138 results on '"Artificial materials"'
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2. Issues of authenticity when conserving historic imitative crafts.
- Author
-
Rix, Hadas and Emmitt, Stephen
- Subjects
- *
STONE , *CULTURAL property , *SURFACES (Technology) , *SIXTEENTH century , *NINETEENTH century , *BUILDING stones - Abstract
The historical imitative crafts discussed in this study, such as scagliola, Coade stone, marbling and graining, were unique and original; their use was promoted and articulated between the end of the sixteenth and the nineteenth century. The conservation of imitative crafts may be compromised without a nuanced and specific approach. Conserving inventions of the past presents unique challenges since the mechanism of deterioration of artificial and natural materials intrinsically differ; the decay of natural stone or marble is different from that of scagliola. Current decision-making often aimed at increasing authenticity through retaining the ageing quality of the original fabric, may paradoxically devaluate the heritage significance if the original imitative intentions are not followed. This work aims to set a theoretical foundation upon which a code of practice could be developed to prevent further cultural heritage loss. The fundamental difference between artificial materials and imitative surfaces should inform guidelines for conservation policy. The skills of imitative crafts should be protected to retain their cultural significance. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
3. On the Design of Modular Reflecting EM Skins for Enhanced Urban Wireless Coverage.
- Author
-
Rocca, Paolo, Ru, Pietro Da, Anselmi, Nicola, Salucci, Marco, Oliveri, Giacomo, Erricolo, Danilo, and Massa, Andrea
- Subjects
- *
MODULAR design , *MILLIMETER waves , *TILES , *FACADES - Abstract
The design of modular, passive, and static artificial metasurfaces to be used as electromagnetic skins (EMSs) of buildings for improving the coverage in urban millimeter-wave communication scenarios is addressed. Toward this end, an ad hoc design strategy is presented to determine optimal tradeoff implementation solutions that assure a suitable coverage of the areas of interest, where the signal from the base station is too weak, with the minimum complexity. More specifically, the admissible surface in the building facade is first partitioned into tiles that are the minimum-size elements of the artificial coating (i.e., the building block of an EMS). Then, the search for the optimal EMS layout (i.e., the minimum number and the positions of the tiles to be installed) is carried out with a binary multiobjective optimization method. Representative numerical results are reported and discussed to point out the features and the potentialities of the EMS solution in the smart electromagnetic environment (SEME) and the effectiveness of the proposed design method. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
4. Pattern Reconfigurable Antennas at Millimeter-Wave Frequencies: A Comprehensive Survey
- Author
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H. Pablo Zapata Cano, Zaharias D. Zaharis, Traianos V. Yioultsis, Nikolaos V. Kantartzis, and Pavlos I. Lazaridis
- Subjects
Active tuning ,antennas ,artificial materials ,beam scanning ,beam shaping ,beam steering ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 - Abstract
Millimeter-wave bands (around 28, 38, 60, and 73 GHz) are anticipated to play a decisive role in the hosting of future wireless systems. The necessity of smart antennas to adaptively meet the requirements of the wireless links calls for new pattern reconfiguration antennas with beam-steering and/or beam-shaping capabilities. This paper reviews the latest research contributions on pattern reconfigurable antennas at mm-Wave frequencies, proposing an original classification according to the reconfiguration technique and technology. The analyzed systems are divided into two main groups: Reconfigurable and non-reconfigurable feeding antennas. Phased-arrays antennas are the main component of the first category, whereas other reconfigurable means such as the use of metasurfaces or advance materials like liquid crystal or graphene form the second group, devoted to non-reconfigurable feeding antennas. Furthermore, some insights and theoretical background are provided to help the reader understand and appreciate the uniqueness of every solution. Similarly, the beam-scanning and beam-shaping performance of some of the discussed works is analyzed. Finally, some instructive remarks and open research challenges are discussed, with the aim of providing some guidelines for potential new works on the field.
- Published
- 2022
- Full Text
- View/download PDF
5. Self-Oscillating Circularly Polarized Active Integrated Antenna Using Zeroth-Order Resonators With Boosted Conversion Efficiency.
- Author
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Ma, Tzyh-Ghuang, Wu, Xuan-Feng, Yeh, Yun-Chieh, and Chu, Huy Nam
- Abstract
A new self-oscillating circularly polarized active integrated antenna (CPAIA) featuring boosted dc-to-RF conversion efficiency is proposed and demonstrated in this letter. The conversion efficiency, 40% better than the second best design in the literature, is achieved by innovative integration of a CP exciter with a pair of anti-symmetrically arranged parasitic radiators. The CP exciter is a linearly polarized self-oscillating active dipole antenna consisting of zeroth-order resonators and a crosscoupled pair oscillator. In addition to oscillate and radiate a linearly polarized electrical field into space, it is responsible for coupling half of the oscillating power into the pair of parasitic radiators to excite another linearly polarized electric field spatially and temporally orthogonal to the original one for CP operation. The proposed CPAIA is fabricated and tested at 879 MHz, and is compared with the state-of-the-arts in the literature. Good agreement between the simulated and measured results validates the design concept, and the performance summary table highlights the advantages of the proposed design. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
6. Artificial materials for microwave applications
- Author
-
Bukhari, Syed S.
- Subjects
621.384 ,Mechanical Engineering not elsewhere classified ,Artificial materials ,Metamaterials ,Metasurfaces ,3D printing ,Microwaves - Abstract
This thesis has focussed on the properties and manufacturing techniques of artificial RF materials. These artificial materials can be divided into two types depending on the whether their individual unit cell is resonant or non-resonant. Both these types have been discussed. It has been shown that the efficiency and bandwidth of a patch antenna using a flexible 3D printed substrate can be improved by using composite materials as heterogeneous substrates. Composite materials with a large range of relative permittivity values were manufactured by combing 3D printing with commercial laminates. An equation to design such composite materials has been presented. The engineering tolerance and repeatability of 3D printing as a manufacturing process to fabricate 'on demand' dielectrics has been presented. For materials with resonant unit cells, 2D materials known as metasurfaces have been considered. Metasurfaces presented in this thesis have been developed by close coupling of two Babinet's complements. It has been shown that the unit cell of a dipole-slot metasurface can be miniaturized by adding an additional layer of dipoles, making a dipole-slot-dipole metasurface. The response of both these metasurfaces was explained with a qualitative circuit model. Miniaturization has been achieved by using square loops as the building blocks for a Babinet complementary metasurface. A λ/17 structure was designed, fabricated and measured by using square loops; however the two layers should be shifted with respect to each other toachieve strong inter-layer coupling, thus miniaturization. The width-optimization of a dipole-slot metasurface has been achieved by maximising the coupling co-efficient. The expression for optimum length to width ratio of a dipole-slot metasurface has been derived. A generalised analytical circuit model, for any Babinet complementary metasurface, has been derived based on integral equations. This analytical model has been used to explain the pass band and compact nature of these metasurfaces. The comparison between this analytical model and full wave analysis showed excellent agreement with high numerical accuracy.
