5,807 research outputs found
Supercritical reactive flow modeling in LRE thrust chambers
No full textThis CFD study is devoted to the characterization and the analysis of the flow field and heat loads evaluation in oxygen/methane liquid rocket engines. Thanks to CFD we obtain a compromise between details and experimental cost and it is possible a full scale engine analysis as support to the engine design phase. Our work is focused on the heat flux evaluation, hot gas and on flame structure in a thrust chamber. The importance of flame position leads to a study of mesh refinement of post tip. As consequence, a small recirculation zone near the post tip is identified and is studied to guarantee a stable flame also in term of position in the chamber. Also three large recirculation zones of hot gases are located in the combustion chamber and their presence assures, near the walls and the plate, the presence of high heat fluxes. We considered the usage of EOSs and a preliminary analysis was realised before the CFD simulations. Simple test cases are simulated and used to identify the best numerical strategy employ. Finally, we reproduced a simulation of the DEMO a regenerative cooled chamber LOX/methane, obtaining by combustion process simulation the heat flux at the chamber and nozzle walls
The End of "Made in Hong Kong"? : De-industrialisation and Industrial Promotion Policy in Hong Kong
No full textThis article explores spatial aspects of Hong Kong's deindustrialisation, related both to the development of closer cross-border ties and to Hong Kong's evolution as a global city. Industrial promotion has always had its place in the generally non-interventionist economic policy ofthe government. However, under the new political and economical conditions industrial promotion has moved up on the agenda. In particular, the promotion of high-tech industries is given special governmental attention. The author wams that the plans for re-industrialising Hong Kong may be based on an obsolete view of the city: the city as an isolated entity rather than as the cross-border economic agglomeration that it is growing into. The aim should be to develop a strong and productive industrial base with intraregional co-operation for the whole agglomeration instead of just for Hong Kong
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Hong Kong: workfare in the world's freest economy
No full textWorkfare was introduced in many countries to suppress welfare dependency and reduce social security expenditures. However, workfare was launched in Hong Kong when there was only a relatively small social security budget and its citizens still strongly adhered to the ideologies of self-reliance. It was found that workfare has performed several functions in Hong Kong. Firstly, it has forced unemployed claimants to give up benefits so that Hong Kong's social security expenditures can be saved. Secondly, workfare had combined with Hong Kong's semi-democratic polity so that extremely stigmatising welfare measures were implemented. Thirdly, it has pushed poor citizens to the labour market without having any protection over wages and working hours. Thus, the combination of workfare and a semi-democratic polity has successfully suppressed Hong Kong's welfare demands and strengthened its self-help spirit. As a result, Hong Kong's minimal social security scheme and its low tax policy have been maintained
Analysis of n-heptane auto-ignition characteristics using computational singular perturbation
No full textTo provide insights into auto-ignition characteristics in low temperature combustion (LTC) engine conditions, computational singular perturbation (CSP) analysis is used to gain fundamental understanding into classification of ignition regimes in n-heptane air mixtures in the presence of temperature and composition inhomogeneities. Parametric studies are conducted using high-fidelity simulations with detailed chemistry and transport. In particular, a key interest is to understand different ignition behavior of the n-heptane mixture at the negative-temperature coefficient (NTC) versus the non-NTC conditions. The CSP analysis for the reference homogeneous system yields the number of exhausted modes (M) at various stages during the ignition event. In addition, the merging of two explosive modes is observed at the onset of auto-ignition. For the one-dimensional system, the M profiles along with the importance index (IT) measured in the upstream of the ignition front are used to determine whether the front propagation is the spontaneous (IT → 0) or deflagrative (IT → 1) regime. At the relatively large temperature fluctuation considered herein, the mixture at non-NTC conditions shows initially a deflagration front which is subsequently transitioned into a spontaneous ignition front. For the mixtures at the NTC conditions which exhibit two-stage ignition behavior, the 1st stage ignition front is found to be more likely in the deflagration regime. On the other hand, the 2nd stage ignition front occurs almost always in the spontaneous regime because the upstream mixture contains active radical species produced by the preceding 1st stage ignition front. The effects of differently correlated equivalence ratio stratification are also considered and the results are shown to be consistent with previous findings
Classification of ignition regimes in HCCI combustion using computational singular perturbation
No full textThe computational singular perturbation (CSP) technique is applied as an automated diagnostic tool to classify ignition regimes encountered in homogeneous charge compression ignition (HCCI) engines. Various model problems representing HCCI combustion are simulated using high-fidelity computation with detailed chemistry for hydrogen-air system. The simulation data are then analyzed by CSP. In a homogeneous system, the occurrence of two branches of explosive eigenvalues characterizes chain-branching and thermal ignition. Their merging point serves as a good indicator of the completion of the explosive stage of ignition. However, the merging point diagnostics is insufficient to differentiate spontaneous ignition from deflagration. As an alternate method, the active reaction zones are first identified by the locus of minimum number of fast exhausted time scales (based on user-specified error thresholds). Subsequently, the relative importance of transport and chemistry is determined in the region ahead of the reaction zone. A new index IT, defined as the sum of the absolute values of the importance indices of diffusion and convection of temperature to the slow dynamics of temperature, serves as a criterion to differentiate spontaneous ignition from deflagration regimes. These diagnostic tools are applied to 1D and 2D ignition problems under laminar and turbulent mixture conditions, respectively, allowing automated detection of different ignition regimes at different times and location during the ignition events. The implication of the results in the context of modeling autoignition of nearly homogeneous turbulent mixtures is discussed. © 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved
sj-docx-1-jer-10.1177_14680874231200759 – Supplemental material for Development of correlation model for cavitating spray using Eulerian simulations
No full textSupplemental material, sj-docx-1-jer-10.1177_14680874231200759 for Development of correlation model for cavitating spray using Eulerian simulations by Xinlei Liu, Junjun Guo and Hong G. Im in International Journal of Engine Research</p
SYNTHESIS AND CHARACTERIZATION OF INORGANIC COMPOSITE MEMBRANE BASED ON SULFONATED POLY(ETHER ETHER) KETONE FOR DIRECT METHANOL FUEL CELL
No full textThe development of university-level distance education in the context of Hong Kong's transition from a British colony to a special administrative region of China
No full textChina resumed sovereignty over Hong Kong on I July, 1997. After being a British
colony for more than 150 years, Hong Kong became a Special Administrative Region
of China following the "one country, two systems" policy. This dissertation is
concerned with the examination of the market changes in Hong Kong's university
distance education in the transition period.
