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Improving frequency response of direct drive valve (DDV) system is a research focus on the hydraulic system. This paper presents a high-frequency response DDV system based on voice coil motor (VCM-DDV). First, a new design of VCM with high acceleration is proposed. A magnetic circuit method and electromagnetic finite element method are adopted in this paper. A 3-D thermal field element method is also employed to analyze the temperature rise of the developed VCM at rated current. Next, a dual closed-loop control structure is applied in the developed VCM-DDV system. Moreover, a nonlinear PID control strategy is proposed to resolve the contradiction between stability and rapidity. The results of performance test indicate that the acceleration of the developed VCM is evidently improved, and it reaches 306 times of gravity acceleration. Experimental investigation indicates that the developed VCM-DDV system has excellent static and dynamic performances. The position bandwidth of the developed VCM-DDV is capable of achieving 350 Hz. [ABSTRACT FROM AUTHOR]

Part I. Describes research in vehicle signal fault diagnosis. Analysis of vehicle faults and corresponding signal features; Signal segmentation; Automatic extraction of important signal features for fault diagnosis; Automatic selection of a quasi optimal set of features; Conclusion.

The degradation of the electrical contact in a gas insulated switchgear (GIS) is closely related to overheating at the contact. However, the disconnector contact is one of the hot contacts in GIS. Therefore, in this paper, the finite element method was used to solve the three-dimensional multiphysics coupling temperature rise field and flow field in the Single Phase in One Tank (SPIOT) type GIS disconnector under different operating conditions. From the perspective of temperature rise field and flow field, this paper analyzed the temperature rise characteristics under different working conditions and explored the feasibility of the direct application of air, CO2 and C4F7N/CO2 mixed gas to an electrical device. The disconnector temperature rise experiment platform was then built to verify the simulation. The results showed that the temperature rise field and the flow field distribution were similar in four gas environments. SF6 gas had the smallest temperature rise, followed by C4F7N/CO2 mixed gas, and the temperature rise of CO2 and air was relatively large. Therefore, from the perspective of the temperature rise field and flow field, it was feasible to directly apply C4F7N/CO2 mixed gas to an electrical device in order to meet insulation requirements. [ABSTRACT FROM AUTHOR]

Using ab initio methods, we have calculated the characteristic inverse length scale for spin polarized tunneling in Langmuir-Blodgett (LB) films contacted by Fe electrodes. As a function of energy, the scale is found to vary significantly around its mean value, and the variation is much more drastic in parallel configuration than that of anti-parallel configuration. This unusual behavior can be understood. from the point of view of interface resonance, which shows very sharp features in the k-space resolved transmission probability. [ABSTRACT FROM AUTHOR]

Efficient thermal management of large vertically stacked integrated circuits (ICs) requires a material with high thermal conductivity inside the micrometer-sized gaps between the IC dies. Such an underfill material can be obtained by adding thermally conductive filler particles at high loadings to the adhesive matrix material. However, viscosity requirements for the state-of-the-art capillary-driven filling of particle-loaded adhesives limit the particle fill fraction to values lower than those necessary to reach true percolation. Accordingly, heat transfer through the composite material is dominated by conduction through the adhesive matrix material. We propose using an alternative, sequential filling method to achieve percolation with particles down to 1~\mu \textm in diameter. The percolating thermal underfill (PTU) can be achieved by a centrifuge-assisted filling of micrometer-sized particles, followed by a backfilling of a low-viscosity epoxy with long open time acting as matrix material, and a final thermal curing step. In this paper, we present and discuss the fabrication and relevant process parameters of the PTU composite material in chip stacks with critical dimensions below 30~\mu \textm . The wet dispensing of alumina particles with a diameter distribution of 1– 15~\mu \textm is proposed for overcoming the agglomeration observed for dry particle filling. Thermal conductivities of up to 3 W/( \ m\cdot \ K ) for the underfill system with a particle fill fraction of 61% were achieved, which is three times higher than those of commercially available capillary thermal underfills. Critical parameters in the formation of the percolating composite, such as the choice of filler material and its refinement, as well as the properties of the particle bed and the process parameters for the centrifugal filling, epoxy capillary backfilling, and composite curing are addressed. [ABSTRACT FROM PUBLISHER]

This paper presents a radar system for extracting human respiratory features. The proposed radar chip comprises three major components: a digital-to-time converter (DTC), a transmitter, and a receiver. The all-digital standard cell-based DTC achieves a timing resolution of 10 ps on a 100-ns time scale, supporting a range-gated sensing process. The transmitter is composed of a digital pulse generator. The receiver comprises a direct-sampling passive frontend for achieving high linearity, an integrator for enhancing the signal-to-noise ratio, and a successive approximation register analog-to-digital converter for signal quantization. A fully integrated CMOS impulse radar chip was fabricated using 65-nm CMOS technology, and the total power consumption is 21 mW. In the backend, a real-time digital signal-processing platform captures human respiratory waveforms via the radar chip and processes the waveforms by applying a human respiratory feature extraction algorithm. Furthermore, a clinical trial was conducted for establishing a new diagnosis workflow for identifying respiratory diseases by the proposed wireless sensor system. The proposed system was validated by applying an adaptive network-based fuzzy inference system and support vector machine algorithm to the clinical trial results. These algorithms confirmed the effectiveness of the proposed system in diagnosing respiratory diseases. [ABSTRACT FROM PUBLISHER]

A multilayer radar-absorbing structure with plasma- and radar-absorbing material (RAM) is established to investigate the stealth mechanisms of the multilayer absorber. The method of impedance transformation with multiple dielectrics is used to analyze the propagation of electromagnetic (EM) waves in the multilayer structure. The dependences of EM waves attenuation on the parameters of the plasma and RAMs are provided. The numerical results indicate that generally speaking, the joint attention effect of RAM and plasma is better than the effect of either RAM or plasma solely. The attenuation of an EM wave in the structure is strongly affected by: a) the characteristics of RAMs; b) the width of the plasma layer; c) the parameters of the outer layer material; d) the electron density of the plasma; and e) the collision frequency between electrons and neutrals. It is demonstrated that detailed numerical analyses are useful in practical applications pertaining to the control of the reflection of EM waves through a multilayer radar-absorbing structure with plasma and RAMs. [ABSTRACT FROM PUBLISHER]

Terahertz (THz) waves have been attracting much attention for a variety of technologies in recent years. However, only limited several experimental investigations on the terahertz characterization of plasmas have been reported. In this paper, a finite-difference time-domain method is applied to model the terahertz wave propagation in a high-temperature unmagnetized plasma. The rational polynomial function is established based on a hot plasma dispersion relation, and then, the relationship between D and E is deduced in the time domain. In the frequency domain, the reflection and transmission coefficients of terahertz waves through the hot unmagnetized plasma slab are computed, and their dependences on plasma frequency, plasma thickness, and collision frequency are studied. The results show theoretically that, when the terahertz wave passes through the plasma layer, its amplitude is obviously modulated by the electron density profile, the collision frequency, and the electron temperature. Finally, the potential application of terahertz waves in plasma diagnostics has been discussed. [ABSTRACT FROM PUBLISHER]