Constant Linear Velocity Research Articles

Plasma enhanced germanium nitride dielectric thin films for phase-change recording systems

The more efficient dielectric material and structure have been developed for fast phase-change optical recording systems. The germanium nitride thin film was reactively sputtered using a d.c. chamber, operated at 3 kW with a mixed gas plasma of argon and nitrogen. The dielectric thin film of 11–13 nm has been designed as the upper dielectric layer between the Ge–In–Sb–Te active layer and the silver reflective layer. The optical storage disks were initialized by a Hitachi POP120-8E device to provide crystalline active layers before the dynamic tests. The initialization was conducted using 810 nm laser at 2300 mW while the disks were rotated at a constant linear velocity of 10 m/s. The optical properties were analyzed using a Steag ETA-RT optical measuring system at 410–1010 nm wavelength. The power margin window was shown to be effectively improved by 60% to 18–26 mW when compared with the traditional ZnS–SiO 2 dielectric system. TEM (transmission electron microscope) micrograph showed clear profile for the standard 3T laser marks on the active layer. The plasma enhanced germanium nitride dielectric thin film could improve digital versatile disk's (DVD) production yield and efficiency.

Predicting the path of a changing sound: Velocity tracking and auditory continuity

Three studies demonstrate listeners' ability to use the rate of a sound's frequency change (velocity) to predict how the spectral path of the sound is likely to evolve, even in the event of an occlusion. Experiments 1 and 2 use a modified probe-signal method to measure attentional filters and demonstrate increased detection to sounds falling along implied paths of constant-linear velocity. Experiment 3 shows listeners perceive a suprathreshold tone as falling along a trajectory of constant velocity when the frequency is near to the region of greatest detection as measured in Experiments 1 and 2. Further, results show greater accuracy and decreased bias in the use of velocity information with increased exposure to a constant-velocity sound. As the duration of occlusion lengthens, results also show a downward shift (relative to a trajectory of constant velocity) in the frequency at which listeners' detection and experience of a continuous trajectory are greatest. A preliminary model of velocity processing is proposed to account for this downward shift. Results show listeners' use of velocity in extrapolating sounds with dynamically changing spectral and temporal properties and provide evidence for its role in perceptual auditory continuity within a noisy acoustic environment.

Catalytic partial oxidation of methane on rhodium and platinum: Spatial profiles at elevated pressure

Under pressure : Spatially resolved species and temperature profiles inside foam monoliths have been investigated. This has been done under catalytic partial oxidation conditions of methane over Rh- and Pt-coated catalysts at pressures up to 1.1 MPa. Our results show that the Rh catalyst is governed by mass transfer limitations, while the Pt is kinetically controlled. Catalytic partial oxidation (CPO) of methane is a potential technology for conversion of methane into synthesis gas, because the process operates autothermally with millisecond residence times and at high temperatures ( > 800 ° C) with no external heating. In an industrial setting, it is required to operate the process at elevated pressure. In this work we present spatially resolved data on the effect of pressure on CPO of methane on Rh- and Pt-coated foams from 0.1 to 1.1 MPa total pressure. There is little effect of pressure over Rh on rate at constant mass flow rate, which can be explained by mass transfer limitations. At constant linear inlet velocity the oxidation zone is extended with increasing pressure, again in accordance with mass transfer limitations. On Pt increasing pressure at constant mass flow rate leads to faster oxygen consumption and higher H 2 production because of higher operating temperature and longer residence times. Catalyst deactivation was not observed for Rh, but initial deactivation was observed for Pt.

Improvement of Electron Beam Recorder for Mastering of Future Storage Media

An electron beam recorder for optical disk mastering was improved for future storage media. One improvement was related to a formatter to record constant angular velocity formats like servo patterns of hard disks. The formatter draws patterns with constant linear velocity by controlling the translation stage, the rotation stage, the beam blanker, and the high-speed deflector synchronously. The operation of the formatter was demonstrated by test drawing standard servo patterns that aligned in the radial direction and along the arc trajectory of a swing-arm actuator. Another improvement was a reduction in electron beam size. An electron beam column with a 50 kV acceleration voltage for optical disk mastering was improved by incorporating a new objective lens, the magnification of which was about 40% of the former lens. As a result, 58.5-nm pitch land-and-grooves were resolved with a linear velocity of 0.55 m/s. Furthermore a 100 kV electron beam column was developed to reduce the beam size to 10 nm or less. The width of fabricated grooves drawn by the column was about 12 nm.

