关于Semigroups of Linear Operators and Applications to Partial Differential Equations的两个注解

基礎講座 電気泳動(Electrophoresis)

This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems. Although we discuss the main points in the application of the finite element method to electromagnetic design, including formulation and implementation, those who seek deeper understanding of the finite element method should consult some of the works listed in the bibliography section.

Introduction to the Finite Element Method

The etch rates for 317 combinations of 16 materials (single-crystal silicon, doped, and undoped polysilicon, several types of silicon dioxide, stoichiometric and silicon-rich silicon nitride, aluminum, tungsten, titanium, Ti/W alloy, and two brands of positive photoresist) used in the fabrication of microelectromechanical systems and integrated circuits in 28 wet, plasma, and plasmaless-gas-phase etches (several HF solutions, H/sub 3/PO/sub 4/, HNO/sub 3/+H/sub 2/O+NH/sub 4/F, KOH, Type A aluminum etchant, H/sub 2/O+H/sub 2/O/sub 2/+HF, H/sub 2/O/sub 2/, piranha, acetone, HF vapor, XeF/sub 2/, and various combinations of SF/sub 6/, CF/sub 4/, CHF/sub 3/, Cl/sub 2/, O/sub 2/, N/sub 2/, and He in plasmas) were measured and are tabulated. Etch preparation, use, and chemical reactions (from the technical literature) are given. Sample preparation and MEMS applications are described for the materials.

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Etch rates for micromachining processing

Any device which senses information such as shape, texture, softness, temperature, vibration or shear and normal forces, by physical contact or touch, can be termed a tactile sensor. The importance of tactile sensor technology was recognized in the 1980s, along with a realization of the importance of computers and robotics. Despite this awareness, tactile sensors failed to be strongly adopted in industrial or consumer markets. In this paper, previous expectations of tactile sensors have been reviewed and the reasons for their failure to meet these expectations are discussed. The evolution of different tactile transduction principles, state of art designs and fabrication methods, and their pros and cons, are analyzed. From current development trends, new application areas for tactile sensors have been proposed. Literature from the last few decades has been revisited, and areas which are not appropriate for the use of tactile sensors have been identified. Similarly, the challenges that this technology needs to overcome in order to find its place in the market have been highlighted.

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A review of tactile sensing technologies with applications in biomedical engineering

Practical Inverse Model of a Magnetorheological Damper for Vehicle Suspension Applications

The paper presents the process planning and scheduling of two types of micromachined capacitive transducers for pressure measurements. The fabrication process includes micromachined silicon and glass components. The different stages, process parameters and the required time to obtain devices with flat and corrugated membranes, are presented. The information generated from a laboratory scale experiment is extended to an industrial system. A process that involves the manufacturing of 4,800 devices once on 100 three-layer sandwich structures is studied. A total of 47 activities and 9 alternate operations are identified. For each of them, the time period is established using the acquired experience of the laboratory process. All the techniques and their parameters, the resources are screened and the time necessary to accomplish the above mentioned devices, starting from the si and glass wafers are determined. The activities are considered according to their priorities and two process networks are considered for the two types of devices for flat plate and for corrugated plate. The critical activities and the necessary resources at each step are established. An optimum activities' scheduling for the processes is proposed, in which the priorities and the critical processes are identified. The resource allocations and their capacity are also determined.

Process planning and scheduling of micromachined transducer

The sound of a conch shell is very unique in nature and has been used in different cultures around the world, mainly in India, Greece and Japan. It was used to mark auspicious occasions, for signaling purposes and on rare occasions as a musical instrument. The conch shell is considered as one of the earliest “horn instruments” used by mankind. However studies on the acoustical properties of the instrument is scarcely found in literature. In order to shed more light on the nature of the conch shell sound, we obtained X-ray images of two different conch shells. The images were processed for analyzing the geometry of the spiral cavity. We tried finding a spiral geometry that best matches and describes the spiral cavity displayed in the X-ray scans. Furthermore, the directivity pattern of a conch shell driven by a small loudspeaker and an electro-pneumatic transducer are measured experimentally. It is found that the shell radiates sound uniformly in space at frequencies near the cavity’s resonance. The shell's sound spectra in three different excitation cases are also compared (lip excitation, loudspeaker and electro-pneumatic transducer). As expected, the sound spectrum of the lip-driven shell contains clear peaks at a fundamental frequency and its harmonics, giving the sound a musical tone. In contrast, the overtones of the loudspeaker and electro-pneumatic transducer driven shell are not harmonics of a fundamental frequency.

/pdf/spectrum-analysis-and-directivity-pattern-of-a-transducer-2b9w2vw2li.pdf

Spectrum Analysis and Directivity Pattern of a Transducer-Driven Conch Shell

^anson, D. B., "Compressible Helicoidal Surface Theory for Propeller Aerodynamics and Noise," AIAA Journal, Vol. 21, June 1983, pp. 881-889. Long, L. N., ''The Compressible Aerodynamics of Rotating Blades Using an Acoustic Formulation," Ph.D. Dissertation, School of Engineering and Applied Science, George Washington University, Washington, D.C., April 1983. Long, L. N., "The Aerodynamics of Propellers and Rotors Using an Acoustic Formulation in the Time Domain," AIAA Paper 831821, 1983. Farassat, F., "The Prediction of the Noise of Supersonic Propellers in Time Domain—New Theoretical Results," AIAA Paper 83-0743, April 1983. Ffowcs Williams, J. E. and Hawkings, D. L., "Sound Generated by Turbulence and Surfaces in Arbitrary Motion," Philosophical Transactions of the Royal Society of London, Vol. A264, 1969, pp. 321-342. Isom, M. P., "The Theory of Sound Radiated by a Hovering Transonic Helicopter Blade," Polytechnic Institute of New York, Rept. Poly-AE/AM 75-4, 1975. Farassat, F., "Advanced Theoretical Treatment of Propeller Noise," Propeller Performance and Noise, von Karmn Institute for Fluid Dynamics, Lecture Series 1982-08, 1982. function, and tf the duration of the pulse within a period. The periodic pulse excitation F( t) is shown in Fig. 1. Assuming that steady-state conditions are obtained after sufficiently large n = N, the system response will satisfy the following conditions:

Rama B. Bhat

Papers

Practical Inverse Model of a Magnetorheological Damper for Vehicle Suspension Applications

Process planning and scheduling of micromachined transducer

Spectrum Analysis and Directivity Pattern of a Transducer-Driven Conch Shell

Steady-state response of vibrating systems to periodic pulse excitation

A friction model of microbearings with thin metallic compliant coatings