• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.6
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• pp.805-810
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• 2002

Development of a small gas-turbine combustor for 100㎾ class APU(Auxiliary Power Unit) has been performed. This combustor is a reverse-annular type and has a tangential swiller in the liner head to improve the fuel/air mixing and flame stability. Three main and three pilot fuel injectors of the simplex pressure-swirl type are used. The performance target at the design condition includes a turbine inlet temperature of l170k, a combustion efficiency of 99%, a pattern factor of 30%, and an engine durability of 3000 hours. Under developing the combustor, we conducted the performance test of our first prototype(TS1) with some variants. As a result of the test, the performance targets of the combustor are satisfied except that the pattern factor is about 4% higher than the target value. Therefore, the second prototype(TS2) was redesigned and the performance test was conducted with the critical focus on the pattern factor and the exit mean temperature. We adopted TS2 four variants to check the improvement of the pattern factor. As a result, the pattern factors of several variants were satisfied with the performance target. Finally, the TS2A variant was chosen as a final combustor fur our APU model.

• Applied Microscopy
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• v.39 no.2
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• pp.199-204
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• 2009

In this study, we observed the effects of repeated perms on the morphology of virgin hair of a healthy thirteen year-old girl with scanning electron microscopy. After the first treatment, the outer parts of cuticle cell were broken unevenly and roughly. Cuticle cells were lifted upward making a space. After the third treatment, cuticle cells were lifted off one another and the folded scales showed irregular surface areas. Broken pieces of cells were stuck on the surface and an empty hole was present in the endocuticle of the cytoplasm. We observed that cortex separated from cuticle layer more easilywith repeated treatments.

• Journal of Fashion Business
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• v.7 no.2
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• pp.15-25
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• 2003

In this study on the Persiandress called Persiandress or Mediandress, its names, styles, and structures that are still subject to a great deal of controversy were investigated. In addition, the reason why the Persiandress was wrongly named as Kandys by the early researchers was also examined. The documents of reliefs on the Apadanastairs in Persepolis and the European papers concerning this themes were subject of this analysis. Such investigation and examination results are summarized as follows. There is still no agreed name describing the Persiandress, which is called "Persiandress" or "Mediandress". Further, there is no definite conclusion on whether the Persiandress was made in one piece or two pieces. The first person who insisted that the Persiandress was made in one piece is a German archaeologist, Ernst Herzfeld. He said that the Persiandress was made in one long tetragonal piece, had a hole in the middle for head, and had lots of pleats when it was tied with a belt. On the contrary, researchers who insisted that the Persiandress was made in two pieces stressed the sleeve pleats in four folds, which is one of the representative characteristics, and said that such four-fold sleeve pleats would not be formed when the Persiandress was made in one piece and worn by a belt. Consequently, they have conducted studies according to their insistence and the resultant pattern. Kandys, the Median's typical dress, is a coat worn over the jacket and trousers. Although it had sleeves, the Median did not use them. Indeed, Kandys was used as a kind of cloak. However, the wrong term, Kandys is still used in Korea. So, it is necessary to correct use of such wrong term.

• Toxicological Research
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• v.28 no.2
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• pp.103-106
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• 2012

The effect of continuous humidifier use on the bioaerosol concentration in an indoor environment was investigated. An ultrasonic humidifier was operated for 10 hr per day for 15 days in an apartment room. During this time period, viable bioaerosol samples were taken using a single-stage Andersen sampler containing culture media plates for bacteria and fungi. The culture plates were then incubated at room temperature for 2~7 days depending on the media. The counts for the air sample plates were corrected for multiple impactions using the positive hole conversion method and are reported as the colony forming units per cubic meter of air (CFU/$m^3$). While the bacterial concentration measured using the tryptic soy agar (TSA) did not show any significant change during the first 3 days, the concentration increased from the $6^{th}$ day (6979 CFU/$m^3$) and reached a maximum on the $9^{th}$ day (46431 CFU/$m^3$). The concentration then decreased to 2470 CFU/$m^3$ on the $12^{th}$ day, at which point the fungal concentration increased rapidly to 14424~16038 CFU/$m^3$. Also, while the fungal concentration showed a significant change until the $9^{th}$ day of humidifier use, fungal growth was observed on the wallpaper and increased rapidly from the $12^{th}$ day. However, the bacterial concentration increased rapidly after the fungi were removed by remediation. The major fungal species identified in the samples were Penicillium representing 34%, Aspergillus representing 31%, Cladosporium representing 24%, and Alternaria representing 1%. The results also indicated that a relative humidity over 80% was easily achieved with continuous humidifier use. Yet, maintaining a high humidity in a room can cause a rapid outbreak of microbial growth.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.519-526
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• 2010

