Chapter 11-The Application Layer - Domain Name System

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Application Layer

2: Application Layer 10
Processes communicating
Process: program running within a host. Ì within same host, two processes communicate using inter-process communication (defined by OS). Ì processes in different hosts communicate by exchanging messages Client process: process that initiates communication Server process: process that waits to be contacted
sending process shoves message out door sending process relies on transport infrastructure on other side of door which brings message to socket at receiving process
Ì API: (1) choice of transport protocol; (2) ability to fix
a few parameters (lots more on this later)
2: Application Layer 12
Addressing processes
Ì to receive messages,
conferencing Ì grid computing
Ì Ì Ì
games Ì streaming stored video clips

An application-layer multicasting protocol for distributed collaboration

HAVE 2005 – IEEE International Workshop onHaptic Audio Visual Environments and their Applications Ottawa, Ontario, Canada, 1-2 October 20050-7803-9377-5/05/$20.00 ©2005 IEEEAn Application-Layer Multicasting Protocol for Distributed CollaborationShervin Shirmohammadi, Abdelfettah Diabi, and Pascal LacombeDistributed Collaborative Virtual Environments Research Lab (DISCOVER Lab)University of Ottawa, Ottawa, Canada [shervin| adiabi]@discover.uottawa.caAbstractAlthough IP multicast can be used to support message transmission among participants in massively large virtual environments, it is typically not available on the Internet. Alternatively, researches have in recent years proposed the use of Application Layer Multicasting techniques (ALM), either using proxies or purely depending on end systems, to allow scalable message passing among peers in a large group of users on the Internet. In this paper, we propose a hybrid application-layer multicast framework that uses both proxies and end-systems to provide scalable and timely-reliable communication among the participants of a distributed virtual environment over the Internet. Our filed trials using a simulation application shows that the framework performs satisfactorily over the Internet.I. INTRODUCTIONLike any other real-time network application, distributed virtual environments have specific requirements from their underlying transmission mechanism. In these simulations, users participate in various activities in real time and perform tasks in a synchronous manner, sometimes in a closely-coupled form that requires precise coordination between the parties, who otherwise are connected to the Internet from geographically distributed locations. Examples include military simulations, multi-player games, and disaster planning and coordination simulations. It has been suggested that in such environments, the end-to-end delay should not exceed 100 msec [6]. Other studies have loosened this requirement to 200 msec as acceptable delay[4]. The reason for such strict requirement is the fact that distributed virtual environments are highly reactive multi-user processes where users interact based on the each other's actions and reactions; therefore requiring very low transmission delay of updates. One of the problems, which has been studied and addressed to some extent in recent years, is network lag. When users participate in a simulation, their interactions with each other and/or the environment must be sent to other participants over the network, such that all entities involved are updated with the latest state. Because of network limitations and traffic conditions, some of these updates are lost, or delayed.Much research has been done to compensate for network lag in order to provide better quality of distributed simulations. Some of these studies provide receiver-initiated and selectively-reliable transport protocols [5] that can be used to deliver important messages with a high degree ofreliability, while others use a sender-initiated approach to transmit key updates with guaranteed reliability [7]. The IEEE DIS standard [3] has also been successfully used in controlled environment with sufficient resources, mostly for military simulations. These approaches; however, are all based on IP multicasting and although they achieve good results in Intranet environment, they are not readily deployable on the Internet.The lack of applicability of IP multicasting on the Internet has been well documented [1] [2]. Reasons include scalability, the fact that IP Multicasting is designed for a hierarchical routing infrastructure and does not scale well in terms of supporting large number of concurrent groups, the deployment hurdles caused by manual configuration at routers and Internet Service Providers’ unwillingness to implement IP multicasting, and marketing reasons such as undefined billing at the source (content provider) and receivers.An alternative has therefore been proposed to shift multicast support from the networking layer to end systems. This is Application Layer Multicasting (ALM). In ALM, data packets are replicated at end-hosts instead of at routers. The end-hosts form an overlay network, and the goal of ALM is to construct and maintain an efficient overlay for data transmission. This is demonstrated in Figure 1. Since the routing information is maintained by the application, it is more scalable than IP multicasting since it can support large number of concurrent groups. Also, because ALM needs no infrastructure support, it is fully deployable on the Internet. In theory, Content Providers can deliver bandwidth-intensive contents such as TV programs and interactive networked games to vast number of clients via the Internet by using ALM. This was impractical before because the bottleneck bandwidth between content providers and consumers is considerably less than the natural consumption rate of such media.IP Multicasting Application Layer MulticastingFigure 1. Network layer multicasting versus application layer multicasting: square nodes are routers and circular nodes are end-hosts.However, ALM does come with a tradeoff: more bandwidth and delay (compared to IP multicasting) for the sake of supporting more users and scalability. But it has been shown that ALM-based algorithms can have “acceptable” performance penalties with respect to IP Multicasting, and compared to other practical solutions [8]. In this article, we design, deploy, and test an ALM based protocol that can support distributed virtual environments the Intranet and on the Internet simultaneously. Our protocol, called the Hybrid Distributed Simulation Protocol (HDSP), supports both best-effort delivery, for frequently occurring updates, and reliable delivery for important or “key” updates. We use a sender-initiated approach to ensure guaranteed delivery of the key messages. We demonstrate, from experiments on the Internet, that home users and LAN users can be supported simultaneously with satisfactory results. Due to usage of an appropriate ALM algorithm, our approach is more scalable than client-server approaches, while it is also more practical than IP-multicast.II. DISTRIBUTED COLLABRATION While a lot of studies have addressed many transport issues related to distributed virtual environments in general [10][11], not much attention has been paid to closely-coupled collaboration in such environments. The general assumption in distributed virtual environments is that objects transmit update messages often, and that the latest state of things can be determined by techniques such as dead-reckoning algorithms because they are somewhat predictable. Experience has shown that these assumptions work very well for scenarios such as simulation of battlefields or multi-user avatar-based games where people, tanks, planes, and other objects are almost constantly moving in a short-term predictable manner and a lost update message is usually followed by many other update messages, or keep-alive messages. However, these assumptions fail for collaborative virtual environments. In fact for some scenarios, the conditions can be quite the opposite: shared objects might not send continuous update messages, and when they do it is not necessarily in a predictable manner. When coordinating closely-coupled tasks in VEs, there can be cases where some updates must be delivered reliably in order to synchronize the most current state among participants. Examples include a sudden stop of a user or object, or a tightly-synchronous collaborative task such as tele-surgery simulation. A framework on top of which distributed VEs are placed must therefore provide transport services suitable for all data: those not requiring reliability (regular updates0 and those requiring reliability (key updates).III. PROTOCOL DESIGNWe propose HDSP (Hybrid Distributed Simulation Protocol) tailored to provide transport services suitable for all types of simulation data. HDSP is a multi-purpose protocol designed and implemented on top of a single multicast tree. The nodes of the tree consist of a Hybrid node which can be placed on a LAN (although this is not mandatory in the absence of a LAN) and connects to both the LAN multicast environment and the Internet. This hybrid node has all the necessary information to construct the ALM tree, maintain it and rearrange it. The ALM tree allows Internet users to not only connect to the hybrid node itself, but also to connect to one another, increasing scalability significantly. This is shown in figure 2 where the two home users on the right are connected to the tree through another home user, which itself directly connects to the hybrid node. The hybrid node’s connectivity to the LAN also allows it to participate in the IP multicast environment that exists there, essentially building a bridge between the LAN and the Internet though the Hybrid node.Hybrid NodeFigure 2. ALM Tree Construction. The thin line indicates physical connection (LAN or Internet); whereas the thick line indicates the overlay network, with the arrow going from parent to child.The hybrid node acts as an entry point, instructing new comers from the Internet to join the tree at specific nodes. A new comer sends a request to the Hybrid node, which in return either accepts it as a “child node” or redirects it to another “parent node”. The process of accepting or redirecting a child node is based on the out-degree parameter: the maximum number of child nodes a given parent van handle based on the parent’s available bandwidth. Messages sent on the LAN are therefore received by everyone on the ALM tree through the hybrid node, and vice versa. The hybrid node will always relay messages to its children, who in turn relay those messages to their own children, etc.HDSP provides support for both reliable and unreliable multicast. For unreliable multicast we use UDP multicast on LAN and unreliable ALM forwarding over UDP on the Internet. For reliable multicast we use SCTP [7] on the LAN, which provides IP-based receiver-initiated reliable multicast. On the ALM tree, reliability is achieved as follows. The hybrid node will require all its children to acknowledge receipt of a key update, and will retransmit that update if such acknowledgement is not received. The children, in turn, will act as parents to their own children, requiring acknowledgements for the key update, etc. This ensures key updates are reliably received by all participantson the Internet. It should be noted that every node in the ALM tree will send a keep-alive message to its parent on a regular basis to make sure that it has not crashed or otherwise unreachable. Note that these control messages are not part of the application, but part of the tree construction algorithm itself.IV. IMPLEMENTATIONHDSP is hybrid because we are using both a P2P architecture between home users on the Internet and a proxy-based architecture for the Hybrid node to act as a bridge to the LAN which itself uses IP multicast. Our implemented HDSP framework allows any combination of the above to be deployed. To test the system, we developed a multi-user virtual environment that simulates movement of a barrel carried by two hooks, as shown in figure 3. The objective is for users to move the barrel collaboratively and in a coordinated fashion. If one user moves too slowly or too fast, the barrel will tip over. Note that for such virtual environments, which can are multi-user, Area of Interest Management or similar techniques must be used to make the application scalable. However in this study we assume such mechanisms are already in place and we concentrate on the efficiency of communication between Internet users in one such area.Figure 3. The distributed simulation.V. PERFORMANCE EVALUATION Performance evaluation was conducted with 3 different home users with high speed connectivity (DSL or cable access) to the Internet. One user was acting as the hybrid node, and the out-degree was set equal to one so that we have a two level tree. For the test, the hybrid node sends messages once a second for a period of 5 minutes, resulting in 300 packets sent. The receiving node forwards the packet to its children and also sends a reply to the parent. Each child then forwards the message to its own children and in turn sends a reply back to its apparent, which sends it back to its own parent, until it reaches the hybrid node. Basically, the distance from the hybrid node to all the leaf nodes in the tree are measured in this way. The Hybrid node can measure the round trip delay of each packet as the time it receives the reply minus the time it actually sent the packet divided by 2. Figure 4 illustrates the test configuration, starting with the hybrid node at the top. Table 1 below shows the averagevalues obtained for different levels in the tree.Figure 4. Test procedure for a period of 5minutes.Table 1. Average delay values in milliseconds.Hybridto level 1Hybrid tolevel 2Betweenany 2 nodes38.30 130.6 84.45We can see that the processing time in the first child before forwarding the packet and also the processing time of the ISPs have an impact of the transmission delay, as expected. A two-level tree is easily supported without violating the 200 ms end-to-end delay requirement, and we anticipate that a third level in the tree might also be supported, but a fourth level would most likely violate the threshold.5.1 Subjective EvaluationThe user experience from the simulation on a LAN was very good, as expected, since the delay was minimal. But interestingly, on the Internet and in the configuration shown in figure 4, the experience was quite comparable and didn’t change much. Subjectively, the players did not notice any significant downgrading of the simulation, although more “wrappings” due to lost updates were observed. Hence, we think that a 3rd level in the tree would be possible.1.ConclusionIn this article, we demonstrated how application layer multicasting can be used in conjunction with sender-initiated reliable communication to support large-scale distributed virtual environments on the Internet. Our performance evaluation results showed that three levels of a tree can be supported in this architecture, although more vigorous tests are needed. The advantage of such system is its scalable support for more users, making it a better choice compared to server-based solutions, and its immediate deployability on the Internet, making it more practical than IP multicasting. HDSP is a hybrid system in two senses: not only both LANs and the Internet are supported in the same simulation, but also both reliable and best effort delivery is provided by the framework.REFERENCES[1] A. El-Sayed and V. Roca, “A Survey of Proposals for an Alternative Group Communication Service,” IEEE Network, 17(1), pp. 46-51, Feb. 2003.[2] B. Zhang, S. Jamin, and L. Zhang, “Host multicast: A framework for delivering multicast to end users,” In Proc IEEE INFOCOM, June 2002. [3]IEEE Standard for Distributed Interactive Simulation, Application Protocols, IEEE 1278-1995.[4]K.S. Park and Robert V. Kenyon, "Effects of Network Characteristics on Human Performance in a Collaborative Virtual Environment", IEEE International Conference on Virtual Reality (VR '99), Houston, Texas, March 1999.[5]M Pullen, "Reliable Multicast Network Transport for Distributed Virtual Simulation", Proc. IEEE Workshop on Distributed Interactive Simulations and Ral-Time Applications (DIS-RT '99), Greenbelt, Maryland, October 1999.[6]M.M. Wloka, "Lag in Multiprocessor VR", Presence: Teleoperators and Virtual Environments (MIT Press), Vol. 4, No. 1, Spring 1995.[7]S. Shirmohammadi and N.D. Georganas, "An End-to-End Communication Architecture for Collaborative Virtual Environments", Computer Networks, Vol. 35, No. 2-3, Feb. 2001, pp. 351-367.[8]Y. Chu, S.G. Rao, S. Seshan, and H.S. Zhang, “A Case for End System Multicast”, IEEE Journal on Selected Areas in Communication, special issue on networking support for multicast, 2002, Volume 20, Issue 8, pp. 1456-1471.[9] B. Blau et al, "Networked Virtual Environments", Proc. ACM SGGRAPH, 1992, pp. 157-164.[10]M. Pullen et al, "Limitations of Internet Protocol Suite for Distributed Simulation in the Large Multicast Environment ", RFC 2502, February 1999.[11] M.R. Macedonia, and M.J. Zyda, "A Taxonomy for Networked Virtual Environments", IEEE Multimedia Magazine, January-March 1997, pp. 48-56.。

