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Expansion and Contraction Functors on Matriods
Rahmati-Asghar, Rahim Department of Mathematics 2017 Kyungpook mathematical journal Vol.57 No.3
Let M be a matroid. We study the expansions of M mainly to see how the combinatorial properties of M and its expansions are related to each other. It is shown that M is a graphic, binary or a transversal matroid if and only if an arbitrary expansion of M has the same property. Then we introduce a new functor, called contraction, which acts in contrast to expansion functor. As a main result of paper, we prove that a matroid M satisfies White's conjecture if and only if an arbitrary expansion of M does. It follows that it suffices to focus on the contraction of a given matroid for checking whether the matroid satisfies White's conjecture. Finally, some classes of matroids satisfying White's conjecture are presented.
Low energy and area efficient quaternary multiplier with carbon nanotube field effect transistors
Rahmati, Saeed,Farshidi, Ebrahim,Ganji, Jabbar Electronics and Telecommunications Research Instit 2021 ETRI Journal Vol.43 No.4
In this study, new multiplier and adder method designs with multiplexers are proposed. The designs are based on quaternary logic and a carbon nanotube field-effect transistor (CNTFET). The design utilizes 4 × 4 multiplier blocks. Applying specific rotational functions and unary operators to the quaternary logic reduced the power delay produced (PDP) circuit by 54% and 17.5% in the CNTFETs used in the adder block and by 98.4% and 43.62% in the transistors in the multiplier block, respectively. The proposed 4 × 4 multiplier also reduced the occupied area by 66.05% and increased the speed circuit by 55.59%. The proposed designs are simulated using HSPICE software and 32 nm technology in the Stanford Compact SPICE model for CNTFETs. The simulated results display a significant improvement in the fabrication, average power consumption, speed, and PDP compared to the current bestperforming techniques in the literature. The proposed operators and circuits are evaluated under various operating conditions, and the results demonstrate the stability of the proposed circuits.
Flying Capacitor DTC Drive with Reductions in Common Mode Voltage and Stator Overvoltage
Rahmati, Abdolreza,Arasteh, Mohammad,Farhangi, Shahrokh,Abrishamifar, Adib The Korean Institute of Power Electronics 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.4
This paper gives a detailed analysis of the direct torque control (DTC) strategy in a five-level drive and proposes a 24-sector switching table. The known problems in low-voltage drives such as bearings currents and an overvoltage phenomenon which leads to premature failure are reviewed and the occurrence of these problems in medium voltage drives has been investigated. Then a solutions to these problems is presented and the switching table to deal with these problems is modified. Simulation and experimental results on a 3kVA prototype confirm the proposed solution. In implementing the above strategy a TMS320F2812 is used.
Diosgenin Inhibits hTERT Gene Expression in the A549 Lung Cancer Cell Line
Mohammad, Rahmati Yamchi,Somayyeh, Ghareghomi,Gholamreza, Haddadchi,Majid, Mobasseri,Yousef, Rasmi Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.11
Background: Diosgenin, a steroidal saponin from a therapeutic herb, fenugreek (Trigonellafoenum-graceum L.), has been recognized to have anticancer properties. Telomerase activity is not detected in typical healthy cells, while in cancer cell telomerase expression is reactivated, therefore providing a promising cancer therapeutic target. Materials and Methods: We studied the inhibitory effect of diosgenin on human telomerase reverse transcriptase gene (hTERT) expression which is critical for telomerase activity. MTT- assays and qRT-PCR analysis were conducted to assess cytotoxicity and hTERT gene expression inhibition effects, respectively. Results: MTT results showed that $IC_{50}$ values for 24, 48 and 72h after treatment were 47, 44 and $43{\mu}M$, respectively. Culturing cells with diosgenin treatment caused down-regulation of hTERT expression. Discussion: These results show that diosgenin inhibits telomerase activity by down-regulation of hTERT gene expression in the A549 lung cancer cell line.
A Note on the Fitting Ideals in Free Resolutions
Farhad Rahmati ...et al KYUNGPOOK UNIVERSITY 2001 Kyungpook mathematical journal Vol.41 No.2
In this paper, we prove the following theorems. If R is ring such that charK = 0, then there exist an integer k such that : (a) J^(k)ExtR^(d+1) (M, N) = 0 for every pair of finitely generated R-modules M and N ; and (b) if M is a finitely generated R-module having a well-defined rank and (F.,Φ.) is any finitely generated free resolution of M, then J^(k)I_(i)(Φ_(j)) ⊆ I_(i+1)(Φ_(j))∀i = 0, … , t_(j) ㅡ 1 and ∀j ≥ d +1 where t_(j)= rank Φ_(j)
Characterization and in vitro evaluation of nanostructure Barium titanate coating on Ti6Al4V
Shahram Rahmati,Mohammad Basir Basiriani,Mohammad Rafienia,Jaber Yaghini,Keyvan Raeissi,Saeid Hosseini,Sattar Kabiri 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.5
Osseointegration has been the concern of implantology for many years. Researchers have used various ceramic coatings forthis purpose however piezoelectric ceramics (e.g. Barium titanate) are a novel field of interest. In this regard, Barium titanate(BaTiO3, BTO) coating were fabricated by electrophoretic deposition (EPD) on Ti6Al4V medical alloy, using sol-gelsynthesized nanometer BTO powder. Structure and morphologies were studied using X-ray diffraction (XRD) and scanningelectron microscopy (SEM) respectively. Results showed homogenous coating with cubic structure and crystallite size of about41 nm. Bioactivity response of coated samples while immersion in simulated body fluid (SBF) were evaluated by SEM andinductively coupled plasma (ICP) analysis. Cell compatibility was also studied via MTT assay and SEM imaging. SEM imagesindicated Apatite formation on the coating after 7 days of SBF immersion, and ICP analysis approved ions concentrationdecrement in SBF. Cells showed flattened morphology in intimate contact with coating after 12 h of culture. Altogether, coatedsamples demonstrated appropriate bioactivity and biocompatibility.
Mehdi Rahmati,Mohammad Reza Neyshaboury,Panah Mohammadi 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.12
Several studies aimed at linking hydraulic conductivity at saturation (Kw,s) to air permeability (Ka(θw)) of soil at given water content (θw) since it can be measured more rapidly and nondestructively than Kw,s especially regarding some new in situ technologies for Ka(θw) measurement. Following this, the current research aimed to develop a semi-theoretical relation between Kw,s and Ka(θw) using measured data in 27 soil samples. The Ka(θw) was measured at 12 different θw contents between 1.5 to 1,500 kPa suctions. Applying these measured data, we proposed a semi-theoretical function to predict Kw,s using Ka(θw) as input variable. The results showed that the proposed function was able to predict Kw,s using Ka(θw) at any individual θw content with really high accuracy consisting of R2 = 0.986 and evaluating error (ER) of the 2% between measured and predicted Kw,s. However, the outcomes revealed that Ka(θw) measurement at lower θw contents resulted in greater accuracy for proposed model. The pertinent section of the article applied multivariate linear regression (MLR) to develop pedo-transfer functions (PTFs) to estimate the parameters of the proposed model. The results revealed that the developed PTFs had relatively greater accuracy and reliability showing average determination coefficient (R2) of 0.807 and 0.729 for training and test datasets, respectively. However, more detailed investigation with wide range of soil parameters are needed for more general PTFs development.