Indian Institute of Technology Hyderabad

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    10651 research outputs found

    Shear capacity of the cold-formed steel beam to column welded moment connection using clip-angle and flange-cleat

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    The current research endeavours to evaluate the shear performance of the cold-formed steel (CFS) welded moment connection between beam-to-column with 36 laboratory tests. The web portions of the beam and column were connected by CFS welded clip-angle to form a CFS welded shear connection. Subsequently, it is converted into a welded moment connection by including a flange cleat between the flange portions. The shear capacity of the welded shear connection increases by an average of 67% after the inclusion of flange cleats, which is quantified using a performance ratio variable. This research presents two shear equations for the CFS welded moment connection (i) a new empirical shear equation; (ii) a new shear equation representing the shear strength of the moment connection as a function of the shear strength of the shear connection. The variability of the shear performance of welded moment and welded shear connections is expressed with force versus displacement plots and failure modes of the clip angles. The failure modes observed in the clip-angle in both welded moment and welded shear connections are (i) Local buckling and (ii) Distortional buckling. The shift in failure modes of some of the clip-angle in the WM connection (Local buckling) and the WS connection (Distortional buckling) indicates the effectiveness of flange-cleat in resisting due to free twisting of the beam because of load offset from the shear center. The design factors were also determined for the LRFD, LSD, and ASD methods by performing reliability studies

    Structural and magnetic properties of Ni/C core–shell nanofibers prepared by one step co-axial electrospinning method

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    Nickel/carbon (Ni/C) nanofibrous structures with magnetic material nickel in the core and carbon in the shell are fabricated by the co-axial electrospinning method. The crystallinity, morphology, elemental composition, and microstructure of the carbonized nanofibers are characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectroscopy (EDX), and high-resolution transmission electron microscope (HRTEM) respectively. Rietveld refinement method of XRD pattern was carried out to determine the structural parameters of face-centered cubic (FCC) Ni with space group Fm3m. The average crystallite size and the lattice strain have been calculated using the Williamson–Hall (W–H) plot method. It is demonstrated that the compressive lattice strain is attributed due to the presence of polymer-derived carbon material. Raman data confirms the formation of pure C in the Ni/C nanofibers. Furthermore, a vibrating sample magnetometer (VSM) is used for the magnetic measurement of the Ni/C nanofibers. It is observed that the nanofibers show typical ferromagnetic behavior having the optimum value of saturation magnetization of 5.12 emu/g. The temperature-dependent magnetic measurements suggest the ferromagnetic behavior of Ni/C nanofibers within the room temperature (300 K)

    Influences of matrix strength and weak planes on fracture response of recycled aggregate concrete

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    The fracture behaviours of concrete made with natural aggregate and recycled coarse aggregate (RCA) derived from crushing old concrete are compared. The performances are evaluated using concrete proportioned for different compressive strengths. The RCA from crushed old concrete produces a composite aggregate with mortar and aggregate phases. An examination of the RCA shows pre-existing cracks in the aggregate phase. Crack propagation and crack opening profiles in the fracture response of concrete beams are evaluated using the Digital Image Correlation (DIC) technique. The displacement profiles across the beam obtained using DIC are evaluated to understand the crack growth in the concrete. The cohesive stress response and an energy measure determined from the fracture test are related to physical observations of the fracture surface. The crack path in the concrete and the contribution of the different interfaces depend on the strength of the matrix surrounding the aggregate. In concrete with lower cementitious and higher water contents, the new mortar interface with RCA and the pre-existing cracks in the RCA contribute to the fracture surface in the RCA. While a larger fracture surface area is created in concrete made with RCA, the energy measure and the cohesive stress determined from the fracture test are lower. In concrete proportioned for higher compressive strength, there is a densification of the RCA-mortar interface and the fracture plane is produced through the aggregates. The pre-existing cracks in the RCA create weak planes, which contribute to the fracture surface created. Improving the mortar-RCA interface does not result in an improvement in tensile strength or fracture characteristics since there is also a significant contribution of the weak planes in the aggregate phase of RCA to the failure surface. The measured fracture surface area does not correlate with the energy measure from fracture test response

    Ti@MoS2 incorporated Polypropylene/Nylon fabric-based porous, breathable triboelectric nanogenerator as respiration sensor and ammonia gas sensor applications

