360 research outputs found
Study on the Performance of Rice Husk Ash as a Cementing Material
No full textThis thesis is submitted to the Department of Civil Engineering, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Engineering in Civil Engineering, May 2007.Cataloged from PDF Version of Thesis.Includes bibliographical references (page 34).Utilization of rice husk has become subject of growing interest. The possibilities of its
utilization of rice husk in various ways have evoked much interest due to its high silica content.
Particularly in the developing countries of South-east Asia where the production of rice is more
than half of the production of entire world. Most important among various methods suggested
for the utilization, is the development of construction materials from rice husk as such and from
its ash. For every 1000 kg of paddy milled, about 220 kg (22%) of husk is produced, and when
this husk is burnt in the boilers, about 55 kg (25%) of rice husk ash (RHA) is obtained. Rice
husk ash is a great threat to environment causing damage to the land and surrounding area in
which it is dumped. Rice husk burnt at 450CC have been found to produce a pozzolana
conforming to the requirements of the ASTM standard C618-72. Therefore, valuable product
from this rice hush ash (RHA) is possible.
The rice husk For the study was collected from rice husking mill and was burnt in muffle
furnace in laboratory (at 450°C) for 60 minutes. Rice husk is found to contain about 76.53 %
organic volatile matter and the balance 23.47 % as ash (Table 3.7). The rice husk ash was
grounded in laboratory by using Industrial Ball Mill to the form of powder. The particles finer
than 200 meshes was collected for further test.
The new product of RHA cement sample was tested for properties like Ordinary Portland
Cement. RAH cement made in this study contains ash, lime and clay in different ratio. For this
purpose a typical samples at the beginning was made with RHA (60%) mixed with finely
grounded lime (30%) and un-burnt clay (10%). Similar samples were made with burnt (800 °C)
clay. The result between two are found to agree. Rest of the cement samples were made with
Un-burnt clay and burnt clay. Results of these samples are shown in table no. 4.1, 4.2, 4.3, 4.4,
4.5. By discussion the test results we find that, (a) in case of un-burnt clay, average water-cement
ratio required for cement paste of normal consistency (CPNC) was found to be 0.56,
initial setting time was found to be 96 minutes, final setting time was found to be 6 hrs. 58
minutes. and 3 days compressive strength for cement mortar cube was found to be 171 psi.
respectively. (b) in case of burnt clay, average water- cement ratio required for cement paste of
normal consistency (CJNC) was found to be 0.56, initial setting time was found to be 96
minutes. final setting time was found to be 7 hrs.13 minutes and 3 days compressive strength for
cement mortar cube was found to be175 psi respectively. These values when compared with
those of Ordinary Portland Cement, it was found that in case of un-burnt clay, CPNC varied
only 7%, initial setting time was double than OPC, final setting time was increased by one
hour than OPC. (b) in case of burnt clay, CPNC was found to be 0.56, initial setting time was
found to be more than double than OPC, final setting time was increased by one and half hour
than OPC and 3 days compressive strength was found to be 175 psi. It is clear from the study
that RHA can be attributed cementing property when combined with lime and clay. The
properties of this cement resembles with those of OPC with compromise of' higher setting time
and lower strength. However this may be recommended for the cases where lower strength can
be used (e.g., boundary walls, normal load bearing residential buildings, partition walls, surface
drains etc.)Md. Azad Hossain KhanMaster of Engineering in Civil Engineerin
Recent changes in ecosystem services and human well-being in the Bangladesh coastal zone
No full textThis study takes an historical approach in order to establish how the form and function of the social-ecological system that represents the Bangladesh south-western coastal zone has changed over recent decades. Time series data for a range of ecosystem services and drivers are analysed to define the range of trends, the presence of change points, slow and fast variables and the significant drivers of change. Since the 1980s, increasing gross domestic product and per capita income mirror rising levels of food and inland fish production. As a result, the size of population below the poverty line has reduced by ~17 %. In contrast, non-food ecosystem services such as water availability, water quality and land stability have deteriorated. Conversion of rice fields to shrimp farms is almost certainly a factor in increasing soil and surface water salinity. Most of the services experienced statistically significant change points between 1975 and 1980, and among the services, water availability, shrimp farming and maintenance of biodiversity appear to have passed tipping points. An environmental Kuznets curve analysis suggests that the point at which growing economic wealth feeds back into effective environmental protection has not yet been reached for water resources. Trends in indicators of ecosystem services and human well-being point to widespread non-stationary dynamics governed by slowly changing variables with an increased likelihood of systemic threshold changes/tipping points in the near future. The results will feed into simulation models and strategies that can define alternative and sustainable paths for land management
Electromagnetic Field Analysis of Lightning Return Stroke Current
No full textThis thesis is submitted to the Department of Electrical and Electronic Engineering, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Electrical and Electronic Engineering, February 2006.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 95-101).Accurate knowledge of the characteristics of lightning electromagnetic fields is needed
for studying the effects of the potentially deleterious coupling of lightning fields to
various circuits and systems, for achieving an efficient insulation design of electric power
networks and for determining electromagnetic compatibility requirements o
telecommunication systems. In the first step, lightning analysis requires the development
of return stroke models, which are able to reproduce the electromagnetic field signature
similar to that generated by natural return stroke.
