Measurement Of Heat Generation Research Articles

Measuring Heat Dissipation and Entropic Potential in Battery Cathodes Made with Conjugated and Conventional Polymer Binders Using Operando Calorimetry.

This study explores the influence of electronic and ionic conductivities on the behavior of conjugated polymer binders through the measurement of entropic potential and heat generation in an operating lithium-ion battery. Specifically, the traditional poly(vinylidene fluoride) (PVDF) binder in LiNi0.8Co0.15Al0.05O2 (NCA) cathode electrodes was replaced with semiconducting polymer binders based on poly(3,4-propylenedioxythiophene). Two conjugated polymers were explored: one is a homopolymer with all aliphatic side chains, and the other is a copolymer with both aliphatic and ethylene oxide side chains. We have shown previously that both polymers have high electronic conductivity in the potential range of NCA redox, but the copolymer has a higher ionic conductivity and a slightly lower electronic conductivity. Entropic potential measurements during battery cycling revealed consistent trends during delithiation for all of the binders, indicating that the binders did not modify the expected NCA solid solution deintercalation process. The entropic signature of polymer doping to form the conductive state could be clearly observed at potentials below NCA oxidation, however. Operando isothermal calorimetric measurements showed that the conductive binders resulted in less Joule heating compared to PVDF and that the net electrical energy was entirely dissipated as heat. In a comparison of the two conjugated polymer binders, the heat dissipation was lower for the homopolymer binder at lower C-rates, suggesting that electronic conductivity rather than ionic conductivity was the most important for reducing Joule heating at lower rates, but that ionic conductivity became more important at higher rates.

Calorimetric methods and thermal management of lithium-ion batteries: A mini-review

Lithium-ion batteries can be employed in various applications, including grid integration, electric vehicles, grid support, and consumer electronics. Lithium-ion batteries are currently one of the most important options for storing electrical energy. Therefore, modelling lithium-ion batteries and examining their temperature distribution and heat transfer using different calorimetric techniques is very important mostly for safety concerns. Thus, the study of battery heat transfer helps designers to propose and develop a suitable cooling or thermal management system. Different sources including overpotential contribute to heat generation. Different understandings were achieved from the previous modelling and experimental studies which involve the necessity for more accurate heat generation measurements of lithium-ion batteries, and improved modelling of the heat generation specifically comprehended at large discharge and charge rates for different applications including electric vehicles.

Integrated Interpretation of Electrical Conductivity Changes, Heat Generation, and Strength Development in the First Week in Cemented Paste Backfill

Underground mining operations need nondestructive test methods to assess placed backfill strength development at early age (especially up to 1 week of curing time) so that they can continue proximate mining quickly. Recent developments in electrical conductivity (EC) transducers for field applications offer this possibility, but the EC measurements must be correlated to backfill strength. To determine the feasibility of this approach, a laboratory test program used a mine’s backfill materials mixed with varying water and binder contents and tested these over a 7-day period. Strength was characterized using unconfined compressive strength (UCS) tests and correlated to EC. Comparisons were also made to complementary test results using Vicat and heat generation measurement techniques. Strong and consistent correlations were determined between EC and UCS for a given binder content and water content. But moreover, a lower-bound correlation was determined and could also be used in the field if as-placed properties vary to an unknown extent within the limits of parameters considered in the study. This provides the basis to use EC measurements in the field and confidently assess the backfill’s minimum attained strength in real time.

An injectable hyperthermic nanofiber mesh with switchable drug release to stimulate chemotherapy potency.

