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RISS 인기검색어
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- 저자 : Rafie, Shervin (검색결과 90 건)
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ON THE C-PROJECTIVE VECTOR FIELDS ON RANDERS SPACES
Rafie-Rad, Mehdi,Shirafkan, Azadeh Korean Mathematical Society 2020 대한수학회지 Vol.57 No.4
A characterization of the C-projective vector fields on a Randers space is presented in terms of 𝚵-curvature. It is proved that the 𝚵-curvature is invariant for C-projective vector fields. The dimension of the algebra of the C-projective vector fields on an n-dimensional Randers space is at most n(n + 2). The generalized Funk metrics on the n-dimensional Euclidean unit ball 𝔹<sup>n</sup>(1) are shown to be explicit examples of the Randers metrics with a C-projective algebra of maximum dimension n(n+2). Then, it is also proved that an n-dimensional Randers space has a C-projective algebra of maximum dimension n(n + 2) if and only if it is locally Minkowskian or (up to re-scaling) locally isometric to the generalized Funk metric. A new projective invariant is also introduced.
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On the $C$-projective vector fields on Randers spaces
Mehdi Rafie-Rad,Azadeh Shirafkan 대한수학회 2020 대한수학회지 Vol.57 No.4
A characterization of the $C$-projective vector fields on a Randers space is presented in terms of ${\bf\Xi}$-curvature. It is proved that the ${\bf\Xi}$-curvature is invariant for $C$-projective vector fields. The dimension of the algebra of the $C$-projective vector fields on an $n$-dimensional Randers space is at most $n(n+2)$. The generalized Funk metrics on the $n$-dimensional Euclidean unit ball $\mathbb{B}^n(1)$ are shown to be explicit examples of the Randers metrics with a $C$-projective algebra of maximum dimension $n(n+2)$. Then, it is also proved that an $n$-dimensional Randers space has a $C$-projective algebra of maximum dimension $n(n+2)$ if and only if it is locally Minkowskian or (up to re-scaling) locally isometric to the generalized Funk metric. A new projective invariant is also introduced.
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Shariati, Mahdi,Rafie, Shervin,Zandi, Yousef,Fooladvand, Rouhollah,Gharehaghaj, Behnam,Mehrabi, Peyman,Shariat, Ali,Trung, Nguyen Thoi,Salih, Musab N.A.,Poi-Ngian, Shek Techno-Press 2019 Advances in concrete construction Vol.8 No.3
Although applying self-consolidating concrete (SCC) in many modern structures is an inevitable fact, the high consumption of cement in its mixing designs has led to increased production costs and adverse environmental effects. In order to find economically viable sources with environmentally friendly features, natural pozzolan pumice and blast furnace slag in 10-50% of replacement binary designs have been investigated for experiments on the properties of fresh concrete, mechanical properties, and durability. As a natural pozzolan, pumice does not require advanced equipment to prepare for consumption and only needs to be powdered. Pumice has been the main focus of this research because of simple preparation. Also to validate the results, in addition to the control specimens of each design, fly ash as a known powder has been evaluated. Moreover, ternary mixes of pumice and silica fume were investigated to enhance the obtained results of binary mixes. It was concluded that pumice and slag powders indicated favorable performance in the high percentage of replacement.
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Nader Ghaffari Khaligh,Mohd Rafie Johan 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.09
The pollution of water due to the release of heavy metals are particularly problematic and supplies of clean water have become a major problem worldwide. The heavy metal ions can cause toxicities and serious side effects toward human health; therefore, these metal ions should be removed from water and wastewater. A variety of strategies have been developed for efficient heavy metal removal from waters. Adsorption/ion exchange strategy play a great important role in removing heavy metal ions due to their advantages. Nanomaterials are excellent adsorbents and extensive studies have been performed to remove heavy metals from wastewater by developing and using various nanomaterials. Recent developments for the heavy metals removal by various nanomaterials, mainly including carbon-based nanomaterials, iron-based nanomaterials and photocatalytic nanomaterials in batch and flow systems are described in this review.
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Shojaei, Abdollah Fallah,Rafie, Mahboubeh Delavar,Loghmani, Mohammad Hassan Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.8
Cr(III) and Co(III) complexes with acetylacetonate were anchored onto a mesoporous MCM-41 through Schiff condensation. The materials were characterized by XRD, FT-IR, BET, CHN and ICP techniques. Elemental analysis of samples revealed that one C=N bond was formed through Schiff condensation on MCM-41 surface. The catalysts were tested for the alcohol oxidations using t-butyl hydroperoxide (TBHP) and $H_2O_2$ as oxidant. The catalytic experiments were carried out at both room temperature and reflux condition. Various solvents such as dichloromethane, acetonitrile and water were examined in the oxidation of alcohols. Among the different solvents, catalytic activity is found more in acetonitrile. Further, the catalysts were recycled three times in the oxidation of alcohols and no major change in the conversion and selectivity is observed, which shows that the immobilized metal-acetylacetonate complexes are stable under the present reaction conditions.
