Wing flutter calculations with the CAP-TSD unsteady transonic small disturbance program

The application and assessment is described of CAP-TSD (Computational Aeroelasticity Program - Transonic Small Disturbance) code for flutter prediction. The CAP-TSD program was developed for aeroelastic analysis of complete aircraft configurations and was previously applied to the calculation of steady and unsteady pressures. Flutter calculations are presented for two thin, swept-and-tapered wing planforms with well defined modal properties. The calculations are for Mach numbers from low subsonic to low supersonic values, including the transonic range, and are compared with subsonic linear theory and experimental flutter data. The CAP-TSD flutter results are generally in good agreement with the experimental values and are in good agreement with subsonic linear theory when wing thickness is neglected

A tunable cavity-locked diode laser source for terahertz photomixing

An all solid-state approach to the precise frequency synthesis and control of widely tunable terahertz radiation by differencing continuous-wave diode lasers at 850 nm is reported in this paper. The difference frequency is synthesized by three fiber-coupled external-cavity laser diodes. Two of the lasers are Pound-Drever-Hall locked to different orders of a Fabry-Perot (FP) cavity, and the third is offset-frequency locked to the second of the cavity-locked lasers using a tunable microwave oscillator. The first cavity-locked laser and the offset-locked laser produce the difference frequency, whose value is accurately determined by the sum of an integer multiple of the free spectral range of the FP cavity and the offset frequency. The dual-frequency 850-nm output of the three laser system is amplified to 500 mW through two-frequency injection seeding of a single semiconductor tapered optical amplifier. As proof of precision frequency synthesis and control of tunability, the difference frequency is converted into a terahertz wave by optical-heterodyne photomixing in low-temperature-grown GaAs and used for the spectroscopy of simple molecules. The 3-dB spectral power bandwidth of the terahertz radiation is routinely observed to be ≾1 MHz. A simple, but highly accurate, method of obtaining an absolute frequency calibration is proposed and an absolute calibration of 10^(-7) demonstrated using the known frequencies of carbon monoxide lines between 0.23-1.27 THz

Food Habits of Large Striped Bass in the Lower Chesapeake Bay and its Tributaries March 1997 - May 1998

Striped bass, Marone saxatilis, are dominant seasonal predators in Chesapeake Bay and support a large recreational and commercial fishery. This document presents the results of a yearlong ( 1997-1998) food habits study of large (\u3e 450mm or 18 inches) striped bass in lower Chesapeake Bay and adjacent ocean waters. These fish comprise the coastal migratory stock and are found in greatest abundance in Chesapeake Bay during the spring and fall. Fish were obtained from a variety of commercial, recreational and fishery-independent sources and were captured by gill, fyke and pound nets as well as recreational hook and line, otter trawl and electroshocking gear. From March of 1997 to May of 1998, stomach contents of 1,988 striped bass were examined. The frequency of occurrence, numerical abundance and weight of prey items in the stomachs were combined into an index of relative importance (IRI). This compound index identifies important food items in the diet of striped bass. Overall, menhaden, Brevoortia tyrannus were the dominant prey, not only in IRI but also by weight and frequency of occurrence. Menhaden became an increasingly important forage species as striped bass size increased. Anchovies were second in overall importance and first in numerical abundance. Seasonally, and at different locations, gizzard shad, spot and herring were next in importance in the diet. Blue crabs appeared infrequently in the stomachs sampled and contributed little to the overall weight of stomach contents. Other invertebrates were of lesser importance. Two measures of stomach fullness were employed, a stomach fullness index which measures the relative fullness of the stomach, and the percent frequency of empty stomachs. The highest percentage of empty stomachs was found during the spring months of March and April and also during the summer months of August and September. The highest percentage of full stomachs and the greatest stomach fullness values were found during the fall months of October and November. Gear type, season and location partially determined the fullness of the stomachs and the percentage of empty stomachs but no single variable accounted solely for the observed differences in stomach fullness

Steady and unsteady transonic small disturbance analysis of realistic aircraft configurations

A transonic unsteady aerodynamic and aeroelastic code called CAP-TSD (Computational Aeroelasticity Program - Transonic Small Disturbance) was developed for application to realistic aircraft configurations. It permits the calculation of steady and unsteady flows about complete aircraft configurations for aeroelastic analysis of the flutter critical transonic speed range. The CAP-TSD code uses a time accurate approximate factorization algorithm for solution of the unsteady transonic small disturbance potential equation. An overview is given of the CAP-TSD code development effort along with recent algorithm modifications which are listed and discussed. Calculations are presented for several configurations including the General Dynamics 1/9th scale F-16C aircraft model to evaluate the algorithm and hence the reliability of the CAP-TSD code in general. Calculations are also presented for a flutter analysis of a 45 deg sweptback wing which agree well with the experimental data. Descriptions are presented of the CAP-TSD code and algorithm details along with results and comparisons which demonstrate the stability, accuracy, efficiency, and utility of CAP-TSD

An Examination of the Negotiability Concept of the Uniform Commercial Code

The aim of this undertaking is to examine the impact, if any, that the new Uniform Commercial Code may have on our concept of negotiability as it has evolved to the present time. Analysis will be confined to this one broad topic, but our considerations are not limited to one section of the Code. Although analytical thought about the negotiability concept has been applied to its many segments, which we call rules, apparently nothing has been written on the Code that has emphasized the expansion of the concept itself which is now possible. The inspiration for this article stems from the ostensibly innocent words “within this article” found in Section 3-104 of the Uniform Commercial Code. It is contended that these words could completely change the historical policy of the courts and launch us into an entirely new era for the negotiability concept. A full understanding of this position can only be gained by an inquiry into the historical development of negotiability

A general formula for Rayleigh-Schroedinger perturbation energy utilizing a power series expansion of the quantum mechanical Hamiltonian

Perturbation theory has long been utilized by quantum chemists as a method for approximating solutions to the Schroedinger equation. Perturbation treatments represent a system`s energy as a power series in which each additional term further corrects the total energy; it is therefore convenient to have an explicit formula for the nth-order energy correction term. If all perturbations are collected into a single Hamiltonian operator, such a closed-form expression for the nth-order energy correction is well known; however, use of a single perturbed Hamiltonian often leads to divergent energy series, while superior convergence behavior is obtained by expanding the perturbed Hamiltonian in a power series. This report presents a closed-form expression for the nth-order energy correction obtained using Rayleigh-Schroedinger perturbation theory and a power series expansion of the Hamiltonian