This thesis attempts to investigate the performance of various reactive power compensation devices, examine the mechanism of reactive power compensation for HVDC systems, and develop guidelines for the design of reactive power compensation schemes for HVDC systems. The capabilities of various reactive power compensators to enhance power system stability are compared in both steady and transient states. An understanding of the capabilities of these compensators provides a basis for further investigation of their performance in HVDC systems. The reactive power requirements of HVDC converters are studied. The voltage dependencies of the HVDC converters at different control modes are derived, which allow for predictions of how HVDC converters impact AC system voltage stability. The transient performance of reactive power compensation options for HVDC Systems is studied by comparing their behavior during DC fault recovery, Temporary Overvoltage (TOV), and commutation failure. How to quantify the system strength when reactive compensators are connected to the converter bus is investigated. A new series of indices are developed based on the Apparent Short Circuit Ratio Increase (ASCRI). The inertia of a synchronous condenser and its impact on the frequency stability of an AC/DC system are discussed. By modelling the inverter side AC system in greater detail, the frequency stability and rotor angle stability following fault transients is examined based on time domain simulation. Finally, a guideline for designing dynamic reactive power compensation for HVDC systems is proposed.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 208-220).

No description available.

Genetic toxicology assesses the genotoxic potential of chemicals in consumer products, pharmaceuticals and from agricultural and industrial processes. Such assessment is integral in hazard identification and risk assessment to prevent unnecessary human exposure and limit cancer risk. Human risk assessments for genotoxic alkylating agents were based upon linear dose-response models where genotoxicity accrues proportionally with dose. Evidence is accumulating to support a non-linear dose-response at low doses of ethyl methanesulfonate (EMS), a model alkylating agent. For acceptance of non-linear dose responses, a strong explanatory mechanism of action needs to be elucidated. In the following work, low dose mutagenic effects of methyl nitorosurea (MNU), the most potent alkylating agent, have been examined in AHH-1 human lymphoblastoid cells using the HPRT assay. An increase in mutant frequency was not observed until 0.01pg/ml MNU (LOGEL, Lowest Observed Genotoxic Effect Level) with a No-Observed Genotoxic Effect Level (NOGEL) at 0.0075pg/ml MNU. Of interest, is the apparent hormesis induced at 0.0025pg/ml MNU. The principle adduct responsible for MNU mutagenesis is 0 6Methylguanine (06MeG) that miscodes during replication and becomes fixed as GC→AT transitions. Accordingly, the non-linear increase in mutant frequency is accompanied by a non-linear increase in GC→AT transitions. Furthermore, evidence is provided that implicates methlyguanine methyltransferase (MGMT) in protecting DNA from MNU induced mutagenesis by repairing 0 6MeG at low doses, thereby creating the NOGEL. AHH-1 cells treated with 0 6Benzylguanine (06BG), to inactivate MGMT, were hypersensitive to low dose MNU mutagenesis. At 0.0075pg/ml MNU, there was a three-fold increase in mutant frequency and an increase in proportion of GC-^AT transitions, from 28% to 48% in MGMT inactivated cells. This thesis presents a non-linear dose-response for MNU with a strong biological mechanism of action involving DNA repair.

No description available.

