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.

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.

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).