Dielectric spectroscopy of metal nanoparticle doped liquid crystal displays exhibiting frequency modulation response

Twisted nematic liquid crystal displays (TN-LCDs), doped with the nanoparticles of metal, such as Pd, Ag, or Ag-Pd, which are protected with ligand molecules, such as nematic liquid crystal, exhibit a frequency modulation (FM) electro-optical (EO) response with short response time of milliseconds (ms) or sub-ms order together with the ordinary rms voltage response. These devices are called FM/AM-TN-LCDs; they are distinct from the ordinary LCDs featured by the amplitude modulation (AM) response. The phenomena of the FM/AM LCDs may be attributed to the dielectric dispersion of a heterogeneous dielectric medium known as the Maxwell-Wagner effect. It is experimentally shown that the frequency range spreads from several tens hertz to several tens kilohertz and the spectrum is more or less centered about the dielectric relaxation frequency. We formulated a theory based on an equivalent circuit model to evaluate the dielectric relaxation frequency and the dielectric strengths; and we succeeded in explaining the dependence of the dielectric relaxation frequency on the concentration of nanoparticles and the their dielectric and electrical properties, whereas conventional theories based on electromagnetic theory are unable to explain this concentration dependence. This paper reports on the experimental results of the EO effects and the dielectric spectroscopy including the dielectric relaxation times and the dielectric strengths of nematic liquid crystal, 5CB (4-pentyl-4'-cyanobiphenyl), doped with the metal nanoparticles of I'd alone and Ag-Pd composite; and discusses how the observed dielectric relaxation frequency or dielectric relaxation time depend on the concentration of the doped nanoparticles and also their electrical and dielectric properties.     

Interference characterization in the unlicensed band

We consider performance of a wireless communication receiver in the presence of a field of continuous wave (CW) interferers that are randomly distributed according to a Poisson process in space and frequency domain in the unlicensed band. From our theoretical model, we derive an accurate analytical expression for average bit error rate (BER). Judging from our results for a strong desired signal, when the user density grows up to ten times its value for a given signal to noise ratio (SNR), BER performance falls by 9.09% and 8.51 % for BPSK and DPSK respectively.     

Scalable architecture for word HMM-based speech recognition and VLSI implementation in complete system

This paper describes a scalable architecture for real-time speech recognizers based on word hidden Markov models (HMMs) that provide high recognition accuracy for word recognition tasks. However, the size of their recognition vocabulary is small because its extremely high computational costs cause long processing times. To achieve high-speed operations, we developed a VLSI system that has a scalable architecture. The architecture effectively uses parallel computations on the word HMM structure. It can reduce processing time and/or extend the word vocabulary. To explore the practicality of our architecture, we designed and evaluated a complete system recognizer, including speech analysis and noise robustness parts, on a 0.18-/spl mu/m CMOS standard cell library and field-programmable gate array. In the CMOS standard-cell implementation, the total processing time is 56.9 /spl mu/s/word at an operating frequency of 80 MHz in a single system. The recognizer gives a real-time response using an 800-word vocabulary.     

Synchronized transform-limited operation of 10-GHz colliding pulse mode-locked laser

We report a 10-GHz colliding pulse mode-locked laser fabricated with integrated active-passive waveguides. The laser fabrication adopted a deep reactive ion etching and single-step metal-organic vapor phase epitaxy regrowth process for forming the buried heterostructure waveguide. Clean output pulses resulted from laterally tilting the active-passive interface and effectively suppressing residual back-reflections at the interface. Hybrid mode-locking resulted in a synchronized transform-limited sech/sup 2/optical waveform. Pulsewidth, chirp, timing jitter, and frequency-locking range were investigated through systematic device biasing condition optimization.     

Budding of fowlpox and pigeonpox viruses at the surface of infected cells

Chick embryo fibroblasts and chorioallantoic membranes infected with fowlpox virus (FWPV) or pigeonpox virus (PPV) were examined by transmission and scanning electron microscopy. Immature virus particles were observed in finely granular areas, i.e. virus factories, of the cytoplasm. These particles had various forms depending on their stages of development. Many tubular structures were also seen in these regions. Mature virus particles with ellipsoidal or brick-shaped forms enclosing electron-dense cores were detected throughout the cytoplasm. Notably, there was a high frequency of virus budding at the cell surface, but only occasional virus wrapping in the cytoplasm. Another remarkable feature of the infected cells was accumulation of many virions just beneath the plasma membrane, indicating that this phenomenon is closely related to virus budding. Based on the observed frequency of budding, this mechanism seems to be the predominant way for FWPV and PPV to exit the cell.     

