Experimental Measurement Methods Research Articles

The study on the performance of air-cooled open-cathode PEMFC with dead-ended anode

ABSTRACT In order to be able to improve the hydrogen utilization as much as possible while ensuring the performance of the air-cooled open-cathode proton exchange membrane fuel cell (AO-PEMFC), the performance of the AO-PEMFC with dead-ended anode (DEA) was studied in this paper. First, the transient voltage model was established and the possible causes of voltage loss were analyzed. Then, the effects of anode inlet pressure, cyclic exhaust, and exhaust duration on the PEMFC performance were investigated by combining the experimental methods of transient voltage monitoring and EIS measurement. The results showed that the effect of anode inlet pressure is not positively correlated with PEMFC performance with DEA and also influenced by the load current. Cyclic exhaust can effectively reduces the voltage degradation, and the optimal exhaust cycle is different for different load current. The exhaust duration has little effect on the PEMFC performance at various load currents. However, the PEMFC performance showed a tendency to be increased and then stabilized with the increase of exhaust duration at higher current density.

Experimental method for internal deformation measurement of 3D solids with embedded cracks based on 3D printing and digital speckle techniques

Quantification of the internal deformation of fractured solids such as rock masses under external loads, especially the deformation around internal fractures, is crucial for understanding and predicting the failure of fractured solids. However, it is very difficult to achieve the goal using conventional experimental methods. In this study, we proposed a novel internal deformation measurement method based on three-dimensional (3D) printing and digital speckle techniques. The 3D printing technology was applied to fabricate a 3D transparent model with an embedded elliptical crack and to set a speckle pattern on the internal section of the transparent model. The digital image correlation (DIC) method was used to determine the internal deformation field of the 3D fractured model. The measured displacements and strains of the internal sections in the fractured model were compared with the numerical simulation results. The comparison indicates that the proposed experimental method can well determine the deformation inside the 3D model. This built-in speckle method can realize real-time observation of the internal deformation of a 3D solid model in a non-contact and non-destructive manner.

RNAfcg: RNA Flexibility Prediction Based on Topological Centrality and Global Features.

The dynamics of RNAs are related intimately to their functions. Molecular flexibility, as a starting point for understanding their dynamics, has been utilized to predict many characteristics associated with their functions. Since the experimental measurement methods are time-consuming and labor-intensive, it is urgently needed to develop reliable theoretical methods to predict RNA flexibility. In this work, we develop an effective machine learning method, RNAfcg, to predict RNA flexibility, where the Random Forest (RF) is trained by features including the topological centralities, flexibility-rigidity index, and global characteristics first introduced by us, as well as some traditional sequence and structural features. The analyses show that the three types of features introduced first have significant contributions to RNA flexibility prediction, among which the topological type contributes the most, which indicates the importance of structural topology in determining RNA flexibility. The performance comparison indicates that RNAfcg outperforms the state-of-the-art machine learning methods and the commonly used Gaussian Network Model (GNM) models, achieving a much higher Pearson correlation coefficient (PCC) of 0.6619 on the test data set. This work is helpful for understanding RNA dynamics and can be used to predict RNA function information. The source code is available at https://github.com/ChunhuaLab/RNAfcg/.

Research on improving heat transfer performance by using wavy ribs with different cross sections

Based on the change of the cross section in blade internal cooling channel rib caused by the service wear, starting from the widely used rectangular cross section, the most likely isosceles trapezoid and rectangular-semicircular cross section are considered, and the extreme design of the cross section (isosceles triangle) and the tentative exploration (spindle) are carried out. In this paper, the numerical calculation of SST k-ω turbulence model and the experimental research method of TSP measurement are used to thoroughly investigate the impact mechanisms of five different wavy rib cross-sections on the flow and heat transfer in turbine blade ribbed channels. The results show that different rib cross-sections alter the flow and heat transfer in channel by modifying flow allocation in height and width directions. The inclined sidewalls of the wavy ribs accumulate most of cooling air near the rib, which is the ultimate cause of the significant cooling effect. Under small rib radius and small rib angle, the heat transfer advantages of isosceles triangle and isosceles trapezoid cross-section wavy ribs are more obvious, which are increased by 14.88 % and 20.66 % respectively, but their friction factor is also 1.2 ∼ 2.0 times that of rectangular cross-section. The heat transfer of the large rib height on the isosceles triangular and isosceles trapezoidal cross-section wavy ribs is increased by 73.29 % and 185.31 %. Changes in Reynolds number have minimal impact on the friction factor, but significantly impact the overall heat transfer.

