Single Stack Research Articles

Cryo-EM structure of a natural prion: chronic wasting disease fibrils from deer

Chronic wasting disease (CWD) is a widely distributed prion disease of cervids with implications for wildlife conservation and also for human and livestock health. The structures of infectious prions that cause CWD and other natural prion diseases of mammalian hosts have been poorly understood. Here we report a 2.8 Å resolution cryogenic electron microscopy-based structure of CWD prion fibrils from the brain of a naturally infected white-tailed deer expressing the most common wild-type PrP sequence. Like recently solved rodent-adapted scrapie prion fibrils, our atomic model of CWD fibrils contains single stacks of PrP molecules forming parallel in-register intermolecular β-sheets and intervening loops comprising major N- and C-terminal lobes within the fibril cross-section. However, CWD fibrils from a natural cervid host differ markedly from the rodent structures in many other features, including a ~ 180° twist in the relative orientation of the lobes. This CWD structure suggests mechanisms underlying the apparent CWD transmission barrier to humans and should facilitate more rational approaches to the development of CWD vaccines and therapeutics.

Advanced Methodology for Simulating Local Operating Conditions in Large Fuel Cells Based on a Spatially Averaged Pseudo-3D Model

Abstract To address the performance and lifetime limitations of Proton Exchange Membrane Fuel Cells, it is essential to have a comprehensive understanding of the operating heterogeneities at the cell scale, requiring the test of a wide range of operating conditions. To avoid experimental constraints, numerical simulations seem to be the most viable option. Hence, there is a need for time-efficient and accurate cell-scale models. In this intention, previous works led to the development and the experimental calibration of a pseudo-3D model of a full-size cell in a stack. To further reduce the computation time, a new spatially averaged, multi-physics, single-phase, non-isothermal, steady state pseudo-3D model is developed and calibrated with the results of the preceding model. Particularly, it captures the influence of the coolant on temperature and water mappings in the cell. Moreover, a new methodology is proposed to calibrate the electrochemical cell voltage law for new membrane-electrode assemblies. The emulation of the local operation conditions in large active surface area is realized with a small differential cell, avoiding the testing of large single cells or stacks. Subsequently, simulations are conducted to investigate the impact of the coolant temperature gradient, coolant outlet temperature and gas relative humidity.

A novel double-arch piezoelectric energy harvester for capturing railway track vibration energy

This study introduces a novel piezoelectric stack energy harvester with a double-arched frame structure. This design effectively cushions impacts from track vibrations, thereby protecting the fragile piezoelectric stack made of brittle materials. The energy harvesting characteristics of the device are studied in detail through experiments and theoretical simulations. The harvester's output voltage depends on the external resistance and increases with higher resistance. The optimal resistance for the single X-direction piezoelectric stack is 340kΩ, which can output 0.519mW of power under a 3Hz frequency and an 8kN sinusoidal load. The Y-direction piezoelectric stack outputs 0.012mW, resulting in a total output of 1.050mW for the entire harvester. The output power of the harvester is positively correlated with the load vibration frequency, increasing rapidly for frequencies below 9Hz. The impact of load magnitude on the harvester's output shows a generally linear increase. In impact experiments, the single X-direction piezoelectric stack successfully lit 54 LEDs under a 5J energy impact, demonstrating the harvester's high power density and potential for practical applications.

Analysis of forming mechanism and influencing factors of thermoacoustic plate end temperature difference

In order to explore the formation mechanism and influencing factors of the temperature difference between two ends of the plate stack, an expression of the temperature change of the stack with time was established based on the two-dimensional heat conduction equation. Based on this, the finite element model of heat transfer between a single thermoacoustic plate stack and the gas above it is established in Ansys, and the temperature of the plate stack is solved. When the sound field is constant, the variation law of the temperature of the stack with the working time and space is obtained, and the formation mechanism of the temperature difference between the two ends of the plate stack is revealed. From the calculation results, it is found that the net heat transfer between the gas and the plate stack is mainly reflected in the two ends of the plate stack, and the contribution of the air mass in the middle part is mainly the relay heat transfer. In the process of working, part of the sound work is converted into the internal energy of the air mass, which makes the gas temperature on the surface of the plate rise as a whole. The working frequency, stack length and stack thermal conductivity are taken as the influencing factors. When no load is added, the variation of the temperature of the high and low end of the stack with the working time under different working conditions is analyzed. And the theory of series between short plates is put forward to explain the formation mechanism of large temperature difference between the two ends of the plates. In order to further reduce the cooling temperature of thermoacoustic refrigerator, a new research method and exploration direction are proposed.

