Arrangement Of Inclusions Research Articles

A sub-wavelength metamaterial layer for reducing underwater noise radiation of marine structures

Reducing the underwater noise radiated by marine structures is a critical issue for improving submarine stealth or limiting the anthropogenic impact of commercial ships. In this study, we propose a lightweight passive solution based on a metamaterial to efficiently reduce the noise at low frequency (< 1000 Hz) that can be transmitted through the shell plating of a marine vessel. This solution is made of a soft acoustically impervious poro-elastic foam in which inclusions are periodically positioned. Added to a plate, this metamaterial outperforms the mass law in the sub-wavelength domain when separating two air domains. This performance is due to the periodic arrangement of inclusions in the foam, creating a vibro-acoustic bandgap. The aim of this study is therefore to assess this solution where the domain of the transmitted acoustic wave is water. Firstly, numerical results on an unbounded plate are validated alongside the theoretical model of a flexible partition. When the metamaterial layer is added to the plate, it is shown that a vibro-acoustic bandgap still exists in the transmitted wavenumber domain, and that this solution is a good candidate for achieving the objectives. Experimental measurements on a finite structure are then conducted and compared to numerical results

Scattering of elastic waves by a cluster of cylindrical inclusions: multiple scattering analysis and equivalent scatterer modeling

Abstract The two-dimensional scattering of elastic waves by a cluster of aligned circular cylindrical elastic inclusions embedded in a circular cylindrical domain of an infinitely extended elastic medium is analysed numerically. The analysis is based on a semi-analytical method where the scattered waves are expressed as the eigenfunction expansions of the time-harmonic displacement potentials and the expansion coefficients are determined by a numerical collocation technique. The wave fields within and around the cluster are demonstrated for different spatial arrangements of inclusions in the cluster. It is also examined if the scattering characteristics of the cluster can be simulated by a single equivalent scatterer which has the effective homogenized properties of the matrix/inclusion composite. As a result, it is shown that for sufficiently small inclusion radius-wavelength ratios, the scattering characteristics of the cluster are relatively insensitive to the spatial inclusion arrangements therein, and can be reasonably simulated by those of the equivalent scatterer.

Resolving the “megacryst paradox”: Feldspar orientation relationships record crystal mobility in granites

K-feldspar megacrysts are common in silicic plutons, but there is a long-running debate around how they form and what their presence tells us about magmatic systems. Field, textural, and geochemical evidence supports growth in a melt-rich environment, but experimental evidence and phase-equilibria modeling indicate that K-feldspar grows late in the crystallization sequence, when the magma is highly crystalline. We provide a new perspective on this problem by examining the arrangement of plagioclase inclusions within megacrysts to test whether they exhibit the systematic low-energy crystallographic relationships expected from attachment by synneusis in melt-rich environments where crystals have space to rotate. We use electron backscatter diffraction to quantify the crystal orientations and find that the megacrysts’ plagioclase inclusions do occupy these preferred orientations and therefore were incorporated in a melt-rich environment. K-feldspar is also present as an interstitial network, but plagioclase crystals hosted within this network have non-systematic orientations. This transition from systematic to non-systematic plagioclase orientations marks the point at which the crystals formed a rigid, interconnected framework that impeded rotation into low-energy orientations. Phase-equilibria modeling indicates that this transition occurred when the magma was ∼55% crystalline. The remaining ∼45% melt crystallized at the eutectic, forming the interstitial phases. Thus, we resolve the “megacryst paradox”; the megacrysts grew freely in melt, and the groundmass K-feldspar formed after crystal lock-up. Megacrysts therefore provide a detailed textural and chemical record of a critical period in the system’s evolution: the transition from a mobile and potentially eruptible magma to an immobile mush.

