Experimental and Numerical Analyses of the Effects of Overload on the Fatigue Life of Aluminum Alloy Panels Repaired with Bonded Composite Patch

N. H. M. Bouchkara,Abdulmohsen Albedah,Faycal Benyahia,Sohail M. A. Khan Mohammed,Bel Abbes Bachir Bouiadjra 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.5

In this study, we analyzed the effect of a single overload fatigue cycle on the efficiency of bonded composite patch repair on a cracked Al 2024 T3 aluminum plate. Experimental and numerical analyses were performed to achieve the objective of the study. In the experimental part of the study, fatigue tests were conducted on a V-notched aluminum plate subjected to a constant amplitude fatigue loading with an overload applied at a relative crack length of 0.06 (a/W = 0.06). The plate was repaired with a carbon/epoxy composite patch. A fatigue life curve (a = f(N)) was plotted for the patched and unpatched specimens using the results of the experimental tests, and scanning electron microscopy images of the fracture surfaces of the failed specimens were observed. In the numerical part, the elastic–plastic finite element method was used to evaluate the plasticity induced by the overload on the patched plate and to analyze the adhesive damage after this overload was applied. The obtained results demonstrate that the patch deposition of the overload can lead to an extended fatigue life, and the adhesive damage after the overload is quite significant, but the risk of total failure of the adhesive layer is not high.

Structure-based magnetic, electrical and transport properties of Ni–Zn–Co ferrite by V5+ substitution

Hossain M.D.,Khan M.N.I.,Hossain Md Sarowar,Ahned S.J.,Alam M.K.,Liba S.I.,Hakim M.A.,Jamil A.T.M.K. 한국물리학회 2022 Current Applied Physics Vol.43 No.-

This article presents the modification of structure-based magnetic, electronic and transport properties along with the conduction mechanism and its relaxation process in a Ni–Zn–Co ferrite tailored by V5+ substitution at B-site replacing Fe3+ ions. The composition Ni0.7Zn0.2Co0.1Fe2-xVxO4 (0≤ x≤ 0.12) was synthesized by standard solid-state reaction method and all samples were crystallized with a single-phase cubic spinel structure belonging to the Fd3m space group. The lattice constants decreased gradually from 8.3673≽A to 8.3602≽A and the average grain sizes (DSEM) are also decreased from 6.92 μm to 1.99 μm due to V5+ ions substitution at Fe3+ of B-site. However, more than 25% of Fe3+ ions migrate to A-site from B-site due to V5+ substitution at Fe3+ of B-site. In all samples θD does not strictly follow the Anderson’s prediction, rather it monotonically decreases to a low value until x = 0.12. Magnetic phase transition temperature shifted to the lower temperature and the net magnetization (ηeB) decreases due to V5+ substitution in Ni–Zn–Co ferrite. Apart this, during conduction charge carriers should require more energy to jump from one cationic site to other for V5+ substitution in the Ni–Zn–Co ferrite and the activation energy (Ea) is much more higher in V5+ substituted sample. Moreover, long-range interaction with localized relaxation mechanism is observed in V5+ doped samples. The resistance at the grain (Rg) is maximum (243.09 Ω) for the sample x = 0.10 while grain boundary resistance (Rgb) is maximum (5.98×105 Ω) for the sample x = 0.07. However, the higher value of ρdC for x = 0.12 sample ensures to be suitable for electromagnets, transformers, electronic inductors, and at high-frequency applications. Moreover, x = 0.07 sample displays high value of TCR ( -8.6%/K at 418 K) which may be utilized as an infrared detector for night vision bolometer material.

