• Title/Summary/Keyword: Growth variation

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A Stochastic Analysis of Variation in Fatigue Crack Growth of 7075-T6 Al alloy (7075-T6 A1 합금의 피로균열진전의 변동성에 대한 확률론적 해석)

  • Kim, Jung-Kyu;Shim, Dong-Suk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.7
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    • pp.2159-2166
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    • 1996
  • The stochastic properties of variation in fatigue crack growth are important in reliability and stability of structures. In this study,the stochastic model for the variation of fatigue crack growth rate was proposed in consideration of nonhomogeneity of materials. For this model, experiments were ocnducted on 7075-T6 aluminum alloy under the constant stress intensity factor range. The variation of fatigue crack growth rate was expressed by random variables Z and r based on the variation of material coefficients C and m in the paris-Erodogan's equation. The distribution of fatigue life with respect to the stress intensity factor range was evaluated by the stochastic Markov chain model based on the Paris-Erdogan's equation. The merit of proposed model is that only a small number of test are required to determine this this function, and fatigue crack growth life is easily predicted at the given stress intensity factor range.

Geographic Variation in Survival Rate and Height Growth of Pinus densiflora S. et Z. in Korea

  • Kim, In-Sik;Ryu, Keun-Ok;Song, Jeong-Ho;Kim, Tae-Su
    • Journal of Korean Society of Forest Science
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    • v.94 no.2 s.159
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    • pp.73-81
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    • 2005
  • This study was conducted to examine the geographic variation among provenances of Pinus densiflora in survival rate and height growth at four test plantations (Jungsun, Chungju, Naju, and Jeju). The plantations were parts of the eleven provenance trials of Pinus densiflora established by Korea Forest Research Institute in 1996. The survival rate and height growth were significantly different among test plantations at $p{\leq}0.01$. Latitude and longitude of test plantation were negatively correlated with survival rate and height growth. On the other hand, annual mean temperature, mean temperature (Nov.~Feb.), extremely low temperature (Dec.~Feb.), and annual mean growing days of test plantation were positively correlated with these two. The relationships between growth variables and geographic variables were analysed with canonical correlation analysis. A considerable amount of variation in survival rate and height growth was explained by latitude, annual mean growing days, extremely low temperature (Dec.~Feb.) and extremely high temperature (Nov.~Feb.) of provenances. It is estimated that up to 47.1% and 67.4% of the genetic variability in survival rate and height growth was attributable to the environmental variability of the provenances, respectively. The response surface curve of survival rate and height growth was plotted against latitude and longitude to examine growth performance of provenances for each test site. Generally, the local provenances showed better survival rate and height growth.

Variation in Demography of Taraxacum officinale Seeds Harvested from Different Seasons

  • Yang, Hyo-Sik;Oh, Man-Ho
    • The Korean Journal of Ecology
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    • v.26 no.2
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    • pp.82-86
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    • 2003
  • We investigated the variation in adaptation to growth for four ecotypically-differentiated population of Taraxacum officinale found naturally in temporal environmental heterogeneity. Seeds collected from the four seasons were germinated in incubators and were grown for four months in greenhouse to test genetic variation among biotypes. Biotypes, segregated by seeds collected seasonally, were the part of natural population in Mokpo, South Korea. Each biotype was different in total dry weight of seeds, biomass, and leaf area, confirming previous finding. Differences between biotypes grown under a common environment indicated a genetic basis to their distinct demographic rates. Therefore, biotypes with similar annual rates of growth and contrasting seasonal rates should persist in the population. This differential response suggests that temporal variation in environment may be responsible, in part, for the maintenance of genetic variation within populations.

