MgNb2O6:Dy3+ nanophosphor: A facile preparation,down conversion photoluminescence and UV driven photocatalytic properties

Series of (1–9 mol %) dysprosium (Dy³⁺) ions doped MgNb₂O₆ (MNO) nanophosphors were synthesized by chemical combustion process and their photo luminescent and photocatalytic behaviours were examined. Powder X-ray diffraction (PXRD) reveals the columbite structure and crystal structure parameters were calculated. The average crystallite size was found to be in the range of 20–30 nm as calculated by Scherrer's method. The photoluminescence (PL) of MgNb₂O₆:Dy³⁺ (λ_exc-393 nm) reflects white emission for the prepared samples as confirmed by CIE and CCT. The photocatalytic activities of these nanophosphors were probed for the decolorization of acid red 88 (AR-88) under UV light irradiation. The photocatalyst with MgNb₂O₆:Dy³⁺ (5 mol %) showed enhanced activity of 97%, attributed to effective separation of charge carriers. All the above experimental results confirm that, the optimized phosphor is quite useful for WLEDs, solid-state lighting applications and as a photocatalyst.     

Simulation of an experimental compartment fire by CFD

This paper analyses the experimental results, obtained in a compartment fire experiment [Kumar R. Studies on compartment fires. Ph.D. thesis. Indian Institute of Technology, Roorkee, 2004], by using CFD modelling. Experiments were conducted in a compartment by burning methanol as a fuel. Temperatures vs. time were recorded at 11 different locations in the compartment for three sizes of fires.     

Growth and characterization of diamond particles,diamond films,and CNT-diamond composite films deposited simultaneously by hot filament CVD

It is important to understand the growth of CNT-diamond composite films in order to improve the inter-link between two carbon allotropes, and, in turn, their physical properties for field emission and other applications. Isolated diamond particles, continuous diamond thin films, and thin films of carbon nanotubes (CNTs) having non-uniformly distributed diamond particles (CNT-diamond composite films) were simultaneously grown on unseeded, seeded, and catalyst pre-treated substrates, respectively, using a large-area multi-wafer-scale hot filament chemical vapor deposition. Films were deposited for four different growth durations at a given deposition condition. The changes in surface morphology and growth behavior of diamond particles with growth duration were investigated ex situ using field emission scanning electron microscopy and 2D confocal Raman depth spectral imaging, respectively. A surface morphological transition from faceted microcrystalline nature to nanocrystalline nature was observed as a function of growth duration in the case of isolated diamond particles grown on both unseeded and catalyst pre-treated substrates. However, such a morphological transition was not observed on the simultaneously grown continuous diamond thin films on seeded substrates. 2D confocal Raman depth spectral imaging of diamond particles showed that the local growth of CNTs did not affect the growth behavior of neighboring diamond particles on catalyst pre-treated substrates. These observations emphasize the importance of surface chemical reactions at the growth site in deciding sp² or sp³ carbon growth and the final grain size of the diamond films.     

Detecting people in dense crowds

We propose a scheme to detect individuals in any image frame of a video sequence showing densely crowded scenes against cluttered backgrounds. The method uses only spatial information, and in an initial pass through the image a trained Viola–Jones-type local detector is used to locate individuals in the densely crowded scene. This yields a large number of false alarms. Hence, in a second step, we seek to reduce the false alarms, and propose two methods for this. In the first, color information from the initially detected windows is passed to a classifier to reduce the false alarms. This classifier consists of a cascade of boosted classifiers with Haar-like features as input and is trained with color information from local windows. In the second method, a weak perspective model of an uncalibrated camera is used to further reduce the false alarm rate while maintaining the detection rate. This is based on the size and locations of the detections in the image frame, without the use of any 3D world information. Results are presented in the form of receiver operating characteristic curves. For instance, at a 79.0% detection accuracy, the false alarm rate is 20.3%.     

