Dynamic Test Conditions Research Articles

A Switched-Capacitor Self-Balanced High-Gain Multilevel Inverter Employing a Single DC Source

Multilevel inverters (MLIs) with self-balanced switched-capacitors (SC) have received wide recognition for increasing power capacity and power quality of the renewable energy and high-frequency power distribution systems. This brief presents a new SC MLI structure using a reduced number of switches and a single dc source. By suitable charging-discharging patterns, the SCs are self-balanced and high voltage boosting is achieved. Comparative analysis with state-of-art MLIs in terms of the number of components, standing voltage, boosting factor, and cost factor demonstrate the merit of presented topology. Further, experimental results confirm the workability of the proposed MLI under linear, non-linear loading and dynamic test conditions using both the 50 Hz and 2.5 kHz modulation.

State of Charge Estimation of Lithium-Ion Batteries Using LSTM and NARX Neural Networks

Highly accurate state of charge (SOC) estimation of lithium-ion batteries is one of the key technologies of battery management systems in electric vehicles. The performance of SOC estimation directly influences the driving range and safety of these vehicles. Due to external disturbances, temperature variation and electromagnetic interference, accurate SOC estimation becomes difficult. To accurately estimate the SOC of lithium-ion batteries, this article presents a novel machine-learning method to address the risk of gradient explosion and gradient decent using the dynamic nonlinear auto-regressive models with exogenous input neural network (NARX) with long short-term memories (LSTM).The proposed hybrid NARX model embeds LSTM memory, which provides jump-ahead connections in the time-unfolded model. These jump-ahead connections provide a shorter path for the propagation of gradient information, therefore reducing long-term dependence on the recurrent neural network. Experimental results show that the estimation performance root mean square error (RMSE) of the proposed model is less than 1%, and this model has better multitime prediction performance. Finally, the hybrid NARX and LSTM model is compared with the standard back propagation neural network based on particle swarm optimization (BPNN-PSO), the least-squares support vector machine (LS-SVM) and LSTM existing models under urban dynamometer driving schedule (UDDS) and dynamic stress test (DST) conditions. The proposed hybrid NARX-LSTM model yield relative to other methods and can estimate the battery SOC with high accuracy. The RMSE of proposed model is improved by approximately 60% compared with the standard LSTM.

Effect of frequency and amplitude on dynamic behaviour, stiffness degradation and energy dissipation of saturated cohesive soil

ABSTRACT Cohesive soil undergoes cyclic softening when experiences the dynamic loading conditions. Evaluation of strength loss under such loading conditions is essential for soil stability analysis. The present study investigates the cyclic response, stiffness degradation behaviour with number of loading cycles and cumulative energy dissipation characteristics within the soil mass of cohesive geomaterial. Slurry consolidated specimens of saturated cohesive soil were prepared to perform several series of strain controlled cyclic triaxial tests at varying loading frequency and axial strain amplitude under consolidated and unconsolidated testing conditions. A great influence of loading amplitude and frequency was observed on the hysteresis response and dynamic properties of cohesive soil under consolidated and unconsolidated testing conditions. Amount and rate of cyclic stiffness degradation in addition to cumulative dissipated energy were also evaluated at different dynamic loading (amplitude and frequency) and testing conditions (consolidated and unconsolidated). Cyclic strength and stiffness of saturated cohesive soil were obtained to be higher under consolidated testing conditions as compared to unconsolidated. A large decay in cumulative dissipated energy was observed with the increment in loading cycles.

