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In order to achieve the purpose of sealing water between adjacent jacked pipes in construction of long-distance and large-section tunnel, an innovative method called Freeze-Sealing Pipe Roof (FSPR) was applied to the Gongbei tunnel, which is a key part of Hong Kong-Zhuhai-Macau Bridge in China. Since the pre-constructed jacking pipes provides great convenience for flexible placement of freezing tubes inside, it is crucial to study the temperature field of different freezing states. This paper first established a new mathematical model considering radial offset of jacking pipe according to the practical engineering, and then the analytical solution to steady-state temperature field was also derived. Moreover, temperature distribution of four typical cross-sections were analyzed to evaluate the freezing effect on different paths. Results show that the analytical results are in good agreement with the numerical results, and the quasi-double-circle freezing model can be well applied to the practical problem of radial offset. Soil between steel pipes will be lowered to a sufficiently low temperature and form a fairly reliable water-sealing curtain. By designing the radial offset between freezing tubes in solid and hollow pipes, the freezing effect can be better ensured. The conclusions have important guiding significance for design and construction of FSPR method in future projects. • Temperature field of a special double-circle-piped freezing model is solved analytically. • The boundary separation property of the harmonic equation is used to solve the heat conduction problem. • The accuracy of complex analytical expressions is verified by numerical simulation. • Water sealing effect of FSPR method considering radial offset of jacking pipes is analyzed. [ABSTRACT FROM AUTHOR]

Abstract: The intermittent characteristic of a solar-alone or a wind-alone power generation system prevents the standalone renewable energy system from being fully reliable without suitable energy storage capability. In this study, the most traditional and mature storage technology, pumped hydro storage (PHS), is introduced to support the standalone microgrid hybrid solar-wind system. This paper explores a new solution for the challenging task about energy storage. A mathematical model of the hybrid system is developed and the operating principle is introduced. The proposed system is applied in a case study to power a remote island in Hong Kong, and its technical feasibility is then examined. The hour-by-hour simulation results indicate that the intermittent nature of the renewables can be compensated by introducing the PHS technology. Therefore, a reliable and environmentally friendly power supply can be provided. The results demonstrate that technically the PHS based renewable energy system is an ideal solution to achieve 100% energy autonomy in remote communities. [Copyright &y& Elsevier]

Abstract: In subtropical Hong Kong, buildings consume the most of the electricity use. Computer simulation technique is a useful tool for predicting building thermal and energy performance. Simulation computer programs require weather data input to drive the mathematical models within the simulation tools for comparative studies and annual energy estimation. Typical weather year data representing the long-term climatic conditions are often used. Recently, there has been an increasing interest in incorporating daylight in the architectural and building designs to reduce building energy consumption. However, daylight parameters are not always available. In 2003, the International Commission on Illumination (CIE) adopted a range of 15 standard skies covering probably the whole spectrum of the usual skies in the world. Once the skies have been identified, the basic solar irradiance and daylight illuminance at various inclined planes can be obtained. This paper presents the work on the development and evaluation of two typical weather datasets, namely Typical Meteorological Year (TMY) and Test Reference Year (TRY). Measured hourly weather data for the 30-year period from 1979 to 2008 were analysed. Building energy simulations were conducted to evaluate the two weather datasets. Daylight parameters were derived using luminous efficacy approach and the sky conditions were categorized based on common climatic variables. [Copyright &y& Elsevier]

Abstract: An investigation of historical database of environmental pollutants (RSP, NO, NO2, NOx, Ozone, SO2, NO/NO2 and NO2/NOx) and meteorological parameters at selected air monitoring stations in Hong Kong, is reported in this paper. Multiple regression and principal component analysis are employed to predict ozone levels from data of pollutants and meteorological variables. The results indicated that the performance of logarithmic transformation of ozone values is better than original data; based on this transformation, the variable NO2/NOx explained 75% of variation of the ozone level at Sha Tin and 83% at Kwun Tong. The ozone level increased exponentially with increase of NO2/NOx but the critical point was judged to be 0.5. In addition, due to close relationships between these studied variables, influence of meteorological variables on ozone concentration was confirmed being incorporated in pollutant variables and could not be segregated in the regression model. The results showed that meteorological variables account for 31% and 34% of ozone variation at Sha Tin and Kwun Tong, respectively. The cloud amount was observed as the most important factor at both stations. Data of Sha Tin and Kwun Tong were compared to ascertain the effect of geographical location on ozone variation. It seems that ozone level depended more heavily on variations in pollutants and meteorological variables. It can be deduced that Kwun Tong located near Victoria harbor and surrounded by hilly terrain of Kowloon and Hong Kong Island is in a disadvantageous position in terms of ozone dispersion, which results in relatively high ozone concentration. [Copyright &y& Elsevier]

