A Coupling between Integral Equations and On-Surface Radiation Conditions for Diffraction Problems by Non Convex Scatterers

The aim of this paper is to introduce an orignal coupling procedure between surface integral equation formulations and on-surface radiation condition (OSRC) methods for solving two-dimensional scattering problems for non convex structures. The key point is that the use of the OSRC introduces a sparse block in the surface operator representation of the wave field while the integral part leads to an improved accuracy of the OSRC method in the non convex part of the scattering structure. The procedure is given for both the Dirichlet and Neumann scattering problems. Some numerical simulations show the improvement induced by the coupling method.

ВИВЧЕННЯ ПРОЦЕСУ ОДНОВІСНОГО РОЗТЯГУ ТРИКОТАЖУ ПЕРЕПЛЕТЕННЯ ЛАСТИК РІЗНИХ РАПОРТІВ

Study of the process of deformation of rib knits, which occurs due to the application of tensile forces in the course direction. Methodology. During the study, methods of theoretical analysis, a camera, a stretching frame, Microsoft Excel software and Autodesk AutoCAD were used. Findings. For producing rib knit samples, a 10th class flat-bed knitting machine PVRK was used. Samples of knitwear were made with repeatable unit patterns of 1x1, 2x2, 3x3, 4x4, 5x5 and 6x6 from bamboo yarn of linear density 29x2 tex, woolen yarn 32x2 tex, half-woolen yarn 31x2 tex and Polyacrylonitrile yarn 32x2 tex. To carry out uniaxial stretching of knitted fabric samples along the line of stitch rows, a stretching frame was used. After fixing the opposite ends of the sample on the needle set of the frame holders, the distance between them gradually increased with an interval of 20 mm. At each stage of stretching, the samples were photographed together with a calibration ruler. Sample photos imported into Autodesk AutoCAD software. After calibration, for each state of stretching of the sample, such characteristics were determined as: the average value of the width of the repeatable unit pattern, the average value of the width of the convex part of the pattern, as well as the visible section of its concave part. The study showed that at the first stages of stretching, there is a mutual displacement of the sections of the pattern, belonging to different layers of knitwear and a decrease in the twisting of the sections of the smooth surface. Further application of the tensile force leads to a more uniform deformation of the ivestigated structural parts of the pattern. Scientific novelty. The change in the geometric characteristics of rib knits with various repeatable units patterns made from various types of raw materials is experimentally determined. Practical value. The characteristics of knitwear, obtained in the course of the study, were used to form a database necessary for the construction of three-dimensional models of rib knits with bamboo, woolen, semi-woolen, and polyacrylonitrile yarns.

http://www.iqnjm.com/wp-content/uploads/2020/01/Unmet-health-care-work-s-2-No..pdf

Background: Clinodactyly or inclination of the digits, particularly the fifth digit, is a congenital anomaly of the hand that occurs in 1% to 19.5% of the population. This deformity requires reconstruction of both the functional and the aesthetic appearance of the finger, if it is severe, to avoid future growth deformity. Objective: The study aims to review the outcomes and the complications associated with closing and reverse wedge osteotomy techniques for treating clinodactyly. Patients and Methods: Ten patients’ ten fingers with clinodactyly were submitted for reconstruction from March 2014 to May 2016 in the Al Wasity teaching hospital in Baghdad. They were treated using the closing and reverse wedge osteotomy techniques. In the closing wedge procedure, a wedge was removed from the most convex part of the middle phalanx. Subsequently, the finger is aligned in the midaxial plane and repaired with 2 K-wires. In the reverse wedge osteotomy, the wedge was rotated 180 degrees and reinserted into the bone gap with the wide end first. This buttressed the osteotomy open. Subsequently, the K-wires were inserted in retrograde fashion, maintaining the graft’s position. Then, dressing was applied with the small splint from the PIP to the tip of the finger. Results: After a 15-month follow-up, all the patients showed satisfactory results aesthetically and the functionally—with full range of motion. There was no recurrence in any case. Only one case had residual angulation and no major complications were encountered. Conclusion: The closing and reverse wedge osteotomy was proven effective in treating clinodactyly. The closing wedge is simpler than the reverse wedge. The technical difficulty of reverse wedge osteotomy may make it a less appealing option to surgeons but the outcomes we had were rewarding, both techniques provided good overall correction of angulation in one stage, and straightforward procedure, with few complications, good aesthetic outcome and patient satisfaction with improved function. Keywords: clinodactyly, closing wedge, reverse wedge

