Dual Heads Research Articles

Dual-element GMR/inductive heads for gigabits density recording using CoFe spin-valves

We have succeeded in designing, fabricating, and testing GMR/inductive heads. 1 /spl mu/m trackwidth CoFe spin-valve read elements showed high sensitivity even after head fabrication due to its good thermal stability. About 1.5 /spl mu/m trackwidth a-CoZrNb write elements with Bs (Saturation flux density) of 1.35 T fabricated by trench filling process showed high potential for Gbit density recording. As a result of the feasibility study, 18 kTPI and 140 kBPI are thought to be within the scope by combining the dual element heads with low-noise media.

Signal processing for single and dual element unshielded magnetoresistive heads

Single and dual element unshielded magnetoresistive (UMR and DMR) heads have potential for extremely high density magnetic recording, but saturation and unusual readback waveforms must be dealt with. Two new peak detector channels take advantage of the unusual waveforms: (1) The quasi-integrating channel for the UMR, whose output is similar to that of integrating channels with inductive read heads. Performance may be enhanced by adding short pulses to the write current at distances greater than T/sub min/ from code 1 transitions. (2) Controlled polarity recording with decision feedback, which is a special case of write equalization where successive pulses may have the same polarity. The detection window is twice that of conventional recording. Simulated performance is comparable to PRML channels. >

Dual stripe magnetoresistive heads for high density recording

The design and recording performance of dual stripe magnetoresistive read/inductive write heads with read widths of 4 /spl mu/m and write widths of 4.5 /spl mu/m are described. A linear density of 75 kfci (D50) was measured in heads with shield-to-shield spacing of 420 nm and 70 nm of dielectric separating the two magnetoresistive stripes. Large signal amplitude, linear cross-track profile, and good second harmonic suppression are observed in accordance with theoretical expectations. Readback waveforms contain little baseline shift and the ratio of positive to negative peak amplitudes is very close to unity. Stable signals are seen for heads with and without exchange stabilization. Conductor topography in the read head is replicated in the write head and can adversely affect cross-track behavior. Non-planarity of the write head must be considered in the design of shared pole magnetoresistive heads.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The performance of ultrasound physiotherapy machines in Lothian region, Scotland, 1992

Eighty-five ultrasound therapy machines in use in Lothian Region, Scotland were tested for performance and their recalibration was expedited where necessary. The performance characteristics reported are the temporal average acoustic output power, the treatment frequency, pulse timing and treatment timer accuracy. Consideration is also given to the performance of the wide dynamic range radiation force balance that was used to make acoustic power measurements. Of the machines tested, 69% had power outputs that differed by more than 30% from the expected values. The results of power measurements are analysed according to continuous and pulsed output, single and dual frequency treatment heads and year of manufacture. Therapy machines more than 10–12 years old and modern dual frequency treatment heads performed particularly badly. This study suggests that the performance of ultrasound therapy machines has improved little in the last 20 years despite the introduction of IEC 601-2–5 in 1984.

Preparation of Giant Magneto-Resistive Multilayers for Dual Truck Complementary Thin Film Heads

Dual truck complementary head has been proposed in this study. It was confirmed that the recording mechanism was correct in principle through the read-write charactristics using conventional thin film head. Thin film with giant magneto-resistivity GMR ratio is required to construct the hybrid type of read-write head. Ni-Fe/Cu multilayers with Cu layer thickness of 10A prepared by ion beam sputtering method exhibited high magneto-resistivity (MR) ratio as large as aobut 16%. The multilayer seemed to be suitable for detecting of flux reversal in dual truck complementary heads.

Micromagnetic track profile asymmetries in dual magnetoresistive heads

An appropriate 3-D micromagnetic model of a shielded, finite stripe height, dual element magnetoresistive (MR) head is developed. It is shown that asymmetric bias profiles in the cross track direction arise from uniform bias magnetic fields. These asymmetric bias profiles appear in addition to the previously reported anisotropic signal flux propagation that occurs with respect to MR sensor width edges. For the case studied, the peak response of the dual MR sensor is 1.5 times that for the single film. Peak-to-peak voltage asymmetry varies considerably for the single-film MR as the line source alignment is changed. However, the differential sensor exhibits very small peak asymmetry for all alignments. Finally, it is shown that for the case studied, the 50% amplitude track width of the dual MR sensor is about 26% broader than that for the single MR response curve.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Integrating tester pin electronics

A 10-V pin electronics driver that can output signals with low distortion and fast risetimes for both narrow and wide voltage swings is described. The features combine to eliminate the need for dual drivers, pin cards, or test heads, which simplifies the testing of mixed-technology devices or modules. A high-voltages process module has been added to a standard 1.5- mu m digital CMOS process, which allows the driver to be in the same silicon as the timing and formatting circuitry. Design and calibration techniques that overcome the limitations of the high-voltage CMOS process are examined. >

