Phd Dissertation

Development of Dielectric Elastomer Nanocomposites as Stretchable and Flexible Actuating Materials

Publication Date

June 30, 2015

Author(s)

Areas of Expertise

Abstract

Dielectric elastomers (DEs) are a new type of smart materials showing promising functionalities as energy harvesting materials as well as actuating materials for potential applications such as artificial muscles, implanted medical devices, robotics, loud speakers, micro-electro-mechanical systems (MEMS), tunable optics, transducers, sensors, and even generators due to their high electromechanical efficiency, stability, lightweight, low cost, and easy processing. Despite the advantages of DEs, technical challenges must be resolved for wider applications. A high electric field of at least 10-30 V/um is required for the actuation of DEs, which limits the practical applications especially in biomedical fields. We tackle this problem by introducing the multiwalled carbon nanotubes (MWNTs) in DEs to enhance their relative permittivity and to generate their high electromechanical responses with lower applied field level. This work presents the dielectric, mechanical and electromechanical properties of DEs filled with MWNTs. The micromechanics-based finite element models are employed to describe the dielectric, and mechanical behavior of the MWNT-filled DE nanocomposites. A sufficient number of models are computed to reach the acceptable prediction of the dielectric and mechanical responses. In addition, experimental results are analyzed along with simulation results. Finally, laser Doppler vibrometer is utilized to directly detect the enhancement of the actuation strains of DE nanocomposites filled with MWNTs. All the results demonstrate the effective improvement in the electromechanical properties of DE nanocomposites filled with MWNTs under the applied electric fields.

Suggested Citation
Yu Wang (2015) Development of Dielectric Elastomer Nanocomposites as Stretchable and Flexible Actuating Materials. PhD Dissertation. UC Irvine. Available at: https://uci.primo.exlibrisgroup.com/permalink/01CDL_IRV_INST/1gpb62p/alma991016230969704701.

Phd Dissertation

Research universities as gateways: The expanding roles of higher education institutions and their contribution to economic development

Publication Date

September 30, 2021

Author(s)

Areas of Expertise

Abstract

The past 30 years have witnessed a gradual expansion in the missions of many universities, and in the ways in which they contribute to local and regional economic development. While teaching and research continue to serve as the foundational core of most university missions, increased attention has been afforded to how universities, by their presence and functions, influence the spatial geographies of neighborhoods, cities, and regions. This dissertation research explores the changing roles of research universities in small and medium-sized metropolitan areas with an emphasis on their impacts across the different geographical scales by investigating associations between university presence and (1) growth in foreign-born populations; (2) the attraction and retention of highly educated residents; and (3) student-driven neighborhood change dynamics. The findings of this dissertation extend previous studies emphasizing the increasing importance of higher education institutions to economic development activities at various scales. Results from metropolitan area level analyses demonstrate that counties with large research universities were associated with an increase in foreign-born residents following the 1990 Immigration and Naturalization Act, as well as an increase in highly educated residents in the 2000-2014 period. More specifically, while findings revealed that the presence of research universities generate significant spatial spillovers of highly educated residents from university host counties to metropolitan levels, there was little evidence of such spatially-explicit dynamics occurring amongst foreign-born residents. Furthermore, findings from neighborhood-level analyses indicated that proximity to large research university campuses may play an outsized role on the likelihood of neighborhoods undergoing studentification (i.e., student-driven neighborhood change) in the 2000-2014 period. These results may be indicative of a bifurcation of neighborhoods in university-dominant counties into wealthy and highly educated renter populations situated near the university campus, and relatively less wealthy and less educated homeowners residing on the further away from the campus or on the periphery of the county. By exploring university contributions beyond the spheres of research, teaching, and service contributions, this dissertation presents scholars, urban planners, and policymakers with a more comprehensive portrait of the relationship between universities and their host communities. The evidence of this work suggests that the evolving role of higher education institutions, including their role as gateways for new populations, should be reflected in policymaking which seeks to leverage the locational advantages of research universities for city building or revitalization efforts. Further, policymakers and planners should also be cognizant that scale matters when considering how higher education institutions can better serve their surrounding communities. The contributions of research universities should not be thought of as monolithic or uniform, but should rather be seen as presenting different opportunities and challenges at different geographical levels.

Suggested Citation
N Osutei (2021) Research universities as gateways: The expanding roles of higher education institutions and their contribution to economic development. PhD Dissertation. UC Irvine. Available at: https://escholarship.org/uc/item/5x68r902.

research report

Development of New Privacy-preserving Method for Traffic Data Collection and Analysis: The Bathtub Model Approach

Publication Date

February 1, 2026

Author(s)

Wenlong Jin, Joseph H. F. Lo

Areas of Expertise

Abstract

Traditional data collection approaches present significant drawbacks in computational costs and limited privacy protection. This research evaluates the bathtub traffic flow model as a privacy-preserving alternative to traditional methods that require detailed network layouts and individual trip data. The study assesses the feasibility of the bathtub model through calibration and validation using Bluebikes data from Metro Boston, focusing on three key components: the unified relative space paradigm, conservation equations, and the generalized bathtub model. Results demonstrate that the unified relative space paradigm successfully integrates network trips by considering remaining trip distances, though the trip distance distribution exhibited a log-normal pattern rather than the time-independent negative exponential distribution in Vickrey’s original bathtub model. Conservation equations for total trips and trip-miles traveled showed high accuracy, and the generalized bathtub model yielded accurate results, particularly for space-mean speed. This novel approach preserves privacy by eliminating the need for origin-destination data while still effectively capturing network dynamics.

research report

CARMEN Project 6: PNT with Signals of Opportunity and Real-World Jammed and Spoofed Environments

Publication Date

November 30, 2023

Author(s)

Zak Kassas

Areas of Expertise

Suggested Citation
Zak Kassas (2023) CARMEN Project 6: PNT with Signals of Opportunity and Real-World Jammed and Spoofed Environments. Final Report. CARMEN UTC. Available at: 10.5281/ZENODO.10256685.

