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排序方式: 共有489条查询结果,搜索用时 15 毫秒
81.
Jose Portillo-Portillo Roberto Leyva Victor Sanchez Gabriel Sanchez-Perez Hector Perez-Meana Jesus Olivares-Mercado Karina Toscano-Medina Mariko Nakano-Miyatake 《Applied Intelligence》2018,48(5):1200-1217
This paper proposes a view-invariant gait recognition algorithm, which builds a unique view invariant model taking advantage of the dimensionality reduction provided by the Direct Linear Discriminant Analysis (DLDA). Proposed scheme is able to reduce the under-sampling problem (USP) that appears usually when the number of training samples is much smaller than the dimension of the feature space. Proposed approach uses the Gait Energy Images (GEIs) and DLDA to create a view invariant model that is able to determine with high accuracy the identity of the person under analysis independently of incoming angles. Evaluation results show that the proposed scheme provides a recognition performance quite independent of the view angles and higher accuracy compared with other previously proposed gait recognition methods, in terms of computational complexity and recognition accuracy. 相似文献
82.
Hector M. Nuñez Dusan Paredes Rafael Garduño-Rivera 《The Annals of Regional Science》2017,59(1):171-187
Since Roback’s seminal work (J Polit Econ 90(6):1257–1278, 1982), the literature on hedonic prices has evaluated the role of amenities in equilibrating regional differentials in nominal wages and prices. While these studies generally find evidence for traditional amenities and disamenities in developed countries, there remains little research on how characteristics such as violence affect the equilibrium in less developed countries. This article explores violence and other local characteristics as an amenity or disamenity for Mexico and employs the hedonic wage and rent theory proposed by Roback. This research uses a multilevel estimation technique using data from the Mexican Household Income and Expenditure Survey, along with other information from the municipal and state levels. This article finds evidence to suggest that illegal earning opportunities outweigh crime disamenity by inhabitants of some traditional drug-trafficking regions, because such crime appears to be the modus vivendi in those regions in a way that does not reduce economic performance. 相似文献
83.
Summary. In a multi-party transaction (also called a distributed commerce transaction) agents face risks from dealing with untrusted
agents. These risks are compounded in the face of deadlines, e.g., an agent may fail to deliver purchased goods by the time
the goods are needed. We characterize the risks, and present a distributed algorithm that mitigates these risks, by using
pairwise exchanges and trusted intermediaries. The algorithm generates a safe sequence of actions that completes a commerce
transaction without risk, if such a sequence exists. We show that the algorithm is sound (produces only safe multi-agent action
sequences) and complete (finds a safe sequence whenever one exists). The initial restriction of guaranteeing safety even when
none of the principals trusts another can be relaxed in some cases, so we show how to handle principals that do trust each
other and interact directly rather than through a trusted intermediary.
Received: September 1997 / Accepted: December 1998 相似文献
84.
Leonardo Mariño-Repizo Hector Goicoechea Julio Raba 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2018,35(8):1622-1632
A novel, simple, easy and cheap sample treatment strategy based on salting-out assisted liquid-liquid extraction for ochratoxin A (OTA) ultra-trace analysis in beer samples using ultra-high-performance liquid chromatography-tandem mass spectrometry determination was developed. The factors involved in the efficiency of pre-treatment were studied employing factorial design in the screening phase and the optimal conditions of the significant variables on the analytical response were evaluated using a central composite face-centred design. Consequently, the amount of salt ((NH4)2SO4), together with the volumes of sample, hydrophilic (acetone) and nonpolar (toluene) solvents, and times of vortexing and centrifugation were optimised. Under optimised conditions, the limits of detection and quantification were 0.02 µg l?1 and 0.08 µg l?1 respectively. OTA extraction recovery by SALLE was approximately 90% (0.2 µg l?1). Furthermore, the methodology was in agreement with EU Directive requirements and was successfully applied for analysis of beer samples. 相似文献
85.
We develop a geometry-based model from first-principles data for the interaction of solutes with a prismatic screw dislocation core, and predict the thermally activated cross-slip stress above room temperature in Mg alloys. Electronic structure methods provide data for the change in prismatic stacking fault energy for different possible fault configurations for 29 different solutes. The direct solute-dislocation interaction energies for solutes that produce stable prismatic screw dislocation cores (K, Na, Sc and Ca) is correlated with stacking fault misfits. This geometric interaction model produces similar prediction errors for all 29 solutes. The model predicts alloys with cross-slip stresses lower than pure Mg for three previously considered solutes (K, Na and Sc) and three new solutes (Ca, Y and Zr). The model also qualitatively confirms the experimental observation that Mg-Li alloys have lower cross-slip stress than pure Mg. In particular, low concentrations of Y are predicted to significantly decrease the cross-slip stress in Mg. 相似文献
86.
