Distortion Index Research Articles

English

This paper presents an improved method in solving the optimization problem related to the optimum placement and sizing of the Distribution Static Synchronous Compensator (D-STATCOM) in distribution systems, which use the firefly algorithm (FA) for power quality improvement. In the proposed method, the voltage total harmonic distortion, voltage deviation, and total investment cost indices are considered as the problem sub-objective functions. The voltage and power limits for individual buses are considered as the constraints to control optimization variables. The proposed FA is implemented using the Matlab software on modified IEEE 16- and 34-bus test systems. The obtained results are compared with the particle swarm optimization and the genetic algorithm. The simulation and comparison results verify the ability of the FA to accurately determine the optimal location and size of the D-STATCOM in radial distribution systems.

Optical structure to improve the γ-curve distortion of a four-domain (4-D) twisted nematic liquid crystal cell

The γ-curve represents the viewing angle characteristics of a liquid crystal (LC) cell in all gray levels, including the dark state. In this paper, we propose a optical configuration of a four-domain (4-D) twisted nematic (TN) LC cell for improving the γ-curve distortion in the oblique direction, without any deterioration in the optical property of a conventional 4-D TN cell. A positive A-plate and a negative A-plate are applied at the top and the bottom of the 4-D TN LC layer, respectively. The two A-films applied can be optimized at all viewing angles by calculating the polarization difference (Δ p ) as functions of the retardation and the optical axis of the films, so that the transmittance distortion in the middle gray scale can be compensated for in all viewing directions. As a result of a calculation of the gamma distortion index (GDI), the γ-curve can be improved by more than 70% in the off-axis at 0° and 180°, and by more than 50% in the off-axis at 90° and 270°.

Structural investigations of the two polymorphs of synthetic Fe-cordierite and Raman spectroscopy of hexagonal Fe-cordierite.

The crystal structures of synthetic hexagonal and orthorhombic Fe-cordierite polymorphs with the space groups P6/mcc and Cccm were refined from single-crystal X-ray diffraction data to R 1, hex = 3.14 % and R 1, ortho = 4.48 %. The substitution of the larger Fe2+ for Mg leads to multiple structural changes and an increase of the unit cell volumes, with a, c (hex) = 9.8801(16) Å, 9.2852(5) Å and a, b, c (ortho) = 17.2306(2) Å, 9.8239(1) Å, 9.2892(1) Å in the end-members. Furthermore Fe incorporation results in an increase of the volumes of the octahedra, although the diameters of the octahedra in direction of the c-axis decrease in both polymorphs. X-ray powder diffraction analysis indicates a high degree of Al/Si ordering in the orthorhombic polymorph, the Miyashiro distortion index is ~0.24. Estimations of site occupancies based on the determined tetrahedral volumes result in the following values for hexagonal Fe-cordierite: ~73 % Al for T1 and ~28 % Al for T2. For the first time Raman spectroscopy was performed on the hexagonal Fe-cordierite polymorph. In the hexagonal Fe-cordierite polymorph most Raman peaks are shifted towards lower wavenumbers when compared with the Mg-end-member.Electronic supplementary materialThe online version of this article (doi:10.1007/s00710-013-0313-3) contains supplementary material, which is available to authorized users.

Vertically Aligned In-Plane-Switching LCD Mode With Novel Pixel Circuits

In this paper, we propose two novel pixel circuits which are able to provide great picture quality at oblique viewing angles. These two pixel circuits are based upon the VA-IPS mode with vertically aligned nematic liquid crystals and in-plane switching electrodes. Comparing to current VA-type LCDs, the VA-IPS mode can be used to improve oblique gamma distortion with its tone rendering distortion index (TRDI) as low as 0.15. With the proposed pixel circuits, we believe the TRDI can be further improved to be less than 0.13. The novel technologies are very likely to be the solution for VA-type LCDs when facing the competition from other display technologies.

FPGA Implementation of Direct Digital Frequency Synthesizer

Direct digital frequency synthesizer (referred to as DDS) is a kind of complete digital frequency synthesizer. In this article the principle of DDS were introduced. Set the design index of distortion and resolution, and design parameters of DDS in accordance with the index. DDS design describes by Verilog HDL, implement controlling four parameters of the waveform, frequency, phase, amplitude. Using FPGA and Quartus II/Nios IIwhich is Altera EDA software, realize DDS and its peripheral input / output and DA platform. The final direct to DDS simulation results and the overall DDS platform oscilloscope experimental data, verify the correctness of the design of DDS with the two data.