Tuning the stability of DNA tetrahedra with base-stacking interactions.

DNA nanotechnology relies on programmable anchoring of regions of single-stranded DNA through base pair hybridization to create nanoscale objects such as polyhedra, tubes, sheets, and other desired shapes. Recent work from our lab measured the energetics of base-stacking interactions and suggested that terminal stacking interactions between two adjacent strands could be an additional design parameter for DNA nanotechnology. Here, we explore that idea by creating DNA tetrahedra held together with sticky ends that contain identical base pairing interactions but different terminal stacking interactions. Testing all 16 possible combinations, we found that the melting temperature of DNA tetrahedra varied by up to 10 °C from altering a single base stack in the design. These results can inform stacking design to control DNA tetrahedra stability in a substantial and predictable way. To that end, we show that a 4 bp sticky end with weak terminal stacking does not form stable tetrahedra, while strengthening the stacks confers high stability with a 46.8 ± 1.2 °C melting temperature, comparable to a 6 bp sticky end with weak stacking. The results likely apply to other types of DNA nanostructures and suggest that terminal stacking interactions play an integral role in formation and stability of DNA nanostructures.

Priority rules for handling containers to improve energy consumption and terminal efficiency

AbstractThis paper addresses the optimization of the yard crane handling processes in a container terminal to reduce energy consumption and improve overall system performance. More precisely, the paper presents and evaluates different sequencing rules, based on predefined priorities, to organize the rail yard to minimize moves during the rail loading operations. The minimization of overall energy consumption and maximum tardiness are considered, simultaneously assessing these two components of the objective function to better understand how they interact and how they can be optimized together. As a novel issue in optimization, a hill climbing algorithm is implemented, searching for the yard configuration that most improves the efficiency of container handling while being able to integrate different management rules of the terminal. The reference case study is the PSA Pra terminal in Genoa, Italy. A full rail yard with known delivery times, and crane operating along a single stack, is the operative scenario. Random due time sequences are generated during test instances, while technical data of crane are used. Moreover, crane movements involve both loading and unloading along multiple axes. From the results, the best priority rules improve energy consumption and lateness of the initial configuration of the yard by up to 55%, thus allowing the terminal management to reorganize the storage areas accordingly and improve their efficiency. The proposed priority rules bridge the gap between theoretical optimization procedures and container terminal practices.

Ultralow degradation cold start of proton exchange membrane fuel cell with alternating hydrogen pump method

Cold start impedes widespread diffusion of fuel cell vehicles (FCVs) in regions with temperatures below zero. Alternating hydrogen pump (AHP) method, distinguished by its unlimited ohmic heating capability without generating water, has been shown to be a quick and efficient method of cold starts in both single cell and short stacks. In this paper, we continue to examine possible degradation with this novel method. For this purpose, we carefully designed three experiments with different levels of stress, aimed to separate the contribution to any degradation from major factors. It was found there was no significant difference among the three cases. AHP method incurred minimal degradation after 3600 times of equivalent −30 °C cold starts. This study concludes that AHP method is not only quick and efficient, but also highly durable, hence AHP is a promising alternative cold start strategy with great potential to facilitate the diffusion of FCVs.

Free-breathing time-resolved 4D MRI with improved T1-weighting contrast.

