京都大学 / 新制・課程博士 / 博士(工学) / 甲第23484号 / 工博第4896号 / 新制||工||1765(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 渦岡 良介, 教授 木村 亮, 准教授 澤村 康生 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Underlay signaling is a robust physical layer technique, allowing for transmitting a very low power signal in conjunction with the primary signals across the entire frequency band of the primary signals. The secondary users of the secondary network (i.e., a wireless network consisting of primary and secondary networks) primarily utilize the underlay, which increases spectral efficiency and improves the network capacity. This thesis focuses on underlay signaling in the context of the cellular (primary) network, where the underlay is an auxiliary channel made available to the primary users and the network, that is, the base stations and users of the cellular network. The current fifth-generation (5G) cellular networks are constructed using Orthogonal Frequency Division Multiplexing (OFDM) modulation. Hence, this thesis delves into the study of underlay coexistence with OFDM, specifically 5G, by performing extensive simulations and analytical analysis and investigating the impact of underlay signaling on the throughput performance of 5G networks. We develop the underlay signaling based on the frequency-domain spread spectrum and add the underlay signal prior to the Inverse Fast Fourier Transform (IFFT) operation of OFDM. Furthermore, we present a real 5G setup built on the srsRAN project, where we showcase a proof-of-concept demonstration of underlay coexistence with the 5G over the air, where the 5G base station transmits both 5G NR and underlay signal simultaneously. Through our research, we conclusively demonstrate that a low-data rate underlay signal can be successfully transmitted alongside the existing 5G signal. Our study concludes by carefully selecting the appropriate design parameters, such as the signal-to-interference power level (5G power in relation to underlay), spreading factor, and coding gain at which we can reliably detect and decode underlay signals having no impact on the 5G performance. The integration of underlay in 5G brings forth a multitude of benefits using underlay for military and tactical applications, massive Machine Type Communications (mMTC) alongside Ultra-Reliable Low Latency Communications (URLLC), and the offloading of crucial control information of 5G to the underlay channel. Thus, this underlay operates as a low-data rate error-free conduit, with the potential to provide Low Probability of Interception (LPI) and Low Probability of Detection (LPD) attributes and heightened reliability while concurrently transmitting with the 5G NR, bolstering the overall effectiveness of the communication. / Master of Science / Underlay signaling is a technique that allows for transmitting a low-power signal alongside the primary signals, occupying the entire frequency band of the primary signals. The secondary users of the secondary network (i.e., a wireless network consisting of primary and secondary networks) primarily utilize the underlay, which increases spectral efficiency and improves the network capacity. This thesis focuses on underlay signaling in the context of cellular (primary) networks where the underlay is an auxiliary channel made available to the primary users and network, that is, the base stations and users of the cellular network. The current fifth-generation (5G) cellular networks are constructed using Orthogonal Frequency Division Multiplexing (OFDM) modulation. OFDM is a multicarrier modulation scheme that divides the available frequency band into multiple narrow subcarriers, each carrying a portion of the data. The key advantage of OFDM is its ability to combat frequency-selective fading, where different frequencies experience different levels of fading and interference. By using many closely spaced sub-carriers, OFDM can effectively mitigate the impact of fading, allowing for robust and reliable communication even in challenging channel conditions. Thus, this thesis investigates the co-existence of underlay signaling and OFDM in 5G. We develop the underlay signaling based on the frequency-domain spread spectrum. Extensive simulations and analytical analysis are performed to understand the impact of underlay signaling on OFDM performance in terms of bit error rates and throughput. Additionally, a real 5G setup is presented, demonstrating a proof-of-concept of underlay co-existence with 5G NR, where the 5G base station transmits both 5G NR and underlay signal simultaneously. Through the research, it is conclusively demonstrated that a low-data rate error-free underlay signal can be successfully transmitted alongside the existing 5G signal. The integration of underlay in 5G brings forth a multitude of benefits using underlay for military and tactical applications, massive Machine Type Communications (mMTC) alongside Ultra-Reliable Low Latency Communications (URLLC), and the offloading of crucial control information of 5G to the underlay channel. Thus, this underlay operates as a low-data rate error-free conduit, characterized by its low interception and low detection attributes, enhancing reliability while concurrently transmitting with 5G NR, bolstering the overall effectiveness of the communication.

In this thesis, a stacked double-layer flat plate oscillating heat pipe charged with degassed DI water was designed, fabricated and characterized under different operating conditions (orientation, system or cooling water temperature and heat load). The oscillating heat pipe was designed to dissipate 500 W within a footprint of 170 x 100 mm2. The oscillating heat pipe had a total of 46 channels (23 channels per layer) with a nominal diameter of 2 mm. Tests were performed to characterize the performance of the oscillating heat pipe for (i) axial heat transfer and (ii) as a heat spreader. The stacked oscillating heat pipe showed a distinctive feature in that it overcame the absence of the gravity effect when operated in a horizontal orientation. The thermal performance was found to be greatly dependent on the operational parameters. The oscillating heat pipe was able to dissipate a heat load greater than 500 W without any indication of dry-out. An increase in the cooling water temperature enhanced the performance and was accompanied with an increase in the on/off oscillation ratio. The lowest thermal resistance of 0.06 K/W was achieved at 500 W with a 50℃ cooling water temperature, with a corresponding evaporator heat transfer coefficient of 0.78 W/cm2K. The oscillating heat pipe improved the heat spreading capability when locally heated at the middle and end locations. The thermal performance was enhanced by 27 percent and 21 percent, respectively, when compared to a plain heat spreader. / Thesis / Master of Applied Science (MASc)

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Scanning spreading resistance microscopy (SSRM) with its high spatial resolution and high dynamic signal range is a powerful tool for two-dimensional characterization of semiconductor dopant areas. However, the application of the method is limited to devices in equilibrium condition, as the investigation of actively operated devices would imply potential differences within the device, whereas SSRM relies on a constant voltage difference between sample surface and probe tip. Furthermore, the standard preparation includes short circuiting of all device components, limiting applications to devices in equilibrium condition. In this work scanning dynamic voltage spreading resistance microscopy (SDVSRM), a new SSRM based two pass atomic force microscopy (AFM) technique is introduced, overcoming these limitations. Instead of short circuiting the samples during preparation, wire bond devices are used allowing for active control of the individual device components. SDVSRM consists of two passes. In the first pass the local sample surface voltage dependent on the dc biases applied to the components of the actively driven device is measured as in scanning voltage microscopy (SVM). The local spreading resistance is measured within the second pass, in which the afore obtained local surface voltage is used to dynamically adjust the terminal voltages of the device under test. This is done in a way that the local potential difference across the nano-electrical contact matches the software set SSRM measurement voltage, and at the same time, the internal voltage differences within the device under test are maintained. In this work the proof of the concept could be demonstrated by obtaining spreading resistance data of an actively driven photodiode test device. SDVSRM adds a higher level of flexibility in general to SSRM, as occurring differences in cross section surface voltage are taken into account. These differences are immanent for actively driven devices, but can also be present at standard, short circuited samples. Therefore, SDVSRM could improve the characterization under equilibrium conditions as well.

Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Bibliography: leaves 51-58. / by Jeremy D. Duschenes. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1980. / Microfiche copy available in Archives and Science. / Vita. / Bibliography : leaves 206-213. / by John Shai-Fu Shih. / Ph.D.