Value Of Phase Shift Research Articles

Повышение коммутационной устойчивости коллекторных тяговых электродвигателей электровозов за счет снижения пульсации тока возбуждения

Statistics of equipment failures of electric locomotives assigned to the operational depots of the East Siberian Traction Directorate shows that about 25% of the total number of equipment failures of electric locomotives are traction electric motors (TEM); most often the collector-brush apparatus fails. The main reason is the problem of TEM low switching stability, associated with the increase in unbalanced electromotive forces (EMF) due to non-sinusoidal values of EMF variables and large phase shifts between their main harmonics. To clarify the processes related to EMF variable components, a vector diagram of their main harmonics is constructed, which determines the qualitative nature of the phenomena. It is revealed that the presence of eddy currents in the massive elements of the TEM magnetic core and the resulting armature reaction lead to significant displacement of the vector of the switching EMF, which forms the unbalanced EMF, causing violation of the TEM switching stability. In this regard, an improved system for attenuating the excitation of traction motors based on IGBT transistors is proposed, which reduces pulsation of the excitation current by at least 80% increasing the TEM life resource.

ЗАКОНОМІРНОСТІ ФОРМУВАННЯ ШТУЧНОЇ ОПТИЧНОЇ АНІЗОТРОПІЇ ПОЛІМЕТИЛМЕТАКРИЛАТА ДЛЯ ПОЛЯРИМЕТРИЧНОГО ВИКОРИСТАННЯ

General principles of wav plate manufacturing are considered. The possibility of the formation of synthetic optical anisotropy of polymethyl methacrylate (PMMA) by the method of its uniaxial stretching is investigated. The most promising is a method for manufacturing waveplates, which includes the stage of controlled stretching of the polymer material to the required phase shift value, which would generally exclude the stage of machining the plates. The general orderliness of the molecules in the polymer resulting from stretching (orientation) leads to the oriented state of the polymer, and, consequently, to the general anisotropy of the physical and optical properties. In this state, a clearly pronounced uniaxial orientation of polymer chains is observed. As a result, chain macromolecules, randomly (statistically) oriented in the initial PMMA, acquire orientation under the influence of an external directed tensile force. The anisotropy of the optical properties of uniaxially stretched PMMA is manifested in the fact that it has different refractive indices for light polarized parallel to the direction of stretching (orientation) and in the perpendicular direction (birefringence). The regularities of the formation of the synthetic optical anisotropy of PMMA have been studied. The dependences of the birefringence values of uniaxially stretched PMMA on the initial sheet thickness, stretching temperature, and degree of stretching have been measured. It has been shown that the value of birefringence is directly proportional to the thickness of the initial sheet and the degree of stretching and inversely proportional to the stretching temperature. The spectral dependence of the birefringence value is measured. Achromatic and superachromatic waveplates were made from uniaxially stretched PMMA. The spectral characteristics of the phase shift of the manufactured waveplates are given. The availability of the starting material, the technological simplicity of the formation of the initial components for waveplates, as well as the possibility of manufacturing waveplates of large dimensions and high quality, make polymethyl methacrylate with artificially induced anisotropy a promising material for the manufacture of achromatic and superachromatic waveplates.

Evaluation of endothelial function, of elasticity of vessel wall and their influence on one-year prognosis of patients with myocardial infarction with obstructive and non-obstructive coronary arteries

