A study of liquid-liquid extraction in a sieve plate column

The literature relating to sieve plate liquid extraction columns and relevant hydrodynamic phenomena have been surveyed. Mass transfer characteristics during drop formation, rise and coalescence, and related models were also reviewed. Important design parameters i.e. flooding, dispersed phase hold-up, drop size distribution, mean drop size, coalescence/flocculation zone height beneath a plate and jetting phenomena were investigated under non-mass transfer and mass transfer conditions in a 0.45m diameter, 2.3m high sieve plate column. This column had provision for four different plate designs, and variable plate spacing and downcomer heights, and the system used was Clairsol `350' (dispersed) - acetone - deionised water (continuous) with either direction of mass transfer. Drop size distributions were best described by the functions proposed by Gal-or, and then Mugele-Evans. Using data from this study and the literature, correlations were developed for dispersed phase hold-up, mean drop size in the preferred jetting regime and in the non-jetting regime, and coalescence zone height. A method to calculate the theoretical overall mass transfer coefficient allowing for the range of drop sizes encountered in the column gave the best fit to experimental data. This applied the drop size distribution diagram to estimate the volume percentage of stagnant, circulating and oscillating drops in the drop population. The overall coefficient Kcal was then calculated as the fractional sum of the predicted individual single drop coefficients and their proportion in the drop population. In a comparison between the experimental and calculated overall mass transfer coefficients for cases in which all the drops were in the oscillating regime (i.e. 6.35mm hole size plate), and for transfer from the dispersed(d) to continuous(c) phase, the film coefficient kd predicted from the Rose-Kintner correlation together with kc from that of Garner-Tayeban gave the best representation. Droplets from the 3.175mm hole size plate, were of a size to be mainly circulating and oscillating; a combination of kd from the Kronig-Brink (circulating) and Rose-Kintner (oscillating) correlations with the respective kc gave the best agreement. The optimum operating conditions for the SPC were identified and a procedure proposed for design from basic single drop data.

From national innovation systems to national innovation capacity:internationalisation and technology transfer perspectives

The last decade or so has witnessed the emergence of the national innovation system (NIS) phenomenon. Since then, many scholars have investigated NIS and its implementation in different countries. However, there are very few investigations into the relationship between the NIS of a country and its national innovation capacity. This paper aims to make a contribution in this area by examining the link that currently exists between these two topics. Whilst examining this relationship, we also explore internationalisation and technology transfer, being cognate areas that have been investigated during the same period. This follows our assertion that the link between NIS and national innovation capacity is the mechanism of internationalisation and technology transfer. The NIS approach was introduced in the late 1980s (see Freeman, 1987; Dosi et al., 1988) and further elaborated later (see Lundvall, 1992; Nelson, 1993; Edquist, 1997). In essence, a country?s NIS is a historically grown subsystem of the entire national economy consisting of organisations and institutions which play a major role in the innovative activity in the country. In the NIS approach, interactions within organisations as well as the interplay between organisations and institutions are of central importance. The NIS approach has been used to reveal the structure of the innovation processes and the main actors involved in them in industrialised and emerging countries. Although the national focus remains strong, it has been accompanied by studies seeking to analyse the notion of systems of innovation at an international level and at a sub-national scale (Archibugi et al., 1999). Dosi in the edition of Archibugi et al. (1999) argues that the general background of the discussion of national systems is the observation of non-random distributions across countries of: corporate capabilities; organisational forms; strategies; and ultimately revealed performances, in terms of production efficiency and inputs productivities, rates of innovation, rates of adoption/diffusion of innovation themselves, dynamics of market shares on the world markets, growth of income and employment. They also mention that there are several approaches to NIS. Nelson (1993) focuses upon the specificities of national institutions and policies supporting directly or indirectly innovation, diffusion and skills accumulation. Patel and Pavitt (1991) have stressed the links between the national patterns of technological accumulation and the competencies and innovative strategies of a few major national companies. Amable et al (1997) and Soskice (1993) and Zysman (1994) focus on the specifics of national institutions including, for example, the forms of organization, financial and labour markets, training institutions, forms of state intervention in the economy etc. However, the most common reference is by Lundvall (1992) who argues that the focus on the national level is associated with the fact that national economies vary according to their production system and their institutional framework and these differences are in turn strengthened by different historical experiences, language and culture. On the other hand, the national innovation capability consists of abilities to create and carry new technological possibilities through to economic practice. The term covers a wide range of activities from capability to invent to capability to innovate and to capability to improve existing technology beyond the original design parameters (Kim, 1997). The term innovation is often associated by many with technological change at international frontiers. However, technological capability is not the same as innovation capability. Technological capability refers to assimilation, use, adaptation, and change to existing technologies. It also enables the creation of new technologies and development of new products and processes in response to changing economic environments. It denotes operational command over knowledge (Kim, 1997). It is manifested not merely by the knowledge possessed, but, more important, by the uses to which that knowledge can be put and by the proficiency with which it is applied in the activities of investment and production and in the creation of new knowledge (Westphal et al., 1985). Therefore, the analytical framework that is used in this paper is based on the way a country derives from its NIS a national innovation capacity. There are two perspectives that are identified on this way. These are internationalisation and technology transfer. Even though NIS is not directly related to national innovation capacity, to achieve national innovation capacity from NIS, the country should have the ability for technology transfer. Technology transfer is a link between these two phenomena. On the other hand, internationalisation can be either the input or the output of the relationship between NIS and national innovation capability. If a company is investing in a country because of its national innovation capacity, this can be regarded as an input to the relationship between NIS and national innovation capacity. If this company is investigating the national innovation capacity of a country then, for its internationalisation, the national innovation capacity should be important, which in turn means this company is active in innovation and innovation is also an important success factor. The interrelationship between the investment of the company and the NIS of the country (assuming that the country is competent and competitive in technology transfer) will generate and improve that country?s national innovation capacity. This is the output of internationalisation from the relationship between NIS and national innovation capacity. When companies are evaluating whether to internationalise, they investigate certain factors in the countries in which they are considering to invest. The ability to transfer technology is dependent on ability to adopt a new technology and also on the learning derived from this technology. If countries wish to attract innovation related investment they need to show their ability to have a NIS and also the capability to transfer technology. Without the technology transfer capability, the NIS is not functioning. Therefore, companies that internationalise will investigate the factors common to NIS, technology transfer, and their business needs. Through this paper we will demonstrate this link though its mechanisms. Our research will be through extensive literature review and identifying relevant aspects of previous research carried out by the authors. It will investigate certain factors of different countries that are successful in attracting innovation related foreign direct investment. Through these, we will point out the factors that are important for the link and mechanisms of NIS and national innovation capability.

