Image selective restoration using multi-scale variational decomposition

In this paper we propose a multi-scale variational decomposition model for image selective restoration. Firstly, we introduce a single-parameter (BV, G, L²) variational decomposition functional and theoretically analyze the relationship between the parameter and the scale of image features. And then, by replacing the fixed scale parameter with a varying sequence in the single-parameter decomposition functional, we obtain the multi-scale variational decomposition which can decompose the input image into a series of image slices of different scales. Furthermore, we show some properties and prove the convergence of the multi-scale decomposition. Finally, we introduce an alternating and iterative method based on Chambolle’s projection algorithm to numerically solve the multi-scale variational decomposition model. Experiments are conducted on both synthetic and real images to demonstrate the effectiveness of the proposed multi-scale variational decomposition. In addition, we use the multi-scale variational decomposition to achieve image selective restoration, and compare it with several state-of-the-art models in denoising application. The numerical results show that our model has better performance in terms of PSNR and SSIM indexes.     

A primal-dual gradient method for image decomposition based on (<Emphasis Type="Italic">BV</Emphasis>, <Emphasis Type="Italic">H</Emphasis><Superscript>−1</Superscript>)

The main aim of this paper is to accelerate the image decomposition model based on (BV, H ⁻¹). It is solved with a particularly effective primal-dual gradient descent algorithm. The algorithm works on the primal-dual formulation and exploits the information of the primal and dual variables simultaneously. It converges significantly faster than some popular existing methods in numerical experiments. This approach is to some extent related to projection type methods for solving variational inequalities.     

On the extreme eigenvalues of Toeplitz and real Hankel interval matrices

The purpose of this paper is to evaluate the extreme eigenvalues of a Hermitian Toeplitz interval matrix and a real Hankel interval matrix. A (n×n)-dimensional Hermitian Toeplitz (HT) matrix is determined by the elements of its first row, sayr. If the elements ofr lie in complex intervals (i.e., rectangles of the complex plane), we call the resulting set of matrices an HT interval (HTI) matrix. An HTI matrix can model real world HT matrices where the elements of the vectorr have finite precision (e.g., because of quantization, or imprecise measurement devices). In this paper we prove that the extreme eigenvalues of a given HTI matrix can be easily obtained from the 2^2(n–1) vertex HT matrices where the first element ofr is set to zero. Similarly, as a special case we obtain that the extreme eigenvalues of a real symmetric Toeplitz interval (RSTI) matrix can be obtained from 2 ^n–1 vertex matrices. Based on the above results we provide boxlike bounds for the eigenvalues on non-Hermitian complex and real Toeplitz interval matrices. Finally, we consider a real Hankel interval matrix. We prove that the maximal eigenvalue of a (n×n)-dimensional real Hankel interval matrix can be obtained from a subset of the vertex Hankel matrices containing 2^2n–3 vertex matrices, whereas the minimal eigenvalue can be obtained from another such subset also containing 2^2n–3 vertex matrices.     

The roles of charged and neutral oxidising species in silicon oxidation from ab initio calculations

We examine the roles of charged oxidising species based on extensive ab initio density functional theory calculations. Six species are considered: interstitial atomic O, O⁻, O²⁻ and molecular species: O₂, O₂⁻, O₂²⁻. We calculate their incorporation energies into bulk silicon dioxide, vertical electron affinities and diffusion barriers. In our calculations, we assume that the electrons responsible for the change of charge state come from the silicon conduction band; however, the generalisation to any other source of electrons is possible, and hence, our results are also relevant to electron-beam assisted oxidation and plasma oxidation. The calculations yield information about the relative stability of oxidising species, and the possible transformations between them and their charging patterns. We discuss the ability to exchange O atoms between the mobile species and the host lattice during diffusion, since this determines whether or not isotope exchange is expected. Our results show very clear trends: (1) the molecular species are energetically preferable over atomic ones, (2) the charged species are energetically more favourable than neutral ones, (3) diffusion of atomic species (O, O⁻, O²⁻) will result in oxygen exchange, whereas the diffusion of molecular species (O₂, O₂⁻, O₂²⁻) is not likely to lead to a significant exchange with the lattice. On the basis of our calculation, we predict that charging of oxidising species may play a key role in silicon oxidation process.     

