Accurate interlaminar stress recovery from finite element analysis

The accuracy and robustness of a two-dimensional smoothing methodology is examined for the problem of recovering accurate interlaminar shear stress distributions in laminated composite and sandwich plates. The smoothing methodology is based on a variational formulation which combines discrete least-squares and penalty-constraint functionals in a single variational form. The smoothing analysis utilizes optimal strains computed at discrete locations in a finite element analysis. These discrete strain data are smoothed with a smoothing element discretization, producing superior accuracy strains and their first gradients. The approach enables the resulting smooth strain field to be practically C1-continuous throughout the domain of smoothing, exhibiting superconvergent properties of the smoothed quantity. The continuous strain gradients are also obtained directly from the solution. The recovered strain gradients are subsequently employed in the integration o equilibrium equations to obtain accurate interlaminar shear stresses. The problem is a simply-supported rectangular plate under a doubly sinusoidal load. The problem has an exact analytic solution which serves as a measure of goodness of the recovered interlaminar shear stresses. The method has the versatility of being applicable to the analysis of rather general and complex structures built of distinct components and materials, such as found in aircraft design. For these types of structures, the smoothing is achieved with 'patches', each patch covering the domain in which the smoothed quantity is physically continuous

Interlaminar Stresses by Refined Beam Theories and the Sinc Method Based on Interpolation of Highest Derivative

Computation of interlaminar stresses from the higher-order shear and normal deformable beam theory and the refined zigzag theory was performed using the Sinc method based on Interpolation of Highest Derivative. The Sinc method based on Interpolation of Highest Derivative was proposed as an efficient method for determining through-the-thickness variations of interlaminar stresses from one- and two-dimensional analysis by integration of the equilibrium equations of three-dimensional elasticity. However, the use of traditional equivalent single layer theories often results in inaccuracies near the boundaries and when the lamina have extremely large differences in material properties. Interlaminar stresses in symmetric cross-ply laminated beams were obtained by solving the higher-order shear and normal deformable beam theory and the refined zigzag theory with the Sinc method based on Interpolation of Highest Derivative. Interlaminar stresses and bending stresses from the present approach were compared with a detailed finite element solution obtained by ABAQUS/Standard. The results illustrate the ease with which the Sinc method based on Interpolation of Highest Derivative can be used to obtain the through-the-thickness distributions of interlaminar stresses from the beam theories. Moreover, the results indicate that the refined zigzag theory is a substantial improvement over the Timoshenko beam theory due to the piecewise continuous displacement field which more accurately represents interlaminar discontinuities in the strain field. The higher-order shear and normal deformable beam theory more accurately captures the interlaminar stresses at the ends of the beam because it allows transverse normal strain. However, the continuous nature of the displacement field requires a large number of monomial terms before the interlaminar stresses are computed as accurately as the refined zigzag theory

Environment of Er in a-Si:H: co-sputtering versus ion implantation

We report a comparative Extended X-Ray Fine Structure (EXAFS) study of Er in a-Si:H prepared by Er implantation in a-Si:H and by co-sputtering undergoing the same cumulative annealing processes. It was found that the Er environment in as-implanted samples is formed by Si atoms, which are replaced by oxygen under annealing. In the co-sputtered samples, the initial low coordination oxygen environment evolves under thermal treatment to an Er2O3 -like neighborhood.756759Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

The Kindred Bonds of Mentally Ill Homeless Persons

While the unraveling of the kinship bond has long been suspected to play a role in the epidemiology of homelessness, the connection between kinship and homelessness has been little studied. Based on a normative analysis of the role of family structure in response to adversity, this article explores the impact of the amount and quality of kinship ties on episodes of homelessness experienced by discharged psychiatric patients in Ohio. Survey data derived from personal interviews with both former patients and their kin indicate more strain in relations with kin of the homeless than the nonhomeless. The strain in the kinship bond appears to emanate from a greater prevalence of chronic disabilities that undermine independent functioning and tax the resources of relatives who choose to remain involved. Consistent with this interpretation, patients with histories of homelessness reported more psychiatric symptoms, more deficits in daily living skills, and more contact with the criminal justice system. In general, patient variables were better able than family variables to differentiate the homeless from the nonhomeless. Nonetheless, the formulation of public policies for reducing the incidence and prevalence of homelessness will surely need to take account of the kinship bond and how it can be strengthened

