Free vibration and damping analysis of the cylindrical shell partially covered with equidistant multi-ring hard coating based on a unified Jacobi-Ritz method

In this study, the aim was to evaluate the vibration suppression performance of the partially covered equidistant multi-ring hard coating damping treatment for the cylindrical shell structure in aviation power equipment. A continuous rectangular pulse function was presented to describe the local thickness variation of arbitrary coating proportion and arbitrary number of coating rings. A semi-analytical unified solution procedure was established by combining the rectangular pulse function, the generalized Jacobi polynomials, and the Rayleigh-Ritz method. The stiffness coefficient k = 1013 N/m2 and the truncation number N = 8 were found to be large enough to achieve an accurate and efficient solution of the vibration analysis of the shell. The modal loss factor generally increased with the increase of the coating proportion ranging from 0.0 to 1.0 for all the circumferential wave numbers. The modal loss factor increased roughly linear with the coating proportion for all the circumferential wave numbers. And the modal loss factor was increased with the circumferential wave number, and the greater the number of circumferential waves, the greater the rate of change. The increase of the ring number was not always beneficial for vibration reduction of the shell, while the modal loss factor increased roughly linear with the coating proportion. The increased ring number and coating proportion tend more to exhibit an obvious incremental damping effect under larger circumferential wave number.

Adaption of Hunter’s Method and generation of synthetic series from disaggregation of flow time series, comparative analysis with existing models

Water demand is a non-deterministic variable; current normative deliver different flow rates than might occur. Adaptations have been developed in different countries mainly for Hunter's method. The Hydro-Sanitary Standard 'Norma Hidrosanitaria Ecuatoriana' (NHE) 2011 in Ecuador proposes a demand calculation through a modification to the Norme Francaise NF P 40–202. This study proposes an adaptation to the Hunter’s Method using a binomial probability function, based on the disaggregation of time series of pressure and flow, during 62 consumption days, in different water meters, in academic facilities in Loja, Ecuador. Flow curves were developed based on consumption units, which gave very assertive values in relation to the maximum recorded flow rates. Also, in order to approach different estimation methods and since water consumption over time follows a Poisson distribution, synthetic series were generated using the Neyman Scott Rectangular Pulse Model (NSRPM), as this is the one that most adheres to the actual user behavior. Maximum flow rate was also determined with Water Demand Calculator (WDC) and NHE 2011 for comparison with NSRP and research results. Current research is an exploratory approach, has a methodological value for subsequent studies. Proposed Hunter's Method adaptation can provide an accurate flow estimation. Flows obtained with NHE 2011 method were closed to observed only in small facilities. NSRPM method showed an exactness high level, with only a 1.1% percentage difference compared to the measured one.

pyBL: An open source Python package for stochastic high-resolution rainfall modelling based upon a Bartlett Lewis Rectangular Pulse model

<p>Stochastic rainfall modelling is an increasingly popular technique used by the water and weather risk industries. It can be used to synthesise sufficiently long rainfall time series to support hydrological applications (such as sewer system design) or weather-related risk analysis (such as excess rainfall insurance product design). The Bartlett-Lewis (BL) rectangular pulse model is a type of stochastic model that represents rainfall using a Poisson cluster point process. It is calibrated with standard statistical properties of rainfall data (e.g. mean, coefficient of variation, skewness and auto-correlation and so on), but it can well preserve extreme statistics of rainfall at multiple timescales simultaneously. In addition, it is found to be less sensitive to observational data length than the existing rainfall frequency analysis methods based upon, for example, annual maxima time series, so it provides an alternative to rainfall extremes analysis when long rainfall datasets are not available. </p><p>In this work, we would like to introduce an open source Python package for a BL model: pyBL, implemented based upon the state-of-the-art BL model developed in Onof and Wang (2020). In the pyBL package, the BL model is separated into three main modules. These are statistical properties calculation, BL model calibration and model sampling (i.e. simulation) modules. The statistical properties calculation module processes the input rainfall data and calculates its standard statistical properties at given timescales. The BL model calibration module conducts the model fitting based upon the re-derived BL equations given in Onof and Wang (2020). A numerical solver, based upon Dual Annealing optimization and Nelder-Mead local minimization techniques, is implemented to ensure the efficiency as well as to prevent from being drawn to local optima during the solving process. Finally, one can use the sampling module to generate stochastically rainfall time series at a given timescale and for any required data length, based upon a calibrated BL model.</p><p>The design of the pyBL is highly modularized, and the standard CSV data format is used for file exchange between modules. Users could easily incorporate given modules into their existing applications. In addition, a team, consisting of researchers from National Taiwan University and Imperial College London, will consistently implement the new breakthroughs in BL model to the package, so users will have access to the latest developments. The package is now undergoing the final quality check and will be available on Github (https://github.com/NTU-CompHydroMet-Lab/pyBL) in due course. </p>

Paralleling insulated-gate bipolar transistors in the H-bridge structure to reduce current stress

In this study we present the new power electronic circuit implementation to create the arbitrary near-rectangular electromagnetic pulse. To this end, we develop a parallel- Insulated-gate bipolar transistors (IGBT)-based magnetic pulse generator utilizing the H-bridge architecture. This approach effectively reduces the current stress on the power switches while maintaining a simple structure using a single DC source and energy storage capacitor. Experimental results from the circuit characterization show that the proposed circuit is capable of repeatedly generating near-rectangular magnetic pulses and enables the generation of configurable and stable magnetic pulses without causing excessive device stresses. The introduced device enables the production of near-rectangular pulse trains for modulated magnetic stimuli. The maximum positive pulse width in the proposed neurostimulator is up to 600 µs, which is adjustable by the operator at the step resolution of 10 µs. The maximum transferred energy to the treatment coil was measured to be 100.4 J. The proposed transcranial magnetic stimulator (TMS) device enables more flexible magnetic stimulus shaping by H-bridge architecture and parallel IGBTs, which can effectively mitigate the current stress on power switches for repetitive treatment protocols.

Research the load capacity of microcircuits

The device for the definition of the integrated circuits load-driving capability is offered. Device for determining the output capability of microcircuits refers to the field of microminiaturization and the technology of radio electronic equipment and can be used to control the parameters of microcircuits during their production. The device contains a rectangular pulse generator, an integrated circuit that is being tested, a repeater, load, a switch, an AND gate, a comparator, a pulse counter and a voltage reference, a vibrator, a reversible pulse counter, a decoder, and an indicator. Technical result when implementing the disclosed solution is high accuracy and reliability of determining load capacity of microcircuits. The proposed device allows increasing accuracy and reliability of defining circuits load-driving capacity. It also allows testing of TTL, Schottky-TTL, and MOSFET circuits. There are two switchable operating modes for testing fan-out for logical high and low levels. It is easy to replace a circuit that is being tested and load.