SOHIO process legacy waste treatment: Uranium recovery using ion exchange

The feasibility of employing ion-exchange resins for the selective removal of uranium from a complex waste effluent has been investigated. The source of the effluent is a treatment process to reduce the volume of a spent uranium containing catalyst prior to its immobilisation and disposal in South Korea. Commercial anion exchange and chelation resins have been screened, along with an in-house synthesized polyamine functionalized resin. The Langmuir isotherm model produced the best fit for UO22+ binding to all resins, with Purolite MTS957, a mixed sulfonic/phosphonic acid functionalised resin, showing the highest equilibrium adsorption capacity for UO22+, 96.15mgg−1. The Modified Dose-Response Model was found to adequately represent breakthrough across all flow rates used and for all resins tested under dynamic testing conditions. The maximum uranium loading capacities under dynamic conditions for simulant and real wastes were established as 131.52mgg−1 and 68.62mgg−1, respectively. Purolite MTS957 effectively decontaminated the real effluent to uranium levels below the Korean release limit of 1mgL−1. Over 99.9% uranium was successfully eluted from the resin bed in under 20 BV with a mixed sodium carbonate/sulfate eluent.

Effect of internal moisture content and dynamic mechanical analysis testing conditions on the Tg values of CFRP tendons

The high temperature and long-term performance of uni-directional pultruded carbon fibre reinforced polymer (CFRP) tendons in prestressed concrete relies on the integrity of the epoxy matrix and the degree of crosslinking. The dynamic glass transition temperature (Tg) obtained using Dynamic Mechanical Analysis (DMA) can be a useful indicator of the degree of cross-linking. However, variations in the epoxy plasticisation due to different initial hygrothermal equilibrium conditions in CFRP tendons can influence the measured Tg leading to inconsistent results. The dependency of Tg on the initial CFRP moisture content, and also DMA test parameters including the thermocouple position, the magnitude of static flexural strain, the static to dynamic strain ratio and the specimen geometry were investigated. Whereas the selected DMA test parameters had only a small influence on the Tg values, the initial moisture content of the CFRP tendon had a significant effect. A decrease in Tg of up to 38 °C was observed with an increase in average moisture content of up to 2.46%. Knowledge of the initial moisture content and the establishment of a comparative baseline are necessary to more accurately infer the crosslinking density and degree of cure of a resin from dynamic Tg results.

An improved Thevenin model of lithium-ion battery with high accuracy for electric vehicles

This paper proposes an improved Thevenin model of the Lithium-ion battery taking into account temperature influence on the calculation accuracy of the open circuit voltage of a battery. The calculation accuracy of the terminal voltage of a battery is improved without increasing the order of the model. Firstly, the model was proposed based on Thevenin model and the relationship between the open-circuit voltage and the state of charge. Then, based on the experimental results of the open-circuit voltage test and hybrid power pulse characteristic test, the parameters of the battery model were identified by polynomial fitting and genetic algorithm, respectively. Furthermore, the temperature effects were considered in both the open-circuit voltage and hybrid power pulse characteristic tests. Finally, the proposed model was tested and verified by experiments under the Dynamic Stress Test condition and the Urban Dynamometer Driving Schedule at different temperatures. The accuracy of the proposed model is high and the parameter identification error is less than 1%.

Characterization of uncertainty contributions in a high-accuracy PMU validation system

The effective deployment of Phasor Measurement Units (PMUs) in Distribution Networks (DNs) requires an enhancement in terms of estimation accuracy beyond the limits of IEEE Std C37.118.1 (IEEE Std), aiming at a Total Vector Error (TVE) in the order of 0.0x% in steady-state test conditions. As a consequence, a rigorous metrological characterization of PMU performance requires a validation system whose accuracy is at least one order of magnitude better than the one of the device under test, i.e. it requires a TVE in the order of 0.00x% in steady-state test conditions and 0.0x% in distorted or dynamic test conditions. In this paper, we consider the hardware and software architecture of a previously published PMU validation system specifically designed for PMUs operating in DNs. In this context, we evaluate the quality of the generated test waveforms, and we carry out a thorough metrological characterization of the uncertainty contributions due to generation, acquisition and synchronization stages. In this sense, the proposed analysis provides a rigorous methodology for the evaluation of such low uncertainty levels, and enables us to identify and discuss the most challenging aspects in the implementation of a high-accuracy PMU validation system.

