• 한국구조물진단유지관리공학회 논문집
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• 제1권1호
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• pp.125-132
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• 1997

This study was intended to investigate the effects of epoxy grout on compressive strength for damaged concrete structures. For this purpose, concrete molds were manufactured and tested for compressive strength at 28 days after water curing. Two kinds of Korea-made and one Japan-made epoxy grouts were injected into the broken concrete molds with the automatic low-pressure injecting method or the hand injecting method.

• 대한물리치료과학회지
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• 제1권2호
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• pp.215-222
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• 1994

The aim of this study was to determine the normative strength value for cervical flexors, extensors and right lateral flexors, left lateral flexors to provide a guideline for rehabilitation of cervical radiculopathy patients. The isometric evaluation of cervical flexors, extensors and lateral flexors by using the Hand-held dynamometer was performed on 50 males and 50 females. The result were as follows. The average cervical muscle strength were 5.7 kg in flexor. 10.5 kg in extensors, and 6.6 kg in right lateral flexor, 6.5 kg in left lateral flexor. There was statistically significant difference between the cervical flexors and extensors(p<0.01) but no significant difference between right lateral flexor and left lateral flexor. There was statistically significant difference between male and female(p<0.01). When one of cervical muscle was strong, also the others did in subjects(p<0.01) and the body weight was significantly releated to the cervical muscle strength(p<0.01).

• 대한음성학회지:말소리
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• 제35_36호
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• pp.145-155
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• 1998

This study intended to determine the most appropriate POS(Part of Speech) sets for predicting prosodic boundary strength efficiently. We used 3-level POB bets which Kim(1997), one of the authors, has devised. Three POS sets differ from each other according to how much grammatical information they have: the first set has maximal syntactic and morphological information which possibly affects prosodic phrasing, and the third set has minimal one. We hand-labelled 150 sentences using each of three POS sets and conducted perception test. Based on the results of the test, stochastic language modeling method was used to predict prosodic boundary strength. The results showed that the use of each POS set led to not too much different efficiency in the prediction, but the second set was a little more efficient than the other two. As far as the complexity in stochastic language modeling is concerned, however, the third set may be also preferable.

• 한국산학기술학회논문지
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• 제5권5호
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• pp.433-437
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• 2004

The MmSH is a process of injecting ABS to produce innovated physical properties compared to the conventional injection process. Physical properties such as thickness and adhesion strength of Ni plate electrolessly coated on a conventional and a MmSH injected ABS have been studied in the pH range 4~8. Thickness of the plate on the MmSH and the conventionally injected ABS appeared to be directly proportional to pH. The ABS processed by the conventional injection showed adhesion strength corresponded to ASTM 4B above pH 5. On the other hand, the ABS processed by the MmSH injection showed a superior adhesion strength corresponded to ASTM 5B above pH 6. It was calculated the shielding effectiveness of above 50 dB in all conditions.

• Composites Research
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• 제34권2호
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• pp.96-100
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• 2021

The lightweight industry continuously demands reliable near-net-shape fabrication where the preform just out-of-machine is close to the final shape. In this study, different half-finished preforms are made π-beams. Then the preforms are unfolded to make a 3D shape with integrated structure of fibers, providing easier handling in the further processing of composites. Several 3D textile preforms are made using weaving technique and are examined after resin infusion for mechanical properties such as inter-laminar shear strength, compressive strength and tensile strength. Considering that the time and labor are important parameters in modern production, 3D weaving technique reduces the manufacturing steps and therefore the costs, such as hand-lay up of textile layers, cutting, and converting into preform shape. Hence this 3D weaving technique offers many possibilities for new applications with efficient composite production.

• Geomechanics and Engineering
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• 제32권5호
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• pp.495-502
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• 2023

In this study, stress relaxation tests were carried out by keeping silt type soil specimens under different strain levels. Decreases in the stress values with time data was collected to better understand the effect of the strain level on the relaxation properties of soil specimens. In addition, the stress relaxation effect on the uniaxial compressive strength (UCS) values of the specimens was investigated with a series of tests. According to the results obtained from this study, the UCS values of the silt specimens significantly vary as a result of the stress relaxation effect. The UCS values were determined to increase with an increase of relaxation strain level to a threshold value. On the other hand, the UCS values were found to be affected adversely in case of high stress levels at the initiation of the relaxation, which are close to the peak level.

