Asymmetric Bridge Research Articles

Spontaneous Release of Metalloradicals and Coordinatively Unsaturated Species in Asymmetric Iridium Dimers to Promote C-N Bond Formation

An unusual iridium dimer 1, [(4-cpbo)Ir(μ-Cl)(μ-O)Ir(4-cpbo)] (4-cpbo = 4-chlorophenylbenzoxazolato-N,C2), was obtained by the oxidative addition of oxygen and reductive elimination of chlorine from a precursor [(4-cpbo)2Ir(μ-Cl)]2. This iridium dimer 1 has a metastable structure with an asymmetric bridge, can spontaneously release metalloradicals and coordinatively unsaturated species in solution at room temperature, and exhibits high catalytic ability for synthetic applications.

Coupled Indirect Torque Control and Maximum Power Point Tracking Technique for Optimal Performance of 12/8 Switched Reluctance Generator-Based Wind Turbines

Maximum power point tracking (MPPT) techniques for wind turbines have a significant effect on renewable energy production. Therefore, the association of the indirect torque control of the switched reluctance generator (SRG) with the wind turbine considering the MPPT technique has been developed in this work. The proposed strategy has a great impact on the production of renewable energy using an SRG machine. The main steps to achieve the object of this work are: First, the wind turbine was modeled and simulated according to the MPPT. In the second step, the indirect torque control strategy, based on the hysteresis current control for SRG 12/8, was realized. This was undertaken using a proportional integral regulator and the hysteresis controller for the torque in order to obtain the appropriate switching based on an asymmetric bridge converter. Moreover, the SRG has high nonlinear characteristics. Thus, the modeling results of this kind of machine are obtained by the use of the finite element method, with its dynamic study performed by the unique estimation of the electromagnetic torque in its generator mode functioning. Finally, the indirect torque control technique of the SRG has also been associated with the MPPT technique to maximize the efficiency power coefficient. The obtained results approve and validate the efficiency of a proposed MPPT of the wind turbine associated with the SRG. This illustrates, simultaneously, the remarkable effects of the turn-switching angles on the operating performances and the high quality of the produced energy. The importance of the effect of varying the turn-switching angles is also presented and discussed.

Design and performance assessment of a novel self-anchored pedestrian suspension bridge

Conventional suspension bridge systems generally adopt a symmetrical layout, which has limited applicability in asymmetric urban terrain. However, the span capacity of the asymmetric bridge system is not as good as that of the conventional suspension bridge. Therefore, under the constraints of limited space, it is very urgent to design a new asymmetric pedestrian bridge with a strong crossing ability on the complex asymmetric terrain of the city. However, the design faced two challenges. (1) Because of the asymmetry of the structure, the cable balance equation and calculation theory of the new bridge need to be redetermined; (2) Because of the restriction of terrain conditions, it is necessary that optimize the preliminary design of the new bridge to achieve better mechanical properties. To address above problems, a new self-anchored continuous steel box girder composite system is proposed for use in suspension footbridges. This system uses connectors to reliably connect the suspension, main girders, and pylons. The continuous beam structure is used in the side span of the pedestrian bridge and the cable-stayed beam composite system is used in the main span. Therefore, the mechanical behavior of the structure is complex. To investigate the mechanical characteristics of the new structural system based on the preliminary conceptual design, the static and dynamic stability of the proposed structural system is comprehensively analyzed. A new force mode is proposed to improve the mechanical properties of the proposed structural system, and the applicability of the tuned mass damper to the new structural system was verified. Finally, an improved multi-objective genetic algorithm (I-MOGA) algorithm is hired to optimize the layout and mechanical properties of the proposed-composite system. The effectiveness and feasibility of the proposed-composite system bridge is verified to design for urban pedestrian bridges in limited terrain. Moreover, I-MOGA is used to optimize the design of the proposed mixed systems and obtain an improved structural layout for a complex pedestrian bridge in terms of forces, stability, and reliability. This study will provide a reference for the design of urban bridges on asymmetric terrain.

