Digital control system programming from process control diagrams

A graphical process control language has been developed as a means of defining process control software. The user configures a block diagram describing the required control system, from a menu of functional blocks, using a graphics software system with graphics terminal. Additions may be made to the menu of functional blocks, to extend the system capability, and a group of blocks may be defined as a composite block. This latter feature provides for segmentation of the overall system diagram and the repeated use of the same group of blocks within the system. The completed diagram is analyzed by a graphics compiler which generates the programs and data structure to realise the run-time software. The run-time software has been designed as a data-driven system which allows for modifications at the run-time level in both parameters and system configuration. Data structures have been specified to ensure efficient execution and minimal storage requirements in the final control software. Machine independence has been accomodated as far as possible using CORAL 66 as the high level language throughout the entire system; the final run-time code being generated by a CORAL 66 compiler appropriate to the target processor.

Development of an on-demand beam pulsing system for Pixe-analysis of thick targets

This work concerns the developnent of a proton irduced X-ray emission (PIXE) analysis system and a multi-sample scattering chamber facility. The characteristics of the beam pulsing system and its counting rate capabilities were evaluated by observing the ion-induced X-ray emission from pure thick copper targets, with and without beam pulsing operation. The characteristic X-rays were detected with a high resolution Si(Li) detector coupled to a rrulti-channel analyser. The removal of the pile-up continuum by the use of the on-demand beam pulsing is clearly demonstrated in this work. This new on-demand pu1sirg system with its counting rate capability of 25, 18 and 10 kPPS corresponding to 2, 4 am 8 usec main amplifier time constant respectively enables thick targets to be analysed more readily. Reproducibility tests of the on-demard beam pulsing system operation were checked by repeated measurements of the system throughput curves, with and without beam pulsing. The reproducibility of the analysis performed using this system was also checked by repeated measurements of the intensity ratios from a number of standard binary alloys during the experimental work. A computer programme has been developed to evaluate the calculations of the X-ray yields from thick targets bornbarded by protons, taking into account the secondary X-ray yield production due to characteristic X-ray fluorescence from an element energetically higher than the absorption edge energy of the other element present in the target. This effect was studied on metallic binary alloys such as Fe/Ni and Cr/Fe. The quantitative analysis of Fe/Ni and Cr/Fe alloy samples to determine their elemental composition taking into account the enhancement has been demonstrated in this work. Furthermore, the usefulness of the Rutherford backscattering (R.B.S.) technique to obtain the depth profiles of the elements in the upper micron of the sample is discussed.

A novel actuated digit with tactile feedback for clinical applications

This thesis describes the work carried out on the development of a novel digit actuator system with tactile perception feedback to a user and demonstrated as a master-slave system. For the tactile surface of the digit, contrasting sensor elements of resistive strain gauges and optical fibre Bragg grating sensors were evaluated. A distributive tactile sensing system consisting of optimised neural networking schemes was developed, resulting in taxonomy of artificial touch. The device is suitable for use in minimal invasive surgical (MIS) procedures as a steerable tip and a digit constructed wholly from polymers makes it suitable for use in Magnetic Resonance Imaging (MRI) environments enabling active monitoring of the patient during a procedure. To provide a realistic template of the work the research responded to the needs of two contrasting procedures: palpation of the prostate and endotracheal intubation in anaesthesia where the application of touch sense can significantly assist navigation. The performance of the approach was demonstrated with an experimental digit constructed for use in the laboratory in phantom trials. The phantom unit was developed to resemble facets of the clinical applications and digit system is able to evaluate reactive force distributions acting over the surface of the digit as well as different descriptions of contact and motion relative to the surface of the lumen. Completing control of the digit is via an instrumented glove, such that the digit actuates in sympathy with finger gesture and tactile information feedback is achieved by a combination of the tactile and visual means.

A production planning system for plastic footwear in a seasonal market

Modern injection-moulding machinery which produces several, pairs of plastic footwear at a time brought increased production planning problems to a factory. The demand for its footwear is seasonal but the company's manning policy keeps a fairly constant production level thus determining the aggregate stock. Production planning must therefore be done within the limitations of a specified total stock. The thesis proposes a new production planning system with four subsystems. These are sales forecasting, resource planning, and two levels of production scheduling: (a) aggregate decisions concerning the 'manufacturing group' (group of products) to be produced in each machine each week, and (b) detailed decisions concerning the products within a manufacturing group to be scheduled into each mould-place. The detailed scheduling is least dependent on improvements elsewhere so the sub-systems were tackled in reverse order. The thesis concentrates on the production scheduling sub-systems which will provide most. of the benefits. The aggregate scheduling solution depends principally on the aggregate stocks of each manufacturing group and their division into 'safety stocks' (to prevent shortages) and 'freestocks' (to permit batch production). The problem is too complex for exact solution but a good heuristic solution, which has yet to be implemented, is provided by minimising graphically immediate plus expected future costs. The detailed problem splits into determining the optimal safety stocks and batch quantities given the appropriate aggregate stocks. It.is found that the optimal safety stocks are proportional to the demand. The ideal batch quantities are based on a modified, formula for the Economic Batch Quantity and the product schedule is created week by week using a priority system which schedules to minimise expected future costs. This algorithm performs almost optimally. The detailed scheduling solution was implemented and achieved the target savings for the whole project in favourable circumstances. Future plans include full implementation.

