• Journal of Information Display
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• v.7 no.3
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• pp.27-30
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• 2006

This paper presents a comprehensive study on threshold voltage $(V_{th})$ control of organic thin-film transistors (OTFTs) with dual-gate structure. The fabrication of dual-gate pentacene OTFTs using plasma-enhanced atomic layer deposited (PEALD) 150 nm thick $Al_{2}O_{3}$ as a bottom gate dielectric and 300 nm thick parylene or PEALD 200 nm thick $Al_{2}O_{3}$ as both a top gate dielectric and a passivation layer was investigated. The $V_{th}$ of OTFT with 300 nm thick parylene as a top gate dielectric was changed from 4.7 V to 1.3 V and that with PEALD 200 nm thick $Al_{2}O_{3}$ as a top gate dielectric was changed from 1.95 V to -9.8 V when the voltage bias of top gate electrode was changed from -10 V to 10 V. The change of $V_{th}$ of OTFT with dual-gate structure was successfully investigated by an analysis of electrostatic potential.

• Computers and Concrete
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• v.11 no.3
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• pp.201-222
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• 2013

A comprehensive simulation model for the transport process of fully coupled moisture and multi-species in non-saturated concrete structures is proposed. The governing equations of moisture and ion diffusion are formulated based on Fick's law and the Nernst-Planck equation, respectively. The governing equations are modified by explicitly including the coupling terms corresponding to the coupled mechanisms. The ionic interaction-induced electrostatic potential is described by electroneutrality condition. The model takes into account the two-way coupled effect of moisture diffusion and ion transport in concrete. The coupling parameters are evaluated based on the available experimental data and incorporated in the governing equations. Differing from previous researches, the material parameters related to moisture diffusion and ion transport in concrete are considered not to be constant numbers and characterized by the material models that account for the concrete mix design parameters and age of concrete. Then, the material models are included in the numerical analysis and the governing equations are solved by using finite element method. The numerical results obtained from the present model agree very well with available test data. Thus, the model can predict satisfactorily the ingress of deicing salts into non-saturated concrete.

• Journal of the Korean Society of Safety
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• v.16 no.2
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• pp.57-62
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• 2001

In order to analyze the mechanism of semiconductor device damages by ESD, this paper adopts a new charged-device model(CDM), field-induced charged nudel(FCDM), simulator that is suitable for rapid routine testing of semiconductor devices and provides a fast and inexpensive test that faithfully represents ESD hazards in plants. The high voltage applied to the device under test is raised by the fie]d of non-contacting electrodes in the FCDM simulator. which avoids premature device stressing and permits a faster test cycle. Discharge current md time are measured and calculated The FCDM simulator places the device at a huh voltage without transferring charge to it, by using a non-contacting electrode. The only charge transfer in the FCMD simulator happens during the discharge. This paper examine the field charging mechanism, measure device thresholds, and analyze failure modes. The FCDM simulator provides a Int and inexpensive test that faithfully represents factory ESD hazards. The damaged devices obtained in the simulator are analyzed and evaluated by SEM Also the results in this paper can be used for to prevent semiconductor devices from ESD hazards.

• Transactions on Electrical and Electronic Materials
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• v.17 no.4
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• pp.183-188
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• 2016

This paper presents the design and characterization of wide band ohmic microswitch with an actuation voltage as low as 20~25 V, and a restoring force of 14.1 μN. The design of the proposed switch is primarily composed of an electrostatic actuator, bridge membrane, cantilever (beam) and coplanar waveguide, suspended over the substrate. The analysis shows an insertion loss of −0.002 dB at 1GHz and remains as low as −0.35 dB, even at 100 GHz. The isolation loss of the switch is sustained at −21.09 dB at 100GHz, with a peak value of −99.58 dB at 1 GHz and up-state capacitance of 4 fF. To our knowledge, this is the first demonstration of a series contact switch, which works over a wide bandwidth (DC-100 GHz) and with such a high and sustained isolation, even at high frequencies and with an excellent figure of merit (f_c=1/2.pi.Ron.Cu= 39.7 THz).

• Korean Journal of Metals and Materials
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• v.46 no.2
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• pp.105-110
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• 2008

Process of the hydroxyapatite (HA) formation on bioactive titanium metal prepared by NaOH treatment in a modified-simulated body fluid (mSBF) containing bovine serum albumin (BSA) was investigated by high resolution transmission electron microscope attached with energy dispersive X-ray spectrometer (EDX). The amorphous titanate, which was formed on titanium surface by NaOH treatment, combined with the calcium ions in the liquid to form an amorphous calcium titanite. With increasing of soaking time in the liquid, an amorphous calcium titanite combined with the phosphate ions to form an amorphous calcium phosphate with low Ca/P atomic ratio, and it grows as aggregates of plate (or needle)-like substance on titanium surface. The crystalline apatite layers, which are needle-shaped with the c axis parallel to the long axis, are formed in an amorphous calcium phosphate with further increase in soaking time. The formation of needle-shaped apatite layers can be explained by electrostatic effects and difference of concentration between calcium, phosphate, and albumin ions.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.348-356
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• 2021

