• The Mathematical Education
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• v.6 no.2
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• pp.1-9
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• 1968

In mathematics, a definition must have authentic reasons to be defined so. On defining geometric figures, there must be adequencies in sequel and consistency in the concepts of figures, though the dimensions of them are different. So we can avoid complicated thoughts from the study of geometric property. From the texts of SMSG, UICSM and others, we can find easily that the same concepts are not kept up on defining some figures such as ray and segment on a line, angle and polygon on a plane, and polyhedral angle and polyhedron on a 3-dimensionl space. And the measure of angle is not well-defined on basis of measure theory. Moreover, the concepts for interior, exterior, and frontier of each figure used in these texts are different from those of general topology and algebraic topology. To avoid such absurdness, I myself made new terms and their definitions, such as 'gan' instead of angle, 'polygonal region' instead of polygon, and 'polyhedral solid' instead of polyhedron, where each new figure contains its interior. The scope of this work is hmited to the fundamental idea, and it merely has dealt with on the concepts of measure, dimension, and topological property. In this case, the measure of a figure is a set function of it, so the concepts of measure is coincided with that of measure theory, and we can deduce the topological property for it from abstract stage. It also presents appropriate concepts required in much clearer fashion than traditional method.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.8
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• pp.1-13
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• 2020

This study examines the effect of managerial ownership on firm value in capital markets where outside governance mechanisms to discipline managers are weak or non-existent. We hypothesize that strong market forces in the U.S. confound the effect of managerial ownership on firm value, i.e., the convergence of interest argument. We test the hypothesis using data from 112 firms from Singapore Stock Exchange and 205 firms from the Stock Exchange of Thailand prior to the Asian financial crisis in 1997 when the market forces were weak, yet the investor protection was sufficient to prevent outright appropriation from management. For ease of comparison, we use methodologies from studies done on the U.S. sample firms during the same study period as ours. We find that, both in Singapore and Thailand, firm value is a function of managerial ownership, and the relation is of the famous inverted U-shaped. Moreover, the relation is robust under different model specifications. The results from Thai sample, with weaker market forces than in Singapore, lend support to many agency cost hypotheses advanced in the U.S. Our results provide useful implication for investors in emerging and frontier markets where outside governance mechanisms are yet to be fully developed.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.97-97
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• 2016

Development of advanced Li-ion battery cells with high durability is critical for safe operation, especially in applications to electric vehicles and portable electronic devices. Understanding fundamental mechanism on the formation of a solid-electrolyte interphase (SEI) layer, which plays a substantial role in the electrochemical stability of the Li-ion battery, in a cathode was rarely reported unlike in an anode. Using first-principles density functional theory (DFT) calculations and ab-initio molecular dynamic (AIMD) simulations we demonstrate atomic-level process on the generation of the SEI layer at the interface of a carbonate-based electrolyte and a spinel $LiMn_2O_4$ cathode. To accomplish the object we calculate the energy band alignment between the work function of the cathode and frontier orbitals of the electrolyte. We figure out that a proton abstraction from the carbonate-based electrolyte is a critical step for the initiation of an SEI layer formation. Our results can provide a design concept for stable Li-ion batteries by optimizing electrolytes to form proper SEI layers.

• KSBB Journal
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• v.26 no.2
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• pp.131-138
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• 2011

Some computational approaches are needed for clarifying RNAi sequences, because it takes much time and endeavor that almost of RNAi sequences are verified by experimental data. Incorrectness of RNAi mechanism and other unaware factors in organism system are frequently faced with questions regarding potential use of RNAi as therapeutic applications. Our massive parallelized pair alignment scoring between dsRNA in Genebank and expressed sequence tags (ESTs) in Caenorhabditis elegans Genome Sequencing Projects revealed that this provides a useful tool for the prediction of RNAi induced cosuppression details for practical use. This pair alignment scoring method using high performance computing exhibited some possibility that numerous unwanted gene silencing and cosuppression exist even at high matching scores each other. The classifying the relative higher matching score of them based on GO (Gene Ontology) system could present mapping dsRNA of C. elegans and functional roles in an applied system. Our prediction also exhibited that more than 78% of the predicted co-suppressible genes are located in the ribosomal spot of C. elegans.

• Smart Structures and Systems
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• v.24 no.3
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• pp.293-301
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• 2019

Bolted joints are commonly used in civil infrastructure and mechanical assembly structures. Monitoring and identifying the connection status of bolts is the frontier problem of structural research. The existing research is mainly on the looseness of a single bolt. This article presents a study of assessing the loosening/tightening health state and identifying the loose bolt by using ultrasonic guided wave in a bolt group joint. A bolt-tightening index was proposed for evaluating the looseness of a bolt connection based on correlation coefficient. The tightening/loosening state of the bolt was simulated by changing the bolt torque. More than 180 different measurement tests for total of six bolts were conducted. The results showed that with the bolt torque increases, value of the proposed bolt-tightening index increases. The proposed bolt-tightening index trend was very well reproduced by an analytical expression using a function of the torque applied with an overall percentage error lower than 5%. The developed damage index based on the proposed bolt-tightening index can also be applied to locate the loosest bolt in a bolt group joint. To verify the effectiveness of the proposed method, a bolt group joint experiment with different positions of bolt looseness was performed. Experimental results show that the proposed approach is effective to detect and locate bolt looseness and has a good prospect of finding applications in real-time structural monitoring.

