eLearning

A comparison of volumetric oxygen consumption to gait mechanical energy in normal and pathological gait

S. Augsburger; C. Tylkowski Pediatric Gait: A New Millennium in Clinical Care and Motion Analysis Technology, 2000

A common denominator between volumetric oxygen consumption (VO2) and gait mechanical energy (Eg) is velocity of gait (v). By measuring VO2 and assessing Eg in a normal population over a range of velocities, a normal VO2 to Eg relationship is established. In pathological gait, such as in cerebral palsy (CP), the degree of involvement (spasticity, motor control, weakness, co- contraction, ...

An exact analysis of a rectangular plate piezoelectric generator

Jiashi Yang; Ziguang Chen; Yuantai Hu IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2007

We study thickness-twist vibration of a finite, piezoelectric plate of polarized ceramics or 6-mm crystals driven by surface mechanical loads. An exact solution from the three-dimensional equations of piezoelectricity is obtained. The plate is properly electroded and connected to a circuit such that an electric output is generated. The structure analyzed represents a piezoelectric generator for converting mechanical energy to ...

The electric power clamping device driven by stepmotor and screw-togge-lever force amplifier in series

Sun Chengfeng; Zhong Kangmin 2011 International Conference on Consumer Electronics, Communications and Networks (CECNet), 2011

Hydraulic clamping device is widely used in modern manufacturing. But, the energy efficiency of a hydraulic clamping device is lower and the environmental pollution is serious. We introduce a new type of electrical power clamping device in this paper. Its working principle is, by using the screw-toggle-lever three-step series force-amplifier, the rotary motion of the stepmotor is changed into linear ...

Brownian motor analysis and its application to nanosystems

M. A. Lyshevski Proceedings of the 2nd IEEE Conference on Nanotechnology, 2002

On the molecular scale biological machines of the size approximately 0.01 μm perform transport guaranteeing functionality of living cells. Thermal and quantum fluctuations are the major source of energy for such minuscule machines. They transport biological materials and ions, build proteins, attain motility of the cell, etc. Fluctuation-driven transport, mapped by the Brownian ratchet principle, gives us the understanding of ...

Vibration damping with piezoceramics shunted to negative capacitance networks

Marcus Neubauer; Jorg Wallaschek 2009 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, 2009

Piezoelectric shunt damping is a well known technique to damp the mechanical vibrations of structures. Due to the piezoelectric effect, the piezoceramics converts mechanical energy into electrical energy. Connecting electrical networks to the electrodes of the piezoceramics allows to dissipate a part of this energy in the electrical shunt. Linear resonant shunts consisting of inductance and resistance (LR) are broadly ...

IEEE-USA E-Books

• Steam Turbines

  This chapter discusses the basic design and components of a high pressure, intermediate pressure, and low pressure steam turbine. Turbines provide the primary means of converting the thermal energy contained in the steam system to the mechanical energy in the turbine shaft. This is used to drive the main generator in a power plant as well as various auxiliary pieces of equipment such as boiler feed pumps. The amount of energy exchanged between the steam system and the turbine system during this thermal to mechanical energy conversion process is a function of both the velocity of the steam flow as well as the differential pressure drop across the steam blades. Superheated steam from the boiler or steam generator enters the high pressure (HP) section of the turbine where the steam is expanded across the high pressure turbine blades. The chapter also describes the safety hazards associated with turbine system equipment.

• Gas Turbines

  This chapter discusses the basic design and components of a combustion turbine. Gas Turbines operate in a fashion similar to steam turbines. Both the steam turbine and gas turbine convert the thermal energy contained in the media that is supplied to the turbine into mechanical energy. Instead of using steam as the media for the transfer of energy, gas turbines use air or gas. In the typical combustion turbine, there are at least six fundamental components to the combustion turbine required to achieve the conversion of energy to mechanical energy. These are air inlet, compressor, combustion system, turbine, exhaust and support systems. To achieve combustion, we need the three elements of the combustion triangle; an oxygen source, a fuel source, and a heat source. Various types of instrumentation are necessary to monitor the status of the operating combustion turbine and provide the control system with the necessary feedback.

• Magnetic Actuators Operated by DC

  Magnetic actuators use magnetic fields to transform electrical energy into mechanical energy. Thus they are a type of transducer. This chapter discusses in detail the most common types of magnetic actuators operated by direct current (DC). The magnetic actuators discussed in the chapter are: solenoid actuators, voice coil actuators, other linear actuators using coils and permanent magnets, proportional actuators, rotary actuators, magnetic bearings and couplings, and magnetic separators.

• Generators

  This chapter discusses the basic design and construction of generators. Generators convert the mechanical energy delivered by the prime mover into electrical energy to be transmitted to the electrical system. Most generators are synchronous machines that have an external field applied to the machine and drive voltage and current into the electrical system at synchronous frequency. One of the more popular applications of an induction machine to be used as a generator is in the field of wind power. The rotor circuit has multiple turns of conductor that form the main field. There are layers of insulating material between these conductors to ensure the insulation integrity between turns. Generators use either air or some type of gas to internally remove heat from components. A common gas used inside generators is hydrogen. Synchronous generators with higher short circuit ratios provide increased stability to system transients.

