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Emerging nanotechnologies have revealed carbon nanotubes (CNTs) as one of the best materials with immense potential. Considering the outstanding physical, mechanical, electrochemical, thermal, and optoelectronic properties of CNTs, extensive studies have been reported assessing their applications in several disciplines. This paper presents a broad review of the studies in the literature that address the contribution of CNTs in terms of their applications as different parts of solar cells such as photoelectrode, photoconductor, top and back electrode, replacement of indium tin oxide (ITO) as transparent conducting electrode (TCE) in a variety of photovoltaics such as silicon, organic, polymer and dye-sensitized with their subsequent efficiencies. [ABSTRACT FROM AUTHOR]

A wide-band (6,5) single-walled carbon nanotube metamaterial absorber design with near unity absorption in the visible and ultraviolet frequency regions for solar cell applications is proposed. The frequency response of the proposed design provides wide-band with a maximum of 99.2% absorption. The proposed design is also simulated with (5,4), (6,4), (7,5), (9,4), and (10,3) chiralities, and results are compared to show that the proposed design works best with (6,5) carbon nanotube (CNT) but also good for other chiral CNTs in the visible and ultraviolet frequency region. The geometric structure was carefully analyzed for its contribution to the absorption behavior. The absorber design is highly flexible and capable of keeping the wide-band with high absorption. Due to the excellent symmetric characteristics of the proposed design, which provides polarization independency under normal incidence (transverse electromagnetic mode), the proposed metamaterial absorber is a good candidate for the solar cell application, where absorbance can be kept high with respect to the polarization angle. [ABSTRACT FROM AUTHOR]

Electrostriction properties of a dilute gas mixture are analytically calculated and derived herein for the first time. Electrostriction in a gaseous mixture is expressed in a standard process based on the energy conservation law using the Lorentz-Lorentz model and a model for calculating the electrostriction is introduced. The internal interactions of the gaseous environment follow the ideal gas law. These relationships show that electrostriction can be controlled by changing the volume ratio of gases. Since, electrostriction is an essential parameter in determining the Brillouin scattering, the proposed modeling is a key theoretical method to control the Brillouin scattering in gases. According to the numerical results, it was found that the electrostriction coefficient is almost independent of the wavelength range. More importantly, the frequency shift induced in an N2-He gas mixture is independent of the volume fraction. E.g., in volume fraction of 0.3 and wavelength of 300 nm, if the volume fraction is increased by 20%, the electrostriction of the gas mixture (γmix\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\gamma }_{mix}$$\end{document}) will change by 4.3%, but the frequency shift almost does not change. On the other hand, if the frequency varies by 20%, the frequency shift will change by 16%, but in practice γmix\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\gamma }_{mix}$$\end{document} almost remains constant. [ABSTRACT FROM AUTHOR]

• Novel multiband (9,4) polarization insensitive nanotubes based metamaterial absorber. • Absorption of the energy in multiband scale with unique design. • Simplicity of the design, ease of the fabrication and the ability to absorb more energy. • Good candidate for the photovoltaic energy generation. A novel multiband (9,4) polarization insensitive metamaterial (MTM) absorber structure based on the vertical nanotubes composited with the silicon dielectric material is proposed in this research. Multiband polarization insensitivity is achieved through the unique geometrical configuration of the design, which provides almost unity absorption in the visible and ultraviolet regions from 300 THz to 1000 THz. The proposed design is selected due to the simplicity of the construction, ease of fabrication and the ability to absorb almost perfectly under changing geometrical parameters. The electromagnetic response of the design is simulated for four maximum absorption peaks at 394.3 THz, 514.9 THz, 632.8 THz, and 773.2 THz with the corresponding absorption rates of 99.8%, 98.35%, 96.66%, and 80.60%, respectively. The sensitivity of the polarization angle of the MTM absorber has also been investigated, which verifies that the current design is insensitive to the different polarization angles. The flexibility of the proposed design has also been investigated by altering the geometrical components, materials, and the dimensions, and it is confirmed that the proposed MTM absorber design provides high absorption rates under all considered circumstances. The MTM absorber designs is found to be capable of improving the efficiency of the solar cell. The implementation of these MTM absorbers in the solar cells can significantly improve the absorption rate by reducing the reflection and transmission. MTM is validated by both prior art investigation and the different solver such as FEM and FIT. Results of interface theory model and simulations are compared against one another, which show good agreement yielding reliable and accurate estimations. [ABSTRACT FROM AUTHOR]

