715 research outputs found
Analysis and evaluation of mechanical performance of reinforced sandwich structures: X-CorTM and K-CorTM
No full textX-CorTM and K-CorTM are foam based lightweight structural cores reinforced with ZFiber
® rods oriented in a truss pattern. They can generate sandwich structures which
possess strength- and stiffness-to-weight ratios such to compete with aerospace grade
honeycomb constructions. The enhanced tailoring ability to specific design needs, the
flexibility in reinforcement type and arrangement, the variety between closed cell foamfilled
or hollow core configurations for ultimate weight savings or structural
multifunctionality, while utilising manufacturing procedures similar to traditional
honeycomb sandwich structures (low cost out-of-autoclave manufacturing techniques
included) make these novel materials an attractive alternative. The process of their
implementation into current engineering practice requires a parallel comparison with
existing competitor cores and a critical evaluation of their performance, identifying
advantages and disadvantages.
This study represents one of the first attempts to create a rigorous methodology for the
analysis and evaluation of their mechanical behaviour and manufacturing sensitivities.
The balance of out-of-plane properties (shear and compression), fundamental for a
sandwich core material, has been investigated. The material energy absorption capacity
for the aforementioned loading cases, as well as for in-plane crushing was evaluated.
For this purpose, a new quasi-static test for progressive crushing of flat sandwich
laminates was designed successfully. The experimental data gathered validate proposed
analytical models which allowed further deductions on core parameters influence to be
made. Those parameters were the pin insertion angle, pin lay-out, pin density and the
role of the foam. A local-global FE modelling approach for Z-pinned sandwich cores is
also provided and validated for X-CorTM structures. Structural differences between XCorTM
and K-CorTM are at the base of a diverse mechanical response; their performance
is sensitive to the manufacturing process, as it determines the quality of the pin-skin and
pin-adhesive film interfaces. An ‘improved’ manufacturing technique designed for XCorTM
resulted in a sandwich panel able to offer the same mechanical performance of a
Nomex® honeycomb structure for a 25% of weight saving
International Conference on Recent Developments in Operator Theory and Its Applications
No full textThe present volume contains the proceedings of the International Conference on Ap plications of Operator Theory held in Winnipeg, Canada (October 2nd to 6th, 1994), which was organized by the Institute of Industrial Mathematical Sciences (IIMS) of the University of Manitoba. At this conference 92 participants representing 15 countries par ticipated, and 64 papers were presented. This meeting was the second of a linked pair. The first was a program of advanced instruction held at the Fields Institute, Ontario, followed by a research conference. The first of these events gave rise to the volume "Lectures on Operator Theory and its Applications", published by the American Mathematical Society for the Fields Institute in 1995. These two events were the creation of the following Program Committee: M. A. Dahleh (M. I. T. ) P. A. Fillmore (Dalhousie) B. A. Francis (Toronto) F. Ghahramani (Manitoba) K. Glover (Cambridge) I. Gohberg (Tel Aviv) T. Kailath (Stanford) P. Lancaster (Calgary), Chair H. Langer (Vienna) P. N. Shivakumar (Manitoba) A. A. Shkalikov (Moscow) B. Simon (Cal. Tech. ) H. Widom (Santa Cruz) Both events focused on the following main topics: Infinite matrices and projection methods, linear operators on indefinite scalar product spaces, differential operators and mathematical systems theory and control. This volume contains a selection of papers in modern operator theory and its appli cations. They are dedicated to recent achievements and many are written by leaders in the mentioned fields
