Knowledge base for automatic generation of online IMS LD
compliant course structures
Ecaterina Giacomini Pacurar1, Philippe Trigano2, Sorin Alupoaie3
Université de Technologie de Compiègne
UMR CNRS 6599 Heudiasyc BP 20529123
60205 Compiègne FRANCE
egiacomi@hds.utc.fr1, philippe.trigano@utc.fr2, salupoai@etu.utc.fr3
Abstract
Our article presents a pedagogical scenarios-based web application that allows the automatic generation and development of pedagogical websites. These pedagogical scenarios are represented in the IMS Learning Design standard. Our application is a web portal helping teachers to dynamically generate web course structures, to edit pedagogical content and to administrate their courses. In this paper we are describing the methodological framework and the theoretical approaches used in our research project. We will also make a brief presentation of how the structures are automatically generated. Our application uses a knowledge-based system developed in the JESS environment (Java Expert System Shell). The knowledge is represented in XML files, then translated in JESS rules. Finally we are presenting an example of an educational website structure model developed using our tool and we are presenting an IMS LD graphic editor for modifying the course structures as well. Keywords: pedagogical scenario, knowledge based system, IMS LD graphic representation, instructional theory, dynamic generation of pedagogical website structures, HCI (Human-Machine Interface) for websites.
1. INTRODUCTION
Today, the Internet and Web development has transformed teaching and training practices. Courses circulate through software platforms in many formats and varied structures.
Considering the diversity of digital material and taking into account that users can access these elements, distribute them, exchange them, update them, the designers of electronic teaching objects have underlined the importance of standards. These are presented in the form of a "common language", which is currently used for indicating, organizing and describing the digital educational resources.
Our analysis regarding various norms and standards (“IEEE, 2001”, “Friesen, 02”, “ADL, 2001”, “IMS, 2003”) enabled us to choose the standard IMS LD for representing the pedagogical content in models of educational websites. In the realization of these teaching models, we are interested in taking into account several concepts like: theories and models of teaching and training, curricular areas, roles of actors (learning, group leaders, professors, tutors, etc.) and interactions between these various actors in the training environment. The use of this language facilitates the implementation of the dynamic evolution of a training course. Consequently, all elements that have been described led us to apply the IMS LD standard in the creation of educational websites.
2. LEARNING DESIGN EXISTING TOOLS: SOME EXAMPLES
(Griffiths et al., 2005) classifies the authoring tools dedicated to the design of a unit of learning in two categories: "low level" tools (use a presentation of terms and structures is close to the IMS LD specification) and "high level" tools (using a presentation of terms and structures distant from the IMS LD specification and also utilising a "hidden mapping" between the interactions of the users and the IMS LD document which must be published). The target for the first category is users (pedagogical
Ecaterina Giacomini Pacurar, Philippe Trigano, Sorin Alupoaie
content creator) with a deep knowledge of IMS LD specification. For the second category ("high level") of tools, the target users are those who aren’t familiar with the IMS LD specification. Therefore, the IMS LD structure and terminology are considered inappropriate for them. In order to be easy to use, these “high level” tools integrate vocabularies and representations well recognized by users. For example, teachers, as well as other actors who take part in the creation of the online courses, are familiar with terms like lesson, module of teaching, exercises etc. Consequently, they must specify and visualize the development of their courses by using these terms, which do not necessarily have a direct equivalent in LD.
Another direction that we can take into account in the classification of the authoring tools refers to the generic and specific dimensions of these tools (Griffiths et al., 2005). Thus, the tools known as "generic" give users access to the whole specification of LD. This category of tools is used by specialists in pedagogy, but also by technical specialists designing the units of learning.
Thereafter we give some examples of tools based on IMS LD. These tools are divided into three main categories: learning design editors, runtime tools and learning design players.
2.1 LEARNING DESIGN EDITORS
2.1.1. RELOAD LD Editor
The RELOAD project (Reusable e-Learning Object Authoring and Delivery) is a project of JISC whose objective is the development of tools in order to facilitate the use of interoperability specifications of pedagogical technology such as those created by ADL and IMS (Reload, 2005). Reload LD Editor is an authoring tool developed at the University of Bolton by Phillip Beauvoir and Paul Sharples. It proposes a graphical environment used for editing and conceiving packages in conformity with the IMS LD specification. The second version supports levels A, B and C of IMS LD and is currently available on the project website (Reload, 2005).
The Reload LD Editor allows the import and the creation of IMS LD packages. For each unit of learning, we can find the buttons corresponding to the principal IMS LD concepts: roles, activities, properties, environments, as well as plays structured in acts and role-parts. The process of conceiving
a unit of learning consists of filling in all the fields, according to the IMS LD specification.
2.1.2. CopperAuthor
CopperAuthor is an IMS LD editor developed by the OUNL (CopperAuthor, 2005). It provides a graphical interface that gives the user the possibility of developing and validating units of learning, visualizing the resulted XML code and unifying incomplete units of learning. It is not yet possible to import units of learning. CopperAuthor provides also a graphical interface to assign roles with runs in Coppercore and a previsualisation with Coppercore the execution of the created course.
2.2 LEARNING DESIGN ENGINE AND PLAYERS
2.2.1. CopperCore
CopperCore (CopperCore, 2005) is an IMS Learning Design engine developed by the OUNL in the context of the Alfanet project which supports all three levels of this standard (A, B and C). It handles the business logic of Learning Design, by providing support for dynamically checking and personalizing the activity workflow in a IMS LD content organization. The implementation of LD business logic as a separate software unit with an API facilitates the development of IMS LD players by hiding all the complexities of this standard. Thus, the CopperCore engine can be used when developing players that interpret the IMS LD.
2.2.2. Reload Learning Design Player
An example of a tool that uses the CopperCore engine is Reload Learning Design Player (Reload, 2005), developed at the university of Bolton by Paul Sharples and Phillip Beauvoir. Using this tool, it is possible to manage several units of leaning at the same time. The features of this LD player are: wraps the Coppercore (version 2.2.2) runtime engine within an easy to use management interface; 290
Knowledge base for automatic generation of online IMS LD compliant course structures
291
automatically launches and deploys Coppercore under a JBoss server; Interface allows for easy import/removal of Learning Designs in the Coppercore engine without the use of command line tools; automatically reads a Learning Design and populates Coppercore with a default run and active user for every role found within the manifest.; easy launch - double click a role within the management interface and it launches in the Native Browser.
In section 8 of this article, we position our tool in comparison to the other tools presented here.
3. APPLICATIONS OF IMS LD: PEDAGOGICAL WEBSITE MODELS
We have designed an online guide called CEPIAH in order to help teachers to implement pedagogical websites and to produce on-line courses. This system is composed of three modules: Help in the Design, Help with the Evaluation and Assistance with the development of online course structures. After having integrated the first two modules into the CEPIAH guide (Trigano and Giacomini, 2004) (Giacomini and Trigano, 2003), in the third module we were interested in assisting the design and development of educational websites structures. We developed a Web portal, named netUniversité, of which the general architecture is represented in Figure 1. Using this application the teacher can automatically generate educational website structures, adding the pedagogical content to these structures, then visualize, manage and participate in his courses. The students can view and participate in courses using the navigator integrated in netUniversité. Our web portal netUniversité, also integrates an QTI editor for interactive exercises (see Giacomini et al, 2005).
These structures are generated starting from answers given by the user (the teacher) by responding to two interactive questionnaires: a pedagogical questionnaire and a GUI related questionnaire (cf. Figure 1).
A more detailed description of the principle of generating educational websites structures will be the subject of the following section.
Ecaterina Giacomini Pacurar, Philippe Trigano, Sorin Alupoaie
4. PROPOSING UNIT OF LEARNING MODELS REPRESENTED IN IMS
LD BY USING AN INDUCTIVE AND DEDUCTIVE APPROACH
In this section we present our approach for the creation of the basic pedagogical models used in the process of automatic generation of the educational website structures. Thus, we applied two approaches: inductive, which consists in analyzing a base of 170 educational websites accessible through the Intranet at our Technology University of Compiegne; another deductive approach, which consists of an analysis of a bibliographical study on various theoretical approaches of learning and teaching. The analysis of the educational websites was made with an aim of achieving two goals: the prime objective was to find the types of pedagogical units (scenarios) most often used; the second objective was to determine the components for the graphical aspects of the interface of pedagogical websites (colors, the shapes of the menus and button, etc). We present below the results of the analysis on the educational websites from a pedagogical point of view and then we present some theoretical approaches which we studied with the aim of enriching typology of the pedagogical units (scenarios) obtained during the inductive analysis. However, the results of the inductive analysis on the graphical aspects will be presented in §5.2.
4.1 INDUCTIVE APPROACH
As we mentioned above, this analysis also allowed us to collect information concerning the pedagogical elements that comprise an educational website. In order to structure the great amount of information concerning the pedagogical concepts, we proposed some criteria like the existence of: theoretical parts in a formation module, exercises of various types (QCM, problems to be solved, text to be completed, etc), projects, types of evaluations, auto-evaluation, etc.
Generalizing these criteria we determined three main types of pedagogical units to be included in a course: presentation of theoretical concepts, exercises (course application) and projects (practical work). From a pedagogical point of view, these pedagogical units were limited to a simple presentation of contents, often not well structured. Moreover, the reduced numbers of proposed projects were not conceived to encourage group work, debates and discussions on forums.
4.2 DEDUCTIVE APPROACH: A REVIEW OF INSTRUCTIONAL DESIGN THEORY AND MODELS
The last century marked the appearance and the development of theories, models and methods of teaching and training, starting with Piaget’s work (Gallagher and Reid, 1981), concerning the constructivist approach, the socio-cultural approach of Vygotski (Vygotski, 1978), and ending with Gagné’s and Medsker’s work (Gagné, 1996) on the conditions of training and Merrill’s work (Merrill, 2002) on the identification of the fundamental principles of teaching and training. We can also mention Reigeluth’s work (Reigeluth, 1999), which proposes several models and methods of teaching, integrating various teaching scenarios as well as the work of Paquette (Paquette, 2002) on teaching engineering for the systems of e-learning. In the first phase of work, we studied some of these models applied to our proposal for teaching scenarios. In the following paragraphs we present the fundamental principles of teaching and training, suggested by Merrill (Merrill, 2002), and give some examples of teaching and training models, respecting these principles, that we take into account in the design of the pedagogical models of the websites. Several methods of teaching suggest that the majority of the training environments are problem solving based and involve the students in four phases of training that Merrill (Merrill, 2002) distinguishes: (1) activation of former knowledge, (2) demonstration of competences, (3) applications of competences and (4) integration of these competences in the activities of the real world.
