Wave Front Steepness and Influence on Horizontal Deck Impact Loads

In design storm sea states, wave-in-deck forces need to be analysed for fixed and floating offshore platforms. Due to the complex physics of wave impact phenomena, numerical analyses should be complemented by model test data. With a large statistical variability, such experiments usually involve running many 3-h storm realisations. Efforts are being done to establish efficient procedures and still obtain improved statistical accuracy, by means of an initial simplified screening based on parameters derived from the incident wave record only. Here, we investigate the vertical rise velocity of the incident wave elevation at a fixed point in space, which indirectly measures both the local slope and the near-surface orbital velocity. A derived simple deck slamming model is also suggested, to support the check of the physical basis of the approach. Correlation against data from a GBS wave-in-deck model test is used for checking this model. The results show that, although there is a significant random scatter in the measured impact forces, especially in the local slamming forces but also in the global forces, there is a correlation to the rise velocity. Comparisons to the simple load model also show promising results when seen on background of the complex physics and random scatter of the impact problem.

Atomic absorption and atomic emission with inductive connected plasma detection of Lead and Iron in strata water using new medias and standard composition samples

An influence of SAS (Тriton Х-100) concentration and ultrasound treatment time on the value of analytical signal at atomic absorption and atomic emission with inductive connected plasma detection of analytes in strata water was studied. Maximal analytical signal at of Lead and Iron was reached at using nonionogenic SAS which let us to decrease surface tension of the analyzed solution and to increase absorptivity at analytes detection. It was shown that using of the modern sample preparation increase sensibility of atomic absorption detection of Lead in 1,5 times and Iron in 1,8 times. By the methods of atomic absorption and atomic emission with inductive connected plasma spectroscopy and using acetylacetonates of Lead and Iron as standard composition samples, that let us to increase sensitivity of the detection of analytes, contain of Lead and Iron in strata water was determined. By variation of the sample volume and by "injected-found out" method we have proved that systematic error is not significant. The results, obtained by two independent methods were compared according to F- and t-criteria. It was proved that dispersions are homogenous and run of the means is not sufficient and proved by random scatter. By atomic absorption method we estimated the detection limit of the analytes according to the developed methodic and show that the obtained results are lower than the same data from literature. The developed methodic, according to its metrological characteristics, is competitive at international level.

Novel method of sound barrier measurement of porous and nonporous materials

Noise is an unwanted sound which creates the pollution and adverse effects on individual. One of the simple ways to reduce the noise is to place the acoustic material in the path between the source and the receiver so that sound waves get either absorbed or blocked while reaching towards the receiver. There are various techniques available to measure sound absorption or sound barrier (blocking) caused by the acoustic material. However these techniques are also associated with certain limitations. Our objective was to design and fabricate simple technique to measure sound barrier which overcomes these limitations and allows larger sample size and random scatter of sound wave to accurately predict actual field measurements. A sound source (i.e. a speaker) and a microphone, placed in different pipes separated by sample in between, were used for the measurement of sound barrier property of porous materials (nonwovens, woven fabric, and foam), nonporous materials (rubber, cardboard) and their composite structures at four different frequencies 250 Hz, 500 Hz, 1,000 Hz, and 2000 Hz. Different set of readings were taken in absence and presence of the sample by measuring the transmitted sound across the sample.

Use of Salt Lake City URBAN 2000 Field Data to Evaluate the Urban Hazard Prediction Assessment Capability (HPAC) Dispersion Model