Centella asiatica extracts as green corrosion inhibitor for mild steel in 0.5 M sulphuric acid medium
No full textThe leaf extracts of centella asiatica(CE) was tested as green corrosioninhibitor for mild steel in 0.5 M H2SO4 by using gravimetric, polarization and electrochemical impedance spectroscopy (EIS) measurements. The data obtained from all the three methods are in good agreement with each other. Results indicate that leaf extracts of CE is a good green corrosion inhibitor for mild steel corrosion in 0.5 M H2SO4 solution. The inhibition efficiency was found to increase with increase in CE extracts concentration. A maximum inhibition efficiency of 95.08% was observed for 1200 ppm at 303K. Polarization measurements showed that the CE extracts acts as mixed type of inhibitor.Temperature studies revealed a decrease in inhibition efficiency with increase in temperature which suggests physisrption mechanism. The adsorption characteristics of CEextracts of on mild steel surface obeys Langmuir isotherm. Both kinetic and thermodynamics adsorption parameters were calculated and discussed,and SEM was used to analyse the surface adsorbed film
Synthesis, characterization and AC conductivity studies of silver doped conducting polyaniline/graphene/SrTiO3 composites
No full textPrevalence of malocclusion and orthodontic treatment needs among middle and high school children of Davangere city, India by using Dental Aesthetic Index
No full textBackground: Malocclusion has large impact on individual and society in term of discomfort, Quality of Life [QoL] Aims and Objectives: To assess prevalence of malocclusion and orthodontic treatment needs among middle and high school children of Davangere city, India by using Dental Aesthetic Index [DAI]. Materials and Methods: A Descriptive cross sectional study was conducted among 1000, in the age group 12 to 15 year old school children studying in middle and high schools of Davangere city, India. 10 schools were selected by simple random sampling procedure and 100 study subjects were selected proportionately for males and females by using systematic random sampling procedures in each school. Data recorded using proforma consisted DAI components. The collected data was subjected to statistical analysis. Statistical Analysis: The Chi-square test [x 2 ] was used for comparison of severity of malocclusion. Analysis of Variance [ANOVA] test was used for comparison of mean DAI scores between the age groups and in DAI scores. ′Z′ test was used for comparing the mean DAI scores between sex group. Results: Of the 1000 children examined, 518[ 51.8%] were males and 482[ 48.2%] were females. 80.1% school children had ≤ 25 DAI scores with no or minor malocclusion requiring no or little treatment, 15.7% had 26-30 DAI scores with definite malocclusion requiring elective treatment, 3.7% had 31-35 DAI scores with severe malocclusion requiring highly desirable treatment and 0.5% had ≥ 36 DAI scores with handicapping malocclusion requiring mandatory treatment. Conclusions: 80.1% school children had no or minor malocclusion which required no or slight treatment, 19.9% had definite/handicapping malocclusion requiring definite/mandatory orthodontic treatment
Cataloguing of articles in periodicals : database approach model in a biomedical library
No full textThe paper deals with providing a separate catalogue/database of articles in periodicals to users for more comprehensive search and retrieval, to solve the difficulties faced by the users during search in the Internet and downloading the selected records. A methodology is developed for cataloguing of articles available in periodicals and to cover the entire journals collection of both current journals and back volumes for any year in the Library. The downloaded materials from PUBMED collection are sent to WINISIS package, after different stages such as separate programme, FANGORN etc
Piecewise Linear Accrual Models: do they really control for the asymmetric recognition of gains and losses?