Generalized limits for energy extraction in a linear constant velocity flow field

AbstractThe Lanchester–Betz limit has long been established as setting an upper bound on the power performance coefficient of an energy extraction device operating in isolation in a linear constant velocity flow field. However, the ideal limiting performance of energy extraction devices operating in conjunction with ducts, diffusers or any systems that further modify inflow local to the plane associated with energy extraction has not been previously established.The present analysis derives the limiting performance in such cases, with the Lanchester–Betz limit emerging as the special case of energy extraction in open flow. The key to this analysis is the characterization of an ideal system in terms of the axial induction that would exist at the plane of energy extraction in the absence of the energy extraction system. The concept of an ‘ideal system’ as one that matches the flow field in every state of loading of the energy extraction device is also crucial.Computational Fluid Dynamics (CFD) analysis of a system with a diffuser provides preliminary validation of the new theory. Generalization of the standard blade element theory is outlined, and the implications for the development of a rationalized design approach and optimization of a system with a rotor operating in a diffuser are addressed.The theory has obvious applicability to systems that are purposefully designed to augment flow, but a wider relevance to wind technology in situations where terrain or other wind turbines modify the flow field is also suggested. Copyright © 2008 John Wiley & Sons, Ltd.

A Method For Guidance of a Wheeled Mobile Robot Based on Received Radio Signal Strength Measurements

We propose a new guidance law for the problem of wheeled mobile robot (WMR) navigation towards an unknown target based on Received Signal Strength (RSS) Information. Given a mobile robot moving with a constant linear velocity, we use the miss-distance derivative as a measure for the angle at which the robot approaches the target. Miss-distance derivative is estimated from RSS, using a Robust Extended Kalman Filter (REKF). Having applied the proposed steering control law, termed Equiangular Navigation Guidance (ENG), the robot approaches the stationary or maneuvering target along a semi-equiangular spiral and eventually goes into a circular trajectory around it. In order to avoid circling, the algorithm is modified to decrease the robot's linear velocity to that of the target as it approaches the moving target and follow it in a smooth trajectory while preserving a safety distance from the target. Eventually, the performance of the guidance law and its effectiveness is confirmed with an extensive simulation study.

Fabrication of optical disk mastering using electron beam and embossing process

For the requirement of higher storage capacity of an optical disk, it is a good choice to shorten pit length and linewidth. However, the conventional laser beam mastering is difficult to fabricate smaller pit length and linewidth because of the optical diffraction limit. In order to solve this problem, optical disk mastering using electron beam lithography is presented. The process parameters of the electron beam mastering such as beam current, constant linear stage velocity, developing time, and focus distance are discussed in this research. In the experiments, it was found that the focus distance is an important parameter to fabricate nano-linewidth. The experimental results reveal that the 10 μm variance in focus distance causes about 12% variation in linewidth. The photoresist with nano-pattern defined by eletron beam was transferred into metal Ni–Co (Nickel–Cobalt) mold by electroplating process. The Ni–Co mold with hardness larger than Vicker Hardness (Hv) 650 was developed. Then, with the Ni–Co mold, LIGA (German: Lithographie GaVanoformung Abformung) process was applied to replicate high-density optical disk. The Ni–Co mold is served as a master for hot embossing process to transfer the nano-pattern onto PMMA sheet. Since the feature size is in nano-meter range, the study presents an innovative demolding mechanism to demold the master from the PMMA sheet without damaging the nano-meter structure. A spiral nano-groove with 112 nm in linewidth and 80 nm in depth has been successfully fabricated about 50 Gbytes storage capacity.

Modelling the spot shape influence on high-speed transmission lap welding of thermoplastics films

Modelling high-speed laser lap welding of thermoplastic films has been accomplished and the influence of laser beam spot shape, dimensions, and position relative to sample displacement was analysed. Engineering parameters predicted by the model were applied to lap weld of high- and low-density polyethylene transparent samples with thickness between 10 and 100 μm, and experimentally validated. Experimental set-up allowed reaching welding constant linear velocities up to 10 m/s. Theoretical and experimental data show coincidence. Weld strength increases for larger beam spot diameters, and elliptical beam spots increase weld efficiency, allowing higher processing speeds or decreasing required laser power. An angular deviation of elliptical beam spot with regard to the sample's movement direction causes an increase of weld strength and a decrease of welding speed.