Frequency response and distortion properties of nonlinear image processing algorithms and the importance of imaging context

The most common metrics for resolution analysis in medical imaging are valid only for (approximately) linear systems. While analogues to these metrics have been used in attempts to describe resolution performance in nonlinear systems, the analysis is incomplete since distortion effects are often ignored. The authors have developed a methodology to analyze the amplitude modulation and waveform distortion properties of nonlinear systems with specific application to medical image processing algorithms. Using sinusoidal basis functions, two metrics were derived which distinguish amplitude modulation from nonlinear waveform distortion: principle frequency response and distortion power spectrum, respectively. Additionally, two figures of merit were developed to describe the relative impact of nonlinear distortion as a result of image processing: distortion index (DI) and ΣDI. Three nonlinear denoising algorithms, the median, bilateral, and wavelet denoising filters, were selected as example functions to demonstrate the utility of the metrics derived in this study. Each filter showed very different resolution and waveform distortion properties. In particular, the amplitude and extent of nonlinear distortion depended strongly on image context and the type of nonlinear mechanism employed. Nonlinear waveform distortion constituted up to 30% of the median filter output signal power in high contrast-to-noise ratio (CNR) scenarios. Conversely, nonlinear distortion never exceeded 1% of the bilateral filter output signal power. The wavelet denoising response contained between 1% and 9% distortion which varied weakly as a function of CNR. The analytical metrics described in the paper demonstrate the importance of considering both resolution- and distortion-related effects in characterizing the performance of nonlinear imaging systems with specific application to image processing algorithms. Findings with three common nonlinear algorithms demonstrate a range of CNR values over which it is important to consider the impact of the nonlinear nature of each algorithm. Background context is also shown to influence the degree to which the nonlinear nature of the algorithm influences resolution and distortion. While no single metric can yet anticipate observer performance in nonlinear systems, the approach described can demonstrate the range of imaging contexts over which such nonlinear effects are important to consider.

P.102: Improvement of Gamma Curve Distortion in VA LCD by using Optical Film Patterned Retarder

AbstractIn this paper, we improved the γ‐curve distortion at off‐axis direction in a 4‐domain (4‐D) patterned vertical alignment (PVA) liquid crystal (LC) cell by applying a pair of the film patterned retarder (FPR) system with the A‐film property at the conventional wide‐view (WV) PVA LC cell. In order to achieve the excellent γ‐curve in the 4‐domain LC cell, we optimized the parameter of the pair of the patterned A‐film by using the two‐dimensional parameter space method, which calculates the polarization difference between the normal direction and the all viewing directions under voltage applied state. As a result, we confirmed that the gamma distortion index (GDI) of the proposed optical structure is reduced to over 80% without any loss of the optical luminance and the contrast ratio in the dark state.

A Hilbert Transform-Based Smart Sensor for Detection, Classification, and Quantification of Power Quality Disturbances

Power quality disturbance (PQD) monitoring has become an important issue due to the growing number of disturbing loads connected to the power line and to the susceptibility of certain loads to their presence. In any real power system, there are multiple sources of several disturbances which can have different magnitudes and appear at different times. In order to avoid equipment damage and estimate the damage severity, they have to be detected, classified, and quantified. In this work, a smart sensor for detection, classification, and quantification of PQD is proposed. First, the Hilbert transform (HT) is used as detection technique; then, the classification of the envelope of a PQD obtained through HT is carried out by a feed forward neural network (FFNN). Finally, the root mean square voltage (Vrms), peak voltage (Vpeak), crest factor (CF), and total harmonic distortion (THD) indices calculated through HT and Parseval's theorem as well as an instantaneous exponential time constant quantify the PQD according to the disturbance presented. The aforementioned methodology is processed online using digital hardware signal processing based on field programmable gate array (FPGA). Besides, the proposed smart sensor performance is validated and tested through synthetic signals and under real operating conditions, respectively.