Defect-induced fracture topologies in Al2O3 ceramic-graphene nanocomposites

Models of ceramic-graphene nanocomposites are used to study how the manufacturing process-dependent arrangement of reduced graphene oxide (rGO) inclusions governs nano-crack network development. The work builds upon recent studies of such composites where a novel combinatorial approach was used to investigate the effect of rGO arrangements on electrical conductivity and porosity. This approach considers explicitly the discrete structure of the composite and represents it as a collection of entities of different dimensions - grains, grain boundaries, triple junctions, and quadruple points. Here, the combinatorial approach is developed further by considering the effects of rGO agglomerations, stress concentrators and adhesion energies on intergranular cracking. The results show that the fracture networks can be effectively controlled by the local ordering of rGO inclusions to allow for a concurrent increase in the strength and conductivity of the ceramic composites. It is shown that the ratio of local stress concentrators related to rGO inclusions and cracks is the most significant factor affecting the nano-crack network topology. The local spatial arrangement of rGO inclusions becomes an effective tool for controlling nano-crack network topology only when this ratio approaches one. It is anticipated that these results will inform future design of toughness-enhanced composites.

Tunable sequential pathways through spatial partitioning and frustration tuning in soft metamaterials.

Elastic instabilities have been leveraged in soft metamaterials to attain novel functionalities such as mechanical memory and sequential pathways. Pathways have been realized in complex media or within a collection of hysteretic elements. However, much less has been explored in frustrated and partitioned soft metamaterials. In this work, we introduce spatial partitioning as a method to localize deformation in sub-regions of a large and soft metamaterial. The partitioning is achieved through the strategic arrangement of soft inclusions in a soft lattice, which form distinct regions behaving as mechanical units. We examine two partitions: an equally spaced layer partition with mechanical units connected in series, and a cross partition, represented by interconnected series of mechanical units in parallel. Sequential pathways are obtained by frustrating the partitioned metamaterial post-manufacture and are characterized by tracking the polarization change in each partition region. Through a combination of experiments and simulations, we demonstrate that partitioning enables tuning the pathway from longitudinal with weak interactions to a pathway exhibiting strong interactions rising from geometric incompatibility and central domain rotation. We show that tuning the level of uniform lateral pre-strain provides a wide range of tunability from disabling to modifying the sequential pathway. We also show that imposing a nonuniform confinement and altering the tilting of one or two of the domain edges enables to program the pathway, access a larger set of states, and tune the level of interaction between the regions.

Envelope enrichment method for homogenization of non-periodic structures

The homogenization of composite materials is critical for accurately predicting their mechanical performance, particularly when complex reinforcement arrangements are involved. Microstructural characteristics exert a substantial influence on the composite’s properties during practical applications. A widely adopted approach for analyzing composites is the numerical simulation of a Representative Volume Element (RVE). Although this method is well-established for periodic RVEs, it encounters difficulties when applied to non-periodic meshes, which complicates the imposition of classical boundary conditions on nodes exhibiting varying properties. To address this challenge, we propose a novel methodology that involves modeling an envelope surrounding the RVE, to which periodic boundary conditions are applied. By defining the envelope as a homogeneous material, stress transmission to the RVE is facilitated. The stiffness tensor of the envelope is updated iteratively through a homogenization process, ultimately converging to the effective properties of the RVE. The method is validated on a non-periodic arrangement of spherical inclusions embedded within a matrix. Convergence is observed in the different cases studied within ten iterations and the results are found within the Voigt and Reuss bound.

Effects of randomness and piezomagnetic coupling on the appearance of stop-bands in heterogeneous magnetorheological elastomers

Phononic crystals (PCs) consist of a periodic arrangement of inclusions in a matrix material, and have garnered a great deal of interest owing to a phenomenon known as band gap frequencies in which particular frequency ranges are not able to propagate through the PCs. The aim of this work is to study the effects of magneto-elastic coupling and other parameters such as randomness in geometrical properties, volume fraction and size of inclusions on longitudinal wave propagation and, in particular, on the appearance of stop-band frequencies. The results indicate that the most important parameters deciding whether a frequency is in a stop-band or a pass-band are the randomness in geometrical properties and piezomagnetic coupling. It was observed that piezomagnetic coupling can lead to a widening of the first stop-band range for a periodic microstructure. Moreover, while randomness in particle size leads to a stop-band range and reduced wave transmission in the second pass region, randomness in particle position leads to removal of the pass band ranges compared to periodic structures. Additionally, the influence of piezomagnetic coupling becomes insignificant in fully random structures.

