Extended Non-Binary Low-Density Parity-Check Codes over Erasure Channels

Based on the extended binary image of non-binary LDPC codes, we propose a method for generating extra redundant bits, such as to decreases the coding rate of a mother code. The proposed method allows for using the same decoder, regardless of how many extra redundant bits have been produced, which considerably increases the flexibility of the system without significantly increasing its complexity. Extended codes are also optimized for the binary erasure channel, by using density evolution methods. Nevertheless, the results presented in this paper can easily be extrapolated to more general channel models.Comment: ISIT 2011, submitte

CFD study of dynamic wind actions on faces of a tall building

Section B: Numerical simulation and theoretical analysisThe article can be viewed at: http://wgy091.ust.hk:8080/document/HKWE1papers.pdfThis paper computes and investigates the fluctuating wind forces on different building faces of a 6:1:1 square-section tall building with LES. Time histories of aerodynamic forces on building faces are computed from which power spectra and cross correlation analysis are made. The computation results are compared to past wind tunnel data from base balance and wind pressure measurements. Most results show qualitative agreement.published_or_final_versio

Dynamic wind loading of H-shaped tall buildings

Fulltext in: http://www.iawe.org/Proceedings/7APCWE/M3A_5.pdfTechnical Session: M3-A High-Rise Building, no.5Dynamic wind loads on a number of H-shaped tall buildings are measured in the wind tunnel with a highfrequency force balance for all wind incidences. The aim is to investigate the size effect of the recessed cavities on the dynamic wind loading behavior of the building. Combinations of three widths and three depths of a cavity are tested. It is found that at most wind incidences, the presence of cavities on the building faces leads to little modifications to the magnitudes and behavior of mean and fluctuating overturning moment coefficients. However, reduced magnitudes of across-wind moment fluctuations are found at normal incidence and different behavior of across-wind excitation is revealed by the across-wind moment spectra. Wind torsion is noticeably modified by the presence of the recessed cavities.link_to_subscribed_fulltex

Understanding ground deformation mechanisms for multi-propped excavation in soft clay

Deep excavation works are carried out to construct underground infrastructures such as deep basements, subways, and service tunnels. The execution of these deep excavation works requires the use of retaining walls and bracing systems. Inadequate support systems have always been of major concern, as excessive ground movement induced during excavation could cause damage to neighboring structures, resulting in delays, disputes, and cost overruns. To gain a better understanding of the mechanisms involved in soil excavations, centrifuge model tests of deep excavations in slightly over-consolidated soft clay have been carried out using a newly developed testing system, in which the construction sequence of a multi-propped wall for deep excavations can be simulated in flight. Deformation mechanisms are observed using Particle Image Velocimetry. Settlements of the ground surface and changes in pore water pressure are monitored during the excavation. The effects of prop stiffness, wall rigidity, and excavation geometry on the characteristics of ground deformation and soil-structure interaction are demonstrated and discussed. The use of the conservation of energy within the framework of the mobilizable strength design in calculating ground movements is validated and shown to perform satisfactorily.This is the author accepted manuscript. The final published version can be found on the publisher website at: http://www.sciencedirect.com/science/article/pii/S0038080614000286 Copyright © 2014 Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved

Upregulation of erythropoietin and its receptor expression in the rat carotid body during chronic and intermittent hypoxia

Proceeding of the XVIIth ISAC Meeting (International Society for Arterial Chemoreception Meeting), School of Medicine of Valladolid, Valladolid, Spain, July 1–5, 2008The carotid body (CB) plays important roles in cardiorespiratory changes in intermittent hypoxia (IH). Erythropoietin (EPO), a hypoxia-inducible factor (HIF)-1 target gene, is present in the chemoreceptive type-I cells in the CB but its expression and role in IH resembling sleep apnoeic conditions are not known. We hypothesized that IH upregulates the expression of EPO and its receptor (EPOr) in the rat CB. The CB expressions of EPO and EPOr were examined in rats breathing 10% O 2 (in isobaric chamber for CH, 24 hour/day) or in IH (cyclic between air and 5% O 2 per minute, 8 hour/day) for 3-28 days. Immunohistochemical studies revealed that the EPO and EPOr proteins were localized in CB glomic clusters. The proportional amount of cells with positive staining of EPO immunoreactivities was significantly increased in both IH and CH groups when compared with the normoxic control. The EPO expression was more markedly increased in the CH than that of the IH groups throughout the time course, reaching a peak level at day 14. The positive EPOr immunostaining was increased significantly in the 3-day CH group. By day 14, the EPOr expression elevated considerably at peak levels in both IH and CH rats, whereas the elevation was greater in the CH rats. These results suggest an upregulation of EPO and its receptor expression in the rat CB under IH and CH conditions, presumably mediated by the activation of HIF-1 pathway. The increased EPO binding to its receptor might play a role in the enhancement of CB excitability during the early pathogenesis in patients with sleep-disordered breathing. © Springer Science+Business Media B.V. 2009.postprin

E-cigarette use was associated with the intention to smoke in Chinese adolescents

