Unknown Phase Research Articles

Euclidean matrix norm algorithm for simultaneous dual-wavelength phase-shifting interferometry with blind phase shifts

In this study, a simultaneous dual-wavelength phase-shifting interferometry system using two reference arms was built, and a simple phase retrieval method for the system with blind phase shifts was proposed using five phase-shifted interferograms. First, the unknown phase shifts were controlled independently to separate the information of single wavelength, which can be calculated directly by using the Euclidean matrix norm algorithm. Second, a wrapped phase of a single wavelength was obtained using a three-step phase-shifting algorithm. Finally, a continuous phase of a synthetic wavelength was obtained. The simulation and experimental results indicated the feasibility and greater accuracy of the proposed method. Moreover, the strict requirement of the phase shifter was eliminated because of the use of arbitrary and unknown phase shifts, thereby making experimental operation easier.

Inverse Optimal Control for Multiphase Cost Functions

In this paper, we consider a dynamical system whose trajectory is a result of minimizing a multiphase cost function. The multiphase cost function is assumed to be a weighted sum of specified features (or basis functions) with phase-dependent weights that switch at some unknown phase transition points. A new inverse optimal control approach for recovering the cost weights of each phase and estimating the phase transition points is proposed. The key idea is to use a length-adapted window moving along the observed trajectory, where the window length is determined by finding the minimal observation length that suffices for a successful cost weight recovery. The effectiveness of the proposed method is first evaluated on a simulated robot arm, and then, demonstrated on a dataset of human participants performing a series of squatting tasks. The results demonstrate that the proposed method reliably retrieves the cost function of each phase and segments each phase of motion from the trajectory with a segmentation accuracy above 90%.

Adaptive Bayesian phase estimation for quantum error correcting codes

Realisation of experiments even on small and medium-scale quantum computers requires an optimisation of several parameters to achieve high-fidelity operations. As the size of the quantum register increases, the characterisation of quantum states becomes more difficult since the number of parameters to be measured grows as well and finding efficient observables in order to estimate the parameters of the model becomes a crucial task. Here we propose a method relying on application of Bayesian inference that can be used to determine systematic, unknown phase shifts of multi-qubit states. This method offers important advantages as compared to Ramsey-type protocols. First, application of Bayesian inference allows the selection of an adaptive basis for the measurements which yields the optimal amount of information about the phase shifts of the state. Secondly, this method can process the outcomes of different observables at the same time. This leads to a substantial decrease in the resources needed for the estimation of phases, speeding up the state characterisation and optimisation in experimental implementations. The proposed Bayesian inference method can be applied in various physical platforms that are currently used as quantum processors.

Accurate blind extraction of arbitrary unknown phase shifts by an improved quantum-behaved particle swarm optimization in generalized phase-shifting interferometry

An optimized method of accurately extracting the arbitrary unknown and unequal phase steps in phase-shifting interferometry is proposed. The approximate phase steps are first calculated based on the statistical nature of the diffraction field, and the mutated adaptive quantum-behaved particle swarm optimization is used to further extract the arbitrary unknown and unequal phase steps. We improve the mutated adaptive quantum-behaved particle swarm optimization by adding mutation operator with Gaussian probability distribution, thereby increasing the population diversity. The developed method here is fast, highly accurate, and can effectively overcomes the “sawtooth-solution phenomenon” often encountered in traditional direct search approach. We demonstrate the speed and quality of the solution by measuring the transmissive object with the four-step phase-shifting interference method, as is verified by both the computer simulations and optical experiments.

Distributed quantum metrology with a single squeezed-vacuum source

We propose an interferometric scheme for the estimation of a linear combination with non-negative weights of an arbitrary number $M>1$ of unknown phase delays, distributed across an $M$-channel linear optical network, with Heisenberg-limited sensitivity. This is achieved without the need of any sources of photon-number or entangled states, photon-number resolving detectors or auxiliary interferometric channels. Indeed, the proposed protocol remarkably relys upon a single squeezed state source, an antisqueezing operation at the interferometer output, and on-off photodetectors.

