排序方式: 共有57条查询结果,搜索用时 15 毫秒
1.
No-Wook Park Phaedon C. Kyriakidis Woojoo Lee Sang-Jin Lyu 《International journal of remote sensing》2016,37(16):3858-3869
This article presents a geostatistical approach for downscaling precipitation products from passive microwave satellites with geostationary Meteorological Satellite observations. More precisely, the Advanced Microwave Scanning Radiometer 2 (AMSR2) precipitation (daily level 3 product) with 0.25° spatial resolution and the Communication, Ocean and Meteorological Satellite (COMS) infrared (IR) data with 5 km spatial resolution were used for the downscaling experiment over the Korean peninsula. Brightness temperature data observed at COMS IR 1 and water vapour channels were incorporated for downscaling via area-to-point residual Kriging with non-linear regression. The evaluation results with densely sampled Automatic Weather Station data revealed that incorporating the COMS IR observations with the AMSR2 precipitation showed similar error statistics to those of the AMSR2 precipitation because of the limitations of IR observations themselves and the inherent errors of the AMSR2 precipitation product over land. However, the area-based evaluation using information entropy indicated that incorporating the COMS observations resulted in more detailed spatial variation in the final product than direct downscaling of the AMSR2 precipitation. In addition, local precipitation patterns could be captured when there were regions with missing precipitation values in the AMSR2 product. Consequently, the downscaling result is useful for understanding the local precipitation patterns with an accuracy similar to that provided by microwave satellite observations. It is also suggested that the spatial variability in the downscaling result and errors in input low-resolution data should be considered when downscaling coarse resolution data using fine resolution auxiliary variables. 相似文献
2.
Yu-Ming Lin Appenzeller J. Knoch J. Avouris P. 《Nanotechnology, IEEE Transactions on》2005,4(5):481-489
State-of-the-art carbon nanotube field-effect transistors (CNFETs) behave as Schottky-barrier-modulated transistors. It is known that vertical scaling of the gate oxide significantly improves the performance of these devices. However, decreasing the oxide thickness also results in pronounced ambipolar transistor characteristics and increased drain leakage currents. Using a novel device concept, we have fabricated high-performance enhancement-mode CNFETs exhibiting n- or p-type unipolar behavior, tunable by electrostatic and/or chemical doping, with excellent OFF-state performance and a steep subthreshold swing (S=63 mV/dec). The device design allows for aggressive oxide thickness and gate-length scaling while maintaining the desired device characteristics. 相似文献
3.
Super-resolution land cover mapping with indicator geostatistics 总被引:3,自引:0,他引:3
Many satellite images have a coarser spatial resolution than the extent of land cover patterns on the ground, leading to mixed pixels whose composite spectral response consists of responses from multiple land cover classes. Spectral unmixing procedures only determine the fractions of such classes within a coarse pixel without locating them in space. Super-resolution or sub-pixel mapping aims at providing a fine resolution map of class labels, one that displays realistic spatial structure (without artifact discontinuities) and reproduces the coarse resolution fractions. In this paper, existing approaches for super-resolution mapping are placed within an inverse problem framework, and a geostatistical method is proposed for generating alternative synthetic land cover maps at the fine (target) spatial resolution; these super-resolution realizations are consistent with all the information available.More precisely, indicator coKriging is used to approximate the probability that a pixel at the fine spatial resolution belongs to a particular class, given the coarse resolution fractions and (if available) a sparse set of class labels at some informed fine pixels. Such Kriging-derived probabilities are used in sequential indicator simulation to generate synthetic maps of class labels at the fine resolution pixels. This non-iterative and fast simulation procedure yields alternative super-resolution land cover maps that reproduce: (i) the observed coarse fractions, (ii) the fine resolution class labels that might be available, and (iii) the prior structural information encapsulated in a set of indicator variogram models at the fine resolution. A case study is provided to illustrate the proposed methodology using Landsat TM data from SE China. 相似文献
4.
