Nanoscale Reciprocating Sliding Contact Behaviors of an Isosceles Trapezoid Textured Surface in Space Environment

Background: In space environment, microgravity and vacuum influence the mechanical behaviors of the devices. In microgravity environment, the mechanical components will vibrate with a small amplitude once there is a disturbance. The vibration can be seen as a reciprocating sliding contact with a small amplitude. In addition to the vibration, adhesion effects are predominant in vacuum, which will induce a high friction force. Objective: To reduce the friction force, textured surfaces are widely used in mechanical engineering on the earth, and nanoscale textures are also verified that they can be used to improve the frictional behaviors of components with the size of nanometers. Methods: In this paper, the adhesion effects are considered by using molecular dynamics (MD) simulation, and the microgravity induced vibration is simplified as a reciprocating sliding contact. Coupling MD simulation and the finite element method, a multiscale method is used to investigate the frictional properties of nanoscale reciprocating sliding contact between rigid multi-asperity tips and an isosceles trapezoid textured surface. Results: Average friction forces for the different tips are presented, and the friction processes are analyzed. A stable friction process is discovered for a specific case, and the average friction forces keep at two stable values corresponding to two sliding directions. Conclusion: Compared with the total average friction forces of a smooth surface, the textured surface can reduce the friction forces greatly. This work could contribute to the textured surface design to improve frictional properties in space environment.

Comb Former Parameters for a Cotton Seeder

Success in cultivating cotton largely depends on the timing and quality of soil preparation for sowing and sowing, and the latter, in turn, depends on how it is carried out and on the perfect design of the machines. The aim of the study is to justify the shape of the ridges and the parameters of the moulder to the cotton seeder. The authors proposed a new technology for sowing with the simultaneous formation of ridges. The shape and parameters of the ridge are theoretically substantiated. When performing the shape of the ridge in the form of an isosceles trapezoid and, accordingly, with a height and width of the ridge surface of at least 100 mm and 160 mm, the seed bed is protected from flooding by rain streams. The design of the developed comb moulder to a cotton seeder for the implementation of the proposed technology is given. Theoretically substantiated the main parameters of the crest moulder. It was found that when the input edge of the moulder is 290-320 mm wide, the output edge is 160 mm, the angle of inclination of the side blade to the direction of movement is 20°, the length of the runner of the moulder is 203-215 mm, the height of the side blade is 100 mm and the angle of installation of the side blade to horizon 42-45° ensures highquality implementation of the technological process of formation of ridges. When sowing cotton seeds on the ridges with the simultaneous formation of the ridge, the seedlings of the plants increase, and the cotton yield increases compared to the smooth sowing method of 9.9%.

Compact Microwave Components with Harmonic Suppression Based on Artificial Transmission Lines

In this paper, compact microwave components, including a Wilkinson power divider and a 3 dB branch-line coupler based on artificial transmission lines (ATLs) with harmonic suppression, are presented. A section ATL is consisted of microstrip stepped impedance transmission lines and a microstrip interdigital capacitor. To achieve a compact size, the stepped impedance transmission lines are folded into a right-angled triangle shape. For the ATL, the interdigital capacitor is used to suppress harmonics. By employing two sections of 70.7 Ω ATLs with a right-angled triangle shape to replace conventional transmission lines, the proposed power divider working at 0.9 GHz achieves a size miniaturization with the 58.8% area of a conventional case. In addition, the power divider has good harmonic suppression performance. In the design of a branch-line coupler, two pairs of ATLs with 50 Ω and 35.4 Ω are utilized. For 50 Ω ATLs, the ATLs are designed to a right-angled triangle shape. Meanwhile, to obtain a more compact size, these 35.4 Ω ATLs are modified to an isosceles trapezoid shape. The proposed branch-line coupler operating at 0.9 GHz accounts for merely 33.4% of a coupler adopting conventional microstrip transmission lines. Moreover, the harmonics of a branch-line coupler are suppressed effectively as well. Finally, measured results of the proposed Wilkinson power divider and branch-line coupler display good performance and agree with their simulated results well.

Design Optimization of Double-Gate Isosceles Trapezoid Tunnel Field-Effect Transistor (DGIT-TFET)

Recently, tunnel field-effect transistors (TFETs) have been regarded as next-generation ultra-low-power semi-conductor devices. To commercialize the TFETs, however, it is necessary to improve an on-state current caused by tunnel-junction resistance and to suppress a leakage current from ambipolar current (IAMB). In this paper, we suggest a novel TFET which features double gate, vertical, and trapezoid isosceles channel structure to solve the above-mentioned technical issues. The device design is optimized by examining its electrical characteristics with the help of technology computer-aided design (TCAD) simulation. As a result, double-gate isosceles trapezoid (DGIT) TFET shows a much better performance than the conventional TFET in terms of ON-state current (ION), IAMB, and gate-to-drain capacitance (CGD). It is confirmed that an inverter composed of DGIT-TFETs can operate with less than 1 ns intrinsic delay time and negligible voltage overshoot.

Behavior of porosity in billet during rolling process of rail

Unlike traditional rolling processes, reduction of rolling process of rail is along two vertical directions and the broadening of rolled piece is controlled. In this study, industrial experiments and a simulation model of the rolling process of rail were conducted to investigate the behaviors of porosities in billet during the rolling process of rail. The experimental and simulated results revealed that porosities moved toward the center on the cross section of the rolled piece and the porosities region reduced from a rectangle with the size (76.7 × 93.3 mm) to an isosceles trapezoid with the size {(12.8 + 18.5 mm) × 47.2 mm} during the rolling process of rail. The shapes of the porosities changed from circles with the diameters smaller than 6 mm to short cracks with the lengths shorter than 10 mm on the cross section. The two vertical reduction directions and the controlled broadening of rolled piece both counted against the closure of porosity. The simulated results were mostly in agreement with the experimental results.

Effect of panel shape on hydrodynamic performances of vertical v-shaped double- slotted cambered otter-board

The effect of panel shape on hydrodynamic performances of a vertical v-shaped double-slotted cambered otter-board was investigated using engineering models in a wind tunnel. Three different shape panels (rhomboid, left trapezoid and isosceles trapezoid) were evaluated at a wind speed of 28 m/s. Parameters measured included: drag coefficient Cx, lift coefficient Cy, pitch moment coefficient Cm, center of pressure coefficient Cp , over a range of angle of attack (0° to 70°). These coefficients were used in analyzing the differences in the performance among the three otter-board models. Results showed that the maximum lift coefficient Cy of the otter-board model with the isosceles trapezoid shape panels was highest (2.103 at α=45°). The maximum Cy/Cx of the otter-board with the rhomboid shape panels was highest (3.976 at α=15°). A comparative analysis of Cm and Cp showed that the stability of otter-board model with the isosceles trapezoid shape panels is better in pitch, and the stability of otter-board model with the left trapezoid shape panels is better in roll. The findings of this study can offer useful reference data for the structural optimization of otter-boards for trawling.

Semiregular Tessellations with Pattern Blocks

Pattern blocks are multifunctional instructional tools with a variety of applications in various strands of mathematics (number sense, geometry, measurement, algebra, probability). The six pattern blocks are an equilateral triangle (green), a blue rhombus, an isosceles trapezoid (red), a regular hexagon (yellow), a square (orange), and a white rhombus. The sides of all pattern blocks are congruent, considered to be 1 unit in length for this article. Photograph 1 depicts a wall painting with squares and rhombuses found in Jersey City, New Jersey.