Jo Apr 5, 2024
Plastic products have high productivity for their high corrosion resistance and large-quantity injection molding. When they are coated with metal decoration, they have higher durability and shock-resistance. It means they have longer life time.
Extrinsic decoration methods include evaporation, plating and electrophoresis, of which plating is most widely used. The most suitable plastic for plating is acrylonitrile-butadiene-styrene (ABS).
Decorative nickel plating of acrylonitrile-butadiene-styrene (ABS) plastics has depended on pretreatment of precious metals including Cr and Pd, but it is subject to restriction due to both environmental pollution by chromium oxides and increasing prices of precious metals.
Kim Kyong Chol, a researcher at the Faculty of Chemical Engineering, has found a reasonable method of etching and forming a conducting layer in the pretreatment process of plastic products, and investigated the influences of some factors.
Permanganate was used for etching and the conducting layer was formed by complexing agent of tartaric acid and lactic acid. First, he investigated the etching characteristics in terms of amounts of potassium permanganate, phosphoric acid and sulfuric acid, and then, he assessed the characteristics of the conducting layer with respect to the amounts of metal ion, mixed ligand and temperature.
The scanning electron microscope (SEM) images, X-ray diffraction (XRD) patterns and electric resistances confirmed that the current etching is environmentally friendly and the electric resistance of formed Cu2S is below 50Ω/cm2.
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Jo Apr 4, 2024
Moran Hill is located on the bank of the Taedong River, which flows through Pyongyang City. It was called Kumsu Hill during the feudal Joson dynasty. Later, it was given the name “Moran Hill” as it resembles a peony (pronounced like ‘moran’ in Korean)
Regarding it as a pride of Pyongyang from olden times, Korean people have created many legends related to the hill.
The legends reflective of the attachment to and love for Moran Hill are associated with the pride in having the beautiful Moran Hill and with the patriotism of Korean people who defended it from foreign aggressors.
The legends in praise of the beauty of Moran Hill are “Hungbudong” and “Story of Chongryu Cliff”. The former is about a mysterious spring and the latter says that the beautiful Chongryu Cliff was formed by the wonder of nature of the Dragon King, who was impressed by a boy with a heart of gold in Pyongyang.
The beautiful and noble customs and manners of Pyongyang people are depicted in such legends like “Chongryu Pavilion in Moonlight” conveying the sincerity of a boy in Kangdong who tried to save a girl in the Walled City of Pyongyang from misery and “Door of Happiness” reflective of the sentiments of the people.
Among the legends that represent the fighting spirit of the Pyongyang people who defended the beautiful city Pyongyang are “Ulmil Warrior” about a warrior who devoted himself to the defense of Pyongyang and Moran Hill, and “Kye Wol Hyang and ‘A Man of Heroic and Noble Mind’” about the struggle of Kye Wol Hyang, a young woman, who turned out in the fight against Japanese invaders.
As mentioned above, the legends of Moran Hill serve as priceless cultural heritage of our nation as they represent the desire and aspiration to boast of the beauty of Moran Hill to the world, the patriotism of Korean people, who defended it against foreign aggressors, and their beautiful sentiments.
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Jo Apr 2, 2024
37th Sci-Tech Festival of Kim Chaek University of Technology was held in the university indoor stadium from February 20 to 22, Juche 113(2024).
The subject was “Science and technology ― decisive guarantee for the fulfillment of the five-year plan”. The festival aimed to solve scientific and technological problems of key importance in fulfilling the five-year plan on the basis of the successes achieved in the research work for the implementation of the resolutions of the 8th Congress of the Workers’ Party of Korea and plenary meetings of its Central Committee by the lecturers, researchers, post-graduate students and students of the university.
The festival took the form of scientific and technological paper readings, exhibition contest of units and exchange of new technology in seven sections including machine and transportation, information and communication, metal and chemistry, and electronics and automation. On display were 190-odd research findings including “establishment of pig iron production process by energy-saving oxygen heat blast furnace”.
“Portable defibrillator” by Ri Yong Chol, a section head at the Bioengineering Institute of Mirae Sci-tech Centre, and other 70-odd items were highly appreciated.
Upholding the noble intention of the respected Comrade
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Jo Apr 1, 2024
Chongmyong means the start of clear weather.
Every year it falls on April 4th or 5th. This year April 4 is Chongmyong.
Chongmyong, which comes in the most beautiful and balmy season of the year, is closely related to the life of Korean people. Considering farming as the mainstay, Korean people used to soak rice seeds in water before Chongmyong and sow them over seedbeds. On the day, they usually started spring sowing.
With regard to this, a historical classic “Tongguksesigi” says, “spring ploughing starts on Chongmyong on all farms”.
About this time of the year they used to sow crops like foxtail millet, sorghum, millet, bean, adzuki bean, etc., and many kinds of vegetables such as pumpkin, radish, pepper, spring onion, etc. They also sowed their well-kept gardens with flowers like balsam and zinnia.
