1,722 research outputs found
Bond Strength and Transfer Length of Pre-tensioned Bridge Girders Cast with Self-Consolidating Concrete
Self-consolidating concrete (SCC) is becoming increasingly popular in the precast/prestressed concrete industry in the United States. However, there have been concerns regarding the bond strength, transfer length, and development length of prestressing strands and mild steel reinforcement with SCC. Further, there are no design guidelines for using SCC. In this study, a literature survey on the bond strength of SCC was conducted. Moustafa pullout tests were performed to determine the bond strength of 0.6 in. (15.2 mm) pretensioning strands with sec. The transfer lengths of three pretensioned concrete bridge girders were measured using Demec points. Pullout tests were also performed on 41 specimens using No. 4, No. 6, and No. 8 mild steel reinforcing bars and 0.6 in. prestressing strands. All the tests were performed using specimens cast with both SCC and conventional concrete. Test data have shown that the bond strength of sec with deformed reinforcing bars is adequate. However, the use of viscosity-modifying admixtures in sec may adversely affect its early compressive strength and its bond strength with pretensioning strands
The fluctuation energy balance in non-suspended fluid-mediated particle transport
Here we compare two extreme regimes of non-suspended fluid-mediated particle
transport, transport in light and heavy fluids ("saltation" and "bedload",
respectively), regarding their particle fluctuation energy balance. From direct
numerical simulations, we surprisingly find that the ratio between collisional
and fluid drag dissipation of fluctuation energy is significantly larger in
saltation than in bedload, even though the contribution of interparticle
collisions to transport of momentum and energy is much smaller in saltation due
to the low concentration of particles in the transport layer. We conclude that
the much higher frequency of high-energy particle-bed impacts ("splash") in
saltation is the cause for this counter-intuitive behavior. Moreover, from a
comparison of these simulations to Particle Tracking Velocimetry measurements
which we performed in a wind tunnel under steady transport of fine and coarse
sand, we find that turbulent fluctuations of the flow produce particle
fluctuation energy at an unexpectedly high rate in saltation even under
conditions for which the effects of turbulence are usually believed to be
small
Sense of place in the changing process of house form: Case studies from Ankara, Turkey
This paper aims to investigate the impact of typomorphological changes of residential environments on residents’ sense of place’. Seven housing developments representing different types introduced in Ankara, Turkey since the late 19th-century are selected as case studies. Their morphological characters at the building, street and neighbourhood scales are examined, and typological transformations among the cases in terms of the degrees of continuity are identified. The paper proposes a conceptual model consisting of ten indicators to assess sense of place at the building, street and neighbourhood scales of the residents of the seven cases. The scores of sense of place are generated through structured interviews with the residents and analysed in SPSS. The results show that sense of place is negatively affected by typomorphological changes over time, particularly when mutational changes occur. Continuity in typomorphological transformation helps to maintain sense of place at a desirable level. Furthermore, physical changes at the street and neighbourhood scales have larger impact on sense of place than that at the building scale. The research thus suggests that planning and design should be responsive to traditional types in residential development, particularly at the street and neighbourhood scales to maintain residents’ sense of place
Elusive vector glueball
If the vector glueball exists in the mass range that theory suggests, its
resonance production cross section can be seen in e+e- annihilation only if the
decay width is very narrow (< a few MeV). Otherwise it willbe observed only
indirectly through its mixing with psi(2S). A few tests of the glueball-psi'
mixing are proposed for future charm factories.Comment: One misleading short sentence delete
Are Some Natural Environments More Psychologically Beneficial Than Others? The Importance of Type and Quality on Connectedness to Nature and Psychological Restoration
