Pole rip recession (PTR) and debris generation lead to signal loss at the head-tape interface. Accelerated tape drive experiments and measurements of head-tape spacing were conducted using heads with different slot orientations. PTR was higher for blind-slotted (slots in the direction of tape travel) heads than for transverse-slotted (slots in the direction transverse to rape travel) heads. More tape debris was found on the surface of transverse-slotted heads, bur most of this debris resided in the sluts rather than on the bearing surface. The slots in the transverse-slotted heads act as tape cleaners, which accounts for tire large debris buildup in the slots. This leaves fewer loose debris particles at rile interface for the transverse-slotted heads. Little difference was found in the head-rape sparing for the two types at the conditions used in the drive experiments. It is proposed that the greater amount of louse debris available at the interface for use in three-body abrasive wear, which is believed to cause PTR, results in higher PTR in blind-slotted heads.

Magnetic tapes, which may be modeled as three-ply laminates, exhibit transverse curvature, or cupping, as manufactured and when mechanical and hygrothermal loads are applied. Among other things, this cupping affects debris generation since it influences the contact between the flawed tape edge and head, the point where much of the debris generation occurs. This influence on debris generation is demonstrated experimentally in this study. Much more debris accumulates near the tape edge-head contact than at other contact locations. No difference in debris generation was found for two tapes with slightly different residual cupping (which is controlled during manufacturing). The target residual cupping is usually negative, which means that the tape bows out towards the tape so that the edges are farther away from the head than the center of contact is, so as to reduce contact pressure with the tape edges. However, cupping generally changes upon application of a tension and generally reduces the importance of residual cupping, which accounts for the failure to find a difference in debris generation for tapes with slightly different residual cupping. A finite element method model that uses laminate shell elements and accounts for in-plane stress stiffening, thus making it suitable for thin laminate modeling, was created. This modeling demonstrates that application of tensile and normal (used to simulate head contact) loads leads to cupping movement in the positive direction, which indicates a more severe edge contact, for an increase in front coat Young's modulus and/or an increase in front coat thickness. The same trends hold for an increase in back coat Young's modulus and/or an increase in back coat thickness. Modeling also demonstrates that cupping moves in the positive direction for an increase in the substrate's Young's modulus in the transverse direction for MP and ME tapes. An analytical model demonstrates that increases in temperature and front coat thermal expansion coefficient leads to cupping movement in the negative direction. The same trends hold for changes in relative humidity.

Phase contrast microscopy, using an atomic force microscope, is used to detect and quantify changes in composition across polymer nanocomposites and molecularly thick lubricated surfaces. The technique takes advantage of the contrast in viscoelastic (viscous energy dissipation) properties of the different materials across the surface. Some materials, especially polymers, are found to display viscoelastic behavior. For such materials, the strain response lags the stress by a phase angle that is characteristic of the material. In tapping (or intermittent contact) mode, phase angle contrast is found to be highly dependent on vibration amplitude and mean tip-to-sample distance (setpoint). Phase angle contrast seems to be a stronger function of viscoelastic properties at relatively high vibration amplitude and low mean tip-to-sample distance. In this regime the effects of sample deformation, and thus viscoelastic properties, are dominant. In these contrast images, low phase angle corresponds to materials with low viscoelastic properties. This technique was used to find fairly reproducible phase angle contrast for polyethylene terephthalate (PET) films with embedded ceramic particles, metal particle (MP) magnetic tape, and Si(100) with a nonuniform Z-15 lubricant film. Very little correlation is found between phase angle images and friction force images for PET films with embedded ceramic particles and MP tape; phase angle images give information that cannot be obtained from topography or friction images. A numerical vibration model verifies that viscoelastic properties are dominant for high vibration amplitude and low mean tip-to-sample distance. For these conditions, the model also verifies that low phase angle corresponds to low viscoelastic properties.

Pole tip recession (PTR), which is caused by differences in wear resistance of the various phases in magnetic disk and tape heads, must be reduced because it is probably the main impediment to reduction of spacing. Here, a numerical model of PTR is presented. Experimental results suggest that three-body abrasion, which leads to primarily plastic wear, is the mode responsible for PTR. In the model, the authors assume this wear mode, and assume that wear is a function of load, sliding distance, hardness of the worn surface, and dimensionless wear coefficients. As sliding proceeds, PTR increases continuously, which leads to a continuous change in contact between three-body abrasives and poles; the load carried by the poles decreases as PTR increases. This is modeled by assuming that asperities of the head and medium deform and wear plastically to accommodate passage of particles through the interface. The pole wears less as PTR increases since the opening for sliding particles increases. This accounts for the decreasing rate of change of PTR with sliding distance found for disk and tape heads numerically and experimentally. For tape heads, the model predicts that each of the following leads to higher PTR: increasing the thickness of three-body particles, increasing tape tension, decreasing pole hardness, and increasing the pole wear coefficient.

