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Noise reduction and retrieval by modified lidar inversion method combines joint retrieval method and machine learning
摘要： To address the problem in which the signal-to-noise ratio of a raw atmospheric lidar signal decreases rapidly as the range increases, which has a tremendous effect on the accuracy and the effective range of lidar retrieval, many de-noising algorithms have been proposed. Among these methods, those based on the ensemble Kalman Filter (EnKF) exhibit good performance. EnKF-based methods can simultaneously denoise lidar signals and yield accurate retrieval results. However, due to poor forecasting in the EnKF step, biases exist in the results of these methods. In this study, a modified lidar inversion method was proposed for horizontal aerosol characteristic retrieval, which combines the joint retrieval method and Gaussian processing machine learning. This method compensates for the poor forecasting in the EnKF step in the joint retrieval method through the Gaussian processing machine learning algorithm, which can reduce the biases in the retrieval results. The modified lidar inversion method was applied to both simulated and real lidar signals, and the results show that the modified lidar inversion method is effective and practical in aerosol extinction characteristics’ analysis.
关键词： lidar,Gaussian processing machine learning,ensemble Kalman Filter,signal-to-noise ratio,aerosol extinction characteristics
更新于2025-09-10 09:29:36
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Theoretical investigations on elastic, thermal and lattice dynamic properties of chalcopyrite ZnSnX <sub/>2</sub> (X = P, As, Sb) under pressure and temperature: The first-principles calculation
摘要： We performed the first-principles calculations on the elastic and thermal properties for chalcopyrite ZnSnX2(X=P, As, Sb), employing the ultrasoft pseudo-potentials and generalized gradient approximation (GGA) under the frame of density functional theory. The equilibrium structural lattice constants are in good agreement with reported data. The elastic characteristics were evaluated under high-pressure condition (0–20 GPa), such as the elastic constants, bulk modulus, shear modulus, Poisson’s ratio, Zener anisotropy and compressibility index. Combining with quasi-harmonic Debye model, the thermal properties were confirmed at different temperatures (0–1200 K) and pressures (0–20 GPa), including the heat capacity, thermal expansion, Debye temperature, entropy, and Gr¨uneisen parameter. Based on the semi-empirical relation, the hardness of materials was determined at various temperatures and pressures. Finally, the phonon spectrum curves and vibration frequencies of phonon were evaluated to confirm the thermodynamic stability of ZnSnX2. The Raman scattering spectrum and infrared absorption spectrum were simulated for chalcopyrite ZnSnX2.
关键词： thermal characteristics,lattice dynamic properties,Chalcopyrite,elastic properties
更新于2025-09-10 09:29:36
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I–V characteristics and conductance of strained SWCNTs
摘要： We present a new procedure to investigate the I–V characteristics and the conductance for strained SWCNTs. These electronic transport properties have been studied theoretically at zero temperature for zig-zag, armchair and chiral SWCNTs under the effect of the uniaxial tension and torsional strain. The analytical expression of the energy spectrum in the tight binding approximation has been used to calculate the induced current and the conductance through Landauer–Büttiker formalism. It is shown that the conductance for unstrained CNTs at initial values of the voltage can take discrete values which are equal to zero and 4 (e2/h) for semiconducting and conducting SWCNTs respectively. The emergence of the kinks in the I–V characteristics is due to the discrete electronic spectrum in the SWCNTs. The location and number of kinks are changeable under the effect of strain process. The conductance in a strained armchair (5, 5) CNT decreases to zero under torsional strain, consequently, it will transform the conducting SWCNTs at a threshold value of strain to a semiconducting SWCNT. In contrast, by applying the uniaxial tension on the armchair (5, 5) CNT, the conductance does not change absolutely. There is a different behavior can be observed by applying the strain on zig-zag (10, 0) CNT, where the conductance decreases rapidly and slightly under the in?uence of uniaxial tension and torsional strain, respectively. We found that the conductance of chiral (10, 9) CNT is not signi?cantly affected by applying the strain under consideration. More interestingly, the band structure of chiral (10, 9) CNT under uniaxial tension and torsional strain have been investigated within the tight binding approximation.
