• Composites Research
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• v.25 no.3
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• pp.65-69
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• 2012

The main objective of this study is to investigate the effect of metal z-pinning on the failure behavior of cocured composite single-lap joints. Three different pin diameters (0.3, 0.5, and 0.7 mm) and three pin areal densities (0.5, 2.0, and 4.0%) were examined. The specimens were fabricated by T700-12K-31E#2510 unidirectional prepreg from Toray. Stainless steel pins were used for z-pinning. Test results showed that except one case with extremely low pin density of 0.5%, all other z-pinned joints exhibited lower initial crack stresses than those of the unpinned joint. However the ultimate strength of the z-pinned joint increased up to 45% at most. Furthermore, even after the complete failure of the joint, the z-pins sustained the carried load to a certain degree experiencing large deformation and provided the stable fracture behavior for the composite joint.

• Elastomers and Composites
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• v.44 no.1
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• pp.47-54
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• 2009

EPDM(Ethylene-propylene-diene-terpolymer) compound reinforced with carbon black having four different particle size, acetylene black(thermal conductivity carbon black), and silica were manufactured by internal mix and open mill. To investigate the effect of particle size of filler and filler type on far-infrared vulcanization, intermal temperature of compound, degree of curing, infrared spectroscopy, and thermal analysis were measured. The thermal conductivity of far-infrared vulcanized EPDM compound increased with increasing particle size of carbon filler, but hot air vulcanized EPDM compound is not affected by particle size. The thermal conductivity was increased in the order of carbon black < silica < acetylene black(thermal conductivity carbon black).

• Polymer(Korea)
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• v.35 no.4
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• pp.342-349
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• 2011

The effect of the amount of vinyltriethoxysilane (VTEOS) in precipitated silica filled silicone rubbers was extensively investigated in terms of the change of mechanical properties, heat resistance, oil resistance, compression set, resilience, and curing characteristics. As the content of VTEOS increased from 0 to 2.0 phr, the hardness of the silicone rubber increased, however, tensile strength, elongation at break, and tear strength decreased. From heat resistance test, the change of mechanical properties was pronounced for silicone rubber treated with more VTOES. The best heat resistance was achieved at 2.0 phr VTOES. In addition, oil resistance was proportionally improved with VTEOS content. From oil resistance test. it was found that the decrease in hardness and maximum elongation was reduced for VTEOS-added systems. Finally, resilience, compression set, degree of cure and crosslink density were significantly enhanced with the amount of VTEOS.

• Restorative Dentistry and Endodontics
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• v.44 no.3
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• pp.28.1-28.10
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• 2019

Objectives: The aim of this study was to evaluate the influence of different concentrations of nanofillers on the chemical and physical properties of ethanol-solvated and non-solvated dental adhesives. Materials and Methods: Eight experimental adhesives were prepared with different nanofiller concentrations (0, 1, 2, and 4 wt%) and 2 solvent concentrations (0% and 10% ethanol). Several properties of the experimental adhesives were evaluated, such as water sorption and solubility (n = 5, 20 seconds light activation), real-time degree of conversion (DC; n = 3, 20 and 40 seconds light activation), and stability of cohesive strength at 6 months (CS; n = 20, 20 seconds light activation) using the microtensile test. A light-emitting diode (Bluephase 20i, Ivoclar Vivadent) with an average light emittance of $1,200mW/cm^2$ was used. Results: The presence of solvent reduced the DC after 20 seconds of curing, but increased the final DC, water sorption, and solubility of the adhesives. Storage in water reduced the strength of the adhesives. The addition of 1 wt% and 2 wt% nanofillers increased the polymerization rate of the adhesives. Conclusions: The presence of nanofillers and ethanol improved the final DC, although the DC of the solvated adhesives at 20 seconds was lower than that of the non-solvated adhesives. The presence of ethanol reduced the strength of the adhesives and increased their water sorption and solubility. However, nanofillers did not affect the water sorption and strength of the tested adhesives.

