Image-based Bilateral Beard Method for measuring weight-based short fiber contents in raw cotton and semi-finished slivers

In this paper, an economical way for accurately determining weight-based short fiber contents in raw cotton and semi-finished slivers by utilizing special bilateral beard specimens and image processing was introduced. In the specimen preparation, cotton fibers were drawn by a manual device into a sliver, then the sliver was combed to form a bilateral beard specimen, and finally the bilateral beard was scanned to generate a grayscale image from which a relative fiber number curve was extracted. An algorithm for calculating the weight-based short fiber contents based on the curve was proposed. Five types of cottons were repetitively measured to investigate the robustness of the results of [Formula: see text] and [Formula: see text], with the weight ratio of fibers shorter than 12.7 and 16 mm, respectively. The results showed that measuring two bilateral beards for each sample could keep the error rate lower than 15%, while four specimens kept the error rate lower than 10%. Compared with AFIS Pro 2, this Image-based Bilateral Beard Method provided results with lower standard deviations and variable coefficients, signifying its analogous or better robustness. In addition, 37 samples from some of the world’s major producing areas were measured by this method and AFIS Pro 2, and a Bland–Altman analysis confirmed a good agreement between the results from the two methods. As only a manual fiber drawing device and an office scanner are needed, this Image-based Bilateral Beard Method is clearly a cheap approach for accurately determining the short fiber contents in raw cotton and semi-finished slivers.

The fatigue stress on laser welded joints of DC06EK steel

The paper analyses the influence of the fatigue characteristics of laser welding steels sheets. The combination of laser welded steel sheets DC06EK has been subjected to fatigue stress testing. To assess the condition of the material under the cyclic stress and to determine the material characteristics such as fatigue or resp. fatigue time limit was performed according to STN 42 0363. Fatigue tests were performed on the test piece. The experimental material had a laser weld with a rough surface. The test specimens were subjected to a pulsating positive disappearing thrust at a constant value of the coefficient of unbalance of 0‹R‹1 and a frequency of 25 Hz. The fatigue limit was determined at 260 MPa. The analysis of fracture surfaces showed on the sides of the weld joint the formation of a de-cohesive fracture. The resulting test values graphically presents stress-number curve.

A Theorem of Fermat on Congruent Number Curves

International audience A positive integer $A$ is called a \emph{congruent number} if $A$ is the area of a right-angled triangle with three rational sides. Equivalently, $A$ is a \emph{congruent number} if and only if the congruent number curve $y^2 = x^3 − A^2 x$ has a rational point $(x, y) \in {\mathbb{Q}}^2$ with $y \ne 0$. Using a theorem of Fermat, we give an elementary proof for the fact that congruent number curves do not contain rational points of finite order.

Three-dimensional wake transition of a square cylinder

Three-dimensional (3-D) wake transition for flow past a square cylinder aligned with sides perpendicular and parallel to the approaching flow is investigated using direct numerical simulation. The secondary wake instability, namely a Mode A instability, occurs at a Reynolds number ($Re$) of 165.7. A gradual wake transition from Mode A* (i.e. Mode A with vortex dislocations) to Mode B is observed over a range of $Re$ from 185 to 210, within which the probability of occurrence of vortex dislocations decreases monotonically with increasing $Re$. The characteristics of the Strouhal–Reynolds number relationship are analysed. At the onset of Mode A*, a sudden drop of the 3-D Strouhal number from its two-dimensional counterpart is observed, which is due to the subcritical nature of the Mode A* instability. A continuous 3-D Strouhal–Reynolds number curve is observed over the mode swapping regime, since Mode A* and Mode B have extremely close vortex shedding frequencies and therefore only a single merged peak is observed in the frequency spectrum. The existence of hysteresis for the Mode A and Mode B wake instabilities is examined. The unconfined Mode A and Mode B wake instabilities are hysteretic and non-hysteretic, respectively. However, a spanwise confined Mode A could be non-hysteretic. It is proposed that the existence of hysteresis at a wake instability can be identified by examining the sudden/gradual variation of the 3-D flow properties at the onset of the wake instability, with sudden and gradual variations corresponding to hysteretic (subcritical) and non-hysteretic (supercritical) flows, respectively.

Wake transition in the flow around a circular cylinder with a splitter plate

A simple way to decrease the drag and oscillating lift forces in the flow around a circular cylinder consists of positioning a splitter plate in the wake, parallel to the flow. In this paper, the effect of the splitter plate on the wake dynamics, more specifically on the wake transition, is described in detail. First, two-dimensional and three-dimensional direct numerical simulations (DNS) using the spectral element method were used to observe the behaviour of the wake in the presence of the splitter plate. Then, a linear stability analysis based on the Floquet theory was performed in order to obtain information on how the splitter plate changes the instabilities that lead to wake transition. Simulations were carried out for several gaps between the splitter plate and the cylinder, with the Reynolds number varying in the range between 100 and 350, which corresponds to the wake transition in the flow around a circular cylinder. The results of the simulations showed a discontinuity in the Strouhal number curve that is consistent with the results available in the literature. The stability analysis showed how the splitter plate modifies the transition of the flow to a three-dimensional configuration. The splitter plate has a stabilizing effect on the flow for small gaps, delaying the appearance of three-dimensional structures to higher Reynolds numbers. Mode A and a quasi-periodic (QP) mode are observed for such small gaps. As the gap is increased the discontinuity in the Strouhal number curve also caused a clear change in the characteristics of the neutral stability curve, and the existence of an unstable period-doubling mode was observed. The onset characteristics of the unstable modes are analysed and discussed in depth.

The Diagnosis Research of Cover Sheet Spring Recover on the Compensate Fuzzy Nerve Net of Multi-Input Defer

The model of compensate fuzzy nerve net on multi-input defer is built. The net frame and studied algorithm of compensate fuzzy nerve net on multi-input defer is introduced .It is used that practical use on multi-input defer and higher containing mistake of compensate fuzzy nerve net, and it is given that the building model error tortuous surface, curve of net input and curve of all error number curve, which is combined with goal example. The result is showed in spring recover of cover sheet that the all error of compensate fuzzy nerve net on multi-input defer is reduced by 7.5 percent, and diagnostic precision is increased by 6.3 percent.

Evolution Characteristics of Existing Bridge Safety Based on Algebraic Topology and Image Processing

This paper investigates the evolution characteristics of existing bridge safety based on algebraic topology and image analysis. Through the calculation of betti numbers of cross section in bridge pier binarization images, evolution curve of betti numbers time series is observed, which reflects the changes in internal structure of bridge piers, due to the variation of external environment. The analysis results show that when the evolution trend of the betti number appears a smooth change, the bridge pier is in safe condition, and when betti number curve appears sudden fluctuations, the internal structure of piers presents some changes. This study has positive significance for long-term monitoring of bridge safety.