Smooth Arc Research Articles

Performance Evaluation of Biomimetic-Designed Rotary Blades for Straw Incorporation in an Intensive Tillage System

A rotary tiller is a common tillage tool for straw incorporation in an intensive tillage system. However, rotary tillage for seedbed preparation in dense-straw mulching conditions experiences high torque and poor performance of straw incorporation. Nowadays, a great deal of studies have been focused on mimicking the morphological features of low-resistance animals to improve the performance of soil-engaging tools. Accordingly, the present study investigated the performance of three C-type rotary blades (i.e., conventional, serrated, and biomimetic) under three straw lengths (50, 100, and 150 mm) for incorporation of straw into the field using an in situ field tillage testing bench. Compared to the conventional and serrated blades, the biomimetic blade had lower straw displacement (decreased by an average of 50 mm and 7 mm, respectively), higher straw burying rate (increased by an average of 5.2% and 7.8%, respectively), better straw distribution (decreased by an average of 9.1% and 10.4% on the coefficient of variation, respectively), as well as lower torque and power (decreased by an average of 3.3 N·m and 4.4 N·m, respectively) under all straw lengths. The improved performance of the biomimetic blade could be attributed to the fact that its typical teeth configuration was designed by mimicking the smooth arc of the mole-rat’s claw. These results demonstrated that the biomimetic-designed blade could be a better option for incorporating dense straw into the field conditions.

Computational analysis of piston shape effects on in-cylinder gas flow, fuel-charge mixing, and combustion characteristics in a two-stroke rod-less spark ignition opposed-pistons engine

Compared with the traditional in-cylinder direct-injection spark ignition engine, the side-injection and side-spark-ignition characteristics of the two-stroke opposed-piston engine increase the ignition kernel offset and flame propagation distance. Increasing the flame propagation speed can to some extent solve the drawbacks caused by the non-central arrangement of spark plugs. The combustion chamber structure plays a crucial role in gas flow, fuel-charge mixing, and combustion characteristics. Therefore, three pistons were designed and comparatively analyzed in this study. The results show that: The pancake piston is beneficial to maintaining the intake swirl strength due to its simple and smooth spherical arc structure. The swirl strength of the pit and pit-guided piston decreases obviously, and the tumble strength can be maintained well. Compared to pancake and pit-guided pistons, the average TKE for the pit piston increased by approximately 25%, with a more concentrated distribution at the spark timing. The pancake piston exhibits the best scavenging performance, reducing the residual exhaust gas ratio by 2.1% and fresh air loss by 3.3% to the pit piston. A stable ignition core can be formed at the spark timing, but significant differences are observed in the flame propagation process for three pistons. Compared to the pit-guided piston, the pit piston has a 0.3% decrease in the indicated thermal efficiency, but a 13.1% decrease in combustion duration, which reduces knock tendency.

Bi‐RRT*: An Improved Bidirectional RRT* Path Planner for Robot in Two‐Dimensional Space

Path planning is one of the fundamental issues in the research field of robot. In the last decades, Rapidly‐exploring Random Tree star (RRT*) was one of the chosen path planner for robot with its probabilistically complete. In this paper, an improved bidirectional RRT* path planner for robot is proposed (Bi‐RRT*), which has planned path with safety and smoothly guarantee. The main contributions of this paper include, firstly, combining the backtracking idea of the Quick‐RRT algorithm with the greedy search strategy of the RRT‐Connect algorithm, which can reduce the path cost and improve the operation efficiency of the algorithm. Second, in order to further reduce the running time of the algorithm, a new collision detection algorithm based on cross‐product is proposed to replace the conventional collision detection strategy. To ensure the quality of the path, two post‐processing strategies, path optimization strategy and path smoothing strategy, are proposed. Path optimization strategy is based on triangle inequality, and two optimization methods are proposed to effectively reduce the path cost. The path smoothing strategy based on the Bezier curve improves the continuity of a smooth arc and is better applied to path smoothing. Simulation results for both virtual and real environments show the advantages of combining Quick‐RRT and RRT‐Connect and verify the effectiveness of the proposed collision detection algorithm. Compared with similar algorithms, the proposed Bi‐RRT algorithm has higher operational efficiency, smaller path cost, smoother planned paths, and improved path quality. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Analogue of Kellogg’s Theorem for Piecewise Lyapunov Domains

In weighted Hölder spaces, classes of smooth arcs and piecewise smooth contours are introduced that are invariant under power mappings. The boundary properties of conformal mappings are described in terms of these classes by analogy with Kellogg’s classical theorem.

