Matrix model for collective phenomena in electron beam’s longitudinal phase space

The possibility to predict, characterize and minimize the presence of spurious harmonic content in the longitudinal profile of high brightness electron beams, namely the microbunching instability, has become vital to ensure accurate modeling and reliable operation of radiofrequency and plasma-based linear accelerators such as those driving free-electron lasers. Recently, the impact of intrabeam scattering (IBS) on the instability has been experimentally demonstrated by the authors. This work complements that experimental study by extending existing theories in a self-consistent, piece-wise calculation of IBS in single pass linacs and multi-bend transfer lines. New expressions for the IBS are introduced in two different semi-analytical models of microbunching. The accuracy of the proposed models and the range of beam parameters to which they apply is discussed. The overall modeling turns out to be a fast comprehensive tool for the optimization of linac-driven free-electron lasers.

Schedule Planning Proceeding of Transfer Batches in Flexible Automated Lines While Sets are Forming and Limits are Recognized

The hierarchical approach while solving the problem of complex scheduling of transferred batches of units using flexible transfer lines is considered, when sets and time limits of flexible transfer lines are formed. Mathematical model of hierarchical game to optimize a mixture of transferred batches is developed. The groups of sets are processing during time intervals of definite lengths. The schedules of batches of units are optimized, using the mathematical model. The way of optimizing a mixture of groups of sets while resulting batches are formed, is developed.

Identifying Key Bus Stations Based on Complex Network Theory considering the Hybrid Influence and Passenger Flow: A Case Study of Beijing, China

In the bus network, key bus station failure can interrupt transfer lines, which leads to the low effectiveness of the whole network, especially during peak hours. Thus, identifying key stations in the bus network before the emergency occurs has a great significance to improve the response speed. In this paper, we proposed a new method considering station hybrid influence and passenger flow to identify key stations in the whole bus network. This method aims to measure the influence of bus stations while combining the topological structure of the bus network and dynamic bus stations passenger flow. The influence of bus stations was calculated based on the local structure of the network, which refines from finding the shortest paths with high computational complexity. To evaluate the performance of the method, we used the efficiency of the network and vehicle average speed at the station to examine the accuracy. The results show that the new method can rank the influence of bus stations more accurately and more efficiently than other complex network methods such as degree, H-index, and betweenness. On this basis, the key stations of the bus network of Beijing in China are identified out and the distribution characteristics of the key bus stations are analyzed.

Development of Stress Intensification Factors for Collared Type Piping Joints

Stress Intensification Factors or SIFs allow piping to be analyzed using beam theory, with a SIF representing local effects of specific piping geometry. However, the current piping codes do not explicitly provide SIFs for collared type piping joints for use in pipe stress calculations. The objective of this paper is to describe the methodology on how a finite element analysis (FEA) was to model the behavior of collared joints, and to ultimately develop appropriate SIFs that can be used in pipe stress analyses. This paper describes a real-life analysis example on collared joints installed on a set of existing fuel transfer lines. The lines, which ranged in size from DN200 to DN350, were concrete lined carbon steel with the collars fillet welded to the carbon steel section of the piping. Test coupons cut from existing pipe-collar sections were tested in a laboratory to determine the forces required to break the collar welds. Using FEA, the same test coupons were modelled to replicate the failure tests. Multiple iterations were undertaken to determine an appropriate bi-linear stress-strain curve fit for the weld material. The curves of different weld electrode materials were considered. The curve which lead to results similar to those observed in physical testing was selected. From this, a failure stress across the weld could be determined. This stress, 435MPa was then used in subsequent models to determine the point at which the weld fails under bending loads. Multiple tests were analyzed to allow for possible effects of inclusions and voids. Finite element models of the collar geometries were constructed and non-linear analyses were undertaken using the weld strengths determined from the coupon testing data. A simple cantilever type arrangement with a point load at one end was analyzed, inducing a bending moment across the collar. The peak stress resulting from the bending moment across the collar weld at the center of the cantilevered pipe arrangement, was investigated across various pipe diameters, wall thicknesses, weld sizes and collar geometries. Based on the results, a relationship between the pipe geometry and SIF was developed. Hence a pipe stress model of the transfer lines could ultimately be developed using these SIFs to predict the behavior of the piping.