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Journal articles on the topic 'Minimized radiated power'
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1
Hall, H. R., W. Brent Ferren, and R. J. Bernhard. "Active Control of Radiated Sound from Ducts." Journal of Vibration and Acoustics 114, no. 3 (July 1, 1992): 338–46. http://dx.doi.org/10.1115/1.2930267.
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The noise radiated by duct and pipe systems is modeled in the laboratory using a circular duct driven by a speaker at one end. Active control is achieved using a control speaker located adjacent to the open end of the duct. The objective of the investigation was to minimize the total sound power radiated by the duct and a single secondary source. However, the adaptive algorithm used by the controller for this investigation seeks to cancel the acoustic pressure only at a single location; that is, the location of the “error” microphone. Analytical studies predict that in order for the total sound power radiated by primary and secondary sources to be minimized, a single secondary source must radiate sound which is of approximately equal magnitude and opposite phase to the noise source and the error microphone must be placed somewhere in the plane of minimum pressure of an ideal acoustic dipole. These analytical results were verified in part, for the case of the secondary source facing the same direction as the primary source in the plane of the pipe outlet. Other cases were studied where the control speaker was located outside the plane of the duct outlet. The performance improved for these alternative orientations for a wide range of error microphone positions. Measured sound power with and without active control is shown for a range of frequencies and error microphone locations for three configurations of the duct and control source.
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Giordano, J. A., K. A. Cunefare, and G. H. Koopmann. "An Experiment on Optimization of Active Noise Control on a Three-Dimensional Extended Radiator." Journal of Vibration and Acoustics 115, no. 1 (January 1, 1993): 53–58. http://dx.doi.org/10.1115/1.2930314.
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In this experiment, a 10.6 dB reduction in the total radiated sound power for an extended radiator was achieved via active control through optimization of active sources. An acoustic boundary element program was used to determine the magnitude and phase of the active sources which minimized the total radiated sound power. This paper details the experimental verification of the numerically predicted active source strengths using a box-shaped acoustic radiator. The top and bottom of the radiator were thin steel plates which were driven in one of their structural modes by an electromagnetic shaker. The four corners of the top plate were removed to accommodate baffled loudspeakers, representing the active sources. To provide precise control of the experiment, the driving signals to the shakers and loudspeakers were generated and monitored by a control computer. The experimental results agreed closely with the analytical prediction, confirming that the optimum reduction had been achieved for the primary and active source configuration. The measured sound pressure reductions in the acoustic field of the radiator ranged from 8 dB to 19 dB for the 1,1 structural mode of the plates.
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St. Pierre, R. L., and G. H. Koopmann. "A Design Method for Minimizing the Sound Power Radiated from Plates by Adding Optimally Sized, Discrete Masses." Journal of Mechanical Design 117, B (June 1, 1995): 243–51. http://dx.doi.org/10.1115/1.2836463.
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In this paper, a novel method for minimizing the sound power radiated from a structure is presented. The method involves placing strategically sized masses at specific locations on the structure’s surface. The minimization procedure modifies the shapes of the resonant modes of the structure in the frequency range of interest such that they are forced to radiate sound inefficiently. Because of this, they are referred to as “weak radiator” mode shapes. The method uses an optimization procedure that directly minimizes the radiated sound power from the surface of a plate in an infinite baffle. The procedure can be carried out for a single frequency or over a range of frequencies. Analytical sensitivities of sound power with respect to the design variables are developed and used in the optimization algorithm. Results on various test cases show sound power reductions of 10 dB or more even when several resonances are included in the frequency band. An acoustic intensity probe is used to experimentally verify the results for one test case. The experiment confirms the sound power reductions predicted by the optimization program.
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St. Pierre, R. L., and G. H. Koopmann. "A Design Method for Minimizing the Sound Power Radiated from Plates by Adding Optimally Sized, Discrete Masses." Journal of Vibration and Acoustics 117, B (June 1, 1995): 243–51. http://dx.doi.org/10.1115/1.2838669.
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In this paper, a novel method for minimizing the sound power radiated from a structure is presented. The method involves placing strategically sized masses at specific locations on the structure’s surface. The minimization procedure modifies the shapes of the resonant modes of the structure in the frequency range of interest such that they are forced to radiate sound inefficiently. Because of this, they are referred to as “weak radiator” mode shapes. The method uses an optimization procedure that directly minimizes the radiated sound power from the surface of a plate in an infinite baffle. The procedure can be carried out for a single frequency or over a range of frequencies. Analytical sensitivities of sound power with respect to the design variables are developed and used in the optimization algorithm. Results on various test cases show sound power reductions of 10 dB or more even when several resonances are included in the frequency band. An acoustic intensity probe is used to experimentally verify the results for one test case. The experiment confirms the sound power reductions predicted by the optimization program.
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Inoue, Katsumi, Masashi Yamanaka, and Masahiko Kihara. "Optimum Stiffener Layout for the Reduction of Vibration and Noise of Gearbox Housing." Journal of Mechanical Design 124, no. 3 (August 6, 2002): 518–23. http://dx.doi.org/10.1115/1.1480817.
