Diatomite Modified With Alkyl Ketene Dimer For Hydrophobicity of Cellulosic Paper

Multi-functionalization of papermaking chemicals is one of its main developing strategies. Fillers and internal sizing agents are often mutually restricted in practice. Therefore, it is feasible to prepare a new papermaking chemical by combining its functions. A process of diatomite modified with Alkyl ketene dimer (AKD) was developed in this study. The modified diatomite (AD) can concurrently play the role of mineral filler and sizing agent in the papermaking process. With the equal dosage of AKD, the AD had better sizing and retention performance than the commercial AKD emulsion in the case of cationic polyacrylamide (CPAM) and the CPAM/ bentonite retention system. The sizing mechanism of the AD can be interpreted as numerous hydrophobic sites and micro-surface structure of the paper sheet caused by the AD. Since the ester linkages were not detected in FT-IR spectra of the paper sheet filled by the AD, the chemical reaction may not be indispensable for its sizing performance. What’s more, an interesting “sticky” hydrophobicity phenomenon was observed when filling with AD. The approach in this study to prepare the “sticky” hydrophobic paper sheet can find its applications in some non-traditional application fields of cellulosic paper.

Investigations on Strategic Element Recovery by an Underground Membrane Pilot Plant from In-Situ Extracted Bioleaching Solutions

Focusing on the selective extraction of the critical raw materials indium and germanium from real bioleaching solutions, extended studies have been carried out using Europe’s first underground hybrid membrane pilot plant (TRL6). In order to transfer former laboratory experiments to pilot scale, NF99 (Alfa Laval) was used for the evaluation of membrane permeance and ion retention. A performance test of microfiltration (MF) and nanofiltration (NF) showed high permeances with low root-mean-square deviation under feed variation (5.2% for MF, 4.7% for NF). Depending on the feed load, a significant permeance drop of up to 57% for MF (3 bar) and 26% for NF (10 bar, 1.1 m s−1) was observed. The NF retention performance showed that, without regular chemical cleaning, the selectivity between the target elements degraded. By introducing acidic-basic cleaning steps, it was possible to keep the retention behavior at an approximately constant level (In 91.0 ± 1.3%; Ge 18.2 ± 5.5%). In relation to the specified target, the best results could be achieved at low pressure (7.5 bar) and a maximum overflow velocity of 1.1 m s−1, with a retention of 88.4% for indium and 8.8% for germanium. Moreover, the investigations proved the functionality and long-term stability of the underground membrane device.

Quality, Price, and Competition Strategy Effects on Performance of Soft Drink Enterprises in Rwanda

Amidst market performance challenges of declining customer numbers and sales for some soft drinks enterprises in Rwanda, that has caused a big concern for academics and professionals, the study set to empirically investigate the effect of quality, price and competition strategies on sales and customer retention performance for these enterprises. The study was quantitative and cross-sectional where researchers obtained data at a single point in time on more than one case. A sample size of 118 marketing managers was taken from these enterprises in the central districts of Kigali that produce carbonated drinks, mineral water and juice. Due to corona virus pandemic, virtual means of data collection were used through telephone-based questionnaire survey. Despite the positive and significant relationship between quality and price strategies with market performance, ( =0.500, t=1.09, p<0.01) for quality, ( =0.23, t=3.05, p<0.01) for price, results for competition strategies ( =0.23, t=3.05, p=0.281), show nonsignificant relationship with market performance in the studied context. This finding manifests a big gap in managing competition and therefore advise these enterprises to revisit their competition management decisions and make investment in those positioning alternatives that impact on consumer perceptions.

Does ‘WOW’ translate to an ‘A’? Exploring the effects of virtual reality assisted multimodal text on Chinese Grade 8 EFL learners’ reading comprehension

Purpose In recent years, the incorporation of multimedia into linguistic input has opened a new horizon in the field of second language acquisition (SLA). In the reading aspect, the advent of virtual reality (VR) technology extends the landscape of reading repertoire by engaging learners with auditory, visual and tactile multimodal input. This study aimed to examine the pedagogical potential of VR technology in enhancing learners’ reading comprehension. Methods Three classes including 131 Chinese 8th grade EFL students participated in this study. This study adopted mixed methods methodology and triangulated pre-post-retention tests, questionnaires, learning journals and interview data to compare three modes of text input on learners’ reading performance and cognitive processing. Results The results indicated that VR-assisted multimodal input significantly improved learners’ macrostructural comprehension in the short term, whereas there was no significant difference in retention performance. The findings revealed that reading multimodal text did not exceed learners’ memory capacity or impose extraneous cognitive load. Participants mainly reported favorably on the efficacy of multimodal input in assisting their reading. Conclusion This study was the first attempt to integrate VR technology with input presentation and cognitive processing and offered a new line of theorization of VR-assisted multimodal learning in the cognitive field of SLA.

