An advanced system for automated certification

An advanced system for automated certification

Ioannis Samoladas, Alexandros Nanopoulos, Athanasis Karoulis, Ioannis Stamelos and Yannis Manolopoulos

Aristotle University of Thessaloniki, Greece

Key words:Tele-learning, Distance Certification Systems, Data Mining Abstract:

Internet has revolutionized many aspects of our everyday life. Education could

not stay intact; Internet has introduced the great ability of distance

learning, which allows the traditional educational process to overcome several

limitations. Among the requirements that accrue naturally, is the assessment of

the results for the new type of educational process. This requirement is

denoted as distance certification. While numerous organizations have emerged to

support the certification process, the presence of systems that will automate

this process and will render it clear and objective, is limited. In this paper,

we first describe the requirements that have to be addressed for the

development of such a system. For a better understanding of the requirements we

modelled the certification process and simulate it. The certification model was

built according to the most recent standards and processes that major

certification providers follow. Next, we propose ASPIS, which is a system that

have been developed to meet these requirements. ASPIS takes into account

various learning parameters and makes use of the feedback of the process. The

proposed system is web based and it is built with a three tier architecture, it

is highly modularized and it can be easily extended and modified. The whole

application utilizes free/open source software, it is written in php, it

functions upon the Apache web server and its database system is MySQL.

Furthermore its web interface is compliant with the most recent web standards,

separating content from presentation, making it accessible by all operating

systems that utilize a web standard browser and with low effort by other

handheld devices. Additionally, ASPIS exploits the advantages offered by the

data-mining technology, to further assist the distance certification. The

advantages of the proposed system are illustrated through several results of

the data mining we applied on the system's preliminary data.

1Introduction

During the last decade the wide spread of the Internet has changed many areas of everyday life, especially in communications and news spreading. Additionally the way business is conducted has also changed and electronic commerce has gained a lot of attention. Another important area of our lifes that has changed with the introduction of the Internet is the way we learn. Distance learning systems are now a reality and a lot of organizations are, now, offering courses that are conducted over the web and a large number of people are enrolled in them.

Additionally, big multinational companies use the Internet to keep their employees up-to-date with their job area, offering to them life long education. These courses cover a wide range of subjects, but the majority of them involve information technology areas.

All these organizations that provide distance learning courses need a mechanism to support this life-long learning process in order to track the performance of their students, a mechanism that provides distance certification. While there are a number of companies in other countries that offer a distance certification application and procedure, this is not the case in Greece. Furthermore, the support for the certification process is limited and there are certain problems with the inflexible process. The certification process does not take account of the learning process (teaching methods, training centers, educational staff, etc.) and there is not a formal process to accredit learning providers (or learning centers) and examination centers. Additionally, the results of the certification process are not used as a feedback in order to evaluate and make the process better.

In order to address the problems mentioned, we propose the ASPIS (the name ASPIS is the Greek acronym for “Automated Certification System”) system. To our best knowledge, this is the first system in Greece that offers an online automation of both the certification process and the accreditation process for learning centers and the examination centers. The system keeps track of the whole learning and examination process.

The ASPIS system provides data (e.g., about examinees, education centers, tests, etc) that can be exploited in order to find useful information, which can be used to assess the whole educational process and carefully monitor specific parts of it. For this purpose, we describe the use of the analysis module that is included in ASPIS, which performs data mining on the data collected by the system. Up to the authors knowledge, relatively little interest has been given during the past years in applying data mining for educational-related purposes. We detail the data-mining methodology that is used and illustrate some sample results, with emphasis on the qualitative characterization of the results according to three parameters of the human cognition.

2Certification - accreditation processes

Before implementing the ASPIS system it was necessary to define a certification process both for the examination process and the accreditation process of the examination centers and learning providers by a central authority (in our case the Aristotle University of Thessaloniki). These processes were used in order to specify the system’s requirements [5]. To take an idea of such process we have conducted interviews with the industrial partners of the ASPIS project, from those interviews we have modeled a general framework that can be easily applied and altered in order to capture a specific process of a learning organization.

Organizations wishing to offer courses leading to certificates have to be accredited by the central authority mentioned above, according to already established standards [4], [7]. Likewise, organizations wishing to implement the process of examinations and offer it to candidates have to be accredited. Once accredited, learning centers (learning providers) and examination centers are monitored in a variety of ways to ensure that standards are fulfilled.

The general process for certifying the candidate is shown in Figure 1. The candidate is registered in the examination center by bringing complete probative elements of his identity. He acquires a unique username and password to log into the examination system and take exams in the required module(s) (e.g. word processing, spreadsheets). The examinations can be written offline or online (in our case, the ASPIS system accommodates only online examinations). Examination results are published shortly after.(e.g. either online or with regular post) and candidates have the right to appeal to any step of the process.

Fig. 1. Process diagram for the exam

The general process for accrediting the organizations wishing to act either as learning providers or examination centers is shown in Figure 2. The interested organization submits an application to the central authority. After a visit of evaluation, the authority decides whether to grant the accreditation. If the accreditation is not granted, the rejected organization has the right to appeal. If the accreditation is granted, the organization that was accredited must comply with the accreditation rules.

Fig. 2. Process diagram for center accreditation

3The ASPIS System

3.1Overview

The ASPIS system is a modern web based system, i.e. a web based database application. The system supports two functions, accreditation and examination. For the first, it offers automation regarding the tracking of the process for the accreditation and the maintenance of the existing accredited centers (e.g. reminders for the periodic audit). It does not support cases and processes that include strong human interference, for example decision making regarding the grant of the accreditation. For the second function the system support almost full automation of the certification process (the automation is not supported when the examination process demands a written exam, which is not the usual case for such system).

3.2Architecture

The ASPIS system is a three-tier application, like most of the recent web based systems. The base of the system is the relational database management system (RDBMS) or the database tier, which is the MySQL database management system [reference]. Above that tier there is the application logic or the middle tier, which performs most of the systems functions and it is also responsible for the communication between the upper tier of the system and the database tier. The language we used to write this tier was PHP, a server side scripting language suitable for building web based applications. This tier also includes the web server that stands above the PHP engine. On the top there is the client tier which is the web browser that interacts with the user. All these three tiers are cooperating in order to carry out the functions that the ASPIS system performs. The general architecture is shown in Figure 3.

Fig. 3. The 3-tier architecture

Particularly, when a client or more precisely a web browser makes a request to the web server (middle tier) for a specific page, five steps occur:

1.The web server passes the request to the PHP engine’s web server interface.

2.The web server interface calls the PHP engine and passes the parameters to the engine.

3.The appropriate PHP script from the ASPIS system is retrieved from the disk by the

engine.

4.The script is executed by the engine and the output is returned to the web server

interface.

5.The web server interface returns output to the web server which in turn returns the

output as an http (common html file) response to the client’s web browser.

