Positive Energy Research Articles

Quantum Multiple Eigenvalue Gaussian filtered Search: an efficient and versatile quantum phase estimation method

Quantum phase estimation is one of the most powerful quantum primitives. This work proposes a new approach for the problem of multiple eigenvalue estimation: Quantum Multiple Eigenvalue Gaussian filtered Search (QMEGS). QMEGS leverages the Hadamard test circuit structure and only requires simple classical postprocessing. QMEGS is the first algorithm to simultaneously satisfy the following two properties: (1) It can achieve the Heisenberg-limited scaling without relying on any spectral gap assumption. (2) With a positive energy gap and additional assumptions on the initial state, QMEGS can estimate all dominant eigenvalues to ϵ accuracy utilizing a significantly reduced circuit depth compared to the standard quantum phase estimation algorithm. In the most favorable scenario, the maximal runtime can be reduced to as low as log⁡(1/ϵ). This implies that QMEGS serves as an efficient and versatile approach, achieving the best-known results for both gapped and gapless systems. Numerical results validate the efficiency of our proposed algorithm in various regimes.

Unified Implementation of Relativistic Wave Function Methods: 4C-iCIPT2 as a Showcase.

In parallel to the unified construction of relativistic Hamiltonians based solely on physical arguments (J. Chem. Phys. 2024, 160, 084111), a unified implementation of relativistic wave function methods is achieved here via programming techniques (e.g., template metaprogramming and polymorphism in C++). That is, once the code for constructing the Hamiltonian matrix is made ready, all the rest can be generated automatically from existing templates used for the nonrelativistic counterparts. This is facilitated by decomposing a second-quantized relativistic Hamiltonian into diagrams that are topologically the same as those required for computing the basic coupling coefficients between spin-free configuration state functions (CSF). Moreover, both time reversal and binary double point group symmetries can readily be incorporated into molecular integrals and Hamiltonian matrix elements. The latter can first be evaluated in the space of (randomly selected) spin-dependent determinants and then transformed to that of spin-dependent CSFs, thanks to simple relations in between. As a showcase, we consider here the no-pair four-component relativistic iterative configuration interaction with selection and perturbation correction (4C-iCIPT2), which is a natural extension of the spin-free iCIPT2 (J. Chem. Theory Comput. 2021, 17, 949), and can provide near-exact numerical results within the manifold of positive energy states (PES), as demonstrated by numerical examples.

Ab initio calculations of high-entropy clusters for oxygen reduction and evolution as well as CO2 reduction reactions

This study introduces a design concept for a high-entropy cluster (HEC) comprising of Fe, Co, Ni, Cu, and Rh metals supported on nitrogen-doped graphene. Five different configurations including CoNiCuRh@FeN4, FeNiCuRh@CoN4, FeCoCuRh@NiN4, FeCoNiRh@CuN4, as well as; FeCoNiCu@RhN4 with the mixing entropy change of ΔSmix = 0.14 meV/K were considered. The positive dissociation potential and negative formation energy suggested the electrochemical and thermodynamic stabilities of these materials. According to density functional theory (DFT + U) calculations, the CoNiCuRh@FeN4 catalyst led to the overpotentials of 0.37 VRHE, 0.37 VRHE, and 0.24 VRHE for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and CO2 reduction reaction (CO2RR) towards CO production, respectively. It was determined that, FeN4 acted as an active site, while CoNiCuRh-HEC behaved as the modulator. Also, FeNiCuRh@CoN4 catalyst led to the CO2RR overpotential of 0.35 VRHE towards CH3OH formation where CoN4 acted as the active site, and FeNiCuRh-HEC species acted as the modulator surpassing the activity of single-atom catalysts (SAC). Moreover, the density of states (DOS) and charge transfer analyses suggested that, the presence of a high-entropy cluster may enhance the charge transfer and stabilize the reaction intermediates, toward selective methanol formation. Therefore, a DFT-based strategy to design a high-entropy cluster was developed through electrochemistry and beyond.

Shower separation in five dimensions for highly granular calorimeters using machine learning

To achieve state-of-the-art jet energy resolution for Particle Flow, sophisticated energy clustering algorithms must be developed that can fully exploit available information to separate energy deposits from charged and neutral particles. Three published neural network-based shower separation models were applied to simulation and experimental data to measure the performance of the highly granular CALICE Analogue Hadronic Calorimeter (AHCAL) technological prototype in distinguishing the energy deposited by a single charged and single neutral hadron for Particle Flow. The performance of models trained using only standard spatial, energy and charged track position information from an event was compared to models trained using timing information available from AHCAL, which is expected to improve sensitivity to shower development and, therefore, aid in clustering. Both simulation and experimental data were used to train and test the models and their performances were compared. The best-performing neural network achieved significantly superior event reconstruction when timing information was utilised in training for the case where the charged hadron had more energy than the neutral one, motivating temporally sensitive calorimeters. All models under test were observed to tend to allocate energy deposited by the more energetic of the two showers to the less energetic one. Similar shower reconstruction performance was observed for a model trained on simulation and applied to data and a model trained and applied to data.

