Sharif Digital Repository

Multilateral well is a promising technology in developing oil reservoirs. Because this technology may increase the production rate per well and reduce the costs of field development, it is rapidly replacing the old methods. This study uses a three-dimensional line-source model with direct search methods, including pattern search and genetic algorithms to optimize the well trajectories. This method was applied to several cases, with different forms of wells and reservoirs. In all cases, significant improvement was observed in the production rate. Furthermore, the production enhancement using the optimized well trajectories which have curved-paths is compared to the case with linear well... 

Our transportation field has recently witnessed an arms race of neural network-based trajectory predictors. While these predictors are at the core of many applications such as autonomous navigation or pedestrian flow simulations, their adversarial robustness has not been carefully studied. In this paper, we introduce a socially-attended attack to assess the social understanding of prediction models in terms of collision avoidance. An attack is a small yet carefully-crafted perturbations to fail predictors. Technically, we define collision as a failure mode of the output, and propose hard- and soft-attention mechanisms to guide our attack. Thanks to our attack, we shed light on the... 

In this article, time-varying formation tracking problem for multi-agent systems is investigated. It is assumed the number of agents is changing and obstacles should be avoided along the trajectory. In addition, the tracking formation should be reached while the leader trajectory is unknown and communication data are noisy. To reach the desired formation tracking, first, a virtual leader is constructed using the local neighbouring data. Second, the reference signal is created based on the virtual leader and the leader data (which is available for some agents). The data fusion at this stage is done based on Kalman filtering to reduce the effect of communication noise. Third, an integral state... 

The separation of cancer cells from a heterogeneous biological sample such as blood plays a vital role in cancer study and future treatments. In this paper, we designed and investigated two microfluidic devices for cancer cell separation, including a serpentine inertial device and an integrated inertial-magnetophoretic device. Firstly, numerical modeling was carried out to study the fluid flow, particles’ trajectories in the inertial device. Then the device was fabricated using soft photolithography and suspension of two types of microparticles with the size of 10 and 15 µm were injected into the microchannel separately to investigate the particles’ trajectories and focusing behavior at... 

The combination of pursuit and line of sight guidance laws, called PLOS, is used to steer an unmanned aerial vehicle along a desired path. In the previous studies, the parameters of this guidance law are tuned by trial and error and are constant, during the flight. In this research, it will be shown that the optimal value of these parameters depends on the initial conditions of the problem and the wind conditions. For this reason, a fuzzy system is proposed to generate the instantaneous optimal value of these parameters, in such a way that the flying vehicle converges to the desired path in less time and follows it more accurately, in the presence of wind. For this purpose, a cost function... 

This letter develops an adaptive actuator failure compensation method for nonlinear systems with unmatched parametric uncertainty based on contraction metrics. The proposed method, which is constructed by benefiting from the recent achievements on contraction metrics based adaptive control techniques, ensures the closed-loop stability and asymptotic tracking of the desired trajectory in the presence of actuator failures. In particular, a sufficient convex condition is derived for constructing a valid metric, by which a quadratic program-based controller is obtained to determine the inputs of the actuators. The introduced method is more general than the common adaptive actuator failure... 

Dust storms are a common phenomenon in arid and semi-arid regions in West Asia, which has led to high levels of PM10 in local and remote area. The Yazd city in Iran with a high PM10 level located downstream of dust sources in the Middle East and Central Asia. In this study, based on meteorological and PM10 monitoring data, backward trajectory modeling of air parcels related to dust events at Yazd station was performed using the HYSPLIT model in 2012–2019. The trajectory cluster analysis was used to identify the main dust transport pathways and wind systems. Three methods of Cross-referencing Backward Trajectory (CBT), Potential Source Contribution Function (PSCF) and Concentration Weighted... 

Capsule endoscopy is a minimally invasive diagnostic technology for gastrointestinal diseases providing images from the human's digestion system. Developing a robust and real-time localization algorithm to determine the orientation and position of the endoscopic capsule is a crucial step toward medical diagnostics. In this paper, we propose a novel model-aided real-time localization approach to estimate the position and orientation of a magnetic endoscopic capsule swimming inside the stomach. In the proposed method, the governing equations of the motion of an ellipsoidal capsule inside the fluid, considering different hydrodynamics interactions, are derived. Then, based on the dynamic model,... 

With the exception of a few works, the current approaches to aerial manipulation control do not typically consider the system constraints in the control design process. Also, the issue of closed-loop stability in the presence of system constraints is not thoroughly analyzed. In this paper, a novel multi-stage model predictive control (MPC)-based approach for aerial manipulation is proposed to ensure the closed-loop stability in the presence of model uncertainties and external disturbances, while satisfying the operational constraints. The detailed nonlinear model of a general aerial manipulator, consisting of a quadrotor equipped with a 3 degrees of freedom manipulator, is first developed... 

Circulating tumor cells (CTCs) isolation from a blood sample plays an important role in cancer diagnosis and treatment. Microfluidics offers a great potential for cancer cell separation from the blood. Among the microfluidic-based methods for CTC separation, the inertial method as a passive method and magnetic method as an active method are two efficient well-established methods. Here, we investigated the combination of these two methods to separate CTCs from a blood sample in a single chip. Firstly, numerical simulations were performed to analyze the fluid flow within the proposed channel, and the particle trajectories within the inertial cell separation unit were investigated to... 

