrain systems; however, new methods for assessing power performance and energy convergence efficiency have to be investigated because the characteristics of an electric motor are entirely different from those of an internal combustion engine (ICE). In this study, an experiment was carried out on a motor (PMSM: Permanent Magnet Synchronous Motor) test bench. One simple driving mode and four other driving modes identified from real-world driving data of a city bus were selected to perform the experiment on the motor test bench. Then, methods for assessing the acceleration performance, energy convergence efficiency, regenerative effect, etc., were investigated. It was found that the energy efficiency of PMSM was about 90% and that 40% of demand energy was regenerated.

• The Journal of Korean Physical Therapy
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• v.15 no.4
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• pp.46-64
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• 2003

Therapeutic angiogenesis is the controlled induction or stimulation of new blood vessel formation to reduce unfavourable tissue effects caused by local hypoxia and to enhance tissue repair. Therapeutic ultrasound can be considered as a physical agent to deliver therapeutic angiogenesis. The purpose of this study was to evaluate the effect of therapeutic ultrasound after muscle contusion injury by observed immunoreactivity of vascular endothelial growth factor(VEGF) that plays an important role in angiogenesis and substance-P in pain transmission. Ultrasound irradiation(1MHz, $1W/cm^2$, continuous mode, treatment time 5 min) was applied through water submersion technique to 1 limb daily by kept off 5cm from muscle belly of gastrocnemius. The result of this study were as follows. 1. In morphological observation, there were no significant changes excepts of 7 days. At 7 days, granular tissue viewed abundantly in control group. In other groups, general feature were increased interspace of muscle fiber; centronucleated muscle fiber; collapsed of muscle and nerve tissue; appeared inflammatory cell. 2. The VEGF was expressed in interspace of muscle fiber. Especially, at 7 days in experimental group, VEGF was showed in connective tissue surrounding gastrocnemius muscle. 3. The VEGF was higher expressed in experimental group at 2 and 3 days, but in control group at 7 days. These data suggest therapeutic ultrasound enhanced production of VEGF in the early day relatively, therefore stimulated angiogenesis in the skeletal muscle induced contusion injury. Also therapeutic ultrasound may stimulate pain relief by diminish of substance-P in dorsal horn of spinal cord.

• Journal of the Korea Convergence Society
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• v.9 no.9
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• pp.47-52
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• 2018

Wi-Fi enabled Internet of Things (IoTs) had a substantial impact on society, economy and industry. However wireless connectivity technologies in unlicensed band such as Wi-Fi are vulnerable to interferences. They also face difficulty providing wireless connectivity over long range in dense networks due to the dynamically changed interference effect and asymmetric interference conditions. In this paper, robust acknowledgement transmission scheme is proposed for long range IoTs. According to the proposed scheme, it is possible to control the transmission rate of the transmission success rate of the response frame by adjusting the transmission rate of the response frame when the interference is present asymmetrically. It is also possible to use higher data rate when high quality link is guaranteed. The evaluation results demonstrated the proposed scheme improves the aggregate throughput by at most 9 Mbps when 20 MHz bandwidth transmission mode was adopted.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.6
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• pp.586-594
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• 2013

This paper proposes a new coupling element of microwave slot coupler for designing waveguide slot array which can reduce the effect of undesired higher order mode coupling between coupling and radiating slots in the branch waveguide. The proposed device is composed of a centered longitudinal shunt-series coupling slot at the center of broad wall shared by two crossed rectangular waveguides and an asymmetric compound iris that excites the coupling slot. We first have obtained scattering parameters for the proposed coupler by use of EM S/W tool HFSS and then extracted the parameters of T- network equivalent circuit for the coupling slot. We also have analyzed the resonant properties such as resonant length and normalized admittance by changing the geometrical dimensions. The measured results for the fabricated coupler with short-circuited block ${\lambda}_g/4$ away from the coupling slot are well agreed with the simulated ones.