A lightweight concrete composite material with improved EMI shielding by using a chiral particle array

This paper proposes a structure for concrete composite materials for electromagnetic interference shielding applications. It comprises an array of helical-shaped conductive particles as chiral additives. Unlike the previous studies using large quantities of conductive additives, this study provides a lightweight concrete composite due to the utilization of a small number of additives with a high level of shielding effectiveness in a wide frequency range. The heart of the proposed structure lies in leveraging the evanescent wave propagation in a circular waveguide, resulting in considerable shielding effectiveness. Under particular conditions, the helical particles can imitate a below-cutoff cylindrical waveguide and its dominant mode surface current on the helical wire. This phenomenon significantly attenuates the transmitted power from the array of helical particles in its resonance frequency range. Besides presenting the composition that exploits the magnetoelectric properties of the particles, this paper compares it with a traditional concrete composite, including randomly distributed sinusoidal steel rods. This second approach is examined using both experimental measurement and full-wave simulation methods. The results of this study indicate that the appropriate geometry of the conductive additives, in this case, chiral particles, and their arrangement in a regular array rather than a random distribution can enhance the efficiency of the conductive additives. This idea paves the way for more robust, efficient, and lightweight concrete composite materials, thanks to the recent advances in modern civil engineering manufacturing methods.

Systematic review for optimizing sample size in dairy cow methane emission studies in temperate regions: A comprehensive methodological approach

This research introduces a systematic framework for calculating sample size in studies focusing on enteric methane (CH4, g/kg of DMI) yield reduction in dairy cows. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we conducted a comprehensive search across the Web of Science, Scopus, and PubMed Central databases for studies published from 2012 to 2023. The inclusion criteria were as follows: studies reporting CH4 yield and its variability in dairy cows, employing specific experimental designs (Latin square design [LSqD], crossover design, randomized complete block design [RCBD], and repeated measures design) and measurement methods (open-circuit respirometry chambers [RC], the GreenFeed system, and the sulfur hexafluoride tracer technique), conducted in Canada, the United States, and Europe. A total of 150 studies, comprising 177 reports, met our criteria and were included in the database. Our methodology for using the database for sample size calculations began by defining 6 CH4 yield reduction levels (5%, 10%, 15%, 20%, 30%, and 50%). Using an adjusted Cohen's f formula and conducting power analysis, we calculated the sample sizes required for these reductions in balanced LSqD and RCBD reports from studies involving 3 or 4 treatments. The results indicate that within-subject studies (i.e., LSqD) require smaller sample sizes to detect CH4 yield reductions compared with between-subject studies (i.e., RCBD). Although experiments using RC typically require fewer individuals due to their higher accuracy, our results demonstrate that this expected advantage is not evident in reports from RCBD studies with 4 treatments. A key innovation of this research is the development of a web-based tool that simplifies the process of sample size calculation (https://samplesizecalculator.ucdavis.edu/). Developed using Python, this tool leverages the extensive database to provide tailored sample size recommendations for specific experimental scenarios. It ensures that experiments are adequately powered to detect meaningful differences in CH4 emissions, thereby contributing to the scientific rigor of studies in this critical area of environmental and agricultural research. With its user-friendly interface and robust back-end calculations, this tool represents an important advancement in the methodology for planning and executing CH4 emission studies in dairy cows, aligning with global efforts toward sustainable agricultural practices and environmental conservation.

