Input Phase Research Articles

Fast compensation for arbitrary focusing through scattering media.

We introduce a fast compensation scheme to realize arbitrary focusing after propagation through a scattering sample. Theoretical analysis of the effect of cross terms on multi-point focusing is conducted based on the transmission matrix theory. The results show that the cross-term influence is very significant, which needs to be considered. The Multi-Population Genetic Algorithm is adopted to retrieve the input mode for the suppression of the cross-term effect. In order to realize fast compensation and reduce measurement noise, the off-axis holographic method is used to measure the large transmission matrix, which reduces the number of measurements compared with the traditional method. In the experiment, after retrieving the input phase, we obtain a high-quality focal output, and the signal-to-noise ratio is increased by 13.6 dB.

Using Needs Analysis to Develop Global Education Based ELT Materials in Transactional Speaking Skills

This research focuses in developing global education based ELT materials for transactional speaking skills by using needs analysis. It is aimed to enhance the quality of teaching English at the tertiary level by adapting the students’ needs, the expectations of the lecturers and inputs from graduates to give beneficial contribution towards the students’ future career. This is a development research method by applying IDO’s model, which implements three systematic phases (Input, Development, and Output). The first phase is input phase. It is set up by needs analysis which is carried out by requiring 130 respondents (110 students, 8 lecturers and 12 graduates). Students and graduates are selected randomly while the lecturers are selected by using purposive sampling technique. The data are collected through needs analysis questionnaire and analyzed by using descriptive approach. The second phase, development, attempts to formulate the aim and the objectives based on the information of needs analysis which is used for selecting course contents. In the last phase is output phase. It is administered by compiling the lesson plan and producing the prototype of the global education based ELT materials for speaking skill, specifically transactional speaking skills. The findings of this research have confirmed the importance of using needs analysis as the basis of obtaining information about students’ linguistic and learning needs as well as for developing well-design ELT materials. This contributes to the prototype of an adaptive developed ELT materials comprising one sample of lesson plan and one unit of global education based instructional materials for transactional speaking skills development.

High step‐up SVMC‐based DC/DC converter for offshore wind farms

This study presents a high step-up scalable voltage multiple cell (SVMC)-based DC/DC converters, which have the features of high gain, low and adjustable components stresses and automatic input-current sharing in each input phase. In virtue of the above features, the converter is applicable for the DC collection grids for offshore wind farms. In this study, the converter in terms of working principle and property characteristics are analysed with four input phases and three SVMCs. The converter has also been evaluated in terms of the component stress and voltage conversion ratio against some other converters for high-power occasions. Moreover, a 2.5 MW simulation model and a 1.2 kW prototype were constructed for verification.

BBPD with wide input phase range

Wireline communication circuits often include serialisers/deserialisers using multiphase signals for multiplexing or sampling. From a power efficiency viewpoint, configurations are desired in which a single differential clock at frequency f is distributed to decentralised multiphase generators as opposed to distribution at 2 f with local frequency dividers. A bang-bang phase detector (BBPD) is presented for such a multiphase generator operated from 4 to 16 GHz. Owing to the 2-octave frequency range, a wide input phase range is required for which the BBPD may not generate false locks. This is achieved by an implementation in which down pulses at the output of a fully symmetrical set/reset latch are stretched via pulse-width extension circuitries. A sampling pulse generated from one of the input phases can then easily capture the extended down pulses across a wide input phase range to unambiguously indicate phase leading or phase lagging to the control logic of the multiphase generator. The proposed circuitry has been implemented in a 7 nm CMOS technology. A comparison to alternative BBPD approaches implemented in the same technology shows that the proposed architecture outperforms them in terms of achievable input phase range.

