Students

Farzin Ahmadi

PH.D. STUDENT

Advisor: Prof. Kimia Ghobadi

Farzin is a PhD student of the Department of Civil and Systems Engineering (CaSE), the Center for Systems Science and Engineering (CSSE) at the Johns Hopkins University, and the Malone Center for Engineering in Healthcare at Johns Hopkins University. His research is focused on data-driven constrained inference models and their applications in healthcare. His recent work includes providing optimal models for hospital occupancy management during the COVID-19 pandemic and data-driven optimized models for health-care decision making processes.

  • Decision Making in Healthcare
  • Inverse Optimization and its applications on Healthcare
  • Optimizations and Simulations
  • Machine Learning Approaches to big data applications in Radiation Therapy

Alisa Hamilton

PH.D. STUDENT

Advisors: Prof. Takeru Igusa & Prof. Lauren Gardner

Nimeesha Chan

PH.D. STUDENT

Advisor: Prof. Kimia Ghobadi

Meibin Chen

PH.D. STUDENT

Advisor: Prof. Takeru Igusa

Zhixi Chen

PH.D. STUDENT

Advisor: Prof. Takeru Igusa

Ensheng Dong

PH.D. STUDENT

Advisor: Prof. Lauren Gardner​

Ensheng Dong is a PhD candidate and Louis M. Brown Engineering Fellow of the Department of Civil and Systems Engineering (CaSE) and the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University. He is also a member of the Infectious Disease Dynamics (IDD) group at the JHU Bloomberg School of Public Health. He is interested in interdisciplinary research on network science, mobility modeling, spatial analysis, geo-visualization, and infectious diseases.

His recent work includes forecasting the risk of measles in the US, predicting dengue outbreaks in Sri Lanka, building and maintaining the JHU CSSE COVID-19 dashboard, and modeling the global coronavirus pandemic. Ensheng Dong has been interviewed by CGTN, NPR, CNN, TIME, WSJ, Nature Index and other mainstream media in the US and the world. With 250 billion requests in 18 months, the dashboard is also recognized as one of TIME’s best inventions in 2020.

  • Network Modeling
  • Spatial Visualization
  • Infectious Disease

Hongru Du

PH.D. STUDENT

Advisor: Prof. Lauren Gardner​

Fardin Ganjkhanloo

PH.D. STUDENT

Advisor: Prof. Kimia Ghobadi

Nathaniel Gordon

PH.D. STUDENT

Advisor: Prof. Gregory Falco

Iliana Maifeld-Carucci

PH.D. STUDENT

Advisor: Prof. Gregory Falco

Matty Golub

PH.D. STUDENT

Advisor: Prof. Takeru Igusa

Jing Liu

PH.D. STUDENT

Advisor: Prof. Kimia Ghobadi

Max Marshall

PH.D. STUDENT

Advisor: Prof. Lauren Gardner​

Kristen Nixon

PH.D. STUDENT

Advisor: Prof. Lauren Gardner​

Felix Parker

PH.D. STUDENT

Advisor: Prof. Kimia Ghobadi

Samee Saiyed

ph.d STUDENT

Advisor: Prof. Lauren Gardner​

Samee is a Ph.D. student of the Department of Civil and Systems Engineering (CaSE), the Center for Systems Science and Engineering (CSSE) at the Johns Hopkins University. He is interested in research that seeks to alleviate societal issues using science and data driven approaches such as network science, data analysis, machine learning, multimodal mobility modeling, remote sensing and GIS, and data visualization.

  • Network Modeling
  • Data Science
  • Systems Analysis and Dynamics

Emmett Springer

PH.D. STUDENT

Advisor: Prof. Kimia Ghobadi

Post-docs and Researchers

Andreas Nearchou

Research scientist

Advisor: Prof. Lauren Gardner

Andreas is a research scientist of the Department of Civil and Systems Engineering (CaSE), the Center for Systems Science and Engineering (CSSE) at the Johns Hopkins University. He is interested in network science, machine learning and data. He is currently working on studying how misinformation spreads on the Twitter platform.