Development of Microstrip Decimeter Antennas with Circular Polarization

Modern design variants of microstrip antennas with circular polarization are considered, in which circular polarization is created using single-point and two-point power supply. To manufacture the studied antenna model with circular polarization, the simplest form of the antenna was chosen; the one with a radiator in the form of a continuous circle, which is powered by a two-point scheme. With regard to use in intra-object telemetry systems, the frequency of operation range of 640 ... 650 MHz was chosen. Two options for a two-point power supply of such an antenna were studied - with the help of a symmetrical and asymmetric square strip bridge. Calculation, coordination and tuning simulation of power divider variants were performed. As a result, the manufactured layout of the first antenna design turned out to be three-layered, the second - two-layered. The technique for creating antennas includes an estimated calculation of geometric dimensions, which was further refined using computer simulation in the CST Microwave Studio program. Frequency tuning of the completed antenna layouts is carried out using adjusting teeth along the contour of the round radiator. The study of the created antenna layouts showed better manufacturability and stability of the characteristics of a two-layer structure compared to a three-layer one. Therefore, a two-layer round antenna with a point-to-point power supply was chosen for production. It is designed for telemetric radio channels inside enclosed spaces. The measurements performed showed that the manufactured antenna operates in right-hand circular polarization with an ellipticity factor of 1.2 dB. The standing wave ratio in the operating frequency band of 640…650 MHz did not exceed 1.32, the gain was at least 5 dBi, the width of the radiation patterns in two planes was 95 and 93 angular degrees, respectively. The antenna provides for an operation mode as a transceiver, since the decoupling of the receiving and transmitting paths is carried out due to different polarization, for which it is necessary to connect the second input of the power divider instead of a balanced resistor to the receiving device.

Comparative analysis of converter topologies used in switched reluctance motor for high torque electric vehicle application

Electric Vehicles (EVs) are gaining interest because of the sky rocketing oil prices and increased pollution level in major cities across the world. Almost all EV motors need rare earth magnet which are in limited supply. In order to reduce this dependency, EVs are looking for magnet free motors. One of the alternatives gaining significant mindshare across industry is Switched Reluctance motor (SRM). SRM largely satisfies all the requirements of EV. However, its performance is mainly dependent on converter and controller topology. This paper critically analyses the various parameter of SRM during dynamic loading condition like speed, torque ripple and current, using various converter topologies. Analysis of 60 kW, 4 phase SRM for EV application has been presented with mid-point converter and asymmetric bridge converters along with the proportional plus integral (PI) hysteresis controller. Results shows that asymmetric bridge converter provides enhanced performance for EV application.

Reasonable completed state evaluation for hybrid cable-stayed suspension bridges: An analytical algorithm

Hybrid cable-stayed suspension bridges have broad application prospects due to their superior spanning ability, excellent overall stiffness, and economical efficiency, which outperform other long-span bridges. An analytical approach is proposed to determine the reasonable completed bridge state of hybrid cable-stayed suspension bridges in the paper. The specific steps are as follows: Firstly, the vertical supports offered by some stay cables and hangers in the main span to the main beam are estimated by assuming a continuous beam on multi-point rigid supports. For regions where both stay cables and hangers are used, the ratio of hanger force to the vertical force in the stay cable is assigned manually. Next, according to the assumption that the horizontal component force exerted by the main cables on both sides of the bridge tower and each pair of stay cables on the bridge tower are equal, the configuration and the internal force of the main cables and the stay cables are determined using the multi-segment catenary theory. The vertical forces exerted by the main and stay cables on the towers are summed up to estimate the axial force and strain acting at each position of the tower. In the side spans, the difference between the vertical support reaction in the continuous beam on multi-point rigid supports and the vertical force in the stay cable is used to calculate the weight of ballast of the main beam. The weight of ballast is apportioned as a uniformly distributed load acting on no more than three segments. The horizontal forces exerted by the stay cables on the main beam are summed up to estimate the axial force and strain acting at each position of the main beam. Finally, the analytical data of the full bridge are obtained as inputs of the finite element model. These data include the node coordinates and internal forces of the main cables, stay cables, towers, and the main beam. The calculation results obtained by the analytical method can be used for the preliminary design of hybrid cable-stayed suspension bridges. The proposed analytical algorithm can quickly solve the reasonable completed bridge state without complex adjustment of cable forces. It has the benefits of simplicity, high accuracy, and a clearly defined physical meaning. Finally, we verify the reasonability and effectiveness of the proposed analytical method in an asymmetric hybrid cable-stayed suspension bridge with a main span of 1400 m.

