• Journal of the Korean Geosynthetics Society
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• v.8 no.4
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• pp.41-46
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• 2009

In this paper, a series of laboratory chamber tests were performed to evaluate the effects of clays mixed into compaction piles due to confining stress of ground on consolidation promoting. For the tests, various compaction piles such as SCP, GCP, and RAPP (Recycled-Aggregate Porous concrete Pile) were used. The ground condition was simulated at 50% and 100% of degree of consolidation. Also, confining stresses were applied to the composite ground corresponding to those of 5m depth. The amount of mixed clays into each compaction pile were estimated by measuring the drainage from the saturated compaction piles. From the test result, it was shown that the drainage area of compaction pile was changing according to the consolidation condition. GCP showed the most change of drainage area as it has relatively large void ratio; however, the amount of change was decreased by progressing consolidation of ground.

• The Journal of Advanced Prosthodontics
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• v.7 no.5
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• pp.386-391
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• 2015

PURPOSE. The purpose of this preliminary study was to investigate the effects of adding 4,4'-bis(N,N-diethylamino) benzophenone (DEABP) as a co-initiator to a binary photoinitiating system (camphorquinone-amine) to analyze on the degree of conversion (DC) of a light-cured resin for dental 3D printing. MATERIALS AND METHODS. Cylindrical specimens (N=60, n=30 per group, ${\phi}5mm{\times}1mm$) were fabricated using bisphenol A glycerolate dimethacrylate (BisGMA) both with and without DEABP. The freshly mixed resins were exposed to light in a custom-made closed chamber with nine light-emitting diode lamps (wavelength: 405 nm; power: $840mW/cm^2$) for polymerization at each incidence of light-irradiation at 10, 30, 60, 180, and 300 seconds, while five specimens at a time were evaluated at each given irradiation point. Fourier-transform infrared (FTIR) spectroscopy was used to measure the DC values of the resins. Two-way analysis of variance and the Duncan post hoc test were used to analyze statistically significant differences between the groups and given times (${\alpha}$=.05). RESULTS. In the DEABP-containing resin, the DC values were significantly higher at all points in time (P<.001), and also the initial polymerization velocity was faster than in the DEABP-free resin. CONCLUSION. The addition of DEABP significantly enhanced the DC values and, thus, could potentially become an efficient photoinitiator when combined with a camphorquinone-amine system and may be utilized as a more advanced photopolymerization system for dental 3D printing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.2
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• pp.211-217
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• 2010

It is important to measure the mechanical properties of nanostructures because they are required to determine the lifetime and reliability of nanodevices developed for various fields. In this study, tensile tests for a multi-walled carbon nanotube (MWCNT) and a ZnO nanorod were performed in a scanning electron microscope (SEM). The force sensor was a cantilever type and was mounted in front of a nanomanipulator placed in the chamber. The nanomanipulator was controlled using a joystick and personal computer. The nanostructures dispersed on the cut area of a transmission electron microscope (TEM) grid were gripped with the force sensor by exposing an electron beam in the SEM; the tensile tests were the performed. The in situ tensile loads of the nanostructure were obtained. After the tensile test, the cross-sectional areas of the nanostructures were observed by TEM and SEM. Based on the TEM and SEM results, the elastic modulus of the MWCNT and ZnO nanorod were calculated to be 0.98 TPa and 55.85 GPa, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1523-1528
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• 2013

It is necessary to develop the simple and efficient technique that ease entry of man and equipment and take the role of foundations of temporary or small structures on the soft ground. This study intends to verify the effects on the increase of bearing capacity of base projecting walls under shallow foundations and to investigate the variance of the bearing capacity of the foundations according to the interval and length of the walls. For this, model soft ground in the chamber equipped with loading apparatus is made and the loading tests on the model foundations with base projecting walls of various intervals and lengths using the apparatus are performed with measuring the loads and settlements. The results show that the base projecting walls under shallow foundations on soft ground are effective on the increase of bearing capacity and the more the number and length of the walls the larger the effects. And, when the ratio of interval to length of the walls is 1, i.e. the shape forming the base of the foundation and the walls is square, the bearing capacity is increased by 25% and the effect is optimum.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.6
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• pp.56-62
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• 2011

