bluuebunny/crossref_metadata_2025 huggingface dataset:
Sedimentation evaluation of high-viscosity linear polysiloxane-based magnetorheological fluids using automated vertical axis inductance monitoring system
Authors: Choi Young T. , Sztein Pablo , Hiemenz Gregory , Wereley Norman M.
Published: February 2024

The sedimentation evaluation of magnetorheological fluids (MRFs) is a key component to developing successful commercial MRF-based engineering applications. In this study, the long-term sedimentation stability of highly stable high-viscosity linear polysiloxane-based MRFs (HVLP MRFs) was experimentally investigated by using an automated vertical axis inductance monitoring system (AVAIMS). The sedimentation evaluation of the HVLP MRFs with high particle loadings up to 45 vol% was tracked for 295 days, and the four different sedimentation zones such as supernatant, original concentration, variable concentration, and sediment were identified. To this end, the automated identification method to determine the sedimentation zone boundaries of highly stable MRFs was proposed. Three HVLP MRF samples with two different high particle loadings of 35 vol% and 45 vol% and two different high carrier viscosities of 5k and 10k cSt were selected as testing samples and one commercial MRF with a particle loading of 40 vol% (i.e., LORD MRF-140CG) also was tested as a baseline.
Repulsive magnetic levitation-based electromagnetic energy harvesting of a low-frequency ocean wave
Authors: Park J. , Pillai N. , Wereley N. M. , Flatau A. B.
Published: February 2024

In this study, an electromagnetic energy harvester for a low-frequency ocean wave was developed in a compact 3D-printed structure. Ocean wave energy conversion technologies exist, but maintaining them in the harsh marine environment is crucial for business. Friction increases maintenance costs. Therefore, magnetic levitation, being friction-free, is used for cost-effective, low-maintenance electromagnetic energy harvesting applications. Low-frequency oscillating energy is captured using repulsive magnetic levitation with a buoy and generating electricity using a permanent magnet and copper coil. A levitating magnet is repelled by a fixed one, inducing electricity as it passes through a coil. Experiments with a 0.1 Hz sine wave mimic the average frequency of ocean waves, showing successful voltage peaks at intervals. The output voltage and measured power from the harvester exhibit variations influenced by multiple parameters. The maximum output voltage observed was 3.4 V and an average of 99 mW of power was calculated. The experiment demonstrates the feasibility of using repulsive magnetic levitation for low-frequency wave energy harvesting and also encompasses various harvester configurations, including transfer magnet forces and top magnets.
US takes another look at recycling nuclear fuel
Authors: Kramer David
Published: February 2024

Proponents see a reduction in the need for uranium mining and more efficient, cheaper reactors. Opponents see a risk of proliferation.
To rule the waves
Authors: Bühler Oliver
Published: February 2024

Physics of Wave Turbulence, Sébastien Galtier
Age, growth and maturity of an endemic valuable resource, the Rio skate (Rioraja agassizii (Chondrichthyes: Rajiformes)), off Uruguay and northern Argentina
Authors: Bianchi Santiago J. , Roman Jorge M. , Lucifora Luis O. , Barbini Santiago A.
Published: February 2024

Context Rioraja agassizii is a vulnerable species endemic to the Southwest Atlantic. It is caught by trawl fisheries throughout its range. Aims To determine the age, estimate growth parameters, and age and size at maturity. Methods Ages were determined using vertebrae readings. To fit growth models, a Bayesian framework was employed with the von Bertalanffy, Gompertz and Logistic candidate models. To estimate age and size at maturity, a logistical ogive was fitted to binomial maturity data. Key results Maximum ages determined for males and females were 12 and 11 years respectively. The von Bertalanffy model was selected as the best one and there were no differences between sexes (mean parameters: L∞ = 684.8 mm, k = 0.33 years−1 and L0 = 105.5 mm). Age and size at maturity were estimated at 3.31 and 4.55 years, and 485.02 and 544.55 mm TL for males and females respectively. Conclusions Rioraja agassizii has a moderate growth rate and age at maturity was similar to those of skate species with a similar body size. Implications Because skate species have different maximum ages, growth rates and maturity parameters, we strongly recommend urgent species-specific management measures for the pool of skate species exploited in Argentina.
Impacts of necrotising disease on the Endangered cauliflower soft coral (Dendronephthya australis)
Authors: Steinberg Rosemary Kate , Turnbull John , Ainsworth Tracy D. , Dafforn Katherine A. , Poore Alistair G. B. , Johnston Emma L.
Published: February 2024

Context Diseases have affected coral populations worldwide, leading to population declines and requiring active restoration efforts. Aims Describe population and individual impacts of necrotising disease in the Endangered octocoral Dendronephthya australis. Methods We quantified population loss and recruitment by using reference photos, survey and GPS mapping and described disease lesions by using histopathology. Key results From December 2019 to January 2020, we observed polyp loss, necrotic lesions and loss of large colonies of D. australis at Botany Bay, New South Wales, Australia. By September 2020, only a few scattered recruits remained, and all large colonies were lost. Histopathology of colonies sampled in January 2020 confirmed that the disease had resulted in necrosis, gastrovascular canal collapse and internal colony integrity loss, leading to mortality. New recruits were recorded within 10 months of disease onset, and large colonies within 18 months. Conclusions Although the necrotising disease had significant impacts on both the individual and population level, natural recruitment began quickly. As such, unlike in other populations, restoration is not currently required in the Bare Island D. australis population. Implications The extent of disease impact at the individual and population levels suggests that monitoring for lesions should be undertaken before developing conservation and restoration strategies for this species.
Targeted demethylation and activation of
NLRC5
augment cancer immunogenicity through MHC class I
Authors: Sun Xin , Watanabe Toshiyuki , Oda Yoshitaka , Shen Weidong , Ahmad Alaa , Ouda Ryota , de Figueiredo Paul , Kitamura Hidemitsu , Tanaka Shinya , Kobayashi Koichi S.
Published: February 2024