Silicon dioxide deposited by ECR-PECVD for low-temperature Si devices processing

Silicon dioxide films have been deposited at temperatures less than 270 °C in an electron cyclotron resonance (ECR) plasma reactor from a gas phase combination of O₂, SiH₄ and He. The physical characterization of the material was carried out through pinhole density analysis as a function of substrate temperature for different μ-wave power (E_w). Higher E_w at room deposition temperature (RT) shows low defects densities (<7 pinhole/mm²) ensuring low-temperatures process integration on large area. From FTIR analysis and Thermal Desorption Spectroscopy we also evaluated very low hydrogen content if compared to conventional rf-PECVD SiO₂ deposited at 350 °C. Electrical properties have been measured in MOS devices, depositing SiO₂ at RT. No significant charge injection up to fields 6–7 MV/cm and average breakdown electric field >10 MV/cm are observed from ramps I–V. Moreover, from high frequency and quasi-static C–V characteristics we studied interface quality as function of annealing time and annealing temperature in N₂. We found that even for low annealing temperature (200 °C) is possible to reduce considerably the interface state density down to 5 × 10¹¹ cm⁻² eV⁻¹. These results show that a complete low-temperatures process can be achieved for the integration of SiO₂ as gate insulator in polysilicon TFTs on plastic substrates.     

A New Scheme to Realize Crosstalk-Free Permutation in Vertically Stacked Optical MINs*

Vertical stacking is a novel alternative for constructing nonblocking multistage interconnection networks (MINs). Rearrangeably nonblocking optical MINs are attractive since they have lower complexity than their strictly nonblocking counterparts. In this paper, we study the realization of crosstalk-free permutations in rearrangeably nonblocking, self-routing banyan-type optical MINs built on vertical stacking. An available scheme for realizing crosstalk-free permutation in this type of optical MINs requires to first decompose a permutation into multiple crosstalk-free partial permutations based on the Euler-Split technique, and then to realize them crosstalk-free in different planes (stacked copies) of the MIN simultaneously. The overall time complexity of this scheme to realize a crosstalk-free permutation in an N × N optical MIN is O(N log N) which is dominated by the complexity of crosstalk-free decomposition. In this paper, we propose a new scheme for realizing permutations in this class of vertically stacked optical MINs crosstalk-free. The basic idea of the new scheme is to classify permutations into permutation classes such that all permutations in one class share the same crosstalk-free decomposition pattern. By running the Euler-Split based crosstalk-free decomposition only once for a permutation class and applying the obtained crosstalk-free decomposition pattern to all permutations in the class, crosstalk-free decomposition of permutations can be realized in a more efficient way. We show that the number of permutations in a permutation class is huge (N!)^N when log₂N is even and (2N!)^N/2 when log₂N is odd), and thus the average time complexity of crosstalk-free decomposition of a permutation becomes O(N).     

A Quick Simulation Technique for a Fluid Information Storage Problem

In this paper we present an application of Importance Sampling (IS) for quick simulation of buffer overflow probability in a statistical multiplexer loaded with a number of independent Markov modulated fluid sources. Runtime improvement is deducible from N_MCσ²(p) and N_ISσ²(p^*) that characterize the trade-offs between sample size and variance of the estimators of buffer overflow probability experienced in Monte Carlo (MC) and Importance Sampling simulations. By assuming that the same precision is achieved for the two kinds of simulations if σ²(p)=σ²(p*), an approximate closed form expression for the ratio N_IS/N_MC is derived, and it is minimized with respect to the load of the multiplexer. In the final part of the paper some numerical examples are presented to illustrate the benefits of IS in evaluating very low overflow probabilities.     

