Modal MRTD approaches for the efficient analysis of waveguidediscontinuities

This paper, the multi-resolution time-domain (MRTD) technique is applied to the waveguide discontinuity problem for fast-scattering parameter computation. To improve the computational efficiency, both three-dimensional (3-D) waveguide regions, including discontinuities, and one dimensional (1-D) homogeneous waveguide region, terminated with the modal absorbing boundary condition (ABC), are simulated in the wavelet domain with the mode composition/expansion algorithm from the modal analysis. A WG-90 rectangular waveguide with a thick asymmetric iris is analyzed and the numerical results are compared with conventional finite-difference time-domain (FDTD) results and mode-matching results     

A moving-actuator type electromechanical total artificial heart.II. Circular type and animal experiment

A new type of electromechanical total artificial heart (TAH) based on circular rolling-cylinder mechanism was developed to overcome critical problems in motor-driven artificial hearts such as large size and difficulties in fitting the heart to atrial remnants and arterial vessels. Its performance and reliability were evaluated in mock circulation and in an animal implant experiment. The total weight and volume of the pump is 650 g and 600 mL, respectively. This new pump was implanted in a calf for total heart replacement and 96 h of survival was achieved. The whole system, including pump, controller, and control algorithm performed well enough to improve the prospect of eventual clinical application of our TAH system.     

A Scheduling Framework for UWB & Cellular Networks

The max-min fair scheduling problem in wireless ad-hoc networks is a non-convex optimization problem. A general framework is presented for this optimization problem and analyzed to obtain a dual problem, which involves solving a series of optimization sub-problems. In the limit of infinite bandwidth ( ), the scheduling solution reduces to simultaneous transmission (spread spectrum) on all links (Negi and Rajeswaran, INFOCOM '04 (March 2004)). This motivates the analysis of the scheduling problem in the Ultra Wide Band (UWB) regime ( , but finite), a model for certain practical radios. A quadratic (in 1/W) lower bound to the single link capacity function is developed, which simplifies the dual sub-problem to a quadratic optimization (Negi and Rajeswaran, GLOBECOM '04, (Dec. 2004)). The solution to this sub-problem is then obtained under both total power and power spectral density constraints. This solution is utilized to iteratively construct the schedule (sub-band sizes) and power allocation, thus optimally solving the UWB max-min fair scheduling problem, to within any desired precision. Simulations on medium sized networks demonstrate the excellent performance of this scheme. A cellular architecture (not necessarily UWB) may also be considered in this framework. It is proved that Frequency Division Multiple Access is the optimal scheduling for a multi-band cellular architecture. This work was supported in part by the National Science Foundation under Career award 0347455. Arjunan Rajeswaran received his Masters degree in Electrical and Computer Engineering from Carnegie Mellon University in 2003. Since August 2003, he has been pursuing his doctoral research at Carnegie Mellon. His reserach interests lie in the area of wireless networks. His focus is in the application of information and communication theoretic tools towards wireless network design. Several IEEE publications reflect his curent research on Medium Access Control design and performance. Arjunan received the best student paper award at IEEE/ACM Broadnets 2004. Gyouhwan Kim received his B.S. and M.S. degree in Electronic Engineering from Sogang University in Korea, in 1994 and 1996, respectively. Since 1996, he has been working in the CDMA cellular system development team in Samsung Electronics. Currently, he is also working toward the Ph.D degree in the Department of Electrical and Computer Engineering at Carnegie Mellon University. His main research interests are in wireless networks and communication theory. Rohit Negi received the B.Tech. degree in Electrical Engineering from the Indian Institute of Technology, Bombay, India in 1995. He received the M.S. and Ph.D. degrees from Stanford University, CA, USA, in 1996 and 2000 respectively, both in Electrical Engineering. He has received the President of India Gold medal in 1995. Since 2000, he has been with the Electrical and Computer Engineering department at Carnegie Mellon University, Pittsburgh, PA, USA, where he is an Assistant Professor. His research interests include signal processing, coding for communications systems, information theory, networking, cross-layer optimization and sensor networks.     

Motion artifact reduction in photoplethysmography using independent component analysis

Removing the motion artifacts from measured photoplethysmography (PPG) signals is one of the important issues to be tackled for the accurate measurement of arterial oxygen saturation during movement. In this paper, the motion artifacts were reduced by exploiting the quasi-periodicity of the PPG signal and the independence between the PPG and the motion artifact signals. The combination of independent component analysis and block interleaving with low-pass filtering can reduce the motion artifacts under the condition of general dual-wavelength measurement. Experiments with synthetic and real data were performed to demonstrate the efficacy of the proposed algorithm.     

