Browsing by Author "Shahjalal, Md."

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Compressive and free vibration response of fiber reinforced rubberized recycled concrete columns
(Department of Civil Engineering(CE), BUET, 2022-04-06) Shahjalal, Md.; Ahsan, Dr. Raquib
The production of sustainable green concrete is getting popularity in concrete industries. The increasing amount of waste tires and construction and demolition (C&D) wastes mounting up in the landfills create a concern for environmental sustainability. The construction industries are nowadays thinking of ways to reduce and reuse these waste materials. The use of recycled coarse aggregate (RCA) produced from the demolition of old concrete infrastructures and waste tires of vehicles in the concrete mixture can play a vital role in providing an economical solution. Thus, this study investigates the compressive behavior of steel-reinforced concrete columns that are made of RCA and waste tire-derived crumb rubber (CR) along with polypropylene (PP) fiber. A total of twenty-six short columns (kL/r = 11) having a size of 150 × 150 × 950 mm were cast and tested under uniaxial loading up to failure. Besides, from those twenty-six columns, nine columns were used for free vibration testing before applying compressive force. Different mechanical properties of rubberized recycled concrete (R2C) and fiber-reinforced rubberized recycled concrete (FR3C) were also evaluated by compressive strength test, tensile strength test, flexural test, ultrasonic pulse velocity test, surface resistivity test, and hardened density test. Test parameters included longitudinal reinforcement ratio (1.4% and 2.0%), tie spacing (75 mm and 150 mm), and content of CR (0%, 5%,10%, and 15%). However, the RCA and PP percentages were fixed at 30% and 0.5%, respectively. The axial capacity, failure mode, influence of longitudinal and transverse reinforcement, effect of RCA, CR, and PP fiber, strain and deflection characteristics, dilation ratio, curvature, toughness, and ductility were examined. The free vibrational responses of columns are presented in terms of damping ratio, time period as well as frequency. Besides, an extensive regression analysis has been carried out based on the experimental data and a number of equations have been proposed for predicting different mechanical properties by considering the effect of CR and fiber. Furthermore, a cost analysis was conducted to examine the cost-effectiveness of these new types of concrete. The axial capacity of columns decreased with increasing CR content by up to 39.6% and 35.5% for R2C columns and FR3C columns, respectively. However, the FR3C columns exhibited higher axial capacity compared to the recycled aggregate concrete (RAC) column and R2C columns. The ductility increased with increasing the CR percentage and the addition of fiber content. Approximately 167% and 70% higher ductility was achieved in 75 mm and 150 mm tie spaced columns by using 0.5% fiber content in the R2C mixture with 15% CR content. The toughness value of R2C columns was initially decreased for 0%, 5%, and 10% CR content but then increased for 15% CR content. However, all FR3C columns exhibited a higher toughness value compared to the conventional column. From the free vibration test, it was found that the damping ratio of all RAC, R2C, and FR3C columns were higher than that of the conventional column. Up to 131% and 301% damping ratio was increased for R2C columns and FR3C columns depending on the percentage of CR content. The cost analysis showed that both the R2C and FR3C mixtures saved more energy costs and decreased fuel consumption. Considering all the parameters, it is recommended to use up to 5% CR content with 30% RCA and 0.5% fiber content. Finally, this study will help to develop sustainable and resilient fiber-reinforced recycled rubberized concrete for the application in structural members.
Effect of Admixture on Physical and Mechanical Properties of Recycled Brick Aggregate Concrete
(R&D Wing, MIST, 2021-06) Islam, Md. Jahidul; Shahjalal, Md.; Hasan, Md. Mehedi; Chowdhury, Zarin Tasnim
With the increasing population of the world, the rate of development of infrastructure is increasing day by day; which has placed a massive demand for natural aggregates. Besides, huge amount of demolished construction wastes are generated all over the world which creates pressure on the environment as well as landfills. Therefore, it is necessary to find a sustainable solution to adopt these C&D wastes as an alternative to natural aggregates for construction purposes. Therefore, the objective of the present study is to explore the influence of superplasticizers while adopting recycled brick aggregate (RBA) in the sustainable concrete application as a coarse aggregate. Six different mixes are considered with 100% replacement of recycled brick aggregate and three diverse water-cement (w/c) ratios, such as 0.40, 0.45, and 0.50. To improve the workability and mechanical characteristics of concrete a superplasticizer is used as an admixture. Fresh properties of concrete, compressive strength at normal and high temperatures, flexural strength and splitting tensile strength are presented. The results indicate that addion of superplasticizer improves slump values and reduces air voids of concrete. Although strengths of RBA concrete are lesser than the virgin brick aggregate concrete, they are still satisfactory in the application for structural concrete and can be also significantly improved by incorporating admixture. Finally, this research will help to recycle the brick aggregate instead of dumping it as waste in a landfill.
