General Electric

About: General Electric is a company organization based out in Boston, Massachusetts, United States. It is known for research contribution in the topics: Turbine & Signal. The organization has 76365 authors who have published 110557 publications receiving 1885108 citations. The organization is also known as: General Electric Company & GE.

Exchange Anisotropy—A Review

Abstract: Exchange anisotropy describes a magnetic interaction across the interface between two magnetic materials. A shifted hysteresis loop, sinθ torque curve, and rotational hysteresis in magnetic fields greater than 2K / Ms may result from this interaction if one of the materials is antiferromagnetic. This interaction has been found to exist between ferro‐antiferromagnetic materials, ferri‐antiferromagnetic materials, and ferri‐ferromagnetic materials. The work of various people is discussed in terms of the expected behavior in these exchange coupled systems. Some interesting results of the exchange interaction are reviewed. These include improved properties of fine particle magnets, a memory effect in a mixed ferrimagnetic spinel, a rotatable anisotropy in thin films, and an explanation for the reverse magnetization of a deposit in the earth's crust. The interfacial conditions necessary to obtain the interaction between the two magnetic systems are discussed, and it is shown that they are met in several cases. Models are presented which yield rotational hysteresis in magnetic fields greater than 2K / Ms as has been found in all of the exchange coupled systems.

Tracking system to follow the position and orientation of a device with radiofrequency fields

Abstract: A tracking system in which radiofrequency signals emitted by an invasive device such as a catheter, are detected and used to measure the position and orientation of the invasive device. The invasive device has a transmit coil attached near its end and is driven by a low power RF source to produce a dipole electromagnetic field that can be detected by an array of receive coils distributed around a region of interest. The position and orientation of the device as determined by the tracking system are superimposed upon independently acquired Medical Diagnostic images, thereby minimizing the radiographic exposure times. One or more invasive devices can be simultaneously tracked.

The Evaporation of Atoms, Ions and Electrons from Caesium Films on Tungsten

Abstract: Precision methods for measuring the number of caesium atoms adsorbed on tungsten are described. With these methods for determining $\ensuremath{\theta}$ (the fraction of the tungsten surface covered with Cs), the rates of atom, ion and electron emission are measured as functions of $\ensuremath{\theta}$ and $T$, the filament temperature. The rate of atom evaporation, ${\ensuremath{ u}}_{a}$, increases rapidly with $\ensuremath{\theta}$ and with $T$. At low filament temperatures and high pressures of Cs vapor the concentration of adsorbed Cs atoms approaches a limit 3.563\ifmmode\times\else\texttimes\fi{}${10}^{14}$ atoms ${\mathrm{cm}}^{\ensuremath{-}2}$ of true filament surface (one Cs atom for four tungsten atoms). This film ($\ensuremath{\theta}=1$) exhibits all the characteristics of a true monatomic layer. The formation of a second layer begins only at filament temperatures corresponding to nearly saturated Cs vapor. A theory of the formation of a second and of polyatomic layers is given and experiments supporting it are described. The heat of evaporation (given by the Clapeyron equation) for Cs atoms from clean tungsten is 2.83 volts (65,140 calories), 1.93 volts or 44,473 calories at $\ensuremath{\theta}=0.67, \mathrm{and} 1.77$ volts or 40,757 calories at $\ensuremath{\theta}\ensuremath{\simeq}1$. The adsorbing tungsten surface after proper aging is homogeneous, except that about 0.5 percent of it (active spots) can hold Cs more firmly than the rest. The procedure in obtaining electron (${\ensuremath{ u}}_{e}$) and ion (${\ensuremath{ u}}_{p}$) emission for zero field and the large changes in the effect of external field with $\ensuremath{\theta}$ are described. From both ${\ensuremath{ u}}_{e}$ and ${\ensuremath{ u}}_{p}$ the contact potential ${V}_{c}$ is calculated, agreeing, except for very concentrated films, with ${V}_{c}$ calculated entirely from data on neutral atom evaporation. At constant temperature the electron emission increases to a maximum at $\ensuremath{\theta}=0.67$ and decreases as $\ensuremath{\theta}=1$ is approached. The positive ion emission increases rapidly to a maximum at $\ensuremath{\theta}\ensuremath{\simeq}0.01$ and then decreases. The work function (exponent in Dushman type equation) for electrons at $\ensuremath{\theta}=0.67$ is 1.70 volts (clean tungsten=4.62 volts). The work function for ions is 1.91 volts at $\ensuremath{\theta}=0, \mathrm{and} 3.93$ volts at $\ensuremath{\theta}=0.67$. It is shown by experiment that the saturated ion current from a clean hot (1200-1500\ifmmode^\circ\else\textdegree\fi{}K) tungsten filament is an accurate measure (experimental error of about 0.2 percent) of the number of atoms striking the filament per second. The condensation coefficient ($\ensuremath{\alpha}$) for atoms striking a tungsten filament is proved by experiment to be unity from $\ensuremath{\theta}=0$ to nearly 1. The important bearing of this fact and of the experimentally observed existence of surface migration or diffusion on the mechanism of evaporation and condensation in dilute and concentrated films is discussed. In addition surface migration is correlated with irregular ion evaporation rates occurring when two phases (dilute and concentrated films of Cs) exist on the tungsten surface. Transient effects in which $\ensuremath{\theta}$ changes with time are studied and entirely explained by the observed rates of evaporation and condensation. This and other facts are used to justify a surface phase postulate according to which all the properties of the adsorbed film are uniquely determined by $\ensuremath{\theta}$ and $T$.

Learning Curve Approach to Reliability Monitoring

Abstract: Several different and complex electromechanical and mechanical systems are shown to have remarkably similar rates of reliability improvement during system development. These similarities provide the basis for a learning curve which can be used to monitor development progress, predict growth patterns, and plan programs for reliability improvement.