Avinash Malik

Avinash Malik
University of Auckland · Department of Electrical & Computer Engineering

PhD

About

86
Publications
10,641
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
497
Citations
Additional affiliations
May 2013 - present
University of Auckland
Position
  • Worker bee
December 2010 - May 2012
Trinity College Dublin
Position
  • PostDoc Position
Description
  • Worked on compiler construction and optimizing data flow graphs

Publications

Publications (86)
Article
Full-text available
General Stochastic Hybrid System (SHS) are characterised by Stochastic Differential Equations (SDEs) with discontinuities and Poisson jump processes. SHS are useful in model based design of Cyber-Physical System (CPS) controllers under uncertainty. Industry standard model based design tools such as Simulink/Stateflow® are inefficient when simulatin...
Article
Background and objective: Gastrointestinal (GI) motility disorders can be significantly detrimental to the quality of life. Pacing, or long pulse gastric electrical stimulation, is a potential treatment option for treating GI motility disorders by modulating the slow wave activity. Open-loop pacing of the GI tract is the current standard for modul...
Article
Optimizations in energy consumption are critical for battery-powered hard real-time embedded systems. Energy management is often accomplished by dynamic frequency scaling which requires compilers to insert special instructions in the code at appropriate places, which are then used by the operating system and the processor to calculate and change th...
Article
Full-text available
Objective: To develop, train and test neural networks for predicting heart surface potentials (HSPs) from body surface potentials (BSPs). The method re-frames traditional inverse problems of electrocardiograpy into regression problems, constraining the solution space by decomposing signals with multidimensional Gaussian impulse basis functions. M...
Article
Full-text available
Hybrid systems are a subset of Cyber-Physical Systems, where a physical process (the plant) is controlled by a discrete controller. The controller induces mode switches, which are modelled as guard conditions leading to sudden discontinuities. Correctly capturing sudden discontinuities during simulation is the primary challenge to maintain fidelity...
Article
Altered electrocardiogram (ECG) morphology is important for assessing cardiac pro-arrhythmic risk of drugs. We propose a basis function method to predict morphological and QT, JT, Tpeak—Tend timing interval changes in ECGs due to drug effects. The method systematically decomposes ECGs for a study population recorded at varying pharmacokinetic state...
Article
Full-text available
Stochastic hybrid systems (SHSs) are a modelling framework for a cyber-physical system (CPS), used to simulate, validate, and verify safety critical controllers under uncertainty. Popular simulation tools can miss detecting discontinuities when simulating SHS, thereby producing incorrect outputs during simulation. We propose a novel adaptive step s...
Preprint
Full-text available
Objective: This paper proposes an neural network approach for predicting heart surface potentials (HSPs) from body surface potentials (BSPs), which reframes the traditional inverse problem of electrocardiography into a regression problem through the use of Gaussian 3D (G3D) basis function decomposition. Methods: HSPs were generated using G3D basis...
Conference Paper
A potential treatment option for chronic and severe motility disorders such as gastroparesis is the implantation of a Gastric Electrical Stimulator (GES), which is designed to modulate the bio-electric slow waves. However, the effectiveness of current GESs remains uncertain since they do not work in a closed-loop by sensing, processing, and modulat...
Article
Full-text available
Cyber–physical Systems (CPS) involve a network of discrete controllers that control physical processes, e.g., pacemakers controlling the heart rhythm. The intuitive and formal Hybrid Automata (HA) based modelling approach for CPS is gaining momentum. HA combines the model of the plant along with its discrete controller resulting in a piece-wise con...
Article
Full-text available
Rear-end collision avoidance relies on mathematical models to calculate the safety distance. Vehicle deceleration is a key parameter for the accuracy of the models. Current models, however, assume a constant deceleration during braking, which is unrealistic. This assumption results in large over-approximation / under-approximation. In this paper, w...
Article
Full-text available
Understanding the slow wave propagation patterns of Interstitial Cells of Cajal (ICC) is essential when designing Gastric Electrical Stimulators (GESs) to treat motility disorders. A GES with the ability to both sense and pace, working in closed-loop with the ICC, will enable efficient modulation of Gastrointestinal (GI) dysrhythmias. However, exis...
Article
Full-text available
Co-simulation--based validation of hardware controllers adjoined with plant models, with continuous dynamics, is an important step in model-based design of controllers for Cyber-physical Systems (CPS). Co-simulation suffers from many problems, such as timing delays, skew, race conditions, and so on, making it unsuitable for checking timing properti...
