bluuebunny/crossref_metadata_2025 huggingface dataset:
Research on Try-before-you-buy Strategy Under Product Fit Uncertainty
Authors: Deng Junwu , Zhang Yinjie , Lu Sichen , Huang Haizhen
Published: August 2023

With the rapid development of online retail, the drawback of product fit uncertainty in online markets are becoming more and more prominent. In order to alleviate the impact of the product fit uncertainty, online retailers continue to introduce new service strategies. Based on the uncertainty of product matching, this paper constructs and solves the model of direct sales and try-before-you-buy(TBYB) strategy by online retailers under the premise of whether to allow returns. And explore the optimal strategy for the e-retailer in different aiming. The results show that: When the product fit is low, the optimal strategy choice for online retailers is TBYB strategy. When the product fit is high, if products are allowed to be returned, sell the product directly is the optimal strategy choice; if not, both TBYB and direct sales are optimal strategies. When the product fit is moderate, for products that are allowed to be returned, sell products directly when aiming to maximize demand and adopt the TBYB strategy when maximize profits. For products that are not allowed to be returned, Online retailers should sell products directly when aiming to maximize demand.
Construction and Application of University Patent Evaluation Model based on Machine Learning
Authors: Yan Jinjiang , Xue Jinghang , Ji Li , Liu Jiting , Jiang Jinshan
Published: August 2023

As the frontier of scientific and technological innovation, universities will produce a large number of patents based on their talent, technology and resource advantages. How to evaluate the value of university patents in a more scientific and efficient manner is of great significance in improving the scientific research and innovation capability of universities and promoting the transfer and transformation of university patents. Firstly, combined with the characteristics of universities and the definition of “high-value patents”, we constructed a scientific evaluation index system of university patent value. Secondly, machine learning algorithms were used to build patent value evaluation models. Finally, we conducted an empirical study with invention patent data from 134 universities in Sichuan Province, and then tested six evaluation models for their performances. The XGB model and GBDT model are found to have better accuracy and reliability. In addition, the number of IPC classifications, patent family citations and independent claims are of higher importance in patent value evaluation, university characteristics are less important to the value of university patents.
A New Paradigm of Open Innovation under Chinese Modernization: Co-innovation Theory Review
Authors: Zhou Guichuan , Dong Hui , Hoongsengpha Soudthida , He Yue , Zheng Shuangyi , Liu Anni
Published: August 2023

Co-innovation is a new paradigm and a new hot spot in the field of technological innovation. This study uses bibliometric analysis and CiteSpace to analyze the co-innovation related literature published at domestic and abroad during 2010-2022 to explore the current status and development trend of co-innovation research. The research results show that co-innovation research at domestic and abroad is developing rapidly and increasingly becoming a research hotspot in the field of technological innovation. Compared with foreign scholars who have begun to quantify and case study the technological paths of co-innovation, domestic research still mainly relies on qualitative methods to theoretically explore the institutional mechanism of co-innovation, which can hardly meet the development needs of co-innovation policy and practice. Therefore, this study proposes future research directions for co-innovation in four major aspects: mechanism of action, network model, empowerment mechanism and governance mechanism. As the first systematic study of co-innovation literature in China and abroad, this study has important theoretical significance and practical value.
The Effect of Non-agriculture Employment on The Rural Household Poverty Alleviation: Evidence from a Deeply Impoverished County in Southwest China
Authors: Wu Mengze , Hu Zhineng
Published: August 2023

Encouraging rural households from deeply impoverished areas to participate in non-agricultural employment has been regarded as an effective way to alleviate rural poverty. China’s targeted poverty alleviation (TPA) project has made significant achievements, with its policy to encourage rural households to participate in non-agricultural employments playing an important TPA role. Taking a deeply impoverished county in Southwest China as an example, this paper used an endogenous switching regression (ESR) model under a counterfactual inference framework to evaluate the effects of nonagricultural employment on alleviating household poverty, with the simplified “Organization for Economic Co-operation and Development (OECD) equivalent scale” formula used to adjust the income to measure household welfare. It was found that non-agricultural employment had reduced participant poverty and greatly improved the welfare of the participating households. However, for the non-participants, the non-agricultural employment income would be lower than the agricultural income, and the transfer of the household labor force to non-agricultural employment would deepen household poverty. This paper concluded with a discussion of the policy options to consolidate the achievements of poverty alleviation in deeply impoverished areas.
The Impact of Knowledge Spillover from Universities in Sichuan-Chongqing Region on Regional Innovation Capacity
Authors: Hu Zihan , Zhan Yong , Wu Min , Wu Dan
Published: August 2023

