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Artykuły w czasopismach na temat "Specific Dissipation technique"
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Samuels, Robert J., i Nancy E. Mathis. "Orientation Specific Thermal Properties of Polyimide Film". Journal of Electronic Packaging 123, nr 3 (10.03.2000): 273–77. http://dx.doi.org/10.1115/1.1347986.
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The present study examines the relationship between thermal conductivity and planarity in polyimide films. The samples tested were specially prepared to range in orientation from three dimensionally random to highly planar. The molecular structure and orientation of the polyimide film have been characterized by polarizing microscope techniques, while the thermal conductivity measurements were done using a new rapid nondestructive technique. This correlation represents the first time thermal conductivity has been measured by modified hot wire techniques and related to the internal structure of polyimide. This work contributes to a deeper theoretical understanding of thermal conductivity and heat transfer mechanisms as they relate to orientation. Thermal conductivity evaluation could provide a new tool in the arsenal of structural characterization techniques. This relationship between thermal conductivity and orientation is key for applications of directional heat dissipation in the passive layers of chip assemblies. Such a correlation has potential to speed the development cycles of new materials during formulation as well as assure properties during production.
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Jamroziak, Krzysztof, i Miroslaw Bocian. "Analysis of Non-Classical Models which Have been Subjected to Percussive Loads Using Equations of Energy and Power". Advanced Materials Research 1036 (październik 2014): 608–13. http://dx.doi.org/10.4028/www.scientific.net/amr.1036.608.
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The article presents an analysis of impact energy dissipation process with selected non-classical dynamic models. Identification of impact energy dissipation phenomena in layered mechanical systems (for example: composite ballistic shields) is a great challenge, because on the one hand a model with parameters responsible for the energy dissipation is being sought on the one hand and on the other it is necessary to optimise the number of parameters. The sought model should be reduced to a simple description of the phenomenon and should contain a complex reproduction of the whole mechanical system. In this case the impact energy dissipation was described using selected degenerate systems. Models were treated by extortion surge having a specific impulse of force. The mathematical description of the pulse excitation was carried out using the energy and potency balance equations. The verification of mathematical identification equations was conducted using a computer simulation technique for the selected model’s parameters.
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Shang, Shou Ping, i Rong Shen. "HPFL Strip Strengthening Method for Masonry Structure". Advanced Materials Research 374-377 (październik 2011): 2593–98. http://dx.doi.org/10.4028/www.scientific.net/amr.374-377.2593.
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Due to the various advantages, e.g. low cost, simple construction and high reliability, the HPFL strip reinforcement technique has been widely used in the field of civil engineering. A survey of related literatures on the research and application of the HPFL strip reinforcement technique for Masonry structures were shown in this paper. The HPFL strip reinforcement technique can significantly improve the properties of the wall, e.g. the aseismatic capacity, shear resistant strength, ductility, energy dissipation. Moreover, based on the real engineering structures, the specific design and construction method were presented in this paper.
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CHEN, CHUNHONG, JIANG ZHAO i MAJID AHMADI. "A NOVEL STATE ENCODING ALGORITHM FOR LOW POWER IMPLEMENTATION". Journal of Circuits, Systems and Computers 14, nr 03 (czerwiec 2005): 597–604. http://dx.doi.org/10.1142/s0218126605002428.
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State encoding problem assigns binary codes to given symbolic states such that a specific objective function such as power dissipation can be optimized in the final implementation. In this paper, we present a novel encoding technique to minimize the switching activity of any given FSMs for low power design. The experiments with standard benchmarks show that the proposed algorithm is a significant improvement over previous ones.
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Yu, Byunggyu, i Seok-Cheol Ko. "Power dissipation analysis of PV module under partial shading". International Journal of Electrical and Computer Engineering (IJECE) 11, nr 2 (1.04.2021): 1029. http://dx.doi.org/10.11591/ijece.v11i2.pp1029-1035.
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Photovoltaic (PV) generation has been growing dramatically over the last years and it ranges from small, rooftop-mounted or building integrated systems, to large utility scale power stations. Especially for rooftop-mounted PV system, PV modules are serially connected to match with PV inverter input voltage specification. For serially connected PV system, shading is a problem since the shaded PV module reduces the output whole string of PV modules. The excess power from the unshaded PV module is dissipated in the shaded PV module. In this paper, power dissipation of PV module under partial shading is analyzed with circuit analysis for series connected PV modules. The specific current and voltage operating point of the shaded PV module are analyzed under shading. PSIM simulation tool is used to verify the power dissipation analysis. When there is no bypass diode and three solar modules are connected in series, upto 39.1% of the total maximum PV power is dissipated in the shaded PV module. On the other hand, when the bypass is attached, 0.3% of the total maximum power is generated as a loss in the shaded PV module. The proposed analysis technique of shaded PV module could be used in PV system performance analysis, especially for maximum power point tracking (MPPT) performance.
