External control electromagnetic fields

The /i-fan operates in a reduced environment and at high temperatures, which will probably present additional difficulties. The concept for technical realization of this device is shown in Fig. 5.39. The /x-fan is driven by an external rotating electromagnetic field, which enables control of part of the recycle flow. 

Models are also required for analysis of the transport. For calculations of current/ voltage curves, current density, inelastic electron scattering, response to external electromagnetic fields, and control of transport by changes in geometry, one builds transport models. These are generally conceptual - more will be said below on the current density models and IETS models that are used to interpret those experiments within molecular transport junctions. 

Modern sensors are remarkable in many ways. Their small dimensions open up new areas of mechanics, flow control, friction, and oscillation. Force measurements are just one example. The once somewhat obscure classical Coriolis force is now the principle means of sensing rotation. And the even more obscure miniscale quantum-mechanical Casimir force, arising between two close interfaces, is now also accessible to sensor structures. Sensitivities are astonishing even now, but will most probably continue to be enhanced. Very many external parameters, such as temperature, pressure, and electromagnetic fields, can be accurately and quickly measured. What a wonderful area of activity for physicists, chemists, engineers - and salespeople alike The prospect of protecting humankind as well as the environment is gratifying. 

A transceiver controlled by a computer is used to interrogate and receive the ID code of each RF tag. The transceiver antenna transmits a specially modulated, 125 kHz electromagnetic field. This field is of very low energy and not harmful. When an RF tag is held within about 1 cm from the transceiver s antenna, energy is picked up by the RF tag s antenna. A rectifier in the chip converts this energy to microwatt levels of DC power, which is enough to power-up the logic circuitry on the chip. In a very real sense, the RF tag is similar to a crystal radio (which does not require an external power source), except that the device serves as both receiver and transmitter. It is self-contained , in that the chip uses no internal batteries and has no external metallic connections. 

Redox reactions at the interface between immiscible liquids fall into two classes. The first class includes spontaneous processes that occur in the absence of external electromagnetic fields [16-77]. This type of redox transformation has been investigated in bioenergetics, model membrane systems and at oil/water interfaces [78-99]. Redox reactions in the second class occur at the interface between immiscible electrolytes when external electrical fields are applied to the interface, and under these conditions interfacial charge-transfer reactions take place at controlled interfacial potentials [100-139]. 

The perturbations exerted by external electromagnetic fields on molecular energy levels are often larger than the kinetic energy of molecules at temperatures below 1K. Collisions of molecules in a cold gas may therefore be significantly affected by the presence of external fields. The purpose of this chapter is to discuss the effects of external fields on dynamics of molecular collisions at cold and ultracold temperatures and outline the prospects for new discoveries in the research of molecule-field interactions at low temperatures. The experimental work on collision dynamics of low-temperature molecules in external fields may lead to the development of the research field of cold controlled chemistry [4] and we will particularly focus the discussion on mechanisms for external field control of intermolecular interactions. Most of the results presented are based on rigorous quantum-mechanical calculations. The quantum theory of molecular collisions in the presence of external fields is described in Chapter 1. 

The CRT produces visible or ultraviolet radiation by bombardment of a thin layer of phosphor material by an energetic beam of electrons. Nearly all commercial applications involve the use of a sharply focused electron beam directed time sequentially toward relevant locations on the phosphor layer by means of externally controlled electrostatic or electromagnetic fields. In addition, the current in the electron beam can be controlled or modulated in response to an externally applied varying electric signal. A generalized CRT consists of the following elements ... 

This structure can be eliminated by controlling the heat removal rate from the casting, realizing inoculation, which consists in the introduction of additives to liquid metal and/or influence of external factors for example infra- and ultrasonic vibrations or electromagnetic field. 

An external magnetic field has also been used to confine the plasma [143]. An arrangement where electromagnets are located under the cathode is known as the controlled plasma magnetron method [144]. The diffusion of electrons to the walls is prevented by the magnetic field between cathode and anode. This results in an increase in electron density, and consequently in a faster decomposition of silane and a higher deposition rate. At a deposition rate of 1 nm/s, device quality material is obtained [144]. In addition, a mesh is located near the anode, and the anode can by biased externally, both in order to confine the plasma and in order to control ion bombardment. 

NMR. The CP/MAS spectra were obtained on a single coil, double-tuned probe similar in design to that reported earlier (15) but modified (16) for the electromagnet of the Varian XL-100-15 system. A homebuilt receiver system allows single coil operation. The probe uses a D2O external lock and a special rotor and stator assembly design to provide MAS. The carbon-13 (25.16 MHz) and the proton (100.06 MHz) radio frequency fields are 17 G and 12 G, respectively for 90 watts of power. The H spin locking pulse of 90° may be varied in terms of length and amplitude while the amplitude of the - C irradiation can be controlled to within 0.1 db to match the Hartmann-Hahn (17) condition. The isolation between the two channels is in excess of... 

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