Two-dimensional Localization Research Articles

A pressure-induced high-pressure metallic GeTe phase.

As an important phase-change material, GeTe has many high-pressure phases as well, but its phase transitions under pressure are still lack of clarity. It is challenging to identify high-pressure GeTe crystal structures owing to the phase coexistence in a wide pressure range and the reversibility of phase transitions. Hence, first-principles calculations are required to provide further information in addition to limited experimental characterizations. In this work, a new orthorhombic Cmca GeTe high-pressure phase has been predicted via the CALYPSO method as the most energetically favorable phase in the pressure range between ∼30 and ∼38.5GPa, which would update the GeTe high-pressure phase transition sequence. The crystal structure of the Cmca phase is composed of alternate stacking puckered layers of Ge six-membered rings and Te four-membered rings along the b direction. The high density of states near the Fermi level and delocalization of electrons from the two-dimensional electron localization function indicate a strong metallic property of the Cmca phase. Electron-phonon coupling calculations indicate that the Cmca phase is superconductive below ∼4.2K at 35GPa. The simulated x-ray diffraction pattern of the Cmca phase implies that this phase might coexist with the Pnma-boat phase under high pressure. These results offer further understanding on the high-pressure structural evolution and physical properties in GeTe and other IV-VI semiconductors.

Quantifying impacts of hearing protection devices on sound localization in azimuth and elevation: Refinement of acoustic predictors

Modern hearing protection devices (HPDs) mitigate the risk of noise-induced hearing loss when used as intended, but negative auditory perceptual side-effects continue to limit usability in critical settings. Dozens of studies have shown that HPDs lead to significant errors in sound source localization. Several studies, including previous studies by our group, have linked such errors to distortions of the spectra of transmitted signals. Here we provide an update on a multi-site effort to develop acoustic predictors and summary metrics to quantify HPD impacts on sound source localization. At two independent study sites, human listeners localized brief broadband signals with open ears and during use of passive and active earplug and earmuff-style devices. Sources spanning 360° in azimuth and −30° to + 60° in elevation enabled measurement of two-dimensional localization error across a broad range of source locations. An initial set of parallel acoustic measurements was obtained using a standardized acoustic test fixture. Present efforts are focused on evaluating prospective advantages of (1) incorporating binaural acoustic data in the prediction of errors and (2) accounting for individual HPD-impacted acoustic variability. The long-term goal of this work is to support application-specific selection of existing HPDs and inform the design of new HPDs.

Snapshot-deficient active target localization in beam-time domain using multi-frequency expectation-maximization algorithm.

The two-dimensional (2D) active target localization is generally hindered by the high temporal and spatial sidelobe levels in snapshot-deficient scenarios, where the adaptive approaches undergo performance degeneration since they require many snapshots to build the sample covariance matrix. Aiming at working robustly in snapshot-deficient active scenarios, a 2D expectation-maximization-based vertical-time-record (EMVTR) approach is proposed to compensate for the snapshot deficiency and achieve the high-resolution active localization by reconstructing the covariance matrix using estimated hyperparameters, i.e., signal powers and noise variance. With the short-time Fourier transform, the proposed approach could reduce echoes' temporal correlation and attain robust beam-time localization in mild reverberation. The multi-frequency EMVTR is derived from the single-frequency case to improve the weak echo localization. The performance is evaluated by considering single and multiple target echoes in simulation and a single moving target with tank experimental data. The results manifest the proposed EMVTR's robustness and effectiveness for the 2D active localization in snapshot-deficient scenarios.

Anisotropic Rashba effect in two-dimensional non-Janus transition-metal dichalcogenide, MSSe (M=Mo,W) alloys

