Logic Scheme Research Articles

Proton exchange membrane fuel cells: Investigation of control schemes for reactants’ flow pressure

ABSTRACTIn this paper, the operation of proton exchange membrane fuel cell systems is introduced by modeling of reactant flow pressure control schemes. Proportional-Integral, Fuzzy logic and Artificial neural network-based schemes are proposed to control the hydrogen and oxygen flow pressure. A MATLAB/Simulink model is developed for the proton exchange membrane fuel cell power generation system by combining the designed controllers. The system performance is tested under different operating conditions for each controller-assisted proton exchange membrane fuel cell and found to be satisfactory. Furthermore, a comparative study is made in terms of controller response and the fuel consumption.

A Developed Voltage Control Strategy for Unbalanced Distribution System During Wind Speed Gusts Using SMES

The fast response, high efficiency and long lifetime of superconducting magnetic energy storage (SMES) compared to other energy storage systems make it a preferable selection for energy storage solution for wind power generation. SMES has attracted many researchers to study its potential applications in power systems. This paper discusses a scheme of fuzzy logic controlled SMES to minimize the voltage fluctuations of three-phase unbalanced radial distribution systems connected to wind energy conversion system (WECS) with large scale penetration level of 30% during wind speed gusts. In this paper, wind turbine used is of squirrel cage induction generator (SCIG) with shunt connected capacitor bank for power factor improvement. SMES unit consists of superconducting coil, DC-DC chopper, step down transformer, power conditioning system, and cryostat/vacuum vessel. The control technique is based on fuzzy logic controller (FLC). The studied system is 33-bus three-phase unbalanced radial distribution system. The SMES and WECS were connected to weakest buses in the system, namely Buses18 and 33. The control strategy is discussed in details and the proposed system is evaluated by simulation in MATLAB/SIMULINK package. The simulation results demonstrate the performance of the proposed fuzzy-logic-controlled SMES in mitigating the voltage fluctuations under wind speed gusts.

Magnetic Domain-Wall Racetrack Memory-Based Nonvolatile Logic for Low-Power Computing and Fast Run-Time-Reconfiguration

The high power and the long global interconnect delay are two of the major bottlenecks that limit the further scaling down of the process nodes in the VLSI systems. Therefore, new technologies and computer architectures are under focused development to reduce the power consumption and the interconnect delay. Current-induced magnetic domain-wall (DW) racetrack memory (RM) has the advantages of nonvolatility, fast switching speed, and high density. It may offer opportunities to open a new paradigm of circuits and architectures to significantly alleviate the power and delay issues. This paper presents the magnetic DW RM-based new nonvolatile logic designs for the low-power computing and fast run-time-reconfiguration. Both data transfer and reconfiguration are achieved by shifting the magnetic strips. Verify-before-shift approach is used to greatly reduce the shifting energy. Compared with the conventional nonvolatile logic gate, the proposed nonvolatile logic scheme doubles the operating speed with 87% lower operating energy. Moreover, the proposed nonvolatile logic gates can be reconfigured after fabrication, which makes the designs more flexible and robust. The reference reconfiguration and the polarity reconfiguration are presented in this paper, which can be finished in 1 ns with 130 fJ/strip energy and 6 ns with 390 fJ/strip energy, respectively.

Nonlinear robust observer for structures with configuration-dependent natural frequencies: experimental and theoretical results

The theoretical development of advanced controllers and observers has greatly surpassed the experimental work in this field. The current study represents a significant step toward an overall objective of providing experimental validation of these advanced concepts. Therefore, the present work focuses on validating the robust performance of a self-tuning nonlinear observer in accurately estimating the state variables of a structure whose natural frequencies are configuration-dependent. The observer design is based on both the variable structure systems theory and the self-tuning fuzzy logic scheme. Its robustness and self-tuning characteristic allows the use of an imprecise model of the system and eliminates the need for the extensive tuning associated with a fixed rule-based expert fuzzy inference system. The physical system is selected to be a spherical robotic manipulator where only the protruding portion of the third link from the second link is considered to be flexible. The prismatic joint causes the length of the flexible link to vary, which induces significant variations in the natural frequencies of the link. The observer has been implemented to estimate the generalized coordinates of the flexible motion under two different types of excitation. The first one involves disturbances in the initial conditions or the use of initial impulsive forces. While in the second type, the structural deformations are induced by the rigid body motion of the arm during a tracking maneuver. Same numerical values for the observer’s parameters were used in conducting both theoretical and experimental works. The results demonstrate the robustness of the observer in accurately estimating the generalized coordinates of the flexible motion of the third link in spite of significant modeling imprecision and external disturbances.

