• Membrane Journal
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• v.13 no.1
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• pp.37-46
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• 2003

The electrokinetic effect can be found in cases of the fluid flowing across the charged membrane micropores. The externally applied body force originated from the electrostatic interaction between the nonlinear Poisson-Boltzmann field and the flow-induced electrical field is taken into 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 pore is obtained via the Green's function. An explicit analytical expression for the flow-induced streaming potential is derived as functions of relevant physicochemical parameters. The influences of the electric double layer, the surface potential of the wall, and the charge condition of the pore wall upon the velocity profile as well as the streaming potential are examined. With increasing of either the electric double layer thickness or the surface potential, the average fluid velocity is entirely reduced, while the streaming potential increases.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.2014-2020
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• 2017

A compact current model applicable to both single-gate (SG) and double-gate (DG) tunneling field-effect transistors (TFETs) is presented. The model is based on Kane's band-to-band tunneling (BTBT) model. In this model, the well-known and previously-reported quasi-2-D solution of Poisson's equation is used for the surface potential and length of the tunneling path in the tunneling region. An analytical tunneling current expression is derived from expressions of derivatives of local electric field and surface potential with respect to tunneling direction. The previously reported correction factor with three fitting parameters, compensating for superlinear onset and saturation current with drain voltage, is used. Simulation results of the proposed TFET model are compared with those from a technology computer-aided-design (TCAD) simulator, and good agreement in all operational bias is demonstrated. The proposed SG/DG-TFET model is developed with Verilog-A for circuit simulation. A TFET inverter is simulated with the Verilog-A SG/DG-TFET model in the circuit simulator; the model exhibits typical inverter characteristics, thereby confirming its effectiveness.

• Advances in Energy Research
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• v.5 no.3
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• pp.219-226
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• 2017

Electrochemical double layer capacitors (EDLCs) have received a tremendous interest due to their suitability for diverse applications. They have been fabricated using different carbon based electrodes including activated carbons, single walled/multi walled carbon nano tubes. But, graphite which is one of the natural resources in Sri Lanka has not been given a considerable attention towards using for EDLCs though it is a famous carbon material. On the other hand, EDLCs are well reported with various liquid electrolytes which are associated with numerous drawbacks. Gel polymer electrolytes (GPE) are well known alternative for liquid electrolytes. In this paper, it is reported about an EDLC fabricated with a nano composite polyethylene oxide based GPE and two Sri Lankan graphite based electrodes. The composition of the GPE was [{(10PEO: $NaClO_4$) molar ratio}: 75wt.% PC] : 5 wt.% $TiO_2$. GPE was prepared using the solvent casting method. Two graphite electrodes were prepared by mixing 85% graphite and 15% polyvinylidenefluoride (PVdF) in acetone and casting n fluorine doped tin oxide glass plates. GPE film was sandwiched in between the two graphite electrodes. A non faradaic charge discharge mechanism was observed from the Cyclic Voltammetry study. GPE was stable in the potential windows from (-0.8 V-0.8 V) to (-1.5 V-1.5 V). By increasing the width of the potential window, single electrode specific capacity increased. Impedance plots confirmed the capacitive behavior at low frequency region. Galvanostatic charge discharge test yielded an average discharge capacity of $0.60Fg^{-1}$.

• Geophysics and Geophysical Exploration
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• v.21 no.4
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• pp.231-243
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• 2018

Streaming potential (SP) arises from fluid flow through effectively connected pores. From this potential, formation water information as well as fluid flow properties can be estimated. As micro particles being located in boundary between subsurface porous media and fluid are charged to form electrical double layer, fluid flow caused by several reasons generates SP, one of electrokinetic phenomena. Occurrence mechanism of SP is complex and signal strength is relatively weak compared to noise. However, application of self potential survey using SP to monitoring of formation fluid is expanding because of its' convenience of exploration without artificial source and repetitiveness of signal. This paper accounts for the occurrence mechanism of SP studied before, including governing equations and analyzes previous various case studies of SP according to the change of physical properties of materials. It helps to increase understanding about SP and also lays the foundations of the application of SP to fields.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.4
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• pp.437-445
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• 2005

Zeta potential is a key parameter of double layer repulsion for individual particles and can usually be used to interpret the trend of coagulation efficiency. This study focused on the measurement of zeta potential of algae and clay under various experimental conditions including water characteristics (pure water, stream water, reservoir water) and coagulant dose (10~50 mg/L). Results showed that the variation of zeta potential was highly sensitive depending on the water characteristics and coagulation conditions. Zeta potential of two genera of algae (anabaena sp. and microcystis sp.) were changed highly with coagulant dosage, especially. On the basis of trajectory analysis, bubble-floc collision efficiency simulated in terms of zeta potential was fitted well with removal efficiency of chlorophyll-a from algae particles. It was found that the control of zeta potential was important for effective removal of algae particles.

