• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.137-145
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• 2003

In this study, direct tensile fatigue tests of the PS bar were performed in terms of diameter, minimum stress level, and maximum stress level. In the static test, the stress - strain curve and ultimate streng th of the PS bar were determined. Results of the fatigue test indicate that the diameter of the PS bar was not influenced by fatigue life. Minimum stress also had quite an influence on the fatigue of the PS bar. Thus, the fatigue characteristic equation was proposed in terms of stress range and minimum stress through statistical process. Strains on specimen that loaded direct tension were measured in the fatigue test, with the secant modulus of elasticity calculated from measured strains. The strain development consisted of three different stages, i.e., rapid increases during the initial fatigue life, uniform increases during the middle stage, and rapid increases until failure. The secant modulus of elasticity decreased during the fatigue life with increasing strain. However, stress level seemed to have no influence on the secant modulus of elasticity.

• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.421-426
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• 2008

Multi-walled carbon nanotube/polystyrene (MWCNT/PS) composites with various MWCNT contents were prepared by using a solution process with an aid of surfactant. Particularly, PS's with 3 different molecular weights (${\bar{M}}_n$ = 101500 g/mole for PS-1, ${\bar{M}}_n$ = 89900 g/mole for PS-2, and ${\bar{M}}_n$ = 85000 g/mole for PS-3) were used in this study. Thermal behavior of these composites was examined by using an oscillator rheometer at $210^{\circ}C$ and $180^{\circ}C$, of above and below the critical flow temperature ($T_{cf}{\sim}195^{\circ}C$) of PS matrix, respectively. The storage and loss modulus, and the complex viscosity of these composites increased with increasing MWCNT content at both temperatures. Largest increases in the frequency-dependent moduli and complex viscosity were observed between 2 wt% and 5 wt% of MWCNTs at $210^{\circ}C$ and $180^{\circ}C$. Only the composite at $210^{\circ}C$ showed the rheological phase transition from a viscous-dominant to an elastic-dominant behavior of the composites at a certain MWCNT content. The MWCNT content at the rheological phase transition of MWCNT/PS composites generally increased with decreasing molecular weight of PS, and was measured to be 3.5 wt% for MWCNT/PS-1, 3.2 wt% for MWCNT/PS-2, and 3.0 wt% for MWCNT/PS-3 composites.

• Korean Journal of Acupuncture
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• v.23 no.2
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• pp.155-166
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• 2006

Objectives: This study was undertaken to determine if Plantaginis Semen(PS) has a protective effect against $CCI_4$ induced hepatoxicity in Rats. Methods: The experimental groups were divided into Normal group (untreated Group), Control group $(group\;treated\;with\;CCI_4)$, Sample 1 (group treated with 0.1 ml Plantaginis Semen herbal acupuncture in both sides of $G\bar{a}nsh\bar{u}\;(BL_{18})$ after $CCI_4$ treating) and Sample 2 (group treated with feeding of 1 cc Plantaginis Semen extraction after $CCI_4$ treating). Rats were administered orally $CCI_4\;(0.1\;ml/kg)$ for 4 days. In experiments for PS effect, rats of Sample 1 group received 0.lml herbal acupuncture of PS extraction in both sides of corresponding $G\bar{a}nsh\bar{u}\;(BL_{18})$ of human body for 3 days after treated $CCI_4$. Rats of Sample 2 group feeded PS extraction (1cc) for 3 days after treated $CCI_4$. Variation of weight and biochemical assays (AST, ALT, LDH, ALP, total cholesterol, triglyceride, total protein, albumin) were performed. Results: In Control group, $CCI_4$ increased serum AST, ALT, LDH, ALP, total protein, albumin and decreased weight, total cholesterol, triglyceride. Sample 1 and Sample 2 significantly decreased serum AST, ALT, LDH, ALP, total protein, albumin as compared with Control group. Conclusion: These results indicate that PS could be used in prevention and treatment of hepatoxicity. However, precise mechanisms of PS protection remain to be determined.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.147-148
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• 2009

The anchorage system unified both PS strand and bar effectively introduced a prestress into a flexural concrete members. This study examined the relation between the anchorages of both ends and the introduced force and derived the equation for design.

• 열병합발전
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• s.80
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• pp.21-27
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• 2011

고전압, 대전류의 송전을 위한 기존의 케이블 포설법과 부스덕트 시공법상 발생하기 쉬운 여러 문제점에 대한 보완 개선되어 새롭게 개발된 HiViPS (High Voltage/Current Insulation Pipe Bus-bar System)라는 복합 차폐 절연관 부스바(Complex Insulation Pipe Tubular Bus-bar)를 소개한다.

