Cavity ignition and flameholding of ethylene–air and hydrogen–air flows by a repetitively pulsed nanosecond discharge

Repetitive nanosecond pulse plasma assisted ignition and flameholding of premixed and non-premixed ethylene–air and hydrogen–air flows are studied in a cavity flow at a pressure of 0.2 atm and flow velocities of up to 100 m/s. Ignition occurs via formation of multiple filaments in the fuel–air plasma, although air plasma remains diffuse until the fuel is added. After ignition occurs in the cavity, with ignition delay time of a few milliseconds, the plasma becomes diffuse and the flame couples out to the main flow. The use of a short cavity (length-to-depth ratio L/D = 1) results in repetitive ignition and flame blow-off, caused by slow mixing between the main flow and the cavity. Increasing the length-to-depth ratio to L/D = 3, as well as choking inlet air and fuel flows resulted in stable flameholding and nearly complete combustion in both premixed and non-premixed ethylene–air and hydrogen–air flows at u = 35–100 m/s. Air plasma temperature before fuel is added ranges from 70 °C to 200 °C. When the nanosecond pulse discharge is operated in repetitive burst mode, continuous ethylene–air flame is maintained only at a high duty cycle, which increases with the flow velocity. In hydrogen–air, the flame remains stable after the plasma is turned off. Nanosecond pulse discharge ignition of ethylene–air is compared with ignition by DC arc discharge of approximately the same power. DC arc discharge results in sporadic ignition and flame blow-off, much lower burned fuel fraction, and significantly lower flow velocity at which ignition can be achieved. Kinetic modeling is used to identify the reduced mechanism of plasma chemical oxidation and ignition of hydrogen, and to demonstrate the mechanism of energy release low-temperature reactions of radicals generated in the plasma (primarily O and H atoms).     

VOLTAGE-MEDIATED CONFORMATIONAL CHANGES OF A POLYELECTROLYTE IN A LINEAR ELASTIC MEMBRANE

The wall of the cylindrically-shaped outer hair cell is piezoelectric, which allows the cell to function as an electromechanical transducer in the mammalian inner ear. Polyelectrolytes, which are located in the cell wall, may be responsible for the cell's piezoelectric properties. The polyelectrolytes can change conformation in response to a change in the external electric field; this conformational change can cause the cell to change its length. We have developed a model to predict the voltage response of a cylindrical cell whose wall contains conformationally-mobile polyelectrolytes. The cell wall is modeled as a rectangular lattice of polyelectrolytes connected by springs. The springs represent the (non-piezoelectric) elastic portion of the cell wall. The polyelectrolytes can exist in one of two possible conformations. The energy of the polyelectrolyte is a function of both the trans-wall electric potential difference and the forces which are applied by the surrounding elastic material in the wall. The fraction of polyelectrolytes in a given conformation is determined by the relative energies of the two conformations, by means of a Boltzmann distribution. If the electric potential difference and the pressure difference between the inside and outside of the cell are known, the model can predict the cell's radius, the length, the fraction of polyelectrolytes in a given conformation, and the electrical capacitance of the cell wall (due to the polyelectrolyte activity). We also propose an experimental scheme which would provide data that could be used to evaluate the parameters in our model. Our simulations predict that the electrical capacitance vs. voltage function should exhibit a peak which simply shifts its location (without a significant change in height) when the intracellular pressure is changed. In addition, we demonstrate that electrical stimulation of the cell, under conditions of constant cell volume, could result in a significant change in the intracellular pressure.     

Fall detection method based on Spatio-temporal feature fusion using combined two-channel classification

Nowadays, the growing population of senior citizens is a challenge for almost all developing countries. New technologies can help monitor elderlies at home by providing an innovative and secure environment and further enhancing their quality of living. Vision-based systems offer promising results in analyzing human posture and detecting abnormal events like falls. Falls appear to possess the most considerable risk for seniors living alone. In this article, a new fall detection method is proposed based on a fusion of motion-based and human shape-based features. Motion History Images (MHI) represent the temporal feature in our approach. Simultaneously, the height-to-width ratio and centroid of the moving person represent the spatial features. A two-channel classification model is designed using a threshold-based and a keyframe-based approach. The two channels are further combined based on any classification disparity for which more information is used to classify between falls and daily activities. Keyframes are selected based on the displacement of the spatial features having a threshold higher than a preset value. Keyframes are subject to a K-NN classification. The proposed algorithm delivers promising results on the UR fall detection dataset’s simulated fall and daily activity sequences. It provides satisfactory performance compared to existing state-of-the-art methods and shows a peak accuracy of 98.6% and recall of 100% in detecting falls. Specificity and precision are over 96%.

