Supercritical Flow Simulation at a Right Channel Junction. Comparison between a Uniform and a Sparse Mesh

Sajjad Haider,Hamza Farooq Gabriel,Shaukat Ali Khan 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.7

This technical note studies the supercritical junction flow occurring at the right-angled confluence of four equal-width channels in which two upstream channels carry flow towards the junction. The note seeks to investigate, firstly, the pertinence of a 2D shallow water equation model to reproduce the typical flow structures at the junction. The second objective is to build a computationally efficient model with more resolution applied at critical point i.e. junction and less in areas where the flow is primarily 1D i.e. channels and compare such model, named, ‘sparse’ with a uniformly meshed model regarding solution accuracy and computational efficiency. The results indicate that the sparse model is able to reproduce typical flow structures appearing at the channel junction in an adequate manner. The discharge distribution is fairly well predicted. The jump angles are almost the same in the two models as well as the location and size of the recirculation zones and the flow depth super-elevation areas. However, the two models diverge in the prediction of very small depths in the recirculation zone where the sparse model overestimates the depths. As regards, computational efficiency, the sparse model is found to be 61% more efficient than the uniform mesh model.

Historical and Projected Shift in Agro-Climatic Zones and Associated Variations of Daily Temperature and Precipitation Extremes using CORDEX-SA over Pakistan

Sajjad Haider,Kalim Ullah 한국기상학회 2021 Asia-Pacific Journal of Atmospheric Sciences Vol.57 No.4

Agro-climatic classification systems based on aridity help to distinguish various features of aridity in different agro-climatic regions around the world revealing potentially serious implications for water and agriculture sectors in light of climate change. This study probed historical and projected variations and shifts in agro-climatic zones associated with dispersion in Probability Density Functions (PDF) for daily temperature (Tmax and Tmin) and precipitation extremes over Pakistan. In this study, a singlemodel RCMsimulation and projection from the output of the Coordinated Regional Climate Downscaling Experiment for South Asia (CORDEX-SA) data were used to evaluate these parameters for three-time spans: near future (2011–2040), mid future (2041–2070), and end of century (2071–2100); each under two different Representative Concentration Pathways (RCP 4.5 and RCP 8.5) after bias-correction for the observed baseline data (1971–2000). The data was collected from 49 weather stations. Future projections based on the used Regional Climate Model (RCM) predicted major changes in extremely arid and semi-arid zones of Pakistan in the future. In terms of statistical moments, the highest magnitude change was noted in the median and mean of the Tmax which increased as much as 5.1 °C, and the 90th percentile of the Tmin increased by up to 6.5 °C under the RCP8.5 by the end of this century in arid and the extremely arid zones. Similarly, the greatest magnitude of change in the precipitation was projected to increase more than 3.3 mm/day under RCPs 4.5 and 8.5 in semi-arid zones by the end of the present century. Projected shifts in agro-climatic zones are coupled with associated changes in the statistical moments of the PDFs for drought and extreme precipitation events in agro-climatic zones in response to climate change.

Hybrid Indoor Position Estimation using K-NN and MinMax

( Fazli Subhan ),( Shakeel Ahmed ),( Sajjad Haider ),( Sajid Saleem ),( Asfandyar Khan ),( Salman Ahmed ),( Muhammad Numan ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.9

Due to the rapid advancement in smart phones, numerous new specifications are developed for variety of applications ranging from health monitoring to navigations and tracking. The word indoor navigation means location identification, however, where GPS signals are not available, accurate indoor localization is a challenging task due to variation in the received signals which directly affect distance estimation process. This paper proposes a hybrid approach which integrates fingerprinting based K-Nearest Neighbors (K-NN) and lateration based MinMax position estimation technique. The novel idea behind this hybrid approach is to use Euclidian distance formulation for distance estimates instead of indoor radio channel modeling which is used to convert the received signal to distance estimates. Due to unpredictable behavior of the received signal, modeling indoor environment for distance estimates is a challenging task which ultimately results in distance estimation error and hence affects position estimation process. Our proposed idea is indoor position estimation technique using Bluetooth enabled smart phones which is independent of the radio channels. Experimental results conclude that, our proposed hybrid approach performs better in terms of mean error compared to Trilateration, MinMax, K-NN, and existing Hybrid approach.

