Search results for " density"
showing 10 items of 2709 documents
The Participation of 3,3,3-Trichloro-1-nitroprop-1-ene in the [3 + 2] Cycloaddition Reaction with Selected Nitrile N-Oxides in the Light of the Exper…
2021
The regioselective zw-type [3 + 2] cycloaddition (32CA) reactions of a series of aryl-substituted nitrile N-oxides (NOs) with trichloronitropropene (TNP) have been both experimentally and theoretically studied within the Molecular Electron Density Theory (MEDT). Zwitterionic NOs behave as moderate nucleophiles while TNP acts as a very strong electrophile in these polar 32CA reactions of forward electron density flux, which present moderate activation Gibbs free energies of 22.8–25.6 kcal·mol−1 and an exergonic character of 28.4 kcal·mol−1 that makes them irreversible and kinetically controlled. The most favorable reaction is that involving the most nucleophilic MeO-substituted NO. Despite P…
Silicatein conjugation inside nanoconfined geometries through immobilized NTA–Ni(ii) chelates
2013
The chemical modification and bioconjugation processes inside confined geometries by His-tagged silicatein promote sensitive changes in the polarity and surface charge density that mainly contribute to the ionic current rectification properties of the single conical nanopores.
Understanding the Mechanism of Nitrobenzene Nitration with Nitronium Ion: A Molecular Electron Density Theory Study
2019
Some experimental issues of AFM tip blind estimation. The effect of noise and resolution
2006
The convolution of tip shape on sample topography can introduce significant inaccuracy in an AFM image, when the tip radius is comparable to the typical dimension of the sample features to be observed. The blind estimation method allows one to obtain information on the AFM tip through an unknown characterizer sample and thus to perform the deconvolution of the tip shape from an image. When applying the blind estimation method to determine the AFM tip shape, some apparently trivial issues relating to the experimental operating parameters must be taken into account. In this paper, the effects of the operating parameters, e.g., sampling intervals (resolution) and instrumental noise, have been …
Experimental determination of the kurtosis of RF noise in microwave low-noise devices
2000
Abstract The degree of the Gaussian nature of the white noise present in microwave low-noise devices is experimentally investigated. The chosen experimental technique consists of simultaneously digitizing four versions of the noise which are amplified by four parallel independent amplifiers. The four independent signals are then used to compute the second, and, to a good approximation, the fourth moment of the noise. The ratio of the fourth moment to the square of the second moment is the kurtosis of the noise. Gaussian processes are characterized by a kurtosis equal to 3. A deviation from this value gives an indication about the degree of non-Gaussian nature of the noise. By using this tec…
Implicit Wiener Filtering for Speech Enhancement In Non-Stationary Noise
2021
Speech quality is degraded in the presence of background noise, which reduces the quality of experience (QoE) of the end-user and therefore motivates the usage of speech enhancement algorithms. A large number of approaches have been proposed in this context. However most of them have focused on the case where the noise is stationary, an assumption that seldom holds in practice. For instance, in mobile telephony, noise sources with a marked non-stationary spectral signature include vehicles, machines, and other speakers to name a few. On the other hand, the usage of frequency-domain information in existing algorithms for speech enhancement in non-stationary noise environments can be made mor…
Skewness and kurtosis of 1/f noise in semiconductor devices
2000
An experimental investigation of the third and fourth moments of the 1/f noise of two different electronic devices is reported. The skewness and the kurtosis of the noise voltage data are estimated. Although the devices under investigation have similar noise power spectral density, the time waveforms are shown to have slightly different statistical properties. In both cases, a small deviation from Gaussian distribution is observed.
Three Different Methods for Determining the Microwave Noise Parameters of HEMT's at Decreasing Temperatures
1998
The noise characteristics of any transistor are usually represented by means of four parameters which are frequency-, bias- and temperature-dependent, similarly to the scattering parameters. The noise parameters are determined by a standard indirect procedure based on multiple noise figure measurements and appropriate data processing techniques requiring a complex instrumentation set-up and skilled operators. As an alterative way, we have shown that the noise parameters of packaged HEAMT's can be computed with very good accuracy from the analysis of a noisy circuit model derived from the scattering parameters plus a single noise figure measurement. A third way exists for the determination o…
On the determination of device noise and gain parameters
1979
The least-squares fitting of measured noise figures and gains versus input termination admittance is an established procedure to determine linear two-port noise and gain parameters. Unfortunately, the method is liable to the serious inconvenience of yielding often erroneous results or even results without physical meaning. Some criteria are suggested which allow the carrying out of measurements in such a manner as to safely avoid the above drawbacks.