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.
...
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.
...
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.
...
Jo Dec 10, 2024
Industry 4.0 is characterized by the unprecedented connection by the Internet of things, Internet of Services, and called cyber-physical system (CPS), which can be considered systems that bring the physical world and the cyber space together.
CPS is defined as engineered systems that are built from and depend upon the synergy of computational and physical components. CPS has attracted a lot of research attention and many CPS-based applications have been built, such as smart healthcare, smart transportation, smart city, cyber-physical vehicle tracking system, etc.
CPSs have two parallel networks to control, namely a physical network of interconnected components of the infrastructure and a cyber-network comprised of intelligent controllers and the communication links among them. CPSs are able to interact with their environment via sensors and actuators. CPSs are expected to enable factories to organize and control themselves autonomously in a decentralized fashion and in real time. These factories are often referred to as smart factories.
The analysis of process history data by the product lifecycle requires new architectures and platforms for dealing with the enormous volume of data of great variation and fast speed. These drive the conventional data ingestion and storage to their limits, so Big Data platforms are needed.
Cloud computing infrastructure can serve as an effective platform for data storage required to perform big data analysis. Cloud computing not only provides facilities for the computation and processing of big data but also serves as a service model.
Kim Ryo Chol, a section head at the Faculty of Information Science and Technology, has proposed a big data aggregation and analysis system model for industrial cyber-physical system and its implementation in cloud computing environment. First, he explored a closed-loop cyber physical system model based on the big data ingestion and analysis system that provides optimization feedback. Second, he proposed an architecture of big data ingestion and analysis system and a vSphere-based private method of cloud environment configuration for its implementation.
He examined the data read performance of the proposed method compared with a traditional database. The experimental results show that the proposed architecture is faster than the one based on MySQL in terms of data processing time.
...
Jo Dec 8, 2024
Seven-storey Tower at Hyonhwa Temple was originally standing on the site of a temple called Hyonhwa Temple at the foot of Mt. Ryongchu in Wolgo-ri, Jangphung County, Kaesong City, but at present it is in Koryo Museum.
According to the historical records, the tower was built in 1020.
It consists of a platform, the body of seven stories and a head.
It is 8.64 meters high and each side of the platform is 3.9 meters long. It is rather tall as a stone tower of the Koryo age.
On each side of the platform are three pillars between which properly faced brick-shaped stones are neatly piled in five layers. Thick plate stones are placed on the top of the platform. Such formation of the platform is rare for stone towers.
What is so unusual about the tower is curved eaves and corner columns.
On the seven body stones are engraved with Buddhist images, which shows excellent and sophisticated engraving.
The tower is large in scale and made in considerable dimensions with exquisite workmanship of parts and a good harmony of the whole and the parts.
The tower is a precious national treasure showing the tower architecture of Korean ancestors and its development.
...
Jo Dec 5, 2024
In recent years, rapid economic development in many countries has resulted in an increase in energy consumption, and hence, a tremendous amount of industrial waste heat is emitted into the atmosphere. The recycling of the waste heat is of great significance in improving the thermal efficiency of systems.
Open cycle absorption heat pump is of great significance in improving the energy efficiency of the system by the latent heat recovery of the exhaust gas. The heat and mass transfer processes between solution and moist air are very complex and many studies have been carried out on them.
The results show that the open cycle AHP is very effective for the latent heat recovery of exhaust gas. As this process depends on the direct contact heat and mass transfer between exhaust gas and solution in the absorber, this process was mostly simulated by numerical analysis by discretizing the heat balance equations for moist air and solution along the flow direction. This method is applicable to the case of uniform distribution of air flow in the absorber. In reality, the velocity is different at each position of the absorber. In this case, the flow distribution inside the absorber should be taken into account together.
Ri Kwang Chol, a researcher at the Faculty of Heat Engineering, has built a mathematical model to describe the heat and mass transfer in the absorber of an open cycle absorption heat pump in consideration of the flow characteristics of air inside, and analyzed it by Ansys Fluent.
The results show that the absorption performance is affected by several parameters among which the solution flux has the greatest effect, and that the temperature and moisture content of outlet air depend on the inlet air velocity whose optimum value in the absorber is 1.5m/s.
...
