Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Signal detection”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

An assessment of plasma instabilities or planetary lightning as a source for the VLF bursts detected at Venus

Very low frequency (VLF) signals detected in the nightside ionosphere of Venus have generally been attributed to atmospheric lightning. However it has recently been suggested that these bursts could be generated by either whistler-mode or lower hybrid drift instabilities. It has previously been shown that the growth rate for whistler-mode instabilities in the nightside ionosphere is too small for appreciable growth at altitudes less than 200 km, where the VLF burst rate is highest. We show that the bursts are usually observed in regions of low electron beta, where whistler-mode attenuation is small. We further show that many of the bursts are detected in regions of high collision frequency, which stabilizes the lower hybrid drift instability. Lastly, the waves are also detected in regions where the wavelength required for Doppler-shift of lower hybrid waves to 100 Hz is shorter than the electron Larmor radius, which also argues against a lower hybrid drift instability. Planetary lightning is consequently a more likely source for the VLF bursts.

Strangeway, R. J.↗
NASA NTRS1988

Field test results with the targeted search MCSA

In April 1985, a 74,000 channel prototype of the multichannel spectrum analyzer (MCSA) that NASA plans to use in a systematic search for extraterrestrial intelligence (SETI) was installed at DSS13, a 26 meter R&D antenna facility at the Goldstone Deep Space Network (DSN) site. Since that time the instrumentation has been used to validate the performance of signal detection algorithms using locally injected signals and the weak carriers from distant spacecraft. This paper describes results from the Goldstone Field Tests and plans to move the prototype equipment to other sites where SETI may be conducted in the future.

Tarter, J. C.↗
NASA NTRS1996

Distinct transcripts are recognized by sense and antisense riboprobes for a member of the murine HSP70 gene family, HSP70.2, in various reproductive tissues

The expression of hsp70.2, an hsp70 gene family member, originally characterized by its high levels of expression in germ cells in the adult mouse testis, was detected in several other reproductive tissues, including epididymis, prostate, and seminal vesicles, as well as in extraembryonic tissues of mid-gestation fetuses. In addition, hybridization with RNA probes transcribed in the sense orientation surprisingly indicated the presence of slightly larger "antisense" transcripts in several tissues. The levels of antisense transcripts varied among the tissues, with the highest signal detected in the prostate and no signal being detectable in the testis. Consistent with these results, in situ hybridization analysis clearly localized the sense-orientation transcripts to pachytene spermatocytes, while no antisense-orientation transcripts were observed in adjacent sections of the same tubules. Our findings have thus shown that although hsp70.2 was expressed abundantly and in a highly stage-specific manner in the male germ line, it was also expressed in other murine tissues. Furthermore, we have made the surprising observation of antisense transcription of the hsp70.2 gene in several mouse tissues, revealing another level of complexity in the regulation and function of heat shock proteins.

Non-NASA Center↗
DOE OSTI2022

Dual-Color Optical Recording of Bioelectric Potentials by Polymer Electrochromism

Optical recording based on voltage-sensitive fluorescent reporters allows for spatial flexibility of measuring from desired cells, but photobleaching and phototoxicity of the fluorescent labels often limit their sensitivity and recording duration. Voltage-dependent optical absorption, rather than fluorescence, of electrochromic materials, would overcome these limitations to achieve long-term optical recording of bioelectrical signals. Electrochromic materials such as PEDOT:PSS possess the property that an applied voltage can either increase or decrease the light absorption depending on the wavelength. In this work, we harness this anticorrelated light absorption at two different wavelengths to significantly improve the signal detection. With dual-color detection, electrical activity from cells produces signals of opposite polarity, while artifacts, mechanical motions, and technical noises are uncorrelated or positively correlated. Using this technique, we are able to optically record cardiac action potentials with a high signal-to-noise ratio, 10 kHz sampling rate, >15 min recording duration, and no time-dependent degradation of the signal. Furthermore, we can reliably perform multiple recording sessions from the same culture for over 25 days.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1975

Multispectral processing based on groups of resolution elements

Several nine-point rules are defined and compared with previously studied rules. One of the rules performed well in boundary areas, but with reduced efficiency in field interiors; another combined best performance on field interiors with good sensitivity to boundary detail. The basic threshold gradient and some modifications were investigated as a means of boundary point detection. The hypothesis testing methods of closed-boundary formation were also tested and evaluated. An analysis of the boundary detection problem was initiated, employing statistical signal detection and parameter estimation techniques to analyze various formulations of the problem. These formulations permit the atmospheric and sensor system effects on the data to be thoroughly analyzed. Various boundary features and necessary assumptions can also be investigated in this manner.