Jeremy Ratcliff

Adjunct Assistant Research Scientist

Team: Prof. Lauren Gardner​

Jeremy is a PhD candidate in the Nuffield Department of Medicine at the University of Oxford funded by a Marshall Scholarship and a researcher at the Johns Hopkins University Applied Physics Laboratory (JHU/APL). His doctoral research focuses on rapid identification and characterization of emerging viral pathogens using clinical and genomic methods and his work with JHU/APL supports the CSSE COVID-19 Dashboard. His research interests span many aspects of pandemic science and he is particularly interested in combining multiple data streams to better detect, predict, and prevent infectious disease transmission.

  • Molecular Diagnostics and Next-Generation Sequencing
  • Infectious Disease Dynamics
  • Phylogenetics and Phylodynamics
  • Epidemiology

Alumni

Ying Zhang

Research Associate
Joint Global Change Research Institute

Teams: Prof. Lauren Gardner & Prof. Lauren Gardner

Charalampos Avraam

Smart Cities Postdoctoral Associate
New York University

Advisor: Prof. Sauleh Siddiqui

Charalampos is a PhD Candidate at the Department of Civil and Systems Engineering at the Johns Hopkins University, affiliated with the Center for Systems Science and Engineering (CSSE), the Mathematical Optimization for Decisions Lab (MODL), the Networked Dynamical Systems Lab (NetDyLab), and an A.G. Leventis Foundation scholar. Charalampos employs optimization-based tools and control theory to study the impact of climate change, resource availability, and renewable policies on networked food and energy infrastructures.

  • Bilevel Optimization
  • Control Theory
  • Food-Energy-Water infrastructure development
  • Power Systems

Hamada Badr

Assoc. Research Scientist

Team: Prof. Lauren Gardner​

Today, there are many skilled and talented research scientists working across industry and applying their abilities to solve challenging problems of their field. It is rare, however, to find a scientist who dynamically combines multiple disciplines (interdisciplinary research), innovative ideas and software approaches to solve complex real-world problems using (big) data analytics and numerical simulations. I am a data scientist with broad and in-depth skills and more than two decades of experience in statistical analysis, numerical modeling of physical processes, data visualization, and software development as well as project management and leadership. I am a software-independent developer who can easily and quickly switch between different platforms and master new solutions. I am trained first in aerospace engineering and earth sciences, and I have developed my skills in programming, mathematics, statistics, and physics to address grand challenges in aerodynamics, hydroclimate, drought monitoring and early warning, food and water security, and global health.

  • Machine Learning & Artificial Intelligence
  • Spatiotemporal Analysis of Hydroclimate Variability
  • Multiscale Hydroclimate Dynamics & Change
  • Satellite Remote Sensing & Earth Observation
  • Numerical Modeling & Data Assimilation
  • Dynamical & Statistical Downscaling
  • Numerical Weather Prediction (NWP)
  • Computational Fluid Dynamics (CFD)
  • High Performance Computing (HPC)
  • Applications of Big Data in Real Life Problems

Chia-Hsiu Chang

PH.D.

Advisor: Prof. Takeru Igusa

Qi Wang​

Advisor: Prof. Takeru Igusa

Sonia Jindal

Advisor: Prof. Lauren Gardner​

Marietta Squire

PH.D.

Advisor: Prof. Takeru Igusa

Marietta Squire is a PhD student that works with the Center for Systems Science and Engineering (CSSE) in the Department of Civil and Systems Engineering (CaSE) at Johns Hopkins University. She applies systems dynamics and mathematical optimization techniques to assess how to allocate budgets and various resources in a healthcare setting. She also applies mathematical modeling to assess how to bolster patient safety in healthcare. This is applied in order to minimize the transmission of healthcare-associated infections (HAIs) within a hospital setting.

She also works with Epidemiology and Infection Control and Prevention teams to quantify the risk of secondary infections at the hospital unit level. This risk quantification can then be used by Infectious Prevention teams in hospitals to inform and serve as a decision support tool to assist in the allocation of infection prevention resources.

