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  • 1.
    Byström, Alexandra
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Cheng, Xudong
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Full-scale experimental and numerical studies on compartment fire under low ambient temperature2012In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 51, p. 255-262Article in journal (Refereed)
    Abstract [en]

    A fire experiment with wood crib was conducted in a concrete building under low ambient temperature of −10 °C to explore fire development and temperature distribution. The concrete building consists of a two-storey compartment with the size of 9.0 m by 5.0 m by 4.8 m high and a four-storey stairwell with the size of 5.0 m by 2.4 m by 10.0 m high. The fuel mass loss rate and temperatures at different positions were measured. Two fire cases, with different assumed ambient temperatures of −10 °C and 20 °C respectively, were then simulated by using FDS software to investigate the effect of ambient temperature and compare with the experimental results. The numerical results show that the calculated heat release rate is in reasonably good agreement with the measured full-scale result before water suppression. The calculated temperatures in the hot combustion gas layer at different positions agree also very well with the measured values. However, the measured fresh air temperature at the floor level near the fire source is higher than the calculated value. This discrepancy may partly depend on measuring errors as analyzed in the paper.

  • 2.
    Cheng, Ka Yuen
    et al.
    School of Architecture, The Chinese University of Hong Kong, New Territories, Hong Kong, China.
    Lau, Kevin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Shek, Ying Ting
    Institute of Future Cities, The Chinese University of Hong Kong, New Territories, Hong Kong, China.
    Liu, Zhixin
    School of Architecture, The Chinese University of Hong Kong, New Territories, Hong Kong, China.
    Ng, Edward
    School of Architecture, The Chinese University of Hong Kong, New Territories, Hong Kong, China; Institute of Future Cities, The Chinese University of Hong Kong, New Territories, Hong Kong, China; Institute of Environment, Energy and Sustainability, The Chinese University of Hong Kong, New Territories, Hong Kong, China.
    Evaluation on the performance of tree view factor in a high-density subtropical city: A case study in Hong Kong2023In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 239, article id 110431Article in journal (Refereed)
  • 3.
    Han, Songyu
    et al.
    College of Mechanical and Vehicle Engineering, Hunan University, Changsha, China.
    Shao, Haidong
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics. College of Mechanical and Vehicle Engineering, Hunan University, Changsha, China.
    Huo, Zhiqiang
    Institute of Health Informatics, University College London, London, UK.
    Yang, Xingkai
    Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada.
    Cheng, Junsheng
    College of Mechanical and Vehicle Engineering, Hunan University, Changsha, 410082, China.
    End-to-end chiller fault diagnosis using fused attention mechanism and dynamic cross-entropy under imbalanced datasets2022In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 212, article id 108821Article in journal (Refereed)
    Abstract [en]

    Fault diagnosis techniques play an increasingly important role in the operation and maintenance of smart city systems. Artificial intelligence improves the efficiency of chiller system fault diagnosis, and greatly reduces the energy consumption of urban buildings. The existing intelligent fault diagnosis methods of chiller mostly rely on balanced training datasets; lacking fault samples makes these methods incompetent to extract reliable features to recognize abnormal machine conditions, resulting in the degraded performance. To overcome the deficiencies of reported studies, a new method, called end-to-end chiller fault diagnosis, is proposed using a fused attention mechanism and dynamic cross-entropy. Firstly, a one-dimensional convolution network (1D-CNN) and long-short term memory (LSTM) are combined to capture the spatial-temporal features from the original data directly. Afterwards, a fused attention mechanism is developed to further refine the extracted features to increase the contribution of crucial features and achieve high-quality diagnostic information mining. Finally, the dynamic cross-entropy (DCE) is designed for updating the imbalance factor in real-time, with more focus on the hard-classified types. The experimental analysis results demonstrate the feasibility and superiority of the proposed method in identifying chiller system faults with imbalanced datasets.

  • 4.
    Ho, Hung Chak
    et al.
    Healthy High Density Cities Lab, The University of Hong Kong, Hong Kong, China; Department of Urban Planning and Design, The University of Hong Kong, Hong Kong, China; Department of Anaesthesiology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
    Wang, Dan
    Faculty of Health Sciences, Ontario Tech University, Canada; Institute for Disability and Rehabilitation Research, Canada.
    Leung, Jason
    Jockey Club Centre for Osteoporosis Care and Control, The Chinese University of Hong Kong, Hong Kong, China.
    Yu, Blanche
    Jockey Club Centre for Osteoporosis Care and Control, The Chinese University of Hong Kong, Hong Kong, China; Department of Medicine & Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.
    Woo, Jean
    Department of Medicine & Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China; Jockey Club Institute of Ageing, The Chinese University of Hong Kong, Hong Kong, China.
    Yui Kwok, Timothy Chi
    Jockey Club Centre for Osteoporosis Care and Control, The Chinese University of Hong Kong, Hong Kong, China; Department of Medicine & Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.
    Lau, Kevin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    “Planned greenspace” or “natural greenspace” in a high-density city with compact environment? An empirical study of osteoporosis among senior population2022In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 219, article id 109117Article in journal (Refereed)
    Abstract [en]

