On the treatment of uncertainty in experimentally measured frequency response functions

Frequency response functions (FRFs) are routinely used within experimental structural dynamics, among other fields. The uncertainty associated with their measurement is typically modelled on the simplified assumption that additive uncorrelated noise is present. This treatment of FRF uncertainty is questioned here by demonstrating that the notion of operator uncertainty (i.e. the uncertainty due to inconsistent force excitation) introduces a correlation between measured FRFs which is not accounted for under the assumption of additive noise. The origin of this correlation is illustrated and its experimental presence verified. The importance of this correlation on the propagation of uncertainty is subsequently investigated as part of a numerical and experimental case study, where its influence on the inversion of an uncertain FRF matrix is considered. It is shown that the neglect of such correlations can lead to large errors in uncertainty estimates, for example in dynamic sub-structuring and the solution of inverse problems. Keywords: Frequency response function, structural dynamics, experimental, measurement, operator uncertaint

The case for (and against) compulsory court-annexed mediation in Hong Kong

This paper examines the development of mediation in Hong Kong to date before turning to the approach of several other common law jurisdictions to compulsory mediation. It then examines the advantages and disadvantages of compulsion and concludes with what lessons, if any, the Hong Kong experience may have for other jurisdictions.postprin

Civil justice reform in Hong Kong: Its progress and its future

The Civil Justice Reform process in Hong Kong began in February 2000 and is expected to reach its culmination with new Rules of the High Court in April 2009. Nine long years therefore separate its beginning and end. This article attempts to answer the questions 'Why did the process begin?', 'Where has it led?' and 'What will it mean for the courts, litigants and the legal profession?'. In doing so, the article considers the English Civil Procedure Rules, which form the basis of many of the new Rules of the High Court in Hong Kong. In particular it looks at the changes that may result from the introduction of the proposed underlying objectives, sanctioned offers and the expanded scope of discovery.published_or_final_versio

Limited liability partnerships in Hong Kong: Challenges and conundrums

On 18th June 2010 the Legal Practitioners (Amendment) Bill was gazetted in the Hong Kong Legislative Council (LegCo). Over two years later, after much to-ing and fro-ing between the Government, the Hong Kong Law Society and LegCo members, the Bill was finally passed as the Legal Practitioners (Amendment) Ordinance (LPAO) on 12th July 2012. The LPAO introduces limited liability partnerships (LLPs) for solicitors’ firms, replacing the existing law by which every partner is jointly and severally liable for each and every one of their firm’s contractual and tortious obligations. This, in turn, will alter the relationship between each firm, its individual partners and their clients. When one considers that there are over 6,500 solicitors holding practicing certificates in Hong Kong, who deal with thousands of private individuals, small businesses and multinational corporations on everything from divorces and bail applications to M&As every day, the significance of the LPAO becomes apparent. This paper examines the reasons for the introduction of LLPs in Hong Kong; how such entities have been introduced and operate in other jurisdictions; the measures in the LPAO and their consequences; and other measures which could be adopted in the future.postprin

In-situ sub-structure decoupling of resiliently coupled assemblies

The context of this paper is the increasing need for vibro-acoustic simulation across many sectors. A procedure is derived for decoupling the components of resiliently mounted assemblies. An independent characterisation of the components is obtained such that they can be mathematically recombined with other elements to form virtual assemblies or Virtual Acoustic Prototypes. Unlike standard decoupling procedures, the proposed approach does not require the assembly to be physically decoupled at any stage. It is argued that this offers significant advantages in terms of convenience and, importantly, representativeness. The boundary conditions within a physically coupled assembly are realistic by definition, which may not be the case for physically decoupled components. The procedure is validated numerically using a lumped parameter model and demonstrated experimentally through several case studies. Keywords: In-situ, measurement, experimental,free-interface, decoupling, FRF, sub-structure, structural, characterisatio

Expert evidence: The new rules

This paper considers the nature of expert evidence before turning to the criticisms made and reforms suggested by the Chief Justice’s Working Party on Civil Justice Reform (“CJR”) insofar as they concern its use in the Hong Kong civil courts. The paper then continues with an examination of the changes that will be brought about to the nature and role of expert evidence by virtue of the implementation of the CJR on 2 April 2009. It concludes with a summary and critique of those changes.postprin

