Publications

Mountain tunnel is inevitably connected to those canyon areas that could result in a very special situation for the related designs. When the airflow goes through the canyon from an open terrain, it is accelerated to a strong canyon wind under the Venturi effect. However, the flow characteristics in tunnels affected by the canyon wind are still not known. Therefore, the flow characteristics in the tunnel, such as structure, velocity and pressure distributions, together with external canyon wind, were investigated, for the first time, through this study. Different canyon wind velocities and tunnel types were analyzed numerically and experimentally. The results showed that the flow structure in tunnels can be divided into the vortex region and the uniflow region. Besides, a linear relationship was found between the average cross-section velocity of uniflow regions and the canyon wind velocity, where a quadratic relationship was also found between the minimum pressure of vortex regions and the canyon wind velocity. Furthermore, the results indicated that the flow characteristics in the tunnel induced by canyon wind are mainly affected by the hydraulic diameter of the tunnel, where the influences of different types of cross-sections with the same hydraulic diameter are limited.

A facile post-doping of magnesium hydroxide (MH) is proposed to improve the flame retardancy of hydrophobic silica aerogels (SA). The lower tap density (0.12 g/cm3) and thermal conductivity (26 mW/m/K) are still maintained at the largest MH content of 20%. Meanwhile, the gross calorific value of the SA/MH is reduced by 15% and the thermal stability is improved to over ~545 °C. The SA/MH pyrolysis process can be divided into four stages, while the hydrophobic SA is a two-stage pyrolysis process. Furthermore, the improved flame retardancy of SA/MH is mainly attributed to the thermal decomposition of MH, the pyrolysis products (MgO, SiO2 and H2O) and the reaction between MgO and SiO2. The research outcomes demonstrate the validity of using MH as dopant to improve the flame retardancy of hydrophobic SA by a facile post-doping, which is beneficial to the expansion of hydrophobic SA in their practical thermal insulation application.

Partial shading (e.g., bird droppings, leaves, dusts, and shadows) on solar photovoltaic (PV) panels not only depresses the energy performance of solar PV panels but also increases their surface temperature. Nowadays, the impact of shaded locations is overlooked, and the quantitative relationship between surface temperature and energy performance of solar PV panels under partial shading is still unknown. This has hampered the solar PV panels' energy output prediction, which is especially important for ensuring their widespread applications. Hence, this study experimentally addressed the impacts of partial shading with variations in shaded ratios and shaded locations on solar PV panels' surface temperature and energy performance. Experimental results showed that the worst scenario was at the upper right cell under 67 % shaded ratio, causing the shaded cell's surface temperature to reach 99.6 °C under 1100 W/m2 solar irradiance and 20 °C ambient temperature. However, the power of solar PV panel could decrease up to 92.9 % when the middle cell was completely shaded. From both aspects of surface temperature and power dissipation of solar PV panels, the potential reduction of energy performance was worse when the middle or bottom cells were shaded. The quantitative relationship describing power dissipation affecting temperature at shaded cell caused by partial shading was also proposed. The obtained results contribute to predicting energy outputs considering typical partial shading scenarios and offer valuable data supporting decision-making and policy formulation aimed at minimizing energy losses in solar PV systems.

A frequency reconfigurable microstrip antenna is proposed. A circular patch and a C-shaped ring are used for different frequency bands and the two parts are connected by the PIN diode. The two parts can be one resonator when the PIN diode is shorted, otherwise to make the two parts independent. Because the main resonators are different for the different bands, the beam widths can be tuned to be similar for both bands. Simulated results show that the proposed antenna can cover frequency bands of 4.64–4.7GHz and 7.77–7.9GHz with reflection coefficient below −10 dB. The 3dB beam widths are between ± 40° to ±47°.

