Abstract: The damage localization accuracy of a Lamb wave detection method is greatly influenced by the multi-mode character and the dispersion effect of Lamb waves. Warped frequency transform (WFT) with a warping function derived from the frequency-dependent phase velocity can be used to suppress the dispersion. Step-pulse excitation is adopted in this paper and the transfer function of the propagation path is extracted from the step-pulse response. WFT is then used to compensate the transfer function, and the compensation of the narrowband signal is realized by convolution of the ideal narrowband burst signal with the compensated transfer function. Considering that wavenumber is a key parameter in designing the warping function for compensation, we presented a method in this paper to calculate the wavenumber directly from the measured signal. This method uses the phase response to estimate the curve of wavenumber. The WFT method is then combined with the delay-and-sum Lamb wave imaging method to improve the imaging resolution. A comparison with traditional delay-and-sum method and time-reversal method verifies the effect of this method in improving the damage localization results. It is shown that the proposed method leverages dispersion to enable good performance in the presence of multiple modes.

Abstract: This paper presents an interesting nanosecond (ns) laser-induced plasma deburring (LPD) effect (from microchannel sidewalls) discovered by the authors, which has been rarely reported before in the literature. Fast imagining study has been performed on plasma produced by ns laser ablation of the bottom of microchannels. It has been found that the plasma can effectively remove burrs from the sidewall of the channels, while on the other hand microscopic images taken in this study did not show any obvious size or shape change of the channel sidewall after LPD. LPD using a sacrifice plate has also been studied, where the plasma for deburring is generated by laser ablation of the sacrifice plate instead of the workpiece. The observed laser-induced plasma deburring effect has several potential advantages in practical micromanufacturing applications, such as high spatial resolution, noncontact and no tool wear, and less possibility of damaging or overmachining useful microfeatures when removing burrs from them. The fundamental mechanisms for the observed laser-induced plasma deburring effect still require lots of further work to completely understand, which may include mechanical breaking of burrs due to high kinetic energies carried by plasma and the associated shock wave, and/or thermal transport from plasma to burrs that may cause their heating and phase change, or other mechanisms.

Abstract: In order to analyze the rules of thermal-oxidative aging on the mechanics of Aero-NBR, a hot air accelerated aging test platform is designed and used to research the influence of thermal-oxidative aging on Aero-NBR’s mechanical property. The experimental results show that the tensile strength of Aero-NBR increases with increasing aging time under a certain temperature, and the elongation at failure first increases and then decreases; under the effect of pressure load, the compression stress relaxation factor decreases with time: the higher the temperature, the faster the stress relaxes. Furthermore, the compression permanent deformation increases with time when the temperature is fixed.

Abstract: The origin and research category of Computational Aeroacoustics (CAA) are introduced firstly. The early progress and applications are summarized, focusing on the two key elements of CAA, high accuracy spatial and time discretization schemes and non-reflecting boundary conditions. Furthermore, the research advances of CAA in the past five years are highlighted, including nonlinear non-reflecting boundary condition, non-uniform time integration method, space discretization method applicable for complex geometry and broadband time domain impedance boundary condition. Finally, the future prospective of CAA is presented briefly.

Abstract: In order to predict the boundary layer transition automatically in viscous flow simulation,γ-Reθt transition model is implemented in a hybrid unstructured Reynolds averaged Navier-Stokes flow solver which was originally developed by the authors and named as HUNS3D.The transition model is built on two locally defined transport equations.The first equation is for intermittency and the second for the transition onset criterion based on momentum-thickness Reynolds number.The numerical algorithms for solving the transition model equations are the same as those for solving turbulence model equations. To validate and assess the ability and the accuracy of the HUNS3D'sγ-Reθt transition model in predicting the boundary layer transition in typical aeronautical engineering cases,a series of free transitional flows around typical configurations,including flat plate,Aerospatial-A airfoil,NLR 7301supercritical airfoil and NASA Trap wing high lift configuration,are simulated and the computed results are compared with corresponding experimental data,which demonstrate that theγ-Reθt transition model is very sensitive to the transition onset location and it predicts the natural transition and separation-induced transition accurately.With this transition model,the performance of the HUNS3Dcode in simulating the engineeringly realistic flow can be greatly enhanced.

Abstract: Kinetics of order-disorder transition at antiphase domain boundary (APDB) formed between DO22 (Ni3V) phases during stress aging was investigated using microscopic phase field model. The results demonstrated that whether order-disorder transition happens or not depends on the atomic structure of the APDB. Accompanied with the depletion of V and enrichment of Ni and Al, order-disorder transition happened at the APDB (001)//(002). Whereas at the APDB {100}·1⁄2[100], which remains ordered with temporal evolution, Ni and Al enrich and V depletes. Composition evolution of APDB with order-disorder transition favors the nucleation of the L12 and disordered phase. Some of the grains grew bigger while the others disappeared, accompanying the formation of disordered phase layer during order-disorder transition of APDBs, and the order-disorder transition of APDBs can be considered as accompanying process of coarsening of ordered domain phases and growth of disordered phases.

