Input Phase Research Articles

Seeing the community's perspective through multiple emic and etic vistas.

Health impact assessment (HIA) researchers regularly use community input in their investigations to help them better understand local health issues. Community data is commonly associated with the lived experiences of local impacted residents known as 'emic' data. It is becoming more common practice for HIA researchers to access outside experts and stakeholders ('etic' data) during the community input phase of their investigations. Utilizing published international HIA data, I look at who HIA researchers invite when they seek to get 'community input' in their HIA investigations. The HIA database was generated from an internet investigation of published HIAs (in English) from 1999 to 2011 and focused particularly on single authored assessments that were conducted by governments, non-governmental organizations (NGOs) or universities. HIA researchers access a wide range of emic and etic community perspectives in their search for the 'community's view'. Government, NGO and university investigators access community perspectives differently, with university HIA researchers inviting more emic-oriented community vistas than both government and NGO researchers. University and government HIA investigators are more likely to invite multiple emic and etic community perspectives during their community participation projects than NGO researchers. NGO HIA investigators tend to either invite emic perspectives or etic perspectives for their community input with less mixing of the two views in a single project. The paper concludes with a discussion on how HIA researchers can frame the 'community's perspective' in their HIA investigations through a combination of both 'insider' and 'outsider' community input sampling strategies.

A Singular Value Decomposition based Space Vector Modulation to Reduce the Output Common-Mode Voltage of Direct Matrix Converters

Large magnitude common-mode voltage (CMV) and its variation dv/dt have an adverse effect on motor drives that leads to early winding failure and bearing deterioration. For matrix converters, the switch states that connect each output line to a different input phase result in the lowest CMV among all of the valid switch states. To reduce the output CMV for matrix converters, this paper presents a new space vector modulation (SVM) strategy by utilizing these switch states. By this mean, the peak value and the root mean square of the CMV are dramatically decreased. In comparison with the conventional SVM methods this strategy has a similar computation overhead. Experiment results are shown to validate the effectiveness of the proposed modulation method.

Adaptive Multiphoton Endomicroscope Incorporating a Polarization-Maintaining Multicore Optical Fibre

We present a laser scanning multiphoton endomicroscope with no distal optics or mechanical components that incorporates a polarization-maintaining (PM) multicore optical fibre to deliver, focus, and scan ultrashort pulsed radiation for two-photon excited fluorescence imaging. We show theoretically that the use of a PM multicore fibre in our experimental configuration enhances the fluorescence excitation intensity achieved in the focal spot compared to a non-PM optical fibre with the same geometry and confirm this by computer simulations based on numerical wavefront propagation. In our experimental system, a spatial light modulator (SLM) is utilised to program the phase of the light input to each of the cores of the endoscope fibre such that the radiation emerging from the distal end of the fibre interferes to provide the focused scanning excitation beam. We demonstrate that the SLM can enable dynamic phase correction of path-length variations across the multicore optical fibre whilst the fibre is perturbed with an update rate of 100 Hz.

Morphological Expression of the Coherence and Relative Phase of Optical Inputs to the Photoelectrodeposition of Nanopatterned Se-Te Films.

Highly anisotropic and ordered nanoscale lamellar morphologies can be spontaneously generated over macroscopic areas, without the use of a photomask or any templating agents, via the photoelectrodeposition of Se-Te alloy films. To form such structures, the light source can be a single, linearly polarized light source that need not necessarily be highly coherent. In this work, the variation in the morphologies produced by this deposition process was evaluated in response to differences in the coherence and relative phase between multiple simultaneous linearly polarized illumination inputs. Specifically, the morphologies of photoelectrodeposits were evaluated when two tandem same-wavelength sources with discrete linear polarizations, both either mutually incoherent or mutually coherent (with defined phase differences), were used. Additionally, morphologies were simulated via computer modeling of the interfacial light scattering and absorption during the photoelectrochemical growth process. The morphologies that were generated using two coherent, in-phase sources were equivalent to those generated using only a single source. In contrast, the use of two coherent, out-of-phase sources produced a range of morphological patterns. For small out-of-phase addition of orthogonal polarization components, lamellar-type patterns were observed. When fully out-of-phase orthogonal sources (circular polarization) were used, an isotropic, mesh-type pattern was instead generated, similar to that observed when unpolarized illumination was utilized. In intermediate cases, anisotropic lamellar-type patterns were superimposed on the isotropic mesh-type patterns, and the relative height between the two structures scaled with the amount of out-of-phase addition of the orthogonal polarization components. Similar results were obtained when two incoherent sources were utilized. In every case, the long axis of the lamellar-type morphology component aligned parallel to the intensity-weighted average polarization orientation. The observations consistently agreed with computer simulations, indicating that the observed morphologies were fully determined by the nature of the illumination utilized during the growth process. The collective data thus indicated that the photoelectrodeposition process exhibits sensitivity toward the coherency, relative phase, and polarization orientations of all optical inputs and that this sensitivity is physically expressed in the morphology of the deposit.

