ON SOME GEOMETRIC PROPERTIES OF QUADRIC SURFACES IN EUCLIDEAN SPACE

( Ahmad T. Ali ),( H. S. Abdel Aziz ),( Adel H. Sorour ) 호남수학회 2016 호남수학학술지 Vol.38 No.3

This paper is concerned with the classifications of quadric surfaces of first and second kinds in Euclidean 3-space satisfying the Jacobi condition with respect to their curvatures, the Gaussian curvature K, the mean curvature H, second mean curvature H< sub >II< /sub > and second Gaussian curvature K< sub >II< /sub >. Also, we study the zero and non-zero constant curvatures of these surfaces. Furthermore, we investigated the (A, B)-Weingarten, (A, B)-linear Weingarten as well as some special (C2, K) and (C2, K □)-nonlinear Weingarten quadric surfaces in E< sup >3< /sup >, where A ≠ B, A, B ∈ {K, H, H< sub >II< /sub >, K< sub >II< /sub >} and C ∈ {H, H< sub >II< /sub >, K< sub >II< /sub >}. Finally, some important new lemmas are presented.

ON SOME GEOMETRIC PROPERTIES OF QUADRIC SURFACES IN EUCLIDEAN SPACE

Ali, Ahmad T.,Aziz, H.S. Abdel,Sorour, Adel H. The Honam Mathematical Society 2016 호남수학학술지 Vol.38 No.3

This paper is concerned with the classifications of quadric surfaces of first and second kinds in Euclidean 3-space satisfying the Jacobi condition with respect to their curvatures, the Gaussian curvature K, the mean curvature H, second mean curvature $H_{II}$ and second Gaussian curvature $K_{II}$. Also, we study the zero and non-zero constant curvatures of these surfaces. Furthermore, we investigated the (A, B)-Weingarten, (A, B)-linear Weingarten as well as some special ($C^2$, K) and $(C^2,\;K{\sqrt{K}})$-nonlinear Weingarten quadric surfaces in $E^3$, where $A{\neq}B$, A, $B{\in}{K,H,H_{II},K_{II}}$ and $C{\in}{H,H_{II},K_{II}}$. Finally, some important new lemmas are presented.

Effect of Tm3+ on the Strong Magnetic Anisotropy in the High-Tc Superconductor TmBa2Cu3Oy

J. H. Lee,김영철,D. Ahmad,김동진,정대영,I. S. Park,최민석,M. H. Sohn,장민수,Rock-Kil Ko,S. S. Ahn 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.4

The rare-earth superconductor TmBa2Cu3Ox(TmBCO) shows strong anisotropies in both para- magnetism and superconductivity. We discussed the eect of Tm3+ on the strong anisotropies of TmBCO. The magnetization (M) of TmBCO above the critical temperature (Tc) is very well described by the Brillouin function BJ (g¹BB=kBT) with J = 6, meaning that the paramagnetic signal of TmBCO is mainly generated from Tm3+ ions. The anisotropy of the magnetization values for T > Tc appears to be much stronger than that of YBCO. This can be explained by spin-orbit coupling of the two unpaired electrons of the Tm3+ ions in noncubic symmetry orbitals. From the superconducting signal below Tc, an anisotropy of the critical current density (Jcjj < Jc?) has been observed, where Jcjj and Jc? are the critical current densities measured under a .eld applied parallel to the c-axis (Hjj) and a .eld applied parallel to the ab-plane (H?), respectively. The super- conducting anisotropy can be explained by the local .eld intensity on the Cu-O planes depending on the spin alignment direction of the two unpaired electrons of the Tm3+ ion determined by H. In addition, Jc?(H) for H > 20 kOe increased a little as H increased, showing non-collective °ux pinning behavior. This means that the Tm3+ ions under H? serve as pinning centers in high .elds.ame=JP0

ON A GENERALIZED DIFFERENCE SEQUENCE SPACES DEFINED BY A MODULUS FUNCTION AND STATISTICAL CONVERGENCE

Bataineh Ahmad H.A. Korean Mathematical Society 2006 대한수학회논문집 Vol.21 No.2

In this paper, we define the sequence spaces: $[V,{\lambda},f,p]_0({\Delta}^r,E,u),\;[V,{\lambda},f,p]_1({\Delta}^r,E,u),\;[V,{\lambda},f,p]_{\infty}({\Delta}^r,E,u),\;S_{\lambda}({\Delta}^r,E,u),\;and\;S_{{\lambda}0}({\Delta}^r,E,u)$, where E is any Banach space, and u = ($u_k$) be any sequence such that $u_k\;{\neq}\;0$ for any k , examine them and give various properties and inclusion relations on these spaces. We also show that the space $S_{\lambda}({\Delta}^r, E, u)$ may be represented as a $[V,{\lambda}, f, p]_1({\Delta}^r, E, u)$ space. These are generalizations of those defined and studied by M. Et., Y. Altin and H. Altinok [7].

