Drift Reduction Research Articles

Comparisons of Drift Reducing/Deposition Aid Tank Mixes for Fixed Wing Aerial Applications

Abstract A field study was conducted to determine the influence of adding spray drift control/deposition aid products to tank mix solutions for fixed wign aerial applications. Downwind horizontal drift, vertical drift, and droplet spectra characteristics in a canopy top were collected on water sensitive paper (WSP) for measurement and analysis. Spread factors for each spray mix sample were determined and were used as part of the analysis procedure with the canopy measurements. DropletScan™ was used to analyze the WSP. Percent area coverage for the horizontal and vertical drift profiles was used as a means to separate differences in treatments. DropletScan™ with adjusted spread factor coefficients was used to calculate Dv.1, Dv.5, and Dv.9 at the canopy top for each treatment. Differences in products at all horizontal and vertical collector positions were measured. When compared to water, results show that some of the products did not provide any benefits for drift reduction and, in fact, may have increased the drift potential. A few of the products exhibited the potential to reduce the amount of drift. Droplet sizes for Dv.1, Dv.5, and Dv.9 increased with the addition of the drift control/deposition aid products into the tank mix. The increases were variable across products and aircraft.

Drift correction in a multichannel integrated optical Young interferometer

We demonstrate that in a sensor based on a multichannel Young interferometer, the phase information obtained for different pairs of channels can be used to correct the long-term instability (drift) due to temperature differences between measuring and reference channels, the drift in the alignment of the setup, etc. Experiments show that the nature of a major part of the drift is such that the drift present in one of the channels can be determined by interpolation of the drift measured in the two adjacent channels. It is shown that a drift reduction of 10 times can be achieved as compared with the situation in which no correction is applied. We anticipate that these findings will permit the exploitation of the extreme sensitivity of interference-based sensors to a much greater extent.

Fluoride Resonant Tunneling Diodes on Si Substrates Improved by Additional Thermal Oxidation Process

An oxidation process was applied to the fabrication of fluoride resonant tunneling diodes (RTDs) on Si substrates. The oxidation process was carried out after the growth of an ultrathin CaF2 layer on Si, and expected to passivate the Si surface in pinholes generated in the CaF2 layer. Leakage currents of Au/Al/CaF2/Si(111) metal insulator semiconductor (MIS) diodes were extremely reduced by introducing this process. Au/Al/CaF2/CdF2/CaF2/Si(111) double-barrier RTDs were also fabricated by introducing this process, the leakage currents of which were extremely reduced and a very large peak to valley current ratio (PVCR) of 1500 was obtained. It was also shown that the chemical reaction between a CdF2 well layer and the Si substrate was suppressed by the oxidation process. Owing to this effect, high-temperature growth (up to 300°C) of the CdF2 well layer was realized for the first time in the fluoride RTDs, and resulted in the reduction of undesirable current drift.

An air-assisted spinning disc nozzle and its performance on spray deposition and reduction of drift potential

An air-assisted system was used with a Micromax III speed spinning disc nozzle and assess its effects on spray penetration, deposition and reduction of drift in an artificial canopy representing cotton plants. The effects of air-assist velocities (10, 15, 25 m s −1) to carry droplets and application volumes (20 and 40 l ha −1) and two droplet sizes obtained by changing disc speed on spray deposition and drift potential were investigated with different cross-wind velocities (1.5, 2.5, 3.5 m s −1) in a wind tunnel. Deposition data produced by the spinning disc nozzle with and without air assistance were compared using a fluorometric method. Spray pattern displacement (SPD) was also determined using a spray patternator in the wind tunnel. Wind velocity, air assistance, application volume, droplet diameter and their interactions significantly affected deposition on plants. The highest deposit on plants was obtained with the combination of no cross-wind, spray volume of 20 l ha −1, an air-assist velocity of 25 m s −1 and droplet diameter of 210 μm. Downwind drift was partly controlled at an air-assist velocity of 25 m s −1 when drift potential could be reduced up to 39%.

