• Journal of Korea Water Resources Association
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• v.38 no.8 s.157
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• pp.655-664
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• 2005

A real-time monitoring and modeling system (RTMMS) for rainfall-induced turbidity flow, which is one of the major obstacles for sustainable use of reservoir water resources, is under development. As a prediction model for the RTMMS, a laterally integrated two-dimensional hydrodynamic and water quality model, CE-QUAL-W2 was tested by simulating the temperature stratification, density flow regimes, and temporal and spatial distributions of turbidity in a reservoir. The inflow water temperature and turbidity measured every hour during the flood season of 2004 were used as the boundary conditions. The monitoring data showed that inflow water temperature drop by 5 to $10^{\circ}C$ during rainfall events in summer, and consequently resulted in the development of density flow regimes such as plunge flow and interflow in the reservoir. The model showed relatively satisfactory performance in replicating the water temperature profiles and turbidity distributions, although considerable discrepancies were partially detected between observed and simulated results. The model was either very efficient in computation as the CPU run time to simulate the whole flood season took only 4 minutes with a Pentium 4(CPU 2.0GHz) desktop computer, which is essentially requited for real-time modeling of turbidity plume.

• Journal of the Korean Arthroscopy Society
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• v.16 no.2
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• pp.167-174
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• 2012

Purpose: The purpose of this study is investigation of clinical and functional outcomes in homogeneous group with positive culture after arthroscopic management for pyogenic knee arthritis and analysis of factors affecting those outcomes. Materials and Methods: Thirty-two patients with positive culture after arthroscopic management were included. Mean follow-up period was 41.6 months. Clinical evaluation included death related to infection, recurrence, time to normalize erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), duration of administration of intravenous antibiotics and readmission. Radiographic evaluation was performed according to Kellgren and Lawrence. The prevalence of total knee arthroplasty was investigated and functional evaluation included modified Lysholm, Tegner activity and Korean version of the Western Ontario and McMaster Universities (K-WOMAC) score. Results: Staphylococcus aureus was identified in 21 patients. Time to normalize ESR and CRP was 78.0 and 67.6 days, respectively. Two patients died while there were six recurrences and five readmissions. Rate of recurrence was significantly high in patients with chronic renal failure (P=0.034) and incidence of readmission was associated with higher radiographic grade of osteoarthritis and rate of reoperation (P=0.032 and P=0.006, respectively). At the final follow-up, radiographic grade worsened in 21 patients and was associated with those at first visit. Five arthroplasties were performed. Average modified Lysholm score, Tegner activity score and K-WOMAC score were 53.5, 2.7, 44.2 points, respectively. Conclusion: The severity of osteoarthritis on final radiographs was associated with those at first visit. Patients with higher grade of osteoarthritis at first visit showed higher incidence of readmission and those with chronic renal failure demonstrated higher chances of recurrence.

• Journal of Preventive Medicine and Public Health
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• v.31 no.2 s.61
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• pp.249-264
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• 1998

Reports on a potential relationship between sensory neural hearing loss(SNHL) and cardiovascular or hematologic factor show that the results are controversial. A detailed analysis of risk factors in the development of SNHL was carried out in 3,050 non-noise exposed healthy worker. The mean hearing threshold of both ears at 500, 1000, 2000, 4000, 8000Hz was measured and the effect of age, possible cardiovascular risk factor and hematologic factor (blood viscosity and hemostatic factors) on SNHL were evaluated. first, each of these were associated with loss of hearing sensitivity when univariately and multivariatively analysed. In a multiple regression model, age, sex, body mass index, WBC and total cholesterol level were independently associated with the mean of hearing sensitivity decrease at 4000 and 8000Hz. Second, study subjects were divided into two group (normal vs SNHL) and we compare the possible risk between both groups, and analysed univariate and multivariative logistic model. In a multiple logistic regression model, age, sex, body mass index, WBC and total cholesterol level, total protein, platelet were independently associated with SNHL. Our results show that we have some reliable indices of susceptibility to SNHL using cardiovascular measures or biochemical factor, but future, more extensive studies are required.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.830-836
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• 1997

The surface modification of iron oxide particle produced from steel-pickled acid by sodium-contained materials was studied. The molar ratio of $SiO_2$ to $Na_2O$ of sodium silicate was 1, 2, 3.5, respectively. The dispersion stability of iron oxide suspension as functions of amount of silica and pH was evaluated by surface charge and sedimentation velocity of iron oxide particle. Then the amount of sodium silicate was determined to provide a dispersion stability of iron oxide particle above pH 7. Finally, the surface modification of iron oxide particle with sodium silicate as silica-contained materials was done by wet ball milling. In the results of study, the dispersion stability of silica modified iron oxide particle was largely depended on amount of silica and pH together. The untreated iron oxide was unstable at pH 8, i.e. isoelectric point, but, the surface modified iron oxide particle with 0.8wt% silica was stable above pH 5. The dispersion stability was enhanced with 0.2wt% of anionic polyelectrolyte.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.85-93
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• 2002