Impaired expression of MHC (major histocompatibility complex) class I in cancers constitutes a major mechanism of immune evasion. It has been well documented that the low level of MHC class I is associated with poor prognosis and resistance to checkpoint blockade therapies. However, there is lmited approaches to specifically induce MHC class I to date. Here, we show an approach for robust and specific induction of MHC class I by targeting an MHC class I transactivator (CITA)/NLRC5, using a CRISPR/Cas9-based gene-specific system, designated TRED-I (Targeted reactivation and demethylation for MHC-I). The TRED-I system specifically recruits a demethylating enzyme and transcriptional activators on the
NLRC5
promoter, driving increased MHC class I antigen presentation and accelerated CD8+ T cell activation. Introduction of the TRED-I system in an animal cancer model exhibited tumor-suppressive effects accompanied with increased infiltration and activation of CD8+ T cells. Moreover, this approach boosted the efficacy of checkpoint blockade therapy using anti-PD1 (programmed cell death protein) antibody. Therefore, targeting
NLRC5
by this strategy provides an attractive therapeutic approach for cancer.
High life satisfaction reported among small-scale societies with low incomes
Authors: Galbraith Eric D. , Barrington-Leigh Christopher , Miñarro Sara , Álvarez-Fernández Santiago , Attoh Emmanuel M. N. A. N. , Benyei Petra , Calvet-Mir Laura , Carmona Rosario , Chakauya Rumbidzayi , Chen Zhuo , Chengula Fasco , Fernández-Llamazares Álvaro , García-del-Amo David , Glauser Marcos , Huanca Tomas , Izquierdo Andrea E. , Junqueira André B. , Lanker Marisa , Li Xiaoyue , Mariel Juliette , Miara Mohamed D. , Porcher Vincent , Porcuna-Ferrer Anna , Schlingmann Anna , Seidler Reinmar , Shrestha Uttam Babu , Singh Priyatma , Torrents-Ticó Miquel , Ulambayar Tungalag , Wu Rihan , Reyes-García Victoria
Published: February 2024

Global polls have shown that people in high-income countries generally report being more satisfied with their lives than people in low-income countries. The persistence of this correlation, and its similarity to correlations between income and life satisfaction within countries, could lead to the impression that high levels of life satisfaction can only be achieved in wealthy societies. However, global polls have typically overlooked small-scale, nonindustrialized societies, which can provide an alternative test of the consistency of this relationship. Here, we present results from a survey of 2,966 members of Indigenous Peoples and local communities among 19 globally distributed sites. We find that high average levels of life satisfaction, comparable to those of wealthy countries, are reported for numerous populations that have very low monetary incomes. Our results are consistent with the notion that human societies can support very satisfying lives for their members without necessarily requiring high degrees of monetary wealth.
Acceleration of infectious disease drug discovery and development using a humanized model of drug metabolism
Authors: MacLeod A. Kenneth , Coquelin Kevin-Sebastien , Huertas Leticia , Simeons Frederick R. C. , Riley Jennifer , Casado Patricia , Guijarro Laura , Casanueva Ruth , Frame Laura , Pinto Erika G. , Ferguson Liam , Duncan Christina , Mutter Nicole , Shishikura Yoko , Henderson Colin J. , Cebrian David , Wolf C. Roland , Read Kevin D.
Published: February 2024

A key step in drug discovery, common to many disease areas, is preclinical demonstration of efficacy in a mouse model of disease. However, this demonstration and its translation to the clinic can be impeded by mouse-specific pathways of drug metabolism. Here, we show that a mouse line extensively humanized for the cytochrome P450 gene superfamily (“8HUM”) can circumvent these problems. The pharmacokinetics, metabolite profiles, and magnitude of drug-drug interactions of a test set of approved medicines were in much closer alignment with clinical observations than in wild-type mice. Infection with
Mycobacterium tuberculosis
,
Leishmania donovani,
and
Trypanosoma cruzi
was well tolerated in 8HUM, permitting efficacy assessment. During such assessments, mouse-specific metabolic liabilities were bypassed while the impact of clinically relevant active metabolites and DDI on efficacy were well captured. Removal of species differences in metabolism by replacement of wild-type mice with 8HUM therefore reduces compound attrition while improving clinical translation, accelerating drug discovery.
DNA combing versus DNA spreading and the separation of sister chromatids
Authors: Meroni Alice , Wells Sophie E. , Fonseca Carmen , Ray Chaudhuri Arnab , Caldecott Keith W. , Vindigni Alessandro
Published: February 2024

