bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elliptical high-order harmonic generation from current-carrying orbitals of prealigned molecules
Authors: Wang Kaiyi , Ding Yulin , Wang Feng , Zhang Xiaofan , Liao Qing 
Published: September 2023

Abstract
The polarization of high harmonics generated from current-carrying state of nitric oxide molecules irradiated by linear laser fields is investigated by numerically solving the three-dimensional time-dependent Schrödinger equation. It is found that the ellipticity of high harmonics is obviously dependent on the polar angle between the driving laser polarization and molecular axis which is interpreted by the strong field approximation model. Moreover, our results also show that the helicity of near-threshold harmonics is opposite to that of plateau harmonics when the molecule is at any polar angle. To analyze this phenomenon, we simulate the dipole matrix element numerically. Finally, the attosecond pulses with opposite helicities can be obtained by synthesizing near-threshold and plateau harmonics. The ellipticity can be tuned by the alignment angle of molecules. Our work may provide a theoretical guiding and detection tool for the electron dynamics of molecular current-carrying states.
Physics of large thermoelectric power factors in SnSe nanoflakes in mid-temperature range
Authors: Panwar Anjali , Sonnathi Neeleshwar , Mahanti Subhendra D , Malik Vikas , Bagga Anjana 
Published: September 2023

Abstract
We have theoretically investigated the underlying physics of observed high electrical conductivity (σ), simultaneous increase of σ and Seebeck coefficient (S) with temperature, and large power factors (PFs) in nominally undoped SnSe nanoflakes sintered at different temperatures, reported recently in Mandava et al (2022 Nanotechnology
33 155710). Given the fact that S and σ show unusual temperature trends and that the undoped SnSe samples are highly porous and disordered, the conventional Boltzmann theory does not appear to be an appropriate model to describe their transport properties. We have, instead, used a strong disorder model based on percolation theory where charge and energy transport take place through hopping between localized states to understand these observations. Our model is able to explain the observed temperature dependence of σ and S with temperature. Large σ can be explained by a high density of localized states and a large hopping rate. The sample sintered at a higher temperature has lower disorder (σ
DOS) and higher hopping rate (1/τ
0). We find σ
DOS = 0.151 eV and 1/τ
0 = 0.143 × 1015 s−1 for sample sintered at 673 K and σ
DOS = 0.044 eV and 1/τ
0 = 2.023 × 1015 s−1 for sample sintered at 703 K. These values are comparable to the reported values of transition frequencies, confirming that the dominant charge transport mechanism in these SnSe nanoflakes is hopping transport. Finally, we suggest that hopping transport via localized states can result in enhanced thermoelectric properties in disordered polycrystalline materials.
Block sparsity promoting algorithm for efficient construction of cluster expansion models for multicomponent alloys
Authors: Thekkepat Krishnamohan , Das Sumanjit , Prosad Dogra Debi , Gupta Kapil , Lee Seung-Cheol 
Published: September 2023

Abstract
Multicomponent alloys are gaining significance as drivers of technological breakthroughs especially in structural and energy storage materials. The vast configuration space of these materials prohibit computational modeling using first-principles based methods alone. The cluster expansion (CE) method is the most widely used tool for modeling configurational disorder in alloys. CE relies on machine learning algorithms to train Hamiltonians and uses first-principles calculated data as training sets. In this paper we present a new compressive sensing-based algorithm for the efficient construction of CE Hamiltonians of multicomponent alloys. Our algorithm constructs highly sparse and physically reasonable models from a carefully selected small training set of alloy structures. Compared to conventional fitting algorithms, the algorithm achieves more than 50% reduction in the training set size. The resultant sparse models can sample the configuration space at least 3 × faster. We demonstrate this algorithm on 4 different alloy systems, namely Ag–Au, Ag–Au–Cu, Ag–Au–Cu–Pd and (Ge,Sn)(S,Se,Te).The sparse CE models for these alloys can rapidly reproduce known ground state orderings and order-disorder transitions. Our method can truly enable high-throughput multicomponent alloy thermodynamics by reducing the cost associated with model construction and configuration sampling.
Physical binding energies using the electron localization function in 4-hydroxyphenylboronic acid co-crystals with aza donors
Authors: Shimpi Mayura Talwelkar , Sajjad Muhammad , Öberg Sven , Larsson J Andreas 
Published: September 2023

