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Order selection in fractional Fourier transform based beamforming

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Journal of Systems Engineering and Electronics 2010年第3期21卷 361-369页

作者： Muhammad Ishtiaq ahmad School of Information and Electronics Beijing Institute of Technology

Traditionally,beamforming using fractional Fourier transform（FrFT） involves a trial-and-error based FrFT order selection which is impractical.A new numerical order selection scheme is presented based on fractional power spectra（FrFT moment） of the linear chirp *** method can adaptively determine the optimum FrFT order by maximizing the second-order central FrFT *** makes the desired chirp signal substantially concentrated whereas the noise is rejected *** improves the mean square error minimization beamformer by reducing effectively the signal-noise cross terms due to the finite data length de-correlation *** results show that the new method works well under a wide range of signal to noise ratio and signal to interference ratio.

关键词： adaptive beamforming fractional Fourier transform (FrFT) fractional moments chirp signal.

ALLOCATING REPAIRABLE SYSTEM'S RELIABILITY SUBJECT TO MINIMAL TOTAL COST-AN INTEGER PROGRAMMING APPROACH

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Journal of Systems Science and Systems Engineering 2007年第4期16卷 499-506页

作者： ahmad A.Moreb Department of Industrial Engineering King Abdul Aziz University JeddahSaudi Arabia

Reliability allocation problem is commonly treated using a closed-form expression relating the cost to reliability. A recent approach has introduced the use of discrete integer technique for un-repairable systems. This research addresses the allocation problem for repairable systems. It presents an integer formulation for finding the optimum selection of components based on the integer values of their Mean Time to Failure （MTTF） and Mean Time to Repair （MTTR）. The objective is to minimize the total cost under a system reliability constraint, in addition to other physical constraints. Although, a closed-form expression relating the cost to reliability may not be a linear; however, in this research, the objective function will always be linear regardless of the shape of the equivalent continuous closed-form function. An example is solved using the proposed method and compared with the solution of the continuous closed-form version. The formulation for all possible system configurations, components and subsystems are also considered.

关键词： Reliability allocation cost minimization integer programming

Finite element model updating for structural damage detection using transmissibility data

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Earthquake Engineering and Engineering Vibration 2024年第1期23卷 87-101页

作者： ahmad Izadi Akbar Esfandiari Department of Maritime Engineering Amirkabir University of TechnologyTehran 15875-4413Iran

This paper presents a new finite element model updating method for estimating structural parameters and detecting structural damage location and severity based on the structural responses(output-only data).The method uses the sensitivity relation of transmissibility data through a least-squares algorithm and appropriate normalization of the extracted *** proposed transmissibility-based sensitivity equation produces a more significant number of equations than the sensitivity equations based on the frequency response function(FRF),which can estimate the structural parameters with higher *** abilities of the proposed method are assessed by using numerical data of a two-story two-bay frame model and a plate structure *** evaluating different damage cases,the number,location,and stiffness reduction of the damaged elements and the severity of the simulated damage have been accurately *** reliability and stability of the presented method against measurement and modeling errors are examined using error-contaminated *** parameter estimation results prove the method’s capabilities as an accurate model updating algorithm.

关键词： damage detection model updating output-only transmissibility sensitivity equation

Correlation between structural phase transition and physical properties of Co^(2+)/Gd^(3+)co-substituted copper ferrite

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Journal of Rare Earths 2024年第7期42卷 1344-1353,I0006页

作者： Mohsen Choupani ahmad Gholizadeh School of Physics Damghan UniversityDamghan36716-45667Iran

The doping of the spinel ferrites with selective cations usually improves the properties of the parent *** effect of Co^(2+)/Gd^(3+)co-substitution on the microstructure,optical,and magnetic properties of Cu1-xCoxFe2-xGdxO4 prepared by the citrate-nitrate auto-combustion synthesis was *** of the samples was performed with powder X-ray diffraction(XRD),Raman and Fouriertransform infrared(FTIR)spectroscopy,field-emission scanning electron microscopy,X-ray energydispersive spectroscopy,UV-Vis spectroscopy,and a vibrating sample *** results of XRD,Raman,and FTIR analysis show a gradual structural phase transition from a tetragonal(I41/amd)structure to a cubic(Fd3m)*** bandgap energy of the studied samples is in a range of 1.57-1.75 eV with a minimum in sample x=0.06 and then *** investigations show that the presence of Co^(2+)/Gd^(3+)cations in an octahedral site of the copper ferrite structure could increase saturation magnetization and coercive field from 567.9 Oe and 23.62 emu/g to 929.4 Oe and 28.27 emu/g,respectively.

