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排序方式: 共有114条查询结果,搜索用时 31 毫秒
1.
In the present paper we evaluate the performance of three different site allocation policies in a 2-level computational grid with heterogeneous sites. We examine the case where service demands of jobs show high variability, and we consider that schedulers are aware of the service times. A simulation model is used to evaluate performance in terms of the average response time and slowdown, under medium and high load. The impact of the various input parameters on performance is also taken into account. Simulation results show that one policy outperforms the other two that are examined, especially at high load. Furthermore, no performance degradation is observed when estimations are used instead of exact knowledge about job service times. 相似文献
2.
Keeseong Park Jon W. Taylor Despina Louca 《Journal of Superconductivity and Novel Magnetism》2014,27(8):1927-1934
The dynamics of the local atomic pair correlations in the FeSe x Te1?x ( x = 0.1, 0.5, and 0.9) system were investigated using the dynamic pair density function analysis obtained from inelastic neutron scattering. Distinct differences are observed between the superconducting and nonsuperconducting compositions, particularly involving the local dynamics of the Fe-Fe correlations. The energy scale of the observed differences is between 25 and 30 meV. In the nonsuperconducting FeSe0.1Te0.9, the Fe-Fe correlations are enhanced with cooling that may signal stronger exchange interactions, while in the superconducting compositions of FeSe0.9Te0.1 and FeSe0.5Te0.5, they are suppressed. 相似文献
3.
Multimedia Tools and Applications - In this paper, we propose a hybrid fog and cloud-aware heuristic for the dynamic scheduling of multiple real-time Internet of Things (IoT) workflows in a... 相似文献
4.
Jing Luo Lisandra Arroyo‐Ramírez Raymond J. Gorte Despina Tzoulaki Dionisios G. Vlachos 《American Institute of Chemical Engineers》2015,61(2):590-597
The three‐phase hydrodeoxygenation reaction of 5‐hydroxymethylfurfural (HMF) with H2 was studied over a 10 wt % Pt/C catalyst using both batch and flow reactors, with ethanol, 1‐propanol, and toluene solvents. The reaction is shown to be sequential, with HMF reacting first to furfuryl ethers and other partially hydrogenated products. These intermediate products then form dimethyl furan (DMF), which in turn reacts further to undesired products. Furfuryl ethers were found to react to DMF much faster than HMF, explaining the higher reactivity of HMF when alcohol solvents were used. With the optimal residence time, it was possible to achieve yields approaching 70% in the flow reactor with the Pt/C catalyst. Much higher selectivities and yields were obtained in the flow reactor than in the batch reactor because side products are formed sequentially, rather than in parallel, demonstrating the importance of choosing the correct type of reactor in catalyst screening. © 2014 American Institute of Chemical Engineers AIChE J, 61: 590–597, 2015 相似文献
5.
Despina Louca S. J. Poon G. J. Shiflet 《Metallurgical and Materials Transactions A》2013,44(5):1990-1993
Using neutron diffraction and the pair density function analysis, the effect of Sc alloying for Y on the local atomic structure of Y56-x Al24Ni10Co10 was investigated. The replacement of Y with Sc significantly changes the local atomic structure of amorphous Y56-x Al24Ni10Co10 as it promotes the formation of nanocrystalline particles. By comparing the structure function in reciprocal space of three alloys with x = 0, 0.1, and 0.2 (in atomic percent), small Bragg peaks are observed that increase in intensity proportionate with the amount of Sc. In real space, the substitution of Sc for Y leads to a drastic structural contraction most likely resulting from efficient cluster packing. 相似文献
6.
Alexandros Kaliontzoglou Pelagia Boutsi Despina Polemi 《Electronic Commerce Research》2006,6(3-4):337-353
Electronic Invoicing services (e-Invoicing) will have a pivotal role in all the stages of handling Value Added Tax (VAT) for
European Member States. Through a systematic introduction of e-invoicing, tax administrators will be able to implement new
tools and procedures to carry out alternative controls that are less intrusive on the trading partners. Nevertheless, successful
European e-invoicing implementations need to be in compliance with the corresponding European Directive 2001/115/EC. Most
contemporary e-Invoicing implementations are proprietary and based on EDI, thus demonstrating great deficiencies. This paper
presents an open electronic invoicing system named eInvoke, based on XML, XML cryptography and Web Services, that addresses
all security requirements imposed by the Directive.
Our e-Invoicing system has been accepted by “CEN/ISSS e-Invoicing Focus Group on Standards and Developments on electronic
invoicing relating to VAT Directive 2001/115/EC” and its summary appears in CEN 2003 report [13] (pg 79–85), forwarded to
EC as a recommendation.
Alexandros Kaliontzoglou holds a Degree in Electrical and Computer Engineering from the National Technical University of Athens (NTUA), Greece. Since
2001 he is a PhD candidate in the area of Network and Information Systems Security at the Telecommunications laboratory in
the School of Electrical and Computer Engineering of NTUA. Since April 2000 he has been working for Expertnet S.A. as a security
engineer specializing at Web Technologies and network applications, and he has been active both in European research projects
in the 5th and 6th Framework Programme (eMayor, Intelcities, SELIS, Reshen, La Mer, TSEC, WebSig) and projects of the Greek
private sector. His research interests focus in the area of IT Security, Service Oriented Architectures, Web Services, Software
Engineering, e-Government, e-Commerce and Public Key Infrastructures.
Pelagia Boutsi has obtained the Degree in Informatics from the University of Piraeus, Greece, in November 2001. Since April 2002, she is
a PhD candidate in the area of Security Information at the Computer Science Department of University of Piraeus. Since September
2001 she is employed at Expertnet S.A. as member of the Technical Department. Her current research interests are in the fields
of PKIs, XML and XML Security. She has participated in European research projects and projects of the private sector.
