Offset Configuration Research Articles

Finite element analysis of the influence of the offset placement of an implant‐supported prosthesis on bone stress distribution

The aim of this study was to evaluate the influence of the straight alignment versus distal offset placement of an implant-supported prosthesis (using implants with different diameters: 4 mm, 4.5 mm, and 5 mm) on bone stress distribution. 3D finite element models of a straight configuration and different offset configurations of the implant-supported prosthesis (until 2.4 mm distal offset) were evaluated for the three implant diameters. A mesial load of 200 N and a distal load of 230 N were applied to the prosthesis. Results showed that implant offset provokes an opposite effect in bone stress depending on the exposed mesial or distal force. The former increases stress whereas the latter induces a dissipation of bone stress proportional to the offset. From these two forces, an optimal offset is created in which maximum bone stress is reduced in the range of 7-8% compared with the straight configuration. Increasing implant diameter from 4 to 5 mm decreased bone stress in 30% for all configurations. These data suggests that offset implant placement apart from enabling an optimal aesthetic restoration, reduces bone stress compared with the straight configuration. The use of wider implants permitted the reduction of the maximum bone stress in all the simulated configurations.

Role of the Asymmetry of the Homodimeric b2 Stator Stalk in the Interaction with the F1 Sector of Escherichia coli ATP Synthase

The b subunit dimer in the peripheral stator stalk of Escherichia coli ATP synthase is essential for enzyme assembly and the rotational catalytic mechanism. Recent protein chemical evidence revealed the dimerization domain of b to contain a novel two-stranded right-handed coiled coil with offset helices. Here, the existence of this structure in more complete constructs of b containing the C-terminal domain, and therefore capable of binding to the peripheral F1-ATPase, was supported by the more efficient formation of intersubunit disulfide bonds between cysteine residues that are proximal only in the offset arrangement and by the greater thermal stabilities of cross-linked heterodimers trapped in the offset configuration as opposed to homodimers with the helices trapped in-register. F1-ATPase binding analyses revealed the offset heterodimers to bind F1 more tightly than in-register homodimers. Mutations near the C terminus of b were incorporated specifically into either the N-terminally or the C-terminally shifted polypeptide, bN or bC, respectively, to determine the contribution of each position to F1 binding. Deletion of the last four residues of bN substantially weakened F1 binding, whereas the effect of the deletion in bC was modest. Similarly, benzophenone maleimide introduced at the C terminus of bN, but not bC, mediated cross-linking to the delta subunit of F1. These results imply that the polypeptide in the bN position is more important for F1 binding than the one in the bC position and illustrate the significance of the asymmetry of the b dimer in the enzyme.

Airborne Volcanic Ash Forecast Area Reliability

Abstract In support of aircraft flight safety operations, daily comparisons between modeled, hypothetical, volcanic ash plumes calculated with meteorological forecasts and analyses were made over a 1.5-yr period. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model simulated the ash transport and dispersion. Ash forecasts and analyses from seven volcanoes were studied. The volcanoes were chosen because of recent eruptions or because their airborne ash could impinge on well-traveled commercial aircraft flight paths. For each forecast–analysis pair, a statistic representing the degree of overlap, the threat score (TS), was calculated. A forecast was classified as acceptable if the TS was greater than 0.25. Each forecast was also categorized by two parameters: the forecast area quadrant with respect to the volcano and a factor related to the complexity of the meteorology. The forecast complexity factor was based on the degree of spread using NCEP ensemble output or using a HYSPLIT offset configuration. In general, the larger the spread of the ensemble or offset forecasts, the greater the complexity. The forecasts were sorted by complexity factor, and then classified by the quartile of the complexity. The volcanic ash forecast area reliability (VAFAR) was calculated for each forecast area quadrant and for each quartile of the complexity factor. VAFAR is the ratio of the number of acceptable forecasts to the total number of forecasts. Most VAFAR values were above 70%. VAFAR values for two of the seven volcanoes (Popocatepetl in Mexico and Tungurahua in Ecuador) tended to be lower than the others. In general, VAFAR decreased with increasing complexity of the meteorology. It should be noted that the VAFAR values reflect the reliability of the meteorological forecasts when compared to the same calculation using analysis data; the dispersion model itself was not evaluated.

