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 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.
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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.
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Jo Nov 24, 2024
Chloride sensors have found wide application in the fields of environment monitoring, tideland agriculture, soil science and water supply systems since chloride is widely distributed in the form of compound in nature. Although high chloride concentrations in environmental samples do not cause harm to the human body, they can cause severe corrosion in metallic pipes, leading to the destruction of water systems and to the increase in the concentration level of metal ions in drinking water. Therefore, the maximum allowable Cl− level of 250mg·L−1 has been established by the World Health Organization (WHO) for drinking water and natural water.
Usually, chloride ions in solution can be measured by gravimetry, titrimetry, spectrophotometry, potentiometry, coulometry and ion chromatography. Among them, the major applications in the industrial field are spectrophotometry, potentiometry (ISE), and coulometry.
For this purpose, optical, fluorescent, and electrochemical sensors have been developed. Optical sensors enable measurement regardless of the pH or temperature of the solution, and fluorescent sensors have the advantages of good selectivity and high sensitivity to Cl- and short response time. However, these sensors are relatively expensive and have shortcomings of short lifetime due to photolysis or bleaching of the sensing materials.
In many cases, electrochemical sensors use potentiometry based on the half-cell potential of a silver/silver chloride (Ag/AgCl) electrode measured compared to a reference electrode at equilibrium. The potentiometric determination of chloride by Ag/AgCl electrode has been widely used in harsh applications due to its low cost, simple fabrication and long-term stability.
Kim Kyong Il, a researcher at the Faculty of Electronics, has proposed a new and simple fabrication method of a highly sensitive Ag/AgCl chloride sensor for real-time measurement of water quality. He fabricated the working electrode by electrodeposition and melt deposition of AgCl + Ag2S on the surface of Ag wire and coating the PVC film on it.
The study showed a good linear relationship between the logarithm of chloride ion concentration and the electrode potential when the chloride ion concentration in tap water, seawater and agricultural irrigation water ranged from 5×10-4 to 1mol·L-1. The potential response was affected by pH, but the ions commonly present in environmental samples such as K+, Ca2+, Na+, NO3-, SO4- were not affected.
For more details, please refer to his paper “A Simple Fabrication Method of Chloride Sensor Based on Hot-Dipped Ag/AgCl@PVC for Water Quality Monitoring” in “Water Air Soil Pollut” (SCI).
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Jo Nov 24, 2024
Grounding plays a very important role in ensuring safe and reliable operation of power systems and protecting people and electrical equipment. The continuous increase in the voltage level and scale of power systems has resulted in the increasing strictness of the technical requirement for grounding devices. Grounding resistance is an important index to evaluate the effectiveness and safety of the grounding system.
The grounding resistance is usually rated at 10Ω for thunderbolt protection, and 1Ω or less than that at large scale substations.
The factors influencing the grounding resistance of the vertical electrode are the radius and length of the electrode, the soil resistivity and the embedding depth. It is essential for the design of the vertical grounding electrode to get a mathematical model of the grounding resistance that comprehensively reflects the influences of the factors on the grounding resistance of the vertical grounding electrode.
Many authors have published their research results for the mathematical modeling on the grounding resistance of vertical grounding electrodes, but they considered only the length and diameter of the vertical grounding electrode and the soil resistivity.
The length and diameter of the vertical electrode as well as the embedding depth affect the grounding resistance.
Kwon Hye Yong, a section head at the Faculty of Electrical Engineering, has obtained a mathematical model for the grounding resistance of a vertical electrode that accurately reflects the influence of embedding depth in a homogeneous soil, and verified its accuracy through computer simulation analysis and field measurements at different soil resistivity conditions.
The computational results by the proposed model agree with the results of computer simulation analysis and field measurements.
For more information, please refer to her paper “A Method for Grounding Resistance Calculation of the Vertical grounding electrode” in “Electric Power Systems Research” (SCI).
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