Shooting device for free-surface impact studies

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (leaves 38-39).The hydrodynamics of free-surface impacts are of great interest to scientists across many disciplines including ocean engineering, fluids mechanics, and biology. This thesis focuses on designing a mechanism to shoot small projectiles downward. Two pneumatic shooting mechanisms were investigated: the potato gun and the paintball gun. Adaptations were made to the paintball gun, as a preliminary design; however, it was later concluded that pneumatics were not the best way to propel the projectile. The final design includes a pinball shooter to propel the ball and an electromagnet to suspend the ball before shooting. This shooting mechanism uses magnetic balls of diameter 1 inch and can achieve velocities of 278 m/s when located 1 m above the free surface. The adaptability of the mechanism to other downward shooting situations is discussed.by Sarah L. Daigh.S.B

Conversion to perennial vegetation: Quantifying soil water regime, aeration, and implications for enhancing soil resilience to climate change

Iowa was once awash with native prairie vegetation, and now it is covered with annual crops. This project looked at the different effects these two systems have on Iowa\u27s landscape and natural resource base

Spatial Response of Near-Surface Soil Water Contents to Newly Imposed Soil Management

Near-surface soil water content (SWC) and its spatial patterns are important for landscape hydrological responses to precipitation as well as our ability to remotely sense and model such responses. Our objective was to measure and evaluate near-surface SWC semivariograms of agricultural fields with newly imposed (i.e., \u3c2 yr) side-by-side soil and residue management practices (i.e., reduced tillage systems and cover crops) in the midwestern United States. Range parameters were consistently smaller when cover crops were planted (20–25 m less) and tillage area and/or intensity was reduced (12–27 m less) compared with no cover crop and chisel plowing, respectively, except in a clayey Vertisol. Nugget and sill parameters did not have consistent trends across soil management practices or sites. These data, although brief and preliminary in scope, provide clear proof of concept that spatial pattern shifts can be clearly detected in newly imposed soil-management systems even though differences in SWC means are not always evident

Spatial and Temporal Dynamics of Soil-Surface Carbon Dioxide Emissions in Bioenergy Corn Rotations and Reconstructed Prairies

The interest in bioenergy crops has raised questions as to the potential of management strategies to preserve soil C pools and soil quality. Since soil-surface CO2 effluxes are a major fate of soil C, knowledge of CO2 efflux’s spatial and temporal trends among bioenergy crops will facilitate advances in research on improving terrestrial C-cycle models as well as decision support tools for policy and land-management. Our objective was to evaluate spatial and temporal dynamics of soil-surface CO2 effluxes in bioenergy-based corn (Zea mays L.) and reconstructed prairie systems. Systems evaluated included continuous corn (harvested for grain and 50% of the corn stover) with and without a cover crop, mixed prairies (harvested for aboveground biomass) with and without N fertilization, and corn–soybean [Glycine max (L.) Merr.] rotations harvested for grain. Soil-surface CO2 effluxes, soil temperature, and soil water contents were monitored weekly from July 2008 to September 2011 and hourly during portions of 2010 and 2011. Annual soil-surface CO2 effluxes were greater in prairies than row crops and are attributed to greater plant root respiration. Soil-surface CO2 effluxes spatially varied among intra-crop management zones only for continuous corn with stover removal. However, the cover crop reduced CO2 efflux spatial variability 70% of the time as compared to stover removal without a cover crop. Spatial variability of effluxes was not explained by soil physical properties or conditions. Temperature-induced diurnal fluctuations of CO2 effluxes were not evident during apparent soil–water redistribution. Further research on the mechanisms behind this process is needed followed by incorporation of mechanisms into CO2efflux models

Beef manual for 4-H club members

Cover title

Connecting Soil Organic Carbon and Root Biomass with Land-Use and Vegetation in Temperate Grassland

Soils containmuch of Earth’s terrestrial organic carbon but are sensitive to land-use. Rangelands are important to carbon dynamics and are among ecosystems most widely impacted by land-use. While common practices like grazing, fire, and tillage affect soil properties directly related to soil carbon dynamics, their magnitude and direction of change vary among ecosystems and with intensity of disturbance. We describe variability in soil organic carbon (SOC) and root biomass—sampled from 0–170 cm and 0– 100 cm, respectively—in terms of soil properties, land-use history, current management, and plant community composition using linear regression and multivariate ordination. Despite consistency in average values of SOC and root biomass between our data and data from rangelands worldwide, broad ranges in root biomass and SOC in our data suggest these variables are affected by other site-specific factors. Pastures with a recent history of severe grazing had reduced root biomass and greater bulk density. Ordination suggests greater exotic species richness is associated with lower root biomass but the relationship was not apparent when an invasive species of management concern was specifically tested.We discuss how unexplained variability in belowground properties can complicate measurement and prediction of ecosystem processes such as carbon sequestration

