AEC Research and Development Report

Technical report describing that voids were measured in a ½-inch by 1-3/4-inch channel with the S-1 insert (B(0)/B(1) = 0.4, L(0) = 0.1 inch), at 2 inches ahead of the insert (position A), ½-inch past the insert (position B), 5 inches past (position C), and 12 inches past (position D). The conditions were: P – 1000 psia, G = 1.00 x 10(6) lb/h-ft(2), and x = 18.8 percent. Average void and void distribution at position A are the same as for flow in a straight channel. Void distribution at position B shows that the stagnation region downstream of the inserts contains a high fraction of voids. Average void and void distribution at positions C and d show that the two-phase mixture becomes strongly mixed (homogenized) as a result of passing through he contraction-expansion inserts. Distribution at position D approaches the distribution at position A; i.e., the straight channel distribution

PVP2008-61243 UNIQUE METHOD FOR GENERATING DESIGN EARTHQUAKE TIME HISTORIES

ABSTRACT A method has been developed which takes a seed earthquake time history and modifies it to produce given design response spectra. It is a multi-step process with an initial scaling step and then multiple refinement steps. It is unique in the fact that both the acceleration and displacement response spectra are considered when performing the fit (which primarily improves the low frequency acceleration response spectrum accuracy). Additionally, no matrix inversion is needed. The features include encouraging the code acceleration, velocity, and displacement ratios and attempting to fit the pseudo velocity response spectrum. Also, "smoothing" is done to transition the modified time history to the seed time history at its start and end. This is done in the time history regions below a cumulative energy of 5% and above a cumulative energy of 95%. Finally, the modified acceleration, velocity, and displacement time histories are adjusted to start and end with an amplitude of zero (using Fourier transform techniques for integration). INTRODUCTION Time history analysis is an important technique for structural seismic analysis especially when the evaluated structural response is nonlinear. To perform such an analysis, a representative earthquake time history (or seed time history) is established for a structure being evaluated. To ensure that the variability in the response is addressed, a design response spectrum is then established using code guidance (e.g. ASCE 4-98 [1]). Because the design response spectrum does not match the response of the seed time history, the seed time history cannot be used for design evaluation. Instead, a modified time history must be used that is based on the seed time history, but provides a response defined by the design response spectrum. The method described in this paper is a way to modify the seed time history in such a way that it produces the design response

PVP2008-61244 UNIQUE METHOD FOR GENERATING DESIGN EARTHQUAKE TIME HISTORY SEEDS

ABSTRACT A method has been developed which takes a single seed earthquake time history and produces multiple similar seed earthquake time histories. These new time histories possess important frequency and cumulative energy attributes of the original while having a correlation less than 30% (per the ASCE/SEI 43-05 Section 2.4 [1]). They are produced by taking the fast Fourier transform of the original seed. The averaged amplitudes are then pared with random phase angles and the inverse fast Fourier transform is taken to produce a new time history. The average amplitude through time is then adjusted to encourage a similar cumulative energy curve. Next, the displacement is modified to approximate the original curve using Fourier techniques. Finally, the correlation is checked to ensure it is less than 30%. This process does not guarantee that the correlation will be less than 30% for all of a given set of new curves. It does provide a simple tool where a few additional iterations of the process should produce a set of seed earthquake time histories meeting the correlation criteria. INTRODUCTION Time history analysis is an important technique for structural seismic analysis especially when the evaluated structural response is nonlinear. To perform such an analysis, a representative earthquake acceleration time history (or seed acceleration time history) is established for a structure being evaluated. Manipulations of the seed are then performed to create a modified acceleration time history (or design acceleration time history) that produces a design acceleration response (per the ASCE/SEI 43-05 Section 2.4 [1]). This design acceleration time history can then be used for seismic analysis. Depending on the type of seismic analysis being performed, several design acceleration time histories may be required. The method described in this paper is a way t

Component Rearrangement on Printed Wiring Boards to Maximize the Fundamental Natural Frequency

A methodology to attain the highest fundamental natural frequency of a printed wiring board by rearranging its components has been developed. A general twodimensional rearrangement algorithm is developed by which the rearrangement of the component-lead-board (CLB Introduction Integrated circuit technology has advanced rapidly in the past twenty years. The means to produce electronic equipment with high reliability and minimum overall cost has captured the attention of numerous researchers. Most of these researchers have been concerned with finding the optimal placement [1-6], minimum chip area Another important aspect of building reliable PWBs is to reduce the probability of failure due to mechanically generated motions, which can cause high relative displacement levels of the components and, consequently, high stress levels. These cyclic stress levels often lead to fatigue-induced cracked components and solder joints. One way to reduce the high cyclic stress is to subject the PWB to dynamic loadings whose frequency content is below the PWB's lowest natural frequency

The Berry phase in inflationary cosmology

We derive an analogue of the Berry phase associated with inflationary cosmological perturbations of quantum mechanical origin by obtaining the corresponding wavefunction. We have further shown that cosmological Berry phase can be completely envisioned through the observable parameters, viz. spectral indices. Finally, physical significance of this phase is discussed from the point of view of theoretical and observational aspects with some possible consequences of this quantity in inflationary cosmology.Comment: 9 pages, Modified version to appear in Classical and Quantum Gravity. arXiv admin note: text overlap with arXiv:quant-ph/0307084 by other author

Hindu-Muslim Violence in India: A Postscript from the Twenty-First Century

The importance of religious conflict today can hardly be overstated. The appalling situation in Syria—stemming from the activism of the Islamic State (ISIS)—is just one cruel reminder of the utter devastation that religious extremism can wreak. The tragic humanitarian crisis in Myanmar involving the displacement of the Rohingya Muslims has strong religious overtones, as do the attacks on Muslims and Christians by Buddhist nationalist groups in Sri Lanka