Low cost urban housing — thermal efficiency

Structural Engineer, Mrs Rahooja, is a Principal Scientific Officer with the National Building Research Institute, Karachi and with her colleages, Mr Muzaffar Hasan and Mr Tanveer Saleem, describes their study into the thermal efficiency of low cost housing in the warm, humid climate of Karachi, with mean outdoor summer temperatures of 35°C.     

Hydrogen recovery from ammonia purge gas by a membrane separator: A simulation study

In this study, a two‐dimensional mathematical model is proposed for modeling the hollow fiber membrane (HFM) separators for hydrogen (H₂) recovery unit implemented in the Razi Petrochemical Company (Imam Khomeini Port, Iran) to capture hydrogen from ammonia (NH₃) purge gas. In this regard, computational fluid dynamics is applied to solve the equations of momentum and mass transfer in the laminar flow conditions. Axial and radial diffusion for mass transfer inside the membrane fibers and axial diffusion within the shell side of separator were considered. The distributions of concentration, velocity, and mass transfer fluxes were achieved by the model. As the new insights, the effects of feed flow rate and feed gas concentration on mass transfer of H₂ were investigated. Moreover, fluid velocity profile and H₂ fluxes in the tube (fiber), membrane, and shell sides of the HFM separator were studied. The results of simulation were compared with the industrial data and showed that the present developed model has excellent agreement with the experimental data with a low mean deviation value of 3.5%.     

Conifer-Derived Metallic Nanoparticles: Green Synthesis and Biological Applications

The use of metallic nanoparticles in engineering and biomedicine disciplines has gained considerable attention. Scientists are exploring new synthesis protocols of these substances considering their small size and lucrative antimicrobial potential. Among the most economical techniques of synthesis of metallic nanoparticles via chemical routes, which includes the use of chemicals as metal reducing agents, is considered to generate nanoparticles possessing toxicity and biological risk. This limitation of chemically synthesized nanoparticles has engendered the exploration for the ecofriendly synthesis process. Biological or green synthesis approaches have emerged as an effective solution to address the limitations of conventionally synthesized nanoparticles. Nanoparticles synthesized via biological entities obtained from plant extracts exhibit superior effect in comparison to chemical methods. Recently, conifer extracts have been found to be effective in synthesizing metallic nanoparticles through a highly regulated process. The current review highlights the importance of conifers and its extracts in synthesis of metallic nanoparticles. It also discusses the different applications of the conifer extract mediated metallic nanoparticles.     

Effects of sodium chloride on the degradation of hexoses and the hydrolysis of sucrose in subcritical water

The effects of sodium chloride on the degradation of hexoses at 220 °C and the hydrolysis of sucrose at 170 °C in subcritical water were examined. Sodium chloride accelerated the degradation at 220 °C of any hexose, especially the degradation of galactose which significantly accelerated depending on the sodium chloride concentration. On the other hand, the hydrolysis of sucrose at 170 °C was not affected by sodium chloride.     

A model for the prediction of structure-property relations in cross-linked polymers

A model is presented that predicts the nonlinear mechanical properties of a highly cross-linked thermosetting polymer as a function of temperature, strain, and strain rate. The model is a significant extension of Group Interaction Modelling (GIM) that was originally developed for linear amorphous thermoplastics. Fundamental energy contributions within and between characteristic mer units are used to model the dynamic mechanical spectrum of the polymer. This enables the model to be applied to the prediction of the full stress-strain profile through yield. Tetraglycidyl 4,4′-diaminodiphenylmethane cured with 4,4′-diaminodiphenylsulphone is used as a detailed example for validation and the model predictions are in good agreement with experiment.     

Fuel management optimization based on power profile by Cellular Automata

Fuel management in PWR nuclear reactors is comprised of a collection of principles and practices required for the planning, scheduling, refueling, and safe operation of nuclear power plants to minimize the total plant and system energy costs to the extent possible. Despite remarkable advancements in optimization procedures, inherent complexities in nuclear reactor structure and strong inter-dependency among the fundamental parameters of the core make it necessary to evaluate the most efficient arrangement of the core. Several patterns have been presented so far to determine the best configuration of fuels in the reactor core by emphasis on minimizing the local power peaking factor (P_q).     

Effect of uni-univalent salts on the mass transfer of isobutyric acid between cumene and water

Effect of NaCl and KCl salts on single drop hydrodynamic and mass transfer of isobutyric acid from aqueous to cumene phases was studied. Drop size, extraction fraction and mass transfer coefficient were decreased as a consequence of isobutyrate ion adsorption which is quite obvious from interfacial tension variations. Both the used salts caused similar trends in variations; however, KCl was to some extent more efficient. These were while solute equilibrium distribution coefficient was shifted toward higher values. Using the combined mass transfer model, accompanied with a derived empirical correlation exhibited a nice agreement, with relative deviation values mostly within ±13.6%.