1,501 research outputs found
Computer program to determine roots of polynomials by ratio of successive derivatives
High speed computing finds roots of polynomials with real number coefficients. Ratios of successive polynomial derivatives approach provides accurate roots-of-polynomial computer programs with very high reliability. With derivative ratio method, root analysis can still be done even though the polynomial and its lower order derivatives cannot be evaluated with sufficient accuracy
Centrifuge liquefaction tests in a laminar box
The difficulties associated with instrumenting earthquake sites in order to record pore pressure changes in a future event led to the use of scaled model tests performed in a centrifuge. Both dry and saturated sands were employed, contained in a box constructed of aluminium laminae designed to move freely on each other. This would result in shearing distortions developing in the soil unimpeded by the container. Accelerometers, displacement transducers and pore pressure sensors were attached to the box and embedded in the soil at various elevations so as to record the response of the soil to an earthquake-like excitation supplied to the base of the container. A special apparatus was constructed to imitate earthquake motion. In some tests on saturated sand, the soil profile was liquefied. Test results of accelerations, lateral and vertical displacements and pore pressures against time for typical earthquake inputs are given. The data, obtained under controlled conditions, can be compared with the various calculation methods for dynamically generated pore pressures
Soil-structure interaction during the San Fernando earthquake
Accelerograms obtained at two sites during the San Fernando earthquake of 1971 were analyzed to investigate the role of soil-structure interaction, using techniques developed by Bielak and others. Analysis of the data from the site of the Hollywood Storage Building, for which data from the Arvin-Tehachapi earthquake of 1952 are also available, showed evidence of soil-structure interaction in the way the transfer functions between parking lot and basement motion decayed with increasing frequency in the two lateral directions. It is concluded also that interaction probably had a small effect on the response near the EW fundamental frequency during the San Fernando earthquake. Although theoretical and experimentally determined transfer functions are broadly similar, they do not agree in detail. The lack of good agreement for reasonable choices of the parameters of the theoretical model indicates a need for some modifications of the theory or its application, and a need for more measurements at the site.
A similar analysis showed no clear evidence of soil-structure interaction for the Millikan Library and Athanaeum buildings on the campus of the California Institute of Technology. If soil-structure interaction caused the major differences measured in the base motions of these two buildings, it is of a more complex form than that considered by present theories
Model Identification and Seismic Analysis of Meloland Road Overcrossing
This report presents the results of research directed toward model identification and
seismic analysis of the MRO. This research has been implemented to meet the requirements of
Tasks 4 and 5 of the UNR-D&M research program (Sec. 1.1.3) and also to provide a basis for
developing improved bridge modeling procedures as required under the D & M research program
on SBOs (Sec. 1.1.4).
The scope of this research effort consisted of our development of a finite element model
of the MRO whose parameters were estimated through the application of state-of-the-art system
identification methods to the MRO's recorded motions from the Imperial Valley Earthquake.
These estimated model parameters were also checked for consistency with an overall range of
model parameter values computed using established engineering procedures. This model was
then used in a series of parametric dynamic analyses of the seismic response of the MRO which
enabled us to evaluate the effects of uncertainties in the various model parameters on the demand
forces and moments in the structural members and the foundation springs. Maximum foundation
spring forces and moments obtained from these analyses were used as input to nonlinear static
analyses of the MRO's pile foundations in order to compute the demand forces and moments
within the piles. The demand forces and moments within the MRO's structural and pile elements
were then compared against the capacities of these elements. These analysis results have been
interpreted to assess the seismic performance and design of the MRO, and also to provide an
important basis for our development of improved modeling and seismic evaluation procedures
for short bridge overcrossing structures.
The above efforts have focused on the modeling and analysis of the MRO's translational
and rotational response to transverse horizontal input motions; i.e., the bridge's response to
vertical and longitudinal input motions was not included in this research. This focus on the
MRO's response to transverse horizontal input motions was adopted because: (a) this response
will lead to more severe earthquake-induced internal forces and moments, particularly in the
central pier which is the element of an SBO that is typically most vulnerable to seismic excitation; and (b) our past evaluations of the MRO's recorded motions have shown that its
response to transverse horizontal input motions is strongly affected by SSI, whereas SSI has only
a negligible effect of the MRO's response to vertical and longitudinal input motions (Werner, et.
