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Acoustic Absorption Characteristics of Perforated Thin Plate with Air Jets and Cavity

Open Journal of Fluid Dynamics 2015年第1期5卷 1-9页

作者： Hiromitsu Hamakawa Hiroki Matsuoka Taiki Yamai Kenta Asakura Toru Otsuru Reiji Tomiku Eru Kurihara Hidechito Hayashi Eiichi Nishida Department of Mechanical Engineering Oita University Oita Japan Graduate School Master’s Program of Engineering Oita University Oita Japan Torishima Pump Mfg. Co. Ltd Takatsuki-shi Osaka Japan Department of Architecture Oita University Oita Japan Department of Mechanical Engineering Nagasaki University Nagasaki Japan Department of Mechanical Systems Engineering Shonan Institute of Technology Fujisawa-shi Kanagawa Japan

The present paper focuses on the effect of air jets through a perforated thin plate on the characteristics of an acoustic absorption coefficient. We measured the flow rate, internal pressure, acoustic pressure, and transfer function by using an improved acoustic impedance tube. The normal incidence absorption coefficient was calculated from the measured transfer function using transfer function methods. As a result, the frequency characteristics of the acoustic absorption coefficient against the frequency showed a maximum value at the local frequency. The peak frequency of the acoustic absorption coefficient depended on the thickness of the background air space and the thickness of the perforated plate. As the flow rate increased through the micropores, the peak level of the acoustic absorption coefficient also increased until a flow rate of 80?l /min. As the flow rate further increased, the peak level of the acoustic absorption coefficient decreased and that of the high frequency band increased.

关键词： Acoustic Absorption Coefficient Perforated Plate Cavity Micropores Air Jets Acoustic Impedance Tube

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Wall to wall optimal transport 15

Wall to wall optimal transport

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15th European Turbulence Conference, ETC 2015

作者： Doering, Charles R. Souza, Andre N. Chini, Gregory P. Hassanzadeh, Pedram Department of Physics University of Michigan United States Department of Mathematics University of Michigan United States Center for the Study of Complex Systems University of Michigan United States Department of Mechanical Engineering Program in Integrated Applied Mathematics and Center for Fluid Physics University of New Hampshire United States Centre for the Environment Department of Earth and Planetary Sciences Harvard University United States

The calculus of variations is employed to find steady divergence-free velocity fields that maximize transport of a tracer between two parallel walls held at fixed concentration for one of two constraints on flow strength: a fixed value of the kinetic energy or a fixed value of the enstrophy (the mean square rate of strain in this situation). The optimizing flows realize upper limits on convective transport in this scenario. We interpret the results in the context of buoyancy-driven Rayleigh–Bénard convection problems that satisfy the flow intensity constraints, enabling us to investigate how optimal transport scalings compare with upper bounds on Nu expressed as a function of the Rayleigh number Ra. © TU Delft.

关键词： Kinetic energy

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Wave Energy Converters and Design Considerations for Gulf of Mexico

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Distributed Generation and Alternative Energy Journal 2015年第4期30卷 55-76页

作者： Guiberteau, Kelly Lee, Jim Liu, Yucheng Dou, Yangqing Kozman, Theodore A. Texas A and M University United States Mechanical Engineering and Program Coordinator of Systems Engineering University of Louisiana Lafayette United States ASME SAE ASEE United States Northwestern Polytechnical University United States University of Louisiana Lafayette Louisiana Industrial Assessment Center United States

This article presents an investigational study on wave energy converters (WECs) and the design considerations for possible implementation in the Gulf of Mexico (GOM). The types of WEC available from the market are studied first. The design considerations for implementing a WEC in GOM are then evaluated. There are several different types of devices that can be used in the system design. Each device type has different attributes that may be helpful or hurtful for the area and wave activity in the GOM. From the evaluation there is a recommendation of the optimal device design conditions, and three device types are recommended for further pursuit as design candidates. Six different WEC projects that are currently being developed and most are ready for commercial testing are examined. Our study evaluates the usefulness of the WECs for the GOM, and provides design factors of both physical and economic scaling. The result of this investigation reveals that while none of the devices can be installed "as is" in the GOM because of wave power or geometry requirements, there are some that have the potential to be modified and scaled down to fit the GOM climate.

关键词： Wave power

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Tissue engineering: Nano-Enabled Approaches for Stem Cell-Based Cardiac Tissue engineering(Adv. Healthcare Mater. 13/2016).

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Advanced healthcare materials 2016年第13期5卷

作者： Mahshid Kharaziha Adnan Memic Mohsen Akbari David A Brafman Mehdi Nikkhah Biomaterials Research Group Department of Materials Engineering Isfahan University of Technology Isfahan *** Iran. Center of Nanotechnology King Abdulaziz University Jeddah 21589 Saudi Arabia. Department of Mechanical Engineering University of Victoria Victoria BC Canada. School of Biological and Health Systems Engineering (SBHSE) Harington Bioengineering Program Arizona State University Tempe Arizona 85287 USA.

