http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Surface Texturing for Low Friction Mechanical Components
Iqbal, K. Y. Mohd,Segu, D. Z.,Pyung, H.,Kim, J. H.,Kim, S. S. Korean Tribology Society 2015 한국윤활학회지(윤활학회지) Vol.4 No.1
Laser surface texturing (LST), a surface engineering modification, has been considered as one of the new processes used to improve tribological characteristics of materials by creating artificially patterned microstructure on the contact surface of mechanical components. In LST technology, the laser is optimized to obtain or manufacture the dimples with maximum precision. The micro-dimples reduce the coefficients of friction and also improve the wear resistance of materials. This study investigates the effect of dimple density is investigated. For this purpose, a ball-on-disc type tester is used with AISI 52100 bearing steel as the test material. Discs are textured with a 5% and 10% dimple density. Experimental work is performed with normal loads of 5 N, 10 N, and 15 N under a fixed speed of 150 rpm at room temperature. The effect of the textured surface is compared to that of the untextured one. Experimental results show that the textured surface yields lower friction coefficients compared to those of untextured surfaces. Specifically, the 10% dimple density textured surface shows better friction reduction behavior than the 5% dimple density textured sample, and has an 18% improvement in friction reduction compared with the untextured samples. Microscopic observation using a scanning electron microscope (SEM) shows that the major friction mechanisms of the AISI 52100 bearing steel are adhesion, plastic deformation, and ploughing.
Iqbal, M.,Ko, P.S.,Kim, S.D. Elsevier 2014 CURRENT APPLIED PHYSICS Vol.14 No.8
We investigate the effects of perhydropolysilazane spin-on-dielectric (SOD) buffer layer adopted prior to Si<SUB>3</SUB>N<SUB>4</SUB> passivation on the dc drain current level and degradation after the electrical stress in the AlGaN-GaN high electron mobility transistors (HEMTs). The SOD-buffered HEMTs show ~1.6 times greater drain current densities (~257 mA/mm) than those of the devices with conventional-Si<SUB>3</SUB>N<SUB>4</SUB> passivations (~155 mA/mm). After the hot electron stresses (step-wise and constant) applied to the devices, it is also found that the SOD-buffered structure produces greatly improved device reliability in terms of the dc current collapse (15% for step-stress and constant stress) compared to the conventional structure (25% for each case). We propose that the enhancement of SOD-buffered structure in dc current collapse is due to the reduction in surface state density at the passivation interface and the suppressed electron trapping.
Enhancing the Performance of Knee Beam-Column Joint Using Hybrid Fibers Reinforced Concrete
S. M. Iqbal S. Zainal,Farzad Hejazi,Raizal S. M. Rashid 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.3
The knee beam–column joint is a critical location in a Reinforced Concrete (RC) structure particularly when subjected to earthquake vibrations. The current structural design codes dictate the use of high amounts of steel reinforcements in the frame joint to manage large strain demands in seismic-prone regions. However, these codes could result in the congestion of steel reinforcements in the limited joint area which can consequently produce numerous construction complications. This study aims to improve the structural performance of Knee Joint (KJ) by reducing the load induced to the embedded steel reinforcements during seismic vibrations. Hence, this study attempted to develop a Hybrid Fiber Reinforced Concrete (HyFRC) by combining multiple synthetic fibers to be introduced onto KJ. Six KJ specimens were cast using five developed HyFRC materials and one Control specimen to be experimentally tested under lateral cyclic loading. The results indicated significant improvements for the HyFRC KJ specimens particularly in energy dissipation capacity, stiffness degradation rate, displacement ductility toughness, steel reinforcement strain and hysteretic behavior. A total of six Finite Element (FE) KJ models were developed using the HyFRC materials to verify the results from the experimental testing. The accuracy of the proposed FE models resulted in average percentage differences of 25.89% for peak load, 3.45% for peak load displacement and 0.18% for maximum displacements from the experimental data. In conclusion, this study developed HyFRC materials that are beneficial in providing cost-efficient alternatives to Reinforced Concrete (RC) KJ structures in areas with low to moderate level of seismic risks.
Vibration of bilayered cylindrical shells with layers of different materials
S. H. Arshad,M. N. Naeem,N. Sultana,Z. Iqbal,A. G. Shah 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.3
In this analysis, a comparative study for natural frequencies of two-layered cylindrical shells was presented with one layer composed of functionally graded material and the other layer of isotropic material. Love’s thin shell theory was exploited for the straindisplacement and curvature-displacement relationships. For governing frequency equations, the Rayleigh-Ritz method was utilized to minimize the Lagrangian functional in the form of an eigenvalue problem. Frequency spectra were computed for long, short, thick, and thin cylindrical shells by varying the nondimensional geometrical parameters, length-to-radius and thickness-to-radius ratios for a simply supported end condition. Influence of different configurations of cylindrical shells on the shell frequencies was studied. For validity, the results obtained were compared with some results of isotropic and single-layered functionally graded cylindrical shells from the literature.
