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Materials Discovery by Crystal Growth: Synthesis, Structure Determination, Magnetic, and Optical Properties of Complex Lanthanide Containing Oxides, Oxyhydroxides, and Oxyfluorides

Materials Discovery by Crystal Growth: Synthesis, Structure Determination, Magnetic, and Optical Properties of Complex Lanthanide Containing Oxides, Oxyhydroxides, and Oxyfluorides

The aims of this study are to go beyond the scope of the existing studies (e.g. (Ferrara and Pandolfi, 2010; Gasser and Holzapfel, 2007; Gasser and Holzapfel, 2006; Leng et al., 2015b)) to gain a mechanical understanding of the plaque rupture phenomenon at the microscopic scale. Firstly, a uniaxial tensile test on a single tow of collagen fibers from porcine arterial wall was performed in order to acquire the elastic modulus, tensile strength and strain at failure. Secondly, the interfacial strength of interface across fibers was obtained through best fitting of the load-displacement curve from the simulation predictions with the experimental measurements. Finally, these parameter values were used as input data for a micromechanical model of a plaque-arterial wall system, which was developed based on experimental observations and the cohesive zone model approach. The failure mechanism at the microscopic scale (such as possible collagen fiber breakage) was incorporated to develop a three-dimensional unit cell model, which will enable the characterization of the cohesive traction-separation relation and the factors at the micromechanical scale affecting this relation that plays an important role for the understanding of micromechanical mechanism in plaque rupture.
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Electronic Band Structure of Graphene  Based on the Rectangular 4 Atom Unit Cell

Electronic Band Structure of Graphene Based on the Rectangular 4 Atom Unit Cell

The Wigner-Seitz unit cell (rhombus) for a honeycomb lattice fails to establish a k -vector in the 2D space, which is required for the Bloch electron dynam- ics. Phonon motion cannot be discussed in the triangular coordinates, either. In this paper, we propose a rectangular 4-atom unit cell model, which allows us to discuss the electron and phonon (wave packets) motion in the k -space. The present paper discusses the band structure of graphene based on the rec- tangular 4-atom unit cell model to establish an appropriate k -vector k for the Bloch electron dynamics. To obtain the band energy of a Bloch electron in graphene, we extend the tight-binding calculations for the Wigner-Seitz (2- atom unit cell) model of Reich et al. ( Physical Review B , 66, Article ID: 035412 (2002)) to the rectangular 4-atom unit cell model. It is shown that the gra- phene band structure based on the rectangular 4-atom unit cell model reveals the same band structure of the graphene based on the Wigner-Seitz 2-atom unit cell model; the π -band energy holds a linear dispersion ( ε − k ) relations near the Fermi energy (crossing points of the valence and the conduction bands) in the first Brillouin zone of the rectangular reciprocal lattice. We then confirm the suitability of the proposed rectangular (orthogonal) unit cell model for graphene in order to establish a 2D k -vector responsible for the Bloch electron (wave packet) dynamics in graphene.
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Modeling and characterization of the moisture-dependent bilinear behavior of regenerated cellulose composites

Modeling and characterization of the moisture-dependent bilinear behavior of regenerated cellulose composites

