Jo Feb 10, 2024
Jon Song Won, a researcher at the Faculty of Materials Science and Technology, prepared carbon nanotube reinforced aluminum composite for wire and cables core using carbon nanotubes.
Nowadays, carbon nanotubes, one of carbon nanomaterials, are widely used as reinforcement materials for various composites due to their superior properties.
Carbon nanotube reinforced aluminum composite wires for wire cables produced by new technology can improve mechanical and electrical properties including tensile strength, elongation, bending number and specific electrical resistance more than conventional aluminum wires, and production of wire cables using low purity aluminum is possible.
The preparation process of carbon nanotube reinforced aluminum composite core for wire cables consists of surface treatment of carbon nanotubes, dissolution of aluminum, addition and dispersion of carbon nanotubes, continuous casting and continuous rolling processes.
In order to examine the effect of carbon nanotubes on the texture and properties of carbon nanotube reinforced aluminum composites for wire cables, he performed a tensile test, a repeated bending test, a hardness test and a microstructure analysis.
He drew the following conclusions.
When the content of carbon nanotube is 0.3%, the tensile strength of carbon nanotube reinforced aluminum matrix composites is 250 MPa and the elongation ratio is 5%.
As the carbon nanotube content increases, the particle size of the composite decreases significantly and the shape turns spherical.
His method is more reasonable and economical than the previous methods as there is no need for new equipment for improving the properties of wire and cable cores.
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Jo Feb 8, 2024
A research team led by Han Jong Su, a section head at the Faculty of Earth Science and Technology, has developed an analysis method of geological structures of irrigation canals and waterway tunnels by magnetic field survey.
Finding out about geological basement is of primary importance for qualitative guarantee of watercourse construction and its safe operation.
Magnetic survey is one of the cheap but speedy and accurate methods.
Magnetic survey based on magnetic susceptibility is considered effective for detecting horizontal and vertical position of boundaries between geological bodies in building a shallow subsurface construction. This method has already contributed to the building of a 100 km watercourse by analyzing the depth and outline of the weathered layers, geological structure and karst.
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Jo Feb 7, 2024
A research team led by Kim Won Ok, a researcher at the Faculty of Information Science and Technology, has developed a system for detailed survey of forest resources whereby detailed indices such as the number, height, species and volume of individual trees can be obtained from UAV RGB images.
Past surveys of forest resources involved many investigators on the spot, but the system makes surveys easier, scientific and rapid only by UAV.
The system consists of two parts ― one is for obtaining orthomosaic images, digital surface model (DSM) and digital elevation models (DEM) from UAV images and the other is for detecting individual treetops and classifying tree species based on these data in a certain area.
To guarantee the quality of UAV images for survey, it is important to properly determine the photographing parameters of UAV, so through lots of photographing and analysis of UAV images she set photographing interval as 2~2.5s, photographing altitude as 70m from the hillside of the area and air speed as 2.5~3m/s.
This system ensures over 85% of treetop detection rate and over 85% of classification accuracy, and reduces labor for survey down to one sixth.
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Jo Feb 6, 2024
Ozone is very good at oxidizing bacteria, viruses, mold and other harmful organic substances existing in water and air by reacting with them.
The strong anti-bacterial effect of ozone is more and more expanding its application, and therefore many industries employ mass output ozone generation technology.
Environmental remediation by industrial application of ozone is a technology that uses germicidal ozone gases to obtain clean air and water and to improve the environment by disinfecting air, water, walls, hand tools, etc. contaminated with bacteria, viruses, organic and inorganic substances.
Many problems arise with industrial application of mass output ozone generators including stability of power supply and generator tube, enhancement of ozone generation efficiency, design of ozone gas mixers for energy efficiency enhancement and rational use of produced ozone, etc.
Won Chol Hyok, a researcher at the Faculty of Physical Engineering, has finally succeeded in making a mass output ozone generator with domestic materials by solving these problems through a lot of efforts.
First, he newly designed a discharge tube of the ozone generator. He chose ozone generation by dielectric barrier discharge and used quartz glass and alumina ceramic as dielectric material. The generator tube was designed to be cooled by water.
Next, power supply and control system were newly designed. He designed a new overvoltage absorption circuit to prevent device breakdown due to back EMF that could occur with increasing power of the ozone generator and made an experimental verification of its characteristics. In order to realize an intelligent control over the system, he used an embedded chip (STM32F series) for a control over power supplies, and adopted a new kind of control algorithm.