Wear of multiphase materials at the micro/nano-scale is important in devices such as magnetic tape and disk drives, where the read-write heads are multiphase. Differential wear, which is caused by differences in wear resistance among the heads’ phases, causes the thin-film poles to recede from the bearing surface; this is called pole tip recession (PTR). It is a problem because it increases spacing between the poles and medium, resulting in lower readback amplitude. Here, PTR in tape heads is studied to understand micro/nano-scale differential wear. Test results suggest that three-body abrasion, which leads to primarily plastic wear, is the operative wear mode. Most of the three-body abrasive particles originate from the tape surface; the alumina head-cleaning agents (HCAs) in the tape, which function as load bearing particles at the interface, are believed to be the primary abrasives. Some of the particles originate from the head. These are important if the substrate material is relatively soft. Differential wear can be reduced by choosing a substrate that is harder than the tape’s HCAs, choosing a pole material that is as close as possible to the hardness of the substrate, and lowering the thickness of the head’s thin-film region. Material hardness matching will not reduce differential wear if a substrate is chosen that is less hard than the HCAs. An analytical model that accounts for the observed wear is presented. The model shows that each of the following leads to higher differential wear: increasing the thickness of three-body particles, increasing tension, decreasing thin-film hardness, and increasing the thin-film wear coefficient. An increase in thin-film wear coefficient can be caused by an increase in thin-film thickness or an increase in the number of particles at the interface.

Problems with corrosion and wear in magnetic tape drives lead the industry to consider the use of ultra-thin diamond-like carbon (DLC) coatings for tape heads and metallic tapes. In this study, corrosion and wear tests are conducted on uncoated and coated tape-write heads and tapes. A multi-component flowing mixed gas test, known as the Battelle Class II test, and an elevated temperature & humidity test are used to accelerate corrosion. While past researchers have evaluated corrosion effects by measurement of changes in magnetic properties of tape, surface analysis is successfully used here to study corrosion products directly. Corrosion specimens are examined using optical microscopy, Auger electron spectroscopy, scanning electron microscopy, and atomic force microscopy. Functional drive tests are conducted to measure the effectiveness of DLC coatings, deposited by ion beam, via study of pole tip recession (PTR) in tape heads. Heads are shown to benefit in both corrosion resistance and in PTR resistance from the addition of DLC. In both cases, 20 nm thick coatings outperform 10 and 5 nm thick coatings. Coatings on ME tape show some limited benefit in corrosion resistance. ME tape specimens exposed in cartridges show much less evidence of corrosion than those exposed outside of cartridges. MP tape shows better corrosion resistance than uncoated and coated ME tapes.

Diamond-like carbon (DLC) coatings were deposited using a commercial direct ion beam deposition technique on thin-film Al2O3–TiC inductive write heads. The coating thicknesses used were 5, 10, and 20 nm. Accelerated wear tests were conducted with metal particle tapes in a linear tape drive. Atomic force microscopy was used to image the thin-film regions to measure pole tip recession (PTR), relative wear of the pole tip with respect to the air bearing surface. It is found that the coating wears off of the head substrate to a significant extent in the first 1000 km of sliding distance. The coating is worn off the substrate long before it wears off of the thin-film region. The existence of the coating on the thin-film region provides close enough wear characteristics between the substrate and thin film that the two wear at similar rates. This results in little growth in pole tip recession. Early in the wear test, the coated substrate wears at a slightly higher rate than the DLC coated thin-film region due to the difference in tape contact pressure between the two materials; decreasing PTR is the result. As the coating on the substrate wears significantly, PTR begins to increase with sliding distance. Failure does not actually occur until the coating has worn off of the thin-film region. Near failure, the coating delaminates locally. Results indicate that coatings of 20 nm thickness may provide protection against PTR in future tape drives.