Applications of ultralong Raman fibre lasers in photonics

This thesis presents a numerical and experimental investigation on applications of ultralong Raman fibre lasers in optical communications, supercontinuum generation and soliton transmission. The research work is divided in four main sections. The first involves the numerical investigation of URFL intra-cavity power and the relative intensity noise transfer evolution along the transmission span. The performance of the URFL is compared with amplification systems of similar complexity. In the case of intracavity power evolution, URFL is compared with a first order Raman amplification system. For the RIN transfer investigation, URFL is compared with a bi-directional dual wavelength pumping system. The RIN transfer function is investigated for several cavity design parameters such as span length, pump distribution and FBG reflectivity. The following section deals with experimental results of URFL cavities. The enhancement of the available spectral bandwidth in the C-band and its spectral flatness are investigated for single and multi-FBGs cavity system. Further work regarding extended URFL cavity in combination with Rayleigh scattering as random distributed feedback produced a laser cavity with dual wavelength outputs independent to each other. The last two sections relate to URFL application in supercontinuum (SC) generation and soliton transmission. URFL becomes an enhancement structure for SC generation. This thesis shows successful experimental results of SC generation using conventional single mode optical fibre and pumped with a continuous wave source. The last section is dedicated to soliton transmission and the study of soliton propagation dynamics. The experimental results of exact soliton transmission over multiple soliton periods using conventional single mode fibre are shown in this thesis. The effect of the input signal, pump distribution, span length and FBGs reflectivity on the soliton propagation dynamics is investigated experimentally and numerically.

