Precast Concrete Deck-to-Girder Connection using UHPC

The implementation of ultra-high-performance concrete (UHPC) in bridge construction has been growing rapidly in the last two decades due to its excellent mechanical properties, workability, and durability. This report presents a new UHPC connection between precast concrete deck panels and bridge girders that eliminates changes to the design and production of girder shear connectors commonly used in conventional cast-in-place concrete deck construction. In conventional construction, girder shear reinforcement or studs are extended into the cast-in-place concrete deck to transfer interface shear and create composite section. In the new connection, girder shear reinforcement or studs are kept underneath the deck panels, while UHPC is used instead to fill the haunch and shear pockets and transfer interface shear between deck panels and girders. Using UHPC and eliminating changes to standard shear connectors make precast concrete deck systems more economical and enhance their constructability. The report presents the experimental investigation conducted to evaluate the interface shear resistance of UHPC using direct shear, slant shear, L-shape push-off, and double shear tests. Also, three full-scale specimens of the new connection were constructed and tested to evaluate its structural performance and constructability. Based on the experimental investigation results, empirical equations were developed to predict the interface shear resistance of the new connection and develop design aids for different bridge types and configurations. Design procedures and construction recommendations were also developed based on the outcomes of the experimental investigation

A Process for Producing Ice Coverage Marine Information Objects (MIOs) in IHO S-57 Format

While global warming may be opening up more Arctic waters in the summer, ice still infests key shipping lanes in the northern hemisphere during the winter months. To safely navigate these areas, mariners rely on daily ice coverage charts produced by national governmental agencies. Ice charts are primarily issued in paper format or as a fax. However, there is increased interest to ice coverage information on vessel navigation systems such as an Electronic Chart and Display Information Systems (ECDIS). However, to do so, the ice information must be provided as a separate layer of information to the Electronic Navigational Chart (ENC)

Breaking the Buildup-time Limit of sensitivity in Avalanche Photodiodes by Dynamic Biasing

Avalanche photodiodes (APDs) are the preferred photodetectors for direct-detection, high data-rate long-haul optical telecommunications. APDs can detect low-level optical signals due to their internal amplification of the photon-generated electrical current, which is attributable to the avalanche of electron and hole impact ionizations. Despite recent advances in APDs aimed at reducing the average avalanche-buildup time, which causes intersymbol interference and compromises receiver sensitivity at high data rates, operable speeds of commercially available APDs have been limited to 10Gbps. We report the first demonstration of a dynamically biased APD that breaks the traditional sensitivity-versus-speed limit by employing a data-synchronous sinusoidal reverse-bias that drastically suppresses the average avalanche-buildup time. Compared with traditional DC biasing, the sensitivity of germanium APDs at 3Gbps is improved by 4.3 dB, which is equivalent to a 3,500-fold reduction in the bit-error rate. The method is APD-type agnostic and it promises to enable operation at rates of 25Gbps and beyond

Incoherent lensless imaging via coherency back-propagation

The two-point complex coherence function constitutes a complete representation for scalar quasi-monochromatic optical fields. Exploiting dynamically reconfigurable slits implemented with a digital micromirror device, we report on measurements of the complex two-point coherence function for partially coherent light scattering from a `scene' comprising one or two objects at different transverse and axial positions with respect to the source. Although the intensity shows no discernible shadows in absence of a lens, numerically back-propagating the measured complex coherence function allows estimating the objects' sizes and locations -- and thus the reconstruction of the scene.Comment: 4 pages, 4 figure

Pseudoscalar mesons with symmetric bound state vertex functions on the light front

We study the electromagnetic form factors, decay constants and charge radii of the pion and kaon within the framework of light-front field theory formalism where we use an ansatz for the quark-meson interaction bound-state function which is symmetric under exchange of quark and antiquark momentum. The above mentioned observables are evaluated for the $+$ component of the electromagnetic current, $J^+$, in the Breit frame. We also check the invariance of these observables in other frames, whereby both the valance and the non-valence contributions have to be taken into account, and study the sensitivity of the electromagnetic form factors and charge radius to the model's parameters; namely, the quark masses, $m_u=m_d$, $m_{\bar s}$, and the regulator mass, $m_R$. It is found that after a fine tuning of the regulator mass, i.e. $m_R=0.6$ GeV, the model is suitable to fit the available experimental data within the theoretical uncertainties of both the pion and kaon.Comment: 8 pages, 8 figures, use revtex, submitted to Phy. Rev. D (2015

Metadata and Cataloging Practices

Metadata standards existing today range from very complex to very simple. Relative simplicity or complexity of metadata standards depends in large part on the resources for which they were created and the depth of description that is deemed necessary to make these resources accessible. This paper reviews the differences between metadata standards and current cataloging practices, and discusses how the various metadata standards are applied in libraries. In addressing these issues, the authors introduce definitions of key concepts of metadata and cataloging standards and provide an overview of the most common metadata schemes. The discussion of current cataloging practices includes an overview of the most commonly used cataloging practices and standards, the impact of metadata on library practice and the role of librarians related to metadata. The authors will discuss the OHIOLINK Electronic Thesis and Dissertations (ETD) as an example of how Anglo-American Cataloging Rules 2nd (AACR2) and Machine Readable Cataloging (MARC21) are used as metadata to store, describe and access this unique information resource

Changes in Technical Services and Their Effect on the Role of Catalogers and Staff Education: An Overview

Summary: Though all library operations are affected by the development of technology, technical services operations are the first to undergo massive organizational restructuring in response. Some current changes and their effects on library cataloging departments are addressed. Two cataloging options are discussed. One is the use of vendor services, such as OCLC's Contract Cataloging, Prompt-Cat, and OCLC Selection. The other is the use of non-traditional staff. The impact of such changes on the role of librarians and on staff education is considered

Experimental and theoretical study of benzene (acetonitrile)(n) clusters, n=1-4

Well-resolved spectra of benzene–acetonitrile binary clustersBAn, with n=1–4 have been obtained by the (one-color) resonant two-photonionization technique using the benzene’s B2u←A1g 000 and 610 resonances. The spectra reveal a rapid increase in complexity with the number of acetonitrile molecules in the cluster, associated with van der Waal modes and isomeric forms. While only single cluster origins are found for the benzene–acetonitrile (BA) and the BA2clusters, two and four distinct isomers are identified for the BA3 and BA4clusters, respectively. The origins of the BA and BA2clusters are blueshifted with respect to the free benzene molecule by 38 cm−1 and 26 cm−1, respectively. Monte Carlo(MC) simulations reveal two types of isomeric structures of the BAnclusters. The clusters containing an even number of the acetonitrile molecules (BA2, BA4, and BA6) are dominated by acetonitrile anti-parallel paired dimers. The BA3cluster consists of a cyclic acetonitrile trimer parallel to the benzene ring. In the BA5clusters, the acetonitrile molecules are assembled in a cyclic trimer + a paired dimer configuration or in two paired dimers + a single monomer structure. The R2PI spectra, in conjunction with the MC structural models and simple energetic arguments, provide a reasonably compelling picture of the spectroscopic and dynamical phenomena associated with dipole pairing molecular cluster systems