As an important subject of the regional innovation system, the scientific research activities of universities are not only the power source of talent cultivation and knowledge innovation but also an important force to promote regional innovation development. This paper examines the influence relationship between knowledge spillover from universities in Sichuan province and Chongqing city and regional innovation capacity from the aspects of teaching and research personnel input, research and development personnel input in research input, monographs, academic papers, technology transfer contracts and transfer income in research output. The results show that the improvement of the innovation capacity in Sichuan province and Chongqing city depends on the increase of teaching and research personnel input and the number of scientific and technological topics in universities, while other indirect scientific research results do not contribute significantly to the regional innovation capacity; further mechanism analysis reveals that the knowledge spillover from universities mainly promotes the improvement of regional innovation capacity through human capital, physical capital, and scientific and technological innovation.
Research on the Change of Cultural Values in Clothing Company Brand Slogans
Authors: Long Yangyang , Niu Yongge , Liu Yan
Published: August 2023

The brand slogan change is an important measure to adjust the brand image and maintain the brand’s vitality in the fierce market competition. Clothing is both a product of culture and a carrier of culture, and changes in clothing company brand slogans are closely related to changes in consumer culture. This study selects clothing company brand slogans that have changed in the Chinese market in the last 20 years (2000-2019) and adopts a combination of statistical analysis and content analysis to discuss the trends and characteristics of brand slogans in the process of change from the perspective of cultural values. It was found that: (1) the individualism, collectivism, and high power distance presented by Chinese clothing companies’ brand slogans increased significantly between the two successive decades during the change process; the low uncertainty avoidance presented by them decreased significantly between the two successive decades; while low power distance, high uncertainty avoidance, masculinity, and feminism did not change significantly. (2) Among the cultural value claims, the claim “Succorance” in collectivism is found to have increased significantly, while the claim “Plain” in low power distance has decreased significantly. The remaining 28 demands did not change significantly. This paper enriches the discussion of brand slogan change from the perspective of cultural values. When designing a new brand slogan, clothing companies need to anticipate the current consumer culture in the context of the times to develop a brand slogan that is in line with consumer values.
A Comparative Study of Preventive Maintenance Thresholds for Deteriorating Systems
Authors: Marugan Alberto Pliego , Marquez Fausto Pedro Garcia , Pinar-Perez Jesús Maria
Published: August 2023

Degradation of engineering systems is a phenomenon that affects the reliability and the lifetime of systems. Maintenance of deteriorating systems has been widely studied over the past 50 years. Numerous maintenance models have been proposed in the literature to manage degradation. In this paper, we focus on a condition-based maintenance strategy for those systems suffering a continuous deterioration process. We propose the use of a non-constant maintenance threshold to determine when a preventive action is required. The main goal is to analyse the effect of non-constant threshold in the long-term maintenance cost rate. We demonstrate numerically the convergence of the long run cost rate and some statistical properties of the proposed model. We compare the use of a constant threshold with a non-constant threshold through two different simulated case studies. The simulations provide some statistical results that reveals interesting advantages and drawbacks of using a non-constant threshold.
Economic-environmental-resilient Equilibrium Oriented Optimal Design Towards Distributed Hybrid Energy System: Case Study From China
Authors: Tian Yalou , Wu Zongze , Wang Fengjuan
Published: August 2023

The planning and transformation of existing energy systems through renewable energy sources and the cleanest fossil fuels is considered to be one of the most promising and effective strategies for achieving the transition to a low-carbon world. At the same time,due to the increasing penetration of renewable energy and the frequent occurrence of extreme disasters comes with decreasing system inertia and much faster frequency drop when contingency of large power loss occurs, which seriously threatens the security of power system operation, so more and more attention is being paid to the safety and security of power systems in key areas. In order to achieve energy transition and emergency security through optimal distributed energy, this paper proposes a hybrid energy system of photovoltaic - natural gas - energy storage. A multi-objective optimization model that simultaneously considers economic costs, environmental benefits and system resilience is then developed, utilizing fuzzy satisfying approach to obtain the optimal system configuration under the decision maker’s attitude parameters. A case study from an industrial park is conducted to demonstrate the practicality and efficiency of the optimization method. The calculations show that multi-objective optimisation of distributed energy systems can reduce carbon emissions by 75,364 to 414,997 tonnes per year, and can also effectively respond to extreme disasters by ensuring the normal operation of critical loads with high priority and the safety of the system through appropriate load shedding for loads with low priority.
The Resource of Creativity and Creative Human Capital for the Management of Knowledge Economy:Implications for the Republic of Moldova
Authors: Duca Svetlana
Published: August 2023

The purpose of the article is to analyze and consider the huge role of the resource of creativity and impact of creative human capital on knowledge economy as a driver for progress and welfare. Bad management inhibits the population to be creative and in this way diminishes the knowledge, meritocracy, innovation and development of the country. The relevance of investments in education, research and innovative systems, valorization of the resource of creativity and encouraging the creative human capital, but also the constraints and opportunities of Republic of Moldova in the context of international flow of talents are targeted in the present paper. The author considers the relevance of the sustainable policies of the governments and their implementation via sound coherent and consistent processes towards the formation, valorization and providing incentives for bringing back to the country the human capital that left for abroad. The author concludes that the strategic correlation of the state policies in the economic sectors aiming the increase of creative indicators per country, with the EU support through programs to which the Republic of Moldova has been engaged, will generate economic impact.
Disaster Relief Role Evolution of the Sichuan Provincial Government
Authors: Wang Yan , Wu Jasmine
Published: August 2023