After the terrorist incidents on 11 September 2001, there is a greatly heightened concern about the potential impacts of acts of terrorism involving the atmospheric release of chemical, biological, radiological, and nuclear (CBRN) materials in urban areas. In response to the need for an urban CBRN model, the Urban Hazard Prediction Assessment Capability (Urban HPAC) transport and dispersion model has been developed. Because HPAC is widely used by the Department of Defense community for planning, training, and operational and tactical purposes, it is of great importance that the new model be adequately evaluated with urban datasets to demonstrate its accuracy. This paper describes evaluations of Urban HPAC using the “URBAN 2000” urban tracer and meteorological field experiment data from Salt Lake City, Utah. Four Urban HPAC model configuration options and five plausible meteorological input data options—ranging from data-sparse to data-rich scenarios—were considered in the study, thus leading to a total of 20 possible model combinations. For the maximum concentrations along each sampling arc for each intensive operating period (IOP), the 20 Urban HPAC model combinations gave consistent mean overpredictions of about 50%, with a range over the 20 model combinations from no overprediction to a factor-of-4 overprediction in the mean. The median of the random scatter for the 20 model combinations was about a factor of 3 of the mean, with a range over the 20 model combinations between a factor of about 2 and 9. These performance measures satisfy previously established acceptance criteria for dispersion models.

Mixed-gas model for predicting decompression sickness in rats

A mixed-gas model for rats was developed to further explore the role of different gases in decompression and to provide a global model for possible future evaluation of its usefulness for human prediction. A Hill-equation dose-response model was fitted to over 5,000 rat dives by using the technique of maximum likelihood. These dives used various mixtures of He, N2, Ar, and O2 and had times at depth up to 2 h and varied decompression profiles. Results supported past findings, including 1) differences among the gases in decompression risk (He < N2 < Ar) and exchange rate (He > Ar ≈ N2), 2) significant decompression risk of O2, and 3) increased risk of decompression sickness with heavier animals. New findings included asymmetrical gas exchange with gas washout often unexpectedly faster than uptake. Model success was demonstrated by the relatively small errors (and their random scatter) between model predictions and actual incidences. This mixed-gas model for prediction of decompression sickness in rats is the first such model for any animal species that covers such a broad range of gas mixtures and dive profiles.

Receptive field and orientation scatter studied by tetrode recordings in cat area 17

The receptive-field positions and orientation preferences of neurons occupying the same tangential location in visual cortex are thought to be similar but to have an associated random scatter. However, previous estimates of this scatter may have been inflated by the use of subjective plotting methods, sequential recording of single units, and residual eye movements. Here we report measurements of receptive-field position and orientation scatter in cat area 17 made with tetrodes, which were able to simultaneously isolate and record up to 11 nearby neurons (ensembles). We studied 355 units at 72 sites with moving light and dark bars. Receptive-field sizes and positions were estimated by least-squares fitting of Gaussians to response profiles. We found that receptive-field position scatter was about half of the ensemble average receptive-field size. We confirmed previous estimates of orientation scatter, but calculations suggested that much of it may be accounted for by anatomical scatter in the positions of recorded neurons relative to the tetrode in a smooth map. Orientation tuning width was positively correlated with the degree of orientation scatter. Scatter was not independent in the two eyes: deviations from the local mean for both preferred orientation and receptive-field position were correlated although a significant amount of residual inter-ocular orientation and receptive-field position scatter was present. We conclude that cortical maps of orientation and receptive-field position are more ordered than was previously thought, and that random scatter in receptive-field positions makes a relatively small contribution to cortical point image size.

Wall thickness referenced to myocardial volume: a new noninvasive framework for cardiac mechanics

Dimensional variables measured for study of left ventricular mechanics are subject to errors arising from difficulty in determining zero-stress dimensions for use as a reference. Based on a method validated for measurements within individuals, we have devised an approach that facilitates comparison between individuals while minimizing random scatter. We define an exact mathematical index of strain, ln( h0/ h), using wall thickness ( h) referenced to extrapolated wall thickness at zero-luminal volume ( h0). Noninvasive data from rabbits, pigs, and humans all yielded highly similar myocardial stress, ln( h0/ h), and work values. The stress-ln( h0/ h) relationship during afterload variation was constant among individual pigs with a twofold variation in ventricular mass. Stress-ln( h0/ h) data from our analysis displayed lower scatter than either pressure-volume data normalized to myocardial mass or stress-ln( h0/ h) data referenced to end-diastolic dimensions. A Frank-Starling-like curve with high correlation ( r2= 0.96) was constructed from single points from different pigs, suggesting a low level of size and intersubject scatter. This method offers high precision for noninvasive characterization of ventricular and myocardial mechanics and for comparisons between subjects and between species.