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Surface Nanocrystallization of Magnesium Alloy AZ91D by High-Energy Shot Peening

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Journal of wuhan university of Technology(Materials {2.) 2009年第4期24卷 515-519页

作者：张津 school of Materials science & Engineering University of Science and Technology Beijing College of Materials science & Engineering Chongqing University of Technology

High-energy shot peening （HESP）, a method to produce severe plastic deformation by high velocity flying balls, was applied on die cast magnesium alloy AZ91D. Effects of surface nanocrystallization by HESP and heat treatment at different temperatures were investigated. The mi- crostructure evolution was conducted using X-ray diffraction （XRD） and field emission scanning electronic microscopy （FESEM）. The hardness was measured by microhardness tester. The experimental results show that surface nanocrystrallization of AZ91D obtained by HESP would lead to the increase of microhardness. Low temperature heated at 100℃ for 1 h do not change the property obviously. However, both the microstructure and microhardness vary greatly after heat treatment at 400℃ for 1 h.

关键词： AZ91 D surface nanocrystallization HESP microhardnss corrosion resistance

A PRICE-SETTING NEWSVENDOR MODEL UNDER CVAR DECISION CRITERION WITH EMERGENCY PROCUREMENT

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Journal of Systems science and Systems Engineering 2010年第1期19卷 85-104页

作者： Minghui XU school of Economics and Management,wuhan {2.,wuhan 430072.china school of Economics and Management Wuhan University Wuhan China

In this paper, we consider a newsvendor model in which a risk-averse manager faces a stochastic price-dependent demand in either an additive or a multiplicative form. An emergency purchase option is allowed after the realization of demand to satisfy the units that are short. By adopting Conditional value-at-risk （CVaR） as the decision criterion, we aim to investigate the optimal pricing and ordering decisions, and the effects of parameter changes in such a setting. We provide sufficient conditions for the uniqueness of the optimal policy for both demand models. We perforl~, comparative statics analysis to show how the optimal pricing and ordering decision behaves when changing parameters. We also compare our results with those of the newsvendor with a general utility function and with CVaR criterion under lost sales assumption. Our key results include：（i） For both demand models, the optimal selling price is decreasing in risk aversion. Hence, the optimal price of a risk-averse newsvendor is not greater than the optimal price of a risk-neutral newsvendor. （it） In contrary to the lost sales case, for the multiplicative demand model, the optimal order quantity may not be monotonic in risk aversion. Consequently, the optimal risk-averse order quantity may be lower or higher than the optimal risk- neutral counterpart. （iii） For the additive model, the optimal order quantity is strictly increasing in the emergency purchase price, while for the multiplicative model the optimal order quantity has no such a monotonic property. Some numerical examples are conducted to verify our claims and gain more insights about the risk-averse decision-making behaviors.

关键词： Newsvendor model inventory pricing risk aversion conditional value-at-risk

Capability of evolutionary cryptosystems against differential cryptanalysis

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science china(Information sciences) 2011年第10期54卷 1991-2000页

作者： ZHANG HuanGuo 1,2.,LI ChunLei 1,2.& TANG Ming 1,2.1 school of Computer,wuhan {2.,wuhan 430072.china 2.Key Laboratory of Aerospace Information Security and Trusted Computing of Ministry of Education,wuhan {2.,wuhan 430072.china 1. school of Computer Wuhan University Wuhan 430072 China2. Key Laboratory of Aerospace Information Security and Trusted Computing of Ministry of Education Wuhan University Wuhan 430072 China

The evolutionary cryptosystem is a new *** paper studies its security level resisting against differential *** is shown that the evolutionary cryptosystem possesses higher resistance than its initial fixed cryptosystem against differential *** the basis of the relationship among the data complexity,the bit advantage and the success rate of differential cryptanalysis,it is proven that more data is needed for attacking the evolutionary cryptosystem when the bit advantage and success rate are ***,it is shown that the time complexity for attacking the evolutionary cryptosystem is higher than that of differential attacking its initial fixed cryptosystem with the same amount of plaintext-ciphertext *** research indicates that the evolutionary cryptosystem is more robust than its initial fixed cryptosystem against differential cryptanalysis.

