bluuebunny/crossref_metadata_2025 huggingface dataset:
Chaotic band-gap modulation mechanism for nonlinear vibration isolation systems based on time-delay feedback control
Authors: Zhang Yongyan , Liu Qinglong , Wu Jiuhui , Liu Hui , Yang Leipeng , Zhao Zebo , Chen Liming , Chen Tao , Li Suobin
Published: September 2024

Systems designed for nonlinear vibration isolation that incorporate chaotic states demonstrate superior capabilities in vibration attenuation, adeptly modulating the spectral constituents of vibrational noise. Yet, the challenge of eliciting low-amplitude chaotic dynamics and perpetuating these states across a diverse array of parameters remains formidable. This study proposes a pioneering strategy and technique for modulating the chaos band by incorporating a time-delayed feedback control mechanism within the framework of nonlinear vibration isolation systems.The investigation commences with an exhaustive analysis of the nonlinear dynamics, shedding light on the principles dictating the evolution of chaos. The study then advances to scrutinize the dynamics of systems with delays to elucidate the chaos-inducing processes engendered by feedback with temporal lags. Building upon the system’s responses, the chaotic performance and the effectiveness of the vibration isolation are crafted. Consequently, the time-delayed feedback control parameters are identified as pivotal design variables, which are then employed to dissect the control mechanisms influenced by the time-delayed feedback on the chaos band. Utilizing the delineated control mechanism, the nonlinear vibration isolation system is precipitously transitioned from a state of stable periodicity to one of chaos, fostering low-amplitude chaotic dynamics across an expansive parameter space, and in turn, resolving the previously stated challenge. Perhaps most significantly, the mechanism for attaining low-amplitude chaos introduced here paves the way for innovative methodologies in the active vibration isolation design of similar systems. Furthermore, it is anticipated to yield theoretical guidance for the manipulation of chaos bands and the formulation of active vibration isolation strategies within the domain of nonlinear vibration isolation systems.
Aging of epoxy cast insulation with different voltages and environmental stresses
Authors: Shang Xingyu , Pang Lei , Tang Wanlin , Bu Qinhao , Zhang Qiaogen
Published: September 2024

Power electronic conversion systems introduce different types of voltage stresses on high-voltage epoxy cast insulation in medium-frequency transformers (MFTs), which challenges the reliability of MFTs. The endurance of epoxy insulation at different voltages (AC, DC and pulse) and environmental (thermal and humidity) stresses was studied using encapsulated electrodes in the absence of partial discharge. To assess aging processes and select aging state indicators, various tests including AC breakdown strength (BDE), broadband dielectric spectroscopy, small-angle x-ray scattering (SAXS), Fourier-transform infrared spectroscopy and differential scanning calorimetry (DSC) were first conducted on aged flat samples. The increase of mesoscopic free volume from the SAXS result and local densification (physical aging) of epoxy network from the DSC result were both found. BDE is proved to be sensitive to various aging conditions and thus determined as a test method for encapsulated samples. It is found that the physical aging effect under thermal stress at early aging stages can cause a reversible increase in BDE compared to non-aged samples. This effect can be erased by coupled medium-low electrical stress during aging. In contrast, a sufficiently high electric field will deepen the physical aging extent. Occasional sample failures were observed simultaneously within this process. According to the SAXS and DSC results on flat samples, the failure of encapsulated samples is possibly attributed to the chain fracture around increased mesoscopic free volume during electron bombardment and microcracks generated by interfacial stress release during physical aging. At longer aging periods, the volumetric absorption and diffusion of chemical reactants (oxygen and water) in epoxy networks at high temperatures determines the eventual decrease in BDE, which can be accelerated by the electric field. Ages with different voltage types were gauged by the reduction of BDE compared to pure environmental stress. Bipolar pulses bring heavier aging effects than ACs at the same RMS value. However, the DC component has opposite effects on the BDE with and without thermal stress.
On the charge transport models in high intrinsic defect doped transparent and conducting p-type Cu–Cr–O delafossite thin films
Authors: Crepelliere Jonathan , Moreira Marco , Lunca-Popa Petru , Leturcq Renaud , Lenoble Damien
Published: September 2024

In contemporary optoelectronic devices, the transparent conductive oxides commonly demonstrate n-type conduction characteristics, with indium-doped tin oxide emerging as a prominent example. However, in applications involving fully invisible electronics that necessitate p-type conductive oxides, there exists a demand for a quintessential material possessing properties akin to its n-type counterpart. CuCrO2, a delafossite semiconductor based on copper, presently represents a notable compromise between optical and electrical attributes within the realm of p-type semiconductors. Despite numerous studies focusing on this material, the charge carrier transport regime within the material remains unclear. The commonly reported hole transport mechanism in CuCrO2 is the small polaron model. However, this work evidences several contradictions when this transport mechanism is assumed. Using the same methodology as previous studies, we investigated the holes’ transport mechanism by the means of the measurement of electrical conductivity and the Seebeck coefficient at varying temperatures. Different charge transport models in high intrinsic defect doped CuCrO2 thin films are explored: small polarons, grain boundaries scattering in degenerate semiconductors, and variable range hopping with nearest neighbor hopping. The small polaron model does not provide conclusive results within the temperature range analyzed. Interestingly, no specific hole transport mechanism can be undoubtedly selected. The limitations of the models highlight the influence of peculiar defects within CuCrO2 thin films on the hole transport mechanism, particularly the adoption of well-ordered copper vacancies columns.
Physical understanding of a normally off p-GaN/AlGaN/GaN HEMT gate stack and a review of VTH measurement techniques
Authors: Murukesan Karthick , Efthymiou Loizos , Udrea Florin
Published: September 2024

