An inexpensive open-source ultrasonic sensing system for monitoring liquid levels

 Liquid levels are measured in a variety of agricultural applications, and are often measured manually, which can be time-consuming and labor-intensive.  Rapid advances in electronic technologies have made a variety of inexpensive sensing, monitoring, and control capabilities available.  A monitoring system was developed and evaluated for automatic measurement of liquid levels, and demonstrated by monitoring water levels in evaporation pans used in evaporation studies and irrigation scheduling.  The system is composed of an ultrasonic sensor, a microcontroller-based data logger, and a temperature sensor.  The ultrasonic sensor measures the distance from the sensor to the liquid surface.  Air temperature is measured by the temperature sensor, and is used to compensate for changes in the speed of sound due to air-temperature variations to improve accuracy of ultrasonic distance measurements.  The datalogger is programmed to take measurements and to store data on a memory card which can be downloaded for processing and analysis.  All components of the system were assembled in a PVC housing.  The system was tested in the field, and resulted in water levels measured by the system corresponding very closely to those measured manually (R2 > 0.98).  This system is inexpensive, with total cost of US$85, and easy to build, install, and maintain.  In addition to monitoring liquid levels, the system could be adapted to a variety of other measurements.   Keywords: Ultrasonic sensor, liquid level, microcontroller, open-source hardware, datalogger, USA

The Effects of PC-Based Training on Novice Drivers\u27 Risk Awareness in a Driving Simulator

Novice drivers are almost nine times more likely to die in a crash thanmore experienced drivers. This increased risk has been found to be largely due tonovice drivers’ inability to predict the risks in the roadway ahead. A PC-basedRisk Awareness and Perception Training Program (RAPT) was developed toteach novice drivers about different categories of risky situations likely to beencountered while driving. The format was an interactive multimedia presentationwith both plan (i.e., top down) views and perspective views of roadway geometrythat illustrated generally risky scenarios along with information about the type ofrisks and the relevant areas that attention should be allocated to in order to detectthe risks. A set of novice drivers was trained with this program. The eyemovementsof the participants were then evaluated in a driving simulator todetermine whether areas of potential risk were fixated, and their performance wascompared to a separate set of untrained novice drivers. The ability of the novicedrivers to identify risks in static views improved after they completed the trainingprogram. More importantly, the trained novice drivers were significantly morelikely to correctly fixate on risk relevant areas in the simulated drivingenvironment than the untrained drivers 3-5 days after training

Spin Reduction Transition in Spin-3/2 Random Heisenberg Chains

Random spin-3/2 antiferromagnetic Heisenberg chains are investigated using an asymptotically exact renormalization group. Randomness is found to induce a quantum phase transition between two random-singlet phases. In the strong randomness phase the effective spins at low energies are S_eff=3/2, while in the weak randomness phase the effective spins are S_eff=1/2. Separating them is a quantum critical point near which there is a non-trivial mixture of S=1/2, S=1, and S=3/2 effective spins at low temperatures.Comment: 4 pages, 3 figures. Typos correcte

USCID fourth international conference

Presented at the Role of irrigation and drainage in a sustainable future: USCID fourth international conference on irrigation and drainage on October 3-6, 2007 in Sacramento, California.Includes bibliographical references.While rice is produced in some parts of the world in an upland, rainfed culture, almost all US-produced rice is grown with flood irrigation. In the dry-seeding system commonly used in the midsouthern US, the crop is usually flooded at approximately the V-4 (early tillering) growth stage and a continuous flood is maintained until after heading. The total amount of water used in rice production is quite large, and soil, fertilizers, and pesticides can be carried in the runoff from agricultural fields. Flood depth affects most aspects of flooded rice production, and remote monitoring of the flood depth could be quite valuable to many producers. The objective of this research is to develop and test a system for monitoring water depths in rice fields and alerting the producer so that less labor and energy is required to efficiently manage flood-irrigated rice. A prototype monitoring station was designed to measure water depth in a flooded rice field and transmit the information over a wireless link. A similar sensor and circuit performed satisfactorily in a raingage in 2006. In 2007, prototype monitoring stations will be installed in production rice fields. Concurrently with sensor durability testing, tests will be conducted to determine the limits of the wireless communication system. With daily reports of the water status in each paddy, field visits can be reduced. Over-pumping should be minimized by allowing better scheduling of field visits to stop the pump, and future systems should work with automatic pump control systems to stop the pump before runoff occurs

