Jo Dec 20, 2024
Research for new deposits using the satellite image analysis method has already been carried out by many previous researchers. Studies to predict mineral prospecting sites by satellite image analysis have been mostly conducted to identify mineralized alteration zones and to detect linear structures.
Satellite image analysis generally begins with remote sensing. The integrated data is prepared for the user. In this stage, the integrated data is interpreted by various methods. In data interpretation, images are interpreted to identify various phenomena with regard to their importance.
It is widely accepted that hydrothermal alteration plays an important role in ore formation. The desirable distribution of alteration zones around the limited borders of an ore body facilitates outdoor exploration activities. Generally, hydrothermal alteration processes lead to emanation of clay and other silicate minerals, including kaolinite, sericite, quartz, chlorite, epidote, and calcite. The application of both spectral and statistical analyses of remotely sensed data can identify the above-mentioned minerals and explore the buried deposits. Hydrothermal alteration zones can be recognized from the spectral characteristics of main mineral assemblages.
Based on the spectral characteristics of main mineral assemblages, Ra Chung Yol, a section head at the Faculty of Earth Science and Technology, has determined the distribution of the hydrothermal alteration zone in the study area, using band-ratio analysis, principal component analysis, and colorimetric synthesis methods.
He has concluded that the hydrothermal alteration zone in the study area was widely distributed over an area of 2 000m×200m above the surface under the control of the ore-bringer structure, especially at the contact with the alkaline rock mass.
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Jo Dec 19, 2024
A large amount of energy is consumed for buildings around the world, and therefore, energy saving is being studied extensively.
Mixing ventilation system (MVS) is one of the mechanical ventilation systems that makes the entire indoor air mixed completely using the jet flow made from blast air. Displacement ventilation system (DVS) is one of the mechanical ventilation systems, which blows air with lower temperature than indoor air into the lower part of a room and causes upward flow of indoor air by buoyant force to exhaust it at the ceiling.
The basic difference between DVS and MVS is that DVS mainly relies on the buoyancy effect, while MVS uses mechanical ventilation force. As DVS is aimed at only meeting the requirements of the workplace, there is a thermal and concentration stratification between the lower and upper parts. DVS is characterized by good air quality, efficient emission of polluted air and significant energy saving effect. In the design of DVS, the height of thermodynamic stratification has to be set to be higher than the height of the workplace, but not too high, because it might cause waste and increase in the amount of air blast. So, the determination of the height of thermodynamic stratification is one of the vital problems arising in the application of DVS. In DVS, ventilation volume for keeping the temperature below the required level is too much when the cooling load is heavy. For DVS, experiments, experiences and engineering design methods have already been presented and mathematical analysis methods have been studied. However, there is little data about DVS for high-ceiling rooms.
Paek Myong Chol, a section head at the Faculty of Heat Engineering, has investigated the temperature change at the workplace when there is heat source in MVS and HDVS with the vertical supply duct by using CFD and presented its effectiveness. In addition, he has verified the existence of the effective length of the vertical supply duct in HDVS with supply ducts from the view of energy saving.
He has found that under the conditions of providing equal temperature and velocity of air inflow, the temperature of the air in the working zone depends on the length of a vertical supply duct, and that the temperature of the air in the working zone increases when the vertical supply duct is longer than the limited value.
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Jo Dec 17, 2024
In general, in the electromagnetic surveying, frequency dispersion of conductivity is neglected. In contrast, in the common excited polarization method, current is indirectly supplied to the underground, so the secondary voltage originated by ramp turn off in the current flow is actually frequency dispersion of conductivity. Hence, electromagnetic (EM) effect and induced polarization (IP) effect come into being at the same time, which leads to distortion, in other words, sign reversal of EM response. For this reason, many researchers deeply studied the mechanism of the sign reversal and the forward modeling in consideration of this phenomenon.
Many researchers simulated the distorted transient response by conductivity related to frequency. Most of the research results concluded that Cole-Cole model is well suited to considering IP effect observed in TDEM.
Transient response of polarizable whole space is surely different from both polarizable half space response and non-polarizable whole space response.
Jon Kwang Bok, a researcher at the Faculty of Earth Science and Engineering, has approximated the whole space electromagnetic transient field originated by rectangular loop in the whole layered space which includes polarizable layers by using the Cole-Cole model and linear digital filtering method.