In this report, a comprehensive review of the variations in threshold voltage (V
TH) that could arise due to different V
TH measurement techniques, V
TH measurement bias conditions and V
TH extraction techniques is made. Notably, a standard deviation of 15% is observed in threshold voltage values due to variations in measurement methodology and bias conditions. This variation is attributed to the change in the dynamic gate charge conditions across the gate stack and lateral electric field conditions across the gate and drain, which occur due to the change in measurement conditions and the bias conditions, respectively. No significant variations arise due to the V
TH extraction technique. Additionally, a simplified physical interpretation of the gate stack in normally off p-GaN gate/AlGaN/GaN on Si high electron mobility transistors is made. The formation of the two-dimensional electron gas, the charge balance within the p-GaN/AlGaN/GaN gate stack and an analytical expression for the threshold voltage are reviewed and examined. Furthermore, various trapping mechanisms within the gate stack are reviewed to comprehend the dynamic conditions potentially contributing to threshold voltage instability during nominal operation.
Ionizing radiation and skin cancer—a review of current evidence
Authors: Caramenti Luca , Breckow Joachim , Hildebrandt Guido , Drexler Hans , Volkmer Beate , Hauptmann Michael
Published: September 2024

Cancer of the skin represents a challenge for radiological protection, as it is very common and involves the largest organ of the human body, which is exposed to environmental stress, including ionizing radiation (IR). The most common subtypes, basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), have very low mortality. Current consideration of skin cancer in radiological protection is mainly based on data from the 1990s, which indicate that BCC may be induced by IR, SCC is only weakly associated with IR, and malignant melanoma (MM) is not considered as IR-induced. In a semi-systematic review of the evidence between 1990 and 2023, we snowballed 20 index articles. We identified 33 articles with information on a potential dose-response relationship between skin cancer and IR exposure and assessed the evidence for a causal association. Exposure situations included a-bomb survivors, therapeutic and occupational exposure (airlines, nuclear and medical facilities) and residents exposed to radon or other radiation sources. There is currently no epidemiological evidence that MM or SCC are caused by IR. The only skin cancer type with evidence for a causal relationship is BCC, and evidence is limited to exposures above about 0.5 Gy with a wide range of risk levels per dose. Thus, IR-inducible skin cancer refers to BBC only and only at levels of exposure beyond those experienced by the vast majority of people exposed today.
Simple, innovative and attractive approach for geometrical optics, chromatic aberration and colour combination experiments
Authors: Rivera-Ortega Uriel
Published: September 2024

The laws of reflection and refraction and therefore the basic concepts of image formation with lenses are some topics that geometric optics deals with. Therefore, in this manuscript, laboratory practices are proposed that will cover concepts of geometric optics using both technological tools and everyday materials that allow the undergraduate or graduate student to obtain these concepts leaving the classical way in which they are usually addressed in classrooms or laboratories. Activities are also proposed that demonstrate phenomena such as chromatic aberration and the combination of red, green and blue (RGB) colours. For this purpose, electronic devices such as a Raspberry-pi (with a sense HAT module), a commercial programmable LED matrix, a hollow Christmas spheres, etc, will be used; giving a novel approach and allowing the use of new motivating technologies for both students and/or educators.
Heating characteristic of electron Bernstein wave using high-field side X-mode injection in QUEST
Authors: Murakami Takahiro , Kojima Shinichiro , Hanada Kazuaki , Idei Hiroshi , Ido Takeshi , Ikezoe Ryuya , Hasegawa Makoto , Onchi Takumi , Kono Kaori , Kuroda Kengoh , Ejiri Akira
Published: September 2024

A comparative investigation was conducted to assess the impact of high-field side (HFS) extraordinary (X) mode (HFS X) injection and low-field side (LFS) ordinary (O) mode (LFS O) injection of 8.2 GHz radio frequency (RF) power in the Q-shu University experimental steady-state spherical tokamak. In the case of the HFS X injection, the ratio of electron plasma frequency and RF frequency

f

pe

/

f

RF

was 1.3, indicating an overdense plasma, whereas in the LFS O injection, this ratio was 0.9. Distinctive features emerged in the electron temperature and density profiles between the two injection scenarios. In the HFS X injection, the profiles peaked between the fundamental electron cyclotron resonance (ECR) layer and the upper hybrid resonance layer. Conversely, in the LFS O injection, the peaks were situated near the 1st ECR layer. This implies effective excitation of the electron Bernstein wave (EBW) in the case of the HFS X injection, with the wave power being absorbed through the doppler-shifted ECR of the EBW. Density and temperature oscillations were observed only in the start-up phase of the HFS X injection, which may correlate with the presence of the left-hand cutoff of the X-mode. These findings will be contributed to understand the distinctive characteristics associated with plasma heating through EBW excitation in the HFS X injection.
Seismic performance improvement of a three-dimensional isolated spherical reticulated shell structure using pseudo-negative-stiffness magnetorheological dampers
Authors: Zhuang Peng , Hu Xiaoyu , Zhang Guowei
Published: September 2024