On Galvanomagnetic Properties of the 2D Rayleigh Model

periodic arrangement of circular inclusions) with the metal–insulator phase transition are considered. The expression obtained for the corresponding effective conductivity tensor σ^e is valid in the entire subthreshold critical region (up to the contacts of circles) in the vicinity of the transition point. The behavior of components of tensor σ^e in weak and strong magnetic fields is determined.

A Survey on RISC-V-Based Machine Learning Ecosystem

In recent years, the advancements in specialized hardware architectures have supported the industry and the research community to address the computation power needed for more enhanced and compute intensive artificial intelligence (AI) algorithms and applications that have already reached a substantial growth, such as in natural language processing (NLP) and computer vision (CV). The developments of open-source hardware (OSH) and the contribution towards the creation of hardware-based accelerators with implication mainly in machine learning (ML), has also been significant. In particular, the reduced instruction-set computer-five (RISC-V) open standard architecture has been widely adopted by a community of researchers and commercial users, worldwide, in numerous openly available implementations. The selection through a plethora of RISC-V processor cores and the mix of architectures and configurations combined with the proliferation of ML software frameworks for ML workloads, is not trivial. In order to facilitate this process, this paper presents a survey focused on the assessment of the ecosystem that entails RISC-V based hardware for creating a classification of system-on-chip (SoC) and CPU cores, along with an inclusive arrangement of the latest released frameworks that have supported open hardware integration for ML applications. Moreover, part of this work is devoted to the challenges that are concerned, such as power efficiency and reliability, when designing and building application with OSH in the AI/ML domain. This study presents a quantitative taxonomy of RISC-V SoC and reveals the opportunities in future research in machine learning with RISC-V open-source hardware architectures.

Load-settlement response of strip footing overlaid fine sand strengthened with different arrangements of geogrid inclusions

ABSTRACT This study reports the results of experiments conducted on strip foundations with and without reinforced geogrids over fine sand and with a wraparound geogrid arrangement. A load up to 25 kN was applied to the strip foundations to determine the loading-settlement response. These tests examined the number of planar and folded geogrid sheets, the placement of folded geogrids in the soil bed, the thickness of folded geogrid sheets, the length of wraps and overlaps, and the spacing between folded and planar geogrid sheets. The results indicate that the performance of the foundations due to static loading is better for folded geogrid-reinforced sand than for planar geogrid-reinforced sand. Overall, the results demonstrate that reinforced soil foundations with sufficiently folded geogrid layers behave much stiffer and thus can support higher loads with a lower settlement than planar reinforced soils. Moreover, the results indicate that the values of the embedment depth of the overlap element (d), the lower part (D), and the thickness (x) of the folded geogrid are 0.2, 0.4, and 0.2 of the foundation widths (B), respectively. As a result, by increasing the number of geogrid layers, the settlement rate is reduced significantly, and it is recommended that these layers be placed vertically without vertical spacing (h/B = 0).

Patient and Public Involvement in Developing and Testing Mental Health-care Interventions

Patient and public involvement (PPI) is valued and widely practiced in mental health research but in different ways. We present three research programs, aiming to develop and test mental healthcare interventions and we discuss their PPI strategies and activities. In all these programs, PPI has been sought from their initial conception and design and has helped their management, intervention development processes, quantitative and qualitative evaluations, and in the assessment of PPI activities themselves. The programs focus on different groups (patients with chronic depression, patients with psychotic disorders, and carers) and develop different interventions. Comparing these programs offers the opportunity to appreciate different models of involvement. These, for example, range from training lived experience collaborators to analyze qualitative data directly to asking them to comment on findings; from involving lived experience collaborators in the design of new interventions to involving them in intervention adaptation to a particular group or circumstance; and from carrying out formal PPI evaluations to collecting informal feedback during meetings. Even in the diversity of programs and PPI activities presented, common themes could be identified in relation to: specifying (and ideally co-designing) expectations and role of contributors; making bureaucratic procedures as user-friendly as possible; appropriately choosing or blending online and offline meetings; and designing flexible and inclusive arrangements to maximize participation. Our experiences contribute to a growing evidence base that can help researchers to develop meaningful, enjoyable, and constructive collaborations with people with lived experience. These collaborations will keep clinical mental health research relevant, impactful, and tailored to patients' needs.

