• Journal of Korean Ophthalmic Optics Society
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• v.9 no.1
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• pp.145-159
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• 2004

A mathematical model and its computer solution program were proposed to analyze the motion of contact lenses which are being subject to lid-blinking. The equation was derived by incorporating an acceleration induced lid's force exerting on the contact lens, the viscous damping resistance in the tear layer beneath the lens and the sliding frictional force between the lid and the contact lens surface into the formulation of differential equation describing the vibration. The model predicts the time-dependent displacement from the equilibrium postion during/after the blinking. During the blinking, as the time for the completion of one cycle of blinking decreases the off-the-equilibrium displacement of contact lens increases while the decrease of diameter in the contact cause the opposite effect. It is found that lid pressure exerting on the lens cause an insignificant lens displacement from the equilibrium position. After blinking the frequency of damped oscillation of contact lens decreases as the diameter of lens increases, due to the incresed surface while the reduced blinking time does not cause a significant frequency change. This is because that driving force for the contact lens movement posterior to blinking is the capillary-induced force not the lid force.

• Membrane Journal
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• v.18 no.1
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• pp.7-25
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• 2008

Sodium dodecyl sulfate, which was anionic surfactant, at a concentration higher than its critical micellar concentration was added to calcium solution for forming micelles. Then aggregates were formed by adsorption or binding of calcium ions on the surface of micelles, and gathering between them, and then rejected by two kinds of ceramic membranes to remove calcium ions. As result, rejection rates of calcium were higher than 99.98%. And in our experimental range the higher TMP trended to increase the resistance of membrane fouling ($R_f$), total permeate volume ($V_T$), dimensionless permeate flux ($J/J_o$) and permeate flux (J) because TMP was driving force. And we investigated effects of $N_2$-back-flushing time and filtration time, that was back-flushing period, during periodic $N_2$-back-flushing on ceramic membranes. As result, optimal BTs for NCMT-623l ($0.07{\mu}m$ pore size) and NCMT-7231 membrane ($0.10{\mu}m$) were 10 sec and 15 sec, respectively. Also, optimal FT was 5 min for both membranes, and the frequent $N_2$-back-flushing could decrease membrane fouling effectively. Then, the optimal conditions resulting from our experiments for synthetic calcium solution were applied to groundwater using as washing process of soymilk package. As result, rejection rates of calcium were higher than 99.98%.

• International Journal of Highway Engineering
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• v.6 no.1 s.19
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• pp.1-11
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• 2004

This study tries to propose the most effective pavement texture method through the performance evaluation of variable texture methods. Noise 2$\sim$3dB is reduced in the section of uniform space 18m longitudinal tinning. This result is proved by comparing the magnitude of noise in two sections. The noise of 26mm longitudinal firming section is greater than that of 18mm section by 2$\sim$3dB(A). The skid resistances measured in all test section show the reasonable results. The roughness or all the test sections satisfies AASHTO roughness standard (PrI 16cm/km). The result or questionnaire survey about driving quality shows that the longitudinal tinning is the most effective method. As the result of a visual measurement, it is proved that the section applied uniform space 26mm longitudinal tinning and the general section applied uniform space 26mm transverse tinning could drain water effectively. As the result of analysis with the ranking method, the 18mm longitudinal tinning in selected as one of the most effective tinning methods. In addition, 26mm longitudinal tinning, random space transverse tinning, and transverse drag are selected in order.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.3
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• pp.243-254
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• 2014

It is essential to predict the coil temperature under over load and over speed conditions for reliability in high speed low torque surface mounted PM synchronous motors(SPM). In the present study, the losses and coil temperature are measured under rated condition and calculated under over speed and over load conditions in the three different motors with 35PN440, 25PN250 and 15HTH1000. The heat transfer modeling has been performed based on acquired losses and temperature. The difference of coil temperature between heat transfer modeling and experiment is less than 6.4% under no load, over speed and over load conditions. Subsequently, the coil temperature of the motor with 15HTH1000 is 84.4% of the coil temperature of the motor with 35PN440 when speed is 0.9 and load is 3.0. The output of motor with 15HTH1000 is 85.2% greater than the output of the motor with 35PN440 when the dimensionless coil temperature is 1.0.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.276-280
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• 2010