• Advances in nano research
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• v.12 no.5
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• pp.489-499
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• 2022

Nanofluids have recently triggered a substantial scientific interest as cooling media. However, their stability is challenging for successful engagement in industrial applications. Different factors, including temperature, nanoparticles and base fluids characteristics, pH, ultrasonic power and frequency, agitation time, and surfactant type and concentration, determine the nanofluid stability regime. Indeed, it is often too complicated and even impossible to accurately find the conditions resulting in a stabilized nanofluid. Furthermore, there are no empirical, semi-empirical, and even intelligent scenarios for anticipating the stability of nanofluids. Therefore, this study introduces a straightforward and reliable intelligent classifier for discriminating among the stability regimes of alumina-water nanofluids based on the Zeta potential margins. In this regard, various intelligent classifiers (i.e., deep learning and multilayer perceptron neural network, decision tree, GoogleNet, and multi-output least squares support vector regression) have been designed, and their classification accuracy was compared. This comparison approved that the multilayer perceptron neural network (MLPNN) with the SoftMax activation function trained by the Bayesian regularization algorithm is the best classifier for the considered task. This intelligent classifier accurately detects the stability regimes of more than 90% of 345 different nanofluid samples. The overall classification accuracy and misclassification percent of 90.1% and 9.9% have been achieved by this model. This research is the first try toward anticipting the stability of water-alumin nanofluids from some easily measured independent variables.

• Advances in nano research
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• v.12 no.5
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• pp.441-455
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• 2022

This study explores the linear and nonlinear solutions of sigmoid functionally graded material (S-FGM) nanoplate with porous effects. A size-dependent numerical solution is established using the strain gradient theory and isogeometric finite element formulation. The nonlinear nonlocal strain gradient is developed based on the Reissner-Mindlin plate theory and the Von-Karman strain assumption. The sigmoid function is utilized to modify the classical functionally graded material to ensure the constituent volume distribution. Two different patterns of porosity distribution are investigated, viz. pattern A and pattern B, in which the porosities are symmetric and asymmetric varied across the plate's thickness, respectively. The nonlinear finite element governing equations are established for bending analysis of S-FGM nanoplates, and the Newton-Raphson iteration technique is derived from the nonlinear responses. The isogeometric finite element method is the most suitable numerical method because it can satisfy a higher-order derivative requirement of the nonlocal strain gradient theory. Several numerical results are presented to investigate the influences of porosity distributions, power indexes, aspect ratios, nonlocal and strain gradient parameters on the porous S-FGM nanoplate's linear and nonlinear bending responses.

• Advances in materials Research
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• v.12 no.1
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• pp.43-65
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• 2023

Free vibration analysis of power law and sigmoidal sandwich plates made up of functionally graded materials (FGMs) has been carried out using finite element based higher-order zigzag theory. The present model satisfies all-important conditions such as transverse shear stress-free conditions at the plate's top and bottom surface along with continuity condition for transverse stresses at the interface. A Nine-noded C0 finite element having eleven degrees of freedom per node is used during the study. The present model is free from the requirement of any penalty function or post-processing technique and hence is computationally efficient. The present model's effectiveness is demonstrated by comparing the present results with available results in the literature. Several new results have been proposed in the present work, which will serve as a benchmark for future works. It has been observed that the material variation law, power-law exponent, skew angle, and boundary condition of the plate widely determines the free vibration behavior of sandwich functionally graded (FG) plate.

• Earthquakes and Structures
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• v.24 no.4
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• pp.237-245
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• 2023

Based on novel Galerkin's technique, the theoretical study gives a prediction to estimate the vibrations of FG rotating cylindrical shell. Terms of ring supports have been introduced by a polynomial function. Three different laws of volume fraction are utilized for the vibration of cylindrical shells. Variation frequencies with the locations of ring supports have been analyzed and these ring supports are placed round the circumferential direction. The base of this approach is an approximate estimation of eigenvalues of proper functions which are the results of solutions of vibrating equation. Each longitudinal wave number corresponds to a particular boundary condition. The results are given in tabular and graphical forms. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing length-to-radius ratio. There is a new form of frequencies is obtained for different positions of ring supports, which is bell shaped. Moreover, on increasing the rotating speed, the backward frequencies increase and forward frequencies decreases.

• Geomechanics and Engineering
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• v.33 no.4
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• pp.381-391
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• 2023

The aim of this work is to analyze and predict the wave propagation behavior of the carbon nanotube reinforced composites (CNTRC) beams within the framework of various higher order shear deformation beam theory. Using the Euler-Lagrange principle, the wave equations for CNTRC beams are derived, where the determining factor is to make the determinant equal to zero. Based on the eigenvalue method, the relationship between wave number and circular frequency is obtained. Furthermore, the phase and group velocities during wave propagation are obtained as a function of wave number, and the material properties of CNTRC beams are estimated by the mixture rule. In this paper, various higher order shear beam theory including Euler beam theory, Timoshenko beam theory and other beam theories are mainly adopted to analyze the wave propagation problem of the CNTRC beams, and by this way, we conduct a comparative analysis to verify the correctness of this paper. The mathematical model provided in this paper is verified numerically by comparing it with some existing results. We further investigate the effects of different enhancement modes of CNTs, volume fraction of CNTs, spring factor and other aspects on the wave propagation behaviors of the CNTRC beams.