Evaluation of three tractor-guidance methods for parallel swathing at two field speeds

This study compared the accuracy (mean error and rms error) and precision (standard deviation of error) of three tractor-guidance methods (foam-marker, light-bar, and assisted-steering systems) at two field speeds (5.6 – and 11.5 km/h) for parallel swathing operations. Eighty-four replications of each combination of guidance method and field speed were conducted between 15 October and 22 December 2006 (504 total field passes). The foam-marker system was found to be significantly less accurate [larger mean error (p \u3c .0001) and had a larger rms error (p \u3c .0001)] than either the light-bar or the assisted-steering system. There was no significant difference in mean error (p = .6718) or rms error (p = .8841) by field speed. There was a significant interaction between guidance method and field speed for both mean error (p = .0009) and rms error (p = .003). Mean and rms errors for the foam-marker and the assisted-steering systems increased at higher field speed, while the mean and rms errors for the light-bar system decreased at higher speed. The assisted-steering system had a significantly lower (p = .0164) standard deviation of error (higher precision) than the foam-marker or the light-bar systems. There was no significant difference in the standard deviation of error by field speed (p = .6258) or by the interaction of guidance method and field speed (p = .2748)

Effects of thinking-aloud pair problem solving on the troubleshooting performance of undergraduate students in a power technology course

A randomized post-test-only experimental design with a counter-balanced internal replication was used to determine the effects of thinking-aloud pair problem solving (TAPPS) on the troubleshooting performance of college students in a power technology course. The experimental results were stable across two troubleshooting tasks. Students who participated in the pair problem solving groups were significantly more successful (p ≤ .05) at troubleshooting engine faults than were students in the control groups. Among students who successfully completed the troubleshooting tasks across both groups, there were no significant differences in time required for completion. These findings indicate that the use of pair problem solving may be an important step in the development of metacognitive skills among students in technological troubleshootin

PTO performance and NOx emissions with D2, B20, and B100 fuels in a John Deere 3203 compact tractor

Tests were conducted in fall 2006 on a John Deere 3203 diesel tractor to determine differences in specific fuel consumption, power take-off (PTO) torque, PTO power, thermal efficiency, and oxides of nitrogen (NOx) emissions between No. 2 diesel (D2), 20% biodiesel (B20), and 100% biodiesel (B100). Four 1-hour tests were conducted on each fuel. The results indicated no statistically significant differences (p≤.05) between D2 or B20 on any variable of interest. However, B100 resulted in significantly (p≤.05) increased, specific fuel consumption and thermal efficiency and decreased PTO torque and PTO power over both D2 and B20. These data suggest that farmers could switch from D2 to B20 without any performance losses, but a switch to B100 would result in the use of more fuel and a loss of power and torque

E-85 vs. regular gasoline: effects on engine performance, fuel efficiency, and exhaust emissions

This study compared the performance, fuel efficiency, and exhaust emissions of a 2.61 kW engine fueled with regular unleaded gasoline (87 octane) and an 85% ethanol blend (E85) under two load conditions. Four 1-h tests were conducted with each fuel at both governor’s maximum (3400 rpm) and peak torque (2800 rpm) conditions for a total of 16 tests. At governor’s maximum engine speed, there were no significant differences (p\u3e0.05) between fuels for engine torque, power, specific carbon dioxide (sCO2 ), specific carbon monoxide (sCO), specific hydrocarbons (sHC), or specific oxides of nitrogen (sNOX) emissions. However, there was a significant difference in specific fuel consumption and specific dioxide (sO2 ) emissions with E85 requiring the consumption of more fuel and emitting fewer oxide gases. Under peak-torque test conditions, there were significant differences by fuel for power, torque, and specific fuel consumption, as ethanol required more fuel while developing less power and torque when compared to gasoline. There were no significant differences by fuel type in sCO2 , sCO, sHC, sO2 , or sNOX emissions. The results indicate that performance was similar when the engine was fueled by regular unleaded gasoline or E85 under rated engine-speed conditions; however, the ethanol-fueled engine produced significantly less power and torque under peak torque testing conditions. In both testing conditions, specific fuel consumption was significantly higher with E85

Using Self-Efficacy Theory to Design Arduino Instruction for Novices: A Replication Study

A replication study was conducted to determine the effectiveness of an instructional treatment based on self-efficacy theory when used with novice Arduino microcontroller users. Students (n = 32) in an introductory university agricultural systems technology course participated in a lesson on Arduino microcontrollers, circuit breadboarding, and Arduino programming which included four hands-on practice tasks, designed to provide students with positive mastery, vicarious and social persuasion experiences. Next, students completed a laboratory activity and were provided additional opportunities for mastery, vicarious, and social persuasion experiences. The one-group pretest-posttest design indicated the instructional treatment had significant (p \u3c .001) and large effects in increasing students’ interest in Arduino, breadboarding self-efficacy, programming self-efficacy, and Arduino knowledge. These findings were consistent with the original study and provided additional evidence for self-efficacy theory as an effective model for developing instruction for novice Arduino users. Students’ written comments provided additional insight concerning the instructional treatment

