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