Material Sphere Research Articles

Wall shear stress sensor based on the optical resonances of dielectric microspheres

We report an optical wall shear stress sensor based on the whispering gallery mode (WGM) shifts of dielectric micro-resonators. The optical resonators are spheres with a typical diameter of several hundred microns and they serve as the sensing element. The wall shear force acting on a movable plate is transmitted mechanically to the microsphere. As a result of the applied force, the shape of the resonator is perturbed leading to a shift of the optical resonance (WGM). The one-dimensional wall shear stress is measured by monitoring these WGM shifts. Shape perturbations of the order of a nanometer can be detected with this optical method. The measurement resolution and range can be optimized by using dielectric sphere materials of different stiffness covering a wide range of flows. Prototype sensors using PDMS spheres have been built and validated in a laminar Poiseuille flow and in a plane wave acoustic tube.

Grip-dependent cortico-spinal excitability during grasping imagination and execution

Studies converge in indicating a substantial similarity of the rules and mechanisms underlying execution, observation and imagery of actions, along with a large overlapping of their neural substrates. Recent transcranial magnetic stimulation (TMS) studies have demonstrated a muscle-specific facilitation of the observer's motor system for force requirement and type of grip during grasping observation. However, whether similar fine-tuned muscle-specificity occurs even during imagination, when subjects are free to select the most convenient grip configuration, is still unknown. Here we applied TMS over the primary motor cortex and measured the corticospinal excitability (MEP) in three muscles (FDI, ADM and FDS) while subjects imagined grasping spheres of different dimensions and materials. This range of object weights and sizes (diameters) allowed subjects to freely imagine the most suitable grip configuration among several possibilities. Activation measured during grasping imagination has been also compared to that obtained during real execution (EMG recorded from the same muscles).We found that during imagination of grasping small objects, the FDI muscle was more active than the ADM and the FDS, whereas the opposite pattern was found for big objects. Imagination of medium size objects, instead, required an equal involvement of the three muscles. The same pattern was observed when subjects were asked to perform the action. This suggests that during imagination, the cortico-spinal system is modulated in a muscle-specific/grip-specific way, as if the action would be really performed. However, when force was required (i.e., for the aluminum objects), the motor activation obtained during action execution was more fine-tuned to object dimensions than the facilitation recorded during imagination, suggesting a separate control of force production.

Ferromagnetism in thin-walled hollow spheres of non-magnetic inorganic materials

To study defect origin of ferromagnetism, hollow spheres are better candidates as they are less agglomerated and has both sides of the wall free, as compared to nanoparticles and thin films respectively. Our results show improved magnetic properties of GaN, ZnAl 2O 4 and MgO hollow spheres over their earlier reported nanoparticle counterparts. Photoluminescence spectroscopy supports our magnetic findings.

Fracture behavior of silicon nitride ceramics subjected to hypervelocity impact

A new advanced ceramic thruster made of monolithic silicon nitride ceramics was developed for the planetary exploration spacecraft AKATSUKI (PLANET-C) at Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA). To ensure its operation onboard the spacecraft, the reliability of the ceramic thruster against micrometeoroid hypervelocity impact has been investigated. Silicon nitride plates were impacted by spheres of stainless-steel and other materials with 0.2–0.8-mm diameters in the velocity range up to 8.0 km/s using a two-stage light-gas gun. Using crater depth data under various impact conditions, the penetration equation of silicon nitride was determined. The impacted samples showed fracture patterns of three types: cratering, cratering with spallation, and perforation. These fracture patterns were well categorized by the multiple forms of the penetration equation.

Shear Capacity of Biaxial Hollow Slab with Donut Type Hollow Sphere

This paper presents the shear capacities of biaxial hollow slab with donut type hollow sphere. Recently, various types of slab systems which can reduce self-weight of slabs have been studied as the height and width of building structures rapidly increase. A biaxial hollow slab system is widely known as one of the effective slab system which can reduce self-weight of slab. According to previous studies, the hollow slab had low shear strength, compared with solid slab and the shear capacities of biaxial hollow slab are influenced by the shapes and materials of hollow spheres. In addition, the present code does not provide a clear computation method for the shear strength of hollow slab. To verify the shear capacities of this hollow slab, shear tests were performed. Four test specimens were used for test parameters. One was conventional RC slab and others were hollow slabs. The test parameters included two different shapes and materials of plastic balls. The shape parameters were donut and non-donut forms. And the material parameters were general plastic and glass fiber plastic

