Part Form Errors Predicted from Machine Tool Performance Measurements

Machine tool performance testing, as defined by IS0 230 and ANSI B5.54 has been successfully used to maintain and improve the accuracy and repeatability of production-level machine tools. In this study, a controlled series of experiments have been used to test the efficacy of these performance tests in the prediction of part form errors. Results are shown for flatness, squareness, position, and profile tolerances. The experimental results suggest that standard machine tool performance tests can also be used to predict the “best-case” tolerances that can be achieved for particular part features

Dilution jet mixing program, phase 3

The objectives of the program were: (1) to extend the data base on mixing of a single-sided row of jets with a confined crossflow, (2) to collect a data base on mixing of multiple rows of jets with confined crossflow, (3) to develop empirical jet mixing correlations, and (4) to perform limited three-dimensional calculations for some of these test configurations. The tests were performed with uniform mainstream conditions for several orifice plate configurations. Schematics of the test section and the orifice configurations are given. Temperature and pressure measurements were made in the test section at 4 axial and 11 transverse stations, using a 60-element rake probe. The measured temperature distributions for these tests are reported

Tip vortices of wings in subsonic and transonic flow: A numerical simulation

Thin layer Navier-Stokes and Euler equations are numerically solved using a multi-block zonal approach to simulate the formation and roll up of tip vortices of wings in subsonic and transonic flows. Several wing planforms were considered to examine the influence of tip-cap shape, planform geometry and free stream Mach number on the formation process. A good definition of the formation and qualitative roll up of tip vortices was achieved

Transonic interactions of unsteady vortical flows

Unsteady interactions of strong concentrated vortices, distributed gusts, and sharp-edged gusts with stationary airfoils were analyzed in two-dimensional transonic flow. A simple and efficient method for introducing such vortical disturbances was implemented in numerical codes that range from inviscid transonic small disturbance to thin-layer Navier Stokes. The numerical results demonstrate the large distortions in the overall flow field and in the surface air loads that are produced by various vortical interactions. The results of the different codes are in excellent qualitative agreement, but, as might expected, the transonic small-disturbance calculations are deficient in the important region near the leading edge

Dilution jet mixing program, phase 3

The main objectives for the NASA Jet Mixing Phase 3 program were: extension of the data base on the mixing of single sided rows of jets in a confined cross flow to discrete slots, including streamlined, bluff, and angled injections; quantification of the effects of geometrical and flow parameters on penetration and mixing of multiple rows of jets into a confined flow; investigation of in-line, staggered, and dissimilar hole configurations; and development of empirical correlations for predicting temperature distributions for discrete slots and multiple rows of dilution holes

Low frequency and Microwave Magnetoelectric Effects in Thick Film Heterostructures of Lithium Zinc Ferrite and Lead Zirconate Titanate

Magnetoelectric (ME) coupling at low frequencies and at x-band have been investigated in layered samples containing zinc substituted lithium ferrite and lead zirconate titanate (PZT). Multilayers of Li0.5-x/2ZnxFe2.5-x/2O4 (LZFO) (x=0-0.4) and PZT were prepared by lamination and sintering of thick films. At low frequencies (10-1000 Hz), the ME voltage coefficient for transverse fields is higher than for longitudinal fields. With Zn substitution in the ferrite, transverse coupling increases to a maximum for x=0.3 and then decreases for higher x. Analysis based on our model for a bilayer implies an efficient magneto-mechanical coupling with Zn substitution, resulting in strong ME interactions. Microwave ME coupling is studied through measurements of shift in the ferromagnetic resonance field due to an applied electric field. Estimated ME constants from such data are in agreement with our model for a ferrite-PZT bilayer.Comment: To be published in Solid State Communication

MICROWAVE DRYING OF ALOE VERA (ALOE BARBADENSIS MILLER): MATHEMATICAL MODELING, KINETICS AND MASS TRANSFER ASPECTS

Aloe vera has extensive application in food and pharmaceutical industry in fact contains 97 percent of water. It’s perishable in nature and poor shelf life makes it essential to study the drying characteristics of aloe vera. The objective of this present study is to investigate the effect of different microwave (MW) respective power levels (180 , 360 ,540 , 720 and 900 Watts ) regarding the  moisture ratio (MR), drying rate (DR), effective moisture diffusivity (EMD), specific energy consumption (SEC) and drying efficiency (DE) of aloe vera. The drying process took 70 - 26 .5 minutes for attainment of equilibrium moisture content. A mathematical model done by Midilli et al.  is considered to be the best and most suitable for a drying conditions among the various thin layer models. The effective moisture diffusivity value at 180 Watts (W) of MW power was found as 4.5 × 10-8 m2/sec. while it was raised to 9.45 x10-7 m2/sec at 900 W in this study. Lowest energy consumption 1.4 MJ/Kg water and maximum drying efficiency occurred at higher microwave power level 900 Watts due to less drying duration (time)

Fast Estimation of Outage Probabilities in MIMO Channels

Fast estimation methods for small outage probabilities of signaling in fading multiple-input multiple-output (MIMO) channels are developed. Communication over such channels is of much current interest, and quick and accurate methods for estimating outage capacities are needed. The methods described herein use adaptive importance sampling (IS) techniques as developed in a series of recent publications. Fast algorithms are provided for evaluating "nonergodic" capacities of Rayleigh fading MIMO channels. The methodology can be extended to more general models. Numerical results on outage capacity are provided, and these extend and complement known results in the literature

Flowfield and acoustic characteristics of telescope cavity in SOFIA platform

Unsteady three-dimensional flowfields are calculated for the Stratospheric Observatory For Infrared Astronomy (SOFIA) at both free-flight cruise and wind tunnel conditions with a view to help in the design process of an acoustically quiet telescope cavity and to understand the flow physics of a three dimensional cavity. The calculation method is based on the numerical solution of thin layer Navier-Stokes equations on a Chimera overset grid system. The Boeing 747-200 aircraft is examined as one option for the SOFIA platform. The flowfield domain is composed of 45 grids consisting of over 4.1 million points. Numerical simulations are performed for both wind tunnel and free-flight cruise conditions at one freestream condition of M(infinity) = 0.85, alpha = 2.5 deg. Comparison of results from wind tunnel simulation show good agreement with experimental data for time-averaged surface pressures, drag for the empennage, and sound pressure levels and power spectra at various locations within the cavity and on the telescope. The presence of the open cavity induces an incremental drag increase, an increased acoustic radiation, and an increase in unsteady pressure loads on the telescope. Its impact on the effectiveness of aircraft control surfaces appears minimal