Jo Mar 10, 2024
“Muyedobothongji”, printed from wood blocks in 1790, is an illustrated book of martial arts by Ri Tok Mu, Pak Je Ga, Paek Tong Su et al. where the traditional martial arts of our nation are comprehensively systemized.
The book illustrates 24 kinds of martial arts.
It is surmised that the illustrations were offered by Kim Hong Do, a famous painter of those days. Preceding books on martial arts were “Muyebo” descriptive of six kinds of martial arts written by Han Kyo in the sixteenth century and a book with addition of twelve more kinds to the six martial arts in the mid-eighteenth century.
“Muyedobothongji” has another addition of six kinds to them.
The book illustrates detailed moves of several fighting skills like swordsmanship, spearsmanship, archery, etc. on the ground and on a horse.
The book has a full collection of data related to Korean boxing that started in Ancient Joson, was improved in Koguryo age and was completed during the Koryo and feudal Joson dynasties.
This book is of weighty importance in showing the long history and superiority of the national martial arts created in our country, the cradle of Taekwon-Do.
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Jo Mar 7, 2024
Submerged arc welding process with high productivity has been one of the widely-used surfacing methods for recycling worn components or fabricating bimetal. Surfacing with a lay-down plate electrode is a new variation of submerged arc surfacing, in which metal is deposited on the surface of a workpiece by arc heat between the workpiece and a plate laid down on it.
Both direct and alternate current can be used as welding power source. Surfacing with a lay-down plate shows the possibility of reducing the cost for restoring worn components like large-scale straight teeth gears with large module, and of improving the productivity and quality of surfacing.
Temperature distribution resulted by spontaneous movement of electric arc has a big effect on the stability and quality of surfacing with a lay-down plate. However, to the best of our knowledge, there have not been many discussions regarding the spontaneous movement of electric arc and the analysis of temperature field during surfacing with a lay-down plate electrode.
In order to make an optimal surfacing process condition, Pak Sang Yun, a researcher at the Faculty of Materials Science and Technology, has modeled the spontaneous movement orbit of arc during surfacing with a lay-down plate electrode and investigated its temperature distribution by ANSYS.
He has drawn the following conclusions.
First, the periodic and stable movement of electric arc, which is self-controlled in the channel during surfacing, results from periodic variation of forces acting on electric arc.
Second, the dimension and shape of the weld pool varies with time, but the boundary of solidus temperature is constant regardless of time. Thus, the temperature field remains in quasi-stationary state during surfacing with a lay-down plate electrode.
Third, the distribution of quasi-stationary temperature field depends on build-up technical conditions and the width of plate electrodes.
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Jo Mar 6, 2024
Our people have regarded dressing themselves up as decorum for themselves and others from olden times, paying special attention to it.
When they needed to go out, they never forgot to examine their clothing, and they never loosed their breast-ties however hot the weather was.
In the house, too, they kept their clothes tidy, and they regarded it as politeness to tidy themselves when they were expecting seniors or guests.
When they visited other people’s houses, they shook dust or anything dirty away from their clothing, tidied them up, and placed their shoes squarely before going in.
However busy and tired they were, they always washed their clothes well regularly and ironed wrinkles out of them.
In addition, they were dressed appropriately in different circumstances, i.e. seasons, ages, happy and sad occasions, etc.
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Jo Mar 5, 2024
The Monument to the Great Victory in the Northern Area, a historic relic in Rimmyong ri, Kim Chaek City, was erected in 1708 in commemoration of the signal victory that Jong Mun Bu’s Volunteer Army won by annihilating the Japanese invaders who had made an inroad into the districts of Hamgyong Province during the Japanese invasion of Korea in 1592.
The first part of the inscription defines the position of the struggle of Jong Mun Bu’s Volunteer Army as a deed no less significant than the battles on Hansan Island or those in the Fort on Mt. Haengju and Yonan Fort, and mentions its organization and major battles. The main part says that volunteers who rose up against the aggression of Japanese invaders fought bravely, and thus the enemies were expelled from the northern part of the country and the people there could do farming safely, and that their exploits should be remembered forever.
The monument is a precious historical relic of our country that has a great significance in studying the history of our ancestors who courageously fought against the invasion of the Japanese foes and in educating our people in the Korean-nation-first spirit.
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Jo Mar 2, 2024
CMM, one of precision measuring instruments, is an important component of advanced manufacturing technology. Nowadays, CMMs are widely used in the fields of machine-building, automobile manufacturing, aerospace, flexible manufacturing system and computer integrated manufacturing system due to the advantages of strong versatility, high degree of automation and high precision.
However, CMMs have some weaknesses. They are large, expensive and not portable.
In comparison with traditional CMMs, AACMM offers many advantages such as large workspace and ease of use, high degree of freedom, portability and low cost. However, it also reveals some drawbacks due to its many articulated arms like bigger accumulated errors and lower measuring precision than CMMs.
In an attempt to improve the measurement accuracy of AACMM and reduce its manufacturing cost, Rim Chang Hyon, a researcher at the Faculty of Mechanical Science and Technology, has performed an error analysis and an optimum tolerance allocation.
Firstly, based on the analysis of error source of AACMM, he constructed a systematic error model.
Next, he calculated by the analytical and numerical methods the position error of measuring probe due to the errors of each structural parameter and that due to the systematic error of individual rotary encoders.
Lastly, from the perspective of processing and assembly, he established a mathematical model that converts the perpendicularity error of the AACMM into the arm’s length error, and performed a calculation about the optimal tolerance allocation of each structural parameter and then verified its accuracy.
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Jo Feb 29, 2024
The geometry of TICS has an influence on the output signal of sensors. This relation is determined by the cell constant given by the size of a sensor.
Several researchers demonstrated three methods to determine the cell constant of TICS― experimental method using standard solutions with known conductivity, single-loop calibration method and analytical method by rough approximation. They pointed out that in order to measure the lower ranges of conductivity which require a smaller cell constant, the diameter of sensor and measuring container must be enlarged.
But until now it has not been suggested to deal with the influence of the geometric parameter of a sensor on the cell constant and the regulation band of the cell constant with the size of a sensor. So, it is worthwhile to do some research on the relation between the cell constant and the size of a sensor.
Jang Hyon, a researcher at the Faculty of Electronics, has analyzed the relation between the geometry of a TICS (inner radius r1, outer radius r2 and height t of the sensor toroid) and its cell constant through simulations by the finite element method and experiments.
Taking account of actual conditions, he considered the sizes (r1, r2 and t) of a sensor within several tens of millimeters.
A key factor which influences the cell constant is the hole diameter (2r1) of the sensor toroid. The effective superior limit of inner radius of the sensor toroid that can give the smallest cell constant is about 30 mm.
The theoretical results on the cell constants of sensors in different sizes coincided with the experiment results with less than about 5% relative error.
The conductivity below limit value that can be adjusted by cell constant is about 0.36 times the lowest bound value of conductance measurement range.
You can find the details in his paper “Optimization of the cell constant for application of the transformer type inductive conductivity sensor (TICS) in low-conductive solution” in “IEEE Sensors Letters” (SCI).
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