196 results on '"Chan PW"'
Search Results
2. Super high resolution numerical weather prediction model simulation of tiny anticyclones observed at the Hong Kong International Airport
- Author
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Chan, PW, primary, HON, KK, additional, and LI, QS, additional
- Published
- 2022
- Full Text
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3. Heat and Park Attendance: Evidence from “Small Data” and “Big Data” in Hong Kong
- Author
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Hao, Tongping, primary, Chang, Haoliang, additional, Liang, Sisi, additional, Jones, Phil, additional, Chan, PW, additional, Li, Lishuai, additional, and Huang, Jianxiang, additional
- Published
- 2022
- Full Text
- View/download PDF
4. Dynamic calibration of two catching type drop-counting rain gauges
- Author
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Stagnaro, M, Cauteruccio, A, Colli, M, Lanza, Lg, and Chan, Pw
- Published
- 2018
5. Eleven years of ARCOM: Bibliometric mapping of studies published between 2005 and 2016
- Author
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Chan, PW, Neilson, CJ, Hosseini, MR, Aibinu, AA, Chileshe, N, Arashpour, M, Chan, PW, Neilson, CJ, Hosseini, MR, Aibinu, AA, Chileshe, N, and Arashpour, M
- Abstract
The study aims at mapping the intellectual discourse that has emerged from Association of Researchers in Construction Management (ARCOM) conference within the last 11 years. To this end, the 1505 studies indexed in Scopus were examined through scientometric analyses of citation networks. The findings show that the most prominent areas of research including “sustainable development”, “health and safety” and “architectural design” have been predominantly conducted from a project management perspective. New fields of research such as Building Information Modelling have gained momentum with several years of delay after their emergence across the construction context. Besides, published studies in ARCOM have for the most part cited studies from journals allocated to managerial areas of construction management as well as management and business journals. Technology and engineering journals nevertheless turned out to have a noticeably lower share of citation. Moreover, the network of collaborations among countries indicated the dominance of the UK and Australia and underrepresentation of North American, emerging markets and developing countries. By providing a view from a meta-perspective, the study exposes the areas in need of extra attention, provides directions for defining future research themes and suggests remedial solutions for addressing the spotted problems.
- Published
- 2017
6. Markets, professions and firms of the construction industry: the changing roles of architects in response to vertical integration
- Author
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Chan, PW, Neilson, CJ, Jia, AY, Kvan, T, Gao, SS, Chan, PW, Neilson, CJ, Jia, AY, Kvan, T, and Gao, SS
- Abstract
The roles of professions in the construction industry in markets globally differ from one another according to the socio-political, cultural and historical contexts they are situated in, reflecting the institutional nature of the markets themselves. The institutional logics of state, market and profession compete to shape firm strategies. We adopt an institutional logics perspective to explore how architecture firms adapt their roles in the project procurement systems in response to vertical integration in the supply chain and the change of logics at the societal and field levels. Three architecture firms were analysed in this exploratory study. Data were collected through structured interviews, completed by company achieves and design documents. As a firm level study, the diversified roles of architects as manifested in their business models and the competition between the profession and market logics nuanced by a bureaucratic state logic. The study sheds light on the role of professionalism in balancing the market logic in shaping the outcome of our built environment. In a more general sense, we discuss the impact of the professional logic of architecture on the making and outcome of the built environment, and the value it can bring to an evolving structure of inter-professional collaboration in an integrating global industry.
- Published
- 2017
7. Green Building Projects: Process Innovation Leading to Project Innovation
- Author
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Chan, PW, Neilson, CJ, Ahmad, T, Aibinu, A, Stephan, A, Chan, PW, Neilson, CJ, Ahmad, T, Aibinu, A, and Stephan, A
- Abstract
Green Building (GB) project delivery is complex since these projects have many different requirements compared to conventional construction. There is not yet an agreement on which delivery approach is more effective in delivering more innovative and environmentally conscious GB projects. This paper investigates the GB project delivery approaches from an innovation perspective by reviewing the various empirical findings from previous research. Using 13 relevant studies identified through a systematic search, the relationship between innovation in delivery process and project innovation is identified. Depending on the extent of innovative features incorporated, each Project Delivery Method (PDM) is found to have the capacity to produce successful results. Incremental process innovation through the use of traditional PDMs is typically associated with a low level of project innovation and environmental performance while radical process innovation using integrated delivery method is found to be associated with a high level of project innovation and environmental performance in GB projects. Delivery process that encourages team work can be valuable as this promotes team integration and collaboration thereby leading to innovative solutions.
- Published
- 2017
8. Colorectal cancer screening
- Author
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Chan, PW, primary, Ngu, JH, additional, Poh, Z, additional, and Soetikno, R, additional
- Published
- 2017
- Full Text
- View/download PDF
9. To reciprocate or not to reciprocate : exploring temporal qualities in reciprocal exchanges in networks
- Author
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Abualqumboz, M and Chan, PW
- Subjects
HD28 - Abstract
In this article, we sought to draw theoretical explanations of reciprocal exchanges in networks and how reciprocity is seen as the building block of network sustainability through employing a temporal perspective. The article’s main contribution was to provide fresh insights into how temporality, drawn upon Bergson’s philosophy, advanced the way we look at reciprocity and consequently provided three perspectives of time, namely; emergent networks, discursive practices, and possible times. The practical implications of such perspectives inform organisation on how to select networks and predict their benefits. The research method included 28 interviews and casual observation of network sessions.
- Published
- 2014
10. Inter-organisational learning in project based organisations: Perspectives on reciprocity
- Author
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Abualqumboz, M and Chan, PW
- Subjects
HD28 - Abstract
This developmental paper discusses early research findings on the role that reciprocity plays in fostering or hindering inter-organisational learning in networks. Reciprocity as a social norm in knowledge creation and sharing networks is the main theme of this research. The paper uses two case studies of networks in UK. The qualitative case studies were developed through a mixture of participant observations, semi-structured interviews and casual conversations with network administrators and participants. Reciprocal exchanges were evident in networks. However, variations in what reciprocal exchanges meant for the participants were observed. Consequently, our findings suggest that the taken-for-granted idea that reciprocity is always good should be critically challenged. Often, we have observed asymmetrical reciprocal exchanges in participants tend to expect more from the networks than they would give. Therefore, this research suggests the need for remaining circumspect about the positive outcomes of networks that are often implicitly assumed.
- Published
- 2013
11. What do networks do to work : the agential role of network
- Author
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Abualqumboz, M and Chan, PW
- Subjects
HD28 - Abstract
The article draws on an ongoing study of interorganisational learning in project based organisations and how organisations learn through network settings. The article aimed at drawing theoretical explanations of network learning especially after learning moved from interorganisational learning to inter-networked learning. The article employs the structure agency relationship by Dave Elder-Vass as theoretical lens to draw conclusions that provides fresh explanations of how network are helpful in fostering learning activities. The research method included interviews, observation and archives. Data were analysed using thematic analysis which generated codes and then conclusion were drawn. The main contributions of this article are (1) to portray agency as another face of structure, (2) stress the agential role of networks, and (3) looking at networks as agents provides fresh understanding of benefits of networks.
