Volume 68 (2017): Issue 4 (August 2017)

In this paper, a review and analysis of different design techniques for (ultra) low-voltage integrated circuits (IC) are performed. This analysis shows that the most suitable design methods for low-voltage analog IC design in a standard CMOS process include techniques using bulk-driven MOS transistors, dynamic threshold MOS transistors and MOS transistors operating in weak or moderate inversion regions. The main advantage of such techniques is that there is no need for any modification of standard CMOS structure or process. Basic circuit building blocks like differential amplifiers or current mirrors designed using these approaches are able to operate with the power supply voltage of 600 mV (or even lower), which is the key feature towards integrated systems for modern portable applications.

We propose a new method of authentication for smartphones and similar devices based on gestures made by user with the device itself. The main advantage of our method is that it combines subtle biometric properties of the gesture (something you are) with a secret information that can be freely chosen by the user (something you know). Our prototype implementation shows that the scheme is feasible in practice. Further development, testing and fine tuning of parameters is required for deployment in the real world.

The paper introduces a theoretical concept of a shielding for horizontal yokes for measurements of rotational power loss and other rotational and two-dimensional properties. Apart from horizontal parts, the shielding relies on vertical pieces distributed uniformly around the sample circumference, symmetrically on both sides. The simulations in 2D and 3D FEM show significant improvement in reduction of H perpendicular to the sample surface (H_z). The gradient of the tangential H is reduced so that the extrapolation of values towards the surface might be no longer required. There is also an added benefit that the required magnetomotive force is significantly lower (20-70%) for achieving the same B in the sample, as compared to the previously used simple horizontal shields.

This paper presents a control model design capable of inhibiting the phenomenal rise in the DC-link voltage during grid- fault condition in a variable speed wind turbine. Against the use of power circuit protection strategies with inherent limitations in fault ride-through capability, a control circuit algorithm capable of limiting the DC-link voltage rise which in turn bears dynamics that has direct influence on the characteristics of the rotor voltage especially during grid faults is here proposed. The model results so obtained compare favorably with the simulation results as obtained in a MATLAB/SIMULINK environment. The generated model may therefore be used to predict near accurately the nature of DC-link voltage variations during fault given some factors which include speed and speed mode of operation, the value of damping resistor relative to half the product of inner loop current control bandwidth and the filter inductance.

In this paper, we study a photonic crystal fiber (PCF) with circular lattice and engineer linear and nonlinear parameters by varying the diameter of air-holes. It helps us obtain low and high zero dispersion wavelengths in the visible and nearinfrared regions. We numerically demonstrate that by launching 100 fs input pulses of 1, 2, and 5 kW peak powers with center wavelength of 532 nm from an unamplified Ti:sapphire laser into a 100 mm length of the engineered PCF, supercontinua as wide as 290, 440 and 830 nm can be obtained, respectively. The spectral broadening is due to the combined action of self-phase modulation, stimulated Raman scattering and parametric four-wave-mixing generation of the pump pulses. The third and the widest spectrum covers the entire visible range and a part of near infrared region making it a suitable source for both white light applications and optical coherence tomography to measure retinal oxygen metabolic response to systemic oxygenation.

This paper deals with a real-time and optimal control of dynamic systems while also considers the constraints which these systems might be subject to. Main objective of this work is to propose a simple modification of the existing Model Predictive Control approach to better suit needs of computational resource-constrained real-time systems. An example using model of a mechanical system is presented and the performance of the proposed method is evaluated in a simulated environment.

The article describes use of an Induction furnace with cold crucible as a tool for real-time measurement of a melted material electrical resistivity. The measurement is based on an inverse problem solution of a 2D mathematical model, possibly implementable in a microcontroller or a FPGA in a form of a neural network. The 2D mathematical model results has been provided as a training set for the neural network. At the end, the implementation results are discussed together with uncertainty of measurement, which is done by the neural network implementation itself.

The paper introduces a simple fitting function for quick assessment of proton ranges in biological targets and human tissues. The function has been found by fitting an extensive data set of Monte Carlo proton ranges obtained with the aid of the SRIM-2013 code. The data has been collected for 28 different targets at 8 energies in the interval from 60 MeV to 220 MeV. The paper shows that at a given kinetic proton-beam energy, the Monte Carlo ranges can be satisfactorily fitted by a power function that depends solely on the target density. This is a great advantage for targets, for which the exact chemical composition is not known, or the mean ionizing potential is not reliably known. The satisfactory fit is meant as the fit that stays within the natural range straggling of the Monte Carlo ranges. In the second step, the energy-scaling yielding a universal fitting formula for proton ranges as a function of proton-beam energy and target density is introduced and discussed.

This paper deals with temperature control of multivariable system of office building. The system is simplified to several single input-single output systems by decoupling their mutual linkages, which are separately controlled by regulator based on generalized model predictive control. Main part of this paper focuses on the accuracy of the office temperature with respect to occupancy profile and effect of disturbance. Shifting of desired temperature and changing of weighting coefficients are used to achieve the desired accuracy of regulation. The final structure of regulation joins advantages of distributed computing power and possibility to use network communication between individual controllers to consider the constraints. The advantage of using decoupled MPC controllers compared to conventional PID regulators is demonstrated in a simulation study.

In the last years, Interleave Division Multiple Access (IDMA) has been presented as a potential alternate of Code Division Multiple Access (CDMA) system. In IDMA systems, the interleavers are used to separate the users of the system in multiple access environments. Random interleaver is popular and basic taxonomy, which scrambles information bits of craving users with different patterns. However the indispensable characteristics of a random interleaver such as bandwidth requirement, computational complexity, and memory restraint at both transmitter and receiver end is uttermost. Further, it has also been observed that the study of role of chaos in interleaver design is very limited in literature. Hence, in this paper, a low complexity chaos based interleaver named as modified Tent map interleaver is designed for further performance improvement of IDMA system and the characteristic parameters are compared with the random interleaver. The IDMA system model uses a BPSK modulation and repetition coder with a code rate of 1/2. The system is simulated in MATLAB and results show that the better BER performance without the need of extra memory resources.

In this manuscript a simple method is presented for constructing run length limited error control codes from linear binary block codes. The run length limited properties are obtained via addition of a carefully chosen fixed binary vector - a modifier to all codewords without introducing any additional redundancy. Modifier selection is based on a specific property, which can be found in some of the linear binary block codes control matrices. Similar known methods are based on properties of generator matrices. However some codes are specified via control matrices, for example low density parity check codes. The method proposed in this letter could be applied to some of them directly. This is illustrated in this manuscript using example in which a run length limited low density parity check code is obtained from Gallager code.