Dual exchange biased NiFe-TbCo unshielded MR heads for high density recording

Narrow-trackwidth unshielded MR (magnetoresistive) heads with both longitudinal and transverse bias supplied by a single TbCo exchange-bias layer were constructed. These preliminary dual-biased NiFe-TbCo MR heads exhibit Barkhausen-noise-free, low-distortion response characteristics over a wide range of recording densities (up to 80 kFCI). A 64- mu m track width, 7- mu m height dual-exchange-biased element exhibited a phase margin of 50% at a raw bit error rate of 10/sup -5/ in a recording channel reproducing

Local Cerebral Blood Flow Mapping by SPECT of N-isopropyl-p-[&lt;SUP&gt;123&lt;/SUP&gt;I] Iodoamphetamine in Comparison with &lt;SUP&gt;81m&lt;/SUP&gt;Kr Image

Local cerebral blood flow in 28 patients (aged from 13 to 71) with cerebrovascular disorders was studied 37 times by single photon emission computed tomography (SPECT) using N-isopropyl-p-[123I] iodoamphetamine (IMP), and compared with findings of X-ray computed tomography (CT) and 81mKr (Kr) perfusion images. There were three patients with occlusion of the internal carotid artery, two with stenosis of the internal carotid artery, six with occlusion of the middle cerebral artery, five with occlusion of the bilateral vertebral arteries, five with moyamoya disease, two with aortitis syndrome, and five with cerebral arteriovenous malformation. Examinations were performed using a rotating gamma camera with dual heads in both SPECT-IMP and SPECT-Kr. In the IMP study, both SPECT and planar images were obtained 30 and 120 minutes after intravenous injection of IMP. SPECT-Kr was performed by continuous infusion into the ascending aorta of 81mKr generated by an 81Rb-81mKr generator. Sampling time was about 20 minutes in 22 examinations and about 10 minutes in 15 examinations by SPECT-IMP, and about 4 minutes in all the examinations by SPECT-Kr. SPECT-IMP images 30 minutes after injection showed low perfusion area in all but four examinations in three patients: one patient with transient ischemic attack alone and two patients with aortitis syndrome. In 26 of the 33 examinations, SPECT-IMP images 30 minutes after injection revealed more extensive or obvious low perfusion areas than the low density lesions in X-ray CT, and low perfusion even in the areas without low density lesions. In all of the 33 examinations, low perfusion areas shown in SPECT-IMP images 30 minutes after injection became obscure after 120 minutes. In respect to representation of local cerebral blood flow, SPECT-IMP images 30 minutes after injection seemed to be better than after 120 minutes. In 26 of the 33 examinations, low perfusion areas in SPECT-Kr images were more extensive and obvious than in SPECT-IMP images. However, SPECT-IMP images seemed to show a more definite anatomy than SPECT-Kr images. The nidus of a cerebral arteriovenous malformation was shown to be a low perfusion area in SPECT-IMP images, but appeared as a high perfusion area in SPECT-Kr images. It is likely that SPECT-Kr images showed mainly intravascular flow of the nidus. In comparison with SPECT-Kr, SPELT-IMP was considered to be an easy and noninvasive three dimensional study of local cerebral blood flow.

Dual Heads

Dual Heads

A motion compensated shipboard precision balance system

A balance system that can rapidly (20 s) weigh to a precision (95% confidence interval) of ± 3 mg (weights below 20 g) or better than ± 0.02% (20 to 300 g) aboard moderate sized ships in moderate sea states is described. The principal factors in this design are: (1) dual electronic balance heads with the reference load matched to within 1 g of the unknown and an analog output of the difference in output between the two balances, (2) digital averaging of the difference in output between the two balances, (3) statistical testing of individual weighings to give confidence intervals for individual weighings, and (4) gimballing of the balance heads.

Dual stripe magnetoresistive read heads for speed insensitive tape readers

Two magnetic detectors spaced one-half data cell apart and coupled with the appropriate simple decode electronics can be employed as a read system for Aiken-encoded magnetic tape. The resultant read system will provide output data which are independent of the speed of the magnetic tape relative to the read head (scan speed). If, in addition, the magnetic detectors respond to the magnetic flux from the magnetic tape rather than to changes in the magnetic flux, the read head output becomes totally independent of the scan speed. Such a system is especially useful for applications which require scan speed-independent reading of low density information, as, for instance, with hand-driven, magnetically encoded credit cards.