• Journal of the Korean Magnetics Society
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• v.21 no.1
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• pp.15-22
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• 2011

It is necessary to describe the hysteresis characteristics of magnetic material precisely for the analysis or design of system with ferromagnetic materials. Although Preisach model is regarded as the most accurate method to describe the hysteresis characteristics, it is not widely applied to the real systems because of some difficulties. The conventional Preisach model shows the numerical instabilities during the iterative computations because the density distribution obtained from the sets of M-H curves are strongly localized. To remove such numerical instabilities, M-B instead of M-H is adopted as an implementation variable in normal Preisach modeling. The two dimensional computations with hysteresis characteristics by using normal Preisach modeling are tested and the result showed that the modeling by using M-B variables showed better stabilities than M-H variables.

• Journal of the Korea Concrete Institute
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• v.21 no.1
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• pp.75-84
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• 2009

An analytical model for predicting the shear strength of prestressed concrete beams without shear reinforcement was developed, on the basis of the existing strain-based shear strength model. It was assumed that the compression zone of intact concrete in the cross-section primarily resisted the shear forces rather than the tension zone. The shear capacity of concrete was defined based on the material failure criteria of concrete. The shear capacity of the compression zone was evaluated along the inclined failure surface, considering the interaction with the compressive normal stress. Since the distribution of the normal stress varies with the flexural deformation of the beam, the shear capacity was defined as a function of the flexural deformation. The shear strength of a beam was determined at the intersection of the shear capacity curve and the shear demand curve. The result of the comparisons to existing test results showed that the proposed model accurately predicted the shear strength of the test specimens.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.197-200
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• 2008

An analytical model for predicting the shear strength of prestressed concrete beams was developed, applying the previously proposed strain-based shear strength model. In flexure-compression member without shear reinforcement, compression zone of intact concrete primarily resist to the shear force rather than tension zone. The shear capacity of concrete at the compression zone was defined based on the material failure criteria. The shear capacity of the compression zone was evaluated along the inclined failure surface considering interaction with the normal stress. Since the distribution of normal stress varies due to the flexural deformation of member, the shear capacity was defined as a function of the flexural deformation. Finally, the shear strength was determined at the intersection of the shear capacity curve and the shear demand curve. As a result of the comparisons to prior test data, the proposed model accurately predicted the shear strength of specimens.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.6
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• pp.781-787
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• 2010

Forecasting possible failure characteristics is very important in maintenance planning because it helps in predicting any future failures and determining the optimum replacement interval. This paper examines the time.to-failure distribution of the transfer gearbox of a J79 engine by using a probability plotting technique which is one of the most convenient techniques for reliability analysis. Various probability distributions are evaluated for determining the suitable probability distribution of the failure data of the transfer gearbox, and the resulting correlation coefficient indicates that failure data have a lognormal distribution. The expected number of unscheduled maintenance actions and the optimum replacement interval for various values of cost ratios are determined.

• Progress in Medical Physics
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• v.14 no.4
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• pp.225-233
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• 2003

The goal of a radiation treatment plan is to deliver a homogeneous dose to a target with minimal irradiation of the adjacent normal tissues. Dose uniformity is especially important for stereotactic radiosurgery using a linear accelerator. The dose uniformity and high dose delivery of a single spherical dose distribution exceed 70％. This also results with a similar stereotactic radiosurgical plan using a Gamma Knife. The dose distribution produced in a stereotactic radiosurgical plan using a Gamma Knife and Linear accelerator is spherical, and the application of the sphere packing arrangement in a real radiosurgical plan requires much time and skill. In this study, we found a characteristic of dose distribution with transformation of beam parameters that must be considered in a radiosurgical plan for effective radiosurgery. First, we assumed a cylinder type tumor model and a cube type tumor model. Secondly, the results of the tumor models were compared and analyzed with dose profiles and DVH_(Dose Volume Histogram) representative dose distribution. We found the optimal composition of beam parameters_(i.e. collimator size, number of isocenter, gap of isocenters etc.), which allowed the tumor models to be involved in the isodose curve at a high level. In conclusion, the characteristics found in this study are helpful for improving the effectiveness and speed of a radiosurgical plan for stereotactic radiosurgery.

• Journal of Preventive Medicine and Public Health
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• v.13 no.1
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• pp.27-34
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• 1980

