Low-voltage characteristics of MgO-CaO films as a protective layer for AC plasma display panels by e-beam evaporation

The MgO-CaO composites films were prepared by e-beam evaporation to improve both operating voltages and memory coefficient of a protective layers for AC plasma display panels (PDPs). The effects of CaO addition to the conventional MgO films on both the electrical properties and the structural changes of the Mg_1–xCa_xO thin films deposited on the slide glass substrates were investigated. Atomic force microscopy (AFM) results revealed that the Mg_0.8Ca_0.2O film had a very rough surface due to the formation of a second phase on the surface. By adding controlled amount of CaO, the Mg-Ca-O films showed a firing voltage of 176 V that is lower than that of the conventional 100% MgO film. The deposition rates of 40–100 nm/min were obtained as a function of [CaO/(MgO+CaO)] ratio of the evaporation source materials.     

TCP-Aware Uplink Scheduling for IEEE 802.16

In IEEE 802.16 networks, a bandwidth request-grant mechanism is used to accommodate various QoS requirements of heterogeneous traffic. However, it may not be effective for TCP flows since (a) there is no strict QoS requirement in TCP traffic; and (b) it is difficult to estimate the amount of required bandwidth due to dynamic changes of the sending rate. In this letter, we propose a new uplink scheduling scheme for best-effort TCP traffic in IEEE 802.16 networks. The proposed scheme does not need any bandwidth request process for allocation. Instead, it estimates the amount of bandwidth required for a flow based on its current sending rate. Through simulation, we show that the proposed scheme is effective to allocate bandwidth for TCP flows     

System analysis study for Korean fusion DEMO reactor

A conceptual design study for a steady-state Korean fusion DEMO reactor (K-DEMO) has been initiated. Two peculiar features need to be noted. First, the major radius is designed to be just below 6.5 m, considering practical engineering feasibilities. But still, high magnetic field at the plasma center around 8 T is expected to be achieved by using current state-of-the-art high performance Nb₃Sn strand technology. Second, a two-stage development plan is being considered. In the first stage, K-DEMO will demonstrate a net electricity generation but will also act as a component test facility. Then, after a major upgrade, K-DEMO is expected to show a net electric generation on the order of 300 MWe and the competitiveness in cost of electricity (COE). Feasibility of such a practical, near-future demonstration reactor is studied in this paper, based on a zero dimensional system analysis code study. It was shown that a net electric generation on the order of 300 MWe can be achieved below the optimistic β_N limit of 5. The elongation of K-DEMO is around 1.8 with single null configuration. Detailed optimization process and the resultant various plasma parameters are described.     

A preliminary conceptual design study for Korean fusion DEMO reactor

As the ITER is being constructed, there is a growing anticipation for an earlier realization of fusion energy, so called fast-track approach. Korean strategy for fusion energy can be regarded as a fast-track approach and one special concept discussed in this paper is a two-stage development plan. At first, a steady-state Korean DEMO Reactor (K-DEMO) is designed not only to demonstrate a net electricity generation and a self-sustained tritium cycle, but also to be used as a component test facility. Then, at its second stage, a major upgrade is carried out by replacing in-vessel components in order to show a net electric generation on the order of 300 MWe and the competitiveness in cost of electricity (COE). The major radius is designed to be just below 6.5 m, considering practical engineering feasibilities. By using high performance Nb₃Sn-based superconducting cable currently available, high magnetic field at the plasma center above 8 T can be achieved. A design concept for TF magnets and radial builds for the K-DEMO considering a vertical maintenance scheme, are presented together with preliminary design parameters.     

Inter-Object Layer Clustering for scalable video streaming

In this work, we develop an efficient storage technique to support real-time streaming of layer encoded video in a single hard disk. The size of a single hard disk drive will soon be able to hold multi-tera bytes and is going to handle relatively larger number of files. We expect that disk layout in a single disk will be rather critical issue in determining the efficiency of the storage system. We propose a novel storage technique, Inter-Object Layer Clustering for layer encoded video objects. In Inter-Object Layer Clustering, storage is partitioned into two regions: lower layer partition and upper layer partition. Lower and upper layer partition harbor the lower layer and upper layer data blocks across all video objects and cluster them together. We develop an elaborate performance model for this placement scheme. We examine the performance of the proposed technique using analytical formulation as well as a physical experiment. We found that clustering the layers across all objects brings 100% increase in the number of concurrent sessions compared to the case where file is stored in temporal order when the clients’ access bandwidth is narrow. Inter-Object Layer Clustering shows 15% performance improvement compared to the clustering of layers within the objects.     

