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Despite the large impact of digital technology on the lives and future of all people on the planet, many people, especially from the Global South, are not included in the debates about the future of the digital society. This inequality is a systemic problem which has roots in the real world. We refer to this problem as “digital coloniality.” We argue that to achieve a more equitable and inclusive global digital society, active involvement of stakeholders from poor regions of the world as co-researchers, co-creators, and co-designers of technology is required. We briefly discuss a few collaborative, community-oriented technology development projects as examples of transdisciplinary knowledge production and action research for a more inclusive digital society.

This paper reports one of the initial NICFD experiments in the nozzle test section of the ORCHID aimed at providing accurate data for the validation of flow solvers, albeit, at this stage of the research, the focus is limited to inviscid phenomena. Notably, a series of schlieren photographs displaying Mach waves in the supersonic flow of the dense vapor of siloxane MM were obtained and are documented here for the commissioning experiment, namely, for inlet conditions corresponding to a stagnation temperature and pressure of \(T_0 = 252~\mathrm {^\circ C}\) and \(P_0 = 18.4~\mathrm {bara}\). At these inlet conditions the compressibility factor of the fluid is \(Z_0 = 0.58\). The digital processing of the schlieren images allowed to estimate multiple angles formed by the Mach waves stemming from the upper and lower nozzle surfaces because of the infinitesimal density perturbations generated by the, albeit small, roughness of the metal surfaces. These values are related to the local Mach number by a simple geometric relation. Moreover, the total expanded uncertainty in the Mach number was computed. This information together with the estimate of the average Mach number was used for a first assessment of the capability of evaluating NICFD effects occurring in a dense organic vapor flow of MM by comparison with the results of CFD simulations. The outcome of the comparison was satisfactory. It can thus be inferred that the nozzle test section has been commissioned and it is ready for experimental campaigns in which its full potential in terms of measurements accuracy, repeatability, and operational flexibility will be exploited.

Background: Psoriasis (Ps) is a chronic systemic autoimmune disease associated with pruritus in 64–98% of patients. However, few modestly sized studies assess factors associated with psoriatic pruritus. Objective: To investigate factors associated with Ps pruritus intensity. Methods: Psoriasis patients 18years or older seen in one of 155 centres in Italy between September 2005 and 2009 were identified from the Italian PsoCare registry. Patients without cutaneous psoriasis and those with missed information on pruritus were excluded. Results: We identified 10802 patients, with a mean age 48.8±14.3years. Mild itch was present in 33.2% of patients, moderate in 34.4%, severe in 18.7% and very severe in 13.7%. Higher itch intensity was associated with female gender, lower educational attainment compared to university degree, pustular psoriasis, psoriasis on the head, face, palmoplantar areas, folds and genitalia, more severe disease, disease duration

This paper documents a numerical study on entropy generation in zero-pressure gradient, laminar boundary layers of adiabatic non-ideal compressible fluid flows. The entropy generation is expressed in terms of dissipation coefficient $$C:\mathrm {d}$$ and its dependency on free-stream Mach number, fluid molecular complexity, and flow non-ideality is investigated systematically by means of a boundary layer code extended to treat fluids modeled with arbitrary equations of state. The results of the study show that the trend of dissipation coefficient follows that of an incompressible flow for complex fluid molecules like siloxanes in all thermodynamic and flow conditions. For simpler fluids like CO$$:2$$ the trend becomes inversely proportional to the free-stream Mach number and the $$C:\mathrm {d}$$ value can significantly reduce in the non-ideal flow regime, where strong thermo-physical property gradients occur near the wall.

Small satellites are receiving increased recognition in the space domain due to their reduced associated launch costs and their shorter lead time when compared to larger satellites. However, this advantage is often at the expense of mission capabilities, such as available electrical power and propulsion. A possible solution is to change from the conventional solar photovoltaic and battery configuration to a microOrganic Rankine Cycle (ORC) and thermal energy storage system that uses the waste energy from a solar thermal propulsion system. This unique approach has the potential to offer higher system efficiency and power density. However, limited literature is available on microORC systems, which are capable of producing a few hundred Watts of electrical power, especially for small satellites. A feasibility study of these systems and a fluid selection study were conducted. This was done by using a multiobjective genetic algorithm to optimise an onboard microORC system for various working fluids such as Toluene (C7H8), Hexamethyldisiloxane (MM), and Octamethylcyclotetrasiloxane (D4). The two objective functions were to minimise the total volume and maximise the thermal energy storage capacity. This paper describes the proposed system layout and model of the integrated microORC system. The specific objectives of this study are: i) the working fluid selection, and ii) the optimisation of the proposed system incorporating the design of the thermodynamic cycle and the sizing of the turbine and heat exchangers. Results show that the design of the microORC system is dependent on the mission designer requirements, and various design configurations are provided from the Pareto frontier. It was also found that when the surface wall temperature of the evaporator is near the thermal stability limit of the working fluid, the evaporator operates in the dispersed film boiling regime which reduces the heat transfer coefficient. Additional challenges include high microturbine rotational speeds, large thermal cycling, small blade heights, and large condensers. Finally, the storage configuration of the concentrator was identified as crucial for the feasibility of the system onboard small satellites.

