Detection system ensures positive alarm activation in digital message loss

Lost Word Detection System /LOWDS/ provides special identification for each error detection message transmitted from receiver to transmitter. The message is identified as an original message or an n-times retransmitted message so the receiver can detect where a retransmission request was not fulfilled and activate an alarm

Dispersal Dynamics in a Wind-Driven Benthic System

Bedload and water column traps were used with simultaneous wind and water velocity measurements to study postlarval macrofaunal dispersal dynamics in Manukau Harbour, New Zealand. A 12-fold range in mean wind condition resulted in large differences in water flow (12-fold), sediment flux (285-fold), and trap collection of total number of individuals (95-fold), number of the dominant infaunal organism (84-fold for the bivalve Macomona liliana), and number of species (4-fold). There were very strong, positive relationships among wind condition, water velocity, sediment flux, and postlarval dispersal, especially in the bedload. Local density in the ambient sediment was not a good predictor of dispersal. Results indicate that postlarval dispersal may influence benthic abundance pat- terns over a range of spatial scales

The Effect of Fluorine on Blood and Respiration

Much interest has been manifested in fluorine during the past few years. This is due to two reasons: first, fluorine is found in several phosphatic mineral supplements, which are fed to farm animals ; and, second, fluorine has been found in drinking waters in this and many other countries of the world. The interest of the authors in fluorine dates from the discovery by Ostrem, Nelson, Greenwood, and Wilhelm of fluorine in the drinking waters of communities in the State of Iowa, with the resulting production of mottled enamel of the teeth. There can be no question that fluorine in excessive amounts in water causes damage to the teeth. Smith, Lantz, and Smith have produced considerable evidence that the presence of excessive fluorine in the drinking water will cause mottled enamel in man. The question naturally arises as to whether fluorine in water produces other harmful effects or pathological changes in the body, aside from the disturbance to the teeth

Relative entropy as a measure of inhomogeneity in general relativity

We introduce the notion of relative volume entropy for two spacetimes with preferred compact spacelike foliations. This is accomplished by applying the notion of Kullback-Leibler divergence to the volume elements induced on spacelike slices. The resulting quantity gives a lower bound on the number of bits which are necessary to describe one metric given the other. For illustration, we study some examples, in particular gravitational waves, and conclude that the relative volume entropy is a suitable device for quantitative comparison of the inhomogeneity of two spacetimes.Comment: 15 pages, 7 figure

Study of fluid transients in closed conduits annual report no. 1

Atmospheric density effect on computation of earth satellite orbit

Toward Empirical Constraints on the Global Redshifted 21 cm Brightness Temperature During the Epoch of Reionization

Preliminary results are presented from a simple, single-antenna experiment designed to measure the all-sky radio spectrum between 100 and 200 MHz. The system used an internal comparison-switching scheme to reduce non-smooth instrumental contaminants in the measured spectrum to 75 mK. From the observations, we place an initial upper limit of 450 mK on the relative brightness temperature of the redshifted 21 cm contribution to the spectrum due to neutral hydrogen in the intergalactic medium (IGM) during the epoch of reionization, assuming a rapid transition to a fully ionized IGM at a redshift of 8. With refinement, this technique should be able to distinguish between slow and fast reionization scenarios. To constrain the duration of reionization to dz > 2, the systematic residuals in the measured spectrum must be reduced to 3 mK.Comment: Submitted to ApJ. 9 pages including 6 figure

Ames collaborative study of cosmic-ray neutrons. 2: Low- and mid-latitude flights

Progress of the study of cosmic ray neutrons is described. Data obtained aboard flights from Hawaii at altitudes of 41,000 and 45,000 feet, and in the range of geomagnetic latitude 17 N less than or equal to lambda less than or equal to 21 N are reported. Preliminary estimates of neutron spectra are made

Validating an Operations Centre Model

An airline operations centre determines the imminent and future operations of an airline by assessing the current situation, considering current constraints and then issuing a high level plan, describing which flights are operating, which are cancelled, which are delayed or rerouted, impacting aircraft, air crew, flight cabin crew, passengers and ground staff. Other departments of the airline transform the high level plan into detailed execution instructions. In the event, the system consists of a mixture of humans and machines both of which often provide and receive incomplete information, on which they make a decision, striving to execute as close as possible the ‘Ideal Plan’, which is the published timetable. The Airline Operations Decision Making Process is the ‘planning’ portion determining the next course of action, and the Airline Operations is the execution portion, putting the plans into action. In this context, the Study Group was asked to address the following problem: How do you validate a model of an airline’s decision processes to ensure a faithful representation of reality? By analysing model outputs and actual data, we found that the model does not satisfy any of our proposed “validation” criteria and have therefore suggested a series of possible ways forward for the model development team. We have provided visualisation tools in both Matlab and R, which will be of use in analysing subsequent model versions. We have also provided a series of statistical indicators of model quality. Lastly, and perhaps most importantly, we have described in detail what can be done if additional information were to be made available, for instance further runs of the model or extra data from the operations centre

Space-times admitting a three-dimensional conformal group

Perfect fluid space-times admitting a three-dimensional Lie group of conformal motions containing a two-dimensional Abelian Lie subgroup of isometries are studied. Demanding that the conformal Killing vector be proper (i.e., not homothetic nor Killing), all such space-times are classified according to the structure of their corresponding three-dimensional conformal Lie group and the nature of their corresponding orbits (that are assumed to be non-null). Each metric is then explicitly displayed in coordinates adapted to the symmetry vectors. Attention is then restricted to the diagonal case, and exact perfect fluid solutions are obtained in both the cases in which the fluid four-velocity is tangential or orthogonal to the conformal orbits, as well as in the more general "tilting" case.Comment: Latex 34 page