A 3-bit soft-decision IC for powerful forward error correction in 10-Gb/s optical communication systems

We describe the design concept and performance of a 3-bit soft-decision IC, which opens a vista for new terabit-capacity optical communication systems by dramatically improving the capability of forward error correction (FEC). The proposed soft-decision IC is composed of five functional blocks, i.e., a soft-decider, an error filter, a 3-bit encoder, a 3:48 de-multiplexer, and a clock recovery circuit. The biggest challenge was the soft-decision block regenerating the common data using seven deciders with separate thresholds. We employed a novel SiGe BiCMOS process and a custom BGA package made from low-temperature co-fired ceramics to achieve a high sensitivity of 20 mVpp with a wide phase margin of 270/spl deg/ for 12.4-Gb/s nonreturn-to-zero (NRZ) data signals. The error filter and the 3-bit encoder, which are incorporated in the IC, prevent the degradation of the FEC performance due to signal noise or fluctuations. The 3:48 de-multiplexer provides an accessible interface with the FEC encoder/decoder LSI. The clock recovery circuit, based on a phase-locked-loop technology, fulfilled the jitter tolerance requirements corresponding to ITU-T G.825, even for 55% duty cycle optical return-to-zero (RZ) signals. The 3-bit soft-decision IC, in cooperation with a block turbo encoder/decoder, achieved a record net coding gain of 10.1 dB with 24.6% redundancy, which is only 0.9 dB away from the Shannon limit for a code rate of 0.8 for a binary symmetric channel.     

Effects of nasal continuous positive airway pressure therapy on respiratory parameters of upper airway patency in patients with obstructive sleep apnea syndrome

OBJECTIVES: To assess whether an initial treatment with nasal continuous positive airway pressure (NCPAP) therapy, applied for one night, had any effect on airway patency. METHODS: In 18 patients with obstructive sleep apnea syndrome (OSAS), we measured the total resistance of the respiratory system (Rrs) and their relevant lung functions before and after polysomnography, with and without NCPAP therapy. The Rrs was measured at 3 Hz with the forced oscillation technique. The overnight changes in the specific respiratory conductance (SGrs=reciprocal of the Rrs per unit lung volume) was also calculated in the sitting position. Since many reports have suggested that obesity, through fat deposits around the pharynx, can affect the mechanical and neuromuscular properties of the upper airway, we also investigated if the degree of obesity was related to the magnitude of improvement in these parameters. RESULTS: After the first night of NCPAP therapy, the Rrs decreased (sitting: 4.8+/-0.4 vs 4.3+/-0.4 cm H20/L/s, p < 0.05; lying: 6.5+/-0.4 vs 5.6+/-0.4 cm H20/L/s, p < 0.05) and the maximal voluntary ventilation increased in the morning (sitting: 101.6+/-5.8% vs 106.4+/-4.5%, p < 0.05; lying: 91.2+/-5.4% vs 97.9+/-4.7%, p < 0.05). The overnight difference in the SGrs showed a significant improvement after the initial treatment with NCPAP therapy (p < 0.05). However, the lung volume, flow volume loop, and closing volume in the morning did not change significantly after the therapy. An overnight decrease in the Rrs following NCPAP therapy is significantly correlated with the body mass index (sitting: r=0.54, p < 0.05; lying: r=0.61, p < 0.01). CONCLUSION: The improvements in Rrs without changes in spirometry may reflect improved upper airway patency after NCPAP therapy. The degree of obesity is suggested to be associated with the treatment effect on upper airway in patients with OSAS.     

TL-10: A programming language for assembly robots

TL-10, Toyoto Robot Language-10, is a BASIC-like robot language. It has functions that define locations and subroutine parameters, which are useful in the accumulation and the transference of robot applied technology. It also has functions to communicate with other computers such as those for vision systems. The important features are described and illustrated by examples.     

Stratified Markov Chain Monte Carlo Light Transport

Markov chain Monte Carlo (MCMC) sampling is a powerful approach to generate samples from an arbitrary distribution. The application to light transport simulation allows us to efficiently handle complex light transport such as highly occluded scenes. Since light transport paths in MCMC methods are sampled according to the path contributions over the sampling domain covering the whole image, bright pixels receive more samples than dark pixels to represent differences in the brightness. This variation in the number of samples per pixel is a fundamental property of MCMC methods. This property often leads to uneven convergence over the image, which is a notorious and fundamental issue of any MCMC method to date. We present a novel stratification method of MCMC light transport methods. Our stratification method, for the first time, breaks the fundamental limitation that the number of samples per pixel is uncontrollable. Our method guarantees that every pixel receives a specified number of samples by running a single Markov chain per pixel. We rely on the fact that different MCMC processes should converge to the same result when the sampling domain and the integrand are the same. We thus subdivide an image into multiple overlapping tiles associated with each pixel, run an independent MCMC process in each of them, and then align all of the tiles such that overlapping regions match. This can be formulated as an optimization problem similar to the reconstruction step for gradient-domain rendering. Further, our method can exploit the coherency of integrands among neighboring pixels via coherent Markov chains and replica exchange. Images rendered with our method exhibit much more predictable convergence compared to existing MCMC methods.     

