Spacing Modulation of Magnetic Head Due to Topographical Feature of Disk Surface

1998 ◽  
Vol 120 (3) ◽  
pp. 542-548 ◽  
Author(s):  
Shoji Suzuki
Keyword(s):  
High Resolution ◽  
Smooth Surface ◽  
Disk Surface ◽  
Magnetic Head ◽  
Signal Modulation ◽  
Height Range ◽  
Smooth Disk ◽  
Topographical Feature ◽  
Fly Height ◽  
Ramp Load

To achieve high recording density, the combination of low flying head and smooth disk surface is very desirable. Although high stiction associated with the smooth surface can be avoided by zone texturing or ramp load, stable flying condition must be assured by a smooth disk surface. Disk topography is an important factor in the flying stability of the head. In this work, read back signal modulation analysis was incorporated to characterize the disk topography. By increasing the writing frequency up to 25 MHz, high resolution was demonstrated in the fly height range between 15 nm to 50 nm. This resolution is sufficient to evaluate today’s low flying heads. A subambient pressure design which is typical for an MR head and a proximity head design for an inductive head were evaluated over very smooth aluminum disks. The effect of various disk clamping forces was also investigated. Relationship between disk waviness and flying stability of heads was studied.

The Simulation of Laser Cleaning of Magnetic Head with Different Temporal Pulses

2015 ◽  
Vol 1101 ◽  
pp. 446-452 ◽  
Author(s):  
Narongpun Rungcharoen ◽  
Mongkol Wannapapra ◽  
Wanchai Pijitrojana
Keyword(s):  
Hard Disk Drives ◽  
Disk Surface ◽  
Laser Cleaning ◽  
User Requirements ◽  
Particle Removal ◽  
Disk Drives ◽  
Magnetic Head ◽  
Small Particles ◽  
Fly Height ◽  
Non Destructive

Nowadays, hard disk drives (HDD) technology are being developed continuously in order to increase the capacity, and reduce the size of HDD to meet user requirements. To increase the capacity which is equivalent to increasing read/write ability, the flying clearance must be reduced. Current new HDD models show that the fly height is lower than 0.3 μm. If the height of a particle or contamination is higher than 0.3 μm, the magnetic head will scratch the magnetic disk surface. However the process of cleaning in the HDD industry cannot remove particles with size smaller than 0.3 μm [1]. Therefore laser cleaning is selected first because this method can remove small particles [2]. and it does not damage the magnetic head. This research compares the range of temperature needed for cleaning the magnetic head between two types of heat source’s profile. The technique used is the heat transfer by finite element: FEM[3]. This technique provides an important factor of the laser cleaning method that increases the efficiency of particle removal. It is also a non-destructive method for cleaning the surface of the magnetic head slider.

Study of Slider Dynamics Over Very Smooth Magnetic Disks

1996 ◽  
Vol 118 (2) ◽  
pp. 382-387 ◽  
Author(s):  
Shoji Suzuki ◽  
Henry Nishihira
Keyword(s):  
Surface Roughness ◽  
High Speed ◽  
Laser Doppler Vibrometer ◽  
Low Frequency ◽  
Surface Characteristics ◽  
Disk Surface ◽  
Low Frequencies ◽  
Smooth Disk ◽  
Ae Signal ◽  
Fly Height

Flying characteristics of 50 percent negative pressure sliders on aluminum, glass, and silicon disks with different surface characteristics are described. By using an AE (acoustic emission) and LDV (Laser Doppler Vibrometer) we were able to study the effect of surface roughness and disk materials on the dynamics of the slider. In the regime where the slider flies below the glide height (30 nm) and contact with the disk surface can occur, the AE signal consisted of low frequencies related to air bearing resonance (around 100 kHz), and high frequency related to slider body vibrations (735 kHz). Interestingly, in the high speed regime the AE signal contained low frequency signals. The signal increased as the fly height of the slider increased when flying on the smooth surfaces except on the silicon disk. LDV measurements revealed that the excitation from the silicon disk surface was smaller than on the aluminum disk or the glass disk by 10 dB, which contributed to suppress the vibration of the slider. For a given excitation from the disk, the surface roughness played a key role in determining the slider vibration. We also determined that a fly height fluctuation occurred due to the surface roughness, but the effect was found to be very small. The difference between the textured and smooth surface was from the damping effect on the slider vibration. The slider was made to collide with a protrusion fabricated on a disk surface to study the damping characteristics of the slider. The textured disk surface gave more damping than on the smooth disk surface by up to 20 percent.

