• Korean Journal of Materials Research
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• v.4 no.8
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• pp.847-854
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• 1994

An amorphous single phase and coexistent amorphous and hcp-Mg phases in Mg-Zn-Ce system were found to form in the composition ranges of 20 to 40% Zn, 0 to 10% Ce and 5 to 20% Zn, 0 to 5% Ce, respectively. A $Mg_{85}Zn_{12}Ce_{3}$ amorphous alloy containing nanoscale hcp-Mg particles was found to form either by melt spinning or by heat treatment of melt -spun ribbon. The particle size of the hcp-Mg phase can be controlled in the range of 4 to 20 nm. The mixed phase alloy prepared thus has a good bending ductility and exhibits high ultimate tensile strength($\sigma_{B}$) ranging from 670 to 930 MPa and fracture elongation($\varepsilon_{f}$) of 5.2 to 2.0%. The highest specific strength($\sigma_{B}$/density =$\sigma_{s}$)$3.6 \times 10^5N \cdot m/kg$. It should be noted that the highest values of flB, US and ？1 are considerably higher than those (690MPa,$2.5 \times 10^5N \cdot m/kg$and 2.5%) for amorphous Mg-Zn-Ce alloys. The increase of the mechanical strengths by the formation of the mixed phase structure is presumably due to a dispersion hardening of the hcp supersaturated solution which has the hardness higher than that of the amorphous phase with the same composition.

• Horticultural Science & Technology
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• v.19 no.4
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• pp.550-554
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• 2001

'Fuyu' persimmon fruits (Diospyros kaki Thunb.) were seal-packaged in $60{\mu}m$ polyethylene (PE) film bags with various $O_2$ and $CO_2$ combinations (0% $O_2$+5% $CO_2$, 2% $O_2$+5% $CO_2$, 2% $O_2$+8% $CO_2$, 5% $O_2$+5% $CO_2$, 5% $O_2$+10% $CO_2$), and in vacuum and air. They were then stored at $-0.5^{\circ}C$ for 95 days. Changes in fruit weight, firmness, soluble solids, Hunter L and a values, $CO_2$ concentrations, and marketability were investigated at 20-day intervals. A combination of 2% $O_2$ and 5% $CO_2$ as well as the vacuum treatment were effective in maintaining firmness, soluble solids, marketability, and Hunter a value of 'Fuyu' fruits. On the other hand, the treatment of 2% $O_2$ combined with 8% $CO_2$ and vacuum treatment were effective in maintaining fresh weight and Hunter L and a values. The highest marketable quality was maintained when the fruits were vacuum-sealed, although fruits softened severely in the area where two fruits contacted with each other.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.4
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• pp.528-535
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• 2014

Objectives: This study compares the differences of fit factors before and after training on the N95 mask. The results will be utilized to suggest the need of providing effective training on respirator use. Methods: A total of 49 study subjects were tested, comprised of nurses from a general hospital and undergraduate nursing students from a medical school. Anthropometric measurements of face length and face width were compared with the NIOSH(National Institute for Occupational Safety and Health) panel. Fit factors(FF) were measured with TSI Portacount Pro+8038 before and after on-site training regarding the proper use of respirators. The FF pass/fail criterion was set at 100. Results: Two subjects(4.1 %) passed the fit test before training on use of the N95. However, 36(73.5%) of the 49 passed the test after training. Overall the FF(GM(GSD)) was 13.4(3.2) before training, but improved to 106.6(2.1) after training, which was statistically significant. These findings suggest the efficacy of educational intervention, and the performance of the direct on-site training proved to be better than that of the traditional educational methods. Conclusions: This study showed the effect of on-site training of the N95 respirator among health care workers(HCW). Therefore, providing effective training on the use of N95 for HCWs before their work assignments will greatly reduce exposure to harmful agents. It is recommended that fit testing be mandated to check for adequate protection being provided by the given respirators.

