MIST International Journal of Science and Technology

Measuring Effectiveness of Non-Motorized Vehicles on Spatial Extent for TOD Development: A Case Study for MRT 6 in Dhaka

2023-06-25T18:38:42+00:00

To improve the effectiveness of conventional walking-based Transit-Oriented Development (TOD), introducing Non-Motorized Vehicles (NMV)-based TOD will be a more efficient alternative since it will increase the spatial extent of the TOD node’s buffer area. This paper discusses the available Bicycle-based TOD (BTOD) concept. Based on this concept, the spatial extent of NMV-based TOD (NTOD) has been calculated. A trip-based survey has been conducted on the selected regions of Dhaka along the line of MRT 6 regarding who uses NMV (Rickshaw, Bicycle) and public transport (PT) for his daily commuting. A trip chain analysis was performed first to capture the trip pattern of daily commuters. From the trip chain analysis, it has been found that PT-based trip chains dominated the city’s entire trip chain. Consequently, it has also been found that walking-only and walking-NVM accessible trips dominate 32% and 23% of the entire PT trip chains. However, based on the findings of trip chain analysis to calculate the spatial extent by developing regression models, it has been observed that the access trip length for walking ranges from 1.2-1.4 km, whereas the access trip length for NVM ranges from 4-4.7 km. In Dhaka, the catchment area of NTOD can increase the accessibility potentially by spatial extent expansion of about 70% from the conventional TOD. Therefore, it can be inferred that NVM will give more spatial accessibility than walking. As a result, a new window of planning and design strategies will be opened for the planners and policymakers around TOD station area planning considering NMV. Along with strategic recommendations, limitations, and future research agendas have also been discussed in this paper.

MIJST, Vol. 11, June 2023 : 1-10

DOI: https://doi.org/10.47981/j.mijst.11(01)2023.368(01-10)

Effect of Heat Input on the Wire-Arc Additive Manufactured Steel Structures

2023-06-25T18:42:40+00:00

Wire arc additive manufacturing (WAAM) is one of the less-explored metal 3D printing technologies that hold up a huge potential for large-scale product manufacturing across multiple industries. The low-cost AM uses arc energy as a heat source and metallic wire as a feedstock material. The process is sustainable and supports green manufacturing. However, the major challenge associated with the WAAM is that heat management leads to the development of residual stress causing dimensional inaccuracy and poor surface finish. Therefore, fourlayer straight wall structures are fabricated by depositing material layer-uponlayer with nine distinct heat inputs (HI). The prime focus of the work is to study the effect of HI on the dimensional accuracy and the quality of deposited structures. The influence of deposition height on the surface topography is investigated. Furthermore, the effect of HI on the mechanical properties of the WAAM-printed thin wall is examined. The results show that with increase in the number of depositing layers, surface roughness values get increased under the similar process parameter used for the part fabrication. Therefore, it is recommended to re-adjust the process parameter after certain layers of deposition with proper monitoring of the thermal condition in the deposited layers while fabricating medium to large WAAM components. The outcomes from the studies show that increases in the HI while fabricating the WAAM component deteriorates the surface quality of the deposited layer and are responsible for reducing the mechanical properties of the WAAM-printed component.

MIJST, Vol. 11, June 2023 : 11-20

DOI: https://doi.org/10.47981/j.mijst.11(01)2023.419(11-20)

A Zero-Equation Model for External Aerodynamics

2023-06-25T18:48:35+00:00

The zero-equation model (ZEM) has been generalized for aerodynamic applications by eliminating the thickness of boundary-layer (BL) dependency to construct the stress length parameter . The SED (Structural Ensemble Dynamics) postulate evaluates the using the order function based on universal multi-layer structures for wall turbulence. The SED concept is further employed to optimize the profiles of the turbulent kinetic energy and dissipation rate with turbulent BL flows. Results demonstrate that the multilayer ZEM receives a remarkable achievement in the prediction of wall-bounded turbulence and thus, prevails over the drawbacks encountered in most algebraic turbulence models.