    Osteoporosis is a major physical health issue in healthy ageing among urban populations. However, few studies have investigated how greenspace can influence osteoporosis, especially to those who lived in a compact city with high-density living environment. Furthermore, no studies have investigated how “planned greenspace” and “natural greenspace” can separately influence osteoporosis among senior population. We hereby conducted an empirical study to evaluate the relationship between osteoporosis, “planned greenspace” and “natural greenspace”, based on the use of land use data derived from local geospatial information and satellite images. Our results showed that seniors who were 1) aged, 2) female, 3) less educated, 4) smokers, and 5) with chronic respiratory diseases were associated with osteoporosis. Considering factors of greenspace, a higher percentage of planned greenspace surrounding the residence may be a protective factor while natural greenspace did not influence the individuals. Specifically, a 10% increase of planned greenspace within the 600-m radius area surrounding the residence was negative associated with osteoporosis (−2.8% [-5.1%, −0.5%]). Based on our results, development of planned greenspace may be necessary, as compact built environment of a high-density city often resulted in a lack of planned greenspace for physical activities. Along with the World Health Organization (WHO) guidelines for an age-friendly city, our findings suggest that improving the planned greenspace in a walkable distance around one's neighboring environment is a potential strategy for prevention of osteoporosis and related physical health issues as well as for life quality improvement among the senior population.

  • 5.
    Liu, Zhixin
    et al.
    School of Architecture, The Chinese University of Hong Kong, New Territories, Hong Kong, China.
    Cheng, Ka Yuen
    Institute of Future Cities, The Chinese University of Hong Kong, New Territories, Hong Kong, China.
    He, Yueyang
    Institute of Future Cities, The Chinese University of Hong Kong, New Territories, Hong Kong, China.
    Jim, C.Y.
    Department of Social Sciences, The Education University of Hong Kong, New Territories, Hong Kong, China.
    Brown, Robert D.
    Department of Landscape Architecture and Urban Planning, Texas A&M University, College Station, TX, 77840, USA.
    Shi, Yuan
    Department of Geography & Planning, University of Liverpool, Liverpool, UK.
    Lau, Kevin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Ng, Edward
    School of Architecture, The Chinese University of Hong Kong, New Territories, Hong Kong, China; Institute of Future Cities, The Chinese University of Hong Kong, New Territories, Hong Kong, China; Institute of Environment, Energy and Sustainability, The Chinese University of Hong Kong, New Territories, Hong Kong, China.
    Microclimatic measurements in tropical cities: Systematic review and proposed guidelines2022In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 222, article id 109411Article, review/survey (Refereed)
    Abstract [en]

    To tackle urban overheating induced by the combined effect of global warming and intensive urbanization, researchers have recommended assimilating microclimate-related strategies into urban design practices. Field measurements, playing a central role in urban climatology, have been widely applied worldwide. Reviewing the last five years' field measurement studies and existing guidelines and standards from WMO (World Meteorological Organization) and ISO (International Organization for Standardization), this study identified a gap between available guidelines and researchers' practical needs to ascertain the collection of high caliber data. Therefore, dedicated guidelines are required to explain the crucial conceptual and application issues and refine systematic field measurement methods. This demand is particularly acute for microscale and urban environments. This study proposed and explained integrated and comprehensive guidelines for systematic microclimate field measurements. The suggested workflow included four main steps: formulating field measurement plan, preparing for field measurements, sustaining measurement quality, and curating data. The complex and heterogeneous environment in urban areas was carefully evaluated to hone the data acquisition campaign and ascertain data quality. Relevant concepts and practices learned from existing guidelines and standards, experiences from actual field studies, and professional recommendations were distilled and incorporated into the guidelines. The significance of a complete report with full metadata was emphasized. Detailed hints, precautions, recommendations, examples, and a metadata checklist were provided as a helpful and actionable package of research procedures.

