Strength Behavior of Mortar Using Fly Ash as Partial Replacement of Cement

This paper reports the results of an experimental investigation carried out to study the effects of fly ash on strength development of mortar and the optimum use of fly ash in mortar. Cement was partially replaced with six percentages (10%, 20%, 30%, 40%, 50% and 60%) of class F fly ash by weight. Ordinary Portland cement (OPC) mortar was also prepared as reference mortar. Compressive as well as tensile strengths of the mortar specimens were determined at 3, 7, 14, 28, 60 and 90 days. Test results show that strength increases with the increase of fly ash up to an optimum value, beyond which, strength values start decreasing with further addition of fly ash. Among the six fly ash mortars, the optimum amount of cement replacement in mortar is about 40%, which provides 14% higher compressive strength and 8% higher tensile strength as compared to OPC mortar

Advanced Digital Signal Processing Based Redefined Power Quality Indices, and Their Applications to Wind Power

This dissertation proposes a time-frequency distribution (TFD) based new method to redefine the power quality (PQ) indices for the assessment of PQ disturbances typically present in electric power systems. The redefined PQ indices are applied to various types of synthetic and real-world PQ disturbances in order to verify the efficacy and applicability of the proposed method. The case studies show that the proposed method provides actual results with respect to the existing TFD-based transient PQ indices, and provides much more accurate results than the traditional fast Fourier transform (FFT) based PQ indices under stationary and nonstationary PQ disturbances. In addition, utilizing the proposed method, the power components contained in the IEEE Standard 1459-2010 are redefined for single-phase, and three-phase power systems under sinusoidal, nonsinusoidal, balanced and unbalanced conditions. Unlike the traditional FFT-based method, the proposed method is able to extract the time information lost in the FFT, and provides very accurate and instantaneous assessment of the power components according to the IEEE Standard 1459-2010. Also, the proposed method will have the advantage of finding the instantaneous direction of time-varying harmonics power flow which can be positive or negative depending on the harmonics flow to the network or to the load. According to the IEEE Standard 1459-2010, the harmonic active power PH is obtained by subtracting the fundamental active power P1 from the total active power P (PH = P−P1). However, the indirect measurement of the harmonic active power may provide imprecise result since harmonic active power is generally very small part of the total active power. In this dissertation, a direct assessment of the harmonic active power is carried out to obtain accurate result based on the proposed method. In addition, a new perspective for wind power grid codes is proposed in order to verify that a wind generating plant conforms to grid codes requirements under stationary and nonstationary PQ disturbances, and to obtain supervisory data to protect system reliability. The proposed method is also able to extract the dynamic signature of PQ disturbances introduced by variable speed wind energy conversion systems onto the electrical grid. Also, a TFD-based newmethod is proposed for the assessment of grid frequency deviation caused by wind power fluctuations in fixed speed wind energy conversion systems

The Utilization of Bacillus Subtilis Bacteria to Improve the Mechanical Properties of Concrete

The utilization of concrete as a building material is well-known worldwide and increasing continuously due to its sustainability, low maintenance cost, durability, performance, etc. The ingredients of concrete, its constructional methodology, and exposure conditions have been observed to be moderating and improving daily but the focus of this research is on the laboratory investigation of Bacterial Concrete which is the technology established on the application of the mineral producing microbes like Bacillus subtilis which have the properties of bio-calcification and the ability to precipitate CaCO3 effectively inside concrete structures. This CaCO3 precipitation is able to fill the pores and cracks internally and this subsequently makes the structure to become more compact. Nutrient Broth (NB) media was employed for the growth and spore formation of Bacillus subtilis bacteria in this experimental study and four different bacterial culture densities including 0.107, 0.2, 0.637, and 1.221 were estimated at OD600 and directly added to the concrete matrix using the previously fixed water to culture ratio of 0.5:0.5. Moreover, 100 mm cubical concrete specimens were cast, subjected to compressive and tensile strength tests for different curing ages, and finally compared with Conventional Concrete with OD600=0. A significant increase was observed in the mechanical strengths due to the addition of Bacillus subtilis bacteria in concretes with a culture density of 0.637. Furthermore, cylindrical concrete specimens with 100 mm diameter and 200 mm height were prepared for Ultrasonic Pulse Velocity (UPV) analysis and the results showed specimens prepared with culture density of 0.637 have higher pulse velocity than other microbial groups. A UPV vs. compressive strength relationship curve was, however, later proposed for different strengths of concrete

Prevalence of musculoskeletal disorders in elderly population in a rural community of Bangladesh

