Modelling of a post-combustion carbon dioxide capture absorber using potassium carbonate solvent in Aspen Custom Modeller

The process models for an equilibrium CO₂ absorber and a rate based CO₂ absorber using potassium carbonate (K₂CO₃) solvents were developed in Aspen Custom Modeller (ACM) to remove CO₂ from a flue gas. The process model utilised the Electrolyte Non-Random Two Liquid (ENRTL) thermodynamic model and various packing correlations. The results from the ACM equilibrium model shows good agreement with an inbuilt Aspen Plus® model when using the same input conditions. By further introducing a Murphree efficiency which is related to mass transfer and packing hydraulics, the equilibrium model can validate the experimental results from a pilot plant within a deviation of 10%. A more rigorous rate based model included mass and energy flux across the interface and the enhancement effect resulting from chemical reactions. The rate based model was validated using experimental data from pilot plants and was shown to predict the results to within 10%. A parametric sensitivity analysis showed that inlet flue gas flowrate and K₂CO₃ concentration in the lean solvent has significant impact on CO₂ recovery. Although both models can provide reasonable predictions based on pilot plant results, the rate based model is more advanced as it can explain mass and heat transfer, transport phenomena and chemical reactions occurring inside the absorber without introducing an empirical Murphree efficiency.     

Temperature/Humidity sensitivity of sustained-release formulations containing Kollidon SR

The effects of temperature and humidity on tablets containing Kollidon® SR have been evaluated using diphenhydramine HCl as a model drug. Exposure of tablets to ICH accelerated stability condition (40°C/75%RH) in an open dish resulted in rapid increases in tablet hardness, accompanied by step-wise decreases in dissolution rate. Such a change can be observed as fast as an hour upon exposure. The tablet matrix appears to rapidly absorb atmospheric moisture, as demonstrated by tablet weight gain and moisture adsorption isotherms. Exposure to 25°C/60%RH similarly resulted in increases in tablet hardness, although with minimal impact on dissolution. Potential implications of such rapid moisture uptake during aqueous film-coating were further evaluated by spraying either water or an Opadry solution in a coating pan. Exposure of Kollidon SR tablets to the aqueous coating process indeed resulted in noticeable changes in both hardness and dissolution. Application of the Opadry solution appears to affect tablet behavior to a lesser degree, compared to water, most likely due to protection via formed barrier film. Attention needs to be paid to the extreme sensitivity of Kollidon SR matrix tablets to temperature and moisture during product development.     

A wideband circularly polarized slot antenna with antipodal strips for WLAN and C‐band applications

A single‐fed circularly polarized square shaped wide slot antenna with modified ground plane and microstrip feed has been presented. The field in the slot is perturbed by introducing an antipodal strips section attached with a microstrip line to produce circular polarization in a wide band of frequencies. The antipodal strip section consists of a group of four strips of unequal length and separation. The presence of asymmetric perturbations in the slot is mainly responsible for exciting two orthogonal modes in the slot having equal magnitude and 90° phase difference which results in circular polarization. A wide bandwidth of 3.3 GHz (4.4 GHz‐7.7 GHz) has been achieved for an axial ratio value AR < 3 dB with the minimum axial ratio value being 0.3 dB. The impedance bandwidth for |S₁₁| < ?10 dB ranges from 4.3 GHz to 8 GHz, and therefore covers most of the C‐band communication systems. The antenna exhibits stable radiation patterns throughout the circular polarization bandwidth with a gain around 6 dBi in entire operational bandwidth. A prototype of antenna was fabricated and measured. The antenna has a planar size 0.40λ₀ × 0.40λ₀ and thickness of 0.02λ₀ where λ₀ is the wavelength in free space at the lowest frequency. With its compact size and low profile, the antenna is a favorable choice for WLAN (5.15‐5.85 GHz) and a wide variety of C‐band wireless applications.     

PAVM: a framework for policy‐aware virtual machine management

The problem of efficient placement of virtual machines (VMs) in cloud computing infrastructure is well studied in the literature. VM placement decision involves selecting a physical machine in the data center to host a specific VM. This decision could play a pivotal role in yielding high efficiency for both the cloud and its users. Also, reallocation of VMs could be performed through migrations to achieve goals like higher server consolidation or power saving. VM placement and reallocation decisions may consider affinities such as memory sharing, CPU processing, disk sharing, and network bandwidth requirements between VMs defined in multiple dimensions. Considering the NP‐hard complexity associated with computing an optimal solution for this VM placement decision problem, existing research employs heuristic‐based techniques to compute an efficient solution. However, most of these approaches are restricted to only a single attribute at a time. That is, a given technique of using heuristics to compute VM placement considers only a single attribute, while completely ignoring the impact of other dimensions of placing VMs. While this approach may improve the efficiency with respect to the affinity attribute in consideration, it may yield degraded performance with respect to other affinities. In addition, the criteria for determining VM‐placement efficiency may vary for different applications. Hence, the overall goal of achieving VM placement efficiency becomes difficult and challenging. We are motivated by this challenging problem of efficient VM placement and propose policy‐aware virtual machine management (PAVM), a generic framework that can be used for efficient VM management in a cloud computing platform based on the service provider‐defined policies to achieve the desired system‐wide goals. This involves efficient means to profile different VM affinities and to use profiled information effectively by intelligent and efficient VM migrations at run time considering multiple attributes at a time. By conducting extensive evaluation through simulation and real experiments that involve VM affinities on the basis of network and memory, we confirmed that the PAVM architecture is capable of improving the efficiency of a cloud system. We elaborate the architecture of a PAVM system, describe its implementation, and present details of our experiments. Copyright © 2016 John Wiley & Sons, Ltd.     

Changes in physicochemical and organoleptic properties of traditional Iranian cheese Lighvan during ripening

Lighvan cheese was studied to determine the physicochemical and biochemical changes over 90 days of ripening in brine. Acidity, pH, dry matter, fat values, lipolysis level, water‐soluble nitrogen (WSN), total nitrogen (TN), ripening index (RI), trichloroacetic acid‐soluble nitrogen (TCA‐SN) and organoleptic assessments were analysed. Dry matter and fat values decreased during ripening. Lipolysis level, RI, TCA‐SN values and salt content increased continuously until the end of the ripening period, but total nitrogen decreased throughout a 90‐day storage period. The ripening stage was the main factor affecting the cheese’s sensory properties.     

ULTRAFILTRATION METHOD OF STUDYING BINDING OF LIGANDS TO MACROMOLECULES

The principles and procedures for studying binding of low molecular weight ligands to macromolecules using ultrafiltration are reviewed. Ultrafiltration methods are much faster and theoretically equivalent to equilibrium dialysis, which is the most commonly used subtractive method. An entire binding isotherm and the effect of free species concentration on the binding equilibrium can be determined with a single run of a few hours duration. The calculations and data analysis, which are normally quite complicated, can be easily performed using popular spread-sheet programs such as Lotus 1-2-3® on a personal computer. The experimental protocol, the control experiments to account for nonspecific binding and the calculation procedures are given in detail using a case study of a typical ligand-protein interaction.