378 research outputs found
Biorthogonal wavelet theory and techniques for image coding
No full textThis paper concentrates on two issues related to wavelet-based image coding. At first, an algebra method is proposed to select biorthogonal wavelets for higher compression ratio and better quality of the reconstructed image. Then, a general algorithm is given to convert a discrete biorthogonal wavelet transform into lifting steps, so that one version of the transform, which maps integers to integers, can support both the lossy and lossless coding to facilitate the region of interest based image compression.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000077172800005&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Computer Science, Software EngineeringCPCI-S(ISTP)
Finite-dimensional integrable systems related to the n-wave interaction equations
No full textUnder a constraint between the potentials and the eigenfunctions, Lax pairs and adjoint Lax pairs of a soliton hierarchy associated with the nxn generalized Zakharov-Shabat eigenvalue problem are transformed into a spatial finite-dimensional Hamiltonian system and a hierarchy of temporal finite-dimensional Hamiltonian systems. The Lax representations, r-matrix structure and integrals of motion are explicitly presented. These integrals of motion are functionally independent and in involution in pairs, which shows that these systems, especially the whole hierarchy of temporal finite-dimensional Hamiltonian systems, are Liouville integrable. (C) 2001 American Institute of Physics.Physics, MathematicalSCI(E)0ARTICLE83554-35644
Pseudo-binary systems CsAlF4-KAlF4 and Cs3AlF6-K3AlF6
No full textPhase relations in the system CsAlF4-KAlF4 and Cs3AlF6-K3AlF6 were investigated by DTA and XRD methods. In the system CsAlF4-KAlF4, two intermediate compounds 3CsAlF(4). KAlF4 and CsAlF4. KAlF4 were confirmed. The first one was indexed as orthorhombic with a = 9.079 +/- 0.003, b = 7.958 +/- 0.002, c = 7.648 +/- 0.004 Angstrom. The second one alpha-CsAlF4. KAlF4 is also orthorhombic, a = 10.982 +/- 0.005, b = 10.093 +/- 0.006, c = 6.160 +/- 0.002 Angstrom. Among the two compounds and KAlF4, two eutectic temperatures e(1) and e(2) are formed. The first eutectic temperature e(1) is located in 42 mol % KAlF4 at 525 degrees C, and e(2) in 70 mol % KAlF4 at 510 degrees C. The system Cs3AlF6-K3AlF6 is a successive solid solution system with the lowest melting point, the composition of which is 75 mol % Cs3AlF6 at 775 degrees C. In the solid solution, compound 2Cs(3)AlF(4). K3AlF6 was formed at 656 degrees C, and was indexed as a cubic cell with a = 8.891 Angstrom. (C) 1999 Elsevier Science B.V. All rights reserved.Chemistry, AnalyticalChemistry, PhysicalSCI(E)4ARTICLE1-2135-13933
Finding and Fixing Traps in II-VI and III-V Colloidal Quantum Dots: The Importance of Z-Type Ligand Passivation
No full textEnergy levels in the band gap arising from surface states can dominate the optical and electronic properties of semiconductor nanocrystal quantum dots (QDs). Recent theoretical work has predicted that such trap states in II-VI and III-V QDs arise only from two-coordinated anions on the QD surface, offering the hypothesis that Lewis acid (Z-type) ligands should be able to completely passivate these anionic trap states. In this work, we provide experimental support for this hypothesis by demonstrating that Z-type ligation is the primary cause of PL QY increase when passivating undercoordinated CdTe QDs with various metal salts. Optimized treatments with InCl3 or CdCl2 afford a near-unity (>90%) photoluminescence quantum yield (PL QY), whereas other metal halogen or carboxylate salts provide a smaller increase in PL QY as a result of weaker binding or steric repulsion. The addition of non-Lewis acidic ligands (amines, alkylammonium chlorides) systematically gives a much smaller but non-negligible increase in the PL QY. We discuss possible reasons for this result, which points toward a more complex and dynamic QD surface. Finally we show that Z-type metal halide ligand treatments also lead to a strong increase in the PL QY of CdSe, CdS, and InP QDs and can increase the efficiency of sintered CdTe solar cells. These results show that surface anions are the dominant source of trap states in II-VI and III-V QDs and that passivation with Lewis acidic Z-type ligands is a general strategy to fix those traps. Our work also provides a method to tune the PL QY of QD samples from nearly zero up to near-unity values, without the need to grow epitaxial shells.ChemE/Opto-electronic Material
Two-Dimensional Self-Assembly of Boric Acid-Functionalized Graphene Quantum Dots: Tunable and Superior Optical Properties for Efficient Eco-Friendly Luminescent Solar Concentrators
No full textCarbon-based
nanomaterials hold promise for eco-friendly alternatives
to heavy-metal-containing quantum dots (QDs) in optoelectronic applications.