Self-Tuning OTA-C Notch Filter with Constant Q-Factor

This paper describes the design of a self-tuning OTA-C notch filter (NF), based on a phase control loop concept. The phases of filter input and output signals are compared and the phase error is used to generate the control voltage, which adjusts the transconductances of operational transconductance amplifiers (OTAs) and, consequently, tunes the NF center frequency without quality factor variation. The proposed solution is robust to filter parameter variations. The filter is implemented in 0.13[Formula: see text][Formula: see text]m SiGe BiCMOS technology. Under the typical circuit operating conditions, the center frequency tuning is within the range from 70[Formula: see text]MHz up to 150[Formula: see text]MHz, with tuning error less than 1%. The power consumption is less than 3.6[Formula: see text]mW, the 1[Formula: see text]dB gain compression point is [Formula: see text]2.5[Formula: see text]dBm, the input (IIP3) and output (OIP3) intercept points are 3.47 and 9.07[Formula: see text]dBm, respectively, and the total filter effective noise voltage is 4.35[Formula: see text][Formula: see text]Vrms. The filter structure is suitable for complementary metal-oxide-semiconductor (CMOS) implementation.

Photonic lantern adaptive spatial mode control in LMA fiber amplifiers.

We demonstrate adaptive-spatial mode control (ASMC) in few-moded double-clad large mode area (LMA) fiber amplifiers by using an all-fiber-based photonic lantern. Three single-mode fiber inputs are used to adaptively inject the appropriate superposition of input modes in a multimode gain fiber to achieve the desired mode at the output. By actively adjusting the relative phase of the single-mode inputs, near-unity coherent combination resulting in a single fundamental mode at the output is achieved.

On the Phase Coupling of Two Components Mixing in Empirical Mode Decomposition

This paper investigates frequency mixing effect of empirical mode decomposition (EMD) and explores whether it can be explained by simple phase coupling between components of the input signal. The input is assumed to be a linear combination of harmonic oscillators. The hypothesis was tested assuming that phases of input signals’ components would couple according to Kuramoto’s model. Using a Kuramoto’s model with as many oscillators as the number of intrinsic mode functions (result of EMD), the model’s parameters were adjusted by a particle swarm optimization (PSO) method. The results show that our hypothesis is plausible, however, a different coupling mechanism than the simple sine-coupling Kuramoto’s model are likely to give better results.

Optical precursors via spontaneously generated coherence

Optical precursors were first studied by Sommerfield and Brillouin in 1914 to resolve the apparent contradictions between fast light propagation and the theory of relativity. They showed theoretically that the front edge of a step-modulated pulse does not interact with the medium and always travels at c because the dispersive material has a finite response time to the optical pulse. The past experimental studies of precursors in classical pulse propagation were always focused on an opaque medium with single or multiple Lorentz absorption lines. In these cases, the precursor signal cannot be separated from the main pulse or otherwise the main field is absorbed. However, the electromagnetically induced transparency (EIT) technique was successfully used to separate precursors from the main pulse due to the slow-light effect in cold atoms. The EIT refers to the absorption suppression or elimination of a probe field through atomic coherence in a certain medium dressed by a strong coupling field. In this paper, a four-level double-lambda atomic system with two upper states coupled to the excited state is explored to separate optical precursors from a square-modulated laser pulse with the effect of spontaneously generated coherence (SGC). The SGC effect occurs in the process of spontaneous emission, in which the atom decays from closely placed upper levels to a single ground level. The quantum interference between the decay channels takes place, which leads to decay induced transparency, thus enhancing the Kerr nonlinearity and amplification without inversion. With the assistance of spontaneously generated coherence, an EIT window appears with steep normal dispersion when the trigger field is far from resonance. Then we can obtain the optical precursors which are separated from the main pulse due to the slow-light effects in the EIT window. In the absence of SGC, the main pulse is absorbed by an opaque medium with Lorentz absorptive lines, so the slow-light effect could not take place. In addition, we obtain the stacked optical precursors with the input probe field amplitude or phase modulated by designing a series of square pulses. For the amplitude modulation case, the peak power reaches about 4.5 times that of the input pulse. With the phase modulation we obtain a transient pulse with a peak power of 14 times that of the input, as a result of constructive interference between the stacked precursors and main field. We expect these findings to be instructive in devising optical devices for optical communication, detection and medical imaging among other applications.

