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The fallback disk model is widely accepted to explain long-period neutron stars (NSs) that cannot be simulated by magnetic dipole radiation. However, there was no confirmed detection of disks from the newly discovered long-period pulsars GLEAM-X 162759.5-523504.3 and GPM J1839-10 and the slowest known isolated NS 1E 161348-5055. This might be because the disks have either been in a noninteracting/inactive state where their emission is too weak to be detected or have been disrupted. In this work, we conduct simulations to examine the lifetime of supernova fallback disks around isolated NSs. We assume that the disks' mass varies in a self-similar way, and their interaction with the NS occurs only in an interacting/active state. Our results reveal that nearly all the interacting lifetimes for the disks are shorter than 105 yr, while the existence lifetimes are considerably longer. [ABSTRACT FROM AUTHOR]

Graphene and its derivatives are widely used in the field of energy conversion and management due to their excellent physical and chemical properties. In this paper, ultra-thin graphite film (GF) with thickness of 100–150 nm prepared by chemical vapor deposition was transferred to oxygen plasma-treated polyimide (PI) substrate as flexible heating film. The electrothermal and photothermal properties of GF on PI substrates with different treatment time were studied. The experimental results show that the PI substrate pretreated by oxygen plasma can change the surface morphology of GF, increase its electrical conductivity and light absorption capacity, and significantly improve the electrothermal and photothermal properties of GF heater. Under the low applied voltage of 5 V (power density of 0.81 W cm−2), the surface temperature of GF on 40 min plasma-treated PI substrate can rise to 250 °C, which is nearly 50 °C higher than that of GF on untreated PI substrate. When 100 nm thick commercial multilayer graphene film (MLG) is used, plasma-treated PI substrate can increase the electric heating temperature of MLG by 70 °C. In terms of photothermal performance, the surface temperature of GF on 50 min plasma-treated PI substrate can reach 73 °C under one Sun irradiation, which is 8 °C higher than that on untreated substrate. The experimental results are in good agreement with the simulation research. Our strategy has important implications for the development of efficient and energy-saving graphene/graphite-based heating films for advanced electrothermal and photothermal conversion devices. [ABSTRACT FROM AUTHOR]

Recently, two ultralong-period radio transients, GLEAM-X J162759.5-523504.3 (J1627) and GPM J1839-10 (J1839), were discovered with spin periods longer than 1000 s. The origin of these two ultralong-period radio transients is intriguing in understanding the spin evolution of neutron stars (NSs). In this work, we examine whether the interaction between strong magnetized NSs and fallback disks can spin NSs down to the observed ultralong period. Our simulations found that the magnetar + fallback disk model can account for the observed period, period derivative, and X-ray luminosity of J1627 in the quasi-spin-equilibrium stage. To evolve to the current state of J1627, the initial mass-accretion rate of the fallback disk and the magnetic field of the NS are in the range of (1.1–30) × 1024 g s−1 and (2–5) × 1014 G, respectively. In the active lifetime of the fallback disk, it is impossible for J1839 to achieve the observed upper limit of the period derivative. Therefore, we propose that J1839 may be in the second ejector phase after the fallback disk becomes inactive. Those NSs with a magnetic field of (2–6) × 1014 G and a fallback disk with an initial mass-accretion rate of ∼1024–1026 g s−1 are possible progenitors of J1839. [ABSTRACT FROM AUTHOR]

