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Parametric Empirical Bayes Estimation of A Constant Hazard with Right Censored Data
Mashayekhi, Mostafa The Korean Reliability Society 2001 International Journal of Reliability and Applicati Vol.2 No.1
In this paper we consider empirical Bayes estimation of the hazard rate and survival probabilities with right censored data under the assumption that the hazard function is constant over the period of observation and the prior distribution is gamma. We provide an estimator of the first derivative of the prior moment generating function that converges at each point to the true value in $L_2$ and use it to obtain, easy to compute, asymptotically optimal estimators under the squared error loss function.
Electron spin relaxation control in single electron QDs
Mashayekhi, M.Z.,Abbasian, K.,Shoar-Ghaffari, S. Techno-Press 2013 Advances in nano research Vol.1 No.4
So far, all reviews and control approaches of spin relaxation have been done on lateral single electron quantum dots. In such structures, many efforts have been done, in order to eliminate spin-lattice relaxation, to obtain equal Rashba and linear Dresselhaus parameters. But, ratio of these parameters can be adjustable up to 0.7 in a material like GaAs under high-electric field magnitudes. In this article we have proposed a single electron QD structure, where confinements in all of three directions are considered to be almost identical. In this case the effect of cubic Dresselhaus interaction will have a significant amount, which undermines the linear effect of Dresselhaus while it was destructive in lateral QDs. Then it enhances the ratio of the Rashba and Dresselhaus parameters in the proposed structure as much as required and decreases the spin states up and down mixing and the deviation angle from the net spin-down As a result to the least possible value.
Topology and size optimization of truss structures using an improved crow search algorithm
Mostafa Mashayekhi,Roghayeh Yousefi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.77 No.6
In the recent decades, various optimization algorithms have been considered for the optimization of structures. In this research, a new enhanced algorithm is used for the size and topology optimization of truss structures. This algorithm, which is obtained from the combination of Crow Search Algorithm (CSA) and the Cellular Automata (CA) method, is called CA-CSA method. In the first iteration of the CA-CSA method, some of the best designs of the crow’s memory are first selected and then located in the cells of CA. Then, a random cell is selected from CA, and the best design is chosen from the selected cell and its neighborhood; it is considered as a “local superior design” (LSD). In the optimization process, the LSD design is used to modify the CSA method. Numerical examples show that the CA-CSA method is more effective than CSA in the size and topology optimization of the truss structures.
Synthesis, antimycobacterial and anticancer activity of novel indole-based thiosemicarbazones
Vida Mashayekhi,Kamaleddin Haj Mohammad Ebrahim Tehrani,Parisa Azerang,Soroush Sardari,Farzad Kobarfard 대한약학회 2021 Archives of Pharmacal Research Vol.44 No.8
Based on the structural elements of bioactiveindole-based compounds, a series of novel 1-substitutedindole-3-carboxaldehyde thiosemicarbazones were synthesizedas potential antimycobacterial and anticancer agents. The derivatives were prepared via a two-step methodologyincluding N-alkylation(benzylation) of indole-3-carboxaldehydeand conversion of the intermediate aldehydes tocorresponding thiosemicarbazones. The derivatives wereevaluated for their antimycobacterial activity and compounds3d (R = propyl) and 3q (R = 4-nitrobenzyl) wereamong the most potent and selective derivatives with IC50values of 0.9 and 1.9 lg/mL respectively. The anticanceractivity of the derivatives was also assessed against a panelof tumor cell lines. Compounds 3t, 3u, 3v and 3w efficiently inhibited the majority of the cancer cell lineswith considerable selectivity.
Eigenstructure Assignment for Four-Wheel Anti-lock Braking System Model
J. Mashayekhi Fard,M.A. Nekoui,A. Khaki Sedigh 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
Minimal Stopping Distance, Guaranteed Steering ability and Stability are the three most important proposes in Anti-lock Braking System(ABS)realm. The ABS system is nonlinear, time variant, multivariable and uncertain. Up to now several researches have been done on ABS control system, but nearly all of them are intricate and expensive. In this paper we exploit a multivariable technique in linear control to attack the problem, which is Designed Linear Control with Multivariable Technique. The Optimal Eigenstructure Assignment with Genetic Algorithm(GA) method is also applied. Simulation and comparison studies are used to show the effectiveness of the proposed methods.