The Design of Phase-Locked-Loop Circuit for Precision Capacitance Micrometer

High precision non-contact micrometer is normally divided into three categories: inductance micrometer, capacitance micrometer and optical interferometer micrometer. The capacitance micrometer is widely used because it has high performance to price ratio. With the improvement of automation level, precision of capacitance micrometer is required higher and higher. Generally, capacitance micrometer consists of the capacitance sensor, capacitance/voltage conversion circuit, and modulation and demodulation circuits. However, due to the existing of resistors, capacitors and other components in the circuit, the phase shift of the carrier signal and the modulated signal might occur. In this case, the specific value of phase shift cannot be determined. Therefore, error caused by the phase shift cannot be eliminated. This will reduce the accuracy of micrometer. In this design, in order to eliminate the impact of the phase shift, the phase-locked-loop (PLL) circuit is employed. Through the experiment, the function of tracking the input signal phase and frequency is achieved by the phase-locked-loop circuit. This signal processing method can also be applied to tuber electrical resistance tomography system and other precision measurement circuit.

AHP and weak consistency in the evaluation of works of art - a case study of a large problem

The paper describes an evaluation methodology based on Saaty's AHP, that relaxes the classical Saaty's consistency condition and works with the concept of weak consistency. Weak consistency is seen as a minimum requirement on the consistency of experts' preferences. The relationship of weak consistency and the linguistic level of consistency description using the Saaty's scale is discussed in the paper. The benefits of using weak consistency with large problems are presented - for data input, for the flexibility of the mathematical model and to facilitate further adjustments of the evaluation methodology. In the case of pairwise comparison matrices with ordered categories, the fulfilment of weak consistency can be checked during the data input phase. This way the weak consistency of pairwise comparison matrices can be achieved even for large numbers of categories - unlike the full consistency in Saaty's sense. The paper also provides a case study of a practical application of the proposed evaluation methodology - the mathematical model for the evaluation of creative work outcomes of Czech Art Colleges. The case presented here combines evaluation based on objective criteria with peer review and suggests a possible solution to the problem of arts evaluation for funding purposes.

Carrier-Based PWM Method to Reduce Common-Mode Voltage of Three-to-Five-Phase Indirect Matrix Converter

In order to reduce the common-mode voltage (CMV) for three-to-five-phase indirect matrix converter (IMC), the CMV with the conventional modulation strategy is analyzed. A novel carrier-based PWM (CBPWM) method is proposed in this paper. The zero vectors in the inverter stage are assigned to the rectifier stage, equivalently, which are not considered in the inverter stage. The zero vectors are selected appropriately to ensure that the dc-link is connected to an input phase with the minimum absolute value, so that the larger CMV can be avoided. Then, the modulation signals are derived by the duty ratios, which are used to compare with the only one carrier signal and generate the gate pulses of switches. With the proposed method, the CMV is reduced effectively compared with the conventional modulation strategy. This method is analyzed and researched with a simulation model established by Matlab/Simulink. Simulation results are provided in detail to verify the feasibility and validity of the proposed method.

Investigating Phase Detectors: Advances in Mature and Emerging Phase-Frequency and Time-to-Digital Detectors in Phase-Locked Looped Systems

Detectors play an important role in many communication systems such as delay locked loops, alias-locked loops, digital-microwave radio, clock-data recovery and phase-locked loops (PLLs). A phase frequency detector (PFD) is one of the mature detector circuit designs used to detect phase and frequency differences of input signals. Time-to-digital converter (TDC) blocks are a modern and emerging technique used to quantify these phase and frequency differences precisely. This article presents the advances in mature and emerging phase-frequency and time-to-digital detectors in phase-locked loop systems.

