Teaching general concepts about sensors and transfer functions with a voltage divider

This work proposes the use of a simple voltage divider circuit composed by one potentiometer and one resistor to simulate the behavior of the electrical output signal of linear and nonlinear sensors. It is a low cost way to implement practical experiments in classroom and it also enables the analysis of interesting topics of electricity. This work induces naturally to a class guide where students can build and characterize a voltage divider to explore several concepts about sensors output signal. As the result of this teaching activity it is expected that students understand fundamentals of voltage divider, potentiometer operation, fundamental sensor characteristics, transfer function, and, besides, associate directly concepts of physics and mathematics with a practical approach.

Rock Hill Fire Department Records - Accession 242 - M102 (131)

The Rock Hill Fire Department Records consist correspondence from W.H. Wylie, for whom Lake Wylie is named, to prominent Rock Hillian Mr. W.T. Roddey and to the Rock Hill Fire Department. Also included is a program book for the 33rd Annual Convention of South Carolina State Firemen’s Association held in Rock Hill in 1928. The program book lists officers of the Association, committee appointments, fire chiefs, in SC, Rock Hill city officials with brief biographical sketches and sketches of the history of SC State Firemen’s Association, city of Rock Hill and Winthrop College.

Fire History at the Eastern Great Plains Margin, Missouri River Loess Hills

The purpose of this paper is to provide quantitative fire history information for a geographically unique region, the Loess Hills of northwest Missouri. We sampled 33 bur oak (Quercus macrocarpa Michx.), chinkapin oak (Q. muehlenbergii Engelm.), and black oak (Q. velutina Lam.) trees from the Brickyard Hill Conservation Area in northwest Missouri. The period of tree-ring record ranged in calendar years from 1671 to 2004 and fire-scar dates (n = 97) ranged from 1672 to 1980. Fire intervals for individual trees ranged from 1 to 87 years. The mean fire interval was 6.6 years for the pre-Euro-American settlement period (1672-1820), and 5.2 years for the entire record (1672-1980). A period of more frequent fire (mean fire interval = 1.6 for 1825 to 1850) coincided with Euro-American settlement of the area. The average percentage of trees scarred at the site was 16.8%, or about 1 in 7 trees sampled per fire. No significant relationship between fire years and drought conditions was found; however, events prior to 1820 may have been associated with wet to dry mode transitions.

Fire History at the Southwestern Great Plains Margin, Capulin Volcano National Monument

This study documents historic fire events at Capulin Volcano National Monument over the last four centuries using dendrochronologically dated fire scars at two sites: the lower volcano lava flows (the Boca) and the adjacent canyon slopes (Morrow Ranch). The mean fire interval (MFI) was 12 years at the Boca site (before 1890) and 5.4 years (1600-1750) and 19.1 years (1751-1890) at the Morrow Ranch site. Data from the Boca and Morrow Ranch sites combined with the extremely pyrogenic landscape position of the volcano slopes indicate that the volcano slopes likely burned more frequently (e.g., MFI <5 yr). Around 1750, the fire regime appeared to transition to longer fire intervals, greater temporal synchrony among fire-scarred trees, and a higher proportion of trees scarred in fire years. Temporal variability in the fire regime at Capulin Volcano may reflect changes in human populations, climate, and land use.

Fire Frequency and the Vegetative Mosaic of a Spruce-Fir Forest in Northern Utah

Fire scar and vegetative analysis were used to construct a fire history for the Engelmann spruce/subalpine fir (Picea engelmannii/Abies lasiocarpa) vegetation type of the Utah State University (USU) T. W Daniel Experimental Forest. Three distinct periods of fire frequency were established-presettlement (1700-1855), settlement (1856-1909), and suppression (1910-1990). Mean fire interval (MFI) decreased during the settlement period and greatly increased during the suppression era. The difference was attributed to the influx of ignition sources during the settlement of nearby Cache Valley, located 40 km to the west. Logging and livestock grazing appear to have led to the reduced MFI, which in turn worked as a factor to create the vegetative mosaic now observed on the study area. The increase in MFI during the suppression era permitted the advancement of shade-tolerant species in the understory of the shade-intolerant lodgepole pine (Pinus contorta var. latifolia) and quaking aspen (Populus tremuloides). Continued suppression of disturbance from wildfire will allow the lodgepole pine cover type, which experienced the lowest MFI during the settlement period, to be further invaded by shade-tolerant species, decreasing spatial stand diversity and increasing the risk of more intense fires.

