Novel Low-Complexity Partial Transmit Sequences Scheme for PAPR Reduction in OFDM Systems Using Adaptive Differential Evolution Algorithm

A low-complexity partial transmit sequence (PTS) technique for reducing the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing signal is presented. However, the conventional PTS scheme requires an exhaustive searching over all combinations of allowed phase factors. Consequently, the computational complexity increases exponentially with the number of the subblocks. This paper presents a novel approach to the PAPR problem to reduce computational complexity based on the relationship between phase weighing factors and transmitted bit vectors. In this paper, we aim to obtain the desirable PAPR reduction with the low computational complexity. Since the process of searching the optimal phase factors can be categorized as combinatorial optimization with some variables and constraints, we propose a novel scheme, which is based on a stochastic optimization technique called modified differential evolution, to search the optimal combination of phase factors with low complexity. To validate the analytical results, extensive simulations have been conducted, showing that the proposed schemes can achieve significant reduction in computational complexity while keeping good PAPR reduction.     

Carbazole and benzimidazole/oxadiazole hybrids as bipolar host materials for sky blue,green, and red PhOLEDs

Two novel bipolar host materials (CBzIm and COxaPh) comprising of a hole-transport (HT) carbazole core functionalized with electron-transport (ET) moieties (benzimidazole/oxadiazole) at C3 and C6 positions have been synthesized. Their thermal, photophysical, electrochemical properties, and carrier mobilities were characterized. Theoretical calculations revealed that the HOMO orbitals were generally delocalized over the hole- and electron-transport moieties for both CBzIm and COxaPh, whereas the LUMO orbitals distribution only involved one benzimidazole moiety in CBzIm instead of fully delocalization over the whole polar moieties for COxaPh, which is consistent with the observation of good hole mobilities for both hosts and better electron mobility for COxaPh over CBzIm. CBzIm with high E_T (2.76 eV) is suitable to serve as a blue phosphor host, where a sky blue phosphor (DFPPM)₂Irpic exhibiting superior properties than those of popular blue emitter FIrpic was used to give highly efficient phosphorescent OLEDs, achieving a maximum external quantum efficiency (η_ext) of 15.7%. The better π-delocalization of COxaPh led to a lower triplet energy (E_T = 2.65 eV), which can be used to accommodate green and red phosphors, providing excellent device performance with η_ext as high as 17.7% for green [(ppy)₂Ir(acac)] and 20.6% for red [Os(bpftz)₂(PPh₂Me)₂], respectively.     

Fabrication of a Large‐Area Al‐Doped ZnO Nanowire Array Photosensor with Enhanced Photoresponse by Straining

The photosensing properties of flexible large‐area nanowire (NW)‐based photosensors are enhanced via in situ Al doping and substrate straining. A method for efficiently making nanodevices incorporating laterally doped NWs is developed and the strain‐dependent photoresponse is investigated. Photosensors are fabricated by directly growing horizontal single‐crystalline Al‐doped ZnO NW arrays across Au microelectrodes patterned on a flexible SiO₂/steel substrate to enhance the transportation of carriers and the junction between NWs and electrodes. The Raman spectrum of the Al:ZnO NWs, which have an average diameter and maximum length of around 40 nm and 6.8 μm, respectively, shows an Al‐related peak at 651 cm^?1. The device shows excellent photosensing properties with a high ultraviolet/visible rejection ratio, as well as extremely high maximum photoresponsivity and sensitivity at a low bias. Increasing the tensile strain from 0 to 5.6% linearly enhances the photoresponsivity from 1.7 to 3.8 AW^?1 at a bias of 1 V, which is attributed to a decrease in the Schottky barrier height resulting from a piezo‐photonic effect. The high‐performance flexible NW device presented here has applications in coupling measurements of light and strain in a flexible photoelectronic nanodevice and can aid in the development of better flexible and integrated photoelectronic systems.     

Neural-network-based motor rolling bearing fault diagnosis

Motor systems are very important in modern society. They convert almost 60% of the electricity produced in the US into other forms of energy to provide power to other equipment. In the performance of all motor systems, bearings play an important role. Many problems arising in motor operations are linked to bearing faults. In many cases, the accuracy of the instruments and devices used to monitor and control the motor system is highly dependent on the dynamic performance of the motor bearings. Thus, fault diagnosis of a motor system is inseparably related to the diagnosis of the bearing assembly. In this paper, bearing vibration frequency features are discussed for motor bearing fault diagnosis. This paper then presents an approach for motor rolling bearing fault diagnosis using neural networks and time/frequency-domain bearing vibration analysis. Vibration simulation is used to assist in the design of various motor rolling bearing fault diagnosis strategies. Both simulation and real-world testing results obtained indicate that neural networks can be effective agents in the diagnosis of various motor bearing faults through the measurement and interpretation of motor bearing vibration signatures     

ECVBA traffic‐smoothing scheme for VBR media streams

We propose an effective and efficient traffic‐smoothing called the efficient changes and variability bandwidth allocation (ECVBA) scheme. This algorithm not only minimizes the peak rate of a stream but also increases the likelihood of successful VBR stream transmission. The main benefit is that it can immediately release bandwidth to other sites in the network. Copyright © 2002 John Wiley & Sons, Ltd.     

