• Geophysics and Geophysical Exploration
• /
• v.4 no.4
• /
• pp.133-144
• /
• 2001

An effective seismic reflection technique for mapping the cavities and bedrock surface in carbonate rocks is described. The high resolution seismic reflection images were successfully registered by using the hydrophones employed in the stream-water driven trench, and were effectively focused by applying optimal data processing sequences. The strategy included enhancement of the signal interfered with the large-amplitude scattering noise, through pre- and post stack processing such as time-variant filtering, bad-trace editing, residual statics, velocity analysis, and careful muting after NMO (normal moveout) correction. The major reflections including the bedrock surface were mapped with the desired resolution and were correlated to the seismic crosshole tomographic data. Shallow major reflectors could be identified and analyzed on the AGC (auto gain control)-applied field records. Three subhorizontal layers were identified with their distinct velocities; overburden (<3000 m/s), sediments (3000-4000 m/s), limestone bedrock (>4000 m/s). Taking into account of no diffraction effects in the field records, gravel-rich overburdens and sediments are considered to be well sorted. Based on the images mapped consistently on the whole survey line and seismic velocity increasing with depth, this area probably lacks in sizable cavities (if any, no air-filled cavities).

• Journal of the Korea Concrete Institute
• /
• v.15 no.2
• /
• pp.314-322
• /
• 2003

Pipe cooling method is widely used for reduction of hydration heat and control of cracking in mass concrete structures. However, in order to effectively apply pipe cooling systems to concrete structures, the coefficient of flow convection relating the thermal transfer between inner stream of pipe and concrete must be estimated. In this study, a device measuring the coefficient of flow convection was developed. Since a variation of thermal distribution caused by pipe cooling has a direct effect on internal forced flows, the developed testing device is based on the internal forced flow concept. Influencing factors on the coefficient of flow convection are mainly flow velocity, pipe diameter and thickness, and pipe material. Using experimental results from the developed device, the coefficient of flow convection was calculated. Finally, a general prediction model was proposed by theoretical procedures. The proposed prediction model is able to estimate the coefficient of flow convection with flow velocity and material properties of pipe. From comparison with experimental results, the coefficient of flow convection by this model was well agreed with those by experimental results.

• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.6
• /
• pp.397-405
• /
• 2012

In this study, performance evaluation of newly developed technology for the economical and safe removal of volatile organic compounds (VOCs) coming out from electronic devices washing operation and offensive odor induction materials was made. Metal oxidization catalyst has shown 50% of removal efficiency at the temperature of $220^{\circ}C$. Composite metal oxidization catalyst applied in this study has shown that the actual catalysis has started at the temperature of $100^{\circ}C$. Comprehensive analysis on the catalyst property using Mn-Cu metal oxidization catalyst in the pilot-scale unit was made and the removal efficiency was variable with temperature and space velocity. Full-scale unit developed based on the pilot-scale unit operation has shown 95% of removal efficiency at the temperature of $160^{\circ}C$. Optimum elimination effective rates for the space velocity was found to be $6,000hr^{-1}$. The most appropriate processing treatment range for the inflow concentration of VOCs was between 200 ppm to 4,000 ppm. Catalyst control temperature showed high destruction efficiency at $150{\sim}200^{\circ}C$ degrees Celsius in 90~99%. External heat source was not necessary due to the self-heat reaction incase of VOCs inflow concentration is more than 1,000 ppm. Equipment and fuel costs compared to the conventional RTO/RCO method can be reduced by 50% and 75% respectively. And it was checked when there was poisoning for sulfide and acid gas.

• Journal of the Korean Ceramic Society
• /
• v.43 no.12 s.295
• /
• pp.812-822
• /
• 2006

This study amis to investigate the functional analysis of anode and cathode materials in Anode supported Solid Oxide Fuel Cell. The concentration polarization of single cell was investigated with CFD (Computational Fluid Dynamics) method for the case of the different morphology by using four types of unit cell and discussed to reduce the concentration polarization. The concentration polarization at anode side effected the voltage loss in Anode supported Solid Oxide Fuel Cell and increased contact areas between fuel gas and anode side could reduce the concentration polarization. For intermediate temperature operation, Anode-supported single cells with thin electrolyte layer of YSZ (Yttria-Stabilized Zirconia) were fabricated and short stacks were built and evaluated. We also developed diesel and methane autothermal reforming (ATR) reactors in order to provide fuels to SOFC stacks. Influences of the $H_2O/C$ (steam to carbon ratio), $O_2/C$ (oxygen to carbon ratio) and GHSV (Gas Hourly Space Velocity) on performances of stacks have been investigated. Performance of the stack operated with a diesel reformer was lower than with using hydrogen as a fuel due to lower Nernst voltage and carbon formation at anode side. The stack operated with a natural gas reformer showed similar performances as with using hydrogen. Effects of various reformer parameters such as $H_2O/C$ and $O_2/C$ were carefully investigated. It is found that $O_2/C$ is a sensitive parameter to control stack performance.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.8
• /
• pp.825-829
• /
• 2011

