Jo Jul 14, 2026
Ultrafine-grained pure titanium is characterized by its exceptional mechanical properties, among which high ultimate strength and high yield value are of utmost importance. Equal channel angular pressing (ECAP) and ECAP+cold extrusion (CE) have been used to process ultrafine-grained pure titanium.
Though many aspect studies on the mechanical deformation behavior of ultrafine-grained (UFG) pure titanium have been carried out, there is little study on systematic qualitative and quantitative characterizations on the temperature-dependent deformation and fracture features of pure titanium processed by ECAP and CE.
The study on the temperature-dependent deformation and fracture features of ultrafine-grained materials is of great interest because of their limited application temperature.
Yun Jong Guk, a section head at the Faculty of Mechanical Science and Technology, investigated the tensile deformation and damage behavior and microstructures of ultrafine-grained (UFG) pure titanium processed by ECAP and ECAP+CE at different temperatures, and carried out quantitative fractal analyses of deformation and damage morphologies by the yard-stick method based on Mathematica.
The results show that as the temperature increases, the diameter and depth of dimples on the fracture surfaces of ultrafine-grained pure titanium increase significantly with corresponding increase in the fractal dimensions. The microstructure observation results of the tensile deformation show that the dislocation density decreases significantly with increasing temperature and the grain boundaries become clear.
For more information, please refer to his paper “Temperature-Dependent Tensile Deformation and Fracture Features of Commercially Pure Ti Processed by ECAP and Cold Extrusion” in “Proceedings of KUTIC-2025”.
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Jo Jul 13, 2026
Coal processing is the most effective method for removing unwanted minerals and pollutants from coal, and there are several techniques for it including physical, chemical and physicochemical separation.
Among various physical separation methods, the selective crushing separation is a promising method for reducing specific energy consumption during the early stages of classification and for treating low-grade ores and tailings disposal.
Currently, toothed roll crushers are commonly used in various stages of mineral processing. The toothed roll crushers can be designed to be with either a single toothed roll or a double toothed roll.
The selective crushing device with hanging rings and a toothed roll is a kind of a single toothed roll crusher in which many hanging rings are supported by the supporting structure including a beam and a supporting rod. The supporting structure for hanging rings not only stands the weight of the rings and the dynamic loads during crushing processes but also constricts the freedom degree of the rings. The supporting structure may have a great influence on the crushing performance of this selective crushing device.
Jon Chol Min, a researcher at the Faculty of Mining Engineering, has proposed a new type of toothed roll based selective crushing device, and investigated the effect of the supporting structure to improve the crushing performance of the device.
The analytical result of the interaction of hanging rings and feed particles shows that the placement of the supporting rod has the greatest influence on the interaction force, and that the placement angle of the supporting rod for hanging rings is a critical design parameter for the improvement of crushing performance of the selective crushing device.
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Jo Jul 12, 2026
Capacitive pressure sensors have been widely studied and applied for their advantages such as high measurement sensitivity, wide pressure measurement range, low power consumption, robust structure, high overload characteristics, low fabrication cost, etc. The research on capacitive pressure sensors mainly focuses on improving the linearity of output characteristics and sensitivity. With this increasing research, touch mode capacitive pressure sensors (TMCPS) have been developed with better sensitivity and linearity than conventional planar electrodes.
The existing TMCPSs have constant touch point pressure (TPP) of different values. These TMCPSs operate in normal mode between zero pressure and TPP when external pressure is applied. The TPP of TMCPS has a direct effect on the effective operating pressure range, sensitivity and linearity of the device.
Rim Chang Sik, a researcher at the Institute of Semiconductor, has proposed a new structure of TMCPS with a spherical substrate electrode with TPP near zero, and investigated its characteristics.
The proposed TMCPS consists of an elastic diaphragm-top moving electrode that causes deformation under external pressure, and a curved bottom fixed electrode. The two electrodes are in touch before the external pressure is applied, and when the external pressure is applied, the upper moving diaphragm acts as a touch type, wrapping the bottom surface electrode from the beginning.
As the TTP of this device is near zero, it has a wider range of effective operating pressure, and its curved bottom surface provides better sensitivity and linearity than a planar CPS.
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Jo Jul 10, 2026
What is important in energy supply is to increase production and raise the level of energy management of energy-consuming units to save energy as much as possible and make effective use of it.
