11,003 research outputs found

    System identification, time series analysis and forecasting:The Captain Toolbox handbook.

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    CAPTAIN is a MATLAB compatible toolbox for non stationary time series analysis, system identification, signal processing and forecasting, using unobserved components models, time variable parameter models, state dependent parameter models and multiple input transfer function models. CAPTAIN also includes functions for true digital control

    Economics of Using On-farm Reservoirs to Distribute Diverted Surface Water to Depleted Ground Water Areas of the Southern Mississippi Valley Region

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    Rapid ground water depletion has become a significant problem for parts of the Southern Mississippi River Valley. In 1997, the Arkansas Soil and Water Conservation Commission (ASWCC) declared six counties in the Grand Prairie of Arkansas critical ground water areas. A proposed solution to the ground water depletion problem in this region is to divert surplus flows from the White River by a canal system to the farmer stakeholders. To make the system work, on-farm reservoirs will be needed to store and manage the diverted surface water for crop irrigation use during the growing season

    Vitamin D Status and Bone Mineral Density in Female Collegiate Dancers and Cheerleaders

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    Bone mineral density reflects an athlete’s cumulative history of energy availability, physical activity, and menstrual status, as well as nutritional and environmental factors. Although sports with high-impact loading are associated with higher bone mineral density than low-impact or non-impact sports, confounding variables are differences in the athletes’ body size and sport-specific training. The purpose of this study was to determine if bone mineral density (BMD) and vitamin D status are different between two groups of female collegiate athletes who have comparable body size/weight requirements, but who engage in qualitatively different training regimens. Full body, spine and dual femur BMD was assessed by dual energy X-ray absorptiometry (DXA) in members of a university pep-dance team (n = 10) or cheer team (n = 9), ages 18-22. Plasma vitamin D status was assessed by ELIZA. There was no significant difference between the groups for total body BMD (1.23 g/cm2 dance vs 1.22 g/cm2 cheer, P = 0.70), spine BMD (1.39 g/cm2 dance vs 1.36 g/cm2 cheer, P = 0.72) or dual femur BMD (1.20 g/cm2 dance vs 1.11 g/cm2, P = 0.23). Insufficient serum vitamin D status (20-32 ng/mL) was found in 74% of the athletes (27 ± 4 ng/mL, dance and 25 ± 8 ng/mL, cheer). In addition, estimated daily vitamin D and calcium intakes were less than the RDA for both dancers and cheerleaders. Despite nutritional insufficiencies, BMD was not significantly different between the low-impact activity pep dance team and high-impact activity cheer team, suggesting that the type of physical activity was not as important for BMD in these athletes as participating in 20+ hours a week of physical activity, which could have counteracted the negative effects of the nutrient insufficiencies on their bone health

    The Mid-IR Spectral Effects of Darkening Agents and Porosity on the Silicate Surface Features of Airless Bodies

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    We systematically measured the mid-IR spectra of different mixtures of three silicates (antigorite, lizardite, and pure silica) with varying effective porosities and amounts of darkening agent (iron oxide and carbon). These spectra have broad implications for interpretation of current and future mission data for airless bodies, as well as for testing the capabilities of new instruments. Serpentines, such as antigorite and lizardite, are common to airless surfaces, and their mid-IR spectra in the presence of darkening agents and different surface porosities would be typical for those measured by spacecraft. Silica has only been measured in the plumes of Enceladus and presents exciting possibilities for other Saturn-system surfaces due to long range transport of E-ring material. Results show that the addition of the IR-transparent salt, KBr, to simulate surface porosity affected silicate spectra in ways that were not predictable from linear mixing models. The strengthening of silicate bands with increasing pore space, even when only trace amounts of KBr were added, indicates that spectral features of porous surfaces are more detectable in the mid-IR. Combining iron oxide with the pure silicates seemed to flatten most of the silicate features, but strengthened the reststrahlen band of the silica. Incorporating carbon with the silicates weakened all silicate features, but the silica bands were more resistant to being diminished, indicating silica may be more detectable in the mid-IR than the serpentines. We show how incorporating darkening agents and porosity provides a more complete explanation of the mid-IR spectral features previously reported on worlds such as Iapetus

    Distributional Impact of U.S. Farm Commodity Programs: Accounting for Alternative Farm Household Typologies

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    Agricultural households adjust to policy changes through market mechanisms by altering: their production mix, labor input, and on- and off-farm investments. Because of the significant heterogeneity among farms in the US agricultural sector, various types of farm households respond to the same policy change in significantly different ways. The parameters used to classify farm households into different typologies may also play a significant role in the interpretation of observed effects of policy changes. This paper, using a highly disaggregated U.S. Computable General Equilibrium (CGE) model, analyzes the distributional impacts of policy changes involving price-contingent government payments on alternative U.S. farm household typologies. We find that farm households do vary their responses to an elimination of price-contingent support based on location, production specialty, and farm categorization.Agricultural and Food Policy,

    Producing College, Career, and Military Ready Graduates: A Study of Efficiency in Texas Public School Districts

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    Public school districts in Texas and policymakers need studies of efficiency in the production of College, Career, and Military Ready graduates to maximize resources in the House Bill 3 funding formula and improve ratings in the Texas public school accountability system. A replication of efficiency studies by Carter (2012) and Thompson (2017), the purpose of this non-experimental quantitative study was to determine what discretionary and non-discretionary factors influence the efficiency of Texas public school districts’ production of College, Career, and Military Ready graduates. With financial and student performance data for 1054 school districts from the 2017-2018 school year, Data Envelopment Analysis (DEA) was used to measure the relative efficiency of each school district. A regression analysis found a significant positive influence on school district efficiency for total student enrollment. The percentage of non-white students and instructional expenditures per pupil did not have a significant influence on school district efficiency. This research study is useful to educators, legislators, and researchers for determining the allocation of resources for programs with the ability to produce College, Career, and Military Ready graduates
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