Fracture surface characteristics of notched angleplied graphite/epoxy composites

Composite fracture surface characteristics and related fracture modes have been investigated through extensive microscopic inspections of the fracture surfaces of notched angleplied graphite/epoxy laminates. The investigation involved 4 ply laminates of the configuration + or - theta (s) where theta = 0 deg, 3 deg, 5 deg, 10 deg, 15 deg, 30 deg, 45 deg, 60 deg, 75 deg, and 90 deg. Two-inch wide tensile specimens with 0.25 in. by 0.05 in. through-slits centered across the width were tested to fracture. The fractured surfaces were then removed and examined using a scanning electron microscope. Evaluation of the photomicrographs combined with analytical results obtained using the CODSTRAN computer code culminated in a unified set of fracture criteria for determining the mode of fracture in notched angleplied graphite/epoxy laminates

Automated gait segmentation and tracking using inertial measurement units

Abstract. In this thesis, a methodology is presented to automate the labelling, event detection, segmentation, tracking, and parameter extraction of IMU gait data for sensors placed on the feet and shanks. The algorithms presented were tested using IMU data from three different styles of gait, normal gait, antalgic gait, and limited mobility gait. The algorithms developed were found effective for all of the simulated gait styles without mislabelling or detecting erroneous gait segments. The resultant gait trajectories and parameters were analyzed and were found to accurately depict the differences between each of the different styles of gait. The methodology presented can be used for the rapid and accurate processing of gait data for multiple styles of gait. This quantification of gait data can enable the collection of IMU gait data on a larger scale. This provides an accessible, low-cost option for out-of-laboratory gait data collection

Solar dynamic power systems for space station

The Parabolic Offset Linearly Actuated Reflector (POLAR) solar dynamic module was selected as the baseline design for a solar dynamic power system aboard the space station. The POLAR concept was chosen over other candidate designs after extensive trade studies. The primary advantages of the POLAR concept are the low mass moment of inertia of the module about the transverse boom and the compactness of the stowed module which enables packaging of two complete modules in the Shuttle orbiter payload bay. The fine pointing control system required for the solar dynamic module has been studied and initial results indicate that if disturbances from the station are allowed to back drive the rotary alpha joint, pointing errors caused by transient loads on the space station can be minimized. This would allow pointing controls to operate in bandwidths near system structural frequencies. The incorporation of the fine pointing control system into the solar dynamic module is fairly straightforward for the three strut concentrator support structure. However, results of structural analyses indicate that this three strut support is not optimum. Incorporation of a vernier pointing system into the proposed six strut support structure is being studied

Effect of rotation and short-term tillage on soil quality after long-term zero tillage

Non-Peer ReviewedA field study was established in 2000, near Brandon Manitoba, to determine the effect of tillage and crop on soil physical and biological properties. Most soil physical and biological properties were not affected by tillage system or current year crop when sampled in the fall after harvest. The proportion of large (38 to 68.8 mm diameter) dry sieved aggregates increased under low compared to high intensities of tillage. Aggregate stability increased with increasing concentration of organic carbon. The effect of high and low intensity tillage over one or two years, after 9 years in zero tillage, on soil organic carbon, physical properties and fertility was not significant

Stubble effects on crop microclimate and crop performance in a sub-humid prairie climate

Non-Peer ReviewedStubble impacts crop microclimate in ways that have not been well-investigated, particularly in the context of crop establishment, growth and yield. In this study, the effects of different stubble heights on crop microclimate, biomass accumulation, and yield were investigated in the black soil , sub-humid climate of southwest Manitoba. Canola, pea, and wheat were sown across stubble treatments, comprised of cultivated wheat stubble, or stubble cut to a height of 10 or 30 cm in the spring of the cropping year. Plots were instrumented to monitor soil and canopy air temperature, near-surface soil moisture, wind speed, and reflected solar radiation during crop establishment. Results are discussed in the context of how changes in crop microclimate induced by stubble treatment affected crop performance. Tall stubble delayed day-time soil warming and night-time cooling, increased day-time canopy air temperature and decreased night-time air temperature, increased surface and sub-surface soil moisture, reduced wind speed near the soil surface, and increased crop canopy reflectance. These micro-climatic effects increased seedling emergence, vegetative biomass, but had minimal impact on final crop yield. The results suggest that maintenance of tall stubble should not result in a yield penalty, and may reduce input costs through reduced energy required in combining

How effective are crop rotations?

