Carrier-induced energy shift in GaAs/AlGaAs multiple quantum welllaser diodes

Emission energy shift due to high carrier density at threshold in multiple quantum well (MQW) laser diodes is investigated theoretically. This energy shift is evaluated through the Schrodinger and the Poisson equations self-consistently as well as the calculation of the gain spectra with carrier-dependent lifetime broadening. The band filling and the gain broadening effects show a blue shift on the emission energy. Larger number of wells, lower barrier height, or wider well thickness, reduces the blue shift dependence on the carrier density. At high injections, this blue shift is offset by the bandgap shrinkage effect, which displays smaller influence on MQW's. While the carrier density is further increased, the transition due to the second quantized state is found in single quantum wells, however it is difficult to be observed in MQW's     

Subcarrier multiplexing by chaotic multitone modulation

Subcarrier multiplexing by chaotic multitone modulation is investigated. Optical chaotic light can be achieved by injecting multiple subcarriers into a self-pulsating laser diode. Synchronization between two identical chaotic systems (drive and response) can be implemented provided that the conditional Lyapunov exponents are all negative. By adding amplitude modulation (AM) signals to each subcarrier, the two systems become asymptotically synchronized. The AM signals in each subcarrier can be recovered by the introduction of a filtering process where the Lyapunov exponent of the synchronized error function matches the cutoff frequency of a first order low pass filter.     

Characterization of Anilinepentacyanoferrate (II) and (III)

The anilinepentacyanoferrate (II) complex has been characterized in aqueous solution. The complex exhibits a predominant ligand field transition at λ_max = 415 nm with ?_max = 494 M^?1 cm^?1. The corresponding Fe(III) complex displays a strong absorption at λ_max = 700nm(?_max = 1.61×10⁴ M^?1 sec^?1) which can be assigned as a ligand to metal charge transfer transition. The rate constants of formation and dissociation for the Fc(II) complex are (3.14±0.18)×10² M^?1W^?1 and 0.985±0.005 sec^?1, respectively, at μ = 0.10 M LiClO₄, pH = 8 and T = 25°C. The cyclic voltammetry of the complex shows that a reversible redox process is observed with E_1/2 value of 0.51±0.01 V vs. NHE at μ = 0.10 M LiClO₄, pH = 8 and T = 25°C. The kinetic study of the oxidation of the Fe(II) complex by ferricyanide ion yielded the rate constant of the reaction k_et = (1.43±0.04)x10 M sec^?1 at μ = 0.10 M LiClO₄, pH = 8 and T = 25°C.     

Structural studies of Na-montmorillonite exchanged with Fe2+, Cr3+, and Ti4+ by N2 adsorption and EXAFS

The structures of Fe(2+)-, Cr(3+)-, and Ti(4+)-modified montmorillonite prepared from ion exchange of the Na-clay with Fe(2+), Cr(3+), and Ti(4+) were investigated. Conventional BET surface area and spectroscopic analysis by extended adsorption fine structure (EXAFS) were applied. It was shown that the BET surface area of Na-clay was similar to that of Fe-clay, but somewhat different from those of Cr- and Ti-clay; it decreased in the order Na- > Fe- > Ti- > Cr-montmorillonite. This sequence appeared to be consistent with the ion size Na(+) (0.95 nm)>Fe(2+) (0.65 nm)>Cr(3+) (0.62 nm), except for Ti(4+) (0.69 nm). EXAFS data showed that some Si atoms within montmorillonite were replaced by Ti atoms and that a neostructure of titanium oxide was formed.     

An Active-Inductor Injection Locked Frequency Divider With Variable Division Ratio

This letter presents a wide-locking range, body-injected, injection locked frequency divider (ILFD) with tunable active inductors (TAIs) and variable division ratio. The ILFD was fabricated in the 0.18 mum 1P6M CMOS technology, and it has the modulus of 2, 3, 4, and 5, and can be used as a first-harmonic injection-locked oscillator (ILO). The divide-by-3 function is performed by injecting differential a signal to the bodies of cross-coupled transistors in the VCO. At the supply voltage of 1.5 V, the free-running divider is tunable from 0.53 to 1.72 GHz. At the incident power of 0 dBm the operation range in the first-harmonic ILO is from the incident frequency 0.53 to 3.2 GHz. The operation range in the divide-by-3 (divide-by-2) mode is about 3.59 (4.13) GHz, from the incident frequency 1.55 to 5.14 (0.87 to 5.0) GHz.     

