The Debate on the Health Effects Attributable to Low Radiation Exposure

[Excerpt] Few scientific issues have aroused passions more than the dispute about the health effects attributable to low levels of exposure to ionizing radiation (or radiation in short) and the currently authoritative dose response hypothesis, termed “linear non-threshold,” or LNT. Finding out whether health effects are induced by low-level radiation exposures, and if so, what they are, has become a kind of contest rather than a serious scientific inquiry. Sometimes it seems that rationality, or a methodical examination of the unknown, has disappeared from this debate. While the confrontation of different hypotheses is typical in academic discussions – at least until analysis and experimental work probes more deeply into what is more correct or plausible – it is strange that the premises under discussion differ to such an extent that they oppose each other. This is the case in the dispute known as “the LNT controversy.” One extreme is the “radiation is- good-for-you” group, advocating not only that low-level-radiation exposure is not detrimental, but that it is in fact beneficial for health. The other extreme is the “radiation-phobic” group advocating that exposure to (artificial) radiation is the fifth rider of the Apocalypse leading to the destruction of the human race. On the one side, the radiation promotion extremists presuppose that, because radiation exposure is an inescapable natural phenomenon that has existed since the beginning of time, after billions of years of life on Earth there must have been a natural – and full – biological adaptation to it (they cannot explain, however, why life has not fully adapted to other primordial harmful natural phenomena). On the other side, the radical contesters seem to believe (perhaps honestly, but wrongly) that, because (artificial) radiation exposure is a pollutant of the modern technological world, it should necessarily be highly detrimental to humans, their descendants, and their environment

Attitude Control and Structural Response Interaction

Interaction between structural or elastic response of spacecraft and attitude control system dynamic

A proposed microcomputer implementation of an Omega navigation processor

A microprocessor navigation systems using the Omega process is discussed. Several methods for correcting incoming sky waves are presented along with the hardware design which depends on a microcomputer. The control program is discussed, and block diagrams of the Omega processor and interface systems are presented

Positronium lifetime in polymers

A model describing the relationship between the ortho--positronium lifetime and the volume of a void, located in a synthetic zeolite, is analyzed. Our idea, which allows us to take into account the effects of temperature, comprises the introduction of a non--hermitian term in the Hamiltonian, which accounts for the annihilation of the ortho--positronium. The predictions of the present model are also confronted against an already known experimental result.Comment: Accepted in Journal of Chemical Physic

Experiences with the design and implementation of flutter suppression systems

Research efforts aim at flutter suppression are discussed. The application of active controls technology to reduce the aeroelastic response of aircraft structures is discussed. Feedback control, control law design processes and synthesis, wind tunnel studies, and delta-wing wind tunnel models are discussed

The identification of continuous, spatiotemporal systems

We present a method for the identification of continuous, spatiotemporal dynamics from experimental data. We use a model in the form of a partial differential equation and formulate an optimization problem for its estimation from data. The solution is found as a multivariate nonlinear regression problem using the ACE-algorithm. The procedure is successfully applied to data, obtained by simulation of the Swift-Hohenberg equation. There are no restrictions on the dimensionality of the investigated system, allowing for the analysis of high-dimensional chaotic as well as transient dynamics. The demands on the experimental data are discussed as well as the sensitivity of the method towards noise

Wind-tunnel evaluation of NASA developed control laws for flutter suppression on a DC-10 derivative wing

Two flutter suppression control laws were synthesized, implemented, and tested on a low speed aeroelastic wing model of a DC-10 derivative. The methodology used to design the control laws is described. Both control laws demonstrated increases in flutter speed in excess of 25 percent above the passive wing flutter speed. The effect of variations in gain and phase on the closed loop performance was measured and compared with analytical predictions. The analytical results are in good agreement with experimental data

Some experiences with active control of aeroelastic response

Flight and wind tunnel tests were conducted and multidiscipline computer programs were developed as part of investigations of active control technology conducted at the NASA Langley Research Center. Unsteady aerodynamics approximation, optimal control theory, optimal controller design, and the Delta wing and DC-10 models are described. The drones for aerodynamics and structural testing (DAST program) for evaluating procedures for aerodynamic loads prediction and the design of active control systems on wings with significant aeroelastic effects is described as well as the DAST model used in the wind tunnel tests