Abstract:
Studying the urban entrepreneurship environment has guiding significance for the development of urban economy and employment. Based on the PSR (Pressure-State-Response) model framework, this paper constructs an index system for evaluation of urban entrepreneurship environment, and uses the multi-factor weighted method to systematically quantitatively analyze and comprehensively evaluate the state of entrepreneurship policies, service systems, and hardware facilities, and use GM(1, 1) model to predict the development trend of urban entrepreneurship environment in Guangzhou. The study shows that the policy measures to optimize the entrepreneurship environment have effectiveness, time lag and accumulation effect, and the government’s response measures are the core factors for the stable development of the urban entrepreneurship environment. It is expected that the entrepreneurship environment in Guangzhou will continue to improve in the future. Finally, it is pointed out that optimizing the urban entrepreneurship environment should start from innovation, attracting talents, increasing financial support, and highlighting regional industrial characteristics to form an entrepreneurship economy.

Abstract:
An alternative presentation of the π-calculus is given. This version of the π-calculus is symmetric in the sense that communications are symmetric and there is no difference between input and output prefixes. The point of the symmetric π-calculus is that it has no abstract names. The set of closed names is therefore homogeneous. The π-calculus can be fully embedded into the symmetric π-calculus. The symmetry changes the emphasis of the communication mechanism of the π-calculus and opens up possibility for further variations. Supported by NNSFC, grant number 69503006. Fu Yuxi is an Associate Professor in the Department of Computer Science, Shanghai Jiao Tong University. He received his Ph.D. degree in computer science in 1992 from Manchester University, England. His current research interests include type theory, semantics and concurrency theory.

Abstract:
Encodings in polymorphism with finite product types are considered. These encodings aregiven in terms of I-algebras. They have the property that the ground terms are precisely theclosed normal terms of the encoded types. The proof of a well-known result is transplantedto the setting and it is shown why weak recursion is admissible. The paper also shows how tocarry out the dual encodingS using the existential quantifier.

Abstract:
The paper proposes reaction graphs as graphical representations of computational objects.A reaction graph is a directed graph with all its arrows and some of its nodes labeled. Compu-tations are modeled by graph rewriting of a simple nature. The basic rewriting rules embodythe essence of both the communications among processes and cut-eliminations in proofs. Cal-culi of graphs are identified to give a formal and algebraic account of reaction graphs in thespirit of process algebra. With the help of the calculi, it is demonstrated that reaction graphscapture many interesting aspects of computations.

Abstract:
We view a facility system as a kind of supply chain and model it as a connected graph in which the nodes represent suppliers, distribution centers or customers and the edges represent the paths of goods or information. The efficiency, and hence the reliability, of a facility system is to a large degree adversely affected by the edge failures in the network. In this paper, we consider facility systems' reliability analysis based on the classical p-median problem when subject to edge failures. We formulate two models based on deterministic case and stochastic case to measure the loss in efficiency due to edge failures and give computational results and reliability envelopes for a specific example.

Abstract:
The development of computer industry is promoted by the progress of distributed computing, parallel computing and grid computing, so the cloud computing movement rises. This study describes the types of cloud computing services, the similarities and differences of cloud computing and grid computing, meanwhile discusses the better aspect of cloud computing than grid computing, and refers the common problems faced to the both computing, and some security issues.

Abstract:
We establish the existence of a conservative weak solution to the Cauchy problem for the nonlinear variational wave equation $u_{tt} - c(u)(c(u)u_x)_x=0$, for initial data of finite energy. Here $c(\cdot)$ is any smooth function with uniformly positive bounded values.

Abstract:
We study the domain of existence of a solution to a Riemann problem for the pressure gradient equation in two space dimensions. The Riemann problem is the expansion of a quadrant of gas of constant state into the other three vacuum quadrants. The global existence of a smooth solution was established in Dai and Zhang [Arch. Rational Mech. Anal., {\bf 155}(2000), 277-298] up to the free boundary of vacuum. We prove that the vacuum boundary where the system is degenerate is the trivial coordinate axes.

Abstract:
In this paper, we prove the global existence and singularity formation for a wave system from modelling nematic liquid crystals in one space dimension. In our model, although the viscous damping term is included, the solution with smooth initial data still has gradient blowup in general, even when the initial energy is arbitrarily small.