The characterization and evaluation of accidental explosions

Accidental explosions are discussed from a number of viewpoints. First, all accidental explosions, intentional explosions and natural explosions are characterized by type. Second, the nature of the blast wave produced by an ideal (point source or HE) explosion is discussed to form a basis for describing how other explosion processes yield deviations from ideal blast wave behavior. The current status blast damage mechanism evaluation is also discussed. Third, the current status of our understanding of each different category of accidental explosions is discussed in some detail

From microscopic to macroscopic descriptions of cell\ud migration on growing domains

Cell migration and growth are essential components of the development of multicellular organisms. The role of various cues in directing cell migration is widespread, in particular, the role of signals in the environment in the control of cell motility and directional guidance. In many cases, especially in developmental biology, growth of the domain also plays a large role in the distribution of cells and, in some cases, cell or signal distribution may actually drive domain growth. There is a ubiquitous use of partial differential equations (PDEs) for modelling the time evolution of cellular density and environmental cues. In the last twenty years, a lot of attention has been devoted to connecting macroscopic PDEs with more detailed microscopic models of cellular motility, including models of directional sensing and signal transduction pathways. However, domain growth is largely omitted in the literature. In this paper, individual-based models describing cell movement and domain growth are studied, and correspondence with a macroscopic-level PDE describing the evolution of cell density is demonstrated. The individual-based models are formulated in terms of random walkers on a lattice. Domain growth provides an extra mathematical challenge by making the lattice size variable over time. A reaction-diffusion master equation formalism is generalised to the case of growing lattices and used in the derivation of the macroscopic PDEs

Going from microscopic to macroscopic on nonuniform growing domains

Throughout development, chemical cues are employed to guide the functional specification of underlying tissues while the spatiotemporal distributions of such chemicals can be influenced by the growth of the tissue itself. These chemicals, termed morphogens, are often modeled using partial differential equations (PDEs). The connection between discrete stochastic and deterministic continuum models of particle migration on growing domains was elucidated by Baker, Yates, and Erban [ Bull. Math. Biol. 72 719 (2010)] in which the migration of individual particles was modeled as an on-lattice position-jump process. We build on this work by incorporating a more physically reasonable description of domain growth. Instead of allowing underlying lattice elements to instantaneously double in size and divide, we allow incremental element growth and splitting upon reaching a predefined threshold size. Such a description of domain growth necessitates a nonuniform partition of the domain. We first demonstrate that an individual-based stochastic model for particle diffusion on such a nonuniform domain partition is equivalent to a PDE model of the same phenomenon on a nongrowing domain, providing the transition rates (which we derive) are chosen correctly and we partition the domain in the correct manner. We extend this analysis to the case where the domain is allowed to change in size, altering the transition rates as necessary. Through application of the master equation formalism we derive a PDE for particle density on this growing domain and corroborate our findings with numerical simulations

Vortex simulations of the Rayleigh–Taylor instability

A vortex technique capable of calculating the Rayleigh–Taylor instability to large amplitudes in inviscid, incompressible, layered flows is introduced. The results show the formation of a steady‐state bubble at large times, whose velocity is in agreement with the theory of Birkhoff and Carter. It is shown that the spike acceleration can exceed free fall, as suggested recently by Menikoff and Zemach. Results are also presented for instability at various Atwood ratios and for fluids having several layers

Application of a helicopter mathematical model to the Langley differential maneuvering simulator for use in a helicopter/fighter evasive maneuver study

A real time simulation study was conducted using a differential maneuvering simulator to determine and evaluate helicopter evasive maneuvers when attacked by fighter aircraft. A general helicopter mathematical model was modified to represent an H-53 helicopter. The helicopter model was compared to H-53 flight test data to determine any differences between the simulated and actual vehicles. The simulated helicopter was also subjectively validated by participating pilots. Two fighter mathematical models validated in previous studies were utilized for the attacking aircraft. The results of this simulation study have been verified in a flight test program conducted by the U. S. Air Force and were found to closely match the flight results

Excerpts from selected LANDSAT 1 final reports in geology

The standard formats for the summaries of selected LANDSAT geological data are presented as checklists. These include: (1) value of LANDSAT data to geology, (2) geologic benefits, (3) follow up studies, (4) cost benefits, (5) optimistic working scales, (6) statistical analysis, and (7) enhancement effects

Static electricity in the Apollo spacecraft

Static electricity ignition hazards in Apollo spacecraf

STS-1 operational flight profile. Volume 5: Descent, cycle 3

The trajectory data presented are to be used for orbiter systems and subsystems evalation, flight and mission control center software verification, flight techniques and timeline development, crew training, and evaluation of operational mission suitability. The entry profile is very similar to cycle 2, however, elevon and body flap temperature margins have increased and the elevon schedule was changed. The terminal area energy management (TAEM) profile was completely reshaped to conform with new angle of attack constraints and left hand turn around the heading alignment cylinder. Also, the entry/TAEM interface was adjusted to minimize guidance induced angle of attack transients across the interface. The approach and landing phase was reshaped for a 20 deg glideslope and reduced velocity at touchdown. The definition of the runway threshold was standardized for all landing sites. This results in a shift at Edwards Air Force Base in aim points and touchdown relative to the threshold of 1000 feet. The rollout remains essentially unchanged with the exception of the speedbrake, which is now deployed to 50 percent at touchdown