Seepage metal concentrations beneath long-term operated bioretention systems

Bioretention systems maintain the natural water cycle and help to mitigate climatic extremes impact on urban areas by retarding, storing, and evaporating stormwater runoff. Although bioretention systems have been operated for more than 25 years, systematic investigations on the hydrological functionality and pollutant retention performance of older systems are rare. We employed laboratory and field experiments to investigate three long-term operated bioretention systems in Germany with the following objectives: (i) physico-chemical substrate characterisation; (ii) an event-based influent and effluent trace metal concentration monitoring covering 22 months and (iii) the calculation of metal retention rates. Regarding the pollution status, we found significantly increased trace metal contents in the soil substrate mainly as a function of the drainage area type and the inflow regime. Nonetheless, all measured metal seepage concentrations fall below the German legislative trigger values. Our current findings demonstrate no risk of groundwater degradation even for old bioretention systems suggesting bioretention as a powerful and sustainable tool for stormwater management. Further research requires the handling of soil substrates modified by stormwater infiltration showing enhanced trace metal contents and a certain amount of technogenic sediments.

Experimental Study on Type and Accuracy Optimization of Sand Control in Sand-Producing Heavy Oil Well

This paper proposes a set of methods for selecting the type of sand control screen and optimizing the accuracy in heavy oil Wells, which take into account the requirements of sand control and productivity protection in heavy oil Wells. Sand retaining experiments are carried out with slotted screen, wire wrapped screen and metal filter screen under the condition of oil and water mixed sand carrying flow. In order to optimize the sand control screen suitable for heavy oil well, this paper uses the weighted average method to quantitatively evaluate the flow performance, sand retention performance and oil conductivity of the screen. Then, repeat the experiment by changing the accuracy of the screen to optimize the accuracy. The experimental results show that the permeability of the three kinds of sand control screens is about 2μm2 when only heavy oil plugging occurs. Under the combined plugging action of formation sand and heavy oil, the slotted screen has the highest permeability, and its conductivity to heavy oil is 10% higher than that of the other two screens. The silk-wound screen has the best sand retention performance, with a sand retention rate of more than 90%. Through the quantitative evaluation of the sand control performance of three kinds of screens in different production stages of heavy oil Wells, the slit screen is selected as the optimal screen. For simulated formation sand with a median particle size of 250μm, the optimal sand control accuracy is 200μm. This paper provides a quantitative optimization method of screen type and accuracy for sand control design of sand-producing heavy oil Wells, so as to maximize the productivity under the premise of ensuring sand-producing control of heavy oil Wells.

Crown Ether-Immobilized Cellulose Acetate Membranes for the Retention of Gd (III)

This study presents a new, revolutionary, and easy method of separating Gd (III). For this purpose, a cellulose acetate membrane surface was modified in three steps, as follows: firstly, with aminopropyl triethoxysylene; then with glutaraldehyde; and at the end, by immobilization of crown ethers. The obtained membranes were characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), through which the synthesis of membranes with Gd (III) separation properties is demonstrated. In addition, for the Gd (III) separating process, a gadolinium nitrate solution, with applications of moderator poison in nuclear reactors, was used. The membranes retention performance has been demonstrated by inductively coupled plasma mass spectrometry (ICP-MS), showing a separation efficiency of up to 91%, compared with the initial feed solution.

Multi-level Memristors based on Two-dimensional Electron Gases in Oxide Heterostructures for High Precision Neuromorphic Computing

Memristors are essential elements for hardware implementation of artificial neural networks. The key functionality of the memristors is to realize multiple non-volatile conductance states with high precision. However, the variation of device conductance limits the number of allowed states. Since actual data for neural network training inherently have a non-uniform distribution, the insufficient number of conductance states and the resultant inaccurate weight quantization may generate significant errors in the memristor-based computation. Herein, we demonstrate a multi-level memristor based on two-dimensional electron gas in a Pt/LaAlO3/SrTiO3 heterostructure. By redistributing oxygen vacancies, we precisely controlled the tunneling conductance of the device, achieving multiple conductance states (more than 27). The multi-level switching capability and the high retention performance allow us to implement a variance-aware weight quantization (VAQ), designed for improved computing accuracy. We verify that the VAQ provides greater accuracy in image classification process, as compared to conventional uniform quantization. These results provide valuable insight into developing high-precision multi-bit memristors for practical neuromorphic processors.

Formulation Development and Performance Characterization of Ecological Dust Suppressant for Road Surfaces in Cities

In order to solve the problem of road dust pollution, an ecological dust suppressant for road surfaces has been developed using monomer, orthogonal, and optimization experiments and based on the dust raising mechanism. A humectant, hygroscopic agent, coagulant and surfactant and their concentration ranges have been determined through monomer experiment. The preliminary formula of the dust suppressant has been obtained through orthogonal experiment, with the water loss rate, moisture content rate, viscosity value, and surface tension value serving as experimental indexes. The optimal formula for the dust suppressor has been calculated through an optimization experiment, with the toxicity, moisture absorption and retention performance of plants, and the relative damage rate of plant seeds serving as experimental indexes. Based on the performance characterization of ecological road dust suppressant, the ecologically and environmentally friendly dust suppressant demonstrates fine moisture absorption and retention performance, good wind and rain erosion resistance, and no toxicity. The ecological road dust suppressant developed herein covers extensive raw material sources. It is ecologically and environmentally friendly, fit for most urban roads, and has a fine dust suppression effect. Meanwhile, it also can bring in good economic and social benefits, demonstrating its broad application prospects.