Two-Stage Spectrum Sensing Scheme Using Fuzzy Logic for Cognitive Radio Networks

Spectrum sensing in cognitive radio networks allows secondary users to sense the unused spectrum without causing interference to primary users. Cognitive radio requires more accurate sensing results from unused portions of the spectrum. Accurate spectrum sensing techniques can reduce the probability of false alarms and misdetection. In this paper, a two-stage spectrum sensing scheme is proposed for cooperative spectrum sensing in cognitive radio networks. In the first stage, spectrum sensing is executed for each secondary user using energy detection based on double adaptive thresholds to determine the spectrum condition. If the energy value lies between two thresholds, a fuzzy logic scheme is applied to determine the channel conditions more accurately. In the second stage, a fusion center combines the results of each secondary user and uses a fuzzy logic scheme for combining all decisions. The simulation results show that the proposed scheme provides increased sensing accuracy by about 20% in some cases.

Drawing from hats by noise-based logic

We utilize the asymmetric random telegraph wave-based instantaneous noise-base logic scheme to represent the problem of drawing numbers from a hat, and we consider two identical hats with the first 2N integer numbers. In the first problem, Alice secretly draws an arbitrary number from one of the hats, and Bob must find out which hat is missing a number. In the second problem, Alice removes a known number from one of the hats and another known number from the other hat, and Bob must identify these hats. We show that, when the preparation of the hats with the numbers is accounted for, the noise-based logic scheme always provides an exponential speed-up and/or it requires exponentially smaller computational complexity than deterministic alternatives. Both the stochasticity and the ability to superpose numbers are essential components of the exponential improvement.

Reconfigurable logic via gate controlled domain wall trajectory in magnetic network structure.

An all-magnetic logic scheme has the advantages of being non-volatile and energy efficient over the conventional transistor based logic devices. In this work, we present a reconfigurable magnetic logic device which is capable of performing all basic logic operations in a single device. The device exploits the deterministic trajectory of domain wall (DW) in ferromagnetic asymmetric branch structure for obtaining different output combinations. The programmability of the device is achieved by using a current-controlled magnetic gate, which generates a local Oersted field. The field generated at the magnetic gate influences the trajectory of the DW within the structure by exploiting its inherent transverse charge distribution. DW transformation from vortex to transverse configuration close to the output branch plays a pivotal role in governing the DW chirality and hence the output. By simply switching the current direction through the magnetic gate, two universal logic gate functionalities can be obtained in this device. Using magnetic force microscopy imaging and magnetoresistance measurements, all basic logic functionalities are demonstrated.

Hybrid Control Using Adaptive Fuzzy Sliding Mode for Diagnosis of Stator Fault in PMSM

In nonlinear control systems when we have a non-constant parameters, conventional control laws may be insufficient because they are not robust especially when the requirement on accuracy and other characteristics dynamic systems are strict. We must use control laws insensitive against to parameter variations, disturbance and nonlinearities. For this purpose, several tools are proposed in the literature, which is quoted a hybrid fuzzy logic and variable structure control (Fl_VSC). This per presents an application of the fuzzy logic scheme to control the speed of PMSM by taking account of the presence of interturn short circuit fault. We were interested in the sliding mode control (SMC) of the PMSM using controller’s fuzzy logic controller (FLC) and Adaptive fuzzy logic controller (AFLC). The combination of these two theories has given great performance with fast dynamic response without overshoot. As it has a very robust control, insensitive against to parameters variation and external disturbances. Simulation results confirm the choice of hybrid controllers compared with the conventional controllers and grants a robust performance and precise response to the reference model regardless of load disturbance, stator faults and PMSM parameter uncertainties.

PROTON+

Optical Networks-on-Chip (ONoCs) are a promising technology to overcome the bottleneck of low bandwidth of electronic Networks-on-Chip. Recent research discusses power and performance benefits of ONoCs based on their system-level design, while layout effects are typically overlooked. As a consequence, laser power requirements are inaccurately computed from the logic scheme but do not consider the layout. In this article, we propose PROTON+, a fast tool for placement and routing of 3D ONoCs minimizing the total laser power. Using our tool, the required laser power of the system can be decreased by up to 94% compared to a state-of-the-art manually designed layout. In addition, with the help of our tool, we study the physical design space of ONoC topologies. For this purpose, topology synthesis methods (e.g., global connectivity and network partitioning) as well as different objective function weights are analyzed in order to minimize the maximum insertion loss and ultimately the system’s laser power consumption. For the first time, we study optimal positions of memory controllers. A comparison of our algorithm to a state-of-the-art placer for electronic circuits shows the need for a different set of tools custom-tailored for the particular requirements of optical interconnects.