Purpose of this study is to find out proper means of estimating the urinary mercury excretion in the normal individuals. Whole void volume was collected every 2 hours beginning from 6 o'clock in the morning until 6 o'clock next morning. Mercury excretion in each urine specimen was measured by NIOSH recommended dithizone colorimetric method (Method No.: P & CAM 145). Urinary concentration of mercury was adjusted by two means: specific gravity of 1.024 and a gram of creatinine excretion per liter of urine comparing the data with the unadjusted ones. Mercury excretion in 24-hour urine specimen was calculated by adding the amounts measured with the hourly collected specimens of each individual. Statistical analysis of the urinary mercury excretion revealed the following results: 1. Frequency distribution curve of mercury excreted in urine of hourly specimens was best fitted to power function expressed in the form of $y=ax^b$. Adjustment of the urinary mercury concentration by creatinine excretion was shown to be superior($y=1674x^{-1.52},\;r^2=0.95$) over nonadjustment($y=2702x^{-1.57},\;r^2=0.92$) and adjustment by specific gravity of 1.024($y=4535x^{-1.66},\;r^2=0.93$). 2. Both log-transformed mercury excretion in hourly voided specimens and mercury excretion itself in 24 hour specimens showed the normal distributions. 3. The frequency distribution of mercury adjusting the urinary concentration of mercury by creatinine excretion was best fitted to a theoretical normal distribution with the sample means and standard deviation than those unadjusted or adjusted with specific gravity of 1.024. 4. Average urinary mercury excretions in 24-hour urine specimen in an individual were as follows: a) Unadjusted mercury excretion mean and standard deviation : $$18.6{\pm}13.68{\mu}gHg/l$$. median : $$16.0\;{\mu}gHg/l$$. range : $$0.0-55.10\;{\mu}gHg/l$$. b) Adjusted with specific gravity mean : $$20.7{\pm}11.76\;{\mu}gHg/l{\times}\frac{0.024}{S.G-1.000}$$ median : $$20.7\;{\mu}gHg/l{\times}\frac{0.024}{S.G-1.000}$$ range : $$0.0-52.9\;{\mu}gHg/l{\times}\frac{0.024}{S.G-1.000}$$ c) Adjusted with creatinine excretion mean and standard deviation : $$10.5{\pm}6.98\;{\mu}gHg/g$$ creatinine/l median : $$9.4\;{\mu}gHg/g$$ creatinine/l range : $$0.0-26.7\;{\mu}gHg/g$$ creatinine/l 5. No statistically significant differences were found between means calculated from 24-hour urine specimens and those from hourly specimens transformed into logarithmic values. (P<0.05).

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.494-505
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• 2006

In this study, using constant normal stiffness(CNS) direct shear tests, side shear load distribution were analyzed by the influencing parameters of unconfined compressive strength, surface roughness, confining stress, and material properties. Based on the CNS tests, side shear load transfer function of drilled shafts in rock is proposed using geological strength index(GSI), which indicates discontinuity and surface condition of rock mass in Hoek-Brown criterion. Though comparisons with results of nine drilled shafts's load tests, it is found that the load-transfer curve by this study is in good agreement with the general trend observed by in situ measurements, and thus represents a significant improvement in the prediction of bearing capacity of drilled shaft.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.267-271
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• 2000

The local heat transfer rate of an axisymmetric submerged air jet impinging on normal to a heated flat plate was investigated experimentally with varying solidity of mesh screen. The mean velocity and turbulent Intensity profiles of streamwise velocity component were measured using a hot-wire anemometry. The temperature distribution on the heated flat surface was measured with thermocouples. The screen installed in front of the nozzle exit(behind of 35mm) modify the jet flow structure and local heat transfer characteristics. For higher solidity screen, turbulence intensity at core lesion is high and increases the local heat transfer rate at nozzle-to-plate spacings(L/D<6). For larger nozzle-to-plate spacings(L/D>6), however, the turbulent Intensities of all screens tested in this study approach to an asymptotic curve, but the small mean velocity at the core region reduces the local heat transfer rate for high solidity screens.

• Toxicological Research
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• v.7 no.1
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• pp.37-46
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• 1991

To evaluate the influence of ochratoxin A on the pharmarcokinetics of gentamicin, gentamicin concentrations in the serum, renal cortex and medulla together with parameters of the renal function and histological changes were compared between ochratoxin A-treated rats (0.1 mg of ochratoxin A/kg of body weight, ip, daily for 14 days) and normal rats. Gentamicin was given with a single intramuscular injection (10mg/kg of body weight). Ochratoxin A resulted in an increase of the half-life, the area under the concentration-time curve, the apparent volume of distribution and a decrease of the total body clearance of gentamicin, and accumulated significantly (p<0.01) more gentamicin in the kidneys.

• Journal of environmental and Sanitary engineering
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• v.12 no.1
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• pp.15-23
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• 1997

The anionic exchange resins with the Dowex-1 and Amberlite CG-400 form were transformed into resin of sulfate and acetate acid form, respectively. The uranyl complex ions with SO$_{4}$$^{2-}$ and CH$_{3}$COO$^{-}$ were adsorbed on the anion exchange resion mentioned above, and these complex ions were eluted as mixture eluents of 0.7M HNO$_{3}$ - 0.5M NH$_{4}$NO$_{3}$ by anion exchange chromatography. The optimum adsorption conditions of uranyl anion complex ions adsorbed on the upper of the resin colmun were 1.5-2.0 ml/min of flow rates at pH 2.0 and adsorptive power of uranyl complex ion of sulfuric acid type were nearly consistent with the Caussion normal distribution curve, whereas the elution state of UO$_{2}$(Ac)$_{2}$$^{4-}$ with acetic acid type was departed. The weighing form obtained from resin of sulfuric acid and aceric acid type was U$_{3}$O$_{8}$ whose recovery was 91.7%. The possibility of recovering uranium from the monazite sulfate solution using a strong base anion resin, Amberlite CG-400(sulfate form), was successfully recovered more than 90%.