In the selection of retrieval tools, comprehensive retrieval tools are generally used first, and then professional retrieval tools are used according to the subject content. The combination of the two can improve the recall and precision. Common methods can be divided into sequential method, reverse method and spot check method according to time range.
Sequential retrieval method is to search from far to near in chronological order from the retrieval subject until the found literature information meets the requirements. The advantage of this method is high recall rate, but the disadvantage is time-consuming and laborious.
Reverse search method is a method to find documents from near to far in reverse time. This method is mostly used in new topics or old topics with new contents, and what is needed is the recently published literature, so as to grasp the level and research trend of this topic in recent years.
Therefore, once you have mastered the required literature information, you can stop searching. The advantage of this method is to save time, but the disadvantage is that the missed detection rate is high.
Spot check method is a method of searching year by year according to the characteristics of the development of research topics, grasping a period of rapid development of disciplines and more published documents. The advantage of this method is that it can obtain more literature information with less retrieval time, but the disadvantage is that it is necessary to be familiar with the characteristics of subject development, otherwise it is difficult to achieve the expected results.
Retrospective method, also known as retrospective method, is a method of tracing from near to far by using the references behind the existing documents. The advantage of this method is intuitive and convenient, and it can be traced back to a large number of references on a certain subject. This is a good way to expand information sources without or without retrieval tools.
The disadvantages are low retrieval efficiency, low recall rate and high missed detection rate. Comprehensive method, also known as circular method, subsection method or alternating method, is the synthesis of common law and retrospective method.
In other words, the references behind the retrieval tools and documents are used for backtracking. These two methods can be used alternately until they are satisfied, and higher recall and accuracy can be obtained. Is one of the commonly used methods.
The way of document retrieval When using retrieval tools, we mainly use its various indexes, that is, through the various retrieval methods provided by the indexes of retrieval tools to find documents. Retrieval methods are mainly divided into the following categories: content feature method classification method is a method to retrieve documents according to subject attributes.
The classification table of retrieval tools provides a method to retrieve documents from the perspective of classification, and the key to its retrieval lies in correctly understanding the classification table in retrieval tools. Classified literature retrieval is convenient to obtain systematic literature clues from the perspective of discipline system, that is, the function of national retrieval.
The texts of most retrieval tools are arranged according to classification, so we can use its classification catalogue table for classified retrieval. Classification can centrally retrieve the literature information of the same discipline, but it is difficult to give the exact categories of some emerging disciplines and marginal disciplines, which is easy to cause false detection and missed detection.
Therefore, when retrieving documents from classification, we must master the classification system and related rules of the subject. Subject method is a retrieval method based on the subject content of literature information.
Use keywords, keywords and descriptors extracted from the document information to represent the content of the document, and arrange them in alphabetical order. As long as the searcher determines the search term according to the subject, he can search one by one in word order like a dictionary, and find the necessary clues from the index items under the search term.
Topic method is flexible and accurate in expressing concepts, and documents with the same topic content can be gathered together and retrieved at the same time. External feature method title method is a method to retrieve documents according to titles.
Generally used to find books, periodicals and individual documents. Author method is a method to find documents according to the names of known authors.
Through the author's way, we can retrieve the main literature information of an author's special research. Numeric method is a method to find documents according to known numbers.
Such as patent number index, standard number index of standard documents, etc. The other way is auxiliary retrieval, which can find the index of the required literature in a special way.
Such as drug name index, molecular formula index, etc. Document retrieval steps Document retrieval is a process of retrieving documents according to certain steps by using retrieval tools according to the requirements of the subject.
The scientific arrangement of retrieval steps is called retrieval strategy. Retrieval strategy is an information retrieval scheme designed for retrieval problems, which adopts retrieval interview and technology to achieve a certain precision and recall.
Literature retrieval generally goes through the following steps: analyzing the theme and formulating retrieval strategies, first of all, we must understand the purpose and significance of the theme, make clear the theme, research points and main characteristics of the theme, and then formulate retrieval strategies according to the characteristics and retrieval requirements of the theme. The formulation of retrieval strategy includes retrieval problems, the selection of retrieval methods, the selection of retrieval tools, and the limitation of retrieval scope (specialty, time, language, and literature type), among which the most important thing is to determine retrieval marks, such as keywords, subject words, classification numbers, authors, author units, etc.
A search query expression consists of a search identifier according to a Boolean logical relationship. Using retrieval tools to find literature clues According to the needs of subject retrieval, select relevant retrieval tools, then use the constructed retrieval questions according to the corresponding retrieval channels to find relevant indexes, and then find corresponding literature clues in the literature part or title record part according to the addresses indicated by the indexes, such as title, content summary, author and author unit, literature source, etc.