Although PHP can be easily embedded in html web pages, for the ASPIS system this was not the case. Instead, PHP was used to build the web pages from scratch without using existing html code. These pages are built according to specific parameters as an input to PHP and the user’s rights. This means, for example, that there are no separate pages for the main page of the student or the administrator, but a single script builds the page according to the role of the user logged into the system. This feature gives an advantage to the whole system in terms of maintainability. New features can be easily implemented by adding new function to the module that builds the pages instead of adding new raw script files to the application.

Fig. 4.ASPIS architecture

The ASPIS system consists of two main modules and one auxiliary module. The main modules are the Pagebuilder module and the Database module. The architectural view is shown in Figure 4. The auxiliary or Data Mining module is separate from the other two (not shown here). This module is not written in PHP and it directly interacts with the database, bypassing the PHP engine that the rest of the system uses. The functionality contained in the first two modules is further divided into other scripts or modules:

?There are three important scripts in ASPIS that contain information for the two main modules. The first script is access.php, which is responsible for user authentication and passes the appropriate role parameters to the Pagebuilder module. The second

important script, metadata.php, contains all of the system’s information - the

database schema and all the information that the second script wants in order to build pages, e.g. information about forms. Additionally, it implements all the validation

functionality, e.g. whether the user has entered an incorrect email address. The

globals.php script is in fact the configuration file for the application and the

database connections, containing information about how to log into the database and other system and database specific constants and parameters.

?The Pagebuilder module, as its name implies, is responsible for the construction of the majority of the web pages that the ASPIS consists of. It constructs the pages that data is entered or displayed in, i.e. the whole application. For each of one displayed item, it uses a separate function; we could say that it is the API for these functions. For

example, the function buildMenu constructs the menu of the main page of the user

according to his rights (for example, the student has a menu in order to take a test and the administrator has options like adding a new user to the system). It also adds the

appropriate html tags, cascading style sheets and javascript code to the page

constructed and uses the scripts mentioned in the first bullet.

?The Database module contains all the appropriate functions that the system uses in order to communicate with the MySQL database management system and either

inserts new data or processes old ones. This module uses the information from the

metadata.php and the globals.php mentioned before. This module has all the

functions that interact with the database in the lower level through the PHP engine, i.e.

the sql queries. Whenever access to the database is needed, this script is used through the function it provides. If a new query has to be inserted to the system, here is where we implement it. This allows, apart from the modularity of the system, future

migration to another database system.

Of course there are web pages that do not belong to the above, like the login page, which passes parameters to the Pagebuilder module.

It worths mentioning that the whole application is written according to the most up-to-date web standards as these are specified by the World Wide Web Consortium (W3C). This means that the content is separate from the presentation. The content is coded in pure xhtml (a reformulation of html as an xml application) and the presentation or the style is applied by various CSS (Cascading Style Sheets) without affecting the content. This means, first that by applying different style sheets the user interface can be replaced easily, leaving content untouched, and second that having the content free from the way it is presented, it can be easily displayed in other media than the computer screen, i.e. handheld devices e.t.c.

3.3ASPIS Functionality

As mentioned earlier, at the beginning of this section, the ASPIS system supports automation both for the accrediation and the certification process. The accreditation process, as it can be seen from the previous sections, is mostrly bureaucratic, it evolves filing applications and granting accreditations. Thus the accreditation subsystem is actually a system that tracks the progress of an accreditation application and its status. Here we are going to present the certification process subsystem.

3.3.1ASPIS Users for the Certification Subsystem

Regarding the certification process, the ASPIS system has three type of users: the students who give tests and take exams, the educator who specify tests, and the administrators who perform tasks such as adding new students to the system. The specific funtions that each user can perform are:

?Student. After a successful login to the system a student can (a) see the tests that are available for him and choose the test he/she wants to take, (b) To see all the past tests he/she has given. We have to note here that a student cannot give a test that has

already given, but when he chooses a past test he/she sees his/her performace for that specific test.

?Instructor. After a successful login an instrustor can (a) input a new test specification to the system, (b) see the performance of the students assigned to him (c) correct

scenarios that students have given and assign a mark to them.

?Administrator. After successful login and administrator can perform tasks such as (a) insert a new question into the database and edit the existing ones, (b) add new users to the system and edit the existing ones and (c) organize the testing material into subjects and sections and edit them

Here we have to mention that the system gives the administrator the ability to assign to specific instructors additional rights in order to insert, view and edit the questions that the system has in his database. Fig. 5 presents the form that adds a new user to the system.

Fig. 5. Add new user to the system

Additionaly for organizational purposes students belong to classes, with every class to be unique. The same is true for the instructors. This creates a relationship between students and instructors by creating these virtual classes.

3.3.2Question Characteristics

A question in the ASPIS system can be one of the following three types: multiple choice (including true/false type questions), fill in the blank and matching questions. Apart from its type, every question has the following characteristics:

?Question text

?Any images that accompany the test

?Possible answer (in case of multiple choice and matching)

?Correct answer

?To which subject and section of the teaching material the question refers to

?Difficulty level of the question

Apart from the question the systems gives tha ability to have scenarios. Scenarios are specific tasks that students have to perform in order to achive a desirable result, that will enable them to pass an exam. For example a scenario could contain task such as to create a Word document containing material from several resources (e.g. Other files and pictures) and format it according with certain instructions, mentioned in the scenario. Fig. 6 shows the form that adds a new question to the system.

Fig. 6. Add new question to the system

3.3.3Test Characteristics

In ASPIS when an instructor inserts to the system a new test, what he/she actualy does is to insert a new specification of a test and not the actual test with specific questions and scenarios. In particular when a test is inserted to the system the instructor enters the following data:

? A descrite name for the test, in order to refer uniquely to it

? A small textual discription of the test

?The subject and the sections that this test examines

?The distribution of the question into the various difficulty categories (e.g. ten questions with difficulty one, five with two and three with one)

?The expiration date of the test. A test can be active for a certain period and it is automatically deactivated after that date

?Whether or not the test includes a scenario

When a student chosses to give a test, the actual test is created in real time, dynamically , according with its specification. Thus the questions are chosen randomly and every student has a different test in front of him, all with the same specifications. Of course some questions are the same, but the order is surely different. Fig. 7 shows a form that it used to submit a test specification.

Fig. 7. Submit a new test specification

4Case Study of ASPIS

Table 1. Usage statistics of the ASPIS system

Total number of accounts2403

Total number of students2309

Total number of educators77

17

Total number of

administrators

Total number of classes448

16

Total number of study

areas

80

Total number of chapters

(of study areas)

Total number of questions1329

27077

Total number of test

specifications submitted

81561

Total number of tests

submitted

In order to evaluate the ASPIS system, we first implemented a prototype and performed a pilot operational use in a real educational environment. The system was installed by a large Greek educational organization (and an industrial partner of the ASPIS project) that offers computer training in a number of cities across Greece. During that period a lot of data was collected and users provided a lot of feedback about the system itself. This feedback helped in improving the system, especially its user interface which changed, without altering its core design and functionality. The final system is also online and used by the same educational

organization mentioned before. Some numbers that indicate the massive usage of the system until March 2005 are shown in Table 1. The size of the database has reached 291.4 megabytes.

