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121.
Norbert Herencsár Jaroslav Koton Kamil Vrba Ivo Lattenberg 《International Journal of Electronics》2013,100(4):365-379
In this article, a new voltage-mode second-order universal frequency filter and sinusoidal oscillator using only single differential-input buffered and transconductance amplifier (DBTA) is presented. The proposed voltage-mode filter structure using single DBTA and four passive elements can provide all standard filter functions, i.e. low-, band-, high-pass, band-stop, and all-pass without changing the circuit topology and enables independent control of the quality factor Q using single passive element. The circuit requires the minimal number of active and passive elements with no conditions for component matching. By slight modification of the proposed filter structure, the new DBTA-based sinusoidal oscillator is easily obtained. The oscillation condition and the oscillation frequency are independently adjustable by different virtually grounded passive elements. The proposed sinusoidal oscillator employs only grounded capacitors. The passive and active sensitivities of all the proposed circuit configurations are low. PSPICE simulations using a BJT realisation of DBTA and experimental results based on commercially available amplifiers OPA860 and MAX436 are included, which prove the workability of the proposed circuits. 相似文献
122.
Norbert Herencsar Abhirup Lahiri Kamil Vrba Jaroslav Koton 《International Journal of Electronics》2013,100(5):609-621
This article presents a new realisation of active RC sinusoidal oscillator with electronically tunable condition and frequency of oscillation (FO). As compared to the class of three resistors, two capacitors (3R-2C)-based canonic oscillators, the circuit proposed here uses only two resistors and two capacitors as the passive components and still provides non-interactive tuning laws for the condition of oscillation and the FO. The proposed circuit employs new bipolar programmable current amplifier as the active building block and is capable of simultaneously providing two explicit quadrature current outputs. SPICE simulation results have been included to verify the workability of the circuit as an oscillator and the tuning range of the FO. 相似文献
123.
Norbert Herencsar Shahram Minaei Jaroslav Koton Erkan Yuce Kamil Vrba 《Analog Integrated Circuits and Signal Processing》2013,74(1):141-154
In this paper, a new active element called voltage differencing inverting buffered amplifier (VDIBA) is presented. Using single VDIBA and a capacitor, a new resistorless voltage-mode (VM) first-order all-pass filter (APF) is proposed, which provides both inverting and non-inverting outputs at the same configuration simultaneously. The pole frequency of the filter can be electronically controlled by means of bias current of the internal transconductance. No component-matching conditions are required and it has low sensitivity. In addition, the parasitic and loading effects are also investigated. By connecting two newly introduced APFs in open loop a novel second-order APF is proposed. As another application, the proposed VM APF is connected in cascade to a lossy integrator in a closed loop to design a four-phase quadrature oscillator. The theoretical results are verified by SPICE simulations using TSMC 0.18 μm level-7 CMOS process parameters with ±0.9 V supply voltages. Moreover, the behavior of the proposed VM APF was also experimentally measured using commercially available integrated circuit OPA860 by Texas Instruments. 相似文献
124.
The methods of human reliability analysis (HRA) form an integral part of probabilistic safety assessment. These methods are currently still under development and there is significant lack of data needed for applications. As a consequence, no unique formal approach for solution of many aspects related to plant staff human performance does exist.In this contribution, some examples of fruitful work are given, which reflect the needs and possibilities specific for HRA field. In the first two examples, methodology, course and results of analysis of concrete matters related to pre-accident errors and shutdown control room crew performance are described. The last example is oriented to one potential human performance related data source-observation of control room crew full-scope simulator exercise. Some conclusions of general validity are presented in the final part of the contribution. 相似文献
125.
Jaroslav Pavlik Petr Spatenka Zdenek Stryhal Vera Hrachova Adolf Kanka Jiri Cap Josef Zicha 《Materials and Manufacturing Processes》2001,16(6):863-874
This paper describes the application of chromatic monitoring of both laboratory and industrial plasmas. The light emitted from the nitrogen plasma generated in the different plasma sources was measured with an imaging spectrograph. The emission spectra were reduced to data points representing the chromatic coordinates of these spectra. The data compression makes this method attractive for monitoring plasma parameter changes. The aim of this work was to test the possibility of application of chromatic monitoring for plasma processing. 相似文献
126.