• Journal of the Korean GEO-environmental Society
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• v.14 no.8
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• pp.37-44
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• 2013

The superiority of bearing ground anchor system has been recognized for the stability and economical efficiency since 1950s in Japan, Europe and etc. The ground anchor introduced in Korea, however, has the structural problem that the tensile strength comes only from the ground frictional force caused by the expansion of the wedge body and it is impossible to evaluate the bearing resistance because the adhering method of the anchor body to hollow wall is not appropriate. In this study, the underreamed ground anchor system was developed so that the bearing pressure of ground anchor can exert as much as possible. And the in-situ tests were performed to evaluate the pullout behavior characteristics and to verify the decreasing effect of the bonded length. The pullout tests were performed with the non-grouted tension condition and grouted tension condition in order to identify the pull-out resistance of each conditions. In addition, it was compared with the results of friction anchor. Finally, the numerical analysis was fulfilled to verify the bearing effect at the bonded part through the detailed modeling by PLAXIS-2D, which is general finite element method analysis program.

• The Korean Journal of Community Living Science
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• v.28 no.3
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• pp.365-375
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• 2017

The purpose of this study was to investigate the maximal elongation rate and area expansion ratio of human skin in various postures. Five males and five females (male: $23{\pm}2yr$ in age, $177.9{\pm}4.8cm$ in height, $76.7{\pm}8.8kg$ in body weight, $24.2{\pm}2.5$ in BMI, $16.2{\pm}3.4%$ in body fat; female: $22{\pm}1yr$, $163.2{\pm}3.6cm$, $51.4{\pm}2.7kg$, $19.3{\pm}1.6$, $27.4{\pm}6.7%BF$) participated in this study. Measurements were conducted using a pen and tape on the elbow, knee, wrist, shoulder, and neck. Subjects held postures so that each joint of the body regions was bent at its maximal level. The results were as follows: 1) The maximal elongation rate of skin showed a significant difference among the regions: $16.6{\pm}3.4%$ for the wrist, $22.4{\pm}5.5%$ for the neck (back), $37.6{\pm}11.3%$ for the shoulder, $42.6{\pm}10.0%$ for the knee, and $43.9{\pm}4.0%$ for the elbow (p<0.05). 2) The maximal expansion rate of the body surface area had the greatest values on the elbow ($93.7{\pm}6.4%$) and knee ($74.8{\pm}10.8%$). 3) No significant difference was found between males and females. In summary, maximal values of skin elongation and expansion rates in vivo were greater than in vitro values known from previous reports. These results can be applied to develop electronic fibers or textiles for wearable tight fit work clothing as well as fitness wear.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.6
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• pp.1277-1285
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• 2015

It has been known that the conventional retaining wall system with timber lagging and H pile has several problems such as the irregular gap between H-piles, cutting or adding to standard timber, back fill over first step excavation, and especially break-down accident at the disjoint of wall system. In the practical excavation, these problems may lead to worker's accident and the inefficiency of construction economy. To solve the above problems, a new method using prefabricated retaining wall was proposed and verified. The characteristics of the new method is to replace timber wall as free-sliding steel-lagging and connector. To check its verification and application, laboratory tests such as bending strength, tensile strength, and fatigue strength were carried out. Also, a pilot test in the field and numerical simulations under various ground conditions were performed. From the researches, it is found that the prefabricated retaining wall plate can be superior to the conventional timber lagging plate in the strength. It is also found that the proposed methods can be effective in the reuse of retaining wall plate and safe in the disjoint of wall system. Finally, it is desired that the proposed method will be effective in the reduction of the imported timbers and helpful in the safety of retaining wall construction.

• International Commerce and Information Review
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• v.19 no.3
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• pp.83-105
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• 2017

I tried to analyze export relation of influence in Chinese H beam(common steel), Hot Rolled Steel(common steel), Plate(common steel) which could be influenced immediately by China's cancellation of the export rebate of value added tax in 2010 through the statistic methods such as cointegration, Granger causality, impulse response and variance decomposition. In the first period they mutually influenced each other in export to Korea but in the second period, this relation of influence was lessoned. Due to production expansion of Hot Rolled Steel(common steel), Plate(common steel) in Korea, the change of import trend, the market change of steel users' industries and China's expedient export of boron steel to Korea, mutual influence among these products was greatly declined. Ever since Hyundai Steel's production expansion involving blast furnace facilities, there is need for the industry to concentrate on developing new markets for its facilities' output in Korea. Therefore, Korea's steel industry desperately needs strength of de-jure standards such as unique quality standards and related certifications, efficient distribution management, as well as export promotion strategy through its global trading network to effectively address its structural supply-demand imbalances.

