Sparse Lagrangian MMC-LES Combustion Modelling of Liquid Sprays

This thesis provides a detailed investigation of turbulent combustion modelling of liquid sprays. Modelling of liquid sprays is a challenging task due to the existence of a wide range of complexities in both liquid and gas phases and their interaction in the spray and combustion process. In such multiphase flow, there is a need to address all physical processes involved in each individual phase and jointly in the interaction of phases. In a multiphase flow, there are physical processes with respect to flow, energy, chemical reactions, and flame propagation. In the liquid phase, the physical processes include dispersion, evaporation, volatile formation and exchange of heat and mass transfer with the gas phase. In the gas phase, there is turbulent flow, mixing and chemical reactions. The model that is derived and validated in this thesis extends the existing capabilities of liquid spray modelling by introducing a novel model for heat and mass transfer in the liquid phase that is coupled with the gas phase simulation. The model is comprised of an Eulerian LES model for the gas phase mass, momentum, and reference mixture fraction, a Lagrangian fuel particle (LFP) model for the dispersion, evaporation, heat and mass transfer and volatile formation, and a second Lagrangian stochastic particle model based on a multiple mapping conditioning (MMC) to represent the turbulent reacting chemistry. This study simulates three experimental validation cases from the University of Sydney combustion lab: non-reacting kerosene, evaporating acetone and reacting acetone. The axial and radial profiles of droplets, gas velocity and gas phase temperature are in good agreement with experimental measurements. Importantly the results of the finite volume and Lagrangian stochastic particle schemes are shown to be consistent with each other

Solidification study of commercial magnesium alloys

In this thesis, the solidification behaviors of AZ9ID, AM60B and AE44 commercial magnesium alloys have been studied experimentally by differential scanning calorimeter (DSC) and optical microscopy. The effect of different cooling rates on the transition temperatures and microstructures were analyzed. It was found that the effect of cooling rate on the solidus temperature is more significant than on the liquidus. The solidus temperature decreases clearly with increasing cooling rates, but for the liquidus temperature there is slightly increasing trend. The latent heat of solidification was also calculated and found that it increases when the cooling rate increases. Thermodynamic calculations were made using FactSage along with VLGM database and were compared with the experimental findings as well as with the literature data. Thermodynamic calculations were also utilized to understand the microstructures as well as the phase distribution. The microstructural details of as-cast and post-DSC samples have also been investigated using optical microscope. Finally, relationships between cooling rate and transition temperature as well as between cooling rate and latent heat of solidification have been established based on the general power law. Using these relationships it is possible to predict the transition temperatures and latent heat of solidification of these alloys at high cooling rate

Comparative Meat Production Performance Evaluation of Buffalo with Cattle at Different Ages

An inquisitive on-station feeding trial was carried out to identify the dexterous species and age for beef production with same plane of nutrition. A 2×3 (2 species × 3 ages) factorial experiment was settled for a period of 105 days with eighteen native buffalo and 18 BCB-1 (BLRI Cattle Breed-1) bulls of three age groups (18 months, 24 months and 30 months) and distributed them randomly in six treatment groups having an equal number (6) of animals in each. Intake of nutrients i.e.: DM, CP of buffalo bulls was significantly (p<0.001) higher than BCB-1 bulls in all the cases. The buffalo bulls had significantly higher digestibility of DM (68.0%, p<0.001), OM (67.9%, p<0.001), CP (66.3%, p<0.05), ADF (59.8%, p<0.001) or NDF (59.6%, p<0.001) than cattle (63.0%, 62.7%, 63.6%, 52.4% & 49.6%, respectively). But, the digestibility of DM, OM, CP, ADF or NDF was not affected significantly (p>0.05) by the age of the bulls with any cases. Buffalo bulls gained body weight more rapidly (p<0.001); 1.11 & 0.88 kg/day, respectively and showed a better FCR (p>0.05; 6.72 & 6.86, respectively) than cattle with low feed cost of per kg gain (US 1.62 & US 1.69, respectively). ADG (p<0.01), FCR (p<0.05) and estimated feed cost (p<0.05) affected significantly and increased linearly by the age of bulls, where 18 months bulls of buffalo and BCB-1 performed best. In an aggregation, it revealed that, buffalo performed better than BCB-1 cattle and 18 months age of both species was more responsive for profitable meat production

Non-Performing Loans: A Catastrophic Phenomena in Banking Sector of Bangladesh

Nonperforming loan (NPL) is one of the most cataclysmic phenomena for the entire banking industry in Bangladesh. NPLs in the banking sector have experienced a monstrous escalation of 300% in the last decade and statistically this figure is more than 1000 billion of Bangladeshi Taka (BDT). Even though international standards of loan classification and provisioning system is being adopted, the management of NPL is found unproductive. Fundamentally, deficiency of good governance, weak supervision, corruption, political interference in approving loans, culture of impunity and professional ineptness of bankers to deal with the pressing issue have played an instrumental role for the swift upsurge of NPLs. Pertaining to preventive measures, prominence needs to be placed on credit screening, loan surveillance, stringent law enforcement, centralized loan authorization system, strong monetary policy and strong loan review functionaries. Therefore, this study has emphasized on the challenges of NPL, evocative ways for improving the debt recovery environment and cracking the NPL problems in order to safeguard a sustainable banking sector of the country.Keywords: non-performing loan, loan classifications, provisioning, good governance, sustainable bankingDOI: 10.7176/EJBM/12-27-14Publication date:September 30th 202

