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Lithium-based batteries are promising and encouraging energy storage devices in different fields such as portable electronic equipment and new-energy vehicles. Separator, which serves as a physical blockade between electrodes as well as a reliable bridge for ion transport, plays a vital role in maintaining the sustainability of batteries. Unfortunately, most studies in the field of lithium-based batteries have only focused on separators between 20-25 μm so as to achieve a balance between battery safety and performance. However, such thick separators come at the expense of less free space for accommodating active materials inside the battery, thus impeding further development of next-generation lithium-based batteries with high energy density. Thin separators with robust mechanical strength are undoubtedly prime choice to make lithium-based batteries more reliable and safer. This review focuses mainly on recent developments in thin separators for lithium-based batteries, lithium-ion batteries (LIBs) and lithium-sulfur (Li-S) batteries in particular, with a detailed introduction of thin separator preparation methodologies and an analysis of new progress in separators owning the thickness less than 15 μm or an ultrathin functional layer less than 1 μm. Effects of separator thickness on energy density are explored through practical evaluation. Furthermore, a brief outlook for realizing an ‘infinitely-thin’ separator with excellent physical performances and negligible resistance is provided.

The electrical properties of materials and their dependence on frequency and temperature are indispensable in designing electromagnetic devices and systems in various areas of engineering and science for both basic and applied researches. A free-space transmission/reflection method measuring the free-space scattering parameters of a material under test (MUT) located at the middle of transmit/receive antennas in a free space is suitable for non-destructively testing the MUT without prior machining or physical contact in high-frequency range. This paper describes a planar offset short applicable to the calibration of a quasi-optic based free-space material measurement system in the millimeter-wave frequency range. The measurement results of the dimensional and electrical properties for the three fabricated planar offset shorts with the phase difference of 120° between the reflection coefficients of the planar shorts in the W-band (75–110 GHz) are presented.

Coupling of light from free space to optical fibers is essential for many applications, while commonly used step-index optical fibers provide insufficient coupling efficiencies especially at large ...

In the current work, the response of heterogeneous magnetorheological elastomers (MREs) which are loaded by external magnetic fields in the absence and also in the presence of free space is studied. A fully-coupled two-scale finite element computational homogenization procedure is used to derive the material response at the macro-scale from the averaged response of the underlying micro-scale problem. Different combinations of boundary conditions, that satisfy the Hill-Mandel condition and are based on the primary variables of the magneto-elastic enthalpy and energy functionals are applied to solve the micro-scale boundary value problem. Furthermore, the influences of various microstructures on the macroscopic response of the MREs are investigated. The results indicate that the choice of microscopic boundary conditions and microstructure types can significantly affect the macroscopic responses of MREs.

In this paper, a new optimized algorithm is presented to classify the liquids with high-level accuracy using raw data which show the transmission parameter (S21) of liquids. The free space ...

A superhydrophobic (SH) sandwich system has been developed to enable "contact-free" airborne singlet oxygen (1O2) delivery to a water droplet. The contact-free feature means that the sensitizer is physically separated from the droplet, which presents opportunities for photodynamic therapy (PDT). Trapping of airborne 1O2 in a H2O droplet residing on a lower SH surface was monitored with 9,10-anthracene dipropionate dianion by varying distances to an upper 1O2-generating surface. Short distances of 20 μm efficiently delivered airborne 1O2 to the droplet in single-digit picomolar steady-state concentrations. Delivery decreases linearly with distance, but 50% of the 1O2 steady-state concentration is trapped at a distance of 300 μm from the generating surface. The 1270 nm luminescence intensity was measured within the SH sandwich system, confirming the presence of airborne 1O2. Physical quenching of 1O2 to ground-state 3O2 by the water droplet itself and both physical and chemical quenching of 1O2 by the water droplet containing the trap 9,10-anthracene dipropionate dianion are observed. Unlike a majority of work in the field of PDT with dissolved sensitizers, where 1O2 diffuses short (hundreds of nanometers) distances, we show the delivery of airborne 1O2 via a superhydrophobic surface is effective through air in tenths of millimeters distances to oxidize an organic compound in water. Our results provide not only potential relevance to PDT but also surface bacterial inactivation processes. Fil: Aebisher, David. University Of Rzeszow; Polonia Fil: Bartusik-Aebisher, Dorota. University Of Rzeszow; Polonia Fil: Belh, Sarah J.. City University of New York; Estados Unidos Fil: Ghosh, Goutam. City University of New York; Estados Unidos Fil: Durantini, Andres Matías. Universidad Nacional de Río Cuarto. Instituto para el Desarrollo Agroindustrial y de la Salud. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto para el Desarrollo Agroindustrial y de la Salud; Argentina Fil: Liu, Yang. City University of New York; Estados Unidos Fil: Xu, QianFeng. City University of New York; Estados Unidos Fil: Lyons, Alan M.. City University of New York; Estados Unidos Fil: Greer, Alexander. City University of New York; Estados Unidos

