A comparative test of differential scanning calorimeters

The Dutch Society for Thermal Analysis has developed tests to measure the resolution and the sensitivity of Differential Scanning Calorimeters. For this test the substance 4,4-azoxyanisole is used. This substance shows two transitions: a solid to liquid crystal transition at about 117°C (H120 J g^–1) and a liquid crystal to isotropic liquid transition at about 134°C (H2 J g^–1). The resolution test is performed using an amount of 5 mg substance and a high heating rate of 20°C min^–1. The resolution is evaluated by measuring how well the two peaks are separated. An amount of 0.25 mg substance and a low heating rate of 0.1 °C min^–1 is used for the sensitivity test. The sensitivity is evaluated as the ratio of the peak height of the LC-transition and the top-top noise level.Members of the TAWN were asked to participate in the test. Each participant was provided with an amount of sample and a test procedure. 47 Contributions were received and these results are presented.All members of the TAWN who participated in the tests are thanked for their contributions.     

Effect of uncertainty on the bifurcation behavior of pitching airfoil stall flutter

In this paper the effect of system parametric uncertainty on the stall flutter bifurcation behavior of a pitching airfoil is studied. The aerodynamic moment on the two-dimensional rigid airfoil with nonlinear torsional stiffness is computed using the ONERA dynamic stall model. The pitch natural frequency, a cubic structural nonlinearity parameter, and the structural equilibrium angle are assumed to be uncertain. The effect on the amplitude of the response, the bifurcation of the probability distribution, and the flutter boundary is considered. It is demonstrated that the system parametric uncertainty results already in 5% probability of pitching stall flutter at a 12.5% earlier position than the point where a deterministic analysis would predict unstable behavior. Probabilistic collocation is found to be more efficient than the Galerkin polynomial chaos method and Monte Carlo simulation for modeling uncertainty in the post-bifurcation domain.     

The parallel magnetic susceptibility and specific heat of the antiferromagnetic Ising linear-chain system with spin S = 2, 52, and 3

The parallel magnetic susceptibility and specific heat of the antiferromagnetic Ising linear-chain system with spin S = 2, $\text{5}\text{2}$, and 3 are calculated using the matrix approach. The results for spin $\text{S =}\text{1}\text{2}$, 1, $\text{3}\text{2}$, and 2 are checked against known results for these cases.