• Journal of the Korean Society for Precision Engineering
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• v.25 no.6
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• pp.134-142
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• 2008

In this paper, we propose a precise linear motion stage supported by magnetically preloaded air bearings. The eight aerostatic bearings with rectangular carbon porous pads were located only one side of vertical direction under the platen where four bearings are in both sides of horizontal direction as wrap-around-design, and this gives simpler configuration than which constrained by air bearings for all direction. Each of the magnetic actuators has a permanent magnet generating static magnetic flux far required preload and a coil to perturb the magnetic farce resulting adjustment of air- bearing clearance. The characteristics of porous aerostatic bearing are analyzed by numerical analysis, and analytic magnetic circuit model is driven for magnetic actuator to calculate preload and variation of force due to current. A 1-axis linear stage motorized with a coreless linear motor and a linear encoder was designed and built to verify this design concept. The load capacity, stiffness and preload force were examined and compared with analysis. With the active magnetic preloading actuators controlled with DSP board and PWM power amplifiers, the active on-line adjusting tests about the vertical, pitching and rolling motion were performed. It was shown that motion control far three DOF motions were linear and independent after calibration of the control gains.

• Advances in materials Research
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• v.9 no.2
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• pp.99-107
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• 2020

Reinforced aluminum alloy base composites have become increasingly popular for engineering applications, since they usually possess several desirable properties. Recently, Warm Accumulative Roll Bonding (WARB) process has been used as a new novel process to fabricate particle reinforced metal matrix composites. In the present study, TiO₂ particles are used as reinforcement in aluminum metal matrix composites fabricated through warm accumulative roll bonding process. Firstly, the raw aluminum alloy 1060 strips with TiO₂ as reinforcement particle were roll bonded to four accumulative rolling cycles by preheating for 5 min at 300℃before each cycle. The mechanical and bonding properties of composites have been studied versus different volume contents of TiO₂ particles by tensile test, peeling test and vickers micro-hardness test. Moreover, the fracture surface and peeling surface of samples after the tensile test and peeling test have been studied versus different amount of TiO₂ volume contents by scanning electron microscopy. The results indicated that the strength and the average vickers micro-hardness of composites improved by increasing the volume content of TiO₂ particles and the amount of their elongation and bonding strength decreased significantly.

• Journal of the Korean Society of Food Culture
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• v.24 no.3
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• pp.308-314
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• 2009

In this study, we examined the composition of catechins, theaflavins and alkaloids in leaves during processing to fermented black tea, which is produced by withering, roll breaking, and fermentation of Korean Yabukida tea plant. In addition, we determined the optimal conditions for the production of fermented black tea. The average moisture content in fresh leaves was 70.85%, which dropped to 3.07% in fermented black tea at the last stage of production. When the leaves were analyzed by HPLC, seven types of catechins, four types of theaflavins and three types of alkaloids were identified. The levels of catechins, theaflavins, and alkaloids were then evaluated after being processed into fermented tea. From these experiments, we found that the level of theaflavins, which determines the property of the tea, increased during fermentation. This effect resulted from the change in EGCG, ECG, EGC, EC during the process of fermentation. We also found that the maximal amount of theaflavins was created after 1-2 hours of fermentation. Thus, our results imply that the best condition for producing fermented black tea would be to ferment for 1-2 hours.

• Korean Journal of Environmental Biology
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• v.34 no.4
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• pp.223-232
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• 2016

Drought is one of important environmental stress for plant. Drought has deleterious effect to plant growth including maize (Zea mays L.) such as vegetative and/or reproductive growth, root extension, photosynthesis efficiency, flowering, anthesis-silking interval (ASI), fertilization, and grain filling. In this study, we screened drought tolerant maize in 21 cultivars from different sources, sixteen NAM parent lines (B73, CML103, CML228, CML247, CML277, CML322, CML333, CML69, Ki11, Ki3, Ky21, M37W, Mo18w, NC350, Oh43 and Tx303), four Korean hybrids (Cheongdaok, Gangdaok, Kwangpyeongok and Pyeonganok) and one Southeast Asian genotype (DK9955). Drought stress (DS) index was evaluated with leaf rolling score at seedling stage and ASI at silking date. The leaf rolling scoring of CML228, DK9955 and Ki11 were determined 1.28, 1.85, 1.86, respectively. However, M37W, Kwangpyeongok, B73 and NC350 were determined over the 3. ASI analysis revealed that CML228, CML103, Cheongdaok, NC350, B73, CML322, Kwangpyeongok and Ki11 are represented less than 5 days under DS and less than 3 days of difference between DS and well-watered (WW), but CML69, Ki3, Pyeonganok, M37W, Mo18w and Gangdaok were represented more than 10 days under DS and more than 8 days of difference between DS and WW. Multi-Dimensional Scaling (MDS) analysis determined CML228, Ki11, and CML322 were regarded as drought tolerance cultivars. Eventually, Ki11 showed genetic similarity with Korean cultivars by QTL analysis and MDS analysis. Ki11 has a potential for development of drought tolerance maize with Korean cultivars.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.680-689
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• 2011