Numerical Simulations of Realistic Lead Trajectories and an Experimental Verification Support the Efficacy of Parallel Radiofrequency Transmission to Reduce Heating of Deep Brain Stimulation Implants during MRI

Patients with deep brain stimulation (DBS) implants may be subject to heating during MRI due to interaction with excitatory radiofrequency (RF) fields. Parallel RF transmit (pTx) has been proposed to minimize such RF-induced heating in preliminary proof-of-concept studies. The present work evaluates the efficacy of pTx technique on realistic lead trajectories obtained from nine DBS patients. Electromagnetic simulations were performed using 4- and 8-element pTx coils compared with a standard birdcage coil excitation using patient models and lead trajectories obtained by segmentation of computed tomography data. Numerical optimization was performed to minimize local specific absorption rate (SAR) surrounding the implant tip while maintaining spatial homogeneity of the transmitted RF magnetic field (B1+), by varying the input amplitude and phase for each coil element. Local SAR was significantly reduced at the lead tip with both 4-element and 8-element pTx (median decrease of 94% and 97%, respectively), whereas the median coefficient of spatial variation of B1+ inhomogeneity was moderately increased (30% for 4-element pTx and 20% for 8-element pTx) compared to that of the birdcage coil (17%). Furthermore, the efficacy of optimized 4-element pTx was verified experimentally by imaging a head phantom that included a wire implanted to approximate the worst-case lead trajectory for localized heating, based on the simulations. Negligible temperature elevation was observed at the lead tip, with reasonable image uniformity in the surrounding region. From this experiment and the simulations based on nine DBS patient models, optimized pTx provides a robust approach to minimizing local SAR with respect to lead trajectory.

Establishing mercury-free medical facilities: a Malaysian case study.

Mercury is widely used in medical and healthcare facilities as dental amalgam, mercury-added medical devices, thiomersal-containing vaccines, laboratory analysis and for other general applications despite the hazards. Various agencies consistently promote mercury-free medical facilities through mercury-free alternatives and better management practices, which are in line with the Minamata Convention on Mercury that aims to protect human health and environment from anthropogenic mercury release. The paper aims to discuss these issues. The authors conducted a gap analysis on recommended practices gathered from the literature and current practices gathered through semi-structured interviews with Malaysian medical personnel. A life cycle approach was adopted covering mercury use: input, storage, handling, accident, waste disposal and governance phases. The authors found that there are significant gaps between recommended and current mercury management practices. Analysis indicates improper mercury management as the main contributor to these gaps. The authors found from recommended practices that core components needing improvement include: mercury management action plan, mercury use identification team, purchasing policy, proper guidelines and monitoring systems. This study helps us to understand mercury management practices and suggests essential steps to establish a mercury-free medical facility. This study explored the gaps between recommended and current mercury management practices in a medical facility and contributes to the Minamata Convention on Mercury aspirations.

An Alternative Carrier-Based Implementation of Space Vector Modulation to Eliminate Common Mode Voltage in a Multilevel Matrix Converter

The main aim of the paper is to find a control method for a multilevel matrix converter (MMC) that enables the elimination of common mode voltage (CMV). The method discussed in the paper is based on a selection of converter configurations and the instantaneous output voltages of MMC represented by rotating space vectors. The choice of appropriate configurations is realized by the use of space vector modulation (SVM), with the application of Venturini modulation functions. A multilevel matrix converter, which utilizes a multilevel structure in a traditional matrix converter (MC), can achieve an improved output voltage waveform quality, compared with the output voltage of MC. The carrier-based implementation of SVM is presented in this paper. The carrier-based implementation of SVM avoids any trigonometric and division operations, which could be required in a general space vector approach to the SVM method. With use of the proposed control method, a part of the high-frequency output voltage distortion components is eliminated. The application of the presented modulation method eliminates the CMV in MMC what is presented in the paper. Additionally, the possibility to control the phase shift between the appropriate input and output phase voltages is obtained by the presented control strategy. The results of the simulation and experiment confirm the utility of the proposed modulation method.

