Reduced-order controller synthesis with regional pole constraint

A reduced order output feedback controller is designed for a linear time invariant system, which guarantees that the closed-loop poles are placed within some pre-specified stability region in the complex plane. A convex approximation of the non-convex constraints is used to pose a sequence of semi-definite programs, which provide the lowest order proper controller satisfying the approximate constraints. The proposed method is demonstrated on two practical controller design applications.     

Formulation of Rosuvastatin-Loaded Self-Nanoemulsifying Drug Delivery System Using Box-Behnken Design

The objectives of present study were to understand the effect of formulation variables of self-nanoemulsifying drug delivery system (SNEDDS) of rosuvastatin (RSV). Box-Behnken design in conjunction with desirability function was used to evaluate the main effect, interaction effect and quadratic effect of independent formulation variables that included amounts of Acconon 200 E6, Cremophor RH40, and Lipoxol 300. For a better understanding of the selected variables for the optimal performance of RSV SNEDDS, the models were presented as three-dimensional response surface graphs. A fresh batch of optimized formulations and were prepared with optimized levels of the independent variables to yield dependent variables (Y1–Y6) values that were remarkably close to the predicted values. Drug excipient compatibility studies using the Fourier transform infrared spectroscopy, differential scanning calorimeter and x-ray diffraction indicated the absence of any incompatibility between RSV and selected excipients. The transmission electron microscopy of selected optimized SNEDDS of RSV showed the spherical shape of globules with no signs of coalescence and precipitation of RSV. The study demonstrates the use of Box-Behnken design for the preparation of RSV SNEDDS. The desirable goals can be obtained by systematic formulation approach in minimum possible time.     

Numerical Analysis of a Vortex Tube: A Review

Ranque–Hilsch vortex tube is a simple devise with no moving parts which could generate cold and hot air/gas streams simultaneously with compressed air/gas as a working fluid. The energy and flow separation in a vortex tube is highly depends on factors like nozzle shape, nozzle number, diameter and length of the vortex tube, inlet pressure, control valve, diaphragm hole size and cold mass fraction. As the energy separation and flow patterns in a vortex tube are highly complex and were not explained successfully by any researcher, a computational study of vortex tube flow and energy separation will give a better understanding about the physics and mechanism involved. Many researchers conducted computational fluid dynamic analysis of the vortex to have a deep insight about the process of flow separation. In this paper computational analysis of vortex by many researchers were presented along with the results obtained and suggestions to improve the performance of the vortex tube. Researchers considered Turbulence models which predict the performance precisely were discussed in the present paper. Researchers considered turbulence models like LES, k–ε, k–ω and RMS to predict the energy separation in vortex tube. Some researchers considered artificial neural networks (ANN) and Taguchi methods for their analysis. Comparison of the predictions with simulation results were also presented to give a clear idea for the reader about the CFD models prediction capabilities.     

Homogeneous Charge Compression Ignition (HCCI) Engines: A Review

The homogeneous charge compression ignition (HCCI) combustion is considered to be the principally promising future IC engine concepts. HCCI is a concept of hybrid combustion, between the Otto engine and Diesel engine. HCCI is however not a modern finding. Already in the early twentieth century hot bulb engines operated with an HCCI-like combustion. They were superior in terms of brake efficiency compared with the contemporary gasoline engines and at the same level as the diesel engines. High engine efficiencies and ultra low NO emissions and low particulates are the benefits of HCCI engines. Volumetric auto ignited combustion of the compressed lean air–fuel mixture is attributed to these benefits. There are few drawbacks also were there in HCCI engines like, low specific output, narrow operating range, lack control over the ignition process, long start up time and high emissions like CO and UHC emissions. The CO and UHC emissions can be after treated using catalytic converters. In this study a literature review on HCCI engine has been performed and the parameters affecting the HCCI combustion phasing, performance and emissions were discussed. Strategies to widen the peak load bearing capacity of HCCI engine, reducing the emissions like NOx, CO and UHC, easy auto-ignition were discussed in the present study.     

Cell proliferation,viability, and in vitro differentiation of equine mesenchymal stem cells seeded on bacterial cellulose hydrogel scaffolds

The culture of multipotent mesenchymal stem cells on natural biopolymers holds great promise for treatments of connective tissue disorders such as osteoarthritis. The safety and performance of such therapies relies on the systematic in vitro evaluation of the developed stem cell-biomaterial constructs prior to in vivo implantation. This study evaluates bacterial cellulose (BC), a biocompatible natural polymer, as a scaffold for equine-derived bone marrow mesenchymal stem cells (EqMSCs) for application in bone and cartilage tissue engineering. An equine model was chosen due to similarities in size, load and types of joint injuries suffered by horses and humans. Lyophilized and critical point dried BC hydrogel scaffolds were characterized using scanning electron microscopy (SEM) to confirm nanostructure morphology which demonstrated that critical point drying induces fibre bundling unlike lyophilisation. EqMSCs positively expressed the undifferentiated pluripotent mesenchymal stem cell surface markers CD44 and CD90. The BC scaffolds were shown to be cytocompatible, supporting cellular adhesion and proliferation, and allowed for osteogenic and chondrogenic differentiation of EqMSCs. The cells seeded on the BC hydrogel were shown to be viable and metabolically active. These findings demonstrate that the combination of a BC hydrogel and EqMSCs are promising constructs for musculoskeletal tissue engineering applications.     

