Engineering topics

Smith, R. C.

Publications and source records attributed to Smith, R. C..

At least 37 records · Page 2

NASA NTRS1991

Numerical recovery of material parameters in Euler-Bernoulli beam models

A fully Sinc-Galerkin method for recovering the spatially varying stiffness parameter in fourth-order time-dependence problems with fixed and cantilever boundary conditions is presented. The forward problems are discretized with a sinc basis in both the spatial and temporal domains. This yields an approximation solution which converges exponentially and is valid on the infinite time interval. When the forward methods are applied to parameter recovery problems, the resulting inverse problems are ill-posed. Tikhonov regularization is applied and the resulting minimization problems are solved via a quasi-Newton/trust region algorithm. The L-curve method is used to determine an appropriate value of the regularization parameter. Numerical results which highlight the method are given for problems with both fixed and cantilever boundary conditions.

Smith, R. C.↗

NASA NTRS1991

A fully Galerkin method for the recovery of stiffness and damping parameters in Euler-Bernoulli beam models

A fully Sinc-Galerkin method for recovering the spatially varying stiffness and damping parameters in Euler-Bernoulli beam models is presented. The forward problems are discretized with a sinc basis in both the spatial and temporal domains thus yielding an approximate solution which converges exponentially and is valid on the infinite time interval. Hence the method avoids the time-stepping which is characteristic of many of the forward schemes which are used in parameter recovery algorithms. Tikhonov regularization is used to stabilize the resulting inverse problem, and the L-curve method for determining an appropriate value of the regularization parameter is briefly discussed. Numerical examples are given which demonstrate the applicability of the method for both individual and simultaneous recovery of the material parameters.

Smith, R. C.↗

NASA NTRS1991

Active noise control - Piezoceramic actuators in fluid/structure interaction models

A model for a 2-D acoustic cavity with a flexible boundary (a beam) controlled via piezoceramic patches producing bending moments in the beam is considered. The associated control problem for this fluid/structure interaction system to reduce the acoustic pressure in the cavity involves unbounded control inputs. Approximation methods in the context of an LQR state space formulation are discussed, and numerical results are presented to demonstrate the effectiveness of this approach in computing feedback controls for noise reduction.

Banks, H. T.↗

NASA NTRS1990

A fully Sinc-Galerkin method for Euler-Bernoulli beam models

A fully Sinc-Galerkin method in both space and time is presented for fourth-order time-dependent partial differential equations with fixed and cantilever boundary conditions. The Sinc discretizations for the second-order temporal problem and the fourth-order spatial problems are presented. Alternate formulations for variable parameter fourth-order problems are given which prove to be especially useful when applying the forward techniques to parameter recovery problems. The discrete system which corresponds to the time-dependent partial differential equations of interest are then formulated. Computational issues are discussed and a robust and efficient algorithm for solving the resulting matrix system is outlined. Numerical results which highlight the method are given for problems with both analytic and singular solutions as well as fixed and cantilever boundary conditions.

Smith, R. C.↗

NASA NTRS1988

Moorable spectroradiometers in the BIOWATT experiment

A new oceanographic instrument, the MER-2020, has been developed for the long term measurement of bio-optical properties. This instrument is a self-contained reflectance spectroradiometer with 40 megabytes of internal data storage and battery power permitting deployments for as long as 6 months. It can serve as the control and recording center for a variety of other sensors including fluorometers, transmissometers, temperature and conductivity probes. Instruments of this type were deployed at depths to 70 meters on a 5000 meter mooring during the BIOWATT experiment between February and November 1987. Measurements of the spectral diffuse attenuation coefficient and of the remote sensed reflectance from the ten month period in 1987 in the Northern Sargasso Sea are presented. In addition, the temperature, pressure, package orientation and sunlight stimulated natural fluorescence of phytoplankton are discussed. This instrument will be a key part of in situ optical calibration for future remote color sensors, and presently permits direct measurement of long term optical variability, important in visibility and communication problems.

Booth, C. R.↗

NASA NTRS1986

Amphibian egg cytoplasm response to altered g-forces and gravity orientation

Elucidation of dorsal/ventral polarity and primary embryonic axis development in amphibian embryos requires an understanding of cytoplasmic rearrangements in fertile eggs at the biophysical, physiological, and biochemical levels. Evidence is presented that amphibian egg cytoplasmic components are compartmentalized. The effects of altered orientation to the gravitational vector (i.e., egg inversion) and alterations in gravity force ranging from hypergravity (centrifugation) to simulated microgravity (i.e., horizontal clinostat rotation) on cytoplasmic compartment rearrangements are reviewed. The behavior of yolk compartments as well as a newly defined (with monoclonal antibody) nonyolk cytoplasmic compartment, in inverted eggs and in eggs rotated on horizontal clinostats at their buoyant density, is discussed.

