bluuebunny/crossref_metadata_2025_split huggingface dataset:
A study of the closed-loop structure of multivariable feedback control systems
Authors: Forsythe W. , Danisman H. , Eissa M.A. 
Published: August 2008

A method of analysis for feedback systems with multiple inputs and outputs is presented, based on the transfer-function matrix representation. It allows the direct computation of any transfer function tij relating the ith input to the jth output, given the forward and feedback transfer function matrices G (s) and H (s), and sets out clearly the relationship between the numerator and denominator of such a transfer function. The derivation of the method from first principles, starting with the system connection matrix, is felt to impart a certain insight into the behaviour of such complex structures.
Controlling SO2 emissions during start-up of multi-bed sulphuric acid converters
Authors: Mann R. 
Published: August 2008

The catalytic converter in sulphuric acid plant is normally designed to work high conversions to avoid recycle, and the associated integrated heat recovery system makes the process relatively tightly constrained. Because of this, considerable care is needed during start-up in order to avoid excessive emissions which would fail to satisfy criteria set by the factory inspectorate. For a fast, clean start-up it is necessary to have a detailed appreciation of the reactor dynamics; the simulation developed here demonstrates how this can be done. In parti cular, it is possible to explore the level of detail necessary to enable operational policies for start-up to be explored. It is shown that, by suitable programming of the flow rates in the system, appropriate to the initial bed temperatures, clean fast start-ups are possible which avoid excessive stack gas emissions of sulphur dioxide.
Methods of quantitative validation fo r dynamic simulation models
Authors: Butterfield M.H. , Thomas P.J. 
Published: August 2008

Four examples, taken from nuclear-power-station experience are described, where model-distortion techniques have been applied successfully. These examples are: (i) Validation of a power-station model for the prediction of behaviour followirag a trip; (ii) validation of a nuclear-reactor model for the purposes of control-system design; (iii) validation of a pump run-down model; and (iv) validation of a model for a hydraulic accumulator.
An investigation of an SDLC-based remote monitoring and control system
Authors: Birch M.R. , Lucas J. 
Published: August 2008

There is a large and increasing demand for remote monitoring and control systems in such applications as pipelines, reservoir systems, sewerage systems and shopping centres, where there are numerous inputs and outputs spread over a large physical area. To monitor and control these inputs and outputs, at a local level, devices known as outstations are used. The outstations are, in turn, controlled by a centralised master station. The purpose of this paper is to investigate the use of the SDLC protocol for controlling the flow of data around such a system. The SDLC protocol is a modern bit-oriented protocol which offers an efficient method for ordering the flow of data around a communication system, As the SDLC protocol places no restrictions on the length or content of the messages sent over the communications link, it offers a very convenient method of communication. It also offers a comprehensive method of detecting any errors that may occur in the communication link, which is of vital importance in any control system. An SDLC software package is described which makes communication between stations extremely easy and reliable. Many applications of remote monitoring and control may now be envisaged, such as factory automation. To take advantage of these new applications, a cheap out-station with built-in modem was designed and constructed. The use of the SDLC software package in hostile environments has been made possible by the introduction of Hamming error-correcting codes. This also widens the number of possible applications for which the SDLC software package may be used,
Optimal steering control of an auto-guided-vehicle with two motored wheels
Authors: Ock Hyun Kim  
Published: August 2008

An optimal control procedure is presented for steering an Auto-Guided- Vehicle (AGV) which has two motored wheels on its left and right side. Steering, running and stopping are enabled by controlling the motor speed independently. An optimal proportional-plus-integral control is employed to eliminate steady-state error which is sustained by a simple proportional control for tracking a circular path. A simple and readily-implemented suboptimal control is also examined. The suboptimal control gives comparable performance and therefore provides an effective approach for industrial application of the AGV. Effects of design parameters of the AGV such as forward velocity, wheel radius and position of sensor are investigated. It is shown that within the practicable values the controlled performance improves rapidly but with an increase of those parameters then the improvement becomes negligible, which suggests base values for the parameters.
Flow imaging for multi-component flow measurement
Authors: Plaskowski A. , Beck M.S. , Krawaczynski J.S. 
Published: August 2008

