信号频谱虚拟分析的实验研究

为了让学生很好地掌握“信号的频谱分析”，建立信号“频域”的概念，开好“信号的频谱分析实验”尤为重要。为此，把计算机技术、虚拟仪器技术、多媒体技术三者融为一体，研制了“基于虚拟仪器的实验教学系统”，建立了虚拟实验教学平台。基于这个虚拟实验教学平台，制作“信号频谱虚拟分析”的实验教学课件。教学实践证明：该实验方法不仅很好地实现了信号的频谱分析，具有重放和再现实验过程和实验现象的特点，而且能同时观察到信号的时／频图，从而强化了实验结果，收到了很好的效果。     

双边频谱复系数简析

详细推导了周期信号双边频谱的两种复系数表达式,并与《信号与系统》教材中的复系数表达式进行比较,发现该教材公式推导中有概念性错误,并更正之.     

电视图象信号的频谱分析

本文从电视信号形成的角度，详细分析了从简单静止图象到复杂运动图象的电视图象信号的频谱结构。由于摄像机采用了扫描的方式将图象变化为图象信号，使得电视图象信号的频谱具有特殊的离散结构。从而为彩色电视技术在展宽频带的情况下，在亮度信号的频带内间插经过处理的色度信号的频谱，实现了彩色电视与黑白电视的兼容。     

频谱细化技术与功率倒频谱在振动信号分析中的应用

频谱细化技术和功率倒频谱是振动信号分析的两种重要辅助方法.采用细化处理,可以对信号频谱上感兴趣的一段频带进行“局部放大”,从而提高频率分辨率;倒频谱可以识别信号中较弱的周期成分,并对识别调制信号的边频县有特殊的效果.本文在介绍这两种方法基本原理的基础上,运用工程实例说明了其在振动信号分析中的实际应用效果.     

基于MATLAB的信号采样与重构的实现

该文基于MATLAB再现了连续信号的采样频谱和重构的时域信号,给出了信号重构的误差,并分析了采样周期对采样频谱叠加和信号重构精度的影响。     

数字电视亮色信号的二维频谱分析

阐述了数字电视的发展概况，对亮度信号和色度信号的二维频谱进行了较为详细的分析。     

基于MATLAB的声音信号频谱分析仪

对声音信号进行频谱分析,是认识声音信号和处理声音信号的重要方法,因而基于声音信号频谱检测具有重要的意义。通过PVDF压电薄膜传感器采集音频信号,利用信号处理模块、声卡和MATLAB工程软件对音频信号进行频谱分析,实现音频数据信息的分析显示。     

频谱概念的建立及其教学法探讨

频谱分析是信号与系统课程中基本理论,在通信学、控制学、测试学等学科都具有重要地位。本文提出一种频谱分析的概念建立的教学方法,该方法利用前修课程如电路分析、电子技术等课程的相关知识,结合具体电路与信号循序渐进地给出频谱及频谱分析的物理意义,然后再给出频谱分析的数学方法。本方法可以让学生更深刻地认识频谱的物理意义,亦在教学中取得了较好的效果。     

基于ARM7的语音采集频谱分析系统的设计实现

语音采集、频谱分析在生产实践中有着广泛的应用。本文基于ARM7设计实现了语音采集频谱分析系统,该系统结构简单、使用方便,充分利用了ARM7和PC机强大的数据处理功能对语音信号进行高精度采集和高准确度的频谱分析。     

连续时间周期信号频域分析的MATLAB实现

周期信号频谱分析是信号与系统课程中的重要内容,连续时间周期信号频谱的分析方法有傅立叶级数分析和傅立叶变换分析,可以通过对周期矩形脉冲信号的频谱分析来说明这两种方法的区别。利用MATLAB软件,结合其图形用户界面接口(GUI),设计具有良好人机交互界面的周期矩形脉冲的频谱分析仿真软件,既可辅助教师进行课堂教学演示,也可供学生进行实验仿真,得出满意的实验结果,进而帮助学生理解周期信号频谱的特点。     

