University Of California At Santa Barbara Research Articles

The Doctor, Ghana, and Me

The Doctor, Ghana, and Me

A computational workflow for rupture‐to‐structural‐response simulation and its application to Istanbul

AbstractScenario‐based earthquake simulations at regional scales hold the promise in advancing the state‐of‐the‐art in seismic risk assessment studies. In this study, a computational workflow is presented that combines (i) a broadband Green's function‐based fault‐rupture and ground motion simulation—herein carried out using the “UCSB (University of California at Santa Barbara) method”, (ii) a three‐dimensional physics‐based regional‐scale wave propagation simulation that is resolved at Hz, and (iii) a local soil‐foundation‐structure finite element analysis model. These models are interfaced with each other using the domain reduction method. The innermost local model—implemented in ABAQUS—is additionally enveloped with perfectly matched layer boundaries that absorb outbound waves scattered by the structures contained within it. The intermediate wave propagation simulation is carried out using Hercules, which is an explicit time‐stepping finite element code that is developed and licensed by the CMU‐QUAKE group. The devised workflow is applied to a km region on the European side of Istanbul, which was modeled using detailed soil stratigraphy data and realistic fault rupture properties, which are available from prior microzonation surveys and earthquake scenario studies. The innermost local model comprises a chevron‐braced steel frame building supported by a shallow foundation slab, which, in turn, rests atop a three‐dimensional soil domain. To demonstrate the utility of the workflow, results obtained using various simplified soil‐structure interaction analysis techniques are compared with those from the detailed direct model. While the aforementioned demonstration has a limited scope, the devised workflow can be used in a multitude of ways, for example, to examine the effects of shallow‐layer soil nonlinearities and surface topography, to devise site‐ and structure‐specific seismic fragilities, and for calibrating regional loss models, to name a few.

Dispatches

Dispatches

Fluctuations in Diffusion Processes in Microgravity

It has been shown recently that diffusion processes exhibit giant nonequilibrium fluctuations (NEFs). That is, the diffusing fronts display corrugations whose length scale ranges from the molecular to the macroscopic one. The amplitude of the NEF diverges following a power law behavior proportional to q(-4) (where q is the wave vector). However, fluctuations of wave number smaller than a critical "rolloff" wave vector are quenched by the presence of gravity. It is therefore expected that in microgravity conditions, the amplitude of the NEF should be boosted by the absence of the buoyancy-driven restoring force. This may affect any diffusion process performed in microgravity, such as the crystallization of a protein solution induced by the diffusion of a salt buffer. The aim of GRADFLEX (GRAdient-Driven FLuctuation EXperiment), a joint project of ESA and NASA, is to investigate the presence of NEFs arising in a diffusion process under microgravity conditions. The project consists of two experiments. One is carried out by UNIMI (University of Milan) and INFM (Istituto Nazionale per la Fisica della Materia) and is focused on NEF in a concentration diffusion process. The other experiment is performed by UCSB (University of California at Santa Barbara) concerning temperature NEF in a simple fluid. In the UNIMI part of the GRADFLEX experimental setup, NEFs are induced in a binary mixture by means of the Soret effect. The diagnostic method is an all-optical quantitative shadowgraph technique. The power spectrum of the induced NEFs is obtained by the processing of the shadowgraph images. A detailed description of the experimental apparatus as well as the ground-based experimental results is presented here for the UNIMI-INFM experiment. The GRADFLEX payload is scheduled to fly on the FOTON M3 capsule in April 2007.

Experiences from the design, deployment, and usage of the UCSB meshnet testbed

In this article we report on our effort and experience in designing, deploying, and using our 30-node wireless mesh testbed, the University of California at Santa Barbara (UCSB) MeshNet. Compared to simulation, the construction and utilization of a wireless mesh testbed poses many new challenges. We discuss the challenges with distributed testbed management, nonintrusive and distributed monitoring, and node status visualization. These are vital components in a sustainable wireless mesh testbed, but at the same time nontrivial to design and. realize. As a case study, we present the UCSB MeshNet architecture, including its management, monitoring, and visualization systems. We share our lessons learned from this effort and believe that they are valuable to other researchers who develop experimental wireless mesh networks

All-optical label swapping networks and technologies

All-optical label swapping is a promising approach to ultra-high packet-rate routing and forwarding directly in the optical layer. In this paper, we review results of the DARPA Next Generation Internet program in all-optical label swapping at University of California at Santa Barbara (UCSB). We describe the overall network approach to encapsulate packets with optical labels and process forwarding and routing functions independent of packer bit rate and format. Various approaches to label coding using serial and subcarrier multiplexing addressing and the associated techniques for label erasure and rewriting, packet regeneration and packet-rate wavelength conversion are reviewed. These functions have been implemented using both fiber and semiconductor-based technologies and the ongoing effort at UCSB to integrate these functions is reported. We described experimental results for various components and label swapping functions and demonstration of 40 Gb/s optical label swapping. The advantages and disadvantages of using the various coding techniques and implementation technologies are discussed.

