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41.
This study aims at proving the validity of a notion that the formation of non-expansive near-surface layer is responsible for surface cracking in ASR-affected concretes by a laboratory experiment. Relationship between the progress rate of the front of non-expansive layer toward inner portions and the formation of the first surface cracks was scrutinized by measuring relative humidity (R.H.) values and strains within a massive concrete cylinder (?450 mm × 900 mm) with reactive aggregates under a dry environment. It was presumed from the measurements that a non-expansive layer of about 40 mm had been formed at the first cracking. Thereafter, the environmental humidity was raised to > 95% R.H. Pursuit of the growth of surface cracks and subsequent measurements of strains and R.H. values within the concrete cylinder under the moist environment suggested that the re-saturation continuously gave rise to the generation of tensile stresses in near-surface regions leading to active extension of surface cracks. 相似文献
42.
Downsizing noble metal nanoparticles,such as Pt,is an essential goal for many catalytic reactions.A non-noble metal sacrificial approach was used to immobilize monodispersed Pt nanoparticles (NPs) with a mean size of 1.2 nm on reduced graphene oxide (RGO).ZnO co-precipitated with Pt NPs and subsequently sacrificed by acid etching impedes the diffusion of Pt atoms onto the primary Pt particles and also their aggregation during the reduction of precursors.The resulting ultrafine Pt nanoparticles exhibit high activity (a turnover frequency of 284 min-1 at 298 K) in the hydrolytic dehydrogenation of ammonia borane.The non-noble metal sacrificial approach is demonstrated as a general approach to synthesize well-dispersed noble metal NPs for catalysis. 相似文献
43.
Parallel Algorithms for Discovery of Association Rules 总被引:2,自引:0,他引:2
Mohammed J. Zaki Srinivasan Parthasarathy Mitsunori Ogihara Wei Li 《Data mining and knowledge discovery》1997,1(4):343-373
Discovery of association rules is an important data mining task. Several parallel and sequential algorithms have been proposed
in the literature to solve this problem. Almost all of these algorithms make repeated passes over the database to determine
the set of frequent itemsets (a subset of database items), thus incurring high I/O overhead. In the parallel case, most algorithms
perform a sum-reduction at the end of each pass to construct the global counts, also incurring high synchronization cost.
In this paper we describe new parallel association mining algorithms. The algorithms use novel itemset clustering techniques
to approximate the set of potentially maximal frequent itemsets. Once this set has been identified, the algorithms make use
of efficient traversal techniques to generate the frequent itemsets contained in each cluster. We propose two clustering schemes
based on equivalence classes and maximal hypergraph cliques, and study two lattice traversal techniques based on bottom-up
and hybrid search. We use a vertical database layout to cluster related transactions together. The database is also selectively
replicated so that the portion of the database needed for the computation of associations is local to each processor. After
the initial set-up phase, the algorithms do not need any further communication or synchronization. The algorithms minimize
I/O overheads by scanning the local database portion only twice. Once in the set-up phase, and once when processing the itemset
clusters. Unlike previous parallel approaches, the algorithms use simple intersection operations to compute frequent itemsets
and do not have to maintain or search complex hash structures.
Our experimental testbed is a 32-processor DEC Alpha cluster inter-connected by the Memory Channel network. We present results
on the performance of our algorithms on various databases, and compare it against a well known parallel algorithm. The best
new algorithm outperforms it by an order of magnitude. 相似文献
44.
The addition of silica fume in concrete causes a remarkable increase in strength and a drastic reduction in chloride ion permeability. These effects may be due primarily to microstructural changes both in the cement paste phase and in the interfacial zone around aggregates. The standard method of test for rapid determination of the chloride permeability of concrete, AASHTO T 277–831, has increasingly been used to evaluate the permeability of concrete. However, for the concrete containing silica fume, the results of the AASHTO T 277–831 test, which is expressed in terms of electrical charge passed, do not necessarily reflect the real diffusion index of chloride ion through the concrete. There seems to be factors other than the pore structure which govern the results of the AASHTO T 277–831 test in the concrete containing silica fume. In this study, the effects of silica fume to reduce the chloride ion permeability of the mortar were investigated based on the results of pore size distribution measurements, X-ray diffraction analysis, SEM observations and pore solution extraction. The application of the AASHTO T 277–831 test to the evaluation of the chloride ion permeability of the concrete containing silica fume was discussed. 相似文献
45.