Conference Paper
Full-text available
Online Peer to Peer Lending (P2PL) systems connect lenders and borrowers directly, thereby making it convenient to borrow and lend money without intermediaries such as banks. Many recommendation systems have been developed for lenders to achieve higher interest rates and avoid defaulting loans. However, there has not been much research in developin...
Article
Full-text available
Abstract—Objective: Cardiovascular Implantable Electronic Devices (CIEDs) are used extensively for treating life-threatening conditions such as bradycardia, atrioventricular block and heart failure. The complicated heterogeneous physical dynamics of patients provide distinct challenges to device development and validation. We address this problem b...
Conference Paper
Full-text available
Simulink/Stateflow® is the de-facto tool for design of Cyber-physical Systems (CPS). CPS include hybrid systems, where a discrete controller guides a continuous plant. Hybrid systems are characterised by their continuous time dynamics with sudden discontinuities, caused by level/zero crossings. Stateflow can graphically capture hybrid phenomenon, m...
Preprint
Full-text available
Online Peer to Peer Lending (P2PL) systems connect lenders and borrowers directly, thereby making it convenient to borrow and lend money without intermediaries such as banks. Many recommendation systems have been developed for lenders to achieve higher interest rates and avoid defaulting loans. However, there has not been much research in developin...
Article
The event-driven model of computation provides a good platform for capturing complex real-time applications with low latency requirements since this model is free of problems like deadlocks, livelocks and performance bottlenecks such as locking overheads. Furthermore, there is great potential for extracting parallelism from an event-driven model on...
Article
Full-text available
Organ level simulation of bioelectric behavior in the body benefits from flexible and efficient models of cellular membrane potential. These computational organ and cell models can be used to study the impact of pharmaceutical drugs, test hypotheses, assess risk and for closed-loop validation of medical devices. To move closer to the real-time requ...
Article
Full-text available
Objective: Evaluating and testing cardiac electrical devices in a closed-physiologic-loop can help design safety, but this is rarely practical or comprehensive. Furthermore, in-silico closed-loop testing with biophysical computer models cannot meet the requirements of time-critical cardiac device systems, while simplified models meeting time-criti...
Chapter
Energy management is very important and sometimes critical for certain classes of hard real-time systems. In this paper, we present effective energy reduction techniques for hard real-time systems developed in Java, which execute on bare metal and run on a time-predictable specialized Java processor. We modified traditional clock gating and dynamic...
Article
Full-text available
Whole electrocardiogram (ECG)waveform analysis is a technique for evaluating aggregate arrhythmic risks of drugs. In this paper, we propose methods for exploring changes to ECG morphology due to drug effects using Gaussian model parameters, and predict patient specific post-drug ECG based on pre-drug ECG. We evaluate the proposed methods using clin...
Article
Full-text available
Objective: Efficient and accurate organ models are crucial for closed-loop validation of implantable medical devices. This paper investigates bio-electric slow wave modeling of the stomach, so that Gastric Electrical Stimulator (GES) can be validated and verified prior to implantation. In particular, we consider high-fidelity, scalable, and efficie...
Conference Paper
Full-text available
Online P2PL systems allow lending and borrowing between peers without the need for intermediaries such as banks. Convenience and high rate of returns have made P2PL systems very popular. Recommendation systems have been developed to help lenders make wise investment decisions, lowering the chances of overall default. However, P2PL marketplace suffe...
Preprint
Full-text available
The prediction of heart surface potentials using measurements from the body's surface is known as the inverse problem of electrocardiography. It is an ill-posed problem due to the multiple factors that affect the heart signal as it propagates through the body. This report details research performed into a machine learning solution to signal reconst...
Article
SystemJ is a programming language based on the Globally Asynchronous Locally Synchronous (GALS) Model of Computation (MoC) used to design safety critical hard real-time systems. SystemJ uses the Java programming language as the “host” language, for carrying out data computations, because Java provides clearly defined operational semantics, type and...
Conference Paper
Invasive cardiac catheterisation is a precursor to ablation therapy for ventricular tachycardia. Invasive cardiac diagnostics are fraught with risks. Decades of research has been conducted on the inverse problem of electrocardiography, which can be used to reconstruct Heart Surface Potentials (HSPs) from Body Surface Potentials (BSPs), for non-inva...
Conference Paper
The electrocardiogram (ECG) is commonly used to monitor or diagnose adverse heart conditions. While general ECG recordings are widely available, parametric ECG models have been proposed to generate ECG-like signals. Such ECG generators can create extended segments of specific beat morphology or cardiac rhythm, especially in disease states, which ca...