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    High output and non-interrupted power supply from fabric-based nanogenerators still remain a major challenge in developing self-powered wearable electronic applications. Addressing this, we demonstrate a low-cost, lead-free triboelectric nanogenerator based on hydrothermally grown Titanium (Ti) functionalized Molybdenum Disulfide (MoS2) interspersed polypropylene (PP) cloth and sandwiched with Nylon cloth for a highly sensitive respiration sensor and self-powered ammonia gas sensor. The nanogenerator with the device configuration Cu/Ti@MoS2/PP: Nylon /Ag is attached to a respiratory mask, and the open-circuit voltage (Voc) and short-circuit current density (JSC) during respiration cycles were obtained as 29.3 V and 42.7 µA/cm2 respectively. A significant difference in the breath pattern of human respiration cycles. Further, a fully self-powered ammonia gas sensor was demonstrated by integrating the triboelectric nanogenerator with Ti@MoS2/PP ammonia sensor. The self-powered Ti- MoS2 on PP cloth-based gas sensor driven by TENG displays an excellent response with a wide dynamic sensing range of ammonia gas from 200 ppb to 2600 ppb at room temperature, with a high sensitivity, selectivity and a rapid response time. This study explores the bifunctional nature of Ti@MoS2 nanoparticles as a respiratory mask and a self-powered ammonia gas sensor fabricated with excellent potential for self-powered health diagnostic applications

    Experimental and numerical study on behaviour of fibre reinforced lightweight hollow core slabs under different flexure to shear ratios

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    The current work explores the behaviour of fibre-reinforced lightweight hollow core slabs (FR-LWHCS) intending to develop sustainable construction solutions. The FR-LWHCS investigated in this work contains sintered fly ash aggregate (SFA) as coarse aggregate. Due to the use of SFA, the behaviour of LWHCS is expected to be different from the hollow core slabs (HCS) constructed using normal density concrete. FR-LWHCS are tested at different shear span to depth (a/d) ratios of 3.5, 7 and 10 to understand the shear and flexure behaviour. Twelve full-scale hollow core slab (HCS) specimens of 3400 mm length, 600 mm width, and 150 mm thickness are tested. FR-LWHCS consists of monofilament macro synthetic fibre dosages of 0.4 %, and 0.6 %, along with fibrillated micro fibre of 0.02 % dosage. The digital image correlation (DIC) technique is adopted to understand the strain profile on the HCS at different levels of loading. The numerical analysis is performed using a commercially available finite element software and is corroborated with experimental findings and parametric studies have been performed. Both LWHCS and normal HCS specimens failed in shear, flexural-shear and flexure modes at a/d ratios of 3.5, 7 and 10, respectively. The addition of fibres increased the peak load by 65 % compared to control LWHCS specimens tested at an a/d ratio of 3.5. The use of fibres increased strain energy absorption and changed the failure to less brittle mode at all a/d ratios. The fibre reinforced specimens have nearly 3.5 times, 2.5 times and 1.3 times the strain energy absorption of the control LWHCS when tested at a/d ratio 3.5, 7 and 10 respectively

    The Perspectives of Individuals with Comorbidities Towards COVID-19 Booster Vaccine Shots in Twitter: A Social Media Analysis Using Natural Language Processing, Sentiment Analysis and Topic Modeling

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    Individuals with comorbidities (i.e., Diabetes Mellitus, hypertension, heart diseases) are more likely to develop a more severe form of coronavirus disease 2019 (COVID-19), thus, they should take necessary precautions to avoid infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and its emerging variants and subvariants by getting COVID-19 vaccination and booster doses. In this regard, we used text analytics techniques, specifically Natural Language Processing (NLP), to understand the perception of Twitter users having comorbidities (diabetes, hypertension, and heart diseases) towards the COVID-19 vaccine booster doses. Understanding and identifying Twitter users' perceptions and perspectives will help the members of medical fraternities, governments, and policymakers to frame and implement a suitable public health policy for promoting the uptake of booster shots by such vulnerable people. A total of 176,540 tweets were identified through the scrapping process to understand the perception of individuals with the mentioned comorbidities regarding the COVID-19 booster dose. From sentiment analysis, it was revealed that 57.6% out of 176,540 tweets expressed negative sentiments about the COVID-19 vaccine booster doses. The reasons for negative expressions have been found using the topic modeling approach (i.e., risk factors, fear of myocardial fibrosis, stroke, or death, and using vaccines as bio-weapons). Of note, enhancing the COVID-19 vaccination drive by administering its booster doses to more and more people is of paramount importance for rendering higher protective immunity under the current threats of recently emerging newer Omicron subvariants which are presently causing a rise in cases in a few countries, such as China and others, and might lead to a feasible new wave of the pandemic with the surge in cases at the global level

    The Hubble constant from galaxy cluster scaling-relation and SNe Ia observations: a consistency test

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    In this paper, we propose a self-consistent test for a Hubble constant estimate using galaxy cluster and type Ia supernovae (SNe Ia) observations. The approach consists, in a first step, of obtaining the observational value of the galaxy cluster scaling-relation YSZEDA2/CXSZYX=C by combining the X-Ray and SZ observations of galaxy clusters at low redshifts (z 0.1. As a result, we obtain H0=73.014-6.688+7.435 km/s/Mpc, in full agreement with the latest results from HST + SH0ES team. We also compare our method with that one where the C parameter is obtained from hydrodynamical simulations of massive galaxy clusters