A dynamic analysis procedure is developed to provide a comprehensive estimation of the dynamic response spectrum for locomotive's wheels running over a Pre-Stressed Concrete (PSC) box girder bridge on the Korea high speed railway. The wheel force spectrum with the bridge behavior are analyzed as the dynamic procedure for various running speeds (50~450km/h). The high-speed railway locomotive (KTX) is used as 38-degree of freedom system. Three displacements(vertical, lateral, and longitudinal) and three rotational components (pitching, rolling, and yawing). For one car-body and two bogies as well as five movements except pitching rotation components for four wheel axes forces are considered in the 38-degree of freedom model. Three dimensional frame element is used to model of the PSC box girder bridges, simply supported span length of 40m. The irregulation of rail-way is derived using the exponential spectrum density function under assumption of twelve level tracks conditions based on the normal probability procedure. The dynamic responses of bridge passing through the railway locomotive with high-speed analyzed by Newmark-${\beta}$ method and Runge-Kutta method are compared and contrasted considering the developed models of bridge, track and locomotive comprehensively. The dynamic analyses of wheel forces by Runge-Kutta method which are able to analyze the forces with high frequency running on the bridge and ground rail-way are conducted. Additionally, wheel forces spectrum and three rotational components of vehicle body for three typical running speeds is also presented.

• Corrosion Science and Technology
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• v.15 no.3
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• pp.141-146
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• 2016

By using Ni-Cr and Co-Cr alloys, porcelain fused to metal (PFM) samples were prepared to examine the interface and the surface corrosion behavior. The potentiodynamic polarization analysis showed that the corrosion current density of Co-Cr alloy ($1.61{\times}10^{-6}A/cm^2$) was three times lower than that of Ni-Cr alloy ($4.83{\times}10^{-6}A/cm^2$) at room temperature. A dental prosthesis consisting of the porcelain fused to Ni-Cr alloy extracted from a patient after approximately four years of usage was examined to assess its resistance to corrosion. OM and SEM images of the metal part revealed a typical pitting corrosion. As compared to porcelain fused to Ni-Cr alloy having a thick layer (${\sim}10{\mu}m$) of oxide at the interface, a relatively thin oxide layer (less than $5{\mu}m$) was formed on Co-Cr alloy, indicating that the interface between Co-Cr alloy and porcelain may have a better adhesion strength than the interface between Ni-Cr alloy and porcelain.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.354-354
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• 2009

We have developed the prototypes of superconducting magnetic separation system with high temperature superconductor wire. This separation filter system consist of magnetized matrix SUS430 wire and acrylic frame. This study introduced rolled steel process coolant wastewater applied superconductor HGMS(High Gradient Magnetic Separation). HGMS treatment have acted high efficient method for various wastewater. We have surveyed superconducting magnetic separation technology and reviewed the status of related industries using applied superconductivity. In our basic preliminary experiment using HGMS, it was made clear that the fine para-magnetic particles in the wastewater obtained from rolling process of steel can be separated with high efficiency. We investigated the ability of magnetic flock formation, which used inorganic materials and polymer coagulants. We had a purpose to remove SS of coolant at steel factory. Maximum coagulation remove rate of SS 98%. Removing ratio of $Fe_3O_4$ fine particles in wastewater showed over than 99% in the wastewater containing magnetic fines after four times of repetition of separation.

