bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical activity changes the regulation of mitochondrial respiration in human skeletal muscle
Authors: Zoll J. , Sanchez H. , N'Guessan B. , Ribera F. , Lampert E. , Bigard X. , Serrurier B. , Fortin D. , Geny B. , Veksler V. , Ventura‐Clapier R. , Mettauer B.
Published: October 2002

This study explores the importance of creatine kinase (CK) in the regulation of muscle mitochondrial respiration in human subjects depending on their level of physical activity. Volunteers were classified as sedentary, active or athletic according to the total activity index as determined by the Baecke questionnaire in combination with maximal oxygen uptake values (peak V̇O2, expressed in ml min−1 kg−1). All volunteers underwent a cyclo‐ergometric incremental exercise test to estimate their peak V̇O2 and V̇O2 at the ventilatory threshold (VT). Muscle biopsy samples were taken from the vastus lateralis and mitochondrial respiration was evaluated in an oxygraph cell on saponin permeabilised muscle fibres in the absence (V̇0) or in the presence (V̇max) of saturating [ADP]. While V̇0 was similar, V̇max differed among groups (sedentary, 3.7 ± 0.3, active, 5.9 ± 0.9 and athletic, 7.9 ± 0.5 μmol O2 min−1 (g dry weight)−1). V̇max was correlated with peak V̇O2 (P < 0.01, r= 0.63) and with V̇T (P < 0.01, r= 0.57). There was a significantly greater degree of coupling between oxidation and phosphorylation (V̇max/V̇0) in the athletic individuals. The mitochondrial Km for ADP was significantly higher in athletic subjects (P < 0.01). Mitochondrial CK (mi‐CK) activation by addition of creatine induced a marked decrease in Km in athletic individuals only, indicative of an efficient coupling of mi‐CK to ADP rephosphorylation in the athletic subjects only. It is suggested that increasing aerobic performance requires an enhancement of both muscle oxidative capacity and mechanisms of respiratory control, attesting to the importance of temporal co‐ordination of energy fluxes by CK for higher efficacy.
Regulation of an ATP‐conductive large‐conductance anion channel and swelling‐induced ATP release by arachidonic acid
Authors: Dutta Amal K. , Okada Yasunobu , Sabirov Ravshan Z.
Published: October 2002

Mouse mammary C127 cells responded to hypotonic stimulation with activation of the volume‐dependent ATP‐conductive large conductance (VDACL) anion channel and massive release of ATP. Arachidonic acid downregulated both VDACL currents and swelling‐induced ATP release in the physiological concentration range with Kd of 4– 6 μm. The former effect observed in the whole‐cell or excised patch mode was more prominent than the latter effect observed in intact cells. The arachidonate effects were direct and not mediated by downstream metabolic products, as evidenced by their insensitivity to inhibitors of arachidonate‐metabolizing oxygenases, and by the observation that they were mimicked by cis‐unsaturated fatty acids, which are not substrates for oxygenases. A membrane‐impermeable analogue, arachidonyl coenzyme A was effective only from the cytosolic side of membrane patches suggesting that the binding site is localized intracellularly. Non‐charged arachidonate analogues as well as trans‐unsaturated and saturated fatty acids had no effect on VDACL currents and ATP release, indicating the importance of arachidonate's negative charge and specific hydrocarbon chain conformation in the inhibitory effect. VDACL anion channels were inhibited by arachidonic acid in two different ways: channel shutdown (Kd of 4– 5 μm) and reduced unitary conductance (Kd of 13–14 μm) without affecting voltage dependence of open probability. ATP4‐‐conducting inward currents measured in the presence of 100 mm ATP in the bath were reversibly inhibited by arachidonic acid. Thus, we conclude that swelling‐induced ATP release and its putative pathway, the VDACL anion channel, are under a negative control by intracellular arachidonic acid signalling in mammary C127 cells.
Role of central command in carotid baroreflex resetting in humans during static exercise
Authors: Ogoh S. , Wasmund W. L. , Keller D. M. , Yurvati A. O‐ , Gallagher K. M. , Mitchell J. H. , Raven P. B.
Published: October 2002

The purpose of the experiments was to examine the role of central command in the exercise‐induced resetting of the carotid baroreflex. Eight subjects performed 30 % maximal voluntary contraction (MVC) static knee extension and flexion with manipulation of central command (CC) by patellar tendon vibration (PTV). The same subjects also performed static knee extension and flexion exercise without PTV at a force development that elicited the same ratings of perceived exertion (RPE) as those observed during exercise with PTV in order to assess involvement of the exercise pressor reflex. Carotid baroreflex (CBR) function curves were modelled from the heart rate (HR) and mean arterial pressure (MAP) responses to rapid changes in neck pressure and suction during steady state static exercise. Knee extension exercise with PTV (decreased CC activation) reset the CBR‐HR and CBR‐MAP to a lower operating pressure (P < 0.05) and knee flexion exercise with PTV (increased CC activation) reset the CBR‐HR and CBR‐MAP to a higher operating pressure (P < 0.05). Comparison between knee extension and flexion exercise at the same RPE with and without PTV found no difference in the resetting of the CBR‐HR function curves (P > 0.05) suggesting the response was determined primarily by CC activation. However, the CBR‐MAP function curves were reset to operating pressures determined by both exercise pressor reflex (EPR) and central command activation. Thus the physiological response to exercise requires CC activation to reset the carotid‐cardiac reflex but requires either CC or EPR to reset the carotid‐vasomotor reflex.
Non‐ionotropic cross‐talk between AMPA and NMDA receptors in rodent hippocampal neurones
Authors: Bai Donglin , Muller Robert U. , Roder John C.
Published: October 2002