Novel Generalized Three-Step Phase-Shifting Interferometry with a Slight-Tilt Reference

A convenient and powerful method is proposed and presented to find the unknown phase shifts in three-step generalized phase-shifting interferometry. A slight-tilt reference of 0.1 degrees is employed. As a result, the developed theory shows that the unknown phase shifts can be simply extracted by subtraction operations. Also, from the theory developed, the tilt angle of the tilt reference can also be calculated, which is important as it allows us to extract the object wave precisely. Numerical simulations and optical experiments were performed to demonstrate the validity and efficiency of the proposed method. The proposed slight-tilt reference allows the full and efficient use of the space-bandwidth product of the limited resolution of digital recording devices as compared to the situation in standard off-axis holography where typically several degrees for off-axis angle is employed.

Influence of Softness on the Stability of Binary Colloidal Crystals.

Mixtures of two types of nanoparticles can self-assemble into a wide variety of binary colloidal crystals (also called binary nanoparticle superlattices), which are interesting for their structural diversity and potential applications. Although so-called packing models-which usually treat the particles as "hard" with only excluded volume interactions-seem to explain many reported dense crystalline phases, these models often fail to predict the right structure. Here, we examine the role of soft repulsive interparticle interactions on binary colloidal crystals comprising two sizes of spherical particles; such "softness" can arise due to ligand shells or screened electrostatics. We determine the ground state phase diagram of binary systems of particles interacting with an additive inverse power law potential using a basin hopping algorithm to calculate the enthalpy of an extremely large pool of candidate structures. We find that a surprisingly small amount of softness can destabilize dense packings in favor of less densely packed structures, which provides further evidence that considerations beyond packing are necessary for describing many of the observed phases of binary colloidal crystals. Importantly, we find that several of the phases stabilized by softness, which are characterized by relatively few interparticle contacts and a tendency for local icosahedral order, are more likely to be observed experimentally than those predicted by packing models. We also report a previously unknown dense AB4 phase and conduct free energy calculations to examine how the stability of several crystals will vary with temperature. Our results further our understanding of why particular binary colloidal crystals form and will be useful as a reference for experimentalists working with softly repulsive colloids.

Sensitivity of the excitation functions of collective flow to relativistic scalar and vector meson interactions in the relativistic quantum molecular dynamics model RQMD.RMF

Relativistic quantum molecular dynamics with scalar and vector interactions based on the relativistic mean meson field theory, RQMD.RMF, is developed.It is implemented into the microscopic transport code JAM.The sensitivity of the directed and of the elliptic proton flow in high energy heavy-ion collisions on the stiffness of the RMF equation of state (EoS) is examined. These new calculations are compared to experimental data at mid-central Au + Au collisions in the beam energy range $2.5 < \sqrt{s_{NN}} < 20$ GeV. This new RQMD model with the relativistic mean field scalar and vector meson interactions does describe consistently, with one RMF parameter set,the beam energy dependence of both the directed flow and the elliptic flow,from SIS18 to AGS and RHIC BES-II energies, $\sqrt{s_{NN}}< 10$ GeV.There are different sensitivities of these different kinds of flow to the EoS: elliptic flow is most sensitive to the nuclear incompressibility constant,at the moderate beam energies $\sqrt{s_{NN}}<3$ GeV,whereas the directed flow is most sensitive to the effective baryon mass at saturation density at $3< \sqrt{s_{NN}}<5 $ GeV. Matters abruptly change in the next higher energy range,$\sqrt{s_{NN}}\gtrsim 10-20$ GeV:the directed flow data show a double change of sign of the slope of $v_1$, inverting twice in this energy range,in sudden contradiction to the RQMD.RMF calculation for a monotonous, stiff EoS. This surprising oscillating behavior,a double change of sign of the $v_1$ slope, points to the appearance of a hitherto unknown first-order phase transition in excited QCD matter at high baryon densities in mid-central Au + Au collisions.