ORGANIZATION OF DECISION SUPPORT FOR CRISIS MANAGEMENT

The article presents structural logic schemes of building decision support systems in crisis situations with providing support for video conferencing based on heterogeneous networks. The proposed structural solutions allow implementing them with the use of any data transmission systems of the conditions of implementation of new compression technology based on the presented methods and models of adaptive encoding digital-out the images of preset quality. It is shown that the use of improved compression technology based on the methods for adaptive coding can be definitely implemented on H.32x protocol type platform without additional technical changes or communication equipment replacement and can achieve higher video transmission speed via communication channels.

Topological computation based on direct magnetic logic communication.

Non-uniform magnetic domains with non-trivial topology, such as vortices and skyrmions, are proposed as superior state variables for nonvolatile information storage. So far, the possibility of logic operations using topological objects has not been considered. Here, we demonstrate numerically that the topology of the system plays a significant role for its dynamics, using the example of vortex-antivortex pairs in a planar ferromagnetic film. Utilising the dynamical properties and geometrical confinement, direct logic communication between the topological memory carriers is realised. This way, no additional magnetic-to-electrical conversion is required. More importantly, the information carriers can spontaneously travel up to ~300 nm, for which no spin-polarised current is required. The derived logic scheme enables topological spintronics, which can be integrated into large-scale memory and logic networks capable of complex computations.

Proposal for a Domain Wall Nano-Oscillator driven by Non-uniform Spin Currents.

We propose a new mechanism and a related device concept for a robust, magnetic field tunable radio-frequency (rf) oscillator using the self oscillation of a magnetic domain wall subject to a uniform static magnetic field and a spatially non-uniform vertical dc spin current. The self oscillation of the domain wall is created as it translates periodically between two unstable positions, one being in the region where both the dc spin current and the magnetic field are present, and the other, being where only the magnetic field is present. The vertical dc spin current pushes it away from one unstable position while the magnetic field pushes it away from the other. We show that such oscillations are stable under noise and can exhibit a quality factor of over 1000. A domain wall under dynamic translation, not only being a source for rich physics, is also a promising candidate for advancements in nanoelectronics with the actively researched racetrack memory architecture, digital and analog switching paradigms as candidate examples. Devising a stable rf oscillator using a domain wall is hence another step towards the realization of an all domain wall logic scheme.

Thermodynamic Study of Energy Dissipation in Adiabatic Superconductor Logic

Adiabatic superconductor logic, in which bit-switching energy can be reduced significantly by changing the potential energy landscape adiabatically, is an attractive candidate for next-generation energy-efficient computing. The authors' simulations of the effect of thermal noise on energy dissipation in this logic scheme show that there is no lower bound on the energy of switching operations, indicating that so-called reversible computing is achievable even at finite temperature, and thus ushering the technique toward practical use.

Delay Insensitive Ternary CMOS Logic for Secure Hardware

As digital circuit design continues to evolve due to progress of semiconductor processes well into the sub 100 nm range, clocked architectures face limitations in a number of cases where clockless asynchronous architectures generate less noise and produce less electro-magnetic interference (EMI). This paper develops the Delay-Insensitive Ternary Logic (DITL) asynchronous design paradigm that combines design aspects of similar dual-rail asynchronous paradigms and Boolean logic to create a single wire per bit, three voltage signaling and logic scheme. DITL is compared with other delay insensitive paradigms, such as Pre-Charge Half-Buffers (PCHB) and NULL Convention Logic (NCL) on which it is based. An application of DITL is discussed in designing secure digital circuits resistant to side channel attacks based on measurement of timing, power, and EMI signatures. A Secure DITL Adder circuit is designed at the transistor level, and several variance parameters are measured to validate the efficiency of DITL in resisting side channel attacks. The DITL design methodology is then applied to design a secure 8051 ALU.

Hardware Design of Digital Parametric Conjunctors and t-Norms

This paper presents the hardware design and its implementation on FPGA of several parametric families of digital conjunctors and t-norms built from simple basic t-norms. The authors propose the method of unified presentation of the p-monotone sum, the simplified versions of the ordinal sum of t-norms and t-subnorms, and the method of extension of t-norms by the drastic t-norm. Such unification gives possibility to join several methods of construction of parametric digital conjunctors and t-norms in one scheme with the efficient FPGA implementation. The logic schemes of the proposed design are presented, and the comparative analysis of the latency time and the resources used for the implementation is given.

Indeterministic Temporal Logic

Abstract The questions od determinism, causality, and freedom have been the main philosophical problems debated since the beginning of temporal logic. The issue of the logical value of sentences about the future was stated by Aristotle in the famous tomorrow sea-battle passage. The question has inspired Łukasiewicz’s idea of many-valued logics and was a motive of A. N. Prior’s considerations about the logic of tenses. In the scheme of temporal logic there are different solutions to the problem. In the paper we consider indeterministic temporal logic based on the idea of temporal worlds and the relation of accessibility between them.