- Published
- 2013
12. Rapid urbanization effect on local climate: intercomparison of climate trends in Shenzhen and Hong Kong, 1968-2013
- Author
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Li, L, primary, Chan, PW, additional, Wang, D, additional, and Tan, M, additional
- Published
- 2015
- Full Text
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13. Predicting the hourly Hong Kong representative sky from Typical Meteorological Year data for dynamic daylighting simulation
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Ho, JCK, primary, Ng, E, additional, and Chan, PW, additional
- Published
- 2014
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14. Observation and numerical simulation of terrain-disrupted wavy motion in the boundary layer with minor temperature inversion/isothermal at the Hong Kong international airport
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CHAN, PW, primary
- Published
- 2014
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15. A novel scheme for hybrid digital video watermarking: Approach, evaluation and experimentation
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Chan, PW, Lyu, MR, Chin, RT, Chan, PW, Lyu, MR, and Chin, RT
- Abstract
We have seen an explosion of data exchange in the Internet and the extensive use of digital media. Consequently, digital data owners can quickly and massively transfer multimedia documents across the Internet. This leads to wide interest in multimedia security and multimedia copyright protection. We propose a novel hybrid digital video watermarking scheme based on the scene change analysis and error correction code. Our video watermarking algorithm is robust against the attacks of frame dropping, averaging and statistical analysis, which were not solved effectively in the past. We start with a complete survey of current watermarking technologies, and noticed that none of the existing schemes is capable of resisting all attacks. Accordingly, we propose the idea of embedding different parts of a single watermark into different scenes of a video. We then analyze the strengths of different watermarking schemes, and apply a hybrid approach to form a super watermarking scheme that can resist most of the attacks. To increase the robustness of the scheme, the watermark is refined by an error correcting code, while the correcting code is embedded as a watermark in the audio channel. It optimizes the quality of the watermarked video. The effectiveness of this scheme is verified through a series of experiments, in which a number of standard image processing attacks are conducted, and the robustness of our approach is demonstrated using the criteria of the latest StirMark test.
- Published
- 2005
16. Cost of hospitalization for respiratory syncytial virus chest infection and implications for passive immunization strategies in a developing nation
- Author
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Chan, PW‐K, primary and Abdel‐Latif, ME‐A, additional
- Published
- 2003
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17. Ethnicity And Asthma Symptoms Associated With Ingestion Of Fruits
- Author
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Chan, PW-K, primary, Samsinah, H, additional, and Azlin, NM, additional
- Published
- 2002
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18. Audit and Cost of Treatment Modalities Provided for Respiratory Syncytial Virus Bronchiolitis in a Malaysian Teaching Hospital
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Chan, PW-K, primary
- Published
- 2002
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19. Functional consequences of trust in the construction supply chain: a multi-dimensional view
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Manu, E., Ankrah, N., Chinyio, E. A., David Proverbs, Chan, PW, and Neison, CJ
- Abstract
Trust is often linked to the emergence of cooperative behaviours that contribute to successful project outcomes. However, some have questioned the functional relevance of trust in contractual relations, arguing that control-induced cooperation can emerge from enforcement of contracts. These mixed views are further complicated by the multi-dimensional nature of trust, as different trust dimensions could have varying functional consequences. The aim of this study was to provide some clarity on the functional consequence of trust in the project supply chain. Data was gathered through passive observations, document reviews and semi-structured interviews with supply chain parties on two case study projects in the UK. A thematic data analysis approach was used to uncover multiple perspectives on the functional consequences of trust in the supply chain. Findings revealed that the weaker dimensions of trust, which are impersonal (cognition-based and systems-based) and the stronger (relational-based) dimension of trust, all fostered beneficial behaviours in the supply chain (effective knowledge sharing and self-organising behaviours). However, additional behavioural consequences (relational flexibility and extra commitment) emerged when trust was relational in nature, implying that different trust dimensions and their associated behavioural consequences can be prioritized in the supply chain based on perceived work package risks.
- Published
- 2016
20. Exploring the work practices of site managers as processes of embodiment
- Author
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Sandberg, R, Räisänen, C, Löwstedt, M, Raidén, A, Chan, PW, and Neilson, CJ
- Abstract
In construction, site managerial work has often been depicted as 'muddling through', skilfully solving problems as these inevitably crop up and trying to be everywhere at\ud the same time. This perspective seems to give precedence to structural conditions in the industry when explaining micro-level practice on construction sites. Recently, \ud however, organisation scholars have highlighted a need to investigate managerial practices as these unfold in everyday work. This means we ought to take into account \ud the actual work activities that influence expectations, meanings and values about what is desirable and necessarily relate to everyday work. The purpose of this paper is to further explore how practice enactment and outcomes are embedded in the lived, everyday work activities of real human beings working on site. The focus is on the work stories of two site managers, a man and a woman, in a large Swedish construction company. Drawing on their stories we \ud take a critical stance towards the established view that certain structural and cultural conditions are strong and \ud sufficient precursors to predict work practice outcomes. We propose instead that practices enacted on site can better be understood as various processes of embodiment.
21. Introducing site sense: Comparing situated knowledge in construction to coalmining
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Aboagye-Nimo, E, Raidén, A, Chan, PW, and Neilson, CJ
- Abstract
The acknowledgment of the use of tacit knowledge as a safety praxis in the mining industry has been in existence for over half a century. This is referred to as pit sense. \ud On the contrary, the use of tacit knowledge for site safety is only gathering steam in the construction industry. Research on common sense in construction suggests that \ud the conflicts with official practices and policies, and resistance from individuals in managerial roles, hold back advancements in employing tacit knowledge. Common sense in construction and pit sense in coalmining substantial similarities including their heavy dependence on self-preservation and the use of a bottom-up approach i.e. \ud both focusing on the discretion of the workers. We\ud introduce the concept of 'site sense' as an approach to site safety which is based on tacit knowledge and reflects \ud situatedness of knowledge. Non-participant observations and semi-structured interviews were used to collect data on the practices of workers of micro construction firms in relation to site safety. The research findings indicate that unlike site sense, pit sense has evolved from first being regarded as a mere informal practice to then \ud being acknowledged by managers as a way of workers \ud taking responsibility and accountability for their own safety. Site sense and pit sense are both recognised as \ud safety practices that are not formally taught but acquired through continuous practice. They are both situational knowledge gained through informal techniques and close \ud interactions among team members. In both schools of thought, it is widely known that experienced workers are proud to possess and demonstrate pit sense and site \ud sense respectively whereas newcomers do not yet possess this tacit and situated knowledge.
22. Synthesis of satellite and ground data provide unique perspectives for discovering the air pollution patterns: A case study in Guangdong Province, China.