Many fast excitatory synapses in the hippocampus are enriched with both AMPARs (α‐amino‐3‐hydroxyl‐5‐methyl‐4‐isoxazolepropionate receptors) and NMDARs (N‐methyl‐D‐aspartate receptors). Their proximity allows them to be activated simultaneously by the same neurotransmitter, L‐glutamate. Activation of AMPARs leads to influx of sodium and calcium ions, which can increase or decrease NMDAR activity through sodium concentration‐dependent cascades or a calcium‐calmodulin‐dependent inactivation process, respectively. Here we provide evidence that the activation of AMPARs inhibits NMDARs through a non‐ionotropic mechanism. NMDA‐induced current in isolated rat CA1 hippocampal cells and nucleated patches of cultured mouse hippocampal neurones decreased when AMPARs were activated. Conversely, when AMPARs were blocked, the NMDA component of glutamate‐induced current increased. The inhibitory action of AMPAR activation on NMDAR‐mediated current depends upon the open state of AMPA channels and rapidly diminishes after deactivation of AMPARs. The inhibitory action was independent of membrane voltage, univalent cation fluxes and calcium influx. The AMPA‐NMDA cross‐inhibition also occurred in evoked synaptic current in CA1 neurones from intact mouse hippocampal slices. This cross‐talk may play a role in preventing overexcitation during bursting activities in the hippocampus.
Passive water and urea permeability of a human Na+–glutamate cotransporter expressed in Xenopus oocytes
Authors: MacAulay Nanna , Gether Ulrik , Klærke Dan A. , Zeuthen Thomas
Published: October 2002

The human Na+‐glutamate transporter (EAAT1) was expressed in Xenopus laevis oocytes. The passive water permeability, Lp, was derived from volume changes of the oocyte induced by changes in the external osmolarity. Oocytes were subjected to two‐electrode voltage clamp. In the presence of Na+, the EAAT1‐specific (defined in Discussion) Lp increased linearly with positive clamp potentials, the Lp being around 23 % larger at +50 mV than at –50 mV. l‐Glutamate increased the EAAT1‐specific Lp by up to 40 %. The K0.5 for the glutamate‐dependent increase was 20 ± 6 μm, which is similar to the K0.5 value for glutamate activation of transport. The specific inhibitor dl‐threo‐β‐benzyloxyaspartate (TBOA) reduced the EAAT1‐specific Lp to 72 %. EAAT1 supported passive fluxes of [14C]urea and [14C]glycerol. The [14C]urea flux was increased in the presence of glutamate. The data suggest that the permeability depends on the conformational equilibrium of the EAAT1. At positive potentials and in the presence of Na+ and glutamate, the pore is enlarged and water and urea penetrate more readily. The Lp was larger when measured with urea or glycerol as osmolytes as compared with mannitol. Apparently, the properties of the pore are not uniform along its length. The outer section may accommodate urea and glycerol in an osmotically active form, giving rise to larger water fluxes. The physiological role of EAAT1 for water homeostasis in the central nervous system is discussed.
Change in endothelial function in mesenteric arteries of sprague‐dawley rats fed a high salt diet
Authors: Sofola O. A. , Knill A. , Hainsworth R. , Drinkhill M.
Published: October 2002

A high salt diet in some species results in elevated arterial blood pressure and alterations in vascular smooth muscle responses to agonists. Weanling male Sprague‐Dawley rats were given either a high salt diet containing 8 % or a low salt diet of 0.4 % sodium chloride for a period of 4 weeks. At the end of the feeding period, tail systolic pressure was higher in the high salt than in low salt rats. The rats were then killed and the intestines removed. Vascular smooth muscle (VSM) responses were estimated from the changes in lumenal diameter of pressurised second order mesenteric resistance arteries. High salt diet resulted in enhanced VSM responses to noradrenaline. The vessels dilated in response both to acetylcholine and to sodium nitroprusside and the responses were similar in vessels from both high and low salt rats. However, vessels from high salt rats were resistant to the blocking of endothelium derived nitric oxide (EDNO) with L‐NAME and the responses were instead abolished by blocking endothelium derived hyperpolarising factor (EDHF) with apamin and charybdotoxin. These results show that in Sprague‐Dawley rats, a high salt diet enhances the vasoconstriction in response to noradrenaline. The vasodilatory responses to acetylcholine were not significantly changed. However, they appeared to be mediated mainly by EDHF rather than by EDNO as in the low salt animals.
Excitation‐contraction coupling and sarcoplasmic reticulum function in lechanically skinned fibres from fast skeletal muscles of aged mice
Authors: Plant David R. , Lynch Gordon S.
Published: October 2002