5Data Mining

5.1Objectinves of applying data mining in ASPIS

During its operation, the ASPIS system produces a relatively large volume of data. This includes data about examinees (personal data like address, education center); data about education centers (name, address); data about the tests, i.e., the contents of the database of questions asked to and answers provided by the examinees during their tests; etc. Evidently, such data can be transformed to valuable information, which can be used to (i) improve the ability to assess the whole process and (ii) to monitor specific parts of it in order to adjust accordingly.

As it has been recognized during the previous years, the technology to attain objectives analogous to the aforementioned ones is data mining. Data mining is the extraction of interesting (non-trivial, implicit, previously unknown and potentially useful) information or patterns from data in large databases [2]. Data mining has been primarily used in

financial/marketing applications like target marketing, determination of customer purchasing patterns, and cross-market analysis. Other application areas include telecommunications, insurance, astronomy, etc. However, relatively little interest has been given during the past years in applying data mining for education-related purposes.

Given the two (i and ii) objectives described previously, we consider the following data mining tasks:

1.Mine relationships between data about the examinees (e.g., region of lodging, level of

class, etc), data about the examination centers (their names), and data about their

examination results (total score). The discovered relationships of this kind will allow

for better assessment of the educational process (objective i), since it is helpful to

understand how the aforesaid factors interrelate and which of them affect the success

or failure of examinees.

2.Mine relationships and investigate patterns between the answers of the participants.

The discovered relationships allow for better monitoring of the educational part of the system, that is, the questions used in the tests and, accordingly, their educational

value. If, for example, one can find questions, or categories of questions, that tend to

be answered in the same way (i.e., correctly or incorrectly), then one may have a better understanding on how the taught subjects interrelate and obtain a picture of the

educational model the particular student develops through the interaction with the

system. So, one could adjust the initial educational approach in order to meet students’ expectations and developed cognitive models on the particular domain.

3.To advocate the understanding of the resulting patterns, we consider their

characterization according to three parameters of the human cognition process, which can interpret phenomena of cognitive associations.

The data mining method that we used to examine the previous issues is association-rules mining, which is detailed in the following.

5.2Mining association rules in ASPIS

Association-rules mining concerns the finding of frequent patterns called associations (other names: correlations, causal structures) among sets of items or objects in transaction databases,

relational databases, and other information repositories. An almost legendary example of a discovered association rule is:

?buys(x, “diapers”) → buys(x, “beers”) [0.5%, 60%]

?which states that if one purchases diapers, then he is also likely to purchase beer. As shown, an association rule is characterized by two measures:

?The support s% (in previous example: 0.5%), which reflects the statistical significance of the rule, that is, how many transactions include the items of the rule.

?The confidence c% (in previous example: 60%), which reflects the assurance of the rule, that is, how sure we are that the items in the head and the body of the rule really relate.

The problem of association-rules mining is, therefore, to find all rules with support higher than a given threshold s% and a confidence higher than a given threshold c%. This problem has attracted a lot of interest and many algorithms have been developed [1]. We focus on the family of algorithms that are based on pattern-growth and more particularly on FP-growth [3], since they have been reported to have very good properties.

In ASPIS, we created a separate module in the architecture, which is responsible for probing the database of questions and answers, and for finding association rules of type 1 and 2, that have been described previously. In particular, the analyst can query the database and formulate a view containing information about the total scores (case 1) or the

correctly/incorrectly answered questions per examinee (case 2). The selection can be further focused by including the time period of interest. Each record in the aforementioned views corresponds to transactions, and we use the FP-growth algorithm to mine associations. Examples of discovered patterns, which indicate the usefulness of this module, are given in the following.

5.3Examples of mined results

By using a sample of the tests’ database, consisting of 81561 tests, we mined association rules for cases 1 and 2 that were described previously.

For the former case (1), we have discretized the ratings of examinees (originally in 0-100 scale) in 8 levels: A, B, … G, by equi-partitioning the original scale. We focused on relationships between the city of residence of examinees and their rating. The rules we detected (support threshold 1%, confidence threshold 55%) were the following:?Residence(x, “Kozani”) → Rating(x, “G”)[2%, 67%]

?Residence(x, “Thessaloniki”) → Rating(x, “A”)[6%, 66%]

?Residence(x, “Florina”) → Rating(x, “A”) [1%, 58%]

The utility of this kind of rules is evident, because they are significant (the original sample was large) and one can detect clear relationships. Thus, such rules can help in monitoring the educational process, since regions that tend to have low ratings can be looked more carefully to examine the reasons. Moreover, it is also useful to know the regions where the education process has good results.

For the case 2, we have mined association rules between the correctly and incorrectly answers by each examinee. A sample of the detected rules for the former case is the following:?“What appears after then end of booting?”, “Give a way to terminate a program that got stuck” → “Which icon do we use to undelete a file?”[76%]

?“What appears after then end of booting?”, “Give a way to terminate a program that got stuck” → “Which of the listed actions cannot be performed with the mouse?”

[76%]

A sample of detected rule for the latter case is the following:

?“Is it possible to minimize a dialog box?”, “In which way can we minimize all opened windows?” → “From the listed items, which is not a component of MS Windows?” [73%] From such rules one can see topics that tend to be understood (correctly answered) or not understood (incorrectly answered), for instance the minimization procedure, and react accordingly by emphasizing such topics (and their relation) during classes.

5.4Analyzing the patterns according to cognitive parameters

In this section we elaborate further on the third task that was described in Section 5.1. According to contemporary literature, human cognition is usually associated to following cognitive parameters: perception, attention, memory, processing, reasoning, problem solving, and time perception. For the purposes of data mining in the results of ASPIS, we focused on the following three parameters in order to elicit useful results from the derived patterns:?Memory: indicates in how far the user can remember the semantic and/or the use of the questioned entity. A typical question of this kind is “which of the following

completes the action…”

?Perception: refers to the ability of the user to recognize the presence and/or the utility of the entity in the interface. A typical question of this kind is “which of the following shoud one activate in order to…”

?Reasoning: refers to the ability of the user to interrelate the particular entity to others, which interfere in a way with the questioned one. In other words, to investigate

relations between entities (and accordingly depict them correctly in the questions). A typical question of this kind is “which of the following statements is correct…”Usually, while the user performs the test, the questioned interface is not available for experimentation, so a great deal of memory is employed by the user in all questions. On the other hand, there is not pure memory or perception or reasoning cognition which would satisfactorily answer the particular question, but merely a combination of these attributes. However, at any given question, one of these parameters clearly dominates over the others, characterizing, thus, the question as memory or perception or reasoning oriented. Bearing that in mind, one can attempt to classify the questions of the tests in one of these categories. Emerging patterns of interrelations between various questions of the tests indicate cognitive interactions between these particular subsets of questions, which can be further analyzed and discussed in detail later.