DNA combing and DNA spreading are two central approaches for studying DNA replication fork dynamics genome-wide at single-molecule resolution by distributing labeled genomic DNA on coverslips or slides for immunodetection. Perturbations in DNA replication fork dynamics can differentially affect either leading or lagging strand synthesis, for example, in instances where replication is blocked by a lesion or obstacle on only one of the two strands. Thus, we sought to investigate whether the DNA combing and/or spreading approaches are suitable for resolving adjacent sister chromatids during DNA replication, thereby enabling the detection of DNA replication dynamics within individual nascent strands. To this end, we developed a thymidine labeling scheme that discriminates between these two possibilities. Our data suggests that DNA combing resolves sister chromatids, allowing the detection of strand-specific alterations, whereas DNA spreading typically does not. These findings have important implications when interpreting DNA replication dynamics from data obtained by these two commonly used techniques.
A zero-shot fault attribute transfer learning method for compound fault diagnosis of power circuit breakers
Authors: Yang Qiuyu , Lin Yuyi , Ruan Jiangjun
Published: February 2024

Diagnosis of compound mechanical faults for power circuit breakers (CBs) is a challenging task. In traditional fault diagnosis methods, however, all fault types need to be collected in advance for the training of diagnosis model. Such processes have poor generalization capabilities for industrial scenarios with no or few data when faced with new faults. In this study, we propose a novel zero-shot learning method named DSR-AL to address this problem. An unsupervised neural network, namely, depthwise separable residual convolutional neural network, is designed to directly learn features from 3D time-frequency images of CB vibration signals. Then we build fault attribute learners (ALs), for transferring fault knowledge to the target faults. Finally, the ALs are used to predict the attribute vector of the target faults, thus realizing the recognition of previously unseen faults. The orthogonal experiments are designed and conducted on real industrial switchgear to validate the effectiveness of the proposed diagnosis framework. Results show that it is feasible to diagnose target faults without using their samples for training, which greatly saves the costs of collecting fault samples. This will help to accurately identify the various faults that may occur during CB’s life cycle, and facilitate the application of intelligent fault diagnosis system.
Adaptive convolutional sparsity with sub-band correlation in the NSCT domain for MRI image fusion
Authors: Hu Qiu , Cai Weiming , Xu Shuwen , Hu Shaohai , Wang Lang , He Xinyi
Published: February 2024

Objective. Multimodal medical image fusion (MMIF) technologies merges diverse medical images with rich information, boosting diagnostic efficiency and accuracy. Due to global optimization and single-valued nature, convolutional sparse representation (CSR) outshines the standard sparse representation (SR) in significance. By addressing the challenges of sensitivity to highly redundant dictionaries and robustness to misregistration, an adaptive convolutional sparsity scheme with measurement of the sub-band correlation in the non-subsampled contourlet transform (NSCT) domain is proposed for MMIF. Approach. The fusion scheme incorporates four main components: image decomposition into two scales, fusion of detail layers, fusion of base layers, and reconstruction of the two scales. We solved a Tikhonov regularization optimization problem with source images to obtain the base and detail layers. Then, after CSR processing, detail layers were sparsely decomposed using pre-trained dictionary filters for initial coefficient maps. NSCT domain’s sub-band correlation was used to refine fusion coefficient maps, and sparse reconstruction produced the fused detail layer. Meanwhile, base layers were fused using averaging. The final fused image was obtained via two-scale reconstruction. Main results. Experimental validation of clinical image sets revealed that the proposed fusion scheme can not only effectively eliminate the interference of partial misregistration, but also outperform the representative state-of-the-art fusion schemes in the preservation of structural and textural details according to subjective visual evaluations and objective quality evaluations. Significance. The proposed fusion scheme is competitive due to its low-redundancy dictionary, robustness to misregistration, and better fusion performance. This is achieved by training the dictionary with minimal samples through CSR to adaptively preserve overcompleteness for detail layers, and constructing fusion activity level with sub-band correlation in the NSCT domain to maintain CSR attributes. Additionally, ordering the NSCT for reverse sparse representation further enhances sub-band correlation to promote the preservation of structural and textural details.
MHD second-grade nanofluid slip flow over a stretching sheet subject to activation energy, thermophoresis, and Brownian effects
Authors: Rath Chinmoy , Nayak Anita
Published: February 2024

In this work, the magnetohydrodynamic flow of two engine oil-based second-grade nanofluids Copper (Cu) and Titanium oxide (TiO
2) over a penetrable stretching sheet is studied. The flow, heat and mass transfer characteristics in the existence of activation energy, inclined magnetic field, Brownian diffusion, elastic deformation, and thermophoresis are examined. The coupled nonlinear model equations are formulated by implementing the Modified Buongiorno model and then are non-dimensionalized by the similarity transformation technique. The non-dimensional equations are simulated numerically using the bvp4c solver. Graphs are plotted to study the flow behaviour of nanofluid with the rate of entropy generation and Bejan number. The outcomes of skin friction coefficient, Nusselt number and Sherwood number are exhibited via surface plots. From the analysis, a higher inclination of the magnetic field decays the velocity and amplifies the temperature profiles. The heat transport rate diminishes with the Brownian diffusion, thermophoresis and elastic deformation parameters. The mass transport rate is accelerated due to the activation energy parameter. The entropy generation rate is enhanced with the Brinkman, Biot and local Reynolds numbers. Furthermore, it is seen that engine oil-based TiO
2 nanofluid has larger velocity, temperature and rate of entropy generation than engine oil-based Cu nanofluid. The current examination has applications in automobile radiators, microchips, biomedical engineering, and extraction of geothermal power.
Optical voice encryption based on speckle-illuminated fourier ptychography and plaintext-related chaotic random phase mask
Authors: Li Jiaxin , Xu Wenjun , Wang Yonghui , Li Fei , Liu Shuaiqi , Su Yonggang
Published: February 2024

