A current operational amplifier (COA) with very high current drive capability is presented in this paper. The principle of
operation of this unique structure is discussed, its most important formulas are derived and its outstanding performance is
verified by HSPICE simulation in TSMC 0.18 μm CMOS, BSIM3, and Level49 technology. Owing to the elaborately arranged components,
the proposed circuit demonstrates very high frequency bandwidth, extremely high CMRR, high output impedance, and true rail
to rail output voltage swing range while operating at very low power supply of ±0.5 V. The interesting results such as current
drive capability of ±1 mA, high output impedance of 5 GΩ, wide gain bandwidth of 220 MHz, extremely high output voltage swing
of ±0.45 V, which interestingly provides the highest yet reported output voltage compliance for current mode building blocks
implemented by regular CMOS technology, low static power consumption of 159 μW, and very high CMRR of 155 dB is achieved utilizing
standard CMOS technology. Full process, voltage, and temperature variation analysis of the circuit is also investigated in
order to approve the well robustness of the structure. The transient stepwise and sinusoidal response analysis is also done
to verify the proposed COA stability. 相似文献
Multi-walled carbon nanotubes (MWCNTs) were grown by chemical vapor deposition. The effect of the composition of carbon paste
electrode on its voltammograms was evaluated in basic solution with 5.0×10−5 M tryptophan (Trp). It was found that addition of MWCNTs to the carbon paste would generate the peak current of Trp because
of its catalytic effect on the redox process. The pH strongly affects the peak potential of Trp. The best analytical response
was obtained at pH 13.0. The anodic peak currents were proportional to Trp concentrations in the range of 1.0×10−9−1.0×10−4 M under the optimized experimental conditions. The detection limit was 2.2×10−10 M. The effect of potential scan rate on the peak potential and peak current of tryptophan was investigated. The correlation
of the peak currents against v1/2 (v is the scan rate) is linear, which is very similar to a diffusion-controlled process. The proposed biosensor was applied
to the determination of Trp in pharmaceuticals formulations successfully. 相似文献
ABSTRACT Artificial drying is an important step in processing of green crops in order to preserve their freshness and nutrients for longer time at relatively lower costs. Forage crops, tea and tobacco are the major green crops where the commercial drying is a major operation in their processing. Fresh green alfalfa at about 75 to 80% moisture is subjected to drying in different types of dryers.ln the case of alfalfa, the raw material consists of leaves, stems, chops and fine stems, each varying distinctly in their physical and structural characteristics. The moisture content is reduced from initial level to about 10%. The drying air temperatures range from 40 b 800°C; the lower temperatures are used inconveyor dryers whereas high temperatures are used in rotary drum drycn.The results on drying behavior, and changes in physico-chemical propedes during drying for components of green alfalfa over the temperature range of 40 m 800°C are presented in this paper. The optimum temperature for drying from the stand point of color and protein solubility was found to be 175°C. 相似文献
The voltage controlled oscillator-based (VCO-based) continuous-time delta-sigma (CTDS) analog to digital converter (ADC) suffers from nonlinearity and mismatch in its feedback network. A new feedback network consisting of a phase shifter is proposed. The phase shifter replaces the digital to analog converter (DAC) in the proposed architecture. Feasibility of the proposed idea is discussed and its higher performance is illustrated through a behavioral simulation approach (CppSim). We have also developed the phase shifter as a variable all-pass filter in the C language. The nonlinearity and mismatch of the system caused by DAC is mitigated, resulting in higher signal to noise ratio (SNR) and signal to noise and distortion ratio (SNDR), respectively. 相似文献
In this paper the results of testing a solar liquid desiccant air conditioner (LDAC) in the tropical climate of Queensland, Australia have been presented. The system uses polymer plate heat exchanger (PPHE) for dehumidification/indirect evaporative cooling, and a cooling pad as the direct evaporative cooler for the dry air leaving the PPHE. Lithium chloride, which is an effective desiccant in air dehumidification, was used in the experiments and a scavenger air regenerator concentrates the dilute solution from the dehumidifier using hot water from flat plate solar collectors. The data obtained from performance monitoring of the solar LDAC operating on a commercial site in Brisbane was compared with a previously developed model for the PPHE. The comparison reveals that good agreement exists between the experiments and model predictions. The inaccuracies are well within the measuring errors of the temperature, humidity and the air and solution flow rates. The above tests further indicate a satisfactory performance of the unit by independently controlling the air temperature and humidity inside the conditioned space.