The breaking of the out of plane mirror symmetry in the Janus transition-metal dichalcogenides (TMDs) has made them appealing candidates for optoelectronic, spintronic, valleytronic, and photocatalytic applications. In this study, we compare the structural and electronic properties of the Janus structure with the more stable TMD alloys of the form $M\mathrm{SSe} (M=\mathrm{Mo},\mathrm{W})$. The charge distribution analysis and two-dimensional electron localization function analysis indicate that the geometry of the system plays a vital role in determining the magnitude of the metal to ligand charge transfer, which in turn dictates the stability of the alloys. The arrangement of the chalcogen atoms in the more stable alloy allows for a better charge distribution, resulting in superior stability. Band structure calculations reveal that both structures are semiconducting with identical direct band gaps and exhibit Rashba splitting near the \ensuremath{\Gamma} point in the presence of the spin-orbit coupling (SOC) effects. While in the Janus structures, the broken mirror symmetry gives rise to an out of plane uniform electric field, the reduced symmetry of the more stable alloy structure produces an anisotropic arrangement of the perpendicular dipole moments. The nonuniformity of the electric dipole moments is reflected in the Rashba effect, which has an anisotropic nature, unlike the isotropic Rashba splitting observed in the Janus structures.

A Survey of 3D Indoor Localization Systems and Technologies

Indoor localization has recently and significantly attracted the interest of the research community mainly due to the fact that Global Navigation Satellite Systems (GNSSs) typically fail in indoor environments. In the last couple of decades, there have been several works reported in the literature that attempt to tackle the indoor localization problem. However, most of this work is focused solely on two-dimensional (2D) localization, while very few papers consider three dimensions (3D). There is also a noticeable lack of survey papers focusing on 3D indoor localization; hence, in this paper, we aim to carry out a survey and provide a detailed critical review of the current state of the art concerning 3D indoor localization including geometric approaches such as angle of arrival (AoA), time of arrival (ToA), time difference of arrival (TDoA), fingerprinting approaches based on Received Signal Strength (RSS), Channel State Information (CSI), Magnetic Field (MF) and Fine Time Measurement (FTM), as well as fusion-based and hybrid-positioning techniques. We provide a variety of technologies, with a focus on wireless technologies that may be utilized for 3D indoor localization such as WiFi, Bluetooth, UWB, mmWave, visible light and sound-based technologies. We critically analyze the advantages and disadvantages of each approach/technology in 3D localization.

The electric transport properties of iridate Sr2-x Bi x IrO4 and Sr2-y Dy y IrO4

Sr2IrO4 is predicted to be a new superconductor in theory, and its electric transport properties have attracted much attention in the field of physics. Here we prepared a series of polycrystalline samples doped with Sr2-xBixIrO4 (x=0,0.02,0.04,0.06,0.08) and Sr2-yDyyIrO4 (y=0,0.02,0.04,0.06) respectively. The influence of the two ions on the lattice structure and electronic structure after the substitution of the Ir site is very similar, which makes the overall reduction trend of IrO6 octahedron and Ir-O1-Ir bond angle. The resistivity shows a non-monotonic change with doping and still maintains the insulation. The low-temperature section, medium-temperature section, and high-temperature section conform to three-dimensional variable range hopping (3D-VRH), thermal activation model, two-dimensional weak localization model respectively.

Two-dimensional localization in GeSn

Localization behaviour is a characteristic feature of the p-type GeSn quantum well (QW) system in a metal–insulator–semiconductor device. The transition to strongly localized behaviour is abrupt with thermally activated conductivity and a high temperature intercept of 0.12 × e 2 ħ −1 at a hole carrier density 1.55 × 1011 cm−2. The activation energy for the conductivity in the localized state is 0.40 ± 0.05 meV compared to an activation energy of ∼0.1 meV for conductivity activation to a mobility edge at carrier densities >1.55 × 1011 cm−2. Insulating behaviour can occur from a system that behaves as though it is in a minimum metallic state, albeit at high temperature, or from a conductivity greater than a minimum metallic state behaviour showing that local disorder conditions with local differences in the density of states are important for the onset of localization. In the presence of a high magnetic field, thermally activated conductivity is present down to Landau level filling factor < but without a magnetic-field-dependent carrier density or a variable range hopping (VRH) transport behaviour developing even with conductivity ≪e 2 h −1. In the localized transport regime in p-type doped Ge0.92Sn0.08 QWs the VRH mechanism is suppressed at temperatures >100 mK and this makes this two-dimensional system ideal for future many body localization studies in disordered hole gases that can be thermally isolated from a temperature reservoir.