Ageing is generally associated with a decline in skeletal muscle mass and strength, and a slowing of muscle contraction, factors that impact upon the quality of life for the elderly. Alterations in Ca2+ handling are thought to contribute to these age‐related changes in muscle contractility, yet the effects of ageing on sarcoplasmic reticulum (SR) Ca2+ handling and the Ca2+ transport system remain unresolved. We used mechanically skinned single fibres from the fast twitch extensor digitorum longus (EDL) muscles from young (4‐month‐old) and old (27‐ to 28‐month‐old) mice to test the hypothesis that the age‐related changes in skeletal muscle contractility, especially the slower rate of contraction, are due to changes intrinsic to the muscle fibres. There were no age‐related differences in the peak height of depolarization‐induced contractile response (DICR) or the number of DICRs elicited before rundown (DICR < 50 % of initial). The time taken to reach peak DICR (TPDICR) was ≈12 % slower in single muscle fibres from old compared with young mice (P < 0.05). The rate of relaxation following DICR was not different in young and old mice. Examination of SR function demonstrated that SR Ca2+ reloading in Ca2+‐depleted skinned fibres was not different in young and old mice, nor was there any age‐related difference in Ca2+ leak from the SR. However, low [caffeine] contracture in fibres from old mice was only half of that observed in fibres from young mice (P < 0.05), indicating a lower sensitivity of the SR Ca2+ release channel (CRC) to caffeine. We found no difference in maximum Ca2+‐activated force (Po) or specific force (sPo; Po corrected for cross‐sectional area) in EDL muscle fibres from young and old mice. Impaired excitation‐contraction (E‐C) coupling and a decrease in SR CRC function are mechanisms which are likely to contribute to the overall slowing of muscle contraction with age.
Nitric oxide signalling by selective β2‐adrenoceptor stimulation prevents ach‐induced inhibition of β2‐stimulated Ca2+ current in cat atrial myocytes
Authors: Dedkova Elena N. , Gao Wang Yong , Blatter Lothar A. , Lipsius Stephen L.
Published: October 2002

The present study determined the effects of acetylcholine (ACh) on the L‐type Ca2+ current (ICa,l) stimulated by β1‐ or β2‐adrenergic receptor (AR) agonists in cat atrial myocytes. When isoproterenol (ISO; 0.1 μm) plus the β2‐AR antagonist ICI 118,551 (ISO‐β1‐AR stimulation) or 0.1 μm fenoterol, a β2‐AR agonist (FEN‐β2‐AR stimulation) increased ICa,l, ACh (1 μm) inhibited ICa,l by –60 ± 4 and –63 ± 6 %, respectively. When ISO plus the β1‐AR antagonist atenolol (ISO‐β2‐AR stimulation) or 1 μm zinterol (ZIN‐β2‐AR stimulation) increased ICa,l, ACh‐induced inhibition of ICa,l was significantly smaller, at –21 ± 3 and −24 ± 3 %, respectively. l‐N5‐(1‐iminoethyl)ornithine (l‐NIO, 10 μm), an inhibitor of nitric oxide (NO) synthase, enhanced ACh‐induced inhibition of ICa,l when stimulated by ZIN‐β2‐ARs, but not when stimulated by ISO‐β1‐ARs or FEN‐β2‐ARs. Haemoglobin (50 μm), a NO scavenger, also enhanced ACh‐induced inhibition when ICa,l was stimulated by ZIN‐β2‐ARs, but not when stimulated by FEN‐β2‐ARs. ACh‐induced inhibition of ICa,l stimulated by ZIN‐β2‐ARs was not affected by 10 μm 1H‐[1,2,4] oxadiazolo[4,3‐a] quinoxaline‐1‐one (ODQ) a guanylate cyclase inhibitor, but was significantly enhanced by 500 μm reduced glutathione or 100 μm dithiothreitol, agents that act as sinks for S‐nitrosylation. ACh‐induced inhibition was smaller when ICa,l was stimulated by spermine/NO, a NO donor, than by milrinone, a phosphodiesterase type III inhibitor. ISO (ISO‐β1/β2‐AR stimulation) increased ICa,l and even though ISO releases NO, ACh prominently inhibited ICa,l. This inhibitory effect of ACh was enhanced by l‐NIO. Stimulation of ZIN‐β2‐ARs increased intracellular NO, whereas ISO‐β1‐ARs or FEN‐β2‐ARs failed to increase intracellular NO. These results indicate that in atrial myocytes, NO released by selective β2‐AR stimulation prevents ACh‐induced inhibition of ICa,l stimulated by β2‐ARs. NO acts via a cGMP‐independent, S‐nitrosylation mechanism. Although FEN acts via β2‐ARs, it fails to stimulate Gi‐/NO signalling and preferentially stimulates Gs‐/adenylate cyclase signalling, similar to β1‐ARs. These findings indicate that NO signalling modulates muscarinic receptor inhibition of atrial function stimulated by β2‐ARs.
KATP channel‐independent targets of diazoxide and 5‐hydroxydecanoate in the heart
Authors: Hanley Peter J. , Mickel Markus , Löffler Monika , Brandt Ulrich , Daut Jürgen
Published: October 2002

