A study of a low-voltage,low-power,current-mode Σ Δ modulator circuit

The possibility of realizing a low-voltage and low-power audio-band Σ Δ modulator has been studied. The current-mode circuit technique has been adopted to enable the modulator to operate at less than 3 V supply voltage. The modulator to uses analog integrators instead of switched-capacitor-type integrators to avoid the use of analog switches, which allows low-voltage operation of the modulator circuit. A newly designed voltage-to-current converter is used to form an analog integrator. The designed circuit was actually fabricated by using a CMOS 0.6 μm process and its characteristics were evaluated. A signal-to-noise ratio of 68 dB in a 20 kHz bandwidth for the first-order modulator construction was measured from the 2.5 V supply voltage at an oversampling ratio of 256. However, only 72 dB of the signal-to-noise ratio and 65 dB of distortion were measured for the second-order modulator construction, although operation of the oversampling ratio of 48 was successfully confirmed. We concluded that low-voltage and low-power operation with less than 3 V of supply voltage is possible for the audio-band Σ Δ modulator, although signal-to-noise ratio and distortion issues in the 2nd-order configuration are left for future study. © 1998 Scripta Technica, Electr Eng Jpn, 124(1): 24–32, 1998     

Terrestrial applications of amorphous silicon solar cells

Eighteen years have passed since the first industrial use of amorphous silicon (a-Si) solar cells for consumer products. At present, a-Si solar cells are entering a new age of use in power generating systems at private residences and other outdoor applications. This paper reviews recent advances in a-Si solar cells and their applications. Technological developments in the field of a-Si solar cells are discussed. Various applications and systems that take advantage of the a-Si solar cell are then introduced. Finally, future prospects are discussed, including a new concept called the GENESIS system for worldwide energy generation and transmission. © 1998 John Wiley & Sons, Ltd.     

Physicochemical interaction mechanism between nanoparticles and tetrasaccharides (stachyose) during freeze-drying

Nanoparticle suspensions are thermodynamically unstable and subject to aggregation. Freeze-drying on addition of saccharides is a useful method for preventing aggregation. In the present study, tetrasaccharides (stachyose) was employed as an additive. In addition, we hypothesize the interactive mechanism between stachyose and the nanoparticles during freeze-drying for the first time. The mean particle size of the rehydrated freeze-dried stachyose-containing nanoparticles (104.7?nm) was similar to the initial particle size before freeze-drying (76.8?nm), indicating that the particle size had been maintained. The mean particle size of the rehydrated normal-dried stachyose-containing nanoparticles was 222.2?nm. The powder X-ray diffraction of the freeze-dried stachyose-containing nanoparticles revealed a halo pattern. The powder X-ray diffraction of the normally dried stachyose-containing nanoparticles produced mainly a halo pattern and a partial peak. These results suggest an interaction between the nanoparticles and stachyose, and that this relationship depends on whether the mixture is freeze-dried or dried normally. In the case of normal drying, although most molecules cannot move rapidly thereby settling irregularly, some stachyose molecules can arrange regularly leading to some degree of crystallization and potentially some aggregation. In contrast, during freeze-drying, the moisture sublimed, while the stachyose molecules and nanoparticles were immobilized in the ice. After sublimation, stachyose remained in the space occupied by water and played the role of a buffer material, thus preventing aggregation.     

Rapid Determination of Iodine Value and Saponification Value of Fish Oils by Near-Infrared Spectroscopy

ABSTRACT: A rapid method for determining the iodine value (IV) and saponification value (SV) offish oils has been developed using near-infrared (NIR) spectroscopy. The partial least squares (PLS) calibration model was made based on a spectral range between 7560 and 9100 cm⁻¹ due to CH bond. The method was validated by comparing the IV and SV of a series of fish oils predicted by the PLS model to the values obtained by the titration methods of the Japan Oil Chemists' Society. The NIR-predicted IV and SV were completely consistent with chemically determined IV and SV. The NIR method showed higher accuracy and reproducibility than the titration method. It would be suitable for IV and SV determinations offish oils, as well as vegetable oils, and it takes only 2 min per sample.     

Anti-obesity role of adzuki bean extract containing polyphenols: in vivo and in vitro effects

BACKGROUND: The aim of this work was to evaluate the effects of polyphenol‐rich adzuki bean extract on lipid metabolism, triglyceride accumulation and proinflammatory cytokine secretion in vivo and in vitro. RESULTS: For the in vivo study, rats were divided into four groups: group C was fed a control diet, group A was fed the control diet with 1% adzuki bean extract, group CF was fed a high fat diet, and group AF was fed a high fat diet with 1% adzuki bean extract. For the in vitro study, the ability of adzuki bean extract to suppress triglyceride incorporation, glycerol phosphate dehydrogenase activity and inflammatory response was investigated in cultured human adipocytes. Data from the animal study showed that adzuki bean extract improved lipid metabolism in both the normal and high‐fat diet groups. Adzuki bean extract treatment in the high‐fat group resulted in significant reductions in total hepatic lipid accumulation and lipid secretion into the feces. Incubation of adipocytes with adzuki bean extract significantly decreased triglyceride accumulation, glycerol phosphate dehydrogenase activity and inflammatory responses without affecting cell viability. CONCLUSION: The results of this study demonstrate that adzuki bean extract has high potential to serve as a natural anti‐obesity agent. Copyright © 2012 Society of Chemical Industry     

Natural convection heat transfer of water in a horizontal circular gap

An experimental study on the natural convection heat transfer on a horizontal downward facing heated surface in a water gap was carried out under atmospheric pressure conditions. A total of 700 experimental data points were correlated using Rayleigh versus Nusselt number in various forms, based on different independent variables. The effects of different characteristic lengths and film temperatures were discussed. The results show that the buoyancy force acts as a resistance force for natural convection heat transfer on a downward facing horizontal heated surface in a confined space. For the estimation of the natural convection heat transfer under the present conditions, empirical correlations in which Nusselt number is expressed as a function of the Rayleigh number, or both Rayleigh and Prandtl numbers, may be used. When it is accurately predicted, the Nusselt number is expressed as a function of the Rayleigh and Prandtl numbers, as well as the gap width-to-heated surface diameter ratio; and uses the temperature difference between the heated surface and the ambient fluid in the definition of Rayleigh number. The characteristic length is the gap size and the film temperature is the average fluid temperature.