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51.
Yu. D. Chistyakov Yu. A. Baikov H. G. Schneider V. Ruth 《Crystal Research and Technology》1983,18(6):711-723
A recently published theory on the solidification of a one-component melt has been extended to the more complex case of binary systems. The theory is based on the model of a two-phase transitional zone existing between the crystalline phase and the melt. The concentration of solid state atoms within each mono-atomic layer of the transitional zone are assumed to fluctuate due to thermal fluctuations. A crystal growth law has been derived expressing the crystallization velocity in terms of probability functions describing these concentrations fluctuations. When certain restricting conditions concerning the atomic interaction energies within the transitional zone and the distribution of the atoms among the solid and liquid phases at supercooling are fulfilled the crystal growth law attains a simple form predicting for small supercoolings a growth rate proportional to supercooling (linear growth law), roughly proportional to physical parameter θAA, and with a weak dependence on another parameter Δ. 相似文献
52.
Boris Kapilevich Yosef Pinhasi Ruth Arusi Michael Anisimov Danny Hardon Boris Litvak Yan Wool 《Journal of Infrared, Millimeter and Terahertz Waves》2010,31(11):1370-1381
A single-pixel imaging remote sensor operating at 330 GHz is described. It is based on a frequency modulated continuous wave
(FMCW) and aimed at detection of concealed objects for ranges up to 40 m. The system consists of 2 horn-lens antennas integrated
with a homodyne transceiver. The synthesized linear FMCW signal at X-band is multiplied by a factor of 32 to generate the
transmitted signal. An intermediate frequency (IF) signal obtained in the output port of the 2-nd harmonic mixer is employed
for image processing. Distance measurements were made by performing data acquisition unit based on LabView interface and resulting
in a range resolution about 1 cm. Examples of 2D and 3D images reconstructed with this sensor are presented. 相似文献
53.
Rui Liu Yuankun Cai Joong‐Mok Park Kai‐Ming Ho Joseph Shinar Ruth Shinar 《Advanced functional materials》2011,21(24):4744-4753
The organic light‐emitting diode (OLED)‐based sensing platform is gaining momentum due to unique attributes of the compact OLEDs that are used as excitation sources. This paper, however, points to issues related to this sensing platform that will affect many (bio)chemical sensing applications, in particular in photoluminescence (PL)‐based sensors operated in the advantageous time domain, where pulsed OLEDs are utilized. The issues are related to the post‐pulse electroluminescence (EL) profile, i.e., transient EL, which depends on the OLED materials and structure, and to the long‐wavelength tail of the typically broad‐band EL spectrum. Depending on materials and device structure, the transient EL may exhibit spikes peaking at ~100–200 ns and μs‐long tails. As shown, these interfere with the determination of PL decay times (that are related to analyte concentrations) of sensing elements. The results also indicate that the long‐wavelength tail of the EL spectrum contributes to the interfering post‐pulse μs‐long EL tail. Hence, it is shown that the choice of OLED materials, the use of microcavity (μC) OLEDs with tunable, narrower EL bands, and the use of UV OLEDs alleviate these issues, resulting in more reliable data analysis. Furthermore, a 2‐D uniform 2 μm‐pitch microlens array that was previously used for improving light extraction from the OLEDs (J.‐M. Park et al., Optics Express 2011 , 19, A786) is used for directional PL scattering toward the photodetector, which leads to a ~2.1–3.8 fold enhancement of the PL signal. This behavior is shown for oxygen sensing, which is the basis for sensing of bioanalytes such as glucose, lactate, ethanol, cholesterol, and uric acid. 相似文献
54.
55.
The cathode–electrolyte interface in a solid oxide fuel cell is examined to understand why premature delamination is observed in alumina substituted YSZ electrolyte. From XRD, SEM and TEM observations it was concluded that after high temperature sintering a tetragonal (Mn,Al)3O4 forms at the interface, which during prolonged fuel cell operation forms a cubic (Mn,Al)3O4 phase. This transformation is associated with volume decrease creating voids which ultimately weaken the cathode–electrolyte interface sufficiently for the cathode layer to delaminate off the YSZ–Al2O3 electrolyte. 相似文献
56.