Encouraging Evidence on a Sector-Focused Advancement Strategy: Two-Year Impacts from the WorkAdvance Demonstration

This report summarizes the two-year findings of a rigorous random assignment evaluation of the WorkAdvance model, a sectoral training and advancement initiative. Launched in 2011, WorkAd-vance goes beyond the previous generation of employment programs by introducing demand-driven skills training and a focus on jobs that have career pathways. The model is heavily influenced by the positive findings from the Sectoral Employment Impact Study (SEIS) completed in 2010. A major component of the WorkAdvance model, in common with the programs studied in the SEIS, is formal training offering industry-recognized certifications, reflecting the hypothesis that skills acquisition is necessary for advancement. The model also requires providers to be far more employer-facing than traditional training programs, taking into account multiple employers' changing skill requirements, employee assessment practices, and personnel needs. This report presents the imple-mentation, cost, participation, and two-year economic impacts of WorkAdvance. The economic results are based on unemployment insurance earnings records and a second-year follow-up survey.The WorkAdvance program operations and evaluation are funded through the federal Social Innovation Fund (SIF), a public-private partnership administered by the Corporation for National and Community Service. This SIF project is led by the Mayor's Fund to Advance New York City and the NYC Center for Economic Opportunity in collaboration with MDRC.Key Findings*All providers translated the WorkAdvance model into a set of concrete services, but it took time— more than a year for some components and providers -- and a substantial amount of tech-nical assistance and support. As a result, at some sites, later study enrollees were more likely than earlier ones to experience a fully implemented and "mature" WorkAdvance program.*Overall, WorkAdvance resulted in very large increases in participation in every category of services, as well as in training completion and credential acquisition, compared with what would have happened in the absence of the program. Expenditures for the operation of WorkAdvance fell between $5,200 and$6,700 per participant at the four providers delivering the program.*WorkAdvance providers increased earnings, with variation in results that closely matched the providers' experience in running sector-based programs and the extent to which the services they offered were demand driven. The most experienced sectoral provider, Per Scholas, had large and consistent impacts on both primary and secondary outcomes. Madison Strategies Group and Towards Employment, providers new to sectoral training, had promising but less consistent results that grew stronger for later enrollees. One provider, St. Nicks Alliance, did not produce positive impacts. The results did not differ dramatically across subgroups, though en-couragingly, WorkAdvance was able to increase earnings among the long-term unemployed.The evaluation as a whole provides important information for workforce development providers interested in pursuing a sector strategy. The analysis considers the role played by providers' sector-specific training and preparation and the role played by the nature of the sectors themselves. Future priorities that emerge from the results are (1) understanding how to help the more disadvantaged access the programs and (2) learning how to build service capacity, given how complex the model is to run

Vulnerability assessment of Massaguaçú Beach (SE Brazil)

With the aim of summarizing several coastal indicators in one index, this paper proposes a vulnerability index to coastal erosion. This index synthesizes coastal and inland indicators quantitatively, becominga useful tool for coastal planning and better management of coastal resources. The index is composed of coastal variables: beach morphology, shoreline position, dune field configuration, wave exposure and presence of rivers and/or inlets; and inland variables: terrain elevation, vegetation, coastal engineeringstructures, occupation percentile and soil permeability. In order to validate the proposed method, it was\ud applied to Massaguaçú Beach (SP) in the Southeast of Brazil. According to its characteristics, the beach was divided into three sectors from south to north. Sectors 1 and 3 are classified as being of moderate vulnerability, both with index 5, while sector 2 is classified as high vulnerability, with index 7.5