- Author
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Li J, Lee KH, Qin K, Wong MS, Chan PW, and Zhang Z
- Subjects
- China, Carbon Monoxide analysis, Seasons, Air Pollution statistics & numerical data, Environmental Monitoring methods, Air Pollutants analysis, Ozone analysis, Particulate Matter analysis, Sulfur Dioxide analysis, Nitrogen Dioxide analysis
- Abstract
Existing studies have analyzed the spatio-temporal patterns of air pollutants by combining ground and satellite measurements, primarily for cross-validation purposes. However, the unique characteristics and discrepancies between satellite and ground measurements have rarely been leveraged to understand pollution patterns and identify air pollution sources. To our best knowledge, this study is the first to utilize these discrepancies to holistically analyze the spatial and temporal patterns and investigate local biomass-burning effects on the five typical air pollutants: particulate matter (PM
2.5 )/aerosol optical depth (AOD), carbon monoxide (CO), nitrogen dioxide (NO2 ), sulphur dioxide (SO2 ), and ozone (O3 ). Guangdong (GD) province was selected as a case study due to its complex air pollution sources and patterns. Ground-based analysis from 2015 to 2023 shows significant decreases in PM2.5 , CO, NO2 , and SO2 , and a significant increase in O3 in urban areas, indicating the efficacy of stringent air pollution control policies. However, satellite analysis shows significant downtrend only in AOD, while the trends of other pollutants are almost negligible, which are likely to be evidence of industrial migration. Both measurements exhibit regular seasonal patterns for all air pollutants. In-depth time-series comparisons between ground and satellite data reveal seasonal consistency for NO2 but noticeable discrepancies for both AOD and CO, which could be attributed to urban-rural differences and local versus transported pollution sources. Spatially, AOD and NO2 exhibits the most significant regional discrepancies, followed by SO2 and CO, with higher values observed over Pearl River Delta (PRD) compared to non-PRD regions. O3 is more evenly distributed, showing more pronounced seasonal variations than regional differences. The synergetic use of satellite and ground measurements collectively verifies the significant local biomass-burning effects on the five pollutants. These findings can aid in developing more targeted air pollution control policies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)- Published
- 2024
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23. An improved machine learning-based model for prediction of diurnal and spatially continuous near surface air temperature.
- Author
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Adeniran IA, Nazeer M, Wong MS, and Chan PW
- Abstract
Near-surface air temperature (Tair) is crucial for assessing urban thermal conditions and their impact on human health. Traditional Tair estimation methods, reliant on sparse weather stations, often miss spatial variability. This study proposes a novel framework using a federated learning artificial neural network (FLANN) for fine-scale Tair prediction. Leveraging spatially complete thermal data from Landsat 8/9, Sentinel 3, and Himawari 8/9 (105 acquisition days, 2013-2023), and data from automatic weather stations, 23 predictor variables were extracted. After rigorous selection processes, nine variables significantly correlated with Tair were identified. Comparative analysis against established machine learning and linear models, using cross-validation data, showed FLANN's superior performance with a Pearson correlation coefficient (r) of 0.98 and a root mean square error (RMSE) of 0.97 K, compared to r and RMSE of 0.85 and 1.09, respectively, for the linear model. FLANN showed greater improvements for urban stations with r and RMSE differences of 0.19 and - 2.03 K. Application of FLANN to predict Tair in Hong Kong in July 2023 enabled detailed urban heat island (UHI) analysis, revealing dynamic spatial and temporal UHI patterns. This study highlights FLANN's potential for accurate Tair prediction and UHI analysis, enhancing urban thermal environment management., (© 2024. The Author(s).)
- Published
- 2024
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24. Suitable temperature indicator for adverse health impacts in sub-tropical cities: a case study in Hong Kong from 2010-2019.
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Ho JY, Guo Y, Chong KC, Chan PW, Ho CK, Law HF, Chao R, Ng EYY, and Lau K
- Abstract
Heat-health warning systems and services are important preventive actions for extreme heat, however, global evidence differs on which temperature indicator is more informative for heat-health outcomes. We comprehensively assessed temperature predictors on their summer associations with adverse health impacts in a high-density subtropical city. Maximum, mean, and minimum temperatures were examined on their associations with non-cancer mortality and hospital admissions in Hong Kong during summer seasons 2010-2019 using Generalized Additive Models and Distributed Lag Non-linear Models. In summary, mean and minimum temperatures were identified as strong indicators for mortality, with a relative risk(RR) and 95% confidence interval(CI) of 1.037 (1.006-1.069) and 1.055 (1.019-1.092), respectively, at 95th percentile vs. optimal temperature. Additionally, minimum temperatures captured the effects of hospital admissions, RR1.009 (95%CI: 1.000- 1.018). In stratified analyses, significant associations were found for older adults, female sex, and respiratory-related outcomes. For comparison, there was no association between maximum temperature and health outcomes. With climate change and projected increase of night-time warming, the findings from this comprehensive assessment method are useful to strengthen heat prevention strategies and enhance heat-health warning systems. Other locations could refer to this comprehensive method to evaluate their heat risk, especially in highly urbanized environments and subtropical cities., (© 2024. The Author(s).)
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- 2024
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25. Case studies of the winds in the urban area of Hong Kong - Microclimate station observations and high resolution numerical simulations.
- Author
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Lo KW, Chan PW, Lai KK, Lau SPW, and Zhao ZH
- Abstract
Hong Kong, renowned for its densely packed urban areas, poses unique challenges for understanding the effects of buildings on local meteorological conditions. To address this, the Hong Kong Observatory has started building a network of urban meteorological monitoring stations since 2017 for monitoring, analysing and studying urban microclimate. This paper presents an observational and numerical study focusing on wind measurements obtained from wind sensors installed on two smart lampposts in Tsim Sha Tsui, a major urban area in Hong Kong. Two representative high wind conditions in Hong Kong, Super Typhoon Saola in 2023 and a strong monsoon case characterized by prevailing easterly winds, are considered. With the use of high resolution computational fluid dynamic simulations, major features of actual observations can be reproduced. This suggests that district scale or even street scale weather services could be possible in the future with sufficient computational power., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors. Published by Elsevier Ltd.)
- Published
- 2024
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26. Interpretable semi-supervised clustering enables universal detection and intensity assessment of diverse aviation hazardous winds.
- Author
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Gao H, Shen C, Wang X, Chan PW, Hon KK, and Li J
- Abstract
The identification of aviation hazardous winds is crucial and challenging in air traffic management for assuring flight safety, particularly during the take-off and landing phases. Existing criteria are typically tailored for special wind types, and whether there exists a universal feature that can effectively detect diverse types of hazardous winds from radar/lidar observations remains as an open question. Here we propose an interpretable semi-supervised clustering paradigm to solve this problem, where the prior knowledge and probabilistic models of winds are integrated to overcome the bottleneck of scarce labels (pilot reports). Based on this paradigm, a set of high-dimensional hazard features is constructed to effectively identify the occurrence of diverse hazardous winds and assess the intensity metrics. Verification of the paradigm across various scenarios has highlighted its high adaptability to diverse input data and good generalizability to diverse geographical and climate zones., (© 2024. The Author(s).)