The synthesis of Nb-doped TiO2 nanoparticles by spray drying: an efficient and scalable method

Nb-doped TiO2 nanoparticles were prepared by a continuous spray drying process using ammonium niobate (V) oxalate and titanium oxysulfate as water-soluble precursors. The structural and electronic properties were investigated using thermogravimetric analysis, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. Nb was found to be mainly incorporated as Nb5+ into the TiO2 lattice resulting in a charge compensation by Ti vacancies. The characterization results indicate that Nb was homogeneously distributed within the titania lattice, and that the surface segregation of Nb, which is commonly observed for Nb-doped TiO2, was significantly less pronounced. The high homogeneity and the lower extent of surface segregation originate from the efficient atomization of homogeneous precursor solutions and the fast evaporation of the solvent in the spray drying process. As a result, the ion mobility is diminished and spheres of well-mixed precursor materials are formed. Using the continuous spray drying process followed by a controlled heat treatment, the phase composition, the crystal size and the surface area of the Nb-doped TiO2 nanoparticles are easily adjustable.

COMPARISON OF SURFACE INTEGRAL EQUATIONS FOR LEFT-HANDED MATERIALS

A wide analysis of left-handed material (LHM) spheres with difierent constitutive parameters has been carried out employ- ing difierent integral-equation formulations based on the Method of Moments. The study is focused on the accuracy assessment of for- mulations combining normal equations (combined normal formula- tion, CNF), tangential equations (combined tangential formulation, CTF, and Poggio-Miller-Chang-Harrington-Wu-Tsai formulation, PM- CHWT) and both of them (electric and magnetic current combined fleld integral equation, JMCFIE) when dealing with LHM's. Relevant and informative features as the condition number, the eigenvalues dis- tribution and the iterative response are analyzed. The obtained results show up the suitability of the JMCFIE for this kind of analysis in con- trast with the unreliable behavior of the other approaches.

Clothes without Bodies: Objects, Humans, and the Marketplace in Eighteenth-Century It-Narratives and Trade Cards

While recent studies of the things of literature call attention to the narrative and psychological slippage between people and their possessions, this essay argues that rather than representing a loss for human agency, humans and things intermingle to the disadvantage of objects. I show how trade cards and object narratives engage with the same nexus of commercial culture, objects, and humans, and share a mutual resistance to “autonomous garments”—petticoats, shoes, gowns, and other garments depicted independently of the human form. Object narratives, read in tandem with trade cards, suggest that the growth of distance between persons and things, as opposed to their collapse into each other, constitutes a central narrative in the period's commodity culture and fiction. Object narratives, even as they transform coats, waistcoats, petticoats, slippers, and shoes into first-person narrators, actively work against the entanglement of human and material spheres. Together these genres place sartorial commodities under human control, emphasizing the human subject's agency over those items worn closest to the self.

Flexural Capacities of One-Way Hollow Slab with Donut Type Hollow Sphere

This paper presents the flexural capacities of one-way hollow slab with donut type hollow sphere. Recently, various types of slab systems which can reduce self-weight of slabs have been studied as the height and width of building structures rapidly increase. A biaxial hollow slab system is widely known as one of the effective slab system which can reduce self-weight of slab. A biaxial hollow slab has hollow spheres within slabs in order to reduce self-weight of slabs. The capacities of biaxial hollow slab are influenced by the shapes, volume and materials of hollow spheres. According to analytical studies, the hollow slab with donut type hollow sphere had good flexural capacities such as strength, stiffness and deflection. To verify the flexural capacities of this hollow slab, flexural tests were performed on the one-way hollow slabs. Five test specimens were used for test parameters. One was conventional RC slab and others were hollow slabs. The test parameters included two different shapes and materials of plastic balls. The shape parameters were donut and non-donut forms. And the material parameters were general plastic and glass fiber plastic.