Preprint Journal Article

Priority Queue Formulation of Agent-Based Bathtub Model for Network Trip Flows in the Relative Space

Abstract

Agent-based models have been extensively used to simulate the behavior of travelers in transportation systems because they allow for realistic and versatile modeling of interactions. However, traditional agent-based models suffer from high computational costs and rely on tracking physical locations, raising privacy concerns. This paper proposes an efficient formulation for the agent-based bathtub model (AB2M) in the relative space, where each agent’s trajectory is represented by a time series of the remaining distance to its destination. The AB2M can be understood as a microscopic model that tracks individual trips’ initiation, progression, and completion and is an exact numerical solution of the bathtub model for generic (time-dependent) trip distance distributions. The model can be solved for a deterministic set of trips with a given demand pattern (defined by the start time of each trip and its distance), or it can be used to run Monte Carlo simulations to capture the average behavior and variation stochastic demand patterns, described by probabilistic distributions of trip distances and departure times. To enhance the computational efficiency, we introduce a priority queue formulation, eliminating the need to update trip positions at each time step and allowing us to run large-scale scenarios with millions of individual trips in seconds. We systematically explore the scaling properties and discuss the introduction of biases and numerical errors. The systematic exploration of scaling properties of the modeling of individual agents in the relative space with the AB2M further enhances its applicability to large-scale transportation systems and opens up opportunities for studying travel time reliability, scheduling, and mode choices.

Suggested Citation
Irene Martinez and Wen-long Jin (2023) “Priority Queue Formulation of Agent-Based Bathtub Model for Network Trip Flows in the Relative Space”. arXiv. Available at: 10.48550/arXiv.2309.01970.

working paper

Used Oil Policies to Protect the Environment: An Overview of Canadian Experiences

Publication Date

September 1, 2001

Working Paper

UCI-ITS-WP-01-5, UCTC 666

Areas of Expertise

Abstract

We examine some consequences of dumping used oil in the environment and review some policies to foster used oil recycling. We then contrast policies adopted in the Canadian Prairie Provinces for managing used oil, used oil filters, and containers, with those put in place in the rest of Canada. Our analysis proposes that public-private partnerships relying on economic instruments and public education can be more effective for recycling used oil than public agencies relying mostly on regulations.

Suggested Citation
Hilary Nixon and Jean-Daniel Saphores (2001) Used Oil Policies to Protect the Environment: An Overview of Canadian Experiences. Working Paper UCI-ITS-WP-01-5, UCTC 666. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/8x15b0x7.

Phd Dissertation

EPITAXIS: A system for syntactic and semantic software queries using deductive retrieval and symbolic execution

Publication Date

January 1, 2010

Author(s)

Areas of Expertise

Abstract

Modern computer hardware (multi-core, multi gigahertz processors with gigabytes of RAM and terabytes of disk) along with IDEs allows programmers to build computer programs which are bigger and more complex than they can understand or keep in their working memories. Additionally, the problems these programs are designed to model are ever more complicated. Consequently, programs are full of inconsistencies, mistakes, and incompleteness’s. These problems are difficult to detect, difficult to locate, and difficult to correct. Often a change is made by a programmer to fix a problem for which understanding all the repercussions of the change is difficult. Consequently, further bugs are introduced into the code base. Because of the pervasiveness of software in society and the potential severity of the consequences of bugs, software developers need ever better tools to help them understand, navigate, and follow the consequences of their development and maintenance activities. This dissertation presents a novel framework based on tree/graph searching and parsing, deductive retrieval, dynamic analysis, symbolic execution, aspect oriented programming, and an open interpreter to allow a software developer to navigate, locate features, find bugs, and abstract information in software. The system is designed to have a fast modify-test cycle such that the programmer can search and test the software as it is being edited without time consuming recompilation, reinstrumenting, or database repopulating each time an edit is made to the code base. The system is language independent, requiring only files to specify the language grammar, control flow graph transformation, and execution semantics. In addition, because of the flexibility and programmability of the system it is an excellent environment to perform further research on program analysis techniques such as dynamic analysis, symbolic execution and abstract interpretation. A prototype system has been built along with data files for the C programming language which demonstrates the feasibility of the system and its ability to scale to “modern-sized” programs.

Suggested Citation
James Benvenuto (2010) EPITAXIS: A system for syntactic and semantic software queries using deductive retrieval and symbolic execution. Ph.D.. University of California, Irvine. Available at: https://uci.primo.exlibrisgroup.com/permalink/01CDL_IRV_INST/17uq3m8/alma991007560609704701 (Accessed: October 13, 2023).