Modal analysis of multi-layer structure for chemical mechanical polishing process

In this study, a three-dimensional finite element model was established to perform modal analysis of the chemical mechanical polishing process. The contact boundary conditions were considered in the wafer and pad, and the influence of the static load exerted on the carrier was considered in order to investigate dynamic behaviour of the wafer. The analysis was in two steps. Firstly, a given pressure was exerted on the carrier and the geometric nonlinear effect and large deformation theory were used to carry out static analysis. Secondly, the results of the analysis were used to perform modal analysis of the wafer. The results gave way to four conclusions. (1) Due to the offset configuration of the wafer and pad, the von Mises stress distribution was asymmetric. Therefore, the stress on the wafer appeared to be almost uniform near its centre, goes through a maximum near the edge, and decreased as the edge is approached. This tendency is similar to that of the removal rate profile experiment, which proved that the proposed finite element model for CMP is acceptable. (2) Due to the extremely thin thickness of the film, wafer and pad, most mode shapes are predominant in out-plane deformation. Furthermore, since the y-axis is symmetric in the three-dimensional model, there were double roots in some modes. (3) When the load was larger, the tangent stiffness and the natural frequency would also be reduced. The pressure changes did not have much affect on mode shape. (4) Since the soft materials of the pad and film have significantly different Young’s modulus’ than hard materials, the natural frequencies of harder materials for the pad and film increase.

Suction energy and offset configuration for double-walled carbon nanotubes

Nanostructures such as carbon nanotubes and fullerenes offer the means to create new mechanical devices operating at the nanoscale. Such devices include oscillators constructed from an inner carbon nanotube sliding inside another carbon nanotube. The resultant oscillatory frequency is found to be in the gigahertz range and they have applications in the computing industry for signalling devices, such as an ultra-fast optical filter. While most research in the area is dominated by molecular dynamics simulations, our approach here is to use elementary mechanical principles and classical applied mathematical modelling techniques to formulate explicit analytical criteria and ideal model behaviour. In this paper, we first investigate the suction force experienced by a single-walled carbon nanotube located near an open end of a semi-infinite single-walled carbon nanotube, using the Lennard–Jones potential and the continuum approximation. Second the equilibrium position of an offset inner tube with reference to the cross-section of the outer tube is determined.

A simulation study for the design of a prototype insert for whole-body PET scanners

We are developing an insert device that will improve image resolution within a smaller field-of-view for clinical whole-body PET scanners. We modified SimSET (Simulation System for Emission Tomography) to simulate the insert and a PET scanner. The system consists of two detector rings. The inner ring represents an insert (r=153 mm) with high-resolution detectors using 10 mm thick LSO. The outer ring represents a PET scanner (R=413 mm) with 25 mm thick LSO. Events were binned into three sets of sinograms assuming a 2.4 and 6.75 mm crystal-pitch for the insert and the PET scanner, respectively. The detectors in the insert are modeled as 1, 2, or 4 layers with different offset configurations to evaluate the corresponding system resolution with the depth-of-interaction (DOI) effect. Results show that image resolution at 1 cm radial offset is improved from 5.6 mm full-width-at-half-maximum (FWHM) of the original PET scanner to 2.0 mm with the insert. At 12 cm offset, the resolution of the original system is 5.9 and 5.5 mm for radial and tangential directions, respectively. With the insert, the radial resolution is 5.0 mm FWHM for a single-layer detector design, but improves to 2.7 and 2.2 mm for 2and 4-layer DOI detectors, respectively. Different offsets for multi-layer detectors have negligible effect on resolution. Sensitivity of the device is, assuming the insert has a 2 cm axial extend, estimated to be 3.3%, including coincidence events from the insert-alone and insert-to-scanner sinograms. In contrast, if the insert is used as a stand-alone microPET scanner, its sensitivity is 1.3%.

A Numerical Analysis of the Thermal Performance of Single Sided and Back-to-Back Tape Ball Grid Array Packages

This paper presents the results of a comprehensive numerical study of the thermal performance of Tape Ball Grid Array package mounted on one side of a printed circuit board as well as packages mounted in back-to-back and offset configurations. A cover plate is attached to the back side of the chips to enhance heat transfer from the module. The assembled organic carrier is placed in a vertical channel. A conjugate heat transfer model is used which accounts for conduction in the packages and the card and convection in the surrounding air. The effect of location of the modules on a card with zero, one and two power planes is evaluated for thermal performance. Heat dissipation is studied for forced convection (2, 1, and 0.5m∕s). Comparison is made for single sided and back-to-back cases.

