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We develop a hierarchy of semilattice bases (S-bases) for frames. For a given (unbounded) meet-semilattice A, we analyze the interval in the coframe of sublocales of the frame of downsets of A formed by all frames with the S-base A. We study various degrees of completeness of A, which generalize the concepts of extremally disconnected and basically disconnected frames. We introduce the concepts of D-bases and L-bases, as well as their bounded counterparts, and show how our results specialize and sharpen in these cases. Classic examples that are covered by our approach include zero-dimensional, completely regular, and coherent frames, allowing us to provide a new perspective on these well-studied classes of frames, as well as their spatial counterparts. [ABSTRACT FROM AUTHOR]

This paper summarizes over 60 years of radar system development at MIT Lincoln Laboratory, from early research on satellite tracking and planetary radar to the present ability to perform the centimeter-resolution imaging of resident space objects and future plans to extend this capability to geosynchronous range. [ABSTRACT FROM AUTHOR]

Dance Coherent Action Generation is a popular research task in recent years to generate movements and actions for computer-generated characters in a simulated environment. It is sometimes referred to as "Motion Synthesis". Motion synthesis algorithms are used to generate physically believable, visually compelling, and contextually appropriate movement using motion sensors. The Dance Coherent Action Generation Model (DCAM) is a generative framework for producing aesthetically pleasing movements using deep learning from small amounts of data. By learning an internal representation of motion dynamics, DCAM can synthesize long sequences of movements in which coherent patterns can be created through latent space interpolation. This framework provides a mechanism for varying the amplitude of the generated motion, allowing further realistic thinking and expression. The proposed model obtained 93.79% accuracy, 93.79% precision, 97.75% recall and 92.92% F1 score. DCAM exploits the balance between imitation and creativity by enabling the production of novel outputs from limited input data and can be trained in an unsupervised manner or fine-tuned with sparse supervision. Furthermore, the framework is easily extended to handle multiple layers of abstraction and can be further personalized to a particular type of movement, enabling the generation of highly individualized outputs. [ABSTRACT FROM AUTHOR]

P-band radiometry has been demonstrated to have a deeper sensing depth than L-band, making the consideration of multilayer microwave interactions necessary. In addition, the scattering and phase interference effects are different at the P-band, requiring a reconsideration of the need for coherent models. However, the impact remains to be clarified, and understanding the validity and limitations of these models at both L- and P-bands is crucial for their refinement and application. Therefore, two general categories of microwave emission models, including two stratified coherent models (Njoku and Wilhite) and four incoherent models (conventional tau-omega model and three multilayer models being zero-order, first-order, and incoherent solution), were intercompared for the first time on the same dataset. This evaluation utilized observations of L- and P-bands radiometry under different land cover conditions from a tower-based experiment in Victoria, Australia. Model estimations of brightness temperature (TB) were consistent with measurements, with the lowest root mean square error (RMSE) at P-band V-polarization under corn (2 K) and the highest RMSE at L-band H-polarization under bare soil (13 K). Coherent models performed slightly better than incoherent models under bare soil (3 K less RMSE), while the opposite was true under vegetated soil conditions (1 K less RMSE). Coherent and incoherent models showed maximum differences (3 K at P-band and 2 K at L-band), correlating strongly with soil moisture variations at 0–10 cm. Findings suggest that coherent and incoherent models performed similarly; thus, incoherent models may be preferable for estimating TB at L- and P-bands due to reduced computational complexity. [ABSTRACT FROM AUTHOR]

Forecast reconciliation of multivariate time series maps a set of incoherent forecasts into coherent forecasts to satisfy a given set of linear constraints. Available methods in the literature either follow a projection matrix-based approach or an empirical copula-based reordering approach to revise the incoherent future sample paths to obtain reconciled probabilistic forecasts. The projection matrices are estimated either by optimizing a scoring rule such as energy or variogram score or simply using a projection matrix derived for point forecast reconciliation. This article proves that (a) if the incoherent predictive distribution is jointly Gaussian, then MinT (minimum trace) minimizes the logarithmic scoring rule for the hierarchy; and (b) the logarithmic score of MinT for each marginal predictive density is smaller than that of OLS (ordinary least squares). We illustrate these theoretical results using a set of simulation studies and the Australian domestic tourism dataset. The estimation of MinT needs to estimate the covariance matrix of the base forecast errors. We have evaluated the performance using the sample covariance matrix and shrinkage estimator. It was observed that the theoretical properties noted above are greatly impacted by the covariance matrix used and highlighted the importance of estimating it reliably, especially with high dimensional data. [ABSTRACT FROM AUTHOR]

Optical transmission impairments are most critical reason to reduce both capacity and achievable transmission distance in optical communication system. Advanced modulation formats are important keys to reduce optical transmission impairments in digital signal processing (DSP) based coherent wavelength division multiplexed (WDM) system. These formats are more robust to non-linearity of optical fiber and results in increasing both spectral efficiency and bandwidth. Coherent detection technique increases sensitivity of receiver up to 30 dB in comparison of direct detection. Simulink seems to be the best cost-effective platform for analyzing mathematical modeling of optical coherent system. In this paper, mathematical model has been developed to analyze the optical transmission impairments by employing the advanced polarization multiplexed QPSK modulation in DSP based WDM coherent system. The simulation results have shown bit error rate (BER) improvement up to 10−6 and enhanced transmission distance to 150 km. These values have seen to be in close proximity with experimental results. The developed mathematical model seems to be more useful for extending the existing WDM optical system for longer distances with acceptable BER. [ABSTRACT FROM AUTHOR]