Preparation of cubic Na3PS4 by liquid-phase shaking in methyl acetate medium

Cubic Na3PS4 (c-Na3PS4), a high temperature phase of Na3PS4, is successfully prepared by liquid-phase shaking from Na2S and P2S5 in methyl acetate medium. The effects of the amount of solvents, Na2S and heat treatment on the formation of c-Na3PS4 are carefully investigated. In addition to c-Na3PS4, an unknown phase is also detected in the sample containing an excess amount of Na2S in the starting materials mixture.

Sintering characteristics and microwave dielectric properties of new high-Q Mg2LaNbO6 ceramics

New microwave dielectric ceramics of Mg2LaNbO6, which had high quality factors (Q × ƒ) and near-zero frequency temperature coefficient (τƒ), were synthesized via conventional solid-state reaction. The sintering characteristic, crystal structure and microwave dielectric properties of Mg2LaNbO6 ceramics were characterized and investigated. As a result, Mg2LaNbO6 ceramics had a complex phase composition: LaNbO4 and MgO as the main and the second phase respectively, with an unknown phase (which related to the MgO) being detected. Well-developed micro-structures of Mg2LaNbO6 ceramics were obtained in the designed sintering temperature zone, with the grain size and its distribution also being investigated. Moreover, the permittivity (εr), which was related to the density, remained almost unchanged. The Q × ƒ values increased first and then decreased, which was governed by the grain size and its distribution. Additionally, the τƒ values of Mg2LaNbO6 ceramics was relatively stable and near to zero.

Motion Control for Platforms Bearing Elastic Links with Unknown Phase States

We consider the problem on the controlled motion of a platform such that a solid body bearing a dissipative oscillator is attached to it by means of a spring. The platform moves along a horizontal line under the action of the control force, undergoing the action of a bounded uncontrolled perturbation, e.g., the dry friction force, as well. It is assumed that the phase state of the oscillator is not accessible for measurement. We propose a control law leading the whole system to the prescribed rest state within a finite time period.

The Mesochronous Dual-Clock FIFO Buffer

To increase system composability and facilitate timing closure, fully synchronous clocking is replaced by more relaxed clocking schemes, such as mesochronous clocking. Under this regime, the modules at the two ends of a mesochronous interface receive the same clock signal, thus operating under the same clock frequency, but the edges of the arriving clock signals may exhibit an unknown phase relationship. In such cases, clock synchronization is needed when sending data across modules. In this brief, we present a novel mesochronous dual-clock first-input–first-output (FIFO) buffer that can handle both clock synchronization and temporary data storage, by synchronizing data implicitly through the explicit synchronization of only the flow-control signals. The proposed design can operate correctly even when the transmitter and the receiver are separated by a long link whose delay cannot fit within the target operating frequency. In such scenarios, the proposed mesochronous FIFO can be extended to support multicycle link delays in a modular manner and with minimal modifications to the baseline architecture. When compared with the other state-of-the-art dual-clock mesochronous FIFO designs, the new architecture is demonstrated to yield a substantially lower cost implementation.

In Situ Detection of Nucleation in High‐Temperature Solutions

AbstractThe state of a sample during crystal growth from high‐temperature solutions is not accessible in conventional furnace systems. An optimization of the growth parameters often requires arduous trial and error procedures, in particular, in the case of novel multicomponent systems with unknown phase diagrams. Here a measurement technique based on lock‐in amplification is presented that allows for in situ detection of the liquidus and solidus temperatures as well as structural phase transitions. A thin, metallic measurement wire is mounted in close vicinity to the melt. Characteristic anomalies in the time‐dependent electrical resistivity of this wire allow for the detection of latent heat release without using a reference crucible. The method is implemented in a “feedback furnace” and enables an adjustment of the temperature profile based on the occurrence or absence of phase transitions. The absolute temperature serves as an additional source of information. Obtained phase transition temperatures are in good agreement with differential thermal analysis.