The chromatographic separation of carbohydrate mixtures

The separation performance of a semicontinuous counter-current chromatographic refiner (SCCR7), consisting of twelve 5.4 cm id x 75cm long columns packed with calcium charged cross-linked polysytrene resin (KORELA VO7C), was optimised. An industrial barley syrup was used containing 42% fructose, 52% glucose and 6% maltose and oligosaccharides. The effects of temperature, flow rates and concentration on the distribution coefficients were evaluated and quantified by deriving general relationships. The effects of flow rates, feed composition and concentration on the separation performance of the SCCR7 were identified and general relationships between them and the switch time, which was found to be the controlling parameter, were developed. Fructose rich (FRP) and glucose rich (GRP) product purities of 99.9% were obtained at 18.6% w/v feed concentrations. When a 66% w/v feed concentration was used and product splitting technique was employed, the throughput was 32.1 kg sugar solids/m3 resin/hr. The GRP contained less than 4.5% fructose, the FRP was over 95% pure, and the respective concentrations were 22.56 and 11.29% w/v. Over 94% of the glucose and 95.78% of the fructose in the feed were recovered in the GRP and FRP respectively. By recycling the dilute product split fractions, the GRP and FRP concentrations were increased to 25.4 and 12.96% w/v; the FRP was 90.2% pure and the GRP contained 6.69% w/v fructose. A theoretical link between batch and semicontinuous chromatographic equipments has been determined. A computer simulation was developed predicting successfully the purging concentration profiles at `pseudo-equilibrium', and also certain system design parameters. An important further aspect of the work has been to study the behaviour of chromatographic bioreactor-separators. Such batch systems of 5.4cm id and lengths varying between 30 and 230cm, were used to investigate the effect of scaling up on the conversion of sucrose into dextran and fructose in the presence of the dextransucrase enzyme. Conversions of over 80% were achieved at 4 hr sucrose residence times. The crude dextransucrase was purified using centrifugation, ultrafiltration and cross-flow microfiltration techniques. Better enzyme stability was obtained by first separating the non-solid impurities using cross-flow microfiltration, and then removing the cells from the enzyme immediately before use by continuous centrifugation.

Generation of triangular pulses in normally dispersive fibre

In this scheme, nonlinearity and dispersion in the NDF lead to various reshaping processes of an initial, conventional pulse according to the chirping value and power level at the input of the fibre. In particular, we have observed that triangular-shaped pulses can be generated for sufficiently high energies and a positive initial chirp parameter. In our experiments, 2.8 ps-FWHM, transform-limited pulses generated from a mode-locked fibre laser source at a repetition rate of 1.25 GHz were pre-chirped by propagating the pulses through different lengths of standard mono-mode fibre. The chirped pulses were then amplified to different power levels before being launched into a 2.3 km section of True Wave fibre (TWF). The corresponding numerically calculated pulse temporal intensity profile and numerical and experimental second-harmonic generation frequency-resolved optical gating (SHG FROG) spectrograms were also derived. In conclusion, we have presented numerical modelling results which show the system design parameters required for the generation of triangular-shaped pulses in a nonlinear NDF, and experimentally demonstrated triangular pulse shaping in conventional NDF.

Knowledge-based system for casting process selection

Design of casting entails the knowledge of various interacting factors that are unique to casting process, and, quite often, product designers do not have the required foundry-specific knowledge. Casting designers normally have to liaise with casting experts in order to ensure the product designed is castable and the optimum casting method is selected. This two-way communication results in long design lead times, and lack of it can easily lead to incorrect casting design. A computer-based system at the discretion of a design engineer can, however, alleviate this problem and enhance the prospect of casting design for manufacture. This paper proposes a knowledge-based expert system approach to assist casting product designers in selecting the most suitable casting process for specified casting design requirements, during the design phase of product manufacture. A prototype expert system has been developed, based on production rules knowledge representation technique. The proposed system consists of a number of autonomous but interconnected levels, each dealing with a specific group of factors, namely, casting alloy, shape and complexity parameters, accuracy requirements and comparative costs, based on production quantity. The user interface has been so designed to allow the user to have a clear view of how casting design parameters affect the selection of various casting processes at each level; if necessary, the appropriate design changes can be made to facilitate the castability of the product being designed, or to suit the design to a preferred casting method.

A novel architecture for all-optical add-drop multiplexing of OFDM signals

We propose a novel architecture for all-optical add-drop multiplexing of OFDM signals. Extensive numerical simulations have been carried out to benchmark the performance of the architecture against critical design parameters.

All-optical add-drop multiplexer for OFDM signals

We summarize our research work on the design and development of an add-drop multiplexer for spectrally overlapping OFDM signals. The standard node functions of sub-channel drop, extraction and insertion were obtained whilst the signals remained fully in the optical domain. Numerical simulations have been carried out to identify the main sources of degradation and to benchmark the architectural performance against critical design parameters, whereas the experimental demonstration of the scheme has been achieved for both single quadrature and dual quadrature signals. The reported scheme enables a fully flexible node compatible with future terabit per second super-channel transmission.

Powertrain optimisation in a hybrid electric bus

This paper describes the use of a formal optimisation procedure to optimise a plug-in hybrid electric bus using two different case studies to meet two different performance criteria; minimum journey cost and maximum battery life. The approach is to choose a commercially available vehicle and seek to improve its performance by varying key design parameters. Central to this approach is the ability to develop a representative backward facing model of the vehicle in MATLAB/Simulink along with appropriate optimisation objective and penalty functions. The penalty functions being the margin by which a particular design fails to meet the performance specification. The model is validated against data collected from an actual vehicle and is used to estimate the vehicle performance parameters in a model-in-the-loop process within an optimisation routine. For the purposes of this paper, the journey cost/battery life over a drive cycle is optimised whilst other performance indices are met (or exceeded). Among the available optimisation methods, Powell's method and Simulated Annealing are adopted. The results show this method as a valid alternative modelling approach to vehicle powertrain optimisation. © 2012 IEEE.

