• Journal of the Korean Society of Safety
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• v.14 no.2
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• pp.3-10
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• 1999

Fatigue crack growth rates in commercial plate of high strength Al 7075-T651 were investigated for the T-L direction in air, water and sea water. In this paper the effect of cyclic load wave-form(trapezoid and triangle) on fatigue crack growth rates in air, water and sea water environments were investigated using standard LEFM testing procedures. It was founded that the fatigue crack growth behaviors were not affected by cyclic load wave-forms. In region II (stable crack growth region), the fatigue crack growth behaviors were insensitive to cyclic load wave-forms and were sensitive to environment i.e. fatigue crack growth behaviors were higher in sea water than in air for all cyclic load wave-form. The result of fractographical morphology in air, water and sea water by SEM showed obvious dimple rupture and typical striation in air, but transgranular fracture surface in water and sea water. The values m are not affected by corrosion environments but C are different values.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.113-120
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• 1998

Fatigue crack growth rates(i.e. crack initiation and crack growth of short and long crack) are investigated using commercial plates of high strength Al alloy 7075-T651 for the transverse-longitudinal(T-L) direction in air, water and sea water. Also, the evaluation direct current potential drop(D.C.P.D) method and the fractographical analysis by SEM are carried out. Near threshold region, short crack growth rates were much faster than those of comparable long cracks, and these short crack growth rates actually decrease with increasing crack growth and eventually merge with long crack data. Fatigue crack propagation rates in aggressive media(i.e. sea water) increase noticeably over three times those in air. One of the most significant characters in this phenomenon as a corrosion-fatigue causes an acceleration in crack growth rates. Sea water environment, particularly Cl$^{[-10]}$ solution brings the most detrimental effects to aluminum alloy. The result of fractographical morphology in air, water and sea water by SEM shows obvious dimpled rupture and typical striation in air, but transgranular fracture surface in water and sea water.

• The korean journal of orthodontics
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• v.16 no.1
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• pp.145-154
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• 1986

The purpose of the present study was to investigate the coordination and correlation of growth pattern between craniomaxillary complex and mandible, and among the craniofacial region, body-weight and stature. 14 boys and 16 girls between 6 and 12 years of age were used in this study. The result were as follows; 1. Total increments and maximum increment in mandible is higher than in oraniomaxillary complex during given period and no significant sexual difference existed. 2. The annual growth of craniofacial region did not assume an aspect of constant growth, periodically. 3. Craniofacial growth pattern was interrelated with stature more than with body-weight. 4. The growth behavior of body-weight and stature coincided with the growth of craniofacial region or preceded it in time.

• 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.

• Journal of Ocean Engineering and Technology
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• v.14 no.2
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• pp.99-105
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• 2000

This paper describes the effect of specimen size on fatigue crack growth rate for the offshore structural high-tensile-strength steel BS4360 and machine structural steel SM45C. The purpose of the present study is to investigate the effect of stress ratio aspect ratio specimen width and specimen thickness of the fatigue crack growth behavior. Compact tension specimens with a LT orientation for BS4360 and SM45C steels were used, All testing was done at constant stress intensity factor range controlled fatigue crack growth condition. The investigation demonstrates that the fatigue crack growth rate is increased with increasing stress ratio and specimen thickness and is decreased with increasing specimen width. The fatigue crack growth rate is unaffected by aspect ratio until a/W=0.50 but is increased by increasing spect ratio from a/W=0.55.

• Asian-Australasian Journal of Animal Sciences
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• v.31 no.11
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• pp.1714-1720
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• 2018

Objective: This study was conducted to analyze the effects of stocking density on growth and carcass quality, and behavior of Hanwoo cattle to conform with global trends, targeting animal welfare production through the practice of environmentally friendly condition. Methods: Thirty six steers were randomly assigned to three treatment groups (C: 5 heads, T1: 4 heads, T2: 3 heads) and reared in separate pens with a constant stocking density of $50m^2$ (C: $10m^2/head$, T1: $12.5m^2/head$, T2: $16.67m^2/head$) per group from 12 to 30 month of age. Growth performance, behavior and carcass quality traits of each steer were recorded and compared between the treatment groups. Results: In general, the average daily gain during the fattening period was lower in group T2 than in T1 and the control groups. However, carcass weight and dressing percentage was lower in the control group than in T1 or T2 groups (p<0.05). Also, marbling score at 30 months of age was the lowest in the control group (p<0.05), while the three heads group (T2) had the greatest longissimus muscle area and marbling score (p<0.05). The behavior of walking time was the greatest in T2 group, while self-grooming and fighting occurred with the most frequency in the control group (p<0.05). Conclusion: Our results show that the steers in more spacious stocking density had better carcass quality and wellbeing related behaviors, indicating that a lower density has a positive effect on raising management and carcass quality. Thus it is a need to install appropriate pens fitted to welfare-oriented management practices from growing to fattening period in Hanwoo cattle.

