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Torque
Kinds of Torque Terms modified by Torque Selected AbstractsEXTRUSION COOKING OF BLENDS OF SOY FLOUR AND SWEET POTATO FLOUR ON SPECIFIC MECHANICAL ENERGY (SME), EXTRUDATE TEMPERATURE AND TORQUEJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 4 2001M. O. IWE Defatted soy flour and sweet potato flour containing 18% moisture were mixed in a pilot mixer, and extruded in an Almex-Bettenfeld single-screw extruder operated at varying rotational speed and die diameter. A central composite, rotatable nearly orthogonal design, which required 23 experiments for three factors (feed composition (fc), screw speed (ss) and die diameter (dd)) was developed and used for the generation of response surfaces. Effects of the extrusion variables on specific mechanical energy (SME), extrudate temperature (ET), and torque (T) were evaluated using response surface analysis. Results showed that product temperature increased with increases in die diameter, screw speed and feed composition. However, the effect of die diameter was greater than those of screw speed and feed composition. Decrease in die diameter with increase in sweet potato content increased torque. Screw speed exhibited a linear effect on torque. [source] Eddy-current induction in extended metallic parts as a source of considerable torsional momentJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2006Hansjörg Graf PhD Abstract Purpose To examine eddy-current-provoked torque on conductive parts due to current induction from movement through the fringe field of the MR scanner and from gradient switching. Materials and Methods For both cases, torque was calculated for frames of copper, aluminum, and titanium, inclined to 45° to B0 (maximum torque case). Conditions were analyzed in which torque from gravity (legal limit, ASTM F2213-02) was exceeded. Experiments were carried out on a 1.5 T and a 3 T scanner for copper and titanium frames and plates (,50 × 50 mm2). Movement-induced torque was measured at patient table velocity (20 cm/second). Alternating torque from gradient switching was investigated by holding the specimens in different locations in the scanner while executing sequences that exploited the gradient capabilities (40 mT/m). Results The calculations predicted that movement-induced torque could exceed torque from gravity (depending on the part size, electric resistance, and velocity). Two experiments on moving conductive frames in the fringe fields of the scanners confirmed the calculations. For maximum torque case parameters, gradient-switching-induced torque was calculated to be nearly 100 times greater than the movement-induced torque. Well-conducting metal parts located off center vibrated significantly due to impulse-like fast alternating torque characteristics. Conclusion Torque on metal parts from movement in the fringe field is weak under standard conditions, but for larger parts the acceptable limit can be reached with a high static field and increased velocity. Vibrations due to gradient switching were confirmed and may explain the sensations occasionally reported by patients with implants. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [source] A robot-assisted study of intrinsic muscle regulation on proximal interphalangeal joint stiffness by varying metacarpophalangeal joint positionJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2006Zong-Ming Li Abstract The tightness of intrinsic hand muscles is a common cause of finger joint stiffness. The purposes of this study were to develop a robot-assisted methodology to obtain torque,angle data of a finger joint, and to investigate the regulation of the intrinsic muscles on finger joint stiffness. Our robot system features the integration of a low payload robot arm, a controller, and a force/torque transducer. The system provided highly reproducible torque,angle curves. Torque,angle data of the proximal interphalangeal joint with the metacarpophalangeal joint at 0 and 60 degrees were obtained from eight asymptomatic hands. The torque,angle curve shifted with the position of the metacarpophalangeal joint. As the metacarpophalangeal joint flexion angle changed from 60 to 0 degrees, the equilibrium of the proximal interphalangeal joint increased more than 20 degrees, and joint stiffness increased more than 50%. The dependence of the stiffness of the proximal interphalangeal joint on metacarpophalangeal joint position supports the regulatory role of the intrinsic muscles on finger joint mechanics. This regulatory mechanics is likely amplified in hands with intrinsic muscle tightness, justifying the commonly used Bunnell Intrinsic Tightness Test. © 2005 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:407,415, 2006 [source] Assessment of Finger Forces and Wrist Torques for Functional Grasp Using New Multichannel Textile NeuroprosthesesARTIFICIAL ORGANS, Issue 8 2008Marc Lawrence Abstract:, New multichannel textile neuroprotheses were developed, which comprise multiple sets of transcutaneous electrode arrays and connecting wires embroidered into a fabric layer. The electrode arrays were placed on the forearm above the extrinsic finger flexors and extensors. Activation regions for selective finger flexion and wrist extension were configured by switching a subset of the array elements between cathode, anode, and off states. We present a new isometric measurement system for the assessment of finger forces and wrist torques generated using the new neuroprostheses. Finger forces (from the middle phalanxes) were recorded using five load cells mounted on a "grasp handle" that can be arbitrarily positioned in space. The hand and the grasp handle were rigidly mounted to a 6-degree of freedom load cell, and the forces and torques about the wrist were recorded. A vacuum cushion was used to comfortably fixate the forearm. The position and orientation of the forearm, wrist, fingers, and handle were recorded using a new three-dimensional position measurement system (accuracy <±1 mm). The measurement system was integrated into the real-time multichannel transcutaneous electrode environment, which