Xie and Yu (2005) proposed a group signature scheme and claimed that it is the most efficient group signature scheme so far and secure. In this paper, we show that two dishonest group members can collude to launch two attacks on the scheme. In the first attack they can derive the group secret key and then generate untraceable group signatures. In the second attack, they can impersonate other group members once they see their signatures. Therefore we conclude that the signature scheme is not secure. We show that some parameters should be carefully selected in the scheme to resist our attacks.

Substantially long round trip time (RTT) in space channel hurts TCP interactions between the sending and receiving ends, and limits the usefulness and effectiveness of TCP feedback. Space Communication Protocol Standards-Transport Protocol (SCPS-TP) is a Transmission Control Protocol (TCP) enhancement method aimed at improving its performance in space and interplanetary Internet and is expected to have capability of being feasible applied to experimental evaluation of the effectiveness of SCPS-TP in coping with long channel delay. This paper presents an experimental evaluation of channel delay impact on throughput performance of SCPS-TP over LEO/GEO-stationary space links using a test-bed, compared with the widely deployed TCP.

A more recent branch of natural computing is DNA computing. At the theoretical level, DNA computing is powerful. This is due to the fact that DNA structure and processing suggest a series of new data structures and operations, and to the fact of the massive parallelism. The insertion-deletion system (insdel system) is a DNA computing model based on two genetic operations: insertion and deletion which, working together, are very powerful, leading to characterizations of recursively enumerable languages. When designing an insdel computer, it is natural to try to keep the underlying model as simple as possible. One idea is to use either only insertion operations or only deletion operations. By helping with a weak coding and a morphism, the family ?? is equal to the family of recursively enumerable languages. It is an open problem proposed by Martin-Vide et al. on whether or not the parameters 4 and 7 appearing here can be replaced by smaller numbers. In this paper, our positive answer to this question is that ?? can also play the same role as insertion and deletion. We suppose that the ?? may be the least only-insertion insdel system in this situation. We will give some reasons supporting this conjecture in our paper.

In cutting tool temperature experiment, a large number of related data could be available. In order to define the relationship among the experiment data, the nonlinear regressive curve of cutting tool temperature must be constructed based on the data. This paper proposes the Particle Swarm Optimization (PSO) algorithm for estimating the parameters such a curve. The PSO algorithm is an evolutional method based on a very simple concept. Comparison of PSO results with those of GA and LS methods showed that the PSO algorithm is more effective for estimating the parameters of the above curve.

Multi-source multi-class classification methods based on multi-class Support Vector Machines and data fusion strategies are proposed in this paper. The centralized and distributed fusion schemes are applied to combine information from several data sources. In the centralized scheme, all information from several data sources is centralized to construct an input space. Then a multi-class Support Vector Machine classifier is trained. In the distributed schemes, the individual data sources are processed separately and modelled by using the multi-class Support Vector Machine. Then new data fusion strategies are proposed to combine the information from the individual multi-class Support Vector Machine models. Our proposed fusion strategies take into account that an Support Vector Machine (SVM) classifier achieves classification by finding the optimal classification hyperplane with maximal margin. The proposed methods are applied for fault diagnosis of a diesel engine. The experimental results showed that almost all the proposed approaches can largely improve the diagnostic accuracy. The robustness of diagnosis is also improved because of the implementation of data fusion strategies. The proposed methods can also be applied in other fields.

In the environment of customization, disturbances such as rush orders and material shortages often occur in the manufacturing system, so rescheduling is necessary for the manufacturing system. The rescheduling methodology should be able to dispose of the disturbance efficiently so as to keep production going smoothly. This aims researching flow shop rescheduling problem (FSRP) necessitated by rush orders. Disjunctive graph is employed to demonstrate the FSRP. For a flow shop processing n jobs, after the original schedule has been made, and z out of n jobs have been processed in the flow shop, x rush orders come, so the original n jobs together with x rush orders should be rescheduled immediately so that the rush orders would be processed in the shortest time and the original jobs could be processed subject to some optimized criteria. The weighted mean flow time of both original jobs and rush orders is used as objective function. The weight for rush orders is much bigger than that of the original jobs, so the rush orders should be processed early in the new schedule. The ant colony optimization (ACO) algorithm used to solve the rescheduling problem has a weakness in that the search may fall into a local optimum. Mutation operation is employed to enhance the ACO performance. Numerical experiments demonstrated that the proposed algorithm has high computation repeatability and efficiency.