Metal-organic frameworks as efficient catalytic systems for the synthesis of 1,5-benzodiazepines from 1,2-phenylenediamine and ketones

Timofeeva, M.N.,Panchenko, V.N.,Prikhod'ko, S.A.,Ayupov, A.B.,Larichev, Yu.V.,Khan, Nazmul Abedin,Jhung, Sung Hwa Academic Press 2017 Journal of catalysis Vol.354 No.-

<P><B>Abstract</B></P> <P>Benzodiazepines and their derivatives are a very important class of nitrogen-containing heterocyclic compounds with biological activity that are widely used in medicine. In this study, we demonstrated synthesis of 1,5-benzodiazepines from 1,2-phenylenediamine and ketones (acetone, cyclohexanone, acetophenone, methyl ethyl ketone) in the presence of isostructural porous metal-benzenetricarboxylates of the families MIL-100(M) (M: V<SUP>3+</SUP>, Al<SUP>3+</SUP>, Fe<SUP>3+</SUP> and Cr<SUP>3+</SUP>) and three porous aluminium trimesates Al-BTCs (MIL-96(Al), MIL-100(Al) and MIL-110(Al)). A combination of catalytic, theoretical and physicochemical methods showed that reaction rates and yields of 1,5-benzodiazepines were adjusted by the type of metal ions and accessibility of active sites. The yield of 1,5-benzodiazepines in the presence of MIL-100(M) was comparable with zeolites, such as HY, H-ZSM−5, β-zeolite and heulandite.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Synthesis of 1,5-benzodiazepines over MIL-100(M), MIL-110 and MIL-96 was studied. </LI> <LI> Effect of Brønsted and Lewis acidity on MIL’s performance was investigated. </LI> <LI> Lewis acidity of MIL-100(Fe, Cr, Al, V) was studied by EPR spectroscopy. </LI> <LI> The type of M<SUP>3+</SUP>(Al, Fe, Cr, V) and structure of MILs affect the yield of product. </LI> <LI> MIL-100(M) samples perform well in compared with zeolites. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

New constituents triterpene ester and sugar derivatives from Panax ginseng Meyer and their evaluation of antioxidant activities

Chung, I.M.,Siddiqui, N.A.,Kim, S.H.,Nagella, P.,Khan, A.A.,Ali, M.,Ahmad, A. Saudi Pharmaceutical Society 2017 Saudi pharmaceutical journal Vol.25 No.5

Panax ginseng C. A. Meyer (Araliaceae), is a well-known herb and used in the old established system of Oriental remedy, especially in Japan, China and Korea. Four new compounds characterized as (cis)- 7β,11α,19,21-tetra-O-decanoyl-18, 22β-dihydroxy-dammar-1-en-3-one (1), 3β,4α,12β-trihydroxystigmast-5-en-21-yl octadecan-9',12'-dienoate (2), dammar-12, 24-dien-3α, 6β, 15α-triol-3α-D-arabinopyranosyl-6β-L-arabinopyranoside (3) and dammar-24-en-3α, 6β, 16α, 20β-tetraol-3α-D-arabinopyranosyl-6β-D-arabinopyranoside (4) were isolated and established from the ethyl acetate and butanol extracts of the roots of P. ginseng. Their structures were established on the basis of spectral data and chemical reactions. Natural compounds indicative a great reservoir of materials and compounds with evolved biological activity, including antioxidant. Compounds 1-4 were investigated in vitro for antioxidant potential using ferric reducing antioxidant power (FRAP), the Nitric oxide (NO) scavenging activity, reducing power, phosphomolybdenum and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging actions, and the decision showed the compounds 3and 4 have probablyessential antioxidant properties than the compounds 1and 2 presented weak activity.

Critical Analysis of Density-based Spatial Clustering of Applications with Noise (DBSCAN) Techniques

Said Akbar,M.N.A. Khan 보안공학연구지원센터 2014 International Journal of Database Theory and Appli Vol.7 No.5

Clustering is the most used technique in data mining. Clustering maximize the intra-cluster similarity and minimize the inter clusters similarity. DBSCAN is the basic density based clustering algorithm. Cluster is defined as regions of high density are separated from regions that are less dense. DBSCAN algorithm can discover clusters of arbitrary shapes and size in large spatial databases. Beside its popularity, DBSCAN has drawbacks that its worst time complexity reaches to O (n2). Similarly, it cannot deal with varied densities. It is hard to know the initial value of input parameters. In this study, we have studied and discussed some significant enhancement of DBSCAN algorithm to tackle with these problems. We analysed all the enhancements to computational time and output to the original DBSCAN. Majority of variations adopted hybrid techniques and use partitioning to overcome the limitations of DBSCAN algorithm. Some of which performs better and some have their own usefulness and characteristics.

