Jo Jan 15, 2023
Ri Jong Ju, a researcher at the Faculty of Communications, has invented a color identification method for HDTV broadcasting video monitors.
Nowadays, there has been a continuous increase in the demand for the quality of TV broadcasting and it includes color as well as video resolution. In order to represent the correct colour, dedicated video monitors supervise colors strictly when TV programs and TV sets are made. However, reference whites in each video monitor which are used as reference are a bit different so it is necessary to calibrate the colours of video monitors.
Colour identification is for adjusting the colour presentation characters of video monitors so that they show exactly the same colours for the same video.
Some equipment and software are used for colour calibration and every video monitor has its own calibration equipment.
The proposed method is useful for video monitors without their own calibration equipment. To display the same colours, the values of three primary colours should be in the same tolerance range. The method employs a colour analyzer and a spectrum analyzer.
First, both the colour analyzer and the spectrum analyzer measure the same video to set a reference value in the colour analyzer. Next, a measurement value and a target value of reference white in the colour calibration program are input before calculating adjustment values. At that time, various colour conversions and colour difference calculation algorithms are used in the program. Then, measurement mode is switched to analysis mode to adjust the colours of monitors to the value. When the target white colour reaches the same value, the monitors display the same colours.
The method was also applied to normal LCD TVs to use them as HDTV broadcasting video monitors. It produced the same effect.
...
Jo Jan 13, 2023
A research team led by Kim Kang Sop, an institute head at the Faculty of Earth Science and Technology, has succeeded in his study on delineation of deep anthracite seams with random forest predictor that learnt multi-geophysical and drill-hole datasets.
Anthracite formed in the upper paleozoic era is a fundamental resource of fuel and raw material in our country. Thus, it is of great significance to improve the accuracy of a deep survey based on drillholes and geophysical data in the vicinity of existing anthracite-mines.
Several geophysical methods are available due to its low-resistivity, density, magnetic susceptibility, and high spontaneous-potential (SP). However, these methods have different limitations of penetration depth and resolution, and are critically affected by noises from powerlines, terrain, and geological complexity.
They conducted multiple-geophysical fieldworks at an anthracite mine, involving transient electromagnetic (TEM), SP, gravity, and magnetic prospectings to construct the database of existing drillholes. The study area in difficult terrain had four anthracite seams under the rough surface to the depth of about 800m. They showed irregular behavoir due to structural activities in the Mesozoic era. Fortunately, many holes which had already been drilled in the anthracite seams, could provide useful information to interpret the given geophysical datasets.
The problem was to build an appropriate strategy to constrain deep anthracite seams and evaluate the reserve by inverting multi-geophysical datasets along with the existing drill-hole database, throughout the study area including the parts with no drillholes.
They had some problems. First, drillhole data may be converted as a priori information for inverting geophysical data. However, seperated inversion may yield subsurface images of physical property with a remarkable difference from the real geology. Next, joint-inversion of multi-geophysical datasets may be another altenative. But this manner requires an elaborate code writing to incorporate realistic terrain and drillhole information.
Thus, they chose the random forest (RF) predictor which is recognized to be the most powerful for solving multiple-classfication problems. The RF is a prediction (classification) algorithm that has a classification tree as the elementary learner and is incorporated with the ensemble aggregation method. It shows higher generalization performance than other machine-learning algorithms.
On the basis of such preparations, they wrote an RF predictor. The inputs of RF predictor involved TEM, SP, gravity, and magnetic datasets and the outputs were designed to yield the upper depth and thickness of deep anthracite seams. The teaching signals were supplied based on the elevation and thickness of seams known from drillholes. The RF predictor, after learning the given teacher signals successfuly, yielded an objective evaluation of the study area including undrilled parts, and enabled them to predict new anthracite-rich regions and evaluate the reserve.
...
Jo Jan 9, 2023
A research team led by Hong Sung Chol, a researcher at the Faculty of Heat Engineering, has developed and introduced various types of energy conservational boilers.
