Effect of fiber content on the performance of UHPC slabs under impact loading - experimental and analytical investigation

Muhammad Umar Khan,Shamsad Ahmad,Mohammed A. Al-Osta,Ali Husain Algadhib,Husain Jubran Al-Gahtani Techno-Press 2023 Advances in concrete construction Vol.15 No.3

Ultra-high-performance concrete (UHPC) is produced using high amount of cementitious materials, very low water/cementitious materials ratio, fine-sized fillers, and steel fibers. Due to the dense microstructure of UHPC, it possesses very high strength, elasticity, and durability. Besides that, the UHPC exhibits high ductility and fracture toughness due to presence of fibers in its matrix. While the high ductility of UHPC allows it to undergo high strain/deflection before failure, the high fracture toughness of UHPC greatly enhances its capacity to absorb impact energy without allowing the formation of severe cracking or penetration by the impactor. These advantages with UHPC make it a suitable material for construction of the structural members subjected to special loading conditions. In this research work, the UHPC mixtures having three different dosages of steel fibers (2%, 4% and 6% by weight corresponding to 0.67%, 1.33% and 2% by volume) were characterized in terms of their mechanical properties including facture toughness, before using these concrete mixtures for casting the slab specimens, which were tested under high-energy impact loading with the help of a drop-weight impact test setup. The effect of fiber content on the impact energy absorption capacity and central deflection of the slab specimens were investigated and the equations correlating fiber content with the energy absorption capacity and central deflection were obtained with high degrees of fit. Finite element modeling (FEM) was performed to simulate the behavior of the slabs under impact loading. The FEM results were found to be in good agreement with their corresponding experimentally generated results.

Stand-alone uncertainty characterization of GLEAM, GLDAS and MOD16 evapotranspiration products using an extended triple collocation approach

Khan, Muhammad Sarfraz,Liaqat, Umar Waqas,Baik, Jongjin,Choi, Minha Elsevier 2018 Agricultural and forest meteorology Vol.252 No.-

<P><B>Abstract</B></P> <P>An optimal use of the global scale actual evapotranspiration (AET) products for various hydro-meteorological applications requires a systematic characterization of their uncertainties. This study presents the first application of an extended triple collocation (TC) approach to provide mutually uncorrelated absolute and relative error structure among three readily available AET (MOD16, GLEAM, and GLDAS) products on the point and spatial scale within the extent of Asia. The physical evaluation results of GLEAM, GLDAS and MOD16 exhibited reasonable accuracy compared to the in-situ AET with mean Index of Agreement >0.71, 0.59 and 0.58, respectively, thereby yielding Root Mean Square Error between ∼4–13 mm/8 day over nine AsiaFlux sites representing forest, rice paddy, and grassland biomes. Theoretical uncertainty assessment of four AET dataset combinations revealed that an average ∼1.5–5.5 mm/8 day random error was contributed from in-situ AET, thereby reducing the accuracy of other datasets. GLEAM performed consistently better with least absolute and relative uncertainties over forest compared with rice paddy and grassland surfaces where GLDAS had almost similar errors as those obtained from GLEAM, while MOD16 showed high uncertainties over all vegetation conditions. Interestingly, all four datasets had large relative uncertainties (>25%) for low vegetation compared to the errors of tall canopies. A spatially merged product generated from the least uncertainties showed better agreement in order of GLDAS > GLEAM > MOD16 over 47%, 42% and 11% of the study area. Overall, the application of extended TC approach on the quality of three AET products is a step forward to develop the merged near real-time accurate AET dataset by processing of theoretical and systematic uncertainties in the current AET algorithms.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Evaluated uncertainty of AET products through an extended triple collocation approach. </LI> <LI> GLEAM and GLDAS showed least absolute uncertainties compared to MOD16 dataset. </LI> <LI> GLEAM revealed low errors in forest but performed similarly as to GLDAS in rice paddy. </LI> <LI> A merged AET map was developed with least uncertainties from three selected products. </LI> </UL> </P>

Two-Dimensional Magnetic Semiconductor in Feroxyhyte

Khan, Imran,Hashmi, Arqum,Farooq, M. Umar,Hong, Jisang American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.40