On page 1533 M. Nikkhah and co-workers review tissue engineering strategies in the treatment of cardiac diseases with emphasis on the use of nanoenabled approaches (e.g. nanoparticles, nanotopographies) in combination... 详细信息

关键词： biomaterials cardiac tissue engineering nanofeatured surfaces nanomaterials stem cells

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Investigating the effect of cryogenic pre-cooling on the friction stir processing of AZ31B

Investigating the effect of cryogenic pre-cooling on the fri...

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World Congress on engineering, WCE 2014

作者： Ammouri, Ali H. Kridli, Ghassan T. Ayoub, George Hamade, Ramsey F. Mechanical Engineering Department American University of Beirut 11-0236 Beirut Lebanon Department of Industrial and Manufacturing Systems Engineering University of Michigan Dearborn United States Mechanical Engineering Program Texas A and M University United States

ISBN: (纸本)9789881925350

This manuscript aims to investigate the effect of cryogenic in-process cooling via liquid nitrogen on the outcomes of the friction stir processing (FSP) of twin roll cast (TRC) magnesium alloy AZ31B. Friction stir processing was performed on 3mm thick sheets of TRC AZ31B at a wide range of processing parameters. The tool rotational speed was varied between 600 RPM and 2000 RPM while the tool feed rate varied between 75 mm/min and 900 mm/min. Thrust force and torque values were experimentally measured using a 4-component dynamometer. Temperature measurements were monitored during the different tests using Infrared sensors and thermocouples. The microstructure of processed samples was observed using optical microscopy. It was found that thrust force and torque values of the pre-cooled samples were 5% higher than those of the room temperature samples due to the material hardening induced by the cooling effect. Finer and more homogenous microstructure was observed for the pre-cooled samples when compared with samples processed at room temperature. The average grain size of pre-cooled samples was predicted using a relation -previously introduced by the authors- that relate grain size and the Zener-Hollomon parameter for TRC AZ31B. This equation was found to correctly predict grain diameter for in-line cooled FSP AZ31B samples at temperatures lower than room temperature.

关键词： Friction

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Repowering of a synchronous generation plant by induction generator

Repowering of a synchronous generation plant by induction ge...

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CHILEAN Conference on Electrical, Electronics engineering, Information and Communication Technologies (CHILECON)

作者： Alana S. Magalhaes C. A. Leovir Calebe A. Matias Alan H. F. Silva Elder G. Domingues Aylton. J. Alves Wesley P. Calixto Program in Electronic Systems and Automation University of Brasilia (UnB) Brasília Brazil Experimental and Technological Research and Study Group (NExT) Federal Institute of Goias (IFG) Goiânia Brazil School of Electrical Mechanical and Computer Engineering Federal University of Gouias (UFG) Goiânia Brazil

ISBN: (纸本)9781467387576

This work proposes itself through mathematical modeling, simulating the electrical interactions between two electrical generators, an induction generator and a synchronous generator connected to a common bus in steady state, subject to non-linear load. By comparing the modeling of the two machines, we can see that the induction generator will present best way for the harmonic currents flowing in common bus. Experimental tests have confirmed the results of comparative modeling of the electric generators. It was evident that the induction generator, in addition to increasing the active power to the electrical system, could reduce current harmonics components present at the connection point improving the voltage profile in the network.

关键词： Induction generators Harmonic analysis Synchronous generators Power system harmonics Reactive power

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EGI/IMU Integration Using Multiple IMUs and Error Damping Loop for SAR Motion Compensation

EGI/IMU Integration Using Multiple IMUs and Error Damping Lo...

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International Conference on Control, Automation and systems

作者： Jin Woo Song Chul Woo Kang Young Bum Park Yong Gon Jong Park Chan Gook Park BK21 Plus Transformative Training Program for Creative Mechanical and Aerospace Engineers Department of Mechanical and Aerospace Engineering Seoul National University Automations and Systems Research Institute Department of Mechanical and Aerospace Engineering Seoul National University Department of Mechanical and Aerospace Engineering/ASRI Seoul National University

ISBN: (纸本)9781479999767

We propose an EGI/IMU integrated smoothing algorithm based on extended Kalman filter (EKF) for synthetic aperture radar (SAR) motion compensation. Conventional navigation algorithms have discontinuities intrinsically which are caused by the measurement update done by the Kalman filter. The discontinuities are as harmful to the SAR image quality significantly as the relative position error. In order to eliminate discontinuities and to reduce relative position error, an additional inertial measurement unit (IMU) is used with master embedded GNSS inertial navigation system (EGI). The additional IMU contributes to smoother output and navigation accuracy. The error correction by EKF is performed gradually between measurement updates, which significantly improves the smoothing performance. Through Monte-Carlo simulation, the performance improvements in relative accuracy and continuity are confirmed.

关键词： Smoothing algorithm SAR motion compensation EGI Extended Kalman filter

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Towards autonomous navigation of unsignalized intersections under uncertainty of human driver intent

Towards autonomous navigation of unsignalized intersections ...