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Dynamic excitation from the gears generates vibration modes in the gearbox which causes radiation of unwanted structure-borne noise. To reduce the noise as well as the vibration, the stiffened plate construction is frequently used for the housing, where the rib stiffener layout is the key to this design. In this paper, the most effective position of stiffeners in order to reduce the vibration and noise radiation is searched and discussed. The analysis considers first a plate fixed at edges and excited at its center, and then a simplified rectangular gearbox excited at the shaft bearing locations. The housing of a simplified single-stage gearbox is modeled by triangular finite shell elements. It is excited by a set of harmonic forces which are applied at the bearing positions. The rib stiffener is modeled by beam elements, and its optimum layout is searched by a genetic algorithm. The vibration energy is adopted as the objective function to be minimized for the design for low vibration. On the other hand, the radiated sound power is the objective function for low noise. Although the noise is caused by the vibration, the optimum stiffener layout to realize low noise is not always identical to the layout that yields low vibration because of the difference in radiation efficiency. This is numerically clarified first from the viewpoint of the vibration mode of a plate. In the case of the design for the gearbox housing concerned, the vibration mode which causes the difference in radiation efficiency is not presented. Consequently, the optimum stiffener is placed along the line from the point of excitation to a fixed point, which reduces the vibration deflection of the faces with bearings as well as the in-plane displacement of the bearings.
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Ranjbar, Mostafa, and Steffen Marburg. "Vibroacoustic Optimization of Mechanical Structures: A Controlled Random Search Approach." Advanced Materials Research 622-623 (December 2012): 158–61. http://dx.doi.org/10.4028/www.scientific.net/amr.622-623.158.
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A combination of controlled random search method and geometry modification concept is used to minimize the root mean square level of structure borne sound for a model. The structure is a rectangular plate made of steel. A specific frequency range for this porpuse is considered. The results show that this approach could produce significant reduction in the value of radiated sound power level of the structure within a limited time.
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Constans, E. W., G. H. Koopmann, and A. D. Belegundu. "THE USE OF MODAL TAILORING TO MINIMIZE THE RADIATED SOUND POWER OF VIBRATING SHELLS: THEORY AND EXPERIMENT." Journal of Sound and Vibration 217, no. 2 (October 1998): 335–50. http://dx.doi.org/10.1006/jsvi.1998.1799.
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Kılkış, Birol, Malik Çağlar, and Mert Şengül. "Energy Benefits of Heat Pipe Technology for Achieving 100% Renewable Heating and Cooling for Fifth-Generation, Low-Temperature District Heating Systems." Energies 14, no. 17 (August 30, 2021): 5398. http://dx.doi.org/10.3390/en14175398.
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This paper addresses the challenges the policymakers face concerning the EU decarbonization and total electrification roadmaps towards the Paris Agreement set forth to solve the global warming problem within the framework of a 100% renewable heating and cooling target. A new holistic model was developed based on the Rational Exergy Management Model (REMM). This model optimally solves the energy and exergy conflicts between the benefits of using widely available, low-temperature, low-exergy waste and renewable energy sources, like solar energy, and the inability of existing heating equipment, which requires higher exergy to cope with such low temperatures. In recognition of the challenges of retrofitting existing buildings in the EU stock, most of which are more than fifty years old, this study has developed a multi-pronged solution set. The first prong is the development of heating and cooling equipment with heat pipes that may be customized for supply temperatures as low as 35 °C in heating and as high as 17 °C in cooling, by which equipment oversizing is kept minimal, compared to standard equipment like conventional radiators or fan coils. It is shown that circulating pump capacity requirements are also minimized, leading to an overall reduction of CO2 emissions responsibility in terms of both direct, avoidable, and embodied terms. In this respect, a new heat pipe radiator prototype is presented, performance analyses are given, and the results are compared with a standard radiator. Comparative results show that such a new heat pipe radiator may be less than half of the weight of the conventional radiator, which needs to be oversized three times more to operate at 35 °C below the rated capacity. The application of heat pipes in renewable energy systems with the highest energy efficiency and exergy rationality establishes the second prong of the paper. A next-generation solar photo-voltaic-thermal (PVT) panel design is aimed to maximize the solar exergy utilization and minimize the exergy destruction taking place between the heating equipment. This solar panel design has an optimum power to heat ratio at low temperatures, perfectly fitting the heat pipe radiator demand. This design eliminates the onboard circulation pump, includes a phase-changing material (PCM) layer and thermoelectric generator (TEG) units for additional power generation, all sandwiched in a single panel. As a third prong, the paper introduces an optimum district sizing algorithm for minimum CO2 emissions responsibility for low-temperature heating systems by minimizing the exergy destructions. A solar prosumer house example is given addressing the three prongs with a heat pipe radiator system, next-generation solar PVT panels on the roof, and heat piped on-site thermal energy storage (TES). Results showed that total CO2 emissions responsibility is reduced by 96.8%. The results are discussed, aiming at recommendations, especially directed to policymakers, to satisfy the Paris Agreement.