A chip-scale atomic clock based on ^87Rb with improved frequency stability

We demonstrate a microfabricated atomic clock physics package based on coherent population trapping (CPT) on the D1 line of 87Rb atoms. The package occupies a volume of 12 mm3 and requires 195 mW of power to operate at an ambient temperature of 200 degrees C. Compared to a previous microfabricated clock exciting the D2 transition in Cs [1], this 87Rb clock shows significantly improved short- and long-term stability. The instability at short times is 4 x?10-11 / tau?/2 and the improvement over the Cs device is due mainly to an increase in resonance amplitude. At longer times (tau?> 50 s), the improvement results from the reduction of a slow drift to ?5 x 10-9 / day. The drift is most likely caused by a chemical reaction of nitrogen and barium inside the cell. When probing the atoms on the D1 line, spin-exchange collisions between Rb atoms and optical pumping appear to have increased importance compared to the D2 line.

The Effect of Conference Calls on Analyst and Market Underreaction to Earnings Announcements

I extend prior research on the information content of conference calls by examining whether they accelerate analysts' and investors' responses to the future implications of currently announced earnings. I find that the initiation of conference calls is associated with a significant reduction in the serial correlation in analyst forecast errors, a measure of initial analyst underreaction. I also find that the initiation of conference calls is associated with significant reductions in two measures of initial investor underreaction: (1) post-earnings announcement drift and (2) the proportion of the total market reaction to firms' earnings announcements that is “delayed” (i.e., that is attributable to post-earnings announcement drift). The reduction in post-earnings announcement drift surrounding conference call initiation is concentrated in the set of sample firms where drift is most severe (i.e., the smallest, least heavily traded sample firms) while the largest, most heavily traded sample firms do not exhibit significant drift either before or after conference call initiation. Robustness tests, including analyses of matched samples of nonconference call firms, indicate that the results are not driven by general increases in analyst and investor sophistication over time or by contemporaneous increases in the information and trading environments of conference call initiators.

The effects of riparian forestry on invertebrate drift and brown trout in upland streams of contrasting acidity

Abstract. Variations in macroinvertebrate drift and benthic invertebrate abundance were assessed in 30 upland Welsh streams of varying acidity (pH < 5.7 or pH.> 6.0) and riparian land-use (conifer, moorland or native broadleaf). The consequences for the diet and condition of wild brown trout Salmo trutta were also assessed. As expected from previous studies, there were significant reductions in benthic invertebrate abundance, aquatic drift density (by >60%), aquatic drift biomass (by >35%), total drift density (by >35%) and total drift biomass (by >20%) at acid sites by comparison with circumneutral sites due largely to the scarcity of mayflies. Absolute drift from terrestrial sources was unrelated to stream pH but formed a significantly greater proportion of total drift at acid sites (30-65% of density) than at circumneutral sites (20-40%) as aquatic contributions declined. Most of this apparent land use effect reflected significantly increased terrestrial drift under broadleaves. There was no significant reduction in terrestrial or aquatic drift at conifer forest sites per se after accounting for low pH. Trout diet varied substantially between locations partly reflecting variations in drift: significantly fewer mayflies and stoneflies were eaten at acid sites, and significantly more terrestrial prey were eaten under broadleaves. However, acidity did not reduce trout condition or gut-fullness. Unexpectedly, trout condition was significantly enhanced at conifer sites, irrespective of their pH. Hence, acidity has greater effects on the benthic abundance and drift density of invertebrates in upland streams than does riparian land use. However, trout forage flexibly enough to offset any possible food deficit, for example by switching to chironomids and terrestrial invertebrates. Enhanced terrestrial contributions to invertebrate drift from riparian broadleaf trees may be important in supplementing foraging opportunities for trout where aquatic prey are scarce. These data illustrate the value of native tree species in riparian locations in upland Britain and the energy subsidy they provide might well be disproportionately important for otherwise impoverished acid streams Keywords: brown trout, land-use, acidification, drift, forestry, streams

