Real collective density variables C(k) [cf. Eq. (1.3)] in many-particle systems arise from nonlinear transformations of particle positions, and determine the structure factor S(k), where k denotes the wave vector. Our...
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Real collective density variables C(k) [cf. Eq. (1.3)] in many-particle systems arise from nonlinear transformations of particle positions, and determine the structure factor S(k), where k denotes the wave vector. Our objective is to prescribe C(k) and then to find many-particle configurations that correspond to such a target C(k) using a numerical optimization technique. Numerical results reported here extend earlier one- and two-dimensional studies to include three dimensions. In addition, they demonstrate the capacity to control S(k) in the neighborhood of ∣k∣=0. The optimization method employed generates multiparticle configurations for which S(k)∝∣k∣α, ∣k∣⩽K, and α=1, 2, 4, 6, 8, and 10. The case α=1 is relevant for the Harrison-Zeldovich model of the early universe, for superfluid He4, and for jammed amorphous sphere packings. The analysis also provides specific examples of interaction potentials whose classical ground states are configurationally degenerate and disordered.
Magnetic paper via lumen loading process was prepared from neverdried and dried kraft pulp. Polyethylenimine (PEI) was used as retention aid during the inter-stage treatment. The paper produced from the magnetic pulp ...
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Magnetic paper via lumen loading process was prepared from neverdried and dried kraft pulp. Polyethylenimine (PEI) was used as retention aid during the inter-stage treatment. The paper produced from the magnetic pulp showed an increase of magnetic properties as the loading increased. The physical properties of the paper such as tensile index, burst index, tear and folding endurance showed a reduction in the strength value as the loading capacity increased. The lumen-loaded paper shows better physical properties than conventionally loaded paper. The flocculation study shows that the magnetic colloid exists in multi particles aggregates form in water solution, which caused by magnetodipole interaction.
We present the use of the polysaccharide chitosan for immobilizing biomolecules on microfabricated device surfaces. The main advantages of chitosan are its abundance of primary amine groups and its ability to be elect...
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ISBN:
(纸本)1424402778
We present the use of the polysaccharide chitosan for immobilizing biomolecules on microfabricated device surfaces. The main advantages of chitosan are its abundance of primary amine groups and its ability to be electrodeposited. Biomolecules are easily attached to chitosan 's amines by standard glutaraldehyde chemistry. The electrodeposition of chitosan allows accurate spatial and temporal control of biomolecule placement. We have demonstrated this biofunctionalization method for two different bioMEMS devices: a biophotonic sensor and a micromechanical biosensor. We have successfully assembled probe DNA on each of them and detected hybridization with target DNA as a demonstration of sensor operation. Here, we briefly present the fabrication procedure and testing results for both of these bioMEMS sensing devices
Hopkinson bar based thick walled cylinder (TWC) method was developed to collapse hollow cylinders with small mass about 0.5 gram made from the mixtures of PTFE and Al particles of different sizes (2 and 95 μm). Diffe...
Hopkinson bar based thick walled cylinder (TWC) method was developed to collapse hollow cylinders with small mass about 0.5 gram made from the mixtures of PTFE and Al particles of different sizes (2 and 95 μm). Different media (water, suspension of alumina particles in water, and glycerol) in different geometrical configurations were investigated to ensure the collapse of hollow cylinders with a single pressure pulse under pressure/time conditions achievable in Hopkinson bar tests. Raman spectroscopy of the samples of PTFE and 2 μm aluminum particles mixtures demonstrated the evidence of the decomposition or reaction of PTFE inside the shear localization area or cracks.
Two spherical cavity expansion experiments were performed with SiC‐N to provide high‐strain rate data for developing ceramic armor penetration models. Here, an explosive charge is detonated within a cavity machined ...
