• Elastomers and Composites
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• v.39 no.2
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• pp.142-152
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• 2004

Tensile tests of two types of injection-molded polystyrene(PS) samples have been carried out over a wide range of temperature and strain rates in order to characterize their crazing behaviors. Mechanical properties were affected by the formation of crazes as well as test variables. Below the brittle-ductile transition temperature, the tensile stress and the ultimate elongation increased with the molecular weight, strain rate, and with decreasing temperature while the number and average length of crazes also increase. The crazing stress increased with molecular weight, strain rate, and with decreasing temperature. However, the dependence was small compared to the tensile stress. The gap between crazing stress and tensile stress which represents time fur craze formation and growth increased with molecular weight, strain rate, and with decreasing temperature. Crazing was activated near the ${\beta}$-relaxation temperature; crazing stress abruptly decreased at this temperature. During the tensile test, the craze density changed exponentially with the applied stress. At the initial stage, crazes formed slowly. Once a certain number of craze formed, however, the craze density increased rapidly. Craze nucleation and growth occur simultaneously.

• Journal of the Korean Society of Clothing and Textiles
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• v.36 no.11
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• pp.1197-1207
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• 2012

This study provides information for the design of pediatric inpatient uniforms with functionality and aesthetic beauty through a questionnaire-survey of the conditions of providing, wearing, preferences and improvement requirements for pediatric inpatient uniforms. As a result of the survey, intravenous injections were mostly given on the back of the hand, and the method of changing uniforms after intravenous injections was (in most cases) to pass the injection bottle through a sleeve or pant leg while the needle is inserted. The respondents answered that the sleeve length and pant length did not match. As a result of the preference of the pediatric inpatient design survey, respondents indicated they preferred pajama type, yellow color and medium size animal patterns. A similar ratio of set-in and raglan with no collar but with 3/4 length sleeve of round neck, front end, sleeve top opening, button closing and two pockets were preferred for shirts; however, a 3/4 length with rubber string on the waist, no opening and inner opening were preferred at the same ratio for pants. As for the method to adjust the length to assign functionality to pediatric inpatient uniforms, the most preferred sleeve was a roll-up sleeve with a strap and the most preferred pants were length adjusted pants that used a strap for both shirts and pants with a both sides strap. In addition, the majority of the respondents answered that a hand wrapper that protects the injection location during intravenous injections needs be developed. As for the development type, a half glove type and glove type were preferred in sequential order.

• Journal of Dental Anesthesia and Pain Medicine
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• v.22 no.1
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• pp.39-47
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• 2022

Background: This was a randomized controlled clinical trial that aimed to evaluate the anesthetic efficacy of 2% lidocaine combined with different concentrations of epinephrine (plain, 1:200,000 and 1:80,000) during endodontic treatment of maxillary molars with symptomatic irreversible pulpitis. Methods: The trial included 144 adult patients who were randomly allocated to three treatment groups. All patients received buccal-plus-palatal infiltration. After 10 min, pulp sensibility testing was performed using an electric pulp test (EPT). If a tooth responded positively, anesthesia was considered to have failed. In the case of a negative EPT response, endodontic access was initiated under rubber dam isolation. The success of anesthesia was defined as having a pain score less than 55 on the Heft Parker visual analog scale (HP VAS), which was categorized as 'no pain' or 'faint/weak/mild' pain on the HP VAS. Baseline pre-injection and post-injection maximum heart rates were recorded. The Pearson chi-square test was used to analyze the anesthetic success rates at 5% significance. Results: Plain 2% lidocaine and 2% lidocaine with 1:200,000 epinephrine and 1:80,000 epinephrine had anesthetic success rates of 18.75%, 72.9%, and 82.3%, respectively. Statistical analysis indicated significant differences between the groups (P < 0.001, 𝛘² = 47.5, df = 2). The maximum heart rate increase was seen with 2% lidocaine solution with epinephrine. Conclusion: Adding epinephrine to 2% lidocaine significantly improves its anesthetic success rates during the root canal treatment of maxillary molars with symptomatic irreversible pulpitis.

• Earthquakes and Structures
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• v.5 no.4
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• pp.477-497
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• 2013

This paper reports extensive experimental study done to compare workability and bond strength of five different types of polymer-based bonding agents for reinforcing bars in pinning retrofit. In pinning retrofit, steel pins of 6 to 10 mm diameters are inserted into holes drilled diagonally from mortar joints. This technique is superior to other techniques especially in retrofitting historic masonry constructions because it does not change the appearance of constructions. With an ordinary cement paste as bonding agent, it is very difficult to insert reinforcing bars at larger open times due to poor workability and very thin clearance available. Here, open time represents the time interval between the injection of bonding agent and the insertion of reinforcing bars. Use of polymer-cement paste (PCP), as bonding agent, is proposed in this study, with investigation on workability and bond strengths of various PCPs in brick masonry, at open times up to 10 minutes, which is unavoidable in practice. Corresponding nonlinear finite element models are developed to simulate the experimental observations. From the experimental and analytical study, the Styrene-Butadiene Rubber polymer-cement paste (SBR-PCP) with prior pretreatments of drilled holes showed strong bond with minimum strength variation at larger open times.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.4
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• pp.867-871
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• 2012

