CA6140車床831008撥叉零件數(shù)控加工工藝及鉆φ20孔夾具工裝設(shè)計【含CAD圖紙和說明書】
CA6140車床831008撥叉零件數(shù)控加工工藝及鉆φ20孔夾具工裝設(shè)計【含CAD圖紙和說明書】,含CAD圖紙和說明書,ca6140,車床,零件,數(shù)控,加工,工藝,20,夾具,工裝,設(shè)計,cad,圖紙,以及,說明書,仿單
20 屆本科畢業(yè)論文（設(shè)計）
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Network architectures
The term architecture is commonly used today to describe networks. A network architecture, such as illustrated in Fig.1.7, describes the components in the network, how they operate , and what form they take . A network encompasses hardware, software, data link controls (DLC), Standards, topology, and protocols.
1. hardware
The physical equipment in the network is referred to as the hardware. Typical of such equipment are computers, modems, telephone, terminals , machines, controllers, and the like.
2. Software
Software consists of programs, procedures, and sometimes, associated documentation of the operation of the communication system. Communications software (CSW), application programs (AP), network control programs (NCP), operating system (OS), and database management system (DBMS) are examples of software.
3. Protocols
A protocol defines how network components establish communications, exchange data, and terminate communications. A protocol is essentially a formal set of conventions, or rules, between communicating processes about of messages to be exchanged. Handshaking and line discipline are also protocols. To make implementation and usage more convenient in sophisticated networks, higher-level protocols may use lower-level in a layered fashion.
4. Data link controls
A data link consists of electronic equipment such as electronic devices, terminals, and machines and the interfacing circuits that are operating in a particular way to permit information to be exchanged between installations. The specific method of operation is defined by transmission codes, transmission modes, and direction control.
There are two major categories link control protocol in use today:
(1) Asynchronous, in which bit streams are transferred at fixed rates with the transmitter and receiver operating in synchronization by the clock.
(2）The flow of date to and from the many points and links within the network must be controlled and orderly. The sending and receiving sites must sequencing of the messages being transmitted among all users. The connection path between sits is usually shared by more than one user, as multipoint configuration.
A multi-point line, sometimes called a multi-drop line, is a communications line having several subsidiary controllers that share time on the line under the control of a central site.
Date line controls provide for all these needs. They manage the flow of data messages across the communications path, or links. In essence, they are special kinds of protocols consisting of a combination of software and hardware located at each site in the network. Through a communication link, the DLC protocol pro-vides for the reliable interchange of information between data terminal equipment. Typical DLC functions in the network are the following:
Synchronizing the sender and receiver
1) Controlling the sending and receiving of data
2) Detecting and recovering transmission errors between two points
3) Maintaining awareness of link conditions
4) Topologies
Topology describes the surface layout the elements comprising the communications network-----that is, it is the shape of the system. Communication system may be implemented in a variety of ways. typical communication system are telephone lines, radio wave links, networks, serial connections, parallel connections and power line system modulations. The choice of topology depends on factors such as cost, response time, throughput, capacity, load sharing, and capacity needs.
5. Local area networks
A local area network (LAN) is a communications network operating in a local area. It extends from several hundred to several thousand feet within a building or other facility. A LAN is owned and operated by an individual or organization and is, therefore, not subject to regulation by either the federal communications commission (FCC) or the state Public Utility Commission (PUS). A LAN is a means of connecting various types of equipment for the purpose of sharing resources and communicating in a distributed processing environment, as illustrated in fig .1.8. that is , all device that must communicate with one another in a CIM environment can be tied together though some form of common interface such as a LAN .
An effective LAN has specific characteristics. Typical of these are the following:
① Is in a moderate-sized geographic area (office, laboratory, building, factory, industrial complex, or campus, for example)
② Has medium –to high –sped data channel(s)
③ Provides reliable communications
④ Is owned and used by a single organization
⑤ Connects independent devices rather than a device and its peripherals
A LAN usually has four major components that serve to transport data between end users: user workstation, protocol control logic. medium interface, and physical path.
6. User workstation
The user workstation is used to accomplish an application. The station can be anything from a word processor to a mainframe computer.