Diazoxide and 5‐hydroxydecanoate (5‐HD; C10:0) are reputed to target specifically mitochondrial ATP‐sensitive K+ (KATP) channels. Here we describe KATP channel‐independent targets of diazoxide and 5‐HD in the heart. Using submitochondrial particles isolated from pig heart, we found that diazoxide (10‐100 μm) dose‐dependently decreased succinate oxidation without affecting NADH oxidation. Pinacidil, a non‐selective KATP channel opener, did not inhibit succinate oxidation. However, it selectively inhibited NADH oxidation. These direct inhibitory effects of diazoxide and pinacidil cannot be explained by activation of mitochondrial KATP channels. Furthermore, application of either diazoxide (100 μm) or pinacidil (100 μm) did not decrease mitochondrial membrane potential, assessed using TMRE (tetramethylrhodamine ethyl ester), in isolated guinea‐pig ventricular myocytes. We also tested whether 5‐HD, a medium‐chain fatty acid derivative which blocks diazoxide‐induced cardioprotection, was ‘activated’ via acyl‐CoA synthetase (EC 6.2.1.3), an enzyme present both on the outer mitochondrial membrane and in the matrix. Using analytical HPLC and electrospray ionisation mass spectrometry, we showed that 5‐HD‐CoA (5‐hydroxydecanoyl‐CoA) is indeed synthesized from 5‐HD and CoA via acyl‐CoA synthetase. Thus, 5‐HD‐CoA may be the active form of 5‐HD, serving as substrate for (or inhibiting) acyl‐CoA dehydrogenase (β‐oxidation) and/or exerting some other cellular action. In conclusion, we have identified KATP channel‐independent targets of 5‐HD, diazoxide and pinacidil. Our findings question the assumption that sensitivity to diazoxide and 5‐HD implies involvement of mitochondrial KATP channels. We propose that pharmacological preconditioning may be reelated to partial inhibition of respiratory chain complexes.
Dynamic Stability of a Rotor Partially Filled With a Viscous Liquid
Authors: Tao M. , Zhang W.
Published: October 2002

By means of the obtained explicit expressions of dynamic forces acting on a rotor partially filled with a viscous liquid, the equations of motion are derived. The corresponding eigenvalue problem is solved accurately in correcting to the first order of magnitude of Re−1/2. Dynamic stability of the rotor is studied in detail and some valuable results are obtained. We can regulate the stable interval so long as we properly choose the value of external damping.
Dynamic Stability of a Flexible Spinning Cylinder Partially Filled With Liquid
Authors: Tao M. , Zhang W.
Published: October 2002

Dynamic stability of a flexible spinning cavity cylinder partially filled with liquid is discussed in the paper. The cylinder is assumed to be slender. Choosing characteristic quantities and estimating the orders of magnitude of all terms in the governing equations and boundary conditions, the three-dimensional flow in the slender cylinder is reduced to a quasi-two-dimensional flow. Using the known formulas of a two-dimensional dynamic force acting on the rotor and regarding the slender cylinder as a Bernoulli-Euler beam, the perturbed equations of the liquid-filled beam-wise cylinder are derived. The analytical stability criteria as well as the stability boundaries are obtained. The results further the study of this problem.
High Cycle Fatigue Resistance and Reliability Assessment of Flexible Printed Circuitry
Authors: Martynenko Elena , Zhou Wen , Chudnovsky Alexander , Li Ron S. , Poglitsch Larry
Published: October 2002

Flexible printed circuitry (FPC) is a patterned array of conductors supported by a flexible dielectric film made of high strength polymer material such as polyimide. The flexibility of FPC provides an opportunity for three dimensional packaging, easy interconnections and dynamic applications. The polymeric core layer is the primary load bearing structure when the substrate is not supported by a rigid plate. In its composite structure, the conductive layers are more vulnerable to failure due to their lower flexibility compared to the core layer. Fatigue data on FPCs are not commonly available in published literature. Presented in this paper is the fatigue resistance and reliability assessment of polyimide based FPCs. Fatigue resistance of a specific material system was analyzed as a function of temperature and frequency through experiments that utilized a specially designed experimental setup consisting of sine servo controller, electrodynamic shaker, continuity monitor and temperature chamber. The fatigue characteristics of the selected material system are summarized in the form of S-N diagrams. Significant decrease in fatigue lifetime has been observed due to higher displacements in high cycle fatigue. Observed temperature effect was however counter-intuitive. Failure mechanisms are discussed and complete fracture analysis is presented. In various FPC systems, it has been found that the changes take place in FPC failure mechanisms from well-developed and aligned single cracks through the width at low temperature to an array of multiple cracks with random sizes and locations at high temperature.
Damage Accumulation During Stress Relaxation of Polymer Films in Bending
Authors: Ingman D. , Michlin Y.
Published: October 2002

A nonlinear viscoelastic damage accumulation model with a physical approach is presented with a view to describing stress relaxation in amorphous and partially crystalline polymers. The deformation is represented as stress-aided transition through a series of symmetrical energy barriers. There is also a stress threshold, introduced by the authors and representing an asymptotic residual stress below which relaxation does not occur. The model comprises three parameters: an activation volume, V; a product of several parameters with physical meaning, A (only the combination of A and V in the form of the relaxation time constant can be reconstructed from the present set of experiments); and the relaxation threshold. It allows a practically unlimited number of energy barriers. The damage depends on the stress history. Experimental data were collected on stress relaxation of three polymers at different temperatures. The experiments involved bending of a polymer strip within a metal cylinder and measurement of the radius of curvature after removal of the strip from the cylinder, using a specially-developed method. The measured radii ranged from infinity to 1.5 cm, and the obtained data were fitted to the model. The results show that the residual stress and other model parameters are temperature-dependent.
Misaligned Flip-Chip Solder Joints: Prediction and Experimental Determination of Force-Displacement Curves
Authors: Josell D. , Wallace W. E. , Warren J. A. , Wheeler D. , Powell A. C.
Published: October 2002