• Journal of the Korean Society of Safety
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• v.27 no.4
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• pp.50-61
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• 2012

In recent years, various research and developments to introduce composite bridges of new concept have been performed. The types of integral bridge and portal rigid frame bridge are having advantages in bridge maintenance and structural efficiency by eliminating expansion joints and bridge supports. However, the detail of typical girder-abutment connection has problems such as complexity of construction and increase of the construction cost. A new type of bridge, called prestress integral composite girder(PIC girder) bridge, is proposed in this study, which decreases the cost of construction and improves the efficiency of construction by simplifying the detail of construction for girder-abutment connection. PIC girder bridge has the connection detail in which the steel girder and the abutment are integrated by using the PS bar installed in the connection. In this study, finite element analysis and mock-up load test are conducted to evaluate the propriety of design, the effective of fabrication and structural safety for PIC girder bridge. The adequacy of the PIC giredr bridge is verified by the results of static/dynamic load test and finite element analyses.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.173-176
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• 2003

Progressive failure analysis of steel composite double T-beam is performed to investigate the mechanical effects of steel composite fabricated in the webs of double-T beam to replace concrete placing forms. The analysis is based on nonlinear finite element scheme considering material nonlinearities of concrete, reinforcing bar and PS steel. Four-parameter strength envelope defines the hardening and softening phenomena of concrete with consideration of the various levels of confining pressures. Rankine maximum strength criterion defines the elasto-plasticity of PS steel and reinforcing bar, and Von Mises $J_2$ failure criterion for steel plate which wraps the concrete webs of double T-beam. A 6m long two-span steel composite double T-beam is analyzed and compared with the experimental results.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.311-322
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• 1998

American Society for Testing and Materials (ASTM) standard test method PS 070-97 has been created for measuring fracture toughness of advanced ceramics. PS 070-97 includes three test methods which use beams in bending: chevron notch (CNB), single-edged precracked beam (SEPB), and surface crack in flexure (SCF). Supporting data has been collected through several Versailles Advanced Materials and Standards round robins. This paper discusses the evolution of the standard including the rationale for the choice of the three methods and the specifications in the standard. Progress on Standard Reference material 2100 which will have certified values of fracture toughness is presented.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.3
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• pp.555-561
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• 2024

This paper derives material properties of steel bars that simulate the distribution of stress and strain of prestressed tendons used in Prestressed concrete(PSC) girders and presents an optimal material model. ABAQUS software was used to establish the 3D solid model of the PSC girder and strand wire rope for a PS(Prestressed) tendon. Then the model of steel wire rope was imported into the Isight interface plugin directly through the ABAQUS and the Data Matching. In ABAQUS, the contact pairs were established, the models were meshed, the constraints were applied to solve the finite element model and an axial tension of 0.5m/s was loaded to analyze the stress and deformation distributions in the normal working range of the PS strand wire rope. In Data Matching, classical experimental data is fitted to the optimal material properties through finite element analysis and multi-objective optimization. The results show that the steel bar with optimal material properties presents a similar linear area and stress distribution with the PS tendon.

• Elastomers and Composites
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• v.23 no.2
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• pp.125-133
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• 1988

The thermal degradation of polymethyl methacrylate(PMMA) blend namely polymethyl methacrylate-polycarbonate(PMMA-PC) blend and polymethyl methacrylate-polystyrene(PMMA-PS) blend were carried out by isothermal method under air at several heating temperature from 220 to $270^{\circ}C$. Molecular weight changes during the thermal decomposition were monitored by means of the viscosity average molecular weight($\bar{M}v$). The viscosity average molecular weight was determined by Gel Permeation Chromatography(GPC). The dominant process in the degradation of PMMA-PC and PMMA-PS blend were main chain scission randomly due to weak links that may be distributed along the polymer backbone and the initial rate which the bonds are broken is not sustained. The infra-red spectra of degraded PMMA-PS blend show that the presence of aromatic ketone band at $1685cm^{-1}$. However, the infra-red spectra of degraded PMMA-PC blend show that the presence of hydroperoxide band at $3450cm^{-1}$. Thus indicating that the weak links are attacked by oxygen from the air and produce hydroperoxide or ketone. The activation energies of PMMA-PC blend and PMMA-PS blend were 18.2 and 17.9 Kcal/mol, respectively.