• Journal of Powder Materials
• /
• v.14 no.6
• /
• pp.354-361
• /
• 2007

The bi-materials with Al-Mg alloy and its composites reinforced with SiC and $Al_2O_3$ particles were prepared by conventional powder metallurgy method. The A1-5 wt%Mg and composite mixtures were compacted under $150{\sim}450\;MPa$, and then the mixtures compacted under 400 MPa were sintered at $773{\sim}1173K$ for 5h. The obtained bi-materials with Al-Mg/SiCp composite showed the higher relative density than those with $Al-Mg/Al_2O_3$ composite after compaction and sintering. Based on the results, the bi-materials compacted under 400 MPa and sintered at 873K for 5h were used for mechanical tests. In the composite side of bi-materials, the SiC particles were densely distributed compared to the $Al_2O_3$ particles. The bi-materials with Al-Mg/SiC composite showed the higher micro-hardness than those with $Al-Mg/Al_2O_3$ composite. The mechanical properties were evaluated by the compressive test. The bi-materials revealed almost the same value of 0.2% proof stress with Al-Mg alloy. Their compressive strength was lower than that of Al-Mg alloy. Moreover, impact absorbed energy of bi-materials was smaller than that of composite. However, the bi-materials with Al-Mg/SiCp composite particularly showed almost similar impact absorbed energy to $Al-Mg/Al_2O_3$ composite. From the observation of microstructure, it was deduced that the bi-materials was preferentially fractured through micro-interface between matrix and composite in the vicinity of macro-interface.

• Journal of Korean society of Dental Hygiene
• /
• v.12 no.1
• /
• pp.81-91
• /
• 2012

Objectives : By investigating antimicrobial activity of natural extracts, identifying its usefulness as antibiotic material to oral bacteria. Methods : Antimicrobial activity tests of 25 natural extracts were implemented on 6 type strains alleged to cause dental caries and 10 clinical strains isolated and identified from dental caries. Results : Among medicinal plants, Coptis japonica, Scutellaria baicalensis, Dictamnus dasycarpus showed antimicrobial activity. Among lichens, 3 methanol extracts and 6 acetone extracts showed antimicrobial activity. Minimum Inhibitory Concentration(MIC) test of Usnea aurantiacoatra KoLRI 004184, an acetone extract of lichen with the highest antimicrobial activity, on 6 type strains involved in dental caries and 10 strains isolated from dental caries resulted as follows; Actinomyces oris 1041 $12{\mu}g/ml$, for Corynebacterium durum 3151 $13{\mu}g/ml$, for Rothia dentocariosa KCTC $3204^T$ $14{\mu}g/ml$, for R. dentocariosa 911 $15{\mu}g/ml$, for R. dentocariosa 1822 $12{\mu}g/ml$, for Lacto-bacillus casei KACC $12413^T$ $12{\mu}g/ml$, for L. acidophilus KACC $12419^T$ $16{\mu}g/ml$, for L. rhamnosus 2421 $15{\mu}g/ml$, for Streptococcus mutans KCTC $3065^T$ $15{\mu}g/ml$, for S. mutans 121 $13{\mu}g/ml$, for Streptococcus oralis 2221 $18{\mu}g/ml$, for S. salivarius KCTC 5512 $14{\mu}g/ml$, for S. salivarius 122 $12{\mu}g/ml$, for S. sanguinis KCTC $3284^T$ $14{\mu}g/ml$, for S. sanguinis 912 $14{\mu}g/ml$, for Neisseria sp. KEM232 $12{\mu}g/ml$. Conclusions : Even a small amount of extract from lichen Usnea aurantiacoatra KoLRI 004184 showed very high level of antimicrobial activation against all 16 bacterial strains involved in dental caries.