This work proposes MP-Grasp4D (magnetization-prepared golden-angle radial sparse parallel 4D) MRI, a free-breathing, inversion recovery (IR)-prepared, time-resolved 4D MRI technique with improved T1-weighted contrast. MP-Grasp4D MRI acquisition incorporates IR preparation into a radial gradient echo sequence. MP-Grasp4D employs a golden-angle navi-stack-of-stars sampling scheme, where imaging data of rotating radial stacks and navigator stacks (acquired at a consistent rotation angle) are alternately acquired. The navigator stacks are used to estimate a temporal basis for low-rank subspace-constrained reconstruction. This allows for the simultaneous capture of both IR-induced contrast changes and respiratory motion. One temporal frame of the imaging volume in MP-Grasp4D MRI is reconstructed from a single stack and an adjacent navigator stack on average, resulting in a nominal temporal resolution of 0.16 seconds per volume. Images corresponding to the optimal inversion time (TI) can be retrospectively selected for providing the best image contrast. Reader studies were conducted to assess the performance of MP-Grasp4D MRI in liver imaging across 30 subjects in comparison with standard Grasp4D MRI without IR preparation. MP-Grasp4D MRI received significantly higher scores (P < 0.05) than Grasp4D in all assessment categories. There was a moderate to almost perfect agreement (kappa coefficient from 0.42 to 0.9) between the two readers for image quality assessment. When the scan time is reduced, MP-Grasp4D MRI preserves image contrast and quality, demonstrating additional acceleration capability. MP-Grasp4D MRI improves T1-weighted contrast for free-breathing time-resolved 4D MRI and eliminates the need for explicit motion compensation. This method is expected to be valuable in different MRI applications such as MR-guided radiotherapy.

(Invited) Techno-Economic Aspects of Hydrogen Production from Water Electrolysis

Hydrogen production today Today, hydrogen is still mainly being used as a specialty chemical, including the synthesis of ammonia and methanol, and during steel and glass manufacturing where it is the preferred reducing gas during annealing and forming processes. The great majority of all these H2 is being produced by 2 large-scale chemical processes : steam methane reforming (SMR) and coal gasification. Both of these processes are heavily CO2 intensive, SMR emitting up to 8 tons of CO2 per ton of H2 produced. Therefore, with the objective of reaching the CO2 emission targets already in today's fossil-based H2 production, the part of electrolytic hydrogen produced from renewable electricity should significantly increase. However, in order to meet the current global H2 demand of around 80 Mton/year, a total of 300 GW installed electrolyser capacity would already be needed today. Such instantaneous massive electrolyser deployment is not very realistic. Alternatively, a selection of technologically feasible market penetrations for electrolytic H2 needs to be made. In the ideal case, such a selection also implies that todays local H2 consumers, besides becoming local (on-site) producers of renewable electricity, also need to become local (on-site) producers of electrolytic H2, at a production scale which still allows to meet the stringent requirement of fossil parity. The cost of electrochemical hydrogen production As compared to an individual large-scale SMR production unit, typically corresponding to an electrolyser power equivalent well above 100 MW, the basic units of a water electrolyser are rather small-scale : both the geometrical area of the electrodes (a few m2 at most) and the number of electrodes that can be compiled in series in a single stack is relatively limited. As a result, the unit size of water electrolysers has long been limited to the kW-range, a typical on-site containerized production unit being a few 100 kW at most. However, in order to be able to realize the coupling to renewables, the power scale of water electrolysers needs to become at least of the same order of magnitude as the renewable electricity source itself, i.e. multi-MW. Such an electrolyser scale-up is typically being realised by increasing the number of cells per stack. However, from the state-of-the-art data that we recently collected from a number of electrolyser manufacturers, such a "keep-on-stacking" approach seems to have a practical limit at around 200 cells/stack [2]. Beyond that number, other balance-of-plant issues come into play. Therefore, for multi-MW applications, multi-stack electrolyser systems are typically being used.While it is technically feasible to produce electrolytic hydrogen with such multi-stack systems at the multi-MW scale (even >100MW), as was already demonstrated several decades ago, the critical question still remains at what price/cost this can be done today. In this respect, the 3 major parameters affecting the electrolytic H2 production cost are the operational time of the electrolyser, the cost of renewable electricity, and the electrolyser CAPEX. Hence, before becoming a realistic alternative production technology, there is a need for cheap(er) renewable electricity (well below 70 €/MWh) and the investment cost of electrolysers needs to be brought down (to about 500 €/kW). Luckily, with respect to all these requirements, significant progress has been made over the past years, as we will highlight in our presentation using the most recent data from both the International Energy Agency (IEA) and the International Renewable Energy Agency (IRENA). The scale of fossil parity for electrolytic hydrogen An important techno-economic aspect then relates to the production scale required for obtaining fossil parity with electrolytic H2. Indeed, one might wrongly conclude that reaching the required reduction in electrolyser CAPEX down to about 500 €/kW would require very large-scale electrolytic H2 production units around 100 MW or above, on the same order of today's SMR units. However, our own recent data suggest that there might be a much smaller production scale for reaching such low CAPEX values. Indeed based on an extrapolation of the currently available CAPEX data for single-stack alkaline electrolysers, the level of 500 €/kW could already be reached at less than 10 MW [3]. Such a significant reduction in the scale required for fossil parity is directly related to the much steeper reduction in CAPEX that can be realised for single-stack as compared to multi-stack water electrolysis systems. Some promising implications of such small-scale fossil parity will be discussed during our presentation as well.[1] Global Hydrogen Review 2023, International Energy Agency, https://www.iea.org/reports/global-hydrogen-review-2023[2] J. Proost, International Journal of Hydrogen Energy, 44, 4406-4413 (2019)[3] J. Proost, International Journal of Hydrogen Energy, 45, 17067-17075 (2020)

