• Journal of the Korea Concrete Institute
• /
• v.22 no.5
• /
• pp.667-673
• /
• 2010

The near fault ground motion (NFGM) is characterized by a single long period velocity pulse with large magnitude. NFGMs have been observed in recent strong earthquakes, Northridge (1994), Japan Kobe (1995), Turkey Izmit (1999), China Sichuan (2008), Haiti (2010) etc. These strong earthquakes have caused considerable damage to infrastructures because the epicenter was close to the urban area, called as NFGM. Extensive research for the far field ground motion (FFGM) have been carried out in strong seismic region, but limited research have been done for NFGM in low or moderate seismic regions because of very few records. The purpose of this research is to investigate and analyze the seismic response of reinforced concrete bridge piers subjected to near-fault ground motions. The seismic performance of six RC bridge piers depending on three confinement steel ratios and three superstructure mass was investigated on the shaking table. From these experimental results, it was confirmed that the reduction of seismic performance was observed for test specimens with lower confinement steel ratio or more deck weight. The displacement ductility of RC bridge piers in terms of the stiffness degradation is proposed based on test results the shaking table.

• Journal of the Korean Institute of Gas
• /
• v.15 no.4
• /
• pp.7-14
• /
• 2011

Using 20 L spherical explosion vessel and differential scanning calorimeter (DSC), an experimental investigation was carried on explosion characteristics and thermal decomposition of some reactive organic dust. As the result, the minimum explosion concentration of Benzoyl peroxide (BPO), Phthalic anhydride (PA) and 1-Hydroxybenzotriazol (HBT) exist between 10 and 15 g/$m^3$, which indicates that their explosion sensitivity are high. The maximum Kst values of HBT, PA and 97 % BPO are 251, 146 and 80 [$bar{\cdot}m/s$], respectively and the explosion severity of HBT is the explosion class of St-2. The flame velocity was also calculated from the combustion time of dust and flame arrival time to estimate the flame propagation characteristics in a closed vessel. The decomposition temperature and heat of decomposition reaction for 97 % BPO and HBT are $107^{\circ}C$ (1025 J/g), $214^{\circ}C$ (1666 J/g), respectively and it was found that these low decomposition temperature and high released heat affect the explosion characteristics.

• Journal of Mushroom
• /
• v.15 no.3
• /
• pp.150-154
• /
• 2017

A self-propelled turner was developed to produce mushroom compost at low costs and high efficiency, and the uniformity of compost produced by an excavator, compost mixer, and self-propelled turner was compared. The material of the compost was mixed with rice straw and chicken manure at a dry weight ratio of 3:1. After the final turning, internal temperature distribution, water content of the compost pile, ash ratio, and uniformity of the compost pile were examined. After the compost was completed, the water content was $69.9{\pm}0.54%$, $72.1{\pm}0.15%$, and $74.5{\pm}0.82%$, respectively. The length of rice straw was $47.5{\pm}15.4cm$, $24.9{\pm}10.1cm$, and $31.0{\pm}10.6cm$, respectively. The ash content in the dry weight of each compost was $25.0{\pm}6.2%$, $33.6{\pm}4.2%$, and $28.2{\pm}1.1%$, respectively. The deviation in the length of rice straw was affected by the linear velocity of the spinner in the compost mixer and the self-propelled turner, which were 21.5 m/sec and 9 m/sec, respectively. As a result, the most uniform mushroom compost was produced by the self-propelled turner.

