257 research outputs found
A Media Approach to China-US Relations
This paper was prepared by Zipeng Li, a Carnegie Mellon University Australia student, who completed an Internship with the Centre for United States and Asia Policy Studies, Flinders University.A comparative study of Chinese and US newspaper reports on the summit between Xi Jinping and Obama in June 2013
Size distributions reveal regime transition of lake systems under different dominant driving forces
Power law size distribution is found to associate with fractal,
self-organized behaviors and patterns of complex systems. Such distribution
also emerges from natural lakes, with potentially important links to the
dynamics of lake systems. But the driving mechanism that generates and shapes
this feature in lake systems remains unclear. Moreover, the power law itself
was found inadequate for fully describing the size distribution of lakes, due
to deviations at the two ends of size range. Based on observed and simulated
lakes in 11 hydro-climatic zones of China, we established a conceptual model
for lake systems, which covers the whole size range of lake size distribution
and reveals the underlying driving mechanism. The full lake size distribution
is composed of three components, with three phases featured by exponential,
stretched-exponential and power law distribution. The three phases represent
system states with successively increasing degrees of heterogeneity and
orderliness, and more importantly, indicate the dominance of exogenic and
endogenic forces, respectively. As the dominant driving force changes from
endogenic to exogenic, a phase transition occurs with lake size distribution
shifted from power law to stretched-exponential and further to exponential
distribution. Apart from compressing the power law phase, exogenic force also
increases its scaling exponent, driving the corresponding lake size power
spectrum into the regime of blue noise. During this process, the
autocorrelation function of the lake system diverges with a possibility of
going to infinity, indicating the loss of system resilience
AI-Oriented Two-Phase Multi-Factor Authentication in SAGINs: Prospects and Challenges
Space-air-ground integrated networks (SAGINs), which have emerged as an
expansion of terrestrial networks, provide flexible access, ubiquitous
coverage, high-capacity backhaul, and emergency/disaster recovery for mobile
users (MUs). While the massive benefits brought by SAGIN may improve the
quality of service, unauthorized access to SAGIN entities is potentially
dangerous. At present, conventional crypto-based authentication is facing
challenges, such as the inability to provide continuous and transparent
protection for MUs. In this article, we propose an AI-oriented two-phase
multi-factor authentication scheme (ATMAS) by introducing intelligence to
authentication. The satellite and network control center collaborate on
continuous authentication, while unique spatial-temporal features, including
service features and geographic features, are utilized to enhance the system
security. Our further security analysis and performance evaluations show that
ATMAS has proper security characteristics which can meet various security
requirements. Moreover, we shed light on lightweight and efficient
authentication mechanism design through a proper combination of
spatial-temporal factors.Comment: Accepted by IEEE Consumer Electronics Magazin
A Mixed-Integer SDP Solution Approach to Distributionally Robust Unit Commitment with Second Order Moment Constraints
A power system unit commitment (UC) problem considering uncertainties of
renewable energy sources is investigated in this paper, through a
distributionally robust optimization approach. We assume that the first and
second order moments of stochastic parameters can be inferred from historical
data, and then employed to model the set of probability distributions. The
resulting problem is a two-stage distributionally robust unit commitment with
second order moment constraints, and we show that it can be recast as a
mixed-integer semidefinite programming (MI-SDP) with finite constraints. The
solution algorithm of the problem comprises solving a series of relaxed MI-SDPs
and a subroutine of feasibility checking and vertex generation. Based on the
verification of strong duality of the semidefinite programming (SDP) problems,
we propose a cutting plane algorithm for solving the MI-SDPs; we also introduce
a SDP relaxation for the feasibility checking problem, which is an intractable
biconvex optimization. Experimental results on a IEEE 6-bus system are
presented, showing that without any tunings of parameters, the real-time
operation cost of distributionally robust UC method outperforms those of
deterministic UC and two-stage robust UC methods in general, and our method
also enjoys higher reliability of dispatch operation
Fluorescence imaging of beta cell primary cilia
Primary cilia are slender cell-surface organelles that project into the intercellular space. In pancreatic beta cells, primary cilia coordinate a variety of cell responses including GPCR signaling, calcium influx, and insulin secretion, along with likely many underappreciated roles in islet development and differentiation. To study cilia function in islet biology, direct visualization of primary cilia by microscopic methods is often a necessary first step. Ciliary abundance, distribution, and morphology are heterogeneous among islet cells and are best visualized by fluorescence microscopy, the tools for which are readily accessible to most researchers. Here we present a collection of fluorescence imaging methods that we have adopted and optimized for the observation of primary cilia in mouse and human islets. These include conventional confocal microscopy using fixed islets and pancreas sections, live-cell imaging with cilia-targeted biosensors and probes, cilia motion recordings, and quantitative analysis of primary cilia waveform in th
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