• Journal of Wetlands Research
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• v.7 no.3
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• pp.57-66
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• 2005

This paper is to present the determination of the optimal loss rate parameters and unit hydrographs from the observed single rainfall-runoff event using optimization model. The linear program models has been formulated to derive the optimal unit hydrographs and loss rate parameters for the site of the Su-Jik Bridge in the HwangGuJichen River; one minimizes the summation of the absolute residual between predicted and observed runoff ordinates. In the perturbation stage of parameters the trial and error method has been adopted to determine the loss rate parameters for Kostiakov's, Philip's, Horton's, and Green-Ampt's equation. The unique unit hydrograph ordinates for a given rainfall-runoff event is exclusively obtained with ${\Phi}$ index, but unit hydrograph ordinates depend upon the parameters for each loss rate equations. In this paper the single rainfall-runoff event observed from the sample watershed is considered to test the proposed method. The optimal unit hydrograph obtained by the optimization model has smaller deviations than the ones by the conventional method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.4
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• pp.313-319
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• 2017

Fiber optics sensors that have been mainly applied to aerospace areas are now finding applicability in other areas, such as transportation, including railways. Among the sensors, the fiber Bragg grating (FBG) sensors have led to a steep increase due to their properties of absolute measurement and multiplexing capability. Generally, the FBG sensors adhere to structures and sensing modules using adhesives such as an epoxy. However, the measurement errors that occurred when the FBG sensors were used in a long-term application, where they were exposed to environmental thermal load, required calibration. For this reason, the thermal curing of adhesives needs to be investigated to enhance the reliability of the FBG sensor system. This can be done at room temperature through cyclic thermal load tests using four types of specimens. From the test results, it is confirmed that residual compressive strain occurs to the FBG sensors due to an initial cyclic thermal load. In conclusion, signals of the FBG sensors need to be stabilized for applying them to a long-term SHM.

• Journal of the Society of Disaster Information
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• v.10 no.2
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• pp.238-243
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• 2014

Recently environmental pollution is serious and therefore, This study aims at reviewing individual mixing ratio and engineering characteristics of concrete due to mixture and mixing using fine powder and fly ash of blast furnace slag having effect on aspects of environmental preservation and resources recycling and performance increase of the concrete, and verifying possibility of application in the field. Test results are as follows: 1)As mixing quantity of the admixture has increased, performance of the slump has been improved, 2)As mixing quantity of the admixture has increased, there is a trend of delayed ending time, 3)As mixing quantity of admixture has increased, it has showed lower strength at short time age, however, as the age has elapsed and mixing quantity has increased, strength improvement has increased and the admixture has effect on the long term age. In this study, the characteristics and critical value of concrete contained blast furnace slag and fly ash are defined, and will be examined about the field applications.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3602-3609
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• 2015

HPFRCC is characterized by a very low water-to-binder ratio which induce extremely large autogenous shrinkage at early age. The restriction of such autogenous shrinkage through the use of forms and reinforcing bars will increase substantially the risk of excessive residual stresses and shrinkage cracking. The exact understanding of the shrinkage behavior and studies on solutions to reduce shrinkage should be imperatively undertaken for further application of HPFRCC to real structures. Therefore, this paper investigated the mechanical properties of HPFRCC with respect to the eventual introduction of expansive admixture(EA) and shrinkage reducing agent (SRA) in the mixture. Autogenous shrinkage test was conducted considering the coefficient of thermal expansion (CTE) measured at early age so as to examine the effects of EA and SRA on the autogenous shrinkage behavior of HPFRCC.

• Korean Journal of Applied Biomechanics
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• v.17 no.3
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• pp.155-164
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• 2007

This study is aimed at determining the effects of rehabilitation training on lumbar extension strength and relief of back pain in middle-aged women of low back pain. Twenty-nine subjects(total 29 people; CLBP 16, HLD 13) were trained twice per week for eight weeks and completed a maximum isometric test at various flexion angle(the degree of $0^{\circ}$, $12^{\circ}$, $24^{\circ}$, $36^{\icrc}$, $48^{\circ}$, $60^{\circ}$, $72^{\circ}$) by lumbar extension machine. The result showed that. 1. Patient group of CLBP were increased the maximum lumbar extension strength at a range of 7 flexion angles after rehabilitation rather than no rehabilitation(on the average 60.75%). The operated patient group in HLD also showed an increase of 56.55%. In view of these cases, all of two groups showed a significant increase of muscle strength(p<.05). But there is no difference between pre-exercise and post-exercise groups. 2. Patient group of CLBP were increased higher rate than 41% for maximum lumbar extension strength(91.79% at $0^{\circ}$, 79.41% at $12^{\circ}$, 65.89% at $24^{\circ}$) at all angles after 8 weeks training. Both groups indicated a significant increase(p<.05) of lumbar extension strength at all degrees. There is no difference between pre-exercise and post-exercise groups. 3. Relief of back pain in Patient group of CLBP showed a decrease of average 105.2% and patient group of HLD indicated a decrease of average 64.57% two groups showed a significant reduction (p<.05, p<.05). But in case of a decrease of pain, CLBP group got 3.44 points and HLD group got 4.77 points. In view of these results, two groups showed remarkable reduction of back pain, however HLD group had residual pain relatively.