Ginzburg–Landau model for a long-pulse low-gain free-electron laser oscillator

The Ginzburg–Landau model for the radiation field of a free-electron laser (FEL) was originally derived for a high-gain amplifier (S.Y. Cai and A. Bhattacharjee, Phys. Rev. A 43 (1991) 6934). With a view to making precise comparisons with experimental data from the long-pulse FEL oscillator at the University of California at Santa Barbara (UCSB) (L.R. Elias, G. Ramian, J. Hu, A. Amir, Phys. Rev. Lett. 57 (1986) 424), we have developed a new formulation of the Ginzburg–Landau model starting from the low-gain oscillator equations. We implement a small-amplitude expansion of the radiation field, and derive the coefficients of the Ginzburg–Landau equation by analysis as well as by Mathematica. Stability analysis of the Ginzburg–Landau equation produces results similar to those obtained by T.M. Antonsen and B. Levush (Phys. Fluids B 1 (1989) 1097). These include the stability of the main mode (no Benjamin–Feir instability), phase-unstable off-centered modes (Eckhaus instability), as well as relaxation to the single mode which occurs much faster in amplitude than in phase. We obtain the saturated radiation amplitude a 0 as functions of the detuning parameter p inj and cavity loss, and determine the phase instability boundary in the a 0− p inj plane. The probability of realizing a single mode starting with random initial conditions is calculated and compared with spectral measurements from the UCSB FEL.

Neural modelling of chemical plant using MLP and B-spline networks

This paper demonstrates the potential of the B-spline neural network (BSNN) for the modelling of nonlinear processes. The performance of this paradigm is compared with the multi-layer perceptron (MLP), for the modelling of experimental and industrial case-studies. The experimental pH neutralisation plant of the University of California at Santa Barbara (UCSB) is modelled using both networks. This case-study demonstrates the higher performance of the B-spline network, for rapid on-line model adaptation. The second casestudy focuses on the prediction of viscosity for an industrial polymerisation reactor. Predictive models of viscosity are developed, based on both networks to predict over and hence remove the measurement time-delay introduced at the viscometer. A novel disturbance modelling approach is also developed here, and demonstrated to perform excellently in online tests

The ready-to-go virtual circuit protocol: a loss-free protocol for multigigabit networks using FIFO buffers

The ready-to-go virtual circuit protocol (or RGVC) is an immediate transmission protocol, in which the source need not wait for an end-to-end roundtrip delay for reservations to be made before transmitting the data. The protocol is designed to handle the lossless transport of ABR traffic, and will be used in the 40 Gb/s Thunder and Lightning testbed being prototyped at the University of California at Santa Barbara (UCSB). An important advantage of the RGVC protocol over previous connection and flow control protocols is that it is suitable for networks in which the switches use FIFO buffers that are shared by multiple sessions. The RGVC protocol ensures lossless communication by coupling link capacity with buffer space, so that when a portion of a buffer at a node is occupied, a proportional fraction of the incoming capacity to that buffer is frozen. Given the constraints on the frozen capacity, an algorithm is executed at each node to allocate the transmission rate to each FIFO buffer so as to maximize capacity utilization. The requirement that the protocol operate with FIFO buffers at the network nodes poses some unique challenges in the design that are not present in rate- and credit-based schemes. Briefly, since several sessions share a common FIFO buffer, per-VC flow control is no longer possible so control over the rate of an individual session is lost. Also, since the contents of the buffers change dynamically, the buffer composition becomes difficult to determine. For the rate-allocation algorithm of the RGVC protocol to be executed, however, the contents of the FIFO buffers at a node must be known, To implement the bookkeeping required, we present two schemes: the measurement-based scheme, where the bookkeeping function is implemented via measurements, done essentially in hardware; and the estimation-based scheme, where the bookkeeping is done analytically via the exchange of control packets between nodes.

