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The purpose of this paper is the production of mechanical meta-material samples by rapid prototyping (RP) and replica technique for patient-specific skin graft or cranial implant applications in tissue engineering.

Positive moulds (patterns) were produced by stereolithography-based RP. Impression moulding method was used for the production of silicone products (skin grafts). Alginate was used as a moulding material (negative mould). Room temperature vulcanising silicone was poured into the cavity of alginate mould and then products were produced. TiO₂ powder and carbon fibres were used as reinforcement. Meta-material structured polyurethane reinforced silicone composites were also produced. Liquid components (diisocyanate and polyol) were poured into the mould and then polyurethane was produced. Then, polyurethane was immersed in the liquid silicone.

It is found that non-destructive ultrasonic test is a fast and reliable method. Meta-material-based composites show dome-shaped tensile/synclastic surface properties which are important for the skin graft and cranial implants. Increasing the amounts of cross-linking agent and TiO₂ particles increased the hardness and elastic modulus. Carbon fibre addition enhanced the elastic modulus.

Although there are studies on the meta-materials, there is limited study on the RP of the meta-materials for patient-specific implants (skin grafts). Auxetic surface shows perfect fit to curved surface of the skull. Although there are studies on the silicone and polyurethane composites, there is limited study on the characterisation of mechanical properties by ultrasonic tests and strain gauge analysis.

Auxetic structures are one type of mechanical meta-materials mainly used for energy absorption applications because of their unique negative Poisson’s ratio. This study is focused on numerical and experimental investigations of fused deposition modeling (FDM) fabricated re-entrant auxetic structures of acrylonitrile butadiene styrene (ABS) and poly-lactic acid (PLA) materials under compressive loading. Influence of geometric parameters, namely, re-entrant angle, height and arm-length on strength, stiffness and specific energy absorption (SEA) of auxetic structures under compressive loading. Optimization of significant parameters is also performed to maximize these responses and minimize weight and time of fabrication. Further, efforts have also been made to develop predictive models for strength, stiffness and SEA of auxetic structures.

A full factorial design of experiment is used for planning experiments. Auxetic structures of ABS and PLA are fabricated by FDM technique of additive manufacturing within the constrained range of geometric parameters. Analysis of variance is performed to identify the influence of geometric parameters on responses. To optimize the geometric parameters Gray relational analysis is used. Deformation of auxetic structures is studied under compressive loading. A numerical investigation is also performed by building nonlinear finite element models of auxetic structures.

From the analysis of results, it is found that re-entrant angle, height and arm-length with their interactions are significant parameters influencing responses, namely, strength, stiffness and SEA of the auxetic structures of ABS and PLA materials. Based on the analysis, statistical nonlinear quadratic models are developed to predict these responses. Optimal configurations of auxetic structure of ABS and PLA are determined to maximize strength, stiffness, SEA and minimize weight and time of fabrication. From the study of deformation of auxetic structures, it is found that ABS structures have higher energy absorption, whereas PLA structures have better stiffness. Results of finite element analysis (FEA) are found in good agreement with experimental results.

The present study is limited to re-entrant type of auxetic structures of ABS and PLA materials only under compressive loading. Also, results from the present study are valid within the selected range of geometric parameters. The findings of the present study are useful in maximizing strength, stiffness and SEA of auxetic structures that have wide applications in the automotive, aerospace, sports and marine sector.

No literature is available on studying the influence of geometric parameters, namely, re-entrant angle, height and arm-length of auxetic structure on strength, stiffness and SEA under compressive loading. Also, a comparative study of feedstock materials, namely, ABS and PLA, is also not reported. The present work attempts to fulfill the above research gaps.

