Generation of pedestal-free 22-fs ultrashort pulse using highly nonlinear fiber and reverse-dispersion fiber

We present an all-fiber system for generating pedestal-free 22-fs ultrashort pulses with a single-peak spectrum. High-power Raman soliton pulses and a normally dispersive highly nonlinear fiber are used to generate a smooth, broadened single-peak spectrum. Then, the higher order dispersion is compensated for using a hybrid fiber composed of a reverse-dispersion fiber and a standard single-mode fiber, which allows pedestal-free ultrashort pulses to be successfully generated. To our knowledge, this is the first demonstration of pedestal-free 20-fs-class ultrashort pulse generation without spectral distortion using an all-fiber configuration.     

A 1 ns, 1 W, 2.5 V, 32 Kb NTL-CMOS SRAM macro using a memory cellwith PMOS access transistors

While an ECL-CMOS SRAM can achieve both ultra high speed and high density, it consumes a lot of power and cannot be applied to low power supply voltage applications. This paper describes an NTL (Non Threshold Logic)-CMOS SRAM macro that consists of a PMOS access transistor CMOS memory cell, an NTL decoder with an on-chip voltage generator, and an automatic bit line signal voltage swing controller. A 32 Kb SRAM macro, which achieves a 1 ns access time at 2.5 V power supply and consumes a mere 1 W, has been developed on a 0.4 μm BiCMOS technology     

A digital coherent receiver suitable for land-mobile satellitecommunications

Describes an advanced coherent demodulation technique suitable for land-mobile satellite communications. The proposed technique features a combined narrow/wide band dual open loop (DOL) carrier phase estimator, which effectively enables the coherent receiver to track fast phase fluctuations caused by fading, without degradation in phase slip characteristics. Additionally, an open loop phase estimator has inherent quick recovery performance. Its bit error rate (BER) performance is shown to be superior to that for existing detection schemes, achieving a 10^-2 BER at 6.3 dB E_b/N₀ (0.9 dB greater than the theoretical E_b/N₀ condition for perfect carrier phase tracking) for QPSK over a Rician fading channel with the 10 dB Rician factor and the 1/16 baud rate fading pitch. The paper also describes a quick bit timing recovery scheme, with interpolation, featuring an open loop structure. Further, it presents an experimental digital modem developed through the use of digital signal processors     

Evaluation of Stress and Crystal Quality in Si During Shallow Trench Isolation by UV-Raman Spectroscopy

Defects and stress gradually accumulate throughout various Si large-scale integration fabrication processes. It is essential to monitor defects and stress carefully to suppress their unintentional introduction. In this study, we measured the stress and crystal quality in shallow trench isolation (STI) samples by ultraviolet (UV)-Raman spectroscopy with an extremely high-resolution wavenumber to evaluate the effect of post-annealing on the recovery of Si crystals. The variations of crystal quality in 200-mm wafers with STI structures gradually decreased after post-annealing for 4 h, 6 h, and 8 h; however, there was no substantial difference in the values of full-width at half-maximum of the Raman spectra. Precise measurements of variations of stress and crystal quality were successfully performed by UV-Raman spectroscopy with a high-resolution wavenumber, which enabled us to evaluate the STI process accurately.     

Optical frequency domain ranging by a frequency-shifted feedbacklaser

This paper describes the theoretical and experimental study of a new technique for optical frequency domain ranging (OFDR) by a frequency-shifted feedback (FSF) laser. In conventional OFDR, a frequency chirped single-mode laser is used as a light source to convert a distance into a beat frequency, and a tradeoff exists between measurement range and resolution. The FSF laser output consists of periodically generated chirped frequency components whose chirp rate is faster than 100 PHz/s (P=10¹⁵), By use of the FSF laser, the tradeoff is removed and long-distance high-resolution OFDR is realized In the experiment, a distance of 18.5 km was measured with a resolution of 20 mm     

Understanding the Structural Evolution and Redox Mechanism of a NaFeO2–NaCoO2 Solid Solution for Sodium‐Ion Batteries