Abstract
Binding energies are traditionally simulated using cluster models by computation of each synthon for each individual co-crystal former. However, our investigation of the binding strengths using the electron localization function (ELF) reveals that these can be determined directly from the crystal supercell computations. We propose a new modeling protocol for the computation of physical binding energies directly from bulk simulations using ELF analysis. In this work, we establish a correlation between ELF values and binding energies calculated for co-crystals of 4-hydroxyphenylboronic acid (4HPBA) with four different aza donors using density functional theory with varying descriptions of dispersion. Boronic acids are gaining significant interest in the field of crystal engineering, but theoretical studies on their use in materials are still very limited. Here, we present a systematic investigation of the non-covalent interactions in experimentally realized co-crystals. Prior diffraction studies on these complexes have shown the competitive nature between the boronic acid functional group and the para-substituted phenolic group forming heteromeric interactions with aza donors. We determine the stability of the co-crystals by simulating their lattice energies, and the different dispersion descriptions show similar trends in lattice energies and lattice parameters. Our study bolsters the experimental observation of the boronic acid group as a competitive co-crystal former in addition to the well-studied phenolic group. Further research on correlating ELF values for physical binding could potentially transform this approach to a viable alternative for the computation of binding energies.
The effect of fission products Xe and Cs on the thermal conductivity of the U3Si2 lattice: a first-principles study
Authors: Qi Hangbo , Li Buda , Li Menglu , Feng Shan , Hu Jutao , Gong Hengfeng , Ren Qisen , Liao Yehong , Xiao Haiyan , Zu Xiaotao 
Published: September 2023

Abstract
In the past decades, uranium silicide (U3Si2) as a promising accident tolerant fuel (ATF) has drawn considerable attention in the field of nuclear physics. In comparison with traditional nuclear fuel (UO2), the U3Si2 has higher thermal conductivity and uranium density, thereby resulting in lower centerline temperatures and better fuel economy. However, during the nuclear fission reaction, some unexpected fission products, such as Xe and Cs, are released and form the defective states. In this study, we explore the influence of Xe and Cs on the thermal conductivity of the U3Si2 lattice from 200 to 1500 K using density functional theory calculations combined with Boltzmann transport equation. Our results reveal that the lattice and electronic thermal conductivities of defective U3Si2 are reduced at a constant temperature, as compared with that of ideal system, thus resulting in a decrease of the total thermal conductivity. In the case of Cs occupation at U1 site, the total thermal conductivity (4.42 W mK−1) is decreased by ∼56% at 300 K, as compared with the value of 9.99 W mK−1 for ideal system. With U1 and Si sites being occupied by Xe, the total thermal conductivities (4.45 and 6.52 W mK−1) are decreased by ∼55% and 35% at 300 K, respectively. The presented results suggest that the U3Si2 has potential as a promising ATF at high temperatures.
A unified path seeking algorithm for IMRT and IMPT beam orientation optimization
Authors: Ramesh Pavitra , Valdes Gilmer , O’Connor Daniel , Sheng Ke 
Published: September 2023