Progression and individual differences in children's series completion after dynamic testing.

BackgroundThe need to focus more on children's abilities to change requires new assessment technologies in education. Process‐oriented assessment can be useful in this regard. Dynamic testing has the potential to provide in‐depth information about children's learning processes and cognitive abilities.AimThis study implemented a process‐oriented dynamic testing procedure to obtain information regarding children's changes in series‐completion skills in a computerised test setting. We studied whether children who received a graduated prompts training would show more progression in series‐completion than children who received no training, and whether trained children would use more advanced explanations of their solutions than their untrained peers.SampleParticipants were 164 second‐grade children with a mean age of 7;11 years. Children were split into an unguided practice or a dynamic testing condition.MethodsThe study employed a pre‐test‐training‐post‐test design. Half of the children were trained in series‐completion, and the other half did not receive any feedback on their problem solving. Using item response theory analysis, we inspected the progression paths of the children in the two conditions.Results and conclusionsChildren who received training showed more progression in their series‐completion skills than the children who received no training. In addition, the trained children explained their solutions in a more advanced manner, when compared with the non‐trained control group. This information is valuable for educational practice as it provides a better understanding of how learning occurs and which factors contribute to cognitive changes.

High strain rate tensile behavior of a quenching and partitioning (Q&P) Fe-0.25C-1.5Si-3.0Mn steel

The mechanical behavior and microstructural evolution of a quenching and partitioning (Q&P) Fe-0.25C-1.5Si-3.0Mn (wt%) steel were investigated in a wide range of strain rates (10−4–103 s−1). The static tensile tests (10−4 and 10−2 s−1) were conducted using a universal testing machine, while high strain rate tests (500–1000 s−1) were carried out on a split Hopkinson tensile bar system. High speed camera imaging combined with the digital image correlation (DIC) technique were employed to study homogeneity of plastic deformation. Electron backscatter diffraction (EBSD) and scanning electron microscopy were used to characterize the microstructure evolution in the deformed zone and the fracture surface, respectively. The results indicate that the yield strength of the Q&P steel in dynamic tests (500–1000 s−1) is by 200 MPa higher compared to static tests (10−4 and 10−2 s−1), while the ultimate tensile strength tends to increase linearly with strain rate. The results of DIC analysis demonstrate that the homogeneity of plastic deformation is similar in static and dynamic test conditions. EBSD characterization shows that the retained austenite (RA) fraction decreases exponentially with the increase of plastic strain during both static and dynamic tensile testing. Additionally, examination of the fracture surfaces reveals the largest dimples in the statically tested specimens.

Evaluation of force‐based and displacement‐based out‐of‐plane seismic assessment methods for unreinforced masonry walls through refined model simulations

SummaryThe performance of force‐based and displacement‐based seismic assessment methods for the life‐safety limit state check of out‐of‐plane loaded unreinforced masonry walls is evaluated on the basis of refined numerical simulations. For this purpose, a discrete element model of a vertically spanning wall is built and validated against experimental results from static and dynamic test conditions. The model is then analysed for a large range of wall configurations. For each configuration, a static pushover analysis and a series of incremental dynamic analyses are run, the latter permitting to determine the capacity of the wall under dynamic loading. The accuracy of the assessment methods in predicting the acceleration at which the walls collapse is evaluated. It is found that the displacement‐based method is more accurate, robust, and safe than the force‐based method. The comparison also shows that for walls characterised by a relatively high ratio of axial load to Euler's critical load, both assessment methods lead to an overestimation of the wall capacity. As a remedy, a modification to the methods based on a recently developed mechanical model is put forward and tested. For the force‐based method, it is additionally suggested to set for walls with relatively high overburden ratios the behaviour factor equal to 1. To ensure reproducibility of this study, all input and output files of the numerical simulations are made publicly available.