This study presented a new method for evaluating the coefficient of consolidation by using inflection point method which was based on the fact that time factor, T corresponding to the inflection point of a semi-logarithmic plot of a time curve is fixed and equals to T = 0.405 at 70.03% consolidation. In the proposed method, as the next load increment is applied as soon as the inflection point is confirmed, the time required to identify the inflection point can be shortened. Thus, the coefficient of consolidation may be easily evaluated. The time required to complete the testing using this rapid consolidation method could be as low as 0.5~9 hours compared with 1 or 2 weeks in the case of the conventional consolidation test. For this study, we designed settlement equipment for normalization of test samples. In test results, the factors of consolidation agreed with undisturbed samples results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.1
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• pp.79-92
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• 1984

The analysis of total load was carried out by using the theory of unit stseam power (USP). The dimensionless USP equation of $S_R$ which was the rate of suspended load and bed load was derived from the USP function by applying the Einstein's reference concentration and Stokes' fall velocity. And the R relationship between the water discharge and Reynolds number (Re) was discussed, and it was shown that USP was closely related with Re. The value of $S_R$ was determined from the experimental data of Han River downstream and Mantz. And it was tested to several observatories of Korean Rivers. A good correlation among USP, suspended load and $S_R$ was shown and USP was increased with the increment of the turbulent intensity. Judging from the above results, it is considered this study can be contributed to estimate the total load.

• Analytical Science and Technology
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• v.24 no.6
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• pp.429-434
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• 2011

In this study, a wet-sampler was developed for collection in water and simultaneous fractionation of micron-sized particles (e.g., pigment, airborne, etc.). In this new device, three cylinders (partially filled with water) through which air was forced to pass for sample collection are connected in a series. Particles of different sizes are collected in different cylinders, allowing simultaneous fractionation. An uniqueness of this new device is that it does not use any membrane filter. Microparticles are collected directly in cylinders filled partially with water. Also the particles are simultaneously fractionated within this device while they are being collected. The new device was employed for collection of airborne particles. The collected airborne particles were fractionated by using sedimentation field-flow fractionation, SdFFF), and observed with an optical microscopy (OM) for size and shape analysis. Also AAS and ICP-AES were used for composition analysis of the airborne particles. It is expected that the new device is applicable to collection and analysis of size distribution of various types of microparticles.

• Korean Journal of Environmental Agriculture
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• v.11 no.1
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• pp.20-25
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• 1992

To understand the fundamental features of reservoir environment and its future aspects, a simple predictive model for water quality was attempted with the aid of data easily obtained, Based on the data from 12 reservoirs in Korea, application of the simple predictive model was successfully made by means of statistical methods and simple physical submodels. Significant information on th effects of retention time on primary production in a reservoir, longitudinal change in water quality affected by certain non-dimensional parameters were also obtained. The chlorophyll-a concentration can be predicted by the equation as ; chlorophyll-a=($395{\time}limiting$ nutrient concentration) - 1.090.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.509-512
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• 2008

The lining concrete of water tunnel is a much capability to occur crack due to drying shrinkage and vibrator compaction etc. Because of crack of concrete induce structural problem and decrease durability of concrete, it is need to reduce crack of concrete. In this an Analytical study to analyze the effect of curing of concrete and compaction on the lining concrete. As the results, it was found that control of construction condition into curing of concrete and compaction improve on construction efficiency of the lining concrete.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.164-170
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• 2002

Measurements of sedimentation, solid loading, zeta potential, and viscosity were employed to determine a proper dispersant and its amount for a well dispersed alumina powders in aqueous alumina tape casting using acrylate as a binder. Polycarboxylic acid was the most effective one among various dispersants considered in the present study and its amount was 0.23∼0.24 g per 100 g alumina for a dispersion. Better dispersion was obtained as an increase of dispersant addition. However, the dispersion was hindered as the amount of dispersant was higher than the optimum amount because of bridging or tangling of polymer chains. Excellent aqueous alumina tapes were prepared from the slurry containing the optimum amount of the polycarboxylic acid (0.2g), alumina powders(100 g), acrylate and Benzoflex as binder and plasticizer, respectively. The viscosity of the slurry was 570 cps and the alumina loading in the tape was 57 vol%.