关键词： Spinel copper ferrite Citrate-nitrate method Structure phase transition Microstructure properties Magnetic properties Rare earths

DFT studies of thermoelectric properties of R-Au intermetallics at 300 K

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Journal of Rare Earths 2018年第2期36卷 197-202页

作者： Sardar ahmad Rashid ahmad Muhammad Bilal Najeeb Ur Rehman Center for Computational Materials Science University of Malakand Department of Chemistry University of Malakand Department of Physics University of Malakand

Thermoelectric and electronic properties of cubic bi-intermetallics R-Au（R = Tb, Ho. Er. Tm and Yb）compounds were explored. Electronic properties i.e. density of states and band structure were computed using first principles calculations which proved the metallic nature of these compounds. Post-DFT（BoltzTraP） calculations were carried out to explore their thermoelectric properties like electrical conductivities. Seebeck coefficient, electronic thermal conductivities and figure of merit. The highest Seebeck coefficient and figure of merit were found for YbAu among these compounds which are 105 μV/K and 0.285 respectively. All the calculations were carried out at 300 K. Large values of figure of merit obtained for these compounds at room temperature indicate that these materials can be used for thermoelectric devices however need experimental verification.

关键词： DFT Seebeck coefficient Figure of merit Thermal conductivity Electrical conductivity R-Au

Remediation of sulfidic wastewater by catalytic oxidation with hydrogen peroxide

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Journal of Environmental Sciences 2009年第12期21卷 1735-1740页

作者： Naveed ahmad Saikat Maitra Binay Kanti Dutta Farooq ahmad Department of Chemical Engineering Universiti Teknologi PETRONAS Department of Chemical Engineering The Petroleum Institute

Oxidation of sulfide in aqueous solution by hydrogen peroxide was investigated in the presence of hydrated ferric oxide catalyst. The ferric oxide catalyst was synthesized by sol gel technique from ferric chloride and ammonia. The synthesized catalyst was characterized by Fourier transform infrared spectroscopy, X-Ray diffraction analysis, scanning electrom microscope and energy dispersive X-ray analysis. The catalyst was quite effective in oxidizing the sulfide by hydrogen peroxide. The effects of sulfide concentration, catalyst loading, H2O2 dosing and temperature on the kinetics of sulfide oxidation were investigated. Kinetic equations and activation energies for the catalytic oxidation reaction were calculated based on the experimental results.

关键词： catalytic oxidation wastewater kinetic equation hydrogen peroxide sodium sulfide remediation

Effect of physiographic factors on qualitative and quantitative charac-teristics of Cornus mas L. natural stands in Arasbaran forests, Iran

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Journal of Forestry Research 2013年第1期24卷 69-74页

作者： ahmad Alijanpour Faculty of Natural Resources Urmia UniversityPardis-e-NazlooSero RoodZip code ***UrmiaI. R. Iran

Arasbaran forests are located in East Azerbaijan （northwest Iran）. Increasing of socio-economic problems in this area causes destruction of biodiversity and structure of these forests. Using multipurpose trees such as cornelian cherry （Cornus mas L） to encourage villagers to produce forest by-products is a basic approach for preserving these forests. This species grows naturally in Arasbaran forests and the fruit is annually exploited using traditional harvest methods. This study aims to assess the ecological requirements of cornelian cherry and the important factors affecting its distribution. For this purpose, 40 circular sampling plots （300 m2） on various slope aspects were demarcated for sampling the occurrence of cornelian cherry in forest stands. DBH and crown cover percentage on north aspects were significantly greater than on other aspects and 4.5% of all trees were cornelian cherry in mature forest stands. North aspects had more seed-origin trees （standards） of cornelian cherry than coppiced trees, while west facing aspects had more coppiced than standard trees. This species had the highest regeneration rate in the sapling stage of 0–2.5 cm DBH. Thus, I recommend cultivation and development of cornelian cherry as a multi-purpose tree in the Arasbaran region on degraded forest lands on north and west aspects.