关键词： I–V characteristics,Mechanical strain,Tight binding approximation,SWCNT,Conductance
更新于2025-09-10 09:29:36
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Improvement of charge transport for hydrothermally synthesized Cd0.8Fe0.2S over co-precipitation method: A comparative study of structural, optical and magnetic properties
摘要： Here, we have elucidated the structural, optical, magnetic and electrical properties of Cd0.8Fe0.2S which is considered as diluted magnetic semiconductor (DMS). Cd0.8Fe0.2S materials were synthesized using co-precipitation (compound 1) and hydrothermal (compound 2) method. The particle size and the polycrystalline phase of the synthesized materials are significantly influenced by the synthesis procedures. Presence of anti-ferromagnetic coupling confirms the magnetic behavior of materials. The current-voltage (I-V) characteristics exhibit lower barrier height for the device based on compound 2 (0.59 eV) than the other device (0.64 eV). Furthermore, the 19 times enhanced mobility and lesser density of states near the Fermi level for the Al/compound 2/ITO configured device is enlightened by the space charge conduction mechanism. But, the interface resistances of the devices cannot be distinguished by the I-V characteristics. Therefore, we have tackled the problem by simulating the Nyquist plots obtained from impedance spectroscopy. We have fitted the Nyquist plots with the appropriate equivalent circuit and explained the mechanism of charge transport through the Schottky interface. The higher dc conductivity and lower relaxation time of diode fabricated by compound 2 confirm the outcomes obtained from I-V characteristics. The effect of particle size on charge transport was also analyzed.
关键词： Schottky diode characteristics,Diluted magnetic semiconductor,Chemical synthesis,Impedance spectroscopy
更新于2025-09-10 09:29:36
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A Global Parameters Extraction Technique to Model Organic Field Effect Transistors Output Characteristics
摘要： After an impressive improvement observed in organic field effect transistors (OFETs) technology, there is a need to have a comprehensive model, which can predict output characteristics of OFETs to facilitate device-to-system integration in an efficient manner. In this paper, a global technique is developed to extract parameters of various OFETs models by evaluating their output characteristics. By involving respective model’s expression, a simulator has been developed wherein the model variables have been extracted by using particle swarm optimization technique. Relative performance of a model is determined by assessing root mean square errors between the experimental and the modeled characteristics. Swarm optimization showed that the accuracy of a model is dependent upon the device dimensions. Thus, by employing the developed swarm optimization technique on devices of various dimensions, a preferred model is identified, which can be employed by the device modeling software. Swarm optimization showed that models, which are more physics based have a wider applicability than those which involved relatively higher number of fitting variables.
关键词： Modeling,Swarm Optimization,I ? V Characteristics,Organic Field Effect Transistors
更新于2025-09-10 09:29:36
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First-principles study of the ordered structures of the single crystal PMN(0.75)-PT(0.25) and their ferroelectric characteristics
摘要： For the various PMN(0.75)-PT(0.25) ordered structures, first principles density functional studies using local density approximation (LDA) framework and augmented projected augmented wave (PAW) pseudopotentials. All possible 20-atom ordering along the [001]-, [011]- and [111]- directions are considered in the ab-initio code VASP. Also, we conducted linear response with density functional perturbation theory (DFPT) which is implemented in the VASP to compute the electronic dielectric tensors and piezoelectric tensors. The polar response is strongly dependent of the ionic ordering. Some PMN(0.75)-PT(0.25) ordered structures show strong piezoelectric characteristics.
关键词： first-principles calculation,piezoelectric characteristics,Pb(Mg1/3Nb2/3)O3-PbTiO3,ordered structure
更新于2025-09-10 09:29:36
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[IEEE 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Kiev (2018.4.24-2018.4.26)] 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - ITO-Nano-Titania Gas Sensors at Adsorption of Ethanol, Acetone and Water Molecules
摘要： The measurements capacitance-voltage characteristics and capacitance kinetics were applied for investigation of physical principle of sensor response in the ITO – nanostructured titanium dioxide heterojunction. The studies were fulfilled for ethanol, acetone and water vapor under various frequencies of probing signal. It was shown that processes of surface states recharging are making the most significant contribution to the total capacitance of the studied heterojunction and playing a major role in forming of sensor response to the molecules of the used analytes.