We developed a smart nanofiber mesh (SNM) with anticancer abilities as well as injectability and fast recovery from irregular to non-compressible shapes. The mesh can be injected at the tumor site to modulate and control anticancer effects by loading the chemotherapeutic drug, paclitaxel (PTX), as well as magnetic nanoparticles (MNPs). The storage modulus of the mesh decreases when applied with a certain shear strain, and the mesh can pass through a 14-gauge needle. Moreover, the fibrous morphology is maintained even after injection. In heat-generation measurements, the mesh achieved an effective temperature of mild hyperthermia (41-43°C) within 5min of exposure to alternating magnetic field (AMF) irradiation. An electrospinning method was employed to fabricate the mesh using a copolymer of N-isopropylacrylamide (NIPAAm) and N-hydroxyethyl acrylamide (HMAAm), whose phase transition temperature was adjusted to a mildly hyperthermic temperature range. Pplyvinyl alcohol (PVA) was also incorporated to add shear-thinning property to the interactions between polymer chains derived from hydrogen bonding, The "on-off" switchable release of PTX from the mesh was detected by the drug release test. Approximately 73% of loaded PTX was released from the mesh after eight cycles, whereas only a tiny amount of PTX was released during the cooling phase. Furthermore, hyperthermia combined with chemotherapy after exposure to an AMF showed significantly reduced cancer cell survival compared to the control group. Subsequent investigations have proven that a new injectable local hyperthermia chemotherapy platform could be developed for cancer treatment using this SNM.

Measurement of the Heat Generation Rate of a Pouch Type Lithium-Ion Battery Using a Multifunctional Calorimeter

Accurate characterization of the heat generation rate of lithium-ion batteries is critical for driving towards a cost-effective and efficient design of a thermal management system for various applications. Because of the increase in battery cell dimensions, as well as more aggressive operating conditions seen in the automotive industry, such as Direct Current Fast Charge (DCFC) and sustained driving under load, heat generation seen at the cell level must be considered as spatially non-uniform during operation. Proper design of the thermal management system requires measurement of the heat generation of the battery cell in both a lumped fashion for system sizing, as well as a distributed mode in order to tailor cooling appropriately to decrease local temperature extremes. Additionally, characterization of both the irreversible and reversible heat generation of the battery cell at various states-of-charge, temperatures, and states-of-life is required. Currently, few commercial calorimeters are available for the measurement of heat generation under dynamic conditions with a reasonable balance of accuracy and cost. In this work, we detail the development of a new calorimeter that allows for the measurement of the heat generation rate, determination of the irreversible and reversible heat generation, and rapid response time to capture dynamic cell responses.

Thermal Lens Spectrometry Reveals Thermo-Optical Property Tuning of Conjugated Polymer Nanoparticles Prepared by Microfluidics

Conjugated polymers display useful thermo-optical properties of high relevance to biomedical applications, which are not only dependent on their intrinsic chemical composition but also related to their physical conformation and manufacturing protocol. In this work, we report that the thermo-optical properties of poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT) encapsulated within poly(ethylene glycol) methyl ether-block-poly(lactide-co-glycolide) (PEG-PLGA) can be tuned by production conditions, generating conjugated polymer nanoparticles (CPNs) with customized applications. Thermal lens spectroscopy (TLS) was used to characterize the CPN light-to-heat conversion efficiency as it provides an absolute measurement of heat generation. Although preparation by traditional bulk production led to a high product yield, the CPNs were characterized by similar sizes and thermo-optical properties, irrespective of the molecular weight of amphiphilic PEG–PLGA. In contrast, a microfluidics production method generated CPNs with variable product yields and sizes and thermo-optical properties that are affected by both the molecular weight of PEG–PLGA and the production settings. Given the growing interest in biomedical applications of CPNs, our work provides useful results on microfluidic production of CPNs and of TLS for the screening of candidates with desirable characteristics.

Evaluation of accuracy for Bernardi equation in estimating heat generation rate for continuous and pulse-discharge protocols in LFP and NMC based Li-ion batteries