- Published
- 2017
7. Experience in the Treatment of Pentalogy of Cantrell with Artificial Materials in a Single Clinical Center.
- Author
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Wang, Gang, Xi, Linyun, Li, Hongbo, Wang, Yi, Wu, Chun, Pan, Zhengxia, Li, Yonggang, Wang, Quan, and Dai, Jiangtao
- Subjects
- *
VENTRICULAR septal defects , *DOPPLER echocardiography , *ATRIAL septal defects , *PATENT ductus arteriosus , *CHILDREN'S hospitals , *DIVERTICULUM , *SURGICAL meshes , *THORACIC surgery , *CONGENITAL heart disease , *NEURAL tube defects , *RETROSPECTIVE studies , *TREATMENT effectiveness - Abstract
Objective: To summarize experience in the treatment of pentalogy of Cantrell (POC) in our hospital and explore the effect of artificial materials in repairing sternal defects.Materials and Methods: A retrospective analysis was performed on treatment of five children with POC treated by using the Gore-Tex patch and titanium mesh in the Department of Cardio-Thoracic Surgery, Children's Hospital of Chongqing Medical University, from January 2010 to January 2019.Results: The concurrent conditions included double outlet of right ventricle (n = 2), ventricular septal defect (VSD) and atrial septal defect (ASD) (n = 1), VSD and ASD and patent ductus arteriosus (n = 1), and VSD and left ventricular diverticulum (n = 1) in five cases with POC. Color Doppler echocardiography and computed tomography (CT) + three-dimensional (3D) reconstruction of the thorax and abdomen were performed preoperatively. The cardiac malformation was corrected according to color Doppler echocardiography, and a Gore-Tex patch was used to repair the pericardial defect. Titanium mesh was made according to CT 3D reconstruction with a 3D printing mold to repair sternal defects. All patients underwent a one-stage operation, all hearts were eventually repositioned, no deaths occurred after the operation, and follow-up was performed for 6 months to 2 years. The patients recovered well, and the exterior thorax was normal.Conclusion: The diagnosis of POC is not difficult. The priority of surgical treatment for POC is to obtain satisfactory corrections of cardiac malformation. The repair of the pericardial defect with the Gore-Tex patch and the sternal defect with the titanium mesh can make the heart return to the mediastinum, reduce the pressure on the heart, reduce the surgical trauma, reduce the difficulty of repairing the sternal defect, and optimally restore the exterior thorax. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
8. Authentic materials in classroom: A case study on students of faculty of social sciences – Kuwait University.
- Author
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Al-Shammari, Abbas Habor
- Subjects
CLASSROOMS ,STUDENTS ,QUESTIONNAIRES - Abstract
This paper examines the influence of authentic materials on the motivation of the Faculty of Social Sciences, Kuwait University. The target population is male and female students of two intermediate levels at the Faculty of Social Sciences, Kuwait University. All students received both artificial and authentic materials. Data from two observation sheets as well as self-report questionnaires showed that on-task behavior and observed motivation increased when authentic materials were used, but selfreported motivation increased for all classes only in the last two to three weeks of the experiment. On the other hand, students believe that artificial materials are more enjoyable than authentic materials. The result of this experiment generally found that artificial materials are more interesting than authentic materials. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
9. Design and application of novel metamaterial elements and configurations
- Author
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Zhu, Jiwen, Stevens, Christopher, and Edwards, David
- Subjects
621.3 ,Communications engineering (optical,microwave and radio) ,metamaterial ,microwave ,electromagnetics ,artificial materials - Abstract
Metamaterials are artificially constructed "materials" which are formed from arrays of engineered elements. By designing individual elements as well as their interactions, the propagation of electromagnetic (EM) waves within the structure can be manipulated, so that new responses can be realised which may not be found in nature. The subject of this research concerns the study of miniaturised elements with strong EM responses so that the constructed metamaterial can better approximate an ordinary low-loss material. The research involves designing miniaturised magnetic resonators operating in the microwave frequency range. A novel resonator prototypes, so-called “helical resonators”, have been successfully designed and fabricated whose physical sizes can fall below 1% of the free space wavelength at resonance. This contributes to a size reduction of 90% compared with previously published work. In addition, an analytical model has been developed, so that the resonance parameters of a helical resonator have explicit expressions. In particular, a constant optimal metallic fill ratio is demonstrated to exist, which can achieve a minimum resonant frequency and a maximum miniaturisation for any given outmost dimension of the element. The accuracy of the model has been verified by both simulation and experiment. The frequency responses of fabricated helical elements were measured using a vector network analyser and a pair of small loop non- resonant dipole probes, and the parameters were extracted using the phase frequency fit method which proves to have the best accuracy and robustness. The properties of a regular square array of helical resonators are subsequently investigated, which can be regarded as a two-dimensional metamaterial. A relevant analytical model has been developed, which characterises the array as an equivalent sheet with surface current distributions, rather than an artificial medium with finite thickness. The relation between the macroscopic EM fields and the small scale properties of individual helical resonators are then established. In particular, the helical resonators are observed to be inherently chiral, thus the assembled interlocking array exhibits dichroism. The transmission coefficients for the circular EM waves with two different polarisation states have been derived, which have been verified by simulation and measurement results as well. In addition, it has been theoretically demonstrated that the resonator elements and their spacings can be engineered, so that the circular EM wave with one particular polarisation state can be totally attenuated around the element resonance, while the other state suffers negligible attenuation. A quadratic relation between the optimal array spacing and the elements’ quality factor has been demonstrated.
- Published
- 2011
10. Impact compression properties of artificial cemented sand material under active confining pressure.
- Author
-
Jinjin Ge and Ying Xu
- Subjects
- *
SAND , *STRESS-strain curves , *ROCK properties , *ROCK analysis , *FAILURE mode & effects analysis , *PRESSURE - Abstract
In order to explore the mechanical properties of rock with deep in-situ stress under explosive impact, cemented sand material (artificial material) instead of rock was used to carry out impact dynamics test under the condition of confining pressure. The experimental results show that the stress-strain curve of cemented sand specimens tested by triaxial impact compression changes significantly compared with those tested by uniaxial impact compression. The dynamic failure mode of cemented sand specimens placed under confining pressure constraints is one of axial tensile failure, while the dynamic compressive growth factor, peak strain, dynamic elastic modulus, and specific energy absorption of cemented sand specimens all have the characteristics correlated with confining pressure. The research results in this study can be as an important basis for the mechanism analysis of rock breaking by blasting in deep rock mass. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
11. Development of Thermoplastic Polyurethane Films for the Replacement of Corneal Endothelial Function of Transparency Maintenance.
- Author
-
Zhang X, Wang H, Sun X, Zhao L, Li T, Qi X, Wang T, Zhou Q, and Shi W
- Subjects
- Animals, Rabbits, Endothelium, Corneal surgery, Cornea, Prostheses and Implants, Polyurethanes, Proteomics
- Abstract
Endothelial keratoplasty is the main surgical procedure for treating corneal endothelial dysfunction (CED), which is limited by the global shortage of donor corneas. Herein, we developed and evaluated the modified thermoplastic polyurethane (M-TPU) films with gelatin-glycidyl methacrylate to replace the corneal endothelial function and maintain corneal transparency. The films displayed comparable light transmission characteristics with normal corneas and clinically favorable mechanical properties for surgical manipulation. After surface modification, the hydrophilicity and biocompatibility of M-TPU films were significantly improved. In the rabbit CED model, the M-TPU implants exhibited firm adhesion to the exposed stromal surface. The rabbit corneal transparency and thickness could be restored completely within 1 week of M-TPU film implantation. There was no significant inflammatory reaction and immune rejection during the follow-up of 1 month. Proteomic analysis suggested that the complement inhibition, the increase of mineral absorption, and the decrease of P53 apoptosis signaling pathway and lysine degradation might be beneficial in maintaining the corneal transparency. Overall, our study demonstrated the potential of M-TPU films as artificial implants for the replacement of corneal endothelial function to restore corneal thickness and transparency.
