1,568 research outputs found
Effects of mixing and pumping energy on technological and microstructural properties of cement-based mortars
Numerous recurrent situations following mixing and pumping of mortars and concretes cause degradation of fluidity and hardening characteristics. Which, in turn, lead to adverse effects on the quality of workmanship and structural defects.
Nonetheless, relatively little research on the mixing and pumping energies used for the onsite transport and preparation of mortar or concrete has been directed at the core reasons or mechanisms for changes in technological properties.
This dissertation describes and explains the effects of various mixing and pumping parameters on the mortar characteristics in a field trial and on a laboratory scale.
Observations using a rheograph revealed that shearing action does exhibit the most pronounced influence on the characteristics of mortars during the pumping. The performed investigations indicate that higher shearing actions, for example, excessive mixing duration and long-distance pumping lead to reduced flowability, accelerated and increased hydration rate, increased early compressive strength and early-age shrinkage.
From these findings, the underlying mechanism responsible for acceleration and increase of hydration rate is pinpointed as: the increased dissolution from the active surface area due to the destruction of the protective superficial layers of cement
grains, as well as a transition from flocculation to dispersion. The creation of new surfaces leads to further consumption of active super plasticizer in solution phase and to subsequent degrading changes in fluidity (decreasing flowability). The degradation of fluidity and densification of microstructure provoked by the hydration changes do increase the early age shrinkage of mortar
Phagocytic Ability of Oyster Hemocytes Measured by a Simple Method Using Bacterial Thin-layer
A simple method called the phagocytic plaque assay was used to visually present and estimate the phagocytic ability of the hemocytes from the giant Pacific oyster, Crassostrea gigas, using adherent Staphylococcus aureus cells on a plastic dish. Many plaques appeared on the bacterial thin-layer when the oyster hemocytes were overlaid and incubated on killed cells of S. aureus. At both 20℃ and 30℃, the phagocytic ability of the oyster hemocytes were more activated with a significantly larger average area of plaques than were the hemocytes at 10℃. This method was considered to be practical and effective evaluating the qualification of phagocytosis by the oyster hemocytes, however, some problems for the quantification analysis still remain to be solved
How Well Can We Reconstruct the ttbar System Near its Threshold at Future e+e- Linear Colliders?
We developed a new method for full kinematical reconstruction of the ttbar
system near its threshold at future linear e+e- colliders. In the core of the
method lies likelihood fitting which is designed to improve measurement
accuracies of the kinematical variables that specify the final states resulting
from ttbar decays. The improvement is demonstrated by applying this method to a
Monte-Carlo ttbar sample generated with various experimental effects including
beamstrahlung, finite acceptance and resolution of the detector system, etc. In
most cases the fit brings a broad non-Gaussian distribution of a given
kinematical variable to a nearly Gaussian shape, thereby justifying
phenomenological analyses based on simple Gaussian smearing of parton-level
momenta. The standard deviations of the resultant distributions of various
kinematical variables are given in order to facilitate such phenomenological
analyses. A possible application of the kinematical fitting method and its
expected impact are also discussed.Comment: 14 pages, LaTeX, 11 figure
A study of the measurement precision of the Higgs boson decaying into tau pairs at the ILC
We evaluate the measurement precision of the production cross section times
the branching ratio of the Higgs boson decaying into tau lepton pairs at the
International Linear Collider (ILC). We analyze various final states associated
with the main production mechanisms of the Higgs boson, the Higgs-strahlung and
WW-fusion processes. The statistical precision of the production cross section
times the branching ratio is estimated to be 2.6% and 6.9% for the
Higgs-strahlung andWW-fusion processes, respectively, with the nominal
integrated luminosities assumed in the ILC Technical Design Report; the
precision improves to 1.0% and 3.4% with the running scenario including
possible luminosity upgrades. The study provides a reference performance of the
ILC for future phenomenological analyses.Comment: 10 pages, 6 figures, 9 tables, revised from v
Functional Profiles of Hemocytes in the bio-defense Process of the Pacific Oyster, Crassostrea gigas
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