• Heat generation in LFP and NMC Li-ion cells is quantified in different conditions. • The specific heat capacities of Li-ion cells are determined. • Bernardi equation accurately predicts the heat generation for continuous discharge. • Heat generation is overestimated by Bernardi equation under pulse discharge. • Individual effects of DoD and temperature on heat generation are examined. Accurate prediction of heat generation in Li-ion batteries during real driving conditions is essential for an efficient thermal management system. In this study, we verify the applicability of a commonly-used heat generation estimator (i.e., Bernardi equation) in Li-ion batteries. The real-world drive cycles comprise of intermittent discharge pulses as opposed to continuous discharge. Therefore, we consider both continuous and pulse-discharge protocols, and compare the heat generation evaluated through Bernardi equation and direct in-situ measurements. It is observed that for continuous discharge, Bernardi equation predicts the heat generation rate with reasonable accuracy. However, the equation substantially overestimates the heat generation under pulse-discharge protocol (realistic scenarios). The heat generation analysis is performed on two leading Li-ion battery chemistries, i.e., LiFePO 4 (LFP) and LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC). Direct measurement shows deviations from the Bernardi equation to be as high as 26% and 49% for LFP and NMC cells, respectively, under high-rate discharge pulses. For the sake of accurate measurement of heat generation, specific heat capacities of Li-ion cells are evaluated with a combined experimental–numerical approach. The heat generation is examined at different cell temperatures and depth of discharge (DoD) levels, and their individual effects on heat generation are analyzed.

Comparative effect of thermo/pH-responsive polymer-coated gold nanocages and hollow nanostars on chemo-photothermal therapy of breast cancer cells

BackgroundCombination chemo-photothermal therapy appears to be one of the next generations of cancer treatment. In this study hollow gold nanostars (HGNSs) and gold nanocages (GNCs) were synthesized and stabilized with thermo-pH-sensitive thiol-end capped ABC triblock copolymer poly(acrylic acid)-b-poly(N isopropylacrylamide)-b-poly (e-caprolactone)-SH; PAA-b-PNIPAAm-b-PCL-SH (GNSs@Pol). Doxorubicin (Dox) was conjugated to the GNSs@Pol nanostructures via ionic interaction, covalent attachment and hydrogen bonding (GNSs@Dox-Pol). The physicochemical characteristics of prepared GNSs@Pol and GNSs were assessed using dynamic light scattering (DLS), transmission electron microscopy (TEM) and zeta potential techniques. Cytocompatibility of the GNSs@Pol was studied by hemolysis assay and MTT assay. The chemo-photothermal therapy (PTT) potential of GNSs@Dox-Pol was compared on MCF7 cells using MTT assay, cell cycle, DAPI staining and Annexin-V apoptosis assay techniques.ResultsCell internalization results showed an almost complete uptake of GNSs@Pol by MCF-7 cells in the first 3 h of treatment. The heat generation measurement results showed that both of GNSs have a potential for light to heat conversion (∆T = 23–27 ºC) and HGNSs demonstrated better efficiency than GNCs after 10-min exposure to NIR irradiation. Following chemo-photothermal treatment, the highest cell mortality (90%) and apoptotic effects (97% apoptosis) were observed in HGNSs@Dox-Pol received laser irradiation treatment group.ConclusionsThis work highlights the potential application of designed GNSs@Dox-Pol in a combinational chemo-PTT to treat breast cancer cells.Graphic abstract

Heat generation measurement and thermal management with phase change material based on heat flux for high specific energy power battery

LiNi0.8Co0.1Mn0.1O2 (NCM811) lithium-ion battery is a kind of high specific energy power battery. By directly measuring the heat flux on the surface of a 21700-type cylindrical battery and the temperature of its inner center, the heat generation rate, the heat energy dissipated and the electric energy released at different discharge rates are all obtained. The results turn out that increasing the discharge rate will reduce the electric energy and correspondingly increase the heat energy released, while the total amount of both remains unchanged. When the discharge rate increases from 1C to 2.5C, the ratio of discharge heat generation to discharged energy increases from 2.89% to 7.89%. According to the heat generation rate obtained from the experimental results, a single cylindrical cell structure and hexagonal cell module were designed for different discharge rates with high thermal conductivity graphene paraffin composite phase change material (PCM). PCM structure can well manage the thermal parameters, which helps to maintain the stability and consistency of battery temperature. The distance between two adjacent batteries has a greater impact on the temperature distribution of the battery module during high rate discharge, and monitoring the change of heat flux can predict the failure of the thermal management of the battery in advance. It is a beneficial attempt to adopt PCM to manage the temperature field of the battery pack and use heat flux to monitor the solid state of PCM, which is also very helpful for the safe operation of the battery system.