Review on convective and radiation heat transfer between bridges and external environments

The heat exchange between bridges and external environments is the primary cause of the temperature effect on bridges. The complexity of the two-phase (gas–solid) heat transfer mechanism, the diversity of the surface characteristics of bridge materials, and the uncertainties of the environment in which bridges are located make the numerical calculation of the heat exchange between bridges and external environments difficult. Several studies have been conducted by scholars around the world. In this work, the research on convective and radiative heat exchange between bridges and external environments is surveyed, analyzed, and summarized. The influencing factors and calculation methods of bridge temperature are examined, and the convective heat transfer and radiation mechanisms, theoretical calculations, and experimental measurement methods used to investigate the relation between bridges and external environments are summarized and analyzed. The value determination methods for convective heat transfer and radiation absorption coefficients in the calculation of the bridge temperature field are summarized. In addition, the problems and shortcomings of current research are evaluated, and future research directions are identified and discussed.

Modeling of ionic liquids viscosity via advanced white-box machine learning.

Ionic liquids (ILs) are more widely used within the industry than ever before, and accurate models of their physicochemical characteristics are becoming increasingly important during the process optimization. It is especially challenging to simulate the viscosity of ILs since there is no widely agreed explanation of how viscosity is determined in liquids. In this research, genetic programming (GP) and group method of data handling (GMDH) models were used as white-box machine learning approaches to predict the viscosity of pure ILs. These methods were developed based on a large open literature database of 2813 experimental viscosity values from 45 various ILs at different pressures (0.06-298.9MPa) and temperatures (253.15-573K). The models were developed based on five, six, and seven inputs, and it was found that all the models with seven inputs provided more accurate results, while the models with five and six inputs had acceptable accuracy and simpler formulas. Based on GMDH and GP proposed approaches, the suggested GMDHmodel with seven inputs gave the most exact results with an average absolute relative deviation (AARD) of 8.14% and a coefficient of determination (R2) of 0.98. The proposed techniques were compared with theoretical and empirical models available in the literature, and it was displayed that the GMDH model with seven inputs strongly outperforms the existing approaches. The leverage statistical analysis revealed that most of the experimental data were located within the applicability domains of both GMDH and GP models and were of high quality. Trend analysis also illustrated that the GMDH and GP models could follow the expected trends of viscosity with variations in pressure and temperature. In addition, the relevancy factor portrayed that the temperature had the greatest impact on the ILs viscosity. The findings of this study illustrated that the proposed models represented strong alternatives to time-consuming and costly experimental methods of ILs viscosity measurement.

PWHT influence on welding residual stress in 45 mm bridge steel butt-welded joint

To investigate the spatial distribution of welding residual stress (WRS) and effect of post welding heat treatment (PWHT) on WRS relaxation in the welded components of steel bridges, a 45 mm-thick Q345qD butt-welded specimen was manufactured. Experimental measurement and numerical simulation methods were employed to examine specimen surface and internal WRSs. The simulated results exhibited good agreement with the measured ones, confirming the rationality of the numerical simulation process. Subsequently, through the PWHT simulation in ABAQUS, the evolution of WRS during PWHT was comprehensively analyzed and the effect of PWHT parameters on the stress relaxation was studied. The measured and simulated results show that the longitudinal welding residual stresses (LWRSs) are tensile in the weld region and compressive away from the weld. High-value stresses are mainly concentrated on specimen surfaces and the mid-thickness. Transverse welding residual stresses (TWRSs) present multi-layered distribution, alternating between tension and compression within the weld region. WRS reduction mainly occurs during the heating stage of PWHT, with slight decrease during the holding stage and an increase during the cooling stage. Optimizing PWHT parameters, including temperature, and holding time, heating/cooling rates, proved effective in achieving substantial WRS relaxation.

Evaluation of the thermo-acoustic instability frequency and growth rate via input reflection coefficient measurement for central heating equipment