  • 6.
    Lundqvist, Petter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Risberg, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Westerlund, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Air heating system design for a sub-Arctic climate using a CFD technique2019In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 160, article id 106164Article in journal (Refereed)
    Abstract [en]

    The thermal comfort in a residential building equipped with an air heating system and located in a sub-Arctic region was investigated with computational fluid dynamics (CFD) software. The predicted percentage of dissatisfied (PPD) was used to identify flaws with the heating system during winter conditions. New scenarios were simulated and compared to each other to see potential improvements of the thermal indoor climate. Comparison was done by combining the discomfort spaces inside rooms, the level of the discomfort and the time spent in these spaces. The discomfort covered 8–38% of the interior volume depending on the test case. The results provide the necessary means to create a satisfactory thermal indoor climate if an air heating system is to be utilized in sub-Arctic regions during the winter. The correct heat demand for each floor and appropriate placement of the supply devices are required. Adding air transfer units or grilles in rooms from which exhaust air is removed further improves the comfort. The results also show the strength of using CFD technique when investigating the indoor discomfort with PPD, and how a fair assessment can be done by combining the PPD with time.

  • 7.
    Ouyang, Wanlu
    et al.
    School of Architecture, The Chinese University of Hong Kong, New Territories, Hong Kong, China; Institute of Future Cities, The Chinese University of Hong Kong, New Territories, Hong Kong, China.
    Liu, Zhixin
    School of Architecture, The Chinese University of Hong Kong, New Territories, Hong Kong, China.
    Lau, Kevin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Shi, Yuan
    Department of Geography & Planning, University of Liverpool, Liverpool, UK.
    Ng, Edward
    School of Architecture, The Chinese University of Hong Kong, New Territories, Hong Kong, China; Institute of Future Cities, The Chinese University of Hong Kong, New Territories, Hong Kong, China; Institute of Environment, Energy and Sustainability, The Chinese University of Hong Kong, New Territories, Hong Kong, China.
    Comparing different recalibrated methods for estimating mean radiant temperature in outdoor environment2022In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 216, article id 109004Article in journal (Refereed)
    Abstract [en]

    Mean radiant temperature (MRT) is a significant variable for outdoor thermal comfort studies. Two measurement-based methods can estimate MRT, one is globe thermometer – cheap, easily-applied but relatively inaccurate, another is integral radiation measurement method (also known as the six-directional method) - accurate but expensive. Due to low-cost and convenience, the globe thermometer has been widely used. Previous studies have improved its estimation accuracy by recalibrating the convection coefficients in the ISO method. Thus, it is pending to cross-compare the performance of these recalibrated methods.

    This study aims to investigate the transferability of the recalibrated methods for estimating MRT in outdoor environment. First, field measurement was conducted in a subtropical city, Hong Kong. MRT was obtained through two methods: globe thermometer and integral radiation method. Second, the existing recalibrated convection coefficients were summarized, and the localized convection coefficient was recalibrated. Third, all recalibrated methods were compared for their performance. The impacts of measurement locations, devices, analysis time intervals were examined.

    The results showed that the newly recalibrated method achieved the lowest estimation errors (RMSE = 3.84 °C). Other recalibrated methods presented higher RMSE (3.84–17.52 °C), similar as conventional ISO method (7.91 °C). Especially for open spaces, the coefficients from other cities should be cautiously applied when the accuracy requirement is less than ±2 °C. Kestrel and Grey globe are more recommended in subtropical cities. This study shed light on the application of globe thermometer for outdoor environment, and emphasized the necessity in recalibrating the convection coefficients locally.

  • 8.
    Pettersson, Maria
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Ljunggren, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Simmons, Christian
    Simmons akustik och utveckling, Chalmers Teknikpark, 412 58, Göteborg, Sweden.
    The effect of furniture when measuring reverberation times at low frequencies from 31.5 Hz2022In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 223, article id 109480Article in journal (Refereed)
    Abstract [en]

    When evaluating impact sound insulation of dwellings, including frequencies below 50 Hz has been reported to improve the correlation between the measurements and the occupants’ rating of annoyance from footstep noise. To determine the impact sound insulation, the reverberation time of the receiving room must be considered, a procedure that may introduce large errors at low frequencies. If it can be shown that normal furniture does not affect the absorption (and thereby neither the reverberation time), the reverberation time below 50 Hz could be omitted in the evaluation of impact sound insulation. This would improve the measurement accuracy of the impact sound insulation and simplify the measurement procedure. The purpose of this paper is to investigate to what extent fully furnished rooms for residential purposes affect the reverberation time. Measurements are conducted using the integrated impulse response method in two empty and furnished bedrooms of different construction. Due to the potential errors in the reverberation time measurement, sound pressure level was measured for comparison. No statistically significant absorption difference due to furniture could be found at frequencies below 50 Hz, neither for the measured reverberation times nor the difference in sound pressure level. As a consequence, impact sound insulation may be evaluated without any reverberation measurement below 50 Hz.