计算机网络英文题库(附答案)chapter2解析

Chapter 2 Application Layer1. In the following four descriptions, which one is correct?A In C/S architecture, clients communicate with each other directly.B In C/S architecture, client has a fixed well-known address.C In P2P architecture, peers communicate with each other directly.D In P2P architecture, peer has a fixed well-known address.2. In the context of a communication session between a pair of process, the process that initiates the communication is labeled as the , the process that waits to be contacted to begin the session is labeled as the .A client process, server processB sending process, receiving processC input process, output processD communicating process, connecting process3. A socket is the interface between within a host.A the network layer and the link layerB the link layer and the physical layerC the application layer and the transport layerD the transport layer and the network layer4. In the following applications, which one is a loss-tolerant application?A E-mailB file transferC instant messagingD real-time audio5. In the following applications, which one is a bandwidth-sensitive application?A E-mailB web applicationC real-time audioD file transfer6. The service of TCP can’t guarantee .A delivery of all data without errorB delivery of all data in the proper orderC the rate of deliveryD congestion control7. In the following applications, which one uses UDP?A E-mailB web applicationC file transferD DNS8. In the following descriptions about HTTP, which one is not correct?A HTTP uses non-persistent connections in its default mode.B HTTP uses TCP as its underlying transport protocol.C HTTP is a stateless protocol.D HTTP is client-server architecture.9. Suppose a web page consists of a base HTML file, 5 JEPG images and a java applet, and also suppose HTTP uses persistent connection without pipelining, the total response time is .A 2RTTB 8RTTC 12 RTTD 14RTT10. In HTTP response message, if the requested HTTP protocol v ersion is not supported, the status code is .A 200B 301C 400D 5051~5 CACDC 6~10 CDABD11. The port number of web application is .A 25B 20C 80D 5312. A network entity that satisfies HTTP requests on the behalf of an origin web server is .A server farmB server stackC proxy serverD edge server13. In the following descriptions about persistent connection, which one is not correct?A The server leaves the TCP connection open after sending a response.B Each TCP connection is closed after the server sending one object.C There are two versions of persistent connection: without pipelining and with pipelining.D The default mode of HTTP uses persistent connection with pipelining.14. FTP uses two parallel TCP connections to transfer a file, there are .A control connection and data connectionB receiving connection and sending connectionC client connection and sever connectionD program connection and process connection15. In the following descriptions about FTP, which one is correct?A FTP is p2p architecture.B FTP sends its control information out-of-band.C FTP uses persistent connection.D FTP is a stateless protocol.16. In the commands of FTP, which one does not have parameter?A USERB PASSC LISTD STOR17. The Internet mail system has three components which they are .A user agent, SMTP, POP3B SMTP, POP3, IMAPC user agent, SMTP, IMAPD user agent, SMTP, mail server18. If the status code in HTTP response message is 404, it means .A Request succeeded.B The requested document doesn’t exit on this server.C This is a generic error code indicating that the request could not be understood by the server.D Requested object has been permanently mover.19. Comparison HTTP with SMTP, the correct is .A HTTP is a push protocol, and SMTP is a pull protocol.B In the default mode, both of them use persistent connection.ts into one message, and SMTP sends every object C HTTP places all of the message’s objecone by one.D HTTP requires each message to be in 7-bit ASCII format, and SMTP doesn’t impose t restriction.20. The headers in the MIME message must include except .A FromB Content-typeC Content-transfer-encodingD MIME version11~15CCBAB 16~20 DDBBD21. In the following protocol, which one is stateless?A POP3B SMTPC FTPD IMAP22. DNS means .A Data Name SystemB Data National SystemC Domain Name SystemD Domain National System23. There are three classes of DNS server except .A Root DNS serverB Local DNS serverC TLD server D Authoritative DNS server24. DNS provides some services except .A Host aliasingB Mail server aliasingC Load distributionD A single point of failure25. There are three architectures for locating content in P2P file sharing, KaZaA uses .A Centralized Directory （Napster）B Query Flooding(Gnutella)C Exploiting Heterogeneity (p141)D Incentive Priorities26. There are three architectures for locating content in P2P file sharing, Napster uses .A Centralized Directory (p137)B Query FloodingC Exploiting HeterogeneityD Incentive Priorities27. The following architectures in P2P file sharing, which is an overlay network?A Centralized DirectoryB Query Flooding(p139)C Exploiting HeterogeneityD Incentive Priorities28. The time it takes for a small packet to travel from client to server and then back to the client is .A round-travel timeB next-hop timeC round-trip timeD prefix-matching time29. Suppose A ( with a Web-based e-mail account ) sends a message to B ( who accesses his mail server using POP3), which application-layer protocol is not used?A HTTPB SMTPC POP3D IMAP30. In the four following options, which protocol is included in Mail Access Protocol?A SMTPB DHCPC IMAPD FTP31. In FTP commands, is used to send user password to the server.A UserB PassC RetrD Stor32. The function of the additional header field in MIME Content-Type is .A to convert the message body to its origin non-ASCII formB to determine what actions it should take on message bodyC to send an E-mail to the receiving user agentD to indicate what type the message is33. In the four following options, which application is organized as hybrid of C/S and P2P architecture?A E-mailB OICQC File transferD Web applicationproblem?34. In the four following options, which is not a centralized DNS design’ｓA a single point of failureB traffic volumeC distant centralized databaseD slow (maintenance)perspective, which is not 35.In the following options, from the application developer’scorrect?A the network architecture is fixedB the network architecture provides a specific set of services to applicationsC the application architecture is designed by the physical devicesD the application architecture dictates how the application is organized over the various end systems36. There are three predominant architectures used in modern network applications, which one is not included?A the client-server architectureB the P2P architectureC a hybrid of the client-server and P2P architectureD a hybrid of the client-server and browser-server architecture37. In the following options about C/S architecture, which is not correct?A In C/S architecture, there is an always-on host, called the server.B In C/S architecture, there is an always-on host, called the client.C The server has a fixed, well-known address, called IP address.D Clients do not directly communicate with each other.38. are often used to create a powerful virtual server in C/S architecture.A PeersB Server farmC server stackD local server39. A process sends messages into, and receives messages f rom, the network through its .A socketB programC clientD peer40. Which one is not defined by an application-layer protocol?A the types of messages exchangedB the syntax of various message typesC the semantics of the fieldsD rules for determining when and how to translate the socket41. HTTP can use two types of connections, which are .A persistent and non-persistent connectionB connection with pipelining and without pipeliningC TCP and UDPD parallel and serial connection42. takes for a small packet to travel from client to server and then back to the client.A RDTB thresholdC RTTD overhead43. The default mode of HTTP uses .A non-persistent connection with pipeliningB non-persistent connection without pipeliningC persistent connection with pipeliningD persistent connection without pipelining44. In HTTP request messages, the request line has three fields, there are .A the method field, the URL field and the HTTP version fieldB the method, the connection and URL fieldC the user-agent, the method and HTTP version fieldD the user-agent, the URL and the HTTP version field45. In the header lines of HTTP request message, i f the field of Connection is close, it specifies .A the host on which object residesB what type of the user agentC that the browser wants the server to close the connection after sending the requested objectD which language can the browser receive46. In HTTP response message, if the status code is 404, it means .A request succeeded and the information is returned in the responseB requested object has been permanently movedC the requested HTTP protocol version is not supported by the serverD the requested document does not exist on this server47. is a network entity that satisfies HTTP requests on the behalf of an origin Web server.A proxy serverB local serverC DNS serverD Web server48. In the following four options about web cache, which one is not correct?A A web cache is both a server and a client at the same time.B A web cache is purchased and installed by an ISP.C A web cache can raise the response time for a client request.D A web cache can reduce traffic on an institution’s access link to the Interne49. The request message in the conditional GET must include the header line.A Last-ModifiedB Last-ReferencedC If-Modified-SinceD If –Referenced-Since50. FTP uses two parallel connections to transfer a file, they are .A TCP and UDP connectionB connection with pipelining and without pipeliningC control an data connectionD client-server and browser-server connection51. In FTP commands, which one is used to ask the server to send back a list of all files in the current remote directory?A USERB PASSC LISTD RETR52. In the Internet mail system, allow users to read, reply to, forward, save and compose message.A User agentsB mail serversC SMTPD TCP53. The two key MIME headers for supporting multimedia are .A Content-Type and MIME-VersionB Content-Type and Content-Transfer-EncodingC Content-Transfer-Encoding and MIME-VersionD MIME-Version and MIME-Type54. For Internet mail, the mail access protocol is used to .A transfer mail from the recipient’s mail server to the recipient’s useB transfer mail from the sender’s mail server to the recipient’s mail seC translate the mail from the sender’s mail serverD translate the mail into the recip ient’s mail server55. POP3 progresses through three phases, which they are .A authorization, translation and transactionB authorization, translation and updateC authorization, transaction and updateD translation, transaction and update56. In the following four services, which one can not provide by DNS?A Host aliasingB Mail server aliasingC translate hostname to IP addressesD translate MAC addresses to IP addresses57. There are three classes of DNS servers, there are .A root DNS server, top-level domain DNS server and local DNS serverB root DNS server, top-level domain DNS server and authoritative DNS serverC root DNS server, local DNS server and authoritative DNS serverD root DNS server, local DNS server and top-level domain DNS server58. In the following four options about POP3, which one is not correct?A The user agent employed only three commands: List, Retr and QuitB The server does not carry state information across POP3 sessionsC The port number is 110D The POP3 protocol does not provide any means for a user to create remote folders and assign messages to folders.59. A resource record in DNS distributed database is a four-tuple, which field can be ignored? (p132) A Name B Value C Type D TTL60. In the following four options about DNSresource record, which one is correct?A The meaning of Name and Value depend on Type.B The meaning of Value and Type depend on Name.C If Type=A, then Name is a domain and Value is the IP address for the hostname.D If Type=MX, then Name is domain and Value is the IP address for the hostname.61. In the following four options about DNS messages, which one is not correct?A There are only two kinds of DNS message.(p133)B Both query and reply message have the same format.C The header section in DNS message has 12 bytes.D The authority section contains the resource records for the same that was originally queried .62. In DNS message, contains information about the query that is being made.(p133)A authority sectionB question sectionC answer sectionD additional section63. There are three techniques are employed in most any P2P file-sharing systems, which one is not include? （p144）A Request queuingB incentive prioritiesC parallel downloadingD Response queuing64. In the following four options about P2P file-sharing, which one is not correct?A P2P file-sharing is highly scalable.B P2P file-sharing relies on P2P architecture.C The means for locating content in different P2P file-sharing are different.D P2P file-sharing systems not only share MP3s,but also videos, software, documents and images.65. In MIME header lines, specifies the name of the SMTP server that sent the message (from),the name of the SMTP server that received the message (by), and the time an which the receiv ing server received the message.A ReceivedB FromC ToD MIME-Version66. If the header line Connection is close, it means that the client wants .A persistent connection with pipeliningB persistent connection without pipeliningC nonpersistent connectionD not connection67. In HTTP request message, the entity body is empty with the method, but is used with the method.A GET, POSTB POST,GETC GET, HEAD D POST, HEAD68. In HTTP response message, if the Date: header ;one indicates the time Fri. 08 Aug. 2008 12:00:00 GMT, the Last-Modified: header line can not be .A Fri. 08 Aug. 2008 11:00:00 GMTB Fri. 08 Aug. 2008 11:30:00 GMTC Fri. 08 Aug. 2008 12:00:00 GMTD Fri. 08 Aug. 2008 12:30:00 GMT69. In the following four options, which one is not the part of cookie technology?A Cookie header lines in the HTTP response message and request message.’s browser.B One cookie header file kept on the user’s end system and managed by the userC A network entity that satisfies HTTP requests on the behalf of an origin Web server.D A back-end database at the Web site70. On-top of stateless HTTP, can be used to create a user session layer.A proxy serverB Web cacheC cookieD socket71. Processes communicate with each other by reading from and writing to .A programsB threadsC socketsD channels72. In the following four options about network architecture, which one is not correct?A The network architecture is fixed.B The network architecture provides a specific set of services to application.C The network architecture is designed by application developer.D The network architecture dictates how the application is organized over special server.73. In Client-Server architecture, the clients visit the server’s through .A client’s socketB client’s IP addressC server’s socketD server’s IP address74. can be thought of as a program that is running within end system.A processB threadC socketD context75. API means .A Application Program InterfaceB Application Process InterfaceC Appellation Program InterfaceD Appellation Process Interface76. One host can be running many network applications, so the system assigns them differentto distinguish each other.A IP addressB port numberC hostnameD section77. In the following four applications, which one is both bandwith-sensitive and require tight timing constraints?A real-time audioB file transferC E-mailD Web documents78. The port number of the Web server is .A 25B 20C 80D 808079. The port number of the mail server is .A 25B 20C 80D 808080. Look the URL /rjxy/index.html, the object’s path name is .A B /rjxyC /rjxy/index.htmlD index.html81. Each URL has components, they are .A transport protocol and object’s path nameB host name and object’s path nameC transport protocol and host nameD client name and server name1. Consider an HTTP client will request a WEB page from a WEB server. Suppose the URL of the page is /somedepartment /somedir/exp.html. The client does not want to use persistent connections and want to receive French version of the object. The user agent is Windows NT 5.1. Give the request message according to the given format.Request line:Header lines:2. Telnet into a Web server and send a multiline request message. I nclude in the request message the I f-modified-since: header line to force a response message with the 304 Not Modified status code.Solution:Request line:Header lines:3. Suppose within you Web browser you click on a link to obtain a Web page. The IP address for the associated URL is not cached in your local host, so a DNS look-up is necessary to obtain the IP address. Suppose that n DNS servers are visited before your host receives the IP address from DNS; the successive visits incur an RTT of RTT1,…，RTT n. Further suppose that the Web page associated with the link contains exactly one object, consisting of a small HTML text. Let RTT0 denote the RTT between the local host and the server containing the object. Assuming zero transmission time of the object, how much time elapses from when the client clicks on the link until the client receives the object?5. Suppose that you send an e-mail message whose only data is a microsoft excell attachment. What might the header lines (including MIME lines) look like?。

软件设计师-计算机专业英语(一)_真题-无答案

软件设计师-计算机专业英语(一)(总分80,考试时间90分钟)Originally introduced by Netscape Communications, (1) are a general mechanism which HTFP Server side applications, such as CGI (2) , can use to both store and retrieve information on the HTTP (3) side of the connection. Basically, Cookies can be used to compensate for the (4) nature of HTTP. The addition of a simple, persistent, client-side state significantly extends the capabilities of WWW-based (5) .1.A. BrowsersB. CookiesC. ConnectionsD. Scripts2.A. graphicsB. processesC. scriptsD. texts3.A. ClientB. EditorC. CreatorD. Server4.A. fixedB. flexibleC. stableD. stateless5.A. programsB. applicationsC. frameworksD. constraintsWebSQL is a SQL-like (6) language for extracting information from the web. Its capabilities for performing navigation of web (7) makes it a useful tool for automating several web-related tasks that require the systematic processing of either all the links in a (8) , all the pages that can be reached from a given URL through (9) that match a pattern, or a combination of both. WebSQL also provides transparent access to index servers that can be queried via the Common (10) Interface.6.A. queryB. transactionC. communicationD. programming7.A. browsersB. serversC. hypertextsD. clients8.A. hypertextB. pageC. protocolD. operation9.A. pathsB. chipsC. toolsD. directories10.A. RouterB. DeviceC. ComputerD. GatewayMIDI enables people to use (11) computers and electronic musical instruments. There are actually **ponents to MIDI, **munications" (12) .", the Hardware Interface and a distribution (13) called "Standard MIDI Files". In the context of the WWW, the most **ponent is the (14) Format. In principle, MIDI files contain sequences of MIDI Protocol messages. However, when MIDI Protocol (15) are stored in MIDI files, the events are also time-stamped for playback in the proper sequence. Music delivered by MIDI files is the **mon use of MIDI today.11.A. personalB. electronicC. multimediaD. network12.A. deviceB. protocolC. networkD. controller13.A. formatB. textC. waveD. center14.A. VideoB. FaxmailC. GraphicD. Audio15.A. messagesB. packetsC. frameD. informationCertificates are (16) documents attesting to the (17) of a public key to an individual or other entity. They allow verification of the claim that a given public key does in fact belong to a given individual. Certificates help prevent someone from using a phony key to (18) someone else. In their simplest form, Certificates contain a public key and a name. As commonly used, a certificate also contains an (19) date, the name of the CA that issued the certificate, a serial number, and perhaps other information. Most importantly, it contains the digital (20) of the certificate issuer.The most widely accepted format for certificates is X.509, thus, Certificates can be read or written by any **plying with X.509.16.A. textB. dataC. digitalD. structured17.A. connectingB. bindingC. composingD. conducting18.A. impersonateB. personateC. damageD. control19.A. communicationB. computationC. expectationD. expiration20.A. signatureB. markC. stampD. hypertextDOM is a platform-and language- (21) API that allows programs and scripts to dynamically access and update the content, structure and style of WWW documents (currently ,definitions for HTML and XML documents are part of the specification). The document can be further processed and the results of that processing can be incorporated back into the presented (22) . DOM is a (23) -based AP1 to documents, which requires the whole document to be represented in (24) while processing it. A simpler alternative to DOM is the event-based SAX, which can be used to process very large (25) documents that do not fit info the memory available for processing.21.A. specificB. neutralC. containedD. related22.A. textB. imageC. pageD. graphic23.A. tableB. treeC. controlD. event24.A. documentB. processorC. discD. memory25.A. XMLB. HTMLC. scriptD. webMelissa and Love Letter made use of the trust that exists between friends or colleagues. Imagine receiving an (26) from a friend who asks you to open it. This is what happens with Melissa and several other similar email (27) . Upon running, such worms usually proceed to send themselves out to email addresses from the victim's address book, previous emails, web pages (28) .As administrators seek to block dangerous email attachments through the recognition of well-known (29) , virus writers use other extensions to circumvent such protection. Executable (.exe) files are renamed to .bat and .cmd plus a whole list of other extensions and will still run and successfully infect target users.Frequently, hackers try to penetrate networks by sending an attachment that looks like a flash movie, which while displaying some cute animation, simultaneously **mands in the background to steal your passwords and give the (30) access to your network.26.A. attachmentB. packetC. datagramD. message,27.A. virtualB. virusC. wormsD. bacteria28.A. memoryB. cachesC. portsD. registers29.A. namesB. cookiesC. softwareD. extensions30.A. crackerB. userC. customerD. clientNetworks can be interconnected by different devices. In the physical layer networks can be connected by (31) or hubs, which just move the bits from one network to an identical network. One layer up we find bridges and switches which operate at data link layer. They can accept (32) , examine the MAC address and forward the frames to a different network while doing minor protocol translation in the process. In network layer, we have routers that can connect two networks. If two networks have (33) network layer, the muter may be able to translate between the packer formats. In the transport layer we find transport gateway, which can interface between two transport connections. Finally, in the application layer, application gateways translate message (34) . As an example, gateways between Internet e-mail and X.400 e-mail must (35) the e-mail message and change various header fields.31.A. reapersB. relaysC. packagesD. modems32.A. framesB. packetsC. packagesD. cells33.A. specialB. dependentC. similarD. dissimilar34.A. syntaxB. semanticsC. languageD. format35.A. analyzeB. parseC. deleteD. createThe purpose of the requirements definition phase is to produce a clear, complete, consistent, and testable (36) of the technical requirements for the software product.During the requirements definition phase, the requirements definition team uses an interative process to expand a broad statement of the system requirements into a complete and detailed specification of each function that the software must perform and each (37) that it must meet. The starting point is usually a set of high level requirements from the (38) that describe the project or problem.In either case, the requirements definition team formulates an overall concept for 'the system and then defines (39) showing how the system will be operated, publishes the system and operations concept document and conducts a system concept review (SCR) .Following the SCR, the team derives (40) requirements for the system from the high level requirements and the system and operations concept using structured or object-oriented analysis. The team specifies the software functions and algorithms needed to satisfy each detailed requirement.36.A. functionB. definitionC. specificationD. statement37.A. criterionB. standardC. modelD. system38.A. producerB. customerC. programmerD. analyser39.A. rolesB. principlesC. scenariosD. scenes40.A. cotailedB. outlinedC. totalD. complete(41) is a protocol that a host uses to inform a router when it joins or leaves an Internet multicast group.(42) is an error detection code that most **munication networks use.(43) is an interior gateway protocol that uses a distance vector algorithm to propagate routing information.(44) is a transfer mode in which all types of information are organized into fixed form cells on an asynchronous or non-periodic basis over a range of media.(45) is an identifier of a web page.41.A. ICMPB. SMTPC. IGMPD. ARP42.A. 4B/5BB. CRCC. Manchester CodeD. Huffman Code43.A. OSPFB. RIPC. RARPD. BGP44.A. ISDNB. X.25C. Frame RelayD. A TM45.A. HTTPB. URLC. HTMLD. TAGSpread spectrum simply means that data is sent in small pieces Over a number of the (46) frequencies available for use at any time in the specified range. Devices using (47) spread spectrum (DSSS) communicate by (48) each byte of data into several parts and sending them concurrently on different (49) . DSSS uses a lot of the available (50) , about 22 megahertz (MHz) .46.A. continuousB. highC. lowD. discrete47.A. direct-sequenceB. discrete-sequenceC. duplicate-sequenceD. dedicate-sequence48.A. splittingB. combiningC. packingD. compacting49.A. bitsB. frequenciesC. packetsD. messagesA. rateB. velocityC. bandwidthD. period(51) is a six bytes OSI layer 2 address which is burned into every networking device that provides its unique identity for point to **munication.(52) is a professional organization of individuals in multiple professions which focuses on effort on lower-layer protocols.(53) functions with two layers of protocols. It can connect networks of different speeds and can be adapted to an environment as it expands.(54) is the popular LAN developed under the direction of the IEEE802.5.(55) is the popular backbone technology for transmitting information at high speed with a high level of fault tolerance which is developed under the direction of ANSI.51.A. The MAC addressB. The IP addressC. The subnet addressD. The virtual address52.A. ISOB. ANSIC. CCITD. IEEE53.A. The hubB. The bridgeC. The routerD. The proxy54.A. EthernetB. Token BusC. Token RingD. DQDB55.A. X.25B. A TMC. FDDID. SMDS**munication uses high-frequency (56) waves that travel in straightlines through the air. Because the waves cannot (57) with the curvature of the earth, they can be (58) only over short distance. Thus, microwave is a good (59) for sending data between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of "dishes" or (60) .These can be installed on towers, high buildings, and mountain tops.56.A. opticalB. radioC. electricalD. magnetic57.A. reflexB. distortC. bendD. absorbA. transmittedB. transformedC. convertedD. delivered59.A. materialB. equipmentC. mediumD. channel60.A. repeatersB. radarsC. telephonesD. antennasA socket is basically an end point of a communication link between two applications. Sockets that extend over a network connect two or more applications running oncomputers attached to the network. A sockettwo addresses:. Sockets provide acommunication channel between one or more systems.There aresockets separately using TCP and UDP.61.A. uniqueB. separateC. sameD. dependent62.A. is made ofB. composed ofC. is composed OfD. is consisted of63.A. E-mail address and IP addressB. MAC address and port addressC. MAC address and IP addressD. port number and IP address64.A. full-duplexB. half-duplexC. simplexD. complex65.A. message and packetB. packet and frameC. stream and datagramD. flow and blockOpen Shortest Path First (OSPF) is a (66) routing algorithm that (67) work done on the OSI IS-IS intradomain routing protocol. This routing, as compared to distance-vector routing, requires (68) processing power. The (69) algorithm is used to calculate routes. OSPF routing table updates only take place when necessary, (70) at regular intervals.66.A. distance-vectorB. link-stateC. flow-basedD. selective floodingA. derived fromB. deviated fromC. was derived fromD. was deviated from68.A. moreB. lessC. sameD. most69.A. Bellman-FordB. Ford-FulkersonC. DijkstraD. RIP70.A. but ratherB. rather tooC. rather thanD. rather thatPacket-switching wireless networks are preferable (71) when transmissions are (72) because of the way charges are (73) per packet. Circuit-switched networks are preferable for transferring large files or for other lengthy transmissions because customers are (74) for the (75) of time they use the network.71.A. toB. forC. thanD. only72.A. longB. shortC. largeD. small73.A. computingB. incuriousC. incurredD. incurred74.A. chargedB. finedC. freeD. controlled75.A. pointB. startC. lengthD. endMultipurpose Internet Mail Extension (MIME) is a (76) document messaging standard in the Internet environment. With MIME, users can send (77) E-mail messages that include audio, video, graphices, and text to any other user of a TCP/IP network. Richtext information can also be (78) into messages. It defines the fonts, formats, and (79) features of a document so the document can be easily (80) on many different types of systems.76.A. completeB. compoundC. simpleD. efficient77.A. analogB. manyC. multimediaD. digital78.A. incorporatedB. filledC. storedD. filed79.A. colorB. sizeC. designD. layout80.A. restoredB. redisplayedC. storedD. executed。