Optimal controller of a buck DC-DC converter using the uncertain load as stochastic noise

This work presents an optimal design approach for the pulsewidth modulation switching control of a buck DC-DC converter by modeling the converter as a stochastic linear system with noise of uncertain load. Firstly, we temporarily assume that the stochastic system is available with complete state, and then derive an optimal state feedback control for the optimal noise regulation in steady state. Secondly, from the steady-state viewpoint, the optimal state feedback control is transferred into an equivalent error-driven servo controller, and then the designed optimal control law is implemented using a phase lead-lag controller. A distinctive advantage of this approach is that the optimal controller's parameters are actually independent of the statistics of the assumed uncertain load noise, so the benefit of optimal noise regulation is assured for global operation. Furthermore, the optimal controller is easily implemented. As a matter of fact, by just using the simplest possible operation amplifier circuits, the controller can be implemented.     

Genetic recurrent fuzzy system by coevolutionary computation with divide-and-conquer technique

A genetic recurrent fuzzy system which automates the design of recurrent fuzzy networks by a coevolutionary genetic algorithm with divide-and-conquer technique (CGA-DC) is proposed in this paper. To solve temporal problems, the recurrent fuzzy network constructed from a series of recurrent fuzzy if-then rules is adopted. In the CGA-DC, based on the structure of a recurrent fuzzy network, the design problem is divided into the design of individual subrules, including spatial and temporal, and that of the whole network. Then, three populations are created, among which two are created for spatial and temporal subrules searches, and the other for the whole network search. Evolution of the three populations are performed independently and concurrently to achieve a good design performance. To demonstrate the performance of CGA-DC, temporal problems on dynamic plant control and chaotic system processing are simulated. In this way, the efficacy and efficiency of CGA-DC can be evaluated as compared with other genetic-algorithm-based design approaches.     

A 250 MHz 14 dB-NF 73 dB-Gain 82 dB-DR Analog Baseband Chain With Digital-Assisted DC-Offset Calibration for Ultra-Wideband

A 250 MHz analog baseband chain for Ultra-Wideband was implemented in a 1.2 V 0.13 $mu$ m CMOS process. The chip has an active area of 0.8 mm $^{2}$. In the analog baseband, PGAs and filters are carried out by current-mode amplifiers to achieve wide bandwidth and wide dynamic range of gain, as well as low noise and high linearity. Besides, a current-mode Sallen–Key low-pass filter is adopted for effective rejection of out-of-band interferers. A 6th-order Chebyshev low-pass filter realized in ${rm G}_{rm m}$ -C topology is designed in the baseband chain for channel selection. Digitally-assisted DC-offset calibration improves second-order distortion of the entire chain. The design achieves a maximum gain of 73 dB and a dynamic range of 82 dB. Measured noise figure is 14 dB, an IIP3 of ${-}$6 dBV, and IIP2 of ${-}$5 dBV at the maximum gain mode. The analog baseband chain consumes 56.4 mA under supply of 1.2 V.      

Power Generation Capabilities of Microbial Fuel Cells with Different Oxygen Supplies in the Cathodic Chamber

Two microbial fuel cells (MFCs) inoculated with activated sludge of a wastewater treatment plant were constructed. Oxygen was provided by mechanical aeration in the cathodic chamber of one MFC, whereas it was obtained by the photosynthesis of algae in the other. Electrogenic capabilities of both MFCs were compared under the same operational conditions. Results showed that the MFC with mechanical aeration in the cathodic chamber displayed higher power output than the one with photosynthesis of algae. Good linear relationship between power density and chemical oxygen demand (COD) loading rate was obtained only on the MFC with mechanical aeration. Furthermore, the relationships between power density and effluent COD and between Coulombic efficiency and COD loading rate can only be expressed as binary quadratic equations for the MFC with mechanical aeration and not for the one with photosynthesis of algae.