The lignocellulose-based dried watermelon rind (WR) was modified with sulfuric acid, namely SWR for enhancement of methylene blue (MB) adsorption from the aqueous solution. According to FT-IR analysis, after the modification of WR with sulfuric acid, the functional groups of R-SO₃H, COOH and -OH groups was formated or enhanced on the surface of the WR. Moreover, the point of zero charge (pHpzc) was changed from 6.3 to 4.1 after modification, which widened the range for adsorbing of cationic dye MB. The adsorption process of MB onto the SWR was suitable for pseudo-2nd-order and Langmuir model and the maximum adsorption capacity of Langmuir was found to be 334.45 mg/g at pH 7. In adition, the adsorption process occurs through the electrostatic interaction, hydrogen bridge formation, electron donor-acceptor relationship, and 𝜋-𝜋 electron dispersing force between functional groups on the carbon surface with MB molecules. Depending on functional groups available on the SWR surface, the MB adsorption mechanism can occur in combination with various interactions.

• Smart Structures and Systems
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• v.29 no.5
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• pp.705-714
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• 2022

In this paper, the effect of magnetic field on the vibration behavior of a Magnetorheological elastomer (MRE) sandwich MEMS actuated by electrostatic actuation with conductive skins are examined within the multiple scales (MMS) perturbation method. Magnetorheological smart materials have been widely used in vibration control of various systems due to their mechanical properties change under the influence of different magnetic fields. To investigate the vibrational behavior of the movable electrode, the Euler-Bernoulli beam theory, as well as Hamilton's principle is used to derive the equations and the related boundary conditions governing the dynamic behavior of the system are applied. The results of this study show that by placing the Magnetorheological elastomer core in the movable electrode and applying different magnetic fields on it, its natural vibrational frequency can be affected so that by increasing the applied magnetic field, the system's natural frequency increases. Also, the effect of various factors such as the electric potential difference between two electrodes, changes in the thickness of the core and the skins, electrode length, the distance between two electrodes and also change in vibration modes of the system on natural frequencies have been investigated.

• Journal of the Semiconductor & Display Technology
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• v.22 no.4
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• pp.7-12
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• 2023

The edge ring placed on the outside of the electrostatic chuck (ESC) is a key component for protecting the ESC and controlling the etching uniformity of the edge of the wafer. Therefore, it is very important to understand the etching phenomenon of edge rings for edge ring management and equipment homeostasis. In this study, a specimen with SiO₂ hard mask and underlying Si mold was installed on the edge ring surface and the etching results were measured by varying the edge ring 2MHz RF power. By developing PI-VM model with high prediction accuracy and analyzing the roles of key parameters in the model, we were able to evaluate the effect of plasma and sheath characteristics around the edge ring on edge ring erosion. This analysis method provided information necessary for edge ring maintenance and operation.

• Applied Chemistry for Engineering
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• v.34 no.6
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• pp.626-632
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• 2023

Acemannan, a highly acetylated glucomannan, was extracted from fresh Aloe vera leaves by ethanol fractionation, resulting in a concentration increase of more than threefold. The presence of acemannan was confirmed using FTIR and ¹H NMR analysis, revealing an average molecular weight of 780 kDa. The flocculating activity of the fractionated aloe gel polysaccharide was assessed through settling tests in a 1% (w/v) bentonite suspension. The results demonstrated that the aloe polysaccharide exhibited remarkable stability within a temperature range of 20~70 ℃. The maximal flocculation rate at different pH levels ranged from 93% to 97%, with an optimal dose for maximum flocculation rate between 0.25 mg/mL. Notably, the minimum dose required for flocculation was achieved at a pH of 3, attributed to the compression of electrostatic repulsion on the surface of bentonite particles. However, the flocs obtained under acidic conditions were less dense and compact, exhibiting lower sedimentation velocity compared to those formed under neutral and alkaline pH conditions. Additionally, the addition of salt showed a slight synergistic effect on flocculation, significantly enhancing the sedimentation velocity. This investigation highlights the potential of Aloe vera polysaccharide as a natural and edible flocculant, offering promising applications in various industries.

• Steel and Composite Structures
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• v.52 no.5
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• pp.501-513
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• 2024

Two-directional functionally graded materials (2D-FGMs) show extraordinary physical properties which makes them ideal candidates for designing smart micro-switches. Pull-in instability is one of the most critical challenges in the design of electrostatically-actuated microswitches. The present research aims to bridge the gap in the static pull-in instability analysis of microswitches composed of 2D-FGM. Euler-Bernoulli beam theory with geometrical nonlinearity effect (i.e. von-Karman nonlinearity) in conjunction with the modified couple stress theory (MCST) are employed for mathematical formulation. The micro-switch is subjected to electrostatic actuation with fringing field effect and Casimir force. Hamilton's principle is utilized to derive the governing equations of the system and corresponding boundary conditions. Due to the extreme nonlinear coupling of the governing equations and boundary conditions as well as the existence of terms with variable coefficients, it was difficult to solve the obtained equations analytically. Therefore, differential quadrature method (DQM) is hired to discretize the obtained nonlinear coupled equations and non-classical boundary conditions. The result is a system of nonlinear coupled algebraic equations, which are solved via Newton-Raphson method. A parametric study is then implemented for clamped-clamped and cantilever switches to explore the static pull-in response of the system. The influences of the FG indexes in two directions, length scale parameter, and initial gap are discussed in detail.