No full textThe asymmetric recognition of gains and losses underlying conservative accounting is not taken into account by Jones (1991)-type accrual models. Recently, Moreira (2002) and Ball and Shivakumar (2005a) have proposed piecewise linear accrual models designed to control for this asymmetric impact. Our paper first discusses the sign of the expected measurement error in discretionary accruals (DAC) estimates when models do not control for the asymmetry underlying conservatism. We find that DAC in firms with bad news (BN) are expected to be understated, while those in good news (GN) firms will be overstated. Based on this original result we empirically test, using graphical and statistical tools, whether piecewise linear accrual models correct such a measurement error. The empirical evidence shows mixed results. For GN firms the estimates are corrected downwards, as expected; for BN firms, unexpectedly, part of the estimates is also corrected downwards. The reason for this unexpected result seems to lie in a non-linear relationship between accruals and the proxy for BN that the models are unable to control for. Thus, DAC estimates under piecewise linear models are not deemed to be of better quality than those of traditional accrual models.accrual models; piecewise linear accrual models; conservatism; earnings management
Aqueous polymerization of methyl methacrylate initiated by manganese (III) pyrophosphate - potassium thiocyanate redox system: A kinetic study
No full textAqueous free radical polymerization of methyl methacrylate monomer M], initiated by manganese (III) pyrophosphate - potassium thiocyanate redox system, has been studied in the pH range 2-3 and in the temperature range 25-40 degrees C at constant ionic strength. The rates of polymerization (R-p) and manganese (III) disappearance have been measured. The effects of certain salts, water miscible organic solvents, and surfactants on the rate of polymerization have been investigated, The temperature dependence of the rate has been studied and the activation parameters computed using the Arrhenius plot. A polymerization mechanism, involving chain initiation by radicals derived from decomposition of manganese (III)-thiocyanate complex formed irt situ and bimolecular chain termination, is suggested. The rate of polymerization is found to be proportional to M](1,2), Mn(III)](1/2), H+](1/2), NCS-] , Mn(II)](-1/2), P2O74-](-1/2). The overall energy of activation in the range studied (25-40 degreesC) is found to be 32.2 kJ mol(-1)
A novel design of an isolated onboard charger for electric vehicles
No full textThe effectiveness of electric vehicles as a form of transportation has been studied in light of the expanding environmental concerns and ever-tighter emission regulations. Electric car battery charger topologies are crucial for boosting the use of electric automobiles (EVs). The study’s onboard plug-in battery charger for electric cars supports SEPIC, resonant inverter, or LLC topology and is suitable for nearby electric e-bikes with a 48V battery pack. In order to obtain the least amount of grid current ripple, an adaptive DC link voltage technique is also recommended for achieving the appropriate DC link voltage under all voltage conditions. The charger also employs a voltage synchronisation strategy to ensure a seamless mode transition between the grid-connected and freestanding modes. MATLAB/Simulink is used to simulate and validate the on-board charger
Paracrine effects of hypoxic fibroblast-derived factors on the MPT-ROS threshold and viability of adult rat cardiac myocytes
No full textCardiac fibroblasts contribute to multiple aspects of myocardial function and pathophysiology. The pathogenetic relevance of cytokine production by these cells under hypoxia, however, remains unexplored. With the use of an in vitro cell culture model, this study evaluated cytokine production by hypoxic cardiac fibroblasts and examined two distinct effects of hypoxic fibroblast-conditioned medium (HFCM) on cardiac myocytes and fibroblasts. Hypoxia caused a marked increase in the production of tumor necrosis factor (TNF)-alpha by cardiac fibroblasts. HFCM significantly enhanced the susceptibility of cardiac myocytes to reactive oxygen species (ROS)-induced mitochondrial permeability transition (MPT), determined by high-precision confocal line-scan imaging following controlled, photoexcitation-induced ROS production within individual mitochondria. Furthermore, exposure of cardiac myocytes to HFCM for 5 h led to loss of viability, as evidenced by change in morphology and annexin staining. HFCM also decreased DNA synthesis in cardiac fibroblasts. Normoxic fibroblast-conditioned medium spiked with TNF-alpha at 200 pg/ml, a concentration comparable to that in HFCM, promoted loss of myocyte viability and decreased DNA synthesis in cardiac fibroblasts. These effects of HFCM are similar to the reported effects of hypoxia per se on these cell types, showing that hypoxic fibroblast-derived factors may amplify the distinct effects of hypoxia on cardiac cells. Importantly, because both hypoxia and oxidant stress prevail in a setting of ischemia and reperfusion, the effects of soluble factors from hypoxic fibroblasts on the MPT-ROS threshold and viability of myocytes may represent a novel paracrine mechanism that could exacerbate ischemia-reperfusion injury to cardiomyocytes
- …
