1,721,114 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Green Hydrogen Production from Residual Lignocellulosic Biomass via Dark Fermentation: Maximizing Hydrogen Yield via Optimal Pretreatment Method and Substrate-to-Inoculum Ratio
Full text linkMaster's thesis in Environmental engineeringThis thesis presents an investigation into the biohydrogen production potential of Lignocellulosic Aquatic Residue (LAR), a byproduct of an industrial process. A detailed examination of the substrate and inoculum characterization, pretreatment methods, biohydrogen production via dark fermentation at different Substrate-to-Inoculum Ratios (SIRs), and kinetics modelling was conducted. The study aims to illustrate that LAR can serve as an effective substrate for renewable biohydrogen production via dark fermentation.
After mild acid hydrolysis and lipid extraction pretreatment, LAR showed a high carbohydrate and lipid content. However, the pretreatment process needs to be optimized to avoid the introduction or release of inhibitory compounds since no gas production was observed from those pretreated LAR. Further examination revealed an optimal SIR of 2.7, where Hydrogen Yield (HY) of LAR reached around 280 mL H2 g −1 VS.
A Continuous Flow Stirred-Tank Reactor (CFSTR) was built to upscale the biohydrogen production, which produced promising preliminary results. Energy output estimation indicated that biohydrogen production from LAR could contribute between 2.6 to 3.5 TWh per year, equating to 1.2 to 1.6 % of Norway’s total energy demand. This approach turns an otherwise waste product into a source of renewable energy.
These findings suggest that the utilization of LAR for biohydrogen production via dark fermentation holds significant potential for future green energy solutions. Continued research is necessary to optimize pretreatment methods, operational conditions, and to fully understand this unique biomass resource
Bioenergy production of wastewater remediated (nitrogen and phosphorus) algal biomass-feasibility and evaluation.
Full text linkMicroalgae are unicellular aquatic microorganisms that can utilize light and carbon dioxide through photosynthesis and produce biomass. Nowadays, they can be used as a source of alternative food, animal feed, biofuel, fertilizer, cosmetics, and for nutraceutical purposes. Additionally, the use of microalgae in wastewater treatment has gained considerable interest recently for its ability to combat environmental pollution and provide cost-effective remediation. However, the high cost of the chemical nutrient medium required for microalgae growth leads to economic inefficiency, while using aquaculture and municipal wastewater could be a viable alternative to synthetic nutrient media in practical applications.
This thesis explores the potential of using aquaculture wastewater (ACWW) and municipal wastewater (MWW) as substitutes for synthetic nutrient media in microalgae cultivation. The study involved cultivating two common microalgae species, Scenedesmus, and Chlorella sp., using various nutrient media compositions. These included a mixture of 50% raw wastewater, 50% filtered wastewater, and a control Bold’s Basal Medium (BBM) for batch cultivation. However, in lab-scale cultivation, only 50% of raw wastewater was utilized as the nutrient media for the cultivation process. Various growth parameters such as optical density (OD), dry cell weight (DCW), and specific growth rate (µ) were assessed to meet the research objectives for both batch and lab cultivation. The highest biomass concentration was observed in filtered ACWW, with values of 0.407 g/L for Scenedesmus sp. and 0.503 g/L for Chlorella sp. in batch cultivation.
Additionally, parameters related to wastewater treatment efficiency, such as chemical oxygen demand (COD), total phosphorus (TP), and total nitrogen (TN), were monitored every third day during the cultivation process. The overall TP removal efficiency was observed higher in filtered ACWW compared to MWW with the removal of 94.1 % in Scenedesmus sp. and 94.4% in Chlorella sp. Similarly, the overall TN removal efficiency was found to be 68.9% in Scenedesmus sp. and 88.5% in Chlorella sp. in the filtered ACWW sample
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Optimization of the Inoculum-to-Substrate Ratio in Solid-State Spent Coffee Grounds Anaerobic Digestion Biorefineries Using Anaerobic Sludge for Maximal Bio-CH4 Production.
