bluuebunny/crossref_metadata_2025_split huggingface dataset:
Peculiarities of current–voltage characteristics of bismuth under elastic wave generation
Authors: Bengus S. V. , Bogod Yu. A. , Finkel’ P. E. 
Published: January 2025

Steady-state IVC of a monocrystalline bismuth sample of thickness d ≃ 2.7 mm in strong crossed electric and magnetic fields (E ∼ Hs/c, Ωτl = (eH/m*c) τl ≫ 1, s being the velocity of sound and τl the relaxation time for mobile charge carriers) reveal two inflections, the first one towards increasing resistance (downwards) and the second one towards decreasing resistance (upwards). The first inflection (from the smaller current side) is observed only at helium temperatures and can be related to phonon generation along the current direction I(I ‖ y, H ‖ z), and the second one to the bulk generation of phonons in a plane normal to the current (Esaki effect). This interpretation is supported by the recordings of nonsteady effects typical of electroacoustics. The longitudinal phonon generation is attributed both to high values of current density in sample areas where the electron mean free path ls ∼ υF/Ω (e.g., in the vicinity of slip and twinning planes), and to a nonuniform concentration of conduction electrons which, in turn, facilitates an increase in the local current density. The characteristic size of the current concentration region h, defined by the relation ⟨jk1⟩ ≃ nesh/d (⟨jk1⟩ is the average current density corresponding to the downward inflection) is about 2·10−3 cm and is practically independent of the magnetic field in the interval 25–140 kOe.
Nonlinear IVC for Hall contacts (nondiagonal IVC) have been studied for the first time. The Ux(I) dependences measured under steady-state conditions contain sections with negative differential resistance (NDR). For T = 4.2 K, the transition to NDR correlates with the downward inflection on the diagonal IVC, while for T = 20.4, it correlates with the upward inflection. The observed phenomena are attributed to the phonon electron drag before the Esaki effect and to an increase in the magnetoresistance after the realization of this effect, respectively. At T = 4.2 K, the nonlinear component of the nondiagonal IVC shows a reversal of the sign of the Hall emf under static and dynamic conditions, which is interpreted as a manifestation of the drag effect for I&gt;Ik1. At T = 20.4 K, acoustoelectronic vibrations of Ux with a period T ≃ d/s are recorded. Signals of the nonlinear response to two successive current pulses with a controllable relative pulse duration are studied. The first pulse leads to nonequilibrium while the second marks its state in time.
Brillouin–Mandelstam scattering in telecommunications optical fiber at millikelvin temperatures
Authors: Cryer-Jenkins E. A. , Leung A. C. , Rathee H. , Tan A. K. C. , Major K. D. , Vanner M. R. 
Published: January 2025

Brillouin–Mandelstam scattering is a strong and readily accessible optical nonlinearity, enabling a wide array of applications and research directions. For instance, the three-wave mixing process has been employed to great success in narrow-linewidth lasers, sensing applications, microscopy, and signal processing. While most of these avenues focus on room temperature operation, there is now increasing interest in cryogenic operation owing to the scattering mechanism’s significant potential for applications and fundamental physics at low temperatures. Here, we measure the Brillouin scattering spectrum in standard single-mode telecommunication optical fibers at millikelvin temperatures using a closed-cycle dilution refrigerator and optical heterodyne detection. Our experiments are performed with a cryostat temperature from 50 mK to 27 K, extending previously reported measurements that utilized liquid helium-4 cryostats with temperatures greater than 1 K. At millikelvin temperatures, our experiment observes coherent acoustic interactions with microscopic defects in the amorphous material—two-level-systems (TLSs)—which has not been previously observed in optical fibers. The measured behavior of the linewidth with temperature is in agreement with the well-established models of ultrasonic attenuation in amorphous materials comprising a background intrinsic scattering, thermally activated scattering, and incoherent and coherent TLS interactions. This work provides a foundation for a wide range of applications and further research, including sensing applications, new approaches to investigate TLS physics, and Brillouin-scattering-based quantum science and technology.
Observation of Superconducting Pair Density Modulation within Lattice Unit Cell
Authors: Wei 魏 Tianheng 天恒 , Liu 刘 Yanzhao 彦昭 , Ren 任 Wei 伟 , Liang 梁 Zhen 振 , Wang 汪 Ziqiang 自强 , Wang 王 Jian 健 
Published: January 2025

