Biomass and Grain Harvesting Advances

Five different approaches to whole plant harvesting of com - with the aim of simultaneous collection of the stover - have been tested. Many of the principles are relevant to other crops. This work has advanced the frontiers of biomass harvesting and handling. The different approaches to corn stover harvesting have been shown publicly

Research to determine failure modes for transistors fifth quarterly report, sep. - dec. 1964

Failure mode determination for transistors - transient spike voltage, life test data on manufacturing processes, and computer calculated distributions for test matri

Farm Machinery Costs: Profitable Options

A study of data collected from interviewing 43 farmers in Iowa shows large variations in machinery costs for producing com and soybeans in 1997/98. The aim of this study is to determine why some farmers are able to produce these crops with half the costs of machinery per acre and per bushel than others. There is nevertheless a trend for larger-acreage operations to have lower unit costs. On the other hand the smaller equipment set eg four-row, operated on a larger area, usually had lower unit costs than a larger set eg eight-row on fewer acres. Low correlation coefficients were indicative of the wide data spread. The study is on-going. Two graphs of preliminary results follow for com

A model for self-defocusing in laser drilling of polymeric materials

A numerical thermal model is presented for laser microvias drilling in multilayer electronic substrates with Nd:YAG (YAG denotes yttrium aluminum garnet) and CO(2) lasers. Such substrates have different optical properties such as the refractive index and absorption coefficient at these two laser wavelengths, resulting in different drilling mechanisms. Since the skin depth of the polymer is large for both the lasers, volumetric heating is considered in the model. As soon as a small cavity is formed during the drilling process, the concave curvature of the drilling front acts as a concave lens that diverges the incident laser beam. This self-defocusing effect can greatly reduce the drilling speed as predicted by the model. This effect makes the refractive index of the substrate at different wavelengths an important parameter for laser drilling. The model was used to calculate the laser ablation thresholds which were found to be 8 and 56 J/cm(2) for the CO(2) and Nd:YAG lasers respectively. Due to the expulsion of materials because of high internal pressures in the case of Nd:YAG laser microvia drilling, the ablation threshold may be far below the calculated value. A particular laser beam shape, such as pitch fork, was found to drill better holes than the Gaussian beam