R Krishna Kumar

The measurement of hand kinematics is important for the assessment and rehabilitation of the paralysed hand. The traditional method of hand function assessment uses a mechanical or electronic goniometer placed across the joint of interest to measure the range of joint movement. Mechanical goniometers are imprecise and lack the ability to provide a dynamic measurement; electronic goniometers are expensive and cumbersome to use during therapy. An alternative to the goniometric based assessment is to use inertial motion sensors to monitor the hand movement - these can be incorporated in a glove. In this paper, we present the design of an instrumented glove equipped with Magnetic, Angular Rate and Gravity (MARG) sensors for the objective evaluation of hand function. The instrumented glove presented in this paper is designed to assess the range of movement of the hand and also monitor the hand function during the course of hand rehabilitation. Static and dynamic calibrations were performed for the Euler angles calculated from the MARG sensors. The results are also presented for physiological flexion/extension of the wrist (relative roll), flexion/extension of elbow (relative pitch), and internal rotation/external rotation (relative yaw). The static calibration results gave mean absolute errors of 4.1° for roll, 4.0° for pitch, and 4.6° for yaw. From the dynamic calibration, the speed of response to a step change gave a convergence time of 0.4 s; sinusoidally oscillating movement gave good tracking at 0.2 Hz but exhibits overshoot errors at higher frequencies which were tested to be 1 Hz. We present the results of the calibration of the instrumented glove (one sensor pair measuring one joint angle) measuring anatomical joint angles - mean absolute errors during static calibration: 6.3° for a relative roll (wrist flexion/extension), 5.0° for relative pitch (elbow flexion/extension), and 4.5° for relative yaw (shoulder internal rotation/external rotation). The experimental results from the instrumented glove are promising, and it can be used as an alternative to the traditional goniometer based hand function assessments.

Background. The major aim of this study was to examine the leaflet/aortic root interaction during the cardiac cycle, including the stresses developed during the interaction. Methods. Dynamic finite element analysis was used along with a geometrically accurate model of the aortic valve and the sinuses. Shell elements along with proper contact conditions were also used in the model. Pressure patterns during the cardiac cycle were given as an input, and a linear elastic model was assumed for the material. Results. We found that aortic root dilation starts before the opening of the leaflet and is substantial by the time leaflet opens. Dilation of the root alone helps in opening the leaflet to about 20%. The equivalent stress pattern shows an instantaneous increase in stress at the coaptation surface during closure. Stresses increase as the point of attachment is approached from the free surface. Conclusions. The complex interplay of the geometry of the valve system can be effectively analyzed using a sophisticated dynamic finite element model. Results not previously brought out by the earlier static analysis shed new light on the root/valve interaction. © 2002 by The Society of Thoracic Surgeons.

This paper evaluates various theoretical failure criteria pertaining to workability in cold forging reported in the published literature for their reliability and sensitivity in predicting the occurrence of ductile fracture in metalworking. Finite element (FE) simulation of the published upsetting experiments on cylindrical test specimens was performed to determine the threshold values attained by various criteria at the fractured locations, for a wide variety of materials. A comparison of the experimental threshold values of different criteria, with those obtained through FEA of complex metalworking processes at fracture was also made. A statistical analysis of the results revealed that none of the criteria are truly friction and geometry-independent for universal application. Nevertheless, within a family of processes such as upsetting, the criteria depending on cumulative specific plastic energy adjusted suitably with the maximum tensile stress, are the most reliable ones in the estimation of workability limits. © 2003 Elsevier Science B.V. All rights reserved.

Objective: To compare the opening mechanics of porcine valve substitutes with those of a normal human aortic valve. Background: All commercially available porcine valves are pretreated with glutaraldehyde. This study was undertaken to evaluate the consequences of such treatment on valve mechanics. Methods: The opening mechanics of the aortic valve, especially the time taken to open fully from a closed position, and the duration for which the valve is maximally open, were compared in a normal aortic valve, a stent-mounted porcine valve, and a stentless porcine valve, using a finite element model. Results: Despite a 4-fold higher gradient, stent-mounted porcine valves were slower in attaining the fully open position, and the time for which the valve was fully open was almost 25% less than a normal valve. In stentless valves, the compliant root made the initial opening mechanics similar to those of a normal valve. Once this effect was over, the effect of porcine leaflet properties took over, and there was a corresponding delay in the valve opening. Conclusions: Fixing the root with a stent and stiffening the leaflets with glutaraldehyde result in delayed valve opening and decrease the duration for which the valve is fully open, thus contributing to inferior hemodynamics. © 2012 The Author(s).

The Belle II experiment started data-taking in March 2019. The silicon vertex detector (SVD), part of the Belle II tracking system, has been operating smoothly and reliably. The data quality has been confirmed through various metrics such as a good signal-to-noise ratio and precise spatial resolution. The radiation damage effects have been continuously monitored, showing good agreement with our expectations. So far, no harmful impact due to the radiation damage on the detector performance has been observed. Additionally, the radiation tolerance of SVD sensors for future high-luminosity runs has been examined in a new irradiation campaign. In the high-luminosity runs, an increase in hit-occupancy is also expected due to the beam-induced backgrounds. To enhance the robustness of offline software in a high-background environment, new algorithms of background suppression using hit-time information have been developed.

