减少了的

Over the last 40 years, though, the global adult bluefin tuna population declined by over 80%.

在过去的40年内，全球成年金枪鱼减少了80%。

Ozonesphere has a strong absorption to ultraviolet radiation of short waves in the sunshine.

最近10年来，全球平均平流层中的臭氧减少了3％以上，高纬度地区更为严重。

Primarily, the thesis assays the condition of network framework, the network was divided into three levels in terms of network management in order to establish the distributed method ,and still pointing out the intention and denotation of studying the Topology Discovery.Next, the thesis analyzes SNMP protocol minutely, including its development, principle, and the Network Management system that established on the SNMP protocol. Have analysed MIB in detail and the application way of MIB in network management .The thesis also assays the ICMP protocol, describing its working principle and the format of datagram minutely , and describing two important tools of ICMP- Ping and TraceRoute in detail. On the base of upper analysis, the thesis expounds a kind of distributed Topology Discovery project, and book it in one autonomy system. Topology Discovery was divided into two levels in terms of network management, and analyses the way of linking up between the two level. The thesis minutely assays Router-Level Topology Discovery technology basing on SNMP and Subnet-Level Topology Discovery technology basing on ARP and ICMP. According to these analyses, the thesis explores the specific methodology and the technology of XML data object which using the WinSNMP API to achieve topology discovering system on the development platform of Visual C++, and also analyses the technology of topology analysis and topology graph minutely. Moreover, the thesis assays the technology of basic firewall and Topology Discovery response strategy. Finally, the thesis analyses the underlying blind problem of the topology finding, and also analyses the reason that the blind problem produced and the way that reduced. The distributed algorithm that this paper puts forward has a certain directive significance in wireless network or other fields.

本文首先分析了网络结构状况，将网络从网络管理的角度划分为三个层次，为分布式的方法奠定了基础，同时还指出拓扑发现研究的目的及意义；接着本文分析了SNMP协议，详细分析了SNMP协议的发展状况，协议的工作原理，以及由SNMP协议基础上建立的SNMP网络管理体系，详细分析了MIB，以及MIB在网络管理上的应用方式；本文又分析了ICMP协议，详细描述了ICMP的工作原理和数据报格式，并详细描述了ICMP的两个重要工具-Ping 和TraceRoute；然后本文在结合上述分析的基础上，提出了一种分布式的拓扑发现方案，将拓扑发现拟订在一个自治系统内，将拓扑发现从网络管理角度划分为路由器级和子网级两个层次，分析了两个层次之间的衔接方式，同时从拓扑地域的角度将拓扑发现过程分布化，分析了分布式算法的具体方法和分布式结点之间的数据通讯方法，本文详细分析了基于SNMP的路由器级拓扑发现技术和基于ARP和ICMP的子网级拓扑发现技术；根据这些分析，本文利用XML数据对象作为分布式算法中的数据对象，分析了XML的技术，本文使用Visual C++开发平台实现网络拓扑发现系统，详细分析了使用WinSNMP API实现基于SNMP的路由器级拓扑发现和基于ARP的子网级拓扑发现，分析了使用Winsock编程实现基于ICMP的子网级拓扑发现，本文还对拓扑分析和拓扑图的绘制技术作了较细致的分析；本文最后还分析了基本防火墙技术，分析了几种类型的防火墙对拓扑发现带来的影响，以及在拓扑发现时的应对策略，本文还分析了拓扑发现中可能产生的盲点问题，分析了盲点产生的原因以及拓扑发现中减少盲点的方法。

Children feel comfortable sharing their problems with parents, reducing the risk of peers having an undue influence on their lives.

孩子们不再觉得和父母共同解决问题让他们不舒服，这就减少了某些同龄人对孩子们的不良影响。

But decreases the advantages to another unit or function.

却减少了对其他单位或职能的好处。

Because brushless motor has no gears or deceleration devices, reducing the unreliability of the motor wear and tear.

由于无刷电机没有齿轮或减速装置，减少了电机磨损的不可靠性。

It improves the performace of Uplink bandwidth utilization and reduces bandwidth waste,improves QoS of the system .

算法提高了上行信道的带宽利用率，减少了带宽的浪费，提高了系统的QoS保证。

The Brazilian government dispatched8 25 million free condoms to help prevent the spread of venereal diseases.

巴西政府免费派送了2500万只安全套。以减少性病的传播。

In order to safeguard Carnival, the Brazilian government dispatched8 25 million free condoms to help prevent the spread of venereal diseases.

为了给狂欢节"保驾护航"，巴西政府免费派送了2500万只安全套，以减少性病的传播。

All of these provide convenient, fast and veracious programming data, reduce programming time in the practical production and greatly improve the efficiency of manufacturing.

这给数控编程提供了方便、快捷、准确的编程数据，减少了实际生产中的编程时间，可大大提高其生产效率。

In the negative and interrogative forms, of course, this is identical to the non-emphatic forms.

。但是，在否定句或疑问句里，这种带有"do"的方法表达的效果却没有什么强调的意思。

Go down on one's knees;kneel down

屈膝跪下。。。下跪祈祷