Materials optimization of the magnonic gap in three-dimensional magnonic crystals with spheres in hexagonal structure

We present the results of plane wave method-based calculations adopted to magnonic band structures for exchange spin waves propagating in three-dimensional magnonic crystals (MCs) composed of two ferromagnetic metals. The crystals under consideration consist of a system of ferromagnetic spheres arranged in sites of a hexagonal lattice and embedded in a ferromagnetic material. Having analyzed all the possible combinations of magnonic crystal component materials from: Co, Ni, Fe, and Py (for spheres and matrix), we find material configurations for which either absolute or partial magnonic gaps occur in the spin-wave spectrum of the MC. We also demonstrate that the opening of a magnonic gap necessitates a sufficiently large contrast of magnetic parameters, and find the exchange length contrast to be the best measure of the capacity of the MC to produce a magnonic gap. Wider magnonic gaps are obtained in MCs in which the exchange length in the sphere material is larger than in the matrix. Among the MCs considered in this study, an absolute magnonic gap is obtained in a crystal with Ni spheres embedded in Fe.

Receiving sensitivity and transmitting voltage response of a fluid loaded spherical piezoelectric transducer with an elastic coating

A method is presented to determine the response of a spherical acoustic transducer that consists of a fluid-filled piezoelectric sphere with an elastic coating embedded in infinite fluid to electrical and plane-wave acoustic excitations. The exact spherically symmetric, linear, differential, governing equations are used for the interior and exterior fluids, and elastic and piezoelectric materials. Under acoustic excitation and open circuit boundary condition, the equation governing the piezoelectric sphere is homogeneous and the solution is expressed in terms of Bessel functions. Under electrical excitation, the equation governing the piezoelectric sphere is inhomogeneous and the complementary solution is expressed in terms of Bessel functions and the particular integral is expressed in terms of a power series. Numerical results are presented to illustrate the effect of dimensions of the piezoelectric sphere, fluid loading, elastic coating and internal material losses on the open-circuit receiving sensitivity and transmitting voltage response of the transducer.

Exact and numerical elastodynamic solutions for spherically symmetric problems of functionally graded thick-walled spheres subjected to pressure shocks

In the present paper, analytical and numerical elastodynamic solutions are developed for spherically symmetric problems of functionally graded thick-walled spheres subjected to arbitrary dynamic and shock loads. Both transient dynamic response and elastic wave propagation characteristics are studied in the mentioned nonhomogeneous structures. Variations of the material properties across the thickness are described according to both polynomial and power law functions. The numerical consistent transfinite element formulation is presented for both functions whereas the exact solution is presented for the power law function. The functionally graded material sphere is not divided into isotropic sub-spheres. An approach associated with dividing the dynamic radial displacement expression into quasi-static and dynamic parts and expansion of the transient wave functions in terms of a series of eigenfunctions is employed to propose the exact solution. Results are obtained for various exponents of the functions of the material properties distributions, various radius ratios, and variety of dynamic and shock loads.

Experimental and Theoretical Study of Metallic Hollow Sphere with Medium Thick Wall

. Metallic hollow sphere (MHS) material is a new type of cellular material characterized by super-light, high specific stiffness and strength, the ability to absorb noise and energy, thermal insulation. It had been widely used in engineering, i.e. automobile, aircraft, civil and military. The basic unit of MHS cellular material was small metallic hollow sphere in macro, and the instability of sphere shell is always the most difficult problem in mechanical field. In this paper, we explored the internal factors and the principle of this phenomenon though the methods of theoretical and experimental. The equation of deformation of MHS was derived. It had shown that the nominal strain was related to the radius of the shell and loads, and the nominal stress was connected with the radius, load and the thickness of shell wall. A series of quasi-static uniaxial compression tests were progressed for a group of single MHSs, which radii were 4mm, 5mm and 7mm. It was found that the deformation planes are circle and symmetry both top and bottom, and the curves of nominal stress-strain were similar to a half parabola. There was a perfectly uniformity of the theoretical model and the experimental results.

Welfare Systems, Support Networks and Subjective Well-Being Among Retired Persons

In this article welfare systems and support networks are empirically analyzed to determine which generate the highest level of subjective well-being among retired persons. Propositions derived from support network theories and national welfare system typologies have been analyzed using causal models that indicate the influence of the various welfare systems and support networks on subjective well-being. The data was taken from the Social Relations and Social Support Systems module of the 2001 International Social Survey Program. The results indicate that liberal welfare systems generate the highest level of subjective well-being. This correlates with a lower degree of confidence in the welfare state, greater interpersonal trust and greater belief in individuals and their capacity to secure their own well-being. In the sphere of material well-being the subjective well-being of individuals is affected by a greater trust in people than in the state.