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Alshabatat, Nabeel T., and Koorosh Naghshineh. "Optimization of Natural Frequencies and Sound Power of Beams Using Functionally Graded Material." Advances in Acoustics and Vibration 2014 (February 20, 2014): 1–10. http://dx.doi.org/10.1155/2014/752361.
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This paper presents a design method to optimize the material distribution of functionally graded beams with respect to some vibration and acoustic properties. The change of the material distribution through the beam length alters the stiffness and the mass of the beam. This can be used to alter a specific beam natural frequency. It can also be used to reduce the sound power radiated from the vibrating beam. Two novel volume fraction laws are used to describe the material volume distributions through the length of the FGM beam. The proposed method couples the finite element method (for the modal and harmonic analysis), Lumped Parameter Model (for calculating the power of sound radiation), and an optimization technique based on Genetic Algorithm. As a demonstration of this technique, the optimization procedure is applied to maximize the fundamental frequency of FGM cantilever and clamped beams and to minimize the sound radiation from vibrating clamped FGM beam at a specific frequency.
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Rambousky, R., J. Nitsch, and H. Garbe. "Matching the termination of radiating non-uniform transmission-lines." Advances in Radio Science 11 (July 4, 2013): 259–64. http://dx.doi.org/10.5194/ars-11-259-2013.
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Abstract. In this contribution a concept of matching the termination of radiating non-uniform transmission-lines is proposed. Using Transmission-Line Super Theory, position and frequency dependent line parameters can be obtained. Therefore, a characteristic impedance can be determined which is also position and frequency dependent. For a single wire transmission-line it could be shown that the maximum value of that characteristic impedance is an optimal termination in the sense of minimizing the variation of the current on the line. This indicates that matching is not a local effect at the position of the concentrated load but a cooperative process including the whole non-uniform transmission-line. In addition this choice of termination minimizes the variation of the radiated power over frequency.
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Araújo, Aurélio L., and José F. Aguilar Madeira. "Optimal passive shunted damping configurations for noise reduction in sandwich panels." Journal of Vibration and Control 26, no. 13-14 (March 6, 2020): 1110–18. http://dx.doi.org/10.1177/1077546320910542.
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This article addresses the issue of vibration and noise reduction in laminated sandwich plates using piezoelectric patches with passive shunted damping. A finite element implementation of a laminated sandwich plate with viscoelastic core and surface bonded piezoelectric patches is used to obtain the frequency response of the panels. The sound transmission characteristics of the panels are evaluated by computing their radiated sound power using the Rayleigh integral method. Resistor and inductor shunt damping circuits are used to add damping to the sandwich panels. The optimal location of the surface-bonded piezoelectric patches is then obtained, along with the resistor and inductor circuits resistance and inductance, using direct multisearch optimization to minimize added weight, number of patches, and noise radiation. Trade-off Pareto optimal fronts and the respective optimal patch configurations are obtained.
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Cox, D. E., G. P. Gibbs, R. L. Clark, and J. S. Vipperman. "Experimental Robust Control of Structural Acoustic Radiation." Journal of Vibration and Acoustics 121, no. 4 (October 1, 1999): 433–39. http://dx.doi.org/10.1115/1.2893999.
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This work addresses the design and application of robust controllers for structural acoustic control. Both simulation and experimental results are presented. H∞ and μ-synthesis design methods were used to design feedback controllers which minimize power radiated from a panel while avoiding instability due to unmodeled dynamics. Specifically, high-order structural modes which couple strongly to the actuator-sensor path were poorly modeled. This model error was analytically bounded with an uncertainty model which allowed controllers to be designed without artificial limits on control effort. It is found that robust control methods provide the control designer with physically meaningful parameters with which to tune control designs and can be very useful in determining limits of performance. However, experimental results also showed poor robustness properties for control designs with ad-hoc uncertainty models. The importance of quantifying and bounding model errors is discussed.
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Xu, Ying, Yeonju Kim, Manos M. Tentzeris, and Sungjoon Lim. "Bi-Directional Loop Antenna Array Using Magic Cube Origami." Sensors 19, no. 18 (September 11, 2019): 3911. http://dx.doi.org/10.3390/s19183911.
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In this paper, we propose a bi-directional loop antenna array using magic cube origami. The proposed antenna array consists of three one-wavelength loop antenna elements with series feeding. Each loop antenna is realized on a single magic cube, and three cubes are connected in series to form the array. The three cubes can be easily folded and unfolded due to being constructed in the form of a magic cube origami. Antenna volume can be minimized for high mobility by folding the array, which radiates a bi-directional pattern with full volume when unfolded. The proposed antenna was designed at 1.39 GHz. When the single antenna is realized on the single cube, the peak gain is 4.03 dBi. The peak gain increased to 5.2 and 5.53 dBi with two and three antennas, respectively. Half-power beam width (HPBW) with three antenna elements decreased to 40° from 360° compared to the HPBW with the single antenna. The proposed antenna performance was assessed numerically and experimentally.