计算机网络英语期末复习试题及答案

《计算机网络英语》期末复习试题及答案一选择题1．A ( ) protocol is used to move a datagram over an individual link.A application-layerB transport-layerC network-layerD link-layer2．The units of data exchanged by a link-layer protocol are called ( ).A datagramsB framesC segmentsD messages3．Which of the following protocols is not a link-layer protocol? ( )A EthernetB PPPC HDLCD IP4．In the following four descriptions, which one is not correct? ( )A link-layer protocol has the node-to-node job of moving network-layer datagrams over a single link in the path.B The services provided by the link-layer protocols may be different.C A datagram must be handled by the same link-layer protocols on the different links in the path.D The actions taken by a link-layer protocol when sending and receiving frames include error detection, flow control and random access.5．Which of the following services can not offered by a link-layer protocol? ( )A congestion controlB Link AccessC Error controlD Framing6．( ) protocol serves to coordinate the frame transmissions of the many nodes when multiple nodes share a single broadcast link.A ARPB MACC ICMPD DNS7．In the following four descriptions about the adapter, which one is not correct? ( )A The adapter is also called as NIC.B The adapter is a semi-autonomous unit.C The main components of an adapter are bus interface and the link interface.D The adapter can provide all the link-layer services.8．Consider CRC error checking approach, the four bit generator G is 1011, and suppose that the data D is 10101010, then the value of R is( ).A 010B 100C 011D 1109．In the following four descriptions about random access protocol, which one is not correct? ( )A In slotted ALOHA, nodes can transmit at random time.B In pure ALOHA, if a frame experiences a collision, the node will immediately retransmit it with probability p.C The maximum efficiency of a slotted ALOHA is higher than a pure ALOHA.D In CSMA/CD, one node listens to the channel before transmitting.10．In the following descriptions about MAC address, which one is not correct? ( )A The MAC address is the address of one node’s adapter.B No two adapters have the same MAC address.C The MAC address doesn’t change no matter where the adapter goes.D MAC address has a hierarchical structure.11．The ARP protocol can translate ( ) into ( ). ( )A host name, IP addressB host name, MAC addressC IP address, MAC addressD broadcast address, IP address12．The value of Preamble field in Ethernet frame structure is ( )A 10101010 10101010……10101010 11111111B 10101011 10101011……10101011 10101011C 10101010 10101010……10101010 10101011D 10101010 10101010……10101010 1010101013．There are four steps in DHCP, the DHCP server can complete ( ).A DHCP server discoveryB DHCP server offersC DHCP requestD DHCP response14．In CSMA/CD, the adapter waits some time and then returns to sensing the channel. In the following four times, which one is impossible? ( )A 0 bit timesB 512 bit timesC 1024 bit timesD 1028 bit times15．The most common Ethernet technologies are 10BaseT and 100BaseT. “10” and “100”indicate( ).A the maximum length between two adaptersB the minimum length between two adaptersC the transmission rate of the channelD the transmission rate of the node16．The principal components of PPP include but not( ).A framingB physical-control protocolC link-layer protocolD network-layer protocol17．In the following four options, which service can not be provided by switch? ( )A filteringB self-learningC forwardingD optimal routing18．In the following four services, which one was be required in PPP? ( )A packet framingB error detectionC error correctionD multiple types of link19．The ability to determine the interfaces to which a frame should be directed, and then directing the frame to those interfaces is( ).A filteringB forwardingC self-learningD optimal routing20．In ( ) transmission(s), the nodes at both ends of a link may transmit packets at the same time.A full-duplexB half-duplexC single-duplexD both full-duplex and half-duplex21．Consider the data D is 01110010001, if use even parity checking approach, the parity bit is( ①), if use odd parity checking approach, the parity bit is( ②). ( )A ①0 ②1B ①0 ②0C ①1 ②1D ①1 ②022．In the following four descriptions about parity checks, which one is correct? ( )A Single-bit parity can detect all errors.B Single-bit parity can correct one errors.C Two-dimensional parity not only can detect a single bit error, but also can correct that error.D Two-dimensional parity not only can detect any combination of two errors, but also can correct them.23．MAC address is ( ) bits long.A 32B 48C 128D 6424．Wireless LAN using protocol ( ).A IEEE 802.3B IEEE 802.4C IEEE 802.5D IEEE 802.1125．The following protocols are belonging to multiple access protocols except for ( ).A channel partitioning protocolsB routing protocolsC random access protocolsD taking-turns protocols26．Which of the following is not belonging to channel partitioning protocols? ( )A CSMAB FDMC CDMAD TDM27．In the following four descriptions about CSMA/CD, which one is not correct? ( )A A node listens to the channel before transmitting.B If someone else begins talking at the same time, stop talking.C A transmitting node listens to the channel while it is transmitting.D With CSMA/CD, the collisions can be avoided completely.28．( ) provides a mechanism for nodes to translate IP addresses to link-layer address.A IPB ARPC RARPD DNS29．A MAC address is a ( )address.A physical-layerB application-layerC link-layerD network-layer30．Which of the following is correct? ( )A No two adapters have the same MAC address.B MAC broadcast address is FF-FF-FF-FF-FF-FF.C A portable computer with an Ethernet card always has the same MAC address, no matter where the computer goes.D All of the above31．In the following four descriptions, which one is not correct? ( )A ARP resolves an IP address to a MAC address.B DNS resolves hostnames to IP addresses.C DNS resolves hostnames for hosts anywhere in the Internet.D ARP resolves IP addresses for nodes anywhere in the Internet.32．In the LAN, ( )protocol dynamically assign IP addresses to hosts.A DNSB ARPC DHCPD IP33．DHCP protocol is a four-step process: ①DHCP request. ②DHCP ACK. ③DHCP server discovery. ④DHCP server offer(s). The correct sequence is ( )A ①②③④B ③②①④C ③④①②D ①④③②34．In the Ethernet frame structure, the CRC field is ( )bytes.A 2B 4C 8D 3235．In the Ethernet frame structure, the Data field carries the ( ).A IP datagramB segmentC frameD message36．In the following four descriptions, which one is not correct? ( )A Ethernet uses baseband transmission.B All of the Ethernet technologies provide connection-oriented reliable service to the network layer.C The Ethernet 10Base2 technology uses a thin coaxial cable for the bus.D The Ethernet 10BaseT technology uses a star topology.37．Ethernet’s multiple access protocol is ( ).A CDMAB CSMA/CDC slotted ALOHAD token-passing protocol38．In the following four descriptions about CSMA/CD, which one is not correct? ( )A An adapter may begin to transmit at any time.B An adapter never transmits a frame when it senses that some other adapter is transmitting.C A transmitting adapter aborts its transmission as soon as it detects that another adapter is also transmitting.D An adapter retransmits when it detects a collision.39．Which of the following descriptions about CSMA/CD is correct? ( )A No slots are used.B It uses carrier sensing.C It uses collision detection.D All of the above.40．The Ethernet 10BaseT technology uses( )as its physical media.A fiber opticsB twisted-pair copper wireC coaxial cableD satellite radio channel41．For 10BaseT, the maximum length of the connection between an adapter and the hub is ( )meters.A 100B 200C 500D 1042．A ( )is a physical-layer device that acts on individual bits rather than on frames.A switchB hubC routerD gateway43．A hub is a ( )device that acts on individual bits rather than on frames.A physical-layerB link-layerC network-layerD ransport-layer44．A switch is a( )device that acts on frame.A physical-layerB link-layerC network-layerD transport-layer45．In the following four descriptions, which one is not correct? ( )A Switches can interconnect different LAN technologies.B Hubs can interconnect different LAN technologies.C There is no limit to how large a LAN can be when switches are used to interconnect LAN segments.D There is restriction on the maximum allowable number of nodes in a collision domain when hubs are used to interconnect LAN segments.46．The ability to determine whether a frame should be forwarded to some interface or should just be dropped is ( ).A filteringB forwardingC self-learningD optimal routing47．Which of the following devices is not a plug and play device? ( )A hubB routerC switchD repeater48．Which of the following devices is not cut-through device? ( )A hubB routerC switchD repeater49．In the following four descriptions, which one is not correct? ( )A Switches do not offer any protection against broadcast storms.B Routers provide firewall protection against layer-2 broadcast storms.C Both switches and routers are plug and play devices.D A router is a layer-3 packet switch, a switch is a layer-2 packet switch.50．Which device has the same collision domain? ( )A HubB SwitchC RouterD Bridge51．IEEE802.2 protocol belong to ( )layerA networkB MACC LLCD physical52．IEEE802.11 protocol defines ( )rules.A Ethernet BusB wireless WANC wireless LAND Token Bus53．In data link-layer, which protocol is used to share bandwidth? ( )A SMTPB ICMPC ARPD CSMA/CD54．When two or more nodes on the LAN segments transmit at the same time, there will be a collision and all of the transmitting nodes well enter exponential back-off, that is all of the LAN segments belong to the same( ).A collision domainB switchC bridgeD hub55．( )allows different nodes to transmit simultaneously and yet have their respective receivers correctly receive a sender’s encoded data bits.A CDMAB CSMAC CSMA/CDD CSMA/CA56．Because there are both network-layer addresses (for example, Internet IP addresses) and link-layer addresses (that is, LAN addresses), there is a need to translate between them. Forthe Internet, this is the job of ( ).A RIPB OSPFC ARPD IP57．PPP defines a special control escape byte, ( ). If the flag sequence, 01111110 appears anywhere in the frame, except in the flag field, PPP precedes that instance of the flag pattern with the control escape byte.A 01111110B 01111101C 10011001D 1011111058．The device ( ) can isolate collision domains for each of the LAN segment.A modemB switchC hubD NIC59．In the following four descriptions about PPP, which one is not correct? ( )A PPP is required to detect and correct errors.B PPP is not required to deliver frames to the link receiver in the same order in which they were sent by the link sender.C PPP need only operate over links that have a single sender and a single receiver.D PPP is not required to provide flow control.60．In the PPP data frame, the( ) field tells the PPP receivers the upper-layer protocol to which the received encapsulated data belongs.A flagB controlC protocolD checksum61．PPP’s link-control protocols (LCP) accomplish ( ).A initializing the PPP linkB maintaining the PPP linkC taking down the PPP linkD all of the above62．The PPP link always begins in the ( ) state and ends in the ( ) state. ( )A open, terminatingB open, deadC dead, deadD dead, terminating63．For( ) links that have a single sender at one end of the link and a single receiver at the other end of the link.A point-to-pointB broadcastC multicastD all of the above64．With ( )transmission, the nodes at both ends of a link may transmit packets at the same time.A half-duplexB full-duplexC simplex(单工)D synchronous65．With ( ) transmission, a node can not both transmit and receive at the same time.A half-duplexB full-duplexC simplex(单工)D synchronous66．Which of the following functions can’t be implemented in the NIC? ( )A encapsulation and decapsulationB error detectionC multiple access protocolD routing67．Which of the following four descriptions is wrong? ( )A The bus interface of an adapter is responsible for communication with the adapter’s parent node.B The link interface of an adapter is responsible for implementing the link-layer protocol.C The bus interface may provide error detection, random access functions.D The main components of an adapter are the bus interface and the link interface. 68．For odd parity schemes, which of the following is correct? ( )A 011010001B 111000110C 110101110D 00011011069．( )divides time into time frames and further divides each time frame into N time slots.A FDMB TMDC CDMAD CSMA70．With CDMA, each node is assigned a different ( )A codeB time slotC frequencyD link71．Which of the following four descriptions about random access protocol is not correct? ( )A A transmission node transmits at the full rate of the channelB When a collision happens, each node involved in the collision retransmits at once.C Both slotted ALOHA and CSMA/CD are random access protocols.D With random access protocol, there may be empty slots.72．PPP defines a special control escape byte 01111101. If the data is b1b201111110b3b4b5, the value is( )after byte stuffing.A b1b20111110101111110b3b4b5B b1b20111111001111101b3b4b5C b5b4b30111111001111101b2b1D b5b4b30111110101111110b2b173．MAC address is in ( ) of the computer.A RAMB NICC hard diskD cache74．Which of the following is wrong? ( )A ARP table is configured by a system administratorB ARP table is built automaticallyC ARP table is dynamicD ARP table maps IP addresses to MAC addresses75．NIC works in ( )layer.A physicalB linkC networkD transport76．In LAN, if UTP is used, the common connector is( ).A AUIB BNCC RJ-45D NNI77．The modem’s function(s) is(are) ( ).A translates digital signal into analog signalB translates analog signal into digital signalC both translates analog signal into digital signal and translates digital signal into analog signalD translates one kind of digital signal into another digital signal78．( )defines Token-Ring protocol.A IEEE 802.3B IEEE 802.4C IEEE 802.5D IEEE 802.279．( )defines Token-Bus protocol.A IEEE 802.3B IEEE 802.4C IEEE 802.5D IEEE 802.280．( ) defines CSMA/CD protocol.A IEEE 802.3B IEEE 802.4C IEEE 802.5D IEEE 802.281．The computer network that concentrated in a geographical area, such as in a building or on a university campus, is ( )A a LANB a MANC a WAND the Internet82．The MAC address is ( ) bits long.A 32B 48C 128D 25683．Which of the following four descriptions about MAC addresses is wrong? ( )A a MAC address is burned into the adapter’s ROMB No two adapters have the same addressC An adapter’s MAC address is dynamicD A MAC address is a link-layer address84．Which of the following four descriptions about DHCP is correct? ( )A DHCP is C/S architectureB DHCP uses TCP as its underlying transport protocolC The IP address offered by a DHCP server is valid foreverD The DHCP server will offer the same IP address to a host when the host requests an IP address85．The ( )field permits Ethernet to multiplex network-layer protocols.A preambleB typeC CRCD destination MAC address86．For 10BaseT, the maximum length of the connection between an adapter and the hub is ( ) meters.A 50B 100C 200D 50087．An entry in the switch table contains the following information excepts for ( )A the MAC address of a nodeB the switch interface that leads towards the nodeC the time at which the entry for the node was placed in the tableD the IP address of a node二、阅读理解The central processing unit (CPU) is the heart of the computer systems. Among other things, its configuration determines whether a computer is fast or slow in relation to other computers. The CPU is the most complex computer system component, responsible for directing most of the computer system activities based on the instructions provided. As one computer generation has evolved to the next, the physical size of the CPU has often become smaller and smaller, while its speed and capacity have increased tremendously. Indeed, these changes have resulted in microcomputers that are small enough to fit on your desk or your lap.The CPU comprises the control unit and the arithmetic / logic unit (ALU).The control unit is responsible for directing and coordinating most of the computer systems activities. It determines the movement of electronic signals between main memory and the arithmetic/logic unit, as well as the control signals between the CPU and input/output devices. The ALU performs all the arithmetic and logical (comparison) functions — that is, it adds, subtracts, multiplies, divides, and does comparisons. These comparisons, which are basically “less than”, “greater than”, and “equal to”, can be combined into several common expressions, such as “greater than or equal to”. The objective of most instructions that use comparisons is to determine which instruction should be executed next.Tell whether the following statements are true(T) or false(F) according to the passage A.（根据上文的内容判断下列句子的正误）1. With the development of computer, the physical size of the CPU has often become bigger and bigger. ( )2. The movement of electronic signals between main memory and the ALU as well as the control signal between the CPU and input /output devices are controlled by the control unit of the CPU. ( )3. The CPU comprises the control unit and memory. ( )4. The control unit performs all the arithmetic and logical (comparison) functions5. The central processing unit (CPU) is the heart of the computer systems. ( )三、翻译下面的文章。

domexception blocked a frame -回复

domexception blocked a frame -回复题目：DOMException阻塞了一个frame - 解析与解决前言：我们在进行Web开发时，经常会遇到各种各样的错误和异常。