Perspectives on Multi‐Material Craft in Basic Education

In Finland, the National Core Curriculum for basic education from 2014 discusses holistic and multi‐material craft, which includes technical work and textile work aiming to break down the gender‐based tradition in craft education. However, teachers have been confused about the concept of multi‐materiality; it has raised tension between textile work and technical work, and teachers have not found practical pedagogical solutions for teaching these subjects. In this systematic literature review, the main aim is to open the concept of multi‐materiality and give examples to implement multi‐materiality in craft during basic education. Twenty articles dealing with craft, multi‐materiality, material or materialisation formed the basis of the analysis. According to the results, the concept of multi‐materiality is open, it does not define the means by which the design and making process is supposed to be implemented or who is the actor. However, the clear impetus is non‐gender‐based and material‐free knowledge‐building and learning activities in craft education. The pedagogical examples presented in this article indicate that multi‐materiality is not an end itself. In advancing creativity, critical thinking, discovering and understanding of the technological and cultural world through multi‐materiality, student learning can have different starting points and can be implemented in diverse ways.     

浅析重要性原则在会计准则中的具体运用

重要性要求是会计信息质量的一项基本要求,在会计理论与实务中有着十分广泛的运用。运用重要性原则,有利于把握住问题的实质,抓住关键点,最终实现“较小的成本、较大的效益”的目的。本文主要介绍重要性原则在会计账户的设置、会计处理方法的选择和会计信息的披露等方面的具体运用。     

Exploring the Materiality of Literary Apps for Children

Children’s literature is increasingly being realized in app format, with its possibilities of combining text, music, sound effects, stills, animated movies, verbal language and, not least, interactivity. This digital and medial literary development calls for new analytical approaches to explore its manifestation in children’s literature – its materiality in particular. Exploring and analyzing the app Sofus and the Moonmachine by Burup et al. (Sofus and the Moonmaschine, The Outer Zone, Copenhagen, 2016), which integrates various art forms and sensory appeals and prompts different reading paths and types of interaction, this article suggests how a materiality approach can shed light on the formation of meaning in literary apps for children. The analysis is founded on three aspects of the materiality of literary apps: its manifestation as text, its embedment in a medium, and its manner of being and interacting with the world. The scholar of literature and technology, N. Katherine Hayles, has particularly emphasized the materiality of literature, and her theoretical framework will be combined with cultural theory on materiality and theory in children’s literature in order to examine how the concept of materiality may be used in approaching an understanding of literary apps for children and cross-media reading.     

审计重要性水平确定与运用中的相关问题

对如何理解审计重要性做了阐释。在此基础上,分析了注册会计师在计算会计报表层次以及各类交易、账户余额重要性水平时存在的问题,最后针对审计实务中如何恰当地确定重要性水平提出了建议。     

Using the (im)materialities framework to trace the contrapuntal lines of allegiance and belonging for globally mobile children

This paper discusses the use of Burnett, Merchant, Pahl and Rowsell’s (im)materiality literacy analysis framework to explore online and offline literacies in the lives of globally mobile children. The voices of these children have been little explored in New Literacies research. Globally mobile ‘third culture’ children who attend International Schools are often foreigners where they live, yet have multiple sites of belonging, including digital worlds. In analysing the abundant data of a year-long multicase study, the theoretical lenses of spatiality, mediation, materiality, and embodiment, as proposed in Burnett el al.’s framework, provided a productive framework through which to explore the complicated intersections of literacy, identity, and digital worlds in these children’s lives. The paper demonstrates how the framework might be applied, focusing on two of the children in the study. Prompted by insights provided by the (im)materiality framework, a contrapuntal metaphor is proposed as a way to understand allegiance and belonging in the lives of these globally mobile children.     

