Papers by Abhishek Tiwari
In this thesis I represent and analyze spatially and temporally constrained multi-agent planning ... more In this thesis I represent and analyze spatially and temporally constrained multi-agent planning problems using tools from geometry and advanced calculus. The two problems considered in this thesis are multi-agent rendezvous and dynamic sensor coverage. Together, these problems encompass the cooperation, constraint representation,and task scheduling aspects of multi-agent planning problems. I have represented the constraint of the rendezvous problem on the phase space and shown that the fulfilment of rendezvous constraints is equivalent to certain conical regions being invariant. Alternatively, for the dynamic coverage problem, the constraints can be adequately represented on the uncertainty space and sensor motion laws can be obtained by partitioning the uncertainty space and making decisions based on which partition the uncertainty lies in. I have examined convergence behavior of sensor motion under such laws.
2004 43rd IEEE Conference on Decision and Control (CDC) (IEEE Cat. No.04CH37601), 2004
In this paper, we pose the N-scalar agent rendezvous as a polyhedral cone invariance problem in t... more In this paper, we pose the N-scalar agent rendezvous as a polyhedral cone invariance problem in the N dimensional phase space. The underlying dynamics of the agents are assumed to be linear. We derive a condition for positive invariance for polyhedral cones. Based on this condition, we demonstrate that the problem of determining a certificate for rendezvous can be stated as a convex feasibility problem. Under certain rendezvous requirements, we show that there are no robust closed-loop linear solutions that satisfy the invariance conditions. We show that the treatment of the rendezvous problem on the phase plane can be extended to the case where agent dynamics are non-scalar.
Monitoring remote access to an enterprise network
International Surgery Journal, 2016
Pediatric inguinal hernias are due to the persistent processus vaginalis. It is diagnosed with th... more Pediatric inguinal hernias are due to the persistent processus vaginalis. It is diagnosed with the classic clinical feature of a lump that transmits a cough impulse. Less clear-cut clinical presentations such as a "bulge," "fullness," and a cough impulse in the absence of a definite lump reduce diagnostic certainty. A patient may also present with pain alone, in which case there is a broad range of differential diagnoses.
Wave Atom based Compression Method for Fingerprint Images
IOSR Journal of Mechanical and Civil Engineering, 2012
Helical compression springs are used generally in fuel injection system of diesel engines, where ... more Helical compression springs are used generally in fuel injection system of diesel engines, where it undergoes cyclic loading for more than 10 8 numbers of cycles. In order to predict probable failure positions in helical compression springs, used in fuel injection system, along the length of the spring at inner side, finite element analyses was carried out, using ABAQUS 6.10. The simulation results show an oscillatory behaviour of stresses along the length at inner side. It was confirmed that the oscillation was due to bending involved with compression. It was also revealed that the bending was due to the geometry of springs. Shear stresses along the length of the spring were found to be asymmetrical and with local maxims at starting of each middle coil. The asymmetry was due to the end coil smaller than 360 degrees.
Homology modeling of dihydroorotase in Plasmodium falciparum
Effect of Pre-strain on Susceptibility of Indian Reduced Activation Ferritic Martensitic Steel to Hydrogen Embrittlement
Journal of Nuclear Materials, 2015
ABSTRACT The role of pre-strain on hydrogen embrittlement susceptibility of Indian Reduced Activa... more ABSTRACT The role of pre-strain on hydrogen embrittlement susceptibility of Indian Reduced Activation Ferritic Martensitic Steel was investigated using constant nominal strain-rate tension test. The samples were pre-strained to different levels of plastic strain and their mechanical behavior and mode of fracture under the influence of hydrogen was studied. The effect of plastic pre-strain in the range of 0.5–2% on the ductility of the samples was prominent. Compared to samples without any pre-straining, effect of hydrogen was more pronounced on pre-strained samples. Prior deformation reduced the material ductility under the influence of hydrogen. Up to 35% reduction in the total strain was observed under the influence of hydrogen in pre-strained samples. Hydrogen charging resulted in increased occurrence of brittle zones on the fracture surface. Hydrogen Enhanced Decohesion (HEDE) was found to be the dominant mechanism of fracture.