The use of radio frequency (rf) plasma techniques to produce fine structures of precise geometry is widespread in the microelectronics industry. An important factor influencing the functionality of fabricated devices is the wall angle of these structures. In certain applications vertical walls are required - for example to minimise mask degradation and maximise gate densities; in others a sloping sidewall is preferred - to minimise stress in metal coatings when making electrical contact through 'via' holes, for instance. This fine control cannot be achieved on micron and sub-micron scale devices using conventional 'wet' chemical processing techniques and has led to the adoption of so-called 'dry' processing techniques using plasmas. Both vertical and sloping wall profiles can be produced depending upon the plasma conditions. It is apparent, therefore, that a thorough understanding of the processes affecting the etch profile is important. Reactive ion etching (RIE) has been employed to produce micron, and sub-micron size structures in polyimide using an oxygen plasma. Present models of etch directionality all make the initial assumption that the directional component of the etching process can be attributed solely to O2+ ion bombardment of the exposed horizontal surface of the wafer driven by the electric 'sheath' field developed above the electrode. Whether species such as O+ and even multiply charged reactive species such as O++ and O+++ can legitimately be neglected in formulating such a model has yet to be established. That such multiply ionized species exist, however, is highly probable given that plasmas are well known to emit strongly in the ultraviolet. The etching system developed to investigate these problems was equipped with diagnostic techniques including optical emission spectroscopy, mass spectrometry, and a grid energy analyser. The optical emission spectrometer was novel in being capable of measuring emission from the far-ultraviolet emission spectrum of the plasma and was therefore able to detect the high energy ultraviolet light and the singly and multiply ionised species from which this radiation is emitted. Using this technique the role of multiply-ionised species in controlling etch anisotropy was investigated. Results are also presented, obtained from a retarding grid, particle energy analyser built into the surface of the earth electrode, which indicate increased charged particle flux and energy at low pressure providing further information with regard to the process dynamics. The influence of gas pressure and rf excitation frequency on the resultant etch profile have been investigated. Results are presented showing the presence of doubly-ionised atomic oxygen O++ in the plasma. It is shown in this work that O++ also has a role in etch anisotropy at low pressure. This and other more highly charged species need to be considered, therefore, in formulating models of etch anisotropy, etch rate, and etch chemistry and reaction mechanisms. The role of ultraviolet irradiation which is itself of sufficient energy to induce surface reactions must also be considered.

Thermite compounds have received a renewed interest due to their ability to store large quantities of energy that is comparable to conventional energetic materials. Such reactive materials can be manipulated to create a nanolaminated structure. It has been shown that an increase in the fraction of nanolaminated particles can reduce the ignition temperature and increase reactivity. In the present study, methods to lower the ignition temperature of aluminium copper-oxide (Al-CuO) are assessed. Arrested reactive milling (ARM) was used on stoichiometric Al-CuO powders to increase the nanolamination and reduce the ignition temperature to 840 Kelvins (K). Milling alone not only reduced the ignition temperature slightly, but for milling times greater than 30 minutes, intermediate phases were produced, which had negative impacts on the reaction characteristics. Another method to reduce the ignition temperature of Al-CuO involved creating a hybrid mixture using a compound with a lower ignition temperature to further decrease the ignition temperature of Al-CuO. ARM was used to lower the ignition temperature of a nickel aluminium (Ni-Al) intermetallic compound down to 480 K. Hybrid mixtures were then created with varying concentrations of milled and unmilled Al-CuO-Ni. Powders were then tested in a tubular furnace to determine the ignition temperature dependence on heating rate and concentration of constituents. It has been shown that an unmilled hybrid mixture with 75% and 50% concentration of Al-CuO has an ignition temperature of 840 K. Higher concentrations of Ni-Al resulted in lowered ignition temperatures which varied between 600 K and 480 K. A milled hybrid mixture has lower ignition temperatures than an unmilled mixture. It was shown that a milled hybrid mixture with a 75% concentration of Al-CuO has an ignition temperature of 840 K, corresponding to pure Al-CuO. The ignition temperature of the milled hybrid mixture was reduced to approximately 520-620 K for concentrations of Ni-Al of 50%, and 473-573 K for concentrations of 75% Ni-Al.

