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Orthogonal Directions (orthogonal + direction)

Distribution by Scientific Domains

Engineering	33%
Medical Sciences	25%

Selected Abstracts

Influence of Orthogonal Overload on Human Vertebral Trabecular Bone Mechanical Properties,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 11 2007
Arash Badiei
Abstract The aim of this study was to investigate the effects of overload in orthogonal directions on longitudinal and transverse mechanical integrity in human vertebral trabecular bone. Results suggest that the trabecular structure has properties that act to minimize the decrease of apparent toughness transverse to the primary loading direction. Introduction: The maintenance of mechanical integrity and function of trabecular structure after overload remains largely unexplored. Whereas a number of studies have focused on addressing the question by testing the principal anatomical loading direction, the mechanical anisotropy has been overlooked. The aim of this study was to investigate the effects of overload in orthogonal directions on longitudinal and transverse mechanical integrity in human vertebral trabecular bone. Materials and Methods: T12/L1 vertebral bodies from five cases and L4/L5 vertebral bodies from seven cases were retrieved at autopsy. A cube of trabecular bone was cut from the centrum of each vertebral body and imaged by ,CT. Cubes from each T12/L1 and L4/L5 pairs were assigned to either superoinferior (SI) or anteroposterior (AP) mechanical testing groups. All samples were mechanically tested to 10% apparent strain by uniaxial compression according to their SI or AP allocation. To elucidate the extent to which overload in orthogonal directions affects the mechanical integrity of the trabecular structure, samples were retested (after initial uniaxial compression) in their orthogonal direction. After mechanical testing in each direction, apparent ultimate failure stresses (UFS), apparent elastic moduli (E), and apparent toughness moduli (u) were computed. Results: Significant differences in mechanical properties were found between SI and AP directions in both first and second overload tests. Mechanical anisotropy far exceeded differences resulting from overloading the structure in the orthogonal direction. No significant differences were found in mean UFS and mean u for the first or second overload tests. A significant decrease of 35% was identified in mean E for cubes overloaded in the SI direction and then overloaded in the AP direction. Conclusions: Observed differences in the mechanics of trabecular structure after overload suggests that the trabecular structure has properties that act to minimize loss of apparent toughness, perhaps through energy dissipating sacrificial structures transverse to the primary loading direction. [source]

Empirical estimate of fundamental frequencies and damping for Italian buildings

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2009
Maria Rosaria Gallipoli
Abstract The aim of this work is to estimate the fundamental translational frequencies and relative damping of a large number of existing buildings, performing ambient vibration measurements. The first part of the work is devoted to the comparison of the results obtained with microtremor measurements with those obtained from earthquake recordings using four different techniques: horizontal-to-vertical spectral ratio, standard spectral ratio, non-parametric damping analysis (NonPaDAn) and half bandwidth method. We recorded local earthquakes on a five floors reinforced concrete building with a pair of accelerometers located on the ground and on top floor, and then collected microtremors at the same location of the accelerometers. The agreement between the results obtained with microtremors and earthquakes has encouraged extending ambient noise measurements to a large number of buildings. We analysed the data with the above-mentioned methods to obtain the two main translational frequencies in orthogonal directions and their relative damping for 80 buildings in the urban areas of Potenza and Senigallia (Italy). The frequencies determined with different techniques are in good agreement. We do not have the same satisfactory results for the estimates of damping: the NonPaDAn provides estimates that are less dispersed and grouped around values that appear to be more realistic. Finally, we have compared the measured frequencies with other experimental results and theoretical models. Our results confirm, as reported by previous authors, that the theoretical period,height relationships overestimate the experimental data. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Uplift-restraining Friction Pendulum seismic isolation system

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 5 2006
Panayiotis C. Roussis
Abstract This paper extends the scope of seismic isolation by introducing an innovative uplift-restraining Friction Pendulum system. Termed the XY-FP isolator, the new isolation device consists of two orthogonal opposing concave beams interconnected through a sliding mechanism that permits tension to develop in the bearing, thereby preventing uplift. Owing to its distinct configuration, the XY-FP isolator possesses unique properties for a seismic isolator, including uplift restraint, decoupling of the bi-directional motion along two orthogonal directions, and capability of providing independent stiffness and energy dissipation along the principal horizontal directions of the bearing. The study concentrates on introducing the concept and establishing the underlying principles of operation of the new XY-FP isolator, formulating the mathematical model for the XY-FP isolator, and presenting its mechanical behaviour through a displacement-control testing program on a single XY-FP isolator. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Tuned mass dampers for response control of torsional buildings

