Academic literature on the topic 'Joints radiaux segmentés'
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Journal articles on the topic "Joints radiaux segmentés"
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Szyszkowski, W., K. Fielden, and D. W. Johnson. "Self-Locking Satellite Boom With Flexure-Mode Joints." Applied Mechanics Reviews 50, no. 11S (November 1, 1997): S225—S231. http://dx.doi.org/10.1115/1.3101840.
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Dynamic analysis, numerical simulation, and experimental results of the deployment of a self-locking lightweight satellite boom are presented. The joints that connect the two segments of the boom are made of flexible semi-cylindrical shells. During the deployment, the shells undergo large deflections and large rotations, up to π radians. The boom is to be launched in the folded configuration and then deployed from a rotating satellite. In the straight configuration, after locking the joints, the boom should be stiff enough to precisely position a heavy sensor in a required location. Several models of the boom are considered for analysis. In order to optimize the sensor trajectory and the locking sequence, a model that includes stiffness of the joints but neglects flexibility of the links is developed. The joints, which are prone to instabilities and snap-through behavior, are analyzed using large deflection quasistatic approach. Finally, nonlinear dynamics FEA is performed to simulate the deployment of the complete boom. The simulation is compared with experimental results obtained from the preliminary tests.
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Wickham, J. B., J. M. M. Brown, R. Green, and D. J. McAndrew. "MUSCLES WITHIN MUSCLES: THE CLASSICAL TRIPHASIC EMG BURST AND ITS APPLICABILITY TO SEGMENTS OF LARGE RADIATE AGONIST/ANTAGONIST MUSCLES." Journal of Musculoskeletal Research 08, no. 02n03 (June 2004): 107–17. http://dx.doi.org/10.1142/s0218957704001272.
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The purpose of the current study was to determine if the classically described triphasic EMG burst was applicable in describing the EMG patterns across the breadth of three large radiate muscles during the production of a rapid shoulder joint movement. Miniature (6.5 mm inter-electrode distance) bipolar surface electrodes were placed across the breadth of the pectoralis major (6 off), latissimus dorsi (6 off) and the deltoid (7 off). Subjects performed a series of rapid shoulder joint adduction movements (<400 ms) against the resistance of a free weight and pulley apparatus whilst seated in an experimental chair. EMG data sampled from the multiple recording sites of the three muscles identified four different types of EMG waveforms. This was based on the presence, or absence, of multiple bursts, the length of each burst and the level of the silent period between bursts from the same segment of a muscle. The four bursts included a one-burst pattern, a one-continuous burst pattern, a two-continuous burst pattern and a two non-continuous burst pattern. Upon further analysis it was established that a relationship existed between the type of burst displayed by a segment and the functional role of that segment (prime mover, synergist, primary or secondary antagonist), hence a uniform type of burst pattern was not apparent across the breadth of the agonist (pectoralis major and latissimus dorsi) and antagonist (deltoid) muscles. It was evident that the triphasic EMG burst was most applicable for the EMG patterns arising from the prime mover segments of the pectoralis major and the latissimus dorsi and the primary antagonist segment of the deltoid. In conclusion, these results suggest that caution is warranted if stating that popular motor control theories10, 11 based on EMG patterns produced by small agonist and antagonist muscles during rapid limb movement, apply to all segments of large radiate muscles.
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Hoffer, J. A., T. R. Leonard, C. L. Cleland, and T. Sinkjaer. "Segmental reflex action in normal and decerebrate cats." Journal of Neurophysiology 64, no. 5 (November 1, 1990): 1611–24. http://dx.doi.org/10.1152/jn.1990.64.5.1611.
