Jo Jul 24, 2022
Jang Ui Jun, a researcher at the Faculty of Earth Science and Technology, has developed a plasma water treatment device, an experimental device for education and research, which enables experiments for improving the quality of groundwater and surface water to be conducted in combination with laboratory conditions and field characteristics, and verified its utility.
In general, water treatment devices for improving the quality of groundwater or surface water include chlorine sterilizers, various kinds of filters such as activated carbon filters, UV disinfecters, ozone sterilizers and plasma sterilizers.
A plasma water treatment device, one of advanced water treatment devices, is able to overcome the limitations of the above-mentioned water treatment devices and conduct sterilization and water treatment comprehensively and efficiently by means of active chemical species as well as ultraviolet and ozone.
It consists of a power supply unit for geneartion of pulsed high voltage, a plasma reactor, a water sample tank and a water control valve and a tank for treated water.
Using this plasma water treatment device, we can do experiments the aim of which is to reduce the contents of various water quality indicators contained in contaminated surface water or groundwater, especially some elements such as Fe2+, to remove bacteria including Escherichia coli, and to improve water quality.
This device, compared to the aeration method, helps increase the rate of oxidation of Fe2+ ions in water by more than 2.5 times and raise recognition effect by providing visual effects.
...
Jo Jul 21, 2022
In recent decades, temperature/pH dual responsive amphiphilic polymers have attracted the interest of researchers as they can perform certain functions by changing hydrophilic and hydrophobic balances corresponding to changes in the external environment. These types of amphiphilic polymers are very useful, especially for drug delivery, tissue engineering, biotechnology and other related fields.
However, most temperature/pH dual responsive polymers are prepared with petroleum chemical monomers as main raw material. This results in its limited applicability due to their toxicity and poor biocompatibility. In recent years, many researchers have focused their work on biomass derivatives to improve the temperature/pH dual responsiveness of polymers.
Jong Kwang Hyok, a section head at the Faculty of Applied Chemistry, has successfully synthesized a novel type of temperature/pH dual responsive polymer, PyHES (2-hydroxy-3-(2-propynyloxy) propyl hydroxyethyl starch)-DMAET (2-(dimethylamino) ethanethiol).
He prepared temperature-responsive polymer PyHES via hydrophobic modification of hydroxyl groups in hydroxyethyl starch (HES) with propynylglycidyl ether (PGE); subsequently, he connected a pH-responsive tertiary amine group to the propynyl group via a thiol-yne click reaction.
As PyHES-DMAET has pH-responsive amino groups and hydrophobic thioether groups, its aqueous solution exhibits excellent temperature/pH dual sensitivity, i.e., a good transference between hydrophobic (or self-assembly) and hydrophilic (or swelling) states resulting from changes in temperature/pH values. These properties can be exploited for hydrophobic drug release.
The experimental results showed that drug release reached 96% at 37℃ and a pH of 6.5, and that the drug-loading capacity of PyHES-DMAET increased with the degree of substitution (DS) of the hydrophobic propynyl groups in the PyHES, and the maximum drug-loading capacity for doxorubicin (DOX) achieved in the study was 33 wt%.
More information about this is in his paper “Temperature and pH dual responsive 2-(dimethylamino)ethanethiol modified starch derivatives via a thiol-yne reaction for drug delivery” presented to SCI Journal “Colloid and Polymer Science”.
...
Jo Jul 19, 2022
Pak Song Chol, a researcher at the Faculty of Physical Engineering, has developed an air purifier by making use of the characteristics of non-equilibrium plasma.
The device employs non-thermal plasma, anti-bacterial nano material, ultra-violet ray(UV) and anion, which enables sterilization and air-purification in a pure physical mechanism without recourse to any chemical disinfectant harmful to human body.
The plasma air purifier consists of pre-filter, non-equilibrium plasma generator, activated carbon filter, nano photo-catalyst grid, ultraviolet ray sterilizer, anion generator, etc.
In the non-equilibrium plasma generator, high voltage of 10~15kV should be applied between the line or needle electrode and the plane electrode so that the nuclei of various microorganisms can be destroyed and burnt, and particles be ionized and absorbed. This ensures about 90% of sterilization and dust-collection efficiency for particles smaller than 0.1㎛ in size.
In the nano photo-catalyst grid, UV rays, electrons, excited molecules, oxygen radicals (O2.) collide with TiO2 on the nano-TiO2 grid and activate it. Various chemical reactions take place on the activated TiO2, resulting in formation of hydroxyl radicals(OH.) and activated oxygen atoms with strong organic destruction and sterilization ability.