To exemplify the aforementioned procedure, we present the following characterization of interactions between the three categories in the results of the case-study that was described in the previous section. The association rules between correctly answered questions mainly involve questions in the memory and perception categories. This may indicate a problem with questions belonging to the third category (reasoning), which can help in improving the teaching methodologies towards increasing the aspect of interrelating entities. Regarding the associations between incorrectly answered questions, among the highly ranked rules (w.r.t. confidence and support thresholds) we found correlations between the three categories that are shown in Table 2:

Table 2. Correlations between cognitive parameters

Memory Perception Reasoning

Memory141

Perception400

Reasoning100

We notice a higher correlation between incorrectly answered questions that belong in categories memory and perception. This may indicate that the teaching process can be improved towards increasing the combined understanding of these two categories. References:

[1]. Agrawal, R., Imielinski, T., Swami, A. N. Mining Association Rules between Sets of Items in Large

Databases. ACM SIGMOD Conference (1993) 207-216

[2]. Fayyad, U. M., Piatetsky-Shapiro, G., Smyth, P., Uthurusamy, R. Advances in Knowledge

Discovery and Data Mining. AAAI/MIT Press (1996)

[3]. Han, J., Pei, J., Yin, Y. Mining Frequent Patterns without Candidate Generation. ACM SIGMOD

Conference (2000) 1-12

[4]. Kirkpatrick, D. Evaluating training programs: The four Levels, San Francisco, CA:Berrett-Koehler

(1996)

[5]. Mooij, T., & Smeets, E. Modeling and supporting ICT implementation in secondary schools.

Computers & Education, 36 (2001), 265-281

[6]. MySQL AB. https://www.wendangku.net/doc/5f18317031.html,

[7]. Wisher, R. A., & Champagne, M. V. Distance learning and training: An evaluation perspective. In

J. D. Fletcher and S. Tobias (Eds.), Training and Retraining: A Handbook for Business, Industry, Government and the Military. MacMillan Reference USA (2000)

Author(s):

Ioannis Samoladas, PhD Candidate

Aristotle University of Thessaloniki, Department of Informatics

Thessaloniki 541 24, Greece

ioansam@csd.auth.gr

Alexandros Nanopoulos, PhD

Aristotle University of Thessaloniki, Department of Informatics

Thessaloniki 541 24, Greece

alex@delab.csd.auth.gr

Athanasis Karoulis, PhD

Aristotle University of Thessaloniki, Department of Informatics

Thessaloniki 541 24, Greece

karoulis@csd.auth.gr

Ioannis Stamelos, Assistant Professor

Aristotle University of Thessaloniki, Department of Informatics

Thessaloniki 541 24, Greece

stamelos@csd.auth.gr

Yannis Manolopoulos, Professor

Aristotle University of Thessaloniki, Department of Informatics Thessaloniki 541 24, Greece

manolopo@delab.csd.auth.gr

(完整word版)微带线带通滤波器的ADS设计

应用ADS设计微带线带通滤波器 1、微带带通微带线的基本知识 微波带通滤波器是应用广泛、结构类型繁多的微波滤波器，但适合微带结构的带通滤波器结构就不是那么多了，这是由于微带线本身的局限性，因为微带结构是个平面电路，中心导带必须制作在一个平面基片上，这样所有的具有串联短截线的滤波器都不能用微带结构来实现；其次在微带结构中短路端不易实现和精确控制，因而所有具有短路短截线和谐振器的滤波器也不太适合于微带结构。 微带线带通滤波器的电路结构的主要形式有5种： 1、电容间隙耦合滤波器 带宽较窄，在微波低端上显得太长，不够紧凑，在2GHz以上有辐射损耗。 2、平行耦合微带线带通滤波器 窄带滤波器，有5％到25％的相对带宽，能够精确设计，常为人们所乐用。但其在微波低端显得过长，结构不够紧凑；在频带较宽时耦合间隙较小，实现比较困难。 3、发夹线带通滤波器 把耦合微带线谐振器折迭成发夹形式而成。这种滤波器由于容易激起表面波，性能不够理想，故常把它与耦合谐振器混合来用，以防止表面波的直接耦合。这种滤波器的精确设计较难。

4、1/4波长短路短截线滤波器 5、半波长开路短截线滤波器 下面主要介绍平行耦合微带线带通滤波器的设计，这里只对其整个设计过程和方法进行简单的介绍。 2、平行耦合线微带带通滤波器 平行耦合线微带带通滤波器是由几节半波长谐振器组合而成的，它不要求对地连接，结构简单，易于实现，是一种应用广泛的滤波器。整个电路可以印制在很薄的介质基片上(可以簿到1mm以下)，故其横截面尺寸比波导、同轴线结构的小得多；其纵向尺寸虽和工作波长可以比拟，但采用高介电常数的介质基片，使线上的波长比自由空间小了几倍，同样可以减小；此外，整个微带电路元件共用接地板，只需由导体带条构成电路图形，结构大为紧凑，从而大大减小了体积和重量。 关于平行耦合线微带带通滤波器的设计方法，已有不少资料予以介绍。但是，在设计过程中发现，到目前为止所查阅到的各种文献，还没有一种能够做到准确设计。在经典的工程设计中，为避免繁杂的运算，一般只采用简化公式并查阅图表，这就造成较大的误差。而使用电子计算机进行辅助设计时，则可以力求数学模型精确，而不追求过分的简化。基于实际设计的需要，我对于平行耦合线微带

养殖场设计方案

生猪标准化规模养殖场建设项目

一、项目承办单位基本情况 目前，养猪场主要从事生猪的饲养。猪场现有5名工作人员，其中饲养员4名，兽医专业技术人员1名（福建农林大学）。 二、项目发展现状与存在问题 1、项目发展现状 猪场占地面积32.6亩（含种植果林、绿化地），建设面积7亩。现有圈舍10座（约2500平方米），其中育肥舍800 平方米，保育舍600 平方米，分娩舍400 平方米，母猪定位舍250 平方米，后备母猪舍200 平方米，公猪舍80 平方米，病猪舍80 平方米，消毒更衣室20 平方米，兽医实验室25 平方米、30 平方米，沼气池3口，生产及生活配套设施约100 平方米。养猪场现有良种母猪43头，后备母猪40头，现役公猪3头，后备公猪2头，现存栏数430头，年出栏860头。 2、项目存在的主要问题 （1）随着公司养殖规模的不断扩大，原有的沼气池的处理能力已无法满足项目的需要； （2）现有的产床数不足，造成母猪生产的时候死胎或小猪成活率低等，严重影响公司的经济效益； （3）现有部分猪舍由于使用年限较长，已出现老化、漏雨等问题，急需进行维修改造； （4）公司现有粪污处理设施不足；

