• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1627-1631
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• 1992

It often occurs in J-R testing that some initial crack extension (.DELTA.a) data points have anomalous negative values. The reason for the apparent negative crack growth is due to the analysis method. The phenomenon as a possible source of error in determining $J_{IC}$ or J-R curve from partial unloading compliance experiments may be eliminated by the compliance correction equation or the offset technique. In this study, the correction methods are suggested and examined by the measurement of the actual crack length and $J_{JC}$ analysis.

• Journal of the Korean Mathematical Society
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• v.60 no.6
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• pp.1137-1169
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• 2023

Let C be a curve and V → C an orthogonal vector bundle of rank r. For r ≤ 6, the structure of V can be described using tensor, symmetric and exterior products of bundles of lower rank, essentially due to the existence of exceptional isomorphisms between Spin(r, ℂ) and other groups for these r. We analyze these structures in detail, and in particular use them to describe moduli spaces of orthogonal bundles. Furthermore, the locus of isotropic vectors in V defines a quadric subfibration Q_V ⊂ ℙV . Using familiar results on quadrics of low dimension, we exhibit isomorphisms between isotropic Quot schemes of V and certain ordinary Quot schemes of line subbundles. In particular, for r ≤ 6 this gives a method for enumerating the isotropic subbundles of maximal degree of a general V , when there are finitely many.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.96-104
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• 1989

The behaviors of acoustic emission emitted in the tests of the fracture toughness and fracture stability are observed by using the specimens of aluminum 2024-T351 and 7039-T6 alloys. The empirical eqution of J-R curve is derived. It is demonstrated from the comparison of the fracture toughness obtained from J-R curve with that from ASTM standard E813-81 that the latter is larger than the former. The discontinuous point in the log-log graph of J-integral vs. total acoustic emission count is observed in between the two offset lines referred from ASTM standard E813-81, but it's physical meaning is uncretain. An empirical material tearing modulus is derived in terms of the total acoustic emission count and proved to be valid in fracture instability test.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.53-63
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• 1988

Using COD-R curves, instability of crack growth in ductile material is studied here. Tearing modulus $T_{\delta}$, based on the COA concept is defined and the instability criterion $T_{{\delta}{\app}}$> $T_{{\delta}{\mat}}$ is compared with experiments. Variations of the COD-R curve and the location of rotation center are experimentally investigated as the initial crack ratio varies. Three-point bend specimens of alloy steel SCM4 are used here and two clip-on gauges are installed in order to obtain the COD-R curve. The results show that the tearing modulus $T_{\delta}$ is a good measure to characterize the instability of crack growth. Also it is found that the location of rotation center is almost constant regardless of the initial crack ratio and the amount of the crack growth.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.6
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• pp.890-894
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• 2002

The accuracy of the gamma function to describe lactation curve of Yankasa ewes was investigated using milk production data obtained from 168 ewes with either complete or incomplete 84 day lactation records. Ewes were daily hand milked after over-night separation from lamb and thorough disinfection of the udder. The daily milk yield on the average was estimated from the weekly total yield. The effect of type of birth, parity, season of birth and lactation length on the components of lactation curve (a, b, c and s) were analysed by least-square procedures. All factors except parity significantly (p<0.01) influenced the curve parameters. The goodness of fit of the function did not differ between the two classes of varying duration of lactation; incomplete lactation however, showed a lower persistency and as expected lower level of production. Correlations ($r_p$) between lamb weight gain and milk yield using the weight records from lamb weighed at weekly intervals indicated a high and positive relationship in the early lactation that decreased in intensity as the lactation advanced.

• Asian-Australasian Journal of Animal Sciences
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• v.4 no.1
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• pp.67-71
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• 1991

The purpose of this study was to investigate the possibility of using the buffer index curve as a criterion of silage quality evaluation. The buffer index (or buffer capacity, $\beta$) value is the amount of 0.1N NaOH consumed in titrating from the beginning to the end of the chosen pH step. This value equals the slope of the titration curve at the chosen pH range (${\beta}={\Delta}NaOH/{\Delta}pH$). There were two patterns of buffer index curve. Poorly preserved silages had a peak at pH 5.0, whereas with well preserved silages the peaks tended to rise to the pH 3.75 or 4.00. Well preserved, wilted silages with high pH also appeared to have peak values at pH 3.75 or 4.00. There was a high positive correlationship between the concentration of lactic acid and peak value of good quality silage (r = 0.994, p < 0.01). Also a high positive correlationship (r = 0.899, p < 0.001) was found between the sums of concentration of acetic and butyric acids and the peak values of poor quality silages. The results of these experiments verified the value of the buffer index method as a criterion of silage quality evaluation.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.1
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• pp.84-90
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• 2023