- Published
- 2023
- Full Text
- View/download PDF
12. A novel cross-polarizer converter formed by twisted F-shaped chiral metamaterial.
- Author
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Sharma, Dushyant Kumar
- Subjects
- *
METAMATERIALS , *OPTICAL rotation , *MAGNETIC fields , *CURRENT distribution , *ELECTRIC fields - Abstract
A bi-layered twisted F-shaped chiral metamaterial is proposed in this work to realize efficient cross-polarizer convertor (CPC). Reported CPC design exhibited high optical activity owing to the cross-coupling between the applied electric field and the induced electric/magnetic field. The mechanism of CPC is described through the surface current distribution. The proposed design is fabricated and tested experimentally to verify the CPC functionality. The obtained experimental results are in good agreement with numerical simulation results. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
13. Updates in biomaterials of bearing surfaces in total hip arthroplasty
- Author
-
Hatem M. Bakr and Ahmed A. Khalifa
- Subjects
musculoskeletal diseases ,medicine.medical_specialty ,Ceramics ,Aseptic loosening ,Dentistry ,Periprosthetic ,Review ,Total hip ,Biomaterials ,Wear ,Joint injection ,Medicine ,Orthopedic surgery ,Artificial materials ,business.industry ,General Engineering ,Joint surface ,Surgical procedures ,musculoskeletal system ,equipment and supplies ,surgical procedures, operative ,Metals ,Polyethylene ,business ,RD701-811 ,Total hip arthroplasty - Abstract
Total hip arthroplasty (THA) is one of the most successful surgical procedures. It entails replacement of the damaged or diseased joint surface with artificial materials. Various materials had been developed and used to achieve optimal outcomes, including longer survivorship and minimal complications. The primary materials used in the manufacture of THA implants are polymers, metal alloys, and ceramics. The failures of THA mainly result from aseptic loosening due to the production of wear particles and the development of periprosthetic joint injection. A lot of advancement and introduction of new biomaterials in THA implants’ armamentarium are designed to avoid the common failure mechanisms and improve the longevity of the implants. In this review, we discussed various aspects of commonly used biomaterials in THA implants, to provide some updated information.
- Published
- 2021
14. Inverse design of EBG waveguides through scattering matrices
- Author
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Palmeri Roberta and Isernia Tommaso
- Subjects
artificial materials ,ebg ,inverse design ,inverse problems ,optimization problem ,scattering matrix ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Physics ,QC1-999 - Abstract
Inverse design procedures aim at determining optimal parameters for a given device in order to satisfy assigned specifications. In this contribution, the design of optimal EBG waveguides through inverse problems tools is addressed. In particular, an inversion tool based on the so called ‘scattering matrices’ is proposed and assessed to optimize the guiding effect for straight and bent waveguides.
- Published
- 2020
- Full Text
- View/download PDF
15. Problems of Increasing the Biocompatibility of Materials Used in Medicine
- Author
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Marufjon Mukhtorovich Mamajonov, Yuri Gennadievich Alekseev, Pavel Evgenievich Lushchik, and Murodjon Turgunbaevich Botirov
- Subjects
H1-99 ,Engineering ,Artificial materials ,Biocompatibility ,business.industry ,Modern literature ,technology, industry, and agriculture ,implants ,New materials ,Social Sciences ,Nanotechnology ,artificial materials ,Biocompatible material ,“metal” hypersensitization ,Metal allergy ,medical materials ,Social sciences (General) ,biocompatibility ,business ,metal allergy - Abstract
A review of modern literature on the development of biocompatible implants based on modern technologies, including bioengineering and nanostructuring, is presented. The advantages and disadvantages of implants based on metals and alloy, ways of improving their biological and mechanical properties are shown. In connection with the rapid development of many branches of science and technology, as well as in medicine, the problem arose of obtaining new materials, in particular, alloys with valuable physicochemical properties, which are used for the implant of cardiology, traumatology, orthopedics and other industries. Study of biocompatibility of medical devices based on metals and alloys, search for ways to overcome the low engraftability of implanted structures.
- Published
- 2021
16. Zeroth-Order Self-Oscillating Active Integrated Antenna Using Cross-Coupled Pair.
- Author
-
Chang, Yu-Wei and Ma, Tzyh-Ghuang
- Subjects
- *
ANTENNAS (Electronics) , *TRANSMITTERS (Communication) , *RADIO frequency identification systems , *RADIO telemetry , *NEAR field communication - Abstract
By ingeniously integrating a pair of zeroth-order resonators (ZORs) with a cross-coupled pair, for the first time, a novel zeroth-order self-oscillating active integrated antenna (AIA) is developed. Unlike the conventional feedback oscillating AIA, the new configuration is realized by, respectively, inserting a ZOR into each of the feedback paths of the cross-coupled pair to satisfy the Barkhausen criterion, and hence stabilize the oscillation. A self-oscillating AIA operates at the UHF radio frequency identification (RFID) band was demonstrated as a proof of concept. Benefitting from the infinite-wavelength property, the embedded ZORs are electrically large and capable of providing efficient power radiation into space. The oscillation parameters, meanwhile, remain good, thanks to the inherent high-quality factor property of metamaterial resonators. Without relying on ground radiation, the new design achieves good radiation and oscillation performances at the same time, hence adding extra flexibility on shaping the radiation pattern. According to the experimental results, the developed AIA, oscillating at 0.92 GHz, features a high dc-to-RF conversion efficiency of 52%, a moderate effective isotropic power of 8.9 dBm, and a low phase noise of −124.7 dBc/Hz at a 1 MHz offset from the carrier frequency. The design principle and experimental demonstration are thoroughly discussed. [ABSTRACT FROM PUBLISHER]
- Published
- 2017
- Full Text
- View/download PDF
17. A potential consequence for urban birds' fitness: Exposed anthropogenic nest materials reduce nest survival in the clay-colored thrush.
- Author
-
Corrales-Moya, Josué, Barrantes, Gilbert, Chacón-Madrigal, Eduardo, and Sandoval, Luis
- Subjects
BIRD nests ,THRUSHES ,URBAN animals ,BIRD mortality ,BIOLOGICAL fitness ,URBAN ecology ,SURVIVAL rate - Abstract
Urban bird dwellers survive and reproduce in highly urbanized ecosystems. Some individuals adjust to these novel conditions by changing natural nesting materials for artificial materials, thus making nests more conspicuous in the environment. The consequences of using artificial materials for nesting remain poorly understood, especially from a nest-predator perspective. We studied if exposed artificial materials on bird nests affect the daily survival rate in a common dweller species, the clay-colored thrush (Turdus grayi). We used previously collected nests with a different area of exposed artificial materials and placed them with clay eggs on the main campus of the Universidad de Costa Rica. During 12 days of the reproductive season, we monitored the nests using trap cameras located in front of each nest. We found that nest survival decreased as the proportion of exposed artificial materials increased in the nest and, unexpectedly, that the principal predators were conspecifics. Thus, artificial materials used in the outer layer of nests make them more susceptible to predation. The use of artificial materials likely reduce reproductive success and population size in urban clay-colored thrush, but further field experiments measuring the effect of waste in birds' nests on the reproductive success of urban birds are needed. [Display omitted] • Exposed human trash used for nesting reduce nest daily survival rate in birds. • Synthetic materials used for nesting make nests more conspicuous in the environment. • Conspecifics (clay-colored thrushes) results the principal nest predators. • Human waste could produce a critical effect on urban wildlife birds reproduction. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
18. Critical issues in soft rocks
- Author
-
Milton Assis Kanji
- Subjects
Rock mechanics ,Soft rocks ,Rock properties ,Geomechanical classification ,Artificial materials ,Engineering geology. Rock mechanics. Soil mechanics. Underground construction ,TA703-712 - Abstract
This paper discusses several efforts made to study and investigate soft rocks, as well as their physico-mechanical characteristics recognized up to now, the problems in their sampling and testing, and the possibility of its reproduction through artificially made soft rocks. The problems in utilizing current and widespread classification systems to some types of weak rocks are also discussed, as well as other problems related to them. Some examples of engineering works in soft rock or in soft ground are added, with emphasis on their types of problems and solutions.