A Survey on Gradient‐Domain Rendering

Monte Carlo methods for physically‐based light transport simulation are broadly adopted in the feature film production, animation and visual effects industries. These methods, however, often result in noisy images and have slow convergence. As such, improving the convergence of Monte Carlo rendering remains an important open problem. Gradient‐domain light transport is a recent family of techniques that can accelerate Monte Carlo rendering by up to an order of magnitude, leveraging a gradient‐based estimation and a reformulation of the rendering problem as an image reconstruction. This state of the art report comprehensively frames the fundamentals of gradient‐domain rendering, as well as the pragmatic details behind practical gradient‐domain uniand bidirectional path tracing and photon density estimation algorithms. Moreover, we discuss the various image reconstruction schemes that are crucial to accurate and stable gradient‐domain rendering. Finally, we benchmark various gradient‐domain techniques against the state‐of‐the‐art in denoising methods before discussing open problems.     

Doubly oriented β-form films of poly(vinylidene fluoride)

PVDF sheets, rapidly quenched, were (1) two-step transversely stretched at various temperatures and (2) stretched at various temperatures, rolled at room temperature and then annealed. The orientation patterns of the β-form crystal (which contains the polar b-axis) in these films were analysed on the basis of X-ray diffraction photographs taken with flat and cylindrical cameras. In the case of (1), when both of the two-step transversely stretching temperatures were below 100°C, a doubly oriented film with the plar b-axis oriented parallel to the film surface was obtained. In the case of (2), when the stretching temperature was below 100°C, the sheets then rolled without annealing, another doubly oriented film with the polar b-axis preferentially oriented at 30° to the film surface was obtained. On the other hand, when these films were annealed above 100°C, or the stretching temperatures were above 100°C, orientation patterns in which the polar b-axis was partially rotated through 60° were obtained. The orientation mechanisms of these films are discussed using the measurements of the lattice spacings of the β-form crystal.     

Synthesis and properties of oligo- and polymethylsilazanes as a precursor for silicon nitride

The synthesis and properties of polymethylsilazanes were investigated. Controlled ammonolysis of methyl(triisocyanato)silane (MTIS) at the molar ratios NH₃/MTIS=4 and 6 gave polymethylsilazanes3 and4, which were soluble in tetrahydrofuran (THF) and dimethyl sulfoxide (DMSO) but insoluble when isolated as powders. The concentrated polymer solution showed spinnability and film formation. Thermogravimetric analysis of3 and4 showed weight losses of 67 and 16%, respectively. Species4 may be a precursor for silicon/carbon/nitrogen ceramics.     

Phase Separation in 12 mol% Ceria-Doped Zirconia Induced by Heat Treatment in H2 and Ar

The phase separation in 12 mol% CeO₂─ZrO₂ ceramic heattreated in a mixture of H₂ and Ar was investigated by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy, and Raman scattering. After heat treatment at temperatures above 1200°C, the tetragonal solid-solution phase separated into Zr₂Ce₂O₇ and the monoclinic phase. Raman scattering measurements also provided supplementary evidence for the phase separation. XPS showed that the valence change from Ce⁴⁺ to Ce³⁺ predominantly occurred, whereas the reduction from Zr⁴⁺ to Zr³⁺ took place above 1200°C. It is concluded, that in the highly reduced sample, where the valence changes from Ce⁴⁺ (Zr⁴⁺) to Ce³⁺ (Zr³⁺), the phase separation is noticeably promoted. Below 1000°C the phase separation was suppressed because of no appreciable valence change to trigger the phase separation, and the single tetragonal phase was retained.     

Observation of recording pits on phase-change film using a scanning probe microscope

A phase-change film is a key material for optical data storage media such as rewritable compact disks (CD-RW) and digital versatile disk random access memory (DVD-RAM). Data pits are recorded as differences in crystal state (crystallized state vs. amorphous state) on phase-change film. It is very important to distinguish the crystal state difference in a very small area for material research of phase-change film. Measuring size and shape of recorded data pits is also very important for the development to achieve good data reliability and high data density of optical data storage media. The crystal state difference in very small areas of phase-change film is successfully observed by Kelvin probe force microscopy (KFM) and scanning near-field optical/atomic force microscopy (SNOAM). The advantage of KFM and SNOAM for measuring physical property differences in a very small area is demonstrated.