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A finite element method is used to study the effect of flow past a circular cylinder with an integral wake splitter. A fractional step algorithm is employed to solve the Navier‐Stokes and Energy equations with a Galerkin weighted residual formulation. The vortex shedding process is simulated and the effect of splitter addition on the time period of shedding is studied at a Reynolds number of 200 and a blockage ratio of 0.25. The effect of splitter and the Strouhal number and heat transfer augmentation per unit pressure drop has been investigated.

This chapter offers an introduction to two leading Sri Lankan Marxist political economists, S. B. D. de Silva and G. V. S. de Silva. By surveying their most influential writings – the 645-page book The Political Economy of Underdevelopment by S. B. D. de Silva and the pungent essays ‘Heretical Thoughts' and ‘Social Change’ by G. V. S. de Silva – -it traces the distinctive and provocative qualities of these two thinkers, especially concerning problems of development and underdevelopment. In doing so, it is argued that S. B. D. de Silva is best understood as a leading anti-imperialist political economist alongside Samir Amin, Immanuel Wallerstein and Giovanni Arrighi, distinguished by a classical Marxist focus on class struggle and relations of production in his narration of the ‘colonial mode of production’ in Sri Lanka. As for G. V. S. de Silva's erudite reflections on the trajectories of transition to capitalism and socialism as well as the prospects of social and economic development in countries emerging from pre-capitalist social formations in the wake of colonization, his remarkable attention to spatial questions at multiple scales – between country and city, colony and metropole – receives special attention. The conclusion underlines the sustained relevance of both de Silvas to making sense of the origins of the present crisis in Sri Lanka.

Better membrane oxygenators need to be developed to enable efficient gas exchange between venous blood and air.

Optimal design and analysis of such devices are achieved through mathematical modeling tools such as computational fluid dynamics (CFD). In this study, a control volume-based one-dimensional (1D) sub-channel analysis code is developed to analyze the gas exchange between the hollow fiber bundle and the venous blood. DIANA computer code, which is popular with the thermal hydraulic analysis of sub-channels in nuclear reactors, was suitably modified to solve the conservation equations for the blood oxygenators. The gas exchange between the tube-side fluid and the shell-side venous blood is modeled by solving mass, momentum and species conservation equations.

Simulations using sub-channel analysis are performed for the first time. As the DIANA-based approach is well known in rod bundle heat transfer, it is applied to membrane oxygenators. After detailed validations, the artificial membrane oxygenator is analyzed for different bundle sizes (L/W) and bundle porosity (epsilon) values, and oxygen saturation levels are predicted along the bundle. The present sub-channel analysis is found to be reasonably accurate and computationally efficient when compared to conventional CFD calculations.

This approach is promising and has far-reaching ramifications to connect and extend a well-known rod bundle heat transfer algorithm to a membrane oxygenator community. As a variety of devices need to be analyzed, simplified approaches will be attractive. Although the 1D nature of the simulations facilitates handling complexity, it cannot easily compete with expensive and detailed CFD calculations.

This work has high practical value and impacts the design community directly. Detailed numerical simulations can be validated and benchmarked for future membrane oxygenator designs.

Future membrane oxygenators can be designed and analyzed easily and efficiently.

The DIANA algorithm is popularly used in sub-channel analysis codes in rod bundle heat transfer. This efficient approach is being implemented into membrane oxygenator community for the first time.

In this paper, the standard Peridynamic Timoshenko beam model accounting for the shear deformation is chosen to describe the thick beam kinematics. Unfortunately, when applied to very thin beam structures, the standard Peridynamics (PD) encounters the shear locking phenomenon, leading to incorrect solutions.

PD differs from classical continuum mechanics and other nonlocal theories that do not involve spatial derivatives of the displacement field. PD is based on the integral equation instead of differential equations to handle discontinuities and other singularities.

The shear locking can be successfully alleviated using the developed selective integration method. In particular, this technique has been implemented in the standard PD, which allows an accurate result for a wide range of slenderness from very thin to thick (10 < L/t < 10³) structures. It can also accelerate the computational time for particular dynamic problems using fewer neighboring integration particles. Several numerical examples are solved to demonstrate the effectiveness of the proposed method for modeling beam structures.