This article is aimed at describing a hybrid scheme for English to Bangla translation. The translated output in English scripts is useful for learning Bengali language. This is a significant contribution to Human Language Technology generation also. About two hundred million people in West Bengal and Tripura (two states in India) and in Bangladesh (a country whose people speak and write Bangla as their first language). This proposed translator would benefit Bengalee society because rural people are not usually very conversant with English. The English to Bangla Translator is being enhanced. This system (English- Bangla-ANUBAD or EB-ANUBAD) takes a paragraph of English sentences as input sentences and produces equivalent Bangla sentences. EB-ANUBAD system is comprised of a preprocessor, morphological parser, semantic parser using English word ontology for context disambiguation, an electronic lexicon associated with grammatical information and a discourse processor, and also uses a lexical disambiguation analyzer. This system does not rely on a stochastic approach. Rather, it is based on a special kind of hybrid architecture of transformer and rule-based Natural Language Engineering (NLE) architectures along with various linguistic knowledge components of both English and Bangla.

The clock generator and OOK modulator for RFID (Radio Frequency Identification) presented in this paper consist of a current source and delay elements. The simple constant-gm structure is adopted in the current source design and the current consumption of the current source is only about 2 μA. The delay elements, the clock generator and OOK modulator are introduced in detail in the paper. The designed circuits are fabricated by 0.6 μm CMOS process. The area of the core circuit is only about 400 μm×80 μm. The delay time of all three samples is in the range of 9 μs to 21 μs when the supply voltage varies from 2 V to 4 V. As the measured results satisfy the system requirements, these circuit structures are suitable for RFID application.

In this paper, we are interested in the following general question: Given a module M which has finite hollow dimension and which has a finite collection of submodules K_i (1≤i≤n) such that M=K₁+...+K_n, can we find an expression for the hollow dimension of M in terms of hollow dimensions of modules built up in some way from K₁,...,K_n? We prove the following theorem: Let M be an amply supplemented module having finite hollow dimension and let K_i (1≤i≤n) be a finite collection of submodules of M such that M=K₁+...+K_n. Then the hollow dimension h(M) of M is the sum of the hollow dimensions of K_i (1≤i≤n) if and only if K_i is a supplement of K₁+...+K_i−1+K_i+1+...+K_n in M for each 1≤i≤n.

Constant solutions to Yang-Baxter equation are investigated over Grassmann algebra for the case of 6-vertex R-matrix. The general classification of all possible solutions over Grassmann algebra and particular cases with 2,3,4 generators are studied. As distinct from the standard case, when R-matrix over number field can have a maximum 5 nonvanishing elements, we obtain over Grassmann algebra a set of new full 6-vertex solutions. The solutions leading to regular R-matrices which appear in weak Hopf algebras are considered.

Bipolar plates for proton exchange membrane fuel cell (PEMFC) where polymer is used as binder and graphite is used as electric filler were prepared by means of compression molding technology. Study on the effects of graphite particle size and shape on the bipolar plate performance, such as electrical conductivity, strength, etc. showed that with decrease of graphite particle size, bulk electrical conductivity and thermometric conductivity decreased, but that flexural strength was enhanced. After spherical graphite occurrence in flake-like form, the flexural strength of the bipolar plate was enhanced, electrical conductivity increased but thermal conductivity decreased in direction paralleling pressure direction, and both electrical conductivity and thermometric conductivity reduced in direction perpendicular to pressure direction.

Proton exchange membrane generation technology is highly efficient, clean and considered as the most hopeful “green” power technology. The operating principles of proton exchange membrane fuel cell (PEMFC) system involve thermodynamics, electrochemistry, hydrodynamics and mass transfer theory, which comprise a complex nonlinear system, for which it is difficult to establish a mathematical model and control online. This paper first simply analyzes the characters of the PEMFC; and then uses the approach and self-study ability of artificial neural networks to build the model of the nonlinear system, and uses the adaptive neural-networks fuzzy infer system (ANFIS) to build the temperature model of PEMFC which is used as the reference model of the control system, and adjusts the model parameters to control it online. The model and control are implemented in SIMULINK environment. Simulation results showed that the test data and model agreed well, so it will be very useful for optimal and real-time control of PEMFC system.

