Single-particle model for a granular ratchet

A simple model for a granular ratchet corresponding to a single grain bouncing off a vertically vibrating sawtooth-like base is studied. Depending on the vibration strength, the sawtooth roughness and the restitution coefficient, horizontal transport in both the preferred and unfavoured directions is observed. A phase diagram indicating the regions in parameter space where each of the three possible regimes (no current, normal current, and current reversal) occurs is presented.Comment: 7 pages, 3 figures, submitted to Physica

Hausdorff dimension of boundaries of self-affine tiles in R^n

We present a new method to calculate the Hausdorff dimension of a certain class of fractals: boundaries of self-affine tiles. Among the interesting aspects are that even if the affine contraction underlying the iterated function system is not conjugated to a similarity we obtain an upper- and lower-bounds for its Hausdorff dimension. In fact, we obtain the exact value for the dimension if the moduli of the eigenvalues of the underlying affine contraction are all equal (this includes Jordan blocks). The tiles we discuss play an important role in the theory of wavelets. We calculate the dimension for a number of examples

A New Method for Multi-Bit and Qudit Transfer Based on Commensurate Waveguide Arrays

The faithful state transfer is an important requirement in the construction of classical and quantum computers. While the high-speed transfer is realized by optical-fibre interconnects, its implementation in integrated optical circuits is affected by cross-talk. The cross-talk between densely packed optical waveguides limits the transfer fidelity and distorts the signal in each channel, thus severely impeding the parallel transfer of states such as classical registers, multiple qubits and qudits. Here, we leverage on the suitably engineered cross-talk between waveguides to achieve the parallel transfer on optical chip. Waveguide coupling coefficients are designed to yield commensurate eigenvalues of the array and hence, periodic revivals of the input state. While, in general, polynomially complex, the inverse eigenvalue problem permits analytic solutions for small number of waveguides. We present exact solutions for arrays of up to nine waveguides and use them to design realistic buses for multi-(qu)bit and qudit transfer. Advantages and limitations of the proposed solution are discussed in the context of available fabrication techniques

Marketing co-operatives

Marketing co-operatives (MCs) are analysed from an incomplete contracting perspective. The requirement of the domination of control by the members of a MC is a threat to the survival of a MC in markets where the level of asset specificity at the processing stage of production is increasing. However, a MC may remain an efficient governance structure when the increasing level of asset specificity is compensated for by a sufficient increase in the extent of product differentiation.incomplete contracts;marketing cooperatives

Marketing Cooperatives and Financial Structure

The relationship between the financial structure of marketing cooperatives and the requirement of the domination of control by the members of the cooperative is analysed with an emphasis on incomplete contracts and system complementarities. It is argued that the disappearance of shortage markets in agricultural and horticultural markets poses a serious threat to the survival of the marketing cooperative as an organizational form. Comparative statics results are presented regarding aspects of financial instruments (e.g. personal liability, financial contributions and bank relationships), organizational form (e.g. democratic decision making and internal control systems) and economic systems.

Marketing Cooperatives and Financial Structure

The relationship between the financial structure of a marketing cooperative (MC) and the requirement of the domination of control by the members is analysed from a transaction costs perspective. A MC receives less favorable terms on outside equity than a conventional firm because the decision power regarding new investments is not allocated to the providers of these funds. This is a serious threat to the survival of a MC in a market where efficient investments are characterized by an increasing level of asset specificity at the processing stage of production. A MC is predicted to be an efficient organizational form when the level of asset specificity at the processing stage of production is at a low or immediate level compared to the level of asset specificity at the farming stage of production.finance;transaction costs economics;marketing cooperative

On The Future of Co-operatives

Two extensions are formulated of the analysis of the allocation ofdecision rights in Hendrikse and Veerman (2001). First, the incompletecontracts in their article can be viewed as simple long-termcontracts, i.e. it is not allowed to make the allocation of authoritycontingent on the circumstances. Contingent long-term contracts arenow considered. Second, another aspect of decision rights is thefrequency of meetings between the owners and managers of enterprises.This aspect will be addressed from a long-term contract perspective aswell as a loss aversion perspective.contingent control rights;frequency of board meetings