An experimental study on design of a catalytic ignitor was performed to use an ignition source for a small bi-propellant liquid rocket engine which use hydrogen peroxide and kerosene as propellants. In the catalytic ignitor, hot gas of hydrogen peroxide which was decomposed by a catalyst induced autoignition of kerosene. Mass flow rate and O/F ratio for the ignitor were calculated by CEA code. A combustion chamber which had a quartz window and thermocouples was manufactured to determine whether the ignition is successful. Ignition performance was investigated according to exit area of fixed rings and mixture ratio. Results showed that reliable ignition performance was achieved at non-choking exit area of fixed ring and O/F ratio of 6~8.

• Smart Structures and Systems
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• v.19 no.3
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• pp.269-277
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• 2017

Recently, there has been significant interest in structural health monitoring for civil engineering applications. In this research, a specially designed tendon, proposed by embedding FBG sensors into the center king cable of a 7-wire strand tendon, was applied for long-term health monitoring of tensile forces on a ground anchor. To make temperature independent sensors, the effective temperature compensation of FBG sensors must be considered. The temperature sensitivity coefficient ${\beta}^{\prime}$ of the FBG sensors embedded tendon was successfully determined to be $2.0{\times}10^{-5}^{\circ}C^{-1}$ through calibrated tests in both a model rock body and a laboratory heat chamber. Furthermore, the obtained result for ${\beta}^{\prime}$ was formally verified through the ground temperature measurement test, expectedly. As a result, the ground temperature measured by a thermometer showed good agreement compared to that measured by the proposed FBG sensor, which was calibrated considering to the temperature sensitivity coefficient ${\beta}^{\prime}$. Finally, four prototype ground anchors including two tension ground anchors and two compression ground anchors made by replacing a tendon with the proposed smart tendon were installed into an actual slope at the Yeosu site. Tensile forces, after temperature compensation was taken into account using the verified temperature sensitivity coefficient ${\beta}^{\prime}$ and ground temperature obtained from the Korean Meteorological Administration (KMA) have been monitored for over one year, and the results were very consistent to those measured from the load cell, interestingly.

• Journal of Fisheries and Marine Sciences Education
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• v.18 no.2
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• pp.77-84
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• 2006

This research evaluates thermal comfort by comparing the case of maintain cooing temperature of room with the case of raising it at the point of time that human body begins to adapt. An experiment uses constant temperature & humidity chamber 2 places. Pretesting room make up summer season environment, the testing room control by air-conditioner. In condition that maintain temperature of $33^{\circ}C$. The subjects stay in the pretesting room during the 30 minute for the heat storage amount of the normal summertime. The subjects stay in the testing room under each case (case 1: maintaining $24^{\circ}C$, case 2: maintaining $26^{\circ}C$, case 3: up $1^{\circ}C$ after maintaining $24^{\circ}C$ during 30 minute, case 4: up $1^{\circ}C$ after maintaining $26^{\circ}C$ during 40 minute). 1. Result of comparison of case 1 and case 2 appears that thermal sensitive vote examine from slight cool to cool and thermal comfort examine slight comfort by temperature rise at human body adaptation point of time.2. Test of case 3 and case 4 appear similar value at thermal sensitive vote and thermal comfort.3. Through the case 2 and case 4, continuous thermal comfort maintain at $24^{\circ}C$, if raise $26^{\circ}C$, same thermal comfort maintain after a human body adaptation temperature rising effect bring energy saving.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.629-632
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• 2009

