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A GENERAL outline of the processes occurring in the working fluid of a rocket engine has been summarized previously, but the total picture is still far from complete, a number of important phenomena not having been taken into account. Their full analysis would be, however, beyond the scope of this paper, and may be left to specialists more qualified than the author to give an account of combustion processes.

Over the past several decades, the need for safety on offshore oil platforms has attracted significant attention from all its stakeholders. This paper seeks to present a mathematical model that could be used to control unsafe conditions on oil platforms.

The model is based on the intuitive notion of safety underlying practices on an offshore platform. The theory of control system combines the human/operator factor gain, maintenance function effectiveness, the component safety quality assurance system, and the safety measurement system in a holistic manner to attain a controlled status of the oil platform.

It is observed that these components relate in a mutually interlinked system that guarantees maximum safety control if all the components are holistically managed.

Practically, the control of an offshore oil platform guarantees the lives and properties of those who utilize the oil platform.

The work is perhaps the first to advance a model of safety on oil platforms with the use of control systems. The work would be of value to safety managers, employees of oil companies and researchers interested in the control of accidents on oil platforms.

This paper mainly aims to deal with the problems of uncertainties including modelling errors, unknown dynamics and disturbances caused by load mutation in control of permanent magnet synchronous motor (PMSM).

This paper proposes an enhanced speed sensorless vector control method based on an active disturbance rejection controller (ADRC) for a PMSM. First, a state space model of the PMSM is obtained for the field orientation control strategy. Second, a sliding mode observer (SMO) based on back electromotive force (EMF) is introduced to replace the encode to estimate the rotor flux position angle and speed. Third, an infinite impulse response (IIR) filter is introduced to eliminate high frequency noise mixed in the output of the sliding mode observer. In addition, a speed control method based on an extended state observer (ESO) is proposed to estimate and compensate for the total disturbances. Finally, an experimental set-up is built to verify the effectiveness and superiority of the proposed ADRC-based control method.

The comparative experimental results show that the proposed speed sensorless control method with the IIR filter can achieve excellent robustness and speed tracking performance for PMSM system.

An enhanced sensorless control method based on active disturbance rejection controller is designed to realize high precision control of the PMSM; the IIR filter is used to attenuate the chattering problem of traditional SMO; this method simplifies the system and saves the total cost due to the speed sensorless technology.

The use of sensorless can reduce costs and be more beneficial to actual industrial application.

The proposed enhanced speed sensorless vector control method based on an ADRC with the IIR filter enriches the control method of PMSM. It can ameliorate system robustness and achieve excellent speed tracking performance.

This study aims to measure the acceptance of digital resources by integrating knowledge management (KM) factors (i.e. acquisition, sharing, application and protection) into the factors of the technology acceptance model (TAM) (i.e. perceived ease of use and perceived usefulness) and their impact on actual system use through behavioural intention.

Using the quantitative research method, a survey was conducted of the public sector universities of Punjab, Pakistan. Data were collected from postgraduate students and analysed using partial least squares structural equation modelling.

The findings showed that the factors of KM with the integration of TAM significantly impact the acceptance of digital resources. The study’s hypotheses are all supported, and the findings demonstrated that knowledge acquisition, knowledge sharing, knowledge application and knowledge protection significantly influenced perceived usefulness and perceived ease of use, and that these factors are positively correlated with behavioural intentions to use digital resources.

This study has considerable significant implications for policymakers, developers and practitioners in designing digital resources. This study will also assist librarians to discover areas for development that may enhance the use of digital resources among users

In most developing countries like Pakistan, the gap between rich and poor has widened over time. This polarization in the society hinders economic growth and acts as a barrier for development and well-being. The proportion of income distribution varies across the population sub-groups in Pakistan. Therefore, it is important to study the income distribution effects across the four provinces of Pakistan.

This study attempts to explore the root causes of income inequality and its changes in a dynamic context across the four provinces of Pakistan over a decade (2005–2006 to 2015–2016) by using a regression-based inequality decomposition method.

Age, gender and higher education are the most prominent factors explaining the level of inequality across the four provinces of Pakistan. Higher education enhances the level of inequality in all provinces but contributes negatively to its changes except for Balochistan. Skilled agricultural and fishery workers in Balochistan have contributed significantly to reducing the level of inequality over the decade but not to its changes. Healthy contribution of the unpaid family workers in economic activities has reduced the level of inequality in Punjab and Balochistan and contributed positively to the change in income inequality. Employer or self-employed workers enhance the level of income inequality but contribute negatively to its changes for Punjab and Balochistan.