Feedforward-assisted coherent-state comparison amplifier

Quantum optical coherent-state comparison amplifiers are nondeterministic devices which can amplify rather noiselessly a weak coherent state with an unknown phase from a finite discrete set. The high fidelity and high success probability of this amplifier are accomplished by a comparison stage and some photon subtraction stages. Due to the heralding nature of these amplifiers, they work part of the time. Here, we propose a feedforward protocol to increase the heralded times by correcting the incorrect guess. Hence, we enhance the fidelity and success probability more. Finally, the schematic experimental configuration of the feedforward-assisted coherent-state comparison amplifier is proposed.

Earthquake Arrival Association with Backprojection and Graph Theory

AbstractThe association of seismic‐wave arrivals with causative earthquakes becomes progressively more challenging as arrival detection methods become more sensitive, and particularly when earthquake rates are high. For instance, seismic waves arriving across a monitoring network from several sources may overlap in time, false arrivals may be detected, and some arrivals may be of unknown phase (e.g., P or S waves). We propose an automated method to associate arrivals with earthquake sources and obtain source locations applicable to such situations. To do so, we use a pattern detection metric based on the principle of backprojection to reveal candidate sources followed by graph‐theory‐based clustering and an integer linear optimization routine to associate arrivals with the minimum number of sources necessary to explain the data. This method solves for all sources and phase assignments simultaneously, rather than in a sequential greedy procedure as is common in other association routines. We demonstrate our method on both synthetic and real data from the Integrated Plate Boundary Observatory Chile seismic network of northern Chile. For the synthetic tests, we report results for cases with varying complexity, including rates of 500 earthquakes/day and 500 false arrivals/station/day, for which we measure true positive detection accuracy of &gt;95%. For the real data, we develop a new catalog between 1 January 2010 and 31 December 2017 containing 817,548 earthquakes, with detection rates on average 279 earthquakes/day and a magnitude‐of‐completion of M∼1.8. A subset of detections are identified as sources related to quarry and industrial site activity, and we also detect thousands of foreshocks and aftershocks of the 1 April 2014 Mw 8.2 Iquique earthquake. During the highest rate of aftershock activity, &gt;600 earthquakes/day are detected in the vicinity of the Iquique earthquake rupture zone.

Antiferromagnetic Semiconductor BaFMn0.5Te with Unique Mn Ordering and Red Photoluminescence.

Semiconductors possessing both magnetic and optoelectronic properties are rare and promise applications in opto-spintronics. Here we report the mixed-anion semiconductor BaFMn0.5Te with a band gap of 1.76 eV and a work function of 5.08 eV, harboring both antiferromagnetism (AFM) and strong red photoluminescence (PL). The synthesis of BaFMn0.5Te in quantitative yield was accomplished using the "panoramic synthesis" technique and synchrotron radiation to obtain the full reaction map, from which we determined that the compound forms upon heating at 850 °C via an intermediate unknown phase. The structure refinement required the use of a (3+1)-dimensional superspace group Cmme(α01/2)0ss. The material crystallizes into a ZrCuSiAs-like structure with alternating [BaF]+ and [Mn0.5Te]- layers and has a commensurately modulated structure with the q-vector of 1/6a* + 1/6b* + 1/2c* at room temperature arising from the unique ordering pattern of Mn2+ cations. Long-range AFM order emerges below 90 K, with two-dimensional short-range AFM correlations above the transition temperature. First-principles calculations indicate that BaFMn0.5Te is an indirect band gap semiconductor with the gap opening between Te 5p and Mn 3d orbitals, and the magnetic interactions between nearest-neighbor Mn2+ atoms are antiferromagnetic. Steady-state PL spectra show a broad strong emission centered at ∼700 nm, which we believe originates from the energy manifolds of the modulated Mn2+ sublattice and its defects. Time-resolved PL measurements reveal an increase in excited-state lifetimes with longer probe wavelengths, from 93 ns (at 650 nm) to 345 ns (at 800 nm), and a delayed growth (6.5 ± 0.3 ns) in the kinetics at 800 nm with a concomitant decay (4.1 ± 0.1 ns) at 675 nm. Together, these observations suggest that there are multiple emissive states, with higher energy states populating lower energy states by energy transfer.