Experimental measurement methods and theoretical evaluations based on low-order modeling approaches for both the growth rate and frequency at the onset of thermo-acoustic combustion instability are proposed, and their performance is evaluated. The developed techniques are demonstrated through a systematic measurement of the linear growth rate and frequency of evolving oscillations in the laboratory setup and also applied for the thermo-acoustic qualification of an industrial domestic boiler and a heat cell unit (combination of a burner with a heat-exchanger). Generic measurements have been done for a burner deck with premixed surface-stabilized Bunsen-type flames. The industrial domestic boiler and the heat cell unit are equipped with burners of a similar type but differ by their perforation pattern. They have been tested at different conditions and the experimental and theoretical results are compared. Two modeling strategies are tested: 1- in Laplace domain, with estimating a rational function in the complex domain to fit the measured frequency response, 2- exclusively in frequency domain, without estimating a rational function. Both methods include measurement of the frequency response of two reflection coefficients from i) the upstream part of the system, Rup, and ii) burner with flame completed by the downstream part of the appliance, Rin. Within the first approach, a procedure for an analytic continuation of the measured frequency response to the complex domain is applied and complex eigenfrequencies are calculated by solving the corresponding dispersion equation. An alternative approach was proposed by Kopitz and Polifke and allows estimating both the frequency of oscillation and the growth rate from the analysis of the polar plot of the system's characteristic equation in the frequency domain. The comparison shows that the unstable frequencies can be predicted accurately by both tested modeling strategies. This conclusion holds also for the tested industrial applications. The prediction of the instability growth rates is closer to the measured one when the modeling method in the complex domain is used. However, the frequency domain analysis provides less accurate, but still reasonable estimates of the growth rates and frequencies. Moreover, a good overview of thermo-acoustic performance of each industrial boiler/burner at different conditions is obtained via Rin measurements.

A high-precision experimental measurement system and method for the parahydrogen concentration and the Ortho-Para hydrogen catalyst's catalytic performance

An experimental system that combines the measurement of parahydrogen concentration with the assessment of ortho-para hydrogen catalyst's catalytic performance was created for this investigation. The concentration of parahydrogen was detected by a thermal conductivity detector integrated into the gas chromatograph. The catalyst sample and the generator of standard gas were integrated into one experimental setup for easier operation. Meanwhile, a new method for catalytic performance evaluation of ortho-para hydrogen catalyst was developed based on this system. This method can decrease test time and yield more valuable test results than the conventional way. Throughout the experiments, the system's dependability was increased by optimizing the utilization of the carrier gas. The deviation analysis and repeatability verification of the relevant test data showed that the relative standard deviation was less than 0.35% and the mean value of the variation coefficient was less than 0.20%, which demonstrated the method had high accuracy, stability, and reliability. Further studies have shown that the catalysts should be densely packed inside the converter and kept out of the air to maximize their catalytic activity. These pertinent findings regarding the application of ortho-parahydrogen catalysts in this study can guide the design of the ortho-parahydrogen converter in actual hydrogen liquefiers. Moreover, the method and the procedure proposed in this study may contribute to the optimization of the ortho-parahydrogen catalyst production process as well as the calibration of the parahydrogen concentration in liquid hydrogen products.

Numerical simulation of the welding process for the prediction of temperature distribution on Al/steel explosion welded joint

Joining steel and aluminum alloys is a common problem in many engineering structures. One of the alternatives for combining these materials is welding them using explosively welded transition joints. The biggest problem is the difference in welding temperatures of steel and aluminum alloys. The higher welding temperature of steel means there is a high risk of overheating the aluminum alloy in the transition joint. One of the methods of optimizing the dimensions of an explosively welded connector is to conduct experimental tests. These tests can indicate the minimum size of the connector in which the steel welding process does not cause changes in the microstructure and strength of the aluminum alloy. Conducting experimental research is time-consuming and expensive. First, it is necessary to produce explosively welded plates. Secondly, specimens of welded joints must be prepared. In order to minimize costs and speed up the design process, the number of experimental tests can be reduced by conducting numerical analyses. The aim of this work is to describe a method for modeling the distribution of temperature fields during welding of steel and aluminum alloy joints using transition joints. The method of manufacturing joint specimens and the method of experimental measurement of temperature during welding are described. The results compare the temperature distributions in an explosively welded connector during steel welding, determined experimentally and using numerical methods.