DEM simulations and experiments for projectile impacting two-dimensional particle packings including dissimilar material layers

The dynamic response of a two-dimensional ordered particle packing composed of nylon-66 spheres 6.35 mm in diameter impacted by a spherical projectile was investigated both experimentally and numerically using the discrete element method (DEM). First, the influence of the number of layers in the particle packing on wave propa- gation and post-impact movement were examined. As the number of layers increased, the contact forces reaching the base plate decreased together with the rebound velocity of the projectiles. Next, the effects of dissimilar material lay- ers were examined. The spheres in one or two layers of the particle packing were replaced with spheres made of dissim- ilar materials, that is, alumina ceramic (Al2O3) or steel, and it was found that the scattering of the nylon spheres above the dissimilar material layers increased. The experimental results obtained using force sensors at the base plate showed that the dissimilar material layers reduced the contact forces at the base plate. Furthermore, as the mass of the dissimi- lar material spheres increased, the magnitude of the contact forces at the base plate decreased, and the rebound velocity of the projectile increased.

A phantom study of nodule size evaluation with chest tomosynthesis and computed tomography

The aim of the present study was to investigate nodule size measurements with chest tomosynthesis (TS) and computed tomography (CT). A 26-mm thick phantom, composed of a Polylite block with embedded spheres of different materials and sizes (4-20 mm), was scanned by both CT and TS. Six observers without prior knowledge of the true diameters of the spheres independently measured the diameter of the spheres on the CT and TS images. Four observers were allowed to change the window settings and two of the observers used predetermined fixed viewing conditions. The mean relative errors for all observers and all measured spheres compared with the known diameter of the spheres were 1.4 % (standard deviation, SD: 5.4 %) on CT images and -1.1 % (SD: 5.0 %) on TS images. With regard to the four observers where the window settings were at the discretion of the observer, the mean relative errors were 1.4 % (SD: 6.4 %) on CT images and -1.7 % (SD: 5.7 %) on TS images. Regarding the two observers using identical viewing conditions the mean relative error was 1.5 % (SD: 2.8 %) on CT images and 0.2 % (SD: 2.6 %) on TS images. In conclusion, the study suggests that nodule size measurements on chest TS might be an alternative to measurements on CT.

Strategy and Innovation as Evolutionary Learning between Capabilities and Routines

Strategy and innovation involves interpretation and learning to develop and adapt an organisation’s actions and reactions to ‘environmental’ challenges. This involves dealing with complex, interrelated structures in social and material spheres, which are the historically grown outcomes of the systematization of past learning in hierarchically organised modules. This paper draws together research and perspectives to find a common micro-level basis for learning in strategy and innovation as systematization of information in hierarchically organised, modular systems. Conceptually, it is based upon a ‘epistemological-cognitive’ interpretation of evolution as learning process that accumulates information and transforms it into ‘knowledge’ via codification and structural organisation of this knowledge. To do so, we refer systemic evolutionary theory and develop a micro-level perspective for social systems on learning in actors and develop tentative links on how the processes may be linked to the constructs of organisational capabilities and routines.

Clothes without Bodies: Objects, Humans, and the Marketplace in Eighteenth-Century It-Narratives and Trade Cards

While recent studies of the things of literature call attention to the narrative and psychological slippage between people and their possessions, this essay argues that rather than representing a loss for human agency, humans and things intermingle to the disadvantage of objects. I show how trade cards and object narratives engage with the same nexus of commercial culture, objects, and humans, and share a mutual resistance to autonomous garments—petticoats, shoes, gowns, and other garments depicted independently of the human form. Object narratives, read in tandem with trade cards, suggest that the growth of distance between persons and things, as opposed to their collapse into each other, constitutes a central narrative in the period's commodity culture and fiction. Object narratives, even as they transform coats, waistcoats, petticoats, slippers, and shoes into first-person narrators, actively work against the entanglement of human and material spheres. Together these genres place sartorial commodities under human control, emphasizing the human subject's agency over those items worn closest to the self.

