On the theory of double injection in solids with traps non-uniformly distributed in energy and in space

A theoretical analysis based on (a) planar double injection and (b) filamentary double injection is presented for the current-voltage characteristics of a solid with traps non-uniformly distributed in the forbidden energy band gap and in space inside it.     

Space charge created by an ohmic injecting contact,and its effects in an electrolyte-insulator system with traps distributed non-uniformly in energy and in space

A theoretical analysis is presented for space charge densities and electric fields, and their effects in an electrolyte-insulator system with traps distributed non-uniformly in energy and in space. The computed results for various forms of trap distributions show that the effect of the non-uniformity of spatial distribution of traps is significant. The theoretical current-voltage characteristics have been used to compare the experimental results of a typical electrolyte-organic thin film system and to demonstrate the use of these results to reveal the form of trap distribution in the system.     

Statistical approach to theory of electron-avalanche ionization in solids

The development of the electron avalanche induced in solid transparent dielectrics by an electromagnetic field where the deterrent lack of seed electrons can be critical is analyzed. Expressions for the breakdown probability as a function of the laser radiation intensity, the focal spot size, and the concentration of defects are obtained.     

Performance of distributed feedback lasers designed to favor the energy gap mode

Distributed feedback lasers with reflecting ends can support a mode in the energy gap that is exponentially confined to the end reflectors. This mode can become the lasing mode in a laser having one high reflecting and one low reflecting end. We have quantitatively compared the properties of such a laser to more conventional DFB lasers having two uncoated cleaved facets or one uncoated and one low reflecting facet. This comparison required computing a distribution of properties for each laser design because the phases of the two end reflections have random values. The gap mode is inherently compact, and the laser favoring this mode has extremely high single-mode selectivity, excellent quantum efficiency, and good resistance to external reflections, when only one Bragg length long. The conventional laser designs have less mode selectivity and require cavity lengths of about two Bragg lengths to reach their optimum performance.     

A unified approach of simultaneous state estimation and anomalous node detection in distributed wireless sensor networks

Detection of anomalous node in distributed wireless sensor networks is extremely important for powerful inference and network reliability. In this paper, we propose a powerful linear statistical model for estimating the state values of the sensor nodes longitudinally, and the estimated state values are used for detecting the anomalous nodes. Our proposed approach is powerful because it considers the effect of the nearest neighbors on the current state values and then detects the anomalous nodes based on the estimated state values. Our method can estimate the missing state values of the sensor nodes, which are kept in sleep mode for energy conservation. We also propose an alternative Bayesian model that is computationally faster for state estimation and anomaly detection. The effectiveness of the proposed model is investigated through extensive simulation studies, and the usefulness of our algorithm is numerically assessed. The performance of the proposed approach is compared to that of the traditional approaches through simulation studies. The proposed model can be effectively used in security surveillance, pattern recognition, habitat monitoring, etc.     

A unified approach to the steady-state and tracking analyses ofadaptive filters

Most adaptive filters are inherently nonlinear and time-variant systems. The nonlinearities in the update equations tend to lead to difficulties in the study of their steady-state performance as a limiting case of their transient performance. This paper develops a unified approach to the steady-state and tracking analyses of adaptive algorithms that bypasses many of these difficulties. The approach is based on the study of the energy flow through each iteration of an adaptive filter, and it relies on a fundamental error variance relation     

A unified approach to the detection of fluctuating pulsed signals in noise

The classical problem of detecting a fluctuating pulsed signal in noise is analyzed when the signal has a Rice amplitude distribution. The results provide a natural bridge between previous analyses of nonfluctuating signals and signals with Rayleigh envelopes.     

Calculation of electron affinity, ionization potential, transport gap, optical band gap and exciton binding energy of organic solids using ‘solvation’ model and DFT

Electron affinity of organic molecules in solids is calculated using density functional theory (DFT) and ‘solvation’ correction using polarizable continuum model. Computed values for 13 molecules show excellent correlation with experimental values obtained from inverse photoemission spectroscopy. The same method was used to calculate ionization potential and transport gap of the 13 organic molecules in solid state. Optical band gap was calculated for the 13 molecules using time-dependent DFT and polarizable continuum model, which in turn was used to calculate exciton binding energy of the molecules in solid state. Calculated and experimental values show good agreement that it is possible to determine the electron affinity, ionization potential, transport gap and optical band gap of organic molecules in solid state using molecular structure as the only input required for the calculation.     