Characterization of surface roughness effects on pressure drop in single-phase flow in minichannels

Roughness features on the walls of a channel wall affect the pressure drop of a fluid flowing through that channel. This roughness effect can be described by (i) flow area constriction and (ii) increase in the wall shear stress. Replotting the Moody’s friction factor chart with the constricted flow diameter results in a simplified plot and yields a single asymptotic value of friction factor for relative roughness values of ε∕D>0.03 in the fully developed turbulent region. After reviewing the literature, three new roughness parameters are proposed (maximum profile peak height Rp, mean spacing of profile irregularities RSm, and floor distance to mean line Fp). Three additional parameters are presented to consider the localized hydraulic diameter variation (maximum, minimum, and average) in future work. The roughness ε is then defined as Rp+Fp. This definition yields the same value of roughness as obtained from the sand-grain roughness [H. Darcy, Recherches Experimentales Relatives au Mouvement de L’Eau dans les Tuyaux (Mallet-Bachelier, Paris, France, 1857); J. T. Fanning, A Practical Treatise on Hydraulic and Water Supply Engineering (Van Nostrand, New York, 1877, revised ed. 1886); J. Nikuradse, “Laws of flow in rough pipes” [“Stromungsgesetze in Rauen Rohren,” VDI-Forschungsheft 361 (1933)]; Beilage zu “Forschung auf dem Gebiete des Ingenieurwesens,” Ausgabe B Band 4, English translation NACA Tech. Mem. 1292 (1937)]. Specific experiments are conducted using parallel sawtooth ridge elements, placed normal to the flow direction, in aligned and offset configurations in a 10.03mm wide rectangular channel with variable gap (resulting hydraulic diameters of 325μm–1819μm with Reynolds numbers ranging from 200 to 7200 for air and 200 to 5700 for water). The use of constricted flow diameter extends the applicability of the laminar friction factor equations to relative roughness values (sawtooth height) up to 14%. In the turbulent region, the aligned and offset roughness arrangements yield different results indicating a need to further characterize the surface features. The laminar to turbulent transition is also seen to occur at lower Reynolds numbers with an increase in the relative roughness.

Largemouth bass catch rates and injury associated with non-offset and offset circle hook configurations

Although circle hooks are being viewed as a means to reduce injury and mortality of recreationally caught-and-released fish, subtle differences in hook configuration (such as the degree that the hook point is offset from the shank) could affect performance. We compared hooking and landing efficiency, anatomical hooking depth and location, ease of hook removal, and amount of bleeding between largemouth bass angled on either non-offset (0°) or slightly offset (2°) circle hooks. Non-offset circle hooks were more efficient at hooking and landing largemouth bass than the offset design. Fish were hooked more deeply with non-offset hooks; non-offset hooks penetrated the corner of the mouth whereas the offset hooks penetrated the terminal upper and lower lip. Overall, there were no differences in the frequency that fish were hooked in potentially lethal locations (e.g. gullet, eye). The design and hooking location of non-offset hooks led to greater difficulty in hook removal and slightly higher rates of bleeding. Offset circle hooks have been identified as more injurious in previous studies but we found little difference in injury that may lead to serious infection or mortality between hook types. Given that non-offset circle hooks have a higher capture efficiency for largemouth bass, anglers will likely adopt their use.

Design of Miniaturized Common-Mode Filter by Multilayer Low-Temperature Co-Fired Ceramic

A miniaturized common-mode filter composed of multiple substrates with positive and negative coils formed on alternate substrates is proposed in this paper. The pattern of each positive coil is interlaced with that of each negative coil, whereby when the positive and negative coils are alternately stacked, the positive coils do not overlap the negative coils. With such offset configuration, the parasitic capacitance introduced between positive and negative traces is reduced, so the thickness of each substrate can be decreased and the size of the entire filter is effectively reduced. Good agreements between simulated and measured results are demonstrated. Further, the effectiveness of this filter is confirmed by eye diagram and radiation emission measurements.