关键词： Arasbaran forests aspect physiographical factors comelian cherry (Cornus mas L.)

Interactive Effects of Silicon and Potassium Nitrate in Improving Salt Tolerance of Wheat

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Journal of Integrative Agriculture 2014年第9期13卷 1889-1899页

作者： ahmad Bybordi East Azerbaijan Research Center for Agriculture and Natural Resources Tabriz 53555-141 Iran

Adequate regulation of mineral nutrients might be effective to ameliorate the deleterious effects of salts and help to sustain crop productivity, particularly in glycophytes, under salt stress. In this study, laboratory and greenhouse experiments were carried out at Agricultural and Natural Resources Research Centre in East Azerbaijan, Iran, to investigate the interactive effects of silicon and potassium nitrate in alleviating NaCl induced injuries in wheat（Triticum aestivum L.）. In the laboratory experiment, three winter wheat cultivars Pishgam, Afagh and Alvand were grown on sterile filter paper moistened with 20, 40, 60, 80, and 100 mmol L-1 NaCl solution. Results revealed that wheat cultivars were significantly different in their growth response to different concentrations of NaCl and Pishgam was found to be the most tolerant to NaCl stress, and used in the second part of study. In the greenhouse experiment, Pishgam was grown in a hydroponic system subjected to different NaCl levels（20, 60 and 100 mmol L-1） and treated by silicon（0, 2 and 4 mmol L-1, final concentration in nutrient solution using K2SiO3） and potassium nitrate（0, 0.5, 1, and 2 mmol L-1, foliar application）. The experimental design was factorial based on a completely randomized design with three replications. It was found that NaCl stress significantly increased proline accumulation and sodium content in the plant tissues while decreased potassium uptake and accumulation by plants. Moreover, plant weight, 100-seed weight, relative water content, chlorophyll content, and photosynthesis were also significantly affected by varying levels of NaCl. However, exogenous application of silicon and potassium nitrate reduced sodium uptake, increased potassium and consequently improved plant weight, 100-seed weight, seed yield, ear length, and photosynthesis rate. This study suggested that utilization of the salt-tolerant cultivar（Pishgam） combined with proper foliar application of potassium nitrate（2 mmol L-

关键词： germination grain yield foliar application photosynthesis proline relative water content

Deep image retrieval using artificial neural network interpolation and indexing based on similarity measurement

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CAAI Transactions on Intelligence Technology 2022年第2期7卷 200-218页

作者： Faiyaz ahmad Department of Computer Engineering Jamia Millia IslamiaNew DelhiIndia

In content-based image retrieval(CBIR),primitive image signatures are critical because they represent the visual *** signatures,which are algorithmically descriptive and accurately recognized visual components,are used to appropriately index and retrieve comparable *** differentiate an image in the category of qualifying contender,feature vectors must have image information's like colour,objects,shape,spatial *** methods such as sketch-based image retrieval by salient contour(SBIR)and greedy learning of deep Boltzmann machine(GDBM)used spatial information to distinguish between image *** requires interest points and also feature analysis emerged image detection ***,a proposed model to overcome this issue and predict the repeating pattern as well as series of pixels that conclude similarity has been *** this study,a technique called CBIR-similarity measure via artificial neural network interpolation(CBIR-SMANN)has been *** collecting datasets,the images are resized then subject to Gaussian filtering in the pre-processing stage,then by permitting them to the Hessian detector,the interesting points are *** on Skewness,mean,kurtosis and standard deviation features were extracted then given to ANN for *** results are stored in a database for *** the testing stage,the query image was inputted that is subjected to pre-processing,and feature extraction was then fed to the similarity measurement ***,ANN helps to get similar images from the ***-SMANN have been implemented in the python tool and then evaluated for its *** show that CBIR-SMANN exhibited a high recall value of 78%with a minimum retrieval time of 980 *** showed the supremacy of the proposed model was comparatively greater than the previous ones.

关键词： Gaussian filtering Hessian detector image retrieval interpolation and similarity measurement repeating pattern