A switching criterion for optimum performance of a third-order contractor acceleration control system having complex roots is presented. Analytical and analog-computer methods are utilized to determine this criterion. The resulting optimum transient responses are presented and compared with those of an equivalent linear system.

From Introduction: "Experimental results for flow in a rectangular channel with injection through a porous wall are given in reference 1. As part of the study to guide future experiments, laminar flow in a semiporous channel is investigated herein. In the present investigation, a third-order perturbation solution for laminar incompressible flow in a semiporous channel is presented."

Report presenting a comparison of wind-tunnel and flight-measured values of stability and control characteristics. Generally, wind tunnels were found to predict all trends of characteristics reasonably well, but there are differences in parameters for certain values.

From Summary: "This report describes a theoretical and experimental investigation of the aerodynamic mixing by a standing sound wave downstream from a continuous line source of heat."

Report presenting a description of a pyrometer that is self-balancing and is able to replace the two conventional manual operations of the line-reversal method. A description of the operation of the pyrometer and the performance and results are provided.

Note presenting the pressure recovery, mass flow, and axial force of four bodies with nose inlets measured at Mach numbers between 1.4 and 2.0 and angles of attack of 0, 3, 6, and 9 degrees. The drag coefficients of axially symmetric diffusers operating at the maximum mass-flow rates were calculated from schileren photographs of the head shock waves and frictional drag considerations. Results regarding open-nose diffusers and conical-shock diffusers are provided.

Note presenting a general set of equilibrium differential equations for the plastic buckling of cylinders, which are based on assumptions that have led to the best agreement between theory and test data on inelastic buckling of flat plates. Test data are presented which indicate satisfactory agreement with the theoretical plasticity-reduction factors in most cases. Some of the topics addressed include compressive buckling and torsional buckling.

Note presenting an investigation of the relationships between conditions of hot-working and properties at high temperatures and the influence of the hot-working on response to heat treatment for an alloy containing nominally 20 percent chromium, 20 percent nickel, 20 percent cobalt, 3 percent molybdenum, 2 percent tungsten, and 1 percent columbium.

Note presenting an investigation of the slip-line structure in a series of aluminum single crystals deformed in tension in an electron microscope. In several of the crystals, the slip-line structure was examined after successive steps in the elongation.

From Summary :"Measurements of Poisson's ratios have been made in three orthogonal directions on aluminum alloy blocks in compression and on stainless-steel sheet in both tension and compression. These measurements, as well as those obtained by density determinations, show that there is no permanent plastic change in volume within the accuracy of observation. A method is suggested whereby a correlation may be effected between the measured individual values of the Poisson's ratios and the stress-strain curves for the material."

Note presenting results of tensile and bend tests on specimens in the T6 condition from 12- by 12- by 24-inch hand forgings of 7075 (75S) and 2014 (14S) aluminum alloy. Thirty-six notched bend specimens were tested as cantilever beams together with 48 tensile specimens of material adjacent to the bend specimens. Marked differences were found in the results of tensile tests on specimens in different directions and from different locations in the billet.

"The frequency characteristics and statistical properties of the buffet loads measured on the unswept wing and tail of a fighter airplane have been studied in the stall and in the shock regime. The results indicate that the wing loads in buffeting can be treated as the Gaussian response of a simple elastic system. The tail loads appear to represent a more complicated process" (p. 1).

Report presenting a method for determining the air forces on an oscillating finite wing of general plan form in subsonic flow, including the limiting case of sonic flow. The method is applied to rectangular and delta wings and is compared to existing theory.

Report presenting a numerical solution of the complete equations of inviscid compressible flow for the case of an inclined flat plate at free-stream Mach number 1. The results for the flow field show that the large changes of velocity that occur near the leading edge are confined to a surprisingly small part of the field. Results regarding the flow field and pressure distribution are provided.

"Specimens of HK31XA-H24 magnesium-alloy sheet from an experimental batch were heated to failure at nominal temperature rates from 0.2 F to 100 F per second under constant-load conditions. Rapid-heating yield and rupture stresses are presented and compared with the yield and ultimate stresses from elevated-temperature tensile stress-strain tests for 1/2-hour exposure. Linear temperature-rate parameters were used to correlate rapid-heating results by constructing master curves which can be used for predicting yield stresses and temperatures and for estimating rupture stresses and temperatures" (p. 1).

"Based on torsional instability theory, buckling charts are presented for determining the critical strain of hinged flanges stiffened by idealized lip and bulb elements" (p. 1).

Report presenting fatigue testing of eighteen box beams constructed according to four designs in order to study fatigue-crack propagation and accompanying stress redistribution. Two designs had stiffeners riveted to the cover, one had stiffeners bonded to the cover, and one had an integrally stiffened cover machined from a plate. Results regarding crack initiation, crack propagation, and stress distribution are provided.

Specimens of AZ31A-0 magnesium alloy sheet were heated to rupture at nominal rates of 0.2 F to 100 F per second under constant tensile load conditions. The data are presented and compared with the results of conventional tensile stress-strain tests at elevated temperatures after 1.2-hour exposure. A temperature-rate parameter was used to construct master curves from which stresses and temperatures for yield and rupture can be predicted under rapid-heating conditions. A comparison of the elevated-temperature tensile properties of AZ31A-0 and HK31XA-H24 magnesium-alloy sheet under both constant-temperature and rapid-heating conditions is included.

Note presenting tables of thermal properties of stream that have been prepared in an NBS-NACA series. They include, for real gas, the compressibility factor, the density, the specific heat at constant pressure, the enthalpy, the entropy, the free-energy function, the viscosity, and the thermal conductivity.

"A method is presented for obtaining the attenuation of a shock wave in a shock tube due to the unsteady boundary layer along the shock-tube walls. It is assumed that the boundary layer is thin relative to the tube diameter and induces one-dimensional longitudinal pressure waves whose strength is proportional to the vertical velocity at the edge of the boundary layer. The contributions of the various regions in a shock tube to shock attenuation are indicated" (p. 1).

Report presenting a combination of two previously published reports with an extension of the data to cover properties of fuels up to temperatures as high as 400 degrees Fahrenheit.