The presence of tape debris at the head-tape interface can cause an increase in spacing and consequently an increase in signal loss. In this study, the generation of tape debris in linear tape drives is analysed. Functional drive tests are conducted using thin-film AlO3-TiC and Ni-Zn ferrite heads run against commercial metal particle (MP) tape. Three types of tape debris are found: magnetic particle rich, polymer rich and adherent (stain). Each type is found at a distinct location on the head surface. Optical microscopy and computerized image analysis are used both to quantify the tape debris and to find its distribution on the head. Atomic force microscopy is used to measure the thickness of adherent debris. The Al2O3-TiC sample generates more of all three types than does the Ni-Zn ferrite sample. This is probably a result of the higher hardness of Al2O3-TiC. The differential wear of Al2O3 and TiC probably accounts for the presence of adherent debris on the Al2O3-TiC head. No adherent debris can be found on the Ni-Zn ferrite head. Since the adherent debris collects near the pole tip and is difficult to remove, it potentially poses the greatest head-tape spacing problem, even though its thickness is only of the order of a few nanometres. A relationship is found between the generation of loose debris and the tape speed, tape tension and head wrap. Loose debris generation increases as the tape speed decreases and as the tape tension and head wrap increase. Its generation is found to be approximately proportional to the frictional force. Loose debris, especially the magnetic-particle-rich type, continues to be generated in abundant amounts beyond the burnishing phase for MP tape. The use of an abrasive tape leader is found to reduce the amount of debris at the interface.

Purpose: Due to the characteristics of complex traits, many traits may not be amenable to traditional epidemiologic methods. We illustrate an approach that defines an isolated population as the “unit” for carrying out studies of complex disease. We provide an example using the Pima Indians, a relatively isolated population, in which the incidence and prevalence of Type 2 diabetes, gallbladder disease, and rheumatoid arthritis (RA) are significantly increased compared with the general U.S. population. A previous study of RA in the Pima utilizing traditional methods failed to detect a genetic effect on the occurrence of the disease.Methods: Our approach involved constructing a genealogy for this population and using a genealogic index to investigate familial aggregation. We developed an algorithm to identify biological relationships among 88 RA cases versus 4,000 subsamples of age-matched individuals from the same population. Kinship coefficients were calculated for all possible pairs of RA cases, and similarly for the subsamples.Results: The sum of the kinship coefficient among all combination of RA pairs, 5.92, was significantly higher than the average of the 4,000 subsamples, 1.99 (p < 0.001), and was elevated over that of the subsamples to the level of second cousin, supporting a genetic effect in the familial aggregation. The mean inbreeding coefficient for the Pima was 0.00009, similar to that reported for other populations; none of the RA cases were inbred.Conclusions: The Pima genealogy can be anticipated to provide valuable information for the genetic study of diseases other than RA. Defining an isolated population as the “unit” in which to assess familial aggregation may be advantageous, especially if there are a limited number of cases in the study population.

Pole tip recession (PTR) in linear tape heads causes an increase in spacing and consequently an increase in signal loss. In this study, PTR in linear tape drives is analysed. Functional drive tests are conducted using thin-film Al 2 O 3 -TiC and Ni-Zn ferrite heads sliding against metal particle tape. Atomic force microscopy is used to measure PTR and the recession of the overcoat material used in the construction of the head. In measuring PTR, care must be taken in correctly orienting the stand-alone atomic force microscope tip with respect to the head sample. Care must also be taken in post-processing the raw stand-alone atomic force microscopy data. Based on PTR data with Al 2 O 3 -TiC and Ni-Zn ferrite heads, no significant differences exist in the PTR of Al 2 O 3 -TiC heads compared with Ni-Zn ferrite heads. In the case of the Ni-Zn ferrite head, the softer Ni-Zn ferrite substrate has mechanical properties close to those of the poles, suggesting that PTR growth should be low. However, additional third-body wear particles from the ferrite substrate result in additional pole tip wear. No significant difference is seen in the wear of Co-Zr-Ta poles and Ni-Fe poles, as they have comparable mechanical properties. No strong conclusion may be drawn about the effect of tape speed on PTR. An increase in tape tension leads to an increase in PTR. This is a result of an increase in the normal force, which causes an increase in the abrasive wear. An increase in interface contamination also leads to an increase in PTR.

