• Journal of the Korean Society of School Health
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• v.12 no.1
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• pp.45-56
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• 1999

Adolescence is vulnerable to various Health Risk Behaviors (HRB). These behaviors can affect his remaining life as well as adolescence, thus prevention of HRB is a critical issue in health education. This study is aimed to provide basic information for prevention of HRB. Thus, this study was conducted to analyze the impact of peer group's health risk behaviors on health risk perception (HRP) and that of health risk perception on health risk behaviors based on 832 respondents. The 852 subjects were selected in six middle and high schools in Seoul through random sampling. Data were collected from September, 18-October, 21, 1998, and the 832 data were analyzed after excluding the 20 incomplete and inaccurate data. Questionnaire items and measures are based on an instrument to measure Perceived Health Risk Perception, which Hodge B.C. developed in 1992. Cronbach alpha is used to test the reliability. The reliability of HRP and HRB is 0.9473, 0.8768 in this study, Statistical analysis divided into four phases. First, the impact of socio-demographic characteristics on HRP is analyzed by oneway ANOV A. Male students have lower HRP than female students. As grade goes up, HRP is getting lower. Perceived higher concern of parents and HRP are correlated. And the experience of school health education and HRP are correlated. Second, the impact of peer group's HRB on the HRP is analyzed by linear regression. Peer group's HRB and HRP are negatively correlated, Third, the impact of HRP on HRB is analyzed by linear regression. There is a correlation between high HRP and low HRB. Fourth, Powerful impact factors on HRB are analyzed by stepwise multiple regression. Grade, gender, peer group's HRB, and related HRP is entered as independent variables. Because of correlation between entered variables, three interaction variables between grade, gender, peer group's HRB and related HRP also entered, In general, peer group's HRB is the most accountable factor to HRB. And Interaction variable between HRP and peer group's HRB and HRB are negatively correlated. These results indicate that HRP may reduce the impact of peer group's HRB on HRB. Some recommendations are as follows: First, health educational programs suitable for gender and grade are required. Second, a systematic cooperation between school and home is necessary for effective prevention of HRB. Third, the educational effect for decreasing HRB by increasing HRP is statistically assisted. However, peer group has much stronger impact on HRB than subjective HRP, thus special consideration and management are necessary for peer group which does HRB more frequently.

• Earthquakes and Structures
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• v.12 no.2
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• pp.201-211
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• 2017

This paper experimentally investigates the effect of yield strength of reinforcing bars and stirrups on the seismic performance of reinforced concrete (RC) circular piers. Reversed cyclic loading tests of nine-large scale specimens with longitudinal and transverse reinforcement of different yield strengths (varying between HRB335, HRB500E and HRB600 rebars) were conducted. The test parameters include the yield strength and amount of longitudinal and transverse reinforcement. The results indicate that the adoption of high-strength steel (HSS) reinforcement HRB500E and HRB600 (to replace HRB335) as longitudinal bars without reducing the steel area (i.e., equal volume replacement) is found to increase the moment resistance (as expected) and the total deformation capacity while reducing the residual displacement, ductility and energy dissipation capacity to some extent. Higher strength stirrups enhance the ductility and energy dissipation capacity of RC bridge piers. While the product of steel yield strength and reinforcement ratio ($f_y{\rho}_s$) is kept constant (i.e., equal strength replacement), the piers with higher yield strength longitudinal bars are found to achieve as good seismic performance as when lower strength bars are used. When higher yield strength transverse reinforcement is to be used to maintain equal strength, reducing bar diameter is found to be a better approach than increasing the tie spacing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.480-483
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• 2002

This paper through shift norm of insulator and research by accident prevention countermeasure special skill authoritativeness verification of insulator and Long Term aging factor for power transmission analysis and evaluate and prove quality of insulator wish to. Assessment technique by aging of own porcelain insulator observes ageing factor for reciprocity comparison through several examinations. Through cool and heat accelerated Aging test, can measure the leakage current change amount that ensue to each Cycle. Can confirm own blazing fire factor as distribution freshness that ensue in HRB Test's hardness value.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.9
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• pp.842-850
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• 2003

The suspension insulators are subjected to harsh environments in service for a long time. The long-term reliability of tile insulators is required for both mechanical and electrical performances. This study describes some basic performance tests and accelerated aging test by cool-heat cycling methods and thermal mechanical performance test methods on alumina porcelain insulators (new and aged) used for transmission line in KOREA. There was no fail in electrical and mechanical performance tests such as a high voltage strength, a flashover voltage, and an impact strength in all samples. But in the case of accelerating aging tests which have above 9$0^{\circ}C$ temperature gradient, fracture phenomena was happened by a thermal shock in tile aged sample(sample A) with low alumina porcelain body. It was indicated that sample A was more severely aged than other samples. According to results of HRB test and microstructural analysis, it was reasoned that insulator bodies with the matrix reinforced with alumina crystalline phase have advantages over the suppression of crack advance. And cool-heat aging and mechanical thermal ageing tests shows that a temperature gradient is more effective to accelerating than a cycling number.

