The Experts below are selected from a list of 89961 Experts worldwide ranked by ideXlab platform

Xianlong Zhang - One of the best experts on this subject based on the ideXlab platform.

Harish Hirani - One of the best experts on this subject based on the ideXlab platform.

  • Development of Analytical Equations for Design and Optimization of Axially Polarized Radial Passive Magnetic Bearing
    Journal of Tribology, 2014
    Co-Authors: Kootta P. Lijesh, Harish Hirani
    Abstract:

    In the present research work, analytical equations have been developed for Design and optimization of radial axial polarized passive magnetic Bearing (PMB) with single layer for facilitating easy and quick solution, obviating the need of costly software. Seven Design variables: eccentricity, rotor width, stator width, rotor length, stator length, clearance, and mean radius were identified as the main factors affecting the Design and were thus considered in the development of analytical equations. The results obtained from the developed analytical equations have been validated with the published results. The optimization of the Bearing Design, with minimization of magnet volume as the objective function, was carried out to demonstrate the accuracy and usefulness of the developed equations.

  • journal Bearing Design using multiobjective genetic algorithm and axiomatic Design approaches
    Tribology International, 2005
    Co-Authors: Harish Hirani
    Abstract:

    This paper describes the optimum Design methodology for improving operating characteristics of fluid-film steadily loaded journal Bearings. This methodology consists of (1) a simplified closed form solution to accelerate the computation, (2) finite difference mass conserving algorithm for accurate prediction of lubricant flow and power loss, (3) Pareto optimal concept to avoid subjective decision on priority of objective functions, (4) a genetic algorithm to deal with multimodal nature of hydrodynamic-Bearing and develop a Pareto optimal front, (5) fitness sharing to maintain genetic diversity of the population used in genetic algorithm, and (6) axiomatic Design to provide inside of objective functions and Design variables. In the optimum Design of journal Bearings, the Design variables such as radial clearance, length to diameter ratio, groove geometry, oil viscosity and supply pressure are used to simultaneously minimize oil flow and power loss. A step-by-step procedure, graphs and tables are presented to demonstrate the concept and effectiveness of suggested Design methodology.

  • rapid performance evaluation of journal Bearings
    Tribology International, 1997
    Co-Authors: Harish Hirani, T V V L N Rao, K Athre, S Biswas
    Abstract:

    This paper describes a rapid method for evaluating the significant Design parameters such as load capacity, maximum pressure, flow, power loss, and maximum temperature in the oil film. The proposed analytical pressure expression is a modification of that given by Reason and Narang. An analytical expression for maximum pressure is presented. The accuracy of the proposed modification is validated up to an eccentricity ratio of 0.99. The effective temperature rise, which depends on the fraction of heat generation carried away by lubricant, is chosen to be a function of the eccentricity ratio. An expression for maximum temperature, based on existing experimental findings, is given. A journal Bearing Design table is provided to help the Designer without the involvement of numerical and mathematical complexities.

Terence J Gioe - One of the best experts on this subject based on the ideXlab platform.

  • mobile and fixed Bearing all polyethylene tibial component total knee arthroplasty Designs surgical technique
    Journal of Bone and Joint Surgery American Volume, 2010
    Co-Authors: Jeffrey Thomas P Luna, Jonathan N Sembrano, Terence J Gioe
    Abstract:

    BACKGROUND: Proponents of mobile-Bearing total knee arthroplasty believe that it has potential advantages over a fixed-Bearing Design in terms of diminished wear and improved motion and/or function, but these advantages have not been demonstrated in a randomized clinical comparison to our knowledge. We conducted a patient-blinded, prospective, randomized clinical trial to compare mobile-Bearing and fixed-Bearing cruciate-substituting total knee arthroplasties of the same Design. METHODS: Patients between the ages of sixty and eighty-five years were prospectively randomized to receive a cruciate-substituting rotating-platform Design or a fixed-Bearing Design with an all-polyethylene tibial component. There were no significant differences in the demographic characteristics (mean age, 72.2 years; mean American Society of Anesthesiologists score, 2.7; mean body mass index, 31.8 kg/m2) or preoperative clinical or radiographic measures between the groups. Routine clinical and radiographic follow-up measures included the Knee Society score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Short Form-36 (SF-36) outcome measures. RESULTS: The results of 312 arthroplasties (136 with an all-polyethylene tibial component and 176 rotating-platform Designs) in 273 patients were analyzed at a minimum of two years (mean, forty-two months) postoperatively. Although there was significant improvement in both groups, there was no significant difference between the groups with regard to the mean postoperative range of motion (110.9° and 109.1°, respectively; p = 0.21), the mean KSS clinical score (90.4 and 88.2 points; p = 0.168), or the mean KSS pain score (44.9 and 43.1 points; p = 0.108) at this follow-up point. There were ten revisions: seven because of infection, one because of patellar fracture, one because of instability, and one because of aseptic loosening. CONCLUSIONS: The two Designs functioned equivalently at the time of early follow-up in this low-to-moderate-demand patient group. The rotating-platform Design had no significant clinical advantage over the Design with the all-polyethylene tibial component. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence. ORIGINAL ABSTRACT CITATION: “Mobile and Fixed-Bearing (All Polyethylene Tibial Component) Total Knee Arthroplasty Designs. A Prospective Randomized Trial” (2009;91:2104-12).

  • mobile and fixed Bearing all polyethylene tibial component total knee arthroplasty Designs a prospective randomized trial
    Journal of Bone and Joint Surgery American Volume, 2009
    Co-Authors: Terence J Gioe, Jason Glynn, Jonathan N Sembrano, Kathleen Suthers, Edward Rainier G Santos, Jasvinder A Singh
    Abstract:

    BACKGROUND Proponents of mobile-Bearing total knee arthroplasty believe that it has potential advantages over a fixed-Bearing Design in terms of diminished wear and improved motion and/or function, but these advantages have not been demonstrated in a randomized clinical comparison to our knowledge. We conducted a patient-blinded, prospective, randomized clinical trial to compare mobile-Bearing and fixed-Bearing cruciate-substituting total knee arthroplasties of the same Design. METHODS Patients between the ages of sixty and eighty-five years were prospectively randomized to receive a cruciate-substituting rotating-platform Design or a fixed-Bearing Design with an all-polyethylene tibial component. There were no significant differences in the demographic characteristics (mean age, 72.2 years; mean American Society of Anesthesiologists score, 2.7; mean body mass index, 31.8 kg/m(2)) or preoperative clinical or radiographic measures between the groups. Routine clinical and radiographic follow-up measures included the Knee Society score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Short Form-36 (SF-36) outcome measures. RESULTS The results of 312 arthroplasties (136 with an all-polyethylene tibial component and 176 rotating-platform Designs) in 273 patients were analyzed at a minimum of two years (mean, forty-two months) postoperatively. Although there was significant improvement in both groups, there was no significant difference between the groups with regard to the mean postoperative range of motion (110.9 degrees and 109.1 degrees, respectively; p = 0.21), the mean KSS clinical score (90.4 and 88.2 points; p = 0.168), or the mean KSS pain score (44.9 and 43.1 points; p = 0.108) at this follow-up point. There were ten revisions: seven because of infection, one because of patellar fracture, one because of instability, and one because of aseptic loosening. CONCLUSIONS The two Designs functioned equivalently at the time of early follow-up in this low-to-moderate-demand patient group. The rotating-platform Design had no significant clinical advantage over the Design with the all-polyethylene tibial component.

Martin Schulze - One of the best experts on this subject based on the ideXlab platform.