Helicopter final assembly critical path analysis

Thesis (M.B.A.)--Massachusetts Institute of Technology, Sloan School of Management; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; in conjunction with the Leaders for Global Operations Program at MIT, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 53).Helicopter final assembly involves the installation of hundreds of components into the aircraft and takes thousands of man-hours. Meeting production targets such as total build days and total aircraft man-hours can be difficult when faced with challenges related to parts, workforce, and scheduling. A tool to identify key installations on which to focus efforts for maximum benefit can help improve performance to targets. The Critical Path Method was developed as a project management tool to aid in scheduling large and complex projects. Its application to manufacturing can provide the insights necessary to improve performance in an environment such as helicopter final assembly. This thesis provides a case study of helicopter final assembly. A critical path analysis is performed on the assembly process, using predecessor, duration, and resource data. The results of the analysis are used to draw conclusions about the system as a whole and to make recommendations to improve system performance.by Sarah L. Daigh.S.M.M.B.A

Increasing carbon sequestration of working prairie by reducing invasive species in a fire and grazing system

The investigators looked at one method for curbing invasive species that limit carbon sequestration potential for tallgrass prairie stands. They also learned that grasslands dominated by either warm-season, cool-season, or mixed stands are likely equal in their carbon sequestration potential

Evaluation of land preparation methods for soil stabilization, revegetation, and renewed productivity in semi-arid climates

In the Williston Basin, land-preparation treatments have not been compared in side-by-side trials to evaluate performance for parameters such as runoff, erosion, and vegetation establishment. Thus, four treatments of wheat-straw crimping, land imprinting, wood-fiber hydromulch, and the combination of land imprinting and hydromulch were evaluated against a bare soil control in a replicated and randomized completed block field experiment near Williston, ND. Rainfall simulations were performed in September 2020 and June 2021 to examine the effectiveness of the treatments to reduce runoff and sediment losses. Vegetation establishment was also evaluated in August 2021. The wheat straw treatment reduced the equivalent depth of runoff by 60% as compared to the bare soil control in 2021. By 2021, the imprinted area had largely become similar in roughness as the control plots and thus sediment losses were not different between these treatments. However, relic effects of the straw and hydromulch treatments reduced sediment loss by 50% or more. Vegetation establishment was not significantly different among treatments and the bare soil control using broadcast seeding, which may have been due to drought conditions causing low establishment in all plots. All the land-preparation practices evaluated in this study may have limitations in assisting plant establishment during severe or persistent droughts

Use of Landsat 8 Image and Meteorological Data to Map Soil Moisture in the Red River Valley

Non-Peer ReviewedSoil moisture is an important variable in hydrology and climate studies and has been a vital factor for various processes such as water infiltration, runoff, evaporation, dryness. The use of remote sensing technology has achieved a varying degree of success in mapping soil properties for frequent temporal and greater area coverage. Soil moisture estimation using satellite image needs information on dynamic nature of actual field circumstances and micrometeorological variability in real time. The objective of this study is to (a) predict field soil moisture with Optical Trapezoidal Model (OPTRAM) using Landsat 8 images (b) use cumulative rainfall (CR), standardized precipitation index (SPI), clay content and OPTRAM in Random Forest Model to estimate field soil moisture. The use of vegetative indices to estimate soil moisture was not effective because they are affected by the growth stages and crop type. We used google earth engine to process Landsat 8 image and predict soil moisture using OPTRAM model. ArcGIS was used to make moisture maps using pixel by pixel method and R software for modeling random forest regression. The soil moisture estimated using OPTRAM model showed low correlation with field soil moisture. Soil factors, rainfall patterns might have affected the correlation. Random Forest Model was used to predict soil moisture using OPTRAM soil moisture, clay percent, four-day CR, SPI as predictor variables. This model provides promising result of r2=0.67 and RMSE= 0.053. This study proposed model that includes soil properties, meteorological information, satellite image to predict soil moisture in the Red River Valley. Link to Video Presentation: https://youtu.be/REU13yTtG8