EFFECT OF ARTIFICIAL ROUGHNESS ON HEAT TRANSFER AND FRICTION CHARACTERSTICS OF DOUBLE PASS SOLAR AIR HEATER

Double pass solar air heater (DPSAH) consisted of rectangular duct provided with artificial roughness on both side of the absorber plate has been experimentally investigated. Circular ribs of aluminium wire is used to provide roughness to increase heat transfer coefficient between absorber plate and air. Ribs are attached to absorber plate at four different angle of attackbetween 30° to 75° . Experiment is carried out over the range of Reynolds Number from 4900 to 12000, and relative roughness height (e/Dh) varies from 0.022 to 0.044. Experimentally different values of Nusselt number(Nu). and friction factor(fr) have been determined for various parameters. The enhance-ment in heat transfer and increment in the friction factor values of Nusselt number and friction factor have also been compared with the smooth one

THERMOHYDRAULIC PERFORMANCE OF AN EQUILATERAL TRIANGULAR DUCT WITH ARTIFICIAL ROUGHNESS USED IN SOLAR AIR HEATER

The thermohydraulic performance of artificially roughened equilateral triangular solar air heater duct has been investigated and the comparision of the same has been presented with that of a conventional smooth solar air heater duct. The range of relative roughness height (e/Dh) is from 0.021 to 0.043, value of angle of attack (α) and relative roughness pitch (p/e) has been 30° and 8 respectively. The range of Reynolds number is from 5600 to 28000 and aspect ratio of the duct is 1.15. It has been found that the thermohydraulic performance of artificially roughened triangular solar air heater duct is always more than that of the smooth absorber plate in the range of Reynolds number investigated

Modern Control Approaches for a Wind Energy Conversion System based on a Permanent Magnet Synchronous Generator (PMSG) Fed by a Matrix Converter

This “paper proposes a super-twisting adaptive Control Approaches for a Wind Energy Conversion System Based on a Permanent Magnet Synchronous Generator (PMSG) Fed by a matrix sliding mode for tracking the maximum power point of wind energy conversion systems using permanent magnet synchronous generators (PMSGs). As the adaptive control algorithm employed retains the robustness properties of classical wind energy conversion system control methods when perturbations and parameter uncertainties are present, it can be considered an effective solution; at the same time, it reduces chattering by adjusting gain and generating second-order adaptive control methods. The Egyptian power system (EPS), a three-zone interconnected microgrid (MG), and a single machine linked to the grid are only a few examples of the power systems for which this article introduces the concept of direct adaptive control (SMIB).The goal of our work is to maximize the captured power by solving a multi-input multi-output tracking control problem. In the presence of variations in stator resistance, stator inductance, and magnetic flux linkage, simulation results are presented using real wind speed data and discussed for the proposed controller and four other sliding mode control solutions for the same problem. The proposed controller achieves the best trade-off between tracking performance and chattering reduction among the five considered solutions: compared to a standard sliding mode control algorithm, it reduces chattering by two to five orders of magnitude, and steadystate errors on PMSG rotor velocity by one order of magnitude”. The purpose of this article is to examine wind turbine control system techniques and controller trends related to permanent magnet synchronous generators. The article presents an overview of the most popular control strategies for PMSG wind power conversion systems. There are several kinds of nonlinear sliding modes, such as direct power, backstepping, and predictive currents. To determine the performance of each control under variable wind conditions, a description of each control is presented, followed by a simulation performed in MATLAB /Simulink. This simulation evaluates the performance of each control in terms of reference tracking, response times, stability, and signal quality. Finally, this work was concluded with a comparison of the four controls to gain a better understanding of their effects. “Moreover, it reduces the above-mentioned steady-state error by four orders of magnitude compared to a previously-proposed linear quadratic regulator based integral sliding mode control law.  A dynamic model is simulated under both variable step and random wind speeds using the DEV-C++ software, and the results are plotted using MATLAB. The obtained results demonstrate the robustness of the proposed controller in spite of the presence of different uncertainties when compared to the classical direct torque control technique

