• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.51 no.4
• /
• pp.175-185
• /
• 2002

In this paper, a new fully digital current control method of UPS inverter, which is based on an internal model control, is proposed. In the proposed control system, overshoots and oscillations due to the computation time-delay are compensated by explicit incorporation of the time-delay in the current control loop transfer function. The internal model controller is adopted to a second order deadbeat reference-to-output response which means that its response reaches the reference in two sampling time including computational time-delays. That is, the average current of filter capacitor is been exactly equal to the reference current with a time lag of two sampling intervals. Therefore, this method has an essentially overshoot free reference-to-output response with a minimum possible rise time. The effectiveness of the proposed control system has been verified by the simulation and experimental respectively. From the simulation and experimental results, the proposed system is achieved the robust characteristics to the calculation time delay and parameter variation as well as very fast dynamic performance, thus it can be effectively applied to the power supply for the critical load.

• Steel and Composite Structures
• /
• v.22 no.3
• /
• pp.691-712
• /
• 2016

In this editorial, buckling analytical investigation of the nanocomposite plate with square cut out reinforced by carbon nanotubes (CNTs) surrounded by Pasternak foundation is considered. The plate is presumed has square cut out in center and resting on Pasternak foundation. CNTs are used as amplifier in plate for diverse distribution, such as uniform distribution (UD) and three patterns of functionally graded (FG) distribution types of CNTs (FG-X, FG-A and FG-O). Moreover, the effective mechanical properties of nanocomposite plate are calculated from the rule of mixture. Domain decomposition method and orthogonal polynomials are applied in order to define the shape function of nanocomposite plate with square cut out. Finally, Rayleigh-Ritz energy method is used to obtain critical buckling load of system. A detailed parametric study is conducted to explicit the effects of the dimensions of plate, length of square cut out, different distribution of CNTs, elastic medium and volume fraction of CNTs. It is found from results that increase the dimensions of plate and length of square cut out have negative impact on buckling behavior of system but considering CNTs in plate has positive influence.

• Structural Engineering and Mechanics
• /
• v.61 no.1
• /
• pp.15-29
• /
• 2017

The recently introduced index Ratio Of Torsion (ROT) quantifies the base shear amplification due to torsional effects on shear cantilever types of building structures. In this work, a theoretical proof based on the theory of elasticity is provided, depicting that the ratio of torsion (ROT) is independent of the forces acting on the structure, although its definition stems from the shear forces. This is a particular attribute of other design and evaluation criteria against torsion such as center of rigidity and center of strength. In the case of ROT, this evidence could be considered as inconsistent, as ROT is a function solely of the forces acting on structural members, nevertheless it is proven to be independent of them. As ROT is the amplification of the shear forces due to in-plan irregularities, this work depicts that this increase of internal shear forces rely only on the structural topology. Moreover, a numerical verification of this theoretical finding was accomplished, using linear statistics interpretation and nonlinear neural networks simulation for an adequate database of structures.

• Korean Journal of Optics and Photonics
• /
• v.24 no.5
• /
• pp.271-278
• /
• 2013

The effective reflection coefficients of an obliquely incident wave on a multi-layered substrate coated with a uniaxially anisotropic alignment layer are derived. The effective reflection coefficients as well as explicit ellipsometric expressions are provided as a function of film constants of multiple layers together with magnitude of anisotropy, direction of optic axis, and thickness of the alignment layer. It is expected that by adapting these expressions to the conventional modelling technique, the ordinary refractive index, the extra-ordinary refractive index, the azimuth angle and the tilt angle of the optic axis, and the thickness of the aligned surface can be determined simultaneously together with the thickness and volume fraction of each layer beneath the alignment layer.

• Structural Engineering and Mechanics
• /
• v.38 no.2
• /
• pp.157-169
• /
• 2011

In this paper the time-dependent closed-form static solution of the suspended pre-stressed biconcave and biconvex cable trusses with unmovable, movable and elastic or viscoelastic yielding supports subjected to various types of vertical load is presented. Irvine's forms of the deflections and the cable equations are modified because the effects of the rheological behaviour needed to be incorporated in them. The concrete cable equations in the form of the explicit relations are derived and presented. From a solution of a vertical equilibrium equation for a loaded cable truss with rheological properties, the additional vertical deflection as a time-function is determined. The time-dependent closed-form model serves to determine the time-dependent response, i.e., horizontal components of cable forces and deflection of the cable truss due to applied loading at the investigated time considering effects of elastic deformations, creep strains, temperature changes and elastic supports. Results obtained by the present closed-form solution are compared with those obtained by FEM. The derived time-dependent closed-form computational model is used for a time-dependent simulation-based reliability assessment of cable trusses as is described in the second part of this paper.