To obtain the original document according to the document source, we must first identify the document source through the document type, and the abbreviation should be restored to the original name. Then according to the full name of the literature source, find the corresponding collection catalogue and collect the collection units, and then borrow or copy the original literature.
2.20 1 1 comprehensive textbook of secretarial management and applied writing assignments 4. Briefly describe the methods of document retrieval. The direct method of document retrieval, also known as the common method, refers to the method of directly using the retrieval system (tool) to retrieve document information.
It is also divided into sequential investigation, reverse investigation and spot check. Sequential retrieval method refers to the method of using retrieval system to retrieve literature information from far to near in time sequence.
This method can collect systematic documents of a certain discipline and is suitable for document retrieval of larger disciplines. For example, to know the initial age of a subject, we need to know the whole process of its development now, so we can use the sequential search method to start from the initial age and gradually find it in the near future.
Reverse retrieval method is a method of literature retrieval by using retrieval tools from near to far, from new to old, and in reverse time sequence. This law focuses on recent literature.
Using this method, you can get the latest information as soon as possible. Spot-check method Spot-check method refers to the method of selecting the most possible or most possible time period of document information related to the project according to the characteristics of the project, and using retrieval tools to carry out key retrieval.
Tracing method refers to the method of tracing the original texts (cited documents) one by one by using the references listed at the back of the documents without using the general retrieval system, and then expanding the scope of literature information one by one from the list of references listed at the back of these original texts and tracing them one by one. It can snowball and get better retrieval results according to the citation relationship between documents.
Circular method is also called subsection method or synthesis method. It uses direct method and backtracking method alternately in stages to learn from each other's strong points and cooperate with each other to obtain better retrieval results.
3. Document retrieval task: Power Quality refers to high-quality power supply in general, including voltage quality, current quality, power supply quality and power consumption quality.
It can be defined as the deviation of voltage, current or frequency that leads to electrical equipment failure or abnormal operation, including frequency deviation, voltage deviation, voltage fluctuation and flicker, three-phase imbalance, temporary or instantaneous overvoltage, waveform distortion (harmonics), voltage sag, interruption, sag and power supply continuity. In modern power system, voltage sag and interruption have become the most important power quality problems, 1, ISTP CD-ROM database H Laaksonen, P Saari, R Komulainen, "Microgrid with Power Quality Compensator to Provide High-quality Power", 2006 15 International Conference on Application Simulation and Modeling, pp. 328-333. Document type: Conference Paper 2, Wanfang Paper Full-text Database, Chen Xiangxun, "Several Methods of Measuring and Classifying Power Quality Disturbances by Wavelet Technology" 2002 Document type: Journal Paper 3, China Journal Network Full-text Database, "Application of Power Quality Monitoring System and Data Analysis Method". Technology,No. 14, 2009: 4 periodical papers, IEE electronic library (IEL) Kushare, Bansidhar E., Ghatol, Ashok A Kara, Sumit; "Development of web-based power quality monitoring system for handling customized power quality queries and automatic power quality monitoring report notifications via e-mail", Information and Communication Technology in Electronic Science (ICTES 2007), 2007.ictes.iet-uk International Conference, 20071February 20-22 (S):/KLOC-. Zhang, Da Hai, "Research on Power Communication Network and Power Quality Monitoring by OPNET", in ICIEA 2007: 2007 Second IEEE Conference on Industrial Electronics and Applications, p 507-5 1 1, 2007, ICIEA 2007: 2007 Literature Types of the Second IEEE Conference on Industrial Electronics and Applications in 2007: Discussion on the Special Topic of "Power Quality" and Experience of Literature Retrieval XXX (Guangzhou 5 10640, School) Based on the analysis of the principle of scientific and technological literature retrieval, this paper studies the research background and present situation of power quality, adopts domestic and foreign literature retrieval tools, and conducts scientific and technological literature retrieval around this topic, and studies the research background and background of this topic.
Keywords: power quality literature retrieval 1 introduction: With the development of science and technology and national economy, the demand for power is increasing, and the requirements for power quality are getting higher and higher. Power quality is becoming more and more important, and power departments and users pay more and more attention to power quality.
What is power quality? The related terms used in many documents and reports in this research field are as follows: ① Voltage quality refers to the deviation between the actual voltage and the ideal voltage, which should be understood as a generalized deviation, that is, it includes amplitude, waveform, phase and so on. , reflecting whether the power provided by power supply enterprises to users is qualified. Although this definition can include most power quality problems, it cannot or should not include quality problems caused by frequency, and does not include the influence of current on quality.
