Zener diode function generator requires no external reference voltage

Function generator utilizing parallel impedance networks with zener diodes produces functions which are discontinuous in slope. The function generated appears at the output of the parallel network in the form of a voltage varying in time

Inclusion of known integrals in the optimal trajectory problem

The classical problem of determination of the rocket trajectory which minimizes mass expenditure during motion between two points in the field of a single gravitating body is analyzed. The known integrals of the system are incorporated into the adjoint equations resulting in a reduction from a seventh-order adjoint system to a third-order adjoint system. The first case which is treated in that of planar motion under specific end conditions. In this case a regularization of the recently derived equations is achieved. The general three-dimensional case is also reduced from a seventh-order adjoint system to a third-order adjoint system. In this case a regularization has not been found

Algae Living in Salamanders, Friend or Foe?

Roughly speaking, our bodies use energy from the sun, but we can\u27t use sunlight directly. Instead, plants and algae collect sunlight and store it as chemical energy through the process of photosynthesis. We can access that fuel directly when we eat plants, or indirectly when we eat other animals that eat plants. However, in some invertebrate animals (those without a backbone) the relationships to algae are more intimate. Tiny single-celled algal symbionts can actually live inside the cells of living corals and small animals like hydra that live in water. The algae live in a safe environment inside animal cells and are provided with building block materials to function. They use sunlight to convert the building block materials into larger molecules to store energy and build cellular structures. At the same time some of that stored solar energy is directly transferred to the host animal, allowing it to live in otherwise nutrient poor environments. Thus the algae and their hosts depend on one another to live and thrive. These mutually beneficial relationships are called photosymbioses. [excerpt

Preliminary study of advanced life-support technology for a Mars surface module

Subsystem definition of advanced life support technology for Mars surface modul

Integrated gasifier combined cycle polygeneration system to produce liquid hydrogen

An integrated gasifier combined cycle (IGCC) system which simultaneously produces electricity, process steam, and liquid hydrogen was evaluated and compared to IGCC systems which cogenerate electricity and process steam. A number of IGCC plants, all employing a 15 MWe has turbine and producing from 0 to 20 tons per day of liquid hydrogen and from 0 to 20 MWt of process steam were considered. The annual revenue required to own and operate such plants was estimated to be significantly lower than the potential market value of the products. The results indicate a significant potential economic benefit to configuring IGCC systems to produce a clean fuel in addition to electricity and process steam in relatively small industrial applications

Silicon strain sensors enable pressure measurement at cryogenic temperatures

Miniature pressure transducers with diffused, heavily doped silicon strain-gage sensor elements, operates over a wide temperature range. Small thermal mass combined with close coupling between a metallic diaphragm and sensor elements minimizes sensitivity to temperature transients