(Invited) Shunt-currents in Alkaline Water-Electrolyzers and Renewable Energy

Shunt-currents in bipolar cell stack design with a common electrolyte-feed and -outlet is an inevitable physical phenomenon governed by Ohms law that causes some extra challenges when alkaline water-electrolysers shall operate on renewable energy that is both dynamic and intermittent. Shunt-currents are also referred to as bypass-current or creep-current. The shunt-currents are to much degree governed by the electrolyte inside the cell stack manifold system that transports lye in and out of the cells. The electrolyte inside the manifold system also electrically connects the individual cells together and enables transport of ions/electricity in parallel to the cell stack. Thus, a small portion of the rectifier current is being shunted outside the cells and does not contribute to any production. Previous work on shunt-current modelling brought new insight on how to design the manifolds and raised the awareness on shunt-current and the use of metallic manifolds which both reduced the ohmic resistivity of the manifold system and was a source of secondary electrolysis.Classic alkaline water-electrolysers are typically using an internal manifold system where the inlet ports are located at the bottom of the cell stack and the outlet ports are located at the top, and where the ports connecting the cell-interior and the common manifold channel are short and straight. Such design has in the past worked satisfactory for alkaline water-electrolysers that have been working on a high nominal load and only being shut-down for maintenance a few times over the stack-lifetime, mainly causing a modest reduction in the current efficiency. Membrane-chlorine electrolysers on the other hand, are designed for very small shunt-currents by using an external manifold system, which enables a current protection system that protects electrodes from corrosion under shutdown conditions.Shunt-currents bypassing the cell stack does not contribute to any product and therefore constitutes a loss in current efficiency and, hence, an accordingly loss in the energy efficiency (the shunt-currents still adds to the electricity bill). The atmospheric alkaline electrolyser has a modest loss in current efficiency at nominal load where the high gas volume blocks much of the current path in the rather open outlet ports. The high-pressure alkaline electrolysers on the other hand, where the gas volumes are much smaller, the current efficiency can be as low as 89% at nominal load due to shunt-currents when using simple internal manifold system. For an electrolyser with already low current efficiency at the nominal load, the current efficiency will drop dramatically as the electrolyser is taken to lower load, severely compromising the energy efficiency. The impact on shunt-currents also dramatically increases for increased number of cells in a cell stack, and eventually limits the number of cells that can be assembled in one single cell stack operating on the same common lye system.Shutdown and discharge of the electrodes may further lead to corrosion and degradation of the electrodes, strongly influenced by the shunt-currents and the manifold system. Large cell stacks will discharge faster and deeper, eventually causing corrosion of the electrodes. As the cell stack is discharged the current in the cell stack is reversed where the hydrogen electrode is being polarized to anodic potentials, and the oxygen electrode is polarized to low cathodic potentials which eventually may challenging the material stability. Thus, evaluation of electrode potentials must be an integral part of development of industrial electrodes [LeRoy] and especially in intermittent operation where frequent shutdown will occur. A good integration of the manifold system into the cell stack can potentially mitigate both the loss of current efficiency under dynamic operation and the electrode corrosion under intermittent operation.

