bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy, economic and environmental benefits of Demand Response for improving building energy flexibility
Authors: Dal Cin Enrico , Rech Sergio , Benetti Marianna
Published: May 2024

The increasing penetration of intermittent renewable sources in power generation at local and building-level poses growing issues in balancing generation and demand. To avoid imbalances, it is therefore necessary to ensure adequate levels of flexibility in the building energy system. This can be done both on the generation side, through the coupling of different energy carriers (cogeneration, power-to-heat solutions) and/or the integration of storage systems, and on the demand side, through smart “demand response” programs. This paper considers a tourist facility located in central Germany as a case study to evaluate the energy, economic and environmental benefits that can be obtained from the application of appropriate demand response strategies. The electrical demand data of the facility are monitored at both aggregate and individual load levels and made available by means of a cloud platform. The facility includes two stationary combined heat and power internal combustion engines powered by natural gas and a photovoltaic system. The results show how, thanks to appropriate load management, it is possible, on the one hand, to increase the self-consumption of PV-generated energy and, on the other hand, to keep more constant the load of the engines, which can therefore operate with better efficiencies. This results in both a reduction in energy expenses and a decrease in carbon dioxide emissions attributable to the building.
Energetic advantages and well-being improvement for building occupants, connected to dynamic building envelope solutions, with special focus on intelligent solar shading and ventilative cooling of NZEB and ZEB buildings
Authors: Gandini Jacques
Published: May 2024

Across Europe, rising outdoor air ambient temperatures connected to the global warming and climate change, combined with an ageing population and urbanisation, are putting in evidence that population is potentially becoming more vulnerable to heat in summer especially during heatwaves. In particular high energy efficient buildings designed without consideration for potential “overheating” mitigation are foreseen in the future to be at risk of summertime discomfort and rising costs (and relative direct or indirect CO2 emissions) for additional air conditioning operation needs. Beside the best HVAC technologies, intelligent solar shading and ventilative cooling are considered, by several EU governments and experts, two key elements for further improving the energy efficiency of existing buildings and optimising the low-energy designs of new buildings. These technologies seems still under-utilised despite the fact it provides a major impact on the reduction of energy consumption of the built environment and, for this reason, present paper is concentred on the evaluation of the advantages represented by the use of intelligent solar shading and ventilative cooling in order to take the best energetic impact form solar heat gains in winter and minimise these heat gains in summer, also using the air ambient cooling energy hence reducing the cooling loads to be solved with mechanical cooling at total benefit of even more energy efficient and resilient / future-proof buildings.
Govern complex systems in the design of an innovative, safe and sustainable hospital
Authors: Prete Daniele , Piscitelli Prisco , Elia Gianluca
Published: May 2024

The hospital is essential for managing the health of citizens with a high degree of complexity. The hospital system is very energy-intensive, presents rapid technological obsolescence and often requires specific and multidisciplinary skills to also manage new clinical-health organizational models for the dynamic change of functional needs and the management of emergencies (e.g. Covid 19 pandemic). The proposed methodology en-visages the pervasive use of renewable energy and the modeling of the digital twin of the building with system solutions specifically designed to increase the comfort of the users of the structure and optimize the maintainability of the systems. These systems, thanks to artificial intelligence software, after an initial period of “learning” the behavior of the building, are able to dynamically simulate different ways of operating the systems in order to pursue the model capable of maximizing the energy saving of the building. The advanced energy monitoring system (BEMS - Building Energy Management System) allows to guarantee the monitoring of the pre-established performance indicators with undoubted advantages from the point of view of the reduction of the primary energy necessary for the functioning of the structure, the study of consumption for cost, air quality and resource consumption.
Potential of Energy Saving of Propane Heat Pump as replacement of gas boilers with low and high temperature emitters
Authors: Camponeschi Corrado , Goni Maurizio , Cioffi Francesca , Dongellini Matteo , Naldi Claudia , Morini Gian Luca , Germano Luca , Genovese Filippo , Cervellati Andrea , Casolari Alessandro , Corsaro Federico , Ciancamerla Matteo , Ballotta Luca
Published: May 2024

This work deals with the analysis of the energy performance and the environmental impact of a Heating, Ventilation and Air Conditioning (HVAC) system based on an innovative Air-to-Water electrical Heat Pump (AWHP) using propane (R290) as the refrigerant. A building of the University of Bologna located in Forlì (North of Italy) is considered for replacing a condensing gas boiler and a conventional chiller with an AWHP using R290. To evaluate the efficiency of the existing heating system and the potential savings linked to the adoption of the propane AWHP, the building energy model was created and calibrated by collecting monthly thermal and electrical consumptions as a function of the actual climate data. In this paper, the main features of the R290-based AWHP are described in detail by emphasising the device performance as a function of the operating conditions (i.e., air and water temperature and speed of the scroll compressor). A series of scenarios have been studied to evaluate the energy performance of the propane AWHP with respect to the reference scenario under various operating conditions. The results show that while the total primary energy demand increases adopting the propane AWHP with respect to the case of a gas boiler, the non-renewable primary energy fraction decreases significantly, with a dramatic increase in the renewable quote. From an economic point of view, lower annual costs are obtained by adopting a propane AWHP coupled to fan coils, mainly when the electrical heat pump is used in a thermally insulated building in which a photovoltaic system is installed.
Analysis of the Physical Phenomena and Modelling Procedures of Building Heating and Cooling Emission System Energy Losses
Authors: Degerfeld Franz Bianco Mauthe , Ballarini Ilaria , Corrado Vincenzo
Published: May 2024