One common method to improve the low signal‐to‐noise ratio of the photoacoustic (PA) signal generated from weak absorbers or absorbers located in deep tissue is to acquire signal multiple times from the same region and perform averaging. However, pulse‐to‐pulse laser fluctuations together with differences in the beam profile of the pulses create undeterministic multiple scattering processes in the tissue. This phenomenon consequently induces a spatiotemporal displacement in the PA signal samples which in turn deteriorates the effectiveness of signal averaging. Here, we present an adaptive coherent weighted averaging algorithm to adjust the locations and values of PA signal samples for more efficient signal averaging. The proposed method is evaluated in a linear array‐based PA imaging setup of ex vivo sheep brain. [ABSTRACT FROM AUTHOR]

We examine the cross-shelf variation of internal tides (ITs) west of the Dongsha Plateau in the northern South China Sea based on observations from 4 moorings deployed between August 2017 and September 2018. On the slope, the amplitude of diurnal baroclinic current ellipses are 5 times larger than that of barotropic currents. The baroclinic energy quickly dissipates during cross-shelf propagation, and barotropic currents become dominant on the shelf outside of the Zhujiang River Estuary, with the amplitude of semidiurnal barotropic current ellipses being 10 times larger than that of the baroclinic ones. Dynamic modal decomposition indicates the first baroclinic mode is dominant for both diurnal and semidiurnal ITs. The total horizontal kinetic energy (HKE) of the first three baroclinic modes shows spatiotemporal differences among the 4 moorings. On the slope, the HKE for diurnal ITs is stronger in summer and winter, but weaker in spring and autumn; for semidiurnal ITs there is a similar seasonal variation, but the HKE in winter is even stronger than that in summer. On the shallow shelf, both diurnal and semidiurnal ITs maintain a certain intensity in summer but almost disappear in winter. Further analysis shows that only the upper water column is affected by seasonal variation of stratification on the slope, variation of diurnal ITs is thus controlled by the semi-annual cycle of barotropic energy input from the Luzon Strait, while the incoherent baroclinic currents make a major contribution to the temporal variation of semidiurnal ITs. For the shelf region, the water column is well mixed in winter, and the baroclinic energy largely dissipates when ITs propagate to the shelf zone despite of a strong barotropic energy input from the Luzon Strait. [ABSTRACT FROM AUTHOR]

We extend several results of Helfer, Wise, Louder and Wilton related to coherence in one-relator groups to the more general setting of one-relator products of locally indicable groups. The methods developed to do so also give rise to a new proof of a theorem of Brodskiĭ. [ABSTRACT FROM AUTHOR]

Let be a left -module with the endomorphism ring . Given two cardinal numbers and and a matrix , is called flat relative to in case, for each , there are a positive integer , and a row-finite matrix over such that and . It is shown that is flat relative to a matrix if and only if is generated by . is called left coherent relative to if Ker is finitely generated. It is shown that is left coherent relative to if and only if Hom is a finitely generated left -module if and only if has an add -precover (add denotes the category of all direct summands of finite direct sums of copies of ). Regarding applications, new necessary and sufficient conditions for epic (monic, having the unique mapping property) add -precovers of are investigated. Also, some new characterizations of left -semihereditary rings and von Neumann regular rings are given. [ABSTRACT FROM AUTHOR]

This paper investigates the performance analysis of RS-coded and un-coded coherent M-QAM modulated OFDM free space optical communication system. The system performance is analyzed using block error rate. Mathematical expressions are derived for the average block error rate under the combined effects of attenuation loss, pointing error, and gamma-gamma distributed atmospheric turbulence, and results are validated using Monte Carlo simulation. M-QAM modulated OFDM system with RS codes enhances the system performance more than an un-coded system. Coherent OFDM-FSO improves the system performance by overcoming the effects of atmospheric factors. [ABSTRACT FROM AUTHOR]

Coherent scatter echoes from disintegrating meteors and from the unstable ionospheric E‐region can overlap considerably between 90 and 110 km altitudes. As the physical origin of plasma irregularities produced by meteor trails differs starkly from that of E‐region auroral irregularities, this has consequences for winds as well as electrodynamic studies, thereby introducing a need to distinguish between the two types of echoes. To that goal, we have developed a novel separation algorithm to automatically sort through arbitrarily large data sets in the region of overlap. This proves very useful when the 3D location of echoes is available. The algorithm uses a definition of crowding, or clustering, in both time and space and has been developed and tested with a comprehensive data set obtained from the recently built Canadian icebear 3D radar. We discuss the characteristics belonging to the two classes of echoes, and present statistical results about the location of each type of echo as a function of conditions. Our proposed algorithm can be applied to any coherent scatter echo data with high resolution 3D location information. Plain Language Summary: Radars measure turbulence in space plasma by bouncing a signal off of sharp plasma density gradients in the ionosphere. For decades, such coherent radars have been useful tools to investigate the ionosphere. However, when probing E‐region plasma, a coherent radar will pick up plasma produced by meteors as they enter Earth's atmosphere. We have developed an automatic algorithm to separate meteor trail echoes, as they are called, from space plasma measurements. We demonstrate the efficiency of this algorithm on the icebear 3D data set, which has an unprecedented resolution, and offers accurate 3D location data for space plasma turbulence. Key Points: Using new data from icebear 3D, we find that ionospheric turbulence overlap with meteor trail echoes between 90 and 110 km altitudeThe starkly different patterns of clustering in time and space of high latitude ionospheric turbulence and meteoric echoes are used to distinguish the echo typesThe spatial and temporal separation between observed meteor trail echoes is normally several orders of magnitude above that of ionospheric turbulence echoes at high latitudes [ABSTRACT FROM AUTHOR]

