Equal Angles Research Articles

Design and simulation of an asymmetrical 23-level inverter with modulation Techniques

For medium voltage, high power regulation the Multilevel Inverters (MLI) are attracting industry and academic researchers. MLI generates the desired output in the form of stepped waveforms with reduced harmonics. The MLI is expected to be realised using a variety of traditional topologies. Traditional MLIs have the disadvantage of requiring additional components, which increases the complexity of gate pulse production. As a result, MLI's overall costs will rise. This research proposes a hybrid topology to alleviate these drawbacks. With the increase in the number of steps in output voltage, the number of dc sources, power switching devices, converter cost, and space required is significantly reduced compared to typical MLIs. The design and simulation of a hybrid converter using several types of PWM approaches are covered in this work. This hybrid converter combines a T-Type structure and a half bridge inverter that is back-to-back connected. The proposed construction is designed and simulated by MATLAB Simulink software. The proposed 23 level inverter circuit is designed and simulated by Equal phase angle modulation technique and half height modulation technique, THD is compared.

Angles of arc-polygons and Lombardi drawings of cacti

We characterize the triples of interior angles that are possible in non-self-crossing triangles with circular-arc sides, and we prove that a given cyclic sequence of angles can be realized by a non-self-crossing polygon with circular-arc sides whenever all angles are ≤π. As a consequence of these results, we prove that every cactus has a planar Lombardi drawing (a drawing with edges depicted as circular arcs, meeting at equal angles at each vertex) for its natural embedding in which every cycle of the cactus is a face of the drawing. However, there exist planar embeddings of cacti that do not have planar Lombardi drawings.

Study of the Enhanced Efficiency of Crystalline Silicon Solar Cells by Optimizing Anti Reflecting Coating using PC1D Simulation

In this paper, simulation of a mono crystalline silicon solar cell was done using PC1D software. The impact of different solar cell parameters, with their effects on power and efficiency, has been investigated. It is seen that the textured surface reduces reflection and increases the efficiency of the solar cell at least 2–3%. From the simulation, it is seen that the optimum value of p-type doping concentration 1 × 10^16 cm^−3, n-type doping concentration 5 × 10^18 cm with pyramid height of 2–3 μm and equal angles of 54.74 degrees produces the best result in simulation. An anti-reflective coating with a refractive index of 1.38 and a thickness of 84 nm is considered optimal. By optimizing the effective parameters, a solar cell with an efficiency of 24.45% was achieved through simulation. For a p-type mono crystalline silicon wafer, with an area of 10 × 10 cm^2 and a thickness of 200 μm, initial simulation shows a 24.45% efficient solar cell.

Deformation mechanism finite element analysis and die geometry optimization of magnesium alloys by equal channel angular processing

Magnesium alloys are one of the highly promising structural metals. hcp structure makes it less plastic at room temperature, which greatly limits the development of magnesium alloys. The problem of poor plastic deformation of magnesium alloy can be solved by grain refinement methods, and equal channel angle pressing is one of the more effective methods in grain refinement. In this paper, two-dimensional dynamic simulation of equal channel angle pressing of magnesium alloy is carried out by using finite element software DEFORM F2™. The deformation of magnesium alloy with different of die angles and die corner angles was analyzed. The results show that in the main deformation zone, when the die angles are different, the deformation of the workpiece in the horizontal direction is very uniform. However, in the longitudinal direction of the workpiece, the larger the die angle is, the more uniform the workpiece deformation is. The die corner angle has no significant effect on the uniformity of workpiece deformation in the longitudinal direction, but it has an effect on the dead zone area and workpiece warpage. The dead zone area and workpiece warpage increase with the increase of die angle.