Background: Musculoskeletal disorders are a leading source of physical impairment in elderly, and the frequency of these disorders is anticipated to increase rapidly as the population ages. In Bangladesh, musculoskeletal disorders among the elderly are on the rise, causing them immense misery. The aim of this study to find out prevalence of musculoskeletal disorder in this age group in a rural community of Bangladesh. Methods: A descriptive cross-sectional study was conducted over the period of one year from April 2017 to March 2018 in a few villages of Mokshedpur union of Dohar Upazila in Dhaka district of individuals with 60 and above. Modified COPCORD (Community Oriented Program for Control of Rheumatic Disorders) questionnaire was used to detect positive respondents. Results: The prevalence of musculoskeletal pain was 52.10%. Prevalence was higher in women, 113 (56.6%) than men, 85 (43.4%). Most of the patient belongs to age group 60-69 (79.3%). Higher prevalence rates were observed in housewife (42%), retired person (24%) and cultivators (17%). Most of the individual had no smoking habit, 145 (73.2) and 42.9% are daily smokeless tobacco users. Lower back pain (42.4%) and knee pain (37.4%) were prevalent among the study group. Non-specific low back pain (28.8%) and osteoarthritis in the knee (26.3%) were prevalent among the study group. Among all the disorder, female is prevalent than male. Conclusions: Musculoskeletal disorders are common causes of morbidity and disability in rural communities of Bangladesh. Women are affected more frequently than men. Mechanical disorders are more common than inflammatory arthropathies

An Experimental Study of the Physio-Mechanical and Microstructural Performances of Escherichia Coli Bacteria-Based Bio-Concrete

A balanced mixture of cement, sand, stone or brick chips, and water is carefully allowed to form concrete, a man-made building material. These elements can be adjusted appropriately to produce concrete with a variety of qualities. Although concrete may endure compressive forces, like natural stone, tensile forces can cause it to crack. As a result, crack formation is a frequent occurrence in concrete, allowing various foreign chemicals and water to enter the structures and shortening their life span. The likelihood of cracking grows with time due to variations in humidity and temperature. It can be exceedingly expensive to maintain or repair concrete construction items. The use of bio-concrete for the construction of durable structures has shown to be quite advantageous in this perspective. It is beneficial for improving the properties of concrete as well as lowering maintenance costs. In this investigation, concrete samples measuring 100×100×100 mm were made and periodically tested for compressive and split tensile strength testing. Following a 28-day curing period, the concrete treated with Escherichia coli bacteria had compressive and split tensile strengths that were 10% and 23% higher than identical bacteria-free. The non-destructive test on cylindrical samples was then conducted to evaluate the material qualities. The mortar samples of crystalline structures were also validated by SEM examination. In order to properly and reliably anticipate the strength of concrete, the RSM model was also formulated

Understanding Dhaka City Traffic Intensity and Traffic Expansion Using Gravity Model

Analysis of traffic pattern recognition and traffic congestion expansion in real time are one of the exciting and challenging tasks which help the government to build a robust and sustainable traffic management system specially in a densely populated city like Dhaka. In this paper, we analyze the traffic intensity for small areas which are also known as junction points or corridors. We describe Dhaka city traffic expansion from a congestion point by using gravity model. However, we process real-time traffic data of Dhaka city rather than depend on survey and interview. We exactly show that traffic expansion of Dhaka city exactly follows gravity model. Expansion of traffic from a congestion point spreads out rapidly to its neighbor and impact of congested point decreases as the distance increases from that congested point. This analysis will help the government making a planned urbanized Dhaka city in order to reduce traffic jam.Comment: 6 pages, 10 citation

A New Perspective of Wind Power Grid Codes Under Unbalanced and Distorted Grid Conditions

Increasing penetration of wind power has led power system operators worldwide to develop new grid codes for integration of a wind power plant (WPP) onto the grid. According to the grid codes issued by Federal Energy Regulatory Commission (FERC) in the US, a WPP must have low voltage ride through (LVRT) capability, power factor design criteria, and supervisory control and data acquisition (SCADA) system to ensure power system reliability. Fast Fourier transform (FFT) is frequently used to measure root mean square (RMS) voltage, power factor, and for supervisory data acquisition in order to verify that a WPP conforms to the grid code requirements. However, FFT inherently assumes signal is periodic in nature, and it provides misleading results under unbalanced and distorted grid conditions. To overcome these issues, this work proposes a new method for wind power grid codes based on time-frequency analysis technique. Unlike FFT, it provides accurate result both in steady-state and transient conditions. The efficacy of the proposed method is verified by applying it to computer simulated and real-world cases provided by National Renewable Energy Laboratory (NREL) in the US. Time-frequency analysis is performed utilizing Time-Frequency Toolbox (TFTB) in MATLAB® developed for the analysis of non-stationary signals

Compact Wrench-Shaped Resonator Loaded UWB Antenna with Notched Frequency Characteristics

In the manuscript, the design of a wrench-shaped resonator loaded ultra-wideband (UWB) antenna has been proposed using notched frequency characteristics. The antenna is composed of the patch with microstrip feed line, a wrench-shaped resonator, and a slotted partial ground plane. A notched frequency is created due to the electromagnetic coupling of wrench-shaped resonator. In order to observe the effects of wrench-shaped resonator, a parametric study has been executed. Measured results are compared with simulations (with and without notched bands) and a stable similarity has been observed. The surface current, radiation patterns and the impedance (imaginary and real) have ensured the compression of wanted notched frequency band

New NRI Metamaterial for Multi-band Operation

A new negative refractive index (NRI) metamaterial unit cell is presented in this study. The negative refractive index property is being displayed by the unit cell of metamaterial in the four distinct microwave frequency bands. Finite integration technique was adopted to evaluate the property of the material. More than 1 GHz bandwidth region was found exhibiting NRI property for the material in the microwave spectra