A Call for a Humanistic Stance Toward K–12 Data Science Education

There is growing interest in how to better prepare K–12 students to work with data. In this article, we assert that these discussions of teaching and learning must attend to the human dimensions of data work. Specifically, we draw from several established lines of research to argue that practices involving the creation and manipulation of data are shaped by a combination of personal experiences, cultural tools and practices, and political concerns. We demonstrate through two examples how our proposed humanistic stance highlights ways that efforts to make data personally relevant for youth also necessarily implicate cultural and sociopolitical dimensions that affect the design and learning opportunities in data-rich learning environments. We offer an interdisciplinary framework based on literature from multiple bodies of educational research to inform design, teaching and research for more effective, responsible, and inclusive student learning experiences with and about data

4-Acetamido-Tempo-mediated oxidation of wood chips and thermomechanical pulp in large scale

The 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation was mainly studied in laboratory scale and needs to be scaled-up for any future industrial implantation. With this objective, the oxidation was applied at several steps in a thermomechanical pulp production system. Softwood chips were impregnated with a TEMPO mixture or treated in batch before refining, leading to a modification of pulp mechanical and optical properties. The TEMPO oxidation was also studied on softwood pulp with a usual batch oxidation, a high consistency treatment or by replacing the diluted water by a TEMPO oxidation medium during the secondary refining. Pulp from high-consistency oxidation presented a significant energy potential gain. However, optical properties were severely affected and could not be totally recovered by a conventional hydrogen peroxide bleaching. The refiner was also used as a nanofiber-producing apparatus for pulp with carboxylic group content higher than 1500 mmol/kg. For this application, the refiner appeared to be a high-efficiency dispersion system to produce significant amounts of nanofibers at low-energy consumption. © 2019 American Chemical Society

The effects of 4-acetamido-TEMPO-mediated oxidation on the extraction components of thermomechanical pulp

Abstract: 4-Acetamido-TEMPO-mediated oxidation was carried out on thermomechanical pulp (TMP) to further investigate the extraction components of the oxidized pulp. Successive extractions on non-oxidized, bleached and oxidized TMP have shown that components were easier to extract from the oxidized pulp. The pulp lignin content demonstrated that the highest content of lignin was removed by sodium hydroxide extraction. Moreover, more than two times the amount lignin was extracted from oxidized pulp compared to non-oxidized pulp. The measured carboxylic groups showed that the highest amounts of the oxidized components were removed after the first extraction. However, after each extraction, reduced but still significant amounts of carboxylic groups were present in the extracted material. Thermogravimetric analysis showed that 4-acetamido-TEMPO oxidation treatment induced a decrease in the fibre degradation temperature caused by a weakening in the fibre structure. The results also demonstrated that some components of the highly oxidized pulp were more easily dissolved because of the critical extraction conditions. Furthermore, the recovered precipitate in the extraction solvent had different XPS characteristics according to the initial pulp treatment. The analysis of the oxidized TMP precipitate showed that the precipitate from hot water extraction was the most highly oxidized, while the precipitate from sodium hydroxide extraction approached pure lignin characteristics. Graphical abstract: [Figure not available: see fulltext.]. © 2019, Springer Nature B.V

Dewatering parameters in a screw press and their influence on the screw press outputs

A Thune SP23 screw press dewatering parameters were studied. The dewatering efficiency was affected more by the rotational speed and the pulp properties. The counter-pressure affects dewatering near the discharge end, and it was observed to influence the outlet consistency and filtrate flow rate of Kraft, which has much longer fibres and fewer fines compared to TMP and BCTMP. The feed stock freeness and consistency are very important variables to consider in the screw press performance. The freeness reflects the degree of drainage, which is an important parameter to consider when optimising the screw press, while the feed consistency is a parameter of the fibre-fibre contact degree. The pulp properties, especially the fines content and fibre flexibility are also two very important parameters that affect the screw press performance. This study was to provide an insight of the screw press performance and to show the complex effect of the operational parameters on the dewatering characteristics. Using three different pulps, Kraft and TMP softwood fibres and a BCTMP hardwood fibres, we have shown that the fines content and fibre properties are two dominant properties that should be highly considered when operating a screw press. © 2019 Institution of Chemical Engineer

Optimizing Refiner Operation with Statistical Modelling

A series of pilot scale refining trials has been conducted to study the impact of refining conditions on the energy efficiency of the process and on the handsheet quality of a chemimechanical pulp. Black spruce (Picea mariana) chips, cooked to a yield of 90% and a sulphonate content of 1.4%, were refined in two atmospheric stages. Plate gap and consistency in each stage was controlled according to a central composite design. Statistical models of refiner performance were constructed from these experimental results and a non-linear optimization of process conditions was conducted. Optimization results were verified with plant trials which indicate that increasing the ratio of specific energy applied in the first stage leads to a reduction of approximately 15% in the total energy required. Inversely, this strategy can be used to obtain significant increases in pulp quality for a given energy input. The results also indicate that the largest proportion of energy must be applied to the fibres at high consistency

Treatment levels of 4-acetamido-TEMPO oxidized thermomechanical pulp to improve paper properties and clay retention

TEMPO-oxidized thermomechanical pulp (TMP) prepared at low-oxidized and highly oxidized levels was compared with untreated TMP to observe the advantage of each pulp on paper properties. While the low oxidized pulp and non-oxidized pulp gave similar properties, highly oxidized TMP significantly increased tensile strength and decreased tear strength. Brightness was negatively affected by oxidation. In order to improve the paper optical properties, the use of a conventional mineral filler retention system was studied, using clay as filler. The high charge induced by the oxidized pulp significantly modified the pulp retention behavior. Moreover, paper made from pulp containing oxidized pulp and clay presented considerably better tensile strength with a loss in tear resistance for the same brightness target, which could be interesting for some paper applications. © 2019, North Carolina State University

Modelling of dewatering wood pulp in a screw press using statistical and multivariate analysis

Statistical modeling of a screw press was established by using an experimental design based on the screw rotational speed, the pulp feed consistency, the pulp feed suspension freeness, the inlet pressure, and the counter-pressure at the discharge end. The statistical models showed that the screw press outputs for each pulp could be predicted. When including all data in a global model to predict the outputs of the press for any pulp, a global statistical model was found not to be efficient by using just the five fixed parameters. The solution to this problem was to use a multivariate analysis to include more parameters, mainly about the fiber characteristics (crowding factor, fiber length, fiber width, and fines content). By including these fiber properties, the differences between each pulp were more properly analyzed. The multivariate analysis predicted the press outsets very well in a global model by using eight parameters instead of five. The R2 values of the multivariate prediction model were all higher than 0.70 and had the goodness of prediction (Q2) higher than 0.60. © 2020 North Carolina State University