D. Ken Giles

Multispectral Machine Vision Identification of Lettuce and Weed Seedlings for Automated Weed Control

Multispectral images of leaf reflectance in the visible and near infrared region from 384 to 810 nm were used to establish the feasibility of developing a site-specific classifier to distinguish lettuce plants from weeds in California direct-seeded lettuce fields. An average crop vs. weed classification accuracy of 90.3% was obtained in a study of over 7,000 individual spectra representing 150 plants. The classifier utilized reflectance values from a small spatial area (3 mm diameter) of the leaf in order to allow the method to be robust to occlusion and to eliminate the need to identify leaf boundaries for shape-based machine vision recognition. Reflectance spectra were collected in the field using equipment suitable for real-time operation as a weed sensor in an autonomous system for automated weed control. Nomenclature: Lettuce, Lactuca sativa L. ‘Capitata’ and ‘Crispa’

An Apparatus for Generating Aged Cigarette Smoke for Controlled Human Exposure Studies

Research has shown that cigarette smoke changes chemically and physically after it is released into indoor air, that these changes can increase secondhand smoke (SHS) toxicity, and that acute exposures to even low levels of SHS increase the risk of cardiopulmonary disease. We designed a system to reproduce realistic SHS exposures in the laboratory for use in controlled human exposure studies. We generated cigarette smoke with a smoking machine, diluted it and conducted it through a 6 m3 stainless steel flow reactor at rates equivalent to the upper ranges of normal residential air exchange rates, to create aged cigarette smoke as a model for secondhand cigarette smoke. We observed that approximately 50% of the particle mass deposited within the system and that particle deposition percentage was higher when absorbent materials were placed within the system. The particle size ranges and deposition percentages, coefficients and velocities observed for this smoke aerosol are in good agreement with published values for SHS observed in residences and vehicles. This apparatus also permits the study of the physical and chemical interactions between SHS and indoor surfaces. The apparatus delivers stable aerosol concentrations to a human subject, which will permit accurate analysis of dose-response relationships in studies of the cardiovascular and respiratory effects of SHS exposure. Copyright 2012 American Association for Aerosol Research

Evaluation of particulate matter abatement strategies for almond harvest.

ABSTRACT Almond harvest accounts for substantial PM10 (particulate matter [PM] ≤10 μm in nominal aerodynamic diameter) emissions in California each harvest season. This paper evaluates the effects of using reduced-pass sweepers and lower harvester separation fan speeds (930 rpm) on lowering PM emissions from almond harvesting operations. In-canopy measurements of PM concentrations were collected along with PM concentration measurements at the orchard boundary; these were used in conjunction with on-site meteorological data and inverse dispersion modeling to back-calculate emission rates from the measured concentrations. The harvester discharge plume was measured as a function of visible plume opacity during conditioning operations. Reduced-pass sweeping showed the potential for reducing PM emissions, but results were confounded because of differences in orchard maturity and irrigation methods. Fuel consumption and sweeping time per unit area were reduced when comparing a reduced-pass sweeper to a conventional sweeper. Reducing the separation fan speed from 1080 to 930 rpm led to reductions in PM emissions. In general, foreign matter levels within harvested product were nominally affected by separation fan speed in the south (less mature) orchard; however, in samples conditioned using the lower fan speed from the north (more mature) orchard, these levels were unacceptable. IMPLICATIONS The results of this research indicate that PM emissions from almond sweeping operations may be reduced by use of reduced-pass sweepers. Additionally, increased efficiencies in fuel consumption and time required for sweeping may be realized by use of reduced-pass sweepers. Reducing harvester separation fan speeds results in lower emissions from nut conditioning, but foreign matter levels in conditioned samples from more mature orchards were unacceptable.

Injection and fluid handling system for machine-vision controlled spraying

A fluid handling system was developed to allow on-demand chemical injection for a machine-vision controlled sprayer. Critical design parameters were to maintain a desired concentration of chemical within the solution and to maintain a constant spray pressure at the nozzles. Unlike conventional agricultural spray injection systems which are designed to respond to relatively slow vehicle speed changes within a relatively narrow range, the system reported in this paper was designed to respond quickly over a wide dynamic range of flowrates. The design was evaluated with two injection rate control methods for accuracy of maintaining a desired concentration and response speed over a prescribed range of flowrate changes, simulating a “real world” weed map. A salt tracer was used to determine concentration changes in real time and spray pressure was recorded using an electronic transducer. The applied concentration was maintained within about 10 % of the desired rate and pressure varied 5 % over a dynamic flow range of 12:1.

AN ELECTRONIC SENSOR TO CHARACTERIZE TRANSIENT RESPONSE OF NOZZLE INJECTION FOR PESTICIDE SPRAYING

An electronic sensor was developed to characterize the transient response of a two-fluid mixture spray emission created by injecting a pulse of concentrated solution into a carrier fluid within a spray nozzle. The test situation simulated an intermittent, at-nozzle chemical injection system for spraying of distinct targets. The principle of sensor operation was measurement of the electrical resistance of an element of the emitted fluid created by injecting a concentrated sodium chloride solution into a water carrier. The sensor was initially calibrated with steady-state flow of carrier liquid over a range of 10 to 1500 ppm NaCl concentration. The high temporal response of the sensor provided measurement of the transient concentration of injected NaCl solution during brief (10 to 100 ms) injection events into the steady-state flow of the carrier liquid. The accuracy and transient response were quantified by comparing the volume of injected salt solution as determined by integrating the instantaneous concentration over the measured event with a direct volumetric measurement of the injected volume. Excellent agreement between volume measurements of injection and predicted injection volumes was found, validating sensor use for injection studies. The relatively simple sensor design provides the accuracy and high-frequency response necessary for at-nozzle injection studies.