• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.389-397
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• 2010

Concrete has excellent mechanical properties, high durability, and economical advantages over other construction materials. Nevertheless, it is not an easy task to apply concrete to long span bridges. That's because concrete has a low strength to weight ratio. Ultra high performance concrete (UHPC) has a very high strength and hence it allows use of relatively small section for the same design load. Thus UHPC is a promising material to be utilized in the construction of long span bridges. However, there is a possibility of crack generation during the curing process due to the high binder ratio of UHPC and a consequent large amount of hydration heat. In this study, adiabatic temperature rise and mechanical properties were modeled for the stress analysis due to hydration heat. Adiabatic temperature rise curve of UHPC was modeled superposing 2-parameter model and S-shaped function, and the Arrhenius constant was determined using the concept of equivalent time. The results are verified by the mock-up test measuring the temperature development due to the hydration of UHPC. In addition, models for mechanical properties such as elastic modulus, tensile strength and compressive strength were developed based on the test results from conventional load test and ultrasonic pulse velocity measurement.

• Journal of Korean Biological Nursing Science
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• v.3 no.2
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• pp.35-50
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• 2001

This study was conducted for the evaluation of the effects of singing program combined with physical exercise on the physiologic changes, perception function and degree of depression. The subjects were the members of elderly women's glee club in D care center for the elderly, who have been singing for more than 6 months. 30 members were allocated to study group and 30 to control group. The singing program designed for both physical therapy and music therapy was consisted of initial physical exercise, singing art songs and classical song and the finishing physical exercise. This program was performed twice a week and about forth minutes was consumed for one session. We checked the heart rate, peripheral arterial oxygen saturation, perception function and degree of depression before and after the program. We used a pulse oxymeter to check the heart rate to oxygen saturation and a questionnaire for the evaluation of perception function and degree of depression. We need SPSS program for data analysis. The results of the investigated personnel complying with general characteristics were analyzed by frequency, two groups by t-test, data before and after the program by paired t-test, respectively. The results were as follows. 1) Heart rate after the program was significantly lower than that before program in test group(p<0.05). 2) Peripheral oxygen saturation after the program was significantly higher than that before the program(p<0.05). 3) Ability to match the right sign with a certain predetermined number was improved after the program. The frequency of wrong matching the sign with number before program was 30. But the frequency was decreased to 8 after the program. 4) Ability to calculate was improved after the program. The frequency of wrong calculation before the program was $1.10{\pm}1.94$. But the frequency after the program was decreased to $0.97{\pm}1.84$. 5) The degree of depression after the program($2.07{\pm}0.49$) was significantly lower than that before program(p<0.001). These results show that singing program combined with physical exercise improves the oxygen delivery to peripheral circulation, stability of heart function, the perception function(calculating and matching ability) and decreases the degree of depression. In conclusion, singing program combined with physical exercise can be used for the effective measure to improve the health of elderly and prevent dementia.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.3
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• pp.155-161
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• 1998

Retardation effect of heavy metals in soils caused by adsorption onto the surfaces of solids particles is well known phenomenon. In this study, we investigated the retardation effect on the mobility of a Zn in a sandy soil by conducting batch and column tests. The column test consisted of monitoring the concentrations of effluent versus time known as a breakthrough curve (BTC). We used NaCl and ZnCl$_2$ solutions with the concentration of 10 g/L as a tracer, and injected them respectively into the inlet boundary of the soil sample as a square pulse type, and monitored the effluent concentrations at the exit boundary under a steady state condition using an EC-meter and ICP-AES. The batch test was conducted based on the standard procedure of equilibrating fine fractions collected from the soil with various initial ZnCl$_2$ concentrations, and analysis of Zn ions in the equilibrated solutions using ICP-AES. The results of column test showed that i) the peak concentration of ZnCl$_2$analyzed by ICP was far less than that of either NaCl or bulk electrical conductivity and ⅱ) travel times of peak concentrations for two tracers were more less identical. The relatively low concentration of Zn can be explained by ion exchange between Zn and other cations, and possible precipitation of Zn in the form of Zn(OH)$_2$due to high pH range (7.0∼7.9) of the effluent. The identical result of travel times of peak concentrations indicates that the retardation effect is not present in the soil. The only way to describe the prominent decrease of Zn ion was to introduce decay or sink coefficient in the CDE model to account for irreversible decrease of Zn ions in the aqueous phase.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.667-673
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• 2010

