Search Results (5,232)

We consider mixed Hamming packings, addressing the maximal cardinality of codes with a minimum codeword Hamming distance. We do not rely on any algebraic structure of the alphabets. We extend known-integer linear programming models of the problem to be efficiently tractable using standard ILP solvers. This is achieved by adopting the concept of contact graphs from classical continuous sphere packing problems to the present discrete context, resulting in a reduction technique for the models which enables their efficient solution as well as their decomposition to smaller subproblems. Based on our calculations, we provide a systematic summary of all lower and upper bounds for packings in the smallest Hamming spaces. The known results are reproduced, with some bounds found to be sharp, and the upper bounds improved in some cases. Full article

This study interrogates the semiotic destabilization of rural cultural symbols in China’s burgeoning short video sphere, with particular focus on the discursive reconstruction of “tǔ wèi” labeling. This paper, through semantic tracing and content analysis, combined with empirical data from over 130,000 “tǔ wèi” videos on Douyin (Tik Tok), categorizes the “tǔ wèi” content into two major styles: the novelty-hunting and ugliness-seeking style and the rural original ecological style. It also compares the differences in popularity, quality, and value orientation between the two. The research finds that the semantic segmentation of the “tǔ wèi” label is rooted in clash of civilizations and the urban–rural dichotomy, as well as the promotion of the traffic logic and symbol abuse of short video platforms. This segmentation has exacerbated the stigmatization of Chinese farming culture and weakened cultural confidence. It is suggested that efforts should be made from three aspects: deep exploration of indigenous “tǔ” cultural resources, optimization of algorithm recommendation mechanisms, and reconstruction of discourse contexts, to promote the semantic return of the “tǔ wèi” label and consolidate cultural subjectivity. Full article

We investigate strictly convex hypersurfaces in Euclidean space that are parameterized by their support function. We obtain a differential equation for the support function restricted to curves on the sphere, and we give explicit parameterizations of ellipsoids in ${\mathbb{R}}^{n+1}$ as the inverse of their Gauss map, where symmetry plays an important role. Full article

The bond market serves dual roles in fiscal and financial spheres, playing a crucial role in coordinating monetary policy. This paper investigates the impact of quantitative and price-based monetary policies on the liquidity level of China’s bond market. A comprehensive index measuring the liquidity of the local bond market is constructed using a combination weighting method that integrates the entropy method and the coefficient of variation. Employing the time-varying stochastic volatility structure vector autoregression (TVP-SV-SVAR) model on data spanning from 2013 to 2021, this study empirically compares the impulse response of local bond market liquidity to monetary policy shocks. The findings reveal that both types of monetary policy operations exhibit asymmetric, nonlinear, and time-varying impacts on bond market liquidity. Quantitative monetary instruments induce deeper impulse responses, with longer-lasting effects. These conclusions offer insights for monetary policy reforms and bond market development in China. Full article