Biomechanical comparison of straight and staggered implant placement configurations

The effect of buccolingual staggered implant placement on stress distribution within the supporting structure was examined photoelastically. Two photoelastic models of a human mandible, edentulous distal to the canine, were fabricated. Three screw-type implants were embedded into the edentulous region of each model. The implants were placed in a straight line in one model and in a buccolingual staggered configuration in the other. Vertical and lateral loads were applied to a fixed partial denture superstructure. No clear biomechanical advantage to a staggered 1.5 mm buccal and lingual offset placement configuration was observed.— Reprinted with permission of Quintessence Publishing.

스테레오 PIV 기법에 의한 임펠러 와류유동의 3차원 구조측정

The three-dimensional spatial structures of impeller flow created by a six bladed Rushton turbine have identified based on the volumetric velocity information from multi-plane stereoscopic PIV measurements. A total of 10 planes with 2 mm space and a 50 mm by 64 mm size of the field of view were targeted. To reduce the depth of focus, we adopted an angle offset configuration which satisfied the Scheimpflug condition. The distortion compensation procedure was utilized during the in situ calibration. Phase-locked instantaneous data were ensemble averaged and interpolated in order to obtain mean 3-D. volumetric velocity fields on a 60 degree sector of a cylindrical ring volume enclosing the turbine blade. Using the equi-vorticity surface rendering, the spatial structure of the trailing vortices was clearly demonstrated. Detail flow characteristics of the radial jet reported in previous studies of mixer flows were easily identified.

Three-dimensional spiraling finite element model of the electrically stimulated cochlea.

The objective of the article is to provide an accurate model of the human cochlea with which potential distributions and thus neural excitation patterns around cochlear implant electrodes can be determined. Improvements on previous models of the implanted cochlea are that this model 1) includes the spiral nature of the cochlea as well as many other anatomical details (and it is a model of the human cochlear rather than the guinea pig cochlea), and 2) facilitates modeling of different electrode geometries, array locations and electrode separations without changing the structure of the model. A three-dimensional spiraling finite element model of the human cochlea was created. The model incorporates the effect of neighboring canals and conduction along the fluid-filled canals of the cochlea. Potential distributions are used as inputs to a nerve fiber model to investigate auditory nerve excitation patterns around intracochlear electrode arrays. Potential distributions around intracochlear electrodes generated with the finite element model are presented. The effects of electrode separation, electrode geometry and array location on excitation threshold, excitation spread and ectopic excitation (i.e., excitation of nerve fibers at an undesirable location) are demonstrated. The following conclusions should be considered preliminary, as their accuracy depends on the exactness of the underlying model. The spiraling geometry of the cochlea causes asymmetry in potential distributions. The location of electrodes along the length of the basilar membrane has a stronger influence on the site of excitation than the polarity of the leading phase of the stimulus. Array location is the primary parameter that controls excitation spread. Threshold currents and the effect of ongoing loss of peripheral dendrites on threshold currents can be limited by placing arrays close to the modiolus. Point electrode geometries are recommended above banded electrode geometries only when the array can be placed close to the modiolus. There is a tradeoff between array location and the degree of ectopic stimulation caused by a specific array location. Bimodal excitation patterns exist at comfortable stimulus intensities for longitudinal bipolar electrode configurations. It is shown that an electrode configuration with an electrode separation of approximately half that of the bipolar electrode separation of the Nucleus electrode can be used instead of radial and offset radial electrode configurations to create unimodal excitation patterns. The stimulation resolution of cochlear implant electrode arrays can potentially be improved by increasing the number of electrode contacts in an array.

Modeling the f and j Characteristics for Transverse Flow Through an Offset Strip Fin at Low Reynolds Number

Analytic models for predicting the thermal-hydraulic characteristics for transverse flow through an offset strip fin array are developed. These models are developed by combining the creeping or low flow asymptotic behaviour with laminar and turbulent boundary layer wake models. Expressions for each of these characteristic regions are developed using fundamental solutions of fluid dynamics and heat transfer. The proposed models are compared with new experimental data for ten offset strip fin configurations. Model predictions are within ± 20 percent for 92 percent of friction factor data and 71 percent for Colburn j factor data.