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Yusuf, Taofeek Ayotunde, Seonghun Pyo, and Yongrae Roh. "A Novel Versatile Approach for Underwater Conformal Volumetric Array Design." Sensors 21, no. 11 (May 21, 2021): 3591. http://dx.doi.org/10.3390/s21113591.
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In this study, we present a novel approach to the design of a conformal volumetric array composed of M × N convex subarrays in two orthogonal curvilinear directions for underwater acoustic imaging for mine detection. Our design targets require that the proposed array transducer has three-dimensional half-power beamwidths of 85° and 25° in either of its convex subarray parts, while also reaching a peak transmitting voltage response above 147 dB. The radiated sound pressure of the subarrays was independently derived as a function of their geometrical parameters. The resulting directional factors were then combined to analyze the beam profile of the entire array. The design was finally optimized to minimize the ripple level. To validate this theoretical design, the structure was modeled and analyzed using the finite element method. The comparison between the resulting beam pattern from the finite element analysis and the analytical computation showed an excellent compliance. The method advanced is a simple and systematic analytical model to facilitate the development of new conformal volumetric arrays for underwater mine detection.
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Amanatiadis, Stamatios, Theodoros Zygiridis, and Nikolaos Kantartzis. "Radiation Efficiency Enhancement of Graphene Plasmonic Devices Using Matching Circuits." Technologies 9, no. 1 (January 2, 2021): 4. http://dx.doi.org/10.3390/technologies9010004.
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In the present work, the radiation properties of a graphene plasmonic patch antenna are investigated and enhanced in terms of efficiency, utilizing circuit-matching techniques. Initially, the reflection coefficient of graphene surface waves due to discontinuities is studied, while the power flow towards free-space is numerically extracted. This analysis indicates that the radiated power is increased for higher values of the chemical potential, although the surface wave is weakly confined and prone to degradation due to interference. For this reason, a graphene sheet that supports strongly confined surface waves is terminated via a matching layer, in order to enhance the radiating power. In particular, the matching layer consists of an appropriately selected larger chemical potential value, in order to minimize the reflection coefficient and boost the radiation performance. The numerical investigation of this setup validates the upgraded performance, since the radiating power is significantly increased. Then, a realistic setup that includes a graphene patch antenna is examined numerically, proving the augmentation of the radiation efficiency when the matching layer is utilized. Finally, the latter is designed with a graded increment in the chemical potential, and the computational analysis highlights the significant enhancement of the graphene plasmonic antenna gain towards the desired direction. Consequently, a more reliable framework for wireless communications between plasmonic devices at THz frequencies is established, which corresponds to the practical significance of the proposed methodology for improved radiation efficiency. All numerical results are extracted by means of an efficient modification of the Finite-Difference Time-Domain (FDTD) scheme, which models graphene accurately.
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Arbekov, A. N. "Selecting a thermodynamic cycle for the closed gas-turbine power plant of spacecraft in order to minimize surface of the cooler-radiator." High Temperature 52, no. 4 (July 2014): 584–87. http://dx.doi.org/10.1134/s0018151x14040014.
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Asef, Pedram, Ramon Bargallo, and Andrew Lapthorn. "Magnetic Noise Reduction of In-Wheel Permanent Magnet Synchronous Motors for Light-Duty Electric Vehicles." Vehicles 2, no. 1 (February 25, 2020): 156–72. http://dx.doi.org/10.3390/vehicles2010009.
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This paper presents study of a multi-slice subdomain model (MS-SDM) for persistent low-frequency sound, in a wheel hub-mounted permanent magnet synchronous motor (WHM-PMSM) with a fractional-slot non-overlapping concentrated winding for a light-duty, fully electric vehicle applications. While this type of winding provides numerous potential benefits, it has also the largest magnetomotive force (MMF) distortion factor, which leads to the electro-vibro-acoustics production, unless additional machine design considerations are carried out. To minimize the magnetic noise level radiated by the PMSM, a skewing technique is targeted with consideration of the natural frequencies under a variable-speed-range analysis. To ensure the impact of the minimization technique used, magnetic force harmonics, along with acoustic sonograms, is computed by MS-SDM and verified by 3D finite element analysis. On the basis of the studied models, we derived and experimentally verified the optimized model with 5 dBA reduction in A-weighted sound power level by due to the choice of skew angle. In addition, we investigated whether or not the skewing slice number can be of importance on the vibro-acoustic objectives in the studied WHM-PMSM.
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Cvok, Ivan, Igor Ratković, and Joško Deur. "Multi-Objective Optimisation-Based Design of an Electric Vehicle Cabin Heating Control System for Improved Thermal Comfort and Driving Range." Energies 14, no. 4 (February 23, 2021): 1203. http://dx.doi.org/10.3390/en14041203.