Thermodynamic Casimir effects involving interacting field theories with zero modes

Systems with an O(n) symmetrical Hamiltonian are considered in a $d$-dimensional slab geometry of macroscopic lateral extension and finite thickness $L$ that undergo a continuous bulk phase transition in the limit $L\to\infty$. The effective forces induced by thermal fluctuations at and above the bulk critical temperature $T_{c,\infty}$ (thermodynamic Casimir effect) are investigated below the upper critical dimension $d^*=4$ by means of field-theoretic renormalization group methods for the case of periodic and special-special boundary conditions, where the latter correspond to the critical enhancement of the surface interactions on both boundary planes. As shown previously [\textit{Europhys. Lett.} \textbf{75}, 241 (2006)], the zero modes that are present in Landau theory at $T_{c,\infty}$ make conventional RG-improved perturbation theory in $4-\epsilon$ dimensions ill-defined. The revised expansion introduced there is utilized to compute the scaling functions of the excess free energy and the Casimir force for temperatures T\geqT_{c,\infty} as functions of $\mathsf{L}\equiv L/\xi_\infty$, where $\xi_\infty$ is the bulk correlation length. Scaling functions of the $L$-dependent residual free energy per area are obtained whose $\mathsf{L}\to0$ limits are in conformity with previous results for the Casimir amplitudes $\Delta_C$ to $O(\epsilon^{3/2})$ and display a more reasonable small-$\mathsf{L}$ behavior inasmuch as they approach the critical value $\Delta_C$ monotonically as $\mathsf{L}\to 0$.Comment: 23 pages, 10 figure

Perinatal Hypoxic-Ischemic Brain Injury Enhances Quisqualic Acid-Stimulated Phosphoinositide Turnover

In an experimental model of perinatal hypoxic-ischemic brain injury, we examined quisqualic acid (Quis)-stimulated phosphoinositide (PPI) turnover in hippocampus and striatum. To produce a unilateral forebrain lesion in 7-day-old rat pups, the right carotid artery was ligated and animals were then exposed to moderate hypoxia (8% oxygen) for 2.5 h. Pups were killed 24 h later and Quis-stimulated PPI turnover was assayed in tissue slices obtained from hippocampus and striatum, target regions for hypoxic-ischemic injury. The glutamate agonist Quis (10 -4 M ) preferentially stimulated PPI hydrolysis in injured brain. In hippocampal slices of tissue derived from the right cerebral hemisphere, the addition of Quis stimulated accumulation of inositol phosphates by more than ninefold (1,053 ± 237% of basal, mean ± SEM, n = 9). In contrast, the addition of Quis stimulated accumulation of inositol phosphates by about fivefold in the contralateral hemisphere (588 ± 134%) and by about sixfold in controls (631 ± 177%, p < 0.005, comparison of ischemic tissue with control). In striatal tissue, the corresponding values were 801 ± 157%, 474 ± 89%, and 506 ± 115% (p < 0.05). In contrast, stimulation of PPI turnover elicited by the cho-linergic agonist carbamoylcholine, (10 -4 or 10 -2 M ) was unaffected by hypoxia-ischemia. The results suggest that prior exposure to hypoxia-ischemia enhances coupling of excitatory amino acid receptors to phospholipase C activity. This activation may contribute to the pathogenesis of irreversible brain injury and/or to mechanisms of recovery.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66017/1/j.1471-4159.1988.tb01046.x.pd

Excess free energy and Casimir forces in systems with long-range interactions of van-der-Waals type: General considerations and exact spherical-model results