  • 9.
    Risberg, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Vesterlund, Mattias
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Westerlund, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Dahl, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    CFD simulation and evaluation of different heating systems installed in low energy building located in sub-arctic climate2015In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 89, p. 160-169Article in journal (Refereed)
    Abstract [en]

    Computational Fluid Dynamics (CFD) simulations were used to study the indoor climate in a low energy building in northern Sweden. The building’s low heat requirement raise the prospect of using a relatively simple and inexpensive heating system to maintain an acceptable indoor environment, even in the face of extremely low outdoor temperature. To explore the viability of this approach, the indoor climate in the building was studied considering three different heating systems: a floor heating system, air heating through the ventilation system and an air heat pump installation with one fan coil unit. The floor heating system provided the most uniform operative temperature distribution and was the only heating system that fully satisfied the recommendations to achieve tolerable indoor climate set by the Swedish authorities. On the contrary, air heating and the air heat pump created a relatively uneven distribution of air velocities and temperatures, and none of them fulfills the specified recommendations. From the economic point of view, the air heat pump system was cheaper to be installed but produced a less pleasant indoor environment than the other investigated heating systems.

  • 10.
    Vassiliades, C.
    et al.
    Department of Architecture, Land and Environmental Sciences, Neapolis University Pafos, Pafos, Cyprus.
    Lau, Kevin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    Moiseos, R.
    Department of Architecture, University of Cyprus, P.O. Box 20537, 1678, Nicosia, Cyprus.
    Buonomano, A.
    Department of Industrial Engineering, University of Naples Federico II, P.le Tecchio, 80, 80125, Naples, Italy.
    Savvides, A.
    Department of Architecture, University of Cyprus, P.O. Box 20537, 1678, Nicosia, Cyprus.
    Rizzo, Agatino
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Architecture and Water.
    A climate sensitive design approach to BIPV: Investigating the nexus between solar energy and thermal comfort in cities in Sweden and Cyprus2023In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 243, article id 110681Article in journal (Refereed)
    Abstract [en]

    The research performed attempts to answer the question of how building integration of active solar systems may affect the thermal comfort in open areas and the interstitial space between buildings in urban environments. This is done by using computer simulation and in-situ observations at the extreme northern and southern geographies of Europe, namely in Luleå, Sweden and in Limassol, Cyprus. A typical example of the urban grid of each city is chosen and active solar systems are integrated on the facades of buildings, respectively foreach case. The thermal conditions at street level are then simulated, using Envi-MET, before and after systems integration, with the aim of assessing the differences between low and high insolation conditions, using the Physiological Equivalent Temperature (PET) indicator. Subsequently, the thermal conditions in the public space between buildings were once again assessed, with reduced emissivity values for the building integrated PV panels. The results point to the fact that the building integration of PVs lacking low emissivity coatings can have an impact in the thermal comfort of users in the locations specified, especially in the summer, wherein it is shown to be negligible in the southern case study but more significant in the northern one.

  • 11.
    Yang, Bin
    et al.
    School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an.
    Olofsson, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Wang, Faming
    Institute of Textiles and Clothing, The Hong Kong Polytechnic University.
    Lu, Weizhuo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Thermal comfort in primary school classrooms: A case study under subarctic climate area of Sweden2018In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 135, p. 237-245Article in journal (Refereed)
    Abstract [en]

    Limited studies were focused on primary school buildings especially under subarctic climate. Thermal comfort of children was assumed to be similar as that of adults, which may cause inaccuracy. To fill data blank and enrich global database, a field study was performed from late fall 2016 to early spring 2017 covering whole heating period in north part of Sweden. Indoor CO2 concentration was continuously monitored to evaluate indoor ventilation. Thermal comfort related parameters were continuously measured and predicted mean vote (PMV) was calculated. Subjective questionnaire surveys were performed every week except holidays. Subjective thermal sensation value (TSV) was always higher than objective PMV, which reflected thermal adaptation. The thermal adaptation became not obvious in middle and late winter because of long term exposure to heating environments. Heating system should be intensified gradually in early heating period, operated based on actual outdoor climate instead of experience in middle and late heating periods, extended under part load operation in early spring if necessary. The new 13─point TSV scale was pointed out by other researchers and tested inthis study, which can explore tiny TSV deviations from thermally neutral status and reflect more accurate thermal sensations.

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