Harmonic Suppression Study on Twin Aperture CCT Type Superconducting Quadrupole for CEPC Interaction Region

From the field calculation, we can also draw a conclusion that the different order harmonics have an independent property, which we can design a combined magnet by adding some high order harmonics, so that it can save space and reduce the magnet cost.Comment: 8 pages, 11 figures, NIMA subimissio

The current unbalance in stacked REBCO tapes -- simulations based on a circuit grid model

Unlike low temperature superconducting cables, there is so far no perfect solution for REBCO coated conductors to form a fully transposed high current cable. Every REBCO cable concept must import a stack of tapes to achieve an operating current as high as tens of kiloamperes. The stacked REBCO tapes, no matter whether they are twisted or not, however, have a nature of non-transposing and therefore could result in current unbalance. In this manuscript, the current unbalance and the related electrical characteristics of a cable made of 40 stacked REBCO tapes are studied with an electrical circuit simulation. The differences in splice resistances and tape inductances that are both related to the non-transposed structure of a REBCO stack are considered. Results show that for a 40 cm long termination, a proper method to keep the contact resistivity between each tape and the copper termination around 1e-8 ohmm is crucial to totally avoid current unbalance lowering the cable performance. Surprisingly, the inter-tape current transfer is found to be able to further exacerbate local high current though it does make the overall distribution more balanced. The inductance difference induced current unbalance is only important if local defects exist at long REBCO tapes, which on the other hand can be cured by good inter-tape current transfer. For a fast-charging rate of 1 kA/s, the inter-tape contact resistivity should also be low to a level of 1e-8 ohmm to ensure a short current transfer length of around 1 m

Concept for a Future Super Proton-Proton Collider

Following the discovery of the Higgs boson at LHC, new large colliders are being studied by the international high-energy community to explore Higgs physics in detail and new physics beyond the Standard Model. In China, a two-stage circular collider project CEPC-SPPC is proposed, with the first stage CEPC (Circular Electron Positron Collier, a so-called Higgs factory) focused on Higgs physics, and the second stage SPPC (Super Proton-Proton Collider) focused on new physics beyond the Standard Model. This paper discusses this second stage.Comment: 34 pages, 8 figures, 5 table

A Mixed Discontinuous Galerkin Approximation of Time Dependent Convection Diffusion Optimal Control Problem

In this paper, we investigate a mixed discontinuous Galerkin approximation of time dependent convection diffusion optimal control problem with control constraints based on the combination of a mixed finite element method for the elliptic part and a discontinuous Galerkin method for the hyperbolic part of the state equation. The control variable is approximated by variational discretization approach. A priori error estimates of the state, adjoint state, and control are derived for both semidiscrete scheme and fully discrete scheme. Numerical example is given to show the effectiveness of the numerical scheme

Edge Computing-Based VANETs’ Anonymous Message Authentication

Vehicular Ad-hoc Networks (VANETs) have high requirements for real-time data processing and security of message authentication. In order to solve the computing power asymmetry between vehicles and road side units (RSUs) in VANETs under high-density traffic, accelerate the processing speed of message authentication, and solve the problems of high computational overhead and long message authentication time caused by the use of bilinear pairing encryption technology in similar message-batch-authentication schemes, we propose introducing the concept of edge computing (EC) into VANETs and using idle nodes’ resources to assist the RSU in quickly authenticating messages to achieve computing power load balancing under multiple traffic flows. We propose introducing the idea of edge computing (EC) into VANETs and using idle nodes’ resources to assist RSUs in quickly authenticating messages. This scheme performs two identity-based message authentications based on the identity signature constructed by elliptic curve cryptography (ECC). One of them is the batch authentication of the vehicle sending messages by the RSU-authenticated vehicles with free resources, as temporary edge computing nodes (TENs), and the other is the authentication of the temporary TEN messages by the fixed-edge-node RSUs. The resources of the TEN are used to reduce the computational burden of RSUs and message authentication time, thereby improving the efficiency of system authentication of messages. We performed a security analysis of the scheme to prove its security properties and compared it with other schemes in terms of performance. The experimental results show that our scheme has a transmission overhead of 2400 bytes when there are four TENs, and the number of verification message requests reaches 20, which outperforms other methods. The gap will be more evident as the numbers of TEN and message verification requests increase

Effect of Si islands on low-temperature hydrothermal stability of Cu/SAPO-34 catalyst for NH3-SCR

The effect of the Si islands on the stability of Cu/SAPO-34 as a selective catalytic reduction (SCR) catalyst during low-temperature hydrothermal treatment (LTH treatment) was experimentally investigated. Cu/TEAOH (high Si islands) and Cu/TEA catalyst (low Si islands) were synthesized and then aged at 70 degrees C with 30 vol.% H2O for 48 h. Importantly, structure defect of SAPO-34 caused by Si islands could reduce the steric hindrance for H2O attacking. The stability of the SAPO-34 framework and isolated Cui-/Cu2+ ions was negatively correlated with high content of Si islands. After LTH treatment, the characterization results showed that an obvious dealumination occurred in Cu/TEAOH-LTH catalyst, with a great loss of relative crystallinity and Bronsted acid sites. Furthermore, the isolate Cu+/Cu2+ aggregated into CuO species in Cu/TEAOH-LTH catalyst, which accounted for the serious decreasing NH3-SCR activities of Cu/TEAOH-LTH catalyst. The results showed that Cu/TEA catalyst with less Si islands showed a better stability of structure and NH3-SCR activity after LTH treatment. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved

Edge Computing-Based VANETs’ Anonymous Message Authentication

Vehicular Ad-hoc Networks (VANETs) have high requirements for real-time data processing and security of message authentication. In order to solve the computing power asymmetry between vehicles and road side units (RSUs) in VANETs under high-density traffic, accelerate the processing speed of message authentication, and solve the problems of high computational overhead and long message authentication time caused by the use of bilinear pairing encryption technology in similar message-batch-authentication schemes, we propose introducing the concept of edge computing (EC) into VANETs and using idle nodes’ resources to assist the RSU in quickly authenticating messages to achieve computing power load balancing under multiple traffic flows. We propose introducing the idea of edge computing (EC) into VANETs and using idle nodes’ resources to assist RSUs in quickly authenticating messages. This scheme performs two identity-based message authentications based on the identity signature constructed by elliptic curve cryptography (ECC). One of them is the batch authentication of the vehicle sending messages by the RSU-authenticated vehicles with free resources, as temporary edge computing nodes (TENs), and the other is the authentication of the temporary TEN messages by the fixed-edge-node RSUs. The resources of the TEN are used to reduce the computational burden of RSUs and message authentication time, thereby improving the efficiency of system authentication of messages. We performed a security analysis of the scheme to prove its security properties and compared it with other schemes in terms of performance. The experimental results show that our scheme has a transmission overhead of 2400 bytes when there are four TENs, and the number of verification message requests reaches 20, which outperforms other methods. The gap will be more evident as the numbers of TEN and message verification requests increase