Improvement of the Static and Dynamic Characteristics of Magnetic Head Sliders by Optimum Design

1999 ◽  
Vol 122 (1) ◽  
pp. 280-287 ◽  
Author(s):  
Hiromu Hashimoto ◽  
Yasuhisa Hattori
Keyword(s):  
Objective Function ◽  
Optimum Design ◽  
Amplitude Ratio ◽  
Optimization Technique ◽  
Hard Disk Drives ◽  
Maximum Amplitude ◽  
Disk Surface ◽  
Operating Conditions ◽  
Magnetic Head ◽  
Design Variables

The aim of this paper is to develop a general methodology for the optimum design of magnetic head sliders in improving the spacing characteristics between a slider and disk surface under static and dynamic operating conditions of hard disk drives and to present an application of the methodology to the IBM 3380-type slider design. To generate the optimal design variables, the objective function is defined as the weighted sum of the minimum spacing, the maximum difference in the spacing due to variation of the radial location of the head, and the maximum amplitude ratio of the slider motion. Slider rail width, taper length, taper angle, suspension position, and preload are selected as the design variables. Before the optimization of the head, the effects of these five design variables on the objective function are examined by a parametric study, and then the optimum design variables are determined by applying the hybrid optimization technique, combining the direct search method and successive quadratic programming. From the obtained results, the effectiveness of optimum design on the spacing characteristics of magnetic heads is clarified. [S0742-4787(00)03701-2]

scholarly journals Early Detection of Invasive Exotic Trees Using UAV and Manned Aircraft Multispectral and LiDAR Data

2019 ◽  
Vol 11 (15) ◽  
pp. 1812 ◽  
Author(s):  
Jonathan P. Dash ◽  
Michael S. Watt ◽  
Thomas S. H. Paul ◽  
Justin Morgenroth ◽  
Grant D. Pearse
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Laser Scanning ◽  
Machine Learning Algorithms ◽  
Detection Methods ◽  
Validation Dataset ◽  
Height Range ◽  
Exotic Trees ◽  
Invasive Trees ◽  
Invasive Exotic

Exotic conifers can provide significant ecosystem services, but in some environments, they have become invasive and threaten indigenous ecosystems. In New Zealand, this phenomenon is of considerable concern as the area occupied by invasive exotic trees is large and increasing rapidly. Remote sensing methods offer a potential means of identifying and monitoring land infested by these trees, enabling managers to efficiently allocate resources for their control. In this study, we sought to develop methods for remote detection of exotic invasive trees, namely Pinus sylvestris and P. ponderosa. Critically, the study aimed to detect these species prior to the onset of maturity and coning as this is important for preventing further spread. In the study environment in New Zealand’s South Island, these species reach maturity and begin bearing cones at a young age. As such, detection of these smaller individuals requires specialist methods and very high-resolution remote sensing data. We examined the efficacy of classifiers developed using two machine learning algorithms with multispectral and laser scanning data collected from two platforms—manned aircraft and unmanned aerial vehicles (UAV). The study focused on a localized conifer invasion originating from a multi-species pine shelter belt in a grassland environment. This environment provided a useful means of defining the detection thresholds of the methods and technologies employed. An extensive field dataset including over 17,000 trees (height range = 1 cm to 476 cm) was used as an independent validation dataset for the detection methods developed. We found that data from both platforms and using both logistic regression and random forests for classification provided highly accurate (kappa < 0.996 ) detection of invasive conifers. Our analysis showed that the data from both UAV and manned aircraft was useful for detecting trees down to 1 m in height and therefore shorter than 99.3% of the coning individuals in the study dataset. We also explored the relative contribution of both multispectral and airborne laser scanning (ALS) data in the detection of invasive trees through fitting classification models with different combinations of predictors and found that the most useful models included data from both sensors. However, the combination of ALS and multispectral data did not significantly improve classification accuracy. We believe that this was due to the simplistic vegetation and terrain structure in the study site that resulted in uncomplicated separability of invasive conifers from other vegetation. This study provides valuable new knowledge of the efficacy of detecting invasive conifers prior to the onset of coning using high-resolution data from UAV and manned aircraft. This will be an important tool in managing the spread of these important invasive plants.

scholarly journals A Dynamic Model of the Magnetic Head Slider With Contact and Off-Track Motion due to a Thermally Actuated Protrusion or a Moving Bump Involving Intermolecular Forces

2016 ◽  
Author(s):  
Saurabh Pathak ◽  
Shao Wang
Keyword(s):  
Dynamic Model ◽  
Rotating Disk ◽  
Disk Surface ◽  
Intermolecular Forces ◽  
Flying Height ◽  
Magnetic Head ◽  
Computationally Efficient ◽  
Normal Contact ◽  
Head Slider ◽  
Thermally Actuated

A computationally efficient five-degree-of-freedom dynamic model was developed to simulate the motion of a magnetic head slider under the conditions of moving-bump collision and of contact due to an expanding protrusion on the slider for thermal flying-height control, with consideration of intermolecular forces. Compared to results obtained without intermolecular forces for a bump on the rotating disk, the intermolecular forces cause a significantly greater normal contact force, a larger roll angle and a larger off-track displacement under nonzero skew. When an expanding protrusion on the slider reaches a position close to the disk surface, the intermolecular forces pull the slider into contact at an earlier time and keep the protrusion in contact for a longer duration, which, with friction under nonzero skew, results in a substantially greater off-track displacement.