Symmetrical Multi-foil Shields for reducing Spray Drift

In this study, two symmetrical multi-foil shields were designed to minimise spray drift in both upwind and downwind travel directions. One shield was a symmetrical double foil that induced direct air assist (an air jet acting directly on the spray droplets), while the other shield was a symmetrical triple foil that induced both direct air assist and an air curtain (an air jet forming a pneumatic shield in front of or behind the spray nozzle). Wind tunnel experiments were conducted to compare the effectiveness (in terms of drift reduction) of these shields with an upwind-oriented double foil shield, using two different nozzles (8001 and 8003), three levels of pressures (138, 276, and 414 kPa), and an average wind tunnel air speed of 6·2 m s −1. A previous study of nine spray shields (that were similar in concept to shields that are commercially available) showed that the best performance in terms of drift reduction was achieved by a double foil shield. This shield, however, was more effective in an upwind than in a downwind travel direction because only in the upwind travel did the shield induce an airflow that formed an air curtain to suppress drift. Although all three shields reduced drift significantly compared to unshielded spraying, overall performances were significantly different from each other (probability P<0·05). The best performance in terms of drift reduction was achieved by the symmetrical triple foil shield (61%), followed by the symmetrical double foil shield (55%), and then the double foil shield (48%).

Aquatic risk assessment of a realistic exposure to pesticides used in bulb crops: a microcosm study.

The fungicide fluazinam, the insecticide lambda-cyhalothrin, and the herbicides asulam and metamitron were applied to indoor freshwater microcosms (water volume approximately 0.6 m3). The treatment regime was based on a realistic application scenario in tulip cultivation. Concentrations of each pesticide were equal to 0%, 0.2%, 0.5%, 2%, and 5% spray drift emission of label-recommended rates. Contribution of compounds to the toxicity of the pesticide package was established by expressing their concentrations as fractions of toxic units. The fate of the compounds in the water, and responses of phytoplankton, zooplankton, periphyton, macroinvertebrates, macrophytes, decomposition, and water quality were followed for 13 weeks. The half-lives of lambda-cyhalothrin, metamitron, and fluazinam were 1 to 2 d; that of asulam was >30 d. No consistent effects could be demonstrated for the 0.2% treatment regime that was therefore considered the no-observed-effect concentration community (NOEC). The macroinvertebrate populations of Gammarus pulex, Asellus aquaticus, and Proasellus meridianus were the most sensitive end points, followed by species of copepods and cladocerans. Responses mainly were due to lambda-cyhalothrin. The 0.5% treatment regime resulted in short-term effects. Pronounced effects were observed at the 2% and 5% treatment levels. At the end of the experiment, the macrophyte biomass that consisted of Elodea nuttallii, showed a decline at the two highest treatment levels, asulam being the causal factor (NOEC: 0.5% treatment level). Primary production was reduced at the 5% treatment level only. In our experiment, the first-tier risk assessment procedure for individual compounds was adequate for protecting sensitive populations exposed to realistic combinations of pesticides. Spray drift reduction measures seem to be efficient in protecting aquatic ecosystems in agricultural areas.

Wind speed indicator

Pesticide spraying is a widespread technique throughout all regions and crops. Among many factors that must be considered when spraying pesticides, there are the weather factors, such as temperature, air humidity, and wind speed. Anemometers, which are the adequate instruments to measure wind speed, are relatively expensive and fragile, and therefore, they are seldom used in agriculture. This paper proposes a new anemometer, which is an easy and cheap solution, that will aid farmers on deciding the best timing for pesticide application. It is made of a stick supporting two panels, perpendicular one to each other. One of them has a rip. According to wind speed, the ripped panel rises, and thus indicates the speed on the other panel. The assemblage rotates freely on the stick, according to wind direction. It is considered that at least 30% of pesticide applications have problems of drift (off target deposition). Windspeed is a key feature to this process. The Brazilian pesticide market is estimated to be around U$ 2 billion. A 10 % drift reduction means a potential saving of U$ 60 million per year. The windspeed indicator may easily disseminate on the rural area. Due to its low production cost, it may be offered as a promotional gift to farmers.