Multi-component flow measurement is of increasing importance for resource exploitation, energy conservation, and biochemical process applications. Conventional flowmeters which endeavour to average a property of the flow over the pipe cross-section are unsuitable for accurate measurement in the many cases where the component distribution is spatially and time varying in a statistically non-stationary manner. Flow imaging which, like medical tomographic imaging, gives a cross-sectional image of the component distribution leads to the possibility of a much more accurate measurement. The paper describes the basic theory of flow imaging and the system arrangement necessary for its implementation. We also describe a specific arrangement using pulsed ultrasound echo transducers and an acoustic backprojection algorithm for image reconstruction. This shows that a 12-transducer view system can resolve a long single 6-mm diameter void parallel to the axis in a physical model corresponding to a liquid/gas flow in a 78-mm diameter pipe.
Dynamic modelling of a three-axis pneumatic robot
Authors: Czarnecki C.A. , Ashworth M.J. , Towill D.R. 
Published: August 2008

To serve any useful function, the model of a system must reflect the salient features of that system and reproduce, to within an acceptable degree of accuracy, the performance which is observed when it is in operation. When the system is a robot, active in three dimensions, the modelling is comparatively complex and the determination of the values to be attributed to the mechanical parameters and to the coefficients which quantify the interactive torques is far from trivial. As a prelude to the design of a controller which is effective throughout the operating envelope of the robot, the paper describes an investigation into the feasibility of simplifying the modelling procedure without incurring a penalty by way of a significant deterioration in performance prediction. If sufficiently accurate, this tentative model will form the basis of a probabilistic model of reduced complexity which will contain the uncertainty of motion which is exhibited by the robot in operation. Essentially, the estimation of the model parameters follows a two-stage process. On the assumption that the Lagrangian expressions defining a simplified mechanical configuration will describe adequately the actual motion of the robot, a preliminary estimation is made by use of a recursive least-squares technique which provides directly the coefficients of the continuous-time model. This is followed by a sequence of trials carried out on both the preliminary model and on the real system, and so arranged as to emphasise the contribution of each coefficient in turn. By comparison of their responses, the model coefficients are then tuned to achieve an acceptable matching. In addition to inherent cross-coupling, the industrial robot on which the investigation was conducted has nonlinearities introduced by way of pneumatic actuators with complex flow-rate characteristics and which operate in a bang-bang manner. The investigation has shown that the procedure is quite feasible and that the quality of response prediction which was achieved is impressive.
Automatic gas-jet parameter estimation for high precision spacecraft attitude control systems
Authors: Dodds S.J. , Milne P.A. 
Published: August 2008

A simple and easily implemented method is presented here for automatic on-board estimation of a critical parameter of the control jet (thruster) impulse transfer characteristic. This facilitates optimal control with regard to thruster lifetime, fucel consumption and pointing accuracy, despite uncertainties in the thruster performance, The new estimator facilitates automatic, in-orbit adaptation of the attitude control system to slow changes in the control jet characteristics, thereby maintaining optimal performance. The parameter estimator is intended for microprocessor implementation and assumes the use of a state estimator. Attention is restricted to a single, isolated axis. No difficulty is envisaged in developing the technique further to cater for three-axis stabilised spacecraft with significant inter-axis coupling The parameters to be determined are the intercepts on the characteristics of each control jet relating the actual jet firing time to that demanded. A mismatch in these parameters gives rise to a state estimator transient following a jet firing. This provides the stimulus to the parameter estimator, which is basically a resettable pure integrator. The intercept estimate is updated by an amount proportional to the integral of the state estimator error taken over a finite period, commencing at the beginning of the jet firing. Suitable choice of the gain of proportionality yields dead-beat parameter estimation. Besides compensating for jet firing time mismatch, the control system is shown to be capable also of compensating for uncertainties in the thrust level for short turn-on times.
TRACER- a practical construct for dealing with complexity in human interactive systems
Authors: Stewart R.W. 
Published: August 2008