SPECIFIC MORPHOMETRIC FEATURES OF SUPERIOR SAGITTAL SINUS IN ADULTS

In order to determine the individual peculiarity of the shape, size, position and relations of the upper sagittal sinus, depending on the type of structure of the head in adults, craniometry and morphometry of the head sinuses were performed. The most significant venous collector of the brain is the upper sagittal sinus, which is located in the sagittal plane along the ridge of the lattice to the inner occipital projection. This formation is characterized by a triangular shape. The upper wall is formed by the leaves of the convex part of the solid membrane, and the two lateral walls by splitting the sickle of the cerebellum in the parasagittal plane. In adults, the upper wall contacts the inner surface of the parietal and occipital bones of the cranial vault. According to our data, the upper sagittal sinus has a specific range of variability depending on age, sex and head shape. The range of individual variability of the structure of the upper sagittal sinus was determined, which is characterized by the greatest values of length and height in adults, irrespective of gender with dolichomorphic head shape (narrow-headed) and increase in latitudinal parameters in people with meso- and brachymorphic head (middle and wide).

Design and Optimization of Skyrmion-Based Racetrack Memory by Overcoming Clogging and Annihilation of Skyrmion Signals

Magnetic skyrmions are promising building blocks for next generation data storage due to their stability, small size and extremely low currents to drive them. Skyrmion-based metallic racetrack memory has potential to replace traditional domain walls to store information as data bits, in which, however, skyrmions can drift from the direction of electron flow due to the Magnus force. In addition, skyrmion-edge effect at the end of the racetrack can cause the clogging of the skyrmions at the end of the racetrack. Here, we show that the clogging of skyrmion signals can be avoided by adding various kinds of notch at the end of the racetracks. On the other hand, by adding high-[Formula: see text] materials (materials with high magnetic crystalline anisotropy) at the edges, the skyrmions can be confined in the center region of the metallic racetrack successfully. This design can overcome the problems of both clogging and annihilation according to our micromagnetic simulation. As a result, skyrmions can pass the right end of the racetrack efficiently at a very high speed (100–300[Formula: see text]m/s), whereas the driving current is much smaller in comparison with other racetrack design. Besides, we study the influence of the uneven part at the joint of the high-[Formula: see text] material and the CoPt racetrack on the skyrmionic motion. It is found that at the joint between the high-[Formula: see text] material and the CoPt racetrack, the concave part basically does not affect the passage of skyrmion, but the convex part does when the length and width of the convex part reach a certain value. The results show that the design has high feasibility.

Surface Finishing of Single-Crystal SiC and GaN Wafers Using a Magnetic Tool in H2O2Solution

To remove the microroughness and subsurface damage on the SiC and GaN surface efficiently, a surface finishing technique using a magnetic tool holding iron particles in a hydrogen peroxide solution is developed. This technique utilizes OH radicals generated from the iron catalytic particles in a hydrogen peroxide solution, and can be used to preferentially remove the topmost convex part on the surface, resulting in an atomically smooth surface. We employed this polishing technique to finish the surfaces of 2-inch SiC and 2-inch GaN wafers. The surface roughness before and after finishing was measured by scanning white light interferometric microscopy and atomic force microscopy. In addition, the material removal rate was calculated by weight loss due to the finishing process. The results show that the surface roughness on the SiC and GaN wafers is markedly improved. Moreover, the surface waviness and flatness of these wafers before and after finishing did not deteriorate. Atomic force microscope images indicate that an atomically flat SiC surface with a roughness value below 0.1 nm RMS and a GaN surface with atomic step and terrace structures were achieved. Our proposed finishing technique is effective in improving the surface microroughness of SiC and GaN wafers.

