hfc-a 中文意思是什麼

hfc-a 解釋

  • hfc : HFC ＝ high-frequency current.
  • a : an 用在以母音音素開始的詞前〉 indefinite art 1 〈普通可數名詞第一次提到時，冠以不定冠詞主要表示類...
  1. The saturated densities, vapour pressures, and latent heats of vaporization for hfc working substances of refrigeration are calculated by using a set of general equations of thermophysical property of liquids

    摘要應用一套通用型流體熱物性方程對hfc類致冷工質的飽和密度、蒸汽壓和汽化潛熱進行計算。
  2. Chapter 4 puts forward a new ethernet / hfc network gateway to transmit internet data through the cable

    第四章介紹了一種新型的在有線電視通道中傳輸ip數據的以太hfc網關。
  3. This paper based on the project that supported by the funds of beijing science and technology committee. the project is a broadband community network management based on hfc

    發達的信息通信干線將高速寬帶網路送到每一個社區，而社區局域網又將高速寬帶網路送到了每一個家庭。
  4. In this thesis, principles of data coding for transferring data among different network hierarchies is described, a channel and program management center and a user authorization center are designed, and the integration and application of the system into sdh / hfc network are investigated and implemented

    本文對系統中支持不同網路體系間數據格式的轉換的數據編碼原理進行了描述。設計了該系統頻道和節目管理中心以及用戶授權管理中心的構架，並對高速數據廣播系統在sdh hfc網路中的集成和應用進行了較為深入的研究。
  5. By adopting qam ( quadrature amplitude modulation ) modulation, we have researched and implemented a high - speed data broadcasting system compatible with dvb ( digital video broadcasting ) standard in the past years, and integrated and applicated the system into sdh / hfc ( synchronous digital hierarchy / hybrid fiber coax ) network for the first time in china

    經過多年的研究，開發出了符合dvb標準、採用qam調制方式的陽光網高速數據廣播系統，同時在國內首次實現了基於sdh hfc網路的高速數據廣播系統集成應用。
  6. With the rapid growth of internet, the demand for network service has gone up quickly. to meet the increasing demands of our local people, we have built a broadband man ( metropolitan - area networks ) in changsha city. this network makes up of gsr ( gigabit switch router ), l3 ( layer three switch ), bas ( broadband access server ), l2 ( layer two switch ), dslam ( digital subscriber line access multiplexer ) and hfc ( hybrid fiber coaxial )

    本文在長沙寬帶城域網現行gsr （吉比特交換路由器） （ l3 （三層交換機） bas （寬帶接入服務器） （ l2 （二層交換機） dslam （數字用戶線接入） hfc （混合光纖同軸技術） ）組網方案和長沙電信已有業務平臺的基礎上，設計了長沙寬帶城域網用戶綜合管理系統。
  7. The combination of cablemodem and hfc is a way to revamp the catv network to a hybrid videodata communications network. however, hfc uses sub - carrier fdm, which requires ad conversion before transmission. in that sense, the transmission quality will be compromised

    雖然cablemodem與hfc配合，是將catv網改造成為視頻、數據混合通信網的一種可能選擇，但hfc採用副載波頻分復用方式，必須進行數模轉換才能傳輸，所以傳輸質量將受到影響。
  8. Upstream channels cover in 5 65mhz, which is a part of the bandwidth of high frequency （ hf ） and very high frequency （ vhf ）. it is liable to incur noises ingress onto the band. since hfc system has the tree - and - branch topology between the fiber - node and subscriber units, subscriber units belonging to one fiber - node share the same upstream channel, forming the " noise funneling " effect

    上行頻帶位於5 - 65mhz之間，這一頻帶為高頻（ hf ）和甚高頻（ vhf ）的一部分，此頻帶易受噪聲干擾；此外，由於從光節點到用戶端為樹型分支結構，同一光節點的多個用戶共享同一通道，形成了漏斗效應。
  9. Based on the study of hfc mac protocol over contention / reservation scheme, an efficient method, which worked on random contention and polling model has been proposed in this article to meet the needs of a multi - priority service access control system

    摘要研究了基於爭用預約機制的混合光纖同軸寬帶接入網媒體接入控制協議原理，提出了隨機爭用與周期查詢排隊系統相結合的終端申請接入方式，使不同優先級的終端申請能以不同的控制機制實現接入。
  10. Having referred to a lot of documents, the author analyzed the hfc network ' s frequency spectrum, topology and channel features

    論文作者查閱了大量文獻，分析了hfc網路的頻譜劃分、拓撲結構、通道特點。
  11. This thesis begins with hfc network theory and docsis, analyses modulation / demodulation process of data communication in hfc. then, several theories are analysed including qam ( quadrature amplitude modulation ), nyquist root square filter, fec ( forward error correction ), map ( bandwidth allocation map ). and digital signal transmission involved the other important international standard ? itu - t j. 83 annex a / b, is discussed