Next neighbors effect along the Ca–Sr–Ba-åkermanite join: Long-range vs. short-range structural features

Abstract An original approach has been developed herein to explore the correlations between short- and long-range structural properties of solid solutions. X-ray diffraction (XRD) and electronic absorption spectroscopy (EAS) data were combined on a (Ca,Sr,Ba) 2 (Mg 0.7 Co 0.3 )Si 2 O 7 join to determine average and local distances, respectively. Instead of varying the EAS-active ion concentration along the join, as has commonly been performed in previous studies, the constant replacement of Mg 2+ by a minimal fraction of a similar size cation (Co 2+ ) has been used to assess the effects of varying second-nearest neighbor cations (Ca, Sr, Ba) on the local distances of the first shell. A comparison between doped and un-doped series has shown that, although the overall symmetry of the Co-centered T1 -site was retained, greater relaxation occurs at the CoO 4 tetrahedra which become increasingly large and more distorted than the MgO 4 tetrahedra. This is indicated by an increase in both the quadratic elongation ( λ T1 ) and the bond angle variance ( σ 2 T1 ) distortion indices, as the whole structure expands due to an increase in size in the second-nearest neighbors. This behavior highlights the effect of the different electronic configurations of Co 2+ (3 d 7 ) and Mg 2+ (2 p 6 ) in spite of their very similar ionic size. Furthermore, although the overall symmetry of the Co-centered T1-site is retained, relatively limited ( 2+ –O occur along the solid solution series and large changes are found in molar absorption coefficients showing that EAS Co 2+ -bands are highly sensitive to change in the local structure.

Direct Surge Margin Control for Aeroengines Based on Improved SVR Machine and LQR Method

A novel scheme of high stability engine control (HISTEC) on the basis of an improved linear quadratic regulator (ILQR), called direct surge margin control, is derived for super-maneuver flights. Direct surge margin control, which is different from conventional control scheme, puts surge margin into the engine closed-loop system and takes surge margin as controlled variable directly. In this way, direct surge margin control can exploit potential performance of engine more effectively with a decrease of engine stability margin which usually happened in super-maneuver flights. For conquering the difficulty that aeroengine surge margin is undetectable, an approach based on improved support vector regression (SVR) machine is proposed to construct a surge margin prediction model. The surge margin modeling contains two parts: a baseline model under no inlet distortion states and the calculation for surge margin loss under supermaneuvering flight conditions. The previous one is developed using neural network method, the inputs of which are selected by a weighted feature selection algorithm. Considering the hysteresis between pilot input and angle of attack output, an online scrolling window least square support vector regression (LSSVR) method is employed to firstly estimate inlet distortion index and further compute surge margin loss via some empirical look-up tables.

Predicting chaos in memristive oscillator via harmonic balance method

This paper studies the possible chaotic behaviors in a memristive oscillator with cubic nonlinearities via harmonic balance method which is also called the method of describing function. This method was proposed to detect chaos in classical Chua's circuit. We first transform the considered memristive oscillator system into Lur'e model and present the prediction of the existence of chaotic behaviors. To ensure the prediction result is correct, the distortion index is also measured. Numerical simulations are presented to show the effectiveness of theoretical results.

Graphene-like titanium carbides and nitrides Tin+1Cn, Tin+1Nn (n = 1, 2, and 3) from de-intercalated MAX phases: First-principles probing of their structural, electronic properties and relative stability

Very recently [32], an elegant exfoliation approach was proposed to prepare a new family of 2D-like transition metal carbides, when selective etching of aluminum layers from some MAX phases yielded 2D materials Ti2C, Ti3C2. Moreover, according to the newest data [47,48], more complex 2D carbides (TiNbC) or carbonitrides (Ti3CNx) can be prepared.Here, employing first-principle band structure calculations, we have examined systematically the trends in structural, electronic properties and relative stability of a representative group of 2D (graphene-like, GL) materials: titanium carbides and nitrides Tin+1Cn, Tin+1Nn (n=1, 2, and 3). The peculiarities of atomic relaxation effects for GL Tin+1Cn and GL Tin+1Nn were established and discussed in terms of so-called distortion indexes of basic polyhedrons. Our analysis of stability of GL Tin+1Cn and GL Tin+1Nn (in terms of cohesive energies and formation energies) has shown relative stabilization of these GL systems with the growth of their thickness (i.e. with the growth of index n). The most interesting feature of the electronic structure for GL Tin+1Cn and GL Tin+1Nn is a considerable growth of the density of near-Fermi states which becomes 2.5 to 4.5 times higher than for the parent MAX phases. The origin of this effect was explained by redistribution of Ti 3d states from broken Ti–Al bonds into delocalized Ti–Ti metallic-like bonding states placed in the window around the Fermi level. We also found that for “ideal” atomic-clean free-standing GL Tin+1Xn magnetization is likely to take place, when the ground state is AFM, with ferromagnetic ordering of the spin moments on Ti1 atoms within each external Ti sheet, and these opposite external titanium sheets of GL are coupled antiferromagnetically, whereas the internal Ti sheets remain non-magnetic. The possibility to design in future experiments a rich variety of new GL materials with variable electronic and magnetic properties (semiconductors, non-magnetic and magnetic metals) by modulating the type and degree of GL termination by various adatoms or molecules was proposed.