al., 1987)
Analysis and Testing of the FBA-11 Force [Balance] Accelerometer
The FBA-11 is a feedback-controlled accelerometer widely used to measure and record accelerations arising from earthquakes. It has found application both for structural response and for ground motion studies. The design intent of the FBA-11 was to provide electronic control of the natural frequency, damping, and output voltage. Included in this paper are (1) a circuit analysis yielding the complete closed-loop transfer function, and (2) the corroborative test results from shake table evaluations. The transfer function can be used to correct recorded accelerations for instrument response
Integrating Automation into a Multi-Mission Operations Center
NASA Goddard Space Flight Center's Space Science Mission Operations (SSMO) Project is currently tackling the challenge of minimizing ground operations costs for multiple satellites that have surpassed their prime mission phase and are well into extended mission. These missions are being reengineered into a multi-mission operations center built around modern information technologies and a common ground system infrastructure. The effort began with the integration of four SMEX missions into a similar architecture that provides command and control capabilities and demonstrates fleet automation and control concepts as a pathfinder for additional mission integrations. The reengineered ground system, called the Multi-Mission Operations Center (MMOC), is now undergoing a transformation to support other SSMO missions, which include SOHO, Wind, and ACE. This paper presents the automation principles and lessons learned to date for integrating automation into an existing operations environment for multiple satellites
Association of Cardiovascular Fitness and Syndrome X in Male Firefighters
Metabolic syndrome has been shown in numerous studies to be related to a higher incidence of coronary artery disease. A study by Jurca and coworkers (Med. Sci. Sports Exerc 36(8):1301-1307, 2004) found a relationship between cardiovascular fitness and the prevalence of metabolic syndrome in a group of men enrolled in the Aerobics Center Longitudinal Study (ACLS). In addition, recent work in our lab (Int J Exerc Sci 2(1): S43, 2009) has supported these findings. However, research exploring this relationship is still lacking in male firefighters, whose leading cause of line-of-duty deaths is heart attacks. Purpose: To further evaluate the association of metabolic syndrome and cardiovascular fitness in male fire fighters. Methods: As part of an annual physical exam, 224 male fire fighters (average age = 36) underwent evaluation of risk factors associated with metabolic syndrome as defined by NCEP III. These include the presence of three or more of the following: Waist Circumference \u3e 40 , HDL Cholesterol \u3c 40 mg/dL, Triglycerides \u3e 150 mg/dL, Blood Glucose \u3e 110 mg/dL, and Resting Blood Pressure \u3e 130/85 mm Hg. Cardiovascular Fitness was determined by estimating VO2max from time on treadmill during a Bruce protocol. Results: The subjects were ranked and divided into quartiles based on VO2max. All data were analyzed using a Chi Square test (p \u3c 0.05). Prevalence of metabolic syndrome increased significantly across quartiles as cardiovascular fitness declined. Conclusion: These data suggest that as cardiovascular fitness improves, the likelihood of male firefighters having metabolic syndrome decreases
Aquatic treadmill running reduces muscle soreness following intense sprint exercise in trained men
Delayed onset muscle soreness is associated with muscle damage, disturbances in proprioception, and decreases in muscular power. The purpose was to determine if short duration aquatic treadmill (ATM) running reduces muscle soreness following intense sprint exercise in trained men. Twenty trained men (180.3±4.4cm, 86.3±5.8kg, 20±1yr) were recruited and randomly divided into two groups: ATM recovery (ATMRec) and passive recovery (PRec). During testing, subjects performed a warm-up followed by sixteen 110yrd cutback runs with a sprint of 60yrds, sharp change of direction, and a return sprint of 50yrds. Work to rest ratio was set at 1:3. Additionally, following exercise, the ATMRec group performed ATM running using a HydroWorx® treadmill at 5mph, 50% maximal jet resistance, and water(33°C) level at chest depth for 10min. Both groups then evaluated their level of soreness/pain using a numerical rating scale (NRS: 0-10, 0=no pain, 10=worst pain) immediately following all exercise (IPE), 24h, and 48h post exercise in the following regions: ARMS, LEGS, BACK, CHEST, SHOULDERS, HIPS, ABDOMEN, NECK, OVERALL. Data were analyzed for group x time interactions using a 2x3 Generalized Linear Mixed Model for non-parametric data (α≤0.05). For significant interactions, the same procedure was used to analyze between group differences at the same measurement timepoint(α≤0.05)
Molecular characterization of the genes encoding the tungsten-containing aldehyde ferredoxin oxidoreductase from Pyrococcus furiosus and formaldehyde ferredoxin oxidoreductase from Thermococcus litoralis
The hyperthermophilic archaea Pyrococcus furiosus and Thermococcus litoralis contain the tungstoenzymes aldehyde ferredoxin oxidoreductase, a homodimer, and formaldehyde ferredoxin oxidoreductase, a homotetramer. herein we report the cloning and sequencing of the P. furiosus gene aor (605 residues; M_r, 66,630) and the T. litoralis gene for (621 residues; M_r, 68,941)
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