The ultraviolet sterilizer uses a UV lamp emitting UV rays of 253.7nm in wavelength with high germicidal power.
The anion generator produces a great number of air anions that are good for human health and effective in purification of atmospheric wastes, nitrogen oxides and smoke, neutralizes charged particles and eliminates room odour in an effective way.
Compared with fiber-based filters (95% dust collection rate for particles larger than 0.5μm in diameter) in terms of sterilization property, the plasma air purifier can sterilize more than 95% of room air within an hour and over 98% within two hours.
With the introduction of this device to production processes of foodstuff, various electronic products such as IC and medical appliances, to the interiors of buildings of medical facilities like hospitals, and to large-scale cultural and welfare facilities crowded with people, you will purify the air and guarantee hygienic safety and quality of products.
...
Jo Jul 18, 2022
The research team led by Pae Ho Rim, a section head at the Faculty of Shipbuilding and Ocean Engineering, has developed a program for checking structural designs of ships.
This program will put checking of structural designs of ships on an IT basis, thus improving checking accuracy and reducing time and effort for checking.
This program consists of input module and check module for structural design.
In the input module, structural design data for checking are input with substructures of a ship hull as a unit. Design data for substructures include information about the locations and dimensions of plates and stiffeners, components of the substructure.
Check module is composed of 3 parts; knowledge base, rule check and redundant size check. In addition, it has an automatic making function of structural design check report. Rules and examples of design check are saved in the knowledge base.
At present, checking of structural design of ships is being conducted manually by many experts in naval architecture, involving a great deal of time and effort.
In contrast, this program needs only one expert to finish design checking with 100% accuracy within 2 days.
...
Jo Jul 17, 2022
The research group led by Ri Ju Hyok, a section head at the Faculty of Heat Engineering, has succeeded in designing and manufacturing a cascade cryogenic refrigerator for new material development and cryogenic environmental experiment.
Operated by the cascade refrigeration cycle, it is composed of two refrigeration cycles ― hot cycle and cold cycle. In the hot cycle, middle refrigerants are used, and in the cold cycle, low refrigerants are used. Each cycle is an individual refrigeration system using one refrigerant each.
Evaporation of the refrigerant in the hot cycle is used for condensation of the refrigerant in the cold cycle. The two cycles are connected by an evaporator-condenser that functions as a condenser for the cold cycle and as an evaporator for the hot cycle. The heat gained from the cold cycle is transferred to the refrigerant in the hot cycle that transfers the heat to the environment. The hot cycle is composed of a hot cycle compressor, an air cooling condenser, a throttle valve and an evaporator-condenser, etc. while the cold cycle is made up of a cold cycle compressor, a capillary tube, an evaporator, an expansion vessel, an evaporator-condenser, etc.
An evaporator-condenser can be designed and manufactured as a high efficiency plate or a dual tube heat exchanger.
This cascade cryogenic refrigerator, which provides a temperature range of -40℃~-160℃, has wide applicability to several fields including machine, chemical and electronic industries, biological and metallic material engineering, public health, national defence and sports.
...
Jo Jul 8, 2022
Cha Myong Song, a researcher at the Faculty of Electrical Engineering, has completed the principle and method for stabilizing voltage from no-load state to normal load state.
Although existing 3 harmonics exciting synchronous generators realized the stabilization of voltage by changing the structure of pole shoes, they failed to provide a reasonable value range of 3 harmonics flux density.
According to the new method, 3 harmonics flux density and the output power of 3 harmonics winding and exciting winding are decided and the windings are connected to exciting regulation resistors in order to improve the efficiency of the generator and decrease voltage changing rate. The 3 harmonics exciting synchronous generator, which consists of 1 harmonics winding, 3 harmonics winding, full-wave recification circuit, exciting winding, exciting regulation resistor, guarantees enough self exciting and decreases voltage changing rate by regulating the parameters of 3 harmonics winding, exciting winding, pole structure and exciting regulation resistors.
If 3 harmonics flux density is much higher than 1 harmonics flux density, voltage waveform gets non-sinusoidal, and if much lower, self exciting may not occur. Therefore, 3 harmonics flux density should be defined within the range of 4~6% of 1 harmonics flux density by the field analysis method.
The parameters of 3 harmonics winding and exciting winding should be defined to be reasonable by the equivalent circuit method.
The efficiency of the generator and the exciting stability depend on the designs of 3 harmonics winding and exciting winding.
The 3 harmonics exciting synchronous generator is low in manufacturing cost and ensures enough self exciting in it. Its voltage changing rate decreases to 1.4% and its efficiency improves to 90.9%.
This method of voltage stabilization is also applicable to small independent gas generators.
...