An example, which includes all the learning stages that Merrill talks about, is the approach based on the collaborative problem solving proposed by Nelson (Nelson, 1999). In this case, much more importance is accorded to the application stage rather than to the demonstration stage. In order to help the designers of pedagogical scenarios such as ‘project based learning’ or ‘collaborative problem solving’, Nelson proposes a guideline including recommendations structured on various stages of activity, as follows: define the goals and the plan of the project, set up groups of learners, define the issues, define and assign the respective roles, involve the learners in a repeating process of problem solving, end the project, reflect upon it, synthesize and assess the results obtained.
292
Knowledge base for automatic generation of online IMS LD compliant course structures The constructivist approach of Jonassen (Jonassen, 1999) is also centered on problem solving or projects by including all the principles of training mentioned by Merrill (Merrill, 2002). Jonassen says that the training is favored when the learners discover the contents of the field through problems solving. Moreover, he recommends a progression in the resolution of problems: "start the learners with the task they know how to perform and gradually add task difficulty until they are unable to perform alone" (Jonassen, 1999).
Schank (Schank, 1999) proposes a model of “learning-by-doing”, GBS (goal-based scenario) centered on the resolution of the problems by using reasoning starting from cases (box based reasoning). This model insists on the phases of application, activation and demonstration; the phase of integration is accentuated. In this model, learners must achieve the goals of training by applying their competencies and using related content knowledge (presented in the form of cases), which can help them in the achievement of their objectives.
Another example is the approach called "Elaboration Theory" proposed by CH Reigeluth (Reigeluth, 1988) (Reigeluth, 1999). With the same point of view as Jonassen, Reigeluth recommends a ?simple towards complex? organization of the teaching contents, by stressing that: "... the simple-to-complex sequence is prescribed by the development theory because it is hypothesized to result in: the cognitive formation of more stable structures, hence causing better long-term retention transfer; the creation of meaningful contexts within which all instructional content is acquired [... ] ". In addition, Reigeluth considers that at the beginning of a course it is desirable to pre-evaluate the participating students.
In general, we can observe that all these approaches take into account the fundamental principles of learning stated by D. Merrill. Another common point aims at the aspect centered on the problem solving or project-based work, which can be carried out individually or by groups.
The study of various theoretical approaches of teaching and training was useful to us as a theoretical support in modeling the teaching models of pedagogical scenarios. The website structures generated by the course generation module are based on teaching models of scenarios that integrate, according to the case, the characteristics of these theories. In section §7 we present an example of a pedagogical scenario based on certain characteristics of the "Elaboration Theory" approach.
4.3 PROPOSING PEDAGOGICAL UNIT MODELS COMBINING THE TWO APPROACHES
As we mentioned above, this analysis also allowed us to collect information concerning the pedagogical elements that comprise an educational website. Starting from these three main types of units obtained by inductive analysis we created 17 models of pedagogical units associated with pedagogical scenarios (plays), by taking into account the characteristics resulting from the theoretical approaches presented above. By using an adaptation of criteria suggested by Reeves (Reeves and Reeves, 1997) for the characterization of a training course, table 1 presents the types of pedagogical units that we integrated in the knowledge-base used by the module of generation of educational website structures (called Generator) implemented in the netUniversité portal. We mention here that these types of pedagogical units are basic models (building blocks) but they can, according to the answers to the teaching questionnaire, also be used like final models (resulting course structures).
293
Ecaterina Giacomini Pacurar, Philippe Trigano, Sorin Alupoaie
294
2, 3 Learning theoretical
concepts with
exercises
Academic no Rather Transmissive Email Formative Rather Academic or inspired by Elaboration Theory 4 Learning
theoretical
concepts, exercises,
problem solving
Academic than Applicative no Rather Transmissive Email Summativ e and Formative Rather Academic (behaviourist ) 5, 6 Problem solving
(Sequential and
flexible itinerary)
Applicative no Rather Transmissive X Formative Rather Academic (behaviourist ) 7, 8 Problem solving
(Sequential
itinerary )
Applicative yes Moderator Email Forum Summativ e and Formative Rather constructivis t 9 Learning
theoretical
concepts, problem
solving
Academic Applicative yes Transmissive Moderator Email Forum Formative Instructivist and constructivis t tendencies 10, 11 Learning
theoretical
concepts Academic, students participation yes Transmissive Moderator Email Forum Formative Instructivist and Constructivi
st tendencies
12 Learning by project Applicative no Guide Email Forum Summativ e Formative
Constructivi
st
13 Collaborative learning by project Applicative yes Guide Email Forum Summativ e Formative Constructivi
st
(social
aspects)
14, 15 Learning by project based on ? active pedagogy ? Applicative yes Observer Email Forum Summativ e Formative Constructivi
st
Active
Pedagogy
16 Modelation and problem solving Applicative (pairs) no Guide Email Forum Formative Constructivi
st
Cognitive
apprenticesh
ip
17 Learning by project based on analysis of questions/problems Applicative yes Moderator
Email Forum Summativ e Formative Constructivi
st
Project of
analysing
questions
/problems Table 1. Analysis of a unit of learning based on the model proposed by Reeves (Reeves and Reeves,
1997)
These different types of pedagogical units are modeled in the UML activity diagram then we formalize them in XML-IMS-LD (IMS, 2003).
5. INTERACTIVE QUESTIONNAIRES FOR THE DYNAMIC
GENERATION OF EDUCATIONAL WEBSITE STRUCTURES
In order to generate the website structures, our system uses as inputs the answers of the two interactive questionnaires represented in XML files: a pedagogical questionnaire and a questionnaire
Knowledge base for automatic generation of online IMS LD compliant course structures
295
for the aspects of the graphical interface. Each generated website structure is represented by two XML files, one for the graphical interface models and another one for storing the pedagogical content organized in IMS LD format.
5.1 THE DESIGN STEP FOR THE PEDAGOGICAL QUESTIONNAIRE
The module for dynamical generation of online course structures (see figure 4), integrates several teaching scenarios represented in various structures of websites. The goal is to help non-competent teachers to create their own course in the form of a website. In order to reach this goal, we have chosen an automatic course generation approach, from dynamic questionnaire. We think this approach will induce or help teachers to think about their pedagogical practice by making them evolve towards different methods, which may be more suitable for current needs in the training domain, by using web technologies.
Our pedagogical questionnaire makes possible for the user to dynamically choose the elements that will be integrated in his and her educational website. This questionnaire is structured on three levels of granularity: a question itself, its reformulation as well as an in depth explanation related to this question (see Figure 2). In the in-depth explanation, we present a short synthesis on the theoretical concepts of teaching and training, connected to this question, while also explaining the consequences for the website structure.
Figure 2. An example of the pedagogical questionnaire web interface
5.2 THE DESIGN STEP FOR THE DYNAMIC QUESTIONNAIRE FOR WEBSITE
INTERFACES
The analysis of the great number of educational websites evoked in section §4 also enabled us to determine various types of possible interface models. Several criteria are taken into account: navigation starting from the menus, the shapes of the buttons of navigation within the various pages of the website, the colors of the menus and the buttons, etc.
In our approach we consider that a website structure is composed of two elements (figure 3): structure and appearance . The structure is made up of two types of navigation (general and secondary) plus a
The question itself
The question
reformulation
Ecaterina Giacomini Pacurar, Philippe Trigano, Sorin Alupoaie
296 central page. Some of these elements are represented in a XML diagram (figure 3), obtained using the XMLSpy software.
The principal navigation relates to the main menus, which are integrated in the websites starting from the banner page. Thus, we can distinguish the menu allowing navigation on top of the page, the menu allowing navigation in the left part of the page as well as the central menu. We can also modify the type of the initial navigation, by adding different menus compared to that which is on the banner page. The navigation resulting from this modification is called secondary navigation. The presentation of the central page relates to the various forms of presentation that can be used, for example: lists, tables, etc. Appearance represents what is related to the esthetics of the interface of an educational website. Thus, we can take into account: colors, the shapes of buttons in the menus and/or for navigation within the pages and images representing a given curricular area.
By using this typology, we designed a dynamic questionnaire that allows the choice of the graphic aspects of the interface for the website. Figure 4 shows an example question implemented in this questionnaire.
Figure 4. Example of question integrated in the dynamic websites interfaces questionnaire
Figure 3. XML diagram for the interface of the pedagogical websites
Knowledge base for automatic generation of online IMS LD compliant course structures Two types of graphical interface are considered for the generated courses: a simple, standard interface and predefined models of interface. While answering a certain question, the teacher has the possibility to choose the desired type of interface before the course is generated. The functions of the selected type of interface, the IHM attributes are used either to define the characteristics of the standard interface (color, position of menus etc), or to select the predefined model of interface, appropriate to the answers of the teacher.
6. AUTOMATIC GENERATION OF EDUCATIONAL WEBSITES STRUCTURES
6.1. MODELING OF THE KNOWLEDGE BASE
The problem of the complexity of the conditions used for the automatic generation lead us to a knowledge-based system. The number of entries (represented by the possibilities of response to the questionnaires) and the great number of choices concerning the teaching models required us to develop a rules-based system. In order to implement these rules we chose an environment for developing the expert systems in Java, named JESS (Java Expert System Shell). JESS is a library written in Java, for Java, which can be used for the development of the Web applications containing applets or JSP pages (Java Server Pages).
The treatment of the answers to the questionnaire is complex because it implies knowledge about several theories and models of training, such as behaviorism, constructivism, socio-constructivism, etc. To obtain independence between the executive part (generator) and the data part (teaching knowledge) we separated these two parts by conceiving a XML schema for representing this knowledge. Thus, the knowledge base can be developed independently by publishing a simple XML file without affecting the generator. Knowledge is stored in XML, in a format similar to a JESS rule. It will be transformed into this language and will be added in the inference engine before being treated by the generator.
6.2 AN AUTOMATIC TOOL FOR GENERATION OF PEDAGOGICAL WEBSITES
In order to generate the pedagogical website structures, we use a list of primary pedagogical models (i.e., basic models) also named building blocks. These building blocks are used to build the final models (structures of course generated). The inference rules in the knowledge base specify the way in which these elementary bricks are associated (figure 5). The latter are IMS LD components which can be created by default at the time of generation or conceived beforehand and recorded in XML files that respect this standard.
