Synthesis of chromium carbide by reduction of chromium oxide with methane

In the present work, production of the chromium carbide was investigated by reduction of chromium oxide with methane-containing gas mixture. The experiments were conducted on the chromium oxide powder and methane gas at different temperatures, times, and gas mixtures. X-ray diffraction (XRD) analysis was used to characterize the products at different stages of reduction. The morphology of the starting chromium oxide powder and Cr₃C₂ were studied by electron microscopy technique. The results showed that the minimum temperature and time for carbide formation in 30%-methane gas mixture is about 850 °C and 20 min, respectively. X-ray diffraction analysis showed that Cr₃C₂ is the only carbide product. The formation of chromium carbide in 30%-methane gas mixture was completed at 1000 °C and 60 min.     

Application of Artificial Intelligent Tools to Modeling of Glucosamine Preparation from Exoskeleton of Shrimp

The objective of this study was to forecast and optimize the glucosamine production yield from chitin (obtained from Persian Gulf shrimp) by means of genetic algorithm (GA), particle swarm optimization (PSO), and artificial neural networks (ANNs) as tools of artificial intelligence methods. Three factors (acid concentration, acid solution to chitin ratio, and reaction time) were used as the input parameters of the models investigated. According to the obtained results, the production yield of glucosamine hydrochloride depends linearly on acid concentration, acid solution to solid ratio, and time and also the cross-product of acid concentration and time and the cross-product of solids to acid solution ratio and time. The production yield significantly increased with an increase of acid concentration, acid solution ratio, and reaction time. The production yield is inversely related to the cross-product of acid concentration and time. It means that at high acid concentrations, the longer reaction times give lower production yields. The results revealed that the average percent error (PE) for prediction of production yield by GA, PSO, and ANN are 6.84, 7.11, and 5.49%, respectively. Considering the low PE, it might be concluded that these models have a good predictive power in the studied range of variables and they have the ability of generalization to unknown cases.     

Production of propionic acid in a fermented dairy beverage

A dairy beverage containing propionic acid was produced using the adjunct starter cultures with Lactobacillus acidophilus and Propionibacterium freudenreichii ssp. shermanii. The impacts of temperature (30, 35 and 40 °C) and inoculation ratio (1:2, 1:4 and 1:8) on propionic acid production and viability of micro‐organisms were studied. The incubation temperature had a significant adverse (P < 0.05) effect on the viability of P. freudenreichii and propionic acid production. Maximum amount of produced propionic acid (in 1:4–30 °C treatment) was 0.77%w/w. P. freudenreichii and L. acidophilus counts remained high (9 × 10⁶ and 1.5 × 10⁶ cfu/mL, respectively) after cold storage.     

Rheological and thermal properties of an enteral nutrition formula for nutritional support patients using a combined mixture of gelatin and maltodextrin

Enteral nutrition is a type of nutritional support that provides the necessary sources of energy and protein for patients who suffer from dysphagia, chronic disease, and loss of appetite. In this study, a gelatin-maltodextrin binary biopolymer system has been incorporated into a semi-solid formula. The I-optimal combination design approach was used to create 19 formulations, and the dynamic rheological properties, dynamic laser scattering, and zeta potential responses were evaluated over 30 days of storage at 5°C. Solid viscoelastic behavior has been approved since G′ > G″ in the frequency sweep test with no cross-over point. Maltodextrin may interfere within the gelatin network, and increasing the maltodextrin to gelatin (from 0.14 to 1) may lead to a wider linear viscoelastic (LVE) strain range (2.16%), a lower storage modulus at LVE (52%), a lower yield stress (46%), and a lower glass transition temperature (34%). The presence of maltodextrin may reduce the temperature of the sol-to-solid transformation by 48% and enhance its flexibility. In contrast, increasing the gelatin-to-maltodextrin ratio following melting at 37°C led to an increase in the cumulant mean and polydispersity index, indicating a relatively unstable system. The range of zeta potential values between −4.4 and 1.7 mV confirmed a tendency toward coagulation. Microscopic images revealed instability because of irregular or compact chains formed in the gelatin matrix by using higher amounts of maltodextrin. Finally, the best formula had the best rheological stability and was suitable for tube-feeding patients, with a gelatin-to-maltodextrin ratio of 4.35:3.64% w/w on day 17.4.     