Richardson, W.↗
NASA NTRS1985

The 50-MHz meteor radar observation at Syowa Station, Antarctica

The 50-MHz Doppler radar installed at Syowa Station (69 deg 00'S, 39 deg 35'E), Antarctica, in 1982 can detect continuously a meteor echo if an operator assigns the meteor mode operation to the radar. The radar has two narrow antenna beams (4 deg in the horizontal plane), one toward geomagnetic south and the other toward approximately geographic south, with a crossing angle of about 33 deg. The minicomputer annexed to the radar controls the transmission and reception of a 50-MHz wave. If the receiver detects a meteor echo, the flag signal is sent to the computer. Then the computer begins to determine the echo range with a time resolution of 1 micro s and to sample every 200 microns/s for 1 s the Doppler signal and echo intensity at the particular range (R). The line-of-sight velocity (V sub D) of the echo trail is calculated from the output from the Doppler signal detection circuit having an offset frequency by using the so-called zero-crossing method. The echo amplitude decay time calculated by a least-mean square method is used to obtain the ambipolar diffusion coefficient (D) and then to calculate the echo height (H). About 120 day observations were made during 1982-1983. Some early results are presented. magnetic tapes together with V sub D, D, H and R for later analysis in Japan. About 120 day observation were made during 1982-1983. Some early results are presented.

Tanaka, T.↗
DOE OSTI2021

Commissioning of the LCLS-II Prototype HOM Detectors with Tesla-Type Cavities at Fast

Experiments at the Fermilab Accelerator Science and Technology* (FAST) facility detected electron beam-induced high order mode (HOM) signals from Tesla superconducting cavities. This paper describes some of the signal detection hardware used in this experiment, as well as measurements of the HOM signal magnitude versus beam trajectory. These measurements were made both with a single bunch and with a train of 50 bunches at bunch charges from 400 pC/b down to 10 pC/b. The detection hardware is designed for use with the Tesla superconducting cavities of LCLS-II at SLAC** and is based on a prototype already in use at Fermilab. The HOM signal passes through a bandpass filter that is centered on several cavity dipole modes and a zero bias Schottky diode detects its magnitude. Direct comparisons were made between the FNAL chassis and the SLAC prototype for identical beam steering conditions. To support measurements with bunch charges as low as 10 pC, the SLAC detector has RF amplification between the bandpass filter and the diode detector. With this hardware, usable HOM signal measurements are obtained with a single bunch of 10 pC in cryomodule cavities as will be needed for LCLS-II.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Ionization yield measurement in a germanium CDMSlite detector using photo-neutron sources

Two photo-neutron sources, Y 88 Be 9 and Sb 124 Be 9 , have been used to investigate the ionization yield of nuclear recoils in the CDMSlite germanium detectors by the SuperCDMS collaboration. In this study, we evaluate the yield for nuclear recoil energies between 1 and 7 keV at a temperature of ~ 50 mK . We use a geant4 simulation to model the neutron spectrum assuming a charge yield model that is a generalization of the standard Lindhard model and consists of two energy dependent parameters. We perform a likelihood analysis using the simulated neutron spectrum, modeled background, and experimental data to obtain the best fit values of the yield model. The ionization yield between recoil energies of 1 and 7 keV is shown to be significantly lower than predicted by the standard Lindhard model for germanium. There is a general lack of agreement among different experiments using a variety of techniques studying the low energy range of the nuclear recoil yield, which is most critical for interpretation of direct dark matter searches. This suggests complexity in the physical process that many direct detection experiments use to model their primary signal detection mechanism and highlights the need for further studies to clarify underlying systematic effects that have not been well understood up to this point.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1971

Quantum detection theory

Statistical estimation theory applied to quantum mechanics and signal detection with optical instruments

Helstrom, C. W.↗
NASA NTRS1985

Microwave responses of the western North Atlantic

Features and objects in the Western North Atlantic Ocean - the Eastern Seaboard of the United States - are observed from Earth orbit by passive microwaves. The intensities of their radiated flux signatures are measured and displayed in color as a microwave flux image. The features of flux emitting objects such as the course of the Gulf Stream and the occurrence of cold eddies near the Gulf Stream are identified by contoured patterns of relative flux intensities. The flux signatures of ships and their wakes are displayed and discussed. Metal data buoys and aircraft are detected. Signal to clutter ratios and probabilities of detection are computed from their measured irradiances. Theoretical models and the range equations that explain passive microwave detection using the irradiances of natural sources are summarized.

