Hybrid Polarity Research Articles

Polarity Inversion of Ga‐Polar GaN Surfaces by Exposing to Mg and NH3 in Metal–Organic Vapor Phase Epitaxy

AbstractA metal–organic vapor phase epitaxy process of polarity inversion (PI) from Ga‐ to N‐polar is reported by exposing the Ga‐polar surface simultaneously to Mg and ammonia flows. This process differs from the conventional Mg heavy‐doping technique by intentionally predepositing a Mg‐rich thin layer on the Ga‐polar surface for PI. A full PI with a smooth surface in the subsequent GaN overgrowth is achieved by an exposure process for 900 s at 700 °C. Atomic force microscopy and piezo‐force microscopy characterizations reveal that the polarity change undergoes simultaneously with pyramid formation after ≈15 nm thick GaN overgrowth. The electron dispersion spectroscopy mapping of Mg indicates high Mg concentrations at the regrowth interface and in the PI domain boundary. A Mg‐rich thin layer is believed to cover the surface after the exposure process and release Mg dopants in the subsequent growth, leading to a high Mg incorporation in the GaN overlayer and therefore inducing PI. P‐type conduction with a hole concentration of ≈2.7 × 1017 cm−3 is achieved in the N‐polar GaN overlayer. It is also demonstrated that such a PI technique can be employed in the growth of a hybrid polarity structured ultraviolet‐light‐emitting diode with a reversed N‐polar contact layer on a Ga‐polar main body.

Hybrid context enriched deep learning model for fine-grained sentiment analysis in textual and visual semiotic modality social data

Detecting sentiments in natural language is tricky even for humans, making its automated detection more complicated. This research proffers a hybrid deep learning model for fine-grained sentiment prediction in real-time multimodal data. It reinforces the strengths of deep learning nets in combination to machine learning to deal with two specific semiotic systems, namely the textual (written text) and visual (still images) and their combination within the online content using decision level multimodal fusion. The proposed contextual ConvNet-SVMBoVW model, has four modules, namely, the discretization, text analytics, image analytics, and decision module. The input to the model is multimodal text, m ε {text, image, info-graphic}. The discretization module uses Google Lens to separate the text from the image, which is then processed as discrete entities and sent to the respective text analytics and image analytics modules. Text analytics module determines the sentiment using a hybrid of a convolution neural network (ConvNet) enriched with the contextual semantics of SentiCircle. An aggregation scheme is introduced to compute the hybrid polarity. A support vector machine (SVM) classifier trained using bag-of-visual-words (BoVW) for predicting the visual content sentiment. A Boolean decision module with a logical OR operation is augmented to the architecture which validates and categorizes the output on the basis of five fine-grained sentiment categories (truth values), namely ‘highly positive,’ ‘positive,’ ‘neutral,’ ‘negative’ and ‘highly negative.’ The accuracy achieved by the proposed model is nearly 91% which is an improvement over the accuracy obtained by the text and image modules individually.

Controllable Transformation of Aligned ZnO Nanorods to ZIF-8 as Solid-Phase Microextraction Coatings with Tunable Porosity, Polarity, and Conductivity.

While a growing number of solid-phase microextraction (SPME) coatings have been developed, a generalized protocol is still needed to tailor-make SPME coatings with desirable properties for efficient extraction of diverse analytes from sample matrixes. In this work, we developed a versatile approach to prepare SPME coatings with tunable properties by controllable in situ transformation of well-aligned ZNRs into zeolitic imidazolate frameworks-8 (ZIF-8) via reaction with 2-methylimidazole (2-MI). During this process, ZNRs supplied Zn2+ and served as a "hard template" for the in situ growth of well-aligned ZIF-8 with enhanced surface area for adsorption. Because ZNRs and ZIF-8 exhibit markedly different properties, we obtained a series of ZNRs/ZIF-8 hybrid composites, whose morphology, porosity, polarity, and charge transfer resistance can be fine-tuned by simply controlling the concentration of 2-MI. Preparing ZNRs/ZIF-8 SPME coatings with desired properties enabled effective extraction of a wide range of polar and nonpolar compounds including aliphatic hydrocarbons, polycyclic aromatic hydrocarbons, alcohols, phenols, anilines, and ionic drugs.