Cyclic wavelet transforms for arbitrary finite data lengths

Multiresolution analysis via decomposition into wavelets has been established as an important transform technique in signal processing. A wealth of results is available on this subject, and particularly, the framework has been extended to treat finite length sequences of size 2ⁿ (for positive integers n) over finite fields. The present paper extends this idea further to provide a framework for dealing with arbitrary finite data lengths. This generalization is largely motivated in part by the need for such transforms for building error correcting codes in the wavelet transform domain. Here we extend the previous two-band formulation of the transform to treat a p-band case in general (i.e. for data length pⁿ), where p is a prime number, and we also give a general result for developing transforms over composite-length sequences. Potential applications and computational complexity issues are discussed as well.     

Fast CORDIC Algorithm Based on a New Recoding Scheme for Rotation Angles and Variable Scale Factors

This work proposes a new rotation mode CORDIC algorithm, which considerably reduces the iteration number. It is achieved by combining several design techniques. Particularly, a new table-lookup recoding scheme for rotation angles and variable scale factors is developed to reduce the iteration numbers for rotation and scale factor compensation. By addressing the MSB parts of the residual rotation angles to a lookup table, two micro rotation angles are retrieved that in combination best matches the MSB parts. We also combine the leading-one bit detection operations for residual rotation angles, to skip unnecessary rotations. The resulting problems of variable scale factors are then solved by our previous fast decomposition and compensation algorithm (C.C. Li and S.G. Chen, in Proceedings of 1996 IEEE International Symposium Circuits and Systems, May 1996, Atlanta, USA, pp. 264–267; C.C. Li and S.G. Chen, in Proceedings of 1997 IEEE International Conference on Acoustic, Speech and Signal Processing, Munich, 1997, Germany, pp. 639–642). To further reduce the iteration number of scale factor compensation, we again apply the mentioned residual recoding technique and the leading-one bit detection scheme to the fast variable scale factor algorithm. Those techniques collectively reduce the iteration number significantly. Simulations show that in average the new design needs only 9.78 iterations to generate results with 22-bit accuracy, including all the iterations for rotations and scale factor compensations. Statistically, the total iteration number is less than n/2 for results with n-bit accuracy. The introduced extra table size is of the same order of magnitude as that for the angle set {tan^–1 2^–i , i = 0,1,...,n}, required by general CORDIC algorithms. The new recoding scheme can be applied to other elementary function such as division and square-root functions.     

Synthesis of cyanated tetracenes as the organic semiconductors

Two novel and air-stable cyanated tetracene derivatives, 5-cyanotetracene (1CT) and 5,11-dicyanotetracene (2CT), were synthesized as high-performance organic semiconductors. The stability of 2CT was evaluated by NMR and the electrochemical property was investigated by cyclic voltammetry (CV) and UV–vis spectrum. The reorganization energy of 2CT predicted by UB3LYP/6-311g(d,p) is 0.0881 eV, which is the lowest among existing compounds. The X-ray crystallographic analysis revealed that the 2CT single crystal has a promising face-to-face packing with a relative short intermolecular distance of 3.403 Å. Based on the theoretical model we previously developed, the calculated hole mobilities of these air-stable cyanated tetracene derivatives in a–b plane are 2.9 cm² V⁻¹ s⁻¹ for 1CT and 2.2 cm² V⁻¹ s⁻¹ for 2CT, respectively. These oxygen-resisted organics may offer potential to fabricate the flexible electronics under air conditions.     

Interfacial charges and electric field distribution in organic hetero-layer light-emitting devices

The electric field distribution in organic hetero-layer light-emitting devices based on N,N^′-diphenyl-N,N^′-bis(1-naphtyl)-1,1^′-biphenyl-4,4^′-diamine (NPB) and 8-tris-hydroxyquinoline aluminium (Alq₃) has been investigated under different bias conditions using capacitance–voltage measurements. Although this method yields primarily information on the differential capacitance, the data give clear evidence for the presence of negative interfacial charges with a density of 6.8×10¹¹e cm⁻² at the NPB/Alq₃ interface at large reverse bias. This leads to a jump of the electric field at the interface and a non-uniform field distribution in the hetero-layer device.     