The primary pedagogical models are specified in the XML file that represents the knowledge base. The elements that characterize these models are a single identifier (id) of the model, a title, a type (teaching unit, scenario, activity of training, etc). If the primary education model was recorded, this information is also specified. These models can be created starting from several levels of depth in IMS LD. For example, we can consider either an entire unit of learning or only some blocks used to build an unit of learning: plays, learning-activities and/or support activities, activity-structures, environments, etc. Thereafter we describe the operation of an automatic tool for generation that we have developed. Thus, the answers from the two questionnaire are translated into the JESS format and are loaded in the inference engine (Figure 5). Once the inference process has completed, the rules will create two types of facts: the facts that represent IHM attributes (description of the graphical interface of the pedagogical website) and the facts that establish links between the primary pedagogical models. These facts become the entries for the CourseBuilder of the models.
297
Ecaterina Giacomini Pacurar, Philippe Trigano, Sorin Alupoaie
Figure 5. Automatic generation of the educational websites
As we mentioned above the generation of course structures is realized starting from answers to the two interactive questionnaires. These answers constitute the initial facts, which are translated into JESS format by the JESS Translator module and are loaded into the inference engine (Figure 6). Two types of facts are distinguished as a result of the inference process: facts describing the GUI attributes of resulting website structure and facts establishing the links between the basic pedagogical models. The significance of the bricks was presented above. These two types of facts represent the inputs for the two blocks: the Interface Builder and the respective CourseBuilder. Thus for each generated website structure, these modules will create two files that describe the resulting course: web-ihm.xml (for the description of the GUI elements) and imsmanifest.xml (for the description of the pedagogical content).
We describe below each software module used in the automatic generation of online courses.
6.2.1. JESS Translator
The JESS Translator module transforms the rules and the initial facts represented in XML and Java objects (in the case of responses to questions) into JESS format. This module is a Java class that has static methods to translate the knowledge base represented in XML (initial facts and rules) into JESS rules and facts. We have also created a function that transforms the Java object containing the responses to the questionnaires (QResponses) in JESS facts (Figures 5 and 6).
298
Knowledge base for automatic generation of online IMS LD compliant course structures
299
Figure 6. JESS Translator
For example, an initial fact (prerequisite) represented in XML (Figure 7) is transformed by the JESS Translator block into a JESS fact (Figure 7). In our case, the fact represented in figure 7 establishes a link between a pair GUI attribute - value (menu_type - vertical ) and a pair question - answer (1-1).
Figure 7. Transformation XML - JESS. a) XML fact. b) JESS fact
6.2.2. Inference engine
After the transformation of the knowledge base into JESS, the rules and facts are then loaded into the JESS inference engine. It will execute the rules in a chain, based on the prerequisites (initial facts), the resulting partial conclusions, and then the final conclusions. These final conclusions are the facts that establish the links between the basic pedagogical models composing the course structure and between the GUI attributes of the resulted website.
6.2.3. The Course Builder
Starting from the links established between the basic pedagogical models, the CourseBuilder loads these models (if they are saved on disk) or it creates them (in conformity with the corresponding specification in XML knowledge base file), and associates them in order to obtain the desired course structure.
The example of figure 8 shows the way in which the links define a resulting model of the course that is generated. Starting from the element "root ", which defines a generic (empty) unit of learning, the CourseBuilder considers each child element associatedwith a parent element, and realizes the link between them in terms of Learning Design specification (e.g. a child element play is added to the parent element learning-design ). This process is repeated recursively for each one of the children (considered as parents) and represents in fact the in-depth creation of an IMS LD tree: unit of learning, play, activity structures and learning activities.
In our case, a fact of type link adds an element child to an element parent . In the structure of this fact we can distinguish:
? model-no : the number of the resulting model
? id-el1 : ID of the basic model parent
? id-el2 : ID of the basic model child
? id-parent : ID of the direct parent (if we want to associate a child to an other element inside
the parent basic model)
? order : order number (establishes the position number of the child element))
Rules Prerequisites Responses JESS Rules&Facts
Ecaterina Giacomini Pacurar, Philippe Trigano, Sorin Alupoaie
300
The generation of the course structures with netUniversité is implemented in all levels of IMS Learning Design: A, B and C. Thus, the predefined models used by the generator can contain elements specific to the advanced levels (B and/or C): properties, conditions (local - within a certain activity - and global) and notifications. On the other hand, to use models on the levels B and/or C in the course structures, it is necessary that these models are predefined. The course builder does not have the capability to create these types of the models during the process of generation.
6.3 FORWARD-CHAINING RULES USED FOR CREATING COURSE STRUCTURES
In the process of creation of the educational websites structures, the Generator module (figure 5 above) integrated in the netUniversité portal, uses a knowledge base represented in a file knowledge.xml . During the process of generation, this knowledge base is loaded in the inference engine JESS. The structure of this file integrates the following main components:
? the declaration of basic models – model-templates
? the definition of facts used by rules – fact-defs
? the initial facts – prerequisites (that includes the responses to questionnaires and
represent the initial state of the knowledge base)
? the inference forward-chaining rules – rules
We present bellow the way these components are used in order to obtain the final structures of educational websites.
6.4 EXAMPLE OF RULE USED TO BUILD THE RESULTING UOL STRUCTURES
The rules are used to generate the links that define associations between the basic pedagogical models in order to obtain the resulting course structure. Each resulting model is associated with a number for identification. We developed three levels of rules corresponding to the three levels of depth in IMS LD.
The rules used to specify the root and the numerical order of a final model constitute the first level of activation. As we can observe in figure 9, the root is specified by a fact named root composed of an order number (model-no ) and the ID of the basic pedagogical model representing the root (usually is a learning-design element).
Figure 8. Example illustrating the principle of creation of a resulting course structure
Knowledge base for automatic generation of online IMS LD compliant course structures
Figure 9. Definition of fact root
The rules of this type use the responses to the questions to create the fact root as well as the facts that specify the pedagogical concepts used in creation of the course (Figure 10). These facts are used by the third level rules in order to select the basic pedagogical models of type activity-structures.
Figure 10. First level rule (creating the root)
Example of a translation in natural language of a first level rule:
If
The plays ? Theory ? AND ? Problems ? AND ? Project ? were selected
AND
The type of ? Theory ? is a model based on ? CDT ?
AND
The type of ? Project ? is a basic model based on individual work
AND
The type ? Exercises ? is a model based on the approach ? programmed teaching ? proposed by Skinner
Then
Associate the root of model n° 1 with the facts CDT, ProjetSimple and Skinner (these facts indicate the scenarios/plays to be used)
301
Ecaterina Giacomini Pacurar, Philippe Trigano, Sorin Alupoaie
A second level of rules is used to associate pedagogical scenarios (plays) to the root, according to the answers to questions referring to the basic pedagogical elements used in the course (theory, exercises, project, etc). For the moment we take into account three types of scenarios that can compose a course: learning of theoretical concepts, problem solving and work by project. For each one of these scenarios we conceived a second level rule (figure 11).
Figure 11. Second level rules (association of scenario)
Example of translation in natural language of a second level rule:
If
The Play ? Theorie ? was selected
Then
Associate a play ? P-Theorie? to the root of the model indicated by “mno”
The third level of rules associates an activity-structure to a play. This activity-structure is specified by the simple facts generated on the first level of rules and represents a basic pedagogical model saved on a disk (or created on runtime) (Figure 12).
302
Knowledge base for automatic generation of online IMS LD compliant course structures
Figure 12. Third level rule (association of an activity-structure)
Example of translation in natural language of a third level rule:
If
The fact CDT is defined
Then
Add into the role-part ? RP-Theorie ? of play ? P-Theorie ? the activity structure ? AS-CDT ? AND
Add into the role-part ? RP-Theorie ? of play ? P-Theorie ? the role
? Student ?
The structure of these inference rules enabled us to easily implement the mechanism of association between various basic pedagogical models, as well as their integration with models of graphical interface in order to obtain the resulting pedagogical website structure, saved into the course base of portal netUniversité.
7. EXAMPLE OF “BRANCHED EXERCISES” UNIT OF LEARNING
This primary pedagogical model, based on problem solving learning corresponds to the first model presented in table 1 (cf §4.3). The idea is to present a series of exercises to learners, following a gradual progression of the difficulty level. According to Merrill [Merrill, 02], learning is facilitated when learners solve a progression of problems that are explicitly compared to one another. Through a progression of increasingly complex problems the students’ skills gradually improve until they are able to solve complex problems. Learning is best when there is a progression of problems to solve and when the problems start easy and then become harder and harder. Elaboration Theory (Reigeluth, 99) is a model advocating a progression of successively more complex problems. Van Merri?nboer's 4C/ID Model (Van Merri?nboer, 1997) also stresses the importance of a progression of carefully sequenced problems. Moreover, the path one student follows depends on his performance at the preceding levels.
The figure 13 shows the UML Activity Diagram corresponding to the Branched Exercises unit of learning. The types of learning content involved are online exercises (multiple choice questions, fill in the blanks, free answer etc).
303
Ecaterina Giacomini Pacurar, Philippe Trigano, Sorin Alupoaie
304
In this model, the learner must solve the first problem and depending on the answer the system gives him a score. Depending on the score obtained, the learner can solve the same problem (insufficient grade), a similar synthesising problem (good grade) or jump directly to another problem type (very good grade). The cycle is repeated until all exercises have been solved.
Figure 13. "Branched Exercises" scenario – UML activity diagram
Knowledge base for automatic generation of online IMS LD compliant course structures It should be noted that the model is at IMS LD level B, because of the use of properties and conditions. We present below a short transcription of this basic pedagogical model in the IMS LD formalism taking into account roles, properties, activities, scenarios and acts as well as the conditions Roles
There is only one role in the UOL – the learner role, as the answers to the questions are automatically provided, as are the scores and the access to the next exercise level (no need for teacher intervention.
Properties
In order to store the results of the tests, a number of local personal properties are defined:
Local personal properties are used, so that their values are set individually for each user and also they are only available for the current run (the value is reset for each run of the UOL and is also not available from another UOL)
Activities
Only learning-activities are present (one for each exercise) since there is no staff role to take support-activities.
