• Title/Summary/Keyword: thickness mode

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Effects of Magnetic Layer Thickness on Magnetic Properties of CoCrPt/Ti/CoZr Perpendicular Media

  • Hwang, M.S.
    • Journal of Magnetics
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    • v.6 no.1
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    • pp.19-22
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    • 2001
  • Change of magnetic properties in CoCrPt/Ti perpendicular media with varying CoCrPt film thickness has been studied. As the CoCrPt film thickness increases from 25 nm, the Ms (saturation magnetization) increases rapidly at first and then more gradually. This Ms behavior is associated primarily with the formation of an "amorphous-like"reacted layer created by intermixing of CoCrPt and Ti at the CoCrPt/Ti interface and secondarily with a change of the Cr segregation mode with varying CoCrPt film thickness. Magnetic domain structure distinctively changes with increasing CsCrPt magnetic layer (ML) thickness. Also the strength of exchange coupling measured from the slope in the demagnetizing region of the M-H loop changes with ML thickness. The expansion of lattice parameters a and c at smaller film thickness suggests that the Cr segregation mode may be connected with the residual stress of the films. Finally, the negative nucleation field (Hn) shows a unique behavior with the change of strength of the exchange interaction.teraction.

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Preparation of x-cut $LiNbO_3$ Optical Waveguide and the Change in Near-field Properties according to Ti thickness (x-cut $LiNbO_3$ 광도파로 제작 및 Ti 두께에 따른 Near-field 특성 변 화)

  • Kim, Seong-Ku;Yoon, Hyung-Do;Yoon, Dae-Won;Han, Sang-Pill;Kim, Chang-Min;Park, Gye-Chun;Lee, Jin;Yoo, Yong-Taek
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.11 no.2
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    • pp.146-153
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    • 1998
  • The optical near-field patterns, propagation loss and mode sizes of x-cut $Ti:LiNbO_3$ optical waveguide which was fabricated by Ti-diffusion varying with Ti strip thickness in wet oxygen atmosphere were discussed at optical wavelength 1550nm. As Ti thickness increased from $760{\AA}$, the insertion loss of waveguide was decreased. But at Ti thickness $1500{\AA}$, mode sizes are widely broadened. The Ti thickness of below $1100{\AA}$ and above $1500{\AA}$ showed negative effects to propagation loss and fiber coupling. The best Ti thickness for fabricating low propagation loss and good fiber coupling was inferred to be between $1100{\AA}-1500{\AA}$ in our conditions. And for Ti thickness $1150{\AA}$, its propagation loss, horizontal/vertical mode sizes were showed 1.61 dB/cm, $11.9/8.9{\mu}m$ for TM, 0.22 dB/cm, $12.0/9.1{\mu}m$ for TE respectively.

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Phase diagrams adn stable structures of stranski-krastanov structure mode for III-V ternary quantum dots

  • Nakajima, Kazuo;Ujihara, Toru;Miyashita, Satoru;Sazaki, Gen
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.9 no.4
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    • pp.387-395
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    • 1999
  • The strain, surface and interfacial energies of III-V ternary systems were calculated for three kinds of structure modes: the Frank-van der Merwe(FM) mode, the Stanski-Krastanov(SK) mode and the Volmer-Weber(VW) mode. The free energy for each mode was estimated as functions of thickness and composition or lattice misfit. Through comparison of the free energy of each mode, it was found that the thickness-composition phase diagrams of III-V ternary systems can be determined only by considering the balance of the free energy and three kinds of structure modes appear in the phase diagrams. The SK mode appears only when the lattice misfit is large and/or the lattice layer is thick. The most stable structure of the SK mode is a cluster with four lattice layers or minimum thickness on a wetting layer of increasing lattice layers. The VW mode appears when the lattice misfit is large and the lattice layer is thin and only in the INPSb/InP and GaPSb/GaP system which have the largest lattice misfit of III-V ternary systems. The stable region of the SK mode in the GaPSb/GaP and InPSb/InP phase diagrams is largest of all because the composition dependence of the strain energy of these systems is stronger than that of the other systems. The critical number of lattice layers below which two-dimensional(2D) layers precede the three-dimensional(3D) nucleation in the SK mode at x=1.0 depends on the lattice misfit.

