A backscattering model for a stratified seafloor

In order to predict the bottom backscattering strength more accurately, the stratified structure of the seafloor is considered. The seafloor is viewed as an elastic half-space basement covered by a fluid sediment layer with finite thickness. On the basis of calculating acoustic field in the water, the sediment layer, and the basement, four kinds of scattering mechanisms are taken into account, including roughness scattering from the water-sediment interface, volume scattering from the sediment layer, roughness scattering from the sediment-basement interface,and volume scattering from the basement. Then a backscattering model for a stratified seafloor applying to low frequency（0.1-10 kHz） is established. The simulation results show that the roughness scattering from the sediment-basement interface and the volume scattering from the basement are more prominent at relative low frequency（below 1.0 kHz）. While with the increase of the frequency, the contribution of them to total bottom scattering gradually becomes weak. And the results ultimately approach to the predictions of the high-frequency（10-100 kHz） bottom scattering model. When the sound speed and attenuation of the shear wave in the basement gradually decrease, the prediction of the model tends to that of the full fluid model, which validates the backscattering model for the stratified seafloor in another aspect.

An overview of the thermography-based experimental studies on roadway excavation in stratified rock masses at CUMTB

This paper presents an overview of experimental investigations conducted at China University of Mining and Technology Beijing(CUMTB) on roadway excavation using large-scale geomechanical model tests.The simulated sedimentary rocks are composed by alternating layers of sandstone, mudstone and coal seam inclined at varied angles with respect to the horizontal including 0°, 45°, 60°, and 90°. During the excavation, infrared thermography was employed to detect the thermal response of the surrounding rocks under excavation. The obtained raw thermograms were processed using denoising algorithm, data reduction procedure and Fourier analysis. The infrared temperature(IRT) characterizes the overall rock response; the processed thermal images represent the structural behavior, and the Fourier spectrum describes damage development in the frequency domain. Deeper understanding was achieved by the comparative analyses of excavation in differently inclined rock masses using the image features of IRTs, thermal images and Fourier spectra.

Stratified Cox Regression Analysis of Survival under CIMAvax^(■)EGF Vaccine

Background: The Center of Molecular Immunology (CIM) is a center in Cuba devoted to the research, development and manufacturing of biotechnological products. CIMAvax?EGF is a vaccine for the treatment of non-small cell lung cancer patients (NSCL). Purpose: The aim of this work is to evaluate the effects of some potential prognostic factors on the overall survival of patients treated with CIMAvax?EGF vaccine, based on data collected in a phase II and a phase III clinical trials. Methods: The stratified Cox regression model is used to evaluate the effects of these prognostic factors, based on separate analysis for each trial, and on the combined data from both trials. Results: Patients with Performance status 0 or 1, with IV stage of tumor and male under 60 years obtain more benefit in terms of overall survival if they receive CIMAvax?EGF. Conclusions: Vaccinated group has a better performance if patients have a performance status 0 or 1, stage IV and age under 60 years. These prognostic factors influence overall survival in a positive way for those patients that received CIMAvax?EGF.

Rock characteristics and dynamic fragmentation process of the 2018 Daanshan rockslide in Beijing,China

This study investigated the failure mechanism associated with the rock mass structure and the dynamic fragmentation process of blocky rocks of the 2018 Daanshan rockslide that occurred on 11 August,2018.It was found that the initially collapsed rock of this rockslide was partitioned along the unconformity and strata interfaces.We analyzed how the unique rock mass structure,coupled with the road cut and the antecedent rainfall,jointly resulted in its failure.Based on the rock types and geological structures,the initial stratified configuration of a discrete element model was setup to reveal the influences of the local structure.The numerical model was divided into three parts.Part 1 is the basalt of the Nandaling Formation,the normal and shear stiffnesses of the basalt particles are set as 80 MPa and 40 MPa.Parts 2 and 3 are the sandstones interbedded with mudstone and sandstone of the Shihezi Formation,and the normal and shear stiffnesses of these parts were set as 6 MPa and 10 MPa,respectively.The dynamic process of the rockslide,particularly the rock fragmentation process,was numerically analyzed using a 3D discrete element method.The numerical results were compared with real-time videos and field investigations.The results show that the rock fragmentation and the final deposition range match well with the real disaster phenomenon,and the calculation accuracy of the rockslide reaches 82.41%.Moreover,a parameter sensitivity analysis was conducted,and classical uniform models under different bonding forces were established;the stratified model can better restore the true state of the fragmentation,movement,and deposition processes of rockslides.Therefore,for complicated rocks with significant differences in lithology,clarifying the rock mass stratigraphy is essential for an accurate reconstruction of the dynamic process of rockslides.