Abstract
In unconventional high-temperature (high-T
c) superconductors, the pair density wave state, an exotic superconducting order showing spatially periodic order parameter modulations with the period of several unit cells and translational symmetry breaking, has attracted broad attention. However, the superconducting pair density modulation (PDM) within a single unit cell has never been carefully investigated before. Here, using scanning tunneling microscopy/spectroscopy, we report the observation of PDM in monolayer high-T
c iron chalcogenide films epitaxially grown on SrTiO3(001). The superconductivity modulations are characterized by the superconducting gap size and the coherence peak sharpness. Further analysis shows that the local maxima and minima in the superconducting gap modulation are centered at the crystallographic locations of the chalcogen atoms, revealing the breaking of the glide-mirror symmetry of the chalcogen atoms in monolayer high-T
c iron chalcogenide films grown on SrTiO3(001). Our findings provide precise microscopic information on superconductivity within the lattice unit cell and may promote the understanding of unconventional high-T
c superconductivity.
Underwater acoustic target signal enhancement algorithm optimized by feature preservation and noise update
Authors: Qu Jianyue , Li Dawei , Liu Xianzhong , Sun Mingming 
Published: January 2025

Abstract
With the development of shock absorption and noise reduction technology, it is difficult to use existing aquatic target feature extraction techniques to extract weak signal features from complex marine environments. Therefore, underwater acoustic signal enhancement has become more important. The overlapping characteristics of underwater acoustic target signals and the variability of the ocean acoustic field make the application of Non-negative Matrix Factorization (NMF) in enhancing underwater acoustic target signals ineffective. To this end, the classic NMF algorithm is adaptively improved by combining the characteristics of underwater acoustic target signals, and an improved NMF underwater acoustic signal enhancement algorithm based on feature preservation is proposed. The algorithm first applies divergence constraints and similarity detection to the NMF feature base matrix to eliminate redundancy, optimizing the NMF features with size invariant characteristics while avoiding coefficient dispersion caused by base vector similarity and resulting in base vector loss. Then, the real-time environmental noise received by sonar is used to improve the adaptability of NMF noise basis vectors, achieving noise reduction and enhancement of underwater acoustic target signals. The experimental results show that compared with classical NMF, manifold-constrained NMF, and other algorithms applied to underwater acoustic target signal enhancement, the method proposed in this paper achieves a better signal enhancement effect.
Directional analysis of aerodynamic noise sources of a high-speed maglev train head based on frequency characteristics
Authors: Liang Yiwen , Huang Jingyu , Zhang Ziyang , Zhang Xinqi 
Published: January 2025

Abstract
The rising speeds of maglev trains have led to increasing concerns regarding aerodynamic noise, which impacts passenger comfort and environmental quality. To investigate the aerodynamic noise characteristics of the front of a high-speed maglev train, the TR08 maglev train is analyzed using Delayed Detached Eddy Simulation (DDES) and the k-epsilon turbulence model to compute the transient flow field around the train. An acoustic finite element-infinite element model is constructed based on Lighthill’s acoustic analogy, focusing on major noise source regions, for numerical calculations of sound propagation and directional analysis of noise. The study reveals that noise directionality is significantly frequency-dependent: low-frequency noise exhibits strong directionality, concentrated at specific angles, while high-frequency noise tends to be isotropic. As the distance from the nose increases, noise directionality broadens, with high-frequency noise becoming significantly omnidirectional in the far field.
The engineering modification of a double-wall plate sound insulation algorithm
Authors: Huang Yikang , Ma Yuchao , Sun Fugui , Qi Wen 
Published: January 2025

Abstract
This paper introduces the impedance analysis method to theoretically refine the conventional sound insulation theory of double-wall plates. It proposes an enhanced model for calculating sound insulation performance, focusing specifically on double-wall aluminum plates as the research object to measure the STL. The results indicate that the improved model significantly enhances the accuracy of sound insulation predictions across various frequency bands, and more accurately represents the actual sound insulation performance, which lays a foundation for the optimized design of future double-wall sound insulation systems.
Numerical study of the flow noise generated by an underwater vehicle with appendages
Authors: Wu Jiafeng , Xu Ziqi , Li Qiaojiao , Wei Wei 
Published: January 2025

Abstract
The appendages of underwater vehicles, such as the stern, are a primary source of flow noise. In the present study, we investigate an underwater vehicle model and analyze the effects of cross-shaped and X-shaped sterns on flow noise using numerical simulation methods. The results indicate that the underwater vehicle with an X-shaped stern exhibits lower resistance and sound pressure levels compared to one with a cross-shaped stern.
Flow characteristics and phase transition analysis of a supercritical carbon dioxide centrifugal compressor
Authors: Hong Shuli , Wang Zetao , Zhang Junyu 
Published: January 2025

