Thunder III

The awesome power of a military convoy in Vietnam can also be a danger. Articles, stories, and other compositions in this archive were written by participants in the Mighty Pen Project. The program, developed by author David L. Robbins, and in partnership with Virginia Commonwealth University and the Virginia War Memorial in Richmond, Virginia, offers veterans and their family members a customized twelve-week writing class, free of charge. The program encourages, supports, and assists participants in sharing their stories and experiences of military experience so both writer and audience may benefit

Investigation of an Optimum Detection Scheme for a Star-Field Mapping System

An investigation was made to determine the optimum detection scheme for a star-field mapping system that uses coded detection resulting from starlight shining through specially arranged multiple slits of a reticle. The computer solution of equations derived from a theoretical model showed that the greatest probability of detection for a given star and background intensity occurred with the use of a single transparent slit. However, use of multiple slits improved the system's ability to reject the detection of undesirable lower intensity stars, but only by decreasing the probability of detection for lower intensity stars to be mapped. Also, it was found that the coding arrangement affected the root-mean-square star-position error and that detection is possible with error in the system's detected spin rate, though at a reduced probability

The Impact of Reinforcer Preference and Variation on Response Rates in Preschool-Aged Children

The Impact of Reinforcer Preference and Variation on Response Rates in Preschool-Aged Children J. Malachi Aldridge1, Allison L. Martin1, Alicia K. Mitchell2 1. Kennesaw State University 2. Appleseeds Behavioral Center In the field of Applied Behavior Analysis, tangible items (i.e. toys) are often used to help learners meet goals in academic, social, and adaptive living skills. While use of high preference reinforcers has been linked to improved performance, repeated use of a single item can cause satiation and reduce effectiveness. Using a variety of reinforcers can allow therapists to minimize these satiation effects (Bowman et al., 1997; Koehler & Iwata, 2005; Keyl-Austin et al., 2012). In the current study, we used a paired-choice preference assessment to determine high, medium, and low-preference items for 6 children (aged 2 – 7) with developmental disabilities. We presented each child with multiple, concurrently available felt boards on which they were taught to place a token. Each board choice corresponded with access to a particular item. We systematically examined the child’s response rates when their response resulted in access to either a single high-preferred stimulus or a variety of medium or low preferred stimuli, hypothesizing that a variety of reinforcers, of either medium or low preference, would produce higher response rates than a single, highly preferred stimulus. Data collected in this study showed variable response allocation based on the individual, with some consistently allocating more responses to the high-preference response option and others allocating more to the variable response option as sessions were run. The results of this study will allow clinical practitioners to make informed choices about the use of reinforcers to better motivate learners to continue progressing towards treatment goals

Ambient ammonia measurements using laser photo-acoustic spectroscopy

Ammonia concentrations reached minimal levels (approximately 0.1 ppb) in early winter, followed by a sudden later winter increase. A direct relationship between ambient ammonia levels and air temperature was inferred from the data (linear correlation coefficient r=0.53). Ammonia concentrations were determined to be directly related to the absolute humidity of the air (r=0.72); a weaker relationship between ammonia concentrations and relative humidity was discovered (r=0.37). The data also indicated that ammonia levels were generally higher within continental air masses than those of maritime origin. Soil parameters such as pH and moisture content were found to have a major bearing on the release of gaseous ammonia from soils in the region

Environment–attitude relationships: girls in inquiry-based mathematics classrooms in the United Arab Emirates

Girls’ attitudes towards mathematics can impact their achievement and career choices in STEM fields. Can the introduction of inquiry-based learning (IBL) in mathematics classes generate positive associations between girls’ perceptions of the learning environment and their attitudes towards mathematics? Based in the United Arab Emirates, this study provided important information about the relationships between learning environment factors central to an inquiry method and student engagement. Data collection involved administering two surveys to female mathematics students (N = 291) in four schools: one to assess students’ perceptions of the learning environment and another to assess students’ attitudes towards mathematics. Positive and statistically-significant (p <.01) associations emerged between learning environment factors important to an inquiry approach and students’ attitudes. These findings provide important information about how IBL might improve girls’ attitudes towards mathematics classes and whether IBL environments are related to their attitudes

