由于测试手段的局限性，对粗化稳定的水流结构，尤其是河床粗化层不断调整的水流结构变化研究较为缺乏。借用多普勒声速仪（Sontec2ADV） 和尼康全站仪（Nikon2DTM），测试了不同水沙组合卵石床面，在清水冲刷条件下的稳定形态及其水流结构。试验表明:在相近的水流条件下，粗化稳定后粗颗粒在床面的暴露程度和排列位置受原始铺沙与前期粗化程度的影响。清水冲刷卵石推移质输沙过程、稳定形态及其相应的水流结构具有较强的相互作用关系。在一定的水沙、床面形态条件下，平均流速分布沿相对水深的变化可由单一的对数分布转变为S 形曲线，且其流速极值转捩位置也受水沙及床面形态条件的影响。

The evolving pattern of ozone level in Hong Kong urban air has undergone various changes and corresponds to the regionalurban and economic development. We assess such changes by reviewing and analyzing the original ozone pollutant databasemonitored in central Hong Kong downtown area during the period of 1984–2002. Both fractal analysis and traditional statisticalmethods are adopted to estimate the ozone evolving characteristics during the studied period. It is found that the ozone evolvingpattern has strong self-similarity and the ozone pollution presents increasing trend in Hong Kong region in recent years basedon the analysis. The typical fractal dimensions for total time series are D=0.894 for available data set (N =5760) and D=0.859for complete data set with interpolation (N =6935), respectively. The fractal analysis can be used to assess the pollution trend inurban environment and may provide an alternative method for environmental study.

天然河流中存在着大量的主支交汇河流，在干支流交汇处，水流结构变得十分复杂。通过水槽试验，应用声速多普勒测速仪（ADv），观测了入汇角为30。时，支流斜接主流入汇型河道的三维水流结构。试验表明：入汇上游受支流顶托影响，产生一定的壅水，出现低速区，而对侧由于束水作用产生高速区。在入汇一侧下游较短的距离，产生回流现象，并形成分离区，而在下游一定范围内，靠支流入汇侧出现水流高速区，并形成二次流结构。交汇区水流流动主要有水流分离区、高流速带、低流速带及剪切面等。

Air pollution is an important and popular topic in Hong Kong as concerns have been raised about the healthimpacts caused by vehicle exhausts in recent years. In Hong Kong, sulphur dioxide SO2, nitrogen dioxide (NO2), nitricoxide (NO), carbon monoxide (CO), and respirable suspended particulates (RSP) are major air pollutants caused by thedominant usage of diesel fuel by goods vehicles and buses. These major pollutants and the related secondary pollutant,e.g., ozone (O3), become and impose harmful impact on human health in Hong Kong area after the northern shifting ofmajor industries to Mainland China. The air pollution index (API), a referential parameter describing air pollution levels,provides information to enhance the public awareness of air pollutions in time series since 1995. In this study, thevarying trends of API and the levels of related air pollutants are analyzed based on the database monitored at a selectedroadside air quality monitoring station, i.e., Causeway Bay, during 1999–2003. Firstly, the original measured pollutantdata and the resultant APIs are analyzed statistically in different time series including daily, monthly, seasonal patterns.It is found that the daily mean APIs in seasonal period can be regarded as stationary time series. Secondly, the autoregressivemoving average (ARMA) method, implemented by Box–Jenkins model, is used to forecast the API timeseries in different seasonal specifications. The performance evaluations of the adopted models are also carried outand discussed according to Bayesian information criteria (BIC) and root mean square error (RMSE). The resultsindicate that the ARMA model can provide reliable, satisfactory predictions for the problem interested and is expectingto be an alternative tool for practical assessment and justification.

天然河流中存在着大量的主支交汇河流，在主支流相汇处，由于河相关系的变化，主支河流原有的水沙平衡状态被打破。通过一系列的水槽试验研究了交汇角为30°时支流来水、来沙对主流输沙特性的影响，获得了在支流有无来水、来沙时不同主支汇流比下的主河输沙率和累积输沙量随时间演化过程。试验表明:单一主河推移质呈“波”状输移，具有时空不连续性;支流仅来水时，由于无泥沙补给，交汇口及其下游会形成冲刷深槽，主流输沙率和输沙量强度在初始阶段很大，随着时间的推移，其值逐步衰减并趋于稳定;支流来水又来沙时，主河输沙特性与主支汇流比密切相关。

Air pollution ina metropolitan city like Hong Kong is a major obstacle to improve air quality and living environmentdue to the high population density and the vehicle emission increases.The high air pollutant levels impose harm tothe human health and impair the city image.The characteristic analysis of air pollutants is very important andnecessary to pollutant monitoring, forecasting and controlling.In this study, the interaction patterns of principle airpollutants, e.g. nitrogen dioxide (NO2), nitric oxide (NO), nitric oxides (NOx) and ozone (O3), a secondary pollutant,are investigated based on the measured database in four selected areas, which covers two urban types (i.e. residentialarea, mixed residentialycommercialyindustrial area) in Hong Kong, during the period of 1999–2001.The studyinvolves analyzing the chemical and physical properties, the characteristics of air pollutants and the factors affectingsuch interactions using statistical method.The results reveal several routines in urban air pollutants’ variations,interaction and trends from macro aspect.

As far as the impact of air pollutants on human heath being concerned, ozone is one of the main pollutants inatmosphere. In particular, the ground level ozone is responsible for a variety of adverse effects on both human beingand plant life. To protect the humankind from such adverse health effects, early information and precautions of highozone level need to be supplied in times. In this study, statistical characteristics of ground level ozone is analyzedaccording to the field monitoring data in mixed residential, commercial and industrial areas, e.g., Tsuen Wan area inHong Kong. The study deals with the characteristics of hourly and daily mean ozone levels under different climaticconditions such as temperature, solar radiation, wind speed, and other pollutant concentration levels. The study aims toinvestigate the importance of meteorological factors and their impact on relevant pollutant concentration levels fromchemical aspect. Further, reasons causing the spatial and temporal variations of ozone levels are discussed. All theseresults will provide a physical basis for accurately predicting ozone concentration in extensive, future research.

As far as the impact of air pollutants on human heath being is concerned, ozone (O3) is one of the most pollutant sources, and, inparticular, the ground level ozone is responsible for a variety of adverse effects on both human being and plant life. To protect the populationfrom such adverse health effects, early information and precautions about the high ozone level need to be ascertained. In this study, statisticalcharacteristics of ground level ozone is analyzed according to field monitoring data in mixed residential, commercial and industrial areas,e.g., Tsuen Wan area in Hong Kong. The study deals with the characteristics of hourly and daily mean ozone levels under different climaticconditions such as temperature, solar radiation (SR), wind speed (WS), and other pollutant concentration levels. The study aims to investigatethe importance of meteorological factors and their impact on relevant pollutant concentration levels from a chemical aspect. Further, reasonsfor the spatial and temporal variation of ozone levels are discussed. All these results will provide a physical basis for accurately predictingozone concentration in similar research.