The efficiency of the electrocoagulation process in reducing fluoride: application of inductive alternating current and polarity inverter

In this study, using hybrid Al and Fe plate electrodes in an electrochemical cell by using inductive alternating current and polarity inverter as an alternative method for decreasing fluoride in drinking water sequentially, by the electrocoagulation process has been evaluated. The effect of operational parameters such as the type of current, paired hybrid electrodes and polarity inverter, pH, current density, electrolysis time, charge loading and flow rate on the percent of fluoride removal along with the amount of energy and electrode consumed and amount of sludge produced was evaluated. In the following optimum operation conditions: paired hybrid Al–Fe electrodes with polarity inverter, pH = 6, current density = 12 mA/cm2, electrolysis time = 40 min, charge loading 0.609 Faradays/m3 and flow rate 75 ml/min, the efficiency of fluoride removal, energy and electrode consumption, flow efficiency, amount of sludge produced and sedimentation capacity were, respectively, 95% (from initial 4.93 to 0.24 mg/l), 0.9 kWh/m3, 1.42 kg/m3, 110%, 0.108 kg/m3 and 0.073 l/g. The results showed that the electrocoagulation process by using alternating current and polarity inverter is a very efficient method for removing fluoride from drinking water.

Classification of Ocean Surface Slicks in Simulated Hybrid-Polarimetric SAR Data

In this paper, we consider hybrid-polarimetric synthetic aperture radar (SAR) data of ocean surface slicks, and hypothesize that we can design a system that is able to discriminate between mineral oil, plant oil, and clean sea. We focus particularly on challenges related to data set shift between the training and test data. In SAR images of ocean surfaces, data set shift is typically caused by the variation of wind level and incident angles that directly impact the backscatter intensities. We evaluate several classifiers, domain adaptation strategies, and multilooking strategies. Hybrid-polarimetric SAR data are simulated from the Radarsat-2 quad-pol images. The proposed methodology was trained using five different Radarsat-2 quad-pol images that cover slicks of known types, and tested on 10 different Radarsat-2 quad-pol images covering various ocean surface slicks. The results show that we were able, to a large degree, to classify the type of various surface slicks. The average classification accuracy obtained from cross-validation on the training data was 91%. The results also show that we were able to correctly classify surface slick in new test images, even if the wind, surface, and acquisition conditions were different from the training images. We conclude that hybrid polarity is an attractive mode for future enhanced SAR-based oil spill monitoring; however, to fully exploit the imaging mode, single-look complex images are necessary.

Implementation of RISAT-1 Hybrid Polarimetric Decomposition Techniques and Analysis Using Corner Reflector Data

With recent advances in polarimetry, Synthetic Aperture Radar (SAR) with Hybrid–polarity architecture, a demonstration of compact polarimetry enabled larger swath coverage, reduced PRF and SAR system complexity as compared to fully polarimetric systems. The first Hybrid Polarimetric Space-borne SAR in Earth Observation orbit, India’s Radar Imaging Satellite (RISAT-1) is a new-fangled gateway to remote sensing user community for land and oceanic applications. In response to a right-circular polarized transmitted signal, based on the derived stokes vectors, Stokes parameters are estimated to produce several useful quantitative measures for generating polarimetric decomposed image. m-delta, m-chi and m-alpha polarimetric decomposition methods along with suitable weighting functions in terms of three principal components are implemented which maps Stokes parameters to RGB image space for representing odd bounce, even bounce and volume scattering targets. Various RISAT-1 Hybrid Fine Resolution Stripmap Single-Look Complex SAR datasets acquired over deployed corner reflectors at calibration site, Shadnagar have been considered over which different hybrid polarimetric decomposition techniques are implemented using in-house developed software. Further analysis produced encouraging results with standard point targets like dihedral and trihedral corner reflectors against distributed targets in the same scene to demonstrate the scattering mechanisms as per their characteristics when interacted with a polarized signal were presented in this paper.