Stacey, J. M.↗
NASA NTRS1987

Digital modulation for an aeronautical mobile satellite system

A review is provided of radio technology, particularly signal modulation, in a satellite-based aeronautical communication system. The propagation environment is examined, and a generic signal-detection strategy is established. The following are then covered: signal bandwidth and carrier modulation; power performance; error detection and block coding; channel spacing; the modulator and demodulator; and coarse frequency error detection.

Davarian, F.↗
NASA NTRS1998

Memory monitoring by animals and humans

The authors asked whether animals and humans would use similarly an uncertain response to escape indeterminate memories. Monkeys and humans performed serial probe recognition tasks that produced differential memory difficulty across serial positions (e.g., primacy and recency effects). Participants were given an escape option that let them avoid any trials they wished and receive a hint to the trial's answer. Across species, across tasks, and even across conspecifics with sharper or duller memories, monkeys and humans used the escape option selectively when more indeterminate memory traces were probed. Their pattern of escaping always mirrored the pattern of their primary memory performance across serial positions. Signal-detection analyses confirm the similarity of the animals' and humans' performances. Optimality analyses assess their efficiency. Several aspects of monkeys' performance suggest the cognitive sophistication of their decisions to escape.

NASA Discipline Space Human Factors↗
NASA NTRS1986

A wide bandwidth electrostatic field sensor for lightning research

Data obtained from UHF Radar observation of direct-lightning strikes to the NASA F-106B airplane have indicated that most of the 690 strikes acquired during direct-strike lightning tests were triggered by the aircraft. As an aid in understanding the triggered lightning process, a wide bandwidth electric field measuring system was designed for the F-106B by implementing a clamped-detection signal processing concept originated at the Air Force Cambridge Research Lab in 1953. The detection scheme combines the signals from complementary stator pairs clamped to zero volts at the exact moment when each stator pair is maximally shielded by the rotor, a process that restores the dc level lost by the charge amplifier. The new system was implemented with four shutter-type field mills located at strategic points on the airplane. The bandwidth of the new system was determined in the laboratory to be from dc to over 100 Hz, whereas past designs had upper limits of 10 Hz to 100 Hz. To obtain the undisturbed electric field vector and total aircraft charge, the airborne field mill system is calibrated by using techniques involving results from ground and flight calibrations of the F-106B, laboratory tests of a metallized model, and a finite-difference time-domain electromagnetic computer code.

Zaepfel, K. P.↗
NASA NTRS1989

A wide bandwidth electrostatic field sensor for lightning research

Data obtained from UHF radar observation of direct-lightning strikes to the NASA F-106B aircraft have indicated that most of the 690 strikes acquired during direct-strike lightning tests were triggered by the aircraft. As an aid in understanding the triggered lightning process, a wide bandwidth electric field measuring system was designed for the F-106B by implementing a clamped-detection signal processing concept originated at the Air Force Cambridge Research Lab in 1953. The detection scheme combines the signals from complementary stator pairs clamped to zero bolts at the exact moment when each stator pair is maximally shielded by the rotor, a process that restores the dc level lost by the charge amplifier. The system was implemented with four shutter-type field mills located at strategic points on the aircraft. The bandwidth of the system was determined in the laboratory to be from dc to over 100 Hz, whereas past designs had upper limits of 10 to 100 Hz. To obtain the undisturbed electric field vector and total aircraft charge, the airborne field mill system is calibrated by using techniques involving results from ground and flight calibrations of the F-106B, laboratory tests of a metallized model, and a finite difference time-domain electromagnetic computer code.

Zaepfel, Klaus P.↗
DOE OSTI2021

Directional Recoil Detection

Searches for dark matter–induced recoils have made impressive advances in the last few years. Yet the field is confronted by several outstanding problems. First, the inevitable background of solar neutrinos will soon inhibit the conclusive identification of many dark matter models. Second, and more fundamentally, current experiments have no practical way of confirming a detected signal's Galactic origin. The concept of directional detection addresses both of these issues while offering opportunities to study novel dark matter– and neutrino-related physics. The concept remains experimentally challenging, but gas time projection chambers are an increasingly attractive option and, when properly configured, would allow directional measurements of both nuclear and electron recoils. In this review, we reassess the required detector performance and survey relevant technologies. Fortuitously, the highly segmented detectors required to achieve good directionality also enable several fundamental and applied physics measurements. As a result, we comment on near-term challenges and how the field could be advanced.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