Na‐ion batteries have become promising candidates for large‐scale energy‐storage systems because of the abundant Na resources and they have attracted considerable academic interest because of their unique behavior, such as their electrochemical activity for the Fe³⁺/Fe⁴⁺ redox couple. The high‐rate performance derived from the low Lewis‐acidity of the Na⁺ ions is another advantage of Na‐ion batteries and has been demonstrated in NaFe_1/2Co_1/2O₂ solutions. Here, a solid solution of NaFeO₂‐NaCoO₂ is synthesized and the mechanisms behind their excellent electrochemical performance are studied in comparison to those of their respective end‐members. The combined analysis of operando X‐ray diffraction, ex situ X‐ray absorption spectroscopy, and density functional theory (DFT) calculations for Na_{1– x} Fe_1/2Co_1/2O₂ reveals that the O3‐type phase transforms into a P3‐type phase coupled with Na⁺/vacancy ordering, which has not been observed in O3‐type NaFeO₂. The substitution of Co for Fe stabilizes the P3‐type phase formed by sodium extraction and could suppress the irreversible structural change that is usually observed in O3‐type NaFeO₂, resulting in a better cycle retention and higher rate performance. Although no ordering of the transition metal ions is seen in the neutron diffraction experiments, as supported by Monte‐Carlo simulations, the formation of a superlattice originating from the Na⁺/vacancy ordering is found by synchrotron X‐ray diffraction for Na_0.5Fe_1/2Co_1/2O₂, which may involve a potential step in the charge/discharge profiles.     

A 320 MFLOPS CMOS floating-point processing unit for superscalarprocessors

A CMOS pipelined floating-point processing unit (FPU) for superscalar processors is described. It is fabricated using a 0.5 μm CMOS triple-metal-layer technology on a 61 mm² die. The FPU has two execution modes to meet precise scientific computations and real-time applications. It can start two FPU operations in each cycle, and this achieves a peak performance of 160 MFLOPS double or single precision with an 80 MHz clock. Furthermore, the original computation mode, twin single-precision computation, double the peak performance and delivers 320 MFLOPS single precision. Its full bypass reduces the latency of operations, including load and store, and achieves an effective throughput even in nonvectorizable computations. An out-of-order completion is provided by using a new exception prediction method and a pipeline stall technique     

An unsteady flow structure on a heated rotating disk under mixed convection

A flow field under mixed convection on a heated rotating disk has been measured using an ultrasonic velocity profiler (UVP). The measured velocity field is a spatio‐temporal one as a function of radial coordinates and time. The objective of this paper is to clarify the vortex structure caused by the instability between buoyancy and centrifugal force. The vortex appears under typical conditions of Reynolds numbers and Grashof numbers and it moves toward the outside of the disk. This behavior can be classified into two patterns. The size of the vortex structure decreases with an increasing Reynolds number and increases with the Grashof number. The traveling velocity of the vortex increases with the Grashof number. Moreover, it decreases with an increasing Reynolds number in spite of increasing centrifugal force. According to these results, the region dominated by natural, forced, and mixed convection is classified in the relationship between Reynolds and Grashof numbers. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(6): 407–418, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20074     

Liver phosphatidylcholine hydroperoxidation provoked by ethionine-containing choline-deficient diet in mice

It is shown that peroxidation of phosphatidylcholine (PC) is enhanced in liver of mice fed a hepatocarcinogenic choline-deficient diet containing 0.1% w/w ethionine. Mice were divided into 4 groups and fed for 3 weeks one of the following diets: choline-supplemented; choline-supplemented containing ethionine; choline-deficient; and choline-deficient containing ethionine. Phosphatidylcholine hydroperoxide (PCOOH) of liver lipids was measured by high performance liquid chromatography using a chemiluminescence detector. Mice fed a choline-deficient diet containing ethionine showed 6-fold higher PCOOH levels than the choline-supplemented control mice: the PCOOH/PC molar ratios of liver lipids were 32.3×10⁻⁵ and 5.6×10⁻⁵, respectively. In addition to this remarkable degree of lipid peroxidation in liver of mice fed the choline-deficient diet containing ethionine, we also observed a significant liver fatty infiltration, a decrease in plasma and liver α-tocopherol, and an increase in liver injury-indicative enzyme activities. Also, marker enzymes for hepatocarcinogenesis, glucose-6-phosphatase and γ-glutamyl transpeptidase were affected. These data suggest that enhanced hydroperoxidation of phosphatidylcholine may participate in hepatocarcinogenesis provoked by choline deficiency in the presence of ethionine.