Admiral John A. B. Dahlgren (1809–1870): His life, times and technical work in U.S. naval ordnance

John Dahlgren served in the U.S. Navy for nearly 35 years, sometimes in a sea-keeping capacity but mostly developing large naval artillery. To-day, his name, when recognised by students of naval ordnance, is associated with teh Dahlgren or ‘soda bottle shaped’ gun of 9 to 11 inch calibre. He designed, developed and lived to see his guns installed aboard warships and used to considerable effect, especially in the American Civil War. However, a nearly indistinguishable external design of gun was developed for the Army by T. J. Rodman, an officer now even less known than Dahlgren and whose researches and contributions are virtually forgotten. This paper and that in Ref. [1] attempt to appreciate (along with other technical questions of the period) the different ways pursued by these men towards the final development of the ‘soda bottle shaped’ gun, though it is a matter still not entirely understood.

Both names are totally omitted from several ‘classic’ books on artillery and this is a grave misfortune. Besides trying to throw factual light on the Dahlgren-Rodman controversy and the priority issue (though not one pursued with acrimony by the men themselves at the time), the paper describes Admiral Dahlgren's general career, the books he wrote, the technical problems he attacked and the problematic ordnance discussions of his day, to which he gave his life.

The work of Dahlgren and Rodman, in particular, saw the elevation of American gun design from the level of mere copying (of early Columbiads in the first decades of the century) to that which compelled attention from, and study by, the super-powers of the day, Great Britain, France and Russia.     

Current and future water issues in the Oldman River Basin of Alberta, Canada.

Long-term trends in alpine and prairie snow pack accumulation and melt are affecting streamflow within the Oldman River Basin in southern Alberta, Canada. Unchecked rural and urban development also has contributed to changes in water quality, including enhanced microbial populations and increased waterborne pathogen occurrence. In this study we look at changing environment within the Oldman River Basin and its impact on water quality and quantity. The cumulative effects include a decline in net water supplies, and declining quality resulting in increased risk of disease. Our data indicates that decreases in the rate of flow of water can result in sedimentation of bacterial contaminants within the water column. Water for ecosystems, urban consumption, recreation and distribution through irrigation is often drawn from waterholding facilities such as dams and weirs, and concern must be expressed over the potential for contaminate build-up and disproportionate potential of these structures to pose a risk to human and animal health. With disruption of natural flow rates for water resulting from environmental change such as global warming and/or human intervention, increased attention needs to be paid to use of best management practices to protect source water supplies.     

Sensitivity analysis in conjunction with evidence theory representations of epistemic uncertainty

Three applications of sampling-based sensitivity analysis in conjunction with evidence theory representations for epistemic uncertainty in model inputs are described: (i) an initial exploratory analysis to assess model behavior and provide insights for additional analysis; (ii) a stepwise analysis showing the incremental effects of uncertain variables on complementary cumulative belief functions and complementary cumulative plausibility functions; and (iii) a summary analysis showing a spectrum of variance-based sensitivity analysis results that derive from probability spaces that are consistent with the evidence space under consideration.     

Electrostatic Droplet Growth in a Neutrally Buoyant Emulsion

Droplet growth is examined in a water-in-oil type emulsion where the droplets are subjected exclusively to viscous and dielectrophoretic forces. The latter are produced by the interaction of the droplets with an otherwise uniformly imposed electric field. Theoretical considerations are presented as a basis for understanding and interpreting the experiments. An emulsion consisting of deionized water droplets in a silicone oil of specific gravity I is subjected to a uniform 60 Hz, ac electrostatic field. Initially, the droplets are fairly monodisperse with mean diameters of approximately 25 , sm. The changes in droplet size distributions with time are examined with a laser diffraction system for water volume fractions ranging from 0.001 to 0.1 and applied fields ranging from 52 to 520 kVm-1. The average droplet size increases exponentially with time; we examine the exponent's dependence on average field strength and droplet volume fraction.     

Towards real CAD

Present-day computer-aided design (CAD) packages play only a small part in the area of mechanical engineering design, which involves the synthesis and embodiment of physical components to perform a pre-determined function without unwanted side effects. The computer cannot properly help the designer in this task until it is able to capture and process the function requirements of the design. This paper describes the computer system being developed for this purpose at the Engineering Design Centre at Cambridge University Engineering Department. The paper also explores some of the geometrical and programming implications raised.     

Genetic algorithms in engineering electromagnetics

This paper presents a tutorial and overview of genetic algorithms for electromagnetic optimization. Genetic-algorithm (GA) optimizers are robust, stochastic search methods modeled on the concepts of natural selection and evolution. The relationship between traditional optimization techniques and the GA is discussed. Step-by-step implementation aspects of the GA are detailed, through an example with the objective of providing useful guidelines for the potential user. Extensive use is made of sidebars and graphical presentation to facilitate understanding. The tutorial is followed by a discussion of several electromagnetic applications in which the GA has proven useful. The applications discussed include the design of lightweight, broadband microwave absorbers, the reduction of array sidelobes in thinned arrays, the design of shaped-beam antenna arrays, the extraction of natural resonance modes of radar targets from backscattered response data, and the design of broadband patch antennas. Genetic-algorithm optimization is shown to be suitable for optimizing a broad class of problems of interest to the electromagnetic community. A comprehensive list of key references, organized by application category, is also provided     

Computational medicine: bioelectric field problems

Applications of large-scale computer modeling and simulation to a class of bioelectric field problems in a variety of biomedical research areas, from single cells to full human structures, are described. The authors focus on a specific subset of bioelectric field problems that have applications in electrocardiography and electroencephalography. The physics and physiology of bioelectric volume conductors are introduced. A specific computational example and the authors' view on the future direction of computational medicine are presented     

Pocket pagers in lots of one CIM

The Fusion program, a method for agile, flexible computer integrated manufacturing (CIM) at Motorola's Paging Products Group, is discussed. Fusion's CIM and automated assembly system can manufacture a wide variety of different products on the same production line. The development of the Fusion program and how it differs from its predecessor, the Bandit program, are described     

Incidence of Lightspeed separation and the potential for bypassing

It is important for endodontic instruments to have a low fracture rate. If a fracture does occur, it would be desirable to have the ability to bypass the broken segment and complete the root canal treatment. One hundred sixty-two root canals in 52 maxillary and mandibular first molars were cleaned and shaped with Lightspeed instruments by three endodontists in their private practices. The canals were instrumented using the technique recommended by the manufacturer. All canals were instrumented to at least a size 45 at the working length. Six instruments separated during treatment. All six had been used more times than recommended by the manufacturer. Five of the six were easily bypassed and treatment completed.