In this study, the results are presented of a computational and experimental investigation on the tensile behavior of Lyocell/epoxy composites. The limitations of assumptions of using linear elastic properties in modeling of regenerated cellulose composites are illustrated. The mechanical properties of Lyocell tows are investigated under dry and wet conditions showing bilinear and nonlinear elastic– plastic responses. A multi-scale unit cell model incorpo- rating a bilinear elastic–plastic stress–strain behavior can be approximated for the dry fibers. As the fibers absorb moisture, the knee of the stress–strain response shifts to the early stages of loading. Nonlinear behavior and a drastic loss in modulus are observed for the wet fibers. In com- posite form, the behavior under wet conditions was less pronounced due to the barrier properties of the epoxy resin. Manufacturing composites from Lyocell fibers possesses unique challenges due to the hydrophilic and pilling nature of these fibers. The use of resin infusion produced higher FVF but some unwetted areas were seen even at high vacuum pressures. The use of wet layup followed by degassing overcomes that problem, but may be an issue when thicker parts or more complex geometries are desired. The speed of preparation is also an issue since the resin takes around 35 min to harden and mold filling of large structures would need to account for this. The FE approach using p-FEA incorporating the bilinear constitu- tive response of Lyocell was proposed for possible mod- eling of these composites and predicting the composite behavioral response. The results show that the model was successfully used to predict the loading behavior of these composites under different fiber contents in dry conditions. The model can also be easily extended to determine the elastic–plastic orthotropic material constants by varying the boundary conditions. Future structural mechanics tools can use the proposed approach to incorporate the effects of moisture absorption on thermoset/regenerated cellulose composites.
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Nonlinear and Rate Dependent Hysteretic Responses of Active Hybrid Composites

Nonlinear and Rate Dependent Hysteretic Responses of Active Hybrid Composites

Nonlinear electro-mechanical behaviors of piezoelectric materials and viscoelastic nature of po- lymers result in the overall nonlinear and hysteretic responses of active polymeric composites. This study presents a hybrid-unit-cell model for obtaining the effective nonlinear and rate-de- pendent hysteretic electro-mechanical responses of hybrid piezocomposites. The studied hybrid piezocomposites consist of unidirectional piezoelectric fibers embedded in a polymeric matrix, which is reinforced with piezoelectric particles. The hybrid-unit-cell model is derived based on a unit-cell model of fiber-reinforced composites consisting of fiber and matrix subcells, in which the matrix subcells are comprised of a unit-cell model of particle-reinforced composites. Nonlinear electro-mechanical responses are considered for the piezoelectric constituents while a viscoelas- tic solid constitutive model is used for the polymer constituent. The hybrid-unit cell model is used to examine the effects of different responses of the constituents, microstructural arrangements, and loading histories on the overall nonlinear and hysteretic electro-mechanical responses of the hybrid piezocomposites, which are useful in designing active polymeric composites.
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On understanding the applicability of Mohr Coulomb failure hypothesis for composite materials using UnitCells©

On understanding the applicability of Mohr Coulomb failure hypothesis for composite materials using UnitCells©

In order to perform micromechanical characterisation of composite materials using unit cells approach, a finite element tool named UnitCells© has been made use of in this work. Based on the systematic consideration of symmetries present in idealised fibre-matrix composites, a comprehensive framework of micromechanical analysis using unit cells to predict the effective properties of the composites has been developed over the years [26][27][28][29]. For accurate predictions of effective properties of the composites, it is necessary to apply appropriate boundary conditions to a unit cell model. Since most of the UD composite laminate materials have regular periodic microstructures, the stress and strain distributions in the regular microstructure are also periodic. Therefore, the smallest periodic volume of a regular microstructure can be regarded as a unit cell. The unit cell model with periodic boundary condition represents a large regular microstructure. Considering the periodic geometry and continuous displacement field, periodic boundary conditions for cubic unit cells are defined as follows [28]: (𝑢| 𝑥=𝑏 − 𝑢| 𝑥=−𝑏 )| 𝑦,𝑧 = 2𝑏ε 𝑥 0 (𝑢| 𝑦=𝑏 − 𝑢| 𝑦=−𝑏 )| 𝑥,𝑧 = 2𝑏γ 𝑥𝑦 0 (𝑢| 𝑧=𝑏 − 𝑢| 𝑧=−𝑏 )| 𝑥,𝑦 = 2𝑏γ 𝑥𝑧 0
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Metal(III)-water interactions

