Magnetic Tracks Research Articles

Development and Navigation of a Mobile Robot for Floating Production Storage and Offloading Ship Hull Inspection

This paper describes the current development status of a mobile robot designed to inspect the outer surface of large oil ship hulls and floating production storage and offloading platforms. These vessels require a detailed inspection program, using several nondestructive testing techniques. A robotic crawler designed to perform such inspections is presented here. Locomotion over the hull is provided through magnetic tracks, and the system is controlled by two networked PCs and a set of custom hardware devices to drive motors, video cameras, ultrasound, inertial platform, and other devices. Navigation algorithm uses an extended-Kalman-filter (EKF) sensor-fusion formulation, integrating odometry and inertial sensors. It was shown that the inertial navigation errors can be decreased by selecting appropriate Q and R matrices in the EKF formulation.

High-resolution and high-coercivity FePtL1 magnetic force microscopy nanoprobes to study next-generation magnetic recording media

A cylindrical probe with almost perfectly flat plateaulike surface was focused ion beam (FIB) milled from an atomic force microscopy probe in order to create the required surface conditions for thin film deposition with finely controlled deposition/growth parameters. A composition of Pd(5 nm)/MgO(8 nm)/FePt(10 nm)/MgO(8 nm) was sputter deposited on the plateau probe, followed by deposition of a Pd (5 nm) protective layer. The plateau probe was then FIB-milled to produce a tip with a curvature radius of ∼25 nm. After annealing the probe at 650 °C for ∼15 min to generate an ultrahigh anisotropy L10 phase, magnetic force microscopy (MFM) imaging was performed with the probe on magnetic tracks with linear densities ranging from 200 to 1200 KFCI. The results show sub-20-nm lateral resolution in ambient conditions and magnetic tracks, which are otherwise invisible to standard MFM probes, are clearly evident with the FIB-fabricated FePt probe. With relatively high spatial resolution and coercivity values higher than 1 T, among other applications, this type of probe may be ideal for high-quality MFM study of next-generation recording media.

High resolution polar Kerr magnetometer for nanomagnetism and nanospintronics

A new high resolution polar magneto-optical (MO) Kerr magnetometer, devoted to the study of nanometer sized elements with perpendicular magnetic anisotropy, is described. The unique performances of this setup in terms of sensitivity (1.2x10(-15) emu), stability (lateral drift +/-35 nm over 3 h), and resolution (laser spot full width at half maximum down to 470 nm) are demonstrated, and illustrated by Kerr hysteresis loop measurements on a unique ultrathin magnetic nanodot, and over small segments of ultranarrow magnetic tracks. Large scanning MO Kerr microscopy images were also obtained with the same performances.

Scanning heterodyne Kerr-effect microscope for imaging of magnetic tracks

Design and performance of a new type of Kerr microscope based on heterodyne cross-polarized technique is presented. Weak depolarization of the probe beam due to longitudinal magneto-optical Kerr effect is detected by means of heterodyne mixing of the two cross-polarized and frequency shifted waves generated by Zeeman-type He–Ne laser. In comparison with the traditional homodyne method the proposed technique has better sensitivity and spatial resolution. Experimental results of imaging service magnetic tracks on real samples of magnetic disks are presented, showing better contrast and spatial resolution with respect to the images obtained from commercial devices available in the market.

Permanent magnetic system design for the wall-climbing robot

This paper presents the design and analysis of the permanent magnetic system for a wall-climbing robot with permanent magnetic tracks. Based on the behaviour of gecko lizards, the architecture of t...

Permanent Magnetic System Design for the Wall-Climbing Robot

This paper presents the design and analysis of the permanent magnetic system for a wall-climbing robot with permanent magnetic tracks. Based on the behaviour of gecko lizards, the architecture of the robot was designed and built, including the structure of the adhesion mechanism, the mechanical architecture and the anti-toppling mechanism. The permanent magnetic adhesion mechanism and the tracked locomotion mechanism were employed in this kind of wall-climbing robot. Through static and dynamic force analysis of the robot under different situations, design requirements for the adhesion mechanism were derived. Two different types of structures were put forward for the permanent magnetic units and are further discussed in this paper. These two types of structures are also analysed in detail. In addition, a finite-element method was used to verify the results of magnetic units. Finally, two wall-climbing robots, equipped with different magnetic systems described previously, are explained and their applications are discussed in this paper.

