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排序方式: 共有193条查询结果,搜索用时 15 毫秒
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Van Giessen JW Viergever MA De Graaf CN Dane HJ 《IEEE transactions on medical imaging》1986,5(4):222-228
In this paper, we discuss the applicability of a time-coded aperture system especially designed for thyroid tomography on the basis of phantom experiments. Our studies show that 1) the quality of the reconstructions is high (e.g., a cold spot of 6 mm diameter in a thyroid phantom can easily be detected), and 2) the reconstruction can be carried out in less than 11 min on a standard 16 bit minicomputer (HP1000). It is therefore concluded that the clinical potentiality of the device is good. 相似文献
3.
Bolette Sandford Pedersen Sanni Nimb Jørg Asmussen Nicolai Hartvig Sørensen Lars Trap-Jensen Henrik Lorentzen 《Language Resources and Evaluation》2009,43(3):269-299
This paper is a contribution to the discussion on compiling computational lexical resources from conventional dictionaries.
It describes the theoretical as well as practical problems that are encountered when reusing a conventional dictionary for
compiling a lexical-semantic resource in terms of a wordnet. More specifically, it describes the methodological issues of
compiling a wordnet for Danish, DanNet, from a monolingual basis, and not—as is often seen—by applying the translational expansion method with Princeton WordNet as the English source.
Thus, we apply as our basis a large, corpus-based printed dictionary of modern Danish. Using this approach, we discuss the
issues of readjusting inconsistent and/or underspecified hyponymy hierarchies taken from the conventional dictionary, sense
distinctions as opposed to the synonym sets of wordnets, generating semantic wordnet relations on the basis of sense definitions,
and finally, supplementing missing or implicit information. 相似文献
4.
X-ray detectors based on straight-channel microchannel plates (MCPs) are a powerful diagnostic tool for two-dimensional, time-resolved imaging and time-resolved x-ray spectroscopy in the fields of laser-driven inertial confinement fusion and fast Z-pinch experiments. Understanding the behavior of microchannel plates as used in such detectors is critical to understanding the data obtained. The subject of this paper is a Monte Carlo computer code we have developed to simulate the electron cascade in a MCP under a static applied voltage. Also included in the simulation is elastic reflection of low-energy electrons from the channel wall, which is important at lower voltages. When model results were compared to measured MCP sensitivities, good agreement was found. Spatial resolution simulations of MCP-based detectors were also presented and found to agree with experimental measurements. 相似文献
5.
6.
Walter F Schroeder Silvana L Asmussen Wayne D Cook Claudia I Vallo 《Polymer International》2011,60(9):1362-1369
The efficiency of 4,4′‐bis(N,N‐diethylamino)benzophenone (DEABP) for the polymerization of dimethacrylate monomers in thick sections ( 1 – 2 mm) was studied. DEABP (λmax = 365 nm) represents a complete initiating system as it contains both ketone and amine functional groups. During irradiation, DEABP photobleaches at a fast rate causing deeper penetration of light through the underlying layers, but the photoinitiation efficiency (rate of polymerization per photon absorption rate) is relatively poor. As a result, irradiation of methacrylate monomers at 365 nm results in a slow average polymerization rate and a reduced monomer conversion for thick sections due to the light attenuation caused by the high absorptivity of DEABP and photolysis products. These results highlight the inherent interlinking of light attenuation and photobleaching rate in polymerization of thick sections. Copyright © 2011 Society of Chemical Industry 相似文献
7.
Methanolic extracts from underripe, ripe, and ripe then dried pawpaw seeds (PPSE) were tested for antioxidative effectiveness. Underripe seeds contained more total phenolic compounds than ripe seeds, but ripe seeds showed the highest reducing potential. PPSE samples effectively scavenged DPPH (>86%). PPSE (0–26.8 μM gallic acid) effectively inhibited lipid oxidation biomarkers in 22:6 phosphatidylcholine (PC) liposome suspensions over 7 day’s incubation at room temperature. PPSE inhibited TBARS in 22:6 PC liposome suspensions induced by peroxyl radical generators, free radical generators that produce reactive oxygen, reactive nitrogen, and reactive sulfur species. After 120 min of storage TBARS inhibition by PPSE was in the order of H2O2 ? SIN-1 = DSSO = AAPH ? Sulfite > ONOO = MMb > iron/ascorbate. PPSE inhibited lipid oxidation biomarkers in skeletal muscle homogenates induced by iron/ascorbate. The development of value added products from pawpaw seeds may lead to successful commercialisation of this underutilised fruit. 相似文献
8.
Anshuman Sharma Chuan Zhang Y. Austin Chang Ray Knoeppel Dane Morgan 《Corrosion Science》2011,(5):1724-1731
This work summarizes the experimental literature to date on Al-alloy sacrificial anodes and shows that the presence of Sn as an alloying element in solid solution form consistently debases the alloy corrosion potential. This study then assesses the lattice expander theory, which states that lattice-expanding dopants can be used to increase Sn solubility in Al and thereby reduce passivation. The thermodynamic effects on Sn solubility of lattice expanders (Ga, Mg, Zr, In and Bi) are predicted with ab-initio methods. Our results support lattice expander theory although we demonstrate that Sn solubility can decrease by alloying with even large dopants if they form compounds with Sn. 相似文献
9.
The He-Ne laser (632.8 nm) and the concept of optothermal window (OW), a variant of the open photoacoustic cell, were combined with the Folin-Ciocalteu colorimetry assay to quantitate phenolics in four red wines. The total polyphenolic content in selected red wines varied between 786 and 1630 mg/L gallic acid equivalent (GAE) as determined by OW-Folin-Ciocalteu colorimetry, which compares well to 778 and 1614 mg/L GAE obtained for the same wines by means of classical spectrophotometry. The originality and merit of OW colorimetry used here is that, unlike what is encountered in conventional spectrometry, no intermediate dilution step is required when total polyhenolics are determined in red wine. The precision, defined as the closeness to each other of 256 replicate readings of the OW signal, is generally better than 2%. 相似文献
10.
Allen Y. Chao Dale Eric Wurster Craig W. Davis Dane O. Kildsig 《Drug development and industrial pharmacy》1982,8(2):293-306
Mass transfer from solutions of m-acetotoluide, phenacetin and salicylamide into a stationary solvent, water, was studied. A sharp concentration jump was found at the leading solute front for all three liquid-liquid systmes. A comparison was made between the mass transferred in solid-liquid and liquid-liquid systems. The dissolution of m-acetotoluide, phenacetin and salicylamide was compared with mass transfer of solute from solutions with concentrations Ci, 2Ci and Cs into the pure solvent. In all cases, the amount dissolved from the solid was approximated by the Ci or the 2Ci-solvent system with the amount transferred in the Cs-solvent system approximately 100 fold greater than was dissolved from the solid. It was concluded that a concentration much less than saturation exists at the solid-liquid interface and that dissolution of the three compounds studied is controlled by the rate of solvent interaction at the solid surface. 相似文献