- Published
- 2024
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27. Interpretable ensemble imbalance learning strategies for the risk assessment of severe-low-level wind shear based on LiDAR and PIREPs.
- Author
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Khattak A, Chan PW, Chen F, and Peng H
- Abstract
The occurrence of severe low-level wind shear (S-LLWS) events in the vicinity of airport runways poses a significant threat to flight safety and exacerbates a burgeoning problem in civil aviation. Identifying the risk factors that contribute to occurrences of S-LLWS can facilitate the improvement of aviation safety. Despite the significant influence of S-LLWS on aviation safety, its occurrence is relatively infrequent in comparison to non-SLLWS incidents. In this study, we develop an S-LLWS risk prediction model through the utilization of ensemble imbalance learning (EIL) strategies, namely, BalanceCascade, EasyEnsemble, and RUSBoost. The data for this study were obtained from PIREPs and LiDAR at Hong Kong International Airport. The analysis revealed that the BalanceCascade strategy outperforms EasyEnsemble and RUSBoost in terms of prediction performance. Afterward, the SHapley Additive exPlanations (SHAP) interpretation tool was used in conjunction with the BalanceCascade model for the risk assessment of various factors. The four most influential risk factors, according to the SHAP interpretation tool, were hourly temperature, runway 25LD, runway 25LA, and RWY (encounter location of LLWS). S-LLWS was likely to happen at Runway 25LD and Runway 25LA in temperatures ranging from low to moderate. Similarly, a high proportion of S-LLWS events occurred near the runway threshold, and a relatively small proportion occurred away from it. The EIL strategies in conjunction with the SHAP interpretation tool may accurately predict the S-LLWS without the need for data augmentation in the data pre-processing phase., (© 2023 Society for Risk Analysis.)
- Published
- 2024
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28. AI-supported estimation of safety critical wind shear-induced aircraft go-around events utilizing pilot reports.
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Khattak A, Zhang J, Chan PW, Chen F, and Matara CM
- Abstract
The occurrence of wind shear and severe thunderstorms during the final approach phase contributes to nearly half of all aviation accidents. Pilots usually employ the go-around procedure in order to lower the likelihood of an unsafe landing. However, multiple factors influence the go-arounds induced by wind shear. In order to predict the wind shear-induced go-around, this study utilized a cutting-edge AI-based Combined Kernel and Tree Boosting (KTBoost) framework with various data augmentation strategies. First, the KTBoost model was trained, tested, and compared to other Machine Learning models using the data extracted from Hong Kong International Airport (HKIA)-based Pilot Reports for the years 2017-2021. The performance evaluation revealed that the KTBoost model with Synthetic Minority Oversampling Technique - Edited Nearest Neighbor (SMOTE-ENN)- augmented data demonstrated superior performance as measured by the F1-Score (94.37%) and G-Mean (94.87%). Subsequently, the SHapley Additive exPlanations (SHAP) approach was employed to elucidate the interpretation of the KTBoost model using data that had been treated with the SMOTE-ENN technique. According to the findings, flight type, wind shear magnitude, and approach runway contributed the most to the wind shear-induced go-around. Compared to international flights, Hong Kong-based airlines endured the highest number of wind shear-induced go-arounds. Shear due to the tailwind contributed more to the go-around than the headwinds. The runways with the most wind shear-induced Go-arounds were 07C and 07R., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Afaq Khattak reports financial support was provided by 10.13039/501100001809National Natural Science Foundation of China. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)
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- 2024
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29. Chromosomal evolution, environmental heterogeneity, and migration drive spatial patterns of species richness in Calochortus (Liliaceae).
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Karimi N, Krieg CP, Spalink D, Lemmon AR, Lemmon EM, Eifler E, Hernández AI, Chan PW, Rodríguez A, Landis JB, Strickler SR, Specht CD, and Givnish TJ
- Subjects
- Phylogeny, Ecosystem, Chromosomes, Genetic Speciation, Biological Evolution, Liliaceae
- Abstract
We used nuclear genomic data and statistical models to evaluate the ecological and evolutionary processes shaping spatial variation in species richness in Calochortus (Liliaceae, 74 spp.). Calochortus occupies diverse habitats in the western United States and Mexico and has a center of diversity in the California Floristic Province, marked by multiple orogenies, winter rainfall, and highly divergent climates and substrates (including serpentine). We used sequences of 294 low-copy nuclear loci to produce a time-calibrated phylogeny, estimate historical biogeography, and test hypotheses regarding drivers of present-day spatial patterns in species number. Speciation and species coexistence require reproductive isolation and ecological divergence, so we examined the roles of chromosome number, environmental heterogeneity, and migration in shaping local species richness. Six major clades-inhabiting different geographic/climatic areas, and often marked by different base chromosome numbers (n = 6 to 10)-began diverging from each other ~10.3 Mya. As predicted, local species number increased significantly with local heterogeneity in chromosome number, elevation, soil characteristics, and serpentine presence. Species richness is greatest in the Transverse/Peninsular Ranges where clades with different chromosome numbers overlap, topographic complexity provides diverse conditions over short distances, and several physiographic provinces meet allowing immigration by several clades. Recently diverged sister-species pairs generally have peri-patric distributions, and maximum geographic overlap between species increases over the first million years since divergence, suggesting that chromosomal evolution, genetic divergence leading to gametic isolation or hybrid inviability/sterility, and/or ecological divergence over small spatial scales may permit species co-occurrence., Competing Interests: Competing interests statement:The authors declare no competing interest.
- Published
- 2024
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30. Characteristics of early short-term traditional Chinese medicine in breast cancer patients: A population-based cohort study.