Exposure to nature can strengthen an individual’s sense of connectedness (i.e., emotional/cognitive bonds to the natural world) and enhance psychological restoration (e.g., feeling relaxed/refreshed). To date, there have been few large studies looking at the role that type and quality of natural environments may have on these outcomes. The present study used data from a large survey in England (sample analyzed = 4,515), which asked participants to recall a recent visit to nature. After controlling for covariates, respondents recalled greater connectedness to nature and restoration following visits to rural and coastal locations compared with urban green space, and to sites of higher environmental quality (operationalized by protected/designated area status, for example, nature reserves). A series of structural equation analyses provided evidence for a bidirectional association between connectedness and restoration. Consideration of the psychological benefits associated with different types and quality of environment has implications for human health, environmental management, and conservation
Search for the Charmonium States as Solution to the CDF Puzzle
The efforts of Roy-Sridhar-Close-Cho-Wise-Trivedi to resolve the CDF
anomaly with cascades from above-threshold states require well
defined signature states require well defined signatures [a small total width
and a large branching fraction for \cp \ra \gamma + \pp] for the solution to
be viable. Here we estimte the production of such states from BR (B \ra \cp +
X)BR (\cp \ra \gamma \pp) and production of
at CLEO II, and comment on the feasbility of testing the hypothesis in terms of
current experimental capabilities.Comment: 8 pages Latex File, No figure
Semantic categories underlying the meaning of ‘place’
This paper analyses the semantics of natural language expressions that are associated with the intuitive notion of ‘place’. We note that the nature of such terms is highly contested, and suggest that this arises from two main considerations: 1) there are a number of logically
distinct categories of place expression, which are not always clearly distinguished in discourse about ‘place’; 2) the many non-substantive place count nouns (such as ‘place’, ‘region’, ‘area’, etc.) employed in natural
language are highly ambiguous. With respect to consideration 1), we propose that place-related expressions
should be classified into the following distinct logical types: a) ‘place-like’ count nouns (further subdivided into abstract, spatial and substantive varieties), b) proper names of ‘place-like’ objects, c) locative property phrases, and d) definite descriptions of ‘place-like’ objects. We outline possible formal representations for each of these. To address consideration 2), we examine meanings, connotations and ambiguities of the English vocabulary of abstract and generic place count nouns, and identify underlying elements of meaning, which explain both
similarities and differences in the sense and usage of the various terms
Math1 Is Essential for the Development of Hindbrain Neurons Critical for Perinatal Breathing
SummaryMice lacking the proneural transcription factor Math1 (Atoh1) lack multiple neurons of the proprioceptive and arousal systems and die shortly after birth from an apparent inability to initiate respiration. We sought to determine whether Math1 was necessary for the development of hindbrain nuclei involved in respiratory rhythm generation, such as the parafacial respiratory group/retrotrapezoid nucleus (pFRG/RTN), defects in which are associated with congenital central hypoventilation syndrome (CCHS). We generated a Math1-GFP fusion allele to trace the development of Math1-expressing pFRG/RTN and paratrigeminal neurons and found that loss of Math1 did indeed disrupt their migration and differentiation. We also identified Math1-dependent neurons and their projections near the pre-Bötzinger complex, a structure critical for respiratory rhythmogenesis, and found that glutamatergic modulation reestablished a rhythm in the absence of Math1. This study identifies Math1-dependent neurons that are critical for perinatal breathing that may link proprioception and arousal with respiration
Ratio of Hadronic Decay Rates of J\psi and \psi(2S) and the \rho\pi Puzzle
The so-called \rho\pi puzzle of J\psi and \psi(2S) decays is examined using
the experimental data available to date. Two different approaches were taken to
estimate the ratio of J\psi and \psi(2S) hadronic decay rates. While one of the
estimates could not yield the exact ratio of \psi(2S) to J\psi inclusive
hadronic decay rates, the other, based on a computation of the inclusive ggg
decay rate for
\psi(2S) (J\psi) by subtracting other decay rates from the total decay rate,
differs by two standard deviations from the naive prediction of perturbative
QCD, even though its central value is nearly twice as large as what was naively
expected. A comparison between this ratio, upon making corrections for specific
exclusive two-body decay modes, and the corresponding experimental data
confirms the puzzles in
J\psi and \psi(2S) decays. We find from our analysis that the exclusively
reconstructed hadronic decays of the \psi(2S) account for only a small fraction
of its total decays, and a ratio exceeding the above estimate should be
expected to occur for a considerable number of the remaining decay channels. We
also show that the recent new results from the BES experiment provide crucial
tests of various theoretical models proposed to explain the puzzle.Comment: 8 pages, no figure, 4 table
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