The incorporation of fly ash into concrete reduces cement consumption by 10–30%, lowers CO₂ emissions by 30–50%, cuts costs by 15–25%, and enhances durability, thus reducing maintenance expenses. However, the predictive model for the elastic modulus of fly ash concrete subjected to calcium leaching is still lacking. Regarding the theoretical method, the content of calcium hydroxide and calcium silicate hydrate in fly ash–cement systems is quantitatively calculated according to the hydration reaction relationship between cement, fly ash, and water, and then the porosity of the fly ash–cement matrix and interface transition zone (ITZ) after calcium leaching can be obtained. Based on the theory of two-phase composite spheres and the non-uniform ITZ model, the prediction method for the elastic modulus of leached fly ash concrete can be constructed, which comprehensively considers key parameters such as fly ash content, non-uniform characteristics of the ITZ, and the water–binder ratio (w/b). Additionally, the corresponding experimental investigation is also designed to study the variation regulation of the leaching depth, leaching extent, and elastic modulus of fly ash concrete with leaching time. The prediction method for the elastic modulus of leached fly ash concrete is validated via self-designed experimental methods and third-party experiments. This study further delves into the specific effects of w/b, aggregate volume fraction (f_a), fly ash content, and ITZ thickness (h_ITZ) on the elastic modulus of leached concrete (E). The research findings indicate that an appropriate amount of fly ash can effectively enhance the leaching resistance of concrete. For a leaching degree of 10.0%, 30.0%, and 50.0%, E at w/b = 0.40 exceeds that of w/b = 0.60 by 26.71%, 28.43%, and 30.28%, respectively; E at h_ITZ = 10 μm exceeds that of h_ITZ = 50 μm by 16.96%, 15.80%, and 15.11%, respectively; and E at f_a = 65% is 39.82%, 43.15%, and 46.12% higher, respectively, than that of concrete with f_a = 45%. Furthermore, a linear correlation exists between the elastic modulus and the degree of leaching. The prediction method for the elastic modulus offers a theoretical foundation for in-depth exploration of the durability of leached mineral admixture concrete and its scientific application in practical engineering. Full article

The effect of creative industries in modern post-industrial realities is increasingly significant, becoming one of the economic drivers for developing countries. The creative sphere is more frequently being considered both in scientific circles and government programs in various countries, and the states of the Eurasian Economic Union (EAEU) are no exception. These countries have significant potential to develop creative industries due to the need for more efficient growth in new areas of the economy. The creative sector, in turn, can stimulate these economies by increasing jobs, heightening export volumes, and attracting investment. Governments are taking active measures to develop this sector by updating the regulatory framework and introducing effective ways to support entrepreneurship. This study analyzes the regulatory legal acts of the EAEU countries in the field of the creative economy. As a result, the main directions of development, measures of state support, and gaps in the existing legislative bases of the countries under consideration were identified. Based on the analysis, the authors have compiled recommendations for the development of policy in the creative sector. The application of the developed recommendations in practice can have a positive impact on the effectiveness of the creative economy’s development, both at the country level and at the level of the Eurasian Economic Union as a whole. Full article

Background/Objectives: Autorefractometers are valuable tools in clinical practice, but their accuracy is often questioned, especially in the pediatric population. This study aimed to compare refraction data from open-field and close-field autorefractometers and subjective refraction without using cycloplegia. Methods: A total of 50 eyes of 50 participants (19 males and 31 females, 11.8 ± 1.56 years) were evaluated. In a single visit, objective refraction was performed using NVision-K 5001 (open-field) and Visionix VX120 (close-field) autorefractometers, and subjective refraction using the fogging technique. Differences between procedures were assessed for sphere, spherical equivalent, and cylindrical vectors J₀ and J₄₅ using the Friedman test, followed by the post hoc Wilcoxon test as needed. Results: Significant differences were found in the sphere between the three procedures (all p ≤ 0.032). For the spherical equivalent, the Visionix VX120 differed significantly with the other two techniques (both p < 0.001), whereas no significant differences were found between NVision-K 5001 and subjective refraction (p = 0.193). Finally, no significant differences were observed for J₀ and J₄₅ vectors among the procedures (both p ≥ 0.166). Conclusions: There are certain discrepancies between autorefractometers and the subjective assessment of refractive error, most evident in measurements taken with the close-field device, possibly due to greater accommodative stimulation. However, in contexts such as visual screening or as a preliminary guide in the clinic, the values obtained by autorefractometry can provide useful information. Full article