（5）防疫化验仪器设备不足。 三、建设目标、建设规模与建设内容 1、建设目标 项目建设以国家农业产业政策和农业产业结构调整为指导思想，结合养猪业生产发展总体情况，推行标准化养殖，做到污水达标排放和废弃物综合利用，走资源节约型和环境友好型的发展路子，提高生猪养殖的技术水平，提高生猪的质量安全水平，增强养猪业的市场竞争力。 2、建设规模与建设内容 项目主要任务是生猪标准化规模养殖场的建设，主要建设内容为粪污处理、猪舍的标准化改造以及防疫等配套设施建设。 （1）改造猪舍700平方米； （2）改造排污渠300米; （3）改建沼气池20立方米； （4）配套体视显微镜1台、产床15张，母猪超声波妊娠测定仪1台、超声波消毒喷雾机1台、恒温培养箱1台、固液分离机1台。 项目主要建设内容见表3-1。 建设内容一览表

(整理)带通滤波器设计

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两边取对数，得： lg 20c uo u n A j A ωω ωlg 20)(-≈ （4） 此时阻带衰减速率为： -20ndB/十倍频或-6ndB/倍频，该式称为衰减估算式。 表1列出了归一化的、n 为1 ~ 8阶的巴特沃斯低通滤波器传递函数的分母多项式。 在表1的归一化巴特沃斯低通滤波器传递函数的分母多项式中，S L = c s ω，ωC 是低通 滤波器的截止频率。 对于一阶低通滤波器，其传递函数： c c uo u s A s A ωω+= )( （5） 归一化的传递函数： 1 )(+= L uo L u s A s A （6） 对于二阶低通滤波器，其传递函数：2 22)(c c c uo u s Q s A s A ωωω++ = （7） 归一化后的传递函数： 1 1)(2 ++= L L uo L u s Q s A s A （8） 由表1可以看出，任何高阶滤波器都可由一阶和二阶滤波器级联而成。对于n 为偶数的高阶滤波器，可以由2n 节二阶滤波器级联而成；而n 为奇数的高阶滤波器可以由2 1-n 节二

养殖场的规划设计

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幅度调制与相位调制

幅度/相位调制 过去几十年随着数字信号处理技术与硬件水平的发展，数字收发器性价比已远远高于模拟收发器，如成本更低，速度更快，效率更高。更重要的是数字调制比模拟调制有更多优点，如高频谱效率，强纠错能力，抗信道失真以及更好的保密性。正是因为这些原因，目前使用的无线通信系统都是数字系统。 数字调制和解调的目的就是将信息以比特形式（0/1）通过信道从发送机传输到接收机。数字调制方式主要分为两类：1）幅度/相位调制和2）频率调制。两类调制方式分别又成为线性调制和非线性调制，在优劣势上也各有不同，因此，调制方式的选择最终还需要取决于多方面的最佳权衡。 本文就对幅度/相位调制加以讨论，全文整体思路如下： 1 信号空间分析 在路径损耗与阴影衰落中已提出发送信号与接收信号的模型以复信号的实部来表示，而在本文中为了便于分析各调制解调技术，我们必须引入信号的几何表示。 数字调制将信号比特映射为几种可能的发送信号之一，因此，接收机需要对各个可能的发送信号做比较，从而找出最接近的作为检测结果。为此我们需要一个度量来反映信号间的距离，即将信号投影到一组基函数上，将信号波形与向量一一对应，这样就可以利用向量空间中的距离概念来比较信号间的距离。 1.1 信号的几何表示 向量空间中各向量可由其基向量表示，而在无线通信中，我们也可把信号用其相应的基函数来表示。本文我们讨论的幅度/相位调制的基函数就是由正弦和余弦函数组成的： 21()()cos (2)c t g t f t φπ=(1) 22()()sin (2)c t g t f t φπ=(2) 其中g (t )是为了保证正交性，即保证 220()cos (2)1T c g t f t dt π=? (3) 20()cos(2)sin(2)0T c c g t f t f t dt ππ=? (4) 则信号可表示为 12()()cos(2)()sin(2)i i c i c s t s g t f t s g t f t ππ=+ (5) 则向量s i =[s i1，s i2]T 便构成了信号s i (t )的信号星座点，所有的星座点构成信号星座图，我们把信号s i (t )用其星座点s i 表示的方法就叫做信号的几何表示。而两个星座点s i 和s k 之间的距离就是采用向量中长度的定义，这里不再赘述。 2 幅度/相位调制 相位/幅度调制主要分为3种： 1）脉冲幅度调制(MPAM)：只有幅度携带信息；

阶有源带通滤波器设计及参数计算

滤波器是一种只传输指定频段信号，抑制其它频段信号的电路。 滤波器分为无源滤波器与有源滤波器两种： ①无源滤波器: 由电感L、电容C及电阻R等无源元件组成 ②有源滤波器: 一般由集成运放与RC网络构成，它具有体积小、性能稳定等优点，同时，由于集成运放的增益和输入阻抗都很高，输出阻抗很低，故有源滤波器还兼有放大与缓冲作用。 利用有源滤波器可以突出有用频率的信号，衰减无用频率的信号，抑制干扰和噪声，以达到提高信噪比或选频的目的，因而有源滤波器被广泛应用于通信、测量及控制技术中的小信号处理。 从功能来上有源滤波器分为： 低通滤波器（LPF）、高通滤波器（HPF）、 带通滤波器（BPF）、带阻滤波器（BEF）、 全通滤波器（APF）。 其中前四种滤波器间互有联系，LPF与HPF间互为对偶关系。当LPF的通带截止频率高于HPF的通带截止频率时，将LPF与HPF相串联，就构成了BPF，而LPF与HPF并联，就构成BEF。在实用电子电路中，还可能同时采用几种不同型式的滤波电路。滤波电路的主要性能指标有通带电压放大倍数AVP、通带截止频率fP及阻尼系数Q等。 带通滤波器（BPF） （a）电路图(b)幅频特性 图1 压控电压源二阶带通滤波器 工作原理：这种滤波器的作用是只允许在某一个通频带范围内的信号通过，而比通频带下限频率低和比上限频率高的信号均加以衰减或抑制。典型的带通滤波器可以从二阶低通滤波器中将其中一级改成高通而成。如图1（a）所示。 电路性能参数 通带增益 中心频率 通带宽度 选择性 此电路的优点是改变Rf和R4的比例就可改变频宽而不影响中心频率。 例．要求设计一个有源二阶带通滤波器，指标要求为： 通带中心频率 通带中心频率处的电压放大倍数： 带宽： 设计步骤： 1）选用图2电路。 2）该电路的传输函数： 品质因数： 通带的中心角频率： 通带中心角频率处的电压放大倍数： 取，则：