Energy conservational unpowered boiler with a package of fire-tube heaters combined with fin array in box type
The boiler satisfies heat requirements needed for production and heating with a small amount of fuel. It costs little to manufacture and install. It is simple in its composition and principle and easy to reset the load. It has the highest heat output for furnaces of the same volume. In addition, for the same heat output, it consumes a lot less fuel and material than other fire-tube heaters. Especially, it is very convenient to introduce them as they are standardized in 10 heat outputs with seven optimized indicators to ensure the scientific accuracy, economy and promptness of introduction in consideration of its various types and conditions of installation. The boiler makes the most use of the produced heat by preheating water from the heat included in waste ash, by using the flue gas from heating and by keeping boiler walls warm. Compared with conventional boilers of the same furnace volume, it provides three times as much heat output (η=88~93%), consumes less fuel by 1/4 [fuel consumption of 162kW hot water heater: B=100~110kg/d(Qar=20MJ/㎏)] and material by over 1/2, and reduces the number of boilers for a unit heating area.
Energy conservational steam bath boiler
It is made up of the cylindrical body that produces both heat and hot water at the same time by recycling wasted heat, a water heater, a feed water inlet, a hot water outlet, a fuel inlet, a fire-grate and a chimney. The annular upper and lower heaters inside the body and the outer collecting heater and economizer outside the body maintain the temperature of a sauna at over 75~85℃ and produce hot water of 40~50℃ at 2~2.5t/h. (fuel consumption B=40kg/d)
Boiler for hot water tank
In the boiler is a hot water heater in the shape of a nest which is combined with a plate and a water pipe. The hot water system consumes no electricity and is operated by natural ventilation and cycle. It can produce hot water of 65~75℃ at 40~45t/d. (fuel consumption B=60kg/d)
...
Jo Jan 6, 2023
There are many multicriteria decision-making (MCDM) methods applicable to material selection. They are simple additive weighting (SAW) method, weighted product method (WPM), analytic hierarchy process (AHP) method, analytic network process (ANP) method, technique for order preference by similarity to ideal solution (TOPSIS) method, gray relational analysis (GRA), VIse Kriterijumska Optimizacija Kompromisno Resenje (VIKOR) method, preference ranking organization method for enrichment evaluations (PROMETHEE), extended PROMETHEE (EXPROM) method, elimination and et choice translating reality (ELECTRE) method, complex proportional assessment (COPRAS) method, preference selection index (PSI) method, range of value method (ROVM), rank sum ratio (RSR) method, graph theory and matrix approach (GTMA), multi-objective optimization on the basis of ratio analysis (MOORA), quadrant constellation graph-based method, etc. These methods may produce considerable differences in the material selection results.
However, it is unknown which MCDM method produces more rational results and there is no rational method to determine final overall performance scores of alternative materials.
Yang Won Chol, a researcher at the Faculty of Materials Science and Technology, has proposed a new method to determine final overall performance scores and final ranks of alternative materials by combining the results from different MCDM methods in material selection.
The steps are as follows.
First, the overall performance scores and ranks of the alternative materials are calculated using some different MCDM methods.
Second, mean values of the rank correlation coefficients between the rankings obtained from different MCDM methods are calculated before the mean values are assigned as the priority weights of each MCDM method.
Finally, the weighted mean values of the overall performance scores obtained from different MCDM methods are calculated. They are determined as final overall performance scores of alternative materials.
To illustrate the effectiveness, he applied the proposed method to selecting the best tool holder materials using some well-known MCDM methods such as SAW, TOPSIS, GRA, VIKOR, PROMETHEE, and RSR methods.
Conclusively, the following conclusions were drawn:
(i) The proposed method can determine not only the final ranks but also the final overall performance scores of alternative materials by combining the results obtained from individual MCDM methods.
(ii) The proposed method reflects the priority weights of individual MCDM methods to the final overall performance scores and ranks of alternative materials.
(iii) The proposed method may be more reasonable, clearer and simpler than previous methods.