is able to control the spatiotemporal position of multiple activation regions. Using the combined system and textile neuroprosthesis, we were able to optimize the activation regions to produce selective finger and wrist articulation, enabling improved functional grasp. [source] Deployable Truss Operation by ETS-VII Robot Arm Using Force Accommodation ControlCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 3 2001Masahiro Nohmi An experiment for teleoperating a truss structure has been performed as part of a space robotics mission on Engineering Test Satellite No. 7 (ETS-VII). This article reports the results from truss experiments conducted by means of the ETS-VII robot arm using force accommodation control, which is a specific control law developed for the ETS-VII robot arm. With this control function, the robot arm moves toward the point where the external force becomes the command value, which is sent from the ground. This control technique is useful especially in the case of teleoperation with time delay, since excessive force and torque can be avoided, and in addition, no a priori trajectory information is required. However, the robot arm cannot attain the desired configuration for itself. These characteristics can be used for deployable and assembly truss operation, making full use of merits and avoiding demerits. The effectiveness is confirmed through an ETS-VII onboard experiment. [source] Resistance training increases in vivo quadriceps femoris muscle specific tension in young menACTA PHYSIOLOGICA, Issue 1 2010R. M. Erskine Abstract Aim:, The present study investigated whether in vivo human quadriceps femoris (QF) muscle specific tension changed following strength training by systematically determining QF maximal force and physiological cross-sectional area (PCSA). Methods:, Seventeen untrained men (20 ± 2 years) performed high-intensity leg-extension training three times a week for 9 weeks. Maximum tendon force (Ft) was calculated from maximum voluntary contraction (MVC) torque, corrected for agonist and antagonist muscle activation, and moment arm length (dPT) before and after training. QF PCSA was calculated as the sum of the four component muscle volumes, each divided by its fascicle length. Dividing Ft by the sum of the component muscle PCSAs, each multiplied by the cosine of the respective fascicle pennation angle, provided QF specific tension. Results:, MVC torque and QF activation increased by 31% (P < 0.01) and 3% (P < 0.05), respectively, but there was no change in antagonist co-activation or dPT. Subsequently, Ft increased by 27% (P < 0.01). QF volume increased by 6% but fascicle length did not change in any of the component muscles, leading to a 6% increase in QF PCSA (P < 0.05). Fascicle pennation angle increased by 5% (P < 0.01) but only in the vastus lateralis muscle. Consequently, QF specific tension increased by 20% (P < 0.01). Conclusion:, An increase in human muscle specific tension appears to be a real consequence of resistance training rather than being an artefact of measuring errors but the underlying cause of this phenomenon remains to be determined. [source] Soleus T reflex modulation in response to spinal and tendinous adaptations to unilateral lower limb suspension in humansACTA PHYSIOLOGICA, Issue 3 2008O. R. Seynnes Abstract Aim:, To investigate the influence of tendinous and synaptic changes induced by unilateral lower limb suspension (ULLS) on the tendon tap reflex. Methods:, Eight young men underwent a 23-day period of ULLS. Muscle cross-sectional area (CSA), torque and electromyographic (EMG) activity of the plantar flexor muscles (normalized to the M wave), Achilles tendon,aponeurosis mechanical properties, soleus (SOL) H and T reflexes and associated peak twitch torques were measured at baseline, after 14 and 23 days of ULLS, and 1 week after resuming ambulatory activity. Results:, Significant decreases in muscle CSA (,9%), in maximal voluntary torque (,10%) and in the associated SOL EMG activity (,16%) were found after ULLS (P < 0.05). In addition to a 36% (P < 0.01) decrease in tendon,aponeurosis stiffness, normalized H reflex increased by 35% (P < 0.05). An increase in the slope (28%, P < 0.05) and intercept (85%, P < 0.05) of the T reflex recruitment curve pointed to an increase in the gain and to a decrease in the sensitivity of this reflex, possibly resulting from the decrease in the tendon,aponeurosis stiffness at low forces. Following ULLS, changes in tendinous stiffness correlated with changes in neuromuscular efficiency (peak twitch torque to reflex ratio) at higher tendon tap forces. Conclusion:, These findings point out the dual and antagonistic influences of spinal and tendinous adaptations upon the tendon tap reflex in humans under conditions of chronic unloading. These observations have potential implications for the sensitivity of the short-latency Ia stretch response involved in rapid compensatory contractions to unexpected postural perturbations. [source] Measurement of the force and torque produced in the calcium response of reactivated rat sperm flagellaCYTOSKELETON, Issue 1 2001Mark J. Moritz Abstract Rat sperm that are demembranated with Triton X-100 and reactivated with Mg-ATP show a strong mechanical response to the presence of free calcium ion. At pCa < 4, the midpiece region of the flagellum develops a strong and sustained curvature that gives the cell the overall appearance of a fishhook [Lindemann and Goltz, 1988: Cell Motil. Cytoskeleton 10:420,431]. In the present study, the force and torque that maintain the calcium-induced hook have been examined quantitatively. In addition, full-length and shortened flagella were manipulated to evaluate the plasticity of the hooks and determined the critical length necessary for maintaining the curvature. The hooks were found to be highly resilient, returning to their original configuration (>95%) after being straightened and released. The results from manipulating the shortened flagella suggest that the force holding the hook in the curved configuration is generated in the basal 60 ,m of the flagellum. The force required to straighten the