Stephen Boon Kean Tan

Nutrients and suspended solids in dry weather and storm flows from a tropical catchment with various proportions of rural and urban land use

The results of an investigation characterizing the nutrients and suspended solids contained in stormwater from Kranji Catchment in Singapore are reported in this paper. Stormwater samples were collected from 4 locations and analyzed for the following eleven analytes: TOC, DOC, TN, TDN, NH(4)(+), NO(2)(-)+NO(3)(-) (NO(x)), TP, TDP, OP, SiO(2) and TSS. Stormwater was sampled from catchments with various proportions of rural and urban land use, including forested areas, grassed areas, agricultural and residential and commercial areas. The event mean concentrations (EMCs) of nutrients and TSS from sampling stations which have agricultural land use activities upstream were found to be higher. Comparison of site EMCs (SMCs) with published data showed that the SMCs of the nutrients and TSS are generally higher than SMCs reported for forested areas but lower than published SMCs for urban areas. Positive correlations (p<5%) were found between loading and peak flow at locations most impacted by ubanisation or agricultural activities. Correlation between loading and rainfall variables was less distinct. EMC was found to correlate less with rainfall and flow variables compared to pollutant loading. Unlike loading, no consistent pattern exists linking EMC to any particular storm or flow variable in any of the catchments. Lastly, positive correlations were obtained between the particulate forms of nitrogen and phosphorus and TSS.

An Active Operator Guidance System for Ship Maneuvers - Prototype System

An active operator guidance system (AOGS) is presented in this paper. The AOGS has been developed as an operator guidance tool for safe container ship maneuvering in coastal and deep waters. System capabilities include ship trajectory prediction in surge, sway and yaw motions; and accounting for current, wind, and water depth effects, as well as rudder and propeller ship command parameters. In actual sea conditions, trial commands can be actively assessed and ship trajectory response predicted on various control-input scenarios by operators under those ambient sea conditions. Predicted vessel response parameters, such as overshoot, turning circle, and track reach, provide guidance on any potential danger through graphic display on the system console. There has been system validation and verification for a container ship using actual sea voyage data and sea trial data from its ship manual. There is reasonable agreement when predictions and data are compared.