数字计算机

In this paper, the concept of network security and security structures of OSI and Internet is introduced, and various threats confronting the computer network are also discussed. Several kinds of network information security technologies, including firewall technology, virtual private network, intrusion detection system, data encryption technology, identity authentication and security protocol etc. are also examined. The security of internal network is the biggest problem in the construction of each network. The solution to this problem lies in setting up a firewall. The theory of a firewall and the approach to its actualization is studied. Intrusion detection system, an important part of the computer network security system, has gained extensive attention. IDS monitors the computer and network traffic for intrusion and suspicious activities. It not only detects the intrusion from the extranet hacker, but also the intranet users. The emergence of virtual private network paves the way for realizing secure connection of LAN quickly and at a relatively low cost. The concept, function, key techniques, including the tunnel technology, and the ways to realize VPN are expounded in this paper. Also introduced is the data encrypt network technology, which is called the soul of computer network security, such as digital digest, digital signature, digital certificate, digital encrypt arithmetic and so on. At the same time, the principle and the process of implementing network security by digital certificate and digital signature, the basic principle and characters of security protocols, and finally, three of the security protocols, concerning the security problems in network, IPsec, SLL and SET are analyzed in detail Computer network system should be a system of dynamic defence, both dynamic and static, passive as well as active, and even offensive, combined with management and technology.

本文系统地介绍了网络安全的概念、OSI及Internet的安全体系结构，并讨论了计算机网络面临的各种安全威胁；内部网络的安全问题是每个建网单位面临的最大问题，可以认为防火墙技术是解决网络安全的一个主要手段，本文研究了防火墙的原理及其实现手段；作为一种主动的防御措施，入侵检测系统作为网络系统安全的重要组成部分，得到了广泛的重视，TDS对计算机和网络资源上的恶意使用行为进行识别和响应，不仅检测来自外部的入侵行为，也监督内部用户的未授权活动；虚拟专用网技术的出现，为实现网络间的连接提供了快速安全但又相对便宜的手段，本文较深入的探讨了实现VPN的隧道技术，并对VPN的概念、功能、实现途径、基本构成、关键技术及发展前景等问题进行了全面论述；数据加密技术是网络安全核心技术之一，本文从数据加密算法、数字摘要、数字签名及数字证书等几方面简要介绍了数据加密技术，并分析用数字证书和数字签名实现网络安全的原理和过程；对安全协议的基本原理、主要特点进行了较为深入的研究，并就网络的安全性问题剖析了三种安全协议：IPsec协议、SLL协议和SET协议。

According to the demand of high magnetic field power supply, reference is increased with a set ramp rate and stops at a set stable value, so reference system is composed of digital setting and digit to analog converting circuit. But the stability of reference is mostly guaranteed by the performance of D/A circuit, so D/A circuit is particularly studied in reference system. The scheme of D/A circuit, the selection of DAC and its voltage reference, hardware anti-jamming design and PCB design are discussed in detail, and software of remote control and PLC are discussed in brief. Zero-flux DC current transformer well satisfies the demands of the high stability of Load current detection unit, so the principle of zero-flux DC current transformer is analyzed; in the mean time a project which detects the long term stability is designed. During 8 hours, analog signal which is detected with high precision digit multimeter is recorded in computer at 1HZ frequency by GPIB communication. The drift error source and related parameters are explained in the compare-amplify part. Detailed subtraction circuit is designed; also amplifier chip and periphery components are selected and verified according to the theory of error analysis.

根据强磁场电源的需求，参考源应按照软件设定的斜率逐渐上升到设定稳态值，则参考源系统应由数字给定和数模转换电路两大部分组成，而参考源的稳定度主要依靠完成数模转换功能的模拟电路的性能来保证，因此本文对参考源系统的研究以数模转换电路为重点，分别从电路方案的确定、数模转换芯片及其基准电压源的选取和验证、电路板硬件抗干扰和PCB设计几方面进行了论述，然后对数字给定部分的远控组态和PLC程序设计作了简要介绍；采用零磁通原理的直流电流转换器很好地满足了对负载电流检测单元高稳定度的需求，本文详细分析了零磁通检测的原理，并在选定此种类型电流转换器的基础上设计了一套检测长期稳定度的方案，8小时内以1秒为采样周期，通过计算机Labview程序和高精度数字电压表的GPIB通讯，将被高精度数字电压表数字化后的模拟信号采样值连续记录至计算机中；比较放大环节简要阐述了漂移产生的原因和相关参数指标，确定了具体的减法电路形式，并根据误差分析理论对运算放大器和外围元器件进行了选取和验证。