Multilayer Graphene on Copper for Corrosion Mitigation
Feasibility of communication planning in Airborne Networks using mission information
MILCOM 2009 - 2009 IEEE Military Communications Conference, 2009
... and K. Hopkinson2 1UtopiaCompression Corporation, 11150 W. Olympic Blvd., #680, Los Angeles, ... more ... and K. Hopkinson2 1UtopiaCompression Corporation, 11150 W. Olympic Blvd., #680, Los Angeles, CA 90064 2Air Force Institute of Technology, Wright-Patterson Air Force Base, OH 45433 1{abhishek, anurag, aditya, sharath, joseph ... [7] A. Tiwari, A. Ganguli, A. Sampath, DS ...
World Journal of Gastroenterology, 2015
Roux-en-Y hepaticojejunostomy anastomosis is the treatment of choice for common hepatic duct inju... more Roux-en-Y hepaticojejunostomy anastomosis is the treatment of choice for common hepatic duct injury type E2. It has been performed laparoscopically with the advancement of laparoscopic skill. Recently, a telemanipulative robotic surgical system was introduced, providing laparoscopic instruments with wrist-arm technology and 3-dimensional visualization of the operative field. We present a case of 36-year-old female patient who had undergone elective cholecystectomy 2 mo ago for gall stones and had a common bile duct injury during surgery. As the stricture was old and complete it could not be tackled endoscopically. We did a laparoscopic assisted adhesiolysis followed by robotic Roux-en-Y hepaticojejunostomy. No intraoperative complications or technical problems were encountered. Postoperative period was uneventful and she was discharged on the 4 th postoperative day. At followup, she is doing well without evidence of jaundice or cholangitis. This is the first reported case of robotic hepaticojejunostomy following common bile duct injury. The hybrid technique gives the patient benefit of laparoscopic adhesiolysis and robotic suturing.
Proceedings of the American Control Conference, 2004
In this paper we present a dynamical systems representation for multi-agent rendezvous on the pha... more In this paper we present a dynamical systems representation for multi-agent rendezvous on the phase plane. We restrict our attention to two agents, each with scalar dynamics. The problem of rendezvous is cast as a stabilization problem, with a set of constraints on the trajectories of the agents, defined on the phase plane. We also describe a method to generate control Lyapunov functions that when used in conjunction with a stabilizing control law, such as Sontag's formula, makes sure that the two-agent system attains rendezvous. The main result of this paper is a Lyapunov-like certificate theorem that describes a set of constraints, which when satisfied are sufficient to guarantee rendezvous.
Proceedings - 2005 Systems Communications: ICW 2005, Wireless - ICHSN 2005, High Speed Networks - ICMCS 2005, Multimedia Communications Systems - SENET 2005, Sensor Networks, 2005
In this paper, we consider the standard state estimation problem over a congested packet-based ne... more In this paper, we consider the standard state estimation problem over a congested packet-based network. The network is modeled as a queue with a single server processing the packets. This provides a framework to consider the effect of packet drops, packet delays and bursty losses on state estimation. We use a modified Kalman Filter with buffer to cope with delayed packets. We analyze the stability of the estimates with varying buffer length and queue size. We use high order Markov chains for our analysis. Simulation examples are presented to illustrate the theory.
HBAT: a complete package for analysing strong and weak hydrogen bonds in macromolecular crystal structures
In silico biology, 2007
The program HBAT is a tool to automate the analysis of potential hydrogen bonds and similar type ... more The program HBAT is a tool to automate the analysis of potential hydrogen bonds and similar type of weak interactions like halogen bonds and non-canonical interactions in macromolecular structures, available in Brookhaven Protein Database (PDB) file format. HBAT is written using PERL and TK languages. The program generates an MSOFFICE Excel compatible output file for statistical analysis. HBAT identify potential interactions based on geometrical criteria. A series of analysis reports like frequency tables, geometry distribution tables, furcations list are generated. A user friendly GUI offers freedom to select several parameters and options. Graphviz based visualization of hydrogen bond networks in 2D helps to study the cooperativity and anticooperativity geometry in hydrogen bond. HBAT supports post docking interaction analysis between PDB files for any target/receptor (in PDB files) and docked ligands/poses (in SDF). This tool can be implemented in active site interaction analysis...
Proactive trust management system (PTMS) for trusted querying in wireless sensor networks
Intelligent Sensing, Situation Management, Impact Assessment, and Cyber-Sensing, 2009
Wireless Sensor Networks (WSNs) are systems that may contain hundreds to thousands of low-power a... more Wireless Sensor Networks (WSNs) are systems that may contain hundreds to thousands of low-power and low-cost sensor nodes. The potential applicability of such systems is enormous; security surveillance and intrusion detection systems for smart buildings and ...