In this paper, a rectangular split ring resonator-type metamaterial (MTM) sensor application is demonstrated in order to examine concrete materials. First, different types of concrete materials including carbon steel fiber with the purity ratio of 0.5%, 1% and 1.5% were prepared by using cement and water and their electrical properties were determined via Nicolson–Ross–Weir tehcnique. After that, compatible MTM-based sensor structure was designed and proposed. In order to find out the effect of the humidity on the concrete material, all samples were kept in the water pool for 28 days, the samples were then taken out and the temperature effect on the concrete materials was observed by increasing the heat up to 30 ∘ and 70 ∘ in the oven. The simulated resonance frequency shifts were observed at 910 MHz for concrete material sensor, 120 MHz for humidity sensor validation and 400 MHz for temperature sensor applications. By having large bandwidth in different fiber contents and validating the physical sensor applications as temperature and humidity, it was shown that the proposed study has novelty in the area of MTM-based sensor applications when it is compared with current state-of-the-art. [ABSTRACT FROM AUTHOR]

Chiral metamaterial-based sensor is designed for sensing the change in substance ratio of chemical substances when combined with distilled water. These samples have been prepared with 10%, 50% and 90% volume fraction of methanol, ethanol, acetone, ammonia and isopropyl alcohol. The complex permittivity of the prepared samples has been measured by Agilent 85070E dielectric probe kit and compared with the simulations. In the proposed design, linear shifts with the frequency bands of more than 100 MHz are observed in different measurements. For different material sensing, pure samples have been used and their reflection coefficient measurement results have been presented. Unique side of this study is that the structure provides very clear and sensitive results and presents a new approach to the microfluidic sensor applications by using the sample holder. [ABSTRACT FROM AUTHOR]

A novel multiband metamaterial absorber (MTMA) is proposed which is capable of well presenting a polarization-insensitive and wide incident angle stability in the microwave frequency range. The proposed MTMA comprising two vertically stacked asterisk-based copper resonators separated by dielectric layer of flame retardant type four and backed with a thin copper film. High-frequency structure simulator was used to simulate the absorber and to depict surface current distribution. The results showed that the absorber is operated at three narrow bands with high absorptivity of about 92, 100 and 100% at frequencies of 2.75, 4.3 and 9.5 GHz, respectively. The position of the resonant peaks can be effectively tuned by adjusting the geometry parameters of the structure, thereby achieving a multiband, polarization-independent and wide-angle absorber. The designed structure is important for the application of sensors, thermal images and in constructing broad multiband signals for electromagnetic compatibility/interference. [ABSTRACT FROM AUTHOR]

In this study, a novel metamaterial absorber (MA) is designed and numerically demonstrated for solar energy harvesting. The structure is composed of three layers with different thicknesses. The interactions of three layers bring about the plasmonic resonances. Although the main operation frequency of the structure is chosen between 430 and 770 THz, which is the visible light regime, the proposed structure is also investigated in the ultra-violet (UV) region. One can see from the results that the proposed structure carries nearly perfect absorption capacity that is more than 91% at the whole visible light spectrum. The proposed structure even has the absorption capacity of 99% between 556 and 657 THz. In addition, the designed MA is also investigated in terms of its polarization and angle independency. Results show that the proposed structure is independent from the polarization and incident angles. Lastly, the designed structure can be considered to be used in solar energy applications as a harvester since it has an ultra-broadband absorption characteristic in visible light regime. [ABSTRACT FROM AUTHOR]

