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排序方式: 共有161条查询结果,搜索用时 15 毫秒
1.
L. Palermo Jr.
M. Rachid
W. S. Venturini 《Engineering Analysis with Boundary Elements》1992,9(4):359-363In this article the direct boundary element formulations of stretching and bending plate problems are combined together to solve thin walled structures and other similar frames. The final system is obtained by assuming each individual plane structural element as a subregion. After the necessary transforms of these equations they can be combined together taking into account the displacement compatibility and equilibrium conditions. 相似文献
2.
KE Ensrud DM Black L Palermo DC Bauer E Barrett-Connor SA Quandt DE Thompson DB Karpf 《Canadian Metallurgical Quarterly》1997,157(22):2617-2624
BACKGROUND: The efficacy of antiresorptive therapy in preventing fractures in women at highest fracture risk, such as very elderly women or those with severe osteoporosis, is uncertain. PARTICIPANTS AND METHODS: Using data from a double-blind, randomized, placebo-controlled clinical trial that enrolled 2027 postmenopausal women aged 55 to 81 years with low femoral neck bone mineral density (BMD) and existing vertebral fractures, we examined the consistency of the effect of treatment with alendronate sodium in preventing fractures within a priori-specified risk subgroups defined at baseline by age, bone density, number of preexisting vertebral fractures, and history of postmenopausal fracture. The women were randomized to oral administration of alendronate or placebo and followed up for an average of 2.9 years. The initial dose of alendronate sodium was 5 mg/d; the dosage was increased from 5 to 10 mg/d at 24 months. New vertebral fractures, the primary end point of this arm of the trial, were defined by morphometry as a decrease of 20% and at least 4 mm in any vertebral height between baseline and a follow-up radiograph at 36 months. Incident clinical fractures, the secondary end point, included nonspine and clinical (symptomatic) vertebral fractures. All clinical fractures were confirmed with x-ray film reports or, in the case of clinical vertebral fractures, x-ray films. RESULTS: Overall, there was a 47% significant reduction in risk of new vertebral fractures in the alendronate group compared with the placebo group. The reduction in risk of new vertebral fracture was consistent across fracture risk categories including age (relative risk [RR], 0.49 in women < 75 years compared with 0.62 in those > or = 75 years), BMD (RR, 0.54 in women with a femoral neck BMD < 0.59 g/cm2 [median] compared with 0.53 in those with a BMD > or = 0.59 g/cm2), and number of preexisting vertebral fractures (RR, 0.58 in women with 1 vertebral fracture compared with 0.52 in those with > or = 2). The overall significant 28% reduction in risk of incident clinical fractures in the alendronate group compared with the placebo group was also observed within these subgroups. Compared with the number of lower-risk women, a similar or smaller number of high-risk women needed to be treated to prevent 1 fracture. For example, 8 women aged 75 years or older compared with 9 women younger than 75 years, or 4 women with 2 or more existing vertebral fractures compared with 16 women with 1 existing vertebral fracture, needed to be treated with alendronate for 5 years to prevent 1 new vertebral fracture. CONCLUSIONS: Alendronate effectively reduces fracture risk in postmenopausal women with vertebral fractures and low BMD, including those women at highest risk because of advanced age or severe osteoporosis. Since the risk reductions observed with alendronate treatment were consistent within fracture risk categories, more fractures were prevented by treating women at highest risk. 相似文献
3.
4.
Renato Colle Giuseppe Grosso Alberto Ronzani Massimo Gazzano Vincenzo Palermo 《Carbon》2012,50(3):1332-1337
We describe the self-assembly of soluble, chemically modified fullerene [6,6]-phenyl C61 butyric acid methyl ester (PCBM) into a new crystalline phase where the C60 moieties are arranged in parallel layers. Minimum C60 center-to-center distance is 10 Å within the layers, and up to 15 Å perpendicular to the layers. Highly anisotropic, mesoscopic hexagonal crystals of this material, with a lateral size of many microns and a thickness below 1 μm, are obtained from chloroform solution by solvent vapor annealing, and characterized by optical microscopy and X-ray diffraction. The crystalline structure is deduced combining experimental data with molecular modeling and ab initio calculations. The large difference in C60–C60 spacing indicates a high anisotropy in electrical and charge transport properties of this new phase. 相似文献
5.