- Published
- 2014
- Full Text
- View/download PDF
19. On the Design of Modular Reflecting EM Skins for Enhanced Urban Wireless Coverage
- Author
-
Paolo Rocca, Pietro Da Ru, Nicola Anselmi, Marco Salucci, Giacomo Oliveri, Danilo Erricolo, and Andrea Massa
- Subjects
Artificial Materials ,Buildings ,Electromagnetics ,Energy management ,Environmental management ,Millimeter wave communication ,Millimeter-wave ,Mobile Communications ,Multi-Objective Optimization ,Skin ,Smart EM Environment ,Tiles ,Systems and Control (eess.SY) ,Electrical Engineering and Systems Science - Systems and Control ,FOS: Electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,Uncategorized - Abstract
The design of modular, passive, and static artificial metasurfaces to be used as electromagnetic skins (EMSs) of buildings for improving the coverage in urban millimeter-wave communication scenarios is addressed. Towards this end, an ad-hoc design strategy is presented to determine optimal trade-off implementative solutions that assure a suitable coverage of the areas of interest, where the signal from the base station is too weak, with the minimum complexity. More specifically, the admissible surface in the building facade is first partitioned into tiles, which are the minimum-size elements of the artificial coating (i.e., the building block of an EMS). Then, the search for the optimal EMS layout (i.e., the minimum number and the positions of the tiles to be installed) is carried out with a binary multi-objective optimization method. Representative numerical results are reported and discussed to point out the features and the potentialities of the EMS solution in the smart electromagnetic environment (SEME) as well as the effectiveness of the proposed design method.
- Published
- 2022
20. Symmetry Properties of Spheroidal Functions With Respect to Their Parameter.
- Author
-
Erricolo, Danilo and Negishi, Tadahiro
- Subjects
- *
SPHEROIDAL functions , *WAVE functions , *ELECTROMAGNETIC wave scattering , *WAVENUMBER , *HELMHOLTZ equation - Abstract
Spheroidal wave functions depend on a parameter $c$ . Their behavior with respect to changes of sign of $c$ is investigated, and explicit formulas are provided. Sample applications of the resulting symmetry rules are provided for some electromagnetic scattering problems. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
21. How Specific Interactions Drive the Complex Organisation of Building Blocks.
- Author
-
Zeravcic, Zorana
- Subjects
MOLECULAR self-assembly ,AUTOPOIESIS ,SIMULATION methods & models ,PARTICLE dynamics analysis - Abstract
Can artificial materials be developed that rival nature's ability to self-assemble and self-replicate? Zorana Zeravcic, lecturer and researcher at the École Supérieure de Physique et de Chimie Industrielles Paris Sciences et Lettres Research University in Paris, outlines investigations on the subject being carried out by her department and by counterparts at Harvard University in the US. Drawing on methodologies and knowledge from across the sciences, their simulations have yielded previously unenvisioned complex functionalities that could transform the way we build. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
22. A Generalized Reaction Theorem That Eliminates Internal Resonances in the Electric and Magnetic Field Integral Equations.
- Author
-
Tsalamengas, John L.
- Subjects
- *
MAGNETIC fields , *ELECTRIC field effects , *ELECTROMAGNETIC wave scattering , *METAMATERIALS , *ELECTROMAGNETISM - Abstract
This paper presents stable magnetic-field and electric-field integral equation formulations for exterior electromagnetic scattering by either penetrable or perfectly conducting closed bodies of general shape. The development relies on an extension of the conventional reciprocity theorem allowing the fields produced by some combination of sources in one environment to be connected with the fields generated by another combination of sources in a different environment. By the use of lossy metamaterials, the internal-resonance problem inherent to the original versions is eliminated, and thus the new formulations are amenable to a unique, highly accurate, and well-conditioned solution. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
23. Non-Invasive Approach to Investigate the Mineralogy and Production Technology of the Mosaic Tesserae from the Roman Domus of Villa San Pancrazio (Taormina, Italy)
- Author
-
Pablo Irizar, Irantzu Martinez-Arkarazo, Clemente Bretti, Lorenzo Campagna, Anna Irto, Olivia Gómez-Laserna, Gabriele Lando, and Paola Cardiano
- Subjects
Crystallography ,Artificial materials ,General Chemical Engineering ,Non invasive ,Coloring agents ,Excavation ,Raman spectroscopy, EDXRF, chemometric analysis, Roman Taormina, Roman mosaics ,Condensed Matter Physics ,Roman mosaics ,Mineralogical composition ,Archaeology ,Mosaic ,Natural (archaeology) ,Inorganic Chemistry ,QD901-999 ,Raman spectroscopy ,EDXRF ,chemometric analysis ,Roman Taormina ,General Materials Science ,Polychrome ,Geology - Abstract
The archaeological excavations at Villa San Pancrazio (Taormina, Italy) are bringing to light a vast Roman-Imperial residential quarter featuring luxurious dwellings decorated with wall paintings and mosaic floors, pointing it out as one of the most significant archaeological sites of the city. The polychrome and black and white mosaics recovered date back to the middle Imperial period, during the 2nd century AD. This work deals with the first archaeometric investigations of the materials employed for the tesserae production with the aim of elucidating the mineralogical composition and obtaining analytical evidence that can contribute to extracting information related to their production technology. For that purpose, a non-invasive methodology, based on micro energy dispersive X-ray fluorescence (μ-EDXRF) spectrometry and Raman spectroscopy, was used to characterize a wide selection of stone, ceramic and glass tesserae. Chemometric tools were exploited to manage the large set of elemental data collected on black and white lithic samples, providing essential clues for the subsequent investigations. The results evidenced the employment of natural lithotypes (calcareous sedimentary, dolomitic and volcanic) local and imported, and also artificial materials, such as ceramic made firing magnesium-rich clays, soda-lime-silica glasses made with different opacifying and coloring agents (such as calcium antimoniate, cobalt and copper) This work was supported by project IT-742-13 for Consolidated Research Groups, funded by the Basque Country Government. P. Irizar gratefully acknowledges his predoctoral grant (PRE2018-085888) from the MINECO Spanish Ministry. O. Gómez-Laserna is grateful to the University of the Basque Country (UPV/EHU) for her postdoctoral contract. P. Cardiano also thanks University of Messina (FFABR UNIME 2020) for funding.
- Published
- 2021
24. High-Efficiency Self-Oscillating Active Integrated Antenna Using Metamaterial Resonators and Its Application to Multicarrier Radio Frequency Identification Systems.
- Author
-
Liu, Zhi-Hong, Chang, Yu-Wei, and Ma, Tzyh-Ghuang
- Subjects
- *
ACTIVE antennas , *DIPOLE antennas , *OSCILLATIONS , *WIRELESS power transmission , *METAMATERIALS - Abstract
A self-oscillating active integrated antenna with very high dc-to-radio frequency (RF) conversion efficiency is proposed and validated with the aid of metamaterial resonators. The key innovation is the new integration scheme which allows an independent control of the resonators used in the feedback oscillator and the radiating element in the integrated antenna. The metamaterial resonator, featuring a high quality factor for good oscillation performances, is applied to excite the dipole-mode ground radiation with good radiation efficiency at the same time. The design principle is introduced; the circuit and antenna parameters including the loop gain, oscillation output power, phase noise, effective isotropic radiated power, and radiation patterns are investigated in detail. Its application to multicarrier RF identification systems as a low-cost continuous-wave source is supported by quantitative measurement results. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
25. Surface Waveguides Supporting Both TM Mode and TE Mode With the Same Phase Velocity.
- Author
-
Li, Mei, Xiao, Shaoqiu, Long, Jiang, and Sievenpiper, Daniel F.
- Subjects
- *
SURFACE wave antennas , *ANTENNAS (Electronics) , *WAVEGUIDE antennas , *OPTICAL dispersion , *MICROWAVE antennas , *WAVEGUIDES - Abstract
Two kinds of surface-wave waveguide (SWG) topologies are proposed in this paper with the objective to achieve the property of supporting both transverse magnetic (TM) and transverse electric (TE) modes with the same phase velocity. The first type is composed of two frequency-selective surfaces (FSSs) as layers whose dominant modes are TM mode and TE mode, respectively. For illustrationC the combination of loop-type FSS and wire-grid-type FSS is analyzed and its dispersion characteristics are examined as well. The second class also consists of two layers. For the top layer, there are gaps in one direction and continuous conducting strips in the orthogonal direction. The bottom layer is created from a 90° rotation of the top layer. As a particular illustration, a modified bow-tie-like SWG structure is investigated. The simulated results show that the two proposed SWG structures exhibit the property of supporting both TM mode and TE mode with the same phase velocity over a broad bandwidth. In addition, the effects of lattice types on dispersion diagrams are discussed in this paper. Near field measurements are also carried out to validate the simulations and good agreements are achieved. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
26. Utilization of double metal-dielectric composite substrates for microwave miniaturization of rectangular patch antennas.
