Silicon active microvalves using buckled membranes for actuation

Design considerations and experiments have been made for obtaining a new type of active microvalves using silicon buckled membranes. The properties of the buckled membranes permitting to obtain high deflections and to actuate them more convenient are demonstrated. A thermal actuation using an aluminium ring layer heated with a polysilicon resistor is analysed. The polysilicon and the aluminium ring layers have been deposited in the region of the membrane having the minimum internal stress. The fabrication process consist of photolithography, LPCVD depositions, diffusion, AI sputtering. isotropic, anisotropic etching and anodic bonding. The design and experiments show a convenient low temperature range necessary to actuate the microvalve.\ud \u

COMMODITY PRICES AND RESOURCE USE UNDER VARIOUS ENERGY ALTERNATIVES IN AGRICULTURE

An interregional, large-scale linear programming model is used to evaluate the economic impact of the energy crisis on U.S. agricultural production. The study examines the changes in crop production under energy minimization, an energy shortage, high energy prices, and high agricultural exports accompanied by high energy prices. Results indicate that reduced supplies or higher prices for energy will have important impacts on commodity prices, irrigated agriculture, and on rural communities.Resource /Energy Economics and Policy,

Buckled membranes for microstructures

Based on energy variation methods we calculated the deflection of membranes under the combined load of an external pressure and an internal lateral stress. A lateral load gives rise to buckling once a critical load is exceeded. The combination of transversal loads and lateral loads changes the properties of the membrane (and other structures) in the vicinity of the buckling load: The membrane deflects at all lateral loads and the critical load, above which two states are possible shifts. A result important for the design of microsystems, which are based on the buckling phenomenon, is the pressure required to switch the membrane from one state to the other. The theory is tested successfully with micromachined silicon/silicon-dioxide membrane

A Survey for Large Separation Lensed FIRST Quasars, II. Magnification Bias and Redshift Distribution

The statistics of large-separation gravitational lensing are a powerful tool to probe mass distributions on the scale of galaxy clusters. In this paper we refine the analysis of our survey for large-separation (>5'') lensed FIRST quasars (Ofek et al. 2001) by estimating the magnification bias and the source redshift distribution. Finding no large separation lens among 8000 likely quasars in that sample, implies an upper bound on the lensed fraction of 3.7 x 10^-4 at 95% CL. From a published deep 1.4 GHz radio survey of the Hubble Deep Field, and corresponding optical searches for faint quasars, we calculate a lower limit to the `double flux magnification bias' affecting our radio-optically selected sample, of B>1.1. From the four-colour information in the SDSS Early Data Release, we calculate the photometric redshift distribution of a sample of FIRST quasar candidates and compare it with the redshift distribution from the FIRST Bright Quasar Survey. We find that the median redshift of the quasars in our sample is about 1.4. With these new results, we find that for all plausible cosmologies, the absence of lensed quasars in our survey is consistent with a model based on an empirical, non-evolving, cluster mass function, where clusters are represented by singular isothermal spheres. On the other hand, comparison of our results to the lensing predictions of published N-body-ray-tracing simulations (Wambsganss et al. 1995, 1998) rejects the COBE normalised \Omega_{0}=1 CDM model at 99.9% confidence.Comment: 6 pages, 3 figures, accepted to MNRA

Chemical Preservation of Alfalfa Hay

Kentucky farmers harvest about 3 million tons of hay annually. In order to minimize dry matter losses and quality deterioration, hay should be baled with about 20% moisture. Unfortunately, adequate time required to field-dry hay to 20% moisture is often not available due to weather conditions. This is especially true for the first cutting of alfalfa in the spring. Many farmers are forced to choose between letting cut hay get rained on or baling hay wetter than is recommended. Hay baled with more than 20-25% moisture generally becomes moldy and undergoes a heating process which makes part of the protein unavailable to animals. At extreme levels of heating the digestibility of protein may be reduced as much as 75% and spontaneous combustion is a possibility

Maximizing Alfalfa in Dairy Feeding Programs

Alfalfa is an excellent feed for dairy cows. When used properly, alfalfa can help cut cost of production and increase level of production. However, like everything else, the feeding of alfalfa needs to be managed to maximize efficient production. There are three key steps involved in maximizing alfalfa in a dairy feeding program. These are: harvest alfalfa at the proper stage of maturity know what the alfalfa contains and feed accordingly get the alfalfa to the cows that need it