In the circumstance of big data, the traditional collaborative filtering recommendation algorithm in e-commerce system is faced with the problems of data sparse, accuracy, real-time and etc., this ...paper proposes an improved clustering-based collaborative filtering recommendation algorithm. The algorithm introduces time decay function for preprocessing the user’s rating and uses project attribute vectors to characterize projects, user interest vectors to users and use clustering algorithms to cluster the users and the projects respectively. Then the improved similarity measure methods are used to find the user’s nearest neighbor and project recommended candidate set in the cluster. Finally, recommendations are produced. Theoretical analysis and experimental results show that the algorithm not only can effectively solve the problems of data sparse and new project, but also can portrait for users in multi dimension and reflect the user’s interest changing. The recommended accuracy of the algorithm is improved obviously, too.
Topological phases of matter that have been recently extended to topological phases of sound can confine acoustic energy at the corners of higher-order topological insulators. We broaden this concept ...by incorporating parity-time symmetry and show new topologically protected confinement rules that are dictated by the geometrical arrangement of gain and loss units. Particularly, our findings reveal how sound trapping occurs at all corners when parity-time symmetry is intact, beyond the exceptional point within the broken phase; however, opposite corners sustain either sink- or sourcelike states that could lead to novel non-Hermitian guides for sound.
Realizing directional acoustic signal transmittance and reception robust against surrounding noise and competing signals is crucial in many areas such as communication, navigation, and detection for ...medical and industrial purposes. The fundamentally wide‐angled radiation pattern of most current acoustic sensors and transducers displays a major limitation of the performance when it comes to precise targeting and probing of sound particular of interest in human speaking and hearing. Here, it is shown how topological acoustic valley transport can be designed to enable a unique beamforming mechanism that renders a superdirective needle‐like sound radiation and reception pattern. The strategy rests on out‐coupling valley‐polarized edge states, whose beam is experimentally detected in the far‐field with 10° width and a sound‐intensity enhancement factor ≈10. Furthermore, anti‐interference communication is proposed where sound is received from desired directions, but background noise from other directions is successfully suppressed. This type of topological acoustic antenna offers new ways to control sound with improved performance and functionalities that are highly desirable for versatile applications.
The valley degree of freedom has emerged to realize a topological state known as the valley‐Hall effect. The acoustic version of the valley refers to frequency extrema of the band structure in momentum space exhibiting topologically nontrivial properties. Along this frontier, it is demonstrated how a topological acoustic antenna enables a unique beam‐forming mechanism rendering a superdirective needle‐like sound radiation.
The discovery of topological acoustics has revolutionized fundamental concepts of sound propagation, giving rise to strikingly unconventional acoustic edge modes immune to scattering. Because of the ...spinless nature of sound, the "spinlike" degree of freedom crucial to topological states in acoustic systems is commonly realized with circulating background flow or preset coupled resonator ring waveguides, which drastically increases the engineering complexity. Here we realize the acoustic pseudospin multipolar states in a simple flow-free symmetry-broken metamaterial lattice, where the clockwise (anticlockwise) sound propagation within each metamolecule emulates pseudospin down (pseudospin up). We demonstrate that tuning the strength of intermolecular coupling by simply contracting or expanding the metamolecule can induce the band inversion effect between the pseudospin dipole and quadrupole, which leads to a topological phase transition. Topologically protected edge states and reconfigurable topological one-way transmission for sound are further demonstrated. These results provide diverse routes to construct novel acoustic topological insulators with versatile applications.
Recycled water has been widely recognized in the world as an effective approach to relieve the issue of water shortage. Meanwhile, with several decades of development, the insufficiency of technology ...is no longer the primary factor that restricts the popularization of recycled water. What makes it difficult to promote the concept of reusing recycled water in China? To solve this issue, a special experiment on the public’s attitude towards the reuse of recycled water was designed based on a Single Category Implicit Association Test (SC-IAT), so as to avoid factors like social preference that can influence the survey results, and to gain the public’s negative implicit attitude towards reusing recycled water reuse, which is close to the public’s real attitude to it. From the perspective of implicit attitude, this research testifies the “spiritual contagion” phenomenon of the public, which refers to refusing recycled water reuse because recycled water is made from sewage treatment. By comparing the implicit attitude to recycled water reuse with the explicit attitude that is acquired from self-reporting questionnaires about reusing recycled water, this research finds that the implicit attitude is more positive than the explicit attitude, which accounts for the phenomenon of “best game no one played” in the promotion of the recycled water reuse, that is, the public though applauding the environment-friendly policy, will not actually use the recycled water.