Математическая модель трехфазного корректора мощности с улучшенным коэффициентом полезного действия

The power circuit of a new three-phase power corrector having reduced power losses is considered. The power circuit mathematical model and the control system operation principle are described. A specific feature of the single-loop control of the device active power with the input phase current synchronized with the input phase and with stabilizing the output DC voltage is shown. The results from computer simulation of the device prototype designed for the 400 V 50 Hz input three-phase voltage, for the 800 V DC output voltage and 70 kW output power are presented. The article is of interest for designers of three-phase power correctors with high efficiency and a reliable control system.

A modernistic PLL based on feed forward frequency estimator with selective harmonic pre filter for grid imperfection

This paper describes a synchronisation technique to track phase and frequency of input signal under abnormal grid condition like frequency variation. Proposed control topology consist of a conventional synchronous reference frame phase locked loop (SRF PLL) type-2 along with a feed forward frequency estimator loop with selective harmonic filtering technique. It eliminates phase and frequency error under wide frequency deviation. Phase error is fed into proportional integral regulator which reduces it to zero. It is observed that faster and better dynamic performance is achieved by frequency estimator with higher stability margin. The stability is evaluated by bode plot. An estimated frequency is smooth and close to fundamental frequency as it uses the information from all three phase to estimate a single value for frequency. The feed forward action is implemented with pre filtering stage to improve dynamic performance of system. Simulation results are presented to validate effectiveness of proposed technique.

Интерференция спиновых волн в решетках из микроволноводов на основе пленок железо-иттриевого граната

AbstractEffects of propagation and interference of spin waves in an eight-port magnonic structure in the form of a 2 × 2 array of microwaveguides based on yttrium-iron garnet films with microantennas placed at the waveguide ends are studied experimentally and numerically. It is shown that conditions for a constructive and destructive interference of spin waves, which is necessary for creating spin-wave logic devices, can be implemented at output transducers by changing the phase of input signals.

Three phase PWM converter using PI and fuzzy with hysteresis current controller

The research work presents hysteresis current controlled three-phase PWM converter. The switching control is applied on three-phase bi-directional switches, to attain sinusoidal input current at unity power factor and constant output voltage. The dc-link voltage is controlled by outer loop fuzzy controller and PI controller. The converter can be used for regeneration or bi-directional power flow. The converter is especially suitable for mid to low power application (i.e., 5-15 kW).The bi-directional switches operate at low frequency, crossover zero voltage (at turn-on) and conduct for 1/12th of line voltage cycle. The THD analysis of the controlled input phase current shows significant reduction in the THD as compared to the uncontrolled input phase current. The dc-link voltage follows the reference value.

Three phase PWM converter using PI and fuzzy with hysteresis current controller

The research work presents hysteresis current controlled three-phase PWM converter. The switching control is applied on three-phase bi-directional switches, to attain sinusoidal input current at unity power factor and constant output voltage. The dc-link voltage is controlled by outer loop fuzzy controller and PI controller. The converter can be used for regeneration or bi-directional power flow. The converter is especially suitable for mid to low power application (i.e., 5-15 kW).The bi-directional switches operate at low frequency, crossover zero voltage (at turn-on) and conduct for 1/12th of line voltage cycle. The THD analysis of the controlled input phase current shows significant reduction in the THD as compared to the uncontrolled input phase current. The dc-link voltage follows the reference value.

THE FORMULATION OF PRODUCTION HOUSE STRATEGY AND COMPETITIVENESS

The aim of this study related community development is a lesson learn that to know how the internal factors and external factors impacted on Production House management. PT. Putra Kusuma Pictures Indonesia which provides services to in-house productions, by using IFE Matrix, EFE Matrix and CPM Matrix for researching Production house’ business strategy in the input phase, which will then be followed by the matching stage which uses SWOT Matrix, IE Matrix and Grand Strategy Matrix. The alternative analysis for Production house was completed using the Blue Ocean Strategy, which has surpassed the Four Action Framework (Eliminate-Reduce-Raise-Create), and the three good strategies which consist of focus, divergence and a good motto. Techniques used in data collection involve direct interview with the head of the company. This study in competitive strategy shows that the best strategy that should be applied by the company is through product development, while the alternative strategy that could be developed as a leading product is through social culture themed films.

