Constant Compression Research Articles

Lateral Behavior of Columns With High-Strength Steel Coiled Strip Confinement

This paper presents the experimental investigation of the behavior of square reinforced concrete columns with high-strength (100 ksi [690 MPa]) steel coiled strips as embedded confinement reinforcement under reversed-cyclic lateral loading and constant axial compression load. Six full-scale specimens (20 × 20 in. [508 × 508 mm] cross section) with the following vari¬ations were tested: confinement type (strip or reinforc¬ing bar), layout (hoops and ties, spirals), and reinforce-ment ratios. The strip-confined specimens had similar peak strengths as a specimen confined by reinforcing bar ties, and this strength exceeded analytical predic¬tions. The stiffness of the strip-confined specimens was greater than the reinforcing-bar-confined specimen. In accordance with the American Concrete Institute’s Acceptance Criteria for Moment Frames Based on Structural Testing (T1.1-01), all specimens met the cri¬terion that the lateral load at 3.5% drift was not below 75% of the peak. Strip-confined specimens demonstrat¬ed improved residual strength behavior relative to the reinforcing-bar-confined specimen. Overall, the study demonstrated the promise of steel strip confinement for reinforced concrete columns in seismic regions.

Experimental investigation on the cyclic behaviour of full-scale reinforced concrete columns under biaxial shear loading

Although reinforced concrete (RC) elements frequently undergo biaxial shear forces, limited experimental investigations on RC elements subject to biaxial shear have been conducted, and studies about the different types of biaxial shear failure (i.e., flexural-shear and brittle shear) are even scarcer. The focus of this experimental study is on the flexural-shear and the shear failure modes of shear-deficient full-scale RC columns tested under constant compression and subject to an oblique cyclic lateral load with respect to the principal axes of the cross-section. Twelve columns with square and rectangular cross-section have been tested by applying the shear load along different directions. A comprehensive set of experimental data is critically presented to investigate the effect of biaxial loading condition on damage patterns, strain distribution of longitudinal and transverse reinforcement, force–displacement curves of the columns, shear capacity, displacement ductility, stiffness and energy dissipation. It has been found that: i) biaxial loading condition affects the cracking morphology and distribution, as the cracks appear steeper and denser for columns subjected to uniaxial loading, and diffused and more gradually inclined for columns subjected to biaxial loading; ii) stirrups being more parallel to the loading direction are more prone to yield than orthogonal ones, while yielding of longitudinal bars occurs subsequently under biaxial loading; iii) the quadratic interaction domain underestimates the shear capacity of brittle shear columns with low amounts of stirrups by around 10%; iv) the quadratic interaction domain provides reasonable predictions of the displacement capacity under biaxial shear.

Pressurizing the Fuel Cell in a Direct Hybrid System for Airborne Applications

The push towards achieving emission-free aviation is intensifying. The number of demonstrator aircraft like the HY4 form H2FLY or the ATR72 from Universal Hydrogen taking flight and gaining experience in electric aviation is increasing. One existing approach for the realization of an all-electric aircraft is a direct hybrid system comprising a fuel cell and a battery. During high-power phases of a mission, such as takeoff and climb, both the battery and the fuel cell contribute power. However, during cruise, power is solely supplied by the fuel cell to leverage the high energy density of hydrogen. In a direct hybrid system, the power share of the fuel cell and the battery is determined by the size and the operating conditions of both.The low ambient pressures at high altitude negatively affect the performance of fuel cells. This is not only important in fuel cell only propulsion systems but also when operating a direct hybrid system. The impact of low pressures on the behavior of a direct hybrid system, linking a fuel cell and a battery without a DC/DC converter, is demonstrated. The effects of a non-pressurized PEM-fuel cell in a direct hybrid with a lithium-ion battery in a low-pressure environment was analyzed previously (see attached figure).However, since weight and volume are crucial factors in an aircraft, the fuel cell reactants can be pressurized to increase the power density of the system. Pressurization improves the fuel cells performance and therefore reduces weight and volume of the system, but the pressurization of the ambient air to the desired inlet pressure of the fuel cell cathode requires energy. The pressurization of a fuel cell also changes its voltage power behavior, which in turn affects the operation of the direct hybrid system.In order to examine and analyze the influence of pressurization on the overall system performance, an open-source two-phase model of a fuel cell is used and compared to experimental measurement data to gain fuel cell data at different pressure levels.The behavior of the direct hybrid system at different operating conditions will be presented, where the net power of the pressurized PEM-fuel cell system is combined with a battery to form a direct hybrid system. At lower state of charge (SOC) levels, the share of the fuel cell increases due to the lower voltage level of the battery over all power levels. In a pressure-driven fuel cell system, we take advantage of the fact that the pressure of the reactants can be controlled. By adjusting the pressure, the power share of the fuel cell and battery can be actively controlled. Lower operating pressure results in a higher battery share, due to the lower fuel cell voltage. By increasing the pressure, the voltage level provided by the fuel cell increases and therefore the power share of the fuel cell also increases.In addition, a realistic flight mission is analyzed with a constant compression ratio for the fuel cell air supply resulting in variable operating pressures of the fuel cell during flight, due to the different environmental pressures. The performance of the pressurized fuel cell direct hybrid under those varying ambient conditions will be presented. Figure 1

