bluuebunny/crossref_metadata_2025_split huggingface dataset:
The nonlinear patterns of the cosmic anisotropy: the spatially flat perfect fluid universes
Authors: Gomes Leandro G 
Published: November 2021

Abstract
In this manuscript, we investigate the patterns of the cosmological anisotropy in the spatially flat Bianchi models filled with a perfect fluid. We analyse the factor

1
+
Δ
R

, the ratio of the Hubble parameter in the anisotropic model over its isotropic counterpart. In general,

Δ
R

starts to deviate significantly from zero at a specific redshift

z

A

, which depends on the type of the fluid and the value of the anisotropy magnitude. We also show that the deceleration and the jerk along the principal directions of the expansion tensor are constrained by simple algebraic equations that do not depend on the type of matter present. These characteristic patterns form a valuable framework to probe the cosmological anisotropy in the late-time universe.
Bayesian approach for the optimal control of high-order harmonics for the generation of ultrashort attosecond laser pulses
Authors: Wang Wei-Teng , Sheu Yae-Lin , Chu Shih-I 
Published: November 2021

Abstract
We present an efficient and powerful method to optimize the production of high-order harmonic generation (HHG) and the synthesis of an isolated attosecond pulse. The system under investigation is the helium atoms that are exposed to the combination of chirped two-color mid-IR laser field and its 1s–2p transition frequency. An ab initio study is conducted by solving the three dimensional time-dependent Schrödinger equation accurately and efficiently by means of the time-dependent generalized pseudospectral method. We applied Bayesian optimization to obtain an optimal laser waveform to generated a HHG spectrum with enhanced harmonics and extended cutoff frequency. Harmonic phases are analysed by the wavelet transform. We demonstrated that an isolated 10 attosecond pulse can be synthesized using a sequence of consecutive and phase-locked harmonics in the plateau region.
CdSe and CsPbBr3 quantum dot Co-doped monolithic glasses as tunable wavelength convertors
Authors: Kıbrıslı Orhan , Erol Erdinç , Ersundu Ali Erçin , Çelikbilek Ersundu Miray 
Published: November 2021

Abstract
CdSe and CsPbBr3 quantum dots (QDs) are well studied photoluminescent materials due to their extraordinary emission properties. However, their vulnerability against environmental conditions limits their integration into further applications. At this point, glass encapsulation offers promising durability features due to its robust and dense structure. In this study, CdSe and CsPbBr3 QDs are successfully synthesized in the same glass host through the melt-quenching technique followed by a single heat-treatment process. Excitation wavelength dependent photoluminescence properties are investigated and emission color tunability of monolithic glasses from yellow-green to red is demonstrated. Favorable quantum yield values are obtained as 21.78% and 16.63% under 345 and 365 nm excitation wavelengths, respectively. The prepared glasses demonstrate high potential to be used as tunable wavelength convertors for state-of-the-art photonic and opto-electronic applications.
Effects of expandable graphite on the flame-retardant and mechanical performances of rigid polyurethane foams
Authors: Wang Xin-chao , Sun Ya-peng , Sheng Jie , Geng Tie , Turng Lih-sheng , Guo Yong-gang , Liu Xian-hu , Liu Chun-tai 
Published: November 2021

