Maximizing System Throughput Using Cooperative Sensing in Multi-Channel Cognitive Radio Networks

In Cognitive Radio Networks (CRNs), unlicensed users are allowed to access the licensed spectrum when it is not currently being used by primary users (PUs). In this paper, we study the throughput maximization problem for a multi-channel CRN where each SU can only sense a limited number of channels. We show that this problem is strongly NP-hard, and propose an approximation algorithm with a factor at least $1/2\mu$ where $\mu \in [1,2]$ is a system parameter reflecting the sensing capability of SUs across channels and their sensing budgets. This performance guarantee is achieved by exploiting a nice structural property of the objective function and constructing a particular matching. Our numerical results demonstrate the advantage of our algorithm compared with both a random and a greedy sensing assignment algorithm

Whatever It Takes: How and When Supervisor Bottom-Line Mentality Motivates Employee Contributions in the Workplace

Given that many organizations are competitive and finance centered, organizational leaders may lead with a primary focus on bottom-line attainment, such that they are perceived by their subordinates as having a bottom-line mentality (BLM) that entails pursuing bottom-line outcomes above all else. Yet, the field is limited in understanding why such a leadership approach affects employees’ positive and negative contributions in the workplace. Drawing on social exchange theory, we theorize that supervisors high in BLM can influence employees’ felt obligation toward the bottom line, which in turn can influence employees’ task performance and unethical pro-organizational behavior (UPB). We also examine employee ambition as a moderator of this process. Using three-wave, multisource data collected from the financial services industry, our results revealed that high-BLM supervisors elevate employee task performance as well as UPB by motivating employees’ felt obligation toward the bottom line. Furthermore, we found that employee ambition served as a first-stage moderator, such that the mediated relationships were stronger when employee ambition was high as opposed to low. Our findings break away from the dominant dysfunctional view of BLM and provide a more balanced view of this mentality

Modeling pulsar time noise with long term power law decay modulated by short term oscillations of the magnetic fields of neutron stars

We model the evolution of the magnetic fields of neutron stars as consisting of a long term power-law decay modulated by short term small amplitude oscillations. Our model predictions on the timing noise $\ddot\nu$ of neutron stars agree well with the observed statistical properties and correlations of normal radio pulsars. Fitting the model predictions to the observed data, we found that their initial parameter implies their initial surface magnetic dipole magnetic field strength ~ 5E14 G at ~0.4 year old and that the oscillations have amplitude between E-8 to E-5 and period on the order of years. For individual pulsars our model can effectively reduce their timing residuals, thus offering the potential of more sensitive detections of gravitational waves with pulsar timing arrays. Finally our model can also re-produce their observed correlation and oscillations of the second derivative of spin frequency, as well as the "slow glitch" phenomenon.Comment: 10 pages, 6 figures, submitted to IJMPD, invited talk in the 3rd Galileo-XuGuangqi Meeting}, Beijing, China, 12-16 October 201

Influential publications in ecological economics revisited

We revisit the analysis of Costanza et al. (2004, Ecological Economics) of influential publications in ecological economics to discover what has changed a decade on. We examine which sources have been influential on the field of ecological economics in the past decade, which articles in the journal Ecological Economics have had the most influence on the field and on the rest of science, and on which areas of science the journal is having the most in- fluence.We find that the field has matured over this period, with articles published in the journal having a greater influence than before, an increase in citation links to environmental studies journals, a reduction in citation links to mainstream economics journals, and possibly a shift in themes to a more applied and empirical direction.Copyright Information: © 2016 Elsevier B.V. http://www.sherpa.ac.uk/romeo/issn/0921-8009/..."Authors pre-print on any website, including arXiv and RePEC" from SHERPA/RoMEO site (as at 3/02/16)

Comparison between Windowed FFT and Hilbert-Huang Transform for Analyzing Time Series with Poissonian Fluctuations: A Case Study

Hilbert-Huang Transform (HHT) is a novel data analysis technique for nonlinear and non-stationary data. We present a time-frequency analysis of both simulated light curves and an X-ray burst from the X-ray burster 4U 1702-429 with both the HHT and the Windowed Fast Fourier Transform (WFFT) methods. Our results show that the HHT method has failed in all cases for light curves with Poissonian fluctuations which are typical for all photon counting instruments used in astronomy, whereas the WFFT method can sensitively detect the periodic signals in the presence of Poissonian fluctuations; the only drawback of the WFFT method is that it cannot detect sharp frequency variations accurately.Comment: 10 pages, 12 figure

Quantum control by von Neumann measurements

A general scheme is presented for controlling quantum systems using evolution driven by non-selective von Neumann measurements, with or without an additional tailored electromagnetic field. As an example, a 2-level quantum system controlled by non-selective quantum measurements is considered. The control goal is to find optimal system observables such that consecutive non-selective measurement of these observables transforms the system from a given initial state into a state which maximizes the expected value of a target operator (the objective). A complete analytical solution is found including explicit expressions for the optimal measured observables and for the maximal objective value given any target operator, any initial system density matrix, and any number of measurements. As an illustration, upper bounds on measurement-induced population transfer between the ground and the excited states for any number of measurements are found. The anti-Zeno effect is recovered in the limit of an infinite number of measurements. In this limit the system becomes completely controllable. The results establish the degree of control attainable by a finite number of measurements