【正文】 這些步驟是以大量不同次序排列的各種模塊，每一模塊通常容許一些參數(shù)值的技術指標，從而進一步擴大了為獲得預期結果而可能采取的處理方案的選擇范圍。遠程醫(yī)療能否取得一般性的成功，將在很大程度上取決于是否能夠滿足真正的挑戰(zhàn)(使這樣的系統(tǒng)接近盡可能的標準方法，在可用的通用原則以及可接受的質量和成本上盡可能采用電信系統(tǒng)。 continued surgical procedure is in certain cases dependent on this type of pathology service, and hospitals without access to frozen section service cannot treat such patients, but has to refer them to another hospital.在某些情況下持續(xù)的外科手術是依賴于這種類型的病理服務，醫(yī)院沒有進入冰凍切片服務時是不能治療這類病人,但他們求助于另一個醫(yī)院。 sources of the information are often reports in the media, reports that are inplete, usually written before all relevant information is gathered, and subject to other sources of inaccuracies and biases.這些資料的來源通常是媒體報道,由于報告不完整,通常在寫之前進行相關信息收集,并受其他來源的錯誤和偏見。這些資源為您提供你需要實現(xiàn)和維護一個入侵管理生命周期。 in most applications scene shading is such that objects cannot be separated from background by any threshold, and even when an appropriate threshold value exists in principle it is notoriously difficult to find it automatically.不幸的是，在大多數(shù)應用中場景陰影的物體不能被任何閾值從背景分離，甚至當一個合適的閾值原則存在但是難以自動找到它。 products use mercially available speech toolkits, such as the IBM’s ViaVoice, Dragon’s Naturally Speaking, or Lamp。 of these early systems had advantages that seemed exciting and intuitive when demonstrated with “toy” programs, but ran into difficult problems when attempts were made to extend them to more realisticallysized programs.這些早期的系統(tǒng)優(yōu)勢，似乎令人興奮的和直觀的表現(xiàn)與“玩具”的項目，但遇到困難的問題時，曾試圖擴大他們更多的實際程序的大小。 a television scanning generator using a pair of freerunning relaxation oscillators, freerunning frequencies of the oscillators are set slightly below the horizontal and vertical pulse rates, and the stripped pulses are used to trigger the oscillators prematurely and thus to synchronize them to the line and halfframe rates.在采用一對自由張弛振蕩器的電視掃描發(fā)生器中，振蕩器的自由頻率被設置得略低于水平和垂直（掃描）頻率，分離出來的脈沖被用來提前觸發(fā)振蕩器從而使它們與行頻和半幀頻（場頻）同步。 image is a 2dimensional distribution of energy, typically of visible electromagnetic radiation (light) but can also be of xrays, ultraviolet, infrared or other radiation: electrons, acoustic waves or even nuclear particles.圖像是一個能量的二維分布，通常是可見的電磁輻射（光）也可以是X射線，紫外線，紅外線或其它輻射：電子，聲波甚至核粒子。例如,如果音頻包含聲音頻率高達8000赫茲, 你需要一個采樣率為每秒16000個樣本復制本音頻準確數(shù)字形式。 higher the sampling rate, the closer the shape of the digital waveform will be to the original analog waveform. Low sampling rates limit the range of frequencies that can be recorded, which can result in a recording that poorly represents the original sound.采樣率越高，數(shù)字波形的形狀越接近原來的模擬波形。在數(shù)字存儲,原始波形分解成單獨的采樣。這是在壓力下將空氣分子周圍的空氣分子，從而推動下一組空氣分子等等,導致一波高壓進入空氣。馬修斯在貝爾實驗室于開發(fā)了音樂于20世紀60年代。7. As mentioned previously, these applications have tended to open up more slowly than originally predicted, as cost was really not much of a consideration in telemunications, where equipment costs are swamped by other considerations.如前所述，（線路）成本并非電信系統(tǒng)中真正重要的考慮因素，通信設備的成本主要受到其他因素的制約，因此這些應用比預料的出現(xiàn)得慢。3. If one were to transmit such information without impressing it on an optical carrier but instead on a radio frequency (RF) carrier a bit higher than the maximum rate, the transmission wavelength of the RF carrier would be centimeters or larger.如果傳輸這樣的信息不是將它加載到光纖上，而是加載在略高于最大速率的射頻載波上，則此射頻載波就會是厘米波或是波長更長一些的波。6. The degradation of the transmitted signal is a result of signal distortion due to imperfect response of the channel and due to undesirable electrical signals (noise) and interference. Noise and signal distortion are two basic problems of electrical munication.傳輸信號的退化是信號失真的結果，而這種失真又是由信道的非理想響應及不想要的電信號（噪聲）和干擾引起的。然而電信與計算機技術的緊密聯(lián)系使得通信從概念到內容和手段都發(fā)生了重大的變化。這種傳送要求信號隨時間發(fā)生的變化不能在接收端預測。為了實現(xiàn)最大的頻譜效率，子載波之間的間隔通常選取為符號周期的倒數(shù)。這是因為在時域上符號周期能選取得比多徑延遲時間長，而在頻域上每個符號只占整個信道帶寬的一小部分，因此多徑衰落的影響被分散到許多符號上，其結果是許多符號都發(fā)生輕度的畸變，而不是使某些符號被完全破壞。Unit 5 Exercises (1) Translate the following passage into Chinese.OFDM consists of a large number of subcarriers equally spaced in a frequency band, each may be digitally modulated by a same scheme such as PSK, QAM, etc., or by different schemes. A serially transmitted sequence is divided into a number of sections, each having N symbols, and the N symbols in each section are used to modulate N carriers for simultaneous transmission. Therefore OFDM is essentially a parallel modulation system. When the number of subcarriers is sufficiently large, the system can resist multipath interference. This is because that, in the time domain, a symbol duration longer than the multipath delay can be chosen, while in the frequency domain, each symbol only occupies a small portion of the channel’s frequency band. Thus, the effect of multipath fading spreads over many symbols, resulting in slight distortion to many symbols rather than plete destroy of a few symbols. In this way, correct demodulation is not affected so that the signal can be accurately recovered at the receiver. In an OFDM system, the principle of choosing the subcarrier interval is to make the subcarriers mutually orthogonal within the entire symbol period. Thus, even if spectral overlap exists between the subcarriers, the symbols can still be recovered without loss. In order to realize maximum spectral efficiency, the interval between subcarriers is usually chosen to equal the reciprocal of the symbol duration T. Therefore the subcarrier frequencies in the base band are fn = n/T, (n = 0, 1, ... , N1). Denoting the nth modulating symbol as X(n), the OFDM waveform within a symbol duration can be expressed as: (1)Sampling this waveform at t = T/N yields (2)It is observed from the above expression that x(k) and X(n) form a discrete Fourier transform pair, therefore the baseband OFDM waveform can be generated from the discrete Fourier transform of N modulating symbols. When N=2m where m is an integer, the fast algorithm of IDFT is easy to implement.OFDM由大量在頻率上等間隔的子載波構成。5. Modulation is the systematic variation of some attribute of a carrier waveform such as the amplitude, phase, or frequency in accordance with a function of the message signal. It is used in munication systems for matching signal characteri