Rail Width Research Articles

Optimization Calculation and Analysis of Moving Load of the Railgun by Newton Method

To explore influences from drive current on the projectile launched speed, and the spacing and width of rails on the maximum value of current in the electromagnetic gun. The motion equation of plasma armature is analyzed by the Newton method. In this paper, considering armature motion subjected to plasma viscous drag and inertial drag, the optimization model between armature speed and drive current was built. The results showed that the projectile launched speed would get the maximum value when the drive current was the specific value. Moreover, the influences from spacing and width of rails on the maximum value of current and the projectile launched speed were proved. Therefore, the optimization model that was built by the Newton method research the electromagnetic railgun is of great significance.

Trophic Relationships of a Marsh Bird Differ Between Gulf Coast Estuaries

Much of North America’s tidal marsh habitat has been significantly altered by both natural and man-made processes. Thus, there is a need to understand the trophic ecology of organisms endemic to these ecosystems. We applied carbon (δ 13C) and nitrogen (δ 15N) stable isotope analysis, along with isotope mixing models, to egg yolk, liver, and muscle tissues of clapper rails (Rallus longirostris) and their likely prey items. This analysis enabled us to explore variation in trophic niche and diet composition in this important marsh bird in two northern Gulf of Mexico tidal marshes that are river and ocean-dominated. For the river-associated estuary, δ 13C and δ 15N of egg yolks, liver, and pectoral muscle tissue samples provided evidence that clapper rails maintained a similar diet during both the winter and the breeding season. A trophic link between C3 primary productivity and the clapper rail’s diet was also indicated as the δ 13C of clapper rail egg yolks related negatively with the aerial cover of C3 macrophytes. Clapper rails from the ocean-dominated estuary had a narrower trophic niche and appeared to be utilizing marine resources, particularly, based on modeling of liver stable isotope values. Variation in stable isotope values between egg yolk and liver/muscle in both systems suggests that endogenous resources are important for egg production in clapper rails. These results demonstrate that diet composition, prey source, and niche width of clapper rails can vary significantly across different estuaries and appear to be influenced by hydrological conditions.

2300 磁気ヘッドスライダの極低浮上化技術(キーノートスピーチ,情報機器コンピュータメカニクス2)

We developed a novel slider design that has less flying height sensitivity to altitude and manufacturing tolerances for application to head-disk interfaces of sub 10nm flying height. This design also predicts less off-track vibration in case of slider-disk contacts and it has been confirmed experimentally. We applied "pivot shift" concept to our slider design in order to reduce the flying height loss due to altitude. In this design, the pivot point of the slider is shifted forward toward the leading edge from the usual center position of the slider. This shift increases the pitch moment, which can compensate for flying height loss due to increase in altitude. We also applied "super shallow step" of a few nanometers in depth to our slider design in order to trim the trailing edge rail width of the slider. The trimmed rail can reduce the flying height loss due to manufacturing tolerances and can also reduce the off-track vibration due to slider-disk contacts. By combining the pivot shift concept with the super shallow step design, the flying height of the slider can be reduced to sub 10nm successfully while maintaining needed clearance to ensure the mechanical reliability of the head-disk interface.

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

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]

Long-term rail stance training in healthy young adult women.

Daily rail stance training was performed for no longer than 3 months on 12 healthy Japanese women volunteers with eyes open and closed. Rail width conditions were varied, during which time rail stance was repeated 30 times every day until volunteers could stand for 60 s in at least half the trials. Prolongation of stance time and retention of training effects were investigated. The rate of progress depended on the difficulty of the stance and was determined by rail width and visual conditions. However, marked differences were seen among subjects even under the same training conditions. The faster the progress, the better preserved was the training effect during the post-training period. There was no obvious difference in the learning curve between narrow rails with eyes open and wide rails with eyes closed. We concluded that the retention of the training effect parallels the rate of progress, and this is determined by the difficulty of action relative to the inherent ability of the subjects.

Design Optimization of the Taper-Flat Slider Positioned by a Rotary Actuator

In this paper, an optimization technique is utilized to find an optimum configuration of the taper-flat slider positioned by a rotary actuator for enhanced static air-bearing characteristics. The aim of optimization consists in simultaneously minimizing the variation in flying height from a target value, maximizing the smallest pitch angle, and minimizing the largest roll angle, over the entire magnetic recording band. As the design variables, the leading edge taper angle and rail width of a taper-flat slider, and the skew angle at the inside track are chosen since they seem to be the most influential parameters on air-bearing characteristics. The optimum design variables are automatically obtained by using the augmented Lagrange multiplier method, and the static characteristics of the optimally designed sliders are found to be superior to those of the taper-flat sliders of typical configuration over the entire recording band. Results obtained for three taper-flat slider models are reported, showing the effectiveness of the proposed design scheme.