Abstract
Micro centrifugal compressors are a key component of the Brayton cycle system with supercritical carbon dioxide (S-CO2) as the working medium in which the system can achieve a higher efficiency cycle. A typical micro centrifugal compressor is investigated. Then, the numerical simulations are performed for two working media; the S-CO2 and air. The results of the 3D flow simulation show that the fluid in the S-CO2 compressor can be divided into three zones: the supercritical zone, the liquid region, and the gas-liquid mixing zone. Research shows that the mechanism of phase transition occurrence is as follows. The larger inertia force of S-CO2 results in a flow separation from the leading edge of the compressor’s suction side, and generates additional centrifugal-effect in such separation zone; this then makes an oblique vortex structure at the suction side of the S-CO2 compressor, because of the higher density of S-CO2. The oblique vortex structure forms a special area with low pressure at the leading edge of the acceleration section, ensuring that the S-CO2 property transfers are sharply leading to the occurrence of a phase transition. Such results show that a special S-CO2 compressor design is necessary to overcome the phase transition problem.
Thermodynamic performance simulation analysis of 2.0T gasoline engine based on GT power
Authors: Zhao Hongxia , Zhu Qingsong , Li Huanhuan , Xing Xiangpeng 
Published: January 2025

Abstract
According to the requirements of the new project development, this analysis applied GT power software to establish a thermodynamic simulation analysis model for a 2.0T direct injection turbocharged inter-cooled gasoline engine with an exhaust cam of 8 mm lift. The input of the calculation model was calibrated based on benchmark prototype test data, and the thermodynamic performance indicators of the external characteristics were simulated and calculated at various operating points. The feasibility of the development goals and related performance and structural design parameters were evaluated, focusing on optimizing the turbocharger matching and valve timing at various operating points of the external characteristics. Main characteristic parameters: rated inlet air flow rate of 650 kg/h, inlet system pressure drop <8 kPa, intercooler pressure drop <15 kPa, and exhaust system pressure drop <60 kPa. Three computational simulation schemes are adopted. The results show that Scheme One is the best, Scheme Two can meet the requirements of the development goals, and Scheme Three has poor performance at low speeds and cannot meet the development goals. By optimizing the phase, a good charging coefficient can be achieved, and the residual exhaust gas in the cylinder is within a reasonable range. The valve timing can meet the performance requirements of the entire machine. The next step is to comprehensively consider factors such as power performance, economy, and residual exhaust gas for more reasonable phase optimization.
Numerical simulation of the vacuum casting process of solid propellants
Authors: Gao Zhe , Wei Ming , Li Wensen , Chen Cunzhuang , Li Changle , Zhao Jie 
Published: January 2025

Abstract
Solid propellant is one of the main components of rocket engines, and the casting of low-viscosity propellant slurry usually uses a vacuum casting process. During the vacuum casting process, the rheological properties of solid propellant slurry are complex, and the theoretical analytical method cannot intuitively and accurately analyze its flow characteristics. Therefore, this paper numerically simulates the casting process through simulation software, uses the Herschel-Bulkley model to characterize the changes in the flow characteristics of solid propellant slurry during the vacuum casting process, and studies the effects of different hopper angles and anti-break vacuum plug shapes on the slurry’s rheological properties. By analyzing parameters such as slurry mass flow rate, velocity, residual amount in the hopper, and surface pressure of the plug, the appropriate hopper angle and the bottom edge angle of the anti-break vacuum plug are selected. Finally, the slurry leveling characteristics under suitable hopper and plug conditions are analyzed. The results indicate that a hopper angle of 140° and an anti-break vacuum plug bottom angle of 120° are optimal. The entire vacuum casting process takes approximately 42 seconds, and the overall slurry leveling is good. As the casting progresses, the slurry gradually compacts and levels out, and the bubbles at the bottom of both sides of the combustion chamber gradually disappear.
Aerodynamic analysis of new low-wind-pressure conductors by numerical simulation
Authors: Qi Lexin , Liu Jiang , Weng Peifen , Qin Dezhao , Fu Zaiguo , Jiang Weiting 
Published: January 2025

Abstract
Low-wind-pressure conductor design aims to reduce the impact of wind on transmission lines and improve the stability and safety of the line so that the transmission system can operate more reliably in harsh climatic conditions. This paper is inspired by the golf ball surface pit structure, the surface structure of the conductor design, the design of a Roman column type low wind pressure conductor, and an imitation golf ball type low wind pressure conductor. The computational fluid dynamics (CFD) method based on the large eddy simulation (LES) is used to study the aerodynamic characteristics of the new low-wind pressure conductor and the mechanism of wind resistance reduction. The results show that the new low wind pressure conductor can reduce the wind resistance by 15%∼20% compared with the traditional cylindrical conductor due to the surface’s pit structure delaying the flow separation and lowering the differential pressure resistance to achieve the effect of resistance reduction.
Anchoring Authority
Authors: Queloz Matthieu 
Published: January 2025