• Applied Microscopy
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• v.32 no.4
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• pp.329-337
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• 2002

The morphology and cellular characteristics of adventitious roots, viz aerial roots, in the epiphytic American Ivy were examined to reveal structural changes of the aerial root upon surface attachment. Immature aerial roots were composed of parenchyma cells with dense cytoplasm containing plastids, however, the upper and lower epidermis were not distinguished. At early development, electron-dense substances (EDS) were constituents of much of the aerial root tissue, but the distribution of EDS varied within the tissue. The deposits appeared most concentrated in the superficial cell layers, with lesser amounts in cell layers closer to the cortex. Electron micrographs revealed that EDS deposits were always found in the vacuole, and were mainly associated with the tonoplast. While most of them occurred in the vacuole as small spherical deposits adjacent to the tonoplast, some deposits were oddly shaped or larger in size. Many of the vacuoles eventually filled with EDS, but the EDS content in those vacuoles decreased substantially after initial attachment to the surface. When the vacuoles became almost empty, cells near the epidermis already exhibited irregularity in outline. Subsequent breakdown of cellular components took place in the cells while they were still attached to the surface. This study suggests the potential role of EDS as substances involved in the surface attachment of the plant, however, further studies must be conducted to reveal the nature of EDS and the effects of EDS storage within these vacuoles.

• Applied Microscopy
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• v.36 no.2
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• pp.131-140
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• 2006

Neurofascin, one of the members of L1CAM, has been known to have some important roles during the development of nerve fibers. In order to investigate the role of neurofascin associated with the myelination of peripheral nerves, the localization of neurofascin in myelinated rat sciatic nerve fibers was studied with the immuno-fluorescence and immune-electron microscopy and the results are as follows; 1. According to the myelination is going on, neurofascin localization was dramatically changed in the sciatic nerve fibers. 2. In the myelinated fibers, neurofascin was weakly localized along the axolemma at the node of Ranvier. 3. Neurofascin was also apparantly localized at the non-compact area of Schwann cell membrane such as paranodal loop, Schmidt-Lantermann incisure, inner & outer mesaxons in the myelinated fibers. From the above results, neurofascin is likely to have a role to sustain the ideal gap of apposing membranes of Schwann cell, so it may enable to materials transport in the myelin sheath.

• Applied Microscopy
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• v.36 no.2
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• pp.73-82
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• 2006

Major contributions has been made in cellular ultrastructure studies with the use of high voltage electron microscopy (HVEM) and tomography. Applications of HVEM, accompanied by appropriate image processing, have provided great improvements in the analysis of three-dimensional cellular structures. In the present study, structural patterns of the crystalline bodies that are distinguished in mesophyll plastids of CAM-performing Sedum rotundifolium L., have been investigated using HVEM and tomography. Tilting, and diffraction pattern analysis were performed during the investigation. The titlting was performed at ${\pm}60^{\circ}\;with\;2^{\circ}$ increments while examining serial sections ranging from 0.125 to $1{\mu}m$ in thickness. The young plastids exhibited crystalline inclusion bodies that revealed a peculiar structural pattern. They were irregular in shape and also variable in size. Their structural attributes affected the plastid morphology. The body consisted of a large number of tubular elements, often reaching up to several thousand in number. The tubular elements typically aggregated to form a fluster The elements demonstrated either a parallel or lattice arrangement depending on the sectioning angle. The distance between the elements was approximately 20nm as demonstrated by the diffraction analysis. HVEM examination of the serial sections revealed an occasional fusion or branching of elements within the inclusion bodies. Finally, a three-dimensional reconstruction of the plastid crystalline bodies has been attempted using two different image processing methods.