A Free-Space Interferometer for Phase-Delay Measurements in Integrated Optical Devices in Degenerate Pump-and-Probe Experiments

The authors report on a free-space interferometer for simultaneous phase and transmittance measurements of an optical signal in an integrated photonic circuit during degenerate pump-and-probe experiments. Differentiation of the weak probe signal from the strong pump relies on a lock-in amplifier. The interferometer shows high flexibility in terms of operating wavelengths, tested devices, and optical powers; it works with any integrated optical device provided with optical input–output channels; it can operate both with high input power (up to 100 mW at the sample input port) and low output power ( $ at the detection stage). Measuring both the transmittance and the phase of the optical signal allows using the phasor representation in the analysis. A dynamic operating mode allows to perform power and/or wavelength scan of the input signal, obtaining transmittance and phase spectra of the tested device. Remote control of the system and insulation from the external environment brings to more stable operating conditions. Characterization of the system properties with photonic-integrated structures (waveguide and ring resonator) is reported, with observed phase stability as high as 0.25°/min and average phase noise below 1°.

2-D Phase Unwrapping Using Minimum Infinity-Norm

2-D phase unwrapping (PU) is a critical image processing step in many interferometric measurement technologies. To avoid the discontinuous phase gradient error spreading from the noisy region to the high-quality region of input interferogram, a skillful PU method should keep the congruency between input phase fringes and rewrapped phase fringes of the PU result as much as possible. However, traditional PU methods often fail in case input interferogram contains “bad” regions, in which the phase information should not be trusted. Under this condition, it is desired that the PU method instinctively keeps the fringe-congruency in the high-quality area and reasonably modifies the input phase fringes in the low quality area. In other words, the PU method with an extra adaptive filtering function would be preferred in practice. Based on this perspective, a novel minimum infinity-norm-based PU method, referred to MIN, is proposed in this letter. Both theoretical analysis and experiments demonstrate that the MIN method is an effective PU method.

Second order compensation scheme for Haven’s technique to annul amplitude and phase mismatch for quadrature circuits

This paper, elucidates a second order Haven’s technique for generation of a pair of sinusoids in perfect quadrature phase. The effects of input amplitude mismatch on output phase mismatch and vice versa have been expounded. The proposed second order Haven’s Technique essentially estimates and corrects the amplitude and phase mismatches. This method aids in correcting amplitude and phase mismatch of any arbitrary magnitude. The developed technique is valid for mismatches occurring in both narrow band as well as wideband. Separate closed form expressions for compensation of both input amplitude and input phase mismatches have been derived. This study facilitates to determine the magnitude of phase angle error for a given amplitude mismatch and vice versa. Error plots for Haven’s technique have been generated and analysed. It is depicted that for every 1% of amplitude mismatch the phase mismatch increases by 0.6 degrees. The developed technique is modelled and simulated using available EDA tool for narrow band as well as wideband signals. The simulation results of the proposed technique confirm that for both narrow band and wideband signals, the input amplitude as well as phase mismatches are annulled completely. The developed Haven’s technique can find potential utility in implementation of Image Reject Mixer Architectures and Quadrature Oscillators for generation of quadrature waveforms.

Ultracompact ultrafast-switching-speed all-optical 4 × 2 encoder based on photonic crystal

A novel two-dimensional photonic-crystal-based all-optical encoder was designed, tested, and optimized. The structure is built on a linear square-lattice photonic crystal platform. An ultracompact, simple design occupying an area of only 128.52 μm2 is constructed, 50 % smaller than the smallest design known to date. Ultrafast switching speed with the lowest known delay time is achieved. The proposed design consists of one ring resonator with cylindrical silicon rods suspended in air. No auxiliary or bias input is required for its operation. The proposed platform is not sensitive to the applied input phase shift. Finite-difference time-domain and plane-wave expansion methods were used to analyze the structure and optimize the radius of the rods at 1.525 µm, with radius of the inner rods of 0.19a, for successful operation, resulting in ultrafast switching speed of 10 THz and shorter delay time reaching 0.1 ps. This maximum switching speed is two times faster than recent literature reports. The contrast ratio is calculated to reach an acceptable record of 7.1138 dB. The trade-off between the switching speed and contrast ratio was also examined.

