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Article
Publication date: 1 September 1951

J. Nightingale

THE determination of orifice parameters was discussed in great detail in an article by G. A. Dirac, ‘The Explicit Determination of Orifice Parameters in Shock Absorbers’…

126

Abstract

THE determination of orifice parameters was discussed in great detail in an article by G. A. Dirac, ‘The Explicit Determination of Orifice Parameters in Shock Absorbers’, published in AIRCRAFT ENGINEERING, Vol. XIX, August 1947, pp. 258–262. The methods there suggested involve a great deal of numerical work, and it has been felt that some rapid approximate method for determining the orifice parameter would be more satisfactory. The present article represents an attempt to obtain a simple explicit relation for this parameter.

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Aircraft Engineering and Aerospace Technology, vol. 23 no. 9
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 November 1948

G.A. Dirac

THE study of the vibration of a straight elastic bar is a very old one. The vibrations may be classified as lateral (or transverse) torsional and longitudinal. The first two are…

84

Abstract

THE study of the vibration of a straight elastic bar is a very old one. The vibrations may be classified as lateral (or transverse) torsional and longitudinal. The first two are the more important ones and also the more difficult. We shall consider the lateral and torsional vibrations of a bar clamped at one end and free at the other, which may rotate like the blades of an airscrew. Both cases, rotation or none, are important problems of civil engineering, marine and aeronautical engineering and the theory of elasticity.

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Aircraft Engineering and Aerospace Technology, vol. 20 no. 11
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 August 1947

G.A. Dirac

THE differential equations governing the behaviour of even the simplest type of oleopneumatic shock absorber have to be integrated by an approximate step‐by‐step method. Such…

30

Abstract

THE differential equations governing the behaviour of even the simplest type of oleopneumatic shock absorber have to be integrated by an approximate step‐by‐step method. Such methods have been given by several writers. The orifices enter into these equations in the form of a parameter. To determine the orifices a value of this parameter is guessed and the equations are solved by the empirical method. If the solution obtained is not satisfactory, further values are guessed until a suitable value is obtained.

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Aircraft Engineering and Aerospace Technology, vol. 19 no. 8
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 5 October 2012

Burcu Tunga and Metin Demiralp

The plain High Dimensional Model Representation (HDMR) method needs Dirac delta type weights to partition the given multivariate data set for modelling an interpolation problem…

147

Abstract

Purpose

The plain High Dimensional Model Representation (HDMR) method needs Dirac delta type weights to partition the given multivariate data set for modelling an interpolation problem. Dirac delta type weight imposes a different importance level to each node of this set during the partitioning procedure which directly effects the performance of HDMR. The purpose of this paper is to develop a new method by using fluctuation free integration and HDMR methods to obtain optimized weight factors needed for identifying these importance levels for the multivariate data partitioning and modelling procedure.

Design/methodology/approach

A common problem in multivariate interpolation problems where the sought function values are given at the nodes of a rectangular prismatic grid is to determine an analytical structure for the function under consideration. As the multivariance of an interpolation problem increases, incompletenesses appear in standard numerical methods and memory limitations in computer‐based applications. To overcome the multivariance problems, it is better to deal with less‐variate structures. HDMR methods which are based on divide‐and‐conquer philosophy can be used for this purpose. This corresponds to multivariate data partitioning in which at most univariate components of the Plain HDMR are taken into consideration. To obtain these components there exist a number of integrals to be evaluated and the Fluctuation Free Integration method is used to obtain the results of these integrals. This new form of HDMR integrated with Fluctuation Free Integration also allows the Dirac delta type weight usage in multivariate data partitioning to be discarded and to optimize the weight factors corresponding to the importance level of each node of the given set.

Findings

The method developed in this study is applied to the six numerical examples in which there exist different structures and very encouraging results were obtained. In addition, the new method is compared with the other methods which include Dirac delta type weight function and the obtained results are given in the numerical implementations section.

Originality/value

The authors' new method allows an optimized weight structure in modelling to be determined in the given problem, instead of imposing the use of a certain weight function such as Dirac delta type weight. This allows the HDMR philosophy to have the chance of a flexible weight utilization in multivariate data modelling problems.

Details

Engineering Computations, vol. 29 no. 7
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 11 March 2019

Vivien Brunel

In machine learning applications, and in credit risk modeling in particular, model performance is usually measured by using cumulative accuracy profile (CAP) and receiving…

533

Abstract

Purpose

In machine learning applications, and in credit risk modeling in particular, model performance is usually measured by using cumulative accuracy profile (CAP) and receiving operating characteristic curves. The purpose of this paper is to use the statistics of the CAP curve to provide a new method for credit PD curves calibration that are not based on arbitrary choices as the ones that are used in the industry.

