Mohammad F. Obeid

Simulation Modeling and Analysis of Complex Port Operations with Multimodal Transportation.

Abstract World trade has been increasing dramatically in the past two decades, and as a result containers exchange has grown significantly. Accordingly, container terminals are expanding to meet this increase and new container ports have opened. Ports with one or more container terminals are considered complex systems in which many resources, entities and transporters interact to achieve the objective of safely moving containers delivered by ships inland as well as loading containers delivered by trucks and rail onto ships. Ports with multimodal transportation systems are in particular complex as they typically operate with ships arriving to one or more terminals, multiple quay cranes, rubber tyred gantry cranes, trains, and trucks delivering containers of different types to terminals. With several resources of different types working and interacting, the system can be so complex that it is not easy to predict the behavior of the system and its performance metrics without the use of simulation. In this paper, a generic discrete-event simulation that models port operations with different resource types including security gates, space, rubber tyred gantry cranes, trains, quay cranes, and arriving and departing ships, trucks, and trains is presented. The analysis will entail studying various scenarios motivated by changes in different inputs to measure their impact on the outputs that include throughput, resource utilization and waiting times.

Patient Specific Modeling of Pectus Excavatum for the Nuss Procedure Simulation

Patient specific models are crucial for both simulation and surgical planning. It is not different for the Nuss procedure, which is a minimally invasive surgery for correcting pectus excavatum (PE)—a congenital chest wall deformity. Typically, patients differ not only in size but also severity of the chest depression and type of the deformity, making the simulation process challenging. In this paper, we approach the problem of a patient specific model creation resulting in the development of a parameterized model of the human torso including the ribcage. All the parameters are obtainable from pre-surgical CT. In order to validate our model, we compared the simulated shape of the chest with surface scans obtained from PE patients for both pre- and post-surgery. Results showed that both shapes are in agreement in the area of the deformity, making this method valid for the need of simulating the Nuss procedure.

Simulation of the critical steps of the Nuss procedure

Simulation can be a critical component in the surgical training, planning and rehearsal process of difficult or new procedures. This is true for the Nuss procedure, which is a minimally invasive surgery for correcting pectus excavatum (PE) – a congenital chest wall deformity. Surgeons who routinely perform this surgery identified the most critical steps during the procedure. We chose to simulate these components which involve the process of creating a pathway anterior to the pericardium underneath the sternum as this step can, if incorrectly performed, lead to the death of a patient or, at least, serious complications. In this paper, we describe the hardware setup of the Nuss procedure surgical simulator, the constructed virtual environment, modelling of anatomical structures, surgical instrument and its insertion point without the aid of physical components, reproducing PE deformity, and eventually physics of the tunnelling process.

West Nile Virus system dynamics investigation in Dallas County, TX

After its first introduction in 1999, West Nile Virus (WNV) has spread very widely along the east coasts of the United States before appearing in Texas where 1792 cases were reported of which 82 were fatal in 2012. The interesting patterns and behavior of the virus and its amplified impact on the county of Dallas drove this work. This paper encompasses a thorough development of a systems dynamics simulation model that imitates the viruss infectious behavior and dynamics in Dallas County, TX utilizing historical data collected and the aid of suitable software packages.

Utilizing Pre- and Postoperative CT to Validate an Instrument for Quantifying Pectus Excavatum Severity

An instrument that objectively quantifies a condition’s severity and its improvement after treatment is of great use. This is also the case for pectus excavatum (PE), a congenital chest wall deformity, for which several severity indices have been introduced. This work describes a system that utilizes chest surface scans generated from CT-data or optical scanning to provide a gauge and visualization of chest wall deviations. A validation experiment is conducted to evaluate the fidelity of such an instrument utilizing pre- and postoperative CT scans. Statistical analysis shows the ability of the instrument to accurately recognize changes in the chest surface profile.

Poster: Modeling insertion point for general purpose haptic device simulations for minimally invasive surgeries

Minimally invasive surgery has revolutionized surgical procedures over the last decades. This trend has impacted the surgical simulation field and promoted a wide use of haptic devices. The majority of minimally invasive surgery simulators follow a visuo-haptic setup where ports are mounted stationary and physical constraints are used to simulate the pivot of surgical tools. This setup may add limitations to certain procedures and result in negative training, as those assumptions may not hold true during surgery. In this work, we investigate challenges in modeling general purpose haptic device simulations for minimally invasive surgeries, namely accurate pivoting around the insertion point, collisions with surrounding objects during procedure, and system scalability for various devices. The system behavior is evaluated on a Nuss procedure surgical simulator and tested by experienced surgeons on the field. The findings are promising and may benefit other surgical simulators in which the kinematics and dynamics of the surgical tool are utilized within the context of minimally invasive surgeries.

Improvement of a Virtual Pivot for Minimally Invasive Surgery Simulators Using Haptic Augmentation

With rapid development of minimally invasive surgery, proficiency with intricate skills is becoming a greater concern. Consequently, the use of out-of-operating room training has increased significantly through employing high-fidelity and anatomically-correct graphics and haptic interfaces in virtual reality simulations. The effort in developing surgical simulators for generic minimally invasive procedures is still, however, suboptimal for many haptic implementations. A main aspect of such simulations is the pivoting behavior of the surgical tool realized using the haptic device. This paper investigates the limitation of a fully-virtual implementation of the pivot and the ability to augment haptic interfaces to achieve a natural representation of forces. The design and implementation of two surgical tool pivoting techniques are introduced. Furthermore, a phantom is constructed from synthesized components to be used to measure and reproduce realistic mechanical properties of the anatomical model and pivot behavior.