Abstract
This chapter reviews extant attempts to anchor the authority of concepts and argues that they present us with a trilemma between foundationalism, ironism, and holism. It is argued that the first, when suitably generalized to cover thick normative concepts, has become incredible; the second results in indiscriminate disengagement from our concepts; and the third results in undiscriminating acceptance of them. To escape this trilemma and find more critical leverage with which to discriminate between concepts that merit confidence and concepts that do not, two things are required: first, the picture of our conceptual apparatus as something harmonious, largely tensionless, and inherently static must be replaced with a kaleidoscopic picture on which our conceptual apparatus is tension-ridden and dynamic; second, the critical leverage of local needs must be harnessed by recognizing that the contingency of our concepts extends also to the standards that these concepts must meet.
Concepts and Concerns
Authors: Queloz Matthieu 
Published: January 2025

Abstract
This chapter argues that concept appraisal should look beyond theoretical virtues and consider how our concepts relate to the concerns that animate their use. Using a little-known debate between Ronald Dworkin and Bernard Williams over the aspiration to eliminate theoretical vices in concepts as a springboard to the needs-based account to be developed, the chapter draws out three general lessons for conceptual ethics: that the merits of a concept have to be judged based on a prior understanding of the concerns it serves; that these concerns cannot be redirected at the drop of a definition; and that if some proposed concept realizes theoretical virtues at the cost of severing its ties to more important concerns, this will not be an improvement. If we are mindful of these lessons, we can appreciate the practical virtues of theoretical vices. Yet tying concepts back to concerns raises four problems of its own.
The Politics of Conflicting Concerns
Authors: Queloz Matthieu 
Published: January 2025

Abstract
This chapter considers how the needs-based approach accommodates the politics of pluralistic and conflicting concerns. Applying the approach to the political concept of liberty, it rounds out the reconstruction of the Dworkin–Williams debate, showing how Williams indicates two needs-based arguments for a conception of liberty on which its realization conflicts with the realization of equality. But the needs-based approach can also be used to come to Dworkin’s defence, revealing that there is a place in politics for the tidy-minded pursuit of theoretical virtues: there is a need for public reasoning to take a thinner and more theoretically virtuous form than personal reasoning. This serves the concern to hold public decision-makers accountable. Once this ideal of public reasoning shapes people’s conception of rationality in personal reasoning, however, it threatens to entrain a loss of substance in personal thought.
Crisis of Liberalism
Authors: Trencsényi Balázs 
Published: January 2025

Abstract
The chapter points to the links of the discourses of spiritual, economic, and societal crisis to the debate on the decline of liberalism—one of the most heated intellectual and political controversies of the interwar years. While the period is usually perceived as marked by the rise of illiberal ideologies, the chapter also shows that in the early 1920s there seemed to be a relatively broad consensus about the hegemony of the liberal democratic ideological script in most European countries. However, this seeming consensus quickly dissolved, and liberalism became a target of radical left- and right-wing criticism. In this context, critics of the liberal democratic framework opted for setting democracy and liberalism against each other, advocating an “illiberal democracy” or an “anti-democratic liberalism” as a way out of the crisis of the political system. From this perspective, the chapter seeks to situate the rise of neoliberalism in the period as a result of a complex and open-ended negotiation both with the nineteenth-century classical liberal tradition and with the different new ideological streams challenging the liberal position.
Crisis of Democracy
Authors: Trencsényi Balázs 
Published: January 2025

Abstract
This chapter looks at the growing discontent with representative democracy from the early 1920s onward, gradually turning into a diagnosis of a “general crisis” of democracy. Democratic institutions were often bitterly criticized for failing to provide an adequate manifestation of the common good, becoming instead the instruments of the uncontrollable and irrational masses. Critics pointed to the opening rift between liberalism and democracy, the lack of underlying absolute values to sustain a liberal democratic system, and the contradiction of formal versus substantial democracy. A central point of contention was that of the pros and cons of majoritarianism and plebiscitary forms of democracy. Liberal critics pointed out that such a reduction of the democratic principle to the act of legitimizing political rule opened the gates to tyranny, while leftist and rightist anti-liberals turned to these instruments as the basis of a more authentic form of popular rule, often combining it with a vision of charismatic leadership, embodying the general will.
Crisis of the Nation-State and the International System
Authors: Trencsényi Balázs 
Published: January 2025

Abstract
The end of the First World War and the ensuing framework of peace treaties could be considered a triumph of the principle of national self-determination and thus the universalization of the model of nation-statehood. However, the postwar polities proved to be increasingly conflict-ridden and the nation-state came to be affected by a deepening crisis of legitimacy. The experience of the Great Depression exposed the problem of economic nationalism and protectionism, while the geopolitical reconfiguration of the 1930s made the discourse of national self-determination increasingly problematic, if not completely illusory. The extensive discussion on the crisis of European civilization, and especially on the specific European combination of the principle of nation-statehood and transcontinental imperialism/colonialism, put all of this into an even more encompassing “global” perspective. This feeling of crisis also opened the space for alternative projects, such as federalism, which reemerged in the 1930s as an alternative to the self-destructive fragmentation, skillfully instrumentalized by the totalitarian powers.