Analysis of the Slider Off-Track Vibration Caused by the Aerodynamic Loads Associated With Different Components of a Head Stack Assembly in a Disk Drive

The paper describes a numerical investigation of the problem of flow-induced, off-track vibration of the slider in a disk drive. The flow field was simulated in a 3.5-in, 10 000 rpm disk drive using FLUENT flow-modeling software, which yielded the aerodynamic forces and moments for various components of the head stack assembly (HSA). The finite-element model of the HSA was developed using ANSYS software. Then off-track vibration of the slider caused by the aerodynamic loads of different HSA components was computed. The computations showed that the arm experiences the largest fluctuations of aerodynamic load. However, the loadbeam base region appears to make the largest contribution to off-track vibration of the slider, due to the vortex shedding generated by the side tabs of the loadbeam base region.     

An intelligent approach to the lateral forces usage in controlling the vehicle yaw rate

A direct yaw moment control system (DYC) is designed to improve the handling and stability of a four‐wheel‐drive electric vehicle. The main task of this paper is to use the lateral forces in the process of optimally controlling vehicle stability. This is performed by defining a variable optimum region for the slip ratio of each wheel. A hierarchical structure is selected to design the control system. The higher‐level control system controls the yaw rate of the vehicle based on the fuzzy logic technique. The lower‐level control system, installed in each wheel, maintains the slip ratio of the same wheel within an optimum region using the fuzzy logic technique. This optimum region for each wheel is continuously modified based on the impact of the lateral force on the generated control yaw moment and the friction coefficient of the road. Therefore, an algorithm for estimation of the friction coefficient is proposed. Computer simulations are carried out to investigate the effectiveness of the proposed method. This is accomplished by comparison of the results of control methods with a fixed slip ratio region and the results of the proposed method with a variable slip ratio region in some maneuvers. The robustness of the proposed controller against hard braking and noise contamination, as well as the effect of steering wheel angle amplitude, is verified. The simulation results show that the influence of the proposed method on enhancing vehicle performance is significant. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Decentralized robust adaptive-output feedback controller for power system load frequency control

In this paper, a new model reference-decentralized robust adaptive-output feedback controller is proposed for the load frequency control (LFC) of large-scale power systems with unknown parameters. This control strategy requires only local input–output data and can follow random changes in the operating conditions. The controller is designed such that the trajectory errors and the control gains of each area remain uniformly bounded. In the proposed method, firstly an adaptive observer is designed to estimate the state variables and system parameters using local data only. Then a locally linear combination of the estimated states and the model reference states are used to design a robust adaptive-output feedback controller for each area. Simulation results for a three-area power system show that the proposed controller achieves good performance even in the presence of plant parameter changes and system non-linearities. Received: 18 October 2001/Accepted: 24 October 2001     

Buckling analysis of stepped plates using modified buckling mode shapes

A new approximate procedure for buckling analysis of simply supported rectangular stepped or perforated plates subjected to uniform edge stresses is formulated. The procedure uses energy method based on modified buckling mode shapes. The change of thickness within a plate is characterized by introducing a stepping index. It is shown that the buckling (vibrational) mode shapes of stepped plates can be predicted by linear combination of various mode shapes of the equivalent flat plates. These buckling mode shapes, in turn, are incorporated to evaluate buckling loads of stepped plates. Some case studies are carried out to demonstrate the accuracy and the versatility of the proposed method by comparing them to the results presented by other researchers.     

Advances in schottky rectifier performance

In conclusion, heteroepitaxial technology has delivered a new device building block for the microwave and millimeter-wave toolbox - a single-crystal Schottky barrier diode made from a lattice matched combination of a semimetal (ErAs) and a semiconductor (InAlGaAs). This article has demonstrated how sensitive such a Schottky diode can be as a room-temperature zero-bias rectifier up to W band and addressed the fundamental device and impedance matching issues when coupled to a planar antenna in a quasi-optical package. As might be expected, the new Schottky diodes also display a very low degree of 1/f noise when used in applications that require bias or large signals, such as frequency mixers and multipliers (Young et al., 2006)     

Interferometric sensor based on coherent imaging of gratings

A sensitive interferometric sensor scheme that is based on coherent imaging of a first phase grating onto a second phase grating, their periods accurately matched, is suggested. Experimental data, obtained with a setup based on the suggested scheme, are presented. The sensor was found capable of measuring an angular tilt of a mirror less than 0.5 microrad. Compared with a previously suggested measuring scheme, the novelty of the one presented here is the inclusion of a second set of gratings, which eliminates measurement ambiguity. Some characteristics of the sensor scheme are discussed.     

Energy efficiency optimization for device‐to‐device communication underlaying cellular networks in millimeter‐wave

This paper studies energy efficiency maximization in device‐to‐device (D2D) communications underlaying cellular networks in millimeter‐wave (mm‐wave) band. A stochastic geometry framework has been used to extract the results. First, cellular and D2D users are modeled by independent homogeneous Poisson point process; then, exact expressions for successful transmission probability of D2D and cellular users have been derived. Furthermore, the average sum rate and energy efficiency for a typical D2D scenario have been presented. An optimization problem subject to transmission power and quality of service constraints for both cellular and D2D users has been defined, and energy efficiency of D2D communication is maximized. Simulation results reveal that by working in millimeter‐wave, significant energy efficiency improvement can be attained, e.g., 20% energy efficiency improvement compared with Rayleigh distribution in the practical scenarios by considering circuit power. Finally, to verify our analytical expressions, the simulation studies are carried out, and the excellent agreements have been achieved.     

Effect of Experimental Conditions on Cementite Formation During Reduction of Iron Ore Pellets

Metallurgical and Materials Transactions B - Experiments have been carried out to study the effect of temperature, gas composition, residence time, and type of iron ore pellets on formation of...     

Effect of Incident Energy and Foil Thickness on Foil Stripping and Scattering Efficiency in Charge Exchange Analyzer Detector

Compact neutral particle analyzer (CNPA) is used to measure ion temperature in tokamaks. Calculating of stripping efficiency and scattering efficiency are most important parameters affecting on CNPA performance. We studied the dependent of these parameters with the thickness of carbon foil and incident energy of neutral hydrogen atoms. In low carbon foil thickness variation of the carbon foil stripping efficiency (η_i) and scattering efficiency of the ions (η_sc) with incident energy is very salient. For foil thickness between 200 and 600 angestrom, scattering efficiency of the chamber will be smaller than 0.11.