Three-dimensional (3D) isolation is a promising solution for providing comprehensive seismic protection to large-span spatial structures against both horizontal and vertical ground motions. This study introduces an innovative 3D isolation system for spatial reticulated shell structures using pseudo-negative-stiffness magnetorheological dampers (PNSMRDs). In the vertical direction, the PNSMRDs are connected in parallel with a prepressed spring device (PSD)-based bearing (PSDB) to form a PSDB-PNSMRD isolator that supports the reticulated shell roof. A set of semi-active control methods was established for the real-time current input to the PNSMRDs, simulating the related pseudo-negative-stiffness and energy dissipation behaviors of the damping device. A single-layer spherical reticulated shell with surrounding columns was taken as a prototype structure. The PSDB-PNSMRD isolators and concave sliding bearings were designed as a decoupled 3D isolation system for this prototype structure. For comparison, a counterpart 3D isolation system featuring passive viscous dampers was also evaluated. Seismic responses of the isolated and non-isolated structures under triaxial seismic excitations were modeled using an integrated OpenSees‒MATLAB platform. The numerical results reveal that both isolation systems are effective in mitigating structural responses, with the PSDB-PNSMRD bearings providing superior vertical isolation effects compared to passive vertical isolation bearings.
Effect of Sm2O3 on thermal, optical, mechanical, gamma and neutron shielding properties of zinc-boro-vanadate glasses
Authors: Devidas Ashwini , Sankarappa T , Malge Amarkumar , Heerasingh Mohansingh , Dyama Aravind , Pallavi Jamadar
Published: September 2024

The effect of Sm2O3 on thermal, optical, mechanical, gamma and neutron shielding properties of newly prepared zinc borovanadate glasses has been investigated. Density is found increased and molar volume decreased with Sm2O3 content. The glass transition temperature

(

T

g

)
,

crystallization temperature

(

T

c

)

and the peak crystallization temperature

(

T

P

)

increased with increase of rare earth oxide content. These findings demonstrated an excellent glass-forming ability and thermal stability of the glasses. The optical properties have been explored through UV–vis spectroscopy. The indirect optical band gap energy

(

E

opt

)

decreased from 2.978 to 2.679 eV, Urbach energy

(
∆
E
)

increased from 0.273 to 0.299 eV and refractive index increased from 2.403 to 2.489 with increase in Sm2O3. Elastic moduli, Poisson’s ratio, Hardness and fractal bond connectivity were computed theoretically as per Makishima Mackenzie model. It is found that these glasses have appreciable mechanical strength and rigidity. Phy-X/PSD software has been used to determine different radiation shielding characteristics for the energy range 0.015–15 MeV. The mass and linear attenuation coefficients are found higher, and half value layer, tenth value layer and mean free paths are found lower than many radiation shielding glasses quoted in the literature values. The obtained

Z

eq

values varied from 15.828–29.118 for energy range from 0.015 to 15 MeV, which are greater than those reported for several commercial glasses, concretes and rocks. Due to the Compton scattering process, exposure build up and energy absorption factor are found to be highest in the medium energy region. The fast neutron removal cross-sections of the glasses are observed to be significantly high. For the first time, thermally stable and mechanically strong zinc borovanadate glasses mixed with Sm2O3 have been thoroughly investigated for various properties and concluded that these glasses are suitable for optoelectronics and γ-shielding applications.
Three different topologies for 4-bit counters in quantum-dot cellular automata technology
Authors: Kiani Vosta Pezhman , Gholami Mohammad
Published: September 2024

QCA (Quantum-dot Cellular Automata) technology is an innovative technology based on quantum principles and uses quantum dots as the basic units for information transfer. This technology enables the fabrication of electronic circuits at high speed, lower power consumption and smaller size. For this reason, in this article, for the first time, three types of counters are designed in QCA technology with the least cell and the smallest area. First, Johnson ring counter with 132 cells, area of

0.16

μ
m

2

and a delay of 2 clock cycles, then synchronous counter with 192 cells and area of

0.2

μ
m

2

and finally synchronous with reset capability with 267 cells and area of ​

0.27

μ
m

2

is designed. Also, the number of cells and the occupied area of the proposed designs have improved by

25.82
%

and

35
%
,

respectively, compared to different authorities. As a result, the proposed designs are among the most optimal designs among different authorities. All the simulations were done in QCAPro and QCADesigner version 2.0.3 softwares.
Exploring thermodynamic, physical and radiative interaction properties of quinary FeNiCoCr high entropy alloys (HEAs): a multi-directional characterization study
Authors: ALMisned Ghada , Güler Ömer , Özkul İskender , Sen Baykal Duygu , Alkarrani Hessa , Kilic G , Mesbahi A , Tekin H O
Published: September 2024

