Simultaneous Determination of Nitrite and Nitrate in Milk Samples by Ion Chromatography Method and Estimation of Dietary Intake

The presence of nitrate and nitrite in foods may be considered hazardous after ingestion in the gastrointestinal tract due to their reaction with naturally occurred secondary amines to form potentially carcinogenic nitrosamines. Due to this fact, a new method was developed in this study for the simultaneous determination of nitrite and nitrate in milk samples using by ion chromatography. Proposed mobile phase composed of sodium hydrogen carbonate and sodium carbonate (1.0 and 3.2 mmol/L) with a flow rate of 0.7 ml/min. The average recoveries for nitrate and nitrite were higher than 86 and 88%, respectively. The limit of detection for nitrate and nitrite were 0.24 and 0.09 mg/L, respectively. The results of 102 real milk samples showed nitrate was found in all of the samples (100%) with a mean of 34 ± 11 mg/L, while nitrite was found in none of the samples. The mean intake of nitrate in all age groups was lower than World Health Organization guideline. The present assessment concludes that the maximum contaminant level was equal to 82.8 mg/L nitrate. This method was fast, sensitive and accurate and is capable of being an alternative method in food control laboratories for investigation of nitrite and nitrate content. This is the first study of the determination and survey of nitrite and nitrate and exposure assessment of the Iranian population to nitrite and nitrate level in milk, which was widely used in infants and adolescents as one of the basic food components.     

Pullout behavior of polymeric strip in compacted dry granular soil under cyclic tensile load conditions

Assessment of the reinforcement behavior of soil under cyclic and monotonic loads is of great importance in the safe design of mechanically stabilized earth walls. In this article, the method of conducting a multistage pullout (MSP) test on the polymeric strip (PS) is presented. The post-cyclic behavior of the reinforcement can be evaluated using a large-scale pullout apparatus adopting MSP test and one-stage pullout (OSP) test procedures. This research investigates the effects of various factors including load amplitude, load frequency, number of load cycles and vertical effective stress on the peak apparent coefficient of friction mobilized at the soil-PS interface and the pullout resistance of the PS buried in dry sandy soil. The results illustrate that changing the cyclic tensile load frequency from 0.1 Hz to 0.5 Hz does not affect the pullout resistance. Moreover, the influence of increasing the number of load cycles from 30 to 250 on the peak pullout resistance is negligible. Finally, the effect of increasing the cyclic tensile load amplitude from 20% to 40% on the monotonic pullout resistance can be ignored. The peak apparent coefficient of friction mobilized at the soil-PS interface under monotonic and cyclic load conditions decreases with the increase in vertical effective stress.     

A Numerical Study on Natural Convention Heat Transfer From a Horizontal Isothermal Cylinder Located Underneath an Adiabatic Ceiling

A numerical analysis is performed for steady-state and two-dimensional natural convection heat transfer from a horizontal isothermal cylinder located underneath a horizontal adiabatic ceiling. The finite-volume method based on the SIMPLE algorithm and a nonorthogonal grid discretization scheme are used to solve the continuity, momentum, and energy equations for the Rayleigh numbers in the range from 10^?1 to 10⁴. The Poisson equations are solved to find the grid points, which are distributed in a nonuniform manner with higher concentration close to the solid regions. In addition, the HYBRID differencing scheme is used for the approximation of the convective terms in the curvilinear coordinate. The effects of the Rayleigh numbers and cylinder spacing from the adiabatic ceiling on both the local and average Nusselt numbers around the cylinder are investigated. Numerical results are performed for the plate-to-cylinder spacing ranging from 0.1 to 1.4.     

