• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1052-1054
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• 2002

This paper presents an analytical model-based approach to detect and isolate faults in a voltage-source inverter. These faults do not affect the existing system protections. A diagnosis system which uses only the input variables of the drive is presented. It is based on the analysis of the current-vector trajectory in faulty mode. The proposed method has been verified in simulation results.

• 한국소음진동공학회논문집
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• 제15권10호
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• pp.1211-1216
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• 2005

Underwater acoustic transducers are widely used for SONAR application, whose important design parameters are shapes. materials, dimensions and supporting structures. Practical design method of transducers consists of manufacturing, experiments and modifications so that it requires much time and expenses. In this study, an analytical method was developed for the Tonpilz type transducers using the commercial finite element analysis code ATILA which can solve the electro-mechanical coupling problems. A finite element model was established including the transducer elements such as ceramic stack, head mass, tail mass, tensile bolt, and molding layers. The proposed model was verified and modified by comparing the in-air and in-water test results of prototypes. The developed analysis method will be effectively used for the sensitivity analysis of design parameters in transducer design process.

• Journal of Electrochemical Science and Technology
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• 제9권4호
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• pp.292-300
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• 2018

The electrocatalytic oxidative behavior of an antiarrhythmic drug, procainamide hydrochloride (PAH) at the gold electrode surface has been examined using different voltammetric methods like cyclic, linear-sweep and differential pulse voltammetry. Voltammograms obtained in this study reveal that the electrode exhibit excellent electrocatalytic activity towards oxidation of the drug. The parameters that can affect the peak current at different pH, scan rate and concentration were evaluated. The number of electrons transferred was calculated. The current displayed a wide linear response ranging from 0.5 to $30.0{\mu}M$ with a limit of detection of 56.4 nM. The impact of potential interfering agents was also studied. The electrode displayed wide advantages such as simple sample preparation, appreciable repeatability, reproducibility and also high sensitivity. Furthermore, the feasibility of the proposed method was successfully demonstrated by determining PAH in the spiked human biological sample.

• Advances in materials Research
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• 제11권4호
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• pp.331-349
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• 2022

In the present work, we proposed an analytical study on buckling behavior of a sandwich plate with polymeric core integrated with piezo-electro-magnetic layers such as BaTiO3 and CoFe2O4 reinforced by graphene platelets (GPLs). The Halpin-Tsai micromechanics model is used to describe the properties of the polymeric core. The governing equations of equilibrium are obtained from first-order shear deformation theory (FSDT) and the Navier's method is employed to solve the equations. The results show the effect of different parameters such as thickness, length, weight fraction of GPLs, and also effect of electric and magnetic field on critical buckling load. The result of this study can be obtained in the aerospace industry and also in the design of sensors and actuators.

• 분석과학
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• 제19권6호
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• pp.519-528
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• 2006

본 연구에서는 뇨시료를 고체상 추출법으로 추출한 후 HPLC/DAD/ESI-MS(high-performance liquid chromatograph/diode array detector/electro-spray ionitation mass spectrometry)를 사용하여 분석하였다. 7종의 thyroid hormones의 HPLC 분리조건은 Hypersil ODS(octadecylsilica) 컬럼(4.6mm I.D., 100 mm length, particle size $5{\mu}m$)을 사용하고 ammonium formate buffer와 acetonitrile을 이동상으로 하여 기울기 용리한 결과 완전 분리가 가능하였으며, UV spectra 및 질량스펙트럼을 확인할 수 있었다. 고체상 추출법에 의한 전처리 최적 조건을 조사한 결과 시료를 pH 3으로 한 후 C18 고체상을 사용하여 4 mL의 methanol/ammonium hydroxide(9:1) 혼합용액으로 용리할 경우 회수율이 89.0-113.1%로 나타났다. HPLC/DAD를 이용하여 10-1000 ng/mL범위에서 검량선을 작성한 결과 $r^2$값은 0.992-0.998 으로 나타났으며 검출한계는 2-4 ng/mL(3.8-13.0 pmol/mL)로 계산되었다.

• Journal of Advanced Marine Engineering and Technology
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• 제23권2호
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• pp.201-209
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• 1999

This paper presents a general analytical method for analyzing mechanical unbalance response of unbalanced electromagnetic forces produced in induction motors with an eccentric rotor and a phase unbalance. The equations to be solved are a set of second order differential equations which give matrices with periodic coefficients that are a function of time due to the unbalanced electro-magnetic force. Unbalance response is processed by Newmark $\beta$ method. Two examples are given including an industrial application. The results show that the method proposed is satisfactory.