  • anteroposterior and rotational stability in fixed and mobile Bearing unicondylar knee arthroplasty a cadaveric study using the robotic force sensor system
    Knee Surgery Sports Traumatology Arthroscopy, 2013
    Co-Authors: Roland Becker, Christian Mauer, Christian Starke, Mathias Brosz, Thore Zantop, Christoph H Lohmann, Martin Schulze
    Abstract:

    Different Bearing Designs in unicondylar knee arthroplasty (UKA) have been developed in order to influence the rate of polyethylene wear. Increased anteroposterior translation and rotation after UKA has been hypothesized due to changes in joint surface geometry. The mobile Bearing Design was expected to show increased anteroposterior translation compared to the fixed Bearing and biconcave Bearing Design. Six human cadaver knees were used for the tests. Anteroposterior and rotational knee stability was analysed in 0°, 30°, 60°, 90° and 120° of knee flexion using a robotic testing system (KR 125, KUKA Robots Augsburg, Germany). Three forces and moments were measured in a Cartesian coordinate system with a resolution of 1.0 N and 0.1 Nm. There was no difference between the native knees and the knees after UKA in AP translation and rotation in all knee flexion angles. The factor knee flexion angle had a significant impact on the anterior translation when the type of Bearing was neglected (p ≤ 0.015). This study shows that the natural knee stability in AP translation and rotation can be preserved in UKA. The preserved knee stability in different planes after UKA underlines the advantage of UKA when surgery is required in osteoarthritic changes of the medial compartment.

D B Bogy - One of the best experts on this subject based on the ideXlab platform.

  • alternate air Bearing slider Designs for areal density of 1 tb in sup 2
    IEEE Transactions on Magnetics, 2006
    Co-Authors: Jiayang Juang, Du Chen, D B Bogy
    Abstract:

    To achieve the areal density goal in hard disk drives of 1 Tb/in/sup 2/ the minimum physical spacing or flying height (FH) between the read/write transducer and disk must be reduced to about 2 nm. At such low spacing new nanoscale forces act between the slider and disk, such as intermolecular and electrostatic forces, which must be taken into consideration in the air Bearing Design. These forces increase the level of flying height modulations (FHMs), which in turn creates dynamic instability and intermittent contact in the flying head slider similar to what has been observed in experiments. Here, we present three possible approaches to minimize such forces and/or reduce FHM by FH control, including a micro-trailing pad slider, a thermal flying height control slider, and a piezoelectric flying height control slider for hard disk drives.

  • hard disc drive air Bearing Design modified direct algorithm and its application to slider air Bearing surface optimization
    Tribology International, 2004
    Co-Authors: Hong Zhu, D B Bogy
    Abstract:

    Hard disk drives continue to increase in areal data density. This requires air Bearing sliders with lower and lower flying heights (FH). Also the uniformity of the FH and the flatness of the roll profile with radius become more critical as the FH gets lower. By using modern optimization techniques, it is possible to optimize slider air Bearing surface (ABS) Designs according to multiple Design goals. In this paper, we discuss two modifications to the DIRECT algorithm: one to handle tolerance and one to deal with hidden constraints. Some numerical experiments were carried out using these modifications and the modified DIRECT algorithm was applied to slider ABS optimization. The results show that these two modifications can improve the efficiency of the DIRECT algorithm and they also provide more flexibility in slider ABS optimization.

  • effect of the intermolecular forces on the flying attitude of sub 5 nm flying height air Bearing sliders in hard disk drives
    Journal of Tribology-transactions of The Asme, 2002
    Co-Authors: D B Bogy
    Abstract:

    When the spacing between the slider and the disk is smaller than 10 nm, the effect of the intermolecular forces between the two solid surfaces can no longer be ignored. This effect on the flying attitude of practical slider Designs is investigated here numerically. The three-dimensional slider surface is discretized into non-overlapping unstructured triangles. The intermolecular forces between each triangular cell of the slider and the disk surface are formulated, and their contributions to the total vertical force, as well as the pitch and roll moments, are included in a previously developed steady state air Bearing Design code based on a multi-grid finite volume method with unstructured triangular grids [3–5]. It is found that the van der Waals force has significant influence on the flying height and has non-negligible effect on the pitch angle for both positive pressure sliders and negative pressure sliders, when the flying height is below 5 nm. When the flying height is below 0.5 nm, the repulsive portion of the intermolecular force becomes important and also has to be included. DOI: 10.1115/1.1456454