Tech Briefs

Compensating for Effects of Humidity on Electronic Noses

Corrections are derived from outputs of separate humidity and temperature sensors.A method of compensating for the effects of humidity on the readouts of electronic noses has been devised and tested. The method is especially appropriate for use in environments in which humidity is not or cannot be controlled — for example, in the vicinity of a chemical spill, which can be accompanied by large local changes in humidity.

Posted in: Briefs, TSP

Read More >>

Farm Equipment Manufacturer Shortens Design Cycle With Analysis Software

The design of new tilling machinery is accelerated using finite element analysis software. Humans have been using tools to make farming easier since the dawn of civilization. Since the turn of the 20th century, the growing use of mechanized power to till and sow fields has enabled farmers to realize incredible efficiency gains in the production of low-cost, safe, and nutritious foods and other crops, such as fibers. Today, bigger machines require less manpower to plant the crops that feed and clothe a swelling world population.

Posted in: Machinery & Automation, Briefs

Read More >>

Coding for Communication Channels With Dead-Time Constraints

Novel coding schemes may offer significant advantages in some applications. Coding schemes have been designed and investigated specifically for optical and electronic data-communication channels in which information is conveyed via pulse-position modulation (PPM) subject to dead-time constraints. These schemes involve the use of errorcorrecting codes concatenated with codes denoted constrained codes. These codes are decoded using an interactive method.

Posted in: Briefs, TSP

Read More >>

System for Better Spacing of Airplanes En Route

Deviations from preferred trajectories can be reduced. An improved method of computing the spacing of airplanes en route, and software to implement the method, have been invented. The purpose of the invention is to help air-traffic controllers minimize those deviations of the airplanes from the trajectories preferred by their pilots that are needed to make the airplanes comply with miles-in-trail spacing requirements (defined below). The software is meant to be a modular component of the Center-TRACON Automation System (CTAS) (TRACON signifies "terminal radar approach control"). The invention reduces controllers’ workloads and reduces fuel consumption by reducing the number of corrective clearances needed to achieve conformance with specified flow rates, without causing conflicts, while providing for more efficient distribution of spacing workload upstream and across air-traffic-control sectors.

Posted in: Briefs, TSP

Read More >>

Algorithm for Training a Recurrent Multilayer Perceptron

An improved algorithm has been devised for training a recurrent multilayer perceptron (RMLP) for optimal performance in predicting the behavior of a complex, dynamic, and noisy system multiple time steps into the future. [An RMLP is a computational neural network with self-feedback and cross-talk (both delayed by one time step) among neurons in hidden layers]. Like other neural-network-training algorithms, this algorithm adjusts network biases and synaptic-connection weights according to a gradientdescent rule. The distinguishing feature of this algorithm is a combination of global feedback (the use of predictions as well as the current output value in computing the gradient at each time step) and recursiveness. The recursive aspect of the algorithm lies in the inclusion of the gradient of predictions at each time step with respect to the predictions at the preceding time step; this recursion enables the RMLP to learn the dynamics. It has been conjectured that carrying the recursion to even earlier time steps would enable the RMLP to represent a noisier, morecomplex system.

Posted in: Briefs

Read More >>

Electrodeionization Using Microseparated Bipolar Membranes

Low concentrations of ions do not inhibit further removal of ions. An electrochemical technique for deionizing water, now under development, is intended to overcome a major limitation of prior electrically–based waterpurification techniques. The limitation in question is caused by the desired decrease in the concentration of ions during purification: As the concentration of ions decreases, the electrical resistivity of the water increases, posing an electrical barrier to the removal of the remaining ions. In the present technique, this limitation is overcome by use of electrodes, a flow-field structure, and solid electrolytes configured to provide conductive paths for the removal of ions from the water to be deionized, even when the water has already been purified to a high degree.

Posted in: Materials, Briefs

Read More >>

Safer Electrolytes for Lithium-Ion Cells

A number of nonvolatile, low-flammability liquid oligomers and polymers based on aliphatic organic carbonate molecular structures have been found to be suitable to be blended with ethylene carbonate to make electrolytes for lithium-ion electro- chemical cells. Heretofore, such electrolytes have often been made by blending ethylene carbonate with volatile, flammable organic carbonates. The present nonvolatile electrolytes have been found to have adequate conductivity (about 2 mS/cm) for lithium ions and to remain liquid at temperatures down to —5 °C. At normal charge and discharge rates, lithiumion cells containing these nonvolatile electrolytes but otherwise of standard design have been found to operate at current and energy densities comparable to those of cells now in common use. They do not perform well at high charge and discharge rates — an effect probably attributable to electrolyte viscosity. Cells containing the nonvolatile electrolytes have also been found to be, variously, nonflammable or at least self-extinguishing. Hence, there appears to be a basis for the development of safer high-performance lithium-ion cells.

Posted in: Materials, Briefs

Read More >>

The U.S. Government does not endorse any commercial product, process, or activity identified on this web site.