Room temperature continuous-wave operation of GaInNAs/GaAs VCSELsgrown by chemical beam epitaxy with output power exceeding 1 mW

The authors present a near 1200 nm wavelength vertical-cavity surface-emitting laser (VCSEL) the active region of which is formed by GaInNAs/GaAs quantum wells grown by chemical beam epitaxy. Room temperature continuous-wave operation has been demonstrated with a high slope efficiency of 0.23 W/A, a high output power of over 1.0 mW, and a singlemode output power of 0.34 mW. The fabricated devices with different aperture sizes show low threshold currents of 1.2-2.1 mA and a record low threshold current density of 2.6 kA/cm² in GaInNAs VCSELs     

On the frame-error rate of concatenated turbo codes

Turbo codes with long frame lengths are usually constructed using a randomly chosen interleaver. Statistically, this guarantees excellent bit-error rate (BER) performance but also generates a certain number of low weight codewords, resulting in the appearance of an error floor in the BER curve. Several methods, including using an outer code, have been proposed to improve the error floor region of the BER curve. We study the effect of an outer BCH code on the frame-error rate (FER) of turbo codes. We show that additional coding gain is possible not only in the error floor region but also in the waterfall region. Also, the outer code improves the iterative APP decoder by providing a stopping criterion and alleviating convergence problems. With this method, we obtain codes whose performance is within 0.6 dB of the sphere packing bound at an FER of 10^-6     

International direct dialing quality in a competitive transitionaltelecommunications market

The introduction of resale-based competition in international direct dialing services in January 1999 triggered a round of extremely fierce competition in Hong Kong's IDD market. In response, both the incumbent operator and new entrants had to adopt aggressive strategies to defend or gain market share. This article reports on an intensive experiment on IDD quality provided by the major IDD operators in Hong Kong after this phase of deregulation. Based on 1790 successful IDD calls to the 10 most popular destinations from Hong Kong, the IDD quality of the major operators was benchmarked. The experiment revealed some interesting findings with significant implications for telecommunications deregulation     

Dictionary design for text image compression with JBIG2

The JBIG2 standard for lossy and lossless bilevel image coding is a very flexible encoding strategy based on pattern matching techniques. This paper addresses the problem of compressing text images with JBIG2. For text image compression, JBIG2 allows two encoding strategies: SPM and PM&S. We compare in detail the lossless and lossy coding performance using the SPM-based and PM&S-based JBIG2, including their coding efficiency, reconstructed image quality and system complexity. For the SPM-based JBIG2, we discuss the bit rate tradeoff associated with symbol dictionary design. We propose two symbol dictionary design techniques: the class-based and tree-based techniques. Experiments show that the SPM-based JBIG2 is a more efficient lossless system, leading to 8% higher compression ratios on average. It also provides better control over the reconstructed image quality in lossy compression. However, SPM's advantages come at the price of higher encoder complexity. The proposed class-based and tree-based symbol dictionary designs outperform simpler dictionary formation techniques by 8% for lossless and 16-18% for lossy compression     

Identification in the presence of side information with applicationto watermarking

Watermarking codes are analyzed from an information-theoretic viewpoint as identification codes with side information that is available at the transmitter only or at both ends. While the information hider embeds a secret message (watermark) in a covertext message (typically, text, image, sound, or video stream) within a certain distortion level, the attacker, modeled here as a memoryless channel, processes the resulting watermarked message (within limited additional distortion) in attempt to invalidate the watermark. In most applications of watermarking codes, the decoder need not carry out full decoding, as in ordinary coded communication systems, but only to test whether a watermark at all exists and if so, whether it matches a particular hypothesized pattern. This fact motivates us to view the watermarking problem as an identification problem, where the original covertext source serves as side information. In most applications, this side information is available to the encoder only, but sometimes it can be available to the decoder as well. For the case where the side information is available at both encoder and decoder, we derive a formula for the identification capacity and also provide a characterization of achievable error exponents. For the case where side information is available at the encoder only, we derive upper and lower bounds on the identification capacity. All characterizations are obtained as single-letter expressions