• Electric Power Generation and Concerns About Greenhouse Gases

  This chapter contains sections titled: Generation's Role Types of Generation Thermal Conversion: Using Fuel as the Energy Resource Thermal Conversion: Nonfuel Heat Sources Mechanical Energy Conversion Renewable Technologies and Greenhouse Gas Emissions Characteristics of Generating Plants Capital Cost of Generation Generator Life Extension The Technology of Generation System Needs and Evaluation of Intermittent Resources

• Solar and Wind Energy

  Wind is the natural movement of the air due to differences in atmospheric temperatures and pressures. The wind turbine converts the kinetic energy of the wind into mechanical energy at the shaft of the turbine. The shaft of the turbine in turn is connected to a generator where this mechanical energy is converter to electrical energy. For utility operations, the generator is required to operate at a substantially faster speed than the shaft of the rotor connected to the wind blade. The power curves for various types of wind turbines are different, depending on the design of the machine. For very low wind speeds below the minimum operational speed of the machine, the wind turbine is not able to convert an adequate amount of energy to drive the generator. Concentrating solar power (CSP) systems receive solar energy and concentrate this energy into a collector.

• Controlling Civil Infrastructures

  Controls is well-established in most of the major engineering disciplines- electrical, chemical, mechanical, aerospace. Historically, an important exception has been civil engineering, and, as this chapter illustrates, recent developments are bridging the gap. The importance of understanding the dynamics of civil structures has been recognized since the 1940 Tacoma Narrows bridge collapse, but feedback control of buildings, bridges, towers, and other structures is a relatively recent development. The concept of active control for such systems was first introduced in 1972. Since then, a vast literature has been generated on the topic, and, more impressively, a number of successful implementations have been completed (the first full-scale one in 1989). Many of the largest applications have been to buildings in Japan, driven by the desire to achieve protection against earthquakes. The first implementation of structural control was based on active mass dampers (AMDs). An AMD system couples an auxiliary mass to the structure through an actuator. Sensor measurements of building movement and stresses are used in a control algorithm to move the auxiliary mass relative to the building. Such systems are versatile and capable, but issues of reliability and power consumption have driven the search for improvements. The next significant development was controllers that employed a combination of active and passive devices. These hybrid active/passive control systems (no relationship to the hybrid discrete/continuous systems discussed in Chapter 7) rely on one of two approaches: hybrid mass damping and hybrid base isolation. The former is especially popular. The largest building in Japan, the Yokohama Landmark Tower, incorporates two hybrid mass dampers (HMDs), each weighing 170 tons. The most recent innovation is the semiactive control device. These devices cannot i nject mechanical energy into the structure but have properties that can be manipulated to achieve structural disturbance rejection. In many cases, they can operate on battery power; this is a significant advantage since seismic events can interrupt main power supplies. Examples of semiactive devices include variable-orifice fluid dampers, variable-stiffness devices, variable-friction devices, controllable and tuned liquid dampers, and magnetorheological dampers. The last topic is discussed at some length in this chapter, and experimental results are shown.

• Basic Thermal Cycles

  This chapter discusses the basic Brayton and Rankine thermodynamic process. It utilizes the American Society of Mechanical Engineers (ASME) steam tables which list properties of water and steam in United States customary units; so the discussion of thermodynamics utilizes United States customary units. Most methods of energy conversion involve the conversion of one form of energy to thermal energy, and generation stations use water and steam as a media to transmit this thermal energy from one part of the system to another where it is then converted to mechanical energy. This mechanical energy is used to drive a generator which converts the mechanical energy to electrical energy. Since water and steam are one of the most common methods used for the thermal part of this energy conversion process, a review of steam fundamentals and basic thermodynamic laws along with the typical types of equipment used in this process is essential.

• Mechanical Energy Harvesting with Piezoelectric Nanostructures: Great Expectations for Autonomous Systems

  This chapter contains sections titled: Introduction Mechanical Energy Harvesting using MEMS Mechanical Energy Harvesting using Piezoelectric Nanostructures Further Improvements at the Nanoscale Towards Completely Autonomous Systems: Multisource Approach Conclusions and Future Prospects

• Hydraulic Turbines

  Hydraulic turbines convert the potential energy contained in a head of water to mechanical energy in the rotor of the turbine. The amount of power transferred is proportional to the amount of head across the turbine blades and the flow through the turbine blades. Therefore, in the application of hydraulic turbines, control of the flow of water through the turbine will control the amount of mechanical power developed by the turbine shaft which will, in turn control the amount of electrical power delivered by the hydraulic turbine generator. Fundamentally, flow control is achieved by the use of either wicket gates that control the flow to the turbine blades and/or by the use of variable pitch blades on the turbine rotor. This chapter discusses the three basic types of hydro???turbine plants: impoundment, diversion, and pumped storage. It also describes the three basic types of hydro???turbine unit blade designs: reaction, impulse, and kinetic energy units.