An important research issue in assessing the energy performance of buildings concerns the modelling of the interaction between the built environment and the heating/cooling emission systems. Several methods can be used to evaluate the effect of the heating emitter characteristics, including the possible embedment in the building structure, non-uniform space temperature distribution, and the accuracy of the indoor temperature control. Generally, technical standards specify simplified, yet insufficiently validated methods, based on tabulated values. This paper outlines the main simplified procedures for assessing the efficiency of the emission subsystem, with a particular focus on the hydronic systems. It describes the essential datasets required for the analysis and highlights the interaction with phenomena related to the emitter heat loss. The simplified calculation procedures are then methodologically compared with detailed simulation tools, such as EnergyPlus, to identify differences and limitations in the models. The main discrepancies in the procedures and the required input data are highlighted, and possible strategies for improving the simplified methods are presented. A building representative of the European residential building stock is then analysed in the Italian climate using different calculation procedures. The results, in terms of thermal output of the emitter, are then analysed and compared.
Readiness of Zero-Emission Buildings (ZEBs) implementation in the European Union
Authors: Maduta Carmen , D’Agostino Delia
Published: May 2024

The building sector plays a central role in the reduction of greenhouse gas (GHG) emissions in the European Union (EU). The revision of the Energy Performance of Buildings Directive (EPBD) sets out ambitious requirements to make the EU building stock decarbonised by 2050. The proposal for a recast EPBD introduces Zero-Emission Building (ZEB) as the building target for all new buildings as of 2030. This paper offers insights into the concept of ZEB, analysing its key methodological aspects, with a focus on ambition, the role of energy efficiency, and the role of renewable energy. Additionally, the paper evaluates the performance levels of new buildings in EU Member States, highlighting the gaps between current Nearly Zero-Energy Buildings’ performance levels and potential ZEB performance levels, specifically in terms of primary energy demand and renewable energy contribution. The findings emphasise the necessity to enhance initiatives aimed at improving energy efficiency and harnessing renewable energy sources to adopt the ambitious ZEB concept as of 2030. Additionally, the paper highlights the importance of addressing GHG emissions comprehensively, extending beyond the operational phase of a building to include embodied impacts, in order to achieve a life-cycle zero-emission building stock.
Virtual energy sharing and energy communities for the Municipality of Milan: The case of the Chiaravalle area
Authors: Ferroni Sibilla , Causone Francesco , Minchio Fabio , Sordi Giuseppina , Giuliani Ilaria , Paci Christina , Cremascoli Elena
Published: May 2024

The development of virtual energy sharing in complex realities such as the territory of the Municipality of Milan requires the integration of political and social strategies, technical analyses and the use of more advanced urban modelling techniques. This work aims to describe the strategy developed by the Municipality of Milan for the implementation of energy communities and virtual energy sharing, on the basis of current legislation, with reference to the case study of the Chiaravalle area. In order to carry out studies on the area, UBEM (Urban Energy Modelling) models were developed and various intervention scenarios were analysed. The results of the analysis and the technical and strategic evaluations developed are presented.
Towards environmental sustainability of non-residential buildings: An integrated approach to combine thermal comfort of people with energy saving strategies for heating system management
Authors: Proietti Maria Giulia , Elefante Marco , Proietti Luca , Longhi Francesco , Moretti Elisa
Published: May 2024

Buildings are constructed and operated to satisfy human needs and improve quality of life. Good indoor air quality and thermal comfort are prerequisites for human health and well-being. At the same time, these aspects are strictly linked to the buildings’ energy consumption, with a direct impact on energy efficiency global goals and climate changes. Global technical regulations and guidelines aim at increasing the energy performance of buildings, with targets of NZEB and ZEB, both for new and existing buildings. In this context the research was carried out in order to investigate energy saving strategies related to heating systems, combining with indoor comfort analyses. The case study is an existing building, located in Perugia (Italy), which is the main seat of Arpa Umbria. The recent energy crisis has imposed strict measures to contain energy consumption, especially for heating; for this reason, the study aims to identify optimal management of the heating, based on a thermal calibrated model of the building and thermo-hygrometric monitoring. With the model, different management strategies were defined and simulated in order to develop schedules to set switch-on/off systems based on indoor and outdoor weather conditions. The results are presented in an integrated approach, combining the estimated reduction of energy consumption with human well-being.
Blood Management Issues: Getting Clots Together When You Want Them
Authors: McMillan Darryl , Potger Kieron , Southwell Joanne
Published: May 2024

