Low Coil Research Articles

薄膜コイルによる単磁極ヘッドの高感度化

A new single-poly-type head with a single-turn thin-film coil is presented. A main pole was laid between two conductive layers of coils to reduce the leakage of magnetic flux from the main pole by means of the eddy current induced in the coils. A ferrite return path core, placed under the lower coil, brought a high read/write sensitivity by shortening the magnetic path in the head. Although only a single-turn coil was used, employment of this scheme with a Co-Cr/Fe-Ni-Nb double-layered medium at a writing current of 50 rnA (0.05 ATo-p) led to saturation of the medium. A high normalized output of 1000 nVp-p/μm·turn·m/s was obtained. The recording and reproducing sensitivity was much higher than that of our conventional inductive single-pole head.

The Indentation Properties of Amorphous Boron Coatings Synthesized by Plasma-Enhanced CVD

ABSTRACTAmorphous boron coatings, ranging in thickness from 4 to 15 μm, have been synthesized via plasma-enhanced chemical vapor deposition using an rf plasma coil having serpentine rather than helical geometry for inductive coupling of the plasma. The power input to the rf coil has been established at five discrete levels ranging from 50 to 200 W during deposition from diborane onto Ti-6Al-4V substrates at 450°C. Deposition rates have been found to depend significantly on coil input power, reach in a saturation level of 15 μm/h at 100 W and higher but decreasing markedly with lower coil power levels. The amorphous nature of the coatings has been confirmed by selected area electron diffraction of extracted particles. Vickers and ultralow-load indentation experiments have been performed on boron coatings in cross-sectional and plan orientations, respectively. The ultralow-load hardnesses of the coatings deposited at all power levels exhibited relative independence from deposition power and ranged from 11.5 to 14.6 GPa. Vickers indentation in cross section produced hardnesses which were significantly greater than those using ultralow loading and an inconsistent dependence on deposition power.

Heat Pump Ground Coil Analysis With Thermal Interference

When two horizontal ground coils are buried in the same trench, one on top of the other, the total energy exchange between coils and ground increases drastically over that of a single coil for the same trench length. However, because of the thermal interference between the two coils, the overall performance of the two-coil trench is very difficult to determine. Traditionally this type of problem is handled by the line source mirror-image approach. However, in applying the line source approach, the strength of the source is not known precisely and must be estimated. Most designers will estimate this value very conservatively in order to be on the safe side, and this will result in a longer coil than is actually needed. This paper provides a detailed mathematical model to describe the operation of the two-coil system that can calculate more realistically the performance of the ground coils, which in turn could make the ground coil heat pump system more economically competitive with other heating and cooling systems. The effect of thermal interference is clearly shown in the calculated soil temperature profile. The effect of fluid inlet positions, from upper or lower coils, is also studied. The comparison of measured and calculated daily energy absorbed from the ground indicated a maximum error of 27 percent, with the average error at less than 12 percent, calculated values are on the conservative side. This model is better than the line source approach for calculating the performance of two coils in the same trench. It can be used for design purposes, or used to check such coil designs by other methods.

Increase in Cochlear Cell Damage as a Function of Variations in Exposure to “Acid Rock” Music

Fourteen guinea pigs were variously subjected to high-intensity rock music peaking at 122 dB SPL. During the stimulation periods, the music was interrupted for 1 min every 4 min to approximate the intermittent exposure occasioned at discotheques. Total exposure time ranged from no exposure to 80 h. Surface preparations of the cochlear tissue were prepared and underwent phase-contrast microscopic inspection. As anticipated, the amount of cell damage increased as a function of increase in exposure time. For example, an ear exposed to the stimulus for a total of 5 h sustained damage to 1.73% of the total cell population. For an ear exposed for 45 h, 1.95% of the cells were damaged. After 80 h of intermittent exposure to the intense music, however, 7.57% of the cell population was found to be irreversibly destroyed, demonstrating a nonlinear growth in cochlear cell damage with increased exposure duration. An important fact is noted in that cell destruction discovered in response to the acoustically complex stimulus was greater at the apical region of the cochlea with gradually lessening amounts of damage noted in specimens removed from lower coils. Numerous phase-contrast photomicrographs illustrate the patterns of cell damage caused by the sound stimulus. The results of this study are compared to an earlier report which had noted more widespread cell damage.

Alteration of acetylicholinesterase in the cochlea.

In an attempt to clarify the aspect of the acetylcholine (Ach) metabolism occurring within the cochlea of the guinea-pig, determinations of aeetylcholin-esterase (ChE) activity within it have been made, and the alteration of ChE under pathological conditions was studied. The animals were exposed to sounds or were given D.H.S.M. and D.F.P. systemically. The ChE activity was quantitatively determined with use of Cartesian diver respirometer. By the freezing and melting procedures, the ChE activity was expressed in terms of “functional and reserve ChE.” The following results were obtained: 1) In normal specimens, ChE activity per mm in the lower coil was greater than in the upper coil, but by the freezing and melting procedure, its activity increased in both coils within a similar range. 2) In the tissues of the sound-exposed animals, functional ChE diminished in the lower coil, while reserve ChE in the upper coil diminished. 3) In the tissues of the D.F.P.-injected animals, both functional and reserve ChE slightly diminished in the both coils. 4) In the tissues of the D.H.S.M.-injected animals, considerable individual differences of ChE were characteristic, though both types of ChE decreased on the average. 5) ChE in the cochlea showed a tendency to change its activity characteristic-ally under each above-mentioned pathological condition.

Determination of Pitch and Yaw Rates of Models in Free-Flight Ranges by Magnetic Induction

V7^AW CARDS and shadowgraph pictures are presently used to determine pitch and yaw of ballistic models in free-flight ranges. Both methods yield information at only a limited number of points. The magnetic induction methodt here outlined yields continuous information on pitch and yaw rates, from which continuous records of pitch and yaw angles can be obtained. The apparatus for determining rate of pitch consists of two long, rectangular multiturn loops, or coils, of wire. One coil is located just above and the other just below the test range with the length and width of the loops corresponding to the length and width, respectively, of the test range (see Fig. 1). The model, containing a permanent bar magnet oriented parallel to its axis, is fired from a gun down the test range between the upper and lower coils. The magnet generates a voltage in the coils proportional to the rate of change of pitch angle of the model. This voltage is amplified and plotted against time, giving a record of pitch rate of the model at any point along its path of flight. A similar pair of coils along the sides of the test range measures the yaw rate. An experimental setup of the system was made in an existing free-flight range at the Ames Research Center. If the model is far enough from the ends of the coil so that end effects can be neglected, if the model is moving along the center line of the coil system, and if the pitching and yawing rotations are small in amplitude, then