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Results for “SIGNAL TRANSMISSION”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Electrical signal transmission in a bone cell network: the influence of a discrete gap junction

A refined electrical cable model is formulated to investigate the role of a discrete gap junction in the intracellular transmission of electrical signals in an electrically coupled system of osteocytes and osteoblasts in an osteon. The model also examines the influence of the ratio q between the membrane's electrical time constant and the characteristic time of pore fluid pressure, the circular, cylindrical geometry of the osteon, and key simplifying assumptions in our earlier continuous cable model (see Zhang, D., S. C. Cowin, and S. Weinbaum. Electrical signal transmission and gap junction regulation in a bone cell network: A cable model for an osteon. Ann. Biomed. Eng. 25:379-396, 1997). Using this refined model, it is shown that (1) the intracellular potential amplitude at the osteoblastic end of the osteonal cable retains the character of a combination of a low-pass and a high-pass filter as the corner frequency varies in the physiological range; (2) the presence of a discrete gap junction near a resting osteoblast can lead to significant modulation of the intracellular potential and current in the osteoblast for measured values of the gap junction coupling strength; and (3) the circular, cylindrical geometry of the osteon is well simulated by the beam analogy used in Zhang et al.

Non-NASA Center↗
NASA NTRS2002

Root gravitropism: an experimental tool to investigate basic cellular and molecular processes underlying mechanosensing and signal transmission in plants

The ability of plant organs to use gravity as a guide for growth, named gravitropism, has been recognized for over two centuries. This growth response to the environment contributes significantly to the upward growth of shoots and the downward growth of roots commonly observed throughout the plant kingdom. Root gravitropism has received a great deal of attention because there is a physical separation between the primary site for gravity sensing, located in the root cap, and the site of differential growth response, located in the elongation zones (EZs). Hence, this system allows identification and characterization of different phases of gravitropism, including gravity perception, signal transduction, signal transmission, and curvature response. Recent studies support some aspects of an old model for gravity sensing, which postulates that root-cap columellar amyloplasts constitute the susceptors for gravity perception. Such studies have also allowed the identification of several molecules that appear to function as second messengers in gravity signal transduction and of potential signal transducers. Auxin has been implicated as a probable component of the signal that carries the gravitropic information between the gravity-sensing cap and the gravity-responding EZs. This has allowed the identification and characterization of important molecular processes underlying auxin transport and response in plants. New molecular models can be elaborated to explain how the gravity signal transduction pathway might regulate the polarity of auxin transport in roots. Further studies are required to test these models, as well as to study the molecular mechanisms underlying a poorly characterized phase of gravitropism that is independent of an auxin gradient.

Non-NASA Center↗
NASA NTRS2000

A Signal Transmission Technique for Stability Analysis of Multivariable Non-Linear Control Systems

Among the difficulties associated with multivariable, non-linear control systems is the problem of assessing closed-loop stability. Of particular interest is the class of non-linear systems controlled with on/off actuators, such as spacecraft thrusters or electrical relays. With such systems, standard describing function techniques are typically too conservative, and time-domain simulation analysis is prohibitively extensive, This paper presents an open-loop analysis technique for this class of non-linear systems. The technique is centered around an innovative use of multivariable signal transmission theory to quantify the plant response to worst case control commands. The technique has been applied to assess stability of thruster controlled flexible space structures. Examples are provided for Space Shuttle attitude control with attached flexible payloads.

Jackson, Mark↗
NASA NTRS1972

L-orthogonal signal transmission and detection.

A study of L-orthogonal signal performance represents an approach wherein the performance of polyphase and orthogonal signal sets stand out as the extreme special cases. The L-orthogonal signal model and its associated bandwidth properties are briefly discussed. System performance is investigated by presenting tight upper and lower bounds on the error probability performance of the maximum-likelihood receiver of L-orthogonal signals suggested by Reed and Scholtz (1966). A study of the error probability performance of the suboptimum receiver in the presence of noisy reference signals is also conducted.

Lindsey, W. C.↗
NASA NTRS1972

L-orthogonal signal transmission and detection.

Investigation of the detailed capabilities and performance characterization of systems that employ L-orthogonal signaling techniques. L-orthogonal signals represent a unified set of signals wherein the polyphase and orthogonal (bi-orthogonal) signal sets are included as special cases. This fact is important, since orthogonal (bi-orthogonal) and polyphase signaling sets represent opposing forces as far as tradeoffs between error probability, energy-to-noise ratio, and bandwidth requirements are concerned. Bounds on the performance of the optimum receiver and the performance of various suboptimum (practical) receiver structures are given. Coherent and differentially coherent detection of differentially encoded signals are also pursued. Various comparisons and tradeoffs are made by means of numerical evaluation of the error probability expressions.

Lindsey, W. C.↗
NASA NTRS2005

High bandwidth magnetically isolated signal transmission circuit

Many current electronic systems incorporate expensive or sensitive electrical components. Because electrical energy is often generated or transmitted at high voltages, the power supplies to these electronic systems must be carefully designed. Power supply design must ensure that the electrical system being supplied with power is not exposed to excessive voltages or currents. In order to isolate power supplies from electrical equipment, many methods have been employed. These methods typically involve control systems or signal transfer methods. However, these methods are not always suitable because of their drawbacks. The present invention relates to transmitting information across an interface. More specifically, the present invention provides an apparatus for transmitting both AC and DC information across a high bandwidth magnetic interface with low distortion.

