• Computers and Concrete
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• v.33 no.4
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• pp.399-407
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• 2024

This study nondestructively examined the evolution of crack density in ultra-high performance concrete (UHPC) upon cyclic loading. Uniaxial compression was repeatedly applied to the cylindrical specimens at levels corresponding to 32% and 53% of the maximum load-bearing capacity, each at a steady strain rate. At each stage, both P-wave and S-wave velocities were measured in the absence of the applied load. In particular, the continuous monitoring of P-wave velocity from the first loading prior to the second loading allowed real-time observation of the strengthening effect during loading and the recovery effect afterwards. Increasing the number of cycles resulted in the reduction of both elastic wave velocities and Young's modulus, along with a slight rise in Poisson's ratio in both tested cases. The computed crack density showed a monotonically increasing trend with repeated loading, more significant at 53% than at 32% loading. Furthermore, the spatial distribution of the crack density along the height was achieved, validating the directional dependency of microcracking development. This study demonstrated the capability of the crack density to capture the evolution of microcracks in UHPC under cyclic loading condition, as an early-stage damage indicator.

• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.141-158
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• 2004

The dependency of criteria used to terminate compatibility tests on the prehydration and quality of bentonite in geosynthetic clay liners (GCLs) is evaluated based on permeation with chemical solutions containing 5, 10, 20, 50, and 100 mM calcium chloride ($CaCl_2$). The hydraulic conductivity tests are not terminated before chemical equilibrium between the effluent and the influent chemistry has been established, resulting in test durations ranging from < 1 day to > 900 days, with longer test durations associated with lower $CaCl_2$ concentrations. The evaluation includes both physical termination criteria (i.e., volumetric flow ratio and steady hydraulic conductivity based on ASTM D 5084, ${\ge}2$ pore volumes of flow, constant thickness of specimen) and chemical termination criteria requiring equilibrium between influent and effluent chemistry (viz., electrical conductivity, pH, and $Ca^{2+}\;and\;Cl^-$ concentrations). For specimens permeated with 5, 10, and 20 mM $CaCl_2$ solutions, only the criterion based on chemical equilibrium in $Ca^{2+}$ concentration correlates well with equilibrium in hydraulic conductivity, regardless of prehydration or quality of bentonite. However, all of the termination criteria, except for the volumetric flow ratio and 2 pore volumes of flow for the prehydrated specimens, correlate well with equilibrium in hydraulic conductivity regardless of prehydration or quality of bentonite when permeated with 50 and 100 mM $CaCl_2$ solutions. The results illustrate the uniqueness of the termination criterion based on solute concentration equilibrium between the effluent and the influent with respect to both prehydration and quality of bentonite in the GCLs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1126-1135
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• 2007

This paper presents the varactor-tuned miniaturized hairpin tunable filter with a single control voltage. The previously proposed miniaturization method is a very straight-forward method to miniaturize a parallel coupled-line filter. In this paper, the miniaturized hairpin tunable filter is proposed with the constant ratio rule of that the capacitances of the each stage always have constant ratio without any dependency to miniaturized electrical length. To show the validity of the proposed method, a 3rd order 0.5 dB ripple Chebyshev fitter with a center frequency of 900 MHz and a fractional bandwidth(FBW) of 10 % was designed and fabricated. The fabricated filter was based on CER-10 substrate of Taconic Inc. with 1SV277 varactor diode of Toshiba Inc. The center frequency of the fabricated filter can be changed from 606 MHz to 944 MHz, 338 MHz with the control voltage from 0.5 V to 4 V. The insertion loss of the proposed filter is increased with the increment of the control voltage, and the filter characteristics are well reserved expect of slight change of the bandwidth with the various control voltage.

• Korean Journal of Materials Research
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• v.11 no.5
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• pp.339-344
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• 2001

An all solid-state thin film supercapacitor (TFSC) with Co$_3$O$_4$/LiPON/Co$_3$O$_4$ structure was fabricated on Pt/Ti/Si substrate using Co$_3$O$_4$ thin film electrode. Each Co$_3$O$_4$ film was grown by reactive dc reactive magnetron sputtering with increasing $O_2$/[Ar+O$_2$] ratio. Amorphous LiPON electrolyte film was deposited on Co$_3$O$_4$/Pt/Ti/Si in pure nitrogen ambient by using reactive rf magnetron sputtering. The electrochemical behavior of the Co$_3$O$_4$/LiPON/Co$_3$O$_4$ multi-layer structures exhibits a behavior of a bulk-type supercapacitor, even though much lower capacity (from 5 to 25 mF/$\textrm{cm}^2$-$\mu\textrm{m}$) than that of the bulk one. It was found that the TFSC showed a fairly constant discharge capacity with a constant current of 50 $\mu\textrm{A}/\textrm{cm}^2$ at the cut-off voltage 0-2V during 400 cycles. It is shown that the electrochemical behavior of the Co$_3$O$_4$/LiPON/Co$_3$O$_4$ TFSC is dependent upon the sputtering gas ratio. The capacity dependency of electrode films on different gas ratios was explained by different structural, electrical, and surfacical properties.