Towards the cosymplectic topology

Abstract In this article, the cosymplectic analogue of the symplectic flux homomorphism of a compact connected cosymplectic manifold ( M , η , ω ) \left(M,\eta ,\omega ) with ∂ M = ∅ \partial M=\varnothing is studied. This is a continuous map with respect to the C 0 {C}^{0} -metric, whose kernel is connected by smooth arcs and coincides with the subgroup of all weakly Hamiltonian diffeomorphisms. We discuss the cosymplectic analogue of the Weinstein’s chart, and derive that the group G η , ω ( M ) {G}_{\eta ,\omega }\left(M) of all cosymplectic diffeomorphisms isotopic to the identity map is locally contractible. A study of an analogue of Polterovich’s regularization process for co-Hamiltonian isotopies follows. Finally, we study Moser’s stability theorems for locally conformal cosymplectic manifolds.

An Introduction to the Special Issue on Paths to Copyright Librarianship

As adults, conversations about work and careers are standard. Copyright librarianship is a unique field and inevitably people ask, “How did you get into that?” Like many folks, I have an origin story that belies the smooth arc we all imagine. I had been thinking about my journey, and wondering how others came to this work. Could they point to a moment or person that helped them along the way? Might my and others’ stories be insightful or beneficial to others? The stories in this issue are all different and compelling. Read on and learn the varied ways lawyers and librarians became copyright librarians.

Basic exploration and research on magnetoelectric synergistic rheological finishing

Both the magnetorheological effect and the electrorheological effect can effectively constrain and clamp abrasives for polishing processing. This paper proposes a magneto-electric synergy rheological finishing (MERF) method. Based on a magnetoelectric composite field simulation, magnetoelectric synergistic rheological finishing equipment is built. A polishing slurry with both electrorheological and magnetorheological effects is prepared for processing a 2-inch single-crystal silicon wafer. Comb-type electrodes and cylindrical flat-bottomed magnetic poles are used to construct magnetoelectric composite fields. Under the action of a magnetoelectric composite field, a hemispherical polishing pad with abrasives distributed in strips can be obtained. By conducting a test, a smooth and gentle arc cross section of the removed contour can be obtained. The removal rate of MERF was 4.04 mg/h, which was between those of electrorheological finishing (ERF) and magnetorheological finishing (MRF). The surface roughness Ra reached 1.80 nm, and the depth and width of the machining traces were the largest. Magnetoelectric synergistic rheological finishing equipment can realize processing under electric fields, magnetic fields, and magnetoelectric composite fields. The MERF method can effectively enhance the semifixed binding force and distributional uniformity of the abrasive and achieve a more efficient and uniform planarization process.

Study on flow distribution of irrigation canal system based on image velocimetry

• The YOLOV5 algorithm combined with the monocular ranging principle is used for fast flow measurement of UAV images for UAV hovering type measurement of local river surface flow fields. • Based on the smooth circular arc channel distribution model, the velocity distribution law of Yongji section, Yonggang section and Yonglan section is studied and summarized. • Based on The Rule of Tyson polygon, combined with the representative point of average velocity, the measurement of flow through water section is calculated, and the contactless measurement is realized. With the development of computer technology, it has become possible to measure surface flow velocity using video technology. Ripples are produced when flowing, and flow velocity can be determined based on the ripples and floating objects in water. A UAV velocity measurement system based on optical flow method and YOLOV5 algorithm in deep learning has been established, to realize the monitoring of surface flow field of large rivers. The optical flow method and the deep learning algorithm are used to track the target, convert the pixel distance to actual distance by monocular ranging, and calculate the actual flow velocity. The method was successfully applied to the surface flow field measurement of the Yongji canal in the river-loop irrigation area of Inner Mongolia, and the results showed that the orthophoto graphic images obtained by the method were of high quality, the flow field calculation results were reasonable, and the calculation results agreed well with the measurements.

