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A modified interval subdividing based geometric calibration method for interior tomography

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Chinese Physics B 2014年第9期23卷 571-577页

作者：张峰闫镔李磊席晓琦江桦 National Digital Switching system engineering & Technology Research Center

The interior tomography is commonly met in practice, whereas the self-calibration method for geometric parameters remains far from explored. To determine the geometry of interior tomography, a modified interval subdividing based method, which was originally developed by Tan et al.,^[11] was presented in this paper. For the self-calibration method, it is necessary to obtain the reconstructed image with only geometric artifacts. Therefore, truncation artifacts reduction is a key problem for the self-calibration method of an interior tomography. In the method, an interior reconstruction algorithm instead of the Feldkamp-Davis-Kress （FDK） algorithm was employed for truncation artifact reduction. Moreover, the concept of a minimum interval was defined as the stop criterion of subdividing to ensure the geometric parameters are determined nicely. The results of numerical simulation demonstrated that our method could provide a solution to the self- calibration for interior tomography while the original interval subdividing based method could not. Furthermore, real data experiment results showed that our method could significantly suppress geometric artifacts and obtain high quality images for interior tomography with less imaging cost and faster speed compared with the traditional geometric calibration method with a dedicated calibration phantom.

关键词： interior tomography geometric calibration interval subdividing minimum interval

A sub-circuit MOSFET model with a wide temperature range including cryogenic temperature

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Journal of Semiconductors 2011年第6期32卷 27-32页

作者：贾侃孙伟锋时龙兴 National ASIC system engineering Research Center Southeast University

A sub-circuit SPICE model of a MOSFET for low temperature operation is *** resistors are introduced for the freeze-out effect,and the explicit behavioral models are developed for *** model can be used in a wide temper... 详细信息

关键词： SPICE model low temperature sub-circuit freeze-out effect voltage control resistor

Incremental forming of free surface with magnesium alloy AZ31 sheet at warm temperatures

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中国有色金属学会会刊：英文版 2008年第A01期18卷 165-169页

作者： Y.H.JI J.J.PARK Department of Mechanical and system Design engineering Hongik University

The formabilityof AZ31 sheet begins to increase drastically at 150℃.The incremental forming technique was thus applied to AZ31 sheet at 150℃to utilize the formability to its fullest capacity at the lowest possible temperature for forming applications.A surface scanning technique was used followed by the tool path generation to incrementally form an egg *** thorough examination of various tool paths,the surface was most successfully produced by forming an intermediate shape followed by a series of tool *** scale stickers were devised to improve the accuracy in the measurement of grid deformation.

关键词：金属材料数控成形加工 AZ31镁合金板材

Enhancing recommender systems by incorporating social information

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Journal of Zhejiang University-Science C(Computers and Electronics) 2013年第9期14卷 711-721页

作者： Li-wei HUANG Gui-sheng CHEN Yu-chao LIU De-yi LI Institute of Command Information system PLA University of Science and Technology Institute of Electronic system engineering

Although recommendation techniques have achieved distinct developments over the decades,the data sparseness problem of the involved user-item matrix still seriously influences the recommendation *** of the existing techniques for recommender systems cannot easily deal with users who have very few *** to combine the increasing amount of different types of social information such as user generated content and social relationships to enhance the prediction precision of the recommender systems remains a huge *** this paper,based on a factor graph model,we formalize the problem in a semi-supervised probabilistic model,which can incorporate different user information,user relationships,and user-item ratings for learning to predict the unknown *** evaluate the method in two different genres of datasets,Douban and *** indicate that our method outperforms several state-of-the-art recommendation ***,a distributed learning algorithm is developed to scale up the approach to real large datasets.

关键词： Recommender system Social information Factor graph model

Electrocaloric Effect of P(VDF-TrFE)/SrTiO_3 Bilayer Thin Films

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Communications in Theoretical Physics 2013年第1期59卷 117-120页

作者：邱建华丁建宁袁宁一王秀琴 Center for Low-Dimensional Materials Micro-Nano Devices and SystemChangzhou University School of Material Science and engineering Jiangsu University Jiangsu Key Laboratory for Solar Cell Materials and Technology

A phenomenological thermodynamic theory is applied to investigate the effect of misfit strgin and electric field on the electrocaloric effect of P（VDF-TrFN）/SrTiO3 bilayer thin films. Theoretical results indicate that the low electric field results in the decrease of the average polarization with the increase of the relative thickness of SrTi03 layer, and the high electric field has an opposite effect on it. Moreover, the electroealoric effect strongly depends on the electric field. The low electric field and the small field change can lead to a maximum of the electrocaloric effect, meanwhile the high electric field or the large field change results in the opposite trend.