Synthesis and Pharmacological Evaluation of Nitrogen Oxide Releasing Prodrugs

The main goals of this research were to synthesize nitrogen oxide releasing diazeniumdiolates and their prodrugs and to evaluate their pharmacological effects. The different projects and their results are described below. i. Comparison of HNO and NO donating properties of cyclic amine diazeniumdiolates Diazeniumdiolates are an attractive class of donor compounds as they can be tuned to release NO or both NO and HNO depending upon the amine backbone. Isopropylamine (IPA/NO) and cyclohexylamine (CHA/NO) diazeniumdiolates are currently the only examples of primary amine based diazeniumdiolates. A series of structurally related cyclic amine based diazeniumdiolates were synthesized and characterized. An acetoxymethyl derivative was also synthesized to facilitate cellular uptake and to achieve higher HNO levels in cells. ii. Nitrogen oxide releasing diazeiumdiolate based adducts of N-des-methyl-tamoxifen Nitrogen oxide (NO/HNO) donating diazeniumdiolate adducts of N-desmethyltamoxifen (a key metabolite of the breast cancer drug tamoxifen) were synthesized. DEA/NO-AcOM, an NO donor was also synthesized to monitor the effect of NO on breast cancer cell survival. Derivatives of N-desmethyltamoxifen were found to be effective towards estrogen receptor positive (ER+) cells only. DEA/NO-AcOM was found to be cytotoxic towards estrogen-dependent and independent cell lines, in combination with tamoxifen, or by itself. iii. Synthesis and characterization of nitrogen oxide adducts with non-steroidal anti-inflammatory drugs (NSAIDs) Our group has shown HNO releasing diazeniumdiolate derivatized aspirin to be comparably effective in preventing gastric ulceration to NO-releasing diazeniumdiolate based aspirin analogues. Series of such NSAID adducts were further extended by synthesizing such derivatives of indomethacin and niflumic acid. NO/HNO releasing analogues of aspirin and indomethacin were cytotoxic towards two different breast cancer cell lines, irrespective of estrogen dependence.iv. Chlorambucil analogue of PABA/NOChlorambucil, an alkylating agent is used in leukemia treatment. Tumor cells resistant to alkylating agents often have increased glutathione levels and increased activity of glutathione-S-transferase (GST). PABA/NO is an NO donor with a promising anticancer profile. The chlorambucil analogue of PABA/NO was synthesized to utilize GST for releasing NO and to potentially overcome cellular resistance.Release after 01-Aug-201

A Facile and Efficient Approach for the Production of Reversible Disulfide Cross-linked Micelles.

Nanomedicine is an emerging form of therapy that harnesses the unique properties of particles that are nanometers in scale for biomedical application. Improving drug delivery to maximize therapeutic outcomes and to reduce drug-associated side effects are some of the cornerstones of present-day nanomedicine. Nanoparticles in particular have found a wide application in cancer treatment. Nanoparticles that offer a high degree of flexibility in design, application, and production based on the tumor microenvironment are projected to be more effective with rapid translation into clinical practice. The polymeric micellar nano-carrier is a popular choice for drug delivery applications. In this article, we describe a simple and effective protocol for synthesizing drug-loaded, disulfide cross-linked micelles based on the self-assembly of a well-defined amphiphilic linear-dendritic copolymer (telodendrimer, TD). TD is composed of polyethylene glycol (PEG) as the hydrophilic segment and a thiolated cholic acid cluster as the core-forming hydrophobic moiety attached stepwise to an amine-terminated PEG using solution-based peptide chemistry. Chemotherapy drugs, such as paclitaxel (PTX), can be loaded using a standard solvent evaporation method. The O2-mediated oxidation was previously utilized to form intra-micellar disulfide cross-links from free thiol groups on the TDs. However, the reaction was slow and not feasible for large-scale production. Recently, an H2O2-mediated oxidation method was explored as a more feasible and efficient approach, and it was 96 times faster than the previously reported method. Using this approach, 50 g of PTX-loaded, disulfide cross-linked nanoparticles have been successfully produced with narrow particle size distribution and high drug loading efficiency. The stability of the resulting micelle solution is analyzed using disrupting conditions such as co-incubation with a detergent, sodium dodecyl sulfate, with or without a reducing agent. The drug-loaded, disulfide cross-linked micelles demonstrated less hemolytic activity when compared to their non-cross-linked counterparts

