基于超声断层成像的小动物器官声速成像

声速是表征组织的一个重要声学参数。我们开发了一种超声断层成像(USCT)系统,用于小动物器官的体外声速成像和评估。该USCT系统采用256个阵元的环形阵列换能器,并允许所有通道同时进行信号传输和接收。该方法不需要复杂的样品制备程序,测量结果准确。实验结果表明,该方法测量的离体大鼠脑、心、肝、脾、肾的声速与已发表的数据接近。这项工作展示了一种新的声速成像方法,并具有在体应用潜力。

Control Effect and Cost Evaluation of Different Sex Pheromones and Trapping Lamps against Spodoptern litura,Helicoverpa assulta and Helicoverpa armigera in Tobacco

[ Objective] The aim was to study the control effect of different sex pheromones and trapping lamps against main pests in tobacco. [ Method] Control effect of sex pheromone of different matrix lures and Jiaduo trapping lamp against Spodoptern litura, Helicoverpa assulta and Helicoverpa armigera in tobacco in Teng- chong of Yunnan were determined and compared, and the control cast was evaluated. [Result] The use of insect sex pheromones and insecticidal light traps had certain effect against S. litura and H. armiger. The trapping effect of sex pheromone traps was better than that of Jiaduo trapping lamp, and the PVC matrix lure had better performance than rubber matrix lure, which had strongest capturing capacity, continuous control effect and significant effort against S. litura. The traps with different settled densities and hanging heights also had different trapping effect against S. litura and H. armiger, and the hanging height of 100 - 150 cm from ground was the best; as the cost was considered, the cast of the area with low density of traps was the lowest, which was reduced by over 44% than conventional chemical control area. [ Conclusion] It is safe and effective to use sex pheromone and insecticidal light traps to control S. litura and H. armigera, and it is a green environmental protection biological physical control technology, having extended application prospect in large area.

Temporal continuity of visual attention for future gaze prediction in immersive virtual reality

Background Eye tracking te chnology is receiving increased attention in the field of virtual reality.Specifically,future gaze prediction is crucial in pre-computation for many applications such as gaze-contingent rendering,advertisement placement,and content-based design.To explore future gaze prediction,it is necessary to analyze the temporal continuity of visual attention in immersive virtual reality.Methods In this paper,the concept of temporal continuity of visual attention is presented.Subsequently,an autocorrelation function method is proposed to evaluate the temporal continuity.Thereafter,the temporal continuity is analyzed in both free-viewing and task-oriented conditions.Results Specifically,in free-viewing conditions,the analysis of a free-viewing gaze dataset indicates that the temporal continuity performs well only within a short time interval.A task-oriented game scene condition was created and conducted to collect users'gaze data.An analysis of the collected gaze data finds the temporal continuity has a similar performance with that of the free-viewing conditions.Temporal continuity can be applied to future gaze prediction and if it is good,users'current gaze positions can be directly utilized to predict their gaze positions in the future.Conclusions The current gaze's future prediction performances are further evaluated in both free-viewing and task-oriented conditions and discover that the current gaze can be efficiently applied to the task of short-term future gaze prediction.The task of long-term gaze prediction still remains to be explored.

Effect of Support Height on Microstructure and Mechanical Properties of Selective Laser Melting Ti-15Mo Alloy

In this research,for the first time,the Ti-15Mo alloy generated via selective laser melting(SLM)with many different support heights was examined.With the increase of the support height,the risks of forming microcracks and small holes increase while the ductility of the sample decreases.The grain sizes of the samples decrease with an increase in support height because of the more efficient heat dissipation rate during the SLM process.The average grain sizes of the samples are 36.95±0.7μm(5 mm-sample I),35.24±0.7μm(10 mm-sample II)and 33.91±0.7μm(15 mm-sample III),respectively.As the support height increases,the intensity of(111)texture increases and the misorientation angles gradually decrease.The ultimate tensile strength,yield strength and ductility of the three samples are 970±13 MPa,769±12 MPa and 9.78%±1.5%(sample I),1051±11 MPa,932±11 MPa and 7.17%±2%(sample II),1123±14 MPa,1089±9 MPa and 5.4%±1.4%(sample III),respectively.The decrease in grain size,increase in dislocation density and enhancement of the(111)texture are all conducive to achieving the higher strength.

Numerical Study of Heat Transfer Enhancement in the Electric Vehicle Battery via Vortex‑Induced Agitator

Convective heat transfer plays an important role in the development of a high-performance battery cell.Electric vehicles carry a large amount of the battery cells to reach a longer range of endurance mileage.Thermal diffusion around the battery cells can be considered as obstacles to improve the convective heat transfer coefficient.In this paper,a novel agitator taking advantage of strong vortices is designed to disrupt the thermal boundary layer around the battery cells,thereby improving the fluid mixing for enhanced convective heat transfer.A fluid–structure interaction algorithm is developed to simulate the convective heat transfer rate at various flapping motion.Under the comparison with clean channel,the vortex-induced vibra-tion by the agitated beam can increase the average Nusselt number by 119.59%.This research can be applied to optimize the thermal-structure design inside the electric vehicle battery.