In order to prevent carryover of the solution particles into the environment, eliminators are used at outlet of the absorber unit and the regenerator. An alternative method in preventing the carryover is the use of indirect cooling, in which the supply air does not contact the solution. The method can be used to produce potable water from the atmospheric air in remote areas.
The liquid desiccant system can be used in the HVAC industry, either as a packaged roof-top air conditioner, or as an air handler unit for commercial applications. The system could also be used for space heating in winter due to the property of desiccants to provide heat when wetted. 相似文献
Two failure criteria are proposed in this paper for brittle fracture in rounded-tip V-shaped notches under pure mode I loading. One of these criteria is developed based on the mean stress criterion and the other based on the point stress criterion which both are well known failure criteria for investigating brittle fracture in elements containing a sharp crack or a sharp V-notch. To verify the validity of the proposed criteria, first the experimental data reported by other authors from three-point bend (TPB) and four-point bend (FPB) tests on PMMA at −60 °C and Alumina–7% Zirconia ceramic are used. Additionally, some new fracture tests are also carried out on the rounded-tip V-notched semi-circular bend (RV-SCB) specimens made of PMMA for various notch opening angles and different notch tip radii. A very good agreement is shown to exist between the results of the mean stress criterion and the experimental data. 相似文献
The purpose of this paper is to revisit the maximum tensile stress (MTS) criterion to predict brittle fracture for mixed mode conditions. Earlier experimental results for brittle fracture of polymethylmethacrylate (PMMA) using angled cracked plates are also re-examined. The role of the T -stress in brittle fracture for linear elastic materials is emphasized. The generalized MTS criterion is described in terms of mode I and II stress intensity factors, K I and K II and the T- stress (the stress parallel to the crack), and a fracture process zone, r c . The generalized MTS criterion is then compared with the earlier experimental results for PMMA subjected to mixed mode conditions. It is shown that brittle fracture can be controlled by a combination of singular stresses (characterized by K ) or non-singular stress ( T -stress). The T -stress is also shown to have an influence on brittle fracture when the singular stress field is a result of mode II loading. 相似文献
A technical and economical study of regenerative absorption chillers with multi-pressure cycle has been undertaken as solar operated refrigeration systems. Referred to as advanced absorption chillers they represent one of the new technology options that are under development. Advanced absorption cooling technology offers the possibility of chillers with thermal COPs of 1.5 or greater at driving temperatures of 140°C, which reduces the collector area and the heat rejection requirements compared to current absorption cooling technology. Two different absorption systems have been considered. The first is an advanced, double-effect regenerative absorption cooling system, driven at 140°C, whose efficiency is about 55% of the Carnot efficiency. The second is an ideal, single-effect regenerative absorption system that achieves 70% of the Carnot efficiency driven at 140°C or 200°C. To evaluate the solar performance of a thermally driven chiller requires a separate analysis of the solar availability for a given location compared to the required monthly average solar input. In this analysis different systems, including the vapour compression chillers, have been compared in terms of the thermal and electrical energy input. An effective electrical COP may be computed assuming that the ratio of electrical energy cost to thermal energy cost is four, which is typical of today’s fossil fuel costs. The effective electrical COPs of different technical options can then be compared. Those systems with higher electrical COPs will have lower energy costs. If solar is to be competitive, then the cost of delivered solar thermal energy should be less than the cost of delivered fossil thermal energy. 相似文献