The paper highlights the severe shear locking phenomenon in the Peridynamic Timoshenko beam available in the literature, especially for very thin structures. A new alternative for the alleviation of shear locking in the Peridynamic Timoshenko beam, using selective integration. Hence the developed Peridynamic Timoshenko beam model is effective for thin and thick structures. A new peridynamic formulation for the low-velocity impact beam models is presented and validated.

1. The paper highlights the severe shear locking phenomenon in the Peridynamic Timoshenko beam proposed in the literature, especially for very thin structures.

2. The developed Peridynamic Timoshenko beam model based on selective integration is effective for thin and thick structures.

3. A new peridynamic formulation for the low-velocity impact beam models is presented and validated.

The paper highlights the severe shear locking phenomenon in the Peridynamic Timoshenko beam proposed in the literature, especially for very thin structures.

The developed Peridynamic Timoshenko beam model based on selective integration is effective for thin and thick structures.

A new peridynamic formulation for the low-velocity impact beam models is presented and validated.

Subcooled flow boiling phenomenon is characterized by coolant phase change in the vicinity of the heated wall. Although coolant phase change from liquid to vapour phase significantly enhances the heat transfer coefficient due to latent heat of vaporization, eventually the formed vapor bubbles may coalesce and deteriorate the heat transfer from the heated wall to the liquid phase. Due to the poor heat transfer characteristics of the vapour phase, the heat transfer rate drastically reduces when it reaches a specific value of wall heat flux. Such a threshold value is identified as critical heat flux (CHF), and the phenomenon is known as departure from nucleate boiling (DNB). An accurate prediction of CHF and its location is critical to the safe operation of nuclear reactors. Therefore, the present study aims at the prediction of DNB type CHF in a hexagonal sub-assembly.

Computational fluid dynamics (CFD) simulations are performed to predict DNB in a hexagonal sub-assembly. The methodology uses an Eulerian–Eulerian multiphase flow (EEMF) model in conjunction with multiple size group (MuSiG) model. The breakup and coalescence of vapour bubbles are accounted using a population balance approach.

Bubble departure diameter parameters in EEMF framework are recalibrated to simulate the near atmospheric pressure conditions. The predictions from the modified correlation for bubble departure diameter are found to be in good agreement against the experimental data. The simulations are further extended to investigate the influence of blockage (b) on DNB type CHF at low operating pressure conditions. Larger size vapour bubbles are observed to move away from the corner sub-channel region due to the presence of blockage. Corner sub-channels were found to be more prone to experience DNB type CHF compared to the interior and edge sub-channels.

An accurate prediction of CHF and its location is critical to the safe operation of nuclear reactors. Moreover, a wide spectrum of heat transfer equipment of engineering interest will be benefited by an accurate prediction of wall characteristics using breakup and coalescence-based models as described in the present study.

Simulations are performed to predict DNB type CHF. The EEMF and wall heat flux partition model framework coupled with the MuSiG model is novel, and a detailed variation of the coolant velocity, temperature and vapour volume fraction in a hexagonal sub-assembly was obtained. The present CFD model framework was observed to predict the onset of vapour volume fraction and DNB type CHF. Simulations are further extended to predict CHF in a hexagonal sub-assembly under the influence of blockage. For all the values of blockage, the vapour volume fraction is found to be higher in the corner region, and thus the corner sub-channel experiences CHF. Although DNB type CHF is observed in corner sub-channel, it is noticed that the presence of blockage in the interior sub-channel promotes the coolant mixing and results in higher values of CHF in the corner sub-channel.

The purpose of the paper is the construction of confidence intervals for the ratio of the values of process capability index C_pm for two processes. These confidence intervals can be used for comparing the capability of any pair of competitive processes.

Two methods for constructing confidence intervals for the ratio of the values of process capability index C_pm for two processes are proposed. The suggested techniques are based on a two-step approximation of the doubly non-central F distribution. Their performance is tested via simulation.

The performance of the suggested techniques seems to be rather satisfactory even for small samples, as illustrated through the use of simulated data.