Study on the characteristics of cavitation and COD removal of an addendum rotational hydrodynamic cavitation reactors

AbstractThis paper presented an addendum rotational hydrodynamic cavitation reactors (ARHCR) that enabled circumferential shear cavitation, axial cavitation, and the Venturi effect, thus increasing cavitation efficiency. The experiments on hydroxyl (·OH) release and chemical oxygen demand (COD) removal demonstrate the feasibility of cavitation performance characterization and COD removal rate. The findings indicate that the COD removal rate can reach a maximum value of 28% or 30% with an increase in flow rate or rotating speed, respectively. Specifically, the maximum values were achieved at a rotation speed of 2,500 rpm or a flow rate of 1.0 m3·h−1. Based on the mechanism of the addendum cavitation, the wedge angles, and the crucial structural parameters, were examined for optimizing cavitation performance. The results revealed that the cavitation number and cavitation bubble were significantly influenced by wedge angles, as well as the efficiency of cavitation energy. The mechanical shear of fluid was enhanced by wedge angles, resulting in constant compression and release of fluid with increased kinetic energy. This led to stronger effects on bulge blocks, and the formation of vortexes that rebounded constantly, resulting in lower pressure areas and expanded regions of cavitation. Among the wedge angles tested, the wedge angle of 15° exhibited the highest cavitation bubbles with a maximum value of 46%. This was 31% higher than the grooves‐type cavitator reported. Furthermore, the cavitation performance was extremely improved with a wedge angle of 15°, as corresponding with the maximum efficiency of cavitation energy. These explorations provide references for the removal of COD in industrial and agricultural wastewater, as well as the development of novel reactors for wastewater treatment.

Modeling and Energy Flow Calculation of Integrated Energy System Based on Partial Differential Equation Model

This paper discusses the modeling and energy flow calculation method of integrated energy system based on partial differential equation model. By constructing a model that integrates power, heat, and natural gas networks, we analyze in detail the process of energy transmission, conversion, and storage in the system. In the process of modeling, the influence of compressor in constant compression ratio, constant outlet pressure and constant natural gas flow is specially considered, and the accuracy of the model is verified by specific data. In terms of energy flow calculation methods, we compare the performance of the unified solution method and the decomposition solution method. Data analysis shows that the non-gradient descent iterative method, gradient descent iterative method and decomposition solution method show consistency in calculation accuracy, that is, the calculation results of the three methods are the same. However, in terms of computational efficiency, the gradient descent iterative method shows significant advantages. Specifically, under identical computing conditions, our analysis reveals that the gradient descent iterative method exhibits a convergence rate approximately 30% faster than the decomposition solution method, resulting in a notable reduction of around 25% in computational time. This pivotal observation serves as a solid foundation for selecting a more computationally efficient approach in practical applications. To further enhance the computational efficiency, we have delved into deriving the Jacobian matrix of the model and subsequently proposed an advanced gradient descent iterative calculation technique. Through the actual test, this method not only improves the calculation speed, but also ensures the stability and accuracy of the calculation. The research in this paper not only provides a strong theoretical support for the optimal operation of the integrated energy system, but also provides a valuable reference for future research in related fields. Through specific data analysis, we prove the effectiveness and practicability of the proposed method, laying a solid foundation for the sustainable development of integrated energy systems.

