| 1. |
- Chen, L., et al.
(author)
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Numerical investigations of wind and thermal environment in 2D scaled street canyons with various aspect ratios and solar wall heating
- 2021
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In: Building and Environment. - : Elsevier. - 0360-1323 .- 1873-684X. ; 190
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Journal article (peer-reviewed)abstract
- Optimizing urban ventilation is an effective way to improve urban air quality and thermal environment. For this purpose, under the validation of wind-tunnel experiments, flow regimes and micro thermal environment in typical reduced-canyon models with aspect ratios (AR) of 1.1, 2.4, 4 and 5.67 were investigated by CFD simulations using periodic boundary condition. ANSYS Fluent 15.0 with a solar ray tracing model and radiation model was performed to numerically study turbulence characteristics with wind-driven force and solar-heating conditions. Results revealed that, with wind-driven condition, a clockwise vortex existed in normal and deep street canyon (AR = 1.1 and 2.4) while two counter-rotating vortices appeared in extremely deep canyon (AR = 4 and 5.67). Moreover, different turbulence structures and air temperature distribution existed in canyons with different solar-heating conditions. When the leeward wall or ground was heated, the pedestrian-level velocity increased and street ventilation was strengthened compared to wind-driven condition for all AR values. Particularly, the single main vortex was strengthened (AR = 1.1 and 2.4), and the two-vortex structure in extremely deep canyons (AR = 4 and 5.67) changed to single-vortex structure. When the windward wall was heated, the clockwise main vortex at AR = 1.1 and 2.4 was deformed, and a new sub vortex gradually appeared near street bottom. Furthermore, at AR = 4 and 5.67, windward solar heating destroyed the two-vortex structure and slightly improved pollutant dilution capacity. This work implied that extremely deep street design with weak pedestrian-level ventilation should be avoided. It also provides a meaningful reference for urban planning.
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| 2. |
- Dong, X., et al.
(author)
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Study on household metering and temperature control in central air-conditioning
- 2010
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In: Proceedings of the 2010 5th IEEE Conference on Industrial Electronics and Applications, ICIEA 2010. - 9781424450466 ; , s. 931-935
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Conference paper (peer-reviewed)abstract
- This paper studies the Frequency Temperature Control mechanism and cold (heat) metering algorithm about central air-conditioning terminal installations. The temperature control and household metering management system for central air-conditioning terminal machine are developed. The system hardware, software design programs and key technologies are expatiated. The terminal machine is integrated with PIC microcontroller, user data acquisition, transmission and control. Delphi language is used in the accounting management system of the host computer. The results show that, the system is no need of new wire, the high performance-price ratio, easy assembly, stable operation and reasonable charge. It is of great significance to adopt the heat and cold metering for the energy conservation, environmental protection and property management. At the same time, it provides the property management with a new technology and channels for the modern intelligent building. © 2010 IEEE.
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| 3. |
- Zhao, B., et al.
(author)
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A NHPP-based reliability model of wireless sensor networks
- 2014
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In: Applied Mechanics and Materials. - 9783038351764 ; , s. 877-882
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Conference paper (peer-reviewed)abstract
- As the Wireless Sensor Networks(WSNs) are widely applied to various fields recent years, the quality of WSN has been increasingly concerned. Since reliability is the most important factor of quality, how to evaluate reliability of WSN through failure counting is our main subject. In this paper, we try to utilize NHPP theorem in the failure process of WSN and propose a reliability model based on NHPP. And also, the model validation is conducted by simulation.
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| 4. |
- Zhao, B., et al.
(author)
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An additive NHPP-Based reliability model of wireless sensor networks
- 2014
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In: Applied Mechanics and Materials. - 9783038351948 ; , s. 3206-3212
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Conference paper (peer-reviewed)abstract
- As the Wireless Sensor Networks(WSNs) are widely implemented in various fields recent years, the quality of WSNs has been increasingly concerned. WSNs can usually be divided into sub-nets, which assumed to work or fail independently. Through the failure data of those sub-nets, the additive NHPP model for reliability evaluation is composed, and then the maximum likelihood estimation is applied to estimate the unknown parameters in the model. Finally, the simulation shows that the additive NHPP model is better than general NHPP model under certain circumstances.
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| 5. |
- Zhao, B., et al.
(author)
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Wireless sensor network reliability modelling based on masked data
- 2015
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In: International Journal of Sensor Networks (IJSNet). - 1748-1279 .- 1748-1287. ; 17:4, s. 217-223
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Journal article (peer-reviewed)abstract
- This paper studies the reliability modelling of wireless sensor networks (WSNs) with the masked data that are often observed in practice. The masked data are the system failure data when exact subsystems or components causing system failures cannot be identified. When the masked data are observed, however, it is difficult to estimate the WSN reliability since the failure processes of the subnets cannot be decomposed into simple subsystem processes. In this paper, an additive non-homogeneous poisson process (NHPP) model is proposed to describe the failure process of the WSN with subnets. The maximum likelihood estimation (MLE) procedure is developed to estimate the parameters in the proposed model. By applying the given procedure, the WSN reliability estimate can be relatively easy to obtain. A numerical example based on simulation data with random masking is also provided to illustrate the applicability of the methodology.
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