Rapid Prototyping of Digital Systems

Hamblen, James O.; Hall, Tyson S.; Furman, Michael D.

doi:10.1007/978-0-387-72671-7

Cited by 42 publications

(38 citation statements)

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“…As expected, there are mutants with defective temperature compensation in both Neurospora crassa and Drosophila melanogaster (Table 1). However, more intriguingly, geneticists (13,14,(20)(21)(22)(23) have identified many circadian rhythm mutations (aberrant period) that leave temperature compensation intact; indeed, 60-70% of the representative mutants in Table 1 maintain temperature compensation. In order for temperature compensation to survive in the face of a variety of mutations at many different places in the mechanism, many terms in the balance equation must be negligible, i.e., ѨT/Ѩk i ⅐ k i E i Х 0 for many i.…”

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confidence: 99%

A proposal for robust temperature compensation of circadian rhythms

Hong

Conrad

Tyson³

2007

Proc. Natl. Acad. Sci. U.S.A.

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The internal circadian rhythms of cells and organisms coordinate their physiological properties to the prevailing 24-h cycle of light and dark on earth. The mechanisms generating circadian rhythms have four defining characteristics: they oscillate endogenously with period close to 24 h, entrain to external signals, suffer phase shifts by aberrant pulses of light or temperature, and compensate for changes in temperature over a range of 10°C or more. Most theoretical descriptions of circadian rhythms propose that the underlying mechanism generates a stable limit cycle oscillation (in constant darkness or dim light), because limit cycles quite naturally possess the first three defining properties of circadian rhythms. On the other hand, the period of a limit cycle oscillator is typically very sensitive to kinetic rate constants, which increase markedly with temperature. Temperature compensation is therefore not a general property of limit cycle oscillations but must be imposed by some delicate balance of temperature dependent effects. However, ''delicate balances'' are unlikely to be robust to mutations. On the other hand, if circadian rhythms arise from a mechanism that concentrates sensitivity into a few rate constants, then the ''balancing act'' is likely to be more robust and evolvable. We propose a switch-like mechanism for circadian rhythms that concentrates period sensitivity in just two parameters, by forcing the system to alternate between a stable steady state and a stable limit cycle.bistability ͉ homoclinic bifurcation ͉ mathematical model ͉ nuclear transport S ince the breakthrough discovery of the period (per) gene by Konopka and Benzer in 1971 (1), molecular biologists have identified many new circadian rhythm genes and have uncovered a complex network of interacting feedback loops which comprise the control system. In the consensus view, an endogenous daily rhythm is created by a negative feedback loop whereby the PERIOD (PER) protein inhibits its own expression by interfering with transcription factors (2, 3). This mechanism has been studied in great detail theoretically by many authors (4-12). The time-delayed negative feedback loop generates limit cycle oscillations with many properties characteristic of physiological daily rhythms, except for one: the autonomous circadian period (T) is quite insensitive to variations of the kinetic constants, a property that is not characteristic of generic limit cycle oscillators. This insensitivity shows up in two ways: (i) T varies little among individual organisms even though individuals show considerable genetic and/or proteomic variability that translates into variations of kinetic parameters, and (ii) T is temperature compensated, even though kinetic constants are strongly temperature dependent. Physiologically, this robustness of the period (T Ϸ 24 h despite genetic variability and environmental fluctuations) is essential to circadian physiology. If the autonomous period of the clock drifts too far from 24 h, then the circadian rhythm would not reliably ...

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confidence: 99%

A proposal for robust temperature compensation of circadian rhythms

Hong

Conrad

Tyson³

2007

Proc. Natl. Acad. Sci. U.S.A.