It includes four parts: 1 Part I, it introduces the basic knowledge of computer viruses such as computer virus definition, history and important viruses events, features, behavior phenomena, difference with computer software and hardware troubles, damage behavior and capability, classification, naming, future trend, etc; 2 Part II, it introduces the corresponding knowledge of computer systems related to computer viruses such as the composing of software and hardware of the computer system, storage media and its working mechanism, interrupt technologies,.com/.exe/.pe file formats and their working mechanism, etc; 3 Part III, it introduces computer virus mechanism and theory such as computer virus structure, work flow, working mechanism of key modules, typical technologies used to design computer viruses including the corresponding traditional technologies (interrupt filching, memory resident, etc.), the corresponding new routine technologies (self-encrypting, Mutation Engine, etc.), and the corresponding new technologies used by some prevalence computer viruses such as macro viruses, e-mail viruses, worm, hacker, Trojan, mobile phone viruses, the working mechanism analysis of some kinds of typical and prevalence computer viruses such as file-type viruses, macro viruses, e-mail viruses, worm viruses, hacker, Trojan, mobile phone viruses, the analysis of some typical and prevalence computer viruses examples including BALL viruses, WORD macro viruses, WantJob viruses, Code Red viruses, BO Trojan, etc; 4 Part IV, it introduces the defense and killing technologies of computer viruses such as the aim and criterion of computer viruses defense and killing, prevention methods and corresponding technologies, detection technologies (comparison method, character code scanning method, behavior inspecting method, analysis method, etc.), manual and automatic killing technologies, immunity technologies such as IBM digital immunity system, new anti-viruses technology trends (real-time anti-viruses technologies, 32 kernel technologies, active kernel technologies, etc.), some typical virus defense and killing softwares (Symantec AntiVirus product, PC-Cillin AntiVirus product, etc.), the defense and killing method analysis of some kinds of typical and prevalence computer viruses (file-type viruses, macro viruses, worm viruses, hacker, etc.), for example, firewall and intrusion detection technologies for anti-hacker, the defense and killing of some typical and prevalence computer viruses examples including WORD macro viruses, Code Red viruses, BO Trojan, etc.

课程内容具体包括四大部分：1）第一部分，介绍计算机病毒基本知识，包括：计算机病毒定义、病毒发展史及重大事件、病毒特点、病毒表现现象及与软硬件故障的区别、病毒破坏行为及危害性、病毒的传播途径及媒介、病毒分类、病毒的命名及计算机病毒技术发展趋势等内容；2）第二部分，介绍与计算机病毒有关的计算机系统相关知识，包括：计算机系统软硬件组成、存储介质结构及工作原理、计算机系统引导机理及流程、中断技术、。com/。exe/。pe等文件格式及工作机理等内容；3）第三部分，讲解计算机病毒机理，包括：计算机病毒的组成结构、病毒工作流程、病毒引导/触发/感染/破坏等模块的工作机理、计算机病毒所采取的编制技术（包括中断窃取/内存驻留等传统编制技术、自加密/隐形/变形机等新的常规编制技术、宏病毒/电子邮件病毒/网络蠕虫/特洛伊木马/黑客/手机病毒等一些新的流行病毒所采取的编制技术等）、一些类型的典型或流行计算机病毒的工作机理分析（包括：引导型病毒、文件型病毒、宏病毒、电子邮件病毒、蠕虫病毒、黑客、特洛伊木马、手机病毒等）、一些典型或流行的计算机病毒实例剖析（包括：小球病毒、WORD宏病毒、求职信病毒、红色代码病毒、冰河木马等）等内容；4）第四部分，讲解计算机病毒防治技术，包括：计算机病毒防治目的、病毒防治策略及规范、病毒在管理和技术上的预防措施、病毒检查技术（包括：比较法/病毒特征码扫描法/行为监测法/虚拟执行法/分析法等）、手工和自动病毒清杀技术、病毒免疫技术（包括：针对某种一次性感染病毒的基于病毒标签的免疫方法/基于自我完整性检查的计算机病毒免疫方法/IBM的数字免疫系统等）、反病毒技术的新发展（包括：实时反病毒技术/32位内核技术/主动内核技术/以毒攻毒技术等）、诺顿/趋势/金山等公司的病毒防治软件产品、一些类型的典型或流行的计算机病毒（包括：引导型病毒、文件型病毒、宏病毒、蠕虫病毒、电子邮件病毒、手机病毒、黑客、特洛伊木马）的防治措施（其中，也包括介绍面向防范黑客攻击的防火墙、入侵检测技术）、一些典型或流行的计算机病毒防治实例剖析（包括：WORD宏病毒、红色代码病毒、冰河木马v1.1/v2.2等）、多层次病毒防护体系等内容。

