Jo May 16, 2023
The maximum operation temperature of a heater is a very important factor for conserving the quality and performance of the heater. Experimentally, it is difficult, expensive and time-consuming to measure the temperature field distribution of materials, but numerical simulation can easily solve such problems.
Kim Yong Il, a researcher at the Nano Physics Engineering Institute, has found through a simulation that the maximum operation temperature of a laser-induced graphene (LIG) heater with a 1.0cm2 heated area which is written directly on a polyimide film is about 225℃ at an electrical power density of 1.4W/cm2 and a response time of 8s.
The numerical simulation was computed on COMSOL Multiphysics 5.3. He produced a 3D finite element model and boundary conditions of a heat conduction equation in order to simulate the temperature field distribution of an LIG heater by electrical power.
The simulation results were in agreement with the experimental results of previous researches.
The simulation showed that the maximum operation temperature of an LIG heater which is written directly on exposed polyimide substrate can be predicted at any power density and response time without any experiments.
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Jo May 14, 2023
A research team led by Jang Tae Il, a researcher at the Nano Physics Engineering Institute, has developed an ozonated water generator by water electrolysis.
Ozone has widely been applied to wastewater treatment and drinking water disinfection due to its significant oxidative property. Especially, O3 dissolved water, ozonated water, is used as a disinfector. There are two methods to produce ozonated water: dissolving gas phase ozone in water and on-site generation by water electrolysis. The advantage of water ozonation by water electrolysis is higher concentration of ozone than other methods.
To make an ozonated water generator by water electrolysis, they developed a nanocomposite catalyst whose ozone evolution efficiency is significant, and determined the factors that affect the efficiency.
The generator consists of an electrolytic device and a power supply unit.
The electrolytic device is a couple of electrodes where an anode and a cathode are spaced. When it is immersed in a water tank and connected to the power source, ozone, oxygen and hydrogen are evolved. Here, α-PbO2, F-doped β-PbO2 and graphene electrodeposited on the stainless steel mesh are used as an anode, and a pristine stainless steel mesh as a cathode.
Galvanostatic switching power supply is used as a power source.
They determined various factors such as an electrode gap, the temperature of electrolyte, current density, kinds of ions in tap water, etc. affecting the ozone evolution by water electrolysis, and they guaranteed generation of up to above 15mg/L of dissolved ozone concentration of ozonated water at the optimum operating condition.
This technology will widely be used in various fields such as wastewater treatment and disinfection for prevention.
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Jo May 8, 2023
Pak Yong Ho, a researcher at the Nano Physics Engineering Institute, by using a polymer jet fluid model by CFD, has calculated the velocity field distribution in it to determine a uniform velocity profile and determined a new curved profile of the collector to obtain uniform fiber in an arched multi-nozzle electrospinning device.
Electrospinning is a method of producing micro fibres by injecting polymer solutions in electrostatic fields. Microfibers obtained by electrospinning have widely been applied in various fields, due to their superior properties such as very small diameter, high porosity, large specific surface area, etc.
Recently, highly productive electrospinning methods such as multi-nozzle electrospinning and nozzle-free electrospinning have been proposed. Multi-nozzle electrospinning is a method of overlapping many nozzles, so it is difficult to realize stable and continuous spinning as nonuniform distribution of electric fields at the nozzle tip creates corona discharge by strong electrical interaction between the nozzles.
Based on the calculation of the flow rate in angular jet flow through a CFD simulation of the jet flow in an electrostatic field, he determined the contour shape of the collector plate obtained by the uniform velocity plane. Then, he drew the curve equation of the curved collector which can obtain uniform diameter electrospun fiber in the multi-nozzle electrospinning system where an arched multi-nozzle and a curved collector are combined. After that, he found the curve equation of the curved collector to obtain uniform electrospun nanofiber with the diameter of 131.3nm, which is suitable for preparing a nanofiber ionexchange membrane for electrodialysis.
The curve equation of the collector profile for obtaining the electrospun nanofiber (131.3nm in diameter) in an arched multi-nozzle electrospining device is y=-2-12x3+0.002x2-2-8x-91.991.
It means that a new methodology to obtain uniform electrospun fibers with arbitrary diameters in a multi-nozzle electrospinning device without additional means was developed.
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Jo May 5, 2023
Ro Myong Gum, a researcher at the Nano Physics Engineering Institute, has investigated the effects of laser power on the reduction of graphene oxide by 355nm UV impulse laser.
Graphene oxide, which is chemically exfoliated from graphite, a precursor of graphene, is a suitable material for producing graphene in large quantities. However, reduction is necessary because graphene oxide is an insulator.
In the past, a chemical method, heating treatment, microwave and plasma, etc. were applied to the reduction of graphene oxide, but nowadays graphene oxide reduction by laser is under study.
She performed some experiments on the thermodynamic change of a graphene oxide film when graphene oxide is irradiated by 355nm UV impulse laser, and confirmed the impact factors of laser on the reduction.
As compared with conventional reduction methods, the proposed method is simple in process and enables reduction and mask at the same time, so it will prove the most suitable for manufacturing micro-electronic devices.
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Jo May 2, 2023
U Yong Nam, a section head at the Robotics Institute, has made a study of the mobile properties of an omnidirectional AGV with Mecanum wheels.
A Mecanum wheel, which is designed to move a vehicle in any direction, consists of a series of rollers attached to its circumference.
ADAMS was used for the simulation, where he analyzed the motion in X and Y directions, turning round on the position and oblique.
The simulation result showed that the velocity error in the X-direction movement and turning round on the position of the AGV is small and stabilization is fast, and vice-versa in the Y-direction movement and oblique.
The results verified that an AGV with four Mecanum wheels can operate in a static state.
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