Efficient scheduling of transmissions in optical broadcast networks

All-optical networks (AONs) with a broadcast-star based physical topology offer the possibility of transmission scheduling to resolve channel and receiver conflicts. This paper considers the problem of scheduling packet transmissions in a wavelength-division multiplexed (WDM) optical network with tunable transmitters and fixed-tuned receivers. The scheduling problem is complicated by tuning latency, a limited number of channels, and arbitrary traffic demands. We first analyze scheduling all-to-all packet transmissions and obtain a new lower bound for the schedule length. The lower bound is achieved by an algorithm proposed by Pieris and Sasaki (1994). We then extend the analysis to the case of arbitrary traffic demands and obtain lower bounds for the schedule length. Two constructions for scheduling algorithms are provided through list scheduling and multigraphs. The upper bounds so obtained not only provide performance guarantees with arbitrary demands, but also nearly meet the lower bound in simulations     

Charge recycling differential logic (CRDL) for low powerapplication

A novel logic family, called charge recycling differential logic (CRDL), has been proposed and analyzed. CRDL reduces power consumption by utilizing a charge recycling technique with the speed comparable to those of conventional dynamic logic circuits. It has an additional benefit of improved noise margin due to inherently static operation. The noise margin problem of true single-phase-clock latch (TSPC) is also eliminated when a CRDL logic circuit is connected to it. Two swing-suppressed-input latches (SSILs), which are introduced for use with CRDL, have better performance than the conventional transmission gate latch. Moreover, a pipeline configuration with CRDL in a true two-phase clocking scheme shows completely race-free operation with no constraints on logic composition. Eight-bit Manchester carry chains and full adders were fabricated using a 0.8 μm single-poly double-metal n-well CMOS technology to verify the relative performance of the proposed logic family. The measurement results indicate that about 16-48% improvements in power-delay product are obtained compared with differential cascode voltage switch (DCVS) logic     

COMPARISON OF PROBE METHODS FOR MEASUREMENT OF BUBBLE PROPERTIES

Direct quantitative comparisons of four different probe methods were performed for determination of local gas holdup, vertical bubble length, bubble rising velocity, and bubble frequency. The methods include vertically projecting electroresistivity, horizontally projecting electroresistivity, U-shape light reflection, and light transmission. The measured bubble properties strongly depended on the size and configuration of the probe tips. The light transmission probe developed in this work can be used to determine the bubble properties effectively. In order to minimize interferences with bubble flow, the size of probe tip should be small as possible and its configuration must be vertically projecting.     

Bioproduct adsorption in immobilized adsorbent: Local thermodynamic equilibrium model

A mathematical model using local thermodynamic equilibrium isotherms for adsorption on immobilized adsorbents is proposed in order to optimize the design parameters inin situ bioproduct separation process. The model accurately follows the experimental data on the adsorption of berberine, secondary metabolite produced in plant cell culture. The result shows that the lower loading capacity in immobilized adsorbents is due to the decrease in the maximum solid phase concentration and the isotherm equilibrium constant, not the effective diffusivity. Design parameters inin situ bioproduct separation process, such as the size of the beads, the ratio of beads to bulk volume and the adsorbent content of the bead, are evaluated by using the model. The decrease of bead size is the most effective parameter for adsorption of berberine in immobilized adsorbent due to a reduction in the overall diffusional resistance.     

Protection of Digital TV from Cognitive Radio Interference

Analytic modeling and computational simulation for the protection of DTV from cognitive radio interference are performed. Protection is achieved by using the protection ratio, which is derived through system modeling and its analysis. On the frequency coordination between digital TV and cognitive radio, an analysis in a co‐channel environment, in a rural area in Korea, is performed.     

Modeling of power supply noise in large chips using the circuit-based finite-difference time-domain method

In this paper, a multilayered on-chip power distribution network consisting of two million passive elements has been modeled using the finite-difference time-domain (FDTD) method. In this method, a branch capacitor has been used. The use of the branch capacitor is important for simulating multilayered power grids. In addition, a method for including the CMOS inverter characteristics into the FDTD simulation has been presented. As an example of the application of this method, an H-tree clock network was simulated to compute the power supply noise distribution across an entire chip. Various scenarios with varying decoupling capacitances, load capacitances, number of clock buffers, and rise times have been analyzed to demonstrate the importance of circuit nonlinearity on power supply noise. Also, a method has been presented for analyzing package and board planes. Based on the methods presented, the interaction between chip and package has been discussed for capturing the resonant behavior that is otherwise absent when each section of the system is analyzed separately.     

Multi-valued static random access memory (SRAM) cell with single-electron and MOSFET hybrid circuit

A new multi-valued static random access memory (MVSRAM) cell with a hybrid circuit consisting of a single-electron (SE) and MOSFETs is proposed. The previously reported MVSRAM with an SE-MOSFET hybrid circuit needs two data lines, one bit line for write operations and one sense line for read operations, to improve the speed of the read-out operation, but the proposed cell has only one data line for read/write operations, resulting in a memory area that is much smaller than that of the previous cell, without any reduction of read-out speed.     

Design and Architecture of Low‐Latency High‐Speed Turbo Decoders

In this paper, we propose and present implementation results of a high‐speed turbo decoding algorithm. The latency caused by (de)interleaving and iterative decoding in a conventional maximum a posteriori turbo decoder can be dramatically reduced with the proposed design. The source of the latency reduction is from the combination of the radix‐4, center to top, parallel decoding, and early‐stop algorithms. This reduced latency enables the use of the turbo decoder as a forward error correction scheme in real‐time wireless communication services. The proposed scheme results in a slight degradation in bit error rate performance for large block sizes because the effective interleaver size in a radix‐4 implementation is reduced to half, relative to the conventional method. To prove the latency reduction, we implemented the proposed scheme on a field‐programmable gate array and compared its decoding speed with that of a conventional decoder. The results show an improvement of at least five fold for a single iteration of turbo decoding.     

Control of linear motor machine tool feed drives for end milling: Robust MIMO approach

Linear motors are getting promising for use as high speed, high accuracy machine tool feed drives. The cutting force in the machining process are directly reflected to the linear motor due to no gearing mechanism. To achieve high accuracy machining, the controller for the linear motor system should be designed to compensate for the cutting force.

In this work, a MIMO H_∞ controller for the linear motor machine tool feed drives has been designed to reduce tracking errors induced by cutting forces for end milling. The controller is designed using normalized coprime factorization method for the dynamic model of the linear motor system. The model includes constant in-line and cross coupling force gain, since the feedback cutting force can be considered as the product of the constant gain and the moving velocity of each axis.

Analysis of the structured singular value shows that the designed controller has good robust performance despite wide variations of the cutting force and physical parameters. It is directly implemented on a linear motor X–Y table which is mounted on a milling machine to have cutting experiments via a DSP board. Experimental results verified effectiveness of the proposed scheme to suppress the effects of the cutting force in the high feed rate.     

An Opportunistic Directional MAC Protocol with Pulse/Tone Exchange in Wireless Ad-Hoc Networks

Wireless Personal Communications - This paper proposes a Medium Access Control (MAC) protocol using directional antennas in wireless ad-hoc networks, which achieves frame-collision reduction,...