Cut-off points between protons in a-methyl and or-methylene groups were proposed for the evaluation of 'H NMR spectra of coal tars. The position of the cut-off points depended on the proton aromaticity and related structural features of the samples. Equations for the calculation of the cut-off points as a function of proton and carbon aromaticity, and atomic H/C ratio were proposed for the range of proton aromaticity between 0.2 and 0.6. 相似文献
127.
Four bituminous coals were comprehensively separated by column chromatography into a number of fractions. Four aromatic hydrocarbon fractions of each tar were analyzed by FTIR spectroscopy, and the 900-700 cm-1 spectral region was evaluated. This spectral region was found to be composed of at least 14 separate bands, which were resolved by using self-deconvolution and curve-fitting procedures. The bands near 821 cm-1, 791 cm-1, and 784 cm-1 were proposed to originate from rocking vibrations of aliphatic C-H bonds. For the tar samples with a proton aromaticity between 0.21 and 0.37, these bands account for on average 12% of the total integral intensity of the 900-700 cm-1 region. This percentage cannot likely be neglected in a correct quantitative evaluation of the region and calculation of the aromatic hydrogen concentration. However, a correct resolution of the bands can be very difficult in the FTIR spectra of a complex material, such as coal. 相似文献
128.
Jií Podeva Jaroslav Stejskal Ondej ProchÎzka Pavel pa
ek Sabine Enders 《应用聚合物科学杂志》1993,48(7):1127-1135
It has been shown that, under specific conditions, a demixing-solvent fractionation according to chemical composition can be applied to statistical copolymers. Formally, identical expressions have been derived for the distribution of a copolymer between coexisting phases in precipitation (sol-gel) and demixing-solvent fractionations. Theory predicts that the effects of molar mass and chemical composition cannot be separated in either of the phaseequilibrium fractionations. With demixing solvents, the partition coefficient depends steeply on copolymer composition, which enables one, e.g., to separate homopolymers from a blend. Multistep demixing-solvent fractionation of a copolymer may proceed only in specific cases, e.g., immediately below the maximum of the coexistence curve. A feasibility study was performed with a chemically heterogeneous statistical copolymer of styrene and 2-methoxyethyl methacrylate; the experimental results have confirmed the theoretical predictions. © 1993 John Wiley & Sons, Inc. 相似文献
129.
The accuracy of mathematical modelling is strongly influenced by the boundary conditions assumed. A shape rolling mill was instrumented to provide on-line temperature measurements during hot rolling of steels. An inverse heat conduction technique was used to convert the measurement data to surface heat fluxes and heat transfer coefficients. The heat transfer coefficient or heat flux could then be used as the necessary boundary condition for the computation of temperature field in the entire roll and workpiece by means of conventional heat transfer analysis. The heat transfer phenomena involved and the influence of the major operating parameters on the heat transfer results have also been discussed. Finally, the paper has shown that the numerical evaluation procedure adopted has at least the same influence on the results as the accuracy of temperature sensors and the properness of experiment design. 相似文献
130.
The preparation of single-phase toluene/sodium bis(2-ethylhexyl)sulfosuccinate(AOT)/water/acrylamide/sodium dodecyl sulfate(SDS) inverse microemulsions is described and their properties prior to polymerization (macroviscosity as a function of volume fraction Φaw of the dispersed aqueous (water + acrylamide(AAm) + SDS) phase, and of SDS/AAm mass ratio) are studied. At 20°C three viscosity maxima are observed. At 50°C all three peaks remain, the viscosity of the first and third peak, respectively, is lowered to 5–8 mPa· s while the second, most prominent peak still marks the level of ca. 250 mPa· s. The polymerization of acrylamide in dispersion systems is initiated by water-soluble ammonium peroxodisulfate (APS) and oilsoluble dibenzoyl peroxide (DBP) at 60°C. The polymerization rate of acrylamide for a given [toluene]/[AOT] molar ratio and AAm/water mass ratio monotonically decreases for Φaw values greater than 20%. The polyacrylamide viscosity molecular mass increases up to a Φaw value of ca. 30%, irrespective of the nature of initiator. For Φaw values over 30% the viscosity molecular mass of polyacrylamide seems to level off with some sings of shallow minimum close to Φaw of 50%. 相似文献