  • Systems Dynamics
  • Healthcare Economics
  • Optimizing Decision Making in Healthcare
  • Decision Support in Assessing Risk
  • Modeling Hospital Energy and Economic Costs for COVID-19 Infection Control Interventions
    Quantifies the energy impact of the application of negative pressured treatment rooms and xenon ultraviolet light decontamination, as well as the reduction in secondary COVID-19 infections, in a hospital setting.
    Paper:
    https://www.medrxiv.org/content/10.1101/2020.08.21.20178855v1
  • Optimal Design to Mitigate Multidrug-Resistant Organisms in Acute Care and Community Hospitals
    Applies clinical data from multiple hospitals and MDRO infection treatment cost (from 400 facilities for MRSA) in order to assess which hospital infrastructure infection control measures best enhance patient safety. The model is externally validated against clinical data from multiple years and patient admission data.
    Paper: https://journals.sagepub.com/doi/abs/10.1177/1937586720976585#abstract
  • Cost-Effectiveness of Multifaceted Built Environment Interventions for Reducing Transmission of Pathogenic Bacteria in Healthcare Facilities
    Cost-Effectiveness Analysis of Infection prevention intervention-pairs for mitigating the transmission of multidrug-resistant organisms (methicillin-resistance, carbapenem-resistance, vancomycin-resistance)
    Paper:
    https://journals.sagepub.com/doi/10.1177/1937586719833360

Siyao Zhu

PH.D.

Advisor: Prof. Takeru Igusa

Fayo Ojo

Advisor: Prof. Takeru Igusa

Wanyu Huang

PH.D.

Advisor: Prof. Takeru Igusa

Mascot (CCO)

TimTam

chief cuteness officer

Assume that a decision-maker’s uncertain behavior is observed. We develop a an inverse optimization framework to impute an objective function that is robust against misspecifications of the behavior. In our model, instead of considering multiple data points, we consider an uncertainty set that encapsulates all possible realizations of the input data. We adopt this idea from robust optimization, which has been widely used for solving optimization problems with uncertain parameters. By bringing robust and inverse optimization together, we propose a robust inverse linear optimization model for uncertain input observations. We aim to find a cost vector for the underlying forward problem such that the associated error is minimized for the worst-case realization of the uncertainty in the observed solutions. That is, such a cost vector is robust in the sense that it protects against the worst misspecification of a decision-maker’s behavior. 

As an example, we consider a diet recommendation problem. Suppose we want to learn the diet patterns and preferences of a specific person and make personalized recommendations in the future. The person’s choice, even if restricted by nutritional and budgetary constraints, may be inconsistent and vary over time. Assuming the person’s behavior can be represented by an uncertainty set, it is important to find a cost vector that renders the worst-case behavior within the uncertainty set as close to optimal as possible. Note that the cost vector can have a general meaning and may be interpreted differently depending on the application (e.g., monetary cost, utility function, or preferences). Under such a cost vector, any non-worst-case diet will thus have a smaller deviation from optimality.  

We introduce a new approach that combines inverse optimization with conventional data analytics to recover the utility function of a human operator. In this approach, a set of final decisions of the operator is observed. For instance, the final treatment plans that a clinician chose for a patient or the dietary choices that a patient made to control their disease while also considering her own personal preferences. Based on these observations, we develop a new framework that uses inverse optimization to infer how the operator prioritized different trade-offs to arrive at her decision. 

We develop a new inverse optimization framework to infer the constraint parameters of a linear (forward) optimization based on multiple observations of the system. The goal is to find a feasible region for the forward problem such that all given observations become feasible and the preferred observations become optimal. We explore the theoretical properties of the model and develop computationally efficient equivalent models. We consider an array of functions to capture various desirable properties of the inferred feasible region. We apply our method to radiation therapy treatment planning—a complex optimization problem in itself—to understand the clinical guidelines that in practice are used by oncologists. These guidelines (constraints) will standardize the practice, increase planning efficiency and automation, and make high-quality personalized treatment plans for cancer patients possible.