A High Gain and Low Flicker Noise CMOS Mixer with Low Flicker Noise Corner Frequency Using Tunable Differential Active Inductor

This paper presents the design of a high conversion gain and low flicker noise down conversion CMOS double balanced Gilbert cell mixer using \(0.18\,\upmu \hbox {m}\) CMOS technology. The high conversion gain and low flicker noise mixer is implemented by using a differential active inductor (DAI) circuit and cross-coupled current injection technique within the conventional double-balanced Gilbert cell mixer. A cross-coupled current bleeding circuit is used to inject the current to the switching stage to decrease the flicker noise. Instead of spiral inductor, a DAI with high tunability of the inductor and quality factor is used to tune out the parasitic capacitance effect and decrease the leakage current that has a harmonic component and produce the flicker noise. By tuning the DAI, the flicker noise corner frequency is reduced to 150 Hz. The proposed circuit is simulated with Cadence Spectra and the simulation results shows the NF of 11.2 dB, conversion gain of 23.7 dB and IIP3 of \(-6\)  dB for an RF frequency of 2.4 GHz. The excellent LO-RF, LO-IF, RF-LO and RF-IF isolations of \(-60, -110, -52\) and \(-64\)  dB are achieved respectively. The total power consumption is 10.5 mW from a 1.8 V DC power supply.     

Numerical simulation of transient heat transfer for tomato paste in semi rigid aluminum container

In this study, numerical model of heat transfer for tomato paste in semi-rigid aluminum container was developed by Fluent software 6.3.26. Grid independence was recognized. The impact of head space (air and water -vapor) and buoyancy force on heat transfer were investigated. Simulation results showed slowest heating zone (SHZ) located in (?11.676?<?X?<??10.738, 0.183?<?Y?<?1.269 and 4.417?<?Z?<?5.560) for model with air head space and in (?11.166?<?X?<??11.370, 0.762?<?Y?<?1.21 and 5.480?<?Z?<?5.506) for model with water–vapor head space in Cartesian system coordinate. A thermocouple was connected to container at (0, 0, 10 cartesian system coordinate) to get experimental data during process. Comparing temperatures of experimental model and predicted model (with head space) illustrated no significant difference (p?<?0.05).     

Electrochemical Synthesis of Cu (II) Coordination Polymer Coatings Based on 2,2′-Thiodiacetic Acid and 1,2,4,5-Benzenetetracarboxylate

Electrochemical synthesis of coordination polymers of Cu(II), [Cu(TDA)]_n and [Cu₂(BTC)(H₂O)₆?6H₂O]_n in which H₂TDA is 2,2′-thiodiacetic acid and BTC stands for 1,2,4,5-benzenetetracarboxylate was carried out by the electrochemical oxidation of Cu anode in the presence of H₂TDA (a flexible ligand), and 1,2,4,5-benzentetracarboxylic acid (H₄BTC) (a rigid ligand) in aqueous solutions. The structure of coordination polymers were characterized by scanning electron microscopy, X-ray powder diffraction, elemental analysis, thermal gravimetric and differential thermal analyses. The crystal structure of the compounds consists of one-dimensional cubical crystal polymeric units of [Cu(TDA)]_n and [Cu₂(BTC)(H₂O)₆?6H₂O]_n. Furthermore, the coordination number of Cu (II) ions in synthesized coordination polymers to be found five. The main advantages of electrosynthesis are the minor synthesis time, the milder conditions and the facile synthesis of coordination polymer coatings.     

Simultaneous multi-objective optimization of a new promoted ethylene dimerization catalyst using grey relational analysis and entropy measurement

