Time-free Solution to Independent Set Problem using P Systems with Active Membranes

Membrane computing is a branch of natural computing aiming to abstract computing models from the structure and functioning of living cells. The computation models obtained in the field of membrane computing are usually called P systems. P systems have been used to solve computationally hard problems efficiently on the assumption that the execution of each rule is completed in exactly one time-unit (a global clock is assumed for timing and synchronizing the execution of rules). However, in biological reality, different biological processes take different times to be completed, which can also be influenced by many environmental factors. In this work, with this biological reality, we give a time-free solution to independent set problem using P systems with active membranes, which solve the problem independent of the execution time of the involved rules.

Asynchronous Floating-Point Adders and Communication Protocols: A Survey

Addition is the key operation in digital systems, and floating-point adder (FPA) is frequently used for real number addition because floating-point representation provides a large dynamic range. Most of the existing FPA designs are synchronous and their activities are coordinated by clock signal(s). However, technology scaling has imposed several challenges like clock skew, clock distribution, etc., on synchronous design due to presence of clock signal(s). Asynchronous design is an alternate approach to eliminate these challenges imposed by the clock, as it replaces the global clock with handshaking signals and utilizes a communication protocol to indicate the completion of activities. Bundled data and dual-rail coding are the most common communication protocols used in asynchronous design. All existing asynchronous floating-point adder (AFPA) designs utilize dual-rail coding for completion detection, as it allows the circuit to acknowledge as soon as the computation is done; while bundled data and synchronous designs utilizing single-rail encoding will have to wait for the worst-case delay irrespective of the actual completion time. This paper reviews all the existing AFPA designs and examines the effects of the selected communication protocol on its performance. It also discusses the probable outcome of AFPA designed using protocols other than dual-rail coding.

Analysis of forward approach for upper bounding end-to-end transmission delays over distributed real-time avionics networks

ABSTRACTDistributed real-time avionics networks have been subjected to a great evolution in terms of functionality and complexity. A direct consequence of this evolution is a continual growth of data exchange. AFDX standardised as ARINC 664 is chosen as the backbone network for those distributed real-time avionics networks as it offers high throughput and does not require global clock synchronisation. For certification reasons and engineering research, a deterministic upper bound of the end-to-end transmission delay for packets of each flow should be guaranteed. The Forward Approach (FA) is proposed for the computation of the worst-case end-to-end transmission delay. This approach iteratively estimates the maximum backlog (amount of the pending packets) in each visited switch along the transmission path, and the worst-case end-to-end transmission delay can be computed. Although it is pessimistic (overestimated), the Forward Approach can provide a tighter upper bound of the end-to-end transmission delay while considering the serialisation effect. Recently, our research finds the computation of the serialisation effect might induce an optimistic (underestimated) upper bound. In this paper, we analyse the pessimism in the Forward Approach and the optimism induced by the computation of the serialisation effect, and then we provide a new computation of the serialisation effect. We compare this new computation with the original one, the experiments show that the new computation reduces the optimism and the upper bound of the end-to-end transmission delay can be computed more accurately.

Design of Completion Detectors in Asynchronous Communication System

In digital design, there are two types of design, synchronous design and asynchronous design. In synchronous design, global clock is one of the main system that consume a lot of power. The power in synchronous design is consumed by clock even if there is no data processing take place. The asynchronous design that depends on data is clockless and as far as the power is concerned, asynchronous design does not consume much power compared with synchronous design and this really make asynchronus design the preffered choice for low power consumption. Besides having low power consumption, there are many advantages of aynchronous design compared with synchronous design. This paper proposed new dual rail completion detector (CD), 3-6 CD, 2-7 CD and 1-4 CD for on-chip communication that are used widely in an asynchronous communication system. The design of CD is based on the principle of sum adder. The circuit is designed by using Altera Quartus II CAD tools, synthesis and implementation process is executed to check the syntax error of the design. The design proved to be successful by using asynchronous on-chip communication in the simulation.