The results of wetting experiments between eutectic lead-tin solder and copper pads on silicon substrates in geometries relevant to flip-chip applications are presented. Measurements of solder joint dimensions, specifically stand-off height and lateral offset (i.e., misalignment), as functions of the applied force (normal and shear), solder volume and pad diameter are presented. The experimentally-measured force-displacement relationships are compared with predictions obtained from the minimum energy model of the Surface Evolver computer code. For the case of the axisymmetric joint (zero shear) an exact solution to the capillary equations is also presented. The comparison of experimental and modeling results indicates that such models are accurate as well as extremely sensitive means for predicting the geometry of these solder joints.
Finned Metal Foam Heat Sinks for Electronics Cooling in Forced Convection
Authors: Bhattacharya A. , Mahajan R. L.
Published: October 2002

In this paper, we present recent experimental results on forced convective heat transfer in novel finned metal foam heat sinks. Experiments were conducted on aluminum foams of 90 percent porosity and pore size corresponding to 5 PPI (200 PPM) and 20 PPI (800 PPM) with one, two, four and six fins, where PPI (PPM) stands for pores per inch (pores per meter) and is a measure of the pore density of the porous medium. All of these heat sinks were fabricated in-house. The forced convection results show that heat transfer is significantly enhanced when fins are incorporated in metal foam. The heat transfer coefficient increases with increase in the number of fins until adding more fins retards heat transfer due to interference of thermal boundary layers. For the 20 PPI samples, this maximum was reached for four fins. For the 5 PPI heat sinks, the trends were found to be similar to those for the 20 PPI heat sinks. However, due to larger pore sizes, the pressure drop encountered is much lower at a particular air velocity. As a result, for a given pressure drop, the heat transfer coefficient is higher compared to the 20 PPI heat sink. For example, at a Δp of 105 Pa, the heat transfer coefficients were found to be 1169W/m2-K and 995W/m2-K for the 5 PPI and 20 PPI 4-finned heat sinks, respectively. The finned metal foam heat sinks outperform the longitudinal finned and normal metal foam heat sinks by a factor between 1.5 and 2, respectively. Finally, an analytical expression is formulated based on flow through an open channel and incorporating the effects of thermal dispersion and interfacial heat transfer between the solid and fluid phases of the porous medium. The agreement of the proposed relation with the experimental results is promising.
Finite Element Simulations of Free Surface Flows With Surface Tension in Complex Geometries
Authors: Wang Gang
Published: October 2002

The finite-element program, ANSYS/FLOTRAN, has been enhanced at Release 5.7 to predict free surface flows with surface tension in complex geometries. The two-dimensional incompressible Navier-Stokes and energy equations are solved in both Cartesian and axisymmetric coordinate systems. At Release 5.6, the free surface capabilities have been incorporated into ANSYS/FLOTRAN using the CLEAR-VOF algorithm. The main contribution of this work is to implement a surface tension model into ANSYS/FLOTRAN to study free surface flows with surface tension in complex geometries. Both normal and tangential components of surface tension forces are modeled at the interface through a continuum surface force (CSF) model. This new algorithm is first validated with two model problems: a droplet in equilibrium and an oscillating droplet. For the first problem, the computed pressure value is compared with the theoretical value, whereas for the second problem, the oscillation frequency is compared with both the analytical solution and experimental data. The computer program is then applied to thermocapillary flows in two types of trapezoidal cavities to investigate the interesting flow and heat transfer characteristics. Systematic calculations are performed to study the influence of Marangoni number, capillary number and static contact angle on Marangoni convection.
Thermomechanical Durability of High I/O BGA Packages
Authors: Davuluri P. , Shetty S. , Dasgupta A. , Young S.
Published: October 2002

Efficient modeling strategies are developed to study thermomechanical durability of high I/O Ball Grid Array (BGA) packages, in order to facilitate virtual qualification and accelerated testing of component designs. A viscoplastic stress analysis technique is developed where the critical solder joint(s) (joint(s) where failure first occurs) are modeled in detail with a multi-domain Rayleigh-Ritz (MDRR) methodology while the load-sharing offered by noncritical joints is modeled with a simplified compact model. This hybrid technique is used to study the behavior of solder interconnects in selected Ball Grid Array (BGA) package under thermal cycling environments. Parametric studies are conducted to determine the optimal scheme for allocating a critical number of solder joints to the MDRR model, and the remaining non-critical joints to the compact models. Damage calculations are made with the Energy Partitioning Solder Durability model and cycles-to-failure predictions are compared with both finite element model predictions as well as experimental failure data provided by CALCE EPSC sponsors. Parametric studies on change in solder joint durability with interconnect volume are also discussed in this paper.
The Influence of the Thermal Conductivity on the Heat Transfer Performance in a Heat Sink
Authors: Ma H. B. , Peterson G. P.
Published: October 2002

