This paper aimed to develop a depth-averaged explicit model for flow and pollutant transport in coastal waters based on the shallow water equations and the mass advection-diffusion equation. The proposed model was discretized using the finite volume method (FVM) with triangular cells. Then, it applied Roe’s approximate Riemann solution to compute the water momentum flux on the grid interfaces. This model enabled the higher accuracy in capturing the dry-wet moving fronts (discontinuous problems for flow and solute). The high-resolution scheme was evaluated to solve the advection and diffusion terms for mass transport. The model was verified by comparing the predictions of analytical solutions, laboratory tests, and other simulations for Gironde estuary with good computational accuracy. The developed model was also used to calculate the circulation and the motion of chemical oxygen demand (COD) pollutants from the sewage outfalls in the Zhuanghe coastal water with dry and wet moving boundaries. The research results showed that the residual current directions of spring and neap tides were basically the same in the Zhuanghe coastal water. However, the tide residual current of spring tide was slightly greater than that of the neap tide. In addition, there were tide residual currents from the northeast to the southwest in nearshore water and from the southwest to the northeast outside the banks, respectively. The tidal flows in the alongshore direction were strong, resulting in highly spread concentration distributions. In particular, the COD concentration reached some parts of the southern water. It could be seen that the excessive pollutant discharge from the sewage outfalls located at Zhuanghe district would cause serious pollution in aquaculture water near Shicheng island. 相似文献
Vehicle interior noise functions at the dominant frequencies of 500 Hz below and around 800 Hz, which fall into the bands that may impair hearing. Recent studies demonstrated that freeway commuters are chronically exposed to vehicle interior noise, bearing the risk of hearing impairment. The interior noise evaluation process is mostly conducted in a laboratory environment. The test results and the developed noise models may underestimate or ignore the noise effects from dynamic traffic and road conditions and configuration. However, the interior noise is highly associated with vehicle maneuvering. The vehicle maneuvering on a freeway weaving segment is more complex because of its nature of conflicting areas. This research is intended to explore the risk of the interior noise exposure on freeway weaving segments for freeway commuters and to improve the interior noise estimation by constructing a decision tree learning–based noise exposure dose (NED) model, considering weaving segment designs and engine operation. On-road driving tests were conducted on 12 subjects on State Highway 288 in Houston, Texas. On-board Diagnosis (OBD) II, a smartphone-based roughness app, and a digital sound meter were used to collect vehicle maneuvering and engine information, International Roughness Index, and interior noise levels, respectively. Eleven variables were obtainable from the driving tests, including the length and type of a weaving segment, serving as predictors. The importance of the predictors was estimated by their out-of-bag–permuted predictor delta errors. The hazardous exposure level of the interior noise on weaving segments was quantified to hazard quotient, NED, and daily noise exposure level, respectively. Results showed that the risk of hearing impairment on freeway is acceptable; the interior noise level is the most sensitive to the pavement roughness and is subject to freeway configuration and traffic conditions. The constructed NED model shows high predictive power (R = 0.93, normalized root-mean-square error [NRMSE] < 6.7%).
Implications: Vehicle interior noise is usually ignored in the public, and its modeling and evaluation are generally conducted in a laboratory environment, regardless of the interior noise effects from dynamic traffic, road conditions, and road configuration. This study quantified the interior exposure dose on freeway weaving segments, which provides freeway commuters with a sense of interior noise exposure risk. In addition, a bagged decision tree–based interior noise exposure dose model was constructed, considering vehicle maneuvering, vehicle engine operational information, pavement roughness, and weaving segment configuration. The constructed model could significantly improve the interior noise estimation for road engineers and vehicle manufactures. 相似文献
The use of coarse recycled concrete aggregates (CRCA) in conjunction with fine recycled concrete aggregates (FRCA) as sub-base materials has been widely studied. Although research results indicate that it is feasible to employ both CRCA and FRCA as granular sub-base, the influence of the unhydrated cement in the adhered mortar of the RCA on the properties of the sub-base materials has not been thoroughly studied. Generally, it is known that the strength of the sub-base materials prepared with RCA increases over time. However, this mechanism, known as the self-cementing properties, is not well understood and is believed to be governed by the properties of the fine portion of the RCA (<5mm). This paper presents an investigation on the cause of the self-cementing properties by measuring X-ray diffraction patterns, pH values, compressive strength and permeability of various size fractions of the FRCA obtained from a commercially operated construction and demolition waste recycling plant. Their influence on the overall sub-base materials was determined. The results indicate that the size fractions of <0.15 and 0.3-0.6mm (active fractions) were most likely to be the principal cause of the self-cementing properties of the FRCA. However, the effects on the properties of the overall RCA sub-base materials were minimal if the total quantity of the active fractions was limited to a threshold by weight of the total fine aggregate. 相似文献