关键词： information security cryptology evolutionary cryptosystem cryptanalysis differential cryptanalysis

On the new results of global attractive set and positive invariant set of the Lorenz chaotic system and the applications to chaos control and synchronization

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science in china(Series F) 2005年第3期48卷 304-321页

作者： LIAO Xiaoxin 1, 2. 3 , FU Yuli 4 & XIE Shengli 4 1. Department of Control science & Control Engineering, Huazhong university of science & Technology, wuhan 430074, china 2. school of Automation, wuhan university of science & Technology, wuhan 4.0070, china 3. school of Information, Central South university of Economy, Politics and Law, wuhan 430064, china 4. school of Electronics & Information Engineering, South china university of Technology, Guangzhou 510640, china Correspondence should be addressed to Liao Xiaoxin (email: xiaoxin_liao@***) 1. Department of Control science & Control Engineering Huazhong University of Science & Technology 430074 Wuhan China 2. school of Automation Wuhan University of Science & Technology 430070 Wuhan China 3. school of Information Central South University of Economy Politics and Law 430064 Wuhan China 4. school of Electronics & Information Engineering South China University of Technology 510640 Guangzhou China

Constructing a family of generalized Lyapunov functions, a new method is proposed to obtain new global attractive set and positive invariant set of the Lorenz chaotic system. The method we proposed greatly simplifies the complex proofs of the two famous estimations presented by the Russian scholar Leonov. Our uniform formula can derive a series of the new estimations. Employing the idea of intersection in set theory, we extract a new Leonov formula-like estimation from the family of the estimations. With our method and the new estimation, one can confirm that there are no equilibrium, periodic solutions, almost periodic motions, wandering motions or other chaotic attractors outside the global attractive set. The Lorenz butterfly-like singular attractors are located in the global attractive set only. This result is applied to the chaos control and chaos synchronization. Some feedback control laws are obtained to guarantee that all the trajectories of the Lorenz systems track a periodic solution, or globally stabilize an unstable (or locally stable but not globally asymptotically stable) equilibrium. Further, some new global exponential chaos synchronization results are presented. Our new method and the new results are expected to be applied in real secure communication systems.

关键词： Lorenz chaotic system global attractive set positive invariant set globally exponential tracking globally exponential synchronization.

A simple lattice Boltzmann scheme for low Mach number reactive flows

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science china(Technological sciences) 2006年第6期49卷 714-726页

作者： CHEN Sheng1,2. LIU Zhaohui2. ZHANG Chao2. HE Zhu2. TIAN Zhiwei2. SHI Baochang 2.& ZHENG Chuguang2.1. Technology Center of wuhan Iron and Steel (Group) Company, wuhan 430080, {2. 2. State Key Laboratory of Coal Combustion, Hua Zhong university of science and Technology, wuhan 430074, {2. Technology Center of wuhan Iron Steel [Group] Company Wuhan 430080 China State Key Laboratory of Coal Combustion Hua Zhong University of Science Technology Wuhan 430074 China

For simulating low Mach number reactive flows, a simple and coupled lattice Boltzmann (CLB) scheme is proposed, by which the fluid density can bear significant changes. Different from the existing hybrid lattice Boltzmann (HLB) scheme and non-coupled lattice Boltzmann (NCLB) scheme, this scheme is strictly lattice Boltzmann style and the fluid density couples directly with the temperature. Because it has got rid of the constraint of traditional thought in lattice Boltzmann scheme,on the basis of the equality among the particle speed c, the time step △t and the lattice grid spacing △x held, both c and △t can be adjusted in this scheme according to a "characteristic temperature" instead of the local temperature. The whole algorithm becomes more stable and efficient besides inheriting the intrinsically outstanding strong points of conventional lattice Boltz-mann scheme. In this scheme, we also take into account different molecular weights of species, so it is more suitable for simulating actual low Mach number reactive flows than previous work. In this paper, we simulated a so-called "counter-flow" premixed propane-air flame, and the results got by our scheme are much better than that obtained by NCLB. And the more important thing is that the exploration in this work has offered a kind of brand-new train of thought for building other novel lattice Boltzmann scheme in the future.

关键词： lattice Boltzmann, low Mach number flows, reactive flows, simulation.

A hybrid matching method for geospatial services in a composition-oriented environment

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science china(Technological sciences) 2010年第S1期53卷 213-220页

作者： LUO An 1,2.WANG YanDong 1,2.& CHEN ShengHua 2.1 State Key Laboratory of Software Engineering,wuhan university,wuhan 430072.china 2.State Key Laboratory of Information Engineering in Surveying,Mapping and Remote Sensing,wuhan university,wuhan 430079,china 1. State Key Laboratory of Software Engineering Wuhan University Wuhan 430072 China 2. State Key Laboratory of Information Engineering in Surveying Mapping and Remote Sensing Wuhan University Wuhan 430079 China

With the development of Internet and GIS,large volumes of spatial data,powerful computing resources and many spatial data processing functions are published in the form of Web *** suitable geospatial services in the composition-oriented environment is a crucial *** semantic Web provides a kind of technology to find and compose various service resources automatically through the *** paper proposes a hybrid method for the semantic matching of geospatial *** method includes two *** 1 puts forward a multi-level semantic matching approach,which matches single geospatial service at four levels:classification,input/output,precondition/effect and the quality of service(QoS).This multi-level matching approach makes single service matching quicker and more *** 2.puts forward a matching algorithm for a geospatial service chain based on the *** algorithm adopts a trace algorithm,taking account of the effect of the *** restricts the input/output parameters of the current service by the input/output parameters of service chain,pre-service and *** matches the atomic service dynamically in a composition-oriented environment,and accurately converts the abstract model of geospatial services into an executable geospatial service chain.A case study of the flood analysis for the Poyang Lake illustrates the effectiveness of our context-based matching method for geospatial services.

