• The Journal of Korean Academy of Prosthodontics
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• v.34 no.1
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• pp.187-200
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• 1996

After loss of tooth, initial healing process is critical to preserve residual alveolar process. This study was conducted to compare the effect of hydroxylapatite particle synthetic graft and guided tissue regeneration procedure on healing of extraction wounds in 5 mongrel dogs. To investigate the maturity of bone and velocity of bone heating, bone-labeled tracers were used. After 16 weeks healing period, dogs were sacrificed. The specimens were treated with Villanueva bone stain. Fluorescence microscopy and polarized microscopy were performed to exam the pattern of bone formation in the extraction socket. The results were following ; 1. Pattern of bone regeneration in the group of hydroxylapatie graft and the group of membrane protection after hydroxylapatite graft was following ; bone regeneration was slow, regenerated bone was immature, and thickness of cortical layer was thin compare to that of untreated control group. 2. Cortical layers in membrane protected group were somewhat thicker but less condense to that of untreated control group. 3. Infiltration of inflammation cells were found in the groups using hydroxylapatite graft and membrane. We concluded that grafting of replamineform hydroxylapatite particles into the extraction socket delayed healing of the wound and disturbed the formation of cortical bone at the roof of extraction socket. The placement of expanded polytetrafluoroethylene membranes on the extraction socket promotes the bone regeneration. But newly formed bone in cortical layer consists of the cortico-cancellous bone in comparison with the cortical bone of the control group.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.38
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• pp.29.1-29.9
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• 2016

Background: The objective of this study was to evaluate xenograft degradation velocity when treated with 4-hexylresorcinol (4HR). Methods: The scapula of a cow was purchased from a local grocery, and discs (diameter 8 mm, thickness 1 mm) were prepared by trephine bur. Discs treated with 4HR were used as the experimental group. Untreated discs were used as the control. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), antibacterial test, endotoxin test, and scanning electron microscopy (SEM) were performed on the discs. In vivo degradation was evaluated by the rat calvarial defect model. Results: The XRD and FT-IR results demonstrated successful incorporation of 4HR into the bovine bone. The experimental disc showed antibacterial properties. The endotoxin test yielded results below the level of endotoxin contamination. In the SEM exam, the surface of the experimental group showed needle-shaped crystal and spreading of RAW264.7 cells. In the animal experiments, the amount of residual graft was significantly smaller in the experimental group compared to the control group (P = 0.003). Conclusions: In this study, 4HR was successfully incorporated into bovine bone, and 4HR-incorporated bovine bone had antibacterial properties. In vivo experiments demonstrated that 4HR-incorporated bovine bone showed more rapid degradation than untreated bovine bone.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.647-656
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• 2011

In radioactive waste repositories constructed in underground, concrete member could be in contact with groundwater for a long time. However, this pure water creates concentration gradients which lead to the diffusion of Ca ions from the pore water and the degradation of underground concrete. Therefore, this study is aimed at investigating the alteration of pore structure and loss of compressive strength associated with dissolution. The results showed that as the leaching period became longer, the pore volume within 50 nm to 500 nm in diameter is greatly increased. Also, the volume of pores larger than 200 nm rapidly increased during initial leaching time and those below 200 nm gradually increased. Furthermore, the compressive strength gradually decreased with increase of degraded thickness. The residual strength of the degraded concrete with OPC was in the range of 33% to 58%.

• Journal of Energy Engineering
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• v.11 no.1
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• pp.18-25
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• 2002

One of the most serious concern in nuclear power plant piping maintenance is thickness reduction due to flow-accelerated corrosion (FAC). Since the FAC occurs under specific conditions of pH, dissolved oxygen, temperature, flow velocity, steam quality of the fluid and materials and geometry of the piping, a systematic approach is required for managing the FAC problem. In this study, construction of a secondary piping database, analyzing the FAC rate using the database and predicting the residual life was performed for a domestic CANDU nuclear power plant. Also FAC mechanism and factors affecting FAC were reviewed. By showing a case study on analysis for a pipe line between a separator and a flash tank, a procedure for managing FAC problem is suggested. The procedure proposed in this paper can be widely applied to the secondary piping of other domestic nuclear polder plants.

• Asian-Australasian Journal of Animal Sciences
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• v.23 no.7
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• pp.848-854
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• 2010

The objectives of this study were to estimate genetic parameters for the carcass price and carcass traits contributing to carcass grading and to investigate the influence of each carcass trait on the carcass price using multiple regression and path analyses. Data for carcass traits and carcass prices were collected from March 2003 to January 2009 on steers of Korean cattle raised at private farms. The analytical mixed animal model, including slaughter house-year-month combination, linear and quadratic slaughter age as fixed effects and random animal and residual effects, was used to estimate genetic parameters. The effects of carcass traits on the carcass price were evaluated by applying multiple regression analyses. Heritability estimates of carcass traits were $0.20{\pm}0.08$ for carcass weight (CWT), $0.33{\pm}0.10$ for back fat thickness (BFT), $0.07{\pm}0.05$ for eye-muscle area (EMA) and $0.25{\pm}0.10$ for marbling score (MS), and those of carcass prices were $0.21{\pm}0.10$ for auction price per 1 kg of carcass weight (AP) and $0.13{\pm}0.07$ for total price (CP). Genetic correlation coefficients of AP with CWT and MS were $-0.35{\pm}0.29$ and $0.99{\pm}0.04$, respectively, and those of CP with CWT and MS were $0.59{\pm}0.22$ and $0.39{\pm}0.29$ respectively. If an appropriate adjustment for temporal economic value is available, the moderate heritability estimates of AP and CP might suggest their potential use as the breeding objectives for improving the gross incomes of beef cattle farms. The large genetic correlation estimates of carcass price variables with CWT and MS implied that simultaneous selection for both CWT and MS would be also useful in enhancing income.

