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101.
Semantics preserving SPARQL-to-SQL translation 总被引:2,自引:0,他引:2
Most existing RDF stores, which serve as metadata repositories on the Semantic Web, use an RDBMS as a backend to manage RDF data. This motivates us to study the problem of translating SPARQL queries into equivalent SQL queries, which further can be optimized and evaluated by the relational query engine and their results can be returned as SPARQL query solutions. The main contributions of our research are: (i) We formalize a relational algebra based semantics of SPARQL, which bridges the gap between SPARQL and SQL query languages, and prove that our semantics is equivalent to the mapping-based semantics of SPARQL; (ii) Based on this semantics, we propose the first provably semantics preserving SPARQL-to-SQL translation for SPARQL triple patterns, basic graph patterns, optional graph patterns, alternative graph patterns, and value constraints; (iii) Our translation algorithm is generic and can be directly applied to existing RDBMS-based RDF stores; and (iv) We outline a number of simplifications for the SPARQL-to-SQL translation to generate simpler and more efficient SQL queries and extend our defined semantics and translation to support the bag semantics of a SPARQL query solution. The experimental study showed that our proposed generic translation can serve as a good alternative to existing schema dependent translations in terms of efficient query evaluation and/or ensured query result correctness. 相似文献
102.
We present a time
algorithm finding a minimum feedback vertex set in an undirected graph on n vertices. We also prove that a graph on n vertices can contain at most 1.8638
n
minimal feedback vertex sets and that there exist graphs having 105
n/10≈1.5926
n
minimal feedback vertex sets.
Preliminary extended abstracts of this paper appeared in the proceedings of SWAT’06 [29] and IWPEC’06 [18].
Additional support of F.V. Fomin, S. Gaspers and A.V. Pyatkin by the Research Council of Norway.
The work of A.V. Pyatkin was partially supported by grants of the Russian Foundation for Basic Research (project code 05-01-00395),
INTAS (project code 04–77–7173).
I. Razgon is supported by Science Foundation Ireland (Grant Number 05/IN/I886). 相似文献
103.
Mahabub A. Bhuiyan Zakhar R. Kudrynskyi Debarati Mazumder Jake D. G. Greener Oleg Makarovsky Christopher J. Mellor Evgeny E. Vdovin Benjamin A. Piot Inna I. Lobanova Zakhar D. Kovalyuk Marina Nazarova Artem Mishchenko Kostya S. Novoselov Yang Cao Laurence Eaves Go Yusa Amalia Patan 《Advanced functional materials》2019,29(3)
The transfer of electronic charge across the interface of two van der Waals crystals can underpin the operation of a new class of functional devices. Among van der Waals semiconductors, an exciting and rapidly growing development involves the “post‐transition” metal chalcogenide InSe. Here, field effect phototransistors are reported where single layer graphene is capped with n‐type InSe. These device structures combine the photosensitivity of InSe with the unique electrical properties of graphene. It is shown that the light‐induced transfer of charge between InSe and graphene offers an effective method to increase or decrease the carrier density in graphene, causing a change in its resistance that is gate‐controllable and only weakly dependent on temperature. The charge transfer at the InSe/graphene interface is probed by Hall effect and photoconductivity measurmentes and it is demonstrated that light can induce a sign reversal of the quantum Hall voltage and photovoltaic effects in the graphene layer. These findings demonstrate the potential of light‐induced charge transfer in gate‐tunable InSe/graphene phototransistors for optoelectronics and quantum metrology. 相似文献
104.
105.
Alexey Y. Zhizhchenko Pavel Tonkaev Dmitry Gets Artem Larin Dmitry Zuev Sergey Starikov Eugeny V. Pustovalov Alexander M. Zakharenko Sergei A. Kulinich Saulius Juodkazis Aleksandr A. Kuchmizhak Sergey V. Makarov 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(19)
Nanophotonics based on resonant nanostructures and metasurfaces made of halide perovskites have become a prospective direction for efficient light manipulation at the subwavelength scale in advanced photonic designs. One of the main challenges in this field is the lack of large‐scale low‐cost technique for subwavelength perovskite structures fabrication preserving highly efficient luminescence. Here, unique properties of halide perovskites addressed to their extremely low thermal conductivity (lower than that of silica glass) and high defect tolerance to apply projection femtosecond laser lithography for nanofabrication with precise spatial control in all three dimensions preserving the material luminescence efficiency are employed. Namely, with CH3NH3PbI3 perovskite highly ordered nanoholes and nanostripes of width as small as 250 nm, metasurfaces with periods less than 400 nm, and nanowire lasers as thin as 500 nm, corresponding to the state‐of‐the‐art in multistage expensive lithographical methods are created. Remarkable performance of the developed approach allows to demonstrate a number of advanced optical applications, including morphology‐controlled photoluminescence yield, structural coloring, optical‐ information encryption, and lasing. 相似文献
106.