Force-velocity and tension transient measurements from Drosophila jump muscle reveal the necessity of both weakly-bound cross-bridges and series elasticity in models of muscle contraction

Muscle contraction is a fundamental biological process where molecular interactions between the myosin molecular motor and actin filaments result in contraction of a whole muscle, a process spanning size scales differing in eight orders of magnitude. Since unique behavior is observed at every scale in between these two extremes, to fully understand muscle function it is vital to develop multi-scale models. Based on simulations of classic measurements of muscle heat generation as a function of work, and shortening rate as a function of applied force, we hypothesize that a model based on molecular measurements must be modified to include a weakly-bound interaction between myosin and actin in order to fit measurements at the muscle fiber or whole muscle scales. This hypothesis is further supported by the model's need for a weakly-bound state in order to qualitatively reproduce the force response that occurs when a muscle fiber is rapidly stretched a small distance. We tested this hypothesis by measuring steady-state force as a function of shortening velocity, and the force transient caused by a rapid length step in Drosophila jump muscle fibers. Then, by performing global parameter optimization, we quantitatively compared the predictions of two mathematical models, one lacking a weakly-bound state and one with a weakly-bound state, to these measurements. Both models could reproduce our force-velocity measurements, but only the model with a weakly-bound state could reproduce our force transient measurements. However, neither model could concurrently fit both measurements. We find that only a model that includes weakly-bound cross-bridges with force-dependent detachment and an elastic element in series with the cross-bridges is able to fit both of our measurements. This result suggests that the force response after stretch is not a reflection of distinct steps in the cross-bridge cycle, but rather arises from the interaction of cross-bridges with a series elastic element. Additionally, the model suggests that the curvature of the force-velocity relationship arises from a combination of the force-dependence of weakly- and strongly-bound cross-bridges. Overall, this work presents a minimal cross-bridge model that has predictive power at the fiber level.

Applying Different Configurations for the Thermal Management of a Lithium Titanate Oxide Battery Pack

This investigation’s primary purpose was to illustrate the cooling mechanism within a lithium titanate oxide lithium-ion battery pack through the experimental measurement of heat generation inside lithium titanate oxide batteries. Dielectric water/glycol (50/50), air and dielectric mineral oil were selected for the lithium titanate oxide battery pack’s cooling purpose. Different flow configurations were considered to study their thermal effects. Within the lithium-ion battery cells in the lithium titanate oxide battery pack, a time-dependent amount of heat generation, which operated as a volumetric heat source, was employed. It was assumed that the lithium-ion batteries within the battery pack had identical initial temperature conditions in all of the simulations. The lithium-ion battery pack was simulated by ANSYS to determine the temperature gradient of the cooling system and lithium-ion batteries. Simulation outcomes demonstrated that the lithium-ion battery pack’s temperature distributions could be remarkably influenced by the flow arrangement and fluid coolant type.

Heat generation quantification of high-specific-energy 21700 battery cell using average and variable specific heat capacities

The electrical performance, safety and life of a battery are closely related to its operating temperature; therefore, a thermal management system is necessary to ensure that the battery operates within its most suitable temperature range. Accurately testing the heat generation of a battery is necessary for the design of a thermal management system. Specific heat capacity is one of the most important parameters of thermophysical properties, and its accurate measurement is a prerequisite for the quantitative analysis of battery heat generation. In the literature on battery heat generation tests, the average specific heat capacity is usually used to calculate the battery heat generation. Thus, the change in the specific heat capacity of the battery is not considered. Considering the high-specific-energy 21700 battery made with a nickel-cobalt-manganese (NCM)/graphite material system, this paper compares for the first time the difference between using the average specific heat capacity and variable specific heat capacity to calculate the instantaneous heat generation of a battery. The experimental results showed that the specific heat capacity in the target temperature range during the actual use of power batteries (i.e., a low temperature range of 25–35 °C) had a more significant impact on the heat generation power calculation error, and the relative error could reach 30%. In addition, based on the obtained variable specific heat capacity, the heat generation characteristics of the 21700 battery under different operating conditions were analysed. The results showed that this battery has a higher specific volume heat generation power compared with the pouch-type batteries reported in the literature. This article provides guidance for battery cell thermal simulation, more accurate quantitative measurement of battery heat generation and thermal management system design.