Laser beam propagation in highly scattering media has attracted much attention for optical sensing fields because the propagation of the light is often limited to the near-surface regions of the media. To increase the sensing capability in such scattering conditions, we focus on the propagation property of an annular beam in a highly scattering media. In our previous work, the non-diffractive beam was generated by propagating an annular beam in a scattering medium of colloidal suspension (diluted milk) up to the concentration of 22%, which is near the human tissue. In this study, the propagation property of a partially blocked annular beam using a fan-like obstacle with different apex angles is investigated to realize object detection in highly scattering media such as human tissue, fog, or cloud. Simulation results show that non-diffractive beams can be generated when partially blocked annular beam with blocking angle from 0° to 30o is propagated in free space. The propagation experiment of partially blocked annular beam in scattering media shows that the center peak intensity in scattered light is detected when the apex angle is set up to 30° . By measuring scattered light at different receiving distances, the experiment results show that the center peak is kept at a certain distance away from the optical cell. This result verifies that the central peak intensity of this scattered light is a non-diffractive beam.

In this paper, the S-parameters of 2mm silicon wafer, 14.345mm wood I, 14.215mm wood II and 13.80mm wood III were measured based on 220-325 GHz quasi optical Vector Network Analyzer measurement system. Basic theory based on free space electromagnetic component equations, boundary conditions and S parameters. The electromagnetic field of "air-MUT-air" three-layer structure between calibrated reference planes is analyzed in detail, and the formula of complex permittivity is derived. The results of complex permittivity of silicon wafer extracted by this method are basically consistent with those in the literature. The measurement of woods can accurately distinguish heartwood from sapwood. This study is helpful for us to better understand the interaction mechanism between terahertz waves and wood media, and can lay a foundation for the identification of woods.