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1. The objective of this study was to evaluate the action of the stretch reflex on the ankle extensor muscles of normal and decerebrate cats. 2. Experiments were performed on nine freely standing, unrestrained cats and repeated after decerebration at the premammillary level. The length, force, and electromyograph (EMG) of the soleus (SOL) and lateral gastrocnemius (LG) muscles were recorded with the use of implanted transducers and electrodes. 3. The left ankle joint was unexpectedly and reproducibly dorsiflexed by briefly stimulating the common peroneal (CP) nerve with electrodes within an implanted nerve cuff. The ensuing twitch contractions of the ankle dorsiflexor muscles stretched the ankle extensor muscles by 0.3-2.0 mm. Lidocaine was infused into another nerve cuff proximal to the stimulation site, to reversibly block the central propagation of evoked volleys in the CP nerve. 4. Reflex action before and after decerebration was measured from the responses to perturbations of similar amplitude and duration delivered at approximately matched background values of muscle length and force. In most cats the temperature of the hindlimb was monitored with an implanted thermistor and was restored to normal values with radiant heat after decerebration. 5. A stretch imposed on the tonically active ankle extensor muscles immediately caused a considerable rise in the force recorded from the triceps tendon. Within 30-40 ms the triceps force peaked, reaching a value 10-20 N greater than background, and then rapidly declined while the extensor muscles were still lengthening. The initial rise in force preceded any change in triceps EMG. It was attributed to the intrinsic viscoelasticity of the stretched muscles and tendons. After decerebration the magnitude and timing of the initial force peak did not change. 6. A short-latency reflex EMG burst was typically recorded from both the SOL and LG muscles, starting 11-17 ms after stimulus onset. After decerebration the area of the reflex EMG burst increased in all nine cats, typically by a factor of 2 or 3. 7. After decerebration a second, smaller increase in force was typically observed starting 60-80 ms after onset of stretch. This later force rise, interpreted to be of reflex origin, was rarely apparent in normal cats. 8. Decerebration introduced consistent modifications in postural behavior that were revealed by pushing down on the back of quietly standing cats. In normal cats, after brief pushes that stretched the ankle extensor muscles by 1-2 mm, the EMG, force, and length quickly stabilized near their initial values.(ABSTRACT TRUNCATED AT 400 WORDS)
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Sinkjaer, T., and J. A. Hoffer. "Factors determining segmental reflex action in normal and decerebrate cats." Journal of Neurophysiology 64, no. 5 (November 1, 1990): 1625–35. http://dx.doi.org/10.1152/jn.1990.64.5.1625.
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1. In the companion paper the gain of the stretch reflex in the ankle extensor muscles of normal cats was shown to increase after decerebration. The objectives of this study were 1) to identify the origin of the increased reflex and 2) to evaluate the contribution from afferents other than ankle extensor muscle afferents to the short-latency reflex. 2. Six cats were trained to stand unaided on four pedestals. Three cats were also trained to control the force exerted with the left hindlimb. The left soleus (SOL) and lateral gastrocnemius (LG) electromyogram (EMG), length, force, and temperature were recorded by chronically implanted electrodes and transducers. Measurements were taken before and after decerebration at the premammillary level. After decerebration limb temperature was returned to its normal range by the use of radiant heat. 3. Reproducible ramp-and-hold stretches and releases of the ankle extensor muscles were produced by a servo-controlled motor that rotated the left rear pedestal about the ankle joint. The length of the ankle extensor muscles changed by 2-3 mm within 30-35 ms after the onset of a ramp perturbation. Reflex responses before and after decerebration were compared at matched background values of muscle length and force. 4. In both the SOL and LG muscles, a short-latency EMG burst appeared 8-12 ms after stretch onset and lasted approximately 20 ms. After decerebration the onset of the rectified and smoothed EMG burst remained unchanged, but its area was increased by 36-89%. 5. The lateral gastrocnemius-soleus (LG-S) electroneurogram (ENG) was chronically recorded in two cats with a nerve cuff recording electrode implanted on the LG-S nerve. LG-S ENG activity started to increase soon after stretch onset and remained high during the entire ramp phase. The stretch-evoked LG-S ENG burst started approximately 8 ms earlier than the short-latency SOL and LG EMG bursts. It was interpreted to reflect mainly an increase in the activity of Group Ia and Ib muscle afferents, caused by increases in both muscle length and muscle force during the stretch. After the cats were decerebrated, for matched postural conditions, the area of the stretch-evoked LG-S ENG burst was increased by 29-35%. Because the length and force changes sensed by the muscle receptors before and after decerebration were similar, this suggests that the sensitivity of muscle spindles was increased as a consequence of altered activity in fusimotor neurons after decerebration.(ABSTRACT TRUNCATED AT 400 WORDS)
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Letarov, A., X. Manival, C. Desplats, and H. M. Krisch. "gpwac of the T4-Type Bacteriophages: Structure, Function, and Evolution of a Segmented Coiled-Coil Protein That Controls Viral Infectivity." Journal of Bacteriology 187, no. 3 (February 1, 2005): 1055–66. http://dx.doi.org/10.1128/jb.187.3.1055-1066.2005.
