Jo Aug 11, 2023
A research team led by Choe Kyong Hyok, a researcher at the Faculty of Mechanical Science and Technology, has newly built an automatic frozen fish block packaging machine to ensure convenient packaging processes and higher productivity.
This machine is for wrapping in thin films frozen fish blocks entering through a thawing machine before storing.
The machine consists of a feeding conveyer, a longitudinal packaging conveyer, a lateral packaging conveyer, a longitudinal adherer, a lateral adherer and a film feeding system.
This machine keeps its feeding velocity at 0.5m/s in order to eliminate inertia of each 10-kilogram frozen fish block when they are stopped.
First of all, each frozen fish block entering through the thawing machine is fed to the feeding conveyer from the longitudinal direction. Each frozen fish block coming out from the feeding conveyer is fed to the longitudinal packaging conveyer pushing a vinyl film linked from top to down. When each frozen fish block is located in place, the longitudinal packaging conveyer is stopped and the longitudinal adherer works for packaging. This time the proximity detector detects the correct position of frozen fish blocks to ensure perfect joint.
Then, the longitudinal packaging conveyer starts up to move the blocks to the lateral packaging conveyer. The same process takes place for lateral packaging.
Finally, the blocks are forwarded through the lateral package conveyer to the transshipping device.
The productivity of this packaging machine is 900 blocks per hour, the output of the conveyer motor is 0.37kW and the reduction ratio is 15.
The packaging machine will find wide application at fisheries for automatically packaging 10-kilogram frozen fish blocks, and for making storage, transportation and supply of them convenient and clean.
...
Jo Aug 10, 2023
A research team led by Kim Song Ho, a section head at the Faculty of Automation Engineering, has developed a multi-agent reinforcement learning experiment system using a process simulator.
In recent years, reinforcement learning has been considered as a learning method for acquiring behavior rules that can be flexibly adapted to complex and diverse environments, and many multi-agent reinforcement learning methods have been developed to effectively perform, in cooperation with several agents, complex problems impossible with one agent.
The multi-agent reinforcement learning experiment system consists of a process simulator, a controller, and an IPC.
On the IPC's experimental program interface, a user can simulate a learning process in detail by randomly changing the multi-agent system configuration and reinforcement learning parameters.
The change of the convergence rate according to the mutual cooperation algorithm of the agents can also be observed.
The research team developed a new multi-agent collaboration algorithm and demonstrated its superiority over previously developed ones.
This system can be used to develop multi-agent collaborative learning algorithms and to simulate real processes.
It can also offer practical trainings on intelligent supervisory control to students majoring in management system engineering and generalization to educational units across the country.
...
Jo Aug 7, 2023
Ri Chang Myong, a researcher at the Faculty of Distance Education, has developed a virtual tour supporting system by modeling the images of places for a visit.
The system consumes less time and effort for modeling and at the same time the photos further raise feeling of actuality.
The system consists of a panoramic image generation module, a modeling and virtual tour editor, a virtual tour module and a management module.
In the panoramic image generation module, image stitching technology is employed so that the photos are stitched to produce images with wider FOV.
In the edition module, the panoramic images generated in the previous stage are modeled. Here, several functions are added for interaction.
The virtual tour module is for a virtual tour. The courses of tour are recorded through the network.
In the management module, registration, modification, deletion and upgrade of objects for virtual tour are performed.
Ordinary cameras can also be used for the system.
It will prove to be useful in the education sector. It will save a lot of time and money by making it possible for students to do production practices, visits and school trips on computer without bothering to go out to the spot.
...
Jo Jul 31, 2023
Direct and inverse scattering problems play a central role in areas such as radar, sonar, geophysical exploration, and nondestructive testing and they have been widely studied in recent years. In particular, the uniqueness and existence of direct scattering problems, the reciprocity relation and completeness of electric far field patterns, etc. are basic in the inverse scattering theory.
In most applications as well as in geophysical exploration and nondestructive testing, it is, in general, assumed that the scattering obstacle is buried in a piecewise homogeneous medium and is partially coated by a dielectric. For example, underground mines and submarines are embedded in a piecewise homogeneous medium with air-earth and air-water interfaces and they consist of metallic and nonmetallic parts.
