Jo Sep 16, 2022
Most practical engineering problems are currently solved by the well-developed standard finite element method (FEM). However, the FEM has its inherent shortcomings as it is a numerical method that relies on meshes. While conventional mesh-based techniques such as FEM can accurately approximate governing equations, labor and computational costs associated with creating the conforming mesh undermine the efficiency of such methods. The Boundary Element Method (BEM) is another technique that can alleviate the difficulties associated with the implementation of the standard FEM, but it still relies on meshes.
Thus, an idea of getting rid of meshes in the process of numerical treatments has naturally evolved, and the concepts of meshfree or boundary meshfree methods have been shaped up.
Boundary meshfree methods can be roughly sorted into two: MFS (Method of Fundamental Solutions)-based type and the BIE (Boundary Integral Equation)-based type. The former is based on the concept of the MFS. The traditional MFS uses only a fundamental solution, which is a response due to a concentrated point source, in the construction of the solution of a problem without using any integrals. It is a natural boundary meshfree method.
Studies show that the MFS has been developed by improving the locations or types of sources. In the traditional MFS, a fictitious boundary is required to have the source points on it to avoid the singularity of fundamental solutions. The determination of the distance between the real boundary and the fictitious boundary is based on experience and therefore it is troublesome. In recent years, a number of efforts have been made aiming to remove this barrier in the MFS so that the source points can directly be placed on the real boundary.
And the MFS has been improved by replacing concentrated point sources of the traditional MFS with area-distributed sources covering the source points for 2D problems (volume-distributed sources for 3D problems).
Kim Un Ok, a lecturer at the Faculty of Applied Mathematics, has successfully improved the boundary meshfree method with area-distributed sources placed on the real boundary called boundary distributed source (BDS) method, by moving distributed sources outside the boundary.
To show the effectiveness of the new improved method, she has plotted the relative errors in the computed results using the BDS method and her new improved method respectively.
She has demonstrated the accuracy of the new method by solving 2D potential problems in a square domain covering 0≤x and y≤1 with Dirichlet BC,Ф(x, y)=x2-y2. She has moved sources 1.5 times d, average distance between the original boundary distributed sources, outside the boundary in the direction of outward normal vectors.
When BDS method is used, the solution is inaccurate near the boundary regions. However, the proposed method works well in improving the accuracy of the numerical solution. The results say that moving distributed sources outside the boundary can improve the BDS method.
...
Jo Sep 15, 2022
The review-centered teaching previously applied to industrial management subject has some disadvantages in developing the creative and cognitive power and practical abilities of students.
Ineffective time allotment: Lecturers should, in his or her lecture, check and evaluate how well the students have reviewed, while they should teach a large amount within a limited time.
Limitations in developing the students’ creative thinking: Students are focused on their review tasks, which gives them no notion of what they are going to learn in their lectures.
Dependence on textbooks only: This prevents students from getting related knowledge from other references.
A preparation-centered self-learning approach is helpful to develop creative and cognitive power and practical application abilities of students.
What is important in introducing this approach to lectures is, first, to give preparation tasks to students with the main focus on the students’ understanding of the principles of the subject by their own thinking and efforts and to precisely evaluate their performance of preparation tasks.
For their preparations, students get to use various kinds of textbooks, reference books, terminal devices, teaching-aid system, etc. At the same time, they can have an initial picture and understanding of next lectures. And as for difficult and complicated problems, they can get a full understanding from the explanation of the teacher in the lecture in a limited time. This approach plays a positive role in cultivating the independent abilities of students — raising challenging problems and making an analysis of them by themselves. It is important to make a proper evaluation of their preparation result.
Proper evaluation encourages students to take interest in preparation, inspire themselves, increase their desire to raise questions and propose ways to solve them.
Second, it is to direct the orientation of the lecture to enhancing the independence and creativity of the students so as to stimulate them to find solutions to practical problems by themselves in an original way.
Practical problems given to the students might include various situations in production and business activities and suitable solutions to them.
With focus on such points, Ri Ji Hye, a researcher at the Faculty of Management of Industrial Economy, has introduced a preparation-centered self-learning approach in her subject. It proves to be effective in helping students to get better understanding of the teaching contents and to raise their abilities of creative cognition and of study of scientific theories.
...
Jo Sep 14, 2022
Horse riding is a game in which riders compete on how fast they run or how skilfully they perform acrobatic acts on running horses.
Ancient Koreans, who regarded speed as the most important merit of a horse, raised native horses in large numbers suited to the topographical conditions of our country with many steep mountains. One of them was Kwahama of Ancient Korea. Kwahama was given the name because it was short enough (about one metre) to pass under fruit trees. It gained great fame in the neighbouring countries, too, as a renowned horse, a swift horse good at running up and down steep mountains.
A large number of horse bones, face pieces and other horse ornaments discovered on several ancient sites including Pomuigusok Site in Musan County, North Hamgyong Province prove that horses were raised in large numbers in Ancient Korea and our ancestors enjoyed riding from early times.
Later in the Middle Ages, excellent riding techniques of ancient Koreans were developed onto a higher level with addition of handling weapons and hurdling on a horse.
People in Koguryo raised numerous kinds of excellent horses like well-known Kwahama and mastered superb riding techniques on them. Such information can also be found in some Chinese historical books. In addition, murals in Koguryo tombs give a lifelike portrayal of riding skills like archery, spear throwing, hunting on horses, etc. In Koguryo there was a hunting competition on Rangnang Hill on March 3 (by lunar calendar) every year. The winners were awarded generous rewards and some of them were offered government positions.
The riding techniques of Koguryo were handed down through Koryo to feudal Joson Dynasty.