The aim of this paper is to show how methodological ideas can be developed from theoretical first principles of complexity, by presenting TRACER, a practical construct for dealing with complexity in human interactive systems. Utilising the concept of a human interactive system life cycle exhibiting discrete phases, it can be seen that the use of a methodologically driven approach can be instrumental in the development of the life and success of a system. The two elements of TRACER are considered. 1 The TRA CER Construct which utilises three linked dimensions: human requirements of the system; human understanding of the system; and capability of the participants in the system. 2 The TRACER Methodology, with discrete but interactive stages of translation, rapport, assessment, comparison, evaluation and recognition. TRACER is eclectic in nature, using techniques from psychology, sociology and cross-cultural studies in order to understand the nature of complexity and human capability to interact with system demands. Using examples within a system to show generic structural attributes (eg, system/ human communication network) and task specific attributes (e g, perception), methods for understanding and controlling complexity are shown to change the dimensions of a human interactive system life cycle.
A fast algorithm for the on-line estimation of polarity correlation using binary patterns
Authors: Harba M.I.A. , Ali F.A. 
Published: August 2008

An algorithm which utilises the binary patterns of the polarity-sampled input signals for polarity correlation is presented. When programmed on a Z-80 microprocessor operating at 4 MHz, a double precision correlator which estimates 128 correlation coefficients with a maximum allowable sampling rate of about 2.5 kHz is realised. All the operations are performed on-line, except for an interval of about 15 ms of off-line processing to estimate the correlation coefficients from the binary patterns. This interval is constant, irrespective of the signal interval used. The efficiency of this algorithm is derived from the ability of microprocessors to handle 8 bits of data simultaneously, and from the fact when the sampling rate: input-signal bandwidth ratio is high (> 15, for the random signal tested) then only a limited set of input signal binary patterns are obtained. The resulting correlator was tested on real natural signals (the Electromyographic signal (EMG)).
Software Reviews : Simulation Cons Tr Uction Kit
Authors: McCaskill James H. 
Published: August 2008

SIMULATION CONSTRUCTION KIT gives the secondary teacher one more way of involving students in class projects, this time in developing computer-based simulation programs. Teachers using the process approach will find this package a helpful new tool. It is probably best for students who can work in small groups. They will need to investigate all options of an issue thoroughly in order to do branching.
The Hour is Coming, the Hour is Come: Church and Feminist Theology in Post-Revolutionary El Salvador
Authors: Taylder Sian 
Published: August 2008

This paper examines the role of church and feminist theology in contemporary El Salvador, looking at their relationship with feminist and women's groups as well as political and civil society as a whole. Field research carried out in the summer of 2000 indicates that church and society have changed greatly in the years since the signing of the peace accords that ended a long and bitter civil war. Faced with increased levels of poverty and domestic violence, political apathy has become endemic and the traditional role of the Catholic Church has been eroded. This article looks at the ways in which women negotiate a complex and ever-changing politico-religious scene, and asks whether feminist theologies of liberation can effect radical changes in society, challenge machismo and compulsory heterosexuality and undermine the perennial constraints of traditional gender codes.
Support for Social Health Insurance in South Africa
Authors: Smith M.J. , Solanki G.C. , Lalloo R. , Myburgh N.G. , Cornell J.E. 
Published: August 2008

A national cross-sectional survey was carried out in South Africa to gain an understanding of the perceptions and priorities of the likely members of a future social health insurance (SHI). More than 1,000 employees were interviewed in a variety of employment sectors, including state and parastatal organisations, formal and informal private sectors. This article reports on respondents’ level of support for a compulsory contribution towards a hospital insurance scheme funding care at public sector hospitals in South Africa. The results showed that only 11 per cent of employees supported an SHI scheme if public hospitals remain as they are. Support increased to 53 per cent if preferential access to treatment was offered to those contributing to the scheme. Support was almost unanimous (87 per cent) if public hospitals were improved. The levels of support differed by current type of health insurance. Thus, support for a compulsory SHI tax to fund care in public hospitals was conditional upon either improving the hospitals or providing differential treatment to contributing members. If one or both of these conditions are not met, its long-term success will be compromised.
A Comparison of Costs to Patients with Tuberculosis Treated in a DOTS Programme with Those in a Non-DOTS Programme in South India
Authors: Muniyandi M. , Rajeswari R. , Balasubramanian R. , Narayanan P.R. 
Published: August 2008