养殖场建设项目实施计划方案

2017年礼县永赢养殖种植农民专业合作社畜禽健康养殖项目 实施方案 二〇一七年九月

目录 实施方案 (1) 一、项目概况 (3) 二、建设背景与编制依据 (3) 三、工艺技术方案 (5) 四、建设内容 (6) 五、投资概算 (7) 六、资金筹措 (7) 七、实施计划 (7) 八、附件 (8)

2017年礼县永赢养殖种植农民专业合作社畜禽健康养 殖项目实施方案 一、项目概况 1、项目名称：2017年礼县永赢养殖种植农民专业合作社畜禽健康 养殖项目 2、项目承建单位：礼县永赢养殖种植农民专业合作社 3、项目建设法人：张永代 4、项目主管单位：甘肃陇南市礼县畜牧兽医局 5、项目建设地点：陇南市礼县肖良乡坪望村 6、项目建设规模： 扩建砖混和彩钢结构猪舍275㎡，修建排污管道150m,新建集污池140m3。 7、项目投资： 项目总投资： 30 万元,其中财政补助25万，自筹资金 5万元。 8、项目建设期限：2017年9月中旬开始2017年11月中旬结束。 二、建设背景与编制依据 1、项目由来 项目由来：根据农业部、财政部《关于做好2017年中央财政农业生产发展等项目实施工作的通知》（农财发〔2017〕11号）和国务院办公厅《关于加快推进畜禽养殖废弃物资源化利用的意见》（国办发〔2017〕48号），牢固树立“创新、协调、绿色、开放、共享”发展理念，坚持

源头减量、过程控制、末端利用的治理路径，以种养结合、循环利用为主要推广模式，以畜禽养殖大县和规模养殖场为重点，以有机肥和沼气等为主要利用方向，加强畜禽规模养殖场粪污处理利用设施建设，全力推进畜禽养殖废弃物资源化利用,积极贡献提升家禽规模养殖标准化水平，推进全省畜禽养殖废弃物资源化利用工作，降低养殖成本，改善防疫条件，提高生猪生产能力的精神。因此，积极响应国家的号召和要求，走标准化生猪养殖，决定建设该项目。 2、项目的必要性：近年来，虽然生猪养殖逐步向规模化方向发展，但是离标准化生产的要求相差很远，存在圈舍建造、废弃物处理、人流、物流等方面缺乏科学的设计和管理，有的圈舍间距太近，有的没有消毒设施，有的没有粪污处理设施，粪便到处堆积，病死畜乱扔等等，使空气和水流受到严重污染，成为疾病流行的隐患。养殖场随时会成为疾病疫源地，一旦引发动物或人畜共患病，所带来的损失和危害更大。动物疫病不但给国家或地区和人民造成巨大的经济损失，而且还危及人民群众生命安全。因此，在日益严峻的动物疫病防控形势和生猪养殖产生的污染日趋严重的情况下，改善生猪规模养殖场排粪污处理设施等的建设，加快生猪规模养殖标准化生产，提高养殖场的排污处理能力和疾病预防能力十分必要和迫切的。 3、实施方案编制依据 （1）、编制依据： 本项目依据《甘肃省农牧厅关于印发2017年畜禽健康养殖项目实施方案的通知》（甘农牧财发〔2017〕73号）的文件精神编制。 （2）、实施方案编制中所采取的建筑工程的建设标准及规范：

相位调制与解调

1.前言 1.1 序言 随着人类社会步入信息化社会，电子信息科学技术正以惊人的速度发展，开辟了社会发展的新纪元。从20世纪90年代开始至今，通信技术特别是移动通信技术取得了举世瞩目的成就。在通信技术日新月异的今天，学习通信专业知识不仅需要扎实的基础理论，同时需要学习和掌握更多的现代通信技术和网络技术。通信技术正向着数字化、网络化、智能化和宽带化的方向发展。全面、系统地论述了通信系统基本理沦、基本技术以及系统分析与设计中用到的基本工具和方法，并将重点放在数字通信系统上。通信系统又可分为数字通信与模拟通信。传统的模拟通信系统，包括模拟信号的调制与解调，以及加性噪声对幅度调制和角度调制模拟信号解调的影响。数字通信的基本原理，包括模数转换、基本AWGN信道中的数字调制方法、数字通信系统的信号同步方法、带限AWGN信道中的数字通信问题、数字信号的载波传输、数字信源编码以及信道编码与译码等，同时对多径信道中的数字通信、多载波调制、扩频、GSM与IS95数位蜂窝通信。随着数字技术的发展原来许多不得不采用的模拟技术部分已经可以由数字化来实现，但是模拟通信还是比较重要的 1.2 设计任务 本设计是基于MATLAB的模拟相位（PM）调制与解调仿真，主要设计思想是利用MATLAB这个强大的数学软件工具，其中的通信仿真模块通信工具箱以及M檔等，方便快捷灵活的功能实现仿真通信的调制解调设计。还借助MATLAB可视化交互式的操作，对调制解调处理，降低噪声干扰，提高仿真的准确度和可靠性。要求基于MATLAB的模拟调制与解调仿真，主要设计思想是利用MATLAB、simulink檔、M檔等，方便快捷的实现模拟通信的多种调制解调设计。基于simulink对数字通信系统的调制和解调建模。并编写相应的m檔，得出调试及仿真结果并进行分析。