Impact of Electrochemical Impedance Spectroscopy Dataset Curation on Solid Oxide Cell Degradation Assessment

Electrochemical impedance spectroscopy (EIS) has become a standard measurement technique for detecting degradation in single cells and stacks of solid oxide cells (SOCs). Depending on the experimental setup and test equipment, instabilities and unexpected results can be observed in EIS measurements. For example, in the low-frequency range, instabilities can be induced by feed gas flow fluctuations. Another phenomenon are parasitic, inductive impedances that degrade the high-frequency range. To compensate for such influences in large EIS data sets, we propose a specially developed EIS data curation pipeline. Based on the results of its application, we demonstrate the impact on the quantitative and qualitative attribution of electrochemical processes from EIS using equivalent circuit modeling and distribution of relaxation times. Furthermore, the substantial differences in the temporal evolution of the latter during long-term experiments are highlighted for EIS measurements obtained at the SOC stack and single cell level. In addition, the significant misestimation of aging rates, especially with respect to the fuel electrode and the high-frequency series resistance, is shown when comparing EIS measurements, few of which exhibit a parasitic inductive impedance.

Recovery characteristics of reversible degradation for proton exchange membrane fuel cell stack under accelerated stress test

The reversible degradation of proton exchange membrane fuel cells (PEMFC) restricts the high efficiency and long-term durability of fuel cells. The reversible loss, restorable only through specific procedures, significantly diminishes both the operational efficiency and the predictability of their remaining service life. Consequently, it is imperative to elucidate the recovery characteristics of reversible loss in high power PEMFC stacks for engineering applications. However, most of the studies focus on small-area single cells or short stacks, researches on the full-size stacks considering the uniformity and consistency differences are scarce. The recovery characteristics of high-power PEMFC stacks remain unclear. Therefore, in this work, an accelerated stress test with the idle and rated currents as the boundary of the cyclic condition was designed for a 100 kW PEMFC stack to investigate the recovery characteristics. The periodic voltage fluctuations along with the shutdown operations indicate that the voltage recovery may be caused by the redistribution of water content within the stack, and the reversible degradation is more pronounced and readily reversible under the high current condition. The impedance results suggest that the redistribution of water within the catalyst layer takes longer compared to that in the membrane. Furthermore, analyses of single cell voltage indicate that the consistency of voltage recovery is more closely related to variations of water content within the catalyst layer. Cells with higher water content exhibit better voltage recovery.

Enhancing Density Maps by Removing the Majority of Particles in Single Particle Cryogenic Electron Microscopy Final Stacks.

Over the past decade, advancements in technology and methodology within the field of cryogenic electron microscopy (cryo-EM) single-particle analysis (SPA) have substantially improved our capacity for high-resolution structural examination of biological macromolecules. This advancement has ushered in a new era of molecular insights, replacing X-ray crystallography as the dominant method and providing answers to longstanding questions in biology. Since cryo-EM does not depend on crystallization, which is a significant limitation of X-ray crystallography, it captures particles of varying quality. Consequently, the selection of particles is crucial, as the quality of the selected particles directly influences the resolution of the reconstructed density map. An innovative iterative approach for particle selection, termed CryoSieve, significantly improves the quality of reconstructed density maps by effectively reducing the number of particles in the final stack. Experimental evidence shows that this method can eliminate the majority of particles in final stacks, resulting in a notable enhancement in the quality of density maps. This article outlines the detailed workflow of this approach and showcases its application on a real-world dataset.