• Journal of Sericultural and Entomological Science
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• v.37 no.1
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• pp.86-91
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• 1995

Isolation and pathogenicity of Fusarium spp. from mulberry shoot rot and severity of diseases which were known as bacterial blight were examined on four mulberry varieties in Suwon, Kongju and Chuncheon, A symptom of mulberry shoot rot was initiated long brown spot on young leaves and shoots. It was developed into dark brown spot and produced white mycelia and spores on the diseased symptoms. A symptom of bacterial blight showed leaf rolling and water soaking spot and produced bacterial ooze on leaf and shoot However later stage of upper two types of symptom was hardly distinguished. Severities of shoot rot and bacterial blight were 7.5% and 4.4% in Suwon, respectively. Isolation of Fusarium spp. on shoot rot symptoms was highter than that on bacterial blight symptoms, but isolation of Pseudomonas spp. was higher on bacterial blight symptoms. Trends of pathogenicity of Fusarium spp. and Pseudomonas spp. were similar to inoculation works, and isolations of pathogenic Fusarium spp. from center of symptom was higher than that from 30cm of symptom of all samples in three cultivation areas. Disease severities of shoot rot on variety of Kaeryangppong were 13.9%, 15.9% and 17.2% in Suwon, Kongju and Chuncheon, respectively. However variety of Cheongolppong was highly resistant to shoot rot disease in three cultivation areas.

• Journal of computational fluids engineering
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• v.21 no.4
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• pp.40-45
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• 2016

The numerical simulation has been performed to predict the performance of the fire suppression system for cabin of shipboard enclosure. The present study aims ultimately at finding the optimal parametric conditions of the mist-injecting nozzles using the CFD methods. The open numerical code was used for the present simulation named as FDS (Fire Dynamics Simulator). Application has been done to predict the interaction between water mist and fire plume. In this study, the passenger cabin was chosen as simulation space. The computational domains for simulation in the passenger cabin were determined following the fire scenario of IMO rules. The full scale of the flow field is $W{\times}L{\times}H=4{\times}3{\times}2.4m^3$ with a dead zone of $W{\times}L{\times}H=1.22{\times}1.1{\times}2.4m^3$. The water mist nozzle is installed in ceiling center of 2.3 m height from the floor, and there are six mattresses and four cushions in the simulation space. The combination patterns of orifices to the main nozzle and the position to install nozzles were chosen as the simulation parameters for design applications. From the present numerical results, the centered-located nozzles having evenly combined orifices were shown as the best performance of fire suppression.

• Water Engineering Research
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• v.5 no.2
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• pp.55-68
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• 2004

The GLEAMS (Groundwater Loading Effects of Agricultural Management System, version 3.0) water quality model was used to predict hydrology and water quality and to evaluate the effects of soil types from a cattle-grazed pasture field of Bermuda-Rye grass rotation with poultry litter application as a fertilizer in North Alabama. The model was applied and evaluated by using four years (1999-2002) of field-measured data to compare the simulated results for the 2.71- ha Summerford watershed. $R^2$ values between observed and simulated runoff, sediment yields, TN, and TP were 0.91, 0.86, 0.95, and 0.69, respectively. EI (Efficiency Index) of these parameters were 0.86, 0.67, 0.70, and 0.48, respectively. The statistical parameters indicated that GLEAMS provided a reasonable estimation of the runoff, sediment yield, and nutrient losses at the studied watershed. The soil infiltration rates were compared with the rainfall events. Only high intensity rainfall events generated runoff from the watershed. The measured and predicted infiltration rates were higher during dry soil conditions than wet soil conditions. The ratio of runoff to precipitation was ranging from 2.2% to 8.8% with average of 4.3%. This shows that the project site had high infiltration and evapotranspiration which generated the low runoff. The ratio of runoff to precipitation according to soil types by the GLEAMS model appeared that Sa (Sequatchie fine sandy loam) soil type was higher and Wc (Waynesboro fine sandy loam, severely eroded rolling phase) soil type relatively lower than the weighted average of the soil types in the watershed. The model under-predicted runoff, sediment yields, TN, and TP in Wb (Waynesboro fine sandy loam, eroded undulating phase) and Wc soil types. General tendency of the predicted data was similar for all soil types. The model predicted the highest runoff in Sa soil type by 105% of the weighted average and the lowest runoff in Wc soil type by 87% of the weighted average