<P>A few years ago, it was claimed that the two-dimensional (2D) feroxyhyte (delta-FeOOH) layer could possess a net magnetic moment and it could be applied for potential spintronics applications because it showed a band gap. However, the exact crystal structure is still unknown. Hereby, we investigate the crystal structure, electronic band structure, and magnetic and optical properties of 2D delta-FeOOH using density functional calculations. On the basis of the experimental observation and dynamical stability calculations, we propose that the 2D delta-FeOOH originates from bulk Fe(OH)(2) via oxidation. A perfect antiferromagnetic ground state was observed in the monolayer structure with an indirect band gap of 2.4 eV. On the other hand, the bilayer structure displayed a direct band gap of 0.87 eV, and we obtained a ferrimagnetic state. The net magnetic moment in the bilayer was 1.49 mu(B) per cell. The interlayer distance and film thickness in bilayer delta-FeOOH were 1.68 and 7.37 angstrom, respectively. This interlayer distance was suppressed to 1.47 angstrom in a trilayer system, and the band gap of 1.6 eV was found. The trilayer delta-FeOOH had a film thickness of 11.57 angstrom, and this is comparable to the experimental thickness of 12 angstrom. To compare with the experimental band gap of 2.2 eV obtained from a UV-visible optical spectrum measurement, we also calculated the absorption spectra, and the onset of the absorption peak in the monolayer, bilayer, and trilayer appeared at 3.2, 2.8, and 2.2 eV, respectively. Overall, considering the magnetic state, optical absorption, and film thickness, we propose that the trilayer structure agrees with the experimentally synthesized structure.</P>

Morphology controlled facile synthesis of MnO2 adsorbents for rapid strontium removal

Umar Asim,Syed M. Husnain,Naseem Abbas,Faisal Shahzad,Abdul Rehman Khan,Tahir Ali 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.98 No.-

MnO2 nanostructures with three distinct architectures, namelyflower, balk and tube-like, have beensynthesized through a single step microwave assisted hydrothermal method at different reactiontemperatures (110 C, 140 C and 180 C). The characterization of as prepared MnO2 samples wereperformed by means of Fourier transform infrared spectroscopy, X-ray diffraction, scanning electronmicroscopy, and transmission electron microscopy. The N2 adsorption–desorption isotherms revealedthe higher specific surface area and porosity of theflower like MnO2 as compared to balk and tube-likeMnO2. The adsorption behavior of as prepared adsorbents was investigated towards Sr2+ radionuclide. Because of the hierarchal structure and the high surface area (62.64 m2/g), MnO2-110 depicted the bestSr2+ adsorption performance with maximum adsorption capacity of 52 mg/g at pH 6 as compared to otherMnO2 morphologies synthesized at 140 C and 180 C. The kinetic studies revealed that the adsorption ofSr2+ onto MnO2-110 followed the pseudo-first-order model whereas the adsorption equilibrium dataobeyed the Freundlich and Sips model. Moreover, the MnO2-110 adsorbent reached the steady statequickly ( 10 min) and is capable to bind Sr2+ in slightly acidic to alkaline solutions.

Energy efficient watchman based flooding algorithm for IoT-enabled underwater wireless sensor and actor networks

Draz, Umar,Ali, Tariq,Zafar, Nazir Ahmad,Alwadie, Abdullah Saeed,Irfan, Muhammad,Yasin, Sana,Ali, Amjad,Khattak, Muazzam A. Khan Electronics and Telecommunications Research Instit 2021 ETRI Journal Vol.43 No.3

In the task of data routing in Internet of Things enabled volatile underwater environments, providing better transmission and maximizing network communication performance are always challenging. Many network issues such as void holes and network isolation occur because of long routing distances between nodes. Void holes usually occur around the sink because nodes die early due to the high energy consumed to forward packets sent and received from other nodes. These void holes are a major challenge for I-UWSANs and cause high end-to-end delay, data packet loss, and energy consumption. They also affect the data delivery ratio. Hence, this paper presents an energy efficient watchman based flooding algorithm to address void holes. First, the proposed technique is formally verified by the Z-Eves toolbox to ensure its validity and correctness. Second, simulation is used to evaluate the energy consumption, packet loss, packet delivery ratio, and throughput of the network. The results are compared with well-known algorithms like energy-aware scalable reliable and void-hole mitigation routing and angle based flooding. The extensive results show that the proposed algorithm performs better than the benchmark techniques.

