• Proceedings of the Korean Vacuum Society Conference
• /
• 2009.02a
• /
• pp.185.1-185.1
• /
• 2009

• Proceedings of the Materials Research Society of Korea Conference
• /
• 1996.11a
• /
• pp.69-69
• /
• 1996

• Journal of Electrical Engineering and Technology
• /
• v.10 no.2
• /
• pp.647-652
• /
• 2015

A fully coupled finite element analysis (FEA) technique was developed for analyzing the discharge phenomena and dielectric liquid flow while considering surface charge density effects in dielectric flow guidance. In addition, the simulated speed of surface charge propagation was compared and verified with the experimental results shown in the literature. Recently, electrohydrodynamics (EHD) techniques have been widely applied to enhance the cooling performance of electromagnetic systems by utilizing gaseous or liquid media. The main advantage of EHD techniques is the non-contact and low-noise nature of smart control using an electric field. In some cases, flow can be achieved using only a main electric field source. The driving sources in EHD flow are ionization in the breakdown region and ionic dissociation in the sub-breakdown region. Dielectric guidance can be used to enhance the speed of discharge propagation and fluidic flow along the direction of the electric field. To analyze this EHD phenomenon, in this study, the fully coupled FEA was composed of Poisson's equation for an electric field, charge continuity equations in the form of the Nernst-Planck equation for ions, and the Navier-Stokes equation for an incompressible fluidic flow. To develop a generalized numerical technique for various EHD phenomena that considers fluidic flow effects including dielectric flow guidance, we examined the surface charge accumulation on a dielectric surface and ionization, dissociation, and recombination effects.

• Proceedings of the KIEE Conference
• /
• 2000.07e
• /
• pp.108-112
• /
• 2000

The electric charge generated by flowing insulation liquid can create hazardous spark in transfer line and receiving tank etc. These electrification has generally been measured by current measurement with a ammeter connected to the receiving tank. This paper reports on the experimental result obtained by this method. As a experimental results: The injected charge value for unit volume increased in the following condition, the edge of the needle electrode was sharp, the number of needle electrode was fewer, the edge of the needle electrode was located close to the inside wall. When the charge density in the charge reducer is constant, electrode current and electrode potential by the charge injection from outside increase with increasing of oil velocity and streaming current. The electrode potential in charge reducer is made maximum value at edge point of reducer inside and minimum value at center line of charge reducer.

• Journal of the Korean Ceramic Society
• /
• v.34 no.10
• /
• pp.1060-1066
• /
• 1997

In this paper, the effects of La addition of PLZT thin film prepared by sol-gel method on the capacitor characteristics are investigated for gigabit generation DRAM applications. The addition of La on the PLZT capacitor results in a trade-off between charge storage density(Qc') and leakage current density(Jl). As La content increases, Qc' and permeability(εr) at 0V are reduced while Jl is significantly decreased. It is demonstrated that 5% La doping of PZT can substantially reduce Jl and also improve resistance to fatigue while incurring only minimal degradation of Qc'. Very low leakage current density (5×10-7 A/㎠ even at 125℃) and high charge storage density (100fC/㎛2) under VDD/2=1V conditions are achieved using 5% La doped PZT thin films for gigabit DRAM capacitor dielectrics. In addition, the fatigue and TDDB measurements indicate good reliability of the PLZT capacitors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.6
• /
• pp.510-514
• /
• 2011

Based on first-principles LCAO method, we study the electronic and atomic structures of DNA nucleobases adenine (A), thymine (T), guanine (G), and cytosine (C) adsorbed on graphene surfaces. The ${\pi}-{\pi}$ stacking interactions between graphene and nucleobases lead to the bilayer geometries similar to the Bernal stacked graphite. Through the density of states and charge density analyses, it is found that nucleobases are physisorbed on graphene by dispersive interactions with negligible charge exchange. Our calculations reproduce the atomic structures obtained in previous plane wave calculations accurately with much less computation, and well describe the delocalized ${\pi}-{\pi}$ interactions in graphene-nucleobases system, indicating that the LCAO method is very efficient for investigating graphene-bio systems.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.11
• /
• pp.110-117
• /
• 1997

This paper discusses numerically and experimenally several design parameters for the plate- type capacitive displacement sensor. The influenences of shape of this sensor on the sensitivity are numerically analyzed with the charge density method. Using many test sensor plates of different shape for verifing the validity of this method can not guarantee the repetibility of experiments. Therefore we made specially the test sensor plate so that experiments of effects of shape of this sensor on sensitivity can be done with only that plate. Results from these experiments agree well with those from numerical analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.124-125
• /
• 2008

The charge trapping and tunnelling characteristics with various thickness of $Si_3N_4$ layer were investigated for application of TBE (Tunnel Barrier Engineered) non-volatile memory. We confirmed that the critical thickness of no charge trapping was existed with decreasing $Si_3N_4$ thickness. Also, the charge trap centroid x and charge trap density were extracted by using CCS (Constant Current Stress) method. Through the optimized thickness of $Si_3N_4$ layer, it can be improve the performance of non-volatile memory.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.2
• /
• pp.278-284
• /
• 2009

The global force and interaction body force density were evaluated in permanent magnets by using the virtual air-gap scheme incorporating the finite-element method. Until now, the virtual air-gap concept has been successfully applied to calculate a contact force and a body force density in soft magnetic materials. These force calculating methods have been called as generalized methods such as the generalized magnetic charge force density method, the generalized magnetizing current force density method, and the generalized Kelvin force density method. For permanent magnets, however, there have been few research works on a contact force and a force density field. Unlike the conventional force calculating methods resulting in surface force densities, the generalized methods are novel methods of evaluating body force density. These generalized methods yield the actual total force, but their distributions have an irregularity, which seems to be random distributions of body force density. Inside permanent magnets, however, a smooth pattern was obtained in the interaction body force density, which represents the interacting force field among magnetic materials. To evaluate the interaction body force density, the intrinsic force density should be withdrawn from the total force density. Several analysis models with permanent magnets were tested to verify the proposed methods evaluating the interaction body force density and the contact force, in which the permanent magnet contacts with a soft magnetic material.

• Journal of Sensor Science and Technology
• /
• v.30 no.2
• /
• pp.71-75
• /
• 2021

Recently, transition-metal-based hydroxide materials have attracted significant attention in various electrochemical applications owing to their low cost, high stability, and versatility in composition and morphology. Among these applications, transition-metal-based hydroxides have exhibited significant potential in supercapacitors owing to their multiple redox states that can considerably enhance the supercapacitance performance. In this study, nanostructured Ni-Mn double hydroxide is directly grown on a conductive substrate using an electrodeposition method. Ni-Mn double hydroxide exhibits excellent electrochemical charge-storage properties in a 1 M KOH electrolyte, such as a specific capacitance of 1364 Fg-1 at a current density of 1 mAcm-2 and a capacitance retention of 94% over 3000 charge-discharge cycles at a current density of 10 mAcm-2. The present work demonstrates a scalable, time-saving, and cost-effective approach for the preparation of Ni-Mn double hydroxide with potential application in high-charge-storage kinetics, which can also be extended for other transition-metal-based double hydroxides.