State-of-charge estimation method of lithium-ion batteries based on long-short term memory network

This paper presents a method to estimate the state-of-charge (SOC) of lithium-ion batteries based on long-short term memory network (LSTM). The method is mainly composed of two parts: (1) A linear neural network is used to identify the parameters of second-order equivalent circuit model. (2) A LSTM network is built to estimate the SOC of lithium-ion battery. The linear neural network is trained using the American Dynamic Stress Test Condition (DST) dataset of battery (1st cycle), while the LSTM network is trained using the Chinese Standard Operating Condition (QCT) datasets of battery (1st, 10th and 20th cycle). After that, the trained LSTM network is tested using DST datasets of the batteries and QCT datasets under different temperatures. The results show that the LSTM network can accurately estimate the SOC of lithium battery under different temperatures, different working conditions and lifespan.

Application of the Basalt Powder as a Filler for Polypropylene Composites With Improved Thermo‐Mechanical Stability and Reduced Flammability

The influence of the basalt powder (BP) on mechanical properties as well as on thermal stability and flammability of the isotactic polypropylene (iPP) composites was investigated. Thermo‐mechanical stability of the pure polypropylene and composite materials containing from 5 up to 40 wt% BP was defined in static and dynamic testing conditions with the use of the heat distortion temperature measurement, vicat softening point temperature test, and dynamic mechanical thermal analysis. All measurements showed, unequivocally, a significant improvement of thermo‐mechanical stability of the composite materials which was directly related to an increasing amount of inorganic filler. A research conducted on the mechanical properties revealed that stiffness and hardness of polypropylene‐based composites was affected by the addition of the filler, leading to a strong increase of both mechanical parameters. Moreover, the application of thermogravimetric analysis and cone calorimetry measurements allowed to determine the composites with highest thermal stability, which was dependent on the concentration of the filler. Changes observed in the polypropylene‐based composites properties were related to an increase of thermal diffusivity caused by presence of the BP measured by modified Angstrom method. POLYM. ENG. SCI., 59:E71–E79, 2019. © 2018 Society of Plastics Engineers

Inhibition of Naphthenates Emulsion Soaps Chemical EOR using Synthesis Compound Derived from Fatty Hydrazide.

Naphthenates soaps emulsion generated from alkaline (A), surfactant (S) and polymer (P) flooding were studied with crude oil contained amphiphilic carboxylic acids, RCOOH from Malaysian oilfield. These naphthenic acids were characterised using high-resolution fourier transform ion-cyclotron resonance mass spectroscopy (FTCIR-MS). Alkaline Na2CO3 resulted in increase in pH of produced water to between pH 9 to 11 and generates in-situ oil-rich colloidal dispersion ultralow interfacial tension (IFT) character of sodium carboxylate soaps emulsion. Predictive measurement and inhibition were evaluated using new naphthenate inhibitor (NI)- demulsifier synthesized from fatty hydrazide. The structures of the synthesized compounds have been established by FTIR, 1H NMR, 13C NMR, and mass spectrometry (LCMS/MS). Inhibition and demulsification properties have been evaluated at operating parameters such as produce water cut level, ASP concentration and temperatures under dynamic testing condition using Multifunctional Mini Flow Loop (MMFLTM).

Comparative studies of the rheological behavior and microstructural properties of emulsions (oil/distilled water phase) and (oil/Lias water phase)

The rheological behavior of crude oil and their emulsions were investigated as a function of two water types (distilled water and the LIAS water). The focus of this work is to obtain more knowledge about the effect of LIAS water concentration, which used to maintain pressure and produced from production of crude oil in the oil fields Tin Fouye Tabankort-south Algeria, on the rheological properties of crude oil. The rheological parameters were measured by using AR-2000 rheometer at 15 °C under dynamic and shear testing conditions. The measured data were first classified into two groups for Newtonian and non-Newtonian fluids. Depends on the type and concentration of water, the non-Newtonian behavior was described in better way by the Casson, Power law and the Herschel–Bulkley models. The results indicated that the viscosity, the yield stress, the elastic modulus, (G′), the loss modulus, (G″), and the microstructure of the prepared emulsions not only varied with water concentration but also by water types.

