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Hierarchical routing protocols for wireless sensor network: a compressive survey
Get PDFWireless Sensor Networks (WSNs) are one of the key enabling technologies for the Internet of Things (IoT). WSNs play a major role in data communications in applications such as home, health care, environmental monitoring, smart grids, and transportation. WSNs are used in IoT applications and should be secured and energy efficient in order to provide highly reliable data communications. Because of the constraints of energy, memory and computational power of the WSN nodes, clustering algorithms are considered as energy efficient approaches for resource-constrained WSNs. In this paper, we present a survey of the state-of-the-art routing techniques in WSNs. We first present the most relevant previous work in routing protocols surveys then highlight our contribution. Next, we outline the background, robustness criteria, and constraints of WSNs. This is followed by a survey of different WSN routing techniques. Routing techniques are generally classified as flat, hierarchical, and location-based routing. This survey focuses on the deep analysis of WSN hierarchical routing protocols. We further classify hierarchical protocols based on their routing techniques. We carefully choose the most relevant state-of-the-art protocols in order to compare and highlight the advantages, disadvantage and performance issues of each routing technique. Finally, we conclude this survey by presenting a comprehensive survey of the recent improvements of Low-Energy Adaptive Clustering Hierarchy (LEACH) routing protocols and a comparison of the different versions presented in the literature
Blessing in Disguise or Bluffing in This Guide: CDA on the Chinese Language Education Policy for Ethnic Minority Students in Hong Kong
No full textSustainable Option for Hydrogen Production: Mechanistic Study of the Interaction between Cobalt Pincer Complexes and Ammonia Borane
Get PDFThe mechanism of the solvolysis/hydrolysis of ammonia borane by iridium (Ir), cobalt (Co), iron (Fe) and ruthenium (Ru) complexes with various PNP ligands has been revisited using density functional theory (DFT). The approach of ammonia borane (NH3BH3) to the metal center has been tested on three dierent possible mechanisms, namely, the stepwise, concerted and proton transfer mechanism. It was found that the theoretical analyses correlate with the experimental results very well, with the activities of the iridium complexes with dierent PNP ligands following the order: (tBu)2P \u3e (iPr)2P \u3e (Ph)2P through the concerted mechanism. The reaction barriers of the rate-determining steps for the dehydrogenation of ammonia borane catalyzed by the active species [(tBu)2PNP-IrH] (Complex I-8), are found to be 19.3 kcal/mol (stepwise), 15.2 kcal/mol (concerted) and 26.8 kcal/mol (proton transfer), respectively. Thus, the concerted mechanism is the more kinetically favorable pathway. It is interesting to find that stable (tBu)2PNP Co-H2O and (tBu)2PNP Co-NH3 chelation products exist, which could stabilize the active I-8 species during the hydrolysis reaction cycle. The use of more sterically hindered and electron-donating PNP ligands such as (adamantyl)2Pprovides similar activity as the t-butyl analogue. This research provides insights into the design of efficient cobalt catalysts instead of using precious and noble metal, which could benefit the development of a more sustainable hydrogen economy
Building information modelling for building services engineering: benefits, barriers and conducive measures
Get PDFPurpose – Mandating the use of building information modelling (BIM) in building projects has sprawled, but the uptake of BIM in building services engineering (BSE) remains sluggish. The purpose of this paper is to explore how to achieve wider adoption of BIM in BSE. Design/methodology/approach – Through an extensive literature review, the benefits of, barriers to and measures conducive to, using BIM for BSE were identified and classified. Built upon the review and a focus group meeting, a questionnaire was devised for an industry-wide survey in Hong Kong and the survey data were processed by statistical analyses. Findings – On the ranking of the benefits, strong agreements existed between the BSE and non-BSE respondent groups; yet no significant agreement was found between the two groups on the rankings of the barriers or the conducive measures. The top conducive measure, according to the BSE group, is “Allow enough time in project programme for BIM model development”. Research limitations/implications – The data collection and analysis methods of this study may be used for similar BIM studies in other places. Practical implications – The priority of the conducive measures, which aid policy or decision makers in formulating how to get BIM effectively implemented in BSE, are useful information in the pursuit of a more productive and sustainable built environment. Originality/value – This BIM study is specifically on BSE rather than the other disciplines (e.g. architecture, structural engineering) that have been widely studied
Improving street walkability: Biometeorological assessment of artificial-partial shade structures in summer sunny conditions