Investigation of power battery heat generation measurement method with insulated cotton

Abstract Thermal management systems of power batteries have attracted a great deal of attention because of thermal safety and thermal runaway problems. The heat generation measurement is significant in researching and designing the thermal management systems. Therefore, effective method of measuring total heat generation experimentally is put forward, which insulated cotton is used as heat preservation layer for temperature rise measurement. The results show that insulated cotton can effectively reduce the heat dissipation. Compared with the absence of insulated cotton, the temperature rise (Δtcot) of battery with insulated cotton is increased by 80.2%, 70.2% and 56.0% at 1 C, 2 C and 3 C, respectively. Furtherly, the heat dissipation during the discharge process has been evaluated by the temperature drop (Δτ) under the shelving condition following the Newton's cooling formula. Towards to the amendment of the battery temperature rise (Δtcot) measurement, the temperature rise of the high and low temperature chamber should be set to ( Δ t cot + Δ τ ) while the battery had discharged in it. In this way, more accurate measurement of the battery temperature rise (Δttotal) is obtained. Compared with the theoretical heat generation calculated by energy conservation law and energy conversion method, it reveals that battery temperature rise (Δttotal) can accurately calculate the heat generation of the battery.

Iron-Doped Sodium Vanadium Oxyflurophosphate Cathodes for Sodium-Ion Batteries-Electrochemical Characterization and In Situ Measurements of Heat Generation.

Sodium-ion batteries (NaIBs) are increasingly being envisioned for grid-scale energy-storage systems because of cost advantages. However, implementation of this vision has been challenged by the low-energy densities delivered by most NaIB cathodes. Toward addressing this challenge, the authors report the synthesis and characterization of a new iron-doped Na3Fe0.3V1.7O(PO4)2F2 cathode using a novel facile hydrothermal route. The synthesized material was characterized using scanning electron microscopy, X-ray diffraction, and Mössbauer spectroscopy techniques. The obtained discharge capacity in the half-cell configuration lies from 119 to 125 to 130 mA h/g at C/10 while tested using three different electrolyte formulations, dimethyl carbonate-ethylene carbonate (EC)-propylene carbonate (PC), diethyl carbonate-EC, and EC-PC, respectively. The synthesized cathodes were also evaluated in full-cell configurations, which delivered an initial discharge capacity of 80 mA h/g with NaTi2(PO4)3MWCNT as the anode. Ionic diffusivity and interfacial charge transfer kinetics were also evaluated as a function of temperature and sodium concentration, which revealed that electrochemical rate performances in this material were limited by charge-transfer kinetics. To understand the heat generation mechanism of the Na/Na3Fe0.3V1.7O(PO4)2F2 half-cell during charge and discharge processes, an electrochemical isothermal calorimetry measurement was carried out at different current rates for two different temperatures (25 and 45 °C). The results showed that the amount of heat generated was strongly affected by the operating charge/discharge state, C-rate, and temperature. Overall, this work provides a new synthesis route for the development of iron-doped Na3Fe0.3V1.7O(PO4)2F2-based high-performance sodium cathode materials aimed at providing a viable pathway for the development and deployment of large-scale energy-storage based on sodium battery systems.

Temperature‐dependent Battery Performance of a Na3V2(PO4)2F3@MWCNT Cathode and In‐situ Heat Generation on Cycling