THE ROLE OF BIRD MANAGEMENT IN FIRE PROTECTION

Two years ago, Mike Fall and I showed you some ideas we had regarding mod¬ern architecture and bird problems. This year we've switched to considering bird hazards in older frame dwellings and on buildings where a fire hazard may be ap¬parent. During a class project some time ago, I was examining a nest of house sparrows and discovered that these birds incorporated cellulose cigarette filters into their nests. Filters were stripped of their paper wrapping and were apparently used by the sparrows as a substitute for or a supplement to fluffy air-born seeds and seed mat¬erials. The incidence of the cigarette filters varied. In the nests that I sampled the numbers varied anywhere from six up to two dozen filter remnants. We feel that the incidence will probably vary with the relative availability of discarded cigarette filter butts. We are concerned with the incidence of filters as an index to the possibility that the birds are picking up live cigarette butts, and this leads us to investigate some records of fires over the past three quarters of a century that were claimed to have been caused by birds.

Measuring Aeolian Saltation: A Comparison of Sensors

SHERMAN, D.J.; LI, B.; FERRELL E.J.; ELLIS, J.T.; COX, W.D.; MAIA, L.P., and SOUSA, P.H.G.O., 2011. Measuring Aeolian Saltation: A Comparison of Sensors. In: Roberts, T.M., Rosati, J.D., and Wang, P. (eds.), Proceedings, Symposium to Honor Dr. Nicholas C. Kraus, Journal of Coastal Research, Special Issue, No. 59, pp. 280-290. West Palm Beach (Florida), ISSN 0749-0208. We report the results of field experiments designed to compare four types of aeolian saltation sensors: the Safire; the Wenglor (R) Particle Counter; the Miniphone; and the Buzzer Disc. Sets of sensors were deployed in tight spatial arrays and sampled at rates as fast as 20 kHz. In two of the three trials, the data from the sensors are compared to data obtained from sand traps. The Miniphone and the Buzzer Disc, based on microphone and piezoelectric technologies, respectively, produced grain impact counts comparable to those derived from the trap data. The Satire and the Wenglor (R) Particle Counter produce count rates that were an order of magnitude too slow. Satires undercount because of their large momentum threshold and because its signal is saturated at relatively slow transport rates. We conclude that the Miniphone and the Buzzer Disc are appropriate for deployment as grain counters because their small size allows them to be installed in closely-spaced sets.

Ab-initio calculations for a realistic sensor: A study of CO sensors based on nitrogen-rich carbon nanotubes

The use of nanoscale low-dimensional systems could boost the sensitivity of gas sensors. In this work we simulate a nanoscopic sensor based on carbon nanotubes with a large number of binding sites using ab initio density functional electronic structure calculations coupled to the Non-Equilibrium Green's Function formalism. We present a recipe where the adsorption process is studied followed by conductance calculations of a single defect system and of more realistic disordered system considering different coverages of molecules as one would expect experimentally. We found that the sensitivity of the disordered system is enhanced by a factor of 5 when compared to the single defect one. Finally, our results from the atomistic electronic transport are used as input to a simple model that connects them to experimental parameters such as temperature and partial gas pressure, providing a procedure for simulating a realistic nanoscopic gas sensor. Using this methodology we show that nitrogen-rich carbon nanotubes could work at room temperature with extremely high sensitivity. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4739280]

Climatic oscillations shape the phylogeographical structure of Atlantic Forest fire-eye antbirds (Aves: Thamnophilidae)

