35,744 research outputs found

    Localized mirror functor for Lagrangian immersions, and homological mirror symmetry for P 1 a,b,c

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    This paper gives a new way of constructing Landau–Ginzburg mirrors usingdeformation theory of Lagrangian immersions motivated by the works of Seidel,Strominger –Yau–Zaslow and Fukaya–Oh–Ohta–Ono. Moreover, we construct acanonical functor from the Fukaya category to the mirror category of matrixfactorizations. This functor derives homological mirror symmetry under someexplicit assumptions.As an application, the construction is applied to spheres with three orbifoldpoints to produce their quantum-corrected mirrors and derive homological mirrorsymmetry. Furthermore, we discover an enumerative meaning of the (inverse)mirror map for elliptic curve quotients

    A simple image intensifying system for Berg-Barrett topography

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    A simple imaging system to facilitate crystal orientation with respect to the x−ray beam for Berg−Barrett topography has been constructed. This system consists of an image intensifier tube with an x−ray phosphor deposited on its fiber−optic input plate and means to manipulate and indicate the crystal orientation. Applications of the system to studies of both crystalline and biological samples are given

    Thermal analysis of Malaysian double storey housing - low/medium cost unit

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    Almost half of the total energy used today is consumed in buildings. In the tropical climate, air-conditioning a housing unit takes much of the energy bill. Malaysia is no exception. Malaysian double storey terrace housing is popular among developers and buyers. Surveys have shown that housing occupants are much dissatisfied with the thermal comfort and artificial cooling is often sought. The objective of this study is to assess the thermal comfort of the low and medium-cost double storey housing in the area surrounding Universiti Teknologi Malaysia. A simulation program using the Weighting Factor Method calculates the heat transfer interaction, temperature distribution, and PMV level in three types of housing units in relation to the size. Fanger's PMV model based on ISO Standard 7730 is used here because it accounts for all parameters that affect the thermal sensation of a human within its equation. Results showed that both the low and medium-cost housing units studied are out of the comfortable range described by ASHRAE Standard 55 with the units all complied with the local bylaws. In view of the uncertainties in energy supply, future housing units should consider natural ventilation as part of the passive energy management

    Simultaneous space charge and conduction current measurements in solid dielectrics under high dc electric field

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    The importance of space charge in solid dielectrics has been recognized for many years and various attempts have been made to map the distribution and assess its influence on the electrical performance of solid dielectrics. Significant development in non-destructive measurement techniques emerged two decades ago. Crosslinked polyethylene (XLPE) has been used for ac power cable insulation up to 500 kV for many years. There is a tendency to use XLPE for dc power cable. However, the easy formation of space charge under dc electric field within XLPE is a major concern for such an application. Space charge in insulation can distort electric field distribution, causing electric field increase in one region and reduction in another. The electric field enhancement could lead to degradation and result in premature failure. Electrical treeing in solid dielectrics is a typical example of local field enhancement due to space charge accumulation. In this report several popular non-destructive techniques are briefly reviewed. This is followed by detailed description of a modified pulsed electroacoustic (PEA) technique that allows simultaneous measurement of space charge and conduction current in a solid dielectric subjected to high dc electric fields. Finally, we report the relationship between space charge dynamics and electrical conduction current in XLPE using the modified PEA system. The effect of electrode material on both charge dynamics and current has been investigated using semiconducting material and aluminium. It has been found charge dynamics in the material depend on electrode configuration. More importantly, it has been noticed that the so called space charge limited transient current peaks are closely related to the meetings of negative and positive charge front in the bulk of the sample

