Optimal operation of heat exchanger networks through energy flow redistribution

This article presents a novel energy flow redistribution methodology to achieve optimal operation of heat exchanger networks. The proposed method aims to manipulate the propagation path of a disturbance through the network to reduce its impact on utility consumption. Specifically, an optimization problem is formulated to generate new duty targets for heat exchangers of the network when a disturbance is encountered. Subsequently, a feedback control system is designed to track these targets by manipulating bypasses around the process heat exchangers. The effectiveness of the proposed framework is illustrated with the help of three benchmark examples. The proposed approach can handle disturbances in inlet as well as target temperature, inlet flow and heat transfer coefficient of individual heat exchangers.     

Tuning the Structural and Optical Properties of SILAR-Deposited Cu_2O Films Through Zn Doping

Undoped and Zn-doped Cu2O films were deposited onto glass substrates using successive ionic layer adsorption and reaction(SILAR) technique with different Zn doping levels(0, 1, 2, 3, 5 and 10 wt%). The structural,optical, and surface morphological studies were carried out and reported. The structural study revealed that the crystalline quality is gradually enhanced up to 5 wt% of Zn doping level, and then quality begins to degrade for further increase in doping level. Moreover, the preferential orientation changes from(111) to(110) for the highest doping level were examined. Optical study shows that the transmittance(65%) and optical band gap values are maximum(2.41 e V) when the Zn doping level is at 5 wt%. The photoluminescence study confirms the presence of various defects in the Cu2O matrix and also the variation obtained in the optical band gap from the transmittance data. SEM images revealed the annealinginduced changes in the surface morphology of the films.     

Compact linear tapered slot antenna for UWB applications

A novel ultra-wideband (UWB) antenna consisting of a linear tapered slot in the ground plane and a microstrip to slotline transition is investigated. The antenna possesses a wide bandwidth from 2.95?14 GHz for |S₁₁| < - dB and shows stable radiation patterns with an average gain of 3 dBi throughout the band. Measured group delay and transmission characteristics indicate that the antenna has good pulse handling capabilities.     

New compact microstrip antenna

A new microstrip antenna geometry with considerable reduction in size, with similar radiation characteristics to those of an equivalent rectangular patch antenna is proposed. A relationship has been suggested for finding out the resonant frequency of the new geometry, and its validity has been established by the experimental results. Without increasing the aperture area, this geometry also offers a facility for considerably reducing the resonant frequency compared to conventional patches     

Synthesis,spectroscopic characterization,and thermal decomposition kinetics of some lanthanide（Ⅲ） nitrate complexes of 2-（N-o-hydroxyacetophenone） amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene

Complexes of La（Ⅲ）, Ce（Ⅲ）, Pr（Ⅲ）, Nd（Ⅲ）, Sm（Ⅲ）, Eu（Ⅲ）, Gd（Ⅲ）, Dy（Ⅲ）, Yb（Ⅲ）, and Lu0ID with 2-（N-o- hydroxyacetophenone）amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene （HAAT） formed by the condensation of o-hydroxyacetophenone and 2-amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene were synthesized and characterized on the basis of elemental analyses, molar conductance measurements, magnetic susceptibility data, UV-Visible, IR, and NMR spectral studies. The spectral data revealed that the ligand acted as a neutral tridentate coordinating to the metal ion through ONO donor sequence. A coordination number nine was proposed for the complexes. Thermal decomposition studies of the ligand and lanthanum（Ⅲ） complex were carried out and kinetic parameters were calculated using Coats-Redfem equation. The decomposition reactions followed random nucleation mechanism with one nucleus on each particle.     