High-precision and non-contact Fiber Optic Gyroscope dynamic calibration system with dual Laser Doppler Vibrometers

Since the advantages of high precision, large dynamic range in angular velocity measurement, Fiber Optic Gyroscopes (FOGs) are recently proposed to be used as angle measuring instrument. However, in dynamic testing condition like sway, the outputs of FOGs contain inevitable angular velocity measurement error, harming angle measuring accuracy. Therefore, FOGs must be calibrated before using. In this paper, we first propose a high-precision and non-contact angle measurement method with dual-Laser Doppler Vibrometers (d-LDVs) to calibrate the angle measurement error of FOGs in sway condition. Firstly, we verify the accuracy and dynamic range of this proposed angle measurement method by using a high-precision rotary table as an angle benchmark. Experimental results indicate that this method can reach the dynamic angle measurement with the range of ±10°, and the maximum angle measurement error is less than 0.0088°. Secondly, in order to calibrate the angle measuring error of FOGs, we establish an angle calibration system for FOGs based on d-LDVs under sway condition. Experimental result shows that the dynamic angle measurement error of the FOG caused by dynamic environment is less than 0.015°. Because of the zero drift of angular velocity, integral angle of the FOG shows angle drift, and the maximum angle drift is 0.06° (during 30s).

Predicting school achievement: Differential effects of dynamic testing measures and cognitive flexibility for math performance

Dynamic testing aims to assess potential for learning by measuring performance improvement as a response to training while testing. Dynamic test outcomes have been argued to be related to children's present and future achievements at school. The current study aimed to investigate whether dynamic measures of inductive reasoning would provide additional predictive value of math achievement while taking into account static inductive reasoning performance. In addition, as cognitive flexibility, one of the core executive functions, has been argued to be significantly involved in children's math performance, it was explored whether dynamic test outcomes would hold unique predictive value for math achievement while taking into account cognitive flexibility. Participants were 152 six- and seven-year-old children who were administered either a dynamic test of series completion comprising a pre-test–training–post-test format or a static series completion test consisting of a pre-and post-test, in combination with a test of cognitive flexibility. Children in the experimental, dynamic test condition were trained in series completion, while the children in the control condition only practiced series completion. The dynamic measures of inductive reasoning and cognitive flexibility were each found to provide additional predictive value to static pre-test performance and to hold unique predictive value for math achievement. The results underline the importance of both dynamic testing and cognitive flexibility in educational assessment and suggest that the assessment of cognitive flexibility should be an integral part of dynamic testing.

Hydrodynamic properties of biomimetic shark skin: effect of denticle size and swimming speed

Biomechanists and biologists alike have yet to fully understand the complex morphology and function of shark denticles, morphologically intricate tooth-like structures embedded into the skin of sharks. Denticles vary in many ways (such as size and shape) depending on shark species, and studies on denticle hydrodynamics have suggested that they may aid in drag reduction as well as increase both lift and thrust. Although previous studies have analyzed the effect of different denticle patterns on hydrodynamic performance, no previous work has focused on the effects of denticle size. Here, we report on the hydrodynamic properties of 3D printed shark skin foils with rigid denticles embedded into a flexible substrate. The patterning of these denticles was based on previously reported designs exhibiting the greatest hydrodynamic performance (which also most closely mimics real shark skin). The size of the denticles and the speed of the flow were varied, and the foils were evaluated under both static and dynamic conditions. Static tests showed drag reduction compared to a smooth control foil (without denticles) for the smallest denticle size, while medium and large denticles exhibited increased drag. Under dynamic testing conditions, the smallest denticles increased the self-propelled swimming speed, while the largest denticles reduced swimming performance. At higher speeds, the smallest denticles were also able to reduce power consumption compared to the control, demonstrating that their hydrodynamic effect depends on both denticle size and swimming speed. Our results thus provide new insights into the role of denticle size in shark swimming hydrodynamics across a range of locomotory modes, while simultaneously providing new design guidelines for the production of high performance low drag surface coatings for aquatic and aerospace applications.