calcium-induced hooks was measured with force-calibrated glass microprobes, and the bending torque was calculated from the measured force. The force and torque required to straighten the flagellum were found to be proportional to the change in curvature of the hooked region of the flagellum, suggesting an elastic-like behavior. The average torque to open the hooks to a straight position was 2.6 (±1.4) × 10 -7 dyne × cm (2.6 × 10 -14 N × m) and the apparent stiffness was 4.3 (±1.3) × 10 -10 dyne × cm2 (4.3 × 10 -19 N × m2). The stiffness of the hook was determined to be approximately one quarter the rigor stiffness of a rat sperm flagellum measured under comparable conditions. Cell Motil. Cytoskeleton 49:33,40, 2001. © 2001 Wiley-Liss, Inc. [source] Changes in hip spasticity and strength following selective dorsal rhizotomy and physical therapy for spastic cerebral palsyDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 4 2002Jack R Engsberg PhD Hip adductor spasticity and strength in participants with cerebral palsy (CP) were quantified before and after selective dorsal rhizotomy (SDR) and intensive physical therapy. Twenty-four participants with cerebral palsy (CP group) and 35 non-disabled participants (ND controls) were tested with a dynamometer (CP group: mean age 8 years 5 months, 13 males, 11 females; ND group: mean age 8 years 6 months, 19 males, 16 females). According to the Gross Motor Function Classification System (GMFCS), of the 24 participants with CP, eight were at level I, six were at level II, and 10 participants were at level III. For the spasticity measure, the dynamometer quantified the resistive torque of the hip adductors during passive abduction at 4 speeds. The adductor strength test recorded a maximum concentric contraction. CP group spasticity was significantly reduced following SDR and adductor strength was significantly increased after surgery. Both pre- and postoperative values remained significantly less than the ND controls. Spasticity results agreed with previous studies indicating a reduction. Strength results conflicted with previous literature subjectively reporting a decrease following SDR. However, results agreed with previous objective investigations examining knee and ankle strength, suggesting strength did not decrease following SDR. [source] Simplified seismic analysis of asymmetric building systemsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2007Jui-Liang Lin Abstract The paper reviews the uncoupled modal response history analysis (UMRHA) and modal pushover analysis (MPA) procedure in the analysis of asymmetric structures. From the pushover curves in ADRS format, showing the relationships of base shear versus roof translation and base torque versus roof rotation, a bifurcating characteristic of the pushover curves of an asymmetric structure is observed. A two-degree-of-freedom (2DOF) modal stick is constructed using lump mass eccentrically placed at the end of beam which is connected with the column by a rotational spring. By converting the equation of motion of a whole structure into 2DOF modal equations, all of the elastic properties in the 2DOF modal sticks can be determined accurately. A mathematical proof is carried out to demonstrate that the 2DOF modal stick is consistent with the single-degree-of-freedom (SDOF) modal stick at elastic state. The bifurcating characteristic of modal pushover curves and the interaction of modal translation and rotation can be considered rationally by this 2DOF modal stick. In order to verify the effectiveness of this proposed 2DOF modal stick, a two-storey asymmetric building structure was analysed by the UMRHA procedure incorporating this novel 2DOF modal sticks (2DMPA) and conventional SDOF modal sticks (SDMPA), respectively. The analytical results are compared with those obtained by nonlinear response history analysis (RHA). It is illustrated that the accuracy of the rotational response histories obtained by 2DMPA is much better than those obtained by SDMPA. Consequently, the estimations of translational response histories on flexible side (FS) and stiff side (SS) of the building structure are also improved. Copyright © 2006 John Wiley & Sons, Ltd. [source] A modal pushover analysis procedure to estimate seismic demands for unsymmetric-plan buildingsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2004Anil K. Chopra Abstract An Erratum has been published for this article in Earthquake Engng. Struct. Dyn. 2004; 33:1429. Based on structural dynamics theory, the modal pushover analysis (MPA) procedure retains the conceptual simplicity of current procedures with invariant force distribution, now common in structural engineering practice. The MPA procedure for estimating seismic demands is extended to unsymmetric-plan buildings. In the MPA procedure, the seismic demand due to individual terms in the modal expansion of the effective earthquake forces is determined by non-linear static analysis using the inertia force distribution for each mode, which for unsymmetric buildings includes two lateral forces and torque at each floor level. These ,modal' demands due to the first few terms of the modal expansion are then combined by the CQC rule to obtain an estimate of the total seismic demand for inelastic systems. When applied to elastic systems, the MPA procedure is equivalent to standard response spectrum analysis (RSA). The MPA estimates of seismic demand for torsionally-stiff and torsionally-flexible unsymmetric systems are shown to be similarly accurate as they are for the symmetric building; however, the results deteriorate for a torsionally-similarly-stiff unsymmetric-plan system and the ground motion considered because (a) elastic modes are strongly coupled, and (b) roof displacement is underestimated by the CQC modal combination rule (which would also limit accuracy of RSA for linearly elastic systems). Copyright © 2004 John Wiley & Sons, Ltd. [source] New structures of vector control systems for permanent magnet synchronous motors with core lossELECTRICAL ENGINEERING IN JAPAN, Issue 3 2010Shinji Shinnaka Abstract This paper investigates and proposes new system structures