To qualify for nuclear applications, materials must meet specific criteria, including mechanical properties, high-temperature behavior, corrosion resistance, and high-temperature oxidation resistance. High Entropy Alloys (HEAs) are particularly suitable for these applications due to their unique properties. Consequently, we conducted a theoretical and simulation-based approaches to assess some critical properties including radiation shielding properties of some quinary FeNiCoCr HEAs. In this study, we focused on quinary FeNiCoCr HEAs, whose corrosion properties have been previously examined in the literature. We investigated the thermodynamic and radiation shielding properties of HEAs with sixteen different compositions. Our methodology included evaluating thermodynamic parameters such as Mixing Entropy (∆Smix) and Mixing Enthalpy (∆Hmix), as well as structural characteristics like Valence Electron Concentration (VEC) and Atomic Size Difference (δ). This allowed us to systematically deduce the phase behavior and stability of various HEAs. Through computational modeling, we assessed the radiation shielding capabilities of these alloys, particularly their effectiveness in attenuating gamma ray and fast neutrons. The results identified FeNiCoCrW as the alloy with the lowest fast neutron removal cross-section values, highlighting its potential for nuclear applications. Its high melting point and the synergistic interplay between its elemental composition and thermodynamic properties suggest broad applicability in extreme environments. Thus, FeNiCoCrW emerges as a promising HEA with multifunctional capabilities, warranting further exploration and potential integration into advanced engineering solutions.
Modeling optical systematics for the Taurus CMB experiment
Authors: Adler Alexandre E. , Austermann Jason E. , Benton Steven J. , Duff Shannon M. , Filippini Jeffrey P. , Fraisse Aurelien A. , Gascard Thomas , Gibbs Sho M. , Gourapura Suren , Hubmayr Johannes , Gudmundsson Jon E. , Jones William C. , May Jared L. , Nagy Johanna M. , Okun Kate , Padilla Ivan , Rooney Christopher , Tartakovsky Simon , Vissers Michael R.
Published: September 2024

We simulate a variety of optical systematics for Taurus, a balloon-borne cosmic microwave background (CMB) polarisation experiment, to assess their impact on large-scale E-mode polarisation measurements and constraints of the optical depth to reionisation τ.
We model a one-month flight of Taurus from Wanaka, New Zealand aboard a super-pressure balloon (SPB).
We simulate night-time scans of both the CMB and dust foregrounds in the 150 GHz band, one of Taurus's four observing bands.
We consider a variety of possible systematics that may affect Taurus's observations, including non-gaussian beams, pointing reconstruction error, and half-wave plate (HWP) non-idealities.
For each of these, we evaluate the residual power in the difference between maps simulated with and without the systematic, and compare this to the expected signal level corresponding to Taurus's science goals.
Our results indicate that most of the HWP-related systematics can be mitigated to be smaller than sample variance by calibrating with Planck's TT spectrum and using an achromatic HWP model, with a preference for five layers of sapphire to ensure good systematic control.
However, additional beam characterization will be required to mitigate far-sidelobe pickup from dust on larger scales.
Quantum metrology with optimal control under an arbitrary non-Markovian bosonic environment
Authors: Zhou Likun , Yang Wen
Published: September 2024

Finding the optimal control is of importance to quantum metrology under a noisy environment. In this paper, we tackle the problem of finding the optimal control to enhance the performance of quantum metrology under an arbitrary non-Markovian bosonic environment. By introducing an equivalent pseudomode model, the non-Markovian dynamic evolution is reduced to a Lindblad master equation, which helps us to calculate the gradient of quantum Fisher information and perform the gradient ascent algorithm to find the optimal control. Our approach is accurate and circumvents the need for the Born–Markovian approximation. As an example, we consider the frequency estimation of a spin with pure dephasing under two types of non-Markovian environments. By maximizing the quantum Fisher information at a fixed evolution time, we obtain the optimal multi-axis control, which results in a notable enhancement in quantum metrology. The advantage of our method lies in its applicability to the arbitrary non-Markovian bosonic environment.
Effect of Mn element on shock response in CoCrFeNiMnx high entropy alloys
Authors: Wen 闻 Peng 鹏 , Du 杜 Changxing 长星 , Tao 陶 Gang 钢 , Ding 丁 Guipeng 贵鹏
Published: September 2024

The effect of Mn element on shock response of CoCrFeNiMn
x
high entropy alloys (HEAs) are investigated using molecular dynamics simulations. Structural analysis shows that Mn-rich CoCrFeNiMn
x
HEA has a larger average atomic volume. The elastic properties of CoCrFeNiMn
x
HEAs under various hydrostatic pressures are studied, revealing that the elastic modulus decreases with increasing of Mn content. The shock thermodynamic parameters are quantitatively analyzed. The Mn-dependent shock Hugoniot relationship of CoCrFeNiMn
x
HEAs is obtained: U
s = 1.25 + (5.21–0.011x)U
p. At relatively high shock pressure, the increase in Mn content promotes the formation of clustered BCC structures and hinders the development of dislocations. In addition, more FCC structures in Mn-rich CoCrFeNiMn
x
HEAs transform into disordered structures during spallation. Spall strength decreases with increasing Mn content. This study can provide a reference for the design and application of CoCrFeNiMn HEAs under shock loading.
Saturation of fishbone instability through zonal flows driven by energetic particle transport in tokamak plasmas
Authors: Brochard G. , Liu C. , Wei X. , Heidbrink W. , Lin Z. , Falessi M.V. , Zonca F. , Qiu Z. , Gorelenkov N. , Chrystal C. , Du X. , Bao J. , Polevoi A.R. , Schneider M. , Kim S.H. , Pinches S.D. , Liu P. , Nicolau J.H. , Lütjens H. ,   the ISEP group
Published: September 2024