The need to raise the level of energy management in enterprises is primarily due to the limited energy resources and secondly due to the need to increase production with limited energy and to ensure economic profitability.
In order to meet these requirements, many researchers have presented several theories and approaches for energy management such as simulation systems, modeling, energy storage, and energy information systems, but no research has been conducted to comprehensively evaluate the level of energy management in enterprises.
Ra Kwang Myong, a researcher at the Faculty of Industrial Economic Management, set the weights of energy consumption per unit of products (work), energy capacity index, energy utilization efficiency and energy consumption elasticity coefficient indices by using the analytic hierarchy process, and proposed a method to evaluate the energy management level of enterprises by the weighted average method.
By setting quantitative indicators for comprehensively reflecting the energy management of an enterprise, i.e. energy consumption per unit of products, energy capacity index, energy use efficiency and energy consumption elasticity coefficient as evaluation indicators, the proposed method makes it possible for enterprises to accurately evaluate energy management and to take necessary economic and technical measures.
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Jo Jul 9, 2026
With the reduction in mining capacity due to the long-term exploitation of thick ore bodies in the world at present, the mining industry has just focused on mining of thin ore bodies. To improve recovery rate, reduce production costs and ensure stable production for thin ore bodies, new mining processes and equipment must be developed.
A pneumatic bucket loader plays the key role in mechanizing difficult and arduous loading operations in the mining industry. In particular, developing a small bucket loader is an important task for mechanizing loading in small pit faces with unfavorable working conditions.
A loader should be designed to meet the following basic requirements: First, it should be kept to a minimum in overall and operating dimensions, while providing a reasonable capacity of the bucket to ensure enough productivity. Second, all components must be simple in structure and convenient for operational maintenance to ensure operational reliability. Third, the pneumatic consumption and working pressure of the loader should be lowered.
To meet these requirements, it is important to select a suitable working mechanism and determine its optimum structural parameters for satisfying required working indices by minimizing the loader and maximizing its capacity.
Kim Hyok Chol, a researcher at the Faculty of Mining Engineering, analyzed the performance of a bucket loader using a pneumatic cylinder as a hoisting mechanism, and conducted a research to minimize its work height and output during hoisting.
He built a mathematical model of the working mechanism by analyzing the motion trajectory of the bucket’s end point and determined optimum structural parameters of the working mechanism for smooth operation in a narrow work face by lowering the bucket loading height to 1 600mm using the MATLAB optimization tool.
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Jo Jul 8, 2026
Currently, SCR (Silicon Controlled Rectifier) is widely used in power electronic devices to convert and control electrical energy.
If a rapidly rising anodic voltage is applied between the anode and the cathode without giving a gate trigger signal, the device is open even if it is much smaller than the breakover voltage under forward-off conditions. This turn-on mode is called dU/dt turn-on or dU/dt failure.
In thyristor fabrication, Al or Ni is used as electrode materials. Unlike the electrode structure of Al elements of p type, the emitter shorts structure was proposed for Ni electrode SCR, but it was not so useful because the emitter shorts effect was not significant and macroscopic shorts structure was found. One of the reasons is that the surface doping concentration of the shunt contact cannot be as high as the emitter region due to the limitation of emitter surface doping concentration when the device is fabricated, and the other is that the Al electrode structure does not suffer from the base-layer ohm contact problems, but the Ni electrode structure does not have ideal ohm contact. Therefore, increasing the p2 region surface doping concentration in a thyristor of Ni electrode structure is very important to improve the forward and reverse blocking voltage symmetry and dU/dt capability.
In order to enhance the cathode emitter shorts effect of SCR of Ni electrode structure, Kim Won Man, a researcher at the Institute of Semiconductor, has proposed a cathode groove etch scheme in which the surface doping concentration in the region p2 can be increased to the emitter region surface doping concentration value, and analyzed the relationship between the dU/dt capability and cathode groove etching structure parameters of the device.
The results show that forward and reverse blocking voltage symmetry is within 5% and the critical forward blocking voltage rise rate dU/dt is improved by 1.5 times.
His study results can be applied to power thyristors including TRIAC (Bidirectional Thyristor) with Ni electrodes and GTO (Gate-Turn-0ff Thyristor).
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