URANS simulations for a free-running container ship:Part 2.Added power

Part 2 reports the validation,local force and local flow study results for the free-running added power simulations whose conditions are the same as the self-pr...     

Improvement of mechanical and electrical properties of epoxy resin with carbon nanofibers

In the present research, the reinforcement effect of vapor grown carbon nanofiber (VGCNF) was studied in relation to the mechanical properties and electrical conduction behavior of fabricated nanocomposites. Different weight fractions of nanofillers into epoxy resin, from 0.05 to 1 wt% and up to 2 wt% for mechanical and electrical properties were investigated. It was found that the optimum improvement in mechanical properties of nanocomposite is obtained at 0.25 wt% of carbon nanofibers. At this filler content, 23 % enhancement in tensile strength and 10 % in flexural strength have been observed. The degree of the VGCNF dispersion has been monitored by means of viscosity variation of the suspension during the sonication process to obtain the optimum sonication time. Finally, the quality of the dispersion for post-cured nanocomposites is characterized by fractured surfaces using the scanning electron microscopy. Agglomerates had a direct effect on the reduction of tensile and flexural strength of nanocomposites. The electrical conductivity was obtained by means of surface measuring method. The optimum amount of filler for the generation of a fine electrical conductivity was found to be around 0.5 wt% of VGCNF. After the threshold point, the electrical conductivity of nanocomposites was slightly raised in spite of adding more filler contents.     

Quantitative Risk Assessment for Process Design Modification and Maintenance Optimization in Refineries and Petrochemical Plants

Quantitative risk assessment is methodology based on calculating probabilities and frequencies of sequential events using Boolean algebra, and it is normally used to perform safety assessments for complex interacting systems. Although quantitative risk assessment has been commonly used in aerospace and nuclear industries, it can also be used for quantifying economic risk and for estimating possibilities of potential production losses in a petrochemical or a manufacturing plant. In developing quantitative risk assessment models for petrochemical plants, component failures as well as human (operator) errors are taken into consideration in developing the plant's fault‐tree logic, in which is used to predict probabilities of future plant upsets. This paper shows how the quantitative risk assessment can be used to rank the economic importance of the production units in a refinery for prioritizing maintenance activities. In addition, two case studies are compared to demonstrate how a quantitative risk assessment model can be used as an invaluable tool in process design optimization. The quantitative risk assessment methodology developed in this work relates production losses to the performance of the major components and the process design. This application of the quantitative risk assessment provides a basis for the risk‐informed decision‐making and optimizing allocation of plant resources in support of plant operation and maintenance activities.     

Synthesis,characterization, and soil biodegradation study of polyamides derived from the novel bioactive diacid monomer 5‐(2‐phthalimidoethanesulfonamido) isophthalic acid

A new bioactive diacid monomer, 5‐(2‐phthalimidoethanesulfonamido) isophthalic acid ( 6 ), was synthesized in three steps. This monomer can be regarded as biologically active aromatic diacid and may be used in the design of biodegradable and biological materials. This monomer was polymerized with several aromatic diamines by step‐growth polymerization to give a series of biodegradable and highly thermally stable polyamides (PAs) with good yield (70–82%) and moderate inherent viscosity between 0.38–0.68 dL/g in a system of triphenylphosphite/pyridine/N‐methyl‐2‐pyrolidone/CaCl_2. The new aromatic diacid 6 and all of the PAs derived from this diacid and aromatic diamines were characterized by Fourier transform infrared, ¹H‐NMR, ¹³C‐NMR, and elemental analysis techniques. The thermal stability of the PAs was determined by thermogravimetric analysis and differential scanning calorimetry techniques under a nitrogen atmosphere, and we found that they were moderately stable. The soil biodegradability behavior of 6 and all of the PAs derived from this diacid and aromatic diamines were investigated in culture media, and we found that the synthesized diacid 6 and all of the PAs were biodegradable under a natural environmental. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

H2S oxidation by multi-wall carbon nanotubes decorated with tungsten sulfide

Tungsten sulfide catalysts decorated on single and multiwall carbon nanotubes (SWNTs & MWNTs) and activated carbon were synthesized, and XRD, ICP, SEM, TEM and ASAP analyses were employed to acquire the characteristics of each catalyst. Afterwards a gas flow containing 5,000 ppm of H₂S was passed over the catalyst in gas hour space velocity (GHSV) of 5,000 h^?1, temperature of 65 °C, steam volume percent of 20 and O₂/H₂S ratio equal to 2. The results revealed that the catalyst supported on MWNTs exhibited higher conversion amongst its counterparts. Then effects of GHSV, steam volume percent in the feed, catalyst loading and temperature were investigated on conversion of hydrogen sulfide to elemental sulfur for tungsten sulfide catalyst decorated on MWNTs.     