(1) Protocol control logic
A protocol control logic takes user is information and converts it to a protocol that can move the LAN network to reach the desired location , the protocol logic also controls the LAN and provides for the end user is access to the network .
（2) Medium Interface
The medium interface function generates the electrical signals to be transmitted on the LAN the interface is between the path the protocol logic can take several forms, typical of which are CATV (cable television) taps , infrared diodes for infrared path , microwave antennas, or complex laser-emitting semiconductors for optic fibers.
(3) Physical Path
A LAN is path may consist of coaxial TV cables, coaxial bade-band cables, twisted pair of wires, optic fibers, and microwaves. Cable TV coaxial cable is used in many networks because it has a high capacity, a very good signal-to-noise ratio, low signal radiation, and low error rates.
(4) Manufacturing Automation Protocol
There are many types and sizes of networks. Some LAN systems are owned by an organization and are confined to the premise of that organization. Others are owned by national or international public networks that may be accessed by the user. In many case, LAN systems may also connect to public networks and be able to access them.
Network are also connected in several configurations (topologies) , as seeing in Fig .1.9.Each topology can constitute an entire network or can be just a portion of a large network .
A star network is a centralized network in which each device is connected virtually to a central controlling point.
A ring network, sometimes called a loop, is a network in which each device is connected to the next in sequence in a closed, circular fashion. This topology has two possible paths, one in each direction.
A bus network is a topology that consists of a single shared line to which all devices are connected.
In a hierarchy network, a central root node has over the entire network. The secondary nodes attached to the root can be front-end processors (EEP) that in turn connect to tertiary nodes of lesser significance. The hierarchy can consist of a large computer that has overall of several smaller control devices connected to their own terminals.
A multiply connected topology requires that there be at least two paths between any pair of nods to assure availability and reliability m the event of failure one path or node.