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Modern electric vehicle heating, ventilation, and air-conditioning (HVAC) systems operate in more efficient heat pump mode, thus, improving the driving range under cold ambient conditions. Coupling those HVAC systems with novel heating technologies such as infrared heating panels (IRP) results in a complex system with multiple actuators, which needs to be optimally coordinated to maximise the efficiency and comfort. The paper presents a multi-objective genetic algorithm-based control input allocation method, which relies on a multi-physical HVAC model and a CFD-evaluated cabin airflow distribution model implemented in Dymola. The considered control inputs include the cabin inlet air temperature, blower and radiator fan air mass flows, secondary coolant loop pump speeds, and IRP control settings. The optimisation objective is to minimise total electric power consumption and thermal comfort described by predictive mean vote (PMV) index. Optimisation results indicate that HVAC and IRP controls are effectively decoupled, and that a significant reduction of power consumption (typically from 20% to 30%) can be achieved using IRPs while maintaining the same level of thermal comfort. The previously proposed hierarchical HVAC control strategy is parameterised and extended with a PMV-based controller acting via IRP control inputs. The performance is verified through simulations in a heat-up scenario, and the power consumption reduction potential is analysed for different cabin air temperature setpoints.
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Bozza, Fabio, Vincenzo De Bellis, and Luigi Teodosio. "A numerical procedure for the calibration of a turbocharged spark-ignition variable valve actuation engine at part load." International Journal of Engine Research 18, no. 8 (October 24, 2016): 810–23. http://dx.doi.org/10.1177/1468087416674653.
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Referring to spark-ignition engines, the downsizing, coupled to turbocharging and variable valve actuation systems are very common solutions to reduce the brake-specific fuel consumption at low-medium brake mean effective pressure. However, the adoption of such solutions increases the complexity of engine control and management because of the additional degrees of freedom, and hence results in a longer calibration time and higher experimental efforts. In this work, a twin-cylinder turbocharged variable valve actuation spark-ignition engine is numerically investigated by a one-dimensional model (GT-Power™). The considered engine is equipped with a fully flexible variable valve actuation system, realizing both a common full-lift strategy and a more advanced early intake valve closure strategy. Refined sub-models are used to describe turbulence and combustion processes. In the first stage, one-dimensional engine model is validated against the experimental data at full and part load. The validated model is then integrated in a multipurpose commercial optimizer (modeFRONTIER™) with the aim to identify the engine calibration that minimizes brake-specific fuel consumption at part load. In particular, the decision parameters of the optimization process are the early intake valve closure angle, the throttle valve opening, the turbocharger setting and the spark timing. Proper constraints are posed for intake pressure in order to limit the gas-dynamic noise radiated at the intake mouth. The adopted optimization approach shows the capability to reproduce with good accuracy the experimentally identified calibration. The latter corresponds to the numerically derived Pareto frontier in brake mean effective pressure–brake specific fuel consumption plane. The optimization also underlines the advantages of an engine calibration based on a combination of early intake valve closure strategy and intake throttling rather than a purely throttle-based calibration. The developed automatic procedure allows for a ‘virtual’ calibration of the considered engine on completely theoretical basis and proves to be very helpful in reducing the experimental costs and the engine time-to-market.
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Rabani, Mehrdad, Habtamu Bayera Madessa, and Natasa Nord. "Building Retrofitting through Coupling of Building Energy Simulation-Optimization Tool with CFD and Daylight Programs." Energies 14, no. 8 (April 14, 2021): 2180. http://dx.doi.org/10.3390/en14082180.
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Simultaneous satisfaction of both thermal and visual comfort in buildings may be a challenging task. Therefore, this paper suggests a comprehensive framework for the building energy optimization process integrating computational fluid dynamics (CFD) daylight simulations. A building energy simulation tool, IDA Indoor Climate and Energy (IDA-ICE), was coupled with three open-source tools including GenOpt, OpenFOAM, and Radiance. In the optimization phase, several design variables i.e., building envelope properties, fenestration parameters, and Heating, Ventilation and Air-Conditioning (HVAC) system set points, were selected to minimize the total building energy use and simultaneously improve thermal and visual comfort. Two different scenarios were investigated for retrofitting of a generic office building located in Oslo, Norway. In the first scenario a constant air volume (CAV) ventilation system with a local radiator in each zone was used, while an all-air system equipped with a demand control ventilation (DCV) was applied in the second scenario. Findings showed that, compared to the reference design, significant reduction of total building energy use, around 77% and 79% in the first and second scenarios, was achieved respectively, and thermal and visual comfort conditions were also improved considerably. However, the overall thermal and visual comfort satisfactions were higher when all-air system was applied.
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Pietrzko, Stanislaw, and Qibo Mao. "Reduction of Structural Sound Radiation and Vibration Using Shunt Piezoelectric Materials." Solid State Phenomena 147-149 (January 2009): 882–89. http://dx.doi.org/10.4028/www.scientific.net/ssp.147-149.882.