M. Palermo L. M. Gil-Martín T. Trombetti E. Hernández-Montes 《Materials and Structures》2013,46(5):841-856
Low reinforced thin concrete panels have been used for the re-construction of living buildings in the devastated zone of L’Aquila. A structural characterization of these types of panels is presented in this paper, paying particular attention to the fact that these panels are subjected mainly to shear forces. Refined compression-field theory (RCFT) has recently been proposed in order to better predict the behaviour of reinforced concrete members subjected to in-plane shear and axial stresses. This theory is based on continuum mechanics, i.e. satisfying compatibility, equilibrium and formulating the constitutive equations in terms of average (i.e. “smeared”) stresses and strains. The improvement of RCFT in comparison with the two most famous theories for reinforced concrete member subjected to shear [i.e. the modified compression-field theory (MCFT), and the rotating-angle softened-truss model (RA-STM)], deals with an embedded bar model based on the tension stiffening model in concrete. After an ad-hoc calibration procedure, the RCFT is employed in order to reproduce the envelope of the experimental load-deflection response of three full-scale thin low reinforced concrete panels subjected to cyclic loading. The predictions provided by RCFT are compared with the experimental data as well as with those provided by MCFT and RA-STM. This paper presents the necessary parameters for the design of thin low reinforced concrete panels using the RCFT. The preliminary numerical validations seem very promising. However, additional experimental data are required for calibrating and validating the parameters of the proposed RCFT theory. 相似文献
6.
Mauro F. La Russa Silvestro A. Ruffolo Natalia Rovella Cristina M. Belfiore Anna M. Palermo Maria T. Guzzi Gino M. Crisci 《Progress in Organic Coatings》2012
Environmental pollution arising from industrial implants and urban factors is constantly increasing, causing aesthetical and durability concerns to urban structures exposed to the atmosphere. 相似文献
7.
Erika Carneiro Riqueza Alcino Palermo de Aguiar Luiz Claudio Santa Maria Mônica Regina Marques Palermo de Aguiar 《Polymer Bulletin》2002,48(4-5):407-414
Summary
The preparation of a chelating ion-exchange network based on acrylonitrile was carried out by chemical modification with hydroxylamine.
The beads of resin were synthesized by aqueous suspension copolymerization of acrylonitrile (AN), styrene (STY) and divinylbenzene
(DVB). The influence of diluent used in the suspension polymerization on the structure of the resulting copolymers was evaluated.
The diluents employed were heptane (HEP), toluene (TOL) and anisole (ANI). It was found that the AN incorporation into copolymer
structure was dependent on the diluent used. Conversion of nitrile groups into the amidoxime was conducted by treatment with
hydroxylamine under alkaline solution. The resins were characterized by apparent density, surface area, average pore diameter,
elemental analysis (CHN), FTIR and optical microscopy. Based on the results obtained, it was possible to control the porosity
by diluent employed in the synthesis and to modify chemically a resin containing nitrile groups by hydroxylamine reaction.
Received: 6 October 2001/Revised version: 2 April 2002/ Accepted: 11 April 2002 相似文献
8.
Evgenij Starikov Pavel Shiktorov Viktoras Gružinskis Alexandr Dubinov Vladimir Aleshkin Luca Varani Christophe Palermo Lino Reggiani 《Journal of Computational Electronics》2007,6(1-3):45-48
A possibility to develop the so called TASER (Terahertz-Amplification-by-the-Stimulated-Emission-of- Radiation) by using two-dimensional
(2D) electron transport in quantum well (QW) structures is investigated by Monte Carlo simulation of the optical-phonon-emission
assisted transit-time resonance (OPTTR) of 2D electrons in momentum space under the low lattice temperature. A considerable
extension of the frequency region for THz radiation generation (upto 5 times) when going from 3D- to 2D-case is predicted. 相似文献
9.
Marcos de Carvalho Barcellos Alcino Palermo de Aguiar Mônica Regina Marques Palermo de Aguiar Luiz Claudio de Santa Maria 《Polymer Bulletin》2005,55(1-2):61-70
Summary This article deals with the handy synthesis of sulfonyl resins, which were produced by the treatment of a commercial sulfonic resin (Lewatit VPOC1812® based at divinylbenzene (DVB) and styrene (STY). The preliminary chemical modification was based on the reaction of the Lewatit VPOC1812® with thionyl chloride aiming to produce the sulfonyl chloride groups. The best conditions to obtain the sulfonyl chloride groups were: SOCl2/SO3H (molar ratio) =13 at 79 °C during 72 h. The resin chlorinated was afterward treated with urea, thiourea or guanidine. The functionalized resins with urea, thiourea or guanidine were produced with 56, 68 and 93% yield, respectively. The commercial and modified resins were characterized by apparent density, swelling degree, elemental analysis (CHNS), FTIR, optical microscopy (OM) and scanning electron microscopy (SEM). 相似文献
10.
Previously, it was reported that the direct partial oxidation (DPO) of CH4 with O2 over HZSM-5 catalysts produces C5+ hydrocarbon liquids when the feed contains a propane or propene additive. This work studies additive effects on C5+ production in this system by processing a CH4/C3H8 feed with subsequent removal of the C3 additive and by processing natural gas feed. Results show C5+ production is maintained at constant yields for HZSM-5 catalysts having different zeolitic Al contents after removal of the C3 additive. Mechanistic implications are discussed. Natural gas DPO consistently produced C5+ liquids due to the presence of C2+ components in the feed. While C5+ yields from natural gas DPO are higher than those observed for CH4/C3 feeds, increasing feed O2 concentration, and thus conversion, deleteriously affected C5+ selectivity. 相似文献