Ultra small integrated optical fiber sensing system

This paper introduces a revolutionary way to interrogate optical fiber sensors based on fiber Bragg gratings (FBGs) and to integrate the necessary driving optoelectronic components with the sensor elements. Low-cost optoelectronic chips are used to interrogate the optical fibers, creating a portable dynamic sensing system as an alternative for the traditionally bulky and expensive fiber sensor interrogation units. The possibility to embed these laser and detector chips is demonstrated resulting in an ultra thin flexible optoelectronic package of only 40 µm, provided with an integrated planar fiber pigtail. The result is a fully embedded flexible sensing system with a thickness of only 1 mm, based on a single Vertical-Cavity Surface-Emitting Laser (VCSEL), fiber sensor and photodetector chip. Temperature, strain and electrodynamic shaking tests have been performed on our system, not limited to static read-out measurements but dynamically reconstructing full spectral information datasets.

Comparative analysis of BER estimation methods in numerical simulation of 40-Gb/s RZ-DPSK transmission with in-line SOAs

Applying direct error counting, we compare the accuracy and evaluate the validity of different available numerical approaches to the estimation of the bit-error rate (BER) in 40-Gb/s return-to-zero differential phase-shift-keying transmission. As a particular example, we consider a system with in-line semiconductor optical amplifiers. We demonstrate that none of the existing models has an absolute superiority over the others. We also reveal the impact of the duty cycle on the accuracy of the BER estimates through the differently introduced Q-factors.

Comparative analysis of BER estimation methods in numerical simulation of 40-Gb/s RZ-DPSK transmission with in-line SOAs

Applying direct error counting, we compare the accuracy and evaluate the validity of different available numerical approaches to the estimation of the bit-error rate (BER) in 40-Gb/s return-to-zero differential phase-shift-keying transmission. As a particular example, we consider a system with in-line semiconductor optical amplifiers. We demonstrate that none of the existing models has an absolute superiority over the others. We also reveal the impact of the duty cycle on the accuracy of the BER estimates through the differently introduced Q-factors. © 2007 IEEE.

Ultra small integrated optical fiber sensing system

This paper introduces a revolutionary way to interrogate optical fiber sensors based on fiber Bragg gratings (FBGs) and to integrate the necessary driving optoelectronic components with the sensor elements. Low-cost optoelectronic chips are used to interrogate the optical fibers, creating a portable dynamic sensing system as an alternative for the traditionally bulky and expensive fiber sensor interrogation units. The possibility to embed these laser and detector chips is demonstrated resulting in an ultra thin flexible optoelectronic package of only 40 µm, provided with an integrated planar fiber pigtail. The result is a fully embedded flexible sensing system with a thickness of only 1 mm, based on a single Vertical-Cavity Surface-Emitting Laser (VCSEL), fiber sensor and photodetector chip. Temperature, strain and electrodynamic shaking tests have been performed on our system, not limited to static read-out measurements but dynamically reconstructing full spectral information datasets.

Synthesis and magnetic properties of Fe-Mn-Cr multinuclear complexes with 4-amino-1,2,4-triazole and oxalate ligands

A multinuclear Fe-Mn-Cr complex with 4-amino-1,2,4-triazole (NH2trz) and oxalate (ox) ligands has been synthesized successfully. The formula of the [Fe(NH2trz)3][ClO4][MnCr(ox)3].4H2O complex has been obtained based on the metal and C, H, N contents. The presence of water molecules, metal-ligand bonding and bridge ligand in the multinuclear complex has been confirmed by its infrared spectrum. The compound crystallizes in the hexagonal system with cell parameters of a = b = 18.695 Å and c = 57.351 Å. The compound shows a gradual spin crossover for iron(II) in the [Fe(NH2trz)3]2+ with transition temperature (T1/2) of 205 K. The antiferromagnetic interaction between Cr(III) and Mn(II) ions in the [MnCr(ox)3]n n- network is observed from the Weiss constant (θ) of –2.3 K.

Bifurcation study for a vertical channel with constant flux and large aspect ratio