Sakai T Hitomi T Sugaya K Kai S Murayama M Maitani T 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2007,48(5):144-147
Simple and reliable methods using LC/MS have been developed for the determination of the beta-agonist ractopamine in swine and cattle tissues. Ractopamine was extracted with ethyl acetate from muscle and liver, and the ethyl acetate layer was evaporated to dryness. The residue was purified by partition with acetonitrile/n-hexane. In the case of fat, ractopamine was extracted and purified by partition with acetonitrile/n-hexane. The resulting acetonitrile solutions were evaporated to dryness. The residue was dissolved in methanol, and subjected to LC/MS. The LC separation was performed on a Wakosil-II 3C18HG column (150 x 3 mm i.d.) in isocratic mode with 0.05% trifluoroacetic acid-acetonitrile (80:20) as a mobile phase at a flow rate of 0.4 mL/min. The MS detection was performed in the selected ion recording (SIR) mode, with detection of the M + H+ ion of ractopamine (m/z 302) produced by electrospray ionization (ESI). The mean recoveries of the drug from swine muscle (0.01 microg fortified), fat (0.01 microg fortified) and liver (0.04 microg/g fortified) were 99.7%, 99.5% and 100.8%, and those from cattle samples were 108.3%, 97.0% and 109.4%, respectively. The relative standard deviations (RSDs) ranged from 0.1% to 9.5%. The limit of quantification (LOQ) of the drug was 1 ng/g. 相似文献
46.
Mitsunori Denda 《中国工程学刊》2013,36(6):677-693
Abstract This study investigates the feasibility of enhancing steam‐driven ejector performance. Initially, a one‐dimensional ejector theory is used to examine the effects on ejector performance of three isentropic efficiencies: nozzle efficiency ηm , mixing efficiency ηm, and diffuser efficiency ηm . Theoretical analysis demonstrates that mixing efficiency profoundly affects ejector performance, but that the other two efficiencies have slightly influenced ejector performance. This finding suggests that efficient mixing can promote ejector performance. This study also attempts to improve mixing efficiency using a petal nozzle. The behavior and characteristics of a petal nozzle are investigated by testing the nozzle under various operating conditions, i.e. primary pressure, secondary pressure, and back pressure. In addition, the study compares the experimental and theoretical results. These results prove that using a petal nozzle can improve ejector performance. The shadowgraph method was used to visualize the inner flow field of an ejector. The flow patterns observed should help to further improve ejector performance. 相似文献
47.
Takuya Oda Mitsunori Hieda Ryo Toda Taku Matsushita Nobuo Wada 《Journal of Low Temperature Physics》2010,158(1-2):262-267
The two-dimensional (2D) 4He fluid films show the Kosterlitz-Thouless (KT) transition where pairing and unpairing of the 2D vortices play an important role. However, the vortex properties (the diffusion constant D, the core diameter a 0) have not been precisely obtained for various conditions. Here, we accurately determined the parameter D/a 0 2 by the high frequency dependence of the superfluid onset up to 180 MHz for the submonolayer 4He fluid films adsorbed on gold and H2 (3.3 layers) preplated on gold, respectively. The superfluid onset coverage changes from 1.6 (gold) to 0.5 layers (H2), which clearly indicates the large difference of the adsorption potential. The parameter D/a 0 2 , on the other hand, has the same value for the coverages with the same KT temperature T KT. This suggests that the vortex diffusions on both substrates have the largest value D~?/m in the quantum limit. The core diameter a 0 was estimated to be the same magnitude as the de Broglie wavelength at T KT between 0.1 and 0.9 K. 相似文献
48.
49.
Yakata M Kuramitsu R Kai S Kudo H Yamoto R Matsuo S 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2012,53(1):45-51
An analytical method of ethephon in feeds by GC-FPD was developed. Ethephon was extracted with ethyl acetate-hydrochloric acid (100 : 1) from feed samples. The extract was treated with added trimethylsilyldiazomethane in acetone-acetic acid (99 : 1) and this methylation procedure was repeated three times. Methylated ethephon was cleaned up on a graphitized carbon mini-column and a silicagel mini-column, and determined by GC-FPD. A method performance study in 7 laboratories was conducted with three kinds of samples spiked with ethephon at 10 mg/kg, 1 mg/kg and 0.5 mg/kg. The recovery of ethephon ranged from 81.8% to 90.8% (the reproducibility standard deviation (RSDr) were within 11%) and HorRat values were 0.58 to 0.94. The limit of detection (S/N≧3) and the limit of quantitation (S/N≧10) of ethephon in samples except hay were 0.02 mg/kg and 0.05 mg/kg, respectively. In the case of hay, the corresponding values were 0.2 mg/kg and 0.5 mg/kg, respectively. 相似文献
50.
This paper presents a solution method for the reliability optimization problem of series-parallel systems which is formulated as a mixed integer nonlinear programming problem with multiple constraints. In the solution method, the optimal solution is obtained by solving the surrogate dual problem. Surrogate problems with only one constraint which appear in the optimization process are solved by a technique using dynamic programming. Some computational experiences are shown along with the comparison with an existing approach. 相似文献