带通滤波器设计步骤

带通滤波器设计步骤 1、根据需求选择合适的低通滤波器原型 2、把带通滤波器带宽作为低通滤波器的截止频率，根据抑制点的频率距离带通滤波器中心频点距离的两倍作为需要抑制的频率，换算抑制频率与截止频率的比值，得出m 的值，然后根据m 值选择低通滤波器的原型参数值。 滤波器的时域特性 任何信号通过滤波器都会产生时延。Bessel filter 是特殊的滤波器在于对于通带内的所有频率而言，引入的时延都是恒定的。这就意味着相对于输入，输出信号的相位变化与工作的频率是成比例的。而其他类型的滤波器（如Butterworth, Chebyshev,inverse Chebyshev,and Causer ）在输出信号中引入的相位变化与频率不成比例。相位随频率变化的速率称之为群延迟（group delay ）。群延迟随滤波器级数的增加而增加。 模拟滤波器的归一化 归一化的滤波器是通带截止频率为w=1radian/s, 也就是1/2πHz 或约0.159Hz 。这主要是因为电抗元件在1弧度的时候，描述比较简单，XL=L, XC=1/C ，计算也可以大大简化。归一化的无源滤波器的特征阻抗为1欧姆。归一化的理由就是简化计算。 Bessel filter 特征：通带平坦，阻带具有微小的起伏。阻带的衰减相对缓慢，直到原理截止频率高次谐波点的地方。原理截止频率点的衰减具有的经验公式为n*6dB/octave ，其中，n 表示滤波器的阶数，octave 表示是频率的加倍。例如，3阶滤波器，将有18dB/octave 的衰减变化。正是由于在截止频率的缓慢变化，使得它有较好的时域响应。 Bessel 响应的本质截止频率是在与能够给出1s 延迟的点，这个点依赖于滤波器的阶数。 逆切比雪夫LPF 原型参数计算公式（Inverse Chebyshev filter parameters calculate equiations ） ) (cosh )(cosh 11Ω=--Cn n 其中 1101.0-=A Cn , A 为抑制频率点的衰减值，以dB 为单位；Ω为抑制频率与截止频率的比值 例：假设LPF 的3dB 截止频率为10Hz,在15Hz 的频点需要抑制20dB,则有： 95.91020*1.0==Cn ；Ω=15/10=1.5 1.39624.0988.2) 5.1(cosh )95.9(cosh 11===--n ,因此，滤波器的阶数至少应该为4

养牛经验：规模化肉牛养殖场规划建设技术

小区规模肉牛养殖牛舍建筑必须综合考虑饲养目的、饲养场所的条件规模及养牛设施等因素。在大规模饲养时，要考虑节省劳力;小规模饲养时，要便于详细观察每头牛的状态，以充分发挥牛的生理特点，提高经济效益。肉牛养殖小区通常是由当地乡、村划出一片空地，由个人投资建设牛场，分户饲养，集体投资建立兽医室或服务站。这样既便于防疫，又可防止环境污染，提高饲养管理水平和产品质量。各地肉牛养殖小区虽然形式不同，但都应遵循以下原则： 一、小区场址的选择：肉牛养殖小区场址的选择，应遵循规模化育肥牛场选择场址的原则。如果条件不具备，也可因地制宜，充分利用当地空闲地、但必须保证交通运输方便，以便于饲料和牛只的进出。 二、小区的形式：肉牛养殖小区主要有自繁自养、架子牛育肥、自繁自养和架子牛育肥相结合三种形式。自繁自养可充分利用粗饲料，降低饲养成本，但饲养周期长，资金周转慢，适于经济条件较差的地区。架子牛育肥投资较大，精饲料需求量大，饲养成本高，但饲养周期短，资金周转快，经济效益高。自繁自养和架子牛育肥相结合，可充分利用上述两者的优点，但饲养管理复杂。 三、小区的布局与设计：肉牛养殖小区的布局、设计要求与规模化牛场近似，也应包括消毒池、兽医室、生产牛舍、隔离牛舍、饲料间、

青贮池、氨化池、贮粪场、粪污处理设施、装牛台等设施，但生活区、生产区的划分不很明显，牛舍一般为单列式，每栋6-12间，为1-2户所有，1-2间为饲料室和宿舍，其余为牛舍。每间牛舍饲养3-5头，基础牛舍、产犊舍、犊牛培育舍、育成牛舍和育肥牛舍的划分不明显。青贮池和氨化池由各养牛户按饲养规模集资建设，一般二池合一，这样既可节约投资，又可提高设备的利用率。青贮池和氨化池一般位于牛舍的两侧，便于取料。 四、小区牛舍的建筑：肉牛养殖小区牛舍的建筑也与规模化牛场相似，但要求较低，可充分利用当地的材料，以降低建筑成本。在气候温暖的地区，搭建简易棚舍即可，可大量节约投资;在夏天炎热、冬季气候较冷的地区，应建造较坚固的开放式牛舍或半开放式牛舍，这样的牛舍夏天可保证通风良好，冬季用塑料布和草席将牛舍封闭起来，以便于保温。

有源带通滤波器设计

RC 有源带通滤波器的设计 滤波器的功能是让一定频率范围内的信号通过，而将此频率范围之外的信号加以抑制或使其急剧衰 减。当干 扰信号与有用信号不在同一频率范围之内，可使用滤波器有效的抑制干扰。 用LC 网络组成的无源滤波器在低频范围内有体积重量大，价格昂贵和衰减大等缺点，而用集成运放 和RC 网络组成的有源滤波器则比较适用于低频，此外，它还具有一定的增益，且因输入与输出之间有良 好的隔离而便于级联。由于大多数反映生理信息的光电信号具有频率低、幅度小、易受干扰等特点，因而 RC 有源滤波器普遍应用于光电弱信号检测电路中。 一.技术指标 总增益为1 ; 通带频率范围为 300Hz —3000Hz ,通带内允许的最大波动为 -1db —+1db ; 阻带边缘频率范围为 225Hz 和4000Hz 、阻带内最小衰减为 20db ; 二?设计过程 1 .采用低通-高通级联实现带通滤波器； 将带通滤波器的技术指标分成低通滤波器和高通滤波器两个独立的技术指标，分别设计出低通滤波器 和高通 滤波器，再级联即得带通滤波器。 低通滤波器的技术指标为： f PH = 3000Hz A max - 1d B G =1 f SH = 4000Hz A min = 20dB 高通滤波器的技术指标为： f pL = 300Hz A max = 1d B G = 1 f si_ - 225Hz A min - 20dB 2. 选用切比雪夫逼近方式计算阶数 (1).低通滤波器阶数 N >ch 4[J(10 0.1Amin -1)/(10 0.1Ami N 1 _ ■ 1 Ch ( f SH / f PH ) (2).高通滤波器阶数 N 2 ch'[ *. (10 0.1Amin -1)/(100.1Amax -1)] Ch^(f pL /f SL ) 3. 求滤波器的传递函数 1) .根据Ni 查表求出归一化低通滤波器传递函数 H LP (S)二 H LP (S)| S S' 2= --- 2冗PH 2) .根据Na 查表求出归一化高通滤波器传递函数 N 2 H_P (S '，去归一化得 H^s '，去归一化得

养殖场工程施工组织方案设计

目录 一、主要施工方法 (2) 二、拟投入的主要物资计划 (19) 三、拟投入的主要施工机械 (21) 四、劳动力安排计划 (21) 五、确保工程质量的技术组织措施 (25) 六、确保安全生产的技术组织措施 (26) 七、确保工期的技术组织措施 (27) 八、确保文明施工的技术组织措施 (28) 九、施工总进度表或施工网络图 (30) 十、造价控制的技术和管理措施 (30) 十一、施工总平面图 (43) 十二、有必要说明的其他问题.......................... 附表一：拟投入本工程的主要施工设备表 附表二：拟配备本工程的试验和检测仪器设备表 附表三：劳动力计划表 附表四：计划开、竣工日期和施工进度网络图 附表五：施工总平面图