Highly compressible ceramic/polymer aerogel-based piezoelectric nanogenerators with enhanced mechanical energy harvesting property

Ceramic piezoelectric materials have orders of magnitude higher piezoelectric coefficients compared to polymers. However, their brittleness precludes imposition of large strains in mechanical energy harvesting applications. We report here that ice templating affords low bulk modulus lead-free aerogel piezoelectric nanogenerators (PENG) with unprecedented combination of flexibility and high piezoelectric response (voltage and power density). A modified ice templating protocol was used to fabricate piezoelectric nanocomposites of surface modified BaTiO₃ (BTO) nanoparticles in crosslinked polyethylene imine. This protocol allowed incorporating a significantly high fraction of BTO particles (up to 83 wt %) in the aerogel, while retaining remarkably high compressibility and elastic recovery up to 80% strain. The output voltage, at an applied compressive force of 20 N (100 kPa), increased with BTO loading and a maximum output voltage of 11.6 V and power density of 7.22 μW/cm² (49.79 μW/cm³) was obtained for PENG aerogels containing 83 wt% BTO, which is orders of magnitude higher than previously reported values for foam-based piezoelectric energy harvesters. The BTO/PEI PENGs also showed cyclic stability over 900 cycles of deformation. PENGs with higher porosity showed better elastic recovery and piezoelectric properties than lower porosity and higher BTO content aerogels. To the best of our knowledge, this is the first report to demonstrate the piezoelectric properties of high ceramic content aerogels having very high compressibility and elastic recovery.     

Effect of annealing temperature on the morphology and antibacterial activity of Mg-doped zinc oxide nanorods

Herein, magnesium-doped zinc oxide nanorods (MgZnO NRs) were synthesized by the co-precipitation method and annealed at different temperatures in the range of 100–500?°C. The increase in the annealing temperature was found to influence both chemical and morphological structures of the MgZnO NRs: Ultraviolet–visible diffuse reflectance spectroscopy showed an increase in band gap with increase in the annealing temperature. Fourier-transform infrared spectra showed that two characteristic peaks at 487?cm^?1 and 442?cm^?1 corresponding to a weak Zn–O stretching initially decreased and then disappeared with increase in the annealing temperature. Moreover, the MgZnO NRs annealed at 100?°C had large crystallite size, high aspect ratio, and narrow edges. Remarkably, the MgZnO NRs annealed at 100?°C exhibited the highest antibacterial activity against both S. aureus and E. coli strains, attributed to the high aspect ratio and diffusion ability of the Zn²⁺ ions and large surface charge, crystallite size, and surface area. The MgZnO NRs annealed at the relatively low temperature of 100?°C could be easily produced commercially, in large quantities, and effectively used to prevent the growth of foodborne microbes in food packaging applications.     

Role of immune cells and inflammatory cytokines in regulation of fibrosis around silicone expander implants

This study aimed to investigate the progress of wound healing around silicone expander with particular emphasis on fibroblasts, myofibroblasts and collagen in the repair phase. Semi-quantitative evaluation of inflammatory cells and their cytokines, fibroblasts and myofibroblasts at the tissue–material interface was carried out. Commercially available silicone expander was implanted in gluteus muscle of young female Wistar rats for 3, 7, 14, 30, 90 and 180 days. Ultra high molecular weight polyethylene served as control. The cellular response was studied by immunohistochemistry and Transmission Electron Microscopy. A thick collagenous fibrous capsule was observed around the silicone expander at 180 days, with persistent myofibroblasts, lymphocytes and macrophages as compared to the thin fibrous encapsulation around the UHMWPE implants. The regulatory role of cytokines and immune cells in myofibroblast persistence in tissue–implant interface around silicone expander has been extensively studied. Results of this study indicate the need to elucidate the signaling molecules in the transition of fibroblast to myofibroblast around silicone expander implants.     

A flexible microwave absorber based on nickel ferrite nanocomposite

Flexible magnetic composite materials were prepared by incorporating precharacterized nickel ferrite nanoparticles in a natural rubber matrix. The complex dielectric permittivity and magnetic permeability of the composites were measured at different microwave frequencies using the cavity perturbation technique. A steady increase in dielectric permittivity was observed with increase in filler concentration. Maxwell-Garnett mixture equations were employed to model the effective permittivity and permeability of the composite. Reflection loss was estimated by employing the model of single layer absorber backed with a perfect conductor. Reflection loss minima of ?5.9 dB at 3.2 GHz for 12 mm thick rubber ferrite composite sheet is obtained in the S-band while a loss up to ?16 dB could be achieved at 9.5 GHz in the X-band.