It has been shown that Relative Humidity (RH) provokes dimensional displacement detectable directly from surfaces using holographic interferometry. RH variations constitute a physical environmental load that drives organic materials to a constant equilibrium cycle. This paper is a small synopsis of the interferometric research direction and a data acquisition on the detection of the dimensional impact of relative humidity on cultural heritage objects. Since RH cycling is unavoidable, the interferometric data change depends on the object structure and RH cycle characteristics. Based on the fact that each artwork is by construction unique, and on the observation that the effects of an RH cycle on the structural condition of any artwork are also unique but the preventive conservation strategies require generalised approaches and not on a case-by-case study, being introduced is a novel, universal, preventive deterioration methodology: "deformation threshold value" (DTV). DTV is assignable to each distinct object in order to control routinely its structural condition and prevent damage. DTV is not assigned hypothetically based on any assumed/expected reactions but from a monitored calibration of the artwork in its environment. Each artwork in its hosted environment has its unique reaction. The reaction, though, is not steady but changes as the artwork changes. DTV can be acquired routinely and valued accordingly to seasonal RH change. Monitoring the seasonal RH and seasonal dimensional reaction has been shown to correspond to a standard DTV pattern whose deviations violate the expected seasonal reaction. Through the interferometric monitoring of surface, the distinct DTV acts as a safeguard for the artwork. In this synopsis, some results of the generation of DTVs are shown. Our future plan is for the DTV numbers to serve as data inputs for preventive models to formulate a distinct risk index representative of each artwork condition and to be used as remote risk warning to prevent its deterioration. Based on the DTV concept, methods and instruments for sequential data acquisition aim to present experimental data outputs as DTVs that identify transient shape changes prior to visible damage have been developed. In this research, the starting point was the interferometric quantification of the displacement of well-characterized fresh samples. The fresh samples are known in terms of density, cut, thickness, moisture content, structural condition and are submitted to RH simulation cycles. Shown here are three exemplary cases: usual, abrupt and smooth. The interferometric monitoring following the cycles of RH is a long-term duration of several weeks; measurements are performed directly from the surface, and relative displacement (RD) from temporal measurements of interference fringes provide the required output data to calculate the rate of displacement (RoD) of the surface. Measuring the impact of RH directly from the artwork surface allows the detection of the temporal diversity of structural reactions to the same RH cycle for distinct artworks. The monitoring system uses interferometric precision provided by digital holographic speckle-pattern interferometry (DHSPI) placed on a specially designed climate chamber DHSPI monitoring workstation. [ABSTRACT FROM AUTHOR]

Biomedical data preprocessing and efficient computing can be as important as the statistical methods used to fit the data; data processing needs to consider application scenarios, data acquisition and individual rights and interests. We review common principles, knowledge and methods of integrated research according to the whole-pipeline processing mechanism diverse, coherent, sharing, auditable and ecological. First, neuromorphic and native algorithms integrate diverse datasets, providing linear scalability and high visualization. Second, the choice mechanism of different preprocessing, analysis and transaction methods from raw to neuromorphic was summarized on the node and coordinator platforms. Third, combination of node, network, cloud, edge, swarm and graph builds an ecosystem of cohort integrated research and clinical diagnosis and treatment. Looking forward, it is vital to simultaneously combine deep computing, mass data storage and massively parallel communication. [ABSTRACT FROM AUTHOR]

Copyright of CT Theory & Applications is the property of Editorial Department of CT Theory & Applications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, by mapping datasets to a set of non-linear coherent states, the process of encoding inputs in quantum states as a non-linear feature map is re-interpreted. As a result of the fact that the radial basis function is recovered when data is mapped to a complex Hilbert state represented by coherent states, non-linear coherent states can be considered as a natural generalisation of the associated kernels. In this paper, as an example of kernels based on non-linear coherent states, we propose kernel functions based on generalized hypergeometric functions, as orthogonal polynomial functions. The suggested kernel is implemented with the support vector machine (SVM) on two well known datasets (make_circles, and make_moons) and outperforms the baselines, even when the level of noise is high. In addition, we study the impact of the geometrical properties of the feature space, obtained by the non-linear coherent states, on the SVM classification task, by considering the Fubiniâ€"Study metric of the associated coherent states. [ABSTRACT FROM AUTHOR]

