Fast-individual-harmonic-extraction technique

One outcome of a PhD project (C H Ng, University studentship) A collaborative work (the Energy Systems Group, Northumbria and Durham University). It deals with the problem of harmonic suppression or elimination in power systems for safety and power quality purposes. The speed of harmonic extraction being is a crucial issue in power systems to avoid damage of electrical equipments. Traditionally, harmonic suppression is done via Fourier transform. The main originality of this paper is on the use of a fast harmonic extraction algorithm, which is six times faster than traditional harmonic extraction techniques

A New Class of MDS Erasure Codes Based on Graphs

Maximum distance separable (MDS) array codes are XOR-based optimal erasure codes that are particularly suitable for use in disk arrays. This paper develops an innovative method to build MDS array codes from an elegant class of nested graphs, termed \textit{complete-graph-of-rings (CGR)}. We discuss a systematic and concrete way to transfer these graphs to array codes, unveil an interesting relation between the proposed map and the renowned perfect 1-factorization, and show that the proposed CGR codes subsume B-codes as their "contracted" codes. These new codes, termed \textit{CGR codes}, and their dual codes are simple to describe, and require minimal encoding and decoding complexity.Comment: in Proceeding of IEEE Global Communications Conference (GLOBECOM

Control of active filters to attenuate harmonic resonance in power distribution networks

Harmonic resonance occurs when the network equivalent shunt harmonic capacitive reactance is associated with the network series harmonic inductive reactance. When such resonance occurs, it amplifies harmonic components with frequency close to the resonance point. Solutions used to solve harmonic resonance problems can be divided into two main categories. One is to reduce the content of harmonic components in the network (e.g. by using active or passive harmonic filters, etc.) and the other is to remove the resonance stimulating factor by shifting away the resonance frequency to a non-critical frequency range (e.g. detuning PFC capacitors, redesigning feeder transformers, etc.). Studies show that these techniques are not adequate to solve harmonic resonance problems in power distribution networks which are dynamic by their nature and with complex interconnections. Due to this, solutions in the category one are designed for localised harmonic distortion compensation, while solutions in the category two lack real-time operation feature. Therefore, it was identified that there is a need for real-time harmonic resonance attenuation that is suitable for power distribution networks. In this thesis, a new real-time Harmonic Resonance Attenuation (HRA) technique is proposed. This technique may be used with ordinary shunt harmonic filters to make them behave like a virtual shunt capacitor or inductor. Thus, looking from the harmonic current source side, the filter alters the network harmonic impedance and hence results in harmonic resonance attenuation. In order to implement the HRA technique, fast measurement of system harmonics in real-time is required. Therefore, in this work, a fast individual harmonic extraction (FIHE) technique is developed to enhance the desired real-time operation of the HRA. The proposed FIHE needs only one sixth of the fundamental cycle to extract any individual harmonic component which is faster than other methods currently available. In addition to the speed, the proposed FIHE provides overshoot free, oscillation free and ripple free extraction characteristics. The proposed HRA and FIHE techniques are described in this thesis with detailed analysis to illustrate their operating principles. A series of simulations and experiments are conducted to evaluate their functionality and performance. Results of the evaluation are presented and discussed in this thesis together with details of the experimental HRA model developed to verify the theoretical and simulation results

