Jo Jul 4, 2022
Kim Chaek University of Technology is on a winning streak in codechef challenges that take place twice a month. Codechef June Long Challenge witnessed its glory once again.
The first contest that was held on June 10 to 13 produced 32 winners in Division 1, nine of whom are students at KUT.
In the meanwhile, a total of 27 contestants won the first place in Division 1 of the second contest that went on from 24 to 27. Eight out of 27 winners are from KUT.
The number of winners of KUT in Division 1 in the two contests every month in the first half of this year is as follows.
January: first contest ― 7 out of 27, second contest ― 7 out of 29
February: first contest ― 8 out of 38, second contest ― 8 out of 30
March: first contest ― 9 out of 48, second contest ― 5 out of 21
April: first contest ― 10 out of 27, second contest ― 2 out of 5
May: first contest ― 6 out of 14, second contest ― 6 out of 17
June: first contest ― 9 out of 32, second contest ― 8 out of 27
The figures show that many students at KUT have taken part in the codechef challenges and that most of them took the first place.
KUT students are still trying to enlarge their store of knowledge in order to keep the national flag of the DPRK flying over the Internet.
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Jo Jul 1, 2022
The Korean nation established glorious traditions in the field of science and culture over the long period from ancient times to the feudal Joson dynasty, during which they developed the science and technology onto a high stage on the basis of numerous scientific and technological achievements gained, thus exalting to the world their fame as a talented and resourceful nation.
Among those achievements is the rain gauge which was made by the Korean nation for the first time in the world.
A rain gauge, an instrument to measure the rainfall, was first invented in the world in the period of feudal Joson dynasty in 1441. The first rain gauge which was made of iron looked like a cylinder and it was 2 ja (about 40cm) in height and 8 chi (about 16cm) in diameter. In 1442 a copper rain gauge which was similar in shape to the first one was made and it was 1 ja 5 chi (about 30cm) in height and 7 chi (about 14cm) in diameter. Several rain gauges were made subsequently.
The rain gauge was placed on a stand to catch the rainwater in it for the measurement of its amount. Such gauges were installed in the yards of government offices in the capital and other provinces. In the capital they were made of copper and in other provinces they were made of porcelain or clay. In every county the time when it started and stopped raining was recorded and the amount of rain in that time was measured, which was reported to the provinces. Then the provinces reported the collected data to Soungwan (an institute for astronomical and meteorological observations in feudal society, also called Kwansanggam), where all the data were recorded. It was made a system at that time.
The scientific measurement of the rainfall by rain gauge and the system of collecting measurement data were found in our country for the very first time in the world.
In Italy it was not until 1639 when the depth of rainwater was measured with a gauge. In addition, many years after it rain gauges were installed all over the country and the system of collecting the data of rainfall by the central institute was established. This explains that the rain gauge devised and used in Joson was about 200 years earlier than in Europe.
The rain gauge is a typical meteorological heritage that made a significant contribution to the development of astronomical and meteorological observation technology of our country and at the same time it is part of the priceless cultural heritage that is permeated with creative talents of the Korean nation.
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Jo Jun 28, 2022
NTC (Negative Temperature Coefficient) thermistors are widely used in industrial applications for temperature measurement, control and compensation. One important problem in the use of NTC thermistors is to overcome aging phenomenon. Their electrical properties change with time particularly when the temperature increases and it is the main reason why they are unable to be used at temperatures above 150℃.
Aging of electrical properties is attributable to non-equilibrium states that exist inherently in semiconducting NTC ceramics.
Sol-gel auto combustion is an advanced process that is widely used in nano-powder synthesis such as magnetic material.
Yu Nam Chol, a researcher at the Science Engineering Institute, successfully prepared Fe0.8Mn1.54Ni0.66O4 nano-ceramics by sol-gel auto combustion and observed the microstructure and phase of these samples by using Scanning Electron Microscope and X-Ray Diffraction. The results showed that powdered Fe0.8Mn1.54Ni0.66O4 ceramics pre-fired at 800℃ and sintered at about 1 050℃ had more compact and uniform spinel structure. In addition, the investigation of the electrical characteristics of these thermistors manufactured at different sintering temperatures proved that the sample sintered at 1 200℃ was suitable for the improvement of the properties of thermistors. It was also shown that the thermistor annealed for 72 hours at 450~550℃ in N2 atmosphere had aging ratio of less than 0.7%.