Coagulation is a complex process that allows whole blood to form clots at tissue and vessel sites where damage has occurred. Activation of the hemostasis system causes platelets and fibrin-containing clot to stop the bleeding. Perfusionists must find ways to preserve the coagulation system if we are to avoid bleeding in the cardiopulmonary bypass patient. It is still unclear what techniques are best to continue maintaining hemostasis and avoiding transfusion in patients requiring cardiopulmonary bypass (CPB). There are numerous factors that come into play with the use of CPB including deactivating the coagulation system with anticoagulants, hemodilution of the circulating blood volume, inflammatory response, and a possible pro-coagulant response from protamine with heparin reversal once the surgical procedure has been completed and CPB terminated. All these factors make achieving hemostasis post CPB extremely difficult. This review attempts to assess what is currently being discussed in the literature, which may improve hemostasis with cardiopulmonary bypass. There is still no one technique that will improve hemostasis post CPB. Perhaps the answer may lie in a combination of reported techniques that may in some way lead to the preserving of coagulation factors during CPB.
Perfusion and Aortic Surgery: Patient Directed Cardiopulmonary Bypass and Quality Improvement
Authors: Poullis Mike
Published: May 2024

Aortic surgery frequently extends the boundaries of perfusion knowledge learned from non aortic cardiac surgery. This is due to the extremes of temperature, prolonged bypass times, hypothermic arrest, and selective organ(s) perfusion. Suboptimal perfusion can potentially affect outcomes even after technically successful aortic surgery. We present the concepts of patient directed bypass with regard to blood pressure, flow during cardiopulmonary bypass (CPB), oxygen delivery, cooling, and carbon dioxide levels on bypass. Quality of perfusion during aortic surgery is then addressed in the context of Perfusion Standards of Reporting Trials (PERFSORT, www.perfsort.net). PERFSORT analyses these variables during bypass: blood pressure, hematocrit, lactate, glucose, and temperature, all of which are known to affect outcomes. PERFSORT can be applied to individual cases or a series, and although primarily designed for research publications, is equally useful in a purely clinical setting. A new concept from engineering called Lissajous figures is then discussed to potentially retrospectively assess the effects of ischemia during aortic surgery. This may help identify why some patients despite flawless surgery, anesthesia, and perfusion, in the absence of bleeding, stroke, and obvious causes of organ damage at the time of aortic surgery develop multi organ dysfunction.
Enantioselective Silylative Desymmetrization of meso-Indane-1,3-diols Catalyzed by Chiral Guanidines
Authors: Nakata Kenya , Ui Ayano , Iwakura Manaya , Yoshimatsu Shuhei
Published: May 2024

Chiral guanidine-catalyzed desymmetrization of meso-indan-1,3-diols was achieved via enantioselective silylation by using chlorosilanes in good yields with high selectivity. The combination of chlorosilanes and catalysts was determined by the substituents at the C-2 position on the substrate. It was found that the fused phenyl ring on the substrate was essential for achieving high selectivity. The proposed method was found to be applicable to several types of substrates under optimized reaction conditions. Double silylative kinetic resolution with additive Horeau amplification was observed to establish high selectivity.
Interstitial Lung Disease Associated with Systemic Sclerosis
Authors: Mismetti Valentine , Si-Mohamed Salim , Cottin Vincent
Published: May 2024

Systemic sclerosis (SSc) is a rare autoimmune disease characterized by a tripod combining vasculopathy, fibrosis, and immune-mediated inflammatory processes. The prevalence of interstitial lung disease (ILD) in SSc varies according to the methods used to detect it, ranging from 25 to 95%. The fibrotic and vascular pulmonary manifestations of SSc, particularly ILD, are the main causes of morbidity and mortality, contributing to 35% of deaths. Although early trials were conducted with cyclophosphamide, more recent randomized controlled trials have been performed to assess the efficacy and tolerability of several medications, mostly mycophenolate, rituximab, tocilizumab, and nintedanib. Although many uncertainties remain, expert consensus is emerging to optimize the therapeutic management and to provide clinicians with evidence-based clinical practice guidelines for patients with SSc-ILD. This article provides an overview, in the light of the latest advances, of the available evidence for the diagnosis and management of SSc-ILD.
Quantum dots may improve space laser communications by tolerating harsh radiation conditions
Authors: Lim Alane
Published: May 2024

Bolstering semiconductor laser diodes’ radiation hardness can facilitate their application in harsh environments like space or nuclear power plants.
Current collapse suppression in AlGaInN/GaN HEMTs with thin unintentionally doped GaN channel and AlN back barrier grown on single-crystal AlN substrate
Authors: Kawaide Tomoyuki , Kometani Yoshinobu , Tanaka Sakura , Egawa Takashi , Miyoshi Makoto
Published: May 2024