Assessment of RISAT-1 and Radarsat-2 for Sea Ice Observations from a Hybrid-Polarity Perspective

Utilizing several Synthetic Aperture Radar (SAR) missions will provide a data set with higher temporal resolution. It is of great importance to understand the difference between various available sensors and polarization modes and to consider how to homogenize the data sets for a following combined analysis. In this study, a uniform and consistent analysis across different SAR missions is carried out. Three pairs of overlapping hybrid- and full-polarimetric C-band SAR scenes from the Radar Imaging Satellite-1 (RISAT-1) and Radarsat-2 satellites are used. The overlapping Radarsat-2 and RISAT-1 scenes are taken close in time, with a relatively similar incidence angle covering sea ice in the Fram Strait and Northeast Greenland in September 2015. The main objective of this study is to identify the similarities and dissimilarities between a simulated and a real hybrid-polarity (HP) SAR system. The similarities and dissimilarities between the two sensors are evaluated using 13 HP features. The results indicate a similar separability between the sea ice types identified within the real HP system in RISAT-1 and the simulated HP system from Radarsat-2. The HP features that are sensitive to surface scattering and depolarization due to volume scattering showed great potential for separating various sea ice types. A subset of features (the second parameter in the Stokes vector, the ratio between the HP intensity coefficients, and the α s angle) were affected by the non-circularity property of the transmitted wave in the simulated HP system across all the scene pairs. Overall, the best features, showing high separability between various sea ice types and which are invariant to the non-circularity property of the transmitted wave, are the intensity coefficients from the right-hand circular transmit and the linear horizontal receive channel and the right-hand circular on both the transmit and the receive channel, and the first parameter in the Stokes vector.

Analysis of Evolving Oil Spills in Full-Polarimetric and Hybrid-Polarity SAR

Oil spill detection using a time series of images acquired off Norway in June 2015 with the uninhabited aerial vehicle synthetic aperture radar is examined. The relative performance of a set of features derived from quad-polarization versus hybrid-polarity (HP) modes in detection of various types of slicks as they evolve on a high wind driven sea surface is evaluated. It is shown that the HP mode is comparable with the full-polarimetric mode in its ability to distinguish the various slicks from open water (OW) for challenging conditions of high winds (9–12 m/s), small release volumes (0.2–0.5 m3), and during the period 0–9 h following release. The features that contain the cross-polarization component are better for distinguishing the various slicks from open water at later and more developed stages. Although these features are not available in the HP mode, we identify alternative features to achieve similar results. In addition, a clear correlation between the results of individual features and their dependence on particular components within the two-scale Bragg scattering theory is identified. The features that show poor detectability of the oil slicks are those that are independent of the small-scale roughness, while the features resulting in good separability were dependent on several factors in the two-scale Bragg scattering model. We conclude that the HP mode is a viable alternative for SAR-based oil spill detection and monitoring that provides comparable results to those from the quad-polarimetric SAR.

Cross-Correlation Between Polarization Channels in SAR Imagery Over Oceanographic Features

This letter discusses cross-correlation features derived from near-coincident RADARSAT-2 quad-polarimetric and RISAT-1 hybrid-polarity (HP) measurements collected during the NOrwegian Radar oil Spill Experiment in 2015 (NORSE2015). We show that the imaginary part of the cross-correlation between RH and RV is an HP parallel to the real part of the cross-correlation between HH and VV earlier proposed for oil spill characterization. We compared the RADARSAT-2 and RISAT-1 scenes, separated in time by less than an hour, and the results show a clear difference between the slicks across these acquisitions. The development of the oil spills was closely monitored during NORSE2015. Due to the evolving nature of the oil spills and the weathering processes acting upon the spills, our results also indicate an importance of a high synthetic aperture radar sampling rate during an actual oil spill event.