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Khoshraftar Mahin,Nazemi-Rafie Javad,Ghobari Hamed 한국응용곤충학회 2021 Journal of Asia-Pacific Entomology Vol.24 No.1
Mitochondrial DNA sequence variations and the geometric morphometric method can be used to differentiate honeybee subspecies and evolutionary lineages. Molecular markers are powerful tools for discriminating hon eybee subspecies. In this study, 19 beekeeping sites were selected to collect Iranian honeybee samples. The honeybee forewing images stored at Oberursel (the Bee Data Bank) were used to compare with those of Iranian honeybees using the geometric morphometric method. Furthermore, the abilities of DNA markers to differentiate Iranian honeybees (A. m. meda) from the most common commercial subspecies (A. m. carnica and A. m. ligustica) were assessed. In the present research, 16S rDNA (Mitochondrial 16S rDNA Region) showed greater ability in differentiating Iranian honeybees from other subspecies compared with ATP 6 and 8 and Cyt b. The phylogenetic tree derived from 16S rDNA differentiated A. m. carnica and A. m. ligustica from Iranian honeybees. Principle component analysis (PCA) discriminated C lineage and Z subgroup from A and M lineages using 16S rDNA. In addition, the phylogenetic tree of the 16S rDNA affirmed the findings of the cluster analysis derived from the geometric morphometric method in differentiating A. m. carnica and A. m. ligustica from Iranian honeybees. The cluster analysis grouped reference subspecies of A. m. meda with Iranian honeybees. Moreover, the Discriminant Function Analyses (DFA) differentiated Iranian honeybees from A. m. ligustica and A. m. carnica.
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Salehi Shahoo,Nazemi-Rafie Javad 한국응용곤충학회 2020 Journal of Asia-Pacific Entomology Vol.23 No.2
The morphological characters of honeybees have an important role for discriminating honeybee subspecies. In the present research, Iranian populations of honeybee (Apis mellifera) were collected from 19 areas in Iran. The samples were collected from stationary beekeeping sites. Moreover, pictures of honeybee forewings held in the Bee Data Bank in Oberursel were compared with Iranian honeybee populations. 19 morphological characters were measured for each forewing of worker honeybee to evaluate differentiation of Iranian honeybee populations from the commercial honeybee subspecies A. m. mellifera, A. m. carnica, A. m. caucasica and A. m. ligustica. Additionally, part of the tRNAleu gene, an intergenic region and part of COII was used to confirm differentiation of the commercial subspecies from Iranian honeybee populations. Results of the cluster analyses showed that 19 morphological characters of forewings differentiated Iranian populations from the commercial subspecies. Moreover, the phylogenetic tree of part of the tRNAleu gene, an intergenic region and part of COII differentiated the commercial subspecies from Iranian honeybee populations. Results of the discriminant function analyses (DFA) indicated that the references samples of A. m. meda overlapped with Iranian populations.
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Design FPGA-Based Chattering-free Sliding Mode Controller for PUMA Robot Manipulator
Mahsa Piltan,Abdolwahab Kazerouni,Ali Rafie 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.12
Design of a robust controller for multi input-multi output (MIMO) nonlinear uncertain dynamical system can be a challenging work. This research focuses on the design and analysis of a high performance chattering free PD plus PD partly sliding mode controller in presence of uncertainties. In this research, sliding mode controller is a robust and stable nonlinear controller, which selected to control of robot manipulator. The proposed approach effectively combines of design methods from switching sliding mode controller, and linear Proportional-Derivative (PD) control to improve the performance, stability and robustness of the sliding mode controller. To reduce the chattering with respect to stability and robustness; linear controller is added to the switching part of the sliding mode controller. The linear controller is to reduce the role of sliding surface slope and switching (sign) function. To improve the flexibility, design high speed and low cost controller, micro-electronic device (FPGA-Based) controller is introduced in this research. The proposed design is 30-bits FPGA-based controller for inputs and 35-bits for output. All joints of robot are used to test the controller in simulation environments, using VHDL code for the purpose of simulation in Xilinx. The maximum frequency in FPGA-based design is about 63.6 MHz and the delay time in this design is about 15.7 ns. It is observed that this controller is able to make as a fast response at 15.716 clock period with 63.6 of a maximum frequency and 4.407 for minimum input arrival time after clock. From investigation and synthesis summary, 30.286 for maximum input arrival time after clock with 33.018 frequencies, this design has 15.716 delays for each controller to 46 logic elements and the offset before CLOCK is 55.773 for 132 logic gates.
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Abdollah Fallah Shojaei,Mahboubeh Delavar Rafie,Mohammad Hassan Loghmani 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.8
Cr(III) and Co(III) complexes with acetylacetonate were anchored onto a mesoporous MCM-41 through Schiff condensation. The materials were characterized by XRD, FT-IR, BET, CHN and ICP techniques. Elemental analysis of samples revealed that one C=N bond was formed through Schiff condensation on MCM-41 surface. The catalysts were tested for the alcohol oxidations using t-butyl hydroperoxide (TBHP) and H2O2 as oxidant. The catalytic experiments were carried out at both room temperature and reflux condition. Various solvents such as dichloromethane, acetonitrile and water were examined in the oxidation of alcohols. Among the different solvents, catalytic activity is found more in acetonitrile. Further, the catalysts were recycled three times in the oxidation of alcohols and no major change in the conversion and selectivity is observed, which shows that the immobilized metal- acetylacetonate complexes are stable under the present reaction conditions.
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