Evaluation of the Crosswind Effect on the Horizontal Curve Safety on Rural Highways Using Vehicle Dynamic Simulation

Horizontal curves, as one of the most accident-prone parts of the road, have always attracted special attention. When a vehicle is moving on a road, the driver has to be constantly on the lookout for small deviations from the main route, possibly due to disturbances such as wind, road roughness, and unwanted entrances by the driver. These types of deviations have a corrosive effect on the driver and will eventually lead to the overturning and slipping of vehicles, so they should be minimized. AASHTO standard procedures, as the most valid road design bylaw, do not consider the effect of lateral wind, in which the effect of lateral wind in arcs has been investigated in this research. The work conducted in this research is to increase knowledge about the directional stability of vehicles that are affected by strong winds and to investigate the parameters of the study using accurate models of dynamic simulation of vehicles that are subject to winds. This study aimed to increase the understanding of vehicle sensitivity to wind due to strong lateral winds. For this purpose, the process of passing different types of vehicles through horizontal arcs in different longitudinal slopes with different velocities of the vehicle under lateral wind is simulated and the mechanical properties of vehicles under such conditions are calculated to compare with the results obtained from the passage of vehicles through a smooth horizontal arc (without longitudinal slope) and without lateral wind. Overturning angle, slip angle, lateral acceleration, and lateral coefficient of friction of vehicles in this study were calculated through software outputs, and the effect of lateral wind on the safety of arcs has been investigated.

Low current arc ignition stability in micro-TIG welding

Micro‑tungsten inert gas (TIG) welding is widely used in electronic component manufacturing. Arc ignition under low current should be employed to avoid burning the micro-component. However, it is relatively complex to manipulate. To improve the stability and reliability of the arc ignition under low current, the effect of the ignition method, cathode spot motion (CSM), and welding circuit inductance is investigated. High voltage arc ignition (HVAI) experiments are carried out with different inductances under various CSM amplitudes. A high-speed digital camera is employed to record the arc image, while a digital oscilloscope is used to simultaneously detect the arc voltage and current waveforms. The results show that HVAI can achieve smooth arc ignition with the low current in a relatively long discharge gap. The inductance in the welding circuit plays an effective role in maintaining the burning of the micro-arc. However, overly high inductance prevents arc formation just after the breakdown of the gap. When a traditional TIG welding torch is used, cathode spots move violently at the beginning of the low current arc ignition. This results in arc oscillation in the space or even rapid extinguishing. By placing an insulating ceramic tube on the tungsten electrode, the emission of electrons can be limited to the electrode tip. This, in turn, restricts the range of motion of the cathode spots to the tip region. Consequently, low-current arc ignition performance is improved.

Single-Arm Archimedean Spiral Antenna with Broadband Circular Polarization

In this paper, a single-arm Archimedean spiral (SAAS) antenna with broadband circular polarization is investigated. Unlike traditional single-arm Archimedean spiral antenna, the antenna arm consists of a hybrid meandered strip line and a smooth arc strip line. Especially at low frequencies, the meandered strip line significantly improves the circular polarization performance by extending the antenna surface current path. The effects of the meandered strip line on the radiation pattern and axial ratio (AR) are studied in detail. To obtain unidirectional radiation, a metallic cavity is added below the SAAS antenna. The measurement results show that the voltage standing wave ratio (VSWR) is less than 2 from 0.88 GHz to 8.82 GHz, which indicates a wide impedance bandwidth of 1 : 10 is realized. A wide AR bandwidth of 1 : 5 is available, that the measured AR is less than 3 dB from 1.6 GHz to 8 GHz.

Combining convex hull and directed graph for fast and accurate ellipse detection

Detecting ellipses from images is a fundamental task in many computer vision applications. However, due to the complexity of real-world scenarios, it is still a challenge to detect ellipses accurately and efficiently. In this paper, we propose a novel method to tackle this problem based on the fast computation of convex hull and directed graph, which achieves promising results on both accuracy and efficiency. We use Depth-First-Search to extract branch-free curves after adaptive edge detection. Line segments are used to represent the curvature characteristic of the curves, followed by splitting at sharp corners and inflection points to attain smooth arcs. Then the convex hull is constructed, together with the distance, length, and direction constraints, to find co-elliptic arc pairs. Arcs and their connectivity are encoded into a sparse directed graph, and then ellipses are generated via a fast access of the adjacency list. Finally, salient ellipses are selected subject to strict verification and weighted clustering. Extensive experiments are conducted on eight real-world datasets (six publicly available and two built by ourselves), as well as five synthetic datasets. Our method achieves the overall highest F-measure with competitive speed compared to representative state-of-the-art methods.