Fast Ego-motion Estimation with Multi-rate Fusion of Inertial and Vision

This paper presents a tracking system for ego-motion estimation which fuses vision and inertial measurements using EKF and UKF (Extended and Unscented Kalman Filters), where a comparison of their performance has been done. It also considers the multi-rate nature of the sensors: inertial sensing is sampled at a fast sampling frequency while the sampling frequency of vision is lower. the proposed approach uses a constant linear acceleration model and constant angular velocity model based on quaternions, which yields a non-linear model for states and a linear model in measurement equations. Results show that a significant improvement is obtained on the estimation when fusing both measurements with respect to just vision or just inertial measurements. It is also shown that the proposed system can estimate fast-motions even when vision system fails. Moreover, a study of the influence of the noise covariance is also performed, which aims to select their appropriate values at the tuning process. The setup is an end-effector mounted camera, which allow us to pre-define basic rotational and translational motions for validating results.

Toward Biological Diagnosis System Based on Digital Versatile Disc Technology

A novel biosensor utilizing an interference of light reflected at the interfaces of a multilayer structure is proposed. This biosensor detects analytes by monitoring the changes in reflection intensity due to their adsorption to the sensor surface, on which functional biomolecules are immobilized to specifically bind to the analytes. The proposed biosensing instrument is based on a commercial digital versatile disc (DVD) system, which allows the instrument to be small and inexpensive. For the preliminary examination, SiO2 thin films with a well-defined thickness were deposited on the sensor surface. The reflection intensity varied almost linearly depending on the thickness of the SiO2 films in a thickness range of 2–10 nm. Subsequently, it was demonstrated that biotin–streptavidin binding events were clearly detectable on a rotating disc substrate at a constant linear velocity of 4.0 m/s. We named this interference-based biosensor BioDVD, which is expected to be useful for high-throughput multi-analyte bioassays.

Encoding rate-based, programmable, linear velocity, compressed audio compact disc player

An audio player permits compressed or uncompressed audio CDs to be played. The preferred player includes a spindle motor control that causes the CD to be spun at a constant linear velocity that is commensurate with the encoding rate of the file being played. In this manner, the data can be continuously pulled of the CD at just the right rate so that, after being decoded and decompressed, the data can be played. The player also dynamically adjusts its constant linear velocity to the encoding rate of the file being played to permit files on the same disc having different encoding rates to be played.

Flow model for coupled-column gas chromatography systems

One of the challenges in performing comprehensive two-dimensional gas chromatographic separations is being able to predict the average linear velocities of the carrier gas in the two columns, especially when they have different diameters. The problem is compounded for loop-type modulators, where two thermal trapping zones that switch from hot to cold and back simultaneously are separated by a delay loop. If the linear velocity in the loop is not tuned to the length of the loop and the modulation period, the dual-stage modulation may cease to work properly. A model has been developed that calculates the flow rates in the columns and predicts appropriate delay loop dimensions for a given set-up. Additionally, the model determines the pressure ramp that needs to be used in order to maintain constant average linear velocity within the modulator loop throughout the course of the separation.

Solution of the Stefan Problem: Silver Electrodeposition under Mass Transfer Control. The Transition from Diffusion to Advection Regime

An analytical solution of Fick's diffusion equation for the formation of a 2D solid-phase involving a growing front (Stefan problem) position changing at a constant linear velocity is proposed. This solution comprises a first diffusion term that includes an exponential correction factor, and a second constant advection term that depends on the front velocity, and it predicts a kinetic transition from a diffusion to an advection-dominated mass transfer control in going from t → 0 to t → ∞. The validity of the analytical solution is tested using potentiostatic cathodic current transient data for silver electrodeposition in a quasi-2D rectangular cell with an initially plane plate cathode. Theoretical and experimental data fulfill a dimensionless correlation after experimental data are properly corrected for the effective cathode area.

Combination of conflicting visual and non-visual information for estimating actively performed body turns in virtual reality

