Integrated FCNP-VWA-MCDM(i) Methods for On-Demand C...

Jo Sep 30, 2025

On-demand charging schemes have been recently proposed to make efficient charging schedules of mobile chargers by introducing MCDM methods in wireless rechargeable sensor networks (WRSNs). However, most of the existing schemes use paired ratio scale (PRS) for weight assignment of multiple criteria to exaggerate the actual paired difference between them, and in the case of using FCNP of paired interval scale (PIS) for weight assignment of multiple criteria, weight compensation is not considered.

What is more, it is still unknown which is the best method for integrating FCNP with several MCDM approaches.

Rim Ju Song, a student at the Faculty of Communications, with the help of Ri Man Gun, an institute head of the same faculty, has proposed novel CS methods by integrated FCNP-VWA-MCDM(i) called FCVM(i) for solving all these problems.

The proposed methods first assign the weights to multiple criteria discriminating charging request node (cRNs) using FCNP and make compensation of them to be relatively exact weights with VWA. Then, on the basis of these weights, MCDM(i) is used to select the most proper next charging position. Recharging schedule is drawn up in this way and, at the same time, reasonable partial charging time at the selected charging locations are determined using the assigned weights with FCNP-VWA.

The extended experimental results prove that the FCVM(1) using TOPSIS gives the best performance among FCVM(i) methods.

You can find the details in his paper “FCVM(i): Integrated FCNP-VWA-MCDM(i) Methods for On-Demand Charging Scheduling in WRSNs” in “Journal of Data Science and Intelligent Systems” (SCI).

Analytical Properties and Box-counting Dimension of...

Jo Sep 29, 2025

Fractal interpolation function (FIF) is a function which interpolates a given data set and whose graph is a fractal set. In 1986, M. F. Barnsley introduced the FIF using an iterated function system (IFS). Ever since, many researchers have studied the FIFs and applied them to a lot of scientific fields such as computer graphics, function approximation, signal processing, metallurgy, earth science, surface physics, geography, geology, medical science, chemistry, etc.

Rakotch contraction is the generalization of Banach contraction, which implies that the use of Rakotch’s fixed point theorem enables modeling of more objects than the use of Banach’s fixed point theorem. Moreover, hidden variable recurrent fractal interpolation functions (HVRFIFs) with Hölder function factors are more general than fractal interpolation functions (FIFs), recurrent FIFs and hidden variable FIFs with Lipschitz function factors.

Ro Chung Il, a researcher at the Faculty of Applied Mathematics, has demonstrated that HVRFIFs can be constructed using the Rakotch’s fixed point theorem, and investigated the analytical and geometric properties of those HVRFIFs.

Firstly, he constructed nonlinear hidden variable recurrent fractal interpolation functions with Hölder function factors on the basis of a given data set using Rakotch contractions. Next, he analyzed the smoothness of the HVRFIFs and showed that they are stable for the small perturbations of the given data. Finally, he obtained the lower and upper bounds for their box-counting dimensions.

If further information is needed, please refer to his paper “Analytical properties and the box-counting dimension of nonlinear hidden variable recurrent fractal interpolation functions constructed by using Rakotch’s fixed point theorem” in “Applied Mathematics and Computation” (SCI).

Vibro-Acoustic Response Analysis of Multi-Stepped C...

Jo Sep 28, 2025

It is well known that cylindrical shell structures are widely used in many industrial fields including mechanical, aerospace, ship building, chemical and architectural industries. Typical examples are fuselage in the aerospace industry or submarines in the shipping industry, and vessels in the chemical industry. In the structures of these examples, various types of composite materials are being applied, either due to their performance or structural requirements. In addition, these structures will be worked in different environments and load conditions.

Generation of vibrations leads to noise. Therefore, there have been many studies to analyze the vibration and acoustic characteristics of these structures and as a result, various shell theories have been proposed. Based on these shell theories, studies have been carried out to develop solution methods with high computational accuracy and computational efficiency for vibration analysis of laminated composite cylindrical shells.

However, the study of the vibro-acoustic analysis of stepped cylindrical shells is limited, and what is more, there is no study of acoustic analysis.

U Ju Hyok, a researcher at the IT Institute, has analyzed the vibro-acoustic responses of laminated composite multi-stepped cylindrical shells immersed in fluid medium by applying the energy and spectral boundary element method.

He has verified the accuracy and reliability of the proposed method by comparing it with the results obtained by references. Then, he has conducted several numerical analyses to provide the influence of geometry, material properties, boundary condition, fluid medium and force types on vibro-acoustic behaviors of the laminated composite multi-stepped cylindrical shells.

For more information, please refer to his paper “Vibro-Acoustic Response Analysis of Laminated Composite Multi-Stepped Cylindrical Shells Immersed in Fluid Medium” in “Journal of Vibration Engineering & Technologies” (SCI).