The Photometric objects Around Cosmic webs (PAC) approach developed in Xu et al. has the advantage of making full use of spectroscopic and deeper photometric surveys. With the merits of PAC, the excess surface density n ¯ 2 w p of neighboring galaxies can be measured down to stellar mass 1010.80 M ⊙ around quasars at redshift 0.8 < z s < 1.0, with the data from the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey and the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys. We find that n ¯ 2 w p generally increases quite steeply with the decrease of the separation. Using the subhalo abundance-matching method, we can accurately model the n ¯ 2 w p both on small and large scales. We show that the steep increase of n ¯ 2 w p toward the quasars requires that a large fraction f sate = 0.29 − 0.06 + 0.05 of quasars should be satellites in massive halos, and we find that this fraction measurement is insensitive to the assumptions of our modeling. This high satellite fraction indicates that the subhalos have nearly the same probability of hosting quasars as the halos for the same (infall) halo mass and that the large-scale environment has negligible effect on the quasar activity. We show that even with this high satellite fraction, each massive halo on average does not host more than one satellite quasar, due to the sparsity of quasars. [ABSTRACT FROM AUTHOR]

The detection of gravitational wave events has stimulated theoretical modeling of the formation and evolution of double compact objects (DCOs). However, even for the most studied isolated binary evolution channel, there exist large uncertainties in the input parameters and treatments of the binary evolution process. So far, double neutron stars (DNSs) are the only DCOs for which direct observations are available through traditional electromagnetic astronomy. In this work, we adopt a population synthesis method to investigate the formation and evolution of Galactic DNSs. We construct 324 models for the formation of Galactic DNSs, taking into account various possible combinations of critical input parameters and processes such as mass transfer efficiency, supernova type, common envelope efficiency, neutron star kick velocity, and pulsar selection effect. We employ Bayesian analysis to evaluate the adopted models by comparing with observations. We also compare the expected DNS merger rate in the galaxy with that inferred from the known Galactic population of pulsar-neutron star systems. Based on these analyses we derive the favorable range of the aforementioned key parameters. [ABSTRACT FROM AUTHOR]

We measure the galaxy-ellipticity (GI) correlations for the Sloan Digital Sky Survey Data Release 12 LOWZ and CMASS samples with the shape measurements from the DESI Legacy Imaging Surveys. We model the GI correlations in an N -body simulation with our recent accurate stellar–halo mass relation from the Photometric object Around Cosmic webs (PAC) method. The large data set and our accurate modeling turns out an accurate measurement of the alignment angle between central galaxies and their host halos. We find that the alignment of central elliptical galaxies with their host halos increases monotonically with galaxy stellar mass or host halo mass, which can be well described by a power law for the massive galaxies. We also find that central elliptical galaxies are more aligned with their host halos in LOWZ than in CMASS, which might indicate an evolution of galaxy–halo alignment, though future studies are needed to verify this is not induced by the sample selections. In contrast, central disk galaxies are aligned with their host halos about 10 times more weakly in the GI correlation. These results have important implications for intrinsic alignment (IA) correction in weak lensing studies, IA cosmology, and theory of massive galaxy formation. [ABSTRACT FROM AUTHOR]

Reconstructing the equation of motion and thus the network topology of a system from time series is a very important problem. Although many powerful methods have been developed, it remains a great challenge to deal with systems in high dimensions with partial knowledge of the states. In this paper, we propose a new framework based on a well-designed cost functional, the minimization of which transforms the determination of both the unknown parameters and the unknown state evolution into parameter learning. This method can be conveniently used to reconstruct structures and dynamics of complex networks, even in the presence of noisy disturbances or for intricate parameter dependence. As a demonstration, we successfully apply it to the reconstruction of different dynamics on complex networks such as coupled Lorenz oscillators, neuronal networks, phase oscillators and gene regulation, from only a partial measurement of the node behavior. The simplicity and efficiency of the new framework makes it a powerful alternative to recover system dynamics even in high dimensions, which expects diverse applications in real-world reconstruction. [ABSTRACT FROM AUTHOR]

