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Tiny nano-scale junction built on B/N doped single carbon nanotube
摘要： The characteristic sizes of carbon nanotube (CNT) based devices are constantly reduced. However, the continuous miniaturization is still facing many problems and requires innovative ideas and structures. By regular doping Boron and Nitrogen atoms in a semiconducting single-wall carbon nanotube (SWCNT), we have constructed an nano-scale junction with rectifying characteristics. The I-V curve of our junction resembles the I-V curve of an ideal diode with a p-n junction. This junction channel is about 0.6nm wide and 3.4nm long, and the footprint is 5.1nm long. Under 0.5V bias, the junction has a leakage current of -8.81×10-3 μA, a rectifying ratio Ion/Ioff of 0.716×103, and a current density of 10.52 mA/μm. Also, our study shows that how different dopant distribution influence I-V curve. Such a nano-scale regular doping method is effective and important, compared with the traditional random doping method.
关键词： B/N doped junction,I-V curve,density functional theory,non-equilibrium Green’s function,carbon nanotube,regular doping,electronic transport
更新于2025-09-11 14:15:04
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[ACM Press the 4th International Conference - Hong Kong, Hong Kong (2018.02.24-2018.02.26)] Proceedings of the 4th International Conference on Virtual Reality - ICVR 2018 - Light Stretch Algorithm for Image Quality Enhancement
摘要： Images taken from outdoor scenes are usually degraded due to weather condition, resulting in reduction in color fidelity as well as contrast of captured images. This gives rise to difficulties when processing these images by an algorithm designed for clear weather condition. In lieu of refining individual algorithms to be bad weather-appropriate, it sounds more reasonable to perform on each input image an enhancement step. Thus, image quality enhancement is currently in great demand. In this paper, we hereby propose the light stretch algorithm, which simultaneously performs intensity expansion and reduction by solving the saturation phenomenon of bright color region and the discoloration of dark color region in an image. The simulation result strengthens its superiority over the other two methods based on unidirectional image enhancement and Photoshop curve adjustment method.
关键词： symmetrical curve,light stretch,crossing curve,quadric curve,Image enhancement
更新于2025-09-10 09:29:36
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Reduction in crystalline quality anisotropy for non-polar a-plane GaN directly grown on titanium patterned sapphire substrate
摘要： Nonpolar a-plane GaN films were directly grown on titanium patterned sapphire substrates (Ti-PSS) by metalorganic chemical vapor deposition (MOCVD). It is demonstrated that the GaN film grown on Ti-PSS has superior surface quality and less surface pits than that on flat sapphire substrate. More importantly, the anisotropic behavior of the X-ray rocking curve-full width at half maximum values for the on-axis reflections were significantly improved. It is found that, the increased mosaic block size along m-direction could be the main reason for the reduction in the crystalline quality anisotropy. This work provides a simple and effective method to improve the crystal quality of non-polar GaN films.
关键词： X-ray rocking curve,crystalline quality anisotropy,MOCVD,titanium patterned sapphire substrates,Nonpolar a-plane GaN
更新于2025-09-10 09:29:36
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Efficient quantitative hyperspectral image unmixing method for large-scale Raman micro-spectroscopy data analysis
摘要： Vibrational micro-spectroscopy is a powerful optical tool, providing a non-invasive label-free chemically specific imaging for many chemical and biomedical applications. However, hyperspectral image produced by Raman micro-spectroscopy typically consists of thousands discrete pixel points, each having individual Raman spectrum at thousand wavenumbers, and therefore requires appropriate image unmixing computational methods to retrieve non-negative spatial concentration and corresponding non-negative spectra of the image biochemical constituents. Here, we present a new efficient Quantitative Hyperspectral Image Unmixing (Q-HIU) method for large-scale Raman micro-spectroscopy data analysis. This method enables to simultaneously analyse multi-set Raman hyperspectral images in three steps: (i) Singular Value Decomposition with innovative Automatic Divisive Correlation which autonomously filters spatially and spectrally uncorrelated noise from data; (ii) a robust subtraction of fluorescent background from the data using a newly developed algorithm called Bottom Gaussian Fitting; (iii) an efficient Quantitative Unsupervised/Partially Supervised Non-negative Matrix Factorization method, which rigorously retrieves non-negative spatial concentration maps and spectral profiles of the samples' biochemical constituents with no a priori information or when one or several samples’ constituents are known. As compared with state-of-the-art methods, our approach allows to achieve significantly more accurate results and efficient quantification with several orders of magnitude shorter computational time as verified on both artificial and real experimental data. We apply Q-HIU to the analysis of large-scale Raman hyperspectral images of human atherosclerotic aortic tissues and our results show a proof-of-principle for the proposed method to retrieve and quantify the biochemical composition of the tissues, consisting of both high and low concentrated compounds. Along with the established hallmarks of atherosclerosis including cholesterol/cholesterol ester, triglyceride and calcium hydroxyapatite crystals, our Q-HIU allowed to identify the significant accumulations of oxidatively modified lipids co-localizing with the atherosclerotic plaque lesions in the aortic tissues, possibly reflecting the persistent presence of inflammation and oxidative damage in these regions, which are in turn able to promote the disease pathology. For minor chemical components in the diseased tissues, our Q-HIU was able to detect the signatures of calcium hydroxyapatite and b-carotene with relative mean Raman concentrations as low as 0.09% and 0.04% from the original Raman intensity matrix with noise and fluorescent background contributions of 3% and 94%, respectively.
