921 research outputs found
Assessing systemic risk due to fire sales spillover through maximum entropy network reconstruction
Assessing systemic risk in financial markets is of great importance but it
often requires data that are unavailable or available at a very low frequency.
For this reason, systemic risk assessment with partial information is
potentially very useful for regulators and other stakeholders. In this paper we
consider systemic risk due to fire sales spillover and portfolio rebalancing by
using the risk metrics defined by Greenwood et al. (2015). By using the Maximum
Entropy principle we propose a method to assess aggregated and single bank's
systemicness and vulnerability and to statistically test for a change in these
variables when only the information on the size of each bank and the
capitalization of the investment assets are available. We prove the
effectiveness of our method on 2001-2013 quarterly data of US banks for which
portfolio composition is available.Comment: 36 pages, 6 figures, Accepted on Journal of Economic Dynamics and
Contro
Handling robot constraints within a Set-Based Multi-Task Priority Inverse Kinematics Framework
Set-Based Multi-Task Priority is a recent framework to handle inverse
kinematics for redundant structures. Both equality tasks, i.e., control
objectives to be driven to a desired value, and set-bases tasks, i.e., control
objectives to be satisfied with a set/range of values can be addressed in a
rigorous manner within a priority framework. In addition, optimization tasks,
driven by the gradient of a proper function, may be considered as well, usually
as lower priority tasks. In this paper the proper design of the tasks, their
priority and the use of a Set-Based Multi-Task Priority framework is proposed
in order to handle several constraints simultaneously in real-time. It is shown
that safety related tasks such as, e.g., joint limits or kinematic singularity,
may be properly handled by consider them both at an higher priority as
set-based task and at a lower within a proper optimization functional.
Experimental results on a 7DOF Jaco$^2
Henri G. Schogt. Linguistics, Literary Analysis, and Literary Translation. University of Toronto Press, 1988, 177 pages.
Safety-related Tasks within the Set-Based Task-Priority Inverse Kinematics Framework
In this paper we present a framework that allows the motion control of a
robotic arm automatically handling different kinds of safety-related tasks. The
developed controller is based on a Task-Priority Inverse Kinematics algorithm
that allows the manipulator's motion while respecting constraints defined
either in the joint or in the operational space in the form of equality-based
or set-based tasks. This gives the possibility to define, among the others,
tasks as joint-limits, obstacle avoidance or limiting the workspace in the
operational space. Additionally, an algorithm for the real-time computation of
the minimum distance between the manipulator and other objects in the
environment using depth measurements has been implemented, effectively allowing
obstacle avoidance tasks. Experiments with a Jaco manipulator, operating in
an environment where an RGB-D sensor is used for the obstacles detection, show
the effectiveness of the developed system
The multiplex structure of interbank networks
The interbank market has a natural multiplex network representation. We
employ a unique database of supervisory reports of Italian banks to the Banca
d'Italia that includes all bilateral exposures broken down by maturity and by
the secured and unsecured nature of the contract. We find that layers have
different topological properties and persistence over time. The presence of a
link in a layer is not a good predictor of the presence of the same link in
other layers. Maximum entropy models reveal different unexpected substructures,
such as network motifs, in different layers. Using the total interbank network
or focusing on a specific layer as representative of the other layers provides
a poor representation of interlinkages in the interbank market and could lead
to biased estimation of systemic risk.Comment: 41 pages, 8 figures, 10 table
Interbank markets and multiplex networks: centrality measures and statistical null models
The interbank market is considered one of the most important channels of
contagion. Its network representation, where banks and claims/obligations are
represented by nodes and links (respectively), has received a lot of attention
in the recent theoretical and empirical literature, for assessing systemic risk
and identifying systematically important financial institutions. Different
types of links, for example in terms of maturity and collateralization of the
claim/obligation, can be established between financial institutions. Therefore
a natural representation of the interbank structure which takes into account
more features of the market, is a multiplex, where each layer is associated
with a type of link. In this paper we review the empirical structure of the
multiplex and the theoretical consequences of this representation. We also
investigate the betweenness and eigenvector centrality of a bank in the
network, comparing its centrality properties across different layers and with
Maximum Entropy null models.Comment: To appear in the book "Interconnected Networks", A. Garas e F.
Schweitzer (eds.), Springer Complexity Serie
Ptolomaeus: the Web Cartographer
The hugeness of the Web and its continuous growth have made navigation in the Internet extremely difficult. The new advanced features provided by HTML extensions and scripting languages allow a common browser to manage powerful hypermedial representation in each single page but leave unsolved some structural problems of the Web. In fact, the process of finding information by surfing the Web is mainly hindered by the lack of a reasonable schema in the hyperspace; broken and redundant links make the problem even worse. This leads the user to become ”lost in the hyperspace” (LH-Syndrome)
An Assistive Shared Control Architecture for a Robotic Arm Using EEG-Based BCI with Motor Imagery
Nitrate-reducing bacterial activity under alkaline conditions in nuclear waste repositories for intermediate-level bituminous nuclear waste
Effects of Dynamic Model Errors in Task-Priority Operational Space Control
Control algorithms of many Degrees Of Freedom (DOFs) systems based on Inverse
Kinematics or Inverse Dynamics approaches are two well-known topics of research
in robotics. The large number of DOFs allows the design of many concurrent tasks
arranged in priorities, that can be solved either at kinematic or dynamic level. This
paper investigates the effects of modeling errors in operational space control algorithms
with respect to uncertainties affecting knowledge of the dynamic parameters. The effects
on the null-space projections and the sources of steady-state errors are investigated.
Numerical simulations with on-purpose injected errors are used to validate the thoughts
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