Experimental assessment of catalytic biofuel effect on performance and exhaust emission of diesel engine

The present experiment is to analyze the effect of blended biodiesel of chicken fat CF10 (10% chicken fat and 90% diesel), waste cooking oil WC10 (10% waste cooking oil and 90% diesel), and combined chicken fat with waste cooking oil CF&WC10 (5% chicken fat + 5% waste cooking oil and 90% diesel) on the performance of diesel engine. The experiment is conducted at a constant compression ratio of 17, mixing 50 ppm alumina alfa (Al2O3-α) catalyst nanoparticles in each blend. The performance of biodiesel is analyzed at 25%, 50%, 75%, and 100% load conditions and is compared with pure diesel. The results show that the brake torque (BT) and brake power of CF&WC10 were found to be 22.48 Nm and 3.58 kW at full load conditions. However, the indicated thermal efficiency and BTE of CF&WC10 are at full loading conditions of 52.45% and 26.78% respectively. Because the supply of A/F ratio is 18.81, at full load condition and also lowering the brake specific fuel consumption up to 0.32 kg/kWh. Therefore, optimization of both performance and exhaust emission of an engine depends on BTE and NOx as well as HC emissions. Hence, from the emissions reduction point of view, CF&WC10 has lower emissions while achieving brake thermal efficiency similar to diesel fuel. The novelty of research shows CF&WC10 leads to enhanced performance of diesel engine compared to pure diesel fuel.

Seismic Performance of Precast Drift-Hardening Concrete Walls Connected by Grout-Sheath Duct.

In order to find a suitable size of sheath duct and a reliable construction method for precast walls, a cast-in-place and five 1/2 scale precast drift-hardening concrete walls reinforced with weakly bonded ultra-high strength SBPDN rebars were fabricated and tested under reserved lateral load and constant compression. The experimental variables were the diameter of sheath ducts (45 mm, 100 mm, and 120 mm), embedded length (20d and 35d; d is the nominal diameter of SBPDN rebars), axial load ratio (0.075 and 0.15), and the construction method. The experimental observations, hysteresis behaviors, envelope curves, residual deformation, crack propagation, and energy dissipation were compared in the study. Moreover, a formula was applied to calculate the bond strength of the sheath duct. The experimental and calculated results revealed that increasing the axial load ratio and embedment length could not enhance the bond strength of the sheath ducts, and increasing the diameter decreased the bond strength significantly. Anchored the SBPDN rebars in smaller sheath ducts separately was a more stable connection method for precast concrete shear walls and provided sufficient drift-hardening capability, even at a large drift level (over 3%).

Equivalent spring-like system for two nonlinear springs in series: application in metastructure units design

The paper deals with the problem of design of unit in auxetic metastructure. The unit is modeled as a two-part spring-like system where each part is with individual stiffness. To overcome the problem of analyzing of each of parts separately, the equivalent spring is suggested to be introduced. In the paper, a method for obtaining the equivalent elastic force of the unit is developed. The method is the generalization of the procedure suggested for substitution of a hard and a soft spring in series with an equivalent one. The nonlinearity of original springs is of quadratic order. As a results, it is obtained that the equivalent elastic force for two equal springs remains of the same type as of the original springs (soft or hard). For two opposite type springs in series with equal coefficients, the equivalent force is soft. The method is applicable for any hard and soft nonlinear springs or spring-like systems. Thus the hexagonal auxetic unit which contains a soft and a hard part in series is analyzed. In the paper, a new analytic method for determination of the frequency of vibration for the unit under action of a constant compression force acting along the unit axis is introduced. The method is applied for units which contain two parts: hard–hard, soft–soft, hard–linear, soft–linear and opposite. The obtained approximate vibration results are compared with numerically obtained ones and show good agreement. The advantage of the method is its simplicity as it does not require the nonlinear equation of motion to be solved.