Measurement of transient smoke emissions from diesel and biodiesel fuel blends in an agricultural tractor

Transient smoke emissions pose potential hazards to human health and the environment. With the increased popularity of biodiesel, there is a need to determine if these fuels produce different levels of particulate matter in exhaust emissions. This study examined the transient smoke emissions of three fuels: No. 2 petroleum diesel fuel (D2, ASTM D 975), a blend of 20% biodiesel and 80% petroleum diesel (B20, ASTM 6751), and a 100% pure biodiesel derived from animal fats (B100, ASTM D 6751). Measurements of smoke emissions were taken using the SAE J1677 snap acceleration test procedure on a John Deere 3203 compact utility tractor. The results indicate there were no statistically significant differences in smoke opacity between the three fuels (p\u3e0.05). The low, non-significant emissions may be due to the diesel engine being EPA Tier II-compliant and the use of ultra-low-sulfur diesel. Recommendations for further study include testing biofuels made of varying feed stocks rather than animal fats, testing steady state load conditions in addition to transient loads, and testing tractors manufactured prior to initiation of EPA tier-compliance standard

Enhancing Student Interest in the Agricultural Sciences through Aquaponics

ABSTRACT Educators in grades K-16 have recently placed renewed interest in experiential learning activities for teaching science and mathematics. Agriculture offers numerous authentic activities that can serve as meaningful contexts for teaching and learning. The AgriScience Education Project at the University of Arkansas was established to develop and disseminate agriculturally related teaching and learning materials and activities that teachers can use to teach science and mathematics. The objective of this paper is to describe the Aquaponics in the Classroom program, one of the most successful components of the AgriScience Education Project. Teachers participating in this program receive a classroom-scale aquaponics unit, a packet of printed instructional materials, and a set of student laboratory activities that use aquaponics as a context for teaching and learning science and mathematics. The project has helped teachers of kindergarten through high school classes create aquaponics programs. Primary interest has been from teachers at the middle-school and junior high school grade levels

Modelling high-resolution ALMA observations of strongly lensed dusty star-forming galaxies detected by Herschel

We present modelling of ∼0.1 arcsec resolution Atacama Large Millimetre/submillimetre Array imaging of seven strong gravitationally lensed galaxies detected by the Herschel Space Observatory. Four of these systems are galaxy–galaxy strong lenses, with the remaining three being group-scale lenses. Through careful modelling of visibilities, we infer the mass profiles of the lensing galaxies and by determining the magnification factors, we investigate the intrinsic properties and morphologies of the lensed submillimetre sources. We find that these submillimetre sources all have ratios of star formation rate to dust mass that are consistent with, or in excess of, the mean ratio for high-redshift submillimetre galaxies and low redshift ultra-luminous infrared galaxies. Reconstructions of the background sources reveal that the majority of our sample display disturbed morphologies. The majority of our lens models have mass density slopes close to isothermal, but some systems show significant differences

The XMM deep survey in the CDF-S II. a 9-20 keV selection of heavily obscured active galaxies at z>1.7

We present results on a search of heavily obscured active galaxies z>1.7 using the rest-frame 9-20 keV excess for X-ray sources detected in the deep XMM-CDFS survey. Out of 176 sources selected with the conservative detection criteria (>8 sigma) in the first source catalogue of Ranalli et al., 46 objects lie in the redshift range of interest with the median redshift z~2.5. Their typical rest-frame 10-20 keV luminosity is 1e+44 erg/s, as observed. Among optically faint objects that lack spectroscopic redshift, four were found to be strongly absorbed X-ray sources, and the enhanced Fe K emission or absorption features in their X-ray spectra were used to obtain X-ray spectroscopic redshifts. Using the X-ray colour-colour diagram based on the rest-frame 3-5 keV, 5-9 keV, and 9-20 keV bands, seven objects were selected for their 9-20 keV excess and were found to be strongly absorbed X-ray sources with column density of nH > 0.6e+24 cm-2, including two possible Compton thick sources. While they are emitting at quasar luminosity, ~3/4 of the sample objects are found to be absorbed by nH > 1e+22 cm-2. A comparison with local AGN at the matched luminosity suggests an increasing trend of the absorbed source fraction for high-luminosity AGN towards high redshifts.Comment: 9 pages, 7 figures. Accepted for publication in A&