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ABSTRACT The wac gene product (gpwac) or fibritin of bacteriophage T4 forms the six fibers that radiate from the phage neck. During phage morphogenesis these whiskers bind the long tail fibers (LTFs) and facilitate their attachment to the phage baseplate. After the cell lysis, the gpwac fibers function as part of an environmental sensing device that retains the LTFs in a retracted configuration and thus prevents phage adsorption in unfavorable conditions. A comparative analysis of the sequences of 5 wac gene orthologs from various T4-type phages reveals that the ∼50-amino-acid N-terminal domain is the only highly conserved segment of the protein. This sequence conservation is probably a direct consequence of the domain's strong and specific interactions with the neck proteins. The sequence of the central fibrous region of gpwac is highly plastic, with only the heptad periodicity of the coiled-coil structure being conserved. In the various gpwac sequences, the small C-terminal domain essential for initiation of the folding of T4 gpwac is replaced by unrelated sequences of unknown origin. When a distant T4-type phage has a novel C-terminal gpwac sequence, the phage's gp36 sequence that is located at the knee joint of the LTF invariably has a novel domain in its C terminus as well. The covariance of these two sequences is compatible with genetic data suggesting that the C termini of gpwac and gp36 engage in a protein-protein interaction that controls phage infectivity. These results add to the limited evidence for domain swapping in the evolution of phage structural proteins.
Dissertations / Theses on the topic "Joints radiaux segmentés"
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Fourt, Erwan. "Étude de joints radiaux en carbone graphite avec application aéronautique." Electronic Thesis or Diss., Poitiers, 2021. http://www.theses.fr/2021POIT2292.
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Cette thèse a pour but d’étudier expérimentalement plusieurs technologies de joints radiaux segmentés. L’introduction permet de situer le contexte du travail tout en évoquant plusieurs technologies d’étanchéités couramment employées dans les moteurs aéronautiques. Au cours de ce chapitre, les contraintes auxquelles les joints radiaux segmentés doivent faire face sont également détaillées. La première étude menée a pour but d’étudier trois technologies différentes de joints radiaux segmentés : sans poche, avec poche sur les patins et enfin une technologie de joint sans poche en vis-à-vis de rainures inclinées sur le rotor. Dans un premier temps, les performances de chaque étanchéité sont évaluées et comparées.Ensuite, une étude métrologique a été menée sur la technologie de joint sans poche afin d’investiguer l’usure subie par ce dernier au cours des essais. Au cours de ce travail, la fragilité de ce type d’étanchéité a été mis en avant. C’est pourquoi, des joints similaires présentant une défaillance ont été étudiés. Comme précédemment, les performances de ces joints ainsi que l’usure subie ont été évaluées. Il a été montré que malgré la défaillance, ces joints n’ont montré aucun signe de détérioration supplémentaire.Enfin, l’influence de la rugosité de surface a été étudié afin de mettre en avant les phénomènes liés au soulèvement des segments. Pour cela, une méthode numérique multi-échelles a été développée. Il a été montré que cette dernière permettait de résoudre un tel problème avec un effort de calcul faible en comparaison des méthodes standardThe main goal of this thesis is the experimental study of several technologies of radial segmented seals. First of all, an introduction presents the context of the study by detailing the most commonly used seals technologies in aero engines.Firstly, three different technologies of radial segmented seals have been studied: without pocket, with pocket and without pocket and inclined grooves on the rotor. The performance of each technologies has been investigated and compared. In complement, the wear of the pocket-free technology has been study. The work highlights the fragility of this kind of seals. It is why the performance and the wear of faulty seals have been investigated.This second study shows that despite the failure, the seals do not show more serious complications.Then, the impact of roughness on a gas flow was investigate to highlight the lift effect of the segments. For this, a multiscale method was developed. It was shown that this method works well to study such a problem with a very low computational effort in comparison with two other existent methods
Book chapters on the topic "Joints radiaux segmentés"
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Nirmal, S. S. "Design of steel fiber reinforced concrete segment with curved radial joints." In Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2804–9. CRC Press, 2020. http://dx.doi.org/10.4324/9781003031635-26.
