288 publications from this institution
Drawing on the composition of shells and the microstructure of cross-laminated sheets, laser sintering technology was used to prepare laser-sintered fabrications of veined red snail powder as an inorganic material and polylactic acid (PLA) as an organic material. The process was optimized using the response surface method based on one-way experiments by adding veined red snail powder. At a 13.27-W laser power, 1.2-m/s scanning rate, 0.17-mm scanning spacing, and 0.23-mm delamination thickness, the bending strength of the veined red conch powder/PLA composite powder parts reached 8.53 ± 0.15 MPa, with an error of only 1.7% from the model’s predicted value. Under these process conditions, the characterization of laser-sintered parts with 0, 5, 10, 15, 20, and 25 wt% veined red snail powder revealed that parts with 15 wt% exhibited optimal mechanical properties, showing a 155.9% improvement over pure PLA parts.
To improve the performance of solar heat storage and reduce the energy consumption of the fresh air system in areas with poor solar conditions, this study investigates the thermal storage and release performance of a low-temperature rectangular thermal energy storage unit (RTESU). A validated Computational Fluid Dynamics (CFD) model is used to address the impacts of configuration parameters on the performance of the thermal storage process in the Phase change material (PCM) module, including the number and eccentric arrangement of tubes. Subsequently, the effect of the air channel width on the air outlet temperature and the heat transfer rate is analyzed for the heat-releasing process. The numerical results show that the number and the eccentricity of the heat exchanger tube have significant impacts on the heat storage performance, and a minimum duration of 117 min can be achieved with a tube pitch of 30 mm (corresponding to 5 water tubes) and an eccentric of 5 mm, respectively. The air channel width of 20 mm is found as the optimal width due to its higher heat release efficiency (83.24 %) and lower pressure drop (4.3 Pa). The identification of key structural impacts helped to optimize the RTESU configuration, which performs at a low heat storage time of 117 min and achieves a heat release efficiency as high as 83.24 % to satisfy the need for poor solar conditions.
No abstract is provided for this article.
No abstract is provided for this article.
No abstract is provided for this article.
The volume of smoke alarm sound in rooms (other than room of sound origin) in real houses and smoke alarm activation time in rooms in full-scale model houses using ionization, photoelectric and dual detector smoke alarms were determined in this study. The alarm sound level measurements indicated that the sound level in many locations is likely to be too low to provide reliable notification, particularly for sleeping people, if smoke alarms are not installed in every room. In addition, changing to a lower frequency (520 Hz square wave) alarm would further aid effective notification of building occupants. The smoke alarm activation measurements showed that the time to detection (given a particular smoke source) was influenced by door position (open versus closed), the room in which the fire occurs, the location (room or hallway) of the detector, the type of detector and the smoke alarm manufacturer. Furthermore time to detection is also influenced by the type and form of the material that is burning. It was observed that photoelectric smoke alarms had the highest incidence of non-activation and when they did activate they, on average, took longer to activate than ionization and dual (ionization and photoelectric) smoke alarms over all smoke sources considered in this study. It is concluded that to achieve early detection and provide adequate notification, smoke alarms are necessary in every room and should be interconnected.
No abstract is provided for this article.
Inspection and maintenance (M&R) of a buried network of stormwater drainage pipes is a challenging task for asset engineers due to a large number of pipes and restricted access. A Markov-based inspection model with a computational procedure was developed to estimate the lowest-cost inspection interval for various pipe conditions and an average total of M&R cost. The computational procedure is based on the innovative application of Markov deterioration model, the cost rate function, and Monte Carlo simulation. The results from a real case study show that the lowest-cost inspection intervals for stormwater pipe assets with a starting good condition of 1 are obtained between 9 and 11 years. The average number of undetected failure condition due to longer inspection interval is also presented and can be important in selecting the inspection interval when failure risk is concerned. The effect of penalty cost is shown to affect both the average cost rate and lowest-cost inspection interval. The annual interest rate is found to have a significant effect on total cost but has no impact on inspection interval.
Vertical shaft is one of the most important approaches for smoke control under tunnel fires. However, the boundary layer separation is a common phenomenon of hampering the smoke exhaust for vertical shafts. A tilted shaft has been proposed to solve problems and improve the capacity of smoke exhaust. In this study, the effect of shaft inclination angle (θ decreases from 90° to 14°) and shaft height on the capacity of smoke exhaust was addressed numerically. A series of scenarios were simulated in a full-scale road tunnel. Numerical results showed that the tilted shaft could eliminate the boundary layer separation. However, small shaft inclination angle could lead to a relatively higher resistance to the smoke and a smaller cross-section area of shaft, which could have an adverse effect on the capacity. Under these two factors, an optimal inclination angle exists in the shaft of around 76° in this study. Based on the smoke flow characteristics and exhaust effect, the inclination angle was roughly divided into three regions. The main influence factor of the inclination angle on the mass flow rate of smoke in each region was examined. For a comprehensive consideration, the low and slightly tilted shaft was applied to tunnel fires, which can improve the capacity of smoke exhaust obviously.
No abstract is provided for this article.
Carbon monoxide (CO) is always a significant judgment criterion in fire risk evaluation. Therefore, a model to predict CO of woods under external heat flux was developed in this study. To improve modeling accuracy, fire processes such as water evaporation, volume shrinkage, liquid and gas transport inside wood slab were considered in this model. Three reactions such as water evaporation, oxidation of virgin wood and char were included. For oxidation reactions of virgin wood and char, CO yields of each reaction were considered constant even under various external heat fluxes. This will expand the applications of this model as limited experimental data of CO yields under different external heat flux. Temperature and moisture dependent thermal properties were used for modeling input. Comparisons between experiment and modeling showed that CO production of woods under different external heat flux can be well predicted by this model. This model intends to provide a practical tool to predict toxic gases of combustible materials under fire conditions. This two-part study contains theory, validation and application of a mathematical model. This paper servers as a precursor for Part II: Validation and application of a model to predict CO of woods under external heat flux.
No abstract is provided for this article.
One-dimensional model is fundamental to two- or three-dimensional modeling of combustible materials, which can be classified into wood, non-charring polymer, charring polymer and intumescent polymer according to their characteristics. Four fire processes are involved in fire development, such as thermal process, physical process, chemical process and failure process. Consideration of all four fire processes for these combustible materials is significant to modeling accuracy and application fields. Therefore, the state of the art of one-dimensional modeling describing all four fire processes of woods, non-charring polymers, charring polymers and intumescent polymers under external heat flux was reviewed. A summary of typical considerations in previous one-dimensional models was provided, including heat conduction, pyrolysis, production of gas volatiles, volume change, water evaporation, internal gas pressure, properties of permeability and porosity, and mechanical behaviors. Empirical models and critical data of fire processes were also collected for modeling input. This paper can provide a guide to one-dimensional modeling and build basis for two- and three-dimensional modeling.