- Author
-
Rybin, Oleg and Shulga, Sergey
- Abstract
The microwave concept of miniaturization of a rectangular patch antenna using two-layer metal-dielectric composite substrate with a large value in the real part of the effective relative permittivity is developed. Each layer is a metamaterial slab in the form of a parallelepiped dielectric matrix with periodically embedded metallic wires. The proposed idea is validated by numerical simulations for sample rectangular patch antennas. The comparative analysis of the simulation results is made at the frequencies of approximately 15 GHz. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
27. In situ synthesised TiO2 ‐chitosan‐chondroitin 4–sulphate nanocomposites for bone implant applications.
- Author
-
Alex, Martina Jenitha, Periasamy, Prabu, Mohan, Kalirajan, Sekar, Sankar, Prabha, Kavitha Kandiah Suriya, and Venkatachalam, Rajendran
- Abstract
The artificial materials for bone implant applications are gaining more importance in the recent years. The series titania‐chitosan‐chondroitin 4–sulphate nanocomposites of three different concentrations (2:1:x, where x ‐ 0.125, 0.25, 0.5) have been synthesised by in situ sol–gel method and characterised by various techniques. The particle size of the nanocomposites ranges from 30–50 nm. The bioactivity, swelling nature, and the antimicrobial nature of the nanocomposites were investigated. The swelling ability and bioactivity of the composites is significantly greater and they possess high zone of inhibition against the microorganisms such as Staphylococcus aureus and Escherichia coli. The cell viability of the nanocomposites were evaluated by using MG‐63 and observed the composites possess high cell viability at low concentration. The excellent bioactivity and biocompatibility makes these nanocomposites a promising biomaterial for bone implant applications. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
28. Alteration of Electromagnetic Scattering Using Hard and Soft Anisotropic Impedance Surfaces.
- Author
-
Quarfoth, Ryan and Sievenpiper, Daniel
- Subjects
- *
ELECTROMAGNETIC wave scattering , *ANISOTROPIC crystals , *IMPEDANCE matrices , *UNIT cell , *SHEAR waves , *BANDWIDTHS - Abstract
The scattering from a rectangular metal sheet is altered by patterning the surface with hard and soft anisotropic impedance surfaces. A plane wave incident normally to an edge of a metal rectangle will have maximum backward scattering in the direction of the source for both transverse magnetic (TM) and transverse electric (TE) polarizations. This scattering lobe is manipulated by patterning the metal sheet in two sections. A hard surface is applied to the incident region which reflects neither TM nor TE waves from the front edge. Similarly, a soft surface prevents reflections of both polarizations from the back edge. The surfaces are patterned with an angled boundary, so that surface waves and incident radiation are scattered at an angle instead of backward. Unit cells are designed and analyzed for both regions for operation centered at 15 GHz. A surface is fabricated and measured, and the scattering alteration effect is achieved over a large bandwidth for each polarization. Curved and zigzag geometries are also discussed. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
29. Settlement preferences of leeches (Clitellata: Hirudinida) for different artificial substrates.
- Author
-
Adamiak-Brud, Żaneta, Jabłońska-Barna, Izabela, Bielecki, Aleksander, and Terlecki, Janusz
- Subjects
- *
LEECHES , *ARTIFICIAL substrates (Biology) , *POLYCARBONATES , *ERPOBDELLA , *HELOBDELLA - Abstract
We examined the settlement preferences of leeches by analysing colonization patterns on artificial substrates. The intention was to check whether the type of material, texture and size of artificial substrates would influence the abundance of leeches. To test substrate type preferences, we used the following nine artificial substrates: polyester, polycarbonate, aluminium, glass, rubber, steel, polyethylene, ceramics and polypropylene. In addition, substrates of different textures (structural vs. smooth) and sizes (900, 400, 100 cm) were used. We found that rubber, polyethylene and aluminium were most frequently chosen by the leeches. Surface structure and size of the objects were other factors which determined substrate selection by these organisms. Leeches more readily inhabited rough surfaces and the surfaces of smaller-sized objects. The species composition of leech assemblages on analysed artificial substrates was dominated by predatory taxa of the genus Erpobdella and Helobdella. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
30. Mechanical Behavior and Constitutive Modeling of Cement–Bentonite Mixtures for Cutoff Walls
- Author
-
Luca Flessati, Gabriele Della Vecchia, and Guido Musso
- Subjects
Pollutant ,Cement ,Cutoff Walls, Cement-Bentonite, Microstructure, Constitutive Modelling ,Artificial materials ,Materials science ,Water flow ,Building and Construction ,Cutoff Walls ,Cement-Bentonite ,Mechanics of Materials ,Bentonite ,Cutoff ,General Materials Science ,Limit (mathematics) ,Composite material ,Constitutive Modelling ,Microstructure ,Civil and Structural Engineering - Abstract
Cement–bentonite mixtures are commonly used to build cutoff walls, which limit water flow and underground transport of pollutants. These artificial materials are employed due to their very ...
- Published
- 2021
31. Analyzing the mechano-bactericidal effect of nano-patterned surfaces on different bacteria species
- Author
-
Mohammad J. Mirzaali, Sara Bagherifard, Erfan Maleki, and Mario Guagliano
- Subjects
Artificial neural network ,Materials science ,Bactericidal surfaces ,02 engineering and technology ,03 medical and health sciences ,Nano ,Materials Chemistry ,Finite element modeling ,Sensitivity analyses ,030304 developmental biology ,Nano-morphology ,0303 health sciences ,Artificial materials ,biology ,Surfaces and Interfaces ,General Chemistry ,Physical interaction ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,biology.organism_classification ,Bactericidal effect ,Surfaces, Coatings and Films ,Surface modification ,Antibacterial surfaces ,0210 nano-technology ,Biological system ,Bacteria - Abstract
Mechano-bactericidal effects exhibited by specific nano-patterns have brought in the prospect of developing sustainable antibacterial materials. Contrary to the standard practices of administrating anti-bacterial agents or chemical surface functionalization, nano-patterns manage to inactivate a wide variety of bacteria species with no risk of toxicity, antibiotic resistance or replenishment. Herein, the experimental data on the bactericidal effect of nano-patterns were collected to develop in-silico models for identifying the impact of individual geometrical features. An artificial neural network was developed considering the three prevalent species of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The roles of individual geometrical features were analyzed and comprehensive parametric and sensitivity analyses were performed to determine the most favorable range for each parameter against different species. Geometrical features that would demonstrate bactericidal effects simultaneously against all the three studied species were identified. The efficient geometrical parameters, obtained from the artificial neural network analysis, were then used to develop a series of finite element models to simulate the physical interaction between the bacteria and the nano-patterns that result in inactivation. The obtained results can pave the way for unlocking the role of geometrical features towards optimized development of artificial materials with sustainable intrinsic antibacterial characteristics.
- Published
- 2021
32. Metamaterial Spheroidal Cavity to Enhance Dipole Radiation.
- Author
-
Negishi, Tadahiro, Erricolo, Danilo, and Uslenghi, Piergiorgio L. E.
- Subjects
- *
METAMATERIALS , *RADIATION , *MAGNETIC dipoles , *COMPOSITE materials , *ELECTROMAGNETISM - Abstract
Metamaterials have been considered for their potential to improve the radiation characteristics of sources. A novel geometry consisting of a semioblate spheroidal cavity containing two layers, one made of DPS and the other made of DNG metamaterial, and built underneath an aperture in infinite metallic plane is considered. An exact analytical solution is obtained and its numerical evaluation demonstrates a significant improvement of the directive radiation of a dipole source, with the appropriate combination of the ordinary double positive (DPS) and DNG layers. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
33. Nonscattering Waveguides Based on Tensor Impedance Surfaces.
- Author
-
Quarfoth, Ryan G. and Sievenpiper, Daniel F.
