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1. Construction of equilibrium phase diagrams: Some errors to be avoided

   https://doi.org/https://doi.org/10.1016/j.pmatsci.2020.100715  

   David E. Laughlin, T.B. Massalski (July 2021, Progress in Materials Science)

   null (Ed.)

   Guided by the laws of thermodynamics, phase diagrams can be constructed to display First Order phase transformations (Gibbsian), as well as Higher Order phase transitions (non-Gibbsian). We discuss one and two-component alloy systems in this paper. The principles of the construction of phase diagrams are presented and some of the documented construction errors mentioned in the literature that can arise in phase diagram construction are noted and discussed. We go on to discuss what have been termed “probable errors” of construction. These are constructions which could only arise from the application of highly unlikely solution thermodynamic expressions. We then discuss the application of the Third Law of Thermodynamics to illustrate how phase boundary extrapolations to low temperatures can sometimes be shown to be in error. In addition, errors which may arise in the construction of phase diagrams that include higher order thermodynamic transitions (e.g. magnetic or atomic ordering) are briefly mentioned. These construction rules and comments should be of help to scientists who rely on phase diagrams in the development of materials. Also, we hope that it will be of help to those who utilize computer programs and compilations to display their modeled phase diagrams properly. 

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2. Online Millimeter Wave Phased Array Calibration Based on Channel Estimation

   https://doi.org/10.1109/VTS.2019.8758627  

   Moon, Thomas; Gaun, Junfeng; Hassanieh, Haitham (April 2019, 2019 IEEE 37th VLSI Test Symposium (VTS))

   This paper proposes a new over-the-air (OTA) calibration method for millimeter wave phased arrays. Our method leverages the channel estimation process which is a fundamental part of any wireless communication system. By performing the channel estimation while changing the phase of an antenna element, the phase response of the element can be estimated. The relative phase of the phased array can also be obtained by collecting all the estimated phase responses with a shared reference state. Hence, the phase mismatches of the phased array can be resolved. Unlike prior work, our calibration method embraces all the array components such as power-divider, phase shifter, amplifier and antenna and thus, spans the full chain. By overriding channel estimation, our proposed technique does not require any additional circuits for calibration. Furthermore, the calibration can be performed online without the need to pause the communication. We tested our method on an eight element phased array at 24GHz which we designed and fabricated in PCB for verification. The measured beam patterns prove the viability of our proposed method. 

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3. Deep Convolutional Neural Network Phase Unwrapping for Fringe Projection 3D Imaging

   https://doi.org/10.3390/s20133691  

   Liang, Jian; Zhang, Junchao; Shao, Jianbo; Song, Bofan; Yao, Baoli; Liang, Rongguang (July 2020, Sensors)

   Phase unwrapping is a very important step in fringe projection 3D imaging. In this paper, we propose a new neural network for accurate phase unwrapping to address the special needs in fringe projection 3D imaging. Instead of labeling the wrapped phase with integers directly, a two-step training process with the same network configuration is proposed. In the first step, the network (network I) is trained to label only four key features in the wrapped phase. In the second step, another network with same configuration (network II) is trained to label the wrapped phase segments. The advantages are that the dimension of the wrapped phase can be much larger from that of the training data, and the phase with serious Gaussian noise can be correctly unwrapped. We demonstrate the performance and key features of the neural network trained with the simulation data for the experimental data. 

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4. Anti-phase collective synchronization with intrinsic in-phase coupling of two groups of electrochemical oscillators

   https://doi.org/10.1098/rsta.2019.0095  

   Sebek, Michael; Kawamura, Yoji; Nott, Ashley M.; Kiss, István Z. (December 2019, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences)

   The synchronization of two groups of electrochemical oscillators is investigated during the electrodissolution of nickel in sulfuric acid. The oscillations are coupled through combined capacitance and resistance, so that in a single pair of oscillators (nearly) in-phase synchronization is obtained. The internal coupling within each group is relatively strong, but there is a phase difference between the fast and slow oscillators. The external coupling between the two groups is weak. The experiments show that the two groups can exhibit (nearly) anti-phase collective synchronization. Such synchronization occurs only when the external coupling is weak, and the interactions are delayed by the capacitance. When the external coupling is restricted to those between the fast and the slow elements, the anti-phase synchronization is more prominent. The results are interpreted with phase models. The theory predicts that, for anti-phase collective synchronization, there must be a minimum internal phase difference for a given shift in the phase coupling function. This condition is less stringent with external fast-to-slow coupling. The results provide a framework for applications of collective phase synchronization in modular networks where weak coupling between the groups can induce synchronization without rearrangements of the phase dynamics within the groups. This article is part of the theme issue ‘Coupling functions: dynamical interaction mechanisms in the physical, biological and social sciences’. 

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5. Identifying noise transients in gravitational-wave data arising from nonlinear couplings

   https://doi.org/10.1088/1361-6382/ad7cb7  

   Hall, Bernard; Suyamprakasam, Sudhagar; Mazumder, Nairwita; More, Anupreeta; Bose, Sukanta (November 2024, Classical and Quantum Gravity)

   Abstract Noise in various interferometer systems can sometimes couple non-linearly to create excess noise in the gravitational wave (GW) strain data. Third-order statistics, such as bicoherence and biphase, can identify these couplings and help discriminate those occurrences from astrophysical GW signals. However, the conventional analysis can yield large bicoherence values even when no phase-coupling is present, thereby, resulting in false identifications. Introducing artificial phase randomization in computing the bicoherence reduces such occurrences with negligible impact on its effectiveness for detecting true phase-coupled disturbances. We demonstrate this property with simulated disturbances—focusing only on short-duration ones (lasting up to a few seconds) and employing mainly the auto-bicoherence in this work. Statistical hypothesis testing is used for distinguishing phase-coupled disturbances from non-phase coupled ones when employing the phase-randomized bicoherence. We also obtain an expression for the bicoherence value that minimizes the sum of the probabilities of false positives and false negatives. This can be chosen as a threshold for shortlisting bicoherence triggers for further scrutiny for the presence of non-linear coupling. Finally, the utility of the phase-randomized bicoherence analysis in GW time-series data is demonstrated for the following three scenarios: (1) Finding third-order statistical similarities within categories of noise transients, such as blips and koi fish. If these non-Gaussian noise transients, or glitches, have a common source, their bicoherence maps can have similarities arising from common bifrequencies related to that source. (2) Differentiating linear or non-linear phase-coupled glitches from compact binary coalescence signals through their bicoherence maps. This is explained with a simulated signal. (3) Identifying repeated bifrequencies in the second and third observation runs (i.e. O2 and O3) of LIGO and Virgo. 

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