Rolling bearings play a vital role in the overall operation of rotating machinery. In practice, many learning methods for variable-speed fault diagnosis ignore task-specific decision boundaries, making it very difficult to completely match feature distribution between different domains. Therefore, to overcome this problem, an adversarial domain adaptation of asymmetric mapping with CORAL alignment is presented. The asymmetric mapping feature extractor is able to extract more specific-domain features with obvious distinction. Meanwhile, combining the maximum classifier discrepancy of deep transfer to give an adversarial approach and taking the task-specific decision boundaries into account, class-level alignment between the features of the source domain and target domain can be attempted. To prevent degenerate learning, which is possibly caused by asymmetric mapping and adversarial learning, the model is constrained by deep CORAL alignment to extract more domain-invariant features. Experimental results show that the proposed method can solve the variable-speed (a small span of intermediate vehicle speeds) fault diagnosis problem well, with high transfer accuracy and strong generalization. [ABSTRACT FROM AUTHOR]

We investigate the [O ii ] emission-line galaxy (ELG)-host halo connection via auto and cross correlations, and propose a concise and effective method to populate ELGs in dark matter halos without assuming a parameterized halo occupation distribution (HOD) model. Using the observational data from VIMOS Public Extragalactic Redshift Survey, we measure the auto and cross correlation functions between ELGs selected by [O ii ] luminosity and normal galaxies selected by stellar mass. Combining the stellarâ€"halo mass relation derived for the normal galaxies and the fraction of ELGs observed in the normal galaxy population, we demonstrate that we can establish an accurate ELGâ€"halo connection. With the ELGâ€"halo connection, we can accurately reproduce the auto and cross correlation functions of ELGs and normal galaxies both in real space and in redshift space, once the satellite fraction is properly reduced. Our method provides a novel strategy to generate ELG mock catalogs for ongoing and upcoming galaxy redshift surveys. We also provide a simple description for the HOD of ELGs. [ABSTRACT FROM AUTHOR]

We provide a method for estimating the projected density distribution n ÂŻ 2 w p (r p) of photometric objects around spectroscopic objects in a spectroscopic survey. This quantity describes the distribution of photometric sources with certain physical properties (e.g., luminosity, mass, and color) around cosmic webs (PAC) traced by the spectroscopic objects. The method can make full use of current and future deep and wide photometric surveys to explore the formation of galaxies up to medium redshift (z s < 2) 33 Throughout the paper, we use z s for redshift, z for the z -band magnitude, z p for the photometric redshift. with the aid of cosmological spectroscopic surveys that sample only a fairly limited species of objects (e.g., emission line galaxies). As an example, we apply the PAC method to the CMASS spectroscopic and HSC-SSP PDR2 photometric samples to explore the distribution of galaxies for a wide range of stellar masses from 109.0 to 1012.0 M ⊙ around massive stars at z s ≈ 0.6. Using the abundance-matching method, we model n ÂŻ 2 w p (r p) in N -body simulation using Markov chain Monte Carlo sampling, and we accurately measure the stellarâ€"halo mass relation and stellar mass function for the whole mass range. We can also measure the conditional stellar mass function of satellites for central galaxies of different mass. The PAC method has many potential applications for studying the evolution of galaxies. [ABSTRACT FROM AUTHOR]

Intelligent diagnosis network is widely used in the field of fault diagnosis because of its good feature self-extraction ability and classification performance. Among them, the transfer learning network is gradually solving the problem of cross-domain intelligent diagnosis under variable speed. However, whether the self-learned features of the diagnostic model in the training process are related to physical features, and the cross-domain feature attention problem in transfer learning, these difficulties have not been solved. In order to solve the above problems, an enhanced attention feature convolutional neural network model is proposed innovatively. The innovation of this model is mainly reflected in the following two aspects: the feature visualization module which is related to the physical concept features and the enhanced attention feature (EAF) module in the cross-domain features. A dual-branching CNN architecture with shared feature weights is applied to the model. At the same time, maximum mean discrepancy module with edge probability distribution alignment function is used for cross-domain feature alignment, and L2 norm is employed to regularize the weights. Through the verification of two kinds of datasets, the proposed model can better explain the correlation between the self-learned features of deep learning model and the features of physical actual meaning, and the EAFs can achieve better diagnostic accuracy in cross-domain diagnosis. [ABSTRACT FROM AUTHOR]