A unified approach to the design of robust narrow-band antennaarray processors

A unified approach to the design of robust narrowband antenna array processors is presented. The approach is based on the idea of minimizing the weighted mean-square-deviation between the desired response and the response of the processor over variations in parameters. Three specific examples of robust design are considered: robustness against directional mismatch, robustness against array geometry errors, and robustness against channel phase errors. Initially, a general quadratic constraint on the weights is developed. However, it is then shown that the quadratic constraint can be replaced by linear constraints or at most linear constraints plus norm constraint. These latter constraints are no more complex than those required for designs which do not incorporate robustness features explicitly. Numerical results show that the proposed approach appears to offer a unified treatment for directly designing narrowband processors which are robust against various types of errors and mismatches between signal model and actual scenario     

A unified approach to the STFT, TFDs, and instantaneous frequency

Cohen's class of time-frequency representations (TFRs) is reformulated into a discrete-time, discrete-frequency, computer-implementable form. It is shown how, in this form, many of the properties of the continuous-time, continuous-frequency formulation are either lost or altered. Intuitions applicable in the continuous-time case do not necessarily carry over to the discrete-time case examined. The properties of the discrete variable formulation examined are the presence and form of cross-terms, instantaneous frequency estimation, and relationships between Cohen's class of TFRs. A parameterized class of distributions which is a blending between the short-time Fourier transform (STFT) and the Wigner-Ville distribution. The two main conclusions are that all TFRs of Cohen's class implementable in the given form (which includes all commonly used TFRs) possess cross-terms and that instantaneous frequency estimation using periodic moments of these TFRs is purposeless, since simpler methods obtain the same result     

A simple yet comprehensive unified physical model of the donorlayer electrons in delta-doped and uniformly doped HEMT's

The trapped and free electrons in the donor layer of a high electron mobility transistor (HEMT) play an important role in limiting the current modulation efficiency and the current-gain cutoff frequency of the device. This paper presents a simple model, which closely tracks accurate but complex numerical calculations of the concentration and capacitance of these electrons as a function of the gate voltage. The model is comprehensive in the sense that it captures the effects of all device parameters including temperature on trapped as well as free electrons, and encompasses both uniformly doped and delta-doped HEMT's. A simple power law charge voltage function, which is both differentiable and integrable, is shown to adequately represent the behavior of the two types of donor layer electrons in both the HEMT's. The model is useful in the design and simulation of ac performance of HEMT devices and circuits. Together with the n_s-V_G model proposed recently by the authors of this paper, it gives a complete yet simple analytical picture of all the charges of significance in a general HEMT     

A unified approach to the design of linear constraints in minimumvariance adaptive beamformers

A simple, systematic procedure for designing linear constraints in minimum-variance beamformers which allows an arbitrary specification of the quiescent response (the beamformer response when only white noise is present) is described. In this approach, the first constraint is dedicated to the imposition of a desired quiescent response, and additional constraints are included to assure proper reception of the desired signal. These additional constraints make the overall beamformer response equal to the quiescent response in the desired signal region so that the signal is not cancelled when it is present. Optionally, the response can be fixed in other regions of interest by adding more constraints. This design procedure demonstrates that the key to designing efficient constraints is finding the weighting coefficients which specify the desired quiescent response, a problem identical to the synthesis of desired beam patterns for nonadaptive arrays. The effectiveness of the procedure is illustrated by examples in both narrowband and broadband arrays     

A unified approach to the effects of symmetry and periodicity on boundary-value problems

A generalized approach to the effects of symmetry and periodicity on boundary-value problems is presented, especially as it pertains to the guiding structures encountered in electromagnetics. Several examples of structures and their dispersion behavior are given, and the theory predicts well that other authors claim.     

A new approach to the design of dual-mode rectangular waveguidefilters with distributed coupling

A synthesis procedure for a new configuration of four-pole dual-mode waveguide filters with distributed coupling is presented. In this configuration the dual-mode coupling is obtained by exploiting the well-known fact that the diagonal polarizations are coupled in an almost square waveguide. The obvious advantage of this type of structure is that the cross sections of all the discontinuities are rectangular, hence the global prediction of the filter is more accurate. The synthesis approach is based on a scattering matrix formulation where the dual-mode coupling is described in terms of a 2×2 propagation matrix. Universal design charts, which directly yield the scattering parameters of the various junctions, have been obtained. Comparisons with experimental results of a four-pole filter are also presented     

Projection spectral analysis: A unified approach to PCA and ICA with incremental learning

Projection spectral analysis is investigated and refined in this paper, in order to unify principal component analysis and independent component analysis. Singular value decomposition and spectral theorems are applied to nonsymmetric correlation or covariance matrices with multiplicities or singularities, where projections and nilpotents are obtained. Therefore, the suggested approach not only utilizes a sum-product of orthogonal projection operators and real distinct eigenvalues for squared singular values, but also reduces the dimension of correlation or covariance if there are multiple zero eigenvalues. Moreover, incremental learning strategies of projection spectral analysis are also suggested to improve the performance.