Dynamic Characteristics of Woodframe Buildings

The dynamic properties of wood shearwall buildings were evaluated, such as modal frequencies, damping and mode shapes of the structures. Through analysis of recorded earthquake response and by forced vibration testing, a database of periods and damping ratios of woodframe buildings was developed. Modal identification was performed on strong-motion records obtained from five buildings, and forced vibration tests were performed on a two-story house and a three-story apartment building, among others. A regression analysis is performed on the database to obtain a period formula specific for woodframe buildings. It should be noted that all test results, including the seismic data, are at small drift ratios (less than 0.1%), and the periods would be significantly longer for stronger shaking of these structures. Despite these low amplitudes, the equivalent viscous dampings for the fundamental modes were usually more than 10% of critical during earthquake shaking

Testing of reciprocating seals for application in a Stirling cycle engine

Six single stage reciprocating seal configurations to the requirements of the Stirling cycle engine were evaluated. The seals tested were: the Boeing Footseal, NASA Chevron polyimide seal, Bell seal, Quad seal, Tetraseal, and Dynabak seal. None of these seal configurations met the leakage goals of .002 cc/sec at helium gas pressure of 1.22 x 10 to the 7th power PA, rod speed of 7.19 m/sec peak, and seal environmental temperature of 408 K for 1500 hours. Most seals failed due to high temperatures. Catastrophic failures were observed for a minimum number of test runs characterized by extremely high leakage rates and large temperature rises. The Bell seal attained 63 hours of run time at significantly lowered test conditions

Development and fracture mechanics data for 6Al-6V-2 Sn titanium alloy

Fracture mechanics properties of 6Al-6V-2Sn titanium in the annealed, solution-treated, and aged condition are presented. Tensile, fracture toughness, cyclic flaw growth, and sustained-load threshold tests were conducted. Both surface flaw and compact tension-specimen geometries were employed. Temperatures and/or environments used were -65 F (220 K) air, ambient, 300 F (422 K) air, and room-temperature air containing 10 and 100% relative humidity

Introductory workshops on remote sensing as related to geological problems in Georgia

There are no author-identified significant results in this report

A new method for the determination of thin film porosity

Internal reflection spectroscopy may be used to determine presence of water in thin film pores. Presence of water in such pores is function of relative humidity and pore size. Thus, one can determine pore size by controlling humidity. Fluids with surface tension different from that of water can be used to detect pores

Application of pushbroom altimetry from space using large space antennas

The capabilities of multibeam altimetry are discussed and an interferometric multibeam technique for doing precision altimetry is described. The antenna feed horn arrangement and the resulting footprint lube pattern are illustrated. Plans for a shuttle multibeam altimetry mission are also discussed

Phase II of the ASCE Benchmark Study on SHM

The task group on structural health monitoring of the Dynamic Committee of ASCE was formed in 1999 at the 12 th Engineering Mechanics Conference. The task group has designed a number of analytical studies on a benchmark structure and there are plans to follow these with an experimental program. The first phase of the analytical studies was completed in 2001. The second phase, initiated in the summer of 2001, was formulated in the light of the experience gained on phase I and focuses on increasing realism in the simulation of the discrepancies between the actual structure and the mathematical model used in the analysis. This paper describes the rational that lead the SHM task group to the definition of phase II and presents the details of the cases that are being considered

Simulations of the Galaxy Cluster CIZA J2242.8+5301 I: Thermal Model and Shock Properties

The giant radio relic in CIZA J2242.8+5301 is likely evidence of a Mpc sized shock in a massive merging galaxy cluster. However, the exact shock properties are still not clearly determined. In particular, the Mach number derived from the integrated radio spectrum exceeds the Mach number derived from the X-ray temperature jump by a factor of two. We present here a numerical study, aiming for a model that is consistent with the majority of observations of this galaxy cluster. We first show that in the northern shock upstream X-ray temperature and radio data are consistent with each other. We then derive progenitor masses for the system using standard density profiles, X-ray properties and the assumption of hydrostatic equilibrium. We find a class of models that is roughly consistent with weak lensing data, radio data and some of the X-ray data. Assuming a cool-core versus non-cool-core merger, we find a fiducial model with a total mass of $1.6 \times 10^{15}\,M_\odot$, a mass ratio of 1.76 and a Mach number that is consistent with estimates from the radio spectrum. We are not able to match X-ray derived Mach numbers, because even low mass models over-predict the X-ray derived shock speeds. We argue that deep X-ray observations of CIZA J2242.8+5301 will be able to test our model and potentially reconcile X-ray and radio derived Mach numbers in relics.Comment: 19 pages, 19 figure

Measuring cosmic magnetic fields by rotation measure-galaxy cross-correlations in cosmological simulations

Using cosmological MHD simulations of the magnetic field in galaxy clusters and filaments we evaluate the possibility to infer the magnetic field strength in filaments by measuring cross-correlation functions between Faraday Rotation Measures (RM) and the galaxy density field. We also test the reliability of recent estimates considering the problem of data quality and Galactic foreground (GF) removal in current datasets. Besides the two self-consistent simulations of cosmological magnetic fields based on primordial seed fields and galactic outflows analyzed here, we also explore a larger range of models scaling up the resulting magnetic fields of one of the simulations. We find that, if an unnormalized estimator for the cross-correlation functions and a GF removal procedure is used, the detectability of the cosmological signal is only possible for future instruments (e.g. SKA and ASKAP). However, mapping of the observed RM signal to the underlying magnetization of the Universe (both in space and time) is an extremely challenging task which is limited by the ambiguities of our model parameters, as well as to the weak response of the RM signal in low density environments. Therefore, we conclude that current data cannot constrain the amplitude and distribution of magnetic fields within the large scale structure and a detailed theoretical understanding of the build up and distribution of magnetic fields within the Universe will be needed for the interpretation of future observations.Comment: 11 pages, 11 figures, comparation between RM data and simulations in fig. 8, submited to MNRAS