Study on seismic performance of the CFST-framed aeolian sand concrete composite shear wall

This study examined the seismic performance of composite shear walls framed with concrete-filled steel tubes (CFST) utilizing aeolian sand concrete. Six specimens were designed and tested under low cyclic load with a constant axial compression ratio. The research aimed to analyze how the CFST frame affects the seismic behavior of shear walls made from aeolian sand concrete and understand the underlying influence mechanism. The results showed significant differences in failure modes between CFST-framed and conventional aeolian sand concrete shear walls, with the former exhibiting a lower degree of failure and instances of plastic hinge failure. The hysteretic curve of CFST-framed walls displayed noticeable pinching, indicating enhanced seismic energy dissipation capacity and ductility. The damage analysis model based on the energy damage principle was found to be suitable for conducting seismic damage analysis of these walls. A shear capacity model was also established to accurately depict the variation in bearing capacity under low cyclic loading, providing valuable insights for engineering applications.

Electrocardiogram Signal Compression Using Deep Convolutional Autoencoder with Constant Error and Flexible Compression Rate

ObjectivesElectrocardiogram (ECG) signals are beneficial for diagnosing cardiac diseases. The cardiac patients' life quality likely increases with continuous or long-period recording and monitoring of ECG signals, leading to better and early diagnosis of disease and heart attacks. However, continuous ECG recording necessitates high data rates and storage, which means high costs. Therefore, ECG compression is a handy concept that facilitates continuous monitoring of ECG signals. Deep neural networks open up new horizons for compression and also for ECG compression by providing high compression rates and quality. Although they bring constant compression ratios with better average quality, the compression quality of individual samples is not guaranteed, which may lead to misdiagnoses. This study aims to investigate the effect of compression quality on the diagnoses and to develop a deep neural network-based compression strategy that guarantees a quality-bound in return for varying compression ratios.Materials and methodsThe effect of the compression quality on the arrhythmia diagnoses is tested by comparing the performance of the deep learning-based ECG classifier on the original ECG recordings and the distorted recordings using a lossy compression algorithm with different compression error levels. Then, a compression error upper limit is calculated in terms of normalized percent root mean square difference (PRDN) error, which also coincides with the findings of the previous studies in the literature. Lastly, to enable deep learning in ECG compression, a single encoder-multi-decoder convolutional autoencoder architecture, and multiple quantization levels are proposed to guarantee a desired upper limit on the error rate.ResultsThe efficiency of the proposed method is demonstrated on a popular benchmark data set for ECG compression methods using a transfer learning approach. The PRDN error is fixed to various values, and the average compression rates are reported. An average of 13.019:1 compression is achieved for a 10% PRDN error rate, assessed as a fair quality threshold for reconstruction error. It has also been shown that the compression model has a runtime that can be run in real-time on wearable devices such as commercial smartwatches.ConclusionThis study proposes a deep learning-based ECG compression algorithm that guarantees a desired upper limit on the compression error. This model may facilitate an eHealth solution for continuous monitoring of ECG signals of individuals, especially cardiac patients.

Lifetime prediction of EPDM sealing materials with thermal aging under constant compression

Abstract EPDM (Ethylene Propylene Diene Monomer) is an important engineering sealing material. Thermal aging leads to a decline in its service life. In this study, the static sealing lifetime of EPDM sealing materials is investigated by thermal aging experiments under constant compression. Based on the variation pattern of compression set over aging time at different aging temperatures (80 °C, 100 °C, and 120 °C), a lifetime prediction model for EPDM sealing materials is derived using chemical reaction kinetics and the Arrhenius equation. The model is compared with the experimental results. The results show that the prediction model is highly reliable. The theoretical life of EPDM after thermal aging at 25 °C is 30.6 years, 53.1 years, and 89.1 years, respectively, when the compression set is 40%, 45%, and 50 %.