• Restorative Dentistry and Endodontics
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• v.30 no.2
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• pp.128-137
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• 2005

In this study we measured the amount of light energy that was projected through the tooth material and analyzed the degree of polymerization by measuring the surface hardness of composites. For polymerization, Optilux 501 (Demetron, USA) with two types of light guide was used: a 12 mm diameter light guide with 840 nW/$cm^2$ light intensity and a 7 mm diameter turbo light guide with 1100 nW/$cm^2$. Specimens were divided into three groups according to thickness of penetrating tooth (1 mm, 2 mm, 0 mm). Each group was further divided into four subgroups according to type of light guide and curing time (20 seconds, 40 seconds). Vickers' hardness was measured by using a microhardness tester. In 0 mm and 1 mm penetrating tooth group, which were polymerized by a turbo light guide for 40 seconds, showed the highest hardness values. The specimens from 2 mm penetrating tooth group, which were polymerized for 20 seconds, demonstrated the lowest hardness regardless of the types of light guides (p < 0.05). The results of this study suggest that, when projecting tooth material over a specified thickness, the increase of polymerization will be limited even if light intensity or curing time is increased.

• Journal of Digital Convergence
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• v.10 no.9
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• pp.435-441
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• 2012

This study is intended to provide a basic clinical data useful for preventing shoulder injuries related to occupation and curing them, by measuring the shoulder muscle activity of normal adults in an arm posture type of a wide shoulder joint angle, according to several differences of hand grip force. In order to examine the shoulder muscle activity during hand grips at a variety of intensity, according to the arm posture type, MVCs of all subjects were measured, and %MVCs of anterior deltoid, supraspinatus, the upper trapezius and infraspinatus at 0 degree, 90 degrees and 160 degrees of shoulder angle were yielded according to the grip force in an arm posture type, changing the maximum grip force into 30%, 50% and 90%, randomly. When measuring the hand grip at 30%, 50% and 70% of the maximum grip force to compare %MVC of each group depending on the arm posture type, there were no significant differences of muscle activity at 0 degree of shoulder angle among anterior deltoid, supraspinatus, the upper trapezius and infraspinatus, but there were significant differences of it among them at 90 degrees and 160 degrees of should angle(p<.001). According to the results of post-hoc test, also, anterior deltoid had the highest muscle activity, whereas the upper trapezius had the lowest muscle activity.

• Journal of agricultural medicine and community health
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• v.22 no.2
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• pp.277-293
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• 1997

This study was conducted to provide basic materials required to enforce and develop welfare policies, as well as the health system, for the aged, by surveying the status of health care utilized by the daily increasing old population and the importance of receiving physical therapy. Data that need in this research was gathered from over ages of 65, during the period from Jan 4, 1996 to Jan 31, using the inquiries previously made by geriatric researchers and through literatures investigator by this writer. The data were analyzed by $X^2$, Z-test, Likert scale. The findings were as follows : 1) General characteristics of subjects. People in the age group between 65 and 69 were 55.6% and the highest number, while male were 37% and female 63%. Analysis of income group disclosed 60.6% whose monthly income, including the pocket money given by children, was less than 200,000 won. 91.1% of the elderly people surveyed owned houses; only 36.4% live with spouses; while 15.6% live alone. 2) Characteristics with respect to utilization of health care institution. 56% of the total medical institutions used by the elderly people were clinics and the rates of chronic disease and musculoskeletal disease were 73.2%. 3) Characteristics with respect to approach of health care institution. 45.1% of the respondent stated it took 20 minutes to arrive at hospital, and bus accounted for 48.6% of all transportation means used to go to hospital. 4) Degree of cognition with respect to the rights of geriatric patients. (1) There is no financial support from the government for geriatric patients(71.4%). (2) Government financial support is needed for geriatric patients(95.3%). (3) Have never been regionally surveyed or called upon for interviews with respect to treatment desire and problems relating to geriatric patients(87.2%). (4) Health and medical policies for geriatric patients must be established rapidly(98.4). (5) Expansion and construction of specialized medical facilities for geriatric patients such as elderly hospital and medical center are needed(90.2%). (6) Government's welfare policies for the elderly people is insufficient(82.0%) 5) Degree of cognition on importance of physical therapy with respect to geriatric patient. (1) Physical therapy is considered most effective in treating geriatric patients(82.9%). (2) Physical therapists specializing in only elderly people must be need of separately(76.2%). (3) It is desirable for medical specialists to visit geriatric patients at home to provide physical therapy(82.9%). (4) Hospitals specializing in physical therapy for geriatric patient are required(85.6%). Based on the result for this research, the following suggestions are presented to facilitate the utilization of health care institution for the welfare of geriatric patients. Medical facilities such as elderly hospital and geriatric patient's medical center specializing in elderly people must be constructed as early as possible; and home-visiting physical therapist system must be important to treat chronic geriatric patients; our government must establish policies to provide the old ages with means for the health care and curing chronic diseases, and carry out the plans of reasonable distribution and effective untilization of medical resources.