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Nirmal, S. S. "Design of steel fiber reinforced concrete segment with curved radial joints." In Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2804–9. CRC Press, 2019. http://dx.doi.org/10.1201/9780429424441-296.
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Nirmal, S. S. "Design of steel fiber reinforced concrete segment with curved radial joints." In Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2804–9. CRC Press, 2020. http://dx.doi.org/10.1201/9781003031635-26.
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Mangione, M., M. Ceccarelli, A. Pillai, and C. Agostini. "Addressing the radial joints behaviour of Steel Fibre Reinforced Concrete (SFRC) segments under concentrated loads." In Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2616–24. CRC Press, 2020. http://dx.doi.org/10.4324/9781003031635-7.
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Mangione, M., M. Ceccarelli, A. Pillai, and C. Agostini. "Addressing the radial joints behaviour of Steel Fibre Reinforced Concrete (SFRC) segments under concentrated loads." In Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2616–24. CRC Press, 2019. http://dx.doi.org/10.1201/9780429424441-277.
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Mangione, M., M. Ceccarelli, A. Pillai, and C. Agostini. "Addressing the radial joints behaviour of Steel Fibre Reinforced Concrete (SFRC) segments under concentrated loads." In Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2616–24. CRC Press, 2020. http://dx.doi.org/10.1201/9781003031635-7.
Full textConference papers on the topic "Joints radiaux segmentés"
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Proksch-Weilguni, Clemens, and Johann Kollegger. "Resource efficient reinforcement concept for precast tunnel segments." In IABSE Symposium, Prague 2022: Challenges for Existing and Oncoming Structures. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2022. http://dx.doi.org/10.2749/prague.2022.1352.
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<p>The global increase in world population and the growing demand of mobility leads to new huge infrastructure projects all over the world. Due to the circumstance, that every infrastructure project is unique and dependent on local conditions the optimization of single structural elements is not that common in the field of reinforced concrete structures. When it comes to building tunnel structures using a tunnel boring machine (TBM), a lot of almost identical tunnel segments called tubbings are needed. Already a reduction of a few centimeters of the tunnel segment thickness, leads to a significant saving of concrete when it comes to tunnel structures with a length of a few kilometers. The thickness of the tunnel segments mostly depends on the design of the radial joints of the individual tunnel segments. That is why the Institute of Structural Engineering of the TU Wien developed a new reinforcement concept for tunnel segments which increases the load bearing capacity of the radial joints significantly. With a patent application submitted, tunnel segments with the new reinforcement concept were manufactured, tested and it was shown that the TU Wien proposal significantly improves the load bearing capacity of tunnel segments.</p><p>Due to a presented design approach for determining the load bearing capacity of the segments and a first simplified quantification of the resource saving potential it can be said that the newly developed joint design is a great possibility for constructing tunnels with thinner tunnel segments.</p>
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Wang, Ke, Yaping Ju, and Chuhua Zhang. "Effects of Curvature Radius of Volute Profile on Aerodynamic Performance of Squirrel Cage Fan." In ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-5078.
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Abstract Volute profile exerts great influences on flow losses and aerodynamic performance of squirrel cage fan. In practical, equilateral- or inequilateral-element method is usually applied to design the volute profile for convenient manufacture. This kind of volute profile consists of several arc segments, however, is discontinuous for curvature radius at the junctions of adjacent arc segments. To overcome this issue, we propose a new volute profiling method to guarantee the continuity of curvature radius along the whole volute profile. By means of three-dimensional computation fluid dynamic simulations, the proposed method is validated through comprehensive comparisons of aerodynamic performances and flow fields of squirrel cage fans with and without continuous curvature radius of volute profile. The results show that the continuous curvature radius of volute profile is of benefit to the aerodynamic performance increase of squirrel cage fan. The velocity downstream the volute tongue is improved. The local sudden diffusion-expansion around the junctions of volute arc segments nearly disappears with continuous increase of static pressure along the volute wall.
