2777 SECOND PUBLIC EXAMINATION Honour School of Physics ...
15 pages
English

2777 SECOND PUBLIC EXAMINATION Honour School of Physics ...

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  • cours - matière potentielle : b3
  • cours - matière : physics
2777 SECOND PUBLIC EXAMINATION Honour School of Physics Part B: 4 Year Course B3: V. GENERAL RELATIVITY AND COSMOLOGY AND VI. CONDENSED-MATTER PHYSICS TRINITY TERM 2011 Wednesday, 22 June, 2.30 pm – 5.30 pm Answer four questions, two from each section: Start the answer to each question in a fresh book. At the end of the examination hand in your answers to Section V and Section VI in separate bundles.
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INTRODUCTION TO BIOINFORMA
TICS AND IT
LESSON 28:
INTRODUCTION TO ADVANCED OPERATING SYSTEMS
Learning Outcomes machines provide network-wide services or applications such as
After reading this lesson students should be able to file storage and printer management. Each computer has its
own private operating system. The network operating system is• Understand what is distributed operating systems and it
simply an adjunct to the local operating system that allowsimportance
application machines to interact with server machines. The user
• Get an overview of technical terminology involved in
is aware that there are multiple independent computers and
computer architecture
must deal with them explicitly. Typically, common communica-
• Get an overview of client and server model and the tions architecture is used to support these network applications.
topologies involved in them
Distributed operating systems: It is a common operating
• Present the exact usage of various methodologies to DBMS. system shared by the network of computers. It looks to its
• Understand the present day technology in the field of science users like an ordinary centralized operating system but provides
and computers the user with transparent access to the resources of a number of
machines. A distributed operating system may rely on commu-Distributed Operating Systems
nications architecture for basic communications functions; more
Introduction commonly, a stripped-down set of communications functions
You must be noticing nowadays that there is increasing is incorporated into the operating system to provide efficiency.
availability of inexpensive yet powerful personal computers and
Architectures of Distributed Systems
servers, and also there has been an increasing trend toward
distributed data processing (DDP), in which processors, data, Client-server
and other aspects of a data processing system may be dispersed Perhaps the most significant trend in information systems in
within an organization. A DDP system involves a partitioning recent years is the rise of client/server computing. This mode
of the computing function and may involve a distributed of computing is rapidly replacing both mainframe-dominated,
organization of databases, device control, and interaction centralized computing approaches and alternative forms of
(network) control. distributed data processing.
In many organizations, there is heavy reliance on personal As with other new waves in the computer field, client/server
computers coupled with servers. Personal computers are used computing comes with its own set of jargon words. Table
to support variety of user-friendly applications, such as word given below lists some of the terms that are commonly found
processing, spreadsheet, and presentation graphics. The servers in the description of client/server products and applications.
house the corporate database plus sophisticated database
Terminology Meaning management and information systems software. Linkages are
needed among the personal computers and between each Application Programming A set of function and call
Interface programs that allow clients personal computers and the server. Various approaches are in
and servers to
common use, ranging from treating the personal computer as a intercommunicate
simple terminal to a high degree of integration between Client A networked information
requester, usually a PC personal computer applications and the server database.
workstation, that can query
These application trends have been supported by the evolution database and/or other
information from the server of the distributed capabilities in the operating system and
Middleware A set of drivers, APIs, or
support utilities. A spectrum of capabilities have been explored: other softwares that improve
connectivity between a client Communication architecture: This is software that supports a
application and a server
network of independent computers. It provides support for Relational database A database in which
distributed applications, such as electronic mail, file transfer, and information access is limited
to the selection to rows that remote terminal access. However, the computers retain a distinct
satisfy all search criteria
identity to the user and to the applications, which must Server A computer, usually a high-
communicate with other computers by explicit reference. Each powered workstations, a
microcomputer, or a computer has its own separate operating system, and a hetero-
mainframe, that houses
geneous mix of computers and operating systems is possible, information for manipulation
as long as all machines support the same communications by network clients
Structured Query A language developed by IBM architecture.
Language and standardized by ANSI for
Network operating system: This is a configuration in which addressing, creating, updating,
or querying relation al there is a network of application machines, usually single user
database
workstations and one or more “server” machines. The server

© Copy Right: Rai University
478 2A.501INTRODUCTION TO BIOINFORMATICS AND IT
Let us now study few examples of examples of client/server
architectures Three Tier
Two tier architectures: With two tier client/server architectures,

the user system interface is usually located in the user’s desktop User System Interface
environment and the database management services are usually
in a server that is a more powerful machine that services many

clients. Processing management is split between the user system Process management
interface environment and the database management server

environment. The database management server provides stored
procedures and triggers. There are a number of software
vendors that provide tools to simplify development of
Database management
applications for the two tier client/server architecture.
Two Tier

User System Interface + Figure 2. Three tier distributed client/server architecture
Some Processing
Management The three tier client/server architecture has been shown to

improve performance for groups with a large number of users
(in the thousands) and improves flexibility when compared to
Database management +
the two tier approach. Flexibility in partitioning can be a simpleSome Processing
Management as “dragging and dropping” application code modules onto
different computers in some three tier architectures. A limitation
Figure 1. Two Tier Client Server Architecture with three tier architectures is that the development environ-
ment is reportedly more difficult to use than theThe two tier client/server architecture is a good solution for
visually-oriented development of two tier applications. Recently,distributed computing when work groups are defined as a
mainframes have found a new use as servers in three tierdozen to 100 people interacting on a LAN simultaneously. It
architectures.does have a number of limitations. When the number of users
exceeds 100, performance begins to deteriorate. This limitation Three tier architecture with transaction processing monitor
is a result of the server maintaining a connection via “keep- technology: The most basic type of three tier architecture has a
alive” messages with each client, even when no work is being middle layer consisting of Transaction Processing (TP) monitor
done. A second limitation of the two tier architecture is that technology. The TP monitor technology is a type of message
implementation of processing management services using queuing, transaction scheduling, and prioritization service where
vendor proprietary database procedures restricts flexibility and the client connects to the TP monitor (middle tier) instead of
choice of DBMS for applications. Finally, current implementa- the database server.
tions of the two tier architecture provide limited flexibility in
moving (repartitioning) program functionality from one server
to another without manually regenerating procedural code.
Three tier architectures: The three tier architecture also referred to
as the multi-tier architecture emerged to overcome the limita-
tions of the two tier architecture. In the three tier architecture, a
middle tier was added between the user system interface client
environment and the database management server environ-
ment. There are a variety of ways of implementing this middle
tier, such as transaction processing monitors, message servers,
or application servers. The middle tier can perform queuing,
application execution, and database staging. For example, if the
middle tier provides queuing, the client can deliver its request to
the middle layer and disengage because the middle tier will Figure 3. Transaction Processing Monitor Technology
access the data and return the answer to the client. In addition The transaction is accepted by the monitor, which queues it and
the middle layer adds scheduling and prioritization for work in then takes responsibility for managing it to completion, thus
progress. freeing up the client. When the capability is provided by third
party middleware vendors it is referred to as “TP Heavy”
because it can service thousands of users. When it is embedded
in the DBMS (and could be considered a two tier architecture), it
is referred to as “TP Lite” because experience has shown
performance degra

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