Jo May 7, 2026
In information security systems, a single authentication mechanism plays a very important role in information processing systems as it provides convenient and secure authentication in multi-Web service environments today when service systems are growing rapidly, and thus there is a lot of research on it around the world. In particular, the access control schemes in single authentication mode have been studied a lot worldwide.
Verifying user’s trust in systems and performing a variety of access controls are very important as a large number of attacks on service systems are attributable to the malicious behavior of registered users.
The characteristics of SSO system make it very difficult to apply the traditional RBAC (Role Based Access Control) model directly because the roles of each service system may be the same but the corresponding rights may be different. Thus, there has been a lot of research on applying RBAC models that can facilitate user management to single authentication systems.
However, the previous dynamic access control schemes based on RBAC model failed to propose a detailed access control scheme according to user’s behavior changes.
Having analyzed the characteristics of the single authentication system and the reliability-based access control scheme, Myong Kwang Min, a section head at the Faculty of Information Science and Technology, has proposed a secure and flexible access control system for SSO system by combining the entropy weighting and the reliability-based access control scheme, and evaluated its performance.
The evaluation results show that the proposed access control model is superior to all single authentication schemes and trust-based access control schemes.
...
Jo May 6, 2026
Among the traditional dishes that the Korean people have enjoyed from olden times are pickles, which reflect their taste and likings.
The Korean ancestors had long known that salt can prevent food spoilage and used it in their dietary life to pickle such foods as vegetables, fish and meat so as to store them for a long time.
Such practice of pickling has a very long history. According to historical records, Koreans produced salt from ancient times and ate salted fish a lot.
Kimchi can also be said to have started from pickling at first.
There were parsley kimchi, chives kimchi, radish kimchi, leaf mustard kimchi, etc.
These kinds of kimchi are salted foods created by Koreans in the course of making wide use of pickles in their dietary life for a long time.
Pickling was further developed in the period of the feudal Joson dynasty.
Pickles in those days were divided into salt pickles directly preserved in salt, pickles preserved in bean paste or soy sauce, vinegared pickles and bran pickles using rice bran according to pickling agents. They were also divided into vegetable pickles, meat pickles, fish pickles and herb pickles according to ingredients.
Pickles are very good preserved foods that make it possible to store seasonal foods for a long time under the climatic conditions of the DPRK with distinctive seasons.
...
Jo May 5, 2026
Field Programmable Gate Array (FPGA) is an important component for modern digital systems. FPGA is a semi-custom integrated circuit for implementing arbitrary logic functions of users by using look-up tables. FPGA has two main resources. One is logic resource and the other is interconnect resource. The logic resources implement the logic functions of user circuits and the interconnect resources connect logic resources to each other. Logic resource includes look-up table, flip-flop and multiplexer, and a net is an example of interconnect resource. When you write the user circuit into FPGA, FPGA is said to be configured. It is possible to write circuits into FPGA several times, i.e., FPGA has reconfigurability.
FPGA test is a processing for finding out whether there is a fault in FPGA’s resources or not, while FPGA diagnosis is for finding out what fault is in which resource of FPGA. There are two methods for testing and diagnosing FPGAs. One is application-independent method and the other is application-dependent method. The application-independent method can test all resources of FPGA, and the application-dependent method can test only the resources used in the circuit mapped into FPGA.
Factories increase the manufacturing yield of FPGAs by performing application-dependent tests and diagnoses. Application-dependent tests and diagnoses of FPGAs are also important to users because there may be FPGAs that have not passed application-independent tests. In FPGAs, the interconnect resource occupies more chip area than other resources. Therefore, faults in FPGA are mostly interconnect faults.
Two methods have been mainly employed for application-dependent tests and diagnoses of interconnect faults of FPGA. These previous methods are all for testing and diagnosing interconnect of circuits with look-up tables and flip-flops when mapped into FPGA. The circuits mapped into FPGA often include multiplexers in addition to look-up tables and flip-flops. The previous methods are not enough for testing and diagnosing the interconnect of circuits that include multiplexers when mapped into FPGA because the function of multiplexers cannot be changed arbitrarily, unlike look-up tables.
Son Yong Jun, a researcher at the Faculty of Electronics, has proposed a new method for diagnosing interconnect faults of circuits with multiplexers when mapped into FPGA.
This method is an application-dependent method for diagnosing only interconnects of FPGA used in circuits. What is special about this method is to use the hierarchical structure of multiplexers and a single-term function.