A high-electron-mobility transistor (HEMT) structure consisting of a 15-nm-thick quaternary AlGaInN top barrier layer, a thin 200-nm-thick unintentionally doped (UID) GaN channel layer, and an AlN back barrier was grown on a single-crystal AlN substrate by metal–organic chemical vapor deposition. The HEMTs fabricated on the grown heterostructure exhibited DC pinch-off characteristics with no large negative resistance owing to the high thermal conductivity of the AlN substrate. The 2-μm-gate-length devices showed the maximum current density of 500 mA/mm and the peak transconductance of 120 mS/mm with the threshold voltage of approximately −4 V. The off-state leakage was less than 30 μA/mm thanks to the thin UID-GaN channel with good crystal quality. The pulsed I–V characteristics for the fabricated HEMTs showed much smaller drain current decreasing compared to the same structured HEMTs with a C-doped GaN back barrier on a SiC substrate. This indicates that the UID-GaN channel grown on the AlN substrate had no harmful impurity levels that cause the current collapse phenomenon. The above-mentioned results demonstrate that the combination of the thin UID-GaN channel and the AlN back barrier works effectively in GaN HEMTs, and it will contribute to the device design and fabrication for future high-power/high-frequency applications.
Strain-induced ferromagnetism and magneto-electric coupling in two-dimensional ferroelectric ZnIn2S4
Authors: Li Dong , Huangfu Yuehua , Zhang Guangbiao , Liu Chang , Ren Fengzhu , Wang Bing
Published: May 2024

Two-dimensional (2D) multiferroic materials are currently in high demand due to their significant potential for applications in the field of high-density data storage devices. However, due to the different requirements for generating ferroelectricity and magnetism, 2D multiferroic materials are rare. In this study, we propose that applying strain can induce magnetism in 2D ferroelectric materials with special electronic structures, thereby creating 2D multiferroics. Taking 2D ZnIn2S4 as an example, it shows robust ferroelectricity with an appropriate switching barrier (79.3 meV), and the out-of-plane ferroelectric polarization is 0.0322 C/m2. Applying biaxial tensile strain can change the energy of the flatband near the Fermi level, ultimately resulting in self-doping phenomena and leading to Stoner-type itinerant ferromagnetism. The reversal of ferroelectric polarization in ZnIn2S4 bilayer and ZnIn2S4–In2Se3 heterostructure can manipulate the magnetic moment of the system, exhibiting significant magnetoelectric coupling phenomena. Our findings provide a pathway for designing 2D ferromagnetic and multiferroic materials.
The GeSe/SnSe heterojunction photodetector with self-powered characteristics and high infrared response performance
Authors: Mao Yuliang , Deng Tongzhou , Li Yuxuan , He Feng
Published: May 2024

We present a GeSe/SnSe van der Waals heterojunction fabricated using the wet transfer technique. GeSe and SnSe were synthesized via a low-temperature and atmospheric-pressure chemical vapor deposition method. The GeSe/SnSe heterostructure photodetector demonstrates remarkable rectification characteristics, boasting a rectification ratio of 102, along with an exceptionally low dark current, indicating minimal power consumption. Furthermore, it exhibits a broad optical response, spanning from the visible spectrum (450 nm) to the near-infrared (1064 nm). Under 808 nm laser illumination and reverse bias, the device achieves a responsivity of 19.82 A/W, a detectivity of 4.74 × 109 Jones, and an external quantum efficiency of 3048.32%. Notably, the GeSe/SnSe heterojunction photodetector also exhibits self-powered characteristics, with a responsivity of 0.11 mA/W and a detectivity of 5.44 × 106 Jones at zero bias voltage, accompanied by a fast response time of 23/61 ms (rise/fall). These findings underscore the effectiveness of the GeSe/SnSe heterojunction as a strategy for near-infrared photodetectors to simultaneously achieve low power consumption, high photoresponsivity, and self-powered photodetection, which is promising for optoelectronic device applications.
Simulations of non-integer upconversion in resonant six-wave scattering
Authors: Griffith A. , Qu K. , Fisch N. J.
Published: May 2024

Resonant upconversion through a sixth order relativistic nonlinearity resulting in a unique resonance was recently proposed [Malkin and Fisch, Phys. Rev. E 108, 045208 (2023)]. The high order resonance is a unique non-integer multiple of a driving pump frequency resulting in a frequency upshift by a factor of ≈3.73. We demonstrate the presence, unique requirements, and growth of this mode numerically. Through tuning waves to high amplitude, in a mildly underdense plasma, the six-photon process may grow more than other non-resonant but lower order processes. The growth of the high frequency mode remains below the nonlinear growth regime. However, extending current numerical results to more strongly coupled resonances with longer pulse propagation distances suggests a pathway to significant upconversion.
Intermittent-like synchronization and desynchronization phenomena in a Colpitts network model
Authors: Camargo Victor E. , Louodop Patrick , Cerdeira Hilda A. , Ferreira Fernando F.
Published: May 2024

