Back-arc extension has been well documented in subduction plate tectonic regimes. However, the reasons why back-arc extensions are associated with some subduction systems but not others have remained elusive. Here, spatio-temporal variations in the composition of Cenozoic basalts in the northeast Asian continental margin are used to constrain the mechanism for episodic back-arc extensions. Using geochemical data sensitive to tectonic affinity, we show that typical volcanic arc compositions are located in the eastern margin of northeast Asia, whereas coeval intraplate volcanic compositions are located in the western part of northeast Asia, and that the intraplate and arc volcanism exhibit two eastward shifts, from 52 Ma to 33 Ma and from 33 Ma to 21 Ma. Intraplate basalts dated at ca. 11 Ma display a weak, arc-like geochemical signature, which suggests that the upwelling of asthenospheric mantle resulted in the remelting of previously melt-extracted lithospheric mantle modified by slab-derived fluids and the cessation of back-arc extensions. Thus, we propose that the eastward mantle flow resulted in eastward shifts of back-arc extensions that led to the development of extensive Cenozoic arc and intraplate volcanism in the northeast Asian continental margin.
A new method has been developed for estimating the capacity of an exclusive left lane with a permitted phase under nonstrict priority. Different from maneuvers under strict priority, these left-turning vehicles were released in the form of a left-turn group. A field survey was first conducted to explore the maximum number of vehicles in a left-turn group, and the releasing process of the permitted left turns. e observations revealed that (1) the maximum number is related to the intersection geometry and (2) the releasing process includes two stages: the first left-turn group crossing at the beginning of a permitted phase and the following leftturn groups crossing using gaps provided by opposing right turns. Next, a method based on probability theory and these observation results were applied to estimate the capacity of an exclusive left lane. e procedure contains two stages and eight steps. Finally, the estimation of the left-turn capacity using the proposed model was validated by comparing the capacity from the strict priority and actual maximum volumes.
This paper is concerned with proposing a decision-making model to determine the suitable type from curbside and offset transit lane, mainly for a double-lane auxiliary road. The significant difference between these two types is the location of the weaving segment. A comparison analysis was first conducted to discuss traffic operations at weaving segments. Then, a decision-making model using random forest technique was developed based on output volume, delay, and the number of person from 1 261 260 VISSIM micro-simulation scenarios which evaluated varying occupancy of a transit vehicle, occupancy of a general vehicle, transit traffic volume, general traffic volume, cycle lengths, green time splits, and ratio of rightturning flow. The results reveal that when determining transit lane options: 1) general traffic volume is the most significant variable; 2) the impact of occupancy of a general/transit vehicle is so small that can be ignored; and 3) signal cycle, general, and transit volume have a negative effect on selecting offset transit lane, but signal splits and right-turning ratio have a positive effect. This paper provides a better understanding of offset transit lane operation and offers a simple determination to select suitable transit lane type for a particular traffic scenario using five input data needs, without the need for complex hand calculations.
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