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The advanced features of three-phase PWM voltage-source converter are not necessarily achieved under unbalanced input voltage conditions due to the generation of even-order harmonics at dc output and the odd-order harmonics in input currents. Both the 2nd harmonic voltage component onto the dc link and the negative sequence part of the input currents can disturb the performance of the attached inverter...
The sustained oscillation often appears in the induction motor (IM) systems with indirect field-oriented control (IFOC) and essentially caused by the unstable equilibrium points undergoing Hopf bifurcation. In order to stabilize these undesirable oscillations, a convenient time-delayed state feedback method is presented and its accomplishing process is indicated for a tested IM system in detail. It...
According to the large size multi-oil pad hydrostatic bearing, the mathematical model of three-dimensional flow of the gap oil film of the hydrostatic bearing is established in considering the influence of variable viscosity and centrifugal force condition. The finite element method and the finite volume method are used to simulate the flow field of the gap oil film of the large size hydrostatic bearing,...
The gap fluid of hydrostatic thrust bearing is studied in this dissertation. By applying computational fluid dynamics and theory of lubrication, and establishing three-dimensional solid model and mathematical model of the gap fluid of hydrostatic thrust bearing, analyzing synthetically three-dimensional pressure distribution of the gap fluid between hydrostatic guideway and the rotary table by using...
Aiming at the problem of deformation of heavy hydrostatic thrust bearing, finite element method (FEM) is used to conduct its numerical simulation, and the law of the influence of temperature and load on bearing deformation is revealed. Experiment of oil film thickness in different velocity is also made. The results demonstrate that: the free thermal deformation of workbench and base is significant...
An effective Hopf bifurcation criterion is provided for an induction motor (IM) drive system with indirect field oriented control (IFOC). According to the criterion, the bifurcation surface is shown to indicate parameters' influences on Hopf bifurcation set. Research results instruct us how to quench Hopf bifurcation by proper setting of PI parameters. Then, time-delayed state feedback method is introduced...
Small signal stability analysis is conducted considering grid connected doubly-fed induction generator (DFIG) type. The modeling of a grid connected DFIG system is first set up and the whole model is formulated by a set of differential algebraic equations (DAE). Then, the mathematical model of rotor-side converter is built with decoupled P-Q control techniques to implement stator active and reactive...
In the hydrostatic thrust bearing with open-loop quantity oil supply system for the heavy NC machine tool, the time-variable oil viscosity and the loads will cause the lubricant film thickness deviating from the optimum value, which reduce the bearing film rigidity and affect the machine tool precision. This paper proposed a controllable hydrostatic thrust bearing, which combined the constant flow...
In this paper, the method of resultants is introduced and achieved, three-dimensional Hopf bifurcation diagrams are showed to indicate the influences of an induction motor (IM) drive system parameters on system stability. Then, a Matlab/Simulink model of the closed-loop IM drive system via time-delayed state feedback is set up, numerical results validate that time-delayed state feedback can stabilize...
S-parameter test structures from a 45 nm SOI CMOS technology show total capacitance per perimeter of poly-bounded ESD diodes ranges from ~0.35-0.42 fF/mum, and silicide-block (SBLK) bounded diodes show ~15-20% capacitance reduction. Floating-body or notched-silicon tied-body Gate-Silicided GGNMOS devices show total capacitance per width of ~0.65 fF/um for thin oxide devices, and ~0.72 fF/mum for thick...
In this paper, the time-delayed feedback control method is introduced to stabilize unstable equilibrium points undergoing Hopf bifurcation for an induction motor (IM) drive system. Stability criterion of a nonlinear time-delayed system is first established, and then an effective procedure is shown how to stabilize the unstable equilibrium points by suitably select the feedback gain k and the time-delay...
In this paper, a method is presented and achieved to accurately determine Hopf bifurcation point for an induction motor (IM) drive system, and Hopf bifurcation diagram is showed to indicate evolvement of the equilibrium points from steady state to undergoing Hopf bifurcation and then achieving stabilization again. At last, the classical Floquet theory is applied to confirm the limit cyclepsilas stability.
S-parameter test structures show total capacitances per perimeter of ESD diodes increased from ~0.42fF/mum in 90nm technologies to ~0.7fF/mum in 65nm and 45nm technologies. To achieve lower capacitances for high frequency circuits, layout and process optimization are needed. SCR devices from a 45nm technology show ~0.32fF/mum and can be used for circuit applications with stringent capacitance requirement...
When users are connected to a Large Scale distributed virtual environment system on internet, downloading speed is a key point to support a life-like world and real time interactions for a large number of avatars in a consistent fashion. We proposed an adaptive multi-node downloading partitioning algorithm to balance the bottleneck problem on multi- node downloading architecture we designed. It facilitates...
Power gain (fMAX) of 350GHz and cut-off frequency (fT) of 280 GHz is demonstrated for 36nm Lpoly devices in a 45nm bulk CMOS process. A record fT of 350GHz (intrinsic fT 425GHz), without any loss of fMAX is seen in 28nm Lpoly devices. Combination of advanced lithography and liner stress effect can be leveraged to further boost fT and fMAX by 14% with a relaxed pitch device. Comparison with 90 and...
A well-suited and applicable methodology is proposed to determine stability of equilibrium points for an induction motor (IM) drive systems. Researches indicate that some equilibrium points will lose stability and undergo Hopf bifurcation for some IM drive systems, numerical results validate the proposed methodology. Then, the center manifold theory is introduced and applied to research stability...
This paper suggests a new criterion for substation voltage regulation and reactive power automatic regulation, which introduces voltage status into reactive power regulation criterion, making the reactive power regulation boundary a fuzzy one variable with voltage status. Being agreeable to human judgement, this criterion can improve compensation effects and effective in keeping a stable voltage and...
An accurate and rapid assay of cardiac nerve growth factor (NGF) levels in blood can provide physicians with critical information regarding myocardial injury and neural remodeling in cardiac tissues to identify patients at risk of impending heart attack, thereby enabling them to receive appropriate lifesaving treatment more quickly. Currently used assay methods, such as enzyme-linked immunosorbent...
An accurate and rapid assay of cardiac nerve growth factor (NGF) levels in blood can provide physicians with critical information regarding myocardial injury and neural remodeling in cardiac tissues to identify patients at risk of impending heart attack, thereby enabling them to receive appropriate lifesaving treatment more quickly. Currently used assay methods, such as enzyme-linked immunosorbent...
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