Gyrokinetic and kinetic-MHD simulations are performed for the fishbone instability in the DIII-D discharge #178631, chosen for validation of first-principles simulations to predict the energetic particle (EP) transport in an ITER pre-fusion baseline scenario. Fishbone modes are found to generate zonal flows, which dominate the fishbone saturation. The underlying mechanisms of the two-way fishbone-zonal flows nonlinear interplay are discussed in details. Numerical and analytical analyses identify the fishbone-induced EP redistribution as the dominant generation mechanism for zonal flows. The zonal flows modify the nonlinear dynamics of phase space zonal structures, which reduces the amount of EPs able to resonate with the mode, leading to a lower saturation amplitude. Simulation results including zonal flows agree quantitatively with DIII-D experimental measurements of the fishbone saturation amplitude and EP transport, supporting this novel saturation mechanism by self-generated zonal flows. Moreover, the wave-particle mode-locking mechanism is shown to determine quantitatively the fishbone frequency down-chirping, as evident in GTC simulation results in agreement with predictions from analytical theory. Finally, the fishbone-induced zonal flows are possibly responsible for the formation of an ion internal transport barrier (ITB) in the DIII-D discharge. Based on the low EP transport and the large zonal flow shearing rates associated with the fishbone instability in gyrokinetic simulations of the ITER scenario, it is conjectured that high performance scenarios could be designed in ITER burning plasmas through fishbone-induced ITBs.
Comparison of chamber beam geometry robustness to mispointing, imbalance and target offset for direct-drive laser fusion facilities
Authors: Viala D. , Colaïtis A. , Barlow D. , Batani D.
Published: September 2024

This study focuses on the optimization of beam chamber geometry designs for future direct-drive laser facilities. It provides a review of leading target chamber geometries, with a particular emphasis on random errors. Through comprehensive solid-sphere illuminations and analysis, we identify an optimized beam geometry design, highlighting its robustness and performance under realistic experimental conditions. Three major sources of random errors are evaluated, closely linked to experimental evaluations at OMEGA. The findings underscore the importance of optimizing the irradiation system alongside beam pattern considerations to enhance the efficiency and reliability of inertial confinement fusion experiments. We conclude that for a desired illumination uniformity of 1% in the presence of system errors, the split icosahedron design is the most robust. However, for a 0.3% uniformity goal, the charged-particle, icosahedron, and t-sphere methods exhibit similar performance.
Detecting neoclassical tearing modes in high-temperature ITER plasma scenarios with the ITER prototype electron cyclotron emission diagnostic
Authors: Ziegel Joseph P. , Rowan William L. , Waelbroeck François L.
Published: September 2024

Electron cyclotron emission (ECE) diagnostics for ITER serve two key purposes. The diagnostics will measure plasma electron temperature with high spatial and temporal resolution. Additionally, they will be used to detect neoclassical tearing modes (NTMs), a deleterious and nonlinearly unstable mode causing the growth of magnetic ‘seed’ islands. Interpreting ECE requires anticipation of physical limits including frequency cut-offs and harmonic overlap. In high temperature plasmas, the relativistic shift and broadening of the emission must also be considered to accurately reconstruct the electron temperature spatial profile. Accounting for these effects allows ECE diagnostics to be used for accurate measurement of the equilibrium electron temperature profile, as well as fluctuations about this equilibrium. One such fluctuation is caused by the fast radial transport of heat across rotating magnetic islands. ECE diagnostics can detect this change as an oscillation at the plasma rotation frequency to determine the existence and location of NTMs. This paper presents work on a synthetic diagnostic for ECE. The synthetic diagnostic tests simulated ECE signals, which are inferred from ITER scenarios perturbed by magnetic islands after accounting for all ECE physics. The synthetic diagnostic tests conventional ECE detection algorithms for NTMs in real-time on ITER-recommended hardware. Combined, these two areas of focus help determine design of the ECE system.
A semi-automated algorithm for designing stellarator divertor and limiter plates and application to HSX
Authors: Davies Robert , Feng Yuhe , Boeyaert Dieter , Schmitt John C. , Gerard Michael J. , Garcia Kelly A. , Schmitz Oliver , Geiger Benedikt , Henneberg Sophia A.
Published: September 2024

We present a semi-automated algorithm for designing three-dimensional divertor or limiter plates targeting low heat loads. The algorithm designs the plates in two stages: firstly, the parallel heat flux distribution is caught on vertically-inclined plates at one or several toroidal locations. Secondly, the power per unit area is reduced by stretching, tilting and bending the plates toroidally. Heat transport is modelled using the EMC3-Lite code, which uses an anisotropic diffusion model. We apply this scheme to HSX, a medium-sized stellarator located at the University of Wisconsin–Madison. Starting from the current machine with an extended vessel wall, we construct plates which are able to effectively catch and spread the heat for three different magnetic configurations. The scheme has a computational cost in the order of tens of CPU-minutes, making it a powerful tool for semi-automated plasma-facing component design in three-dimensional environments.
2D PIC modeling of the helical scrape-off layer current driven by hybrid divertor biased targets in tokamak plasmas
Authors: Cui B.T. , Sun T.F. , Zhong W.L. , Gao Z. , Ji X.Q. , Wu N. , Hao G.Z. , Liang S.Y. , Wang A. , He M.Y , Gao J.M. , Xu M. , Duan X.R.
Published: September 2024