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In this paper, structural sound and vibration control using passive and semi-active shunt piezoelectric damping circuits is presented. A piezoelectric patch with an electrical shunt circuit is bonded to a base structure. When the structure vibrates, the piezoelectric patch strains and transforms the mechanical energy of the structure into electrical energy, which can be effectively dissipated by the shunt circuit. Hence, the shunt circuit acts as a means of extracting mechanical energy from the base structure. First, different types of shunt circuits (such as RL series circuit, RL parallel circuit and RL-C circuit), employed in the passive damping arrangement, are analyzed and compared. By using the impedance method, the general modelling of different shunt piezoelectric damping techniques is presented. The piezoelectric shunt circuit can be seen as additional frequency-dependence damping of the system. One of the primary concerns in shunt damping is to choose the optimal parameters for shunt circuits. In past efforts most of the proposed tuning methods were based on modal properties of the structure. These methods are used to minimize the response of a particular structural mode whilst neglecting the contribution of the other modes. In this study, a design method based on minimization of the sound power of the structure is proposed. The optimal parameters for shunt circuits are obtained using linear quadratic optimal control theory. In general, the passive shunt circuit techniques are an effective method of modal damping. However, the main drawback of the passive shunt circuit is that the shunt piezoelectric is very sensitive to tuning errors and variations in the excitation frequency. To overcome this problem, the pulse-switching shunt circuit, a semi-active continuous switching technique in which a RL shunt circuit is periodically connected to a bonded piezoelectric patch, is introduced as structural damping. The switch law for pulse-switching circuit is discussed based on the energy dissipation technique. Compared with a standard passive piezoelectric shunt circuit, the advantages of the pulse-switching shunt circuit is a small required shunt inductance, a lower sensitivity to environmental changes and easier tuning. Very low external power for the switch controller is required so it may be possible to extract this energy directly from the vibration of the structure itself. Numerical simulations are performed for each of these shunts techniques focusing on minimizing radiated sound power from a clamped plate. It is found that the RL series, RL parallel and pulse-switching circuits have basically the same control performance. The RL–C parallel circuit allows us to reduce the value of the inductance L due to the insertion of an external capacity C. However, the control performance will be reduced simultaneously. The pulse-switching circuit is more stable than RL series circuit with regard to structural stiffness variations. Finally, experimental results are presented using an RL series/parallel shunt circuit, RL-C parallel shunt circuit and pulse-switching circuit. The experimental results have shown that the vibration and noise radiation of a structure can be reduced significantly by using these shunt circuits. The theoretical and experimental techniques presented in this study provide a valuable tool for effective shunt piezoelectric damping.
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Llorente Monleón, Sandra. "Design and development of a new modular bathroom system = Diseño y desarrollo de un novedoso sistema de baños modulares." Building & Management 1, no. 1 (April 30, 2017): 18. http://dx.doi.org/10.20868/bma.2017.1.3521.
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The techniques of production and in particular of construction tend to be technified, improving its precision, optimizing costs and times of production. This is the strategy to follows for those companies who need to increase its competitiveness. This is the way how modular or prefabrication systems have been introduced in the new construction processes. The modular construction no longer only applies to the structure of a building, but has also specialized in other parts, such as wet rooms; bathrooms and kitchens. Being those stays of the house more reproducible. Modular bathrooms are more common in buildings where houses have the same dimensions and /or distributions, and where therefore their construction is repetitive. The basis of this work is the development of a series production system of modular bathrooms that can be customized, maintaining the specifications and the lines indicated in the project. Also the development of a lifting and assembly tool that allows to minimize the transfer of the modules and facilitate the speed of its installation in its definitive location. The result is an industrialized bath module of high quality, with traceability of the materials and components used, tested and guaranteed, in a assembly line of fast manufacture. The bathroom is delivered completely finished and installed, minimizing the construction deadlines and improving its quality and safety.ResumenLas técnicas de producción y en particular de construcción tienden a tecnificarse, mejorando su precisión, optimizando costes y tiempos de producción. La construcción modular ya no solo se aplica a la estructura de una edificación, sino que también se ha especializado en otras estancias de la casa menos personales y con una composición de elementos más reproducible y por tanto industrializable. Los baños modulares cada vez son más comunes en aquellas edificaciones donde las viviendas tienen las mismas dimensiones y/o distribuciones, y donde por tanto su construcción es repetitiva. La base de este trabajo es el desarrollo de un sistema de fabricación en serie de baños modulares que puedan ser personalizables, manteniendo las especificaciones y prestaciones indicadas en el proyecto. La necesidad de poder introducir sistemas de baja temperatura, como suelos radiantes, para completar las estrategias energéticas del conjunto edificatorio, así como el desarrollo para la introducción en los módulos de una red de saneamiento que incluya cierres hidráulicos de conjunto (bote sifónico) se ve desarrollada de manera que el producto final pueda proporcionar los estándares solicitados por el cliente. Igualmente el desarrollo de un útil de elevación y montaje que permita minimizar el trasiego de los módulos y facilitar la rapidez de su instalación en su ubicación definitiva. El resultado es un módulo de baño industrializado de alta calidad, con trazabilidad de los materiales y componentes utilizados, probado y garantizado, en una cadena de montaje de rápida fabricación y que incluye todas las prescripciones técnicas del proyectista. El baño se entrega totalmente terminado e instalado, minimizando los plazos de obra y mejorando su calidad y seguridad...
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Myniv, R. M. "Modern technologies of equipping of animal husbandry rooms." Scientific Messenger of LNU of Veterinary Medicine and Biotechnologies 22, no. 92 (May 8, 2020): 56–61. http://dx.doi.org/10.32718/nvlvet-a9210.