This study investigates the dynamics of a modified Colpitts oscillator, exhibiting complex periodic and chaotic behaviors. Our research explores the dynamics and synchronization of coupled chaotic Colpitts oscillators, crucial for understanding their potential applications and behaviors. The main discovery is the emergence of a phase in which the systems achieve either complete synchronization or desynchronization. This behavior depends on the values of the coupling parameter. The subsequent challenge involves understanding how the coupling parameter influences the emergence of this synchronization phenomenon.
Numerical investigation on cavitation and induced noise reduction mechanisms of a three-dimensional hydrofoil with leading-edge protuberances
Authors: Yang Chen , Zhang Jinsong , Huang Zhenwei
Published: May 2024

In this work, a National Advisory Committee for Aeronautics 66 hydrofoil with leading-edge protuberances is designed. The large eddy simulation combined with the Schnerr–Sauer cavitation model is used to obtain a satisfactory result as compared with the experimental measurement, integrating the permeable Ffowcs Williams–Hawkings equation for cavitation-induced noise analysis. It is found that the special leading-edge geometric structure deflects the incoming flow, creating two counter-rotating streamwise vortices at the peak shoulders. These lead to upwash and downwash effects and alter the pressure distribution on the suction side. The low pressure localized in the trough facilitates the advancement of the leading-edge cavitation while severely limiting the spanwise development of the cloud cavity, shortening the cavitation evolution by about 20% and reducing the maximum cavitation volume by about 35%. Analysis using the vorticity transport equation indicates that different vorticity transport equation splitting terms play dominant roles at different stages of cavitation evolution. Although the cavitation induces disturbances in the primary vortex, the effect is limited. Acoustic simulation shows that the bionic structure can reduce the total sound pressure level by 7.8–8.3 dB. The spherical noise reduction is not as effective as expected due to the similar cavitation volume acceleration processes of the two hydrofoils. However, the pressure fluctuation caused by the collapse of the cloud cavity is reduced by cavitation suppression, which reduces the linear noise. In addition, the protuberances suppress the generation of large-scale vortex systems and transform them into smaller ones, resulting in reduced spanwise correlation and coherence of the shedding vortices. This is a critical factor in noise reduction. Finally, we hypothesize that the unstable noise reduction is related to the streamwise vortices in the trough regions. These vortices increase the momentum exchange within the boundary layer, affecting its stability and weakening the acoustic feedback loop.
Microfluidic paper analytic device (μPAD) technology for food safety applications
Authors: Soman Soja Saghar , Samad Shafeek Abdul , Venugopalan Priyamvada , Kumawat Nityanand , Kumar Sunil
Published: May 2024

Foodborne pathogens, food adulterants, allergens, and toxic chemicals in food can cause major health hazards to humans and animals. Stringent quality control measures at all stages of food processing are required to ensure food safety. There is, therefore, a global need for affordable, reliable, and rapid tests that can be conducted at different process steps and processing sites, spanning the range from the sourcing of food to the end-product acquired by the consumer. Current laboratory-based food quality control tests are well established, but many are not suitable for rapid on-site investigations and are costly. Microfluidic paper analytical devices (μPADs) are a fast-growing field in medical diagnostics that can fill these gaps. In this review, we describe the latest developments in the applications of microfluidic paper analytic device (μPAD) technology in the food safety sector. State-of-the-art μPAD designs and fabrication methods, microfluidic assay principles, and various types of μPAD devices with food-specific applications are discussed. We have identified the prominent research and development trends and future directions for maximizing the value of microfluidic technology in the food sector and have highlighted key areas for improvement. We conclude that the μPAD technology is promising in food safety applications by using novel materials and improved methods to enhance the sensitivity and specificity of the assays, with low cost.
Dissipative particle dynamics for coarse-grained models
Authors: Curk Tine
Published: May 2024

We develop a computational method based on Dissipative Particle Dynamics (DPD) that introduces solvent hydrodynamic interactions to coarse-grained models of solutes, such as ions, molecules, or polymers. DPD-solvent (DPDS) is a fully off-lattice method that allows straightforward incorporation of hydrodynamics at desired solvent viscosity, compressibility, and solute diffusivity with any particle-based solute model. Solutes interact with the solvent only through the DPD thermostat, which ensures that the equilibrium properties of the solute system are not affected by the introduction of the DPD solvent, while the thermostat coupling strength sets the desired solute diffusivity. Thus, DPDS can be used as a replacement for traditional molecular dynamics thermostats such as Nosé–Hoover and Langevin. We demonstrate the applicability of DPDS in the case of polymer dynamics and electroosmotic flow through a nanopore. The method should be broadly useful as a means to introduce hydrodynamic interactions to existing coarse-grained models of solutes and soft materials.
Multiparticle collision dynamics simulations of hydrodynamic interactions in colloidal suspensions: How well does the discrete particle approach do at short range?
Authors: Peng Ying-Shuo , Sinno Talid
Published: May 2024