The Dependency of Takeoff Velocity and Friction on Head Geometry and Drive Configuration

Wear at the head-disk interface of magnetic recording devices is dependent on the contact sliding distance between the head and disk. The sliding distance is dependent on the head takeoff velocity and frictional drag. In this study, the dependence of takeoff velocity and friction on selected head parameters was measured with an air bearing spindle equipped with a strain gauge. For the thin film head, crown had the greatest influence on takeoff velocity, followed by bolt pattern runout, suspension preload, camber, skew angle, and rail width in decreasing order. For the metal-ingap head, ski jump had the greatest influence. The rest of the parameters followed in the same order as they did for the thin film head. Twist and edge blend did not affect takeoff velocity, but larger edge blends did improve contact start-stop performance. Lower mass disk stacks did better in contact start-stop tests because of their shorter sliding distance before reaching the takeoff velocity or after achieving the landing velocity. Finally, both crown and skew angle affected the coefficient of friction between the head and disk. Heads with a more positive crown or zero skew angle had the lowest coefficient of friction.

The influence of head parameters on take-off velocity

The dependence of take-off velocity (TOV) on selected head parameters was measured with an air bearing spindle equipped with a strain gauge. Considering the range that was studied for each parameter, TOV was found to be strongly dependent on crown, skew angle, ski jump and suspension preload, in decreasing order. Camber height and rail width were found to have a lesser influence. Edge blend did not affect TOV; however, increasing edge blend improved the head-disk performance in contact start-stop (CSS) tests.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Determination of Parameters of the Arc Plasma of Electrodynamic Macro‐Particle Accelerator by the Method of Simulation of Surface Energy Losses

AbstractIn the paper we have presented the model method of calculating electrical arc parameters in the macroparticles' electrodynamic accelerator at the given rail width and the given width between them. The method is based on energy losses simulation at the arc's boundary surfaces and is a modification of the one‐dimensional version of Powell and Batteh's method. It has been shown that the proposed method is adequate for operative use and that it enables the determination of both macroscopic arc parameters · acceleration, length, electroconductivity, mean temperature and density of particles etc., as well as local arc plasma parameters. The values of these parameters are determined by numerical solutions of the self‐consistent system of mangetic‐hydro‐dynamic, material and thermodynamic equations, at the arc's given mass and muzzle voltage between rails. It has also been shown that the proposed method allows the comparison of one‐, two‐ and three‐dimensional arc approximations. In the present paper we have used the method assuming that arc plasma is at most doubly ionized and produced exclusively by copper atoms.

Study of head and disk interface in contact start/stop test

The dependence of takeoff velocity (for head and disk combinations) on head parameters has shown that the takeoff velocity depends primarily on the rail width and crown of the air bearing surface. No significant dependence of the air bearing surface was found. Measurements of static friction for similar disks and heads with different takeoff velocities showed higher static friction for heads with higher takeoff velocities. By plotting the static friction data versus sliding distance rather than the number of contact start/stop (CSS) cycles, it was found that the higher static friction observed for heads with higher takeoff velocities was greater than what would be expected if the head dependence of the static friction increase were solely due to the total sliding distance of the heads. The significant dependence of takeoff velocity on head crown is an important parameter to control for acceptable static friction after a large number of CSS cycles.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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. >

The effect of head/disk design parameters on the transition from sliding to flying of Winchester-type sliders

The contact behavior and stability of a typical Winchester-type slider are investigated during its transition from sliding to flying using numerical simulation. Regions of stable and unstable flying behavior are determined as functions of the initial disturbance velocities of the slider and head/disk design parameters, such as surface roughness, coefficient of friction, and slider rail width. Factors that produce large negative pitch motions tend to increase the region for which unstable contact behavior occurs. Configurations that tend to decrease the possibility of contact tend to decrease the region of instability. The results can be used to establish qualitative criteria to guide the design of improved slider bearings with less vulnerability to a head crash during in-contact start/stop.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>