Dick Henze

The PES Pareto method: uncovering the strata of position error signals in disk drives

Describes a method of breaking down the position error signal (PES) of a magnetic disk drive to its contributing components. Once these components are identified, they can be ranked in terms of their overall effect on PES and thus the most critical ones can be worked on first. This method is based on three things: an understanding of how Bodes integral theorem ties into noise measurements, a measurement methodology that allows for the isolation of individual noise sources, and a system model that allows these sources to be recombined to form the drives position error signal. We have found this method to be dramatically useful in identifying the key contributors to PES noise.

An accurate locally active memristor model for S-type negative differential resistance in NbOx

A number of important commercial applications would benefit from the introduction of easily manufactured devices that exhibit current-controlled, or “S-type,” negative differential resistance (NDR). A leading example is emerging non-volatile memory based on crossbar array architectures. Due to the inherently linear current vs. voltage characteristics of candidate non-volatile memristor memory elements, individual memory cells in these crossbar arrays can be addressed only if a highly non-linear circuit element, termed a “selector,” is incorporated in the cell. Selectors based on a layer of niobium oxide sandwiched between two electrodes have been investigated by a number of groups because the NDR they exhibit provides a promisingly large non-linearity. We have developed a highly accurate compact dynamical model for their electrical conduction that shows that the NDR in these devices results from a thermal feedback mechanism. A series of electrothermal measurements and numerical simulations corroborate this model. These results reveal that the leakage currents can be minimized by thermally isolating the selector or by incorporating materials with larger activation energies for electron motion.

Influence of Surfactant Structure on Reverse Micelle Size and Charge for Nonpolar Electrophoretic Inks

Electrophoretic inks, which are suspensions of colorant particles that are controllably concentrated and dispersed by applied electric fields, are the leading commercial technology for high-quality reflective displays. Extending the state of the art for high-fidelity color in these displays requires improved understanding and control of the colloidal systems. In these inks, reverse micelles in nonpolar media play key roles in media and particle charging. Here we investigate the effect of surfactant structure on reverse micelle size and charging properties by synthesizing different surfactants with variations in polyamine polar head groups. Small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS) were used to determine the micelle core plus shell size and micelle hydrodynamic radius, respectively. The results from SAXS agreed with DLS and showed that increasing polyamines in the surfactant head increased the micelle size. The hydrodynamic radius was also calculated on the basis of transient current measurements and agreed well with the DLS results. The transient current technique further determined that increasing polyamines increased the charge stabilization capability of the micelles and that an analogous commercial surfactant OLOA 11000 made for a lower concentration of charge-generating ions in solution. Formulating magenta inks with the various surfactants showed that the absence of amine in the surfactant head was detrimental to particle stabilization and device performance.

Decomposition of baseline noise sources in hard disk position error signals using the PES Pareto method

This paper uses the position error signal (PES) Pareto method and measurement techniques for isolating noise sources to decompose the PES of a Lynx II hard disk drive manufactured by Hewlett-Packard. This accomplishes three things: it demonstrates the utility of the PES Pareto method in a practical example, it allows us to discover which noise sources are insignificant to PES, and it identifies which noise sources are significant to PES. In this particular hard disk drive, it is discovered that the two most significant sources of baseline noise at the disks position error signal are the turbulent wind flow generated by the spinning disks (windage) and the noise involved in the actual readback of the Position Error Signal (position sensing noise).

SANBoost: automated SAN-level caching in storage area network

The storage traffic for different logical units (LUs) of a disk array converge at the arrays cache. The cache is allocated among the LUs approximately according to their relative I/O rates. In the case of nonuniform I/O rates and sensitivity to storage response times between differing applications in a storage area network (SAN), undesirable cache interference between LUs can result in unacceptable storage performance for some LUs. This paper describes SANBoost, a SAN-level caching approach that can be enabled selectively on a per-LU basis to provide a performance isolation mechanism for response time metrics related to storage quality of service (QoS). SANBoost automates hot data detection and migration processes in block-level storage. The design consists of a migration module implemented in a fabric-based SAN virtualization appliance and a solid-state disk (SSD) that acts as a cache resource within the same SAN. Simulation results quantify the impact of a specific static SANBoost caching policy on the SPC-1 benchmark workload and address the relative impact of adapting a threshold in the placement algorithm.

69.4: Novel Flexible Reflective Color Media Integrated with Transparent Oxide TFT Backplane

A novel architecture and proprietary electrically addressable inks have been developed to provide disruptive, print-like full color reflective digital media solutions based on an electrokinetic technology platform. The thin, flexible, low-power, reflective electronic media is fabricated with a new roll-to-roll manufacturing platform. Here we demonstrate the integration of this media with multi-component oxide (MCO) thin-film transistor (TFT) backplane for an active matrix reflective electronic display.

Effects of constrained-layer damping on the dynamics of a Type 4 in-line head suspension

Experimental frequency-response functions were obtained for several Type 4 inline suspension assemblies with lateral excitation. Mode shapes are described for all the modes observed between 1 and 15 kHz. The effect of a constrained-layer damper on several of the most important modes is described. It is shown that the damper is not an optimal solution for reducing the amplitude of the sway mode for the Type 4 inline suspension. It is also shown that the partial effectiveness of the damper for the sway mode results primarily from the damper region near the base of the suspension, and that the tip region of the damper has a negligible contribution towards energy dissipation for this mode. Of the load beam modes investigated, the sway mode was most affected by the addition of mass to the slider. >

Multi-channel interferometric measurements of slider flying height and pitch

A multichannel interferometer which measures relative displacements from the top of the slider and disk is used to make concurrent measurements of absolute slider flying height and pitch. This technique is applied to actual disks and sliders and is not subject to limitations of low spacing and surface textures which are problematic for white light interferometry and modeling. It is applicable to both constant speed operation and dynamic events including takeoff and landing. It has the bandwidth necessary for dynamic measurements of the interface, depending on the sampling rates used when acquiring data. These features combine to make this an excellent tool for various aspects of head-disk interface development including low flying heights, slider stability, and tribology. The results obtained with this technique are compared with those of white light interferometry and modeling for absolute flying height and pitch measurements. >

Novel flexible reflective color media with electronic inks

A novel architecture and proprietary electronic inks were developed to provide disruptive digital-media solutions based on an electrokinetic technology platform. The flexible reflective electronic media (eMedia) was fabricated by imprinting three-dimensional microscale structures with a roll-to-roll manufacturing platform. The HP technologies enable the required attributes for eMedia, such as low power, transparency, print-quality color, continuous levels of gray, and low-cost scalability. Pixelation was also demonstrated by integrating with the prototype oxide thin-film transistor backplane, and the system architecture was further developed by stacking primary-colorant layers for color reflective-display application. The innovations described in this paper are currently being developed further for the eSkins, eSignage, and ePaper applications.

An air bearing minimizing the effects of slider skew angle

A minislider incorporating a single transverse slot across both rails is presented which greatly reduces the effect of slider skew. The slots, in conjunction with wide rails, allow a slider mounted on a rotary actuator to access the entire disk at a spacing of 100 to 120 nm. Skew decreases the head-to-disk spacing of conventional minisliders and is a particular problem in disk drives equipped with rotary actuators as slider rail width is decreased. The flying characteristics of this slider are investigated by a computer simulation program and by measurements on actual sliders with a multichannel laser interferometer. >