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Modern technologies for the construction of livestock rooms, inexpensive foundations, short construction time, low material capacity of the building, the possibility of using a leasing payment scheme are factors that will minimize construction costs. At much lower initial cost, frame and awning livestock rooms pay off much faster than capital buildings, with the construction of livestock rooms cost 3–5 times cheaper. The standard hangar designs are versatile and versatile. The form determines the amount of working space inside the hangar, depending on the purpose of the operation. Width standard up to 30 m. Length – proportional, step between arches 3 m. They are tent, arched and straight. Frame and awning hangars up to 1500 square meters, m. are considered to be high-speed mobile structures of temporary type. No permits are required for their construction. There is no need for the construction of the foundation, the involvement of large machinery. Despite the “temporary type”, metal construction is reliable. Construction is carried out according to the developed design standards – SP 384.1325800.2018. If necessary, the awning membrane can be easily and quickly repaired or replaced with a new one after 10–15 years. The most effective way to insulate a hangar today is to insulate it by spraying polyurethane foam. Depending on the technological scheme of installation of equipment of livestock premises, the required number, size and location of the farm gate is determined. The ends of the livestock premises are equipped with swing gates for the entry of transport, distributing feed to the feeding table, the gates can be awning or metal, sectional, recoil or swing. At the request of the customer can be designed passages for pushing. In order to reduce electricity consumption for heating purposes and to save money on electricity, we propose to equip the heating system of frame and awning hangars with another source of heat supply – a heat pump. To reduce electricity costs for heating radiators, it is necessary to install thermostatic valves at the rate of one valve per radiator. The electric power of the heat pump with a minimum conversion factor (KP) will be 12.5 kW. Electricity costs for circulation of such volume of a brine at resistance of 8 m make about 0,5 kW. Energy savings when using a heat pump in monetary terms at an electricity tariff of 193.28 kopecks. without VAT for 1 kW. year will be 59976 × 193.28 = 115.922 thousand UAH without VAT.
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Gutiérrez-Gil, J., X. Garcia-Andrés, J. Martínez-Casas, E. Nadal, and F. D. Denia. "Optimized Perforation Schemes in Railway Wheels Toward Acoustic Radiation Mitigation." Journal of Vibration and Acoustics 142, no. 4 (April 9, 2020). http://dx.doi.org/10.1115/1.4046681.
Full textAbstract:
Abstract Rolling noise emitted by railway wheels is a problem that affects human health and limits the expansion of the railway network. It is caused by the wheel vibration due to the wheel-rail contact force, and it is important in almost all the vehicle velocity range. The minimization of noise radiation associated with changes on the wheel web is discussed in this work, focusing on potential shape modifications in existing wheels in the form of a perforation distribution over the web. Such a post-manufacturing technique is a cost-effective solution that can be performed in a relatively short term. The implemented objective function is directly related to the overall radiated sound power, which is minimized using a genetic algorithm-based optimizer. In the acoustic model, radiation efficiencies are approximated to unity, the accuracy of this assumption being also studied in the work. The results reflect that an optimized distribution of perforations on the web of a railway wheel can reduce the total sound power level, by about 5 dB(A) and 2 dB(A) for curved and straight web, respectively. The mitigation of the radiated sound power is due to the fact that certain wheel vibration modes are modified and shifted to other frequencies where they are less excited. Finally, the relevance of the cross-sectional curvature of the web is explored by studying two different web geometries, suggesting that it can strongly influence the noise mitigation effects of the perforation pattern.
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Chen, Yuanlong, Tingbo Hou, and Minqiang Pan. "Comparative Analysis Between Water-Cooled and Air-Cooled Heat Dissipation in a High-Power Light-Emitting Diode Chipset." Journal of Thermal Science and Engineering Applications 11, no. 6 (May 3, 2019). http://dx.doi.org/10.1115/1.4043004.
Full textAbstract:
With a substantial increase in thermal power density, the operating temperature of high-power light-emitting diodes (LEDs) rises rapidly, exerting a notable effect on chipsets’ performance. A water-cooled microchannel radiator and an air-cooled radiator are proposed to solve this problem. The effects of key factors of both radiators on heat dissipation in a high-power LED chipsets, and general comparisons between each method, are analyzed via Fluent. The simulation results indicate that heat dissipation from the water-cooled microchannel radiator is readily affected by the microchannel’s flow rate and aspect ratio. A larger flow rate and larger aspect ratio favor improved heat dissipation in the water-cooled microchannel radiator. Heat dissipation in the air-cooled radiator is related to volumetric flow rate, rib number, rib height, rib thickness, and substrate thickness. A larger volumetric flow rate, rib number, and rib height favor heat dissipation in the air-cooled radiator. However, there is a critical thickness value: if the thickness is less than the critical value, heat dissipation is greatly affected by rib thickness and substrate thickness, if the thickness is larger than the critical value, the influence is insignificant. The high-power LED chipsets’ temperature is also related to the insulating substrate’ input power and thermal conductivity. A large input power leads to a substantial increase in temperature, and larger thermal conductivity of the insulating substrate minimizes temperature increase in the high-power LED chipsets. When comparing the two radiators, results show an air-cooled radiator should be used in low-power LED chipsets. When an air-cooled radiator cannot satisfy the chipset’s needs, a water-cooled microchannel radiator should be utilized.