The proposed method can be applied to diagnosing any single stuck-at fault and bridging fault in the net of circuits comprised of look-up tables and multiplexers.
...
Jo May 4, 2026
Horse riding is a sports event to decide who rides faster on horseback and who performs more spectacular stunts on horseback.
Our country has a very long history of using horses. The Koreans have bred many horses of native kinds suitable for breeding in the mountainous and rugged terrain of the country since long time ago.
The excellent riding skills of the ancestors were inherited and developed at a high level, with such contents as handling weapons and hurdling on horseback being added to them. The best horse riders in the history of the country were the Koguryo people.
The technical contents of horse riding include preparation for horse riding, methods of mounting and dismounting a horse, standard sitting position, learning how to ride at a walking pace, quick pace and gallop and others.
Horsemanship is particularly conspicuous in horse riding.
It is literally performing stunts on horseback, including those of standing on a running horse, turning over from one side to the other by holding the saddle and dragging feet on the ground by clinging to the horse.
As the country has full conditions for horse riding good for health, the enthusiasm for riding is steadily growing stronger among working people, youth and children.
...
Jo Apr 28, 2026
Composite shell structures with varying thickness are often used in different industrial fields because it could exhibit structural advantages at minimum material cost.
Recently, many works have been reported for static and dynamic analyses of different structures with variable thickness. Various methods such as Haar wavelet method, Jacobi-Ritz method spectral-Tchebychev method, dynamic stiffness method, finite element method and meshfree method have been employed for numerical analysis of composite structures. In recent years, the meshfree method has attracted significant attention of many scholars.
Jo Ju Chol, a researcher at the Faculty of Mechanical Science and Technology, developed a meshfree Jacobi-radial point interpolation (Jacobi-RPI) method for free vibration and stochastic response analyses of laminated composite sectorial and annular plates with straight fibers and variable thickness.
First, he adopted the Hamilton’s principle to establish the equations of motion of the laminated composite sectorial plate with straight fiber and variable thickness in the framework of first-order shear deformation theory (FSDT). Then, he approximated the displacement components of the plate by using the meshfree Jacobi-RPI shape function. As the laminated annular plate with straight fiber is not symmetrical, he obtained its motion equations by combining the equations of several sectorial plates.
He validated the accuracy and reliability of the proposed method through a sufficient number of numerical studies.
For more details, you can refer to his paper “A meshfree formulation for free vibration and stationary stochastic response analyses of laminated composite annular plate with straight fibers and variable thickness” in “Acta Mech” (SCI).
...
Jo Apr 26, 2026
As is known, in a ball screw–driven servomechanism, the servo motor and the ball screw can be connected directly or via a tooth belt drive, a gear pair or a commercial reducer. However, more complex systems cause more kinematic errors in the machines, so in precision machine tools, the former is more common, but in conventional machine tools it is more economical to use the latter. This is because the latter can improve the resolution in an open system, replace the output of a high-speed low-torque servo motor with the output of a low-speed high-torque unit, significantly reduce the load inertia torque in terms of the motor shaft to favor inertial matching and has the potential to significantly reduce electric consumption by reducing the size of the motor. Especially, tooth belt drives are commercially available and inexpensive but have a relatively small backlash compared to other speed reducers, which makes them a large part of industrial applications. On the other hand, since the former is a special case of the latter, the results of the latter study can also be applied to the former. Certainly, the study on optimal selection of the key components of ball screw–driven servomechanisms with tooth belt drives is a subject of great socio-economic significance.
Jang Rim Chol, a researcher at the Faculty of Mechanical Science and Technology, proposed a method for determining the optimal combination of the key components (servo motor, ball screw, and tooth pulley pair) of a ball screw–driven servomechanism with a tooth belt drive transmission. The proposed method deals with a more generalized optimization problem because it focuses on the optimization of a ball screw–driven servomechanism with a reducer (tooth belt drive transmission) unlike previous works that focused only on the optimization of a system where the servo motor and the ball screw are directly connected.
The proposed method enables optimal selection of the key components of a ball screw–driven servomechanism for different purposes including machine tools, without subjective selection or prediction of some components or some parameters for different objective functions.
You can find the details in his paper “Selection of key components in ball screw–driven servomechanisms with toothed belt drive transmission for machine tools through combinational optimization” in “The International Journal of Advanced Manufacturing Technology” (SCI).
...