9682 research outputs found
Sort by
On MMSE Properties of Codes for the Gaussian Broadcast and Wiretap Channels
No full textThis work concerns the behavior of "good" (capacity achieving) codes in several multi-user settings in the Gaussian regime, in terms of their minimum mean-square error (MMSE) behavior. The settings investigated in this context include the Gaussian wiretap channel, the Gaussian broadcast channel (BC) and the Gaussian BC with confidential messages (BCC). In particular this work addresses the effects of transmitting such codes on unintended receivers, that is, receivers that neither require reliable decoding of the transmitted messages nor are they eavesdroppers that must be kept ignorant, to some extent, of the transmitted message. This work also examines the effect on the capacity region that occurs when we limit the allowed disturbance in terms of MMSE on some unintended receiver. This trade-off between the capacity region and the disturbance constraint is given explicitly for the Gaussian BC and the secrecy capacity region of the Gaussian BCC
Race, Democracy, and Empire: Delegates to Congress from DC and the Territories
No full textBoth democracy and empire are central to American political development. Yet, the role of Congress—that organ of democratic politics—in the expansion of US empire is not well understood. This article explains how and why Congress institutionalized representation from Washington, DC and the US territories in the mid-twentieth century. We uncover the history of a puzzling position: the Congressional delegate, who is permitted to debate, but not vote. Drawing on extensive original archival research and quantitative analysis of legislative voting behavior, this article explicates how racial attitudes structured conflict over the delegate position. We highlight the centrality of racial ideas to the institutional- ization of American empire in the mid-twentieth century
Single-cell massively-parallel multiplexed microbial sequencing (M3-seq) identifies rare bacterial populations and profiles phage infection
No full textBacterial populations are highly adaptive. They can respond to stress and survive in shifting environments. How the behaviours of individual bacteria vary during stress, however, is poorly understood. To identify and characterize rare bacterial subpopulations, technologies for single-cell transcriptional profiling have been developed. Existing approaches show some degree of limitation, for example, in terms of number of cells or transcripts that can be profiled. Due in part to these limitations, few conditions have been studied with these tools. Here we develop massively-parallel, multiplexed, microbial sequencing (M3-seq)—a single-cell RNA-sequencing platform for bacteria that pairs combinatorial cell indexing with post hoc rRNA depletion. We show that M3-seq can profile bacterial cells from different species under a range of conditions in single experiments. We then apply M3-seq to hundreds of thousands of cells, revealing rare populations and insights into bet-hedging associated with stress responses and characterizing phage infection
Few-Shot Machine Learning at the Grid-Edge: Data-Driven Impedance Models for Model-Free Smart Inverters
No full textThe future electric grid will be pervasively supported by a large number of smart inverters distributed at the grid edge, whose dynamics are critical for grid stability and resiliency. The operating conditions of these inverters may vary across a wide range, leading to various impedance patterns and complicated grid-inverter interaction behaviors. Existing analytical impedance models require thorough and precise understandings of system parameters and make numerous assumptions to reduce the system complexity. They can hardly capture complete electrical behaviors of physical systems when inverters are controlled with sophisticated algorithms or performing complex functions. Real-world impedance acquisitions across multiple operating points through simulations or measurements are expensive and impractical. Leveraging the recent advances in artificial intelligence and machine learning, we present the InvNet, a few-shot machine learning framework that is capable of characterizing inverter impedance patterns across a wide operation range when only limited impedance data for each inverter is available. The InvNet is capable of extrapolating from physics-based models to real-world models and from inverters to inverters. Comprehensive evaluations were conducted to verify the effectiveness of the proposed approach in
various application scenarios. All data and models were open-sourced. We showcase machine learning and neural networks as powerful tools for modeling black-box characteristics of sophisticated grid-edge energy
systems and their capabilities of analyzing behaviors of larger-scale systems that cannot be described via traditional analytical methods
MSC-PoL: Hybrid GaN-Si Multistacked Switched Capacitor 48V PwrSiP VRM for Chiplets
No full textThis paper presents a multistack switched-capacitor point-of-load (MSC-PoL) voltage regulation module (VRM) with coupled magnetics for ultrahigh-current chiplet systems. In the MSC-PoL architecture, the stacked switched-capacitor cells split the high input voltage into several intermediate voltage rails,
which are loaded with the switched-inductor cells to achieve soft charging and voltage regulation. Automatic capacitor voltage balancing and inductor current sharing are realized during the soft charging process. Many inductors of the switched-inductor cells are coupled into one and operated in interleaving to reduce
the inductor current ripple and boost the transient speed. A 48-to-1-V/450-A VRM containing two MSC-PoL modules is built and tested, leveraging high voltage GaN devices for the frontend and high current Silicon devices for the back-end. Two ladder-structured coupled inductor designs are developed and