Fragmentation of inviscid liquid and destination of satellite droplets

The breakup process of the inviscid liquid bridge sandwiched between two coaxial and equal-sized rods is investigated by tracking its profile. Here, the focus is on the quasi-static profile of the liquid bridge close to rupture and its influence on the subsequent dynamic breakup behaviors. With the increasing distance between the two rods, the profile of the liquid bridge close to rupture undergoes a transition from symmetry to asymmetry. We found there exists a critical slenderness above which the liquid bridge will be asymmetric and present a profile that can be well fitted by one cycle of the sine wave. It is demonstrated both experimentally and theoretically that the ratio of the length of the bridge to its equivalent radius, defined as geometric mean of the radii at the peak and trough of the bridge, is always 2π for the asymmetric bridge close to rupture. Different with the symmetric evolution of the short bridge, the long asymmetric bridge pinches off first from the side near the bigger sessile drop and then from the other side, which endows the satellite droplet with a lateral momentum, resulting in the satellite re-collected by the sessile drop. The influence of the slenderness on the time interval among the asymmetric pinch-off, velocity, destination, and size of the satellite was investigated. A scaling law was proposed to describe the relationship between the lateral momentum of the satellite and the time interval between two pinch-off. This work is expected to benefit the utilizing or suppressing the satellite in practice.

Investigation on Voltage Boosting Technique in Four Phase SR Motor Drive with Front End Converter

ABSTRACT In this work, a quasi-impedance source (QIS) converter is employed as a front-end converter for four-phase switched reluctance (SR) motor drive. The QIS converter is used for dc-link voltage boosting and to enhance the dynamicperformance. The proposed converter can increase the power output in each stage, by increasing the excitation voltage and controlling based on the drive specifications. The demagnetisation terminal is separated from the excitation terminal, and then the voltage is increased further to achieve the quick commutation. Therefore, with the proposed converter, the SR motor can operate with higher voltages at each interval to reach the end goal of faster excitation and commutation. Thus, it eliminates the production of negative torque and reduces the torque ripple. Initially, the steady-state characteristics have been analyzed with the classical asymmetric bridge (CAB) converter and the proposed converter. According to the steady-state characteristics, the proposed converter can provide higher torque and increased power output than the CAB converter. The effectiveness of the proposed converter is validated in a MATLAB/Simulink environment and compared with the CAB converter. Finally, the experimental response is tested using Xilinx SPARTAN 6 FPGA processor and compared with the simulation results.

Unipolar sinusoidal current excited switched reluctance motor control based on a 3D space vector modulation

This paper reports on a novel unipolar current excited control scheme for the asymmetric bridge converter (ABC)-based switched reluctance drive (SRD), where the 3D space vector modulation under three modes is developed to reduce the total harmonic distribution (THD) and torque ripple. Firstly, two different 3D vector distributions, namely, the small voltage amplitude mode and large mode are presented based on the asymmetric converter. For both distributions, the zero-sequence voltages generated by the effective vectors are considered. Additionally, zero-sequence vectors (1,1,1) and (−1,−1,−1) are no longer treated as null vectors and involved in the control of zero-sequence current. Then, the duty cycles of both two modes are obtained by the combination of the zero-sequence and two adjacent active vectors. Moreover, based on the large modulation mode, a novel method combined with the small mode is proposed to further optimise the switching costs and torque ripples. The effectiveness of the proposed modes is verified through the simulation in MATLAB and the experiment on a dSPACE-1103-based prototype. Compared with the conventional switched reluctance motor vector control, the proposed scheme delivers better performances of THD, efficiency and torque ripple reduction.

Wind-Induced Response Analysis for a Fatigue-Prone Asymmetric Steel Arch Bridge with Inclined Arch Ribs

Steel arch bridges with inclined arch ribs under strong wind fields are prone to fatigue damage due to the stress concentration at the position of hanger connections. Therefore, it is essential to perform the wind-induced response analysis for specified shape hangers, such as inclined hangers, to determine the stress distribution and corresponding influencing factors. In this study, wind-induced response analysis for a fatigue-prone asymmetric steel arch bridge with inclined arch ribs is performed by the numerical simulation approach. The investigated bridge hangers’ models are established by using the COMSOL Multiphysics software. The wind-induced stress of the bridge hangers under different wind directions is obtained based on the finite element method. The influential factor of the stress distribution of the bridge hangers on both the windward side and the leeward side is discussed. In addition, the stress peaks of the long hanger and short hanger are achieved for further fatigue analysis. This paper provides a reference for determining the critical fatigue-prone position of an asymmetric steel arch bridge with inclined arch ribs.

High-Efficiency Directional Ejection of Coalesced Drops on a Circular Groove.