[ES] Las comunicaciones ópticas inalámbricas (OWC) constituyen una tecnología muy prometedora para el desarrollo de futuras comunicaciones inalámbricas. De hecho, ha despertado un interés creciente entre los investigadores y varias empresas de todo el mundo trabajan actualmente en el desarrollo de redes inalámbricas de muy alta velocidad. Las comunidades científica e industrial consideran la OWC como una tecnología complementaria en sus diversas formas: comunicaciones ópticas en el espacio libre (FSO), comunicaciones de luz visible (VLC) o fidelidad de la luz (Li-Fi). El espectro óptico ha sido considerado durante muchos años como una gran oportunidad para las comunicaciones inalámbricas, especialmente debido a la saturación del espectro de radiofrecuencia (RF). Esta disertación trata del uso de fuentes de banda ancha en sistemas de transmisión de luz visible (VLC), así como en sistemas de transmisión en el espectro infrarrojo por fibra óptica. En el trabajo de investigación realizado se pueden distinguir tres partes: En la primera parte, se considera el estudio y la simulación de componentes de Diodos Emisores de Luz (LED) con el software WIEN2k centrándose en las propiedades ópticas y eléctricas de los elementos II-VI. La segunda parte trata del diseño, la implementación y las pruebas de diferentes prototipos de comunicación VLC para la transmisión analógica y digital en modo simplex y semidúplex. Hemos demostrado un sistema OWC empleando una fuente de banda ancha (LED) para la transmisión no sólo de datos, sino también para la transmisión inalámbrica de energía. Además, se aborda el problema de la sincronización y la detección del nivel "1" o "0" de un bit en los sistemas de comunicación inalámbrica óptica implementados que surge como consecuencia de la atenuación de la luz a lo largo de la distancia y al problema de la pérdida de línea de visión (NLOS) entre el emisor y el receptor. Para hacer frente a este problema, se ha proporcionado un protocolo de comunicación que garantiza la transmisión fiable de datos digitales con un algoritmo de detección de nivel de bits adaptativo y se ha demostrado su eficacia mediante la transmisión de textos e imágenes. Además, esta tesis aporta una solución para la implementación de transmisores multiplexados en redes con división de longitud de onda (WDM) para formatos de modulación con multiplexación por división de frecuencia ortogonal (OFDM) basados en el uso de fuentes de banda ancha en el espectro infrarrojo para redes de fibra bidireccionales centralizadas. A pesar de las limitaciones impuestas por la dispersión cromática en el uso de este tipo de fuentes ópticas, la inclusión de ciertas estructuras antes de la detección permite la transmisión de señales OFDM en enlaces ópticos. En este trabajo se ha demostrado experimentalmente la reutilización de portadoras, la asignación dinámica de ancho de banda y la transmisión de señales OFDM multibanda mediante el uso de fuentes ópticas de banda ancha en redes WDM. Los principales resultados obtenidos en cada parte de esta tesis doctoral muestran los procedimientos de estudio, la eficacia de las soluciones propuestas y las limitaciones encontradas., [CA] Les comunicacions òptiques sense fils (OWC) constitueixen una tecnologia molt prometedora per al desenvolupament de futures comunicacions sense fils. De fet, ha despertat un interés creixent entre els investigadors i diverses empreses de tot el món treballen actualment en el desenvolupament de xarxes sense fils de molt alta velocitat. Les comunitats científica i industrial consideren la OWC com una tecnologia complementària en les seues diverses formes: comunicacions òptiques en l'espai lliure (FSO), comunicacions de llum visible (VLC) o fidelitat de la llum (Li-Fi). L'espectre òptic ha sigut considerat durant molts anys com una gran oportunitat per a les comunicacions sense fils, especialment a causa de la saturació de l'espectre de radiofreqüència (RF). Aquesta dissertació tracta de l'ús de fonts de banda ampla en sistemes de transmissió de llum visible (VLC), així com en sistemes de transmissió en l'espectre infraroig per fibra òptica. En el treball de recerca realitzat es poden distingir tres parts: ¿ En la primera part, es considera l'estudi i la simulació de components de Díodes Emissors de Llum (LED) amb el software WIEN2k centrant-se en les propietats òptiques i elèctriques dels elements II-VI. ¿ La segona part tracta del disseny, la implementació i les proves de diferents prototips de comunicació VLC per a la transmissió analògica i digital de manera simplex i semidúplex. Hem demostrat un sistema OWC emprant una font de banda ampla (LED) per a la transmissió no sols de dades, sinó també per a la transmissió sense fil d'energia. A més, s'aborda el problema de la sincronització i la detecció del nivell "1" o "0" d'un bit en els sistemes de comunicació sense fil òptica implementats, que sorgeix a conseqüència de l'atenuació de la llum al llarg de la distància i al problema de la pèrdua de línia de visió (NLOS) entre l'emissor i el receptor. Per a fer front a aquest problema, s'ha proporcionat un protocol de comunicació que garanteix la transmissió fiable de dades digitals amb un algorisme de detecció de nivell de bits adaptatiu i s'ha demostrat la seua eficàcia mitjançant la transmissió de textos i imatges. ¿ A més, aquesta tesi aporta una solució per a la implementació de transmissors multiplexats en xarxes amb divisió de longitud d'ona (WDM) per a formats de modulació amb multiplexació per divisió de freqüència ortogonal (OFDM) basats en l'ús de fonts de banda ampla en l'espectre infraroig per a xarxes de fibra bidireccionals centralitzades. Malgrat les limitacions imposades per la dispersió cromàtica en l'ús d'aquest tipus de fonts òptiques, la inclusió d'unes certes estructures abans de la detecció permet la transmissió de senyals OFDM en enllaços òptics. En aquest treball s'ha demostrat experimentalment la reutilització de portadores, l'assignació dinàmica d'amplada de banda i la transmissió de senyals OFDM multibanda mitjançant l'ús de fonts òptiques de banda ampla en xarxes WDM. Els principals resultats obtinguts en cada part d'aquesta tesi doctoral mostren els procediments d'estudi, l'eficàcia de les solucions proposades i les limitacions trobades., [EN] Optical wireless communication (OWC) is a very promising technology for future wireless communications developments. It has attracted increasing interest from researchers and several companies around the world are currently working on the development of very high-speed wireless networks. The scientific and industrial communities believe that OWC will be a complementary technology in its various forms: Free Space Optical communications (FSO), Visible Light Communications (VLC), Light Fidelity (Li-Fi). In fact, the optical spectrum has been considered for many years as a great opportunity for wireless communications especially due to the saturation of the radio frequency (RF) spectrum. This dissertation deals with the use of broadband sources in visible light transmission systems (VLC) as well as fiber optic systems. To carry out the research, three parts can be distinguished: In the first part, we consider the study and simulation of Light Emitting Diode (LED) components with the WIEN2k software by focusing on the optical and electrical properties of elements II-VI. The second part deals with the design, implementation and testing of different VLC communication prototypes for analog and digital transmission in simplex and half-duplex mode. We have demonstrated that an OWC system using a broadband source (i.e. an LED) can be used not only for data transmission, but also for wireless power transmission. Moreover, the synchronization problem and the detection of level "1" or "0" of a bit often arise in the optical wireless communication systems. This is a result of the attenuation nature of the light over the distance and the problem of Non Line-Of-Sight (NLOS) between the emitter and the receiver. To deal with this problem, a communication protocol ensuring reliable digital data transmission with an adaptive bit level detection algorithm has been provided and its effectiveness has been demonstrated by the transmission of texts and images. In addition, this thesis provides a solution for the implementation of wavelength division multiplexed - orthogonal frequency division multiplexed (WDM-OFDM) transmitters based on the use of broadband sources in the infrared spectrum for centralized bidirectional fiber networks. Despite the chromatic dispersion that avoids the use of this type of optical sources, the inclusion of certain structures before detection allows the transmission of OFDM signals in optical links. Carrier reuse, dynamic bandwidth allocation and multiband OFDM signals transmission will be experimentally demonstrated by using optical broadband sources in WDM networks. The main results obtained during this thesis work demonstrate the study procedures, for each part, the effectiveness of the proposed solutions as well as the constraints encountered.