Reflective SOA-Based Bidirectional WDM-PON Sharing Optical Source for Up/Downlink Data and Broadcasting Transmission

We proposed and experimentally demonstrated the reflective semiconductor optical amplifier (RSOA)-based wavelength-division-multiplexed passive optical network (WDM-PON) scheme where not only up/downlink data services but also broadcasting service could be provided using a single optical source. In the proposed scheme, the digital signal and subcarrier multiplexing (SCM) signal for downstream were simultaneously modulated by a single distributed feedback laser diode and RSOA in optical network unit remodulated downstream source as an upstream. Without performance deterioration of digital signals both in up- and downstream, the proposed WDM-PON scheme can stably offer the SCM signal for broadcasting service. In the experiment, 1-Gb/s digital signals both for up- and downstream and 20-Mb/s SCM signal at 2.2 GHz for broadcasting were demonstrated in 10-km bidirectional link     

Low-Complexity Symbol Detector for MIMO-OFDM-Based Wireless LANs

In this brief, a low-complexity hardware architecture for multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) symbol detectors with two transmit and two receive antennas is proposed. The detectors support two MIMO-OFDM schemes of space-frequency block coded OFDM and space-division multiplexing OFDM in order to achieve higher performance and throughput. However, symbol detection processes for these two schemes have high computational complexity, which is a burden to hardware implementation of MIMO-OFDM symbol detectors. In order to reduce complexity, the proposed symbol detector is designed with shared architecture, where similar functional blocks are merged and share the hardware resources, and results in the reduction of logic gates by 34% over a conventional architecture employing two individual detectors     

A Fast Intra Skip Detection Algorithm for H.264/AVC Video Encoding

A fast intra skip detection algorithm based on the rate‐distortion (RD) cost for an inter frame (P‐slices) is proposed for H.264/AVC video encoding. In the H.264/AVC coding standard, a robust rate‐distortion optimization technique is used to select the best coding mode and reference frame for each macroblock (MB). There are three types of intra predictions according to profiles. These are 16×16 and 4×4 intra predictions for luminance and an 8×8 intra prediction for chroma. For the high profile, an 8×8 intra prediction has been added for luminance. The 4×4 prediction mode has 9 prediction directions with 4 directions for 16×16 and 8×8 luma, and 8×8 chrominance. In addition to the inter mode search procedure, an intra mode search causes a significant increase in the complexity and computational load for an inter frame. To reduce the computational load of the intra mode search at the inter frame, the RD costs of the neighborhood MBs for the current MB are used and we propose an adaptive thresholding scheme for the intra skip extraction. We verified the performance of the proposed scheme through comparative analysis of experimental results using joint model reference software. The overall encoding time was reduced up to 32% for the IPPP sequence type and 35% for the IBBPBBP sequence type.     

Selective wet etching of p-GaN for efficient GaN-based light-emitting diodes

The selective wet etching of a p-GaN layer by using a solution of KOH in ethylene glycol (KE) was studied to enhance the optical and electrical performance of the GaN-based light-emitting diodes (LEDs). The surface of the p-GaN, which was selectively etched in the KE solution, showed hexagonal-shaped etch pits. The light-output power of etched LEDs was improved by 29.4% compared to that of the nonetched LED. This improvement was attributed to the increase in the probability of photons to escape due to the increased surface area of textured surface and the reduction in contact resistance of the ohmic layer resulting from the increased contact area and hole concentration on the textured p-GaN. The reverse leakage current of the LED was also greatly decreased due to the surface passivation and the removal of defective regions from the p-GaN.     

A novel hidden station detection mechanism in IEEE 802.11 WLAN

The popular IEEE 802.11 wireless local area network (WLAN) is based on a carrier sense multiple access with collision avoidance (CSMA/CA), where a station listens to the medium before transmission in order to avoid collision. If there exist stations which can not hear each other, i.e., hidden stations, the potential collision probability increases, thus dramatically degrading the network throughput. The RTS/CTS (request-to-send/clear-to-send) frame exchange is a solution for the hidden station problem, but the RTS/CTS exchange itself consumes the network resources by transmitting the control frames. In order to maximize the network throughput, we need to use the RTS/CTS exchange adaptively only when hidden stations exist in the network. In this letter, a simple but very effective hidden station detection mechanism is proposed. Once a station detects the hidden stations via the proposed detection mechanism, it can trigger the usage of the RTS/CTS exchange. The simulation results demonstrate that the proposed mechanism can provide the maximum system throughput performance.     

Development of intracranial brain-computer interface system using non-motor brain area for series of motor functions

An intracranial brain-computer interface (BCI) system using the neuronal activity of a non-motor brain area to fulfil a series of motor functions has been developed. The presented BCI system encodes a series of motor functions into a small number of neuronal units of the primary somatosensory cortex of a rat and generates real-time command signals to control a machine according to the animal's motor intentions. The results of this study demonstrate the practical usability of the BCI system using a non-motor brain area in the field of rehabilitation.