The multiparticle collision dynamics (MPCD) simulation method is an attractive technique for studying the effects of hydrodynamic interactions in colloidal suspensions because of its flexibility, computational efficiency, and ease of implementation. Here, we analyze an extension of the basic MPCD method in which colloidal particles are discretized with a surface mesh of sensor nodes/particles that interact with solvent particles (MPCD + Discrete Particle or MPCD + DP). We use several situations that have been described analytically to probe the impact of colloidal particle mesh resolution on the ability of the MPCD + DP method to resolve short-ranged hydrodynamic interactions, which are important in crowded suspensions and especially in self-assembling systems that create high volume fraction phases. Specifically, we consider (A) hard-sphere diffusion near a wall, (B) two-particle diffusion, (C) hard-sphere diffusion in crowded suspensions, and (D) the dynamics of aggregation in an attractive colloidal suspension. We show that in each case, the density of sensor nodes plays a significant role in the accuracy of the simulation and that a surprisingly high number of surface nodes are needed to fully capture hydrodynamic interactions.
Stress-induced phase stability and optoelectronic property changes in cesium lead halide perovskites
Authors: Ju Jiayao , Chen Jianlin , Zhao Wei , He Jintao , Peng Zhuoyin , Chen Jian
Published: May 2024

Over the past decade, the certified power conversion efficiency of perovskite solar cells (PSCs) has increased to 26.1%. However, phase instability originating from lattice strains, has limited their commercialization. Strains will inevitably be generated during the PSC fabrication and service process due to the “soft lattice” nature of halide perovskites. In particular, flexible PSCs are subjected to not only mechanical tensile and compressive loads, but also suffer from thermal stresses. In this study, strain-induced changes in the phase stability and the corresponding optoelectronic properties of CsPbI3−xBrx (CsPbI3, CsPbBr3, and CsPbI2Br) systems under tensile and compressive stresses were investigated using first-principles calculations. The results showed that compressive stresses reduce the bandgap value and increase the light absorption coefficient; thus, the optoelectronic performance is improved, whereas the light absorption coefficient decreases regardless of how the bandgap changes under tensile stresses. Moreover, under the same stress, the tensile strain value was twice that of the compressive strain, and the critical value of the transition from the cubic to tetragonal phase was lower, indicating that phase stability was worse under tensile stresses. Therefore, during the fabrication of PSCs, the tensile stress state should be adjusted to the compressive stress state, which is favorable for enhancing PSCs photovoltaic performance and phase stability. The results not only provide direct evidence of tensile and compressive strains influencing the phase stability and optoelectronic property changes in halide perovskites, but also highlight lattice-strain tailoring for the composition design, process optimization, and interface engineering of efficient and stable PSCs.
Exact wave solver for nonparaxial laser beam propagation
Authors: Belyaev Mikhail A. , Banks Jeffrey , Chapman Thomas
Published: May 2024

Simulations of inertial confinement fusion (ICF) experiments require high-fidelity models for laser beam propagation in a nonuniform plasma with varying index of refraction. We describe a new numerical wave solver that is applicable to centimeter-scale length plasmas encountered in indirect drive ICF applications. The one-way Helmholtz equation (OHE) generalizes the time-harmonic paraxial wave equation to large angles. Here, we present a methodology to numerically evaluate the exact solution to the OHE. This solution is computed by analytically advancing eigenfunctions of the one-way Helmholtz operator along a propagation direction and is applicable to any given index of a refraction profile. We compare our exact method with a commonly used approximate split-step technique for solving the OHE. As a test problem, we consider nonparaxial propagation of Gaussian and speckled beams in a plasma density channel with internal reflection. We find that the split-step approach incurs significant errors compared to the exact solution computed using the novel algorithm.
Magnetic leakage behavior assessment in pipeline stress-concentrated areas using improved force–magnetic coupling model
Authors: Huang Ping , Li Yue , Zheng Fuyin , Yang Lijian , Su Yuming , Ma Long , Wang Chuang , Dou Jie , Li Yuanyuan , Qiu Zhichuan , Zhang Xiaodan , Bai Shi
Published: May 2024

Magnetic flux leakage (MFL) technology is remarkable for its capability to detect pipeline geometric deformation and general corrosion defects. However, it cannot characterize the MFL behavior in stress-concentrated areas, thereby greatly challenging the subsequent pipeline maintenance. This study suggests that the MFL characteristics of pipeline in stress-concentrated areas are caused by the combined effect of the face magnetic charge on the deformed end-face and the body magnetic charge of the dislocation stack. In addition, an improved force–magnetic coupling model of the pipeline in stress-concentrated areas is established based on the magnetic dipole model and Jiles–Atherton (J–A) theory. In the verification experiment, the Q235 steel plate is magnetized along the extension direction (axis of the pipeline) through the solenoid coil to obtain the distribution law of the MFL signal in the stress-concentrated area under different excitation intensities. The results show that with the increase in excitation intensity, the deformation of the MFL field signal caused by the end-face of the stress-concentrated area gradually increases to a stable state. Moreover, the internal stress of the MFL field signal generated by the pipe dislocation rapidly increases to a peak value and then decays exponentially to a certain base value. The overall change trend is in good agreement with the calculation results of the established force–magnetic coupling model. Meanwhile, the differentiation research between deformation and internal stress MFL field signals under different magnetic field intensities can provide a reliable theoretical basis for the subsequent accurate identification and quantification of pipeline stress-concentrated areas.
Multiple topological phase transitions unveiling gapless topological superconductivity in magnet/unconventional superconductor hybrid platform
Authors: Subhadarshini Minakshi , Pal Amartya , Chatterjee Pritam , Saha Arijit
Published: May 2024

