• Journal of the Korean Institute of Gas
• /
• v.23 no.1
• /
• pp.12-18
• /
• 2019

Exhaust gas recirculation method is widely used among various methods for reducing nitrogen oxides in automobile engines and incinerators. In the present study, the computational fluid dynamic analysis was accomplished to derive the optimal location of air nozzle exit position by changing its position in a venturi tube for the maximum flue gas recirculation effect. In addition, the flue gas recirculation characteristics with a cone at the exit of air nozzle was elucidated with flue gas recirculation flow rate ratio and mixed gas exit temperature. When the air nozzle exit position was changed from the start position (z = 0) to the end position (z = 0.6m) of the exhaust gas recirculation exit pipe, the change of streamline and temperature distribution in the venturi tube was observed. The exhaust gas recirculation flow rate and the average temperature at the mixed gas exit position was quantitatively compared. From the present study, the optimal location of air nozzle exit position for the maximum flue gas recirculation flow rate ratio and maximum mixed gas exit temperature is z = 0.15m (1/4L). In addition, when the cone is installed at the outlet of the air nozzle, the velocity of the air nozzle outlet is increased, the flue gas recirculation flow rate was increased by about 2 times of the flow rate without cone, and the mixed gas exit temperature is increased by $116^{\circ}C$.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
• /
• v.9 no.5
• /
• pp.427-436
• /
• 2019

This study investigated the effect of extracorporeal shock wave therapy on the knee angle, MAS, and TUG of the affected side in patients with hemiplegic strokes. This study selected 20 patients who received rehabilitation treatment at a hospital after having been diagnosed with stroke. The control group (n=10) received the general physiotherapy (proprioceptive neuromuscular facilitation), and the experimental group (n=10) applied the extracorporeal shock wave therapy (ESWT) to the injured limb after PNF treatment. This study used an integrated kinematics analyzer (4D-MT, Relive, Korea) to analyze walking, timed up and go test to evaluate the dynamic balance ability of patients, and MAS to evaluate the spasticity. In the study results, knee angle were significantly different in all groups(p<0.05) but there was no significant difference between the groups(p>0.05). In the study results, TUG were significantly different in all groups(p<0.05) but there was no significant difference between the groups(p>0.05). Based on the results of this study, I hope that more detailed research will proceed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.41 no.1
• /
• pp.21-28
• /
• 2021

The main purpose of this study is to assess the safety of the fixed anchorages subjected to the seismic motion for an operating facilities in the actual power plant. Thus, the experimental study was conducted to investigate the load response in the event of an actual seismic to the anchorages of a nonstructural components. Since there are economic and spatial constraints to study nonstructural components that actually have various forms, alternative test specimens of steel frames with mass were built and the shaking table test was carried out. In order to evaluate the dynamic characteristics and seismic performance, the natural frequency of the target structure was identified through the shaking table test and then the load response characteristics of the anchorage were evaluated by generating an artificial seismic effect like actual seismic. Finally, the structural stiffness was reinforced by fixing the steel frame to the test specimen using bolts, thereby reducing the load transmitted to the anchorage. It will be carried out on the reliability verification of the experiments and areas that have not been carried out due to the site conditions through the analytical approach in the future.

• Analytical Science and Technology
• /
• v.34 no.1
• /
• pp.23-35
• /
• 2021

In order to measure the volatile organic compounds (VOCs) of a sample which is too large to use commercially available chamber, a stainless steel vacuum chamber (VC) (with an internal diameter of 205 mm and a height of 50 mm) was manufactured and the temperature of the chamber was controlled using an oven. After concentrating the volatiles of the sample in the chamber by helium gas, it was made possible to remove residual volatile substances present in the chamber under reduced pressure ((2 ± 1) × 10-2 mmHg). The chamber was connected to a purge & trap (P&T) using a 6 port valve to concentrate the VOCs, which were analyzed by gas chromatography-mass spectrometry (GC-MS) after thermal desorption (VC-P&T-GC-MS). Using toluene, the toluene recovery rate of this device was 85 ± 2 %, reproducibility was 5 ± 2 %, and the detection limit was 0.01 ng L-1. The method of removing VOCs remaining in the chamber with helium and the method of removing those with reduced pressure was compared using Korean drinking water regulation (KDWR) VOC Mix A (5 μL of 100 ㎍ mL-1) and butylated hydroxytoluene (BHT, 2 μL of 500 ㎍ mL-1). In case of using helium, which requires a large amount of gas and time, reduced pressure ((2 ± 1) × 10-2 mmHg) only during the GC-MS running time, could remove VOCs and BHT to less than 0.1 % of the original injection concentration. As a result of analyzing volatile substances using VC-P&T-GC-MS of six types of cell phone case, BHT was detected in four types and quantitatively analyzed. Maintaining the chamber at reduced pressure during the GC-MS analysis time eliminated memory effect and did not affect the next sample analysis. The volatile substances in a cell phone case were also analyzed by dynamic headspace (HT3) and GC-MS, and the results of the analysis were compared with those of VC-P&T-GC-MS. Considering the chamber volume and sample weight, the VC-P&T configuration was able to collect volatile substances more efficiently than the HT3. The VC-P&T-GC-MS system is believed to be useful for VOCs measurement of inhomogeneous large sample or devices used inside clean rooms.