An extensive numerical analysis of the temperature distribution and fluid flow in a heat sink currently being used for cooling desktop computers was conducted, and demonstrated that if the base of a heat sink was fabricated as a heat pipe instead of a solid material, the heat transfer performance could be significantly increased. It was shown that as the heat sink length increases, the effect of the thermal conductivity of the base on the heat transfer performance increases to be a predictable limit. As the thermal conductivity is increased, the heat transfer performance of heat sinks is enhanced, but cannot exceed this limit. When the thermal conductivity increases to 2,370 W/m-K, the heat transfer performance of the heat sinks will be very close to the heat transfer performance obtained assuming a base with infinite thermal conductivity. Further increases in the thermal conductivity would not significantly improve the heat transfer performance of the heat sinks.
Validation of Electronic Package Reliability Using Speckle Interferometry
Authors: Yeh H.-Y. , Cote K.
Published: October 2002

In-situ measurements were performed on organic based substrates under mechanical loading as well as land grid array electronic packages under thermal cycling. Whole field displacement measurements obtained from this analysis were compared with results obtained from similar finite element models. The experimental flexibility and results obtained from speckle interferometry indicate that this method has several substantial benefits over moire´ interferometry. Due to coefficient of thermal expansion mismatches between the package and printed circuit board, creep shear strains developed in the 63/37 SnPb solder. When thermally loaded, these creep shear strains develop cracks in the joint leading to Mode II failure. A single thermal half cycle from 25°C to 125°C was applied to a specimen to simulate the fatigue life of the solder joints undergoing thermal loading and the resulting strains were entered into the Engelmaier reliability prediction model for 63/37 SnPb solder. The experimental results yielded 0.59% strain per cycle with 7485 cycles to failure.
A Universal, Nonintrusive Method for Correcting the Reading of a Flow Meter in Pipe Flow Disturbed by Installation Effects
Authors: Wildemann C. , Merzkirch W. , Gersten K.
Published: October 2002

A method is described that allows the correction of the reading of a flow meter that is exposed to pipe flow disturbed by installations upstream of the meter. The method is aimed at minimizing the distance between installation and meter and is based on characterizing the flow by “fundamental” disturbances, physically interpretable as vortical structures, and on the detection of these disturbances by a measuring device located slightly upstream of the meter. A functional relationship between fundamental disturbances and “error shift” of the meter is postulated, and its existence is demonstrated by a number of experiments. It is concluded that the correction method is applicable to any type of installation and flow meter.
Development of Swirling Flow in a Rod Bundle Subchannel
Authors: McClusky Heather L. , Holloway Mary V. , Beasley Donald E. , Conner Michael E.
Published: October 2002

Experimental measurements of the axial development of swirling flow in a rod bundle subchannel are presented. Swirling flow was introduced in the subchannel from a split vane pair located on the downstream edge of the support grid. Particle image velocimetry using an optical borescope yielded full-field lateral velocity data. Lateral flow fields and axial vorticity fields at axial locations ranging from 4.2 to 25.5 hydraulic diameters downstream of the support grid were examined for a Reynolds number of 2.8×104. The lateral velocity fields show that the swirling flow was initially centered in the subchannel. As the flow developed in the axial direction, the swirling flow migrated away from the center of the subchannel. Radial distributions of azimuthal velocity and circulation are presented relative to the centroid of vorticity, and are compared to that of a Lamb-Oseen vortex. The angular momentum decreased as the flow developed in the axial direction. The spatial decay rate of the angular momentum is compared to that of decaying, swirling flow in a pipe.
Optimum Design of Mechanical Systems Involving Interval Parameters
Authors: Rao S. S. , Cao Lingtao
Published: October 2002

The imprecision or uncertainty present in many engineering systems can be modeled using probabilistic, fuzzy or interval methods. This work presents the optimum design of uncertain mechanical systems using interval analysis for the prediction of system response. Each of the uncertain parameters is defined by a range of values. Since the interval ranges of response parameters is found to increase with an increase in the number and/or ranges of input interval parameters with the use of interval arithmetic operations, a truncation procedure is used to obtain approximate but reasonably accurate response of the system. This procedure is found to be simple, economical and fairly accurate. The optimum design of a brake is considered to illustrate the computational aspects of the methods. The procedures outlined in this work are quite general and can be used for the design of any uncertain mechanical system when either the probability distribution functions or the preference information of uncertain parameters are unknown.
From Random Tolerances to Random Rotor Vibrations
Authors: Vinogradov Oleg
Published: October 2002

In the paper a statistical distribution of reaction forces in a vibrating rotor is traced back to assigned tolerances on components making up this rotor. First, the statistics of the unbalanced mass in an n-ring assembly is considered and an explicit expression for it is derived in terms of tolerances assigned to individual rings. As an illustrative example, the problem of vibrations of a rotor with two assembled disks is considered. The disks are manufactured to different specifications and the statistical distributions of reaction forces are found by Monte Carlo simulation. The latter allows to estimate the probability of vibrations or forces exceeding a specified level for a given accuracy of manufacturing. The methodology presented establishes a direct link between the manufacturing specifications for the components and the quality of performance of the equipment.
Polyhedral Single Degree-of-freedom Expanding Structures: Design and Prototypes
Authors: Agrawal Sunil K. , Kumar Saravana , Yim Mark
Published: October 2002

Some engineering applications require structures to expand and contract in size, while retaining their exterior shape. The applications range from mundane daily life objects to more fancy art structures. In contrast to a multi degree-of-freedom structure, a single degree-of-freedom structure can be driven by a single actuator, reducing cost and simplifying the control. In this paper, we study single degree-of-freedom structures that can be formed by a lattice of single degree-of-freedom polyhedral expanding units. Due to built-in symmetries, the entire structure can expand and contract as one of the units in the structure is actuated. The paper describes the design of polyhedral single degree-of-freedom systems, the structures of their dynamics/optimal control, and results from construction prototypes.
Optimum Stiffener Layout for the Reduction of Vibration and Noise of Gearbox Housing
Authors: Inoue Katsumi , Yamanaka Masashi , Kihara Masahiko
Published: October 2002

