Jo Jul 29, 2025
In wireless rechargeable sensor networks (WRSNs), charging request nodes (RNs) are characterized by several criteria which are contradictory.
Recently, on-demand charging scheduling schemes, which use two or more multicriteria decision-making (MCDM) methods, have been proposed. However, these schemes use a pairwise ratio scale which can magnify the actual pairwise difference between multicriteria, and do not take into account the trade-off between performance metrics.
Ri Man Gun, an institute head at the Faculty of Communications, has proposed an on-demand charging scheduling method based on a fuzzy cognitive network process (FCNP) which uses a fuzzy pairwise interval scale.
The proposed method, called an integrated FCNP-Q-learning-based scheduling (iFQS), first uses FCNP to exactly assign the relative weights to five multicriteria for charging prioritization and to three multicriteria for partial charging time (PCT) determination, respectively.
Then, in charging path planning with Q-learning, the BS uses these five criteria’s weights to design the reward function and select the most suitable next charging sojourn point. On the other hand, the three criteria’s weights are used to reasonably determine the PCT at charging sojourn points while achieving a desirable trade-off between charging metrics.
The results of the extensive simulation show that the iFQS significantly improves charging performance in comparison with the existing MCDM-based methods.
You can find the details in his paper “iFQS: An Integrated FCNP-Q-Learning-Based Scheduling Algorithm for On-Demand Charging in Wireless Rechargeable Sensor Networks” in “International Journal of Distributed Sensor Networks” (SCI).
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Jo Jul 28, 2025
We often see people with splints at the fracture site after operation on the fractures of arms, legs, wrists or ankles caused by various accidents or severe exercises. However, conventional splints are esthetically unpleasant and bulky. Moreover, patients feel uncomfortable if the splints are not customized and suitable for them. Also, their heavy weight can impose a great burden on patients, and their poor ventilation conditions might lead to several skin diseases in hot weather, thus prolonging the recovery time.
The Additive Manufacturing (AM) technique has been widely used in many medical practices, including fabrication of orthoses, thus, providing increased satisfaction to patients and effective rehabilitation therapy. Several papers have been published on the fabrication of customized orthoses using the Fused Deposition Modeling (FDM) technique. In particular, customized orthoses fabricated by FDM can provide patients with best comfort with reduced incidence of various complications due to air permeability.
Om Myong Song, a section head at the Faculty of Materials Science and Technology, has determined a reasonable structural dimension of orthopedic orthoses fabricated by FDM, using a finite element simulation based on the uniform design, the simple additive weighting method, the multiple linear regression model and the grid search optimization method.
The reasonable values for the structural dimension factors of the orthosis are shell thickness of 2.2mm, lattice thickness of 6.4mm, and number of ventilation holes of 15.
If further information is needed, you can refer to his paper “A reasonable approach to determine structural dimension of FDM fabricated orthopedic orthosis using finite element simulation and simple additive weighting method” in “Journal of Mechanical Engineering Science” (SCI).
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Jo Jul 25, 2025
In Wireless Sensor Networks (WSNs), each sensor node uses a battery with limited capacity, so it is important to extend its lifetime. Wireless rechargeable sensor networks (WRSNs) use wireless energy transfer technology to provide energy to sensor nodes, and thus, they have the potential to extend the lifetime of energy-limited sensor nodes to infinity, unlike traditional wireless sensor networks.
WRSNs provide energy to sensor nodes with the help of an MC. Thus, in WRSNs, it is one of the most important challenges to develop a charging scheduling scheme that determines an effective order in which sensor nodes should be charged, due to charging capability constraint such as the limited MC’s battery capacity.
Recently, several multi-criteria decision making (MCDM) based charging scheduling schemes have been proposed. However, these schemes have still connoted the problems from the viewpoint of assigning weights to multi-criteria and exploiting redundant capability of a Mobile Charger (MC).
In order to solve the above-mentioned problems, Ri Man Gun, an institute head at the Faculty of Communications, has proposed an efficient charging scheduling scheme by using an integrated FCNP-TOPSIS.
He has conducted some extensive simulation experiments to show that the proposed scheme greatly improves the charging and network performance at various performance metrics compared to the existing ones.
For more information, please refer to his paper “An integrated MCDM-based charging scheduling in a WRSN with multiple MCs” in “Peer-to-Peer Networking and Applications” (SCI).