• Korean Journal of Metals and Materials
• /
• v.56 no.12
• /
• pp.861-869
• /
• 2018

To determine the origin of the inhomogeneous microstructure and texture observed in drawn and annealed high purity copper wires, two kinds of drawing process conditions and their influence was investigated. The regular condition, based on a symmetric die, and a condition designed intentionally to produce an inhomogeneous shear deformation using an asymmetric die were employed. The difference in intensity of <111>-<100> distributed texture between the two wires confirmed that the wire drawn under the asymmetric die condition experienced a higher amount of shear deformation. The extensive shear strain in the wire drawn under the asymmetric die condition gave rise to inhomogeneous primary and secondary recrystallization behavior. After annealing at $200^{\circ}C$, grains with <100> texture, which were larger than the surrounding recrystallized grains, were extensively present on one half circle of the wire drawn under the asymmetric die condition, while larger grains with <100> were sparsely observed around the middle region of the wire drawn under the regular condition. Interestingly, the area where the larger grains with <100> texture existed was identical to the area where the high shear strain occurred during drawing in both wires. During annealing at $400^{\circ}C$, grains with <112> texture started to grow abnormally at the center of both wires as a result of secondary recrystallization. After annealing at $900^{\circ}C$ grains with <112> due to secondary recrystallization occupied the entire region of the wire drawn under the regular condition. On the other hand, in the wire drawn under the asymmetric die condition and then annealed at $900^{\circ}C$, the <100> oriented grains as a result of the normal grain growth of the larger <100> grains which were observed after annealing at $200^{\circ}C$, coexisted with the abnormally grown <112> grains. These results indicate that dynamic recrystallization induced by the shear strain during drawing plays an important role in the inhomogeneity of the microstructure and texture of wires after annealing.

• Journal of the Korean Geosynthetics Society
• /
• v.20 no.1
• /
• pp.1-8
• /
• 2021

In urban areas, structures are installed deep underground in the lower part of the structure to utilize space. Therefore, a retaining wall is used to prevent earth pressure from the ground when constructing a structure. Due to the development of construction technology, retaining wall applied to excavation work are used to prevent danger such as falling rocks and landslides in temporary facilities when construction or retaining walls are installed. In general, the application of a retaining wall to a temporary facility during the embankment construction is the case of expanding an existing roads or railways. Therefore, it is necessary to study the retaining wall applied to the embankment construction such as the double-track site of the high-speed railway. In this study, two types of common one row H-pile retaining wall and two types of IER retaining wall were analyzed, and the stability of the retaining wall applied to the construction of double-track of the high-speed railway was analyzed. The earth retaining wall is a construction method that combines forced pile applied to the stabilization of the slope with the wall of the earth retaining wall. As a result of the analysis, the IER retaining wall had maximum lateral displacement of 19.0% compared to the type with H-plie installed only in the front while dynamic load was applied. In addition, the slower the speed of high-speed railway, the more displacement occurred, and the results show that more caution is needed when designing the ground in low-speed sections.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.16 no.3
• /
• pp.1-12
• /
• 2021