其中一个常见的错误是“DOMException阻塞了一个frame”。

本文将以此错误为主题，逐步为你解析这个错误的原因和解决方案。

第一部分：理解DOMException1.1 DOMException定义与解释DOMException是一种JavaScript对象，用于表示在执行DOM操作期间发生的异常情况。

DOM（文档对象模型）表示网页的结构，它允许程序通过JavaScript动态地更新和修改网页的内容。

当JavaScript尝试执行对DOM的操作时，如果发生错误，就会抛出DOMException。

1.2 常见的DOMException当JavaScript执行DOM操作时，可能会触发许多不同的异常，其中一种是“DOMException阻塞了一个frame”。

其他常见的DOMException包括：- HierarchyRequestError：当执行DOM操作引起结构错误时抛出。

- NotFoundError：当DOM查找操作找不到指定节点时抛出。

- NotSupportedError：当执行的DOM操作不受支持时抛出。

第二部分：DOMException阻塞了一个frame的原因2.1 同源策略DOMException阻塞了一个frame通常是由于同源策略引起的。

同源策略是浏览器的安全机制，它限制了来自不同源的脚本访问彼此的内容。

源是由URL的协议、主机名和端口号组成的标识。

2.2 跨域访问当一个frame中的脚本试图通过DOM操作跨域访问另一个frame的内容时，同源策略将会被触发，从而引发DOMException错误。

例如，如果一个来自第三部分：解决DOMException阻塞了一个frame的方法3.1 代理页面一种解决方法是使用代理页面。

快速了解layui中layer的使用

快速了解layui中layer的使⽤这两天写项⽬的时候⽤到layer，于是⼜把layui找出来看了看，layui确实是⼀个⽐较强⼤的前端框架，⾥⾯涵盖了很多的前端元素，⽽这对于前端的开发者来说是省了很⼤的⿇烦，从⼀些页⾯元素到内置模块，都是采⽤了尽量少的代码来渲染页⾯，所以，我觉得⾃从⽤了layui就觉得对我的整个写项⽬过程中节省了不少时间。

今天就来说说关于layui⾥的layer的使⽤，主要提及的是pc端的⽤法，有时间再专门聊聊关于移动这⼀块的，其实应该都是⼤同⼩异。

layer说⽩了属于layui⾥的⼀个独⽴出来的弹层框架，但是由于近期layui在⼀直更新，所以现在的layer可以独⽴使⽤，也可以通过Layui 模块化使⽤。

所以请按照你的实际需求来选择。

⼀、引⽤场景不同 1、作为独⽴组件使⽤：如果你只是单独想使⽤ layer，你可以去独⽴版本官⽹下载组件包。

你需要在你的页⾯引⼊jQuery1.8以上的任意版本，并引⼊layer.js。

引⼊好layer.js后，直接⽤即可<script src="layer.js"></script><script>layer.msg('hello');</script> 2、 layui 模块化使⽤：如果你使⽤的是 layui，那么你直接在官⽹下载 layui 框架即可，⽆需引⼊ jQuery 和 layer.js，但需要引⼊layui.css和layui.js在 layui 中使⽤ layere('layer', function(){var layer = yer;layer.msg('hello');});⼆、layer提供了不同的类型 layer提供了5种层类型。

可传⼊的值有： 0（信息框，默认）； 1（页⾯层）； 2（iframe层）； 3（加载层）； 4（tips层）。

IBM Cognos 软件开发工具包版本 11.0.0 混搭服务开发人员指南说明书

Chapter 3. Cognos Mashup Service samples......................................................... 11
Java samples..............................................................................................................................................11 Java sample file locations.................................................................................................................... 11 Running the Java samples................................................................................................................... 12
Chapter 2. Overview of the Mashup Service............................................................ 7
Programming interfaces...............................................................................................................................7 Identifying reports....................................................................................................................................... 8 Output formats.............................................................................................................................................9 Sample programs.......................................................................................................................................10

Effect of metal films on the photoluminescence and electroluminescence of conjugated polymers

