Mathematical and Computer Modelling最新文献

The electric power consumption of information systems has to be reduced in addition to increasing the performance and fault tolerance in order to realize green societies. Here, servers mainly consume electric power to perform processes requested by clients compared with clients. We consider computation (CP) and storage (ST) types of application processes on servers. In CP processes, CPU is mainly consumed as in scientific computation. In ST processes, files in storage drives are mainly manipulated. First, we present the storage and computation based power consumption (SCBPC) model of a server to perform ST and CP processes. In the SCBPC model, the power consumption rate of a server depends on the types of processes concurrently performed and is independent of the number of processes. Then, we discuss the storage and computation based processing (SCBP) model to perform CP and ST processes on a server. Here, the execution times of a CP process and an ST process depend on the number of CP processes and the number of CP and ST processes concurrently performed, respectively. By using the SCBPC and SCBP models, we discuss an energy-aware (EA) algorithm to select a server for a process so that not only the execution time but also the power consumption can be reduced. We evaluate the EA algorithm in terms of total power consumption of servers and total execution time of processes. We show not only the total power consumption but also the total execution time can be reduced in the EA algorithm.

Recently, wireless networks, such as Wi-Fi and 3G, have been widely equipped and popularly used in the world. People holding smart devices can conveniently access the Internet services through modern wireless networks. However, when people are enjoying using wireless systems, network security has been a crucial challenge because wireless messages, encrypted or unencrypted, may be maliciously intercepted by hackers. After analyzing and/or decrypting the messages, hackers can illegally capture or steal important information, such as credit card numbers or usernames/passwords, carried in the messages. Currently, SSL and IPsec are utilized to protect the delivery of these types of information. However, each of the two security protocols has its own drawbacks both in their key exchange and message encryption/decryption processes. To solve these drawbacks, in this paper, we propose a secure communication system, named the Wireless Security System with Data Connection Core (WiSDC for short), which consists of two security schemes, including a symmetric key exchange process and a two-dimensional stream cipher mechanism. The former employs random numbers and the connection keys contained in the Data Connection Core (the DCC for short) to generate internal keys, through which the security level of the key exchange process can be enhanced. Here, the DCC is a set of random numbers created when the underlying user registers himself/herself with the wireless system being considered, and the random numbers are only known to the user and AAA server of the wireless system. The latter invokes two operators, including exclusive-or$\oplus$ and binary adder ${+}_2$ operators, and two Pseudo Random Number Sequences (PRNSs) to encrypt plaintext so as to well protect the ciphertext. The WiSDC also adopts a pseudo random number generator, which feeds back keys in current stage as a part of the inputs of the next stage, to generate more complicated keys for data encryption. Experimental results show that the WiSDC can effectively protect transmitted messages for wireless environments. The analytical results indicate that the WiSDC has higher security level and execution efficiency than those of the SSL and IPsec.

During the fast developing process of the Chinese economy, China consumes lots of energy and environmental pollution caused by energy consumption currently urgently needs solving. So, paying more attention to energy saving and emission reduction is very important. Therefore, to reasonably allocate resources and reduce emissions in China’s different regions has practical significance. So this paper firstly considers the model construction method for resource allocation considering undesirable outputs between different decision making units based on the DEA framework under the CRS and VRS assumption. We have proposed some resource allocation models as a multiple objective linear problem which considers the input reduction, desirable output reduction and undesirable output reduction. Then, to demonstrate the practical application of the resource allocation model, numerical examples are used to illustrate the approach. In addition, we explore the resource allocation problem of China’s regions in 2006–2010. The empirical results show that the resource allocation models dealing with undesirable outputs have effective configuration results, that is, the reduction proportion for desirable output is smaller than the reduction proportion for undesirable output. From the resource allocation results in China’s regions, we find that the eastern area has more emission reduction than the central and western areas corresponding to the same energy consumption reduction, and the energy and environmental policy should focus more on the central and western areas. All of these conclusions will give some policy recommendations on saving energy and reducing pollution emissions.

In communication networks, a cognitive network (CN) is a new type of data network which is used to solve some of the problems that face current networks. Cognitive radio (CR) is part of a cognitive network and a smart wireless communication system. CR is conscious of its surrounding environment, learns from the environment and adapts its internal states by making corresponding real-time changes in certain operating parameters. In this paper, we propose a Cognitive RBAC scheme which can be applied to Small Heterogeneous Networks (SHNs) with handover function. We propose the Cognitive RBAC model applying with handover function in SHNs by extending from the well-known RBAC model. The required definitions for the model are proposed in this paper. They can increase the ability of the conventional RBAC model to meet new challenges. In our scheme, we assume that Cognitive Server (CS) provides and manages the permissions of services, and also supports a variety of CRs and CNs. For more efficiently managing CR and CN and meeting the SHNs, we let a mobile user actively perceive current network situations to get permissions and access corresponding services under the negotiation made among CSs to get better QoS if handover occurs either by Inter-CS Handover or Intra-CS Handover. In this paper, the cognitive RBAC functions and their definitions are proposed and defined for new applications in a SHN environment.