• Advances in concrete construction
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• 제3권4호
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• pp.283-293
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• 2015

This paper presents the effects of elevated temperatures of $400^{\circ}C$ and $800^{\circ}C$ on the residual compressive strength and failure behaviour of fibre reinforced concretes and comparison is made with that of unreinforced control concrete. Two types of short fibres are used in this study e.g., steel and basalt fibres. The results show that the residual compressive strength capacity of steel fibre reinforced concrete is higher than unreinforced concrete at both elevated temperatures. The basalt fibre reinforced concrete, on the other hand, showed lower strength retention capacity than the control unreinforced concrete. However, the use of hybrid steel-basalt fibre reinforcement recovered the deficiency of basalt fibre reinforced concrete, but still slightly lower than the control and steel fibres reinforced concretes. The use of fibres reduces the spalling and explosive failure of steel, basalt and hybrid steel-basalt fibres reinforced concretes oppose to spalling in deeper regions of ordinary control concrete after exposure to above elevated temperatures. Microscopic observation of steel and basalt fibres surfaces after exposure to above elevated temperatures shows peeling of thin layer from steel surface at $800^{\circ}C$, whereas in the case of basalt fibre formation of Plagioclase mineral crystals on the surface are observed at elevated temperatures.

• Elastomers and Composites
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• 제52권4호
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• pp.295-302
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• 2017

Polyurethane dispersion (PUD) polymers were synthesized by using polyether and polyester polyol. The effect of ionomeric centers, r(NCO / OH) values, chain extender process, and chain extender types on the adhesion properties was investigated. In the case of polyether-based PUD, the ionic center, r value, chain extension process and chain extender types were not adjusted even after adjustment. In the case of polyester-based PUD, when the ionic center content was more than 2.5%, the state of adhesive strength was $2.0kgf/cm^2$ or more. On the other hand, the initial adhesive strength was excellent at about $1kgf/cm^2$ when the ionic center content was over 3.5%. When the r value was 1.3 or more, it was found that the initial bonding strength and the state of bonding strength were excellent at about $1kgf/cm^2$ and $2.1kgf/cm^2$ or higher, respectively. An IR spectrum analysis of the synthesized PUD confirmed that PUD was composed of urethane based on the N-H characteristic peak at $3340cm^{-1}$ and the urethane characteristic peak at $1730cm^{-1}$. Moreover, the characteristic peaks of the isocyanate ($2260cm^{-1}$) used in the preparation of the prepolymer were not observed. As a result, the residual -NCO was not observed, and urethane was completely synthesized.

• 한국임상수의학회지
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• 제13권2호
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• pp.184-194
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• 1996

A comparative study of three absorbable suture materials of chromic catgut, Dexon II (a polyglycolic acid suture with a polycaprolate coating system) and Coated Vicryl (a polyglactin 910 suture with a glycolide-lactide-calcium stearate coating system) was undertaken in terms of tensile strength, breaking elongation, appearances of the suture materials in the subcutaneous layer of rats and of tissue reaction in the intramuscular layer of rats. The initial tensile strength of chromic catgut and the tensile strength after 21 days were about 1.55 kg and 0.19 kg, respectively. Those of Dexon II were about 2.01 kg and 0. 20 kg, respectively. Those of Coated Vicryl were about 2.39 kg and 0.48 kg, respectively. Coated Vicryl showed the highest tensile strength among the three materials during the whole period. On the other hand, Dexon II showed the highest breaking elongation among the three materials during the first week. But the breaking elongation of Dexon II rapidly continuously decreased during the whole period. The appearances of the suture materials in the subcutaneous layer of rats showed that chromic catgut was the fastest among the three materials, whereas it formed comparatively much connective tissue. The intramuscular absorption rate and tissue reaction of Dexon II were similar to those of Coated Vicryl. The intramuscular absorption rate of these was fairly late when compared with chromic catgut. And the tissue reaction appearance of these showed the formation of a granuloma with foreign body giant cells, macrothages and epitheloid cells by the 28th day in the experimental period.

• The Korean Journal of Ceramics
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• 제3권2호
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• pp.73-81
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• 1997

In this paper, it is intended to present more reproducible and quantitative method for adhesion assemssement. In scratch test, micromechanical analysis on the stress state beneath the indenter was carried out considering the additional blister field. The interface adhesion was quantified as work of adhesion through Griffith energy approach on the basis of the analyzed stress state. The work of adhesion for DLC film/WC-Co substrate calculated through the proposed analysis shows the identical value regardless of distinctly different critical loads measured with the change of film thickness and scratching speed. On the other hand, uniaxial loading was imposed on DCL film/Al substrate, developing the transverse film cracks perpendicular to loading direction. Since this film cracking behavior depends on the relative magnitude of adhesion strength to film fracture strength, the quantification of adhesion strength was given a trial through the micromechanical analysis of adhesion-dependence of film cracking patterns. The interface shear strength can be quantified from the measurement of strain $\varepsilon$s and crack spacing $\lambda$ at the cessation of film cracking.