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2002
Mahendra P. Singh
Abstract This paper presents an approach for optimum design of tuned mass dampers for response control of torsional building systems subjected to bi-directional seismic inputs. Four dampers with fourteen distinct design parameters, installed in pairs along two orthogonal directions, are optimally designed. A genetic algorithm is used to search for the optimum parameter values for the four dampers. This approach is quite versatile as it can be used with different design criteria and definitions of seismic inputs. It usually provides a globally optimum solution. Several optimal design criteria, expressed in terms of performance functions that depend on the structural response, are used. Several sets of numerical results for a torsional system excited by random and response spectrum models of seismic inputs are presented to show the effectiveness of the optimum designs in reducing the system response. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Multiscalet basis in Galerkin's method for solving three-dimensional electromagnetic integral equations

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 4 2008
M. S. Tong
Abstract Multiscalets in the multiwavelet family are used as the basis and testing functions in Galerkin's method. Since the multiscalets are orthogonal to their translations under the Sobolev inner product, the resulting Galerkin's method behaves like a collocation method but possesses the ability of derivative tracking for unknown functions in solving integral equations. The former makes the method simple in implementation and the latter allows to use coarse meshes in discretization. These robust features have been demonstrated in solving two-dimensional (2D) electromagnetic (EM) problems, but have not been exploited in three-dimensional (3D) scenarios. For 3D problems, the unknown functions in the integral equations are dependent on two coordinate variables. In order to preserve the use of coarse meshes for 3D cases, we realize the omnidirectional derivative tracking by tracking the directional derivatives along two orthogonal directions, or equivalently tracking the gradient. This process yields a nonsquare matrix equation and we use the least-squares method (LSM) to solve it. Numerical examples show that the multiscalet-based Galerkin's method is also robust in solving for 3D EM integral equations with a minor cost increase from LSM. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Influence of Orthogonal Overload on Human Vertebral Trabecular Bone Mechanical Properties,

Particle surface temperature measurements with multicolor band pyrometry

AICHE JOURNAL, Issue 1 2009
Hong Lu
Abstract A noncontact, color-band pyrometer, based on widely available, inexpensive digital imaging devices, such as commercial color cameras, and capable of pixel-by-pixel resolution of particle-surface temperature and emissivity is demonstrated and described. This diagnostic instrument is ideally suited to many combustion environments. The devices used in this method include color charge-coupled device (CCD), or complementary metal oxide semiconductor (CMOS) digital camera, or any other color-rendering camera. The color camera provides spectrally resolved light intensity data of the image, most commonly for three color bands (Red, Green, and Blue,), but in some cases for four or more bands or for a different set of colors. The CCD or CMOS sensor-mask combination has a specific spectral response curve for each of these color bands that spans the visible and often near infrared spectral range. A theory is developed, based on radiative heat transfer and camera responsivity that allows quantitative surface temperature distribution calculation, based on a photograph of an object in emitted light. Particle surface temperature calculation is corrected by heat transfer analysis with reflection between the particle and reactor wall for particles located in furnace environments, but such corrections lead to useful results only when the particle temperature is near or below the wall temperatures. Wood particle-surface temperatures were measured with this color-band pyrometry during pyrolysis and combustion processes, which agree well with thermocouple measured data. Particle-surface temperature data simultaneously measured from three orthogonal directions were also mapped onto the surface of a computer generated 3-D (three-dimensional) particle model. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source]

Strain rate sensitivity of Cu after severe plastic deformation by multiple compression

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2005
Y. J. Li
Abstract Coarse-grained Cu99.99 was prestrained by ,pre in multiple compression in three orthogonal directions at room temperature. While the flow stress , saturates at ,pre , 2, the strain rate sensitivity of , at 318 K increases by a factor of , 2.7 from ,pre = 2 to 7. This increase is attributed to decrease of grain size and corresponding increase in fraction of high-angle grain boundaries. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Microstructure and magnetic properties of backward extruded NdFeB ring magnets by the CAPA process

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2004
Hyoung-Tae Kim
Abstract The inhomogeneity in microstructure and magnetic properties of a ring magnet prepared by backward extrusion with a current-applied pressure-assisted process has been investigated. The initial part (top part) of a ring magnet prepared by back extrusion shows a high coercivity which is comparable to the raw powder. It exhibits isotropic characteristics along the three orthogonal directions probably due to small deformation. The last part (bottom part) of the ring magnet has a a low coercivity with large grains because high current flows through the pressurized punches during the whole deformation process as to increase the temperature and grain growth. The middle part is under an appropriate deformation with short time exposure at high temperature, therefore it maintains a relatively high remanent polarization with high coercivity. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Identification and removal of above-ground spurious signals in GPR archaeological prospecting,