Correlating the 3D melt electrospun polycaprolactone fiber diameter and process parameters using neural networks

In the present work, we developed an artificial neural networks (ANN) model to predict and analyze the polycaprolactone fiber diameter as a function of 3D melt electrospinning process parameters. A total of 35 datasets having various combinations of electrospinning writing process variables (collector speed, tip to nozzle distance, applied pressure, and voltage) and resultant fiber diameter were considered for model development. The designed stand-alone ANN software extracts relationships between the process variables and fiber diameter in a 3D melt electrospinning system. The developed model could predict the fiber diameter with reasonable accuracy for both train (28) and test (7) datasets. The relative index of importance revealed the significance of process variables on the fiber diameter. Virtual melt spinning system with the mean values of the process variables identifies the quantitative relationship between the fiber diameter and process variables.     

On the modeling of electro-hydrodynamic flow in a wire-plate electrostatic precipitator

Modeling of the flow velocity fields for the electrohydrodynamic (EHD) flow in a wire-to-plate type electrostatic precipitator (ESP) was achieved. Solutions of the steady, two-dimensional Navier-Stokes equations have been computed. The equations were solved in the conservative finite-difference form on a fine uniform rectilinear grid of sufficient resolution to accurately capture the momentum boundary layers. The numerical procedure for differential equations was used by SIMPLEST [Michel, 2002], a derivative of Patankar’s SIMPLE algorithm, to bring rapid convergence. The Phoenics (Version 3.5.1) CFD code, coupled with Poisson’s and ion transport equations and electric body force in the momentum equation, developed in this study, was used for the numerical simulation. From calculations for the flow employing different flow models, the Chen-Kimk-ε turbulent model appeared to be the most appropriate choice to obtain a quantitative image of the resulting mean flow field and downstream wake flow of the rear wire, although this was obtained from a qualitative analysis due to the lack of experimental verification. The flow velocity field pattern showed a strong EHD secondary flow, which was clearly visible in the downstream regions of the corona wire despite the low Reynolds number for the electrode (Re_CW=12.4). Secondary flow vortices were also caused by the EHD with increases in the discharge current     

Refractive sapphire microlenses fabricated by chlorine-based inductively coupled plasma etching

We have fabricated refractive sapphire microlenses and characterized their properties for what we believe to be the first time. We use thermally reflown photoresist lenslet patterns as a mask for chlorine-based dry etch of sapphire. Pattern transfer to the mechanically hard and chemically inert sapphire substrate is made possible by an inductively coupled plasma etch system that supplies a high-density plasma gas. Processed sapphire microlenses exhibit properties close to the ideal and operate nearly in the diffraction limit.     

Chiral Se Nanobrooms with Wavelength and Polarization Sensitive Scattering

High-index dielectric nanostructures offer strong magnetic and electric resonances in the visible range and low optical losses, stimulating research interest in their use for light manipulation technologies. Lithographic fabrication of dielectric nanostructures, while providing precise control over the pattern dimensions, limits the scalability of this approach for practical applications due to an inefficient fabrication process and limited production quantity. Here, the colloidal synthesis of high-index chiral dielectric nanostructures with a broom-like geometry made from trigonal Se is demonstrated. The anisotropic morphology and crystal structure of Se nanobrooms enable both linearly and circularly polarized scattering, as well as spectrum variation along the particle axis, which is, to the authors’ knowledge, the first observation of such behavior from dielectric colloidal nanostructures. To show the versatility of the highly scattering Se NB suspensions, 2D and 3D printing of Se NB inks are demonstrated as a proof of concept. This approach provides a way to manipulate light using aqueous dispersions of high-index dielectric nanostructures, unlocking their potential to fit in various morphologies and dimensions in 2D and 3D for broad applications.     

A Current-Gain Scheme for High Density and Low Voltage FeRAM

The proposed current-gain scheme provides a key technical solution for a high density, low cost and high performance ferroelectric random access memory. The proposed sensing scheme shows maximum sensing-signal window because of divided sub-bitline (SBL) structure. The unit cell array section is composed of the cell array of 64 rows and 128 columns with SBL, SBL switch (SBSW) devices and current-gain transistor (CGT) device. The global main bitline (MBL) is biased by MBL sensing load (MSL) device and connected to common MBL bus (CMB) through block selection switch (BSS) device. The device sizes of CGT and MSL devices are key factors for determining the transfer characteristics of SBL and MBL. The 128 sense amplifiers in peripheral circuit region are shared to all cell array blocks through CMB with 128 MBL columns of each cell array block. The address access time of the 16 Mb chip is evaluated to less than 70 ns at 3 V.