Partial Replacement of Whole Milk with Vitamin-mineral Fortified Soymilk for Rearing Calves

A.K.M. Masum, M.N. Islam, M.A.S. Khan, S.M.E. Rahman, Myoung-su Park, Fereidoun Forghani, Jun Wang, Joong-Hyun Park, Deog-Hwan Oh 忠北大學校 農業科學硏究所 2011 農業科學硏究 Vol.27 No.4

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Effects of Feeding High and Low Energy Levels during Late Pregnancy on Performance of Crossbred Dairy Cows and Their Calves

Khan, M.A.A.,Islam, M.N.,Khan, M.A.S.,Akbar, M.A. Asian Australasian Association of Animal Productio 2004 Animal Bioscience Vol.17 No.7

The present research was designed to evaluate the effects of pre and post-partum energy level and feeding pattern on the performance of crossbred dairy cows and their calves under farm conditions. A total of 16 crossbred dairy cows were divided into two equal groups on the basis of their body weight and milk production. One group was given 30% less and the another was given 30% more energy than MAFF's (1984) recommendation. After calving all cows were given same ad.libitum diet to assess the effects of feeding during pregnancy on their performance. It was observed that just before calving cows on low energy group gained less (p<0.05) weight than that of the cows on high energy group (12.9$\pm$11.71 vs. 42.25$\pm$12.74 kg/cow. Birth weight of calves of low energy group was lower (p<0.05) than that of the calves of high energy group (17.87$\pm$1.78 vs. 20.73$\pm$2.24 kg/calf). Cows that were on low pre-calving dietary energy level produced less milk during lactation than the cows of high energy pre-calving group (3.45$\pm$0.75 vs. 4.27$\pm$0.79 lit./cow). No significant difference was noticed on calf growth rate and reproductive parameters of cow. Energy level that was 30 % less than MAFF's (1984) recommendation was found to be very low and not suitable for our crossbred cows during their last three months of pregnancy.

Filler Effect of Pozzolanic Materials on the Strength and Microstructure Development of Mortar

M. N. N. Khan,M. Jamil,M. R. Karim,M. F. M. Zain,A. B. M. A. Kaish 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.1

The utilization of pozzolans in cementitious system (concrete and mortar) minimizes both cost and energy. It also enhances mechanical strength and durability of the system. The total contribution of pozzolans can be categorized into two: (i) physical or filler effect which is attributed by the fineness of the particles and (ii) chemical or pozzolanic effect which is attributed by the pozzolanic reaction. It is difficult to quantify the strength development of cementitious system caused by the filler and pozzolanic effect separately. Therefore, the individual contribution of pozzolans in cementitious system because of its physical and chemical effects need to be profoundly understood by the scientific community. This paper reviews available literatures to understand the effect of non-reactive fillers that attributed as the microfiller effect of pozzolans in cementitious systems. The previous studies utilized chemically inactive materials that attributed only the microfiller activity of pozzolans for a partial replacement of cement. It was reported that filler effect is equal or sometimes more significant than pozzolanic effect in concrete. A larger range of replacement percentages (like 5%, 10%, 15% or 10%, 20%, 30% etc.) was used in the previous studies. However, probabilities of the optimum compressive strength because of the filler effect may lie in between two larger range of replacement percentages. Therefore, an experimental work is also carried out using natural ground sand of size 7.6-μm at a lower range of cement replacement percentages (like 2.5%, 5%, 7.5% etc.) in mortar. Compressive strength of mortar at different ages and microstructure analysis of mortar at 28 days were performed in this study. Test results showed that the filler effect is more pronounced at a lower replacement percentages of cement (0-10%) while using smaller non-reactive fillers. The maximum strength due to filler effect of ground sand is acheieved at 7.5% replacement of cement. Scanning Electron Microscope (SEM) images also confirmed the effect of fillers on the microstructure development of mortar.

