Silveirinha and Engheta have recently proposed that electromagnetic waves can tunnel through a material with an electric permittivity (epsilon) near zero (ENZ). An ENZ material of arbitrary geometry ...can thus serve as a perfect coupler between incoming and outgoing waveguides with identical cross-sectional area, so long as one dimension of the ENZ is electrically small. In this Letter we present an experimental demonstration of microwave tunneling between two planar waveguides separated by a thin ENZ channel. The ENZ channel consists of a planar waveguide in which complementary split ring resonators are patterned on the lower surface. A tunneling passband is found in transmission measurements, while a two-dimensional spatial map of the electric field distribution reveals a uniform phase variation across the channel--both measurements in agreement with theory and numerical simulations.
This study addressed the critical role of isolating switches in controlling circuit connections for the stable operation of the substation. Our research introduced an innovative state detection ...system that utilized depth information guidance, comprising a controllable pan-tilt mechanism, a depth camera, and an industrial computer. The software component employed a two-stage strategy for precise isolating switch detection. Initially, the red green blue with depth (RGB-D) saliency network identified the approximate area of the isolating switch target. Subsequently, a fully connected conditional random field was applied to extract accurate detection results. The real-time state of the isolating switch was determined based on the geometric relationship between its arms. This approach enhanced the accuracy of isolating switch detection, ensuring practical applicability in engineering scenarios. The significance of this research lies in its contribution to advancing isolating switch monitoring through depth information guidance, promoting a more robust and reliable power system. The key improvement is implementing a two-stage strategy, combining RGB-D saliency analysis and conditional random field processing, resulting in enhanced accuracy in isolating switch detection. As validated through extensive experiments, the proposed system's successful application in practical engineering underscores its effectiveness in meeting the accuracy requirements for isolating switch detection and state detection. This innovation holds promise for broader applications in power systems, showcasing its potential to elevate the reliability and efficiency of electrical networks. Code of the proposed system is available at: <ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://github.com/miaomiao0909/Isolating-Switch-Detection/tree/master">https://github.com/miaomiao0909/Isolating-Switch-Detection/tree/master</ext-link>.
Metamaterials have earned their name with extraordinary properties such as negative refractive index and invisibility cloaking. With over 15 years of research and development, metamaterials show ...their debut in real world applications, especially in the areas of telecommunication, sensing, aerospace ＆ defense, optics and medical instrumentation. In the meanwhile, metamaterials are expanding their concept in areas beyond electromagnetics. In this paper, the authors would like to focus on the research and applications in telecommunication and sensing. Octave-bandwidth horn antennas, flat-panel satellite antennas and air-borne holographic satellite antennas are all fabulous examples of clever implementation that bring metamaterials into practical devices. We would like to discuss the features that differentiate metamaterials from conventional counterparts in case studies. With the advancement in design, manufacturing, packaging, detection and testing, more sophisticated features are expected in the telecommunication, sensing, and beyond.
► The novel La(III)-loaded granular ceramic adsorbents were prepared. ► Maximum adsorption of phosphate was achieved within the pH range 7.0–9.0. ► Adsorption process followed the pseudo-second-order ...kinetic model. ► Adsorption mechanism was investigated and assumed.
A La(III)-loaded granular ceramic adsorbent, consisting mainly of different forms of metal oxide minerals, was developed for phosphorus removal from aqueous solution. Batch experiments were performed to investigate the effects of various experimental parameters, such as contact time (3–48h), initial phosphorus concentration (5–25mg/L), pH (2.0–12.0), temperature (20, 30 and 40°C) and anions on phosphorus adsorption. The adsorption process was well described by a pseudo-second-order kinetic model and equilibrium was achieved at 30h. The adsorption data closely fitted the Langmuir isotherm model at temperatures ranging from 20°C to 40°C. Thermodynamic study indicated a spontaneous, favorable and exothermic adsorption on the La(III)-loaded granular ceramic adsorbent. The optimum pH for phosphorus removal ranged from 7.0 to 9.0. Phosphorus adsorption was impeded by the presence of F−, followed by Cl−, SO42− and NO3− and the adsorption process appeared to be controlled by a chemical precipitation process. The mechanism may involve ion complexation during subsequent adsorption of phosphorus on lanthanum hydroxides.