Abstract: Multi-constellations provide much better satellite geometrics, thus RAIM algorithms areexpected to achieve greater reliability and integrity performance. This paper mainly discusses different RAIM algorithms and gives simulations of RAIM availability and reliability of standalone GPS and integrated GPS/GLONASS, GPS/BEIDOU and GPS/GLONASS/BEIDOU constellations.The results show that multi-constellation improve RAIM availability and reliability greatly. It is no less than 99.7%for APV I. Also MDB values indicate thatinternal and external reliability of satellite navigation system can be enhanced by multi-constellation.

Abstract: In-flight failure scenarios often involve flight control law switching that can potentially result in adverse aircraft-pilot-coupling or unwanted airframe loads. The experimental setup and results from an investigation focusing on the effects of control law switching on pilot manual control dynamics using desktop based pilot-in-the-loop simulation are presented in this paper. Pilots were presented with tasks requiring them to compensate for disturbances in aircraft longitudinal dynamics due to medium and severe turbulence. Off-line parameter identification was then used to derive pilot model parameters from simulation data and thus, infer changes in manual control characteristics due to switching between three control laws. This resulted in piecewise linear pilot models and quantified the inter-subject differences suitable for inclusion in the future design of robust flight control systems. Increased turbulence intensity was found to reduce inter-subject differences both in terms of pilot model parameters and the open-loop pilot-vehicle system crossover frequency.

Abstract: A new method to predict the ultimate strength of fiber reinforced composites under arbitrary load condition is introduced. The micromechanics strength theory is used to perform the final failure prediction of composite laminates. The theory is based on unit cell analytic model which can provide the ply composite material properties by only using the constituent fiber and matrix properties and the laminate geometric parameters without knowing any experimental information of the laminates. To show that this method is suitable for predicting the strength of composite laminates, the micromechanics strength theory is ranked by comparing it with all the micro-level and the best two macro-level theories chosen from the World Wide Failure Exercise. The results show that this method can be used for predicting strength of any composite laminates and provide a direct reference for composite optimum design.

Abstract: This paper presents design and implementation of an attitude and heading reference system (AHRS) based on low-cost MEMS sensors and complementary filtering (CF). Different from traditional solutions, information fusion is performed with Euler angles directly, which is more straightforward for understanding; however it proposes many challenges for reaching a stable and accurate estimation as when these angles approach or traverse their range boundaries, estimation may get discontinuous. Thus an effective discontinuity avoiding strategy is suggested in this paper to refine the estimation. Besides, instead of extended Kalman filtering (EKF), CF is utilized for state estimation of AHRS as it features fusion of high-frequency and low-frequency signals. In order to make up for shortcomings of MEMS sensors such as multiple errors, drifts, and bad accuracy, some effective calibration and filtering algorithms are proposed to guarantee agreeable AHRS performance. Also, architecture of the MEMS IMU (inertial measure...

Abstract: Temperature variations have significant effects on guide wave propagation and therefore increase the detection uncertainty of the guided wave–based structural health monitoring system. A novel temperature compensation technique combining an adaptive filter and optimal baseline selection is developed to enhance the robustness and effectiveness of guided wave–based damage detection. The adaptive filter is the finite length unit impulse response digital filter based on adaptive linear neuron network. This article focuses on three main issues for practically implementing the proposed method: (a) establishment of temperature compensation standard, (b) parameter design of compensation filter, and (c) determination of temperature gradient to reduce the number of selected baselines. Experiments are conducted on two stiffened composite plates to verify the proposed method for effective and robust temperature compensation under a large temperature range from −40°C to 80°C. Results show that temperature interval for...

Abstract: Objective To evaluate a new levonorgestrel-releasing intrauterine system (LNG-IUS) called Levosert® for the treatment of heavy menstrual bleeding (HMB) in comparison to the reference product Mirena®.Methods A multicentre, randomised, controlled trial, in non-menopausal women diagnosed with functional HMB (defined as menstrual blood loss [MBL] ≥ 80 mL) randomised to either Levosert® or Mirena® and followed for up to one year. MBL was evaluated using a validated modified version of the Wyatt pictogram.Results A total of 280 women were randomised (141 to Levosert® and 139 to Mirena®). During the one-year treatment period, both Levosert® and Mirena® dramatically decreased MBL and increased haemoglobin and ferritin levels. There were no statistically significant differences between Levosert® and Mirena® regarding any of the parameters evaluated during the study. Similar bleeding patterns were observed in both groups. Levosert® was inserted with the same ease as Mirena®. Both treatments were associated ...