Experimental analysis and simulation study on turning behavior of pedestrians in L-shaped corridor

In our study, the unidirectional pedestrian flow in an L-shaped corridor is taken as the research object, and the pedestrian turning behavior is studied based on controllable experiments and micro simulations. First of all, three experimental scenarios, namely, no obstacles in the turning zone, diagonal layout of obstacles along the turning zone, and diagonal layout of obstacles in the vertical turning zone, are constructed. Behavioral characteristics such as pedestrian movement trajectory and velocity distribution are analyzed through controllable experiments of pedestrians. Then, a velocity correction model based on the Voronoi diagram is constructed, and the turning rules of pedestrians passing through a 90-degree L-shaped curve are embedded in the model. Finally, simulation research is conducted on the scene with both obstacles and asymmetric L-shaped corridors as well as the scene with neither of them to simulate and reproduce the turning behavior of pedestrians, and analyze the distributions of pedestrian velocities and individual densities at different stages. The research shows that when pedestrians move in a normal non-panic status, they rarely present disorderly behavior and always approach to the inside of the corner of the L-shaped corridor. In the turning area, pedestrians always follow their original moving mode to pass through the corner like a stable arc. And in the process of moving, pedestrians do not move in a straight line, but keep shaking back and forth for zipper effect. Besides, in the process of turning, the longer the distance from the center of the corner, the longer the distance of the pedestrian around the arc will be. And the L-shaped corridor can be divided into vertical straight area, transition area, turning area, and horizontal straight area. When pedestrians pass through the turning walking area, the “invisible bottleneck” phenomenon and the “curved triangle idle area” phenomenon can be observed. Besides, the streamline compression and multiple rows of pedestrian track clusters can be seen in the region. According to the characteristics of pedestrians walking through the L-shaped corridor, the turning rules of pedestrians are made, and the scene with both of obstacles and asymmetric L-shaped corridor as well as the scene with neither of them is simulated. Then, through the pedestrian simulation by using our model, the turning behavior of pedestrians passing through curve like a smooth arc can be effectively reproduced. Moreover, the “invisible bottleneck” phenomenon and the “curved triangle idle area” phenomenon in the turning walking area can be seen in the simulation. At the same time, when the pedestrian flow passes through the four areas of the L-shaped corridor successively, the velocity distribution is consistent with the experimental data of the pedestrian, showing an increasing-decreasing-increasing “wavy” change characteristic. The simulation model is also used to simulate the local density change of pedestrians due to the turning behavior, which verifies the unity of pedestrian velocity and local density change. The cognition of invisible bottleneck is helpful in rationally utilizing and designing the L-shaped corridor turning area.

Semimeander Crossing Number of Knots and Related Invariants

The minimum number of crossings among all of the diagrams of a knot K composed of at most k smooth simple arcs is called the k-arc crossing number of K. This number is denoted by crk(K). The 2-arc crossing number is also called the semimeander crossing number. The article studies connections of the k-arc crossing numbers with the classical crossing number cr(K) of K. It is proved that for each knot K, the following inequalities are fulfilled: $$ {\mathrm{cr}}_2(K)\le {\sqrt[4]{6}}^{\mathrm{cr}(K)} $$ and $$ {\mathrm{cr}}_k(K)\le {\mathrm{cr}}_{k+1}(K)+2\frac{{\left({\mathrm{cr}}_{k+1}(K)\right)}^2}{{\left(k+1\right)}^2}. $$