• International Area Studies Review
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• v.15 no.1
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• pp.549-570
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• 2011

The purpose of this article is to review the current states and future trends in the more developed countries(MDC), the less developed countries(LDC), and Korea. In 2009, the percentage of persons ages 65 and older in the world's population is 8%. However, the ratio of elderly to the total population is higher in MDC than LDC (and Korea). In future, population ageing will be a serious social problem in the LDC (and Korea). Population ageing process will occur at a much faster rate in LDC (and Korea). The reason is that the demographic transition in LDC (and Korea) has occurred in much shorter and recent periods. Though the ageing indices such as the old-age dependency ratio, aging index, and the median ages are higher in MDC, they will change rapidly in LDC. In addition, the oldest old population will increase in LDC than MDC. Therefore, when establishing the government policy related to population ageing, we need to consider the different population ageing process between in MDC and in Korea(or LDC).

• Progress in Medical Physics
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• v.22 no.4
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• pp.216-223
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• 2011

Recently PTW developed a MicroLion liquid ionization chamber which is water_equivalent and has a small sensitive volume of $0.002cm^3$. The aim of this work is to investigate such dosimetric characteristics as dose linearity, dose rate dependency, spatial resolution, and output factors of the chamber for the external radiotherapy photon beam. The results were compared to those of Semiflex chamber, Pinpoint chamber and Diode chamber with the sensitive volumes of $0.125cm^3$, $0.03cm^3$ and $0.0025cm^3$, respectively and evaluated to be suitable for small fields. This study was performed in the 6MV photon energy from a Varian 2300 C/D linac accelerator and the MP3 water phantom (PTW, Freiburg) was used. Penumbras in the varios field sizes ranged from $0.5{\times}0.5cm^2$ to $10{\times}10cm^2$ were used to evaluate the spatial resolution. Output factors were measured in the field sizes of $0.5{\times}0.5$ to $40{\times}40cm^2$. Readings of the chamber was linearly proportional to dose. Dose rate dependency was measured from 100 MU/min to 600 MU/min, showed a maximum difference of 5.0%, and outputs decreased with dose rates. The spatial resolutions determined with comparing profiles for the field sizes of $0.5{\times}0.5cm^2$ to $10{\times}10cm^2$ agreed between every detector except the Semiflex chamber to within 2%. Outputs of detectors were compared to that of Semiflex chamber and showed good agreements within 2% for every chamber. This study shows that MicroLion chamber characterized by a high signal-to-noise ratio and water equivalence could be suitable for the small field dosimetry.

• Journal of agricultural medicine and community health
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• v.38 no.1
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• pp.1-13
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• 2013

Objectives: This study is to investigate the prevalence and related factors of metabolic syndrome among Korean adults aged 20 years and above. Methods: From the database of the $5^{th}$ Korea National Health and Nutrition Examination Survey (KNHANES V) conducted in 2010, data of 5,670 adults who responded to all the questionnaires of health interview and had metabolic syndrome in the health examination were included in this analysis. SAS 9.2 was used for statistical analysis with complex sample survey modules and commands. Results: The prevalence rate of metabolic syndrome based on the criteria proposed by International Diabetes Federation (IDF) was 18.8%. The prevalence of metabolic syndrome in each group was: 20.7% of women, 43.1% among elderly over 70 years old, 40.6% of the divorced or the separated, 27.6% of recipients of economic support from the government, 23.6% of people who had alcohol dependency problem, and 43.7% of overweight or obese adults. Independent risk factors based on the multiple logistic regression analysis revealed that prevalence of metabolic syndrome was associated with female (odds ratio 1.59 [95% confidence interval 1.20-2.11]), age (50s 3.95 [2.11-7.37], 60s 5.62 [2.98-10.61], 70s 10.56 [5.25-21.25]), high school education (0.52 [0.37-0.74]), clerk occupation (2.14 [1.27-3.60]), divorced marital status (1.72 [1.15-2.59]), alcohol dependency (1.86 [1.16-2.98]), higher BMI (14.08 [10.60-18.70]). Conclusions: The metabolic syndrome is prevalent among Korean adult population according to IDF criteria. Several demographic characteristics and potentially modifiable factors are associated with metabolic syndrome. Identification of this high-risk group and management of these modifiable factors are warranted to reduce the prevalence of metabolic syndrome.