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Osgoui, R., A. Poli, and M. Pescara. "Critical comparison between the double-convex and flat radial joints features in segmental tunnel lining." In The 2016 Isrm International Symposium, Eurock 2016. Taylor & Francis Group, 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742: CRC Press, 2016. http://dx.doi.org/10.1201/9781315388502-121.
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Hyer, Michael W., and Jaret C. Riddick. "Displacement Response of Segmented-Stiffness Composite Cylinders." In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-1192.
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Abstract With advanced manufacturing technology such as tow placement devices and filament winders, cylindrical composite structures may well be constructed in such a fashion that the lamination sequence varies with circumferential location around the cylinder. For example, the stacking sequence at the top and bottom of the cylinder may be axially stiff to resist bending and axial loads, while the sides of the cylinder may be designed to resist shear loads. The variation in stacking sequence may be continuous, with the stacking sequences on the top and bottom making a smooth transition to another stacking sequence on the sides. Alternatively, as a manufacturing convenience the cylinder may be constructed in circumferential sections, or segments, using more conventional manufacturing technology. There would then be discrete changes in laminate stacking sequence at specific locations around the circumference which would result in stepwise changes in laminate properties at the circumferential locations where the different segments join. In reality, there may be stiffeners incorporated into the cylinder, particularly at the locations where the segments join. For the present work stiffeners will not be considered and as a result of the discrete change in stiffness rather unusual displacement response will occur, even for simple loadings. The present paper examines the response of a segment-stiffness composite cylinder to compressive axial end shortening and internal pressure. For more conventional nonsegmented construction where the cylinder is constructed of a single laminate, these loadings cause axisymmetric response, at least in the range of linear response. The specific cylinder considered has its top and bottom segments made of the same laminate, and the sides made of another laminate. It is further assumed that the bending-twisting stiffnesses D16 and D26 are negligible. As a result, the problem exhibits quarter symmetry and this feature is exploited in the analysis. For pedagogical reasons an infinitely long cylinder is initially studied. This problem can be solved in closed form and the solution indicates that the primary feature that distinguishes the response of an infinitely-long segmented-stiffness cylinder from that of a more conventional single-laminate cylinder is the existence of circumferential displacements. For the case of axial end shortening, it is the difference in Poisson’s ratios between the various segments that is responsible for the existence of circumferential displacements. For the case of internal pressure, it is the difference in the extensional stiffnesses that causes the circumferential displacements. In both cases the radial displacement is independent of circumferential location, and therefore an infinitely long round cylinder remains round. Motivated by the results for an infinitely long cylinder, a finite-length cylinder is studied by using the principle of minimum total potential energy in combination with the Kantorovich approach. For the application of the latter approach, the dependence of the response on the circumferential coordinate is assumed to be harmonic, and the dependence on the axial coordinate is solved for from the resulting system of ordinary differential equations that are obtained by taking the first variation of the total potential energy. Like the infinite-length cylinder, circumferential displacements characterize the response, but the boundary conditions greatly influence the magnitude of the circumferential displacement. Also, unlike the infinite-length cylinder, the finite-length cylinder does not stay round, rather, the radial displacements are a function of the circumferential location. The eigenvalues of the system of ordinary differential equations indicate that the characteristic lengths (St. Venant effect) for the circumferential and radial displacements are not the same. There is a bending boundary layer associated with the radial displacements, as with nonsegmented construction, but there is no boundary layer associated with the circumferential displacements. These eigenvalues help explain the behavior of the finite-length cylinder.
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Vehar, Christine, Sridhar Kota, and Robert Dennis. "Closed-Loop Tape Springs as Fully Compliant Mechanisms: Preliminary Investigations." In ASME 2004 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/detc2004-57403.