By means of this corrigendum, the authors would like to include relevant information regarding the validation of the meanline turbine model employed in the original article. The improvement regarding the validation of the model was made possible thanks to the contribution of Prof. Jürg Schiffmann. The additional results documented here provide more confidence on the reliability of the model when it applied to mini-ORC turbines. Therefore, we kindly ask the Editor to add his name to the authors list. The following paragraph extends the one that discusses the meanline validation located in Section 2. The turbine preliminary design is performed by means of a meanline code, which is based on the loss models listed in Ref. [1]. These models have been developed for conventional turbomachinery operating with fluids in the ideal gas state, featuring subsonic flows and large Reynolds numbers. The meanline code has been validated with the results of literature test cases presenting these characteristics [2]. It has been also compared against an experimentally validated turbine model for mORC machines operating in the subsonic regime [3]. Table 1 shows the information of the machine geometry for which results of the two codes were compared, while Fig. 1 presents the meridional channel of the turbine. Table 2 shows the corresponding operating conditions. The results of the total-to-static efficiency computation are presented in Fig. 2. It can be observed that the efficiency trend obtained with zTurbo is similar to that computed with the validated EPFL code. The comparison between the two models suggests a deviation lower than 2.5% for all the tested operating conditions. This deviation occurs because each model uses a different set of loss correlations. These correlations are described in Refs. [1,3].

Adjoint-based shape optimization methods for turbomachinery are mainly derived under steady-state assumption. However, due to the inherent unsteadiness of turbomachinery flows, including unsteady effects in the design process can pave the way to further performance gains and to con-sider multi-disciplinary time-dependent optimization problems (e.g. noise minimization and fatigue). In this paper, the adjoint-sensitivities obtained with steady and unsteady methods are compared by considering an exemplary axial turbine stage. The steady calculations are performed by using a flux-conservative mixing plane method. The unsteady results areobtainedwithaharmonic-balancemethodusingaslidingmeshinterface, thus mitigating the high computational costs associated with time-accurate unsteady adjoint, while retaining a sufficient level of accuracy for design purposes. Results show relevant differences between steady and unsteady adjoint sensitivities, with higher deviations in the rotor., {"references":["Albring, T., Sagebaum, M., and Gauger, N. R. (2016). Efficient aerodynamic design using the discrete adjoint method inSU2. In 17th AIAA/ISSMO multidisciplinary analysis and optimization conference.","Economon, T. D., Palacios, F., Copeland, S. R., Lukaczyk, T. W., and Alonso, J. J. (2015). SU2: An Open-Source Suite for Multiphysics Simulation and Design. AIAA Journal , 54(3):828--846.","Giles, M.(1991). Unsflo: Anumericalmethodforthecalculation of unsteady flow in turbomachinery. Technical report, Cambridge, Mass.: Gas Turbine Laboratory, Massachusetts Institute of Technology,[1991].","Giles, M. B. (1990). Nonreflecting boundary conditions for euler equation calculations. AIAA journal , 28(12):2050-- 2058.","Gopinath, A., Van Der Weide, E., Alonso, J., Jameson, A., Ekici, K., and Hall, K. (2007). Three-dimensional unsteady multi-stage turbomachinery simulations using the harmonic balance technique. In 45th AIAA Aerospace Sciences Meeting and Exhibit , page 892.","Hall, K. C., Thomas, J. P., and Clark, W. S. (2002). Computation of unsteady nonlinear flows in cascades using a harmonic balance technique. AIAA journal , 40(5):879--886","Mavriplis, D. J. (2006). Multigrid solution of the discrete adjoint for optimization problems on unstructured meshes. AIAA journal , 44(1):42--50.","Naik, K. R. (2017). Fourier collocation methods for unsteady flows . PhD thesis, Stanford University.","Palacios, F., Alonso, J., Duraisamy, K., Colonno, M., Hicken, J., Aranake, A., Campos, A., Copeland, S., Economon, T., Lonkar, A., et al. (2013). Stanford University Unstructured (SU2): an open-source integrated computational environment for multi-physics simulation and design. In 51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition , page 287.","Rubino, A., Pini, M., and Colonna, P. (2017a). Unsteady simulation of quasi-periodic flows in Organic Rankine Cycle cascades using a Harmonic Balance method. Energy Procedia, 129:1101--1108.","Rubino, A., Pini, M., Colonna, P., Albring, T., Nimmagadda, S., Economon, T., and Alonso, J. (2017b). Adjoint-based fluid dynamics optimization of almost-periodic unsteady flows using a harmonic balance method. Manuscript sub- mitted for publication.","Sagebaum, M., Albring, T., and Gauger, N. R. (2017). High- Performance Derivative Computations using CoDiPack. arXiv preprint arXiv:1709.07229 .","Samareh, J. (2004). Aerodynamic shape optimization based on free-form deformation. In 10th AIAA/ISSMO multidisci- plinary analysis and optimization conference , page 4630.","Saxer, A. P. (1992). A numerical analysis of 3-D inviscid stator/rotor interactions using non-reflecting boundary conditions. Technical report, Cambridge, Mass.: Gas Turbine Laboratory, Massachusetts Institute of Technology,[1992].","Stephan, B., Gallus, H., and Niehuis, R. (2000). Experimental investigations of tip clearance flow and its influence on secondary flows in a 1-1/2 stage axial turbine. In ASME Turbo Expo 2000: Power for Land, Sea, and Air , pages V001T03A099--V001T03A099. American Society of Mechanical Engineers.","Vitale, S., Albring, T. A., Pini, M., Gauger, N. R., and Colonna, P. (2017). Fully turbulent discrete adjoint solver for non-ideal compressible flow applications. Journal of the Global Power and Propulsion Society , 1:252 -- 270.","Yi, J. and Capone, L. (2017). Adjoint-based sensitivity analysis for unsteady bladerow interaction using space--time gradient method. Journal of Turbomachinery ,139(11):111008."]}