Abstract
Polyurethane foams (PUFs) are found everywhere in our daily life, but they suffer from poor fire resistance. In this study, expansible graphite (EG) as flame retardant was incorporated into PUFs to improve material fire resistance. With the presence of EGs in the PU matrix, bubble size in PUF became smaller as confirmed by the scanning electron microscopy. The mass density of PUFs is directly proportional to the content of EG additive. The compression strengths of EG0/PUF and EG30/PUF decrease from 0.51 MPa to 0.29 MPa. The Fourier transform infrared spectroscopy (FTIR) analysis of RPUFs showed that the addition of EGs did not change the functional group structures of RPUFs. Thermo-gravimetric analysis (TGA) testing results showed that the carbon residue weight of EG30/PUF is higher than other PU composite foams. The combination of TGA and FTIR indicated that the EG addition did not change the thermal decomposition products of EG0/PUF, but effectively inhibited its thermal decomposition rate. Cone calorimeter combustion tests indicated that the peak of the heat release rate of EG30/PUF significantly decreased to 100.5 kW m−2 compared to 390.6 kW m−2 for EG0/PUF. The ignition time of EG/PUF composites also increased from 2 s to 11 s with incorporation of 30 wt% EGs. The limiting oxygen index (LOI) and UL-94 standard tests show that the LOI of EG30/PUF can reach 55 vol%, and go through V-0 level. This study showed that adding EG into PU foams could significantly improve the thermal stability and flame retardancy properties of EG/PUF composites without significantly sacrificing material compression strength. The research results provide useful guidelines on industrial production and applications of PUFs.
Magnetic field effect on topological properties of Dirac semimetals PdTe2/PtTe2/PtSe2
Authors: Li Y Z , Zhao L L , Zhao X M , Dai T A , Zhong J X , Meng L J 
Published: November 2021

Abstract
We investigated magnetic field effect on the topological properties of transition metal dichalcogenide Dirac semimetals (DSMs) PdTe2/PtTe2/PtSe2 based on Wannier-function-based tight-binding (WFTB) model obtained from first-principles calculations. The DSMs PdTe2/PtTe2/PtSe2 undergo a transition from DSMs into Weyl semimetals with four pairs of Weyl points (WPs) in the entire Brillouin zone by splitting Dirac points under external magnetic field
B
. The positions and energies of WPs vary linearly with the strength of the
B
field under the
c
-axis magnetic field
B
. Under the
a
- and
b
-axis
B
field, however, the positions of magnetic-field-inducing WPs deviate slightly from the
c
axis, and their k

z
coordinates and energies change in a parabolic-like curve with the increasing
B
field. However, the system opens an axial gap on the A–Γ axis, and the gap changes with the direction of the
B
field when the out of
c
-axis
B
field is applied. When we further apply the magnetic field in the ac, bc, and ab planes, the results are more diverse compared to the axial magnetic field. Under the ac and bc plane
B
field, the k

z
and energies of WPs within angle θ = [0°, 90°] and θ = [90°, 180°] are mirror symmetrically distributed. The distribution of WPs shows broken rotational symmetry under the ab plane
B
field due to the difference of non-diagonal part of Hamiltonian. Our theoretical findings can provide a useful guideline for the applications of DSM materials under external magnetic field in the future topological electronic devices.
Tomographic background oriented schlieren using plenoptic cameras
Authors: Davis Jenna K , Clifford Christopher J , Kelly Dustin L , Thurow Brian S 
Published: November 2021

Abstract
The development of a tomographic background oriented schlieren implementation system utilizing up to four plenoptic cameras is presented. A systematic set of experiments was performed using a pair of solid dimethylpolysiloxan cylinders immersed in a nearly refractive index matched gylcerol/water solution to represent discrete flow features with known sizes, shapes, separation distances, and orientation. A study was conducted to assess the influence of these features on the accuracy of 3D reconstructions of the refractive index field. It was determined that the limited angular information collected by a single plenoptic camera is insufficient for single-camera 3D reconstructions. In multi-camera configurations, the additional views collected by a plenoptic camera were shown to improve the overall reconstruction accuracy compared to an equivalent single view per camera reconstruction, potentially reducing the number of overall cameras needed to achieve a desired accuracy. For the imaging of two cylinders, three or more cameras are generally needed to avoid significant ghosting artifacts in the reconstruction. Quantitative results are presented that show that: (1) two separate cylinders will be individually resolved as long as measurements from one camera are able to observe separation between the cylinders; (2) the error in the reconstructed 3D refractive index field increases as the size of the feature decreases; and (3) the use of volumetric masking within the reconstruction algorithm is critical in order to improve the accuracy of the solution.
A hybrid random laser using dye with self-organized GaN nanorods
Authors: Maryam W , Tan H H , Jagadish C , Dawes J M , Zhao B , Wan Ismail WZ 
Published: November 2021

