This thesis investigates the fundamental building blocks of physical-layer network coding (PNC). Most prior work on PNC focused on its application in a simple two-way-relay channel (TWRC) consisting of three nodes only. Studies of the application of PNC in general networks are relatively few. This thesis attempts to fill this gap by three steps: / In first step, we put forth two ideas: 1) A general network can be decomposed into small building blocks of PNC, referred to as the PNC atoms, for scheduling of PNC transmissions. 2) We identify nine PNC atoms, with TWRC being one of them. / In second step, we formulate the PNC scheduling problem as a linear program based on the atom-decomposition. Three major results are got from performance valuation: First, the throughput performance of PNC is shown to be significantly better than those of the traditional multi-hop scheme and the conventional network coding scheme. For example, under heavy traffic volume, PNC can achieve 100% throughput gain relative to the traditional multi-hop scheme. Second, PNC decomposition based on a variety of different PNC atoms can yield much better performance than PNC decomposition based on the TWRC atom alone. Third, three out of the nine atoms are most important to good performance. Specifically, the decomposition based on these three atoms is good enough most of the time, and it is not necessary to use the other six atoms. We have also designed a low-overhead MAC protocol to coordinate the transmissions of different nodes according to the scheduling results of PNC decomposition. / In third step, we investigate ARQ (Automatic Repeat request) designs for PNC systems (building blocks). The above building blocks studies assumed what is sent always get received. In practice, that is not the case. Error control is needed to ensure reliable communication. Here, we focus on the use of ARQ to ensure reliable PNC communication. In some of PNC building blocks, receivers can obtain side information through overhearing. Although such overheard information is not the target information that the receivers desire, the receivers can exploit the overheard information together with a network-coded packet received to obtain a desired native packet. This leads to throughput gain. The availability of overhead information and its potential exploitation make the ARQ design of a network-coded system different from that of a non-network-coded system. In this these, we lay out the fundamental considerations for such ARQ design: 1) We address how to track the stored coded packets and overheard packets to increase the chance of packet extraction, and derive the throughput gain achieved by tracking 2) We investigate two variations of PNC ARQ, coupled and non-coupled ARQs, and prove that non-coupled ARQ is more efficient; 3) We show how to optimize parameters in PNC ARQ—specifically the window size and ACK frequency—to minimize the throughput degradation caused by ACK feedback overhead and wasteful retransmissions due to lost ACK. Our throughput analyses and performance evaluations indicate that for our investigated atoms, our PNC ARQ yield considerable throughput gains. / In a conclusion, the decomposition based on a variety of different PNC atoms that we investigated can yield much better performance than the traditional multi-hop scheme and the conventional network coding scheme. In practical wireless systems where transmission errors can occur, adopting our PNC ARQ design can efficiently maintain the throughput gain achieved by PNC atom decomposition. / 本論文致力於研究基於物理層網絡編碼（PNC, Physical-layer Network Coding）的基礎構建模塊。現有的物理層網絡編碼的研究大都基於最簡單的雙向中繼信道（TWRC）系統上。TWRC是一個由三節點組成的小型通信網絡——兩個終端節點通過一個中繼節點通信。而基於大型網絡應用的PNC研究卻非常少見。為了填補這一空白，本論文分三步驟進行PNC研究: / 研究第一步，我們提出兩個問題： 1）為了PNC網絡調度，一個網絡可以被分解成若干小的PNC基礎構建模塊。 2）我們發現了除9個基本的PNC構建模塊（包含PNC TWRC）。 / 研究第二步，我們通過建立基於模塊分解的線性規劃方程來解決PNC網絡的調度問題。從性能評估中我們發現了三個重要結論： 第一，PNC分解的輸出效率遠高於傳統的多步傳輸和普通的網絡編碼傳輸。例如，在網絡運輸量很重的情況下，相比于傳統的多步傳輸，PNC分解傳輸可以取得100%輸出增益。第二，基於多種不同PNC模塊的分解傳輸，其效率高於只基於PNC TWRC的分解傳輸。