Due to its special geographical location, three major earthquakes have been experienced in Sichuan Province, China over the past two decades. In response to the three earthquakes, the provincial government has served as a connective link between the central government and the county governments, thus demonstrating its unique and indispensable role in the disaster relief process. Taking the 2008 Wenchuan earthquake, the 2013 Lushan earthquake and the 2017 Jiuzhaigou earthquake as the research objects, this paper used the field research and interview method to make a longitudinal comparison of the roles and functions of the Sichuan Provincial Government in terms of policy, funding and emergency rescue in the three major earthquakes. It was found that (1) the role of Sichuan Provincial Government in the disaster relief process has changed; (2) although the government’s earthquake relief investment decreased, the proportion of the total investment in Sichuan earthquake disaster relief from the government’s own expenditure generally rose; (3) the emergency response and disposal capacity of Sichuan Provincial Government has been greatly improved. References and suggestions were also given for disaster relief and mitigation system construction for other disasters and other areas from a provincial government perspective.
Two-Stage Stochastic Programming Model for Improving Transportation Network Resilience of Relief Supplies in Sequential Hazards Scenario
Authors: Zeng Ziqiang , Jia Cuicui , Chang Yurui , Han Yu
Published: August 2023

Cascading failure of road transport networks caused by complex sequential natural hazards adversely affects the use of pre-positioning relief supplies. Therefore, it is vital to improve the transportation network resilience of relief supplies by using an optimization model. The purpose of this paper is to pre-position and distribute relief supplies in uncertain scenarios of sequential hazards. A two-stage stochastic programming model to maximize the total resilience is proposed to provide an optimal plan against the uncertain impact of sequential natural hazards. The combined impact of the Jiuzhaigou 7.0 magnitude earthquake and its associated landslide is a prototype disaster scenario for the implementation of the method proposed in this paper. The model is solved by a neighborhood search-based genetic algorithm (NS-based GA), which has both the global search capability of a genetic algorithm and the local search capability of a large-scale neighborhood search algorithm, can improve the solution finding capability. A case study focusing on finding the optimal solution for the pre-position and distribution of relief supplies in the sequential hazard of Jiuzhaigou earthquake is conducted to illustrate the validity of the proposed model.
The Moderating Role of Uncertainty Avoidance on Consumer Brand Engagement and Band Loyalty in Virtual Brand Communities
Authors: Muhammad Ibrahim Shahid , Muhammad Hashim , Sajjad Ahmad Baig , Muhammad Nazam
Published: August 2023

This study aims to investigate the role of consumer brand engagement (CBE) in virtual brand communities regarding loyalty attitudes and uncertainty avoidance. Data set of 750 responses was collected from the students of NTU who joined any brand community on Facebook or Instagram. SPSS was used for descriptive statistics and SmartPLS 4.0 for Structural Equation Modeling. The results revealed positive association of brand community identifications and rewards on CBE, and a positive effect of CBE on brand loyalty. The results revealed partial mediating effect of CBE between brand community identification, loyalty reward and brand loyalty. Moreover, results showed that culture is an important factor in defining the moderating effect of uncertainty avoidance on brand loyalty. This paper is among the first to provide empirical, and practical insights into the impact of uncertainty avoidance in virtual brand communities regarding consumer brand engagement and brand loyalty. The study is helpful for brand managers concerned about attitude of customers connected with online communities.
A kinematic modeling scheme of three-axis "Satcom-on-the-Move" antenna based on modified Denavit-Hartenberg method
Authors: REN Jiao , JI Xiaoxiang , LI Jianghong , HAN Lei , WU Yafeng
Published: August 2023

The current three-axes Satcom-on-the-Move(SOTM) antenna modeling method has some shortcomings, such as low model accuracy, poor portability and so on. In order to solve the above-mentioned shortcomings, a new modified Denavit-Hartenberg(NMDH) kinematics modeling scheme for the three-axes SOTM antenna was proposed. To overcome the modeling difficulties caused by the inherent mechanical structure of the antenna, and meet the requirements of the modified Denavit-Hartenberg(MDH) method, the virtual coordinate system and auxiliary coordinate systems are designed and added respectively on the basis of the MDH method, the forward kinematics model and inverse kinematics solution of the three-axes SOTM antenna are obtained. The correctness of the NMDH modeling scheme is verified by digital simulation. Finally, the system tests are carried out. The test results show that the NMDH modeling scheme proposed in this paper achieves good effect of antenna tracking satellite, and has stronger portability than the system identification modeling method commonly used in engineering.
Search task oriented path planning method of airborne radar network
Authors: QIN Ting , HE Tao , LYU Jindong , YAN Junkun , QIN Tianqi , LIU Hongwei
Published: August 2023