The proportion of renewable energy mainly including hydropower, photovoltaic and wind power is growing rapidly. DC transmission technology has become the main tool of new energy transmission. The ...protection scheme of the voltage source converter-based high voltage DC (VSC-HVDC) power grid is the prerequisite for the DC system. But, problems such as high resistance faults, distributed capacitance, and noise interference reduce the reliability of existing protection schemes. To solve the problem of resistance and noise interference in existing protection schemes, a double-ended protection scheme based on traveling wave JS divergence is proposed. First, the flexible HVDC transmission system is analyzed, according to which the expression of traveling wave power is derived, and its fault characteristics are summarized. Subsequently, a combined algorithm of the JS divergence based on the energy of the S-transform was proposed, and the modified algorithm was used to express the fault characteristics of traveling wave power. Finally, a flexible DC transmission system model is built. The performance of the scheme is verified by setting different interference factors (resistance, noise, distributed capacitance, synchronization error).
Long-distance transmission of renewable energy
via
DC is currently a more economical transmission scheme. As the proportion of renewable energy at the generation end continues to rise, the inertia ...and damping level of the system is reduced, causing serious frequency-related issues. This paper first analyzes the working principle and control method of the LCC-HVDC system, summarizes the frequency control methods of the sending end power grid and their existing problems, and proposes a frequency control scheme for the LCC-HVDC sending end system based on the concept of rapid power compensation (RPC). Finally, the LCC-HVDC system model integrated with the large-capacity wind farm and thermal power plant is built in MATLAB/Simulink. Under conditions of load power fluctuation and sudden wind speed change, the proposed strategy fully utilizes the spare capacity of the system, effectively improves the frequency indexes of the system, and improves the frequency characteristics of the renewable energy sending end grid.
Utilizing non-resonant metamaterial elements, we demonstrate that complex gradient index optics can be constructed exhibiting low material losses and large frequency bandwidth. Although the range of ...structures is limited to those having only electric response, with an electric permittivity always equal to or greater than unity, there are still numerous metamaterial design possibilities enabled by leveraging the non-resonant elements. For example, a gradient, impedance matching layer can be added that drastically reduces the return loss of the optical elements due to reflection. In microwave experiments, we demonstrate the broadband design concepts with a gradient index lens and a beam-steering element, both of which are confirmed to operate over the entire X-band (roughly 8-12 GHz) frequency spectrum.
SWIPT in MISO full-duplex systems Okandeji, Alexander Akpofure; Khandaker, Muhammad R. A.; Kai-Kit Wong ...
Journal of communications and networks,
10/2017, Letnik:
19, Številka:
5
Journal Article
Odprti dostop
This paper investigates a multiuser multiple-input singleoutput (MISO) full-duplex (FD) system for simultaneous wireless information and power transfer (SWIPT), in which a multiantenna base station ...(BS) simultaneously sends wirelessly information and power to a set of single-antenna mobile stations (MSs) using power splitters (PSs) in the downlink and receives information in the uplink in FD mode. In particular, we address the joint design of the receive PS ratio and the transmit power at the MSs, and the beamforming matrix at the BS under signal-to-interferenceplus- noise ratio (SINR) and the harvested power constraints. Using semidefinite relaxation (SDR), we obtain the solution to the problem with imperfect channel state information (CSI) of the selfinterfering channels. Furthermore, we propose another suboptimal zero-forcing (ZF) based solution by separating the optimization of the transmit beamforming vector and the PS ratio. Simulation results are provided to evaluate the performance of the proposed beamforming designs.
Performance of a submerged hollow fiber membrane bioreactor (MBR) for treatment of hospital wastewater was investigated. The removal efficiency for COD, NH
4
+–N, and turbidity was 80, 93 and 83% ...respectively with the average effluent quality of COD <25
mg/l, NH
4
+–N <1.5
mg/l and turbidity <3 NTU.
Escherichia coli removal was over 98%. The effluent had no colour and no odour. The transmembrane pressure increased slowly during 6 months operation. No membrane cleaning operation was used and no sludge was discharged during the 6-month operation period.
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