Two-dimensional charge localization at the perovskite oxide interface

The effects of atomic-scale disorder and charge (de)localization hold significant importance, and they provide essential insights to unravel the role that strong and weak correlations play in condensed matter systems. In the case of perovskite oxide heterostructures, while disorders introduced via various external stimuli have strong influences over the (de)localization of interfacial two-dimensional (2D) electrons, these factors alone could not fully account for the system's charge dynamics where interfacial hybridization holds very strong influence. Here, we determine that the displaced 2D free electrons have been localized in the specific hybridized states of the LaAlO3/SrTiO3 interface. This experimental study combines both transport measurements and temperature-dependent x-ray absorption spectroscopy and suggests that the localization of 2D electrons can be induced via temperature reduction or ionic liquid gating. Furthermore, this localization effect is found to be applicable to both amorphous and crystalline interfacial systems. In particular, we demonstrate that interfacial hybridization plays a pivotal role in regulating the 2D electron localization effects. Our study resolves the location where the 2D electrons are localized not only does it highlight the importance of interfacial hybridization but it also opens a new avenue for device fabrication in amorphous film systems where charge localization can be done at much great ease as compared to epitaxial crystalline heterostructures.

Entropy reduction from strong localization – an explanation for enhanced reaction rates of organic synthesis in aqueous micelles

HypothesisThe underlying mechanism for increased reaction rates in micellar catalysis-based organic synthesis is a reduced entropy barrier for the reaction. A two-dimensional localization of reactants and catalyst in the surfactant micelle reduces the translational entropy of all components. The entropy is reduced less for the reaction intermediate than for the reactants, which leads to the lower barrier. SimulationsQuantum chemistry, the COSMO-RS implicit solvent model and statistical thermodynamics were employed to predict the stability of a range of reactants, catalysts and intermediates in a series of surfactant micelles. The localized stability in the linker region between the lipophilic and hydrophilic regions and the resulting decrease in entropy were also calculated. FindingsThe predicted reaction rates for the proposed mechanism show that the entropy reduction leads to a larger prefactor for the reaction. The resulting reaction rate can be significantly higher than conventional organic synthesis in an organic solvent even when the smaller reaction volume and lower reaction temperatures typically needed under micellar catalysis conditions are considered. The results are general across a wide range of types of reactions, reactants and catalysts and a selection of surfactants commonly used in organic synthesis, strongly supporting the hypothesis.

Two-dimensional atom localization and formation of waveguide channels using Bragg diffraction law

Atoms of four-level atomic medium are doped in a crystal slab of silica which is immersed in a four-level atomic medium. We incorporated Bragg law in the Rabi frequencies of the driving fields and obtained absorption spectrum which exhibits atom localization inside the crystal plane and generation of waveguide channels. Varying the Bragg angle θ, leads to a number of localized peaks and craters. The number of peaks decreases as we increase the Bragg angle θ from π/8 to π/2 and the peaks disappear beyond this angle. The localization probability is independent of the Bragg angle, while the spatial resolution varies with change in Bragg angle. However, the probe detuning and amplitudes of Rabi frequencies change the localization probability. Inside the optical lattice of the silica crystal, waveguide channels and particle traps are generated which may be utilized to guide electromagnetic radiations and trap quantum particles. This work is useful for coherent control information of crystal planes, optical trapping, waveguide channels of nano crystals and data storage.

Ultraprecise Off-Axis Atom Localization With Hybrid Fields

Atom localization enables a high-precision imaging of the atomic position, which has provided vast applications in fundamental and applied science. In the present work, we propose a scheme for realizing two-dimensional off-axis atom localization in a three-level Λ system. Benefiting from the use of a hybrid coupling field, which consists of one Gaussian beam and one Laguerre–Gaussian beam, our scheme shows that the atoms can be localized at arbitrary position with high spatial resolution. Considering realistic experimental parameters, our numerical simulation predicts that the atoms can be precisely localized with a spatial resolution of ∼200 nm in the range of a radial distance of a few micrometers to the beam core. Our results provide a more flexible way to localize atoms in a two-dimensional system, possibly paving one-step closer to the nanometer scale atom lithography and ultraprecise microscopy.