In this thesis, the lightning return stroke is, firstly, assumed as a current pulse originating
at ground level and propagating along the channel of perfect electrical conductor. Then
the effects of channel resistance and inductance both on the current and the
electromagnetic fields are investigated. The results show that the inclusion of channel
resistance and inductance will change the prediction of the model in such a direction that
they will come closer to the experimental observations.
Reviewing different models, electromagnetic model is used in the present study. For the
accurate analysis of the transient electromagnetic field around a three-dimensional (31))
conductor system, application ol electromagiietic modeling codes are more appropriate.
Among many available codes, Numerical Electromagnetic Code (NEC-2) based on the
4 method of moments is chosen for the above purpose since it has been widely and
successfully used in analyzing thin-wire antennas.
The effect of ground electrical parameter on the channel current and remote
electromagnetic fields is deduced in the present thesis for several grounds. With different
methodologies different input data are involved in the lightning analysis: one of them is
related to the lightning current itself. The effect of different current wave-shapes is also
investigated in this work.
Experimental observations and theoretical investigations have shown that the presence of
an elevated strike object (such as a tall tower) could affect lightning current and their
radiated electromagnetic fields substantially. lherefore, an analysis of tower current and
remote electromagnetic fields radiated by lightning return strokes to tall towers is
presented taking two towers of different heights. In the work, both the slow-front and
steep-front wave-shapes, corresponding respectively to typical first and subsequent
return strokes, are adopted as injected current wavefonii. Because, the subsequent return
strokes that are characterized by lower current peaks but higher front steepness and
return stroke speed may result in higher field peaks. It is shown in particular that the
presence of a tower tends, in general, to increase substantially the electric and magnetic
field peaks and their derivatives. Furthermore, the presented results are shown to be
consistent with recent experimental observations of current in lightning strokes to the
high stack in Japan and Toronto CN Tower and of the associated electromagnetic fields.
Finally, to show the validity of the model, some results calculated by NEC-2 are
compared with the results calculated by Virtual Surge Test Lab (VSTL), which is based
on Finite Difference Time Domain (FD'l'D) method. In such case, reduced scale model is
considered because of large computation time of FI)TD method.Md. Faruque HossainMaster of Science in Electrical and Electronic Engineerin
“Exploring Microbial Approaches to Polymer Biodegradation: Trends and Innovations”
No full textThere is a growing concern in the world use synthetic polymers, especially because the products produced from them are non-biodegradable and have greatly polluted the environment. Biodegradation of polymers by microbes has lately been postulated as the best environmentally friendly method to tackle this issue. This review aims at reviewing the recent developments in the bio degradation of polymers using microorganisms The review traces the metabolic pathways, enzymatic systems and novel techniques that have been used in the degradation of polymers including plastics. Also, the review gives possible trends, evolving issues, and probable biotechnological uses of polymers for the environmentally sound disposal of polymer wastes
Incidence of Visually Significant Pseudophakic Macular Edema after Uneventful Clear Corneal Phacoemulsification
No full textBackground: Pseudophakic macular edema (PME) is a known cause of delayed visual recovery following cataract surgery, even in cases with uneventful phacoemulsification. This study aimed to determine the incidence of visually significant PME in a low-risk population using optical coherence tomography (OCT).