A review of in situ upgrading technology for heavy crude oil

With the growing demand of oil worldwide,heavy oil has increasingly become vital in the world energy market.However,further development of heavy oil reservoirs are limited by regular enhanced oil recovery(EOR)methods.In situ upgrading technology provides potential for the development of heavy oil and bitumen reservoirs.This study reviews three categories of in situ upgrading methods:solvent-based,in situ combustion(ISC),and catalytic.Solvent-based methods,including cyclic solvent injection,vapor extraction,and hybrid processes,have recently received attention and have been progressed in both laboratory and field applications.However,high solvent costs in relation to the low price of heavy oil have continued to limit the field applications of these techniques.ISC,which may have the potential to develop particularly harsh reservoirs with extremely viscous crude oil,involves complex reaction mechanisms and consists of three main steps:oxidation,combustion,and gas flooding.Yet,complex operating conditions and a low success rate have restricted its application.Catalytic methods,which have demonstrated the potential to refine and upgrade crude oil in a more economic and environmentally friendly way,are often accompanied by conventional thermal EOR methods,such as steam flooding and ISC,and involve a series of hydroprocessing or hydrotreating reactions,such as hydrocracking,hydrodesulfurization,hydrodenitrogenation,hydrodeoxygenation,and hydrodemetallization.However,the high cost and complexity of the reaction mechanisms have limited their applications.

Toward automatic estimation of urban green volume using airborne LiDAR data and high resolution Remote Sensing images

Urban green volume is an important indicator for analyzing urban vegetation structure, ecological evaluation, and green-economic estimation. This paper proposes an object-based method for automated estimation of urban green volume combining three-dimensional （3D） information from airborne Light Detection and Ranging （LiDAR） data and vegetation information from high resolution remotely sensed images through a case study of the Lujiazui region, Shanghai, China. High resolution airborne near-infrared photographs are used for identifying the urban vegetation distribution. Airborne LiDAR data offer the possibility to extract individual trees and to measure the attributes of trees, such as tree height and crown diameter. In this study, individual trees and grassland are identified as the independent objects of urban vegetation, and the urban green volume is computed as the sum of two broad portions： individual trees volume and grassland volume. The method consists of following steps： generating and filtering the normalized digital surface model （nDSM）, extracting the nDSM of urban vegetation based on the Normalized Difference Vegetation Index （NDVI）, locating the local maxima points, segment- ing the vegetation objects of individual tree crowns and grassland, and calculating the urban green volume of each vegetation object. The results show the quantity and distribution characteristics of urban green volume in the Lujiazui region, and provide valuable parameters for urban green planning and management. It is also concluded from this paper that the integrated application of LiDAR data and image data presents an effective way to estimate urban green volume.

Guided Wave Propagation in Multilayered Two-dimensional Quasicrystal Plates with Imperfect Interfaces

An analytical solution of the guided wave propagation in a multilayered twodimensional decagonal quasicrystal plate with imperfect interfaces is derived.According to the elastodynamic equations of quasicrystals(QCs),the wave propagating problem in the plate is converted into a linear control system by employing the state-vector approach,from which the general solutions of the extended displacements and stresses can be obtained,These solutions along the thickness direction are utilized to derive the propagator matrix which connects the physical variables on the lower and upper interfaces of each layer.The special spring model,which describes the discontinuity of the physical quantities across the interface,is introduced into the propagator relationship of the multilayered structure.The total propagator matrix can be used to propagate the solutions in each interface and each layer about the multilayered plate.In addition,the traction-free boundary condition on the top and bottom surfaces of the laminate is considered to obtain the dispersion equation of wave propagation,Finally,typical numerical examples are presented to illustrate the marked influences of stacking sequence and interface coeficients on the dispersion curves and displacement mode shapes of the QC laminates.

Physical simulation experiment and numerical inversion of the full life cycle of shale gas well

The ultra-low porosity and permeability,as well as complex occurrence and transport state of shale reservoir make it possess special L-type production characteristic curve and complicated shale gas flow mechanism.To solve the difficulty of collecting complete production data due to short production time and operation discontinuity,a full-diameter core physical simulation experiment on the full lifecycle production process of shale gas well depletion is conducted with the purpose of obtaining many important production data including complete pressure and daily gas output in the simulated production process of shale gas well.The experimental results show the production characteristic from simulation is consistent with those from gas well.Based on the simulation data,the critical desorption pressure(12 MPa)of core,free gas production(3820.8 mL),adsorbed gas production(2151.2 mL),the proportion of the daily gas production between free and absorbed gas under different time and formation pressure,as well as the production time and final recovery rate corresponding to abandoned pressure,can be determined accurately.Numerical inversion is carried out to calculate the production performance curve of shale gas well and predict the development effect of gas well based on well testing and similarity analysis of the dimensionless time between core experiment and gas well production.Finally,the permeability and the fracturing effect(fracture network density)as the keys to the effective development of shale gas reservoirs are proposed.The permeability is the fundamental factor and the fracturing technology is the major means.