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This work involves a study on laser ignition (LI) in an internal combustion (IC) engine and investigates the effects on control of engine combustion performance and stability of varying specific laser parameters (beam energy, beam quality, minimum beam waist size, focal point volume and focal length). A Q-switched Nd?:?YAG laser operating at the fundamental wavelength 1064?nm was successfully used to ignite homogeneous stoichiometric gasoline and air mixtures in one cylinder of a 1.6?litre IC test engine, where the remaining three cylinders used conventional electrical spark ignition (SI). A direct comparison between LI and conventional SI is presented in terms of changes in coefficient of variability in indicated mean effective pressure (COVIMEP) and the variance in the peak cylinder pressure position (VarPPP). The laser was individually operated in three different modes by changing the diameter of the cavity aperture, where the results show that for specific parameters, LI performed better than SI in terms of combustion performance and stability. Minimum ignition energies for misfire free combustion ranging from 4 to 28?mJ were obtained for various optical and laser configurations and were compared with the equivalent minimum optical breakdown energies in air.

A technique based on Horowitz’s nonlinear quantitative feedback theory is presented, in which the size of the uncertainty is reduced by cancellation of the plant nonlinearity through nonlinear inverse compensation. Linear identification of the open loop nonlinear inverse compensated plant is used to obtain an unstructured uncertainty representation, however, rather than computing QFT templates based on parametric uncertainty. An increase in achievable robust performance with any linear robust performance control design technique may then be obtained. The method is experimentally validated by application to a SISO automotive SI engine idle speed control problem using an electric dynamometer.

A novel λ -normalised air-fuel ratio (AFR)estimator for port-fuel injected (PFI) spark-ignition (SI) internal combustion (IC) engines is proposed. The estimator has an algebraic NARMAX structure which is developed by identification from dynamometer based engine test data. The estimated λ signal has significantly less time delay than the measured λ signal. A slow acting PID trimming loop is implemented to remove long time-scale drift between estimated and measured λ. Two robust linear controllers are designed each to provide a 2 x 2 MIMO feedback system to regulate λ and to allow tracking of torque demand. Both a mixed-sensitivity (MS) maximum singular value H∞ controller and a MS Frobenius norm H∞ controller are implemented and evaluated experimentally. The Frobenius norm H∞ controller, allows the use of an intuitive Hadamard element-by-element weighting selection. This is implemented to decouple the torque and AFR paths. Both controllers are otherwise found experimentally to have similar robustness and performance, but the Frobenius norm H∞ controller achieves a superior decoupling.

This paper describes a neural-network (NN)-based scheme for the control of a cylinder peak pressure position (PPP)—also known as the location of peak pressure (LPP)—by spark timing in a gasoline internal combustion engine. The scheme uses the ionization current to act as a virtual sensor, which is subsequently used for PPP control. A NN is trained offline on principal-component analysis data to predict the cylinder peak pressure position under dynamically varying engine load, speed, and spark advance (SA) settings. Experimental results demonstrate that the PPP prediction by the NN correlates well with those measured from in-cylinder pressure sensors across transients of load, SA, and engine speeds. The dynamic training data allow rapid model identification across the identified engine range, as opposed to just fixed operating points. A linear robust constrained-variance controller, which is a robustified form of the minimum variance controller, is used to regulate the PPP by SA control action, using the NN as a PPP sensor. The control scheme is validated by experimental implementation on a port fuel-injected four-cylinder 1.6 l gasoline internal combustion engine.

Population-based data from 10 centres in Burma, Thailand, China and Vietnam, have been analysed to assess those social and environmental factors which may be associated with pre-term delivery and low birth-weight. The philosophy behind the study was that if the same association was found in different countries, then the association may be causal; if associations differed in the various countries, then causality was unlikely. The major findings were as follows: a strong association between low birth-weight and pre-term delivery and the unmarried state (RR 1.64, 1.39), a consistent reduced risk of pre-term delivery when the father was in a managerial post (RR 0.77), an excess risk of pre-term delivery if the mother was a housewife (RR 1.16), lifting heavy objects at the time of quickening (RR 1.63) or frequently bending and stooping at the time of quickening (1.15). Strong associations were found with both paternal and maternal education levels but these were strongest for the mother's education level. The association was far stronger for pre-term delivery than for low birth-weight and it is assumed that the low birth-weight effect is secondary to pre-term delivery. The only variation with maternal age concerned an excess of low birth-weight among teenage mothers, but not of pre-term delivery, and an excess of low birth-weight but not pre-term delivery among mothers with small head circumferences or small arm circumferences. We conclude that the aetiology of growth retardation and pre-term delivery are probably different in South-east Asia, and point out the need to elucidate further the strong variation with education level.

We report a 53-year-old patient (AWF) who has an acquired deficit of audiovisual speech integration, characterized by a perceived temporal mismatch between speech sounds and the sight of moving lips. AWF was less accurate on an auditory digit span task with vision of a speaker's face as compared to a condition in which no visual information from the lower face was available. He was slower in matching words to pictures when he saw congruent lip movements compared to no lip movements or non-speech lip movements. Unlike normal controls, he showed no McGurk effect. We propose that multisensory binding of audiovisual language cues can be selectively disrupted.