for vector control of permanent-magnet synchronous motors (PMSMs) with core loss. The proposed vector control systems have the following versatile features. (a) The systems employ the structures allowing control of the stator current through control of the load current. (b) The systems employ unique "stator voltage feedback-use" structures in order to accomplish simply the load current control. (c) The produced torque is directly related to the load current, and the precise torque control can be attained through the load current control. (d) The relation between produced torque and the load current is nonlinear for salient-pole PMSMs similar to the case of no core loss, and a variety of the load current commands can be selected from viewpoints of minimum loss and/or wide speed range drives. The system structures add no constraint to the selection of the load current commands. (e) In addition to the torque control, the speed control can be allowed, where linearity between output of the speed controller and produced torque is kept. The validity of versatile features is verified through the numerical experiments. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(3): 28,39, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/eej.20910 [source] Damping torque analysis for DC bus implemented damping control,EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2010W. Du Abstract Damping torque analysis is a well-developed technique for understanding and studying power system oscillations. This paper presents the applications of damping torque analysis for DC bus implemented damping control in power transmission networks in two examples. The first example is the investigation of damping effect of shunt voltage source converter (VSC) based flexible AC transmission systems (FACTS) voltage control, i.e. static synchronous compensator (STATCOM) voltage control. It is shown in the paper that STATCOM voltage control mainly contributes synchronous torque and hence has little effect on the damping of power system oscillations. The second example is the damping control implemented by a battery energy storage system (BESS) installed in a power system. Damping torque analysis reveals that when BESS damping control is realized by regulating exchange of active and reactive power between the BESS and power system, respectively, BESS damping control exhibits different properties. It is concluded by damping torque analysis that BESS damping control implemented by regulating active power is better with less interaction with BESS voltage control and more robust to variations of power system operating conditions. In the paper, all analytical conclusions obtained are demonstrated by simulation results of example power systems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Discrete modeling of the air-gap field of synchronous machines for computation of torque and radial forcesEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 2 2008Marc Bekemans Abstract In this paper, we exploit the multiple symmetries and the discrete character of the current distribution to express the torque and the radial forces in a PM synchronous machine. Under some assumptions, the magnetic field can be built with a limited number of discrete functions. These functions can constitute an orthogonal base of a vector space for the representation of the machine magnetic state. The representation of the stator and rotor fields as vectors of this space makes it possible to interpret the torque and the radial forces from the concept of distance between these vectors. The proposed method for torque and radial forces computation is well suited for a real-time evaluation and can be used for a generalization of the Field-Oriented Control to machines with non-sinusoidal flux distribution. Copyright © 2007 John Wiley & Sons, Ltd. [source] Small-variation linear model of the three-phase double-fed induction motor under synchronous operation: stabilityEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2005D. Pereira Gonzaga Abstract The double-fed induction motor (DFIM) is analysed in this paper with regard to stability. Firstly, its characteristic equation is obtained by means of a linear model for small variations, with the stator resistance equal to zero. The range of speeds for which the DFIM/Load system presents stable synchronous operation is obtained by applying the Routh,Hurwitz Criterion to the characteristic equation. Secondly, by employing the equation for the steady-state electromagnetic torque, with a non-zero stator resistance, another range of speeds giving stable synchronous operation is obtained, and confirmed by some experimental results. In order to confirm the stability, some results of the DFIM/Load system simulation and the characteristic equation root-locus are also presented. Copyright © 2005 John Wiley & Sons, Ltd. [source] Electromagnetic torque of a synchronous machine during a single out-of-phase reclosingEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2000A. C. Ammari The adoption of single-pole switching for a radial transmission line which connects large synchronous machines to the power system would submit these machines to repetitive mechanical stress. To evaluate the total mechanical stress, it is first necessary to determine the electromagnetic torque and to evaluate its transient maximum values at reclosing. In this paper, maximum values of the electromagnetic transient torque at single-pole reclosing are first computed using a simplified analytical approach. The analytical results are then validated by numerical simulations and by an experimental test on a laboratory synchronous machine. It will be shown that single-pole reclosing would be, in the worst case, as restricting as three out-of-phase synchronisation. [source] Die Festgesteinsschildmaschine, Interaktion zwischen Gebirge und Vortriebssystem, Kompetenz- und RisikoverteilungGEOMECHANICS AND TUNNELLING, Issue 6 2008Harald Lauffer Dipl.