Neff, A. W.↗

NASA NTRS1985

Response of amphibian egg non-yolk cytoplasm to gravity orientation

In order to study amphibian egg cytoplasmic organization and egg symmetrization at the molecular level, a library of seventeen monoclonal antibodies (MoAbs) against Xenopus laevis non-yolk egg proteins was produced. Several of these MoAbs react with non-yolk cytoplasmic antigens which are unevenly distributed in the fertile Xenopus egg.

Smith, R. C.↗

NASA NTRS1985

Chronology of warm-core ring 82B

The chronology presently derived from satellite thermal imagery to describe the formation and life history of the warm core ring 82B furnishes insight into a classification of features and discrete events associated with Gulf Stream warm core rings; these events are thereby put in a broader spatial and temporal context. The interactions of the ring with surrounding waters are noteworthy, and the existence of vortex-vortex interactions is shown to be a significant cause of local water advection through streamer activity. Acoustic velocity profiling and drifter trajectories have been used to corroborate hydrographic features of the ring and its environs.

Evans, R. H.↗

NASA NTRS1985

Spatial and temporal patterns in pigment biomass in Gulf Stream warm-core ring 82B and its environs

A chronology of the horizontal and vertical distribution of phytoplankton pigment biomass provides a biological life history of Gulf Stream warm-core ring 82B. Development of ring 82B is followed through three distinct periods: a winter/early spring period of deep convective overturn with uniform and relatively high pigment concentrations to depths of 400 m, a late spring stratification period with subsurface (20-30 m) pigment maxima and relatively high ring center values compared to surrounding waters, and a Gulf Stream interaction period when ring characteristics are dominated by intrusions of low pigment concentration waters. While the ring maintains a unique identity throughout these periods of its life, prolonged deep vertical mixing as well as episodic interactions with its surrounding have a significant influence on pigment distributions within the ring. These interactions generally enhance pigment biomass compared to the water mass from which it is derived. A consistent feature of pigment distribution is the remarkable coherence between this measure of phytoplankton biomass and the corresponding physical hydrodynamic structure of the upper water column.

Smith, R. C.↗

NASA NTRS1984

Influence of clinostat rotation on fertilized amphibian egg pattern specification

Pattern specification in fertile Xenopus eggs rotated on horizontal clinostats was monitored with respect to primary embryonic axis formation, subsequent morphogenesis, and compartmentalization of the cytoplasm. At the speeds of 1 to 24 rpm (which are believed to simulate microgravity) a large percentage of eggs developed normal axial structures. Eggs clinostated at 12 rpm showed a randomization of dorsal/ventral polarity. The cytoplasmic compartments showed some clinostat effects but no abnormal mixing, disruption or dislocation of compartments. It is predicted that Xenopus eggs fertilized and allowed to develop in space will retain normal cytoplasmic density compartments, establish primary axes and undergo normal morphogenesis in space. Their dorsal/ventral polarity may not, however, be determined by the sperm entrance site (as is the case for 1 g eggs).

Neff, A. W.↗

NASA NTRS1984

Oceanographic biooptical profiling system

A new oceanographic instrument to measure underwater optical, biological, and physical properties has been designed, built, and used extensively at sea. The new instrument system is a significant advance that permits optimum sampling strategies using ship, aircraft, and satellite optical sensors for ocean research. The design criteria for the biooptical profiling system included the rapid acquisition of data to accommodate shipboard synoptic sampling; the measurement of the necessary parameters for providing appropriate contemporaneous surface data for remote sensors; the compatibility of the data acquisition system with conventional conductivity temperature depth-type cables and winches on the oceanographic fleet; the capability of real-time display of data along with rapid preliminary data reduction at sea. The primary instrument package in this profiling system is a new microprocessor controlled multiwavelength spectroradiometer. A description of the instrument and examples of data are presented.