Automated setup planning in CAPP: a modified particle swarm optimisation-based approach

Comprehensive process planning is the key technology for linking design and the manufacturing process and is a rather complex and difficult task. Setup planning has a basic role in computer-aided process planning (CAPP) and significantly affects the overall cost and quality of machined parts. This paper presents a generative system and particle swarm optimisation algorithm (PSO) approach to the setup planning of a given part. The proposed approach and optimisation methodology analyses constraints such as the TAD (tool approach direction), the tolerance relation between features and feature precedence relations, to generate all possible process plans using the workshop resource database. Tolerance relation analysis has a significant impact on setup planning to obtain part accuracy. Based on technological constraints, the PSO algorithm approach, which adopts the feature-based representation, optimises the setup planning using cost indices. To avoid becoming trapped in local optima and to explore the search space extensively, several new operators have been developed to improve the particles’ movements, combined into a modified PSO algorithm. A practical case study is illustrated to demonstrate the effectiveness of the algorithm in optimising the setup planning.     

Design and simulation of high-performance lateral bipolar junction transistor on partial buried oxide

In this work, we propose a new structure of a lateral bipolar junction transistor (LAT-BJT) on partial buried oxide (PBOX). The novelty of the proposed LAT-BJT device is the use of PBOX, covering just base and emitter regions only. A two-dimensional (2D) calibrated simulation study of the proposed LAT-BJT device has shown that the proposed LAT-BJT on PBOX’s performance is unique when the PBOX is just covering base and emitter regions. At this length of PBOX, a sharp enhancement in cut-off frequency (f_T) (~10 times higher) is achieved in the proposed LAT-BJT on PBOX in comparison to an LAT-BJT on silicon-on-insulator (SOI). The breakdown voltage of the proposed LAT-BJT on PBOX is double than that of the LAT-BJT on SOI device at this PBOX length. A notable enhancement in current gain (β) is observed in the proposed LAT-BJT on PBOX in comparison to the LAT-BJT on bulk device. To check the performance of the proposed LAT-BJT on PBOX at the circuit level, two inverters have been designed and simulated using the mixed-mode simulations of Atlas simulator. It has been observed that the proposed LAT-BJT on PBOX significantly outperforms the conventional LAT-BJT device in switching performance. A notable improvement of 32% in ON delay and 72.9% in OFF delay is obtained in the proposed LAT-BJT on PBOX device in comparison to the conventional LAT-BJT device.     

A generalized set of correlations for plus fraction characterization

The importance of accurate determination of the critical properties of plus fractions in prediction of phase behaviour of hydrocarbon mixtures by equations of state is well known in the petroleum industry. It has been stated in various papers (Elsharkawy, 2001) that using the plus fraction as a single group in equation of state calculations reduces the accuracy of the results. However in this work it has been shown that using the proper values of critical temperature and pressure for the plus fraction group can estimate the properties of hydrocarbon mixtures, and they are accurate enough to be used in reservoir engineering and enhanced oil recovery calculations. In this paper, a new method is proposed for calculating the critical properties of plus fractions of petroleum fluids. One can use this method either in predicting critical pressure and temperature of single carbon numbers (SCNs) after the splitting process or in predicting critical pressure and temperature of the plus fraction as a single group. A comparison study is performed against Riazi-Daubert correlation (Riazi and Daubert, 1987) and Sancet correlations (Sancet, 2007) for 25 oil samples taken from 14 fields from southwest Iran. The results indicate the superiority of the proposed method to the Riazi-Daubert and Sancet correlations.     

Use of axial dispersion and plug flow models for determination of axial mixing and mass transfer coefficient in an l‐shaped pulsed packed extraction column

In this study, the volumetric overall mass transfer and phases axial mixing coefficients have been investigated in a pilot plant of an L‐shaped pulsed packed extraction column by using two liquid systems of toluene/acetone/water and n‐butyl/acetone/water. The mass transfer performance has been evaluated using two methods of axial dispersion and a plug flow model. The effect of the operational variables and physical properties, including the dispersed and continuous phases flow rates, pulsation intensity, and interfacial tension, on mass transfer and phases axial mixing coefficients have been considered. It has been found that the pulsation intensity and the continuous phase flow rate seriously affect the mass transfer coefficient, however, the dispersed phase flow rate has a weaker effect. Also, the axial mixing of a phase is strongly affected by the pulsation intensity and the flow rate of the phase itself and it is not affected by the second phase flow rate. Finally, new correlations are proposed to accurately predict the mass transfer and axial mixing coefficients.     

