Northwest Institute of Nuclear Technology

Xi'an, China

Northwest Institute of Nuclear Technology

Xi'an, China
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Zhang D.,National University of Defense Technology | Wang X.,Northwest Institute of Nuclear Technology
Journal of Intelligent and Robotic Systems: Theory and Applications | Year: 2017

This paper describes our work on autonomous landing control of fixed-wing unmanned aerial vehicles (UAVs). A hierarchical control structure is developed for autonomous landing of fixed-wing UAVs. In the hierarchical control structure, active disturbance rejection controllers are designed for attitude control. A proportional guidance law is proposed for height tracking. Other controllers, such as flight path angle controller, heading angle controller and taxiing controller, are designed using proportion integration differentiation technique. A test system is developed to validate the hierarchical structure and narrow the gap between the theory and practice. The test system includes an X-Plane based hardware-in-the-loop(HIL) simulation subsystem and a flight test subsystem. The interface and protocol between the autopilot and X-plane are designed same with that of the flight test platform. Consequently, the autopilot passed the validation in the HIL simulation can be directly moved on to the flight test platform. Finally, results of the HIL simulation and field experiment are presented to demonstrate the performance of the proposed approach and the entire test system. © 2017 Springer Science+Business Media Dordrecht

Ma Q.,National University of Defense Technology | Xu T.,Northwest Institute of Nuclear Technology
Journal of Alloys and Compounds | Year: 2017

SiAlOC ceramics were fabricated by pyrolysis of Al-doped polymethyl(phenyl)siloxane at 1000 °C. Then SiAlOC ceramics were annealed under inert atmosphere at 1200 °C, 1400 °C, 1500 °C and 1600 °C, respectively, to investigate their high-temperature evolution behaviors. The transformations of microstructural units resulting from bonds redistribution are observed from 1000 °C to 1400 °C. Creation of mullite at 1400 °C and its crystallization at higher temperatures are confirmed. Carbothermal reaction is effectively suppressed due to low content of free carbon and formation of mullite in SiAlOC ceramics. Accordingly, enhanced thermal stability of SiOC ceramics is realized by incorporation of Al element. © 2017 Elsevier B.V.

Liu J.,Northwest Institute of Nuclear Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

High power excimer laser has essential applications in the fields of high energy density physics, inertial fusion energy and industry owing to its advantages such as short wavelength, high gain, wide bandwidth, energy scalable and repetition operating ability. This overview is aimed at an introduction and evaluation of enormous endeavor of the international high power excimer laser community in the last 30 years. The main technologies of high power excimer laser are reviewed, which include the pumping source technology, angular multiplexing and pulse compressing, beam-smoothing and homogenous irradiation, high efficiency and repetitive operation et al. A high power XeCl laser system developed in NINT of China is described in detail. © 2013 SPIE.

Feng J.,National University of Defense Technology | Zhang C.,National University of Defense Technology | Jiang Y.,National University of Defense Technology | Zhao N.,Northwest Institute of Nuclear Technology
ACS Applied Materials and Interfaces | Year: 2011

Carbon fiber-reinforced carbon aerogel composites (C/CAs) for thermal insulators were prepared by copyrolysis of resorcinol-formaldehyde (RF) aerogels reinforced by oxidized polyacrylonitrile (PAN) fiber felts. The RF aerogel composites were obtained by impregnating PAN fiber felts with RF sols, then aging, ethanol exchanging, and drying at ambient pressure. Upon carbonization, the PAN fibers shrink with the RF aerogels, thus reducing the difference of shrinkage rates between the fiber reinforcements and the aerogel matrices, and resulting in C/CAs without any obvious cracks. The three point bend strength of the C/CAs is 7.1 ± 1.7 MPa, and the thermal conductivity is 0.328 W m -1 K -1 at 300 °C in air. These composites can be used as high-temperature thermal insulators (in inert atmospheres or vacuum) or supports for phase change materials in thermal protection system. © 2011 American Chemical Society.

Wu G.,Northwest Institute of Nuclear Technology
IEEE Transactions on Electromagnetic Compatibility | Year: 2014

Double exponential function and its modified forms are widely used in high-power electromagnetics such as high-altitude electromagnetic pulse and ultrawide-band pulse study. Physical parameters of the pulse, typically the rise time tr, full width at half maximum tw, and/or fall time tf, usually need to be transformed into mathematical characteristic parameters of the functions, commonly denoted as α and β. This paper discusses the dependences of pulse shape properties, represented by ratios of tw/tr and tf/tr, on a dimensionless parameter A = β/α or B = α/β; and focuses on their limit correlations associated with the mathematical forms. It has been proven that pulses with tw/tr < 4.29 cannot be expressed by the commonly used difference of double exponentials function. This limit can be mitigated partially by the latest proposed p-power of double exponentials function with a well-chosen p parameter. A novel form, difference of double Gaussian functions is also proposed to describe pulses with low t w/tr ratios better. Quotient of double exponentials, however, is shown to be the most flexible function for describing transient pulses with arbitrary tw/tr ratios, despite of its intrinsic drawbacks. All these functions are applied for several examples and further compared in both time and frequency domains. © 2014 IEEE.