A Redox-Electrodialysis Model with Zero Fitting Parameters: Insights into Process Limitations, Design, and Material Interventions

Redox-Electrodialysis (r-ED) is an electrochemical desalination cell architecture that has recently received considerable interest, due to its low energy demand relative to electrochemical desalination technologies that rely on electrode-based ion removal. To further improve the energy efficiency of r-ED, we developed a lumped mathematical model with no adjustable parameters to investigate the various sources of overpotential within the cell. Existing models of electrodialysis and r-ED cells either do not accurately incorporate all phenomena contributing to the overpotential or utilize empirical fitting parameters. The model developed here indicates that ohmic overpotentials, especially in the diluate chamber, are the most significant contributors to energy losses. Based on this insight, we hypothesized that adding an ion exchange resin wafer in the diluate compartment would increase the ionic conductivity and decrease the energy demand. Experimental results showed an 18% reduction in specific energy use while achieving the same degree of salt removal (20 mM to 12 mM). Furthermore, the resin wafer enabled complete desalination to potable drinking levels at a current density previously unachievable within practical operating voltage limits (4.93 mA cm−2). We also expanded the model to explore differences in r-ED energy use between configurations using multiple cells and a single cell with increased area.

Concave and convex small radius bending behavior of single and multiple layers reinforcement fabrics

Multilayer reinforcement fabrics are increasingly used for manufacturing structural polymer composites. In liquid molding processes, dry reinforcement fabrics are draped on a mold first, and infused with a liquid resin such as an epoxy in a subsequent manufacturing step. This presents major advantages in terms of operational flexibility and costs. However, draping multilayer reinforcement fabrics on complex mold geometries is challenging. Small radius mold corners constitute a major manufacturing challenge as they lead to variability in dry fabric positioning and resin-rich corners in polymer composite parts. Spring-back of fabrics bent over or into single curvature mold corners is a widespread industrial concern. However, contrary to draping over double-curvature surfaces, bending spring-back from convex or concave single-curvature corners has received very limited attention. No testing method is available. This paper quantifies reinforcement fabric bending spring-back. Single and multiple layer stacks were bent along three directions over convex and into concave 90° corners with five radii spanning 1.59 mm to 12.70 mm. In all cases, five replicated tests enabled variability quantification. Fabric stacks were also quantified using cantilevered bending tests for comparison purposes. Mold radius was found to affect the behavior to a larger extent than testing direction, number of layers or use of a binder.

Large-scale research on durability test cycle of fuel cell system based on CATC

Durability is one of the technical bottlenecks restricting fuel cell electric vehicle development. As a result, significant time and resources have been invested in research related to this area worldwide. Current durability research mainly focuses on the single cell and stack levels, which is quite different from the usage scenarios of actual vehicles. There is almost no research on developing durability test cycles on the fuel cell system level. This paper proposes a universal model for developing a durability test cycle for fuel cell system based on the China automotive test cycle. Large-scale comparison tests of the fuel cell systems are conducted. After 1000 h test, the output performance degradation of three mass-produced fuel cell system is 14.49%, 9.59%, and 4.21%, respectively. The test results show that the durability test cycle proposed in this paper can effectively accelerate the durability test of the fuel cell system and evaluate the durability performance of the fuel cell system. Moreover, the methodology proposed in this paper could be used in any other test cycles such as NEDC (New European Driving Cycle), WLTC (Worldwide Harmonized Light Vehicles Test Procedure), etc. And it has comprehensive application value and are significant for reducing the cost of durability testing of fuel cell systems and promoting the industrialization of fuel cell electric vehicles.