Numerical investigation of all-optical add-drop multiplexing for spectrally overlapping OFDM signals

We propose a novel architecture for all-optical add-drop multiplexing of OFDM signals. Sub-channel extraction is achieved by means of waveform replication and coherent subtraction from the OFDM super-channel. Numerical simulations have been carried out to benchmark the performance of the architecture against critical design parameters.

RIN transfer in 2nd-order distributed amplification with ultralong fiber lasers

We investigate numerically the effect of ultralong Raman laser fiber amplifier design parameters, such as span length, pumping distribution and grating reflectivity, on the RIN transfer from the pump to the transmitted signal. Comparison is provided to the performance of traditional second-order Raman amplified schemes, showing a relative performance penalty for ultralong laser systems that gets smaller as span length increases. We show that careful choice of system parameters can be used to partially offset such penalty. © 2010 Optical Society of America.

Design of experiments to study the impact of process parameters on droplet size and development of non-invasive imaging techniques in tablet coating

Atomisation of an aqueous solution for tablet film coating is a complex process with multiple factors determining droplet formation and properties. The importance of droplet size for an efficient process and a high quality final product has been noted in the literature, with smaller droplets reported to produce smoother, more homogenous coatings whilst simultaneously avoiding the risk of damage through over-wetting of the tablet core. In this work the effect of droplet size on tablet film coat characteristics was investigated using X-ray microcomputed tomography (XμCT) and confocal laser scanning microscopy (CLSM). A quality by design approach utilising design of experiments (DOE) was used to optimise the conditions necessary for production of droplets at a small (20 μm) and large (70 μm) droplet size. Droplet size distribution was measured using real-time laser diffraction and the volume median diameter taken as a response. DOE yielded information on the relationship three critical process parameters: pump rate, atomisation pressure and coating-polymer concentration, had upon droplet size. The model generated was robust, scoring highly for model fit (R2 = 0.977), predictability (Q2 = 0.837), validity and reproducibility. Modelling confirmed that all parameters had either a linear or quadratic effect on droplet size and revealed an interaction between pump rate and atomisation pressure. Fluidised bed coating of tablet cores was performed with either small or large droplets followed by CLSM and XμCT imaging. Addition of commonly used contrast materials to the coating solution improved visualisation of the coating by XμCT, showing the coat as a discrete section of the overall tablet. Imaging provided qualitative and quantitative evidence revealing that smaller droplets formed thinner, more uniform and less porous film coats.

A hierarchical latent variable model for data visualization

Visualization has proven to be a powerful and widely-applicable tool the analysis and interpretation of data. Most visualization algorithms aim to find a projection from the data space down to a two-dimensional visualization space. However, for complex data sets living in a high-dimensional space it is unlikely that a single two-dimensional projection can reveal all of the interesting structure. We therefore introduce a hierarchical visualization algorithm which allows the complete data set to be visualized at the top level, with clusters and sub-clusters of data points visualized at deeper levels. The algorithm is based on a hierarchical mixture of latent variable models, whose parameters are estimated using the expectation-maximization algorithm. We demonstrate the principle of the approach first on a toy data set, and then apply the algorithm to the visualization of a synthetic data set in 12 dimensions obtained from a simulation of multi-phase flows in oil pipelines and to data in 36 dimensions derived from satellite images.

Emulation of random output simulators

Computer models, or simulators, are widely used in a range of scientific fields to aid understanding of the processes involved and make predictions. Such simulators are often computationally demanding and are thus not amenable to statistical analysis. Emulators provide a statistical approximation, or surrogate, for the simulators accounting for the additional approximation uncertainty. This thesis develops a novel sequential screening method to reduce the set of simulator variables considered during emulation. This screening method is shown to require fewer simulator evaluations than existing approaches. Utilising the lower dimensional active variable set simplifies subsequent emulation analysis. For random output, or stochastic, simulators the output dispersion, and thus variance, is typically a function of the inputs. This work extends the emulator framework to account for such heteroscedasticity by constructing two new heteroscedastic Gaussian process representations and proposes an experimental design technique to optimally learn the model parameters. The design criterion is an extension of Fisher information to heteroscedastic variance models. Replicated observations are efficiently handled in both the design and model inference stages. Through a series of simulation experiments on both synthetic and real world simulators, the emulators inferred on optimal designs with replicated observations are shown to outperform equivalent models inferred on space-filling replicate-free designs in terms of both model parameter uncertainty and predictive variance.