Copper(Cu) as an interconnecting metal layer can replace aluminum (Al) in IC fabrication since Cu has low electrical resistivity, showing high immunity to electromigration compared to Al. However, it is very difficult for copper to be patterned by the dry etching processes. The chemical mechanical polishing (CMP) process has been introduced and widely used as the mainstream patterning technique for Cu in the fabrication of deep submicron integrated circuits in light of its capability to reduce surface roughness. But this process leaves a large amount of residues on the wafer surface, which must be removed by the post-CMP cleaning processes. Copper corrosion is one of the critical issues for the copper metallization process. Thus, in order to understand the copper corrosion problems in post-CMP cleaning solutions and study the effects of DC biases and post-CMP cleaning solution concentrations on the Cu film, a constant voltage was supplied at various concentrations, and then the output currents were measured and recorded with time. Most of the cases, the current was steadily decreased (i.e. resistance was increased by the oxidation). In the lowest concentration case only, the current was steadily increased with the scarce fluctuations. The higher the constant supplied DC voltage values, the higher the initial output current and the saturated current values. However the time to be taken for it to be saturated was almost the same for all the DC supplied voltage values. It was indicated that the oxide formation was not dependent on the supplied voltage values and 1 V was more than enough to form the oxide. With applied voltages lower than 3 V combined with any concentration, the perforation through the oxide film rarely took place due to the insufficient driving force (voltage) and the copper oxidation ceased. However, with the voltage higher than 3 V, the copper ions were started to diffuse out through the oxide film and thus made pores to be formed on the oxide surface, causing the current to increase and a part of the exposed copper film inside the pores gets back to be oxidized and the rest of it was remained without any further oxidation, causing the current back to decrease a little bit. With increasing the applied DC bias value, the shorter time to be taken for copper ions to be diffused out through the copper oxide film. From the discussions above, it could be concluded that the oxide film was formed and grown by the copper ion diffusion first and then the reaction with any oxidant in the post-CMP cleaning solution.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.2
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• pp.29-35
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• 2017

In this paper, we investigated a manufacturing process of metal micro-wire interconnection on submillimeter diameter catheter. Over the years, flexible electronic researches have focused on flexible plane polymer substrate and micro electrode manufacturing on its surface. However, a curved polymer substrate, such as catheter, is very important for medical application. Among many catheters, importance of submillimeter diameter steerable catheter is increasing to resolve the several limitations of neurosurgery. Steering actuators have been researched for realizing the steerable catheter, but there is no research about practical wiring for driving these actuators. Therefore we developed a new manufacturing process for metal micro-wire interconnection on submillimeter diameter catheter. We designed custom jigs for alignment of the metal micro-wires on the submillimeter diameter catheter. An UV curing system and commercial products were used to reduce the manufacturing time and cost; Au micro-wire, UV curable epoxy, UV lamp, and submillimeter diameter catheter. The assembled catheter was characterized by using an optical microscope, a resistance meter, and a universal testing machine.

• Journal of Biosystems Engineering
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• v.25 no.3
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• pp.213-220
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• 2000

Grafting of fruit-bearing vegetables has been widely used to increase the resistance to soil-borne diseases, to increase the tolerance to low temperature or to soil salinity, to increase the plant vigor, and to extend the duration of economic harvest time. After grafting, it is important to control the environment around grafted seedlings for the robust joining of a scion and rootstock. Usually the shading materials and plastic films are used to keep the high relative humidity and low light intensity in greenhouse or tunnel. It is quite difficult to optimally control the environment for healing and acclimation of grafted seedlings under natural light. So the farmers or growers rely on their experience for the production of grafted seedling with high quality. If artificial light is used as a lighting source for graft-taking of grafted seedlings, the light intensity and photoperiod can be easily controlled. The purpose of this study was to develop a prototype system for the graft-taking enhancement of grafted seedlings using artificial lighting and to investigate the effect of air current speed on the distribution of air temperature and relative humidity in a graft-taking enhancement system. A prototype graft-taking system was consisted by polyurethane panels, air-conditioning unit, system controller and lighting unit. Three band fluorescent lamps (FL20SEX-D/18, Kumho Electric, Inc.) were used as a lighting source. Anemometer (Climomaster 6521, KANOMAX), T-type thermocouples and humidity sensors (CHS-UPS, TDK) were used to measure the air current speed, air temperature and relative humidity in a graft-taking system. In this system, air flow acted as a driving force for the diffusion of heat and water vapor. Air current speed, air temperature and relative humidity controlled by a programmable logic controller (UP750, Yokogawa Electric Co) and an inverter (MOSCON-G3, SAMSUNG) had an even distribution. Distribution of air temperature and relative humidity in a graft-taking enhancement system was fairly affected by air current speed. Air current speed higher than 0.1m/s was required to obtain the even distribution of environmental factors in this system. At low air current speed of 0.1m/s, the evapotranspiration rate of grafted seedlings would be suppressed and thus graft-taking would be enhanced. This system could be used to investigate the effects of air temperature, relative humidity, air current speed and light intensity on the evaportranspiration rate of grafted seedlings.