Preprint
Full-text available
Cyber-physical systems involve a network of discrete controllers that control physical processes. Examples range from autonomous cars to implantable medical devices, which are highly safety critical. Hybrid Automata (HA) based formal approach is gaining momentum for the specification and validation of CPS. HA combines the model of the plant along w...
Article
Full-text available
Invasive cardiac catheterisation is a common procedure that is carried out before surgical intervention. Yet, invasive cardiac diagnostics are full of risks, especially for young children. Decades of research has been conducted on the so called inverse problem of electrocardiography, which can be used to reconstruct Heart Surface Potentials (HSPs)...
Article
Full-text available
Car-following is the activity of safely driving behind a leading vehicle. Traditional mathematical car-following models capture vehicle dynamics without considering human factors, such as driver distraction and the reaction delay. Consequently, the resultant model produces overly safe driving traces during simulation, which are unrealistic. Some re...
Conference Paper
IEC61499 is an emerging standard for the design of automation systems. While many compilers and associated tools for IEC61499 have been developed, systematic techniques for modelling the continuous dynamics of the physical processes are lacking. Current practices involve using co-simulation, where plants are modelled in a tool such as Simulink and...
Article
Full-text available
Models of the cardiac conduction system are usually at two extremes: (1) high fidelity models with excellent precision but lacking a real-time response for emulation (hardware in the loop simulation); or (2) models amenable for emulation, but that do not exhibit appropriate dynamic response, which is necessary for arrhythmia susceptibility. We intr...
Article
Full-text available
Hybrid systems combine discrete controllers with adjoining physical processes. While many approaches exist for simulating hybrid systems, there are few approaches for their emulation, especially when the actual physical plant is not available. This paper develops the first formal framework for emulation along with a new compiler that enables large-...
Article
Full-text available
In scheduling theory and practise for parallel computing, representing a program as a task graph with communication delays is a popular model, due to its general nature, its expressiveness and relative simplicity. Unfortunately, scheduling such a task graph on a set of processors in such a way that it achieves its shortest possible execution time (...
Article
Full-text available
Automation systems used in smart grids, transportation, and medical electronics are cyber-physical in nature. Automation standards, such as IEC-61499, while well suited to the design of discrete controllers, are not ideally suited to model the dynamics of the plant. Such modelling is essential for emulation-based validation of the controllers in th...
Conference Paper
Full-text available
Virtual heart models have been proposed to enhance the safety of implantable cardiac devices through closed loop validation. To communicate with a virtual heart, devices have been driven by cardiac signals at specific sites. As a result, only the action potentials of these sites are sensed. However, the real device implanted in the heart will sense...
Article
Scalability and performance in multicore processors for embedded and real-time systems usually don't go well each with the other. Networks on Chip (NoCs) provide scalable execution platforms suitable for such kind of embedded systems. This article presents a NoC-based Heterogeneous Multi-Processor system, called NoC-HMP, which is a scalable platfor...
Article
Full-text available
Objective: A flexible, efficient and verifiable pacemaker cell model is essential to the design of real-time virtual hearts that can be used for closed-loop validation of cardiac devices. A new parametric model of pacemaker action potential is developed to address this need. Methods: The action potential phases are modeled using hybrid automaton...
Article
Full-text available
Virtual heart models have been proposed to enhance the safety of implantable cardiac devices through closed loop validation. To communicate with a virtual heart, devices have been driven by cardiac signals at specific sites. As a result, only the action potentials of these sites are sensed. However, the real device implanted in the heart will sense...
Article
The synchronous model of computation is well suited for real-time systems, because it allows static analysis in order to find and guarantee their reaction times. Today’s multi-core systems are becoming the predominant computing platforms. Synchronous programs are typically compiled into single threaded code, which makes them unsuitable for exploiti...
Conference Paper
Virtual heart models have been proposed for closed loop validation of safety-critical embedded medical devices, such as pacemakers. These models must react in real-time to off-the-shelf medical devices. Real-time performance can be obtained by implementing models in computer hardware, and methods of compiling classes of Hybrid Automata (HA) onto FP...
Article
Full-text available
The heart is a vital organ that relies on the orchestrated propagation of electrical stimuli to coordinate each heartbeat. Abnormalities in the heart’s electrical behaviour can be managed with a cardiac pacemaker. Recently, the closed-loop testing of pacemakers with an emulation (real-time simulation) of the heart has been proposed. This enables de...