Magnetic properties of two-dimensional layer structured materials

Imran Khan,M. Umar Farooq,M. Moaied,S. Fazle and Jisang Hong 한국자기학회 2018 한국자기학회 학술연구발표회 논문개요집 Vol.2018 No.3

A Low-Complexity Pedestrian Detection Framework for Smart Video Surveillance Systems

Bilal, Muhammad,Khan, Asim,Khan, Muhammad Umar Karim,Kyung, Chong-Min Institute of Electrical and Electronics Engineers 2017 IEEE transactions on circuits and systems for vide Vol.27 No.10

<P>Pedestrian detection is a key problem in computer vision and is currently addressed with increasingly complex solutions involving compute-intensive features and classification schemes. In this scope, histogram of oriented gradients (HOG) in conjunction with linear support vector machine (SVM) classifier is considered to be the single most discriminative feature that has been adopted as a stand-alone detector as well as a key instrument in advance systems involving hybrid features and cascaded detectors. In this paper, we propose a pedestrian detection framework that is computationally less expensive as well as more accurate than HOG-linear SVM. The proposed scheme exploits the discriminating power of the locally significant gradients in building orientation histograms without involving complex floating point operations while computing the feature. The integer-only feature allows the use of powerful histogram inter-section kernel SVM classifier in a fast lookup-table-based implementation. Resultantly, the proposed framework achieves at least 3% more accurate detection results than HOG on standard data sets while being 1.8 and 2.6 times faster on conventional desktop PC and embedded ARM platforms, respectively, for a single scale pedestrian detection on VGA resolution video. In addition, hardware implementation on Altera Cyclone IV field-programmable gate array results in more than 40% savings in logic resources compared with its HOG-linear SVM competitor. Hence, the proposed feature and classification setup is shown to be a better candidate as the single most discriminative pedestrian detector than the currently accepted HOG-linear SVM.</P>

Two-dimensional honeycomb hafnene monolayer: stability and magnetism by structural transition

Hashmi, Arqum,Umar Farooq, M.,Khan, Imran,Hong, Jisang Royal Society of Chemistry 2017 Nanoscale Vol.9 No.28

<P>A few years ago, it was claimed that the two-dimensional ferromagnetic planar Hf monolayer could be synthesized on Ir(111). However, several questions remained unanswered. Herein, we unravel the structural stability of the HF monolayer and its influence on magnetism using first principles calculations. Despite the ferromagnetic state in the planar free-standing Hf layer, extensive systematic calculations with phonon spectra reveal that the planar free-standing Hf layer is unstable and it has a non-magnetic high-buckled structure in the ground state. We also find a structural transition from buckled to flat honeycomb geometry on the Ir(111) substrate. Nonetheless, 2D hafnene has no magnetic state due to strong hybridization with the Ir(111) surface. The evolution from the non-magnetic to the ferromagnetic state combined with structural transition is observed by adding BN as a spacer layer on the Ir(111) substrate (BN/Ir(111)). In addition, we find that 2D Hf on BN/Ir(111) has a giant perpendicular magnetic anisotropy of 3.41 meV.</P>

Evolvulus alsinoides: A potential antihypertensive herb

Siraj, Mantasha Binth,Khan, Asim Ali,Jahangir, Umar,Hashimi, Ayshah,Ahmad, Yasmeen Cellmed Orthocellular Medicine and Pharmaceutical 2019 셀메드 (CellMed) Vol.9 No.4

In spite of the fact that a variety of unfailing guidelines are existing for the management of hypertension, the problem of inadequate managing of this condition still continues. Several classes of existing antihypertensive drugs are associated with various side-effects. Since ancient times before the advent of anti-hypertensive drugs, this disease has been treated by the prominent classical scholars. Various herbal drugs are being used since ages for the treatment of hypertension and some of them are validated too. Evolvulus alsinoides is also one such herb used in classical literature since ages for various disorders like insanity, anxiety, nervous debility, epilepsy, melancholy, palpitation and many others. This review is to highlight the antihypertensive potential of Evolvulus alsinoides.

A Novel Approach to Enhance Dual-Energy X-Ray Images Using Region of Interest and Discrete Wavelet Transform

Burhan Ullah,Aurangzeb Khan,Muhammad Fahad,Mahmood Alam,Allah Noor,Umar Saleem,Muhammad Kamran 한국정보처리학회 2022 Journal of information processing systems Vol.18 No.3

The capability to examine an X-ray image is so far a challenging task. In this work, we suggest a practical andnovel algorithm based on image fusion to inspect the issues such as background noise, blurriness, or sharpness,which curbs the quality of dual-energy X-ray images. The current technology exercised for the examination ofbags and baggage is “X-ray”; however, the results of the incumbent technology used show blurred and lowcontrast level images. This paper aims to improve the quality of X-ray images for a clearer vision of illegitimateor volatile substances. A dataset of 40 images was taken for the experiment, but for clarity, the results of only13 images have been shown. The results were evaluated using MSE and PSNR metrics, where the averagePSNR value of the proposed system compared to single X-ray images was increased by 19.3%, and the MSEvalue decreased by 17.3%. The results show that the proposed framework will help discern threats and theentire scanning process.