Pavlo Sergienko Victor Kazmirenko Artem Chernov Yuriy Prokopenko 《Radioelectronics and Communications Systems》2016,59(2):89-95
The paper presents research of quality factor in the micro-mechanically tunable microstrip resonator and its change in response to tuning. In the presented design unloaded quality factor increases about 10% during tuning due to reduction of dielectric loss in substrate’s medium and ohmic loss in metal electrodes. When total loss in the device is relatively small, loss mechanisms contribute additively, so complex effective permittivity can be used to account loss reduction and frequency tuning. 相似文献
107.
Nadezhda Nikolaeva Tatyana Aleksandrova Artem Romashev 《Mineral Processing and Extractive Metallurgy Review》2018,39(4):231-234
The effects of size reduction on oil shales from the Yaregskoye oil field were conducted. These shales are characterized by lamination and by high degree of schistosity and expressed zones of pyritization and bituminization. The influence of the level of crushing on the distribution and composition functions was studied. Size separation as a method for the preconcentration of this material at the ore preparation stage was substantiated. The results obtained using predictive formulas showed the possibility of obtaining a product with an increased TiO2 content at the ore preparation stage and a reduced amount of material requiring processing. 相似文献
108.
V. G. Shcherbinskii S. A. Artem’ev N. M. Antonova K. V. Panferov A. Yu. Grachev A. P. Kopylov A. F. Zakharov S. A. Miroshin 《Russian Journal of Nondestructive Testing》2014,50(5):249-253
A new generation of devices for ultrasonic checking of flats for metallurgical works has been developed. The new ЛИСТ-4 mobile device from the Central Research Institute of Mechanical Engineering (CNIITMASH) reveals discontinuity flaws according to GOST (State Standard) 22727-88, GOST 28831-90, and foreign standards. 相似文献
109.
110.
Larisa I. Privalova Boris A. Katsnelson Nadezhda V. Loginova Vladimir B. Gurvich Vladimir Y. Shur Irene E. Valamina Oleg H. Makeyev Marina P. Sutunkova Ilzira A. Minigalieva Ekaterina P. Kireyeva Vadim O. Rusakov Anastasia E. Tyurnina Roman V. Kozin Ekaterina Y. Meshtcheryakova Artem V. Korotkov Eugene A. Shuman Anastasia E. Zvereva Svetlana V. Kostykova 《International journal of molecular sciences》2014,15(7):12379-12406
In the copper metallurgy workplace air is polluted with condensation aerosols, which a significant fraction of is presented by copper oxide particles <100 nm. In the scientific literature, there is a lack of their in vivo toxicity characterization and virtually no attempts of enhancing organism’s resistance to their impact. A stable suspension of copper oxide particles with mean (±SD) diameter 20 ± 10 nm was prepared by laser ablation of pure copper in water. It was being injected intraperitoneally to rats at a dose of 10 mg/kg (0.5 mg per mL of deionized water) three times a week up to 19 injections. In parallel, another group of rats was so injected with the same suspension against the background of oral administration of a “bio-protective complex” (BPC) comprising pectin, a multivitamin-multimineral preparation, some amino acids and fish oil rich in ω-3 PUFA. After the termination of injections, many functional and biochemical indices for the organism’s status, as well as pathological changes of liver, spleen, kidneys, and brain microscopic structure were evaluated for signs of toxicity. In the same organs we have measured accumulation of copper while their cells were used for performing the Random Amplification of Polymorphic DNA (RAPD) test for DNA fragmentation. The same features were assessed in control rats infected intraperitoneally with water with or without administration of the BPC. The copper oxide nanoparticles proved adversely bio-active in all respects considered in this study, their active in vivo solubilization in biological fluids playing presumably an important role in both toxicokinetics and toxicodynamics. The BPC proposed and tested by us attenuated systemic and target organs toxicity, as well as genotoxicity of this substance. Judging by experimental data obtained in this investigation, occupational exposures to nano-scale copper oxide particles can present a significant health risk while the further search for its management with the help of innocuous bioprotectors seems to be justified. 相似文献