• Korean Journal of Community Nutrition
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• v.3 no.1
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• pp.3-11
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• 1998

This study was aimed to evaluate any influence of environmental factors associated with feeding on infants' growth. One hundred infants(62 males and 38 females) aged 4-9 months were measured for length and were weighed. Their mothers were interviewed using questionnaires including general and environmental characteristics and maternal feeding attitude, ideal body habitus, infant's food behavior, and infant's food behavior, and infant's temperament. A further study was conducted on 29 infants at the time their ages reached 12 months. Their dietary intakes were assessed, and blood hemoglobin and serum ferritin concentrations were measured. Z-scores of weight-for-age(WAZ) and Z-scores of height-for-age(HAZ) of 4-9 month- old infants were not correlated with age, education level, income, weight, and height of their parents. Formula-fed infants had significantly lower WAZ and body mass index (BMI) than those of breast fed infants. WAZ was significantly correlated with maternal feeding attitude, but not with ideal body habitus, infant's food behavior or infant's temperament. WAZ of 12-months after birth because of supplementary foods introduced from 6 months of age. WAZ and BMI were positively correlated with blood hemoglobin concentration. Therefore, to ensure proper growth of infants, efforts should be given to postental factors such as breast-feeding, maternal feeding attitude, adequate iron status as well as prenatal factors. (Korean J Community Nutrition 3(1) : 3∼11, 1998)

• Macromolecular Research
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• v.14 no.5
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• pp.530-538
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• 2006

There are three important components in tissue engineering: the cells, signaling factors (cytokines and growth factors), and scaffolds. To obtain finely engineered tissue, all three components should perform their individual functions and be fully integrated with each other. For the past few years, we have studied the characteristics of photodimerizable HA (CHA)/alginate (CA) composite materials. CHA/CA complex hydrogels, which were irradiated under UV light and, then treated with calcium ions, were found to have good biocompatibility, mechanical properties and water resistance for implantable tissue scaffolds. In this study, we introduced a cell growth factor (basic fibroblast growth factor; bFGF) into the CHA/CA scaffolds and studied its release behavior. We also introduced tetracycline hydrochloride and flurbiprofen into the same scaffolds as model activation factors and evaluated their release behaviors from the scaffolds. The drug release rate from the materials was influenced by various parameters, such as the degree of crosslinking, the cross linker type, the physico-chemical properties of the drug, and the amount of the drug in the polymer. The results indicated that the negatively charged CHA/CA composite materials showed sustained release behavior and that HA has a particularly strong negative charge, making it attractive toward tetracycline hydrochloride and bFGF, but repulsive toward flurbiprofen.

• Animal Bioscience
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• v.37 no.2
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• pp.253-260
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• 2024

Objective: The objectives of the present study were to evaluate the effects of once-a-day milk feeding on growth performance and routine behavior of preweaning dairy calves. Methods: At 22nd day of age, twenty-four Holstein calves were randomly assigned to one of two treatment groups (n = 12/treatment) based on milk feeding frequency (MF): i) 3 L of milk feeding two times a day; ii) 6 L of milk feeding once a day. The milk feeding amount was reduced to half for all calves between 56 and 60 days of age and weaning was done at 60 days of age. To determine the increase in weight and structural measurements, each calf was weighed and measured at 3 weeks of age and then at weaning. The daily behavioral activity of each calf was assessed from the 22nd day of age till weaning (60th day of age) through Nederlandsche Apparatenfabriek (NEDAP) software providing real-time data through a logger fitted on the calf's foot. Results: There was no interaction (p≥0.17) between MF and sex of the calves for routine behavioral parameters, body weight and structural measurements. Similarly, there was no effect of MF on routine behavioral parameters, body weight and structural measurements. However, the sex of the calves affected body weight gain in calves. Male calves had 27% greater total body weight and average daily gain than female calves. There was no effect of the sex of the calves on behavioral measurements. Collectively, in the current study, no negative effects of a once-a-day milk feeding regimen were found on routine behavioral and growth parameters of preweaning calves in group housing. Conclusion: Once-a-day milk feeding can be safely adopted in preweaning calves from 22nd day of age.

• Proceedings of the Korean Society of Rheology Conference
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• 2000.05a
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• pp.66-69
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• 2000