• Structural Engineering and Mechanics
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• 제72권1호
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• pp.113-129
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• 2019

A four-variable shear deformation refined plate theory has been proposed for dynamic characteristics of smart plates made of porous magneto-electro-elastic functionally graded (MEE-FG) materials with various boundary conditions by using an analytical method. Magneto-electro-elastic properties of FGM plate are supposed to vary through the thickness direction and are estimated through the modified power-law rule in which the porosities with even and uneven type are approximated. Pores possibly occur inside functionally graded materials (FGMs) due the result of technical problems that lead to creation of micro-voids in these materials. The variation of pores along the thickness direction influences the mechanical properties. The governing differential equations and boundary conditions of embedded porous FGM plate under magneto-electrical field are derived through Hamilton's principle based on a four-variable tangential-exponential refined theory which avoids the use of shear correction factors. An analytical solution procedure is used to achieve the natural frequencies of embedded porous FG plate supposed to magneto-electrical field with various boundary condition. A parametric study is led to carry out the effects of material graduation exponent, coefficient of porosity, magnetic potential, electric voltage, elastic foundation parameters, various boundary conditions and plate side-to-thickness ratio on natural frequencies of the porous MEE-FG plate. It is concluded that these parameters play significant roles on the dynamic behavior of porous MEE-FG plates. Presented numerical results can serve as benchmarks for future analyses of MEE-FG plates with porosity phases.

• Structural Engineering and Mechanics
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• 제78권5호
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• pp.557-572
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• 2021

The current study considers free vibration of the spherical panel with magnetorheological (MR) fluids core and magneto-electro-elastic face sheets. The panel is subjected to electro-magnetic loads and also is located on an orthotropic visco-Pasternak elastic foundation. To describe the displacement components of the structure, the first-order shear deformation theory (FSDT) is used and the motion equations are extracted by employing Hamilton's principle. To solve the motion differential equations, Navier's method is selected as an exact analytical solution for simply supported boundary conditions. Effect of the most important parameters such as magnetic field intensity, loss factor, multi-physical loads, types of an elastic medium, geometrical properties of the panel, and also different material types for the face sheets on the results is considered and discussed in details. The outcomes of the present work may be used to design more efficient smart structures such as sensors and actuators.

• Structural Engineering and Mechanics
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• 제73권5호
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• pp.565-584
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• 2020

The nonlinear thermo-electro-elastic buckling behavior of viscoelastic nanoplates under magnetic field is investigated based on nonlocal elasticity theory. Employing nonlinear strain-displacement relations, the geometrical nonlinearity is modeled while governing equations are derived through Hamilton's principle and they are solved applying semi-analytical generalized differential quadrature (GDQ) method. Eringen's nonlocal elasticity theory considers the effect of small size, which enables the present model to become effective in the analysis and design of nano-sensors and nano actuators. Based on Kelvin-Voigt model, the influence of the viscoelastic coefficient is also discussed. It is demonstrated that the GDQ method has high precision and computational efficiency in the buckling analysis of viscoelastic nanoplates. The good agreement between the results of this article and those available in literature validated the presented approach. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of the several parameters such as electric voltage, small scale effects, elastomeric medium, magnetic field, temperature effects, the viscidity and aspect ratio of the nanoplate on its nonlinear buckling characteristics. It is explicitly shown that the thermo-electro-elastic nonlinear buckling behavior of viscoelastic nanoplates is significantly influenced by these effects. Numerical results are presented to serve as benchmarks for future analyses of viscoelastic nanoplates as fundamental elements in nanoelectromechanical systems.

• Smart Structures and Systems
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• 제9권6호
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• pp.489-504
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• 2012

For the safety of prestressed structures such as cable-stayed bridges and prestressed concrete bridges, it is very important to ensure the prestress force of cable or tendon. The loss of prestress force could significantly reduce load carrying capacity of the structure and even result in structural collapse. The objective of this study is to present a smart PZT-interface for wireless impedance-based prestress-loss monitoring in tendon-anchorage connection. Firstly, a smart PZT-interface is newly designed for sensitively monitoring of electro-mechanical impedance changes in tendon-anchorage subsystem. To analyze the effect of prestress force, an analytical model of tendon-anchorage is described regarding to the relationship between prestress force and structural parameters of the anchorage contact region. Based on the analytical model, an impedance-based method for monitoring of prestress-loss is conducted using the impedance-sensitive PZT-interface. Secondly, wireless impedance sensor node working on Imote2 platforms, which is interacted with the smart PZT-interface, is outlined. Finally, experiment on a lab-scale tendon-anchorage of a prestressed concrete girder is conducted to evaluate the performance of the smart PZT-interface along with the wireless impedance sensor node on prestress-loss detection. Frequency shift and cross correlation deviation of impedance signature are utilized to estimate impedance variation due to prestress-loss.