This paper proposes a new series resonant dc-dc converter with four configurable operation states depending on the input-voltage and output-voltage levels. It suits well for the dc-dc stage of ...grid-connected photovoltaic systems with a wide-input voltage range and different grid voltage levels, i.e., 110/120 V and 220/230/240 V. The proposed converter consists of a dual-bridge structure on the primary side and a configurable half- or full-bridge rectifier on the secondary side. The root-mean-square (RMS) currents are kept low over a fourfold voltage-gain range; the primary-side mosfets and secondary-side diodes can achieve zero-voltage switching on and zero-current switching off , respectively. Therefore, the converter can maintain high efficiencies over a wide voltage gain range. A fixed-frequency pulsewidth-modulated control scheme is applied to the proposed converter, which makes the gain characteristics independent of the magnetizing inductance and thereby simplifies the design optimization of the resonant tank. The converter topology and operation principle are first described. Then, the characteristics, i.e., the dc voltage gain, soft switching, and RMS currents, are detailed before a performance comparison with conventional resonant topologies is carried out. Furthermore, the design guidelines of the proposed converter are also presented. Finally, the experimental results from a 500-W converter prototype verify the feasibility of the proposed converter.
In this paper, a multifunctional active frequency selective surface (MAFSS) is presented based on the switching responses of active components. The proposed structure comprises periodic arrays of ...metallic patterns imprinted on both sides of an FR4 substrate on which p-i-n diodes are embedded with parallel feed networks. The novelty of the design lies in its multifunctional characteristics with independent control of the biasing states (ON/OFF) of the diodes mounted on opposite layers. This leads to four different working states (dual bandpass for OFF-OFF state, single-band absorber for OFF-ON state, single-bandpass for ON-OFF state, and reflector for ON-ON state) being facilitated by the proposed reconfigurable AFSS. Furthermore, the effects of the design parameters and active components on multifunctional responses are extensively analyzed by deriving equivalent circuit models. Even though the topology is polarization sensitive, multiple dividable working functions (transmission, absorption, and reflection) have been realized in single geometry, unlike the earlier reported designs. The proposed structure has also been fabricated, and the measured responses show reasonable agreement with the simulated results under normal incidence. An MAFSS with such diverse characteristics is an essential element for regulating electromagnetic wave propagation in manifold applications.
This study investigates how combination of different stories in a Kresling origami-inspired structure design can improve the desired mechanical characteristics such as fatigue, stability, modal, ...energy analyses, and folding pattern. Because of the possibility of fatigue failure and axial buckling, we provide a crease modeling approach that could improve the mechanical characteristics as well as the folding efficiency. In the first step, we observe the folding pattern of an origami structure design composed of multiple stories. It is shown that every two stories have a similar folding pattern. If the number of stories is odd, the middle one experiences different behavior. In the next step, we employ different heights, length ratios, and rotation directions of stories in the designs to demonstrate how these variations affect origami’s mechanical properties. It is indicated that the structure with the same story height can enhance the life cycles while decreasing the stories’ height can postpone the buckling failure. Although the stability of the structure can be compromised if there are more stories with greater length ratios, it can achieve the highest total strain energy level in the folding operation and improves fatigue life. Furthermore, it is determined that the stories’ rotation does not affect the folding process. In the reverse rotation, the stability is decreased substantially, but the life cycles are slightly reduced.
•If the number of stories is odd, the middle one is independent in folding.•The structure with the same story height postpones fatigue failure.•Decreasing the stories’ height increases the buckling load.•The maximum strain energy can be achieved when stories have a greater length ratio.•The reverse-rotated structure’s stability decreases substantially.
Architectural windows that smartly regulate the indoor solar irradiation are promised to economize the building energy consumption. Here, we demonstrate a method for adaptive, broadband, and highly ...efficient solar modulation for energy-efficient smart windows through active plasmonics in reconfigurable structures. We develop a kirigami-inspired elastomer containing plasmonic vanadium dioxide (VO2) nanoparticles, in which the geometrical transition and the temperature-dependent localized surface plasmon resonance (LSPR) present dominant controls in ultraviolet-visible and near-infrared regions, respectively. The active LSPR control, via stretch-induced local dielectric changes is mitigated on reconfigurable metamaterials because of their unique strain distributions. This method demonstrated a desirable property in energy-efficient smart windows facilitating improved solar energy modulation (37.7%), surpassing the best-reported modulation in passive and transparent VO2 thermochromism systems. This first attempt to integrate the plasmonics and reconfigurable structures may inspire developments in smart windows, building energy economization, as well as fundamental studies of plasmonic controls in metastructures.
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•The design of smart windows based on plasmonic-enhanced reconfigurable elastomer•A solar modulation of ΔTsol = 37.7% on VO2-based thermochromic films•The strain- and thermal-responsive localized surface plasmon resonance•A facile method for adaptive, broadband, and highly efficient optical modulation
Thermochromic windows can smartly modulate the indoor solar irradiation, leading to energy saving for architectural heating and cooling systems. Adaptive solar energy modulation with a high on-off ratio is the key; enhancing the performance, however, is an inevitable challenge as it is limited by materials’ intrinsic properties. Conventional improvement methods are to develop the multilayer, porosity, composite, grid, and biomimetic structures. Herein, we are thinking out of the box by integrating the active plasmonic VO2 nanoparticles in kirigami-inspired reconfigurable elastomers to achieve adaptive, broadband, and highly efficient solar modulation. The smart window demonstrates a high solar energy modulation (ΔTsol = 37.7%), outperforming those methods, and has exhibited superior performance in Houston, Hong Kong, and Madrid.