- Author
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Chan PW, Yu H, Hsu CH, and Liu CY
- Subjects
- Humans, Female, Medicine, Chinese Traditional, Retrospective Studies, Cohort Studies, Practice Patterns, Physicians', Taiwan, Breast Neoplasms drug therapy, Drugs, Chinese Herbal therapeutic use
- Abstract
Background: Traditional Chinese medicine (TCM) is frequently utilized as a complementary therapy for breast cancer patients. TCM primarily involves the use of Chinese herbal products (CHPs), which consist of single or multiherb formulas with diverse therapeutic effects documented in medical classics. The study aims to investigate the association between medication possession ratios to CHPs within 2-year post breast cancer diagnosis and 5-year survival, to explore the potential beneficial class effect of TCM., Methods: This retrospective population-based cohort study included newly diagnosed breast cancer patients between 2003 and 2006, identified from the National Health Insurance Research Database of Taiwan. Logistic regression and Cox proportional hazards analysis were utilized to assess the likelihood of medication possession ratios (MPRs) for CHPs and to examine the association of variables with 5-year survival., Results: A total of 3472 patients with breast cancer were included. Patients who had MPR of 1% to 9% and 10% to 19% for CHPs within 2 years after breast cancer diagnosis exhibited better 5-year survival rates compared with those who did not use CHPs (adjusted hazard ratio [aHR] 0.69, 95% confidence interval [CI] 0.55-0.86, p = 0.001; aHR 0.50, 95% CI 0.28-0.88, p = 0.016). Furthermore, the use of TCM formulations specifically targeting insomnia, such as Tian-wang-bu-xin-dan and Suan-zao-ren-tang, demonstrated a significantly positive association with survival (aHR 0.71, 95% CI 0.52-0.98, p = 0.035) among patients who were short-term users of CHPs (MPR of 1% to 19%)., Conclusion: Short-term use of TCM (ie, MPR to CHPs 1~19%) within 2-year post breast cancer diagnosis present positive association with survival outcome. Tian-wang-bu-xin-dan and Suan-zao-ren-tang may have benefits to 5-year survival, but their causality still need further investigation., Competing Interests: Conflicts of interest: Dr. Chun-Yu Liu, an editorial board member at Journal of the Chinese Medical Association , had no role in the peer review process of or decision to publish this article. The other authors declare that they have no conflicts of interest related to the subject matter or materials discussed in this article., (Copyright © 2023, the Chinese Medical Association.)
- Published
- 2024
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31. Numerical simulation research on the overturning of gantry crane by downbursts.
- Author
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Su JC, Li L, Chan PW, Zhou QJ, and Yang HL
- Abstract
Based on the simulation of the fluid-structure interaction response, the cause of an overturning of a gantry crane induced by a downburst in Shenzhen is studied in this paper. According to the results, (1) Vicroy's downburst model could establish the steady-state wind field of the downburst more reasonably when there was only low-level wind speed observation data, and its simulation results were close to the two-dimensional downburst numerical simulation results; (2) Compared with the normal exponential vertical profile of wind speed, the disturbance caused by the front girder of the double-girder gantry crane structure under the downburst wind field was more severe, which increases the probability of the gantry crane overturning. (3) The downwind displacement of the main girder of the gantry crane under the condition of downburst is far greater than that under the normal condition. At the same time, under the condition of downburst, the pressure difference on the surface of the gantry crane was greater, and the distribution of the support reaction force was more uneven, resulting in a stronger overturning tendency of the gantry crane. (4) Under the condition of downburst, the overturning moment and the shearing force borne by the foundation of gantry crane exceeded the critical value to maintain the stability of the gantry crane by the gravity, resulting in the overturning of the gantry crane., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors. Published by Elsevier Ltd.)
- Published
- 2023
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32. Assessing wind field characteristics along the airport runway glide slope: an explainable boosting machine-assisted wind tunnel study.
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Khattak A, Chan PW, Chen F, and Peng H
- Subjects
- Bayes Theorem, Hong Kong, Airports, Aircraft
- Abstract
Aircraft landings are especially perilous when the wind is gusty near airport runways. For this reason, an aircraft may deviate from its glide slope, miss its approach, or even crash in the worst cases. In the study, we used the state-of-the-art glass-box model, the Explainable Boosting Machine (EBM), to estimate the variation in headwind speed and turbulence intensity along the airport runway glide slope and to interpret the various contributing factors. To begin, the wind field characteristics were examined by developing a scaled-down model of Hong Kong International Airport (HKIA) runway as well as and the surrounding buildings and complex terrain in the TJ-3 atmospheric boundary layer wind tunnel. The placement of probes along the glide slope of the model runway aided in the measurement of wind field characteristics at different locations in the presence and absence of surrounding buildings. Next, the experimental data was used to train the EBM model in conjunction with Bayesian optimization approach. The counterpart black box models (extreme gradient boosting, random forest, extra tree and adaptive boosting) as well as other glass box models (linear regression and decision tree) were compared with the outcomes of the EBM model. Based on the holdout testing data, the EBM model revealed superior performance for both variation in headwind speed and turbulence intensity in terms of mean absolute error, mean squared error, root mean squared error and R-square values. To further evaluate the impact of different factors on the wind field characteristics along the airport runway glide slope, the EBM model allows for a full interpretation of the contribution of individual and pairwise interactions of factors to the prediction results from both a global and a local perspective., (© 2023. The Author(s).)
- Published
- 2023
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33. Observations of boundary layer wind and turbulence of a landfalling tropical cyclone.
- Author
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Zhao Z, Gao R, Zhang JA, Zhu Y, Liu C, Chan PW, and Wan Q
- Abstract
This study investigates the atmospheric boundary layer structure based on multiple-level tower observations with a height of 350 m during the landfall of Super Typhoon Mangkhut (2018). Results show a layer of log wind profile outside of the radius of maximum wind speed with a height of 100 m or larger. The log layer height increases with the wind speed. The height of the constant flux layer reaches ~ 300 m for 10-m wind speeds less than 13 m s
-1 while this height decreases with the wind speed. Momentum fluxes and turbulent kinetic energy increase with the wind speed at all vertical levels. The drag coefficient and surface roughness length estimated at the tower location have values of 7.3 × 10-3 and 0.09 m, respectively, which are independent of wind speed. The estimated vertical eddy diffusivity and mixing length increase with height up to ~ 160 m and then slowly decrease with height. The vertical eddy diffusivity increases with the wind speed while the vertical mixing length has no dependence on the wind speed. Comparing our results with previous work indicates that the vertical eddy diffusivity is larger over land than over ocean at a given wind speed range., (© 2022. The Author(s).)- Published
- 2022
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- View/download PDF
34. Probable cross-corridor transmission of SARS-CoV-2 due to cross airflows and its control.
- Author
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Cheng P, Chen W, Xiao S, Xue F, Wang Q, Chan PW, You R, Lin Z, Niu J, and Li Y
- Abstract
A COVID-19 outbreak occurred in May 2020 in a public housing building in Hong Kong - Luk Chuen House, located in Lek Yuen Estate. The horizontal cluster linked to the index case' flat (flat 812) remains to be explained. Computational fluid dynamics simulations were conducted to obtain the wind-pressure coefficients of each external opening on the eighth floor of the building. The data were then used in a multi-zone airflow model to estimate the airflow rate and aerosol concentration in the flats and corridors on that floor. Apart from flat 812 and corridors, the virus-laden aerosol concentrations in flats 811, 813, 815, 817 and 819 (opposite to flat 812, across the corridor) were the highest on the eighth floor. When the doors of flats 813 and 817 were opened by 20%, the hourly-averaged aerosol concentrations in these two flats were at least four times as high as those in flats 811, 815 and 819 during the index case's home hours or the suspected exposure period of secondary cases. Thus, the flats across the corridor that were immediately downstream from flat 812 were at the highest exposure risk under a prevailing easterly wind, especially when their doors or windows that connected to the corridor were open. Given that the floorplan and dimension of Luk Chuen House are similar to those of many hotels, our findings provide a probable explanation for COVID-19 outbreaks in quarantine hotels. Positive pressure and sufficient ventilation in the corridor would help to minimise such cross-corridor infections., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 Elsevier Ltd. All rights reserved.)