Soil texture prediction through stratification of a regional soil spectral library

Knowing the spatial distribution of soil texture,which is a physical property,is essential to support agricultural and environmental decision making.Soil texture can be estimated using visible,near infrared,and shortwave infrared(Vis-NIR-SWIR)spectroscopy.However,the performance of spectroscopic models is variable because of soil heterogeneity.Currently,few studies address the effects of soil sample variability on the performance of the models,especially for larger spectral libraries that include soils that are more heterogeneous.Therefore,the objectives of this study were to:i)apply Vis-based color parameters on the stratification of a regional soil spectral library;ii)evaluate the performance of the predictive models generated from the spectral library stratification;iii)compare the performance of stratified models(SMs)and the model without stratification(WSM),and iv)explain possible changes in prediction accuracy based on the SMs.Thus,a regional soil spectral library with 1535 samples from the State of Santa Catarina,Brazil was used.Soil reflectance data were obtained by Vis-NIR-SWIR spectroscopy in the laboratory using a spectroradiometer covering the 350–2500 nm spectral range.Sand,silt,and clay fractions were determined using the pipette method.Twenty-two components of color parameters were derived from the Vis spectrum using the colorimetric models.A cubist regression algorithm was used to assess the accuracy of the applicability of the initial models(SMs and WSM)and of the validation between the clusters.Fractional order derivatives(FODs)at 0.5,1.5,and 2 intervals were used to explain possible changes in the performance of the SMs.The SMs with higher contents of clay and iron oxides obtained the highest accuracy,and the most important spectral bands were identified,mainly in the 480–550 and 850–900 nm ranges and the 1400,1900,and 2200 nm bands.Therefore,stratification of soil spectral libraries is a good strategy to improve regional assessments of soil resources,reducing prediction errors in the qualitative determination of soil properties.

Extension and Comparative Study of AUSM-Family Schemes for Compressible Multiphase Flow Simulations

Several recently developed AUSM-family numerical flux functions(SLAU,SLAU2,AUSM+-up2,and AUSMPW+)have been successfully extended to compute compressible multiphase flows,based on the stratified flow model concept,by following two previous works:one by M.-S.Liou,C.-H.Chang,L.Nguyen,and T.G.Theofanous[AIAA J.46:2345-2356,2008],in which AUSM+-up was used entirely,and the other by C.-H.Chang,and M.-S.Liou[J.Comput.Phys.225:840-873,2007],in which the exact Riemann solver was combined into AUSM+-up at the phase interface.Through an extensive survey by comparing flux functions,the following are found:(1)AUSM+-up with dissipation parameters of Kp and Ku equal to 0.5 or greater,AUSMPW+,SLAU2,AUSM+-up2,and SLAU can be used to solve benchmark problems,including a shock/water-droplet interaction;(2)SLAU shows oscillatory behaviors[though not as catastrophic as those of AUSM+(a special case of AUSM+-up with Kp=Ku=0)]due to insufficient dissipation arising from its ideal-gas-based dissipation term;and(3)when combined with the exact Riemann solver,AUSM+-up(Kp=Ku=1),SLAU2,and AUSMPW+are applicable to more challenging problems with high pressure ratios.