To date, inequality literature on Pakistan focuses on economic growth and poverty. A handful studies focus on the determinants of income inequality in a static context. This study goes beyond the static decomposition tools and attempts to explore the determinants of inequality in a dynamic context.

The peer review history for this article is available at https://publons.com/publon/10.1108/IJSE-09-2021-0573.

Due to large amounts of coal burning, huge carbon dioxide emission and poor environmental quality, it is important to identify whether environmental Kuznets curve exists in China and India since in downward period of environmental Kuznets curve, economic growth in these countries will largely contribute to world environmental quality. Further, it helps to make a comparative analysis between China and India on how economic growth will contribute to the environmental quality in both upward and downward period of environmental Kuznets curve due to energy consumption.

This study uses the data of carbon dioxide emission, per capita GDP and energy consumption from 1972 to 2017 to identify individual and panel-level environmental Kuznets curve of China and India. Before going to regression and causality analysis, unit root and cointegration tests are performed.

This study finds the existence of environmental Kuznets curve in China and India at both individual and panel level. Further, due to high energy consumption, environmental quality in China will deteriorate at a lower rate in the long run than that of India. Next, the increase in economic growth or per capita GDP in the long run will deteriorate environmental quality at a lower rate in China than that of India. Besides, with the zero level of energy consumption and per capita GDP, the environmental quality of China will be worse than that of India. However, increase in per capita GDP after threshold level will improve environmental quality in India at a higher rate than that of China.

It helps to formalize the comparative relationship between the two large Asian economies by knowing the influence of economic growth on environmental degradation due to energy consumption. However, this study cannot conclude exactly when China and India can avail the downturn in environmental Kuznets curve.

It firstly establishes a link among energy consumption, economic growth and environmental quality between China and India including comparative pace in both upward and downward period of environmental Kuznets curve.

This paper deals with economic manufacturing quantity (EMQ) models with stochastic machine breakdown and repairs. Under two minimal repair policies to maintain a production machine, the expected cost functions per unit time in the steady state, incurred in the manufacturing operation, are formulated and the optimal policies which minimize them are calculated. As a special case, we consider the case where the machine breakdown time follows the homogeneous Poisson process and calculate the optimal EMQ policies numerically. Also, an approximation method is used to represent the expected cost.

This study aims to compare the performance of the conventional and fractional order proportional-integral-derivative (PID and FOPID) controllers tuned with a particle swarm optimization (PSO) and genetic algorithm (GA) for quadrotor control.

In this study, the gains of the controllers were tuned using PSO and GA, which are included in the heuristic optimization methods. The tuning processes of the controller’s gains were formulated as optimization problems. While generating the objective functions (cost functions), four different decision criteria were considered separately: integrated summation error (ISE), integrated absolute error, integrated time absolute error and integrated time summation error (ITSE).

According to the simulation results and comparison tables that were created, FOPID controllers tuned with PSO performed better performances than PID controllers. In addition, the ITSE criterion returned better results in control of all axes except for altitude control when compared to the other cost functions. In the control of altitude with the PID controller, the ISE criterion showed better performance.

While a conventional PID controller has three parameters (Kp, Ki, Kd) that need to be tuned, FOPID controllers have two additional parameters (µ). The inclusion of these two extra parameters means more flexibility in the controller design but much more complexity for parameter tuning. This study reveals the potential and effectiveness of PSO and GA in tuning the controller despite the increased number of parameters and complexity.

African countries are generally fragile. This and other related characteristics affect the potential for growth and development. The purpose of this paper is to investigate whether the effect of FDI on economic growth is contingent on a financial system that accounts for financial market fragility. An important point of departure from earlier studies is the adoption of a new measure of financial market fragility.

Given the uniqueness of the data set, the study uses a panel data and estimates an econometric model using an instrumental variable approach. For robustness purposes, a pooled ordinary least square is also estimated.

The study provides evidence that if the financial market is fragile as in the case of Africa, FDI inflows may have a marginally significant positive impact on economic growth. The findings suggest that fragility in the financial market is a key absorptive capacity and cannot be trivialised when exploring FDI–growth nexus in Africa.

The uniqueness of the data set limited the time period of the study. Nonetheless, the findings are still crucial to policy makers in Africa and other developing countries with similar characteristics.

To the best of the authors’ knowledge, this is the first study in Africa to investigate the FDI–growth nexus which accounts for financial market fragility.