    A pentagonal bipyramidal Co(II) single-ion magnet based on an asymmetric tetradentate ligand with easy plane anisotropy

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    High-coordinate 3d single-ion magnets(SIMs) especially with pentagonal bipyramidal geometry as an emerging class of representative molecular magnets have received considerable concern. Whereas, it is not easy to construct and obtain 3d SIMs with high coordination numbers (CN = 7 or 8). Herein, a mononuclear Co(II) complex ([Co(pypzbeyz)(NCS)2(DMF)], pypzbeyz = N-((6-(1H-pyrazol-1-yl)pyridin-2-yl)methylene)benzohydrazide) based on a tetradentate ligand has been synthesized and structurally and magnetically characterized. Single-crystal X-ray diffraction analysis reveals that the Co(II) complex adopts a seven-coordinate distorted pentagonal bipyramidal geometry. Magnetic investigations show that the Co(II) complex has large easy plane anisotropy with a positive D value (D = +36.8 cm−1) and a small E value, and exhibits slow magnetic relaxation behavior under a dc field. Theoretical calculations show a positive zero-field splitting of 33.5 cm−1, which is in excellent agreement with the experiment. The results support that the 3d high-coordinate SIMs could be effectively achieved by using a suitable multi-dentate ligand with a certain ligand field

    Nickel MXene Nanosheet and Heteroatom Self-Doped Porous Carbon-Based Asymmetric Supercapacitors with Ultrahigh Energy Density

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    For high-energy-density supercapacitors, two-dimensional (2D) MXenes are being increasingly explored due to their inherent conductivity and excellent chemical properties. However, MXenes failed to achieve high power density and exceptional stability. Addressing this, we report the fabrication of an asymmetric supercapacitor with nickel MXene (cathode) and nitrogen (N), sulfur (S), and phosphorus (P) self-doped biomass-derived activated carbon (anode). Detailed structural and chemical characterization studies reveal layered nanosheets in NiMX caused due to solvothermal etching cum exfoliation and unique micro-mesopore distribution in the optimized Euphorbia milii plant leaf-derived heteroatom self-doped activated carbon (EMAC-700) because of KOH activation. NiMX and EMAC-700 delivered high capacitances of 474.3 and 575.8 F/g, respectively, at 1 A/g with a 6 M KOH electrolyte. This is attributed to the pseudonature of NiMX and the presence of heteroatoms and the large surface area (2349 m2/g) of EMAC-700, facilitating fast electrolytic ion transfer. Finally, an asymmetric device with NiMX//EMAC configuration in 6 M KOH delivered a 152.6 F/g cell capacitance at 0.5 A/g under 0-1.5 V. Additionally, an ultrahigh energy density of 47.6 W h/kg at a 375 W/kg power density was achieved along with an 81.7% capacitance retention after 30,000 cycles at 15 A/g, signifying its potential for next-generation energy storage applications

    Understanding the Operating Speed Profile Patterns Using Unsupervised Machine Learning Approach: Short-Term Naturalistic Driving Study

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    Several studies have measured the minimum operating speed on horizontal curves to model the operating speed to assess the geometric design consistency. Most of these studies approximated equal lengths of deceleration and acceleration in the operating speed profiles for the curves and assumed the minimum operating speed position at the midpoint of the curve. In contrast, a few recent studies showed different percentages of deceleration lengths on the curve and measured the minimum operating speed at the deceleration end on the curve to model the operating speed. A defined pattern of the operating speed profile on the horizontal curve was not reported in the previous studies and therefore presents opportunities to determine the patterns of the operating speed profiles on curves. In this study, the operating speed profiles of different drivers for the given features of the horizontal curve were studied, and the clustering technique was used to categorize the different patterns in the operating speed profiles on horizontal curves. The optimal number of clusters was determined using four methods: silhouette, elbow, gap statistic, and NbClust function. The different patterns observed from the clustering results are as follows: (1) complete deceleration on the curve, (2) complete acceleration on the curve, (3) deceleration length slightly greater or lower than acceleration length, and (4) longer deceleration/acceleration lengths followed by shorter acceleration/deceleration lengths, respectively. The study results imply that all operating speed profiles are not symmetric around the midpoint of the curve (MC), and the group of drivers exhibited defined patterns of the operating speed profiles on the curves. This study helps in understanding the different patterns of operating speed profiles exhibited by the drivers and the measurement of the minimum operating speed at the deceleration end to model the operating speed to assess the geometric design consistency


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    Research Archive of Indian Institute of Technology Hyderabad is based in India
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