CO2 emissions from building operations have increased to their highest level globally, moving away from the Paris Agreement goal of below 2 °C. While geothermal is recognised as a promising renewable source, the lack of an integrated framework guiding investigating ground source heat pumps for building operations, along with the incapability of well-known simulation tools in accurately capturing ground thermal performance, hinders its application. This research aims to unlock ground source heat pumps for building operations through an integrated framework, including an overarching improved U.S. National Renewable Energy Laboratory (NREL) monitoring guideline, a sensor-based monitoring prototype, and a g-function-based simulation approach. This research proposes amendments and improvements to the NREL guideline for monitoring geothermal energy by separating Thermal Energy Net Production from Thermal Energy Gross Production. A state-of-the-art case building located in Melbourne, Australia, housing advanced technologies, including ground source heat pump systems, is used to demonstrate and validate the research framework. A typical winter month in the southern hemisphere, July 2021, is monitored for the ground source heat pump systems designed and used for space heating. The findings reveal that the thermal energy generation during working days in July 2021 is close to the simulation results, with a difference of 2.2% in gross thermal energy production and a difference of 0.92% in inlet temperature. This research develops and validates an integrated approach for evaluating ground source heat pump systems, contributing to the utilisation of geothermal energy for building operations.

Urban parks are an important component of urban public green space and a public place where a large number of urban residents choose to conduct outdoor activities. An important factor attracting people to visit and stay in urban parks is its outdoor thermal comfort, which is also an important criterion for evaluating the liability of the urban environment. In this study, through field meteorological monitoring and a questionnaire survey, outdoor thermal comfort of different types of landscape space in urban parks in Chengdu, China was studied in winter and summer. Result indicated that (1) different types of landscape spaces have different thermal comforts, (2) air temperature is the most important factor affecting outdoor thermal comfort; (3) because the thermal sensation judgment of outdoor thermal comfort research in Chengdu area, an ASHRAE seven-sites scale can be used; (4) the neutral temperature ranges of Physiological Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI) in Chengdu in winter and summer were obtained through research; (5) and UTCI is the best index for evaluating outdoor thermal comfort in Chengdu. These findings provide theoretical benchmarks and technical references for urban planners and landscape designers to optimize outdoor thermal comfort in urban areas to establish a more comfortable and healthy living environment for urban residents.

Under the fact that solar chimney was less investigated in multi-storey buildings, a theoretical model was then developed for solar chimney-induced buoyancy-driven natural ventilation. This is the first study addressing the influences of the storey number on ventilation rates for multi-storey solar chimney (SC) buildings. A storey correction coefficient was proposed to predict the SC-induced ventilation at various floors with identical air inlet areas. The theoretical model was established to elucidate the relationship among ventilation flow rates, solar radiation intensity, vent sizes and storey number (f), where the numerical results have also been validated. Although the total SC ventilation performance is enhanced, its enhancement with a higher chimney cavity was less effective when compared to those solar chimneys in single-storey buildings. This is due to the higher chimney cavity hindering the ventilation performance of the lower floors. The volume flow rate decreased exponentially for the top floors of each building when the two-storey building increased to a seven-storey building. For buildings with more than three storeys, the overall volume flow rate was more sensitive to the cavity gap than the solar radiation intensity, with an improvement in ventilation by 45.6% compared to 26.0% under the same conditions, respectively. To maximize the total flow rate, the optimal cavity gap should increase gradually from 0.2 m to 1.5 m for single-to seven-storey buildings. The findings of this study contribute to a further application of solar chimneys in multi-storey buildings.

Under the rapid development of subway systems, a fundamental understanding of subway fire safety is critically needed to benefit its designs and assessment. Previous studies on train carriage fires are limited to single-carriage fires under natural ventilation. However, it is still unclear how longitudinal ventilation affects the smoke movement in the train carriage with lateral openings. Therefore, a series of 1:3 reduced-scale experimental tests were conducted to investigate the smoke temperature characteristics in a train carriage located in a longitudinally ventilated tunnel. Under various fire sizes and ventilation rates, the ceiling gas temperature and smoke layer height were measured. Compared to the traditional fire scenario with end openings, the maximum ceiling gas temperature and the downstream temperature distribution decay factor are relatively smaller because of the lateral flame tilt and less heat loss during smoke propagation. The effects of ventilation velocity on the maximum ceiling gas temperature are significantly weakened under the blockage effect of the train carriage. The downstream temperature distribution followed a single exponential attenuation function, independent of the fire size and ventilation rate. However, the upstream temperature distribution is much more complex under the restriction of the end wall. A four-segment model was proposed to predict the upstream temperature distribution based on the relationship between the back-layering length and half the carriage length. The fire size and ventilation rate also show limited influence on the smoke stratification, with a layer height of 0.316 m in the stable region. The research outcomes offer adeeper understanding of the smoke propagation of the subway train carriage fire and a theoretical guide on the designs of future tunnels.