In recent years, transfer learning has become more and more favored by scholars from all walks of life. At present, although transfer learning has achieved certain results in the field of fault diagnosis, the use of transfer learning alone may lead to poor transfer effects or even negative transfer due to the sample gap being under variable conditions in the same machinery. Therefore, deep domain adaptation with adversarial idea and coral alignment (DAACA) is proposed in this paper in order to solve the problem. DAACA is briefly summarized below. The domain adaptation with adversarial idea is added on the basis of transfer learning. The deep coral is then appended to further reduce the distribution difference between the data from the source and the target domain, which improves the invariant features of adversarial domain adaptation learning. In addition, a gradient reversal layer is introduced in the method to achieve gradient reversion and avoid the adversarial disadvantage of fixing parameters separately. It can be seen from the experimental results that the DAACA can not only solve the problem caused by the sample gap in variable conditions, but also achieve higher diagnosis accuracy and generalization ability. [ABSTRACT FROM AUTHOR]

We demonstrate a 2.15 MHz repetition-rate mode-locked figure-of-9 erbium-doped fiber laser at a center wavelength of 1550 nm by using an all-polarization-maintaining nonlinear amplifying loop mirror configuration. This laser can be self-started mode-locked and generate Gaussian-shape noise-like pulses (NLPs). The single pulse energy is approximately 11.68 nJ at a repetition rate of 2.15 MHz. Dispersion compensation fibers are added into the cavity to make the laser operate in a net normal dispersion regime and generate NLPs at the center wavelength of 1550 nm. These characteristics give it a great application potential, such as low spectral coherence interference, optical sensing and micromachining. In addition, we have investigated the evolution of these characteristics, contributing to further understanding the Gaussian-shape NLP. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs) are mysterious radio transients with millisecond durations. Recently, ∼16 days of periodic activity and ∼159 days of possible periodicity were detected to arise from FRB 180916.J0158+65 and FRB 121102, respectively, and the spin period of a slow-rotation magnetar was further considered to be one of the possible explanations of the periodic activities of repeating FRBs. For isolated neutron stars, the spin evolution suggests that it has difficulty reaching several hours. In this work, we mainly focus on the possible maximum spin period of isolated NSs/magnetars dominated by an interaction between a star's magnetic field and the disk. We find that the disk wind plays an important role in spin evolution, whose influence varies the power-law index in the evolution equation of mass flow rate. For a magnetar without disk wind, the longest spin period is tens of hours. When the disk wind with a classical parameter is involved, the maximum spin period can reach hundreds of hours. But for an extremely large index of mass flow rate due to disk wind or other angular momentum extraction processes, a spin period of ∼(16–160) days is still possible. [ABSTRACT FROM AUTHOR]

Lateral epitaxial growth in vertical β-Ga2O3 nanowires was studied on sapphire substrates via metal organic chemical vapor deposition by controlling growth temperature and O2 flow rate. The lateral epitaxial growth rate of β-Ga2O3 rise up with increasing growth temperature and decreasing O2 flow rate, which are related to reaction kinetics and parasitic reaction, respectively. In addition, a growth model is proposed to explain the morphology of nanowires when growth condition changes. These results can provide important guidance on addressing slow coalescence rate of β-Ga2O3 nuclear islands on heterogeneous substrates and open new doors to β-Ga2O3 optoelectronic and electronic devices on cost-effective foreign substrates. [ABSTRACT FROM AUTHOR]

