• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.4
• /
• pp.1051-1061
• /
• 1995

In order perform leak-before-break design of nuclear piping systems and integrity evaluation of reactor vessels, full stress-strain (.sigma. - .epsilon.) curves and fracture resistance (J-R) curves are required. However it is time-consuming and expensive to obtain J-R curves experimentally. The objective of this paper is to develop two methods for J-R curve prediction. In the first method, elastic-plastic finite element analyses for a series of crack length / specimen width ratio were performed. Accordingly the load versus load line displacement (P .delta.) curve corresponding to the fracture strain is obtained and the J-R curve based on the generalized locus method is obtained. In the second method, the correlation between .sigma.-.epsilon. curves and J-R curves was statistically analyzed and an empirical equation to predict the J-R curve from the .sigma.-.epsilon. test result is proposed. A good correlation between the predicted results based on the proposed methods and the experimental ones is obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.993-996
• /
• 2005

High speed machining(HSM) technique is widely used in the appliance, automobile part and mold industries, which has many advantages such as good quality, low cost and rapid machining time. but it also has problems like tool break, smooth tool path, and so on. In particular, small size end mill is easy to break, so it must be changed before interrupting operation. Generally, the tool life of small size end mill is effected by the milling conditions whose evaluated parameters are spindle, feedrate, and width of cut. The experiments are carried out by full factorial design of experiments using and orthogonal array. This paper shows optimal combination and mathematical model for tool life, and the analysis of variance(ANOVA) is employed to analyze the main effects and the interactions of these milling parameters and the second-order polynomial regression model with three independent variables is estimated to predict tool life by multiple regression analysis.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1997.05a
• /
• pp.484-488
• /
• 1997

Fission product release (FPR) assessment for 100% reactor outlet header (ROH) break in CANDU reactor loaded with CANFLEX-NU fuel bundles has been performed. The predicted results are compared with those for the reactor loaded with standard 37-element bundles. The fuel failure thresholds for the CANFLEX and standard bundle elements are very similar. All the sheaths at the corresponding fuel failure thresholds for the CANFLEX and standard bundles fail due to the significant cracks in the surface oxide, except those for the CANFLEX inner element at burnups of 220 to 240 MW.h/kg(U), which fail due to the excessive diametral strain. The fuel failure analysis predicts that the number of failed fuel elements for the CANFLEX bundle case is none, while that for the standard bundle case is 1827. The total (gap plus bound) I-131 releases for the CANFLEX and standard bundles are none and 5889 TBq, respectively The significant reduction of the number of failed fuel elements and FPR for the CABFKEX fuel bundle is attributed to the lower linear power of the CANFLEX fuel bundle compared with the standard fuel bundle.

• Journal of Korea Society of Industrial Information Systems
• /
• v.23 no.3
• /
• pp.131-142
• /
• 2018

Since income growth rate and poverty level are related, there is a possibility that the poverty rate may converge in the long run steady state as well. If the poverty rate converges, then for this study the state that begins with the high poverty rate would have a higher poverty reduction rate. To examine the convergence of poverty rate among the US states, this study uses two times series methodologies. First, in order to prevent the power loss from ignoring the structural break when testing for a unit root in a single time series, this study employs the newly developed panel LM unit root tests with level and trend shifts. The results of unit root tests of the log of poverty rate without allowing for structural breaks show that twenty six states reject the null hypothesis of unit root test for the ADF test, twenty five states for the LM test, and thirty five states for the RALS-LM test. The result of unit root tests that allow one structural break shows that the null hypothesis of a unit root test is rejected for twenty two states with the LM test, and thirty three states with the RALS-LM test. This supports poverty rates are converging among US states.

• Macromolecular Research
• /
• v.14 no.2
• /
• pp.187-193
• /
• 2006

Organoclay, was applied as a filler, in place of carbon black and silica, to a natural rubber (NR)/butadiene rubber (BR) blend. A compounding method was used to disperse and separate the layered silicates. The effect of a coupling agent on the vulcanizates was evaluated using both the silica and organoclay filled compounds. After the compounding processes were completed, the XRD diffraction peaks disappeared, but then reappeared after vulcanization. The scorch times for the organoclay-filled compounds were very short compared to those for carbon black and silica-filled compounds. The organoclay-filled compounds showed high values of tensile strength, modulus, tear energy, and elongation at the break. When ranked by viscosity, the compounds appeared in the following order: silica > silica (Si-69) > organoclay > organoclay (Si-69) > carbon black. Fractional hysteresis, tensile set, and wear rates were very consistent with the viscosity of the vulcanizates. The Si 69 coupling agent increased reversion resistance, the maximum torque values in the ODR, modulus, and wear resistance, but decreased elongation at the break, fractional hysteresis, and tension set of the vulcanizates.

