An Improved 3-D Ray Tracing Method Using Linear Traveltime Interpolation

An approach of three-dimensional seismic ray tracing is presented,which is derived from adopting two-dimensional linear traveltime interpolation（LTI）.By adjusting the forward process using the partition of grid interface,and backward step by considering more directions,the new approach is suitable for the application of three-dimensional models.The calculation results show that,with the same accuracy,the improved 3-D method is much faster than the method of traditional LTI directly applied in the three-dimensional case.

A Three-Dimensional Ray Tracing Study on Whistler-Mode Chorus During Geomagnetic Activities

A three-dimensional ray tracing study of a whistler-mode chorus is conducted for different geomagnetic activities by using a global core plasma density model. For the upperband chorus, the initial azimuthal wave angle affects slightly the projection of ray trajectories onto the plane （Z, √（x^2 ＋ y^2））, but controls the longitudinal propagation. The trajectory of the upper-band chorus is strongly associated with the plasmapause and the magnetic local time （MLT） of chorus source region. For the high geomagnetic activity, the chorus trajectory moves inward together with the plasmapause. In the bulge region, the plasmapause extends outward, while the chorus trajectory moves outward together with the plasmapause. For moderately or high geomagnetic activity, the lower-band chorus suffers low hybrid resonance （LHR） reflection before it reaches the plasmapause, leading to a weak correlation with the geomagnetic activity and magnetic local time of the chorus source region. For low geomagnetic activity, the lower-band chorus may be reflected firstly at the plasmapause instead of suffering LHR reflection, exhibiting a propagation characteristic similar to that of the upper-band chorus. The results provide a new insight into the propagation characteristics of the chorus for different geomagnetic activities and contribute to further understanding of the acceleration of energetic electron by a chorus wave.

A"messenger zone hypothesis"based on the visual three-dimensional spatial distribution of motoneurons innervating deep limb muscles

Coordinated contraction of skeletal muscles relies on selective connections between the muscles and multiple classes of the spinal motoneuro ns.Howeve r,current research on the spatial location of the spinal motoneurons innervating differe nt muscles is limited.In this study,we investigated the spatial distribution and relative position of different motoneurons that control the deep muscles of the mouse hindlimbs,which were innervated by the obturator nerve,femoral nerve,inferior gluteal nerve,deep pe roneal nerve,and tibial nerve.Locations were visualized by combining a multiplex retrograde tracking technique compatible with three-dimensional imaging of solvent-cleared o rgans(3DISCO)and 3-D imaging technology based on lightsheet fluorescence microscopy(LSFM).Additionally,we propose the hypothesis that"messenger zones"exist as interlaced areas between the motoneuron pools that dominate the synergistic or antagonist muscle groups.We hypothesize that these interlaced neurons may participate in muscle coordination as messenger neurons.Analysis revealed the precise mutual positional relationships among the many motoneurons that innervate different deep muscles of the mouse.Not only do these findings update and supplement our knowledge regarding the overall spatial layout of spinal motoneurons that control mouse limb muscles,but they also provide insights into the mechanisms through which muscle activity is coordinated and the architecture of motor circuits.

3-D seismic tomography for velocity and interface structure of the crust and upper mantle(theoreticalpart)

A method of three dimensional (3-D) model parameterization is presented that makes forward and inverse problems become easy. The velocity and interface structure of crust and upper mantle are described by a set of highly smoothed functions. Shooting ray tracing method is chosen to calculate the ray paths for both forward and inverse problems. The partial derivatives of traveltime with respect to parameters of the model grids are calculated analytically while rays are being traced. Because velocity and interface functions have second-order continuous partial derivatives, the geometrical shadow zones at the surface caused by scattering and focusing of ray paths can be prevented. After ray tracing, an equation consisting of matrix and vectors for inverse problem is obtained. We use singular value decomposition method with damped factor to solve the equation. A synthetic data set which consists of several in-line profiles is used to test the methods. The results show that the methods are robust. Compared with the two dimensional method, the 3-D inversion method can give the right position of interfaces and the velocity structure when the crustal model is complicated.

Indirect-approach method for specified-end points seismic ray tracing in three dimen-sional inhomogeneous media

Generally speaking, the factors of both medium and tectonic that give rise to heterogeneity of the earth crust and mantle structures should be taken into account simultaneously in three dimensional seismic ray tracing. In this paper, the three dimensional structure models are constructed with the model similar to generation system in computer aid design and manufacturing (CAD/CAM). Based on the algorithm proposed by Cerveny et al . for complete seismic ray tracing in complex three dimensional structures, a new technique called the indirect approach method for two point seismic ray tracing in three dimensional laterally heterogeneous media has been put forward, and its numerical computing examples were given.

3-D structural reconstruction of Moho in the Tangshan earthquake area by using inversion of curved interface

A method for inverting 3 D curved interface and layer velocity by using travel time of reflected waves is studied. Each interface is described with sectional, incomplete cubic polynomial. A fast 3 D ray tracing method is used in forward problem, and a least squares method with variable damping is adopted in the inverse problem. Result from numerical modelling shows that the solution can converge fast on the true model. Observational data from the Tangshan earthquake area are processed, 3 D Moho discontinuity in the area is rebuilt, and finally, the relationship between the regional structure and seismicity is revealed.