In the present study, mitochondrial (mt)DNA sequence data were used to examine the genetic structure of fire-eye antbirds (genus Pyriglena) along the Atlantic Forest and the predictions derived from the river hypothesis and from a Last Glacial Maximum Pleistocene refuge paleomodel were compared to explain the patterns of genetic variation observed in these populations. A total of 266 individuals from 45 populations were sampled over a latitudinal transect and a number of phylogeographical and population genetics analytical approaches were employed to address these questions. The pattern of mtDNA variation observed in fire-eye antbirds provides little support for the view that populations were isolated by the modern course of major Atlantic Forest rivers. Instead, the data provide stronger support for the predictions of the refuge model. These results add to the mounting evidence that climatic oscillations appear to have played a substantial role in shaping the phylogeographical structure and possibly the diversification of many taxa in this region. However, the results also illustrate the potential for more complex climatic history and historical changes in the geographical distribution of Atlantic Forest than envisioned by the refuge model. (c) 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 900824.

In-Flight Collision Avoidance Controller Based Only on OS4 Embedded Sensors

The major goal of this research was the development and implementation of a control system able to avoid collisions during the flight for a mini-quadrotor helicopter, based only on its embedded sensors without changing the environment. However, it is important to highlight that the design aspects must be seriously considered in order to overcome hardware limitations and achieve control simplification. The controllers of a UAV (Unmanned Aerial Vehicle) robot deal with highly unstable dynamics and strong axes coupling. Furthermore, any additional embedded sensor increases the robot total weight and therefore, decreases its operating time. The best balance between embedded electronics and robot operating time is desired. This paper focuses not only on the development and implementation of a collision avoidance controller for a mini-robotic helicopter using only its embedded sensors, but also on the mathematical model that was essential for the controller developing phases. Based on this model we carried out the development of a simulation tool based on MatLab/Simulink that was fundamental for setting the controllers' parameters. This tool allowed us to simulate and improve the OS4 controllers in different modeled environments and test different approaches. After that, the controllers were embedded in the real robot and the results proved to be very robust and feasible. In addition to this, the controller has the advantage of being compatible with future path planners that we are developing.

Spectroradiometry of soil and comparison with orbital sensors

The aim of this study was to characterize and compare the spectral behavior of different soil classes obtained by orbital and terrestrial sensors. For this, an area of 184 ha in Rafard (SP) Brazil was staked on a regular grid of 100x100 m and soil samples were collected and georeferenced. After that, soil spectral curves were obtained with IRIS sensor and the sample points were overlaid at Landsat and ASTER images for spectral data collection. The soil samples were classified and mean soil curves for all sensors were generated by soil classes. The soil classes were differentiated by texture, organic matter and total iron for all sensors studied, the orbital sensors despite the lower spectral resolution, maintained the characteristics of the soil and the curves of reflectance intensity.

Designing piezoresistive plate-based sensors with distribution of piezoresistive material using topology optimization

Piezoresistive sensors are commonly made of a piezoresistive membrane attached to a flexible substrate, a plate. They have been widely studied and used in several applications. It has been found that the size, position and geometry of the piezoresistive membrane may affect the performance of the sensors. Based on this remark, in this work, a topology optimization methodology for the design of piezoresistive plate-based sensors, for which both the piezoresistive membrane and the flexible substrate disposition can be optimized, is evaluated. Perfect coupling conditions between the substrate and the membrane based on the `layerwise' theory for laminated plates, and a material model for the piezoresistive membrane based on the solid isotropic material with penalization model, are employed. The design goal is to obtain the configuration of material that maximizes the sensor sensitivity to external loading, as well as the stiffness of the sensor to particular loads, which depend on the case (application) studied. The proposed approach is evaluated by studying two distinct examples: the optimization of an atomic force microscope probe and a pressure sensor. The results suggest that the performance of the sensors can be improved by using the proposed approach.

