Conversion Matrix Method of Moments for Time-Varying Electromagnetic Analysis

A conversion matrix approach to solving network problems involving time-varying circuit components is applied to the method of moments for electromagnetic scattering analysis. Detailed formulations of this technique's application to the scattering analysis of structures loaded with time-varying circuit networks or constructed from general time-varying media are presented. The computational cost of the method is discussed, along with an analysis of compression techniques capable of significantly reducing computational cost for partially loaded systems. Several numerical examples demonstrate the capabilities of the technique along with its validation against conventional methods of modeling time-varying electromagnetic systems, such as finite difference time domain and transient circuit co-simulation.Comment: 11 pages, 11 figure

Advanced modulation technology development for earth station demodulator applications. Coded modulation system development

A jointly optimized coded modulation system is described which was designed, built, and tested by COMSAT Laboratories for NASA LeRC which provides a bandwidth efficiency of 2 bits/s/Hz at an information rate of 160 Mbit/s. A high speed rate 8/9 encoder with a Viterbi decoder and an Octal PSK modem are used to achieve this. The BER performance is approximately 1 dB from the theoretically calculated value for this system at a BER of 5 E-7 under nominal conditions. The system operates in burst mode for downlink applications and tests have demonstrated very little degradation in performance with frequency and level offset. Unique word miss rate measurements were conducted which demonstrate reliable acquisition at low values of Eb/No. Codec self tests have verified the performance of this subsystem in a stand alone mode. The codec is capable of operation at a 200 Mbit/s information rate as demonstrated using a codec test set which introduces noise digitally. The measured performance is within 0.2 dB of the computer simulated predictions. A gate array implementation of the most time critical element of the high speed Viterbi decoder was completed. This gate array add-compare-select chip significantly reduces the power consumption and improves the manufacturability of the decoder. This chip has general application in the implementation of high speed Viterbi decoders

NILM techniques for intelligent home energy management and ambient assisted living: a review

The ongoing deployment of smart meters and different commercial devices has made electricity disaggregation feasible in buildings and households, based on a single measure of the current and, sometimes, of the voltage. Energy disaggregation is intended to separate the total power consumption into specific appliance loads, which can be achieved by applying Non-Intrusive Load Monitoring (NILM) techniques with a minimum invasion of privacy. NILM techniques are becoming more and more widespread in recent years, as a consequence of the interest companies and consumers have in efficient energy consumption and management. This work presents a detailed review of NILM methods, focusing particularly on recent proposals and their applications, particularly in the areas of Home Energy Management Systems (HEMS) and Ambient Assisted Living (AAL), where the ability to determine the on/off status of certain devices can provide key information for making further decisions. As well as complementing previous reviews on the NILM field and providing a discussion of the applications of NILM in HEMS and AAL, this paper provides guidelines for future research in these topics.Agência financiadora: Programa Operacional Portugal 2020 and Programa Operacional Regional do Algarve 01/SAICT/2018/39578 Fundação para a Ciência e Tecnologia through IDMEC, under LAETA: SFRH/BSAB/142998/2018 SFRH/BSAB/142997/2018 UID/EMS/50022/2019 Junta de Comunidades de Castilla-La-Mancha, Spain: SBPLY/17/180501/000392 Spanish Ministry of Economy, Industry and Competitiveness (SOC-PLC project): TEC2015-64835-C3-2-R MINECO/FEDERinfo:eu-repo/semantics/publishedVersio

Checking graphite and stainless anodes with an experimental model of marine microbial fuel cell

A procedure was proposed to mimic marine microbial fuel cell (MFC) in liquid phase. A graphite anode and a stainless steel cathode which have been proven, separately, to be efficient in MFC were investigated. A closed anodic compartment was inoculated with sediments, filled with deoxygenated seawater and fed with milk to recover the sediment’s sulphide concentration. A stainless steel cathode, immersed in aerated seawater, used the marine biofilm formed on its surface to catalyze oxygen reduction. The cell implemented with a 0.02 m2-graphite anode supplied around 0.10 W/m2 for 45 days. A power of 0.02 W/m2 was obtained after the anode replacement by a 0.06 m2-stainless steel electrode. The cell lost its capacity to make a motor turn after one day of operation, but recovered its full efficiency after a few days in open circuit. The evolution of the kinetic properties of stainless steel was identified as responsible for the power limitation

