Adaptive fault-tolerant controller design for airbreathing hypersonic vehicle with input saturation

The problem of fault-tolerant control is discussed for the longitudinal model of an airbreathing hypersonic vehicle （AHV） with actuator faults and external disturbances. Firstly, a fault-tolerant control strategy is presented for the longitudinal model of an AHV, which guarantees that velocity and altitude track their reference trajectories at an exponential convergence rate. However, this method needs to know the minimum value of the actuator efficiency factor and the upper bound of the external disturbances, which makes it not easy to implement. Then an improved adaptive fault-tolerant control scheme is proposed, where two adaptive laws are employed to estimate the upper bound of the external disturbances and the minimum value of the actuator efficiency factor, respectively. Secondly, the problem of designing a control scheme with control constraints is further considered, and a new adaptive fault-tolerant control strategy with input saturation is designed to guarantee that velocity and altitude track their reference trajectories. Finally, simulation results are given to show the effectiveness of the proposed methods.

Downregulation of ceramide synthase 1 promotes oral cancer through endoplasmic reticulum stress

C18 ceramide plays an important role in the occurrence and development of oral squamous cell carcinoma.However,the function of ceramide synthase 1,a key enzyme in C18 ceramide synthesis,in oral squamous cell carcinoma is still unclear.The aim of our study was to investigate the relationship between ceramide synthase 1 and oral cancer.In this study,we found that the expression of ceramide synthase 1 was downregulated in oral cancer tissues and cell lines.In a mouse oral squamous cell carcinoma model induced by 4-nitroquinolin-1-oxide,ceramide synthase 1 knockout was associated with the severity of oral malignant transformation.Immunohistochemical studies showed significant upregulation of PCNA,MMP2,MMP9,and BCL2 expression and downregulation of BAX expression in the pathological hyperplastic area.In addition,ceramide synthase 1 knockdown promoted cell proliferation,migration,and invasion in vitro.Overexpression of CERS1 obtained the opposite effect.Ceramide synthase 1 knockdown caused endoplasmic reticulum stress and induced the VEGFA upregulation.Activating transcription factor 4 is responsible for ceramide synthase 1 knockdown caused VEGFA transcriptional upregulation.In addition,mild endoplasmic reticulum stress caused by ceramide synthase 1 knockdown could induce cisplatin resistance.Taken together,our study suggests that ceramide synthase 1 is downregulated in oral cancer and promotes the aggressiveness of oral squamous cell carcinoma and chemotherapeutic drug resistance.

Study of seasonal snow cover influencing the ground thermal regime on western flank of Da Xing'anling Mountains,northeastern China

Although many studies relevant to snow cover and permafrost have focused on alpine, arctic, and subarctic areas, there is still a lack of understanding of the influences of seasonal snow cover on the thermal regime of the soils in permafrost regions in the mid-latitudes and boreal regions, such as that on the westem flank of the Da Xing＇anling （Hinggan） Mountains, northeastern China. This paper gives a detailed analysis on meteorological data series from 2001 to 2010 provided by the Gen＇he Weather Station, which is located in a talik of discontinuous permafrost zone and with sparse meadow on the observation field. It is inferred that snow cover is important for the ground thermal regime in the middle Da Xing＇anling Mountains. Snow cover of 10-cm in thickness and five to six months in duration （generally November to next March） can reduce the heat loss from the ground to the atmosphere by 28%, and by 71% if the snow depth increases to 36 cm. Moreover, the occurrence of snow cover resulted in mean annual ground surface temperatures 4.7-8.2℃ higher than the mean annual air temperatures recorded at the Gen＇he Weather Station, The beginning date for stable snow cover establishment （SE date） and the initial snow depth （SDi） also had a great influences on the ground freezing process. Heavy snowfall before ground surface freeze-up could postpone and retard the freezing process in Gen＇he. As a result, the duration of ground freezing was shortened by at least 20 days and the maximum depth of frost penetration was as much as 90 cm shallower.