Comparing carbon nanotube transistors - the ideal choice: a novel tunneling device design 总被引:1,自引:0,他引:1
Appenzeller J. Yu-Ming Lin Knoch J. Zhihong Chen Avouris P. 《Electron Devices, IEEE Transactions on》2005,52(12):2568-2576
Three different carbon nanotube (CN) field-effect transistor (CNFET) designs are compared by simulation and experiment. While a C-CNFET with a doping profile similar to a "conventional" (referred to as C-CNFET in the following) p-or n-MOSFET in principle exhibits superior device characteristics when compared with a Schottky barrier CNFET, we find that aggressively scaled C-CNFET devices suffer from "charge pile-up" in the channel. This effect which is also known to occur in floating body silicon transistors deteriorates the C-CNFET off-state substantially and ultimately limits the achievable on/off-current ratio. In order to overcome this obstacle we explore the possibility of using CNs as gate-controlled tunneling devices (T-CNFETs). The T-CNFET benefits from a steep inverse subthreshold slope and a well controlled off-state while at the same time delivering high performance on-state characteristics. According to our simulation, the T-CNFET is the ideal transistor design for an ultrathin body three-terminal device like the CNFET. 相似文献
5.
6.
Carbon-based electronics 总被引:2,自引:0,他引:2
The semiconductor industry has been able to improve the performance of electronic systems for more than four decades by making ever-smaller devices. However, this approach will soon encounter both scientific and technical limits, which is why the industry is exploring a number of alternative device technologies. Here we review the progress that has been made with carbon nanotubes and, more recently, graphene layers and nanoribbons. Field-effect transistors based on semiconductor nanotubes and graphene nanoribbons have already been demonstrated, and metallic nanotubes could be used as high-performance interconnects. Moreover, owing to the excellent optical properties of nanotubes it could be possible to make both electronic and optoelectronic devices from the same material. 相似文献
7.
J.W. Lyding T.-C. Shen G.C. Abeln C. Wang P.A. Scott J.R. Tucker PH. Avouris R.E. Walkup 《Israel journal of chemistry》1996,36(1):3-10
Nanofabrication on silicon surfaces has been achieved in a manner similar to e-beam/resist technology, in which hydrogen serves as a monolayer resist for exposure by the electron beam from an ultrahigh vacuum (UHV) scanning tunneling microscope (STM). In this scheme, hydrogen is selectively desorbed from Si(100)2×1:H surfaces that have been prepared by atomic hydrogen dosing under UHV background conditions. To remove hydrogen, the tip bias is raised, under feedback control, and then the desired pattern is drawn. Two regimes of hydrogen desorption are observed: at higher energies, above ∼6.0 V, direct electron-stimulated desorption occurs, whereas at lower biases, desorption occurs via a multiple excitation vibrational heating mechanism and exhibits a strong current dependence. Patterning linewidth down to a single dimer row has been achieved in the vibrational heating regime. The selective removal of hydrogen suggests many possibilities for subsequent chemical treatments in which the hydrogen-terminated silicon remains inert. We have performed experiments which demonstrate selective oxidation of, and nitrogen incorporation into, the STM-patterned regions. 相似文献
8.
This paper proposes a methodology for simulation of binary random fields with application to the problem of generating sample realizations of two-phase random media. The methodology is based on the concept of nonlinear transformations with memory of Gaussian random fields. The simulation is performed according to the autocorrelation function of the binary field which contains considerable information about the microstructural characteristics of the medium. The determination of the probabilistic characteristics of the underlying Gaussian field is achieved through an iterative procedure that was introduced in a previous paper by the same authors in one dimension and is extended here to multiple dimensions. Limiting cases and alternative mappings are also presented. The capabilities of the methodology are demonstrated in a series of examples. 相似文献
9.
Yu-Ming Lin Appenzeller J. Zhihong Chen Zhi-Gang Chen Hui-Ming Cheng Avouris P. 《Electron Device Letters, IEEE》2005,26(11):823-825
We report on a high-performance back-gated carbon nanotube field-effect transistor (CNFET) with a peak transconductance of 12.5 /spl mu/S and a delay time per unit length of /spl tau//L=19 ps//spl mu/m. In order to minimize the parasitic capacitances and optimize the performance of scaled CNFETs, we have utilized a dual-gate design and have fabricated a 40-nm-gate CNFET possessing excellent subthreshold and output characteristics without exhibiting short-channel effects. 相似文献
10.
Elias Kalapanidas & Nikolaos Avouris 《Computer-Aided Civil and Infrastructure Engineering》2002,17(2):119-130
Management of urban atmospheric pollution necessitates advanced modeling and information processing techniques. The design of the prototype system DNEMO, which is based on a distributed adaptive problem-solving approach is the focus of the research reported in this paper. Issues covered in the paper relate to the distributed nature of this environmental problem, handling noise and uncertainty in monitoring data, achieving graceful degradation of performance and system robustness, and adaptation of system performance to long-term evolution of the monitored phenomena. The research reported can be applicable to a broad class of environmental monitoring applications, since the problems addressed are common to many environmental problems. 相似文献