On time-step in structural seismic response analysis under ground displacement/acceleration

There are two models in use today to analyze structural responses when subjected to earthquake ground motions, the Displacement Input Model （DIM） and the Acceleration Input Model （AIM）. The time steps used in direct integration methods for these models are analyzed to examine the suitability of DIM. Numerical results are presented and show that the time-step for DIM is about the same as for AIM, and achieves the same accuracy. This is contrary to previous research that reported that there are several sources of numerical errors associated with the direct application of earthquake displacement loading, and a very small time step is required to define the displacement record and to integrate the dynamic equilibrium equation. It is shown in this paper that DIM is as accurate and suitable as, if not more than, AIM for analyzing the response of a structure to uniformly distributed and spatially varying ground motions.

A Hazard Assessment Method for Potential Earthquake-Induced Landslides – A Case Study in Huaxian County, Shaanxi Province

The hazard assessment of potential earthquake-induced landslides is an important aspect of the study of earthquake-induced landslides. In this study, we assessed the hazard of potential earthquake-induced landslides in Huaxian County with a new hazard assessment method. This method is based on probabilistic seismic hazard analysis and the Newmark cumulative displacement assessment model. The model considers a comprehensive suite of information, including the seismic activities and engineering geological conditions in the study area, and simulates the uncertainty of the intensity parameters of the engineering geological rock groups using the Monte Carlo method. Unlike previous assessment studies on ground motions with a given exceedance probability level, the hazard of earthquake-induced landslides obtained by the method presented in this study allows for the possibility of earthquake-induced landslides in different parts of the study area in the future. The assessment of the hazard of earthquake-induced landslides in this study showed good agreement with the historical distribution of earthquake-induced landslides. This indicates that the assessment properly reflects the macroscopic rules for the development of earthquake-induced landslides in the study area, and can provide a reference framework for the management of the risk of earthquakeinduced landslides and land planning.

The Separation Efficiency of Biopolymers with Short Column in Liquid Chromatography

The separation efficiency of biopolymers with a short column in liquid chromatography has been investigated in this paper. It was found that the column length has slight effect on the resolution of biopolymers under gradient elution. The reasons have been explained by stoichiometric displacement model for retention of solute. The column 1.0 cm long was also used in the separation and purification of recombinant human granulocyte colony-simulating factor (rhG-CSF). It only took 40 min and the purity by one step was found to be almost 100%.

Probabilistic seismic landslide hazard assessment: a case study in Tianshui, Northwest China

Probabilistic analysis in the field of seismic landslide hazard assessment is often based on an estimate of uncertainties of geological, geotechnical,geomorphological and seismological parameters.However, real situations are very complex and thus uncertainties of some parameters such as water content conditions and critical displacement are difficult to describe with accurate mathematical models. In this study, we present a probabilistic methodology based on the probabilistic seismic hazard analysis method and the Newmark’s displacement model. The Tianshui seismic zone(105°00′-106°00′ E, 34°20′-34°40′ N) in the northeastern Tibetan Plateau were used as an example. Arias intensity with three standard probabilities of exceedance(63%, 10%, and 2% in 50 years) in accordance with building design provisions were used to compute Newmark displacements by incorporating the effects of topographic amplification.Probable scenarios of water content condition were considered and three water content conditions(dry,wet and saturated) were adopted to simulate the effect of pore-water on slope. The influence of 5 cm and 10 cm critical displacements were investigated in order to analyze the sensitivity of critical displacement to the probabilities of earthquake-induced landslide occurrence. The results show that water content in particular, have a great influence on the distribution of high seismic landslide hazard areas. Generally, the dry coverage analysis represents a lower bound for susceptibility and hazard assessment, and the saturated coverage analysis represents an upper bound to some extent. Moreover, high seismic landslide hazard areas are also influenced by the critical displacements. The slope failure probabilities during future earthquakes with critical displacements of 5 cm can increase by a factor of 1.2 to 2.3 as compared to that of 10 cm. It suggests that more efforts are required in order to obtain reasonable threshold values for slope failure. Considering the probable scenarios of water content condition which is varied with seasons, seismic landslide hazard assessments are carried out for frequent, occasional and rare earthquake occurrences in the Tianshui region, which can provide a valuable reference for landslide hazard management and infrastructure design in mountainous seismic zones.

