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 13, 2022
Koryo ceramics are representative of ceramics art of the Middle Ages, holding a prominent position in the world medieval history of ceramics.
Koryo ceramics are priceless cultural wealth that demonstrates the extraordinary artistic talents and the high level of science and technology of the Korean nation.
Koryo ceramics are divided into celadon, white, black, brown and crimson according to their colours while they are classified into embossed design, engraved design, perforated design, scratched design, inlaid design, disguised design, powdered gold design, etc. in terms of ornamental techniques. The most produced and excellent of all these were celadon ceramics among which inlaid-design celadon ceramics reached the acme of ceramic craftsmanship, attracting admirations from people all over the world.
Koryo ceramics were made in almost every part of the country except northern mountainous areas. The most typical areas were Kaesong and its vicinity, capital of Koryo Feudal State, Kangso in South Phyongan Province, Phyongsan in North Hwanghae Province, Songhwa, Ongjin and Haeju in South Hwanghae Province, Ryoju, Ansong, Koyang, Kwangju and Kanghwa in Kyonggi Province, Kongju in South Chungchong Province, Taedok District in Taejon City, Puan and Jonan in North Jolla Province, Kangjin and Mua in South Jolla Province, Koryo and Kyongju in North Kyongsang Province, etc.
One of the excellent characteristics of Koryo ceramics is, first of all, their unique colours.
The most beautiful and famous of all those various and harmonious colours is jade. Jade green, which looks like green shining against a white pebble in the clear water, reflects the sentiments of life of the Korean people, who are in favour of cheerful, honest, gentle and graceful manner. The discovery of colours, especially jade green that is obtained from reducing flames of iron contained in clay is attributable to a long period of practice and the high level of development of science and technology. Ceramics in this colour was called jade ceramics (celadon ceramics) and became a synonym for Koryo ceramics among the world people. Jade ceramics were first made in the first half of the 10th century.
Another superior characteristic of Koryo ceramics is the variety of their original shapes.
Koryo ceramics are of a variety of types ― glass, brass bowl, bottle, bowl, plate, kettle, jug, flower pot, censer, fire pot, make-up box, container for inkstone water, inkstone, brush holder, etc. and they are in different shapes. In particular, object-shaped ceramics that imitated animals, plants and humans are charming and novel. The objects include humans like civil officials in official outfits, children, etc., animals such as lions, giraffes, fish, turtles, dragons, phoenixes, rabbits, tigers, monkeys, mandarin ducks, ducks, pigeons, etc., and plants including melons, pomegranates, bamboo shoots, lotus flowers, bottle gourds, etc. With softly curved outlines, they look cheerful, slim and harmonious as a whole.
Yet another feature of Koryo ceramics is their diverse and outstanding designs. What makes Koryo ceramics even more famous is their inlaid designs along with other decorative designs by a pictorial technique by brush and sculptural techniques like engraving, embossing, perforating, scratching, stamping, etc. Such elegant looks of elaborately inlaid designs that show faintly through transparent coating of clay are found only on Koryo ceramics.
With the organic combination of all these distinguished colours and designs and original shapes, Koryo ceramics are well-known to the world for their elegance.
In those days, Koryo ceramics were widely exported, thus achieving world-wide fame. They exerted a great influence upon the development of ceramic workmanship of both our country and the neighbouring countries in the later years. In this sense they deserve to be called treasures of all mankind.
Indeed, Koryo ceramics, which are regarded as treasures by the world people for their pre-eminently beautiful colours, designs and shapes and show the extraordinary talents and beautiful and noble sentiments of the Korean people, are outstanding creations of the Korean nation and great treasures of the country.
...
Jo Jul 12, 2022
Ri Kwang Hwi, a researcher at the Faculty of Mechanical Science and Technology, has been improving the practical scientific research capability of postgraduate students in close combination of scientific research and education based on a virtual factory.
Universities and research institutes in many countries are in contact with production enterprises so as to bring education and scientific research close to production, resulting in great changes in teaching methods. In particular, they are getting rid of cramming methods to introduce heuristic, inductive and discussion teaching methods.
Introduction of virtual factories allows the contents of selective subjects in postgraduate course to be organized in conformity with the world trend of developing education and pedagogical requirements.
The first step is to let students grasp the actual conditions of the virtual factory in order to combine scientific research and education.
Let’s take “expert system for process planning” as an example. Here the first thing they have to do is to visit the technical department to investigate the work of the technical preparing office, where they learn about the technical process sheet and technical guidance. Then in the technical equipment office they check fixture design and tool design. The next thing to do is to find out about production scheduling in the production department. All these are conducted at the virtual factory, not an actual one.
In real situations, comprehensive investigation is impossible as they do not have everything needed for scientific research and education. This requires the model of a virtual factory, which involves a lot of effort.
The next step is to let students inquire into the trend of development of science and technology and scientific foundations in every element of the production site. Of course, profound scientific inquiry may be impossible, but at least they can get the gist, for they have already finished basic technology subjects and major subjects in undergraduate course.
This part enables them to select a research seed in the course of studying and investigating deep into literature and the world trend of development to break through the cutting edge.
The last step is to let students return to the technical preparing office and the technical equipment office after fixing the direction of scientific research in order to bring their research closer to production. This helps them decide their selective subjects for themselves.
In summary, if virtual factory investigation precedes, postgraduate students can decide their selective subjects after setting the direction of their research before laying scientific foundations for it.
...
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.
...