Reasonable planning the trajectory of the airborne radar network can decrease its repeated surveillance region, and improve the search efficiency. To complete a wider range of reconnaissance searches within a certain time, a search task oriented path optimization method of airborne radar network is proposed. Firstly, the single-platform search range by combing the radar equation is characterized, and the multi-radar area coverage function based on the rasterization idea is calculated. A trajectory optimization model with the goal of maximizing the search coverage function is constructed, by combining with the motion constraints of each node and adopting an intelligent method. Simulation results show that the present method can obtain higher search coverage within specified time.
MUSIC algorithm based on eigenvalue clustering
Authors: ZHANG Mingyang , ZHA Songyuan , LIU Yudong
Published: August 2023

The traditional MUSIC algorithm needs to know the number of target signal sources in advance, and further determine the dimensions of signal subspace and noise subspace, and finally search for spectral peaks. In engineering, it is impossible to predict the number of target signal sources to be measured. To solve the above-mentioned problem, an improved MUSIC algorithm without estimating the number of target signal sources is proposed. In the present algorithm, all eigenvectors of covariance matrix are regarded as noise subspace for spectral estimation, but the existence of signal subspace will make the result unreliable. In order to make the estimation result more accurate, a new weighting method for the spectral estimation results of noise subspace and signal subspace is proposed. The simulation results show that the improved algorithm can accurately estimate the number and direction of signal sources when the number of signal sources is unknown, and has greater practicability than the traditional MUSIC algorithm. In addition, the improved algorithm has better robustness.
Experimental study of hydrodynamic performances of pre-swirl pumpjet propeller
Authors: QIN Denghui , HUANG Qiaogao , PAN Guang , LI Fuzheng , HAN Peng
Published: August 2023

A pre-swirl pumpjet propeller(PJP) is widely used in the new generation of quiet submarines all over the world, although the experimental study of its hydrodynamic performances is still rare. This paper carries out experimental tests of the pre-swirl PJP with a 9-blade stator and a 7-blade rotor in a cavitation water tunnel. The thrust coefficient and torque coefficient of the pre-swirl PJP in open water are tested with a force measurement device, and the wake flow field of the pre-swirl PJP is tested with a laser particle velocimetry system. The experimental results show that the rotor thrust coefficient, stator-duct thrust coefficient and rotor torque coefficient of the pre-swirl PJP decrease with increasing the advance coefficient J, but the absolute value of the torque coefficient of the stator-duct thrust increases with increasing J. The open water efficiency of the pre-swirl PJP reaches the maximum when J=1.0, being 61.91%. The thrust of the pre-swirl PJP is mainly provided by the rotor. In addition, the wake flow field of the pre-swirl PJP is composed of jet acceleration zone, hub low-speed zone and mixed zone. The transient velocity and average velocity in the wake flow field under different working conditions are obtained.
Waveguide invariant estimation based on correlation coefficient of tonal acoustic intensity interference fluctuation
Authors: YAO Yuan , SUN Chao , LIU Xionghou , LI Mingyang
Published: August 2023

The waveguide invariant is usually not extracted from the striation pattern of broadband continuous spectrum in the low frequency analysis and recording spectrum at low signal-to-noise ratio. In this paper, the correlation coefficient of multi-tonal acoustic intensity interference fluctuation is utilized to estimate waveguide invariant. Since the proportional relationship between the reference intensity interference fluctuation and the scaled intensity interference fluctuation is dependent on waveguide invariant, the waveguide invariant estimation can be done. Firstly, the tonal intensity interference fluctuation has been resampled in the new time domain under the radial and non-radial motion models respectively. Then, the similarity degree between the resampling reference tonal intensity interference fluctuation and the scaling tonal intensity interference fluctuation can be described by correlation coefficient, and the peak of correlation coefficient is corresponding to the true value. Finally, the numerical results and the experimental results prove the proposed method's effectiveness.
Financing and coordination of the agricultural supply chain considering government-enterprise guarantee
Authors: Lu Qihui , Liao Changhua , Xu Tingting
Published: August 2023

We examine an agricultural supply chain consisting of a core enterprise and a capital constrained farmer and assess the yield uncertainty of farmer’s production. We explore two kinds of financing models: traditional bank financing and government-enterprise guarantee financing. To coordinate the supply chain, a price commitment contract and a revenue-sharing contract are considered. Our results show that no matter in bank or government-enterprise guarantee financing model, we can find the conditions for full coordination of the supply chain with any contract. However, in the government enterprise guarantee financing model, when a farmer has bankrupt risk in a low-yield season and no bankrupt risk in a high-yield season, the revenue-sharing contract can simultaneously make the supply chain fully coordinated and achieve Pareto improvement to maximize the profits of the entire supply chain and achieve a win-win situation. In addition, the farmer and enterprise prefer to choose the financing model with a higher promised price and a higher revenue-sharing ratio, and the social welfare under the government-enterprise guarantee financing model is higher than that under the traditional bank financing model.
Digitale Weichteilvorhersage im Kontext der
kieferorthopädisch-kieferchirurgischen Behandlung
Authors: Möhlhenrich Stephan Christian , Lohn Britta , Peters Florian , Danesh Gholamreza , Modabber Ali
Published: August 2023