We performed a dynamic characterization of passive flow-rate regulators, which compensate for inlet pressure variation and maintain a constant flow rate for precise liquid control in microfluidic systems. To measure the flow rate for a short time, much less than the period of the dynamic inlet pressure, we use the particle image velocimetry (PIV) method. DI water containing fluorescent beads with a $0.7-{\mu}m$ diameter was supplied to the flow-rate regulators, and two successive images of the particles were taken by a pulse laser and a fluorescent microscope to measure the flow velocity. For a dynamic inlet pressure of frequency 60 Hz, the flow velocity was constant with an average of 0.194 ${\pm}$ 0.014 m/s as the inlet pressure varied between 20 kPa to 50 kPa. The flow-rate regulators provided a constant flow rate of $5.82{\pm}0.29\;{\mu}l/s$ in the frequency range of the inlet pressure from 1 Hz to 60 Hz.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.11 no.3 s.55
• /
• pp.53-62
• /
• 2007

This paper presents a new vibration control method for long-span bridges using complex damper system. The new system presents simple mechanical configuration with oil and elasto-plastic dampers which have velocity and displacement dependency in vibration energy absorbing. This system can produce various damping forces according to the applied external forces by the velocity and displacement-dependent characteristics of the dampers. The oil damper dissipates vibration energy for relatively frequent and small amplitude like in the case for small to moderate earthquakes, whereas the elasto-plastic damper system works for rare and large amplitude vibration such as high seismic excitation. Thus, the proposed system exhibits the advantage of low cost with high performance since the roles of the two different dampers are effectively separated. A numerical model is established for the complex damper system, and the response characteristics and effectiveness of the proposed system are presented through numerical simulations. Numerical results show that the proposed complex damper system can significantly improve the seismic performance of long-span bridge structures with much more effective damping mechanism than single conventional passive damper systems.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.4
• /
• pp.48-56
• /
• 2022

Controlling the setting time of cementitious materials is one of the most important factors in securing early-age performance of concrete structures. Recently, the use of retarding admixtures, which enable the inhibition of some hydration products to control the securing time due to average temperature rise is suggested. Although various non-destructive evaluation methods have been proposed to evaluate cement hydration and hardening of cement-based materials to overcome the limitations of Vicat needle test, experimental research is still required to use the non-destructive evaluation method with added retarding admixtures. In this study, measurements of electrical resistivity and ultrasonic wave velocity in early-aged cement pastes were performed according to the addition of retarding admixture(tartaric acid). The setting time of the cement pastes was evaluated by obtained rising time of the both non-destructive measurements. As a result, the possibility of evaluating the setting delay in cement pastes was confirmed through comparative analysis with the initial and final setting times by Vicat test. In addition, X-ray diffraction results at the rising time of electrical resistivity showed a key hydration product affecting the setting delay.

• Journal of Bio-Environment Control
• /
• v.14 no.1
• /
• pp.1-6
• /
• 2005

A multipurpose operating system was developed to adjust both spray times and ventilation method without a configuration of the moving path and the type of the greenhouse. The multipurpose working system proved to be a reliable system for testing the growth quality of the fruit vegetables in the greenhouse. The results are as follows. The first leaf, diameter of a stem, leaf area, and average stem diameter in the Cucumber seedling growth were repressed by high-speed ventilation, but was not repressed by spray times. The first leaf in the Tomato seedling growth was repressed as ventilation velocity was high, but the average stem diameter was not repressed. While the Tomato was given water three times a day, the diameter of a stem and the leaf area were increased as ventilation speed became higher. However, those were different other factors. The Tomato leaf area was larger when given water twice a day than that in hand spray, but showed no difference with ventilation speed. The first leaf, the diameter of a stem and the leaf area of a Red pepper were lower in automatic spraying with ventilation than those in hand spray.

