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電的道路電是已經得到了。强大的電子流準備着在有軌和無軌電車的發動機中大顯身手,使大大小小工廠裏的機床轉動,讓千千萬萬電燈泡發出明亮的光輝來。巨大的、久經訓練的‘電荷軍隊’正等侯着‘指揮员’的命令,他將給它們指出正確的前进道路。 現代化的軍隊到處都能够通行。在空中,有流的很好的絕缘體。電子愈來愈多了,積集在一塊金属片 相似文献
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在未曾發現近代應用的發電機以前,電的唯一的來源,要靠電池。因此在過去的時候,電池有它獨拈的一個時期。到發電機發明以後,發電機所供給的電量,遠遠比較電池大得多,大部份的電的來源,已經為發電機所替代了。然而有些特殊的用途,是仍然需要電池的,像手電筒、無線電(直流)等用電池就比較攜帶發電機便利得多。電池的種類也有許多種,如蓄電池、乾電池、硫酸銅電池、鎘標準電池等。就中以乾電池用途比較廣,製法也 相似文献
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時常有這種現象發生,就是電車行駛的時候,雖然車內的位子很空,但是司機台上却總有幾個小伙子站着。他們站在司機台內倒並不是因为前面風大涼快些,或者可以清晰地瞭望街景,享一享‘兜風之樂’,而是在看司機怎樣駕駛電車。久而久之,他們自己也就會覺得“我也會駕駛電車了”。這種情况,說明了青年朋友對學習技術的欲望是很高的,因此我想借科學大衆這個園地來談一談怎樣駕驶電車的問題。在談電車輸電路之前,先來談一下關於電車所用的電動機。我們知道,電車本身是很重的,搭載了乘客當然要更重些。電車開動的時候,因为惰性的關係,使得電車有保持靜止的趨勢,所以電車開動的時候,電動機所產生的扭力(即轉矩)除了克服空氣阻力、輪軌間摩擦力及其他的機械阻力以外,還要克服這種惰性,電車才能開動。電車一經開動以 相似文献
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《科学大众》1952,(10)
浮動電氣捕魚廠是利用近海上層魚類的趨光性,根據華南近海數百年來漁民積累的經驗,學習蘇聯電氣化及機械自動化的生產方法,在增產節約運動中由華南水產館水產研究組提出的合理化建議。係用一艘鐵躉船改裝,設有30(千瓦)220伏交流發電機一部,一百噸容積的冷藏庫設備一間,及半自動式的製罐室一间,主要設備為各種新式電氣自動化捕魚工具。因其可在近海港灣移動作業,故稱浮動電氣捕魚廠。趨光性魚類有很多種,如墨魚、柔魚仔、帶魚、公魚仔、力魚仔、春魚仔、池魚仔、花搶魚、交仔、青鱗、鳳尾魚等。舊式作業是用(舟古)仔艇(廣東以火引魚的船 圖2 浮動電氣捕魚廠放出捕鱼艇帶出刺網。稱(舟古)仔),晚上在海邊發见漁羣時就點起煤油燈將魚 相似文献
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在無邊的火烧般的太陽照耀下的草原上,高聳着巨型掘土機的龐大的金屬軀體。在蔚藍色的天空中挥動着它的懸臂,而在它俯瞰着的採掘场上,掘土斗正由一系列的鋼鏈操縱着,往土里掘進去,好像一隻大田鼠一樣。這隻大斗每掘一次要装進十四立方公尺多的土塊。然後,它突然輕巧地飛向上空。畫出一道平滑的曲線。剛才的田鼠現在變成了飛烏,在飛翔中把啣着的泥土完全抛掉。於是,掘土斗又降落到採掘場上,以便再去掘上滿满的一斗土塊……。掘土機的全部機構是由好些電動機帶動的。鋼的血管(電纜)把充沛的熱血(高壓電流)輸送給掘土機電流給各部電絞車的鋼鐵肌肉帶來了精力,於是,它們就把筋(钢纜和網鏈)給拉緊或者放鬆,操縱掘土斗的工作。電流還帶動強力的油泵,把油打到走動裝置的圓筒裹去。油的壓力非常高,整部龐大的掘土機雖然有一千多噸重,但是就能夠像浮在這油上似的,一步步地走動。這样看起來,掘土巨人手下的這些電動機负担的任務真是既艱巨又繁雜呢! 相似文献
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一 舊中國的機械工業是一個落後的殖民地性質的工業 舊中國的機械製造工業,從封建官僚李鴻章同治元年(1862)在上海設製砲局算起,到国民黨反動政權在大陸上被徹底推翻,已經有將近九十年的歷史。但是,在這漫長的歲月里,由於帝國主義与封建勢力的壓迫和束縛,機械工業和其他民族工業一樣,得不到正常的發展。官僚資本、帝國主義和部分民族資本,雖然也興辦了一些機械 相似文献
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This paper is concerned with some aspects of database interfaces for casual, naive users. A “casual user” is defined as an individual who wishes to execute queries once or twice a month, and a “naive user” is someone who has little or no expertise in operating computers. The study focuses on a specific group of casual, naive users, analyzes their needs and proposes a solution. The proposed interface consists of a graphical display of a model of a database and a natural language query language. One of the unique properties of the database interface is that it allows the user to see local item names within the context of a global structure. The interface was then tested to determine whether it was acceptable to the user population and to discover the level of graphical model that the users would find most comfortable. 相似文献
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Downloading software via Web is a major solution for publishers to deliver their software products. In this context, user interfaces for software downloading play a key role. Actually, they have to allow usable interactions as well as support users in taking conscious and coherent decisions about whether to accept to download a software product or not. This paper presents different design alternatives for software download interfaces, i.e. the interface that prompts the user if he wishes to actually complete its download, and evaluates their ability to improve the quality of user interactions while reducing errors in user decisions. More precisely, we compare Authenticode, the leading software download interface for Internet Explorer, to Question-&-Answer, a software download interface previously proposed by the authors Dini, Foglia, Prete, & Zanda (2007). Furthermore, we evaluate the effect of extending both interfaces by means of a reputation system similar to the eBay Feedback Forum. The results of the usability studies show that (i) the pure Question-&-Answer interface is the most effective in minimizing users incoherent behaviors, and (ii) the differences in reputation rankings significantly influence users. Overall results suggest guidelines to design the best interface depending on the context (brand reputation and product features). 相似文献
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企业人力资源开发是一个组织学习的过程。对企业人力资源开发角色的定位：学习建筑师、知识管理者、人力过程的协调者和现代开发工具的实践者，为人力资源开发更好服务于企业的战略发展提供了指导意义。 相似文献