Research on porosity characterization methods of shale oil reservoirs in Lianggaoshan Formation, Sichuan Basin

Shale oil, an important component of unconventional oil and gas resources, mainly exists in the storage spaces such as shale pores, microfractures, etc. Porosity is commonly used to quantitatively describe the storage space of shale oil and is a key parameter in reservoir evaluation. However, there are significant differences in the results by existing experimental methods for porosity measurement, and moreover, it is difficult to compare the porosity obtained by the experimental measurement method with the logging calculation method. It is urgent to explore reasons for the differences in porosity measurement between various porosity experiments and logging calculations of the shale oil reservoir, and propose an effective method for shale oil reservoir to characterize porosity. In this research, core samples of shale oil reservoirs from the Lianggaoshan Formation of the Sichuan Basin were selected to measure the porosity by means of experimental methods including helium gas charging, saturation liquid method, nuclear magnetic resonance (NMR), etc. Meanwhile, porosity was calculated using the combination method of lithology scanning (LS) logging and conventional logging as well as the NMR logging method. Subsequently, porosity experimental results and logging calculation results were compared to clarify the applicability of various porosity characterization methods. The research results indicate that: 1) The porosity measurement results by the saturation liquid method and the NMR experimental method are close, both greater than that using the helium gas charging method; 2) The hydrogen signal of the dry-state sample is significant in the NMR experiment, mainly originating from organic matter and clay minerals; 3) The NMR short relaxation component in the water-saturated state primarily reflects the signal of organic matter and clay mineral matrix, while the long relaxation component reflects the pore fluid component; 4) After deducting the NMR signal of the dry-state core, the core NMR porosity measurement results under the water-saturated state agree well with that using the saturation liquid method, which is an indicative of effective reservoir porosity; 5) The NMR logging is limited by its echo spacing and cannot reflect the signal from organic matter and the crystal water in clay minerals at T2 < 0.3 ms. Taken together, the porosity measurement method of subtracting the dry-state NMR signal from the water-saturated state NMR signal is considered effective and can be used to reflect the porosity of shale oil reservoirs in the Lianggaoshan Formation of the Sichuan Basin.

Efficient grain size evaluation based on single direction measurement of ultrasonic backscattering coefficient

<sec>GH4742 nickel-based superalloy exhibits excellent mechanical properties, and grain size is a key factor affecting its performance. A physical model-based ultrasonic backscattering method makes grain size measurement accurate and efficient. Nevertheless, it is constrained by complex models or multiple measurements taken from various beam angles. As a result, a backscattering coefficient method that requires only a single measurement for grain size evaluation is proposed. In contrast to the existing methods, the proposed method solely focuses on the backscattering coefficient component of the backscattering signal. It effectively eliminates the influence of unrelated factors, such as the measurement system and the acoustic field, through the utilization of reference signals.</sec><sec>The independent scattering model is employed to derive the backscattering coefficient, which solely pertains to the material itself. The relationship between grain size and backscattering coefficient is described by using a spatial correlation function. To consider the irrelevant factors, an experimental measurement method is developed by using the reference signals. Through numerical calculation and analysis, it has been observed that the backscattering coefficient is closely related to the frequency. When the product of the wavenumber and the grain size is significantly greater than 1 (<inline-formula><tex-math id="M1">\begin{document}$ ka\gg 1 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231959_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231959_M1.png"/></alternatives></inline-formula>), a Stochastic scattering limit is reached. Conversely, when <inline-formula><tex-math id="M2">\begin{document}$ ka\ll 1 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231959_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231959_M2.png"/></alternatives></inline-formula>, a Rayleigh scattering limit is observed. Furthermore, the backscattering coefficient is directly proportional to the grain size. As a general trend, larger grain sizes result in higher backscattering coefficient.</sec><sec>Three sets of GH4742 specimens with different grain sizes are prepared for phased array ultrasound experiments. It can be observed that the experimental backscattering coefficients, root mean square (RMS) values, and the amplitude trend of time domain signal are consistent. To perform grain size inversion, the backscattering coefficients in the effective bandwidth range of the probe are selected. By utilizing the least-square method, the theoretical backscattering coefficient is employed to fit the curves of the experimental backscattering coefficients. The evaluation results are compared with those obtained by metallographic analysis. The results show that the grain sizes obtained by the proposed method have a maximum relative error of –22.7% and a minimum relative error of –3.7%.</sec>

Precision measurement based on rovibrational spectrum of cold molecular hydrogen ion

