With the development of activated sludge model, the simulation software for the design and operation of wastewater treatment plant (WWTP) was produced and has been widely used. The dynamic change of the quality and flow of influent are major factors causing the unstable operation of wastewater treatment process. As a basic model, ASMI model was used for the simulation of activated sludge process, and double exponential model was selected for the simulation of secondary sedimentation tank. The influences of influent change to the aeration tank and secondary sedimentation tank were investigated, and the relationship among influent change, the quality of effluent and the level of sludge blanket in secondary sedimentation tank was established. On the basis of the simulation results, the operation of the WWTP could be adjusted under the dynamic change of the influent. Furthermore, the controlling strategy combined the feed-forward on the influent flow and the feedback on the level of sludge blanket in the secondary sedimentation tank was studied. 相似文献
This study was undertaken to determine the importance of riparian buffers to stream ecology in agricultural areas. The original
Maryland Biological Stream Survey (MBSS) data set was partitioned to represent agricultural sites in Maryland's Coastal Plain
and Piedmont regions. ANOVA, multiple linear regression (MLR), and CART regression tree models were developed using riparian
and site catchment landscape characteristics. MBSS data were both stratified by physiographic region and analyzed as a combined
data set. All models indicated that land management at the site was not the controlling factor for fish IBIs (FIBI) at that
site and, hence, using FIBI to evaluate site-scale factors would not be a prudent procedure. Measures of instream habitat
and location in the stream network were the dominant explanatory factors for FIBI models. Both CART and MLR models indicated
that forest buffers were influential on benthic IBIs (BIBI). Explanatory variables reflected instream conditions, adjacent
landscape influence, and chemistry in the Coastal Plains sites, all of which are relatively site specific. However, for Piedmont
sites, hydrologic factors were important, in addition to adjacent landscape influence, and chemistry. Both Coastal Plain and
Piedmont CART models identified several hydrologic factors, emphasizing the dominant control of hydrology on the physical
habitat index (PHI). Riparian buffers were a secondary influence on PHI in the Coastal Plain, but not in the Piedmont. Between
40% and 70% of the variation in FIBI, BIBI, and PHI was explained by the “easily obtainable” variables available from the
MBSS data set. While these are empirical results specific to Maryland, the general findings are of use to other locations
where the establishment of forest buffers is considered as an aquatic ecosystem restoration measure. 相似文献
Objective: This article discusses differences between a side impact procedure described in United Nations/Economic Commission for Europe (UN/ECE) Regulation 129 and scenarios observed in real-world cases.
Methods: Numerical simulations of side impact tests utilizing different boundary conditions are used to compare the severity of the Regulation 129 test and the other tests with different kinematics of child restraint systems (CRSs). In the simulations, the authors use a validated finite element (FE) model of real-world CRSs together with a fully deformable numerical model of the Q3 anthropomorphic test device (ATD) by Humanetics Innovative Solution, Inc.
Results: The comparison of 5 selected cases is based on the head injury criterion (HIC) index. Numerical investigations reveal that the presence of oblique velocity components or the way in which the CRS is mounted to the test bench seat fixture is among the significant factors influencing ATD kinematics. The results of analyses show that the side impact test procedure is very sensitive to these parameters. A side impact setup defined in Regulation 129 may minimize the effects of the impact.
Conclusions: It is demonstrated that an artificial anchorage in the Regulation 129 test does not account for a rotation of the CRS, which should appear in the case of a realistic anchorage. Therefore, the adopted procedure generates the smallest HIC value, which is at the level of the far-side impact scenario where there are no obstacles. It is also shown that the presence of nonlateral acceleration components challenges the quality of a CRS and its headrest much more than a pure lateral setup. 相似文献