Excellent structural stability, high operating voltage, and high capacity have made Na3 V2 (PO4 )2 F3 a promising cathode material for sodium-ion batteries. However, high-temperature battery performances and heat generation measurements have not been systematically reported yet. Carbon-coated Na3 V2 (PO4 )2 F3 @MWCNT (multi-walled carbon nanotube) samples are fabricated by a hydrothermal-assisted sol-gel method and the electrochemical performances are evaluated at three different temperatures (25, 45, and 55 °C). The well-crystallized Na3 V2 (PO4 )2 F3 @MWCNT samples exhibit good cycling stability at both low and high temperatures; they deliver an initial discharge capacity of 120-125 mAhg-1 at a 1 C rate with a retention of 53 % capacity after 1,400 cycles with 99 % columbic efficiency. The half-cell delivers a capacity of 100 mAhg-1 even at a high rate of 10 C at room temperature. Furthermore, the Na3 V2 (PO4 )2 F3 @MWCNT samples show good long-term durability; the capacity loss is an average of 0.05 % per cycle at a 1 C rate at 55 °C. Furthermore, ionic diffusivity and charge transfer resistance are evaluated as functions of state of charge, and they explain the high electrochemical performance of the Na3 V2 (PO4 )2 F3 @MWCNT samples. In-situ heat generation measurements reveal reversible results upon cycling owing to the high structural stability of the material. Excellent electrochemical performances are also demonstrated in the full-cell configuration with hard carbon as well as antimony Sb/C anodes.

In‐situ heat generation measurement of the anode and cathode in a single‐layer lithium ion battery cell

In‐situ heat generation measurement of the anode and cathode in a single‐layer lithium ion battery cell

Uncertainty of the Entropy Change Calculation By Cylindrical Li-Ion Cell Heat Flux Measurements: Temperature and C-Rate Effect

The entropy change (ΔS) of a Li-ion battery during its charging and discharging is one of the important parameters, which has a strong effect on the heat generation in a Li-ion battery during its operation. Moreover, the behavior of the entropy change during an aging of the Li-ion battery may be used for the analysis of the battery degradation, the state of health estimation and prediction. Unfortunately, the determination of the ΔS with a high accuracy is a difficult task. Currently, the potentiometric method for the determination of the ΔS is considered as the most popular method. However, measurements of the ΔS by the potentiometric method takes a lot of time as all measurements should be done in steady-state conditions to obtain acceptable accuracy. ΔS can be also measured by the calorimetric method but this method requires utilization of expensive equipment such as a very accurate calorimeter and, therefore, it is rarely used. A method, recently presented for the ΔS determination by using heat flux measurements on the surface of a cylindrical Li-ion cell, may be considered as a modification of the calorimetric method. According to this method, the ΔS is obtained from the total heat generation during charging and discharging of a Li-ion battery, similarly as it is done in the calorimetric method. However, the heat generation is calculated by using a thermal model of the cell and measured values of the temperature on the cell surface and heat flux from this surface. This method does not require any expensive equipment and the required time of measurements is significantly smaller than in case of the potentiometric method, as steady-state conditions are not required for the determination of ΔS. Unfortunately, the uncertainty of the presented method is still under a question. Therefore, this work is dedicated to the analysis of the effect of different test conditions on the uncertainty of the ΔS measurements when using heat flux and temperature sensors. Energy and power -type cylindrical Li-ion cells are used during the analysis. The two different types of the cylindrical cell are selected with purpose to verify the applicability of the method not only for the power cells, as it was done previously, but also for the energy cells, where the effect of the ΔS on the total heat generation is lower than in power cells. Cylindrical Li-ion cells are used in the research, because the heat generation in them is usually lower than in pouch or prismatic Li-ion cells. Therefore, the uncertainty for the heat generation measurements in cylindrical cells should be higher than in pouch and prismatic cells. The entropy changes in both selected Li-ion cells are measured by the potentiometric method for different values of the state of charge (SoC) and these curves are used as a reference for the analysis of the effect of the test conditions. The heat generation in the considered Li-ion cells is measured with the help of a thermal model of the cylindrical cell and measured values of the temperature and the heat flux flowing out from the cell surface during its charging and discharging. The effect of the ambient temperature and current C-rate on the uncertainty of the ΔS determination is presented by considering different ambient temperatures and current C-rates during the heat measurements and following the calculation of the ΔS and its uncertainty.