Previous studies have demonstrated that both visual and proprioceptive feedback influence motor control. The relative contributions of these sensory modalities to the on-line computation of body position—that is, the body schema—remain unclear. We report a study designed to explore the roles of vision and proprioception in motor planning. The task required subjects to judge if a pictured stimulus was a right or left hand; stimuli included pictures of a right or left hand in a palm up or palm down position and in six different angular rotations (0 ◦ ,6 0 ◦ , 120 ◦ , 180 ◦ , 240 ◦ , 300 ◦ ). Each subject was tested with his/her right hand palm down and palm up. There were three conditions: a “control” condition (real hand in view), a “fake hand” condition (fake hand in view, real hand out of view), and a “proprioception” condition (no fake hand, real hand out of view). We found that proprioceptive input (that is, the subject’s “felt position”) had a significant influence on mental rotation whereas the visually perceived posture of the hand did not. We suggest that, at least under some circumstances, proprioceptive inflow may represent the dominant sensory input to the on-line representation of the body in space. © 2004 Elsevier Ireland Ltd. All rights reserved.

Various types of optical fibres have been investigated and compared for delivering high power laser beams to an optical plug (comprising of lenses and an optical window) for the application of laser-induced ignition of gasoline and air mixtures in an automotive internal combustion engine. Three main types of optical fibre were examined: multi-mode step index silica, sapphire and photonic crystal. The fibres had various core sizes ranging from 35 to 600 μ ma nd numerical apertures between 0.046 and 0.64. A Q-switched Nd:YAG laser operating at the fundamental wavelength 1064 nm with a pulse length of 15 ns was used for the testing. Fibre output beam properties, including beam mode quality, output divergence, transmission losses, beam energy thresholds and effects of engine vibration were investigated. These fibre beam properties were compared with known beam parameters for laser ignition to assess the suitability of such fibres for a laser ignition system. Online fibre delivery laser ignition engine tests were performed with the most suitable fibres, which showed that combustion could be achieved with this system despite a relatively large percentage of misfires.

Socioeconomic factors relating to all maternal deaths identified during the 12 months of the Jamaican Perinatal Morbidity and Mortality Survey were compared with a control population of over 10,000 women. The maternal mortality rate was 11.5 per 10,000 livebirths. Initial analyses revealed (a) that the risk of maternal death declined with increasing maternal education level, (b) that mothers who lived in households with direct pumped water and/or flush toilets enjoyed a reduced risk; (c) mothers who were themselves the major wage earner and (d) those living in households where the major wage earner and source of income was an agricultural worker or farmer were at increased risk of maternal death. A previous analysis showed that the mother's age, her parity and variables indicating access to medical care were important. Logistic regression showed that only maternal age and toilet facilities were independently associated with maternal mortality.

Prospectively gathered data from eight geographically defined areas in south-east Asia included serial measures of blood pressure, proteinuria and oedema during pregnancy. A total of 15,476 pregnancies were included. Both antenatal oedema and proteinuria were markers of increased risk of antenatal diastolic hypertension, proteinuric pre-eclampsia and eclampsia. However they identified fetuses at high risk of low birthweight and perinatal mortality only in areas where the incidence of hypertension was low. As a screening strategy to identify women who are at increased risk of antenatal diastolic hypertension, of proteinuric pre-eclampsia and of eclampsia, the most efficient strategy is probably to use the presence of oedema and/or proteinuria. The sensitivity of using this method for identifying women with proteinuric pre-eclampsia is high, but for identifying eclampsia it is still relatively low. Where resources are available there is probably no substitute for using a sphygmomanometer and measuring blood pressure.

STUDY OBJECTIVE: The objective was to test the hypothesis that easy access to sophisticated hospitals is associated with a reduction in perinatal mortality. DESIGN: The study was a nationwide questionnaire survey of a birth cohort. SUBJECTS: All deliveries greater than 500g weight of singleton live births and stillbirths occurring throughout Greece during April 1983 were included. Completed questionnaires were returned for 10,953 deliveries (8% of total annual registered births in Greece), and data on 10,790 singleton births were analysed, including 127 stillbirths and 137 early neonatal deaths. MEASUREMENTS AND MAIN RESULTS: The questionnaires contained information on demographic characteristics of each parent, mother's reproductive history, and clinical course of pregnancy, labour and perinatal period. Mothers living in big urban centres were compared with the rest of the country. Overall mortality rates were similar but births in the big urban centres were of significantly lower weight due to fetal growth retardation. Logistic regression analysis, taking account of birthweight, parity, maternal age, and maternal education showed that there was an advantage to mothers living in big urban centres, perinatal mortality being 63% higher in the rest of the country (chi 2 = 7.4, p less than 0.01). CONCLUSION: The evidence obtained supports the original hypothesis and suggest that a reduction in the high perinatal mortality rate in Greece may be achieved by restructuring the perinatal services.