Conference Theme: Tobacco and Non-Communicable DiseasesPoster Discussion 28. E-cigarettes: Evidence and Analysis: no. PD-923-20BACKGROUND: E-cigarette use arguably could reduce cigarette smoking and the intention to smoke, although such studies are few, especially in adolescents. We investigated the association between e-cigarette use and the intention to smoke in Chinese adolescent smokers and never-smokers. DESIGN/METHODS: A total of 45857 secondary 1-6 (US Grade 7-12) students (response rate 96%) from 75 randomly selected schools completed an anonymous questionnaire in 2012/13 in Hong Kong. Students were classified as never-smokers, experimenters (smoked just a few puffs), ex-smokers and current smokers (occasional or daily smoking). E-cigarette use in the past 30 days was …published_or_final_versio

E-cigarette use was associated with respiratory symptoms among Chinese adolescents in Hong Kong

Conference Theme: Tobacco and Non-Communicable DiseasesOral Presentation - 05. Innovative Ways for Achieving Tobacco Free Generations: no. OP-229-20BACKGROUND: Adverse effects of e-cigarette use were not clear. Some studies have found harmful effects on respiratory function (respiratory flow resistance and impedance) in adult smokers. We assessed the association between cigarette use and respiratory symptoms in adolescents. DESIGN/METHODS: A school-based smoking survey was conducted on 45857 secondary 1-6 (US Grade 7-12) students (response rate 96%) from 75 randomly selected secondary schools in Hong Kong in 2012/13 …published_or_final_versio

Overestimation of peer smoking prevalence predicts smoking initiation among primary school students in Hong Kong

Purpose: To investigate the relationship between perceived prevalence of smoking and smoking initiation among Hong Kong primary second- to fourth-grade-students. Methods: A cohort of 2,171 students was surveyed in 2006 and again in 2008. Students who perceived ever-smoking prevalence in peers as "none" or "some" were considered as correct (reference group), whereas those who perceived it as "half" (overestimation) or "most/all" (gross overestimation) were considered as incorrect. Results: At baseline, overestimation was found to be cross-sectionally associated with ever-smoking (p < .01). At follow-up, 7.2% of never-smoking students with incorrect estimation at baseline had started smoking, which was 79% (95% confidence interval: 3%-213%), greater than that of 3.7% for those with correct estimation. Among the never-smoking students with incorrect estimation, subsequent correct estimation was associated with 70% (95% confidence interval: 47%-83%) lower risk of smoking initiation compared with persistent incorrect estimation. Conclusion: Overestimation of the prevalence of peer smoking predicted smoking initiation among children. Interventions should be carried out to evaluate whether correcting children's overestimation of peer smoking could reduce smoking initiation. © 2011 Society for Adolescent Health and Medicine.postprin

Positive reactions to third-hand smoke exposure are associated with smoking susceptibility among young children in Hong Kong

Poster Discussion 43. Monitoring the Impact of FCTC Implementation: no. PD-1089-21Conference Theme: Tobacco and Non-Communicable DiseasesBACKGROUND: Positive reactions to the first cigarette and secondhand smoke (SHS) predict future smoking. Whether such reactions to third-hand smoke (THS) affect smoking is uncertain. We investigated the cross-sectional associations of reactions to THS with smoking susceptibility and ever smoking among Chinese children. METHODS: A school-based survey was conducted on 5365 primary 2-4 students (54.5% boys; mean age 8.6 years, SD 1.3) from 34 randomly selected schools in Hong Kong using an anonymous self-administered questionnaire. Students were asked “when you can smell cigarette from objects or people, yet no one smokes around, which of …published_or_final_versio

A new apparatus for modelling excavations

Underground space is commonly exploited both to maximise the utility of costly land in urban development and to reduce the vertical load acting on the ground. Deep excavations are carried out to construct various types of underground infrastructure such as deep basements, subways and service tunnels. Although the soil response to excavation is known in principle, designers lack practical calculation methods for predicting both short- and long-term ground movements. As the understanding of how soil behaves around an excavation in both the short and long term is insufficient and usually empirical, the judgements used in design are also empirical and serious accidents are common. To gain a better understanding of the mechanisms involved in soil excavation, a new apparatus for the centrifuge model testing of deep excavations in soft clay has been developed. This apparatus simulates the field construction sequence of a multi-propped retaining wall during centrifuge flight. A comparison is given between the new technique and the previously used method of draining heavy fluid to simulate excavation in a centrifuge model. The new system has the benefit of giving the correct initial ground conditions before excavation and the proper earth pressure distribution on the retaining structures during excavation, whereas heavy fluid only gives an earth pressure coefficient of unity and is unable to capture any changes in the earth pressure coefficient of soil inside the zone of excavation, for example owing to wall movements. Settlements of the ground surface, changes in pore water pressure, variations in earth pressure, prop forces and bending moments in the retaining wall are all monitored during excavation. Furthermore, digital images taken of a cross-section during the test are analysed using particle image velocimetry to illustrate ground deformation and soil–structure interaction mechanisms. The significance of these observations is discussed.The authors would also like to acknowledge the Platform grant (GR/T18660/01) awarded by the UK Engineering and Physical Sciences Research Council.This is the final published version. It first appeared at http://www.icevirtuallibrary.com/content/article/10.1680/ijpmg.2012.12.1.24