Carbon nanotube–graphene-based nanofluids: a comprehensive review on the role of thermal conductivity and its solar energy applications

Nowadays, nanofluids are considered as excellent working fluids with good thermophysical properties for augmenting the heat transfer in solar systems. Consisting of single-phase nanopowder, metal oxide-based nanofluids exhibit either a good thermal network or good physicochemical properties. Allotropes of carbon (e.g., carbon nanotubes; CNTs and graphene) have their own set of distinct structural and thermal properties to enhance the thermophysical properties of base fluids (e.g., water, ethylene glycol, etc.). For working fluids, researchers tried to optimize the preparation methodology in which a two-step method has been preferred due to the synergistic involvement of solid (i.e., particulate) and liquid (i.e., base fluid) phase. Also, several research groups have discussed the thermal behavior of different nanofluids with the help of correlations. A combination of MgO and CNTs has also been studied thoroughly to distinguish the effect of temperature and concentration of solid phase on the thermal conductivity of nanofluid. Further, CNT/graphene-based nanofluids serve a critical role in improving the thermal performance of solar collectors, solar stills, solar ponds, and solar cookers. It can also be utilized to reduce the surface temperature of solar cells in photo voltaic thermal (PV/T) systems which in turn increases the electrical efficiency of these systems. The present work illustrates a detailed review on the CNT/graphene-based nanofluids and their structural features for different solar energy applications

Bulk synthesis of highly conducting graphene oxide with long range ordering

Graphene oxide with high conductivity is today's demand not only for high quality graphene synthesis but also for direct applications in electronic devices. Here we demonstrate a milder bulk synthesis approach for graphene oxide (mGO) from tattered graphite showing long range ordering and much higher conductivity (27 S m(-1)) compared to Hummers graphene oxide (H-GO) (0.8 S m(-1)). A two step mild oxidation process is adapted instead of excessive oxidation of graphite based on Hummers method which creates permanent defects in carbon sheets. This work demonstrates the mild oxidation process for highly conducting GO preparation without use of NaNO3 inhibiting the evolution of toxic gases and also possessing bulk synthesis possibilities

Deep Learning for Multi-Tissue Segmentation and Fully Automatic Personalized Biomechanical Models from BACPAC Clinical Lumbar Spine MRI.

STUDY DESIGN: In vivo retrospective study of fully automatic quantitative imaging feature extraction from clinically acquired lumbar spine magnetic resonance imaging (MRI). OBJECTIVE: To demonstrate the feasibility of substituting automatic for human-demarcated segmentation of major anatomic structures in clinical lumbar spine MRI to generate quantitative image-based features and biomechanical models. SETTING: Previous studies have demonstrated the viability of automatic segmentation applied to medical images; however, the feasibility of these networks to segment clinically acquired images has not yet been demonstrated, as they largely rely on specialized sequences or strict quality of imaging data to achieve good performance. METHODS: Convolutional neural networks were trained to demarcate vertebral bodies, intervertebral disc, and paraspinous muscles from sagittal and axial T1-weighted MRIs. Intervertebral disc height, muscle cross-sectional area, and subject-specific musculoskeletal models of tissue loading in the lumbar spine were then computed from these segmentations and compared against those computed from human-demarcated masks. RESULTS: Segmentation masks, as well as the morphological metrics and biomechanical models computed from those masks, were highly similar between human- and computer-generated methods. Segmentations were similar, with Dice similarity coefficients of 0.77 or greater across networks, and morphological metrics and biomechanical models were similar, with Pearson R correlation coefficients of 0.69 or greater when significant. CONCLUSIONS: This study demonstrates the feasibility of substituting computer-generated for human-generated segmentations of major anatomic structures in lumbar spine MRI to compute quantitative image-based morphological metrics and subject-specific musculoskeletal models of tissue loading quickly, efficiently, and at scale without interrupting routine clinical care