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Modified DEBA for determining size dependent shear fracture energy of laminates

  • Goodarzi, M. Saeed;Hosseini-Toudeshky, Hossein
    • Steel and Composite Structures
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    • v.28 no.1
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    • pp.111-121
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    • 2018
  • It has been argued that fracture energy of composite laminates depends on their thickness and number of layers. In this paper a modified direct energy balance approach (DEBA) has been developed to evaluate the mode-II shear fracture energy for E-glass/Epoxy laminates from finite element model at an arbitrary thickness. This approach considers friction and damage/plasticity deformations using cohesive zone modeling (CZM) and nonlinear finite element modeling. The presence of compressive stress and resulting friction was argued to be a possible cause for the thickness dependency of fracture energy. In the finite element modeling, CZM formulation has been developed with bilinear cohesive constitutive law combined with friction consideration. Also ply element have been developed with shear plastic damage model. Modified direct energy balance approach has been proposed for estimation of mode-II shear fracture energy. Experiments were performed on laminates of glass epoxy specimens for characterization of material parameters and determination of mode-II fracture energies for different thicknesses. Effect of laminate thickness on fracture energy of transverse crack tension (TCT) and end notched flexure (ENF) specimens has been numerically studied and comparison with experimental results has been made. It is shown that the developed numerical approach is capable of estimating increase in fracture energy due to size effect.

Influence of dimensional ratio on collapse characteristics for the thin-walled structures of light weight (경량화용 박육부재의 형상비가 압궤특성에 미치는 영향)

  • 정종안;김정호;양인영
    • Journal of the Korean Society of Safety
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    • v.13 no.3
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    • pp.11-23
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    • 1998
  • In this study, collapse test of thin-walled structure is performed under axially quasi-static and impact load in collapse characteristic to develop the optimum structural member for a light-oriented automobile. Furthermore, the energy-absorbing capacity is observed according to the variety of configuration(circular, square), aspect ratio in aluminum specimen to obtain basic data for the improved member of vehicle. In both quasi-static and impact collapse test, Al circular specimens collapse, in general, with axisymmetric mode in case of thin thickness while collapse with non-axisynmetric mode according to the thickness increase. For Al rectangular specimens, they collapse with axisymmetric mode in case of thin thickness, with mixed collapse mode according to the increase of thickness. In terms of initial max. load, Al square specimen turns out the best member among specimens, and then Al square, circular and circular with large scaling ratio, respectively. In case of quasi-static compression test, the absorbed energy per unit volume and mass shows higher in Al circular specimen, and then Al square, circular with large scaling ratio, respectively, according to shape ratio the absorbed energy per unit volume and mass in case of max. impact compression load is higher than that of static load. But the absorbed energy per unit volume and mass shows that Al circular specimen is the best member. Especially, unlike max. compression loan, the absorbed energy per unit volume and mass in impact test turns out the low value.

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Development of a Thickness Mode Piezoelectric Oscillator Sensor to Detect Damages in a Structure (구조물 손상 탐지를 위한 두께 방향 모드 압전 오실레이터 센서 개발)

  • Kim, Dong-Young;Roh, Yong-Rae
    • The Journal of the Acoustical Society of Korea
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    • v.26 no.2
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    • pp.95-101
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    • 2007
  • This paper presents the feasibilityof a thickness mode piezoelectric oscillator to detect damages in structures. The thickness mode oscillator sensor is composed of an electronic feedback oscillator circuit and a piezoelectric thickness mode vibrator to be attached to a structure of interest. Damage to the structure causes a change in the impedance spectrum of the structure, which results in a corresponding change of a resonant frequency of the structure. The oscillator sensor can instantly detect the frequency change in a very simple manner. Feasibility of the piezoelectric oscillator sensor was verified with a sample aluminum plate where artificial cracks of different lengths and number were imposed in sequence. Validity of the measurement was confirmed through comparison of the experimental data with the results of finite element analyses of a plate with cracks.