Modeling the vivid white color of the beetle Calothyrza margaritifera

The elytra of the longhorn Calothyrza margaritifera exhibit bright white zones which appear, under SEM, to be composed of structures looking like long white hairs: flat cone-shaped rods of 100–200 μm in length and a base of 10–20 μm. Each hair is composed of an envelope of chitin or chitin and associated proteins, filled with small agglomerated spheres of the same material, of mean diameter 550 nm. The optical properties of this multiscale structure have been characterized: hemispherical reflectance spectra, bidirectional reflectance spectra, spatial scattering maps. A multiscale optical model, taking into account this complex structure has been developed for predicting the optical properties. Starting from the SEM image, the representative basic scattering structure is extracted, from the scale of the nanometer to the millimeter. By using the Mie theory and solving the Radiative Transfer Equation, the local optical properties of this structure are calculated. Thanks to a 3D modeler the basic structural element is then duplicated with small deviations in its shape, position and orientation for reproducing the overall SEM image. A photon-mapping is then implemented on this 3D structure with a spectral evaluation of illumination maps based on Monte–Carlo ray shooting. The first predictions of this multiscale model are in qualitative and almost quantitative agreement with the white color measured on the elytron of this insect and of its spatial dispersion. The brightness of the visual effect is explained by considerations about the human vision.

Optimal composition of ceramic binder for highly porous abrasive tools

1043 The operational characteristics of abrasive tools largely depend on the structure and properties of the materials from which they are made. Machining experience shows that highly porous abrasive tools are the most effective. In comparison with standard tools, their productivity is higher, while the depth of the defect layer in the ground surface is smaller by a factor of 5‐6. The pore volume may be increased by reducing the proportion of grains and/or binder. Increasing the porosity by reducing the grain content is the most promising, since it significantly (by a factor of 3‐5) exceeds the binder content, as a rule. However, simply decreasing the content of grains will now work, for the following reasons. With uniform grain distribution in the abrasive mass, the intergrain contact will include a binder layer. On baking, the binder melts, and the grains begin to move toward one another under the action of their own weight and the surface tension of the binder at contact, to form a more compact rigid framework. The abrasive tool shrinks: its density is increased, and the pore volume declines. Existing tool-manufacturing technology calls for the use of various fillers to replace the withdrawn grains. The most promising fillers—hollow spheres of corundum, glass, ceramic, and other materials—were listed in [1]. In that case, the hollow sphere acts both as a pore and as a structural element of the tool. The benefits of corundum spheres are strength and adhesion to the ceramic binder. However, the tools obtained using this filler have a closed pore system, since the melting point of the spheres is above the conventional baking temperatures. In tool operation, the chip and the coolant fluid are packed in pores at the working surface, which consequently becomes clogged, with increase in the stress and thermal stress of the process as a whole. Glass spheres whose melting point is lower than the baking temperature dissolve in the binder, and a single pore system is formed in the resulting tool. However, glass spheres, although fusible, reduce the refractory properties of the binder and hence increase the risk of extreme tool shrinkage. This may be avoided by increasing the proportion of relatively infusible components in the binder or reducing the baking temperature. Both methods reduce the binder reactivity and hence the tool strength, on account of the chemical inhomogeneity of the binder bridges, and also reduce the proportion of corundum that passes to the binder from the grain. The optimal approach is to use spheres made of the binder material. The benefits are obvious: the chemical composition of the material is unchanged; the melting point of the sphere corresponds to the tool-baking temperature; and the binder reactivity remains unchanged. We have selected the filler that best meets these requirements: the spheres are close to the ceramic binder in composition (no more than 5‐10% difference in the Al 2 O 3 and SiO 2 content), while the refractory properties are 10% higher. In terms of their physicomechanical properties, the spheres are intermediate between glass and corundum spheres (Table 1). In developing the composition of the tool material, we have taken into account that the spheres will contribute to the binder content. For example, in wheels of structure 12 with hardness VM0, 12% of the grains must be replaced by the spheres, with the addition of 5.5% binder. Since the porosity of the spheres is about 80%, they account for around 2.4% of the binder after melting. In other words, we reduce the amount of binder added from 5.5% to 3.1%.