In this work, poly(sodium styrene sulfonate) brushes have been employed as a precursor to prepare thermosensitive strong polyelectrolyte brushes (SPBs) through a counterion exchange strategy. The substitution of hydrophilic Na+ counterions by hydrophobic tetraalkylphosphonium counterions leads to a thermoresponsivity of the SPBs. The thermosensitive properties including hydration, stiffness, and surface water wettability of the SPBs can be modulated by the type of the tetraalkylphosphonium counterions. Nevertheless, the wet thickness of the SPBs with tetraalkylphosphonium counterions does not exhibit an obvious temperature dependency due to the high steric barrier in the crowded environment of SPBs generated by the large tetraalkylphosphonium counterions. The mixtures of small Na+ counterions and large tetraalkylphosphonium counterions are employed to realize the thermosensitive wet thickness without sacrificing other thermoresponsive properties of the SPBs because the mixed counterions can bring both a certain hydrophobicity and some free space to the brushes. This work opens up the opportunities available for the use of counterions to tune the thermosensitivity of SPBs.

Using a simple three-dimensional printed element, i.e., ridge prism, we generate a new diffraction-free structured terahertz (THz) beam: THz sheet in free space. Numerical and experimental results show that the output beam from such an element has an one-dimensional invariant transverse profile. Note that the THz sheet generated by a ridge prism is always close to the element, which limits its application. Thus, we design a lens group system to deliver the THz sheet to a distance, as well as increase the diffraction-free length of the THz sheet six times. Finally, we experimentally demonstrate that this structured beam can be used to extend the depth of fields of a THz transmission imaging system.

It is still a great challenge to prepare novel CuO-based crystal materials with low-dimensional magnetic structures. A new copper oxyborate, namely, PbCu6B6O16 was synthesized and structurally characterized for the first time. Its structure features a novel 3D framework which can be considered as building from the layers of [Cu6B6O16]2−∞ interconnected by corner or edge sharing of CuO4、BO3、B2O5、and B3O7 groups, where Pb2+ cations are located in the free space within the layer. It is unexpected that the compound contains fundamental building block (FBB) formed by three different borate anionic groups, including BO3 triangle, and condensed branched BO3 triangles (B2O5 and B3O7). In particular, according to our survey, the branched B3O7 group is unprecedented. Our work provides useful information on the design and search for novel low dimensional copper borates, and also helps to strengthen the understanding of the investigation of borate structures.

Electrides are ionic crystals in which the electrons prefer to occupy free space, serving as anions. Because the electrons prefer to be in the pockets, channels, or layers to the atomic orbitals around the nuclei, it has been challenging to find electrides with partially filled d-shell transition metals, since an unoccupied d-shell provides an energetically favorable location for the electrons to occupy. We recently predicted the existence of electrides with partially filled d-shells using high-throughput computational screening. Here, we provide experimental support using X-ray absorption spectroscopy and X-ray and neutron diffraction to show that Sr3CrN3 is indeed an electride despite its partial d-shell configuration. Our findings indicate that Sr3CrN3 is the first known electride with a partially filled d-shell transition metal, in agreement with theory, which significantly broadens the criteria for the search for new electride materials.