Side chain assisted nanotubular self-assembly of cyclic peptides at the air–water interface

Kwak, Byeongdo,Shin, Kwanwoo,Seok, Sangjun,Kim, Doseok,Ahmad, Farhan,Geckeler, Kurt E.,Seeck, Oliver H.,Seo, Young-Soo,Satija, Sushil K.,Kubik, Stefan Royal Society of Chemistry 2010 SOFT MATTER Vol.6 No.19

<P>Langmuir monolayers of two artificial cyclic peptides with an alternating sequence of <SMALL>L</SMALL>-glutamic acid and 3-aminobenzoic acid subunits, a cyclohexapeptide (<B>C6G</B>) and a cyclooctapeptide (<B>C8G</B>), were investigated using a variety of techniques, including <I>π</I>–<I>A</I> isotherms, <I>in situ</I> surface sum-frequency generation (SFG) and Brewster angle microscopy. The monolayers were also transferred onto a solid substrate by the Langmuir–Blodgett technique and characterized by grazing incident X-ray diffraction (GIXD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The investigations indicated that <B>C6G</B> forms 2D crystallite structures at the air–water interface, whereas no such structures were observed for <B>C8G</B>. Being amphiphilic, both peptides attain a horizontal orientation on the water surface after spreading. Surface compression causes the molecules to flip to a perpendicular state, thus minimizing the molecular area. The measurements also indicate that, in the perpendicular state, self-assembly of <B>C6G</B> leads to a tubular arrangement of the peptide rings. According to GIXD and TEM data, pairs of tubes arrange in a well defined and oriented order producing 2D crystals. Surface vibrational spectroscopic methods (sum-frequency generation and polarization modulation IR reflection–absorption) combined with molecular modeling gave insight into the arrangement of individual <B>C6G</B> molecules in the tubes. Overall, our results indicated that the tubular assembly of <B>C6G</B> is most likely due to intermolecular H-bonding between the CO group in the glutamic acid side chains and peptide NH group of a neighboring peptide ring.</P> <P>Graphic Abstract</P><P>Compression of the Langmuir monolayer of a cyclohexapeptide with alternating <SMALL>L</SMALL>-glutamic acid and 3-aminobenzoic acid subunits causes the rings to adopt an orientation perpendicularly to the subphase and to self-assemble into tubular structures. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0sm00143k'> </P>

A Uniquely Finned Tube Heat Exchanger Design of a Condenser for Heavy-Duty Air Conditioning Systems

Ahmad M. Abubaker,Yousef S. H. Najjar,Adnan Darwish Ahmad 대한설비공학회 2020 International Journal Of Air-Conditioning and Refr Vol.28 No.1

This study introduces the design of a novel condenser for air conditioning systems. Enhancement of performance of the system was manifested by increasing the coefficient of performance (COP), decreasing the pressure drop and the power consumed by the refrigerant compressor and the cooling water pump. The design consists of an adiabatic double-pipe heat exchanger with longitudinal rectangular fins. This model can enhance heat transfer coefficient and expose more area per unit length. This novel design supersedes other conventional condenser designs by 4.7% higher COP, 8.2% lower water pressure drop, 4.68% lower compressor power. Two refrigerants have been examined in the study; R-134a which is used in commercial and industrial chillers and R-1234ze which has low global warming potential.

Insights into the Incidence of Watermelon chlorotic stunt virus Causing Yellowing Disease of Watermelon in Western and Southwestern Regions of Saudi Arabia

Ahmad, M.H.,Shakeel, M.T.,Al-Shahwan, I.M.,Al-Saleh, M.A.,Amer, M.A. The Korean Society of Plant Pathology 2018 Plant Pathology Journal Vol.34 No.5

During the spring season of 2014, a total of 148 melon and watermelon leaf samples were collected from symptomatic and asymptomatic plants in the western and southwestern regions of Saudi Arabia and were tested for the presence of Watermelon chlorotic stunt virus (WmCSV) and other suspected cucurbit viruses by double antibody sandwich enzyme-linked immunosorbent assays. Ninety-eight samples were found to be positive for the presence of WmCSV, nine samples were positive for the presence of Cucurbit yellow stunting disorder virus (CYSDV), and 22 showed a mixed infection with both WmCSV and CYSDV. No other cucurbit viruses were detected in any of the samples. Host range experiments revealed that eight out of fourteen tested plant species were susceptible to WmCSV. PCR products of approximately 1.2 kb were obtained after amplification using primers specifically targeting the coat protein region of WmCSV. Positive PCR results were confirmed by dot blot hybridization. Coat protein gene sequences from eleven WmCSV isolates indicated that the highest identity was between the 104WMA-SA isolate from the Wadi Baish location and a previously reported isolate from the AL-Lith location in Saudi Arabia. The lowest identity was observed between the 42WMA-SA isolate and an isolate from Palestine.