We present a two-dimensional particle–particle–particle-mesh (P3M) algorithm with an optimized Green's function and adaptive softening length for gravitational lensing studies in N-body simulations. The analytical form of the optimized Green's function is given. The softening schemes (S) are studied for both the particle-mesh (PM) and the particle–particle (PP) calculations in order for accurate force calculation and suppression of the particle discreteness effect. Our method is two orders of magnitude more accurate than the simple PM algorithm with the poor man's Green's function (∝ 1/k2) at a scale of a few mesh cells or smaller. The force anisotropy is also much smaller than the conventional PM calculation. We can achieve a force accuracy better than 0.1% at all scales with our algorithm, which makes it an ideal (accurate and fast) algorithm for microlensing studies. When we apply the algorithm to computing weak and strong lensing quantities in N-body simulations, the errors are dominated by the Poisson noise caused by particle discreteness. The Poisson noise can be suppressed by smoothing out the particle distribution, which can be achieved by simply choosing an adaptive softening length in the PP calculation. We have presented a criterion to set the adaptive softening length. Our algorithm is also applicable to cosmological simulations. We provide a python implementation P3Mlens for this algorithm. [ABSTRACT FROM AUTHOR]

Magnetocaloric materials with first-order phase transition are potential refrigerant media for solid state refrigeration. In this work, the Ni45Co5Mn35In15 alloy possesses a representative first-order martensitic transition (MT), which is found to be sensitive to both magnetic field and isostatic pressure with rates of ∼−6.4 K T−1 and ∼4.24 K kbar−1. Such an active response to multi-stimuli derives from the strong coupling of the spin and the lattice. A low magnetic field of 1 T can drive nearly 100% of the total entropy change corresponding to the whole transformation in this alloy. However, the prominent magnetocaloric effect (MCE) is almost irreversible owing to the intrinsic hysteresis of the first-order phase transition. By virtue of the strong magnetostructural coupling during the MT, a hydrostatic pressure assisted magnetic field loading loop has been constructed for eliminating the hysteresis and to a large extent improve the reversibility of the MCE. [ABSTRACT FROM AUTHOR]

Controllable deposition of Ga droplets on a GaN template is discussed in detail in the present work. It is found that the Ga droplet density shows apparent nonlinear dependence on the flux of triethylgallium under certain annealing conditions. A simplified model based on the weakening of cluster mobility is proposed to explain the phenomenon. In addition, based on the different mobility of Ga on different substrates, a SiO2 mask with ordered nanopore array is designed and optimized for controllable catalyst deposition. By further optimizing the deposition and annealing process, a higher filling rate of nanopores is obtained, and ordered β-Ga2O3 nanowire arrays perpendicular to substrates are then achieved. The controllable uniform vertical nanowire array would further promote optimization of nanowire growth and device fabrication. [ABSTRACT FROM AUTHOR]

It is believed that massive galaxies have quenched their star formation because of active galactic nucleus feedback. However, recent studies have shown that some massive galaxies are still forming stars. We analyze the morphology of star formation regions for galaxies of stellar masses larger than 1011.3M⊙ at around redshift zr = 0.5 using u − z color images. We find that about 20% of the massive galaxies are star-forming (SF) galaxies, and most of them (∼85%) have asymmetric structures induced by recent mergers. Moreover, for these asymmetric galaxies, we find that the asymmetry of the SF regions becomes larger for bluer galaxies. Using the Illustris simulation, we can qualitatively reproduce the observed relation between asymmetry parameter and color. Furthermore, using the merger trees in the simulation, we find a correlation between the color of the main branch galaxies at zr = 0.5 and the sum of the star formation rates of the recently accreted galaxies, which implies that star formation of the accreted galaxies has contributed to the observed star formation of the massive (host) galaxies (ex situ star formation). Furthermore, we find two blue and symmetric galaxies, candidates for massive blue disks, in our observed sample, which indicates that about ∼10% of massive SF galaxies are forming stars in the normal mode of disk star formation (in situ star formation). With the simulation, we find that the disk galaxies at zr ≈ 0.5 should have experienced few major mergers during the last 4.3 Gyr. [ABSTRACT FROM AUTHOR]