-Ing. Festgesteinsschildmaschinen mit ihren Bauformen Einfachschild (TBM-S) und Doppelschild (TBM-DS) haben sich einen wesentlichen Markanteil erobert. Sie werden für einen Vortrieb im Festgestein geringer Standzeit im nachbrüchigen bis gebrächen Gebirge empfohlen. Die Überlegungen über die Interaktion zwischen Gebirge und Vortriebssystem bestätigen die Annahme, dass eine systematische Gebirgsstützung weder im Schneidradbereich noch im Schildbereich gegeben ist. Unter gewissen Umständen kann es jedoch im Schildbereich zur Ausbildung eines sekundären Traggewölbes im aufgelockerten Gebirge kommen. Es zeigt sich, dass vermutete negative Wirkungen des Schneidrads auf die Ortsbrust nicht auftreten und das Lösen weitgehend schonend erfolgt. Der Einsatz von Schaum zur Auffüllung von Nachbrüchen und zur Stabilisierung des Gebirges hat sich bewährt. Portalbereiche und Bereiche geringer Überdeckung sind erforderlichenfalls möglichst vorweg von über Tage aus zu ertüchtigen. Im Fall von Nachbruch- und Verbrucherscheinungen an der Ortsbrust und der Tunnelleibung können Maschinenparameter wie Drehmoment und Vorschubkraft und Bohrkopfdetails das Verhalten einer Festgesteinsschildmaschine in dieser Grenzsituation stark beeinflussen. Da das Baugrundrisiko grundsätzlich dem Auftraggeber zuzuordnen ist, muss sich der Auftraggeber mit diesen Szenarien intensiv auseinandersetzten und eventuell entsprechende Vorgaben für die Gestaltung der TBM machen ohne den Auftragnehmer allzu sehr einzuschränken. Für einen erfolgreichen Vortrieb mit Festgesteinsschildmaschinen im Grenzbereich ist eine partnerschaftliche Zusammenarbeit in allen Phasen der Bauabwicklung von der Vergabe, über die Abstimmung der TBM-Details bis zur Abwicklung des Vortriebs von größerer Bedeutung. Kürzere und längere, planbare und ungeplante Unterbrüche sind bei TBM-Vortrieben unvermeidbar und systembedingt. Die baubetrieblichen Risiken von Unterbrüchen sind der Auftragnehmer-Sphäre, die Folgen für das Verhalten des Gebirges aufgrund einer verlängerten Stehzeit sind der Risikosphäre des Auftraggebers zuzuordnen. The Hard-Rock Shield Machine, Interaction between Rock and TBM System, Distribution of Responsibility and Risk Single-shield and Double-shield machines have gained a significant market share. They are recommended for tunnel driving in unstable and friable rock with short stand-up time. Looking into the interaction between rock and TBM system confirms the assumption that a systematic rock support through the cutterhead or shield does not exist. But it is possible that under specific circumstances a secondary-load bearing arch is formed inside a loosened rock mass above a shield. It appears that the suspected negative effects of the cutter head on the tunnel face do not exist and that tunnel boring is a relatively gentle process. Filling up overbreak volumes with foam has proved successful in stabilising loosening rock mass. The portal areas and areas of low overburden should be treated from above-ground well in advance if necessary. In case of massive overbreak or even downfalls TBM data such as cutterhead torque and thrust or cutterhead details can influence the behaviour of the TBM significantly. As the ground risk rests basically with the owner, he has to give serious consideration to such situations. He may have to specify basic TBMdata and TBM details without imposing too many restrictions on the contractor. A trustful partnership between owner and contractor during all stages of tunnel driving is of utmost importance for successful tunnel boring with hard-rock shield machines in difficult rock conditions. [source] Magnetic and viscous coupling at the core,mantle boundary: inferences from observations of the Earth's nutationsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2007B. A. Buffett SUMMARY Dissipative core,mantle coupling is evident in observations of the Earth's nutations, although the source of this coupling is uncertain. Magnetic coupling occurs when conducting materials on either side of the boundary move through a magnetic field. In order to explain the nutation observations with magnetic coupling, we must assume a high (metallic) conductivity on the mantle side of the boundary and a rms radial field of 0.69 mT. Much of this field occurs at short wavelengths, which cannot be observed directly at the surface. High levels of short-wavelength field impose demands on the power needed to regenerate the field through dynamo action in the core. We use a numerical dynamo model from the study of Christensen & Aubert (2006) to assess whether the required short-wavelength field is physically plausible. By scaling the numerical solution to a model with sufficient short-wavelength field, we obtain a total ohmic dissipation of 0.7,1 TW, which is within current uncertainties. Viscous coupling is another possible explanation for the nutation observations, although the effective viscosity required for this is 0.03 m2 s,1 or higher. Such high viscosities are commonly interpreted as an eddy viscosity. However, physical considerations and laboratory experiments limit the eddy viscosity to 10,4 m2 s,1, which suggests that viscous coupling can only explain a few percent of the dissipative torque between the core and the mantle. [source] Role of Chronic Infection and Inflammation in the Gastrointestinal Tract in the Etiology and Pathogenesis of Idiopathic ParkinsonismHELICOBACTER, Issue 4 2005Part 2: Response of Facets of Clinical Idiopathic Parkinsonism to Helicobacter pylori Eradication. ABSTRACT Background., Links between etiology/pathogenesis of neuropsychiatric disease and infection are increasingly recognized. Aim., Proof-of-principle that infection contributes to idiopathic parkinsonism. Methods., Randomized, double-blind, placebo-controlled efficacy study of proven Helicobacter pylori eradication on the time course of facets of parkinsonism. Intervention was 1 week's triple eradication therapy/placebos. Routine deblinding at 1 year (those still infected received open-active), with follow-up to 5 years post-eradication. Primary outcome was mean stride length at free-walking speed, sample size 56 for a difference, active vs. placebo, of 3/4 (between-subject standard deviation). Recruitment of subjects with idiopathic parkinsonism and H. pylori infection was stopped at 31, because of