Iodination of stable aromatic diazonium salt using crosslinked poly (4‐vinylpyridine)‐supported iodide

In this article, a series of carboxylated acrylate copolymer latices were prepared based on the semicontinuous emulsion polymerization via the pure monomer dropwise manner with three different kinds of carboxylic monomers in presence of reactive emulsifier. The effects of the carboxylic monomers [acrylic acid, methacrylic acid, and monobutyl itaconate (MBI)] on the conversion and the properties of acrylate latices and films have been investigated. The carboxylic groups ( COOH) distribution of these three kinds of latices were investigated as well. The results show that the concentration of surface  COOH (C_S) and embedded  COOH (C_b) both increase with the increase of the amount of carboxylic monomers. It shows that MBI, the most hydrophobic of the three carboxylic monomers used, tends to be concentrated inside the particle core, and the latex particles have a narrow size distribution. The results of common stability test have demonstrated that the stability of the latex is satisfactory. Moreover, the water absorption and the acid and alkaline resistance of the latex depend on the kind of carboxylic monomer. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Bulk and surface mechanical properties of clay modified HDPE used in liner applications

High‐density polyethylene (HDPE)/clay nanocomposites were prepared by melt blending process. The HDPE was mixed with different organoclays and polyethylene‐grafted‐maleic anhydride was used as a compatibiliser. A masterbatch procedure was used to obtain final organoclays concentrations of 1, 2.5 and 5 wt%. The effects of various types of nanoclays and their concentrations on morphological, thermal and mechanical properties of nanocomposites were investigated. Surface mechanical properties such as instrumented nanohardness, modulus of elasticity and creep were also measured using a nanoindentation technique. Young's, storage and loss moduli, were found to be higher than that of the neat polymer at low loading (2.5 wt%) for clay Cloisite 15A and at higher loading (5 wt%) for clay Nanomer 1.44P. The ultimate strength and the toughness decreased slightly compared to pure HDPE. The differential scanning calorimetry analysis revealed that the peak temperature of the nanocomposites increased with increased clay content while the crystallinity decreased. Also, dynamic mechanical analysis revealed the storage and loss moduli are enhanced by addition of nanoclay. Both mechanical and thermal properties of HDPE/Nanomer 1.44P nanocomposite showed interesting trends. All properties first dropped when 1 wt% of the clay was added. Thereafter, a gradual increase or decrease then followed as the loading of Nanomer was increased. These trends were observed for all mechanical properties. The results obtained from nanoindentation tests for surface mechanical properties also showed similar trend to that of bulk measurements. Based on these measurements a nanoclay additive for a liner grade HDPE was selected. © 2011 Canadian Society for Chemical Engineering     

Influence of Temperature and Air Velocity on Drying Time and Quality Parameters of Pistachio (Pistacia vera L.)

Abstract

Drying is one of the important steps in pistachio processing. In this step kernel moisture content is decreased from 50 to less than 5% (d.b.) which will result in suitable condition for storage. Study of effective parameters in pistachio drying is important since these parameters influence drying time and kernel quality. In this research, a mono layer of pistachios was dried at three different temperatures (60, 75, and 90°C), and three levels of drying air velocity (1.5, 2, and 2.5 m/s). Changes of drying time, protein, fat and peroxide value were investigated for two common Iranian pistachio varieties Kalehghouchi and Fandoghi. Sensory tests were also used to check flavor of pistachios dried at the three temperature levels (60, 75, and 90°C). Statistical analysis of the data indicated that increasing the temperature to 90°C reduced drying time down by about 37% and caused a change in pistachio flavour. Taste tests indicated a consumer preference for pistachios dried at 75°C. If the air velocity is increased from 1.5 to 2.5 m/s, drying time reduces about 10 percent. Changes in temperature and air velocity have no significant effects on protein and fat content of pistachios, but if temperature reaches 90°C, peroxide value will increase to 0.55 meq/kg, which is still within the permissible limit for processed pistachios.     

Extended Kalman Filter frequency tracker for nonstationary harmonic signals

In this paper, we propose a frequency tracking algorithm based on an Extended Kalman Filter (EKF). We introduce a generalized state space model to estimate and track frequency of a harmonic signal embedded in broad-band noise. Such nonstationary noisy harmonic signals are characterized by time-varying frequencies and amplitudes. Developing a modified state-space model, we improve performance of EKF frequency tracker for these signals. The proposed method is also used in an adaptive algorithm to estimate noise variance which is assumed to be unknown. Simulation results reveal superiority of the proposed method compared with typical EKF, short time Fourier transform, and interpolated discrete Fourier transform.