• Journal of Fashion Business
• /
• v.16 no.1
• /
• pp.52-68
• /
• 2012

To achieve the aim of this study, 9 different types of samples were made to examine mechanical property according to structured pattern and type of Machi of pullover armhole of WholeGarment(seamless knitwear). With respect to samples, from which comparisons are made and anaylzed among basic characteristics of material, tensile strength & elongation and residual elongation due to repeated extension of armhole connecting part, the following conclusions could be obtained. It's revealed that the tensile strength of Machi part as being armhole connecting part of samples is more affected by Machi type than pattern structure. Of Machi types, it showed stronger tensile strength in the order of Normal(Normal Machi)< Machi_B(unilateral Machi)

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.38 no.4
• /
• pp.307-316
• /
• 2002

In order to evaluate the deformation and stiffness of frame structure for fishery, composed of unit platforms which made of two concentric high density polyethylene buoys fixed by clamps and belts and rubber hinge components, under wave, the structural analysis for the square type of the structure was carried out by using finite element methods. The accurate physical properties of rubber hinge components determined by material tests were an important parameter to evaluate more reliable structural stability for the structure. The idealization to beam element with equivalent stiffness and rubber element with linearity for rubber hinges was necessary for the modeling of rubber component which has hyper-elastic characteristics. In addition, it was shown that the structural response of the structure under wave was larger in the hogging condition than that of in the still water or in the sagging condition.

• Applied Chemistry for Engineering
• /
• v.25 no.6
• /
• pp.592-597
• /
• 2014

The graphite/$SiO_2$ composites as anode materials for lithium-ion batteries were prepared by sol-gel method to improve the graphite's electrochemical characteristics. The prepared graphite/$SiO_2$ composites were analysed by XRD, FE-SEM and EDX. The graphite surface modified by silicon dioxide showed several advantages to stabilize SEI layer. The electrochemical characteristics were investigated for lithium ion battery using graphite/$SiO_2$ as the working electrode and Li metal as the counter electrode. Electrochemical behaviors using organic electrolytes ($LiPF_6$, EC/DMC) were characterized by charge/discharge, cycle, cyclic voltammetry and impedance tests. The lithium ion battery using graphite/$SiO_2$ electrodes had better capacity than that of using graphite electrodes and was able to deliver a discharge capacity with 475 mAh/g at a rate of 0.1 C. Also, the capacity retention ratio of the modified graphite reaches 99% at a rate of 0.8 C.

• Health Policy and Management
• /
• v.22 no.1
• /
• pp.129-144
• /
• 2012

Purpose : The purpose of this study was to investigate the level of emotional labor and to identify affecting factors on emotional labor among one university hospital employees. Material and Method : This study was based on cross-sectional, self-administered, and Internet-based survey. The survey was conducted from Mar. 2 to Mar. 28. 2011. Total subjects were 812 employees working in one university hospital. Total response rate was 61.5%. Modified evaluation tool was used, which was originally developed by Morris and Feldman, to measure the level of emotional labor among hospital personnel. In order to identify the affecting factors on high level of emotional labor, we conducted logistic regression. The SPSS statistical software package was used to perform the statistical analysis. All statistical tests were 2-sided and a p-value<0.05 was considered statistically significant. Results : Average score of emotional labor was 3.06. Employees(3.39) who are working at the emergency department and hemodialysis room indicated the highest level of emotional labor, followed by wards(3.14), department of administration(3.14), department of ambulatory cares(3.06). The factors affecting on the high level of emotional labor were the highest level of schooling, types of department, and types of personality(p<0.05). Conclusion : The survey results showed that there was significant level of emotional labors among hospital employees. Therefore, the efforts to reduce the level of emotional labors are needed.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.2
• /
• pp.107-115
• /
• 2011

This research studies the behavior of the FRP-concrete interface subjected to two environmental substances. Frist is to investigate the behavior by the application of different bonding materials at the interface between FRP and concrete, second is to understand a long-term performance at the interface by Freeze-thaw actions. The parameters considered in this research are the maximum bonding strength and the effective bonding length at the FRP-concrete interface. In the first experimental phase, three types of specimens are fabricated and tested considering the number of applied bonding materials and the Freeze-thaw tests are performed to evaluate the behavior of the interface in the cycle range of 0 to 300 cycles. Finally, it is known that there is a 5~7% difference of the effective bonding length between applied bonding materials and the values for the maximum stress and the effective length under Freeze-thaw action are varied randomly as the freeze-thaw cycle is increased even though initial reduction of their capacities are occurred.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2018.06a
• /
• pp.72-72
• /
• 2018