Correlation and prediction of dynamic human isolated joint strength from lean body mass

A relationship between a person's lean body mass and the amount of maximum torque that can be produced with each isolated joint of the upper extremity was investigated. The maximum dynamic isolated joint torque (upper extremity) on 14 subjects was collected using a dynamometer multi-joint testing unit. These data were reduced to a table of coefficients of second degree polynomials, computed using a least squares regression method. All the coefficients were then organized into look-up tables, a compact and convenient storage/retrieval mechanism for the data set. Data from each joint, direction and velocity, were normalized with respect to that joint's average and merged into files (one for each curve for a particular joint). Regression was performed on each one of these files to derive a table of normalized population curve coefficients for each joint axis, direction, and velocity. In addition, a regression table which included all upper extremity joints was built which related average torque to lean body mass for an individual. These two tables are the basis of the regression model which allows the prediction of dynamic isolated joint torques from an individual's lean body mass

Distribution of natural disturbance due to wave and tidal bed currents around the UK

The UK continental shelf experiences large tidal ranges and winter storm events, which can both generate strong near-bed currents. The regular tidal bottom currents from tides plus wind driven ‘benthic storms’ (dominated by wave-driven oscillatory currents in shallow water) are a major source of disturbance to benthic communities, particularly in shallow waters. We aim to identify and map the relative impact of the tides and storm events on the shallower parts of the North West European continental shelf. A ten-year simulation of waves, tides and surges on the continental shelf was performed. The shelf model was validated against current meter observations and the Centre for Environmental, Fisheries and Aquaculture Science (CEFAS) network of SmartBuoys. Next, the model performance was assessed against seabed lander data from two sites in the Southern North Sea; one in deep water and another shallow water site at Sea Palling, and a third in Liverpool Bay. Both waves and currents are well simulated at the offshore Southern North Sea site. A large storm event was also well captured, though the model tends to underpredict bottom orbital velocity. Poorer results were achieved at the Sea Palling site, thought to be due to an overly deep model water depth, and missing wave-current interactions. In Liverpool Bay tides were well modelled and good correlations (average R–squared=0.89) observed for significant wave height, with acceptable values (average R–squared=0.79) for bottom orbital velocity. Using the full ten-year dataset, return periods can be calculated for extreme waves and currents. Mapping these return periods presents a spatial picture of extreme bed disturbance, highlighting the importance of rare wave disturbances (e.g. with a return period of 1 in 10 years). Annual maximum currents change little in their magnitude and distribution from year to year, with mean speeds around 0.04 ms−1, and maximums exceeding 3 ms−1. Wave conditions however are widely variable throughout the year, depending largely on storm events. Typical significant wave heights (Hs) lie between 0.5–2 m, but storm events in shallow water can bring with them large waves of 5 m and above and up to 18 m in North West Approaches/North West Scotland ( Sterl and Caires, 2005). The benthic disturbance generated by waves and currents is then estimated by calculating the combined force on an idealised object at the bed. The patterns of this disturbance reflect both regular tidal disturbance and rare wave events. Mean forces are typically 0.05–0.1 N, and are seen largely in areas of fast currents (View the MathML source>1ms−1). The pattern of maximum force however is more dependent on water depth and exposure to long-fetches (View the MathML source>1000km) suggesting it is dominated by wave events

Noise-enabled precision measurements of a Duffing nanomechanical resonator

We report quantitative experimental measurements of the nonlinear response of a radiofrequency mechanical resonator, with very high quality factor, driven by a large swept-frequency force. We directly measure the noise-free transition dynamics between the two basins of attraction that appear in the nonlinear regime, and find good agreement with those predicted by the one-dimensional Duffing equation of motion. We then measure the response of the transition rates to controlled levels of white noise, and extract the activation energy from each basin. The measurements of the noise-induced transitions allow us to obtain precise values for the critical frequencies, the natural resonance frequency, and the cubic nonlinear parameter in the Duffing oscillator, with direct applications to high sensitivity parametric sensors based on these resonators.Comment: 5 pages, 5 figure