Cosmological constraint on Brans-Dicke Model

We combine new Cosmic Microwave Background (CMB) data from Planck with Baryon Acoustic Oscillation (BAO) data to constrain the Brans-Dicke (BD) theory, in which the gravitational constant $G$ evolves with time. Observations of type Ia supernovae (SNeIa) provide another important set of cosmological data, as they may be regarded as standard candles after some empirical corrections. However, in theories that include modified gravity like the BD theory, there is some risk and complication when using the SNIa data because their luminosity may depend on $G$. In this paper, we assume a power law relation between the SNIa luminosity and $G$, but treat the power index as a free parameter. We then test whether the difference in distances measured with SNIa data and BAO data can be reduced in such a model. We also constrain the BD theory and cosmological parameters by making a global fit with the CMB, BAO and SNIa data set. For the CMB+BAO+SNIa data set, we find $0.08\times10^{-2} < \zeta <0.33\times10^{-2}$ at the 68\% confidence level (CL) and $-0.01\times10^{-2} <\zeta <0.43\times 10^{-2}$ at the 95\% CL, where $\zeta$ is related to the {BD} parameter $\omega$ by $\zeta=\ln(1+1/\omega)$.Comment: 13pages, 7 figures, to appear on RA

Time To Live: Temporal Management of Large-Scale RFID Applications

In coming years, there will be billions of RFID tags living in the world tagging almost everything for tracking and identification purposes. This phenomenon will impose a new challenge not only to the network capacity but also to the scalability of event processing of RFID applications. Since most RFID applications are time sensitive, we propose a notion of Time To Live (TTL), representing the period of time that an RFID event can legally live in an RFID data management system, to manage various temporal event patterns. TTL is critical in the "Internet of Things" for handling a tremendous amount of partial event-tracking results. Also, TTL can be used to provide prompt responses to time-critical events so that the RFID data streams can be handled timely. We divide TTL into four categories according to the general event-handling patterns. Moreover, to extract event sequence from an unordered event stream correctly and handle TTL constrained event sequence effectively, we design a new data structure, namely Double Level Sequence Instance List (DLSIList), to record intermediate stages of event sequences. On the basis of this, an RFID data management system, namely Temporal Management System over RFID data streams (TMS-RFID), has been developed. This system can be constructed as a stand-alone middleware component to manage temporal event patterns. We demonstrate the effectiveness of TMS-RFID on extracting complex temporal event patterns through a detailed performance study using a range of high-speed data streams and various queries. The results show that TMS-RFID has a very high throughout, namely 170,000 - 870,000 events per second for different highly complex continuous queries. Moreover, the experiments also show that the main structure to record the intermediate stages in TMS-RFID does not increase exponentially with the number of events. These illustrate that TMS-RFID not only has a high processing speed, but also has a good scalability

Arbitrary Multi-way Parallel Mathematical Operations Based on Planar Discrete Metamaterials

Multi-way parallel mathematical operations along arbitrary transmission paths are constructed based on realizable planar discrete metamaterials in this paper. The introduced method of “computational metamaterials” is used to perform the desired mathematical operations. For producing high-efficiency devices, the function of multi-way parallel mathematical operations is indispensable in advanced analog computers. Therefore, in this paper, we propose the arbitrary transmission paths that can be implemented by the bending of the electromagnetic waves based on the finite embedded coordinate transformations, which has a strong potential to realize the function of multi-way parallel computation. Nevertheless, owing to the inherent inhomogeneous property, metamaterials are difficult to be achieved in nature currently. In order to make it possible for fabricating in practical applications, the planar discrete metamaterial is a promising medium due to its homogeneous property. Numerical simulations validate the novel and effective design method for parallel optical computation