Distributed Compressed Sensing for Sensor Networks with Packet Erasures

We study two approaches to distributed compressed sensing for in-network data compression and signal reconstruction at a sink in a wireless sensor network where sensors are placed on a straight line. Communication to the sink is considered to be bandwidth-constrained due to the large number of devices. By using distributed compressed sensing for compression of the data in the network, the communication cost (bandwith usage) to the sink can be decreased at the expense of delay induced by the local communication necessary for compression. We investigate the relation between cost and delay given a certain reconstruction performance requirement when using basis pursuit denoising for reconstruction. Moreover, we analyze and compare the performance degradation due to erased packets sent to the sink of the two approaches.Comment: Paper accepted to GLOBECOM 201

Walking the Talk: How to Identify Anti-Pluralist Parties

The recent increase of democratic declines around the world – “the third wave of autocratization” – has sparked a new generation of studies on the topic. Scholars tend to agree that the main threat to contemporary democracy arises from democratically elected rulers who gradually erode democratic norms. Is it possible to identify future autocratizers before they win power in elections? Linz (1978) and Levitsky and Ziblatt (2018) suggest that a lacking commitment to democratic norms reveals would-be autocratizers before they reach office. This article argues that the concept of anti-pluralism rather than populism or extreme ideology captures this. We use a new expert-coded data set on virtually all relevant political parties worldwide from 1970 to 2019 (V-Party) to create a new Anti-Pluralism Index (API) to provide the first systematic empirical test of this argument. We find substantial evidence validating that the API and Linz’s litmus-test indicators signal leaders and parties that will derail democracy if and when they come into power

Cabinets, Prime Ministers and Corruption. A Comparative Analysis of Parliamentary Governments in Post-War Europe

Why are some states more corrupt than others? Previous research explaining corruption suggests that multiparty governments are associated with higher levels of corruption since it is difficult for voters to hold parties in such cabinets accountable. Drawing on the literature on coalition governance, we suggest that a lack of government corruption has more to do with the ability of other key political actors to control the agents that have been delegated power in cabinet. We use a new dataset (Varieties of Democracy), giving us more specific measures on governmental corruption across a longer time-period. We show that corruption is significantly lower when the Prime Minister (PM) has strong constitutional powers, suggesting that the PM as a principal reduces agency problems

Regimes of the World (RoW): Opening New Avenues for the Comparative Study of Political Regimes

Classifying political regimes has never been more difficult. Most contemporary regimes hold de-jure multiparty elections with universal suffrage. In some countries, elections ensure that political rulers are - at least somewhat - accountable to the electorate whereas in others they are a mere window dressing exercise for authoritarian politics. Hence, regime types need to be distinguished based on the de-facto implementation of democratic institutions and processes. Using V-Dem data, we propose with Regimes of the World (RoW) such an operationalization of four important regime types - closed and electoral autocracies; electoral and liberal democracies - with vast coverage (almost all countries from 1900 to 2016). We also contribute a solution to a fundamental weakness of extant typologies: The unknown extent of misclassification due to uncertainty from measurement error. V-Dem's measures of uncertainty (Bayesian highest posterior densities) allow us to be the first to provide a regime typology that distinguishes cases classified with a high degree of certainty from those with "upper" and "lower" bounds in each category. Finally, a comparison of disagreements with extant datasets (7%-12% of the country-years), demonstrates that the RoW classification is more conservative, classifying regimes with electoral manipulation and infringements of the political freedoms more frequently as electoral autocracies, suggesting that it better captures the opaqueness of contemporary autocracies

Self-consistent Langmuir waves in resonantly driven thermal plasmas

The longitudinal dynamics of a resonantly driven Langmuir wave are analyzed in the limit that the growth of the electrostatic wave is slow compared to the bounce frequency. Using simple physical arguments, the nonlinear distribution function is shown to be nearly gaussian in the canonical particle action, with a slowly evolving mean and fixed variance. Self-consistency with the electrostatic potential provide the basic properties of the nonlinear distribution function including a frequency shift that agrees well with driven, electrostatic particle simulations. This extends earlier work on nonlinear Langmuir waves by Morales and O'Neil [G. J. Morales and T. M. O'Neil, Phys. Rev. Lett. 28, 417 (1972)], and could form the basis of a reduced kinetic treatment of Raman backscatter in a plasma.Comment: 11 pages, 4 figures, submitted to Physics of Plasma