Laser heterodyne cross-polarized technique for inspection of magnetic disks

Abstract A new optical technique for observation of service magnetic tracks on magnetic disks is developed. Weak depolarization of the probe beam due to longitudinal magneto-optical Kerr effect is detected by means of heterodyne mixing of the two cross-polarized and frequency shifted waves generated by Zeeman-type laser. In comparison with the traditional homodyne method the proposed technique has better sensitivity and spatial resolution. Experimental results obtained with standard sample magnetic disks showed the signal-to-noise ratio of about 10, and the spatial resolution of about 30 μm. A possibility of the phase-contrast super-resolution is discussed.

In vivo magnetic resonance imaging tracks adult neural progenitor cell targeting of brain tumor

Using magnetic resonance imaging (MRI), we described a method for noninvasively tracking grafted neural progenitor cells and bone marrow stromal cells (MSCs) in brain tumor of the rat. Neural progenitor cells and MSCs were labeled with lipophilic dye-coated superparamagnetic particles. The labeled neural progenitor cells and MSCs were transplanted to rats via the cisterna magna and a tail vein, respectively, 1 week after 9L-gliosarcoma cell implantation. Three-dimensional (3D) gradient echo and contrast agent images revealed dynamic migration of adult neural progenitor cells and MSCs detected by loss of MRI signals towards tumor mass and infiltrated tumor cells. Prussian blue staining and fluorescent microscope analysis showed that grafted cells targeted tumor cells and areas with grafted cells corresponded to areas with loss of MRI signals. These results demonstrate that the MRI technique provides a sensitive method for in vivo assessment of grafted cells targeting tumor mass and infiltrated tumor cells and that adult neural progenitor cells and MSCs can target tumor aggregates in the brain.

The man-loading high-temperature superconducting maglev test vehicle

The first man-loading high-temperature superconducting (HTS) Maglev test vehicle in the world was successfully developed on Dec. 31, 2000 in the Applied Superconductivity Laboratory, Southwest Jiaotong University, China. Heretofore over 24 500 passengers took the vehicle, and it has been operating back and forth for about 400 km. The HTS Maglev vehicle provides inherent stability both in the vertical and lateral direction, so no control system is needed. The only control system is used for linear motor driving devices. The melt-textured YBaCuO bulk superconductors are fixed on the bottom of a liquid nitrogen vessel and cooled by liquid nitrogen. The bottom thickness of the rectangle liquid nitrogen vessel with its thin wall is only 3 mm. The onboard HTS Maglev module is placed over the guideway. The guideway consists of two parallel permanent magnetic tracks, whose concentrating magnetic field at 20 mm height above the surface is about 0.5 T. The levitation forces of 8 HTS Maglev modules were measured. The total levitation force of 8 onboard Maglev modules was 10431 N at the levitation gap of 10 mm, and 8486 N at the levitation gap of 15 mm, respectively. These results were measured on May 28, 2002.

Experiment results of high temperature superconducting Maglev vehicle

The first man-loading high temperature superconducting (HTS) magnetic levitation (Maglev) test vehicle in the world has normally operated over one year after its birth on December 31, 2000. Heretofore over 23 000 passengers have taken the vehicle, and it operates very well from first running to now. The HTS Maglev vehicle is over guideway, which consists of two parallel permanent magnetic tracks. The levitation force of the entire Maglev vehicle is measured. Three times measurement results on December 24, 2000, July 1, 2001, and December 24, 2001 are reported respectively, it will be seen from this that the levitation forces do not change nearly after long running. Total levitation force of entire vehicle is 1050 kg at the 8 mm net levitation gap, which the gap between the bottom of liquid nitrogen vessels and guideway face. A measuring equipment of the guidance force of the entire Maglev vehicle is designed and manufactured. The guidance force of the vehicle is obtained by the equipment.