S. M. Iqbal S. Zainal,Farzad Hejazi,Farah Nora Aznieta Abd. Aziz,Mohd Saleh Jaafar 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.1
The use of fibers in cement composites has been shown to improve the mechanical properties of concrete through the fiber-bridging effect, which implies the fiber’s crack-resisting property. Additionally, the combination of two or more different fibers in the concrete mixture yielded better strength than the individual fibers due to its more versatile applications. Therefore, this study was conducted to investigate the combination of multiple synthetic fibers to improve the concrete residual strength and evaluate the hybridization synergistic effect. Ferro macro-sized fiber (FF) as the primary load-bearing fiber and four different secondary synthetic microfibers comprising Ultra-Net (UN), Super-Net (SN), Econo-Net (EN), and Nylo-Mono (NM) were utilized to develop a total of 16 hybrid fiber reinforced concrete (HyFRC) combinations and the performance were compared against their single-fiber counterpart. The tensile strength, bonding power, physical form, length, and volume fraction of the fibers were measured under the ASTM C1399 test standard in order to calculate the average residual strength (ARS) of concrete in the post-cracking region as well as to assess the synergistic effect of the fiber combination. The results recorded positive fiber synergy for all specimens tested. In addition, the Ferro-Nylo, Ferro-Super, Ferro-Econo, and Ferro-Ultra hybrids improved the ARS compared to the controlled specimens by 20.41, 10.2, 7.48, and 6.12%, respectively.
Impact of Environmental Factors on Birth Weight in Teddy Goat
Raza, S.H.,Tahir, M.,Zia, S.,Iqbal, Arshad,Ahmad, Shafiq Asian Australasian Association of Animal Productio 1998 Animal Bioscience Vol.11 No.2
The data 1241 birth, weights of Teddy goats maintained at Livestock Production Research Institute, Bahadurnagar, Okara, Pakistan, during 1975-1990 were used for this study. The mean birth weight during study period ranged from $1.55{\pm}0.06$ to $1.78{\pm}0.09kg$ with and over all mean of $1.66{\pm}0.031kg$. It was found that year of birth, type of birth, sex of kid and age of dam had significant (p < 0.01) effects on birth weight while the effect of season was found to be non-significant. It was inferred that single born kids were significantly heavier than twins and twins were heavier than triplets. The mean values of birth weight for male and female kids were $1.70{\pm}0.032$ and $1.61{\pm}0.03kg$ respectively. The birth weight was found to be the highest in 8 year age group that was $1.82{\pm}0.016kg$ and the lowest in one year group $(1.55{\pm}0.02kg)$.
B. Y. Chen's Inequality and Its Application to Slant Immersions into Kenmotsu Manifolds
Ram Shankar Gupta,Iqbal Ahmad,S. M. Khursheed Haider 경북대학교 자연과학대학 수학과 2004 Kyungpook mathematical journal Vol.44 No.1
In this paper, we have studied an inequality similar to B. Y. Chen's Inequality for a submanifold of a Kenmotsu manifold.
The fourth element: characteristics, modelling and electromagnetic theory of the memristor
Kavehei, O.,Iqbal, A.,Kim, Y. S.,Eshraghian, K.,Al-Sarawi, S. F.,Abbott, D. The Royal Society 2010 Proceedings, Mathematical, physical, and engineeri Vol.466 No.2120
<P> In 2008, researchers at the Hewlett-Packard (HP) laboratories published a paper in <I>Nature</I> reporting the development of a new basic circuit element that completes the missing link between charge and flux linkage, which was postulated by Chua in 1971 (Chua 1971 <I>IEEE Trans. Circuit Theory</I>18 , 507-519 ( doi:10.1109/TCT.1971.1083337 )). The HP memristor is based on a nanometre scale TiO 2 thin film, containing a- doped region and an undoped region. Further to proposed applications of memristors in artificial biological systems and non-volatile RAM, they also enable reconfigurable nanoelectronics. Moreover, memristors provide new paradigms in application-specific integrated circuits and field programmable gate arrays. A significant reduction in area with an unprecedented memory capacity and device density are the potential advantages of memristors for integrated circuits. This work reviews the memristor and provides mathematical and SPICE models for memristors. Insight into the memristor device is given via recalling the quasi-static expansion of Maxwell’s equations. We also review Chua’s arguments based on electromagnetic theory. </P>