Spectral Amplitude-Coding Optical CDMA System Using Mach-Zehnder Interferometers

[[abstract]]In this paper, we propose a family of newly constructed codes to suppress the phase-induced intensity noise (PIIN) in spectral amplitude-coding (SAC) optical code division multiple access (OCDMA) systems. These new codes are derived from modified prime codes and their cross-correlation is not larger than one. We also present a novel SAC-OCDMA system employing the new codes together with Mach-Zehnder interferometers to eliminate the multi-user interference (MUI). Compared with the systems employing modified quadratic congruence codes (MQC codes), numerical results verify that our proposed system can more effectively suppress the PIIN and eliminate MUI. Hence, the number of simultaneously users and total transmission rate increases significantly.[[incitationindex]]SCI[[incitationindex]]EI[[booktype]]紙本[[booktype]]電子

Oxygen 1s x-ray-absorption near-edge structure of Zn-Ni ferrites : a comparison with the theoretical calculations

[[abstract]]We present the electronic structure of ferrimagnetic ZnxNi1-xFe2O4 compounds obtained by a combination of O K-edge x-ray-absorption measurements and first-principles spin-unrestricted calculations using the pseudofunction method. The two distinct preedge features are found to vary systematically as a function of the Zn content. From both experimental and theoretical analyses, we find that substitution of Ni with Zn enhances localization of the 3d states of Fe on the octahedral sites, so that the O 2p–Fe 3d hybridized states can be resolved into two distinct twofold and threefold features.[[incitationindex]]SCI[[booktype]]紙本[[booktype]]電子

Theory for the rate of crack closure

[[abstract]]The theory for the constant rate of crack closure was investigated. The aim of this theory is to explain why the rate of crack closure is constant during the wetting stage of healing. Assuming that a surface crack in a material is treated by compression or with solvent, its crack closes up at a constant rate and its shape is independent of time. This approach was based on the Gibbs energy of an atom near the boundary between healed and unhealed zones. The results are in satisfactory agreement with experimental data in the literature.[[booktype]]紙本[[booktype]]電子

Thermal conductivity modeling of compacted type nanocomposites

[[abstract]]Due to different interface densities and arrangements, the compacted type nanocomposites may yield even lower thermal conductivity than embedded type nanocomposites. In this paper, the phonon transport and thermal conductivity in compacted type nanocomposites (nanowires and nanoparticles) are investigated using a deterministic phonon Boltzmann transport equation solver. The effects of interface density and characteristic size on the phonon energy transport in nanocomposites are studied. It is found that the silicon-germanium compacted nanoparticle composites can have lower value of thermal conductivity than that of compacted nanowire composites under the same characteristic size (21.6% lower when the characteristic size is 3 nm).[[incitationindex]]SCI[[booktype]]紙本[[booktype]]電子

On Providing Temporal Full-Coverage by Applying Energy-Efficient Hole-Movement Strategies for Mobile WSNs

[[abstract]]This paper considers a mobile WSN that contains a big hole but there exists no redundant mobile sensor to heal the hole. To achieve the temporal full-coverage purpose or enhance the tracking quality, three distributed algorithms are proposed for moving the existing big coverage hole to a predefined location. Firstly, the sink chooses a promising direction for hole-movement. Then the basic, forward-only and any-direction movement mechanisms are proposed to move the hole along the promising direction in a manner of minimizing the total power consumption or balancing the energy consumption of the given WSN. Simulation results reveal that the proposed hole-movement mechanisms enhance the coverage of WSN and balance the energy consumption of mobile sensor nodes.[[conferencetype]]國際[[conferencedate]]20070311~20070315[[iscallforpapers]]Y[[conferencelocation]]Kowloon, Hong Kon

The effects of microwave oven over the IEEE 802.11 FHSS wireless LAN card

[[abstract]]We have investigated the effects of microwave ovens over the IEEE 802.11 FHSS wireless LAN card. The measured MAC frame error rate (FER) is affected by the microwave ovens. The signal spectrum radiated from the microwave oven can be used to verify the measured FER data. The performance of the specific bands assigned to some geographic locations in the IEEE 802.11 standard have been discussed in the paper. From these measurement results we can obtain that the performance of some channels within the IEEE 802.11 FHSS wireless LAN card can be seriously deteriorated. Therefore, the location of the microwave oven and the specific channels for the wireless LAN card should be pre-determined according to the experience guideline.[[conferencetype]]國際[[conferencedate]]19991018~19991022[[booktype]]紙本[[conferencelocation]]Beijing, Chin

A Two-Leve Approach to Establishing a Marketing Strategy in the Electronic Marketplace

[[abstract]]This study concerns an analysis of what kinds of products are more suitable for distribution via the Internet than via traditional markets. The purpose of the analysis is to identify and fit marketing strategy to product in the virtual marketplace. The amount of product information needed by the consumer to reach a purchasing decision varies with the degree of consumer involvement with the purchase. We conjecture that two major factors affect the consumer's disposition toward online shopping: (1) the purchase involvement on the part of consumer, and (2) product information exposure provided by the Web. Therefore, in the virtual market products may be grouped into four categories. The implication of this is that online marketing functions at two levels. (1) Level-1: PNF (primitive network function), which is derived from the primitive network characteristics associated with the product's attributes fitting with the consumer's involvement. (2) Level-2: ANF (advanced network function), which is the marketing communication created by the virtual store to meet the demands of consumers purchasing online.[[notice]]補正完畢[[conferencetype]]國際[[conferencedate]]20010103~20010106[[booktype]]紙本[[conferencelocation]]Hawaii, US

The Highly Lose Image Inpainting Method Based on Human Vision

[[abstract]]Currently, noise interference and data loss are two major problems that affect the processing results of image data transmission and storage. In order to restore damaged image data effectively, we propose a novel image inpainting technique based on wavelet transformation. The primary feature of our proposed technique is to separate the given image into two principal components which encompass image texture and color respectively. Then, according to the distinctive qualities of the given image, various image inpainting methods are adopted to perform image repair. By taking advantage of the separation of an image into its individual frequency components, we use the multi-resolution characteristics of wavelet transform, from the lowest spatial-frequency layer to the higher one, to analyze the image from global-area to local-area progressively. In order to substantiate the effectiveness of our proposed image inpainting method, we employed various images subject to high noise interference and/or extensive data loss or distortion. The experimental results were perfect, even if the distortion portions of the repaired images were higher than 90%[[notice]]補正完畢[[conferencetype]]國際[[conferencedate]]20060901~20060901[[conferencelocation]]Beijing, Chin

OFRD:Obstacle-Free Robot Deployment Algorithms for Wireless Sensor Networks

[[abstract]]Node deployment is an important issue in wireless sensor networks (WSNs). Sensor nodes should be efficiently deployed in a predetermined region in a low cost and high coverage quality manner. Random deployment is the simplest way for deploying sensor nodes but may cause the unbalanced deployment and therefore increase the hardware cost. This paper presents an efficient obstacle-free robot deployment algorithm, called OFRD which involves the design of node placement policy, snake-like movement policy, and obstacle handling rules. By applying the proposed OFRD, the robot rapidly deploys near-minimal number of sensor nodes to achieve full sensing coverage even though there exist unpredicted obstacles. Performance results reveal that OFRD outperforms the existing robot deployment mechanism in terms of power conservation and obstacle resistance, and, therefore achieves a better deployment performance.[[incitationindex]]Y[[conferencetype]]國際[[conferencedate]]20070311~20070315[[conferencelocation]]Kowloon, Hong Kon