Tan Xuesong. / "June 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 247-251). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Zhang Liang. / "August 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Finally, a four-channel SIMO converter with direct combination but optimal switching sequence for arbitrary converter sequence and converter type is presented. The theoretical optimal 1st-order inductor waveform from this proposed control algorithm is introduced. FCL is involved in this design to realize the algorithm. Moreover, a current-modulated ramp signal, which couples to different controllers, is included to compensate the original deep correlated power stages. By using all of the proposed techniques, Measurement results show that both conduction loss and dynamic loss can be suppressed because of the optimized switching sequence. The load transient response time is around 100mus. The peak efficiency is 89% with a 2.5-V power supply. A maximum output power of 1.66W can be achieved. / Firstly, a pseudo-PWM hysteresis voltage-mode buck converter is proposed. It achieves fast transient speed by the hysteresis control, estimable switching spectrum with a locking frequency and fast mode switching between PWM and PFM depending on the loading change. Measurement results show that the recovery time under the load transient is around 5mus, which is 5 times of the switching period. The boundary of the recovery time is defined by the value of the off-chip inductor. / Switching-mode power converter (SMPC) is an important circuit block in electronic systems. In the modem SMPC system, constant frequency voltage or current-mode control technique is commonly used. However, some limitations are raised due to some preliminary settings in the design. In this thesis, the switching frequency or period is no longer a constant but a design variable. Then, an additional frequency-control loop (FCL) is introduced in order to obtain a fixed frequency operation in the steady state. Three individual designs implemented with different types of FCL are proposed to verify the concept. / Then, a four-channel SIMO converter based on FCL is developed, together with auto-phase allocation technique. This circuit not only solves the problem of imbalance loading of different channels, but it also keeps the idle period of the inductor sufficient short in the full operation region. By combining with all channel controllers, FCL makes fast load transient response without degrading the power efficiency. Moreover, linear auto converter-type adaption technique is also used, which makes the converter surviving from a wide input range and output range. Measurement results show that the proposed converter can achieve a peak efficiency of 89%, a total output power of 1.46W, a load transient response time of less than 70muS, and an idle inductor period of <10%. / Zheng, Yanqi. / Adviser: Leung Ka Nang. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

The suggestion that bilinguals show enhanced cognitive control compared to monolinguals in certain aspects of executive function has received much contention. While this has been explained as a result of the extensive training in bilinguals having to manage the conflict that arises from their concurrently active langauges, others have argued that the superiority in executive control is attenuated when background variables such as immigration status, education and general cognitive ability is taken into account. This thesis was motivated by the general question: How is executive control influenced by differing bilingualism experiences? To this end, we compared attentional control performance in bilinguals and monolinguals on the Attention Network Test, the auditory Elevator task (Test of Everyday Attention), and the number Stroop task. The main aim of the thesis was to examine the role of two bilingualism factors: (i) interactional context (defined in the Adaptive Control Hypothesis, Green & Abutalebi, 2013), which pertains to how bilinguals switch between their languages, and (ii) linguistic distance, which refers to the extent of similarity between the bilingual's languages. The comparison between Edinburgh monolinguals, Edinburgh late bilinguals, Edinburgh early bilinguals, and Singapore early bilinguals as differentiated by their interactional context revealed better performance in bilinguals on two specific test components. Singapore bilinguals, who came from a dual-language and dense code-switching context, showed enhanced conflict resolution on the Attention Network Test, whilst Edinburgh late bilinguals, who were from a single-language context, were better on the Elevator reversal subtest tapping on attentional switching. The results thus suggest differential effects of interactional context on attentional control. We further compared task performance of bilinguals with related or distant L1-L2 combinations as defined by the linguistic and orthography overlap between their two languages. The data did not support a role of linguistic distance on attentional control. Edinburgh bilinguals studying an Indo-European language performed similarly to those studying the non Indo-European languages of Chinese and Japanese. In Singapore bilinguals, English-Chinese bilinguals also did not differ from English-Malay bilinguals on any of the test components. We supplemented the investigation by further examining if the factors of test-order and age could impact on how differences between monolinguals and bilinguals are exhibited. Our results suggest that monolinguals may show an improvement in attentional control after relatively short periods of engagement in experimental tasks, whilst bilinguals did not receive this boost. Test order may therefore partly explain the inconsistencies in literature regarding the claimed bilingual advantage. The comparison between older and younger adults also implied an effect of age. In young adults, bilinguals outperformed monolinguals on the Elevator reversal subtest of auditory switching, whereas the advantage shown in older bilinguals was on visual attentional orienting. The results across the various themes are reviewed and discussed with relevance to the current standing in the field, and suggestions for future research directions are put forth.