Abstract

Objective. Fully automated beam orientation optimization (BOO) for intensity-modulated radiotherapy and intensity modulated proton therapy (IMPT) is gaining interest, since achieving optimal plan quality for an unknown number of fixed beam arrangements is tedious. Fast group sparsity-based optimization methods have been proposed to find the optimal orientation, but manual tuning is required to eliminate the exact number of beams from a large candidate set. Here, we introduce a fast, automated gradient descent-based path-seeking algorithm (PathGD), which performs fluence map optimization for sequentially added beams, to visualize the dosimetric benefit of one added field at a time. Approach. Several configurations of 2–4 proton and 5–15 photon beams were selected for three head-and-neck patients using PathGD, which was compared to group sparsity-regularized BOO solved with the fast iterative shrinkage-thresholding algorithm (GS-FISTA), and manually selected IMPT beams or one coplanar photon VMAT arc (MAN). Once beams were chosen, all plans were compared on computational efficiency, dosimetry, and for proton plans, robustness. Main results. With each added proton beam, Clinical Target Volume (CTV) and organs at risk (OAR) dosimetric cost improved on average across plans by [1.1%, 13.6%], and for photons, [0.6%, 2.0%]. Comparing algorithms, beam selection for PathGD was faster than GS-FISTA on average by 35%, and PathGD matched the CTV coverage of GS-FISTA plans while reducing OAR mean and maximum dose in all structures by an average of 13.6%. PathGD was able to improve CTV [Dmax, D95%] by [2.6%, 5.2%] and reduced worst-case [max, mean] dose in OARs by [11.1%, 13.1%]. Significance. The benefit of a path-seeking algorithm is the beam-by-beam analysis of dosimetric cost. PathGD was shown to be most efficient and dosimetrically desirable amongst group sparsity and manual BOO methods, and highlights the sensitivity of beam addition for IMPT in particular.
Automatic brain extraction for rat magnetic resonance imaging data using U2-Net
Authors: Liang Shengxiang , Yin Xiaolong , Huang Li , Huang Jiayang , Yang Junchao , Wang Xiuxiu , Peng Lixin , Zhang Yusi , Li Zuanfang , Nie Binbin , Tao Jing 
Published: September 2023

Abstract

Objective. Skull stripping is a key step in the pre-processing of rodent brain magnetic resonance images (MRI). This study aimed to develop a new skull stripping method via U2-Net, a neural network model based on deep learning method, for rat brain MRI. Approach. In this study, 599 rats were enrolled and U2-Net was applied to segment MRI images of rat brain. The intercranial tissue of each rat was manually labeled. 476 rats (approximate 80%) were used for training set while 123 rats (approximate 20%) were used to test the performance of the trained U2-Net model. For evaluation, the segmentation result by the U2-Net model is compared with the manual label, and traditional segment methods. Quantitative evaluation, including Dice coefficient, Jaccard coefficient, Sensitivity, Specificity, Pixel accuracy, Hausdorff coefficient, True positive rate, False positive rate and the volumes of whole brain, were calculated to compare the segmentation results among different models. Main results. The U2-Net model was performed better than the software of RATS and BrainSuite, in which the quantitative values of training U2-Net model were 0.9907 ± 0.0016 (Dice coefficient), 0.9816 ± 0.0032 (Jaccard coefficient), 0.9912 ± 0.0020 (Sensitivity), 0.9989 ± 0.0002 (Specificity), 0.9982 ± 0.0003 (Pixel accuracy), 5.2390 ± 2.5334 (Hausdorff coefficient), 0.9902 ± 0.0025 (True positive rate), 0.0009 ± 0.0002(False positive rate) respectively. Significance. This study provides a new method that achieves reliable performance in rat brain skull stripping of MRI images, which could contribute to the processing of rat brain MRI.
B3X: a novel efficient algorithm for accurate automated auscultatory blood pressure estimation
Authors: Centracchio Jessica , De Caro Davide , Bifulco Paolo , Andreozzi Emilio 
Published: September 2023