This article presents a pulsed-coherent lidar that uses a 19-GHz pulse-modulated optical carrier and segmented time-of-flight (ToF) detection. The receiver analog frontend (AFE) employs a down-conversion chain that consists of a phase-invariant programmable-gain low-noise amplifier (PI-PGLNA), a sub-harmonic mixer (SHM), and an inverter-based phase-invariant programmable-gain amplifier (PI-PGA). The local oscillator (LO) is generated from a phase-locked loop (PLL) with a ring-type voltage-controlled oscillator (VCO). An analog-to-digital converter (ADC) subsamples the down-converted signal, and a digital signal processor (DSP) calculates the coarse, intermediate, and fine ToF. At the receiver input, a narrowband matching is implemented between the p-i-n photodiode and the PI-PGLNA with direct wire bonding. The system achieves 6- $\mu \text{m}$ precision with a 5-MSa/s sampling rate at a 2.5-m distance. The 2-D scanning is achieved with this lidar with the use of an MEMS mirror. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Direction of arrival (DOA) estimation of coherent sources with a uniform circular array (UCA) is an intractable problem. The method-of-direction-estimation (MODE) algorithm has strong superiority in handling coherent sources compared with the classical MUSIC, and ESPRIT algorithms. However, MODE is sensitive to source numbers and does not work well in the UCA scenario. In order to improve the performance of MODE, a robust DOA estimation method named UCA-PUMA (principal-eigenvector-utilization for- modal-analysis) is proposed. The complicated non-Vandermonde structured steering vector of UCA is transformed into a virtual Vandermonde structured steering vector in mode space. The proposed method gives a closed-form solution compared with the original UCA-MODE algorithm. The performance of the UCA-PUMA method is evaluated by simulations. Simulation results demonstrate that the UCA-PUMA is more robust to source numbers than the UCA-MODE, and coherent sources can be handled without spatial smoothing. In addition, the UCA-PUMA fully takes advantage of the UCA, which is able to discriminate sources coming from a 360° azimuthal field of view. [ABSTRACT FROM AUTHOR]

Our main result states that if G is a finitely generated soluble group having a normal Abelian subgroup A, such that G/A and are nilpotent (respectively, finite-by-nilpotent, periodic-by-nilpotent, nilpotent-by-finite, finite-by-supersoluble, supersoluble-by-finite) for all (x, a) ∈ G × A, then so is G. We deduce that if 픛 is a subgroup and quotient closed class of groups and if all 2-generated Abelian-by-cyclic groups of 픛 are nilpotent (respectively, finite-by-nilpotent, periodic-by-nilpotent, nilpotent-by-finite, finite-by-supersoluble, supersoluble-by-finite), then so are all finitely generated soluble groups of 픛. We give examples that show that our main result is not true for other classes of groups, like the classes of Abelian, supersoluble, and FC-groups. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Different constraints to the neutrino electric millicharge (NEM) have been obtained by considering interactions such as the elastic neutrino-electron scattering (ENES). However, the great potential of the coherent elastic neutrino-nucleus scattering (CE NS) in future reactor neutrino experiments could be an alternative to improve the current limits on the NEM. In this work we study the sensitivity of ENES and CE NS interactions in reactor experiments to the neutrino charge through a combination of different experimental data. Bounds up to the order of are achieved from CE NS at reactor neutrino experiments. [ABSTRACT FROM AUTHOR]

We have studied the characteristic feature of coherent photon transport in a semiconductor waveguide. We have presented a semiconductor master equation formalism that accurately simulated coherent input or output coupling of semiconductor cavity quantum electrodynamics systems such as planar photonic crystals and micropillar cavities. The role of quantized multiphoton effects pointed out the possible failure of weak excitation approximation, which was found to fail even for low input powers and small mean cavity photon numbers. For increasing field strengths, possible failure of the semiclassical approach was taken into account. In the weak coupling regime, higher order quantum correlation effects, were shown to be significant. We have introduced the general theoretical technique to simulate coherent photon transport outside both the weak excitation approximation and the semi classical approximation. Electron-phonon interactions at a microscopic level were derived using polaron transformation. We have demonstrated that substantial deviations from the weak excitation approximation resulted for very small mean photon numbers. We have modified the master equation approach to include the mechanism of electron-acoustic scattering and studied the impact of electron-phonon interaction on incoherent scattering and coherent renormalization of the exciton cavity coupling rate, qualitative differences from simple Lorentzian decay model containing quantum dot were found. We have also studied the transmission of light in the strong coupling regime and simulated a phase gate. We have found that coupling to an acoustic phonon bath caused considerable qualitative changes in light propagation characteristics modeled by a simple pure dephasing process. We have used the model to simulate a conditional phasegate. The obtained results were found in good agreement with previously obtained results. [ABSTRACT FROM AUTHOR]

Let be a ring graded by an arbitrary grading abelian group Γ. We say that R is a uniformly graded-coherent ring if there is a map ϕ : ℕ → ℕ such that for every n ∈ ℕ, and any nonzero graded R-module homomorphism of degree 0, where λ1 , ... ,λn are degrees in Γ, ker f can be generated by ϕ(n) homogeneous elements. In this paper, we provide the elementary properties of uniformly graded-coherent rings. [ABSTRACT FROM AUTHOR]

As fiber-optic systems turn toward multi-band transmission (MBT), exploiting the complete low loss window of optical fibers, novel optical components, able to operate in bands other than the conventional C-band, become necessary. In light of this, we report on a multi-band photonic integrated $\mathbf {1\times 2}$ wavelength selective switch (WSS) operating in the O, S, C and L-bands. The photonic integrated WSS presented in this work uses a folded arrayed-waveguide grating (AWG) as the filtering element, while the wideband operation of the thermo-optic switches allows the routing of the individual channels from those bands to any of the device output ports. The operation of the WSS is experimentally validated for different bands and modulation formats. Results show error-free operation with limited penalty with intensity-modulation direct-detection (IM/DD) non-return-to-zero on-off keying (NRZ-OOK) up to 35 Gb/s in O, S, C and L-bands and up to 169.83 Gb/s with coherent 64-quadrature amplitude modulation (QAM) data transmission in the S, C and L-bands. [ABSTRACT FROM AUTHOR]