Design/methodology/approach

The author maps CAP curves to a ball–box problem and uses statistical physics techniques to compute the statistics of the CAP curve from which the author derives the shape of PD curves.

Findings

This approach leads to a new type of shape for PD curves that have not been considered in the literature yet, namely, the Fermi–Dirac function which is a two-parameter function depending on the target default rate of the portfolio and the target accuracy ratio of the scoring model. The author shows that this type of PD curve shape is likely to outperform the logistic PD curve that practitioners often use.

Practical implications

This paper has some practical implications for practitioners in banks. The author shows that the logistic function which is widely used, in particular in the field of retail banking, should be replaced by the Fermi–Dirac function. This has an impact on pricing, the granting policy and risk management.

Social implications

Measuring credit risk accurately benefits the bank of course and the customers as well. Indeed, granting is based on a fair evaluation of risk, and pricing is done accordingly. Additionally, it provides better tools to supervisors to assess the risk of the bank and the financial system as a whole through the stress testing exercises.

Originality/value

The author suggests that practitioners should stop using logistic PD curves and should adopt the Fermi–Dirac function to improve the accuracy of their credit risk measurement.

Details

The Journal of Risk Finance, vol. 20 no. 2
Type: Research Article
ISSN: 1526-5943

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Article
Publication date: 5 July 2013

Krzysztof Kluszczyński and Marek Kciuk

The main purpose of the paper is to develop model basing on the modified and properly‐adopted Fermi‐Dirac equation which combines proper accuracy with adequate simplicity as well…

526

Abstract

Purpose

The main purpose of the paper is to develop model basing on the modified and properly‐adopted Fermi‐Dirac equation which combines proper accuracy with adequate simplicity as well as to show how steady state and transient curves resulting from this model can be applied for solving design task.

Design/methodology/approach

The standard Fermi‐Dirac equation was modified and extended. Full performance cycle for the SMA actuator was characterized by double‐valued function describing the actuator activation and the actuator deactivation. All these functions and parameters can be easily determined by analysis of measurement data or with use of Hooke‐Jeeves optimization algorithm.

Findings

SMA linear actuator can be used in mechatronic systems as a special non‐standard drive when ultra‐light mass and very simple mechanical construction of power feed system is required. The proposed steady‐state and transient performance curves as well as operation diagram constitute sufficient base for effective designing SMA drive systems.

Research limitations/implications

The greatest disadvantage of a SMA actuator is long time of deactivation resulting from slow self‐cooling process. As far as efficiency is concerned as essential factor for choosing the most suitable linear actuator, there is no sense to take into account a linear SMA actuator because of its very low efficiency.

Practical implications

Designer can use performance curve which determines proper length of SMA actuator and range of its motion. The proposed model can be implemented in SMA drive control unit for controlling position of the actuator.

Originality/value

Similarities between change of martensitic phase during transition process and probability P of electron energy level distribution described by the Fermi‐Dirac two‐variable equation were taken into account. Such an approach seems to express in the most suitable way the physical nature of m‐a transition. The authors decided to extend concept (proposed in Jayender et al.) and to adopt the Fermi‐Dirac equation for describing behaviour of a SMA linear actuator.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 32 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 21 August 2009

Anas N. Al‐Rabadi

The purpose of this paper is to introduce new non‐classical implementations of neural networks (NNs). The developed implementations are performed in the quantum, nano, and optical…

347

Abstract

Purpose

The purpose of this paper is to introduce new non‐classical implementations of neural networks (NNs). The developed implementations are performed in the quantum, nano, and optical domains to perform the required neural computing. The various implementations of the new NNs utilizing the introduced architectures are presented, and their extensions for the utilization in the non‐classical neural‐systolic networks are also introduced.

Design/methodology/approach

The introduced neural circuits utilize recent findings in the quantum, nano, and optical fields to implement the functionality of the basic NN. This includes the techniques of many‐valued quantum computing (MVQC), carbon nanotubes (CNT), and linear optics. The extensions of implementations to non‐classical neural‐systolic networks using the introduced neural‐systolic architectures are also presented.