With increasing strain on the civil aviation industry to meet strict targets to reduce the adverse effects aviation has on the environment by 2050, significant advances in aircraft design and research are required. Aerodynamic improvements have been a focus for several decades now, however, current and future civil transport aircraft are based on traditional designs originating from the 1950s. Optimisation of aircraft external geometry for aerodynamic gain is reaching maturity and is becoming increasingly non-cost-effective. New advances in sensor and actuator technology has allowed for the development of active flow control (AFC) devices that have shown promising results in laboratory and even full-scale flight conditions, as seen by the joint NASA-Boeing ecoDemonstrator. One such device is the synthetic jet actuator (SJA), that synthesises periodic jets without the requirement for external air supply, while adding momentum to the surrounding flow. For this reason, SJAs are also referred to as zero-net-mass-flux actuators. There exists extensive work on the use of these devices for flow control applications in a laboratory setting. One of the key issues that remains unresolved, hindering successful aircraft application to-date, is the actuator self-noise generated. The noise level of SJAs can be so severe that they were rejected for application on the ecoDemonstrator in favour of a higher authority, quieter AFC device. SJAs were only considered for use in emergency situations on aircraft. Furthermore, the actuators were also not permitted to operate simultaneously at full power, which may severely limit scope for flow control on aircraft. Other applications that would benefit from SJAs include heat transfer for cooling in electronic devices. Studies in this field identify the same problem with noise levels of up to 73 dB reported. It is clear that work towards the self-noise reduction of SJAs is required to harness the full potential of this actuator technology. In the work presented, passive and active noise control measures in the form of lobed orifices and antiphase operation of two jets, respectively, on the noise reduction of SJAs are ii investigated. Noise sources of synthetic jet actuators include mechanical (diaphragm) and jet induced noise, where the focus of this work is on the latter type. Tests were conducted in quiescent conditions using jet velocity measurements, acoustic measurements, and flow visualisation. Tests were carried out using a single chamber SJA with variable cavity height and both circular and lobed orifices. These tests helped identify a SJA self-noise generation mechanism when using a circular orifice. This mechanism is characterised by a constant frequency behaviour visible in acoustic spectra for a specific jet Reynolds number range of 600 < Rej < 750 and Strouhal number range of 0.22 < St < 0.50. The geometries of the lobed orifices used in this work differ in lobe count and penetration. It was shown that a broadband noise reduction is possible with such orifices, with a maximum noise reduction of 14 dB at particular frequencies. The results indicate that a high number of lobes and penetration are preferred for noise reduction, however, at the expense of quickly dissipating downstream jet velocity. Flow visualisation reveals that this adverse effect is caused by enhanced mixing of lobed jets with ambient air that leads to earlier and more aggressive breakup of flow structures. A double chamber SJA is also used to demonstrate the noise attenuation through the antiphase operation of two cavities, caused by the interference pattern of the sound field of each source. The maximum reduction measured using this actuator configuration is 14 dB, depending on directivity.

by Kin-Yu Cheung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 64-[68]). / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Multistage Interconnection Architectures --- p.2 / Chapter 1.2 --- Interconnection Topologies --- p.4 / Chapter 1.3 --- Design of Switch Module-An Example of Multichannel Switch --- p.7 / Chapter 1.4 --- Organization --- p.8 / Chapter 1.5 --- Publication --- p.9 / Chapter 2 --- BMSN and SpiderNet: Two Large Scale ATM Switches --- p.13 / Chapter 2.1 --- Introduction --- p.13 / Chapter 2.2 --- Architecture --- p.14 / Chapter 2.2.1 --- Topology --- p.14 / Chapter 2.2.2 --- Switch Modules --- p.15 / Chapter 2.3 --- Routing --- p.17 / Chapter 2.3.1 --- VP/VC Routing --- p.18 / Chapter 2.3.2 --- VP/VC Routing Control --- p.22 / Chapter 2.3.3 --- Cell Routing --- p.23 / Chapter 2.3.4 --- Alternate Path Routing for Fault Tolerance --- p.24 / Chapter 2.4 --- SpiderNet --- p.25 / Chapter 2.5 --- Performance and Discussion --- p.26 / Chapter 2.5.1 --- BMSN vs SpiderNet --- p.26 / Chapter 2.5.2 --- Network Capacity --- p.29 / Chapter 2.6 --- Concluding Remarks --- p.30 / Chapter 3 --- Multichannel ATM Switching --- p.39 / Chapter 3.1 --- Introduction --- p.39 / Chapter 3.2 --- Switch Design --- p.40 / Chapter 3.3 --- Channel Allocation Algorithms --- p.41 / Chapter 3.3.1 --- VC-Based String Round Robin (VCB-SRR) Algorithm --- p.41 / Chapter 3.3.2 --- Implementation of the VCB-SRR Algorithm --- p.43 / Chapter 3.3.3 --- Channel Group Based Round Robin (CGB-RR) Algorithm --- p.50 / Chapter 3.3.4 --- Implementation of the CGB-RR Algorithm --- p.51 / Chapter 3.4 --- Performance and Discussion --- p.53 / Chapter 3.5 --- Concluding Remarks --- p.57 / Chapter 4 --- Conclusion --- p.62 / Bibliography --- p.64