305
Ecaterina Giacomini Pacurar, Philippe Trigano, Sorin Alupoaie
The first learning-activity is the only one visible from the very beginning, the rest being hidden from the user. The learning-activities are all grouped into a single activity-structure of type "selection" (in order to insure appropriate visibility options by means of conditions). All the activities are set to be completed by the learners themselves ("user-choice") in order to provide complete independence.
Plays and acts
This model uses only one play, containing one act, since there is no need for synchronization between students. Thus each student can work in his own rhythm, independent from the other students.
The act is naturally set to "completed" when the corresponding role-part completes, just as the play is set to "completed" when the last act is completed.
Conditions
Conditions in this UOL are used to show the next exercises to the user, according to the results obtained at the previous ones. The adaptability property of the scenario is thus hard-coded into these conditions. The following condition, for example, makes sure that the second exercise is made visible to the learner in case he obtained a score between 50 and 79 after completion of the first exercise.
306
Knowledge base for automatic generation of online IMS LD compliant course structures
8. POSITIONING OF NETUNIVERSITé IN THE CONTEXT OF EXISTING LD TOOLS
The netUniversité web portal offers a global tool, integrating a number of other tools such as: a course generator based on a questionnaire (creation from templates), an editor for all 3 IMS LD levels (including a graphical interface for editing the IMS LD tree), an IMS LD web player for all 3 levels, an administration tool for adding and subscribing students and teachers to courses and an HTML content editor.
The functionality that is out of the scope for netUniversité includes: a constraints editor, the possibility to create UOLs starting from scratch, a way of editing the presentation of LDs, a material repository, advanced testing support (debugging, validity checking, simulations).
A desirable feature is the possibility of importing an already created UOL (whether by netUniversité editor or by other editors) and also the other way around – the possibility to export a UOL to use with some other player. Providing import/export functionality is an important feature since it would allow reusability and interoperability between platforms, which is one of the main goals of IMS LD standard.
The main difference between the editor integrated in netUniversité and CopperAuthor is that the target users of CopperAuthor are those who have a strong background in the IMS LD standard. Our editor was built especially for users who don’t have experience with the specification. Although some of the LD notions were kept, most were renamed and explained, the language of interaction with the users being much more clear and easy to understand. Our IMD LD player has its own engine, basically different from the CopperCore engine.
To sum up, netUniversité is one of the first platforms to support all three levels of IMS LD and the first one to integrate full functionality in a single product, freely available online.
9. CONCLUSIONS
In this article, we presented our research tasks concerning the design and the development of the netUniversité portal integrated in the interactive guide CEPIAH (Design and Evaluation of the Interactive Products for the Human Training). We continued the development of this first version of the prototype by adding functionality for the integration of teaching resources (interactive exercises
307
Ecaterina Giacomini Pacurar, Philippe Trigano, Sorin Alupoaie
and tools for communication personalized according to types of activities suggested in the generated courses). This new functionality will allow us to generate structures of educational websites based on scenarios that are even more interactive. We think that this interactivity as well as the addition of the tools for communication in the online courses could motivate more students to realize their training tasks.
It is worth mentioning the fact that the IMS Learning Design specification was proposed very recently and netUniversité is among the first platforms to support it. Furthermore, the design of course templates using IMS LD is in its infancy, especially when it comes to levels B and C of the specification. Apart from its novelty, the netUniversité approach also has a sound pedagogical component, reflected in the richness and variety of the learning theories is supports. However, our application has some limitations. The limitations of the proposed pedagogical models first come from the restrictions imposed by the netUniversité platform, namely the simplifications applied when implementing the engine and consequently the player (missing elements such as set-property, view-property, set-property-group, view-property-group, the class attribute, the properties of type file etc). Another limitation is that it is not possible to reference a UOL from inside an activity-structure, which represents a mechanism for aggregating elementary bricks.