P‐53: A Slim Display System for OLED TV Using TCON Memory Merged IC

The Proposed new T‐Con which packaged in one chip is made up of memory for compensation and OLED TV T‐Con ASIC die. In external compensation OLED TV system, the one chip packaged T‐Con enable to reduce T‐con Board area by 53%. Also experimental result shows that the proposed one packaged T‐Con improves the DDR timing margin by 15%. In heat generation measurement, it is equivalent to conventional 55” UHD OLED TV T‐Con that has been mass‐produced

Anisotropy of the high‐power piezoelectric properties of Pb(Zr,Ti)O3

AbstractPiezoceramics are widely‐used in high‐power applications, whereby the material is driven in the vicinity of the resonance frequency with high electric fields. Evaluating material's performance at these conditions requires the consideration of inherent nonlinearity, anisotropy, and differences between individual vibration modes. In this work, the relation between electromechanical properties at large vibration velocity and the utilized vibration mode is investigated for a prototype hard piezoceramic. The nonlinear behavior is determined using a combined three‐stage pulse drive method, which enables the analysis of resonant and antiresonant conditions and the calculation of electromechanical parameters. The deviations of coupling coefficients, compliances, and piezoelectric coefficients at high‐power drive were found to be strongest for the transverse length vibration mode. Differences in the mechanical quality factors were observed only between the planar and transverse length modes, which were rationalized by the different strain distribution profiles and the contribution of different loss tensor components. In addition, the influence of the measurement configuration was investigated and a correction method is proposed. The differences between vibration modes are further confirmed by heat generation measurements under continuous drive, which revealed that the strongest heat generation appears in the radial mode, while transverse and longitudinal length modes show similar temperature increase.Piezoceramics are widely‐used in high‐power applications, whereby the material is driven in the vicinity of the resonance frequency with high electric fields. Evaluating material's performance at these conditions requires the consideration of inherent nonlinearity, anisotropy, and differences between individual vibration modes. In this work, the relation between electromechanical properties at large vibration velocity and the utilized vibration mode is investigated for a prototype hard piezoceramic. The nonlinear behavior is determined using a combined three‐stage pulse drive method, which enables the analysis of resonant and antiresonant conditions and the calculation of electromechanical parameters. The deviations of coupling coefficients, compliances, and piezoelectric coefficients at high‐power drive were found to be strongest for the transverse length vibration mode. Differences in the mechanical quality factors were observed only between the planar and transverse length modes, which were rationalized by the different strain distribution profiles and the contribution of different loss tensor components. In addition, the influence of the measurement configuration was investigated and a correction method is proposed. The differences between vibration modes are further confirmed by heat generation measurements under continuous drive, which revealed that the strongest heat generation appears in the radial mode, while transverse and longitudinal length modes show similar temperature increase.

Muscle Measurements Show Weakly Bound Cross-Bridges Act as a Viscous Drag

Molecular measurements of muscle myosin interacting with actin are described by a four-state mechanochemical model. The model contains two bound states, where myosin is attached to actin, and two unbound states, where myosin does not interact with actin. However, previous experiments in solution and on muscle fibers suggest another short-lived interaction between myosin and actin, the weakly bound state. While each of the two bound states can be directly observed at the single molecule level, this third, weakly bound, state is too brief to observe with the typical resolution of these experiments (∼1ms). Does this weakly bound state contribute to muscle force generation and, if so, what is its role? To begin addressing these questions, we compared two models, 1) a four-state model (lacking a weakly bound state) and 2) a five-state model (including a weakly bound state), to published experimental measurements made with whole muscles or muscle fibers. We found that both models fit classical measurements of heat generation as a function of work done by a muscle (the Fenn effect), and measurements of shortening rate as a function of resistive force (the Hill force-velocity relation). However, only the five-state model describes both data sets with a consistent set of parameters. Additionally, both models predict a phenomenon called stretch-activation, defined as a delayed increase in force following rapid lengthening of an otherwise isometric muscle. However, experimental results show the delayed increase in force upon stretch is preceded by an initial peak (phase I) and transient decrease (phase II) in force. Phase II is missing in the four-state model, but present in the five-state model. These results are consistent with the weakly bound state acting as a viscous drag on the thin filament.