- Published
- 2022
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35. Short-Term Nationwide Airport Throughput Prediction With Graph Attention Recurrent Neural Network.
- Author
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Zhu X, Lin Y, He Y, Tsui KL, Chan PW, and Li L
- Abstract
With the dynamic air traffic demand and the constrained capacity resources, accurately predicting airport throughput is essential to ensure the efficiency and resilience of air traffic operations. Many research efforts have been made to predict traffic throughputs or flight delays at an airport or over a network. However, it is still a challenging problem due to the complex spatiotemporal dynamics of the highly interacted air transportation systems. To address this challenge, we propose a novel deep learning model, graph attention neural network stacking with a Long short-term memory unit (GAT-LSTM), to predict the short-term airport throughput over a national air traffic network. LSTM layers are included to extract the temporal correlations in the data, while the graph attention mechanism is used to capture the spatial dependencies. For the graph attention mechanism, two graph modeling methods, airport-based graph and OD-pair graph are explored in this study. We tested the proposed model using real-world air traffic data involving 65 major airports in China over 3 months in 2017 and compared its performance with other state-of-the-art models. Results showed that the temporal pattern was the dominate factor, compared to the spatial pattern, in predicting airport throughputs over an air traffic network. Among the prediction models that we compared, both the proposed model and LSTM performed well on prediction accuracy over the entire network. Better performance of the proposed model was observed when focusing on airports with larger throughputs. We also conducted an analysis on model interpretability. We found that spatiotemporal correlations in the data were learned and shown via the model parameters, which helped us to gain insights into the topology and the dynamics of the air traffic network., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Zhu, Lin, He, Tsui, Chan and Li.)
- Published
- 2022
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36. Intercomparison of Local Warming Trends of Shanghai and Hong Kong Based on 120-Year Temperature Observational Data.
- Author
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Yang Y, Li L, Chan PW, Zhou Q, and Sheng B
- Subjects
- China, Cities, Hong Kong, Humans, Temperature, Hot Temperature
- Abstract
Using surface air temperature observations from 1901 to 2020, this study compared the warming trends of Shanghai and Hong Kong over a period of 120 years. The statistical results reveal the following: (1) The average temperatures of the two cities underwent fluctuating increases during the past 120 years, with linear warming rates of 0.23 °C/decade in Shanghai and 0.13 °C/decade in Hong Kong. (2) The fluctuation ranges of maximum temperature in the two cities were considerably higher than those of mean temperature. Moreover, in both cities, the annual mean maximum temperature decreased during a phase of more than a decade. The fluctuation ranges of minimum temperature were smaller, whereas the linear increases were higher than those for the mean temperature. (3) The diurnal temperature ranges (DTRs) of the two cities decreased; a certain phase of the decreases in DTR in the two cities was caused by decreases in the maximum temperature. (4) At a certain stage of urban development, owing to the shading effect of new high-rise buildings, the solar shortwave radiation reaching the Earth's surface decreased, and anthropogenic heat generated by the energy consumption of buildings and urban human activities at that time was not sufficient to make up for the reduced shortwave radiation. This result may have led to the declines in the maximum temperature experienced by both cities. (5) Currently, the number of hot days and extremely hot days in the two cities has increased significantly compared with that a century ago, indicating that climate warming has an adverse impact on human settlements.
- Published
- 2022
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37. Impact of the COVID-19 on the vertical distributions of major pollutants from a tower in the Pearl River Delta.
- Author
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Li L, Lu C, Chan PW, Lan Z, Zhang W, Yang H, and Wang H
- Abstract
The outbreak of the 2019 novel coronavirus (COVID-19) had a large impact on human health and socio-economics worldwide. The lockdown implemented in China beginning from January 23, 2020 led to sharp reductions in human activities and associated emissions. The declines in primary pollution provided a unique opportunity to examine the relationship between anthropogenic emissions and air quality. This study reports on air pollutant and meteorological measurements at different heights from a tall tower in the Pearl River Delta. These measurements were used to investigate the vertical scale response of pollutants to understand reductions in human activities. Compared to that in the pre-lockdown period (from December 16, 2019), the concentrations of surface layer nitric oxide (NO
x ), fine particulate matter (PM2.5 ), and daily maximum 8 h average ozone (MDA8O3 ) declined significantly during the lockdown by 76.8%, 49.4%, and 18.6%, respectively. Although the vertical profiles of NOx and O3 changed during the lockdown period, those of PM2.5 remained the same. During the lockdown period, there were statistically significant correlations between PM2.5 and O3 but not between PM2.5 and NOx at four heights, indicating that the main composition of PM2.5 have dramatically changed, during which the impact of NOx on PM2.5 became insignificant. Additionally, O3 concentrations were also insensitive to NOx concentrations during the lockdown, implying that O3 levels were more of a representative of regional background level. In this case, local photochemical formation is no longer a significant ozone source. This evidence suggests that it is possible to mitigation of PM2.5 and O3 levels simultaneously by significant reductions in anthropogenic emissions., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this paper., (© 2022 Elsevier Ltd. All rights reserved.)- Published
- 2022
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38. Dual challenges of heat wave and protective facemask-induced thermal stress in Hong Kong.
- Author
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Shi D, Song J, Du R, and Chan PW
- Abstract
During the COVID-19 pandemic, wearing protective facemasks (PFMs) can effectively reduce infection risk, but the use of PFMs can amplify heat-related health risks. We studied the amplified PFM-induced human thermal stress via both field measurements and model simulations over a typical subtropical mountainous city, Hong Kong. First, a hot and humid PFM microenvironment has been observed with high temperature (34-35 °C) and high humidity (80-95%), resulting in an aggravated facial thermal stress with a maximal PFM-covered facial heat flux of 500 W/m
2 under high-intensity activities. Second, to predict the overall PFM-inclusive human thermal stress, we developed a new facial thermal load model, SPFM and a new human-environment adaptive thermal stress (HEATS) model by coupling SPFM with an enhanced thermal comfort model to resolve modified human-environment interactions with the intervention of PFM under realistic climatic and topographical conditions. The model was then applied to predict spatiotemporal variations of PFM-inclusive physiological subjective temperature (PST) and corresponding heat stress levels during a typical heat wave event. It was found wearing PFM can significantly aggravate human thermal stress over Hong Kong with a spatially averaged PST increment of 5.0 °C and an additional spatial area of 158.4% exposed to the severest heat risks. Besides, PFM-inclusive PST was found to increase nonlinearly with terrain slopes at a rate of 1.3-3.9 °C/10°(slope), owing to elevated metabolic heat production. Furthermore, urban residents were found to have higher PFM-aggravated heat risks than rural residents, especially at night due to synergistic urban heat and moisture island effects., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 Elsevier Ltd. All rights reserved.)- Published