marked deterioration with eradication failure. Interim analysis was made in the 20 who had reached deblinding, seven of whom were receiving antiparkinsonian medication (long- t1/2, evenly spaced) which remained unchanged. Results., Improvement in stride-length, on active (n = 9) vs. placebo (11), exceeded size of effect on which the sample size was calculated when analyzed on intention-to-treat basis (p = .02), and on protocol analysis of six weekly assessments, including (p = .02) and excluding (p = .05) those on antiparkinsonian medication. Active eradication (blind or open) failed in 4/20, in whom B-lymphocyte count was lower. Their mean time course was: for stride-length, ,243 (95% CI ,427, ,60) vs. 45 (,10, 100) mm/year in the remainder (p = .001); for the ratio, torque to extend to flex relaxed arm, 349 (146, 718) vs. 58 (27, 96)%/ year (p < .001); and for independently rated, visual-analog scale of stance,walk videos (worst,best per individual , 0,100 mm), ,64 vs. ,3 mm from anterior and ,50 vs. 11 lateral (p = .004 and .02). Conclusions., Interim analysis points to a direct or surrogate (not necessarily unique) role of a particular infection in the pathogenesis of parkinsonism. With eradication failure, bolus release of antigen from killed bacteria could aggravate an effect of ongoing infection. [source] Energy model based loss-minimized speed control of induction motor with a full-order observerIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 1 2006Mohammad Abdul Mannan Student Member Abstract In this paper, a loss-minimization algorithm is developed to achieve maximum efficiency in terms of slip frequency. The optimal value of slip frequency can be obtained by minimizing all controllable losses of the induction motor (IM). The ratio of magnetic energy converted to torque (WT) to magnetic energy stored in the rotating field (Wq) is defined in terms of slip frequency to obtain an error function that is used to design a controller to achieve the desired speed. Since the energy model of the IM can be expressed by the multi-input and multi-output (MIMO) system, an MIMO optimal regulator is proposed to achieve the desired speed with maximum efficiency. To design an optimal regulator, it is necessary to measure all state quantities. But WT and Wq cannot be measured directly. Therefore, a full-order observer is proposed to estimate these state quantities. The gains of the observer system are calculated by using the pole placement technique. Consequently, the observer system becomes stable. The performance of the proposed controller and observer system are verified by using simulation. With regard to the simulation results, it can be concluded that the desired speed can be achieved by using the proposed controller and the unknown state quantities can be estimated properly by using the proposed observer system. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Root canal preparation with FlexMaster: asessment of torque and force in relation to canal anatomyINTERNATIONAL ENDODONTIC JOURNAL, Issue 12 2003W. Hübscher Abstract Aim, To investigate physical parameters of FlexMaster nickel-titanium instruments while preparing curved canals in maxillary molars in vitro. Methodology, A torque-testing platform was used to prepare root canals in 11 extracted human maxillary molars with FlexMaster rotary instruments. Peak torque and force was registered along with numbers of rotations required to shape the canals. Canals were divided into ,wide' and ,constricted' groups depending on canal volumes assessed by microcomputed tomography. Resistance to cyclic fatigue was also tested. Mean scores for each instrument type were calculated and statistically compared using anova and Scheffé post hoc tests. Results, Mean torque varied between 0.1 ± 0.1 and 0.8 ± 0.5 N cm while mean force ranged from 4.2 ± 2.0 to 7.3 ± 3.5 N. Mean numbers of rotations totalled up to 18. All three variables registered showed weak correlations to preoperative canal volumes (P < 0.01) and differed significantly between ,wide' and ,constricted' canals (P < 0.001). Numbers of rotations to fracture in a cyclic fatigue test were between 348 and 1362. Conclusion, FlexMaster instruments generated low torque scores and were highly resistant to cyclic fatigue, whilst three instruments fractured in extremely narrow canals. Consequently, more research is required to limit fracture incidence and to optimize instrumentation guidelines. [source] The effect of cleaning procedures on fracture properties and corrosion of NiTi filesINTERNATIONAL ENDODONTIC JOURNAL, Issue 11 2003P. Y. Z. O'Hoy Abstract Aim, To evaluate the effect of repeated cleaning procedures on fracture properties and corrosion of nickel-titanium (NiTi) files. Methodology, New NiTi instruments were subjected to 2, 5 and 10 cleaning cycles with the use of either diluted bleach (1% NaOCl) or Milton's solution (1% NaOCl plus 19% NaCl) as disinfectant. Each cleaning cycle consisted of scrubbing, rinsing and immersing in NaOCl for 10 min followed by 5 min of ultrasonication. Files were then tested for torsional failure and flexural fatigue, and observed for evidence of corrosion using scanning electron microscope (SEM). Four brands of NiTi files were immersed in either Milton's solution or diluted bleach overnight and evaluated for corrosion. Results, Up to 10 cleaning cycles did not significantly reduce the torque at fracture or number of revolutions to flexural fatigue (P > 0.05, two-way anova), although decreasing values were noted with increasing number of cleaning cycles using Milton's solution. No corrosion was detected on the surface of these files. Files immersed in 1% NaOCl overnight displayed a variety of corrosion patterns. The extent of corrosion was variable amongst different brands of files and amongst files in each brand. Overall, Milton's solution was much more corrosive than diluted bleach. Corrosion of file handles was often extreme. Conclusions, Files can be cleaned up to 10 times without affecting fracture susceptibility or corrosion, but should not be immersed in NaOCl overnight. Milton's solution is much more corrosive than