Aim. To carry out comparative analysis of the state of the endothelial function (EF), elasticity of the vessel wall and their influence on one-year prognosis of patients with myocardial infarction (MI) with obstructive and non-obstructive coronary arteries (CA).
 Materials and Methods. In the first stage, 206 patients were selected diagnosed with MI, of them 103 patients with MI with non-obstructive CA (MINOCA) according to the results of coronaroangiography, and 103 patients with MI with obstructive CA (MIOCA). Using the method of random numbers, 59 patients were selected (34 patients of the first group and 25 of the second group), in whom EF and elastic properties of the arterial wall were evaluated. Patients of both groups were initially comparable in age, gender, clinical and anamneustic characteristics, and also in frequency of application of the main groups of medical drugs that influence prognosis. One-year prognosis of the two groups of patients was studied depending on the presence/absence of functional and morphological alterations of the vessel wall.
 Results. In evaluation of EF in patients MINOCA, the occlusion index by amplitude (OIA) below threshold values was recorded in 22 of 34 (64.7%) cases of MINOCA and in 22 of 25 (88.0%, р0.05) cases of MIOCA. Here, the average values of OIA were 1.7 (1.5; 2.3) and 1.4 (1.2; 1.8), respectively (р0.05). The values of phase shifts between the channels below the norm were equally frequent in two groups (88.2 and 88.0%, р0.05), and comparison of the average values of this parameter did not show any statistically significant difference. The calculated augmentation index normalized to the pulse rate 75 beats per minute (AIp75), in the study groups was 12.5 (9.9; 17.9) and 18.8 (12.9; 20.8), respectively (р0.05). Reduction of the elasticity of the vessel wall in the group with MINOCA was noted in 82.4% of patients, in the group MIOCA in 100% of cases (р0.05). No statistically significant differences were found in the frequency of cardiovascular events between the groups during a year (р0.05).
 Conclusion. Functional alterations of the vessel wall (endothelial dysfunction and reduction of elasticity of the vessel wall) in patients with MINOCA were recorded almost in 2/3 of cases, however, their incidence in MIOCA was still higher (88.0%). The one-year prognosis in the study groups MINOCA and MIOCA showed no differences.

Switchable and Flexible Comb Filter/Interleaver Based on Ring-Resonators With Tunable Couplers

We demonstrate a switchable and flexible comb filter/interleaver based on ring-resonator (RR) in which the directional couplers are replaced by tunable couplers. The tunable coupler is composed of an even-arm-length Mach-Zehnder interferometer (MZI) with a micro-heater embedded in one of the arms. For the sake of discussion, we convert the heating power of the micro-heater into a pure phase shift value independent of the waveguide material and size. By changing the phase shift value, the filter can be switched between comb filter and interleaver. Meanwhile, the insertion loss ( IL ), full width at half maximum ( FWHM ), extinction ratio ( ER ), and the shape of the response spectrum can also be reconfigured. The switchable and flexible comb filter/interleaver may provide a potential application in dense wavelength division multiplexing (DWDM) optical communication systems.

On the performance of electronically tunable fractional-order oscillator using grounded resonator concept

Recent works target the design of fractional-order oscillators. However, some features of such circuits are not frequently considered in the design despite their importance in practice. This work provides an analysis of the fractional-order oscillator design procedure with a simple but still beneficial electronic tuning feature. The presented design allows us to keep a stable and non-standard phase shift between produced harmonic signals while tuning the oscillation frequency of the oscillator. Grounded fractional-order elements and modern commercially available active elements are implemented in the designed topology. Time domain results as well as spectral analysis are obtained from experimental measurements. Moreover, several values of non-standard phase shifts are tested. The experimental verification targets the low-frequency bandwidth from several hundreds Hz up to several kHz because of possible application areas in these bands (audio) and due to a very low-impedance character of the used RC constant phase elements as approximants of fractional-order capacitors.

$$\boldsymbol{p}\boldsymbol{-}^{\mathbf{12}}$$C and $$\boldsymbol{p}\boldsymbol{-}\boldsymbol{d}$$ Scattering within the Separable Model of Interaction

Differential equation approach is adapted to construct exact analytical expressions for the regular, Jost, and physical states for Hulthen plus separable nonlocal potential. The Jost function and the Fredholm determinant for physical boundary condition are exploited to compute scattering phase shifts for proton–deuteron and proton–carbon systems within this two-body model of interaction. Excellent agreement in phase shift values with other sophisticated calculations is obtained.

Phase-shifted PT -symmetric periodic structures

We report the spectral features of a phase-shifted parity and time ($\mathcal{PT}$)-symmetric fiber Bragg grating (PPTFBG) and demonstrate its functionality as a demultiplexer in the unbroken $\mathcal{PT}$-symmetric regime. The length of the proposed system is of the order of millimeters and the lasing spectra in the broken $\mathcal{PT}$-symmetric regime can be easily tuned in terms of intensity, bandwidth and wavelength by varying the magnitude of the phase shift in the middle of the structure. Surprisingly, the multi-modal lasing spectra are suppressed by virtue of judiciously selected phase and the gain-loss value. Also, it is possible to obtain sidelobe-less spectra in the broken $\mathcal{PT}$-symmetric regime, without a need for an apodization profile, which is a traditional way to tame the unwanted sidelobes. The system is found to show narrow band single-mode lasing behavior for a wide range of phase shift values for given values of gain and loss. Moreover, we report the intensity tunable reflection and transmission characteristics in the unbroken regime via variation in gain and loss. At the exceptional point, the system shows unidirectional wave transport phenomenon independent of the presence of phase shift in the middle of the grating. For the right light incidence direction, the system exhibits zero reflection wavelengths within the stopband at the exceptional point. We also investigate the role of multiple phase shifts placed at fixed locations along the length of the FBG and the variations in the spectra when the phase shift and gain-loss values are tuned. In the broken $\mathcal{PT}$-symmetric regime, the presence of multiple phase shifts aids in controlling the number of reflectivity peaks besides controlling their magnitude.

