Spring 2023 seminar

2 pm on 2/2

Steinman Hall Room 254

https://ccny.zoom.us/j/81357159148?pwd=Ym1maGRUeURDeTN3Y3RZOThaNUg0dz09

ABSTRACT

When an initial contact occurs between two drops, a liquid bridge is formed between them and grows rapidly. This phenomenon is known as drop coalescence. Although the evolution of the liquid bridge is driven by surface tension during the coalescence process, there exist regimes dominated by viscous or inertial force, which are identified by scaling relations of the temporal growth of the bridge. These scaling relations have been obtained by studying unconfined drops (i.e., spherical drops) or partially confined drops (i.e., drops resting on a plane). We experimentally investigated confined drop coalescence in Hele-Shaw cell devices, which were formed by two parallel hydrophobic surfaces with controllable spacing. Two aqueous drops were slowly grown in a Hele-Shaw cell that was pre-filled with a different continuous phase (CP), air for three-phase and mineral oil for two-phase drop coalescence, respectively. The growing bridge of drops coalescing in the Hele-Shaw cell was captured using high-speed video microscopy, and the time-dependent diameter of the liquid bridge was measured. The scaling exponent of the growth of the liquid bridge between drops at the early stage was identical (= 1) in both two-phase and three-phase confined drop coalescence studies, consistent with the scaling exponent of unconfined drop coalescence at the early stage. When the CP of drop coalescence in Hele-Shaw cells had high viscosity, the transition to the late stage of drop coalescence occurred before the diameter of the liquid bridge approached the gap width of the Hele-Shaw cell. It suggested that the effect of the confinement was diffused to drops through the surrounding fluid with high viscosity because of momentum diffusion. In addition, we studied the location and generation mechanism of entrapped air bubbles specific to the three-phase confined drop coalescence experimentally. These results from this study helped to unveil the effects of confinement on drop coalescence.

BIO

Haipeng Zhang is currently a Postdoctoral Research Associate in the Department of Pharmacology and Regenerative Medicine at the University of Illinois at Chicago. He received his Ph.D. degree and M.S. degree in Mechanical & Materials Engineering from the University of Nebraska-Lincoln in 2022 and in 2018, respectively, and his B.S. degree in Mechanical Engineering from the Kitami Institute of Technology, Japan in 2007. He also worked for the pump department at the Beijing Office (China) of the KUBOTA Corporation between 2009 to 2015. His previous work experimentally characterized the interfacial phenomena of liquid drop behaviors in multiphase systems, particularly the effects of the confining substrates on drop coalescence and pinch-off. He was the recipient of 2020-2021 Graduate Returning Scholarship Award, 2019-2020 Graduate Student Scholarship Award from the ASME Fluids Engineering Division, and 2022 Reviewers of the Year Award from ASME.

2 pm on 2/9

Steinman Hall Room 254

https://ccny.zoom.us/j/81357159148?pwd=Ym1maGRUeURDeTN3Y3RZOThaNUg0dz09

ABSTRACT

After millions of years, living organisms have evolved to develop well-adapted structures and compositions. Nature has been able to solve numerous biological problems such as self-healing, self-assembly, and solar energy harnessing. Humans have looked to nature for solutions to our problems throughout our existence. In this talk, several bioinspired multifunctional materials including nanostructured coatings with outstanding mechanical, barrier, and flame retardant properties (inspired by nacre) and highly sensitive and reversible/irreversible mechanochromisms (inspired by cephalopod and skin wrinkles) will be presented. The macro/nano-scale designs for these materials were all inspired by the diverse biological solutions found in nature, with the goal to potentially surpass their natural counterparts and bring new functionalities to these brilliant structures. Their broad applications in construction, packaging, biomedical engineering, and wearable electronics will also be discussed.

BIO

Dr. Luyi Sun is a professor in the Department of Chemical and Biomolecular Engineering, as well as a member of the Polymer Program at the University of Connecticut. His research focuses on the design and synthesis of nanostructured materials for various applications. Dr. Sun has published >270 peer-reviewed journal articles. He is the inventor/co-inventor of >70 international/US patents and patent applications. Many of his patents have been licensed or commercialized. The scientific results by Dr. Sun’s group have been reported by major media including Chemical & Engineering News of the American Chemical Society, Plastics Engineering magazine of the Society of Plastics Engineers (SPE), New Scientist, Smithsonian Magazine, Yahoo, MSN, etc. He is a Fellow of the Society of Plastics Engineers (SPE), the Royal Society of Chemistry (RSC), and the National Academy of Inventors (NAI), and a member of the Connecticut Academy of Science and Engineering (CASE).