Operative Eingriffe im Rahmen einer
kieferorthopädisch-kieferchirurgischen Behandlung werden zunehmend
digital geplant. Moderne Softwarelösungen erlauben neben der virtuellen
Kieferumstellung auch die Simulation einer möglichen
Weichgewebsreaktion. Etablierte Programme werden hinsichtlich der
Simulationsmöglichkeiten vorgestellt und mögliche Unterschiede
und Fehlerquellen aufgezeigt.
The role of ultrasound in first-trimester screening after the introduction of NIPT as a service of public health insurance – a consensus statement of the Fetal Medicine Foundation (FMF) Germany
Authors: Merz Eberhard , Eiben Bernd , Thode Christian , Hackelöer Bernhard-Joachim , Faber Renaldo , Tercanli Sevgi , Alkier Rudolf
Published: August 2023

Combined first-trimester screening (FTS) and noninvasive prenatal testing (NIPT) have been proven to be reliable noninvasive procedures to detect the most common chromosomal abnormalities (trisomies 21, 18, 13) in the first trimester. The aim of this paper is to demonstrate the strengths and limitations of these two procedures and to give a consensus statement of the Fetal Medicine Foundation (FMF) Germany on how to use the two techniques in the first trimester after the introduction of NIPT as a service of the statutory health insurance companies in Germany.
Significant effect of thin oxide layer on characteristics of p-InGaN/GaN nonalloyed ohmic contacts
Authors: Zhang Fan , Wang Rongxin , Li Fangzhi , Tian Aiqin , Liu Jianping , Yang Hui
Published: August 2023

In an interconnected high-vacuum illustration system, the surfaces of p-InGaN/GaN heterostructures grown with integrated metalorganic chemical vapor deposition were treated in O2 gas for different times at room temperature and then transferred to another chamber for fabricating ohmic contacts via sputtering Pd/Pt/Au multi-layers. X-ray photoelectron spectroscopy measurements unveil that the proportions of Ga–O of the treated samples significantly increase compared with that of the as-grown sample, indicating that a thin layer of GaOx forms on the p-InGaN/GaN surface after exposing to oxygen or air atmospheres. Meanwhile, the samples exposed to O2 or air were found to have much higher specific contact resistance, i.e., higher by two orders of magnitude than that of the as-grown sample. The specific contact resistance of the as-grown sample was derived as 9.3 × 10−5 Ω cm2 using the circular transmission line measurement. Furthermore, the Schottky barrier height of the samples was determined from the measured I–V curves with the thermionic field emission model and was revealed to be closely related to surface treatments. Despite the fact that the insulating layer of GaOx was as thin as 1.2–1.4 Å for the samples exposed to oxygen at room temperature, it can act as an extra barrier layer causing significant increase in the specific contact resistance via blocking the tunneling of carriers. Therefore, the effective removal of p-InGaN surface oxide plays a vital role in preparing good ohmic contacts.
Using electron energy-loss spectroscopy to measure nanoscale electronic and vibrational dynamics in a TEM
Authors: Kim Ye-Jin , Palmer Levi D. , Lee Wonseok , Heller Nicholas J. , Cushing Scott K.
Published: August 2023

Electron energy-loss spectroscopy (EELS) can measure similar information to x-ray, UV–Vis, and IR spectroscopies but with atomic resolution and increased scattering cross-sections. Recent advances in electron monochromators have expanded EELS capabilities from chemical identification to the realms of synchrotron-level core-loss measurements and to low-loss, 10–100 meV excitations, such as phonons, excitons, and valence structures. EELS measurements are easily correlated with electron diffraction and atomic-scale real-space imaging in a transmission electron microscope (TEM) to provide detailed local pictures of quasiparticle and bonding states. This perspective provides an overview of existing high-resolution EELS (HR-EELS) capabilities while also motivating the powerful next step in the field—ultrafast EELS in a TEM. Ultrafast EELS aims to combine atomic-level, element-specific, and correlated temporal measurements to better understand spatially specific excited-state phenomena. Ultrafast EELS measurements also add to the abilities of steady-state HR-EELS by being able to image the electromagnetic field and use electrons to excite photon-forbidden and momentum-specific transitions. We discuss the technical challenges ultrafast HR-EELS currently faces, as well as how integration with in situ and cryo measurements could expand the technique to new systems of interest, especially molecular and biological samples.
Laser ultrasonic inspection for mechanical properties of materials at high temperature
Authors: Meng Jiajian , Hou Weiguang , Li Xianke , Song Changhao , Zhang Jianhai
Published: August 2023

The measurement of mechanical properties of high-temperature resistant materials at high temperatures is particularly critical, and laser ultrasonic non-destructive testing technology is a prospective approach for measuring mechanical properties in high-temperature environments. Laser ultrasonic propagation models are constructed by finite element analysis, which reveals the effects of different excitation mechanisms on acoustic velocity measurements. It is found that the shear wave in the main propagation direction is hardly detected, and the distinction between shear waves and surface waves in the time domain signal is difficult. Based on the conclusions, the relationships between surface waves, longitudinal waves, and mechanical properties of materials are established by theoretical derivation. According to the propagation characteristics of surface waves and longitudinal waves, the eccentricity detection scheme of the same side and the concentricity detection scheme of the opposite side are, respectively, designed. The velocities of surface waves and longitudinal waves are measured, considering the thermal expansion coefficient and density changes with temperature. The mechanical properties of materials at different temperatures (25–1000 °C) are successfully calculated, and the experimental results are well in accordance with the reference values. It gives a reliable basis for efficient measurement of mechanical properties of materials at high temperatures.
Twisted magnetic knots and links
Authors: Candelaresi S. , Beck C.
Published: August 2023