In this study, the surface chemistry, skeleton structure and thermal safety of three different methylsilyl modified silica aerogels (SAs) have been explored under heat treatment in an argon atmosphere. With the heat treatment temperature increasing to 700 °C, the secondary particles aggregate, the silica skeletons get denser and the pore volumes diminish. Meanwhile, the excellent thermal insulation performance is still maintained, with the thermal conductivity not exceeding 30 mW⋅m − 1⋅k − 1. It finds the Si-(CH3)3 groups are converted to Si-(CH3)2 groups, and further transformed to Si-CH3 groups. The generated and original Si-CH3 groups can be maintained until 700 °C, which constitutes the chemical basis for the high-temperature hydrophobicity. The improved thermal stability and reduced gross calorific values both verify that the thermal safety of the heat-treated SAs has been obviously enhanced. This study provides an engineering reference for the high-temperature thermal insulation application for hydrophobic SAs.

With the rapid development of subway systems, the related fundamental knowledge is critically needed to benefit their designs and fire hazard assessment. The experimental study was performed in a 1/5th scale subway train model to characterize the fire inside subway train, and the experiment in open space was also conducted as a control group. Results show that in the case where the ceiling flame has not yet propagated to the sidewalls of the subway train, the normalized ceiling flame length varies as 1/4 power of the non-dimensional ceiling heat release rate. In addition, the temperature distributions at different transverse distances from the fire source follow the exponential decay law effectively, the decay rate is indeed a function of normalized transverse distance from the longitudinal centerline. An empirical model involving dimensionless transverse and longitudinal coordinates is proposed to predict the two-dimensional temperature underneath the ceiling, which is reasonably well fitting with experimental results from this study and literatures.

Although solar chimneys have been extensively investigated, their performance in multi-zone buildings have been overlooked previously. This study aims to examine the airflow characteristics inside a wall solar chimney and the attached ventilated multiple zones, together with the solar chimney performance, under various configurations (i.e., chimney cavity and room) and external environment (i.e., solar radiation intensity). The critical geometrical parameters of solar chimney and building layouts are then suggested based on the trade-offs between the buoyant flow patterns and the volumetric flow rate. Like those single zone applications, an increase in the chimney height and inlet location (until the middle height of the wall) results in a straight improvement in the airflow rate. By increasing the chimney height from 3.0 to 5.0 m, the ventilation capacity increases by about 90%; and moving the air inlet upward can get a 57.28% improvement of the ventilation rate. The maximum airflow rate in this study was observed for a solar chimney with a cavity gap of 0.2 m and an inlet size of 0.2 m, while enlarging the window area enhances the volume flow rate by up to 14.98%. In addition, when the cavity gap and inlet size exceed the optimal value, their influences on the airflow rate are observed insignificant, and the growth rate of volume flow rate decreases gradually. The multiple rooms with different aspect ratios seem to show a limited impact on the ventilation performance. The volume flow of four groups of room layouts shows a fluctuation of within 5%. The velocity distribution of the long and narrow room layout shows an average improvement of 2.5% than that of the two-room with a significant difference in width.

In this study, 13 tumor cell line derived subcutaneous models and one intracranial tumor model were evaluated by the application of X-ray radiation. The response of radiation levels on different tumor types and different tumor models were assessed by using the device (X-RAD225, Pxi precision, USA) delivering the targeted radiation directly on the focal tumor site. Furthermore, we investigated the combined benefits of radiation and a chemotherapy medication, Gemcitabine, on the H22 murine hepatic carcinoma cells derived subcutaneous syngeneic model. The impact of radiation treatment on the NCI-H1975-luc, human non-small cell lung cancer intracranial model in combination with Human checkpoint kinase ataxia telangiectasia-mutated (ATM) kinase inhibitor AZD0156 was studied. In addition, the integrity of the blood-brain barrier and the presence of the pharmacodynamic marker pRAD50 of AZD0156 were evaluated. The study outcome demonstrated that X-ray radiation has anti-tumor effects across all studied models, and also in combination treatment with radiosensitizer, Gemcitabine or AZD0156. We believe this study demonstrates there is a lot of potential fully utilizing radiation platform identifying radiation sensitizer or chemo candidates to benefit the management of oncology society.