Nickel-cobalt layered double hydroxide ultrathin nanosheets coated on reduced graphene oxide nonosheets/nickel foam for high performance asymmetric supercapacitors

Here in, for the first time, we report a new and simple procedure for preparing reduced graphene oxide/nickel-cobalt double layered hydroxide composite on the nickel foam (Ni-Co LDH/rGO/NF) via a fast and simple two-step electrochemical method including potentiostatic routes in the presence of CTAB as a cationic surfactant. Graphene oxide coated nickel foam prepared by simple immersion method. After that, the prepared electrode reduced electrochemically to obtain rGO/NF electrode. Finally, the rGO/NF electrode was used as cathode for electrodeposition of Ni-Co LDH in the presence of CTAB as cationic surfactant. The prepared electrodes were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDS), Brunauer, Emmett and Teller (BET) and electrochemical techniques such as voltammetry (CV), galvanostatic charge-discharge curves (GCD) and electrochemical impedance spectroscopy (EIS). The resulting electrode which prepared in the presence of CTAB afforded extremely high specific capacitance of 2133.3 F g^?1 at a current density of 4 A g^?1. FE-SEM, TEM and EDS mapping results showed that Ni-Co LDH nanosheets uniformly covered the surface of rGO/NF in the presence of CTAB, and is closely packed and thinner in thickness compared with the sample prepared in similar way without using surfactant. Such new thin and dense morphology facilitates electrolyte ions diffusion through the prepared electrode. A good cycling stability was obtained for the electrode in alkaline media. EIS measurements showed low values of internal resistance (R_s) and charge transfer resistance (R_ct), indicating that the prepared nanocomposite is a promising candidate for supercapacitor applications. The asymmetric supercapacitor (ASC) based on the Ni-Co LDH/CTAB/rGO/NF as a positive electrode and rGO/NF as a negative electrode was assembled and it exhibited a C_s of 71.4 F g^?1 at a current density of 2 A/g and correspondingly energy density of as high as 68 Wh kg^?1.     

A modified honey bee mating optimization algorithm for multiobjective placement of renewable energy resources

Electrical generators of renewable electricity resources are quiet, clean and reliable. Optimal placement of renewable electricity generators (REGs) results in reduction of objective functions like losses, costs of electrical generation and voltage deviation. Because of recent technology developments of photovoltaic units, wind turbine and fuel cell units, only these generators are considered in this paper. This work presents a multiobjective optimization algorithm for the siting and sizing of renewable electricity generators. The objectives consist of minimization of costs, emission and losses of distributed system and optimization of voltage profile. This multiobjective optimization is solved by the Improved honey bee mating optimization (HBMO) algorithm. In the proposed algorithm, an external repository is considered to save non-dominated (Pareto) solutions found during the search process. Since the objective functions are not the same, a fuzzy clustering technique is used to control the size of the repository within the limits. This algorithm is executed on a typical 70-bus test system. Results of the case study show the proper siting and sizing of REGs are important to improve the voltage profile, reduce costs, emission and losses of distribution system. The main feature of the algorithm refers to its accuracy and calculation speed.     

Impact of Optimal Unified Power Flow Controller in Electrical Transmission Systems in Reducing Transmission Cost

This paper presents an approach to optimal placement of optimal unified power flow controller (OUPFC) in electrical transmission systems utilizing genetic algorithm (GA), while reducing transmission systems cost using MATLAB and MATPOWER. The proposed approach is based on optimal power flow (OPF) considering optimization of power systems operation conditions. In order to determine the appropriate place for installation of OUPFC, while considering power injection model of this controller, OPF is utilized to obtain multi-objective function of the optimization problem. In this regard, the objective function comprises generation cost, transmission cost, and OUPFC installation cost. The proposed approach is applied to IEEE 30-bus test system, where the obtained results demonstrate remarkable reduction in overall cost of power system.