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排序方式: 共有260条查询结果,搜索用时 35 毫秒
251.
Farshid Manoocheri Meelis Sildoja Timo Dönsberg Mikko Merimaa Erkki Ikonen 《Optical Review》2014,21(3):320-324
Silicon photodiodes with induced junction structure can reach low-loss photon-to-electron conversion. The calculated conversion efficiency in the visible wavelength range typically deviates less than 10 ppm from unity and its uncertainty is about 100 ppm at room temperature or as low as 1 ppm at 78 K. Here we show experimentally that our dedicated induced junction photodiodes indeed have very low conversion losses when they are assembled in a light trapping structure as provided by, for example, the predictable quantum efficient detector (PQED). It is concluded that the remaining measured losses, if any, are probably due to surface recombination of electrons and holes close to the silicon/silicon dioxide interface of the photodiode. 相似文献
252.
Single-layer one-dimensional nonpolarizing guided-mode resonance filters under normal incidence 总被引:1,自引:0,他引:1
Alasaarela T Zheng D Huang L Priimagi A Bai B Tervonen A Honkanen S Kuittinen M Turunen J 《Optics letters》2011,36(13):2411-2413
We demonstrate that properly designed one-dimensional guided-mode resonance filters (GMRFs) with only one grating layer can exhibit a nonpolarizing resonant filtering effect under normal incidence. A sinusoidal profile nonpolarizing GMRF is realized by photoinduced surface-relief grating formation on thin films of polymer-azobenzene complexes and subsequent atomic layer deposition, showing the feasibility of fabrication of such compact GMRFs. 相似文献
253.
The reaction of 3-aminopropylamide of cholic acid with CS? produced a bile acid derivative of dithiocarbamic acid which further formed an ammonium salt with another molecule of 3-aminopropylamide of cholic acid. The cationic 3-ammonium propylamide of cholic acid did not react further with CS? and the formed salt was stable in the reaction mixture, even when excess CS? was used. When the reaction was carried out in the presence of aqueous sodium hydroxide, only the bile acid derivative of sodium dithiocarbamate was formed. The dithiocarbamate derivatives were characterized by 1H- and 13C-NMR spectroscopy and ESI-TOF mass spectrometry. 相似文献
254.
Borys Ośmiałowski Erkki Kolehmainen Reijo Kauppinen Magdalena Kowalska 《Supramolecular chemistry》2013,25(8):579-586
The association of 2,6-bis(cycloalkylcarbonylamino)pyridines with rigid and non-rigid counterparts in chloroform solution was studied using 1H NMR and computational methods. The angles within the cycloalkyl ring and the rotation of these substituents determine the strength of the association via triple hydrogen bonding. The dimerisation and methyl–methyl repulsion have been addressed as mechanisms restricting heterocomplexation of diacetamide. The association constants obtained by the shift changes of hydrogen-bonded protons are in agreement with those of methine protons. This ‘dual shift’ method was proposed as an additional verification of association constants obtained generally by amino protons. 相似文献
255.
Svobodová H Nonappa Wimmer Z Kolehmainen E 《Journal of colloid and interface science》2011,361(2):587-593
An efficient synthesis of three novel stigmasterol-amino acid (glycine, L-leucine and L-phenylalanine) conjugates as stimuli responsive gelators is reported. The gelation properties of the prepared compounds were investigated in a variety of organic as well as aqueous solvents. The most striking finding of our investigation was that the hydrochloride salts of the prepared conjugates acted as gelators, whereas the neutral conjugates were either non-gelators or formed only a weak gel in anisole. The hydrochloride salts of stigmasteryl glycinate and L-leucinate form gels in n-alcohols (n=4-10) and in ethane-1,2-diol, and that of stigmasteryl L-phenylalaninate forms gels in aromatic solvents and in tetrachloromethane. These unique properties of the gelators were explored to prepare stimuli responsive, "acid-base" triggered reversible sol-gel transitions. The gelators and their gels were characterized by liquid and solid-state NMR as well as FT-IR. The morphology of their corresponding xerogels was investigated by SEM. 相似文献
256.
