Facilitating Collocated Crowdsourcing on Situated Displays

Online crowdsourcing enables the distribution of work to a global labor force as small and often repetitive tasks. Recently, situated crowdsourcing has emerged as a complementary enabler to elicit labor in specific locations and from specific crowds. Teamwork in online crowdsourcing has been recently shown to increase the quality of output, but teamwork in situated crowdsourcing remains unexplored. We set out to fill this gap. We present a generic crowdsourcing platform that supports situated teamwork and provide experiences from a laboratory study that focused on comparing traditional online crowdsourcing to situated team-based crowdsourcing. We built a crowdsourcing desk that hosts three networked terminal displays. The displays run our custom team-driven crowdsourcing platform that was used to investigate collocated crowdsourcing in small teams. In addition to analyzing quantitative data, we provide findings based on questionnaires, interviews, and observations. We highlight 1) emerging differences between traditional and collocated crowdsourcing, 2) the collaboration strategies that teams exhibited in collocated crowdsourcing, and 3) that a priori team familiarity does not significantly affect collocated interaction in crowdsourcing. The approach we introduce is a novel multi-display crowdsourcing setup that supports collocated labor teams and along with the reported study makes specific contributions to situated crowdsourcing research.     

Multi‐parametric linear programming under global uncertainty

Multi‐parametric programming has proven to be an invaluable tool for optimisation under uncertainty. Despite the theoretical developments in this area, the ability to handle uncertain parameters on the left‐hand side remains limited and as a result, hybrid, or approximate solution strategies have been proposed in the literature. In this work, a new algorithm is introduced for the exact solution of multi‐parametric linear programming problems with simultaneous variations in the objective function's coefficients, the right‐hand side and the left‐hand side of the constraints. The proposed methodology is based on the analytical solution of the system of equations derived from the first order Karush–Kuhn–Tucker conditions for general linear programming problems using symbolic manipulation. Emphasis is given on the ability of the proposed methodology to handle efficiently the LHS uncertainty by computing exactly the corresponding nonconvex critical regions while numerical studies underline further the advantages of the proposed methodology, when compared to existing algorithms. © 2017 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 63: 3871–3895, 2017     

可待续建筑与现实和谐

中国建筑学会本次年会关注建筑与我们这个星球的和谐关系,这不是一个巧合.它表明中国建筑师为建立这种和谐关系做出贡献的决心.同样,国际建协主席加埃唐·修和副主席路易斯·考克斯同时出席本次会议也不是一个巧合.     

Uncertainty in estimating the performance of solar thermal systems

The scope of this article is to present a methodology for the estimation of the uncertainty characterizing the energy performance of solar domestic hot water systems. The work concentrates on the uncertainty characterizing the expected annual energy output, as calculated through tests implemented according to the valid international standards. In order to cope with difficulties related to the algorithmic character of the measurement model, which cannot be explicitly formulated, Monte-Carlo simulation techniques are implemented. The component of uncertainty associated with measurement errors is estimated, on the basis of the metrological quality anticipated by the relevant testing standards. Errors due to imperfections of the energy model used through the test are also counted in, as well as uncertainties attributed to the variability of meteorological conditions. The proposed uncertainty analysis allows the realistic assessment of the actual energy provided to the user by a solar domestic hot water system. Implementation of the proposed methodology for a typical system leads to an expanded uncertainty in the order of 9% for the expected annual energy output.     

Optical performance and instantaneous efficiency calculation of linear Fresnel solar collectors

The main objective of this study is the investigation of the effect of the optical path of incident beam solar radiation on the performance of a linear Fresnel concentrating solar collector. The requirements regarding the kinematics of the reflectors are examined, allowing the effective focus of the reflected radiation on the receiver cover. A methodology for the calculation of the reflection angles of the sun rays incident on the mirrors, as well as of the incidence angles of the reflected rays on the cover, as a function of the sun position and the geometry of the collector is proposed. Specific scenarios, describing the effect of the solar radiation optical path on the collected heat, are formulated, each of them leading to a different form for the instantaneous efficiency equation. The evaluation and analysis of these scenarios, on the basis of actual operation conditions, has shown that the effect of the reflection and incidence angles throughout the modeling of the collector and the calculation of the useful thermal power cannot be neglected.     