• Asian-Australasian Journal of Animal Sciences
• /
• v.14 no.11
• /
• pp.1527-1533
• /
• 2001

Garole is a prolific, rare, less known and small size Indian sheep breed found in low and humid Sunderban region of West Bengal. Although information on stored Garole ram liquid semen upto 24 h is available, but there is a need to further investigate the short-term and long-term preservability of Garole ram semen for extensive utilization of this valuable germplasm by artificial insemination. The aim of the present study was to apply computer-assisted sperm analysis technique for assessing the motion characteristics of Garole ram semen stored (i) in liquid state at refrigeration temperature for short-term preservation upto 48 h and (ii) in frozen state at $-196^{\circ}C$ for long-term preservation after packaging in mini straws. Short-term preservation had a significant effect on motility (p<0.01) as the motility progressively decreased from 90.1% at 0 h to 85.5% and 73.2% after 24 and 48 h of storage, respectively. Although the decline in rapid moving sperms was also significant (p<0.01) on storage but the decrease was more pronounced at 48 h as compared to 24 h of storage period. Storage of chilled semen had also a significant effect on % linearity (p<0.05), % straightness (p<0.01), sperm velocities (p<0.01), amplitude of lateral head displacement (p<0.01) and beat frequency (pO.Ol) of spermatozoa. The replication had a significant effect for all the variables except average path and straight line velocity. However, the interactions of short-term storage and replication were non-significant for most of the variables except % of medium moving sperms, sperm velocities and beat frequency. On long-term preservation of Garole ram spermatozoa under controlled conditions the mean post-thaw recovery of 70.4 and 71.4% motile spermatozoa was achieved having 48.8 and 48.9% of rapidly motile spermatozoa, respectively in both the replicates. The effect of replication on cryopreservation was significant (p<0.05) on amplitude of lateral head displacement and beat frequency, but there was no significant effect on motility, rapidly motile spermatozoa, linearity, straightness and sperm velocities of frozen-thawed spermatozoa. It can be concluded from these results that an average 70% motility can be achieved on storage of Garole ram semen in chilled liquid state upto 48 h or in liquid nitrogen after freezing under controlled conditions in straws. However, further studies are required to evaluate the fertility of short-term and long-term preserved Garole ram semen for extensive use of this prolific sheep breed.

• Journal of Navigation and Port Research
• /
• v.31 no.5 s.121
• /
• pp.325-332
• /
• 2007

This study develops a control algorithm on berthing/unberthing system using a joystick for ships with thrusters and a rudder. A nonlinear mathematical model for low speed maneuvering of typical container ships is used to develop a MIMO(multi-input multi-output) nonlinear control algorithm for velocity feedback joystick control. Also a virtual HILS(hardware in the loop simulation) software program for berthing/unberthing is developed to test the performance of the nonlinear and a PID control algorithm. The program is developed using LabWindow/CVI, and a user can see current position and desired trajectory of ship in a monitor, then he can control forward and yaw velocities of a ship using a joystick. The simulation results show that the nonlinear mfd the PID controller have superior performance over a simple open loop joystick control algorithm.

• Journal of Korea Water Resources Association
• /
• v.48 no.11
• /
• pp.891-903
• /
• 2015

This paper presents numerical simulations of flow around a circular patch of vegetation using a depth-averaged two-dimensional numerical model which is capable of simulating flow structure in vegetated open channel. In order to account for vegetation effect, drag force terms are included in governing equations. Numerical simulations are conducted with various solid volume fractions (SVF). Flow passes through a circular patch and low velocity region, which is called wake region, is formed downstream of the patch. When SVF is larger than 0.08, a recirculation is observed. The location of the recirculation is moved further downstream as SVF decreases. Von-$K{\acute{a}}rm{\acute{a}}n$ vortex street is developed beyond the wake region due to interaction between two shear layers induced by a circular patch of vegetation. The vortex is developed as SVF is larger than 0.08, and the location of the vortex is consistent with the maximum of turbulence kinetic energy. The location of the peak of turbulence kinetic energy is moved further downstream as SVF decreases.