一、主要施工办法 1、施工组织设计编制依据 1.1国家现行的技术标准；施工规及验收标准；工程质量检验评定标准和施工操作规程；国家、省、市颁发的有关规定及相应文件。 1.2 建设部颁发的《建筑工程施工现场管理规定》。 1.3 **省发布的建筑工程文明施工的有关规定。 1.4 本工程招标文件。 1.5 我公司ISO-9001质量管理认证颁布的《质量手册》、《程序文件》、第三层次文件。 2、工程概况 本工程为***养殖场工程，主要包括怀孕舍、中转池、消毒池、降温池、垃圾池、蓄水池、清洗池、料灌基础、发电机房、厕所、伙房宿舍、封闭通道、大门、饲料道路、哺乳舍、洗澡间、公猪站、进猪通道及配套装饰工程等工程。 建设地点为********，资金来源为自筹，本工程实行包工包料、包安全、包文明施工、包质量、包工期的总承包负责制。 3、工程建设任务目标 本工程项目施工的指导思想是：运用科学管理手段，认真执行ISO-9001质量保证体系；运用先进的计算机工程管理软件对本工程进行及时、科学的管理，使本工程创出良好的经济效益和社会效益。 3.1工期目标：自开工之日起135天完工。 3.2 质量目标：确保合格标准。 3.3 安全目标:杜绝重伤与死亡事故发生。

无线通信系统中的调制解调基础(二)：相位调制

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6、地形要求： ?地形整齐开阔、有足够的面积。 地形整齐，便于合理布局畜牧场建筑和各种设施，有利于充分利用场地；开阔的地形对养殖场通风采光、施工运输和管理提供方便；足够的面积可为畜牧场的发展留有空间。 ?土壤透气性好、透水性好的砂壤土。 畜牧场场地的土壤情况对畜禽影响很大。透气、透水性好的土壤，一般持水力和毛细管作用较差，不潮湿，易干燥。受污染后容易氧化分解而达到净化，场区空气卫生状况较好，，抗压能力较大，且不易冻结，建筑物不易受潮。 ?化学和生物学特性、地方病和疫情情况 受客观条件限制，不宜过分强调土壤种类和物理特性，应着重化学和生物学特性，注意地方病和疫情调查。 7、地势要求： 地势较高、干燥、平坦或有缓坡，坡度在25%以下，背风向阳，北高南低，坐北朝南，偏东南12°- 15°。 8、生物安全要求： 场址的选择必须符合人畜相处的公共卫生和生物安全要求。 场址应选择在城镇居民区常年主导风向的下风向或侧风向处。 选择荒坡闲置地建场，避免人畜争地。 场址周围有广袤的种植区域，可保证较大的粪污及建设配套的排污处理，使有机废弃物经过处理达标后循环利用。 禁止在旅游区、自然保护区、人口密集区、水资源保护区、环境公害污染严重的地区及国家规定的禁养区建场。

带通滤波器电路及参数的确定.

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基于labview的频率调制

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种经济实用的材料。若从坚固耐用考虑可选用混凝土预制构件。无论哪种材料，工艺上都要求食槽内壁呈流线形，以便清扫。 (四)其他建筑用材料依当地自然和资源条件而定，主要有两种类型；即砖木结构，如牛舍用砖柱和木材顶梁；钢铁结构，如工字钢立柱与角铁构件的顶梁。 三、肉牛场规模大小选择 规模大小是场区规划与牛场设计的重要依据，规模大小的确定应考虑以下几个方面： 1．自然资源特别是饲草饲料资源，是影响饲养规模的主要制约因素。生态环境对饲养规模也有很大影响。 2．资金情况肉牛生产所需资金较多。资金周转期长，报酬率低。资金雄厚，规模可大，总之要量力而行，进行必要的资金运行分析。 3．经营管理水平社会经济条件的好坏，社会化服务程度的高低，价格体系的健全与否，以及价格政策的稳定性等，对饲养规模有一定的制约作用。在确定饲养规模时，应予以考虑。 4．场地面积肉牛生产，牛场管理，职工生活及其他附属建筑等需要一定场地、空间。牛场大小可根据每头牛所需面积、结合长远规划计算出来。牛舍及其他房舍的面积为场地总面积的15％一20％。由于牛体大小、生产目的、饲养

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电子系统设计实验报告 姓名 指导教师 专业班级 学院 提交日期2011年11月1日

目录 第一章设计题目 (1) 1.1 设计任务 (1) 1.2 设计要求 (1) 第二章原理分析及参数计算 (1) 2.1 总方案设计 (1) 2.1.1 方案框图 (1) 2.1.2 原理图设计 (1) 2.2 单元电路的设计及参数计算 (2) 2.2.1 二阶低通滤波器 (2) 2.2.2 二阶高通滤波器 (3) 2.3 元器件选择 (4) 第三章电路的组装与调试 (5) 3.1 MultiSim电路图 (5) 3.2 MultiSim仿真分析 (5) 3.1.1 四阶低通滤波器 (5) 3.1.2 四阶高通滤波器 (5) 3.1.3 总电路图 (6) 3.3 实际测试结果 (6) 第四章设计总结 (6) 附录………………………………………………………………………………… 附录Ⅰ元件清单………………………………………………………………… 附录Ⅱ Protel原理图…………………………………………………………… 附录Ⅲ PCB图（正面）………………………………………………………… 附录Ⅳ PCB图（反面）………………………………………………………… 参考文献…………………………………………………………………………

第一章 设计题目 1.1 设计任务 采用无限增益多重反馈滤波器，设计一四阶带通滤波器，通带增益01A =， 1L f kHz =，2H f kHz =，设计方案如图1.1所示。 图1.1 四阶带通滤波器方案图 1.2 设计要求 1.用Protel99 画出原理图，计算各元件参数，各元件参数选用标称值； 2.用Mutisum 对电路进行仿真，给出幅频特性的仿真结果； 3.在面包板上搭接实际电路，并测试滤波器的幅频特性； 4.撰写设计报告。 第二章 设计方案 2.1 方案设计 2.1.1方案框图(如图2.1.1) 图2.1.1 四阶带通滤波器总框图 2.1.2原理图设计 本原理图根据结构框图组成了4个二阶滤波器，上面两个分别为c f =2kHz ，Q=0.541，A=1的低通滤波器和c f =2kHz ，Q=1.306，A=1的低通滤波器；下面两个分别为c f =1kHz ，Q=0.541，A=1的高通滤波器和c f =1kHz ，Q=1.306，A=1的高通滤波器，其中P1、P2、P3作为接线座用来接线，原理图如图2.1.2,具体参数计算见2.2节。 V i V o 二阶低通滤波器 二阶低通滤波器 二阶高通滤波器 二阶高通滤波器