Physiological response of cotton genotypes against NaCI salt stress under solution culture

( Muhammad Ibrahim ),( Muhammad Sajjad Haider ),( Uman Saleem ),( Saif Ur Rehman ),( Kafeel Ahmad ),( Zafar Iqbal Khan ),( Muhammad Aleem Sarwar ) 한국토양비료학회 2011 한국토양비료학회 학술발표회 Vol.2011 No.-

Preparation and properties of the single-walled carbon nanotube(SWNT)/cellulose nanocomposites using N-methymorpholine-N-oxide (NMMO) monohydrate

박수영,김동훈,( Khalid Saeed ),( Sajjad Haider ) 한국공업화학회 2008 한국공업화학회 연구논문 초록집 Vol.2008 No.1

Synthesis and characterization of graphene oxide, reduced graphene oxide and their nanocomposites with polyethylene oxide

Alghyamah Abdulaziz A.,Haider Sajjad,Khalil Uzma,Khan Rawaiz,Haider Adnan,Almasry Waheed A.,Ihsan Rida,Tahira Perveen,Wazeer Irfan,Chafidz Achmad 한국물리학회 2022 Current Applied Physics Vol.40 No.-

This work describes the synthesis of GO, rGO and their nanocomposites with PEO. GO and rGO were prepared by the modified Hummers method and in-situ reduction of GO utilizing green reductant L (+) Ascorbic acid. The nanocomposites were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Thermogravimetric Analysis (TGA), and Universal Testing Machine (UTM). FT-IR and XRD confirmed the synthesis of GO and rGO. FE-SEM confirmed the uniformly exfoliated GO and rGO nanosheets in the polymer matrix. Hydrogen bonding was the main interaction mechanism for GO with PEO while no interaction was detected by FT-IR for rGO. Enhanced thermal stability was observed for both GO/PEO and rGO/PEO nanocomposites. The mechanical analysis showed an increase in Young’s modulus, tensile strength, and elongation at break for GO/PEO nanocomposites, which is attributed to the homogeneous dispersion and hydrophilic hydrogen bonding interaction of GO with PEO.

Physiological response of cotton genotypes against NaCl salt stress under solution culture

Muhammad Ibrahim,Muhammad Sajjad Haider,Usman Saleem,Saif-ur-Rehman,Kafeel Ahmad,Zafar Iqbal Khan,Muhammad Aleem Sarwar 한국토양비료학회 2011 한국토양비료학회 학술발표회 초록집 Vol.2011 No.5

In situ Polymerization of Multi-Walled Carbon Nanotube/Nylon-6 Nanocomposites and Their Electrospun Nanofibers

Saeed, Khalid,Park, Soo-Young,Haider, Sajjad,Baek, Jong-Beom Springer 2009 NANOSCALE RESEARCH LETTERS Vol.4 No.1

<P>Multiwalled carbon nanotube/nylon-6 nanocomposites (MWNT/nylon-6) were prepared by in situ polymerization, whereby functionalized MWNTs (F-MWNTs) and pristine MWNTs (P-MWNTs) were used as reinforcing materials. The F-MWNTs were functionalized by Friedel-Crafts acylation, which introduced aromatic amine (COC<SUB>6</SUB>H<SUB>4</SUB>-NH<SUB>2</SUB>) groups onto the side wall. Scanning electron microscopy (SEM) images obtained from the fractured surfaces of the nanocomposites showed that the F-MWNTs in the nylon-6 matrix were well dispersed as compared to those of the P-MWNTs. Both nanocomposites could be electrospun into nanofibers in which the MWNTs were embedded and oriented along the nanofiber axis, as confirmed by transmission electron microscopy. The specific strength and modulus of the MWNTs-reinforced nanofibers increased as compared to those of the neat nylon-6 nanofibers. The crystal structure of the nylon-6 in the MWNT/nylon-6 nanofibers was mostly γ-phase, although that of the MWNT/nylon-6 films, which were prepared by hot-pressing the pellets between two aluminum plates and then quenching them in icy water, was mostly α-phase, indicating that the shear force during electrospinning might favor the γ-phase, similarly to the conventional fiber spinning.</P>