Recent research has shown that constrained bistable structures can display negative stiffness behavior and provide extremal vibrational and acoustical absorptive capacity. These bistable structures are therefore compelling candidates for constructing new meta‐materials for noise reduction, anechoic coatings, and backing materials for broadband imaging transducers. To date, demonstrations of these capabilities have been primarily theoretical because the geometry of bistable elements is difficult to construct and refine with conventional manufacturing methods and materials. The purpose of this paper is to leverage the geometric design freedoms provided by selective laser sintering (SLS) technology to design and construct constrained bistable structures with negative stiffness behavior.

A meso‐scale negative stiffness system is designed and fabricated with SLS technology. The system includes a bistable structure in the form of a pre‐compressed/pre‐buckled beam. The dynamic transmissibility of the system is measured, and its behavior is compared to the predictions of analytical models.

Experimental results demonstrate that pre‐compression and pre‐buckling can be used to induce negative stiffness behavior and thereby increase the damping and shift the resonant frequency of an unconstrained beam.

The results support the usefulness of SLS and other additive manufacturing technologies for acoustic and dynamic applications. Specifically, the demonstrated advantages of SLS include the ability to rapidly redesign, functionally 2 prototype, and tune physical models for acoustic and dynamic experimentation. Of significant importance is the ability of SLS to enable consolidation of parts that are traditionally separate, thereby reducing vibrational noise in these systems. In this specific application, SLS enables a proof‐of‐concept comparison of the theoretical and experimental behavior of a meso‐scale negative stiffness system. The demonstrated acoustical and vibrational absorptive capacity of these systems is expected to lead to designs for new structures and materials that offer significantly improved energy absorbing capabilities over a broad range of tunable frequencies without compromising structural stiffness.

Online calendar services (OCS) are primarily used for temporal orientation and reminding. Nonetheless, calendar work may also entail generic activities such as scheduling, tracking, archive and recall and retrieval which are not adequately supported by available systems. The purpose of the paper is to explore how online calendaring may be re-configured and re-aligned to alleviate these shortcomings, thus servicing accountability in team work and flexibility in organizational routines.

Following a design science research methodology, the authors review “justifiable failures” or deliberate non-use of OCS and establish the rationale for, design and evaluate a digital service that configures calendaring as an ecology of separate digital materials supporting file-, photo- and video-sharing services, online argumentation, project/task management and social bookmarking. The new service is a digital composite of materials that incrementally co-adapt and co-evolve to serve primary and secondary work-oriented activities. The authors assess the value of the digital composite in two empirical settings and discuss intrinsic features that create new possibilities for action.

The authors present the rationale, design, implementation and evaluation of a new digital composite calendaring service which is deployed in two empirical settings, namely group vacation planning and collective information management. Each case features different re-configurations of calendaring to serve human intentions. In vacation planning, the digital composite of the calendar operates as a mashup allowing peers to negotiate, schedule and track vacation options and archive, recall or retrieve digital memories of vacations. In the case of collective information management, the digital composite is further augmented so as to re-align performative and ostensive aspects of routines in a regional organic farming partnership.

Digital composites rely on the interdependent operation of different bounded systems and services to establish configured ecologies of (previously) separate digital artifacts. The practical implications of digital composites are that they can appropriate performative capacities which are already established and embedded across different settings. As a result, they enact complex digital assemblages which can re-align not only daily activities but also organizational routines. On the other hand, digital composites remain in flux, since their state, at any moment in time, is partly determined (even temporarily) by the state of their constituent parts.

Calendaring as presented in this paper defines a genre of digital artifacts that promote flexible and accountable collaborative work while exploiting material agency and resources distributed across digital settings. As such, it establishes a kind of meta-material that invokes collective social agency, thus re-aligning performative and ostensive aspects of organizational routines.

The purpose of this paper is to bring a new scientific theory into practice in the hotel industry.

In‐depth open‐ended interviews were used with eight hospitality practitioners, consumers, and academic researchers.

The article lays out current practices of security and privacy measurements in the hospitality industry and points out the related limitations. More importantly, it provides insights to hotel operators on possible future applications of a new scientific invention and how it could help alleviate the limitations found in the existing security and privacy measures.