Designs for an infrared free-electron laser based on gyrotron-powered electromagnetic wigglers

The possibility of developing gyrotron-powered electromagnetic wiggler free-electron laser (FEL) oscillators is of considerable interest for reducing the electron energy required for operation in the infrared spectrum. This paper considers the design of a 10.6 /spl mu/m electromagnetic wiggler FEL experiment based on the University of California at Santa Barbara (UCSB) 6 MeV electrostatic accelerator. Both waveguide and quasioptical wiggler resonator configurations are considered. A prescription for optimizing the gain of a waveguide electromagnetic wiggler FEL is derived and the nonlinear regime is treated by relating the electromagnetic wiggler FEL equations-of-motion to the universal normalized FEL equations. Point designs are given showing accelerator, gyrotron, and output parameters for 10.6 /spl mu/m Proof-of-Principle FEE experiments based on both waveguide gyrotron and quasioptical gyrotron wigglers. Designs are given for both a 5- and a 2-A FEL electron beam. >

Bandwidth narrowing of the UCSB FEL by injection seeding with a cw laser

Narrow bandwidth operation of a free electron laser (FEL) at the University of California at Santa Barbara (UCSB) by seed injection from an external continuous wave molecular laser has been demonstrated. The pulse-to-pulse frequency bandwidth was reduced by one order of magnitude, from 1.6 to 0.16 GHz and an order of magnitude reduction of the sideband mode beating was observed in a single pulse together with a 30% reduction in laser startup time. Numerical simulations of the multimode FEL show that in normal operation of the UCSB FEL sideband mode suppression is rather slow underlining the importance of seeding to obtain single-mode operation for the available pulse length.

Computers for GIS

The National Center for Geographic Information and Analysis at the University of California at Santa Barbara (UCSB) announced October 30 a joint project with International Business Machines Corp. to work on the next generation of geographic information systems (GIS).Under the 3‐year contract, IBM's University and College Systems organization will supply $23 million in computer equipment. The center will evaluate the IBM hardware and software and make available to IBM hardware, software, curriculums and other materials developed using the computers.

New group to focus on crust

Earth scientists from the University of California at Santa Barbara (UCSB) will form an interdisciplinary research group to study Earth's crust and lithosphere, it was announced recently. The Institute for Crustal Studies (ICS) will consist of members of the Department of Geological Sciences and other departments at UCSB.

Volcanoes and Extinctions: Round Two

In 1979, a group of researchers injected new life into an old study of death. Led by Alvarez at the University of California at Berkeley, they proposed that an asteroid had crashed into the earth at the end of the Cretaceous period, 65 million years ago. This impact, they suggested, threw a blanket of dust into the atmosphere, which blocked out the sunlight, causing famine and mass extinctions (SN: 6/2/79, p.356). most famous casualties were the dinosaurs. Now, after stimulating a whirlwind of research in paleontology, stratigraphy, geochemistry, astrophysics and statistics, Alvarez believes the impact theory of the Cretaceous-Tertiary (K-T) extinctions on solid enough ground for him to move on to other geologic pursuits. As he concluded last fall in Eos, the weekly newspaper of the American Geophysical Union, ... the unusual features of the K-T [stratigraphic] boundary layer are exactly compatible with a major impact. competing theory that intense volcanic eruptions caused the extinctions (SN: 3/16/85, p.172), he suggested, simply cannot account for all of the evidence. Alvarez may have hoped that his Eos article, by carefully outlining all the evidence and what he sees as the shortcomings of the volcanic hypothesis, would put the debate to rest. But for some researchers, it only sparked more arguments for the volcanic cause. At issue the resolution of one of the most intriguing puzzles in science. By understanding what killed off the dinosaurs and three-quarters of the species living on earth 65 million years ago, researchers not only would solve a longstanding mystery of the past, but might catch a glimpse of what could befall the planet in the future. Walter [Alvarez] says the volcanic road shut. I think, on the contrary, it very wide open, says Vincent E. Courtillot, who visiting the University of California at Santa Barbara (UCSB) from the Institut de Physique du Globe in Paris. In a letter in the April 7 Eos, Courtillot and Stanley Cisowski of UCSB respond to Alvarez's Eos paper. The purpose of this letter, they write, is to stress that answers have changed rapidly in recent years and may still evolve, and that the case for a volcanic cause may have been determined extinct by Alvarez somewhat prematurely Courtillot and Cisowski are not alone. Charles Officer at Dartmouth College in Hanover, N.H., and his colleagues published a paper in the March 12 NATURE that outlines the volcanic arguments and looks in detail at how a series of large volcanic eruptions could affect the environment and life. Among the recent lines of evidence and theory that have motivated Courtillot and Officer to write their papers are: *A date for the Deccan Traps. Deccan Traps in India are vast flood basalts, or lava flows, that today cover an area about the size of France and may once have contained 1 million cubic kilometers of volcanic material. Proponents of the volcanic theory have suggested that the Deccan eruptions caused the K-T extinctions by spewing out sulfur and other volcanic material that darkened the skies, cooled the planet and produced acid rain. But the correlation between the K-T extinctions and the Deccan Traps has been sketchy at best, says Courtillot, because the traps have not been very precisely dated. While the most frequently quoted age for the traps falls around 60 million to 65 million years old, he says, other estimates, determined 6 68 7 72; .--.76 80 B4 88 92 96 36! (' '. |