In this paper, we propose an optical voice encryption scheme based on speckle-illuminated Fourier ptychography (FP) and plaintext-related chaotic random phase mask (CRPM). In this proposed encryption scheme, the plaintext-related CRPMs are generated by chaotic Lozi map and secure hash algorithm (SHA-256). During the encryption process, the voice signal to be encrypted is first converted into a two-dimensional (2D) voice map. Then, with the help of CRPMs and speckle-illuminated FP, the voice map is encrypted into a series of noise-like low-resolution images. During the decryption process, the original voice signal can be recovered from the series of noise-like low-resolution images via Fourier ptychographic phase retrieval algorithm and the CRPMs. To the best of our knowledge, it is the first time to use the Fourier ptychography and chaotic random phase mask to implement the optical encryption of the voice signal. In addition, in this proposed encryption scheme, the chaotic parameters can replace the whole random phase masks as the secret keys, which makes the management and transmission of the secret keys become more convenient. Moreover, since the plaintext-related chaotic parameter keys can be updated dynamically, the security of the proposed encryption scheme can be further improved. The feasibility, security and robustness of the proposed encryption scheme are further analyzed by numerical simulations.
Annealing effects on the structural, positron annihilation parameters, and electrical properties of Fe2O3- PbO2-TeO2 glasses
Authors: El-Desoky M M , Abdel-Hady E E , Mohamed Hamdy F M , Hassanien Mohamed H M , Abdallah N , Harby Amany E
Published: February 2024

This study focuses on the transformation of selected glasses consisting of 20Fe2O3–xPbO2–(80–x)TeO2 (where x = 5, 10, 15, 20, and 25 mol%) with varying concentrations of PbO2, into nanomaterials through annealing at a temperature close to the crystallization temperature (Tc). The physical and chemical properties of the resulting samples were investigated. The chemical structure was analyzed using Fourier Transform Infrared spectroscopy (FTIR), which revealed no significant chemical changes except for an increase in the concentration of PbO2. X-ray diffraction (XRD) was used to study the crystal structure. Improvements were seen with increasing PbO2 concentrations, and these improvements were further increased after the sample was annealed. Furthermore, positron annihilation lifetime (PAL) spectroscopy was used to study the microstructure, more precisely the size of vacancy-type defects. A correlation was established between the PAL and the properties of the samples. The size of the vacancy-type defects was confirmed by calculating the distribution of the long lifetime deduced from the PAL. In this work, the overall influence of PbO2 concentration and thermal treatment on the chemical and crystalline structures, electrical conductivity, and microstructure of the studied nanomaterials is highlighted. The results provide valuable insights into the relationship between the PAL and the properties of the samples and provide potential opportunities to tailor their properties for different applications.
Using machine learning to optimise chameleon fifth force experiments
Authors: Briddon Chad , Burrage Clare , Moss Adam , Tamosiunas Andrius
Published: February 2024

The chameleon is a theorised scalar field that couples to matter and possess a screening mechanism, which weakens observational constraints from experiments performed in regions of higher matter density. One consequence of this screening mechanism is that the force induced by the field is dependent on the shape of the source mass (a property that distinguishes it from gravity). Therefore an optimal shape must exist for which the chameleon force is maximised. Such a shape would allow experiments to improve their sensitivity by simply changing the shape of the source mass. In this work we use a combination of genetic algorithms and the chameleon solving software SELCIE to find shapes that optimise the force at a single point in an idealised experimental environment. We note that the method we used is easily customised, and so could be used to optimise a more realistic experiment involving particle trajectories or the force acting on an extended body. We find the shapes outputted by the genetic algorithm possess common characteristics, such as a preference for smaller source masses, and that the largest fifth forces are produced by small `umbrella'-like shapes with a thickness such that the source is unscreened but the field reaches its minimum inside the source. This remains the optimal shape even as we change the chameleon potential, and the distance from the source, and across a wide range of chameleon parameters. We find that by optimising the shape in this way the fifth force can be increased by 2.45 times when compared to a sphere, centred at the origin, of the same volume and mass.
Pulsar Timing Array signature from oscillating metric perturbations due to ultra-light axion
Authors: Hwang Jai-chan , Jeong Donghui , Noh Hyerim , Smarra Clemente
Published: February 2024