The heat flux control of the divertor plate via strike-point splitting generated by biased targets was proposed in the HL-2A tokamak (Cui et al 2021 Fusion Eng. Des.
173 112963). To understand the helical scrape-off layer (SOL) currents driven by hybrid biasing, two SOL current models (model A and B) are employed. Model A is a simplified 2D model that focuses on investigating the effect of biasing on the sheath and elucidating the fundamental physical mechanism of bias-driven SOL current paths. The potential, charge density, electric field and current densities are calculated. Model B takes into account the actual tokamak geometry and computes the resonant magnetic perturbations (RMPs) generated by bias-driven linear decay currents. Additionally, strike-point splitting is observed in the HL-2A tokamak, indicating that the SOL currents generated by hybrid biasing are capable of generating strong RMPs and consequently influence the magnetic topology. These results confirm the potential of heat/particle flux control by hybrid divertor biased targets.
Credibility Evaluation of Sand-Casting Technique for Manufacturing Francis Runner
Authors: Poudel Ravi , Chitrakar Sailesh , Shrestha Pratisthit Lal , Shakya Tejesh Man , Qian Zhongdong , Guo Zhiwei , Thapa Bhola
Published: September 2024

Francis turbine with its intricate design and the critical nature of its components, involves several complexities and challenges for manufacturing. Francis runners are usually fabricated using high-quality alloy steel. In this study, a 2 kW model Francis runner was manufactured from brass material with sand casting. 3D printing technology was used to create separate molds for the hub, shroud, and runner blade of the Francis turbine. Each component was then sand cast and later joined by brazing. Compared to traditional casting techniques this approach proved to be faster and more cost-effective. Moreover, the defects encountered in the turbine components achieved through the method employed were observed to be less compared to that of investment casting used in previous models. The accuracy of the fabricated model was checked by conducting 3D scanning using the highly precise EinScan HX 3D scanner with a precision of 0.1 mm. The comparisons were made between the 3D scan and the original design. It was found that the deviations on the fabricated runner dimensions as compared to the original designs were below 2 mm. The efficiency measurement of the runner was made at a low head of 4.3 meters and the maximum efficiency obtained was 51.5% at 35% opening of guide vanes. Overall, this method of fabrication proved to be effective in terms of cost and time required for fabrication. This method could be a valuable alternative for smaller-scale turbine production. Further evaluation will be necessary for full-scale commercial applications of this method using high-quality alloy steel.
Comparative Study of Different Erosion Models in Francis Runner Blade Using OpenFOAM
Authors: Shrestha Suprim , Bijukchhe Pawan Lal , Chitrakar Sailesh , Thapa Bhola , Qian Zhongdong , Guo Zhiwei
Published: September 2024

Francis turbine serves as a prominent hydro turbine choice for harnessing water-based energy. However, the presence of sediment particles in river environments poses a considerable challenge for constructing hydropower facilities along sediment-laden rivers. This challenge is particularly pronounced in scenarios involving high- and medium-head hydroelectric power installations. Erosion emerges as a significant concern in such contexts due to the abrasive impact of sediment particles on hydro turbines, which can have adverse effect on its performance, flow dynamics, potentially leading to operational failures. Erosion model is one of the methods used for predicting the erosion rate in hydro turbines. State-of-the-art modelling and simulation using computational fluid dynamics (CFD) are widely adopted methods for predicting erosion. In this study, various commonly used erosion models were implemented and followed by a comparative analysis of the erosion rates predicted by each model. The study utilizes a model runner of Jhimruk Hydropower Plant using OpenFOAM for conducting numerical simulation. The results show variations among the models in identifying areas with the erosion rates due to factors considered by each model. These insights provide a better understanding of how erosion occurs and help in developing strategies for optimizing hydro turbine performance in sediment-laden environments.
Performance analysis of the blade for the v-shaped vertical axis wind turbine
Authors: Sharma Aastik , Zhang Lei , Qu Jianjun , Panthi Sagar
Published: September 2024