• Journal of information and communication convergence engineering
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• v.14 no.2
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• pp.115-121
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• 2016

Currently there is a lack of literature on SPICE-level models of double-gate (DG) tunnel field-effect transistors (TFETs). A DG TFET compact model is presented in this work that is used to develop a SPICE model for DG TFETs implemented with Verilog-A language. The compact modeling approach presented in this work integrates several issues in previously published compact models including ambiguity about the use of tunneling parameters A_k and B_k, and the use of a universal equation for calculating the surface potential of DG TFETs in all regimes of operation to deliver a general SPICE modeling procedure for DG TFETs. The SPICE model of DG TFET captures the drain current-gate voltage (I_ds-V_gs) characteristics of DG TFET reasonably well and offers a definite computational advantage over TCAD. The general SPICE modeling procedure presented here could be used to develop SPICE models for any combination of structural parameters of DG TFETs.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1387-1390
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• 2006

Several actuation mechanism for carton nanotubes has teen reported recently, including actuation by double-layer charge injection and ac voltages applyied to multiple electrodes. Carbon nanotube actuator based on double layer charge injection work well in electrolyte at low voltage. AC dielectrophoresis based on four electrode geometry demonstrated carton nanotubes in solution phase can be oriently manipulated by dielectrophoresis. From this point of view, and in regard to their performance, bucky paper actuator may alternate natural muscle. also, applied AC signal with appropriate magnitude and frequency together with four electrode arrangement has potential to realize nanotube electrokinetics.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.162-169
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• 1999

Intentionally weakened girders near the beam-to-colum connection lead ductile failures at the weakened points prior to potential brittle failure at the connection points subjected to strong earthquake. Recent research investigated cyclic behavior of composite beams with a rectangular web opening and find out ductile failure of such beams due to plastic hinge formation of T-section at the four corners of the rectangular opening. But eventual failures of T-sections are resulted from local buckling of T-section having a narrow stem and a narrow bound of plastic hinge formation. This continuing research proposes double-circular opening instead of rectangular one in ofter to improve energy dissipation capacity as well as composite beam strength, Experimental test of two specimens was carried out and its results are compared with those of nonlinear finite element analyses

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.15-27
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• 2014

양자화학 (quantum chemistry)을 처음 접했을 때, 이전까지의 고전역학 (classical mechanics)에 익숙한 대다수의 학생들은 양자화학을 받아들이는 데 어려움을 겪는다. 모형계에 양자역학 (quantum mechanics)을 직접 적용하여 봄으로써 생소한 양자 개념에 대한 이해를 도울 수 있다. 본 논문에서는 양자동역학 (quantum dynamics)을 수치적으로 구현하는 계산 프로그램을 모형계에 적용하여 양자 개념을 설명할 수 있는 몇 가지 예를 보이고자 한다. 1 차원 시간의존 슈뢰딩거 방정식 (1-D time-dependent $Schr{\ddot{o}}dinger$ equation)의 해를 얻어 양자동역학을 구현하였으며, 그에 해당하는 고전동역학은 뉴턴 방정식 (Newton's equation)의 해로 얻어졌다. 조화 진동자 퍼텐셜 (harmonic oscillator potential), 모스 진동자 퍼텐셜 (Morse oscillator potential), 이중 우물 퍼텐셜 (double-well potential), 네모 퍼텐셜 장벽 (rectangular potential barrier), 그리고 에카트 퍼텐셜 (Eckart potential)에 대한 계산을 수행하였다. 두 가지 동역학을 비교하기 위하여 계산 결과의 시각화 (visualization)를 이용하고 동역학 특성의 차이를 비교하는 차별화 (differentiation)를 강조한다. 영점에너지 (zero-point energy), 위상어긋남 (dephasing), 터널링 (tunneling), 그리고 반사 (reflection) 현상과 같은 양자동역학의 특징을 고전동역학과 비교함으로써 직관적인 이해를 도울 수 있었다. 이러한 결과는 양자화학에 입문하는 학생들을 대상으로 쓰일 수 있는 효율적인 강의 모델을 제시할 것으로 기대한다.

• Membrane Journal
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• v.12 no.1
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• pp.41-50
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• 2002

The streaming potential generated by the electrokinetic flow within electric double layer of charged microchannel is applied to determine the zeta potential of hollow-fiber membrane pore by using the general Helmholtz-Smoluchowski equation. The streaming potential is know to provide a useful real-time information on the surface property and the interaction between pore and particles in actual situations and physicochemical conditions. The influence of physicochemical parameters upon the filtration with hollow-fibers has been examined with an in-situ and simultaneously monitoring the streaming potential as well as permeate flux. In particular, the present study examined an experimental method to identify the effect of cake layer which can vary according to the axial position of a hollow-fiber and the progress of membrane fouling by measuring the position-dependent streaming potential. As the latex concentration increases, the permeate flux decreased but the streaming potential increased. The growth of cake layer has been mire developed with increasing latex concentration, however, the effect of surface charges of latexes deposited on the membrane surface leads to increase the streaming potential. With increasing ionic concentration of KCI, both the permeate flux and the streaming potential decrease. The increase of ionic concentration provides a compact cake layer due to the shrinkage of Debye length and the decreased streaming potential results from the weakened ionic flows owing to a thin diffusive double layer.