Restricted adaptive cluster sampling

Adaptive cluster sampling can be a useful design for sampling rare and patchy populations. With this design the initial sample size is fixed but the size of the final sample (and total sampling effort) cannot be predicted prior to sampling. For some populations the final sample size can be quite variable depending on the level of patchiness. Restricted adaptive cluster sampling is a proposed modification where a limit is placed on the sample size prior to sampling and quadrats are selected sequentially for the initial sample size. As a result there is less variation in the final sample size and the total sampling effort can be predicted with some certainty, which is impor- tant for many ecological studies. Estimates of density are biased with the restricted design but under some circumstances the bias can be estimated well by bootstrapping. © Rapid Science 1998     

Semi-parametric statistical approaches for space-time process prediction

The problem of estimation and prediction of a spatial-temporal stochastic process, observed at regular times and irregularly in space, is considered. A mixed formulation involving a non- parametric component, accounting for a deterministic trend and the effect of exogenous variables, and a parametric component representing the purely spatio-temporal random variation is proposed. Correspondingly, a two-step procedure, first addressing the estimation of the non- parametric component, and then the estimation of the parametric component is developed from the residual series obtained, with spatial-temporal prediction being performed in terms of suitable spatial interpolation of the temporal variation structure. The proposed model formula-tion, together with the estimation and prediction procedure, are applied using a Gaussian ARMA structure for temporal modelling to space-time forecasting from real data of air pollution concentration levels in the region surrounding a power station in northwest Spain.     

Parents' views of teen driving risks, the role of parents, and how they plan to manage the risks

PROBLEM: There is limited information about how parents view teen driving risks and intend to handle these risks during the licensing process, and how they will respond to graduated licensing provisions. METHODS: Parents in Connecticut were interviewed when their teens got their learner's permit. The survey was undertaken when the state did not have a midnight restriction or a passenger restriction. RESULTS: Generally, parents were well aware of teen driving risks, thought parents should be thoroughly involved in the licensing process, and plan to be active participants themselves. DISCUSSION: Parents were concerned about the risk of driving after midnight and already restrict that behavior. However, parents do not seem to see or understand the risks of having even one teen passenger in the vehicle. IMPACT ON INDUSTRY: The views and existing practices of parents need to be taken into account in deciding on the provisions of graduated licensing legislation and how to best ensure acceptance and compliance.     

Characteristics of speeders

OBJECTIVE: To determine the characteristics of speeders, defined as drivers of vehicles traveling at least 15 mph above the posted speed limit and relatively faster than surrounding vehicles. METHODS: Vehicle speeds were recorded on 13 roads in Virginia with speed limits ranging from 40 to 55 mph. Speeders were compared with slower drivers, defined as drivers of adjacent vehicles traveling no more than 5 mph above the speed limit. License plates were used to identify vehicle owners; owners were inferred to have been driving if observed gender and estimated age matched those of the registered owner. For these drivers, information on exact driver age and gender, vehicle make and model, and driving record was obtained from the Virginia Department of Motor Vehicles. RESULTS: Five percent of the vehicles observed were traveling at least 15 mph above the limit, and 3% qualified as speeders, as defined in this study. Speeders were younger than drivers in the comparison group, drove newer vehicles, and had more speeding violations and other moving violations on their records. They also had 60% more crashes. DISCUSSION: Speeders are a high-risk group. Their speeding behavior is not likely to be controlled without vigorous, consistent enforcement, including the use of automated technology.     

Integrated Estimation of the Effect of Physical Factors on Human Functional State During Mental Work

The purpose of this study was to develop a model for an integrated estimation of the functional state of the human organism (FSHO) and an integral estimation of physical factors (PF) for hygienic rating. Tests were performed twice with 3 men in 0.7-clo clothing during 4-hr mental work with 9 combinations of 4 PF: wideband noise (55–83 dB(A)), whole-body vibration (6 Hz, a_z = 0.2–1.8 ms^?2), air temperature (18–30 °C), and illumination (1, 3, 5 lx). Thermoregulatory, cardiovascular, and psychophysiological reactions and temporary threshold of hearing (TTS₂) shifts were studied. For the integral estimation of PF influence on FSHO the model F(y₁, y₂, ... y_m) = f(x₁, x₂, ... x_n) was used, relating both FSHO and PF sets. The most important physiological parameters in creating FSHO are defined and the contribution of individual parameters of FSHO and PF is found.     

