4 research outputs found
Optimasi Proses Hidrolisis Rumput Laut Ulva Reticulata dengan Pelarut HNO3 untuk Produksi Bioetanol
No full textOne alternative to make biofuels and replace petroleum-based fuels is to convert non-food ingredients from Ulva reticulata seaweed into bioethanol. Seventy percent of the earth's surface is covered by microalgae and seaweeds that can be converted into bioethanol. Ulva seaweed contains 50.3% carbohydrates in the form of heteropolysaccharides such as glucose, arabinose, rhamnose and xylose. Optimization of the seaweed hydrolysis catalyzed by HNO3 using Microwave irradiation was done by varying acid concentration (1, 3, 5, 7%), hydrolysis time (30, 40, 50, and 60 minutes), and hydrolysis temperature (75, 100, 125, 150°C). Fermentation was carried out by varying inoculum concentrations (6, 8, and 10% (v/v)) for 5, 6 and 7 days at a temperature of 30°C and a pH of 4.5. Analysis of the surface texture of the sample was carried out by Scanning Electron Microscopy (SEM). The analysis of reducing sugars concentration was carried out using the dinitrosalicylate (DNS) method. Ethanol analysis was carried out by Gas Chromatography (GC). The results of SEM analysis showed that prior to hydrolysis, the surface morphology of the powder was still compact and intact. Whereas after being hydrolyzed with HNO3 it was seen that the surface texture of the powder suffered significant damage. The hydrolysis results showed that the optimum conditions during the pretreatment of U. reticulata powder was at acid concentration of 7%, reaction time of 50 minutes, reaction temperature of 150°C and 250 watts of power which gave hydrolysate with reducing sugar concentration of 86.5 g/L. Fermentation of the hydrolysate using yeast Saccharomyces cerevisiae produced bioethanol with concentration of 37.2% as analyzed using a gas chromatograph
Tinkering for soil care
No full textThe authors would like to thank the farmers and their associations for taking part in the survey about tinkering. We also acknowledge the contribution of the academic and industrial members of the Chaire Agro-Machinisme et Nouvelles Technologies in understanding the trends in the agricultural machinery sector.International audienceThis study discusses the concept of tinkering with agricultural equipment, framed within the philosophical realist concept of “technical fact” and subsequent agronomic literature. This concept emphasises the time-bound realisation of technical tendencies in agriculture and highlights the critical role of farmers’ actions, mediated by equipment, in shaping farming practices. Tinkering, characterised by small, ingenious adaptations to existing tools, contrasts with the structured engineering approach, and exemplifies the flexibility and creativity inherent in farmers’ practices. Through a three-phase study involving stakeholders in the French agricultural sector, we investigate how farmers adapt equipment through tinkering to meet the challenges of soil management in the face of climate change and socio-technical dynamics. The results show that tinkering allows farmers to bridge the gap between conceptual farming practices and their practical implementation, thus promoting innovation and adaptability. Tinkering is motivated by limited availability of adapted equipment and economic constraints, especially in the context of conservation agriculture. It contributes to sustainability by promoting resource efficiency, reducing costs and increasing farmers’ autonomy. However, tinkering also poses challenges, including potential safety issues and the need for technical evaluation before widespread adoption. The study highlights the importance of modular and adaptable equipment design to facilitate farmer-driven innovation. We conclude that tinkering is an important strategy for farmers to translate broader technical trends into specific, contextualised technical facts, ultimately contributing to more sustainable and resilient agricultural systems
A Weighted Eigenvalue Problems Driven by both -Harmonic and -Biharmonic Operators
No full textsummary:The existence of at least one non-decreasing sequence of positive eigenvalues for the problem driven by both -Harmonic and -biharmonic operators \begin {gather*} \Delta _{p(x)}^2 u-\Delta _{p(x)}u=\lambda w(x)|u|^{q(x)-2}u \quad \text {in } \Omega ,\\ u\in W^{2,p(\cdot )}(\Omega )\cap W_0^{1,p(\cdot )}(\Omega )\,, \end {gather*} is proved by applying a local minimization and the theory of the generalized Lebesgue-Sobolev spaces and
Attitude Towards Sport Practice: What Makes an Individual Continued Practice of Sport?
No full textSport practice is conditioned by different factors; previous studies have shown that the attitude towards physical activity and sports practice is largely conditioned by the individual. This study proposes to examine whether the classic model of the theory of planned behaviour reinforces the main motivations for people to adhere to a sport practice. An empirical model based on the classic model of the theory of planned behaviour was proposed, adding three motivational variables to sport practice. A sample was composed of 1008 valid questionnaires collected online in Spain and Colombia. The analysis of the data was performed using the partial least squares technique using the Smart PLS 3.0 statistical programme. The proposed model presents a statistical validity that proves that the practice of physical and sporting activity is determined by the individual’s evaluation of their abilities and perceptions and their relationship with the motivations generated by continuing the practice of physical or sports activity, consequently how adherence is generated. © 2020, Associação Brasileira de Psicologia