scholarly journals High-resolution spectroscopic view of planet formation sites

2010 ◽  
Vol 6 (S276) ◽  
pp. 50-53 ◽  
Author(s):  
Zsolt Regály ◽  
Laszlo Kiss ◽  
Zsolt Sándor ◽  
Cornelis P. Dullemond
Keyword(s):  
High Resolution ◽  
Planet Formation ◽  
Giant Planet ◽  
Circumstellar Disks ◽  
Disk Surface ◽  
Line Profiles ◽  
Molecular Line ◽  
Near Ir ◽  
Velocity Flow ◽  
Core Accretion

AbstractTheories of planet formation predict the birth of giant planets in the inner, dense, and gas-rich regions of the circumstellar disks around young stars. These are the regions from which strong CO emission is expected. Observations have so far been unable to confirm the presence of planets caught in formation. We have developed a novel method to detect a giant planet still embedded in a circumstellar disk by the distortions of the CO molecular line profiles emerging from the protoplanetary disk's surface. The method is based on the fact that a giant planet significantly perturbs the gas velocity flow in addition to distorting the disk surface density. We have calculated the emerging molecular line profiles by combining hydrodynamical models with semianalytic radiative transfer calculations. Our results have shown that a giant Jupiter-like planet can be detected using contemporary or future high-resolution near-IR spectrographs such as VLT/CRIRES or ELT/METIS. We have also studied the effects of binarity on disk perturbations. The most interesting results have been found for eccentric circumprimary disks in mid-separation binaries, for which the disk eccentricity - detectable from the asymmetric line profiles - arises from the gravitational effects of the companion star. Our detailed simulations shed new light on how to constrain the disk kinematical state as well as its eccentricity profile. Recent findings by independent groups have shown that core-accretion is severely affected by disk eccentricity, hence detection of an eccentric protoplanetary disk in a young binary system would further constrain planet formation theories.

scholarly journals Impact of black carbon aerosol over Italian basin valleys: high-resolution measurements along vertical profiles, radiative forcing and heating rate

2014 ◽  
Vol 14 (18) ◽  
pp. 9641-9664 ◽  
Author(s):  
L. Ferrero ◽  
M. Castelli ◽  
B. S. Ferrini ◽  
M. Moscatelli ◽  
M. G. Perrone ◽  
...  
Keyword(s):  
High Resolution ◽  
Black Carbon ◽  
Heating Rate ◽  
Radiative Forcing ◽  
Transfer Model ◽  
Vertical Profiles ◽  
Radiative Effect ◽  
Mixing Height ◽  
Atmospheric Absorption ◽  
Height Range

Abstract. A systematic study of black carbon (BC) vertical profiles measured at high-resolution over three Italian basin valleys (Terni Valley, Po Valley and Passiria Valley) is presented. BC vertical profiles are scarcely available in literature. The campaign lasted 45 days and resulted in 120 measured vertical profiles. Besides the BC mass concentration, measurements along the vertical profiles also included aerosol size distributions in the optical particle counter range, chemical analysis of filter samples and a full set of meteorological parameters. Using the collected experimental data, we performed calculations of aerosol optical properties along the vertical profiles. The results, validated with AERONET data, were used as inputs to a radiative transfer model (libRadtran). The latter allowed an estimation of vertical profiles of the aerosol direct radiative effect, the atmospheric absorption and the heating rate in the lower troposphere. The present measurements revealed some common behaviors over the studied basin valleys. Specifically, at the mixing height, marked concentration drops of both BC (range: from −48.4 ± 5.3 to −69.1 ± 5.5%) and aerosols (range: from −23.9 ± 4.3 to −46.5 ± 7.3%) were found. The measured percentage decrease of BC was higher than that of aerosols: therefore, the BC aerosol fraction decreased upwards. Correspondingly, both the absorption and scattering coefficients decreased strongly across the mixing layer (range: from −47.6 ± 2.5 to −71.3 ± 3.0% and from −23.5 ± 0.8 to −61.2 ± 3.1%, respectively) resulting in a single-scattering albedo increase along height (range: from +4.9 ± 2.2 to +7.4 ± 1.0%). This behavior influenced the vertical distribution of the aerosol direct radiative effect and of the heating rate. In this respect, the highest atmospheric absorption of radiation was predicted below the mixing height (~ 2–3 times larger than above it) resulting in a heating rate characterized by a vertical negative gradient (range: from −2.6 ± 0.2 to −8.3 ± 1.2 K day−1 km−1). In conclusion, the present results suggest that the BC below the mixing height has the potential to promote a negative feedback on the atmospheric stability over basin valleys, weakening the ground-based thermal inversions and increasing the dispersal conditions.

A high-resolution detecting system based on machine vision for defects on large aperture and super-smooth surface

2015 ◽  
Author(s):  
Yongying Yang ◽  
Limin Zhao ◽  
Shitong Wang ◽  
Pin Cao ◽  
Dong Liu ◽  
...  
Keyword(s):  
High Resolution ◽  
Machine Vision ◽  
Smooth Surface ◽  
Large Aperture
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