    Semantic keyword search for expert witness discovery

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    In the last few years, there has been an increase in the amount of information stored in semantically enriched knowledge bases, represented in RDF format. These improve the accuracy of search results when the queries are semantically formal. However framing such queries is inappropriate for inexperience users because they require specialist knowledge of ontology and syntax. In this paper, we explore an approach that automates the process of converting a conventional keyword search into a semantically formal query in order to find an expert on a semantically enriched knowledge base. A case study on expert witness discovery for the resolution of a legal dispute is chosen as the domain of interest and a system named SKengine is implemented to illustrate the approach. As well as providing an easy user interface, our experiment shows that SKengine can retrieve expert witness information with higher precision and higher recall, compared with the other system, with the same interface, implemented by a vector model approach

    Semantic keyword search for expert witness discovery

    Get PDF
    In the last few years, there has been an increase in the amount of information stored in semantically enriched knowledge bases, represented in RDF format. These improve the accuracy of search results when the queries are semantically formal. However framing such queries is inappropriate for inexperience users because they require specialist knowledge of ontology and syntax. In this paper, we explore an approach that automates the process of converting a conventional keyword search into a semantically formal query in order to find an expert on a semantically enriched knowledge base. A case study on expert witness discovery for the resolution of a legal dispute is chosen as the domain of interest and a system named SKengine is implemented to illustrate the approach. As well as providing an easy user interface, our experiment shows that SKengine can retrieve expert witness information with higher precision and higher recall, compared with the other system, with the same interface, implemented by a vector model approach

    Radioactive silicon as a marker in thin-film silicide formation

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    A new technique using radioactive 31Si (half-life =2.62 h), formed in a nuclear reactor, as a marker for studying silicide formation is described. A few hundred angstroms of radioactive silicon is first deposited onto the silicon substrate, followed immediately by the deposition of a few thousand angstroms of the metal. When the sample is heated, a silicide is first formed with the radioactive silicon. Upon further silicide formation, this band of radioactive silicide can move to the surface of the sample if silicide formation takes place by diffusion of the metal or by silicon substitutional and/or vacancy diffusion. However, if the band of radioactive silicide stays at the silicon substrate interface it can be concluded that silicon diffuses by interstitial and/or grain-boundary diffusion. This technique was tested by studying the formation of Ni2Si on silicon at 330 °C. From a combination of ion-beam sputtering, radioactivity measurement, and Rutherford backscattering it is found that the band of radioactive silicide moves to the surface of the sample during silicide formation. From these results, implanted noble-gas marker studies and the rate dependence of Ni2Si growth on grain size, it is concluded that nickel is the dominant diffusing species during Ni2Si formation, and that it moves by grain-boundary diffusion

    Dissociation mechanism for solid-phase epitaxy of silicon in the Si <100>/Pd2Si/Si (amorphous) system

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    Solid-phase epitaxial growth (SPEG) of silicon was investigated by a tracer technique using radioactive 31Si formed by neutron activation in a nuclear reactor. After depositing Pd and Si onto activated single-crystal silicon substrates, Pd2Si was formed with about equal amounts of radioactive and nonradioactive Si during heating at 400 °C for 5 min. After an 1-sec annealing stage (450-->500 °C in 1 h) this silicide layer, which moves to the top of the sample during SPEG, is etched off with aqua regia. From the absence of radioactive 31Si in the etch, it is concluded that SPEG takes place by a dissociation mechanism rather than by diffusion

    Ti and V layers retard interaction between Al films and polycrystalline Si

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    Fine-grained polycrystalline Si (poly Si) in contact with Al films recrystallizes at temperatures well below the Si-Al eutectic (577 °C). We show that this interaction can be deferred or suppressed by placing a buffer layer of Ti or V between the Al film and the poly Si. During annealing, Ti or V form TiAl3 or Val3 at the buffer-layer–Al-film interface, but do not react with the poly Si so that the integrity of the poly Si is preserved as long as some unreacted Ti or V remains. The reaction between the Ti or V layer and the Al film is transport limited ([proportional]t^1/2) and characterized by the diffusion constants 1.5×10^15 exp(–1.8eV/kT) Å^2/sec or 8.4×10^12 exp(–1.7eV/kT) Å^2/sec, respectively
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