A coherently oscillating ultra-light axion can behave as dark matter. In particular, its
coherently oscillating pressure perturbations can source an oscillating scalar metric
perturbation, with a characteristic oscillation frequency which is twice the axion Compton
frequency. A candidate in the mass range 10(-24,-21) eV can provide a signal in the
frequency range tested by current and future Pulsar Timing Array (PTA) programs. Involving the
pressure perturbations in a highly nonlinear environment, such an analysis demands a relativistic
and nonlinear treatment. Here, we provide a rigorous derivation of the effect assuming
weak-gravity and slow-motion limit of Einstein's gravity in zero-shear gauge and show that dark
matter's velocity potential determines the oscillation phase and frequency change. A monochromatic
PTA signal correlated with the velocity field would confirm the prediction, for example, by
cross-correlating the PTA results with the future local velocity flow measurements.
BaTiO3/p-GaN/Au self-driven UV photodetector with bipolar photocurrent controlled by ferroelectric polarization
Authors: Han 韩 Wushuang 无双 , Liu 刘 Kewei 可为 , Yang 杨 Jialin 佳霖 , Zhu 朱 Yongxue 勇学 , Cheng 程 Zhen 祯 , Chen 陈 Xing 星 , Li 李 Binghui 炳辉 , Liu 刘 Lei 雷 , Shen 申 Dezhen 德振
Published: February 2024

Ferroelectric materials are promising candidates for ultraviolet photodetectors due to their ferroelectric effect. In this work, a BaTiO3/p-GaN/Au hybrid heterojunction–Schottky self-driven ultraviolet photodetector was fabricated with excellent bipolar photoresponse property. At 0 V bias, the direction of the photocurrent can be switched by flipping the depolarization field of BaTiO3, which allows the performance of photodetectors to be controlled by the ferroelectric effect. Meanwhile, a relatively large responsivity and a fast response speed can be also observed. In particular, when the depolarization field of BaTiO3 is in the same direction of the built-in electric field of the Au/p-GaN Schottky junction (up polarized state), the photodetector exhibits a high responsivity of 18 mA/W at 360 nm, and a fast response speed of < 40 ms at 0 V. These findings pave a new way for the preparation of high-performance photodetectors with bipolar photocurrents.
Mixed convection in turbulent particle-laden channel flow at Re
τ
= 180
Authors: Zaza D , Iovieno M
Published: February 2024

A numerical investigation of mixed convection in a turbulent particle-laden channel flow is presented. Using Eulerian-Lagrangian Direct Numerical Simulations (DNSs) within the point-particle approach, the interaction between wall turbulence, particle inertia and thermal inertia, and buoyancy in the two-way coupling regime has been studied. The flow dynamics is controlled by the friction Reynolds number, Richardson number, particle Stokes and thermal Stokes numbers, and the Prandtl number. The effects of particle inertia and buoyancy on fluid and particle statistics are shown for a friction Reynolds number of 180, Stokes numbers ranging from 0.6 to 120, Richardson numbers ranging from 2.72 × 10−4 to 27.2 at a single Prandtl number, 0.71. The results indicate that the effect of particle inertia is significant on particle statistics, but not as pronounced on fluid statistics at the relatively low volume fraction considered. Particle inertia modulates the overall heat flux in a non-monotonic way.
Assessment of a Flow-dependent Subgrid Characteristic Length for Large-Eddy Simulation on Anisotropic Grids
Authors: D’Alessandro V , Delorme Y , Falone M , Wasserman M , Ricci R
Published: February 2024

This paper presents the latest results of a long track development activity in the context of low-dissipative finite volume method for compressible flows. Specifically, here we focus our attention on the Large-Eddy Simulation (LES) approach which can be considered a good candidate for turbulent flow simulations over the next decades. One of the key ingredients of LES models is the subgrid length scale which is typically evaluated based on the local mesh size. This standard approach suffers from loss of accuracy on anisotropic grids that are commonly employed to obtain sufficient wall-normal resolution, whilst keeping the total cell count to a minimum. In order to avoid this issue, we assess the effectiveness of a velocity-gradient-based length scale, referred to as least square length (LSQ) [1]. In this paper, we present for the first time results obtained with the LSQ length scale in the context of compressible LES. The superiority of the LSQ approach over the standard cubic-root length scale is demonstrated in terms of accuracy and overall time to solution.
Numerical and experimental study to examine methods to increase the convectional heat transfer of recuperator tubes
Authors: Trampe E , Hauch J , Büschgens D , Pfeifer H
Published: February 2024

The use of structured tubes in tube bundle recuperators is intended to improve the energy efficiency of gas-fired industrial furnace systems with central air preheating. Currently, smooth tubes as well as smooth tubes with internal twisted tape are commonly utilised. The increased surface area of structured tubes leads to an increased heat transfer between the off-gas and the combustion air. However, structuring leads to an increased pressure loss. The aim is to find an optimal operating range in which the pressure losses are still acceptable and the greatest increase of heat transfer compared to the reference will be achieved. Smooth tubes and also smooth tubes with twisted tapes are considered as reference systems in comparison to two concave structured tubes. CFD simulations were used to investigate the influence of the operating parameters of combustion air velocity and off-gas velocity on heat transfer according to industrial scale. The simulations have shown that the heat flow increases with the honeycomb depth and strongly depends on the operating conditions. Experimental measurements in a test bench were carried out to validate the model and confirm the positive influence of structuring on heat transfer.
Investigating the relationship between surface roughness and reflectance properties of building materials
Authors: Marchini F , Chiatti C , Fabiani C , Latterini L , Pisello AL
Published: February 2024