A dynamic fatigue characteristic of dental implant system has been evaluated with applying single axial compressive shear loading based on the ISO 14801 standard. For the advanced dynamic fatigue test, multi-directional force and motion needed to be accompanied for more information of mechanical properties as based on mastication in oral environment. In this study, we have prepared loading and motion protocol for the multi-directional fatigue test of dental implant system with single (Apical/Occlusal; AO), and additional mastication motion (Lingual/Facial; LF, Mesial/Distal; MD). As following the prepared protocol (with modification of ISO 14801), fatigue test was conducted to verify the worst case results for the development of highly stabilized dental implant system. Mechanical testing was performed using an universal testing machine (MTS Bionix 858, MN, USA) for static compression and single directional loading fatigue, while the multi-directional loading was performed with joint simulator (ADL-Force 5, MA, USA) under load control. Basically, all mechanical test was performed according to the ISO 14801:2016 standard. Static compression test was performed to identify the maximum fracture force with loading speed of 1.0 mm/min. A dynamic fatigue test was performed with 40 % value of maximum fracture force and 5 Hz loading frequency. A single directional fatigue test was performed with only apical/occlusal (AO) force application, while multi directional fatigue tests were applied $2^{\circ}$ of facial/lingual (FL) or mesial/distal (MD) movement. Fatigue failure cycles were entirely different between applying single-directional loading and multi-directional loading. As a comparison of these loading factor, the failure cycle was around 5 times lower than single-directional loading while applied multi-directional loading. Also, the displacement change with accumulated multi-directional fatigue cycles was higher than that of single directional cycles.

• Journal of the Korean Geotechnical Society
• /
• v.27 no.8
• /
• pp.17-30
• /
• 2011

A variety of in-situ geotechnical investigation methods are currently used to measure the properties of each site, but in-situ tests for "Intermediate Geomaterial (IGM)", which is the transitional geomaterial between soil and rock, have only limited application. In the United States, "The Texas Cone Penetrometer Test (TCPT)", which is the geotechnical investigation technology for IGM, is utilized to create foundation designs. This paper introduces "The Driving Cone Penetrometer Test (DCPT)", which can be performed using general geotechnical investigation equipment and also analyzes the correlation between various in-situ geotechnical investigation methods by applying DCPT on the ground. The results showed that the correlation between the driving cone penetrometer test (DCPT) and standard penetration test (SPT) was quite high. Additionally, the scope of DCPT properties was wide, depending on soil types.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.33 no.3
• /
• pp.410-419
• /
• 2009

The purpose of this study was to develop the functionally improved winter work clothing for the Korean railroad workers. Based on the questionnaires, sample clothing for the Korean railroad workers was produced. The design, materials, and patterns were modified to increase mobility and comfort for workers. Water-repellent treatment was added to the material in order to decrease the dirt and stains while working. Also, reflective strips were added to side seams and hems of the trousers in order to increase the visibility and safety of the workers. In terms of the design and pattern, a circumference of 4.5cm was added to the crotch area in order to minimize tightness on the hip and crotch areas, but no additional circumference was added to the hip area. And a 1cm width dart was inserted between the side seams and yoke in order to add activity. Also three 1.4cm width tucks were used at 2.5cm space on the knees to alleviate tightness at the knees. The prototype was evaluated objectively and subjectively to compare with the existing working uniform. The assessment group consisted of 5 subject groups and 11 expert groups to evaluate external appearance and adaptability of the movements. Subject and panels were asked to evaluate the prototype that followed an ergonomic design and pattern. According to the results, the prototype was evaluated better than the existing working uniform in appearance and adaptability. A field test was conducted to compare the prototype and the existing working uniform. The field tests were performed by 6 workers in the Korean railroad. According to the results, the prototype advanced in terms of adaptability and comfort.