Optimal Calibration Method of PIGA’s Orthogonal Poses for Gravity Field Testing

With the increasing requirements for accuracy of pendulous integrating gyroscopic accelerometer (PIGA), the key to the development of accuracy of PIGA is the advanced calibration methods. This paper focuses on the calibration method of the main error coefficients of PIGA on the indexing head table. The precise input accelerations and angular velocities are deduced and the complete error calibration model is established based on the corresponding coordinate systems. Then, the orthogonal 4‐pose calibration method of dual PIGAs is proposed to identify the harmonic term coefficients of angle error. The calibration uncertainty and efficiency of equal angle sequency and equal acceleration sequency calibration schemes are analyzed. Then, the optimal calibration method is proposed and the complete test process is designed, which can accurately and efficiently calibrate PIGA by compensating with the angle error and combining the two different sequency schemes. Simulation results show that 22‐position equal acceleration sequency scheme can calibrate bias and scale factor more accurately and the test cost of equal angle sequency scheme is lower. After compensation with angle error, the magnitudes of calibration uncertainties are decreased from 10−6 to 10−7 and the maximum value of relative fitting accuracy is decreased from 6.6 × 10−5 to 2.7 × 10−5 g by the proposed 22‐position optimal calibration method.

Spur gears with contact ratio less than unity

The objective of this research is to evaluate the design of a pair of spur gears and another analogous pair with a contact ratio of less than unity. Considering two pairs of normalized gears with equal diametral pitches and pressure angles, as well as equal pitch radii in their driving gears and equal pitch radii in their driven gears. For the first pair of gears with normalized tooth numbers, the contact ratio greater than unity es obtained. For the second pair of gears, the number of teeth is proportionally reduced, consequently obtaining a contact ratio of less than one. For both pairs, the maximum von Mises stresses are obtained using the finite element method. The pairs are compared qualitatively and quantitatively. This work contributes with novel elements of judgment for a better decision making of the industrialists interested in reducing the problems of normalized spur gears such as noise, abrasive wear, adhesive wear, temperature, and efforts induced by the overlapping relationship between coupled teeth; proposing them a practical solution that will open new avenues of research.

Design and Simulation Analysis of a Flexible Clamping and Conveying Device of a Green Leafy Vegetable Cutting and Bundling Integrated Machine

In order to improve the harvesting production efficiency of green leafy vegetables, this paper designs and simulates the flexible clamping and conveying device of the green leafy vegetable cutting and bundling integrated machine. Through theoretical calculation and 3D modeling, the design optimization of key components is carried out in this paper. The cutter head of the guillotine cutting and throwing device is a wheel cutter type. The throwing blades are axially symmetrically distributed on the cutter head, and the movable blades are radially distributed at equal angles and are located in the middle of the two throwing blades. The electronic control system of the wrapping device uses a pressure sensor to cooperate with the baling device to realize automatic wrapping after baling. In addition, the drive chassis of the machine is a hydrostatic drive system, which is convenient for step-less speed change and automatic control within a certain range. Through the simulation study, it can be seen that the flexible clamping and conveying device of the green leafy vegetable cutting and bundling integrated machine proposed in this paper can meet the industrialization needs of green leafy vegetables.

Influence of predefined angle of attack on piezoelectric energy harvesting from transverse galloping of different bluff bodies

The development of smart Internet-of-Things (IoT) solutions requires sensor nodes to be placed at different locations of monitored structures. Wireless solutions are quite attractive because of their simplicity although requiring for local energy supply. In this context, this study investigates the influences of the predefined angle of attack on the piezoelectric energy harvesting based on transverse galloping of different bluff bodies. The investigation is based on a lumped electro-aero-mechanical model with linear electrical and mechanical properties and nonlinear aerodynamic forces evaluated using the quasi-steady theory. The performances of energy harvesters with six different bluff bodies are analyzed at various predefined angles of attack: four rectangular cross-sections with different width-to-height ratios (i.e., b/d), one trapezium section, and one equal angle section. The main purpose is to understand the sensitivity of various bluff body-based energy harvesters on the predefined angle of attack, and further suggest a bluff body-based energy harvester that is robust to the predefined angle of attack. The results show that the response is quite dependent on the characteristic of the electro-mechanical system and the bluff body cross-section and angle of attack. In all cases, the load resistance should be tuned to maximize energy production. The largest vibration amplitude (i.e., largest power output) is predicted for the rectangular bluff body with b/d = 1.0 at a 0° angle of attack. However, its performances are quite dependent on the angle of attack, resulting in a zero-power output for an angle of attack exceeding 4°. A rectangular bluff body with b/d within 1.62 to 2.5 exhibits a reduced energy production compared with b/d = 1.0 at a 0° angle of attack but better robustness varying the angle of attack. Finally, the trapezium and the angle bluff bodies are not suitable for energy harvesting due to their very high onset velocities within the considered range of angles of attack.