The construction site for $\bigcirc\bigcirc$ transformer substation was located at a mountain valley. In order to prepare the site, the valley was first filled with crushed rock debris up to 63m. Since the main concern of this project is to minimize differential settlement of the foundation of transformer facilities, dynamic compaction was performed every 7m followed by reinforcement with EMP(Ez-Mud Piling). The EMP is one of bored piling methods, in which a hole is bored by means of air percussion and maintain by injecting Ez-Mud. Then a PHC pile (Pretensioned spun High strength Concrete pile) is embedded and finalized with a hammer. In this study, bearing capacities and long term behavior of a pile installed by EMP were investigated. To achieve these objectives, a series of tests such as static and dynamic load tests were conducted. In addition, a construction quality control standard was proposed based on the test results.

• Journal of the Korean Institute of Gas
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• v.12 no.4
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• pp.1-7
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• 2008

In the last five years, 36 people died and 79 were wounded because of carbon monoxide poisoning accident. A CO poisoning accident is higher than any other gas accident in the rate of deaths/incidents. Most of these CO poisoning accidents were caused by defective exhaust tube in the old gas boiler and multi-use facility. In this study, the spread mechanism of CO gas released from leakage hole of exhaust tube was analyzed by concentration measuring test. A CO gas leaked form exhaust tube in a building was the highest concentrated near the ceiling. CO alarm sets installation test confirmed that the alarm sets near the ceiling operated first, and the bottom and middle sets operated after $30{\sim}40$ minutes. Through these experiments, the reasonable installation location of CO alarm was made certain and suggested.

• Steel and Composite Structures
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• v.36 no.2
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• pp.143-161
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• 2020

In nanosized structures as the surface area to the bulk volume ratio increases the classical continuum mechanics approaches fails to investigate the mechanical behavior of such structures. In perforated nanobeam structures, more decrease in the bulk volume is obtained due to perforation process thus nonclassical continuum approaches should be employed for reliable investigation of the mechanical behavior these structures. This article introduces an analytical methodology to investigate the size dependent, surface energy, and perforation impacts on the nonclassical bending behavior of regularly squared cutout nanobeam structures for the first time. To do this, geometrical model for both bulk and surface characteristics is developed for regularly squared perforated nanobeams. Based on the proposed geometrical model, the nonclassical Gurtin-Murdoch surface elasticity model is adopted and modified to incorporate the surface energy effects in perforated nanobeams. To investigate the effect of shear deformation associated with cutout process, both Euler-Bernoulli and Timoshenko beams theories are developed. Mathematical model for perforated nanobeam structure including surface energy effects are derived in comprehensive procedure and nonclassical boundary conditions are presented. Closed forms for the nonclassical bending and rotational displacements are derived for both theories considering all classical and nonclassical kinematics and kinetics boundary conditions. Additionally, both uniformly distributed and concentrated loads are considered. The developed methodology is verified and compared with the available results and an excellent agreement is noticed. Both classical and nonclassical bending profiles for both thin and thick perforated nanobeams are investigated. Numerical results are obtained to illustrate effects of beam filling ratio, the number of hole rows through the cross section, surface material characteristics, beam slenderness ratio as well as the boundary and loading conditions on the non-classical bending behavior of perforated nanobeams in the presence of surface effects. It is found that, the surface residual stress has more significant effect on the bending deflection compared with the corresponding effect of the surface elasticity, Es. The obtained results are supportive for the design, analysis and manufacturing of perforated nanobeams.