This literature review tests a framework for coherent implementation of school improvement initiatives. Often in education, initiatives are introduced as disparate, isolated approaches towards improved student learning. As a result, teachers, school-based administration and school districts frequently change their focus, contributing to fragmentation, stagnation and initiative fatigue. Robinson et al. offer 'five domains of organizational activity' as key areas of focus for coherent school improvement. We investigate application of Robinson et al.'s five domains to two seemingly disparate school improvement initiatives: outcomes-based assessment (OBA) and trauma-informed practice (TIP) as both represent significant areas of focus in our context. We construct our literature review around the central question: Can two divergent aspects of school improvement: outcomes-based assessment and trauma-informed practice, be aligned through Robinson et al.'s five domains, to coherently support their integration in schools? We found that Robinson et al.'s five domains were a useful tool for alignment of these diverse initiatives and were able to extrapolate beyond application to OBA and TIP, to other school improvement initiatives. Coherence benefits administration, teachers, and most importantly, promotes student achievement. When all elements of school improvement are part of a cohesive whole, all members the school community are better able to understand their role in driving student achievement. [ABSTRACT FROM AUTHOR]

Copyright of Roca: Revista Científico-Educacional de la Provincia de Granma is the property of Universidad de Granma, Departamento Editorial and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We develop a ‘perfect’ design for PAM4 Segmented Mach-Zehnder Modulators (SEMZM), featuring a fully linear (uniform) optical DAC (oDAC) staircase (i.e., having equi-spaced PAM4 levels) and no intrinsic modulation loss (the qualifier ‘perfect’ pertains to ideal conditions, barring optical excess losses and other impairments). This is achieved by leveraging our recently introduced maximin optimization strategy, enabling to locate the hitherto unknown optimal operating point in the serial oDAC parameters space, gaining ~7 dB relative to conventional PAM4 designs (typically based on a pair of segment electrodes in 2:1 lengths ratio and using 3 dB modulation backoff in order to compensate for degradation in oDAC linearity). The same photonic design may be reused to generate DAC-free coherent PAM4 (bipolar symmetric field-domain equi-spaced max-full-scale constellations), for efficient I/Q tributaries of 16QAM. [ABSTRACT FROM AUTHOR]

The aim of this paper is twofold. Firstly, to give short proofs of the celebrated results of Rudd (1970), De Marco (1972), Brookshear (1977), Neville (1990), and Vechtomov (1996) with the help of some well-known results in ring theory. Secondly, to establish new algebraic characterizations for when C(X) is von Neumann regular, semihereditary, or a Bézout ring. The notions of the greatest common divisor and least common multiple in the ring C(X) are studied. Finally, the space X, for which every idempotent of the classical quotient ring of C(X) is actually an element of C(X) itself, is completely determined. [ABSTRACT FROM AUTHOR]

We review the most important WDM system innovations motivated by the evolution of DCI transport. State-of-the-art coherent transmission has already exceeded 6 b/s/Hz in transatlantic deployments. Moreover, the adoption of software innovations in automation and programmability, which DCI pioneered in transport networks, has also simplified operations and enables the emergence of open transport architectures. Combining these advances with emerging network analytic frameworks allows exciting innovations in network design and management optimization. [ABSTRACT FROM AUTHOR]

A method, hereinafter referred to as discrete chaff cloud model (DCCM), for the electromagnetic modeling of general chaff clouds is presented, with which harmonic or wideband impulse scattering responses can be evaluated. The model applies to a wide range of scenarios, for any combination of illumination and observation angles and polarizations. The technique considers the geometry of the cloud and the statistical distributions of the elements, both in density and orientation. After a 1-D discretization of the cloud, the complete statistical response or single-experiment observations can be evaluated. The model is formulated in a very general form to extend its applicability as much as possible. Its limitations have been identified and assessed in relevant scenarios. Validation cases have been included, comparing results obtained with DCCM, other published formulations, and full-wave simulations. [ABSTRACT FROM AUTHOR]

We propose a novel implementation of a complex analog equalization filter for the compensation of frequency-dependent variations in coherent optical links. The analog compensation filter can be used in coherent-lite optical communication links where digital signal processing (DSP) is removed to limit the complexity and power consumption. In these links, the filter can compensate for electrical bandwidth limitations and distortion introduced by chromatic dispersion in the fiber. The complex filter is implemented by combining four distributed analog finite-impulse response (FIR) filters to obtain the necessary response. The filter delays are implemented using active delay cell structures to create a compact solution. The analog filter is implemented in a 55-nm BiCMOS technology and consumes 185-mW core power for five complex filter taps. Performance is evaluated using the S-parameter measurements, noise and linearity measurements, and real-time system experiments using 112-Gb/s 16-QAM-modulated signals. [ABSTRACT FROM AUTHOR]

The article discusses the study "Identification of Critical Isthmus Using Coherent Mapping in Patients With Scar-Related Atrial Tachycardia," by J. J. B. Vicera, Y. Lin, P. Lee and colleagues, that was published in this issue of the publication. Topics covered include complex atrial tachycardia, coherent versus standard local activation time mapping, and the interpretation and optimization of the coherent-mapping module.