Toward Absolute Phase Change Recovery With InSAR: Correcting for Earth Tides and Phase Unwrapping Ambiguities

Radar interferograms provide a map of the phase difference between the reference and repeat acquisitions modulo ${2\pi }$ . Under ideal conditions, the phase can be unwrapped to provide an absolute phase connection across the map, although there is always an unknown integer phase ambiguity (i.e., ${N2\pi }$ ) for the entire map. Here, we demonstrate a practical time series method to solve for these integer ambiguities in order to recover the absolute phase change between the first and last SAR images. An important first step is to correct the phase of each SAR image for the well-known solid earth tide, which typically produces a line of sight offset ±150 mm, as well as, trends along and across each image of ~20 mm. This tide correction significantly reduces the noise in the InSAR time series, especially at the L-band. These tidally corrected interferograms are then unwrapped and used to solve for a set of integer ambiguities that achieves phase closure when summing around loops in the stack. There is an infinite number of ambiguity combinations that achieve loop closure; thus, regularization is required. In contrast to previous studies that use a least-squares approach to find the ambiguities, we adopt an ${L}_{1}$ -norm approach to find the minimum number of ambiguity corrections needed to achieve loop closure. We note that the split-spectrum ionospheric correction can introduce ${N\pi }$ ambiguities and suggest two approaches for correcting both ${N2\pi }$ and ${N\pi }$ ambiguities.

Properties of central stars of planetary nebulae with distances in Gaia DR2

Context. We have compiled a catalogue of central stars of planetary nebulae (CSPN) with reliable distances and positions obtained from Gaia Data Release 2 (DR2) astrometry. Distances derived from parallaxes allow us to analyse the galactic distribution and estimate other parameters such as sizes, kinematical ages, bolometric magnitudes, and luminosities. Aims. Our objective is to analyse the information regarding distances together with other available literature data about photometric properties, nebular kinematics, and stellar effective temperatures to throw new light on this rapid and rather unknown evolutionary phase. We seek to understand how Gaia distances compare with other indirect methods commonly used and, in particular, with those derived from non-local thermodynamic equilibrium (non-LTE) models; how many planetary nebulae (PNe) populate the Galaxy; and how are they spatially distributed. We also aim to comprehend their intrinsic luminosities, range of physical sizes of the nebulae; how to derive the values for their kinematical ages; and whether those ages are compatible with those derived from evolutionary models. Methods. We considered all PNe listed in catalogues from different authors and in Hong Kong/AAO/Strasbourg/Hα (HASH) database. By X-matching their positions with Gaia DR2 astrometry we were able to identify 1571 objects in Gaia second archive, for which we assumed distances calculated upon a Bayesian statistical approach. From those objects, we selected a sample of PNe with good quality parallax measurements and distance derivations, we which refer to as our Golden Astrometry PNe sample (GAPN), and obtained literature values of their apparent sizes, radial and expansion velocities, visual magnitudes, interstellar reddening, and effective temperatures. Results. We found that the distances derived from DR2 parallaxes compare well with previous astrometric derivations of the United States Naval Observatory and Hubble Space Telescope, but that distances inferred from non-LTE model fitting are overestimated and need to be carefully reviewed. From literature apparent sizes, we calculated the physical radii for a subsample of nebulae that we used to derive the so-called kinematical ages, taking into account literature expansion velocities. Luminosities calculated with DR2 distances were combined with literature central stars Teff values in a Hertzsprung–Russell (HR) diagram to infer information on the evolutionary status of the nebulae. We compared their positions with updated evolutionary tracks finding a rather consistent picture. Stars with the smallest associated nebular radii are located in the flat luminosity region of the HR diagram, while those with the largest radii correspond to objects in a later stage, getting dimmer on their way to become a white dwarf. Finally, we commented on the completeness of our catalogue and calculated an approximate value for the total number of PNe in the Galaxy.

