A Joint Criterion for Reachability and Observability of Nonuniformly Sampled Discrete Systems

A joint characterization of reachability (controllability) and observability (constructibility) for linear SISO nonuniformly sampled discrete systems is presented. The work generalizes to the nonuniform sampling the criterion known for the uniform sampling. Emphasis is on the nonuniform sampling sequence, which is believed to be an additional element for analysis and handling of discrete systems.Comment: 8 pages, 1 figur

Cote d'Ivoire : private sector dynamics and constraints

Private sector assessments provide information and analysis essential to formulating strategies for alleviating constraints on private sector development. They are meant to contribute both to the Bank's policy dialogue with borrowing governments and to the formulation of country assistance strategies. Theauthors examine the constraints on growth faced by private enterprises and how these relate to the policy and institutional environment in Cote d'Ivoire. They employ new data sources as well as surveys of, and in-depth interviews with, private entrepreneurs. They focus on: the effects of taxes and labor regulation on private firms; the impact of public spending on private sector development; and the role of informality in enterprise activity. Following are some of their findings. Tax policy and enforcement impose a heavy financial burden on a shrinking base of formal enterprises, whose regulatory burden has also grown. Taxes are increasingly independent of a firm's profits. This substantial fixed cost may lead some businesses to exit prematurely and may discourage others from formal entry. The overall tax burden on small and medium-size enterprises has risen disproportionately, to levels that discourage formal participation in the economy. Informal firms pay some taxes, but there is considerable leakage in collection. Unnecessary rigidities in labor policies weigh less heavily than expected on firms, because they avoid their full costs through such means as subcontracting and apprenticeships. The restrictions nonetheless limit firms'flexibility of operation and ability to reward merit. In the 1980s, public spending increasingly channeled limited financial resources and human capital toward nondevelopment purposes, including poorly performing enterprises and elite-oriented services, precluding their use in the private sector. The methods of financing public spending (such as withholding taxes and accumulating arrears) have sharply curtailed the capital available to private enterprises. The public sector's dramatic accumulation of arrears and growing reputation as a bad customer are undermining the competitive private supply of goods and services to the government. Government employment policies attract many of the most qualified potential entrepreneurs and business professionals to governmentemployment. Rather than a sharp divide, there is a continuum between small informal and large formal firms. Some medium-size and large formal firms engage in informal behavior, and large firms sometimes lower their costs through links with informal firms - including purchases of inputs that have escaped regulation and taxes.Banks&Banking Reform,Environmental Economics&Policies,Public Sector Economics&Finance,Private Participation in Infrastructure,Microfinance

Linear solutions for cryptographic nonlinear sequence generators

This letter shows that linear Cellular Automata based on rules 90/150 generate all the solutions of linear difference equations with binary constant coefficients. Some of these solutions are pseudo-random noise sequences with application in cryptography: the sequences generated by the class of shrinking generators. Consequently, this contribution show that shrinking generators do not provide enough guarantees to be used for encryption purposes. Furthermore, the linearization is achieved through a simple algorithm about which a full description is provided