Advances in Information Storage Systems, pp. 93-102 (1998) No AccessMagnetic Tape Debris Generation with Sliding Against Al2O3-TiC and Ni-Zn Ferrite HeadsWilliam w. Scott, Bharat Bhushan, Frank Shelledy, Subrata Dey, and Anand LakshmikumaranWilliam w. ScottComputer Microtribology and Contamination Laboratory, Department of Mechanical Engineering, 206 West 18th Avenue, The Ohio State University, Columbus, Ohio 43210-1107, USA, Bharat BhushanComputer Microtribology and Contamination Laboratory, Department of Mechanical Engineering, 206 West 18th Avenue, The Ohio State University, Columbus, Ohio 43210-1107, USA, Frank ShelledyStorage Technology Corporation, 2270 South 88th Street, Louisville, Colorado 80028-8110, USA, Subrata DeyStorage Technology Corporation, 2270 South 88th Street, Louisville, Colorado 80028-8110, USA, and Anand LakshmikumaranStorage Technology Corporation, 2270 South 88th Street, Louisville, Colorado 80028-8110, USAhttps://doi.org/10.1142/9789812816610_0007Cited by:0 (Source: Crossref) PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: The presence of tape debris at the head/tape interface can cause an increase in spacing and consequently an increase in signal loss. In this study, we analyze the generation of tape debris in linear tape drives. Functional drive tests are conducted using thin-film Al2O3-TiC heads and Ni-Zn ferrite heads. These are run against metal particle (MP) tape. Optical microscopy and computerized image analysis are used both to quantify the tape debris and to find its distribution on the head. Three types of tape debris are found: magnetic particle rich, binder rich, and adherent (stain). Each type is found at a distinct location on the head. The Al2O3-TiC sample generates more of all three types than does the Ni-Zn ferrite sample. In fact, no adherent debris can be found on the Ni-Zn ferrite head. Since the adherent debris collects near the pole tip and is difficult to remove, it potentially poses the greatest head/tape spacing problem. FiguresReferencesRelatedDetails Recommended Advances in Information Storage Systems Metrics History PDF download

In the third National Health and Nutrition Examination Survey (NHANES III) conducted by the National Center for Health Statistics, Centers for Disease Control and Prevention, radiographs of the hands and knees were taken of participants 60 years and older as part of the study of arthritis and musculoskeletal conditions. The purpose of the study was to decide the digitizing resolution to be used for these radiographs. A set of wrist and hand radiographs (N=49) was graded by two radiologists for degree of bone erosions and served as a “gold standard.” The radiographs were then digitized at three resolution levels; low-resolution 150μm (2001×1634×12 bit matrix); intermediate-resolution 100 μm (3000×2400×12 bit matrix); and high-resolution 50 μm (4900×3000×12 bit matrix). A comparison of the digital images versus the gold standard reading was made at the three resolutions by two radiologists. Kappa statistics suggested fair (K>.4) to excellent (K>.75) agreement between the gold standard and the images at all levels. Intraclass correlation coefficient suggested high agreement between readers (ICC>.5), with minimal individual reader effect. Variance component estimates showed that the major contribution (78–83%) to scoring came from variability in the images themselves, not from the readers. The 100μm resolution was selected over the 150 and 50 μm on the basis of practical considerations such as storage requirements, display time, and easier manipulation of the digital images by the readers.

At the National Library of Medicine (NLM) we are developing a digital atlas to serve as a reference tool for the interpretation of cervical and lumbar spine x-rays. The atlas contains representative images for four grades of severity for cervical/lumbar anterior osteophytes and disc space narrowing, and presence/absence for cervical subluxation and lumbar spondylolisthesis. A prototype version of the atlas has been built using images for which expert rheumatologist readers reached exact agreement in grading.The atlas functionality includes the ability to display cervical and lumbar anatomy, display of single images or multiple simultaneous images, image processing functions, and capability to add user-defined images to the atlas. Images are selected for display by the user specifying feature and grade (example: ''anterior osteophytes, grade 2''). Currently, the atlas runs on a Sun SPARC workstation under the Solaris operating system.The initial use of the atlas is to aid in reading a collection of 17,000 NHANES II digitized x-rays. The atlas may also be used as a general digital reference tool for the standardized interpretation of digital x-rays for osteoarthritis. We are investigating further development of the atlas to accommodate a wider set of Images, to operate on multiple platforms, and, to be accessible via the World Wide Web.

Magnetic coatings are made up of either magnetic particles dispersed in a polymeric matrix or thin continuous films of magnetic material. Magnetic tape stiffness, in both the machine and transverse directions, influences the way in which tapes conform to magnetic heads in magnetic tape drives. For this reason tape stiffness plays an important role in the friction, stiction and wear characteristics of a magnetic head-tape interface. In this study, a test method for measuring bending stiffness is developed. A tape segment is pressed against a load cell to measure the change in force as a function of the tape's normal displacement. Stiffness values are obtained from load vs. displacement data and a derived analytical model for the displacement of the tape segment in terms of load and geometry. Stiffness measurements of finished tapes and tape substrates are presented. The correlation between tape stiffness in the machine and transverse directions, and read/write head contouring and edge wear, is also presented. (C) 1997 Elsevier Science S.A.