Co-array Processing Assisted Bayesian Beamforming (CABB): A Nonlinear Beamforming Technique for Joint Aerial Layer Network (JALN) Backbone
MILCOM 2013 - 2013 IEEE Military Communications Conference, 2013
ABSTRACT In this paper we describe a novel non-linear digital beamforming technique that we refer... more ABSTRACT In this paper we describe a novel non-linear digital beamforming technique that we refer to as Co-array processing assisted Bayesian Beamforming (CABB) for directional line of sight networks like USAF Joint Aerial Layer Network (JALN) backbone. CABB leverages recently proposed signal processing techniques that can extract directions of arrivals of O(N2) sources using an antenna array that has only O(N) elements with non-uniform inter-element separation. The benefits of CABB for directional LOS networks are (1) reduced size of antenna array, (2) improved spectral efficiency (3) adaptation to changing channel conditions as a result of mobility. The main disadvantage in comparison to linear digital beamforming techniques is increased computations. In this paper we validate these tradeoffs via high fidelity simulations. We also argue that since most practical USAF directional LOS networks are sparse, it is possible to realize the CABB technique using existing hardware despite high computational requirements.
MILCOM 2009 - 2009 IEEE Military Communications Conference, 2009
Despite "airborne network (AN) topology design" and careful planning of AN trajectories, unexpect... more Despite "airborne network (AN) topology design" and careful planning of AN trajectories, unexpected disruptions (from hardware failures to changes in mission requirements and hostile attacks) may cause nodes not to connect to one another directly or indirectly either because they are out of one another's range or because nodes do not meet one another according to their preplanned trajectories. Since an end-to-end path within the AN is not always guaranteed, packets have to be delivered in a delay-tolerant fashion, namely, some intermediate nodes will need to buffer packets during times of disconnectivity. In our earlier work we developed Mobility Aware Routing Protocol and Mobility Dissemination Protocol (MARP/MDP) that used preplanned trajectories of airborne nodes to make intelligent routing decisions preemptively. In this paper we present a delay-tolerant strategy (MARP/MDP+DTN) to predict the minimum end-to-end delay and obtain the corresponding path. In addition, MARP/MDP+DTN accounts for local queueing (MARP/MDP+DTN+QC) to minimize congestion and further improves end-to-end delay with the positive side effect of load-balancing. Simulation results have shown an improvement of 52% in packet delivery ratio in MARP/MDP+DTN. MARP/MDP+DTN+QC also exhibits extremely short latency, about 90% reduction from MARPIMDP+DTN in highly congested network. Moreover, MARP+DTN+QC balances local traffic 67% better than MARP+DTN in high traffic load scenarios.
Thin Layer approach to increase reliability in ad hoc network
MILCOM 2009 - 2009 IEEE Military Communications Conference, 2009
Reliability support in a tactical area network is cru-cial since critical information is exchange... more Reliability support in a tactical area network is cru-cial since critical information is exchanged to achieve military missions. However, it is extremely challenging due to mobility, unstable channel condition, and possi-ble jamming attack from an adversary. To increase re-liability, we ...
The role of peripheral energy management for wireless health applications
Wireless Health 2010, 2010
... Tejaswi Tamminedi, Aditya Kothari, Abhishek Tiwari, Anurag Ganguli, Sharath Avadhanam UtopiaC... more ... Tejaswi Tamminedi, Aditya Kothari, Abhishek Tiwari, Anurag Ganguli, Sharath Avadhanam UtopiaCompression Corporation 11150 Olympic Blvd. ... without fee provided that copies are not made or distributed for profit or commercial advantage and that cop-ies bear this notice ...
IFAC Proceedings Volumes, 2005
We introduce a theoretical framework for the dynamic sensor coverage problem for the case with mu... more We introduce a theoretical framework for the dynamic sensor coverage problem for the case with multiple discrete time linear stochastic systems placed at spacially separate locations. The objective is to keep an appreciable estimate of the states of the systems at all times by deploying a few limited range mobile sensors. The sensors implement a Kalman filter to estimate the states of all the systems. In this paper we present results for a single sensor executing two different random motion strategies. Under the first strategy the sensor motion is an independent and identically distributed random process and a discrete time discrete state ergodic Markov chain under the second strategy. For both these strategies we give conditions under which a single sensor fails or succeeds to solve the dynamic coverage problem. We also demonstrate that the conditions for the first strategy are a special case of the main result for the second strategy. Copyright
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Papers by Abhishek Tiwari