Evolution of modern aviation and experimental and technical researches in aerodynamic laboratories

The evolution of construction techniques and the use of metal in wings is presented. Drag is discussed along with the fuselage and tail. The interaction of these parts is also investigated

Dynamics of quantum adiabatic evolution algorithm for Number Partitioning

We have developed a general technique to study the dynamics of the quantum adiabatic evolution algorithm applied to random combinatorial optimization problems in the asymptotic limit of large problem size $n$. We use as an example the NP-complete Number Partitioning problem and map the algorithm dynamics to that of an auxilary quantum spin glass system with the slowly varying Hamiltonian. We use a Green function method to obtain the adiabatic eigenstates and the minimum excitation gap, $g_{\rm min}={\cal O}(n 2^{-n/2})$, corresponding to the exponential complexity of the algorithm for Number Partitioning. The key element of the analysis is the conditional energy distribution computed for the set of all spin configurations generated from a given (ancestor) configuration by simulteneous fipping of a fixed number of spins. For the problem in question this distribution is shown to depend on the ancestor spin configuration only via a certain parameter related to the energy of the configuration. As the result, the algorithm dynamics can be described in terms of one-dimenssional quantum diffusion in the energy space. This effect provides a general limitation on the power of a quantum adiabatic computation in random optimization problems. Analytical results are in agreement with the numerical simulation of the algorithm.Comment: 32 pages, 5 figures, 3 Appendices; List of additions compare to v.3: (i) numerical solution of the stationary Schroedinger equation for the adiabatic eigenstates and eigenvalues; (ii) connection between the scaling law of the minimum gap with the problem size and the shape of the coarse-grained distribution of the adiabatic eigenvalues at the avoided-crossing poin

Teaching tactual discrimination of braille characters to beginning braille readers

We taught three children with visual impairments to make tactual discriminations of the braille alphabet within a matching-to-sample format. That is, we presented participants with a braille character as a sample stimulus and they were to select the matching stimulus from an array of three comparisons. In order to minimize participant errors, we arranged braille characters into training sets in which the target and non-target stimuli in the comparison arrays were initially maximally different in terms of the number of dots comprising each character. As participants mastered these discriminations, we then increased the similarity between target and non-target comparisons (i.e., an approximation of stimulus fading). All three participants’ accuracy systematically increased following the introduction of this procedure

New Application of Principle of Variable-camber Airfoil : Lachassagne System

In studying the application of his system of varying the camber of airfoil sections, Mr. Lachassagne has just obtained a series of airfoil sections whose polar envelope presents truly remarkable aerodynamic properties

Lecture on aerodynamics

This lecture deals with four main subjects: methods of studying air resistance, experimental aerodynamics, propellers and stability of airplanes

Drag or negative traction of geared-down supporting propellers in the downward vertical glide of a helicopter

Discussed here are computations of drag or negative traction of geared down supporting propellers in the downward vertical glide of a helicopter. By means of Frounde's Theory, the maximum value of the drag of a windmill is calculated. For wooden propellers, the author finds that the difference between the drag and the weight is proportional to the number of blades and is larger for propellers of small diameter; thus it is 25 kg. for a six blade propeller with a diameter of 2 m. 50. The author notes that if we are to adopt large propellers, we must have recourse to a different method of construction, resulting in large dimension propellers much lighter than those made of wood. In discussing insufficient drag, the author notes that the question of the drag of geared down supporting propellers can only be decided by experiment

High density QCD with static quarks

We study lattice QCD in the limit that the quark mass and chemical potential are simultaneously made large, resulting in a controllable density of quarks which do not move. This is similar in spirit to the quenched approximation for zero density QCD. In this approximation we find that the deconfinement transition seen at zero density becomes a smooth crossover at any nonzero density, and that at low enough temperature chiral symmetry remains broken at all densities.Comment: LaTeX, 18 pages, uses epsf.sty, postscript figures include