• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.123-125
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• 2015

A study has been conducted to investigate the effect of swirl angle in low swirl combustor. In this study, the employed swirl angles were $28^{\circ}$, $32^{\circ}$ and $37^{\circ}$. Direct flame photos show that the width of the flame is expanded and the length of the flame is shortened when swirl angle is increased. Also, as the swirl angle was increased, the flame stability region could be widened due to the expansion of lower flammable limit. Between 3 and 7kW, CO emissions was below 10 ppm and NOx emissions was also below 27 ppm at $O_2$ 15% basis over the lean burning range of 0.6 < ${\Phi}$ < 0.9. From this investigation of stability expansion effect and emission performance, it was identified that the swirl angle $37^{\circ}$ is most suitable swirling condition in the low swirl model combustor.

• Journal of the Korean Geosynthetics Society
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• v.18 no.1
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• pp.91-101
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• 2019

Recently, small-scale excavation like ground cavity restoration and buried pipe replacement works are being carried out in urban area, in order to improve living convenience. This paper describes experiment results on the ground reinforcement method that can reduce the buried pipe damage, when the differential settlement occurred due to poor compaction of ground below the buried pipe. Plate load tests were conducted to evaluate a reinforcement effect of ground using concrete mat and expansion mat in the ground below the buried pipe. The results showed that the stress reduction ratio by concrete mat and expansion mat according to the surcharge load was about 46%~48% and 39%~42%, respectively. Therefore, the differential settlement of the buried pipe and the ground deformation below the buried pipes were reduced by the reinforcement effect of the concrete mat and expansion mat. This means that it is possible to prevent a buried pipe damage due to underground cavity and ground subsidence, if concrete mat and expansion mat are reinforced in the ground below the buried pipe or on the ground between the buried pipes.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.1053-1055
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• 2002

Recently CRT is getting large-sized, Flatness and High Fine Pitched in the meantime the raw material for shadow mask is in rapid progress of thinness, Low Thermal Expansion and high strength.Until now we have used AK(Aluminum Killed) & Invar(Fe-Ni alloy) materials for main raw material of shadow mask component. However recently Nb and Co addition and Nb+Co addition, which has advantage of Low Thermal Expansion and High Strength. has been developed as well as applying in mass production as CRT's trend has become more flat and fine pitch. Among of them, Co addition has been mass production as forming type (Flat CRT) with the beneficial effect of low thermal expansion & high strength for the first time. Since then Nb+Co addition has been used in mass production by the request of much higher strength of shadow mask component. In case of Nb addition, It's thermal expansion coefficient is a little lower than normal Invar and a little higher than Co addition, meanwhile Its Mechanical property is almost similar to Co Addition. The used samples of this experiment are 36%Ni + Fe, 32%Ni + 5%Co + Fe, 32%Ni + 5%Co + 0.3%Nb + Fe, 32%Ni + 0.3%Nb + Fe with heat treatment temperature of 600$^{\circ}C$, 650$^{\circ}C$, 700$^{\circ}C$, 750$^{\circ}C$, 800$^{\circ}C$, 850$^{\circ}C$, 900$^{\circ}C$ respectively under the condition of 15min holding time. After heat treatment, we have observed the change of mechanical property with addition of small elements through mechanical property investigation and metal structure observation as well as transition of thermal expansion coefficient by measuring of thermal expansion coefficient at 850$^{\circ}C$. In conclusion, 5%Co addition indicates that its thermal expansion coefficient is very similar under the condition of at 850$^{\circ}C$ for 15min 's heat treatment. From the experimental result it is suggested that Co addition is mostly suitable for Doming property and Nb addition is mostly suitable for Drop property.

• The Korean journal of sports medicine
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• v.36 no.4
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• pp.197-206
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• 2018

Purpose: This study analyzed the muscle activity changes induced by motions of reaching forward and chest expansion that were examined from the bilateral muscles with rectus abdominis, external oblique, multifidus, and longissimus thoracic using Pilates cadillac instrument. Methods: Nine young adult women, who have no musculoskeletal disorder and any of chronic diseases, were participated. Surface electromyography system was used for recording of all signals produced by muscles, and then normalized as percentage of maximum voluntary isometric contraction (%MVIC). The paired t-test and repeated measures of analysis of variance was performed. Results: Reaching-forward motion showed a higher muscle activity from non-dominant external oblique muscle than that of the chest-expansion motion. During both reaching-forward motion and chest-expansion motion, MVIC values collected from dominant side of external oblique muscle were shown a significantly lower than the values obtained from non-dominant side (p<0.05). Conversely, %MVIC values in external oblique muscle collected from dominant side showed a significantly higher than the values obtained from non-dominant side of the same oblique muscle (p<0.05). Reaching-forward motion was caused a higher %MVIC on non-dominant external oblique muscle than that of the chest-expansion motion (p<0.05). Regardless of dominant or non-dominant sides, external oblique muscle was shown the highest activation rate of all the other muscles during reaching forward action, and longissimus thoracic muscle was shown the highest activation rate of all the other muscles during chest expansion action. Conclusion: Reaching-forward motion is suitable for activating an external oblique muscle, and chest-expansion motion is an effective enough in activating of longissimus thoracic muscle.