Building a load characteristic of the fuel injection system of a ship’s medium-speed engine diesel in dynamic tests conditions

The object of research in the work is hydrodynamic processes in the high pressure fuel system of the ship’s medium-speed engine on variable modes. Variable regimes constitute a significant part of the operational time of a number of types of ships (tugs, fishing vessels, etc.), and for transport fleets they are characteristic for maneuvering. In the latter case, reliability and environmental safety for sanitary control zones are of particular importance. Studies of fuel supply processes in variable modes are important, since they largely determine all the operating characteristics of a diesel engine and are not well studiedThe article presents an experiment in which the task is obtaining the load characteristics and the study of transients in the fuel equipment of the ship’s medium-speed diesel engine under dynamic testing conditions. In the course of the research, a developed hardware and software complex is used to ensure the implementation of the experiment plan, fixation, processing and oscillography of the obtained data. An electromechanical system is developed by rack displacement of a high-pressure fuel pump with programmed computer control. The experiment program provides for changing the rack position in the whole range covering the operational load characteristic. The discrete displacement includes five fixed rack positions with a step transition between them. During testing, the high-pressure fuel pump completes 80 injection cycles over 44 s. The transition time between the individual fixed positions of the racks is 0.44 s. The stabilization period of hydrodynamic processes in the fuel supply system is close to 0.22 s. In the investigated range of rack positions mr=25–5 mm the main parameters of the fuel injection are as follows: рn.с=474–232 bar; рn.i=457–222 bar; рp=445–162 bar.The possibility of obtaining load characteristics by dynamic tests is shown, which significantly reduces the test time and increases the reliability of the data, eliminating the influence of the time trend parameters.

The role of cognitive flexibility in young children\u2019s potential for learning under dynamic testing conditions

The aim of the current study was to investigate to what extent children’s potential for learning is related to their level of cognitive flexibility. Potential for learning was measured through a dynamic testing procedure that aimed to measure how much a child can profit from a training procedure integrated into the testing process, including the amount and type of feedback the children required during this training procedure. The study followed a pre-test–training–post-test control group design. Participants were 153 6–7-year-old children. Half of this group of children were provided with a standardised graduated prompts procedure. The other half of the participants performed a non-inductive cognitive task. Children’s cognitive flexibility was measured through a card sorting test and a test of verbal fluency. Results show that cognitive flexibility was positively related to children’s performance, but only for children in the practice-only condition who received no training. These outcomes suggest that dynamic testing, and more in particular, the graduated prompting procedure, supports children’s cognitive flexibility, thereby giving children with weaker flexibility the opportunity to show more of their cognitive potential as measured through inductive reasoning.

Mechanical Behavior of Alumina based Reticulated Foams Encapsulated and Infiltrated with Polymer under Quasistatic and Dynamic Conditions

ABSTRACTCellular ceramic structures, due to their unique combination of thermal, structural and mechanical properties, are widely explored for the wide range of thermo-structural applications. However, the ceramic based structures have not been well explored for energy absorption properties due to their inherent brittleness. In the present study, alumina based ceramic foams were fabricated by polymeric sponge replication process and further these foams were encapsulated and infiltrated respectively in epoxy resin. All the three foams – bare, encapsulated and infiltrated were evaluated comparatively under quasistatic compression and dynamic impact conditions. The study revealed that the energy absorption properties can be significantly enhanced through encapsulation and infiltration of bare foam with epoxy resin. Extent of enhancement in energy absorption in case of infiltration was superior in comparison to encapsulation in both static and dynamic test conditions. The study demonstrated the possibility of exploring the potential of encapsulated and infiltrated ceramic foams in various shock attenuating applications.