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101.
This paper addresses estimating the frequency of a cisoid in the presence of white Gaussian noise, which has numerous applications in communications, radar, sonar, and instrumentation and measurement. Due to the nonlinear nature of the frequency estimation problem, there is threshold effect, that is, large error estimates or outliers will occur at sufficiently low signal‐to‐noise ratio (SNR) conditions. Utilizing the ideas of averaging to increase SNR and weighted linear prediction, an optimal frequency estimator with smaller threshold SNR is developed. Computer simulations are included to compare its mean square error performance with that of the maximum likelihood (ML) estimator, improved weighted phase averager, generalized weighted linear predictor, and single weighted sample correlator as well as Cramér‐Rao lower bound. In particular, with smaller computational requirement, the proposed estimator can achieve the same threshold and estimation performance of the ML method. 相似文献
102.
Seul‐Ki Park So‐Eun Kim Dae‐Yoon Kim Shin‐Woong Kang Seunghan Shin Shiao‐Wei Kuo Seok‐Ho Hwang Seung Hee Lee Myong‐Hoon Lee Kwang‐Un Jeong 《Advanced functional materials》2011,21(11):2129-2139
Robust coatable polarizer is fabricated by the self‐assembly of lyotropic chromonic liquid crystals and subsequent photo‐polymerizing processes. Their molecular packing structures and optical behaviors are investigated by the combined techniques of microscopy, scattering and spectroscopy. To stabilize the oriented Sunset Yellow FCF (H‐SY) films and to minimize the possible defects generated during and after the coating, acrylic acid (AA) is added to the H‐SY/H2O solution and photo‐polymerized. Utilizing cross‐polarized optical microscopy, phase behaviors of the H‐SY/H2O/AA solution are monitored by varying the compositions and temperatures of the solution. Based on the experimental results of two‐dimensional wide angle X‐ray diffraction and selected area electron diffraction, the H‐SY crystalline unit cell is determined to be a monoclinic structure with the dimensions of a = 1.70 nm, b = 1.78 nm, c = 0.68 nm, α = β = 90.0° and γ = 84.5°. The molecular arrangements in the oriented H‐SY films were further confirmed by polarized Fourier‐transform infrared spectroscopy. The polymer‐stabilized H‐SY films show good mechanical and chemical stabilities with a high polarizability. Additionally, patterned polarizers are fabricated by applying a photo‐mask during the photo‐polymerization of AA, which may open new doors for practical applications in electro‐optic devices. 相似文献
103.
Galileo Sarasqueta Kaushik Roy Choudhury Jegadesan Subbiah Franky So 《Advanced functional materials》2011,21(1):167-171
A PbSe solution‐processed nanocrystal‐based infrared photodetector incorporating carrier blocking layers is demonstrated, and significant reduction of dark current is achieved. Detectivity values close to 1012 Jones are achieved by using poly[(9,9′‐dioctylfluorenyl‐2,7‐diyl)‐co‐(4,4′‐(N‐(4‐sec‐butyl))diphenylamine)] (TFB) and ZnO nanocrystals (NC) as the electron blocker and hole blocker, respectively. An improvement in lifetime is also observed in the devices with the ZnO NCs hole blocking layer. 相似文献
104.
Common mass spectrometric techniques, e.g., electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI), require samples to be soluble in suitable solvents. Samples with solubility problems have difficulties for their mass spectrometric characterization. In this paper, an oil-assisted sample preparation (OASP) method was introduced for the analysis of solid samples using MALDI-MS. The novel method involves the use of a droplet of oil (i.e., paraffin oil) as the mixing and loading media for solid analyte and solid matrix. Using this method, rapid on-target sample preparation can be easily achieved, and only a transferable minimal amount of analyte and matrix is required. This method was demonstrated to be applicable for a wide range of analytes, including poorly soluble organic compounds, polymers, organometallic compounds, membrane peptides, and biological solid samples. The novel method can also be used for the analysis of "wet" and solution samples. The limit of detection of the OASP MALDI-MS was determined to be 1 ng with reserpine. 相似文献
105.
Class C β-lactamases mediate antibiotic resistance in bacteria by efficiently hydrolyzing a broad range of β-lactam antibiotics. With their clinical significance and the lack of commercially available effective inhibitors, development of class C β-lactamase inhibitors has become one of the recent hot issues in the pharmaceutical industry. In this paper, we report the protein engineering of a fluorescent Amp C β-lactamase mutant designated as V211Cf for the in vitro screening of class C β-lactamase inhibitors. When a fluorescein (f) was incorporated at the entrance of the enzyme's active site (position 211), Amp C β-lactamase from Enterobacter cloacae P99 was tailor-made into a novel fluorescent biosensing protein that could display a fluorescence enhancement upon binding with its β-lactam substrates/inhibitors. With its catalytic activity close to the wild-type level, V211Cf can act as a "natural" fluorescent drug target for screening small binding molecules. In addition, V211Cf can allow specific detection for its active-site binding molecules and discriminate them from nondruglike molecules in the screen. Furthermore, V211Cf is amenable to a high throughput format. Taken together, V211Cf demonstrates the potential as an efficient tool for screening class C β-lactamase inhibitors and facilitates the discovery of therapeutics that can combat the clinically important class C β-lactamases. 相似文献
106.
以肌肤肌理作为设计主题,设计师采纳了当代的演绎方式,为这脱毛中心的420m2室内空间,重塑了人类的亲密与和谐。白色与橙色为主题颜色,而线条与肌理则为主题元素勾勒出现代与人性化的设计风格。 相似文献
107.
108.
Hongyun So Hyun Gi Yoon Myung Kyoon Chung 《Journal of Mechanical Science and Technology》2011,25(3):721-729
To study the detailed flow structure of the unconfined plane impinging jet, a 3-dimensional flow analysis is carried out focused
on the flow mechanism with the non-dimensional distance, L/d, as flow parameter by using the LES turbulent technique. The
symbols d and L represent the nozzle width and the nozzle-to-plate distance, respectively. Then, the flow structures along
both the stream-wise and spanwise direction are investigated. For these purposes, the plane impinging jet with Reynolds number
of 11,000 is analyzed. The nozzle width was fixed at 1.5mm, but the nozzle-to-plate distance was varied between 4mm and 24mm.
As a result, the plane impinging jet shows different flow patterns with L/d. In conclusion, the plane impinging jet is classified
into three types with the non-dimensional variable, L/d. L/d≤4: Stable impinging jet, 4<L/d<11: periodically-stable impinging
jet and L/d≥11: Unstable impinging jet. 相似文献
109.
This study performs a webometric analysis to explore the communication characteristics of scientific knowledge in a national
scholarly Web space comprising top ranking universities and government supported research institutions in South Korea. We
found significant differences in scholarly communication activity as well as linking behavior among different subspaces in
addition to institutional differences. We also found the usefulness of the ADM approach in analyzing the metric data containing
extreme outliers and discovered the directory model as the most appropriate. Page counts were found significantly correlated
with inlinks as well as with outlinks at the directory level in the whole scholarly Web space. 相似文献
110.