- Subjects
- *
WAVEGUIDES , *METAMATERIALS , *METAMATERIAL antennas , *SURFACE wave antennas , *ANTENNAS (Electronics) - Abstract
A tensor impedance surface waveguide is built using anisotropic unit cells. The waveguide can propagate a confined waveguide mode along its axis while waves incident to the guide at an orthogonal direction pass through as if the waveguides were not present. Both straight and curved implementations are demonstrated. Surface waves incident at an angle to the waveguide show reflection and refraction at the impedance interface. A theoretical model for tensor impedance surface waveguides is generalized to include dispersive unit cells and bending loss around curves. Dispersion results for modes propagating in the waveguide show agreement between the theory, simulation, and experimental measurements. A curved waveguide is also constructed which guides surface waves around a curve and is transparent to surface waves incident at an orthogonal angle. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
34. On a Lossy Electric–Magnetic Uniaxial Medium and Its Applications to Boundary Conditions.
- Author
-
Khalid, Muhammad, Tedeschi, Nicola, and Frezza, Fabrizio
- Subjects
- *
ELECTROMAGNETIC waves , *METAMATERIALS , *ELECTROMAGNETISM , *SURFACE chemistry , *ISOTROPIC properties - Abstract
In this paper, we investigate the reflection behavior of electromagnetic waves incident on an interface between an isotropic medium and a general electric–magnetic uniaxial lossy medium. We analyze this interface by applying the general Soft-Hard/DB (SH/DB) boundary conditions and discuss its response for some particular cases as well. The propagation of both homogeneous and inhomogeneous waves in a uniaxial lossy medium is discussed. It is found that for low losses the uniaxial medium under consideration is very suitable, while for higher losses it decreases its appeal for the realization of the SH/DB medium. The results obtained in the lossy case are compared with those of the lossless one, presented in the literature. Many metamaterials proposed can be homogenized as electric–magnetic uniaxial media. We investigate their characteristics and try to understand their limitations due to the presence of losses. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
35. Broadband Unit-Cell Design for Highly Anisotropic Impedance Surfaces.
- Author
-
Quarfoth, Ryan and Sievenpiper, Daniel
- Subjects
- *
ANISOTROPY , *DIELECTRICS , *SUBSTRATES (Materials science) , *RESONANT vibration - Abstract
A unit-cell design for highly anisotropic impedance surfaces is simulated and experimentally demonstrated. The unit cell consists of a grounded dielectric substrate with a metal patch and plated metal via. The design has a ring of metal removed from the patch so that the resonant effect of the via is reduced. The reduced resonance prevents backward-wave modes which are difficult to excite experimentally. On grounded dielectric substrates, the transverse-magnetic mode is fundamental and the transverse-electric (TE) mode is bound above a cutoff frequency. It is shown that highly anisotropic surface impedance can only be achieved below the TE cutoff frequency. The proposed unit cell is constructed using printed-circuit-board fabrication technology, and the result is a unit cell that obtains highly anisotropic impedance over a broader frequency range than traditional patch or mushroom unit cells. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
- Full Text
- View/download PDF
36. Multi-Band Miniaturized Antenna Loaded by ZOR and CSRR Metamaterial Structures With Monopolar Radiation Pattern.
- Author
-
Mehdipour, Aidin, Denidni, Tayeb A., and Sebak, Abdel-Razik
- Subjects
- *
MONOPOLE antennas , *METAMATERIALS , *RESONATORS , *CURRENT distribution , *RADIATION - Abstract
Miniaturized low-profile monopole antennas loaded by metamaterial (MTM) structures are presented. The antenna is loaded by zeroth-order resonator (ZOR) and complimentary split-ring resonator (CSSR) units, resonating over three frequency bands so that they can be tuned by changing the geometrical parameters of the MTM structures. Surface current distribution and equivalent circuit models are provided to describe the principle of operation. The experimental results are presented to validate the numerical results. Showing the monopole-shape radiation pattern characteristics at all resonant frequencies, the proposed MTM antennas are suitable for vehicular wireless applications. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
- Full Text
- View/download PDF
37. Surface Wave Scattering Reduction Using Beam Shifters.
- Author
-
Quarfoth, Ryan and Sievenpiper, Daniel
- Abstract
A surface wave beam shifter is designed using ringmushroom unit cells. The unit cell consists of a rectangular ring that surrounds an interior patch and plated via. The unit cell is anisotropic, and surface waves propagate with different directions of phase velocity and power flow. Two adjacent regions are designed such that the shift direction in each region is mirrored. The result is that an incident beam is split apart, and power does not radiate in the original direction of the beam. It is shown that an object placed in line with a source scatters surface waves in multiple directions from the object. By using a beam-splitting surface, the incident beam avoids the object, and scattering is significantly reduced. When the wave is incident in series with the two beam shifters, the surface shifts the wave in one direction followed by a shift in the opposite direction. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
38. Inverse Design of Artificial Materials Based Lens Antennas through the Scattering Matrix Method
- Author
-
Roberta Palmeri and Tommaso Isernia
- Subjects
Optimization problem ,High interest ,Computer Networks and Communications ,Computer science ,Inverse ,lcsh:TK7800-8360 ,artificial materials ,02 engineering and technology ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Homogenization (chemistry) ,010309 optics ,0103 physical sciences ,Scattering-matrix method ,0202 electrical engineering, electronic engineering, information engineering ,inverse design ,Electrical and Electronic Engineering ,lens antenna ,Artificial materials ,Scattering ,Lens antennas ,scattering ,lcsh:Electronics ,020206 networking & telecommunications ,Hardware and Architecture ,Control and Systems Engineering ,Signal Processing ,antennas ,optimization problem ,Algorithm - Abstract
The design of spatially varying lens antennas based on artificial materials is of high interest for their wide range of applicability. In this paper, we propose a novel design procedure relying on an inverse formulation of the scattering matrix method (SMM). Differently from many adopted approaches, which resort to global optimizations or homogenization procedures, the inverse SMM (I-SMM) allows the synthesis of optimal parameters (geometrical and/or electromagnetic) for the inclusions realizing the overall device in a very effective manner. With reference to the 2D TM case, the proposed tool has been successfully assessed through the synthesis of different kinds of lenses radiating a pencil beam.
- Published
- 2020
39. Programmable droplet manipulation by a magnetic-actuated robot
- Author
-
Kaixuan Li, Zhipeng Zhao, An Li, Zheng Li, Huizeng Li, Yanlin Song, and Mingzhu Li
- Subjects
Medical diagnostic ,Multidisciplinary ,Artificial materials ,Computer science ,technology, industry, and agriculture ,Mechanical engineering ,SciAdv r-articles ,equipment and supplies ,Water collection ,Physics::Fluid Dynamics ,body regions ,Computer Science::Robotics ,Robot ,Materials Sciences ,human activities ,Research Articles ,Research Article - Abstract
We demonstrate a magnetic-actuated robot with adjustable structure to operate fluids for transport, split, release, and rotation., Droplet manipulations are fundamental to numerous applications, such as water collection, medical diagnostics, and drug delivery. Structure-based liquid operations have been widely used both in nature and in artificial materials. However, current strategies depend mainly on fixed structures to realize unidirectional water movement, while multiple manipulation of droplets is still challenging. Here, we propose a magnetic-actuated robot with adjustable structures to achieve programmable multiple manipulations of droplets. The adjustable structure redistributes the resisting forces from the front and rear ends of the droplets, which determine the droplet behaviors. We can transport, split, release, and rotate the droplets using the robot. This robot is universally applicable for manipulation of various fluids in rough environments. These findings offer an efficient strategy for automated manipulation of droplets.