No full text© 2019, ISB. Recent rapid urbanization has rendered outdoor space a key quality-of-life factor, yet walkability studies especially in hot-humid climates have seldom considered human biometeorology. This site-level study investigated microclimatic functions of an overhead structure in improving walkability, and identified biometeorology-related factors influencing pedestrian behaviour. A walkway with overhead tinted glass cover, demarcated into sunny zone and shaded zone, was equipped with hanging aluminium fins. Human thermal sensation was approximated by physiologically equivalent temperature (PET) and universal thermal climate index (UTCI), both closely related to global solar radiation and black-globe temperature. Pedestrian flow was tallied by demographic factors to assess the choice between shaded or sunny zones. Compared with sunny zone, shaded zone slashed maximum global solar radiation by 432 W/m2 in full effect to achieve 90% solar radiation reduction. The maximum cooling in air and black-globe temperatures reached 0.8 °C and 6.1 °C respectively. The overhead structure imposed minimal effect on wind field in both zones. Contrast in maximum PET and UTCI between the two zones reached 8.2 °C and 5.3 °C respectively. In shaded zone, the dominant biometeorological condition was moderate heat stress or slightly warm sensation in contrast to strong heat stress or warm sensation in sunny zone. An overall preference for shaded zone was detected. Pedestrian gender and age, namely female and elderly, were significantly associated with shaded zone preference. The findings could inspire a biometeorological perspective in understanding walking behaviour and pedestrian-friendly facilities. Biometeorological-sensitive design of artificial shade could improve walkability in urban environment that increasingly demands climate change proofing
Re-evaluating effectiveness of vehicle emission control programmes targeting high-emitters
No full text© 2020, The Author(s), under exclusive licence to Springer Nature Limited. Estimating emission distribution within a vehicle fleet is critical for air pollution control. Previous studies reported that more than half of total fleet emissions were produced by only the highest 10% emitters, making repairing or deregistering a small percentage of high-emitters the most cost-effective measure to control vehicle emissions. With diesel emissions data from chassis dynamometer testing and on-road remote sensing, we show that such a strategy may be oversimplified
Stability analysis of rock wedge slide subjected to groundwater dynamic evolution
Get PDF© 2020 Elsevier B.V. Heavy rainfall may increase the infiltration rate, raising the groundwater table after a short period time. Variation in the hydrostatic pressure on potential sliding surfaces and trailing edges of fissures in a rock slope may contribute to slope failure. The failure mechanisms of rainfall-triggered rock wedge slides have been widely studied in the literature. However, studies on the dynamic evolution of groundwater in rock failure are still limited. In this study, a typical rock wedge slide that occurred in Chengkou County, Chongqing, China is selected as a case study to analyze the stability of rock wedge with double planes and tension crack subjected to groundwater dynamic evolution. Model tests were designed and performed to reproduce the dynamic evolution of groundwater in the rock slope and analyze its role in wedge failure. Development and distribution characteristics of water pressure are investigated through monitoring the water pressure distributed along the surfaces of wedge failures. From the experimental study, it is found that the initial formation process of water pressure along the sliding surface consists of four types of distribution patterns, i.e., triangular distribution, Type I trapezoidal distribution, Type II trapezoidal distribution, and Type III trapezoidal distribution. Based on the model tests and theoretical analysis, the order of the calculated safety factors of the Chengkou rock wedge slide are: triangle \u3e type I trapezoid \u3e type II trapezoid \u3e type III trapezoid. The existence of inflection points in the trapezoidal distribution mode significantly increases water pressure on both sides of rock wedge, which contributes instability. The new approach for investigation of the effect of dynamic evolution groundwater on stability of rock wedge slide is developed based on fundamental mechanism and experimental study. It can be adopted for stability assessment of similar rock wedge slides in other areas
Day in the Life 餐飲人生
Get PDFSam Chong 莊炳森
HTI graduate with an Advanced Certificate in Sommelier Studies and a Certificate in Food and Beverage Supervision, who is now assistant director of food and beverage at the New World Millennium Hong Kong Hotel
畢業於酒店及旅遊學院高級品酒師證書及餐飲督導管理證書課程，現任千禧新世界香港酒店助理餐飲總
Chemical and toxicological characterization of particulate emissions from diesel vehicles
No full textThis paper presents a detailed chemical and toxicological characterization of the diesel particulate matter (PM) emitted from diesel vehicles running on a chassis dynamometer under different driving conditions. Chemical analyses were performed to characterize the contents of organic carbon (OC), elemental carbon (EC), and 31 polycyclic aromatic hydrocarbons (PAHs) in the collected PM samples. The OC–EC analysis results revealed that PM emissions from diesel vehicles in this study were dominated by OC and that the emission of vehicles equipped with diesel particulate filters had high OC/EC ratios. The PAH analysis results revealed that 4- and 5-ring PAHs were the dominant PAHs in the OC fraction of the PM samples. Particle toxicity was evaluated through three toxicological markers in human A549 cells, namely (1) acellular 2,7-dichlorofluorescein (DCFH) for oxidative potential, (2) interleukin-6 (IL-6) for inflammation, and (3) glutathione (GSH) for antioxidation after exposure. Statistical analyses revealed that vehicle sizes have statistically significant effects on the concentrations of the markers. Correlation analysis between PAHs and toxicological markers revealed that significant correlations existed between specific compounds and markers. Our results can be used as a reference by policy makers to formulate emission control strategies and as a dataset for other modeling studies