Closed-loop approach to tuning deep brain stimulation parameters for Parkinson's disease

Deep brain stimulation (DBS) is used to treat motor symptoms of patients with Parkinson's disease (PD). However, tuning stimulation parameters is currently done using a time intensive trial-and-error process until maximum therapy is achieved with minimal side effects [1]. There is a need for a systematic approach to tuning parameters based on patient physiology. With the development of DBS electrodes that can simultaneously stimulate and record [2], a closed-loop approach may be taken. It is hypothesized that emergent oscillations in the basal ganglia network, particularly in the beta range (12-35 Hz) lead to motor symptoms of PD [3], and that DBS works by disrupting these oscillations. Our hypothesis is that stimulating at a specific phase in the pathological oscillation will optimally disrupt the oscillatory activity, and that this phase can be predicted from the phase response curve (PRC). Here, we use a computational network model of PD with an emergent pathological 34 Hz oscillation [4] to test this closed-loop approach to DBS and confirm the results in vitro. By stimulating at a specific phase in the beta oscillation we are able to modulate the power of the oscillation in the model. By stimulating soon after the peak in the oscillation, we disrupt the 34 Hz oscillation, while stimulating later in the period enhances it. Hence, the timing of stimulation affects how well the population of neurons desynchronized. Next, we test this concept in vitro by synchronizing patch-clamped neurons in the substantia nigra pars reticulata (an output nucleus of the basal ganglia) to an oscillatory input, such as a beta oscillation. We show that stimulating at a particular phase of the oscillatory input affects how well neurons synchronize or desynchronize to that input. Finally, we show it is possible to use the PRC to predict how stimulating at a specific phase will affect the neuron's ability to synchronize or desynchronize from the oscillatory input in vitro. This work shows that stimulating at specific phases in an oscillation can synchronize or desynchronize neurons in a computational model and in vitro. By stimulating at specific phases of an emergent pathological oscillation in a closed-loop approach to DBS, we were able to suppress a pathological oscillation in a computational model of PD. In this approach, a frequency of 34 Hz was used for DBS, which is much lower than the value used clinically (>100 Hz). Through closed-loop stimulation, precisely timed stimuli with respect to the phase of the oscillation can dramatically decrease stimulus power needed for DBS. The ability to synchronize or desynchronize a neuron to an oscillatory input by stimulating at a certain phase was also validated in vitro. It is possible to predict the phase of stimulation to maximally disrupt neuronal synchronization to an external oscillatory input in single neurons using a PRC. We have previously shown a novel method to estimate a PRC from population data [5] in a computational model of PD. This suggests it may be possible to predict the phase at which to stimulate in order to optimally disrupt a pathological population oscillation in PD using the PRC, and apply this in a closed-loop approach to DBS.

Propagation equation for tight-focusing by a parabolic mirror.

Part of the chain in petawatt laser systems may involve extreme focusing conditions for which nonparaxial and vectorial effects have high impact on the propagation of radiation. We investigate the possibility of using propagation equations to simulate numerically the focal spot under these conditions. We derive a unidirectional propagation equation for the Hertz vector, describing linear and nonlinear propagation under situations where nonparaxial diffraction and vectorial effects become significant. By comparing our simulations to the results of vector diffraction integrals in the case of linear tight-focusing by a parabolic mirror, we establish a practical criterion for the critical f -number below which initializing a propagation equation with a parabolic input phase becomes inaccurate. We propose a method to find suitable input conditions for propagation equations beyond this limit. Extreme focusing conditions are shown to be modeled accurately by means of numerical simulations of the unidirectional Hertz-vector propagation equation initialized with suitable input conditions.

An Iterative Learning Control Approach for Radio Frequency Pulse Compressor Amplitude and Phase Modulation

Radio Frequency (RF) pulse compressors are used in linear accelerators (Linac) to achieve high power levels by shortening the RF pulse length. In their original form, the phase of the incoming pulse is reversed by 180 $^{\circ} $ which generates a high peak power at the output of the pulse compressor, followed by an exponential decay. This pulse shape however is not appropriate with regard to timing stability as well as for having equal energy gain for multi-bunch operation. To achieve flat-topped pulses, a method has been previously proposed that analytically modulates the input phase waveform. In the present contribution an alternative way to producing flat-topped RF pulses is proposed which is based on Iterative Learning Control techniques. This approach manipulates the input waveforms iteratively in order to generate flat-topped amplitude and phase pulses at the output of the pulse compressor.