Abstract

Objective. The auscultatory technique is still considered the most accurate method for non-invasive blood pressure (NIBP) measurement, although its reliability depends on operator’s skills. Various methods for automated Korotkoff sounds analysis have been proposed for reliable estimation of systolic (SBP) and diastolic (DBP) blood pressures. To this aim, very complex methodologies have been presented, including some based on artificial intelligence (AI). This study proposes a relatively simple methodology, named B3X, to estimate SBP and DBP by processing Korotkoff sounds recordings acquired during an auscultatory NIBP measurement. Approach. The beat-by-beat change in morphology of adjacent Korotkoff sounds is evaluated via their cross-correlation. The time series of the beat-by-beat cross-correlation and its first derivative are analyzed to locate the timings of SBP and DBP values. Extensive tests were performed on a public database of 350 annotated measurements, and the performance was evaluated according to the BHS, AAMI/ANSI, and International Organization for Standardization (ISO) quality standards. Main results. The proposed approach achieved ‘A’ scores for SBP and DBP in the BHS grading system, and passed the quality tests of AAMI/ANSI and ISO standards. The B3X algorithm outperformed two well-established algorithms for oscillometric NIBP measurement in both SBP and DBP estimation. It also outperformed four AI-based algorithms in DBP estimation, while providing comparable performance for SBP, at the cost of a much lower computational burden. The full code of the B3X algorithm is provided in a public repository. Significance. The very good performances ensured by the proposed B3X algorithm, at a low computational cost and without the need for parameter training, support its direct implementation into clinical blood pressure (BP) monitoring devices. The results of this study pave the way for solving/overcoming the trade-off between the accuracy of the auscultatory technique and the objectivity of oscillatory measurements, by bringing an automated auscultatory BP measurement method in clinical practice.
A novel bio-inspired helmet with auxetic lattice liners for mitigating traumatic brain injury
Authors: Chen Zeyao , Li Junhao , Wu Baisheng , Chen Xin , Ren Xin , Xie Yi Min 
Published: September 2023

Abstract
The human head is most vulnerable to injury during activities such as road traffic and sports. To mitigate the risk of traumatic brain injury (TBI), helmets serve as an important protective device. This study proposes a hedgehog biomimetic helmet with auxetic lattice liners in the shape of a hemisphere. The helmeted head impact configuration is built based on a high bio-fidelity head-neck finite element model incorporated into our novel helmet model. Biomechanical responses including acceleration, intracranial pressure, and von Mises strain of head are extracted from the simulation model to assess TBI risks. The results indicate that the helmet featuring auxetic lattice liners outperforms those without liners or with other liner designs, offering superior protection. Compared to the threshold, the novel helmet design was found to reduce the head injury criterion value by 72.65%. Additionally, parametric studies of lattice’s bar radius for uniform and graded auxetic lattice liners are discussed. Finally, this study also carries out the optimization design of lattice strut radius and height, resulting in a lightweight auxetic lattice liner with superior protective performance. The outcomes of this study extend the application of auxetic materials and provide guidance for designing helmet liners that better mitigate TBI.
Adaptive piezoelectric metamaterial beam: autonomous attenuation zone adjustment in complex vibration environments
Authors: Jian Yupei , Hu Guobiao , Tang Lihua , Shen Yincheng , Zhan Yulin , Aw Kean 
Published: September 2023

Abstract
Programmable metamaterials for broadband vibration control draw growing interest due to their abilities to tailor dynamic responses. However, the deterministic dynamic behavior of any traditional metamaterial is a challenge to cope with the complex and variable vibration conditions in real environments. This work proposes an adaptive piezoelectric metamaterial beam (piezo-meta-beam) that consists of bimorph piezoelectric arrays. The shunt circuits are designed with self-tuning abilities by integrating microcontroller-driven digital potentiometers into synthetic inductive circuits. Two typical scenarios are considered, i.e., harmonic and white noise excitations with different spectra. Different self-tuning strategies based on bandgap prediction are contrapuntally developed. However, a flaw in the analytical bandgap expression widely appearing in the literature is noted through a verification study. A modified bandgap expression based on the 3D finite element model is proposed for correction. This modified bandgap expression is adopted in formulating the control strategy of the microcontroller. A series of experiments are conducted to investigate the adaptive behavior of the piezo-meta-beam. In the harmonic sweep excitation test, the adaptive piezo-meta-beam shows an ultra-broad attenuation zone (220–720 Hz), while the traditional counterpart only has a bandgap width of less than 20 Hz. In the case of noise excitation, autonomous adjustment of the center frequency and attenuation zone is achieved for noises over different spectra. In general, this work presents a methodology for designing intelligent metamaterials that can adapt to environmental vibrations with vast potential for real applications.
Effects of vacancy defects on the electronic and magnetic properties of monolayer CrOCl
Authors: Xu Chunyan , Zhang Jing 
Published: September 2023