Evaluating the performance of gamma irradiated okra fiber reinforced polypropylene (PP) composites: comparative study with jute/PP

A. N. M. Masudur Rahman,Shah Alimuzzaman,Ruhul A. Khan,Jamal Hossen 한국의류학회 2018 Fashion and Textiles Vol.5 No.1

In this study, two bast fibers such as okra and jute were selected to manufacture composites taking polypropylene (PP) as matrix material by means of compression molding technique with maintaining 40% fiber content on the total weight of the composites. Investigation was done on tensile properties such as tensile strength (TS), tensile modulus (TM), elongation at break (EB%), bending properties such as bending strength (BS), bending modulus (BM) and impact properties like impact strength (IS) and hardness (Shore-A) of the composites. From analyzed data, it was found that Okra/ PP composites showed very competitive mechanical properties to Jute/PP composites. Non-irradiated okra composite showed the value of TS, TM, BS, BM, IS and hardness to be 32.2 MPa, 602 MPa, 55.6 MPa, 3.6 GPa, 19.54 kJ/m2 and 95 (Shore-A), respectively, whereas that value for non-irradiated jute composite was 35.5 MPa, 629 MPa, 71.5 MPa, 4.5 GPa, 21.48 kJ/m2 and 96 (Shore-A), respectively. The composite samples were exposed to different intensities of gamma radiation (250‒1000 krad) at a dose rate of 330 krad/h and changes in mechanical properties were examined. Both irradiated composites (500 krad) showed significant improvement of mechanical properties compared to that of the non-irradiated composites. Maximum TS, TM, BS, BM and IS value were found to be 41.9 MPa, 685 MPa, 72 MPa, 4.7 GPa and 22.6 kJ/m2, respectively for irradiated okra composite and 45.3 MPa, 717 MPa, 88 MPa, 6.7 GPa and 24.3 kJ/m2, respectively for irradiated jute composite. Fourier transform infrared spectroscopy was used to identify the surface groups of the composites. Water absorption, degradation behavior of the composites under soil and heat medium were also performed. Degradation tests revealed that okra composite retained its original mechanical properties higher than that of jute composite. The morphology of the composites was inspected by scanning electron microscope.

Comparative study of electron temperature and excitation temperature in a magnetic pole enhanced-inductively coupled argon plasma

A.W. Khan,F. Jan,A. Saeed,M. Zaka-ul-Islam,M. Abrar,N.A.D. Khattak,M. Zakaullah 한국물리학회 2013 Current Applied Physics Vol.13 No.7

Magnetic Pole Enhanced-Inductively Coupled Plasmas (MaPE-ICPs) in analogy to the conventional ICPs exhibit two modes of operation, depending on the power coupling mechanism, i.e., a low power mode with dominant capacitive coupling (E-mode) and a high power mode with dominant inductive coupling (H-mode). A comparative study of the electron temperature measured by a Langmuir probe ðTLP e Þ and the electron excitation temperature ðTOES exc Þ determined by Optical Emission Spectroscopy (OES) is reported in the two distinct modes of a MaPE-ICP operated in argon. The dependence of TLP e , TOES exc and their ratio ðTLP e =TOES exc Þ on applied power (5-50 W) and gas pressure (15-60 mTorr) is explored, and the validity of TOES exc as an alternative diagnostic to TLP e is tested in the two modes of MaPE-ICP. The OES based noninvasive measurement of the plasma parameters such as electron temperature is very useful for plasma processing applications in which probe measurements are limited.