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Marsden, J. E., i M. West. "Discrete mechanics and variational integrators". Acta Numerica 10 (maj 2001): 357–514. http://dx.doi.org/10.1017/s096249290100006x.
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This paper gives a review of integration algorithms for finite dimensional mechanical systems that are based on discrete variational principles. The variational technique gives a unified treatment of many symplectic schemes, including those of higher order, as well as a natural treatment of the discrete Noether theorem. The approach also allows us to include forces, dissipation and constraints in a natural way. Amongst the many specific schemes treated as examples, the Verlet, SHAKE, RATTLE, Newmark, and the symplectic partitioned Runge–Kutta schemes are presented.
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Zhang, Qi, Xi Chen i David Guéry-Odelin. "Connection between Inverse Engineering and Optimal Control in Shortcuts to Adiabaticity". Entropy 23, nr 1 (9.01.2021): 84. http://dx.doi.org/10.3390/e23010084.
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We consider fast high-fidelity quantum control by using a shortcut to adiabaticity (STA) technique and optimal control theory (OCT). Three specific examples, including expansion of cold atoms from the harmonic trap, atomic transport by moving harmonic trap, and spin dynamics in the presence of dissipation, are explicitly detailed. Using OCT as a qualitative guide, we demonstrate how STA protocols designed from inverse engineering method can approach with very high precision optimal solutions built about physical constraints, by a proper choice of the interpolation function and with a very reduced number of adjustable parameters.
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Zhang, Qi, Xi Chen i David Guéry-Odelin. "Connection between Inverse Engineering and Optimal Control in Shortcuts to Adiabaticity". Entropy 23, nr 1 (9.01.2021): 84. http://dx.doi.org/10.3390/e23010084.
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We consider fast high-fidelity quantum control by using a shortcut to adiabaticity (STA) technique and optimal control theory (OCT). Three specific examples, including expansion of cold atoms from the harmonic trap, atomic transport by moving harmonic trap, and spin dynamics in the presence of dissipation, are explicitly detailed. Using OCT as a qualitative guide, we demonstrate how STA protocols designed from inverse engineering method can approach with very high precision optimal solutions built about physical constraints, by a proper choice of the interpolation function and with a very reduced number of adjustable parameters.
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Majzik, Zsolt, Martin Setvín, Andreas Bettac, Albrecht Feltz, Vladimír Cháb i Pavel Jelínek. "Simultaneous current, force and dissipation measurements on the Si(111) 7×7 surface with an optimized qPlus AFM/STM technique". Beilstein Journal of Nanotechnology 3 (15.03.2012): 249–59. http://dx.doi.org/10.3762/bjnano.3.28.
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We present the results of simultaneous scanning-tunneling and frequency-modulated dynamic atomic force microscopy measurements with a qPlus setup. The qPlus sensor is a purely electrical sensor based on a quartz tuning fork. If both the tunneling current and the force signal are to be measured at the tip, a cross-talk of the tunneling current with the force signal can easily occur. The origin and general features of the capacitive cross-talk will be discussed in detail in this contribution. Furthermore, we describe an experimental setup that improves the level of decoupling between the tunneling-current and the deflection signal. The efficiency of this experimental setup is demonstrated through topography and site-specific force/tunneling-spectroscopy measurements on the Si(111) 7×7 surface. The results show an excellent agreement with previously reported data measured by optical interferometric deflection.
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Tharajak, Jirasak, Tippaban Palathai i Narongrit Sombatsompop. "Scratch Resistance and Adhesion Properties of PEEK Coating Filled with h-BN Nanoparticles". Advanced Materials Research 747 (sierpień 2013): 303–6. http://dx.doi.org/10.4028/www.scientific.net/amr.747.303.