As a result, he has drawn two conclusions.
First, induced voltage measured has no relationship with whether the polarizable conductive layers are above or below the measurement spot. Second, polarization must be considered in the whole space inversion as in half space because the response computed by common whole space modeling method is a lot different from that by polarizable whole space modeling method.
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Jo Dec 16, 2024
Unmanned Surface Vessel (USV) is gaining great popularity in various fields including marine environmental monitoring and coastal waters protection and it is becoming world-focused marine equipment.
USV can reduce direct human intervention and perform safe operations in hazardous environments such as marine exploration, personnel rescue, environmental monitoring and survey, etc.
When the USV is sailing, it will deviate from the given course due to the disturbances of wave, current, wind and other marine environment.
Although several technical proposals have been proposed to solve this problem, ship control still remains a very challenging problem.
Ship course is mostly controlled by the conventional PID control law. Conventional controllers are still regarded as a good choice for an auto-steering system when they have typical SISOs, but not suitable for a complex and strong nonlinear MIMO system like USV. Indeed, this method is easy and simple, but its parameters are set by manual experience and control is possible in the limited range, which leads to low adaptability.
Choe Kum Song, a section head at the Faculty of Shipbuilding and Ocean Engineering, has obtained USV’s hydrodynamic parameters from its sailing test data and built a linear mathematical model of 3-DOF for USV planar motion. On this basis, he has proposed a course control algorithm for USV based on fuzzy PD and compared it with the conventional PID law.
The simulation results show that the designed fuzzy PD law is more effective than the conventional PID law.
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Jo Dec 13, 2024
Particle size distribution measurement is indispensable for pharmaceutical industry, material manufacturing, food industry, microbiological industry, health-friendly environmental support, etc. In particular, it is very important to visualize dust particle distribution in real time in order to reliably and intuitively ensure the steady-state operation of a dust filtration system for high quality filtration.
Optical measurement techniques with laser light sources of excellent optical properties such as laser diffraction metrology, phase Doppler metrology, photon correlation spectroscopy, laser-induced fluorescence method, light extinction method, etc. have been developed and used in the field of particle size distribution measurement for short measurement time, real-time measurement, remote measurement, etc.
However, above optical dust measurement methods are independent of the visualization of dust particle distribution in the measurement area of interest.
With the recent development of high-resolution, high-sensitivity and high-speed digital cameras which are easy to control automatically, there has been a growing interest in determining particle velocity, size, and shape while visualizing particle distribution using direct imaging of particles. At present, however, the direct imaging method by digital cameras is limited to spherical particles of relatively large size (50㎛).
The size of dust particles that are particularly detrimental to human body is in the range of 0.3~5㎛, so in general cases, such digital camera optical system cannot separate dust particles from the imaging plane.
Ri Chol Man, a researcher at the Faculty of Physical Engineering, has theoretically and experimentally investigated the possibility of magnification of the particle images by introducing intense light irradiation to the imaging system, and based on the results, he has constructed a particle size distribution measurement apparatus and confirmed its usefulness.
The results demonstrate that the proposed method can be used instead of the light scattering particulate counting method, which is widely used in portable applications for measuring dust particles in the size range harmful to human body.
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Jo Dec 11, 2024
The Monument to the Great Victory in Yonsong Area is in Yonan County Town, South Hwanghae Province. It was erected in 1608, in commemoration of the victory in the battle on Yonan Fort during the Imjin Patriotic War.
During the war, the Korean people organized themselves into volunteer armies in all parts of the country and waged a vigorous struggle to drive out the Japanese invaders.
During those days, there was a proud story in which the righteous volunteers led by Ri Jong Am defended Yonan Fort to the last by beating back three thousand Japanese invaders.
The monument tells about the death-defying battles to repulse the Japanese invaders who attacked the fort from late August to early September in 1592.
The monument is standing on a double-layer rectangular pedestal block of granite. The body is made of black marble and the top is faced to form a semicircle without a head stone.
The inscription is said to have been composed by Ri Hang Bok, who was known as a clever writer in those days.
The Monument to the Great Victory in Yonsong Area, like the Monument to the Great Victory in Pukgwan, is a precious national treasure relic that tells about the victory won by the Korean people in the struggle to drive back the Japanese aggressors during the Imjin Patriotic War.
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