A compact Doherty power amplifier for massive multi‐input multi‐output applications

AbstractA Doherty power amplifier composed of GaAs IPDs (Lange coupler and Doherty combiner) and GaN MMICs (carrier amplifier and peaking amplifier) is presented for 5G massive multi‐input multi‐output (MIMO). No input phase compensation circuit and no output offset lines were used for a compact design and the assembled Doherty power amplifier is as small as 6.6 mm × 3.6 mm with a saturation output power of 46 dBm. The asymmetric Doherty power amplifier exhibits a gain greater than 27.8 dB, PAE greater than 39.8% at average output power of 38 dBm, and ACLR less than −27.7 dBc using a 20 MHz LTE signal with 7.5 dB PAR across 3.6‐3.8 GHz.

Feasibility of 4DCBCT-based proton dose calculation: An ex vivo porcine lung phantom study

Inter-fractional variations of breathing pattern and patient anatomy introduce dose uncertainties in proton therapy. One approach to monitor these variations is to utilize the cone-beam computed tomography (CT, CBCT) scans routinely taken for patient positioning, reconstruct them as 4DCBCTs, and generate ‘virtual CTs’ (vCTs), combining the accurate CT numbers of the diagnostic 4DCT and the geometry of the daily 4DCBCT by using deformable image registration (DIR). In this study different algorithms for 4DCBCT reconstruction and DIR were evaluated.For this purpose, CBCT scans of a moving ex vivo porcine lung phantom with 663 and 2350 projections respectively were acquired, accompanied by an additional 4DCT as reference. The CBCT projections were sorted in 10 phase bins with the Amsterdam-shroud method and reconstructed phase-by-phase using first a FDK reconstruction from the Reconstruction Toolkit (RTK) and again an iterative reconstruction algorithm implemented in the Gadgetron Toolkit. The resulting 4DCBCTs were corrected by DIR of the corresponding 4DCT phases, using both a morphons algorithm from REGGUI and a b-spline deformation from Plastimatch. The resulting 4DvCTs were compared to the 4DCT by visual inspection and by calculating water equivalent thickness (WET) maps from the phantom's surface to the distal edge of a target from various angles. The optimized procedure was successfully repeated with mismatched input phases and on a clinical patient dataset. Proton treatment plans were simulated on the 4DvCTs and the dose distributions compared to the reference based on the 4DCT via gamma pass rate analysis.A combination of iterative reconstruction and morphons DIR yielded the most accurate 4DvCTs, with median WET differences under 2mm and 3%/3mm gamma pass rates per phase between 89% and 99%.These results suggest that image correction of iteratively reconstructed 4DCBCTs with a morphons DIR of the planning CT may yield sufficiently accurate 4DvCTs for daily time resolved proton dose calculations.

Calibration of Phase Shifters on Basis of Vector-Sum Signals

Attenuators and phase shifters which are the circuits for amplitude-phase distribution control are key elements of antenna arrays. Dispersion of technology parameters results in deviation of the characteristics of integral circuits from rated values that requires application of the techniques for this effect compensation. In this paper there are considered the methods for development and calibration of the circuits in a basis of vector-sum signals allowing to modify both amplitude and phase of input high-frequency signal. It is proposed the method of calibration on a basis of interpolation of measured dependences of absolute value and phase of transfer factor on controlling voltage. Application of proposed method for calibration of vector phase shifter with operating frequency band 2.8–3.2 GHz fabricated with 0.18 mm CMOS allows to provide mean square deviation of phase error is not greater than 0.9°. At that amount of required measurements is 20 times decreased comparing known approach on a basis of measurement of all amplitude-phase states.