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The paper introduces tape springs as elements of fully compliant mechanisms. The localized folds of tape springs serve as compact revolute joints, with a very small radius and large range of motion, and the unfolded straight segments serve as links. By exploiting a tape spring’s ability to function as both links and joints, we present a new method of realizing fully compliant mechanisms with further simplification in their construction. Tape springs, typically found in carpenter tape rules, are thin-walled strips having constant thickness, zero longitudinal curvature, and a constant transverse curvature. The paper presents a closed-loop tape spring mechanism. By representing its folds as idealized revolute joints and its variable length links as sliding joints connecting rigid links, we present a modified Gruebler’s equation to determine its kinematic and idle degrees of freedom. To realize practical utility of tape spring mechanisms, we propose a simple actuation scheme incorporating shape memory alloy (SMA) wire actuators and successfully demonstrate its performance with a proof-of-concept prototype. The paper also presents potential applications for actuated tape spring mechanisms including a large displacement translational mechanism, planar positioning mechanisms, bi-stable, multi-stable, and variable stiffness mechanisms.
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Pramuditya, Syeilendra, and Hisashi Ninokata. "Subchannel Analysis of Single-Phase Flow Sodium Tests With Non-Uniform Radial Power Distributions." In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-03058.
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Subchannel analysis calculations for sodium experimental data have been performed. Performance of several conventional flow resistance and mixing models was assessed, by comparing predicted outlet temperature profiles against experimental data. By using conventional method, it was found that the results agree well with the experimental data, with RMS errors between 3.4–5.6%. Calculations by employing non-uniform control volume for each subchannel have also been performed. This variation of control volume is due to the presence of wire spacer. The subchannel control volumes are varied based on dividing every wire axial pitch into 12 segments (H/12). It is showed that this simple method is able to simulate the flow field in a relatively more realistic way. It was found that the results by employing this simple method agree well with experimental data, in which the RMS errors are between 4.1–9%. The advantages of this H/12 method are its simplicity and its ability to reproduce the flow field inside subassembly.
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Bruce, William A., Bill Amend, and Steve Rapp. "Guidance for Field Segmentation and Welding of Induction Bends and Elbows." In 2012 9th International Pipeline Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ipc2012-90093.
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The use of cold field bends is not practical for some pipeline construction applications, particularly for large diameter pipelines built with restricted work space. For many reasons, the use of segmented induction bends and long-radius elbows becomes a necessary part of normal construction practice. This paper describes the results of the second phase of a recently-completed joint industry project pertaining to welding of field segmented induction bends and elbows for pipeline construction. In this phase, optimal methods for mapping, cutting, beveling, and transitioning induction bends and elbows were developed. Recommended practices for welding in the field and for a variety of related issues were also developed. The information was summarized and used to develop a generic specification for segmenting and welding of induction bends and elbows.
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Su, Hai-Jun. "A Load Independent Pseudo-Rigid-Body 3R Model for Determining Large Deflection of Beams in Compliant Mechanisms." In ASME 2008 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/detc2008-49041.
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Modeling flexible beams that undergo large deflection is one of the key steps in analyzing and synthesizing compliant mechanisms. Geometric nonlinearities introduced by large deflections often complicate the analysis of mechanism systems comprising such members. Several pseudo-rigid-body (PRB) or multi segment models in the literature have been proposed to approximate the tip deflection and slope. However these models are either dependent on external loads or too complicated to analyze. They are neither appropriate for analyzing mechanisms in which loads change significantly as they move, nor for synthesizing mechanisms where a parametric model is preferred. In this paper, a load independent PRB 3R model which comprises of four rigid links joined by three revolute joints and three torsion springs is proposed. The traditional PRB 1R models are first studied for both small deflection beams and large deflection beams. These studies provide fundamental insights to the geometric nonlinearity of large deflection beams. Numerical integration is applied to compute tip deflections for various loads. A three-dimensional search routine has been developed to find the optimal set of characteristic radius factors for the proposed PRB 3R model. Detailed error analysis and comparison against the result by the numerical integration and the PRB 1R model are accomplished for different load modes. The benefits of the PRB 3R model include (a) high accuracy for large deflection beams, (b) load independence which is critical for applications where loads vary significantly and (c) explicit kinematic and static constraint equations derived from the model. To demonstrate the use of the PRB 3R model, a compliant 4-bar linkage is studied and verified by a numerical example. The result shows a maximum tip deflection error of 1.2% compared with the FEA model.