The practical implication of the suggested techniques is that they can be implemented in real-world applications, since they can be used for comparing the capability of any pair of competitive processes.

The paper presents two new methods for constructing confidence intervals for the ratio of the values of process capability index C_pm for two processes.

This study was aimed at examining the motivations, elements and channels of sustainability reporting of a multinational mining company that operates a subsidiary in Ghana. Semi-structured interviews were conducted among the company’s key stakeholders. These informants were drawn from the case company, a public regulatory agency, members and the opinion leaders of the company’s host community. In addition to the primary data, secondary documents were relied upon to corroborate the views shared by the interviewees. We discovered that while the sustainability reporting mechanism was necessary for gaining internal legitimacy with the parent company, to a large extent, the host community did not appreciate the importance of that report. In place of that the management of the mining subsidiary employed less-formal channels of communication to engage the community representatives on matters relating to sustainability. Our findings suggest that the sustainability reporting process must be adaptable and not always communicated formally. Therefore, the process needs to be re-organised to meet the expectations of all key stakeholders within the subsidiary companies’ jurisdictions. To meet the expectation of stakeholders and gain legitimacy, those charged with the governance of subsidiary companies need to contextualise their sustainability reporting strategies.

Drawing on both the stakeholder theory and Carroll’s Corporate Social Responsibility Pyramid, this chapter explores sustainability practice challenges of a gold minning multinational enterprise in Ghana. Primary data was collected through observation and the interviewing of multi-stakeholder groups. We found that internal stakeholders perceive sustainability expenditure as costly. However, while employees of the case enterprise see the cost as depleting shareholders’ wealth, managers view them as investment with possible long-term benefits. Meanwhile, the external stakeholders perceive the gold mining enterprise’s sustainability expenditure as meagre and that beneficiary communities are not economically empowered to sustain those investments. Again, we found that government’s inability to clamp down illegal gold mining threatens economic and environmental sustainability. Additionally, members of the host community identify the lack of adequate employment opportunities within the entity as a hindrance to their economic empowerment. We submit that the resolution of the sustainability challenges would contribute to the balancing of stakeholders’ expectations: the conduct of ethical business through compliance to environmental laws; promotion of host communities’ social well-being; and improved economic returns for shareholders. By meeting the needs of stakeholders, gold mining enterprises could gain acceptance in their host communities and boost corporate reputation.

The purpose of this paper is to develop a novel active disturbance rejection attitude controller for quadrotors and propose a controller parameters identification approach to obtain better control results.

Aiming at the problem that quadrotor is susceptible to disturbance in outdoor flight, the improved active disturbance rejection control (IADRC) is applied to design attitude controller. To overcome the difficulty that adjusting the parameters of IADRC controller manually is complex, paired coevolution pigeon-inspired optimization (PCPIO) algorithm is used to optimize the control parameters.

The IADRC, where nonlinear state error feedback control law is replaced by non-singular fast terminal sliding mode control law and a third-order tracking differentiator is designed for second derivative of the state, has higher control accuracy and better robustness than ADRC. The improved PIO algorithm based on evolutionary mechanism, named PCPIO, is proposed. The optimal parameters of ADRC controller are found by PCPIO with the optimization criterion of integral of time-weighted absolute value of the error. The effectiveness of the proposed method is verified by a series of simulation experiments.

IADRC can improve the accuracy of attitude control of quadrotor and resist external interference more effectively. The proposed PCPIO algorithm can be easily applied to practice and can help the design of the quadrotor control system.

An improved active disturbance rejection controller is designed for quadrotor attitude control, and a hybrid model of PIO and evolution mechanism is proposed for parameters identification of the controller.

In this introduction to the special issue, ‘Marxist Thought in South Asia’, we detail the long history of Marxist politics and theorizing in South Asia and highlight the unique contributions and perspectives of South Asian Marxists to global Marxism. Three contributions we find particularly significant are (1) South Asian Marxists' approach to thinking about questions of capitalism, colonialism and imperialism, (2) the treatment of agrarian and feudal continuities in Marxist theories from South Asia and (3) unique South Asian contributions to theorizing caste from a Marxist perspective.