Tuberculosis is a curable disease, yet it is the largest single infectious cause of death among adults in the world. India accounts for one-third of the global TB burden. Its economic burden in India is enormous as it perpetuates and exacerbates poverty. The revised national Tuberculosis Control Programme (the DOTS Strategy) is currently being implemented in India. The purpose of this study was to compare the costs to tuberculosis patients treated in a DOTS Programme with the costs to patients treated in a non-DOTS Programme in south India. Patients registered between June and December 2000 (455 in DOTS area, 441 in non-DOTS area) in Tiruvallur district were interviewed, collecting information on demographics, socio-economic characteristics of patients, expenditure incurred due to illness, and effect of illness on employment. Results showed that in the DOTS area, treatment success rate was higher, patient costs were less, and patients returned to work early. These findings establish the economic benefits to patients treated under DOTS and lend support to rapid expansion of the programme, particularly in low-income countries.
A Study of Drug Expenditure at a Tertiary Care Hospital
Authors: Vaz F.S. , Ferreira A.M. , Kulkarni M.S. , Motghare D.D. , Pereira-Antao I. 
Published: August 2008

This article analyses the annual drug expenditure at Goa Medical College Hospital using ABC-VED analysis in order to identify drug categories requiring greater supervisory monitoring. Inventory control techniques ABC, VED and ABC-VED matrix analysis were utilised to study the drug expenditure at the hospital. The data was collected for the financial year 2005–6. Out of the 348 drugs, around 12.93 per cent of the drugs were found to account for 69.45 per cent of the annual drug expenditure (45 drugs) and were classified as category A drugs. Another 19.54 per cent of the drugs (68 drugs) consumed 20.48 per cent of the budget (B category), while the remaining 67.53 per cent (235 drugs) accounted for only 10.07 per cent of the annual drug expenditure (C category). Forty-three drugs (12.36 per cent) were classified as vital drugs, and 164 (47.12 per cent) and 141 (40.52 per cent) were considered essential and desirable drugs respectively. Based on ABC-VED matrix analysis, around 22.99 per cent of drugs were classified as category I, accounting for 74.80 per cent of the total drug expenditure. Category II drugs (41.67 per cent) consumed 21.68 per cent of the total drugs budget, while the remaining 35.34 per cent drugs (category III) accounted for only 3.52 per cent of the total drug expenditure. It was concluded that the use of inventory control techniques needs to be made a routine practice in health care. Substantial improvement could be brought about not only in patient care, but also in the optimal use of resources by judicious practice of these methods.
Influence of Pathologic Blood Cell Microrheology on Myocardial Microcirculation in Cardiac Surgery Using Cardiopulmonary Bypass
Authors: Al-Khaja N. , Bergman P. , Belboul A. , Roberts D. , William-Olsson G. 
Published: August 2008

