The catalytic deacidification of acidic crude oil using Cu-doped alkaline earth metal oxide catalysts

Naphthenic acids (NAs) tend to cause operational problems that can lead to the deactivation of catalysts. To overcome the problem, catalytic deacidification was introduced utilizing an ammonia solution in ethylene glycol with the aids of alkaline earth metal catalyst with alumina as a support. The initial total acid number observed for NAs in n-dodecane was 4.21 mg KOH/g. In total, 1,000 mg/L of 0.4% NH₃-EG were used as the acid removal agent. Calcium, barium, and magnesium catalysts were tested in this study. The results showed Cu/Ca/Al₂O₃ was found to be the best catalyst that could be used to enhance the reaction.     

Thermal properties and aging characteristics of chemically modified oil palm ash-filled natural rubber composites

The chemically modified oil palm ash (OPA) with the cetyltrimethylammonium bromide (CTAB) solution was prepared prior to compounding with the natural rubber and other curing ingredients. The aging resistance and thermal stability of CTAB-modified OPA-filled natural rubber composites were evaluated in the same manner as non-modified OPA samples. The retention tensile properties after thermal aging was measured and based on the result shown, the CTAB-modified OPA-filled natural rubber composites imparted insignificant effect to aging resistance as compared to the non-modified OPA-filled natural rubber composites at very low OPA loading; however, the effect became apparent beyond 3 phr OPA loading where the CTAB-modified OPA-filled natural rubber composites provided better aging resistance than the corresponding non-modified OPA-filled natural rubber composites. The thermogravimetric analysis indicated that the CTAB-modified OPA-filled natural rubber composites exhibited lower thermal stability which showed lower temperature at their respective weight loss and lesser char residue than that of non-modified OPA-filled natural rubber composites. This was attributed to the CTAB which started to decompose at the temperature of 210 °C. However, for the range from ambient temperature to 210 °C, the CTAB-modified OPA-filled natural rubber composites produce better thermal stability than those of non-modified OPA-filled natural rubber composites.     

A review of the stabilization of tropical lowland peats

The Deep Mixing Method, which involves the formation of in situ stabilized peat columns, is suitable for deep peat stabilization, whereas the mass stabilization technique is used to stabilize the soil of shallow peat deposits instead of the costly and problematic removal and replacement method. The concept of soil-cement stabilization involves the addition of water to cement, resulting in a chemical process known as cement hydration. Stabilization of peat by cement, which requires a significant strength increase in the cement-stabilized peat or organic soil, is attributed largely to physicochemical reactions that include cement hydration, hardening of the resulting cement paste and interactions between soil substances and primary and secondary cementation hydration products. The factors that affect these physicochemical reactions and the interactions of peat soil-cementation products that influence peat stabilization are the amount of solid particles, the water: soil ratio, the quantity of binder, the presence of humic and/or fulvic acids, the soil pH and the amount of organic matter in the peat. With the Air Curing Technique, stabilized peat samples for unconfined compressive strength (UCS) tests were kept at a normal air temperature of 30 ± 2 °C and strengthened by gradual moisture content reduction instead of the usual water-curing technique or water submersion methods that have been common practice in past experiments involving the stabilization of peat with cement. The principle of using the Air Curing Technique to strengthen stabilized peat is that peat soil at its natural moisture content contains sufficient water (water content from 198 to 417 %) that, when mixed with cement, a curing process takes place that causes the stabilized peat soil to gradually lose its moisture content and to become drier and harder throughout the curing period. This process does not require the addition of water.     

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.     

Effects of Modified Atmosphere Packaging with Various Carbon Dioxide Composition on Biogenic Amines Formation in Indian Mackerel (Rastrelliger kanagurta) stored at 5 ± 1°C

The profile of major biogenic amines was investigated in Indian mackerel packed in modified atmosphere for up to 12 days at 5 ± 1°C. Beheaded and gutted Indian mackerel was packed under different carbon dioxide compositions to study the effects on biogenic amines formation. The treatments were control air (C), vacuum packaging (VP), 30% CO₂/65% N₂/5% O₂ (M30C), 60% CO₂/35% N₂/5% O₂ (M60C), 80% CO₂/15% N₂/5% O₂ (M80C) and 100% CO₂ (M100C). Each amine responded differently to different CO₂ levels. After 12 days of storage, concentrations of histamine were reduced by 6.4%, 8.5%, 70.3%, 78.8% and 90.2% in fish packed under VP, M30C, M60C, M80C and M100C, respectively as compared with control air. Changes in putrescine and cadaverine showed a similar pattern. Gas mix of M30C and VP stimulated the formation of tyramine reaching 203 and 172 ppm, respectively. Higher composition of CO₂ had a significant inhibitory effect on tyramine concentration (p < 0.05). There were parallel increases of putrescine and spermidine in C, VP and M30C. No significant effect of CO₂ was observed on spermine (p > 0.05). After 9 days of storage, more than 300 ppm of histamine was detected in mackerel packed in VP and M30C; therefore, these atmospheres pose a histamine intoxication risk. Copyright © 2013 John Wiley & Sons, Ltd.     