Dynamic excitation from the gears generates vibration modes in the gearbox which causes radiation of unwanted structure-borne noise. To reduce the noise as well as the vibration, the stiffened plate construction is frequently used for the housing, where the rib stiffener layout is the key to this design. In this paper, the most effective position of stiffeners in order to reduce the vibration and noise radiation is searched and discussed. The analysis considers first a plate fixed at edges and excited at its center, and then a simplified rectangular gearbox excited at the shaft bearing locations. The housing of a simplified single-stage gearbox is modeled by triangular finite shell elements. It is excited by a set of harmonic forces which are applied at the bearing positions. The rib stiffener is modeled by beam elements, and its optimum layout is searched by a genetic algorithm. The vibration energy is adopted as the objective function to be minimized for the design for low vibration. On the other hand, the radiated sound power is the objective function for low noise. Although the noise is caused by the vibration, the optimum stiffener layout to realize low noise is not always identical to the layout that yields low vibration because of the difference in radiation efficiency. This is numerically clarified first from the viewpoint of the vibration mode of a plate. In the case of the design for the gearbox housing concerned, the vibration mode which causes the difference in radiation efficiency is not presented. Consequently, the optimum stiffener is placed along the line from the point of excitation to a fixed point, which reduces the vibration deflection of the faces with bearings as well as the in-plane displacement of the bearings.
The Proportional-Damping Matrix of Arbitrarily Damped Linear Mechanical Systems
Authors: Angeles J. , Ostrovskaya S.
Published: October 2002

The vibration of linear mechanical systems with arbitrary damping is known to pose challenging problems to the analyst, for these systems cannot be analyzed with the techniques pertaining to their undamped counterparts. It is also known that a class of damped systems, called proportionally damped, can be analyzed with the same techniques, which mimic faithfully those of single-degree-of-freedom systems. For this reason, in many instances the system at hand is assumed to be proportionally damped. Nevertheless, this assumption is difficult to justify on physical grounds in many practical applications. What this assumption brings about is a damping matrix that admits a simultaneous diagonalization with the stiffness matrix. Proposed in this paper is a decomposition of the damping matrix of an arbitrarily damped system allowing the extraction of the proportionally damped component, which, moreover, approximates optimally the original damping matrix in the least-square sense. Finally, we show with examples that conclusions drawn from the proportionally damped approximation of an arbitrarily damped system can be dangerously misleading.
Wave Propagation Induced by Multiple Piezoelectric Actuators in Electromechanical Structures
Authors: Wang X. D. , Huang G. L.
Published: October 2002

This paper provides a theoretical analysis of the elastic wave propagation in an elastic medium induced by embedded piezoceramic actuators under dynamic electric loads. A new actuator model involving the deformation in both the transverse and longitudinal directions of the actuators is used to study the wave propagation induced by multiple actuators. The resulting waveform is determined using a pseudo-incident wave technique and solving the resulting integral equations in terms of the interfacial shear stress and transverse displacement of the actuators. Numerical simulation is conducted to evaluate the effects of the geometry, the loading frequency, and the interaction between actuators upon the resulting wave propagation.
Prediction and Improvement of Steady-State Performance of a Power Controlled Axial Piston Pump
Authors: Gad Osama , Rabie M. Galal , El-Taher Refaat M.
Published: October 2002

This paper deals with the static and dynamic behavior of a variable displacement bent axis axial piston pump with power control. A mathematical model is deduced to predict the performance of the pump and its controller. The pump static and dynamic characteristics are also evaluated experimentally. A good agreement between the experimental and theoretical results is obtained which validates the deduced pump model. A redesign of the original pump controller is carried out, in order to produce constant output power (hyperbolic P-Q relation). The proposed controller includes a hydraulic accumulator used as a gas spring. A mathematical model for the pump, equipped with the proposed controller, is developed and used for the computer simulation. The effect of the proposed controller parameters on the pump performance is studied. The proposed controller produced a P-Q relation too close to the required hyperbola. In the dynamic mode of operation, the transient pressure oscillations and settling time are considerably reduced, but the maximum over shoot is increased.
A Note About the Stability of a String of LTI Systems
Authors: Darbha Swaroop
Published: October 2002

This note concerns the stability of a string of LTI systems; it is shown here that, if the “weak interaction” condition among systems in the string is satisfied (i.e., the sum of the ∞-norms of the interaction/error propagation transfer functions is less than unity), then the string is Lp stable for every p⩾1. Since the ∞-norm of a transfer function is the smallest of all its induced Lp norms, the result presented here enables one to obtain a tighter estimate of the geometric rate of attenuation of the states of systems in the string.
Mathematical Modeling of a Two Spool Flow Control Servovalve Using a Pressure Control Pilot1
Authors: Anderson Randall T. , Li Perry Y.
Published: October 2002

