Magnetotellurics (MT) is widely used for oil exploration. In MT, the time series of two telluric and three magnetic components of the magnetotelluric field are generally recorded at the ground surface in the Cartesian coordinate system. In practice, however, there are some difficult cases for setting two telluric lines orthogonally to record telluric components due to obstacles like roads, wetlands, rivers, cliffs, rice banks, buildings, etc. at a given MT site.

Kim Ji Yang, a researcher at the Faculty of Earth Science and Technology, proposed a method of converting telluric components recorded in non-orthogonal coordinate systems to those in orthogonal coordinate systems by means of mathematical coordinate transformation and verified its possibility and applicability through model and field tests.

This method makes it more convenient for MT field crews to choose site positions and set electric lines.

For more information, you can refer to his paper “Dealing with Non-orthogonally Measured Telluric Components in Magnetotellurics” in “Journal of Mathematical Methods in Engineering” (SCI).

A belt conveyor is an efficient continuous carriage machine which successively moves powder or particles such as mineral, coal, gravel, sand, fertilizer, grains as well as packaged products by using a belt. To accurately measure the total weight of bulk materials conveyed continuously or the weight of individual packaged products moving quickly on a belt conveyor is important for developing a belt checkweigher.

There have been many studies to improve weighing accuracy. Those studies are basically focused on two kinds of methods; one is model-based and the other is filter-based.

Most of those studies are focused on dynamic weighing of packaged products in fast motion on a belt conveyor. However, there has been little literature for improving weighing accuracy of the belt conveyor that successively conveys bulk materials unequally distributed on the belt.

Kim Mun Hyok, a section head at the Faculty of Automatics, proposed a new hybrid weighing scheme using the discrete wavelet transform (DWT) and adaptive noise cancellation (ANC) to more accurately weigh the successively conveyed bulk material unequally distributed on the belt.

The proposed scheme uses wavelet decomposition and reconstruction to remove noises of high frequency and uses an adaptive filter to suppress noises of low frequency.

The simulation and experimental results show that the proposed scheme optimally removes various types of noises from belt conveyors and measures the weight with accuracy degree of ±0.5%.

If further details are needed, please refer to his paper “A DWT and ANC-based continuous weighing scheme of bulk materials in belt conveyor” in “Journal of Instrumentation” (SCI).

Calcium fluoride (CaF₂) is one of the common fluorine compounds, which is mineralogically known as fluorite. It is widely used in the production of 3-dimensionally integrated circuits, optical glass, hydrofluoric acid and ceramics, and as a flux in metallurgic industry. Owing to the increased demand for high-quality fluorite and the decrease in available resources, much attention has been paid to the study on fluorite.

There have been several studies on the characteristics of fluorite surfaces with various Miller indexes by first principles calculations. Fluorite is known as an ionic compound and it is generally cleaved along {111}, {110}, {100} and {310} planes. The cleavage along {111} plane is the easiest, followed by {110} plane and then {310} plane.

Previous studies mainly focused on the characteristics of possible surfaces with different Miller indexes and concluded that fluorite {111} surface is the safest and this is the main cleavage plane. Fluorite is an ionic crystal and calcium and fluorine layers are likely to be stacked alternatively along [111] direction. So, there may be several terminations with the same Miller index {111} surface. However, there have been few reports on the detailed characteristics of fluorite {111} surface.

Ri Chol Jin, a section head at the Faculty of Earth Science and Technology, constructed 3 kinds of possible terminations for fluorite {111} surface and calculated their surface energies, broken bond densities and relaxation degrees by using DFT calculation to determine the safest termination.

This investigation on various terminations offers a new understanding of the characteristics of fluorite {111} surface and provides useful information for further study of surface reactivity and dissolubility of fluorite.

For more information, please refer to his paper “Characteristics of Fluorite {111} Surface with Various Terminations: A DFT Investigation” in “Iranian Journal of Science” (SCI).