Metal(III)-water interactions

Figure 3.2.13 shows the powder diffraction pattern for RbVSH. Two sets of scans were recorded. High angle data recorded between 20 values of 126° and 156° were recorded first, followed by a long scan from 14° to 156°. This was done in order to check that the high angle data was consistent Figure 3.2.13 (b) shows the two sets of high angle data recorded. The top scan was recorded first; the bottom scan was recorded ca. 16 hours later. In this alum, there is negligible change in both the positions and intensities of the high angle data for the two data sets. Figure 3.2.14 shows a plot of unit cell parameters for several high angle reflections versus the function l/2[cos^0/0 + cos%/sin0]. A straight line can be drawn through the points. The unit cell parameter is the value at the intercept which is 12.347(1) Â. No value of the unit cell obtained from any reflection is greater than 0.001 Â from the straight line joining the points indicating that this is a precise measurement Figure 3.2.15 shows the powder diffraction pattern for "Pmix45" whose Raman spectra are shown in figures 3.2.5 - 3.2.7. It is noted that there is a slight change in the relative intensities of the peaks from the two scans. This can only mean that there is some change in atomic positions, likely to be a result of either aerial oxidation or acquisition of water fi*om the atmosphere. Similar behaviour was observed for other alums whose diffraction patterns were recorded in this study. The peaks do, however, occur at the same positions for the two scans indicating that within experimental error, there is no change in the unit cell parameter.
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Comparative Investigation of Resonance Characteristics and Electrical Size of the Double-Sided SRR, Bc-SRR and Conventional SRR Type Metamaterials for Varying Substrate Parameters

Comparative Investigation of Resonance Characteristics and Electrical Size of the Double-Sided SRR, Bc-SRR and Conventional SRR Type Metamaterials for Varying Substrate Parameters

The unit cell geometries used for the SRR, BC-SRR and DSRR structures are described in Figures 1(a), 1(b) and 1(c), respectively, where the overall cell sizes as well as the split ring dimensions are kept the same for all three structures for fair comparison of the simulation results. The unit cells shown in Figure 1 have the common geometrical parameters of L = 5 mm (side length of the square shaped substrate surface), l = 4 mm and h = 3 mm (side lengths of the rectangular shaped outer ring), g = 0.5 mm (gap distance or slit length) and w = 0.3 mm (width of the metal ring). The rings of the resonators are made of copper lines with the metal thickness of 0.03 mm and conductivity of 5.8 × 10 7 S/m. The parameter s refers to the planar
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Wide Beam Tapered Slot Antenna for Wide Angle Scanning Phased Array Antenna

Wide Beam Tapered Slot Antenna for Wide Angle Scanning Phased Array Antenna

The design parameters of a doubly layered exponentially Tapered Slot Antenna (DTSA) are defined in Figures 1 and 2. Figure 1(a) illustrates the commercially available electromagnetic simulator HFSS model of the proposed geometry of DTSA. It consists of a section of slotline that is narrow at one end and has opening in an exponential flare at the other end. The antenna geometry can be classified into two categories: substrate parameters (relative dielectric constant, ε r , and thickness,

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Datapro C25 Memorex Telex pdf

Datapro C25 Memorex Telex pdf

Three models are available: Model S4C is a remote SNA/ SDLC unit; Model S4A is a local SNA/SDLC unit; and Model S4D is a local BSC unit.The 2074 supports attachment of the following devi[r]

