Journal of Science and Transport Technology

Nonlinear dynamic thermal buckling behavior of FG-GPLRC spherical shells and circular plates with porous core

2024-11-01T04:35:02+00:00

A semi-analytical approach for dynamic buckling of sandwich functionally graded graphene platelet-reinforced composite (FG-GPLRC) spherical shells and circular plates under dynamic thermal loads with porous core is reported in the present research. Based on the higher-order shear deformation theory (HSDT), the formulations are established, and the large deflection nonlinearity of von Karman with the visco-elastic model of the nonlinear foundation is applied. The structure's nonlinear equations of motion can be obtained utilizing the Euler-Lagrange equations combined with Rayleigh dispersion functions. The dynamic thermal load is assumed to be a linear function of time. Numerical studies are investigated employing the Runge-Kutta method to obtain the dynamic thermal behavior, and the dynamic criterion of Budiansky-Roth can be used to determine the critical buckling temperature. Significant remarks on the dynamic thermal behavior of structures are presented through the investigated examples.

Geotechnical Challenges and Solutions in the Construction of Underground Powerhouse with Shallow Basalt Rock Cover: A Review of Sardar Sarovar Narmada Project Case Study

2024-10-21T02:54:55+00:00

The Sardar Sarovar Narmada Project in Gujarat, India, provides a critical case study of underground powerhouse construction, completed in 2003, under challenging geological conditions, specifically with a shallow basalt rock cover. This paper begins by detailing the assessment of the geotechnical challenges encountered during the excavation of a 58-meter-high powerhouse chamber, including the evaluation of rock mass properties and in-situ stress using flat jack and hydro-fracture tests. These assessments identified significant stress redistribution and distress in the rock mass, leading to cracks aligned parallel to the cavern’s longer axis, which impacted critical structures such as pressure shafts and bus galleries. To address these challenges, a comprehensive engineering geological analysis was conducted, employing modern instruments like DEMAC gauges to monitor shear zones and crack development. Advanced analytical methods, including the 3-D Finite Element Method (FEM) and the 3-D Distinct Element Code (DEC), were utilized to assess the cavern's behavior under the identified stresses. This study underscores the critical importance of detailed geotechnical analysis and the careful selection of support systems for ensuring the stability of excavations in challenging environments like shallow basalt cover. The findings highlight the value of adaptive support systems and comprehensive geotechnical assessments in managing stress relief and deformation in similar geological conditions. Although the results are based on the specific case of the Sardar Sarovar Narmada Project, they provide valuable insights for the design and construction of underground powerhouses in jointed rock masses with shallow cover. These insights contribute to the broader geotechnical literature by offering practical guidance for similar underground construction projects. Future research should apply these lessons across a range of geological settings and rock types, refining and generalizing design practices to enhance construction strategies for underground caverns in various geotechnical contexts.

Impact of MoS2 Layer Thickness and Donor Concentration on Saturation Current in 4-Layer MOSFET: A Comsol Simulation

2024-11-02T10:30:45+00:00

This study investigates the effects of the thickness and donor concentration of a hybrid MoS₂ semiconductor layer on the saturation current of a four-layer MOSFET, utilizing Comsol Multiphysics simulation software. By leveraging the software's capabilities to adjust physical parameters, we systematically analyze the influence of these variables on the device performance. Our findings indicate that increasing the MoS₂ layer thickness and donor concentration significantly enhances the saturation current, thereby improving the overall efficiency of the four-layer MOSFET. These simulation results align closely with experimental data and create a robust foundation for future studies and fabrication efforts aimed at optimizing the performance of MOSFETs through material engineering.

Nonlinear buckling and postbuckling of FG-CNTRC sandwich plates with multi-layer corrugated FG-CNTRC core

2024-12-03T02:16:26+00:00

This paper proposes an analytical solution for the nonlinear buckling behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) sandwich plates under axial compressive and external pressure loads is analytically examined in this paper. The considered plates are designed with the multi-layer corrugated FG-CNTRC core and face sheets. The CNT distribution laws of the multi-layer corrugated core are proposed to ensure the material continuity between FG-CNTRC face sheets and multi-layer corrugated core. Classical plate theory (CPT) with geometrical nonlinearities is utilized to formulate the fundamental expressions. In addition, the Ritz energy method is used to achieve the expressions of compression and pressure postbuckling curves, and axial critical buckling loads. The investigations numerically display the influences of multi-layer corrugated core, material, and geometrical properties on the nonlinear buckling and postbuckling behavior of plates.

Comparative Life Cycle Assessment of the Use of Coconut Biodiesel Blends and Neat Diesel in Public Utility Jeepneys in Metro Manila, The Philippines

2024-12-02T02:10:32+00:00

This study aims to compare the CO₂ emissions from conventional diesel and coconut biodiesel blends from raw material extraction up to use as fuel for public utility jeepneys (PUJs) in the Philippines. This work used the process-based LCA approach with 1 kilometer distance travelled by PUJs as the functional unit. The kg CO₂ emissions from coconut farming and harvesting until the use phase of the coconut biodiesel blends in Metro Manila jeepneys were estimated in this work. The calculated emission factor of Coconut Methyl Ester (CME) from its fatty acid composition is 2.5539 kg CO₂ per 1 kg CME. The total CO₂ emissions in the life cycle of 2% CME blend (B2) and 5% CME blend (B5) were lower by 0.767% and 5.37%, respectively, compared to those from life cycle of neat diesel. In the life cycle of neat diesel, B2 blend, and B5 blend, the use phase contributed 75-78% of the CO₂ emissions. The kg CO₂ emissions from Metro Manila public utility jeepneys decreased from 0.400kg/ km using neat diesel to 0. 381 kg/km and 0.363 kg/km using B2 blend and B5 blend, respectively. In the life cycle of coconut biodiesel from raw material extraction to CME production, 52-58% of CO₂ emissions come from the production of material inputs to the trans-esterification process. Three main recommendations are proposed by this work: (1) Extend the LCA to higher blend percentage. This entails measurement of specific fuel consumption of jeepneys using this fuel. (2) Increase engine efficiencies of Public Utility Jeepneys to reduce fuel consumption and realize higher CO₂ emission reductions. (3) Further studies on optimization of mole ratio of methanol to coconut oil in trans-esterification process must be done. Explore use of methanol from sources-other than natural gas- with less CO₂ emissions.