• Membrane Journal
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• v.12 no.1
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• pp.8-20
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• 2002

In this study using $N_2$-back flushing, which wwas not the general back-flushing method of membranes, the discharged wastewater from a paper plant was filtrated by 4 kinds of tubular carbon ceramic ultrafiltration membranes. We could in vestigate effects of $N_2$-back flushing period, transmembrane pressure (TMP)and flow rate and find optimal operating conditions. The $N_2$-back flushing time (BT) was fixed at 40 sec, filtration times (FT) were changed in 4~32 min, TNP in $1.0~3.0kg_f/cm^2$ the flow celocities in 0.53~1.09cm/s. The optimal conditions were discussed in the viewpoints of dimensionless permeate flux ($J/J_0$), toal permeate volume ($V_T$) and resistance of membrane fouling ($R_f$). Optimal back-flushing period was BT/FT=0.167 (FT=8 min ), in which more $V_T$ was obtained than that in BT/FT=0.083 (FT=4 min) which was the most friquent back-flushing condition. Then rising TMP should increase the driving force, and more $V_T$ could be accumulated. And rising flow rate should decrease membrane fouling increase permeate flux, and more $V_T$could be produced. Average rejection rates of pollutants were higher than 95% for turbidity and 45~83% for $COD_{Cr}$, but rejection rates of total dissolved solid (TDS) were lower than 10%.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.908-914
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• 2017

In this study, we developed a system that automatically removes the scale in the piping by using electrolysis principle in order to solve the cooling performance of the refrigeration and air conditioning system by acting as heat resistance in the heat transfer process by forming the scale in the heat exchanger for refrigeration air conditioning. We want to check the performance through experiments. Therefore, by circulating the treated water using the principle of electrolysis without stopping the system, Ca, Mg and $SiO_2$ are precipitated in the form of solids and discharged to the outside of the pipe system, thereby preventing scale formation in the pipe and removing the scale. Thereby maintaining the heat transfer performance of the pipe. As a result of the experiment, the heat transfer rate of the scaled pipe was 86.66% when the heat transfer rate of the new pipe was 100, and the heat transfer rate was recovered to 90.5% when the scaled pipe was operated for 1 month. The heat transfer rate recovered to 97.86% when driving for two months and to 98.72% for three months. It was confirmed that the scaling effect of the scale formed in the piping was understood in a relatively short experiment period, and the heat transfer performance was also influenced.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.50-57
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• 2022

Ti-In-Zn-O (TIZO)/Ag/TIZO multilayer transparent electrodes were prepared on glass substrates at room temperature using RF/DC magnetron sputtering. Obtained multilayer structure comprising TIZO/Ag/TIZO (10 nm/10 nm/40 nm) with the total thickness of 60 nm showed a transmittance of 86.5% at 650 nm and a sheet resistance of 8.1 Ω/□. The multilayer films were expected to be applicable for use in energy-saving smart window based on polymer-dispersed liquid crystal (PDLC) because of their transmittance properties to effectively block infrared rays (heat rays). We investigated the effects of the content ratio of prepolymer, the thickness of the PDLC coating layer, and the ultraviolet (UV) light intensity on electro-optical properties, and the surface morphology of polyester acrylate-based PDLC systems using new TIZO/Ag/TIZO transparent conducting electrodes. A PDLC cell with a thickness of 15 ㎛ PDLC layer photocured at an UV intensity of 1.5 mW/cm² exhibited good driving voltage, favorable on-state transmittance, and excellent off-haze. The LC droplets formed on the surface of the polymer matrix of the PDLC composite had a size range of 1 to 3 ㎛ capable of efficiently scattering incident light. Also, the PDLC-based smart window manufactured using TIZO/Ag/TIZO multi-layered transparent electrodes in this study exhibited a light brown, which will have an advantage in terms of aesthetics.