关键词： Baseline correction,Biochemical quantification,Hyperspectral image analysis,Multivariate curve resolution,Non-negative matrix factorization,Raman spectroscopy
更新于2025-09-10 09:29:36
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DESIGN OF 2D METAL PHOTONIC CRYSTAL ARRAY OF DIRECTIONAL RADIATION IN MICROWAVE BAND
摘要： A 2D metal photonic crystal structure with a rectangular lattice is designed for directed wave propagation in the microwave frequency band. The dispersion curve of EPC is computed for designing the directed period array. In order to favor the computing, the rectangular period array is studied, which is di?erent from the reference that is designed in optical range and uses the dielectric rods and hexagonal structure to compose the period array. The computed dispersion curves are combined with the theory of ?nite thick period array for obtaining the directed wave propagation structure. The in?uence of the number of metal rods on the antenna directionality is investigated, and the simulation results are compared and analyzed. It is found that when the number of transverse metal rods increases, the directionality of the antenna is enhanced, and the radiant power of the sidelobe radiation can be reduced. Based on the simulation results, the actual 2D metal photonic crystal array is constructed for the measurement validation. According to measurement results, the antenna located in the center of the array can get good directionality at 3.1 GHz.
关键词： 2D metal photonic crystal,antenna directionality,microwave band,directional radiation,dispersion curve
更新于2025-09-10 09:29:36
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[IEEE 2018 53rd International Universities Power Engineering Conference (UPEC) - Glasgow, United Kingdom (2018.9.4-2018.9.7)] 2018 53rd International Universities Power Engineering Conference (UPEC) - A Modified P&O-MPPT based on Pythagorean Theorem and CV-MPPT for PV Systems
摘要： Maximum power point tracking MPPT techniques are a crucial part in photovoltaic PV system design to maximise the output power of a PV array which depends on weather conditions. Although several techniques have been developed, Perturb and Observe P&O is widely used for MPPT due to its low cost and simple implementation. However, the main drawbacks of this method are a low converging time, high oscillation around the maximum power point, and drift problem associated with changing irradiance rapidly. In this paper, a modified P&O-MPPT based on Pythagorean theorem and constant voltage CV-MPPT is presented. To assess this modification, conventional and modified P&O methods are simulated by a MATLAB-SIMULINK. Simulation results demonstrate that the modified P&O-MPTT has a highly effective to solve the problem of conventional P&O-MPPT.
关键词： Perturb and Observe (P&O),constant voltage (CV),variable step size (VSS),photovoltaic (PV),Maximum power point tracking (MPPT),Power-Voltage curve
更新于2025-09-10 09:29:36
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Characterization of optical performance with defocusing curve: Analysis of two refractive intraocular lens models with high and medium addition
摘要： Purpose: To characterize the optical performance of two models of refractive bifocal intraocular lenses, with medium and high addition, using defocus curves. Methods: 20 eyes from 20 subjects were included in this study. 10 eyes underwent cataract surgery with an implant of a medium addition refractive bifocal intraocular lens (IOL) (Lentis LS-313 MF20) and the other 10 eyes underwent cataract surgery with an implant of a high addition refractive bifocal IOL (Lentis LS-313 MF30). Six weeks after surgery, subjective refraction and defocus curve were made. Results: Mean final residual refraction in spherical equivalent was +0.10 ± 0.07 D in the LS-313MF30 group and +0.12 ± 0.10 D in the LS-313MF20 group. Defocus curve showed a different optical performance in intermediate/near distance depending on the IOL model. The medium addition IOL provided good visual acuity (VA) at far and intermediate distance up to 50 cms, and the high addition IOL provided better VA in near distance up to 25 cms. Conclusions: The high addition intraocular lens provides better visual acuity in the spatial range from infinity to the point close to 25 cm. The medium addition intraocular lens provides excellent visual acuity in far and intermediate vision. The defocus curve seems to be a valid and reproducible tool for evaluating the optical behavior of multifocal sector refractive lenses.