• Journal of Powder Materials
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• v.11 no.1
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• pp.34-42
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• 2004

The effect of extrusion temperature on the microstructure and mechanical properties were studied in He-gas atomized $Al_{81-(x＋y)}Si_{19}Ni_xCe_y$ alloy powders and their extruded bars using SEM, tensile testing and thermal expansion testing. The extruded bar of $Al_{73}Si_{19}Ni_7Ce_1$ alloy consists of a mixed structure in which fine Si particles with a particle size below 20∼500nm and very fine $Al_3Ni,\;Al_3Ce$ compounds with a particle size below 200nm are homogeneously dispersed in Al martix with a grain size below 500nm. With increasing extrusion temperature, the microstructural scale was decreased. The ultimate tensile strength of the alloy bars has incresed with decreasing extrusion temperature from 500 to 35$0^{\circ}C$ and $Al_{73}Si_{19}Ni_7Ce_1$ alloy extreded at 35$0^{\circ}C$ shows a highest tensile strength of 810 MPa due to the fine namostructure. The addition of Ni and Ce decreased the coefficients of thermal expansion and the effects of extression temperature on the thermal expansion were not significant.

• Membrane and Water Treatment
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• v.11 no.4
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• pp.247-255
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• 2020

Sand filter is a key unit process for particle removal in water purification treatments. Its long-standing use is due to on-site customized retrofit. Proper selection of filter media is one of the retrofit approaches to improve filter performance. This study described a series of controlled laboratory column tests and examined the effects of media property on filtration and backwash. When sand media of 0.51 mm in effective size was replaced by sand of 0.60 mm, the filter run increased up to 5 times in the given bed depth. The change of media property required an increase of backwash rate by 0.05 m/min to satisfy the requirement of bed expansion, more than 20%. When the anthracite was changed with lower effective size and uniformity coefficient, correlation with sand in the filter bed could be satisfied within the permissible error between media and bulk characteristics. Besides, this selection resulted in a well-stratified configuration of media layers after bed expansion. The column study showed that the correlation of property between the dual media had a significant effect on the filter productivity and backwash interval.

• Journal of Hydrogen and New Energy
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• v.20 no.6
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• pp.464-470
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• 2009

In order to analysis the possibility of high expansion and performance without backfire in a hydrogenfueled engine using external mixture injection, combustion characteristics and performance enhancement were analyzed in terms of retarding valve timing and increasing the boosting pressure. As the results, it was found that thermal efficiency increased by retarding intake valve timing with the same level of supplied energy is over 6.6% by the effect of high expansion including effect of combustion enhancement due to supercharging. It was also shown that the achievement of high power (equal to that of a gasoline engine), low brake specific fuel consumption and low emission (NOx of less than 16 ppm) without backfire in a hydrogen-fueled engine is possible around a boosting pressure of 1.5 bar, intake valve opening time of TDC and $\Phi$=0.35 in fuel-air equivalence ratio.

• Tunnel and Underground Space
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• v.8 no.1
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• pp.26-36
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• 1998

To assess the groundwater flow near high-level radioactive waste repositories, it is important to understand the effect of coupling among thermal, hydraulic, and mechanical effects. In this paper, detailed mathematical approach to model the groundwater flow near the waste form surrounded by buffer, influenced by decay heat of radioactive waste along with stress change is developed. Two cases(1) before the full expansion of buffer and (2) after the full expansion of buffer are modelled. Based on the mathematical models in this paper, detailed numerical study shall be pursued later.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.360-363
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• 2004

The effectiveness of Meta-Kaolin to prevent detrimental expansion due to alkali-silica reaction was investigated through the ASTM C 1260 method. Reactive aggregate used is a metamorphic rock. The replacement proportions of portland cement by Meta-Kaolin were 0, 5, 10, 15, 25 and 35 percent, respectively. The results indicate that 25 percent replacement of portland cement by Meta-Kaolin seems to be most effective to reduce alkali-silica reaction expansion under this experimental conditions.

• IE interfaces
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• v.1 no.1
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• pp.27-37
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• 1988

In the multi-stage and multi-process plant, it is not an easy task to describe the interrelationships among each process and facility. The purpose of this simulation study is to analyze the effect of additional facilities on productivity in a steel mill. The simulation was performed using SLAM Simulation Language for Alternative Modeling. The results of this study was used by the plant engineers in making decisions on the expansion of the plate mill. The prediction of which process would cause bottle-necks enabled the plant engineers to invest most effectively.