We consider systems confined to a $d$-dimensional slab of macroscopic lateral extension and finite thickness $L$ that undergo a continuous bulk phase transition in the limit $L\to\infty$ and are describable by an O(n) symmetrical Hamiltonian. Periodic boundary conditions are applied across the slab. We study the effects of long-range pair interactions whose potential decays as $b x^{-(d+\sigma)}$ as $x\to\infty$, with $2<\sigma<4$ and $2<d+\sigma\leq 6$, on the Casimir effect at and near the bulk critical temperature $T_{c,\infty}$, for $2<d<4$. For the scaled reduced Casimir force per unit cross-sectional area, we obtain the form L^{d} {\mathcal F}_C/k_BT \approx \Xi_0(L/\xi_\infty) + g_\omega L^{-\omega}\Xi\omega(L/\xi_\infty) + g_\sigma L^{-\omega_\sigm a} \Xi_\sigma(L \xi_\infty). The contribution $\propto g_\sigma$ decays for $T\neq T_{c,\infty}$ algebraically in $L$ rather than exponentially, and hence becomes dominant in an appropriate regime of temperatures and $L$. We derive exact results for spherical and Gaussian models which confirm these findings. In the case $d+\sigma =6$, which includes that of nonretarded van-der-Waals interactions in $d=3$ dimensions, the power laws of the corrections to scaling $\propto b$ of the spherical model are found to get modified by logarithms. Using general RG ideas, we show that these logarithmic singularities originate from the degeneracy $\omega=\omega_\sigma=4-d$ that occurs for the spherical model when $d+\sigma=6$, in conjunction with the $b$ dependence of $g_\omega$.Comment: 28 RevTeX pages, 12 eps figures, submitted to PR

On the finite-size behavior of systems with asymptotically large critical shift

Exact results of the finite-size behavior of the susceptibility in three-dimensional mean spherical model films under Dirichlet-Dirichlet, Dirichlet-Neumann and Neumann-Neumann boundary conditions are presented. The corresponding scaling functions are explicitly derived and their asymptotics close to, above and below the bulk critical temperature $T_c$ are obtained. The results can be incorporated in the framework of the finite-size scaling theory where the exponent $\lambda$ characterizing the shift of the finite-size critical temperature with respect to $T_c$ is smaller than $1/\nu$, with $\nu$ being the critical exponent of the bulk correlation length.Comment: 24 pages, late

Asymmetric Primitive-Model Electrolytes: Debye-Huckel Theory, Criticality and Energy Bounds

Debye-Huckel (DH) theory is extended to treat two-component size- and charge-asymmetric primitive models, focussing primarily on the 1:1 additive hard-sphere electrolyte with, say, negative ion diameters, a--, larger than the positive ion diameters, a++. The treatment highlights the crucial importance of the charge-unbalanced ``border zones'' around each ion into which other ions of only one species may penetrate. Extensions of the DH approach which describe the border zones in a physically reasonable way are exact at high $T$ and low density, $\rho$, and, furthermore, are also in substantial agreement with recent simulation predictions for \emph{trends} in the critical parameters, $T_c$ and $\rho_c$, with increasing size asymmetry. Conversely, the simplest linear asymmetric DH description, which fails to account for physically expected behavior in the border zones at low $T$, can violate a new lower bound on the energy (which applies generally to models asymmetric in both charge and size). Other recent theories, including those based on the mean spherical approximation, have predicted trends in the critical parameters quite opposite to those established by the simulations.Comment: to appear in Physical Review

Transport Properties near the z=2 Insulator-Superconductor Transition

We consider here the fluctuation conductivity near the point of the insulator-superconductor transition in a system of regular Josephson junction arrays in the presence of particle-hole asymmetry or equivalently homogeneous charge frustration. The transition is characterised by the dynamic critical exponent $z=2$, opening the possibility of the perturbative renormalization-group (RG) treatment. The quartic interaction in the Ginzburg-Landau action and the coupling to the Ohmic heat bath, giving the finite quasiparticle life-time, lead to the non-monotonic behavior of the dc conductivity as a function of temperature in the leading logarithmic approximation.Comment: Revised version for publication. To appear in PR