bleach with the same NaOCl concentration. [source] ProTaper rotary root canal preparation: assessment of torque and force in relation to canal anatomyINTERNATIONAL ENDODONTIC JOURNAL, Issue 2 2003O. A. Peters No abstract is available for this article. [source] Influence of rotational speed, torque and operator proficiency on failure of Greater Taper filesINTERNATIONAL ENDODONTIC JOURNAL, Issue 1 2002G. M. Yared Abstract Aim The purpose of this study was to evaluate the influence of rotational speed, torque, and operator experience on the incidence of locking, deformation, and separation of instruments when using a specific Ni,Ti rotary instrumentation technique in extracted human teeth. Methodology Greater Taper Ni,Ti rotary instruments (GT) were used in a crown-down technique. In one group (rotational speed evaluation) of canals (n = 300) speeds of 150, 250 and 350 r.p.m. (subgroups 1, 2 and 3) were used. Each one of the subgroups included 100 canals. In a second group (evaluation of torque) (n = 300) torque was set at 20, 30 and 55 Ncm (subgroups 4, 5 and 6). In the third group (evaluation of operator proficiency) (n = 300) three operators with varying experience (subgroups 7, 8 and 9) were also compared. Each subgroup included the use of 10 sets of GT rotary instruments and 100 canals of extracted human molars. Each set of instruments was used in up to 10 canals and sterilized before each case. NaOCl 2.5% was used as an irrigant. The number of locked, deformed, and separated instruments was recorded for each group. Statistical analysis was carried out with pairwise comparisons using Fisher's exact tests for each of the failure type. Results When the influence of rotational speed was evaluated, instrument deformation and separation did not occur in subgroups 1 (150 r.p.m.), 2 (250 r.p.m.), and 3 (350 r.p.m.). Instrument locking occurred in subgroup 3 only. Statistical analysis demonstrated a significant difference between the 150 and 350 r.p.m. groups and between the 250 and 350 r.p.m. groups with respect to instrument locking. In torque evaluation, neither separation, deformation nor locking occurred during the use of the instruments, at 150 r.p.m., and at the different torque values. When the operators were compared, although two instruments were separated in canals prepared by the least experienced operator, Fisher's exact tests did not demonstrate a significant difference between the three subgroups. Instrument locking, deformation, and separation did not occur with the most experienced operator. None of the instruments separated with the trained operator. Conclusions Preclinical training in the use of the GT rotary instruments when used with a crown-down technique at 150 r.p.m. was crucial in avoiding instrument separation and reducing the incidence of instrument locking and deformation. [source] An in vitro comparison of canal preparation using two automated rotary nickel,titanium instrumentation techniquesINTERNATIONAL ENDODONTIC JOURNAL, Issue 4 2000S. J. Jardine Abstract Aim The aim of this study was to compare the efficacy of root canal preparation using two automated rotary nickel,titanium instrumentation techniques with a double flared balanced forces hand preparation technique, using stainless steel files in extracted human teeth. Methodology Sixty root canals in extracted human teeth were matched for curvature, length and diameter and divided evenly between three groups (group 1 = double flare using Flexofiles®, group 2 = rotary nickel,titanium using McXIM® instruments and group 3 = rotary nickel,titanium using Profile® .04 TaperTM Series 29 instruments). The instruments were used according to the manufacturer's instructions in a torque controlled motor and handpiece (groups 2 and 3) and according to a predetermined procedure in group 1. A standardized radiographic technique using mercury as a contrast medium was used to evaluate the canal shape before and after preparation in the plane of maximum curvature. The pre- and postoperative radiographic images were compared against each other and with a predicted ,ideal preparation' calculated from a projection of the final instrument dimensions. The outcome measures were changes in canal dimensions as quantified by measuring the changes in the position of the inner and outer wall at 1 mm intervals. Alteration in canal curvature could be inferred by comparison with the ideal preparation. Results The degree of canal curvature did not influence the effectiveness of any of the techniques. The results showed no statistically significant differences in the outcome measures between the groups (two-way anova). There were no significant differences in canal wall position changes at any level except the apical three, where significantly less change occurred in all groups (P = 1%). Instruments fractured in three canals, with acute curves in groups 2 and 3. Conclusions Canal curvatures were equally and well maintained following preparation in all the groups, as long as the instrument did not fracture. [source] Use of neural networks for the prediction of frictional drag and transmission of axial load in horizontal wellboresINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 2 2003Tanvir Sadiq Abstract The use of mud motors and other tools to accomplish forward motion of the bit in extended reach and horizontal wells allows avoiding large amounts of torque caused by rotation of the whole drill string. The forward motion of the drill string, however, is resisted by excessive amount of friction. In the presence of large compressive axial loads, the drill pipe or coiled tubing tends to buckle into a helix in horizontal boreholes. This causes additional frictional drag resisting the transmission of axial load (resulting from surface slack-off force) to the bit. As the magnitude of the frictional drag increases, a buckled pipe may become ,locked-up' making it almost impossible to drill further. In case of packers, the frictional drag may inhibit the transmission of set-up load to the packer. A prior knowledge of the magnitude of frictional drag for a given axial load and radial clearance can help avoid lock-up conditions