Information about respondents' demographics, evaluation and intention to pursue
further study through distance education programmes was collected by sending
questionnaires to two types of subject: current students using distance education
programmes and potential adult students in Hong Kong. A total of five groups were
identified as representing the first type of subject: students of the Henley Management
College/Brunel University (UK) - MBA programme, the Curtin University of
Technology - Bachelor of Commerce and Master of Accounting programme
(Australia), and the Open University of Hong Kong - Bachelor of Business
Administration and MBA programmes. The second type of subject comprised Hong
Kong adults who were interested in studying via distance education programmes. One
group of subjects were visitors to the Hong Kong Education Expo 1996, and they
were classified as potential students who wished to study in distance education
programmes in Hong Kong.
All the data were processed using the Statistical Package for Social Science software
programme. The research questions were tackled by the resultant data and analysis.
The important findings obtained from the subjects are:
a) The need for higher-degree-level programmes is very great among Hong Kong's
distance learners. The decision to undertake further study to distance Master
degree level after completing a distance Bachelor degree aptly demonstrates this
situation. Consideration should, therefore, be given to developing distance Master
degree programmes for students currently studying distance Bachelor degree
programmes, and distance Doctorate degree programmes for students currently
studying distance Master degree programmes. The majority of distance students,
particularly at the higher-degree-level, tend to be in the higher-income bracket.
b) Hong Kong adults who are interested in distance education programmes come
from different occupation segments. Their choice of further study varies according
to their needs and occupations. Consideration should be given to repositioning the
current distance education programmes, particularly at Bachelor's degree or
Diploma level. In addition, a segment comprising housewives has been identified
as potential students for Bachelor's degree programmes by this study.
In the further discussion about Hong Kong during the transition period, Fägerlind and
Saha's Dialectical Model is used to examine the development of Hong Kong's higher
education system with three important dimensions: political, economic and social
forces. Finally, this analysis provides three possible alternatives of development for
the integration of Hong Kong's and China's higher education systems in the post-transition
period: "One Country, One System", "One Country, Two Systems", and
"One Country, Many Systems"
Political Uncertainty and the Real Estate Risk Premiums in Hong Kong
No full textThis study investigates the effects of political uncertainty associated with the 1997 repossession of Hong Kong by China on the real estate market. Such effect is reflected in the change in the real estate risk premiums. A model is derived to estimate the trend of real estate risk premium for each subsector of the real estate market from observable market data. The results suggest that there was a discrete jump in the risk premiums when the 1997 issue was revealed to the public in 1983, indicating investor concern about the post-1997 future of Hong Kong. The increase in the risk premium is much more obvious in nonresidential real estate than in the residential sector. This is probably due to its dual nature (an investment good as well as a good for self-consumption) and the effects of rent control, which only applies to the residential units. However there is also very strong evidence that investor confidence has been increasing recently, thus leading to a decline in the implied post-1997 risk premium, although the increasing confidence is still not sufficient to bring the risk premium back to pre-1983 levels. If the concern about the repossession of Hong Kong by China turns out to be unnecessary after 1997, a revaluation of the risk premium will take place. This will bring the risk premium level back to the pre-1983 level, assuming no other significant changes have taken place. Other things being equal, such revaluation will result in a one-time discrete increase in property prices. This is in contrast to the common view that investors have already discounted the 1997 Hong Kong/China issue completely.
Education reform as an agent of change: the development of media literacy in Hong Kong during the last decade
No full textAlthough media education is a comparatively new area of studies in Hong Kong, it is already flourishing. Why? This contribution identifies the education reform as an important factor in encouraging the development of media education in the last decade, and the three major driving forces of this reform have been: the emphasis on civic education since Hong Kong’s return to China sovereignty, the introduction of information technology (ICT), and the recent review of the curriculum. The author also aims to find out whether the patterns used in media education development are their own Asian models or, on the contrary, they follow Wes tern patterns
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