A hybrid approach between the Taguchi method and grey relational analysis (GRA) with entropy measurement was applied to determine a single optimum setting for reaction factors of the proposed ethylene dimerization catalyst having overall selectivity to 1-butene (S_1-btn (%)) and turnover frequency (TOF (h^-1)) as multiple quality characteristics. Titanium tetrabutoxide (Ti(OC₄H₉)₄) catalyst precursor in combination with triethyl aluminum (TEA) activator, 1,4-dioxane as a suitable modifier, and ethylene dichloride (EDC) as a novel promoter were used in the catalysis. Control factors of temperature, pressure, Al/Ti, 1,4-dioxane/Ti, and EDC/Ti mol ratios were investigated on three levels and their main effects were discussed. The effect of the binary interaction between temperature, pressure, and Al/Ti mol ratio was also examined. Weight of the responses was determined using entropy. Analysis of variance (ANOVA) for data obtained from GRA indicated that EDC/Ti mol ratio with 27.64% contribution had the most profound effect on the multiple quality characteristics. Development of the weighted Grey-Taguchi method used the Taguchi method as its basic structure, adopted GRA to deal with multiple responses, and entropy to enhance the reasonability of the comprehensive index produced by GRA to make the results more objective and accurate. Overall, these combined mathematical techniques improved catalytic performance for 1-butene production.     

Application of mesoporous magnetic carbon composite for reactive dyes removal: Process optimization using response surface methodology

Discharging the effluents of textile wastewaters into potable water resources can endanger the ecosystem, due to their reactivity, toxicity, and chemical stability. In this research, the application of powder activated carbon modified with magnetite nanoparticles (PAC-MNPs) as an adsorbent for removal of reactive dyes (Reactive black 5 (RB5) and reactive red 120 (RR120)) was studied in a batch system. The adsorption performance was evaluated as a function of temperature, contact time and different adsorbent and adsorbate concentrations. The levels of factors were statistically optimized using Box-Behnken Design (BBD) from the response surface methodology (RSM) to maximize the efficiency of the system. The adsorption process of both dyes was fit with the pseudo-second order kinetic and Langmuir isotherm models. The identified optimum conditions of adsorption were 38.7 °C, 46.3 min, 0.8 g/L and 102 mg/L for temperature, contact time, adsorbent dose, and initial dyes concentration, respectively. According to the Langmuir isotherm, the maximum sorption capacities of 175.4 and 172.4 mg/g were obtained for RB5 and RR120, respectively. Thermodynamics studies indicated that the adsorption process of the reactive dyes was spontaneous, feasible, and endothermic. After five cycles, the adsorption efficiency was around 84 and 83% for RB5 and RR120, respectively. A high value of desorption was achieved, suggesting that the PAC-MNPs have a good potential in regeneration and reusability, and also can be effectively utilized in industrial applications. PAC-MNPs also show a good anti-interference potential for removal of reactive dyes in dye-industry wastewaters.     

Mechanistic study of electrochemical oxidation of 4-tert-butylcatechol: A facile electrochemical method for the synthesis of new trimer of 4-tert-butylcatechol

The electrochemical trimerization of 4-tert-butylcatechol via anodic oxidation of 4-tert-butylcatechol (1) is described. The mechanism of trimerization has been studied in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The electrochemical synthesis of trimer 3a has been successfully performed in an undivided cell in good yield and purity.     

Phospholipids and oxophospholipids in atherosclerotic plaques at different stages of plaque development

We identified and quantified the hydroperoxides, hydroxides, epoxides, isoprostanes, and core aldehydes of the major phospholipids as the main components of the oxophospholipids (a total of 5–25 pmol/μmol phosphatidylcholine) in a comparative study of human atheroma from selected stages of lesion development. The developmental stages examined included fatty streak, fibrous plaque, necrotic core, and calcified tissue. The lipid analyses were performed by normal-phase HPLC with on-line electrospray MS using conventional total lipid extracts. There was great variability in the proportions of the various oxidation products and a lack of a general trend. Specifically, the early oxidation products (hydroperoxides and epoxides) of the glycerophosphocholines were found at the advanced stages of the plaques in nearly the same relative abundance as the more advanced oxidation products (core aldehydes and acids). The anticipated linear accumulation of the more stable oxidation products with progressive development of the atherosclerotic plaque was not apparent. It is therefore suggested that lipid infiltration and/or local peroxidation is a continuous process characterized by the formation and destruction of both early and advanced products of lipid oxidation at all times. The process of lipid deposition appears to have been subject to both enzymatic and chemical modification of the normal tissue lipids. Clearly, the appearance of new and disproportionate old lipid species excludes randomness in any accumulation of oxidized LDL lipids in atheroma.