• Journal of Conservation Science
• /
• v.24
• /
• pp.1-11
• /
• 2008

The Unhyungung Water Container in the possession of the Seoul Museum of History in Korea is consisted of a calcareous marble developed laminated bedding and numerous argillaceous veinlets. This monument should need to conservation treatment because of black discoloration and seriously numerous cracks. Vertical and horizontal cracks in the monument are developed following stratification and argillaceous veinlets that are relatively low coherence between the rock materials. We have proved that the material inducing discoloration on the surface is carbon which is formed by deposited organic matters. As the result of the ultrasonic measurements, although highly surface weathering degree, the physical properties of the Unhyungung Water Container is confirmed slightly weathered state. The depths of cracks in the monument are calculated at maximum 60mm in some cracks completely penetrating into the wall and at minimum 9mm in the other crack. The cracks, developed following veinlet, are revealed that there penetrate from an outer wall to an inside wall for the monument. And most depths of cracks, developed following stratification, are calculated 20 to 30mm. This result will offer a significant data for conservation of the Unhyungung Water Container.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.3
• /
• pp.293-301
• /
• 2008

A study on the operational variables of the UV-TiO$_2$ based photocatalytic air cleaning system was tried. In this study, to examine effects as various air cleaning system conditions, a duct-type reactor was made, and TiO$_2$ was immobilized on a stainless mesh. Benzene was chosen as a target compound. Removal experiments for benzene were done under different initial benzene concentration, air velocity, TiO$_2$ loading, area coated TiO$_2$ as the same TiO$_2$ loading, and UV light intensity conditions. During the experiments, relative humidity was 55%, and reactor temperature was 45$^{\circ}C$. As a result, the photocatalytic degradation of benzene decreased as the inlet concentration increased. But the photocatalytic degradation increased as the concentration boundary layer thickness, amount of TiO$_2$, area coated TiO$_2$ as the same amount of TiO$_2$, and UV light intensity increased. Based on results of current study, they can be applied to the design of air cleaning system over low level VOCs in the indoor air.

• Tunnel and Underground Space
• /
• v.29 no.6
• /
• pp.480-507
• /
• 2019

This paper aims at optimizing the auxiliary ventilation system in large-opening limestone mines with unducted fans. An extensive CFD and also site study were carried out for optimization at the blind entries. The fan location, operating mode, and layout are the parameters for optimization. Since the jet stream discharged from the auxiliary fan is flowing faster than 15 m/s in most of the cases, the stream collides with floor, sides or roof and even with the jet stream generated from the other fan placed upstream. Then, it is likely to lose a large portion of its inertial force and then its ventilation efficiency drops considerably. Therefore, the optimal fan installation interval is defined in this study as an interval that maximizes the uninterrupted flowing distance of the jet stream, while the cross-sectional installation location can be optimized to minimize the energy loss due to possible collision with the entry sides. Consequently, the optimization of the fan location will improve ventilation efficiency and subsequently the energy cost. A number of different three-dimensional computational domains representing a full-scale underground space were developed for the CFD study. The velocity profiles and the CO concentrations were studied to design and optimize the auxiliary ventilation system without duct and at the same time mine site experiments were carried out for comparison purposes. The ultimate goal is to optimize the auxiliary ventilation system without tubing to provide a reliable, low-cost and efficient solution to maintain the clean and safe work environment in local large-opening underground limestone mines.

• Journal of Science Education
• /
• v.38 no.3
• /
• pp.569-584
• /
• 2014

The Purpose of this study was an analysis of high school student's understanding level about concepts of special relativity through in-depth interview. The 8 participants were 10th grade students in H high school in Ulsan city, who were interviewed and analyzed in the results of the interview about basic concepts of special relativity using achievement checklist in 6 situations(principle of constancy of light velocity, principle of relativity, relativity of simultaneity, garage paradox, rocket paradox). As results of the checklist, the participants showed high achievement in the content level of simple phenomena and simple concepts related to special relativity. But they showed low achievement in the concept level for fundamental understanding of special relativity. As results of the interview, it was found that the participants decided the order of events depending on their intuition and had a difficulty to apply the coordinate system to real situation, even though they mathematically understood it. In addition, some participants who could not understand the inertial coordinate system explained paradoxes of relativity depending on their intuition and had learner's chaos. Finally, though high school students usually being in formal operational stage, some students had difficulty to draw phenomena of space and time in two dimensional plane.