Adaptive extraction of characteristic ridges from time-frequency representation for wheelset bearings failure diagnosis under time-varying speed

Instantaneous frequencies-based order tracking is an excellent approach for bearing faults diagnosing at time-varying speeds. The key is to extract ridges from time-frequency representation. However, their precision seriously relies on the cost function and bandwidth selection. To address these issues, an adaptive extraction of characteristic ridges (AECR) method that integrates a variable-bandwidth ridge edge detection (VBRED) and an adaptive exponential cost function (AECF) is presented. VBRED provides a variable-bandwidth search area-based clustering algorithm to isolate neighboring components. AECF can be automatically adjusted based on the signal signature to ensure the smoothness of the ridge. The average frequency ratios of the extracted ridges are used to identify the health conditions of the bearings. Finally, the effectiveness of the proposed AECR is validated by simulations and experiments. The results prove that it performs excellently when the energy and relative position of the ridges are close, compared to other state-of-the-art methods.

The Role of Public-Private Investment Partnerships in Overcoming Challenges and Seizing Opportunities in Poland’s Renewable Energy Sector

Poland’s renewable energy sector is undergoing a significant transformation as the country strives to reduce its reliance on coal and align with European Union (EU) climate targets. However, this transition faces several challenges, including regulatory instability, financial constraints, and outdated infrastructure. PPPs have emerged as a vital mechanism for overcoming these barriers, offering a collaborative approach that blends public financial support with private sector expertise and innovation. This paper explores the critical role of PPPs in addressing Poland’s renewable energy challenges, such as financing large-scale projects, stabilizing regulatory frameworks, and modernizing the energy grid. It also examines the opportunities for growth in offshore wind, solar energy, and green hydrogen production, highlighting how PPPs can help Poland capitalize on these emerging sectors. Through effective collaboration between the public and private sectors, Poland is poised to accelerate its clean energy transition and position itself as a leader in renewable energy development within Central and Eastern Europe.

Tip-induced local Fermi level alignment: A Stark shift in vacuum level in scanning tunneling microscope configurations

Electric fields in the junction of a scanning tunneling microscope (STM) are generally considered to have a negligible impact on the vacuum level (VL) of materials. We employed field emission resonance (FER) in the STM, combined with the triangular potential model, to measure the VL of the Ag(100) surface under varying electric currents. Unexpectedly, our results reveal that the VL exhibits a linear positive energy shift with increasing electric field strength. We suggest that this Stark shift in the VL arises from local Fermi level alignment induced by the STM tip. Additionally, we examined the VL of Ag islands grown on Cu(111) and Au(111) surfaces under different currents. Despite the Ag island having a lower work function than the Cu(111) and Au(111) surfaces, the energy shift in the VL with respect to the electric field on the Ag island is almost identical to that on the substrate under the same tip structure. This suggests that the Stark shift of the VL is insensitive to the work function. These findings are crucial for utilizing FER to measure local work function variations on surfaces, as the measured value is not influenced by the STM tip structure or the tunneling current, both of which can alter the electric field.

Going beyond Climate Neutral Cities: Evidence from a Positive Energy District in the Stuttgart Region

Abstract To successfully develops Positive Energy Districts (PEDs), it is essential to increase citizen awareness and encourage their engagement. Without acceptance and active participation from the citizens, they might not benefit from the technologies and inclusive business models that PEDs offer to foster energy efficiency, productivity, and flexibility. This contribution provides new evidence about the importance of prioritising citizens’ needs when developing PEDs, describing key findings from a case study recently conducted by the authors, in Nürtingen, in the Stuttgart Metropolitan Region, Germany. The research used urban building energy modeling tools, analyzed on-going projects of the city administration, and directly engaged with citizens by different research methods such as d go-along interviewing, SWOT analysis, and the promotion of best practices. The analysis and conclusions on working on the municipality project “Bahnstadt” were checked against the understanding of a “human-centred” PED. Five action areas were considered: energy efficiency, production and flexibility, carbon footprint, water management, and capital expenditures. This action research, part of the EU-funded project TELOS (2020-2024), aimed to provide recommendations to improve the quality of life of the community and enhancing citizen participation in planning and implementation processes, and towards the ambitious European climate neutrality goals.