An adaptive fuzzy handover triggering approach for Long-Term Evolution network

To cope with the increasing demand for efficient data delivery, self-organizing networks have been introduced in the Long Term Evolution (LTE) system to provide autonomous and flexible mobility management. The existing handover triggering scheme for LTE is not flexible enough to incorporate new performance metrics, and it introduces handover latency. There are studies on non-conventional handoff algorithms for LTE applications, for instance, the fuzzy logic approach. However, the fuzzy logic approach needs regular manual tuning to constantly produce optimal output. In this paper, we address this issue by proposing an adaptive fuzzy logic-based handoff decision algorithm, which can cope with environmental changes and improve efficiency by reducing human intervention. Performance results show that the proposed algorithm can reduce unnecessary handovers by about 20% compared with the fuzzy logic and conventional LTE handover triggering scheme, leading to reduced packet loss rates.

Comparison of in‐flight aircraft icing algorithms based on ECMWF forecasts

ABSTRACTThis study presents an objective verification of different icing algorithms for two periods from 5 December 2012 to 17 April 2013 and from 9 October to 11 December 2013. The predicted icing potential and severity are evaluated against pilot reports of aircraft icing below 23 000 feet over Eastern United States. The icing algorithms are applied to the deterministic forecasts of European Centre for Medium‐Range Weather Forecasts (ECMWF). Two of these algorithms are based only on forecasts of temperature (T) and relative humidity (RH), but the first uses fixed thresholds and the second uses a fuzzy logic approach. Although the second algorithm detects less icing events, it is more efficient with respect to the warning area, i.e. it forecasts icing over a smaller percentage of the airspace than the first algorithm. The impact of adding information from cloud liquid water (CLW) content and/or vertical velocity in the fuzzy logic scheme is assessed. Algorithms using T, CLW and vertical velocity as predictors are also tested. Most of the algorithms reveal a good performance in discriminating between icing and no‐icing conditions, but are less skilful in forecasting the icing severity. The results also show that the use of CLW is essential to avoid issuing too many warnings. Moreover, the algorithm combining T, RH, CLW and vertical velocity attains the best performance. This algorithm, SFIPO, has been operational at the Portuguese Meteorological Watch Office since June 2013, and an example of a severe icing episode in February 2014 over mainland Portugal is presented.

THE USE OF CASE TECHNOLOGIES IN TEACHING STUDENTS

Аbstract. The aim of the article is to consider the possibilities of use of case technologies in educational process of the university; to prove the efficiency and perspectivity of the given method while training the future expertsprofessionals Methods. Retrospective and abstract analyses of the scientific-theoretical and practical literature are used while describing the history of development of case-study technology and its didactic possibilities. Test materials are used as the measuring tool of dynamics of informative activity of students, changes of level of their knowledge and abilities in the process of skilled-experimental work. Results and scientific novelty. The way of formation of concept «case technology» is shown; examples of various approaches to understanding of the given method are given; author's experience of research of the given problem is described; stages of work with case technology are allocated. It is experimentally proved that case technologies not only help to fix subject knowledge, to find professional the competence, but also promote development of creative thinking, and form skills of behaviour in a group: abilities to operate in a team, to state and defend the point of view, to listen, to carry on dialogue, to ask questions, to operate with the knowledge, building logic schemes of the problem solution. Besides, during the training period using a case technology students study independent ways of knowledge acquisition which are necessary for the modern professional in constantly ever-changing economic and social realities. The case method reveals creative potential, learns to think and operate differently not only students, but also teachers. This method promotes democratisation of educational process, formation of teachers’ progressive thinking, raises motivation of pedagogical activity. Practical significance. The article provides conclusions and recommendations for the use of case technologies in the educational process at the university.

AWG-Based Non-Blocking Clos Networks

The three-stage Clos networks remain the most popular solution to many practical switching systems to date. The aim of this paper is to show that the modular structure of Clos networks is invariant with respect to the technological changes. Due to the wavelength routing property of arrayed-waveguide gratings (AWGs), non-blocking and contention-free wavelength-division-multiplexing (WDM) switches require that two calls carried by the same wavelength must be connected by separated links; otherwise, they must be carried by different wavelengths. Thus, in addition to the non-blocking condition, the challenge of the design of AWG-based multistage switching networks is to scale down the wavelength granularity and to reduce the conversion range of tunable wavelength converters (TWCs). We devise a logic scheme to partition the WDM switch network into wavelength autonomous cells, and show that the wavelength scalability problem can be solved by recursively reusing similar, but smaller, set of wavelengths in different cells. Furthermore, we prove that the rearrangeably non-blocking (RNB) condition and route assignments in these AWG-based three-stage networks are consistent with that of classical Clos networks. Thus, the optimal AWG-based non-blocking Clos networks also can achieve 100% utilization when all input and output wavelength channels are busy.