Sing-Ant: RFID Indoor Positioning System Using Single Antenna with Multiple Beams Based on LANDMARC Algorithm

RFID localization methods have been widely used in indoor positioning systems (IPS). Most localization techniques involve the use of multiple antennas and the placement of antennas and readers in order to ensure accurate positioning results. However, most localization techniques are complex and require high overhead costs in terms of needing multiple antennas and RFID readers. In this paper, we proposed a method to use a single antenna to perform all the reads and rely rather on the antenna beams to acquire multiple positioning data. A single array of antennas is configured to have multiple angles of operation and rely on different power levels as compared to regular antennas. By manipulating the beam pattern, direction and power, multiple sub-antennas can be conceived and the method utilizes antenna beams and relies mainly on one antenna to realize two-dimensional localization.

Flexible Dual-Channel Digital Auscultation Patch With Active Noise Reduction for Bowel Sound Monitoring and Application.

Bowel sounds (BSs) have important clinical value in the auxiliary diagnosis of digestive diseases, but due to the inconvenience of long-term monitoring and too much interference from environmental noise, they have not been well studied. Most of the current electronic stethoscopes are hard and bulky without the function of noise reduction, and their application for long-term wearable monitoring of BS in noisy clinical environments is very limited. In this paper, a flexible dual-channel digital auscultation patch with active noise reduction is designed and developed, which is wireless, wearable, and conformably attached to abdominal skin to record BS more accurately. The ambient noise can be greatly reduced through active noise reduction based on the adaptive filter. At the same time, some nonstationary noises appearing intermittently (e.g., frictional noise) can also be removed from BS by the cross validation of multichannel simultaneous acquisition. Then, two kinds of typical BS signals are taken as examples, and the feature parameters of the BS in the time domain and frequency domain are extracted through the time-frequency analysis algorithm. Furthermore, based on the short-term energy ratio between the four channels of dual patches, the two-dimensional localization of BS on the abdomen mapping plane is realized. Finally, the continuous wearable monitoring of BS for patients with postoperative ileus (POI) in the noisy ward from pre-operation (POD0) to postoperative Day 7 (POD7) was carried out. The obtained change curve of the occurrence frequency of BS provides guidance for doctors to choose a reasonable feeding time for patients after surgery and accelerate their recovery. Therefore, flexible dual-channel digital auscultation patches with active noise reduction will have promising applications in the clinical auxiliary diagnosis of digestive diseases.

3D Localization of Hand Acupoints Using Hand Geometry and Landmark Points Based on RGB-D CNN Fusion.

Acupoint stimulation has proven to be of significant importance for rehabilitation and preventive therapy. Moxibustion, a kind of acupoint therapy, has mainly been performed by practitioners relying on manual localization and positioning of acupoints, leading to variance in the accuracy owing to human error. Developments in the automatic detection of acupoints using deep learning techniques have proven to somewhat tackle the problem. But the current methods lack depth-based localization and are thus confined to two-dimensional (2D) localization. In this research, a new approach towards 3D acupoint localization is introduced, based on a fusion of RGB and depth convolutional neural networks (CNN) to guide the manipulator. This research aims to tackle the challenge of real-time 3D acupoint localization in order to provide guidance for robot-controlled moxibustion. In the first step, the 3D sensor (Kinect v1) is calibrated and transformation matrix is computed to project the depth data into the RGB domain. Secondly, a fusion of RGB-CNN and depth-CNN is employed, in order to obtain 3D localization. Lastly, 3D coordinates are fed to the manipulator to perform artificially controlled moxibustion therapy. Furthermore, a 3D acupoint dataset consisting of RGB and depth images of hands, is constructed to train, validate and test the network. The network was able to localize 5 sets of acupoints with an average localization error of less than 0.09. Further experiments prove the efficacy of the approach and lay grounds for development of automatic moxibustion robots.

2D sound source localization technology based on diaphragm EFPI fiber microphone array

The technologies of two-dimensional sound source localization based on diaphragm extrinsic Fabry–Perot interferometer (EFPI) fiber microphone array have been studied in this paper. The fiber microphone array consists of three EFPI. Self-calibrated intensity demodulation technology with simple structure and low cost is adopted to demodulate the sound signals. Using effective sound signal extraction technology to find the starting point and end point of sound signal, combining with time differences of arrival (TDOA) positioning technology, high-precision sound source location is successfully realized. The average positioning error of this system is no larger than 4.82%. The system has the advantages of low cost, high practicability and wide application scenarios.