Degradation induced by 2-MeV alpha particles on AlGaN/GaN high electron mobility transistors

We studied the degradation of AlGaN/GaN High Electron Mobility Transistors (HEMT) after 2-MeV alpha irradiation for two different fluences, namely 10¹³α/cm² and 10¹⁴α/cm². After the exposure and depending on the irradiation fluence, we observed a drop both in drain current and transconductance, and a reduction in the leakage current of the gate diode. We attributed these effects to bulk damage, radiation-induced formation of deep-level trap sites in the channel layer, and doping compensation/removal in the barrier layer.     

Luminescence and microstructure of Er/O co-doped Si structures grown by MBE using Er and SiO evaporation

Er and O co-doped Si structures have been prepared using molecular-beam epitaxy (MBE) with fluxes of Er and O obtained from Er and silicon monoxide (SiO) evaporation in high-temperature cells. The incorporation of Er and O has been studied for concentrations of up to 2×10²⁰ and 1×10²¹ cm⁻³, respectively. Surface segregation of Er can take place, but with O co-doping the segregation is suppressed and Er-doped layers without any indication of surface segregation can be prepared. Si_1−xGe_x and Si_1−yC_y layers doped with Er/O during growth at different substrate temperatures show more defects than corresponding Si layers. Strong emission at 1.54 μm associated with the intra-4f transition of Er³⁺ ions is observed in electroluminescence (EL) at room temperature in reverse-biased p–i–n-junctions. To optimize the EL intensity we have varied the Er/O ratio and the temperature during growth of the Er/O-doped layer. Using an Er-concentration of around 1×10²⁰ cm⁻³ we find that Er/O ratios of 1 : 2 or 1 : 4 give higher intensity than 1 : 1 while the stability with respect to breakdown is reduced for the highest used O concentrations. For increasing growth temperatures in the range 400–575°C there is an increase in the EL intensity. A positive effect of post-annealing on the photoluminescence intensity has also been observed.     

Three-dimensional linear prediction and its application to digital angiography

In this article, we apply three-dimensional (3-D) linear least-squares (LS) prediction technique to the processing of digital subtraction angiography (DSA) image sequences. The main goal of this processing is the cancellation of motion artifacts, which is a visual structured noise that appears in current DSA images. We address two important issues with this new technique: first the misregistration between the mask and the contrast image and, second, the temporal filtering of DSA image sequence. Instead of treating these two issues separately, as conventional DSA methods do, we combine them into a 3-D LS prediction problem. Based on this approach, we develop a new efficient algorithm for the solution of normal equations. The algorithm is based on a new property of T ⁿ (Toeplitz to then) matrices that we prove. In order to match the image sequence physical characteristics, we further optimize practical parameters of this algorithm. Actual patient data is used for the evaluation of this new technique. Results show a significant improvement over the existing methods.     

Techniques for efficient and effective transformed image identification

In many applications, one common problem is to identify images which may have undergone unknown transformations. We define this problem as transformed image identification (TII), where the goal is to identify geometrically transformed and signal processed images for a given test image. The TII consists of three main stages – feature detection, feature representation, and feature matching. The TII approach by Lowe [D.G. Lowe, Distinctive image features from scale-invariant keypoints, Int. J. Comput. Vision 60 (2) (2004) 91–110] is one of the most promising techniques. However, both of its feature detection and matching stages are expensive, because a large number of feature-points are detected in the image scale-space and each feature-point is described using a high dimensional vector. In this paper, we explore the use of different techniques in each of the three TII stages and propose a number of promising TII approaches by combining different techniques of the three stages. Our experimental results reveal that the proposed approaches not only improve the computational efficiency and decrease the storage requirement significantly, but also increase the transformed image identification accuracy (robustness).     

Aging of the over-voltage protection elements caused by over-voltages

The aim of this work is examining the influence of the number of the activation––over-voltage pulses to the aging of over-voltage protection elements. Both non-linear (gas-filled surge arresters (GFSA), varistors, over-voltage diodes) and linear (capacitors––constituents of filters) over-voltage protection elements were tested. The instruments employed allow reliable measurements, 1000 consecutive activation were tested. The double-exponential current pulse (amplitude I₁^max=13 A, I₂^max=16 A, rise time T₁=8 μs, fall time T₂=20 μs) for non-linear elements and a double-exponential over-voltage pulse (rise time T₁=1.2 μs, fall time T₂=50 μs) of the amplitude U₁^max=320 V, U₂^max=480 V and U₃^max=640 V for capacitors were used. The experimental results show that the over-voltage diodes are the most reliable elements in view of characteristic modifications that are consequence of aging. However, it was observed that varistors, GFSA and capacitors undergo noticeable changes in characteristics.     