A large-scale vertical axis wind turbine (VAWT) can lower the installation, operation, and maintenance cost for offshore areas as compared to the current offshore horizontal axis wind turbine (HAWT) designs. This is because of its simplicity of design and the location of heavy and complex mechanical parts near the water’s surface. On that account, this article studies the aerodynamic performance capacity- the ability to efficiently capture and convert wind energy into rotational mechanical energy- of different blade models for novel V-shaped VAWT It has always been a challenging task to formulate a mathematical model for the complex aerodynamic behavior of the air around the VAWT blades. Nevertheless, previous studies have shown that prediction of the performance has been done more accurately using the CFD model compared to other models. Hence, a similar approach is used for the blade models in this research. The article studies the change in aerodynamic performance of V-VAWT with the change in the shape of its blade using 3D CFD simulation. A transient RANS simulation is carried out for different models of blades. For this, a hybrid mesh model is developed and simulations are conducted in ANSYS Fluent. The mesh independence, time-step independence, and rotation independence tests are completed to reduce errors in the simulation. The coefficient of moment (Cm) developed by the blade for five different blade models is studied. The aerodynamic performance of higher solidity constant chord blades is found to be higher than lower solidity constant chord blades. Also, the performance of tapered blades is found to be better than the constant chord blade, and tapered blades are suggested for the V-VAWT turbine models.
Applications of multi-attribute group decision-making models under triangular interval-type 2 fuzzy to risk preference
Authors: Garg Harish , Kanchana A , Nagarajan D
Published: September 2024

Triangular interval type-2 fuzzy sets, which can handle data with greater ambiguity and uncertainty, can be created by extending type-1 fuzzy sets. They are defined by two membership functions, which are also fuzzy sets. The triangular interval type-2 fuzzy set’s bottom and upper bounds are represented by the membership functions defined over the universe discourse. An improved fuzzy multi-attribute interval-valued approach to group decision-making that takes the decision-maker’s risk preferences into account. The multi-attribute group decision-making problem can be resolved by using triangular interval type-2 fuzzy numbers since the attribute weight information is completely unknown. The triangular type 2 fuzzy entropy and the data from the group decision matrix are used to calculate the attribute and relative weights; the combination of similarity and proximity yields the decision-maker weight of each attribute; the formula for the triangular type 2 fuzzy distance measure yields the overall superiority of each scheme; comparison and sequencing determine which scheme is the best; and finally, a decision pertaining to the manufacturing company’s supplier serves as an example to illustrate the rationale and effectiveness of the proposed strategy.
Prediction of flow stress of Ta–W alloys using machine learning
Authors: Kedharnath A , Kapoor Rajeev , Sarkar Apu
Published: September 2024

The primary aim of this article was to predict the flow stress of Ta–W alloys using the eXtreme Gradient Boosting (XGBoost) machine learning model and to explain the outcome using SHapley Additive exPlanations (SHAP). The article details the effect of temperature, strain rate, and alloying content on the deformation behavior. Though grain size, dislocation density, texture and impurities are also important factors affecting the deformation behavior, these have not been considered in this work. Data and constitutive models from the literature were used to find and compare the predictiveness of the flow stress in Ta–W alloys. XGBoost predicted flow stress with a root mean square error of 12 MPa during training and 40 MPa during testing, while constitutive models such as Johnson–Cook (JC), Zerilli–Armstrong (ZA) and mechanical threshold stress (MTS) models showed a root mean square error of 208, 131 and 149 MPa respectively. The linear correlation between the predicted and experimental flow stress at 10% strain was calculated using the Pearson correlation coefficient and found to be 0.64, 0.93, and 0.70 for JC, ZA and MTS models respectively, while XGBoost showed 0.99 during training and 0.98 during testing. The optimized XGBoost model was validated using five-fold and leave-one-group-out cross-validations. The flow stress at 10% strain was predicted using XGBoost at various temperatures, strain rates, and alloying content. The flow stress was low at temperatures above 1000 K and strain rates below 10−2 s−1. From SHAP analysis, it was found that the base flow stress value (at which the SHAP value is zero) was 477 MPa. For temperatures less than 275 K, strain rates greater than 1 s−1, and alloying content greater than 2.5 wt.% W, the flow stress showed an increase from its base value.
General higher order 𝐿^{𝑝} mean zonoids
Authors: Langharst Dylan , Xi Dongmeng
Published: September 2024

In 1970, Schneider introduced the

m
m

th-order difference body and the associated Rogers-Shephard inequality. Recently, Haddad, Langharst, Putterman, Roysdon and Ye expanded the concept to a burgeoning

m
m

th-order Brunn-Minkowski theory. In 1991, Zhang introduced mean zonoids of a convex body, which was extended to the Firey-Brunn-Minkowski theory setting by Xi, Guo and Leng in 2014. In this note, we extend these

L
p

L^p

mean zonoids to the

m
m

th-order setting and establish the associated isoperimetric inequality.
Civic Solitude
Authors: Talisse Robert B
Published: September 2024

“This is what democracy looks like.” An internet search of that phrase returns thousands of images of people assembled in public to convey a common political sentiment. This makes good sense. Without active citizens, democracy devolves into rule by elites or worse. Public collective action is essential to democracy. Although the images are inspiring, they also present a problem. In addition to being politically active, democratic citizens must be reflective. Their political advocacy must be informed by the perspectives of their fellow citizens. The trouble is that indispensable modes of democratic participation can corrode citizens’ reflective capacities. The culprit is a dynamic called belief polarization. As we interact with our allies, we are exposed to forces that render us more radical in our beliefs and increasingly hostile to those who do not share them. What’s more, we are surrounded by triggers of political extremity and animosity. Thus, our ordinary activities encourage the attitude that democracy is possible only when everyone agrees. That’s a profoundly antidemocratic stance. Drawing on extensive research about polarization and partisanship, Robert Talisse argues that certain core democratic capacities can be cultivated only at a distance from the political fray. If we are to meet the responsibilities of democratic citizenship, we must occasionally step away from our allies and opponents alike. This can be achieved only in secluded settings where we can engage in civic reflection that is not prepackaged in the idiom of our political divides.
What Does Democracy Look Like?
Authors: Talisse Robert B
Published: September 2024