Currently we are in the phase of validating the current version of the prototype with teachers at the UTC as well as the University Aurel Vlaicu in Romania. In a first stage of this experimentation, our goal consists in presenting the portal netUniversité to them and explaining its use. Then, in order to gain their opinions about the ease of use of the system, we ask them to answer a questionnaire of evaluation. We are interested to know (after the analysis of the results of the evaluation questionnaires) if the utilization of the two questionnaires (for the pedagogical and GUI aspects) in the process of generation of the course structures encourages them to reflect more on their practices of teaching, but also on the graphical aspects of the interface of their educational websites. ACKNOWLEDGMENTS
This thesis benefits from the financial support of the Pole of research STEF (Systems and Technology for Education and Training) of the Picardy Region, within the framework of the State/Region plan. Also, we thank Elvira Popescu, (Master Student in Computer Science at University of Craiova, in Romania) for her contribution in this research project.
REFERENCES
Advanced Distributed Learning Technical Team (2001). The SCORM Overview : Sharable Content Object Reference Model Version 1.2..
Friesen Norm, Anthony Roberts, et Sue Fisher. (2002). Cancore: Learning Object Metadata, s.l., Canadian Core Learning Resource Metadata Application Profile, 17 p.
Gallagher, J.M. & Reid, D.K (1981). The Learning Theory of Piaget and Inhelder, Monterey, CA: Brooks/Cole.
Gagné R., Medsker K. (1996). ? The conditions of learning: Training applications ?, ASTD, Harcourt Brace College Publishers, USA.
Giacomini E., Trigano Ph. (2003). Flexible navigation for the pedagogical hypermedia design and evaluation improvement. In proceedings World Conference on E-Learning in Corp., Govt.,
Health., & Higher Education, 206-212.
Giacomini E, Trigano Ph., Alupoaie S. (2005). A QTI editor integrated into the netUniversité web portal using IMS LD, in Advances in Learning Design, Colin Tattersall and Rob Koper (Special Issue Editorial). Journal of Interactive Media in Education (special issue), ISSN: 1365-893X,
2005.
Griffits D., Blat J, Garcia R, Vogten, Kwong KL. (2005). Learning Design Tools, in Learning Design,
A Handbook on Modelling and Delivering Networked Education and Training, in Koper R. et
Tattersall C. (Eds), ISBN 3-540-22814-4, Springer-Verlag Berlin Heidelberg, 2005.
308
资料编码产品名称 使用对象产品版本 编写部门资料版本 以太网标准和物理层、数据链路层专题 拟制：日期： 审核：日期： 审核：日期： 批准：日期： 华为技术有限公司 版权所有侵权必究 修订记录 日期修订版本作者描述
目录 1 以太网标准 5 1.1 以太网标准 5 1.2 IEEE标准 5 1.3 物理层 8 1.3.1 以太网接口类型 8 1.3.2 电口 8 1.3.3 光口 11 1.4 FE自协商 12 1.4.1 自协商技术的功能规范 13 1.4.2 自协商技术中的信息编码 14 1.4.3 自协商功能的寄存器控制 16 1.4.4 GE自协商 18 1.5 物理层芯片和MAC层芯片接口简介 19 1.5.1 MII 19 1.5.2 MDIO管理寄存器 20 1.5.3 RMII 20
1.5.4 SMII 21 1.5.5 SS－SMII 21 1.5.6 GMII 22 1.5.7 TBI 22 2 以太网数据链路层 23 2.1 以太网的帧格式 23 2.2 以太网的MAC地址 25 2.3 CSMA/CD算法 26 2.3.1 CSMA/CD发送过程 27 2.3.2 CSMA/CD如何接收 28 2.4 半双工以太网的限制 31 2.5 以太网流量控制 34 2.5.1 反压（Backpressure） 34 2.5.2 PAUSE 流控 34 关键词： 以太网物理层数据链路局域网城域网协议标准祯结构
摘要： 本文详细地阐述了以太网的标准，以太网在各个传输层面的具体结构和工作方式以及控制方式。 缩略语清单： 无。 参考资料清单 无。 以太网标准和物理层、数据链路层专题 1 以太网标准 1.1 以太网标准 局域网(LAN)技术用于连接距离较近的计算机，如在单个建筑或类似校园的集中建筑中。城市区域网(MAN)是基于10－100Km的大范围距离设计的，因此需要增强其可靠性。但随着通信的发展，从技术上看，局域网和城域网有融合贯通的趋势。 1.2 IEEE标准 IEEE是电气和电子工程师协会（Institute of Electrical and Electronics Engineers）的简称，IEEE组织主要负责有关电子和电气产品的各种标准的制定。IEEE于1980年2月成立了IEEE 802委员会，专门研究和指定有关局域网的各种标准。IEEE 802委员会由6个分委员会组成，其编号分别为802.1
的度数；
三角形强化训练和深化 ? 1、如图a 是长方形纸带，∠DEF=25°，将纸带沿EF 折叠成图b ，再沿BF 折叠成图c ，则图c 中的∠CFE 的度数是_________°． 解析： 由题意可知折叠前，由BC//AD 得： ∠BFE=∠DEF=25°将纸带沿EF 折叠成图b 后， ∠GEF=∠DEF=25° 所以图b 中，∠DGF=∠GEF+∠BFE=25°+25°=50° 又在四边形CDGF 中，∠C=∠D=90° 则由：∠DGF+∠GFC=180° 所以：∠GFC=180°－50°＝130° 将纸带再沿BF 第二次折叠成图C 后 ∠GFC 角度值保持不变 且此时：∠GFC ＝∠EFG+∠CFE 所以：∠CFE=∠GFC-∠EFG=130°-25°=105 2、在Rt △ABC 中，∠A ＝90°，CE 是角平分线，和高AD 相交于F ，作FG ∥BC 交AB 于G ，求证：AE ＝BG ． 解法1： 【解析】证明：∵∠BAC=900 AD ⊥BC ∴∠1= ∠B ∵CE 是角平分线 ∴∠2＝∠3 ∵∠5＝∠1+∠2 ∠4＝∠3+∠B ∴∠4＝∠5 ∴AE ＝AF
过F作FM⊥AC并延长MF交BC于N ∴MN//AB ∵FG//BD ∴四边形GBDF为平行四边形 ∴GB=FN ∵AD⊥BC,CE为角平分线 ∴FD=FM 在Rt△AMF和RtNDF中 ∴△AMF≌△NDF ∴AF＝FN ∴AE＝BG 解法2： 解：作EH⊥BC于H，如图， ∵E是角平分线上的点，EH⊥BC，EA⊥CA， ∴EA=EH， ∵AD为△ABC的高，EC平分∠ACD， ∴∠ADC=90°，∠ACE=∠ECB， ∴∠B=∠DAC， ∵∠AEC=∠B+∠ECB， ∴∠AEC=∠DAC+∠ECA=∠AFE， ∴AE=AF， ∴EG=AF， ∵FG∥BC， ∴∠AGF=∠B， ∵在△AFG和△EHB中， ∠GAF=∠BEH ∠AGF=∠B AF=EH ，∴△AFG≌△EHB（AAS） ∴AG=EB， 即AE+EG=BG+GE， ∴AE=BG． 3、如图，等腰直角三角形ABC中，∠ACB＝90°，AD为腰CB上的中线，CE⊥AD交AB 于E．求证∠CDA＝∠EDB．
课程设计 题目加密解密程序设计 学院自动化学院 专业电气工程及其自动化班级 姓名 指导教师 年月9 日
课程设计任务书 学生姓名：专业班级： 指导教师：工作单位：自动化学院 题目：加密解密程序设计 初始条件： 掌握8086汇编语言程序设计方法，设计一个电子时钟，实现分、秒、时的显示与刷新功能。 要求完成的主要任务：（包括课程设计工作量及其技术要求，以及说明书撰写等具体要求） 1. 定义显示界面。 2. 调用系统时间，并将调用的用二进制表示的时间数转换成ASCII码，并将时间数存入内存区。 3. 将存在系统内存区的时间数用数字式或指针式钟表的形式显示出来。 4. 获取键盘的按键值，判断键值并退出系统。 5. 撰写课程设计说明书。内容包括：摘要、目录、正文、参考文献、附录（程序清单）。正文部分包括：设计任务及要求、方案比较及论证、软件设计说明（软件思想，流程，源程序设计及说明等）、程序调试说明和结果分析、课程设计收获及心得体会。 时间安排： 12月26日-----12月28日查阅资料及方案设计 12月29日----- 1月 2 日编程 1月3日----- 1月7日调试程序 1月8日----- 1月9日撰写课程设计报告 指导教师签名：年月日 系主任（或责任教师）签名：年月日
目录 摘要 (1) 1设计任务及要求 (2) 1.1 加密解密设计的意义 (2) 1.2 程序设计任务 (2) 2 加密方法及方案比较 (3) 2.1 加密方法 (3) 2.2 加密方案及比较 (3) 3 加密解密设计流程及描述 (5) 3.1程序所需模块 (5) 3.2程序运行界面 (5) 3.3响铃程序 (6) 3.4功能选择程序 (6) 3.5数据循环输入子程序 (7) 3.6加密过程程序 (8) 3.7解密过程程序 (9) 3.8退出程序 (10) 3.9总体程序流程图 (11) 4 程序调试说明和结果分析 (12) 4.1 程序调试 (12) 4.2 程序运行结果 (12) 5 心得体会 (15) 参考文献 (16) 附录：设计原程序 (17) 本科生课程设计成绩评定