Full text linkMaster's thesis in Environmental TechnologyThe optimization of bio-CH4 production from spent coffee grounds (SCGs) using anaerobic sludge (AS) under different inoculum-to-substrate ratios (ISRs) using solid-state batch-fed anaerobic digestion (AD) reactors was tested. All reactors were operated under mesophilic conditions (37 °C) and run at least in duplicates. The working volume was fixed at 400 ± 20 mL. The initial moisture content of the SCGs was measured at 58.4%. The tested ISRs were 0.5, 1, 2, 3, 4, 5, and 6 on a volatile solids (VS) basis (g VSAS /g VSSCGs). The biomethane potential (BMP) was determined after subtracting the blank AS BMP. Reactors with an ISR of 2 (8g VSAS 4g-1 VSSCGs) showed the highest cumulative BMP of 1401 ± 137 NmL CH4. However, reactors with an ISR of 6 (8g VSAS 1.33g-1 VSSCGs) exhibited the highest specific BMP of 533 ± 22 NmL CH4 g1 VSSCGs. The lowest was attributed to reactors with an ISR of 0.5 with a BMP of 271 ± 12 NmL CH4 g-1 VSSCGs, where after 41 days, anaerobic bioprocesses had not yet ceased. Placed in descending order of specific BMP, it follows ISR 6 > ISR 4 > ISR 3 > ISR 5 > ISR 2 > ISR 1 > ISR 0.5. Linear regression showed a clear trend between the achievable BMP and the ISR used. No pretreatments were applied to enhance biomethanation. Microbial growth was modelled using the modified Gompertz equation and showed a near perfect fit to the model (R2 = 0.98 to 0.99). The hydrolysis constant (kh) at ISR 0.5 was revealed to be as low as 0.02 days-1, and assumed to be inhibited by high VFA concentrations, especially propionic acid. The VS reduction was 76.2 ± 12.6% in ISR 0.5 reactors. The COD removal efficiency was 61.6 ± 3.2% in ISR 1 reactors. A total of 5881 kgs of SCG were produced in 2018 at the University of Stavanger (UiS). This can yield an average of 39088 MJ of heat and 369 kWe of power yearly. This enables SCGs bioprocessing in sustainable AD biorefineries whilst maintaining the integrity of their circular bioeconomy
Synthesis, characterization, and Batch adsorption analysis of Spent coffee grounds, Chitosan, and PVA composite beads for the removal of Cadmium and Lead from aqueous solutions.
Full text linkAdsorption of Cadmium and Lead in aqueous solutions by Spent coffee grounds/chitosan/PVA composite beads was studied.
An adsorption Batch experimental model was used to determine the Isotherms and kinetics of 4 different compositions of beads, it was developed according to the individual adsorption capacity of the constituents stated in the literature and assigned in 4 groups: Control bead (BC; containing only 4% chitosan), Bead 1 (B1; 1 gr of SCG, 4% chitosan and 7,5% of PVA), Bead 2 (B2; 2 gr of SCG, 4% chitosan and 7,5% PVA) and Bead 3 (B3; 3 gr of SCG, 4% chitosan, 10% PVA).
Morphological variables were measured using TGA, FTIR, BET, and SEM, and the adsorption capacity and removal efficiency were calculated.
The adsorption behavior was studied through non-linear and linear Isotherms and pseudo-first and second order kinetic modeling. All beads presented a non-linear Langmuir and Temkin and a pseudo-second-order fit only for cadmium adsorption according to the R2 correlation coefficients. Maximum values for adsorption capacity (qmax) were obtained for the adsorption of cadmium using the non-linear Langmuir model (B2 199,61 mg/g, B1 with 176,619 mg/g and B3 103,587 mg/g). B1 shown the highest value for lead adsorption among both approaches (263,16 mg/g).
These results could become a good contribution to the current knowledge along with a strong incentive to further research, about the valorization of waste and its important utilization in the synthesis of composites as remediators of contaminated water
A feasibility study of piggery wastewater as a cost-effective media using sodium alginate immobilized microalgae
No full textIn recent years, microalgal biotechnology has experienced significant growth across multiple industry sectors due to the versatility of various microalgae species. Manny applications for both microalgae themselves and microalgae products derived from algal biomass are mentioned in this thesis. However, the economic inefficiency and difficulties in commercial scale-up production arise from the high costs of chemical nutrient media used for algal cultivation. Piggery wastewater offers an alternative to commonly used chemicals, like Bolds basal media, and contain much of the nutrients needed for algal growth.
This thesis explores the possibility of using PWW as a nutrient media when cultivating Chlorella sp. microalgae immobilized in sodium alginate. Different concentrations diluted with distilled water were tested in order to find the optimal concentration yielding the most growth. Growth patterns were measured by optical density and nutrient depletion were measured by analyzing the total nitrogen and total phosphorous in the samples.
A 70% depletion of total nitrogen was observed from all variants of immobilized microalgae beads, while a 90% depletion of total phosphorus was observed from all variants of immobilized microalgae.
The thesis also explores microalgae immobilization optimization using sodium alginate. Different sized beads were tested to find the bead yielding the best growth conditions for the immobilized algae inside.
The results from these experiments offer information useful for future applications of microalgae cultivation and sodium alginate immobilization.
From Coffee Waste to Biofuels: Techno-Economic Assessment of Two Scenarios for Hydrogen and Methane Generation
Full text link- …