Vibration Characteristics of Conical Shells with Linearly Varying Thickness (선형적으로 두께가 변하는 원추형 셸의 진동특성)

  • Yeo, D.J.;Cho, I.S.
    • Journal of Power System Engineering
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    • v.12 no.2
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    • pp.35-40
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    • 2008
  • This paper deals with the free vibrations of conical shells with linearly variable thickness by the transfer influence coefficient method. The classical thin shell theory based upon the Flugge theory is assumed and the governing equations of a conical shell are written as a coupled set of first order matrix differential equations using the transfer matrix. The Runge-Kutta-Gill integration method is used to solve the governing differential equation. The natural frequencies and corresponding mode shapes are calculated numerically for the conical shells with linearly variable thickness and various boundary conditions at the edges. The present method is applied to conical shells with linearly varying thickness, and the effects of the semi-vertex angle, the number of circumferential waves and thickness ratio on vibration are studied.

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Effect of Diameter and Thickness on the Failure Location and Orientation of 90° Elbows Under In-plane Mode Cyclic Bending (In-plane 모드 반복굽힘 조건에서 90° 엘보우의 손상 위치와 방향에 미치는 직경과 두께 영향)

  • Jin Ney Hong;Jin Weon Kim
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.18 no.2
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    • pp.77-86
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    • 2022
  • This study investigates the effect of the diameter and thickness on crack initiation location and orientation of 90° elbows under in-plane mode displacement-controlled cyclic bending loads. Finite element (FE) analysis of cyclic failure test is conducted for elbow specimens under in-plane mode displacement-controlled cyclic bending to identify the parameters affecting crack location and orientation. Furthermore, parametric FE analysis of the pipe elbows with various pipe nominal sizes and Schedules is performed, and the crack location and orientation from the results of FE analysis are determined. It is found that the crack location and orientation in the pipe elbows are determined mianly by the radius to thickness ratio of pipe elbows (Rm/t). It is also found that the presence of internal pressure slightly increases the value of Rm/t at which the failure mode changes.

Piezoelectric Properties of 0-3 Composite with PZT / Epoxy (PZT/Epixy 0-3형 조합적믈의 압전특성에 관한 연구)

  • 김용혁;김호기;이덕철
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.36 no.7
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    • pp.447-452
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    • 1987
  • In this paper, the dependence of piezoelectric properties in the 0-3 composite system of piezoelectric-ceramics polymer materials on particle size of ceramics were investigated. Radial mode and thickness mode of composite were observed similar to single phase of piezoelectric ceramics. The measured values of dielectric constant and dissipation factor were dependent on particle size, which increased with the increasing particle size. the planar coupling factor, thickness coupling factor and thickness frequency constant with the particle size were almost constant, while planar frequency constant increased. The thickness coupling factor decreased with the increasing thickness of specimen. It is found that maximum voltage coeffidient was calculated on the specimen with particle size smallar than 46 ${\mu}m$.

Effect of Subthreshold Slope on the Voltage Gain of Enhancement Mode Thin Film Transistors Fabricated Using Amorphous SiInZnO

  • Lee, Sang Yeol
    • Transactions on Electrical and Electronic Materials
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    • v.18 no.5
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    • pp.250-252
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    • 2017
  • High-performance full swing logic inverters were fabricated using amorphous 1 wt% Si doped indium-zinc-oxide (a-SIZO) thin films with different channel layer thicknesses. In the inverter configuration, the threshold voltage was adjusted by varying the thickness of the channel layer. The depletion mode (D-mode) device used a TFT with a channel layer thickness of 60 nm as it exhibited the most negative threshold voltage (-1.67 V). Inverters using enhancement mode (E-mode) devices were fabricated using TFTs with channel layer thicknesses of 20 or 40 nm with excellent subthreshold slope (S.S). Both the inverters exhibited high voltage gain values of 30.74 and 28.56, respectively at $V_{DD}=15V$. It was confirmed that the voltage gain can be improved by increasing the S.S value.