Periodic rhomboidal cells for symmetry-preserving homogenization and isotropic metamaterials

In the design and analysis of composite materials based on periodic arrangements of sub-units it is of paramount importance to control the emergent material symmetry in relation to the elastic response. The target material symmetry plays also an important role in additive manufacturing. In numerous applications it would be useful to obtain effectively isotropic materials. While these typically emerge from a random microstructure, it is not obvious how to achieve isotropy with a periodic order. We prove that arrangements of inclusions based on a rhomboidal cell that generates the face-centered cubic lattice do in fact preserve any material symmetry of the constituents, so that spherical inclusions of isotropic materials in an isotropic matrix produce effectively isotropic composites.

Получение стеклокерамики системы MgO-SiO-=SUB=-2-=/SUB=- методом плазменной плавки

Results of experimental studies of the synthesis glass ceramics of the MgO–SiO2 system by plasma melting at atmospheric pressure are presented. According to electron microscopy data, during melt crystallization rate of 287 ± 5 K/s, the surface morphology is represented by dense packing of rhombic dodecahedral Mg2SiO4 crystals (there is no open porosity). In this case, the matrix is ​​characterized by the formation of dense framework with clear linear arrangement of spherical inclusions corresponding to the MgSiO3 phase. Result of synthesis by plasma melting, glass ceramics with density of 3.56 g/cm3 and microhardness of up to 15 GPa were obtained. It is assumed that glass-ceramics with such a composition can be considered as an excellent option for the development of economical high-quality refractory.

Obtaining glass ceramics of the MgO-SiO-=SUB=-2-=/SUB=- system by the plasma melting method

Results of experimental studies of the synthesis of glass ceramics of the MgO-SiO2 system by plasma melting at the atmospheric pressure are presented. Electron microscopy data showed that, during the melt crystallization with the rate of 287-5 K/s, the surface morphology is represented by a dense packing of rhombic dodecahedral Mg2SiO4 crystals (without open porosity). In this case, the matrix is characterized by the formation of a dense framework with a clear linear arrangement of spherical inclusions corresponding to the MgSiO3 phase. As a result of the plasma melting synthesis, glass ceramics with the density of 3.56 g/cm3 and microhardness of up to 15 GPa was obtained. It is assumed that glass ceramics with such a composition can be considered as an excellent option for the development of a cost-effective high-quality refractory. Keywords: forsterite, glass ceramics, electric arc synthesis.

Krystalograficky orientovaný srůst rutilu a ilmenitu a doprovodné minerály z Pasek nad Jizerou (krkonošsko-jizerské krystalinikum)

A detailed mineralogical study of a sample of quartz gangue containing macroscopically visible acicular rutile, which was collected in area of former Cu(-Ag) ore deposit NE from Paseky nad Jizerou, yielded a number of mineralogical findings. The mineralization is bound to strongly elongated quartz lenses, arranged conformably with schistosity of host phyllite of the Krkonoše-Jizera Crystalline Complex. Rutile is polysynthetically lamelled and compositionally zoned, with elevated contents of Fe (0.004 - 0.015 apfu), Nb (0.001 - 0.004 apfu), V (0.001 - 0.002 apfu) and W (0.000 - 0.006 apfu). It contains microscopic platy inclusions of ilmenite, which are regularly distributed in up to three crystallographic directions (probably cleavage planes) regardless of compositional zoning of host rutile. In addition, sporadic occurrence of aggregates composed of fluorapatite, phengitic muscovite and clinochlore was found too. The studied mineralization has metamorphic-secretory origin. The observed microstructural arrangement of inclusions of ilmenite in rutile host is very uncommon worldwide. With respect to evidently LP-LT origin of mineralization, we interpret its origin not in terms of exsolution but in terms of younger hypogene alteration of pre-existing rutile by fluids with relatively low Eh. The activity of such “suitable” fluids can be illustrated during crystallization of chlorite, which was formed at temperatures 137 - 160 °C and at log fO2 between -49.2 and -53.1 bar.