The details about this are carried in his paper “Preparation of Fe-Mn-Ni-O Nano-Ceramics by sol-gel auto combustion for NTC thermistor” presented to the SCI Journal “International Journal of Materials”.
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Jo Jun 26, 2022
Ri Yong Ho, a section head at the Faculty of Heat Engineering, has developed an instrument that can measure and analyze vibration of rotating machinery such as steam turbine generators real-time.
As a steam turbine generator is composed of rotors that are supported by their pedestals, vibration state of all the pedestals should be measured and analyzed at the same time by a multi-channel instrument.
The multi-channel vibration instrument acquires vibration signals of up to 16 channels at high speed at the same time and transmits them to the computer so that one can measure and analyze vibration state of all the pedestals of turbine generators, diagnose vibration fault and decrease vibration level by taking necessary measures like balancing.
The multi-channel vibration instrument is composed of analog signal processing circuit, key-phase pulse input circuit, digital signal processing circuit, USB communication circuit and power supply circuit.
The analog signal processing circuit does overvoltage protection, filtering and amplification of vibration signals, and then sends them to the digital signal processing circuit.
Digital signal processing is performed by a microchip, in which AD conversion of 16-channel analog signals, measurement of the rotating speed and vibration phase by key-phase pulse, saving of vibration waveforms and communication control take place.
The acquired vibration waveforms of 16 channels are transmitted immediately to the microchip which has USB communication function by means of parallel communication mode and then they are real-time transmitted to computers through USB ports.
In the power supply circuit, AC 220V power is converted to stable direct current voltages 5V and ±12V and then supplied to every signal processing circuit.
The computer performs digital filtering and integral of multi-channel vibration waveforms received from the vibration instrument, transforms vibration acceleration signals into vibration velocity signals and vibration displacement signals, calculates vibration amplitude to measure vibration level, and then makes vibration analyses such as spectrum analysis by fast Fourier transformation, phase analysis and trend analysis.
Besides, it can perform one-plane balancing and two-plane balancing by method of influence coefficient, so field balancing of steam turbine generators can be realized.
We can measure pedestal vibration by linking this instrument with piezoelectric acceleration sensors and electromagnetic speed sensors, and shaft vibration is also measurable when it is connected with eddy displacement sensors.
The measurement range is 0~200㎛ in the case of pedestal vibration and 0~500㎛ in the case of shaft vibration, and the measurement accuracy is 2%.
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Jo Jun 25, 2022
The research group led by Pae Ho Rim, a section head at the Faculty of Shipbuilding and Ocean Engineering, has developed an experiment device for measuring natural frequency of a ship hull.
The device measures the natural frequency of a ship hull model by the principle that resonance occurs when natural frequency is coincident with the frequency of forced vibration caused by decentration mass.
The device consists of ship hull model, vibration generator, unit for motor velocity control, frequency sensor, acceleration sensor, amplification and integration circuit, communication interface, user interface, etc.
The model is 1.2 metres long, 0.1 metres wide and 0.1 metres high. The cross section is rectangular and the bow and stern assume a pyramidal form.
The user interface shows the graphs and values of real-time signals of revolution, displacement, acceleration and velocity.
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Jo Jun 22, 2022
Cast aluminum alloys are quite widespread and they find more and more applications in modern industry such as aerospace, navigation and railway transport thanks to their good mechanical property, castability, corrosion resistance, etc.
Quality indices are a measure to quantify quality of the alloy on the basis of its mechanical properties.
The indices are Q, QR, QC, QD(Q0), QE, etc. Each one has its own unique features and individual one cannot display the overall performance of cast aluminium alloys.
The most representative indices to evaluate their overall performance can be chosen by two methods ― method of correlation analysis between quality indexes and mechanical properties and method of correlation analysis and rank deviation analysis between overall performance scores obtained from quality indices and MCDM method.
The analysis result showed that Q0 proved to be the most representative one of all the indices Q, QR, QC and Q0, and that Q0 can be used instead of MCDMs for evaluation of overall performance of cast aluminum alloys and selection of optimal cast aluminum alloys.
Detailed information about this can be found in the paper “ Method to evaluate overall performance of cast aluminum alloys using most representative quality index instead of MCDM method” presented by Yang Won Chol, a researcher at the Faculty of Materials Science and Technology, to the SCI Jounal “International Journal of Metalcasting”.
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