Identification and control of acoustic radiation modes

A formulation is given of reduced-order acoustic radiation sensors and\ud reduced-order actuators for broadband sound fields. Methods are presented\ud to determine these descriptions from measured data, and their\ud application in systems for broadband active noise control is discussed.\ud One application area is the reduction of sound radiated from plates with\ud structural actuators and structural sensors, using measured or modeled\ud versions of the most efficiently radiating patterns of a vibrating body,\ud the so-called radiation modes. The second application of the radiation\ud mode theory is in active noise barriers for the reduction of traffic noise.\ud Without special precautions most of these systems suffer from spillover;\ud a technique is given to arrive at good reductions at the error sensors with\ud reduced spillover

Trade and exchange

If the history of Mediterranean trade during the period c800-1200 is one of decline and reluctant recovery that of Northern Europe is decidedly one of growth. One reason for this is the different points of departure. By c700, Europe’s northern seas had never witnessed a system of exchange on the scale and complexity of that in the Mediterranean during Antiquity. During the following centuries, however, the development of commerce in the North corresponded ever closer to that of the Mediterranean, resulting in a twelfth-century economy no less advanced or extensive than that of Imperial Rome, but within an even wider geographical frame. Intriguingly, and hardly by accident, this process was set in motion at the very moment when the Late Antique economy ceased in the Mediterranean, in the closing decades of the seventh century. Throughout much of the period concerned here, trade remained a modest appendage to traditional forms of exchange. Its key historical importance was as a steady motor of social change and innovation

Disruptive design innovation: reflections on the relationship of design, science and art

The title of designer conveys a large number of historical, cultural, philosophical drivers and working practises that effectively range from the traditional engineer through to the individual interested in personal expression. The considerable differences originate and have evolved for a variety of reasons. The range is from capitalist necessity through to social inclusion. Today, the designer needs to have the ability to understand significant changes in technology, art and science as well as being an astute observer of human behaviour. Ultimately, the designer will need to convert ideas into objects and systems that people can understand and use. It is important to consider serendipitous design and disruptive design as it often involves risk taking and may be unpredictable in character. Disruptive design innovation can improve a design in ways that the customer or a market does not expect. The authors suggest a refreshing approach to design that is inclusive in purpose to enrich the act of designing and advocate a greater correlation between the art, sciences and design in reflecting the values, virtues and methods of working and the principles that guide the methodologies and processes which can be correlated into a coherent whole and with a clearer focus

The attitude of the clergy toward education for family living in the public schools of Massachusetts.

Thesis (Ed.M.)--Boston Universit

Flowers Associations and Mating Behavior or its Absence at Blossoms by \u3ci\u3eSpilomyia\u3c/i\u3e Spp. (Diptera, Syrphidae)

(excerpt) Syrphid flies of many species visit blossoms to obtain nectar and pollen (see Waldbauer 1983 for referencesl. Many of these syrphids, in common with other insects (Parker 1978), also find mates at the blossoms. Males of these syrphid species make aerial patrols of inflorescences frequented by females, alternating these patrols with sitting on foliage. l11ey pounce on or chase insects of various species and swiftly initiate copulation with can specific females (Collet and Land 1975; Maier 1978; Maier and Waldbauer 1 979a,b)

Constraint-consistent Runge-Kutta methods for one-dimensional incompressible multiphase flow

New time integration methods are proposed for simulating incompressible multiphase flow in pipelines described by the one-dimensional two-fluid model. The methodology is based on 'half-explicit' Runge-Kutta methods, being explicit for the mass and momentum equations and implicit for the volume constraint. These half-explicit methods are constraint-consistent, i.e., they satisfy the hidden constraints of the two-fluid model, namely the volumetric flow (incompressibility) constraint and the Poisson equation for the pressure. A novel analysis shows that these hidden constraints are present in the continuous, semi-discrete, and fully discrete equations. Next to constraint-consistency, the new methods are conservative: the original mass and momentum equations are solved, and the proper shock conditions are satisfied; efficient: the implicit constraint is rewritten into a pressure Poisson equation, and the time step for the explicit part is restricted by a CFL condition based on the convective wave speeds; and accurate: achieving high order temporal accuracy for all solution components (masses, velocities, and pressure). High-order accuracy is obtained by constructing a new third order Runge-Kutta method that satisfies the additional order conditions arising from the presence of the constraint in combination with time-dependent boundary conditions. Two test cases (Kelvin-Helmholtz instabilities in a pipeline and liquid sloshing in a cylindrical tank) show that for time-independent boundary conditions the half-explicit formulation with a classic fourth-order Runge-Kutta method accurately integrates the two-fluid model equations in time while preserving all constraints. A third test case (ramp-up of gas production in a multiphase pipeline) shows that our new third order method is preferred for cases featuring time-dependent boundary conditions