People-Centric Sensing (PCS) is a new sensing paradigm, in which people’s context information is described by attributes. However, due to the nature of “people centric” and dynamicity, the prevalence of PCS faces two main challenges, including authentication with privacy preservation and complex identity revocation.

In this paper, we propose the ABS-KR, an attribute-based signature scheme supporting key revocation. ABS-KR inherits the advantage of most attribute-based signature schemes, that is, a signature only shows that whether the user owns attributes satisfying the verification policy, no more information about his identifier or attributes, implementing authentication with privacy preservation. Furthermore, we introduce a mediator responsible for the key revocation to reduce the workload of the attribute authority managing users’ attributes and generating secret key for them. The core idea of performing flexible revocation is to divide a user’s secret key into two shares, and give one part to the mediator, making the user asking the mediator for help to generate a valid signature. Before answering the user, the mediator performs a revocation check for the user’s identifier and claimed attributes. If and only if the signer owns unrevoked attributes satisfying the policy, he can generate a valid signature. In addition, the mediator realizes instantaneous key revocation through revocation check during signing a message. Moreover, our ABS-KR supports monotone policies in the form of attribute trees under the computational Diffie–Hellman assumption.

This paper presents a directional distance function approach to measure two technical efficiencies with respect to the two technologies characterized by strong and weak disposability of pollutants. The environmental efficiency index, defined as the ratio of the two technical efficiencies, reflects the opportunity cost to transform the strong disposability of pollutants into a weak one. The proposed approach is applied to measure the environmental efficiency index of the Chinese industrial sector, with the input and output data of the sector in 284 cities at the prefecture level and above in China from 2003 to 2009, including the emissions of wastewater, sulfur dioxide, and soot. Several factors of environmental efficiency are also investigated by using a panel Tobit model.

Over the past few years, modern mobile subscriber devices such as Smartphones, tablets and PDAs have become more and more popular which use network resources in a more aggressive way and last for longer durations involving dramatically increasing traffic volumes. But traditional mobility management schemes have hardly taken this issue into account. Distributed mobility management is considered as a new trend for developing a mobility management scheme to address such an issue. This paper proposes D-PMIPv6, which is to achieve a distributed mobility management scheme supported by data and control plane separation based on PMIPv6. In the architecture of D-PMIPv6, the traditional functional entity Local mobility anchor (LMA) is split into two parts: Control plane LMA and Data plane LMA. We conclude with the three goals of distributed mobility management. With its elaborate design, D-PMIPv6 is proved to achieve these goals. Numerical results show that a single Control plane LMA can hold quite a number of MNs and the handover performance of D-PMIPv6 is acceptable compared to PMIPv6. Meanwhile, D-PMIPv6 can improve the performance in terms of the packet delivery cost compared to other mobility management schemes.

The main challenge for sustainable development of resource cities is to work out a feasible strategy for transformation processes. This paper introduces a new approach for analysis of transformation performance. Using the environmental production technology and a Malmquist resource performance index (MRPI), we conduct $\sigma$, absolute $\beta$ and conditional $\beta$ convergence tests for the transformation performance of 21 resource cities in China. The results show that MRPI does not follow the same trend as economic strength of three Chinese regions. In addition, the transformation performance results exhibit a convergence trend for the 21 resource cities.

As peer-to-peer (P2P) systems have gained popularity and evolved to encompass different scenarios beyond simple file-sharing, such as ubiquitous and cognitive computing, awareness on the need for inclusion of security mechanisms into its design, has also raised. JXTA is an open P2P protocols specification that, for these reasons, has slowly incorporated security improvements such as message privacy and resource authentication, up to its latest version to this date, 2.7. However, under some contexts, even more advanced security requirements should be met. Anonymity, for which privacy is necessary but not a sufficient requirement, is a good example. Unfortunately, even though several approaches to message anonymization exist within the context of P2P networks, there is no perfect solution. In this work, we study the feasibility of anonymous access to JXTA community services using a split message-based approach. On that regard, we adapt a recently proposed anonymous protocol to JXTA’s idiosyncrasies and assess its actual performance under typical JXTA network configurations.

The Foreign Exchange Market is the biggest and one of the most liquid markets in the world. This market has always been one of the most challenging markets as far as short term prediction is concerned. Due to the chaotic, noisy, and non-stationary nature of the data, the majority of the research has been focused on daily, weekly, or even monthly prediction. The literature review revealed that there is a gap for intra-day market prediction. Identifying this gap, this paper introduces a prediction and decision making model based on Artificial Neural Networks (ANN) and Genetic Algorithms. The dataset utilized for this research comprises of 70 weeks of past currency rates of the 3 most traded currency pairs: GBP∖USD, EUR∖GBP, and EUR∖USD. The initial statistical tests confirmed with a significance of more than 95% that the daily FOREX currency rates time series are not randomly distributed. Another important result is that the proposed model achieved 72.5% prediction accuracy. Furthermore, implementing the optimal trading strategy, this model produced 23.3% Annualized Net Return.