Thermal protective performance of clothing exposed to radiant heat

Designing firefighter protective clothing requires many factors to be taken into consideration. Constructional parameters along with proper selection of materials are very critical and need to be extensively studied. In the present work, construction parameters of Kevlar woven and conex non-woven materials have been studied. Full factorial experiments have been conducted by varying factors like pick density of woven cloth and punch densities of non-woven fabric at three levels at three different heat fluxes. ANOVA has been done to analyse the significance of different factors and interaction between them. Time to cause second-degree burn injury has been found to be linearly related to pick and punch densities, where as it has non-linear relationship with variation in heat fluxes. Kevlar woven material with higher pick density combined with lower punch density produced maximum time before second-degree burn occurs.     

Modeling and simulation of HVDC Bridge Converters

Abstract

This paper presents a converter model for dynamic digital simulation of HVDC systems. The simulation is simplified by representing the converter as a time varying equivalent circuit on the dc side, which is derived from graph theoretic formulation. The converter model presented has a modular structure and hence can be used to simulate a converter terminal with any number of bridges connected in series.     

Design theory and performance analysis of paraboloidal solar cooker

A paraboloidal collector having aperture diameter 1.3 m, depth 0.30 m, and focal length 0.35 m was designed and fabricated. The paraboloidal solar cooker was tested under no-load conditions at a recorded maximum temperature of 326°C. The analysis was made from the sensible heating and cooling curves. The values of the overall heat loss factor (F′ UL) obtained from the sensible cooling curve were smaller on different days. The minimal heat loss was due to the wind shield provided at the paraboloidal receiver. Analysis of the sensible heating curve gave the values of the optical efficiency factor (F′ η₀). The performance of the paraboloidal collector was determined, and the thermal efficiency was found to be 26%. The performance curve was plotted to predict the approximate time required to boil a known amount of water under given climatic conditions. The solar cooker was found to be useful in cooking a variety of foods.     

Line outage ranking for voltage limit violations with corrective rescheduling avoiding masking

This paper describes a technique for ranking line outages causing voltage limit violations taking into account the post-outage correctability of the network during contingency selection process. Due to the choice of large even powered of performance index (PI): (i) masking is avoided; and (ii) complete potential of correctability of power network is utilised. Fletcher and Reeves conjugate gradient method is used for optimisation. Use of newly derived compensated voltage shift factor has been made. To restrict the reactive power limit violations at generation buses, use of newly derived reactive power compensated shift factor has been made. Control corrections have been optimised for each line outage in the same base case pre-outage condition itself. This allows the use of same set of pre-outage sensitivity coefficients and line outage distribution factors. It is to be stressed here that the control corrections have been obtained for each line outage in pre-contingency condition mainly for computational convenience. But actually these corrections are applied in respective post-outage conditions. The algorithm is tested on IEEE 25-bus, 30-bus and 91-bus test systems.     

High-resolution magnetic resonance imaging: three-dimensional trabecular bone architecture and biomechanical properties

The development of vectors that are capable of efficient gene delivery is crucial to the success of gene therapy. We have developed both recombinant viral and nonviral vectors with the goal of correcting genetic abnormalities in cancer cells that are responsible for malignant transformation. Infection of cancer cells by recombinant adenovirus (Adv) indicates that the level of transduction is variable and dependent on the virus-to-cell ratio. Infection of cells with Adv/p53 resulted in levels of tumor suppressor p53 gene expression that could mediate tumor cell growth suppression and apoptosis, both in vitro and in vivo. The treatment of cancer cells with cisplatin prior to Adv transduction resulted in a higher level of therapeutic gene expression. Epidermal growth factor (EGF)/DNA complexes targeted to cancer cells overexpressing the EGF receptor resulted in efficient transduction of several lung cancer cell lines in vitro. As a result, these vectors provide improved methods with which to treat cancer in the clinical setting with gene therapy.     

Bibliography on the application of induction generators in nonconventional energy systems

Induction generators are increasingly being used in nonconventional energy systems such as wind, mini/micro-hydro, biogas, etc. The advantages of using an induction generator instead of synchronous generator are well known. Some of them are reduced unit cost and size, ruggedness, absence of separate DC source, ease of maintenance, self-protection against severe overloads and short circuits, etc. An attempt is made in this paper to present an exhaustive bibliography on the application of induction generators in nonconventional energy systems.     

Nonlinear formation control strategies for agents without relative measurements under heterogeneous networks

This paper proposes cooperative control protocols for a group of unmanned vehicles to make a stable formation around a maneuvering target. The control protocols are proposed on the basis of heterogeneous communication networks, which represents more challenging and generalized situations. Two different scenarios are considered. Separate control protocols are developed for each case. In both scenarios, agents do not have relative position, velocity, and acceleration measurements as feedback. In the first scenario, each agent uses its own position and velocity measurement in a consensus algorithm. In the second scenario, each agent needs only its own position information for the consensus algorithm. For both protocols, agents compute virtual estimates of a target's position and velocity and exchange these among the neighbors. Three different communication networks are used for exchanging two virtual estimates calculated by each agent and a time derivative of one virtual estimate. Each interagent communication network is represented by a fixed, undirected, and connected graph. Furthermore, it is considered that at least one agent receives the position, velocity, and acceleration information of the maneuvering target. It is not necessary that the agent receiving the target's position and the agent receiving the velocity and/or the acceleration information of the target be the same. However, the target does not receive any information about any agent. Stability of the formation is analyzed by using Barbalat's lemma. It is also shown that, despite the large difference in received information, the acceleration of the agents remains bounded for all time. The performance of the proposed formation control protocols is illustrated through numerical simulations.     

Electrical conduction and dielectric behaviour of the oxidic spinel Li0.5+0.5xCr0.3TixFe2.2−1.5XO4

The electrical conductivity of polycrystalline lithium-chromium ferrites substituted successively with Ti⁴⁺ was studied as a function of composition and temperature. The resistivity increased with composition and all the samples exhibited a change in slope in the resistivity-temperature curve. Two different regions with a large variation in activation energies were found. The dielectric constant and loss factor for different compositions were measured in the frequency range of 10kHz to 10 MHz. The dielectric permittivity showed a dispersion with frequency for all the samples. Peaks were observed for the samples with 0.4 x 0.8. The possible mechanisms involved are discussed.     

Steady‐State Creep Analysis of Functionally Graded Rotating Cylinder

Axi‐symmetric component like cylinder etc. has to operate under severe thermo‐mechanical loads, which cause significant creep. It, thus, reduces its service life. The present study investigates the steady‐state creep in a functionally graded rotating cylinder at constant angular speed. The cylinder is made up of aluminium matrix and reinforced with silicon carbide particles. The thermal gradient in the functionally graded rotating cylinder is estimated by performing finite element analysis on ANSYS software (ANSYS Inc., Canonsburg, USA). The creep behaviour of the cylinder has been described by threshold stress‐based creep law. The creep parameters are obtained by conducting regression analysis. The mathematical models have been developed to describe steady‐state creep in the cylinder. The study reveals that the radial, tangential, axial and effective stresses in the cylinder are significantly affected by the presence of particle gradient alone as well as with the presence of particle & thermal gradient both. It has been found that the creep rates have been reduced significantly by imposition of particle and thermal gradients together and thus increases the service life of cylinder.