Some of the different aspects of the DSP enabled receivers in access networks will be addressed in this article. A revision of the main topics which may impact DSP design will be discussed through application examples. Modulation formats, KK receivers, and coherent receivers are analyzed at light of the DSP enabled receivers’ impact. Also, relevant are FEC and burst mode which are debated at the light of PON requirements. Simplified analog coherent receivers are presented as a use case to serve as simplification path for non-DSP high performance receivers. On the other end, aiming at discussing current PON limits, an ultra dense wavelength division multiplexing (UDWDM) use case is also presented where several advanced topics like pulse shaping, high density, and simplified DSP operations are considered. [ABSTRACT FROM AUTHOR]

In recent years, the sources localization has noticed an increase in research conducted on the problem of mixed far-field sources (FFSs) and near-field sources (NFSs). The main assumption of the existing researches is that the signals should be uncorrelated. Therefore, they cannot be used for multipath environments. The present paper provides a method called components separation algorithm (CSA) for the localization of multiple mixed FFSs and NFSs, including uncorrelated, lowly correlated and coherent signals. Firstly, by constructing one special cumulant matrix, and using a MUSIC-based technique, the noncoherent DOA vector (NDOAV) is extracted. By constructing another special cumulant matrix, and with respect to NDOAV, an estimate of the range, as well as a signal classification is obtained for noncoherent sources. Then, by estimating their kurtosis, the noncoherent component and consequently the coherent one of the second cumulant matrix is obtained. Finally, by introducing a novel approach based on squaring, projection, spatial smoothing, array interpolation transform and coherent component restoring, the parameters of coherent signals in each coherent group are estimated separately. The CSA prevents severe loss of the aperture. Furthermore, it does not require any pairing. The simulation results validate its satisfactory performance in terms of estimation accuracy, resolution, computational complexity, reasonable classification, and also its robustness against lowly correlated sources. [ABSTRACT FROM AUTHOR]

We demonstrate an all-analogue converter from optical intensity modulated direct-detection double-side-band signals to field-modulated optical coherent signals, which is based on the Weaver method of generating SSB radio signals. Our format converter is designed to interface short-haul datacentre links to coherent metro/long-haul links. It has almost-zero latency, as it is based on analog electronic processing. As a proof of principle, we demonstrate a system with a 10-km short haul link and a noise-loaded coherent link, transmitting QPSK and 16-QAM. By reconfiguring the link with subsets of its components, we are able to demonstrate that the main impairments are due to the performance of the RF mixers and the directly modulated laser. The performance could be improved by using higher-bandwidth directly modulated lasers and RF mixers. [ABSTRACT FROM AUTHOR]

Nuclear fusion reaction is greatly enhanced by the coherent properties of bosons in its product. A simple model calculation yields an enhancement factor m 2 for each coherent boson in its product. Explicit calculation is carried out for d + d → α + γ. Its coherent reaction rate is shown to increase as m 4 , where m is the number of coherent nuclear reactions among deuterons. The number m must be greater than a certain critical value before coherent nuclear fusions occur. Several decoherent effects need to be minimized so that the nuclear reaction can become coherent. Current technical levels for extreme ultraviolet lasers, ultrashort laser pulse, the strongest transient magnetic field and nanotechnology are found sufficient to construct the first nuclear coherent fusion experiment. [ABSTRACT FROM AUTHOR]

Boosting is a machine learning approach built upon the idea of producing a highly precise prediction rule by combining many relatively weak and imprecise rules. The Adaptive Boosting (AdaBoost) algorithm was the first practical boosting algorithm. It remains one of the most broadly used and studied, with applications in many fields. In this paper, the AdaBoost algorithm is utilized to improve the bit error rate (BER) of different modulation techniques. By feeding the noisy received signal into the AdaBoost algorithm, it is able to recover the transmitted data from the noisy signal. Consequently, it reconstructs the constellation diagram of the modulation technique. This is done by removing the noise that affects and changes the signal space of the data. As a result, AdaBoost shows an improvement in the BER of coherently detected binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK). The AdaBoost is next used to improve the BER of the noncoherent detection of the used modulation techniques. The improvement appears in the form of better results of the noncoherent simulated BER in comparison to that of the theoretical noncoherent BER. Therefore, the AdaBoost algorithm is able to achieve a coherent performance for the noncoherent system. The AdaBoost is simulated for several techniques in additive white Gaussian noise (AWGN) and Rayleigh fading channels so, as to verify the improving effect of the AdaBoost algorithm. [ABSTRACT FROM AUTHOR]

