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81.
82.
In this paper multivariate response surface methodology (RSM) has been used for the optimization of hydrodistillation-headspace solvent microextraction (HD-HSME) of thymol and carvacrol in Thymus transcaspicus. Quantitative determination of compounds of interest was performed simultaneously using gas chromatography coupled with flame ionization detector (GC-FID). Parameters affecting the extraction efficiency were assessed and the optimized values were 5 min, 2 μL and 3 min for the extraction time, micro-drop volume and cooling time after extraction, respectively. The amounts of analyte extracted increased with plant weight. The calibration curves were linear in the ranges of 6.25-81.25 and 1.25-87.50 mg L−1 for thymol and carvacrol, respectively. Limit of detection (LOD) for thymol and carvacrol was 1.87 and 0.23 mg L−1, respectively. Within-day and between-day precisions for both analytes were calculated in three different concentrations and recoveries obtained were in the range of 89-101% and 95-116% for thymol and carvacrol, respectively. 相似文献
83.
F. Hosseinzadeh Lotfi T. Allahviranloo M. Alimardani Jondabeh L. Alizadeh 《Applied Mathematical Modelling》2009
This paper discusses full fuzzy linear programming (FFLP) problems of which all parameters and variable are triangular fuzzy numbers. We use the concept of the symmetric triangular fuzzy number and introduce an approach to defuzzify a general fuzzy quantity. For such a problem, first, the fuzzy triangular number is approximated to its nearest symmetric triangular number, with the assumption that all decision variables are symmetric triangular. An optimal solution to the above-mentioned problem is a symmetric fuzzy solution. Every FLP models turned into two crisp complex linear problems; first a problem is designed in which the center objective value will be calculated and since the center of a fuzzy number is preferred to (its) margin. With a special ranking on fuzzy numbers, the FFLP transform to multi objective linear programming (MOLP) where all variables and parameters are crisp. 相似文献
84.
S. M. Hosseini R. Alizadeh E. Fatehifar A. Alizadehdakhel 《Heat and Mass Transfer》2014,50(10):1393-1403
This study is an attempt to investigate the chemical absorption of CO2 in aqueous monoethanolamine (MEA) solution in a wetted-wire column consisting of one wire. Computational fluid dynamics method along with volume of fluid model was employed for modeling of two-phase flow, mass transfer and chemical reaction inside the column. The modeling results were compared with available experimental data and very good agreement was achieved. The simulation results showed that the diameter and intervals of liquid beads increases by increasing the gas and liquid flow rates. The beads velocity increases by increasing the liquid flow rate and decreasing mass fraction of MEA in the liquid phase. Also, mass transfer resistance in the liquid phase reduces by formation of the beads. It was concluded that the developed model is capable to predict the effect of operating and physical parameters on the investigated chemical absorption process. 相似文献
85.
The new method which has been proposed by Groetz et al., for reading the SSNTDs by He–Ne laser SCATTERING was applied, in this work, on CR-39 and CN-85 detectors irradiated with neutrons and alpha particles. The intensity of the transmitted laser light through the etched SSNTD was measured using a photodiode. The method appeared as a good technique for dose reading but it is extremely dependent on the etching time, the type of incident particles and the type of the detector. In general, the response of CN-85 was found to be faster and better than CR-39. 相似文献
86.
The present paper deals with the prediction of three-dimensional fluid flow and heat transfer in rib-roughened ducts of square
cross-section, which are either stationary, or rotate in orthogonal mode. The main objective is to assess how a recently developed
variant of a cubic non-linear k−ε model (proposed by Craft et al. Flow Turbul Combust 63:59–80, 1999) can predict three-dimensional flow and heat transfer characteristics through stationary and rotating ribbed ducts. The present
paper discusses turbulent air flow and heat transfer through two different configurations, namely: (I) a stationary square
duct with “in-line” normal and (II) a square duct with normal ribs in a “staggered” arrangement under stationary and rotating
conditions, with the axis of rotation normal to the flow direction and parallel to the ribs. In this paper the flow and thermal
predictions of the linear k−ε model (EVM) are also included, as a set of baseline predictions. The mean flow predictions show that both linear and non-linear
k−ε models can successfully reproduce most of the measured data for stream-wise and cross-stream velocity components. Moreover,
the non-linear model is able to produce better results for the turbulent stresses. The heat transfer predictions show that
both EVM and NLEVM2, the more recent variant of the non-linear k−ε, with the algebraic length-scale correction term, overestimate the measured Nusselt numbers for both geometries examined.
While the EVM with the differential length-scale correction term underestimates heat transfer levels, the Nusselt number predictions
with the NLEVM2 and the ‘NYP’ term are in close agreements with the measured data. Comparisons with our earlier work, Iacovides
and Raisee (Int J Heat Fluid Flow, 20:320–328, 1999), show that the NLEVM2 thermal predictions are of similar quality to those of a second-moment closure. 相似文献
87.
Abdolali Alizadeh Sadegh Rostamnia Qasem Oskueyan 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):1779-1784
Heterocyclic systems 4,5-dihydrothiazol-2-ylamine derivatives are synthesized via an intramolecular thioiminoformamide annulation reaction. 相似文献
88.
Saleh Ashrafi Okhtay Jahanbakhsh Davood Alizadeh Behrooz Salehpour 《Central European Journal of Physics》2013,11(5):560-567
Compton scattering tomography is widely used in numerous applications such as biomedical imaging, nondestructive industrial testing and environmental survey, etc. This paper proposes the use of the genetic algorithm (GA), which utilizes bio-inspired mathematical models, to construct an image of the insides of a test object via the scattered photons, from a voxel within the object. A NaI(Tl) scintillation detector and a 185 MBq 137Cs gamma ray source were used in the experimental measurements. The obtained results show that the proposed GA based method performs well in constructing images of objects. 相似文献
89.
In this paper, chance-constrained 0–1 integer programming models for the stochastic traditional and U-type line balancing (ULB) problem are developed. These models are solved for several test problems that are well known in the literature and the computational results are given. In addition, a goal programming approach is presented in order to increase the system reliability, which is arising from the stochastic case. 相似文献
90.
The purpose of this note is to give a probability bound on symmetric matrices to improve an error bound in the Approximate S-Lemma used in establishing levels of conservatism results for approximate robust counterparts. 相似文献