百度文库-让每个人平等地提升自我 10GBase-ER 5.5.1万兆以太网规范 5.5.1万兆以太网规范 从前面的介绍可以得出，就目前来说，万兆以太网标准和规范都比较繁多，在标准方面，有2002 年的IEEE ，2004 年的IEEE ，2006 年的IEEE、IEEE 和2007 年的IEEE ;在规范方面，总共有10多个（是一比较庞大的家族，比千兆以太网的9个又多了许多）。在这 10多个规范中，可以分为三类：一是基于光纤的局域网万兆以太网规范，二是基于双绞线 （或铜线）的局域网万兆以太网规范，三是基于光纤的广域网万兆以太网规范。下面分别予 以介绍。 1 ?基于光纤的局域网万兆以太网规范 就目前来说，用于局域网的基于光纤的万兆以太网规范有：10GBase-SR、10GBase-LR、10GBase-LRM、10GBase-ER、10GBase-ZR 和10GBase-LX4 这六个规范。 10GBase-SR 10GBase-SR中的"SR"代表”短距离”（short range）的意思，该规范支持编码方式为 64B/66B的短波（波长为850nm）多模光纤（MMF ），有效传输距离为2?300m，要支持300m 传输需要采用经过优化的50艸线径0M3 （Optimized Multimode 3，优化的多模3）光纤（没有优化的线径50 ^m光纤称为OM2光纤，而线径为叩的光纤称为OM1光纤）。 10GBase-SR具有最低成本、最低电源消耗和最小的光纤模块等优势。 10GBase-LR 10GBase-LR中的"LR"代表"长距离”（Long Range）的意思，该规范支持编码方式为 64B/66B的长波（1310nm）单模光纤（SMF），有效传输距离为2m到10km，事实上最高可达到25km。 10GBase-LR的光纤模块比下面将要介绍的10GBase-LX4光纤模块更便宜。 10GBase-LRM 10GBase-LRM中的"LRM"代表"长度延伸多点模式"（Long Reach Multimode ），对应的标准为2006年发布的IEEE。在1990年以前安装的FDDI ?m多模光纤的FDDI网络和100Base-FX网络中的有效传输距离为220m，而在OM3光纤中可达260m,在连接长度方面，不如以前的10GBase-LX4规范，但是它的光纤模块比10GBase-LX4规范光纤模块具有更低的成本和更低的电源消耗。
Web of Science 中文使用手冊
目次 Welcome to the Web of Science (2) ISI Web of Knowledge介紹 (3) Cross Search 跨資料庫檢索 (4) 簡易Cross Search (4) 詳細Cross Search (4) 檢索結果 (6) ISI Web of Knowledge檢索結果 (6) 勾選清單 (7) 全記錄—以WOS為例 (7) External Collections 檢索結果 (8) WOK平台個人化功能 (9) Register註冊個人帳號 (9) Web of Science首頁 (11) 進入ISI Web of Knowledge (11) 進入Web of Science首頁 (12) 選擇資料庫和時間 (12) Quick Search快速查詢 (12) General Search (13) 檢索結果 (16) Full Record全記錄 (18) 引用文獻（Cited Reference） (19) 被引用文獻（Time Cited） (20) 共同引用記錄（Related Record） (21) Citation Alert (21) 檢索技巧 (23) 被引用參考文獻查詢（Cited Reference Search） (27) 進階檢索（Advanced Search） (30) 結構式查詢（Structure Search） (30) 檢索歷史 (32) Combine Sets結合檢索策略 (32) Save History儲存檢索歷史 (33) Open Saved History開啟已儲存檢索歷史 (34) 管理在ISI Web of Knowledge Server上的檢索歷史 (37) Mark List勾選清單 (38) 附錄一 (40) Contacting Us 聯絡我們 (40) 1
图2图图 期末检测题 【本检测题满分：120分，时间：120分钟】 一、选择题（每小题3分，共30分） 1.(2013?湖南张家界中考)-2 013的绝对值是（ ） A.-2 013 B.2 013 C. D.12013 12013 -2.已知两数在数轴上的位置如图所示，则化简代数式,a b 的结果是（ ） 12a b a b +--++A.1 B. C. D.-1 23b +23a -3.某商店把一件商品按标价的九折出售（即优惠10％），仍可获利20％，若该商品的标价为每件28元，则该商品的进价为（ ） A.21元 B.19.8元 C.22.4元 D.25.2元 4.(2013?湖南株洲中考)一元一次方程的解是（ ） 24x =A. B. C. D.1x =2x =3x =4 x =5.如图，，则与之比为（ ）11,,34 AC AB BD AB AE CD ===CE AB A.1∶6 B.1:8 C.1:12 D.1:16 6.如果∠1与∠2互补，∠2与∠3互余，则∠1与∠3的关系是（ ） A.∠1=∠3 B.∠1=180°-∠3 C.∠1=90°+∠3 D.以上都不对 7.如图是某班学生参加课外兴趣小组的人数占总人数比 例的统计图，则参加人数最多的课外兴趣小组是（ ） A.棋类组 B.演唱组 C.书法组 D.美术组 8.某中学开展“阳光体育活动”，九年级一班全体同学分别参加了巴 山舞、乒乓球、篮球三个项目的活动，陈老师统计了该班参加这三项活动的人数，并绘制了如图所示的条形统计图和扇形统计图．根据这两个统计图，可以知道该班参加乒乓A B C D E 第5题图 习题到位。在管设备进行调整使度内来确保机组
实验报告 课程：计算机保密_ _ 实验名称：数据的加密与解密_ _ 院系(部)：计科院_ _ 专业班级：计科11001班_ _ 学号： 201003647_ _ 实验日期： 2013-4-25_ _ 姓名： _刘雄 _ 报告日期： _2013-5-1 _ 报告评分：教师签字：
一. 实验名称 数据加密与解密 二.运行环境 Windows XP系统 IE浏览器 三.实验目的 熟悉加密解密的处理过程，了解基本的加密解密算法。尝试编制基本的加密解密程序。掌握信息认证技术。 四.实验内容及步骤 1、安装运行常用的加解密软件。 2、掌握加解密软件的实际运用。 *3、编写凯撒密码实现、维吉尼亚表加密等置换和替换加解密程序。 4、掌握信息认证的方法及完整性认证。 （1）安装运行常用的加解密软件,掌握加解密软件的实际运用 任务一：通过安装运行加密解密软件（Apocalypso.exe；RSATool.exe；SWriter.exe等（参见：实验一指导））的实际运用，了解并掌握对称密码体系DES、IDEA、AES等算法，及非对称密码体制RSA等算法实施加密加密的原理及技术。 ?DES：加密解密是一种分组加密算法，输入的明文为64位，密钥为56位，生成的密文为64位。 ?BlowFish：算法用来加密64Bit长度的字符串或文件和文件夹加密软件。 ?Gost(Gosudarstvennyi Standard)：算法是一种由前苏联设计的类似DES算法的分组密码算法。它是一个64位分组及256位密钥的采用32轮简单迭代型加密算法. ?IDEA：国际数据加密算法：使用128 位密钥提供非常强的安全性； ?Rijndael：是带有可变块长和可变密钥长度的迭代块密码（AES 算法）。块长和密钥长度可以分别指定成128、192 或256 位。 ?MISTY1：它用128位密钥对64位数据进行不确定轮回的加密。文档分为两部分：密钥产生部分和数据随机化部分。 ?Twofish：同Blowfish一样，Twofish使用分组加密机制。它使用任何长度为256比特的单个密钥，对如智能卡的微处理器和嵌入在硬件中运行的软件很有效。它允许使用者调节加密速度，密钥安装时间，和编码大小来平衡性能。 ?Cast-256：AES 算法的一种。 （同学们也可自己下载相应的加解密软件，应用并分析加解密过程） 任务二：下载带MD5验证码的软件（如：https://www.doczj.com/doc/a413157156.html,/downloads/installer/下载（MySQL）：Windows (x86, 32-bit), MSI Installer 5.6.11、1.5M；MD5码: 20f788b009a7af437ff4abce8fb3a7d1），使用MD5Verify工具对刚下载的软件生成信息摘要，并与原来的MD5码比较以确定所下载软件的完整性。或用两款不同的MD5软件对同一文件提取信息摘要，而后比较是否一致，由此可进行文件的完整性认证。
以太网：新标准新应用 以太网：新标准新应用 网络世界大会2011暨第十届以太网世界大会于2011年9月23日在北京隆重召开。IEEE802标准委员会的副主席、IEEE802.1数据中心桥接任务组主席PatriciaThaler为大会带来了以太网标准领域的最新进展的精彩报告。 从最开始用于在实验室和企业做研究的上个世纪80年代的标准开始，到90年代的校园、中小企业和家庭的局域网标准，再到2000年能够支持以太网在城域网和广域网的标准。在数据中心、运营商网络和其他流量密集的高性能计算环境下，新的标准不仅可以为高速的以太网服务器连通性和核心交换产品提供标准，例如更宽的带宽，网络存储，视频、音频流处理方法，还能降低网络连接两端设备的能耗，也能支持云计算、铜缆EPON、家庭或专业娱乐、汽车和工业智能等方面的需求。 由于虚拟机的激增，企业的数据中心也不可避免的引发了管理难题，于是802.1Qbg和802.1BR应运而生。这两项标准的目的是把大量策略以及安全和管理方面的处理方法从网卡上的虚拟机和刀片服务器上面卸下来，并且将其重新交给连接存储和计算资源的物理以太交换机，简化数据中心系统的管理，帮助网络管理员和系统管理员更加便利地合作。 借助新的以太网标准，数据中心使用数据中心桥接可以支持融合的网络，进行基于优先级的流量控制，增强拥塞控制。在802.1Qbg标准中，通过边缘虚拟桥接，可增强虚拟机的可见性，提供终端设备到虚拟机之间
的桥接。其中的VDP协议可以发现并配置桥接器，CDCP协议可以通过为桥接器和边缘虚拟机提供虚拟端口，VEPA协议可以降低与高度虚拟化部署有关的复杂性。 802.1BR标准用于网络对虚拟机迁移做出动态调整，可以将远程交换机部署为虚拟环境中的策略控制交换机，而不是部署成邻近服务器机架的交换机，通过多个虚拟通道，让边缘虚拟桥复制帧到一组远程端口，利用瀑布式的串联端口灵活地设计网络，更有效地为多播帧、广播帧和单播帧分配带宽。 预计这两项标准的基础功能会在2012年中期推出。 IEEE802.1Qbg与IEEE802.1BR的区别在于，前者主要是解决允许边界桥对虚拟机迁移进行恰当反应。它主要关注服务器设备(EVB终端站)和边界桥(EVB桥)之间的操作，以及两个设备之间的物理链路信道，在组播或大量信息通过物理链路时，会导致物理链路中相同帧出现多个副本的问题。而IEEE802.1BR可通过添加额外标签信息解决这个问题，也就是只允许一个帧副本被发送和复制在服务器中，从而减少了组播状况下的带宽占用，当然这需要更多的硬件资源来支持，可以看出IEEE802.1Qbg与IEEE802.1BR各有千秋。 802.3ba即40/100G以太网标准，不仅仅提高数据中心的物理层数据传输速率，还解决了数据中心、运营商网络和其他流量密集高性能计算环境中数量越来越多的应用的宽带需求，为更高速的以太网服务器连通性和核心交换产品铺平发展之路，千兆到桌面的理想也会逐渐成为事实。802.3bj是关于100Gb/s背板和铜线的标准，目前802.3研究组正在考