Methods: This prospective observational study was conducted in the Department of Ophthalmology at Dr. Sirajul Islam Medical College & Hospital Ltd, Dhaka and Bangladesh Eye Hospital Malibagh, Dhaka, Bangladesh, from March 2023 to February 2024. A total of 130 patients aged ≥50 years undergoing uneventful clear corneal phacoemulsification with posterior chamber intraocular lens (IOL) implantation were enrolled consecutively. Patients with pre-existing macular disease, diabetic retinopathy, glaucoma, uveitis, or intraoperative complications were excluded. Postoperative follow-up was conducted up to 6 weeks, and OCT was used to detect PME. Visually significant PME was defined as a reduction of ≥2 lines in best-corrected visual acuity (BCVA).
Results: The mean age of participants was 62.4 ± 8.9 years, with 54.6% males. Diabetes mellitus and hypertension were present in 21.5% and 30.8% of patients, respectively. OCT detected PME in 6 patients (4.6%), of which 3 (2.3%) were visually significant. Mean BCVA improved from 0.82 ± 0.21 logMAR preoperatively to 0.16 ± 0.11 logMAR at 6 weeks. PME cases showed delayed visual recovery. All PME cases were managed with topical corticosteroids and NSAIDs; five fully recovered and one had partial improvement.
Conclusion: The incidence of visually significant PME following uncomplicated phacoemulsification was 2.3%. Early OCT detection and conservative treatment resulted in favorable outcomes
BVQA: Connecting Language and Vision Through Multimodal Attention for Open-Ended Question Answering
No full textVisual Question Answering (VQA) is a challenging problem of Artificial Intelligence (AI) that requires an understanding of natural language and computer vision to respond to inquiries based on visual content within images. Research on VQA has gained immense traction due to its wide range of applications in aiding visually impaired individuals, enhancing human-computer interaction, facilitating content-based image retrieval systems, etc. While there has been extensive research on VQA, most were predominantly focused on English, often overlooking the complexity associated with low-resource languages, especially in Bengali. To facilitate research in this arena, we have developed a large scale Bengali Visual Question Answering (BVQA) dataset by harnessing the in-context learning abilities of the Large Language Model (LLM). Our BVQA dataset encompasses around 17,800 diverse open-ended QA Pairs generated from the human-annotated captions of ≈3,500 images. Replicating existing VQA systems for a low-resource language poses significant challenges due to the complex nature of their architectures and adaptations for particular languages. To overcome this challenge, we proposed Multimodal CRoss-Attention Network (MCRAN), a novel framework that leverages pretrained transformer architectures to encode the visual and textual information. Furthermore, our method utilizes a multi-head attention mechanism to generate three distinct vision-language representations and fuses them using a sophisticated gating mechanism to answer the query regarding an image. Extensive experiments on BVQA dataset show that the proposed method outperformed the existing baseline across various answer categories. The benchmark and source code is available at https://github.com/eftekhar-hossain/Bengali-VQA
Hybrid Rice: Economic Assessment of a Promising Technology for Sustainable Food Grain Production in Bangladesh
No full textHybrid rice, one of the viable and proven technologies has been considered as a new frontier to increase rice production for meeting growing demand for staple food in Bangladesh. Using farm survey data this paper examines comparative profitability of hybrid and inbred rice cultivation and estimates a Stochastic Frontier Function to determine the effect of key variables on farm efficiency. Results show that hybrid rice gives substantially higher yield as well as net return compared to inbred rice which leads to increase and sustainable growth of food grain production. Analysis of Stochastic Frontier model shows hybrid rice farms are technically more efficient than inbred.Hybrid Rice, Technology, Economics, Food Self-sufficiency, Crop Production/Industries, International Development, Research and Development/Tech Change/Emerging Technologies,
Design and characterization of a circularly polarized microstrip-line-fed slot array antenna for S-band applications