Effect of metalﬁlms on the photoluminescence and electroluminescence of conjugated polymersH.Becker,S.E.Burns,and R.H.FriendCavendish Laboratory,Madingley Road,Cambridge CB30HE,United Kingdom͑Received12February1997;revised manuscript received15April1997͒We report the modiﬁcation of photoluminescence͑PL͒and electroluminescence͑EL͒from conjugatedpolymers due to the proximity of metalﬁlms.The presence of a metalﬁlm alters the radiative decay rate of anemitter via interference effects,and also opens up an efﬁcient nonradiative decay channel via energy transferto the metalﬁlm.We show that these effects lead to substantial changes in the PL and EL quantum efﬁcienciesand the emission spectra of the polymers studied here͓cyano derivatives of poly͑p-phenylenevinylene͒,PPV͔as a function of the distance of the emitting dipoles from the metalﬁlm.We have measured the PL quantumefﬁciency directly using an integrating sphere,and found its distance dependence to be in good agreement withearlier theoretical ing the spectral dependence of the emission,we have been able to investigatethe effect of interference on the radiative rate as a function of the wavelength and the distance between theemitter and the mirror.We compare our results with simulations of the radiative power of an oscillating dipolein a similar system.From our results we can determine the orientation of the dipoles in the polymerﬁlm,andthe branching ratio that gives the fraction of absorbed photons leading to singlet excitons.We propose designrules for light-emitting diodes͑LED’s͒and photovoltaic cells that optimize the effects of the metalﬁlm.Bymaking optimum use of above effects we have substantially increased the EL quantum efﬁciencies of PPV/cyano-PPV double-layer LED’s.͓S0163-1829͑97͒09228-X͔I.INTRODUCTIONConjugated polymers have attracted much attention since the discovery that these materials can be used as emissive layers in light emitting diodes͑LED’s͒.1,2Research has been particularly focused on poly͑p-phenylenevinylene͒͑PPV͒and its derivatives because of their high efﬁciencies.With these materials a wide range of emission colors and elec-troluminescence efﬁciencies up to4%have been reported.3 The competition between radiative and nonradiative decay processes in conjugated polymers is currently of great inter-est since it governs the efﬁciency of light emission in conju-gated polymer devices such as LED’s and lasers as well as the quantum yield of photovoltaic devices.1,4–7Most of these devices contain metalsﬁlms either as electrodes for charge injection in electroluminescent devices or as mirrors in order to manipulate the radiative properties of the emissive species in the polymer.The presence of a metalﬁlm will always inﬂuence the properties of the emitting material.Microcavi-ties have been used to narrow the linewidth and tune the color of emission from conjugated polymers.8–10It has re-cently been shown that the spontaneous emission rate can be greatly enhanced or suppressed in metal mirror microcavity structures containing conjugated polymers,depending on the overlap of the electric-ﬁeld distribution within the microcav-ity with the emissive layer.11,12It has also been demonstrated that enhancement of the stimulated emission rate leading to lasing can be achieved with conjugated polymers using simi-lar microcavity structures.7More generally,the radiative and nonradiative rates of an excited dipoleﬂuorescing in front of a metalﬁlm or between two metalﬁlms have been extensively investigated,both theoretically and experimentally.13–20The luminescence life-time␶is related to the rate constants for radiative(k R)and nonradiative(k NR)decay by1␶ϭk Rϩk NR,͑1͒where the radiative lifetime is1/k R,and the nonradiative lifetime is1/k NR.The quantum efﬁciency for luminescence q is given byqϭbͩk R k Rϩk NRͪ,͑2͒where the branching ratio b is the fraction of absorbed pho-tons leading to singlet excitons.The balance between the radiative and the nonradiative decay rates therefore deter-mines the luminescence efﬁciency.Different methods have been used to predict the lifetime and luminescence quantum efﬁciency for an excited molecule in front of a mirror.The interference method successfully predicts the effects of a re-ﬂective surface on the radiative properties of the dipole.15 However,at short distances nonradiative energy transfer to the metal becomes an effective decay channel for an excited molecule near a metal,thus increasing the nonradiative de-cay rate close to the metal.In the‘‘mechanical model’’14the excited molecule is considered as a harmonic oscillator with theﬁeld reﬂected by the metalﬁlm acting as a driving force on the oscillator.By introducing a reﬂection coefﬁcient smaller than unity and a phase factor into the perfect mirror equations,some of the aspects of nonradiative energy trans-fer could be reproduced.14However,the best agreement be-tween theory and experiment has been achieved with the energyﬂux method where the total energyﬂux through inﬁ-nite planes above and below the dipole is calculated.19It gives separate expressions for the effects of interference on the radiative lifetime and of nonradiative energy transfer on the nonradiative lifetime.The nature of the nonradiative en-ergy transfer depends on the distance of the oscillating dipolePHYSICAL REVIEW B15JULY1997-IIVOLUME56,NUMBER4560163-1829/97/56͑4͒/1893͑13͒/$10.001893©1997The American Physical Societyto the metal.The interaction of the dipole with the electron gas of the metal is dominated by scattering by the metal surface at short (Ͻ20nm)distances and scattering in the bulk,e.g.,by phonons or impurities,for longer distances.21,22The decay time of an emitting molecule in front of a metal ﬁlm has previously been reported.15,19,23In order to deduce the quantum efﬁciency from those measurements it was nec-essary to make assumptions about the orientation of the di-poles and the free-space efﬁciency of the emitting molecule.In this paper we present direct measurements of the photo-luminescence ͑PL ͒and electroluminescence ͑EL ͒quantum efﬁciencies of two cyanoderivatives of poly ͑p -phenylenevinylene ͒,MEH-CN-PPV and DHeO-CN-PPV,the structures of which are shown in Fig.1,and compare our results with the theoretical predictions for the quantum efﬁ-ciency of a dipole in front of a mirror.Measurements of the PL quantum efﬁciency rather than the luminescence lifetime are of particular relevance for electroluminescent devices.The effect of interference on the radiative properties of an excited molecule is dependent on the emission wavelength.This wavelength dependence is again a function of the dis-tance between the emitting molecule and the mirror.For broad bandwidth emitters such as conjugated polymers,this leads to substantial changes in the shape of the emission spectrum depending on the separation between the emitter and the mirror.We have investigated the changes in the PL emission spectrum of a 15–20-nm-thick MEH-CN-PPV ﬁlm separated by a SiO 2layer from a 35-nm-thick aluminium ﬁing a simple model that describes the effects of in-terference on the radiative rates,we have been able to relate the spectral shape of the emission to the radiative power of an oscillating dipole in front of a mirror as a function ofwavelength and distance between the polymer and the metal.We compare our results with earlier 24and recent simulations of the radiative power of an emitting dipole in front of a metal mirror.The internal electroluminescence efﬁciency of a LED is deﬁned as the number of emitted photons per charge carrier ﬂowing through the circuit.Because the light-emitting spe-cies is thought to be the same in EL and PL,we expect the effects of a metal ﬁlm on the EL to be the same as measured for the PL.The maximum EL efﬁciency of a device is ex-pected to be one-fourth of the PL efﬁciency of the emitting polymer where the factor 4derives from the spin degeneracy of the singlet and triplet excitons,with only the singlet exci-tons decaying radiatively.25So far,the highest EL efﬁcien-cies for polymer LED’s have been achieved with PPV/MEH-CN-PPV and PPV/DHeO-CN-PPV double-layer devices.3,26This has been attributed to various reasons,but it has been unclear what role interference effects and nonradiative en-ergy transfer to the metal electrode play.In these devices it has been proposed that emission occurs from a thin layer at the interface between the polymer layers,although there has been little direct evidence that this is the case.We have systematically changed the position of the interface between the two polymer layers relative to the metal ﬁlm.We mea-sured the dependence of the EL efﬁciency of PPV/MEH-CN-PPV double-layer devices on the distance between the polymer-polymer interface and the Al electrode.This allows us to comment on the effect of the Al ﬁlm on the radiative and nonradiative properties of the emitting species and the increased EL efﬁciencies in double-layer devices.We com-pare the EL efﬁciencies with the PL efﬁciencies measured on thin polymer ﬁlms separated from a 35-nm Al ﬁlm by a SiO 2layer.The interface between conjugated polymers and metals has recently been studied in order to obtain information about the chemistry that occurs at the interface and about diffusion of metal atoms into the near-surface region of the polymer.27The effects of these processes on PL and EL are important for device operation.It has also been reported that thin calcium ﬁlms efﬁciently quench the PL of thin conju-gated polymer ﬁlms if deposited on top of them.28In this context it is important to understand the origin and conse-quences of nonradiative energy transfer from the polymer to the metal and of interference effects on the quantum efﬁ-ciency and the emission spectrum.II.METHODA.Experimental proceduresWe have built three device structures as shown schemati-cally in Fig.2.Thin metal ﬁlms of Al or Au were thermally evaporated onto one-half of a quartz substrate.We used semitransparent Al and Au ﬁlms of thicknesses around 2–3nm with a transmittance of more than 70%in the visible,and 35-nm-thick nontransparent Al ﬁlms.Films of MEH-CN-PPV and DHeO-CN-PPV ͑Fig.1͒were prepared by spin coating onto the metal-coated substrates.A series of thick-nesses between 15and 200nm was prepared.On a second set of samples,transparent SiO 2spacer layers ͑Schott glass 8329͒of differing thicknesses were evaporated on top of the metal-ﬁlm coated substrates using an electron-beamevapo-FIG. 1.Chemical structures of PPV,MEH-CN-PPV,and DHeO-CN-PPV.189456H.BECKER,S.E.BURNS,AND R.H.FRIENDration technique.The refractive index of the glass was taken to be 1.47.A thin polymer layer of 15–20-nm thickness was then spin coated onto the SiO 2layer.In order to investigate the effect of indium-tin oxide ͑ITO ͒on the PL quantum ef-ﬁciency MEH-CN-PPV ﬁlms of different thicknesses were spin coated onto commercially-available ITO-coated glass substrates ͑Balzers ITO-coated glass substrates type 257;ITO layer thickness ϳ100nm ͒.The PL efﬁciency ͑number of photons emitted per number of photons absorbed ͒and the emission spectra of the PL samples ͑structures 1and 2,Fig.1͒were measured using an integrating sphere and a charge-coupled device ͑CCD ͒array spectrometer ͑Oriel Instaspec IV ͒.29,30A 458-nm laser served as the excitation source.The samples were illuminated from the polymer side.The PL efﬁciency and the PL spectrum were measured on the metal-coated half,and as a reference on the noncoated half of the sample as a function of the thickness of both the polymer ﬁlm and the SiO 2layer.A series of PPV/MEH-CN-PPV double-layer LED de-vices was built by spin-coating the PPV precursor onto ITO coated substrates.After thermal conversion of the PPV pre-cursor,MEH-CN-PPV was spin coated onto the PPV ﬁlm.Finally,Al electrodes were thermally evaporated on top of the structure.The PPV layer was 120nm thick.The thick-ness of the MEH-CN-PPV layer varied between 24and 110nm.A schematic diagram of the devices is shown in Fig.1.The electroluminescence in the forward direction was mea-sured using a calibrated photodiode.The batches of MEH-CN-PPV and DHeO-CN-PPV used showed PL quantum efﬁciencies between 33%and 39%when spin coated onto glass substrates.These are similar to those reported previously.29The samples were kept in a nitrogen-ﬁlled atmosphere or in vacuum at all times,and the experiments were performed within a few hours after the preparation of the samples in order to avoid oxidation of the polymer or the metal.B.ModelingSimulations of the radiative power of oscillating dipoles embedded in the top layer of a three-layer structure similar to structure 2shown in Fig.2were carried out using the transfer-matrix method and multilayer stack theory.The model is based entirely on classical electromagnetic theory,and is described in more detail in Ref.24.We simulated the radiative power of dipoles distributed uniformly throughout a 20-nm-thick layer separated from a 35-nm Al ﬁlm by a trans-parent layer with the same refractive index as the SiO 2that was used to build structure 2.The radiative power of the dipoles was normalized to be 1in free space.By integrating the emitted power over all angles,the changes in radiative rate due to the metal ﬁlm were calculated as a function of the distance between the emission layer and the metal,the wave-length and the orientation of the dipoles.The refractive index data for the aluminum was taken from Ref.31.The refractive index of MEH-CN-PPV was taken to be 1.7,where any bi-refringence and the dispersion of the refractive index was neglected.The refractive index of MEH-CN-PPV at 633nm has been measured to be 1.695for TM and 1.77for TE modes.32III.RESULTSA.PL spectra and PL efﬁciencyThe PL emission and absorption spectra of MEH-CN-PPV are shown in Fig.3.Due to the large Stokes’shift typical of this class of materials,the overlap between absorp-tion and emission is very small.For wavelengths above 550nm this allows us to use the spectra measured in the integrat-ing sphere,since reabsorption of the emitted light is low and the shape of the emission spectrum is therefore the same as for the free-space emission.1.Polymer on metal (structure 1)Figure 4shows the PL efﬁciency of MEH-CN-PPV and DHeO-CN-PPV ﬁlms in front of different metal ﬁlms as a function of the ﬁlm thickness.2-and 3-nm-thick gold and aluminum ﬁlms were used as well as 35-nm-thick aluminium ﬁlms.The data were corrected for the absorption of laser light by the metal mirror,which was calculated from the transmission spectra of the metal ﬁlms,simulations of the absorption of light by the metal,33the transmission spectra of the polymer ﬁlms,and the absorption by the whole structure measured in the integrating sphere.The 2–3-nm-thick metal ﬁlms are highly transparent for light in the visible range ͑Ͼ70%transmittance ͒.Hence we expect interferenceeffectsFIG.2.Schematic diagram of the PL ͑1,2͒and EL ͑3͒devicestructures.FIG.3.Normalized emission spectrum ͑solid line ͒and absorp-tion spectrum ͑dotted line ͒of MEH-CN-PPV.561895EFFECT OF METAL FILMS ON THE ...to play a minor role.Figure 5shows the spectra measured in the integrating sphere for MEH-CN-PPV ﬁlms of different thicknesses on 3nm of Al.We measured the absorption coefﬁcient for the MEH-CN-PPV at 458nm to be ␣ϭ1.24ϫ105cm Ϫ1,so that approxi-mately half of the excitation light is absorbed in the ﬁrst 56nm.Since the diffusion range for the excitons in these ma-terials is of the order of a few nanometers,we take the spatial distribution of the emission to be identical to the absorption proﬁle.For thick polymer ﬁlms,where most of the light is emitted in regions far away from the metal,the shape of the emission spectrum is the same as for thin ﬁlms,where the light is emitted close to the metal.This conﬁrms that inter-ference effects are negligible for 2–3-nm-thick metal ﬁlms.We see from our measurements that the PL is efﬁciently quenched for polymer ﬁlms up to a thickness of 90nm for thin metal ﬁlms,and up to 60nm for a thick Al ﬁlm.Within a critical distance of 20nm almost all luminescence is quenched.Figure 4also shows the dependence on the polymer ﬁlm thickness of the PL quantum efﬁciency of MEH-CN-PPVﬁlms deposited on 35nm of Al.The reﬂectance of the metal ﬁlm was around 90%.As shown in Fig.6,the shape of the emission spectrum changes with the polymer ﬁlm thickness due to interference effects.Surprisingly,the PL quantum ef-ﬁciency rises faster with polymer ﬁlm thickness than for thin metal ﬁlms.The difference in the distance dependence of the energy transfer rate to the metal cannot explain this.How-ever,interference effects not only affect the emission prop-erties of a material but also change the absorption in the same fashion.As we will see in Sec.III A 2,the radiative power of dipoles parallel to the mirror plane increases with the distance between the mirror and the dipole for distances comparable to the maximum MEH-CN-PPV ﬁlm thickness.We therefore expect the absorption of light to increase with distance from the metal.The majority of light is therefore absorbed and emitted further away from the metal than in the case of thin metal ﬁlms with a low reﬂectivity.As a conse-quence,the maximum PL efﬁciency is reached for thinner polymer ﬁlms.The same experiment was performed with polymer ﬁlms of differing thicknesses spin-coated on ITO-coated glass sub-strates.ITO,which is commonly used as a hole injector in electroluminescent devices,was not found to quench the PL for polymer ﬁlms thicker than 20nm.Only for a 20-nm-thick ﬁlm was a reduction of the PL efﬁciency of 12%observed.This might be explained in terms of exciton diffusion toward the polymer-ITO interface where the excitons are quenched.Our results are in agreement with reports in the literature.28,34,35Discussion .The suppression of light emission near the polymer metal interface cannot be explained by absorption of emitted light by the metal.Although this effect reduces the measured quantum efﬁciency,it is independent of the distance between the metal and the emitter,and can therefore not explain the increase in quantum efﬁciency with polymer ﬁlm thickness.At long distances the PL efﬁciency ap-proaches a constant value below the free-space quantum ef-ﬁciency of our samples.As we will see below this is consis-tent with our assumption that interference effects can be neglected for very thin metal ﬁlms.Our data agree qualita-tively with a calculation of the quantum yield of an oscillat-ing dipole with a quantum efﬁciency of unity in front ofaFIG.4.PL quantum efﬁciency as a function of the polymer ﬁlm thickness of MEH-CN-PPV on 2nm of gold ͑triangles ͒,MEH-CN-PPV on 3nm of aluminium ͑circles ͒,DHeO-CN-PPV on 2nm of gold ͑ﬁlled squares ͒and of MEH-CN-PPV on 35nm of aluminum ͑open squares ͒.The solid lines are guides to theeye.FIG.5.Normalized PL emission spectra of 15–90-nm-thick MEH-CN-PPV ﬁlms on 3nm of aluminum measured in the inte-gratingsphere.FIG.6.Normalized PL emission spectra of three selected thick-nesses of MEH-CN-PPV ﬁlms on 35nm of aluminum measured in the integrating sphere.189656H.BECKER,S.E.BURNS,AND R.H.FRIENDmirror.19We conclude that nonradiative energy transfer from the excited state of the polymer to the metal efﬁciently quenches luminescence in the proximity of a metalﬁlm,as predicted by the simulations by Chance,Prock,and Silbey.19 However,for three reasons our results are not directly comparable with the calculation of Chance,Prock,and Sil-bey.First,in their model,the quantum efﬁciency of a single dipole at a given distance is calculated.In our experiments the light is emitted over a broad region in the polymerﬁlm depending on where it is absorbed.Even for thick polymer ﬁlms light penetrates far into theﬁlm,where it is absorbed and subsequently emitted in regions close to the metal where it can be quenched.Because of the penetration of light into the polymerﬁlm we expect a reduction in the quantum efﬁ-ciency for relatively thick polymerﬁlms.Second,Chance, Prock,and Silbey,used a model in which the emitter had a quantum yield of unity in free space.It follows that in free space no nonradiative energy decay occurs.Energy transfer to the metal is therefore the only nonradiative decay channel. This means that interference effects do not change the quan-tum efﬁciency for distances where nonradiative energy trans-fer to the metal is negligible.They do,however,alter the quantum efﬁciency at short distances where nonradiative en-ergy transfer to the metal is present.In our structures,shown in Figs.4–6,interference effects alter the PL efﬁciency at all distances when the reﬂectivity of the metalﬁlms is high, since our materials have a free-space quantum efﬁciency around36%,and therefore intrinsic nonradiative decay chan-nels not associated with the metalﬁlm are present.However, interference is negligible for all distances when the reﬂectiv-ity of the metalﬁlms is low.Third,highly transparent metal ﬁlms show a slightly different distance dependence of the nonradiative energy-transfer rate than thick metalﬁlms.At short distances very thinﬁlms quench luminescence more efﬁciently than thick metalﬁlms,whereas for longer dis-tances the opposite is true.182.Polymer on spacer on metal(structure2)We also investigated the PL efﬁciency and the emission spectra of structures where a20-nm-thick polymer layer is separated from the Alﬁlm by a SiO2space ing spacer layers avoids several problems.The emission zone is conﬁned to a thin layer at a given distance to the metal, which gives better spatial resolution and allows better com-parison with simulations for dipoles in front of metal ﬁlms.15,19,24It avoids chemical reactions between the poly-mer and the metal that can alter the emission characteristics of the polymer,e.g.,covalent bonding of Al atoms to the polymer.27It also rules out diffusion of the exciton to the metal as a necessary precondition for quenching.Further-more,no diffusion of metal atoms into the polymer layer͓of the order or3–4nm for Al͑Ref.27͔͒occurs.In addition,a comparison of the EL results with the PL quantum efﬁciency of a polymerﬁlm at various distances to the metal allows us to draw conclusions about the nature of the recombination zone.The measured quantum efﬁciencies were corrected for the absorption of laser light by the Alﬁlm.In Fig.7the PL quantum efﬁciency of a15–20-nm-thick polymerﬁlm separated from2–3-nm-thick Au and Alﬁlms by a transparent SiO2spacer layer is shown as a function of the spacer layer thickness.For a polymerﬁlm spin coated directly onto the metalﬁlm or a5-nm-thick spacer layer,the efﬁciency is reduced from36%in free space to a value be-tween0.06%and3%.We note that contact between the polymerﬁlm and the metal is not necessary for efﬁcient quenching of the PL.The PL quantum efﬁciency increases with increasing SiO2layer thickness.For a separation of ap-proximately60nm,the PL quantum efﬁciency approaches a constant value which is less than the free-space quantum efﬁciency of36%.The excitation density throughout such a thinﬁlm is taken to be approximately constant.For our samples we therefore consider60nm as the distance above which nonradiative energy transfer to the metal becomes negligible.The PL spectra obtained from the polymerﬁlms are shown in Fig.8.As expected,for highly transparent metalﬁlms the shape of the emission spectrum is almost independent of the distance between the polymer layer and the metalﬁlm.Figure9shows the results of the same measurement on samples with a35-nm-thick highly reﬂective Alﬁlm.The FIG.7.PL quantum efﬁciency of a15–20-nm-thick MEH-CN-PPVﬁlm on a SiO2spacer layer on2nm of gold or3nm of aluminum as a function of the SiO2thickness.The solid lines are guides to theeye.FIG.8.Normalized PL emission spectra of15–20-nm-thick MEH-CN-PPVﬁlms separated by SiO2spacer layers of different thicknesses from2nm of gold and3nm of aluminum measured in the integrating sphere.561897EFFECT OF METAL FILMS ON THE...reﬂective and quenching properties of such an Al ﬁlm are identical to that of the bulk.The PL quantum efﬁciency os-cillates as a function of the SiO 2layer thickness.With no spacer layer present,the PL quantum efﬁciency is again re-duced to around 3%.With increasing SiO 2layer thickness the quantum efﬁciency rises to a maximum of 35.5%for a separation of about 75nm between the polymer layer and the metal ﬁlm.For larger distances,the PL is signiﬁcantly re-duced,with the quantum efﬁciency dropping to 5.3%for a SiO 2layer of 210-nm thickness.The PL quantum efﬁciency peaks again,with the quantum efﬁciency reaching 32%,a value slightly lower than that for the ﬁrst peak.We note that the PL quantum efﬁciencies shown in Fig.9have been cal-culated neglecting the absorption of emitted light by the Al.Correction for absorption of PL by the Al would give a maximum PL quantum efﬁciency of 37%,and a minimum PL quantum efﬁciency of 5.6%,as discussed below.The PL spectra from these samples are shown in Fig.10.Interference effects shift the emission peak of a thin MEH-CN-PPV layer on top of a SiO 2spacer and a 35-nm-thick Al ﬁlm over therange of 580–640nm.The emission from a MEH-CN-PPV ﬁlm spin coated onto a glass substrate peaks at 595nm.Discussion .In our experiments we can distinguish be-tween two cases.For very thin metal ﬁlms with low reﬂec-tivities,interference effects are negligible.This is supported by the lack of any dependence of the shape of the emission spectrum on the thickness of the polymer ﬁlm or the SiO 2spacer layer.Nonradiative energy transfer to the metal has,however,been identiﬁed as an efﬁcient decay channel for an emitter in the proximity of a thin metal ﬁlm.19,22The samples with thin metal ﬁlms thus allow us to measure the effect of the metal ﬁlm on the nonradiative energy transfer only and to neglect the effect of interference on the radiative rate.For thick metal ﬁlms we expect both interference effects and energy transfer to the metal to inﬂuence the radiative as well as the nonradiative properties of the light emitter.14,15,19We can identify two different regimes.For short distances ͑below 60nm ͒we see efﬁcient quenching of the lumines-cence for both highly transparent and highly reﬂective metal ﬁlms.We conclude that nonradiative energy transfer to the metal plays an important role in this region.For longer dis-tances the PL efﬁciency remains constant for polymer ﬁlms on thin metal layers but oscillates as a function of distance for highly reﬂective metal ﬁlms.For thicker metal ﬁlms we also observe a signiﬁcant dependence of the shape of the emission spectrum from the distance between the emitter and the metal.We assign these effects to interference between directly emitted waves and waves reﬂected from the metal layer.The effect of interference on the radiative lifetime of an emitting dipole in front of a metal mirror as a function of wavelength and dipole metal separation has been investi-gated in great depth,15,23and,as we discuss below,can ac-count for our observations here.In order to interpret our results,we have analyzed them in terms of the competition between radiative and nonradiative decay processes.The radiative lifetime of an excited mol-ecule oscillates with increasing distance of the molecule from a reﬂective surface.However,when the nonradiative energy transfer to the metal is negligible,the radiative decay channels in a material with a quantum efﬁciency of unity do not compete with any nonradiative decay channels.Changes in the radiative lifetime therefore have no effect on the quan-tum efﬁciency.We note that this is the case for the simula-tions carried out in Ref.19.If,however,nonradiative decay channels are present,as in our materials,an oscillation in the radiative lifetime due to interference effects will allow the nonradiative decay channels to compete more or less favor-ably,depending on whether the radiative lifetime is in-creased or decreased.This leads to an oscillation in quantum efﬁciency.For materials where radiative and intrinsic and extrinsic ͑i.e.,due to the metal ͒nonradiative decay channels compete with each other,we therefore expect a combination of both the effects of interference on the radiative lifetime and of energy transfer to the metal on the nonradiative life-time.At long distances we expect the PL efﬁciency to oscil-late in the same fashion as the radiative lifetime ͑see Fig.9͒.At short distances nonradiative energy transfer will reduce the efﬁciency ͑see Figs.9and 4͒.This effect will be en-hanced by an increase in the radiative lifetime ͑decrease in the radiative rate ͒due to destructiveinterference.FIG.9.Solid circles:PL quantum efﬁciency of a 15–20-nm-thick MEH-CN-PPV ﬁlm on a SiO 2spacer layer on a 35nm of aluminum as a function of the SiO 2thickness.The solid line is a guide to theeye.FIG.10.Normalized PL emission spectra of 15–20-nm-thick MEH-CN-PPV ﬁlms separated by SiO 2spacer layers of four se-lected thicknesses from 35nm of aluminum measured in the inte-grating sphere.189856H.BECKER,S.E.BURNS,AND R.H.FRIEND。

ApplicationLayer

浏览器和服务器交换HTTP 报文（通过各自的套接字）
关闭TCP 连接
HTTP是“无状态的” 服务器不保存有关客户
请求的任何信息
aside
Protocols that maintain “state” are complex!
past history (state) must be maintained
进程编址
为了接收报文，每个进程必须有标识
主机使用IP地址进行标识
Q: 用进程所在主机的IP地
址能否标识进程？
A: 不能，因为同一个主机
上可能运行着许多进程。
进程标识包括： ❖ IP地址 ❖ 与该进程关联的端口号
端口号的例子: ❖ HTTP server: 80 ❖ Mail server: 25
2.2.1 超文本传输协议--HTTP 概述
Web采用客户-服务器模式
❖ client: 浏览器请求、接收
和显示web对象
❖ server: Web服务器应客
户请求发送对象
PC running Explorer
HTTP协议定义了浏览器和 web服务器之间的通信规则
HTTP 1.0（RFC 1945）和 HTTP 1.1（RFC 2068）
专用协议:
e.g., Skype
2: Application Layer 15
Chapter 2: outline
2.1 principles of network applications
❖ app architectures ❖ app requirements
2.2 Web and HTTP 2.3 FTP 2.4 electronic mail
❖ 发送进程将报文推出门 ❖ 门外的运输设施（因特网）将报文送到接收进程的门口