Object-based terminal positioning solution within task-boosted global constraint for improving mobile robotic stacking accuracy

Wall building is labor-intensive and time-consuming as a typical construction task. It is expected to perform this heavy task using robots. However, laborers are still largely employed, mainly because high continuous stacking precision for mobile robots has always been a bottleneck problem. This paper examines the characteristics of continuous robotic stacking in wall-building tasks and finds the key challenge lies in precisely manipulating the robot arm terminal to the target pose and guaranteeing the wall’s verticality. We propose an object-based terminal positioning solution for this issue. The core of this solution is establishing a reference coordinate system as a measurement reference and designing a multi-sensor measurement system to measure the relative pose between the robot and the object. The solution allows the robot to reposition multiple times and iteratively correct the terminal’s pose, which greatly reduces the impact of positioning errors and loaded deflections of mobile systems on terminal positioning accuracy. Furthermore, we propose for the first time the construction of an active reference feature using a planar laser as a global constraint to provide a consistent reference for establishing reference coordinate systems. Global constraint eliminates the cumulative stacking errors due to relying only on the previously stacked object’s reference features for terminal positioning in continuous stacking tasks and guarantees the wall’s verticality. Finally, an autonomous mobile stacking robot is developed, and continuous block stacking experiments are conducted with this robot in a laboratory environment simulating real application sites. Experimental results demonstrate that the developed robotic system can achieve millimeter-level stacking accuracy, where a single vertical stack error of 3 mm meets the high requirements of the construction industry. Thus, it is reasonable to believe the proposed solution is extremely competitive compared to existing studies and provides valuable insights for improving the continuous stacking accuracy of mobile robots in large-scale unstructured environments.

Vibration Energy Harvesting with Printed P(VDF:TrFE) Transducers to Power Condition Monitoring Sensors for Industrial and Manufacturing Equipment

A vibration energy harvesting system based on fully printed piezoelectric transducers is realized. The transducers have a butterfly‐like architecture based on two single‐optimized cantilevers with a resonance frequency tuned to 49.5 Hz and can be easily mounted to an industrial engine. By comparing single‐ and multistack configurations of the piezoelectric layers combined with full‐wave or voltage doubler rectifiers, the power transfer characteristics and impedance can be matched to the electrical requirements of the sensing circuitry. A single stack with 21 μm thickness results in the maximum power output of 14.4 μW at a vibration velocity of 11.5 mm s−1, typical for industrial engines. The system is used to power a wireless sensor node on a 1 kW rotary pump in normal operation. The system can harvest up to 138 mJ within 24 h, sufficient for daily remote monitoring of the engine's vibration spectrum and temperature state. The system is thus suitable as a low‐cost, ecofriendly power source for industrial IoT applications.

Influence of shunt currents in industrial-scale alkaline water electrolyzer plants

The aim of this paper is to analyze through simulation how the energy efficiency of a single electrolysis stack at various loads is affected by shunt currents and to determine the energy-optimal load distribution between lines in a multiline electrolysis system under various magnitudes of shunt current losses. A dynamic energy and mass balance model of an industrial 3MW, 16bar alkaline water electrolyzer (AWE) process was developed using MATLAB. The optimization goal is to determine the power supply for each AWE line so that it can meet any hydrogen demand while minimizing the global specific energy consumption (SEC). The Particle Swarm Optimization (PSO) algorithm is used to minimize the objective function. According to the results of the single stack investigation, shunt current reduction could significantly improve the energy efficiency of partial-load operation. In addition, the optimization study revealed that whenever two or more lines are required to run in order to satisfy the hydrogen demand, the global SEC is minimized when the lines operate at equal loads.

Pulsating strings in I-brane background

We study pulsating strings both on a single stack of NS5-branes and two orthogonal stacks of NS5-branes (the so called I-brane) by using the Polyakov form of the fundamental string action. For the I-brane background, by using a symmetry that decouples the two spheres from the flat geometry, we study pulsating solutions of the string when it pulsates on both the spheres independently and simultaneously. We finally derive the energy of pulsating strings as a function of adiabatic invariant oscillation number in these cases and studied some limiting cases in detail.