Simultaneous removal of SO 2 and NO x from flue gas using a CuO/Al 2O 3 catalyst sorbent : II. Promotion of SCR activity by SO 2 at high temperatures

Promoting effect of SO 2 on selective catalytic reduction (SCR) of NO by NH 3 over a CuO/Al 2O 3 catalyst sorbent has been investigated. Transient experiment, X-ray photoelectron spectroscopy (XPS), in situ DRIFT, NH 3-TPD, and temperature-programmed reduction (TPR) were used to evaluate the promoting mechanism. The results show that the presence of SO 2 in the reaction stream can significantly promote catalytic activity of NO reduction at temperatures above 300 °C due to the formation of sulfate species on the catalyst surface. Sulfate species affect SCR activity by changing the acidity and redox property of the catalyst sorbent. In situ DRIFT shows that only ammonia coordinated on Lewis acid sites is found on the CuO/Al 2O 3 catalyst sorbent. Sulfation of CuO/Al 2O 3 catalyst sorbent greatly increases the concentration and strength of Lewis acid sites and the concentration of Brønsted acid sites. However, the ammonia bound to Brønsted acid sites does not play an important role in the SCR reaction in the catalyst system. Moreover, there is a close relationship between the SCR activity and ammonia oxidation activity. Ammonia oxidation experiments and TPR in H 2 suggest that sulfation of the catalyst sorbent weakens the catalyst's oxidation ability and inhibits NH 3 oxidation to NO in the process of SCR, which may be another main promoting effect of SO 2 on SCR.

Analysis, testing, and implementation of seismic isolation of buildings in Chile

AbstractThis article summarizes the work done by the authors in seismic isolation over the past six years in Chile. First, a general evaluation of the optimal values of the yield level of the isolation system is performed, focusing on the idea of, but not restricted to, the use of lead–rubber bearings. These optimal values are obtained for two performance objectives: to minimize the base shear in the superstructure and to control the isolator deformation. They were used in the design and construction of two important isolated buildings that are described herein; a short description of the more relevant aspects of the design and implementation of the isolation system in these two buildings is also presented. Furthermore, results from a long testing program conducted on more than 260 full‐size elastomeric isolators are summarized and discussed. It is shown that these experimental results enable the elastomeric compounds to be characterized quite accurately by testing reduced‐scale specimens with elastomer thickness identical to that used in the full‐size isolators. Also, results from isolator constitutive modeling, scragging, and creep in the short term are briefly discussed. Inelastic analyses were performed in the structures in order to evaluate realistic interstory drift and floor acceleration response reduction factors due to the isolation design used. It is shown that in spite of the isolation system, minor inelastic excursions of the primary structure are expected, leading to smaller drift and acceleration reduction factors than those obtained from assuming an elastic response of the superstructure. In any case, seismic isolation is shown to be a very competitive alternative, technically and economically, for building design in Chile. Although it may be difficult to extrapolate this experience to other environments, the results presented herein demonstrate that seismic isolation is a technique that can be effectively used to mitigate seismic hazards in developing countries. Copyright © 2004 John Wiley &amp; Sons, Ltd.

An Enhanced Two-Stage Multiple Description Video Coder With Drift Reduction

Multiple description coding (MDC) is a source coding technique that exploits path diversity to increase the robustness of transmitting a compressed signal over error-prone channels. However, the application of MDC to video coding is still problematic because a prediction mismatch problem, called drift, may occur at the decoder when one description is lost. In the literature, it has been shown that drift can be effectively prevented by encoding this prediction mismatch and sending it as side information in a three-prediction-loop structure. However, this side information is totally redundant when both descriptions are received. We propose a very simple, but efficient two-stage MDC in the central prediction loop based on the three-prediction-loop structure of A. Reibman et al. (see Proc. IEEE Int. Conf. Image Processing - ICIP'99, p.837-41, 1999). We introduce an additional multiple description scalar quantizer into the central prediction loop. The encoding of the side information is modified in such a way that it can be used to improve the video quality when no drift occurs, but still maintain a drift prevention capability. The simulation results, with different video sequences at various packet loss rates, demonstrate that the proposed two-stage MDC structure indeed enhances the quality when the channel is error-free, yet effectively avoids drift when one description is completely lost.