Two spherical cavity expansion experiments were performed with SiC‐N to provide high‐strain rate data for developing ceramic armor penetration models. Here, an explosive charge is detonated within a cavity machined in the ceramic, generating a pulse that moves radially outward. The particle velocity at multiple radial locations from the charge, including at the charge radii, was measured and the fractured ceramic was recovered for posttest evaluation. From the particle velocity histories we derived displacement, radial strain and circumferential strain histories. In the recovered samples we observed the regions where comminution, radial cracking and circumferential cracking occurred. The elastic properties of initial undamaged SiC‐N and shocked damaged material were measured using a resonant ultrasound spectroscopy (RUS). Comparison of these measurements illustrated the posttest condition of the SiC‐N material. Hot isostatic pressing of “as is” SiC‐N material demonstrated a significant increase in the quality factor. The same procedure applied to SiC‐N damaged in spherical cavity experiments resulted in a significant recovery of the elastic properties.
BioMEMS devices are proposed for use in medicine as in-dwelling sensors and as effectors of direct action upon diseased organs. Understanding the role of proteins in mediating adhesion force and friction for bioMEMS d...
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In the past two decades, calcium phosphates, and especially hydroxyapatite (HA), have been used as bone substitutes, and the mechanical strength is one of the most important properties in this application. The flexura...
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ISBN:
(纸本)9781617820632
In the past two decades, calcium phosphates, and especially hydroxyapatite (HA), have been used as bone substitutes, and the mechanical strength is one of the most important properties in this application. The flexural strength of an HA object depends on the nature of the HA powder, specimen preparation, flex test geometry and experimental conditions. HA was prepared by two methods, namely: wet and hydrothermal. The fundamental difference between these methods lies in the method of mixing the reactants and the reaction temperature. The obtained powders were pressed into pellets at 150 MPa and tested for flexural strength using a ring-on-disc method. The two-parameter Weibull and normal distributions were used to characterize the observed flexural strengths. Results were correlated with scanning microscope observations of fracture surfaces of the polished broken discs. The two-parameter Weibull distribution was found to be superior for the samples made with HA from the hydrothermal method. For the samples from the wet method, the normal distribution was equally suitable. The reason for this difference was sought by examining the discs for surface flaws.
We have used neutron diffraction (ND) and transmission electron microscopy (TEM) to determine the effects of extrusion variables on the texture and grain structure of extruded Zr-2.5wt%Nb tubes in the range of 925 to ...
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ISBN:
(纸本)0919784828
We have used neutron diffraction (ND) and transmission electron microscopy (TEM) to determine the effects of extrusion variables on the texture and grain structure of extruded Zr-2.5wt%Nb tubes in the range of 925 to 1250K. The final textures are correlated with the shape and morphology of the grains produced during extrusion. The texture variations from front-to-back ends of the tubes were also analyzed by using the ND techniques. These were found to correlate with variations in temperature from front to back end during extrusion. The results will eventually be used to modify the manufacturing route of pressure tubes to optimize in-service performance.
We present an experimental approach to systematically produce nanostructures with various grain sizes and twin densities in the Ni-Co binary system. Using electrodeposition with various applied current densities and o...
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We present an experimental approach to systematically produce nanostructures with various grain sizes and twin densities in the Ni-Co binary system. Using electrodeposition with various applied current densities and organic additive contents in the deposition bath, we synthesize nanostructured fee and hcp solid solutions with a range of compositions. Due to the low stacking fault energy (SFE) of these alloys, growth twins are readily formed during deposition, and by adjusting the deposition conditions, a range of twin boundary densities is possible. The resulting nanostructured alloys cannot be described by a single characteristic length scale, but instead must be characterized in terms of (1) a true grain size pertaining to general high-angle grain boundaries and (2) an effective grain size that incorporates twin boundaries. Analysis of Hall-Petch strength scaling for these materials is complicated by their dual length scales, but the hardness trends found in Ni-80Co are found to be roughly in line with those seen in pure nanocrystalline nickel.
作者：
Lu SunLei ZhuLixia RongBenjamin S. HsiaoPolymer Program
Institute of Materials Science and Department of Chemical Materials and Biomolecular Engineering University of Connecticut Storrs CT 06269‐3136 USA Fax: (+1) 860‐486‐4745 http://www.ims.uconn.edu/∼lzhu Department of Chemistry
State University of New York at Stony Brook Stony Brook NY 11794‐3400 USA
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