A nonlinear dynamic model for an unconventional, commercially available electrohydraulic flow control servovalve is presented. The two stage valve differs from the conventional servovalve design in that: it uses a pressure control pilot stage; the boost stage uses two spools, instead of a single spool, to meter flow into and out of the valve separately; and it does not require a feedback wire and ball. Consequently, the valve is significantly less expensive. The proposed model captures the nonlinear and dynamic effects. The model has been coded in Matlab/Simulink and experimentally validated.
Yoyo Dynamics: Sequence of Collisions Captured by a Restitution Effect
Authors: Jin Hui-Liang , Zackenhouse M.
Published: October 2002

This paper focuses on modeling the dynamics of a yoyo—a popular toy, which presents a challenging task for robotic control. A dynamic two-degree-of-freedom (DOF) model of the yoyo with a unilateral constraint is first proposed. The flight of the yoyo is naturally split into four phases, namely, a free-motion phase, a constrained-motion phase, a bottom phase, and a transition phase. It is shown that the energy loss is mainly due to a sequence of collisions that occur between the yoyo and the string during the bottom and transition phases. The dynamics in the bottom and transition phases is simplified by a single impulsive effect with an equivalent restitution coefficient, which depends only on the mass, inertia and axle radius of the yoyo. The resulting one-DOF model captures the energy loss while greatly simplifying the dynamic model, and thus facilitating the analysis and design of yoyo control. Both models are verified by experiments conducted on three different yoyos.
Origin of the Biomechanical Properties of Wood Related to the Fine
Structure of the Multi-layered Cell Wall
Authors: Yamamoto H. , Kojima Y. , Okuyama T. , Abasolo W. P. , Gril J.
Published: October 2002

In this study, a basic model is introduced to describe the biomechanical properties of the wood from the viewpoint of the composite structure of its cell wall. First, the mechanical interaction between the cellulose microfibril (CMF) as a bundle framework and the lignin-hemicellulose as a matrix (MT) skeleton in the secondary wall is formulated based on “the two phase approximation.” Thereafter, the origins of (1) tree growth stress, (2) shrinkage or swelling anisotropy of the wood, and (3) moisture dependency of the Young’s modulus of wood along the grain were simulated using the newly introduced model. Through the model formulation; (1) the behavior of the cellulose microfibril (CMF) and the matrix substance (MT) during cell wall maturation was estimated; (2) the moisture reactivity of each cell wall constituent was investigated; and (3) a realistic model of the fine composite structure of the matured cell wall was proposed. Thus, it is expected that the fine structure and internal property of each cell wall constituent can be estimated through the analyses of the macroscopic behaviors of wood based on the two phase approximation.
Concurrent Design of Input Shaping and Proportional Plus Derivative Feedback Control
Authors: Kenison Michael , Singhose William
Published: October 2002

Systems that exhibit flexible dynamics are widespread and present a very challenging control problem when their performance is pushed to the limit. If there is some knowledge of the flexible modes, then command signals can be generated to negate the detrimental dynamics. These vibration-reducing commands are dependent on the feedback controller gains because the gains influence the flexible modes. This paper presents a method for concurrently designing a PD feedback controller and a command generator so that performance is optimized. The design method takes into account limits on allowable overshoot, residual vibration, and actuator effort. Furthermore, the structure of the method allows a wide range of performance requirements, such as disturbance rejection, to be integrated into the design. Results demonstrate that a PD controller cannot achieve the same performance as a PD controller augmented with a command generator.
A New In Vitro Model to Evaluate Differential
Responses of Endothelial Cells to Simulated Arterial Shear Stress Waveforms
Authors: Blackman Brett R. , García-Cardeña Guillermo , Gimbrone Michael A.
Published: October 2002

In the circulation, flow-responsive endothelial cells (ECs) lining the lumen of blood vessels are continuously exposed to complex hemodynamic forces. To increase our understanding of EC response to these dynamic shearing forces, a novel in vitro flow model was developed to simulate pulsatile shear stress waveforms encountered by the endothelium in the arterial circulation. A modified waveform modeled after flow patterns in the human abdominal aorta was used to evaluate the biological responsiveness of human umbilical vein ECs to this new type of stimulus. Arterial pulsatile flow for 24 hours was compared to an equivalent time-average steady laminar shear stress, using no flow (static) culture conditions as a baseline. While both flow stimuli induced comparable changes in cell shape and alignment, distinct patterns of responses were observed in the distribution of actin stress fibers and vinculin-associated adhesion complexes, intrinsic migratory characteristics, and the expression of eNOS mRNA and protein. These results thus reveal a unique responsiveness of ECs to an arterial waveform and begin to elucidate the complex sensing capabilities of the endothelium to the dynamic characteristics of flows throughout the human vascular tree.
Multi-Parameter Sensing With a Thermal Silicon Flow Sensor
Authors: van Putten M. J. A. M. , Kleijn C. R. , van den Akker H. E. A.
Published: October 2002

We present a method for multi-parameter sensing in the application of thermal vector flow sensors. The method is based on the property that two independent signals can be obtained from a single sensing element, viz. a thermal vector flow sensor. For particular applications, this reduces the number of sensors in the measurement process. It may also allow redundant measurement of physical parameters, such as temperature; these redundant measurements are important for self-diagnostics of proper operation of a measurement system. The method is applied to a bidirectional silicon flow sensor, that generates two independent signals, both being a function of the Re number and the fluid temperature. This allows both temperature and mass flow measurement by use of a single sensor. Temperature estimates are accurate within 0.64 K and mass flow estimates within 5.6%.