For magnetic knots and links in plasmas, we introduce an internal twist and study their dynamical behavior in numerical simulations. We use a set of helical and non-helical configurations and add an internal twist that cancels the helicity of the helical configurations or makes a non-helical system helical. These fields are then left to relax in a magnetohydrodynamic environment. In line with previous works, we confirm the importance of magnetic helicity in field relaxation. However, an internal twist, as could be observed in coronal magnetic loops, does not just add or subtract helicity, but also introduce an alignment of the magnetic field with the electric current, which is the source term for helicity. This source term is strong enough to lead to a significant change in magnetic helicity, which for some cases leads to a loss of the stabilizing properties expressed in the realizability condition. Even a relatively weak internal twist in these magnetic fields leads to a strong enough source term for magnetic helicity that for various cases even in a low diffusion environment, we observe an inversion in sign of magnetic helicity within timescales much shorter than the diffusion time. We conclude that in solar and stellar fields, an internal twist does not automatically result in a structurally stable configuration and that the alignment of the magnetic field with the electric current must be taken into account.
Self-generated magnetic collimation mechanism driven by ultra-intense LG laser
Authors: Dong H. , Wang W. P. , He J. Z. , Shi Z. Y. , Leng Y. X. , Li R. X. , Xu Z. Z.
Published: August 2023

Collimation control of energetic plasma beams is crucial in the laser–plasma field. In this paper, we report on a self-collimated acceleration scheme for a plasma beam using an ultra-intense Laguerre–Gaussian (LG) laser irradiating a solid target. Three-dimensional (3D) particle-in-cell simulations show that a plasma beam with a high current density is stably formed by the radiation pressure of the hollow LG laser. The initial interaction of LG laser with solid target can be approximately researched by a deformable mirror model. Under the effect of the ponderomotive force of the LG laser, the plasma converges in the center axis to form a narrow beam. An elongated strong-magnetic tunnel (B ∼ 2 kT) is self-generated around the plasma beam, capable of trapping some electrons in a region with a radius of less than 500 nm (r < 500 nm). Compared with the case driven by the conventional Gaussian laser, the beam radius size is dramatically reduced from the microscale to hundreds on the nanoscale. The beam density is increased by at least ten times. Such an interesting scheme can provide a feasible and efficient way to achieve and enhance the collimation of energetic particle beams, which may benefit the general applications of fast ignition in inertial fusion, radiotherapy, realization of high-energy density states, and so on.
BiFeO3-PDMS hybrids: Development of visible-active floating photocatalysts with minimal catalyst loading
Authors: Eledath Manjusha , Viswanathan Shalini , Kallingal Aparna , Chandran Maneesh
Published: August 2023

Recent advances in photocatalysis include the development of floating catalysts since they assure efficient and rapid recollection of the catalysts from the purified liquid, besides enhancing the availability of photons at the catalytic surface. Bismuth ferrite (BiFeO3 and BFO) is a multifunctional perovskite material renowned for its excellent photocatalytic properties. Since bandgap of BFO falls in the visible spectrum, BFO nanoparticles could be combined with a suitable floating substrate to develop efficient visible light photocatalysts. Here, we report the synthesis of BFO–polydimethylsiloxane (PDMS) hybrids for photocatalytic applications, where sol-gel–synthesized BFO nanoparticles are immobilized on a floating porous PDMS sponge. The successful incorporation of the nanoparticles on PDMS is confirmed using Raman spectroscopy, scanning electron microscopy, and energy dispersive x-ray spectroscopy. The photocatalytic activity of the floating catalysts was studied by monitoring the degradation of malachite green dye under visible light irradiation. The effect of the amount of BFO immobilized, and the area and thickness of the PDMS sponge on the photocatalytic activity of the floating catalysts were investigated. An efficiency of 80.5% was obtained when the weight of BFO immobilized on the PDMS sponge was 5 mg. The method yields degradation efficiencies comparable with or higher than that of conventional BFO powder catalysts, even with 6–18 times less catalyst loading. The method introduces the fabrication of recyclable floating photocatalysts of notable efficiency using significantly less amount of BFO nanoparticles, which could be further modified by approaches such as doping, functionalization, or composite formation.
Hybrid graphene-plasmon gratings
Authors: Guo Tianjing , Argyropoulos Christos
Published: August 2023