A possible link between blood trauma and the myocardial microcirculation was prospectively studied in 27 patients undergoing cardiac surgery. Blood trauma was assessed microrheologically by analysis of gross red cell filtration rate (RFR) and plasma white cell filtration rate (p-WFR). Laser Doppler flow metry (LDF) was used to assess microflow in the myocardium before and after coronary bypass grafting. The LDF% was significantly reduced in the ischemic parts of the myocar dium, by 25% compared with 52% in the nonischemic myocardium (p < 0.01). After grafting, the grafted ischemic myocardium increased the LDF to 55% (p < 0.001) to levels comparable to those of the nonischemic myocardium, but the normal nonischemic, nongrafted myocardium reduced its microflow to 42% (p < 0.02). The RFR taken simultaneously showed a significant reduction by 34% from 45 to 30μL/sec (p < 0.001). The p-WFR fell significantly by 39% from 33 to 20 μL/sec (p < 0.05). The type of operation did not significantly influence the RFR and p-WFR values. There was a positive correlation between the LDF and RFR (r=0.86, p < 0.01) and between LDF and p-WFR (r=0.77, p < 0.01). Surgery with cardiopulmonary bypass (CPB) reduces the microcirculation in the myocardium. The rheology of blood cells is reduced during CPB. Studies to preserve the blood cells and the microcirculation during and after CPB are required.
Thrombosis Following Radial Artery Cannulation: A Prospective, Randomized Study in a Community Hospital Setting
Authors: Thimsen Daniel A. , Carty George A. 
Published: August 2008

A prospective, randomized study of radial artery cannulation was under taken in patients about to undergo myocardial revascularization. Fifty-seven patients were entered in the study. The incidence of thrombosis was 33% among females and 9% among males. The occurrence of radial artery thrombosis, even in the presence of an incomplete palmar arch, did not result in clinical symp toms. The factors influencing postcatheterization radial artery thrombosis are re veiwed.
Study of Peripheral Flow During Successful Aortoiliac and Aortofemoral Prosthetic Reconstructions by Intraoperative Above-Ankle Pressure Index Monitoring
Authors: Giulini Stefano Maria , Colombi Aldo , Bonardelli Stefano , Maffeis Roberto , De Lucia Maurizio , Tosoni Fabio , Coniglio Arianna , Floriani Marco , Tiberio Giorgio 
Published: August 2008

Doppler above-ankle pressure index (API) was monitored during 368 consec utive bilateral aortoiliac or aortofemoral graft reconstructions performed for aneurysmal or occlusive disease. The aim of this study was to investigate the variations of peripheral pressure, during and just after completion of the proce dure, either when followed by immediate and definitive success or when an intraoperative correction or an early postoperative reoperation was necessary owing to postreconstructive ischemia. For this purpose the API courses were subdivided into three groups: A (705 limbs), which underwent immediately suc cessful reconstructions; B (22 limbs), which needed intraoperative correction; C (9 limbs), which required early reoperation. All 736 limbs were studied individ ually as monolateral reconstructions and classified into six subgroups: 1, pervi ous iliac, pervious femoral artery; 2, occluded iliac, pervious femoral; 3, pervi ous iliac, stenotic femoral (i.e, stenosis > 75% of the superficial femoral artery); 4, occluded iliac, stenotic femoral; 5, pervious iliac, occluded femoral; 6, oc cluded iliac, occluded femoral. APIs were monitored before the operation (PRE), at the completion of the distal anastomosis (DEC), and five, fifteen, thirty, and forty-five minutes after. Data were statistically analyzed by multivariate analysis in regards to 705 immediately successful limbs (group A) and by comparison of all corrected or reoperated cases (groups B and C) with the lower bound of the fifth centiles of group A. The results in group A show that: API-PRE is different in the six subgroups (p < 0.001); API-DEC is lower than API-PRE in the patent iliac artery sub groups (1,3, and 5) and higher than API-PRE in the occluded iliac artery sub groups (2,4, and 6) (p always < 0.001). From declamping time to the forty-five- minutes observation, the mean courses turn out parallel and rising but on dif ferent levels (p < 0.001): pervious femoral, stenotic femoral, occluded femoral. API-forty-five minutes is higher than API-PRE in occluded iliac artery subgroups (2, 4, and 6) (p < 0.001), whereas in the patent iliac artery subgroups only the fifth subgroups reveals a slight but significant rise (p < 0.01), probably owing to the high rate of profunda femoral endarterectomy or angioplasty asso ciated with aortofemoral reconstructions. APIs values of 31 cases in groups B and C, compared with the lower bound of the fifth centile of group A, show that 8/31 cases (26%) remain above that bound, while 23/31 cases (74%) fall below it.