In this paper, we proposed and demonstrated a low loss $1{\times}4$ type plastic optical fiber(POF) coupler incorporating a polymer tapering waveguide region. To avoid leakage loss at the interfaces between the POF and the polymer waveguide, we employed two POF transition regions, in which the cross section of the POF is adiabatically converted from a circular to a rectangular shape without change of its cross-section area. The device was fabricated based on a injection mold made of a silicon rubber. The fabricated POF coupler showed 1.33 dB of excess loss and 2.2 dB of flatness.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.547-550
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• 2011

We have developed a laser-based needle-free liquid drug-injection device. A laser beam is focused inside the liquid contained in the rubber chamber of a micro-scale. The focused laser beam causes explosive bubble growth, and the sudden volume increase in a sealed chamber drives a microjet of liquid drug through the micronozzle. The exit diameter of a nozzle is less than 100 ${\mu}m$, and we verify that the injected microjet is fast enough to penetrate soft human tissue. In the experiment, the microjet penetrated a 5% gelatin-water solution that replicates the human thrombus and pork-fat tissue.

• Elastomers and Composites
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• v.35 no.4
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• pp.296-302
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• 2000

The surfaces of injection and pressure-molded sheets of poly(ethylene-covulylacetate)(EVA) foams used for shoe mid-sole were treated with low temperature plasma to improve adhesion with a water-based polyurethane adhesives. Several experimental variables were considered, such as radio frequency power, treating time, type of gas. gas flow, and distance between electrode and sample. The modificated surface by plasma treatment were characterized using contact angle meter, scanning electron microscopy(SEM), universal testing machine(UTM). Adhesion was tested by T-peel tests of treated EVA foams/polyurethane adhesive joints. The treatment in the low temperature plasma produced a noticeable decrease in contact angle. The peel strength of EVA foams treated with plasma was increased with plasma treating time, and gas flow.

• Elastomers and Composites
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• v.50 no.3
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• pp.184-188
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• 2015

There is a need for light weight and high stiffness characteristics in the building structure as well as aircraft and cars. So fiber reinforced plastic with the addition of reinforcing agent such as glass fiber, carbon fiber, aramid fiber is utilized in this regard. In this study, mechanical strength, flow property and part shrinkage of glass fiber and carbon fiber reinforced PA6 were examined according to reinforcement content such as 10%, 20%, and 30%, and reinforcement type. The mechanical property was measured by a tensile test with specimen fabricated by injection molding and the flow property was measured by spiral test. In addition, we measured the part shrinkage of fiber reinforced PA6 that affects part quality. As glass fiber content increases, mechanical property increased by 75.4 to 182%, and flow property decreased by 18.9 to 39.5%. And part shrinkage decreased by 52.9 to 60.8% in the flow direction, and decreased by 48.2 to 58.1% in the perpendicular to the flow direction. As carbon fiber content increases, mechanical property increased by 180 to 276%, flow property decreased by 26.8 to 42.8%, and part shrinkage decreased by 65.0 to 71.8% and 69.5 to 72.7% in the flow direction and the direction perpendicular to the flow respectively.

• Elastomers and Composites
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• v.40 no.4
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• pp.242-248
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• 2005

To study the fatigue properties of three type of foams for footwear midsole, polyurethane(PU), phylon(PH) and injection phylon(IP) foams were prepared with different hardnesses. Three types of foams were repetitively compressed for 50,000 cycles at 50 rpm. Cell shapes of foams were deformed with repetitive compression. The extent of cell deformation of IP was larger than those of PH and PU. Permanent strain of foam was made by repetitively compressing the foam, and the extent of IP was larger than those of PU and PH. Maximum compression forces of three types of the foams were decreased with the repetitive compression, and IP had the largest decrease in compression load of foam with compression. Decreases in maximum compression force of three types of foams were increased with increase of the hardness of foam.

• Elastomers and Composites
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• v.40 no.4
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• pp.258-265
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• 2005

To study the compressive stress, recovery force and permanent strain of foams for footwear midsole, polyurethane(PU), phylon(PH) and injection phylon(IP) foams were repetitively compressed with constant compressive stress. Maximum compressive stress of PU did not decrease with repetitive compression on the constant compressive stress, but that of IP largely decreased. Engineering strain of foams were formed by repetitively compressing the three types of foam. The engineering strain of PU was smaller than that of IP and PH. Compressive stress and recovery force of IP and PH at certain strain were decreased with repetitive compression, but that of PU was not noticeably changed.