• 연구논문집
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• s.33
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• pp.39-51
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• 2003

This paper deals with the noise measurement and evaluation method of a reciprocating air-compressor and its noise reduction. Lead-wrapping techniques are employed to identify the contribution of principal noise sources which are generally known as motor, belts, suction/discharge valves, moving piston, and flow-induced noise which are caused by edges or discontinuities along the flow path e.g. expansions, contractions, junctions and bends. As a result, it can be found that main noise sources of the air-compressor can be categorized by the suction/discharge noise, valve noise, and compressed-air tank noise. Based on the investigations, mufflers are designed to reduce both the suction/discharge noise and the compressed-air tank noise. Instead of the conventional valve plate, engineering plastics are used as a new one for the reduction of valve impact noise. In addition, attempts are made to reduce the valve noise propagation to the cylinder head and the compressor tank by using the insulation casings in the cylinder head. As a result of the countermeasure plans, it can be achieved that the noise reduction of the air-compress is up to 10 dB.

• Korean Journal of Cleft Lip And Palate
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• v.13 no.2
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• pp.85-92
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• 2010

Vascular malformations (VMs) in the head and neck region are present at birth and grow commensurately with the child, they can result in significant cosmetic problems for the patient, and some may lead to even serious life threatening hemorrhage. Although the molecular mechanisms underlying the formation of these VMs remain unclear, lesions are known to result from abnormal development and morphogenesis. Histologically, there are no evidence of cellular proliferation, but rather progressive dilatation of abnormal channels, which VMs are designated to their prominent channel types such as capillary, venous, lymphatic, arterial, and combined malformations. VMs with an arterial component are rheologically fast-flow, whereas capillary, lymphatic, and venous components are slow-flow. In this article, we review the clinical presentations, diagnosis, and management of VMs of facial regions with author's embolization and surgical treatment cases.

• Journal of the Korean Society of Costume
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• v.67 no.2
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• pp.88-100
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• 2017

This study is for the textiles of at Sun Am Temple and characteristic of embroidery. Tak Ui was composed of orange body and green upper cover, and had no strings. The body plate was covered with embroidery, with Gauze base, and upper part was appliqued, by cutting dragon pattern, cloud pattern on satin damask. The thread for embroidery was silk floss, silk twisted thread, rapped gold thread, and rapped silk thread. For padding, it was used cotton thread in the part of dragon's scales. It was used satin stitch, outline stitch, split stitch, couching, and counted stitch, etc. as method of embroidery. In particular, it embroidered counted stitch of diamond shape consecutively on the whole of Tak Ui, it does so with counted stitch of same effect of weaving Brocade in the part of cloud. Besides, it is one of the characteristic for couching rapped silk thread. Such lead embroidery is the popular method in the Ming dynasty of China, in the 16~17 century. The design of Tak Ui is dragon, cloud, and wave in the theme. In the center, 'Seong-su-man-nyeon' was placed on the heads of dragon. This is similar to Dragon Robe of Four-petalled medallion patterns, period of Ming dynasty in China. Therefore, it confirmed that Tak Ui was remodeled the embroidered textiles, made for royal robe, originally, with Tak Ui at temple.

• Journal of the Ergonomics Society of Korea
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• v.25 no.3
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• pp.1-15
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• 2006

Loss of postural balance can possibly lead to increased risk of slips and falls in work places. Present study was performed to investigate the effects of noisy environments on postural stability during standing. It is known that a sound is characterized by the frequency and pressure level of the sound. Therefore, effects of the frequency and pressure level on postural stability were of primary concern. Ten male subjects participated in the experiment. Subject's center of pressure(COP) position was collected on a force plate while they were exposed to different frequency and pressure levels of the sound. Measured COP was then converted into the length of postural sway path in both anterior-posterior(AP) and medio-lateral(ML) axis. Results showed that the length of sway path in AP axis was significantly affected by the frequency of sound. The length of sway path was lowest at frequency level of 2000Hz and increased below and above this frequency range. The sound pressure level, however, did not significantly affect the postural sway length in both AP and ML axis. The results imply that industrial workers in noisy environments should be aware that their abilities of postural balance can be disturbed significantly.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.10-11
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• 2013

Green Frame is a column-beam system formed by composite precast concrete column and beam connected with steel buried in both members. During the installation of Green columns, the columns of Green Frame, covering 3 floors per each piece and beams, the eccentricity can be observed due to the construction error and the weight of beam itself. Such eccentricity may have a little influence on a single frame, yet, it can develop critical issues to the installation of subsequent beams or beams on the upper floors in the context of a building as a whole that has multiple frames. These issues lead to delay in frame installation, decrease of productivity and increase of cost, etc. Therefore, this study presents a steel-joint connection method in order to solve the issues. The steel-joint connection method exists on slope plane and reinforcing plate in steel frame buried in composite PC members. Through this method, the issues can be resolved without requiring additional equipment or manpower.