Effect of Compost and Gypsum Application on the Chemical Properties and Fertility Status of Saline-Sodic Soil

Ghulam Sarwar,Muhammad Ibrahim,Mukkram Ali Tahir,Yasir Iftikhar,Muhammad Sajjad Haider,Noor-us-Sabah,한경화,하상건,장용선 한국토양비료학회 2011 한국토양비료학회지 Vol.44 No.3

Salt-affected soils are present in Pakistan in significant quantity. This experiment was conducted to assess the effectiveness of compost for reclamation and compare its efficiency with gypsum. For this purpose,various combinations of compost and gypsum were used to evaluate their efficacy for reclamation. A saline-sodic field having pHs 8.90, ECe 5.94 dS m^–1 and SAR 34.5 (mmol L^–1)^1/2, SP (saturation percentage)42.29% and texture Sandy clay loam, gypsum requirement (GR) 8.75 Mg ha^–1 was selected for this study. The experiment comprised of seven treatments (control, gypsum alone, compost alone and different combinations of compost and gypsum based on soil gypsum requirements). Inorganic and organic amendments (gypsum and compost) were applied to a saline sodic soil. Rice and wheat crops were grown. Soil samples were collected from each treatment after the harvest of both crops and analyzed for chemical properties (electrical conductivity, soil reaction and sodium adsorption ratio) and fertility status (organic matter,available phosphorus and potassium contents) of soil. Results of this study revealed that compost and gypsum improved chemical properties (electrical conductivity, soil reaction and sodium adsorption ratio) of saline sodic soil to the desired levels. Similarly, all parameters of soil fertility like organic matter, available phosphorus and potassium contents were built up with the application of compost and gypsum.

Effect of Compost and Gypsum Application on the Chemical Properties and Fertility Status of Saline-Sodic Soil

Sarwar, Ghulam,Ibrahim, Muhammad,Tahir, Mukkram Ali,Iftikhar, Yasir,Haider, Muhammad Sajjad,Noor-Us-Sabah, Noor-Us-Sabah,Han, Kyung-Hwa,Ha, Sang-Keun,Zhang, Yong-Seon Korean Society of Soil Science and Fertilizer 2011 한국토양비료학회지 Vol.44 No.3

Salt-affected soils are present in Pakistan in significant quantity. This experiment was conducted to assess the effectiveness of compost for reclamation and compare its efficiency with gypsum. For this purpose, various combinations of compost and gypsum were used to evaluate their efficacy for reclamation. A saline-sodic field having $pH_s$ 8.90, $EC_e$ $5.94dS\;m^{-1}$ and SAR $34.5(mmol\;L^{-1})^{1/2}$, SP (saturation percentage) 42.29% and texture Sandy clay loam, gypsum requirement (GR) $8.75Mg\;ha^{-1}$ was selected for this study. The experiment comprised of seven treatments (control, gypsum alone, compost alone and different combinations of compost and gypsum based on soil gypsum requirements). Inorganic and organic amendments (gypsum and compost) were applied to a saline sodic soil. Rice and wheat crops were grown. Soil samples were collected from each treatment after the harvest of both crops and analyzed for chemical properties (electrical conductivity, soil reaction and sodium adsorption ratio) and fertility status (organic matter, available phosphorus and potassium contents) of soil. Results of this study revealed that compost and gypsum improved chemical properties (electrical conductivity, soil reaction and sodium adsorption ratio) of saline sodic soil to the desired levels. Similarly, all parameters of soil fertility like organic matter, available phosphorus and potassium contents were built up with the application of compost and gypsum.