A new metamaterial absorber (MA) having distinct properties than those given in the literature is investigated. Although several designs have been studied for achieving absorption characteristics in single-band, dual-band and multiple bands within the whole spectrum of solar light, there has been limited number of researches examining the broadband MA in the visible light section of the spectrum. The designed structure is composed of the combination of three layers having different thicknesses including a metallic substrate, dielectric and a metal layer. Due to the sandwich-like structure, it can support the plasmonic resonance. The proposed structure, which provides a maximum absorption level of 99.42% at 579.26 THz, has a high absorption rate of 99% between the frequency band 545 and 628 THz. Numerical results indicate that the proposed structure has perfect absorption which is greater than 90.98% through the whole working frequency band. The dependency of the designed structure on the polarization angle is investigated for different incident angles with TE and TM polarizations as well as the TEM mode. In addition to its potential applications such as solar cells and cloaking, the designed structure can also be considered as a color sensor and an optical frequency sensor. [ABSTRACT FROM AUTHOR]

The analytically obtained algebraic equation systems for the TM/TE-z polarized monochromatic waves scattering from eccentrically layered circular cylinders are ill-conditioned for numerical calculations. Therefore, such ill conditioned systems must be regularized for reliable numerical results. Here, the steps of the regularization of the ill conditioned system obtained for the scattered field from a circular metamaterial cylinder includes three parallel circular cylinders: a dielectric, an impedance and a perfect electric conductor is explained. In the regularization procedure used here each circular boundary brings block(s) correspond to its electromagnetic property and the regularization procedure is done according to this block(s). For this end a system that consists of perfect electric conductor (PEC), impedance, dielectric, and metamaterial cylinders is discussed and thus the steps of a regularization procedure for a general system that has all the type of boundaries in terms of electromagnetics will be explained here. As a result, if a new boundary is included to the system then it is sufficient to locate the blocks related to this boundary suitably. [ABSTRACT FROM AUTHOR]

A metamaterial-based energy harvesting structure has been designed and experimentally tested in this study. The proposed structure has square and split ring resonators placed in different angles on the back and front sides for compatible multiband operation in energy harvesting. Resonance points have been defined at 900 MHz, 1.37 GHz, 1.61 GHz, 1.80 GHz, and 2.55 GHz, by simulation and experimental methods. These points correspond to Global System for Communication (GSM) 900, GSM 1800, Universal Mobile Telecommunication System (UMTS), satellite navigation, and Industrial Scientific and Medical (ISM) band frequencies. Supporting multiband application in a single structure without changing dimensions or design is one of the properties of this study. To harvest captived electromagnetic energy, an HSMS 2860 Schottky diode has been used. For wireless power transmission efficiency, voltage across the Schottky diode has been measured by a spectrum analyzer in different points experimentally. The maximum obtained voltage across the Schottky diode is 90 mV at 1800 MHz when a 500 mV signal is applied from a 5 cm distance. Simulated and experimental results prove that the proposed structure can effectively be used in GSM, satellite communication, and UMTS electromagnetic bands for energy harvesting and filtering applications. [ABSTRACT FROM AUTHOR]

In this study, we both numerically and experimentally present a metasurface (MS) polarization converter to transform linearly polarized signal into circularly polarized one. The unit cell consists of two rectangular metallic patches placed at the crossed corners of rectangularly arranged inclusions. The results of a full-wave Electromagnetic (EM) simulator are compared to those of free space measurement using two horn antenna at microwave frequency regime. For a linearly polarized antenna, the s-parameters are obtained for both co-polarized and cross-polarized responses. The polarization quality referred to as axial ratio (AR) is expressed by the ratio of these two responses. It is found that, strong polarization conversion activity is obtained with the proposed MS at the frequency of about 3 GHz. As a result, we can generate polarization converter with a wide bandwidth, of interest for microwave filtering, coating, and especially polarization conversion devices. [ABSTRACT FROM AUTHOR]

