• Journal of the Korean Ceramic Society
• /
• v.36 no.8
• /
• pp.871-875
• /
• 1999

Theoretical equation to calculate thermal fatigue life was derived in which slow crack growth theory was adopted. The equation is function of crack growth exponent n. Cyclic thermal fatigue tests were performed at temperature difference of 175, 187 and 200$^{\circ}C$ respectively. At each temperature difference critical thermal fatigue life cycles of the alumina ceramics were 180,37 and 7 cycles. And theoretical thermal fatigue life cycles were calculated as 172, 35 and 7 cycles at the same temperature difference conditions. Therefore thermal fatigue behavior of alumina ceramics can be represented by derived equation. Also theoretical single cycle critical thermal shock temperature difference can be calculated by this equation and the result was consistent with the experimental result well.

• Atmosphere
• /
• v.33 no.2
• /
• pp.73-104
• /
• 2023

Over the past 60 years, Korean numerical weather prediction (NWP) has advanced rapidly with the collaborative effort between the science community and the operational modelling center. With an improved scientific understanding and the growth of information technology infrastructure, Korea is able to provide reliable and seamless weather forecast service, which can predict beyond a 10 days period. The application of NWP has expanded to support decision making in weather-sensitive sectors of society, exploiting both storm-scale high-impact weather forecasts in a very short range, and sub-seasonal climate predictions in an extended range. This article gives an approximate chronological account of the NWP over three periods separated by breakpoints in 1990 and 2005, in terms of dynamical core, physics, data assimilation, operational system, and forecast application. Challenges for future development of NWP are briefly discussed.

• Structural Engineering and Mechanics
• /
• v.32 no.3
• /
• pp.459-475
• /
• 2009

This paper presents analytical methodologies for remaining life prediction of plain concrete structural components considering tension softening and size effects. Non-linear fracture mechanics principles (NLFM) have been used for crack growth analysis and remaining life prediction. Various tension softening models such as linear, bi-linear, tri-linear, exponential and power curve have been presented with appropriate expressions. Size effect has been accounted for by modifying the Paris law, leading to a size adjusted Paris law, which gives crack length increment per cycle as a power function of the amplitude of a size adjusted stress intensity factor (SIF). Details of tension softening effects and size effect in the computation of SIF and remaining life prediction have been presented. Numerical studies have been conducted on three point bending concrete beams under constant amplitude loading. The predicted remaining life values with the combination of tension softening & size effects are in close agreement with the corresponding experimental values available in the literature for all the tension softening models.

• Journal of the Korean Data and Information Science Society
• /
• v.25 no.6
• /
• pp.1481-1489
• /
• 2014

For predicting yearly total attendances in Korean probaseball games, ARIMA models have been widely adopted so far. In this paper, we discuss two other ways of ARIMAX and growth curves with an exogenous variable to predict the attendances. By using the exogenous variable, it turns out that the prediction has been improved compared to ARIMA. It is concluded that various statistical methods must be considered for better prediction, and its results can be applied to predict the attendances of other pro sports.

• Journal of Applied Reliability
• /
• v.14 no.4
• /
• pp.225-229
• /
• 2014

A one-shot device is defined as a product, system, weapon, or equipment that can be used only once. After use, the device is destroyed or must undergo extensive rebuild. Determining the reliability of a one-shot device poses a unique challenge to the manufacturers and users due to the destructive nature and costs of the testing. This paper presents a reliability growth prediction for a one-shot system. It is assumed that 1) test duration is discrete(i.e. trials or rounds); 2) trials are statistically independent; 3) the number of failures for a given system configuration is distributed according to a binomial distribution; and 4) the cumulative expected number of failures through any sequence of configurations is given by AMSAA model. When the system development is represented by three configurations and the number of trials and failures during configurations are given, the AMSAA model parameters and reliability at configuration 3 are estimated by using a reliability growth analysis software. Further, if the reliability growth predictions do not meet the target reliability, the sample size of an additional test is determined for achieving the target reliability.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.8 no.2
• /
• pp.126-136
• /
• 1999

We studied on crack growth retardation in single overloading condition. Crack tip branching which as the second mechanism on crack growth retardation was examined. Crack tip branching was observed to kinked type and forked type. It was found that the branching angle range was from 25 to 53 degree. The variations of crack driving force with branching angle were calculated with finite element method The variation of {{{{ KAPPA _I}}}}, {{{{ KAPPA _II}}}} and total crack driving force(K) were examined respectively So {{{{ KAPPA _I}}}}, {{{{ KAPPA _II}}}} and K mean to mode I, II and total crack driving force. Present model(Willenborg's model) for crack growth retardation prediction was modified to take into consideration the effects of crack tip branching When we predicted retardation with modified model. it was confirmed that predicted and experimental results coincided with well each other.