Applying configurational analysis to IS behavioural research: a methodological alternative for modelling combinatorial complexities

An important limitation of regression‐based analysis stems from the assumption of symmetric relationships between variables, which is often violated. To overcome this limitation within IS research, we propose the use of the fuzzy‐set qualitative comparative analysis (FsQCA) method. The paper elaborates on the rationale for applying this approach to IS behavioural research and how to tailor FsQCA for this purpose. A systematic interpretation of the technique covering its mathematical properties and advanced features is provided. Drawing from an illustrative study of mobile government services adoption by residents of rural areas, the paper demonstrates FsQCA's potential to supplement regression‐based IS behavioural research, by (i) examining asymmetric relationships between a set of antecedents and the IS phenomenon of interest, (ii) providing nuanced coverage of necessary and sufficient conditions for emergence of an IS behavioural outcome, and (iii) identifying various configurations of conditions in association with users' demographic characteristics. © 2015 Blackwell Publishing Ltd     

Hydrogen production via solar-aided water splitting thermochemical cycles: Combustion synthesis and preliminary evaluation of spinel redox-pair materials

Redox-pair-based thermochemical cycles are considered as a very promising option for the production of hydrogen via renewable energy sources like concentrated solar energy and raw materials like water. This work concerns the synthesis of various spinel materials of the iron and aluminum families via combustion reactions in the solid and in the liquid-phase and the testing of their suitability as redox-pair materials for hydrogen production by water splitting via thermochemical cycles. The effects of reactants' stoichiometry (fuel/oxidizer) on the combustion synthesis reaction characteristics and on the products' phase composition and properties were studied. By fine-tuning the synthesis parameters, a wide variety of single-phase, pure and well crystallized spinels could be controllably synthesized. Post-synthesis, high-temperature calcination studies under air and nitrogen at the temperature levels encountered during solar-aided thermochemical cyclic operation have eliminated several material families due to phase composition instabilities and identified among the various compositions synthesized NiFe₂O₄ and CoFe₂O₄ as the two most suitable for cyclic water splitting – thermal reduction operation. First such thermochemical cyclic tests between 800 and 1400 °C with NiFe₂O₄ and CoFe₂O₄ in powder form in a fixed bed laboratory reactor have demonstrated capability for cyclic operation and alternate hydrogen/oxygen production at the respective cycle steps for both materials. Under the particular testing conditions the two materials exhibited hydrogen/oxygen yields of the same magnitude and similar temperatures of oxygen release during thermal reduction.     

A CFD methodology for the design of sedimentation tanks in potable water treatment: Case study: The influence of a feed flow control baffle

Computational fluid dynamics simulations are employed to assess the effect of adding a vertical baffle at the feed section of a full-scale sedimentation tank for the improvement of solids settling in potable water treatment. A general CFD-based simulation strategy is developed based on the specific features and conditions met in practice for potable water treatment. The linearity of the particle conservation equations allows separate calculations for each particle size class – but performed for all classes of interest – leading to the uncoupling of the CFD problem from a particular inlet particle size distribution. The usually unknown and difficult to be measured particle density is found by matching the theoretical to the easily measured experimental total settling efficiency. The proposed strategy is computationally much more efficient than the corresponding strategies used for the simulation of wastewater treatment. This work compares simulations from a standard and a baffle-equipped tank. It is found that the baffle decreases the inlet recirculation zone and enhances the settling of solids by directing them towards the bottom of the tank with high velocities. It is noteworthy that even small differences in the particle velocity can cause large changes in the percent of settled particles; in this work, the overall solids removal efficiency increased when using the baffle from 90.4 to 98.6% leading to a reduction of the effluent solids concentration of approximately 85%.     

A polarimetric CFAR ship detector based on the joint probability function of simulated first-order Markov chains

In this work, a novel ship detection procedure is presented for radar signals whose backscattering power is of the same order while their polarimetric characteristics differ greatly. The stochastic nature of the polarimetric characteristics of the background (clutter) and the target signal (ship) can be adequately described by first-order Markov chains (FMCs). The proposed feature corresponds to the joint probability of sequential states of variable finite sequential segments of the FMCs. The classic Constant False Alarm Rate (CFAR) detection theory is adapted to the discrete space of the Markov experimental distributions of the proposed feature while the adaptive thresholding technique is overcome by considering a global model for describing the clutter. Performance assessment of the proposed detection procedure is carried out by means of three sets of FMCs each one corresponding to a clutter-target pair for different lengths of the finite FMC segments. The experimental results present high detection scores making the proposed detection procedure ideal for signals characterized by the Markov property. A comparative study of previous detection approaches has been implemented that shows the superiority of the proposed detection procedure.