First and second law investigations of a new solar‐assisted thermodynamic cycle for triple effect refrigeration

This investigation is persuaded for the first and second law analyses of a new solar‐driven triple‐effect refrigeration cycle using Duratherm 600 oil (Duratherm Extended Life Fluid, NY, USA) as the heat transfer fluid is performed. The proposed cycle is an integration of ejector, absorption, and cascaded refrigeration cycles that could produce refrigeration output of different magnitude at different temperature simultaneously. Both exergy destruction and losses in each component and hence in the overall system are determined to identify the causes and locations of the thermodynamic imperfection. The effects of some influenced parameters such as hot oil outlet temperature, refrigerant turbine inlet pressure, and the evaporator temperature of ejector and cascaded refrigeration cycle have been observed on the first and second law performances. It is found that maximum irreversibility occurs in central receiver as 52.5% and the second largest irreversibility of 25% occurs in heliostat field. The second law efficiency of the solar driven triple effect refrigeration cycle is 2%, which is much lower than its first law efficiency of 11.5%. Analysis clearly shows that performance evaluation based on the first law analysis is inadequate and hence, more meaningful evaluation must be included in the second law analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

Interfacial tension approach toward drug loading with two-dimensional crosslinked polymer embedded gold: Adsorption kinetics evaluation

Interfacial tension of drugs with hydrophilic polymer (A) embedded gold resulting into selective drug adsorption, which also affected the drug adsorption kinetics. Two-dimensional crosslinked polymer embedded gold was synthesized for drug loading application in an acidic buffer. Lower interfacial tension of pantoprazole sodium (B) revealed the exponential loading inversely loading was gradual for chloroquine (C) having more interfacial tension with adsorbent. Initial 2 h was the exponential adsorption period for a pantoprazole sodium whereas exponential adsorption begins after 12 h for a chloroquine. Monolayer drug adsorption was obtained because Langmuir adsorption isotherm was obeyed by both drugs. Moreover, pseudo first- and pseudo second-order kinetics was also evaluated which demonstrated that reactive sites of the adsorbent are homogeneous and drug adsorption mechanism is chemisorption and not the physisorption. Thermal analysis was evaluated to confirm the polymer thermostability and glass transition temperature during catalytic applications in thermal reactions.     

Numerical studies on evaluation of smoke control system of underground metro rail transport system in India having jet injection system: A case study

The rail based urban transport system is being developed for national capital of India, New Delhi. The smoke control using ventilation in case of fire inside the tunnel, similar to Delhi Metro corridor has been investigated using computational fluid dynamics technique. A section of tunnel having dimensions 400 m long, 5.5 m wide and 6 m high is considered for simulation. The analysis has been carried out by assuming a variable fire source with a peak heat release rate (HRR) of 16 MW, located at the center of the tunnel. Ventilation ducts are located in the ceiling near the tunnel portals and are inclined at 10 degrees to the plane of the ceiling through which fans discharge air. The influence of the fire HRR curve slope on the smoke flow dynamics in a realistic tunnel model fitted with jet injection type longitudinal ventilation system has been investigated. In case of fire two cases are studied: (1) fans activated immediately after detection, (2) fans activated at delayed times to take into account the response time for the fans to achieve its maximum speed. The velocity of supply and exhaust fans necessary to remove smoke in 30 s from the upstream direction is determined. The velocities of fan required to produce desired critical velocity in the longitudinal direction for different HRR of fire is predicted.     

Effect of wall friction on variation of formwork pressure over time in self-consolidating concrete

In order to accurately predict the varying of formwork pressure over time, it is necessary to consider various factors influencing the development of formwork pressure. A prediction model has been previously proposed, but that model has some limitations in that only intrinsic material characteristics are taken into account. Extrinsic effects such as wall friction, formwork flexibility, and external temperature are excluded in the model. This study focuses on the wall friction effect as one of the extrinsic factors. First, by incorporating the intrinsic model and friction stress acting on the interface, a method of calculating formwork pressure considering the wall friction effect is suggested. To find out how much friction stress is acting on the interface and how it varies over time, formwork pressure tests were performed with circular column formworks having three different diameters. In these columns, the vertical pressure at the bottom and the lateral pressures were measured. To calibrate parameters of the intrinsic model for the same material as that used in the formwork pressure tests, additional tests were conducted with a specially designed apparatus that can exclude effects of extrinsic factors. From tests and analysis results, it was found that wall friction greatly affects the variation of formwork pressure over time. The newly suggested calculation method can give a good prediction of real formwork pressure.