The first man-loading high temperature superconducting Maglev test vehicle in the world

The first man-loading high temperature superconducting Maglev test vehicle in the world is reported. This vehicle was first tested successfully on December 31, 2000 in the Applied Superconductivity Laboratory, Southwest Jiaotong University, China. Heretofore over 17,000 passengers took the vehicle, and it operates very well from beginning to now. The function of suspension is separated from one of propulsion. The high temperature superconducting Maglev provides inherent stable forces both in the levitation and in the guidance direction. The vehicle is 3.5 m long, 1.2 m wide, and 0.8 m high. When five people stand on vehicle and the total weight is 530 kg, the net levitation gap is more than 20 mm. The whole vehicle system includes three parts, vehicle body, guideway and controlling system. The high temperature superconducting Maglev equipment on board is the most important for the system. The onboard superconductors are melt-textured YBaCuO bulks. The superconductors are fixed on the bottom of liquid nitrogen vessels and cooled by liquid nitrogen. The guideway consists of two parallel permanent magnetic tracks, whose surface concentrating magnetic field is up to 1.2 T. The guideway is 15.5 m long.

Detection of magnetic data using a magnetooptic indicator

We investigate the detection of magnetic data using magnetooptical indicators with in-plane magnetization. A simple model for the magnetooptical detection system is presented. We find that the signal to noise ratio changes strongly with the bit size, the polarization noise, and the distance between the magnetic carrier and the indicator. In particular, it is found that our model a signal to noise ratio of 30 is possible for a bit size of 200 nm. We also estimate the resolution of the system, and find that a spot size of ∼200 nm can be obtained using a suitably designed solid immersion lens. Finally, we discuss detection of several magnetic tracks simultaneously.

A wall-climbing robot for labelling scale of oil tank's volume

A Wall-Climbing Robot (WCR) with magnetic tracks is presented in this paper. The robot is designed for labeling the scale of oil tank.5 The Wall-Climbing Robot (WCR) uses a permanent magnet sucker as its sucking mode, and a track as its moving mode. We designed an elastic brace mechanism, a load-scatter mechanism and parallelogram mechanism to improve the robot's adaptability on the steel wall surface. The control system utilizes two-level computer control systems, achieving control of the robot's moving track and processing data collected by the robot.

High-resolution magnetic resonance imaging tracks changes in organ and tissue mass in obese and aging rats

Magnetic resonance imaging (MRI) has the ability to discriminate between various soft tissues in vivo. Whole body, specific organ, total adipose tissue (TAT), intra-abdominal adipose tissue (IAAT), and skeletal muscle (SM) weights determined by MRI were compared with weights determined by dissection and chemical analysis in two studies with male Sprague-Dawley rats. A 4.2-T MRI machine acquired high-resolution, in vivo, longitudinal whole body images of rats as they developed obesity or aged. Weights of the whole body and specific tissues were determined using computer image analysis software, including semiautomatic segmentation algorithms for volume calculations. High correlations were found for body weight (r = 0.98), TAT (r = 0.99), and IAAT (r = 0.98) between MRI and dissection and chemical analyses. MRI estimated the weight of the brain, kidneys, and spleen with high accuracy (r > 0.9), but overestimated IAAT, SM, and liver volumes. No differences were detected in organ weights using MRI and dissection measurements. Longitudinal MRI measurements made during the development of obesity and aging accurately represented changes in organ and tissue mass.

Transition position jitter in longitudinal magnetic recording media

We have quantitatively analyzed magnetic force microscope images of magnetic tracks written at 10000 flux changes per mm in longitudinal magnetic recording media. In this study, transition positions and transition position jitter have been extracted as a function of the write current and compared to spin-stand measurements. Jitter is important as it limits how closely transitions can be spaced. Excellent quantitative agreement is achieved. Moreover, the MFM tip provides much better spatial resolution in the cross-track direction than a read element of a head. The high resolution allows the characterization of recording parameters for simulated read elements with various widths before heads are available for experiments. This ability, which is illustrated with transition position jitter and a comparison with theory, is important to advance the recording technology.