• International Journal of Highway Engineering
• /
• v.8 no.3 s.29
• /
• pp.77-88
• /
• 2006

The maintenance / repair of concrete pavements has become an issue as a result of increasing of concrete pavements' service year. Asphalt overlay is applied to the concrete pavements after partial repairs on all occasions. This thesis discusses the application standard, evenness, skid resistance, noise, economical efficiency, extension of life span, etc. of diamond grinding, a method of maintenance about concrete pavements. Based on this, it was applied to the field and measured the performance. It was measured the longitudinal evenness of before and after the construction through measurement equipment. and surveyed the skid resistance the each lane classified using the SN standard value. In case of noise, it is selected the kind of vehicle, velocity, then measured the noise between control and constructed site. In addition, it is evaluated the average texture depth. As a result of the analysis, longitudinal evenness is improved about $6{\sim}40%$, skid resistance is improved 66% at first section,37% at second section. Noise is reduced 3.4dB average, and average texture depth is 79% deeper than control section. Therefore, it can be concluded that diamond grinding is suitable as maintenance / repair method of concrete pavements.

• Journal of Sericultural and Entomological Science
• /
• v.15 no.1
• /
• pp.37-48
• /
• 1973

The purpose of this studies is to improve the cohesion of raw silk through various analyses on cocoon drying, cooking, reeling, re-reeling, and on the properties of water. Also we investigated the correlation between silk testing items which we have reached to the following results. 1. Drying of cocoon When cocoons were slowly dried with 100$^{\circ}C$, the results of cohesion became much better. On the other hand, the results were considerably decreased in case the temperature with 115$^{\circ}C$. 2. Cooking of cocoon In case of the cooking of cocoon, we found that the result of cohesion was best with incomplete cooking, that of the control was next, while in over cooking, the results were very low. Also the results of cohesion were much better when using the method of over cooking with sericin arrestive agent than that of incomplete cooking with sericin agglutinating agent. 3. Reeling of cocoon A) When the temperature of reeling bath was 25-45$^{\circ}C$, the results of cohesion test were much better, but at the temperature below 25$^{\circ}C$ or above 45$^{\circ}C$, the results became worse. B) With out the process of croissieur, the results of cohesion were too bad, but in case of croissieur more than 1cm, cohesion became better rapidly. Further more, we understood that the results of cohesion were improving slightly with longer length of croissieur. C) When the velocity of reeling was increased, the results of cohesion also improved. The best results were shown when reeling velocity was 180-220 r.p.m. But when the velocity was increased more than 220 r.p.m., the results of cohesion got worse more or less. D) When the temperature of the drying pipe in reeling machine was raised, the results of cohesion also showed a tendency to improve. 4. Re-reeling A) We could net reach a conclusion as to have correlation between the number of dipping repeat in vacuum tank and the results of cohesion before re-reeling process. B) When we used Seracol 500 as an agglutination protective agent with l/1000 to l/2000 of water, the results of cohesion test were better. C) When we used Pearl-lite as an agglutination protective agent with 1/1000 to 1/2000 of water, the results of cohesion were considerably better. D) We gained tile best results when used Cohesion Improving Chemical, A-80, with 500-1500 times diluted. 1) Results of cohesion was improved when humidity was low or temperature was high in the rereeling machine. 5. Filature water A) The water pH near the isoelectric point of protein showed the best cohesion, but the farther water pH, the worser results were obtained. B) With the increasing of M-alkalinity in filature water, the results of cohesion were worse. Above all, we understood the tendency of the results of cohesion get worse when the M-alkalinity is increased above 200 ppm. C) By increasing the total hardness of the filature water, it improved the results of cohesion. Especially, when the total hardness was above 300ppm, the results were extremely high. 6. Effects combination of each results A) The result of effects combination in filature processes with the obtained best conditions was distinctively improved. But the results could not reach in mathematicaly double effect. When reelied under worse conditions, the results of cohesion test were too bad. There was "effect limit" for the promotion. B) Generally the results of cohesion were bad when the filature conditions(the temperature, pressure and the properties of water, etc) are processed as sericin loss to be high. On the other hand, the results were very good when lower sericin loss was controlled in filature conditions. C) When filature conditions such as reeling velocity and croissieur length provide pysical cohesion ability and when raw silk dry fast during reeling and re-reeling, we found the result of cohesion was better. 7. Correlation of silk testing items. A) A negative correlation exists between the results of cohesion test and cleanness defect. Another word, the result of cohesion test was found to be worse as cleanness defect increased. B) In cleanness, cohesion has negative correlation against the number of slugs, but we could not find any correlation against long loops, loose ends. C) Cohesion has negative correlation against average neatness and low neatness defect. The better the results of neatness respectively, the better the results of cohesion found. D) There is no correlation between tenacity and the results of cohesion test, but there was high positive correlation between the results of elongation and those of cohesion test. The more elongation, the better the results of cohesion was found.