Design and simulation of an analog beamforming phased array antenna

In this paper, a phased array antenna is designed and simulated. The antenna array consists of four circularly polarized slotted waveguide elements. The antenna array is simulated using CST MWS. The simulation results for the proposed antenna array at different values of progressive phase shift demonstrate that the S‒parameters for all four ports are less than ‒10 dB over at least 2% bandwidth, the simulated maximum gain is 13.95 dB, the simulated beamwidth can be 19˚ or narrower based on the value of the progressive phase shift. , the range of frequencies over which the simulated Axial Ratio (AR) is below 3 dB is not fixed and varied according to the selected progressive phase shift. The proposed four-element RF front-end is simulated using Advanced Design System (ADS) at operating frequency of 9.6 GHz. The obtained simulation results by ADS indicate the feasibility of implementing the proposed RF-front end for feeding the antenna array to realize analog beamforming.

Generalized characteristics of expanded sector beams formed by phased antenna arrays obtained by scaling phase distributions

This paper considers specific features of the phase synthesis of expanded sector beams formed by phased antenna arrays by the method of fan partial diagrams. Partial radiation patterns are formed by pairs of adjacent emitters. The synthesis results have the property of scaling, which allows many expansion options to be obtained on the basis of one expansion option. This is achieved by multiplying the phase shift values of the signals from all emitters by the same value. It is shown that, when the beam expands along the sum channel, a radiation pattern with an extended angular distance between the maxima is formed in the difference channel. An analysis of the initial sections of the difference radiation patterns in the formation of expanded beams of the sum radiation pattern was conducted. The behaviour of the generalized characteristics of expanded beams across the range of expansion coefficients was analysed. The conclusion was made about the possibility of timely and predictable control of the width of the difference radiation pattern of a phased antenna array

Demonstration and suppression of respiration-related artifacts in Bloch-Siegert shift-based B1+ maps of the human brain.

Respiration-induced movement of the chest wall and internal organs causes temporal B0 variations extending throughout the brain. This study demonstrates that these variations can cause significant artifacts in maps obtained at 7 T with the Bloch-Siegert shift (BSS) mapping technique. To suppress these artifacts, a navigator correction scheme was proposed. Two sets of experiments were performed. In the first set of experiments, phase shifts induced by respiration-related B0 variations were assessed for five subjects at 7 T by using a gradient echo (GRE) sequence without phase-encoding. In the second set of experiments, maps were acquired using a GRE-based BSS pulse sequence with navigator echoes. For this set, the measurements were consecutively repeated 16 times for the same imaging slice. These measurements were averaged to obtain the reference map. Due to the periodicity of respiration-related phase shifts, their effect on the reference map was assumed to be negligible through averaging. The individual maps of the 16 repetitions were calculated with and without using the proposed navigator scheme. These maps were compared with the reference map. The peak-to-peak value of respiration-related phase shifts varied between subjects. Without navigator correction, the interquartile range of percentage error in varied between 4.0% and 8.3% among subjects. When the proposed navigator scheme was used, these numbers were reduced to 2.5% and 2.9%, indicating an improvement in the precision of GRE-based BSS mapping at high magnetic fields.

Fast and accurate tilt-shift-immune phase-shifting algorithm based on self-adaptive selection of interferogram subblocks and principal component analysis.