Abstract: This paper reports the investigation results on application of the solar assisted air source heat pump systems for hot water production in Hong Kong. A mathematical model of the system is developed to predict its operating performance under specified weather conditions. The optimum flow rate from the load water tank to the condenser is proposed considering both the appropriate outlet water temperature and system performance. The effect of various parameters, including circulation flow rate, solar collector area, tilt angle of solar collector array and initial water temperature in the preheating solar tank is investigated, and the results show that the system performance is governed strongly by the change of circulation flow rate, solar collector area and initial water temperature in the preheating solar tank. [Copyright &y& Elsevier]

Abstract: This paper examines the effects of nonlinear fare structures in taxi markets using an extended taxi model with an explicit consideration of perceived profitability. The expected profit, defined as the profit per unit time (inclusive of both occupied and vacant taxi times), that a taxi driver expects to receive from picking up a customer in a particular zone or location, has great impact on the taxi driver’s choice of location in the search for customers. The fare structure directly governs the profitability of taxi rides of different distances originating from different locations. With these explicit considerations, the extended model is intended to look into the market effects of adopting a nonlinear fare structure with declining incremental charges. The proposed nonlinear fare structure could help restore a level-playing field for taxi operators whose businesses have been affected by some taxi drivers who resort to practices such as offering fare discounts or accepting requests for discounted fares from passengers for long-haul trips. Analysis of sensitivity of social welfare and profit gain as well as taxi/customer wait/search times is conducted with respect to the parameters in the nonlinear fare structure for the Hong Kong taxi market, and Pareto-improving nonlinear fare amendments are identified that neither disadvantage any customer nor reduce the taxi operators’ profits. [Copyright &y& Elsevier]

Abstract: This paper describes a study of local biogenic volatile organic compounds (BVOC) emissions from the Hong Kong Special Administrative Region (HKSAR). An improved land cover and emission factor database was developed to estimate Hong Kong emissions using MEGAN, a BVOC emission model developed by . Field surveys of plant species composition and laboratory measurements of emission factors were combined with other data to improve existing land cover and emission factor data. The BVOC emissions from Hong Kong were calculated for 12 consecutive years from 1995 to 2006. For the year 2006, the total annual BVOC emissions were determined to be 12,400 metric tons or 9.82 × 109 g C (BVOC carbon). Isoprene emission accounts for 72%, monoterpene emissions account for 8%, and other VOCs emissions account for the remaining 20%. As expected, seasonal variation results in a higher emission in the summer and a lower emission in the winter, with emission predominantly in day time. A high emission of isoprene occurs for regions, such as Lowest Forest-NT North, dominated by broadleaf trees. The spatial variation of total BVOC is similar to the isoprene spatial variation due to its high contribution. The year to year variability in emissions due to weather was small over the twelve-year period (−1.4%, 2006 to 1995 trendline), but an increasing trend in the annual variation due to an increase in forest land cover can be observed (+7%, 2006 to 1995 trendline). The results of this study demonstrate the importance of accurate land cover inputs for biogenic emission models and indicate that land cover change should be considered for these models. [Copyright &y& Elsevier]

Abstract: In 1988, Dr. Kyoji Sassa proposed a geotechnical model [Sassa, K., 1988. Geotechnical model for the motion of landslides. In: Proceedings, 5th International Symposium on Landslides, vol. 1, pp. 37–56] to simulate landslide motion and to establish a theoretical framework for landslide simulation. In 2002, based on the experimental results of using a ring-shear apparatus for simulation of landslide motion, Wang and Sassa proposed a model for apparent friction coefficient change (which is a key parameter of landslide motion) that can be combined with Sassa’s original geotechnical model. As presented in the model for apparent friction coefficient change, a landslide is considered as a two-layer structure, i.e., a debris layer and a sliding zone. During landsliding, the thickness of the debris layer changes, while shear resistance changes in the sliding zone. In this paper, after a brief introduction of the two models, a parametric study is presented to show the differing importance of each parameter. Also included is a presentation of three case studies: The 1995 Fei Tsui Road landslide, and the 1995 Shum Wan landslide, both in Hong Kong, and the 1903 Frank slide in Alberta, Canada to show the advantage of combining the two models. [Copyright &y& Elsevier]

Abstract: Soil nails have been widely used to stabilize slopes and earth retaining structures in many countries and regions, especially, in Hong Kong. The analysis of the interaction between a soil nail and the surrounding soil is of great interests to both design engineers and researchers. In this paper, authors present a simple mathematical model for the interaction analysis of a soil nail and the surrounding soil considering a few key factors which are soil dilation, bending of the soil nail, vertical pressure, and non-linear subgrade reaction stiffness. The lateral subgrade reaction between the soil and the soil nail is assumed to obey a hyperbolic relation. Reported test data in the literature are used to verify the present model. The contributions of the soil-nail bending on the pull-out resistance are evaluated in two case studies. [Copyright &y& Elsevier]