Abstract
Self-organized GaN nanorods with population densities ranging between 0.1 and 0.5 μm−2 and average heights in the range 1.7–16.5 µm, prepared by metal-organic chemical vapor deposition, were used as scattering centers for random lasing by incorporating Rhodamine 6G liquid dye solutions as the gain media. A lasing threshold as low as 11.3 J cm−2 was obtained from samples with nanorod density above 0.3 μm−2. The threshold depended on the nanorod density and diameter, but not the nanorod height. Lasing emission was observed at multiple angles, a clear indication of random lasing.
Multi-resonant metamaterials based on self-sensing piezoelectric patches and digital circuits for broadband isolation of elastic wave transmission
Authors: Yi Kaijun , Liu Zhiyuan , Zhu Rui 
Published: November 2021

Abstract
This paper proposes a general method to design multi-resonant piezoelectric metamaterials. Such metamaterials contain periodically distributed piezoelectric patches bonded on the surfaces of a host structure. The patches are shunted with digital circuits and working on self-sensing mode. A transfer function to be implemented in the digital circiots is designed to realize multi-resonance. The transfer function is derived only using the parameters of the patches. Consequently, it can be used to realize any type of multi-resonant metamaterial structures, like beams, plates and shells. The mechanism of generating multi-bandgaps by the transfer function is explained by analytically studying the effective bending stiffness of a multi-resonant piezo-metamaterial plate. It is shown that the transfer function induces multiple frequency ranges in which the effective bending stiffness becomes negative, consequently results in multiple bandgaps. The characteristics of these bandgaps are investigated, coupling and merging phenomena between them are observed and analyzed. Isolation effects of vibration transmission (elastic wave) in the metamaterials at multiple line frequencies or within a broad frequency band are numerically verified in frequency domain. Further time domain simulations accounting for the full dynamics of the metamaterials with digital circuits are also performed, stability and functionality of the metamaterials are demonstrated. The proposed multi-resonant piezoelectric metamaterials may open new opportunities in vibration mitigation of transport vehicles and underwater equipment.
Localisation determines the optimal noise rate for quantum transport
Authors: Coates Alexandre R , Lovett Brendon W , Gauger Erik M 
Published: November 2021

Abstract
Environmental noise plays a key role in determining the efficiency of transport in quantum systems. However, disorder and localisation alter the impact of such noise on energy transport. To provide a deeper understanding of this relationship we perform a systematic study of the connection between eigenstate localisation and the optimal dephasing rate in 1D chains. The effects of energy gradients and disorder on chains of various lengths are evaluated and we demonstrate how optimal transport efficiency is determined by both size-independent, as well as size-dependent factors. By discussing how size-dependent influences emerge from finite size effects we establish when these effects are suppressed, and show that a simple power law captures the interplay between size-dependent and size-independent responses. Moving beyond phenomenological pure dephasing, we implement a finite temperature Bloch–Redfield model that captures detailed balance. We show that the relationship between localisation and optimal environmental coupling strength continues to apply at intermediate and high temperature but breaks down in the low temperature limit.
Can strangelets be detected in a large LAr neutrino detector?
Authors: Pârvu Mihaela , Lazanu Ionel 
Published: November 2021

Abstract
Predicted as possible bound states of up, down and strange quarks, strangelets could be more energetically favourable and more stable than nuclear matter. In this paper we explore the possibility of detecting such particles with the future large liquid argon detectors developed for neutrino physics. Using signals from ionization and scintillation, as well as measuring the range, we suggest that a calorimetric TPC detector is able to put in evidence and to discriminate between light strangelets and normal isotopes at intermediate energies.
Use of machine-learning for monitoring solar thermal plants
Authors: Hofmann Joachim Werner , Sitzmann Bernd , Dickinson John , Kunz Dominique , Eismann Ralph 
Published: November 2021