The sub-optimal Hankel norm approximation problem is solved under the assumptions that the system is given in terms of a triple of operators (–A, B, C), where–A is the infinitesimal generator of an exponentially stable, analytic semigroup on the Hilbert spaceZ,B L (
m
,Z
where –1<0,C L is obtained in terms of the system parameters–A, B, C. (Z,
p
), and the system is approximately controllable. An explicit parameterization of all solutions 相似文献
57.
A.A. Ruth T. FernholzR.P. Brint M.W.D. Mansfield 《Journal of Molecular Spectroscopy》2002,214(1):80-86
The T1←S0 absorption spectrum of 4H-pyran-4-thione (PT) was measured in a static cell at room temperature (550-620 nm) and in a seeded cold supersonic jet (580-600 nm) using the cavity ring-down (CRD) method. In the static cell absolute extinction coefficients were determined between 573 and 610 nm with an accuracy of ∼±5%. In this region 22 harmonic sequences and 18 hot bands were observed. The energetically lowest ground state vibration at 167.5 cm−1 was identified as the promoting mode in the static PT gas. The mode in the triplet state was found at 152.3 cm−1. The CRD absorption spectra of static PT gas and jet-cooled PT are compared with the phosphorescence excitation spectrum of isolated PT. The weak S1, 0←S0, 0 absorption was tentatively assigned to a transition at ∼17433 cm−1. 相似文献
58.
Avalos M Babiano R Cintas P Clemente FR Gordillo R Hursthouse MB Jiménez JL Light ME Palacios JC 《The Journal of organic chemistry》2002,67(7):2378-2381
The present contribution discloses a simple and unexpected acid-catalyzed cleavage of tetrahydrotetrazines leading to 1,2-bis(hydrazones). Incorporation of a chiral fragment derived from carbohydrates enables the rapid preparation of glycosazones, a family of compounds employed by Emil Fischer to elucidate the configuration of sugars. In addition, a mechanistic proposal accounts for experimental observations. 相似文献
59.
Donohue R Mazzaglia A Ravoo BJ Darcy R 《Chemical communications (Cambridge, England)》2002,(23):2864-2865
Cationic amphiphilic beta-cyclodextrins, substituted with hydrophobic n-alkylthio chains at the primary hydroxyl side and hydrophilic omega-amino-oligo(ethylene glycol) units at the secondary side, form bilayer vesicles with a diameter of 30-35 nm (when alkyl = hexadecyl) or nanoparticles with a diameter of ca. 120 nm (when alkyl = hexyl) in water. 相似文献
60.
The release of aroma compounds from rehydrated French beans in an artificial mouth system and in the mouths of 12 assessors was studied by gas chromatography combined with flame ionisation detection and sniffing port detection. In an artificial mouth system, volatile compounds were isolated under mouth conditions, such as temperature, salivation, and mastication. No significant differences were determined between the aroma release from the beans in the artificial mouth and release in the mouths of assessors. However, both the real and artificial mouth systems differed significantly from a purge-and-trap and a dynamic headspace system in aroma release. In order to study aroma release over time, volatile compounds were isolated from rehydrated French beans for 1, 1.5, 3 and 12 min in the artificial mouth system and analysed by gas chromatography/sniffing port analysis. 2-Methylpropanal, 2-/3-methylbutanal, hexanal, 2-methyl-2-butenal, 1-octen-3-one, and dimethyl trisulphide possessed detectable odours when isolated from the French beans in the artificial mouth for all time periods. The odour active compounds 2-/3-methylbutanal and hexanal were shown to be released at a constant rate. Different sampling times resulted in identical selections of aroma compounds, while mutual proportions were retained. 相似文献