• Design & Manufacturing
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• v.9 no.2
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• pp.20-24
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• 2015

Recently, the light guide plate (LGP), a component of the BLU, becomes thinner and larger than ever. In industrial field, specialized injection molding technique is applied to mold the ultra-thin LGP such as a ultra-high speed injection molding. Usually very high melt temperature is used for low viscosity. High injection speed and melt temperature lead to yellowing of LGP. In the present paper a series of injection molding experiment was performed under various injection molding conditions. Yellow index, CIE xy, spectral transmittance of sample were measured using the UV-Visible spectrophotometer. Systematic decrease of spectral transmittance in UV-B range was found as the melt temperature was higher. Yellow index and CIE xy were became higher near the gate location in LGP. From the result of analysis of variance, the main factor to affect for yellow index was mold temperature and that for spectral transmittance(at 315 nm) was melt temperature.

• Steel and Composite Structures
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• v.29 no.4
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• pp.423-435
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• 2018

There are presently two general ways of accounting for hazardous metal creep in structural fire analyses: either we incorporate creep strains implicitly in hardening model ('implicit-creep' plasticity) or we account for creep explicitly ('explicit-creep' plasticity). The first approach is simpler and usually used for fast engineering applications, e.g., following proposals of EN 1993-1-2. Prioritizing this approach without consideration of its limitations, however, may lead to significant error. So far the possible levels of such error have been demonstrated by few researchers for individual structural elements (i.e., beams and columns). This paper, however, presents analyses also for selected beam-girder assemblies. Special numerical models are developed correspondingly and they are validated and verified. Their important novelty is that they do not only account for creep in individual members but also for creep in between-member connections. The paper finally shows that outside the declared applicability limits of the implicit-creep plasticity models, the failure times predicted by the applied alternative explicit-creep models can be as much as 40% shorter. Within the limits, however, the discrepancies might be negligible for majority of cases with the exception of about 20% discrepancies found in one analysed example.

• Bulletin of the Korean Chemical Society
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• v.22 no.7
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• pp.703-708
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• 2001

K2NiF4-type organic-based perovskites of the (C4H9NH3)2FexPb1-xCl4 (x=0.00, 0.25, 0.50, and 0.75) system have been synthesized using a low-temperatu re solution method under a flowing argon gas. When stoichiometric butylamine, iron chloride, and lead chloride are mixed, a yellow solution are obtained from slow cooling of 90 to -10 $^{\circ}C.$ The final product is a plate-like yellow crystal. The X-ray crystallographic analysis has been carried out using XRD in the range of $5^{\circ}{\leq}$ 2${\theta}$ ${\leq}80^{\circ}.$ The local symmetry around the absorbing Pb atom of the samples has been determined by the EXAFS spectroscopic study. The crystals assign to orthorhombic system by the XRD analysis. The FT-IR spectra are analyzed in the range of 600 to 3300 cm-1 . DSC and TGA are measured to detect thermal stability between 30 and 300 $^{\circ}C.$ Two endothermic peaks are detected in all samples. The electrical conductivity has been measured using the four-probes technique for the (C4H9NH3)2FexPb1-xCl4 system in 300-460 K. Photoluminescence phenomenon was also investigated at room-temperature.

• Tribology and Lubricants
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• v.35 no.5
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• pp.317-322
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• 2019

In spite of progress in tribological research, machine component failure due to friction and wear has been reported frequently. This failure may lead to secondary damage that can cause huge expense for maintenance and repair. To prevent economic loss, it is important to detect and predict the initial failure point. In this sense, various researchers have been tried to develop Condition Monitoring (CM) method using Acoustic Emission (AE) generated while the materials undergo failure. In this study, effect of particles on friction and wear was investigated using the pin-on-plate friction test and AE signal was recorded with a band-width type AE sensor. The experiments were performed in dry and lubricant conditions using steel and glass as specimens. After the experiment, 3D laser microscope image was captured to evaluate the wear behavior quantitatively. The AE signal was analyzed in time-domain and frequency-domain. The amplitude was compared with the frictional results. The results of this study showed that particle generation accelerate wear, generate high magnitude AE signal and change the frequency characteristics of the signal. Also, lubricant condition test results showed low coefficient of friction, low wear rate, and low magnitude of AE signal compared to the dry condition. It is expected that the results of this study will aid in better assessment of wear in CM technology

• Safety and Health at Work
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• v.7 no.2
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• pp.130-137
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• 2016

At a brewery, the base plate-to-shell weld seam of a $90-m^3$ vertical cylindrical steel tank failed catastrophically. The 4 ton tank "took off" like a rocket leaving its contents behind, and landed on a van, crushing it. The top of the tank reached a height of 30 m. The internal overpressure responsible for the failure was an estimated 60 kPa. A rupture disc rated at < 50 kPa provided overpressure protection and thus prevented the tank from being covered by the European Pressure Equipment Directive. This safeguard failed and it was later discovered that the rupture disc had been installed upside down. The organizational root cause of this incident may be a fundamental lack of appreciation of the hazards of large volumes of low-pressure compressed air or gas. A contributing factor may be that the standard piping and instrumentation diagram (P&ID) symbol for a rupture disc may confuse and lead to incorrect installation. Compressed air systems are ubiquitous. The medium is not toxic or flammable. Such systems however, when operated at "slight overpressure" can store a great deal of energy and thus constitute a hazard that ought to be addressed by safety managers.