Search

Since tungsten is considered as the optional divertor target material for the future fusion devices, e.g., China Fusion Engineering Test Reactor (CFETR), it is crucial to have a good screening of the tungsten impurity to keep a low core tungsten concentration. In this paper, based on the two-point model, possible divertor plasma parameters are predicted in high recycling regime for CFETR. Further analysis of tungsten ionization lengths shows that when target temperature is low enough (less than 15 eV), the increase of upstream density may cause an increase of ionization length, and thus a degradation of divertor tungsten screening effect may happen. The 2-D simulations of tungsten transport are then performed by using Osm-Eirene-Divimp edGE [onion skin model (OSM)-EIRENE-DIVvertor IMPurities (DIVIMP)] code package. The target plasma parameters, in the region of those predicted by the two-point model, are set as input in OSM-EIRNEN to generate the background plasma. DIVIMP code is used to further simulate the tungsten impurity transport process. The results reveal that although the decrease of target plasma temperature may reduce the tungsten impurity prompt redeposition rate, the benefit of a lower erosion rate can make compensation. Therefore, to control the core tungsten concentration, lower target plasma temperature is preferred in high recycling regime. [ABSTRACT FROM AUTHOR]

The system code is under developing aiming to integrate the design of engineering and physics for China fusion engineering testing reactor. The system code comprises the engineering design platform and the physics design platform. The integration platform is developed to handle the data exchange and workflow interaction of submodules and to integrate the engineering platform and the physics platform together. In this paper, a methodology of developing the integration platform of system code with Java, OPTIMUS, and MySQL is presented. We develop the GUI of the integration platform with the help of Java JRE System library, such as AWT and Swing. Second, we choose EXCEL and TXT documents as the carrier of system data. Then, OPTIMUS is employed to establish the core workflow of the system code. Finally, the relational database software, MySQL, is chose to create user database, material database, criterion database, and manipulate record database. Besides that, the workflow of a vacuum vessel module is described in this paper as an instance. [ABSTRACT FROM AUTHOR]

We introduce a tomographic reconstruction method implemented using a shape-based regularization technique. Spatial models of known features in the structure being reconstructed are integrated into the reconstruction process as regularizers. Our regularization scheme is driven locally through shape information obtained from segmentation and compared with a known spatial model. We demonstrated our method on tomography data from digital phantoms, simulated data, and experimental electron tomography (ET) data of virus complexes. Our reconstruction showed reduced blurring and an improvement in the resolution of the reconstructed volume was also measured. This method also produced improved demarcation of spike boundaries in viral membranes when compared with popular techniques like weighted back projection and the algebraic reconstruction technique. Improved ET reconstructions will provide better structure elucidation and improved feature visualization, which can aid in solving key biological issues. Our method can also be generalized to other tomographic modalities. [ABSTRACT FROM PUBLISHER]

Geometric flows have been successfully used for surface modeling and designing, largely because they are inherently good at controlling geometric shape evolution. Variational image segmentation approaches, on the other hand, detect objects of interest by deforming certain given shapes. This motivates us to revisit the minimal partition problem for segmentation of images, and propose a new geometric flow-based formulation and solution to it. Our model intends to derive a mapping that will evolve given contours or piecewise-constant regions toward objects in the image. The mapping is approximated by B-spline basis functions, and the positions of the control points are to be determined. Starting with the energy functional based on intensity averaging, we derive a Euler–Lagrange equation and then a geometric evolution equation. The linearized system of equations is efficiently solved via a special matrix-vector multiplication technique. Furthermore, we extend the piecewise-constant model to a piecewise-smooth model which effectively handles images with intensity inhomogeneity. [ABSTRACT FROM AUTHOR]

In this paper, we describe a new method to generate a smooth algebraic spline (AS) approximation of the molecular surface (MS) based on an initial coarse triangulation derived from the atomic coordinate information of the biomolecule, resident in the Protein data bank (PDB). Our method first constructs a triangular prism scaffold covering the PDB structure, and then generates a piecewise polynomial F on the Bernstein-Bezier (BB) basis within the scaffold. An ASMS model of the molecular surface is extracted as the zero contours of F, which is nearly C^1 and has dual implicit and parametric representations. The dual representations allow us easily do the point sampling on the ASMS model and apply it to the accurate estimation of the integrals involved in the electrostatic solvation energy computations. Meanwhile comparing with the trivial piecewise linear surface model, fewer number of sampling points are needed for the ASMS, which effectively reduces the complexity of the energy estimation. [ABSTRACT FROM PUBLISHER]