The Ripsok Formation, which dates back to Pennsylvanian age, is one of the most typical transitional zones in Kangso-Samdung synclinorium.

Studies of the Ripsok Formation have focused mainly on lithostratigraphy, biostratigraphy and palaeontology; and detailed sedimentological research and study of microfacies are still needed.

Kim Myong Hak, a section head at the Faculty of Earth Science and Technology, investigated the microfacies and sedimentary environment of the Ripsok Formation in the Sungho area.

In the study area, the Ripsok Formation was subdivided into 2 microfacies that are characterized by petrographic analysis based on their depositional textures and fauna. In addition, one major depositional environment was identified in the Ripsok Formation. This is a shelf lagoon, which was interpreted as a transition zone separating the platform from the open ocean.

A vertical electrode is one of the most widely-used electrodes to construct a grounding device. As an increase in the length of a vertical electrode leads current into deeper soil, it is possible to effectively reduce grounding resistance. In practice, however, the length of a vertical electrode is limited to below a certain threshold according to working conditions.

When the soil resistivity is high, it is difficult to provide a reference grounding resistance with a vertical electrode, in which case a composite grounding device with multiple vertical electrodes interconnected with one horizontal grounding body is used. The composite grounding device is one of the grounding devices that have been widely applied to today’s grounding equipment construction. Therefore, obtaining a mathematical model for the grounding resistance of a composite grounding device is an essential issue in the design of a grounding system using it.

In the past, many studies on composite grounding devices have been carried out, and only one-sided problems have been dealt with, such as individual vertical and horizontal grounding resistances, shielding effect between them when multiple vertical electrodes are connected in parallel, and adoption of the utility coefficient to the mathematical model of the grounding resistance of the composite grounding device, etc. However, a complete mathematical model of the grounding resistance of a composite grounding device has not been obtained.

Kim Tae Song, a researcher at the Faculty of Electronics, has obtained a mathematical model that accurately reflects the logical relationship between the ratio of the distance between vertical electrodes to the electrode length and the grounding resistance of a composite grounding device, and verified its validity through computer simulations and field measurements in soil conditions with different resistivity.

The proposed mathematical model comprehensively reflects the influence of factors on the grounding resistance of composite grounding devices and it can be effectively used in the design of composite grounding devices using multiple vertical electrodes.

Up to now, many nickel production methods have been researched and industrialized, and the hydrometallurgical process of copper-nickel matte has been studied for many years. Hydrometallurgy of copper-nickel matte includes several treatment methods such as selective sulfuric acid leaching, oxygen-ammonia leaching, chlorine leaching, etc. Among them, selective sulfuric acid leaching which consists of atmospheric pressure leaching and pressure leaching has been most widely used.

However, selective sulfuric acid leaching process consisting of single stage atmospheric pressure leaching followed by pressure leaching is regarded to be ineffective for copper-nickel matte with low Cu and high Ni content.

Cha Su Gyong, a section head at the Faculty of Metallic Engineering, has proposed a 3-stage counter-current selective leaching for improving nickel leaching efficiency and copper separation efficiency of copper-nickel matte with high Ni/Cu ratio by increasing the stage number of atmospheric pressure leaching, and investigated the effects of factors such as temperature, leaching time, oxygen pressure, etc. on nickel leaching efficiency and copper separation efficiency, based on the mineralogical and metallurgical analysis of the matte.

The total nickel leaching rate determined through atmospheric pressure and high-pressure leaching experiments reaches 92.18%.