ARCHAEOLOGICAL PROSPECTION, Issue 2 2005
Luigia Nuzzo
Abstract Ground-penetrating radar (GPR) is a shallow geophysical method increasingly used in archaeological prospecting to detect buried remains and to map the stratigraphy of the uppermost earth layers embodying the archaeological features. The GPR sections, however, can be contaminated by spurious correlated signals caused by above-ground obstacles (buildings, trees, fences, power lines) placed either in-line or off-line with respect to the profile (surface scattering). In the case study presented this problem is analysed for a 35,MHz GPR survey carried out for stratigraphical purposes in the archaeological site of the Roman Ships near Pisa (Italy). The investigation inside the archaeological excavation, when the level was about 5,m below the ground surface, produced a severe surface scattering problem caused by the iron sheet-piling protecting the excavation walls and bordering some of the partly excavated boats. An attempt to interpret the profiles was carried out in a zone where the relatively simple geometry of the metallic enclosure allowed understanding of the possible origin of spurious events, also thanks to the high density of profiles acquired along two orthogonal directions. Migration at the air velocity and geometrical considerations helped the identification of hyperbolic and slightly slanted features as surface scattering phenomena from different sides of the iron sheet-piling. A simple but original subtraction procedure was successful for the attenuation of some of the spurious reflections. After this partial removal, other spurious signals could be recognized more easily as well as two weak subhorizontal reflections of probable stratigraphical meaning. Subsequently, filtering procedures based on f-k and Radon transform methods were tried to further reduce the spurious signals, thus enhancing the visibility of the interesting reflections. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Fractionation of cell mixtures using acoustic and laminar flow fields

BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2005
Manoj Kumar
Abstract A fractionation method applicable to different populations of cells in a suspension is reported. The separation was accomplished by subjecting the suspension to a resonant ultrasonic field and a laminar flow field propagating in orthogonal directions within a thin, rectangular chamber. Steady, laminar flow transports the cell suspension along the chamber, while the ultrasonic field causes the suspended cells to migrate to the mid-plane of the chamber at rates related to their size and physical properties. A thin flow splitter positioned near the outlet divides the effluent cell suspension into two product streams, thereby allowing cells that respond faster to the acoustic field to be separated from those cells that respond more slowly. Modeling of the trajectories of individual cells through the chamber shows that by altering the strength of the flow relative to that of the acoustic field, the desired fractionation can be controlled. Proof-of-concept experiments were performed using hybridoma cells and Lactobacillus rhamnosus cells. The two populations of cells could be effectively separated using this technique, resulting in hybridoma/Lactobacillus ratios in the left and right product streams, normalized to the feed ratio, of 6.9 ± 1.8 and 0.39 ± 0.01 (vol/vol), respectively. The acoustic method is fast, efficient, and could be operated continuously with a high degree of selectivity and yield and with low power consumption. © 2004 Wiley Periodicals, Inc. [source]

Anisotropic elastic properties of cancellous bone from a human edentulous mandible

CLINICAL ORAL IMPLANTS RESEARCH, Issue 5 2000
Aisling M. O'Mahony
The elastic moduli have not been reported for cancellous bone from the edentulous mandible. Accurate values are needed for finite element modeling of the mandible. The aim of this study was to determine elastic modulus values in three orthogonal directions for cancellous bone taken from an edentulous jaw and to relate these values to apparent density and volume fraction. Seven samples were obtained from the edentulous mandible of a 74-year-old female. Young's modulus was determined by compression testing of cubes cut with the faces aligned with the anatomic axes. Bone volume fraction averaged 0.33 (SD 0.14) and apparent density averaged 0.55 g/cc (SD 0.29). Young's modulus was greatest in the mesio-distal direction (mean 907 MPa, SD 849 MPa), followed by the bucco-lingual (mean 511 MPa, SD 565 MPa) and infero-superior direction (mean 114 MPa, SD 78 MPa). The infero-superior direction was less than the bucco-lingual (P=0.03) and mesio-distal (P=0.002). The mesio-distal and bucco-lingual directions could not be shown to be different (P=0.32). This suggests a model of transverse isotropy for cancellous bone in the jaw, where the symmetry axis is along the infero-superior (weakest) direction. [source]