The OSI 7 Layer Model

The OSI 7 Layer ModelFor the next several weeks we are going to work on one of the critical areas of the MCSE program. It is the OSI 7 Layer Model, a structure generated to separate different parts of networking into different categories and defining the relationships between categories. This is BY FAR the most complex part of the Networking Essentials test, as it pulls together protocol stacks, network types, hardware, software, and every other component of networking into a single view. You can pass the test without fully understanding the OSI model, but you will never fully understand networking without it.What Is The OSI Model?The International Organization for Standardization (ISO) began developing the Open Systems Interconnection (OSI) reference model in 1977. It was created to standardize the rules of networking in order for all systems to be able to communicate. In order for communication to occur on a networking using different device drivers and protocol stacks, the rules for communication must be explicitly defined. The OSI model deals with the following issues;•How a device on a network sends it's data, and how it knows when are where to send it•How a device on a network receives it's data, and how to know where to look for it.•How devices using different languages communicate with each other.•How devices on a network are physically connected to each other.•How protocols work with devices on a network to arrange data.The OSI model is broken down into 7 layers. Although the first layer is #1, it is always shown at the bottom of the model. We'll explain why later. For now, remember this little trick; Please Do Not Tell Secret Passwords Anytime. (From A+ Certification For Dummies, IDG 1999) Here are the seven layers.1. Physical Layer2. Data Link Layer3. Network Layer4. Transport Layer5. Session Layer6. Presentation Layer7. Application LayerProtocol StacksIn order for each layer of the model to communicate with the levels above and below it, certain rules were developed. These rules are called Protocols, and each protocol provides a specific layer of the model with a specific set of tasks or services. Each layer of the model has it's own set of protocols associated with it. When you have a set of protocols that create a complete OSI model, it is called a Protocol Stack. An example of a protocol stack is TCP/IP, the standard for communication over the internet, or Appletalk for Macintosh computers.As stated before, protocols define how layers communicate with each other. Protocols specifically work with ONLY the layer above and below them. They receive services from the protocol below, and provide services for the protocol above them. This order maintains a standard that is common to ALL forms of networking.In order for two devices on a network to communicate, they must both be using the same protocol stack. Each protocol in a stack on one device must communicate with it's equivalent stack, or peer, on the otherdevice. This allows computers running different operating systems to communicate with each other easily, such as having Macintosh computers on a Windows NT network.Communications Between StacksWhen a message is sent from one machine to another, it travels down the protocol stack or layers of the model, and then up the layers of the stack on the other machine. As the data travels down the stack, it picks up headers from each layer (Except the physical layer). Headers contain information that is read by the peer layer on the stack of the other computer. As the data travels up the levels of the peer computer, each header is removed by it's equivalent protocol. These headers contain different information depending on the layer they receive the header from, but tell the peer layer important information, including packet size, frames, and datagrams. Each layer's header and data are called data packages, or service data units. Although it may seem confusing, each layer has a different name for it's service data unit. Here are the common names for service data units at each level of the OSI modelThe Physical LayerThe lowest layer on the OSI model, and probably the easiest to understand is the physical layer. This layer deals with the physical, electrical, and cable issues involved with making a network connection. It associates with any part of the network structure that doesn't process information in any way.The physical layer is responsible for sending the bits across the network media. It does not define what a bit is or how it is used merely how it's sent. The physical layer is responsible for transmitting and receiving the data. It defines pin assignments for serial connections, determines data synchronization, and defines the entire network's timing base.Items defined by the physical layer include hubs, simple active hubs, terminators, couplers, cables and cabling, connectors, repeaters, multiplexers, transmitters, receivers, and transceivers. Any item that does not process information but is required for the sending and receiving of data is defined by this layer.There are several items addresses by this layer. They are;•Network connections types, including multi-point and point-to-point networks.•Network Topologies, including ring, star, bus, and mesh networks.•Analog or Digital signaling.•Bit Synchronization (When to send data and when to listen for it).•Baseband Vs. Broadband transmissions.•Multiplexing (Combining multiple streams of data into one channel).•Termination, to give better signal clarity and for node segmentation.The Data Link LayerThe Data Link Layer is responsible for the flow of data over the network from one device to another. It accepts data from the Network Layer, packages that data into frames, and sends them to the Physical Layer for distribution. In the same way, it receives frames from the physical layer of a receiving computer, and changes them into packets before sending them to the Network Layer.The Data link Layer is also involved in error detection and avoidance using a Cyclic Redundancy Check (CRC) added to the frame that the receiving computer analyses. This second also checks for lost frames and sends requests for re-transmissions of frames that are missing or corrupted at this level.The most important aspect of the Data Link Layer is in Broadcast networks, where this layer establishes which computer on a network receives the information and which computers relay or ignore the information. It does so by using a Media Access Control (MAC) address, which uniquely identifies each Network Interface Card (NIC).Bridges, Intelligent Hubs, And NICs are all associated with the Data Link Layer.The Data Link Layer is sub-divided into two layers. This is done because of the two distinct functions that each sub-division provides.Logical Link Control - Generates and maintains links between network devicesMedia Access Control - Defines how multiple devices share a media channelThe Logical Link Control provides Service Access Points (Saps) for other computers to make reference to when transporting data the to upper layers of the OSI Model.Media Access Control gives every NIC a unique 12 digit hexadecimal address. These addresses are used by the Logical Link Control to set up connections between NICs. Every MAC address must be unique or they will cause identity crashes on the network. The MAC address is normally set at the factory, and conflicts arerare. But in the case of a conflict, the MAC address is user set-able.The Network LayerThe third layer of the OSI model is the Network layer. This layer is responsible for making routing decisions and forwards packets that are farther then one link away. By making the network layer responsible for this function, every other layer of the OSI model can send packets without dealing with where exactly the system happens to be on the network, whether it be 1 hop or 10 hops away.In order to provide it's services to the data link layer, it must convert the logical network address into physical machine addresses, and vice versa on the receiving computer. This is done so that no relaying, routing, or networking information must be processed by a level higher in the model then this level. Essentially, any function that doesn't provide an environment for executing user programs falls under this layer or lower. Because of this restriction, all systems that have packets routed through their systems must provide the bottom three layers' services to all packets traveling through their systems. Thus, any routed packet must travel up the first three layers and then down those same three layers before being sent farther down the network. Routers and gateways are the principal users of this layer, and must fully comply with the network layer in order to complete routing duties.The network layer is also responsible for determining routing and message priority. By having this single layer responsible for prioritization, the other layers of the OSI model remain separated from routing decisions.This layer is also responsible for breaking large packets into smaller chucks when the original packet is bigger then the Data Link is set. Similarly, it re-assembles the packet on the receiving computer into the original-sized packet. There are several items addresses by this layer. They are;•Addressing for logical network and service addresses.•Circuit message and packet switching•Route discovery and selection•Connection services, including layer flow control and packet sequence control.•Gateway ServicesTransport LayerThe transport layer's main duty is to unsure that packets are send error-free to the receiving computer in proper sequence with no loss of data or duplication. This is accomplished by the protocol stack sending acknowledgements of data being send and received, and proper checksum/parity/synchronization of data being maintained.The transport layer is also responsible for breaking large messages into smaller packets for the network layer, and for re-assembling the packets when they are received from the network layer for processing by the session layer.Session LayerThe session layer is the section of the OSI model that performs the setup functions to create the communication sessions between computers. It is responsible for much of the security and name look-up features of the protocol stack, and maintains the communications between the sending and receiving computers through the entire transfer process. Using the services provided by the transport layer, the session layer ensures only lost or damaged data packets are re-sent, using methods referred to as data synchronization andcheckpointing. This ensures that excess traffic is not created on the network in the event of a failure in the communications.The session layer also determines who can send data and who can receive data at every point in the communication. Without the dialogue between the two session layers, neither computer would know when to start sending data and when to look for it in the network traffic.The Presentation and Application LayersThe presentation layer is responsible for protocol conversation, data translation, compression, encryption, character set conversion, and graphical command interpretation between the computer and the network.The main working units in the presentation are the network redirectors, which make server files visible on client computers. The Network redirector is also responsible for making remote printers appear as if they were local.The application layer provides services that support user applications, such as database access, e-mail services, and file transfers. The application layer also allows Remote Access Servers to work, so that applications appear local on remotely hosted servers.How NT and OSI Work Together.In order for Windows NT to work with all standard protocols, and to fit the OSI model, a metric had to be formed that fit both systems. Systems inside of Windows NT had to comply with all the rules of the OSI model in order for standardization to take place. The following is how Windows NT fits into OSI.DriversIn order for any piece of equipment to work on any system, drivers are required to standard the communication path between the equipment and the operating system. The same is true for networking components, which require drivers to provide the communication path so that NIC's can work efficiently and properly with the rest of the network and the computer itself.The network redirector uses the network adaptor card's driver to provide services such as file storageand printing to the user's application. Originally drivers for a NIC could only bound to a single protocolstack. This is okay for client-side computing because normally only one protocol stack and one NIC were needed. Server's presented a new problem, as they often required more then one protocol to deal with the large number of machines they were linked to.ODI and NDISTo solve this problem, two different solutions were established to allow single cards to be bound to multiple stacks. ODI (Open Driver Interface) was developed by Novel, Apple, and others was one solution. The other was NDIS (Network Driver Interface Specifications), created by Microsoft for Windows. Microsoft products require you to use NDIS, where as programs like Novell Netware require ODI.ODI and NDIS both allowed you to accomplish the same task. They made it possible to have one NIC bind to several protocol stacks simultaneously, such as TCP/IP and IPX, or have several adaptor cards using the same TCP/IP stack.In the OSI model, network drivers fall into the Data Link layer of the model, as do the network cards themselves. The Data Link Layer is split by the IEEE model into two sub-layers. The Logical Link Control (LLC) sub layer corresponds to the software drivers section, and the Media Access Control (MAC) sub layer corresponds to the network card itself.Essentials of Networking - Physical Connections of A NetworkThe MCSE Exams require you to understand the physical connections that make up a network. There are two main components of a network, consisting of the network media and the network interface card.Network Media : There are many forms of network media, but they fall into two distinct categories; Physical and Wireless.There are three major types of physical cabling. They are Coaxial, Twisted Pair, and Fiber Optics. They all share certain attributes, but differ in their uses.Coaxial cabling is much like the cable used on cable television wiring, but has certain shielding and impedance properties that make it different from that kind of wiring. It is also sub-divided into two different categories; RG-8 and RG-58. They differ in their shielding, and therefore their methods of use.Twisted Pair consists of pairs of wires that looks much like telephone cabling, but with a much different connection end. Again, there are two forms of Twisted Pair; UTP (Unshielded Twisted Pair) and STP (Shielded Twisted Pair). They also can differ on the number of pairs of wires used to connect, usually using either 2 or 4 pairs of wires.Fiber Optic Cable is different from the other two forms of wiring. Instead of using electricity to send signals across the cable, it uses light. Depending on the Spectrum used, Fiber Optics is generally the fastest form of network cabling.Wireless media consist of Infra-red (IR), Radio Frequency (RF), Microwave, and Satellite systems. All these media forms share one common element; Instead of using a physical form of transfer, they use wave forms designed to flow through the air to send their signals.Wireless media is not as efficient as physical media, and has a much higher cost. Therefore, it is mostly used to bridge distances that can't be connected by wired media, such as to make the connections between individual LAN's to the larger WAN.Next week we will look more extensively at Wired and Wireless Media, and the theories that make them work. Network Interface Cards (NICs) : Each form of networking media requires it's own special form of connection to the computer system. A Coaxial connector will not work with a Fiber Optic NIC, and a UTP connection will not transmit to an IR NIC. Therefore, which ever form of media you choose to connect your network, you must choose the equivalent form of Network Interface Card。

domexception blocked a frame with -回复

domexception blocked a frame with -回复Title: Understanding DOMException: Blocked a Frame With [...]Introduction:The web development ecosystem has significantly evolved over the years, providing developers with powerful tools and frameworks to create dynamic and interactive websites. However, despite these advancements, developers often encounter challenges while working with the Document Object Model (DOM). DOMException with the message "Blocked a Frame With [...]" is a common error that developers may encounter. This article aims to explain the intricacies of this error and guide readers through the step-by-step process to resolve it effectively.I. Understanding the DOM and the Document Object Model:To comprehend DOMException, it is crucial to have a basic understanding of the Document Object Model (DOM). DOM is a representation of an HTML or XML document that provides developers with a comprehensive set of objects, properties, and methods to manipulate and interact with the respective document.II. Exploring DOMException:DOMException is a standardized mechanism by which DOM interfaces report error conditions. It is an exception object that represents an abnormal event triggered during DOM operations. The "Blocked a Frame With [...]" message specifically indicates that a frame or an iframe is trying to access a resource from another domain, as part of a "Cross-Origin Resource Sharing" (CORS) policy.III. Causes of "Blocked a Frame With [...]" Error:1. Same-Origin Policy Violation: The Same-Origin Policy restricts web pages from making requests to another domain. Any attempt to access resources (such as JavaScript, CSS, or images) from a different origin or protocol triggers this error.2. CORS Misconfiguration: Cross-Origin Resource Sharing (CORS) policy allows controlled access to resources on other domains. If CORS is misconfigured or not enabled on the server-side, a "Blocked a Frame With [...]" error may occur.IV. Troubleshooting and Resolving "Blocked a Frame With [...]" Error:1. Checking for Same-Origin Policy Violation: Ensure that the code is not accessing resources (such as images, scripts, or stylesheets) from a different origin. Cross-origin requests may require the use of server-side techniques like JSONP or CORS.2. Enabling CORS: If your application depends on resources from other domains, enable CORS on the server-side by configuring the appropriate response headers, allowing the cross-origin requests. Consult the server documentation to understand the specific steps for enabling CORS.3. Specifying Appropriate CORS Headers: When accessing resources from another domain, ensure that the server'sAccess-Control-Allow-Origin header allows the requesting domain. Additionally, verify that the Access-Control-Allow-Credentials and the Access-Control-Allow-Methods headers are set correctly.4. Using Relative Paths: Utilize relative paths while referencing different resources within the application. This approach avoidsdomain-specific issues and potential cross-origin errors.5. Validating Certificate and Security Measures: If the error occurs when accessing resources from a secure (HTTPS) domain, ensure that the SSL/TLS certificate is valid and implemented correctly. Invalid or expired certificates can trigger the “Blocked a Frame With [...]" error.6. Debugging and Logging: Implement logging mechanisms to capture relevant information about the error. This helps in diagnosing the root cause and identifying potential solutions.Conclusion:The "Blocked a Frame With [...]" error can be a daunting problem for web developers. However, understanding the concepts behind DOMException and the underlying causes can significantly ease the troubleshooting process. By following the step-by-step guide mentioned in this article, developers can effectively tackle the error and ensure seamless functioning of their web applications. Remember to verify the CORS configuration, adhere to theSame-Origin Policy, and validate security measures to prevent such errors and enhance the overall user experience.。

端午节粽子英文介绍课件

要点三
Hangzhou Zongzi
This type of Zongzi is common for its unique shape and filling It is usually filled with sweet red bean paste or sweet lotus root, giving it a characteristic Hangzhou flavor.
Preparation of filling
Choose filling according to personal taste, such as mung beans, pork, salted egg yolks, etc., and process them.
Boil Zongzi
put the wrapped Zongzi into the pot, add enough water, boil it and turn to low heat for 2-3 hours until the glutinous rice is fully cooked.
In modern times, Zongzi has evolved and can be made with variable fillings and wrappers, such as glutinosus rice wrapped in bamboo leaves, sweet bean passed, and lotus leaf wrapped
Dragon Boat Fesustom of Zongzi on Dragon Boat Festival
• Nutritional Value and Healthy Diet of Zongzi in Dragon Boat Festival

domexception blocked a frame with -回复

domexception blocked a frame with -回复DOMException是一种与Web API操作相关的异常类型。

它通常在一个网页尝试访问或操作不被允许的数据时被触发。

而"[DOMException blocked a frame with]"则是一个常见的浏览器错误信息，它表示在加载页面时，浏览器因为安全策略的限制而阻止了某些iframe或frame的显示。

在本文中，我们将一步一步探讨关于DOMException、blocked frame 和相关解决方法的知识。

第一步：了解DOMException1. DOM是指文档对象模型（Document Object Model），它定义了访问和处理HTML和XML文档的标准方法。

2. DOMException是由W3C（World Wide Web Consortium）定义的异常类型，用于在DOM操作期间报告错误。

3. DOMException包含了许多不同的错误代码，例如"SecurityError"、"NotAllowedError"等，每个代码对应不同的错误场景。

4. 这些异常通常是由于浏览器的安全限制、权限问题或操作非法数据而引起的。

第二步：了解blocked frame1. 在网页中，可以使用iframe或frame元素来加载其他网页或外部资源。

2. 有时，当一个网页中的frame被阻止或拦截时，浏览器会显示"[DOMException blocked a frame with]"的错误信息。

3. 这种情况通常出现在浏览器出于安全考虑，阻止了iframe中加载的内容。

第三步：解决blocked frame问题1. 检查浏览器安全设置：有时，浏览器的安全设置可能导致frame被阻止加载。

检查浏览器的安全选项，确保它们没有被设置为过于严格的级别。

hyperf 单词

hyperf 单词英文回答：Hypertext Transfer Protocol (HTTP) is an application-layer protocol designed for use in distributed, collaborative, hypermedia information systems. It enables communication between clients and servers over a network.HTTP is a text-based protocol that uses a request-response model. Clients send requests to servers, and servers send responses back to clients. Requests and responses are structured using a series of headers and a body.HTTP is a versatile protocol that can be used to transfer a variety of data types, including HTML, CSS, JavaScript, images, and videos. It is also used to transfer data between web services and applications.Hypertext Markup Language (HTML) is a markup languageused to create web pages. HTML documents are made up of a series of elements, which are used to define the structure and content of the page. HTML elements can be nested within other elements to create complex layouts.HTML is a relatively simple language to learn, but it can be used to create powerful web pages. HTML is often used in conjunction with CSS and JavaScript to create interactive and dynamic web pages.Cascading Style Sheets (CSS) is a style sheet language used to define the appearance of web pages. CSS documents are made up of a series of rules, which are used to specify the properties of different HTML elements. CSS rules can be combined to create complex styles.CSS is a powerful language that can be used to create a wide variety of visual effects. CSS is often used in conjunction with HTML and JavaScript to create visually appealing and interactive web pages.JavaScript is a scripting language used to createdynamic web pages. JavaScript code can be embedded in HTML pages, and it is executed by the web browser. JavaScript code can be used to manipulate the DOM, respond to events, and perform a variety of other tasks.JavaScript is a versatile language that can be used to create a wide variety of interactive web pages. JavaScript is often used in conjunction with HTML and CSS to create complex and dynamic web applications.中文回答：Hyperf文本传输协议（HTTP）是用于分布式、协作式、超媒体信息系统中的应用层协议。

