Investigation of improved approaches to bayes risk decoding

Bayes risk (BR) decoding methods have been widely investigated in the speech recognition area due to its flexibility and complexity compared with the maximum a posteriori (MAP) method regarding to minimum word error (MWE) optimization. This paper investigates two improved approaches to the BR decoding, aiming at minimizing word error. The novelty of the proposed methods is shown in the explicit optimization of the objective function, the value of which is calculated by an improved forward algorithm on the lattice. However, the result of the first method is obtained by an expectation maximization (EM) like iteration, while the result of the second one is achieved by traversing the confusion network (CN), both of which lead to an optimized objective function value with distinct approaches. Experimental results indicate that the proposed methods result in an error reduction for lattice rescoring, compared with the traditional CN method for lattice rescoring.     

Identity-based key-insulated proxy signature without random oracles

In an identity based proxy signature (IBPS) scheme, a designated proxy signer can generate the signature on behalf of an original signer. Traditional IBPS schemes normally rely on the assumption that private keys are kept perfectly secure. However, due to viruses, worms or other break-ins allowed by operating-system holes, key exposure seems inevitable. To minimize the damage caused by key exposure in IBPS, we propose an identity-based key-insulated proxy signature (IBKIPS) scheme in the standard model, i.e. without random oracles.     

Properties and electronic structure of iron under pressure up to 30GPa

The properties and electronic structure of Fe under pressures of 0–30GPa have been studied by first principles employing the density functional theory (DFT), the ultra-soft pseudo-potentials (USPP) and the generalized gradient approximation (GGA). The calculating results show that there is a structural transition from magnetic body-centered cubic (bcc) to nonmagnetic hexagonal-close-packed (hcp) structure for Fe around 11GPa pressure. There is a pseudogap both in the density of states (DOS) for bcc and hcp Fe. The pseudogap of bcc Fe is deeper and wider than that of hcp Fe. The elastic modulus is obtained by Voigt-Reuss-Hill averaging scheme. The results indicate that the elastic properties of bcc Fe enhance with pressure except for elastic stiffness constant C ₁₁, shear modulus G and elastic modulus E at the transition pressure, while the elastic properties of hcp Fe increase linearly with pressure. Magnetic bcc Fe is ductile, and hcp Fe becomes ductile from brittle around 25GPa.     

Threshold signature scheme with threshold verification based on multivariate linear polynomial

Secret sharing schemes are multi-party protocols related to key establishment. They also facilitate distributed trust or shared control for critical activities (e.g., signing corporate cheques and opening bank vaults), by gating the critical action on cooperation from t(t ∈ Z ⁺) of n(n ∈ Z ⁺) users. A (t, n) threshold scheme (t < n) is a method by which a trusted party computes secret shares Γ _i (1 ⩽ i ⩽ n) from an initial secret Γ ₀ and securely distributes Γ _i to user. Any t or more users who pool their shares may easily recover Γ ₀, but any group knowing only t−1 or fewer shares may not. By the ElGamal public key cryptophytes and the Schnorr’s signature scheme, this paper proposes a new (t, n) threshold signature scheme with (k,m) (k,m ∈ Z ⁺) threshold verification based on the multivariate linear polynomial.     

梁柱式支架法在客运专线高墩连续梁施工中的应用

结合广深港客运专线铁路水田特大桥（40＋64＋40）m高墩连续梁现浇施工,介绍跨路高墩梁柱式支架的设计与施工。该桥梁主墩高31 m,跨越繁忙的石观公路及河流,受地形条件限制,在跨路、跨河处支架采用19.46 m和19.23 m跨径的加强型贝雷梁式支架,贝雷支架上部搭设碗扣支架以满足箱梁变截面要求,下部结构采用钢管支墩、钢筋砼扩大基础,距离河岸边仅3.5 m的扩大基础采用河床堆载反压的方式增强地基承载力,顺利完成了现浇桥梁浇筑,为解决跨路、跨河支架搭设难题积累了经验。     

Security analysis of application layer protocols on wireless local area networks

This paper aims at analyzing the security issues that lie in the application layer (AL) protocols when users connect to the Internet via a wireless local area network (WLAN) through an access point. When adversaries launch deauthentication flood attacks cutting users’ connection, the connection managers will automatically research the last access point’s extended service set identifier (ESSID) and then re-establish connection. However, such re-connection can lead the users to a fake access point with the same ESSID set by attackers. As the attackers hide behind users’ access points, they can pass AL’s authentication and security schemes, e.g. secure socket layer (SSL). We have proved that they can even spy on users’ account details, passwords, data and privacy.     

Effect of rotation speed on temperature field and axial shortening of inertia friction welded GH4169 joints by numerical simulation

A 2D finite element model was established for inertia friction welding of GH4169 nickel-base superalloy based on the ABAQUS environment. The remeshing and map solution techniques were adopted to solve the problem of element distortion. The effect of rotation speed on the temperature field and axial shortening of joints was investigated. The results show that the interface temperature increases rapidly to higher than 900°C within 1 s. And then, it increases slowly to a quasi-stable value. The axial shortening begins to augment quickly when a uniform interface temperature field has formed and the plasticized material is extruded from the interface to form an obvious flash. The rotation speed of the flywheel controls the welding process and has a significant influence on the temperature evolution and axial shortening of joints.     

Numerical simulation of defect inspection using electromagnetically stimulated thermography

The feasibility of electromagnetically stimulated thermography non-destructive testing (NDT) for the detection of defects in metallic conductive materials has been carried out by finite element analysis. Aluminum plates with defects of different diameters, depths, locations, shapes and orientation with respect to eddy current are numerically investigated. ANSYS software is used to solve the coupled electromagnetic and temperature field equations. The peak temperatures on the top surface of circular defects with different diameters and depths are calculated at varying excitation frequencies. It is demonstrated that the obtained temperature inreases with increase of the defect diameter and decrease of its depth. The dependence of the temperature over the top surface of the defect on its location and orientation is also presented. The results indicate that we can detect the subsurface defect and estimate its depth and location by choosing a suitable coil-specimen configuration.     

Modeling on directional solidification of solar cell grade multicrystalline silicon ingot casting

Solar energy is considered as one of the best alternative energy in the future. Multicrystalline silicon ingot casting is the main production process for major supply of solar cell. However, the casting process cannot be understood clearly because of some difficulties, such as enclosed furnace, long cycle time of production and so on. In this paper, an integrated model, including casting process analysis, quality prediction and production parameters optimization, is proposed and the preliminary results are acquired. The framework of the proposed model is introduced and the numerical simulation results on the temperature field and grain growth process are also given out and discussed.     

Effect of remelting current on molten pool profile of titanium alloy ingot during vacuum arc remelting process

The performance of vacuum arc remelting (VAR) ingot depends largely on ingot structure and chemical uniformity, which are strongly influenced by molten pool profile that is influenced by VAR process. To better understand the effect of remelting current on molten pool profile of titanium alloy ingot during VAR process, a 3D finite element model is developed by the ANSYS software. The results show that there are three remelting stages during VAR process when the remelting current is 2.0 kA. The molten pool depth increases gradually from 30 to 320 s, then the change of molten pool depth is very small during the steady state stage from 320 to 386 s, and lastly the molten pool depth becomes shallow after 386 s. The melting rate and temperature of superheat increase with the remelting current increasing, which leads to the augment of molten pool volume. In the end, the total remelting time and steady state molten pool time decrease with the melting current from 1.6 to 2.8 kA.