Stochastic modeling of mean-wind profiles for in-flight wind estimation--A new approach to lower order stochastic realization schemes

A new approach has been proposed for the design of approximate, lower order discrete time realizations of stochastic processes from the output covariance matrix over a finite time interval. No restrictive assumptions are imposed on the process, that is, it can be nonstationary and also can lead to higher dimension realization. Classes of fixed order models ("guaranteed models") are defined having the joint covariance matrix of the combined vector of the outputs in the interval of definition greater than or equal to the process covariance matrix. The design is achieved by minimizing, in one of those classes, the approximation between the model and the process measured by the trace of the difference of the respective covariance matrices. The method has been employed in a practical problem of developing lower order wind models from a higher order covariance matrix in numerical form. The wind model is intended to be incorporated on board an aircraft maneuvering according to a four-dimensional guidance scheme in the neighborhood of the terminus of a flight. Choice of the order of the model and the resulting accuracies of the estimation schemes are compared.     

Further studies on redoxokinetic titrations

The previously described “redoxokinetic effect” is used to indicate the end-points of titrations of Fe²⁺ with Cr₂O₇^2-, sulphuric acid with sodium hydroxide, AsO₂- with I₂ and Ag⁺ with Cl⁻. With the first three systems an accuracy of 0·1 per cent is possible. The method is not suited to the fourth system.

Abstract

Titrations of sulphuric acid vs. sodium hydroxide at 0·1 N concentration and ferrous ammonium sulphate vs. potassium dichromate at 0·05 N concentration can be carried out with an accuracy of ±0·1 per cent using the redoxokinetic technique. A very sharp end-point was obtained in the case of iodine vs. arsenite titration at 0·1 N concentration. Silver nitrate vs. chloride titrations cannot be carried out by the redoxokinetic technique.

Addition of MnSO₄ to the extent of 50 g/l. of the solution enhances the precision considerably in the titration of dilute solutions of ferrous ammonium sulphate with dichromate.     

Composite organic-inorganic nanoparticles (COINs) with chemically encoded optical signatures

To obtain a coding system for multiplex detection, we have developed a method to synthesize a new type of nanomaterial called composite organic-inorganic nanoparticles (COINs). The method allows the incorporation of a broad range of organic compounds into COINs to produce surface enhanced Raman scattering (SERS)-like spectra that are richer in variety than fluorescence-based signatures. Preliminary data suggest that COINs can be used as Raman tags for multiplex and ultrasensitive detection of biomolecules.     

The kinetics of hydrogen attack of steels

The hydrogen attack of steel involves the formation of methane bubbles along the grain boundaries and their subsequent link-up to form fissures. This paper presents a detailed model for the kinetics of growth of such methane bubbles. The model considers two parallel processes which can control the growth—one involving the bubble growth by direct power-law creep and the other involving combinations of surface diffusion, grain boundary diffusion and matrix accommodation processes. The proposed model is more general and complete than the earlier ones and considers for the first time the possibility of bubble growth being controlled by surface diffusion and accommodation processes. The predictions of the model are shown to compare well with the experimental results obtained in our lab and with the literature data. The model also indicates the relative importance of lower carbon activity and increased creep stength of steel to its hydrogen attack resistance.     

Irradiation Target Cooling Using Circular/Slot Air Jet

To study the effect of irradiation on materials, sample coupons are irradiated in cyclotron facilities. During the irradiation process, these samples produce significant heat. This heat needs to be continuously removed from the samples in order to avoid melting of the samples as well as to keep the samples at a particular temperature during irradiation. The area available for heat transfer is limited due to small size of the samples. To increase the heat transfer rate, jet cooling is used as it provides large heat transfer co-efficient. To understand the heat transfer characteristics of jet cooling under these conditions, experiments have been carried out. Two inclined jets hitting on both sides of the target plate give maximum cooling and uniform temperature distribution. This paper gives the details of the numerical and experimental studies carried out and the discussions about the results obtained.     