Yes / The “sliding graft copolymer” (SGC), in which many linear poly-ε-caprolactone (PCL) side chains are bound to cyclodextrin rings of a polyrotaxane (PR), was prepared and employed to toughen brittle polylactide (PLA) with methylene diphenyl diisocyanate (MDI) by reactive blending. The SGC was in situ crosslinked and therefore transformed from a crystallized plastic into a totally amorphous elastomer during reactive blending. Meanwhile, PLA-co-SGC copolymer was formed at interface to greatly improve the compatibility between PLA and SGC, and the chain extension of PLA also occurred, were confirmed by FTIR, GPC, SEM, and TEM. The resulting PLA/SGC/MDI blends displayed super impact toughness, elongation at break and nice biocompatibility. It was inferred from these results the crosslinked SGC (c-SGC) elastomeric particles with sliding crosslinking points performed as stress concentrators and absorbed considerable energy under impact and tension process. / This work was supported by the National Natural Science Foundation of China (50933001, 51221002 and 51320105012).

Color removal of some reactive dyes (Blue 19, Black 5 and Red 195) using a local Poly Aluminium Chloride (PAC) was investigated with Jar-test experiment. The dyes were removed (above 94%) at optimal pH 7 (Red 195) and pH 10 (Blue 19 and Black 5). The PAC dosage of 220 mg/L (Blue 19 and Black 5) and 160 mg/L (Red 195) were found to be best for decreasing dye up to 50 mg/L (Black 5, Red 195) and 100 mg/L (Blue 19). Reaction time and agit ation speed also affected the decolorization process. That result indicates that Vietnamese PAC can be a robust and economical coagulant for discolorization of reactive dyeing process. / Chất keo tụ Poly Aluminium Chloride (PAC) sản xuất tại Việt nam được ứng dụng khử màu của một số màu nhuộm hoạt tính phổ biến (Blue 19, Black 5 and Red 195) trên thí nghiệm Jar-test. Kết quả cho thấy màu bị loại gần như hoàn toàn (trên 94 %) tại pH 7 (Red 195) hoặc 10 (Blue 19 và Black 5). Nồng độ PAC đạt hiệu quả tốt nhất tại 220 mg/L (Blue 19 và Black 5) và 160 mg/L (Red 195) ứng với nồng độ màu 50 mg/L (Black 5, Red 195) hay 100 mg/L (Blue 19). Thời gian phản ứng, tốc độ khuấy cũng có tác động đến hiệu suất khử màu. Kết quả nghiên cứu cho thấy PAC sản xuất tại Việt nam không những là một chất keo tụ tốt mà còn rất kinh tế cho việc khử màu hoàn toàn trong nước thải nhuộm hoạt tính.

Color removal of some reactive dyes (Blue 19, Black 5 and Red 195) using a local Poly Aluminium Chloride (PAC) was investigated with Jar-test experiment. The dyes were removed (above 94%) at optimal pH 7 (Red 195) and pH 10 (Blue 19 and Black 5). The PAC dosage of 220 mg/L (Blue 19 and Black 5) and 160 mg/L (Red 195) were found to be best for decreasing dye up to 50 mg/L (Black 5, Red 195) and 100 mg/L (Blue 19). Reaction time and agit ation speed also affected the decolorization process. That result indicates that Vietnamese PAC can be a robust and economical coagulant for discolorization of reactive dyeing process. / Chất keo tụ Poly Aluminium Chloride (PAC) sản xuất tại Việt nam được ứng dụng khử màu của một số màu nhuộm hoạt tính phổ biến (Blue 19, Black 5 and Red 195) trên thí nghiệm Jar-test. Kết quả cho thấy màu bị loại gần như hoàn toàn (trên 94 %) tại pH 7 (Red 195) hoặc 10 (Blue 19 và Black 5). Nồng độ PAC đạt hiệu quả tốt nhất tại 220 mg/L (Blue 19 và Black 5) và 160 mg/L (Red 195) ứng với nồng độ màu 50 mg/L (Black 5, Red 195) hay 100 mg/L (Blue 19). Thời gian phản ứng, tốc độ khuấy cũng có tác động đến hiệu suất khử màu. Kết quả nghiên cứu cho thấy PAC sản xuất tại Việt nam không những là một chất keo tụ tốt mà còn rất kinh tế cho việc khử màu hoàn toàn trong nước thải nhuộm hoạt tính.