5.5.1 万兆以太网规范 5.5.1 万兆以太网规范 从前面的介绍可以得出，就目前来说，万兆以太网标准和规范都比较繁多，在标准方面，有2002年的IEEE 802.3ae，2004年的IEEE 802.3ak，2006年的IEEE 802.3an、IEEE 802.3aq 和2007年的IEEE 802.3ap；在规范方面，总共有10多个（是一比较庞大的家族，比千兆以太网的9个又多了许多）。在这10多个规范中，可以分为三类：一是基于光纤的局域网万兆以太网规范，二是基于双绞线（或铜线）的局域网万兆以太网规范，三是基于光纤的广域网万兆以太网规范。下面分别予以介绍。 1．基于光纤的局域网万兆以太网规范 就目前来说，用于局域网的基于光纤的万兆以太网规范有：10GBase-SR、10GBase-LR、10GBase-LRM、10GBase-ER、10GBase-ZR和10GBase-LX4这六个规范。 10GBase-SR 10GBase-SR中的"SR"代表"短距离"（short range）的意思，该规范支持编码方式为 64B/66B的短波（波长为850nm）多模光纤（MMF），有效传输距离为2～300m，要支持300m传输需要采用经过优化的50μm线径OM3（Optimized Multimode 3，优化的多模3）光纤（没有优化的线径50μm光纤称为OM2光纤，而线径为62.5μm的光纤称为OM1光纤）。 10GBase-SR具有最低成本、最低电源消耗和最小的光纤模块等优势。 10GBase-LR 10GBase-LR中的"LR"代表"长距离"（Long Range）的意思，该规范支持编码方式为 64B/66B的长波（1310nm）单模光纤（SMF），有效传输距离为2m到10km，事实上最高可达到25km。 10GBase-LR的光纤模块比下面将要介绍的10GBase-LX4光纤模块更便宜。 10GBase-LRM 10GBase-LRM中的"LRM"代表"长度延伸多点模式"（Long Reach Multimode），对应的标准为2006年发布的IEEE 802.3aq。在1990年以前安装的FDDI 62.5?m多模光纤的FDDI 网络和100Base-FX网络中的有效传输距离为220m，而在OM3光纤中可达260m，在连接长度方面，不如以前的10GBase-LX4规范，但是它的光纤模块比10GBase-LX4规范光纤模块具有更低的成本和更低的电源消耗。 10GBase-ER
最新版人教版七年级数学下册知识点 第五章相交线与平行线 一、知识网络结构 相交线 相交线垂线 同位角、内错角、同旁内角 平行线：在同一平面内，不相交的两条直线叫平行线 定义 : __________ __________ ________ 平行线及其判定判定 1：同位角相等，两直线平行 判定 2 平行线的判定：内错角相等，两直线平行 相交线与平行线判定 3：同旁内角互补，两直线平行 判定 4：平行于同一条直线的两直线平行 平行线的性质性质 1：两直线平行，同位角 性质 2：两直线平行，内错角 性质 3：两直线平行，同旁内 性质 4：平行于同一条直线 相等 相等 角互补 的两直线平行命题、定理 平移 二、知识要点 1、在同一平面内，两条直线的位置关系有两种：相交和平行，垂直是相交的一种特殊情况。 2、在同一平面内，不相交的两条直线叫平行线。如果两条直线只有一个公共点，称这两条直线相交；如果两条直线没有公共点，称这两条直线平行。 3、两条直线相交所构成的四个角中，有公共顶点且有一条公共边的两个角是邻补角。邻补角的性质：邻补角互补。如图 1 所示，与互为邻补角，与互为邻补角。+=180°；+ =180° ； + =180°；+ =180°。321 4 4、两条直线相交所构成的四个角中，一个角的两边分别是另一个角的两边的图 1反 向延长线，这样的两个角互为对顶角。对顶角的性质：对顶角相等。如图1
所示，与互为对顶角。=； =。 5、两条直线相交所成的角中，如果有一个是直角或90° 时，称这两条直线互相垂直， 其中一条叫做另一条的垂线。如图 2 所示，当= 90°时，⊥b。 a 垂线的性质：2 1 3 4 性质 1：过一点有且只有一条直线与已知直线垂直。 图 2 性质 2：连接直线外一点与直线上各点的所有线段中，垂线段最短。 性质 3：如图 2 所示，当 a⊥ b 时，==== 90°。点到直线的距离：直线外一点到这条直线的垂线段的长度叫点到直线的c距离。 6、同位角、内错角、同旁内角基本特征：21 3 46 a 75 8 ①在两条直线 ( 被截线 ) 的同一方，都在第三条直线 ( 截线 ) 的同一侧，这样 b 同位角。图 3 中，共有图 3 的两个角叫对同位角：与是同位角； 与是同位角；与是同位角；与是同位角。 ②在两条直线 ( 被截线 )之间，并且在第三条直线 ( 截线 ) 的两侧，这样的两个角叫内错角。图 3中，共有对内错角：与是内错角；与是内错角。 ③在两条直线 ( 被截线 ) 的之间，都在第三条直线 ( 截线 ) 的同一旁，这样的两个角叫同旁内角。图 3中，共有对同旁内角：与是同旁内角；与是同旁内角。 7、平行公理：经过直线外一点有且只有一条直线与已知直线平行。 平行公理的推论：如果两条直线都与第三条直线平行，那么这两条直线也互相 平行。c 2 3 1 4 6 5 平行线的性质：a78性质 1：两直线平行，同位角相等。如图 4 所示，如果 a∥ b，图4 b 则 =； =； =； =。
数据加密方案
一、什么是数据加密 1、数据加密的定义 数据加密又称密码学，它是一门历史悠久的技术，指通过加密算法和加密密钥将明文转变为密文，而解密则是通过解密算法和解密密钥将密文恢复为明文。数据加密目前仍是计算机系统对信息进行保护的一种最可靠的办法。它利用密码技术对信息进行加密，实现信息隐蔽，从而起到保护信息的安全的作用。 2、加密方式分类 数据加密技术要求只有在指定的用户或网络下，才能解除密码而获得原来的数据，这就需要给数据发送方和接受方以一些特殊的信息用于加解密，这就是所谓的密钥。其密钥的值是从大量的随机数中选取的。按加密算法分为对称密钥和非对称密钥两种。 对称密钥：加密和解密时使用同一个密钥，即同一个算法。如DES和MIT的Kerberos算法。单密钥是最简单方式，通信双方必须交换彼此密钥，当需给对方发信息时，用自己的加密密钥进行加密，而在接收方收到数据后，用对方所给的密钥进行解密。当一个文本要加密传送时，该文本用密钥加密构成密文，密文在信道上传送，收到密文后用同一个密钥将密文解出来，形成普通文体供阅读。在对称密钥中，密钥的管理极为重要，一旦密钥丢失，密文将无密可保。这种
方式在与多方通信时因为需要保存很多密钥而变得很复杂，而且密钥本身的安全就是一个问题。 对称加密 对称密钥是最古老的，一般说“密电码”采用的就是对称密钥。由于对称密钥运算量小、速度快、安全强度高，因而如今仍广泛被采用。 DES是一种数据分组的加密算法，它将数据分成长度为64位的数据块，其中8位用作奇偶校验，剩余的56位作为密码的长度。第一步将原文进行置换，得到64位的杂乱无章的数据组；第二步将其分成均等两段；第三步用加密函数进行变换，并在给定的密钥参数条件下，进行多次迭代而得到加密密文。 非对称密钥：非对称密钥由于两个密钥（加密密钥和解密密钥）各不相同，因而可以将一个密钥公开，而将另一个密钥保密，同样可以起到加密的作用。
计算机网络应用 标准以太网 标准以太网也常被称为传统以太网或共享式以太网，它是最早时期的以太网类型，其带宽只有10Mbps ，它使用载波监听多路访问/冲突检测（CSMA/CD ）访问控制方法，解决了连接在同一总线上的多个网络节点有秩序的共享同一传输信道的问题，提高了局域网共享信道的利用率，因此得以发展和流行。 以太网的传输介质主要以双绞线为主，所有的以太网都必须遵循IEEE 802.3标准，如表5-1所示为IEEE 802.3定义的标准以太网标准。 表5-1 IEEE 802.3 标准以太网标准 在该标准中，前面的数字表示数据传输速率，单位是“Mb/s ”，最后一个数字表示一段网线的长度（基准长度为100m ），Base 表示“基带”，Broad 表示“带宽”。下面详细介绍10Base-5、10Base-2、10Base-T 、10Base-F 和10Base-36标准。 1．10Base-5和10Base-2 10Base-5是最早的以太网IEEE 802.3标准，它采用直径为10mm 、电阻为50Ω的粗同轴电缆进行连接，允许每段有100个站点，最大传输距离为500m ，在设计时需要遵循5-4-3标准。 提 示 在5-4-3标准中，数字5表示网络中任意两个端到端的节点之间最多只能有5个电缆段；数字 4表示网络中任意两个端到端的节点之间最多只能有4个中继器；数字3表示网络中任意两个 端到端的节点之间最多只能有3个共享网段。 在使用10Base-5标准以太网时，站点必须使用收发器连接到电缆上，或者使用介质连接单元（MAU ），这些设备用一个“吸血鬼”龙头压倒电缆上，其安装规则如下： ● 网段的最大长度为500m ； ● 电缆最大长度为2500m ； ● 收发器间的最短距离为2.5m ； ● 网段两端必须使用终结器，一端还必须接地； ● 收发器电缆不能超过45m 。 10Base-2与10Base-5基本相同，如在使用的传输介质、传输速度及遵循5-4-3标准等方面。其主要的不同就是10Base-2采用细同轴电缆，电缆段上工作站间的距离为0.5m 的整数倍，每个电缆段内最多只能使用30台终端，且每个电缆段不能超过185m 。
第五章知识结构如下图所示： 第六章知识结构 第七章知识结构框图如下：
（二）开展好课题学习 可以如下展开课题学习： （1）背景了解多边形覆盖平面问题来自实际． （2）实验发现有些多边形能覆盖平面，有些则不能． （3）分析讨论多边形能覆盖平面的基本条件，发现问题与多边形的内角大小有密切关系，运用多边形内角和公式对实验结果进行分析． （4）运用进行简单的镶嵌设计． 首先引入用地砖铺地，用瓷砖贴墙等问题情境，并把这些实际问题转化为数学问题：用一些不重叠摆放的多边形把平面的一部分完全覆盖．然后让学生通过实验探究一些多边形能否镶嵌成平面图案，并记下实验结果：
（1）用正三角形、正方形或正六边形可以镶嵌成一个平面图案（图1）．用正五边形不能镶嵌成一个平面图案． （2）用正三角形与正方形可以镶嵌成一个平面图案．用正三角形与正六边形也可以镶嵌成一个平面图案． （3）用任意三角形可以镶嵌成一个平面图案, 用任意四边形可以镶嵌成一个平面图案(图2)．
观察上述实验结果，得出多边形能镶嵌成一个平面图案需要满足的两个条件: （1）拼接在同一个点（例如图2中的点O）的各个角的和恰好等于360°（周角）； （2）相邻的多边形有公共边（例如图2中的OA两侧的多边形有公共边OA）． 运用上述结论解释实验结果，例如，三角形的内角和等于180°，在图2中，∠1+∠2+∠3=180°．因此,把6个全等的三角形适当地拼接在同一个点（如图2）, 一定能使以这点为顶点的6个角的和恰好等于360°,并且使边长相等的两条边贴在一起．于是, 用三角形能镶嵌成一个平面图案．又如，由多边形内角和公式，可以得到五边形的内角和等于 (5－2)×180°=540°． 因此,正五边形的每个内角等于 540°÷5=108°, 360°不是108°的整数倍,也就是说用一些108°的角拼不成360°的角．因此，用正五边形不能镶嵌成一个平面图案． 最后，让学生进行简单的镶嵌设计，使所学内容得到巩固与运用．１．利用二（三）元一次方程组解决问题的基本过程 ２．本章知识安排的前后顺序
Web of Knowledge平台服务功能使用简介 ISI Web of Knowledge为读者提供了个性化服务和定题服务功能。个性化定制指用户可以在Web of Konwledge主页上注册并设置自己密码，然后每次登录后即可浏览自己订制主页，包括：保存检索策略、建立并编辑自己经常阅读期刊列表；浏览保存检索策略、及时了解一个定题服务是否有效及过期时间。 电子邮件定题服务可让用户方便地跟踪最新研究信息。新定题服务功能允许用户通过web of science中任一种检索途径（普通检索、引文检索、化学结构检索）创建定题服务服务策略，将检索策略保存并转化为用电子邮件通知定题服务。 如图，在Web of Knowledge主页右侧提供了个性化定制服务和定题服务管理功能，下面就这几项功能一一说明如下： 图一：web of knowledge主页 一、注册 点击“Register”超链接，进入注册页面。如图二：分别按要求填入您电子邮件地址，您选择密码以及您姓名。您可以选择自动登录或者普通方式进入您个性化服务管理功能。自动登录可以免除您每次登录Web of Knowledge平台时输入电子邮件地址和密码。该功能使用是cookie技术。如果使用公共计算机，最好选择普通登录方式。 在完成以上操作之后，点击“Submit Registration”完成整个注册过程。