Nanoscale active devices, such as all-optical modulators and electro-optical transducers, can be implemented in heterostructures that integrate plasmonic nanostructures with functional active materials. Here, we demonstrate control over absorption properties in such a heterostructure by coupling the localized surface plasmon resonance (LSPR) of gold nanoantennas to a phase change material (PCM), Ge2Sb2Te5 (GST). The peak absorption of this hybrid absorber approaches near unity at resonance due to the simultaneous excitations of electric and magnetic resonant modes. Moreover, such a hybrid absorber can realize arbitrary wavelength-selective spectral absorption in the mid-infrared region simply by altering the square nanoantennas side length. By controlling the total power of the incident light, the intermediate phases composed of different proportions of the amorphous and crystalline molecules of the GST can be correspondingly tailored, and thus the absorption can be continuously tuned, which provides a flexible and encouraging way to achieve active features once fabricated. Importantly, by converting GST from the amorphous to crystalline state or vice versa, the hybrid absorber can realize bidirectional switching of "ON" and "OFF" states, with an outperformed modulation depth of 98% (or 95%) and extinction ratio of (or), respectively, indicating its excellent optical modulation performance. Notably, all the stable and intermediate phases of the GST are stable at room temperature, and therefore no sustained external thermal consumption is needed to maintain a desired absorption band for the hybrid scheme. Additionally, the structure can tolerate a wide range of incident angles as well as show polarization-independent features. With these extraordinary optical responses, the proposed scheme could find potential applications in active photonic devices such as optical modulation, thermal imaging and optical switching. [ABSTRACT FROM AUTHOR]

The performance of the oxide-confined surface-relief (SR) structure vertical-cavity surface-emitting laser (VCSEL) is simulated and analyzed by using the three-dimensional finite-difference time-domain (FDTD) method. The impacts of the device structure parameters on the far-field characteristics are researched. A single-fundamentalmode SR VCSEL with an oxide-aperture of 15 &mg;m is designed and produced. The single-mode power of the VCSEL is 5mW, the threshold current is 2.5 mA, far-field divergent angles range from 7.8° to 10.8° and the sidemode suppression ratio is over 30 dB. The optical and electrical properties of the device are in agreement with the results of FDTD simulation, which shows that the SR technology can effectively suppress the higher-order-mode lasing, and make the SR VCSEL work in a single mode under a larger oxide aperture [ABSTRACT FROM AUTHOR]

A novel cold-seeding approach of top-seeded melt growth of RE-Ba-Cu-O bulk was studied by employing a MgO crystal seed and a buffer pellet. The growth process is divided into two steps. The MgO seed is used to texture-grow the small RE-Ba-Cu-O pellet with high melting point (Tp) and the textured pellet induces the texture growth of the bulk at lower temperature. Undercooling and RE211 content of the pellet are adjusted to avoid the misorientation caused by lattice mismatch between MgO and the RE-Ba-Cu-O matrix. Bulk samples prepared with this method show good growth sections and superconducting performance. One of the promising advantages of this method is to process high Tp RE-Ba-Cu-O bulks with a cold-seeding method, for example Nd-Ba-Cu-O bulk. [ABSTRACT FROM AUTHOR]

This paper demonstrates a room-temperature multiwavelength fibre laser with spacing-adjustability and wavelength-tunability. The nonlinear gain of self-excited stimulated Brillouin scattering can suppress mode competition induced by homogeneous broadening of Erbium-doped fibre. With the use of a birefringence fibre loop filter, the wavelength spacing can be adjusted by changing the length of the used birefringence fibre, and the lasing wavelengths can be finely tuned through modifying the filtering profile of the birefringence filter. Multiwavelength output with spectral spacing as small as 0.076 nm and a wavelength number of more than 80 has been successfully produced. [ABSTRACT FROM AUTHOR]