In the last 50 years, an important aim of molecular and materials design has been the generation of space for the uptake of guest molecules in macrocycles and cryptands, in dendrimers as monomolecular containers, and recently in porous networks like metal-organic and covalent organic frameworks. Such molecular, oligomeric, and polymeric materials can be applied for sensing, separation, catalysis, drug delivery, and gas storage, among others. The common goal is the recognition of molecules and their uptake into and release from an appropriate space. Typically, completely empty space is unfavorable in crystalline materials. Therefore, the elimination of molecules from the cavities is often accompanied by the collapse of the cavities, that is, by a change in the molecular conformation. In contrast to this solid matter, in which the cavities are rationally designed by covalent or coordinative bonds, liquid crystals (LCs) are fluid materials with high molecular mobility. Thus, the proposal of empty space in LCs is certainly a scientific provocation. However, various recent publications on columnar mesophases claim the existence of pores with low electron density or even completely empty space on the basis of X-ray and solid-state NMR studies. Although the latter may be debated, there are many examples in which LCs take up dopants such as polymerizable monomers in disclination lines, perdeuterated chains in the interstices between columns, or electron acceptors to fill mesogens with incommensurate building blocks, which eventually stabilize the LC phases. It seems that in LC science the generation and usage of free space has been studied only occasionally and were lucky discoveries rather than investigations based on rational design. This Account summarizes the research on the formal generation of void in LCs and highlights that rational design of molecules can lead to unconventional mesophases by efficient filling of the provided space, as was shown with shuttlecock mesogens and discotic mesogens related to the concept of complementary polytopic interactions. The topic was recently further developed by the investigation of shape-persistent star mesogens. Despite the formally empty space between their arms, they all form columnar liquid crystals. Such shape-persistent oligo(phenylenevinylene) molecules fill the void and efficiently nanosegregate by helical packing in columns and deformation of the molecular scaffold at the expense of the torsional energy. This inspired us to fill the intrinsic free space by guest molecules either via supramolecular or covalent bonds or just by physical mixing in order to avoid the increase in torsional energy and to stabilize the structure. This strategy led to complex filled liquid-crystalline matter with high structural control and may in the future be used for the design of organic electronic materials that are easily alignable for device applications.

In this work, simple, low profile, compact quarter-mode substrate-integrated waveguide (QMSIW)-based antennas are proposed for Wireless Local Area Network (WLAN) at 5.2/5.5 GHz and Wireless Body Area Network (WBAN) at 5.8 GHz, respectively. By implementing QMSIW technique, the electrical size of the antenna is reduced up to 1/4th of the conventional circular SIW cavities. Thanks to the quarter mode concept, the antenna size is reduced significantly by preserving its dominant mode. The resonant frequency of the dominant mode TM010 is independently tuned at 5.2, 5.5, and 5.8 GHz after loading the QMSIW cavity with metalized via holes, subsequently. The on-body performance of the antenna is verified on pork tissues at 5.8 GHz and it is found to be insensitive with respect to surroundings. The measured gain and simulated efficiency of the proposed antenna at 5.8 GHz in free space are 4.8 dBi and 92%, while in the proximity of pork tissues values are 3.25 dBi and 57%, respectively. Moreover, the measurement results demonstrate a good matching with the simulation results.

The authors introduce a notched optical microdisk cavity by combining total internal reflection and transmission at Brewster's angle. The corresponding high-quality modes are excitable with an attached waveguide and have their intensity partially trapped in the free space of the notch.

An extraction method for the equivalent electromagnetic parameters (EEP) of grading honeycomb absorbing materials (GHAM) is proposed based on the asymmetric property of GHAM, EEP was modified by gradient factors related to its physical parameters in this paper. Considering that the strength of electromagnetic wave loss is dominated by the imaginary part of the complex dielectric constant, the EEP extraction method is built by optimizing the imaginary part of the complex dielectric constant according to the GHAM’s physical properties, such as the coating thickness of each layer for the GHAM, the increment between two adjacent gradient coatings, the layers of the GHAM, and the total axial height of graded honeycomb. The GHAM were prepared by the immersion process, and the reflectance measured by the free space method was consistent with that calculated by the EEP extraction method proposed in this paper within 2–18 GHz. The proposed EEP extraction method is simple, convenient, high precision, and it has played a certain role in solving the problems in actual engineering applications.

In this paper, we introduce a special device, in which the topological rejection effect in the study of biomacromolecule translocation competes with the entropic tensile force. The expected results for the translocation of the polymer chain given by these two different theories do not coincide with each other, so we call this problem the “translocation paradox”. The dynamics of the polymer chain and the preference translocation in such device are studied using computer simulation method. Surprisingly, these results do not completely satisfy all these hypothesis. We provide a plausible explanation which coincides our simulation results perfectly. Meanwhile, this explanation provides a possible solution to the design of translocation device in biophysics field.

This article discusses the performance of the free space optics (FSO) systems for short-range applications with the input signal power optimization. The BER eye diagram analyzer used to compute the optimum bit error rate and also compute the maximum Q factor for the previous and proposed models. The previous model has outlined the maximum Q factor of 206.45, where the proposed model Q factor value is 569.867 under the same operating parameters such as the wavelength of the transmitter of 1550 nm, the power of the transmitter of 10 mW, and the range of FSO is 800 m and signal attenuation 0.4 dB/km. The proposed study has outlined better performance than the previous study by about 21.76% enhancement percentage ratio.