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Numeric on-line databases (NDBs) have become essential in information retrieval (IR). NDBs differ from traditional bibliographic databases (BDBs) with respect to their content, structural complexity, data manipulation capabilities and the complexity of the user interfaces and user charging schemes. Recent trends in user charging for all on-line IR are toward charging for the information actually retrieved from the database rather than for the connect-time. However, the viability of such charging schemes depends on the user's possibilities of estimating the charges in advance, during the query negotiating phase. The problem of advance charge estimation in NDBs is addressed in this paper. In order to solve this problem, a method for estimating the numbers of data items satisfying the query expressions, i.e. the query cardinalities, is required. In this paper, an approach for advance estimation of query charges is developed and, based on it, a systematic and general method for query cardinality estimation is defined. The approach and the method are based on the well-known relational data model (RDM). The method is adapted to the new application area, user charge estimation in NDBs, and provides several improvements with respect to earlier cardinality estimation methods. Based on the method, several types of user charges can be estimated in advance. Tools based on the method are necessary components of query interfaces to NDBs if non-connect-timebased charging is used. The approach and the method are directly applicable to RDM-based NDBs. 相似文献
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Elke Duncker 《The Information Society》2000,16(3):187-199
Electronic computers in information systems are often seen as "ready-to-use" technology, which simply becomes applied to certain domains. This article explores the sociotechnical processes involved in the development of information systems by studying two cases of medical informatics, the Laboratory Instrument Computer (LINC) and a medical information system at a hospital. They show that information systems have from the beginning been a result of multiple alignment processes between the relevant actors, among which are users, developers, and the technology itself. The first case reveals that information systems are successful when actors become aligned and coordinated across boundaries. This alignment includes user interfaces as well as parts and components of the computer. The second case exhibits disalignment between relevant actors, which leads to an unstable information system. The two mechanisms are found coexisting in medical informatics. 相似文献
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图书馆数字资源整合与管理 总被引：26，自引：0，他引：26
过去我们使用的各种数字资源都以一种零散的、孤立的状态存在着，相互之间缺乏联系，检索界面繁多且不统一，给读者利用数字资源带来很大不便。因此，本文笔者认为主要是对大量的数字资源进行整合，并提出了理想的整合目标和研究方向，最后介绍了国内外数字资源整合最新研究成果。 相似文献
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uC/OS-II是一款非常优秀的开源实时嵌入式操作系统,但由于其简单功能特性,限制了应用范围,与其它支撑软件如TCP/IP、文件系统(FS)、图形界面(GUI)等结合使用构建嵌入式应用软件是一个必然的趋势。针对目前嵌入式系统对开发图形用户界面应用的迫切要求,详细介绍了图形用户界面软件uC/GUI在SmartARM2200的硬件平台上的移植过程和应用方法,归纳出整合移植的具体步骤,经任务实现证明,该整合移植工作是成功的,整合出的平台是稳定的,可靠的。 相似文献
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《International Journal of Information Management》2016,36(4):653-667
This study examines the effects of user experience on user resistance to change—particularly, on the relationship between user resistance to change and its antecedents (i.e. switching costs and perceived value) in the context of the voice user interface of an in-vehicle infotainment (IVI) system. This research offers several salient findings. First, it shows that user experience positively moderates the relationship between uncertainty costs (one type of switching cost) and user resistance. It also negatively moderates the association between perceived value and user resistance. Second, the research test results demonstrate that users with a high degree of prior experience with the voice user interface of other smart devices exhibit low user resistance to change to the voice user interface in an IVI system. Third, we show that three types of switching costs (transition costs, in particular) may directly influence users to resist a change to the voice user interface. Fourth, our test results empirically demonstrate that both switching costs and perceived value affect user resistance to change in the context of an IVI system, which differs from the traditional IS research setting (i.e. enterprise systems). These findings may guide not only platform leaders in designing user interfaces, user experiences, and marketing strategies, but also firms that want to defend themselves from platform envelopment while devising defensive strategies in platform and standards competition. 相似文献