    本文從hfc網路理論和docsis協議入手，分析了hfc數據通信的調制解調過程，對qam調制、奈奎斯特均方根濾波器、前向糾錯（ forwarderrorcorrection ，簡稱fec ） 、 map通信等進行了闡述；還從中探討了電纜數據機需要用到的另一個國際標準ituj . 83annexa / b所設計的mpeg信號的數字傳輸。
  12. Hfc ( hybrid of fiber and coax ) network is a competitive means to support wide varieties of video, voice and data services. the thesis describes and analyzes the system framework, frequency assignment and signal modulation schemes of hfc. recently hfc and adsl are aggressive among broadband access technologies

    本文對hfc網的系統結構、網路拓撲、頻譜分配方案和業務信號的調制方式等進行了詳細的闡述和分析，並且全面地比較了hfc和adsl的優缺點，總結出hfc具有較高的性價比，是我國寬帶接入網的優選方案。
  13. In the hfc network, the uplink channel is applied a spectrum of 5 to 42mhz. although such a spectrum is of good attenuation characteristics, one fact is that other services also share the same spectrum, making the noise introduction a serious concern. also the noise will gradually accumulate, thus severely affecting the transmission performance of cablemodem

    在hfc網路中，上行通道採用5 ~ 42mhz的頻帶，雖然這一頻帶具有良好的衰減特性，但是因為其他服務也採用這一頻帶，所以引入噪聲成了一個嚴重的問題，並且這個噪聲將逐步積累，嚴重地影響cablemodem的傳輸性能。
  14. The thesis makes a thorough analysis on the overall hfc network management platform systems, and on this base, designs emulation programs of hfc network management system and hfc proxy agent, in which it presents numerous c + + codes of high reference value

    文章對整個hfc網管平臺體系結構的進行了詳細的分析，並在此基礎上設計了hfc網路管理站和hfc委託代理的實用程序，給出了大量的c + +代碼，具有較高的參考價值。
  15. At the same time, the performance and the security problems appear and cannot be ignored. so it ' s urgent to build a management system that can manage the analogous devices and digital devices together and can correspond with the catv trunk network management system. to meet the need analyzed above, we recommend using snmp to build the broadband hfc access network management system

    為了保障網路高效安全地運營，寬帶hfc接入網需要一套網管系統；為了與現代有線電視網路的干線網管系統相協調，寬帶hfc接入網需要一套標準的網管系統；為了能同時支持模擬業務和數字業務的管理，寬帶hfc接入網需要一套能同時管理模擬設備和數字設備的標準的網管系統。
  16. Therefore to solve the noises in the upstream channel and to share the sources of the upstream channels becomes one of the key technologies for hfc system to become a multimedia communication platform

    因此，解決上行通道的噪聲問題和上行資源共享是hfc網路能否成為一個多媒體業務通信平臺的關鍵技術之一。
  17. Due to its particular mixed topology of star and branch as well as its asymmetric upstream and downstream, the upstream channel ' s bandwidth allocation algorithm in hfc network has been a research hotspot domestic and abroad

    由於hfc網路特有的星型與樹枝型相混合的拓撲結構以及它的上下行非對稱特性，使得hfc網路中上行帶寬分配演算法的研究成為了國際國內研究的熱點。
  18. The history ^ culture ^ external opportunities and threats ^ internal strengths and weaknesses of l - g have been analysed deeply by using the basic theory and analysis methods of strategic management. there existing external opportunities, such as : broadband network construction, hfc ( hybrid fiber - coax ) upgrading reconstruction, catv digitization. also there existing threats, such as : uncertainty policies and substituted technologies. only a correct company strategy what fully utilize the external opportunities and avoid the internal weaknesses, can a company is promoted to develop

    本文利用戰略管理的基本理論和分析方法，對中國有線電視的現狀和發展、行業內的競爭和競爭對手的優劣勢做了客觀真實的對比研究，得出了對外部環境給公司的發展提供了巨大的發展機會，如：寬帶網建設、 hfc雙向網改造、有線電視的數字化、 「三網融合」 、有線電視網的多功能開發等，同時也有政策的不確定性和技術風險等威脅。
  19. Hfc ( hybrid fiber - coax ) - a cable or network using both coaxial and fiber optic technology. since fiber is more expensive than coaxial, hfc makes for a more cost - effective solution

    混合光纖同軸電纜- -一種既使用同軸技術又使用光纖技術的電纜或網路。因為光纜費用較高、混合光纖同軸電纜通常能夠達到節省費用的目的。
  20. It provides a new dispensing mechanism “ auto - deliver mechanism ”, which utilizes hfc network to transfer program to a lower level. although this mechanism has not been realized in the system now, it provides

    提出了一種全新的節目分發機制? ?自動推送機制，此種利用hfc網進行節目下發的方法具有獨創性和高效性，雖然現階段還未實際運用到系統運營中，但為以後的發展提供了很好的參考方案。
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