     

A novel approach for mitigating gray hole attack in MANET

Mobile ad hoc network (MANET) is defined as the category of wireless network that is capable of operating without any fixed infrastructure. The main assumption considered in this network is that all nodes are trusted nodes but in real scenario, some nodes can be malicious node and therefore can perform selective dropping of data packets instead of forwarding the data packets to the destination node. These malicious nodes behave normally during route discovery phase and afterwards drop fractions of the data packets routed through them. Such type of attack is known as smart gray hole attack which is variation of sequence number based gray hole attack. In this paper, we have launched smart gray hole attack and proposed a new mechanism for mitigating the impact of smart gray hole attack. Mitigating Gray hole Attack Mechanism (MGAM) uses several special nodes called as G-IDS (gray hole-intrusion detection system) nodes which are deployed in MANETs for detecting and preventing smart gray hole attack. G-IDS nodes overhear the transmission of its neighbouring nodes and when it detects that the node is dropping the data packets which are greater than threshold value then it broadcast the ALERT message in the network notifying about the identity of malicious node. The identified malicious is then blocked from further its participation by dropping the request and reply packet. In order to validate the effectiveness of our proposed mechanism, NS-2.35 simulator is used. The simulation results show that the proposed mechanism performs slightly well as compared with the existing scheme under smart gray hole attack.     

The sorption of lead(II) ions on rice husk ash

Present study deals with the adsorption of Pb(II) from aqueous solution on rice husk ash. Rice husk is a by-product generally obtained from rice mill. Rice husk ash is a solid obtained after burning of rice husk. Batch studies were performed to evaluate the influences of various experimental parameters like pH, initial concentration, adsorbent dosage, contact time and the effect of temperature. Optimum conditions for Pb(II) removal were found to be pH 5, adsorbent dosage 5 g/L of solution and equilibrium time 1h. Adsorption of Pb(II) followed pseudo-second-order kinetics. The effective diffusion coefficient is of the order of 10(-10)m(2)/s. The equilibrium adsorption isotherm was better described by Freuindlich adsorption isotherm model. The adsorption capacity (q(max)) of rice husk ash for Pb(II) ions in terms of monolayer adsorption was 91.74 mg/g. The change of entropy (DeltaS(0)) and enthalpy (Delta H(0)) were estimated at 0.132 kJ/(mol K) and 28.923 kJ/mol respectively. The negative value of Gibbs free energy (Delta G(0)) indicates feasible and spontaneous adsorption of Pb(II) on rice husk ash. The value of the adsorption energy (E), calculated using Dubinin-Radushkevich isotherm, was 9.901 kJ/mol and it indicated that the adsorption process was chemical in nature. Application study was also carried out to find the suitability of the process in waste water treatment operation.     

Densification of Pond Ash by Blasting

Fly ash from thermal power plants is disposed, in huge quantities in ash ponds, which occupy large land areas otherwise useful for agriculture, housing, or other development. For effective rehabilitation of ash ponds, densification of the slurry deposit is essential to increase the bearing capacity and to improve its resistance to liquefaction. Extensive field trials were carried out to evaluate the effectiveness of deep blasting for densification of deposited fly ash. Ninety explosions comprising 15 single blasts, with varying depths and quantities of charges, and 3 group blasts, each having 25 charges placed at various spacings, were carried out. The compaction achieved in terms of an increase in relative density was evaluated from surface settlement measurements. Extensive field monitoring was undertaken through pore-water pressure measurements, vibration measurements, penetration tests, and block vibration tests. For the average charge of 2–4 g of explosive per cubic meter of untreated deposit, the average relative density was found to improve from 50% to 56–58%. Analysis of the test results indicates that deep blasting may be an effective technique for modest compaction of loose fly ash deposits. The field testing program presented in this paper provides valuable information that can be used for planning blast densification of fly ash deposits.     

THE INFLUENCE OF AXIAL LOADING ON THE ELECTROMECHANICAL RESPONSE OF THE OUTER HAIR CELL

The cylindrically-shaped outer hair cell functions as an active support beam in the inner ear. We develop a model for electromechanical transduction when the cell supports a load. The model is an extension of Jerry and Dutta [Chemical Engineering Communications, 166 (1998), 81 -110]. We use our model to simulate a “tensile test” on the cell, similar to that used to measure the elastic modulus for plastic, metal and ceramic specimens. Our work demonstrates the importance of accurate control of cell volume or intracellular pressure during experiments, and also suggests that voltage clamping may not be necessary when measuring the elastic properties of the cell. A plot of the polyelectrolyte-associated charge (that is moved across the wall) vs. the load reveals a charge reversal effect: at a particular value of the load, the direction of charge movement changes. The effect can be explained using our model.