Effect of passive plates on vertical instability in the EAST tokamak

The effect of passive plates on vertical displacement control in the EAST tokamak is investigated by open loop experiments and numerical simulations based on a rigid displacement model. The experiments and simulations indicate that the vertical instability growth rate is reduced by a factor of about 2 in the presence of the passive plates, where the adjacent segments are not connected to each other. The simulations also show that the vertical instability growth rate is reduced by a factor of about 10 if all adjacent segments on each passive plate loop are connected to each other. The operational window is greatly enlarged with the passive plates.

The effect of silica nanoparticle aggregates on wax dissolution in diesel oil

In recent years, silica nanoparticle aggregates （SNPAs） have been used to decrease the injection pressure of wells in low permeability reservoirs achieving good results. In order to study the mechanisms for reduction in the injection pressure of low permeability wells by the SNPA-diesel oil system injection, the microstructure of SNPAs was observed with a transmission electron microscope （TEM）. The particle size distribution of SNPAs was also measured by the laser scattering method. The viscosities of diesel oil and SNPA-diesel oil system were measured with a capillary viscometer. The effect of SNPAs on the solubility of wax in the diesel oil was experimentally studied. The influencing factors, including temperature and SNPA concentration in diesel oil, on wax solubility were analyzed. A pore-throat film displacement model （PTFDM） was built for mechanism explanation. The microstructure and size distribution analyses show that the SNPAs are in the nanometer size range. The viscosity of the SNPA-diesel oil system is lower than that of the diesel oil. The solubility of wax in the diesel oil increases greatly due to SNPA addition, the solubility ratio reaches 7.5. The solubility of wax in diesel oil increases with increases in the concentration of SNPAs in the diesel oil and with the temperature. It is proved that the addition of SNPAs to diesel oil helps remove the wax deposited near the wellbore. This maybe one of the main mechanisms for injection pressure decreases in low permeability reservoirs.

Double⁃Shear Experiments of Cold⁃Formed Steel Stud⁃to⁃Sheathing Connections at Elevated Temperatures

The behavior of cold⁃formed steel(CFS)stud⁃to⁃sheathing connections at elevated temperatures is an important parameter for the fire resistance design and modeling of mid⁃rise CFS structures.In this paper,three kinds of sheathings,namely,medium⁃and low⁃density calcium⁃silicate boards and oriented strand board,were selected for double⁃shear experiments on the mechanical properties of 253 screw connections at ambient and elevated temperatures.The effects of the shear direction,screw edge distance and the number of screws on the behavior of the connections were studied.The results showed that the shear direction and the screw edge distance more significantly influenced the peak deformation,while their impacts on the peak load varied with the type of sheathings.Compared with the single⁃screw connections,the peak loads of the specimens with double⁃screw connections obviously increased but did not double.Finally,a simplified load⁃displacement curve model of stud⁃to⁃sheathing connections at elevated temperature was generated first by establishing the prediction formula for characteristic parameters,such as the peak load,the peak deformation and the elastic stiffness,and then by considering whether the curves corresponded to stiffness increase phenomena.The present investigation provides basic data for future studies on the numerical modeling of CFS structures under fire conditions.

Internal co-seismic deformation and curvature effect based on an analytical approach

In this study, we present a new method to compute internal co-seismic deformations of a homoge- neous sphere, based on our previous approach （Dong et al. 2016）. In practical numerical computations, we consider a strike-slip point source as an example, and compute the vertical co-seismic displacement on different internal spherical surfaces （including the Earth surface）. Numerical results show that the internal co-seismic deformations are generally larger than that on the Earth surface; especially, the maximum co-seismic displacement appears around the seismic source. The co-seismic displacements are opposite in sign for the areas over and beneath the position of the seismic source. The results also indicate that the curvature effect of the internal deformation is pretty large, and larger than that on the Earth surface. The results indicate that the dislocation theory for a sphere is necessary in computing internal co-seismic deformations.