• Biomedical Science Letters
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• v.22 no.4
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• pp.140-149
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• 2016

All pesticides must be assessed strictly whether safe or not when agricultural operators are exposed to the pesticides in farmland. A pesticide is commonly regarded as safe when estimated dermal absorption amount is lower than the acceptable operator's exposure level (AOEL). In this study, dermal absorption rate of chlorpyrifos, a widely used organophosphate insecticide, was investigated using rat dermal tissue model. Chlorpyrifos wettable powder solved in water (250, 500 and 2,500 ppm) was applied to freshly excised rat dermal slices ($341{\sim}413{\mu}m$ thickness) on static Franz diffusion cells at $32^{\circ}C$ for 6 hours. After exposure period of 6 hours, and then washing-at residual amount of chlorpyrifos was analyzed in dermal tissues, tape strips, washing solution, washing swabs of receptor bottles and receptor fluids at 1, 2, 4, 8 and 24 hours. Chlorpyrifos was only detected in dermal tissue but not found in receptor fluid at each concentration and time point, and the absorption rate of 250, 500 and 2,500 ppm was 2.36%, 1.96% and 1.69%, respectively. The estimated exposure level of chlorpyrifos was calculated as 0.012 mg/kg bw/day. The health risk for farmers in this condition is a level of concern because the estimated exposure level is 12 times higher than AOEL 0.001 mg/kg bw/day. However, actual health risk will be alleviated than estimated because absorbed chlorpyrifos is not permeated into internal body system and only retained in skin layer.

• Journal of Korean Society of Steel Construction
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• v.27 no.4
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• pp.377-386
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• 2015

In this study, inelastic buckling strength of HSA800 steel columns were tested to investigate the applicability of current column curve (KBC2009, 2010 AISC-LRFD) to HSA800 steel. Key test variables included width-thickness ratio, plate-edge restraints, and column slenderness ratio. Specimens made of ordinary steel (SM490) were also tested for comparison purposes. All the concentrically loaded HSA800 specimens exhibited sufficient buckling strength compared to the current column curve, but some of SM490 specimens showed understrength. This difference can be explained by the lower residual stress present in HSA800 specimens.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.204-210
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• 2004

Most auto-body members fabricated by the sheet metal forming process. During this process the thickness and material properties of the sheet metal are changed with the residual stress and plastic strain. This paper deals with the material properties of the sheet metal at the high strain rate considering the pre-strain effect. Specimens are selected from sheet metals for outer panels and inner members, such as SPCEN, SPRC45E, SPRC35R and EZNCD. The specimens are prepared with the pre-strain of 2, 5 and 10 % by tensile elongation in Instron 5583, which could be equivalent to the plastic strain in sheet metal forming. High speed tensile tests are then carried out with the pre-stained specimens at the strain rate of 1 to 100/sec. The experimental result informs that the material properties are noticeably influenced by the pre-strain when the yield stress of the specimens is moderate as SPCEN, SPRC35R and EZNCD. The result also demonstrates that the ultimate tensile strength as well as the yield stress is increased as the amount of the pre-strain is increased.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.3
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• pp.89-93
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• 2020

Complex warpage behavior of the electronic packages causes internal stress so many kinds of mechanical failure occur such as delamination or crack. Efforts to predict the warpage behavior accurately in order to prevent the decrease in yield have been approached from various aspects. For warpage prediction, silicon is generally treated as a homogeneous material, therefore it is described as showing no warpage behavior due to thermal loading. However, it was reported that warpage is actually caused by residual stress accumulated during grinding and polishing in order to make silicon wafer thinner, which make silicon wafer inhomogeneous through thickness direction. In this paper, warpage behavior of the single-side polished wafer at solder reflow temperature, the highest temperature in packaging processes, was measured using 3D digital image correlation (DIC) method. Mechanism was verified by measuring coefficient of thermal expansion (CTE) of both mirror-polished surface and rough surface.

• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1259-1265
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• 2020

A beta ray scanner was proposed for in-situ discrimination of beta and gamma ray radioactivity. This scanner is based on the principle that gamma and beta rays experience different changes in detection efficiency in scintillators with different geometries, especially with regard to the scintillator thickness. The ratios of the counting rates of gamma rays (R_gamma), beta rays (R_beta), and sample measurements (R_total) in a thick scintillator to those in a thin one are reported. The parameter X_thick, which represents the counting rate contributed by beta rays to the total counting rate in the thick scintillator, was derived as a function of those ratios. The values of R_gamma and R_beta for ⁶⁰Co and ⁹⁰Sr sources were estimated as 3.2 ± 0.057 and 0.99 ± 0.0049, respectively. The estimated beta ray contributions had relative standard deviations of 2.05-4.96%. The estimated range of the beta rays emitted from ⁹⁰Sr was 19 mm as per the Monte Carlo N-Particle simulation, and this value was experimentally verified. Homogeneous and surface contaminations of ⁶⁰Co and ⁹⁰Sr-⁹⁰Y were simulated for application of the proposed method. The counting rate contributed by the beta rays was derived and found to be proportional to the concentration of ⁹⁰Sr-⁹⁰Y contamination.