Fabrication of oxygen-defective tungsten oxide nanorods for deep oxidative desulfurization of fuel

Owing to the increasingly serious environmental issues caused by the sulfur burnt in fuel, desulfurization has become an important topic. In this work, an amphiphilic oxygen-defective tungsten oxide was synthesized by a colloidal chemistry method. The amphiphilic property and oxygen defects were well characterized, and the structure of the oxygen-defective tungsten oxide catalyst was investigated. In addition, the catalyst was employed in oxidative desulfurization system of fuel,and deep desulfurization was achieved. It was found that the very high oxidative desulfurization performance of oxygendefective tungsten oxide catalyst resulted from both the amphiphilic property and oxygen defects. This work can provide a strategy for preparation of highly active metal oxide catalysts with oxygen defects in oxidative desulfurization reaction of fuel.

Preparation of V2O5 Porous Hollow Spheres and Study on Excellent Cycling Stability of Lithium Battery

Through one-step simple polyol-assisted (ethylene glycol) process, V2O5 hollow mi-cro-spheres about 3 micrometres in size were successfully synthesized. The structure is neat, the outer wall were porous. Testing its electrochemical properties with V2O5 hollow materials as cathode materia of lithium ion battery, the results showed that under the ratio of 1 C, the initial charge and discharge specific capacity were 236.8 mAh g^-1, 213 mAh g^-1, even if after 100 cycles, the charge and discharge specific capacity were still 220 mAh g^-1 and 219.7 mAh g^-1 respectively. Relative to the charge and discharge capacity of the second cycle, the keep rate were 93.2%, 92.9% respectively, has good cycle stability.

Modified room temperature solid-state synthesis of yttria-stabilized zirconia(YSZ) nano-powders for solid oxide fuel cells

High-performance solid oxide fuel cell(SOFC) is in urgent need of high-quality electrolyte powders with high reactivity and chemical uniformity.Here,8 mol% Y_(2)O_(3) doped ZrO_(2)(YSZ) nano-powders were synthesized by an improved solid-state reaction method at ambient temperature,and were applied to the fabrication of SOFC electrolytes.YSZ nano-powders show average grain sizes of ^(2)0 nm and high dispersibility,which is comparable with or even better than some other chemical methods.Benefitting from their high reactivity,dense YSZ electrolytes(relative density of 97.9%) can be obtained at a relatively low sintering temperature of 1400℃.The optimized electrical conductivity reaches up to a high value of0.034 S/cm at 800 0C in air.The anode supported single cell with the construction of Ni-YSZ/YSZ/Sm_(0.2)Ce_(0.8)O_(2-δ)(SDC)/La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ)(LSCF) exhibits the peak power density of 0.827 W/cm^(2) at800℃ while taking wet H_(2) as fuels and ambient air as oxidants.

Enhanced Fracture Toughness of Pressureless-sintered SiC Ceramics by Addition of Graphene

To enhance the fracture toughness of pressureless-sintered SiC ceramic, graphene was introduced as an additive. The effects of graphene contents on the fracture toughness, bending strength, micro-hardness, phase compositions, and microstructure evolutions of the SiC ceramics were investigated in detail by scanning electron microscopy, energy dispersive X-ray spectroscopy, and metallographic microscopy. The fracture toughness, bending strength and micro-hardness increased initially, and then decreased with the graphene content increasing from 0 to 5.0 wt%. The highest fracture toughness of 5.65 MPa m1/2 was obtained for sample with 1.0 wt% graphene sintered at 2130 ℃ for 1 h in At, which was about 22.6% higher than that of SiC sample without graphene. In addition, the highest bending strength and microhardness of 434.14 MPa and 29.21 GPa corresponded to the SiC samples with graphene content of 0.5 wt% and 2.0 wt%, respectively.

Stabilization of switched linear systems under asynchronous switching subject to admissible edge-dependent average dwell time

The problem of stabilizing switched linear systems under asynchronous switching is addressed.The admissible edge-dependent average dwell time method is applied to design a switching signal that comprises slow admissible edge-dependent average dwell time and fast admissible edge-dependent average dwell time.Under this switching signal,the restriction that the maximum delay of asynchronous switching is known in advance is removed.The constructed Lyapunov function is associated with both the system mode and controller mode.The stabilization criteria and the corresponding algorithm are presented to obtain the controller gains and to design the switching signal.Finally,two examples are given to demonstrate the effectiveness of the proposed results.