10,520 research outputs found
Economic Integrations and their Role in Intra-Africa Trade
Open access articleThis paper investigates the roles of economic integrations (EIs) in the development of trade within Africa region vis-à-vis Africa’s
trade with the rest of the world. Specifically, we examine how the removal of trade barriers could eventually lead to
harmonization of trade policies in Africa and in turn the growth of trade between the member countries. Our study focuses on a
20-year period in which we observe that as the domestic markets for the developing economies continue to expand, the expected
trend is that their export competitiveness will also expand. However, data shows that while African Nations put EIs at the core
of their development, only 10 percent of total value of African trade is intra-African in nature, and 90 percent is with countries
outside the region. Using a gravity model adapted for African context, our analysis indicates that streamlining and employing
similar policies encouraged and promoted trade. As trade entails the interaction of many other sectors, our results imply that
policy reforms to deepen their economic integrations should proceed at a faster rate to stimulate investment flows from both
intra-regional and extra-regional sources in addition to the diversification of products for export
Phase transitions in the Shastry-Sutherland lattice
Two recently developed theoretical approaches are applied to the
Shastry-Sutherland lattice, varying the ratio between the couplings on
the square lattice and on the oblique bonds. A self-consistent perturbation,
starting from either Ising or plaquette bond singlets, supports the existence
of an intermediate phase between the dimer phase and the Ising phase. This
existence is confirmed by the results of a renormalized excitonic method. This
method, which satisfactorily reproduces the singlet triplet gap in the dimer
phase, confirms the existence of a gapped phase in the interval
Comment: Submited for publication in Phys. Rev.
Effective Capacity and Randomness of Closed Sets
We investigate the connection between measure and capacity for the space of
nonempty closed subsets of {0,1}*. For any computable measure, a computable
capacity T may be defined by letting T(Q) be the measure of the family of
closed sets which have nonempty intersection with Q. We prove an effective
version of Choquet's capacity theorem by showing that every computable capacity
may be obtained from a computable measure in this way. We establish conditions
that characterize when the capacity of a random closed set equals zero or is
>0. We construct for certain measures an effectively closed set with positive
capacity and with Lebesgue measure zero
Stochastic Tools for Network Intrusion Detection
With the rapid development of Internet and the sharp increase of network
crime, network security has become very important and received a lot of
attention. We model security issues as stochastic systems. This allows us to
find weaknesses in existing security systems and propose new solutions.
Exploring the vulnerabilities of existing security tools can prevent
cyber-attacks from taking advantages of the system weaknesses. We propose a
hybrid network security scheme including intrusion detection systems (IDSs) and
honeypots scattered throughout the network. This combines the advantages of two
security technologies. A honeypot is an activity-based network security system,
which could be the logical supplement of the passive detection policies used by
IDSs. This integration forces us to balance security performance versus cost by
scheduling device activities for the proposed system. By formulating the
scheduling problem as a decentralized partially observable Markov decision
process (DEC-POMDP), decisions are made in a distributed manner at each device
without requiring centralized control. The partially observable Markov decision
process (POMDP) is a useful choice for controlling stochastic systems. As a
combination of two Markov models, POMDPs combine the strength of hidden Markov
Model (HMM) (capturing dynamics that depend on unobserved states) and that of
Markov decision process (MDP) (taking the decision aspect into account).
Decision making under uncertainty is used in many parts of business and
science.We use here for security tools.We adopt a high-quality approximation
solution for finite-space POMDPs with the average cost criterion, and their
extension to DEC-POMDPs. We show how this tool could be used to design a
network security framework.Comment: Accepted by International Symposium on Sensor Networks, Systems and
Security (2017
Equilibrium problems for Raney densities
The Raney numbers are a class of combinatorial numbers generalising the
Fuss--Catalan numbers. They are indexed by a pair of positive real numbers
with and , and form the moments of a probability
density function. For certain the latter has the interpretation as the
density of squared singular values for certain random matrix ensembles, and in
this context equilibrium problems characterising the Raney densities for and have recently been proposed. Using two
different techniques --- one based on the Wiener--Hopf method for the solution
of integral equations and the other on an analysis of the algebraic equation
satisfied by the Green's function --- we establish the validity of the
equilibrium problems for general and similarly use both methods to
identify the equilibrium problem for ,
and . The Wiener--Hopf method is used to extend the latter
to parameters for a non-negative integer,
and also to identify the equilibrium problem for a family of densities with
moments given by certain binomial coefficients.Comment: 13 page
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