Materials used in the exterior envelope of buildings and open urban surfaces, in general, strongly affect the urban thermal balance, determining the general magnitude of urban overheating. The surface temperature of reflective materials varies as a function of physical and geometrical properties. Quantifying the influence of surface roughness on reflectance properties has crucial relevance since reflectance can significantly affect the reduction of the absorbed solar radiation and, in turn, the energy demand for cooling. Through an experimental and statistical investigation, this research aims to analytically assess the impact of surface roughness on the reflectance and thermal performances of building materials and, in turn, the role that roughness could play towards urban cooling and mitigation. Results show that the surface’s different roughness affects the sample’s reflectance coefficient, leaving it basically unchanged in the Ultraviolet and Visible ranges but with appreciable differences in the Near-Infrared wavelengths. This outcome confirms the correlation between the surface roughness and the optical and thermal characteristics of the building materials, making evident the importance of the study of superficial topography towards the mitigation of Urban Heat Island phenomena.
Numerical investigation of radiative transfer during oxyfuel combustion of hydrogen and hydrogen enriched natural gas in the container glass industry
Authors: Ott F , Losacker J , Schmitz N , Pfeifer H
Published: February 2024

The substitution of natural gas with hydrogen is one way to eliminate direct CO2 emissions. However, oxyfuel combustion of hydrogen or hydrogen enriched natural gas leads to different exhaust gas properties due to a changed composition compared to conventional combustion. In combustion simulation, the emissivity of a gas mixture is usually approximated using a Weighted Sum of Gray Gases (WSGG) model. Most of the existing WSGG models have been validated for natural gas combustion with air or oxyfuel and are therefore not applicable to hydrogen-oxyfuel combustion. CFD simulations showed, that none of the investigated WSGG models is able to predict the radiative heat transfer for all considered combustion scenarios with appropriate accuracy. In addition, in container glass manufacturing more than 95% of the heat flux to the glass surface is transferred by radiation because of the high process temperatures. Due to the changed gray gas emissivity, the high content of water vapor leads to a different emission spectrum of the exhaust gas. The influence of the changed emission spectrum on radiative heat transfer and the penetration depth of radiation in the glass melt is investigated using a simulation model of a pilot plant and non-gray modelling of the radiation transport. The CFD simulations show slightly enhanced radiative heat transfer to the glass and a slightly deeper penetration depth especially for wavelength below 2.2 μm for hydrogen-oxyfuel combustion.
Numerical performance investigation of High Vacuum Flat Plate Hybrid Photovoltaic-Thermal devices.
Authors: Strazzullo P , De Luca D , Caldarelli A , Gaudino E , Musto M , Gennaro Emiliano Di , Russo R
Published: February 2024

We propose an innovative flat plate hybrid Photovoltaic-Thermal system under high vacuum (HV PV-T) optimized for solar-to-thermal energy conversion. It consists of a glass cover, metallic vessel, and the actual PV-T device, which englobes a low-emissive Transparent Conductive Oxide (TCO), a perovskite-based PV cell, a Solar Absorber, and a copper substrate. We investigate, through a 1-D model developed in MATLAB, the performances of the proposed PV-T system, still mined by radiative losses, varying the operating temperature (Top) and the emittance of the TCO (εTCO
) in the ranges of (25÷175) °C and (0.05÷0.45) respectively. The annual thermal and electrical productions are evaluated considering the Typical Meteorological Year of Naples, Italy. Specific annual costs and emission savings are evaluated and compared with the ones assured by commercial High Vacuum Flat Plate Solar-Thermal (HVFP ST) and PV collectors. Results indicate that the proposed HV PV-T increases the annual cost savings by 34% and 11% when compared to HVFP ST and PV collectors, respectively. Moreover, the presented HV PV-T increases the annual CO2 emissions savings by 7% and 48% when compared to HVFP ST and PV collectors, respectively.
Thermally adaptive wall to enhance indoor comfort and energy performance
Authors: Bianchi F , Baldinelli G , Schnotale J A , Lechowska A A , Presciutti A
Published: February 2024

In the present work, a new environment-adaptive wall is proposed, based on an inside and outside radiant panel with pipes drowned on the panels themselves and hosting a heat-carrying liquid pushed by a pump. The purpose consists of transferring heat across the thickness of the wall, in the direction required for energy saving and enhancement of inner indoor thermal comfort. A Computational Fluid Dynamic (CFD) analysis is reported and the results are applied on a single zone box-shaped building, where a whole-year study is implemented by means of the transient simulation tool TRNSYS. The efficiency of this solution respect to the state-of the-art static walls is finally discussed. A concept of a laboratory setup of an adoptive wall along with first result are presented and discussed.
A new dry deposition model implemented in CALPUFF code to simulate contamination of radionuclides released into atmospheric environment post-nuclear accidental event
Authors: Giardina M , Buffa P , Cervone A , Lombardo C , Giaiotti D , Oshurok D , Skrynyk O
Published: February 2024

Long-range transport and deposition analyses of 137Cs following a hypothetical incident at Gösgen nuclear power plant are studied by using CALMET-CALPUFF model system. Comparisons are performed with results obtained from a version modified of CALPUFF using a new dry deposition velocity model. This model is based on a combination of aerodynamic resistances and considers local features of the mutual influence of inertial impact and turbulent processes. The results show that the modified CALPUFF code seems to be an appropriate tool for performing impact assessments on long-range transport in complex terrain contexts or to support preparedness and response capabilities for nuclear and radiological accidents.
Heat flux measurement approach for an enhanced thermometric method: preliminary tests
Authors: Evangelisti L , Barbaro L , De Cristo E , Guattari C , D’Orazio T , Asdrubali F , De Lieto Vollaro R
Published: February 2024