Coalescence-induced drop jumping has received significant attention in the past decade. However, its application remains challenging as a result of the low energy conversion efficiency and uncontrollable drop jumping direction. In this work, we report the high-efficiency coalescence-induced drop jumping with tunable jumping direction via rationally designed millimeter-sized circular grooves. By increasing the surface-droplet impact site area and restricting the oscillatory deformation, the energy conversion efficiency of the jumping droplet reaches 43.5%, 600% as high as the conventional superhydrophobic surfaces. The droplet jumping direction can be tuned from 90° to 60° by varying the principal curvature of the circular groove, while the energy conversion efficiency remains unchanged. We show through theoretical analysis and numerical simulations that the directional jumping mainly originates from reallocation of droplet momentum enabled by the asymmetric liquid bridge impact. Our study demonstrates a simple yet effective method for fast, efficient, and directional droplet removal, which warrants promising applications in jumping droplet condensation, water harvesting, anti-icing, and self-cleaning.

Dynamics and Seismic Performance of Asymmetric Rocking Bridges

Dynamics and Seismic Performance of Asymmetric Rocking Bridges

Development of a variable‐magnet switched reluctance motor drive

This paper introduces a variable magnet switched reluctance motor (VM‐SRM) drive that can be characterized with adjustable performance. It consists of a switched reluctance (SR) motor with low coercive force (LCF) magnets buried on stator yoke and a modified asymmetric half bridge (AHB) converter. Magnetization level of the LCF magnets is adjusted by injecting a current pulse to a phase winding of the VM‐SRM. The magnetization process does not need any extra coil and provides a simplicity owing to modified AHM converter. Possible magnetic saturation that limits the magnetization level is overcome by injecting current pulses to two phase windings at the same time. Thus, LCF magnets can be used with their full capacity. The presented analysis results demonstrate that proposed VM‐SRM drive provides a variable performance and might be a candidate for future variable speed applications. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

A Study of Hysteresis Reduction of Small AC Magnetic Field Modulated Tunneling Magnetoresistive Sensor

In this study, a hysteresis reduction technique for tunneling magnetoresistive (TMR) sensor for low magnetic field sensing is proposed, where a small ac modulation magnetic field is applied. The magnetic tunnel junctions (MTJs) were connected into an asymmetric Wheatstone bridge to form a sensor, and the output voltage of the TMR sensor was measured using a small ac modulation field and test field along the sensor’s sensing direction. The results showed that hysteresis in the TMR sensor can be effectively reduced to exhibit a linear response. Further, the frequency response of the TMR sensor was studied. Finally, the feasibility of the TMR sensor for low-field detection with small ac modulation was demonstrated.

Fault Diagnosis for Power Transistors in a Converter of Switched Reluctance Motors Based on Current Features

Fault diagnosis technique is necessary for high reliability system. For switched reluctance motor, asymmetric half bridge converter is the most commonly used. The transistor is the most fragile component in converters. To the transistor in asymmetric half bridge converter, a fault diagnosis method is proposed in this paper. When faults of transistors occur, the conducting loop will be changed. The current slope can reflect the change of the conducting loop. Through reconfiguring current sensors, the sign of the measurements will reverse with the change of the conducting loop. By the current slope and the sign of the measurements, present conducting loop is determined. The changes and the fault types are one-to-one correspondence. Therefore, the fault type is known. Conditions that may lead to misdiagnosis are illustrated and avoided in online execution. Comparisons of the proposed fault diagnosis method and relevant existing methods are made according to the cost, the response speed, the application scope and so on. The proposed fault diagnosis method is demonstrated under all possible fault types of the transistor by simulations and experiments, which validates effectiveness of it.

Effect of Ground Motion Orientation on Seismic Responses of an Asymmetric Stress Ribbon Pedestrian Bridge

The stress ribbon bridge uses ribbon in high tension to transfer loads and exhibits geometric nonlinearity under dynamic earthquake excitations. A typical double‐span asymmetric stress ribbon pedestrian bridge was introduced as a prototype, and nonlinear time history analysis was performed to investigate the effect of ground motion orientation on the structural responses. Non‐pulse‐type and pulse‐type ground motions were considered, and the influence of vertical ground motions was investigated. Numerical results showed that the stress ribbon bridge’s vertical and transverse displacements were sensitive to the excitation of the vertical ground motion. No single orientation led to the most critical values in all response indexes, and the critical orientation was approximately independent of the vertical ground motion. The negative bending moment of the ribbons, the pier top displacement, and the pier base moment at the transverse direction were sensitive to the ground motion orientation. Checking the responses resulting from different directions is necessary for a comprehensive estimation of the seismic performance of the stress ribbon bridge.