Findings

Novel NN implementations are introduced in this paper. NN implementation using the general scheme of MVQC is presented. The proposed method uses the many‐valued quantum orthonormal computational basis states to implement such computations. Physical implementation of quantum computing (QC) is performed by controlling the potential to yield specific wavefunction as a result of solving the Schrödinger equation that governs the dynamics in the quantum domain. The CNT‐based implementation of logic NNs is also introduced. New implementations of logic NNs are also introduced that utilize new linear optical circuits which use coherent light beams to perform the functionality of the basic logic multiplexer by utilizing the properties of frequency, polarization, and incident angle. The implementations of non‐classical neural‐systolic networks using the introduced quantum, nano, and optical neural architectures are also presented.

Originality/value

The introduced NN implementations form new important directions in the NN realizations using the newly emerging technologies. Since the new quantum and optical implementations have the advantages of very high‐speed and low‐power consumption, and the nano implementation exists in very compact space where CNT‐based field effect transistor switches reliably using much less power than a silicon‐based device, the introduced implementations for non‐classical neural computation are new and interesting for the design in future technologies that require the optimal design specifications of super‐high speed, minimum power consumption, and minimum size, such as in low‐power control of autonomous robots, adiabatic low‐power very‐large‐scale integration circuit design for signal processing applications, QC, and nanotechnology.

Details

International Journal of Intelligent Computing and Cybernetics, vol. 2 no. 3
Type: Research Article
ISSN: 1756-378X

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Article
Publication date: 19 June 2007

Dwijesh K. Dutta Majumder and Swapan K. Dutta

To develop a mathematical and algorithmic approach of avoiding the limitations of deterministically computing the values of energy, time, position and momentum imposed by…

614

Abstract

Purpose

To develop a mathematical and algorithmic approach of avoiding the limitations of deterministically computing the values of energy, time, position and momentum imposed by Heisenberg's uncertainity principle (HUP) which is of profound significance from the point of view of some emerging science and technology like quantum computing, nano scale technology and chaotic dynamical systems.

Design/methodology/approach

A parametric method of establishing deterministic solutions for energy and momentum on the basis of quantized energy limits (instead of HUP) if developed in the non‐infinite non‐zero quantized energy limits where hidden deterministic solutions can be obtained for micro/nano structures.

Findings

The philosophical foundations of quantum mechanics as developed by Max Planck, Neils Bohrz, Werner Heisenburg, Dirac and Edwein Schrodinger is based on a duality concept of complimentarity notions. In most general logical sense for any physical reality qualitative dualism have to have a quantitative dualism may be hidden or virtual. The upper and lower limits of the dynamical quantum mechanical observables are determined based on the dimensional considerations for the physical constants H, C, G and H0. The conceptual basis and mathematical framework of the paper in based Norbert Wiener's work on theory of cybernetics and D. Dutta Majumdars' unified cybernetic and general dynamical systems theory.

Research limitations/implications

The testability of the theory needs to be established.

Originality/value

Without challenging HUP this is a contribution of tremendous practical implications.

Details

Kybernetes, vol. 36 no. 5/6
Type: Research Article
ISSN: 0368-492X

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Article
Publication date: 30 January 2018

Saeid Masoumi, Hassan Hajghassem, Alireza Erfanian and Ahmad Molaei Rad

Smart sensors based on graphene field effect transistor (GFET) and biological receptors are regarded as a promising nanomaterial that could be the basis for future generation of…

396

Abstract

Purpose

Smart sensors based on graphene field effect transistor (GFET) and biological receptors are regarded as a promising nanomaterial that could be the basis for future generation of low-power, faster, selective real-time monitoring of target analytes and smaller electronics. So, the purpose of this paper is to provide details of sensors based on selective nanocoatings by combining trinitrotoluene (TNT) receptors (Trp-His-Trp) bound to conjugated polydiacetylene polymers on a graphene channel in GFET for detecting explosives TNT.

Design/methodology/approach

Following an introduction, this paper describes the way of manufacturing of the GFET sensor by using investigation methods for transferring graphene sheet from Cu foil to target substrates, which is functionalized by the TNT peptide receptors, to offer a system which has the capability of answering the presence of related target molecules (TNT). Finally, brief conclusions are drawn.

Findings

In a word, shortly after graphene discovery, it has been explored with a variety of methods gradually. Because of its exceptional electrical properties (e.g. extremely high carrier mobility and capacity), electrochemical properties such as high electron transfer rate and structural properties, graphene has already showed great potential and success in chemical and biological sensing fields. Therefore, the authors used a biological receptor with a field effect transistor (FET) based on graphene to fabricate sensor for achieving high sensitivity and selectivity that can detect explosive substances such as TNT. The transport property changed compared to that of the FET made by intrinsic graphene, that is, the Dirac point position moved from positive Vg to negative Vg, indicating the transition of graphene from p-type to n-type after annealing in TNT, and the results show the bipolar property change of GFET with the TNT concentration and the possibility to develop a robust, easy-to-use and low-cost TNT detection method for performing a sensitive, reliable and semi-quantitative detection in a wide detection range.