关键词： titanium dioxide,surface states,adsorption,capacitance-voltage characteristics,capacitance kinetics,gas sensor,electronic traps,hysteresis
更新于2025-09-10 09:29:36
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A 400-GHz Wideband High-Gain Quartz-Based Single-Layered Folded Reflectarray Antenna for Terahertz Applications
摘要： Compact high-gain antennas are highly desired in the high speed terahertz (THz) wireless system, especially for the space limited application such as the high speed inter-link inside the high density wireless communication base station. To this end, a 400-GHz folded reflectarray (FRA) antenna with high gain, high aperture efficiency and compact profile is proposed in this paper. It is composed of a feed source, a single-layered reflectarray using a lithography process on quartz, and a wire-grid polarizer implemented by the printed-circuit-board (PCB) technology. A 3-D printed fixture is used to assemble all parts together. In order to design accurately the THz electromagnetic properties of the supporting dielectric materials are extracted by using a THz time-domain spectrometer system. Then, a single-layered phasing element, made up of a pair of orthogonally I-shaped structures with an open square ring, is proposed and designed based on the extracted material characteristics. Both phase compensation and polarization conversion can be realized by the proposed unit cell. A reflectarray is designed by using the proposed phasing element with the conventional array synthesizing theory, and a THz grid polarizer is designed with strips on a 0.127 mm Taconic TLY-5 substrate. The THz grid is placed in front of the THz feed and the reflectarray, which is fully reflective to the feed and transparent to the reflectarray. All components of the FRA antenna have been fabricated and assembled. Experiments show that the FRA prototype has a peak gain of 33.66 dBi at 400 GHz with an aperture efficiency of 33.65%, and a 3-dB gain bandwidth of 16% (357-421 GHz).
关键词： terahertz,3-D printing,high-gain,material characteristics,quartz substrate,single-layer,Folded reflectarray antenna,THz time-domain spectrometer
更新于2025-09-10 09:29:36
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Analysis of Dendrite Images Formed by Electrochemical Migration in a Semiconductor Sensor
摘要： Dendrites were observed in the failure of semiconductor sensor devices. EDX analysis showed that the dendrites grown from bare sensor dice consisted of tin metal. The tin dendrites exhibited massive and dense branches. Dendrites grown from mechanically decapped parts consisted of silver. The silver dendrites exhibited delicate, lace-like structure. Binary and grey scale images of dendrites were analyzed for fractal dimension number and branch density. The tin dendrites had a higher, statistically significant branch density number than silver, due to tin’s more intricate branching pattern. Fractal numbers can be used to differentiate between tin and silver dendrites, even in the absence of EDX analysis equipment.
关键词： dendrites,fractal characteristics
更新于2025-09-10 09:29:36
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AIP Conference Proceedings [Author(s) 6TH INTERNATIONAL CONFERENCE ON PRODUCTION, ENERGY AND RELIABILITY 2018: World Engineering Science & Technology Congress (ESTCON) - Kuala Lumpur, Malaysia (13–14 August 2018)] - Electrical and optical properties of graphene oxide modified by nitrogen and methane plasma
摘要： The current-voltage (I-V) characteristic and photoresponse of partially reduced graphene oxide (rGO) treated with nitrogen and methane plasmas have been studied. Measurements of I-V characteristics showed that the illumination (incandescent lamp) of samples after plasma exposure leads to the appearance of a bend in the initially linear characteristic. The di?erence in the value of the currents with the illumination turned on and o? was up to 100 μA at a voltage of ±10 V. The relaxation time of the process is about 1 s. The observed e?ect depends on the plasma processing conditions, as well as on the thickness of the ?lms. The largest values of the photoresponse was observed at thicknesses of GO ?lms from 20 nm to 60-80 nm.
关键词： methane plasma,graphene oxide,nitrogen plasma,photoresponse,current-voltage characteristics
更新于2025-09-09 09:28:46