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“…The user can program the functions realized by each logic cell and the connections between the cells. Such PGAs are often called FPGAs since they are field programmable [7], [8]. …”

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Hardware Implementation of Artificial Neural Network Using Field Programmable Gate Array

Mohammed¹,

Ali²

2013

IJCTE

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Abstract-In this paper a hardware implementation of an artificial neural network on Field Programmable Gate Arrays (FPGA) is presented. A digital system architecture is designed to realize a feed forward multilayer neural network. The designed architecture is described using Very High Speed Integrated Circuits Hardware Description Language (VHDL). The parallel structure of a neural network makes it potentially fast for the computation of certain tasks. The same feature makes a neural network well suited for implementation in VLSI technology. Hardware realization of a Neural Network (NN), to a large extent depends on the efficient implementation of a single neuron. FPGA-based reconfigurable computing architectures are suitable for hardware implementation of neural networks. FPGA realization of ANNs with a large number of neurons is still a challenging task.Index Terms-Artificial neural network, hardware description language, field programmable gate arrays (FPGAs), sigmoid activation function. I. INTRODUCTIONArtificial neural networks (ANN) have found widespread deployment in a broad spectrum of classification, perception, association and control applications [1].The aspiration to build intelligent systems complemented with the advances in high speed computing has proved through simulation the capability of Artificial Neural Networks (ANN) to map, model and classify nonlinear systems. Real time applications are possible only if low cost high-peed neural computation is made realizable. Towards this goal numerous works on implementation of Neural Networks (NN) have been proposed [2].Artificial neural networks (ANNs) have been mostly implemented in software. This has benefits, since the designer does not need to know the inner workings of neural network elements, but can concentrate on the application of the neural network. However, a disadvantage in real-time applications of software-based ANNs is slower execution compared with hardware-based ANNs.Hardware-based ANNs have been implemented as both analogue and digital circuits. The analogue implementations exploit the nonlinear characteristics of CMOS (complementary metal-oxide semiconductor) devices, but Manuscript received November 18, 2012; revised February 27, 2013 The artificial neuron given in this figure has N inputs, denoted as x1, x2,…..xN,. Each line connecting these inputs to the neuron is assigned a weight, denoted as w1, w2,…..wN respectively. The activation, a, determines whether the neuron is to be fired or not. It is given by the formula: A negative value for a weight indicates an inhibitory connection while a positive value indicates excitatory connection.The output, y of the neuron is given as:Originally the neuron output function f(a) in McCulloch Pitts model was proposed as threshold function, however linear, ramp, and sigmoid functions are also used in different situations. The vector notationcan be used for expressing the activation of a neuron. Here, the jth element of the input vector x is xj, the jth element of the weight vector of w is wj....

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“…2. Motor control signals in this R/C toy truck were tapped at the RF decoder chip in order to control the DC motors using the toy's existing motor drive circuits [3].…”

Section: Selecting a Robot Base 1 Introductionmentioning

confidence: 99%

“…Two modified radio controlled (R/C) servos with a plastic disk and a battery pack can be used to build a simple robot base that moves slowly on flat surfaces [1][2][3]. Fig.…”

Section: Selecting a Robot Base 1 Introductionmentioning

confidence: 99%

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Engaging Undergraduate Students with Robotic Design Projects

Hamblen

Hall

Second IEEE International Workshop on Electronic Design, Test and Applications

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For the past two years in ECE 4006, our team-based senior design project course, we have had a wide variety of mobile robot projects. Students are allowed to select their own projects and teams subject to instructor approval. Many students with an interest in computers have selected robotics projects. The total cost for these various robot projects runs from two hundred to around two thousand dollars. This paper describes the different approaches that student design teams have taken. AbstractThis paper describes our experiences developing robotics design projects for undergraduate students in our electrical and computer engineering curriculum at Georgia Tech. Several low-cost alternatives for developing robot-based design projects and designing the associated electronics and sensors to control them are included.

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Rapid Prototyping of Digital Systems

Cited by 42 publications

References 0 publications

A proposal for robust temperature compensation of circadian rhythms

A proposal for robust temperature compensation of circadian rhythms

Hardware Implementation of Artificial Neural Network Using Field Programmable Gate Array

Engaging Undergraduate Students with Robotic Design Projects

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