The unconstrained network occurs most commonly. The term unconstrained merely means that the configuration is not restricted to one specific kind of connection.
Many LAN systems are available today. All use either base-bands, broad-bands, or both, in a base-band, the line is pulsed, as in the on/off conditions. Because these pulses are still the square wave direct current, they require no additional special handling or modulation, which makes the process relatively inexpensive, it is impossible to mix voice and data unless the analog voice signals have been previously digitized.
The broadband technology requires a conversion process and is therefore more expensive. The advantages gained are that voice, video, and data can all be sent on the same channels. Facilities can be shared through assignment of frequency channels to allow all devices to operate simultaneously. Popular modulation and multiplexing techniques can be used because a wide range of frequencies is available.
網(wǎng)絡(luò)建筑學(xué)
現(xiàn)在在今天，建筑學(xué)這個術(shù)語通常用來描述網(wǎng)絡(luò)系統(tǒng)。例如圖表1.7所示的，建筑描述了一個網(wǎng)絡(luò)的各個組成部分他們之間是如何的操作以及以一種什么方式進(jìn)行連接的。一個網(wǎng)絡(luò)系統(tǒng)包括硬件、軟件、數(shù)據(jù)線控制端、技術(shù)規(guī)范和數(shù)據(jù)傳輸?shù)膮f(xié)議。
1、 硬件
網(wǎng)絡(luò)系統(tǒng)中的物理組成部分叫做硬件；電腦、調(diào)制解調(diào)器、電話機(jī)、接線端、機(jī)器、控制端等等是這種設(shè)備的典型。
2、 軟件
軟件包括一系列程序、步驟，有時還有通訊系統(tǒng)操作的相關(guān)文檔。通訊軟件CSW、應(yīng)用程序AP、網(wǎng)絡(luò)控制程序NCP、操作系統(tǒng)OS和數(shù)據(jù)庫管理系統(tǒng)DBMS是軟件的例子。
3、 指令
指令規(guī)定網(wǎng)絡(luò)系統(tǒng)各個組成部分是如何的建立通訊、傳輸數(shù)據(jù)和停止通訊的。實際上，一條指令是在通訊過程中關(guān)于信息被交換的形式和內(nèi)容的一系列的習(xí)慣或規(guī)則。轉(zhuǎn)移和排準(zhǔn)則也是指令。為了使執(zhí)行和運(yùn)用在復(fù)雜的網(wǎng)絡(luò)系統(tǒng)中更方便，高級指令可以用同一級的低級指令來實現(xiàn)。
4、 數(shù)據(jù)連接控制
一個數(shù)據(jù)連接有允許以數(shù)字化的形式自動傳輸信息的電子設(shè)備組成。他是一個安裝的裝備的集合，比如說：電子設(shè)備、終端機(jī)器和那些一特殊方式運(yùn)行的允許信息在不同的設(shè)備之間被交換的界面電路。這種運(yùn)行的特殊方式被界定為傳輸密碼、傳輸方式和反方向控制。
在今天使用的主要有兩種連接控制協(xié)議：
（1） 異步的方式，用這種方式小的數(shù)據(jù)流被一定和接受以一種異步比率。
（2） 同步的方式，小的數(shù)據(jù)流被移動以一種固定的比率隨著時間轉(zhuǎn)換和接收操作同步進(jìn)行。
數(shù)據(jù)在網(wǎng)絡(luò)系統(tǒng)之中的很多點(diǎn)和線之間的傳輸流動可以被控制和排序。反發(fā)送和接收站必須了解在所有的用戶間被翻譯的信息的辨認(rèn)行為和序列站一站之間的連接線路，像多點(diǎn)格局一樣，通常被多個用戶共同使用。
多點(diǎn)連接有時又稱之為復(fù)合連接是在中心站控制下有若干個在連接上共享時間的補(bǔ)充控制者的一種交流。
數(shù)據(jù)連接控制為下列所有的需要提供服務(wù)，他們管理者數(shù)據(jù)信息在交流通路或連接之間的流動。實質(zhì)上，他們是本網(wǎng)絡(luò)系統(tǒng)中各個站點(diǎn)中的軟件和硬件聯(lián)合而構(gòu)成的特殊種類指令。通過交流鏈接，數(shù)據(jù)連接指令在數(shù)據(jù)接線端設(shè)備之間提供可靠的內(nèi)部交流信息，在網(wǎng)絡(luò)系統(tǒng)中數(shù)據(jù)控制的典型作用如下：
1） 使和接收同步進(jìn)行；
2） 控制數(shù)據(jù)的發(fā)送和接收；