Structural and optical properties of Co-doped ZnS nanoparticles synthesized by a capping agent

Cobalt-doped Zinc sulfide (ZnS) nanoparticles were prepared by a simple chemical method using alkyl hydroxyl ethyl dimethyl ammonium chloride (YH) as capping agent. The structural and optical properties of prepared cobalt-doped ZnS nanoparticles have been characterized. X-ray diffraction patterns and transmission electron microscope images reveal pure cubic ZnS phase with size of about 5–2 nm for all cobalt-doped ZnS nanoparticles. The lattice constant of the samples decreases slightly by the introduction of Co²⁺ The absorption edge of the ZnS:Co²⁺ nanoparticles is blue-shifted as compared with that of bulk ZnS, indicating the quantum confinement effect. The photoluminescence emission band exhibits a blue shift for Co-doped ZnS nanoparticles as compared to the ZnS nanoparticles.     

Inhibition of Aluminum Alloy Corrosion in 0.5 M Nitric Acid Solution by 4-4-Dimethyloxazolidine-2-thione

The corrosion inhibition of Al-Alloy (Al2024) in 0.5 M nitric acid solution at 30 °C was achieved using 4-4-dimethyloxazolidine-2-thione (DMT) as a corrosion inhibitor. The electrochemical performance of the DMT was studied by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization measurements, and scanning electron microscopic study (SEM). The results indicated that DMT acts as an inhibitor for Al2024 in 0.5 M nitric acid. Polarization curves indicated that DMT was a mixed-type inhibitor. Inhibition efficiencies were observed to be increased with an increase in DMT concentration and attains approximately to 93.4% at 2 mM of DMT in 0.5 M nitric acid. The adsorption of DMT model on Al2024 surface obeyed in accordance with Langmuir adsorption isotherm model. The value of the free energy of adsorption ΔG _ads indicated that the adsorption of DMT molecule was a spontaneous process and was typical of physical and chemical adsorption.     

Woven hybrid composites: Tensile and flexural properties of oil palm-woven jute fibres based epoxy composites

In this research, tensile and flexural performance of tri layer oil palm empty fruit bunches (EFB)/woven jute (Jw) fibre reinforced epoxy hybrid composites subjected to layering pattern has been experimentally investigated. Sandwich composites were fabricated by hand lay-up technique in a mould and cured with 105 °C temperatures for 1 h by using hot press. Pure EFB and woven jute composites were also fabricate for comparison purpose. Results showed that tensile and flexural properties of pure EFB composite can be improved by hybridization with woven jute fibre as extreme woven jute fibre mat. It was found that tensile and flexural properties of hybrid composite is higher than that of EFB composite but less than woven jute composite. Statistical analysis of composites done by ANOVA-one way, it showed significant differences between the results obtained. The fracture surface morphology of the tensile samples of the hybrid composites was performed by using scanning electron microscopy.     

Performance analysis of a double-pass photovoltaic/thermal (PV/T) solar collector with CPC and fins

The use of PV/T in combination with concentrating reflectors has a potential to significantly increase power production from a given solar cell area. A prototype double-pass photovoltaic-thermal solar air collector with CPC and fins has been designed and fabricated and its performance over a range of operating conditions was studied. The absorber of the hybrid photovoltaic/thermal (PV/T) collector under investigation consists of an array of solar cells for generating electricity, compound parabolic concentrator (CPC) to increase the radiation intensity falling on the solar cells and fins attached to the back side of the absorber plate to improve heat transfer to the flowing air. Energy balance equations have been developed for the various nodes of the system. Both thermal and electrical performance of the collector are presented and discussed.     

Feasibility of Kelvin probe force microscopy to measure the surface potential decay of polystyrene film due to relative humidity

The feasibility of measuring the surface potential decay of polystyrene (PS) film is investigated at room temperature by using Kelvin probe force microscopy (KPFM). The PS film was charged by an ion injection method utilizing Bruker's atomic force microscope (AFM) Nanoman module with a pulse duration of 1 ms, SCM-PIT electrically conductive probe, and a voltage pulse of −250 mV. The surface potential decayed linearly on a semi-log scale with time, where the time decay constant was quantified for relative humidity (RH) = 5% by KPFM at room temperature. The surface potential decayed due to the interaction of the PS film with the hydronium ions available in the environment. Furthermore, the effect of the material forms (film vs. microspheres) on the time decay constant at RH = 5% was investigated. The time decay constants measured using different methods exhibited excellent correlation with the AFM-KPFM. This also confirmed that the results are independent of the material form (microspheres vs. film form). As a result, the proposed method can be used to measure the effect of RH for any PS surface (i.e., particles of various sizes and films) exposed to these environmental conditions.