Compressed Sensing in Wireless Sensor Networks without Explicit Position Information

Reconstruction in compressed sensing relies on knowledge of a sparsifying transform. In a setting where a sink reconstructs a field based on measurements from a wireless sensor network, this transform is tied to the locations of the individual sensors, which may not be available to the sink during reconstruction. In contrast to previous works, we do not assume that the sink knows the position of each sensor to build up the sparsifying basis. Instead, we propose the use of spatial interpolation based on a predetermined sparsifying transform, followed by random linear projections and ratio consensus using local communication between sensors. For this proposed architecture, we upper bound the reconstruction error induced by spatial interpolation, as well as the reconstruction error induced by distributed compression. These upper bounds are then utilized to analyze the communication cost tradeoff between communication to the sink and sensor-to-sensor communication

The Forum: Global Challenges to Democracy?:Perspectives on Democratic Backsliding

There is a widespread perception that we are witnessing a period of democratic decline, manifesting itself in varieties of democratic backsliding such as the manipulation of elections, marginalization and repression of regime opponents and minorities, or more incremental executive aggrandizement. Yet others are more optimistic and have argued that democracy is in fact resilient, or that we are observing coinciding trends of democratic decline but also expansion. This forum highlights key issues in the debate on democracy's decline, which center on conceptual and measurement issues, agreement on the phenomenon but not its nature or severity, the importance of international factors, the emphasis we should put on political elites versus citizens, and the consequences of backsliding for global politics. Staffan I. Lindberg provides an empirical perspective on the scope and severity of democracy's decline, and argues that polarization and misinformation are important drivers for this current wave of autocratization. Susan D. Hyde highlights the detrimental consequences of reduced support for democracy by the international community, which has affected civil society organizations—important arbiters of democracy—especially severely. Challenging some of these conclusions, Irfan Nooruddin claims that any gains for democracy after the end of the Cold War were short-lived, failing to sustain democracy because of an overemphasis on elections and a disregard for structural factors. Finally, Larry M. Bartels argues that we need to look to political elites and not citizens if we want to protect democracy in the United States and elsewhere, which has important implications for how we study democracy and its challenges.<br/

Evidence for a chemically differentiated outflow in Mrk 231

Aims: Our goal is to study the chemical composition of the outflows of active galactic nuclei and starburst galaxies. Methods: We obtained high-resolution interferometric observations of HCN and HCO$^+$ $J=1\rightarrow0$ and $J=2\rightarrow1$ of the ultraluminous infrared galaxy Mrk~231 with the IRAM Plateau de Bure Interferometer. We also use previously published observations of HCN and HCO$^+$ $J=1\rightarrow0$ and $J=3\rightarrow2$, and HNC $J=1\rightarrow0$ in the same source. Results: In the line wings of the HCN, HCO$^+$, and HNC emission, we find that these three molecular species exhibit features at distinct velocities which differ between the species. The features are not consistent with emission lines of other molecular species. Through radiative transfer modelling of the HCN and HCO$^+$ outflow emission we find an average abundance ratio $X(\mathrm{HCN})/X(\mathrm{HCO}^+)\gtrsim1000$. Assuming a clumpy outflow, modelling of the HCN and HCO$^+$ emission produces strongly inconsistent outflow masses. Conclusions: Both the anti-correlated outflow features of HCN and HCO$^+$ and the different outflow masses calculated from the radiative transfer models of the HCN and HCO$^+$ emission suggest that the outflow is chemically differentiated. The separation between HCN and HCO$^+$ could be an indicator of shock fronts present in the outflow, since the HCN/HCO$^+$ ratio is expected to be elevated in shocked regions. Our result shows that studies of the chemistry in large-scale galactic outflows can be used to better understand the physical properties of these outflows and their effects on the interstellar medium (ISM) in the galaxy.Comment: 12 pages, 8 figures, accepted for publication in A&