第三，在我們研究的九個模塊中，三個模塊對輸出的貢獻最多。我們同時為PNC調度專門設計了介質訪問控制（MAC）的網絡協議。 / 研究第三步，我們研究了PNC系統的自動重傳請求（ARQ）設計。上述的PNC模塊研究假設了網絡的傳送總能被成功接收。但不符合實際的網絡狀況。需要採取錯誤控制來保護實際傳輸的穩定性。這裡，我們致力於研究用ARQ來保證PNC系統的穩定傳輸。在一些PNC模塊中，接受點可以利用旁聽到的信息包裹來解碼編碼過的包裹以獲得需要的自然包裹。這種對於旁聽信息的利用可以增加網絡的傳輸效率。同時也使PNC系統的ARQ設計不同於傳統網絡。在本論文中，我們列舉了三個基本的PNC ARQ設計原則： 1）我們強調了如何追蹤存儲的和旁聽到的信息包裹來增加提取有效包裹的機會并推導出了由此取得效率增益。 2）我們研究了兩種PNC ARQ系統，一種是綁定的ARQ，一種是非綁定的ARQ,并證明非綁定的ARQ效率更高。 3）我們展示了如何優化PNC ARQ的參數設置——傳輸窗口的大小和確認通知（ACK）的頻率——以最小化由ACK開銷和不必要的重傳引起的輸出損失。 / 總結來講，基於不同PNC模塊的網絡分解調度方法比傳統的多步傳輸方法和普通的網絡編碼傳輸更有效率。在實際的無線網絡中，當網絡傳輸出現錯誤時，採用我們的PNC自動重傳設計可以有效的保留PNC模塊分解所取得網絡增益。 / He, Jianghao. / Thesis Ph.D. Chinese University of Hong Kong 2015. / Includes bibliographical references (leaves 126-128). / Abstracts also in Chinese. / Title from PDF title page (viewed on 24, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

The problem considered in this study arose from the need for an emperlcal analysis of the sale value of land to determine if the increased price benefits of the governmental flue-cured tobacco program have been absorbed by higher land rents. If acreage allotments giving the right to produce tobacco under the program are capitalized into farmland values to an appreciable extent, the program objective of increasing farm incomes would be partially defeated through higher rents. The objective of this study was to determine the extent to which allotments have been capitalized into land values. Data on sale value of farms and factors expected to influence the farm sale value were secured from primary public record sources for the four-year period from 1954 to 1957 in two distinctly different flue-cured tobacco regions--Pittsylvania County, Virginia, and Wilson, Greene, and Pitt Counties, North Carolina. These data were analyzed by a multiple regression statistical technique designed to measure the value of an acre of tobacco allotment es a right to produce. The statistical coefficients indicated that an acre of tobacco allotment increased in value from $962 in 1954 to $1,673 in 1957 for Pittsylvania County and from $1,830 to $3,308 for Wilson, Greene, and Pitt Counties. The size of the values for an acre of tobacco allotment as well as the increase in values over the four-year period during which allotments were reduced under the program by 33 percent indicate that an appreciable proportion of the price·rais1ng benefits of the program have been capitalized into land values. / Master of Science

The objective of this study was to investigate what effect the concentration of microorganisms would have on substrate removal, microbial substrate storage, and oxygen utilization at a constant food-to-microorganism ratio. Batch experiments were conducted, under aerated and completely mixed conditions, using a domestic wastewater, a paper mill wastewater, and a food processing wastewater. A series of three batch experiments were run for each of these wastes. The food-to-microorganism ratio for each series was kept constant while the mixed liquor suspended solids concentration was varied for each of the experiments within the series. The following analyses were conducted on samples that were withdrawn at specified time intervals: filtered and settled COD, oxygen uptake, mixed liquor volatile suspended solids (MLVSS), pH, protein concentration and carbohydrate concentration. No significant uptake and subsequent release of organic substrate was observed for any of the wastewaters studied. For the same F/M ratio, the rate of removal of organic substrate and the degree to which it was removed in the activated sludge system was found to be a direct function of the MLVSS concentration. The change in the cellular carbohydrate to cellular protein ratio in the activated sludge during substrate metabolism was a function of the MLVSS concentration. As the MLVSS concentration increased, the carbohydrate to protein ratio, which is an indicator of substrate storage, also increased, even though the F/M ratio was held constant. / Master of Science