3） 檢測和改善點(diǎn)與點(diǎn)之間的翻譯誤差；
4） 布局。
布局描述了構(gòu)成通訊網(wǎng)絡(luò)系統(tǒng)的各個單元的表面規(guī)劃，也就是說，是網(wǎng)絡(luò)系統(tǒng)的外形。通訊系統(tǒng)可以由很多方法實現(xiàn)。典型的通訊系統(tǒng)是電話連接、無線電連接、網(wǎng)絡(luò)系列連接、并列連接和電源連接一同調(diào)整。布局的選擇取決于，比如，成本、反應(yīng)時間、生產(chǎn)量、電容、承載量和生產(chǎn)量需求等因素。
5、 局域網(wǎng)
局域網(wǎng)是在局部地區(qū)操作的網(wǎng)絡(luò)系統(tǒng)，它在建筑物或其他設(shè)備中由幾百英尺擴(kuò)展到幾千英尺。局域網(wǎng)是由私人或組織團(tuán)體擁有和操作的。因此，它不是由聯(lián)邦通訊委員會和國家公共事業(yè)控制的項目。局域網(wǎng)是為了在一個緩緩前進(jìn)的環(huán)境里邊共享資源和交流的目的而連接各種類型的設(shè)備的一種工具正如圖表1.8所示。也就是說，所有的裝置必須在一個能夠有連接在一起的通過一個常用形式的通訊口接收的界面環(huán)境和其他的相交流，像局域網(wǎng)。
一個有效的局域網(wǎng)有一些具體的特點(diǎn)，典型的是以下這些：
① 在中型的地理地區(qū)，辦公實驗室，建筑物、工廠、工業(yè)綜合體、校園等。
② 有中高速的數(shù)據(jù)傳輸頻道。
③ 提供可靠的交流。
④ 被當(dāng)各機(jī)構(gòu)擁有和使用。
⑤ 以獨(dú)立的裝置相連接，而不是一個裝置和它的外圍設(shè)備。
通常有四個主要的部分在眾多的用戶之間運(yùn)輸數(shù)據(jù)服務(wù)于局域網(wǎng)。比如說，用戶工作站、協(xié)議控制邏輯、中等的界面和物理通路。
6、用戶工作站
用戶工作站是用來完成一個申請，這個工作站可以是一個信息處理器到電腦主機(jī)的任何東西。
（1） 協(xié)議控制邏輯
協(xié)議控制邏輯接收用戶的信息并且把它轉(zhuǎn)換成可以在局域網(wǎng)間相互移動以達(dá)到渴望未知的協(xié)議，它也可以控制局域網(wǎng)，為用戶提供機(jī)會接近網(wǎng)絡(luò)。
（2） 中等界面
中等界面的功能使電子信息在局域網(wǎng)上被傳輸位于路徑和協(xié)議控制邏輯中間的界面有好幾種形式，典型的像有線電視的旋塞，紅外線路徑的二極管微波天線和復(fù)雜的能散發(fā)激光的視覺光纖的半導(dǎo)體。
（3） 物理通路
局域網(wǎng)的路徑包含有線電視，有線電視的光纜被用在許多網(wǎng)絡(luò)里，因為它有局性能、好的信號噪比性、低信號輻射和低錯誤比。
（4） 制造自動化協(xié)議
這有很多類型和大小的網(wǎng)。一些局域網(wǎng)系統(tǒng)被一個機(jī)構(gòu)所擁有被限制在那個機(jī)構(gòu)的前提下，國家的或全球的公共網(wǎng)絡(luò)擁有它們的被用戶接近在多數(shù)情況下，局域網(wǎng)可能也和公共網(wǎng)絡(luò)連接，人們可以接近。
網(wǎng)絡(luò)也被鏈接用幾種布局，正如在1.9的圖片中看到一樣，每一種布局能組成一個完整的網(wǎng)絡(luò)或僅僅是一個大型網(wǎng)絡(luò)的一部分。
一個星狀網(wǎng)絡(luò)是一個中心網(wǎng)絡(luò)，在這個網(wǎng)絡(luò)里面，每一個裝置實質(zhì)上都和控制點(diǎn)相連接。
一個圓狀網(wǎng)絡(luò)有時又被稱為環(huán)，在這個網(wǎng)絡(luò)里面，每一個裝置都按照順序和下一個相連接以一種封閉的迂回方式，這個布局有兩種可能的路徑，每一種朝一個方向。
一個公共汽車網(wǎng)絡(luò)是這樣一個布局，所有的裝置和單個共享的線相連接。
在一個等級森嚴(yán)的網(wǎng)絡(luò)組織網(wǎng)絡(luò)中心的根部節(jié)點(diǎn)已經(jīng)控制了整個網(wǎng)絡(luò)，次要結(jié)點(diǎn)和前面結(jié)束處理器和根部節(jié)點(diǎn)連接，它反過來又和地位稍低的第三個結(jié)點(diǎn)相連接。等級森嚴(yán)的網(wǎng)絡(luò)組織由幾個大的電腦組成，它從整個控制幾個小的控制裝置并和它們各自的終端相連接。
一個使用乘法連接的布局要求在任何一對節(jié)點(diǎn)中間兩條路徑，即如果一條路徑或節(jié)點(diǎn)發(fā)生錯誤的話，確信它 可以利用和可靠。
不帶有強(qiáng)制性的網(wǎng)絡(luò)很常見了，詞條不帶有強(qiáng)迫性不僅僅意味著布局不被限制在具體的某一種連接上。
今天許多局域網(wǎng)是可以的，所有使用基帶、寬頻或者兩個在基帶線在開關(guān)條件搏動。因為這些脈沖仍然是矩形直流電，他們不需要額外的處理或調(diào)整就能使過程相對廉價，除非類似的聲音信號從以前已經(jīng)被數(shù)字化，那么聲音和數(shù)據(jù)是不可能混合的。
寬帶技術(shù)需要一個轉(zhuǎn)化過程，因此更加昂貴，獲得好處是聲音，視頻和數(shù)據(jù)都可以在同一個通道被發(fā)送。設(shè)備通過允許所有設(shè)備同時操作的頻率通道的協(xié)議被共同使用，因為頻率可以廣泛的變化、流行調(diào)頻和多屏幕放映技術(shù)是可以使用的。
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