Micro-indentation and scanning probe microscopy to assess multilayer magnetic film damage

We have combined several techniques to evaluate the effect of mechanical deformation on the topography and magnetics of an underlying thin magnetic film. Micro-indentation techniques are used to introduce tailored deformations to magnetic recording disks. Atomic force microscopy (AFM) and magnetic force microscopy (MFM) then map out the topography of the indentations and the effect on the underlying magnetic film. Indentation morphology includes pyramidal and conical indents, linear scratches, and reciprocating wear tracks. The extent of topographical damage assessed by AFM correlates with the carefully controlled normal and tangential forces of the micro-indenter. Sub-surface `damage’ is assessed by MFM, monitoring for loss of resolution in pre-written magnetic data tracks. Mechanical tests are conducted at very low speeds and loading rates; hence, frictional heating or other thermo-mechanical factors that might cause ambiguities in data interpretation can be safely ruled out. By using the combination of micro-mechanical testing, Raman spectroscopy, and AFM/MFM techniques, we have found that mechanically introduced bit contrast degradation is attributed to physical modification of the magnetic coating and protective overlayer. The indentation and scratch tests both confirm that static pressure alone is not sufficient to cause the observed magnetic degradation; other mechanical factors must be invoked, including alteration of the geometry of the magnetic coating. Micro wear is capable of causing magnetic damage at much lower pressures than indentations or scratches. From wear track data, the degree of disk surface damage is correlated with the degree of magnetic bit contrast degradation. From wear track data on DC-erased samples it is concluded that mechanical deformation can induce magnetic contrast via concerted reorientation of grain c-axis and, hence, reorientation of magnetic moments.

Permanent Magnetic System Design for the Wall‐Climbing Robot

This paper presents the design and analysis of the permanent magnetic system for a wall‐climbing robot with permanent magnetic tracks. Based on the behaviour of gecko lizards, the architecture of the robot was designed and built, including the structure of the adhesion mechanism, the mechanical architecture and the anti‐toppling mechanism. The permanent magnetic adhesion mechanism and the tracked locomotion mechanism were employed in this kind of wall‐climbing robot. Through static and dynamic force analysis of the robot under different situations, design requirements for the adhesion mechanism were derived. Two different types of structures were put forward for the permanent magnetic units and are further discussed in this paper. These two types of structures are also analysed in detail. In addition, a finite‐element method was used to verify the results of magnetic units. Finally, two wall‐climbing robots, equipped with different magnetic systems described previously, are explained and their applications are discussed in this paper.

Magnetic recording drive dynamics during seeking and parking

A novel magnetic characterization technique has been developed to monitor head-disk spacings at high bandwidths during seeking, parking and during operational vibration and shock. This technique relies upon measurements of the magnetic amplitude of a constant frequency pattern written on every second track and on the readout of the graycode and servo bursts during seeking or parking. Magnetic data obtained during the crossing of thousands of magnetic tracks is analyzed with two subsequent envelope calculations. With well designed inductive and magnetoresistive head drives in normal seeking modes, head-disk spacing variations are within /spl plusmn/5 nm. Large head-disk spacing fluctuations are detected when using hard crash stops and parking at velocities in excess of 0.5 m/sec.

Steinmetz, EM radiation and the obtrusive π/2

Steinmetz was regarded as one of the most brilliant engineers of his day, yet he published a book containing a section on the effect of one radio antenna on another which seems to be wrong. This article compares Steinmetz's analysis with a `modern' approach using the magnetic vector potential and tracks down the discrepancy.

Magnetoresistive sensors based on Ni/sub 81/Fe/sub 19//Ag multilayers

Because of their good magnetoresistive properties and thermal stability, sputtered NiFe/Ag multilayers (MLs) produce sensors with attractive characteristics. Thermal treatments up to 280 degrees C are carried out. They lead to improved sensitivity; the magnetoresistance (MR) ratio remains practically constant, while the saturation field decreases from 24 kA/m to 6 kA/m after annealing. Sensors are made from these MLs using a microtechnology process. They are tested by reading magnetic tracks on a hard magnetic disk. Their performance is compared with sensors based on classical anisotropic MR in ferromagnetic 3-D alloys. The signal is found to be about ten times greater with this new ML than with sensors based on NiFe or NiFeCo alloys.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>