On the Capability of Hybrid-Polarity Features to Observe Metallic Targets at Sea

In this paper, target at sea detection is addressed using hybrid-polarity (HP) synthetic aperture radar (SAR) architecture. Wave polarimetry concepts are used to define HP features that are used to observe targets at sea. The sensitivity of HP features to both targets and the surrounding environment is analyzed through a novel objective norm, namely the Relative Sensitivity for Polarimetric Features (RSPolF) index. Detection performance is evaluated by the novel Dependency of Sea state and Target (DoST) surface characteristics metric, and by the well-known Figure of Merit (FoM). Experiments undertaken on HP measurements emulated from Radarsat-2 and ALOS-PALSAR full-polarimetric actual SAR data demonstrate the effectiveness of the proposed HP approach and the different sensitivity of HP features to targets and background sea characteristics. Following those results, a ranking of the HP features performance is proposed which mainly highlights that HP features complement each other in the detection process. Finally, a constant false alarm rate (CFAR) approach is proposed to exploit two HP features for target detection in an unsupervised way.

Hybrid-Polarity and Reconstruction Methods for Sea Ice With L- and C-Band SAR

The potential of using the hybrid polarity (HP) mode for sea ice surveillance in L- and C-band synthetic aperture radar (SAR) is investigated. The objective is to study the possibilities to reconstruct a pseudo-quad-polarimetric (QP) covariance matrix using existing and novel reconstruction methods. Our main goal is to study how close the HP mode, in terms of polarimetric information, is to the QP mode. Two new reconstruction methods are proposed and investigated. Although they exhibit similar performance to the known method developed by Souyris et al. , they are less complex and do not require any user input. We discovered that the median and standard deviation of the relative error between the true and the estimated cross-polarization intensity are better for the L-band compared to the C-band SAR data. This discovery is based on four pairs of quasi-simultaneous QP SAR images of Arctic sea ice acquired by Radarsat-2 and ALOS-2.

Sea Oil Slick Observation Using Hybrid-Polarity SAR Architecture

In this study, hybrid-polarity (HP) architecture is exploited to observe sea oil slicks. HP features are interpreted in terms of sea surface scattering with or without oil slicks, under low-to-moderate wind conditions. They are shown to exhibit a different sensitivity with respect to slick-free, weak-damping slick-covered, and oil-covered sea surfaces. This sensitivity is verified against HP measurements obtained transforming actual L- and C-band quad-polarimetric synthetic aperture radar (SAR) data where both oil slicks and weak-damping look-alikes are present. Experiments demonstrate: 1) the remarkable performance of HP features to both observe oil slicks and distinguishing them from weak-damping look-alikes; 2) the marginal effect played by the sensor's noise floor on HP features performance; 3) the pronounced sensitivity of the HP features to the damping properties of the surfactants; and 4) the comparable performance that characterizes polarimetric entropy derived by HP and conventional polarimetric measurements.

Hybrid polarity and carrier injection of gold and gadolinium oxide bi-nanocrystals structure

In this study, the carrier injection mechanism of gold and gadolinium oxide bi-nanocrystals (BNCs) with hafnium dioxide NC separation layer was investigated. Further, an N-shaped carrier injection curve was observed under positive gate bias. It is resulted from the hybrid polarity and carrier injection. To identify the injection, the activation energies of charge loss were analyzed, and it was found that the substrate-injected electrons and gate-injected holes were stored in the BNCs. The gate-injected carriers were trapped at the Au-NCs and HfO2 interface, exhibiting high-density (>2.45 × 1012 cm−2) and high-speed (∼μs) operation characteristics suitable for future use in flash memories.

The Lunar Mini-RF Radars: Hybrid Polarimetric Architecture and Initial Results

The two mini-radio-frequency (mini-RF) radars flown in near-polar lunar orbits (on Chandrayaan-1 and the Lunar Reconnaissance Orbiter) were the first of their kind, hybrid-polarimetric. This new paradigm transmits circular polarization, and receives coherently on orthogonal linear polarizations. The resulting data support calculation of the 2 × 2 covariance matrix of the backscattered field, from which follow the four Stokes parameters. These are the basis of science products from the observations, which include images that are traditional in radar astronomy, as well as polarimetric decompositions. The instruments all have mass less than 15 kg, antenna areas of about 1 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and modest power and spacecraft accommodation requirements. Data quality and instrument characteristics suggest that hybrid polarity is highly desirable for future exploratory radar missions in the Solar system.

