1,293 research outputs found
Experimental Evaluation of Fragments from TBM Disc Cutting under Different Load Cases
The Tunnel Boring Machine (TBM) tunneling process always contains a certain degree of vibrations due to the step broken phenomenon of the cutting tools. Undoubtedly, there is a quite difference in the fragment characteristics which are related to the construction efficiency of TBM under the static load and the combination of static and impact load. In this study, a series of rock breaking tests with a 216 mm diameter disc cutter and marble samples were conducted under different load cases. Based on the Rosin–Rammler distribution curve, the fragments from the cutting tests were also sieved to calculate the absolute size constant (x’) and coarseness index (CI). The relationship between coarseness index, absolute size parameter and the cutting parameters, specific energy, production rate was evaluated. The results show that there is an increasing trend of x’ and CI with the increase of cut spacing and penetration as well as adding impact load component. An overall downtrend in specific energy and upward trend in production rate which are associated with the high efficiency can be observed with the increasing CI and x’. It is believed that the conclusions are of great significance for improving TBM construction efficiency and cutterhead design
Pixel is All You Need: Adversarial Trajectory-Ensemble Active Learning for Salient Object Detection
Although weakly-supervised techniques can reduce the labeling effort, it is
unclear whether a saliency model trained with weakly-supervised data (e.g.,
point annotation) can achieve the equivalent performance of its
fully-supervised version. This paper attempts to answer this unexplored
question by proving a hypothesis: there is a point-labeled dataset where
saliency models trained on it can achieve equivalent performance when trained
on the densely annotated dataset. To prove this conjecture, we proposed a novel
yet effective adversarial trajectory-ensemble active learning (ATAL). Our
contributions are three-fold: 1) Our proposed adversarial attack triggering
uncertainty can conquer the overconfidence of existing active learning methods
and accurately locate these uncertain pixels. {2)} Our proposed
trajectory-ensemble uncertainty estimation method maintains the advantages of
the ensemble networks while significantly reducing the computational cost. {3)}
Our proposed relationship-aware diversity sampling algorithm can conquer
oversampling while boosting performance. Experimental results show that our
ATAL can find such a point-labeled dataset, where a saliency model trained on
it obtained -- performance of its fully-supervised version with
only ten annotated points per image.Comment: 9 pages, 8 figure
Structural parameter variation working on the performance of anti-uplift multibell underreamed anchors
The structural parameters of multibell underreamed anchors play a crucial role in anchoring performance. The parameters of multibell underreamed anchor investigations are helpful when exploring optimized anchor structures. Based on the results of small-scale physical modelling tests, two types of multibell underreamed anchors were adopted under vertical uplifting loads. Numerical investigations were employed to study the effect of bell spacing, underream structure and bell dimension on the ultimate uplift bearing capacity. After an analysis of the anchorage mechanism, the anchoring efficiency was evaluated by the anchoring force provided by the unit concrete usage of the anchor, and the structural parameter λ equal to the surface area ratios of the expanded bell cone to the straight shaft between bells was defined. Then, the anchoring efficiency optimized structural parameters were presented. An analysis of model tests and simulation results showed that compared to concave bell surfaces, the convex shape could enhance the ultimate bearing capacity of a multibell underreamed anchor. There is an optimal value for the spacing of neighbouring bells, and there are three models of mechanisms for multibell anchors pulling out. When λ ∈ [1, 1.8], the multibell anchors can perform most efficiently to achieve their structural advantages
Multi-frequency test of dark matter annihilation into long-lived particles in Sirius
New long-lived particles produced at the colliders may escape from
conventional particle detectors. Using satellites or ground telescopes, we can
detect the photons generated from the annihilation of the star-captured dark
matter into a pair of long-lived particles. When the propagation length of
these long-lived particles surpasses the interplanetary distance between the
Sun and Jupiter, it becomes unfeasible to detect such dark matter signals
originating from the Sun or Jupiter on Earth. Our analysis of the dark
matter-induced photons produced by prompt radiation, inverse Compton
scattering, and synchrotron radiation mechanisms reveals that a decay length of
about pc for long-lived particles is required for maximum
detectability. We investigate the parameters that allow the long-lived
particle's lifetime to be consistent with Big Bang nucleosynthesis while also
allowing it to escape the confines of our solar system. The Sirius system is
proposed as a promising target for the indirect detection of such long-lived
particles. Utilizing the prompt, inverse Compton scattering, and synchrotron
radiation, upper limits on the dark matter-proton spin-independent and
spin-dependent cross section are estimated with the Fermi-LAT null-signal
observation and the capabilities of the upcoming Square Kilometre Array radio
telescope.Comment: 30 pages, 6 figures, JCAP accepte
The double charm decays of B Mesons in the mSUGRA model
Based on the low energy effective Hamiltonian with naive factorization, we
calculate the branching ratios(BRs) and CP asymmetries (CPAs) for the twenty
three double charm decays in both the
standard model (SM) and the minimal supergravity (mSUGRA) model. Within the
considered parameter space, we find that (a) the theoretical predictions for
the BRs, CPAs and the polarization fractions in the SM and the mSUGRA model are
all consistent with the currently available data within errors;
(b) For all the considered decays, the supersymmetric contributions in the
mSUGRA model are very small, less than numerically. It may be difficult
to observe so small SUSY contributions even at LHC.Comment: 15 pages, 5tables, no figure
A “Double-Multi” Model for Electromigration of Lithiums and Chlorides in ASR Affected Concrete
Existing reinforced concrete structures experience severe durability degradation when subjected to alkali– silica reaction (ASR) and chloride attack. A special electrochemical rehabilitation treatment, containing lithium compound anolyte, has been developed to drive lithium ions into concrete as well as remove chlorides simultaneously, for mitigating both the ASR-induced cracks and the chloride-induced corrosion. Good performance of introduced lithiums in controlling ASR-induced expansion has already been proved. Unfortunately, the migration mechanism of lithium in concrete under an external electric field is seldom investigated in existing literature. In this study, with help of the “double-multi” model, the efficiency of impregnation of lithium ions and simultaneously the removal of chloride ions through a specific electrochemical treatment are numerically evaluated, which results into the distribution profiles of all typical ionic species. The heterogeneous concrete model examines the aggregate effect, especially on the interaction with lithiums which are supposed to mitigate ASR. The ionic interaction between different species and the electrochemical reaction at electrodes are also considered. Through a relative thorough modelling of multi-phase and multi-species, a systemic parametric analysis based on a series of significant factors during electrochemical treatment (e.g., current density, treatment time, temperature, cathode position and concentration of lithium solution) reveals some important tendencies of ionic electromigration in concrete, which are supposed to guide the field application
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