Two-phase jet releases,droplet dispersion and rainout,II. Rainout experiments

This paper describes the results of the first experimental stage of Phase IV of a Joint Industry Project (JIP) on liquid jets and two-phase droplet dispersion. The objective of this stage of the JIP was to generate experimental rainout data for non-flashing water and xylene experiments. See the overview companion paper I for a wider overview of the problem, model implementation and associated model validation.A range of orifice sizes (2.5 and 5 mm) and stagnation pressures (4–16 barg) were applied. Measurements included flow rate, initial droplet size, plume concentrations/temperatures for a range of downstream locations, and distributed rainout.Instead of the Phase Doppler Anemometry method used for droplet size measurements earlier in the JIP, a photographic technique was applied in an attempt to include measurement of the larger (non-spherical) droplets. This enabled a more accurate evaluation of the initial droplet size distribution and a much clearer understanding of the droplet morphology. The results showed that the droplet behaviour in the jet is more complex than had been anticipated with the mass distribution dominated by a very small number of large non-spherical droplets. Consequently a large number of spray images were required to evaluate an accurate size distribution.Distributed rainout was measured by weighing the amount of rainout in trays positioned along the jet direction. The rainout results showed a good degree of repeatability and internal consistency. They indicated that an increasing proportion of the released material did not rainout for increasing pressure. Rainout distance also increased with increasing pressure. Evaporation of the liquid was confirmed by temperature measurements, which showed the effect of evaporative cooling.Xylene concentration measurements (up to 1%) were carried out using a direct reading photoionization detector calibrated for xylene (measuring vapour only). For a limited dataset, the accuracy of these measurements was estimated by means of comparison against an alternative more time-consuming concentration method (xylene absorption onto a charcoal filter; measuring both vapour and liquid). The concentration measurements displayed several consistent qualitative features. For example, at a given downstream distance, the peak concentration increases with increasing pressure and nozzle diameter and the vertical height at which the peak is achieved increases. The cross-stream profiles displayed a consistent tendency to increased concentration at the edge of the jet, and the reason for this has not been established.Finally recommendations are provided for potential future work.     

Experimental determination of dust cloud deflagration parameters of selected hydrogen storage materials: Complex metal hydrides,chemical hydrides,and adsorbents

This paper discusses the results of an experimental program carried out to determine dust cloud deflagration parameters of selected solid-state hydrogen storage materials, including complex metal hydrides (sodium alanate and lithium borohydride/magnesium hydride mixture), chemical hydrides (alane and ammonia borane) and activated carbon (Maxsorb, AX-21). The measured parameters include maximum deflagration pressure rise, maximum rate of pressure rise, minimum ignition temperature, minimum ignition energy and minimum explosible concentration. The calculated explosion indexes include volume-normalized maximum rate of pressure rise (K_St), explosion severity (ES) and ignition sensitivity (IS). The deflagration parameters of Pittsburgh seam coal dust and Lycopodium spores (reference materials) are also measured. The results show that activated carbon is the safest hydrogen storage media among the examined materials. Ammonia borane is unsafe to use because of the high explosibility of its dust. The core insights of this contribution are useful for quantifying the risks associated with use of these materials for on-board systems in light-duty fuel cell-powered vehicles and for supporting the development of hydrogen safety codes and standards. These insights are also critical for designing adequate safety features such as explosion relief venting and isolation devices and for supplementing missing data in materials safety data sheets.     

An approach for domino effect reduction based on optimal layouts

An approach to reduce the probability of producing a domino effect in process industry is developed in this work. It is assumed that optimal layouts should include appropriate analysis to reduce risk during the process design stage. The model developed for this approach combines the estimation of probability of damage due to overpressure, proposed by Mingguang and Juncheng (2008), and escalation threshold values defined by Cozzani, Gubinelli, and Salzano (2006). These equations are combined with other typical layout constraints as well as bounding the probability constraint, which has resulted in a highly non-linear MINLP problem. Solving a case study used by other authors provides evidence for reliability of the developed approach. In this way, layouts are designed to reduce the escalation probability yielding safe distributions.     

Experimental and theoretical investigations for mitigating NaAlH4 reactivity risks during postulated accident scenarios involving exposure to air or water

Experimental and theoretical studies were conducted to investigate the pyrophoricity and water-reactivity risks associated with employing sodium alanate (NaAlH₄) complex metal hydride in on-board vehicular hydrogen (H₂) storage systems. The ignition and explosivity of NaAlH₄ upon exposure to oxidizers in air or water were attributed to the spontaneous formation of stable hydroperoxyl intermediates on the NaAlH₄ surface and/or H₂ production, as well as the large driving force for NaAlH₄ conversion to favorable hydroxide products predicted by atomic and thermodynamic modeling. The major products from NaAlH₄ exposure to air: NaAl(OH)₄, gibbsite and bayerite Al(OH)₃, and Na₂CO₃ observed by XRD, were identified to be formed by surface-controlled reactions. The reactivity risks were significantly minimized, without compromising de-/re-hydrogenation cyclability, by compacting NaAlH₄ powder into wafers to reduce the available surface area. These core findings are of significance to risk mitigation and H₂ safety code and standard development for the safe use of NaAlH₄ for on-board H₂ storage in light-duty vehicles.