Whereas constant-weight linear models suffice for understanding many phenomena in the domain of perception and action, how the weights given to each sensory input are determined remains an open question. Notably, it has been suggested that weighting depends on the sensory context (e.g. the inconsistency between sensory signals) as well as on the subject. In the present study, the problem of non-linearity in multisensory interaction for estimating actively performed body turns was addressed at the level of group and individual data. Standing subjects viewed a virtual corridor in which forward movements were simulated at a constant linear velocity, and rotations were actually performed. Subjects were asked to learn the trajectory and then reproduce it from memory in total darkness. In the baseline condition, the relative amplitudes of visual and non-visual information for the performed rotations were the same, but were systematically manipulated in six ‘sensory conflict’ conditions. The subjects performed the task in these seven conditions 10 times (10 sessions), with a delay of at least 2 days between sessions. Five subjects placed more weight on visual than on non-visual information. The other 5 subjects placed more weight on non-visual than on visual information. Interestingly, the difference between ‘visual’ and ‘non-visual’ subjects in their use of conflicting information seemed to be accentuated by the fact of becoming aware of the sensory conflict. In all subjects, conflicting sensory inputs were combined in a linear way in order to estimate the angular displacements. However, signatures of non-linearity were detected when the data corresponding to the day on which subjects became aware of the conflict were considered in isolation. The present findings support the hypothesis that subjects used conflicting visual and non-visual information differently according to individual ‘perceptive styles’ (bottom-up processes) and that these ‘perceptive styles’ were made more observable by the subjects changing their perceptive strategy, i.e. re-weighting (top-down processes).

Frequency adaptive control technique for rejecting periodic runout

This paper proposes a novel adaptive controller for rejecting the periodic runout of a track-following system in the compact disk drive (CDD) with dual actuators. The control objective is to attenuate adaptively the specific frequency contents of runout disturbances without amplifying its rest harmonics. This controller can be implemented in a plug-in manner to an existing feedback control system without changing the original control setup. It is applicable to both the spindle modes of constant linear and constant angular velocity for various operation speeds. The experimental results show that the novel control strategy leads to a satisfactory performance in terms of the reduction of tracking error of CDDs.

In Situ Temperature Measurement During Oxide Chemical Mechanical Planarization

AbstractThis paper presents temperature and friction force data at the pad-slurry-wafer interface during real time CMP polishing with in situ pad conditioning. Experiments are performed on a 1:2 scale laboratory tabletop rotary polisher with variable pad speed and wafer down force control. Dual emission laser induced fluorescence (DELIF) techniques are used to optically measure the temperature directly beneath the wafer during polishing using a two camera imaging system. An infrared camera and a thermocouple are alternately used to measure bow wave temperatures. Optically transparent BK-7 glass wafers with either concave (wafer edges sloping toward the pad) or convex (wafer edges sloping away from the pad) curvature were used. When concave wafers are polished, the bow wave temperatures are 3°C to 5°C higher than the corresponding value for convex wafers. Similarly, slurry temperatures under the concave wafers are 5°C to 6°C higher than the value for convex wafers (±0.5°C). The friction force per unit area is typically 2 kPa to 3 kPa higher for concave wafers. Temperatures beneath the wafer are as high as 12°C above the ambient temperature for a concave wafer at a high applied wafer pressure (41.4 kPa) or linear velocity (0.93 m/sec). Bow wave temperatures reach as high as 9°C above ambient at a linear velocity of 0.93 m/sec. The lowest temperatures, within 1°C of ambient at the bow wave and 5°C above ambient under the wafer, were found with convex wafers at low applied wafer pressures (20.7 kPa). Linear velocity has little effect on the slurry temperature while polishing convex wafers. Increasing slurry abrasive concentration causes an increase in temperature, despite a decrease in friction force. A correlation, with an R-squared value greater than 0.96, exists between the bow wave temperature and the temperature beneath the wafer. This correlation holds at constant linear velocities across wafer shapes, applied wafer pressures, and slurry concentrations.

Nature and characteristics of pulsing flow in trickle-bed reactors

Pulsing flow is well known for its advantages in terms of an increase in mass and heat transfer rates, complete catalyst wetting and a decrease in axial dispersion compared to trickle flow. The operation of a trickle-bed reactor in the pulsing flow regime is favorable in terms of a capacity increase and the elimination of hot spots. Extending the knowledge on the hydrodynamic nature and characteristics of pulsing flow stands at the basis of further exploitation of the effects of this flow regime on reactor performance. An analysis of the hydrodynamics of pulsing flow reveals that pulse properties as liquid holdup, velocity and duration, are invariant to the superficial liquid velocity at a constant gas flow rate. The pulse frequency, however, increases with increasing superficial liquid velocity. The relative contribution of the pulses and the parts of the bed in between pulses to an average measured property can thus be obtained. By applying this concept it is shown that the linear liquid velocity inside the pulses varies between 0.1 and 0.2 m s −1 . The linear liquid velocity in between pulses, however, is invariant to gas and liquid flow rates and packing properties and equal to about 0.05 m s −1 . This suggests that a linear liquid velocity of about 0.05 m s −1 is the maximum velocity possible in the bed to maintain the trickle flow regime. All liquid in excess is transported as pulses. The liquid holdup in the parts of the bed in between pulses equals the liquid holdup at the transition to pulsing flow at all gas flow rates. The same trend holds for the linear liquid velocity in between pulses. Pulsing flow then is a hybrid of two transition states. The pulses reside at the transition to bubble flow, while the parts of the bed in between pulses reside at the transition to trickle flow. The enhanced particle-liquid heat transfer coefficient inside the pulses is mainly the result of the high linear liquid velocity inside the pulses. Particle-liquid heat transfer rates in between pulses are constant due to the constant linear liquid velocity.

