| 1. |
- Cheng, Xiaogang, et al.
(author)
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A variational approach to atmospheric visibility estimation in the weather of fog and haze
- 2018
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In: Sustainable cities and society. - : Elsevier. - 2210-6707. ; 39, s. 215-224
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Journal article (peer-reviewed)abstract
- Real-time atmospheric visibility estimation in foggy and hazy weather plays a crucial role in ensuring traffic safety. Overcoming the inherent drawbacks with traditional optical estimation methods, like limited sampling volume and high cost, vision-based approaches have received much more attention in recent research on atmospheric visibility estimation. Based on the classical Koschmieder's formula, atmospheric visibility estimation is carried out by extracting an inherent extinction coefficient. In this paper we present a variational framework to handle the nature of time-varying extinction coefficient and develop a novel algorithm of extracting the extinction coefficient through a piecewise functional fitting of observed luminance curves. The developed algorithm is validated and evaluated with a big database of road traffic video from Tongqi expressway (in China). The test results are very encouraging and show that the proposed algorithm could achieve an estimation error rate of 10%. More significantly, it is the first time that the effectiveness of Koschmieder's formula in atmospheric visibility estimation was validated with a big dataset, which contains more than two million luminance curves extracted from real-world traffic video surveillance data.
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| 2. |
- Cheng, Xiaogang, et al.
(author)
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A total bounded variation approach to low visibility estimation on expressways
- 2018
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In: Sensors. - : MDPI. - 1424-8220. ; 18:2
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Journal article (peer-reviewed)abstract
- Low visibility on expressways caused by heavy fog and haze is a main reason for traffic accidents. Real-time estimation of atmospheric visibility is an effective way to reduce traffic accident rates. With the development of computer technology, estimating atmospheric visibility via computer vision becomes a research focus. However, the estimation accuracy should be enhanced since fog and haze are complex and time-varying. In this paper, a total bounded variation (TBV) approach to estimate low visibility (less than 300 m) is introduced. Surveillance images of fog and haze are processed as blurred images (pseudo-blurred images), while the surveillance images at selected road points on sunny days are handled as clear images, when considering fog and haze as noise superimposed on the clear images. By combining image spectrum and TBV, the features of foggy and hazy images can be extracted. The extraction results are compared with features of images on sunny days. Firstly, the low visibility surveillance images can be filtered out according to spectrum features of foggy and hazy images. For foggy and hazy images with visibility less than 300 m, the high-frequency coefficient ratio of Fourier (discrete cosine) transform is less than 20%, while the low-frequency coefficient ratio is between 100% and 120%. Secondly, the relationship between TBV and real visibility is established based on machine learning and piecewise stationary time series analysis. The established piecewise function can be used for visibility estimation. Finally, the visibility estimation approach proposed is validated based on real surveillance video data. The validation results are compared with the results of image contrast model. Besides, the big video data are collected from the Tongqi expressway, Jiangsu, China. A total of 1,782,000 frames were used and the relative errors of the approach proposed are less than 10%.
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| 3. |
- Kabanshi, Alan, et al.
(author)
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Energy simulation and analysis of an intermittent ventilation system under two climates
- 2017
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In: 10th International Conference on Sustainable Energy and Environmental Protection. - Maribor : University of Maribor Press. - 9789612860509 ; , s. 1-10
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Conference paper (peer-reviewed)abstract
- Energy use on heating, ventilation and air conditioning (HVAC) accounts for about 50% of total energy use in buildings. Energy efficient HVAC systems that do not compromise the indoor environmental quality and at the same time meet the energy reduction directives/policies are necessary and needed. The study herein, evaluates the energy saving potential of a newly proposed ventilation system in spaces with high occupancy density, called Intermittent Air Jet Strategy (IAJS). The aim of the study was to evaluate through simulations the potential energy savings due to IAJS as compared to a mixing ventilation (MV) system in a classroom located in a ‘hot and humid’ climate (Singapore), and in a ‘hot and dry’ climate (Kuwait). The analysis is based on IDA Indoor Climate Energy simulation software. The results herein demonstrate significant reduction of cooling energy use of up 54.5% for Singapore and up to 32.2% for Kuwait with IAJS as compared to MV. Additionally, supply fan energy savings can also be realized if well implemented.
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| 4. |
- Zhang, Ying, et al.
(author)
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Field measurements and numerical analysis on operating modes of a radiant floor heating aided by a warm air system in a large single-zone church
- 2022
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In: Energy and Buildings. - : Elsevier. - 0378-7788 .- 1872-6178. ; 255
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Journal article (peer-reviewed)abstract
- Space heating can constitute 60–80% of the total energy use of buildings in cold climates. Efficient heating techniques in buildings still rely on operating strategies. In this paper, a church with radiant floor heating in a cold climate is taken as a case of a large single-zone building to analyze the energy use for heating. Field measurements and numerical analysis are both used in the study. Different operating modes of heating, including intermittent heating and constant set-point heating, are compared for energy saving, reliability on indoor climate, and thermal comfort. The intermittent heating by an all-air system with supplied air temperature control results in the highest energy use. The constant set-point air temperature radiant floor heating aided by a warm air system (return air temperature control) is least affected by outdoor temperature with the best reliability and met the thermal comfort requirements throughout the heating season. The main novelty is that an operating mode of cyclic set-point air temperature is proposed. It is found that the small thermal inertia of heating systems should be preferred when the operating mode of cyclic set-point temperature is used to reduce the warm-up period. The results suggest how to operate and reduce the energy use of radiant floor heating systems in a large single-zone building.
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