In this paper, a least perturbation-based method of pattern restoration is proposed. Faulty array elements, have an adverse effect on the radiation pattern of a linear antenna array. Consequently, it is imperative to mitigate adverse effects on radiation pattern. Unlike previous fully compensating approaches, the proposed method optimises the excitation amplitude and phase of only the edge elements. As a result, unlike the completely compensating approaches, the entire array elements do not need to be reconfigured for pattern restoration, reducing hardware complexity. In order to illustrate the effectiveness of the proposed method, 20 elements and 31 elements uniform linear antenna array with random faults have been considered. Further comparative study indicates the acceptability of the method.

Present article investigates a binary sequence-based (BS) method of fault detection for linear antenna array. The method considers generation of possible combination of binary sequence depending on number of elements of the array. Based on the binary sequence generated corresponding array factor is calculated and compared with the reference array factor which happens to be array factor of faulty linear antenna array. Once the suitable match is anticipated, number of faulty elements along with their respective locations can be obtained. Effectiveness of the method has been demonstrated with 12 elements linear antenna array with both uniform and non-uniform excitation with different faulty elements position. Acceptability of the method has been illustrated through comparative study with previously reported fault detection methods. All the simulations are carried out using MATLAB simulator version R2020a on desktop with 16 GB RAM and Intel® Core™ i7-9700F Processor.

In this article, a novel method of fault detection in nonuniformly excited linear antenna array has been reported. This method uses an evolutionary algorithm-based technique to generate approximate radiation pattern in tune with reference faulty pattern for a nonuniformly excited linear antenna array. Based on the approximation, a binary sequence-based method of exact fault detection has been developed. In order to illustrate the effectiveness of the method, 12- and 20-element Dolph Tschebyscheff linear antenna array with amplitude fault has been considered. Superiority of the proposed method has been demonstrated through comparative study.

This paper presents a comparative study of three inset-fed patch antennas of different shapes like rectangular, circular and triangular for body wearable applications. Antenna parameters such as gain, bandwidth and return loss are simulated for best performance and the optimized antenna so obtained is mounted on a triple layered phantom. Simulation studies are being carried out to study and analyse the effects of such antenna-phantom composite structure as wearable antenna. The antennas are designed on FR4-epoxy substrate at the resonating frequency of 2.4 GHz (ISM band).

A new toolbox for the design of Proportional-Integral-Derivative (PID) controllers has been implemented in LabVIEW. The entire stabilizing set of PID controller parameters are obtained for continuous as well as discrete time systems. The plant can be a transfer function model or it can be model-free, based on frequency response or impulse response data. For continuous time systems, time delays can also be handled. Subsets simultaneously achieving various design specifications like gain margin, phase margin and maximum overshoot can be obtained. In this paper, we discuss the algorithms achieving these objectives and illustrate them with examples.

In the formulation of low cement castables, microfine additives are so selected that predominating phase will be mullite in the matrix of the alumina based castable refractories. Andalusite behaves like a reactive mullite as during mullitization the expelled glass from the grains can be easily combined with required amount of micronised alumina, giving rise to a secondary mullite acting as a binder and converting the total castable matrix into a well distributed mullite. Mullitization process in andalusite depends on its grain size; attrition milled micronised andalusite grains undergo Mullitization even at 1200°C with release of glassy phase through a topochemical and topotactic process resulting in volume stability and high thermal shock resistance. The effect of micronised andalusite and coarse grained andalusite on the properties like bulk density, apparent porosity, volume change, strength before and after spalling cycles of the low cement castables have been compared. XRD studies have been made to identify the phases and SEM studies have been performed to get an idea about the microstructure.

In this paper, we present a procedure for designing a digital proportional-integral-derivative (PID) controller based on input-output data of an arbitrary stable plant without identifying plant models. Based on an impulse input to the plant, the response of the plant is obtained which is then used to directly find the stabilizing set of PID controllers. The method makes use of Tchebyshev representation for discrete- time systems and the set is determined by obtaining a set of linear inequalities with two unknowns while keeping the third parameter fixed. By sweeping on the third parameter, the entire set can be obtained. This result is useful because it does not depend upon knowing the model of the system and the operations performed are directly on the data obtained. It is also observed that the region becomes more and more accurate as more and more sample points are included. This is shown through illustrative examples.

In this paper, the problem of finding the set of Proportional Integral Derivative (PID) controllers that can robustly stabilize a system based on its frequency response has been solved. The model of the system is not necessary for this problem. A band of uncertainty is assumed in the frequency response of the plant. The controller is so designed that it can robustly stabilize this plant in the entire range of its uncertainties. Interval coefficient linear inequalities are used to arrive at the final result.

We present a theoretical study of resonant two-photon dissociation (TPD) of the molecule in the presence of pulsed two-colour laser fields using the density matrix formalism. The study includes the calculation of dissociation probabilities and decay rates as functions of time and the variation of total dissociation probabilities with detuning when both fields are assumed to have the same temporal shape and duration. Results are reported for two simultaneous laser pulses as well as for two pulses with a time delay. The investigations were done with different values of peak intensities , for the initial and intermediate levels as v = 0, J = 0 and v'=17, J'=1, respectively, of the ground electronic state and the final continuum energy reached by photons was taken to be . The time variation and delay between pulses lead to interesting features in the time-dependent decay rates and spectral shapes of total dissociation probabilities.

