lights on and off at high frequency (10,000 s of times per second). Within each on/off cycle, the fraction of time that the LEDs are on (duty cycle) can be precisely controlled. Reducing the duty cycle creates the perception of dimming, even though in
(top) and a simplified diagram of the duty cycle control board (bottom). A fluorometer is used to measure the quantum yield of photosystem II and the datalogger calculates the electron transport rate from this and the photosynthetic photon flux density
An evaporative cooling system for apple trees was implemented. The system is automated to conserve irrigation water. The automation is based on the digital, integrated thermometer and thermostat chip embedded in the artificial fruit. The thermometer–thermostat chip drives a solid state relay. The relay controls a solenoid operated valve. A typical duty cycle consisted of 1 to 2 minutes of wetting (water on) to 4 to 10 minutes drying (water off). Differences in the length of duty cycles between individual chips were observed. The reliability of the system was adequate. The waterproofing of the system's electrical components was its weak point. Irrigation water deposits accumulated on the apple fruit surface during the growing season were readily removable with a simulated brush technique.
. The reason for this difference is that the intelligent spray system controls individual nozzle flow rates with duty cycles of PWM solenoid valves attached to their corresponding nozzles to match sectional canopy foliage volume. To prevent trees from
responsible insecticide application, nor as familiar with the codling moth life cycle and appropriate insecticide timing. A simpler management method with potential appeal to small-scale or noncommercial growers combines fruit thinning and bagging early during
development whereby plants, such as desert ephemerals, complete their life cycle before a serious plant water deficit develops. Avoidance involves mechanisms whereby plants maintain high water potential in tissues by maintaining water uptake or reducing water
(Model 3210; Oxbo International). In 2009, the harvester was operated at a ground speed of 0.8 or 1.6 km·h −1 in combination with two shaker head frequencies (185 and 210 cycles/min) for a total of four ground speed × shaker head frequency combinations
; Kelway, Wyckoff, NJ), moisture content between 40% and 65%, and temperatures meeting the minimum requirements given the results of the oven mortality tests (Super Duty - Fast Response Windrow Compost Thermometer; Reotemp Instrument Corp., San Diego, CA
duty soil heating cables (Wrap-On Company Inc., Bedford Park, IL) were installed as directed by the manufacturer. Cables were buried ≈2–3 cm below the soil surface and were spaced 30 cm apart. Each cable was attached to a Model 18500 heater controlled
, Netherlands Jao, R.C. Fang, W. 2001 Adjusting frequency and duty cycle to promote growth of potato plantlets in vitro using super-bright red and blue LEDs. Proc. Intl. Symp. Design Environ. Control Trop. Subtrop. Greenhouses 4:15–18 Jao, R.C. Fang, W. 2004