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Effects of h-BN particles on mechanical properties and adhesion of semi-crystalline poly (ether-ether-ketone) (PEEK) coatings were studied. PEEK powder was mixed with various contents of h-BN nanoparticle in ethanol under ultrasonic mixing. As-mixed powders were sprayed onto low carbon steel substrate with thermal spray technique. The hardness, scratch hardness, specific scratch wear rate, prevailing deformation mechanisms and adhesion were obtained from scratch tests by varying the applied load. The damage geometry on scratched polymer surfaces and scratch wear volume loss were examined using scanning electron microscope (SEM) and surface profilometer, respectively. The results indicated that the addition of h-BN content improved the hardness of the composite. In addition, the specific scratch wear rate and the adhesion between PEEK coatings and substrate decreased with increasing h-BN content. The poor adhesion resulted from the reductions of flow-ability and viscosity between PEEK and substrate caused by heat dissipation from the h-BN particles.
Rozprawy doktorskie na temat "Specific Dissipation technique"
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Ng, Eton Yat-Tuen, i eton_ng@hotmail com. "Vehicle engine cooling systems: assessment and improvement of wind-tunnel based evaluation methods". RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2002. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080422.100014.
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The high complexity of vehicle front-end design, arising from considerations of aerodynamics, safety and styling, causes the airflow velocity profile at the radiator face to be highly distorted, leading to potentially reduced airflow volume for heat dissipation. A flow visualisation study showed that the bumper bar significantly influenced the cooling airflow, leading to three-dimensional vortices in its wake and generating an area of relatively low velocity across at least one third of the radiator core. Since repeatability and accuracy of on-road testing are prejudiced by weather conditions, wind-tunnel testing is often preferred to solve cooling airflow problems. However, there are constraints that limit the accuracy of reproducing on-road cooling performance from wind-tunnel simulations. These constraints included inability to simulate atmospheric conditions, limited tunnel test section sizes (blockage effects) and lack of ground effect simulations. The work presented in this thesis involved use of on-road and wind-tunnel tests to investigate the effects of most common constraints present in wind tunnels on accuracy of the simulations of engine cooling performance and radiator airflow profiles. To aid this investigation, an experimental technique for quantifying radiator airflow velocity distribution and an analytical model for predicting the heat dissipation rate of a radiator were developed. A four-hole dynamic pressure probe (TFI Cobra probe) was also used to document flow fields in proximity to a section of radiator core in a wind tunnel in order to investigate the effect of airflow maldistribution on radiator heat-transfer performance. In order to cope with the inability to simulate ambient temperature, the technique of Specific Dissipation (SD) was used, which had previously been shown to overcome this problem.
Części książek na temat "Specific Dissipation technique"
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Datta, Mallika, Srijan Das i Devarun Nath. "Textiles for Noise Control". W Textiles for Functional Applications [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.99274.
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This chapter includes the mechanism of sound absorption and the classes of sound absorbing material to control the noise. The basic phenomena related to the reduction of sound by allowing it to soak in and dissipate also were introduced first, which, can be realised by viscous effects, heat conduction effects, and internal molecular energy interchanges. Porous absorbers are materials where sound propagates through an interconnected pore network resulting in sound energy dissipation. They are only effective at the mid-to-high frequency range, which is most sensitive to the human ear. The applications of different textile fibres and their various forms were identified later in the chapter. Finally, specific discussions are given to sound parameters, noise absorption coefficient, and its measurement technique. The chapter also deals with various factors influencing sound absorption.
Streszczenia konferencji na temat "Specific Dissipation technique"
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Mathew, B., T. J. John, W. Dai i H. Hegab. "Performance of Cross Flow Microchannel Heat Exchangers Subjected to Viscous Dissipation". W ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-31159.
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This paper analyzes the effect of viscous dissipation on the thermal performance of balanced flow cross flow microchannel heat exchangers. The cross flow microchannel heat exchanger analyzed in this paper is one that is subjected to axial heat conduction. Governing equations are developed for each of the fluids and the wall separating the fluids. The equations are solved simultaneously using the numerical technique of finite difference method to obtain the temperature profile. The effectiveness of each fluid is determined using the temperature profile thus obtained. The effectiveness and the temperature of the fluids are found to depend on NTU, axial heat conduction parameters and the viscous dissipation parameter. In the presence of axial heat conduction the effectiveness of the fluid decreases for a specific NTU. In addition, the effectiveness of the fluids decreases with increase in axial heat conduction parameters at a particular NTU. The effectiveness of the hot fluid in the presence of viscous heat dissipation alone decreased at a particular NTU. On the other hand the effectiveness of the cold fluid for the same amount of viscous heating improved at a specific NTU. The combined effect of axial heat conduction and viscous dissipation on the hot fluid is to decrease its effectiveness. With regard to the cold fluid effectiveness it can either increase or decrease due to the combined effect of axial heat conduction parameter and viscous dissipation.