The paper raises the awareness of a new scientific breakthrough that sheds new lights to security and privacy strategies in hotel operations. Hotels, which are able to react quickly to gain the first‐mover‐advantage in leading the industry on the application of such technology, will certainly gain tremendous publicity, and more importantly will be the first to create a new level of confidence in the market on security and privacy strategies implemented in their daily hotel operations.

This paper communicates a recent scientific development and its possible applications in the hotel industry. In this way, it bridges the gap between a scientific invention and its real‐world application. It is expected to provide insights for hoteliers who are interested in technology applications.

Metamaterial unit cells composed of deep subwavelength resonators brought up new aspects to the antenna miniaturization problem. The paper experimentally demonstrates a metamaterial-inspired miniaturization method for circular patch antennas. In the proposed layouts, the space between the patch and the ground plane is filled with a proper metamaterial composed of either multiple split-ring or spiral resonators (SRs). The authors have manufactured two different patch antennas, achieving an electrical size of λ/3.69 and λ/8.26, respectively. The paper aims to discuss these issues.

The operation of such a radiative component has been predicted by using a simple theoretical formulation based on the cavity model. The experimental characterization of the antenna has been performed by using a HP8510C vector network analyzer, standard horn antennas, automated rotary stages, coaxial cables with 50 Ω characteristic impedance and absorbers. Before the characterization measurements we performed a full two-port calibration.

Electrically small circular patch antennas loaded with single layer metamaterials experimentally demonstrated to acceptable figures of merit for applications. The proposed miniaturization technique is potentially promising for antenna applications and the results presented in the paper constitute a relevant proof for the usefulness of the metamaterial concepts in antenna miniaturization problems.

Rigorous experimental characterization of several meta material loaded antennas and proof of principle results were provided.

Millimeter wave spectrum represents new opportunities to add capacity and faster speeds for next-generation services as fifth generation (5G) applications. In its Spectrum Frontiers proceeding, the Federal Communications Commision decided to focus on spectrum bands where the most spectrums are potentially available. A low profile antenna array with new decoupling structure is proposed and expected to resonate at higher frequency bands, i.e. millimeter wave frequencies, which are suitable for 5G applications.

The presented antenna contains artificial magnetic conductor (AMC) surface as decoupling structure. The proposed antenna array with novel AMC surface is operating at 29.1GHz and proven to be decoupling structure and capable of enhancing the isolation by reducing mutual coupling as 8.7dB between the array elements. It is evident that, and overall gain is improved as 10.1% by incorporating 1x2 Array with AMC Method. Mutual coupling between the elements of 1 × 2 antenna array is decreased by 39.12%.

The proposed structure is designed and simulated using HFSS software and the results are obtained in terms of return loss, gain, voltage standing wave ratio (VSWR) and mutual coupling. The S-Parameters of each stage of design is tabulated and compared with each other to prove the decoupling capability of AMC surface in antenna arrays.

The proposed structure is designed and simulated using HFSS software, and the results are obtained in terms of return loss, gain, VSWR and mutual coupling. The S-Parameters of each stage of design is tabulated and compared with each other to prove the decoupling capability of AMC surface in antenna arrays.

Conventional sportswear design does not take into account body size changes that many individuals experience (e.g. through pregnancy, puberty, menstruation, etc.). This paper aims to detail both the construction of a novel wearable shape-adaptive composite and a new meso-scale material design method, which enables the optimal creation of these structures.

This work reports the development of a predictive computational model and a corresponding design tool, including results of a tensile testing protocol to validate their outputs. A mathematical model was developed to explore the geometric parameter space of a bi-stable composite system, which then feeds into an optimization design tool.