- Published
- 2020
40. Longitudinal and transversal elasticity of natural and artificial materials for musical instrument reeds
- Author
-
Enis Ukshini and Joris J.J. Dirckx
- Subjects
Acoustics ,Airflow ,Musical instrument ,Data_CODINGANDINFORMATIONTHEORY ,02 engineering and technology ,lcsh:Technology ,01 natural sciences ,Article ,Musical acoustics ,0103 physical sciences ,General Materials Science ,Hardware_ARITHMETICANDLOGICSTRUCTURES ,Elasticity (economics) ,lcsh:Microscopy ,010301 acoustics ,Elastic modulus ,lcsh:QC120-168.85 ,Mathematics ,Computer Science::Information Theory ,Artificial materials ,lcsh:QH201-278.5 ,biology ,lcsh:T ,Physics ,synthetic reeds ,Arundo donax ,musical instruments ,021001 nanoscience & nanotechnology ,biology.organism_classification ,Physics::Classical Physics ,elasticity modulus ,arundo donax ,lcsh:TA1-2040 ,musical acoustics ,lcsh:Descriptive and experimental mechanics ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,lcsh:Engineering (General). Civil engineering (General) ,0210 nano-technology ,Energy source ,lcsh:TK1-9971 - Abstract
The reed is the primary component in single-reed woodwind instruments to generate the sound. The airflow of the player&rsquo, s mouth is the energy source and the airflow is modulated by the reed. The oscillations of the reed control the airflow. Traditionally, instrument reeds are made out of natural cane (Arundo Donax), but in efforts to overcome variability problems, synthetic reeds have been introduced. Previous investigations mainly focused on natural cane reeds and direct elasticity measurements did not discriminate between elasticity moduli along different directions. In order to obtain the mechanical properties along the direction of the reed fibres and in the orthogonal direction separately, a three-point bending testing setup was developed, which accommodates the small samples that can be cut from an instrument reed. Static moduli of elasticity were acquired in both directions. Much higher ratios between longitudinal and transversal moduli were seen in the natural cane reed as compared to the artificial reeds. Wet natural reeds showed a strong decrease in moduli of elasticity as compared to dry reeds. Elasticity was significantly higher in artificial reeds. The force&ndash, displacement curves of the wet natural reed show hysteresis, whereas the artificial materials did not. In the cane reed, higher energy losses were found in the transversal direction compared to the longitudinal direction
- Published
- 2020
41. Nonlinear optical response and self-trapping of light in biological suspensions
- Author
-
Anna Bezryadina, Yinxiao Xiang, Tobias Hansson, Josh Lamstein, Zhigang Chen, Nicolas Perez, Benjamin Wetzel, Yi Liang, Rekha Gautam, Roberto Morandotti, Guo Liang, XLIM (XLIM), Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS), Photonique Fibre et Sources Cohérentes (XLIM-PHOT), and Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS)-Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Materials science ,Other Physics Topics ,Optical force ,optical force ,General Physics and Astronomy ,Nanotechnology ,02 engineering and technology ,Trapping ,01 natural sciences ,010309 optics ,Nonlinear optical ,[NLIN.NLIN-PS]Nonlinear Sciences [physics]/Pattern Formation and Solitons [nlin.PS] ,0103 physical sciences ,self-trapping and soliton ,Soft matter ,nanosuspension ,[PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics] ,Artificial materials ,[PHYS.PHYS.PHYS-ATM-PH]Physics [physics]/Physics [physics]/Atomic and Molecular Clusters [physics.atm-clus] ,Annan fysik ,021001 nanoscience & nanotechnology ,[PHYS.PHYS.PHYS-GEN-PH]Physics [physics]/Physics [physics]/General Physics [physics.gen-ph] ,lcsh:QC1-999 ,bio-soft matter ,biological waveguide ,0210 nano-technology ,lcsh:Physics - Abstract
In the past decade, the development of artificial materials exhibiting novel optical properties has become a major scientific endeavor. One particularly interesting system is synthetic soft matter, which plays a central role in numerous fields ranging from life sciences, chemistry to condensed matter and biophysics. In this paper, we review briefly the optical force-induced nonlinearities in colloidal suspensions, which can give rise to nonlinear self-trapping of light for enhanced propagation through otherwise highly scattering media such as dielectric and plasmonic nanosuspensions. We then focus on discussing our recent work with respect to nonlinear biological suspensions, including self-trapping of light in colloidal suspensions of marine bacteria and red blood cells, where the nonlinear response is largely attributed to the optical forces acting on the cells. Although it is commonly believed that biological media cannot exhibit high optical non-linearity, self-focusing of light and formation of soliton-like wave-guides in bio-soft matter have been observed. Furthermore, we present preliminary results on biological waveguiding and sensing, and discuss some perspectives towards biomedical applications. The concept may be developed for subsequent studies and techniques in situations when low scattering and deep penetration of light is desired. Funding Agencies|NIHUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA; NSFNational Science Foundation (NSF); NSERCNatural Sciences and Engineering Research Council of Canada; Canada Research Chair programCanada Research Chairs
- Published
- 2020
42. Inverse design of EBG waveguides through scattering matrices
- Author
-
Roberta Palmeri and Tommaso Isernia
- Subjects
Optimization problem ,Computer science ,Bent molecular geometry ,Inverse ,artificial materials ,02 engineering and technology ,Topology ,01 natural sciences ,Inversion (discrete mathematics) ,010309 optics ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,General Materials Science ,inverse design ,scattering matrix ,Artificial materials ,Scattering ,ebg ,inverse problems ,020206 networking & telecommunications ,Inverse problem ,Condensed Matter Physics ,lcsh:QC1-999 ,Mechanics of Materials ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,optimization problem ,lcsh:TK1-9971 ,lcsh:Physics - Abstract
Inverse design procedures aim at determining optimal parameters for a given device in order to satisfy assigned specifications. In this contribution, the design of optimal EBG waveguides through inverse problems tools is addressed. In particular, an inversion tool based on the so called ‘scattering matrices’ is proposed and assessed to optimize the guiding effect for straight and bent waveguides.
- Published
- 2020
43. Investigating the Impact of Microwave Breakdown on the Responses of High-Power Microwave Metamaterials.
- Author
-
Liu, Chien-Hao and Behdad, Nader
- Subjects
- *
METAMATERIALS , *RESONATORS , *RESONANCE , *MICROWAVE materials , *PROTOTYPES - Abstract
We investigate the effect of microwave-induced breakdown on the frequency responses of a class of metamaterials composed of planar sub-wavelength periodic structures. When breakdown occurs in such a structure, its frequency response changes based on the nature of the plasma created within its unit cell. We examine how the frequency responses of such periodic structures change as a result of creation of microwave-induced discharges within their unit cells. To do this, we examine single-layer metasurfaces composed of miniature LC resonators arranged in a 2-D periodic lattice. These metasurfaces are engineered to be opaque at microwave frequencies when operated at low power levels but can be made transparent if a localized discharge is created within the LC resonators. By measuring their transmission and reflection coefficients under high-power excitation in different conditions, the impact of breakdown on the frequency responses of these devices is determined. Several prototypes of such structures are examined both theoretically and experimentally. It is demonstrated that when breakdown occurs in air and at atmospheric pressure levels, the responses of such periodic structures can be predicted with a reasonable degree of accuracy. Additionally, when the unit cell of the metasurface is composed of two different resonators, breakdown is always observed to occur in both resonators despite their different topologies and local field enhancement factors. In such structures, the discharge in one resonator appears to be mediated by the one in the other. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