- 2021
- Full Text
- View/download PDF
39. On the Use of Dynamic Calibration to Correct Drop Counter Rain Gauge Measurements.
- Author
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Stagnaro M, Cauteruccio A, Lanza LG, and Chan PW
- Abstract
Dynamic calibration was performed in the laboratory on two catching-type drop counter rain gauges manufactured as high-sensitivity and fast response instruments by Ogawa Seiki Co. Ltd. (Japan) and the Chilbolton Rutherford Appleton Laboratory (UK). Adjustment procedures were developed to meet the recommendations of the World Meteorological Organization (WMO) for rainfall intensity measurements at the one-minute time resolution. A dynamic calibration curve was derived for each instrument to provide the drop volume variation as a function of the measured drop releasing frequency. The trueness of measurements was improved using a post-processing adjustment algorithm and made compatible with the WMO recommended maximum admissible error. The impact of dynamic calibration on the rainfall amount measured in the field at the annual and the event scale was calculated for instruments operating at two experimental sites. The rainfall climatology at the site is found to be crucial in determining the magnitude of the measurement bias, with a predominant overestimation at the low to intermediate rainfall intensity range.
- Published
- 2021
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- View/download PDF
40. A Micropatterned Human-Specific Neuroepithelial Tissue for Modeling Gene and Drug-Induced Neurodevelopmental Defects.
- Author
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Sahni G, Chang SY, Teo JCM, Tan JZY, Fatien JJC, Bonnard C, Utami KH, Chan PW, Tan TT, Altunoglu U, Kayserili H, Pouladi M, Reversade B, and Toh YC
- Published
- 2021
- Full Text
- View/download PDF
41. Influence of Traditional Chinese Medicine on Medical Adherence and Outcome in Estrogen Receptor (+) Breast Cancer Patients in Taiwan: A Real-World Population-Based Cohort Study.
- Author
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Chan PW, Chiu JH, Huang N, Chen CM, Yu H, Liu CY, and Hsu CH
- Subjects
- Adult, Aged, Aged, 80 and over, Drugs, Chinese Herbal therapeutic use, Female, Humans, Medication Adherence statistics & numerical data, Medicine, Chinese Traditional statistics & numerical data, Middle Aged, Receptors, Estrogen metabolism, Retrospective Studies, Taiwan, Treatment Outcome, Young Adult, Breast Neoplasms drug therapy, Breast Neoplasms mortality, Breast Neoplasms psychology, Medication Adherence psychology, Medicine, Chinese Traditional psychology
- Abstract
Background: Medical adherence is often higher in clinical trials than in real world practice. The aim of this study was to investigate the effects of traditional Chinese medicine (TCM) on medical adherence to hormonal therapy (HT) and survival outcome in ER (+) breast cancer patients in Taiwan., Subjects and Methods: Using a nationwide longitudinal population-based database, we enrolled patients with newly diagnosed ER-positive breast cancer who had received HT, and followed for up to 5 years (N = 872). Medication adherence in terms of medication possession ratios (MPR) and patient outcome were evaluated with or without TCM exposure. We applied logistic regression and Cox proportional hazards (PH) analysis to identify factors, including TCM exposure, associated with adherence to HT and mortality., Results: MPR to HT in general decreased over the 5-year period post breast cancer diagnosis. Both TCM and MPR to HT ≥ 80% were significantly associated with reduced risk of breast cancer-associated mortality. Subgroup analysis revealed that TCM annual visits ≥ 3 times with CHP prescription 1~90 days per year affected mortality reduction most significantly (HR: 0.26; 95% CI = 0.08-0.83; p < 0.05) compared to other TCM use. In contrast, using TCM (either short-term or long-term) was not associated with MPR in HT., Conclusions: Our results supported the potential advantage of TCM on breast cancer-associated mortality, whereas TCM use does not compromise medical adherence to HT. This study offers important insights in integrative therapy for HT in patients with estrogen receptor (+) breast cancer., (Copyright © 2020. Published by Elsevier GmbH.)
- Published
- 2021
- Full Text
- View/download PDF
42. A loss-of-function NUAK2 mutation in humans causes anencephaly due to impaired Hippo-YAP signaling.
- Author
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Bonnard C, Navaratnam N, Ghosh K, Chan PW, Tan TT, Pomp O, Ng AYJ, Tohari S, Changede R, Carling D, Venkatesh B, Altunoglu U, Kayserili H, and Reversade B
- Subjects
- Actins metabolism, Actomyosin metabolism, Amino Acid Sequence, Base Sequence, Cell Aggregation, Consanguinity, Down-Regulation genetics, Female, Fetus pathology, Genes, Recessive, Hippo Signaling Pathway, Humans, Male, Neural Stem Cells metabolism, Neural Tube pathology, Organoids pathology, Pedigree, Protein Domains, Protein Serine-Threonine Kinases chemistry, Signal Transduction, Transcription, Genetic, Turkey, YAP-Signaling Proteins, Adaptor Proteins, Signal Transducing metabolism, Anencephaly genetics, Loss of Function Mutation genetics, Protein Serine-Threonine Kinases genetics, Protein Serine-Threonine Kinases metabolism, Transcription Factors metabolism
- Abstract
Failure of neural tube closure during embryonic development can result in anencephaly, one of the most common birth defects in humans. A family with recurrent anencephalic fetuses was investigated to understand its etiology and pathogenesis. Exome sequencing revealed a recessive germline 21-bp in-frame deletion in NUAK2 segregating with the disease. In vitro kinase assays demonstrated that the 7-amino acid truncation in NUAK2, a serine/threonine kinase, completely abrogated its catalytic activity. Patient-derived disease models including neural progenitor cells and cerebral organoids showed that loss of NUAK2 activity led to decreased Hippo signaling via cytoplasmic YAP retention. In neural tube-like structures, endogenous NUAK2 colocalized apically with the actomyosin network, which was disrupted in patient cells, causing impaired nucleokinesis and apical constriction. Our results establish NUAK2 as an indispensable kinase for brain development in humans and suggest that a NUAK2-Hippo signaling axis regulates cytoskeletal processes that govern cell shape during neural tube closure., Competing Interests: Disclosures: The authors declare no competing interests exist., (© 2020 Bonnard et al.)
- Published
- 2020
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- View/download PDF
43. Gold and Brønsted Acid Catalyzed Spirocyclization of 2- and 3-Indolyl-Tethered 1,4-Enyne Acetates to Spiro[4, n ]alkyl[ b ]indoles.