关键词： High addition,Intraocular lens,Defocus curve,Bifocal,Medium addition
更新于2025-09-10 09:29:36
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Discriminating Normal Regions within Cancerous Hen Ovarian Tissue Using Multivariate Hyperspectral Image Analysis
摘要： Identification of subregions under different pathological conditions on cancerous tissue is of great significance for understanding cancer progression and metastasis. Infrared matrix-assisted laser desorption electrospray ionization mass spectrometry (IR-MALDESI-MS) can be potentially used for the diagnostic purpose since it can monitor spatial distribution and abundance of metabolites and lipids in biological tissues. However, the large size and high dimensionality of hyperspectral data make analysis and interpretation challenging. To overcome these barriers, multivariate methods were applied to IR-MALDESI data for the first time, aiming at efficiently resolving mass spectral images, from which these results were then used to identify normal regions within cancerous tissue.
关键词： Mass Spectrometry Imaging,Multivariate curve resolution-Alternating Least Squares,IR-MALDESI,Ovarian Cancer,Principle Component Analysis
更新于2025-09-10 09:29:36
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Investigation of modifier effect on the spectroscopic properties of Sm3+ ions in binary boro?bismuth glasses
摘要： Trivalent samarium (Sm3+)-doped boro?bismuth glass systems are prepared using the well-known melt quenching technique and studied their physical and spectroscopic properties. Theoretical optical basicity of the glasses are evaluated using the glass compositions. The optical absorption spectra are used to predict the optical band gap and bonding parameters of glasses. The ultra violet (UV) cutoff wavelength is increasing towards the higher wavelength side with increase in bismuth concentration. Judd-Ofelt parameters are obtained from absorption spectrum and are inturn used to estimate radiative properties for various excited states of the Sm3+ ions in boro?bismuth glasses. Luminescence decay curves of the 4G5/2 level in the Sm3+-doped boro?bismuth glasses are measured under 402 nm excitation. The decay times exhibit single exponential nature for lower concentrations (≤0.1 mol%) and tends towards non-exponential with increase in Sm3+ concentrations (≥0.5 mol %). The non-exponential decay curves of higher Sm3+-doped glasses are fitted to the Inokuti-Hiriyama model to know the nature of interaction for energy transfer between the Sm3+ ions. The chromaticity color coordinates for present glass systems are also evaluated and found that the luminescence color falls in the reddish-orange region.
关键词： Sm3+ ion,Judd-Ofelt theory,Spectroscopic properties,Decay curve analysis,Binary boro?bismuth glasses
更新于2025-09-10 09:29:36
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[IEEE 2018 17th International Conference on Ground Penetrating Radar (GPR) - Rapperswil, Switzerland (2018.6.18-2018.6.21)] 2018 17th International Conference on Ground Penetrating Radar (GPR) - Structural Planes Parameters Extraction Method Based on Borehole Digital Optical Image and GPR
摘要： This paper combines the borehole ground penetrating radar imaging and digital optical borehole imaging, presents an efficient method to recognize and extract the structural planes parameters of rock mass. In this method, it’s necessary to transform the digital optical image in color modeling. Processing such as segmentation and edge refinement are essential steps. Afterwards, matching algorithm is employed by using a transform of sinusoidal curve to extract the fitting parameters. Finally, the image feature data acquired by the borehole GPR image is integrated for verification. With this method, the physical and geometrical characteristics of the rock mass at and around the borehole can be revealed. It can effectively exert the respective characteristics of the two exploration technologies to identify the structural planes in a continuous and rapid way. It has proven highly reliable and efficient.
关键词： structural plane,curve fitting algorithm,borehole digital optical image,identification,borehole GPR image
更新于2025-09-09 09:28:46