Thermochromic windows can smartly modulate the indoor solar irradiation, leading to energy saving for architectural heating and cooling systems. Herein, we integrate the active plasmonic VO2 nanoparticles in kirigami-inspired reconfigurable elastomers to achieve adaptive, broadband, and highly efficient solar modulation. The smart window promises a UV-visible-NIR traverse state in cold days and a UV-visible-NIR blocked state in hot days to reduce the architectural heating and cooling energy consumption.
In this paper, a novel concept of the adaptive vibration isolator is presented. The proposed adaptive isolator is based on the thin-walled Yoshimura-patterned tube, which is able to reconfigure its ...shape to tune the stiffness. Multiple numbers of reconfigurable modules compose the proposed vibration isolator; thus, the force transmissibility of the isolator can be adjusted by systematic reconfiguration of the modules to show the best performance for the subjected vibration environment. The paper presents the analytical and experimental analysis of the force transmissibility of the proposed adaptive vibration isolator. The dynamic equation of the motion for the isolator system is established, and the force transmissibility is analyzed for the various configuration that a single design can have. The prototype of the proposed adaptive isolator is manufactured with an embedded actuation mechanism for reconfiguration. The performance of the isolator is experimentally confirmed through the vibration test of the fabricated prototype. Both the results of the analytical and the experimental investigation well demonstrate the adaptive characteristics of the proposed isolator concept.
In this paper, a dual band graphene square patch antenna is designed for operation in 4 THz and 7.75 THz. The main idea of this paper is partitioning the graphene patch into pieces to have more ...degrees of freedom to reconfigure the polarization of antenna. Antennas polarization is controlled by partitioning the patch into 9 elements, resizing them and changing their chemical potential. The main operation mode of antenna has linear polarization in its boresight. Circular polarization is reached in five different modes; each mode has its own advantages. The main purpose is to achieve minimum efficiency loss modes among all chemical potential combination modes. Each mode has two separate types, one type will have RHCP and the other one will have LHCP, switching types will change RHCP to LHCP or LHCP to RHCP.
In this letter, a novel printed frequency-reconfigurable microstrip square slot antenna for switchable Bluetooth, WiMAX, and WLAN applications is presented. The proposed antenna has a small size of ...20 × 20 mm 2 in order to be able to cover lower frequencies; as for Bluetooth applications, miniaturization techniques such as modification of the ground plane and inserting an adjustable backplane cross-shaped sleeve have been employed. Moreover, by implementation of p-i-n diodes within the antenna structure, switchable frequency responses are achieved. The presented antenna has a small size while providing suitable switchable radiations at 2.3-2.51 GHz (BW = 8.7%) Bluetooth, 3.35-3.75 GHz (BW = 11.2%) WiMAX, and 4.95-5.53 GHz (BW=11%) WLAN.
In this letter, a dual-band tunable bandstop frequency selective surface (FSS), which is capable of exhibiting independent tuning for the top and bottom layers, has been presented. The proposed ...design comprises periodic patterns of cross diagonals printed on the opposite sides of a thin substrate, where the varactor diodes are mounted symmetrically. Both the layers use novel biasing circuitries to independently regulate their corresponding responses, thereby resulting in two tunable stopbands. Each of these two stopbands has wide bandwidths (having fractional bandwidths of 110.71%) as well as offers large tuning ranges of 128.21% (with respect to their center frequencies). Furthermore, the geometry is low profile, polarization insensitive, and angularly stable. A prototype has been fabricated, and the varactors have been modulated through parallel biasing. The experimental results show a reasonable agreement with the theoretical responses, thus confirming the proposed concept.
In today's highly competitive industrial market, reconfigurable manufacturing systems (RMSs) have been invented for diverse products, high quality and quick manufacturing. However, the changeable ...system structure brings new challenges for multi-unit maintenance scheduling. Thus, this research attempts to develop a novel dynamic maintenance strategy for those reconfigurable structures. In the machine-level decision-making, dynamical maintenance intervals are scheduled according to individual machine degradation. For responding rapidly to various system-level reconfigurations, RMS characters and maintenance opportunities are comprehensively considered. Then, a reconfigurable maintenance time window (RMTW) method is proposed to make real-time schedules for system-level opportunistic maintenance. This reconfiguration-oriented maintenance policy is demonstrated through the case study in a hydraulic steering factory. It is concluded that the proposed methodology can efficiently achieve rapid responsiveness and cost effectiveness for reconfigurable manufacturing systems.
•A reconfiguration-oriented maintenance policy is developed for newly reconfigurable structures.•Reconfigurable manufacturing systems face open-ended diverse reconfigurations.•Changeable structures and maintenance opportunities are comprehensively considered.•Reconfigurable maintenance time window makes real-time opportunistic maintenance schedules.•RMTW methodology can efficiently achieve rapid responsiveness and cost effectiveness.
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