“Taejonhoethong” (1865) and “Haedongmyongjangjon” (1794) keep detailed records of archery, spear throwing and hurdling on horses in the first half period of feudal Joson Dynasty. It is recorded that Han Hui Yu, a military officer in the mid-thirteenth century used to fly into and out of the flames on a horse and Kim Tok Ryong, a famous swordsman in the period of Japanese invasion of Korea in 1592, was good at running through and immediately jumping back out narrow doors while Jong Ki Ryong could lightly jump over as wide a pit as six fathoms and leap onto the top of a precipice like a flying bird.
This fully demonstrates the superb riding techniques of our people in the past.
Im Sung Bin, section head at the Academy of Social Sciences
...
Jo Sep 12, 2022
Ho Myong Guk, a lecturer at the Faculty of Information Science and Technology, has realized CDIO education by means of a comprehensive measurement and experimental device in the practice course of programming technology.
The device is one of the most representative terminal measurement devices for the realization of the process control system needed in the establishment of an integrated production system. With wired communication and wireless communication, it is a multifunctional integrated experimental device whereby a number of indicators such as temperature, humidity, illumination, etc. can be measured real time.
First, he developed a communication application program to accurately and quickly collect necessary indicators through the device, and built the collected data in the database in various forms for convenient history analysis. It was designed to carry out both real-time graphic processing of the data and file processing at the same time so that the data would prove useful in all future analyses.
Next, he ensured that various characteristic analyses to be displayed in the history analysis underwent various mathematical processing such as Newton interpolation, Lagrange interpolation and spline interpolation to give scientific guarantees in the characteristic analysis.
In order to realize CDIO education in the practice course, he, first of all, encouraged the students to conceive a question rather than considering given questions.
He explained to the students an air conditioning system and a cold storage management system on the basis of the collected data (external temperature, internal temperature, humidity, illuminance, water level, motor rotation speed, etc.)
Then, the students in groups were able to decide their own tasks ― for example, air conditioning systems and cold storage management systems for libraries, zoos, gymnasiums, cultural centres, swimming pools, hospitals, museums, factories, corporations, public buildings, and their classrooms and dormitories.
As the same collected indicators needed different processing for different application objects, the students could further enhance their practical ability while performing their tasks.
Second, he let the students design the selected tasks in groups drawing on what they had learnt in the lecture.
The items for program designing included interface, file processing, graphic processing, database and network communication, analysis method determination, and self-standard setting.
Third, he made the students implement their tasks.
The students worked in groups to complete the codes they wrote.
Fourth, he asked the students to operate and test their programs.
While he was running the prepared programs, he conducted error inspection and result analysis, and pointed out the characteristics, advantages and shortcomings of the tasks submitted by each group.
In the group presentation, the overall evaluation of the convenience of interface design, the speed and accuracy of communication data collection, database construction and history management, graphic processing results and history analysis and result analysis and group cooperation were made.
In conclusion, the realization of CDIO education helped students to further raise their practical abilities.
...
Jo Sep 7, 2022
Tug-of-war is a folk game in which two teams pull at opposite ends of a long rope until one team drags the other over a line on the ground.
From ancient times our people with strong cohesion enjoyed doing tug-of-war that demonstrated communal might involving a lot of people.
Tug-of-war came into being through creative labour of mankind for survival. Whenever they needed to pull or drag up something in remote primitive times, our ancestors used to fasten ropes to them. This turned into a game little by little and eventually became tug-of-war, a competitive sport.
According to historical records, tug-of-war was usually done by peasants, especially in areas with a high proportion of paddy farming.
“Rimhaphilgi” (19th century) wrote that tug-of-war was already popular in the period of Three Kingdoms ― Koguryo, Paekje and Silla.
It became even more popular later in the period of Koryo and feudal Joson Dynasty. “Tongguksesigi”, “Hwagyejip”, “Tonggukyojisungram”, “Thamraji” and other historical books containing contemporary historical records give details of tug-of-war at that time.
Present-day tug-of-war is a little different in the ways of playing and ropes.
First, the thickness and length of a rope were altered to be convenient. After the national liberation, the thickness and length were fixed at 4~5cm and 20～30m each.
Next, unlike the past tug-of-war with main focus on strength only, the teams with tens of prearranged players have to pull the rope over one metre first to be the winner.
That is how tug-of-war was able to develop into a popular folk game in which many people can highly display the collectivist spirit of pooling their strength and wisdom, and players as well as spectators can enjoy themselves anywhere amidst tension, cheerfulness and laughter.
Im Sung Bin, section head at the Academy of Social Sciences
...
Jo Sep 5, 2022
“Genetic algorithm” is one of the optimization techniques whereby the principles of genetics and evolution of living organisms are mathematically modeled and global optimization problems are solved based on them.
In the past, teaching genetic algorithms mainly focused on mathematical basis, principles and algorithmic description, and so it revealed that students had difficulty in selecting the best one of all different methods used to solve a problem.
To solve this problem, Kang Kum Sik, a lecturer at the Faculty of Applied Mathematics, let his students to write genetic algorithms and compare and analyse them.
Firstly, he encouraged the students to decide by themselves which methods are the best among different selection methods, crossover methods, and mutation methods used in each genetic algorithm, thereby enhancing their analytical and practical abilities.
Secondly, he led the students to synthesize the relationship of each genetic algorithm and find a genetic algorithm best suited for solving real-world problems, thus raising their synthesizing and systemizing ability and the creative ability of finding optimal solutions.
That is how students came to fully understand what they learn in both theoretical and programmatic ways, and acquire methods of finding optimal solutions while solving practical problems.
...