Reliable electromagnetic simulators are of prime importance for the design of radar sounder instruments and for supporting the subsequent analysis of their data. In this paper, we present a coherent, facet method-based simulator that can compute radar echoes from the subsurface of a target area with an arbitrary number of geological layers, thus going beyond the surface-only or the two-layer descriptions so far implemented in coherent ray-tracing radar sounder simulators. Propagation of fields throughout the subsurface is computed according to Snell’s law following a ray-tracing approach. For each ray interacting with the surface, be it a direct reflection or a refracted ray coming from the subsurface, the phase contribution of each facet is calculated through the linear phase approximation, while the total field received at the antenna is computed using Huygen’s principle. Validation simulations have been performed against the radar data of lunar and martian areas characterized by a multilayer nature and collected by the Lunar Radar Sounder instrument of JAXA’s Kaguya lunar probe and the Shallow Radar instrument onboard NASA’s Mars Reconnaissance Orbiter, respectively. Results confirm the effectiveness of the proposed simulator. [ABSTRACT FROM AUTHOR]

The satellite-to-ground optical communication system suffers from atmosphere turbulence severely. It is well-known that the coherent detection can increase the receiver sensitivity and performing aperture averaging can reduce the scintillation caused by the atmosphere turbulence. In this paper, the bit error rate, the outage probability and the average capacity of a coherent satellite-to-ground optical communication downlink with aperture averaging are analyzed. The Log-normal atmosphere turbulence model and BPSK (Binary Phase Shift Keying) modulation is employed. The analyzing focuses on the improvement of aperture averaging with different atmospheric conditions and zenith angles of the satellite. The bit error rate performance based on measuring data is given too. The results demonstrate the bit error rate and the outage probability can be reduced and the average capacity can be improved by aperture averaging efficiently. When the turbulence is stronger and the zenith angle is larger, the effect of aperture averaging is more obvious. The aperture averaging effect on BER (Bit Error Rate) is better than the effect on average capacity. [ABSTRACT FROM AUTHOR]

This work presents the exact symbol error rate (SER) analysis of semi-coherent demodulated systems in the presence of imperfect knowledge of the channel estimates. The SER is derived in the context of orthogonal frequency division multiplexing (OFDM) systems where a modulation-hybrid frame structure is considered to enable blind channel estimation using a decision-directed approach. The exact SER is derived and presented in a closed-form analytical expression, which is then used to compute an accurate formula for the mean squared error (MSE) of the channel estimates. The obtained analytical and simulation results show that the SER and MSE are highly dependent on the channel correlation factor. However, reliable SER can still be obtained for most practical channel models, particularly when receiver diversity is incorporated. [ABSTRACT FROM AUTHOR]

In the field of array signal processing, direction of arrival (DOA) estimation is a prime area of research. DOA estimation and adaptive beamforming (ABF) are the main issues in smart antennas, which dynamically find the direction of desired and interfering users and finds the optimum weights for beamforming. There are numerous spectral and eigen structure algorithms for estimating the direction of narrow band sources. However, in a complex multipath channel environment, received signals from different directions are fully or partially correlated, which prevents the applications of high resolution techniques to estimate the direction of incoming signals. Maximum likelihood (ML) is an efficient technique for DOA estimation in a low signal to noise ratio (SNR) and coherent channel environment. In this paper, we use particle swarm optimization (PSO) for estimating ML solution by optimizing complex non linear multimodal function over a high dimensional space in linear arrays. PSO-ML estimator has been compared with conventional DOA estimation techniques in uncorrelated, partially correlated and coherent channel environment. The performance of PSO-ML estimator and conventional algorithms are analyzed in varying partially correlated channel environment. The simulation results demonstrate that PSO based estimator gives superior statistical performance. [ABSTRACT FROM AUTHOR]

Nonlinear frequency division multiplexing (NFDM) with the modulation of the nonlinear Fourier spectrum (both discrete and/or continuous parts) have been recently considered as a potential transmission method to combat the fiber nonlinearity impairments. However, due to many challenges in design, digital signal processing (DSP), numerical algorithms, and hardware implementation, reported data rates of NFDM systems have been so far limited to 50 Gb/s. In this paper, we experimentally demonstrate a practical approach for increasing the data rate of NFDM transmission systems by increasing the number ofmodulated nonlinear subcarriers together with the application of a precompensation technique for the channel-induced phase-shift in the nonlinear Fourier domain. As a result, a record-high data rate of 125 Gb/s and spectral efficiency over 2 bits/s/Hz in burst-mode, single-polarization NFDM transmissions were achieved over 976 km of standard single mode fiber with EDFA-only amplification by transmitting and processing 222 32 QAM-modulated nonlinear subcarriers simultaneously. [ABSTRACT FROM AUTHOR]

Subsurface eddies are known features of ocean circulation, but the sparsity of observations prevents an assessment of their importance for biogeochemistry. Here we use a global eddying (0.1°) ocean‐biogeochemical model to carry out a census of subsurface coherent eddies originating from eastern boundary upwelling systems (EBUS) and quantify their biogeochemical effects as they propagate westward into the subtropical gyres. While most eddies exist for a few months, moving over distances of hundreds of kilometers, a small fraction (<5%) of long‐lived eddies propagates over distances greater than 1,000 km, carrying the oxygen‐poor and nutrient‐rich signature of EBUS into the gyre interiors. In the Pacific, transport by subsurface coherent eddies accounts for roughly 10% of the offshore transport of oxygen and nutrients in pycnocline waters. This “leakage” of subsurface waters can be a significant fraction of the transport by nutrient‐rich poleward undercurrents and may contribute to the well‐known reduction of productivity by eddies in EBUS. Furthermore, at the density layer of their cores, eddies decrease climatological oxygen locally by close to 10%, thereby expanding oxygen minimum zones. Finally, eddies represent low‐oxygen extreme events in otherwise oxygenated waters, increasing the area of hypoxic waters by several percent and producing dramatic short‐term changes that may play an important ecological role. Capturing these nonlocal effects in global climate models, which typically include noneddying oceans, would require dedicated parameterizations. [ABSTRACT FROM AUTHOR]

