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<p> With the increasing demand for data rate and transmission distance, the trend in fiber-optic communications is to build an ultra-high, long-haul transmission system. One of the challenges in this kind of systems comes from the fiber dispersion and dispersion slope. For the wide-band wavelength-division multiplexing (WDM) system or ultra-high bit rate optical time-division multiplexing (OTDM) system, the dispersion slope could be a serious problem to impair the system performance.</p> <p> Many studies have shown that the dispersion and dispersion slope affect the long-haul fiber transmission dramatically, especially for the high-capacity systems. Most of them recommend to totally compensate the dispersion and the dispersion slope simultaneously. And a lot of compensating techniques are proposed. However, it is not easy to realize the simultaneous compensation for the dispersion and dispersion slope in the practical systems. Therefore, the necessity of compensating the dispersion slope in wide-bandwidth systems should be verified.</p> <p> We focus on the study of ultra-high bit rate (160-Gb/s) single-channel fiber-optic transmission. The results show that the dispersion slope is not necessary for the dispersion-managed system when the optimal launch parameters are given. Then we present how to find out the optimum in fiber-optic systems and a novel optimizing technology, space mapping technology (SM) is introduced, which has been successfully applied to the electromagnetic area. An application of SM in optical systems is implemented. By using this smart optimization technique, lots of computational efforts for evaluating the fine model in optimization process are saved.</p> / Thesis / Master of Applied Science (MASc)

No / This paper reports the results of an investigation into the selective laser sintering of a prealloyed high-speed steel powder. The structured development of processing conditions for single lines, single layers and multiple layers of material is reported, as are the flexural modulus and strength of the single- and multiple layer components. Infiltration with bronze was used to improve the mechanical properties of the components and it is concluded that selective laser sintering of high-speed steel allied to bronze infiltration can produce material with the mechanical properties to allow for use in load-bearing applications, but that further work is required to improve the density, mechanical properties and build rate if selective laser sintering is to develop as a general manufacturing process for hard metals.

The increasing capabilities of multimedia appliances demand arithmetic circuits with higher speed and reasonable power dissipation. A common technique to attain those goals is synchronous pipelining, which increases the throughput of a circuit at the expense of longer latency, and it is therefore suitable where throughput takes priority over latency. Two synchronous pipelining approaches, conventional pipelining and wave pipelining, are commonly employed. Conventional pipelining uses registers to divide the circuit into shorter paths and synchronize among sub-blocks, while wave pipelining uses the delay of combinational elements to perform those tasks. As wave pipelining does not introduce additional registers, in principle, it can attain a higher throughput and lower power consumption. However, its throughput is limited by delay variations, while delay balancing often leads to increased power dissipation. This dissertation proposes a hybrid pipelining method called HyPipe, which divides the circuit into sub-blocks using conventional pipelining, and applies wave pipelining to each sub-block. Each sub-block is derived from a single base circuit, leading to a better delay balance and greater throughput than with heterogeneous circuits. Another requirement for wave pipelining to achieve high speed is short signal rise and fall times. Since CMOS wide-NAND and wide-NOR gates exhibit long rise and fall times and large delay variations, they should be decomposed. We show that the straightforward decomposition using alternating levels of NAND and NOR gates results in large delay variations. Therefore, we propose a new decomposition method using only one gate type. Our method reduces delay variations by up to 39%, and it is appropriate for wave pipelining based on standard-cells or sea-of-gates. We laid out a 4x4 HyPipe multiplier as a proof of concept and performed a post-layout SPICE simulation. The multiplier achieves a throughput of 4.17 billion multiplications per second or a clock period of 2.52 four-load inverter delays, which is almost twice the speed of any existing multiplier in the open literature. When the supply voltage is reduced to 1.2 V from 1.8 V, its power consumption is reduced from 76.2 mW to 18.2 mW while performing 2.33 billion multiplications per second. / Ph. D.

This thesis addresses the synthesis of a new mix-metal trimetallic nitride template endohedral metallofullerene (TNT-EMF) and the functionalizations of M3N@C80 (M = Sc, Gd, Ho) under the high-speed vibration milling (HSVM) condition. In addition, this thesis discusses the internal motion of the cluster, Sc3N inside three different carbon cages, C68, C78 and C80. Water-soluble derivatives of endohedral metallofullerenes possess a unique potential for medical applications, such as magnetic resonance imaging (MRI) contrast agents, X-ray contrast agents and nuclear medicine. The TNT-EMFs have inherent advantages over other endohedral metallofullerenes, such as M@C60 and M@C82, due to the encapsulation of up to three metal atoms inside the carbon cages. M3N@C80(OH)m(O)n (M = Sc, Gd, Ho) were synthesized under the HSVM condition and characterized by FT-IR, MALDI-TOF and XPS. The relaxivity studies on these water-soluble derivatives have shown that Gd-based metallofullerols have significantly higher relaxivities than commercially used MRI contrast agents (e.g. OmniscanTM) and can be the next generation MRI contrast agent. The Ho containing species has a high R2/R1 ratio compared to other samples showing the potential to be a T2 agent. In contrast to homonuclear M3N clusters, there is a paucity of mixed-metal cluster cases of TNT-EMFs reported to date because the mixed-metal metallofullerenes are difficult to be separated and purified. In this thesis, CeSc2N@C80 was synthesized, separated in pure form and fully characterized. Single-crystal X-ray diffraction shows that CeSc2N@C80 consists of a four atom asymmetric top (CeSc2N) inside a C80 (Ih ) carbon cage and the nitride ion is not located at the center of the carbon cage but is offset by 0.36 &Aring;. The NMR studies, together with the XPS results, show that CeSc2N@C80 is a weakly paramagnetic system with a single buried f electron spin. A new cage isomer of the Sc3N@C80 (D5h) metallofullerene was also isolated from the Ce-Sc mixture and the cage symmetry was confirmed by single-crystal X-ray diffraction. The internal motion of the metal-nitride cluster, Sc3N within the carbon cages (C68, C78 and C80) was studied at various temperatures using 45Sc NMR spectroscopy. The reorientation barriers (presumably dominated by motion internal to the cage) were calculated for these three TNT-EMFs. The preliminary results show that the quadrupole coupling constant of Sc3N@C80 (Ih) is quite close to that of Sc3N@C68. / Master of Science