关键词： geospatial services semantic context composition service match

Electron microscopy study of the sakhaite from endogenous borate deposit in Hunan, china

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science china Earth sciences 2004年第3期47卷 232-238页

作者： LIU Xiangwen1,2. YANG Guangming2. ZOU Huamin3, QU Jing1 & ZHAO Wenxia4 1. Graduate school, china {2. of Geosciences, wuhan 430074, china 2. Test Center, china {2. of Geosciences, wuhan 430074, china 3. Physics and Technology College, wuhan {2., wuhan 430072. china 4. Test Center, Zhongshan {2., Guangzhou 5102.5, china china Univ Geosci Grad Sch Wuhan 430074 Peoples R China china Univ Geosci Test Ctr Wuhan 430074 Peoples R China wuhan Univ Phys & Technol Coll Wuhan 430072 Peoples R China Zhongshan Univ Test Ctr Guangzhou 510275 Peoples R China

Sakhaite specimens from an endogenous borate deposit in Hunan Province, china have been studied in detail by means of transmission electron microscopy (TEM). The selected area electron diffraction (SAED) patterns obtained with different crystal zone axes show that the crystal system is cubic, with a = 1.463 nm. The convergent beam electron diffraction (CBED) patterns indicate that the point group and space group of sakhaite is m3m and Fd3m, respec-tively. The space group of synthetic sakhaite determined by Chichagov (1974) is F4132. The possible reasons why the space groups of the natural and the synthetic sakhaites are different are discussed.

关键词： sakhaite, space group, convergent beam electron diffraction (CBED).

Sandwich Magnetoelectric Composites of Polyvinylidene Fluoride,Tb-Dy-Fe Alloy,and Lead Zireonate Titanate

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Journal of wuhan university of Technology(Materials {2.) 2007年第4期22卷 596-599页

作者：赵广辉熊传溪 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing school of Computer science and Technology Wuhan University of TechnologyWuhan 430070China school of Materials science and Engineering Wuhan University of TechnologyWuhan 430070China

The novel sandwich composites were prepared by sandwiching a polyvinylidene fluoride/Tb- Dy-Fe alloy composite （PVDF/Terfenol-D） between polyvinylidene fluoride/lead zirconate titanate composites （PVDF/PZT）. The maximum magnetoelectric effect voltage coefficient, （dE/dn）33max, of the sandwich composites is higher than that of three-phase composites at their own optimal loading level of Terfenol-D. This is attributed to less interface relaxations of strain and better polarization of the sandwich composites. When the volume fraction of Terfenol-D is higher than 0.10, no coupling interaction for three-phase composites could be observed, but （dE/dn）33max of sandwiched composites still reached 2. mV/（***）. At high magnetic field intensity, the magnetoelectric effect voltage coefficient, （dE/dn）33, of sandwich composites is higher than that of three-phase composites; at low magnetic field intensity, （dE/dn）33 of sandwich composites is lower than that of three-phase composites. At their resonance frequency, the （dE/dn）33max of the sandwich composites and the three phase composites are 150 mV/（***） and 42.mV/（cmoOe）, respectively. This significant increase of （dE/ dn）33max at resonance frequency confirms the improvement of maximum magnetoelectric effect coefficient via sandwich-structured composites.

关键词： magnetoelectric piezoelectric sandwiched composites

Photocatalytic Degradation of Rhodamine B Dye with High Purity Anatase Nano-TiO_2.Synthesized by a Hydrothermal Method

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Journal of wuhan university of Technology(Materials {2.) 2011年第4期26卷 600-605页

作者：史晓亮 school of Mechanical and Electronic Engineering Wuhan University of Technology State Key Laboratory of Advanced Technology for Materials Synthesis & Processing Wuhan University of Technology

High purity anatase nano-TiO2.powders with high photocatalytic activity were prepared by a hydrothermal synthesis method. X-ray diffraction （XRD）, field emission transmission electron microscopy （FETEM）, ultraviolet-visible （UV-Vis） light absorption spectrum and photoluminescence （PL） spectrum were adopted to characterize the catalyst. Effects of temperature, time and sol concentration of hydrothermal synthesis on particle size and phases were investigated. Photocatalytic activities in the degradation of Rhodamine B Dye were studied. The experimental results indicated that photocatalytic activity of the nano-TiO2.powers was much higher than that of P2. （Degussa）.

关键词： TiO2 hydrothermal synthesis photocatalytic activity high purity anatase