Transformation Pathways: Drumul Taberei Neighbourhood - a Positive Energy District?

Abstract Positive Energy Districts (PED) have surged in prominence amidst Europe’s ambitious climate targets and the fluctuating energy landscape, influenced notably by geopolitical uncertainties such as the Ukraine conflict. Aligned with European and national priorities, which emphasises the renovation of its housing stock as part of the Renovation Wave initiative, PED emerges as a viable solution for urban areas. However, the challenge remains in how PED can address energy poverty, promote renewable energy, and align with renovation priorities of the outdated infrastructures (including buildings). The KINETIC project addresses PED transformation challenges at the neighbourhood level by deploying an intensive co-creation process for identifying key transformation directions. The Romanian DEMO area (along with DK and IT study cases) is the Drumul Taberei neighbourhood in Bucharest Sector 6, a dense neighbourhood composed of multifamily buildings realised in the 60s and 70s during the communist regime. The area needs comprehensive regeneration and renewal initiatives. If proven feasible through mathematical modelled data paired with strategic integrated planning, the outcomes of KINETIC for the Drumul Taberei neighbourhood will be able to revolutionise the future rehabilitation project of collective housing districts in Romania, and beyond. The paper will outline PED transformation pathways stemming from initial co-design workshops involving local stakeholders. It will also explore collaboration and investment prospects between municipality-housing associations and NGOs. Given the privately owned housing estate and state-funded rehabilitation, the project will assess innovative models to meet PED’s ambitious goals.

Modifying x-ray streak cameras for operation on igniting fusion experiments.

The National Ignition Facility produced the first nuclear fusion experiment demonstrating net positive energy gain on December 5, 2022. The x-ray streak camera that measures the bang time and burn-width from this landmark experiment had an electronic failure and did not record data. The CCD sensor was replaced with a radiation hardened CMOS sensor that has since demonstrated successful operation on repeat ignition shots. Concurrently, an instrument artifact was identified that occurs when the signal consists primarily of energetic x rays >15keV (common on burning plasma experiments). This artifact, which appears as a background pedestal, arises from the x-ray back-fluorescence generated by the solid metal accelerating mesh behind the photocathode in the streak tube. We have mitigated this background signal by limiting the sensitive area of the photocathode. Herein, the details of the modifications and the results are presented.

The effect of water molecule configurations on the type of core ionized site: O1s core ionization of ascorbic acid in water

The analysis of photoelectron spectra can be a complex and uncertain process, primarily due to the overlap of the peaks in the spectra. This overlap can lead to inaccuracies in the reported ionization energies derived from the binding energy positions of the visible peaks. This constraint explains the absence or inaccurate reporting of ionization energy values for certain biomolecules in the articles. Reliable theoretical methods are required for the interpretation of experimental results. In the present work, the overlap of photoelectron spectrum peaks is of particular importance, given the similarity between the molecular oxygen signatures of ascorbic acid (AA) and water. We used the SAC-CI method, based on the ONIOM model, to examine how the first coordination shell of water molecules affected the O1s core ionization energy of AA at 298 and 350 K temperatures. Our investigation shows that water’s photoelectron spectrum covers the O1s spectrum of AA.

Band Structure Engineering in 2D Metal-Organic Frameworks.

The design of 2D metal-organic frameworks (2D MOFs) takes advantage of the combination of the diverse electronic properties of simple organic ligands with different transition metal (TM) centers. The strong directional nature of the coordinative bonds is the basis for the structural stability and the periodic arrangement of the TM cores in these architectures. Here, direct and clear evidence that 2D MOFs exhibit intriguing energy-dispersive electronic bands with a hybrid character and distinct magnetic properties in the metal cores, resulting from the interactions between the TM electronic levels and the organic ligand π-molecular orbitals, is reported. Importantly, a method to effectively tune both the electronic structure of 2D MOFs and the magnetic properties of the metal cores by exploiting the electronic structure of distinct TMs is presented. Consequently, the ionization potential characteristic of selected TMs, particularly the relative energy position and symmetry of the 3d states, can be used to strategically engineer bands within specific metal-organic frameworks. These findings not only provide a rationale for band structure engineering in 2D MOFs but also offer promising opportunities for advanced material design.