Here, boric acid-functionalized graphene quantum dots (B-GQDs) were
prepared using bottom-up molecular fusion based on nitrated pyrenes
and boric acid. Such B-GQDs with crystalline graphitic structures
and hydrogen-bonding functionalities would be suitable model systems
for unraveling the photoluminescence (PL) mechanism, while serving
as versatile building blocks for supramolecular self-assembly. Unlike
conventional GQDs with multiple emissive states, the B-GQDs exhibited
excitation-wavelength-independent, vibronic-coupled excitonic emission.
Interestingly, their PL spectra can be tuned without largely sacrificing
the quantum yield (QY) due to two-dimensional self-assembly. In addition,
such B-GQDs in a polystyrene matrix possessed an ultrahigh QY (∼90%)
and large exciton binding energy (∼300 meV). Benefiting from
broadband absorption, ultrahigh QY, and long-wavelength emission,
efficient laminated luminescent solar concentrators (100 × 100
× 6.3 mm3) were fabricated, yielding a high
power conversion efficiency (1.4%)
Isolation and characterization of a group of oligopeptides related to oxidized glutathione from the root of Panax ginseng
No full textJournal of Peptide Research522137-142JPER
Radioisotopic tracing of lanthanide uptake in erythrocyte, using ytterbium (Yb-169(3+)) and mouse erythrocytes
No full textThis study describes a highly sensitive and simple method of Yb-169 tracing to investigate the uptake of Yb3+ in mouse erythrocyte. The amounts of Yb3+ absorbed by erythrocyte, membrane and cytoplasm at different time were determined after erythrocytes were incubated with 1.0.10(-6) mol.1(-1) Yb-169(3+) solution at 37 degreesC. The results indicated that Yb3+ absorbed on the membrane was transferred promptly to the cytoplasm during the separation process. The observation of a very low level of Yb3+ in the cytoplasm could not lead to a verdict that Yb3+ could travel across the erythrocyte membrane.Chemistry, AnalyticalChemistry, Inorganic & NuclearNuclear Science & TechnologySCI(E)0ARTICLE1145-14926
A model experiment of the plate movement
No full textDetailed analysis of some difficult aspects has been made from modeling the platemovement. A new method of using differential density of material (instead of differentialtemperature) has been developed in the experiments. The effect of convection of mantleon the plate movement has been studied using a centrifugal technique, and a patternshowing the recurrence of the plate movement has been successfully obtained. In this paper, a criterion De=Dm is presented for the similarity of the model to thecounterpart of the original mantle. According to the criterion, what happens in the modelin a span of ten minutes suggests a process of the "original model" going on in geologi-cal time of three million years
Copper-Ion-Assisted Precipitation Etching Method for the Luminescent Enhanced Assembling of Sulfur Quantum Dots
No full textIn this study, we report a metal-ion-assisted
precipitation etching
strategy that can be used to manipulate the optical properties associated
with the assembling of sulfur quantum dots (S dots) using copper ions.
Transmission electron microscopy confirmed that the S dots were mainly
distributed within 50–80 nm and that they exhibited an ambiguous
boundary. After the post-synthetic Cu2+-assisted modification
was completed, the assisted precipitation-etching S dots (APE-S dots)
were observed to exhibit a relatively clear boundary with a high fluorescence
(FL) quantum yield (QY) of 32.8%. Simultaneously, the Fourier transform
infrared radiation, X-ray photoelectron spectra, and time-resolved
FL decay spectra were used to illustrate the improvement in the FL
QY of the APE-S dots
Asymptotic correction of Numerov's eigenvalue estimates with general boundary conditions
No full textThe error in the estimate of the kth eigenvalue of ?y??+qy=?y, y(0)=y(?)=0, obtained by Numerov's method with uniform step length h, is O(k 6 h 4 ). The author and J. Paine showed that a correction technique of Paine, de Hoog and Anderssen reduced this to O(k 4 h 5 /sin(kh)), with negligible extra effort. Later the author extended the method to deal with boundary conditions of the form y?(a)=0. This paper shows how a similar increase in accuracy can be obtained, with a little more effort, for problems with one or more boundary conditions of the form y?(a)=?y(a) where ? ? 0
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