We propose a theoretical framework for generating gapless topological superconductivity (GTSC) hosting Majorana flat edge modes (MFEMs) in the presence of a two-dimensional (2D) array of magnetic adatoms with noncollinear spin texture deposited on top of an unconventional superconductor. Our observations reveal two distinct topological phase transitions within the emergent Shiba band depending on the exchange coupling strength (J) between magnetic adatom spins and superconducting electrons: the first one designates transition from gapless non-topological to gapless topological phase at lower J, while the second one denotes transition from gapless topological to a trivial gapped superconducting phase at higher J. The gapless topological superconducting phase survives at intermediate values of J, hosting MFEMs. Furthermore, we investigate the nature of the bulk effective pairings, which indicate that GTSC appears due to the interplay between pseudo “s-wave” and pseudo “px+py” types of pairing. Consequently, our study opens a promising avenue for the experimental realization of GTSC in 2D Shiba lattice based on d-wave superconductors as a high-temperature platform.
Perspective: Atomistic simulations of water and aqueous systems with machine learning potentials
Authors: Omranpour Amir , Montero De Hijes Pablo , Behler Jörg , Dellago Christoph
Published: May 2024

As the most important solvent, water has been at the center of interest since the advent of computer simulations. While early molecular dynamics and Monte Carlo simulations had to make use of simple model potentials to describe the atomic interactions, accurate ab initio molecular dynamics simulations relying on the first-principles calculation of the energies and forces have opened the way to predictive simulations of aqueous systems. Still, these simulations are very demanding, which prevents the study of complex systems and their properties. Modern machine learning potentials (MLPs) have now reached a mature state, allowing us to overcome these limitations by combining the high accuracy of electronic structure calculations with the efficiency of empirical force fields. In this Perspective, we give a concise overview about the progress made in the simulation of water and aqueous systems employing MLPs, starting from early work on free molecules and clusters via bulk liquid water to electrolyte solutions and solid–liquid interfaces.
Cascading symmetry constraint during machine learning-enabled structural search for sulfur-induced Cu(111)-(43×43) surface reconstruction
Authors: Brix Florian , Verner Christiansen Mads-Peter , Hammer Bjørk
Published: May 2024

In this work, we investigate how exploiting symmetry when creating and modifying structural models may speed up global atomistic structure optimization. We propose a search strategy in which models start from high symmetry configurations and then gradually evolve into lower symmetry models. The algorithm is named cascading symmetry search and is shown to be highly efficient for a number of known surface reconstructions. We use our method for the sulfur-induced Cu (111) (43×43) surface reconstruction for which we identify a new highly stable structure that conforms with the experimental evidence.
Cyclicity of slow–fast cycles with two canard mechanisms
Authors: Yao Jinhui , Huang Jicai , Huzak Renato
Published: May 2024

In this paper, we study the cyclicity of some degenerate slow–fast cycles with two canard mechanisms in planar slow–fast systems. One canard mechanism originates from a slow–fast Hopf point and the other from a point of self-intersection where the so-called entry–exit relation can be used. By studying the difference map, we show that the cyclicity of such slow–fast cycles is at most two (the associated slow divergence integral is nonzero or vanishes). As an example, we apply this result to the modified Holling–Tanner model.
Investigation on laser-induced bubble collapse among triple particles based on high-frame-rate photography and the Kelvin impulse model
Authors: Zhang Yuning , Ding Zhiling , Hu Shuzheng , Hu Jingrong , Wang Xiaoyu , Zheng Xianghao , Zhang Yuning
Published: May 2024

In fluid machinery, the concurrent presence of cavitation bubbles and particle clusters leads to considerably damage to material surfaces. This study investigates the dynamics of a bubble situated among triple particles based on the Kelvin impulse model and high-frame-rate photography, focusing on the impact of the dimensionless distance of particles and the bubble size. Specifically, the jet, bubble motion, and bubble interface evolution characteristics are quantitatively evaluated. The following conclusions are obtained: (1) The collapse shapes of the bubble can be divided into three typical cases: equilateral triangle shape, isosceles triangle shape, and arcuate shape. (2) Among the triple particles, four zero-Kelvin-impulse locations are present, around which the jet direction is extremely sensitive to the bubble initial position. As the bubble initial position moves along the central line, the bubble motion direction dramatically changes during its collapse. (3) The relative position of bubble and particles is the key parameter that affects the bubble dynamics. As the bubble–particle distance decreases, the non-uniformity of bubble collapse morphology and the bubble motion distance will become more significant.
A state-of-the-art review of normal and extreme flow interaction with spur dikes and its failure mechanism
Authors: Nandhini D. , Murali K. , Harish S. , Schüttrumpf Holger , Heins Kira , Gries Thomas
Published: May 2024