Chromophores that exhibit aggregation-induced emission (i.e., aggregation-induced emission luminogens [AIEgens]) emit intense fluorescence in their aggregated states, but show negligible emission as discrete molecular species in solution due to the changes in restriction and freedom of intramolecular motions. As solvent-swollen quasi-solids with both a compact phase and a free space, gels enable manipulation of intramolecular motions. Thus, AIE-active gels have attracted significant interest owing to their various distinctive properties and promising application potential. Herein, a comprehensive overview of AIE-active gels is provided. The fabrication strategies employed are detailed, and the applications of AIEgens are summarized. In addition, the gel functions arising from the AIE moieties are revealed, along with their structure-property relationships. Furthermore, the applications of AIE-active gels in diverse areas are illustrated. Finally, ongoing challenges and potential means to address them are discussed, along with future perspectives on AIE-active gels, with the overall aim of inspiring research on novel materials and ideas.

We present a novel Brillouin fibre probe to achieve background-free remote mapping of micromechanical properties in tissue-mimicking hydrogel-water phantom. This Brillouin imaging system is designed using a low loss hollow core optical fibre and miniature objective for efficient light delivery and scattered light collection. The system efficiency and focusing power is comparable to free space Brillouin optical systems. This demonstration paves the way towards a wide range of biomedical and bioengineering applications where non-contact, label-free and damage-free mechanical imaging is required to retrieve in situ and in vivo microscopic viscoelastic properties of tissues and biomaterials.

An inverse problem of reconstructing real permittivity of a plane‐parallel layer in a perfectly conducting rectangular waveguide or in free space from experimental data using an explicit expression for the scattering matrix is considered. In general, this problem is improperly posed and may be unsolvable due to inaccuracy of the experimental data, and for a perfect noiseless experiment the solution may be not unique because the scattering coefficients curve has self‐intersection points. It is shown that the traditional multi‐frequency method of measurements applied in vector network analyzers can be justified. The following facts are rigorously proved in the paper: nonuniqueness of the solution can be removed if the frequency resolution is sufficiently small; and an algorithm for processing measurement results using least squares provides an approximate solution to the problem that converges to the exact one when the quality of the experiment improves, the convergence rate depends on the number of frequencies used in the experiment.

Recent interest in communication and sensing at millimetre wave frequencies has led to a need for accurate characterization of dielectric materials for antennas and components. Historically, broad-band free space methods have suffered from poor accuracy when determining the loss tangent of very low-loss materials. This paper provides several new corrections that improve the loss tangent accuracy of these methods by over an order of magnitude. Specifically, corrections that account for beam shift and focusing effects are described and demonstrated on several dielectric materials known for their low loss. These corrections are demonstrated on both focused beam and non-focused, free-space probe measurements.

International audience; An accurate quasi-optical S-parameter measurement method implemented in the normalized frequency bands Ka, W and J is presented in this paper. Permittivity extraction of various solid or non-solid dielectric materials is performed using the 4 S-parameters without time domain gating nor filtering. The procedure is validated through the comparison between the simulated and measured 4 S-parameters in magnitude and phase. Results are given for the Rexolite over a wide frequency span from the Ka to J band while some non-solid materials were characterized in the W band. Moreover, effects of rain flow on a dielectric slab were investigated for automotive radar applications in the W band and preliminary results are given.

Inadequate characteristics of marine clay often lead to engineered structures being damaged. There is a need to perform soil improvement prior to any construction activity. This study intends to ascertain marine clay strength from samples obtained from the West-Coast Expressway (WCE) project; the samples are planned to be strengthened using magnesium chloride (MgCl2). Specifically, the determination of the compressive strength of magnesium chloride-treated marine clay is a key objective of the study. The testing process comprises lab assessment to ascertain the Unconfirmed Compressive Strength (UCS) to treated and untreated marine clay samples. Laboratory tests confirmed that, typically, marine clay treated with MgCl2 had enhanced strength. The UCS test indicated that an addition of 6% MgCl2 to marine clay led the strength peaking at 137 kPa.In contrast, the addition of MgCl2 upwards of 4% led to a decrease in strength. Marine clay treated with 6% MgCl2 recorded an increase in UCS to 137 kPa and 110 kPa at seven and three days of curing, respectively. Subsequently, at fourteen and eighteen days, the strength values were 132 kPa and 125 kPa, respectively. It indicates that, typically, there is an increase in strength till the seventh day of curing and, subsequently, strength values begin to decrease. The change in strength can be attributed to the formation of cementation products that lead to soil particles getting bound together, and they occupy the free space between clay particles and MgCl2. With an increase in positive surcharge, soil particles begin to repel, thereby leading to reduced soil strength.