Operational Semantics of Annotated Reflex Programs

Reflex is a process-oriented language that provides a design of easy-to-maintain control software for programmable logic controllers. The language has been successfully used in a several reliability critical control systems, e. g. control software for a silicon single crystal growth furnace and electronic equipment control system. Currently, the main goal of the Reflex language project is to develop formal verification methods for Reflex programs in order to guarantee increased reliability of the software created on its basis. The paper presents the formal operational semantics of Reflex programs extended by annotations describing the formal specification of software requirements as a necessary basis for the application of such methods. A brief overview of the Reflex language is given and a simple example of its use – a control program for a hand dryer – is provided. The concepts of environment and variables shared with the environment are defined that allows to disengage from specific input/output ports. Types of annotations that specify restrictions on the values of the variables at program launch, restrictions on the environment (in particular, on the control object), invariants of the control cycle, pre- and postconditions of external functions used in Reflex programs are defined. Annotated Reflex also uses standard annotations assume, assert and havoc. The operational semantics of the annotated Reflex programs uses the global clock as well as the local clocks of separate processes, the time of which is measured in the number of iterations of the control cycle, to simulate time constraints on the execution of processes at certain states. It stores a complete history of changes of the values of shared variables for a more precise description of the time properties of the program and its environment. Semantics takes into account the infinity of the program execution cycle, the logic of process transition management from state to state and the interaction of processes with each other and with the environment. Extending the formal operational semantics of the Reflex language to annotations simplifies the proof of the correctness of the transformation approach to deductive verification of Reflex programs developed by the authors, transforming an annotated Reflex program to an annotated program in a very limited subset of the C language, by reducing a complex proof of preserving the truth of program requirements during the transformation to a simpler proof of equivalence of the original and the resulting annotated programs with respect to their operational semantics.

Lightspeed

This book tells the human story of one of mankind’s greatest intellectual adventures—how we understood that light travels at a finite speed, so that when we look up at the stars we are looking back in time. And how the search for an absolute frame of reference in the universe led inexorably to Einstein’s famous equation E = mc2 for the energy released by nuclear weapons which also powers our sun and the stars. From the ancient Greeks measuring the distance to the Sun, to today’s satellite navigation and Einstein’s theories, the book takes the reader on a gripping historical journey. How Galileo with his telescope discovered the moons of Jupiter and used their eclipses as a global clock, allowing travellers to find their longitude. How Roemer, noticing that the eclipses were sometimes late, used this delay to obtain the first measurement of the speed of light, which takes eight minutes to get to us from the Sun. From the international collaborations to observe the transits of Venus, including Cook’s voyage to Australia, to the extraordinary achievements of Young and Fresnel, whose discoveries eventually taught us that light travels as a wave but arrives as a particle, and the quantum weirdness which follows. In the nineteenth century we find Faraday and Maxwell, struggling to understand how light can propagate through the vacuum of space unless it is filled with a ghostly vortex Aether foam. We follow the brilliantly gifted experimentalists Hertz, discoverer of radio, Michelson with his search for the Aether wind, and Foucault and Fizeau with their spinning mirrors and lightbeams across the rooftops of Paris. The difficulties of sending messages faster than light, using quantum entanglement, and the reality of the quantum world conclude this saga.

Introduction

This book tells the human story of one of mankind’s greatest intellectual adventures - how we understood that light travels at a finite speed, so that when we look up at the stars we are looking back in time. And how the search for an absolute frame of reference in the universe led inexorably to Einstein’s famous equation E = mc2 for the energy released by nuclear weapons, which also powers our sun and the stars. From the ancient Greeks measuring the distance to the sun, to today’s satellite navigation and Einstein’s theories, the book takes the reader on a gripping historical journey. How Galileo with his telescope discovered the moons of Jupiter and used their eclipses as a global clock, allowing travellers to find their Longitude. How Roemer, noticing that the eclipses were sometimes late, used this delay to obtain the first measurement of the speed of light, which takes eight minutes to get to us from the Sun. From the international collaborations to observe the Transits of Venus, including Cook’s voyage to Australia, to the extraordinary achievements of Young and Fresnel, whose discoveries eventually taught us that light travels as a wave but arrives as a particle, and the quantum weirdness which follows. In the nineteenth century we find Faraday and Maxwell, struggling to understand how light can propagate through the vacuum of space unless it is filled with a ghostly vortex Aether foam. We follow the brilliantly gifted experimentalists Hertz, discoverer of radio, Michelson with his search for the Aether wind, and Foucault and Fizeau with their spinning mirrors and lightbeams across the rooftops of Paris, competing to be the first to measure the speed of light on earth. The difficulty of sending messages faster than light using quantum entanglement, and the reality of the quantum world conclude this saga.

Mathematical modeling informs the impact of changes in circadian rhythms and meal patterns on insulin secretion

Disruption of circadian rhythms has been associated with metabolic syndromes, including obesity and diabetes. A variety of metabolic activities are under circadian modulation, as local and global clock gene knockouts result in glucose imbalance and increased risk of metabolic diseases. Insulin release from the pancreatic β cells exhibits daily variation, and recent studies have found that insulin secretion, not production, is under circadian modulation. As consideration of daily variation in insulin secretion is necessary to accurately describe glucose-stimulated insulin secretion, we describe a mathematical model that incorporates the circadian modulation via insulin granule trafficking. We use this model to understand the effect of oscillatory characteristics on insulin secretion at different times of the day. Furthermore, we integrate the dynamics of clock genes under the influence of competing environmental signals (light/dark cycle and feeding/fasting cycle) and demonstrate how circadian disruption and meal size distribution change the insulin secretion pattern over a 24-h day.