Swelling damage characteristics induced by CO2 adsorption in shale: Experimental and modeling approaches

Carbon dioxide (CO2) geological sequestration represents a critical technology in mitigating climate change. Shale reservoirs demonstrate a pronounced affinity for CO2, resulting in adsorption-induced swelling that significantly impacts permeability, mechanical strength, injection efficiency, and sequestration safety. For this, we tried to explore the key factors driving the swelling of shale upon CO2 injection and its subsequent impact on reservoir properties. Utilizing a self-developed high-temperature-pressure gas adsorption apparatus, we measured strain in Jurassic shale at 308 K under constant hydrostatic pressure with helium (He) at 1300 psi (1 psi = 6.895 kPa) and CO2 at 850 psi. Next, we investigated the influence of CO2 concentration on swelling protentional while maintaining constant pressure, uncovering the anisotropic deformation in relation to pressure. It shows that CO2 adsorption induces significant swelling in shale, following a Langmuir-type pressure relationship. Deformation is more pronounced perpendicular than that parallel to the bedding plane. At low pressure, vertical swelling is 2.28 times greater than the horizontal; while at high pressure, the vertical compression is 31.26 times greater than the horizontal. It seems that the anisotropic swelling enhances permeability predictions during CO2 injection. Mixed gases under constant compression can prompt gas desorption, stress redistribution, and alterations in pore structure, amplifying He compression effect. The strain induced after replacing CO2 with He exceeds that from pure He injection. The asynchronous response of CO2-induced swelling and mechanical compression can precipitate crack propagation and fracturing. Overall, anisotropic swelling from CO2 adsorption changes pore structure and permeability, affecting fluid flow and storage. Considering CO2 concentration and anisotropic characteristics in reservoir modeling is essential for optimizing injection strategies and enhancing reservoir efficiency.

Prediction of flow stresses for a typical Nickel-Based superalloy during hot deformation based on constitutive equation

Abstract Utilizing the Gleeble-3500 thermal simulation testing machine, a series of isothermal constant strain rate thermal compression tests were executed to study the high-temperature rheological properties of the GH4169 alloy. These tests were carried out under deformation temperatures between 900°C and 1100°C, with strain rates from 0.001 to 1 s−1, and involved a deformation of 60%. The results reveal that the peak stress of the GH4169 alloy decreases as the temperature increases, and the strain rate decreases during hot deformation. The activation energy for thermal deformation is calculated to be 806.39 kJ/mol. Through regression analysis and polynomial fitting of true stress-strain curves from thermal compression tests, an Arrhenius constitutive equation integrating strain compensation for high-temperature deformation was established. The model exhibits an average relative error of 8.86% between predicted and experimental values, indicating the model’s good accuracy in predicting the alloy’s rheological behavior during thermal deformation. By adjusting the strain rate and deformation temperature, this model can be utilized to control the stress level in the hot working process.

Seismic performance of the ST-RC columns to RC beams exterior joint with assembled connection details

An innovative composite column type, the steel tube-reinforced concrete column (ST-RC), consists of a core of concrete-filled steel tube (CFST) and reinforced concrete (RC) encasement. This study aims to validate the reliability of two convenient and rapid assembly methods between RC beams and ST-RC columns. Four full-scale beam-column joint specimens were tested, comprising two prefabricated assembly joints of ST-RC column-RC beam frames, one integrally cast joint of ST-RC column-RC beam frames, and one traditional integrally cast joint of RC column-RC beam frames for comparison. The experiments were conducted based on the principles of a self-balanced system, and quasi-static tests under constant axial compression on the ST-RC columns were performed. Hysteresis curves, skeleton curves, failure modes, strength degradation, energy dissipation capacity, stiffness degradation, deformation capacity and the influence of connection method and joint form on mechanical performance were analyzed and obtained based on the test results. The results indicate that, compared to integral casting, the assembly surrounding method with steel sleeves reduces specimen energy dissipation by 19.8 % and damping ratio by 21 % at 4 % drift, with minimal impact on other mechanical properties. In contrast, reinforcement surrounded and connected by steel plates reduces initial stiffness and peak load-carrying capacity by 1.0 %, along with decreasing negative ductility. It also lowers total energy dissipation by 37.4 % and damping ratio by 45.4 % due to compressive effects from bottom steel plate connections. Despite these effects, its impact on negative ductility and load-carrying capacity remains minimal. Additionally, experimental observations and rebar strain data indicate higher stress on rebars at the base of steel plate connection beams, suggesting a need to strengthen transverse rebars at the beam’s base. The study confirms the feasibility of two convenient and rapid assembly methods for the joints of ST-RC column. Both methods meet current Chinese standards for MCE, with failure modes characterized by “strong columns and weak beams” in both cases.

