Sea Surface Effects on Sound Scattering in the Persian Gulf Region Based on Empirical Relations

In this paper, sound scattering from the sea surface in the Persian Gulf region is investigated. Chapman-Harris and Ogden-Erskine empirical relations coupled with perturbation theory are implemented. Based on the Ogden and Erskine＇s experiments, sound scattering from the sea surface has three different regimes in which two mechanisms of surface roughness and subsurface bubble clouds are involved. Ogden-Erskine＇s scattering relation which consists of perturbation theory and Chapman-Harris＇s scattering terms are verified by the experimental data of Critical Sea Tests 7. Subsequently, wind speed in the Persian Gulf is provided based on three data bases of Arzanah station, ERA40, and PERGOS. Accordingly, surface scattering strength in the Persian Gulf region is calculated at different grazing angles, frequencies and provided wind speeds. Based on the resulted values of scattering strength, scattered intensity from the sea surface is also studied. These studies indicate that both scattering strength and scattered intensity generally increase as grazing angle, frequency and wind speed increase.

Strength and deformation characteristics of irregular columnar jointed rock mass: A combined experimental and theoretical study

The irregularity of jointed network poses a challenge to the determination of field mechanical param-eters of columnar jointed rock mass(CJRM),and a reasonable prediction of deformation and strength characteristics of CJRM is important for engineering construction.The Voronoi diagram and three-dimensional printing technology were used to make an irregular columnar jointed mold,and the irregular CJRM(ICJRM)specimens with different dip directions and dip angles were prepared.Uniaxial compression tests were performed,and the anisotropic strength and deformation characteristics of ICJRM were described.The failure modes and mechanisms were revealed in accordance with the final appearances of the ICJRM specimens.Based on the model test results,the empirical correlations for determining the field deformation and strength parameters of CJRM were derived using the dip angle and modified joint factor.The proposed empirical equations were used in the Baihetan Project,and the calculated mechanical parameters were compared with the field test results and those obtained from the tunneling quality index method.Results showed that the deformation parameters determined by the two proposed methods are all consistent with the field test results,and these two methods can also estimate the strength parameters effectively.

Gas condensate reservoirs: Characterization and calculation of dew-point pressure

A large data bank of more than 700 gas-condensate samples collected from literature and experiments was established.On this basis,empirical correlations and equations of state commonly used to calculate dew-point pressure(DPP)were evaluated.A new model for estimating DPP was proposed.All the empirical correlations and the Peng-Robinson state equation were compared,and sensitivity of parameters was analyzed.The current standards used to identify gas condensate were evaluated and found to be not accurate enough.The Peng-Robinson state equation has no unique solution and is affected by multiple factors such as the characterization of C7+components and the splitting scheme.The Nemeth-Kennedy correlation has the highest accuracy when applied to the data bank established in this study,followed by Elsharkawy correlation and Godwin correlation.While Shokir correlation cannot be used for samples without C7+components,it is therefore the lowest in accuracy.The newly proposed model has an average absolute error,root mean square error and coefficient of determination of 7.5%,588,and 0.87,respectively,and is better than the above four correlations statistically.The proposed model proved to be more accurate and valid when compared to experimental results and simulation with the Peng-Robinson state equation.

Measurement and temperature effect on soil thermal conductivity in Changchun area

The study on soil thermal conductivity (STC) was an important side of research on ground source heat pump technique,geological disposal of high-level radioactive wastes,heat distribution of buried cable. Especially owing to technical requirement for shallow terrestrial heat recently, it directly influenced the design and solution in engineering problems. The authors measured the STC in the studied area with QTM-D2 and discussed the effect of samples in size, the measurement error between the samples in lab and in site. The results indicate measuring STC by heat pole method with less influence upon the samples in size, and measuring results on the different geometry size approach very much. The STC is fit for the empirical relation between the temperature and TC under the condition of normal temperature. It is significance for understanding STC in northern China and simulation of temperature field.

Nonlinear Effect of Wave Propagation in Shallow Water

In this paper, a nonlinear model is presented to describe wave transformation in shallow water with the zero- vorticity equation of wave- number vector and energy conservation equation. The nonlinear effect due to an empirical dispersion relation (by Hedges) is compared with that of Dalrymple's dispersion relation. The model is tested against the laboratory measurements for the case of a submerged elliptical shoal on a slope beach, where both refraction and diffraction are significant. The computation results, compared with those obtained through linear dispersion relation, show that the nonlinear effect of wave transformation in shallow water is important. And the empirical dispersion relation is suitable for researching the nonlinearity of wave in shallow water.

Estimation of relations among hysteretic response measures and design parameters for RC rectangular shear walls

Seismic design of RC structures requires estimation of structural member behavioral measures as functions of design parameters. In this study, the relations among cyclic behavioral measures and design parameters have been investigated for rectangular RC shear walls using numerical simulations calibrated based on the published laboratory tests. The OpenSEES numerical simulations modeling of plastic hinge hysteretic behavior of RC shear walls and estimation of empirical relations among wall hysteretic indices and design parameters are presented. The principal design parameters considered were wall dimensions, axial force, reinforcement ratios, and end-element design parameters. The estimated hysteretic response measures are wall effective stiffness, yield and ultimate curvatures, plastic moment capacity, yield and ultimate displacements, flexural shear capacity, and dissipated energy. Using results of numerous analyses, the empirical relations among wall cyclic behavioral measures and design parameters are developed and their accuracy is investigated.

The robustness of contextuality and the contextuality cost of empirical models

In this paper, we introduce and discuss the robustness of contextuality（Ro C） R_C（e） and the contextuality cost C（e） of an empirical model e. The following properties of them are proved.（i） An empirical model e is contextual if and only if R_C（e） ＆gt; 0;（ii） the Ro C function R_C is convex, lower semi-continuous and un-increasing under an affine mapping on the set E M of all empirical models;（iii） e is non-contextual if and only if C（e） = 0;（iv） e is contextual if and only if C（e） ＆gt; 0;（v） e is strongly contextual if and only if C（e） = 1. Also, a relationship between RC（e） and C（e） is obtained. Lastly, the Ro C of three empirical models is computed and compared. Especially, the Ro C of the PR boxes is obtained and the supremum 0.5 is found for the Ro C of all no-signaling type（2, 2, 2） empirical models.

Variation in reach-averaged bankfull discharge in the Yellow River Estuary in recent years

The Yellow River Estuary(YRE)alternatively experienced channel aggradation and degradation during the period 1990-2016.To study the variation in flood discharge capacity during the process of river bed evolution,bankfull characteristic parameters were investigated on the basis of measured hydrological data and surveyed cross-sectional profiles,which was crucial for comprehending the processes and the key factors to cause these rapid changes.A reach-averaged method was presented in this study in order to calculate the characteristic bankfull parameters in the YRE,and this method integrated the geometric mean using the logarithmic transformation with a weighted mean based on the distance between the two successive sections.The reach-averaged bankfull parameters in the tail reach of the Yellow River Estuary(the Lijin-Xihekou reach)during the period 1990-2016 were then calculated.Calculated results indicated that the adoption of a concept of reach-averaged bankfull discharge was much more representative than the cross-sectional bankfull discharge,and the results also indicated that bankfull discharges decreased during the process of channel aggradation,and increased during the process of channel degradation.Finally,an empirical formula and a delayed response function were established between the reach-averaged bankfull discharge and the previous 4-year average fluvial erosion intensity during flood seasons,and both of them were adopted to reproduce the reach-averaged bankfull discharges,and calculated results showed high correlations(R^(2)>0.8)of these two methods.