1,594 research outputs found
DIC-hole drilling method for in-situ residual stress measurement
Residual stress measurement carries an important significance in ensuring safety and reliability of steel structures. In order to simplify the measurement procedure and enhance flexibility of the conventional hole drilling method to adopt in in-situ residual stress measurement, digital image correlation (DIC) is applied to measure the displacement field caused by the localized stress relief associated due to hole drilling. It is referred to as DIC-hole drilling method. The residual stress theoretical expressions of the DIC-hole drilling method are discussed. The requirements of drilling device, camera and lens are determined by accounting for the accuracy of the in-situ residual stress measurement. A benchmark experiment by using steel beam specimens is developed to verify the feasibility and reliability of DIC-hole drilling method. Test data are compared with theoretical calculations and FEM results. The comparison indicates the DIC-hole drilling method has enough accuracy for the in-situ residual stress measurement. The displacement field in the regions centred at 2 to 2.5 times drilling hole radius far from the hole is proposed for the accurate residual stress measurement
Unified Normalization for Accelerating and Stabilizing Transformers
Solid results from Transformers have made them prevailing architectures in
various natural language and vision tasks. As a default component in
Transformers, Layer Normalization (LN) normalizes activations within each token
to boost the robustness. However, LN requires on-the-fly statistics calculation
in inference as well as division and square root operations, leading to
inefficiency on hardware. What is more, replacing LN with other
hardware-efficient normalization schemes (e.g., Batch Normalization) results in
inferior performance, even collapse in training. We find that this dilemma is
caused by abnormal behaviors of activation statistics, including large
fluctuations over iterations and extreme outliers across layers. To tackle
these issues, we propose Unified Normalization (UN), which can speed up the
inference by being fused with other linear operations and achieve comparable
performance on par with LN. UN strives to boost performance by calibrating the
activation and gradient statistics with a tailored fluctuation smoothing
strategy. Meanwhile, an adaptive outlier filtration strategy is applied to
avoid collapse in training whose effectiveness is theoretically proved and
experimentally verified in this paper. We demonstrate that UN can be an
efficient drop-in alternative to LN by conducting extensive experiments on
language and vision tasks. Besides, we evaluate the efficiency of our method on
GPU. Transformers equipped with UN enjoy about 31% inference speedup and nearly
18% memory reduction. Code will be released at
https://github.com/hikvision-research/Unified-Normalization.Comment: ACM MM'2
Solar microwave millisecond spike at 2.84 GHz
Using the high time resolution of 1 ms, the data of solar microwave millisecond spike (MMS) event was recorded more than two hundred times at the frequency of 2.84 GHz at Beijing (Peking) Observatory since May 1981. A preliminary analysis was made. It can be seen from the data that the MMS-events have a variety of the fast activities such as the dispersed and isolated spikes, the clusters of the crowded spikes, the weak spikes superimposed on the noise background, and the phenomena of absorption. The marked differences from that observed with lower time resolution are presented. Using the data, a valuable statistical analysis was made. There are close correlations between MMS-events and hard X-ray bursts, and fast drifting bursts. The MMS events are highly dependent on the type of active regions and the magnetic field configuration. It seems to be crucial to find out the accurate positions on the active region where the MMS-events happen and to make co-operative observations at different bands during the special period when specific active regions appear on the solar disk
A study of influencing parameters on conductor galloping for transmission lines
Factors influencing conductor galloping are so complicated that the development of galloping theories and anti-galloping technologies for transmission lines is limited. Study on influence parameters to the galloping is crucial to investigate galloping mechanism and anti-galloping methods. In this paper, three important dimensionless parameters, damping ratio, reduced wind velocity and reduced mass ratio, are proposed by dimensionless analysis based on the conductor galloping model. The expression of galloping equivalent amplitude is derived by using the average method, and the analytic solution is obtained when the aerodynamic curve is fitted by cubic and quintic polynomials respectively. For the aerodynamic coefficients, wind tunnel testing results of three typical eccentric ice accretion shapes, D shape, U shape and airfoil shape, are introduced to analyze the influence of the dimensionless parameters to the conductor galloping. Firstly, a new formula to calculate the galloping critical wind velocity is derived, which is more accurate than the result given by Den Hartog criterion. Secondly, the influence of reduced wind velocity and damping ratio to the galloping equivalent amplitude is studied. The results have an important guidance to anti-galloping design for transmission lines
Interaction between Granulation and Small-Scale Magnetic Flux Observed by Hinode
We study the relationship between granular development and magnetic field
evolution in the quiet Sun. 6 typical cases are displayed to exhibit
interaction between granules and magnetic elements, and we have obtained the
following results. (1) A granule develops centrosymmetrically when no magnetic
flux emerges within the granular cell. (2) A granule develops and splits
noncentrosymmetrically while flux emerges at an outer part of the granular
cell. (3) Magnetic flux emergence as a cluster of mixed polarities is detected
at the position of a granule as soon as the granule breaks up. (4) A dipole
emerges accompanying with the development of a granule, and the two elements of
the dipole root in the adjacent intergranular lanes and face each other across
the granule. Advected by the horizontal granular motion, the positive element
of the dipole then cancels with pre-existing negative flux. (5) Flux
cancellation also takes place between a positive element, which is advected by
granular flow, and its surrounding negative flux. (6) While magnetic flux
cancellation takes place at a granular cell, the granule shrinks and then
disappears. (7) Horizontal magnetic fields enhance at the places where dipoles
emerge and where opposite polarities cancel with each other, but only the
horizontal fields between the dipolar elements point orderly from the positive
element to the negative one. Our results reveal that granules and small-scale
magnetic flux influence each other. Granular flow advects magnetic flux, and
magnetic flux evolution suppresses granular development. There exist extremely
large Doppler blue-shifts at the site of one cancelling magnetic element. This
phenomenon may be caused by the upward flow produced by magnetic reconnection
below the photosphere.Comment: 8 figures, 13 pages. RAA, in pres
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