• Restorative Dentistry and Endodontics
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• v.27 no.2
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• pp.158-174
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• 2002

The aim of this study was to investigate the effect of light irradiation modes on polymerization shrinkage, degree of cure and microleakage of a composite resin. VIP$^{TM}$ (Bisco Dental Products, Schaumburg, IL, USA) and Optilux 501$^{TM}$ (Demetron/Kerr, Danbury, CT, USA) were used for curing Filtek$^{TM}$ Z-250 (3M Dental Products, St. Paul., MN, USA) composite resin using following irradiation modes: VIP$^{TM}$ (Bisco) 200mW/$\textrm{cm}^2$ (V2), 400mW/$\textrm{cm}^2$ (V4), 600mW/$\textrm{cm}^2$ (V6), Pulse-delay (200 mW/$\textrm{cm}^2$ 3 seconds, 5 minutes wait, 600mW/$\textrm{cm}^2$ 30seconds, VPD) and Optilux 501$^{TM}$ (Demetron/Kerr) C-mode (OC), R-mode (OR). Linear polymerization shrinkage of the composite specimens were measured using Linometer (R&B, Daejeon, Korea) for 90 seconds for V2, V4, V6, OC, OR groups and for up to 363 seconds for VPD group (n=10, each). Degree of conversion was measured using FTIR spectrometer (IFS 120 HR, Bruker Karlsruhe, Germany) at the bottom surface of 2 mm thick composite specimens V2, Y4, V6, OC groups were measured separately at five irradiation times (5, 10, 20, 40, 60 seconds) and OR, VPD groups were measured in the above mentioned irradiation modes (n=5 each). Microhardness was measured using Digital microhardness tester (FM7, Future-Tech Co., Tokyo, Japan) at the top and bottom surfaces of 2mm thick composite specimens after exposure to the same irradiation modes as the test of degree of conversion(n=3, each). For the microleakage test, class V cavities were prepared on the distal surface of the ninety extracted human third molars. The cavities were restored with one of the following irradiation modes : V2/60 seconds, V4/40 seconds, V6/30 seconds, VPD , OC and OR. Microleakage was assessed by dye penetration along enamel and dentin margins of cavities. Mean polymerization shrinkage, mean degree of conversion and mean microhardness values for all groups at each time were analyzed using one-way ANOVA and Duncan's multiple range test, and using chi-square test far microleakage values. The results were as follows : . Polymerization shrinkage was increased with higher light intensity in groups using VIP$^{TM}$ (Bisco) : the highest with 600mW/$\textrm{cm}^2$, followed by Pulse-delay, 400mW/$\textrm{cm}^2$ and 200mW/$\textrm{cm}^2$ groups, The degree of polymerization shrinkage was higher with Continuous mode than with Ramp mode in groups using Optilux 501$^{TM}$ (Demetron/Kerr). . Degree of conversion and microhardness values were higher with higher light intensity. The final degree of conversion was in the range of 44.7 to 54.98% and the final microhardness value in the range of 34.10 to 56.30. . Microleakage was greater in dentin margin than in enamel margin. Higher light intensity showed more microleakage in dentin margin in groups using VIP$^{TM}$ (Bisco). The microleakage was the lowest with Continuous mode in enamel margin and with Ramp mode in dentin margin when Optilux 501$^{TM}$ (Demetron/Kerr) was used.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.3
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• pp.375-382
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• 1986