MANETs中基于链路有效性预测的高效AODV路由协议

针对传统AODV路由协议中周期性Hello消息广播机制会造成协议效率低下的问题,提出了一种利用无线链路有效性预测来降低Hello控制报文的新策略.首先给出了适用于视距无线传输环境下新的链路有效性预测模型,根据此模型所预测的无线链路生命周期来动态更新AODV路由协议中的Hello Interval配置参数,从而实现在不同链路稳定性下以不同频率广播Hello消息的目的.仿真结果表明,相比于采用周期性Hello消息广播机制的原协议而言,改进协议有效减少了不必要的报文开销,并在平均端到端时延和协议效率这2个性能指标上都获得了明显改善.     

媒体多任务一定会消极影响在线学习吗?——基于不同干扰条件下八年级学生学习数学视频的实验分析

媒体多任务通常被认为是影响在线学习的主要负面因素之一,而这种消极影响可能取决于多任务处理的频率。文章通过即时信息干扰数学视频学习的实验,对54名八年级学生在不同干扰条件下的学习效果进行了比较,结果发现:多任务处理频率是影响在线学习效果的关键条件,媒体多任务经验是影响在线学习效果的重要条件;对于媒体多任务经验丰富者来说,一定范围内的即时消息干扰并不影响学习效果,但当多任务处理超过一定范围时,学习效果将显著降低。基于实验分析结果,文章指出学习者可适当进行媒体多任务训练,以适应在线学习环境;在线学习过程中,教育工作者需注意将多任务处理频率控制在一定的范围内。     

东周文献对炎黄以前古史体系的构拟——兼论科学的中国古史体系重建的方法和理论

三皇合称始见于《周礼》,但最初三皇只是一种极笼统的总称或泛称,并无具体所指。直到北宋,三皇人物并未统一,统一的三皇古史体系尚未形成。从《左传》、《国语》等更早的东周文献,不难看出,汉人将祝融、共工纳入三皇古史体系,疑窦丛生,破绽百出。东周文献所记燧人氏、有巢氏、伏羲氏、女娲氏、神农氏的传说,明显具有人神不分、年代不明确、地点不固定、世系不清晰、史事自相矛盾等突出的特点,不可将其视为实录。然而结合考古学、民族学资料进行综合分析,则不难发现,东周文献所记三皇传说仍从一个侧面揭示出远古社会的某些真实可信的历史信息。由于东周文献和田野考古资料固有的复杂性,依靠田野考古资料和传统文献记载,试图重建中国上古时期尤其是远古时期的古史体系,迄今还面临着诸多难以克服的困难。徐中舒先生开创并积极实践的,将文献记载、考古学材料和民族学资料有机结合的＂古史三重证＂法,对于科学的中国古史体系的重建具有重要的方法论意义。     

1:1 (Dis)section ‐ Learning through Full‐Scale Dissection and Transformations of Abandoned Buildings

The section is an essential tool for understanding, exploring, representing and communicating spatial relations, structure and materiality in architecture, design and engineering, and therefore a recurring topic in the curricula. The section itself is destructive of nature and incompatible with a built environment in use or under construction. Hence, students throughout their education meet the section in the form of diagrammatic representations, that is, as forms of meaning emptied from scale, spatiality and materiality. This article reports on a series of four workshops, held in the spring semesters from 2011 to 2014 for first‐year students at Aarhus School of Architecture. The aim was to provide first‐year students with an experience of the relation between the section as a diagrammatic representation and the materiality, structure and spatial relations of a concrete building. The climax of each workshop was a full‐scale dissection and transformation of an abandoned house. As we shall see, the workshops fulfilled not only the intended learning goals, but created an initially unforeseen and unique context for learning about the relations between building and place and introduced the question regarding depopulation of rural areas as a pertinent processional challenge. Beyond an educational value, the research project ‘Transformation on abandonment, a new critical practice?’ transpired from the workshops. This research project and the interplay between teaching and research are discussed in the last part of the article.     

高校图书馆微信公众平台使用情况的调查与分析——以北京、上海8所211高校为例

通过对北京、上海8所211高校图书馆微信公众平台使用情况的调查,分析了大学生使用图书馆微信平台频率较低的原因。建议提高高校图书馆微信公众平台的认知度,构建丰富的微信平台信息内容体系,规范信息推送的时间和频率,并结合自身馆情向大学生提供个性化信息服务。