No full textA 2×2 slot array antenna fed by microstrip line for circular polarization operated in the S band frequency range is designed in this paper. Single cross slot with single port feed as well as dual port feed is taken into consideration for realizing circular polarization and combining these two processes, the slot array is designed with single feed for circular polarization. The antennas are designed on a Teflon glass fiber substrate of thickness 0.8 mm. The slot array dimension is 120×142×1.636 mm3. Smith chart of single cross slot antenna with single feed as well as dual feed has a dip at 2.69 and 2.53 GHz respectively indicate the capability of realizing circular polarization in the S band frequency range. The return loss of the slot array antenna is -58 dB shows good input impedance matching of the antenna. A dip in the smith chart of the slot array shows circular polarization near 2.4 GHz ensuring wireless applications as well. Axial ratio is found to be less than 1 dB in the resonance frequency. The impedance bandwidth percentage of the slot array antenna is 12.24%. The simulation is done by using keysight advanced design system (ADS) software
Isolation of Cerebroside from Gynura procumbens Leaves and Biological Activities of the Leaves Extracts
No full textSeveral plants have been used in folk medicine to treat various types of diseases. Gynura procumbens (G. procumbens), a medicinal plant is widely used in traditional treatment of many aliments due to the presence of potent bioactive components. In this study,G. procumbens leaves were extracted with three different polarities of solvents viz., ethyl acetate (EA), methanol (MeOH) and methanol-water (MeOH-H2O). A cerebroside and a pure compound were isolated from the EA and MeOH crude extracts respectively. Antibacterial, antifungal activities and cytotoxicity of the crude extracts of G. procumbens leaves were investigated using six bacterial strains (three gram positive and three gram negative), one fungal strain and brine shrimp lethality bioassay, respectively. The EA extracts showed moderate antimicrobial activity, whereas MeOH and MeOH-H2O extracts exhibited very minute sort of sensitivities. The MeOH-H2O extract showed a significant cytotoxic activity having LC50 of 3.98 μg/mL on the other hand EA and MeOH exhibited mild and moderate cytotoxic activities having LC50 values of 63.10 and 4.47 μg/mL, respectively. These results demonstrate the presence of potential bioactive components in the studied crude extracts of the G. procumbens leaves
EFFECT OF PLANTING CONFIGURATION ON THE GROWTH AND YIELD OF WHITE MAIZE
No full textA Thesis
Submitted to the Faculty of Agriculture,
Sher-e-Bangla Agricultural University, Dhaka,
in partial fulfilment of the requirements
for the degree of
MASTER OF SCIENCE (MS)
IN
AGRONOMYThe present piece of work was performed at the experimental field of Sher-e-
Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka during the period
from November, 2015 to April, 2016 to study effect of effect of planting
configuration on the growth and yield of white maize. The experiment
comprised of two factors viz. factor A: Two white maize varieties (V
= KS510
and V
2
= PSC-121) and factor B: five plant spacing (T
= 40 cm × 25 cm
spacing, T
2
= 50 cm × 25 cm spacing, T
3
1
= 60 cm × 25 cm spacing, T
= 70 cm ×
25 cm spacing and T
= Double rows of 50 cm × 25 cm spacing). The
experiment was laid out in Randomized Complete Block Design (RCBD) with
three replications. The results of the experiment revealed that, both varieties of
white maize showed similar result in most of the plant characters. The highest
grains cob
-1
5
(506.5), grains row
-1
(36.05) and rows cob
-1
(14.11) were recorded
from plant spacing 70 cm × 25 cm. Plant spacing double rows of 50 cm × 25
cm performed best among five plant spacing in case of 100 grain weight (40.17
g), grain yield (9.68 t ha
-1
), stover yield (13.62 t ha
-1
), biological yield (23.30 t
ha
-1
) and harvest index (41.47 %). Plant spacing 40 cm × 25 cm showed the
lowest result in all yield and yield contributing characters. Interaction of variety
PSC-121 with double rows of 50 cm × 25 cm plant spacing gave highest 100
grain weight (40.33 g), grain yield (10.50 t ha
-1
4
), stover yield (14.01 t ha
),
biological yield (24.51 t ha
-1
) and harvest index (42.84 %). On the other hand
interaction of variety PSC-121 with plant spacing 40 cm × 25 cm showed the
lowest results. So, it may be concluded that white maize variety PSC-121along
with double rows of 50 cm × 25 cm plant spacing might be suggested to be
followed in white maize production
- …
