Inspection of fine wires simplified by capillary tube wire holder

Capillary tube wire holder provides a mount for fine wires for photomicrographs. The holder is mounted in a stainless steel tube and cast in a transparent casting material. It protects and permits easy location of the wire

Pocket Banks and Out-of-Pocket Losses: Links between Corruption and Contagion

The author describes a model with a corrupt banking system, in which bankers knowingly lend at market interest rates to back projects riskier than the market rate indicates. Faced with early withdrawals, bankers turn to an interbank market, which may be available in an unfettered way, available but subject to screening, or unavailable. The presence of corruption increases the probability of contagious bank failure significantly. This fact holds in a perfect information environment, as well as in some environments with imperfect information. The model suggests that financial stability can be imperilled by corrupt lending.Financial institutions; Financial stability

When Bad Things Happen to Good Banks: Contagious Bank Runs and Currency Crises

The author develops a twin crisis model featuring multiple banks. At each bank, domestic and foreign depositors play a banking game. This game has a run and a no-run equilibrium. Bank failures drain reserves in addition to those drained when foreign agents convert domestic currency to foreign. The fixed exchange rate collapses if a threshold number of banks fail. Agents observe sunspots to aid their equilibrium selection. The numerical solution matches somewhat the Turkish financial sector prior to the crisis of 2001. The Turkish exchange rate appears to have exposed the financial system to a 10 per cent risk of collapse.Exchange rates, Financial institutions

Computational aspects of sensitivity calculations in transient structural analysis

A key step in the application of formal automated design techniques to structures under transient loading is the calculation of sensitivities of response quantities to the design parameters. This paper considers structures with general forms of damping acted on by general transient loading and addresses issues of computational errors and computational efficiency. The equations of motion are reduced using the traditional basis of vibration modes and then integrated using a highly accurate, explicit integration technique. A critical point constraint formulation is used to place constraints on the magnitude of each response quantity as a function of time. Three different techniques for calculating sensitivities of the critical point constraints are presented. The first two are based on the straightforward application of the forward and central difference operators, respectively. The third is based on explicit differentiation of the equations of motion. Condition errors, finite difference truncation errors, and modal convergence errors for the three techniques are compared by applying them to a simple five-span-beam problem. Sensitivity results are presented for two different transient loading conditions and for both damped and undamped cases

Reducing distortion and internal forces in truss structures by member exchanges

Manufacturing errors in the length of members or joint diameters of large truss reflector backup structures may result in unacceptable large distortion errors or member forces. However, it may be possible to accurately measure these length or diameter errors. The present work suggests that a member and joint placement strategy may be used to reduce distortion errors and internal member forces. A member and joint exchange algorithm is used to demonstrate the potential of this approach on several 102-member and 660-member truss reflector structures. It is shown that it is possible to simultaneously reduce the rms of the surface error and the rms of member forces by two orders of magnitude by member and joint exchanges

Are Currency Crises Low-State Equilibria? An Empirical, Three-Interest-Rate Model

Suppose that the dynamics of the macroeconomy were given by (partly) random fluctuations between two equilibria: "good" and "bad." One would interpret currency crises (or recessions) as a shift from the good equilibrium to the bad. In this paper, the authors specify a dynamic investment-savings-aggregate-supply (IS-AS) model, determine its closed-form solution, and examine numerically its comparative statics. The authors estimate the model via maximum likelihood, using data for Argentina, Canada, and Turkey. Since the data show no support for the multiple-equilibrium explanation of fluctuations, the authors cast doubt on the third-generation models of currency crisis.Uncertainty and monetary policy

Are Suburban Firms More Likely to Discriminate Against African Americans?

This paper presents a test of the hypothesis that employers in suburban locations are more likely to discriminate against African Americans than are employers located in central cities. Using a difference-in-difference framework, we compare central-city/suburban differences in racial hiring outcomes for firms where a white person is in charge of hiring (white employers, for short) to similar geographic differences in outcomes for firms where a black person is in charge of hiring (black employers). We find that both suburban black and white employers hire fewer blacks than their central-city counterparts. Moreover, the central-city/suburban hiring gap among black employers is as large as, or larger than, that of white employers. Suburban black employers, however, receive many more applications from blacks and hire more blacks than do white firms in either location.

Complexity of colouring problems restricted to unichord-free and \{square,unichord\}-free graphs

A \emph{unichord} in a graph is an edge that is the unique chord of a cycle. A \emph{square} is an induced cycle on four vertices. A graph is \emph{unichord-free} if none of its edges is a unichord. We give a slight restatement of a known structure theorem for unichord-free graphs and use it to show that, with the only exception of the complete graph $K_4$, every square-free, unichord-free graph of maximum degree~3 can be total-coloured with four colours. Our proof can be turned into a polynomial time algorithm that actually outputs the colouring. This settles the class of square-free, unichord-free graphs as a class for which edge-colouring is NP-complete but total-colouring is polynomial

Weather-Based Crop Insurance Contracts for African Countries

Weather constitutes the major source for production risk in agriculture. Weather index can be used construct crop insurance that demand less information and can avoid moral hazard and adverse selection problems. Based on mean-variance model, theoretical results on the optimal insurance coverage and its impact from risk preference, basis risk, and premium loading are derived, which are quite consistent to the empirical results from the expected utility model. Using South Africa corn data, we investigate growers' demand and efficiency of alternative hypothetical weather index crop insurance programs. In contrast to previous work that suggests that a single-variable weather index suffices to develop an insurance contract, this study shows that the insured grower achieves a higher utility from multivariate weather indices. The most important single weather index we found in the study area was GDD, and the combination of rainfall and either temperature or GDD outperformed the single variable indices by a large margin. Depending on the growers risk preference, s/he may choose to buy o r offer such insurance for sale if the price is not actuarially fair. The risk protection value of weather-indexed-insurance follows the predictive power of the index on yield in general, though not exactly.Risk and Uncertainty, C51, C61, G22, Q14,