• Journal of the Korean Professional Engineers Association
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• v.17 no.3
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• pp.6-21
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• 1984

A rock slide in amount of 100 tons in weight happened at 7: 10 a.m., 4th October 1982, on the southwestern ridge of Mt. Seunghag, Busan City. The original rock mass of the rock slide is located 850m west from the Dangri Crushed Stone Quarry. The geology of the area consists of agglomerate, andesite, andesitic tuff, and shale hornfels of the Cretaceous Yucheon Group. The rock blocks were first shifted along the steep joint plane on an andesite outcrop at the site and then to the eastern foot of the mountain slope where some private houses are placed. The mountain slope is covered with thick superficial soil. A slided monolithic-block with 83 tons in weight from the rock slide met with an accident of striking against a house with a tremendous force, to which much damage was done as much as its half was destroyed. The rock-slided block pierced the board-floored room only posited at the center and by the bedroom of the house making a pass like a bullet hole, and hence cut a big pine tree with 24 centimeters in diameter at a distance of 26 meters down the house. However nobody was killed or injured in the stricken house, though seven family members were stayed therein at the very time of accident. They really met a rare opportunity in an unhappy disaster. Measurements of the rock slide were made in the course of the field survey. The monolithic mass was transported by way of saltation, rolling, and sliding to a distance of 300 meters down along the slope dipping 30$^{\circ}$ east. It took about 16 seconds front tile outcrop to the terminal. The acceleration value of the monolithic rock slide is 2.35m/sec$^2$.

• Journal of Korean Neurosurgical Society
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• v.29 no.6
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• pp.738-743
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• 2000

Objectives : The less invasive stereotactic surgery of hypertensive intracerebral hematoma has been preferred. Many techniques were developed to facilitate aspiration of a dense blood clot in acute stage. Authors describe a method for evacuation of putaminal hematoma via computerized tomography(CT)-aided free-hand stereotactic infusion of urokinase and frequent negative pressure aspiration. Patients and Methods : A total of ten patients with spontaneous putaminal hematoma underwent surgery with negative pressure aspiration in the three-year period. All procedures were performed within 12 hours of insult. A silicone ventricular catheter was inserted into the center of hematoma through a burr hole at the Kocher's point under local anesthesia. In a typical case of putaminal hematoma, the trajectory of catheter was pointed the center of hematoma parallel to sagittal plane vertically and the external auditory meatus posteriorly. Immediately after the first trial of hematoma aspiration low-dose urokinase solution(2,000IU/5ml saline) was administrated through the catheter and drain was clipped for 30 minutes. Subsequently, the partially liquified hematoma was manually aspirated using a 10ml syringe with a negative pressure of less than 2 to 3ml. The procedure was carefully repeated every 1 hour until the hematoma was near totally evacuated. Results : The patients population consisted composed of 4 men and 6 women with a mean age of 61.6 years. All had major neurological deficits preoperatively. The mean hematoma volume was 44.3 ml and hematoma was drained for 20 to 48 hours. No complications such as rebleeding, meningitis, or malplaced catheter were noted. Outcome was moderately disabled in four patients and good recovery in three patients. Conclusion : Although the frequent negative pressure aspiration and low-dose urokinase infusion has the disadvantage of possbility of rebleeding and infection, it is consisdered to be an effective method because it allows a simple, safe, and complete removal of hematoma.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.6
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• pp.515-521
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• 2017

Large Cavitation Tunnel (LCT) of KRISO enables us to conduct cavitation tests of the propeller attached to a ship model. As the ship model tests are done at rather high Reynolds number of 107~108, flow measurement system such as pitot tube cannot be employed because of structural safety problems in its system and difficulties in installing it within the test section. Thus, KRISO has developed new 3-D LDV system used in large test section of LCT. There are several difficulties in using 3-D LDV, which did not allow efficient operation of it. The first trouble was the calibration using the conventional pin hole. To make the focus with same laser-beam waists at the wanted position, the high spatial resolution CCD is utilized in the calibration procedure for 3-D LDV. The off-axis configuration provides two velocity components in the horizontal plane and on-axis configuration gives third velocity component in the vertical plane. The horizontal velocity components are also obtained in the coincidence mode, which prevents any misleading results in the off-axis configuration. The nominal wake of Aframax tanker model is measured by the developed 3-D LDV system. The measured hull wake showed good agreement with that obtained by CFD calculation.