Abstract
A machine-learning algorithm (MLA) was developed to assess the operational state of solar thermal plants, based on the data of only one temperature sensor, and the irradiance and ambient temperature data from the nearest weather station. A detailed requirements analysis of the situation results in the classification of a multivariate time series problem. Neural networks used in the field of data science are ideally suited for problems of this type. Data from the operational monitoring system, which runs a rule-based algorithm, were used to train the neural network using the software framework TensorFlow. It was shown that the chosen MLA can detect malfunctions such as heat loss due to gravity-driven circulation during night. However, further development towards a practical tool requires not only far more data for training and validation. It became clear that corresponding pressure data are needed to classify temperature transients and to attribute these classes to certain malfunctions.
Quantification of existing rooftop PV hourly generation capacity and validation against measurement data
Authors: Walch Alina , Rüdisüli Martin , Castello Roberto , Scartezzini Jean-Louis 
Published: November 2021

Abstract
The spatio-temporal patterns of the existing rooftop photovoltaic (PV) production can provide valuable insights for the design of effective strategies for PV integration at large scale. In this work, we quantify the hourly production of existing rooftop PV installations by combining two large-scale methods, for detecting rooftop solar panels and for estimating their hourly PV generation, which are both applicable at the Swiss national scale. A validation against measured data of PV installations from 16 roofs in the Swiss Canton of Aargau shows that the existing PV area is detected accurately, while the hourly profiles overestimate the PV production, with higher errors in winter than in summer. These errors result in a mean overestimation of the annual PV production by 16%, assuming a triangular panel placement at low tilt (15°) on flat roofs.
Big Building Data 2.0 - a Big Data Platform for Smart Buildings
Authors: Linder Lucy , Montet Frédéric , Hennebert Jean , Bacher Jean-Philippe 
Published: November 2021

Abstract
The modern built environment is now connected. Multiple software and protocols are used in buildings of many kinds, thus creating a fascinating and heterogeneous environment. Within this context, applied research can be complicated and would benefit from a single data location across projects and users. The first version of BBData tried to solve this problem, BBData v2.0 is an update with a better-defined scope and a new codebase.
The solution has been open sourced and simplified with a full software rewrite. Its components are now state-of-the-art and proven to be stable in industrial settings. The achieved performances have been thoroughly tested. Together with its new architecture, BBData v2.0 now accommodates the needs of modern experiments; efficient for simple proof of concepts while keeping the possibility to scale up to city-level projects. This flexibility makes BBData a good candidate for research while being able to scale in production settings.
Short-Term Load Forecasting in a microgrid environment: Investigating the series-specific and cross-learning forecasting methods
Authors: Genov Evgenii , Petridis Stefanos , Iliadis Petros , Nikopoulos Nikos , Coosemans Thierry , Messagie Maarten , Camargo Luis Ramirez 
Published: November 2021

Abstract
A reliable and accurate load forecasting method is key to successful energy management of smart grids. Due to the non-linear relations in data generating process and data availability issues, load forecasting remains a challenging task. Here, we investigate the application of feed forward artificial neural networks, recurrent neural networks and crosslearning methods for day-ahead and three days-ahead load forecasting. The effectiveness of the proposed methods is evaluated against a statistical benchmark, using multiple accuracy metrics. The test data sets are high resolution multi-seasonal time series of electricity demand of buildings in Belgium, Canada and the UK from private measurements and open access sources. Both FFNN and RNN methods show competitive results on benchmarking datasets. Best method varies depending on the accuracy metric selected. The use of cross-learning in fitting a global RNN model has an improvement on the final accuracy.
Building Materials for Cities and Climate Change – a Material Catalogue with Recommendations
Authors: Hoffmann C , Geissler A , Mutti M , Wicki A , Schwager F 
Published: November 2021