We present free-space luminescent solar concentrators (LSCs), analytical performance calculations, and experiments. This will enable concentrating diffused light onto commercial solar modules mitigating performance challenges of conventional LSCs.

This paper investigates electrical characterization (such as permittivity and permeability) of materials using the free space method. The technique employs a simulation design using full wave software CST consisted of two slotted patch antennas at 2.4 GHz and a slab of FR4 that has been placed in between of the antennas. The S parameters (S 11 and S 21 ) were extracted from simulation and the electrical characteristics of FR4 were calculated using Nicolson-Ross-Weir (NRW) and Smith methods. It comes to the knowledge that the NRW technique has limitation in terms of material thickness which affects the value of permittivity and permeability of materials. Thus, a comparison has been made between these two methods by varying the material thickness of FR4 versus its permittivity and permeability. The thickness was varied from 5mm to 60mm. It was observed that these two techniques produce similar values of permittivity and permeability when the thickness has been varied up to 50 mm but differs when it was greater than 50 mm. On top of that, this paper also investigates the slotted patch antenna as a potential of RF sensor to investigate the unknown materials at 2.4 GHz.

Metasurfaces are planar structures that enable us to manipulate electromagnetic wavefronts by using subwavelength elements. Here, we propose a new tunable metasurface based on phase change materials and graphene heaters to operate in the near-IR regime. In the proposed structure, by incorporating electrical heaters, the optical properties of the phase change material layer and, consequently, the metasurface response can be adjusted. Finally, to investigate the potential capability of the proposed metasurface as a free space beam shaper, its beam steering capability is investigated.

An ADAM optimization method, implemented using the Theano framework, for water-vapor effect removal from THz-TDS (terahertz time-domain spectroscopy) data is proposed. The cost function is derived from the ratio between the energy in the main THz pulse and the oscillation after the pulse as in [1]. A quantitative experimental validation of the method is performed. For free space measurement, the cost function is 0.018 in a sealed N2 environment, 0.043 in an open environment and 0.020 for the open environment data after applying the method. In addition, a qualitative improvement of D-(-)-Quinic acid's THz absorbance measurement in an open environment, where atmospheric humidity exists, is demonstrated. The cross-correlation between the D-(-)-Quinic acid's absorbance spectrum measured in a sealed N2 environment and one measured in an open environment increases from 0.044 to 0.62 after the water-vapor effect removal method is applied.

Edge enhancement is fundamental in image processing for recognizing or highlighting image features. Existing methods can only function in free space or transparent media. It remains challenging to achieve edge enhancement in the presence of multiple scattering. In this work, we present an implementation of digital optical phase conjugation to achieve effective edge enhancement through scattering media. The hypothesis is verified through experiments; the performance is promising and can be tuned by adjusting the beam ratio. The method may potentially enrich the interpretation of images obtained from complex environments.

The authors report on strong anomalous transmission in dielectric electrically thin binary structures comprising only two materials in alternating rectangular posts.

The unique heating mechanisms of microwaves and dielectrics permit dramatic energy savings in many instances, as well as providing other benefits. Thermal conductivity often plays a lesser role in microwave and dielectric heating than in conventional heating because of the great speed with which the former heat thus reducing the time in which thermal conductivity can be effective. Heating and drying with microwave and dielectric energy is distinctly different from conventional means. The mechanism for drying with microwave and dielectric energy is quite different from that for ordinary drying. The heating mechanisms for microwave and dielectric heating are similar, but the means of achieving them are somewhat different. The means of applying microwave and dielectric energy to a work piece differ in a very significant manner. Microwave energy may be transported through free space and must be focused upon the load.

Multiplexed detection of single particles in an optofluidic chip is demonstrated by free space excitation of encoded patterns milled on a metal-coated liquid core waveguide. Encoded signals from nanobeads are distinguished with high fidelity, showing promise for differential biomarker diagnosis.

A novel metasurface antenna is proposed with capacitive loading and dual-layer metasurface array. The antenna consists of dual-layer array using different period and four strips are inserted into unit of the upper array. This structure increases surface capacitance, thus reduces operating frequency and make the antenna miniaturized. The proposed antenna with a low profile of 0.064λ 0 and a metasurface size of 0.4λ 0 ×0.4λ 0 (λ 0 is the center operating wavelength in free space) attains 26.2% simulated bandwidth (|S 11 | < -10dB) with 6.19-7dBi gain at 3.78-4.92GHz. Compared to the traditional metasurface antenna, the antenna size reduced to 30%.