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The atomic diffusion of a Fe–Al system under spark plasma sintering was investigated at temperatures ranging from 773 to 873K. A significant increase in the growth rate constant of ...Al13Fe4 and Al5Fe2 under the pulse current of spark plasma sintering was observed compared with the absence of current. The interdiffusion coefficient under pulse current was about 46 times higher than that without current at 873K. The activation energy for the interdiffusion was 332kJ/mol, which is higher than that without current of 155–190kJ/mol. Although the diffusion kinetics were enhanced, the thermodynamics state is not altered.
The coronavirus disease 2019 (COVID-19) pandemic continues to affect the mental health of college students in the post-epidemic era. We assessed the status and related factors of college students who ...are vulnerable to anxiety and depression during the COVID-19 lockdown.
This cross-sectional study was conducted two weeks after the beginning of the COVID-19 lockdown, from November 6, 2022, to December 2, 2022, with 1176 valid samples using convenience sampling. The Generalized Anxiety Disorder-7 (GAD-7) and Patient Health Questionnaire-9 (PHQ-9) were used to measure levels of anxiety and depression in college students. Factors related to anxiety, depression, and their comorbidity were analyzed using binary logistic regression.
The prevalence of anxiety, depression, and their comorbidity were 27.04%, 34.10%, and 25.60%, respectively. There was a higher risk of anxiety, depression, and their comorbidity among those who were currently living in rural areas. Compared with individuals with low monthly living expenses, those with higher monthly living expenses were less prone to anxiety, depression, and their comorbidity.
High prevalence of anxiety, depression, and their comorbidity were detected among college students during the COVID-19 lockdown. These were most common among college students who were senior students, had abnormal body mass index (BMI), were rural area residents, did study arts and humanities, were one-child in the family, and had low monthly living expenses and poor academic performance. Intervention practitioners and policymakers should formulate individualized prevention and intervention measures during the COVID-19 lockdown in the post-epidemic and possible future pandemics for college students.
To reduce the side effects of chemotherapy, nontoxic prodrugs activated by the tumor microenvironment are urgently required for use in cancer treatment. In this work, we developed prodrug 4 for ...tumor-targeting treatment and imaging of the anticancer drug release in vivo. Taking advantage of the high glutathione (GSH) concentration in cancer cells, the disulfide bond in prodrug 4 was cleaved, resulting in the release of an active anticancer drug and a near-infrared (NIR) fluorescence dye turn-on. Furthermore, contrast to the free anticancer drug, the prodrug exhibited higher cytotoxicity to hepatoma cells than that to normal HL-7702 cells. Thus, prodrug 4 is a promising platform for specific tumor-activatable drug delivery system, because of its favorable features of in situ and in vivo monitoring of the drug release and therapeutic efficacy.
In proof-of-work-based blockchain networks, the block miners participate in a crypto-puzzle solving competition to win the reward of publishing (i.e., mining) new blocks. Due to the remarkable ...difficulty of the crypto-puzzle, individual miners tend to join mining pools to secure stable profits. We study the dynamics of mining pool selection in a blockchain network, where mining pools may choose arbitrary block mining strategies. We identify the hash rate for puzzle-solving and the block propagation delay as two major factors determining the mining competition results. We then model the strategy evolution of individual miners as an evolutionary game. We provide the theoretical analysis of evolutionary stability in the pool selection dynamics for a two-pool case. Numerical simulations support our theoretical findings as well as demonstrate the stability in the evolution of miners' strategies in a general case.
Photodeformable liquid crystal polymers (LCPs) are a typical representative of shape‐changing systems capable of remotely converting light energy into mechanical actuation. Such smart polymeric ...materials combining the features of polymers and liquid crystals (LCs) are envisioned to bring new functionality and drive innovation in the fields of soft robotics, solar‐energy harvesting, and microfluidics. The photodeformable LCPs and their soft actuators fueled by light from ultraviolet to near infrared, including basic actuation as well as the primary mechanisms are focused on. The complex actuation is also highlighted with emphasis on the designed LC alignment, such as splayed, twisted, out‐plane, and patterned, which bridges the gap between the shape change and practical applications. Special attention is devoted to the progress of light‐fueled soft actuators, which are classified into different categories and comprehensively summarized in the aspects of materials, alignment, mechanisms, and light stimuli. An outlook on future challenges and limitations in the light‐fueled soft actuators are discussed at the end of this review.
Photodeformable liquid crystal polymers as typical shape‐changing systems are envisioned to bring new functionality in the fields of soft robotics, solar‐energy harvesting, and microfluidics. Recent advances in complex actuation are highlighted with the emphasis on the liquid crystal alignment. The light‐fueled soft actuators are classified and summarized in the aspects of materials, alignment, mechanisms, and light stimuli.
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