197,278 research outputs found
Performance of Molasses Waste as a Cement Replacement to Study Concrete Compressive Strength
No full textTo reduce the negative environmental impact of cement production and preserve natural resources, an experimental investigation was conducted to study the performance of concrete specimens at different curing ages and to determine the compressive strength of these specimens by replacing cement with molasses. Experimentation was carried out on the concrete specimens at a temperature range of 25 degrees C to 30 degrees C; six specimens were cast for each replacement ratio, except for 0.75% wt. of cement (86.55 g) and 1% wt. of cement (113.6 g), where five samples were considered for each ratio. The average 28-day compressive strength of the conventional concrete specimens came out to be 29 MPa, but increased to 40 MPa with the addition of 0.25% wt. of cement molasses (28.85 g). It was observed that as the percentage of molasses waste in the concrete mix was further increased by replacing the cement, the compressive strength of the concrete specimens increased gradually and then significantly decreased. The findings shed light on the prospect of using molasses waste instead of cement in the concrete mix. Also, it is worth mentioning that about 30% of the cost-benefit was obtained with reference to that of conventional admixtures available in the market for the production of concrete. However, it is notable that a long-term durability study needs to be conducted before making it viable. This work not only addresses a sustainable and innovative method of waste management (SDG12), but also contributes to low carbon emissions (SDG13). The novelty of this work lies in the fact that no such kind of study has been conducted in Pakistan so far, in addition to the very limited international literature available, and, in particular, no evidence on the compressive strength results at higher molasses dosages, i.e., 1% wt. of cement (113.6 g) and 2% wt. of cement (230.8 g)
Alkali–Silica Reactivity Potential of Aggregates from Different Sources in Pakistan
No full textThis paper aims to support stakeholders in the sustainable construction sector by exploring the potential of unexamined aggregates from five distinct origins: the Jandol River, the Swat River, the Panjkorha River, the Kitkot Drain, and the Shavey Drain situated in Malakand division, North Waziristan, Pakistan, concerning Alkali–Silica Reaction (ASR) prior to their incorporation into large-scale construction practices. Petrographic examination for the determination of the mineralogical composition of all collected aggregates revealed that aggregates stemming from the Swat River, Panjkorh River, Kitkot Drain, and Shavey Drain exhibited no reactive minerals. In contrast, those from the Jandol River showed reactive mineral content. Physical analysis of the aggregates revealed that Jandol River aggregates had superior resistance to impact, crushing, and abrasion, having values of 18.53%, 18.53%, and 20.10%, respectively. Moreover, the chemical analysis exhibited the highest silica content (SiO2) in Jandol River aggregates, i.e., 94.7%, respectively. Samples in the form of cubes, prisms, and mortar bars were prepared to study both the mechanical properties and the expansion tendencies of specimens prepared from different aggregate sources. Validation of the reactive nature of the Jandol River aggregates was corroborated by the expansion results obtained from the mortar bars and the reduction in compressive strength and flexure strength by 8.2% and 9.2%, respectively, after 90 days, higher than that of aggregates exposed to ASR sourced from the other four origins. It can be asserted that aggregates from the Jandol River source are more susceptible to ASR as compared to other aggregates. To mitigate the potential of ASR, various strategies, such as using low reactivity, natural, or processed aggregates; low alkali-containing cement; inducing pozzolanic substances in concrete; etc., are recommended. Simultaneously, an economic feasibility study and environmental assessments are recommended as future developments
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Regenerative or traumatized pastoral?: Barker's double vision
No full textGrapevine endophytes and plant health: a culture-independent approach
No full textThis chapter addresses the potential of culture-independent tools for the study of endophytes (including bacteria and fungi as biological control agents and/or growth promoters) of the grapevine (Vitis vinifera) and the potential of as yet uncultured endophytes for plant health. These tools include the molecular techniques such as denaturing gradient gel electrophoresis, automated ribosomal intergenic spacer analysis, length heterogeneity-PCR, fluorescence in situ hybridization, and next generation sequencing. Some potential roles for endophytes in epidemics include altering the uptake of plant nutrients, thereby potentially affecting nutrient stress as well as susceptibility to infectious disease, altering plant susceptibility through processes such as induced systemic resistance and systemic acquired resistance, or through potentially complex network structures related to microbial association
Temperature and climate affect the endophytes community in grapevine
No full textScience has just started understanding how the environment drives the composition of microbial communities. Endophytes, as host-associated microbes, respond to environmental stimuli in a host-mediated fashion. To study how temperature and climate may affect endophytic microbial communities we studied grapevine-associated microbial populations using a cultivation independent approach.