Non-Peer ReviewedCurrent crop rotation recommendations suggest at least 3 non-susceptible crops be grown between planting of Sclerotinia susceptible crops such as canola and pea. However current pricing of pea and canola make production of these crops more profitable providing their yields are not greatly reduced by disease. Under center pivot irrigation the soil surface and plants are wetted every 2-4 days during periods of high water use; this results in a good environment for spore production and germination. Levels of Sclerotinia infection were generally somewhat lower than predicted by the petal test method. Yields were not improved by the application of iprodione at 250, 500 or 700 g/ha at the 40% bloom stage. The yield levels obtained and visual observation of time and severity of stem damage indicated that the disease probably occurred late enough in the season to limit damage. No lodging occurred and Sclerotinia levels were near zero in 1991 as a result of a very hot dry August. In 1992, 2 of 3 tests showed significant lodging. Sclerotinia levels increased with an increase in lodging (r2 = 0.85* and 0.73*). Lodging reduction can be accomplished by the use of resistant cultivars and by lowering seeding rates to less than 100 seeds/m2. Yields were not reduced at lower seeding rates at wider row spacings. Sclerotinia is an environmentally influenced disease which is not well controlled by crop rotations up to 5 years however its severity can be limited by reducing lodging. When canola prices are at least 1.9 times that of cereal grains, shortening rotations to 2-3 years between crops, such as pea and canola, could be a viable risk

Applied research and feasibility studies, experimental investigations and conceptual or preliminary design engineering applicable to inverters for motors program Quarterly progress report, period ending Jun. 25, 1968

Design and evaluation of motor inverter with current sensing and limiting circui

Applied Research and Feasibility Studies, Experimental Investigations and Conceptual or Preliminary Design Engineering Applicable to Inverters for Motors Program Final Report, Jun. 1967 - Jan. 1969

Feasibility and engineering studies on inverter-motor systems using alternating current induction type motors and quasi-square wave output inverter

Prediction of blanket peat erosion across Great Britain under environmental change

A recently developed fluvial erosion model for blanket peatlands, PESERA-PEAT, was applied at ten sites across Great Britain to predict the response of blanket peat erosion to environmental change. Climate change to 2099 was derived from seven UKCP09 future projections and the UK Met Office’s historical dataset. Land management scenarios were established based on outputs from earlier published investigations. Modelling results suggested that as climate changes, the response of blanket peat erosion will be spatially very variable across Great Britain. Both relative changes and absolute values of sediment yield were predicted to be higher in southern and eastern areas than in western and northern parts of Great Britain, peaking in the North York Moors of eastern England. Areas with high precipitation and low temperature were predicted to have low relative erosion changes and absolute sediment yield. The model suggested that summer desiccation may become more important for blanket peat erosion under future climate change, and that temperature was more dominant than precipitation in controlling long-term blanket peat erosion change. However, in the North York Moors, precipitation appeared to be more dominant in driving long-term erosion change. Land management measures were shown to provide a means to mitigate against the impacts of climate change on blanket peat erosion

Drawing bobbin lace graphs, or, Fundamental cycles for a subclass of periodic graphs

In this paper, we study a class of graph drawings that arise from bobbin lace patterns. The drawings are periodic and require a combinatorial embedding with specific properties which we outline and demonstrate can be verified in linear time. In addition, a lace graph drawing has a topological requirement: it contains a set of non-contractible directed cycles which must be homotopic to $(1,0)$, that is, when drawn on a torus, each cycle wraps once around the minor meridian axis and zero times around the major longitude axis. We provide an algorithm for finding the two fundamental cycles of a canonical rectangular schema in a supergraph that enforces this topological constraint. The polygonal schema is then used to produce a straight-line drawing of the lace graph inside a rectangular frame. We argue that such a polygonal schema always exists for combinatorial embeddings satisfying the conditions of bobbin lace patterns, and that we can therefore create a pattern, given a graph with a fixed combinatorial embedding of genus one.Comment: Appears in the Proceedings of the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017