• Radiation Oncology Journal
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• v.13 no.3
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• pp.291-296
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• 1995

Purpose : In general, the wedge factors which are used clinical practices are ignored of dependency on field sizes and depths. In this present, we investigated systematically the depth and field size dependency to determine the absorbed dose more accurately. Methods : The wedge factors for each wedge filter were measured at various depths (depth of Dmax, 5cm, 10cm, and 15cm) and field sizes ($5cm{\times}5cm,\;10cm{\times}10cm,\;15cm{\times}15cm, and 20cm{\times}20cm$) by using 4-, 6-, and 10-MVX rays. By convention, wedge factors are determined by taking the ratio of the central axis ionization readings when the wedge filter is in place to those of the open field in same field size and measurement depth. In this present work, we determined the wedge factors for 4-, 6-, and 10-MV X rays from Clinac 600C and 2100C linear accelerators (manufactured by Varian Associates, Inc., Palo Alto, CA). To confirm that the wedge was centered, measurements were done with the two possible wedge position and various collimator orientations. Results : The standard deviations of measured values are within $0.3\;\%$ and the depth dependence of wedge factor is greater for the lower energies. Especially, the variation of wedge factor is no less than $5\%$ for 4- and 6- MV X rays with more than $45^{\circ}$ wedge filters. But there seems to be a small dependence on field size. Conclusion : The results of this study show a dependence on the point of measurement. There also seems to be a small dependence on field size. And so, we should consider the depth and field size dependence in determining the wedge factors. If one wedge factor were to be used for each wedge filter it seems that the measurement for a 10cm x 10cm field size at a depth of loom would be a reasonable choice.

• The Korean Journal of Pharmacology
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• v.23 no.1
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• pp.1-7
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• 1987

The renal handling and tissue distribution of pyrazinamide were studied after administration of single dose intravenous injection for 15 min or constant infusion in New Zealand White rabbits. Peak pyrazinamide serum concentration ranged from 57.3 to $105.0{\mu}g/ml$ ($mean{\pm}SD;83.0{\pm}17.8$). The mean half-life of the a phase was $0.143{\pm}0.047$ hr while the ${\beta}$ phase ranged from 1.66 to 3.25 hr($mean{\pm}SD;2.38{\pm}0.57$). The mean steady-state volume of distribution in non-compartmental model was $0.935{\pm}0.362\;L/kg$ Excretion ratio of pyrazinamide was dramatically reduced from 1.02 to 0.30 when unbound serum pyrazinamide concentration was increased from 6.04 to $60.9\;{\mu}g/ml$. The urine flow dependency of renal clearance of pyrazinamide was demonstrated in steady-state serum concentration. The tissue/serum concentration ratio of pyrazinamide was highest in kidney and lowest in skeletal muscle among the tissues examined. The results suggested that a large fraction of pyrazinamide filtered by glomerulus and secreted by renal tubule was reabsorbed and this tubular reabsorption of pyrazinamide might be greatly influenced by urine flow.

• Journal of the Korean Institute of Landscape Architecture
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• v.40 no.5
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• pp.63-72
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• 2012

In contemporary times, "environmental designers" need to consider both exterior and interior aspects because of the growing trend in dissolution between exterior and interior spaces. To quantify "spatial sense" which serves as the standard for environmental design, this study has asked 63 subjects to evaluate 15 interior and 14 exterior spaces. The "spaciousness (small-large)", "openness(closed-open)", "warmness(warm-cold)", "brightness(bright-dark)", "softness(soft-hard)", "spatial intimacy" and "frequency of visit" were adopted as variables of spatial sense. Through the analysis of these variables, this study could gain the difference between spatial sense for exterior and interior environments, quantify the spatial sense that physically and psychologically appropriates to human beings. The result of this study can be summarized as follows: Twice the amount of spaciousness was observed between the interior and exterior spaces. And the standard on intimate space is established with W/H ratio of 5.71 and high Window/Wall Area ratio in the interior and an area of 3,800m2 and a W/H ratio of 5.57 in exterior. The difference between the spatial sense in the interior and exterior space is mostly dependent on the psychological sense. The increase of physical size caused by the interior space to be perceived as cold, dark and hard psychologically, but exterior space to be perceived as warm, bright and soft. Psychological senses, especially softness, affect spatial intimacy to the greatest extent among the given variables. As the psychological senses for interior spaces were largely independent from the given space's size and perceptive senses, the size of the interior space, which exhibited spatial intimacy, could not be deduced. In comparison to this, due to the high dependency between the psychological senses for exterior spaces and the given space's size and perceptive senses. The study also showed that interior and exterior spaces have relatively different spatial sense and physical standards. Such research results are predicted to provide applicable standards for environmental designers for exterior and interior spaces in the future.