If an external point charge and the movable charges of an isolated quantum-dot cellular automata (QCA) cell have the same polarity, the point charge greatly affects the polarization (P) of the cell only when it is in a narrow band with periodically changing width. The center of the band is on a radius R circle. The ratio of R to the electric charge (q) is a constant determined by the parameters of the cell. A QCA cell can be used as charge detector based on the above phenomenon.

This investigation and morphology analysis of porous structure of some kinds of natural materials such as chicken eggshell, partridge eggshell, pig bone, and seeds of mung bean, soja, ginkgo, lotus seed, as well as the epidermis of apples, with SEM (Scanning Electronic Microscope) showed that natural structures’ pores can be classified into uniform pores, gradient pores and multi pores from the viewpoint of the distribution variation of pore density, size and geometry. Furthermore, an optimal design of porous bearings was for the first time developed based on the gradient configuration of natural materials. The bionic design of porous structures is predicted to be widely developed and applied in the fields of materials and mechanical engineering in the future.

A wastewater evaporation-desalination pretreatment method was introduced to remove the Na⁺ and K⁺ salts in volatile organic compounds (VOCs) wastewater before it was fed into the incinerator. VOCs in the wastewater were volatilized in the evaporation system and then the vapor was combusted in an incinerator. Simulated phenol wastewater containing sodium chloride was evaporated and concentrated and sodium chloride was crystallized in different parameters. The experimental results showed that the higher initial concentration of sodium chloride increases the ratio of volatilization of VOCs, which was due to the effect of “salting out” (^{a decrease in the solubility of the nonelectrolyte in the solution, or more rigorously, an increase in its activity coefficient, caused by the salt addition (Furter and Cook, 1967)}). When evaporation speed was increased from 1.67 ml/min to 2.73 ml/min, the total removal coefficient of sodium chloride was about 99.88%~99.99%. This pretreatment procedure eliminates the slag phenomenon caused by Na⁺ and K⁺ salts during wastewater incineration, so the incinerator could operate continuously, and the wastewater evaporation could increase the heat value of wastewater, and the operation cost would be reduced.

This paper reports results of the authors’ studies on the virtual design method used in the development of low noise intake system of I.C. engine. The resulting high pass-by noise at level above the legislative target at full throttle when engine speed was around 5200 r/min necessitated a BEM-aided redesign task, following the typical process of design and development of an intake system. During the initial design, based on the acoustic theory and the requirements (1. The air flux of the redesigned should equal to or exceed the value of the original flux; 2. The filtering area must not be degraded), and considering the constraint of space in the engine compartment, total volume and rough internal dimensions were determined. During the detailed design, the exact internal dimensions of the air cleaner were determined, and an effective method was applied to improve the acoustic performance at low frequency. The predicted sound power of the intake system indicated that the objective of reducing the overall engine noise by minimizing intake system noise was achieved.

The cleaning parameters affecting cleaning rate using pure waterjets to clean road surface was researched. A mathematical model for predicting cleaning rate was established using fuzzy mathematical method. A fuzzy rule base characterizing the relationship between input and output parameters was built through experiments. The prediction of cleaning rate was achieved under the condition of given input parameters by rule-based fuzzy reasoning. The prediction results were analyzed through experimental verification.

Donnell’s thin shell theory and basic equations based on the wave propagation method discussed in detail here, is used to investigate the natural frequencies of thin finite length circular cylindrical shells under various boundary conditions. Mode shapes are drawn to explain the circumferential mode number n and axial mode number m, and the natural frequencies are calculated numerically and compared with those of FEM (finite element method) to confirm the reliability of the analytical solution. The effects of relevant parameters on natural frequencies are discussed thoroughly. It is shown that for long thin shells the method is simple, accurate and effective.

To investigate the influence of coherent structures in the gas-particle wake flow, direct numerical simulation (DNS) method was adopted to compute a two-dimensional particle laden wake flow. A high accuracy spectral element method (SEM) was employed to simulate the gas flow field and a Lagrangian approach was used to compute the particles movement. Numerical results showed that at the same Stokes numbers, particles would be greatly impacted by the development of the coherent structure. But with different Stokes numbers, it can be seen that the large-scale vortex structures would influence the particle flow differently. While under different Reynolds numbers (150 and 200), there are no great changes in the particle laden flow.