Two-dimensional atom localization by absorption spectrum using superposition of two super-Gaussian beams

Two-dimensional atom localization by absorption spectrum using superposition of two super-Gaussian beams

Two-dimensional planar sound source localization based on microphone array

In recent years, people’s awareness of wildlife protection has been increasing, and the demand for wildlife observation and recording has increased. However, the existing sound source localization system needs to continuously collect sound signals and convert the time-domain signals of the sound into frequency-domain signals. These shortcomings will increase the power consumption of the device, adversely affect the battery life, and the sound source localization result is easily interfered by the echo of environmental noise and target sound waves. In this study, the algorithm and hardware are improved on the basis of the existing sound source positioning system, which can improve the positioning accuracy and reduce the power consumption and cost of the whole machine. The adaptive circuit is used to filter and adjust the sound signal in real time to eliminate the influence of the difference between the individual microphones in the microphone array, which makes the sound source localization system more robust to the environmental noise and the echo of the target sound wave, and more suitable for the forest scene of wildlife protection. Through the research of this sound source localization system, we hope to provide some new ideas for producing economical and practical sound source localization equipment and lay a foundation for the intelligent development of wildlife protection in the future.

An Adaptive Three-Dimensional Improved Virtual Force Coverage Algorithm for Nodes in WSN

The original virtual force algorithm (VFA) is proposed for the two-dimensional node coverage and localization of wireless sensor networks (WSN). This work proposes a novel three-dimensional improved virtual force coverage (3D-IVFC) algorithm for the 3D coverage of nodes in WSN. Firstly, the node coverage theory is analyzed, which is about node coverage in three-dimensional space. Secondly, an improved three-dimensional space virtual force coverage method is proposed with an adaptive virtual force parameter control strategy. Finally, simulation experiments are utilized to verify the performance of the 3D-IVFC approach. Experimental results show that during random initialization, the average coverage rate of the improved 3D space coverage algorithm was increased by 0.76% and the deployment time was reduced by 0.1712 s; during center initialization, the average coverage rate of the improved 3D space coverage algorithm was increased by 0.65% and the coverage time increased slightly. Moreover, the proposed method is also used to solve the three-dimensional surface node coverage of the WSN.

Underground Vibration-Print Extraction and Spatial Attenuation Law Study of Ground-Borne Source Sensed by DAS

Complexity of underground environment brings great challenges to vibration source detection, recognition and localization for fiber-optic distributed acoustic sensor (DAS), which utilizes the buried optical communication cable as its sensing media. In order to explore the spatial attenuation laws of the ground-borne vibration propagated through the complicated underground media to the fiber, the theoretical and experimental studies are carried out for fundamental research and underground vibration-print based on the spatial power spectral distribution is proposed to represent the spatial spectral attenuation characteristics in both the axial and radial directions. Field tests with both the narrowband and broadband vibration sources have further proved that the proposed spatial power spectral distribution can reflect the distinguishability at different radial distances well and even the event types, which contributes to improve the perception ability such as accurate two-dimensional (2-D) localization and identification with DAS.

Three-dimensional localization of gas leakage using acoustic holography

Gas leakage localization is essential to prevent accidents from gas transportation or storage failures. There have been extensive studies on one-dimensional (1D) and two-dimensional (2D) gas leakage localization problem. This paper is the first to report the demonstration of a three-dimensional (3D) localization of gas leaks using far-field acoustic holography. This approach simultaneously provides 2D sound field imaging and depth position information regarding the leakage source. A virtual phased array composed of only two sensors collects the needed data, resulting in improved accuracy, enhanced feasibility and reduced cost. Various parameters, including the number of sensors, the spacing of array elements and the distance to the leakage source, are analyzed by a simulation of leakage sound field reconstruction. A series of experiments validated the effectiveness and accuracy of the proposed approach. Our results demonstrate that the proposed method achieves 3D localization and high-resolution imaging recognition of gas leaks.