Using suitable coupled Navier-Stokes Equations for an incompressible Newtonian fluid we investigate the linear and non-linear steady state solutions for both a homogeneously and a laterally heated fluid with finite Prandtl Number (Pr=7) in the vertical orientation of the channel. Both models are studied within the Large Aspect Ratio narrow-gap and under constant flux conditions with the channel closed. We use direct numerics to identify the linear stability criterion in parametric terms as a function of Grashof Number (Gr) and streamwise infinitesimal perturbation wavenumber (making use of the generalised Squire’s Theorem). We find higher harmonic solutions at lower wavenumbers with a resonance of 1:3exist, for both of the heating models considered. We proceed to identify 2D secondary steady state solutions, which bifurcate from the laminar state. Our studies show that 2D solutions are found not to exist in certain regions of the pure manifold, where we find that 1:3 resonant mode 2D solutions exist, for low wavenumber perturbations. For the homogeneously heated fluid, we notice a jump phenomenon existing between the pure and resonant mode secondary solutions for very specific wavenumbers .We attempt to verify whether mixed mode solutions are present for this model by considering the laterally heated model with the same geometry. We find mixed mode solutions for the laterally heated model showing that a bridge exists between the pure and 1:3 resonant mode 2D solutions, of which some are stationary and some travelling. Further, we show that for the homogeneously heated fluid that the 2D solutions bifurcate in hopf bifurcations and there exists a manifold where the 2D solutions are stable to Eckhaus criterion, within this manifold we proceed to identify 3D tertiary solutions and find that the stability for said 3D bifurcations is not phase locked to the 2D state. For the homogeneously heated model we identify a closed loop within the neutral stability curve for higher perturbation wavenumubers and analyse the nature of the multiple 2D bifurcations around this loop for identical wavenumber and find that a temperature inversion occurs within this loop. We conclude that for a homogeneously heated fluid it is possible to have abrup ttransitions between the pure and resonant 2D solutions, and that for the laterally heated model there exist a transient bifurcation via mixed mode solutions.

Anomalies in stiffness and damping of a 2D discrete viscoelastic system due to negative stiffness components

The recent development of using negative stiffness inclusions to achieve extreme overall stiffness and mechanical damping of composite materials reveals a new avenue for constructing high performance materials. One of the negative stiffness sources can be obtained from phase transforming materials in the vicinity of their phase transition, as suggested by the Landau theory. To understand the underlying mechanism from a microscopic viewpoint, we theoretically analyze a 2D, nested triangular lattice cell with pre-chosen elements containing negative stiffness to demonstrate anomalies in overall stiffness and damping. Combining with current knowledge from continuum models, based on the composite theory, such as the Voigt, Reuss, and Hashin-Shtrikman model, we further explore the stability of the system with Lyapunov's indirect stability theorem. The evolution of the microstructure in terms of the discrete system is discussed. A potential application of the results presented here is to develop special thin films with unusual in-plane mechanical properties. © 2006 Elsevier B.V. All rights reserved.

Span design for reduced noise and nonlinear impairments in a dispersion-managed Raman amplified system

We study a periodic Raman amplified dispersion-managed system with backward-pumping configuration, considering noise and nonlinear impairments. A general optimization method based on nonlinearity management is applied in order to find the configuration that maximizes the system performance. The system is later tested using a full numerical implementation of the nonlinear Schrödinger equation and shown to effectively deliver its longest propagation distance in the same optimal region.

Optimisation of optical regeneration at 40 Gbit/s in dispersion-managed transmission lines with modified synchronous modulators

Numerical optimisation of a 40 Gbit/s dispersion-managed soliton transmission system with in-line synchronous intensity modulation is performed. Using a time-saving numerical approach, superiority of the modified synchronous modulation over conventional synchronous modulation is demonstrated and an optimal operational regime is found.

Optical regeneration at 40 Gb/s in dispersion-managed transmission lines with in-line synchronous modulators

Numerical optimization is performed of the 40-Gb/s dispersion-managed (DM) soliton transmission system with in-line synchronous intensity modulation. Stability of DM soliton transmission results from a combined action of dispersion, nonlinearity, in-line filtering, and modulation through effective periodic bandwidth management of carrier pulses. Therefore, analysis of the multiparametric problem is typically required. A two-stage time-saving numerical optimization procedure is applied. At the first step, the regions of the stable carrier propagation are determined using theoretical models available for DM solitons, and system parameters are optimized. At the second stage, full numerical simulations are undertaken in order to verify the tolerance of optimal transmission regimes. An approach developed demonstrates feasibility of error-free transmission over 20 000 km in a transmission line composed of standard fiber and dispersion compensation fiber at 40 Gb/s.

Simultaneous strain and temperature measurement of advanced 3-D braided composite materials using an improved EFPI/FBG system

Simultaneous strain and temperature measurement for advanced 3-D braided composite materials using fibre-optic sensor technology is demonstrated, for the first time. These advanced 3-D braided composites can virtually eliminate the most serious problem of delamination for conventional composites. A tandem in-fibre Bragg-grating (FBG)/extrinsic Fabry-Perot interferometric sensor (EFPI) system with improved accuracy has been used to facilitate simultaneous temperature and strain measurement in this work. The non-symmetric distortion of the optical spectrum of the FBG, due to the combination of the FBG and the EFPI, is observed for the first time. Experimental and theoretical studies indicate that this type of distortion can affect the measurement accuracy seriously and it is mainly caused by the modulation of the periodic output of the EFPI. A simple method has been demonstrated to improve the accuracy for detection of the wavelength-shift of the FBG induced by temperature change. A strain accuracy of ∼ ±20 με and a temperature accuracy of ∼ ±1 °C have been achieved, which can meet the requirements for practical applications of 3-D braided composites. © 2002 Elsevier Science Ltd. All rights reserved.