• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.78-83
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• 2020

The information and knowledge of modern society in the 2lst century is changing rapidly. Based on this social change, the ministry of education introduced STEAM (Science Technology Engineering Art Music) in 2011 to foster creative convergence talents. Therefore, this study is based on the PBL model that learners participate in the class voluntarily to develop appropriate talents in the 21st century. The combined subjects were English, which is the world's official language, and Science, which is found in almost all the fields with the development of the 4th industrial revolution. As a result, learners could define the problems and solutions during the English class and take part in the group activity actively to obtain the problems and solutions of environmental pollution during the Science class. Through this, learners answered that they had a great understanding of learning (86%), high motivation for learning (100%), improved self-confidence (100%), and improved collaboration and creativity (100%). Unfortunately, this study does not progress actively due to the entrance exams, which still require accurate answers rather than the necessity and effectiveness of convergence education. To foster talents suitable for the present age, more active research should be applied to a range of educational sites.

• Journal of Korea Water Resources Association
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• v.53 no.1
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• pp.1-13
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• 2020

The most common approach for computing engineering flow problems at high Reynolds number is still the Reynolds-averaged Navier-Stokes (RANS) computations based on turbulence models with wall functions. The recently developed generalized wall functions blending between the wall-limiting viscous and the outer logarithmic relations ensure a smooth transition of flow quantities across two regions. The performances and convergence properties of widely used turbulence models with wall functions that are applicable for turbulence kinetic energy (TKE), turbulent and specific dissipation rates, and eddy viscosity are presented through a series of near wall flow simulations. The present results show that RNG k-𝜖 model should be carefully applied with small tolerance to get the stable solution when the first grid lies in the buffer layer. The standard k-𝜖 and RNG k-𝜖 models are not sensitive to the selection of wall functions for both TKE and eddy viscosity, while the k-ω SST model should be applied together with kL-wall function for TKE and nutUB-wall functions for eddy viscosity to ensure accurate and stable boundary conditions. The applications to a backward-facing step flow at Re=155,000 reveal that the reattachment length is reasonably well predicted on appropriately refined mesh by all turbulence models, except the standard k-𝜖 model which about 13% underestimates the reattachment length regardless of the grid refinement.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.42-57
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• 1995

An efficient and accurate scheme has been constructed by taking advantages of the hi-quadratic spline scheme and the higher-order boundary element method selectively depending on computation domains. Boundary surfaces are represented by 8-node boundary elements to describe curved surfaces of a ship and its neighboring free surface more accurately. The variation of the velocity potential complies with the characteristics of the 8-node element on the body surface. But on the free surface, it is assumed to follow that of the hi-quadratic spline scheme. By which, the free surface solution is free from numerical damping and has better numerical dispersion property. As numerical examples, steady and unsteady Neumann-Kelvin problems are considered. Numerical results for a submerged spheroid, Series 60($C_B=0.6$) and a modified support the proposed method. Finally, a new upstream radiation condition is derived using a wave equation operator in order to deal with problems for subcritical reduced frequency. The relevance of this operator has been confirmed in the case of unsteady Kelvin source potential.

• Progress in Medical Physics
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• v.17 no.3
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• pp.144-152
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• 2006

The telemedicine using independent client-server system via networks can provide high quality normalized services to many hospitals, specifically to local/rural area hospitals. This will eventually lead to a decreased medical cost because the centralized institute can handle big computer hardware systems and complicated software systems efficiently and economically, Customized cancer radiation treatment planning for each patient Is very useful for both a patient and a doctor because it makes possible for the most effective treatment with the least possible dose to patient. Radiation planners know that too small a dose to the tumor can result in recurrence of the cancer, while too large a dose to healthy tissue can cause complications or even death. The best solution is to build an accurate planning simulation system to provide better treatment strategies based on each patient's computerized tomography (CT) image. We are developing a web-based and a network-based customized cancer radiation therapy simulation system consisting of four Important computer codes; a CT managing code for preparing the patients target data from their CT image files, a parallel Monte Carlo high-energy beam code (PMCEPT code) for calculating doses against the target generated from the patient CT image, a parallel linear programming code for optimizing the treatment plan, and scientific data visualization code for efficient pre/post evaluation of the results. The whole softwares will run on a high performance Beowulf PC cluster of about 100-200 CPUs. Efficient management of the hardware and software systems is not an easy task for a hospital. Therefore, we integrated our system into the client-sewer system via network or web and provide high quality normalized services to many hospitals. Seamless communication with doctors is maintained via messenger function of the server-client system.