This paper reports results of investigations of some surface characteristics, and resulting performance of parts processed using non-traditional finishing methods. The friction factor, precision keeping and anti-conglutination performance of the finished surfaces are considered, and surface characteristics such as microtopography and machining texture were investigated. The overall performance of surfaces finished using non-traditional finishing methods was found to be significantly better than that of traditional finishing methods.

It is important to segment image correctly to extract guidance information for automatic agriculture vehicle. If we can make the computer know where the crops are, we can extract the guidance line easily. Images were divided into some rectangle small windows, then a pair of 1-D arrays was constructed in each small windows. The correlation coefficients of every small window constructed the features to segment images. The results showed that correlation analysis is a potential approach for processing complex farmland for guidance system, and more correlation analysis methods must be researched.

A bi-harmonic potential function was constructed in this study. Love solution was employed to obtain analytical solutions of uniformly loaded plates with two different types of clamped edges. The treatment of clamped boundary conditions was the same as that adopted by Timoshenko and Goodier (1970). The analytical solution for the first type of clamped boundary condition is identical with that obtained by Luo et al.(2004), and the solutions for both types were compared with the FEM results and the calculations of thin plate theory.

This paper presents a comparison among Adomian decomposition method (ADM), Wavelet-Galerkin method (WGM), the fully explicit (1,7) finite difference technique (FTCS), the fully implicit (7,1) finite difference method (BTCS), (7,7) Crank-Nicholson type finite difference formula (C-N), the fully explicit method (1,13) and 9-point finite difference method, for solving parabolic differential equations with arbitrary boundary conditions and based on weak form functionals in finite domains. The problem is solved rapidly, easily and elegantly by ADM. The numerical results on a 2D transient heat conducting problem and 3D diffusion problem are used to validate the proposed ADM as an effective numerical method for solving finite domain parabolic equations. The numerical results showed that our present method is less time consuming and is easier to use than other methods. In addition, we prove the convergence of this method when it is applied to the nonlinear parabolic equation.

A special device was designed to measure temperature difference in this study of heat transfer of water and oil cross flow inside vertical upward tubes. A new heat transfer correlation was obtained for cross flow. The experimental results showed that the dependence of heat transfer on Reynolds is much smaller in a narrow space than that in a wide space. It was found that the heat transfer correlation of cross flow in a narrow space is obviously different from that in a wide space, and that the heat transfer correlation obtained in a wide space may not be applicable to the cross-flow heat transfer in a narrow space. Further, the single-phase heat transfer capability of water cross flow was compared with that of oil cross flow. The experimental results showed that the average heat transfer coefficient of water is about 2~3 times that of oil when they have the same superficial velocity.

Three-dimensional transient numerical simulation of gas exchange process in a four-stroke motorcycle engine with a semi-spherical combustion chamber with two tilt valves was studied. Combination of the grid re-meshing method and the snapper technique made the valves move smoothly. The flow structure and pattern in a complete engine cycle were described in detail. Tumble ratios around the x-axis and y-axis were analyzed. Comparison of computed pressure with experimental pressure under motored condition revealed that the simulation had high calculation precision; CFD simulation can be regarded as an important tool for resolving the complex aerodynamic behavior in motorcycle engines.

Parts of complex surface are widely used now in many fields, and their detection has caused much concern. In China many manufactories still carry on the traditional way of manual detection, which requires highly skilled personnel and efficiency is low. Some large manufactories have imported auto-detecting equipments, which require CAD data on the parts, or just divide the surface into several approximate planes for automatic detection. Phased-array system is seldom used, and the cost is high. Besides, most of the systems have not considered the automatic sensitivity compensation of parts with varying thickness. To improve the detection quality and efficiency of nondestructive test (NDT) of parts of complex surface, this paper puts forward an integrated ultrasonic NDT system characterized by: (1) Use of ultrasonic measurement and reverse of curved surface to solve the CAD data problem; (2) Use of an automatic sensitivity compensation algorithm (based on the part’s modelling information obtained in surface reverse) to fit the variety of the thickness; (3) Use of template matching and pseudo-color imaging to improve the quality of detection results. The system features integration of low cost mature technologies, and is suitable for detection of various parts of different complex surfaces in medium-and-small enterprises. The test results showed that the system can automatically detect parts of complex surface successfully, and that the inspection result is good and reliable.