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Novel Video Steganography Algorithm Based on Secret Sharing and Error-Correcting Code for H.264/AVC

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Tsinghua Science and Technology 2017年第2期22卷 198-209页

作者： Yingnan Zhang Minqing Zhang Xiaoyuan Yang Duntao Guo longfei liu Key Laboratory of Network & Information Security of PAP Engineering College of PAPXi’an 710086China

In this paper, we analyze the video steganography technique, which is used to ensure national security and the confidentiality of the information of governmental agencies and enterprises. Videos may be used to transmit secrets and conduct covert communication. As such, we present an algorithm based on a secret sharing scheme and an Error-Correcting Code（ECC）, which combines Grey Relational Analysis（GRA） with a partition mode in video compression standard H.264/AVC. First, we process secret information by secret sharing, and then use an ECC to process the obtained information. Moreover, we choose the Discrete Cosine Transform（DCT） blocks using GRA, and then use rules to hide the pretreated information in DCT coefficients of the video frames. Experimental results indicate that our algorithm has good invisibility, better robustness, good anti-steganalysis ability, and little influence on the bit rate of the video carrier. In addition, the bit error rate is low after attacks such as noise, filtering,or frame loss in the simulation environment.

关键词： steganography video secret sharing error-correcting code robustness grey relational analysis partition mode

New Identity Based Proxy Re-Encryption Scheme from Lattices

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China Communications 2019年第10期16卷 174-190页

作者： Liqiang Wu Xiaoyuan Yang Minqing Zhang longfei liu Key Lab of Network and Information Security Engineering University of Chinese Armed Police ForceXi’an 710086China Key Lab of Computer Network and Information Security Xi Dian UniversityXi’an 710071China

Identity-Based Proxy Re-Encryption (IB-PRE) allows a semi-trusted proxy to convert the ciphertext encrypted under Alice’s identity into Bob’s ciphertext of the same message without leaking plaintext. Lattice-based cryptography enjoys potential resistance to quantum analysis and low computational complexity. A multi-hop and unidirectional IB-PRE from lattices is presented. We split the functions of decryption and ciphertext transformation separately, and design the double private keys mechanism, where two keys are generated for each user, one key is used to decrypt the ciphertext by Pre-Image Sampling technique, and the other is used to generate the re-encryption key by Bonsai Trees technique. The generation of the re-encryption key is non-interactive and collusion resistant. Moreover, its IND-sID-CPA security over the decisional Learning With Errors (LWE) assumption under the standard model is proved. Compared with some previous IBPRE schemes from Bilinear Pairings, the format of transformed ciphertext in our scheme remains unchanged, furthermore, it can also resist quantum analysis. Compared with some existing IB-PRE schemes from lattices with similar properties, the space of the message in our scheme is a vector of length l and the encryption process remains a lower encryption blowup factor. At last, a proof-of-concept implementation is provided.

关键词： IB-PRE lattices bonsai trees collusion resistance

Comparison of shear banding in BMGs due to thermal-softening and free volume creation

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Science China(Physics,Mechanics & Astronomy) 2008年第9期51卷 1367-1379页

作者： liu longfei DAI LanHong BAI YiLong KE FuJiu Hunan Provincial Key Laboratory of Health Maintenance for Mechanical Equipment Hunan University of Science and TechnologyXiangtan 411201China State Key Laboratory of Nonlinear Mechanics(LNM) Institute of MechanicsChinese Academy of Sci-encesBeijing 100190China Department of Applied Physics Beijing University of Aeronautics and AstronauticsBeijing 100088China

This paper reports a comparative study of shear banding in BMGs resulting from thermal softening and free volume creation. Firstly,the effects of thermal softening and free volume creation on shear instability are discussed. It is known that ther-mal softening governs thermal shear banding,hence it is essentially energy related. However,compound free volume creation is the key factor to the other instability,though void-induced softening seems to be the counterpart of thermal softening. So,the driving force for shear instability owing to free volume creation is very dif-ferent from the thermally assisted one. In particular,long wave perturbations are always unstable owing to compound free volume creation. Therefore,the shear instability resulting from coupled compound free volume creation and thermal softening may start more like that due to free volume creation. Also,the compound free volume creation implies a specific and intrinsic characteristic growth time of shear instability. Finally,the mature shear band width is governed by the corre-sponding diffusions (thermal or void diffusion) within the band. As a rough guide,the dimensionless numbers: Thermal softening related number B,Deborah number (denoting the relation of instability growth rate owing to compound free volume and loading time) and Lewis number (denoting the competition of different diffusions) show us their relative importance of thermal softening and free volume creation in shear banding. All these results are of particular significance in understanding the mechanism of shear banding in bulk metallic glasses (BMGs).