Xiao R.,Northwest Institute of Nuclear Technology | Chen C.,Northwest Institute of Nuclear Technology | Zhang X.,Northwest Institute of Nuclear Technology
Applied Physics Letters | Year: 2013

In a klystron-like relativistic backward wave oscillator, the velocity modulation is mainly obtained from the resonant reflector. By introducing two pre-modulation cavities between the input cavity and the resonant reflector, the amplitude and phase of density modulation can be adjusted relatively independently, to ensure an improved fundamental harmonic current distribution. Two peaks of harmonic current with high modulation coefficient of 1.2 appear in the second slow wave structure and the dual-cavity extractor and result in large beam energy losses in both regions. Particle-in-cell simulations show that a microwave with power of 11.5 GW and efficiency of 57 can be obtained. © 2013 American Institute of Physics.

Duan L.,Northwest Institute of Nuclear Technology | Yan X.,Max Planck Institute of Colloids and Interfaces | Wang A.,CAS Beijing National Laboratory for Molecular | Jia Y.,CAS Beijing National Laboratory for Molecular | Li J.,CAS Beijing National Laboratory for Molecular
ACS Nano | Year: 2012

Seeking safe and effective artificial blood substitutes based on hemoglobin (Hb) as oxygen carriers is an important topic. A significant challenge is to enhance the loading content of Hb in a well-defined structure. Here we report a facile and controllable avenue to fabricate Hb spheres with a high loading content by templating decomposable porous CaCO 3 particles in collaboration with covalent layer-by-layer assembly technique. The surface of the Hb spheres was further chemically modified by biocompatible polyethylene glycol to protect and stabilize the system. Multiple characterization techniques were employed to reveal the loading and density of Hb in an individual CaCO 3 particle. The results demonstrate that the strategy developed in this work is effective and flexible for construction of the highly loaded Hb spheres. More importantly, such Hb spheres retain their carrying-releasing oxygen function. It may thus have great potential to develop Hb spheres with highly loaded content as realistic artificial blood substitutes in the future. © 2012 American Chemical Society.

Zeng Z.,Northwest Institute of Nuclear Technology
Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams | Year: 2011

Approximate series solutions of the output pulse waveforms and transmission efficiencies of transmission line with exponential impedance profile have been developed based on distributed-parameter model for typical incident pulses suitable for next generation of Z -pinch plasma drivers. The transmission efficiencies are studied computationally with these solutions for petawatt-class Z-pinch driver's exponential transmission line taking account of the line's length and ratio of output impedance to the input as well as the pulse's shape and parameter. The voltage transmission efficiency increases with the increase of the ratio of output impedance to the input, line length and pulse frequencies; the power transmission efficiency increases with the increase of pulse frequencies and with the decrease of steepness of the line's impedance variation.

Xiao R.,Northwest Institute of Nuclear Technology | Chen C.,Northwest Institute of Nuclear Technology | Sun J.,Northwest Institute of Nuclear Technology | Zhang X.,Northwest Institute of Nuclear Technology | Zhang L.,Northwest Institute of Nuclear Technology
Applied Physics Letters | Year: 2011

A klystronlike relativistic backward wave oscillator (RBWO) with a dual-cavity extractor is presented. The phase of the axial electric field component Ez varies by 0° in the dual-cavity extractor, and a larger electric field appears in the second extraction cavity, in comparison with a single-cavity extractor. Such an improved field distribution is beneficial for converting modulated beam power into microwave power. The particle in cell simulation results reveal that microwaves with power of 10 GW, frequency of 4.3 GHz are generated, and conversion efficiency is 48% when diode voltage is 1.2 MV and beam current 17.3 kA. © 2011 American Institute of Physics.

Zeng Z.,Northwest Institute of Nuclear Technology
Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams | Year: 2011

It was demonstrated, based on the PSPICE circuit simulation, that the sectioning number for the circuit simulation of an exponential transmission line should be determined as twice the line's one-way electromagnetic wave transport time (electric length) divided by the wave-front of input pulse, owing to elimination of the wave reflections caused by artificial impedance discontinuity in the line's circuit simulation model, which employs a serial and sectional transmission line with impedances constant in each section but stair-step-varied between sections, and with total electric length the same as that of the exponential line under simulation. A pulse of 112.2 ns wave-front propagates through an exponential water transmission line of 1234.2 ns one-way transport time will give the best sectioning number of 22, when the constant impedance of each section is given by the geometric mean of the two ends' impedances of the corresponding section on the exponential line under simulation. This sectioning rule is equivalent to the statement that the two-way transport time of each section should be equal to the input pulse's wave-front.

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