2745933
Compositional verification of real-time systems with Explicit Clock Temporal Logic
To specify and verify real-time systems, we consider a real-time version of temporal logic called Explicit Clock Temporal Logic. Timing properties are specified by extending the classical framework of temporal logic with a special variable which explicitly refers to a global notion of time. Programs are written in an Occam-like real-time language with synchronous message passing. To show that a program satisfies a specification, we formulate a proof system which is proved to be sound and relatively complete. The proof system is compositional, which makes it possible to decompose the design of a large system into the design of subsystems. This is shown by the verification of a small part of an avionics system.
40982114
A proof theory for asynchronously communicating real-time systems
A compositional proof system is presented to axiomatize the real-time behavior of asynchronously communicating processes. Programs are written in a real-time version of CSP where processes asynchronously send and receive messages along channels that are capable of buffering an arbitrary number of messages. Timing properties are expressed in explicitly clock temporal logic, which extends linear temporal logic with a special time variable, referring to a global clock.<<ETX>>
37285882
Dynamic adaptation of CSMA/CA MAC protocol for wide area wireless mesh networks
Though the popular IEEE 802.11 DCF is designed primarily for Wireless LAN (WLAN) environments, today it is being widely used for wide area wireless mesh networking. The protocol parameters of IEEE 802.11 such as timeout values, interframe spaces, and slot durations, sufficient for a general WLAN environment, need to be modified in order to efficiently operate in wide area wireless mesh networks. The current wide area wireless mesh network deployments use manual configuration of these parameters to the upper limit which essentially makes the networks operate at lower system efficiency. In this paper, we propose d802.11 (dynamic 802.11) which dynamically adapts the protocol parameters in order to operate at varying link distances. In fact, in 802.11, a transmitter can face ACK/CTS timeout even when it started receiving ACK/CTS packet before the timeout value. We present three strategies, (i) multiplicative timer backoff (MTB), (ii) additive timer backoff (ATB), and (iii) link RTT memoization (LRM), to adapt the ACK_TIMEOUT in d802.11 in order to provide better adaptation for varying link dimensions. Through extensive simulation experiments we observed significant performance improvement for the proposed strategies. We also theoretically modeled the maximum link throughput as a function of the link dimension for the proposed system. Our results show that the LRM technique provides the best adaptation compared to all other schemes.
123438379
Explicit Construction of Multivariate Padé Approximants for a q-Logarithm Function
We explicitly construct the non-homogeneous multivariate Pade approximants to a two variable version of the q-logarithm functionL"q(x, y)@[email protected]?i, j=0~(q-1)x^iy^jq^i^+^j^+^1-1, for |q|>1 and |x|, |y|<|q|, by using the residue theorem and functional equation method.
16634499
An Approximate Controller for Nonlinear Networked Control Systems with Time Delay
An approximation controller is developed to obtain an optimal control for nonlinear networked control systems (NCS) with time delay. In the approach only the non-linear compensating term, solution of a sequence of adjoint vector differential equations, is required iteration. By taking the finite iteration of non-linear compensating term of optimal solution sequence, a suboptimal control law for NCS can be obtained.
19223951
A comparison between the China Scientific and Technical Papers and Citations Database and the Science Citation Index in terms of journal hierarchies and interjournal citation relations
The journal structure in the China Scientific and Technical Papers and Citations Database (CSTPCD) is analysed from three perspectives: the database level, the specialty level and the institutional level (i.e., university journals versus journals issued by the Chinese Academy of Sciences). The results are compared with those for (Chinese) journals included in the Science Citation Index. The frequency of journal-journal citation relations in the CSTPCD is an order of magnitude lower than in the SCI. Chinese journals, especially high-quality journals, prefer to cite international journals rather than domestic ones. However, Chinese journals do not get an equivalent reception from their international counterparts. The international visibility of Chinese journals is low, but varies among fields of science. Journals of the Chinese Academy of Sciences (CAS) have a better reception in the international scientific community than university journals.
16952040
A Speaker Verification System Based on EMD
Most of the speech utterance feature extraction methods are based on the assumptions: utterance signal is short-term stable and independent between each other adjacent frames. This approach ignores the dynamic characteristics of speech signal. For the time-varying characteristics of the speech utterance, we propose a new feature extraction method based on empirical mode decomposition EMD. We can extract the LPCC feature parameters from different stages of IMFs which are decomposed by EMD process. A speaker verification system based on EMD is proposed and it is shown that it is better performance than the one with traditional LPCC features based on short-term process.