A Study on the Fatigue Crack Propagation Behavior by the Variation of Heat Treatment Temperature and Thickness in ATOS 55 Steel (ATOS 55강의 열처리 온도와 두께 변화에 따른 피로균열성장거동에 관한 연구)

  • 오환교
    • Journal of the Korean Society of Safety
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    • v.12 no.4
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    • pp.15-20
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    • 1997
  • This study is to investigate the behavior of fatigue crack growth with ATOS 55 steel which can be applied to the commercial car Dump Frame. It is to obtain the material coefficients after tensile and fatigue crack growth test with the variation of thickness or heat treatment. Also, that is proved the Pari's law by experiment. The summarized results are as follows ; 1) Increasing thickness, tensile and yield strength measured highly regardless to heat treatment and measured lowly as variation of heat treatment temperature. 2) Specimen of thickness 8.0㎜ measured the faster of crack growth rate than another thickness according to the results of experiment. It was the different of stress conditions in crack tip. 3) It was found that the experimental constant m was range of 2∼5 to the relationship between fatigue crack growth rate and stress intensity factor range. Also, it was to prove the Paris's law by the experiment.

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Intraspecific Variation in the Temperature Niche Component of the Diatom Skeletonema costatum from Korean Coastal Waters

  • YIH Wonho;SHIM Jae Hyung
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.28 no.6
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    • pp.805-811
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    • 1995
  • Final biomass yields (peak optical density) and growth rates (divisions/day) of seven clones of Skeletonema costatum from Korean coastal waters were measured to understand their intraspecific variations in the light intensity niche component under $25^{\circ}C$ condition. Daily growth rates of 6 of 7 S. costatum, clones were maximum at 6000 lux while that of YS4, a neritic clone, was maximum at 9000 lux. The final biomass yields of 4 of the 7 S. costatum clones were maximum at the lowest light intensity of 2000 lux. Minimum final biomass yields were found at 9000 lux in all the S. costatum clones other than an estuarine clone, HDC9. The intraspecific variations of the mean growth rate and mean final biomass yield under each of the three different light intensity in terms of the coefficient of variation were not greater than 10% in any of the 7 S. costatum clones.

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A Study On the Factors that Affect Fatigue Crack Growth Rate in Steels - Specimen Thickness Effect - (강재의 피로균열전파율에 미치는 영향인자에 관한 연구)

  • Kim, Seon-Jin;Nam, Ki-Woo;Hong, Jin-Pyo
    • Journal of Ocean Engineering and Technology
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    • v.13 no.2 s.32
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    • pp.58-65
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    • 1999
  • The effect of specimen thickness on fatigue crack growth rate was studied. The objective of the present study is to investigate the effect of specimen thickness on the fatigue crack growth behavior at various stress intensity factor ranges and also the variation of material restance to fatigue crack growth. The fatigue crack growth resistance was treated as a spatial stochastic process, which varies randomly on the crack path, Compact tension specimens with a LT orientation for structural steel were used. All testing was done at a constant stress intensity level. The experimental data were analyzed for the size effect to determine the Weibull distributions of the material resistance.

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Assessment of Teak (Tectona grandis Linn. f.) Provenance Tests in the Bago Yoma Region, Myanmar

  • Lwin, Ohn;Hyun, Jung-Oh;Yahya, Andi Fadly
    • Journal of Korean Society of Forest Science
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    • v.99 no.5
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    • pp.686-692
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    • 2010
  • This study described the general pattern of genetic variation among ten teak (Tectona grandis Linn. f.) provenances in Myanmar and determined the most suitable seed sources for the plantation program in Bago Yoma region. Seeds of ten provenances were collected to cover the whole teak natural distribution in Myanmar and planted at four trial sites in Bago Yoma region in 1998. Seven years after planting, variation was assessed for growth, morphological characteristics and their correlation with geoclimatic factors. Statistical analysis using ANOVA revealed that there were significant differences in most of the traits measured among provenances, trial sites and provenance ${\times}$ site interaction at five percent level. A positive significant correlation (p<0.01) was found among most of the traits. The regression analyses between all traits and geoclimatic factors indicated the existence of ecoclinal variation in teak. Most of the traits were negatively correlated with the latitude while a positive significant correlation was found between longitude and C/B ratio, crown-diameter, average branch angle and leaf-remain. There was no significant correlation between the mean temperature and any other traits in this study. Furthermore, growth traits and crown diameter were positively correlated with the mean annual rainfall while negative correlation was found between the geographical distance and growth traits. Results indicate that the latitudinal pattern of teak genetic variations in growth performance was attributed to the limit of mean annual rainfall. Comparative assessment showed that local provenances were generally the best and could be use as suitable seed sources for the plantation program in the Bago Yoma region.