Spin wave scattering and interference in ferromagnetic cross

Magnetostatic spin wave scattering and interference across a CoTaZr ferromagnetic spin wave waveguide cross junction were investigated experimentally and by micromagnetic simulations. It is observed that the phase of the scattered waves is dependent on the wavelength, geometry of the junction, and scattering direction. It is found that destructive and constructive interference of the spin waves generates switching characteristics modulated by the input phase of the spin waves. Micromagnetic simulations are used to analyze experimental data and simulate the spin wave scattering and interference.

Photonic radio frequency phase-shift amplification by radio frequency interferometry.

We present a new technique for radio frequency (RF) phase-shift amplification based on RF interferometry and demonstrate it in an optical system. A striking feature of this amplifier is that the input phase noise is not amplified together with the input phase signal, so the phase sensitivity improves with higher phase amplification. We also predict that in the case of correlated amplitude noise, the sensitivity is not affected by the amplitude noise. With 600 MHz of modulated light and a phase amplification of 100, we demonstrate a phase resolution of 0.2 mrad, giving a distance resolution of 8 μm. We postulate that nanometric distance resolution can be achieved with sub-gigahertz modulation.

Simple high‐resolution CMOS phase frequency detector

A high-resolution phase frequency detector (PFD) is designed for high-frequency signal detection and low jitter phase locked loop applications. The proposed PFD eliminates the reset path delay and usage of any latches, minimise the dead zone to near zero by generating narrow pulses at each input rising edge. In addition, the designed PFD completely removes unwanted output glitches, accepts inputs with a large difference in frequency, and also has the ability to drive a large capacitive load with minimal impact on performance. The proposed PFD is designed in 90 nm CMOS technology with a 1.2 V power supply. Simulation results indicate that the proposed design can operate over a wide range of frequencies from 10 kHz to 6 GHz and can detect phase differences for inputs as small as 125 fs for all frequencies of operation and for all process corners. The simulated power consumption is 75 µW at 166.6 MHz with an input phase difference of 125 fs.

Rebound spiking in layer II medial entorhinal cortex stellate cells: Possible mechanism of grid cell function

Rebound spiking properties of medial entorhinal cortex (mEC) stellate cells induced by inhibition may underlie their functional properties in awake behaving rats, including the temporal phase separation of distinct grid cells and differences in grid cell firing properties. We investigated rebound spiking properties using whole cell patch recording in entorhinal slices, holding cells near spiking threshold and delivering sinusoidal inputs, superimposed with realistic inhibitory synaptic inputs to test the capacity of cells to selectively respond to specific phases of inhibitory input. Stellate cells showed a specific phase range of hyperpolarizing inputs that elicited spiking, but non-stellate cells did not show phase specificity. In both cell types, the phase range of spiking output occurred between the peak and subsequent descending zero crossing of the sinusoid. The phases of inhibitory inputs that induced spikes shifted earlier as the baseline sinusoid frequency increased, while spiking output shifted to later phases. Increases in magnitude of the inhibitory inputs shifted the spiking output to earlier phases. Pharmacological blockade of h-current abolished the phase selectivity of hyperpolarizing inputs eliciting spikes. A network computational model using cells possessing similar rebound properties as found in vitro produces spatially periodic firing properties resembling grid cell firing when a simulated animal moves along a linear track. These results suggest that the ability of mEC stellate cells to fire rebound spikes in response to a specific range of phases of inhibition could support complex attractor dynamics that provide completion and separation to maintain spiking activity of specific grid cell populations.

Generation of photons with all-optically-reconfigurable entanglement in integrated nonlinear waveguides

We predict that all-optically-reconfigurable generation of photon pairs with tailored spatial entanglement can be realized via spontaneous parametric down conversion in integrated nonlinear coupled waveguides. The required elements of the output quantum wave function are directly mapped from the amplitudes and phases of the classical laser pump inputs in each waveguide. This is achieved through special nonuniform domain poling, which locally inverts the sign of quadratic nonlinear susceptibility and accordingly shapes the interference of biphoton quantum states generated along the waveguides. We demonstrate a device configuration for the generation of any linear combination of two-photon Bell states.