Fundamental Investigation of Reactive-Convective Transport: Implications for Long-Term Carbon dioxide (CO2) Sequestration

The density-driven convection coupled with chemical reaction is the preferred mechanism for permanently storing CO2 in saline aquifers. This study uses a 2D visual Hele-Shaw cell to evaluate and visualize the density-driven convection formed due to gravitational instabilities, also known as Rayleigh-Taylor instability. The primary goal of the experiments is to understand the various mechanisms for the mass transfer of gaseous CO2 into brine with different initial ionic concentrations and flow permeability. Moreover, the impact of CO2 flow rates, injection locations, reservoir dipping angle, and permeability heterogeneity is also investigated. We observed that the presence of salts resulted in earlier onset of convection and a larger convective finger wavelength than the case with no dissolved salts. In addition, experimental data showed a higher lateral mixing between CO2 fingers when dipping is involved. The visual investigation also revealed that the CO2 dissolution rate, measured by the rate of the convective fingers advance, depends on the type and concentration of the ions present in the brine. The CO2 dissolution for solutions with varying salt dissolved, indicated by the area of the pH-depressed region, is observed to be 0.38-0.77 times compared to when no salt is present. Although convective flow is slowed down in the presence of salts, the diffusive flux is enhanced, as observed from both qualitative and quantitative results. Moreover, the reduced formation permeability, introduced by using a flow barrier, resulted in numerous regions not being swept by the dissolved CO2, indicating an inefficient dissolution. We also investigated the effect of discrete high conductivity fractures within the flow barriers, which showed an uneven vertical sweep and enhanced flow channeling. Lastly, the parameters regarding CO2 leakage risk during storage are identified and discussed

A Review of Literature on Takaful and Conventional Insurance. Evidence from Bangladesh

Takaful and conventional insurance are the most important financial products that significantly contributes the financial sectors. This paper review and discuss challenges and factors of Takaful and conventional insurance in Bangladesh. Specially several challenges and factors are reviewed and discussed. The authors have been able to review more than thirty investigations over a eighteen years period, from 2006 to 2023. The paper is theoretical and analytical in nature and secondary method has applied. Through a literature review, this paper provides an account of main findings of the literature as well as examines the extent to which insurance gives impact towards financial sectors in terms of challenges and factors. The findings reveal that Takaful industry faces some challenges in Bangladesh such as lack of awareness among customers, regulatory barriers, expert Shariah committees and operational inefficiencies. While factors such as religiosity, Shariah board and regulatory framework have impact on promoting Takaful industry in Bangladesh. The paper concludes with several recommendations for future research, the most important of which is the need for a systematic effort on conceptual analysis as well as empirical study on Takaful and conventional insurance

Application of Numerical Method in Assessing the Variations in Pile Group Efficiency under Different Circumstances

Rapid urbanization creates a demand to expand the cities where using pile foundation became a recurrent practice. To ensure sustainability of projects pile load tests are important but may not be always feasible in terms of costing, on-site constrains etc. In this circumstance numerical analysis is a good alternate to estimate precise pile load capacity rather than conventional conservative approaches. This research illustrates the pile group efficiency fluctuation due to pile diameter, spacing, pile number and orientation in prescribed sandy soils. Using the conventional method the individual pile capacities are calculated for a constant depth with variable diameters and soil profiles. For simulating the piles, geometric models of sandy soils with sufficient boundaries are generated in PLAXIS 3D FOUNDATION software where the parameters of pile and soil components are considered as per predetermined values from reliable references. The analysis results have thoroughly been scrutinized by plotting several graphs at different aspects. The outcomes indicate that the conventional pile spacing i.e. 2.5D to 3.5D has an insignificant effect on pile group efficiency, irrespective to pile diameter and soil type. It also exhibits that the increment of pile number significantly decreases pile group efficiency for diameters of 600mm, 800mm, 1000mm and 1200mm in sandy soils. With a few exceptions as the diameter of the pile increases, the group efficiency decreases. The arrangement of piles in group has minor impact on pile group efficiency which enhances onsite flexibility. It is expected that these outcomes will facilitate the practicing engineers for efficient solutions

Trails of Media Trial: Impacts on Judiciary and Society in Bangladesh

The media is supposed to be a light bearer of truth and justice as people tend to trust the circulations of media. However, using this as an advantage, the media often brings delicate judicial issues on a trial which results in the suffering of the victim. The key objective of this research was to explore the impacts of the trials of media on the justice system and society of Bangladesh. Primary data were collected using qualitative tools like In-Depth Interviews to understand the rigor of the research problem. At the same time, secondary data such as several case studies were collected to depict the history of media trials in Bangladesh. The research found the capability of media trials to impact the judicial system and society of Bangladesh adversely through indirect influence on the juror, evasion of privacy of the personnel associated with the cases, and misuse of social media. The research opted for effective policies to be formed by the government to regulate media influence on judicial cases so that media trials cannot impact the system. Keywords: Media trial, Press, Judiciary, Justice System, Impact, Society. DOI: 10.7176/NMMC/106-0

Accounting for aerodynamic Interference effects for a quadplane in transition flight