Despina Polemi has obtained the Degree in Applied Mathematics from Portland State University(USA) in 1984, Ph.D. in Applied Mathematics
(Coding Theory) from City University of New York (Graduate Center) in 1991. She held teaching positions (1984– 1995) in Queens
College and Baruch College of City University of NewYork. From 1991 to 1996 was assistant professor (tenure track) in State
University of New Yorkat Farmingdale in the department of Mathematics. During 1996–2002 she was an associate researcher in
ICCS. From 2000 to 2003 she acted as President of the BoD in a security consulting company Expertnet (www.expertnet.net.gr)
and technical manager of the company from 2000–2004. She nowa Professor in the University of Piraeus R&D department. Her current
research interests are in the fields of cryptology, security and e-business. She has over ninety publications in the above
areas. She has received many research grants from various organizations such as the Danish Research Foundation, MSI Army Research
Office/Cornell University, IEEE, State University of New York (SUNY), and The Graduate School of City University of New York
(CUNY). She has been project manager (PM)/technical manger (TM) in security projects of various programmes such as National
Security Agency (NSA), Dr. Nuala McGann Drescher Foundation, Greek Ministry of Defense, INFOSEC TELEMATICS for Administrations
(COSACC), the Fifth Framework IST Programme (HARP, BEE, SEED, WebSig, TSEC, CORAS, RESHEN, SEED, La Mer, SECRETS) and the
6FP (e-Mayor, Intelcities, BIOSEC, SELIS). She participated in the EC security projects of the programs COST, ACTS, and NATOs’
security projects. She is a member of IEEE. She serves as an evaluator, reviewer and expert in the European Commission and
consultant for the FP6. 相似文献
7.
Lattice polarons play an important role in the mechanism of colossal magnetoresistance in the (La/Sr)
n+1Mn
n
O3n+1 manganites. Local lattice distortions were characterized by the pulsed neutron pair density function (PDF) analysis. The result shows that the doped holes form polarons related to the Jahn–Teller (JT) effect, both in the two-dimensional layered crystals (n=2) and in the perovskites (n=). The temperature effects are also similar in both systems suggesting that lattice polarons are largely independent of the crystal symmetry. 相似文献
8.
T. Egami Despina Louca R. J. McQueeney 《Journal of Superconductivity and Novel Magnetism》1997,10(4):323-327
Local lattice distortions suggesting nonuniform charge distributions were found to be a common feature of manganites and cuprates
in the metallic state by neutron scattering studies. The atomic pair-density function (PDF) determined by pulsed neutron powder
diffraction showed that in La1-xSrxMnO3 doped holes form lattice polarons which persist even in the metallic state. In La1.85Sr0.15CuO4 the energy width of the LO phonons around (π,0) determined by inelastic neutron scattering reflects magnetic satellites indicative
of spin charge stripe formation. The implications of such nonuniform charge distribution for metal-insulator transition and
superconductivity are discussed. 相似文献
9.
Effects of Monoterpenoids, Acting Alone or in Pairs, on Seed Germination and Subsequent Seedling Growth 总被引:1,自引:0,他引:1
We compared the potential allelopathic activity of 47 monoterpe- noids of different chemical groups, by estimating their effect on seed germination and subsequent growth of Lactuca sativa seedlings. Apart from individual compounds, eleven pairs at different proportions were also tested. As a group, the hydrocarbons, except for (+)-3-carene, were the least inhibitory. Of the oxygenated compounds, the least inhibitory were the acetates; whenever the free hydroxyl group of an alcohol turned into a carboxyl group, the activity of the resulting ester was markedly lower (against both germination and seedling growth). Twenty-four compounds were extremely active against seedling growth (inhibiting it by more than 85%), but only five against seed germination. The compounds that were most active against both processes belonged to the groups of ketones and alcohols; they were terpinen-4-ol, dihydrocarvone, and two carvone stereoisomers. We used a model to investigate whether compounds acted independently when applied in pairs. The combined effect varied. In half of the cases, it followed the pattern expected under the assumption of independence; in the rest, either synergistic or antagonistic interactions were found in both germination and elongation. However, even in cases of synergistic interactions, the level of inhibition was not comparable to that of a single extremely active compound, unless such a compound already participated in the combination. The specific structural factors that operate and determine the activity of monoterpenoids still remain rather obscure. The same holds true for the combined effect; its character cannot in general be predicted on the basis of individual compounds acting alone. 相似文献
10.
Vasileios Megalooikonomou Despina Kontos Dragoljub Pokrajac Aleksandar Lazarevic Zoran Obradovic 《Journal of Intelligent Information Systems》2008,31(3):217-242
Mining discriminative spatial patterns in image data is an emerging subject of interest in medical imaging, meteorology, engineering,
biology, and other fields. In this paper, we propose a novel approach for detecting spatial regions that are highly discriminative
among different classes of three dimensional (3D) image data. The main idea of our approach is to treat the initial 3D image
as a hyper-rectangle and search for discriminative regions by adaptively partitioning the space into progressively smaller
hyper-rectangles (sub-regions). We use statistical information about each hyper-rectangle to guide the selectivity of the
partitioning. A hyper-rectangle is partitioned only if its attribute cannot adequately discriminate among the distinct labeled
classes, and it is sufficiently large for further splitting. To evaluate the discriminative power of the attributes corresponding
to the detected regions, we performed classification experiments on artificial and real datasets. Our results show that the
proposed method outperforms major competitors, achieving 30% and 15% better classification accuracy on synthetic and real
data respectively while reducing by two orders of magnitude the number of statistical tests required by voxel-based approaches. 相似文献