Magnetic Force-Assisted Nonlinear Three-Dimensional Wideband Energy Harvester Using Magnetostrictive/Piezoelectric Composite Transducers.

This paper presents a nonlinear magnetoelectric energy harvester which has the potential to harvest vibrational energy over a wide bandwidth in arbitrary motion directions. Three springs with equal intersection angles are adopted to absorb the multi-directional vibration energy. Magnetic interaction between the magnets and ME transducers allows the nonlinear motion with enhanced harvesting frequency range. Very good agreement is observed between the numerical and experimental open-circuit voltage output frequency response curves. The experimental results show that the harvester can harvest vibrational energy in an arbitrary direction, exhibiting a further bandwidth of 5.2 Hz. This study provides a new solution to effectively use the magnetoelectric energy harvester for multi-directional and bandwidth vibrational energy scavenging in the surrounding environment.

Resistance of Closely Spaced Back‐to‐back Connected Equal Leg Angle Sections

AbstractIn the framework of the European RFCS project ANGELHY, the resistance of built‐up members fabricated from angle sections is studied, amongst others. This paper focusses on the resistance of back‐to‐back connected angle sections. The studied built‐up members are connected through bolted packing plates. Due to the flexibility of this connection, the back‐to‐back connected members do not fully act as a single homogeneous member but the connection stiffness has to be accounted for. However, Eurocode 3 does not provide a clear and generally accepted method for the determination of the buckling resistance of back‐to‐back connected members that do not respect a limit distance of 15imin between the packing plates. This limit is very low and therefore there exists a need of a design method overcoming the limitations. Throughout this paper, a design method will be derived based on a comprehensive numerical study. The numerical model is based on solid finite elements and has been validated with physical tests. Owing to the use of solid elements, it is possible to model explicitly the bolts, the packing plates and all contact regions.

Energetic stability and spatial inhomogeneity in the local electronic structure of relaxed twisted trilayer graphene

We study the energetic stability and the local electronic structure of the general twisted trilayer graphene (TTG) with the top and bottom layers rotated with respect to the middle layer respectively by $\theta$ and $\theta'$. Approximate supercells of the moir\'{e}-of-moir\'{e} superlattices with $\theta$ and $\theta^{\prime}$ within $1^{\circ}\sim 2^{\circ}$ are established to describe the structural and electronic properties of relaxed TTG with the periodic boundary condition. Full relaxation demonstrates that the commensurate TTG with $\theta=\theta^{\prime}$ has the local minimum total energy ($E_{tol}$) at a fixed $\theta$, while $E_{tol}$ first reaches a local maximum and begins to drop with decreasing $\theta^{\prime}$ for $\theta^{\prime} < \theta$. Some regions exhibit enhanced in-plane relaxation in the top and bottom layers but suppressed relaxation in the middle layer and form a hexagonal network with the moir\'{e}-of-moir\'{e} length scale. The stacking configurations with the atoms in the three layers vertically aligned at the origin of the relaxed TTG supercells at $\theta$ around $1.6^{\circ}$ and $\theta^{\prime}$ around $1.4^{\circ}$ have a high density of states (DOS) near the Fermi level ($E_F$), which can reach that of the mirror symmetric TTG with equal twist angles of about $1.7^{\circ}$. In contrast, some other stackings can have rather low DOS around $E_F$. The significant stacking dependence of DOS for some TTG supercells demonstrates that the local electronic structure of TTG can exhibit strong spatial inhomogeneity when the twist angles are slightly away from those of the small supercells with large variations of DOS among different stackings. Moreover, the structural relaxation of TTG plays a crucial role in the high DOS and its strong stacking dependence.