In this work, we present the procedure to obtain exact spherical shape functions for finite element modeling applications, without resorting to any kind of approximation, for generic prismatic spherical elements and for the case of spherical six-node tri-rectangular and eight-node quadrangular spherical prisms. The proposed spherical shape functions, given in explicit analytical form, are expressed in geographic coordinates, namely colatitude, longitude and distance from the center of the sphere. We demonstrate that our analytical shape functions satisfy all the properties required by this class of functions, deriving at the same time the analytical expression of the Jacobian, which allows us changes in coordinate systems. Within the perspective of volume integration on Earth, entering a variety of geophysical and geodetic problems, as for mass change contribution to gravity, we consider our analytical expression of the shape functions and Jacobian for the six-node tri-rectangular and eight-node quadrangular right spherical prisms as reference volumes to evaluate the volume of generic spherical triangular and quadrangular prisms over the sphere; volume integration is carried out via Gauss–Legendre quadrature points. We show that for spherical quadrangular prisms, the percentage volume difference between the exact and the numerically evaluated volumes is independent from both the geographical position and the depth and ranges from 10⁻³ to lower than 10⁻⁴ for angular dimensions ranging from 1° × 1° to 0.25° × 0.25°. A satisfactory accuracy is attained for eight Gauss–Legendre quadrature points. We also solve the Poisson equation and compare the numerical solution with the analytical solution, obtained in the case of steady-state heat conduction with internal heat production. We show that, even with a relatively coarse grid, our elements are capable of providing a satisfactory fit between numerical and analytical solutions, with a maximum difference in the order of 0.2% of the exact value. Full article

Efficient autonomous exploration in unknown obstacle cluttered environments with interior obstacles remains a challenging task for mobile robots. In this work, we present a novel exploration process for a non-holonomic agent exploring 2D spaces using onboard LiDAR sensing. The proposed method generates velocity commands based on the calculation of the solution of an elliptic Partial Differential Equation with Dirichlet boundary conditions. While solving Laplace’s equation yields collision-free motion towards the free space boundary, the agent may become trapped in regions distant from free frontiers, where the potential field becomes almost flat, and consequently the agent’s velocity nullifies as the gradient vanishes. To address this, we solve a Poisson equation, introducing a source point on the free explored boundary which is located at the closest point from the agent and attracts it towards unexplored regions. The source values are determined by an exponential function based on the shortest path of a Hybrid Visibility Graph, a graph that models the explored space and connects obstacle regions via minimum-length edges. The computational process we apply is based on the Walking on Sphere algorithm, a method that employs Brownian motion and Monte Carlo Integration and ensures efficient calculation. We validate the approach using a real-world platform; an AmigoBot equipped with a LiDAR sensor, controlled via a ROS-MATLAB interface. Experimental results demonstrate that the proposed method provides smooth and deadlock-free navigation in complex, cluttered environments, highlighting its potential for robust autonomous exploration in unknown indoor spaces. Full article

Traditionally, formal education has favored boys, while girls, in the past, were relegated to the domestic sphere. This has been the case for centuries, without considering the possible specific cognitive needs of girls, which have been ignored. In Western countries, this has generated significant educational problems, especially in the learning of more technical subjects, with which girls not only do not identify but also often exclude themselves with the excuse that “it is not for them” (i.e., they tend to display a strong stereotype, a false belief, regarding these disciplines). The consequences have not been long in coming. Currently, in many Western countries, the low percentage of women in technical careers (such as Physics, Engineering, and Computer Science) is alarming. Is it possible to change stereotypes? This article addresses this complex issue, placing particular emphasis on the learning of spatial abilities, so important in all STEM careers (i.e., science, technology, engineering, and mathematics). This study concludes with examples of other stereotypes (mainly cultural) that have been eliminated or significantly reduced thanks to virtual reality (VR) and the help of artificial intelligence (AI). Could the same be achieved in the spatial domain? Full article