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Guerout, Fabrice M., Ladji Cisse i Richard Boor. "New Non-Destructive Condition Monitoring Techniques for On-Site Assessment of Low-Voltage Cables". W 17th International Conference on Nuclear Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/icone17-75333.
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The number of techniques available for on-site monitoring of low-voltage cables at nuclear plants is limited because of the requirement from station personnel to use non-destructive and non-intrusive techniques. This paper summarizes the results obtained to date using two new non-destructive methods. The first technique is based on the indentation of the cable insulation or cable jacket material and the study of post-indentation parameters to characterize the visco-elastic properties of the material tested. The novelty of the technique consists of measuring the time taken by the polymeric material to recover a set portion of the initial deformation and using this duration as a material degradation indicator. The technique can be used locally on the insulation of hook-up cables, on the insulation at the termination of jacketed cables, or directly on cable jackets. The second technique is based on the measurement of electrical dissipation factors (or tan delta) in the insulating material. A broadband frequency tan delta analyser was used to measure electrical dissipation factors at various frequencies, and identify the frequency ranges showing increased sensitivity to cable degradation. Specific electrodes and measurement methods were developed for practical on-site condition monitoring work. The measurement of electrical dissipation factors can be used to assess the local degradation of cable insulation in hook-up cables and global degradation of multi-pair conductor cables. When used on multi-pair conductor cables, the technique presents the advantage of providing a global indication of the cable condition.
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Li, Guoyi, Rajesh Kumar Neerukatti i Aditi Chattopadhyay. "Fully Coupled Numerical Simulation for Wave Propagation in Composite Materials". W ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66159.
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Composite materials are used in many advanced engineering applications because of their high specific strength and specific stiffness. However, the complex damage mechanisms and failure modes are still not well-understood and limit their wide-spread applications. It is critical to monitor the structural heath for improved understanding of damage evolution and accurate life estimation. Ultrasonic wave based structure health monitoring (SHM) technique is a promising approach and has been investigated by many researchers. However, for the techniques to be reliable, it is necessary to understand the wave propagation behavior in composites. A fully coupled numerical simulation model has been developed to understand wave propagation and dissipation in composites under different excitation frequencies. The model is based on the local interaction simulation approaches/sharp interface model (LISA/SIM), and is computationally efficient compared to traditional finite element methods. This model is used to emulate wave behavior in composites in the current work. The output sensor signals are processed using matching pursuit decomposition algorithm to study the zero-order anti-symmetric and symmetric Lamb wave modes, including attenuation effects and dispersion. The results show good agreement with published experiments. Sensitivity studies show that wave velocities and amplitudes vary significantly with changes in the material properties and stiffness.
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Malavasi, Stefano, Gianandrea Vittorio Messa i Giacomo Ferrarese. "Solid-Liquid Flow Through a Wellhead Choke Valve". W ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97737.
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Wellhead choke valves are often subjected to the flow of solid-liquid mixtures due to sand production in oil extraction processes. Generally, the mixture is very dilute, and the main concern of engineers is the extensive wear arising from the continuous impacts between the particles and the internal parts of the valve. However, specific heavy oil extraction processes, such as the CHOPS technique, involve the production of a large amount of sand in the flow during the first months of life of the well. Many problems may arise from these high solid loadings, such as the change of regulation and dissipation characteristics of the device, and the risk of occlusion due to sand accumulation. In the present work the flow of sand-water mixtures through a choke valve is investigated by means of a two-fluid model which has already proved reliable for simpler flows. Starting from the single-phase flow case, validated with respect to our own experimental data, the effect of the presence of sand is studied, focusing on the influence of solids concentration (5 to 20%) and particle size (90 to 200 μm) on the dissipation characteristics of the device. Moreover, the distribution of the solids concentration is investigated to understand the behavior of the mixture and identify the most critical areas within the device.
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Locateli, Cristiano Cardoso, Paulo Leonel Teixeira, Edson Roberto De Pieri, Petter Krus i Victor Juliano De Negri. "Digital Hydraulic System Using Pumps and On/Off Valves Controlling the Actuator". W 8th FPNI Ph.D Symposium on Fluid Power. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fpni2014-7839.