Superlattice-like structure for phase change optical recording

In order to increase the crystallization speed and data transfer rate (DTR), a superlattice-like structure (SLL) was applied to the recording layer of phase change optical disks. Unlike the conventional phase change layer, the recording layer with the SLL structure consisted of alternating thin layers of two different phase change materials, i.e., GeTe and Sb2Te3. Although neither GeTe nor Sb2Te3 could be used as a phase change layer material for practical applications, present experimental results revealed that the phase change optical disk with the SLL structure demonstrated an excellent recording property that could meet practical recording requirements. X-ray photoelectron spectroscopy was employed to confirm that the SLL structure could be preserved after many times of melting and quenching. Dynamic properties of the optical recording disk with the SLL structure were investigated with a 1 T pulse duration of 8 ns and a constant linear velocity of 19 m/s. A clear eye pattern was observed. The carrier-to-noise ratio was about 58 dB and a DTR of 47 Mbit/s was achieved. The DTR would be as high as 140 Mbit/s if the blue light is used. It has been proven that the SLL structure is a useful means to increase the DTR of phase change optical recording disks.

Influence of a sensorimotor conflict on the memorization of a path traveled in virtual reality

Studies of visual–vestibular and vestibular–proprioceptive interactions suggest that prolonged exposure to sensory conflicts induces a modification of the relation between sensory modalities for self-motion perception. With most models conflicts are solved by a weighting process. However, the brain could also switch between conflicting cues. The present study focused on the effect of mismatched visual and non-visual information on the reproduction of actively performed turns. Standing subjects viewed a virtual corridor in which forward movements were simulated at a constant linear velocity, and rotations were actually performed. They were asked to learn the trajectory and then to reproduce it from memory in total darkness. In the baseline condition, the relative amplitudes of visual and non-visual information for the rotations performed were the same, but were manipulated in the two ‘sensory conflict’ conditions. The results show that even when subjects did not notice the sensory conflict, the discrepancy between visual and non-visual information affected their ability to reproduce the angular displacements. In one conflict condition, subjects relied on visual information when asked to draw the trajectory traveled, yet reproduced rotations on the basis of non-visual information during active blindfolded movements. This dissociation suggests that for mental simulation of the same path, there are at least two cognitive strategies of memory storage and retrieval, using either visual or non-visual information, according to the task and the sensory context.

A comprehensive analytical performance model for disk devices under random workloads

Our goal is to contribute a common theoretical framework for studying the performance of disk-storage devices. Understanding the performance behavior of these devices will allow prediction of the I/O cost in modern applications. Current disk technologies differ in terms of the fundamental modeling characteristics, which include the magnetic/optical nature, angular and linear velocities, storage capacities, and transfer rates. Angular and linear velocities, storage capacities, and transfer rates are made constant or variable in different existing disk products. Related work in this area has studied Constant Angular Velocity (CAV) magnetic disks and Constant Linear Velocity (CLV) optical disks. We present a comprehensive analytical model, validated through simulations, for the random retrieval performance of disk devices which takes into account all the above-mentioned fundamental characteristics and includes, as special cases, all the known disk-storage devices. Such an analytical model can be used, for example, in the query optimizer of large traditional databases as well as in an admission controller of multimedia storage servers. Besides the known models for magnetic CAV and optical CLV disks, our unifying model is also reducible to a model for a more recent disk technology, called zoned disks, the retrieval performance of which has not been modeled in detail before. The model can also be used to study the performance retrieval of possible future technologies which combine a number of the above characteristics and in environments containing different types of disks (e.g., magnetic-disk-based secondary storage and optical-disk-based tertiary storage). Using our model, we contribute an analysis of the performance behavior of zoned disks and we compare it against that for the traditional CAV disks, as well as against that of some possible/future technologies. This allows us to gain insights into the fundamental performance trade-offs.