2 pm on 2/28

Steinman Hall Room 312

Simultaneous Zoom Link [Please note passcode is required: blevich]

ABSTRACT

During embryonic development, groups of cells reorganize into functional tissues with complex form and structure. Tissue reorganization can be rapid and dramatic, often occurring through striking embryo-scale flows that are mediated by the coordinated actions of hundreds or thousands of cells. In Drosophila, cell rearrangements in the embryonic epithelium rapidly narrow and elongate the tissue, producing a tissue flow that doubles the length of the body axis in just 30 minutes. These types of tissue movements can be driven by internal forces generated by the cells themselves or by external forces. While much is known about the molecules involved in these cell and tissue movements, it is not yet clear how these molecules work together to coordinate cell behaviors, give rise to emergent tissue mechanics, and generate coherent flows at the embryo scale. To gain mechanistic insight into this problem, my lab combines genetic and biophysical approaches with emerging optogenetic technologies for manipulating molecular and mechanical activities inside cells with high precision. I will discuss some of our recent findings on how cellular properties and mechanical forces are regulated in the Drosophila embryo to allow (or prevent) rapid cell rearrangements and tissue flows during specific events in embryonic development.  

BIO

Karen received a B.A. in Physics from the University of Chicago, a Ph.D. in Applied Physics from Harvard University, and did her postdoctoral research at the Sloan Kettering Institute. Since 2016, she has been a faculty member in the Department of Mechanical Engineering at Columbia University, where she is currently an associate professor. Karen is the recipient of a Sloan Research Fellowship in Physics, 2022; Packard Fellowship for Science and Engineering, 2018; NSF CAREER Award, 2018; Clare Boothe Luce Assistant Professorship, 2016; Burroughs Wellcome Fund Career Award at the Scientific Interface, 2014.

2 pm on 5/30

Steinman Hall Room 254

https://ccny.zoom.us/s/86054592177

password: 123456

ABSTRACT

Dr. Sanz-Pena’s research focuses on developing wearable assistive robots and orthotics with embedded sensing capabilities for healthcare applications to increase biofeedback monitoring capabilities and improve the quality of life. His approach is the implementation of metamaterials in the components of biomechatronic devices using additive manufacturing and computational design. He is currently working on modular additively manufactured wearable robots to improve biomimicry and personalization and increase the proprioception of exoskeletons. As part of this effort, he is focusing on embedding pressure and motion sensing in the material and structural properties of robots using piezoresistive elements and parametric design of architected materials.

BIO

Dr. I. Sanz-Pena is a Postdoctoral Research Associate at the Rehabilitation Robotics Laboratory at the University of Illinois at Chicago, Department of Mechanical and Industrial Engineering. He received his Ph.D. with Summa Cum Laude honors from Universidad de La Rioja, Spain, in collaboration with New York University (NYU) and held post-doctoral appointments at Imperial College London at the Biomechanics Group. He was a Research Associate at the NYU Langone Orthopedic Hospital and a project engineer at Biele Group.

2 pm on 6/1

Steinman Hall Room 254

https://ccny.zoom.us/s/86054592177

password: 123456

ABSTRACT

Heterogeneous networks are multi-agent systems that contain different dynamical models. A multi-vehicle system usually contains different types of vehicles that may possess different parameters and dynamics. For instance, a combination of ground, marine, and aerial vehicles can be used for military operations to increase the striking force from multiple sources. Nevertheless, efforts to develop cooperative control approaches applicable to heterogeneous multi-vehicle systems have been limited. Moreover, nonholonomicity and underactuation are two main obstacles in the control design for multi-vehicle systems. The problem of cooperative control of underactuated networks is far more complicated than control of fully-actuated networks.

This talk is devoted to introducing several distributed control approaches that are applicable to multi-vehicle systems. We shall present the following problems for heterogeneous underactuated and nonholonomic multi-vehicle systems:

1)  Robust formation control. By exploiting the structural properties of the planar vehicle model, a robust formation control framework is proposed for planar underactuated vehicle networks.

2) Formation stabilization and tracking control. A time-varying control strategy is presented to solve the simultaneous formation stabilization and tracking control problem for planar vehicles based on persistency of excitation.

3) Source seeking control. We propose a source seeking scheme for generic force-controlled underactuated vehicles by surge force tuning. The controller requires only real-time measurements of the source signal and ensures practical stability with respect to the linear motion coordinates for the closed-loop system.

In addition to the above theoretical analysis and control designs, we also apply these theoretical tools to real vehicle systems, including nonholonomic mobile robots, underactuated surface vessels, and quadcopters, to validate our control algorithms.