(2) The current quality requires users to take the current with constant frequency and sine wave shape, and make the current waveform in phase with the power supply voltage to ensure the system to run with high power factor. This definition is helpful to improve the power quality of power grid and reduce line loss, but it can't summarize most quality problems caused by voltage, and the quality problems caused by voltage are often not always caused by electricity consumption.
(3) Power supply quality should include technical meaning and non-technical meaning. The technical meaning includes voltage quality and power supply reliability. Non-technical meaning refers to service quality, including the response speed of power supply enterprises to users' complaints and complaints, the rationality and transparency of electricity prices. (4) the quality of electricity should include the current quality and non-technical meaning, such as whether the user pays the electricity bill in full and on time. , reflecting the responsibilities and obligations of power users in the interaction and influence between supply and demand.
[1] It can be seen that improving power quality is of great significance for the safe and economic operation of power grid and electrical equipment, ensuring product quality and scientific experiments, as well as people's normal life and production. Power quality is directly related to the overall benefits of the national economy.
The main way for me to study power quality is through scientific and technological literature retrieval. Document retrieval is the behavior, equation and procedure of finding the needed information quickly and accurately from a large number of documents.
It plays a very important role for researchers, such as promoting the development of intellectual resources; Save scientific research time; Avoid repeated research and detours. A great deal of literature information about research topics can be obtained by consulting various databases, and a great number of excellent domestic periodical papers can be obtained by searching the full-text database of China Journal Network. Other Chinese literature databases include Wanfang Database.
In addition, excellent foreign periodical papers can be retrieved by searching IEEE/IEE Electronic Library (IEL), EI, ISTP CD-ROM database, etc. This paper mainly shows the research results of literature retrieval on the subject of power quality, and generally discusses the research status, achievements and development of power quality. The methods and development of literature retrieval are also discussed.
2. Basic principles of scientific and technological literature retrieval 2. 1 retrieval system The tools used to report, store and retrieve documents are retrieval tools or retrieval system computer retrieval system.
4. How to write a book in literature retrieval: author and editor? Title and chapter name.
Other authors. Place of publication.
Publication shooting. Publication time.
Page number publishing house, her bookstore, periodical, author's name. The title of the article.
Journal name. Number of cycles.
Date of publication. Page journal transaction progress letter annual action report review progress report meeting document? Author's name.
Title of the article. The name of the meeting.
Matters for convening the meeting. Count.
Page conference CGA pter PDF symp. Author of the seminar report of the Congress of Osim Seminar.
Report name. The New York Times reported that.
Report number. Report completion unit.
Report completion time Report the name of the patent inventor. Name of invention.
International patent number. Date of application for transfer.
Patent number: patent country code-serial number Patent standard document cover: project name retrieval unit entrustment time completion time text: project key points retrieval: retrieval system, database selection, retrieval year, retrieval strategy (this part is more important, which reflects the scientific nature of retrieval and directly affects the recall and precision of retrieval) Retrieval result: conclusion retrieval time (seal) of the retrieval unit where the searcher works.
5. Help me find a document retrieval report, an example information retrieval report-topic analysis of graduation thesis "Research on New Waterproof Coatings" Waterproof coatings can be divided into many kinds according to their uses. My graduation thesis mainly studies the most widely used building waterproof coatings. Waterproof coatings for buildings are mainly composed of synthetic polymer materials, asphalt, polymer modified asphalt and inorganic materials. , with appropriate additives and modified materials. Filler materials, etc. Compared with waterproof coiled material, waterproof coating is simple in construction, suitable for any shape of base surface, and can form dense and seamless coating film. Therefore, waterproof coatings are widely used in various waterproof projects and have achieved rapid development. The research of this topic is mainly divided into three stages. +0. 1 Preparation for the research of new waterproof: (1) Understand the research status and development prospect of waterproof coatings at home and abroad. (2) Understand the application status of building waterproof coatings in China. Compared with foreign countries, there are some shortcomings. (3) Further research on waterproof coatings at home and abroad. (4) Research status and application status of new waterproof coatings. (5) Problems still to be solved in the application of waterproof coatings. (1.2) Research and preparation of new waterproof coating. (1) At present, there are studies on the formulation of the preparation. (2) Preparation of laboratory products. (3) Performance test of products. (4) Comprehensive accounting and evaluation of product environmental protection and application promotion. 