Three dimensional star-like mesoporous nitrogen-doped carbon anchored with highly dispersed Fe and Ce dual-sites for efficient oxygen reduction reaction in Zn-air battery

Metal‑nitrogen‑carbon materials (M-N-C) have attracted much attention due to their low cost, high abundance, and efficient catalytic performance. Nevertheless, Fe-N-C materials are considered the most promising oxygen reduction reaction (ORR) catalysts for replacing noble metals. Ce is chemically active and has many metal valence states, and empty orbitals that can participate in coordination. On this basis, Fe, Ce-codoped catalyst was constructed in this study. The synergistic effect of the dual metal centers was verified, and a Fe, Ce-codoped nitrogen-doped carbon (FeCeNC) with six equal branch angles was proposed. The half-wave potential for the ORR catalyzed by FeCeNC is 0.855 V. As a rechargeable Zn-air battery cathode catalyst, FeCeNC exhibits excellent electrochemical performances, with an open-circuit voltage of 1.427 V, a maximum power density of 169.2 mW cm−2 and a stable cycling time of 80 h, demonstrating an excellent cycle performance.

ANN-based estimation of MEMS diaphragm response: An application for three leaf clover diaphragm based Fabry-Perot interferometer

In this study, an artificial neural network (ANN) based model is developed for MEMS diaphragm analysis, which does not require difficult and time-consuming FEM processes. ANN-based estimator is generated for static pressure response (d) and dynamic pressure response (f) analysis of TLC (three leaf clover) diaphragms for Fabry-Perot interferometers as an example. TLC is one of the unsealed MEMS design diaphragms formed by three leaves of equal angles. The diaphragms used to train ANNs are designed with SOLIDWORKS and analyzed with ANSYS. A total of 1680 TLC diaphragms are simulated with eight diaphragm parameters (3 for SiO2 material, 4 for geometry, and 1 for pressure) to create a data pool for ANN’s training, validation, and testing processes. 80% of the data is used for training, 15% for validation, and the remaining for testing. Only four geometric parameters are used as input in the ANN estimator, and the material parameters are added to the model with an analytical multiplier. Thus, network models that estimate d and f values for all kinds of diaphragm materials are proposed, with a material-independently trained ANN structure. The performance of the ANN model is compared with the empirical equation suggested in the literature, and its superiority is demonstrated. In addition, the d and f parameters of TLC diaphragms designed with five different materials (Si, In2Se3, Ag, EPDM, Graphene) are estimated to be very close to the real ones. By using the proposed method, analyses of TLC diaphragms are quickly performed without the need for time-consuming and costly design and analysis programs.

New dualities in convex quadrilaterals

In [1] de Villiers points out the duality between sides and angles of quadrilaterals. The first objective of this article is make explicit two new dualities in the quadrilaterals. For this we will consider the diagonal segments: if diagonals AC and BD of a quadrilateral ABCD intersect at O, we call the diagonal segments OA, OB, OC, OD. According to [2, pp. 179-188], hierarchical classifications of the convex quadrilaterals are made taking as classification criteria the quantity and position of sides, angles and diagonal segments. In hierarchical classifications the more particular concepts form subsets of the more general concepts. Through classification according to the number and position of equal sides it is possible to define six families: four sides equal, at least three equal, two opposite pairs equal, two consecutive pairs equal, at least one opposite pair equal, at least one consecutive pair equal. In the families two opposite pairs equal and two consecutive pairs equal, the pairs may be equal to each other and then the four sides are equal. So in these two families the possibility DA = AB and AB = BC is excluded. Families analogous to the previous ones can be defined taking as a criterion of hierarchical classification the quantity and position of equal angles or the quantity and position of equal diagonal segments.

Curvature estimates for stable minimal surfaces with a common free boundary

The minimal surfaces meeting in triples with equal angles along a common boundary naturally arise from soap films and other physical phenomena. They are also the natural extension of the usual minimal surfaces. In this paper, we consider the multiple junction surface and show the Bernstein’s Theorem still holds for the stable multiple junction surfaces in some special cases. The key part is to derive the \(L^p\) estimates of the curvature for multiple junction surfaces.

