Mechanism and optimum shape of knife edge for metal sealing

The contacting state of knife-edge seals was investigated and a new type of knife edge was developed. The contacting state of knife-edge seals was divided into three types according to the apex width of the knife edge: (a) penetration type, (b) indentation type, and (c) intermediate type. The developed knife edge had a contacting state of penetration type (a). Because of the narrow apex width of the knife edge, the values of P_c/l for the compressive forces per unit length required for sealing were lower than those of other types of knife-edge seals. The contact pressure required for sealing was nearly equal to the Meyer's hardness in the sealing surface layer, regardless of the surface roughness in turning. The optimum shape of the knife edge was of type (a) and had a ridge in a V-shaped cross-section with a plane inclined 30° off normal and the flat area of its apex finished by lapping was about 35 μm wide. The knife edge made of hard material with optimum shape could be utilized in the cases where the sealing materials were copper, carbon steel and stainless steel, and the values of P_c/l were approximately 15–40, 45–110 and 80–190 kN m⁻¹, respectively.     

Sensor-less maximum power point tracking control for wind generation system with squirrel cage induction generator

This paper proposes a technique that determines the optimal windmill operation speed and the optimal rotor flux. Moreover, the position and speed sensor-less wind generation system using the electromotive voltage observer to estimate rotor position and full-order observer to estimate rotor speed and the windmill output torque are proposed. The position and speed sensor-less maximum power point of wind power generation system is controlled by using the above estimated values, optimized windmill operation speed for maximum output power and optimized rotor flux for minimum generator losses. The effectiveness of the position and speed sensor-less maximum power point tracking control for wind power generation system with squirrel cage induction generator is verified by simulations. The simulation results confirm that the proposed method can estimate the operation speed efficiently.     

Influence of fault arc characteristics on the accuracy of digitalfault locators

This paper proposes a time domain model of a fault locator with special reference to fault are nonlinearities by applying the MODELS language of the EMTP. It has been found that an impedance relay type locator is significantly influenced by the fault arc nonlinearities, while the current diversion ratio method is not influenced. This validates the advantage of the current diversion approach over the impedance approach     

Stochastic inequality constrained closed-loop model-based predictive control of MW-class wind generating system in the electric power supply

Wind turbines have become the most cost-effective renewable energy systems available today and are now completely competitive with essentially all conventional generation systems. However, wind stochasticity results in fluctuations in output power as well as undesirable dynamic loading of the drive train during high turbulence. A model-based predictive control strategy for the field-oriented control of a doubly fed induction generator is presented. The control region is defined over two wind profiles: average wind speeds below and above equipment rating, subject to assigned constraints of the maximum allowable system frequency fluctuations and the power limit of the wind generating system. To meet the control objectives of maximising energy capture and alleviation of drive train fatigue loads, each of the WGS component blocks is modelled separately so as to explore the associated trade-offs. Simulations, carried out under a Matlab environment, serve to verify that the proposed paradigm performs better than the classical linear proportional?integral controller in achieving the regulation of torsional dynamics while maintaining optimal operation.     

Effects of directional properties of roughness and tangential force on pressure flow between contacting surfaces

The fluid flow phenomena between contacting surfaces which exhibit roughness are interesting for the lubrication mechanisms and the sealing problems. The effects of the directional properties of roughness and tangential forces on the pressure flow are examined in this paper. Annular sealing surfaces ground in a radial direction and in a peripheral direction were prepared, and the leakage rates were measured. The experimental results showed that directional properties and tangential forces affected the leakage rates. In the last part of this paper, the directional properties of roughness are discussed, based on two-dimensional Fourier analysis.     

Process integration of single-wafer technology in a 300-mm fab, realizing drastic cycle time reduction with high yield and excellent reliability

In this paper, we discuss a new technology implemented with single-wafer processing for a 300-mm fab. Newly developed equipment and chemicals reduce the process time and provide cost savings. The combination of fully automated systems and single-wafer processing significantly reduces queuing time. The process has been re-integrated to eliminate long time processes and make it suitable for single-wafer technologies. As a result, a very aggressive cycle time (0.25 days/layer) with high yield, in double-polysilicon, sextuple-metal, 0.18-/spl mu/m logic process has been demonstrated. High-performance devices with excellent reliability are also obtained. A new methodology for detecting parametric errors effectively in the early stages of production is implemented for quick yield ramp up.     

V-band HJFET MMIC DROs with low phase noise, high power, and excellent temperature stability

This paper describes the development, along with detailed phase-noise analysis, of V-band monolithic-microwave integrated-circuit (MMIC) dielectric-resonator oscillators (DROs) achieving state-of-the-art performances. A TE/sub 01/spl delta//-mode Ba(Mg,Ta)O/sub 3/ cylindrical dielectric resonator (DR) is directly placed on a MMIC GaAs substrate to avoid the loss and uncertainty of bonding wires. A 0.15-/spl mu/m AlGaAs-InGaAs heterojunction field-effect transistor with optimized structure is developed as an active device. A design procedure proposed by the authors is employed, which allows us to analyze and optimize circuits in consideration for the output power, phase noise, and temperature stability. A developed DRO co-integrated with a buffer amplifier exhibits a low phase noise of -90 dBc/Hz at 100-kHz offset, a high output power of 10.0 dBm, and an excellent frequency stability of 1.6 ppm//spl deg/C at an oscillation frequency of 59.6 GHz, all of which are state-of-the-art performances reported for MMIC DROs above V-band. An experimental and theoretical analysis for the phase-noise-reduction effect of a DR is also addressed.     

Unit commitment by heuristics and absolutely stochastic simulated annealing

A new approach to unit commitment problem is presented using absolutely stochastic simulated annealing method. In every iteration, a solution is taken with a certain probability. Typically in simulated annealing minimisation method, a higher cost feasible solution is accepted with temperature-dependent probability; however, other solutions are accepted deterministically. That may lead to the near optimisation slowly. However, all the solutions of both higher and lower costs, are associated with acceptance probabilities to make an early jump from one local minimum to other so that it can search and compare more local minima within the same time/iteration limit. Besides, the number of bits flipping is decided by the appropriate distribution. Excess units with system-dependent probability distribution handle constraints efficiently. Sensitivity of the distribution parameters is tolerable. To reduce economic load dispatch calculations, a sign bit vector is introduced as well. The proposed method is then tested using the reported problem data set. Simulation results are compared to previous reported results. Numerical results show an improvement in solution cost and time compared to the results obtained from powerful algorithms     

Linear protrusion structure on carriage-arm surface for reduction of flow-induced carriage vibration in hard disk drives

One of the major contributors to head positioning errors is carriage vibration in low frequency due to an air flow caused by disk rotation. It is necessary to suppress the disturbance for Hard Disk Drives (HDDs) to have more capacity. We experimentally studied a reduction in the flow-induced carriage vibration using linear protrusion structures by putting wires on carriage arms. This study was carried out using 2.5?inch HDD which has high rotational speed of 10,000?rpm. We measured position error signals (PES) and compared with a conventional carriage. From the experimental results, we found that the linear protrusion structure was effective to reduce the carriage vibration. Leading edge wire configuration and 2 linear protrusion configuration improved average non-repeatable position errors (NRPE) by 6.9% and 6.4%, respectively.