During automated packaging of white tea, uneven tea pile thickness leads to reduced weighing accuracy, while traditional experimental methods struggle to reveal the underlying particle flow mechanisms, hindering equipment optimization. Addressing the lack of discrete element method (DEM) parameters for Baihao Yinzhen tea, this study calibrates its DEM parameters based on the DEM approach, providing input for virtual commissioning of packaging machinery. Through physical experiments, the static friction coefficient (0.546), restitution coefficient (0.326), and rolling friction coefficient (0.133) between tea leaves and steel plates were determined. A three-dimensional DEM model of tea leaves was established using slicing techniques and the multi-sphere aggregation method. The steepest-ascent method and Box–Behnken design were employed to optimize the simulation parameters, resulting in the following optimal parameter combination: inter-particle restitution coefficient (0.16), static friction coefficient (0.14), and rolling friction coefficient (0.15). Validation simulations demonstrated that the mean angle of repose of tea leaves under the optimized parameter combination was 22.51°, with a relative error of only 1.29% compared to the actual experimental result of 22.80°. The calibrated parameters can be directly applied to the simulation of the feeding system in white tea automatic packaging machines, enabling optimization of vibration parameters through prediction of pile behavior, thereby reducing weighing errors. Full article

In this paper, we investigate the geometry and topology of compact warped product minimal submanifolds of arbitrary codimension immersed in a sphere. These submanifolds satisfy a specific pinching condition relating the length and Laplacian of the warping function to the dimensions of the warped product. Our results extend previous work on minimal immersions into the sphere. Full article

Environmental protection is one of the key challenges facing mankind today. Finding out what young people, referred to as Generation Z, think about this issue is extremely important, as they will be the first to experience the negative effects of environmental degradation. Research has shown that Generation Z has the greatest hope for solutions from the technological sphere. Thus, the economic and political spheres should support the development of technology in this area. The social sphere is rated lowest, which may reflect young people’s personal withdrawal and the delegation of responsibility for the environment’s future to engineers, entrepreneurs, and politicians. It is equally important to learn what constitutes an environmental imperative for Generation Z. It is based on new energy sources, energy producers, and the state’s pursuit of a policy of international cooperation in this area, supported by national legislative activity toward entrepreneurs and citizens. Research has demonstrated the need to raise awareness among young people, with a focus on individuals treated as subjects in their interaction with modern technology. Full article

We experimentally demonstrate high-resolution imaging using micro-objectives fabricated by two-photon polymerization (2PP) lithography, highlighting its potential as a flexible and precise fabrication method. The 2PP manufacturing process offers the ability to develop micro-optics with customized geometries and material properties, including tailored refractive indices. This flexibility introduces new degrees of freedom in optical system design and expands the applicability of micro-optics to advanced imaging tasks where other materials and fabrication methods are insufficient. For our study, bi-convex micro-optics with different geometries with radii of curvature of <15 $\mathsf{\mu }$m and minimized contact areas (<1 $\mathsf{\mu }$${\mathrm{m}}^2$) to ensure easy release from the substrate were fabricated with 2PP and investigated for their optical performance. With these micro-optics, the tracks with a pitch of 320 nm and the pits and lands as small as 130 nm were successfully resolved on a BluRay disc surface, demonstrating for the first time the high-resolution imaging capabilities of bi-convex spherical micro lenses. Full article

Accurate determination of the quantum yield (${\mathrm{\Phi }}_f$) in scattering media is essential for numerous scientific and industrial applications, but it remains challenging due to re-absorption and scattering-induced biases. In this study, we present a GPU-accelerated Monte Carlo simulation framework that solves the full fluorescence radiative transfer equation (FRTE), incorporating spectrally dependent absorption, scattering, and fluorescence cascade processes. The model accounts for re-emission shifts, energy scaling due to the Stokes shift and implements a digital optical twin of the experimental setup, including the precise description of the applied integrating sphere. Using Rhodamine 6G in both ethanol and PDMS matrices, we demonstrate the accuracy of the method by comparing simulated reflectance and transmission spectra with independent experimental measurements. ${\mathrm{\Phi }}_f$ and emission distributions are optimized using a Levenberg–Marquardt algorithm. The obtained quantum yields agree well with literature values for Rhodamine 6G. This approach eliminates the need for empirical correction factors, enabling the reliable determination of actual, undistorted emission spectra and the ${\mathrm{\Phi }}_f$ in complex scattering media. Full article