The near fault ground motion (NFGM) is characterized by a single long period velocity pulse with large magnitude. NFGMs have been observed in recent strong earthquakes, Northridge (1994), Japan Kobe (1995), Turkey Izmit (1999), China Sichuan (2008), Haiti (2010) etc. These strong earthquakes have caused considerable damage to infrastructures because the epicenter was close to the urban area, called as NFGM. Extensive research for the far field ground motion (FFGM) have been carried out in strong seismic region, but limited research have been done for NFGM in low or moderate seismic regions because of very few records. The purpose of this research is to investigate and analyze the seismic response of reinforced concrete bridge piers subjected to near-fault ground motions. The seismic performance of six RC bridge piers depending on three confinement steel ratios and three superstructure mass was investigated on the shaking table. From these experimental results, it was confirmed that the reduction of seismic performance was observed for test specimens with lower confinement steel ratio or more deck weight. The displacement ductility of RC bridge piers in terms of the stiffness degradation is proposed based on test results the shaking table.

• Journal of radiological science and technology
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• v.32 no.2
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• pp.177-182
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• 2009

Purpose : This study presents the optimization of flip angle (FA) to obtain higher contrast to noise ratio (CNR) and lower specific absorption rate (SAR). Materials and Method : T1-weighted images of the cerebrum of brain were obtained from 50$^\circ$ to 130$^\circ$ FA with 10$^\circ$ interval. Signal to noise ratios (SNRs) were calculated for white matter (WM), gray matter (GM), and background noise. The proper FA was analyzed by T-test statistics and Kruskal-wallis analysis using R1 = 1- exp ($\frac{-TR}{T1}$) and Ernst angle cos $\theta$ = exp ($\frac{-TR}{T1}$). Results : The SNR of WM at 130$^\circ$ FA is approximately 1.6 times higher than the SNR of WM at 50$^\circ$. The SNR of GM at 130$^\circ$ FA is approximately 1.9 times higher than the SNR of GM at 50$^\circ$. Although the SNRs of WM and GM showed similar trends with the change of FA values, the slowdown point of decrease after linear fitting were different. While the SNR of WM started decreasing at 120$^\circ$ FA, the SNR of GM started decreasing at less than 110$^\circ$. The highest SNRs of WM and GM were obtained at 130$^\circ$ FA. The highest CNRs, however, were obtained at 80$^\circ$ FA. Conclusion : Although SNR increased with the change of FA values from 50$^\circ$ to 130$^\circ$ at 3T SE T1WI, CNR was higher at 80$^\circ$ FA than at the usually used 90$^\circ$ FA. In addition, the SAR was decreased by using smaller FA. The CNR can be increased by using this optimized FA at 3T MR SE T1WI.

• Tuberculosis and Respiratory Diseases
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• v.53 no.4
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• pp.369-378
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• 2002

Background : The effects of chemotherapy on pulmonary function are mainly a reduced diffusion capacity and a restrictive ventilatory impairment. Exercise can expose cardiovascular and pulmonary abnormalities not evident at rest. Exercise related cardiopulmonary function is important in patients with malignant disease as a determinant of quality of life. We performed this study to evaluate the changes of body composition and cadiopulmonary exercise perfoemance of patients with locally advanced, non-small cell, lung cancer (NSCLC) before and after chemotherapy. Methods : We evaluated resting pulmonary function, body composition, physiologic performance status, and cardiopulmonary exercise function in 11 patients with locally advanced NSCLC, at diagnosis and prior to the fourth cycle of chemotherapy. Results : After chemotherapy, 4 patients (36.4%) showed partial response and 7 (63.4%) had stable disease. After chemotherapy, diffusion capacity of the lung for carbon monoxide was reduced ($89.7{\pm}34.1%$, vs. $71.9{\pm}20.5%$) but not significantly. There were no significant changes in body composition or the state of physiologic performance after chemotherapy. There was a significant impairment of cardiopulmonary exercise tolerance in patients with NSCLC, evidenced by a reduction of maximal oxygen uptake ($VO_2$max, ml/kg/min, $17.9{\pm}2.6$ : $12.6{\pm}6.1$, <0.05) and $O_2$pulse ($O_2$ pulse, ml/beat, $7.0{\pm}1.7$, $5.2{\pm}2.1$, <0.05). Conclusion : Systemic chemotherapy resulted in a loss of cardiopulmonary exercise function in patients with locally advanced NSCLC within the short-term period, but not a physiologic change of body composition within the same period.

