Continuous-time delta-sigma modulator using vector filter in feedback path to reduce effect of clock jitter and excess loop delay

In this paper, we propose a novel delta-sigma modulator (DSM) that reduces the effects of clock jitter and excess loop delay by using a vector filter in the feedback path. The vector filter divides the input signal into a high-frequency part and a low-frequency part. The low-pass signal is placed in the path to the first-stage digital-to-analog converter for reducing the effects of the clock jitter, and the high-pass signal is placed in the feedback path to the last integrator in order to compensate for the excess loop delay. The DSM using the vector filter in the feedback path (DSM-VF) is verified using MATLAB/Simulink. Further, a clock jitter (0.1 %) in DSM-VF leads to an improvement in the signal-to-noise-ratio (SNR) to 22.5 dB as compared to the SNR of a conventional CTDSM. Moreover, the SNR deterioration caused by the excess loop delay is improved.     

One-compartment electrochemical H2 generator from borohydride

A one-compartment membrane-less electrochemical H₂ generator from borohydride was realized using a Rh porphyrin and RuO₂ as the anode and cathode, respectively. H₂ generation from this cell was successfully controlled electrochemically by varying the potential applied. The regulation of H₂ generation was based on the selectivity of the anode and cathode. We found that RuO₂ exhibits H₂O electro-reduction activity without electro-oxidation or chemical decomposition of borohydride, and used the catalyst as a selective cathode in the electrochemical H₂ generator. Anode and cathode potentials of the electrochemical H₂ generator were measured separately. The both potentials were discussed in terms of the catalytic activities of a Rh porphyrin and RuO₂.     

3D visualization of an ancient Egyptian mummy

The visualization of the 3D shape of an ancient Egyptian mummy from CT images, and the analysis of the internal bony structure using a surgical simulation system are discussed. The applications of 3D image analysis to mummies by various research groups are outlined. The advantages of 3D image analysis of mummies are summarized     

Environmental marginal cost evaluation by non-inferiority surface[power systems]

A decision-making methodology is discussed for determining the optimal generation dispatch and environmental marginal cost for power system operation with multiple conflicting objectives. In this study, the generation dispatch problems are formulated as a multiple objective optimization problem with two noncommensurable objectives (economy and environmental impacts). Each objective is optimized by Powell's method in the light of the individual performance index. Goal programming, a powerful tool for multiple criteria decision-making, is quantitatively performed to identify trade-off relations among these conflicting objectives. After a trade-off relation has been determined, sensitivity analysis is applied to evaluate the environmental marginal cost which indicates the increased portion of the monetary cost of system operation while the impact on the environment is improved. Numerical examples on a sample power system consisting of 10 buses, 11 transmission lines and five generators are provided to demonstrate the capabilities of the proposed approach     

InP/InGaAs buried-structure avalanche photodiodes

Planar InP/InGaAs avalanche photodiodes with a new guardring structure have been designed and fabricated. The diodes had a buried n-InP layer and an n?-InP multiplication region under p-n junctions. A successful guardring effect was obtained. The diode exhibited a uniform multiplication over the active region, a maximum multiplication factor of 30, low dark currents of around 20 nA at 90% of breakdown voltage and a flat frequency response up to 1 GHz. Multiplication noise was measured up to a multiplication factor of 17.     

An approach for transmission expansion planning using neurocomputing hybridized with a genetic algorithm

The aim of transmission expansion planning is to determine which right-of-way to use when constructing new lines in order to meet a forecasted load in the most economical way. This problem has been solved previously by mathematical sensitivity analysis (which finds a single nonoptimal solution). It is difficult to plan for economical and reliable expansion due to its discrete and combinatorial nature. Although another method that has efficiency for combinatorial problems is neurocomputing, this approach saves computational efforts but obtains poor solutions. The most desirable approach for this planning problem is one in which many good solutions are found in reasonable time, because planning experts will then be able to plan economical and reliable expansion according to these solutions. This paper presents an approach for solving transmission expansion planning based on neurocomputing hybridized with a genetic algorithm. This approach generates suitable initial states, which include past information, of neural networks utilizing genetic algorithm. Mingling neurocomputing and a genetic algorithm, the proposed approach can find many good solutions in reasonable time making full use of their merits. Computational examples show the effectiveness of the proposed approach by comparison with conventional approaches.     

Preparation and thermal decomposition of hexa-ammonium tetraphosphate dihydrate(NH4)6P4O13·2H2O

Hexa-ammonium tetraphosphate dihydrate, (NH4)6P4O13·2H2O (HATP), was prepared by the hydrolysis of sodium cyclo-tetraphosphate with sodium hydroxide solution, followed by ion-exchange with ammonium. Thermal decomposition in static air was first carried out dynamically, at a heating rate of 5 K min-1 as used in thermal analysis (thermogravimetric-differential thermal analysis), and also isothermally. To examine the effect of humidity on the thermal decomposition, HATP was heated isothermally in streams of dry and humid air. The products were characterized by X-ray diffraction analysis and high-performance liquid chromatography–flow injection analysis. At 100°C, HATP was decomposed to mono- and triphosphates and to 2 mol diphosphate, and this was accelerated by humidity. Further degradation of the triphosphate to mono- and diphosphates took place slowly. The 2 mol diphosphate also decomposed slowly to 4 mol monophosphate. At temperatures above 150°C, the form I of ammonium polyphosphate (I-APP) was produced. I-APP was further hydrolysed by humidity to shorter-chain phosphates, such as mono-, di- and triphosphates. This revised version was published online in November 2006 with corrections to the Cover Date.