High-frequency rapid B-mode ultrasound imaging for real-time monitoring of lesion formation and gas body activity during high-intensity focused ultrasound ablation

The goal of this study was to examine the ability of high-frame-rate, high-resolution imaging to monitor tissue necrosis and gas-body activities formed during high-intensity focused ultrasound (HIFU) application. Ex vivo porcine cardiac tissue specimens (n = 24) were treated with HIFU exposure (4.33 MHz, 77 to 130 Hz pulse repetition frequency (PRF), 25 to 50% duty cycle, 0.2 to 1 s, 2600 W/cm(2)). RF data from Bmode ultrasound imaging were obtained before, during, and after HIFU exposure at a frame rate ranging from 77 to 130 Hz using an ultrasound imaging system with a center frequency of 55 MHz. The time history of changes in the integrated backscatter (IBS), calibrated spectral parameters, and echo-decorrelation parameters of the RF data were assessed for lesion identification by comparison against gross sections. Temporal maximum IBS with +12 dB threshold achieved the best identification with a receiver-operating characteristic (ROC) curve area of 0.96. Frame-to-frame echo decorrelation identified and tracked transient gas-body activities. Macroscopic (millimetersized) cavities formed when the estimated initial expansion rate of gas bodies (rate of expansion in lateral-to-beam direction) crossed 0.8 mm/s. Together, these assessments provide a method for monitoring spatiotemporal evolution of lesion and gas-body activity and for predicting macroscopic cavity formation.     

Improvement in performances of dye-sensitized solar cell with SiO2-coated TiO2 photoelectrode

The pure TiO2 and the nano-porous SiO2-coated TiO2 (STO) films were deposited on the FTO substrates by spray technique for the application of dye-sensitized solar cells (DSSCs). XRD pattern shows the pure TiO2 and STO films exhibits the same structure. We found that there is no much difference in dye absorption between the STO and the pure TiO2 films. The electrochemical impedance spectra reveal that insulating nature of the porous SiO2 increases surface resistance of the TiO2 film and supresses back transfer of the photogenerated electrons to the electrolyte. The field-emission scanning electron microscopy (FE-SEM) and energy dispersion X-ray spectroscopy (EDS) reveal that the surface morphology and the existence of SiO2 layer on the surface of the TiO2 films, respectively. The photoelectrochemical results show that the short-circuit photocurrent (J(SC)) increased from 16.73 mA cm(-2) to 18.31 mA cm(-2) and the open-circuit voltage (V(OC)) value changed from 0.71 V to 0.74 V for the STO films. The efficiency of cell has been greatly improved from 8.25 to 9.3%.     

Isolation improvement in dual-band astroid shaped MIMO DRA for LTE and ISM applications

This article presents the design of a novel astroid shaped dielectric resonator antenna (DRA) constructed from PTFE Teflon material with a dielectric constant of ε_r = 2.1 and a loss tangent tan δ = 0.0002 on an FR4 grounded substrate for LTE and ISM band applications. Inverted Omega ?-shaped feed along with asymmetric E-shaped dual metallic strips in the partial ground is used to obtain dual-band characteristics. A light weight, cost-effective plastic material is used to design the antenna. An isolation of 26.5 dB and 24.6 dB is achieved in the two frequency bands 1.8 GHz and 2.4 GHz respectively by modifying the ground plane. Metallic strips and stubs in the ground are used to enhance the isolation in the proposed MIMO system. The obtained impedance bandwidths in both the bands are 14.5% and 13%. The performance of the MIMO system is characterized by the envelope correlation coefficient and diversity gain. Good agreement is found between simulated and measured results.     

Use of essential oils and phytochemicals against the mycotoxins producing fungi for shelf-life enhancement and food preservation

Mycotoxin-producing fungi are a significant source of crop and food contamination, posing a significant threat to global food safety and security. Essential oils, plant extracts and phytochemicals have emerged as green preservatives to extend the shelf-life of foods due to their unique antimicrobial properties. Unlike conventional synthetic preservatives, they are a sustainable and safe way to preserve food with no or little harmful effects on the environment. Use of nanoformulations containing essential oils and phytochemicals offer enormous potential as a mitigation strategy to lower mycotoxin contamination incidences in food and crop with enhanced release behaviour to efficiently transport them to the target location for a rapid reaction without much impact from environmental variables. Hence, this review overviews various essential oils and phytochemicals utilized through nanoformulations to control the mycotoxigenic fungi, probable mechanism of actions involved as well as emerging mycotoxins and associated safety concerns to ensure food sustainability.     

Ambient Protection of Few‐Layer Black Phosphorus via Sequestration of Reactive Oxygen Species

Few‐layer black phosphorous (BP) has emerged as a promising candidate for next‐generation nanophotonic and nanoelectronic devices. However, rapid ambient degradation of mechanically exfoliated BP poses challenges in its practical deployment in scalable devices. To date, the strategies employed to protect BP have relied upon preventing its exposure to atmospheric conditions. Here, an approach that allows this sensitive material to remain stable without requiring its isolation from the ambient environment is reported. The method draws inspiration from the unique ability of biological systems to avoid photo‐oxidative damage caused by reactive oxygen species. Since BP undergoes similar photo‐oxidative degradation, imidazolium‐based ionic liquids are employed as quenchers of these damaging species on the BP surface. This chemical sequestration strategy allows BP to remain stable for over 13 weeks, while retaining its key electronic characteristics. This study opens opportunities to practically implement BP and other environmentally sensitive 2D materials for electronic applications.