Smith, R. C.↗

NASA NTRS1984

Aerodynamic test results for a wing-mounted turboprop propulsion installation

The paper provides an overview of the renewed interest in turboprop propulsion systems for future commercial transport designs. The potential operating cost advantage of advanced turbofan designs. Critical technology items for the aerodynamic installation of turboprop propulsion systems are presented, along with experimental results addressing the main technology issue for wing-mounted turboprop installations. Nacelle installation effects are presented for overwing and underwing nacelles. The drag reduction for nacelle contouring is also shown. Wing/nacelle/power data are presented for the baseline wing geometry and for a wing modified to reduce the propeller power effects.

Page, G. S.↗

NASA NTRS1984

Introduction to ocean optics

In this introductory survey of optical oceanography, the fundamental inherent and apparent optical properties of natural waters are presented. Relationships between these inherent and apparent optical properties, as related through the radiative transfer equation, are then examined. Following the first three theoretical sections, brief discussions describing the application of ocean optics to geophysics, biological oceanography, and ocean remote sensing are then presented.

Gordon, H. R.↗

NASA NTRS1984

The analysis of ocean optical data

A new oceanographic instrument to measure underwater optical, biological and physical properties simultaneously has been built and used extensively at sea. The Bio-Optical Profiling System (BOPS) was designed for the rapid acquisition of data to accommodate shipboard 'synoptic' sampling strategies, often in conjunction with concurrent aircraft and satellite sensors. The data rates and associated quantity of data from the BOPS are some orders of magnitude larger than those traditionally encountered in optical oceanography. The rapid acquisition of optical data in a wide range of environmental conditions requires new methodologies in ocean optical data analysis.

Smith, R. C.↗

NASA NTRS1983

Satellites for the study of ocean primary productivity

The use of remote sensing techniques for obtaining estimates of global marine primary productivity is examined. It is shown that remote sensing and multiplatform (ship, aircraft, and satellite) sampling strategies can be used to significantly lower the variance in estimates of phytoplankton abundance and of population growth rates from the values obtained using the C-14 method. It is noted that multiplatform sampling strategies are essential to assess the mean and variance of phytoplankton biomass on a regional or on a global basis. The relative errors associated with shipboard and satellite estimates of phytoplankton biomass and primary productivity, as well as the increased statistical accuracy possible from the utilization of contemporaneous data from both sampling platforms, are examined. It is shown to be possible to follow changes in biomass and the distribution patterns of biomass as a function of time with the use of satellite imagery.

Smith, R. C.↗

NASA NTRS1983

Installed nacelle drag-improvement tests of an M = 0.8 turboprop transport configuration

An unpowered semispan model of a representative turboprop configuration was tested to determine the effect of configuration modifications on the the nonmetric body and wing juncture. It is indicated that the jet off nacelle-installation drag can be approximately 25% of the cruise drag. However, the losses can be reduced to 17% by changes to the wing leading edge and nacelle intersection. Comparison of test results from a semispan nonmetric fuselage model with those from a full span metric fuselage show differences in angles of attack produced the same lift. It is found that the constant lift drag rise of the semispan model is higher because of the increased angle of attack to achieve the same lift.

Levin, A. D.↗

NASA NTRS1982

Ship and satellite bio-optical research in the California Bight

Mesoscale biological patterns and processes in productive coastal waters were studied. The physical and biological processes leading to chlorophyll variability were investigated. The ecological and evolutionary significance of this variability, and its relation to the prediction of fish recruitment and marine mammal distributions was studied. Seasonal primary productivity (using chlorophyll as an indication of phytoplankton biomass) for the entire Southern California Bight region was assessed. Complementary and contemporaneous ship and satellite (Nimbus 7-CZCS) bio-optical data from the Southern California Bight and surrounding waters were obtained and analyzed. These data were also utilized for the development of multi-platform sampling strategies and the optimization of algorithms for the estimation of phytoplankton biomass and primary production from satellite imagery.

Smith, R. C.↗

NASA NTRS1981

The CZCS geolocation algorithms

The Coastal Zone Color Scanner (CZCS) on board the Nimbus 7 satellite was designed to measure surface radiance upwelled from the ocean in 6 spectral bands. The CZCS spectrometer obtains its information from a rotating mirror and is timed to collect data when the mirror views the Earth surface between ca. 40 degrees to the left and right of the subsatellite track. Each scan is divided into 1968 picture elements, pixels, of 0.04 degrees scan each. In order to avoid direct reflected Sun glint, the rotating mirror shaft can be tilted so that scans across the subsatellite track up to 20 degrees forward or aft of the point directed beneath the satellite. The CZCS is the first satellite borne instrument to have this tilted scan capability and therefore poses some new problems in locating the Earth surface position of viewed pixels.

Wilson, W. H.↗