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Cited by 2

Cited by 2

consists of two identical but oppositely oriented split tube resonators (Figure 6d). The gap between two adjacent unit cells allows air to flow through the structure. The high absorption of the sound wave has resulted from the weak coupling of two split tube resonators. A 3D printed sample is fabricated from polylactide (PLA) plastic for the experimental measurements (Figure 6d). The experimental result shows the maximum sound absorption of 82.1% at 342 Hz and no significant change in absorption under the oblique incidence (up to 60 ◦ ). Shen et al. [84] presented the two-dimensional ventilated acoustic metacages with a subwavelength thickness (Figure 6e). A ring-shaped structure is created by the radial arrangement of the metacages, and each metacage is composed of several shunted Helmholtz resonators with increasing heights along the radial direction. The structure is capable of shielding the noise coming from all directions while allowing substantial airflow through a gap between two adjacent metacage. An omnidirectional acoustic shielding is realized by the fabricated structure. Li et al. [85] demonstrated a broadband compact acoustic absorber for the low-to-mid frequency noise absorption while ensuring high ventilation for air passage. The structure is constructed by attaching the eight unit cells to the outer periphery of the square-shaped hollow tube. Each unit cell consists of a double-layered metastructure with micro-perforated holes on opposite sides. Figure 6f shows the schematics of the proposed absorbers. The perforated unit cells serve for the sound attenuation while the hollow tube provides the passage for air ventilation (70% cross-section open). They experimentally showed the high absorption (>0.5) in the frequency range of 850–1000 Hz.
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Micro- and macroscopic simulation of periodic metamaterials

Micro- and macroscopic simulation of periodic metamaterials

The effective material values which are obtained by such techniques are an important result for the synthesis of the composites. However, their main purpose is to be used in the design process of large-scale components, where the novel properties of metamaterials shall be profitably used. Thus, the extraction results should of course be as accurate as pos- sible, in the sense that the equivalent model can describe the behavior of the metamaterial within the interesting frequency band. However, the model should also be physical, i.e. it should be passive (as long as no active materials are present on the microscopic scale) and last but not least it should be causal. As a critical review of published results (such as, e.g., in Simovski and Tretyakov, 2007) shows, these properties are sometimes not fulfilled, and it seems as if this is not a result of shortcomings in the respective implementations.
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Polyomino models of molecular monolayers

Polyomino models of molecular monolayers

The properties of molecular monolayers can depend strongly on whether the system is above or below a phase transition. For the side-aligning domino system below the critical temperature, the system enters a crystalline phase shown in Figure 1.13, where the domino-domino correlations extend indefinitely. This phenomena can be thought of in the context of the large scale behaviour of the height function of the domino tiling, which is affected by the interactions between dominoes. In the large scale limit, the height function approximates a continuous function, with a corresponding action to determine the behaviour at a given temperature [49]. At low temperature, a potential term promotes domino ordering. Conversely, at high temperature, an entropic term dominates, causing the height function to become rough. Indeed, in the high-temperature regime, the height fluctuations have the same Gaussian free field property as those of the non-interacting model [51]. This property in the interacting model has been suggested for some time, but was proved recently [52].
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Ab initiostudies of the phase transitions inK2SeO4

Ab initiostudies of the phase transitions inK2SeO4

1, we see that the unit cell in the Pna2, structure can be considered as formed by tripling the unit cell in the Pnam structure and then slightly modulating along the a direction the ori[r]

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Unit II (a) Introduction to Aberrant cell growth.pdf

Unit II (a) Introduction to Aberrant cell growth.pdf

Chemotherapy may be combined with surgery, radiation therapy, or both to reduce tumor size preoperatively (neoadjuvant), to destroy any remaining tumor cells postoperatively (adjuvant), [r]

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A Broadband Reflectarray Using Phoenix Unit Cell

A Broadband Reflectarray Using Phoenix Unit Cell

The Phoenix cell reflectarray using proposed radiating elements has been designed and fabricated. A photograph of the reflectarray prototype is given in Figure 6. The reflectarray consists of 15 × 15 elements printed on a grounded substrate with thickness h = 1 . 6 mm and relative permittivity ε r = 4 . 4 and tan δ = 0 . 02. The element spacing is h 1 = 8 mm so that the size of the reflectarray is 180 × 180 mm 2 .