In situ tests are suitable to confirm the real thermal performance of building components, and several significant on-site measurement techniques have been studied in literature. However, among them the Thermometric (THM) method has been poorly examined by the scientific community, thus having opportunities for improvement, being a quite a new and non-standardized technique. The theory behind this technique is the Newton’s law of cooling and the main issue is associated to the heat transfer coefficient for which there is no agreement about the value to use. Here, a simple experimental apparatus characterized by a vertical heated sample, suitably thermally insulated was realized. Sensors were installed and direct heat flux measurements through a heat flux plate were performed and compared with (i) the heat flows obtained through the THM method (test conducted using the internal heat transfer coefficient recommended by the ISO 6946) and (ii) the heat fluxes obtained through the proposal of an enhanced THM method based on dimensionless groups analysis, thus requiring data processing based on convective and radiative components.
An overview of the Transient Hot Wire and preliminary studies for its implementation
Authors: Ricciu R , Congedo P M , Baglivo C , Baccoli R , Buonomo P L M , Mastino C C , Floris F , Cambuli F , Ostrogorsky A G
Published: February 2024

The opportunity to design a new portable system for measuring thermal conductivity in fluids arose from the need to measure the phase state (liquid and/or vapour). As is well known, thermal conductivity varies in relation to the phase state of the fluid. The Transient Hot Wire Method was used to measure thermal conductivity. First, the work includes innovations in the analytical model of heat transfer, progressing over time to contemporary numerical models used in standards. The applications in the bibliography span a wide range, including gases, liquids, and the latest advances in the field of nanofluids. Secondly, the study delves into the transient model of heat exchange, focusing on conduction. The authors used standardized correction equations for the prototype, ensuring accuracy and relevance. Finally, the work includes the design and construction of the transducer. This process begins with a Monte Carlo simulation, predicting the expected results. This simulation helps to define measurement system components based on their performance characteristics and in-depth analysis.
Retro-reflective plaster coatings after outdoor aging and soiling: an in-lab optical performance characterization
Authors: Di Giuseppe A , Pazzaglia A , Castellani B , Nicolini A , Rossi F , Cotana F
Published: February 2024

The potential benefits of highly reflective and retro-reflective (RR) materials on urban context have been performed by several studies through their optical characterization. During their lifetime, outdoor aging and soiling can affect the RR optical behaviour. To this aim, this study investigates the performance of RR plaster coatings after outdoor aging and soiling from May to October 2022 in Perugia, Italy. The same RR plaster coatings in pristine conditions were already characterized in lab in terms of optical performance. In particular, RR samples obtained by using glass beads with different diameters (i.e., 40 ÷ 70 μm and 70 ÷ 110 μm) distributed in three superficial density ranges (i.e., 0.30 ÷ 0.40 kg/m2, 0.20 ÷ 0.30 kg/m2 and 0.10 ÷ 0.20 kg/m2) have been investigated in this study through spectrophotometric and angular reflectivity analyses. In all cases, the post-aging RR samples exhibit lower global reflectance values with respect to the same RR samples in pristine condition. Concerning the angular reflection distribution analysis, a stronger relative RR component was found for the post-aging RR sample with an average diameter of 70 ÷ 110 µm and superficial density distribution equal to 0.10 ÷ 0.20 kg/m2 for each investigated incident direction.
Two Phase Bubble Columns: the Determinants of the Flow Regime Transitions
Authors: Varallo N , Besagni G , Mereu R , Inzoli F
Published: February 2024

The fluid dynamics in large-diameter bubble columns can be described by an analytical relation between two global flow parameters, the drift flux and the gas holdup. This relation, named bubble column operating curve, builds on five flow regime transitions. In order to determine the variables influencing the flow regime transitions, a statistical approach was derived by coupling: (1) the ordinary least squares method (OLS) to determine the relationship between the variables, (2) the variance inflation factor (VIF) to check for multicollinearity issues, and (3) the least absolute shrinkage and selection operator (LASSO), to select suitable variables. It was found that the geometrical characteristics of the sparger strongly influence the flow regime transitions, and uniform aeration is essential for all the regimes to exist. Increasing the superficial liquid velocity in the counter-current mode destabilises the mono-dispersed and poly-dispersed homogeneous flow regimes. As for the aspect ratio, an increase in the column aspect ratio slightly destabilises the existing flow regimes. The statistical method identifies viscosity as the only significative variable concerning the liquid phase properties.
Experimental data for flow boiling of R450A in a horizontal tube
Authors: Mastrullo R , Mauro A W , Passarelli A F , Viscardi I , Viscito L
Published: February 2024

According to the new European policies aimed at the replacement of highly-pollutant greenhouse gases refrigerants, the scientific community has focused on new synthetic environmentally friendly substances to be employed in vapor compression cycles for the refrigeration and the air conditioning fields.