An Analysis of Crack Growth Rate Due to Variation of Fatigue Crack Growth Resistance (피로균열전파저항의 변동성에 의한 균열전파율의 해석)

  • Kim, Seon-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.23 no.7 s.166
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    • pp.1139-1146
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    • 1999
  • Reliability analysis of structures based on fracture mechanics requires knowledge on statistical characteristics of the parameter C and m in the fatigue crack growth law, $da/dN=C({\Delta}K)^m$. The purpose of the present study is to investigate if it is possible to predict fatigue crack growth rate by only the fluctuation of the parameter C. In this study, Paris-Erdogan law is adopted, where the author treat the parameter C as random and m as constant. The fluctuation of crack growth rate is assumed only due to the parameter C. The growth resistance coefficient of material to fatigue crack growth (Z=1/C) was treated as a spatial stochastic process, which varies randomly on the crack path. The theoretical crack growth rates at various stress intensity factor range are discussed. Constant ${\Delta}K$ fatigue crack growth tests were performed on the structural steel, SM45C. The experimental data were analyzed to determine the autocorrelation function and Weibull distributions of the fatigue crack growth resistance. And also, the effect of the parameter m of Paris' law due to variation of fatigue crack growth resistance was discussed.

Protein variation and involvement of insulin-like growth factor during embryonic development in the olive flounder Paralichthys olivaceus

  • Kim, Kang-Woong;Nam, Taek Jeong;Choi, Youn Hee
    • Fisheries and Aquatic Sciences
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    • v.21 no.2
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    • pp.4.1-4.5
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    • 2018
  • Insulin-like growth factors (IGFs), along with IGF-binding protein and IGF receptor, are well-known regulators in the growth and survival of vertebrates. In this study, we investigated the involvement of IGFs and protein variation during embryonic development of the olive flounder (Paralichthys olivaceus). Morphological stages were divided into six main developments as blastula, gastrula, cephalization, cranial regionalization, tail lift, and hatch. During embryonic development, protein variation was investigated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electrospray ionization quadrupole time-of-flight mass spectrometry/mass spectrometry. In addition, the mechanism of signaling of IGF-I receptor was examined using immuno-blot analysis. We found marked changes in protein expression at four stages of embryonic development and identified proteins as belonging to the vitellogenin 2 family. As development progresses, expression of IGF-II, phosphotyrosine, and phospho-Akt increased, while expression of growth factor receptor-bound protein 2 (GRB2) and one of guanine-nucleotide-binding proteins (Ras) decreased. These results provide basic information on the IGF system in the embryonic development of the olive flounder.

The Effectiveness of Information Telecommunication (IT) Capital and R&D Stock Variation on the Korean Industrial Sector (정보통신자본과 R&D스톡변동이 국내 산업부문별 성장에 미치는 영향연구)

  • 박추환
    • Journal of Korea Technology Innovation Society
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    • v.4 no.1
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    • pp.79-95
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    • 2001
  • This paper examines the effects of information telecommunication (IT) capital and R&D stock variation on the growth of Korean industry, using a time series approach. Most specifically, we apply the Granger causality and impulse response analysis to our examination of Koreas industrial growth, IT capital, and R&D stocks. The Johansen co-integration test is performed in order to analyze long-term relations among these variables. This research explores the way in which IT capital and R&D stocks variation from economic shocks affects the growth of Koreas industrial sector. The effects are ambiguous, however, across industrial sectors. An impulse response function analysis shows that the effects of IT capital and R&D stock fluctuations in each industrial sector are presented for different time periods.

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