ADJUSTABLE ACCURACY BEHAVIORAL MODELS FOR SYSTEM-LEVEL ANALOG SIMULATION

Hamad,Hatem,Huss,Sorin A. 대한전자공학회 1995 ICVC : International Conference on VLSI and CAD Vol.4 No.1

Methods for generating macromodels for analog functional blocks, as reported in literature, are of limited use in general circuit simulation due to either accuracy or efficiency problems. In this paper we propose a new approach to model the behavior of nonlinear analog functional blocks which produces application specific simulation models of adjustable accuracy. Experimental results are presented for an operational amplifier and art active RC-filter operating in large signal, nonlinear domain. The outlined methodology results in an increase of the simulation speed by at least one order of magnitude and opens an opportunity of system-level simulation of complex analog modules.

Mechanical properties and compatibility of polylactic acid/polystyrene polymer blend

Hamad, Kotiba,Kaseem, Mosab,Deri, Fawaz,Ko, Young Gun Elsevier 2016 Materials letters Vol.164 No.-

<P><B>Abstract</B></P> <P>In this work, compatibility and stress transfer of polylactic acid/polystyrene (PLA/PS) polymer blends were determined using tensile measurements at room temperature. For this purpose, blend compositions ranging from neat PLA to neat PS, in 25wt% increments, were extruded and molded for tensile tests. The results showed that the blends containing 50wt% and 75wt% PLA exhibited improved mechanical properties (tensile strength and elongation) as compared to neat PS. In addition, the stress transfer calculations of PLA/PS blend revealed that this blend exhibited a higher degree of compatibility compared to other biodegradable polyesters/PS blends.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The compatibility between PLA and PS was investigated using mechanical properties. </LI> <LI> The blend containing 75wt% PLA showed improved properties compared to neat PS. </LI> <LI> PLA/PS blend showed some degree of partial compatibility. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Experimental validation of a dynamic analysis and fuzzy logic controller of greenhouse air temperature

Hamad, Imen Haj,Chouchaine, Amine,Bouzaouache, Hajer International Journal of Computer ScienceNetwork S 2021 International journal of computer science and netw Vol.21 No.5

The greenhouse is a complex system. It is subject to multiple input disturbances that are highly dependent on meteorological conditions, which are generally nonlinear and have a great influence on the agricultural production. The objective of this paper is to study the fuzzy logic technique as one of the most efficient technologies to control the greenhouse. The fuzzy logic controller (FLC) was developed to activate the actuator based on a ventilator was installed in an experimental greenhouse to obtain a desired temperature of the microclimate despite the externals disturbances.

Tunable electronic and optical properties of GaS/GaSe van der Waals heterostructure

Hamad Rahman Jappor,Majeed Ali Habeeb 한국물리학회 2018 Current Applied Physics Vol.18 No.6

We have used first-principles calculations to investigate the electronic and optical properties of GaS/GaSe van der Waals heterostructures formed by stacking two-dimensional GaSe and GaSe monolayers. Our findings confirm that the GaS/GaSe heterostructures transform from an indirect to a direct band gap material for the two stackings considered in this study. In addition, we found that the direct band gaps are 1.780 eV and 1.736 eV for AA and AB stacking, respectively. It is observed that the behavior of the optical properties of AA stacking is similar to AB stacking with some differences in details and both heterostructures located in UV range. The refractive index values are 2.21 (AA pattern) and 2.18 (AB pattern) at zero photon energy limit and increase to 2.937 for AA and 2.18 AB patterns and both located in the visible region. More importantly, the GaS/GaSe heterostructures have a variety of extraordinary electronic and optical properties. Accordingly, these heterostructures can be useful for the solar cell, nanoelectronics, and optoelectronic applications.

A Cross-Platform Malware Variant Classification based on Image Representation

( Hamad Naeem ),( Bing Guo ),( Farhan Ullah ),( Muhammad Rashid Naeem ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.7

Recent internet development is helping malware researchers to generate malicious code variants through automated tools. Due to this reason, the number of malicious variants is increasing day by day. Consequently, the performance improvement in malware analysis is the critical requirement to stop the rapid expansion of malware. The existing research proved that the similarities among malware variants could be used for detection and family classification. In this paper, a Cross-Platform Malware Variant Classification System (CP-MVCS) proposed that converted malware binary into a grayscale image. Further, malicious features extracted from the grayscale image through Combined SIFT-GIST Malware (CSGM) description. Later, these features used to identify the relevant family of malware variant. CP-MVCS reduced computational time and improved classification accuracy by using CSGM feature description along machine learning classification. The experiment performed on four publically available datasets of Windows OS and Android OS. The experimental results showed that the computation time and malware classification accuracy of CP-MVCS was higher than traditional methods. The evaluation also showed that CP-MVCS was not only differentiated families of malware variants but also identified both malware and benign samples in mix fashion efficiently.

A computational study of internal flow characteristics of an agricultural air induction nozzle with a flat fan nozzle

Hamad M. Abdelmotalib,Reza Alidoost Dafsari,Foad Vashahi,Jeeken Lee 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11

The flat fan nozzle is most common used in many agricultural applications. Therefore, the present work gives a computational study for a two-phase flow on a flat fan nozzle of an air-induction system. The gas-liquid interaction was simulated using a volume of fluid (VOF) method of RANS model where water was used as liquid phase while air was used as gas phase. The simulation study was carried out using commercial software STAR CCM+ from Siemens. The spray characteristics were studied for two different V- cut angles of 43˚ and 27˚ corresponding to spray angles of 80˚ and 110˚, respectively. The spray characteristics were studies in terms of velocity components, vorticity and water boundaries distribution, and water volume fraction.