关键词： metallic glasses shear bands diffusion instability

Effect of Ti（lll） Surface Defects on the Process of Photocatalytic Reduction of Hexavalent Chromium

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Chinese Journal of Chemistry 2017年第2期35卷 203-208页

作者： Hongxia Qin Yingying Bian Yaxi Zhang longfei liu Zhenfeng Bian Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials Shanghai Normal University Shanghai 200234 China

In this paper, the process of photocatalytic reduction of hexavalent chromium was investigated over Ti3＋- modified TiO2 photocatalysts. The Ti3＋ surface defects were repaired by annealing as-prepared sample at different temperatures to control the amount of Ti3＋ sites. The samples were characterized by SEM, XRD, BET, UV-Vis absorption, EPR and XPS. The results showed Ti3＋ defects were successfully doped in TiO2. The surface selective adsorption of hexavalent chromium [Cr2072 （Cr（VI））] and the desorption of trivalent chromium [Cr3＋（Cr（III））] were investigated during the process ofphotocatalytic reduction positive charges due to more Ti3＋ defects on the surface show a Accordingly, the surface positive reduction of Cr（VI）. charges controlled by the Ti3＋ Zeta potential results presented that the increased significant improvement for adsorption of Cr（VI）. defects play important roles in the photocatalytic

关键词： Ti3+ modification titanium dioxide photocatalytic reduction hexavalent chromium surface selective adsorption and desorption

High speed cutting of AZ31 magnesium alloy

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Journal of Magnesium and Alloys 2016年第2期4卷 128-134页

作者： Liwei Lu Shaohua Hu longfei liu Zhenru Yin College of Mechanical and Electrical Engineering Hunan University of Science and TechnologyXiangtan 411201HunanChina School of Materials Science and Engineering Central South UniversityChangsha 410083HunanChina

Using LBR-370 numerical control lathe,high speed cutting was applied to AZ31 magnesium *** influence of cutting parameters on microstructure,surface roughness and machining hardening were investigated by using the methods of single factor and orthogonal *** results show that the cutting parameters have an important effect on microstructure,surface roughness and machine *** depth of stress layer,roughness and hardening present a declining tendency with the increase of the cutting speed and also increase with the augment of the cutting depth and feed ***,we established a prediction model of the roughness,which has an important guidance on actual machining process of magnesium alloy.

关键词： AZ31 magnesium alloy High speed cutting Cutting parameters Hardening Roughness Stress lay

Degassing effect of ultrasonic vibration in molten melt and semi-solid slurry of Al-Si alloys

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China Foundry 2012年第3期9卷 201-206页

作者： Wu Shusen liu longfei Ma Qianqian Mao Youwu An Ping State Key Lab.of Materials Processing and Die&Mould Technology Huazhong University of Science and TechnologyWuhan 430074China

In the process of semi-solid slurry preparation with direct ultrasonic vibration (UV) by dipping the horn into the melt, one of the questions is whether the gas content in the melt would be increased or not by the cavitation effect of ultrasonic vibration. By application of quantitative gas content measurement technique, this paper investigated the effect of the ultrasonic vibration on the gas content of both the melt and the semi-solid slurry of Al-Si alloys, and the variations of the gas contents in two kinds of aluminum alloys, i.e., A356 alloy and Al-20Si-2Cu-1Ni-0.6RE alloy (Al-20Si for short). The results show that ultrasonic vibration has an obvious degassing effect on the molten melt, especially on the semi-solid slurry of Al-Si alloy which is below the liquidus temperature by less than 20 ℃. The ultrasonic degassing efficiency of the A356 alloy decreases with the reduction of the initial gas content in the melt, and it is nearly unchanged for the Al-20Si alloy. The gas content of both alloys decreases when the ultrasonic vibration time is increased. The best vibration time for Al-20Si alloy at the liquid temperature of 710 ℃ and semi-solid temperature of 680 ℃ is 60 s and 90 s, respectively; and the degassing efficiency is 48% and 35%, respectively. The mechanism of ultrasonic degassing effect is discussed.

关键词： ultrasonic vibration semi-solid slurry aluminum alloy gas content degassing

Hot Compression Mechanical Behavior of Solution Heat‑Treated and Pre‑aged Mg–Zn–Gd–Er Alloys

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Acta Metallurgica Sinica(English Letters) 2023年第3期36卷 469-485页

作者： Bo Che Liwei Lu longfei liu Yan Yang Wei Kang Jun Luo Zhiqiang Wu Yongfeng Qiu School of Materials Science and Engineering Hunan University of Science and TechnologyXiangtan 411201China College of Materials Science and Engineering Chongqing UniversityChongqing 400044China Hunan Provincial Key Laboratory of Vehicle Power and Transmission System Hunan Institute of EngineeringXiangtan 411104China Guiyang Aluminum Magnesium Design&Research Institute Co. LtdGuiyang 550081China School of Automation Central South UniversityChangsha 410083China