the digitized mapping technique is to combine the field data collection system with the computer assisted mapping system in surveys by computer technology.it aims to realize the information collected and processed digitally and automaticaity.the digitized mapping technique can cut short the working time,lighten the labor intensity and enhance the precision of the productions.the system consists of three parts,such as data input,data processing and data output.the survey-record digitized mapping technique is widely used in the digitized mapping working pattern.for its superiority over traditional plane-table mapping in accuracy and efficiency,the large scale digital mapping is becoming more and more popular.compared with traditional analogue mapping,digital mapping has more quality control pivotai points,and its contents and methods are more complex.with the appearance of new technology gps ,the coordinate of different levels controlling points may be surveyed in high precision and it has been applied widely in topographic survey.the operation process of gps electronic tachometer is introduced and its application in topographic survey is br

计算机应用论文，计算机论文， rtk ，全站仪，数字测图，地形测量， gps论文摘要：数字测图是在测量工作中利用电子计算机技术将野外数据采集系统与内业机助制图系统相结合，其目标是实现信息采集处理的数字化、自动化、信息化。数字测图可以缩短作业时间，减轻劳动强度，提高成果精度。数字测图系统主要由数据输入、数据处理和数据输出3部分组成，数字测图作业模式中测记式数字测图应用最为广泛。大比例尺数字测图正以其测图精度高，成图速度快等优势逐步的取代传统的，以平板仪为主的模拟测图。与传统的模拟测图相比，数字测图的质量控制关键点更多、内容与方法更为复杂。gps 新技术的出现，可以高精度并快速地测定各级控制点的坐标，在地形测量中已得到广泛地应用。本文介绍了gps 配合全站仪的作业流程，简要阐明了其在地形测量中的应用。在利用实测数据成图的过程中，解决一些常见的问题，并给出解决的办法及依据，同时给出一些有益的结论，以适应实际使用的需要。

These ideas , usually referred to as the stored-program technique , become essential for future generations of high-speed digital computers and were universally adopted.

这些思想对以后高速数字计算机的发展十分必要，因此被普遍采纳。

The digital computer, in its computation section, can do mainly two things -- add or substract.

数字计算机的运算部分主要有两项功能：加和减。一事物在英语中有两个名称，而在汉语中只有一个，或者为了汉语行文简洁，在不影响句意的情况下，均可不译。例如

The digital computer, in its computation section, can do mainly two things -- add or substract.

数字计算机的运算部分主要有两项功能：加和减。四、有时可不译出，一事物在英语中有两个名称，而在汉语中只有一个，或者为了汉语行文简洁，在不影响句意的情况下，均可不译。

The digital computer, in its computation section, can do mainly two things -- add or substract.

数字计算机的运算部分主要有两项功能：加和减。有时可不译出，一事物在英语中有两个名称，而在汉语中只有一个，或者为了汉语行文简洁，在不影响句意的情况下，均可不译

Other defense projects included gyroscope-based and other complex control systems for gun and bombsights and inertial navigation under Charles Stark Draper's Instrumentation Laboratory, the development of a digital computer for flight simulations under Project Whirlwind, and high-speed and high-altitude photography under Harold Edgerton.

斯塔克。德雷珀的仪表实验室研发的基于回转仪等的复杂控制系统，可辅助枪支，轰炸瞄准仪和惯性导航仪，由旋风计划研发的能模拟飞行轨迹的数字计算机，由哈罗格。艾格顿发明的高速度高海拔摄影技术等。

To deal with the problems and present situation of field data capture by computer in geological mapping in 20 years, this paper has created PRB digital mapping techniques to standardize the digital mapping process and discussed PRB mapping technique-method system, including PRB digital mapping techniques, the model of PRB data and the related process, combinational regulations of PRB process, common mechanism and basic procedure of PRB process, data processing and dictionary of PRB, three-class PRB system,...

从近 2 0年地质填图中计算机野外数据采集技术研究的现状和存在的问题入手，在确定地质填图空间数据表达的基础上，遵循传统地质填图的规律，在不约束地质学家地质思维的前提下，既能满足计算机处理的需要，又能保证地质工作者取全、取准各项地质观测数据，在描述各类地质信息空间关系的基础上，创建了数字地质填图过程标准化和规范化的PRB数字填图技术，并对构成PRB数字填图技术、PRB数据模型、PRB基本过程、PRB基本过程组合的规则、PRB过程的公共机制、PRB过程基本程式、PRB数据操作、PRB字典、三级PRB体系、PRB数据流&栈&、PRB数据质量定量评价体系的PRB数字填图技术与方法体系进行了讨论。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。