Time-resolved magnetic sensing with electronic spins in diamond

Quantum probes can measure time-varying fields with high sensitivity and spatial resolution, enabling the study of biological, material, and physical phenomena at the nanometer scale. In particular, nitrogen-vacancy centers in diamond have recently emerged as promising sensors of magnetic and electric fields. Although coherent control techniques have measured the amplitude of constant or oscillating fields, these techniques are not suitable for measuring time-varying fields with unknown dynamics. Here we introduce a coherent acquisition method to accurately reconstruct the temporal profile of time-varying fields using Walsh sequences. These decoupling sequences act as digital filters that efficiently extract spectral coefficients while suppressing decoherence, thus providing improved sensitivity over existing strategies. We experimentally reconstruct the magnetic field radiated by a physical model of a neuron using a single electronic spin in diamond and discuss practical applications. These results will be useful to implement time-resolved magnetic sensing with quantum probes at the nanometer scale.Comment: 8+12 page

自励燃焼不安定性に関する数値解析に関する研究

Nowadays, combustion provides more than 80% of the worldwide energy sources. However, practical combustion systems are often susceptible to combustion instabilities characterized by large-amplitude and low-frequency pressure oscillations. This dissertation presents a nonlinear analysis and a Computational Fluid Dynamics (CFD) simulation of those self-excited combustion instabilities with a Rijke tube combustor. It is necessary to learn the mechanisms of combustion instabilities in-depth to prevent combustion instabilities or control them at acceptable levels. The nonlinear analysis of the combustion is implemented first. A model of a one-dimensional (1D) Rijke tube burner with both ends opened is built. The nondimensional momentum equation and energy equation of the acoustic perturbation are derived and solved in the time domain by using the Galerkin technique. A saturated n-τ model is proposed to descript the nonlinear flame heat release rate. The time evolution of the combustion instability is calculated. The stabilities of the systems under given conditions are determined by calculating the eigenvalues. Next, the bifurcation analysis of the dynamics behavior for the Rijke burner is performed for the variation of flame location, flame heat release intensity, and the time lag between heat release and flow velocity perturbation. Nonlinear phenomena, including hysterical, critical bifurcation, and stability switching, were observed, verifying the nonlinear characteristic of the Rijke tube burner. Further, the phase diagram and Poincaré map of the limit cycle oscillations are given, showing the oscillations' periodic character. The growth rates of the onset for the exciting case and decay for the stable case are calculated too. This nonlinear analytical method helps to understand the nature of combustion instability. Second, the self-excited combustion instability in a two-dimensional (2D) Rijke tube burner with a center-stabilized premixed methane-air flame is numerically studied. The simulation considers the reacting flow, flame dynamics, and radiation model to investigate the essential physical processes. A finite volume-based approach is used to simulate reacting flows. Chemical reaction modeling is conducted via the species transport model with one-step reaction mechanisms, and the radiation heat flux is determined by using the P-1 model. The steady-state reacting flow is first simulated for model verification. Then, the dynamic pressure, velocity, and reaction heat evolutions are determined to show the onset and growth rate of self-excited instability in the burner. The growth rates of the acoustic disturbances at the onset stages are calculated by curve fitting. Using the fast Fourier transform (FFT) method, the limit cycle oscillation frequency is obtained, which agrees well with the theoretical prediction. The dynamic pressure and velocity along the tube axis provide the acoustic oscillation mode and amplitude, agreeing well with the prediction. Finally, the unsteady flow field at different times in a limit cycle shows that flame-induced vortices occur inside the combustor. The temperature distribution indicates that the back-and-forth velocity changes in the tube vary the distance between the flame and honeycomb in turn, forming a forward feedback loop in the tube. The results reveal the route of flame-induced thermoacoustic instability and indicate periodical vortex formation and breakdown in the Rijke burner. In summary, the combustion instability in a Rijke type burner is numerically investigated from the nonlinear dynamics analysis and CFD simulation. The nonlinear analysis results show that combustion instability is a nonlinear system. There are bifurcation, stability switching phenomenons that exist, and the systems may have stable and unstable results for a given state. The CFD results verify the predictions of 1D analytical results and reveal details of the dynamics flow field, showing that even in very low Reynold numbers, the coupling of flow perturbation and heat release may induce vortices. These results provide people new perspective in studying the mechanisms of combustion