• Korean Journal of Clinical Pharmacy
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• v.7 no.2
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• pp.86-90
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• 1997

This study was to find a more accurate method fur measuring small vancomycin dosages which are commonly used in neonates by comparing single and double dilution method. For single dilution method, 500 mg of vancomycin powder was accurately measured and reconstituted with 5 ml of distilled water to make a concentration of 100 mg/ml. Volumes of 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, and 0.5 ml, which equal the target dosages of 5, 10, 15, 20, 30, 40, and 50 mg, were measured using syringes made by Shina and each sample was further diluted with 2 ml of $5\%$ dextrose. The solution of 100 mg/ml concentration was further diluted with $5\%$ dextrose to make a concentration of 20 mg/ml. Volumes of 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, and 2.5 ml, which correspond to 5, 10, 15, 20, 30, 40, and 50 mg, were sampled by the same Shina's syringe as in single dilution method and then each sample was further diluted to make a total volume of 10 ml. Each sample was analyzed by HPLC. The measured dosages of each sample in both single and double dilution methods were lower than the target dosages; however, e values in double dilution method were higher than those in single dilution method for seven target dosages. Percent target dosages in single dilution method were 65 to $90\%$, while in double dilution method 91 to $94\%$. Statistically significant difference between two groups was shown in 5, 10, 15, 20, and 40 mg dosages (p<0.05). In conclusion, when preparing small vancomycin dosages lower an 20 mg $(volume{\leq}0.2\;ml)$, using Shina's syringes, the double dilution method has a closer value to the target dosage than single dilution method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.5
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• pp.323-334
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• 2020

Since boundary layer transition has a significant impact on the aero-thermodynamic performance of hypersonic flight vehicles, capability of accurate prediction of transition location is essential for design and performance analysis. In this study, γ-Re_θt model is improved to predict transition of hypersonic boundary layers and validated. A coefficient in the production term of the intermittency transport equation that affects the transition onset location is constructed and applied as a function of Mach number, wall temperature, and freestream stagnation temperature based on the similarity numerical solution of compressible boundary layer. To take into account a Mach number dependency of transition onset momentum thickness Reynolds number and transition length, additional correlation equations are determined as function of Mach number and applied to Re_θc and F_length correlations of the baseline model. The suggested model is implemented to a commercial CFD code in consideration of practical use. Analysis of hypersonic flat plate and circular cone boundary layers is carried out by using the model for validation purpose. An improvement of prediction capability with respect to variation of Mach number and unit Reynolds number is identified from the comparison with experimental data.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1527-1527
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• 2001