River protection structures, especially spur dikes, play a vital role in the hydrodynamic and morphological changes in a river system. Since the earliest days, numerous studies have been carried out to understand the flow characteristics around spur dikes by varying the spacing between them, the length, the shape, the permeability, and the submergence. Despite several studies, knowledge of flow characteristics around spur dikes is still poorly understood, resulting in damages and failures worldwide. Furthermore, such failures get aggravated under extreme conditions like floods, land-slide-induced surges and tidal bores. Therefore, this state-of-the-art review paper provides a comprehensive account of relevant studies on the flow interaction and its characteristics in the vicinity of spur dikes during normal and extreme scenarios. Possible failure mechanisms with a detailed examination of scour in the proximity of spur dikes are deliberated. Suitable design features and international standards of various types of spur dikes are appraised through this comprehensive review. Furthermore, we also identified a number of research gaps that need immediate attention. This review paper, as a whole, provides concrete knowledge of the flow interaction with spur dikes and design components of spur dikes, thereby helping researchers to understand the advancement in the research area and providing hydraulic engineers with guidance for designing the spur field at a specific site based on the requirements.
High stability of dark current enables stretchable near-infrared self-powered organic photodetectors
Authors: Wang Chen , Xiao Mengfei , Qiao Jiawei , Cui Fengzhe , Jiang Dongcheng , Meng Kaiwen , Lian Gang , Yin Hang , Meng Zhigang , Hao Xiaotao , Du Xiaoyan
Published: May 2024

Ultra-flexible and stretchable organic photodetectors (s-OPDs) sensitive in the near-infrared (NIR) region hold great potential for wearable health monitoring with excellent physiological signal and skin conformability. However, the development of OPDs that combines NIR sensitivity, low power consumption, low cost, simple fabrication structure, and good mechanical properties is still challenging and has not been well explored. In this work, we report a self-powered s-OPD with a simple fabrication structure used for organic solar cells and a detectivity of more than 1 × 1012 Jones (corrected by noise current) in the NIR region at 10% tensile strain and short response time (2.46 μs), representing state-of-the-art performances. Reducing energetic disorders other than discrete traps in photoactive layers is more crucial to further reduce the dark current at zero bias. The dark current of the OPDs exhibits higher mechanical stability than photocurrent due to the slower degradation of the parallel resistance than the series resistance under tensile strain. The higher stability of dark current enables the s-OPDs as a stretchable organic photoplethysmogram heart rate sensor, showing excellent detectivity under 30% strain or 800 stretching–release cycles at 10% strain, indicating the great potential for application in wearable optoelectronics.
Ultrahigh energy efficiency from a supersonic underwater ultrasound source
Authors: Novac Bucur M. , Frost Thanasi , Senior Peter
Published: May 2024

The present work is dedicated to an experimental and theoretical study of an innovative underwater ultrasound source. The source works using a technique in which a pulsed power generator using the impedance mismatch of a long high-voltage coaxial cable generates a train of voltage impulses with a very high pulse repetition frequency of the order of a few MHz. Applying this train of voltage impulses to a pair of underwater electrodes generates a streamer-initiated breakdown of water and, subsequently, a plasma column connecting the electrodes over a very large inter-electrode gap of 55 mm. The interaction of the long plasma column thus formed with the surrounding water produces a rapidly expanding vapor bubble, an “instrument” producing a strong pressure wave with an overall energy efficiency of 24%, an order of magnitude higher than most underwater pressure sources reported in the literature.
Unveiling interatomic distances influencing the reaction coordinates in alanine dipeptide isomerization: An explainable deep learning approach
Authors: Okada Kazushi , Kikutsuji Takuma , Okazaki Kei-ichi , Mori Toshifumi , Kim Kang , Matubayasi Nobuyuki
Published: May 2024

The present work shows that the free energy landscape associated with alanine dipeptide isomerization can be effectively represented by specific interatomic distances without explicit reference to dihedral angles. Conventionally, two stable states of alanine dipeptide in vacuum, i.e., C7eq (β-sheet structure) and C7ax (left handed α-helix structure), have been primarily characterized using the main chain dihedral angles, φ (C–N–Cα–C) and ψ (N–Cα–C–N). However, our recent deep learning combined with the “Explainable AI” (XAI) framework has shown that the transition state can be adequately captured by a free energy landscape using φ and θ (O–C–N–Cα) [Kikutsuji et al., J. Chem. Phys. 156, 154108 (2022)]. In the perspective of extending these insights to other collective variables, a more detailed characterization of the transition state is required. In this work, we employ interatomic distances and bond angles as input variables for deep learning rather than the conventional and more elaborate dihedral angles. Our approach utilizes deep learning to investigate whether changes in the main chain dihedral angle can be expressed in terms of interatomic distances and bond angles. Furthermore, by incorporating XAI into our predictive analysis, we quantified the importance of each input variable and succeeded in clarifying the specific interatomic distance that affects the transition state. The results indicate that constructing a free energy landscape based on the identified interatomic distance can clearly distinguish between the two stable states and provide a comprehensive explanation for the energy barrier crossing.