Abstract
High urban density with heat accumulating materials and sealed surfaces can cause heat stress and reduced nocturnal cooling in summer. Appropriate building materials may contribute to the mitigation of this effect. The research project evaluates building materials for façades and outer surfaces (ground) on the resulting urban microclimate and on factors like glare, acoustics and embedded energy. The present publication focuses on the impact on the microclimate. The analysis comprises the simulation of forty-seven data sets in a microclimatic model with ENVI-met. The results show that during daytime the PET for the whole neighborhood ranges between 30.1 and 36.4 °C. Choosing a bright instead of a dark color can lower the PET between 0.2 and 1.0 K. Dark colored metal sheets may cause turbulences which lead to a reduction of the PET between 2.0 and 3.8 K (compared to a bright metal sheet). However, this effect may not be reproducible under varying boundary conditions. During night-time, the resulting span of ambient temperatures between the materials reaches 21.4 to 22.0 °C (level 1.7 m). The temperature difference between the materials at the level of 10.7 m (for night ventilation) is found to be approx. 0.3 K and can be considered irrelevant.
Implementing air-based thermally activated building systems in retrofitted tertiary buildings – Towards the proof of concept
Authors: Cézard M , Labat M , Lorente S 
Published: November 2021

Abstract
Here we document the design method of an air-based thermally activated building system (TABS) suited for the retrofitting of tertiary buildings, for cooling purposes mainly. The first phase of this work provides a general design and checks its consistency with the specifications of tertiary buildings by means of basic energy balances. Second, a numerical model of both the TABS and the room is developed under a finite element method multi-physics environment to better estimate the transient heat transfer for the proposed retrofitting solution. This results in the specifications for building at 1:1 scale prototype whose construction is documented.
Information model development for the quality assurance of technical equipment in small buildings
Authors: Stobbe M , Gerber A , Herkel S , Réhault N , Nytsch-Geusen C 
Published: November 2021

Abstract
Ensuring energy quality, i.e. compliance with specified or standardised energy performance indicators of buildings over the entire life cycle, can reduce the climate impact of the building sector. In this work, the causes for quality deficiencies in small building services installations as well as the structure of actors interacting with building services were analysed. On this basis, we developed a solution approach in the form of an information model including a catalogue of all requirements and the necessary content to address and improve the quality assurance of HVAC in small buildings. This information model will serve as the basis for future digital tools that can perform (partially) automated heating load calculations and the design of heating systems, improve installation logistics and installation quality through providing information and the necessary processing, and enable improved hydraulic balancing and control.
Evaluation of a new user-centric sensor-based lighting control approach for circulation areas
Authors: Karaman Madan Ö , Pekeriçli MK 
Published: November 2021

Abstract
Suitable lighting control strategies are essential for energy efficiency in buildings. Occupancy sensors are highly promoted by the building codes as one of the most cost-effective solutions in the sector. However, widespread use of these systems is still limited due to lack of user satisfaction. In this study, it is hypothesized that the “conventional use” of occupancy sensors (where user steps inside a dark area, and only afterwards the area becomes lit) is the reason behind the dissatisfaction. To overcome this problem, a new user-centric sensor-based lighting control approach is proposed in this study where users walk into an already lit area. An experiment was carried out in the circulation areas of a university building to test the feasibility of the proposed scenarios along with a conventional occupancy sensor scenario and the existing “no sensor” scenario. The main results revealed that the conventional use of occupancy sensors was not favoured by the participants in circulation areas while use of the proposed user-centric approach was as favourable as the existing constantly lit situation. It is the claim of this study that both energy efficiency and user satisfaction can be provided by the use of user-centric control systems.
Non-domestic building stock energy and carbon modelling for policy advice – a user requirements survey
Authors: Bischof Julian , Duffy Aidan 
Published: November 2021

Abstract
In recent years, many building stock models have been developed to advise and guide policymakers. In most models, however, user needs were not formally established. Therefore, the aim of this paper is to formally undertake a user needs‘ assessment for building stock energy and carbon models. To achieve this aim, a bilingual exploratory online user requirements’ survey was developed. The survey was designed to gather information in the following areas: the general interests of the potential model users; their experiences with related studies and models; the desired properties of non-domestic building stock energy models; and any technical limitations, such as computational resources. A total of 19 responses were obtained. Users favour tools which are: usable, transparent; flexible; compatible with other tools; and provide clear, understandable results.