Repp, John Donald↗
NASA NTRS2008

Method and apparatus for low-loss signal transmission

The present invention relates to the field of radio-frequency (RF) waveguides. More specifically, the present invention pertains to a method and apparatus that provides ultra-low-loss RF waveguide structures targeted between approximately 300 GHz and approximately 30 THz. The RF waveguide includes a hollow core and a flexible honeycomb, periodic-bandgap structure surrounding the hollow core. The flexible honeycomb, periodic-bandgap structure is formed of a plurality of tubes formed of a dielectric material such as of low-loss quartz, polyethylene, or high-resistivity silicon. Using the RF waveguide, a user may attach a terahertz signal source to the waveguide and pass signals through the waveguide, while a terahertz signal receiver receives the signals.

Siegel, Peter↗
NASA NTRS1972

Data Transmission Signal Design and Analysis

The error performances of several digital signaling methods are determined as a function of a specified signal-to-noise ratio. Results are obtained for Gaussian noise and impulse noise. Performance of a receiver for differentially encoded biphase signaling is obtained by extending the results of differential phase shift keying. The analysis presented obtains a closed-form answer through the use of some simplifying assumptions. The results give an insight into the analysis problem, however, the actual error performance may show a degradation because of the assumptions made in the analysis. Bipolar signaling decision-threshold selection is investigated. The optimum threshold depends on the signal-to-noise ratio and requires the use of an adaptive receiver.

Moore, J. D.↗
NASA NTRS1977

Rotating optical coupler for signal transmission

Optical coupler using Dove prism assembly to form stationary image of rotating object, transmits data across rotating interface without sliprings or other mechanical contacts. Device can handle many high-bit-rate data channels.

Ivie, C. V.↗
NASA NTRS1987

High speed semiconductor lasers and integrated receivers for microwave and millimeter wave signal transmission

This project was proposed to be a three-year contract, but was cut off after one year (1987) of support. Sufficient progress was made to allow continuation for a year on minimal internal funds before proper support levels were received from a combination of ONR, RADC, and IBM contracts at about the start of 1989. A major DARPA grant, expected to start August 1, 1990, will sharply expand this effort to include several faculty members. During the course of this project, two students did thesis research, one Ph.D. on lasers and one M.S. on high speed photodetectors. These theses were finished in September 1988, nine months after the contract was cut off. This report covers excerpts from those theses as well as information obtained on other programs since that time.

Eastman, L. F.↗
NASA NTRS1997

Electrical signal transmission and gap junction regulation in a bone cell network: a cable model for an osteon

A cable model is formulated to estimate the spatial distribution of intracellular electric potential and current, from the cement line to the lumen of an osteon, as the frequency of the loading and the conductance of the gap junction are altered. The model predicts that the characteristic diffusion time for the spread of current along the membrane of the osteocytic processes, 0.03 sec, is nearly the same as the predicted pore pressure relaxation time in Zeng et al. (Annals of Biomedical Engineering. 1994) for the draining of the bone fluid into the osteonal canal. This approximate equality of characteristic times causes the cable to behave as a high-pass, low-pass filter cascade with a maximum in the spectral response for the intracellular potential at approximately 30 Hz. This behavior could be related to the experiments of Rubin and McLeod (Osteoporosis, Academic Press, 1996) which show that live bone appears to be selectively responsive to mechanical loading in a specific frequency range (15-30 Hz) for several species.

NASA Discipline Musculoskeletal↗
NASA NTRS2011

Wireless acoustic-electric feed-through for power and signal transmission

An embodiment provides electrical energy from a source on one side of a medium to a load on the other side of the medium, the embodiment including a first piezoelectric to generate acoustic energy in response to electrical energy from the source, and a second piezoelectric to convert the received acoustic energy to electrical energy used by the load. Other embodiments are described and claimed.

Sherrit, Stewart↗
NASA NTRS2003

Passive Fetal Heart Monitoring System

A fetal heart monitoring system and method for detecting and processing acoustic fetal heart signals transmitted by different signal transmission modes. One signal transmission mode, the direct contact mode, occurs in a first frequency band when the fetus is in direct contact with the maternal abdominal wall. Another signal transmission mode, the fluid propagation mode, occurs in a second frequency band when the fetus is in a recessed position with no direct contact with the maternal abdominal wall. The second frequency band is relatively higher than the first frequency band. The fetal heart monitoring system and method detect and process acoustic fetal heart signals that are in the first frequency band and in the second frequency band.

Zuckerwar, Allan J.↗
NASA NTRS1994

Optical communications for transport aircraft

Optical communications for transport aircraft are discussed. The problem involves: increasing demand for radio-frequency bands from an enlarging pool of users (aircraft, ground and sea vehicles, fleet operators, traffic control centers, and commercial radio and television); desirability of providing high-bandwidth dedicated communications to and from every aircraft in the National Airspace System; need to support communications, navigation, and surveillance for a growing number of aircraft; and improved meteorological observations by use of probe aircraft. The solution involves: optical signal transmission support very high data rates; optical transmission of signals between aircraft, orbiting satellites, and ground stations, where unobstructed line-of-sight is available; conventional radio transmissions of signals between aircraft and ground stations, where optical line-of-sight is unavailable; and radio priority given to aircraft in weather.

Stengel, Robert↗