Class actions in Hong Kong– yes, no, maybe

Although the Civil Justice Reform brought about many changes to the Hong Kong courts, multi-party claims are still governed by rules whose origins are over a hundred years old. In 2006, the Hong Kong Law Reform Commission undertook the task of considering whether a scheme for multi-party litigation should be adopted in Hong Kong and, if so, to make whatever recommendations were needed to bring this into being. The Law Reform Commission eventually proposed the creation of a ‘class action regime’. This proposal has met with a mixed response from the legal profession, industry groups and the wider public. Its fate may soon be decided by a cross-sector working group chaired by the Solicitor General.postprin

Broadband characterisation of in-duct acoustic sources using an equivalent source approach

This paper is concerned with the development of an experimental method capable of independently characterising low Mach number, in-duct fluid machines, such as pumps, fans, etc. The aim is to propose and test a source characterisation method that is suitable for acoustic simulation and the construction Virtual Acoustic Prototypes. Such a requirement demands that the source characterisation be (a) independent, so that components can be virtually (re)combined within different assemblies and (b) valid over a wide frequency range so as to enable the output of a virtual assembly to be auralised. In this regard, standard methods based on sound power are not suitable. An equivalent source approach is proposed, based on a two-stage measurement procedure in which source strengths are obtained by solving an inverse problem. The experimental application of the procedure is illustrated as part of a case study where a high speed compressor unit is independently characterised and the resulting source data used to predict the operational response in a new assembly. Three frequency ranges are identified based on plane wave, modal and statistical behavior within the duct. The same measured data is used within each regime but subject to different processing according to different assumptions. Predictions are shown to be in good agreement with the directly measured response over a broad frequency range (100 Hz–10 kHz)

Multi-epoch Doppler tomography and polarimetry of QQ Vul

We present multi-epoch high-resolution spectroscopy and photoelectric polarimetry of the long-period polar (AM Herculis star) QQ Vul. The blue emission lines show several distinct components, the sharpest of which can unequivocally be assigned to the illuminated hemisphere of the secondary star and used to trace its orbital motion. This narrow emission line can be used in combination with Nai-absorption lines from the photosphere of the companion to build a stable long-term ephemeris for the star: inferior conjunction of the companion occurs at HJD = 244 8446.4710(5)+E×0. d 15452011(11). The polarization curves are dissimilar at different epochs, thus supporting the idea of fundamental changes of the accretion geometry, e.g. between one- and two-pole accretion modes. The linear polarization pulses display a random scatter by 0.2 phase units and are not suitable for the determination of the binary period. The polarization data suggest that the magnetic (dipolar) axis has a co-latitude of 23 ◦ , an azimuth of −50 ◦, and an orbital inclination between 50 ◦ and 70 ◦. Doppler images of blue emission and red absorption lines show a clear separatio

The Three Dimensional Structure of EUV Accretion Regions in AM Herculis Stars: Modeling of EUV Photometric and Spectroscopic Observations

We have developed a model of the high-energy accretion region for magnetic cataclysmic variables and applied it to {\it Extreme Ultraviolet Explorer} observations of 10 AM Herculis type systems. The major features of the EUV light curves are well described by the model. The light curves exhibit a large variety of features such as eclipses of the accretion region by the secondary star and the accretion stream, and dips caused by material very close to the accretion region. While all the observed features of the light curves are highly dependent on viewing geometry, none of the light curves are consistent with a flat, circular accretion spot whose lightcurve would vary solely from projection effects. The accretion region immediately above the WD surface is a source of EUV radiation caused by either a vertical extent to the accretion spot, or Compton scattering off electrons in the accretion column, or, very likely, both. Our model yields spot sizes averaging 0.06 R$_{WD}$, or $f \sim 1 \times 10^{-3}$ the WD surface area, and average spot heights of 0.023 R$_{WD}$. Spectra extracted during broad dip phases are softer than spectra during the out-of-dip phases. This spectral ratio measurement leads to the conclusion that Compton scattering, some absorption by a warm absorber, geometric effects, an asymmetric temperature structure in the accretion region and an asymmetric density structure of the accretion columnare all important components needed to fully explain the data. Spectra extracted at phases where the accretion spot is hidden behind the limb of the WD, but with the accretion column immediately above the spot still visible, show no evidence of emission features characteristic of a hot plasma.Comment: 30 Pages, 11 Figure