On this regard, R450A is a new blend made up of R134a (42%) and R1234ze (58%), having a GWP equal to 604, and therefore represents an attractive solution as pure R134a substitute. In this paper, new flow boiling heat transfer and pressure drop data of R450A collected at the refrigeration lab of Federico II University of Naples are presented. The data refer to a horizontal stainless-steel tube having an internal diameter of 6.0 mm. The effects of mass flux (from 150 to 400 kg m−2s−1), heat flux (from 10 to 20 kW m−2) and saturation temperature (from 30 to 50 °C) are presented and discussed, together with the assessment of the most quoted two-phase heat transfer and pressure drop prediction methods.
The DEPLOY! Project: Development of a Deployable Pulsating Heat Pipe experiment on a parabolic flight
Authors: Billi A. , Perna R. , Picchi S. , Rosellini V. , Saltmarsh E. , Bocelli M. , Ricci N. , Miché N. , Bozzoli F. , Mameli M. , Filippeschi S.
Published: February 2024

DEPLOY! Project aims at analysing the behaviour of Deployable Pulsating Heat Pipe (PHP) shaped as a helicoidal torsional spring in the adiabatic section on board a Parabolic Flight platform. A PHP is a passive thermal control device where the heat is efficiently transported by means of the self-sustained oscillatory fluid motion driven by the phase change phenomena. The microgravity environment allows to eliminate the buoyancy force contribution in the liquid phase momentum. Consequently, it is possible to isolate the contribution of the pressure drop caused by the 3D arrangement and infer on their effect on the PHP performance. As a result, a proper design based on the previous considerations would increase the flexibility of the PHP for use in space applications without significant reductions in efficiency. The goal of DEPLOY! is to demonstrate the functionality of a Deployable Pulsating Heat Pipe in various unfolding configurations by analysing its thermal-hydraulic response throughout a Parabolic Flight. The presented Deployable PHP is composed of an aluminium tube (inner/outer diameters 1.6mm/2.6 mm) and filled with HFE-7000. It is heated at the evaporator using a flat heater and cooled at the condenser with a water-cooled cold plate. T-type thermocouples are used to measure the wall temperature in several locations, while two pressure transducers (one located in the evaporator section and another in the condenser section of the same pipe) measure the local fluid pressure. Additionally, an IR Camera will be used to observe a section of the pipe for further analysis of the flow frequency. The device operation will be tested on ground and 0-g at different heat loads (24W, 34W), in multiple static positions corresponding to different opening angles (0°, 45°, 90°, 135°, 180°) and during its dynamic opening from 0° to 180°, thanks to a remotely controllable motion system.
Estimation of Internal Heat Flux on Pulsating Heat Pipes using Kalman Filter: Numerical and Experimental Results
Authors: Margotto B H M , Colaço M J , Kopperschmidt C E P , Bozzoli F , Pagliarini L , Cattani L , da Silva W B , Hamada M , Nagano H
Published: February 2024

Pulsating Heat Pipes (PHPs) are two-phase passive thermal devices characterized by the presence of significant fluid oscillations inside the tubes that permit to fast and efficiently transfer heat from a hot region to a cold one. They are present in many engineering applications, e.g., electronics, sustainable energies, aerospace. They are very attractive due to their high heat removal capability, flexibility, and low manufacturing cost. Although they have been widely studied their working principles are still not fully understood. To better comprehend their thermal behaviour recent works presented different approaches to assess the internal heat flux in PHPs. However, all the adopted approaches are based on whole-domain techniques that require a higher computational cost compared with sequential estimations. Therefore, to allow heat flux estimation with lower computational effort, in this work a procedure based on the Kalman filter has been adopted. The heat flux has been estimated by solving the inverse heat conduction problem in the PHP’s wall adopting as input data the temperature measurement on the external surface of the pipe acquired by an infrared camera. Firstly, the procedure has been validated adopting synthetic data. Then, experimental data referring to actual operating conditions have been employed to estimate the internal heat flux. The Kalman filter has been adopted as technique to solve the classical instability intrinsically present in inverse problems. It is relatively simple to implement and requires only previous time information, requiring low computational costs. Moreover, the Kalman filter allows the real time estimation of the heat flux: assessing the heat flux on PHPs during operation could be a useful instrument to provide information about on-time working conditions and thus avoid any possible malfunctioning.
Numerical study of the Thermo-hydrodynamic behavior of a non-Newtonian nanofluid in a backward facing step
Authors: Mokhefi A. , Rossi di Schio E. , Valdiserri P. , Biserni C. , Derbal D.
Published: February 2024

In the present work, a numerical simulation of a laminar non-isothermal flow of a non-Newtonian nanofluid in a backward facing step (BFS) is presented. It deals with Cu-water nanofluid, where the mixture shows a shear thinning behavior flowing from the restricted part of the duct with a fully developed velocity and a cold temperature. The lower part of the extended area of the backward facing step is maintained at a hot temperature, while all the other boundaries are considered thermally insulated. Moreover, a uniform magnetic field according to different angle is applicated on the nanofluid flow. The numerical simulation is based on the resolution of the mass, momentum and energy balance equations using Comsol Multiphysics. The aim of the sensitivity study is to highlight the impact of the Reynolds number, the nanoparticles concentration, the Hartmann number and the angle of the magnetic field on the flow and the thermal behaviours, as well as on the Nusselt number. Surprisingly, the results show that an increase in the Hartmann number, corresponding to a more intense magnetic field, resulted in a significant reduction in flow intensity.