A new metamaterial absorber (MA) is investigated and shown numerically for solar energy harvesting for future solar cell applications. The structure consists of two metals and one dielectric layer having different thicknesses. Owing to this combination, the structure exhibits plasmonic resonance characteristics. In the entire spectrum of visible frequency region, the obtained results show that investigated structure has perfect absorptivity which is above 91.8%. Proposed structure also has 99.87% absorption at 613.94 THz and 99% absorption between 548 and 669 THz. The proposed structure also shows both polarization and angle independency for the entire visible region. The MA based solar cell proposes high absorption with an upper ratio of 90% in the widest range of visible spectrum comparing to the studies in literature. Hence, the proposed metamaterial absorber solar cells can be used for invisibility in entire spectrum of visible light. The absorption characteristics of the solar absorber are also investigated for infrared and ultraviolet region. The enhancement of absorption of the structure will provide new type of sensors in these frequency ranges. [ABSTRACT FROM AUTHOR]

We propose the design of a multiband absorber based on multi-layered square split ring (MSSR) structure. The multi-layered metamaterial structure is designed to be used in the frequency bands such as WIMAX, WLAN and satellite communication region. The absorption levels of the proposed structure are higher than 90% for all resonance frequencies. In addition, the incident angle and polarization dependence of the multi-layered metamaterial absorber and harvester is also investigated and it is observed that the structure has polarization angle independent frequency response with good absorption characteristics in the entire working frequency band. The energy harvesting ratios of the structure is investigated especially for the resonance frequencies at which the maximum absorption occurs. The energy harvesting potential of the proposed MSSRs is as good as those of the structures given in the literature. Therefore, the suggested design having good absorption, polarization and angle independent characteristics with a wide bandwidth is a potential candidate for future energy harvesting applications in commonly used wireless communication bands, namely WIMAX, WLAN and satellite communication bands. [ABSTRACT FROM AUTHOR]

A novel broad-band polarization-independent with wide-angle metamaterial absorber(MA) is investigated and demonstrated for solar energy harvesting applications. The proposed MA is composed of two metal layers which have different thickness and a dielectric layer which is sandwiched between these metal layers. By this combination, the proposed MA indicates plasmonic resonance characteristic. Numeric results show that proposed MA has perfect absorption characteristic which is above 88.28% with wide-angle for all visible region. It shows almost perfect absorption of 98.4% at the resonance frequency of 621.76 THz and has also 90% absorption between frequencies of 445 THz and 770 THz which is nearly all visible light region. Besides, numerical results validate that the proposed MA could achieve very high absorption at wide-angles of incidence for both transverse electric (TE) and transverse magnetic (TM) waves.. The proposed MA and its variations enable for solar cell applications due to have upper ratio of 90% in the widest range of visible spectrum comparing to the studies in literature. In order to show additional features of the proposed structure, parametric studies are realized and discussed. Furthermore, the absorption characteristic of proposed MA is investigated for infrared and ultraviolet region. The enhancement of absorption of the structure will provide new type of sensors in these frequency ranges. [ABSTRACT FROM AUTHOR]

We present numerically and experimentally a dynamic chiral metamaterial (MTM) that creates strong optical activity and circular dichroism. The proposed tunable structure has a very simple and more efficient configuration which introduces flexibility to adjust its EM properties. In addition, it gives a giant negative refractive index due to the high chirality. Our experimental results confirm the strong optical activity for a wide frequency range and agree with the simulation results. Moreover, the proposed chiral MTM provides a wideband and constant/flat chirality over a certain frequency band and thus it can be concluded that the developed chiral MTM based model offers a strong optical activity in terahertz, infrared and even in visible frequencies. [ABSTRACT FROM AUTHOR]