Grafted cuttings were used to analyse how temperature affects microbial endophytic communities in a controlled environment. The composition of microbial endophytes in the field was assessed by surveying potted plants at different altitudes representing diverse climatic conditions. Seasonal fluctuations in the microbial endophytes were also considered by sampling test plants at different times throughout the year.
We adopted a DNA-based, cultivation-independent approach to the analysis of microbial populations variability in the conditions considered in this study. The analysis of DNA amplified by PCR involved the use of both Automated Ribosomal Intergenic Spacer Analysis (ARISA) and Roche 454 GS FLX+ technology
Metagenomic analysis of bacterial endophytic communities associated with grapevine (Vitis vinifera L.)
No full textIn recent years, interest in endophytic microorganisms has increased, as they play a
key role in agricultural environments and are promising because of their potential
use in sustainable agriculture. These microorganisms include both commensal
species, which have no direct effect on the host plant, and mutualistic symbionts,
which could be used in the biological control of pathogens or plant growth
promotion. In the present study we investigated how microbial communities in
plants from organically managed farms differ from those obtained from integrated
pest management (IPM) farms. Microbial DNA isolated from grapevines (Vitis
vinifera L.) cv Merlot and Chardonnay cultivated in a subalpine area in Northern
Italy was PCR amplified to fingerprint endophytic communities, and to assess the
distribution of important functional genes in the grapevine microbiome in the
studied areas.
Here we report the composition of endophytic microbial communities assessed
through a cultivation independent approach: Automated Ribosomal Intergenic
Spacer Analysis (ARISA). The changes in community structure and composition are
interpreted in the light of the environmental variables considered. Fingerprinting
results were validated by multivariate analysis. Other metagenomics approaches are
being considered
다물체 동역학 기반 생체모방형 초소형 날갯짓 비행체의 동적 안정성 및 비행 제어
No full text학위논문(석사) - 한국과학기술원 : 항공우주공학과, 2021.8,[viii, 93 p. :]Since the demand for biomimetics-based aerospace systems is surging rapidly for the past few years, Flapping-wing Micro Air Vehicles (FWMAVs) are not an exception to these necessities. With the growing advancements in science and technology, scientists have realized that nature-inspired designs generally produce optimal solutions at minimal cost. One of the key bioinspired-based aerospace systems is an insect-like FWMAV that is considered quite impressive owing to its efficient flight utilizing complex aerodynamics. As real insects generally do the optimum flight, engineers are doing their best to explore the aerodynamics, kinematics, flight dynamics, and control to better mimic their flight. However, mimicking insects’ flight using FWMAVs has limited functionality considering the difficulty in understanding its complex aerodynamics and applying control.
Many studies have been conducted to characterize the stability of insect-like FWMAVshowever, they have limitations based on different areas such as the fidelity of the aerodynamic model, assumptions taken to modify the flight mechanics equations, wing kinematics adopted, rigid or flexible model used, and the type of trim search algorithm adopted. The present study considers a hawkmoth-scaled FWMAV model for characterizing its stability using a multibody dynamics simulation environment that involves fully coupled nonlinear equations of motion. The simulation environment incorporates a quasi-steady aerodynamic model, real and simplified hawkmoth wing kinematics and morphological data, kinematic constraints, and finally a gradient-based trim search algorithm. The complete simulation is run for five different speeds involving equal intervals from 0 to 1 m/s, and 6 Degrees of Freedom (6-DOF) stability is characterized based on it. The FWMAV model shows unstable behavior both in longitudinal and lateral directions (slightly damped) based on the results of the trim search.
The longitudinal direction instability is mainly related to the forward-backward direction velocities coupled with the pitching rate that results in unstable oscillatory modes. On the other hand, lateral instability augments as sideways velocity pairs with rolling and yawing rates. Firstly, the influence of body to wings mass ratio on longitudinal and lateral dynamic stabilities is investigated. Since longitudinal unstable oscillatory mode’s influence increases with speed, this study focuses on longitudinal motion control. LQR controller is implemented first to control the speed of linear FWMAV system using integral action. Next, the controller is implemented for 3-DOF motion control of the nonlinear model at five different speeds. Then, reference velocity profile tracking, involving hovering, acceleration, constant speed, and deceleration phases, is achieved for the non-linear model. Finally, various reference trajectories tracking is achieved by implementing a dual loop control technique.한국과학기술원 :항공우주공학과
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