1.3 Current problems (1) Limitation of laboratory conditions (2) Purchase of various raw materials (3) Cost of performance testing (2). Background information 2. 1 Concept of building waterproof coating Building waterproof material is an important part of building materials and belongs to functional materials. The main purpose of using waterproof materials in buildings and structures is to prevent moisture, seepage and leakage. Building waterproof coating (hereinafter referred to as waterproof coating) is a kind of building waterproof material. The coating can be painted or sprayed on the surface of the base layer that needs waterproof treatment alone or in combination with the matrix reinforcing material, forming a continuous and seamless coating waterproof layer with a certain thickness at room temperature, which can meet the requirements of buildings such as roofs and basements. Waterproof and impermeability requirements for toilets and external walls. Waterproof coating is generally a composite material with asphalt, synthetic polymer, synthetic polymer and asphalt, synthetic polymer and cement or inorganic composite material as main raw materials, with appropriate amount of pigments, additives and solvents, and no fixed shape of solvent, emulsion or reactive, viscous liquid or liquefied solid powder at room temperature. See the search results (1) for its development overview. 2.3 Problems to be solved in the research and application of waterproof coatings at present (1) Most waterproof coatings are solvent-based and pollute the environment, but the quality of water emulsion polymer modified waterproof coatings is not stable enough. (2) The mechanical properties, waterproof properties and durability of some polymer waterproof coatings are not ideal. (3) Some manufacturers try to reduce costs. As a result, a large number of unqualified products flow into the market. 3. Problems to be solved (1) Search the background knowledge and related basic knowledge of building waterproof coating preparation. (2) Find out the research status of building waterproof coatings in China. (3) Find out the application status of building waterproof coatings. (4) Understand the problems that need to be solved urgently at present. (5) Learn the production formula and technology of various waterproof coatings. 4. Retrieval Process and Method 4. 1 Database of Tunnel and Retrieval Process of Search Engine (1) The Chinese and foreign literature databases of Tunnel are: China Journal Network (CNKI), VIP Chinese Journal Full-text Database, Wanfang Database, China Patent Database, EBSCO Database and CSA Database. (2) Search engines used in the retrieval process: Google, Baidu.4. 2 Search mode Keywords: waterproof coating Google search engine: search terms include: ① waterproof coating ② search results: research and development of building waterproof coating ③ preparation of building waterproof coating; cnki database search: ① database: full-text database of China journals ② search keywords: building waterproof coating ③ literature classification: building chemical industry ④ cross-database search: title: matching of building waterproof coating: fuzzy. 1960-2006 Directory: Building Chemical Wanfang Database Search ① Search Keywords: Building Waterproof Coatings ③ Literature Classification: Building Chemical Weipu Chinese Journal Full-text Database Search Keywords: Building Waterproof Coatings Theme: Research and Preparation 5. Search results (1) Title: Present situation and development of my building waterproof coatings by Yu Jianying; Dong Lianbao; Kong Xianming; Author Wuhan University of Technology; Jinan iron and steel group company raw materials division; Petroleum University (East China); Wuhan, Hubei; Jinan, Shandong; Dongying, Shandong; Title: New Building Materials, E-mail 10 of editorial department, 2004. Honors: An Overview of China's Core Journals. The key words of building waterproof coating are included in China periodical square CJFD, an ASPT source periodical; Current situation; Development; This paper introduces the present situation and existing problems of building waterproof coatings in China, and puts forward that the development of building waterproof coatings in China should be from solvent to water emulsion, from thin to thick, from dark to bright, from low-grade to high elasticity, high durability and functionality. Vigorously research and promote high-performance, high-weather-resistant, environmentally-friendly waterproof coatings and multifunctional waterproof coatings, focusing on the development of environmentally-friendly polyurethane and acrylic acid. Asphalt rubber and cement-based permeable crystalline waterproof coatings will increase the proportion of middle and high-grade waterproof coatings and accelerate the development and popularization of engineering machines and tools. Doicnki: ISSN:1001-702x.0.2004-10/0/2 (2) The theme of Guangsha, the author of architectural waterproof coating in China. Title: E-mail of the editorial department of Building Materials Industry Information No.08, 2003 Journal Honor: Ye The subject author of Building Waterproof Coatings was included in CJFD Source Journal: ISSN:1002-9885.0.2003-08-003; Title: monthly magazine of construction workers and architects, editor's mailbox, No.3 issue in 2006. Honors: ASPT source journal, China periodical phalanx CJFD included journal, doi CNKI: ISSN:1002-3232.0.2006-03.0 (4) Li Changren, author of Waterproof Coatings for Environmentally Friendly Buildings; Chinese name technology in newspapers.
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