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# Mathematics Colloquium Schedule

**Fall 2016 **

**Date: 11-18-2016 (12-1pm, F03-200A), Dr. Catherine Pfaff, UCSB**

**Title:** TBA

**Abstract:** TBA

**Date: 11-10-2016 Thursday (12:30-1:30pm, F03-200A), Dr. Bob Stein, Professor Emeritus of Mathematics, Cal State San Benardino**

**Title:** The Remarkable History of Exponents and Logarithms

**Abstract:** Today we rarely compute with logarithms, and we take exponents largely for granted, but those topics were once at the center of mathematical interest. This talk will focus both on the development of these ideas, and on the astonishing people involved. No mathematics beyond first year calculus will be needed to understand this talk.

**Date: 10-28-2016 (12-1pm, F03-200A), Dr. Lee Peterson, Jet Propulsion Laboratory**

**Title:** Simulating Space: Role of Advanced Modeling and Uncertainty Quantification in JPL Missions

**Abstract:** Critical phases of spacecraft missions often cannot be completely tested on Earth, because of differences in the environments found in space and on other planetary bodies. When this happens, engineers resort to high fidelity models, informed by tests, are needed to verify readiness for flight. This talk will provide an overview of some recent applications of high fidelity models and simulations at JPL. It will include some discussion of the role of uncertainty quantification (UQ) as part of a Quantification of Margins and Uncertainties (QMU) engineering approach.

**Date: 10-21-2016 (1pm-2pm, F03-200A), Dr. Khue Duong, CSULB library**

**Title:** Data Science, Data Services, a Sabbatical Reflection

**Abstract:** Data comes in different sizes and formats: computer codes, spreadsheets, audio recording, images, fieldnotes, genome sequences, or geospatial coordinates. Data science, as an interdisciplinary study, incorporates many academic disciplines from mathematics and statistics to computer science, information science and geographic information system. Furthermore, research articles from scientific journals such as Science, Nature, or PLOS One increasingly require supplementary data or pointers to data repositories where one can access the dataset for further analysis or replication of the original research. My talk approaches data from a librarian’s perspectives and is a direct result of a four-month sabbatical to learn about how academic libraries support of data services—from providing reviews of mandated data management plans and finding discipline-specific datasets or data repositories to teaching data literacy workshops. I hope to highlight a few resources where one can learn more about data science.

**Date: 10-11-2016 (Tuesday! 12-1pm, F03-200A), Dr. Geng Chen, University of Kansas**

**Title:** Lipschitz metric for a nonlinear wave equation

**Abstract:** The nonlinear wave equation: u_{tt} - c(u)[c(u)u_x]_x = 0 is a natural generalization of the linear wave equation. In this talk, we will discuss a recent breakthrough addressing the Lipschitz continuous dependence of solutions on initial data for this quasi-linear wave equation. Our earlier results showed that this equation determines a unique flow of conservative solution within the natural energy space H^1(R). However, this flow is not Lipschitz continuous with respect to the H^1 distance, due to the formation of singularity. To prove the desired Lipschitz continuous property, we constructed a new Finsler type metric, where the norm of tangent vectors is defined in terms of an optimal transportation problem. For paths of piecewise smooth solutions, we carefully estimated how the distance grows in time. To complete the construction, we proved that the family of piecewise smooth solutions is dense, following by an application of Thom's transversality theorem. This is a collaboration work with Alberto Bressan.

**Date: 9-23-2016 (12-1pm, F03-200A), Dr. Gabriel Udomkesmalee, Jet Propulsion Laboratory**

**Title:** JPL Robotics

**Abstract:** The Robotics Section of the Jet Propulsion Laboratory (JPL), California Institute of Technology, is engaged in a full spectrum of flight project and research activities. This talk will provide an overview of the efforts and discuss the recent accomplishments and future directions of them. Specific activities will be high-lighted based on their level of accomplishment, impact on the community, maturity, or novelty. Robotics activities on flight projects are a significant subset of the full effort for these large missions. Complementing flight activities is a diverse set of research efforts for NASA and other U.S. Government agencies. Future directions will be motivated by NASA and other sponsor objectives, as well as success experienced in these current endeavors.

**Date: 9-2-2016 (12-1pm, F03-200A), Dr. Minh N. Tran, Department of Mechanical and Aerospace Engineering, UC Davis**

**Title:** Nuclear Engineering for Everyone

**Abstract:** External loads are important, often well understood, and taken into account in the design of mechanical or structural components. However, there are other factors that can significantly affect the performance of materials, such as pre-existing defects and residual stresses. Those factors are usually difficulty to detect and quantify, and thus they are easy to overlook and ignore in the design phase. The work presented in this talk focuses on the residual stresses due to welding and was developed in the context of research with the nuclear power industry. Weld process models, based on nonlinear finite element computations, are frequently employed to estimate residual stresses in plant components, and those estimates are used to support plant management decisions. Therefore, we will begin with an introduction of a finite element model to predict residual stresses due to the manufacturing process of a pressurizer surge nozzle, used in the cooling system of pressurized water reactors. Modeling results are commonly evaluated at room temperature in order to validate against measurements, which are conducted at room temperature. However, in addition to weld residual stress produced in the course of manufacturing, plant components are subject to internal water pressure and elevated temperature during operation. Thus, we will next investigate the changes in weld residual stress state due to the presence of internal pressure and temperature at operating conditions. In the end, the purpose of computing residual stress is most often to determine its effect on component operability. For that reason, we will conclude the talk with a service life assessment of the pressurizer surge nozzle presented in this talk.