Trajectory planning and motion control of full-row seedling pick-up arm

Frequent start-stops of automatic seedling transplanters would lengthen the seedling picking time due to alternating movement of the motor, and cause positioning errors and frequent motor vibrations when starting the machine. To solve these problems and ensure the pick-up continuity of automatic transplanters, in this study the smooth circular arc interpolation algorithm and the least square method for multinomial curve fitting were used to conduct the trajectory planning of automatic transplanter based on the movement of the pick-up arm of the transplanter. Velocity and time curves were fitted in segments to acquire motion control parameters and further tracking control was conducted. The mathematical model of the control system was established using Simulink, and simulation analysis and system debugging test were performed. Experiments show that the trajectory curves obtained by MATLAB’s data processing can realize the continual and smooth motion trajectory of the pick-up arm; stepper motor velocity control can effectively track the planning curve and improve the seedling pick-up efficiency. The pick-up and pushing time of each motion of the planned plug seedling transplanter reduced by 1.0678 s and the start-stop times reduced from 6 to 1, which solved the frequent motor vibrations when starting the machine and improved the stability of the system. In addition, overstep and out-of-step of the motor at the start-stop moment were avoided and displacement error was reduced. Keywords: trajectory planning, motion control, motion trajectory simulation, transplanter, stepper positioning DOI: 10.25165/j.ijabe.20201303.5264 Citation: Ren L, Wang N, Cao W B, Li J Q, Ye X C. Trajectory planning and motion control of full-row seedling pick-up arm. Int J Agric & Biol Eng, 2020; 13(3): 41–51.

Times of Fraud

A scientist’s career is not a smooth arc but rather a series of targets and deadlines, some more necessary than others. Several forms of research misconduct are specific to and incentivized by such deadlines, making a fine-grained understanding of those professional ecologies a necessary step toward preventing misconduct.

Trajectory planning and motion control of full-row seedling pick-up arm

Frequent start-stops of automatic seedling transplanters would lengthen the seedling picking time due to alternating movement of the motor, and cause positioning errors and frequent motor vibrations when starting the machine. To solve these problems and ensure the pick-up continuity of automatic transplanters, in this study the smooth circular arc interpolation algorithm and the least square method for multinomial curve fitting were used to conduct the trajectory planning of automatic transplanter based on the movement of the pick-up arm of the transplanter. Velocity and time curves were fitted in segments to acquire motion control parameters and further tracking control was conducted. The mathematical model of the control system was established using Simulink, and simulation analysis and system debugging test were performed. Experiments show that the trajectory curves obtained by MATLAB’s data processing can realize the continual and smooth motion trajectory of the pick-up arm; stepper motor velocity control can effectively track the planning curve and improve the seedling pick-up efficiency. The pick-up and pushing time of each motion of the planned plug seedling transplanter reduced by 1.0678 s and the start-stop times reduced from 6 to 1, which solved the frequent motor vibrations when starting the machine and improved the stability of the system. In addition, overstep and out-of-step of the motor at the start-stop moment were avoided and displacement error was reduced. Keywords: trajectory planning, motion control, motion trajectory simulation, transplanter, stepper positioning DOI: 10.25165/j.ijabe.20201303.5264 Citation: Ren L, Wang N, Cao W B, Li J Q, Ye X C. Trajectory planning and motion control of full-row seedling pick-up arm. Int J Agric & Biol Eng, 2020; 13(3): 41–51.

Zigzags and Spirals in Boundary-Value Problems

The notice is dealing with contour integrals over non-smooth paths and their applications for solving of boundary-value problems. There is established that solvability of the Riemann boundary-value problem on non-smooth arc essentially depends on the type of its non-smoothness: on a zigzag-like arc we obtain the same picture of solvability as on smooth arcs, but on spiral-like arcs the number of solutions depends on geometry of the spiral.

Dirichlet Type Problems for First Order Strictly Hyperbolic Systems with Constant Coefficients in a Two-Dimensional Domain

We consider a first order strictly hyperbolic system of four equations with constant coefficients in a bounded domain with piecewise boundary consisting of eight smooth noncharacteristic arcs. In this domain, we consider boundary value problems with two linear relations between components of the solution and show show that these problems are uniquely solvable under certain assumptions.

On existence of a smooth arc without bifurcations joining source-sink diffeomorphisms on 2-sphere

In this paper we construct a smooth arc without bifurcation points joining source-sink diffeomorphisms on the two-dimensional sphere.