图二：用户注册页面 二、登录 作为注册用户，您可以实现以下功能： ?自动登录到Web of Knowledge平台。 ?选择一个自己常用开始页面，每次登录后则自动进入该页面。 ?将检索策略保存到ISI Web of Knowledge服务器。 ?创建用户关注期刊列表以及期刊目次定题服务。 登录时，在web of knowledge主页右侧输入您电子邮件地址和密码，点击“Sign in”则可进入您个人定制信息服务管理页面。 三、个人信息管理和选择开始页面 点击“My Preferences”超链接，可以编辑个人信息和选择开始页面。 编辑个人信息： 点击“Edit my Information”超链接可以更新您联系信息，如电子邮件地址、密码及姓名。如图三。
以太网是当今现有局域网采用的最通用的通信协议标准，组建于七十年代早期。Ethernet(以太网）是一种传输速率为10Mbps的常用局域网（LAN）标准。在以太网中，所有计算机被连接一条同轴电缆上，采用具有冲突检测的载波感应多处访问（CSMA/CD）方法，采用竞争机制和总线拓朴结构。基本上，以太网由共享传输媒体，如双绞线电缆或同轴电缆和多端口集线器、网桥或交换机构成。在星型或总线型配置结构中，集线器/交换机/网桥通过电缆使得计算机、打印机和工作站彼此之间相互连接。 以太网具有的一般特征概述如下： 共享媒体：所有网络设备依次使用同一通信媒体。 广播域：需要传输的帧被发送到所有节点，但只有寻址到的节点才会接收到帧。 CSMA/CD：以太网中利用载波监听多路访问/冲突检测方法（Carrier Sense Multiple Access/Collision Detection）以防止twp 或更多节点同时发送。 MAC 地址：媒体访问控制层的所有Ethernet 网络接口卡（NIC）都采用48位网络地址。这种地址全球唯一。 Ethernet 基本网络组成： 共享媒体和电缆：10BaseT（双绞线），10Base-2（同轴细缆），10Base-5（同轴粗缆）。转发器或集线器：集线器或转发器是用来接收网络设备上的大量以太网连接的一类设备。通过某个连接的接收双方获得的数据被重新使用并发送到传输双方中所有连接设备上，以获得传输型设备。 网桥：网桥属于第二层设备，负责将网络划分为独立的冲突域获分段，达到能在同一个域/分段中维持广播及共享的目标。网桥中包括一份涵盖所有分段和转发帧的表格，以确保分段内及其周围的通信行为正常进行。 交换机：交换机，与网桥相同，也属于第二层设备，且是一种多端口设备。交换机所支持的功能类似于网桥，但它比网桥更具有的优势是，它可以临时将任意两个端口连接在一起。交换机包括一个交换矩阵，通过它可以迅速连接端口或解除端口连接。与集线器不同，交换机只转发从一个端口到其它连接目标节点且不包含广播的端口的帧。 以太网协议：IEEE 802.3标准中提供了以太帧结构。当前以太网支持光纤和双绞线媒体支持下的四种传输速率： 10 Mbps – 10Base-T Ethernet（802.3） 100 Mbps – Fast Ethernet（802.3u） 1000 Mbps – Gigabit Ethernet（802.3z)） 10 Gigabit Ethernet – IEEE 802.3ae 以太网简史： 1972年，罗伯特?梅特卡夫(Robert Metcalfe)和施乐公司帕洛阿尔托研究中心(Xerox PARC)的同事们研制出了世界上第一套实验型的以太网系统，用来实现Xerox Alto（一种具有图形用户界面的个人工作站）之间的互连，这种实验型的以太网用于Alto工作站、服务器以及激光打印机之间的互连，其数据传输率达到了2.94Mbps。 梅特卡夫发明的这套实验型的网络当时被称为Alto Aloha网。1973年，梅特卡夫将其命名为以太网，并指出这一系统除了支持Alto工作站外，还可以支持任何类型的计算机，而且整个网络结构已经超越了Aloha系统。他选择“以太”（ether）这一名词作为描述这一网络的特征：物理介质（比如电缆）将比特流传输到各个站点，就像古老的“以太理论”（luminiferous
第一章：整式的运算 单项式 式 多项式 同底数幂的乘法 幂的乘方 积的乘方 同底数幂的除法 零指数幂 负指数幂 整式的加减 单项式与单项式相乘 单项式与多项式相乘 整式的乘法 多项式与多项式相乘 整式运算 平方差公式 完全平方公式 单项式除以单项式 整式的除法 多项式除以单项式 一、单项式 1、都是数字与字母的乘积的代数式叫做单项式。 2、单项式的数字因数叫做单项式的系数。 3、单项式中所有字母的指数和叫做单项式的次数。 4、单独一个数或一个字母也是单项式。 5、只含有字母因式的单项式的系数是1或―1。 6、单独的一个数字是单项式，它的系数是它本身。 7、单独的一个非零常数的次数是0。 8、单项式中只能含有乘法或乘方运算，而不能含有加、减等其他运算。 9、单项式的系数包括它前面的符号。 10、单项式的系数是带分数时，应化成假分数。 11、单项式的系数是1或―1时，通常省略数字“1”。 12、单项式的次数仅与字母有关，与单项式的系数无关。 二、多项式 1、几个单项式的和叫做多项式。 2、多项式中的每一个单项式叫做多项式的项。 3、多项式中不含字母的项叫做常数项。 4、一个多项式有几项，就叫做几项式。 5、多项式的每一项都包括项前面的符号。 6、多项式没有系数的概念，但有次数的概念。 7、多项式中次数最高的项的次数，叫做这个多项式的次数。 三、整式 1、单项式和多项式统称为整式。 2、单项式或多项式都是整式。 3、整式不一定是单项式。 4、整式不一定是多项式。
5、分母中含有字母的代数式不是整式；而是今后将要学习的分式。 四、整式的加减 1、整式加减的理论根据是：去括号法则，合并同类项法则，以及乘法分配率。 2、几个整式相加减，关键是正确地运用去括号法则，然后准确合并同类项。 3、几个整式相加减的一般步骤： （1）列出代数式：用括号把每个整式括起来，再用加减号连接。 （2）按去括号法则去括号。 （3）合并同类项。 4、代数式求值的一般步骤： （1）代数式化简。 （2）代入计算 （3）对于某些特殊的代数式，可采用“整体代入”进行计算。 五、同底数幂的乘法 1、n个相同因式（或因数）a相乘，记作a n，读作a的n次方（幂），其中a为底数，n为指数，a n的结果叫做幂。 2、底数相同的幂叫做同底数幂。 3、同底数幂乘法的运算法则：同底数幂相乘，底数不变，指数相加。即：a m﹒a n=a m+n。 4、此法则也可以逆用，即：a m+n = a m﹒a n。 5、开始底数不相同的幂的乘法，如果可以化成底数相同的幂的乘法，先化成同底数幂再运用法则。 六、幂的乘方 1、幂的乘方是指几个相同的幂相乘。（a m）n表示n个a m相乘。 2、幂的乘方运算法则：幂的乘方，底数不变，指数相乘。（a m）n =a mn。 3、此法则也可以逆用，即：a mn =（a m）n=（a n）m。 七、积的乘方 1、积的乘方是指底数是乘积形式的乘方。 2、积的乘方运算法则：积的乘方，等于把积中的每个因式分别乘方，然后把所得的幂相乘。即（ab）n=a n b n。 3、此法则也可以逆用，即：a n b n =（ab）n。 八、三种“幂的运算法则”异同点 1、共同点： （1）法则中的底数不变，只对指数做运算。 （2）法则中的底数（不为零）和指数具有普遍性，即可以是数，也可以是式（单项式或多项式）。 （3）对于含有3个或3个以上的运算，法则仍然成立。 2、不同点： （1）同底数幂相乘是指数相加。 （2）幂的乘方是指数相乘。 （3）积的乘方是每个因式分别乘方，再将结果相乘。 九、同底数幂的除法
目录 一.摘要 (1) 二.网络安全简 (2) 安全技术手段 (3) 三.现代密码技术分类 (3) 1．对称密码体制 (4) 2．非对称密码体制 (4) 四．RSA加密解密体制 (5) 1．RSA公钥密码体制概述 (5) 2．RSA公钥密码体制的安全性 (6) 3．RSA算法工作原理 (6) 五.实现RSA加密解密算法 (7) 六．RSA的安全性 (11) 七．结语 (13)
实现加密解密程序 摘要：随着计算机网络的广泛应用，网络信息安全的重要性也日渐突出，计算机信息的保密问题显得越来越重要，无论是个人信息通信还是电子商务发展，都迫切需要保证Internet网上信息传输的安全，需要保证信息安全；网络安全也已经成为国家、国防及国民经济的重要组成部分。密码技术是保护信息安全的最主要手段之一。使用密码技术可以防止信息被篡改、伪造和假冒。加密算法：将普通信息（明文）转换成难以理解的资料（密文）的过程；解密算法则是其相反的过程：由密文转换回明文；密码机包含了这两种算法，一般加密即同时指称加密与解密的技术。 关键字：密码技术、加密算法、解密算法、密码机、RSA 正文 一、网络安全简介 网络安全是指网络系统的硬件、软件及其系统中的数据受到保护，不因偶然的或者恶意的原因而遭受到破坏、更改、泄露，系统连续可靠正常地运行，网络服务不中断。网络安全从其本质上来讲就是网络上的信息安全。从广义来说，凡是涉及到网络上信息的保密性、完整性、可用性、真实性和可控性的相关技术和理论都是网络安全的研究领域。网络安全是一门涉及计算机科学、网络技术、通信技术、密码技术、信息安全技术、应用数学、数论、信息论等多种学科的综合性学科。 网络安全的具体含义会随着“角度”的变化而变化。比如：从用户（个人、企业等）的角度来说，他们希望涉及个人隐私或商业利益的信息在网络上传输时受到机密性、完整性和真实性的保护，避免其他人或对手利用窃听、冒充、篡改、抵赖等手段侵犯用户的利益和隐私。 二、安全技术手段
常见硬盘加密解密的几种方法解析 一、修改硬盘分区表信息 硬盘分区表信息对硬盘的启动至关重要，假设找不到有效的分区表，将不能从硬盘启动或即使从软盘启动也找不到硬盘。素日，第一个分区表项的第0子节为80H，透露显示C 盘为活动DOS分区，硬盘能否自举就依*它。若将该字节改为00H，则不能从硬盘启动，但从软盘启动后，硬盘仍然可以接见。分区表的第4字节是分区类型标志，第一分区的此处素日为06H，透露显示C盘为活动DOS分区，若对第一分区的此处中止批改可对硬盘起到一定加密浸染。 详细表现为： 1.若将该字节改为0，则透露显示该分区未运用，当然不能再从C盘启动了。从软盘启动后，原来的C盘不见了，你看到的C盘是原来的D盘，D盘是原来的E盘，依此类推。 2.若将此处字节改为05H，则不但不能从硬盘启动，即使从软盘启动，硬盘的每个逻辑盘都弗成接见，多么等于整个硬盘被加密了。另外，硬盘主指导记录的有效标志是该扇区的最后两字节为55AAH。若将这两字节变为0，也可以完成对整个硬盘加锁而不能被接见。硬盘分区表在物理0柱面0磁头1扇区，可以用Norton for Win95中的Diskedit直接将该扇区调出并批改后存盘。或者在Debug下用INT 13H的02H子功用将0柱面0磁头1扇区读到内存，在响应位置中止批改，再用INT 13H的03H子功用写入0柱面0磁头1扇区就可以了。
上面的加密措置，对通俗用户来讲已足够了。但对有阅历的用户，即使硬盘弗成接见，也可以用INT 13H的02H子功用将0柱面0磁头1扇区读出，根据阅历将响应位置数据中止批改，可以完成对硬盘解锁，因为这些位置的数据素日是固定的或有限的几种景遇。另外一种保险但显得笨拙的方法是将硬盘的分区表项备份起来，然后将其悉数变为0，多么别人由于不知道分区信息，就无法对硬盘解锁和接见硬盘了。 二、对硬盘启动加口令 我们知道，在CMOS中可以设置系统口令，使非法用户无法启动比赛争论机，当然也就无法运用硬盘了。但这并未真正锁住硬盘，因为只需将硬盘挂在其他比赛争论机上，硬盘上的数据和软件仍可运用。要对硬盘启动加口令，可以首先将硬盘0柱面0磁头1扇区的主指导记录和分区信息都储存在硬盘并不运用的隐含扇区，比如0柱面0磁头3扇区。然后用Debug重写一个不超越512字节的轨范(理论上100多字节足矣)装载到硬盘0柱面0磁头1扇区。该轨范的功用是执行它时首先需求输进口令，若口令纰谬则进入死轮回;若口令正确则读取硬盘上存有主指导记录和分区信息的隐含扇区(0柱面0磁头3扇区)，并转去执行主指导记录。 由于硬盘启动时首先是BIOS调用自举轨范INT 19H将主硬盘的0柱面0磁头1扇区的主指导记录读入内存0000：7C00H处执行，而我们曾经偷梁换柱，将0柱面0磁头1扇区变为我们自己设计的轨范。多么从硬盘启动时，首先执行的不是主指导轨范，而是我们设计的轨范。在执行我们设计的轨范时，口令若纰谬则无法继续执行，也就无法启动了。即使从软盘启动，由于0柱面0磁头1扇区不再有分区信息，硬盘也不能被接见了。当然还可以将我们设计的轨范像病毒一样，将个中一部分驻留在高端内存，看守INT 13H的运用，防止0柱面0磁头1扇区被改写。