Correlated theory of triplet photoinduced absorption in phenylene-vinylene chains

In this paper we present results of large-scale correlated calculations of triplet photoinduced absorption (PA) spectrum of oligomers of poly-(para)phenylenevinylene (PPV) containing up to five phenyl rings. In particular, the high-energy features in the triplet PA spectrum of oligo-PPVs are the focus of this study, which, so far, have not been investigated theoretically, or experimentally. The calculations were performed using the Pariser-Parr-Pople (PPP) model Hamiltonian, and many-body effects were taken into account by means of multi-reference singles-doubles configuration interaction procedure (MRSDCI), without neglecting any molecular orbitals. The computed triplet PA spectrum of oligo-PPVs exhibits rich structure consisting of alternating peaks of high and low intensities. The predicted higher energy features of the triplet spectrum can be tested in future experiments. Additionally, theoretical estimates of exciton binding energy are also presented.Comment: To appear in Phys. Rev.

Environment of Erbium in a-Si : H and a-SiOx : H

The chemical environment of Er in a-Si:H and a-SiOx:H was determined by extended x-ray absorption fine structure. Only one family of Er sites is found, coordinated on average with two to three O atoms (compared to six in Er2O3). We devised a new model for the incorporation of Er in a-Si:II and a-SiOx:H. According to the model, Er is incorporated in the form of [ErOdelta](+3-2 delta) complexes, with delta less than or equal to 3. The minimum configuration energy is achieved for delta = 3 when the valence requirements of Er are fulfilled. The complexes are low symmetry environments that allow the Er3+ luminescent transition at 1.54 mu m and make Er an acceptor in a-Si:H whereas it is donor in crystalline silicon. [S0031-9007(98)07668-6].81214652465

Tramadol hydro­chloride–benzoic acid (1/1)

In the cation of the title co-crystal salt {systematic name: [2-hydroxy-2-(3-meth­oxy­phen­yl)cyclo­hexyl­meth­yl]dimethyl­aza­nium chloride–benzoic acid (1/1)}, C16H31NO2 +·Cl−·C7H6O2, the N atom is protonated and the six-membered cyclo­hexane ring adopts a slightly distorted chair conformation. The dihedral angle between the mean planes of the benzene rings in the cation and the benzoic acid mol­ecule is 75.5 (9)°. The crystal packing is stabilized by weak inter­molecular O—H⋯Cl, N—H⋯Cl and C—H⋯π inter­actions, forming a two-dimensional chain network along the b axis. The benzoic acid mol­ecule is not involved in the usual head-to-tail dimer bonding, but instead is linked to the ammonium cation through mutual hydrogen-bonding inter­actions with the chloride anion

Prediction of infrared light emission from pi-conjugated polymers: a diagrammatic exciton basis valence bond theory

There is currently a great need for solid state lasers that emit in the infrared, as this is the operating wavelength regime for applications in telecommunications. Existing $\pi$--conjugated polymers all emit in the visible or ultraviolet, and whether or not $\pi$--conjugated polymers that emit in the infrared can be designed is an interesting challenge. On the one hand, the excited state ordering in trans-polyacetylene, the $\pi$--conjugated polymer with relatively small optical gap, is not conducive to light emission because of electron-electron interaction effects. On the other hand, excited state ordering opposite to that in trans-polyacetylene is usually obtained by chemical modification that increases the effective bond-alternation, which in turn increases the optical gap. We develop a theory of electron correlation effects in a model $\pi$-conjugated polymer that is obtained by replacing the hydrogen atoms of trans-polyacetylene with transverse conjugated groups, and show that the effective on-site correlation in this system is smaller than the bare correlation in the unsubstituted system. An optical gap in the infrared as well as excited state ordering conducive to light emission is thereby predicted upon similar structural modifications.Comment: 15 pages, 15 figures, 1 tabl