Abstract
Two-dimensional intrinsic ferromagnetic materials have received considerable attention for their potential applications in spintronic devices. The possible defects during experimental synthesis can affect the properties of magnets. However, the study of vacancies in two-dimensional ferromagnetic CrOCl is still lacking. Based on first-principles calculations, we investigate the electronic and magnetic properties of monolayer CrOCl by introducing vacancies. Vacancies transform monolayer CrOCl from semiconductor to half-metal. The magnetic moment of monolayer CrOCl can be modulated depending on the types of vacancies. Vacancy defects enhance the magnetic anisotropy of monolayer CrOCl but not alter the easy axis. By varying the concentration of Cl vacancy in monolayer CrOCl, the electronic property can be tuned from semiconductor to half-metal, the magnetic anisotropy can be improved by 133% compared to the pristine one. The controllability of the transition from ferromagnetic semiconductor to half-metallicity in monolayer CrOCl makes it an ideal spintronic material for spin injection and spin transport.
Synthesis of flower like microstructured CdZnS films for optoelectronic applications by powder vapor transport technique
Authors: Khan I A , Rasheed A , Farid A , Yousaf Misbah , Raza A 
Published: September 2023

Abstract
Cadmium zinc sulfide (CdZnS) is a remarkable semiconducting material used as window layer in solar cells. Herein, the flower’s like microstructured CdZnS film is synthesized by powder vapor transport (PVT) technique. The structural parameters like lattice constant, various diffraction planes, crystallinity, preferential orientation factor and standard deviation of CdZnS film of good quality growing preferentially along (110) orientations. The growth of longitudinal optical phonons modes at 303 and 599 cm−1 confirms the synthesis of CdZnS film. The values of transmittance and refractive index are ranged from 89.9%–95.2% and 1.53–2.67 whereas the values of energy band gap, oscillator energy and dispersion energy are found to be 2.79, 0.73 and 1.73 eV respectively. The values of dielectric constant are increased with increasing photon energy. The smaller values of dissipation factor and volume/surface energy loss functions of CdZnS film is suitable to make it a good quality capacitor. The electrical conductivity (1.68×103
S cm

−1
) of CdZnS film is increased nonlinearly with increasing temperature and the activation energy is found to be 0.31 eV. It is determined that the synthesized CdZnS film may be used as window layer in solar cells and to make good quality capacitor, hence it may be used in optoelectronic applications.
Excess noise factor measurement for low-noise high-speed avalanche photodiodes
Authors: Liu Yijun , Yang Xiaohong , Wang Rui , Tang Yongsheng 
Published: September 2023

Abstract
The excess noise factor(F) is an important parameter for Avalanche Photodiodes (APDs), indicating the extent to which the noise of the diodes exceeds what it would be without multiplication. This paper presents a method of measuring the excess noise factor for high-speed low-noise APDs using the high-sensitivity spectrum analyzer. The F factor test for the high-speed low-noise APDs was performed by comparing two conditions with and without illumination to remove the interference of the system, including the thermal noise and analyzers. The setup conditions of the light source are analyzed in detail. The F factor was obtained as 3.03 when the multiplication factor M is 10, which corresponds to an effective ionization coefficient ratio k of 0.14 for the high-speed InAlAs APD. For comparison, the k value of a commercial Si APD is tested to be ∼0.06.
High-order harmonic generation, attosecond pulse, and non-sequential double ionization in the helium atom under high-intensity femtosecond laser pulses
Authors: Zakavi Marjan , Sabaeian Mohammad 
Published: September 2023

Abstract
High-order harmonic generation (HHG), attosecond pulse train (APT), isolated attosecond pulse (IAP), and non-sequential double ionization (NSDI) in the Helium atom under intense femtosecond laser pulses are computed using the time-dependent Schrodinger equation (TDSE) in one dimension (1D). By taking into account the electron–electron and electron-nucleus interactions, as well as determining the Helium atom’s ground state wave function through the imaginary time propagation (ITP) method, we are able to observe the widely recognized ‘knee structure’ in the ionization probability of the Helium atom as a function of intensity within an ionization boundary condition model. The results are in good agreement with the experimental data reported by (Walker et al (1994) Phys. Rev. Lett. 73, 1227).