A molecular hydrogen ion HD<sup>+</sup>, composed of a proton, a deuteron, and an electron, has a rich set of rovibrational transitions that can be theoretically calculated and experimentally measured precisely. Currently, the relative accuracy of the rovibrational transition frequencies of the HD<sup>+</sup> molecular ions has reached 10<sup>–12</sup>. By comparing experimental measurements with theoretical calculations of the HD<sup>+</sup> rovibrational spectrum, the precise determination of the proton-electron mass ratio, the testing of quantum electrodynamics(QED) theory, and the exploration of new physics beyond the standard model can be achieved. The experiment on HD<sup>+</sup> rovibrational spectrum has achieved the highest accuracy (20 ppt, 1 ppt = 10<sup>–12</sup>) in measuring proton-electron mass ratio. This ppaper comprehensively introduces the research status of HD<sup>+</sup> rovibrational spectroscopy, and details the experimental method of the high-precision rovibrational spectroscopic measurement based on the sympathetic cooling of HD<sup>+</sup> ions by laser-cooled Be<sup>+</sup> ions. In Section 2, the technologies of generating and trapping both Be<sup>+</sup> ions and HD<sup>+</sup> ions are introduced. Three methods of generating ions, including electron impact, laser ablation and photoionization, are also compared. In Section 3, we show the successful control of the kinetic energy of HD<sup>+</sup> molecular ions through the sympathetic cooling, and the importance of laser frequency stabilization for sympathetic cooling of HD<sup>+</sup> molecular ions. In Section 4, two methods of preparing internal states of HD<sup>+</sup> molecular ions, optical pumping and resonance enhanced threshold photoionization, are introduced. Both methods show the significant increase of population in the ground rovibrational state. In Section 5, we introduce two methods of determining the change in the number of HD<sup>+</sup> molecular ions, i.e. secular excitation and molecular dynamic simulation. Both methods combined with resonance enhanced multiphoton dissociation can detect the rovibrational transitions of HD<sup>+</sup> molecular ions. In Section 6, the experimental setup and process for the rovibrational spectrum of HD<sup>+</sup> molecular ions are given and the up-to-date results are shown. Finally, this paper summarizes the techniques used in HD<sup>+</sup> rovibrational spectroscopic measurements, and presents the prospects of potential spectroscopic technologies for further improving frequency measurement precision and developing the spectroscopic methods of different isotopic hydrogen molecular ions.

A Meta-Analysis of the Effects of Taekwondo on Physical Self-Concept.

In this meta-analysis we explored whether Taekwondo practice has improved its participants' physical self-concepts. We also tested the mediating influence of factors in past research such as country, participant age, and measurement properties in their associations with these taekwondo effects. We reviewed extensive data collected from Chinese, English and Korean participants in articles listed in Cnki, Wanfang, PubMed, Web of Science, KISS, RISS, and DBPIA databases. First, we evaluated the methodological quality of these published articles with Review Manager 5.4 software according to the Cochrane System Evaluation Manual. Then, we used Comprehensive Meta-Analysis 3.7 software for statistical analysis. We based these analyses on nine research studies containing a total of 1154 participants. We found a significant association between taekwondo activity and an improved body self-concept (ES = .688, p < .001). Subgroup analyses showed a stronger association between these variables in Korea (ES = .90, p < .001) than in China (ES = .34, p < .001), a stronger association for children (ES = 1.04, p < .001) compared to adults (ES = .46, p < .001), and a stronger association with the modified version of the Physical Self-Description Questionnaire (PSDQ) (ES = .99, p < .001) than with the original PSDQ (ES = .57, p < .001). We concluded that practicing Taekwondo led to improved physical self-concept, especially in a younger population. In addition, the experimental design and measurement methods may influence the apparent link between these variables.