MIJST, Vol. 11, June 2023 : 21-30

DOI: https://doi.org/10.47981/j.mijst.11(01)2023.403(21-30)

Numerical Modeling of Low-Velocity Impact on Composite Laminates

2023-06-25T18:52:15+00:00

The response over the low-velocity impact of various shape impactors on a glass fiber reinforced polymer composite has been numerically analyzed with a hemispherical, flat, partially flat and truncated shaped impactor used to analyze the behavior of resistance of a GFRP composite at various speeds. The numerical analysis was carried out using finite element analysis software, ABAQUS (Dynamic/Explicit). To assess the response of the composite laminates while impacting, finite element models were developed. The Hashin failure criteria were used to represent braided glass-fiber reinforced composite plate damage. Regarding projectile shape, the impact reaction of the composite was examined. The results also show that the mechanical response of woven glass fiber polymer composite under low-velocity projectile impact largely depends on the impactor’s nose shape and the velocity of the impactor.

MIJST, Vol. 11, June 2023 : 31-38

DOI: https://doi.org/10.47981/j.mijst.11(01)2023.375(31-38)

Importance of Stress and Temperature-Dependent Permeability of Rocks and its Application in Underground Nuclear Waste Disposal

2023-06-25T19:00:48+00:00

Water flow is an essential factor in the sealability of any underground cavern, including those for nuclear waste disposal, and is significantly affected by the permeability of the rock. The permeability of rocks is affected by various factors, including stress and temperature. The rock stress changes by excavating a cavern, and rock temperature changes by decay heat from nuclear waste, and the temperature change induces thermal stress. Therefore, water flow around such caverns must be evaluated considering the effects of stress and temperature. Numerical analyses of water migration around underground nuclear waste disposal caverns have been carried out. However, studies considering the stress and temperature-dependent permeability may not be published yet. To demonstrate the necessity to consider the stress and temperature-dependency in permeability, equations that represent the postfailure permeability as a function of average effective stress and temperature were proposed. The water inflow was numerically calculated for a simple underground nuclear waste disposal cavern with or without stress and temperature dependency which showed the significance of the dependency. Also, the importance of rock types was demonstrated by considering the three rocks of granite, sandstone, and tuff for a full-scale underground radioactive disposal site for the stress and temperature-dependent permeability. A high sealability could be expected for granite and sandstone but not for the tuff. Introducing the stress and temperature-dependent permeability could contribute to the thoughtful design of an underground repository for radioactive waste disposal considering rock types.

MIJST, Vol. 11, June 2023 : 39-49

DOI: https://doi.org/10.47981/j.mijst.11(01)2023.413(39-49)

Prevalence of Multidrug-Resistant Salmonella in Raw Salad Vegetables in Dhaka Metropolitan Area

2023-06-25T19:20:07+00:00

Raw salad vegetables have become very popular among consumers due to their multiple health benefits. The bacteriological quality of these salad vegetables is of great public health concern. This study was conducted to determine the presence of potential pathogenic and multidrug-resistant (MDR) bacteria in raw salad vegetables served in different restaurants in Dhaka, the capital city of Bangladesh. A total of 50 samples, comprising different types of raw salad vegetables were collected from restaurants in Mirpur (n=10), Dhanmondi (n=10), Old Dhaka (n=10), Gulshan (n=10) and Bashundhara Residential Area (n=10). The highest counts for total coliforms and fecal coliforms were 4.02 × 103 cfu/ml and 1.3×103 cfu/ml, respectively. The isolates were E. coli, total coliform, fecal coliform and Salmonella spp. Among them, fecal coliform and Salmonella spp. were found to be more pathogenic. As potential pathogenic bacteria, Salmonella spp. were tested for antibiotic sensitivity and all of them showed resistance against amoxicillin, ampicillin, azithromycin, chloramphenicol, ciprofloxacin, erythromycin, kanamycin, streptomycin, tetracycline, norfloxacin, and trimethoprim. The findings assist to understand the level of contamination of pathogenic and MDR bacteria in raw salad vegetables, which will create awareness of food safety and public health.

MIJST, Vol. 11, June 2023 : 51-57

DOI: https://doi.org/10.47981/j.mijst.11(01)2023.396(51-57)

Foreword vol.11(1)

2023-06-25T17:06:38+00:00

Abstract not available

MIJST, Vol. 11, June 2023 : xi

DOI: https://doi.org/10.47981/j.mijst.11(01)2023.436(xi)

Editorial Vol. 11(1)

2023-06-25T18:35:29+00:00

Abstract not available

MIJST, Vol. 11, June 2023 : xii

DOI: https://doi.org/10.47981/j.mijst.11(01)2023.435(xii)