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Jo Jul 24, 2025
Electrochemical energy storage systems have been extensively studied because they provide stable and reliable electricity for power systems. Among them, Vanadium Redox Flow Batteries (VRFBs) have attracted a great attention because of their high stability, wide application range, technological maturation, low maintenance cost and long lifetime compared to lithium batteries. In the VRFB systems, the ion exchange membrane (IEM) is a core component that transports protons while preventing both anolyte and catholyte from cross-mixing.
In general, Nafion membranes, which are widely used in fuel cells and redox flow cells, have high proton conductivity and chemical stability but their commercialization is limited by their high cost and low ion selectivity. At present, some cheaper ion exchange membrane materials are being used: sulfonated aryl-based polymers such as sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly (ether sulfone) (SPES) and sulfonated poly(phthalazinone ether ketone) (SPPEK). Of them, the SPEEK ionomer is considered as the most promising alternative to Nafion for VRFBs due to its ease of preparation, low cost, relatively good ionic conductivity, and chemical and mechanical stabilities.
Han Song Il, a post-graduate student at the Faculty of Chemical Engineering, has prepared composite membranes incorporating SPEEK as a proton conductive medium into TiO2 nanopapers to improve the mechanical and chemical stabilities of SPEEK membranes for VRFBs.
The SPEEK/TiO2 nanopaper composite membranes exhibited almost twice the tensile strength and only one-third the vanadium ion permeability compared to pristine SPEEK (DS=60%).
For more information, please refer to his paper “High durable SPEEK/TiO2 nanopapercomposite membrane for vanadium redoxflow battery” in “Journal of Saudi Chemical Society” (SCI).
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Jo Jul 23, 2025
Drying is necessary for the storage of food and agricultural products such as rice and for the extension of their shelf life. Thus, it is an important post-processing step that consumes a considerable amount of energy.
Grain dryers include fixed bed dryers, fluidized bed dryers, moving bed dryers, etc. In an attempt to get a large amount of grain with the required moisture in a given time, a packed moving bed dryer was developed. The advantages of a packed moving bed dryer are the use of a lower-temperature air source and the realization of waste heat recovery. Therefore, it is very convenient to use a packed moving bed dryer to dry large amounts of cereals to the desired moisture content in a limited time. Furthermore, it is an important task to reasonably manipulate the drying process of grain in the packed moving bed dryer of high capacity.
Jon Chol Jin, a section head at the Faculty of Heat Engineering, has proposed a numerical approach for grain drying process in a packed moving grain dryer to study the steady process of the moisture content of grains based on a newly proposed steady state equation.
He has validated the accuracy of the proposed method through a comparison with precedent experimental results for moisture content and temperature of grains dried in a fixed bed dryer.
You can find the details in his paper “Steady state analysis for heat and mass transfer of grain dried in a packed moving bed dryer” in “International Journal of Food Engineering” (SCI).
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Jo Jul 22, 2025
With excellent hardness, low density, strong corrosion resistance, high melting point, titanium is extensively applied in our daily life and industries such as aviation, aerospace, machine-building, etc.
A researcher proposed a method for the industrial production of titanium, which is energy-consuming and expensive, but titanium production has still been dependent on this process, where the titanium chloride is reduced with metallic magnesium. There were some other methods, but they only achieved successes in the laboratory. The issues of energy consumption, equipment, environment, cost reduction, raw materials supply, etc. made its industrialization difficult.
An Hyo Song, a researcher at the General Assay Office, has investigated the direct electrolysis of CaTiO3 in molten salts, with the aim of reducing the electrolysis time and of improving the electrolysis efficiency in the production of titanium by electrolysis, and compared it with the direct electrolysis of titanium dioxide.
After mixing TiO2 and CaO well in a ball mill, he prepared porous CaTiO3 by sintering the mixture at 1 100℃ for 2 hours. He used this compound as cathode, the graphite as anode and the molten CaCl2-NaCl as electrolyte for electrolysis, which was performed at 800℃ and the constant-voltage of 3.2V in dry argon atmosphere.
The CaTiO3 was electrolyzed directly to Ti2O3 initially. Oxygen ions were removed gradually with the increase of electrolysis time, and Ti3O and Ti were prepared in 50h. The time of electrolysis was reduced to 80% of the time for reduction of TiO2 alone.
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