Analysis of interior degradation of a laser waveguide using an OBIC monitor

We propose a novel optical-beam-induced current (OBIC) measurement technique for detecting the degradation in the interior of a waveguide. This technique uses an incident light with a wavelength longer than that of the band edge of the active layer. An OBIC scan image was obtained at a wavelength of 1.6 μm, which was 50 nm longer than the PL peak wavelength in the active layer of the degraded laser, and the OBIC became sensitive to some degradation when a long distance guided light was used. Furthermore, we confirmed that the degradation mechanism of the t^0.5 deterioration property is mainly governed by diffused defects at the waveguide other than those in the vicinity of the AR facet in a DFB laser.     

A Practical Parallel Architecture for Stacks Filters

Stack filters belong to the class of non-linear filters and include the well-known median filter, weighted median filters, order statistic filters and weighted order statistic filters. Any stack filter can be implemented by using the parallel threshold decomposition architecture which allows implementing their non-linear processing by means of a collection of identical binary filters (Boolean logic circuits). Although it is conceptually simple and useful to study the filter properties, this architecture is not practical for direct hardware implementation because as many as (M – 1) binary filters are required for a M-valued input signal and M is large in many applications.In this paper we introduce a new parallel architecture for stack filter implementations. The complexity is now proportional to the window width L of the filter, instead of to M. In most applications L is much smaller than M which translates into efficient hardware implementations. The attractive characteristic of ease of design exhibited by the threshold decomposition architecture is kept. In fact, for a given stack filter both in the conventional implementation and in the proposed one, the same binary filter is required. The key concept supporting the new architecture is a modified decomposition scheme which generates L binary signals for a multi-valued input. As an application example, a complex WOS filter is designed and prototyped in an FPGA.     

Low-temperature conductance measurements of surface states in HfO2–Si structures with different gate materials

Metal-oxide-semiconductor capacitors based on HfO₂ gate stack with different metal and metal compound gates (Al, TiN, NiSi and NiAlN) are compared to study the effect of the gate electrode material on the trap density at the insulator–semiconductor interface.C–V and G–ω measurements were made in the frequency range from 1 kHz to 1 MHz in the temperature range 180–300 K. From the maximum of the plot G/ω vs. ln(ω) the density of interface states was calculated, and from its position on the frequency axis the trap cross-section was found. Reducing temperature makes it possible to decrease leakage current through the dielectric and to investigate the states located closer to the band edge.The structures under study were shown to contain significant interface trap densities located near the valence band edge (around 2×10¹¹ cm⁻²eV⁻¹ for Al and up to (3.5–5.5)×10¹² cm⁻² eV⁻¹ for other gate materials). The peak in the surface state distribution is situated at 0.18 eV above the valence band edge for Al electrode. The capture cross-section is 5.8×10⁻¹⁷ cm² at 200 K for Al–HfO₂–Si structure.     

Generation–recombination noise in bipolar transistors

The generation–recombination (g–r) noise in bipolar junction transistors (BJTs) is due to the deep-level impurities in the p–n junctions. The larger the amplitude of g–r noise, the worse the quality of BJTs, so that measuring the amplitude of the g–r noise is way of estimating the reliability of BJTs. In some papers, it is assumed that the amplitude of g–r noise is proportional to the square of base current (I_b²), but in a few papers it has been reported that this relation is more complex. In this paper the amplitude of g–r noise versus base current is discussed, the theoretical and experiment results demonstrate that the g–r noise and burst noise signal may be observed only in a certain range of base current, and the law S(f)∝I_b² is not valid. It means that we must measure g–r noise and observe burst noise signal over a wide range of base current to estimate the concentration of deep-level impurities in p–n junction and hence the reliability of BJTs.