Two-layer Thermally Driven Turbulence: Mechanisms for Interface Breakup

It is commonly accepted that the breakup criteria of drops or bubbles in turbulence is governed by surface tension and inertia. However, also {\it{buoyancy}} can play an important role at breakup. In order to better understand this role, here we numerically study Rayleigh-B\'enard convection for two immiscible fluid layers, in order to identify the effects of buoyancy on interface breakup. We explore the parameter space spanned by the Weber number $5\leq We \leq 5000$ (the ratio of inertia to surface tension) and the density ratio between the two fluids $0.001 \leq \Lambda \leq 1$, at fixed Rayleigh number $Ra=10^8$ and Prandtl number $Pr=1$. At low $We$, the interface undulates due to plumes. When $We$ is larger than a critical value, the interface eventually breaks up. Depending on $\Lambda$, two breakup types are observed: The first type occurs at small $\Lambda \ll 1$ (e.g. air-water systems) when local filament thicknesses exceed the Hinze length scale. The second, strikingly different, type occurs at large $\Lambda$ with roughly $0.5 < \Lambda \le 1$ (e.g. oil-water systems): The layers undergo a periodic overturning caused by buoyancy overwhelming surface tension. For both types the breakup criteria can be derived from force balance arguments and show good agreement with the numerical results.Comment: 13 pages, 7 figure

How do national employment policies influence Human Resource practices? A comparative study of the Integrated Resort and Hotel Industry in Macau and Singapore

Asia’s growth in prominence over the last decade is a phenomenon that has seen some governments and international financial institutions defining the twenty-first century as the Asian Century, in which Asia will be the focus of economic growth (Kohli, Sharma & Sood, 2011). The wealth in the major economies of Asia will see an increase in a dominant middle-income group, with strong spending power not only in terms of lifestyle domestically, but also internationally. This group’s quest for the finer things in life will transform the hospitality industry in countries such as Singapore and Macau: both are international metropolises with numerous five-star hotels and resorts. The subsequent expansion in the hospitality industry in these countries has resulted in a tight labour market whereby the respective governments introduced national policies with varying impact on the labour market. This research will investigate how these national policies are translated into Human Resources (HR) policies by HR managers; what the influencing factors in the translation process are; and the difference between the HR policies between Singapore and Macau. Before 2002, the then Sociedade de Turismo e Diversoes de Macau (STDM) (now Sociedade de Jogos de Macau) was the only organisation in Macau with a casino within its hotel. This changed when the Special Administrative Region (SAR) government liberalised the hospitality and gaming industry to enable the entry of other operators into the market, in the form of Integrated Resorts and Hotels (IR&H) with both gaming and non-gaming facilities. In 2005 Singapore passed legislation that allowed for the establishment of IR&H that encompass Meetings, Incentives, Conventions and Exhibitions (MICE) and a theme park. The relationship between the national employment policy, the constantly changing labour landscape and the political environment that impacts on the national regulatory policies requires HR personnel to keep abreast of the regulatory changes that could be translated into the HR practices of the IR&H. It is these various and varying factors as they relate to Macau and Singapore that will be examined in this study. The aim of this research, therefore, is to examine and compare the national employment policies of Macau and Singapore to determine how organisations translate these policies into their HR practice

Penawaran Kursus Bahasa Asing di universiti: meninjau pemilihannya dari perspektif nilai ekonomi

Kursus Bahasa Asing merupakan kursus elektif di universiti tempatan. Terdapat tiga kategori bahasa Asing yang ditawarkan, iaitu bahasa-bahasa Eropah (misalnya bahasa Jerman, Perancis, Sepanyol dan sebagainya), bahasa di Asia Timur (terutamanya bahasa Mandarin, Korea dan Jepun) dan bahasa di Asia Tenggara (seperti bahasa Thai, Burma, Vietnam, Kemboja dan sebagainya). Di antaranya, kursus bahasa Eropah dan Asia Timur, yang dipersepsikan sebagai bahasa Tinggi (bahasa H) menjadi kursus pilihan utama para pelajar. Bahasa Asia Tenggara sebaliknya diabaikan oleh pelajar (dan juga universiti tempatan) dan dianggap sebagai bahasa Rendah (Bahasa L). Dengan kenyataan bahawa negara-negara ASEAN mengalami perkembangan ekonomi yang pesat dan kehadiran ramai penutur yang berbahasa Asia Tenggara di sekitar kita, makalah ini menegaskan tentang kelebihan menguasai bahasa-bahasa serantau daripada bahasa yang dipersepsikan berprestij seperti bahasa di Eropah atau di Asia Timur