• Computers and Concrete
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• v.13 no.3
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• pp.411-421
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• 2014

A central pullout test was conducted to investigate the bonding properties between high strength rebar and reactive powder concrete (RPC), which covered ultimate pullout load, ultimate bonding stress, free end initial slip, free end slip at peak load, and load-slip curve characteristics. The effects of varying rebar buried length, thickness of protective layer and diameter of rebars on the bonding properties were studied, and how to determine the minimum thickness of protective layer and critical anchorage length was suggested according the test results. The results prove that: 1) Ultimate pull out load and free end initial slip load increases with increase in buried length, while ultimate bonding stress and slip corresponding to the peak load reduces. When buried length is increased from 3d to 4d(d is the diameter of rebar), after peak load, the load-slip curve descending segment declines faster, but later the load rises again exceeding the first peak load. When buried length reaches 5d, rebar pull fracture occurs. 2) As thickness of protective layer increases, the ultimate pull out load, ultimate bond stress, free end initial slip load and the slip corresponding to the peak load increase, and the descending section of the curve becomes gentle. The recommended minimum thickness of protective layer for plate type members should be the greater value between d and 10 mm, and for beams or columns the greater value between d and 15 mm. 3) Increasing the diameter of HRB500 rebars leads to a gentle slope in the descending segment of the pullout curve. 4) The bonding properties between high strength steel HRB500 and RPC is very good. The suggested buried length for test determining bonding strength between high strength rebars and RPC is 4d and a formula to calculate the critical anchorage length is established. The relationships between ultimate bonding stress and thickness of protective layer or the buried length was obtained.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.353-359
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• 2004

In this study. porcelain insulator samples which have a different alumina composition were manufactured in order to test electrical and mechanical properties and make an analysis of the propagation phenomena of micro cracks on porcelain body. From XRD quantitative analysis the crystalline phases were different with alumina composition, sample C and D which have about l7wt％ Corundum phase without the Cristobalite phase shows better electrical and mechanical properties than sample A and B which have the Cristobalite phase. In dielectrics test on porcelain samples with below l7wt％ alumina composition, it was found that the amount of glass phase(SiO$_2$) have an main effect to decrease the dielectric loss(tan$\delta$), and the dielectric breakdown voltage of aluminous porcelain insulators was largely affected by its relative density. As a micro tracks analysis, HRB were measured, then the intensity of HRB increased with the amount of alumina composition. On the other hand, the propagation behaviors of cracks was fairly influenced by the distribution of pores.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.462-463
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• 2008

36,000lbs porcelain insulators (D-1995, D-1997, D-2002) investigated mechanical and electrical qualities, which were installed in the Korea 154kV transmission lines. This paper assessed Weibull distribution function, quality index, and uniformity index to forecast the remaining life expectancies of insulators. Applying Weibull distribution function on year lapse change test, electro-mechanical failing load test, and HRB values confirmed a significant degree of correlation. Statistically calculating the life expectancy through quality indices for aging and new products and uniformity indices that are associated with uniformity of insulation materials revealed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.317-318
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• 2005

This paper presents the analysis on the properties of porcelain insulators with the manufactured year. The domestic porcelain insulators manufactured in 1995, 1997, and 2002 and the imported one are prepared. The content of alumina was increased with the manufactured year, and the hardness of ceramic parts showed the same trend. Moreover, the distribution and the size of pore were more decreased and reduced on the junction parts between the glaze and the ceramic. Therefore, we concluded that the domestic porcelain insulators have been improved with the lapse of time.

• Journal of the Korean Magnetics Society
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• v.21 no.4
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• pp.136-140
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• 2011

Mechanical properties of degraded materials must be measured for evaluating the integrity of the facilities operating at high temperature. In fact it is complicated to obtain the different degraded specimens from an operating facility. Specimens of 1Cr-0.5Mo steel prepared by the isothermal heat treatment at $700^{\circ}C$ were tested, which has been widely used as tubes for heat exchangers and as plates for pressure vessels. The magnetic properties and Rockwell hardness (HRB) were measured at room temperature. The peak interval of Barkhausen noise envelope (PIBNE), coercivity, and hardness decreased with the increase of degradation. The magnetic and mechanical softening of matrix is likely to govern the properties of the specimen more than the hardening of grain boundary by carbide precipitations. The degradation of test material may be determined by the linear correlation of PIBNE and HRB. Degradation of 1Cr-0.5Mo steel could well be nondestructively evaluated by PIBNE measured with surface type probe.

• Earthquakes and Structures
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• v.9 no.4
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• pp.699-718
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• 2015

The effect of reinforcing concrete members with high strength steel bars with yield strength up to 600 MPa on the overall seismic behavior of concrete moment frames was studied experimentally and numerically. Three geometrically identical plane frame models with two bays and two stories, where one frame model was reinforced with hot rolled bars (HRB) with a nominal yield strength of 335 MPa and the other two by high strength steel bars with a nominal yield strength of 600 MPa, were tested under simulated earthquake action considering different axial load ratios to investigate the hysteretic behavior, ductility, strength and stiffness degradation, energy dissipation and plastic deformation characteristics. Test results indicate that utilizing high strength reinforcement can improve the structural resilience, reduce residual deformation and achieve favorable distribution pattern of plastic hinges on beams and columns. The frame models reinforced with normal and high strength steel bars have comparable overall deformation capacity. Compared with the frame model subjected to a low axial load ratio, the ones under a higher axial load ratio exhibit more plump hysteretic loops. The proved reliable finite element analysis software DIANA was used for the numerical simulation of the tests. The analytical results agree well with the experimental results.