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991.
Quantised phase filters with binary low and high pass amplitude response: the effect of quantisation for scale and rotation input distortions 总被引:1,自引:0,他引:1
Triantafillos Koukoulas Rupert C.D. Young Chris R. Chatwin 《Optics and Lasers in Engineering》2005,43(9):963
In the field of optical pattern recognition, there are a large number of filters that possess identification capabilities for certain kinds of input distortions. The resolution of the spectral components plays an important role in the overall processing time of a correlator that may employ such filters. In this paper, two different techniques are discussed: low pass phase filtering and high pass phase filtering. This is achieved by binarizing the amplitude information which then allows certain frequencies to pass and others to be blocked. Their response to different kinds of input distortions is presented and the effect of phase quantisation is considered in detail. 相似文献
992.
993.
The asymmetric [2,3]-Wittig rearrangement of the dienolates of various chiral β-pyrrolidinyl-γ-allyloxyl-α,β-unsaturated esters was investigated using different chiral secondary alcohol substitutions. When (1S,2R,4R)-2-hydroxy-7,7-dimethylbicyclo[2,2,1]heptane-1-carboxylic acid diisopropylamide was used as chiral auxiliary, it provided the best enantioselectivity in the rearrangement. When various γ-allyloxy substitutions underwent temperature and additive studies, 1,1-dimethylpropenoxy substitution was found to give the best enantioselectivity. The methodology was applied to the total synthesis of (+)-eldanolide. 相似文献
994.
995.
Ah Yeon Park So‐Young Park Jaehyun Lee Mihye Jung Jinwoong Kim Sam Sik Kang Jeong‐Rok Youm Sang Beom Han 《Biomedical chromatography : BMC》2009,23(10):1034-1043
Rapid, simple and reliable HPLC/UV and LC‐ESI‐MS/MS methods for the simultaneous determination of five active coumarins of Angelicae dahuricae Radix, byakangelicol (1), oxypeucedanin (2), imperatorin (3), phellopterin (4) and isoimperatorin (5) were developed and validated. The separation condition for HPLC/UV was optimized using a Develosil RPAQUEOUS C30 column using 70% acetonitrile in water as the mobile phase. This HPLC/UV method was successful for providing the baseline separation of the five coumarins with no interfering peaks detected in the 70% ethanol extract of Angelicae dahuricae Radix. The specific determination of the five coumarins was also accomplished by a triple quadrupole tandem mass spectrometer equipped with an electrospray ionization source (LC‐ESI‐MS/MS). Multiple reaction monitoring (MRM) in the positive mode was used to enhance the selectivity of detection. The LC‐ESI‐MS/MS methods were successfully applied for the determination of the five major coumarins in Angelicae dahuricae Radix. These HPLC/UV and LC‐ESI‐MS/MS methods were validated in terms of recovery, linearity, accuracy and precision (intra‐ and inter‐day validation). Taken together, the shorter analysis time involved makes these HPLC/UV and LC‐ESI‐MS/MS methods valuable for the commercial quality control of Angelicae dahuricae Radix extracts and its pharmaceutical preparations. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
996.
M. Farsari S. Huang R. C. D. Young M. I. Heywood C. D. Bradfield C. R. Chatwin 《Optics and Lasers in Engineering》1999,31(3):10
The optical characteristics of a commercial UV curable resin are investigated using non-degenerate four-wave mixing. The material assessed is an epoxy resin, DuPont SomosTM 7100. The holographic gratings were written at a wavelength of λ=351.1 nm for an irradiance range 0.5–3.0 W/cm2 and read at λ=632.8 nm in order to assess the reactivity, curing speed, shrinkage and resolution of the resin. 相似文献
997.
998.
J.L. Pan J.E. McManis M. Gupta M.P. Young J.M. Woodall 《Applied Physics A: Materials Science & Processing》2008,90(1):105-112
Materials exhibiting strong optical emission also exhibit strong absorption at the same wavelengths because both emission
and absorption are governed by the same optical dipole and density-of-states. Laser action requires a carrier injection large
enough for emission to exceed absorption at laser wavelengths. Thus, strong self-absorption at luminescent wavelengths raises
the operating current of LEDs, lasers, and optical amplifiers. Here we demonstrate that, contrary to conventional expectations,
materials designed with novel deep centers achieve surprisingly large optical emission while, simultaneously, the inverse
process of optical absorption remains very small. A striking consequence is that materials designed with our novel deep centers
achieve transparency at a carrier injection which is four-orders-of-magnitude lower than in all technologically important
semiconductors. Simultaneously, and surprisingly, our novel deep centers in GaAs achieve an optical gain, Einstein B coefficient,
and radiative efficiency significantly larger than in direct-band-gap materials at 1.3–1.5 μm. We engineered this dramatic
reduction of the injection to achieve transparency while retaining strong optical emission in our novel material by making
use of a Franck–Condon shift of absorption away from luminescent wavelengths.
PACS 71.55.Eq; 71.55.-i; 78.67.-n; 81.10.-h; 85.60.Jb 相似文献
999.
Local and global synchronization of complex dynamical networks are studied in this paper. Some simple yet generic criteria ensuring delay-independent and delay-dependent synchronization are derived in terms of linear matrix inequalities (LMIs), which can be verified easily via interior-point algorithm. The assumption that the coupling configuration matrix is symmetric and irreducible, which is frequently used in other literatures, is removed. A network with a fixed delay and a special coupling scheme is given as an example to illustrate the theoretical results and the effectiveness of the proposed synchronization scheme. 相似文献
1000.
Bi-Zen Hsieh Hung-Yi Chuang Liang Chao Ying-Jie Huang Po-Hao Tseng Tar-Hwa Hsieh Yu-Kai Han Ko-Shan Ho 《Polymer Degradation and Stability》2008,93(5):983-989
The first-order thermal transitions including side-chain melting, crystal-LC, biphasic chimney-like, and isotropic transitions of poly(n-undecyl isocyanate) (PUDIC) were investigated by varying its thermal history. After annealing at 140 °C for different periods of time, it leads to different degrees of backbiting degradation into n-undecyl isocyanurate trimer which behaves as a solvent for the rest non-degraded/rigid PUDIC to change into a lyotropic LC from thermotropic transition. Based on the degree of degradation, various amounts of trimers are present and the PUDIC demonstrates different types of thermal transitions found in DSC thermograms due to the variation of the non-degraded PUDIC concentration in solvent trimers. Finally, a phase diagram includes all types of crystallines, LC, and isotropic regions can be drawn according to the DSC thermograms. 相似文献