Glucose, fructose and sucrose being the main sugars that can be found in natural fruit juice. Many instrumental methods, such as GC, LC, electrochemical or spectrometric methods provide information about both the total content of sugars and the specific concentration of each carbohydrate[1]. The simplicity of sample handling and measurement in the near IR(NIR) wavelength region, which allows the use of long pathlength, optical glass cells and optical fibers, makes NIR a good alternative for sugar determination [2]. In the present study, six varieties of persian grapes were harvested at intervals through august to october and analysed for sugars by NIR. The results were processed by principal component regression (PCR) and partial least squares (PLS) analysis. Sample juice was prepared by squeezing through gauze from crashed grape. This solution was treated by zinc ferrocyanide prior to analysis in order to eliminate colored compounds and all optically active nonsugar substances. For glucose and fructose the most characteristic wavelengths were 1456nm corresponding to the first harmonic O-H stretching and the second at 2062nm corresponding to O-H stretching and deformation; secondary characteristic combination bands were also seen at 2265 nm (O-H and C-C stretching) and at 2240 nm (C-H and C-C stretching). However these spectra were taken over a wavelength range from 1100-2500nm at room temperature of 25-$30^{\circ}C$. To test the accuracy of the described procedure, samples of six varieties of grape were analysed by the proposed NIR and a standard method[2]. Good agreement were found between these two sets of the results. To perform the recovery studies , samples of grape juices previously analysed by the proposed method, were spiked with known amounts of each individual sugars and then analysed again. Relative standard deviations varied from 1.4 to 1.8% for six independent measurements of individual and total sugar concentration. In the analysis of real and synthetic samples, precise and accurate results were obtained , providing accuracy errors lower than 1.9% in all cases. Average recoveries of ${97}{\pm}{4%}$ for total sugar and between ${95}{\pm}{5%}$ and ${99}{\pm}{2%}$ for sing1e sugars demonstrate the applicability of the methodology developed to the direct analysis of grape Juice.

• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.585-593
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• 2007

This paper presents a model for durability evaluation of concrete structures exposed to marine environment, considering mainly a build-up of surface chloride $(C_s)$ as well as diffusion coefficient (D) and chloride threshold level $(C_{lim})$. In this study, time dependency of $C_s$ and D were extensively studied for more accurate evaluation of service life of concrete structures. An analytical solution to the Fick's second law was presented for prediction of chloride ingress for time varying $C_s$. For the time varying $C_s$, a refined model using a logarithm function for time dependent $C_s$ was proposed by the regression analysis, and averaging integrated values of the D with time over exposed duration were calculated and then used for prediction of the chloride ingress to consider time dependency of D. Durability design was also carried out for railway concrete structures exposed to marine environment to ensure 100 years of service life by using the proposed models along with the standard specification on durability in Korea. The proposed model was verified by the so-called performance-based durability design, which is widely used in Europe. Results show that the standard specification underestimates durability performances of concrete structures exposed to marine environment, so the cover depth design using current durability evaluation in the standard specifications is very much conservative. Therefore, it is found that utilizing proposed models considering time dependent characteristics of $C_s$ and D can evaluate service lift of concrete structures in marine environment more accurately.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.501-509
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• 2020

Earthwork in the construction field is a core process of construction, and it is used in almost all processes and is connected to the safety of the structure directly. Therefore, it is essential to analyze and confirm the road tamping through a plate bearing test and a field density test. The current analog measurement methods for road tamping measurement is difficult to check in real-time, accurate location information, time information, and the history management of workers in the field. Therefore, IoT (Internet of Things)-based DCPT (Dynamic Cone Penetration Test) was developed for a smart construction environment with a solution to the problem. The Smart DCPT system operated in a smartphone environment is IoT-based. The Smart DCPT system can apply various applications and has advantages of flexibility, low cost, and high efficiency. The IoT-based DCPT records the digital road tamping information, location information, time information, and worker information per measurement count. In addition, the various information is transmitted in real-time to the management center through a smartphone. This system is expected to contribute to the management of the construction process.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.06a
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• pp.107-108
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• 2014

As the demand for precise navigation has increased, more focus is put on the precise positioning, RTK(Real Time Kinematics) which has been used in the surveying field. The Position of Single Reference Station RTK or two-way network RTK such as VRS (Virtual Reference Station) is accurate enough to be used as a main technology in land surveying, however its service area and number of users is limited and the users are assumed static. This characteristic is not suitable to the navigation, whose service target is infinite number of users moving over a wide area. One-way network RTK has recently been suggested as a solution for the precise navigation technique for the mobile user. This paper shows the performance prediction of the one-way network RTK such as MAC(Master-Auxiliary Concept), or FKP (Flachenkorrekturparameter). To show the performance variation by the rover position, we constructed a simulation data of users on the grid with 0.1 degree spacing between 36.5 and 37 degree latitude and between 127 and 127.5 degree longitude.