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IEEE/RSJ International Conference on Intelligent Robots and systems

作者： V. Sezer T. Bandyopadhyay D. Rus E. Frazzoli D. Hsu Department of Mechanical Engineering Istanbul Technical University Istanbul Turkey Tirthankar Bandyopadhyay is with Autonomous Systems Program Commonwealth Scientific and Industrial Research Organization Australia Daniela Rus and Emilio Frazzoli are with the Department of Electri-cal&Engineering and Aeronautics&Astronautic respectively Massachusetts Institute of Technology USA Department of Computer Science National University of Singapore Singapore

In a mixed environment of autonomous driverless vehicles and human driven vehicles operating on the same road, identifying intentions of human drivers and interacting with them in a compliant and responsible manner becomes a challenging problem for the driverless vehicles. In this paper, the problem of vehicle interaction at an intersection merging scenario is formulated as an Intention-Aware motion planning problem using the tools from Mixed Observability Markov Decision Process (MOMDP). We utilize the tools from recent intention aware planning framework to demonstrate a merging behavior in the presence of human drivers by trying to infer and act according to the intentions of the human drivers. A driver behavior model for T-junction intersections is developed in order to calculate the probabilistic state transition functions of the MOMDP model. With proposed solution, it is demonstrated that using intention aware planning improves performance in comparison to present time to merge approach by lowering accident probability and intersection navigation duration. The proposed method is tested on a real autonomous vehicle (AV) in the presence of human driven vehicles to validate our approach.

关键词： Vehicles Navigation Mobile robots Roads Hidden Markov models Uncertainty

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Finite Capacity Scheduling of Make-Pack Production: Case Study of Adhesive Factory

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Journal of engineering, Project, and Production Management 2014年第2期4卷 114-123页

作者： Theppakarn Chotpradit Pisal Yenradee Logistics and Supply Chain Systems Engineering Program School of Manufacturing Systems and Mechanical Engineering Sirindhorn International Institute of Technology Thammasat University Logistics and Supply Chain Systems Engineering Program School of M

This paper developed a Finite Capacity Scheduling (FCS) system for make-pack production based on a real case of an adhesive factory. The FCS determines production quantity of each machine to conform with resource capacities and due date of customer orders while minimizes related total cost. The total cost includes total production, inventory, and cleaning cost. A Mixed Integer Linear programming (MILP) model is formulated and solved by LINGO software. The computational time is very long since the model has a lot of integer variables. Thus, the model is solved for a reasonable time and the best but not optimal solution is reported with the lower bound. This paper tries fixed horizon and rolling horizon scheduling methods. The fixed horizon plans for an entire horizon of 30 days. The rolling horizon plans for a sub-horizon of 10, 15, and 17 days. An overlapping of sub-horizons is applied to reduce end-of-horizon effect. Three scenarios (high, normal, and low) of demands are considered. The fixed horizon method is applied first to all scenarios of demand. If the best solution is far away from the lower bound, the rolling horizon method is applied. The results indicated that the rolling horizon method may significantly reduce the total cost with the same computational time. Moreover, the rolling horizon method is more applicable for a dynamic situation where customers frequently change orders. The proposed MILP model can generate reasonable solutions and they are useful for scheduling decision of make- pack production.

关键词： Make-pack FCS finite capacity scheduling MILP rolling horizon scheduling optimization

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Cyclic strain resistance, stress response, fatigue life, and fracture behavior of high strength low alloy steel 300 M

Cyclic strain resistance, stress response, fatigue life, and...

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作者： Manigandan, K. Srivatsan, T.S. Tammana, Deepthi Poorgangi, Behrang Vasudevan, Vijay K. Department of Mechanical Engineering University of Akron Akron OH 44325-3903 United States School of Dynamic Systems Materials Science and Engineering Program University of Cincinnati Cincinnati OH 45221-0072 United States

The focus of this technical manuscript is a record of the specific role of microstructure and test specimen orientation on cyclic stress response, cyclic strain resistance, and cyclic stress versus strain response, deformation and fracture behavior of alloy steel 300 M. The cyclic strain amplitude-controlled fatigue properties of this ultra-high strength alloy steel revealed a linear trend for the variation of log elastic strain amplitude with log reversals-to-failure, and log plastic strain amplitude with log reversals-to-failure for both longitudinal and transverse orientations. Test specimens of the longitudinal orientation showed only a marginal improvement over the transverse orientation at equivalent values of plastic strain amplitude. Cyclic stress response revealed a combination of initial hardening for the first few cycles followed by gradual softening for a large portion of fatigue life before culminating in rapid softening prior to catastrophic failure by fracture. Fracture characteristics of test specimens of this alloy steel were different at both the macroscopic and fine microscopic levels over the entire range of cyclic strain amplitudes examined. Both macroscopic and fine microscopic observations revealed fracture to be a combination of both brittle and ductile mechanisms. The underlying mechanisms governing stress response, deformation characteristics, fatigue life, and final fracture behavior are presented and discussed in light of the competing and mutually interactive influences of test specimen orientation, intrinsic microstructural effects, deformation characteristics of the microstructural constituents, cyclic strain amplitude, and response stress. © 2014 ASM International.

关键词： Microstructure

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