Graphene can support surface plasmons with higher confinement, lower propagation loss, and substantially more tunable response compared to usual metal-based plasmonic structures. Interestingly, plasmons in graphene can strongly couple with nanostructures and gratings placed in its vicinity to form new hybrid systems that can provide a platform to investigate more complicated plasmonic phenomena. In this Perspective, an analysis on the excitation of highly confined graphene plasmons and their strong coupling with metallic or dielectric gratings is performed. We emphasize the flexibility in the efficient control of light–matter interaction by these new hybrid systems, benefiting from the interplay between graphene plasmons and other external resonant modes. The hybrid graphene-plasmon grating systems offer unique tunable plasmonic resonances with enhanced field distributions. They exhibit a novel route to realize practical emerging applications, including nonreciprocal devices, plasmonic switches, perfect absorbers, nonlinear structures, photodetectors, and optical sensors.
Microstructural and thermodynamic characterization of wormlike micelles formed by polydisperse ionic surfactant solutions
Authors: Flores Stephen L. , Mu Junju , Cabry Christopher P. , Peterson Joseph , De Hert Sergio Carrillo , Morrison Lisa , Stott Ian P. , Cook Joanne L. , Masters Andrew J. , Hardacre Christopher , Avendaño Carlos
Published: August 2023

For industrial applications of self-assembled wormlike micelles, measurement and characterization of a micellar material’s microstructure and rheology are paramount for the development and deployment of new high-performing and cost-effective formulations. Within this workflow, there are significant bottlenecks associated with experimental delays and a lack of transferability of results from one chemistry to another. In this work, we outline a process to predict microscopic and thermodynamic characteristics of wormlike micelles directly from rheological data by combining a more robust and efficient fitting algorithm with a recently published constitutive model called the Toy Shuffling model [J. D. Peterson and M. E. Cates, J. Rheol. 64, 1465–1496 (2020) and J. D. Peterson and M. E. Cates, J. Rheol. 65, 633–662 (2021)]. To support this work, linear rheology measurements were taken for 143 samples comprising a common base formulation of commercial sodium lauryl ether sulfate, cocamidopropyl betaine, and salt (NaCl). The steady state zero shear viscosity evident in linear rheology was measured in duplicate via direct steady and oscillatory shear experiments. Fitting the collected data to the model, we found trends in the microstructural and thermodynamic characteristics that agree with molecular dynamics simulations. These trends validate our new perspective on the parameters that inform the study of the relationship between chemical formulation and rheology. This work, when implemented at scale, can potentially be used to inform and test strategies for predicting self-assembled micellar structures based on chemical formulation.
Long-range polaritonic heat conduction in asymmetric surrounding media
Authors: Li Sichao , Shin Sunmi
Published: August 2023

Surface Phonon Polaritons (SPhPs) as an evanescent electromagnetic surface wave supports long propagation which readily surpasses the mean free path of classical heat carriers, e.g., phonons and electrons in solids. SPhPs have emerged as a promising candidate to dominate heat transfer in thin films. Polaritonic heat transfer has two distinct advantages: superior thermal conduction and a wide range of manipulation. Here, we study the upper limit of the thermal conductivity mediated by long-range polaritons in asymmetric surrounding media, where its surface effect overwhelms the volumetric one. The thin film structure strengthens the interactions of two surface waves at the top and bottom surfaces, and the asymmetric surrounding media makes an evanescent surface wave to further penetrate the free space with a higher refractive index, but it requires a fine tuning of asymmetric permittivity of the surrounding media to reach the upper limit of energy transmission efficiency near to the modal cut-off, where the transverse wavevector becomes zero. Both analytical and numerical simulations were introduced to investigate dispersion in asymmetric surrounding media and to model the thermal conductivity of glass thin films. Anomalously high thermal conductivity of 248 W/m-K was achieved with a 50 nm thick SiO2 film in asymmetric surrounding media, yet subtly dissimilar.
Lightweight stiffness-dominated acoustic metamaterial barrier for low-frequency sound
Authors: Nagami Tadashi , Miura Susumu , Miyakawa Takayuki , Sawada Hiroyuki , Minami Kenta , Ichikawa Atsushi , Horibe Norifumi , Enomoto Toshio , Fang Nicholas X.
Published: August 2023

In this study, we experimentally demonstrate a class of lightweight acoustic metamaterial barriers that block low-frequency sound. The acoustic metamaterial barrier is composed of a thin rubber membrane coated over a stiff honeycomb plate. Our findings, combined with high-fidelity finite element simulations, demonstrate that the sound insulation performance of the acoustic metamaterial surpasses the mass law in three distinct frequency ranges: (a) the stiffness law dominates insulation up to 140 Hz, (b) degeneracy and destructive superposition of high-order natural modes dominate within the frequency range of 300–500 Hz, and (c) destructive interference between high-order resonance and membrane resonance dominates in the frequency range of 800–1200 Hz. Notably, our study highlights the potential of high-order shear vibration of the periodic structure for the resonant bending waves of the honeycomb cell that coincide with the wavelengths of longitudinal sound waves in air, thereby offering new design guidelines for lightweight acoustic metamaterial barriers. This study reports for the first time the coincidence of high-order and membrane resonance modes within the honeycomb cell by employing an accurate finite element model and experimental validation.
Magnetic field stabilized atmospheric pressure plasma nitrogen fixation: Effect of electric field and gas temperature
Authors: Li Zhiyu , Wu Erqi , Nie Lanlan , Liu DaWei , Lu Xinpei
Published: August 2023