A 03-months old boy presented with pale stool, jaundice and gradual abdominal distension since birth

Abstract not available BSMMU J 2021; 14(3): 92-9

Effect of trip attributes on ridehailing driver trip request acceptance

A generalized additive mixed model was estimated to investigate the factors that impact ridehailing driver trip request acceptance choices, relying on 200 responses from a stated preference survey in Seattle, US. Several policy recommendations were proposed to promote trip request acceptance based on ridehailing drivers willingness to accept compensation for undesired trip features. The findings could be useful for transportation agencies to improve ridehailing service efficiency, better fulfill urban mobility needs, and reduce environmental burden.Comment: Paper in print at Journal of Sustainable Transportatio

The role of heat flux in an idealised firebreak built in surface and crown fires

The disruptions to wildland fires, such as firebreaks, roads and rivers, can limit the spread of wildfire propagating through surface or crown fire. A large forest can be separated into different zones by carefully constructing firebreaks through modification of vegetation in firebreak regions. However, the wildland fire behaviour can be unpredictable due to the presence of either wind‐ or buoyancy‐driven flow in the fire. In this study, we aim to test the efficacy of an idealised firebreak constructed by unburned vegetation. The physics‐based large eddy simulation (LES) simulation is conducted using Wildland–urban interface Fire Dynamic Simulator (WFDS). We have carefully chosen different wind velocities with low to high values, 2.5~12.5 m/s, so the different fire behaviours can be studied. The behaviour of surface fire is studied by Australian grassland vegetation, while the crown fire is represented by placing cone‐shaped trees with grass underneath. With varying velocity and vegetation, four values of firebreak widths (Lc), ranging from 5~20 m, is tested for successful break distance needed for the firebreak. For each failure or successful firebreak width, we have assessed the characteristics of fire intensity, mechanism of heat transfer, heat flux, and surface temperature. It was found that with the inclusion of forest trees, the heat release rate (HRR) increased substantially due to greater amount of fuel involved. The non‐dimensional Byram’s convective number (NC) was calculated, which justifies simulated heat flux and fire characteristics. For each case, HRR, total heat fluxes, total preheat flux, total preheat radiation and convective heat flux, surface temperature and fire propagation mode are presented in the details. Some threshold heat flux was observed on the far side of the firebreak and further studies are needed to identify them conclusively

Framework for transfer learning: Maximization of quadratic mutual information to create discriminative subspaces

In the area of pattern recognition and computer vision, Transfer learning has become an emerging topic in recent years. It is motivated by the mechanism of human vision system that is capable of accumulating previous knowledge or experience to unveil a novel domain. Learning an effective model to solve a classification or recognition task in a new domain (dataset) requires sufficient data with ground truth information. Visual data are being generated in an enormous amount every moment with the advance of photo capturing devices. Most of these data remain unannotated. Manually collecting and annotating training data by human intervention is expensive and hence the learned model may suffer from performance bottleneck because of poor generalization and label scarcity. Also an existing trained model may become outdated if the distribution of training data differs from the distribution where the model is tested. Traditional machine learning methods generally assume that training and test data are sampled from the same distribution. This assumption is often challenged in real life scenario. Therefore, adapting an existing model or utilizing the knowledge of a label-rich domain becomes inevitable to overcome the issue of continuous evolving data distribution and the lack of label information in a novel domain. In other words, a knowledge transfer process is developed with a goal to minimize the distribution divergence between domains such that a classifier trained using source dataset can also generalize over target domain. In this thesis, we propose a novel framework for transfer learning by creating a common subspace based on maximization of non-parametric quadratic mutual information (QMI) between data and corresponding class labels. We extend the prior work of QMI in the context of knowledge transfer by introducing soft class assignment and instance weighting for data across domains. The proposed approach learns a class discriminative subspace by leveraging soft-labeling. Also by employing a suitable weighting scheme, the method identifies samples with underlying shared similarity across domains in order to maximize their impact on subspace learning. Variants of the proposed framework, parameter sensitivity, extensive experiments using benchmark datasets and also performance comparison with recent competitive methods are provided to prove the efficacy of our novel framework

Performance Appraisal of Selected Islamic Banks in Bangladesh

The banking system in Bangladesh plays a vital role in the progress of economic development. It works as the backbone of our economic progress and prosperity. In this paper, our attempt is to analyze the performance, development and growth of selected Islamic Banks of Bangladesh. The time span used for the study was elaborated from 2008 to 2012. For assessment, statistics were composed from five Islamic banks of Bangladesh i.e. Islami Bank Bangladesh Ltd., Al-Arafa Islami Bank Ltd., Shahjalal Islami Bank Ltd., Export Import Bank Ltd., and Social Islami Bank Ltd. There were following variables used in this research to compose statistics i.e. No. of Branches, No. of Employees, Total Deposits, Total Investments, Total Remittance, Net Income and Earning per Share. It is observed that all sample banks are achieved the strong growth of employees, branches, deposits, investments, remittance, net asset per value share, net income and earnings per share. The different activities of Islamic Banks have been tested by eight trend equations. Among them the trend value of branches, employees, deposits and net income are positive in case of all the selected banks. Square of correlation coefficient (r2) has also been tested for all trend equations. The r2 of branches, deposits and net income is more than 0.5. It indicates that the future of the Islamic Banks in Bangladesh is very bright. Keywords: [Islamic Banking System, Deposit, Investment