BIO

Bo Wang is a Postdoctoral Scholar of Mechanical Science and Engineering at the University of Illinois Urbana-Champaign. He received the M.S. degree in Control Theory and Engineering from the University of Chinese Academy of Sciences in 2018, and the Ph.D. degree in Mechanical Engineering (dynamics and control) from Villanova University in 2022. His doctoral thesis focused on the study of cooperative control for heterogeneous underactuated multi-vehicle systems and extremum seeking control. His research interests include nonlinear control theory (robust, adaptive, passive, etc.), underactuated systems, nonholonomic systems, geometric control theory, networked control systems, extremum seeking control, and robotics.

2 pm on 7/10

Steinman Hall Room 254

https://ccny.zoom.us/j/81357159148?pwd=Ym1maGRUeURDeTN3Y3RZOThaNUg0dz09

ABSTRACT

Nuclear science and technology benefit human society in many ways.  The nuclear power plants contribute to about 20% of the electricity generated in the United States in the past 10 years.  While the existing light-water reactors have demonstrated their stability over decades of commercial operation, the next-generation reactors (i.e., Gen IV reactors) that employ different coolants (e.g., liquid-metal, molten-salt, helium) can make nuclear power safer and more economically competitive.  To assist in the development of Gen IV reactors, a testing capability in a fast neutron environment is essential and several projects are established to address this need.  These include the development of a sodium cartridge loop for Versatile Test Reactor (VTR) and the development of a novel fast/thermal hybrid nuclear system using lead-bismuth-eutectic as coolant.  On the other hand, some of the radioisotopes, produced from nuclear reactions, are widely used in disease diagnostic procedures, medical imaging, and cancer treatments.  This talk will also discuss the development of nuclear systems driven by accelerators to provide commercial scale radioisotopes for medical purposes (e.g., Mo-99 and Ac-225).  One unique feature differentiating nuclear systems from other systems is the radioactive materials contained.  To prevent the release of radioactive materials into the environment in any accidental scenarios, reactor safety analysis is of great importance.  Efforts are made to improve the safety analysis of nuclear systems through improved modeling of gas-liquid two-phase flows in different flow orientations, and jet impingement in postulated pipe rupture accidents.

BIO

Dr. Ran Kong earned his Ph.D. degree in nuclear engineering from Purdue University, after which he continued his postdoc training in the same research laboratory for about three years.  His research focuses on various topics in nuclear thermal-hydraulic experiments and simulations, including gas-liquid two-phase flow, liquid metal flow, advanced nuclear system design, reactor safety analysis, safety analysis code development, flow instrumentation development.  His work has established the technical basis to support the design, licensing, and operation of various nuclear engineering systems.

2 pm on 7/13

Steinman Hall Room 254

https://ccny.zoom.us/j/81357159148?pwd=Ym1maGRUeURDeTN3Y3RZOThaNUg0dz09

ABSTRACT

Wind energy has made significant progress in the United States, accounting for approximately 9% of total energy production. While this falls slightly short of the Department of Energy's proposed target of 10% by 2020, the growing focus on renewable energy sources highlights the importance of expanding wind energy. Proponents have aimed to reduce the Levelized Cost of Energy (LCOE) to enhance the competitiveness of wind energy and expand its adoption. One prevalent strategy involves increasing the size of turbine rotors. This strategy presents new engineering challenges. Notably, larger rotors amplify wake interactions between turbines, resulting in 10% to 20% potential power generation losses, and increased fatigue loads may lead to higher maintenance costs. A control co-design of wind farms approach is proposed to address these challenges. This approach integrates weather research forecasting tools, high-fidelity wind turbine simulations, and machine learning models. Combining these elements makes it possible to address the multi-physics and multi-scale problems associated with wind energy. The co-design approach offers a comprehensive solution that optimizes wind farm performance, paving the way for further adoption of renewable energy sources.

BIO

Dr. Christian Santoni completed his Ph.D. in Mechanical Engineering in 2018 at The University of Texas at Dallas. Prior to that, he earned an M.Sc. and a B.Sc. in Mechanical Engineering from the University of Puerto Rico-Mayagüez in 2013 and 2010, respectively. With a keen interest in computational fluid dynamics, Dr. Santoni has dedicated his research to the field of renewable energy and transport processes. He focuses on applying this knowledge to modeling wind turbines and wind farms, geophysical and biological flows using high-fidelity large-eddy simulations. He is a co-developer of the in-house codes UTD-WF and the Virtual Flow Simulator (VFS-Wind). In addition, Dr. Santoni is an instructor of Wind Turbine and wind farm aerodynamics at the Offshore Wind Energy Training Institute at Stony Brook University.