Using a comprehensive approach to investigate the interaction between Kinesin-5/Eg5 and the microtubule

Kinesins are microtubule-based motor proteins that play important roles ranging from intracellular transport to cell division. Human Kinesin-5 (Eg5) is essential for mitotic spindle assembly during cell division. By combining molecular dynamics (MD) simulations with other multi-scale computational approaches, we systematically studied the interaction between Eg5 and the microtubule. We find the electrostatic feature on the motor domains of Eg5 provides attractive interactions to the microtubule. Additionally, the folding and binding energy analysis reveals that the Eg5 motor domain performs its functions best when in a weak acidic environment. Molecular dynamics analyses of hydrogen bonds and salt bridges demonstrate that, on the binding interfaces of Eg5 and the tubulin heterodimer, salt bridges play the most significant role in holding the complex. The salt bridge residues on the binding interface of Eg5 are mostly positive, while salt bridge residues on the binding interface of tubulin heterodimer are mostly negative. Such salt bridge residue distribution is consistent with electrostatic potential calculations. In contrast, the interface between α and β-tubulins is dominated by hydrogen bonds rather than salt bridges. Compared to the Eg5/α-tubulin interface, the Eg5/β-tubulin interface has a greater number of salt bridges and higher occupancy for salt bridges. This asymmetric salt bridge distribution may play a significant role in Eg5′s directionality. The residues involved in hydrogen bonds and salt bridges are identified in this work and may be helpful for anticancer drug design.

Experimental Study of Mitigation of Wind-Induced Vibration in Asymmetric Cable-Stayed Bridge Using Sharp Wind Fairings

This paper investigated the aerodynamic response features of an asymmetric cable-stayed bridge. The wind resistance design parameters for judging the response were first determined, afterwards the bridge dynamic characteristics were analyzed for subsequent aerodynamic analysis. The vortex-induced vibrations (VIV) and flutter response at various wind fairing angles were then examined by using a 1:50 sectional model in the wind tunnel test. Finally, a 1:150 full bridge aeroelastic model was employed to explore the aerodynamic stability and characteristics of the whole asymmetric bridge under different wind attack angles in various flow fields. The results show that the sharp wind fairings could reduce the VIV amplitude of the steel box girder cable-stayed bridge to some extent, and the example bridge has examined to have enough flutter stability through sectional and full bridge aeroelastic model wind tunnel tests. Unlike symmetric bridges, the bridge’s maximum displacement of first torsion mode shape is at the closure rather than the mid-span, which is the essential reason to lead this unique vibration feature. The results from the present study could highlight the important effect of structural asymmetry and fairing shape to the wind-induced bridge vibration and hence may facilitate more appropriate wind design of asymmetric cable-stayed bridges.

Power electronic converter topologies for switched reluctance motor towards torque ripple analysis

The power converter circuit plays a vital role in electric drives. The converters performance has a significant impact on the drive performance as well as cost. There are different motors applied in electric drives, this study primarily focused on torque ripple analysis of Switched Reluctance Motor (SRM) drive and its converter topologies. The SRM salient poles have the stator outer side and the rotor inner side, which is different from the other polyphase machines. Although there have been a number of converters for SRM drives through the years, each converter has its own set of benefits and drawbacks. The choice of a converter is dictated by the application, this article includes a comparative analysis of SRM converter topologies, two level converters branches and multi-level converters branches were discussed in detail with schematic diagram. Based on the survey it is found that an asymmetrical bridge converter best suits for Electric vehicle application due to its advantage of reducing fault tolerant, fast demagnetization and regenerative braking capability. This paper presents the study of 10 kW SRM Drive controlled by asymmetrical bridge converter, in three different phase modification mode such as 6/4, 8/6 and 10/8 using MATLAB simulation and the torque ripples are analysed for each case.

Modified PWM Direct Instantaneous Torque Control System for SRM

Torque ripple is a defect of switched reluctant motors. DITC (direct instantaneous torque control) is harnessed to solve the problem as a traditional method, which is superior to TSF (torque sharing function). In this paper, a new controller is proposed with modified hysteresis and PWM in DITC. With the modified algorithm, the torque error will be reduced with PWM in DITC. The proposed algorithm is effective to improve sample and 0 status in a period. The modified algorithm is based on application of zero in the asymmetric half bridge, which is implemented as the buffer zone. In case of big torque error, hysteresis will mitigate error under the characteristic of fast responding. In case of small errors, the modified PWM will solve torque error in the equivalent strategy, which has adopted the essence of the impulse equivalent method. The modified controller is designed to reduce responding time and minimize the torque ripple under the proposed algorithm, which has been designed to harness different functions in different torque errors. Based on final simulation and experimental results, responding speed and reduction of output torque ripple are enhanced effectively.