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Toroidal moments as indicator for magneto electric coupling: the case of BiFeO3 versus FeTiO3

Toroidal moments as indicator for magneto electric coupling: the case of BiFeO3 versus FeTiO3

tion of the individual magnetic moments, it follows from Eq. (1) that the toroidal moment contains information about where the magnetic moments are located as well as on how they are oriented. Furthermore, the toroidal moment is a macroscopic multipole moment that is re- lated to the (magnetic) point group symmetry, whereas a proper symmetry analysis of antiferromagnetic order requires a treatment based on the full space group sym- metry. In particular, antiferromagnetic order is not con- nected to any particular macroscopic symmetry break- ing, i.e. all 90 magnetic point groups are compatible with the existence of antiferromagnetic order. On a mi- croscopic space group level, antiferromagnetic order of course always breaks time reversal symmetry. However, for systems where the magnetic unit cell is a multiple of the crystallographic unit cell, a primitive translation of the original nonmagnetic lattice can be combined with time reversal, and as a result the corresponding magnetic point group still contains time reversal as a symmetry element. 34 In contrast, a toroidal moment always breaks
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Influence of C Axis Inter Unit Cell Resonant Tunneling on the Spectral Function in Bilayer Cuprates

Influence of C Axis Inter Unit Cell Resonant Tunneling on the Spectral Function in Bilayer Cuprates

systems like Y-123 and Bi-2212. Most of the recent theoretical studies related to ARPES electronic spectra are based on the two dimensional tight binding Hubbard model and its extension within numerical and analytical approaches and the role of third dimensional coupling on the spectra in the presence of electrons correlation effect has not been clearly understood so far. Therefore, it would be interesting to study the effect of intra cell cou- pling, inter unit cell resonant tunneling, and electronic correlations simultaneously on the spectral function in doped multilayer cuprates in normal state.
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DESIGN OF NOVEL IMPROVED UNIT- CELL FOR COMPOSITE RIGHT LEFT HANDED TRANSMISSION LINE BASED MICROWAVE CIRCUITS

DESIGN OF NOVEL IMPROVED UNIT- CELL FOR COMPOSITE RIGHT LEFT HANDED TRANSMISSION LINE BASED MICROWAVE CIRCUITS

A novel improved version of unit-cell for the design of composite right left handed transmission line (CRLH TL) is reported in this paper. Comparative results of both conventional design of unit-cell and proposed design of unit-cell for CRLH TLs are presented in this article. The conventional unit-cell is designed based on inter digital capacitor (IDC) in series and vias to the ground plane at the stub ends in shunt, whereas proposed unit- cell is designed based on wire bonded interdigital capacitor (WBIDC) in series and vias to the ground plane at the stub ends in shunt . Use of WBIDC in the proposed unit-cell improves high frequency performance by reducing undesired self resonances generated in IDC at lower frequency end. A simple technique is also used in both designs to miniaturize the unit-cell profiles. Dispersion diagrams of the unit-cells show the presence of self resonances in the conventional IDC based unit-cell and absence of such self resonances in the proposed WBIDC based unit-cell, which causes the wider operational frequency band of WBIDC based unit-cell. The performances of both unit-cells are compared from dispersion curve and S-parameters characteristics. The frequency parameter and performance of the both unit-cells are evaluated by full-wave electromagnetic simulator using Ansoft Designer, based on method of moment.
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Unique determination of “subatomic” contrast by imaging covalent backbonding

Unique determination of “subatomic” contrast by imaging covalent backbonding

In this paper, we unambiguously show that “sub-atomic like” features can arise from the back bonding configuration of a surface atom being imaged during DFM. This is done by utilising the change in bonding configuration of the surface adatoms of the Si(111) unit cell between the faulted and unfaulted half. Due to this change in symmetry across the unit cell, the features we observe cannot be assigned to any tip, or feedback artefacts. At the same time, they suggest caution should be used when interpreting “sub-atomic like” features, as our data cannot be interpreted as arising from within a single atom.
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Biology Study guide Cells & Cell energetics

Biology Study guide Cells & Cell energetics

**B2.5h Explain the role of cell membranes as a highly selective barrier (diffusion, osmosis, and active transport). **B2.1C Explain cell division, growth, and development as a conseque[r]

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