and costly failure of the tubular. In this study a neural network model, for the prediction of frictional drag and axial load transmission in horizontal wellbores, is presented. Several neural network architectures were designed and tested to obtain the most accurate prediction. After cross-validation of the Back Propagation Neural Network (BPNN) algorithm, a two-hidden layer model was chosen for simultaneous prediction of frictional drag and axial load transmission. A comparison of results obtained from BPNN and General Regression Neural Network (GRNN) algorithms is also presented. Copyright © 2002 John Wiley & Sons, Ltd. [source] Underwater shock-free surface,structure interactionINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2003T. G. Liu Abstract A recently developed numerical method has been employed to evaluate the influence of free surface on shock loading in a cylindrical underwater explosion carried out near to both a free surface and a cylindrical rigid structure. In the usual simulation of underwater shock,structure interaction, the shock loading tends to accelerate/move the (rigid) structure only in the resultant force direction. The presence of a free surface and explosion bubble suggests the existence of a reverse loading and provides an additional torque (rotational moment) on the loaded structure. The numerical results also demonstrate the possible existence of a cavitation zone/region in the immediate vicinity of the free surface due to the near-surface underwater explosion. Copyright © 2003 John Wiley & Sons, Ltd. [source] Three-dimensional immersed boundary conditions for moving solids in the lattice-Boltzmann method,INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2007O. Erik Strack Abstract This paper establishes the range of validity for a previously published three-dimensional moving solid boundary condition for the lattice-Boltzmann method. This method was reasonably formulated from a mass and momentum balance perspective, but was only verified for a small range of (primarily two-dimensional) problems. One of the advantages of this boundary condition is that it offers resolution at the sub-grid scale, allowing for accurate and stable calculation of the force and torque for solids which are moving through a lattice, even for small solid sizes relative to the computational grid size. We verify the boundary condition for creeping flows by comparison to analytical solutions that include both the force and the torque on fixed and moving spheres, and then follow this with comparisons to experimental and empirical results for both fixed as well moving spheres in inertial flows. Finally, we compare simulation results to numerical results of other investigators for the settling of an offset sphere and the drafting,kissing,tumbling of two sedimenting spheres. We found that an accurate calculation of the collision-operator weighting used to obtain sub-grid-scale resolution was necessary in order to prevent spikes in the velocities, forces, and moments when solid objects cross-computational cells. The wide range of comparisons collected and presented in this paper can be used to establish the validity of other numerical models, in addition to the one examined here. Published in 2007 by John Wiley & Sons, Ltd. [source] On the orbital motion of a rotating inner cylinder in annular flowINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2007Shunxin Feng Abstract In this paper, numerical calculations have been performed to analyse the influence of the orbital motion of an inner cylinder on annular flow and the forces exerted by the fluid on the inner cylinder when it is rotating eccentrically. The flow considered is fully developed laminar flow driven by axial pressure gradient. It is shown that the drag of the annular flow decreases initially and then increases with the enhancement of orbital motion, when it has the same direction as the inner cylinder rotation. If the eccentricity and rotation speed of the inner cylinder keep unchanged (with respect to the absolute frame of reference), and the orbital motion is strong enough that the azimuthal component (with respect to the orbit of the orbital motion) of the flow-induced force on the inner cylinder goes to zero, the flow drag nearly reaches its minimum value. When only an external torque is imposed to drive the eccentric rotation of the inner cylinder, orbital motion may occur and, in general, has the same direction as the inner cylinder rotation. Under this condition, whether the inner cylinder can have a steady motion state with force equilibrium, and even what type of motion state it can have, is related to the linear density of the inner cylinder. Copyright © 2006 John Wiley & Sons, Ltd. [source] Microstructure development in concentrated suspensions in a spinning ball rheometer,INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2006Anne M. Grillet Abstract The spinning ball rheometer has been proposed as a method to measure the microstructure effect on the bulk rheological properties of concentrated suspensions. Recent experiments have shown that the measured extra torque on the spinning ball decreases as the radius of the spinning ball becomes comparable to the size of the suspended particle. We have performed a series of three-dimensional boundary element calculations of the rheometer geometry to probe the microstructure effects that contribute to that apparent slip. We present a series of quasi-static results based on random initial configurations as well as fully three-dimensional transient calculations, both of which are compared to the available experimental data. For the two cases, the apparent viscosity decreased as the size of the spinning ball decreased relative to the suspended particle. Comparison of the quasi-static and transient simulations indicates that the microstructure development is critical even at short times. In the transient calculations, the viscosity was observed to increase substantially relative to the torque based on the random initial configuration. Published in 2005 by John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||||||||||||||