Finally, he designed a new type of ozone mixer. The ozone mixer, which is made up of venturi, mixing tank, pump and inlet-outlet pipelines, dissolves ozone into water.
The generator he manufactured can be applied to various fields such as drinking water disinfection, wastewater disinfection, aquaculture, poultry farming and so on.
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Jo Jan 30, 2024
Many practical casting process optimization problems are ascribable to multi-attribute optimization problems with multiple conflicting quality attributes.
Yang Won Chol, a researcher at the Faculty of Materials Science and Technology, has proposed a reasonable multi-attribute optimization and influence assessment methodology of casting process parameters combined with integrated multi-attribute decision making (MADM) and Taguchi method.
The proposed methodology consists of the following steps:
(1) design experiment arrangement based on Taguchi orthogonal array, and measure multiple quality attributes of castings at every experimental trial, (2) calculate comprehensive quality score (CQS) values of the experimental trials using some MADMs, (3) calculate final CQS (FCQS) values of the experimental trials by integrating the CQS values from some MADMs, (4) calculate mean FCQS values of the casting process parameters at different levels, (5) calculate ranges of mean FCQS and influence indices of the casting process parameters, and (6) determine optimal casting process parameters to maximize the comprehensive quality of castings.
To demonstrate its usage and effectiveness, he applied it to one illustration example to determine four optimal casting process parameters such as pouring temperature (PT), degasser amount (DA), holding time (HT) and mould type (MT) for optimizing three quality attributes such as density of casting (D), ultimate tensile strength (UTS) and elongation to fracture (Ef) of A356 Al alloy sand castings.
The proposed methodology could be widely applied to not only casting process optimization but also various advanced manufacturing process optimization problems.
For more information, you can refer to his paper “Multi-attribute optimization and influence assessment methodology of casting process parameters combined with integrated MADM and Taguchi method” in “The International Journal of Advanced Manufacturing Technology” (SCI).
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Jo Jan 26, 2024
Redox flow battery (RFB) is an electrochemical device that stores and releases energy through redox reactions of active ion species in electrolyte. The main advantage of RFB over other electrochemical devices such as lead acid battery and lithium ion battery is that the power system could be made very flexible because of the independence of its power from its energy and that its cost per energy in high-capacity systems is particularly low.
Up to now, there have been developed many kinds of RFBs and they have anolyte and catholyte containing different active ion species. An ion selective membrane is introduced to prevent the active ion species from mixing. During charge and discharge, the anolyte and the catholyte are cycled through their own reservoirs by using pumps, respectively. Examples of RFBs include all-vanadium series, iron-chromium series and bromine-polysulfide series. The ion selective membrane for these RFBs is very expensive and should satisfy very strict requirements for several aspects including ion selectivity, electric conductivity and chemical stability. For this reason, recent works are targeted to using no membranes.
SLFB is acknowledged as a promising battery and it attracts attentions of researchers because it needs no membrane and is cheap. Unlike RFBs, SLFB does not require any ion selective membranes because both the anolyte and the catholyte are the same. Hence, SLFB possesses only one electrolyte reservoir and one flow canal, thus making its design simple. Moreover, electrolyte cross through the medium of diaphragm never exists and the possibility of electrolyte leaking diminishes because of a small number of cell components.
Kim Ju Song, a researcher at the Faculty of Chemical Engineering, has suggested HBF4 and Pb(BF4)2 as the electrolyte of SLFB because it is commercially favorable with a low cost and has a high solubility of lead and conductivity compared to the methylsulfonic acid (MSA), and he has investigated the availability of fluoroboric acid and lead fluoroborate prepared with recovered lead as the electrolyte of SLFB.
He first measured the average cell efficiency, average quantum efficiency and average voltage efficiency of the SLFB using lead fluoroborate prepared with recovered lead. Then, he compared them with those of conventional MSA electrolyte. As many as 30 times of charge/discharge tests showed that the average cell efficiency, average quantum efficiency and average voltage efficiency of the recovered lead electrolyte are much better than the efficiencies obtained in methylsulfonic acid electrolyte, and that the average charge/discharge efficiency was 87 % and there was no significant decrease in the performance during charge/discharge cycles, thus proving the availability of electrolyte prepared with recovered lead for SLFB.
You can find the details in his paper “Electrochemical properties of electrolyte for lead fluoroborate redox flow battery prepared with recovered lead” in “Journal of Saudi Chemical Society” (SCI).
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