Lunar Reconnaissance Orbiter (LRO): Observations for Lunar Exploration and Science

The Lunar Reconnaissance Orbiter (LRO) was implemented to facilitate scientific and engineering-driven mapping of the lunar surface at new spatial scales and with new remote sensing methods, identify safe landing sites, search for in situ resources, and measure the space radiation environment. After its successful launch on June 18, 2009, the LRO spacecraft and instruments were activated and calibrated in an eccentric polar lunar orbit until September 15, when LRO was moved to a circular polar orbit with a mean altitude of 50 km. LRO will operate for at least one year to support the goals of NASA’s Exploration Systems Mission Directorate (ESMD), and for at least two years of extended operations for additional lunar science measurements supported by NASA’s Science Mission Directorate (SMD). LRO carries six instruments with associated science and exploration investigations, and a telecommunications/radar technology demonstration. The LRO instruments are: Cosmic Ray Telescope for the Effects of Radiation (CRaTER), Diviner Lunar Radiometer Experiment (DLRE), Lyman-Alpha Mapping Project (LAMP), Lunar Exploration Neutron Detector (LEND), Lunar Orbiter Laser Altimeter (LOLA), and Lunar Reconnaissance Orbiter Camera (LROC). The technology demonstration is a compact, dual-frequency, hybrid polarity synthetic aperture radar instrument (Mini-RF). LRO observations also support the Lunar Crater Observation and Sensing Satellite (LCROSS), the lunar impact mission that was co-manifested with LRO on the Atlas V (401) launch vehicle. This paper describes the LRO objectives and measurements that support exploration of the Moon and that address the science objectives outlined by the National Academy of Science’s report on the Scientific Context for Exploration of the Moon (SCEM). We also describe data accessibility by the science and exploration community.

Reducing Interconnect Delay Uncertainty via Hybrid Polarity Repeater Insertion

Capacitive crosstalk between adjacent signal wires has significant effect on performance and delay uncertainty of point-to-point on-chip buses in deep submicrometer (DSM) VLSI technologies. We propose a hybrid polarity repeater insertion technique that combines inverting and non-inverting repeater insertion to achieve constant average effective coupling capacitance per wire transition for all possible switching patterns. Theoretical analysis shows the superiority of the proposed method in terms of performance and delay uncertainty compared to conventional and staggered repeater insertion methods. Simulations at the 90-nm node on semi-global METAL5 layer show around 25% reduction in worst case delay and around 86% delay uncertainty minimization compared to standard bus with optimal repeater configuration. The reduction in worst case capacitive coupling reduces peak energy which is a critical factor for thermal regulation and packaging. Isodelay comparisons with standard bus show that the proposed technique achieves considerable reduction in total buffers area, which in turn reduces average energy and peak current. Comparisons with staggered repeater which is one of the simplest and most effective crosstalk reduction techniques in the literature show that hybrid polarity repeater offers higher performance, less delay uncertainty, and reduced sensitivity to repeater placement variation.

Polarity reversal of inside-out thyroid follicles cultured on the surface of a reconstituted basement membrane matrix

When cultured in suspension, epithelial thyroid cells organized into inside-out follicles. We studied the behavior of these structures after seeding on polystyrene, type I collagen, and reconstituted basement membrane (RBM) gel. When seeded on plastic, type I collagen or mixed type I collagen-RBM gel, inside-out follicles attached and spread, forming polarized cell monolayers. In contrast, on thick RBM gel, inside-out follicles attached, penetrated into the gel, and reorganized into properly oriented follicular structures. Polarity of the cell layer was progressively inverted while, after adhesion, cells penetrated the soft RBM gel. In the process of reorientation, cells with hybrid polarity were observed. The fraction of the apical pole which was not yet in the gel showed an inside-out orientation, while a modified orientation was observed in contact with the RBM gel. Cells which had penetrated completely in the matrix formed a new apical pole and displayed an opposite orientation of their polarity. A continuous basement membrane was observed, lining the basal cell surface when native RBM gel was present in the substratum.