Quadplane is a unique unmanned air vehicle (UAV) which has horizontal rotors and fixed wings. This prominent formation allows the vehicle to take off or land vertically, hover and transit to horizontal flight. This thesis explores and demonstrates the aerodynamic interference appearing between the wings of a quadplane in its transition phase, for better perception of its performance and wing orientations. Numerical models are established using the lumped vortex model, to analyse the upwash and downwash effects from the wings for unsteady loads and moments. Influence of upwash encountered by the front-wing and downwash on the back-wing are recognized from the dissimilar lift outcomes. The study is done for two separate tandem wing layouts consisting of symmetric wings and cambered wings. Results show that, both wing arrangements are found to be analogous with different vehicle trim conditions. Quasi-steady evaluation of the quadplane models are compared to the unsteady solutions process to examine the importance of unsteady interactions. An analysis is performed to address the effects of a disturbance on the moving quadplane. Full flight simulations of the quadplane models are performed with the utilization of tuned controllers. The simulations are conducted for the specified cases of wing interactions and quasi-steady analysis to investigate the respective 3–DoF longitudinal dynamics of the quadplanes.Master of Science (Aerospace Engineering

Physics-Based Proxy Modeling of CO₂ Sequestration in Deep Saline Aquifers

The geological sequestration of CO2 in deep saline aquifers is one of the most effective strategies to reduce greenhouse emissions from the stationary point sources of CO2. However, it is a complex task to quantify the storage capacity of an aquifer as it is a function of various geological characteristics and operational decisions. This study applies physics-based proxy modeling by using multiple machine learning (ML) models to predict the CO2 trapping scenarios in a deep saline aquifer. A compositional reservoir simulator was used to develop a base case proxy model to simulate the CO2 trapping mechanisms (i.e., residual, solubility, and mineral trapping) for 275 years following a 25-year CO2 injection period in a deep saline aquifer. An expansive dataset comprising 19,800 data points was generated by varying several key geological and decision parameters to simulate multiple iterations of the base case model. The dataset was used to develop, train, and validate four robust ML models—multilayer perceptron (MLP), random forest (RF), support vector regression (SVR), and extreme gradient boosting (XGB). We analyzed the sequestered CO2 using the ML models by residual, solubility, and mineral trapping mechanisms. Based on the statistical accuracy results, with a coefficient of determination (R2) value of over 0.999, both RF and XGB had an excellent predictive ability for the cross-validated dataset. The proposed XGB model has the best CO2 trapping performance prediction with R2 values of 0.99988, 0.99968, and 0.99985 for residual trapping, mineralized trapping, and dissolution trapping mechanisms, respectively. Furthermore, a feature importance analysis for the RF algorithm identified reservoir monitoring time as the most critical feature dictating changes in CO2 trapping performance, while relative permeability hysteresis, permeability, and porosity of the reservoir were some of the key geological parameters. For XGB, however, the importance of uncertain geologic parameters varied based on different trapping mechanisms. The findings from this study show that the physics-based smart proxy models can be used as a robust predictive tool to estimate the sequestration of CO2 in deep saline aquifers with similar reservoir characteristics

Dielectrophoresis spectroscopy for nucleotide identification in DNA

DNA sequence with a known physical position on a chromosome is called a genetic marker, so the causal gene may identify with genetic markers in different kinds of hereditary diseases. DNA segments near one another on a chromosome often inherit the other concurrently; as a result, the inheritance of a neighboring gene that has not yet been discovered but whose general position is tracked by using genetic markers. So, Genetic markers can play a significant role in biological research because they can contribute to identifying many diseases. Single nucleotide polymorphism, or SNP (pronounced “snip”), is the variation of a single nucleotide in a DNA due to genetic disorders. For example, in a specific region of DNA, an SNP may displace the nucleotide cytosine (C) with the nucleotide thymine (T). SNPs, or single nucleotide polymorphisms, are one of the most common genetic variations that assist in detecting many human diseases such as Migraine, Cancer, Schizophrenia, Sickle Cell Anemia, Alzheimer's Disease, etc. Hyperchromicity, Short Oligonucleotide Analysis Program (SOAP), quantitative PCR techniques, Fluorescence Polarization Melting Curve Analysis, SNP Microarrays, Intercalating Dyes, and many other techniques are commonly used to identify SNPs nowadays. However, those methods are not much reliable, a bit costly, time-consuming, and difficult to use, whereas dielectrophoresis can be an excellent way to detect SNP easily. A non-uniform electric field generated by electrodes interacts with polarizable suspended particles to regulate and alter particle movement; this process is known as dielectrophoresis (DEP). Cell transfer, in vitro fertilization, and biological testing are a few uses for dielectrophoresis, particularly in the biomedical industry. Cell fusion using dielectrophoresis has also improved crossbreeding, cancer treatment, and scientific research. Most notably, dielectrophoresis is used to classify changes in the electrical characteristics of cells. In this phenomenon, when a dielectric particle is exposed to a non-uniform electric field, a force is produced on it, and this DEP force may be utilized to recognize the variations in a single location in a DNA sequence. DEP is less time-consuming, cheap, and reliable than other processes to detect SNPs easily

Recent trends and future potential of microwave-assisted fish drying

Microwave (MW) offers a unique heating mechanism, which volumetrically pushes internal moisture to the surface during the drying of water-rich foods such as fish. However, due to the uneven power distribution, the continuous application of MW energy causes excessive localized heating, resulting in the deterioration of food quality. Incorporation of other drying techniques such as convective, vacuum, osmotic, and freeze-drying with MW has been attempted in the past to solve these shortcomings and applied in different drying systems. This paper investigates the current trends in microwave-assisted drying (MWAD) methods for fish. The available literature on MWAD methods is critically analyzed in terms of energy consumption and change in nutritional components as well as other properties. Additionally, this review explores the potential of MWAD methods for fish drying. This article shows that pulsed microwave convective drying (PMCD) can be implemented in fish drying effectively. Considering the critical need for improving energy efficiency and quality retention in fish drying, PMCD would be a highly promising drying method.</p