Effect of external pulsation on kinematics of fluid particles in the field of Lamb–Oseen vortex pair

The effect of external pulsation on a pair of stationary Lamb–Oseen vortices of equal strength has been analyzed to investigate kinematic behavior of a fluid particle. The assumption of vortices being treated stationary or fixed vortex filaments is valid in a reference frame attached to the vortex system with axes along and perpendicular to the line of their centers. Also, it is assumed that change in core shape and size is much small, with least possibility of core merger. In such situations, periodic particle paths are observed and superposition of pulsation becomes beneficial. In the present work, motion of a representative fluid particle is modeled as a non-linear dynamical system by varying both amplitude and frequency of external pulsation. Effect of external pulsation has been brought out with the help of quantification of deviation from periodic paths by using the concept of total average deviation. Results are presented in terms of particle paths, velocity phase plots, velocity signals and their spectra for varying amplitude and frequency of external pulsation.     

Secured and QoS Based Energy-Aware Multipath Routing in MANET

Wireless Personal Communications - In MANET, energy aware multipath routing is major concern for securable transmission which is possible by avoiding the attackers or selfish nodes from the...     

Performance Analysis in Digital Circuits for Process Corner Variations,Slew-Rate and Load Capacitance

The aggressive scaling of CMOS technology has inevitably led to vastly increased power dissipation, process variability and reliability degradation, posing tremendous challenges to robust circuit design. To continue the success of integrated circuits, advanced design research must start in parallel with or even ahead of technology development. In this paper, an attempt is made to analyze various circuits’ delay and power performance by introducing certain level of variation to important process parameters like threshold voltage (V_th), mobility of carriers (μ₀), oxide thickness (t_ox) and doping concentration (n_sd). Basic Monte Carlo simulation is carried out on these circuits to ascertain the stability in performances. A 16 × 1 multiplexer is considered for detailed analysis. SPICE characterization is done for three different input slew rates (0.1, 0.5 and 1 ns) against four different output load drive strengths (1×, 2×, 3× and 4× output capacitive load). From the obtained results, output slew rates and average power results are observed and discussed.     

Model for thermal conductivity of CNT-nanofluids

This work presents a simple model for predicting the thermal conductivity of carbon nanotube (CNT) nanofluids. Effects due to the high thermal conductivity of CNTs and the percolation of heat through it are considered to be the most important reasons for their anomalously high thermal conductivity enhancement. A new approach is taken for the modeling, the novelty of which lies in the prediction of the thermal behaviour of oil based as well as water based CNT nanofluids, which are quite different from each other in thermal characteristics. The model is found to correctly predict the trends observed in experimental data for different combinations of CNT nanofluids with varying concentrations.     

On-Line Learning Failure-Tolerant Neural-Aided Controller for Earthquake Excited Structures

This paper presents an on-line learning failure-tolerant neural controller capable of controlling buildings subjected to severe earthquake ground motions. In the proposed scheme the neural controller aids a conventional H∞ controller designed to reduce the response of buildings under earthquake excitations. The conventional H∞ controller is designed to reduce the structural responses for a suite of severe earthquake excitations using specially designed frequency domain weighting filters. The neural controller uses a sequential learning radial basis function neural network architecture called extended minimal resource allocating network. The parameters of the neural network are adapted on-line with no off-line training. The performance of the proposed neural-aided controller is illustrated using simulation studies for a two degree of freedom structure equipped with one actuator on each floor. Results are presented for the cases of no failure and failure of the actuator on each of the two floors under several earthquake excitations. The study indicates that the performance of the proposed neural-aided controller is superior to that of the H∞ controller under no actuator failure conditions. In the presence of actuator failures, the performance of the primary H∞ controller degrades considerably, since actuator failures have not been considered for the design. Under these circumstances, the neural-aided controller is capable of controlling the acceleration and displacement structural responses. In many cases, using the neural-aided controller, the response magnitudes under failure conditions are comparable to the performance of the H∞ controller under no-failure conditions.