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Hydraulic systems employed in several industrial and mobile applications present significant advantages, such as a high power-to-weight ratio and fast dynamic response. However, these systems have low efficiency due to high power dissipation. A recent concept called “digital hydraulics” comprises particularities that create opportunities for a reduction in load loss. This paper proposes a configuration and control method for actuator speed control based on the principles of digital hydraulics. In this context, several fixed displacement units and on/off valves are connected directly to the actuators without throttling valves. The system studied here presents three operation methods (pump mode, motor mode and idle mode), which allows discrete valves to replace continuous or flow control valves in order to control the actuator. Furthermore, a fixed or variable displacement pump with large displacement is replaced by several small, fixed displacement units. Simulations are performed with a co-simulation technique using AMESim and MATLAB. The actuator speed, inlet and outlet pressures on the fixed displacement units and flow rate in the circuit lines are analysed. Preliminary simulation results exhibit smooth transitions between speed levels, adequate dynamic performance, low power dissipation and high energy-storage capacity. A specific limitation of this technology is the obtained actuator discrete speed. The main contributions of this research are the development of a digital hydraulic system configuration and its control strategy, which allows speed control of hydraulic actuators and provides the capacity to store energy.
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Bhatti, Riaz A., i Yanrong Wang. "Damping Performance of a Particle Damper in Two Dimensions". W ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/detc2009-86862.
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Particle damping is a technique of achieving high structural damping with small metallic particles embedded within a cavity that is attached to the vibrating structure at the location of high vibration amplitudes. In this work, a simple yet detailed analytical model that takes into account normal as well as oblique impacts is presented to study particle damping in two dimensions under transient vibrations. The focus of the research presented here is to determine the role of major energy dissipation mechanisms such as friction and impact phenomena involved in particle damping in context of varying two dimensional cavity sizes. Particle damping is measured experimentally for an L-shaped beam in a fixed free configuration with a cavity attached at the top free end to investigate the effect of cavity size on its performance. It is observed that the peak value of the damping is mainly influenced by the cavity size in vertical direction, but the increase in cavity size in horizontal direction, makes this peak even bigger and shifts it slightly towards lower dimensionless acceleration amplitudes values. It has been found that normal impact phenomenon remains dominant in energy dissipation but the role of impact friction becomes very important and effective in the vicinity of peak specific damping capacity value with the increase in the size of the cavity. The model predictions regarding the effect of particles to structure mass ratio on the performance of particle damper are also in agreement with the reported data in the literature.
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Rodriguez, Oscar O., Juan Carbone, Arturo A. Fuentes, Robert E. Jones i Constantine Tarawneh. "Heat Generation in the Railroad Bearing Thermoplastic Elastomer Suspension Element". W 2016 Joint Rail Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/jrc2016-5823.
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The main purpose of this ongoing study is to investigate the effect of heat generation within a railroad thermoplastic elastomer suspension element on the thermal behavior of the railroad bearing assembly. Specifically, the purpose of this project is to quantify the heat generated by cyclic loading of the elastomer suspension element as a function of load amplitude, loading frequency, and operating temperature. The contribution of the elastomer pad to the system energy balance is modeled using data from dynamic mechanical analysis (DMA) of the specific materials in use for that part. DMA is a technique that is commonly used to characterize material properties as a function of temperature, time, frequency, stress, atmosphere or a combination of these parameters. DMA tests were run on samples of pad material prepared by three different processes: injection molded coupons, transfer molded coupons, and parts machined from an actual pad. The results provided a full characterization of the elastic deformation (Energy Storage) and viscous dissipation (Energy Dissipation) behavior of the material as a function of loading frequency, and temperature. These results show that the commonly used thermoplastic elastomer does generate heat under cyclic loading, though the frequency which produces peak heat output is outside the range of common loading frequency in rail service. These results can be combined with a stress analysis and service load measurements to estimate internally generated heat and, thus, enable a refined model for the evolution of bearing temperature during operation.
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Pátý, Marek, i Sergio Lavagnoli. "A Novel Vortex Identification Technique Applied to the 3D Flow Field of a High-Pressure Turbine". W ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90462.