To eliminate the effect of tilt-shift error on the accuracy of phase-shifting interferometry (PSI), a fast and accurate tilt-shift-immune phase-shifting algorithm based on the self-adaptive selection of interferogram subblocks and principal component analysis (SSPCA) is proposed. First, each interferogram is divided into several subblocks, and principal component analysis and the least-squares method (LSM) are applied to obtain the phase-shift value of each subblock. Next, according to the correlation coefficients between each phase-shift curve, valid and invalid subblocks can be distinguished. Finally, all phase-shift values of the valid subblocks are used to fit the tilt phase-shift plane, and phase results can be obtained using the LSM. Simulations indicate that the accuracy of SSPCA can reach 0.03 rad both for small (1 rad) and large (${2}\pi $2π rad) tilt amplitudes, and it takes only one-tenth or less of the processing time of iterative algorithms. Experiments proved that SSPCA can be applied even without a precision phase shifter and thus provides a low-cost approach for PSI with both high precision and speed.

Suppressing ripple distortions and spurious pistons in phase-shifting interferometry.

In this paper, we present new phase-shifting algorithms (PSAs) that suppress the ripple distortions and spurious pistons in phase-shifting interferometry. These phase errors arise when non-uniform phase-shifting interferograms are processed with PSAs that assume uniform phase shifts. By modeling the non-uniform phase shifts as a polynomial of the unperturbed phase-shift value $\omega_0$ω0, we show that the conditions for eliminating the ripple distortion and the spurious piston are associated with the $m$mth derivative of the PSA's frequency transfer function (FTF). Thus, we propose an approach to design robust algorithms based on the FTF formalism and we present four ready-to-apply PSAs formulas. Finally, our conclusions are supported by computer simulations.

Differential phase shifters based on Schiffman type‐C and type‐F networks with wide phase shift range

This study proposes a class of differential phase shifters based on the Schiffman type-C and type-F networks with wide phase shift range. After the phase and bandwidth properties of these two distinct networks are numerically analyzed, two unique advantages of wide phase shift range and wide phase shift bandwidth are revealed. Next, the optimal design parameters for different phase shift values up to 405° are presented to allow for a quick design process. To verify the proposed approach, a 180° differential phase shifter is designed, fabricated and measured. Good performance is achieved with an impedance ratio of 1.959 and 3.7° phase deviation over a phase shift bandwidth of 61%.

Wideband Phase Shifters With Miniaturized Size on Multiple Series and Shunt Resonators: Proposal and Synthetic Design

In this article, a new class of wideband phase shifters with very compact size, large phase shift value, low insertion loss (IL), and low cost are presented and developed. The proposed phase shifter consists of N series and shunt resonators, which can achieve the magnitude and phase shift bandwidth of more than 120% thanks to N transmission poles. Besides the wideband property, the proposed phase shifter is able to achieve a small size of nearly 1/10 guided wavelength (λg), which has a size reduction of more than 90% as compared with conventional wideband phase shifters on printed circuit board (PCB). Meanwhile, insertion phases for the both series and shunt resonators are zero at their resonant frequencies; thus, the length of reference line can be also greatly reduced. What is more, a detailed synthesis method with closed-form equations is presented and employed to determine all circuit parameters of the proposed phase shifter with the specified in-band return loss (RL), phase shift value AΦ, and resonator number N. To validate the design concept, three design examples of 90° and 180° phase shifters on N = 3 and N = 5 are synthesized and tested. Theoretical, simulated, and measured results are in a fairly close agreement. In particular, the proposed phase shifters feature very low IL. The measured maximum in-band IL is only 0.38 dB for N = 3 (AΦ = 90°) and 0.50 dB for N = 5 (AΦ = 180°).

. Analysis of spectral components for phase method with multiplies frequencies for use in communication lines

In article feature usage of the phase method with multiplies frequencies for determining damage in wiring line when applying constraints imposed properties of the object of study – conductor line. Found that lower frequency boundary is due to the stabilization parameter of line, upper boundary – by upper allowed frequency for signal passing. Determined that the total received signal will consist of signal reflections that have different rotational speed of reflection angle. The analysing signal must always be within the allowable frequency. This leads to the fact that the reflection signals get additional value of phase shift as initial angle. It is established that the usage of different methods of digital spectral analysis require to determine the signal components with unknown values of the initial phase shift , as well as with noninteger number of periods that fall within the window of analysis. Figs.: 3. Refs.: 8 titles. Keywords: total signal; analysis window; initial phase angle; display angle; spectral analysis.

