A compact thin-film-based all-pass device for the compensation of the in-band dispersion in FBG filters

Fiber Bragg grating (FBG)-based bandpass filters, while possessing close to ideal sharp rolloff characteristics, can suffer from a significant amount of in-band dispersion. Results concerning the compensation of the in-band dispersion of a typical 100-GHz FBG using two thin-film all-pass filters, each composed of two coupled-cavities packaged in a compact configuration, are presented. The total peak insertion loss of the compensation package is less than 2.5 dB.     

Transverse-junction-stripe GaAs-AlGaAs lasers for squeezed lightgeneration

We fabricated 850-nm GaAs transverse-junction-stripe (TJS) lasers by an improved metal-organic chemical vapor deposition (MOCVD) and double Zn diffusion process. The high V/III ratio used during the MOCVD growth significantly reduced the intermixing of GaAs active layer and AlGaAs cladding layers. The modified process realized good confinement for both carriers and photons and smaller saturable loss. We measured squeezing of -2.8 dB (-4.5 dB after correction for detection efficiency) at a pumping rate of I/I_th≈20 from these lasers, which is in close agreement with the theoretical limit. This squeezing remained unchanged under injection locking, indicating almost perfect conservation of the intensity noise correlation among the longitudinal modes. These TJS lasers had very small low-frequency 1/f noise     

A theoretical discussion on the foundation of Stone??s blind source separation

This paper discusses the theoretical foundation of Stone’s BSS (Stone in Neural Comput 13:1559–1574, 2001; Stone in Independent Component Analysis: A Tutorial Introduction, A Bradford Book, London, 2004), and it proposes a novel BSS approach based on second-order statistics of the responses of two different linear filters to source signals. The proposed approach which includes Stone’s BSS as a special case helps us to understand how generalized eigenvalue decomposition (GEVD) concludes separating vectors in Stone’s BSS. It obtains the separating vectors by simultaneous diagonalization of covariance matrices of two different linear filters responses to the mixtures. The two employed linear filters are selected dependent on source signals structures under the assumption that they have different responses to source signals. Here, two FIR filters with coefficients selected in an opposite probabilistic way have been suggested for the proposed BSS. The proposed BSS method has been compared with Stone’s BSS, SOBI and AMUSE over speech and image mixtures in different noise levels.     

Multiobjective control of a vehicle with triple trailers

We consider the backing-up control of a vehicle with triple trailers using a model-based fuzzy-control methodology. First, the vehicle model is represented by a Takagi-Sugeno fuzzy model. Then, we employ the so-called "parallel distributed compensation" design to arrive at a controller that guarantees the stability of the closed-loop system consisted of the fuzzy model and controller. The control-design problem is cast in terms of linear matrix inequalities (LMIs). In addition to stability, the control performance considerations such as decay rate, constraints on input and output, and disturbance rejection are incorporated in the LMI conditions. In application to the vehicle with triple trailers setup, we utilize these LMI conditions to explicitly avoid the saturation of the steering angle and the jackknife phenomenon in the control design. Both simulation and experimental results are presented. Our results demonstrate that the fuzzy controller effectively achieves the backing-up control of the vehicle with triple trailers while avoiding the saturation of the actuator and "jackknife" phenomenon.     

Ultrahigh Electrical Resistance of Poly(cyclohexyl methacrylate)/Carbon Nanotube Composites Prepared Using Surface‐Initiated Polymerization

Multiwalled carbon nanotubes on which poly(cyclohexyl methacrylate)s are densely grafted (PCHMA‐CNTs), are synthesized using a modified surface‐initiated atom transfer radical polymerization technique. The electrical resistance of PCHMA‐CNT is systematically characterized under direct current (DC) and alternating current and compared to that of conventional nanocomposites prepared by blending PCHMA with the CNT (PCHMA/CNT). At a comparable volume fraction of CNT, DC volume resistivity of PCHMA‐CNT is 14 orders of magnitude higher than that of PCHMA/CNT. This is because the grafted polymer with a combination of the high molecular weight and the high grafting density isolates individual CNTs at a long distance in the PCHMA‐CNT system. In addition, impedance analysis reveals that the highly insulated PCHMA‐CNT has the same electrical nature as neat PCHMA, i.e., it is a dielectric. Furthermore, dynamic mechanical analysis shows PCHMA‐CNT has a good mechanical properties as well as ultrahigh electrical resistance.     

Beam alignment and related problems of spherical aberration corrected high-resolution TEM images

For spherical aberration corrected transmission electron microscopes recently developed, the Scherzer resolution in proportion to C(s) 1/4 lambda 3/4 is still inevitably limited by the influence of some other electron optical factors, such as chromatic aberration coefficient of objective lens (C(c)), beam divergence and alignment, incident electron energy spread (deltaE), and the instability of accelerating voltage (deltaV) and of lens current (deltaI). Depending on the image resolution guaranteed by C(s) correction, the defocus spread caused by C(c), deltaV, deltaI and deltaE would need to be reduced. The effect of beam alignment as a phase shift in contrast transfer function is also studied for the C(s) corrected microscopes with different values of C(s), defocus and spatial frequency. There is a relationship between the phase shift and defocus that allows us to find a series of 'alignment-free' focal conditions. A triangular relation among C(s), defocus and lattice spacing is established for proper image contrast and 'alignment-free' imaging with the C(s) corrected microscope.     

Advanced base station technologies for UTRAN

To achieve high capacity and to support high-data-rate services in the terrestrial access network (UTRAN) of the third generation Universal Mobile Telecommunications System (UMTS), it is essential to employ some advanced transceiver techniques at the base stations. Three such techniques are presented: adaptive antennas, multistage parallel interference cancellers and a new hybrid scheme. The operation principles and some simulation results of the techniques are given and some challenging implementation issues are discussed     

Studies on Effective Utilization of SOFC Exhaust Heat Using Thermoelectric Power Generation Technology

Solid oxide fuel cells (SOFCs) are being researched around the world. In Japan, a compact SOFC system with rated alternative current (AC) power of 700 W has become available on the market, since the base load electricity demand for a standard home is said to be less than 700 W AC. To improve the generating efficiency of SOFC systems in the 700-W class, we focused on thermoelectric generation (TEG) technology, since there are a lot of temperature gradients in the system. Analysis based on simulations indicated the possibility of introducing thermoelectric generation at the air preheater, steam generator, and exhaust outlet. Among these options, incorporating a TEG heat exchanger comprising multiple CoSb₃/SiGe-based TEG modules into the air preheater had potential to produce additional output of 37.5 W and an improvement in generating efficiency from 46% to 48.5%. Furthermore, by introducing thermoelectric generation at the other two locations, an increase in maximum output of more than 50 W and generating efficiency of 50% can be anticipated.     

A high-density NAND EEPROM with block-page programming formicrocomputer applications

A high-density, 5-V-only, 4-Mb CMOS EEPROM with a NAND-structured cell using Fowler-Nordheim tunneling for programming is discussed. The block-page mode is utilized for high-speed programming and easy microprocessor interface. On-chip test circuits for shortening test time and for evaluating cell characteristics yield highly reliable EEPROMs. The NAND EEPROM has many applications for microcomputer systems that require small size and large nonvolatile storage systems with low power consumption     

Built-in folded monopole antenna for handsets

A built-in folded monopole antenna for handsets (BFMA) is introduced and investigated. The characteristics of the BFMA are compared with those of a planar inverted-F antenna (PIFA), which is one of the conventional handset antennas. As a result, it has been confirmed that the BFMA has smaller size and wider bandwidth compared with the PIFA.