This study was carried out to obtain the basic information for the clarification of spring growth habits mechanism of naked barleys. The isozyme patterns and activities of peroxidase in the young spike and leaf blade were analyzed during the differentiation and development of young spike. The characteristic differences between the normal and rosetted type were in c and g isozymes in young spike, and in i isozyme in the leaf blade. In the normal type, c and i isozymes disappeared at the stage of spi-kelet differentiation, g isozyme at the stage of flolet differentiation. But, in the rosetted type, those three isozymes remained in dark stained condition until the time of final sampling. Especially, those three isozymes were higher in the rosetted type than those in the normal type even at the stage of bract differentiation(BDS), just prior to the reproductive stage. The activities of peroxidase decreased slowly after BDS in the young spike and leaf blade in the normal type, While, in the rosetted type, increased linearly, and the degree of increasing was remarkable in the young spike. It was interesting that the degree of activities in young spike was higher in the rosetted type than that in the normal type even at BDS. From the above results, the remarkable differences of the isozyme patterns and activities at BDS between the normal and rosetted type were considered to be the physiological expression of the varieties concerned with the degree of spring growth habits.

• The Journal of Korean Medicine
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• v.18 no.2
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• pp.340-354
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• 1997

Background : The stenosis of the coronary artery results in a decrease in the myocardial oxygen supply, ischemia and infarction. Jakamchotang as a drug of liquid is generally regarded to have the effect of arrythmia, palpitation from Heart disease and promoting the flow of Ki and Blood. Methods : The purpose of this experimental study is to find whether Jakamchotang is effective or not in curing ischemia in isolated perfused rat hearts and to measure the degree of its curing effect. In this study, under the Langendorff apparatus, ischemia was induced in isolated Sprague-Dawley rat hearts by ceasing the perfusion for 20 minites. Subjects were divided into a normal saline orally administered group(control group), an Jakamchotang orally 100mg administered group (sample A), an Jakamchotang orally 300mg administered group (sample B), and an Jakamchotang injection perfused group(sample C). The heart rates, left ventricular pressure, myocardial dilatation/contraction, cardiac perfusion flow and cardiac ezyme(LDH, CPK) of the four group were measured and compared in order to assess the influence of Jakamchotang on isolated perfused rat hearts recovering abillity from ischemia and infarction. results : 1. Heart rates were increased significantly in Jakamchotang orally 100mg administered group, Jakamchotang orally 300mg administered group and Jakamchotang injection perfused group on perfusion and reperfusion(p<0.01). 2. Left ventricular pressure were increased significantly in Jakamchotang orally 100mg administered group and 300mg administered and Jakamchotang injection perfused group(p<0.01) in comparison with control group on perfusion, but every group did not significant on reperfusion. 3. While there were no differances in each group's abillities of myocardial dilatation, the ability of myocardial constriction of Jakamchotang 100mg administered group only on perfusion was significantly greater than that of control group(p<0.05). 4. CBF was no significant on perfusion and reperfusion in comparison with control group(N.S.) 5. LDH was not significantly decreased on perfusion, but significactly decreased in Jakamchotang orally 100mg administered group, Jakamchotang orally 300mg administered group on reperfusion. 6. CPK was significantly decreased in Jakamchotang orally 100mg administered group, 300mg administered and Jakamchotang injection perfused group on perfusion(p<0.01), but was not significantly in Jakamchotang 300mg administered group only on reperfusion(P<0.05) Conclusion : According to the result above, Jakamchotang have an effect to recover in the isolated perfused rat hearts. Especially, the effect of Jakamchotang in orally adminstered group is greater than that of Jakamchotang injection perfused group on preischemia. The followings are the two important results of this study: First, the effect of Jakamchotang used traditionally on heart disease was proved statistcally under the Langendorff apparatus. Second, on the basis of this study, the effect of other type medications on myocardial ischemia can be evaluted in further studies.