ASL estimation of public building is based on how appropriate the maximum age of the asset is derived based on the age record of the asset in the statistical data owned by public institutions. This is because we get a 'constrained' ASL by that number. And it is especially true because other studies have assumed that the building is an Iowa curve R3. Also, in this study, the survival rate is 1% as the threshold value at which the survival curve and the predictable life curve almost coincide. Rather than a theoretical basis, in the national statistical survey, the value of residual assets was recognized from the net value of 10% of the acquisition value when the average service life has elapsed, and 1% when doubling the average service life has elapsed. It is based on the setting mentioned above. The biggest constraint in fitting statistical data to the Iowa curve is that the maximum ASL is selected at R3 150%, and the 'constrained' ASL is calculated by the proportional expression on the assumption that the Iowa curve is followed. In like manner constraints were considered. First, the R3 disposal curve for the RCC(reinforced cement concrete) building was prepared according to the discarding method in the 2000 work, and it was jointly worked on with the National Statistical Office to secure the maximum amount of vintage data, but the lacking of sample size must be acknowledged. Even after that, the National Statistical Office and the Bank of Korea have been working on estimating the Iowa curve for each asset class in the I-O table. Another limitation is that the asset classification uses the broad classification of buildings as a subcategory. Second, if there were such assets with a lifespan of 115 years that were acquired in 1905 and disposed of in 2020, these discarded data would be omitted from this ASL calculation. Third, it is difficult to estimate the correct Iowa curve based on the stub-curve even if there is disposal data because Korea has a relatively shorter construction history, accumulated economic wealth since the 1980's. In other words, "constrained" ASL is an under-estimation of its ASL. Considering the fact that Korea was an economically developing country in the past and during rapid economic development, environmental factors such as asset accumulation and economic ability should be considered. Korea has a short period of accumulation of economic wealth, and the history of 'proper' architectures faithful to building regulations and principles is short and as a result, buildings 'not built properly' and 'proper' architectures are mixed. In this study, ASL of RCC public building was estimated at 70 years.

• Journal of the Chungcheong Mathematical Society
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• v.23 no.2
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• pp.197-206
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• 2010

We study the restriction estimate of Fourier transform to arbitrary convex curves in $R^2$ with no regularity assumption. Assuming that the convex curve has the lower bound of curvatures, we extend the restriction results from smooth convex curves to arbitrary convex curves. Our work has been motivated by the lecture notes of Terence Tao. The bilinear approach and geometric observations play an important role.

• Tribology and Lubricants
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• v.14 no.4
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• pp.114-120
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• 1998

The T-curve, wear and erosion behaviors of two different silicon carbides, i.e., the fine grained SiC and the in situ-toughened SiC(IST-SiC). Both materials exhibited an increasing T-curve behavior, although the T-curve of IST-SiC was steeper than that of fine grained SiC. The fracture toughness of IST-SiC was larger than that of fine grained SiC at long crack regime, whereas an opposite tendency occurred at short crack regime. The rate of material removal during wear and erosion tests was higher in IST-SiC compared to fine grained SiC. The difference between the material removal rates of two materials was discussed in the light of their R-curve behaviors.

• Transactions of Materials Processing
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• v.29 no.6
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• pp.316-322
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• 2020

The flow stress curve is usually determined via uniaxial tensile or simple compression test. However, the flow stress curve up to high strain cannot be obtained using these two tests. This study presents a simple method for obtaining the flow stress curve up to high strain via FE analysis, a simple compression test, and an indentation test. In order to draw the flow stress curve up to high strain, the indentation test was carried out with the pre-stained specimen using the simple compression test. The flow stress curve of Al6110 was evaluated up to high strain using the proposed method, and the result was compared with the flow stress curve of the uniaxial tensile test of the initial material.