• Nuclear Engineering and Technology
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• v.48 no.6
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• pp.1321-1329
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• 2016

To get an insight into the operating characteristics of the passive residual heat removal system of molten salt reactors, a two-phase natural circulation test facility was constructed. The system consists of a boiling loop absorbing the heat from the drain tank, a condensing loop consuming the heat, and a steam drum. A steady-state experiment was carried out, in which the thimble temperature ranged from $450^{\circ}C$ to $700^{\circ}C$ and the system pressure was controlled at levels below 150 kPa. When reaching a steady state, the system was operated under saturated conditions. Some important parameters, including heat power, system resistance, and water level in the steam drum and water tank were investigated. The experimental results showed that the natural circulation system is feasible in removing the decay heat, even though some fluctuations may occur in the operation. The uneven temperature distribution in the water tank may be inevitable because convection occurs on the outside of the condensing tube besides boiling with decreasing the decay power. The instabilities in the natural circulation loop are sensitive to heat flux and system resistance rather than the water level in the steam drum and water tank. RELAP5 code shows reasonable results compared with experimental data.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.356-356
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• 2010

Tribological behaviors of the hard film on soft substrate system were explored using the hard thin film of diamond-like carbon (DLC) coated the soft polymer of polydimethysiloxane (PDMS). A DLC film with the Young's modulus of 100 GPa was coated on PDMS substrate with Young's modulus of 10 MPa using plasma enhanced chemical vapor deposition (PECVD) technique. The deposition time was varied from 10 sec to 10 min, resulting in nanoscale roughness of wrinkle patterns with the thickness of 20 nm to 510 nm, respectively, at a bias voltage of $400\;V_b$, working pressure 10 mTorr. Nanoscale wrinkle patterns with 20-100 nm in width and 10-30 nm height were formed on DLC coating due to the residual stress in compression and difference in Young's modulus. Nanoscale roughness effect on tribological behaviors was observed by performing a tribo-experiment using the ball-on-disk type tribometer with a steel ball of 6 mm in diameter at the sliding speed of 220 rpm, normal load of 1N and 25% humidity at ambient temperature of $25^{\circ}C$. Friction force were measured with respect to thickness change of coated DLC thin film on PDMS. It was found that with increases the thickness of DLC coating on PDMS, the coefficient of friction decreased by comparison to that of the uncoated PDMS. The wear tracks before and after tribo-test were analyzed using SEM and AFM.

• Journal of Korean Society on Water Environment
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• v.23 no.2
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• pp.193-200
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• 2007

The AOPs research defined by creating a sufficient amount of OH radicals from the dissolution of organic materials through photoxidation and research for a complete elimination of residual organic materials by membrane are actively ongoing. This research focuses on the hybrid processing of AOPs and M/F membrane to dissolve and eliminate organic chemicals in drinking water which are suspected of carcinogens. For this purpose, underground water was used as a source of drinking water for the hybrid processing of AOPs oxidation and M/F membrane, and a pilot plant test device was installed indoor. Carcinogenic chemicals of VOCs and pesticide were artificially mixed with the drinking water, which was then diluted close to natural water in order to examine treatment efficiency and draw optimal operation conditions. The samples used for this experiment include four chemicals phenol, chloroform, in VOCs and parathion, carbaryl in pesticide. As a result of the experiments conducted with simple, and compound solutions, the conditions to sufficiently dissolve and eliminate carcinogenic chemicals from the hybrid processing of where carcinogens were artificially added are : (hydrogen peroxide) prescribed solution 100 mg/L under pH 5.5~6.0, and the temperature $12{\sim}16^{\circ}C$, at the normal temperature and pressure. $d-O_3$ volume of 5.0 ppm and above and 30-40 minutes of reaction time are most appropriate and using MF/UF for membrane was ideal.

• Resources Recycling
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• v.21 no.1
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• pp.75-81
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• 2012

Porous pellets for immobilizing heavy metals were manufactured from coal tailings and iron oxide powder. Coal tailings was pulverized and mixed with iron oxide powder. The mixed powder was granulated into spherical pellets and roasted. Over $1100^{\circ}C$, residual coal in coal tailings reduced iron oxide to ZVI(Zero-Valent Iron). The pellets have 34.63% of porosity, 1.31 g/mL of bulk density, and 9.82.urn median pore diameter. The pellets were reacted with synthetic solutions containing each heavy metals: arsenic(V), copper(II), chrome(VI), and cadmium(II), respectively. On the test of immobilizing heavy metal, the pellets made at $1100^{\circ}C$ were superior to the other pellets made under $1000^{\circ}C$. Immobilizing over 99.9% of 10ppm heavy metal solutions required I hour for arsenic, 2 hours for chrome, and 4 hours for copper. However, immobilizing capacity of cadmium was inferior to that of the other metals and it was decreased in reversely proportion to initial concentration of the solutions.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.5
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• pp.827-831
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• 2004

This study was carried out to investigate the supplementary effects of ${\gamma}$-oryzanol on the blood glucose level in diabetic mice. We supplied 2 experimental diets (CO without and GO with 0.2% ${\gamma}$-oryzanol) to diabetic mice for 8 weeks. Diet intake, body weight and levels of blood glucose, hemoglobin $A_{lc}$ and insulin were measured. Though there was no significant difference in diet intake between experimental groups, the concentration of fasting blood glucose and blood glucose area from glucose tolerance test in diabetic mice was lower in GO group than CO group during the supplementary period of experimental diets. Hemoglobin Ai, was lower and serum insulin level was higher in GO group than CO group without significance. These results suggest that r-oryzanol decrease the blood glucose level, and ${\gamma}$ -oryzanol produced from residual product of rice may be developed with high value.