In this paper, we propose a methodology for characterization and homogenization of substrated metasurfaces by considering the behavior of the constituting scatterers and the interactions between them, independently. Then the proposed method is used to calculate the characteristic parameters of two different cases. At first, we consider a two-dimensional array of silicon nano-spheres placed in free space. Next, a two-dimensional array of silicon nano-spheres located on a glass substrate is studied. Finally, transmission and reflection coefficients of these metasurfaces are compared with those obtained by HFSS commercial software to show the efficiency and accuracy of the proposed method. The results are in good agreement.

MACKEY (Meta-surface inspired antenna chip developed by KIT EOE Laboratory), that operates not only in free space but also on a metal plate has been proposed. In this study, a new model MACKEY II with reduced thickness is proposed. Subsequently, the feed method of MACKEY II is studied and the analysis results are presented.

A meta-surface inspired antenna chip developed by KIT EOE Laboratory (MACKEY), which operates in a free space and on a metal plate, is proposed herein. The improved operation on metal is proposed to occur via change in the substrate vertical width W.

Previously, a simple transmission-only method was applied to extract the complex permittivity of common building materials in the 4–40 GHz range using a low-cost anechoic chamber and a vector network analyzer. This technique is validated using small dielectric resonators fabricated from the same materials as used in the free-space measurements. Agreement of the two methods indicates acceptable accuracy of the developed techniques. Measurement of Teflon, a well characterized material at microwave and millimeter-wave frequencies, is also reported, further validating these methods.

Motivated by the recent experimental realization of twisted double bilayer graphene (TDBG) samples we study, both analytically and numerically, the effects of circularly polarized light propagating in free space and confined into a waveguide on the band structure and topological properties of these systems. These two complementary Floquet protocols allow us to selectively tune different parameters of the system by varying the intensity and the frequency of the light. For the drive protocol in free space, in the high-frequency regime, we find that in TDBG with AB/BA stacking, we can selectively close the zone-center quasienergy gaps around one valley while increasing the gaps near the opposite valley by tuning the parameters of the drive. In TDBG with AB/AB stacking, a similar effect can be obtained upon the application of a perpendicular static electric field. Furthermore, we study the topological properties of the driven system in different settings, provide accurate effective Floquet Hamiltonians, and show that relatively strong drives can generate flat bands. On the other hand, longitudinal light confined into a waveguide couples to the components of the interlayer hopping that are perpendicular to the TDBG sheet, allowing for selective engineering of the bandwidth of Floquet zone center quasienergy bands without breaking the symmetries of the static system., 12 pages, 12 figures

A three-dimensional (3-D) band-stop frequencyselective structure (FSS) with high selectivity is presented in this paper. The FSS unit cell is composed of an annular resonator loaded with two lumped capacitances. The simulation results show that the proposed 3-D FSS has high selectivity and small size (3mm×5mm×6mm, 0.095λ 0 ×0.158λ 0 ×0.190λ 0 , λ 0 refers to the resonant wavelength in free space at 9.5 GHz). The simulated results exhibit stable band-stop performance under different incident angles (up to 45°). By cascading two 3-D FSS unit cells, the bandwidth and selectivity could be further enhanced. Compare to the traditional two-dimensional (2-D) FSS, the presented FSS shows higher selectivity and better angle stability.

High-pressure volumetric analysis (HPVA) experiments were carried out using Particulate System’s HPVA-II 200 at temperatures of 25 and 40 °C and pressures up to 7 MPa to quantify methane adsorption...

The purpose of this paper is to demonstrate an implementation of Er3+/Yb3+ codoped glass waveguide amplifiers (EYDWA) as a post-amplifier can provide an extended reach and a high split-ratio for the cost-effective implementation of hybrid fiber-to-the-x (FTTx) and free space optical (FSO) technologies. The performance has been compared on the basis of transmission distance, however the results of simulation show enhancement offered by EYDWA. This amplifier was able to reach transmission distance ratio of 160:5 km for GPON:FSO. Moreover in this paper, was study different characterizations of EYDWA amplifier, which depend essentially on the opt-geometric parameters, such as concentrations of ions erbium, length of the waveguide amplifier and the effect of those parameters to optimize the gain G, quality factor Q, min of BER and eye diagram.

By considering a group of atoms as a whole, the superatom state concept has been proposed to understand complex chemical systems. Superatom states distributed in free space are important in determining the interactions between superatoms and also the reactions of a superatom system with other external molecules. Unfortunately, all free-space superatom states reported to date are unoccupied states, which strongly limit their applications. In this study, we predict that both occupied and unoccupied free-space superatom states exist in an encapsulated Ca2N nanotube. In this composite system, the inner Ca2N nanotube provides anionic electrons in free space inside the tube, which form occupied s-, p-, and d-like superatom states. The outer carbon nanotube layer provides an effective protection for these free-space superatom states from the ambient environment. Such protected superatom states with flexible occupation statuses are expected to have a great potential in various application fields including catalys...