A reflective metasurface for generating dual‐mode dual‐polarized high‐order Bessel vortex beams with equal divergence angle

A single-layer reflective metasurface is proposed in this study to generate dual-mode dual-polarized high-order Bessel vortex beams with equal divergence angle in Ka-band. The metasurface consists of two different subwavelength elements with different polarisations, which are located in the inner disk region and the outer ring region respectively. The inner element, composed of a square ring and a regular octagon, is proposed to achieve a phase response of 360°. The outer element, which consists of a microstrip line and a double W-shaped line, is designed to achieve the phase compensation and polarization conversion simultaneously. Equal divergence angle of different orbital angular momentum (OAM) modes is achieved by theoretically calculating the radii of the inner and outer regions. The metasurface prototype is fabricated and tested at 29 GHz, and the results show that the high-order Bessel beams with +1 mode of x-polarization and +2 mode of y-polarization are successfully generated. This work provides a simple and practical method to generate dual-mode dual-polarized high-order Bessel vortex beams for high-capacity OAM communications.

Cold-Formed Steel Equal Angles with Complex Edge Stiffeners under Axial-Compression Laboratory Testing, Numerical Simulation, and Design

This paper investigates the axial-compression capacity of cold-formed steel (CFS) equal angle sections with complex edge stiffeners. Both experimental and numerical analyses were carried out. In total, 10 tests were carried out and the results are presented in this paper. Preceding to compression tests, the material properties were determined and initial geometric imperfections of all the test specimens were measured. From the results of compression tests, the specimens were all susceptible to flexural buckling. A numerical model was created using the finite-element (FE) software ABAQUS version 6.11. The results of finite-element analysis (FEA) substantiated with the experimental results. The FE models were found to accurately predict the experimental behavior. Thus, the validated FE models were used for a parametric study to analyze the effect of slenderness ratio and the orientation of edge stiffeners on the axial capacity. The axial strengths obtained from parametric study were compared with the design strengths calculated by the direct strength method (DSM) from the American Iron and Steel Institute (AISI) specification. Upon comparison, it was found that the axial strengths calculated based on the current DSM are overconservative by 58% on an average.

The Pentagonal Pizza Conjecture

The pentagonal pizza conjecture says that it is impossible to cut a pentagonal pizza into eight slices by four concurrent straight lines that make four equal smaller angles alternating with four equal bigger angles, and such that all smaller angle slices have the same area and all bigger angle slices have the same area. The conjecture is proved to be true when the pizza is shaped as an ellipse, triangle, or quadrilateral, except for a square, and is proved not true for all n-gons, where . These results are closely related to the first theorem of convex geometry, Zindler’s theorem of 1920. Similar results are proved for perimeter instead of area.

21 LEVEL HYBRID SINGLE T TYPE DOUBLE HBRIDGE MULTILEVEL INVERTER TOPOLOGY

Inverters are the power electronic circuits which transfers power from direct current source to alternating current load. It manages voltage, current and frequency of the signal. Inverter comprises of various applications like adaptable velocity AC motor drives, uninterruptible power supply, running appliances of AC used in automobile battery, etc. The simulation of 21 level multilevel inverter is taken out using MATLAB/Simulink and the simulated circuit model is discussed. The input DC voltage sources for inverter are assigned with the magnitudes 96V, 96V and 96V satisfying the ratio 3:3:3 for the frequency of 50 Hz and the results analyzed for resistive load and inductive load with fundamental switching pattern. The circuit is simulated with half height method and fundamental equal phase angle method and the THD is calculated and compared.

Plasma-Beam Processing of Tools Made of SiAlON Dielectric Ceramics to Increase Wear Resistance When Cutting Nickel–Chromium Alloys

This research aimed at an increase in wear resistance of round cutting plates manufactured with SiAlON dielectric ceramics through deposition of wear-resistant coatings. To increase effectiveness of the coatings, their adhesion was improved by the removal of defective surface layers from the cutting plates before the deposition. As the depth of caverns and grooves appearing on the cutting plates due to manufacturing by diamond grinding reached 5 µm, a concentrated beam of fast argon atoms was used for the removal of defective layers with a thickness exceeding the depth of caverns and grooves. At the equal angles of incidence to the front and back surfaces of the cutting wedge amounting to 45 degrees, two-hour-long etching of rotating cutting plates provided removal of defective layers with thickness of ~10 µm from the surfaces. After the removal, the cutting edge radius of the plates diminished from 20 to 10 µm, which indicates the cutting plates’ sharpening. Wear-resistant TiAlN coatings deposited after the etching significantly improve the processing stability and increase wear resistance of the cutting plates by not less than 1.7 times.