柴油发电机组噪声控制研究

柴油发电机组噪声强,发热量大。针对此,采用隔声、吸声、消声、通风散热等具体措施。实践证明：方案设计合理,达到了预期的降噪效果,符合工业企业噪声排放标准。     

我国图书馆网络导读研究分析

本文采用文献法收集20世纪90年代以来我国图书馆网络导读研究的一些相关文献,从网络导读的定义及产生背景、内容、特点、技术手段等方面进行分析,提出我国网络导读存在的问题及建议,旨在为学者对网络导读研究提供参考,并推动图书馆网络导读工作的开展。     

基于MAX260的程控滤波器设计

为了在移频信号检测中能够去除工频信号及其谐波的干扰,在移频信号检测仪的前端采用程控滤波器达到在不同中心频点滤除干扰信号的目的。通过程控改变其频率和品质因数的控制字可以实现多个频点的切换,并给出基于MAX260芯片的程控多频点切比雪夫带通滤波器的设计实例和示波器测试结果,测试结果显示在偏离中心频率40Hz内达到平坦度为0...     

用“英特尔@未来教育”理念实施小学数学“自主、合作、探究”研究性教学

英特尔@未来教育理念是一种以教师为主导,学生为主体,实施研究性课题和问题导向式的学习模式,它为我们提供了一种崭新自主、合作、探究的学习模式。本文结合教学实例从小学数学新课程倡导研究性学习的探究性、自主性、开放性、合作性等4个方面探索了怎样在平时数学教学中运用英特尔未来教育理念。     

A mobile augmented reality system to conduct electrical machines laboratory for undergraduate engineering students during the COVID pandemic

Education and Information Technologies - This paper reported an AR based teaching method adopted during the movement control period for undergraduate engineering students to perform electrical...     

Secondary Students’ Stable and Unstable Optics Conceptions Using Contextualized Questions

This study focuses on elucidating and explaining reasons for the stability of and interrelationships between students’ conceptions about Light Propagation and Visibility of Objects using contextualized questions across 3 years of secondary schooling from Years 7 to 9. In a large-scale quantitative study involving 1,233 Korean students and 1,149 Singaporean students, data were analyzed from responses to the Light Propagation Diagnostic Instrument consisting of four pairs of items, each of which evaluated the same concept in two different problem situations. Findings show that only about 10–45 % of students could apply their conceptions of basic optics in contextualized problem situations giving rise to both stable and unstable alternative conceptions. Students’ understanding of Light Propagation concepts compared with Visibility of Objects concepts was more stable in different problem situations. The concepts of Light Propagation and Visibility of Objects were only moderately correlated. School grade was not a strong predictive variable, but students’ school achievement correlated strongly with their conceptual understanding in optics. The teaching and learning approach and education systems in the two countries may have had some influence on students’ conceptual understanding.     

Academic social bookmarking: An empirical analysis of Connotea users

Three groups of social bookmarking users, namely experienced users, users with moderate level of experience, and novice users, were investigated, in terms of their reported tagging behaviors, perceived usefulness of social bookmarking in information discovery and management, and perceived usefulness of the bookmarking features provided. Based on the empirical analysis of the Connotea users, who are primarily in academia, the study shows that experienced academic users generally prefer to use social bookmarking while moderately experienced and novice users still prefer to use the traditional bookmarking methods, such as creating and using bookmarks on a dedicated computer. Experienced academic users were also found to create more tags per bookmark comparing to the other two groups. Most novice academic users, however, only created one tag per bookmark, which just met Connotea's minimum requirement. Surprisingly different from the collaborative design nature of the social bookmarking systems, the study finds that our participants, particularly experienced academic users, prefer to create and use their own bookmarks rather than sharing bookmarks created by others. In fact, experienced users have significantly higher frequency (once every two weeks) of creating bookmarks than the other two groups (once a month or less). In addition, website design features and functions, such as automatic collection of bibliographic information, are regarded by all participants as helpful for information discovery. The in-depth examination and discussion of the opinions of Connotea users may be useful for further improvement of the design features and usage applications, particularly for academic social bookmarking websites. The results may also have potential implications to the future development of social bookmarking services in general.     

Magnetically encoded 3D mesostructure with high-order shape morphing and high-frequency actuation

Inspired by origami/kirigami, three-dimensional (3D) mesostructures assembled via a mechanics-guided approach, with reversible and maneuverable shape-morphing capabilities, have attracted great interest with regard to a broad range of applications. Despite intensive studies, the development of morphable 3D mesostructures with high-order (multi-degree-of-freedom) deformation and untethered high-frequency actuation remains challenging. This work introduces a scheme for a magnetically encoded transferable 3D mesostructure, with polyethylene terephthalate (PET) film as the skeleton and discrete magnetic domains as actuation units, to address this challenge. The high-order deformation, including hierarchical, multidirectional and blending shape morphing, is realized by encoding 3D discrete magnetization profiles on the architecture through ultraviolet curing. Reconfigurable 3D mesostructures with a modest structural modulus (∼3 GPa) enable both high-frequency (∼55 Hz) and large-deformation (∼66.8%) actuation under an alternating magnetic field. Additionally, combined with the shape-retention and adhesion property of PET, these 3D mesostructures can be readily transferred and attached to many solid substrates. On this basis, diverse functional devices, including a switchable colour letter display, liquid mixer, sequential flashlight and biomimetic sliding robot, are demonstrated to offer new perspectives for robotics and microelectronics.     

深化民族团结进步教育的几个基本问题

铸牢中华民族共同体意识是推动我国新时代民族团结进步教育高质量发展的主线和“纲”。同时,铸牢中华民族共同体意识也提出了深化民族团结进步教育的要求。在铸牢中华民族共同体意识视域下开展深化民族团结进步教育的背景、含义、意义、价值旨归与实施路径等问题的研究,以此为深化民族团结进步教育提供根本遵循、认识基础和学理依据。     

(NH4)3B11PO19F3: a deep-UV nonlinear optical crystal with unique [B5PO10F]∞ layers

Deep-ultraviolet (DUV) nonlinear optical (NLO) crystals that can extend the output range of coherent light below 200 nm are pivotal materials for solid-state lasers. To date, KBe₂BO₃F₂ (KBBF) is the only usable crystal that can generate DUV coherent light by direct second harmonic generation (SHG), but the layered growth habit and toxic ingredients limit its application. Herein, we report a new fluoroborophosphate, (NH₄)₃B₁₁PO₁₉F₃ (ABPF), containing four different functional units: [BO₃], [BO₄], [BO₃F] and [PO₄]. ABPF exhibits a KBBF-like structure while eliminating the limitations of KBBF crystal. The unique [B₅PO₁₀F]_∞ layers enhance ABPF’s performance; for example, it has a large SHG response (1.2 × KDP) and a sufficient birefringence (0.088 at 1064 nm) that enables the shortest phase-matching wavelength to reach the DUV region. Meanwhile, the introduction of strong B-O-P covalent bonds decreases the layered growth habit. These findings will enrich the structural chemistry of fluoroborophosphate and contribute to the discovery of more excellent DUV NLO crystals.