compared, one of which installs a leakage magnetic plate to adjust the leakage inductance for lower current ripple. Featuring 3D stacked packaging, the entire power stage, gate drivers, and bootstrap circuits of one MSC-PoL module are enclosed into a 1/16-brick/0.31-in3/6-mm-thick package. The peak and the fullload efficiencies as well as the full-load power density (including both gate loss and size) of the MSC-PoL prototype with and without using the leakage plate are 91.7% and 89.5%, 85.8% and 85.6%, and 621 W/in3
and 724 W/in3, respectively. The 6-mm-thick MSC-PoL converter can be embedded into the chiplet
or CPU socket, enabling power-supply-in-package (PwrSiP) for extreme efficiency, density, and control bandwidth
North Atlantic Tropical Cyclone Outer Size and Structure Remain Unchanged by the Late Twenty-First Century
No full textThere is a lack of consensus on whether North Atlantic tropical cyclone (TC) outer size and structure (i.e., change in outer winds with increasing radius from the TC) will differ by the late twenty-first century. Hence, this work seeks to examine whether North Atlantic TC outer wind field size and structure will change by the late twenty-first century using multiple simulations under CMIP3 SRES A1B and CMIP5 RCP4.5 scenarios. Specifically, our analysis examines data from the GFDL High-Resolution Forecast-Oriented Low Ocean Resolution model (HiFLOR) and two versions of the GFDL hurricane model downscaling climate model output. Our results show that projected North Atlantic TC outer size and structure remain unchanged by the late twenty-first century within nearly all HiFLOR and GFDL hurricane model simulations. Moreover, no significant regional outer size differences exist in the North Atlantic within most HiFLOR and GFDL hurricane model simulations. No changes between the control and late-twenty-first-century simulations exist over the storm life cycle in nearly all simulations. For the simulation that shows significant decreases in TC outer size, the changes are attributed to reductions in storm lifetime and outer size growth rates. The absence of differences in outer size among most simulations is consistent with the process that controls the theoretical upper bound of storm size (i.e., Rhines scaling), which is thermodynamically invariant. However, the lack of complete consensus among simulations for many of these conclusions suggests nontrivial uncertainty in our results
Reverse Modernization Analysis: Exploring a History of How Vested Interests Were Politically Marginalized before Modern Economic Development.
No full textThis working paper experiments with what the author calls “reverse modernization analysis,” that is, revisiting the historical West from the perspective of today’s developing countries instead of the teleological approach of modernization theory (just like engineers do reverse engineering). We know today that democracy and authoritarianism alike have witnessed both positive and negative cases of economic development. Therefore, instead of questioning the economic consequence of polity, the paper commences an exploration of an alternative historiography of development focused on how underproductive vested interests were politically marginalized—a political settlement necessary for modern economic development. It briefly examines five major country cases in the period before the 20th century: Britain, France, Germany, Italy, and Japan. The preliminary empirical analysis shows that the decline of conservative elites, which is divided into three patterns—revolution, ruler’s alliance, and parliamentary politics—was caused by sui generis courses of events rather than by common systematic factors. This finding may be frustrating, but implies that political games are like sports games: even if a team does its best, victory is not guaranteed when the opponent plays well. The team still needs to stay ready to take advantage of windows of opportunity when they open
Ruminations on matrix convexity and the strong subadditivity of quantum entropy
No full textThe familiar second derivative test for convexity, combined with resolvent calculus,
is shown to yield a useful tool for the study of convex matrix-valued functions. We
demonstrate the applicability of this approach on a number of theorems in this field.
These include convexity principles which play an essential role in the Lieb–Ruskai
proof of the strong subadditivity of quantum entropy
Relics and rapprochement: The intricacies of cultural diplomacy in China’s first archaeological exhibition in the U.S. during the Cold War era
No full text‘The Exhibition of Archaeological Finds of the People’s Republic of China’ was unveiled at the National Gallery of Art in Washington, D.C. in December 1974. It was the first exhibition of Chinese archaeological relics organised by the People’s Republic of China (PRC) in the United States. This occasion marked a significant moment in Sino-American relations and cultural exchange during the Cold War. This paper explores the intricacies of the planning, organisation, and curation of the exhibition, highlighting the strategic use of cultural diplomacy by China to promote its state ideology on an international scale. This paper argues that the exhibition had far-reaching implications for US–China relationship at the time. On one hand, it represented a significant step towards cultural engagement and rapprochement between the two nations. On the other hand, it served to disrupt the relationship further by exposing ideological differences and triggering contentions. Thus, the exhibition’s impact on US–China relations was complex and multifaceted, reflecting the delicate act of cultural diplomacy in the context of Cold War politics