Local Coordination Geometry and Spin State in Novel FeII Complexes with 2,6‐Bis(pyrazol‐3‐yl)pyridine‐Type Ligands as Controlled by Packing Forces: Structural Correlations

A substituted 2,6-bis(pyrazol-3-yl)pyridine (3-bpp) ligand, H(4)L, created to facilitate intermolecular interactions in the solid, has been used to obtain four novel Fe(II) complexes: [Fe(H(4)L)(2)](ClO(4))(2)⋅2 CH(3)NO(2)⋅2 H(2)O, [Fe(H(4)L)(H(2)LBF(2))](BF(4))⋅5 C(3)H(6)O (H(2)LBF(2) is an in situ modified version of H(4)L), [Fe(H(4)L)(2)](ClO(4))(2)⋅2 C(3)H(7)OH and [Fe(H(4)L)(2)](ClO(4))(2)⋅4 C(2)H(5)OH. Changing of spin-inactive components (solvents, anions or distant ligand substituents) causes differences to the coordination geometry of the metal that are key to the magnetic properties. Magnetic measurements show that, contrary to the previously published complex [Fe(H(4)L)(2)](ClO(4))(2)⋅H(2)O⋅2 CH(3)COCH(3), the newly synthesised compounds remain in the high-spin (HS) state at all temperatures (5-300 K). A member of the known family of Fe(II)/3-bpp complexes, [Fe(3-bpp)(2)](ClO(4))(2)⋅1.75 CH(3)COCH(3)⋅1.5 Et(2)O, has also been prepared and characterised structurally. In the bulk, this compound exhibits a gradual and incomplete spin transition near 205 K. The single-crystal structure is consistent with it being HS at 250 K and partially low spin at 90 K. Structural analysis of all these compounds reveals that the exact configuration of intermolecular interactions affects dramatically the local geometry at the metal, which ultimately has a strong influence on the magnetic properties. Along this line, the geometry of Fe(II) in all published 3-bpp compounds of known structure has been examined, both by calculating various distortion indices (Σ, Θ, θ and Φ) and by continuous shape measures (CShMs). The results reveal correlations between some of these parameters and indicate that the distortions from octahedral geometry observed on HS systems are mainly due to strains arising from intermolecular interactions. As previously suggested with other related compounds, we observe here that strongly HS-distorted systems have a larger tendency to remain in that state.

Market power assessment in electricity markets: supply function equilibrium-based model

SUMMARY Because of the oligopoly structure of the electricity markets, the Generation Companies (GenCos) may exert market power by using bidding strategies such as capacity withholding. This brings the market clearing price higher and the quantity generated of the market lower. In this article, capacity withholding in an oligopolistic electricity market in that all GenCos bid in the supply function equilibrium model is analyzed and the capacity withheld index, the capacity distortion index and the price distortion index are formulated. Demand elasticity and forward contracts can significantly affect the GenCos' capacity withholding in the market. The potential ability of market for capacity withholding is measured by the distortion–withheld index proposed in this article. The finding in this article is helpful for market power monitoring and mitigating. A two-settlement market including a forward market and a spot market is used to describe GenCos' strategic forward contracting and spot market competition. Copyright © 2012 John Wiley & Sons, Ltd.

Fiscal and Monetary Policy Interaction: A Simulation-Based Analysis of a Two-Country New Keynesian DSGE Model with Heterogeneous Households

This paper models a fiscal policy that pursues primary balance targets to stabilize the debt-to-GDP ratio in an open and heterogeneous economy where firms combine public and private capital to produce their goods. The model extends the European NAWM presented in Coenen et al. (2008) and Christoffel et al. (2008) by broadening the scope for fiscal policy implementation and allowing for heterogeneity in labor skills. The domestic economy is also assumed to follow a forward looking Taylor-rule consistent with an inflation targeting regime. We correct the NAWM specification of the final-goods price indices, the recursive representation of the wage setting rule, and the wage distortion index. We calibrate the model for Brazil to analyze some implications of monetary and fiscal policy interaction and explore some of the implications of fiscal policy in this class of DSGE models.