The influence of the laser pulse shape on the multiple photon excitation dynamics of a large molecule like has been studied numerically in the pico- and nanosecond scale. In the theoretical model used multiphoton excitations are described in terms of the optical Bloch equations for the density matrix of four anharmonically shifted discrete vibrational levels coupled by the laser field and undergoing irreversible loss from the topmost level to the quasicontinuum (QC). The excitation in the QC is described by rate equations with loss from the discrete region as input. These equations are solved using the Monte Carlo technique suitably modified for a sharply varying laser intensity profile. The results show that the excitation of the QC and absorption due to a shaped laser pulse is greater than the corresponding quantities for a constant-intensity pulse of the same frequency, fluence and duration around the fundamental. The differences are small when the discrete-level bottleneck is very low (e.g. at the three-photon resonance frequency) or very high (e.g. when the frequency is blue shifted from the fundamental). The time dependence of multiphoton absorption (MPA) and temporal distribution of excited populations, is modified greatly by the pulse shape. The energy distributions of populations in the QC at different times, however, are not affected very much.

The infrared multiphoton absorption (IRMPA) and dissociation (IRMPD) of SF6 have been studied incorporating specific dissociation rate constants K(E, J) obtained from a simplified statistical adiabatic channel model (SACM) in an excitation model investigated by the authors recently. This model includes a rotationally resolved coherent-incoherent interface and rotationally selective excitation in the quasicontinuum. The J specific dissociation rates have been adjusted to match the results at intermediate J with RRKM rates. Use of the SACM rates K(E, J) show changes in the intensity, temperature and pressure dependence of the dissociation yields and rovibrational energy distribution of the molecules dissociating during the laser pulse from that obtained using the simple RRKM rates. The vibrational energy distribution of the molecules below and above the dissociation threshold and the average number of photons absorbed, however, remain unaffected. The differences between the results predicted by the two models decrease with increasing rotational temperature. The collisional quenching of the dissociation after the laser pulse in an argon buffer has also been studied. The nature of ground and excited state rotational distributions of molecules at different pulse times and fluences over wide ranges of experimental parameters are investigated. The various predictions of the model obtained using both linear and non-linear down transition rates in the low energy region of QC are discussed in the light of experimental results on SF6 and CF3I.

Collisional interruption of coherent excitation of SF6 in the lower discrete region of its laser absorbing mode (ν3) have been studied using the recently developed quantum Monte Carlo wave function (QMCWF) method. The usual pure pump mode description up to 3ν3 and complete mixing of all modes (QC) above it have been assumed. The rotational and anharmonic splitting of the vibrational states upto 3ν3 are taken into account but splitting due to tensor interaction terms are neglected. Excitation to QC is represented by irreversible leakage from the coherent ladder modeled by an imaginary term in the Hamiltonian of the coherently excited vibrational rotational levels. QMCWF study has been carried out at the laser frequency 942.8 cm−1 for which the local time average populations in the intermediate excited vibrational states are found to be negligible. Large leakage occurs only from narrow band of ground rotational states due to 3 photon resonances but their number increases with increasing intensity. Two different collisional energy transfer models, one obeying symmetry imposed restrictions and propensity rule, and the other free from such restrictions except the fact that collisions restore the thermal distribution, have been used. Results show different pressure effects at different temperature and for different intensities. However, the two different models used for collisional rotational transition probabilities give similar enhancement of leakage at high intensities.

A computationally simple model incorporating a rotationally resolved interfacing scheme between the regions of coherent and incoherent excitation (3-nu-3) and rotational structure in the quasicontinuum (QC) describes the total excitation and dissociation process of SF6 in an argon buffer. The effective cross section from a particular rotational sublevel of 3-nu-3 mode is obtained from the sum of Lorentzian functions of all allowed transitions to 4-nu-3 from that particular sublevel. The many resonances in the allowed transitions cause a large decrease in the bottleneck to the transition to the QC and a shift of the spectrum to the blue compared with that in our earlier model where the interface was rotationally unresolved.Using these cross sections, an effective two-level scheme demonstrates the formation of holes in the rotational distribution of molecules in the discrete levels and their subsequent disappearance at various buffer gas pressures and for different incident laser frequencies. incorporation of the effect of vibrational deactivation in the QC, investigated for different variations of the average energy transfer per collision shows that the vibrational distribution depends on the competing contributions from the hole filling at the ground state and collisional deactivation from the higher vibrational levels in the QC. At high temperatures and intensities the effect of rotational relaxation is dominant and there is good agreement between the full model and the simple two-level model. At low temperatures, when average energy transfer per collision in the QC is high, this is no longer true.

The influence of assumed properties of the quasicontinuum on the frequency and temperature dependence of the MPA and MPD of SF6 as determined by the lower discrete region has been studied using a simple interfacing model. Here the discrete region is interfaced with the quasicontinuum at nu =3 of the nu 3 mode using the time averaged population of nu 3 ( nu =3) level P3, as the ground-state population of the quasicontinuum. The dependence of P3 on the laser frequency (henceforth called the P3 spectrum) at different rotational temperatures has been obtained using different levels of approximation for the molecular Hamiltonian, i.e. by ignoring (case I), and incorporating the anharmonic splitting of the degenerate nu 3 vibrational mode (case II).

The model Hamiltonian formulated by Pytte and Feder (1969) and later by Gillis and Koehler (1973-74) for describing a second-order displacive phase transition has been utilised to describe the phase transitions of dilute crystals whose active atoms remain unaltered as a result of mixing. The effect of dilution has been taken into account through a weighted and uniform mixing of the harmonic and anharmonic part of the potential of the two-component crystals. The soft-mode contributions to the specific heat of pure and dilute crystals have been calculated using the model Hamiltonian. Variations of transition temperature of the mixed crystals with composition have been computed using different values for the potential coefficients. The results obtained agree qualitatively with the general behaviour of mixed crystals having second-order displacive phase transitions.