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Abstract The efficiency of modern axial turbomachinery is strongly driven by the secondary flows within the vane or blade passages. The secondary flows are characterized by a complex pattern of vortical structures that origin, interact and dissipate along the turbine gas path. The endwall flows are responsible for the generation of a significant part of the overall turbine loss because of the dissipation of secondary kinetic energy and mixing-out of non-uniform momentum flows. The understanding and analysis of secondary flows requires a reliable vortex identification technique to predict and analyse the impact of specific turbine designs on the turbine performance. However, literature shows a remarkable lack of general methods to detect vortices and to determine the location of their cores and to quantify their strength. This paper presents a novel technique for the identification of vortical structures in a general 3D flow field. The method operates on the local flow field and it is based on a triple decomposition of motion proposed by Kolář. In contrast to a decomposition of velocity gradient into the strain and vorticity tensors, this method considers a third, pure shear component. The subtraction of the pure shear tensor from the velocity gradient remedies the inherent flaw of vorticity-based techniques which cannot distinguish between rigid rotation and shear. The triple decomposition of motion serves to obtain a 3D field of residual vorticity whose magnitude is used to define vortex regions. The present method allows to locate automatically the core of each vortex, quantify its strength and determine the vortex bounding surface. The output may be used to visualize the turbine vortical structures for the purpose of interpreting the complex three-dimensional viscous flow field, as well as to highlight any case-to-case variations by quantifying the vortex strength and location. The vortex identification method is applied to a high-pressure turbine with three optimized blade tip geometries. The 3D flow-field is obtained by CFD computations performed with Numeca FINE/Open. The computational model uses steady-state RANS equations closed by the Spalart-Allmaras turbulence model. Although developed for turbomachinery applications, the vortex identification method proposed in this work is of general applicability to any three-dimensional flow-field.
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Leggett, John, Edward Richardson, Stephan Priebe, Aamir Shabbir, Vittorio Michelassi i Richard Sandberg. "Loss Analysis of Unsteady Turbomachinery Flows Based on the Mechanical Work Potential". W ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91253.
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Abstract Loss analysis is a valuable technique for improving the thermodynamic performance of turbomachines. Analysing loss in terms of the ‘mechanical work potential’ (Miller, R.J., ASME Turbo Expo 2013, GT2013-95488) provides an instantaneous and local account of the thermal and aerodynamic mechanisms contributing to the loss of thermodynamic performance. This study develops the practical application of mechanical work potential loss analysis, providing the mathematical formulations necessary to perform loss analysis using practical Reynolds-Averaged Navier-Stokes (RANS) or Large Eddy Simulations (LES). The analysis approach is demonstrated using RANS and LES of a linear compressor cascade, both with and without incoming wakes. Spatial segmentation is used to attribute loss contributions to specific regions of the flow, and phase-averaging is performed in order to associate the variation of different loss contributions with the periodic passage of wakes through the cascade. For this un-cooled linear cascade, viscous dissipation is the dominant source of loss. The analysis shows that the contribution of the viscous reheat effect depends on the operating pressure of the compressor stage relative to the ambient ‘dead state’ pressure — implying that the optimal blade profile for a low-pressure compressor stage may be different from the optimal profile for a high-pressure compressor stage in the same engine, even if the operating conditions for both stages are dynamically-similar.
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Krikkis, Rizos N., Stratis V. Sotirchos i Panagiotis Razelos. "Bifurcation Analysis for Horizontal Longitudinal Fins Under Multi-Boiling Conditions". W ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33632.
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A numerical bifurcation analysis is carried out in order to determine the solution structure of a fin subject to multi-boiling heat transfer mode. The thermal analysis can no longer performed independently of the working fluid since the heat transfer coefficient is temperature dependent and includes the nucleate, the transition and the film boiling regime where the boiling curve is obtained experimentally for a specific fluid. The heat transfer process is modeled using one-dimensional heat conduction with or without heat transfer from the fin tip. Furthermore, five fin profiles are considered: the constant thickness, the trapezoidal, the triangular, the convex parabolic and the parabolic. The multiplicity structure is obtained in order to determine the different types of bifurcation diagrams, which describe the dependence of a state variable of the system (for instance the fin temperature or the heat dissipation) on a design (CCP) or operation parameter (base TD). Specifically the effects of the base TD, of CCP and of the Biot number are analyzed and presented in several diagrams since it is important to know the behavioral features of the heat rejection mechamism such as the number of the possible steady states and the influence of a change in one or more operating variables to these states. Stability analysis is carried out using the “resonance integral” technique and the Sturm-liouville eigen system analysis.