Article
Automatically exploiting short vector instructions sets (SSE, AVX, NEON) is a critically important task for optimizing compilers. Vector instructions typically work best on data that is contiguous in memory, and operating on non-contiguous data requires additional work to gather and scatter the data. There are several varieties of non-contiguous ac...
Article
Full-text available
The Semantic Web comprises enormous volumes of semi-structured data elements. For interoperability, these elements are represented by long strings. Such representations are not efficient for the purposes of applications that perform computations over large volumes of such information. A common approach to alleviate this problem is through the use o...
Article
Full-text available
Hybrid systems are discrete controllers that are used for controlling a physical process (plant) exhibiting continuous dynamics. A hybrid automata (HA) is a well known and widely used formal model for the specification of such systems. While many methods exist for simulating hybrid automata, there are no known approaches for the automatic code gene...
Conference Paper
The synchronous approach featuring deterministic concurrency is widely used to design and verify real-time embedded systems. The synchronous model of computation divides the execution of a program into discrete instants, called ticks. For correctly capturing all input events from the environment, it is pivotal to statically estimate the worst case...
Article
Most of today's embedded systems are very complex. These systems, controlled by computer programs, continuously interact with their physical environments through network of sensory input and output devices. Consequently, the operations of such embedded systems are highly reactive and concurrent. Since embedded systems are deployed in many safety-cr...
Conference Paper
Full-text available
Modern manufacturing systems are best examples where networked embedded controllers and mechatronic devices form the so-called distributed cyber physical systems (CPS). Design and deployment of such systems pose significant challenges to traditional PLC-based software design approaches. In this paper, a unified framework for the design and deployme...
Article
Safety-critical software systems need to guarantee functional correctness and bounded response times to external input events. Programs designed using reactive programming languages, based on formal mathematical semantics, can be automatically verified for functional correctness guarantees. Real-time guarantees on the other hand are much harder to...
Article
We present a simulated annealing based partitioning technique for mapping task graphs, onto heterogeneous processing architectures. Task partitioning onto homogeneous architectures to minimize the makespan of a task graph, is a known NP-hard problem. Heterogeneity greatly complicates the aforementioned partitioning problem, thus making heuristic so...
Article
In this paper we introduce exact and non-exact real-time waits in the reactive Globally Asynchronous Locally Synchronous (GALS) programming languages and synchronous languages as their subset. The language constructs that allow use of real-time waits are illustrated on the SystemJ GALS language. They allow system designers to explicitly use, at the...
Article
In this article, we partition and schedule Synchronous Dataflow (SDF) graphs onto heterogeneous execution architectures in such a way as to minimize energy consumption and maximize throughput. Partitioning and scheduling SDF graphs onto homogeneous architectures is a well-known NP-hard problem. The heterogeneity of the execution architecture makes...
Article
Full-text available
This paper presents a novel approach to including non-instantaneous discrete control transitions in the linear hybrid automaton approach to simulation and verification of hybrid control systems. In this paper we study the control of a continuously evolving analog plant using a controller programmed in a synchronous programming language. We provide...
Article
We present a novel approach for design of manufacturing automation systems with formal verification of selected properties based on the use of Globally Asynchronous Locally Synchronous programming language SystemJ and industrial-proof verification tools. By being able to prove properties of the automation control logic that consists of multiple con...
Conference Paper
Full-text available
A cardiac pacemaker example is used to compare and contrast the Synchronous Reactive (SR) programming model of SystemJ with the SCJ programming model. Our pacemaker is implemented in the synchronous subset of the Globally Asynchronous Locally Synchronous (GALS) SystemJ, which extends the Java language with reactivity, concurrency and real-time cons...
Conference Paper
Static estimation of the Worst Case Reaction Time (WCRT) of synchronous programs is pivotal for designing hard-real time systems in these languages. The current approaches to WCRT estimation suffer from either large overestimation of the WCRT value or the state space explosion problem. In this paper, we present TACO: a framework that integrates mod...
Conference Paper
Full-text available
We tackle the problem of designing and programming dynamic and reactive systems with four objectives: being based on a formal model of computation, using different types of concurrency, being efficient, and tolerating failures. The challenge lies in the fact that good formal models with very high level of abstraction generally result in non-efficie...
Article
Full-text available
The Semantic Web comprises enormous volumes of semi-structured data elements. For interoperability, these elements are represented by long strings. Such representations are not efficient for the purposes of Semantic Web applications that perform computations over large volumes of information. A typical method for alleviating the impact of this prob...