A Framework to Enhance Flexible Blended Architectural Design Education

In the last few years, there have been lots of challenges facing the world from pandemics and wars that have raised a series of challenges facing architectural education, which create a challenge for both teachers and students and to which extent they can adapt to the post-digital adaptation period, as well as the future of architectural education in general. Architecture and design environments mainly require face-to-face learning and teaching techniques that depend on the interaction between the student and the teacher, where application and practical education take place. Furthermore, studio-designed spaces provide solidarity, positive energy, and motivation for students. Therefore, activating the distance learning process that affect the architectural education strategy and directed institutions and teachers to the necessity of flexibility and adaptation as a part of the structure of architectural education curricula. this study is a humble try to evaluate the role of blended learning experiences incorporating architectural design programmes that were first applied after the last pandemic. It focuses on the importance of flexible architectural education through the overlap between the traditional studio and the virtual studio to achieve a positive experience for students and staff members. This is done by observing a design studio procedure during a blended learning period and with the help of a questionnaire for a diverse number of students and faculty members on the subject of architectural design at one of the Egyptian universities that host the architecture department. It is conducted for the purpose of flexible handling through the integration of distance learning with architectural design education in relation to the era of pandemics, the digital age, and the like in the future. The research contributes to developing a future framework that enhances the flexibility of architectural design education, supports self-education, and turns the architectural design studio into an opportunity for reproduction and renewal.

Improving Performance of Cluster Heads Selection in DEC Protocol Using K-Means Algorithm for WSN.

Wireless sensor networks (WSN) have found more and more applications in remote control and monitoring systems. Energy management in the network is crucial because all nodes in the WSN are energy constrained. Therefore, the design and implementation of WSN protocols that reduce energy depletion in the network is still an open scientific problem. In this paper, we propose a new clustering protocol that combines DEC (deterministic energy-efficient clustering) protocol with K-means clustering, called DEC-KM (deterministic energy-efficient clustering protocol with K-means). DEC is a very energy-efficient clustering protocol that outperforms its predecessors, such as LEACH and SEP. K-means ensures more effective clustering and shorter data transmission distances within the network. The shorter distances improve the network's lifetime and stability and reduce power consumption. Additional heuristic rules in DEC-KM ensure improved cluster head selection, taking into account node energy level and position and minimising the risk of premature cluster head exhaustion. The simulation results for the DEC-KM protocol using MATLAB show that cluster heads have shorter distances to nodes in cluster areas than for the original DEC protocol. The proposed protocol ensures reduced energy consumption, outperforms the standard DEC, and extends the stability period and lifetime of the network.

Insights into gypsum and silica scaling behaviors of dense Janus membranes in membrane distillation: The effect of varied surface properties

Dense Janus membranes (JMs) have emerged as potential candidates to address the tough scaling issue in hypersaline wastewater treatments for membrane distillation (MD). However, behaviors and mechanisms of various scalants on dense JMs have not been systematically investigated. Herein, we designed three dense JMs to simultaneously compare their anti-scaling properties against gypsum and silica in MD and focus on the critical role of varied surface property in scaling control. Results showed that dense JMs with highly positive gypsum-membrane interfacial energy and with strong electrical repulsion against silica species were more effective in resisting gypsum and silica, respectively. Scaled membrane characterization, quartz crystal microbalance monitoring, interfacial energy analysis and AFM force measurement revealed the distinct anti-scaling mechanisms. Highly hydrophilic surfaces without specific interactions with scaling ions provided robust thermodynamic barriers and less kinetically affected local supersaturations, preventing gypsum nucleation and growth. In contrast, positively charged surfaces favorably attracted negatively charged silica species with high reactivity, promoting subsequent polymerization with silicic acid that kinetically dominated silica scaling. Moreover, coexisting oversaturated gypsum and silica influenced the scaling behavior of each other, and surface properties of the preferentially formed scaled layer might also matter in scaling process. This study shall provide useful insights into the anti-scaling mechanisms of dense JMs in MD and highlight the potential of dense surface design as an effective scaling control strategy to pave the way for potential MD applications.

Numerical investigation of the fractional-soliton mode-locked fiber laser.

We propose and numerically investigate a fractional-soliton mode-locked fiber laser by utilizing an intracavity spectral pulse shaper (SPS). The fiber laser can generate stable fractional-soliton pulses for three different Lévy index α (1 < α < 2), whose profiles are all close to the sech shape. We find that the positions of Kelly sidebands, pulse energy, and peak power of the emitted fractional pulses conform to three theoretical expressions, respectively. The numerical results are in good agreement with the theoretical analyses. In addition, the intracavity dynamics of the fractional pulses have been discussed. Our findings not only deepen the fundamental understanding of temporal fractional soliton but also provide a novel, to the best of our knowledge, approach to generating stable ultrashort fractional pulses.