• Earthquakes and Structures
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• v.14 no.3
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• pp.215-227
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• 2018

Supplemental passive control devices are widely considered as an important tool to mitigate the dynamic response of a building under seismic excitation. Nevertheless, a systematic method for strategically placing dampers in the buildings is not prescribed in building codes and guidelines. Many deterministic and stochastic methods have been proposed by previous researchers to investigate the optimum distribution of the viscous dampers in the steel frames. However, the seismic performances of the retrofitted buildings that are under large earthquake intensity levels or near collapse state have not been evaluated by any seismic research. Recent years, an increasing number of studies utilize genetic algorithms (GA) to explore the complex engineering optimization problems. GA interfaced with nonlinear response history (NRH) analysis is considered as one of the most powerful and popular stochastic methods to deal with the nonlinear optimization problem of damper distribution. In this paper, the effectiveness and the efficiency of GA on optimizing damper distribution are first evaluated by strong ground motions associated with the collapse failure. A practical optimization framework using GA and NRH analysis is proposed for optimizing the distribution of the fluid viscous dampers within the moment resisting frames (MRF) regarding the improvements of large drifts under intensive seismic context. Both a 10-storey and a 20-storey building are involved to explore higher mode effect. A far-fault and a near-fault earthquake environment are also considered for the frames under different seismic intensity levels. To evaluate the improvements obtained from the GA optimization regarding the collapse performance of the buildings, Incremental Dynamic Analysis (IDA) is conducted and comparisons are made between the GA damper distribution and stiffness proportional damping distribution on the collapse probability of the retrofitted frames.

• Journal of Nutrition and Health
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• v.37 no.8
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• pp.675-687
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• 2004

This study is designed to assess the prevalence at risk of malnutrition according to the Mini Nutritional Assessment (MNA) and evaluate the factors influencing on the nutritional risk of the elderly. Three hundred and nine elderly (110 men and 199 women: mean age =74.1) who participated in meal service in the Chung-buk province were investigated. Mean MNA total score was 21.9 and women had significantly lower MNA scores than men (respectively, 21.5 and 22.8). In the mean time mean MNA-SF (Short Form) score was 10.7, respectively 10.6 for the women and 11.0 for the men, with the difference being statistically significant. The MNA classified 33% of the elderly as well-nourished, 61.7% as at risk of malnutrition and 5.3% as overt malnourished. However, MNA-SF categorized the examinees 40.2% as good and 59.8% at nutritional risk. Those who identified as malnourished elderly had significantly lower mean BMI, mid-arm and calf circumference, poorer functional abilities (ADL, IADL) , lower MAR and food habits scores, and higher number of nutrient $\leq$ 75% of RDA than those with at risk of malnutrition and well nourished. Also socioeconomic status such as educational level, self-rated economic status, poverty level, and marital status significantly influenced nutritional status. Similar effect was observed in self-rated nutritional status and health status, dental status, appetite change according to MNA score. Stepwise multiple regression analysis indicated that weight loss was the most predictive item in the total MNA and MNA-SF score. It was found that items such as mobility, living status (home vs institution) , mode of feeding, and pressure sores were inappropriate for assessment of the elderly who are able to participate meal service program. Also, some modifications of items in MNA are needed in order to apply to Korean elderly. Even though the MNA seems to be an useful tool to screen those old people at risk of malnourished, a lot of work is still to be done with this assessment tool to secure its reliability.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1817-1825
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• 2000

The purpose of this study is to examine the fracture toughness of the welded pipe from the viewpoint of FATT for the S38 and S42 steels used widely as the pipe material. Post weld heat treatment(PW HT) was carried out like following conditions: temperature of 67$0^{\circ}C$, I hour of holding time and cooling in furnace. Fracture toughness was obtained by measuring the crack opening displacement(COD) of the notched specimens over the range of temperature from -14$0^{\circ}C$ to -$25^{\circ}C$. Hardness values at fusion line near around were the highest and the microstructures at welded zone were coarsened. Regardless of the pipe materials, COD and temperature curves of the as-welds were moved toward higher temperature compared with those of the parents. However, COD and temperature curves of the PWHT specimens were positioned at lower temperature compared with those of the as-welds. The more heat input causes to decrease the COD values at the constant temperature. It was verified through the recrystallization treatment that PWHT was attributed to move toward lower temperature region considerably due to the improved plastic deformation at the same applied COD value of 0.3mm and softening effect. In case of the weldment of S38 steel, cleavage fracture was observed at -105$^{\circ}C$ unlike the structural steels, in which brittle fracture mode was generally shown at - 196$^{\circ}C$.