On the Intrinsic Concordance between the Wide Scattering Feature of Synchronized Flow and the Empirical Spacing Distributions

We discuss the intrinsic concordance between the wide scattering feature of density-flow plot and the empirical spazing distributions for traffic flows. It is shown that by choosing a proper threshold parameter, the boundaries of truncated spacing distributions could well determine the envelope of the 2D region of synchronized flow.     

地源热泵U形换热器数值模拟

以地源热泵系统U形地埋管换热器为研究对象,主要研究其温度场对周围土壤温度的影响,并通过An-sys软件对地埋管换热器的温度场进行了模拟.结果表明,中心距为2.5 m的地埋管换热器对土壤温度有一定影响.若中心距过小,则会影响U形管的换热;反之,土壤面积将得不到充分利用.     

肋片间距对环形通道流动和换热的影响

本文用稳态层流模型对几种具有不同肋片间距的环型通道内的流动和换热进行了数值模拟.计算结果表明:长直肋片截断后,流动和换热沿长度方向具有周期性的入口段效应,从而增强了换热.与长直肋片通道相比,βL=13/7时,换热增强了27%,而阻力仅增加6.8%.对于带肋环形通道,Re数增大,换热增强.     

聚3-己基噻吩：非富勒烯太阳能电池中的量子效率损失和电压损失

From the industrial perspective, poly(3-hexylthiophene) (P3HT) is one of the most attractive donor materials in organic photovoltaics. The large bandgap in P3HT makes it particularly promising for efficient indoor light harvesting, a unique advantage of organic photovoltaic (PV) devices, and this has started to gain considerable attention in the field of PV technology. In addition, the up-scalability and long material stability associated with the simple chemical structure make P3HT one of the most promising materials for the mass production of organic solar cells. However, the solar cells based on P3HT has a low power conversion efficiency (PCE), which is less than 11%, mainly due to significant voltage losses. In this study, we identified the origin of the high quantum efficiency and voltage losses in the P3HT: non-fullerene based solar cells, and we proposed a strategy to reduce the losses. More specifically, we observed that: 1) the non-radiative decay rate of the charge transfer (CT) states formed at the donor–acceptor interfaces was much higher for the P3HT: non-fullerene solar cells than that for the P3HT: fullerene solar cells, which was the main reason for the more severely limited photovoltage; 2) the origin of the high non-radiative decay rate in the P3HT: non-fullerene solar cell could be ascribed to the short packing distance between the P3HT and non-fullerene acceptor molecules at the donor–acceptor interfaces (DA distance), which is a rarely studied interfacial structural property, highly important in determining the decay rate of CT states; 3) the lower voltage loss in the state-of-the-art P3HT solar cell based on the 2, 2'-((12, 13-bis(2-butyldecyl)-3, 9-diundecyl-12, 13-dihydro-[1, 2, 5]-thiadiazolo[3, 4-e]thieno[2', 3': 4', 5']thieno[2', 3': 4, 5]p-yrolo[3, 2-g]thieno[2', 3': 4, 5]thieno[3, 2-b]indole-2, 10-diyl)bis(methanelylidene))bis(5, 6-dichloro-1H-indene-1, 3(2H)-dion-e) (ZY-4Cl) acceptor could be associated with the better alignment of the energy levels of the active materials and the longer DA distance, compared to those based on the commonly used acceptors. However, the DA distance was still very short, limiting the device voltage. Thus, improving the performance of the P3HT based solar cells requires a further increase in the DA distance. Our findings are expected to pave the way for breaking the performance bottleneck of the P3HT based solar cells.