伊顿 EDA 406 技术数据表

STAINLESS STEEL-PRESSURE FILTER, change over acc. to ASMEWeight: approx. 298 lbs.Dimensions: inches1) Connection for the potential equalization,only for application in the explosive area.Switch lever standard in the front.2) On request:The switch lever ca be moved to backside of the changeover valve,opposite to the inlet and outlet.Please specify this configuration on the order.Assignment of connections and functions:A: process inlet SAE 2” 3000 PSI B: process outlet SAE 2” 3000 PSI C1/C2: air bleeding NPT ½” D1/D2: drain, dirt side NPT ½” E1/E2: drain, clean side NPT ½”F1: measuring connection BSPP ¼ dirt side F2: measuring connection BSPP ¼ clean sidePosition I: Filter 1 in operation Position II: Filter 2 in operationDescription: Stainless steel-pressure filter series EDA 406 have a working pressure up to 580 PSI. Pressure peaks can beabsorbed with a sufficient safety margin.A changeover ball valve between the two filter housings makes it possible to switch from the dirty filter side to the clean filter side without interrupting operation.The filter element consists of star-shaped, pleated filter material which is supported on the inside by a perforated core tube and is bonded to the end caps with a high-quality adhesive. The flow direction is from outside to inside.For cleaning the mesh element or changing the microglass element, remove the cover and take out the element. The mesh elements are not guaranteed to maintain 100% performance after cleaning.For fil tration finer than 40 μm use disposable elements made of microglass . Filter elements as fine as 5 μm(c) are available; finer filter elements are available upon request.Eaton filter elements are known for a high intrinsic stability and an excellent filtration capability, a high dirt-retaining capacity and a long service life.Eaton filter are suitable for all petroleum based fluids, HW-emulsions, most synthetic hydraulic fluids and lubrication oils.Ship classifications available upon request.Type index:Complete filter: (ordering example)series: EDA = stainless steel-pressure filter change over, acc. to ASME-Code nominal size: 406filter material:25VG, 16VG, 10VG, 6VG, 3VG microglassTechnical data:operating temperature: +14°F to +212°Foperating medium: mineral oil, other media on requestmax. operating pressure (pressure vessel): 580 PSItest pressure acc. to ASME VIII Div. 1: 1,3 x operating pressure = 754 PSItest pressure acc. to API 614, Chapter 1: 1,5 x operating pressure = 870 PSIprocess connection system: SAE-flange 3000 PSI orANSI-flange B16.5 CLASS 150/300 PSIhousing material: stainless steel, see sheet-no. 69578sealing material: Nitrile (NBR) or Viton (FPM), other materials on requestinstallation position: verticalbleeder connection: NPT ½“ or ANSI ¾” CLASS 150/300 PSIdrain connection dirt side: NPT ½“ or ANSI ¾” CLASS 150/300 PSIdrain connection clean side: NPT ½“volume tank: 2x 1.18 Gal.operating pressure adapter flanges: a ccording to B16.5 CLASS 150 PSI (FA11/FA12 max. 232 PSI)according to B16.5 CLASS 300 PSI (FA1/FA2 max. 580 PSI)Classified under the Pressure Equipment Directive 2014/68/EU for mineral oil (fluid group 2), Article 4, Para. 3. Classified under ATEX Directive 2014/34/EU according to specific application (see questionnaire sheet-no. 34279-4)Pressure drop flow curves:Filter calculation/sizingThe pressure drop of the assembly at a given flow rate Q is the sum of the housing ∆p and the element ∆p and is calculated as follows:∆p assembly= ∆p housing+ ∆p element∆p housing = (see ∆p= f (Q) - characteristics)For ease of calculation our Filter Selection tool is available online at /hydraulic-filter-evaluationMaterial gradient coefficients (MSK) for filter elementsThe material gradient coefficients in mbar/(l/min) apply to mineral oil (HLP) with a density of 0.876 kg/dm³ and a kinematicviscosity of 139 SUS (30 mm²/s) . The pressure drop changes proportionally to the change in kinematic viscosity and density.∆p=f(Q) – characteristic according ISO 3968The pressure drop characteristics apply to mineral oil (HLP) with a density of 0.876 kg/dm³. The pressure drop changes proportionally to the density.Symbols:without accessories withshut-off blockwith electric indicator AE30/AE40 withvisual-electric indicator AE50/AE62 withvisual-electric indicatorAE70/AE80/AE90 with visual indicator OP with visual-electric indicator OE with electronic sensor VS5Spare parts:Test methods:Filter elements are tested according to the following ISO standards:ISO 2941 Verification of collapse/burst resistance ISO 2942 Verification of fabrication integrityISO 2943 Verification of material compatibility with fluids ISO 3723 Method for end load testISO 3724 Verification of flow fatigue characteristicsISO 3968 Evaluation of pressure drop versus flow characteristics ISO 16889Multi-pass method for evaluating filtration performanceNorth America18684 Lake Drive East Chanhassen, MN 55317 Toll Free: +1 800-656-3344 (North America only) Tel: +1 732-212-4700Europe/Africa/Middle East Auf der Heide 253947 Nettersheim, Germany Tel: +49 2486 809-0 Friedensstraße 4168804 Altlußheim, Germany Tel: +49 6205 2094-0An den Nahewiesen 2455450 Langenlonsheim, Germany Tel: +49 6704 204-0Greater China No. 7, Lane 280, Linhong RoadChangning District, 200335 Shanghai, P.R. China Tel: +86 21 2899-3687Asia-Pacific100G Pasir Panjang Road #07-08 Interlocal Centre Singapore 118523 Tel: +65 6825-1620For more information, please email us at ********************or visit /filtration© 2024 Eaton. All rights reserved. All trademarks and registered trademarks are the property of their respective owners. All information and recommendations appearing in this brochure concerning the use of products described herein are based on tests believed to be reliable. However, it is the user’s responsibility to determine the suitability for his own use of such products. Since the actual use by others is beyond our control, no guarantee, expressed or implied, is made by Eaton as to the effects of such use or the results to be obtained. Eaton assumes no liability arising out of the use by others of such products. Nor is the information herein to be construed as absolutely complete, since additional information may be necessary or desirable when particular or exceptional conditions or circumstances exist or because of applicable laws or government regulations.。

the _make_layer method -回复

the _make_layer method -回复中括号内的内容是"_make_layer"方法。

本文将逐步回答与该方法相关的问题，并详细阐述其作用和实现方式。

第一步：什么是"_make_layer"方法？"_make_layer"方法是指在编程中使用的一种函数或方法。

在某些编程语言中，开发者可以使用这种方法来创建一个由多个子层组成的层。

该方法在神经网络中经常被用于构建深度学习模型的不同层级。

第二步："_make_layer"方法的作用是什么?"_make_layer"方法的主要作用是在神经网络中创建多个层，并将它们组合在一起形成一个更复杂的结构。

这些组合的层可以是相同类型的层，也可以是不同类型的层。

使用"_make_layer"方法可以极大地提高代码的可维护性和可读性，同时也能实现更高级的功能，如模型定制和灵活性。

第三步：如何使用"_make_layer"方法？使用"_make_layer"方法需要传入一些必要的参数，如层的类型、层的数量和相应的超参数。

例如，在使用"_make_layer"方法创建一个卷积层时，可以指定卷积核的数量、大小和步长等。

同时，开发者还可以根据需要，在参数中传入其他自定义的参数。

第四步："_make_layer"方法的实现原理是什么？具体实现"_make_layer"方法的方式因编程语言和框架而异。

下面以Python和PyTorch为例进行说明。

在Python中，使用这种方法可以通过定义一个类，并在该类中创建相应的函数来实现。

以神经网络为例，可以创建一个名为"LayerCreator"的类，其中定义一个名为"_make_layer"的函数。

华为E156G HSDPA USB穿插V100R001问题1日期2008-09-26 HUAWEI

Product DescriptionHUAWEI E156G HSDPA USB Stick V100R001Issue 01Date 2008-09-26HUAWEI TECHNOLOGIES CO., LTD.Huawei Technologies Co., Ltd. provides customers with comprehensive technical support and service. Please feel free to contact our local office or company headquarters.Huawei Technologies Co., Ltd.Address: Huawei Industrial BaseBantian, LonggangShenzhen 518129People's Republic of ChinaWebsite: Email: ******************Copyright © Huawei Technologies Co., Ltd. 2008. All rights reserved.No part of this document may be reproduced or transmitted in any form or by any means without prior written consent of Huawei Technologies Co., Ltd.Trademarks and Permissionsand other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd.All other trademarks and trade names mentioned in this document are the property of their respective holders.NoticeThe information in this document is subject to change without notice. Every effort has been made in the preparation of this document to ensure accuracy of the contents, but all statements, information, and recommendations in this document do not constitute the warranty of any kind, express or implied.About This DocumentSummaryThis document provides information about the major functions, supported services,system architecture, and technical references of HUAWEI E156G HSDPA USB Stick(hereinafter referred to as the E156G).The following table lists the contents of this document.Chapter Describes1 Overview The supported network modes, basic services and functions,and the appearance of the E156G.2 Features The supported features and technical specifications of theE156G.3 Services and Applications The services and applications of the E156G.4 System Architecture The architecture of the E156G.5 Technical Reference The technical references of the E156G.6 Packing List The items contained in the package of the E156G.A Acronyms and Abbreviations The acronyms and abbreviations mentioned in this document.HistoryIssue Details Datecompleted. 2008-09-26 01 InitialdraftContents1 Overview (6)2 Features (8)2.1 Main Features (8)2.2 Technical Specifications (9)2.2.1 Hardware (9)2.2.2 Dashboard (10)3 Services and Applications (12)3.1 Packet Data Service (12)3.2 SMS (12)4 System Architecture (13)4.1 System Architecture (13)4.2 Functional Modules (14)5 Technical Reference (15)5.1 Layer 1 Specifications (Physical) (15)5.2 Layer 2 Specifications (MAC/RLC) (15)5.3 Layer 3 Specifications (RRC) (15)5.4 Layer 3 NAS/Core Network (MM/CM) (15)5.5 GSM Protocol Specifications (16)5.6 GPRS Protocol Specifications (16)5.7 General Specifications (16)5.8 Performance/Test Specifications (17)5.9 SIM Specifications (17)6 Packing List (18)1OverviewHUAWEI E156G HSDPA USB Stick (hereinafter referred to as the E156G) is arsal serial bus (USB) modem. It is a mu SDPA) TS) (EDGE) z e a nd essages/emails cordlessly. The E156G is fast, reliable, and easy to new features and services with the able a large number of users to use the E156G and the average revenue per user (ARPU) of operators will increase substantially.Figure 1-1 shows the profile of the E156G.high-speed downlink packet access (HSDPA) unive lti-mode wireless terminal for business professionals.The E156G supports the following standards:z High speed downlink packet access (H z Universal Mobile Telecommunications System (UM z Enhanced data rates for global evolution General packet radio service (GPRS)zGlobal system for mobile communications (GSM)Th E156G provides the following services:z HSDPA/UMTS packet data service of up to 3.6 Mbps z EDGE/GPRS packet data service of up to 236.8 kbps zWCDMA/GSM Short Message Service (SMS)You can connect the E156G with the USB interface of a computer. In the service are of the HSDPA/UMTS/EDGE/GPRS/GSM network, you can surf the Internet a send/receive m operate. Thus, mobile users can experience many E156G. These features and services will enFigure 1-1 E156G profile2Features2.1 Main F a e tures:900/1800/1900 MHzrvice of up to 85.6 kbps ain data service based on UMTS and GSM d on CS/PS domain of GSM and WCDMA Smart card (PC/SC) Driver z External antennaz Micro Secure Digital Memory (Micro SD) CardzWindows 2000/ Windows XP/ Windows Vista/ MAC operating system (OS)e turesTh E156G mainly supports the following fea z HSDPA/UMTS 2100 MHz, GSM/GPRS/EDGE 850/z HSDPA Equalizer and receive diversity z HSDPA data service of up to 3.6 Mbpsz UMTS PS domain data service of up to 384 kbps z EDGE packet data service of up to 236.8 kbps z GPRS packet data se z CS dom z SMS base z Plug and play (PnP) z USSD z EAP-SIMz Personal computer/z USB Extension Cable ，easy to connect z Standard USB interface （Type A ）2.2 Technical Specifications2.2.1 HardwareTable 2-1 lists the hardware specifications. Table 2-1 Hardware specifications Item SpecificationsTechnical standard z WCDMA/HSDPA R5 zGSM/GPRS/EDGE R99 Operating frequencyHSDPA/UMTS 2100 MHz :z Uplink: 1920–1980 MHz zDownlink: 2110–2170 MHz EDGE/GPRS/GSM 1900 MHz:z Uplink: 1850–1910 MHz zDownlink: 1930–1990 MHz EDGE/GPRS/GSM 1800 MHz:z Uplink: 1710–1785 MHz zDownlink: 1805–1880 MHz EDGE/GPRS/GSM 900 MHz:z Uplink: 880–915 MHz zDownlink: 925–960 MHz EDGE/GPRS/GSM 850 MHz:z Uplink: 824–849 MHz zDownlink: 869–894 MHzUSB interface: supporting USB 2.0 high speed External antenna interface standard micro SD card interfaceExternal interfacesSIM/USIM card: standard 6-pin SIM card interfaceHSDPA/UMTS 2100 MHz ：+24dBm （Power Class 3）GSM/GPRS 850/900 MHz: +33 dBm (Power Class 4) GSM/GPRS 1800 MHz/1900 MHz: +30 dBm (Power Class 1) EDGE 850/900MHz: +27 dBm (Power Class E2) Maximum transmitter powerEDGE 1800MHz/1900MHz: +26 dBm (Power Class E2)Static receiver HSDPA/UMTS 2100 MHz : compliant with 3GPP TS 25.101 (R5)Item Specificationssensitivity EDGE/GPRS/GSM 850/900/1800/1900 MHz: compliant with3GPP TS 05.05 (R99)Maximum power≤ 2.5 WconsumptionPower supply 5 V/500 mALED indicating the status of the E156GDimensions70.15 mmⅹ25.64 mmⅹ11.60 mm(D × W × H)Weight <40gTemperature z Operating: –10℃ to +45℃z Storage: –20℃ to +70℃Humidity 5% to 95%Notes:3GPP = The 3rd Generation Partnership ProjectLED = light-emitting diodeSIM = subscriber identity moduleTS = technical specificationUSIM = UMTS subscriber identity module2.2.2 DashboardTable 2-2 lists the dashboard specifications.Table 2-2 Dashboard specificationsItem DescriptionSMSWriting/Sending/ReceivingSending/Receiving extra-long messagesGroup sendingStorage: The messages are saved in the hard disk of thePC.SortingImporting: You can import messages from the SIM/USIMcard to a laptop.New message prompt (visual prompt/audio prompt)ItemDescription Current connection:z Durationz Send/Receive flow zSend/Receive rateFlow display and statistics (data services)Traffic statistics: You can view the traffic information of the day, the month, or the year.Capacity: It depends on the SIM/USIM card capacity or the hard disk space.Messages can be sent from the phonebook.PhonebookImporting/Exporting: Import/Export contacts between the SIM/USIM card and a laptop or a file of supported formats.Network connection setupzAPN management: create, delete, edit, import, and export.zSet up network connection.Software installation Automatic installation (PNP) Network connection settings:z Automatic network selection and registration zManual network selection and registrationNetwork status display: signal, operator name, system mode, and so on.Selection of network connection types, for example:z 3G preferred zGPRS preferredOtherPIN management: activate/deactivate PIN, PIN lock, changing PIN, unblocking by using the PUK.System requirementz Windows 2000 SP4, Windows XP SP2, Windows Vista z Mac OS X 10.4 and 10.5 with latest upgrades zYour computer’s hardware system should meet orexceed the recommended system requirements for the installed version of OSzDisplay resolution: 800 × 600 or aboveNotes:PIN = personal identification number PUK = PIN unblocking key3Services and Applications3.1 Packet Data Servicever and the client software are installed on the PC automatically. You can configure APN through ings) and set up a network conn he network through wire To u teps: 1. Enter *99# or *98# to launch the packet data service.2. In the Choose Connection Type dropdown box, choose a network type, forexample: 3G preferred, GPRS preferred.3.2 SMSThe E156G supports message writing/sending/receiving and group sending (up to 20 contacts at a time). You can manage messages through the dashboard, such as sorting the messages by telephone number or time. You can also import/export messages between the SIM/USIM card and a laptop.The E156G supports the PS domain data service based on HSDPA/UMTS /EDGE/GPRSAfter you connect the E156G to a PC with a USB interface, the E156G dri the E156G application (or directly use the default sett ection. Then you can send or receive E-mail, access t less connection, and download files through wireless data channels. se the data service, perform the following s4System Architecture4.1 System ArchitectureFigure 4-1 shows the system architecture.Figure 4-1 System architectureE156GDMSSBackground moduleHardware modulePC driver4.2 Functional ModulesRadio Frequency Modulee frequency (RF) signals and baseban Baseband Signal c ocesses HDSPA/UMTS/EDGE/GPRS/GSM baseband digital signals, including:nals z Modulating/Demodulating EDGE/GPRS/GSM baseband signals g/Decoding HSDPA/UMTS channel Bottom Layer Driv als, including USB, LED, and SIM/USIM.Platform Service Subs ams, diagnoses the running of the system, downloads data and Protocol Stack Sy It pro f HSDPA/UMTS/EDGE/GPRS/GSM.Application SystemIt sends laptop command r protocol for processing and returns the value to the laptop.z Call management sage managementUser InterfaceIt provides interfaces to connect peripherals. Interfaces are for LED and SIM/USIM.Application ManagementThrough the application window, you can set the parameters of the E156G and operate the E156G.It s nds/receives radio signals and modulates/demodulates the radio d signals.Pro essingIt pr z Modulating/Demodulating HSDPA/UMTS baseband sig z Encodin zEncoding/Decoding EDGE/GPRS/GSM channelerIt drives peripher ystemIt initializes progr serves as a watchdog.stemcesses protocols o s to the bottom laye Existing applications include the following:z Mes zCS/PS domain service management5Technical Reference5.1 Layer 1 S z nel Coding and Multiplexing TR 25.944 Channels onto Physical Channels 3 4 z Physical Layer–Measurements (FDD) TS 25.215 z 3GPP HSDPA overall description 25.308 5.2 Layer 2 Specifications (MAC/RLC)z MAC Protocol Specification TS 25.321 5.3 Layer 3 S z UE Interlayer Procedures in Connected Mode TS 25.303 z UE Procedures in Idle Mode TS 25.304 5.4 Layer 3 N ode TS 23.122 zMobile Radio Interface Signaling Layer 3–General Aspects TS 24.007pecifications (Physical)Examples of Chan z Physical Layer–General Description TS 25.201z Physical Channels and Mapping of Transport (FDD) TS 25.211z Multiplexing and Channel Coding (FDD) TS 25.212z Spreading and Modulation (FDD) TS 25.21z Physical Layer–Procedures (FDD) TS 25.21z3GPP UE radio access capabilities 25.306zRLC Protocol Specification TS 25.322pecifications (RRC)zRRC Protocol Specification TS 25.331AS/Core Network (MM/CM)z Architectural Requirements for Release 1999 TS 23.121z NAS Functions Related to Mobile Station (MS) in Idle Mz Mobile Radio Interface Layer 3 Specifi zPP SMS Support on Mobile Radio Inte cation–Core Network TS 24.008 rface TS24.0115.5 GSM P o ocol k (DL) Layer z unications System (Phase 2+); Multiplexing and z up GERAN; Channel coding TS 05.03z Digital Cellular Telecommunications System (Phase 2+); Radio Subsystem Link Control TS 05.08(Phase 2+); Radio Subsystem 5.6 GPRS r z z ace Layer 3 Specification: Radio Resource Control Protocol zS): Mobile Station (MS)–Base Station/MAC) ical Link Control S 04.64g GPRS Support Node (MS–SGSN); Subnetwork S 04.65 2 z Radio Transmission and Reception TS 05.05z General Packet Radio Service (GPRS); Stage 1 TS 22.060 ent (MexE) TS 23.057ice (GPRS) Service description; stage 2 TS 23.0605.7 General SpecificationszVocabulary TR 25.990r tocol Specificationsz Mobile Radio Interface Layer 3 Specification, Radio Resource Control Prot TS 04.18z Mobile Station–Base Station System (MS–BSS) interface; Data Lin Specification TS 04.06Digital Cellular Telecomm Multiple Access on the Radio Path TS 05.02Technical Specification Gro zDigital Cellular Telecommunications System Synchronization TS 05.10P otocol Specificationsz Overall Description of the GPRS Radio Interface; stage 2 TS 3.64 Mobile Radio Interface Layer 3 Specification TS 04.08Mobile Radio Interf TS 04.18General Packet Radio Service (GPR System (BSS) interface; Radio Link Control/Medium Access Control (RLC protocol TS 04.60z Mobile Station–Serving GPRS Support Node (MS–SGSN) Log (LLC) Layer Specification T z Mobile Station–Servin Dependent Convergence Protocol (SNDCP) T z Multiplexing and Multiple Access on the Radio Path TS 05.0z Channel Coding TS 05.03 z Modulation TS 05.04z Mobile Execution Environm zGeneral Packet Radio Serv z UE Capability Requirements TR 21.904 z UE Radio Access Capabilities TR 25.926z Radio Interface Protocol Architecture TS 25.3z Services Provided by the Physical Layer TS 201 5.302 5.8 Perfor a z nsmission and Reception (FDD) TS 25.101 z rmance Testing Functions TS 34.109 z Terminal Conformance Specification TS 34.121formance Specification; Part 1: Protocol Conformance z2: Protocol Conformance 5.9 SIM Specificationsz SIM and IC Card Requirements TS 21.111z3rd Gen. Partnership Proj Tech. Spec. Group Terminals; SIM App. Toolkit (USAT) TS 31.111zSynchronization in UTRAN Stage 2 TS 25.402m nce/Test SpecificationsUE Radio Tra z Common Test Environments for User Equipment (UE) TS 34.108 Special Confo z User Equipment (UE) Con TS 34.123-1User Equipment (UE) Conformance Specification; Part TS 34.123-26Packing ListThis chapter describes the items contained in the package of the E156G. T -1 lists the items contained in the package of the E15T able 66G.able 6-1 Packing list of the E156G ItemQuantity Remarks HUAWEI E156G HSDPA USB Stick 1 Standard USB Extension Cable1 Standard HUAWEI E156G HSDPA USB Stick Quick Start 1 Standard Micro SD Card 1 Optional Ex alternal Antenna1Option Note:z Only the external antenna dedicated for Huawei devices can be used on the E156G. z The external antenna is wrapped separately.zWhen an external antenna is required, you need to purchase.AAcronyms and Abbreviations3G The Third Generationroject U main tion N M Mobile Communications A Packet Access l ment ment m r uter/Smart Card 3GPP 3rd Generation Partnership P APN Access Point Name ARP Average Revenue Per User BSS Base Station Subsystem CM Connection Management CS do Circuit Switched domainEDGE Enhanced Data Rates for GSM Evolu FDD Frequency Division Duplex GERA GSM/EDGE Radio Access Network GPRS General Packet Radio ServiceGS Global System for HSDP High Speed Downlink IC Integrated Circuit LED Light Emitting Diode MAC Medium Access Contro MexE Mobile Execution Environ MM Mobility Manage Mode Modulator Demodulato MS Mobile Station NAS Non-Access Stratum OS Operating SystemPC/SC Personal Comp PINPersonal Identification NumberPnP Plug and Play PP Point-to-PointPS domain omain de erviceCP Convergence Protocol communications System UTRAN UMTS Terrestrial Radio Access Network WCDMA Wideband Code Division Multiple AccessPacket Switched d PUK PIN Unblocking Key RF Radio Frequency RLC Radio Link Control RRC Radio Resource Control SGSN Serving GPRS Support No SIM Subscriber Identity Module SMS Short Messaging S SND Subnetwork Dependent TR Technical Report TS Technical Specification UE User EquipmentUMTS Universal Mobile Tele USAT USIM Application Toolkit USB Universal Serial BusUSIM UMTS Subscriber Identity Module。