A novel scheme for pulse generation with a self-cascaded electroabsorption modulator is presented and experimentally demonstrated at 10 GHz. In the case of optimal tuning of time delay in the fibre loop, the improvement of 50 on pulsewidth with improved extinction ratio is obtained and the narrowest pulse generated with this method is about 11 ps. [ABSTRACT FROM AUTHOR]

Polarization stable characteristic of vertical cavity surface emitting laser array with rectangular element structure based on proton implantation is achieved. Arrays with different aperture sizes and different array scales are investigated. The maximum orthogonal polarization suppression ratio of a 6 × 6 array with 6 μm; × 4 μm elements is as high as 16.1 dB at 51 mA. The x-polarization dominates y-polarization in the operation current range from the threshold to the saturated current. The full widths at half maximum in far-field profiles for x-polarization and y-polarization are 8.8° and 10.7°, respectively. These results suggest that stable polarization is available in the implant-defined VCSEL array. [ABSTRACT FROM AUTHOR]

A new microchannel that enables continuous three-dimensional (3D) particle focusing with a single sheath flow is reported. The 3D particle focusing is based on the combination of the microfluidic drifting effect induced by a curved microchannel and the momentum-change-induced inertial effect induced by a series of repeated symmetric sharp corner structures on both side walls of the microchannel. The microfluidic drifting effect induces particle focusing in the vertical direction (z direction) while the momentum-change-induced inertial effect induces particle focusing in the horizontal direction (on the x–y plane). Eventually, particles are three-dimensionally focused at the center of the microchannel. The 3D particle focusing behavior in the present microchannel was demonstrated by the experiment using 7.32 μm particles at a sample flow rate of 66.7 μL min−1 and a sheath flow rate of 400 μL min−1. Force analysis and computational fluid dynamics (CFD) simulation confirmed particles of different sizes (from 5 to 15 μm) could also be three-dimensionally focused in the present microchannel over a wide range of flow rates. In comparison with other 3D passive focusing techniques, this microchannel built in a single layer only requires a single sheath flow, and hence avoids complex flow control. With its simple structure and operation, this device can potentially be used in 3D particle focusing processes in many lab-on-a chip applications, such as micro flow cytometer. [ABSTRACT FROM AUTHOR]

A three-dimensional electrical-thermal coupling model based on the finite element method is applied to study thermal properties of implant-defined vertical cavity surface emitting laser (VCSEL) arrays. Several parameters including inter-element spacing, scales, injected current density and substrate temperature are considered. The actual temperatures obtained through experiment are in excellent agreement with the calculated results, which proves the accuracy of the model. Due to the serious thermal problem, it is essential to design arrays of low self-heating. The analysis can provide a foundation for designing VCSEL arrays in the future. [ABSTRACT FROM AUTHOR]

An ac voltage-modulated thermal probe technique based on the atomic force microscope is developed to measure local Seebeck coefficients (S) of thermoelectric bulk and films. The characterization principle is based on the strictly quadratic relationship between the excited local dc Seebeck voltage and the applied ac voltage at high frequency. Excellent agreement is found between local S values and their corresponding macro-S values of thermoelectric bulk and thin films. This thermoelectric probe technique provides a very convenient, promising tool for local thermoelectric parameters with sub-micrometer scale resolution. [ABSTRACT FROM AUTHOR]

A dual probe, i.e., high resolution scanning piezo-thermal microscopy, is developed and employed to characterize the local piezoresponse and thermal behaviors of ferroelastic domains in multiferroic BiFeO3 thin films. Highly inhomogeneous piezoelectric responses are found in the thin film. A remarkably local thermal transformation across ferroelastic domain walls is clearly demonstrated by the quantitative 3ω signals related to thermal conductivity. Different polarization oriented ferroelastic domains are found to exhibit different local thermal responses. The underlying mechanism is possibly associated with the inhomogeneous stress distribution across the ferroelastic domain walls, leading to different phonons scattering contributions in the BiFeO3 thin film. [ABSTRACT FROM AUTHOR]