Evaluation of Kinetic Parameters and Thermal Stability of Melt-Quenched Bi_xSe_100-x Alloys (x≤7.5 at%) by Non-Isothermal Thermogravimetric Analysis

Ahmad, Mais Jamil A.,Abdul-Gader Jafar, Mousa M.,Saleh, Mahmoud H.,Shehadeh, Khawla M.,Telfah, Ahmad,Ziq, Khalil A.,Hergenroder, Roland Korean Society of Microscopy 2017 Applied microscopy Vol.47 No.3

Non-isothermal thermogravimetry (TG) measurements on melt-quenched $Bi_xSe_{100-x}$ specimens (x=0, 2.5, 7.5 at%) were made at a heating rate ${\beta}=10^{\circ}C/min$ in the range $T=35^{\circ}C{\sim}950^{\circ}C$. The as-measured TG curves confirm that $Bi_xSe_{100-x}$ samples were thermally stable with minor loss at $T{\leq}400^{\circ}C$ and mass loss starts to decrease up to $600^{\circ}C$, beyond which trivial mass loss was observed. These TG curves were used to estimate molar (Se/Bi)-ratios of $Bi_xSe_{100-x}$ samples, which were not in accordance with initial composition. Shaping features of conversion curves ${\alpha}(T)-T$ of $Bi_xSe_{100-x}$ samples combined with a reliable flow chart were used to reduce kinetic mechanisms that would have caused their thermal mass loss to few nth-order reaction models of the form $f[{\alpha}(T)]{\propto}[1-{\alpha}(T)]^n$ (n=1/2, 2/3, and 1). The constructed ${\alpha}(T)-T$ and $(d{\alpha}(T)/dT)-T$ curves were analyzed using Coats-Redfern (CR) and Achar-Brindley-Sharp (ABS) kinetic formulas on basis of these model functions, but the linearity of attained plots were good in a limited ${\alpha}(T)-region$. The applicability of CR and ABS methods, with model function of kinetic reaction mechanism R0 (n=0), was notable as they gave best linear fits over much broader ${\alpha}(T)-range$.

Transesterification of waste cooking palm oil by MnZr with supported alumina as a potential heterogeneous catalyst

H. Amani,Z. Ahmad,M. Asif,B.H. Hameed 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.6

The transesterification of waste cooking palm oil (WCPO) with methanol into fatty acid methyl esters(FAMEs) was investigated using solid acidic mixed oxide catalysts Mn3.5xZr0.5yAlxO3 prepared viacoprecipitation. The effects of reaction temperature, time, molar methanol-to-oil ratio, and catalystloadingwere investigated. The stability of the catalytic activitywas examined via leaching and reusabilitytests through five consecutive batch runs. The catalyst achieved a FAME content of more than 93%, and theoptimal reaction conditions are as follows: reaction temperature of 150 C, reaction time of 5 h, molarmethanol-to-WCPO ratio of 14:1, and catalyst loading of 2.5 wt.%.

Impact resistance efficiency of bio-inspired sandwich beam with different arched core materials

Ahmad B.H. Kueh,Chun-Yean Tan,MOHD YAZID YAHYA,Mat Uzir Wahit 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.1

Impact resistance efficiency of the newly designed sandwich beam with a laterally arched core as bio-inspired by the woodpecker is numerically investigated. The principal components of the beam comprise a dual-core system sandwiched by the top and bottom laminated CFRP skins. Different materials, including hot melt adhesive, high-density polyethylene (HDPE), acrylonitrile butadiene styrene (ABS), epoxy resin (EPON862), aluminum (Al6061), and mild carbon steel (AISI1018), are considered for the side-arched core layer of the beam for impact efficiency assessment. The aluminum honeycomb takes the role of the second core. Contact force, stress, damage formation, and impact energy for beams equipped with different materials are examined. A diversity in performance superiority is noticed in each of these indicators for different core materials. Therefore, for overall performance appraisal, the impact resistance efficiency index, which covers several chief impact performance parameters, of each sandwich beam is computed and compared. The impact resistance efficiency index of the structure equipped with the AISI1018 core is found to be the highest, about 3-10 times greater than other specimens, thus demonstrating its efficacy as the optimal material for the bio-inspired dual-core sandwich beam system.