The polymeric desiccant rotor is made from the super absorbent polymer by ion modification. The moisture sorption capacity of the super desiccant polymer(SDP) is 4 to 5 times larger than those of common desiccant meterials such as silica gel or zeolite. It is also known that SDP can be regenerated even at the relatively low temperature. To fabricate the desiccant rotor, firstly the SDP was laminated by coating the SDP on polyethylene sheet. Then corrugated and rolled up into a rotor. The diameter, the depth, the dimensions of the corrugated channel, etc. were pre-determined from numerical simulation on the heat and mass transfer in the desiccant rotor. The dehumidification performance was tested in a climate chamber. The relevant tests were carried out at the process air inlet temperature of $32^{\circ}C$, the regeneration air inlet temperature of $60^{\circ}C$ and the inlet dew-point temperature of both the process air and the regeneration air of $18.5^{\circ}C$, when the rotation period is long, the moisture sorption is not effective. In the desiccant rotor developed in this study, the optimum rotation period is found about 350s at the regeneration temperature of $60^{\circ}C$. It was found from further experiments that the optimum rotation tends to decreases as the regeneration temperature increases. Meanwhile, the outlet temperature of the process air deceases monotonically as the rotation period increases.

• Safety and Health at Work
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• v.3 no.3
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• pp.224-234
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• 2012

Objectives: This study was conducted in order to obtain information concerning the health hazards that may result from a 13 week inhalation exposure of n-pentane in Sprague-Dawley rats. Methods: This study was conducted in accordance with the Organization for Economic Co-operation and Development (OECD) guidelines for the testing of chemicals No. 413 'Subchronic inhalation toxicity: 90-day study (as revised in 2009)'. The rats were divided into 4 groups (10 male and 10 female rats in each group), and were exposed to 0, 340, 1,530, and 6,885 ppm n-pentane in each exposure chamber for 6 hour/day, 5 days/week, for 13 weeks. All of the rats were sacrificed at the end of the treatment period. During the test period, clinical signs, mortality, body weights, food consumption, ophthalmoscopy, locomotion activity, urinalysis, hematology, serum biochemistry, gross findings, organ weights, and histopathology were assessed. Results: During the period of testing, there were no treatment related effects on the clinical findings, body weight, food consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, gross findings, relative organ weight, and histopathological findings. Conclusion: The no-observable-adverse-effect level (NOAEL) of n-pentane is evaluated as being more than 6,885 ppm (20.3 mg/L) in both male and female rats. n-pentane was not a classified specific target organ toxicity in the globally harmonized classification system (GHS).

• Journal of the Korean Society of Clothing and Textiles
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• v.23 no.1
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• pp.30-41
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• 1999

This study was conducted to verify the advantages of Gal-Ot. Gal-Ot is defined the clothings dyed with persimmon juice. Firstly the physical properties of fabrics were examined. Secondly the wear tests were conducted. The wear tests were performed in climatic chamber controlled 3$0^{\circ}C$ air temperature 50$\pm$5% R.H and 0.2m/s air movement. Four women subjects participated in this experiment and 4 times experiments were performed per one subject. The expeimental schedule was planned following 4 steps that is sedentary posture during 30 minutes-walking the 5。slope treadmill by 70m/min during 20 minutes-sedentary posture during 20 minutes-standing posture on toward the blowing wind during 10 minutes. The results obtained is as folows : The insulation of fabric was increased with dyeing with persimmon juice. The air permeability of fabric was remarkably increased with dyeing with persimmon juice. The mean skin temperatures of subjects were apt to be higher in wearing Gal-Ot than undyed clothing. The clothing micro temperature of subjects were slightly inclined to become lower in wearing Gal-Ot than undyed clothing, The clothing micro humidity was decreasee when: the subjects were gal-Ot than wore undyed clothing, And then it brought about more comfortable on wear sensation. The differences of physiological reactions were not consistent between clothing types except for sweat rate on the back. This result may be attributed the to complex experimental schdules consisted of four steps and to a little difference between open type and close type. However I consider that the clothing type of Gal-Ot is suitable for open type because Gal-Ot is summer wear for blocking the sultry heat.