Dynamic steady-state crack growth has been analyzed under mode I plane stress, small-scale yielding conditions using a finite element procedure. A Perzyna type viscoplastic constitutive equation has been employed in this analysis. The viscoplastic work rate is converted into heat input and the temperature distribution is determined by solving the governing conduction/convection equation also by a finite element method. The Stream-line Upwinding Petrov-Galerkin formulation has been employed for this purpose because of the high Péclet number that results in such a type of analysis. The effect of strain rate sensitivity and crack speed on the temperature distribution near the crack tip is examined. © 1991 Kluwer Academic Publishers.

Pneumatic tires play an important role in the overall performance of a vehicle. Force and moment (FM) characteristics generated at the tire-road contact interface during various vehicle operating conditions such as cornering, braking and combined cornering-cum-braking play a crucial role in the vehicle handling performance. Experimental techniques to determine tire dynamic characteristics are expensive, cumbersome and time-consuming as testing facilities are available only at a few places in the globe. Simulations of tire dynamic behavior during cornering and braking using implicit and explicit Finite Element (FE) solution techniques are presented in this paper. Mixed Lagrangian Eulerian computational algorithm has also been considered. ABAQUS/Standard and ABAQUS/Explicit, the popular non-linear FE codes, are used to simulate the dynamics of a radial tire. The simulation results from all the FE techniques are compared with the experimental FM characteristics. The mixed Lagrangian Eulerian computational algorithm is found to be the most efficient and cost-effective tool to simulate steady state behavior. Computational resources form a major limitation with both the implicit and explicit dynamic procedures. Numerical noise and hourglassing are the major limitations of the explicit FE technique.

Two novel mixed-valent tellurium(II and IV) dithiocarbamate complexes have been prepared and their structures determined by X-ray diffraction studies. Complex 1, [TeIV(S2CNEt2)3]2[Te II(S2CNEt2)2](PF6) 2, was obtained from the metathesis reaction of [TeIV(S2CNEt2)3ClO4] with KPF6 due to the partial reduction of the primary product [TeIV(S2CNEt2)3]PF6, which is thermodynamically unstable. The preparation of tellurium(IV) dithiocarbamate in dilute perchloric acid medium results in complex 2, which has a composition [TeIV(S2CNEt2)3][Te II(S2CNEt2)2](ClO4). These two complexes represent the first examples of mixed valent complexes of tellurium consisting only the sulphur ligands. Their structural investigation shows that these complexes are stabilized primarily due to the supramolecular Te⋯Te interaction, the distance of which is shorter than the earlier known complex. While TeII(S2CNEt2)2 is sandwiched between two TeIV(S2CNEt2)3 molecules in 1, two such Te(II) molecules are sandwiched in complex 2. © 1998 Elsevier Science Ltd. All rights reserved.

Multibody dynamics and tyre models have made possible detailed analysis not only for ride and handling, but also for determining their effects on tyre nonuniformities. The aim of this paper is to analyse the steering wheel vibration, both shimmy and shake, excited by different tyre imperfections by using the commercial simulation package ADAMS/car 2005R2 and FTire. Different settings with respect to imperfection locations, amount, and the combined effects of defects have been studied. An interesting beat phenomenon is observed when all the wheels have imperfections. A procedure to determine the type of imperfections in the tyre from the results of the test rig has also been proposed.

Objective: To use finite element modelling to look at the impact of lumen shape and vessel geometry on stress distribution in a vessel. Methods: A finite element model of an atherosclerotic plaque in a coronary artery was created and a non-linear analysis with Ogden strain energy function was done. The three most common shapes seen in an artery with an eccentric plaque-namely an elliptical lumen inside a circular vessel (A), a circular lumen inside an elliptical vessel, typical of a vessel with positive remodelling (B), and a circular lumen inside a circular vessel (C)-were modelled with and without lipid. Stress was analysed in the region of the fibrous cap separating the lumen from the plaque and the region of maximum stress along the circumference of the lumen was noted. Results: In a normal circular shaped coronary artery, the haemodynamic stresses were uniformly distributed all around the circle. However, if the circle was changed to an ellipse, the stresses were redistributed along the major axis and dropped substantially along the minor axis. The stresses in a positively remodelled vessel (B) were significantly greater than in A and C, by almost 100%. Moreover, the haemodynamic stresses increased significantly towards the major axis or the shoulder in A and B, due to lumen shape and vessel geometry alone, even in the absence of lipid in the model. The stresses also had a direct relation with the thickness of the lipid pool and an inverse relation with cap thickness and lumen stenosis. Conclusions: The increased vulnerability of the shoulder region of a plaque and a remodelled coronary artery are due, apart from other factors, to increased biomechanical stresses as a result of lumen shape and vessel geometry.