Pérez-Trujillo M Lindon JC Parella T Keun HC Nicholson JK Athersuch TJ 《Analytical chemistry》2012,84(6):2868-2874
Differences in molecular chirality remain an important issue in drug metabolism and pharmacokinetics for the pharmaceutical industry and regulatory authorities, and chirality is an important feature of many endogenous metabolites. We present a method for the rapid, direct differentiation and identification of chiral drug enantiomers in human urine without pretreatment of any kind. Using the well-known anti-inflammatory chemical ibuprofen as one example, we demonstrate that the enantiomers of ibuprofen and the diastereoisomers of one of its main metabolites, the glucuronidated carboxylate derivative, can be resolved by (1)H NMR spectroscopy as a consequence of direct addition of the chiral cosolvating agent (CSA) β-cyclodextrin (βCD). This approach is simple, rapid, and robust, involves minimal sample manipulation, and does not require derivatization or purification of the sample. In addition, the method should allow the enantiodifferentiation of endogenous chiral metabolites, and this has potential value for differentiating metabolites from mammalian and microbial sources in biofluids. From these initial findings, we propose that more extensive and detailed enantiospecific metabolic profiling could be possible using CSA-NMR spectroscopy than has been previously reported. 相似文献
87.
H Villagarcia E Dervishi K de Silva AS Biris MV Khodakovskaya 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(15):2327-2327
A tomato plant grows on medium supplemented with multi-walled carbon nanotubes. The correlations between the level of aggregation, the type of functional group on the surface of applied carbon nanotubes, plant growth performance and the expression of tomato water channel protein in the cell membranes of roots exposed to multi-walled carbon nanotubes are documented and discussed by A. S. Biris, M. V. Khodakovskaya, and co-workers. 相似文献
88.
Hector M. Henao Claudio Pizarro Jonkion Font Alex Moyano Peter C. Hayes Evgueni Jak 《Metallurgical and Materials Transactions B》2010,41(6):1186-1193
Limited data are available on phase equilibria of the multicomponent slag system at the oxygen partial pressures used in the copper smelting, converting, and slag-cleaning processes. Recently, experimental procedures have been developed and have been applied successfully to characterize several complex industrial slags. The experimental procedures involve high-temperature equilibration on a substrate and quenching followed by electron probe X-ray microanalysis. This technique has been used to construct the liquidus for the “Cu2O”-“FeO”-SiO2-based slags with 2 wt pct of CaO, 0.5 wt pct of MgO, and 4.0 wt pct of Al2O3 at controlled oxygen partial pressures in equilibrium with metallic copper. The selected ranges of compositions and temperatures are directly relevant to the copper slag-cleaning processes. The new experimental equilibrium results are presented in the form of ternary sections and as a liquidus temperature vs Fe/SiO2 weight ratio diagram. The experimental results are compared with the FactSage thermodynamic model calculations. 相似文献
89.
Taufiq Hidayat Hector M. Henao Peter C. Hayes Evgueni Jak 《Metallurgical and Materials Transactions B》2012,43(5):1034-1045
Phase equilibria of the Cu-Fe-O-Si system have been investigated in equilibrium: (1) with air atmosphere at temperatures between 1373?K and 1673?K (1100?°C and 1400?°C) and (2) with metallic copper at temperatures between 1373?K and 1573?K (1100?°C and 1300?°C). High-temperature equilibration/quenching/electron-probe X-ray microanalysis (EPMA) techniques have been used to accurately determine the compositions of the phases in equilibrium in the system. The new experimental results are presented in the form of ??Cu2O??-??Fe2O3??-SiO2 ternary sections. The relationships between the activity of CuO0.5(l) and the composition of slag in equilibrium with metallic copper are discussed. The phase equilibria information of the Cu-Fe-O-Si system is of practical importance for industrial copper production processes and for the improvement of the existing thermodynamic database of copper-containing slag systems. 相似文献
90.
Fabio Freschi Hector Sanchez Lopez Elliot Smith Fangfang Tang Maurizio Repetto Stuart Crozier 《Numerical Heat Transfer, Part A: Applications》2013,63(3):265-282
ABSTRACTThis article proposes a numerical formulation for handling mixed-dimensional elements embedded in a standard three-dimensional (3d) mesh, avoiding thus the volume meshing of filaments and strips. The method is then applied to predict the temperature heating and cooling profile of gradient coils in magnetic resonance imaging. These coils are typically constructed from copper wires or tracks and embedded in an epoxy layer. It was found that the new method significantly reduces the computational time of steady-state and transient simulations, with speedups in the range of 3.5-5. The method proved to be accurate, with relative errors below 0.5% for steady-state simulations and 1.5% with respect to a complete 3d simulation. 相似文献