Systematic Generation of Current-Mode Linear Transformation Filters Based on Multiple Output CCIIs

A transformation called current-mode linear transformation (CMLT) and its filter applications using multiple output second-generation current conveyors (MOCCIIs) are presented. The systematic method is developed to realize CMLT MOCCII-based filters efficiently. Based on the proposed design tables, we can synthesize high-order current-mode all-pole and elliptic filters with MOCCIIs, grounded resistors and capacitors. Moreover, the high-frequency elliptic filter can also be efficiently realized by adding capacitors to the relative all-pole filter, although floating capacitors are needed. Third-order Chebychev and elliptic lowpass filters are described in this paper. Experimental results that confirm the theoretical analysis are obtained. Furthermore, the proposed circuits can be extended to higher-order filters.     

Dual-output switched-capacitor DC–DC converter with pseudo-three-phase swap-and-cross control and amplitude modulation mechanism

This paper presents an inductorless dual-output switched-capacitor DC–DC converter employing pseudo-three-phase swap-and-cross control (PTPSCC) and an amplitude modulation mechanism (AMM). The AMM circuit scales the amplitudes of the driving signals for the switches according to the loading conditions in order to minimize switching losses. To reduce output ripples, average charge distribution, and improve regulation, the PTPSCC circuit continuously switches power transistors to deliver enough charge to the outputs by keeping at least one flying capacitor connected to each output. The switched capacitor DC–DC converter was implemented in a standard 0.18-μm 3.3-V CMOS process. Measurements were used to verify that the proposed converter provides dual independently regulated output voltages without cross regulation. The two outputs were regulated at 2.5 and 0.8 V with input ranges of 1.7–2 V. The maximum output loading was 100 mA for both outputs. A power efficiency of 90.5% was achieved at a maximum total output power of 330 mW with a switching frequency of 500 kHz, and a maximum power efficiency of 92.1% was achieved for a total output power of 210 mW. The maximal peak-to-peak output ripple voltages for the two outputs at 100 mA load currents were suppressed to below 26 and 20 mV, respectively.     

performance Evaluation of IPv4/IPv6 Networks for Ubiquitous Home-Care Service

Because of rapid development in network technology,Internet usage has become widespread.It allows users with sensing devices to obtain medical data for healthcare,such as physiological signals,voice,and video streams from telemedicine systems,and to send the healthcare data to back-end database systems,creating a ubiquitous healthcare environment.However,this environment requires a widespread and suitable network.IPv6(Internet protocol version 6) is the next-generation Internet protocol that will be the protocol of future networks;it improves many shortcomings of IPv4.In this paper,we propose an IPv6/IPv4 U-home-care test system and analyze the network’s parameters though a series of tests by adjusting network parameters to find the optimal design for applications in the IPv6/IPv4 U-home-care service so as to assure good performance and high quality.     

Polarization-based cooperative directional MAC protocol for ad hoc networks

Numerous directional medium access control (DMAC) protocols have been developed to enhance the capacity of ad hoc networks using the underlying advanced physical layer techniques, such as beam-forming, multiuser detection (MUD), and multiple-input–multiple-output (MIMO). In this paper, we propose an innovative fully distributed DMAC protocol that cooperatively makes use of polarization diversity in low-mobility urban/suburban outdoor wireless ad hoc network environment. In the proposed cooperative polarization DMAC protocol (CPDMAC), each node directionally senses on both vertical and horizontal polarizations and dynamically adapts polarization that minimizes overall interference in the ad hoc network. Analysis is performed to establish relationship between vertically and horizontally polarized nodes in the network. Further, a theoretical lower bound is derived for probability of successful transmission to show capacity improvement as a function of cross polarization ratio (CPR). Simulation results confirm from 2% up to 400% improvement in average node throughput at data rate of 1.95 Mbps when compared to the traditional DMAC protocol. Moreover, our study clearly shows that the average throughput difference increases with increasing node density when compared to the traditional DMAC protocol.     

Background removal of multiview images by learning shape priors.

Image-based rendering has been successfully used to display 3-D objects for many applications. A well-known example is the object movie, which is an image-based 3-D object composed of a collection of 2-D images taken from many different viewpoints of a 3-D object. In order to integrate image-based 3-D objects into a chosen scene (e.g., a panorama), one has to meet a hard challenge--to efficiently and effectively remove the background from the foreground object. This problem is referred to as multiview images (MVIs) segmentation. Another task requires MVI segmentation is image-based 3-D reconstruction using multiview images. In this paper, we propose a new method for segmenting MVI, which integrates some useful algorithms, including the well-known graph-cut image segmentation and volumetric graph-cut. The main idea is to incorporate the shape prior into the image segmentation process. The shape prior introduced into every image of the MVI is extracted from the 3-D model reconstructed by using the volumetric graph cuts algorithm. Here, the constraint obtained from the discrete medial axis is adopted to improve the reconstruction algorithm. The proposed MVI segmentation process requires only a small amount of user intervention, which is to select a subset of acceptable segmentations of the MVI after the initial segmentation process. According to our experiments, the proposed method can provide not only good MVI segmentation, but also provide acceptable 3-D reconstructed models for certain less-demanding applications.