On the other hand, Korean people regarded it as an ancestral custom to visit their ancestors’ graves dressed in traditional costumes on the day. They used to climb the mountain to take good care of the graves by turfing them and heaping up earth over the mounds lowered throughout the winter before expressing their condolences to the ancestors. And some people moved graves to other places, which was called chonmyo or ijang. The custom of repairing or removing graves is connected with the fact that the day is seasonally suitable for piling earth up or grave removal with high rate of rooting of turfs and unfrozen ground.
It is also associated with beautiful and noble sense of moral obligation of Korean people, who treated their ancestors with utmost courtesy.
The custom is still being handed down.
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Jo Mar 29, 2024
In recent decades, temperature/pH dual responsive amphiphilic polymers have attracted the interest of researchers because they can perform certain functions by changing the hydrophilic hydrophobic balance in conformity with changes in the external environment. Therefore, these types of amphiphilic polymers are very useful, especially for drug delivery, tissue engineering, biotechnology, and related fields.
However, most of the temperature/pH dual responsive polymers are prepared using petroleum chemical monomers as the main raw material and their use has biocompatibility and toxicity problems. In recent years, many researchers have focused on biomass derivatives to improve the temperature/pH dual responsiveness of polymers.
Jong Kwang Hyok, a section head at the Faculty of Chemical Engineering, has synthesized a novel type of temperature-pH dual responsive amphiphilic hydrogel, PD(Hydroxyethyl starch(HES)-propynyl glycidylether(PGE)-2-dimethylamino ethanethiol (DMAET)- Triethoxyvinylsilane(TEVS)) and studied its characteristics.
First, HES, a hydrophilic polysaccharide, underwent etherification of hydroxyl groups in its glucose units with PGE and then click reaction between carbon-carbon triple bonds in PGE and thiol groups in DMAET, thereby possessing a hydrophilic-hydrophobic structure to be used for the preparation of PD, a temperature-pH dual responsive material, with pH-responsive tertiary amine groups. Next, it further became a dual responsive hydrogel through the formation of its internal network by TEVS.
He found that during the test experiments to use it as a drug carrier for oral delivery, the doxorubicin(DOX) release was ≤15% in acidic conditions in the stomach (pH < 2.0) and ≤94% in basic conditions in the small intestine, which ensures that it exhibits relatively good protective and release properties of drugs.
You can find the details in his paper “ Preparation of temperature-pH dual responsive hydrogel from hydroxyethyl starch for drug delivery” in “Colloid and Polymer Science” (SCI).
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Jo Mar 28, 2024
Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation technique widely used in different wireless communication systems such as Digital Video Broadcasting (DVB), Digital Radio Mondiale (DRM), Wireless Local Area Network (WLAN), Long Term Evolution (LTE), etc.
But OFDM signals are prone to suffer from spectral spreading and in-band distortion due to the large envelope fluctuations.
As solutions to this problem, several methods have been presented. For reducing the signal envelope fluctuations without any in-band distortion, some methods such as Partial Transmit Sequence (PTS), Selected Mapping (SLM) and their hybrid techniques have been investigated, but they are in high computational complexity and need side information. Tone Reservation (TR) can reduce the signal envelope fluctuations significantly, but it does not use some subcarriers and depends on computationally intensive optimization. Systematic coding techniques are distortion-less methods, which can bound signal fluctuations but they require data rate compensation. As the simplest method, Amplitude Clipping could reduce the out-of-band radiation, but these non-linear techniques cause in-band distortion and the additional clipping noise compensation requires high computational complexity.
Among the presented methods, constellation extension based ACE would be one of the promising methods because ACE maintains the minimum Euclidean distance between symbols in a constellation and causes no reduction of BER performance and, especially, it does not require any side information. However, because the reduction performance of signal envelope fluctuations of ACE depends on the number of iterative computations, its computational complexity is usually very high. So, it is necessary to find an approach to maintain high reduction performance of signal envelope fluctuations and low computational complexity.
Jon Ji Hyon, a researcher at the Faculty of Communications, has proposed a novel ACE-DE approach to deal with this issue, where the anti-peak signal decomposition based double extension is applied to improving reduction performance of signal envelop fluctuations.
By using Fourier transform properties, an anti-peak signal is decomposed into 4 sub-signals in the time domain, and then recomposed via Second Order Cone Programming optimization. To realize the low computational complexity of ACE-DE, MPT algorithm is also proposed.
The simulation results show that ACE-DE with MPT outperforms other approaches in terms of CCDF, BER and OOB radiation.
For more information, please refer to his paper “Reduction of Signal Envelope Fluctuations in OFDM Systems Using ACE with Double Extension” in “Wireless Personal communications” (SCI).
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