Transition Approaches towards Positive Energy Districts: A Systematic Review

The positive energy district (PED) concept is attracting growing research interest; however, the need for practical approaches to facilitate their implementation remains crucial. This study, framed in the COST Action ‘Positive Energy Districts European Network’, offers a comprehensive review of the roadmaps, pathways, and guidelines—namely ‘PED-Transition Approaches’—currently available to support the implementation of district-scale innovative models, thereby advancing energy transitions and enhancing livability at the city level. The review involved a systematic search and web scraping of documents, including scientific and grey literature, as well as EU-funded projects’ reports. The studies were identified according to multiple filters and eligibility criteria, then categorised in a structured repository using a multidimensional matrix, and finally examined following three-levels of detail (i.e., bibliometric study) overview and in-depth analysis. The findings reflect the main characteristics, gaps, and challenges in PED implementation by underlying the growing need for effective step-by-step, user-centric, and context-based transition approaches. In conclusion, the research, building on an extensive literature of multiple inspirational methodologies and their associated use cases, is a strong basis to develop sequential pathways to facilitate PED implementation among key stakeholders in a short–medium-term perspective towards a climate-neutral city vision.

Optimization of microwave-assisted drying of scallions (Allium fistulosum L.): A comprehensive study on drying kinetics, energy consumption, CO2 emissions, and thermodynamic properties

This study explores the effectiveness of microwave-assisted drying for scallions (Allium fistulosum L.), focusing on drying kinetics, energy consumption, CO2 emissions, and thermodynamic properties. Scallion samples were subjected to different microwave power levels (136 W and 264 W) and varying sample masses (5 g, 10 g, and 20 g) to assess the drying process. The Page model was identified as the most suitable for describing the drying kinetics, providing a precise fit to the experimental data. The study revealed that higher microwave power levels significantly enhanced the drying efficiency by increasing moisture diffusivity, thereby reducing drying time. The thermodynamic analysis indicated that the drying process is endothermic, requiring external energy for moisture removal, with positive enthalpy and Gibbs free energy values confirming the non-spontaneous nature of the process. Entropy analysis suggested a decrease in molecular disorder during drying. In terms of energy consumption and CO2 emissions, the results highlighted that microwave-assisted drying offers a lower environmental impact, with specific energy consumption (SEC) values demonstrating efficient energy use during the drying process. This study supports the viability of microwave-assisted drying as a sustainable and efficient method for processing scallions. The findings provide valuable insights for optimizing drying processes in the food industry, emphasizing the potential for microwave drying technologies to improve energy efficiency and reduce environmental impact.

All-multiplicity amplitudes in impulsive PP-waves from the worldline formalism

We use the worldline formalism to derive Bern-Kosower type Master Formulae for the tree-level scattering of a charged particle and an arbitrary number of photons on impulsive PP-waves, where the coupling of the PP-wave to matter is treated fully non-perturbatively. We show that, in a certain kinematic regime characterised by a semi-classical positive energy condition, both off-shell currents and scattering amplitudes exhibit two novel factorisation structures. First, they may be written as currents in vacuum but with a single additional photon, averaged over the momentum of that photon. This converts the all-orders interaction with the PP-wave into a single effective interaction. Second, the currents and amplitudes may be written as a weighted average of the corresponding quantities in an impulsive plane wave background, with the average taken over all possible field strengths of the plane wave. This generalises a known single-photon result to arbitrary multiplicity.

Synthesis and NEXAFS and XPS Characterization of Pyrochlore-Type Bi1.865Co1/2Fe1/2Ta2O9+Δ

A cubic pyrochlore with the composition Bi1.865Co1/2Fe1/2Ta2O9+Δ (space group Fd-3m, a = 10.5013(8) Å) was synthesized from oxide precursors using solid-phase reactions. These ceramics are characterized by a porous microstructure formed by randomly oriented grains of an elongated shape with a longitudinal size of 0.5–1 µm. The electronic state of cobalt and iron ions in oxide ceramics was studied by NEXAFS and XPS spectroscopy. The parameters of the XPS spectra of Bi4f, Bi5d, Ta4f, Co2p, and Fe2p ionization thresholds for a complex pyrochlore were compared with the parameters of the corresponding oxides of the transition elements. The energy position of the XPS-Ta4f and -Ta5p spectra is shifted towards lower energies compared to the binding energy in tantalum(V) oxide by 0.75 eV. According to XPS spectroscopy, bismuth and tantalum cations have the corresponding effective charge of +3 and +(5-δ). The NEXAFS-Fe2p spectrum of ceramics coincides with the spectrum of Fe2O3 in its main spectrum characteristics and indicates the content of iron ions in the oxide ceramics in the form of octahedral Fe(III) ions, and according to the character of the Co2p spectrum, cobalt ions are predominantly in the Co(II) state.