The process control and robust design for the reduction of vehicle drift and brake pulling

The purpose of this study was to reduce vehicle drift and brake pulling by implementing process control and robust design. The flat road drift and split brake pulling cases were studied. For the case of flat road drift, design of experiments (DOE) was performed to investigate the influences of main factors. The differences between left and right toe angle and tyre conicity proved to have the greatest influence on the drift. The root cause of problems were statistically analysed based on the measured values of the samples. The toe angle adjustment and the tyre conicity management processes were improved. The tolerance of the respective toe angle for the adjustment process was obtained using the Monte-Carlo simulation. The results were verified by statistical testing. In the case of split brake pulling, the optimal and robust design of the suspension hard points were obtained to reduce the pulling torque.

Earthquake behavior of structures with copper energy dissipators

AbstractThe earthquake behavior of structures with supplemental copper dampers is evaluated in this study. The investigation is divided into two parts: (i) an experimental work with seven pairs of hourglass copper dampers of different aspect ratios and side profiles; and (ii) a parametric study of 6‐, 12‐, and 25‐story planar structures with elastic as well as inelastic behavior in the primary structure and copper dampers. The copper used in this study is electrolytic tough pitch (ETP) copper C11000; probably the most commonly used of all coppers; ductile, with a low‐yield, and highly resistant to corrosion. Experimental results demonstrate that all copper plates reached stable angular distortions of the order of γ=25%, which implies transverse distortions in the devices larger than 40mm. The behavior of the devices is highly dependent on the aspect ratio of the plate, h/t, and a recommendation is made to use plates in the range 11 h/t≤18. Plates beyond this range exhibit either large stress and strain concentrations in the neck of the device or a strong influence of axial deformations in their cyclic behavior. The inelastic earthquake response of structures with such devices shows that drift reduction factors of the order of 30 to 40% can be achieved with reasonably economic designs. It is also shown that the efficiency of these devices depends on the soil conditions and flexibility of the primary structure. Finally, it is concluded that supplemental copper dampers are a good alternative for drift reduction in a wide range of structural layouts, ranging from coupled shear‐wall systems to moment‐resisting frames, and for impulsive as well as non‐impulsive ground motions. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Drift reduction of gas sensor by wavelet and principal component analysis

This paper mainly deals with the sensor drift in the application of gas concentration measurement, but little has been done in previous works. The algorithm of detecting the drift of sensors presented in this paper is based on the combination of the principal component analysis (PCA) with the wavelet analysis. By this algorithm the sensor drift can be detected online sensitively. For compensating the drift of sensors, an adaptive dynamic drift compensation algorithm (ADDC) based on a drift model is also provided in this paper. From the drift model, the drift compensation factors used to compensate the drifting sensor’s data are calculated. When the drift feature changed, the drift model will be updated online adaptively. In this way, a lifelong efficient drift compensation is made possible for every sensor. The superior performance of this drift counteraction strategy is illustrated with the examples using real semiconductor sensor array data.