Bragg-curve simulation of carbon-ion beams for particle-therapy applications: A study with the GEANT4 toolkit

Hamad, Morad Kh. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.8

We used the GEANT4 Monte Carlo MC Toolkit to simulate carbon ion beams incident on water, tissue, and bone, taking into account nuclear fragmentation reactions. Upon increasing the energy of the primary beam, the position of the Bragg-Peak transfers to a location deeper inside the phantom. For different materials, the peak is located at a shallower depth along the beam direction and becomes sharper with increasing electron density NZ. Subsequently, the generated depth dose of the Bragg curve is then benchmarked with experimental data from GSI in Germany. The results exhibit a reasonable correlation with GSI experimental data with an accuracy of between 0.02 and 0.08 cm, thus establishing the basis to adopt MC in heavy-ion treatment planning. The Kolmogorov-Smirnov K-S test further ascertained from a statistical point of view that the simulation data matched the experimentally measured data very well. The two-dimensional isodose contours at the entrance were compared to those around the peak position and in the tail region beyond the peak, showing that bone produces more dose, in comparison to both water and tissue, due to secondary doses. In the water, the results show that the maximum energy deposited per fragment is mainly attributed to secondary carbon ions, followed by secondary boron and beryllium. Furthermore, the number of protons produced is the highest, thus making the maximum contribution to the total dose deposition in the tail region. Finally, the associated spectra of neutrons and photons were analyzed. The mean neutron energy value was found to be 16.29 MeV, and 1.03 MeV for the secondary gamma. However, the neutron dose was found to be negligible as compared to the total dose due to their longer range.

Correlation Between Functional Movement Screen Scores, Lower Limb Strength, Y-Balance Test, Grip Strength, and Vertical Jump and Incidence of Injury Due to Musculoskeletal Injury Among Abu Dhabi Police Recruits

Hamad Alkaabi,Everett Lohman,Mansoor Alameri,Noha Daher,Aleksandar Cvorovic,Hatem Jaber 물리치료재활과학회 2023 Physical therapy rehabilitation science Vol.12 No.3

Objective: Training-related injuries and attrition put an additional burden on police and military institutions. Preventing and minimizing musculoskeletal injuries is the primary concern of the Abu Dhabi Police. Therefore, this study aimed to evaluate the correlation between functional movement screen, lower-limb strength, Y-balance test, grip strength and vertical jump and the incidence of musculoskeletal injuries among Abu Dhabi police recruits. Design: Observational analytical study. Methods: An observational study was conducted on 400 male police recruits of Abu Dhabi Police Academy. Physical performance was assessed before the 16-weeks basic police training. Spearman’s correlation evaluated the correlation between the performance parameters and the outcome measures and logistic regression predicted the risk factors associated with musculoskeletal injuries. Results: 149 (34.4%) participants reported at least one injury during the basic police training. Comparison between injured and non-injured participants showed significant difference in mean right Y-balance, back-leg-chest dynamometer, and vertical jump (p=0.02, p=0.02, and p=0.04, respectively). Spearman’s correlation showed a significant negative correlation between risk of injury and back-leg-chest dynamometer and right Y balance (ρ= -0.11, p=0.03). Logistic regression showed that back-leg-chest dynamometer and right Y balance were significant predictors of injury (p =.036 and p=0.037; Odds ratio=0.96; 95% CI (0.92, 0.99) and Odds ratio=0.99; 95% CI (0.98,0.99). Conclusions: Our findings suggest functional movement screen and grip strength may not independently predict injury rates, balance and lower-limb strength needs to be considered in injury prevention strategies to reduce musculoskeletal injuries.

Microstructure and mechanical properties of severely deformed Mg-3%Al-1%Zn alloy via isothermal differential speed rolling at 453K

Hamad, K.,Chung, B.K.,Ko, Y.G. Elsevier Sequoia 2014 JOURNAL OF ALLOYS AND COMPOUNDS Vol.615 No.suppl1

The paper reported the microstructure evolution and mechanical properties of the severely deformed Mg-3%Al-1%Zn alloy sample via isothermal differential speed rolling (DSR) at 453K. The present samples were subjected to DSR operations with the height reduction of 30% at the roll speed ratio of 1:3 for the lower and upper rolls, and these results were compared to those deformed by equal speed rolling (ESR). After two-pass of the DSR, most of the grains were refined markedly to ~3.3μm with a globular shape whose grain size was lower than that via ESR. In addition, Vickers microhardness values of the samples via DSR were higher than those via ESR. The results of tension tests revealed that yield and ultimate tensile strengths of the severely deformed samples via DSR were measured to be ~198 and ~228MPa, respectively. It is worth noting that, with increasing numbers of operations, the tensile ductility of the sample deformed by the DSR was restored whilst the elongation of the sample deformed by the ESR was monotonously deteriorated although both of the cases exhibited lower elongation compared to the as-homogenized. Such phenomenon underlying the restoration of the tensile ductility was discussed by taking the role of the conjugated macro-shear deformation into account.

Finite Element Analysis of Deformation Behavior in Al-2.2 wt.%Mg Alloy Subjected to Differential Speed Rolling

Hamad, K.,Park, J. H.,Ko, Y. G. Springer Science + Business Media 2015 JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE Vol.24 No.8