Comparative analysis of the seismic performance of ECC jacket reinforced columns with different cross-sectional forms subject to different load modes

Based on the high tensile strength and tensile strain of (engineered cementitious composites) ECC, it is applied to the weak link central columns of subway stations to enhance their seismic resilience. In this study, the effects of the column's cross-sectional shape, ECC jacket form, and the vertical gravity load and vertical dynamic load during seismic action on the hysteretic performance of the column were thoroughly analyzed. A constrained constitutive model for cementitious materials, a reinforced hysteresis constitute model, and a calculated damage factor for concrete were adopted to establish a three-dimensional refined column model with an experimentally verified error of less than 10 %. After that, the damage distribution and damage degree of the columns, as well as the changes in hysteretic performance such as hysteretic curve, skeleton curve, energy dissipation, and stiffness degradation were analyzed by the static model analysis. The results showed that the columns had higher damage levels under high frequency and high amplitude of dynamic axial compression ratio in the vertical direction compared to the constant high axial compression ratio, and the ECC jacket could effectively reduce the damage levels of the columns, but the use of the in-built ECC (IB-ECC) jacket was better than the out-sourced ECC (OS-ECC) jacket. In addition, the IB-ECC jacket did not significantly improve the peak bearing capacity of the columns, but significantly improved the ultimate bearing capacity and displacement ductility of the columns, while the OS-ECC jacket significantly improved the peak bearing capacity of the columns. The ECC jacket was also effective in slowing down the stiffness degradation of the columns. This study significantly contributes to the design strategies for enhancing the resilience of columns in subway stations.

Innovative reinforcement method for metal foam cell wall using CNTs

Carbon nanotubes (CNTs) and their composites are gaining popularity due to their exceptional strength qualities. It is well known that adding CNTs to metal foam composites boosts compressive strength. On the other hand CNT addition is still a costly process due to high cost of the CNTs. This study presents a novel and cost-effective solution by selectively adding CNTs to the structurally weakest regions of aluminum foam materials produced via powder metallurgy, employing a newly developed focused multi-step additive method. The cell borders of aluminum foam are strengthened with multiple spherical layers of CNTs, using a transfer method by initially coating the space holders used at the foaming process. The strength increase effect of this CNT addition method was compared with the widely known aluminum foam production parameters via a 4-parameter design of experiment (DOE) study. Compressive strength values of the samples were evaluated using a constant speed compression test acc. to ISO13314. The compacting pressure, CNT concentration, sintering temperature, and sintering period were chosen as DOE parameters, and 78% of the interactions effecting on final compressive strength could be explained with the model. As a result, it was established that, compared to the other parameters, sintering duration had the highest influence on compressive strength. But besides It has also been shown that adding 0.53% CNT by weight only to the cell border regions increases overall strength by 9%. This weight-strength increase ratio is compared with similar studies in the literature and found to be providing a production cost advantage due to the lower amount of CNT addition requirement for the comparable weight relative strength increase. Focused strength increase method has potential to enable controlled failure of foam materials by selectively strengthening strength critical areas of a component.

In-situ measurements of contact evolution for fractal rough surfaces under normal compression

The contact interface plays a key role in the overall functionality and stability of structures. Understanding the evolution of the contact interface over time and its dependency on materials and load is crucial for functional integrity and operational safety assessment. In this study, we employ in-situ three-dimensional X-ray computed tomography (3DXRCT) to examine the creep behavior of 3D-printed surfaces exhibiting various roughness under constant normal compression. We observe that the overall contact area enlargement during the contact creep decreases with roughness amplitude and fractal dimension. The variation of interfacial separation distance is found to increase with roughness amplitude and decrease with fractal dimension. Correlation analysis reveals that the microcontact size played a more important role than the asperity shape in determining the microcontact enlargement. By examining the calculated interfacial strains extracted from XRCT measurements, significant deformations are found to occur at the non-contacting zones, indicating strong asperity interactions. This study offers high-resolution experimental measurements and unravels the asperity micromechanics for contact creep on rough surfaces, providing insights into understanding and optimizing the performance of rough interfaces.