关键词： bilayer thin film polymer electrocaloric effect

Parallel Algorithm Core: A Novel IPSec Algorithm Engine for Both Exploiting Parallelism and Improving Scalability

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Journal of Computer Science & Technology 2008年第5期23卷 792-805页

作者：程东年胡宇翔刘彩霞 National Digital Switching system engineering & Technological Research Center

To deal with the challenges of both computation-complexity and algorithm-scalability posed to the design of an IPSec engine, we develop PAC （parallel algorithm core）, called PAC, employed in an IPSec engine, which can meet requirements of both exploiting parallelism existing in IPSec packets and offering scalability in both the scales and types of cryptographic algorithms. With three kinds of parallelism and two kinds of transparency defined, a novel hierarchy of the specifically-designed parallel structure for PAC is presented, followed by corresponding mechanisms. With a simulation, the scalability of PAC is examined. For the purpose of performance evaluation, a Quasi Birth-and-Death （QBD） process is then established to model a simplified version of the proposed PAC. Performance evaluation of PAC in terms of two representative measures, throughput and mean packet waiting time, is numerically investigated. A comparison study is done on a simulation basis. Conclusions are finally drawn for providing a helpful guideline for both the design and implementation of our proposal.

关键词： computer network architecture IPSec queuing theory parallel processing numerical analysis

Cone-beam local reconstruction based on a Radon inversion transformation

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Chinese Physics B 2012年第11期21卷 541-546页

作者：汪先超闫镔李磊胡国恩 National Digital Switching system engineering and Technological Research Center

The local reconstruction from truncated projection data is one area of interest in image reconstruction for com- puted tomography （CT）, which creates the possibility for dose reduction. In this paper, a filtered-backprojection （FBP） algorithm based on the Radon inversion transform is presented to deal with the three-dimensional （3D） local recon- struction in the circular geometry. The algorithm achieves the data filtering in two steps. The first step is the derivative of projections, which acts locally on the data and can thus be carried out accurately even in the presence of data trun- cation. The second step is the nonlocal Hilbert filtering. The numerical simulations and the real data reconstructions have been conducted to validate the new reconstruction algorithm. Compared with the approximate truncation resistant algorithm for computed tomography （ATRACT）, not only it has a comparable ability to restrain truncation artifacts, but also its reconstruction efficiency is improved. It is about twice as fast as that of the ATRACT. Therefore, this work provides a simple and efficient approach for the approximate reconstruction from truncated projections in the circular cone-beam CT.

关键词： computed tomography image reconstruction truncated data Radon inversion transform

New Insights into Divide-and-Conquer Attacks on the Round-Reduced Keccak-MAC

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Chinese Journal of Electronics 2019年第4期28卷 698-705页

作者： YE Chendong TIAN Tian National Digital Switching system engineering and Technological Research Center

Keccak is the final winner of SHA-3 competition and it can be used as message authentic codes as well. The basic and balanced divide-and-conquer attacks on Keccak-MAC were proposed by Dinur et *** Eurocrypt 2015. The idea of cube attacks is used in the two attacks to divide key bits into small portions. By carefully analysing the mappings used in Keccak-MAC, it is found that some cube variables could divide key bits into smaller portions and so better divide-and-conquer attacks are obtained. In order to evaluate the resistance of Keccak-MAC against divide-and-conquer attacks based on cubes, we theoretically analyse the lower bounds of the complexities of divide-and-conquer attacks. It is shown that the lower bounds of the complexities are still not better than those of the conditional cube tester proposed by Senyang Huang et al.. This indicates that KeccakMAC can resist the divide-and-conquer attack better than the conditional cube tester. We hope that these techniques still could provide some new insights on the future cryptanalysis of Keccak.

关键词： Keccak-MAC Divide-and-conquer attacks Cube attacks

Differential Fault Attack on the Stream Cipher LIZARD

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Chinese Journal of Electronics 2021年第3期30卷 534-541页

作者： MA Zhen TIAN Tian QI Wenfeng National Digital Switching system engineering Technological Research Center

In this paper, we try to give a security evaluation of LIZARD stream cipher in regard to fault attacks, which, to the best of our knowledge, is the first fault analysis on LIZARD. We design a differential engine of LIZARD to track the differential trail of the keystreams. It is shown that the distributions of the keystream differences are heavily biased. Utilizing this characteristic, we propose an improved method to identify the fault location for LIZARD whose success probability approaches 1. Then we use the fault-free keystream and faulty keystreams to generate system of equations in internal state variables and solve it by SAT solver. The result shows that with 100 keystream bits, only 6 different faults are needed to recover the internal state. Finally,the comparison between LIZARD and Grain v1 shows that LIZARD is more resistable than Grain v1 in regard to fault attacks.

关键词： cryptography fault tolerant computing probability keystream differences faulty keystreams differential fault attack LIZARD stream cipher fault attacks fault analysis differential trail fault-free keystream fault location differential engine stream cipher LIZARD