Algorithm for Solution of Non-convex Optimization Problem Through Piece-wise Convex Transformation

Optimization is central to any problem involving decision making. Thearea of optimization has received enormous attention for over 30 years and it is still popular in research field to this day. In this paper, a global optimization method called Kerk and Rohanin’s Trusted Interval will be introduced. The method introduced is able to identify all local solutions by converting non-convex optimization problems into piece-wise convex optimization problems. A mechanism which only considers the convex part where minimizers existed on a function is applied. This mechanism allows the method to filter out concave parts and some unrelated parts automatically. The identified convex parts are called trusted intervals. The descent property and the globally convergent of the method was shown in this paper. 15 test problems have been used to show the ability of the algorithm proposed in locating global minimizer.

Polarity of concavo-convex intervertebral joints in the necks and tails of sauropod dinosaurs

The highly elongated necks, and often tails, of sauropod dinosaurs were composed of concavo-convex vertebrae that provided stability without compromising mobility. Polarities of these concavo-convex joints in the neck and tail are anatomically opposite one another but mechanically equivalent. Opisthocoelous cervical vertebrae and procoelous caudal vertebrae have the convex articular face directed away from the body and the concave articular face directed toward the body. This “sauropod-type” polarity is hypothesized to be (1) more resistant to fracturing of the cotylar rim and (2) better stabilized against joint failure by rotation than the opposite polarity. We used physical models to test these two functional hypotheses. Photoelastic analysis of model centra loaded as cantilevers reveals that neither polarity better resists fracture of the cotylar rim; strain magnitude and localization are similar in both polarities. We assessed the rotational stability of concavo-convex joints using pairs of concavo-convex centra loaded near the joint. Sauropod-type joints withstood significantly greater weight before failure occurred, a pattern we interpret to be dependent on the position of the center of rotation, which is always within the convex part of the concavo-convex joint. In sauropod-type joints, the free centrum rotates about a center of rotation that lies within the more stable proximal centrum. In contrast, the opposite polarity results in a free centrum that rotates about an internal point; when the condyle rotates down and out of joint, the distal end rotates back toward the body, unopposed by ligamentous support. Sauropod-type joints remained stable with greater mobility, more mechanically advantageous tensile element insertions, and greater distal loads than the opposite polarity. The advantages conferred by this joint polarity would have facilitated the evolution of hyperelongated necks and tails by sauropods. Polarity of concavo-convex joints of the appendicular skeleton (e.g., hip, shoulder) is also consistent with the demands of rotational stability.

Audio Watermarking Scheme Based on Singular Spectrum Analysis and Psychoacoustic Model with Self-Synchronization

This paper proposes a blind, inaudible, and robust audio watermarking scheme based on singular spectrum analysis (SSA) and the psychoacoustic model 1 (ISO/IEC 11172-3). In this work, SSA is used to analyze the host signals and to extract the singular spectra. A watermark is embedded into the host signals by modifying the singular spectra which are in the convex part of the singular spectrum curve so that this part becomes concave. This modification certainly affects the inaudibility and robustness properties of the watermarking scheme. To satisfy both properties, the modified part of the singular spectrum is determined by a novel parameter selection method based on the psychoacoustic model. The test results showed that the proposed scheme achieves not only inaudibility and robustness but also blindness. In addition, this work showed that the extraction process of a variant of the proposed scheme can extract the watermark without assuming to know the frame positions in advance and without embedding additional synchronization code into the audio content.

A Two-Feet Linear Ultrasonic Motor for Fuze Safety System

In modern weapons systems, fuze is known as the “brain” of the ammunition, whose performance will directly affect the combat effectiveness. It guarantees the safety of ammunition during the logistical processing and makes the ammunition reliably function after launch. In the fuze system, the delay arming device is closely related to the fuze performance and safety reliability, which affects the muzzle safety distance. After years of development, the performance of delay arming device has been developed and improved, but malignant accidents such as explode in the chamber, early burst and dud have occurred from time to time. This paper investigated a standing wave linear ultrasonic motor applied to the fuze delay arming device as the arming actuator. The motor is made up of a cuboid with two drive feet and a slider with a convex part, both having a through hole. The first order longitudinal vibration and second order bending vibration of the stator were selected as working modes. The prototype was fabricated and the vibration mode test was carried out, indicating the motor can generate two-phase required oscillation modes. The frequency sweep test was also performed and two-phase frequency is proved quite close. The experiments on the motor mechanical performance were done, and the speed of the motor is 88.2 mm/s, furthermore the reciprocating motion of the slider is flexible.