High temperature anti‐oxidation behavior of in situ and ex situ nanostructured C/SiC/ZrB2‐SiC gradient coatings: Thermodynamical evolution,microstructural characterization,and residual stress analysis

Nanostructured C/SiC/ZrB₂–SiC oxidation protective gradient coating was prepared by a two‐step reactive melt infiltration method. In order to reduce production cost, ZrB₂ phase was synthesized by the in situ reactive that included low‐cost ZrO₂ and B₂O₃ powders as raw materials. High‐temperature oxidation behavior of coatings was evaluated by isothermal oxidation test at 1773 K in air for 10 hours. Thermodynamical behavior of the coatings at various temperatures during oxidation test and coating process was predicted by HSC Chemistry 6.0 software. Compressive residual stresses of 36.9 MPa and 41 MPa were calculated for in situ and ex situ coatings by Williamson‐Hall method. After 10 hours of isothermal oxidation at 1773K, in situ and ex situ coatings showed 12.84% and 15.69% of weight losses with oxidation rates of 1.87 × 10^?2 g cm^?3 h^?1 and 0.91 × 10^?2 g cm^?3 h^?1, respectively. These results indicated that the oxidation protection ability of the coating produced by the in situ method was very close to ex situ coating.     

Optical properties of conjunctiva, sclera, and the ciliary body and their consequences for transscleral cyclophotocoagulation: erratum

Corrections are given to the reported [Appl. Opt. 35, 3321 (1996)] units of the absorption and scattering coefficients mu (a) and mu (s), respectively. The corrections pertain to two figures, several tables, and the text describing results.     

Pricing the financial Heston–Hull–White model with arbitrary correlation factors via an adaptive FDM

This paper is concerned with the pricing procedure of one of the most challenging models known as the Heston–Hull–White partial differential equation (PDE) in option pricing, at which the model is a time-dependent 3D linear PDE including three mixed derivative terms. The model comes from the fact that the price, the volatility and the interest rate are assumed to be stochastic processes. To contribute and avoid huge discretized systems, an adaptive distribution of the nodes (viz, nonuniform nodes) is taken into account with emphasis on the hot area of the solution curve. New adaptive finite difference (FD) formulas of higher orders are constructed on these meshes. Then, a set of semi-discretized equations is attained which is tackled by a time-stepping method. Several financial tests are discussed in detail to reveal the superiority of the proposed approach.     

Perceived barriers to effective knowledge sharing in agile software teams

While the literature offers several frameworks that explain barriers to knowledge sharing within software development teams, little is known about differences in how team members perceive these barriers. Based on an in‐depth multi‐case study of four software projects, we investigate how project managers, developers, testers and user representatives think about barriers to effective knowledge sharing in agile development. Adapting comparative causal mapping, we constructed causal maps for each of the four roles and identified overlap and divergence in map constructs and causal linkages. The results indicate that despite certain similarities, the four roles differ in how they perceive and emphasize knowledge‐sharing barriers. The project managers put primary emphasis on project setting barriers, while the primary concern of developers, testers and user representatives were project communication, project organization and team capabilities barriers, respectively. Integrating the four causal maps and the agile literature, we propose a conceptual framework with seven types of knowledge‐sharing barriers and 37 specific barriers. We argue that to bridge communication gaps and create shared understanding in software teams, it is critical to take the revealed concerns of different roles into account. We conclude by discussing our findings in relation to knowledge sharing in agile teams and software teams more generally.     

Simulation and optimization of an industrial gas condensate stabilization unit to modify LPG and NGL production with minimizing CO2 emission to the environment

In the present study, a great effort was made to improve the performance of an industrial liquefied petroleum gas(LPG) and natural gas liquid(NGL) production unit in one of the major gas refinery located at Pars special economic zone in Iran. To demonstrate and obtain the optimal condition, the unit was simulated by using a steady-state flowsheet simulator, i.e. Aspen Plus, under different operational conditions. According to the simulation results,the unit was not operational under its optimal conditions due to some defects in the cooling system at top stage of the debutanizer tower(DBT) during hot and humid seasons. Additionally, the vapor pressure of produced LPG and accordingly the amount of its flaring were decreased by reducing the temperature of debutanizer tower at top stages. In the optimization section, the DBT condenser and reboiler heat duty, temperature, and pressure were regulated as adjustable parameters. The simulation results demonstrated that by applying the optimum suggestion in the hot months, the reflux stream temperature was reached about 55 ℃ which caused an efficient increment in LPG production(about 4%) with adjusting the propane component in LPG, based on the standard range as the plant criteria. Moreover, after applying modifications, about 750 t of LPG product was saved from flaring during five hot months of the year, which resulted in 360000 USD extra annual income for the company.Finally, from environmental point of view, this optimization caused to reduce 81 t of CO_2 emission to the environment. Therefore, the current investigation must be introduced as a friendly environmentally process.