莎士比亚哈姆雷特读后感英语作文

莎士比亚哈姆雷特读后感英语作文1. From the moment I began "Hamlet," I was captivated by Shakespeare's brilliant storytelling and intricate plot.2. The play's exploration of themes such as revenge, depression, and doubt left a lasting impression on me.3. Hamlet's soliloquies are particularly remarkable, offering deep insight into his inner turmoil and conflict.4. Shakespeare's ability to create complex characters like Hamlet is truly awe-inspiring.5. Hamlet's relationship with his mother, Gertrude, adds another layer of complexity to his character development.6. The Ghost's relentless pursuit of revenge sets the stage for the play's intense drama.7. The themes of loyalty and deceit are seamlessly woven throughout the narrative.8. The play's use of foreshadowing is masterful, keeping the audience on the edge of their seats.9. Ophelia's plight as a victim of her society's expectations was heartbreaking to witness.10. The play's portrayal of madness, both real and feigned, adds depth to the overall story.11. Polonius' overzealousness as a parent and courtier proved to be his downfall.12. Hamlet's delay in seeking revenge became a point of contention among the characters and audience alike.13. The play's language is a testament to Shakespeare's genius, filled with elaborate metaphors and witty puns.14. The play's setting in Denmark added a sense of historical context and cultural significance.15. The character of Claudius, the deceitful king, is both cunning and despicable.16. The play's exploration of male friendship,particularly between Hamlet and Horatio, is notable.17. The play's exploration of gender roles is both surprising and thought-provoking.18. The ending of the play left me with a mix of satisfaction and sorrow.19. Shakespeare's portrayal of characters like Rosencrantz and Guildenstern as mere puppets of circumstance was intriguing.20. The play's use of Norse mythology adds an interesting element to the overall narrative.21. The role of the Oracle in the play serves as a catalyst for the main plot's progression.22. The play's allusions to other works of literature area testament to Shakespeare's scholarly mind.23. Hamlet's relationship with Ophelia is a poignant tale of unrequited love and broken hearts.24. The play's exploration of the consequences of power and ambition was eye-opening.25. The play's emphasis on the perils of kingdom intrigue highlighted the fragility of leadership.26. Shakespeare's use of dialogue to reveal characters' secrets and motivations was brilliant.27. The character of Fortinbras, the foreign prince, serves as an interesting foil to Hamlet.28. The play's exploration of the divine and the supernatural is both mesmerizing and chilling.29. The character of Laertes adds a younger perspective to the older generation of Hamlet's world.30. Shakespeare's ability to create characters that defy typical expectations is evident in "Hamlet."31. The play's unanswered questions leave the audience pondering for years to come.32. The play's哈哈element of surprise at key moments keeps the story unpredictable and gripping.33. Hamlet's encounters with the players underscore the idea that even the most fake can sometimes feel more real than the truth.34. The play's exploration of moral corruption within the royal court was disturbingly relatable.35. The character of Polonius' pride in his intelligence leads to his own demise, a testament to humility's value.36. Shakespeare's exploration of the nature of good and evil is both profound and unsettling.37. The character of Hamlet's outward sanity and inward turmoil are a Shakespearean dichotomy that feels timeless.38. The role of fairies in the "play within a play" is both whimsical and prophetic.39. The play's use of symbolism highlights themes of death, corruption, and decay.40. Hamlet's indecisiveness on whether to act or react adds to his complexity as a character.41. The play's exploration of the psychological effects of grief is hauntingly accurate.42. The play's focus on the cyclical nature of violence is both terrifying and necessary.43. The characters' names in "Hamlet" hold significant meaning and reflect their personalities.44. Shakespeare's use of dramatic irony is a highlight of the play's storytelling.45. The play's reference to the "auf wiedersehen" song adds a touch of European influence to the story.46. The role of the player kings in "Hamlet" questions the nature of kingship and leadership.47. The character of Claudius' betrayal of Hamlet'sfather sets the stage for the play's tragic outcome.48. The play's exploration of madness and psychological instability is unsettling but compelling.49. Shakespeare's ability to create characters that are both relatable and unfathomable is truly remarkable.50. The play's use of language to mask truth with lies isa study in human nature.51. Hamlet's relationship with Horatio is a beautiful example of friendship and loyalty.52. The play's ending raises questions about fate versus free will, a debate that still resonates today.53. The role of Hamlet's education and his ability to question societal norms is refreshing.54. The play's exploration of the supernatural world putsa spooky twist on the familiar.55. The character of Ophelia's descent into madness is haunting and poignant.56. Shakespeare's focus on the power of language is a recurring theme in "Hamlet."57. The play's political commentary still feels relevant, showcasing the saying "power corrupts."58. The character of Hamlet's indecision is a mirror to our own hesitation and inaction.59. The play's exploration of madness as both a metaphor and a literal state is profound.60. The character of Hamlet's cunning intellect combined with moral ambiguity makes him a fascinating study.61. The play's ending leaves the audience in a state of shock, a testament to Shakespeare's mastery of storytelling.62. The character of Hamlet's feigned madness serves both as a means of protection and psychological turmoil.63. The play's exploration of friendship versus enmity isa timeless lesson.64. Shakespeare's use of foreshadowing is subtle yet undeniable, adding a layer of depth to the narrative.65. The play's focus on family dynamics adds an emotional weight to the story.66. The character of Hamlet's love for Ophelia is both innocent and tragically short-lived.67. The play's use of soliloquies reveals the true nature of Hamlet's thoughts and feelings.68. Shakespeare's exploration of the afterlife and morality in "Hamlet" is introspective and philosophical.69. The play's use of imagery to personify abstract concepts is a testament to Shakespeare's creativity.70. The character of Hamlet's struggle with the concept of "to be or not to be" touches on existential debates.71. The role of the play's setting in Elsinore Castle is both symbolic and practical.72. The play's exploration of the impact of a flawed reign on court is a stark reminder of leadership's weight.73. The character of Hamlet's resourcefulness in disguise highlights his ability to manipulate his environment.74. Shakespeare's use ofBOTTOM festival scene brings a rare touch of whimsy to the otherwise dark drama.75. The play's exploration of loyalty and betrayal is a Shakespearean staple, relevant even in today's world.76. The character of Hamlet's time spent in the madhouse raises questions about the relationship between appearance and reality.77. The play's use of the "get thee to a nunnery" line serves as a commentary on feminine purity and societal norms.78. Shakespeare's exploration of the dangerous allure of mentorship is evident in the relationship between Polonius and Laertes.79. The play's discussion of justice versus retributionis a moral and philosophical conundrum.80. The character of Hamlet's struggle with his own identity leads to a tragic discovery of deception at the hands of others.81. Shakespeare's portrayal of the Danes' moral and political decadence is a commentary on human nature.82. The character of Laertes' transition from son to avenger is a study of resolve and retribution.83. The play's exploration of the idea of "the writer" versus the "reader" comes to light as it's acted out in the "play within a play."84. The character of Hamlet's elevated sense of self-awareness and introspection is a Shakespearean trait that adds to his complexity.85. Shakespeare's use of the把他angle adds a new perspective to the narrative, highlighting the outside observer's viewpoint.86. The play's exploration of the mental health issues faced by characters such as Ophelia and Hamlet raises important questions today.87. The character of Hamlet's tragic fate as a result of his indecision highlights the thin line between action and inaction.88. The play's emphasis on the human condition is what makes it an enduring classic and relatable to audiences.89. Shakespeare's exploration of the ethics of war and the futility of violence casts a long shadow over the action on stage.90. The character of Hamlet's name carries weight beyond the text, embodying the universal struggle with identity and purpose.91. The play's focus on the对口开启的dress reveals the complex relationships between characters and their power dynamics.92. Shakespeare's use of the "star-cross'd lovers" idea adds a romantic subplot that deepens Hamlet's character.93. The character of Hamlet's willingness to question the validity of his own existence echoes the existential concerns on stage.94. The play's awareness of the past haunts its characters, a haunting parallel to the way our past defines us.95. The character of Hamlet's ability to manipulate words with ease for his own gain is a mirrored by the words he scripturally twists and through which finds kmelishment.96. The play's emphasis on the importance of honor versus duty and their consequences for Hamlet are thought-provoking.97. Shakespeare's representation of the cultural and religious aspects of the1600s world enriches the narrative.98. The character of Hamlet's encompassing of a literal and figurative pendulum further complicates his designation as mad.99. The play's exploration of the bonds of family and the notion of filial duty are complex and relatable.100. The character of Hamlet's use of theucation to question everything makes him a nuanced and towering figure in literature.101. The play's transparency about the human ability to fail at basic human tasks reveals the depth of Shakespeare's insight into our nature.102. The character of Hamlet's engagement with his preciso digest, whether through direct interaction comme interactions with his dead father's ghost or others, with his mentor sought by his sister,rosences, suggests his constancy to seek self-information.103. Shakespeare's tone in Hamlet teeters between tragedy and laughter, giving us a peek into the duality of human existence.104. The character of Hamlet's interaction with the Venetian convention refers to his role in encapsulating aconvention that delineates how things "ought to be," thereby saddleing responsibility for upholding societal mores.105. Fiction is an exploration of the word itself, but Shakespeare’s ability to make not only words but theirprecise arrangement matter so much within "Hamlet" is stupefying focusing on the conversations portraying relationships, interactions, and intentions.106. The thematic bow администрации, flanked by the political, personal, and tragic dimensions, offers the viewer a territory rich with the possibility of summary and analysis—a land of endless reflection on humanity, authority, bilge, presence, and the interrogation of existence itself.107. In conclusion, "Hamlet" remains a decomposition ofthe human mind and heart, the magnitude of the noble soul campaigning against coexisting human Falından.。