Solvent-Resistant Polymeric Sensors for Adulteration Detection in Liquid Fuels

Polymeric sensors with improved resistance to organic solvents were produced via the layer-by-layer thin film deposition followed by chemical cross-linking. According to UV-vis spectroscopy, the mass loss of polyaniline/poly(vinyl alcohol) and polyaniline/novolac-type resin based films deposited onto glass slides was less than 20% when they were submitted to successive immersions (up to 3,000 immersion cycles) into commercially available ethanol and gasoline fuel samples. Polyallylamine hydrochloride/nickel tetrasulfonated phthalocyanine films presented similar stability. The electrical responses assessed by impedance spectroscopy of films deposited onto Au-interdigitated microelectrodes were relatively unaffected after continuous or cyclic immersions into both fuels. After these studies, an array including these polymeric sensors was employed to detect adulteration in ethanol and gasoline samples. After principal component analysis, it was possible to conclude that the proposed sensor array is capable to discriminate with remarkable reproducibility ethanol samples containing different amounts of water or else gasoline samples containing different amounts of ethanol. In both examples, more than 90% of data variance was retained in the first principal component. For each type of sample, ethanol and gasoline, it was found a linear correlation between one of the principal components and the sample's composition. These findings allow one to conclude that these films present great potential for the development of reliable and low-cost sensors for fuel analysis in liquid phase.

STRUCTURE AND DYNAMICS: THE TRANSITION FROM NONEQUILIBRIUM TO EQUILIBRIUM IN INTEGRATE-AND-FIRE DYNAMICS

The transient and equilibrium properties of dynamics unfolding in complex systems can depend critically on specific topological features of the underlying interconnections. In this work, we investigate such a relationship with respect to the integrate-and-fire dynamics emanating from a source node and an extended network model that allows control of the small-world feature as well as the length of the long-range connections. A systematic approach to investigate the local and global correlations between structural and dynamical features of the networks was adopted that involved extensive simulations (one and a half million cases) so as to obtain two-dimensional correlation maps. Smooth, but diverse surfaces of correlation values were obtained in all cases. Regarding the global cases, it has been verified that the onset avalanche time (but not its intensity) can be accurately predicted from the structural features within specific regions of the map (i.e. networks with specific structural properties). The analysis at local level revealed that the dynamical features before the avalanches can also be accurately predicted from structural features. This is not possible for the dynamical features after the avalanches take place. This is so because the overall topology of the network predominates over the local topology around the source at the stationary state.

Synthesis and Characterization of Gold/Alanine Nanocomposites with Potential Properties for Medical Application as Radiation Sensors

Radiation dose assessment is essential for several medical treatments and diagnostic procedures. In this context, nanotechnology has been used in the development of improved radiation sensors, with higher sensitivity as well as smaller sizes and energy dependence. This paper deals with the synthesis and characterization of gold/alanine nanocomposites with varying mass percentage of gold, for application as radiation sensors. Alanine is an excellent stabilizing agent for gold nanoparticles because the size of the nanoparticles does not augment with increasing mass percentage of gold, as evidenced by UV-vis spectroscopy, dynamic light scattering, and transmission electron microscopy. X-ray diffraction patterns suggest that the alanine crystalline orientation undergoes alterations upon the addition of gold nanoparticles. Fourier transform infrared spectroscopy indicates that there is interaction between the gold nanoparticles and the amine group of the alanine molecules, which may be the reason for the enhanced stability of the nanocomposite. The application of the nanocomposites as radiation detectors was evaluated by the electron spin resonance technique. The sensitivity is improved almost 3 times in the case of the nanocomposite containing 3% (w/w) gold, so it can be easily tuned by changing the amount of gold nanoparticles in the nanocomposites, without the size of the nanoparticles influencing the radiation absorption. In conclusion, the featured properties, such as homogeneity, nanoparticle size stability, and enhanced sensitivity, make these nanocomposites potential candidates for the construction of small-sized radiation sensors with tunable sensitivity for application in several medical procedures.