Optical coherence tomography (OCT), a technique for the noninvasive imaging of turbid media, based on low-coherence interferometry,
was originally developed for the imaging of biological tissues. Since the development of the technique, most of its applications
have been related to the area of biomedicine. However, from early stages, the vertical resolution of the technique has already
been improved to a submicron scale. This enables new possibilities and applications. This article presents the possible applications
of OCT in paper industry, where submicron or at least a resolution close to one micron is required. This requirement comes
from the layered structure of paper products, where layer thickness may vary from single microns to tens of micrometers. This
is especially similar to the case with high-quality paper products, where several different coating layers are used to obtain
a smooth surface structure and a high gloss. In this study, we demonstrate that optical coherence tomography can be used to
measure and evaluate the quality of the coating layer of a premium glossy photopaper. In addition, we show that for some paper
products, it is possible to measure across the entire thickness range of a paper sheet. Furthermore, we suggest that in addition
to topography and tomography images of objects, it is possible to obtain information similar to gloss by tracking the magnitude
of individual interference signals in optical coherence tomography. 相似文献
257.
J. P. Vary H. Honkanen Jun Li P. Maris A. M. Shirokov S. J. Brodsky A. Harindranath G. F. de Teramond E. G. Ng C. Yang M. Sosonkina 《Pramana》2010,75(1):39-49
Nuclear structure physics is on the threshold of confronting several long-standing problems such as the origin of shell structure from basic nucleon-nucleon and three-nucleon interactions. At the same time those interactions are being developed with increasing contact to QCD, the underlying theory of the strong interactions, using effective field theory. The motivation is clear — QCD offers the promise of great predictive power spanning phenomena on multiple scales from quarks and gluons to nuclear structure. However, new tools that involve non-perturbative methods are required to build bridges from one scale to the next. We present an overview of recent theoretical and computational progress with a Hamiltonian approach to build these bridges and provide illustrative results for the nuclear structure of light nuclei and quantum field theory. 相似文献
258.
Prokhor A. Alekseev Vladislav A. Sharov Pavel Geydt Mikhail S. Dunaevskiy Volodymyr V. Lysak George E. Cirlin Rodion R. Reznik Artem I. Khrebtov Ilya P. Soshnikov Erkki Lähderanta 《固体物理学:研究快报》2018,12(1)
Generation of electric current is observed when GaAs nanowires with wurtzite crystal structure are bent by the probe of an atomic force microscope. The current originates from a piezo active phase in the nanowires due to the piezoelectric effect. Increasing of the piezo‐potential in bent nanowires enhances tunneling through the probe–nanowire Schottky barrier due to the thermionic field emission. Laser illumination amplifies short‐circuit current pulses by two orders of magnitude from 9 pA to 1 nA due to the piezo‐phototronic effect. Utilization of such piezo‐phototronic effect in GaAs nanowires is a solution to accelerate the efficiency of hybrid energy sources “piezoelectric nanogenerator ? solar cell” comprised of III–V nanowires. 相似文献
259.
The realization of spectrophotometric quantities at the Helsinki University of Technology is based on our reference spectrometer. The reference spectrometer is a high-accuracy instrument developed for measuring spectral specular transmittance and reflectance in a wavelength range extending from ultraviolet to near-infrared. The relative uncertainty estimates for transmittance measurements of neutral-density filters are ca. 0.05%. For spectral reflectance the estimated uncertainties are between 0.14% and 0.34% depending on the sample reflectance and the measurement geometry. We have derived and verified equations that enable both the reflectance and transmittance of various samples to be predicted. Utilizing these equations, the reflectance and transmittance can be accurately calculated for samples with known refractive index. For precise calculations, the characteristics of the measurement beam must be taken into account. 相似文献
260.
Timo V. Laine Kristian Lappalainen Jonas Liimatta Erkki Aitola Barbro Lfgren Markku Leskel 《Macromolecular rapid communications》1999,20(9):487-491
Three pyridylimine based complexes of NiII and CoII were reacted with methylaluminoxane (MAO) and tested as catalysts in ethylene polymerization. The two nickel catalysts produced mainly methyl branched polymers with good to moderate activity, while the cobalt compound showed only marginal activity. Reaction conditions strongly affect the polymer properties, such as molecular weight, melting temperature, degree of branching, and chain end unsaturation type. 相似文献