Schiffman Phase Shifters With Wide Phase Shift Range Under Operation of First and Second Phase Periods in a Coupled Line

In this article, a class of improved Schiffman phase shifters with two C-section coupled lines separately operating in the first and second phase periods is presented and analyzed. Theoretical model and closed-form synthesis formulae are utilized to analyze the phase performances of the proposed phase shifters, which reveals significant differences compared to the phase shifters solely operating in the first or second phase period. Compared to the traditional counterparts, the proposed phase shifters can achieve a larger phase shift value and a wider phase shift range at the same impedance ratio. Moreover, under the same impedance ratio, the phase shifter can obtain wider phase shift bandwidth. These features are believed to be very useful in the limitedly realizable coupling strength for a wide phase shift range case. Finally, two sets of comparative experiments, including the operations in the first phase period, second phase period, and the proposed type, are designed and fabricated to validate the proposed approach. The simulated and measured results agree well with the theory and achieve a 33.6% (36.7%) increase in phase shift bandwidth when the phase shift value is 90° (150°) under the impedance ratio of 1.5822 (2.0312).

High-Performance Anticorrosive Polyester Coatings on Mild Steel in Mixed Acid Mixtures Environments

Mild steel sample was selected from acid storage tanks used in industry as a substrate, and two advanced technological polymeric resin-based coatings were developed, designated as LAM-P resin based which is LAM-P/FR coating and LAM-V resin based which is LAM-V/FR coating. These coatings were applied over steel samples by using the hand lay-up process. FTIR test was conducted to confirm complete curing, and SEM analyses were used to investigate surface morphology. A series of electrochemical tests were performed in acidic environment (mixed acid solution 56% H2SO4 + 26% HNO3 + 18% H2O by weight). The results indicated successful development of LAM-P/FR and LAM-V/FR to obtain coatings with desirable characteristics such as anticorrosion, thickness, adhesion, stability, charge store and more resistance to acidic environments. EIS data for mixed acid storage media demonstrated that LAM-V/FR coating has higher strength in mixed acid solution, higher values of impedance and phase shift, higher value of Rpore, and low value of Cc; corrosion rate percentage reduction is 96% of LAM-P/FR and 99.96% of LAM-V/FR compared to bare mild steel sample. The outcomes of this study can lead to assist in design guidelines for anticorrosive coating for industrial applications.

Optimal phase estimation with photon-number difference measurement using twin-Fock states of light**Project supported by the National Natural Science Foundation of China (Grant Nos. 91636108, 11775190, and 11774024), Science Foundation of Zhejiang Sci-Tech University, China (Grant No. 18062145-Y), Open Foundation of Key Laboratory of Optical Field Manipulation of Zhejiang Province, China (Grant No. ZJOFM-2019-002), and Science Challenge Project, China (Grant No.

Quantum phase measurement with multiphoton twin-Fock states has been shown to be optimal for detecting equal numbers of photons at the output ports of a Mach–Zehnder interferometer (i.e., the so-called single-fringe detection), since the phase sensitivity can saturate the quantum Cramér–Rao lower bound at certain values of phase shift. Here we report a further step to achieve a global phase estimation at the Heisenberg limit by detecting the particle-number difference (i.e., the measurement). We show the role of experimental imperfections on the ultimate estimation precision with the six-photon twin-Fock state of light. Our results show that both the precision and the sensing region of the measurement are better than those of the single-fringe detection, due to combined contributions of the measurement outcomes. We numerically simulate the phase estimation protocol using an asymptotically unbiased maximum likelihood estimator.

Image Reconstruction from Digital Holograms Obtained by Specifying Random Phase Shifts

A new method for image reconstruction from a series of digital holograms obtained by stepped phase shift with random values of phase shifts is under consideration. It is shown that images reconstructed from a digital hologram in a Fresnel region at a distance matching a distance from the object to the hologram consist of two parts, one of which is a clear image of the object and the other one being formed by incorrect phase shifts consists of a set of defocused images of the object. At the same time, the quality of the reconstructed image is slightly reduced. This effect eliminates the necessity to use precision systems for setting the phase shift and significantly reduces requirements for stabilizing the optical device.

Photonic Displays in Augmented Reality

Our quantum harmonics electronic system will be based on jump-resonance phenomena of nonlinear feedback control systems of any order. The nonlinearities are those whose outputs are single-valued odd functions of the inputs and are independent of frequencies of the photonic inputs. The general conditions under which jump-resonance occurs will be given and the system with saturation nonlinearity will be analyzed. The essential objective is to define the contours on the complex plane for the constant values of system variables, e.g., input amplitude, amplitude ratio, and phase shift.