44. Authentic or Artificial Materials: The Effects of Material-Types on L2 Motivation.
- Author
-
Shirai, Akira
- Subjects
TEACHING aids ,ACADEMIC motivation ,FOREIGN language education in universities & colleges ,LANGUAGE acquisition ,INSTRUCTIONAL systems ,STUDENTS - Abstract
This preliminary study sets out to examine the extent to which authentic materials affect Japanese university students' classroom motivation, seeking an effective way to teach mixedlevel language classes at universities. The motivation questionnaires consisting of eight motivation items as quantitative data and journal entries and learners' comments in semistructured interviews as qualitative data were collected and analyzed. The results of null hypothesis tests on the questionnaires indicate that authentic materials had a significantly more positive effect on freshmen's self-reported motivation than artificial textbook materials, but not on second-year and fourth-year students'. The study also explores the relationship between enjoyableness and meaningfulness of teaching materials to seek the most effective way of using authentic materials, and discusses the effects of other possible factors such as activities and topics. The conclusion suggests that appropriate use of authentic materials, especially enjoyable ones, can be helpful for university teachers of relatively larger classes of freshmen with mixed proficiency levels to raise their L2 motivation. The challenges of conducting this research and suggestions about future studies are also discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
45. Modeling of the mesenchymal stem cell microenvironment as a prospective approach to tissue bioengineering and regenerative medicine (a short review)
- Author
-
I. A. Khlusov, L. S. Litvinova, K. A. Yurova, E. S. Melashchenko, O. G. Khaziakhmatova, V. V. Shupletsova, and M. Yu. Khlusova
- Subjects
0301 basic medicine ,Scaffold ,Artificial materials ,bioengineering ,Computer science ,extracellular matrix ,Multipotent Mesenchymal Stromal Cells ,Animal Organs ,Regenerative medicine ,Material technology ,microenvironment ,bone ,03 medical and health sciences ,030104 developmental biology ,0302 clinical medicine ,stem cells ,Molecular Medicine ,Medicine ,Stem cell ,Neuroscience ,030217 neurology & neurosurgery ,biomaterials - Abstract
One of the promising areas is the design and modification of materials for control over the fate of multipotent mesenchymal stromal cells (MMSCs) that will allow stroma of various human and animal organs and tissues to be constructed. However, the discussion about the existence and functioning of microenvironment for the MMSCs is just beginning to develop. The design of artificial materials that are able to reproduce biomimetically the cellular and tissue microenvironment and based on ideas and main elements borrowed from wildlife is current direction in a development of medical materials technology and tissue bioengineering. Scaffold technology is a promising experimental approach to simulate the properties of natural microenvironment of stem cells. Our aim is a short review of key elements of MMSC microterritories, its advanced investigations and the attempts of modeling in application to tissue bioengineering and regenerative medicine.
- Published
- 2018
46. Artificial Tensor Impedance Surface Waveguides.
- Author
-
Quarfoth, Ryan and Sievenpiper, Daniel
- Subjects
- *
SURFACE waves (Fluids) , *WAVEGUIDES , *SURFACE impedance , *BOUNDARY value problems , *GEOMETRICAL optics - Abstract
A surface waveguide structure is studied using a theoretical model and simulated using Ansoft HFSS. A tensor impedance surface is surrounded by two lower impedance surfaces on a plane. Surface waves are guided losslessly within the inner region as long as it has higher impedance than the outer region. A theoretical model is proposed which predicts the dispersion relation of the waveguide using a ray optics method. Our tensor impedance surface theory can also predict the dispersion of scalar impedance surfaces. The theory and simulation show agreement for scalar and tensor impedance surfaces. Two applications of tensor impedance surface waveguides are presented. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
47. Broadband Compact Horn Antennas by Using EPS-ENZ Metamaterial Lens.
- Author
-
Ramaccia, Davide, Scattone, Francesco, Bilotti, Filiberto, and Toscano, Alessandro
- Subjects
- *
HORN antennas , *METAMATERIALS , *APERTURE antennas , *RADIATION , *ANTENNAS (Electronics) , *RADIO antennas - Abstract
We present the design of a flat lens, made by a conventional material and an epsilon near-zero metamaterial, to plug up the aperture of a short horn antenna, in order to achieve radiation performances similar to the ones of the corresponding optimum horn over a broad frequency range. Lens operation is based on the phase-compensation concept: phase-fronts of the field propagating along the short flare of the horn propagate with different phase velocities in the two lens materials, resulting in an uniform phase distribution on the aperture. Starting from the theoretical study of the transmission properties of a bulk epsilon near-zero slab, we derive the analytical formulas for the design of the flat lens and validate them through full-wave numerical simulations. Then, a realistic version of the lens, realized with a wire-medium and exhibiting a near-zero real part of the effective permittivity in the frequency range of interest, is presented. Considering two examples working in the C-band, we show that the lens can be designed for both conical and pyramidal horn antennas. In both cases, the length of the horns is half the one of the corresponding optimum versions, while the obtained radiation performances are similar to those of the optimum horns over a broad frequency band. This result may open the door to several interesting applications in satellite and radar systems. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
48. Optical Hybrid-Superlens Hyperlens for Superresolution Imaging.
- Author
-
Cheng, Bo Han, Ho, You Zhe, Lan, Yung-Chiang, and Tsai, Din Ping
- Abstract
This study proposes an innovative device called “Hybrid-Superlens Hyperlens” with superresolution imaging ability and confirms it by using simulation. This device consists of two multilayered metal-dielectric anisotropic metamaterials: the upper planar superlens and the lower cylindrical hyperlens with different signs in their dielectric tensors and different isofrequency dispersion curves. In our simulation, 100-nm center-to-center resolution is obtained by using an incident wavelength of 405 nm, which is smaller than the optical diffraction limit. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
49. Equivalent Transmission Line Model With a Lumped X-Circuit for a Metalayer Made of Pairs of Planar Conductors.
- Author
-
Capolino, Filippo, Vallecchi, Andrea, and Albani, Matteo
- Subjects
- *
ELECTRIC lines , *MAGNETISM , *MAGNETIC resonance , *POWER transmission , *FREQUENCY selective surfaces - Abstract
We present an equivalent X-shaped lumped circuit network to be interposed in the transmission line (TL) modelling reflection and transmission through a recently proposed metalayer in planar technology. The metalayer consists of arrayed pairs of planar conductors that support two main resonant modes, corresponding to either a symmetric or an antisymmetric current distribution in the pairs. The antisymmetric mode is associated with artificial magnetism. We show that reflection and transmission features of a metalayer are accurately predicted by this simple but effective TL model. We also make a clear distinction for the first time between transmission peaks and resonance frequencies, and their relations are investigated in detail. This paper clearly defines the concept of magnetic resonance and identifies the analytical conditions corresponding to total reflection and transmission through a metalayer made of pairs of conductors supporting symmetric and antisymmetric modes. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
50. Modeling and Analysis of Printed-Circuit Tensor Impedance Surfaces.
- Author
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Patel, Amit M. and Grbic, Anthony
- Subjects
- *
PRINTED circuits , *ELECTRIC impedance , *ANISOTROPY , *SURFACE waves (Fluids) , *ELECTROMAGNETIC waves - Abstract
Analysis of a printed-circuit tensor impedance surface (PCTIS) is presented. The surface consists of a periodic, subwavelength-patterned metallic cladding printed over a grounded dielectric substrate. First, the dispersion equation for an idealized tensor impedance boundary condition is derived by expressing the field in terms of TE and TM waves. A similar method is then used to find the dispersion equation of the PCTIS consisting of a tensor sheet impedance, which models the metallic cladding, over a grounded dielectric substrate. In addition, a method for extracting the tensor sheet impedance of a periodic, metallic cladding printed over a grounded dielectric substrate, is reported. It involves performing two normal-incidence scattering simulations using a full-wave electromagnetic solver. The method is strictly valid when the ground plane is sufficiently far from the metallic cladding to avoid evanescent-wave interactions. By combining the tensor sheet extraction method with the dispersion equation, the full dispersion characteristics of the PCTIS are analytically predicted in the homogenous limit. The results are verified through full-wave eigenmode simulations. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
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