Finite Element Simulation of Flexible Roll Forming with Supplemented Material Data and the Experimental Verification

Flexible roll forming is a promising manufacturing method for the production of variable cross section products. Considering the large plastic strain in this forming process which is much larger than that of uniform deformation phase of uniaxial tensile test, the widely adopted method of simulating the forming processes with non-supplemented material data from uniaxial tensile test will certainly lead to large error. To reduce this error, the material data is supplemented based on three constitutive models. Then a finite element model of a six passes flexible roll forming process is established based on the supplemented material data and the original material data from the uniaxial tensile test. The flexible roll forming experiment of a B pillar reinforcing plate is carried out to verify the proposed method. Final cross section shapes of the experimental and the simulated results are compared. It is shown that the simulation calculated with supplemented material data based on Swift model agrees well with the experimental results, while the simulation based on original material data could not predict the actual deformation accurately. The results indicate that this material supplement method is reliable and indispensible, and the simulation model can well reflect the real metal forming process. Detailed analysis of the distribution and history of plastic strain at different positions are performed. A new material data supplement method is proposed to tackle the problem which is ignored in other roll forming simulations, and thus the forming process simulation accuracy can be greatly improved.

Preliminary proposal of scientific data verification in CSES mission

China Seismo-Electromagnetic Satellite （CSES） will be launched at the end of 2016 and the orbit is sun- synchronous and the altitude is about 500 km. The design of CSES satellite and ground segment are introduced in this paper first. And then the preliminary proposals of scientific data verification and cross-verification in CSES mission are given, which can be used to classify the payloads＇ operation state, and validate the reliability of data.

A privacy-preserved indexing schema in DaaS model for range queries

In a database-as-a-service(DaaS)model,a data owner stores data in a database server of a service provider,and the DaaS adopts the encryption for data privacy and indexing for data query.However,an attacker can obtain original data’s statistical information and distribution via the indexing distribution from the database of the service provider.In this work,a novel indexing schema is proposed to satisfy privacy-preserved data management requirements,in which an attacker cannot obtain data source distribution or statistic information from the index.The approach includes 2 parts:the Hash-based indexing for encrypted data and correctness verification for range queries.The evaluation results demonstrate that the approach can hide statistical information of encrypted data distribution while can also obtain correct answers for range queries.Meanwhile,the approach can achieve nearly 10 times and 35 times improvement on encrypted data publishing and indexing respectively,compared with the start-of-the-art method order-preserving Hash-based function(OPHF).

Flexible CP-ABE Based Access Control on Encrypted Data for Mobile Users in Hybrid Cloud System

In hybrid cloud computing, encrypted data access control can provide a fine-grained access method for organizations to enact policies closer to organizational policies. This paper presents an improved CP-ABE (ciphertext-policy attribute-based encryption) scheme to construct an encrypted data access control solution that is suitable for mobile users in hybrid cloud system. In our improvement, we split the original decryption keys into a control key, a secret key and a set of transformation keys. The private cloud managed by the organization administrator takes charge of updating the transformation keys using the control key. It helps to handle the situation of flexible access management and attribute alteration. Meanwhile, the mobile user's single secret key remains unchanged as well as the ciphertext even if the data user's attribute has been revoked. In addition, we modify the access control list through adding the attributes with corresponding control key and transformation keys so as to manage user privileges depending upon the system version. Finally, the analysis shows that our scheme is secure, flexible and efficient to be applied in mobile hybrid cloud computing.