Methodological Approach to Reconstructing Lost Monuments from Archaeological Findings: The San Francesco di Castelletto Church in Genoa

Throughout history, natural hazards, wars, political changes and urban evolution have contributed to the obliteration of outstanding monuments. The study of their remains, frequently recovered as archaeological findings, can be the basis for a reconstruction of the lost structures, by way of their size, function, decoration and stylistic evolution. The present study developed a multidisciplinary approach to gather and interpret archaeological fragments and archive sources, in order to gain as much information as possible on “lost monuments”. The approach was tested with remnants (i.e., several hundreds of marble fragments found during archaeological excavations) of the monastic complex of San Francesco di Castelletto (Genoa), which was demolished after the Napoleonic suppressions. A preliminary organisation of the sample set was attained through cataloguing shape, size, and decoration. After this, a comparison with similar complexes still existing in Genoa allowed the inference of the age and specific ornamental functions for the majority of the pieces. Surface analysis, carried out in situ (portable microscope) and on micro-samples (petrographic analysis and SEM-EDS), allowed the characterisation of the materials (e.g., assessing marble provenance and identifying pigments). As a whole, the method evolved into an operational protocol, which helped both the organisation of the archaeological findings and the reconstruction of unknown phases of the lost monument.

Intensive phase treatment outcome and associated factors among patients treated for multi drug resistant tuberculosis in Ethiopia: a retrospective cohort study

BackgroundMulti-drug resistant Tuberculosis (MDR-TB) is a strain of Mycobacterium tuberculosis that is resistant to at least Rifampicin and Isoniazid drugs. The treatment success rate for MDR-TB cases is lower than for drug susceptible TB. Globally only 55% of MDR-TB patients were successfully treated. Monitoring the early treatment outcome and better understanding of the specific reasons for early unfavorable and unknown treatment outcome is crucial for preventing the emergence of further drug-resistant tuberculosis. However, this information is scarce in Ethiopia. Therefore, this study aimed to determine the intensive phase treatment outcome and contributing factors among patients treated for MDR-TB in Ethiopia.MethodsA 6 year retrospective cohort record review was conducted in fourteen TICs all over the country. The records of 751 MDR-TB patients were randomly selected using simple random sampling technique. Data were collected using a pre-tested and structured checklist. Multivariable multinomial logistic regression was undertaken to identify the contributing factors.ResultsAt the end of the intensive phase, 17.3% of MDR-TB patients had an unfavorable treatment outcome, while 16.8% had an unknown outcome with the remaining having a favorable outcome. The median duration of the intensive phase was 9.0 months (IQR 8.04–10.54). Having an unfavorable intensive phase treatment outcome was found significantly more common among older age [ARRR = 1.047, 95% CI (1.024, 1.072)] and those with a history of hypokalemia [ARRR = 0.512, 95% CI (0.280, 0.939)]. Having an unknown intensive phase treatment outcome was found to be more common among those treated under the ambulatory care [ARRR = 3.2, 95% CI (1.6, 6.2)], rural dwellers [ARRR = 0.370, 95% CI (0.199, 0.66)], those without a treatment supporter [ARRR = 0.022, 95% CI (0.002, 0.231)], and those with resistance to a limited number of drugs.ConclusionWe observed a higher rate of unfavorable and unknown treatment outcome in this study. To improve favorable treatment outcome more emphasis should be given to conducting all scheduled laboratory monitoring tests, assignment of treatment supporters for each patient and ensuring complete recording and reporting which could be enhanced by quarterly cohort review. Older aged and rural patients need special attention. Furthermore, the sample referral network should be strengthened.