The separation of cancer cells from a heterogeneous biological sample such as blood plays a vital role in cancer study and future treatments. In this paper, we designed and investigated two microfluidic devices for cancer cell separation, including a serpentine inertial device and an integrated inertial-magnetophoretic device. Firstly, numerical modeling was carried out to study the fluid flow, particles’ trajectories in the inertial device. Then the device was fabricated using soft photolithography and suspension of two types of microparticles with the size of 10 and 15 µm were injected into the microchannel separately to investigate the particles’ trajectories and focusing behavior at... 

We have introduced a new low-Reynolds-number microrobot with high 3D maneuverability. Our novel proposed microrobot has a higher rank of the controllability matrix with respect to the previous microswimmers which makes it capable of performing complex motions in space. In this study, governing equations of the microswimmer's motion have been derived and simulated. Subsequently, we have proposed a cascade optimal control technique to control the swimmer trajectory. In the proposed control scheme, the actuation is provided in a way that an exponential stability on the system trajectory error as well as minimum fluctuations of control signals are achieved. © The Author(s), 2021. Published by... 

In this study, we use the concept of Bohmian trajectories to present a dynamical and deterministic interpretation for the gravity-induced wave function reduction. We shall classify all possible regimes for the motion of a particle, based on the behavior of trajectories in the ensemble and under the influence of quantum and gravitational forces. In the usual approaches all the information is obtained from the wave function evolution. But, on the basis of Bohm's deterministic quantum theory, we can investigate the motion of the particle during the reduction processes. This leads to analytical and numerical results for the reduction time and equation of motion of the particle. In this regard, a... 

Fast finite time adaptive sliding mode control of a quadrotor in the presence of uncertainties and unbounded external disturbances is dealt in this paper. To this end, a fractional order sliding surface is first defined and then, an adaptive sliding mode controller is designed to guarantee finite time stability with fast convergence of quadrotor states to the desired trajectory. In this controller, it is assumed that the upper bound of the model uncertainties and external disturbances is a nonlinear function with unknown coefficients. These coefficients are estimated via stable adaptive laws. Finite time stability of the closed-loop system is analyzed using Lyapunov theorem. Simulation... 

Given a set of n segments and a query shape Q, the windowing length query asks for finding the sum of the lengths of the parts of the segments that lie inside Q. The popular places problem of a set of curves asks for the subset of the plane where each query shape centered at a point of that region intersects with at least f distinct curves. For square queries, an optimal O(n2) time algorithm and a matching lower bound exist. We solve the length query problem for convex polygons and disks as query shapes, with O(log n+ k) query time and polynomial preprocessing time that depends on the complexity of the query shape. We define a new version of the problem of finding popular places in a set of... 

A novel fault-tolerant model predictive control (MPC)-based trajectory tracking approach for an aerial vehicle is presented in this study. A generalised online sequential extreme learning machine is introduced first to identify the corresponding coefficients of actuator faults. Subsequently, a robust trajectory tracking control is developed based on MPC, where the system constraints can be effectively considered in the designed control scheme. Trajectory tracking control is achieved by controlling only the acceleration of the aerial robot in the MPC structure. This leads to less computational burden and faster closed-loop dynamics. In addition, an effective disturbance observer is employed,... 

Sound source localization has always been one of the most challenging subjects in different fields of engineering, one of the most important of which being tracking of flying objects. This article focuses on sound source localization using fuzzy fusion and a beamforming method. It proposes a new fuzzy-based algorithm for localizing a sound source using distributed sensor nodes. Eight low-cost sensor nodes have been constructed in this study each of which consists of a microphone array to capture sound waves. Each node is able to record audio signals synchronously on an SD card to evaluate different algorithms offline. However, the sensor nodes are designed to be able to estimate the location... 

In recent years, unmanned aerial systems have attracted great attention due to the electronic systems technology advancements. Among these vehicles, unmanned helicopters are more important because of their special abilities and superior performance. The complex nonlinear dynamic system (caused by main rotor flapping dynamics coupled with the rigid body rotational motion) and considerable effects of ambient disturbance make their utilization hard in actual missions. Attitude dynamics have the main role in helicopter stabilization, so implementing proper control system for attitude is an important issue for unmanned helicopter hovering and trajectory tracking performance. Besides this,... 

There is a famous criterion for objective wave function reduction which is derived by using the Shrödinger–Newton equation [L Diosi, Phys. Lett. A105(4–5), 199 (1984)]. In this regard, a critical mass for the transition from quantum world to the classical world is determined for a particle or an object. In this paper, we shall derive that criterion by using the concept of Bohmian trajectories. This study has two consequences. The first is, it provides a geometric framework for the problem of wave function reduction. The second is, it represents the role of quantum and gravitational forces in the reduction process. © 2020, Indian Academy of Sciences  

This paper proposes a solution for multiple-impulse orbital maneuvers near circular orbits for special cases where orbital observations are not globally available and the spacecraft is being observed through a limited window from a ground or a space-based station. The current study is particularly useful for small private launching companies with limited access to global observations around the Earth and for orbital maneuvers around other planets for which the orbital observations are limited to the in situ equipment. An appropriate cost function is introduced for the sake of minimizing the total control/impulse effort as well as the orbital uncertainty. It is subsequently proved that for a...