- Author
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Chen X, Baratay CA, Mark ME, Xu X, and Hong Chan PW
- Abstract
A synthetic method to prepare spiro[4, n ]alkyl[ b ]indoles ( n = 4-6) efficiently that relies on the gold(I) and Brønsted acid mediated spirocyclization of 2- and 3-indolyl-tethered 1,4-enyne acetates at room temperature and open to air is described.
- Published
- 2020
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- View/download PDF
44. Path integration (PI) method for the parameter-retrieval of aircraft wake vortex by Lidar.
- Author
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Li J, Shen C, Gao H, Chan PW, Hon KK, and Wang X
- Abstract
Aircraft wake is a pair of strong counter-rotating vortices generated behind a flying aircraft. It might be very hazardous to a following aircraft and the real-time detection of it is of great interest in aviation safety field. Vortex-core positions and velocity circulations, which respectively represent the location and strength of a wake, are two characteristic parameters that have attracted the main attention in wake vortex detection. This paper introduces a new algorithm, the Path Integration (PI) method, to retrieve the characteristic parameters of wake vortex. The method uses Doppler velocity distribution to locate the vortex-core positions, and the integration of Doppler velocity along a LOS (line-of-sight) is derived as a linear expression about the circulations. From this expression, the circulations can be solved with the least square method. Moreover, an vortex-core position adjusting method is proposed to compensate the compressing and expanding effects of wake vortex caused by the scanning of Lidar beam. Basically, the use of Doppler velocity integration can improve the method's adaptability in turbulence environment and mitigate the impact of noise. Numerical examples and field detection data from Hong Kong international airport and Tsingtao Liuting airport have well verified the good performance of the method, in terms of both accuracy and efficiency.
- Published
- 2020
- Full Text
- View/download PDF
45. Gold-Catalyzed 1,2-Acyloxy Migration/Coupling Cascade of Propargyl Diazoacetates: Synthesis of Isomycin Derivatives.
- Author
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Bao M, Wang X, Qiu L, Hu W, Hong Chan PW, and Xu X
- Abstract
An efficient gold(I)-catalyzed carbocyclization reaction for the synthesis of isomycin derivatives from propargyl diazoacetates has been developed. The suggested cyclization pathway delineated the first example of a vinyl gold carbenoid species generated in situ from gold(I)-catalyzed 1,2-acyloxy migration and intercepted by a cross-coupling reaction with the remaining tethered diazo functionality. The use of protic additives was essential to regulating the reaction outcome by fine-tuning the catalytic preference of the gold(I) complex.
- Published
- 2019
- Full Text
- View/download PDF
46. A Fiber Bragg Grating-Based Anemometer.
- Author
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Huang CY, Chan PW, Chang HY, and Liu WF
- Abstract
A novel fiber anemometer based on two pairs of fiber gratings is experimentally demonstrated and can simultaneously detect wind speed and wind direction. One pair of gratings, which are separated by 90° in space, is fixed on a small stainless steel pipe driven by a rotating disc for measuring the wind-direction angle. The other pair is composed of a sensing and a matched grating. The frequency of the spectrum-shifted of the sensing grating to overlap with that of the matched grating is employed for determining the wind speed. The errors in the wind-speed and wind-angle measurements are experimentally demonstrated to be less than 1%. The proposed fiber anemometer with a simple and durable structure can be applied in wind-powered electricity generators.
- Published
- 2018
- Full Text
- View/download PDF
47. Parameter-retrieval of dry-air wake vortices with a scanning Doppler Lidar.
- Author
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Gao H, Li J, Chan PW, Hon KK, and Wang X
- Abstract
A wake vortex is a form of irregular airflow generated by a flying aircraft, which can cause a severe hazard for aviation. To quantify the hazard of a wake after fully roll-up and before rebound, this paper proposes an algorithm to retrieve its characteristic parameters (circulations, vortex-core positions, and vortex-core radii) with a scanning Doppler Lidar. In the algorithm, a governing equation related to the Doppler velocities and characteristic parameters is established based on the aerosols' weak inertia, from which the target parameters are solved with an optimization method. During the process, the distortion of Doppler velocity caused by the scanning of the Lidar beam is adjusted by the Doppler acceleration to achieve better estimations of the target characteristic parameters. Good performance of the algorithm has been verified by simulation and field detection data.
- Published
- 2018
- Full Text
- View/download PDF
48. A review of vedolizumab and ustekinumab for the treatment of inflammatory bowel diseases.
- Author
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Shim HH, Chan PW, Chuah SW, Schwender BJ, Kong SC, and Ling KL
- Abstract
Recent advancement in the understanding of the pathophysiology of inflammatory bowel disease has seen an expansion in therapeutic options. Vedolizumab, a selective α4β7 inhibitor, and ustekinumab, an IL 12/23 p40 inhibitor, have provided the much-awaited out-of-class alternatives for patients who have failed or who are intolerant to anti-Tumor Necrosis Factor (TNF) therapy. However, questions remain as to how we may best use these novel therapeutic agents. We evaluate the evidence available from randomized controlled trials and postmarketing cohort studies and discuss their safety, efficacy, and limitations, in relation to anti-TNF therapy, in optimizing the treatment outcomes.
- Published
- 2018
- Full Text
- View/download PDF
49. Chiral Brønsted Acid Catalyzed Enantioselective Dehydrative Nazarov-Type Electrocyclization of Aryl and 2-Thienyl Vinyl Alcohols.
- Author
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Jin J, Zhao Y, Gouranourimi A, Ariafard A, and Hong Chan PW
- Abstract
An efficient chiral Brønsted acid-catalyzed enantioselective dehydrative Nazarov-type electrocyclization (DNE) of electron-rich aryl- and 2-thienyl-β-amino-2-en-1-ols is described. The 4π conrotatory electrocyclization reaction affords access to a wide variety of the corresponding 1 H-indenes and 4 H-cyclopenta[ b]thiophenes in excellent yields of up to 99% and enantiomeric excess (ee) values of up to 99%. Experimental and computational studies based on a proposed intimate contact ion-pair species that is further assisted by hydrogen bonding between the amino group of the substrate cation and chiral catalyst anion provide insight into the observed product enantioselectivities.
- Published
- 2018
- Full Text
- View/download PDF
50. Gold-Catalyzed Formal [4 + 2] Cycloaddition of 5-(Ethynylamino)pent-2-yn-1-yl Esters to 1,2,3,5-Tetrahydrobenzo[ g]quinolines.
- Author
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Chen X, Merrett JT, and Hong Chan PW
- Abstract
A synthetic method to prepare 1,2,3,5-tetrahydrobenzo[ g]quinolines efficiently that relies on gold(I)-catalyzed cycloisomerization of 5-(ethynylamino)pent-2-yn-1-yl esters at room temperature under atmospheric conditions is described. The proposed reaction mechanism presents a unique instance of an in situ formed allenic ester and gold keteniminium species to undergo a formal [4 + 2] cycloaddition pathway.
- Published
- 2018
- Full Text
- View/download PDF
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