Imaging of atomic stress at grain boundaries based on machine learning

The mechanical behaviors of crystalline materials, in particular the atomic scale deformation and failure processes, are strongly influenced by the local atomic stress near crystalline defects such as vacancies, dislocations and grain boundaries (GBs). Modern electron microscopy techniques have achieved unprecedented capabilities to image the internal microstructure of crystalline materials with atomic resolution. In comparison, our ability to map the corresponding atomic stress field, especially at grain boundaries with complex atomic structures, remains lagging behind due to the lack of direct experimental methods for stress measurement. Here, we propose a machine learning-based framework to realize atomic structure-stress (Atom-S2) mapping based on in situ transmission electron microscopy images. We demonstrate that, with optimized anti-noise performance and generalization ability, the Atom-S2 framework enables quantitative mapping of atomic stress in symmetrical tilt GBs, twin boundaries (TBs) as well as general GBs with changing curvature in crystalline metals. Moreover, the Atom-S2 can help understand, interpret and predict grain boundary stress evolution and plastic deformation mechanisms based on high-resolution transmission electron microscopy images, which provides a powerful tool to study atomic scale deformation behaviors and holds promises for accelerating materials design through defect engineering.

Beyond simple laboratory studies: Developing sophisticated models to study rich behavior.

Psychology and neuroscience are concerned with the study of behavior, of internal cognitive processes, and their neural foundations. However, most laboratory studies use constrained experimental settings that greatly limit the range of behaviors that can be expressed. While focusing on restricted settings ensures methodological control, it risks impoverishing the object of study: by restricting behavior, we might miss key aspects of cognitive and neural functions. In this article, we argue that psychology and neuroscience should increasingly adopt innovative experimental designs, measurement methods, analysis techniques and sophisticated computational models to probe rich, ecologically valid forms of behavior, including social behavior. We discuss the challenges of studying rich forms of behavior as well as the novel opportunities offered by state-of-the-art methodologies and new sensing technologies, and we highlight the importance of developing sophisticated formal models. We exemplify our arguments by reviewing some recent streams of research in psychology, neuroscience and other fields (e.g., sports analytics, ethology and robotics) that have addressed rich forms of behavior in a model-based manner. We hope that these "success cases" will encourage psychologists and neuroscientists to extend their toolbox of techniques with sophisticated behavioral models - and to use them to study rich forms of behavior as well as the cognitive and neural processes that they engage.

The influence of external operating conditions on membrane drying faults of proton-exchange membrane fuel cells

A study of the influence of water management failure can help improve water management strategies, relieve flooding or drying faults. To explore the influence of drying faults on proton-exchange membrane fuel cells (PEMFCs) under different operating conditions, this study adopted an experimental measurement method combining a cathode voltage drop, voltage signal and electrochemical impedance spectroscopy (EIS). First, multiple sets of drying experiments were performed under different operating conditions, cathodic pressure drop and voltage data were collected during the experiments, and dynamic EIS measurements were performed. Then, by analyzing the pressure drop and voltage trends, the influence of different operating conditions on drying faults was obtained. In addition, the EIS results were parametrically identified using an RL(RQ-RC) equivalent circuit model to obtain ohmic, charge transfer, and mass transfer impedance values. Finally, the evolution and influence of drying faults were verified by impedance variations. The experimental results showed that the ohmic and charge transfer impedance increased significantly with the degree of drying fault, while the mass transfer impedance showed only a small fluctuation or slight increase. Increasing the cathodic back-pressure relieved drying; a larger cathodic stoichiometric ratio increased the drying rate, and a higher cell temperature was more likely to cause severe drying.

Designing and Commissioning an Experimental Setup to Evaluate AC Losses in Superconductors Under Transverse Rotating Fields

The development of low AC loss MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> conductors and the increasing interest in a liquid hydrogen-based economy have reignited research into high power density fully superconducting (SC) electrical machines. In these machines, the armature winding experiences rotating fields that generate AC losses, making it essential to estimate these losses during machine design. While analytical and finite element analysis (FEA) models are available in the literature for estimating AC losses, these models for multi-filament MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> superconductors have yet to be experimentally validated for machine operating regions. This paper presents a high-precision AC-loss test setup to measure AC losses in SC MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> windings under rotating fields at the air-gap field, frequency, and operating temperature levels relevant to electrical machine applications. The experimentally measured AC losses are then compared with analytical and FEA models. Results demonstrate good agreement between measurements and predictions. The paper discusses the experimental setup, sample preparation, calibration, measurement method, and results. The study provides a significant contribution to the development of high power density fully SC electrical machines.