Medicine Shop
(Daffodil International University, 2019-05) Shahjalal, Md.
Medicine Shop is a stage for the all level clients, This project is used mainly for pharmacy stores to maintain the details of the pharmacy store such as medicine stock.Everyday we face many problem for find our medicine and we run one pharmacy to another pharmacy.Medicine shop project helps people find medicine easily.If any one need any types of medicine he or she visit my Medicine Shop web application and easily find his or her medicine.There are many types of medicine available in my medicine shop project like Ayurvedic medicine, Antibiotic medicine,Syrup,Drops,Tablet etc.We serve our customer 24 hours. Customer can search medicine and easily find his/her medicine if available in stock.All the stock of medicine is update daily by admin.My medicine shop web application is user friendly.User can view details of the medicines withouth going anywhere.
Prevalence and Determinants of Hypertension in South-Asian Urban Communities: Findings From Demographic and Health Surveys (DHS) Data of South Asian countriesPrevalence and Determinants of Physical Violence Against Doctors in Bangladeshi Tertiary Ca
(Springer Nature, 2023-03-28) Shahjalal, Md.; Alam, Mohammad Morshad; Khan, Md. Nafiul Alam; Sultana, Arifa; Zaman, Sanjana; Hossain, Ahmed; Hawlader, Mohammad Delwer Hossain
Background The increasing physical violence against doctors in the health sector has become an alarming global problem and a key concern for the health system in Bangladesh. This study aimed to determine the prevalence and associated factors of physical violence against doctors in Bangladeshi tertiary care hospitals. Methods A cross-sectional survey was performed among 406 doctors working in tertiary care hospitals. Data were collected using a self-administered questionnaire and the binary logistic regression model was employed for predicting physical violence against doctors. Results Of the participants, 50 (12.3%) doctors reported being exposed to physical violence in 12 months prior to the survey. According to logistic regression analysis, aged less than 30 years or younger, male and never-married doctors were prone to physical violence. Similarly, doctors from public hospitals and those worked in emergency departments were at higher risk of physical violence. More than 70% of victims reported that patients’ relatives were the main perpetrators. Two-thirds of the victims referred to violence in the hospitals as a grave concern. Conclusions Physical violence against doctors is relatively common in the emergency departments and public hospitals in Bangladesh. This study found that male and younger doctors were at high risk of exposing physical violence. To prevent hospital violence, authorities must develop human resources, bolster patient protocol and offer physician training.
Speed Control of An Inverter Fed Three-Phase Induction Motor Using IP Controller Considering Core Loss and Stray Load Loss
(STM Journals, an imprint of CELNET (Consortium e-Learning Network Pvt. Ltd.), 2015) Riadh, Ridown Rashid; Al-Imran, Mohammad; Shobial, Abdullah Mohammed; Shahjalal, Md.; Mannan, Mohammad Abdul
Consideration of core losses and stray load losses to design a controller of an inverter fed induction motor are affected to the flux and torque decoupling strategy adversely. As a consequence, the detuning of field-oriented control (FOC) is required. The detuning strategies have been developed in some literatures. But the implementation of detuning becomes difficult because of higher order expression. In general, the controlling and estimation of AC drives are considerably more complex than those of DC drives. This complexity increases substantially if high performances are demanded. The main reasons for this complexity are the need of variable frequency, harmonically optimum converter power supplies, the complex dynamics of AC machines, machine parameter variations, and the difficulties of processing feedback signals in the presence of harmonics. To avoid the detuning strategies and to minimize the overshoot and steady state error problems which occur while using a conventional PI controller, the decoupling control strategies with integral plus proportional controller have been proposed in this paper.