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"Dielectric Resonator Rectenna for RF Energy Harvesting System." International Journal of Engineering and Advanced Technology 9, no. 2 (December 30, 2019): 4834–39. http://dx.doi.org/10.35940/ijeat.b4504.129219.
Full textAbstract:
Recently, the various methods for RF energy harvesting and reutilizing has become the challenging matter around the world to minimize the wastage of RF energy in the form of electromagnetic waves within the atmosphere. An associate approach of collecting a particular range of frequencies & conversion into dc current- Rectenna is proposed here. Star shaped Dielectric Resonator Antenna is implemented as antenna for receiving RF energy at 2.44 GHz resonant frequency. It is observed that Star shaped DRA exhibits a radiated power of 0.8825 W with respect to 1W incident power and maximum gain of 5.9672 dBi. The RF power received by Antenna is given to a Rectifier circuit via proper impedance matching circuit. The rectified pulsating DC power is given to capacitor filter to suppress harmonics .
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Thomaz, Fabrício, Augusto César Teixeira Malaquias, Glauber Assunção Resende de Paula, and José Guilherme Coelho Baêta. "Thermal management of an internal combustion engine focused on vehicle performance maximization: A numerical assessment." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, December 29, 2020, 095440702098282. http://dx.doi.org/10.1177/0954407020982825.
Full textAbstract:
In extreme ambient conditions, engine temperature and air charge temperature (ACT) can be so high that they compromise the vehicular performance. To preserve the structural engine reliability, it is necessary to reduce the load through an increase in the engine speed to maintain the power output, which minimizes fuel conversion efficiency degradation. However, high engine speeds also lead to enhanced friction losses and combustion frequency, which reduces the engine thermal efficiency. Therefore, this work seeks to numerically study the best thermal management strategy to minimize performance losses arising from an engine power derate strategy, while also optimizing the design of a cooling system to withstand extreme engine stress conditions, characteristics of the Davis Dam tests. Different radiator lengths and fan power were numerically simulated to conclude about the most influential parameter on fuel consumption in the FTP-75 + HWFET cycle. The results showed positive effects from the engine power derate strategy, and the engine speed control was able to mitigate up to 23% derate by cooling temperature. There was a 0.8% increase in fuel consumption for every 2.5% aerodynamic drag coefficient increase, which reinforces the need to perform robust thermal management procedures instead of oversizing a vehicular cooling system for high-load operation.
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"Optimisation of Automobile Radiator by Linear and Helical Tubes." International Journal of Innovative Technology and Exploring Engineering 9, no. 5 (March 10, 2020): 1172–78. http://dx.doi.org/10.35940/ijitee.e2780.039520.
Full textAbstract:
An automobile radiator is a component of an automotive cooling system which plays a major role in transferring the heat from the engine parts to the environment through its complex working system. Heat losses through the radiator and the tailpipe add up to 58 to 62 percent of the total losses. Insufficient heat dissipation can result in the overheating of the engine, which leads to the breakdown of the lubricating oil, corrosion and metal weakening of engine parts, and significant wear between engine parts. To minimize the stress on the engine as a result of heat generation, automotive radiators must be designed to be more effective while still maintaining high level of heat transfer within components. This leads to the increased demand of power packed radiators, which can dissipate maximum amount of heat for any given space. In this paper we have designed and analyzed the performance of radiators by comparing linear tube radiator and two helical tube radiators as coolant inside radiator follows triple pass flow pattern. The modeling is done using CATIA. The fluid flow analysis is done with ANSYS FLUENT.
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Cheng, W. N., C. C. Cheng, and G. H. Koopmann. "A New Design Strategy for Minimizing Sound Radiation of Vibrating Beam Using Dimples." Journal of Vibration and Acoustics 133, no. 5 (September 20, 2011). http://dx.doi.org/10.1115/1.4003939.
Full textAbstract:
A method is proposed for minimizing the sound radiation of a vibrating beam by patterning the beam with a series of cylindrical dimples such that one or more of the vibration modes have the same shape as the corresponding weak modes. In implementing the proposed approach, the objective is to minimize the shape difference between the vibration mode(s) and the designated weak mode(s) rather than to minimize the radiated sound power at a specific frequency or over a certain bandwidth. The design objective is achieved by calculating the weak modes of the beam using the finite element method and then applying an optimization scheme with the modal assurance criterion (MAC) as the objective function. The optimization results, which cause the vibration mode(s) of the dimpled beam to approach the corresponding weak modes(s), determine the dimple angle and dimple depth. The numerical results show that the radiation efficiency of the optimized dimpled beam using MAC as the objective is generally lower than that of a uniform beam. However, the effectiveness of the proposed design strategy depends on the degree of closeness between the shape of the vibration mode(s) of the dimpled beam and that of the designated weak mode(s).