Environmental impact assessment (EIA) is a policy tool used for evaluating a project proposal from physical and socioeconomic environmental perspectives. Its aim is to reduce the impact of development on environment, hence, ensuring environmental sustainability. It is mandatory to submit an Environmental Impact Statement before starting a mega project as required by Environmental Protection Act of 1997 and Environmental Policy of Pakistan. Public consultation plays a key role in an EIA system, identifying the likely aspects and impacts of a development activity. This aspect has been ignored in effective enactment of environmental legislation in Pakistan. Sufficient legislative instruments are there to support EIA system in the country but the agencies responsible for the enforcement of environmental regulations have failed to do so. The current research gives an insight into the actual status of EIA system in Pakistan along with the feedback of EIA specialists and university teachers of the concerned departments. A new index has been devised on the basis of questionnaire response to work out the overall performance of EIA system in Pakistan or any other country. The weaknesses and deficiencies of each EIA stage have been worked out for Pakistan and elaborated with the help of the controversial Zero point Interchange Project in the capital city of Pakistan.
Plant-mediated nanoparticles are gaining popularity due to biologically active secondary metabolites that aid in green synthesis. This study describes a simple, environmentally friendly, dependable, and cost-effective production of silver nanoparticles utilizing Cucumis sativus and Aloe vera aqueous leaf extracts. The aqueous leaf extracts of Cucumis sativus and Aloe vera , which worked as a reducing and capping agent, were used to biosynthesize silver nanoparticles (AgNPs). The formation of surface plasmon resonance peaks at 403 and 405 nm corresponds to the formation of colloidal Ag nanoparticles. Similarly, the Bragg reflection peaks in X-ray diffraction patterns observed at 2θ values of 38.01°, 43.98°, 64.24°, and 77.12° representing the planes of [111], [200], [220], and [311] correspond to the face-centered cubic crystal structure of silver nanoparticles. Fourier transform infrared spectroscopy confirms that bioactive chemicals are responsible for the capping of biogenic silver nanoparticles. The size, structure, and morphology of AgNPs with diameters ranging from 8 to 15 nm were examined using transmission electron microscopy. Water contamination by azo dyes and nitrophenols is becoming a more significant threat every day. The catalytic breakdown of organic azo dye methyl orange (MO) and the conversion of para -nitrophenol (PNP) into para -aminophenol using sodium borohydride was evaluated using the prepared biogenic nanoparticles. Our nanoparticles showed excellent reduction ability against PNP and MO with rate constants of 1.51 × 10 –3 and 6.03 × 10 –4 s –1 , respectively. The antibacterial activity of the nanomaterials was also tested against four bacteria: Staphylococcus aureus , Klebsiella pneumoniae , Enterobacter , and Streptococcus pneumoniae . These biogenic AgNPs displayed effective catalytic and antibacterial characteristics by reducing MO and PNP and decreasing bacterial growth.
Composite structures are extensively used in various fields ranging from, but not limited to marine, aerospace, automotive, agricultural and industrial equipment due to their unique and excellent properties like weight associated with density. On an increase in their applications, it also requires special attention to manufacture and process the composites to acquire the high level of stability. Most critical defect in composite structures that have attracted many researchers is delamination. Delamination in composite structures are inevitable during service period. Present work is focused on investigating the effect of presence of delamination in the carbon fiber reinforced composite plate using finite element solver software, ANSYS. Present analysis will focus to find the effect of delamination size, boundary constraints and layups on the natural frequency of carbon fiber composite plate. Analytical results were also analyzed using MATLAB environment. Governing equations were derived using Rayleigh-Ritz method. The natural frequency reduced on an increase in delamination size and it is high in clamped-clamped boundary conditions rather than simply supported constraints. The finite element results are then compared with analytical results for clamped-clamped boundary conditions and found in close agreement.
Radomes are usually constructed from sandwich structures made of materials which usually have a low dielectric constant so that they do not interfere with electromagnetic waves. Performance of the antenna is increased by the appropriate assortment of materials enabling it to survive under marine applications, and it depends on composite strength-to-weight ratio, stiffness, and resistance to corrosion. The design of a sandwich core submarine radome greatly depends on the material system, number of layers, orientation angles, and thickness of the core material. In this paper, a conceptual design study for a sandwich core submarine radome is carried out with the help of finite element analysis (FEA) using two unidirectional composite materials—glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP)—as a skin material and six different core materials. Conceptual designs are obtained based on constraints on the composite materials’ failure, buckling, and strength. The thickness of the core is reduced under constraints on material and buckling strength. Finite element analysis software ANSYS WORKBENCH is used to carry out all the simulations.
Composites are one of the rapidly consuming materials due to their utmost attractive applications ranging from the aerospace to the agricultural products. The composite structures usually experience vibration during service. Experiments showed that presence of delamination in composite structures is one of the major causes of failures in laminated structures. Presence of delamination in a structure not only significantly impacts the stiffness of the structure with declining trends but also affect their vibration properties. The purpose of this paper is to review the literature studies on the effect of vibration on composite delaminated structures subjected to different boundary conditions. The literature studies have been classified on the basis of methodology adapted to analyze the problem i.e experimental work, analytical approaches and finite element methods. In this review particular attention has been given to the study of results attained from the analytical analysis, finite element and experimental works. Comparison of the results conducted by other researchers in the field of the free and forced vibration behavior of the composite laminates subjected to delamination or cracked structures has also been studied. Studies have shown that the location and size of delamination in composite structures significantly impacted the natural frequencies and mode shapes.
The purpose of this study was to investigate the effect of polypropylene fiber reinforced self-compacting concrete (SCC) at both the fresh and hardened stages, as well as their durability behavior. Properties of marble powder-based fiber reinforced SCC at fresh state were studied by means of slump flow diameter and flow time, V-funnel, and L-box test. The concrete properties at the hardened state were examined regarding compressive strength, split tensile strength, and flexural strength. Cement was replaced with marble powder with a substituting ratio of 4%, 8%, 12%, and 16% while polypropylene fibers were added as 0.1%, 0.2%, 0.3%, and 0.4%. The durability properties were analysed in the form of water permeability and chloride migration. In accordance with the outcomes of the tests, the workability of SCC deteriorated with an increase in fiber content, although it performed effectively at higher marble dosages. There was little impact of fibers on compressive strength and water permeability property of SCC. However, by adding the fibers in SCC improved both the split tensile strength and flexural strength by 16.92% and 11.36%, respectively. The addition of marble powder showed a synergetic effect with polypropylene fibers, which showed its applicability in SCC. The chloride resistance was improved at lower content of polypropylene fiber addition. For optimizing polypropylene fibers (pp) and marble powder substitution, the polynomial work expectation justifies the response surface technique (RSM). When a p value of 0.05 is used to analyse the variation in the (Linear-ANOVA), the model is considered statistically significant. Performance of concrete was greatly enhanced by substituting 12% marble powder with cement and adding 3% polypropylene fiber.
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