• Korean Journal of Optics and Photonics
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• v.11 no.6
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• pp.452-456
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• 2000

A measurement unit and signal processing algorithm have been developed for predicting arterial oxygen saturation noninvasively. The measurement set-up was composed of a probe including light source and photodetector, optical signal processing section, LED driving circuit, PC interface software for data acquisition and data processing software. Light from the LED's was irradiated onto the finger nail bed and transmitted light was measured at different wavelengths. An effective baseline correction method was developed and measured data were analyzed by using various data processing methods and prediction algOlithms. For performance evaluation, a pulse oximeter simulator (Bio- Tek Instrument Inc.) was used as reference. The best performance in terms of the correlation coefficient and the standard deviation was obtained under the following conditions; when the arterial signals were computed in terms of area rather than peak-valley difference, and when the algorithm calculating by $In(I_p/I_v)/I_{avr}$ value for pulsation waveform was used. In in vivo test, prediction was improved when the developed baseline correction method was used. In addition, wavelengths of 660 nm and 940 nm provided better linearity and precision than wavelengths of 660 nm and 805 nm. 05 nm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.2
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• pp.220-228
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• 2012

In this paper, we explained the design technique about Ka-band active limiter for protecting the receiver of a millimeter wave seeker. To implement low flat leakage power, we proposed the control circuit of active limiter to control limiter voltage with PRF(Pulse Repetition Frequency) signal and input power. This active limiter consisted of the conventional 2 stage passive limiter, a feedback circuit with a directional coupler, detector, non-inverting amplifier and over-current protection resistance. As the test result of the fabricated Ka-band limiter, it had 1 GHz bandwidth, 3.5 dB insertion loss at the small input power and -7.5 dBm flat leakage at the 4 W RF input power, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5372-5378
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• 2012

In this paper, we propose a new method to quickly deinterleave the stagger PRI signals and D&S(Dwell and Switch) PRI signals from the EP radar using the electronic warfare system. While former algorithms were based on stochastic methods only using the first deviation of the TOA of radar signals, this paper uses the first and the second deviation of the TOA of radar signals to deinterleave multiple PRIs of EP radars. When we simulate multiple PRIs of EP radars and test the simulated radar signals using the proposed algorithm, various PRI signals such as fixed, jitter, D&S and stagger PRI are well deinterleaved in a short time. This algorithm is found to be very useful for electronic warfare systems.

• Journal of Astronomy and Space Sciences
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• v.37 no.2
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• pp.143-156
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• 2020

Korea Polar Research Institute (KOPRI) installed an ionospheric sounding radar system called Vertical Incidence Pulsed Ionospheric Radar (VIPIR) at Jang Bogo Station (JBS) in 2015 in order to routinely monitor the state of the ionosphere in the auroral oval and polar cap regions. Since 2017, after two-year test operation, it has been continuously operated to produce various ionospheric parameters. In this article, we will introduce the characteristics of the JBS-VIPIR observations and possible applications of the data for the study on the polar ionosphere. The JBS-VIPIR utilizes a log periodic transmit antenna that transmits 0.5-25 MHz radio waves, and a receiving array of 8 dipole antennas. It is operated in the Dynasonde B-mode pulse scheme and utilizes the 3-D inversion program, called NeXtYZ, for the data acquisition and processing, instead of the conventional 1-D inversion procedure as used in the most of digisonde observations. The JBS-VIPIR outputs include the height profiles of the electron density, ionospheric tilts, and ion drifts with a 2-minute temporal resolution in the bottomside ionosphere. With these observations, possible research applications will be briefly described in combination with other observations for the aurora, the neutral atmosphere and the magnetosphere simultaneously conducted at JBS.