This paper establishes a tensor model for wideband coherent array processing including multiple physical diversities. A separable coherent focusing operation is proposed as a preprocessing step in order to ensure the multilinearity of the interpolated data. We propose an alternating least squares algorithm to process tensor data, taking into account the noise correlation structure introduced by the focusing operation. We show through computer simulations that the estimation of direction of arrival and polarization parameters improves compared to existing narrowband tensor processing and wideband MUltiple SIgnal Classification. The performance is also compared to the Cramér-Rao bounds of the wideband tensor model. [ABSTRACT FROM PUBLISHER]

A 170-GHz fully integrated single-chip heterodyne frequency modulated continuous-wave (FMCW) imaging radar using a 130-nm SiGe BiCMOS technology ( fT/f\max = 220/280 GHz) is reported. This system demonstrates a wide bandwidth of 27.5 GHz (16.3%) at a center frequency of 168 GHz. A design methodology to maximize the tuning range of the voltage-controlled oscillator (VCO) is presented. A co-design of the VCO, coupler, and antenna is performed to minimize the chip area and the dc power consumption. The transmitter radiates a peak power of −1 dBm with a dc-to-RF efficiency of 1.42%. At the receiver side, a subharmonic mixer is used for signal down-conversion. The system achieves a measured sensitivity of 87 fW with a total dc power consumption of 67 mW. The prototype is capable of forming 2-D and 3-D images with a range resolution of 7 mm. To the best of our knowledge, this fully integrated imaging radar demonstrates the highest sensitivity and radiation efficiency among all imaging systems around 200 GHz. Moreover, the system is capable of practical 2-D and 3-D imaging with significantly lower dc power consumption compared to the state-of-the-art FMCW radars. [ABSTRACT FROM AUTHOR]

There has been an increase in the amount and complexity of traffic on Dutch inland waterways. Traffic management shifted from local traffic control to corridor traffic management. Due to these changes, operators in nautical traffic management centers experience difficulty to gain and maintain sufficient situation awareness. In our previous research, three groups of deficiencies of current situation awareness support have been identified. To overcome these deficiencies, a theoretical framework for information engineering user interface concepts was developed and used for designing three interface concepts. A coherent, an integrated and a context-dependent adaptable user interface were designed and implemented as testable prototypes. To support the process of information engineering, we combined user-centered design techniques with the formalism of set theory, directed graphs and semantic networks. From a methodological point of view, these proved to be useful both in conceptualization and implementation of the concepts. The usability of these concepts was tested in a simulator environment. The results show that the implemented prototypes represent an important improvement compared to the traditional interface solutions currently used by nautical traffic management operators. However, it was recognized that the coherent user interface implementation still suffered from a number of deficiencies. The context-dependent adaptable user interface was evaluated most positively. [ABSTRACT FROM AUTHOR]

Nonlinear frequency division multiplexing (NFDM) with the modulation of the nonlinear Fourier spectrum (both discrete and continuous parts) has been recently considered as a promising transmission method to combat fiber nonlinearity impairments. In this paper, we experimentally demonstrate the generation, detection, and transmission performance of NFDM systems where the transmitted information is encoded directly onto the continuous part of the nonlinear spectrum using 64 overlapped 0.5 Gbaud channels with high order QAM formats (e.g., 16 QAM, 32 QAM, and 64 QAM). In comparison with the conventional orthogonal frequency division multiplexing transmission, which is the linear counterpart of NFDM transmission, clear performance advantage of NFDM systems, up to 1.3 dB, has been observed. This result indicates for the first time the performance benefit of NFDM transmission over its linear counterpart, showing the high potential of this emerging technology. [ABSTRACT FROM PUBLISHER]

A general linearly constrained narrowband adaptive array is examined in the eigenvector space. The optimum weight vector in the eigenvector space is shown to have the same performance as in the standard coordinate system, except that the input signal correlation matrix and look direction steering vector are replaced with the eigenvalue matrix and transformed steering vector. It is observed that the variation in gain factor results in the variation in the distance between the constraint plane and the origin in the translated weight vector space such that the increase in gain factor decreased the distance from the constraint plane to the origin, thus affecting the nulling performance. Simulation results showed that the general linearly constrained adaptive array performed better at an optimal gain factor compared with the conventional linearly constrained adaptive array in a coherent signal environment and the former showed similar performance as the latter in a noncoherent signal environment. [ABSTRACT FROM AUTHOR]

First, we show that every coherent tree that contains a Countryman suborder is $${\mathbb {R}}$$ -embeddable when restricted to a club. Then for a linear order O that can not be embedded into $$\omega $$ , there exists (consistently) an $${{\mathbb {R}}}$$ -embeddable O-ranging coherent tree which is not Countryman. And for a linear order $$O'$$ that can not be embedded into $${\mathbb {Z}}$$ , there exists (consistently) an $${\mathbb {R}}$$ -embeddable $$O'$$ -ranging coherent tree which contains no Countryman suborder. Finally, we will see that this is the best we can do. [ABSTRACT FROM AUTHOR]