In this paper, we study empirically examined the adventurous investments in corporate venture capital (CVC) firms' investment in the U.S. based corporate venture capital industry. Unlike existing studies focusing CVC firm's characteristics related to parent corporates and regarding CVC firm as a vehicle of corporate venturing, we identified CVC firm as an independent learning agent to adapt to dynamic environment and investigate their exploration and exploitation in investments based on organizational learning theory. Specifically, we investigate the market-environmental factors affecting CVC's adventurous investment in different sector rather than previously done. First, we examined competition intensity in CVC industry might be related to CVC firm's explorative investments. Second, CVC firm's investment experiences might affect as an inertia to invest on unexperienced sector. Finally, we investigated risk preference effect on CVC firm's venturing investments. The empirical data analyzed in the study contained a total of 85 U.S. based CVC firms and their 2,306 investments from 1996 until 2017. After conducting a GEE regression analysis and a Logit regression analysis, we found the significance and direction of our independent and moderating variables strongly supported all of our four hypotheses in a highly robust manner.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.1
• /
• pp.109-116
• /
• 2021

In order to replace mineral aggregate used as road pavement materials with steel slag aggregate, this present study evaluated mechanical properties of SMA Concrete mixtures using steel slag aggregate as oxidized slag from electric furnace in iron works. The variables of this experiment are the aggregate type of mineral and steel slag and the sieve sized of 10mm and 13mm. The physical properties inclu ding the specific gravity and absorption rate etc. of the slag aggregate mixtu res satisfied the KS standard as asphalt mixtu re. As a resu lt of evalu ating the mechanical properties of the asphalt mixtures, the optimum asphalt content of the slag aggregate mixtures were lower than that of the mineral aggregate mixtures, but other quality standards were all satisfied. In the deformation strength evaluation, the slag aggregate mixtures were measu red slightly higher than that of the mineral aggregate mixtu res, and the dynamic stability test satisfied the 2,000pass/mm standard value in all specimens. And, the moduli of resilient of the slag aggregate mixtures showed an improved value compared with the mineral aggregate mixtures. Therefore, as the resilient rate of the slag aggregate mixtures improved, it is speculated that there will be an effect of improving public performance according to the repeated traffic load of the vehicle.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.5
• /
• pp.126-134
• /
• 2020

In the case of an earthquake, the fluid storage structure generates hydraulic pressure due to the fluctuation of the fluid. At this time, the hydraulic pressure of the fluid changes not only the peaked acceleration of the earthquake but also the sloshing height of the fluid free water surface. Factors influencing this change in load include the shape of the seismic wave, the maximum seismic strength, the size of the fluid storage structure, the width of the structure, and the height of the fluid. In this study, the effect of the ratio between the height of the fluid and the width of the structure was investigated on the fluctuation characteristics of the fluid. 200mm and 140mm of fluid were placed in a water storage tank with a width of 500mm, and a real seismic wave was applied to measure the shape of the fluctuation of the fluid free water surface. The similarity between the experiment and the analysis was verified through the S.P.H(Smoothed Particle Hydrodynamic) technique, one of the numerical analysis techniques. It was confirmed that the free water surface of the fluid showed a similar shape, through comparison of experiment and analysis. And based on this results, SPH technique was applied to analyze the fluctuation shape of the fluid free water surface while varying the ratio between the fluid height and the structure width. An equation to predict the maximum and minimum heights of the fluid free water surface during an earthquake was proposed, and it was confirmed that the error between the maximum and minimum heights of the fluid free water surface predicted by the proposed equation was within a maximum of 3%.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.6
• /
• pp.34-41
• /
• 2020

In recent years, magnitude and frequency of earthquakes have increased in Korea. Damage to a bridge, which is one of the main infrastructures, can directly lead to considerable loss of human lives. Therefore, engineers need to evaluate the seismic fragility of the structure and prepare for the possible seismic damage. In particular, the number of aging bridges over 30 years of service increases, and thus the seismic analysis and fragility requires accounting for the aging and retrofit effects on the bridge. In this study, the nonlinear static and dynamic analyses were performed to evaluate the effects of the aging and FRP retrofit on a PSC bridge. The aging and FRP retrofit were applied to piers that dominate the response of the bridge during earthquakes. The maximum displacement of the bridge increased due to the aging of the pier but decreased when FRP retrofit applied to the aged pier. In addition, seismic fragility analysis was performed to evaluate the seismic behavior of the bridge combined with the seismic performance of the pier. Compared with the aged bridge, the FRP retrofit bridge showed a decrease in the seismic fragility in all levels of damage. The reduction of the seismic fragility in the FRP bridge was prominent as the value of PGA and level of damage increased.