It is common to think that democracy happens out in the open, where everyone can see. So, we tend to regard our civic responsibilities as duties to engage in public and collective action. To be sure, democracy does require us to act together in public. But democracy is more fundamentally a matter of what we bring to collective public engagement—the attitudes, habit, and dispositions that drive us to political action. This chapter set out a conception of the internal requirements of responsible citizenship. It argues that democratic citizens need to advocate in ways that are public-minded, responsive, and transparent. Together, these requirements form a conception of civility. Democratic citizens thus must advocate in ways that are civil. But civility is not a matter of maintaining polite relations with opponents. It rather has to do with our civic character.
The Need for Solitude
Authors: Talisse Robert B
Published: September 2024

The triggers of the polarization dynamic are embedded within our ordinary social spaces. Our day-to-day lives expose us to forces that undermine our democratic capacities. To manage that exposure, we need occasionally to remove ourselves from our typical social surroundings. But we must also distance ourselves from the conceptual and ideological constraints of current partisanship. To manage polarization, then, we need sometimes to engage in solitary reflection that is insulated from triggers of partisan identity. This calls not only for non-commercial spaces where we can be alone with our thoughts, but also access to materials that confront us with political perspectives that are not readily translatable into our partisan idiom.
Fat Grafting and Adipose Stem Cells for Facial Systemic Sclerosis: A Systematic Review of the Literature
Authors: Almadori Aurora , Fung Sze Ching , Denton Christopher P , Butler Peter E M
Published: September 2024

Background

Orofacial modifications occurring in systemic sclerosis are detrimental for patients, but the therapeutic options are limited.

Objectives

This systematic review aimed to perform an up-to-date appraisal of the literature focusing on fat grafting and other adipose stem cell–based therapies for the treatment of facial systemic sclerosis, determining its efficacy and safety, and investigating the current practice for treatment optimization.

Methods

The review was prospectively registered in PROSPERO (CRD42021286268) and followed the PRISMA principles. Multiple databases were searched and only original studies were included.

Results

Over the 12 studies matching the inclusion criteria, 174 patients were treated. Of these, 87.3% (n = 152) were considered to have improved. The complications, graded with the Clavien-Dindo grading system, were Grade 1 (no treatment required) or Grade 2 (antibiotic required). Patients received a mean [standard deviation] of 2.5 [3.68] (median, 1.35; range, 1-14) lipotransfer procedures. Overall, an average volume of 14.60 [6.24] mL was injected in the facial area (median, 16 mL; range, 3-27 mL). The average interval between procedures was 5.30 [2.04] months (median, 6 months; range 3-6.91 months). At the time of inclusion, patients were diagnosed with scleroderma disease on average after 14.7 [7.35] years.

Conclusions

Fat grafting for facial systemic sclerosis is effective and safe. The definitive durability of the effect is still unclear, and the optimal number of treatments must be determined to define a precise evidence-based protocol. The body of evidence is highly fragmented, with disagreements over surgical techniques and outcome assessments, making results from different studies often not comparable. The level of evidence is overall low or very low, and the risk of bias of published studies is overall medium to high. Randomized controlled trials are urgently needed.

Level of Evidence: 3 (Therapeutic)
Evolution of pollen morphology in Calyceraceae and insights into its early evolutionary differentiation
Authors: San Martin Juca A B , Johnson Leigh A , Denham Silvia S , Pozner Raúl
Published: September 2024

Pollen morphology has been a fundamental tool in the study of evolution and phylogeny in angiosperms. As sister to Asteraceae, Calyceraceae provides critical insights into understanding the early diversification of the sunflower family. To date, the most comprehensive palynological studies of Calyceraceae have been based on just a few species and lack a phylogenetic framework. Here we present an evolutionary study of pollen morphology in Calyceraceae based on an almost complete sampling and in light of recent phylogenetic hypotheses for this family. Twenty-seven palynological characters were established after morphological studies with scanning electron and bright field microscopy for 44 species of Calyceraceae. Character analyses included phylogenetic signal and reconstruction of ancestral states. Morphology of the mesocolpium, amb, and apertures support most genera, and provide support for the two main clades of Calyceraceae. We propose five pollen types, namely I–V. Most genera are nearly uniform in pollen morphology except for Gamocarpha, which includes four pollen types. Pollen types I and III, related to the most recent common ancestors (MRCAs) of Acicarpha and Gamocarpha respectively, possess the most apomorphic character states. Pollen types II and V, related to Calycera and Moschopsis MRCAs respectively, retain the most plesiomorphic character states. The major evolutionary changes between pollen of Calyceraceae and its sister group (whether it is Asteraceae or Barnadesioideae) involve mesoaperture development and exine structure. Our results support an independent origin of the mesocolpal concavities in Calyceraceae and its sister group (Asteraceae or Barnadesioideae), and for colpal ledges in Goodeniaceae and Calyceraceae.