Vortex Diffusivity and Core Diameter of 2D Superfluid in 4He Films on Gold and H2 Substrates

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.     

Gestural cue analysis in automated semantic miscommunication annotation

The automated annotation of conversational video by semantic miscommunication labels is a challenging topic. Although miscommunications are often obvious to the speakers as well as the observers, it is difficult for machines to detect them from the low-level features. We investigate the utility of gestural cues in this paper among various non-verbal features. Compared with gesture recognition tasks in human-computer interaction, this process is difficult due to the lack of understanding on which cues contribute to miscommunications and the implicitness of gestures. Nine simple gestural features are taken from gesture data, and both simple and complex classifiers are constructed using machine learning. The experimental results suggest that there is no single gestural feature that can predict or explain the occurrence of semantic miscommunication in our setting.     

Surrogate Constraints Algorithm for Reliability Optimization Problems with Multiple Constraints

This paper presents a surrogate constraints algorithm for solving nonlinear programming, nonlinear integer programming, and nonlinear mixed integer programming problems. The algorithm contains a new technique for generating a succession of vector values of surrogate multiplier (ie, surrogate problems). By using this technique, a computer can keep a polyhedron, which is a vector space of surrogate multipliers to be considered at a certain time, in its memory. Furthermore it can cut the polyhedron by a given hyperplane, and produce the remaining space as the next polyhedron. Simple examples are included.     

Competition Between the Superfluid Overlayer and the Mobile Solid Layer of 3He-4He Mixture Films on Porous Gold

In the previous quartz crystal microbalance measurements for ⁴He films adsorbed on porous gold, we have observed a competition between superfluidity and slippage: In low areal densities, the resonance frequency increases gradually below T _S due to the slippage of solid layer, while at high areal densities the slippage disappears and the superfluid onset of liquid overlayer is observed at T _C . In the crossover region, the slippage below T _S is suddenly suppressed at T _D , which is much lower than T _C . In the present work, we introduced a small amount of ³He onto ⁴He films, and studied the competition as a function of ³He areal density ρ ₃. As ρ ₃ is increased, T _C is monotonically lowered. In contrast, T _D increases up to a certain value of ρ ₃, and then turns over to decrease in parallel to T _C .     

Monodispersed Pt nanoparticles on reduced graphene oxide by a non-noble metal sacrificial approach for hydrolytic dehydrogenation of ammonia borane

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.     

Pore structure and chloride ion permeability of mortars containing silica fume

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.     

Parallel Algorithms for Discovery of Association Rules

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.     

Relation between formation rates of methane and hydrogen on pyrolysis of coal under pressure

In an earlier paper¹ it became clear that secondary-methane formation occurs under certain experimental conditions during pyrolysis of coal. In order to study this more deeply, the evolution rates of methane and hydrogen were measured simultaneously for an anthracite and a lignite. The secondary-methane formation was accompanied by a corresponding decrease in hydrogen formation. It is suggested that secondary-methane formation occurs according to the equation C + 2H₂ = CH₄ on an average and is proportional to the partial pressure of evolved hydrogen.     

Direct Measurement of Crack Tip Stresses

Raman microprobe spectroscopy was used to measure the crack tip stress distribution in single-crystalline silicon using a wedge-loaded double cantilever beam (dcb) specimen. The wedge was advanced until the crack just propagated. After the crack arrested, the stresses were measured between 3 and 20 μm directly ahead of the crack. An average value of –0.43 was obtained for the slope of log stress vs log distance from the crack tip, rather than the theoretical value of –0.5. The value of K _I was determined from (1) the intercept of this curve and (2) the slope of stress against     . The values were in good agreement. The average experimental value of K _I was determined to be 0.71 MPa · m^1/2, compared to literature values for the K _IC ranging from silicon of 0.8 to 0.94 MPa · m^1/2. The value measured with the Raman is the arrest value of K _I and is expected to be lower from kinetic energy considerations associated with wedge-loaded dcb specimens.