(iv) The proposed method could widely be used to get more reasonable, appropriate, and robust material selection results by combining different available MCDM methods.
If further information is needed, please refer to his paper “A New Material Selection Method Based on Weighted Mean Values of Overall Performance Scores from Different Multicriteria Decision-Making Methods” published in the SCI Journal “Advances in Materials Science and Engineering”.
...
Jo Jan 3, 2023
Thin-walled structures such as ship and offshore structures basically consist of a number of plates stiffened by different types of stiffeners.
Continuous welding may be used for attaching stiffeners to plates, but this technique requires a large amount of welding, adds weight to the structures, and increases construction costs. In order to reduce the costs of labour and materials and save weight of the stiffened plate structures, non-continuous welding is frequently applied to the attachment of plates and stiffeners. This method of fabrication also lowers the magnitudes of welding residual stresses more than continuous welding.
Over the past few decades, the buckling and collapse behaviors of continuously welded stiffened plates under different loading conditions have been widely investigated in order to develop analytical, empirical, numerical and experimental methods.
However, little has been studied on the behavior of intermittently welded stiffened plates and, furthermore, only some numerical and experimental studies have been carried out.
Mun Ji Song, a section head at the Mirae Academy of Science and Technology, has proposed a simplified method for ultimate strength estimation of intermittently welded stiffened plates under uniaxial compression. The plate and stiffener of a stiffened plate were considered as individual beam-columns. The whole span of an intermittently welded stiffened plate was divided into welded and non-welded segments. For modeling the behavior of the intermittently welded stiffened plate, the differential equations which describe the bending of the beam-columns in welded and non-welded segments were considered.
Special attention was paid to the following two cases.
i) Case 1
It was assumed that beam-columns 1 and 2 are deformed in contact and deflections of the beam-columns 1 and 2 are equal to each other.
ii) Case 2
In this case, it was assumed that beam-columns 1 and 2 are deformed in non-contact and behaviors of the beam-columns 1 and 2 are independent of each other.
Based on the model, the Euler limit load of the intermittently welded stiffened plate was calculated. The intermittently welded stiffened plate was changed into a continuously welded one with the equivalent Euler limit load. The Paik’s empirical formulation was used to estimate the ultimate strength of the changed continuously welded stiffened plate under uniaxial compression.
The proposed method demonstrated a good agreement with FEA results. This suggests that ultimate strength of chained and staggered welded stiffened plates can be estimated by the proposed method.
For more information, please refer to his paper “Study on Ultimate Strength Estimation of Intermittently Welded Stiffened Plates under Uniaxial Compression” published in the SCI Journal “Marine Structures”.
...
Jo Dec 30, 2022
Ozone is the second to fluorine in oxidation and sterilization power and it reacts with organic and inorganic materials very well. In addition, it leaves no remainders harmful to the environment. Thus, it has been used not only for food containers but also in fish farming, medical and chemical industries etc. Recently, positive attempts are being made to use it to prevent various infectious diseases.
Accurate measurement of ozone concentration is important for its effective use. One of the most cost-effective measurements is using detector paper.
The ozone detector paper for determining concentration of ozone in the atmosphere has already been developed. When indigo carmine reacts with ozone, the paper turns from blue to white. This principle is used to measure albedo for determination of ozone concentration. The measurement range of the paper is 0~400ppb and the CT value is 0~400ppb×h. The unit of time is hour. It is impossible to precisely measure concentration over the range because the detector paper immediately turns into white completely. The response time of the detector paper is over 30 minutes.
However, research into dissolved ozone detector paper has not been conducted.
Kim Yong Ok, a researcher at the Faculty of Applied Chemistry, has developed detector paper for dissolved ozone.
The dissolved ozone reacts with KI to produce iodine, which then reacts with starch to turn the paper blue. This means that the paper turns from white to blue according to the ozone concentration. Thus, the chromaticity of the paper helps determine concentration of dissolved ozone.
This paper guarantees precise and quick measurement for up to 8ppm of concentration of ozone within a short time of 30~40s.
...