Stereoscopic particle image velocimetry measurements of the flow around a Rushton turbine

The principles of stereoscopic particle image velocimetry (PIV), including distortion compensation, were applied to the turbulent flow in a vessel stirred by a Rushton turbine. An angular offset configuration was used and tilt-axis lens mounts were incorporated in order to satisfy the Scheimpflug condition, significantly reducing the ordinarily large depth of field requirements of such configurations. A distortion compensation procedure, or in situ calibration, was utilized in place of the ray tracing, or mechanical registration, used in previous studies. The calibration procedure was validated using two tests, one a rigid translation of a speckle target, the other the viscous flow between two concentric cylinders. The results of the tests suggest the success with which the distortion compensation procedure may be applied to real fluid flows. Phase-locked instantaneous data were ensemble averaged and interpolated in order to obtain mean 3-D velocity fields on a cylindrical shell enclosing the turbine blade. From these fields, the tip vortex pairs and the radial jet documented in previous studies of mixer flows were easily identified.

Tension Wire Position for Hybrid External Fixation of the Proximal Tibia

To compare a new configuration of proximal wires for hybrid external fixation with the standard configuration. Biomechanical testing of five matched pairs of fresh cadaveric tibia. The authors compared the standard tension wire configuration of the three proximal wires with a more sagittal orientation of the oblique wires. A second study compared the new configuration with two wires and an offset half-pin. A two-centimeter segmental defect was created just distal to the tibial tubercle and the tibias fixed in a Montecelli Spinelli (Howmedica, NJ, U.S.A.) hybrid frame. The constructs were biomechanically tested using an Instron servohydraulic biaxial testing machine. There was a significant 67 percent decrease in displacement during anterior posterior bending and a significant 40 percent decrease in displacement in posterior bending with the new configuration compared with the standard configuration (p < 0.05). The differences in stability in all other testing modes were not significant. There was no significant difference between the new configuration and the two wire and off-set half-pin configuration. We recommend anterior placement of the oblique tension wires in the proximal tibia to more effectively resist bending in the sagittal plane, which is the most common deforming force on proximal metaphyseal fractures.

Instability of Stacked Pallet Loads Due to Misalignment

Abstract Double-stacked empty corrugated fiber-board boxes were conditioned in normal and tropical climates and then compression tested in aligned, laterally offset, and diagonally offset configurations to determine the effect on compression strength. The results showed that offsets caused a greater reduction in strength than humidity effects. In a separate experiment, three-high pallet loads of infant formula in two-piece plastic cans were stacked in various staggered positions to evaluate the effect of pallet offset on stack stability. It was found that factors other than the amount of offset, such as pallet strength, uneven floors, and stretch wrapping were most influential.

Multipole theory analysis of a slab line family with offset cylindrical bars

A new approach, the multipole theory (MT) combined with the conformal transformation method, is presented for the computation of the capacitances of slab lines with offset cylindrical bars. With this new method, the capacitances of a slab line family with offset cylindrical bars are given. These data not only permit the exact design of various offset configurations of slab lines, but also provide a known accuracy for manufacturing various coaxial configurations of slab lines. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 260–262, 1999.

Correction of Adolescent Idiopathic Thoracic Scoliosis with a New Type of Offset Apical Instrumentation

Twenty patients were operated on with the same method using the AO Universal Spine System. The entire apex of the curvature was instrumented on the concave side with a newly designed pedicle hook augmented by 3.2-mm endplate screw. An offset configuration of apical and end vertebrae implants was done to maximize translation. The concave rod was derotated to 120 degrees without any distraction. The convex side was instrumented in the usual fashion. Prospective analysis showed a mean Cobb angle correction of 63% for a mean preoperative angle of 54 degrees. The apical vertebral translation was corrected to 72%. There was no major complication at the last follow-up (18-30 months). This technique compares favorably with the ones using CD principles, but needs no distraction and no instrumentation in the canal (supra or infralaminar hook).

Effects of a fin edge close to a point caustic of a Gregorian antenna

Author(s): Capolino, F; Bussotti, P; Borselli, L; Albani, M; Maci, S | Abstract: The problem of edge diffraction close to a point caustic is analyzed in a typical dual-reflector Gregorian antenna in offset configuration. The diffraction phenomenon is produced by a perfectly conducting fin located between the feeder and the main reflector. This fin is sometimes used to reduce the coupling between the primary feed and the main reflector. For the sake of simplicity, the two-dimensional case is studied here, but the present technique can also be applied to practical three-dimensional configurations. © 1997 John Wiley a Sons, Inc.