The fatigue life of a nose landing gear is assessed to increase the fatigue life computing efficiency in the structural optimization cycles. The metamodels of the structural fatigue life have been researched systemically. Three kinds of metamodels were compared: the polynomial response surface model, the kriging model, and the radial basis function model constructed by the central composite design and the Latin hypercube design. It is found that the radial basis function model constructed by the Latin hypercube has the highest fitting precision and higher fitting efficiency. The research results offer a guidance for selection and construction of the metamodel of structural fatigue life. Improved particle swarm optimization algorithm is implemented. As an example, the forward strut of one aircraft's nose landing gear is optimized by using the improved particle swarm optimization algorithm.
A series of lanthanum/beta-zeolite catalysts was prepared via hydrothermal ion exchange, and characterized by inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and ammonia temperature-programmed desorption. The lanthanum-doping effect on beta-zeolite catalysts was investigated through catalytic cracking of supercritical methylcyclohexane under the system pressure of 4.0 MPa and the mass flow rate of 1.0 g=s. For lanthanum/beta catalyst of the Cat-2 type, the gas yield of 28.3% and heat sink of 3.35 MJ · kg −1 could be achieved at the temperature of 700°C, much higher than those for the pure beta zeolite without lanthanum modification and for the thermal pyrolysis. Correspondingly, Cat-2 has a better performance on coking inhibition with the reduction of 56.2 and 29.5% at 700°C compared to beta zeolite and thermal cracking. Therefore, it was indicated that beta zeolite with the suitable lanthanum content, still maintaining its high activity and stability of the zeolite framework at high temperature due to lanthanum doping, had a great contribution to high heat sink and coking inhibition at high temperature. Nomenclature c = mass fraction of methylcyclohexane in the residues G = mass flow rate, g∕s I = current, A I 550 = intensity of the peak at 2θ 22.6 deg after calcination at 550°C for 3 h I 850 = intensity of the peak at 2θ 22.6 deg after calcination at 850°C for 30 min m 0 = initial feeding mass of methylcyclohexane, kg m 1 = mass of residues collected after a cracking reaction, kg P C = critical pressure, MPa Q m = heat sink, MJ∕kg R crystal = relative crystallinity T C = critical temperature,°C U = voltage, V W = heating power, W α MCH = conversion of methylcyclohexane, wt. % γ gas = gas yield of methylcyclohexane, % η = thermal efficiency
A super-ultra-wideband (UWB) bandpass filter (BPF) with fractional bandwidth of 138% and wide upper stopband is proposed based on a simplified composite right/left-handed transmission line (SCRLH TL) structure. The non-uniform periodical structure can help the SCRLH TL to realise a wider passband, while the complementary split-ring resonators are etched in the ground plane to achieve better performance of the upper stopband. In addition, the slots carved around the via make it feasible to reduce the overall size. The super-UWB BPF has been designed, fabricated and measured. Good agreement is shown between measurement and simulation.Introduction: The UWB system has received much attention in both academic and industrial fields since it was approved for civilian use in 2002 by the US Federal Communications Commission (FCC). The UWB filter is an important component in the UWB system. This presents a new challenge to the bandpass filter (BPF) design for UWB systems since the required fractional bandwidth exceeds 110%, which makes traditional techniques for bandpass filter design inapplicable. Recently, several methodologies and structures have been adopted to design UWB BPFs [1 -4]. A multiple-mode resonator (MMR) with a stepped-impedance configuration is presented to construct an UWB BPF [1]. In [2], a broadside-coupled microstrip-coplanar waveguide (CPW) structure with tightened coupling degree is utilised to design an alternative UWB filter with one, two and three sections. The method of cascading a single lowpass filter and a single highpass filter on a microstrip line is explored in [3]. A novel design method for the UWB filter using the composite right/left-handed transmission line (CRLH) theory is presented in [4]. These UWB BPFs have a good performance in the operating band; however, their fractional bandwidth is only about 110%. A super-UWB BPF can be considered to have its applications in future wireless communication systems and other possible radio systems which require a wider passband than that of the conventional UWB system.
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