The Development and Validation of an Instrument to Measure Student Orientation to Humanistic Instructional Values

IN an attempt to identify the essential components in humanistic instruction, a content analysis of the writings of 40 well-known and representative humanistic educators yielded 15 major operating values. An interrater index of agreement of .83 was found. Preliminary construct validity on two of the 15 variables was demonstrated in that a sample of Master of Arts (MA) students in Confluent Education (involving a humanistic orientation) at the University of California at Santa Barbara (UCSB) showed significantly higher scores than did other MA groups of comparable ability and educational background. In the current study all 15 variables were measured in two 135-item equivalent forms A and B of the Orientation to Learning (OTL) scale. Predictions were that Confluent Education students would score highest, that Counseling Psychology students would fall at an intermediate level, and that three remaining MA and Credential groups would score lowest. Further, to establish external validity, Forms A and B were correlated with the N plus F subscales (NF Temperament) on the Kiersey Temperament Sorter instrument and with the Concrete plus Reflective subscales (Divergent Learning Style) on the Kolb Learning Style Inventory (LSI). A sample of 99 students from five programs was randomly assigned forms A and B of the OTL questionnaire. Reliabilities for Forms A and B of the OTL ranged from .93 to .95. The rank order of student groups on the variables studied was as predicted. There was a highly significant main effect associated with group differences, (p < .0001). Correlations with the NF temperament (Kiersey) and the Concrete learning subscale (LSI) were statistically significant. It was concluded that the instrument is apparently reliable and that it has promising construct and external validity.

Scientific research with the UCSB free electron laser

The University of California at Santa Barbara (UCSB) free electron laser (FEL) operates as a high-power, continuously tunable, coherent source of radiation in the submillimeter and far infrared (FIR) region. As an initial phase of the UCSB FEL science research program, a set of experiments in condensed matter science have been selected to demonstrate the unique capabilities of this new source. A summary of the proposed studies is presented here.

Harmonic Approximation with Dirichlet Data on Doubly Connected Regions

We consider finding a solution to Laplace's equation in certain doubly connected regions for which one of the boundary curves is given by a trigonometric polynomial. Reflection in parametric form is used to reduce the problem to solving a single integral equation in one unknown. Numerical results are compared with exact solutions for regions bounded by two concentric circles and by two ellipses. A finite element method using Gaussian quadrature is used to solve the singular integral equation. 1. Introduction. We examine a method for obtaining the numerical solution of the plane Dirichlet problem for Laplace's equation for a doubly connected region D; one boundary curve L 1 is assumed to be piecewise smooth and the other Lo is assumed to be analytic. The method has been investigated theoretically in (8). The method is based on utilizing reflection to reduce the solution of the problem to solving an integral equation. By restricting the region to be bounded by an analytic Lo, of a type to be explained later, the number of integral equations is reduced from two equations in two unknowns to one equation in one unknown. In the approximation this reduces the number of linear equations to be solved by one half. The integral equation was applied to two test cases, the case when Lo was (i) a circle and (ii) an ellipse. There are many methods available for solving integral equations of this type see e.g. (1), (2), (3), (4), (6), (9). We used a modified finite element method with two point Gaussian quadrature. This method is particularly well suited for integral equations of the type treated, since the Gauss points are not nodal points and hence the singularity of the kernel causes little trouble. Also the spacing on the curve need not be of equal arc length. The curve Lo was generated on the University of California at Santa Barbara (UCSB) On-Line System and once L1 is given, the reflected curve L1 is easily obtainable. For the two examples, an exact solution is compared with approximate solutions at various points in the field. See Tables 1, 2 and 3 in ? 5. Though the method is not universal, when it can be applied it reduces the number of linear equations to be solved and gives an accurate approximate solution.

Authors

Authors

A Training Program for Supervisors: Anatomy of an Educational Development

In mid-1970 the University of California at Santa Barbara (UCSB) initiated development of a training program for supervising teachers who work with student teachers. After three years of development work, UCSB produced a self-contained Instructional Supervision Training Program (ISTP) which has demonstrated its capability for advancing selected supervisory skills in both college and local school system contexts. A preliminary version of ISTP was tested in nine field sites across the U.S. in 1972-73. All told, sixty different scores were available for the analysis of training effects; fifty-three of the scores are in the desired direction and forty five were statistically significant. The preliminary version was subsequently modified on the basis of field test results and feedback from field test users.