Adaptive Fuzzy Control with Supervisory Compensator for Three‐Phase Active Power Filter

An adaptive fuzzy control system with supervisory controller is proposed to improve dynamic performance of three‐phase active power filter (APF). The proposed adaptive fuzzy controller for APF does not build an accurate mathematical model but approximates the nonlinear characteristics of APF using fuzzy approximation. The adaptive law based on the Lyapunov analysis can adaptively adjust the fuzzy rules; therefore the asymptotical stability of the adaptive fuzzy control system can be guaranteed. Simulation results demonstrate that the APF control system has excellent dynamic performance such as small current tracking error, reduced total harmonic distortion (THD) index, strong robustness in the presence of parameters variation, and nonlinear load.

Response Distortion on the NEO PI-R among Candidates Taking the Entrance Examination to the National School of Civil Aviation (ENAC-France)

This study examined the effect of a selection context on the responses to a five factor personality questionnaire (Revised NEO Personality Inventory) of 974 candidates taking the entrance examination to the ENAC (National School of Civil Aviation, France). A response distortion index was calculated using Schinka, Kinder and Kremer (1997)’s method. The results indicate: 1) lower neuroticism scores but higher conscientiousness, agreeableness and extraversion scores compared to standard conditions; 2) a high estimated effect of the response distortion index on all dimensions of the NEO PI-R except for Openness to experience; 3) substantial stability of scores at a one-year interval (N = 117). The paper discusses the conceptual and practical value of this response distortion index for measuring the dimensions of the NEO PI-R in candidates taking the entrance examination to the ENAC.

Extending Tlusty's rate distortion index theorem method to the glycome: Do even ‘low level’ biochemical phenomena require sophisticated cognitive paradigms?

Unlike the universal genetic code and ordered protein folding, direct application of Tlusty's method to the glycome produces a reducto ad absurdum: From the beginning a complicated system of chemical cognition is needed so that external information constrains and tunes what would otherwise be a monstrously large ‘glycan code error network’. Further, the glycan manufacture machinery itself must be regulated by yet other levels of chemical cognition to ensure that what is produced matches what was chosen for production. Application of a rate distortion index theorem/operator method at this second stage appears possible, permitting analytic characterization of the complicated ‘glycan spectra’ associated with cellular interactions and their dynamics. The regulation of ‘low level’ biochemical processes, ranging from gene expression and protein folding through the production of flexible glycan surface signalling fronds, appears to require systems of chemical cognition whose sophistication may rival that of high order neural process.

Application of adaptive noise canceller based on fixed-point algorithm for real-time somatosensory evoked potential monitoring

Objective To efficiently detect somsatosensory evoked potential (SEP) using field programmable gate array (FPGA) real-time system, fixed-point algorithm based adaptive noise canceller (ANC) was designed to improve signal to noise ratio (SNR). Methods With the optimization of important parameters that influence the performance of fixed-point algorithm ANC, the performance was compared to that of floating-point algorithm ANC which was isolated from the effect of quantization error. Results In the simulation study, the outputs of fixed-point-based ANC showed a little higher distortion from real SEP signals than that of floating-point algorithm ANC. In the optimal selection of μ value, fixed-point algorithm ANC could get as good results as floating-point algorithm. Conclusion With appropriate parameter values, fixed-point algorithm ANC is able to improve SNR of SEP as well as that of fixed-point algorithm ANC. Key words: Somsatosensory evoked potential; Fixed-point algorithm; Adaptive noise canceller; Step-size parameter, Distortion index

Assessment of Image Quality Degraded by Tone Rendering Distortion

The tone rendering distortion index (TRDI), which assesses image quality degradation via the distortion within a display of the tone rendering curve (TRC), is introduced and investigated. The effect of the tone rendering distortion upon image quality is different from the effect of data-loss during image compression. The tone rendering distortion changes the lightness, hue and chroma, which results in degradation of an image into irregular patterns depending upon the shape of the distorted TRC. While peak-signal-to-noise ratio (PNSR) and color differences do not represent the image quality very well, the TRDI shows a strong agreement with the human-perceived image quality, despite its simplicity. The method is useful for developing new display technology as well as for refining the image processing within display systems.