Influence from Mechanical Stress on State of Health of Large Prismatic Lithium-Ion-Cells under Various Temperatures

The expansion of lithium-ion cells is an aging phenomenon that causes deformation of the cell’s external and internal geometry due to physicochemical reactions during aging and operation. This deformation leads to degradation effects such as capacity loss and increased internal resistance in the cell. In a cell module, expansion of the cells presents a challenge to the mechanical design due to resulting swelling forces. This work presents expansion measurements performed on large prismatic lithium-ion cells cycled at 1 C for up to 1000 cycles at different ambient temperatures and constant compression forces to evaluate the impact of mechanical stress on cell health. Intermediate tests were conducted every 50 cycles to determine cell capacity and perform electrochemical impedance spectroscopy measurements. Thickness measurements showed cell expansion during charging and contraction during discharging due to lithiation and de-lithiation. Additionally, an irreversible change in cell thickness occurred due to aging. Electrochemical impedance spectroscopy data were analyzed using distribution of relaxation time analysis to quantify the increase in internal resistance. The results suggest that compression force has a negligible impact on cells cycled at high temperature. However, at lower temperatures, higher compression force resulted in more rapid aging compared to lower compression force.

Quantitative in-situ investigation of dislocation loop motion in Fe9Cr1.5W ferritic/martensitic steel under the coupling effects of constant stress and irradiation

Dislocation loop motion plays an important role in irradiation creep but their dynamic evolution is hardly investigated. In this work, the one-dimensional motion of loops was investigated by in-situ TEM in Fe9Cr1.5W ferritic/martensitic steel under the combination of irradiation and constant compression stress and compared with the case of irradiation only to highlight the synergistic effect. Loops preferred to glide along one side that was close to the compression direction and the other side was retarded.. The proportion of large mobile loops was also increased. Jump frequency was doubled after the addition of compression, indicating the high sensitivity to stress.

Standardisation facilitates reliable interpretation of ETCO2 during manual cardiopulmonary resuscitation

BackgroundInterpretation of end-tidal CO2 (ETCO2) during manual cardiopulmonary resuscitation (CPR) is affected by variations in ventilation and chest compressions. This study investigates the impact of standardising ETCO2 to constant ventilation rate (VR) and compression depth (CD) on absolute values and trends. MethodsRetrospective study of out-of-hospital cardiac arrest cases with manual CPR, including defibrillator and clinical data. ETCO2, VR and CD values were averaged by minute. ETCO2 was standardised to 10 vpm and 50 mm. We compared standardised (ETs) and measured (ETm) values and trends during resuscitation. ResultsOf 1,036 cases, 287 met the inclusion criteria. VR was mostly lower than recommended, 8.8 vpm, and highly variable within and among patients. CD was mostly within guidelines, 49.8 mm, and less varied. ETs was lower than ETm by 7.3 mmHg. ETs emphasized differences by sex (22.4 females vs. 25.6 mmHg males), initial rhythm (29.1 shockable vs. 22.7 mmHg not), intubation type (25.6 supraglottic vs. 22.4 mmHg endotracheal) and return of spontaneous circulation (ROSC) achieved (34.5 mmHg) vs. not (20.1 mmHg). Trends were different between non-ROSC and ROSC patients before ROSC (–0.3 vs. + 0.2 mmHg/min), and between sustained and rearrest after ROSC (–0.7 vs. –2.1 mmHg/min). Peak ETs was higher for sustained than for rearrest (53.0 vs. 42.5 mmHg). ConclusionStandardising ETCO2 eliminates effects of VR and CD variations during manual CPR and facilitates comparison of values and trends among and within patients. Its clinical application for guidance of resuscitation warrants further investigation.