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Soranna, Francesco, Yi-Chih Chow, Oguz Uzol, and Joseph Katz. "Structure of Turbulence Within a Sheared Wake of a Rotor Blade." In ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98401.
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Stereoscopic PIV measurements examine the flow structure and turbulence within a rotor near wake located within a non-uniform field generated by a row of Inlet Guide Vanes (IGVs). The experiments are performed in a refractive index matched facility that provides unobstructed view of the entire flow field. The data are acquired at 10 closely spaced radial planes located near mid-span, enabling measurements of all the components of the phase averaged velocity and strain rate, as well as the Reynolds stress and the triple correlation tensors. The rotor wake is sheared and bent towards the pressure (inner) side by a non-uniform flow field generated by IGV wake segments that propagate along the suction and pressure sides of the rotor passage with different speeds. The axial velocity fluctuations increase along the suction/outer side of the wake, while the other components decay. On the pressure/inner part of the bent wake the circumferential velocity fluctuations are higher. The Reynolds shear stress has a complex distribution, but is higher on the suction side. The turbulent kinetic energy is also consistently higher on the outer (suction) side of the wake. This trend is fundamentally different from those observed in prior studies of curved wakes where turbulence is enhanced on the inner side of the wake due to the destabilizing effect of curvature. To explain the difference, we examine the contributors to turbulent kinetic energy production rate in a curvilinear coordinate system aligned with the wake-centerline. The contribution of streamwise curvature to the production rate of turbulent kinetic energy, although consistent with expected trends, is overwhelmed by effects of wake shearing. The primary contributor to turbulent kinetic energy production rate is the product of Reynolds shear stress with cross-stream gradients of streamwise (in a frame of reference relative to the rotor blade) velocity in the wake. The location of peak in turbulent kinetic energy is almost aligned with that of production rate. The turbulence diffusion term opposes the production rate peaks, but also has high values along the edge of the wake.
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Vick, Michael, Trent Young, Matthew Kelly, Steven Tuttle, and Katherine Hinnant. "A Simple Recuperated Ceramic Microturbine: Design Concept, Cycle Analysis, and Recuperator Component Prototype Tests." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-57780.
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Ceramic recuperators could enable microturbines to achieve higher fuel efficiency and specific power. Challenges include finding a suitable ceramic fabrication process, minimizing stray heat transfer and gas leakage, mitigating thermal stress, and joining the ceramic parts to neighboring metal components. This paper describes engine and recuperator design concepts intended to address these obstacles. The engine is sized to produce twelve kilowatts of shaft power, and it has a reverse-flow compressor and turbine. Motivations for this layout are to balance axial thrust forces on the rotor assembly; to minimize gas leakage along the rotating shaft; to reduce heat transfer to the compressor diffuser; to enable the use of a simple, single-can combustor; and to provide room for lightweight ceramic insulation surrounding all hot section components. The recuperator is an annular, radial counterflow heat exchanger with the can combustor at the center. It is assembled from segmented wafers made by ceramic injection molding (CIM). These are housed in a pressure vessel to load the walls mainly in compression, and are joined together by flexible adhesives in the cool areas to accommodate thermal expansion. A representative wafer stack was built by laser-cutting, laminating, and sintering tapecast ceramic material. The prototype was tested at temperatures up to 675°C, and the results were used to validate analytical and computational fluid dynamics (CFD) models, which were then used to estimate the effectiveness of the actual design. Turbomachinery efficiencies were also calculated using CFD, and allowances were made for additional losses like bearing friction and gas leakage. Based on these component performance estimates, a cycle model indicates the engine could achieve a net fuel-to-electrical efficiency of 21%, at a core weight including the recuperator of 11 kg, or about 1 kg/kW electric output.