Panicle-3D: A low-cost 3D-modeling method for rice panicles based on deep learning, shape from silhouette, and supervoxel clustering

Self-occlusions are common in rice canopy images and strongly influence the calculation accuracies of panicle traits. Such interference can be largely eliminated if panicles are phenotyped at the 3 D level.Research on 3 D panicle phenotyping has been limited. Given that existing 3 D modeling techniques do not focus on specified parts of a target object, an efficient method for panicle modeling of large numbers of rice plants is lacking. This paper presents an automatic and nondestructive method for 3 D panicle modeling. The proposed method integrates shoot rice reconstruction with shape from silhouette, 2 D panicle segmentation with a deep convolutional neural network, and 3 D panicle segmentation with ray tracing and supervoxel clustering. A multiview imaging system was built to acquire image sequences of rice canopies with an efficiency of approximately 4 min per rice plant. The execution time of panicle modeling per rice plant using 90 images was approximately 26 min. The outputs of the algorithm for a single rice plant are a shoot rice model, surface shoot rice model, panicle model, and surface panicle model, all represented by a list of spatial coordinates. The efficiency and performance were evaluated and compared with the classical structure-from-motion algorithm. The results demonstrated that the proposed method is well qualified to recover the 3 D shapes of rice panicles from multiview images and is readily adaptable to rice plants of diverse accessions and growth stages. The proposed algorithm is superior to the structure-from-motion method in terms of texture preservation and computational efficiency. The sample images and implementation of the algorithm are available online. This automatic, cost-efficient, and nondestructive method of 3 D panicle modeling may be applied to high-throughput 3 D phenotyping of large rice populations.

Modeling of Large ELM Suppressions for High Confinement Plasma in D Ⅲ-D

The H-mode discharges with high edge pressure gradients are expected for the economic feasibility of future fusion reactors. However, the high edge pressure gradients easily produce ELM instability , which generally can expel large, heat and particle loading to the divertor targets. These ELMs limit the core plasma performance and reduce the lifetime of divertor target plates. The transports of heat and particles outward across plasma boundary are useful to control density and impurity profiles for achieving steady state, high performance plasmas. Consequently, any technique to eliminate or mitigate large fast ELM impulses must replace the transient heat and particle transports with another slow process. Such a technique is high priority for a burning plasma device such as ITER.

COMPARISONS OF RAY-TRACING AND PARABOLIC EQUATION METHODS FOR THE LARGE-SCALE COMPLEX ELECTROMAGNETIC ENVIRONMENT SIMULATIONS

It is important for the wireless communication field to conduct research on large-scale complex electromagnetic environment(CEME)simulation.There exist many models for computing CEME simulation,including empirical models,half-empirical or halfdeterministic models and deterministic models.Most of these models cannot obtain satisfactory results due to the limitation of the capacity of computers.The ray tracing(RT)and parabolic equation(PE)methods are very suitable for large-scale CEME simulation.Based on the introduction of RT and PE,qualitative comparisons of the two methods are analyzed in view of algorithm theory,the category of the model,solution to the model and the application field,and then four specific indices are focused on to analyze the computational complexity,accuracy,speed and parallelism in details.The numerical experiments are presented by the three-dimensional(3D)RT method employing the software of Wireless InSite(WI)and a quasi-3DPE method using the sliced method.Although both RT and PE methods can achieve high speedup using coarse-grained parallel computing,the experimental results indicate that the PE method can obtain a higher speed than the RT method,and the two methods can acquire an approximate precision.A hybrid procedure using both RT and PE methods can obtain a better result for solving CEME problems.

Modeling of Stochastic Magnetic Perturbation by RWMEF-Coils on NSTX

A 3-D field line integration code, TRIP3D has been modified to model stochastic magnetic perturbation produced by a resistive wall mode, error field （ RWMEF ） coil in the NSTX tokamak with very low aspect ratio. The RWMEF-coil has two turns, which may produce stochastic fields with the toroidal mode number of n = 1 or 3. In this study, it is found that the stochastic field of n = 3 is larger than that of n=-1 for the same coil current. Two divertor discharges with lower single null （ LSN ） and double null （ DN ） configurations in the NSTX have been modeled with different RWMEF-coil currents and toroidal modes.

准周期聚焦-加速耦合系统的均温设计方法

强流质子直线加速器要求严格控制束流损失和束流发射度增长 .理论已经证明 ,强的空间电荷作用在不同自由度之间的耦合 ,会因为其间的温度差异 ,通过束流的相干不稳定性 ,使束流发射度增长 .因此 ,有必要按照均温的原则设计强流加速器 .但是 ,由于质子直线加速器的各种加速结构均为准周期耦合系统 ,使得均温设计十分繁琐而难以达到完全均温 .我们利用国际上通用的束流动力学软件TRACE3 D ,给它补充了均温设计功能 ,通过与PARMILA程序的配合使用 ,可以方便地在加速器设计中实现均温条件 .本文将介绍我们对TRACE3 D的修改补充 ,并以强流质子直线加速器设计实例 ,说明均温设计的必要性 .