• Journal of East-West Nursing Research
• /
• v.26 no.1
• /
• pp.17-27
• /
• 2020

Purpose: This study aimed to examine the effect of auricular acupressure therapy on reducing the ocular symptoms and signs for dry eye syndrome. Methods: The participants who were aged ≥ 40 years old and met the inclusion criteria of the ocular surface disease index score ≥ 13 and a tear film break-up time ≤ 10 seconds were enrolled into the two groups: experimental group (n=29) and control group (n=27). Experimental group received auricular acupressure therapy for 8 weeks. Seed stickers were applied to the eye, liver and tubercle point of each ear once a week. Data were collected at pre and 4 and 8 weeks after the treatment and analysed the efficacy of intervention by repeated measures ANOVA. Results: There were significant differences in the ocular surface disease index, standard patient evaluation of eye dryness and a tear film break-up time in both eyes at 8 weeks after the treatment between the two groups. Conclusion: The findings indicate that the auricular acupressure therapy may be helpful for relieving symptoms of dry eye as a nursing intervention. In addition, it could also be utilized as a self-care practice using proper education and training.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.11
• /
• pp.2796-2803
• /
• 2000

For traditional Leak-Before-Break(LBB) analyses, symmetric conditions were assumed for a pipe-nozzle interface to simplify the analysis in calculating J-integral. However. this assumption could result in an overly conservative design criteria for a pipe-nozzle interface, Since the pipe-nozzle interface is asymmetric due to the difference of stiffness between pipe and nozzle, it is required to develop a new methodology considering the nozzle effect. The objective of this paper is to evaluate the effect of nozzle no the development of LBB design criteria for nuclear pipings. For this purpose, extensive finite element analysis were performed to evaluate the effect of nozzle on Crack Opening Area(COA), Detectable Leakage Crack(DLC) length and J-integral values. In conclusion, it was proven that the application of LBB concept could be extended for more nuclear piping system by considering the nozzle.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.12
• /
• pp.3-13
• /
• 2013

This paper contains two algorithms proposed for synchronization in OFDM system. The first is having 1 symbol offset while calculating the timing metric, and the second is introduced in new parameter such as Reduction Factor(${\rho}$), Break Constant(${\beta}_k$) and Implant Depth(${\delta}_I$) in order to control the power of CP(Cyclic Prefix) area. Two proposed method are evaluated performance with conventional methode, and than the result of simulation show proposed methods is better than conventional methode while it experience into multipath fading channel.

• Nuclear Engineering and Technology
• /
• v.49 no.2
• /
• pp.349-359
• /
• 2017

During the past 25 years, in the context of probabilistic safety assessment, efforts have been directed towards establishment of comprehensive pipe failure event databases as a foundation for exploratory research to better understand how to effectively organize a piping reliability analysis task. The focused pipe failure database development efforts have progressed well with the development of piping reliability analysis frameworks that utilize the full body of service experience data, fracture mechanics analysis insights, expert elicitation results that are rolled into an integrated and risk-informed approach to the estimation of piping reliability parameters with full recognition of the embedded uncertainties. The discussion in this paper builds on a major collection of operating experience data (more than 11,000 pipe failure records) and the associated lessons learned from data analysis and data applications spanning three decades. The piping reliability analysis lessons learned have been obtained from the derivation of pipe leak and rupture frequencies for corrosion resistant piping in a raw water environment, loss-of-coolant-accident frequencies given degradation mitigation, high-energy pipe break analysis, moderate-energy pipe break analysis, and numerous plant-specific applications of a statistical piping reliability model framework. Conclusions are presented regarding the feasibility of determining and incorporating aging effects into probabilistic safety assessment models.

• Journal of Environmental Science International
• /
• v.19 no.3
• /
• pp.365-370
• /
• 2010

In this study, we carried out the evaluation of EPDM(Ethylene Propylene Diene Monomer) reclaimed rubber mixing with natural rubber at various mixing ratio to reuse as rubber filler. The scorch time and moony viscosity was analyzed to evaluate the effect of cure behavior. And also, we analyzed the tensile strength, the elongation at break and cure time to evaluate the variation of cure behavior. As the results, the scorch time and optimal cure time was decreased according to the increasing of EPDM reclaimed rubber. However, the moony viscosity was increased at each mixing ratio. In case of the added EPDM reclaimed rubber was 20 phr(parts by weight per 100 parts by weight of rubber), the hardness and specific gravity was increased a little. The hardness and specific gravity was increased in rapidly under 40 phr of the added EPEM reclaimed rubber. The tensile strength and elongation at break of the compound of natural and EPDM reclaimed rubber was rapidly decreased compared with its natural rubber when the ratio of adding EPDM reclaimed rubber was over 40 phr.