by Wai-Hung Kwok. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Preliminaries - Routing in Classical Circuit Switching Clos Net- work --- p.9 / Chapter 2.1 --- Formulation of route assignment as bipartite multigraph coloring problem --- p.10 / Chapter 2.1.1 --- Definitions --- p.10 / Chapter 2.1.2 --- Problem formulation --- p.11 / Chapter 2.2 --- Edge-coloring of bipartite graph --- p.12 / Chapter 2.3 --- Routing algorithm - Paull's matrix --- p.15 / Chapter 3 --- Principle of Routing Algorithm --- p.18 / Chapter 3.1 --- Definitions --- p.18 / Chapter 3.1.1 --- Bandwidth quantization --- p.18 / Chapter 3.1.2 --- Connection splitting --- p.20 / Chapter 3.2 --- Non-blocking conditions --- p.20 / Chapter 3.2.1 --- Rearrangeably non-blocking condition --- p.21 / Chapter 3.2.2 --- Strictly non-blocking condition --- p.22 / Chapter 3.3 --- Formulation of route assignment as weighted bipartite multigraph coloring problem --- p.23 / Chapter 3.4 --- Edge-coloring of weighted bipartite multigraph with edge splitting --- p.25 / Chapter 3.4.1 --- Procedures --- p.25 / Chapter 3.4.2 --- Example --- p.27 / Chapter 3.4.3 --- Validity of the color rearrangement procedure --- p.29 / Chapter 4 --- Routing Algorithm --- p.32 / Chapter 4.1 --- Capacity allocation matrix --- p.32 / Chapter 4.2 --- Connection setup --- p.34 / Chapter 4.2.1 --- Non-splitting stage --- p.35 / Chapter 4.2.2 --- Splitting stage --- p.36 / Chapter 4.2.3 --- Recursive rearrangement stage --- p.37 / Chapter 4.3 --- Connection release --- p.40 / Chapter 4.4 --- Realization of route assignment in packet level --- p.42 / Chapter 5 --- Performance Studies --- p.45 / Chapter 5.1 --- External blocking probability --- p.45 / Chapter 5.1.1 --- Reduced load approximation --- p.46 / Chapter 5.1.2 --- Comparison of external blocking probabilities --- p.48 / Chapter 5.2 --- Connection splitting probability --- p.50 / Chapter 5.3 --- Recursive rearrangement probability --- p.50 / Chapter 6 --- Conclusions --- p.52

This dissertation studies the problem of identifying the ideological perspective of people as expressed in their written text. One's perspective is often expressed in his/her stance towards polarizing topics. We are interested in studying how nuanced linguistic cues can be used to identify the perspective of a person in informal genres. Moreover, we are interested in exploring the problem from a multilingual perspective comparing and contrasting linguistics devices used in both English informal genres datasets discussing American ideological issues and Arabic discussion fora posts related to Egyptian politics. %In doing so, we solve several challenges. Our first and utmost goal is building computational systems that can successfully identify the perspective from which a given informal text is written while studying what linguistic cues work best for each language and drawing insights into the similarities and differences between the notion of perspective in both studied languages. We build computational systems that can successfully identify the stance of a person in English informal text that deal with different topics that are determined by one's perspective, such as legalization of abortion, feminist movement, gay and gun rights; additionally, we are able to identify a more general notion of perspective–namely the 2012 choice of presidential candidate–as well as build systems for automatically identifying different elements of a person's perspective given an Egyptian discussion forum comment. The systems utilize several lexical and semantic features for both languages. Specifically, for English we explore the use of word sense disambiguation, opinion features, latent and frame semantics as well; as Linguistic Inquiry and Word Count features; in Arabic, however, in addition to using sentiment and latent semantics, we study whether linguistic code-switching (LCS) between the standard and dialectal forms for the language can help as a cue for uncovering the perspective from which a comment was written. This leads us to the challenge of devising computational systems that can handle LCS in Arabic. The Arabic language has a diglossic nature where the standard form of the language (MSA) coexists with the regional dialects (DA) corresponding to the native mother tongue of Arabic speakers in different parts of the Arab world. DA is ubiquitously prevalent in written informal genres and in most cases it is code-switched with MSA. The presence of code-switching degrades the performance of almost any MSA-only trained Natural Language Processing tool when applied to DA or to code-switched MSA-DA content. In order to solve this challenge, we build a state-of-the-art system–AIDA–to computationally handle token and sentence-level code-switching. On a conceptual level, for handling and processing Egyptian ideological perspectives, we note the lack of a taxonomy for the most common perspectives among Egyptians and the lack of corresponding annotated corpora. In solving this challenge, we develop a taxonomy for the most common community perspectives among Egyptians and use an iterative feedback-loop process to devise guidelines on how to successfully annotate a given online discussion forum post with different elements of a person's perspective. Using the proposed taxonomy and annotation guidelines, we annotate a large set of Egyptian discussion fora posts to identify a comment's perspective as conveyed in the priority expressed by the comment, as well as the stance on major political entities.

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