In this paper, we investigate the influence of plasma characteristics on nitrogen fixation efficiency and explore the optimization of discharge parameters by utilizing a magnetic field stabilized atmospheric pressure plasma. The gas temperature and electric field of the plasma are maintained at a constant level and can be independently adjusted by controlling the discharge current, gas flow rate, and external magnetic field. The spatial distribution of the gas temperature of the plasma is measured by laser-induced Rayleigh scattering. The results show that reducing the electric field and gas temperature leads to an increase in NOx production. The optimal parameters for nitrogen fixation are identified as a discharge current of 55 mA, a gas flow rate of 6 l·min−1, and an O2 fraction of 40%. These settings result in the lowest recorded energy cost of 2.29 MJ·mol−1 and a NOx concentration of approximately 15 925 ppm. The stable characteristics of the magnetically stabilized atmospheric pressure plasma make it suitable for further investigations into the effect of plasma characteristics on nitrogen fixation.
Non-line-of-sight imaging with absorption backprojection
Authors: Zhou Hongyuan , Zhang Dejian , Wang Tongbiao , Liao Qinghua , Yu Tianbao
Published: August 2023

The backprojection algorithm is a commonly used technique in non-line-of-sight imaging, but it is plagued by artifacts that significantly reduce the quality of the final reconstruction. To address this issue, we refer to the absorption of surrounding dust by celestial bodies and propose the absorption backprojection (ABP) algorithm by imitating the law of gravitation. This algorithm absorbs low confidence value voxels in hidden space into high confidence value voxels so that the majority of the artifacts surrounding the object are eliminated. The results of our study demonstrate that the ABP algorithm is highly effective in reducing the artifacts of backprojection in both simulation and laboratory experiments. Furthermore, it achieves better reconstruction results than other backprojection reconstruction algorithms, including filtered backprojection and error backprojection.
A numerical study on the benefits of passive-arc plates on drag and noise reductions of a cylinder in turbulent flow
Authors: Eydi Faezeh , Mojra Afsaneh
Published: August 2023

In this study, we introduce a novel arrangement consisting of two arc plates around a cylinder with the privilege of improved fluid flow and noise control. The arc plates are placed symmetrically and concentrically at the rear portion of a circular cylinder. The coverage angle (30 °≤β≤75°) of the plates and the normalized radius of arc plates (1.125≤Rd≤1.625) are varied to find the optimum case in terms of drag and noise reductions. The simulations are performed for a turbulent flow with a Reynolds number of 22 000. The numerical analysis is based on an unsteady Reynolds-averaged Navier–Stokes (URANS) solver and Ffowcs Williams and Hawkings (FW–H) acoustic analogy. It is found that by implementing the arc plates, the noise level and drag coefficient decrease dramatically. The results also reveal a strong correlation between the vortex shedding suppression and the noise reduction. It is shown that as the fluctuation of lift force decreases, the performance of flow and noise control enhances simultaneously. Furthermore, the noise assessment indicates that in a specific configuration of the arc plates, the overall sound pressure level decreases by around 51 dB compared to the uncontrolled case with no arc plates. Also, a maximum noise reduction of 27 dB is achieved, in which the drag coefficient reduces by 39% compared to the case with no arc plates. In conclusion, the results provide strong support for the proposed passive method as a beneficial strategy for noise reduction and wake control of cylindrical structures, which have wide applications in industry.
Laser-induced structural modulation and superconductivity in SrTiO3
Authors: Bhakar Monika , Garg Mona , Bhardwaj Pooja , Mehta Nikhlesh Singh , Sheet Goutam
Published: August 2023

Under normal conditions, stoichiometric SrTiO3 is an excellent dielectric. It shows a structural phase transition, from cubic to tetragonal, below 105 K. In this structure, well separated domains hosting tetragonal phases with different long axes exist giving rise to the so-called X, Y, and Z domains. At very low temperatures, it becomes a quantum paraelectric in which local ferroelectric domains are found at the X, Y, and Z domain boundaries. Creation of oxygen vacancy in SrTiO3 makes it conducting with low carrier density which also undergoes an unconventional superconducting transition at sub-kelvin temperatures. We have created structural phase separation with clear domain boundaries (as in the X, Y, and Z domains) at room temperature on single crystals of SrTiO3 by irradiating the surface with high power density excimer laser pulses. We find that the domain boundaries are dominantly conducting, and the irradiated crystals undergo a superconducting phase transition below 180 mK indicating that the superconducting phase appears at the domain boundaries. This concurrence of local ferroelectricity and superconductivity in lightly doped SrTiO3 supports a ferroelectric fluctuation mediated Cooper pairing in the system. The results also point out the possibility of controlling ferroelectricity and superconductivity in functional electronic devices through surface engineering.