A. H. Mashayekhi,M. Gerami,N. Siahpolo 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.5
Near fi eld earthquakes with forward directivity effects have pulse in the velocity record, thus this phenomenon causes signifi cant demands on the steel frames more than the ordinary earthquakes. Therefore, structural behavior of steel frames and the higher modes effects of structures under near fault earthquakes are essential. For this purpose 5 intermediate (ductility) steel moment resisting frames with 4, 7, 10, 15 and 20 stories under 20 far and near fault, 40 strike-parallel (SP) and strikenormal (SN) records have been investigated. Finally, the elastic responses of equivalent single degree of freedom structure (ESDOF) under mentioned records and response modifi cation factors to convert the response of ESDOF structure to the response of MDOF structure have been presented. The results of this research show that higher modes effects under the far fault earthquakes are greater than the near fault earthquakes. Also, the inter-story drift angle of structures under near fault earthquakes with forward directivity effect is greater than far fault earthquakes for about 30–50% of structure height in upper stories. The high-rise structures demands under the SP earthquakes, because of higher modes effects, are greater than the SN earthquakes. When the ratio of the building period to the pulse period, is greater than 0.5, the effects of SP earthquakes increase more than the fault normal (SN) earthquakes.
Naeimeh Sousaraei,Kambiz Mashayekhi,Seyyed Javad Mousavizadeh,Vahid Akbarpour,Joaquín Medina,Sasan Aliniaeifard 한국원예학회 2021 Horticulture, Environment, and Biotechnology Vol.62 No.4
To investigate the effects of water withholding on 17 tomato (Solanum lycopersicum L.) landraces collected from different climatic zones of Iran and two commercial hybrids, the polyphasic OJIP fluorescence transient, relative water content (RWC), electrolyte leakage (EL) and vegetative growth parameters were analyzed. Duncan’s multiple range test (DMRT) for all the studied parameters and drought factor index (DFI) based on performance index on the absorption basis (PIabs) were used for screening the plants based on their tolerance to drought condition. Result showed that compared to the control plants, vegetative growth parameters, RWC, PIabs, relative maximal variable fluorescence (FM/F0), maximum quantum efficiency of PSII (FV/FM), quantum yield of electron transport (ΦE0) and electron transport flux per reaction center (RC) (ET0/RC) were decreased, whereas, EL, quantum yield of energy dissipation (ΦD0), specific energy fluxes per RC for energy absorption (ABS/RC) and dissipated energy flux (DI0/RC), which are closely related to the incidence of photoinhibition were increased in plants exposed to water withholding. DMRT and DFI screening results clearly categorized the landraces into three groups (tolerant, moderately sensitive and sensitive). Tolerant landraces showed less change for most of the measured parameters compared to sensitive and moderately sensitive landraces. We found that adapted landraces to dry climates had a higher tolerance to drought stress. Principal component analysis (PCA) revealed that FM/F0, FV/FM, ΦE0, ΦD0, PIabs, ABS/RC, ET0/RC and DI0/RC parameters are the most sensitive parameters for detection of impact of drought stress on tomato plants. In conclusion, the eight parameters have the potential to identify the drought injury in tomato seedlings.
Sayyahfar Shirin,Choobdar Farhad Abolhasan,Mashayekhi Mahdi,Jazi Faramarz Masjedian 대한감염학회 2021 Infection and Chemotherapy Vol.53 No.1
Acinetobacter baumannii is one of the most important etiologies of nosocomial infections in recent years mainly because of increasing in frequency of multidrug and pan-resistant pathogens. Meningitis caused by this organism is a dilemma; because polymyxins are the only effective antibiotics against pan-resistant serotypes, but have poor penetration via blood brain barrier; however, it has still remained uncertain whether the intravenous therapy with these agents is an effective treatment with the sufficient concentration of the drug in the cerebrospinal fluid. Herein, we report a neonate who suffered from pan-resistant A. baumannii nosocomial meningitis successfully treated with intravenous colistin combined with meropenem and rifampin. It seems that intravenous colistin at least in combination with rifampin and meropenem might be considered as an option to try in patients in whom daily intrathecal injection or insertion of intraventricular device is not possible.