• International Journal of Highway Engineering
• /
• v.15 no.3
• /
• pp.93-101
• /
• 2013

PURPOSES : This study is to investigate the relationship of socioeconomic characteristics and road network structure with traffic growth patterns. The findings is to be used to tweak traffic forecast provided by traditional four step process using relevant socioeconomic and road network data. METHODS: Comprehensive statistical analysis is used to identify key explanatory variables using historical observations on traffic forecast, actual traffic counts and surrounding environments. Based on statistical results, a multiple regression model is developed to predict the effects of socioeconomic and road network attributes on traffic growth patterns. The validation of the proposed model is also performed using a different set of historical data. RESULTS : The statistical analysis results indicate that several socioeconomic characteristics and road network structure cleary affect the tendency of over- and under-estimation of road traffics. Among them, land use is a key factor which is revealed by a factor that traffic forecast for urban road tends to be under-estimated while rural road traffic prediction is generally over-estimated. The model application suggests that tweaking the traffic forecast using the proposed model can reduce the discrepancies between the predicted and actual traffic counts from 30.4% to 21.9%. CONCLUSIONS : Prediction of road traffic growth patterns based on surrounding socioeconomic and road network attributes can help develop the optimal strategy of road construction plan by enhancing reliability of traffic forecast as well as tendency of traffic growth.

• Transactions of Materials Processing
• /
• v.20 no.7
• /
• pp.491-497
• /
• 2011

This work describes a method for determining material parameters included in recrystallization and grain growth models of metallic materials. The focus is on the recrystallization and grain growth models of Ni-Fe based superalloy, Alloy 718. High temperature compression test data at different strain, strain rate and temperature conditions were chosen to determine the material parameters of the model. The critical strain and dynamically recrystallized grain size and fraction at various process conditions were generated from the microstructural analysis and strain-stress relationships of the compression tests. Also, isothermal heat treatments were utilized to fit the material constants included in the grain growth model. Verification of the determined material parameters is carried out by comparing the average grain size data obtained from other compression tests of the Alloy 718 specimens with the initial grain size of $59.5{\mu}m$.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.17 no.2
• /
• pp.85-92
• /
• 2015

This study was conducted to analyze the relationship among climatic factors and radial growth of Pinus koraiensis in South Korea. To determine climate-growth relationships, cluster analysis was applied to group climatically similar surveyed regions, and dendroclimatological model was developed to predict radial growth for each climate group under the RCP 4.5 and RCP 8.5 scenarios for greenhouse gases. The dendroclimatological models were developed through climatic variables and standardized residual chronology for each climatic cluster of P. koraiensis. 2 to 4 climatic variables were used in the models ($R^2$ values between 0.35~0.49). For each of the climatic clusters for Pinus koraiensis, the growth simulations obtained from two RCP climate-change scenarios were used for growth prediction. The radial growth of the Clusters 2 and 3, which grow at high elevation, tend to increase. In contrast, Cluster 1, which grows at low elevation, tends to decrease with a large difference. Thus, the growth of Pinus koraiensis, which is a boreal species, could increase along with increasing temperature up to a certain point.

• Asian-Australasian Journal of Animal Sciences
• /
• v.17 no.11
• /
• pp.1484-1490
• /
• 2004

Mitochondrial DNA haplotypes from the displacement-loop (D-loop) region (436 bp) were genotyped and sequenced in Japanese Black beef cattle raised in the same herd. Correlation coefficients between mitochondrial DNA haplotypes, maternal lineage, birth weight, preweaning average daily gain, weaning weight, post weaning average daily gain and yearling weight were computed. The objective was to study the relationship between maternal and postnatal growth traits and to investigate if postnatal growth of calves to yearling age could be accurately predicted from mitochondrial DNA haplotypes. Results of the phylogenetic analysis revealed 17 maternal lineages and four mitochondrial DNA haplotypes. There were strong, positive and highly significant (p<0.001) correlations among maternal traits ranging from 0.52 to 0.98. Similarly, among postnatal growth traits, most of the correlations were also strong, positive and highly significant (p<0.001); the highest correlation of 0.94 was between preweaning average daily gain and weaning weight. However, correlations between mitochondrial DNA haplotypes and postnatal growth traits were very low, mostly negative and non-significant (p>0.05) ranging from -0.05 to 0.1. Prediction of postnatal growth from mitochondrial DNA yielded very low $R^{2}$ values ranging from 0.002 to 0.019. It was concluded that mitochondrial DNA polymorphism has no significant association with postnatal growth from birth to yearling age, and by implication, nuclear rather than cytoplasmic DNA, accounts for most of the genetic variation observed in postnatal growth of Japanese Black cattle. Therefore, mitochondrial DNA genotyping at an early age has no bearing on the accurate prediction of the future growth performance of calves.