The authors found that it is possible to fabricate shape-adaptive composites via 3D printing bi-stable structures, and adhering them to a base textile. Experimental mechanical tensile testing showed good agreement with the predictive model in mid-range unit cell amplitude designs. To illustrate how the optimization design tool works this paper details two design examples, one for expected shape change during pregnancy and one for targeted compression for high performance swimwear. The optimized design parameters are shown to replicate the target parameters, however there is potential for further improvement with a lower stiffness base textile.

Although there is a wealth of research on multi-stable mechanisms, there is a dearth of studies that apply these structures in the wearable composite space. Additionally, there is a need for design methods which leverage the structurally-programmable capabilities of multi-stable structures to create optimized, high-performance functional composites.

To achieve right-hand circular polarization (RHCP), a 3-dB Wilkinson power divider with a λ/4 phase shifter is used. The crossed-dipoles are placed at almost λ/4 elevation on the ground plane and connected to two coaxial cables. Experiments show that the impedance bandwidth of 49.40% (913.7–1,513.1 MHz) and axial ratio bandwidth (ARBW) of 22.88% (1,145.8–1,441.8 MHz) are achieved.

In this study, a wideband crossed-dipole antenna with circularly polarized (CP) radiation for L-band satellite and radar applications is presented. The proposed CP antenna comprises two orthogonally placed printed dipoles, a quadrature coupler and a box-shaped ground plane.

Furthermore, by fixing the box-shaped ground plane under the radiators, 5.13 dBic RHCP peak gain at 1,300 MHz and maximum half-power beamwidth (HPBW) of 84.5° at 1,170 MHz are realized for the antenna.

Eight metallic walls are connected to four corners of the substrate to stabilize the radiation properties in this study. Results show that the ARBW and front-to-back ratio are improved and the maximum HPBW around 127° across the operating frequency band is achieved. The proposed CP antenna is a good candidate for Global Positioning System (GPS) L2 (1.227 GHz), GPS L5 (1.176 GHz) and air route surveillance radar system at 1,215–1,390 MHz frequency band.

This paper aims to present the design and implementation of a circularly polarized co-planar waveguide (CPW) fed wideband pie-shaped monopole antenna for multi-antenna techniques. Multi-antenna techniques are promising solutions for higher data rate and enhanced reliability of wireless applications. They find numerous applications in 4G/5G networks and in most wireless standards such as wireless local area networks (WLAN), wireless fidelity and worldwide interoperability for microwave access systems to enhance the channel capacity without additional spectrum by means of multi-path propagation techniques.

The antenna is designed to operate at three WLAN frequency bands of 4.8, 5.2 and 5.8 GHz. The measured 10 dB impedance bandwidth of the proposed antenna element is 1.2 GHz (24.23 per cent). The proposed CPW fed, pie-shaped monopole antenna has a gain of 5.4 dB and an efficiency of 72.8 per cent at 4.8 GHz.

To use the proposed antenna in a multi-antenna environment, the antennas have to be placed in a close proximity to each other. The close proximity introduces strong mutual coupling between the antennas, which in turn degrades the performance of multi-antenna systems. A multi-antenna system with two antenna elements has been constructed with an edge to edge spacing of 0.24 λ₀ (15 mm), and the mutual coupling level is −17 dB. To enhance the isolation between the antenna elements, a shorting pin-based interconnected semicircles enclosed decoupling structure is proposed, which improves the isolation by a factor of 12.67 dB at 4.8 GHz.

To validate the performance of the proposed multi-antenna in working environment, the performance metrics such as envelope correlation coefficient (ECC), diversity gain (DG) and total active reflection coefficient (TARC) are computed for the proposed multiple-input multiple-output (MIMO) antenna. The ECC value is 0.000366 at center frequency and below 0.09 for the entire operating bandwidth, which is well below the acceptable level of 0.5 as per 3GPP standard. The DG value lies above 9.5 dB for the entire operating bandwidths and it is well above the minimum value of 3 dB. The TARC values are calculated based on S parameters, and it proves that the proposed antenna a good candidate for the multi-antenna systems.