Search results for "Elastic Modulu"
showing 10 items of 189 documents
Compressive behavior of short high-strength concrete columns
2010
Abstract The focus of the present paper is the compressive response of short high strength reinforced concrete members. Members have square transverse cross-sections and they are reinforced with longitudinal steel bars and transverse stirrups. A preliminary analysis to check the stability condition of longitudinal bars was made to verify that buckling occurs after yielding in compression. Prescriptions on required diameter and spacing of stirrups are given. In the following, a model is presented which allows us to evaluate the confinement pressures exercised by transverse steel and by longitudinal bars during the loading process taking into account the interaction of the stirrups with the i…
Influence of steel reinforcements on the behavior of compressed high strength R.C. circular columns
2012
Abstract In the present paper the focus is on the compressive response of short high strength reinforced concrete members having circular transverse cross-sections and reinforced with longitudinal steel bars and transverse spirals or hoops. An analytical model is proposed which allows one to estimate the confinement pressures exerted by transverse steel and by longitudinal bars during the loading process, taking into account the interaction of the hoops or spirals with the inner core both in the plane of the transverse steel and in the space between two successive hoops. Yielding of steel spirals or hoops and longitudinal bars including buckling phenomena and damage to the concrete core are…
Mechanical Characterization of Polymers on a Nanometer Scale through Nanoindentation. A Study on Pile-up and Viscoelasticity
2007
The analysis of nanoindentation force curves collected on polymers through the common Oliver and Pharr procedure does not lead to a correct evaluation of Young’s modulus. In particular, the estimated elastic modulus is several times larger than the correct one, thus compromising the possibility of a nanomechanical characterization of polymers. Pile-up or viscoelasticity is usually blamed for this failure, and a deep analysis of their influences is attempted in this work. Piling-up can be minimized by indenting on a true nanometer scale, i.e., at penetration depth smaller than 200 nm. On the other side, it is common knowledge that fast indentations minimize the effect of viscoelasticity. How…
Locking Reconstruction Double Plating of Distal Humeral Fractures: How Many Screws in the Distal Ulnar Column Segment in A3 Fracture Provide Superior…
2009
Objectives: Two 90-degree configurations of locking reconstruction plates with different numbers of screws in the distal ulnar column segment of distal extra-articular humeral fractures with metaphyseal comminution (A3) were biomechanically investigated. Methods: Eight pairs of fresh-frozen human humeri were used. For paired comparison, the humeri were divided into 2 randomized groups. In both groups, double-plate osteosyntheses with locking reconstruction plates were performed in 90-degree configurations. In group 1, the posteriorly placed radial column plate exceeded the capitellum and the ulnar column plate extended into the ulnar sulcus. The ulnar plate was molded around the medial epic…
Evaluation of viscoelastic constants of metallic materials by laser-ultrasonics at elevating temperature
2002
The main objective of this study is the determination of elastic moduli and viscosity coefficients of metals at elevating temperature up to melting point. More specifically, it involves the analysis of the propagation of acoustic waves generated and detected simultaneously by laser-ultrasonic for the measurement of longitudinal and shear velocities. This preliminary work primarily concerns Tin (Sn) metal known for its low melting point and attenuation coefficient.
A New Sampling Method for Spleen Stiffness Measurement Based on Quantitative Acoustic Radiation Force Impulse Elastography for Noninvasive Assessment…
2014
In our study, we evaluated the feasibility of a new sampling method for splenic stiffness (SS) measurement by Quantitative Acoustic Radiation Force Impulse Elastography (Virtual Touch Tissue Quantification (VTTQ)).We measured SS in 54 patients with HCV-related cirrhosis of whom 28 with esophageal varices (EV), 27 with Chronic Hepatitis C (CHC) F1–F3, and 63 healthy controls. VTTQ-SS was significantly higher among cirrhotic patients with EV (3.37 m/s) in comparison with controls (2.19 m/s,P<0.001), CHC patients (2.37 m/s,P<0.001), and cirrhotic patients without EV (2.7 m/s,P<0.001). Moreover, VTTQ-SS was significantly higher among cirrhotic patients without EV in comparison with bot…
A preliminary study of hardness and modulus of elasticity in sheep mandibles submitted to distraction osteogenesis and low-level laser therapy
2011
Objectives: To investigate the quality of newly formed bone in sheep mandibles submitted to distraction osteogenesis and low-level laser therapy (LLLT), based on hardness and modulus of elasticity values. The ideal moment for laser application (during the latency/activation period vs. during the bone consolidation period) was also evaluated. Computed tomography imaging was used to assess relapse as a result of early device removal. Study design: Extraoral distraction devices were placed in five sheep so as to achieve 1.5 cm of lengthened bone in 60 days. Distraction devices were removed 50, 40, and 33 days after surgery. Four animals were treated with LLLT, at different times, and one was u…
In Vivo Strain Analysis of Dilated Ascending Thoracic Aorta by ECG-Gated CT Angiographic Imaging
2017
Accurate assessment of aortic extensibility is a requisite first step for elucidating the pathophysiology of an ascending thoracic aortic aneurysm (ATAA). This study aimed to develop a framework for the in vivo evaluation of the full-field distribution of the aortic wall strain by imaging analysis of electrocardiographic- (ECG) gated thoracic data of 34 patients with ATAA. Seven healthy controls (i.e., non-aneurysmal aorta) from patients who underwent ECG-gated CT angiography for coronary artery diseases were included for comparison. To evaluate the systolic function, ECG-gated computed tomography (CT) angiography was used to generate patient-specific geometric meshes of the ascending aorta…
Collagen-low molecular weight hyaluronic acid semi-interpenetrating network loaded with gelatin microspheres for cell and growth factor delivery for …
2015
Intervertebral disc (IVD) degeneration is one of the main causes of low back pain. Current surgical treatments are complex and generally do not fully restore spine mobility. Development of injectable extracellular matrix-based hydrogels offers an opportunity for minimally invasive treatment of IVD degeneration. Here we analyze a specific formulation of collagen-low molecular weight hyaluronic acid (LMW HA) semi-interpenetrating network (semi-IPN) loaded with gelatin microspheres as a potential material for tissue engineering of the inner part of the IVD, the nucleus pulposus (NP). The material displayed a gel-like behavior, it was easily injectable as demonstrated by suitable tests and did …
Compliance and Pulse Wave Velocity Assessed by MRI Detect Early Aortic Impairment in Young Patients With Mutation of the Smooth Muscle Myosin Heavy C…
2008
Purpose To evaluate aortic elasticity with MRI on young asymptomatic individuals with mutation of the smooth muscle myosin heavy chain in whom aortic enlargement is not present. Materials and Methods Aortic compliance, aortic distensibility, and pulse wave velocity (PWV) were semiautomatically measured from MRI in 8 asymptomatic subjects having a mutation of the MYH11 gene (M+) and 21 nonmutated relatives (M−) of similar age, sex, and blood pressure characteristics. Results Despite a similar aortic diameter in both groups, the aortic compliance and distensibility were significantly lower in M+ subjects compared with M− (0.84 ± 0.33 versus 2.03 ± 0.54 mm2/mmHg, 1.18 ± 0.62 10−3 versus 5.11 ±…