Originality/value

In this timeframe of history, TNT is a common explosive used in both military and industrial settings. Its convenient handling properties and explosive strength make it a common choice in military operations and bioterrorism. TNT and other conventional explosives are the mainstays of terrorist bombs and the anti-personnel mines that kill or injure more than 15,000 people annually in war-torn countries. In large, open-air environments, such as airports, train stations and minefields, concentrations of these explosives can be vanishingly small – a few parts of TNT, for instance, per trillion parts of air. That can make it impossible for conventional bomb and mine detectors to detect the explosives and save lives. So, in this paper, the authors report a potential solution with design and manufacture of a GFET sensor based on a biological receptor for real-time detection of TNT explosives specifically.

Details

Sensor Review, vol. 38 no. 2
Type: Research Article
ISSN: 0260-2288

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Article
Publication date: 30 August 2019

Saeid Masoumi and Hassan Hajghassem

Smart biosensors that can perform sensitive and selective monitoring of target analytes are tremendously valuable for trinitrotoluene (TNT) explosive detection. In this research…

207

Abstract

Purpose

Smart biosensors that can perform sensitive and selective monitoring of target analytes are tremendously valuable for trinitrotoluene (TNT) explosive detection. In this research, the pre-developed sensor was integrated with biological receptors in which they enhanced the sensitivity of the sensor. This is due to conjugated polydiacetylene onto a peptide-based molecular recognition element (Trp-His-Trp) for TNT molecules in graphene field-effect transistors (GR-FETs) as biosensor that is capable of responding to the presence of a TNT target with a colorimetric response. The authors confirmed the efficacy of the receptor while being attached to polydiacetylene (PDA) by observing the binding ability between the Trp-His-Trp and TNT to alter the electronic band structure of the PDA conjugated backbones. The purpose of this paper is to demonstrate a modular system capable of transducing small-molecule TNT binding into a detectable signal. The details of the real-time and selective TNT biosensor have been reported.

Design/methodology/approach

Following an introduction, this paper describes the way of fabrication GR-FETs with conventional photolithography techniques and the other processes, which is functionalized by the TNT peptide receptors. The authors first determined the essential TNT recognition elements from UV-visible spectrophotometry spectroscopy for PDA sensor unit fabrication. In particular, the blue percentage and the chromic response were used to characterize the polymerization parameter of the conjugated p backbone. A continuous-flow trace vapor source of nitroaromatics (two, four, six-TNT) was designed and evaluated in terms of temperature dependence. The TNT concentration was measured by liquid/gas extraction in acetonitrile using bubbling sequence. The sensor test is performed using a four-point probe and semiconductor analyzer. Finally, brief conclusions are drawn.

Findings

Because of their unique optical and stimuli-response properties, the polydiacetylene and peptide-based platforms have been explored as an alternative to complex mechanical and electrical sensing systems. Therefore, the authors have used GR-FETs with biological receptor-PDAs as a biosensor for achieving high sensitivity and selectivity that can detect explosive substances such as TNT. The transport property changed compared to that of the field-effect transistors made by intrinsic graphene, that is, the Dirac point position moved from positive Vg to negative Vg, indicating the transition of graphene from p-type to n-type after annealing in TNT, and when the device was tested from RT, the response of the device was found to increase linearly with increasing concentrations. Average shifting rate of the Dirac peak was obtained as 0.1-0.3 V/ppm. The resulting sensors exhibited at the limit ppm sensitivity toward TNT in real-time, with excellent selectivity over various similar aromatic compounds. The biological receptor coating may be useful for the development of sensitive and selective micro and nanoelectronic sensor devices for various other target analytes.

Originality/value

The detection of illegally transported explosives has become important as the global rise in terrorism subsequent to the events of September 11, 2001, and is at the forefront of current analytical problems. It is essential that a detection method has the selectivity to distinguish among compounds in a mixture of explosives. So, the authors are reporting a potential solution with the designing and manufacturing of electrochemical biosensor using polydiacetylene conjugated with peptide receptors coated on GR-FETs with the colorimetric response for real-time detection of TNT explosives specifically.

Details

Sensor Review, vol. 39 no. 6
Type: Research Article
ISSN: 0260-2288

Keywords

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