• Nuclear Engineering and Technology
• /
• v.49 no.4
• /
• pp.692-699
• /
• 2017

The determination of the shape and rising velocity of gas bubbles in a liquid pool is of great importance in analyzing the radioactive aerosol emissions from nuclear power plant accidents in terms of the fission product release rate and the pool scrubbing efficiency of radioactive aerosols. This article suggests a simple parameterization for the gas bubble rising velocity as a function of the volume-equivalent bubble diameter; this parameterization does not require prior knowledge of bubble shape. This is more convenient than previously suggested parameterizations because it is given as a single explicit formula. It is also shown that a bubble shape diagram, which is very similar to the Grace's diagram, can be easily generated using the parameterization suggested in this article. Furthermore, the boundaries among the three bubble shape regimes in the $E_o-R_e$ plane and the condition for the bypass of the spheroidal regime can be delineated directly from the parameterization formula. Therefore, the parameterization suggested in this article appears to be useful not only in easily determining the bubble rising velocity (e.g., in postulated severe accident analysis codes) but also in understanding the trend of bubble shape change due to bubble growth.

• Journal of Fisheries and Marine Sciences Education
• /
• v.21 no.3
• /
• pp.347-360
• /
• 2009

The purpose of this study was to investigate the characteristics of a teacher's questions in each context of musical activity by analyzing those questions in kindergarten music activity qualitatively. The participant in research was a teacher in charge of the class of children aged 7. Analysis was carried out on the data collected for 3 months through participation observance note, recording material, interview material and weekly plan. As a result, the teacher's questions were leaned upon the convergent questions to confirm the reflection of information and the understanding of function in singing and performing activity. On the other hand, the teacher's questions were leaned upon the diffusive questions for the thought of integration of information in composition activity and upon the diffusive questions for representing feeling or image with no relation to musical meaning in appreciation activity. However, the teacher's questions for control were conducted together with one of the questions, the question mentioned ahead. The tacit control question in singing and performing activity and the explicit control question in composition activity were conducted together, and in appreciation activity, the simple questions to lead the class, though not with the purpose to control attention, was conducted together.

• Steel and Composite Structures
• /
• v.35 no.3
• /
• pp.405-413
• /
• 2020

Current study on the buckling analysis of steel plate in composite structures normally focuses on applying finite element method to derive the buckling stress. However, it is time consuming, computationally complicated and tedious for general use in design by civil engineers. Therefore, in this study an analytical study is conducted to predict the buckling behavior of steel plates in composite structures. Hand calculation method was proposed based on energy principle. Novel buckling shapes with biquadratic functions along both loaded and unloaded direction were proposed to satisfy the boundary condition. Explicit solutions for predicting the critical local buckling stress of steel plate is obtained based on the Rayleigh-Ritz approach. The obtained results are compared with both experimental and numerical data. Good agreement has been achieved. Furthermore, the influences of key factors such as aspect ratio, width to thickness ratio, and elastic restraint stiffness on the local buckling performance are comprehensively discussed.

• Korea-Australia Rheology Journal
• /
• v.15 no.2
• /
• pp.83-90
• /
• 2003

In cases of the microfluidic channel, the electrokinetic influence on the transport behavior can be found. The externally applied body force originated from the electrostatic interaction between the nonlinear Poisson-Boltzmann field and the flow-induced electrical field is applied in the equation of motion. The electrostatic potential profile is computed a priori by applying the finite difference scheme, and an analytical solution to the Navier-Stokes equation of motion for slit-like microchannel is obtained via the Green's function. An explicit analytical expression for the induced electrokinetic potential is derived as functions of relevant physicochemical parameters. The effects of the electric double layer, the zeta potential of the solid surface, and the charge condition of the channel wall on the velocity profile as well as the electroviscous behavior are examined. With increases in either electric double layer or zeta potential, the average fluid velocity in the channel of same charge is entirely reduced, whereas the electroviscous effect becomes stronger. We observed an opposite behavior in the channel of opposite charge, where the attractive electrostatic interactions are presented.

• Journal of Integrative Natural Science
• /
• v.2 no.4
• /
• pp.243-251
• /
• 2009

This paper surveys some researches to accomplish on bioinformatics. These researches wish to propose a database architecture combining a general view of bioinformatics data as a graph of data objects and data relationships, with the efficiency and robustness of data management and query provided by indexing and generic programming techniques. Here, these invert the role of the index, and make it a first-class citizen in the query language. It is possible to do this in a structured way, allowing users to mention indexes explicitly without yielding to a procedural query model, by converting functional relations into explicit functions. In the limit, the database becomes a graph, in which the edges are these indexes. Function composition can be specified either explicitly or implicitly as path queries. The net effect of the inversion is to convert the database into a hyperdatabase: a database of databases, connected by indexes or functions. The inversion approach was motivated by their work in biological databases, for which hyperdatabases are a good model. The need for a good model has slowed progress in bioinformatics.