The mechanical behavior of solution heat-treated and pre-aged Mg–6Zn–1Gd–1Er alloys during hot compression(from 180 to 330℃)has been *** results showed that the flow stress curves of the pre-aged sample(PAS)intersected with that of the solution heat-treated sample(SHTS)during hot *** 180℃,when the true strain is 0.27 and 0.47,the PAS showed larger and smaller stress(210.80 MPa vs.207.58 MPa and 205.67 MPa vs.207.93 MPa)than the SHTS,*** phenomena were due to the stronger interaction of W phase and dislocations/twins under the strain of 0.27,while dynamic recrystallization softening occurred under the strain of *** the temperature increased to 330℃,the flow stress of PAS and SHTS showed an opposite trend to that of 180℃.Continuous dynamic recrystallization and particle stimulated nucleation based on slip operations are the main deformation mechanisms under 330℃.At the true strain is 0.33 and 0.53,the PAS has smaller and larger stress(61.32 MPa vs.63.69 MPa and 58.75 MPa vs.57.09 MPa)than the SHTS,*** increasing deformation resistance of dynamic precipitation improved the flow stress under smaller strain and dynamic recrystallization decreased the flow stress under high strain,which resulted the opposite phenomena of SHTS.

关键词： Mg-6Zn-1Gd-1Er alloy Mechanical behavior Precipitates Twin Dynamic recrystallization

Review on loss prevention of chemical reaction thermal runaway:Principles and application

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Emergency Management Science and Technology 2022年第1期2卷 81-88页

作者： Qiang Chen Jianshen Wang Mengjia Gao longfei liu Junjun Tao School of Materials Engineering Changshu Institute of TechnologyChangshu 215500China Suzhou Institute of Emergency Technology and Management Changshu 215500China

Reaction thermal runaway has been extensively characterized as a major hazard for fine chemical *** is necessary to develop safety technologies for the control of reaction thermal runaway in emergencies and mitigating the subsequent *** date,literature review on the loss prevention methods of chemical reaction thermal runaway is *** this paper,a comprehensive review is delivered to outline the progress of emergency response technologies for reaction thermal runaway in recent years,major principles and potential applications of those loss prevention *** is expected that this review article has certain reference value for the further understanding of thermal runaway,the design of mitigation systems,and the formulation of emergency response strategy for runaway reactions.

关键词： prevention chemical formulation

Surgical treatment of large pheochromocytoma(>6 cm):A 10-year single-center experience

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Asian Journal of Urology 2022年第3期9卷 294-300页

作者： Liang Zhang Danlei Chen Yingxian Pang Xiao Guan Xiaowen Xu Cikui Wang Qiao Xiao longfei liu Department of Urology Xiangya HospitalCentral South UniversityChangshaChina National Clinical Research Center for Geriatric Disorders Xiangya HospitalCentral South UniversityChangshaChina

Objective:Clinical practice guidelines recommend open adrenalectomy(OA)for large pheochromocytoma(LPCC)>6 cm in *** laparoscopic adrenalectomy(LA)for the treatment of LPCC has been reported,its role remains *** study aimed to compare the effectiveness of LA and OA,and summary the surgical treatment ***:Data concerning LPCC,from January 2010 to June 2019 of a single institution,were retrospectively *** 82 patients with a tumor larger than 6 cm were included(52 patients in LA group and 30 patients in OA group).Groups were balanced by propensity score matching(PSM)into 15 ***’demographics,preoperative characteristics,and prognosis were ***:Before PSM,the OA group had larger tumor sizes(median[interquartile range,IQR]:8.9[7.3-10.3]vs.7.2[6.7-8.0]cm;p=0.000)and higher vanillylmandelic acid level(median[IQR]:114.3[67.8-326.4]vs.66.6[37.8-145.8]μmol/24 h;p=0.004)and needed a higher cumulative dose of prazosin(median[IQR]:83.5[37.0-154.0]vs.38.0[21.0-81.0]mg;p=0.028).After PSM,the baseline data showed no significant differences between both *** LA group had relatively more stable blood pressure in surgery,with a lower fluctuation of systolic blood pressure(mean±standard deviation[SD]:70.9±25.1 vs.107.4±46.2 mmHg,p=0.012)and a lower percentage of hemodynamic instability(46.7%vs.86.7%,p=0.020).The LA group had shorter postoperative hospital stays(mean±SD:6.4±2.7 vs.10.1±3.4 days;p=0.003)than the OA *** regarding metastasis rate(6.7%vs.0,p=1.000)were not statistically significant between LA and OA *** median(IQR)follow-up time of 82 patients was 72.5(47.0-103.5)*** logistic regression showed that right-side tumors or those>8 cm in size were independent risk factors of ***:LA is a safe,minimally invasive procedure for LPCC and has relatively better perioperative characteristics in large medical *** with tumors on the right side or larger than 8

关键词： Pheochromocytoma Laparoscopic adrenalectomy Open adrenalectomy Surgery Treatment