Kim Yun Chol, a section head at the Faculty of Applied Mathematics, has studied uniqueness and existence for a direct electromagnetic obstacle scattering problem in a piecewise homogeneous medium, some properties of a scattered field and a far field pattern, including boundedness, reciprocity relation and completeness, where it is assumed that the obstacle is a partially coated perfect conductor and the incident field is given by the electromagnetic plane wave.
He has conclusively proved that the electric far field pattern of the solution of the scattering problem of the electromagnetic plane wave as well as uniqueness and existence for the solution of the direct problem of scattering of time-harmonic electromagnetic waves by a partially coated obstacle buried in a piecewise homogeneous medium satisfies the reciprocity relation, and that the set of electric far-field patterns is complete in a Hilbert space.
These results are of great significance to the study on the solution of inverse electromagnetic scattering problems, i.e. determination of the location, shape and physical property of obstacles from the knowledge of electric far field patterns.
For further information, please refer to his paper “Electromagnetic wave scattering by a partially coated obstacle in a piecewise homogeneous medium” in “Mathematical Methods in the Applied Sciences” (SCI).
...
Jo Jul 27, 2023
Analytic hierarchy process (AHP) is a well-known attribute weighting method in multi attribute decision-making. Its major requirement is to satisfy the consistency of pairwise matrix (PM).
To meet these requirements, Yang Won Chol, a researcher at the Faculty of Materials Science and Technology, proposed a new consistency improvement method of PM based on consistency ratio (CR) decreasing rate. In this method, the CR decreasing rates of all the PMs reconstituted by replacing all elements of the PM with the lower and upper neighbouring 9-point scales are calculated, and an element with maximum CR decreasing rate is found before it is modified to its lower or upper neighbouring scale.
Then, he developed a third order approximate polynomial for random consistency index by least square method. It enables determination of the RI value according to the number of attributes without a numerical table.
Finally, he proposed a final PM determination method and a final attribute weighting method with decision makers’ levels in consideration, on the basis of the CR values of individual PMs, when several decision makers perform their own pairwise comparisons.
With two numerical examples, he tested the performances of the proposed and some previous consistency improvement methods.
The results demonstrate that the proposed method improves the consistency of PM better and faster with smaller amount of modification than that of the previous methods, while it modifies the elements of the PM to 9-point scales necessarily.
He has applied the proposed method to hip joint prosthesis material selection to verify that the proposed method may be widely used in practical applications of AHP.
More information about this is found in his paper “Consistency Improvement Method of Pairwise Matrix Based on Consistency Ratio Decreasing Rate and Attribute Weighting Method Considered Decision Makers’ Levels in Analytic Hierarchy Process: Application to Hip Joint Prosthesis Material Selection” in “Mathematical Problems in Engineering” (SCI).
...
Jo Jul 26, 2023
Attention to ship energy efficiency and CO2 emission is significantly increasing.
Both are related to fuel consumption and they can be assessed by ship energy efficiency operational indicator (EEOI).
Jon Min Hyok, a section head at the Faculty of Shipbuilding and Ocean Engineering, has developed a formula for estimation of an operational carbon intensity indicator (CII) and an optimal model of ship’s route and operational speed to minimize the EEOI with navigational environment and ship’s safety in consideration.
He developed a formula for estimation of CII, assuming that it is a function of ship’s main particulars such as block coefficient, and the ratio of operation speed to design speed of the ship.
For navigational environment, he considered wave and wind, which greatly influence ship’s performance including resistance and seakeeping.
For ship’s safety, he considered motion sickness incidence (MSI), one of the seakeeping indices.
Particle Swarm Optimization (PSO) algorithm was adopted to solve the model.
He illustrated the proposed method with a numerical example, comparing with full-scale data. The comparison results showed the proposed method can effectively reduce CO2 emission and improve ship energy efficiency.
If further information is needed, please refer to his paper “Optimization of ship energy efficiency considering navigational environment and safety” published in “Proceedings of the 5th International Conference on Numerical Modelling in Engineering (NME 2022)”.
...
