Early Grouping Gets the Skew

We propose a new algorithm for external grouping with large results. Our approach handles skewed data gracefully and lowers the amount of random IO on disk considerably. Contrary to existing grouping algorithms, our new algorithm does not require the optimizer to employ complicated or error-prone procedures adjusting the parameters prior to query plan execution. We implemented several variants of our algorithm as well as the most commonly used algorithms for grouping and carried out extensive experiments on both synthetic and real data. The results of these experiments reveal the dominance of our approach. In case of heavily skewed data we outperform the other algorithms by a factor of two

A Robust Scheme for Multilevel Extendible Hashing

Dynamic hashing, while surpassing other access methods for uniformly distributed data, usually performs badly for non-uniformly distributed data. We propose a robust scheme for multi-level extendible hashing allowing efficient processing of skewed data as well as uniformly distributed data. In order to test our access method we implemented it and compared it to several existing hashing schemes. The results of the experimental evaluation demonstrate the superiority of our approach in both index size and performance

Science for loss and damage: four research contributions to the debate

The Loss and Damage Network is a network of scientists and practitioners informing the loss and damage debate and includes members from about 20 institutions. This summary paper, written on the occasion of COP22 in Marrakesh, summarizes four recent research contributions to the debate

Statistically robust representation and comparison of mortality profiles in archaeozoology

Archaeozoological mortality profiles have been used to infer site-specific subsistence strategies. There is however no common agreement on the best way to present these profiles and confidence intervals around age class proportions. In order to deal with these issues, we propose the use of the Dirichlet distribution and present a new approach to perform age-at-death multivariate graphical comparisons. We demonstrate the efficiency of this approach using domestic sheep/goat dental remains from 10 Cardial sites (Early Neolithic) located in South France and the Iberian Peninsula. We show that the Dirichlet distribution in age-at-death analysis can be used: (i) to generate Bayesian credible intervals around each age class of a mortality profile, even when not all age classes are observed; and (ii) to create 95% kernel density contours around each age-at-death frequency distribution when multiple sites are compared using correspondence analysis. The statistical procedure we present is applicable to the analysis of any categorical count data and particularly well-suited to archaeological data (e.g. potsherds, arrow heads) where sample sizes are typically small

Processing of hydrothermal liquefaction biochar from biogas residue for direct use as fertilizer

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Optimizing hydrothermal dechlorination of PVC in a SS-316 reactor:From chemistry knowledge to material considerations

PVC remains one of the most challenging wastes for environmental activists and industrial recyclers because its decomposition products cause severe corrosion to equipment and our planet. The current study was designed to systematically investigate PVC dechlorination using the well-known Response Surface Methodology (RSM) to mature the process chemistry and assess the corrosion rate in the common SS-316 alloy. Undercover non-catalytic experiments, Cl removal, reactor wall corrosion rate, and H/C molar ratio of the products made the most argument to comprehend the chemistry and find the optimum operating condition. Based on data collected from different analytic techniques, like FESEM, SEM-EDX, TG, FT-IR, CHN, and AAS, it was found that water drove Cl removal through a combination of SN2 and Elimination pathways where the in-situ production of hydrochloric acid at high Severity Factor (SF) resulted in a desirably high dechlorination rate of 89.42%. However, significant metal leakage into the aqueous phase, e.g., 278.01 mg of Fe, in the Aqueous Phase (AP) necessitated the valorization of different approaches, including multistage dechlorination and application of various hetero and homogeneous catalysts, dealing with chloride and metal salts inside the reaction chamber. Among the solutions applied, the dual-stage and Ni-assisted dechlorination showed promising performances receptively with a corrosion rate as low as 0.034 g and the highest Cl removal efficiency of 96.18%.</p

Continuous hydrothermal liquefaction of biomass:A critical review

Hydrothermal liquefaction (HTL) of biomass is emerging as an effective technology to efficiently valorize different types of (wet) biomass feedstocks, ranging from lignocellulosics to algae and organic wastes. Significant research into HTL has been conducted in batch systems, which has provided a fundamental understanding of the different process conditions and the behavior of different biomass. The next step towards continuous plants, which are prerequisites for an industrial implementation of the process, has been significantly less explored. In order to facilitate a more focused future development, this review&#8212;based on the sources available in the open literature&#8212;intends to present the state of the art in the field of continuous HTL as well as to suggest means of interpretation of data from such plants. This contributes to a more holistic understanding of causes and effects, aiding next generation designs as well as pinpointing research focus. Additionally, the documented experiences in upgrading by catalytic hydrotreating are reported. The study reveals some interesting features in terms of energy densification versus the yield of different classes of feedstocks, indicating that some global limitations exist irrespective of processing implementations. Finally, techno-economic considerations, observations and remarks for future studies are presented