We demonstrate theoretically and numerically a chiral slab that can exhibit optical activity, circular dichroism, and antireflection in detail. Copolar and crosspolar transmitted and reflected waves depending on permittivity, chirality and thickness are analyzed in order to display the characteristic features of the proposed chiral slab both for TE and TM incident waves. The suggested chiral slab is realized by a commercial full-wave EM solver to confirm theoretical results. From the results, the theoretical results are in good agreement with the numerical study. It can be seen that the suggested system can be used for the application to design efficient EM filters and polarization converter at microwave, millimeter wave and optical frequency regions. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a review study on the effects of sun tracking and cooling systems. So far, many studies (and case studies too) have been analyzed and evaluated in the literature. Existing studies show that sun tracking system is significantly affecting energy generation capacity of photovoltaic panel. Other effecting parameter is the cooling system which has small effect on PV panel power generation but this totally depends on the location of installation system. [Copyright &y& Elsevier]

In this study, a chiral metamaterial sensor applications are created by placing asymmetrically two meander line front and back side of the substrate layer. Characterization of the dielectric constant, thickness and loss tangent have been performed both in simulation and experimental methods. Different Arlon type materials used for showing the effects of dielectric constant on transmission coefficient. Obtained bandwidths for characterization are greater than the similar studies which verifyies increased sensitivity. This study also differs from similar studies by presenting permeability and loss tangent effects on transmission coefficient as well as having wider bandwidth that increase sensitivity due to its special chiral design. Set of experimental study performed to verify simulated ones for change in thickness, dielectric constant and loss tangent and compatible results with simulated ones obtained. According to simulation and experimental study results, proposed structurecan be used myriad microwave sensing applications effectively due to high sensitivity property. [ABSTRACT FROM AUTHOR]

• Metamaterial energy harvester based subwavelength-imaging structure. • Energy harvesting by metamaterials. • Image quality enhancement by metamaterials. • Various applications in energy harvesting, wave tracing, crack detection, spy device detection, medical imaging, and so on. Metamaterial energy harvester based subwavelength imaging structure is presented. Besides, 2×2 array patch antenna is designed to create incident radiated signal towards the proposed harvester structure. Harvested energy is converted to DC voltage signal by using Schottky diodes and each cell is represented by 256 grey levelled pixel value. Therefore, any incident electromagnetic wave placed in the operating frequency range can be monitorized. In the experimental study, experiments are realized with and without antenna to investigate the effects of instantaneous electromagnetic waves and the observed images. Afterwards, another experiment is conducted to observe the effects of metal plate which is located between the antenna and the harvester structure. The last experiment is performed by using a Yagi Uda antenna for sub-wavelength imaging. The proposed harvester structure can be used in various applications such as energy harvesting, incident wave tracing, crack detection, spy device detection, medical imaging, and so on. [ABSTRACT FROM AUTHOR]

In this work, a novel, to the best of our knowledge, metamaterial-based microwave sensor is designed, numerically simulated, and experimentally tested for milk and dairy products in the frequency range of 8 to 9 GHz. The proposed structure is composed of copper split-ring resonators printed on Arlon Diclad 527 dielectric substrate. Reflection coefficient S 11 was determined by using numerical simulation, and the structure was experimentally tested to validate the sensor at the X band frequency. The material under the test was placed in the sensor layer just behind the proposed structure, and the design was optimized to sense the change in the dielectric constant via resonance frequency shifts. The proposed study was not only used for fat contents and freshness checking of milk, it was also applied to other dairy products such as cheese, ayran, and yogurt. The maximum resonance frequency shift was observed in yogurt to be 140 MHz, and the minimum frequency shift was observed in fresh and spoiled ayran to be around 40 MHz. This work provides a new approach to the current metamaterial sensor studies existing in literature by having novel material applications with new microwave metamaterial sensors.