High performance solvent vapor identification with a two sensor array using temperature cycling and pattern classification

Temperature modulation of semiconductor gas sensors is a powerful strategy to improve selectivity and stability of gas sensor arrays in applications where different gases have to be identified [IEEE Sens. J. 1 (3) (2001) 207; Sens. Actuators B 40 (1997) 33; Sens. Actuators B 43 (1997) 45; Anal. Chim. Acta 361 (1998) 93; Anal. Chem. 68 (1996) 2067; Sens. Actuators B 33 (1996) 142]. A recent review can be found in [Sens. Actuators B 60 (1999) 35]. We present an array composed of two commercial metal oxide gas sensors allowing discrimination of six organic solvents over a wide concentration range from 2 to 200ppm in air. Temperature cycling reduces sensor baseline drift considerably over a test period of several months. Additional signal pre-processing suppresses the influence of humidity and leads to further drift reduction. The system comprises a hierarchical pattern classification evaluating shape features generated from the sensor response curve during temperature cycling, which are compared with other feature generation methods (like FFT and wavelet, see also [Sens. Actuators B 41 (1997) 105]). The classification requires comparatively little computing power and allows flexible adaptation to different operating environments, for example, to suppress false alarms from interfering gases.Reproducibility of sensor performance was checked using four systems with identical sensors. The same features can be used for the classification with all systems but the areas for classification have to be adapted to the individual sensors.

Avaliação de estratégias para redução da deriva de agrotóxicos em pulverizações hidráulicas

A deriva nas aplicações de agrotóxicos é considerada um dos maiores problemas da agricultura. Entre os fatores que a influenciam, o tamanho das gotas pulverizadas tem-se mostrado primordial. Dessa forma, o presente trabalho teve como objetivo a avaliação dos efeitos da adição de óleo vegetal emulsionável à calda de pulverização e do uso de pontas antideriva sobre o espectro de gotas e sobre o potencial de deriva de bicos de pulverização hidráulicos de jato plano. Em ambiente controlado, avaliou-se a população de gotas, por meio de um analisador de gotas por difração de raio laser, em tempo real, pulverizadas utilizando-se bicos standard, com e sem a adição de adjuvante, e bicos antideriva, na faixa de pressão de 200 a 400 kPa. Como complementação, avaliou-se também a deriva em campo, utilizando-se alvos artificiais fora da área de aplicação, procedendo-se à contagem de gotas em diferentes distâncias. Observou-se que a adição de óleo vegetal à calda de pulverização e o uso de bicos de pulverização antideriva, dotados de pré-orifício, alteraram o espectro de gotas pulverizadas, aumentando o diâmetro das gotas e diminuindo a percentagem de gotas propensas à ação dos ventos, constituindo-se, portanto, em fator auxiliar para redução da deriva.

Invariant Manifold Tracking for First-Order Nonlinear Hill's Equations

Abstract : An approach to provide nonlinear active control for the first-order nonlinear classical Hill's equations is described. Both the linearized and nonlinear Hill's equations are controlled to remain close to specific invariant manifolds defined through the various system Hamiltonians. It is then shown that trajectories similar to the periodic trajectories of the linearized system can be maintained by the nonlinear equations on invariant manifolds defined by the linearized system of equations. Forcing the nonlinear system trajectories onto an invariant manifold of the linearized system, with an appropriate choice of initial conditions, provides a significant reduction in the along-track drift of the first-order nonlinear Hill's equations as compared to the linearized equations. There is also a small drift reduction in the radial coordinate direction. The cross-track position suffers only a slight increase in the maximum amplitude of its oscillation.

Low temperature dependence three-axis accelerometer for high temperature environments with temperature control of SOI piezoresistors

Abstract In this paper, a three-axis accelerometer for high temperatures using constant temperature control of silicon on insulator (SOI) piezoresistors is proposed for reduction of temperature drift. The accelerometer has surrounding mass structure, and piezoresistors for four wheatstone bridges to detect three-axis acceleration. A temperature sensor using the whole resistance of four wheatstone bridges and micro-heaters are integrated on the beam structures. The structure of accelerometer was optimized with finite element method (FEM) simulation program, ANSYS. The accelerometer was fabricated with SOI wafers by bulk-micromachining. Temperature dependence of the fabricated three-axis accelerometer on variation of atmospheric temperature (from room temperature to 300 °C) is much reduced by keeping the temperature of piezoresistors at 300 °C. Temperature coefficient of sensitivity (TCS) is much reduced to 72% of the original TCS.