Effect of the number and arrangement of inclusions on the strength of concrete specimens

In concrete structures, we identify deformation fields of nodes with applied concentrated stress, which are accompanied by a change in the density and shape of force trajectories. These changes are caused by the presence of large grains of aggregate and/or reinforcing bars (inclusions) in the concrete, clumps of grains of normal size, or the presence of a cavern around the grain of the aggregate. These internal imperfections are among the important parameters that affect the failure process of concrete test specimens, and thus the initiation and development of cracks in concrete and can have a negative impact on the strength of concrete elements. This paper deals with the influence of the number of inclusions in their symmetrical arrangement on a series of test specimens of three different sizes, which are subjected to uniaxial compression. Attention is paid to the selection of a suitable standardization parameter, which will consider the different quality of concrete test specimens

Blast resistant enhancement of meta-panels using multiple types of resonators

A new design is proposed for the meta-panel that consists of three components including two thin face-sheets bonded to meta-truss cores to enhance its blast resistance and energy absorption capacity. The meta-truss core comprising solid inclusions with coated soft layers exhibits exceptional wave-filtering properties by activating the local vibration of the inclusions, leading to the negative effective mass and stiffness of the meta-truss core in the corresponding frequency bandgaps, hence reducing the wave propagations. When frequencies of the applied loading fall within the bandgaps, the loading effects are not able to be transferred or significantly mitigated by the meta-truss core. In this study, the result from a previous theoretical derivation of wave propagation in an idealized meta-truss bar is used to validate the numerical model. Then, analyses of the meta-truss core configurations, e.g. the inclusion arrangement and inclusion shape on its bandgap regions and the transient responses of the meta-panel are carried out with the verified numerical model. It is revealed that a complete wave attenuation design can be achieved by utilizing properly tailored arrangements of inclusions, leading to a significantly improved protective effectiveness of the panel against blast loading. The results present a base for the optimal design of the meta-panel for structural protections against blast loading.

Field Observations, Petrography, and Microstructures of Granite from Abeokuta Southwestern Nigeria

Abstract in English The granite of Abeokuta is part of the Older Granite suite of the basement complex of southwestern Nigeria. Field observation has identified the granite as porphyritic in texture, with a preferred alignment of megacrysts of K-feldspar >5 cm that are mostly euhedral to subhedral in shape. K-feldspar megacrysts are predominantly yellowish, but whitish and pinkish colouration has also been observed. The dark grey porphyritic, mafic rock composition occurs as enclaves within the granite, with phenocrysts having a preferred alignment as the enclosing granite. Also, K-feldspar megacrysts show zoning defined by concentric arrangement of inclusions of biotite relative to the crystal faces. Petrographic study shows the following minerals in order of abundance: K-feldspar, biotite, quartz, and plagioclase, with K-feldspar having a microperthitic intergrowth and biotite crystals aligned in a preferred direction. Evidence such as the crystal shape of K-feldspars, preferred alignment of K-feldspar phenocrysts, and concentric crystallographic arrangements of inclusions of biotite in K-feldspar support a magmatic/phenocrystic origin of K-feldspar megacrysts of Abeokuta granite rather than originating by growing in a solid state as porphyroblasts.

The Influence of Structural Arrangement of Inclusions on Dual Composite Strength

The Influence of Structural Arrangement of Inclusions on Dual Composite Strength

Improved properties of soft magnetic composites with hollow microstructures

Soft magnetic composites (SMCs) possess promising electromagnetic characteristics and attract intense research and application interest in the engineering community. Fabrication of composites with customized architecture is feasible due to the recent advances in additive manufacturing (AM) techniques. The systematic progress of computational optimization has opened up the possibility of devising such structures. This article presents newly structured SMCs which can recently be possible by AM. The effective permeability and eddy current losses are studied in comparison to those properties of traditionally fabricated SMCs. With this hollow inclusion arrangement, for the same iron volume fraction, the effective permeability can be greatly enhanced (more than tenfold) while the eddy current losses decrease considerably. For the same magnetic property, we save iron material, make the composite lighter, and benefit from a lower level of eddy current losses with the hollow configuration.