科研成果 by Type: Conference Paper

The past five years have witnessed the significant breakthrough of perovskite solar cells (PSCs). High certificated power conversion efficiency (PCE) of 22.1% was achieved in a short time after the inorganic-organic perovskite was firstly used as the light absorber in the solar cells. It is believed that PSCs now become one of the most promising photovoltaic in the new-generation solar cells, which may rival silicon based solar cells. In this article, simplified planar perovskite solar cells without a hole-blocking layer were fabricated by a two-step spin-coating method, and the highest PCE of 15.1% was achieved with an average PCE of 13.6%. Moreover, it is found that the hysteresis effect is reduced in this kind of devices. The research on improved performance for the PSCs with simplified device architecture is very important both for understanding the working mechanism of cells, and for fabricating low-cost and high-performance PSCs to approach commercial applications. (C) 2017 Published by Elsevier Ltd.

This work reports a kilovolt and low current collapse normally-off GaN MOSHEMT on silicon substrate. The device with a drift length of 3 mum features a threshold voltage of 1.7 V and an output current of 430 mA/mm at 8 V gate bias. The off-state breakdown voltage (BV) is as high as 1021 V (800 V) defined at a drain leakage criterion of 10 muA/mm with floating (grounded) substrate. The corresponding breakdown electric field is 3.4 MV/cm and the Baliga's figure-of-merit (BFOM) is 1.6 GW/cm2. A small degradation of the dynamic on-resistance (Ron, d) about 30% is observed with a short pulse width of 500 ns and a quiescent drain bias of 60 V. The record value is supposed to benefit from the intrinsic step-graded field plate, high quality LPCVD Si3N4 passivation and material optimization of 4.5 mum thick epitaxial layer.

Despite a lot of research efforts devoted in recent years, how to efficiently learn long-term dependencies from sequences still remains a pretty challenging task. As one of the key models for sequence learning, recurrent neural network (RNN) and its variants such as long short term memory (LSTM) and gated recurrent unit (GRU) are still not powerful enough in practice. One possible reason is that they have only feedforward connections, which is different from the biological neural system that is typically composed of both feedforward and feedback connections. To address this problem, this paper proposes a biologically-inspired deep network, called shuttleNet. Technologically, the shuttleNet consists of several processors, each of which is a GRU while associated with multiple groups of hidden states. Unlike traditional RNNs, all processors inside shuttleNet are loop connected to mimic the brain's feedforward and feedback connections, in which they are shared across multiple pathways in the loop connection. Attention mechanism is then employed to select the best information flow pathway. Extensive experiments conducted on two benchmark datasets (i.e UCF101 and HMDB51) show that we can beat state-of-the-art methods by simply embedding shuttleNet into a CNN-RNN framework.

© 2017 IEEE. FPGAs play a crucial role in the space of customizable accelerators over the next few years. A chief limiting factor is that FPGA CAD tools are cumbersome and time-consuming to most application developers. Routing is the most complex step in FPGA design flow and NP-complete problem. The PathFinder routing algorithm is in dominant use in FPGA CAD research. However, PathFinder is sequential in nature and lengthy in runtime. Parallelization has the potential to solve the issue but faces non-trivial challenges. In this work we introduce Megrez that uses strictly-ordered partitioning to explore the parallelism on GPU. Experimental results show that Megrez achieves an average of 15.13× speedup on GPU with negligible influence on the routing quality.

In the Epistulae ex ponto, Ovid describes how he dealt with the arrival of the silver images of Augustus, Livia and Tiberia that Cotta Messalinus sent him (2.8). He also described his sacrum Caesaris while celebrating the Pomponius brothers for attaining consulships (4.9). The theme of emperor worship as a medium of communication between patrons and their exiled client is striking. Millar noted how Ovid was kept informed of the metamorphoses of the imperial household (Millar 1993, 15-17), and Syme pointed to Ovid’s ability to use concurrent language of homage at Rome (Syme 1978, 167-8). As such, Ovid’s descriptions bear significance beyond proving that domestic worship of living emperors and his household existed (Gradel 2002, 202-203; Martelli 2013, 200).   This paper argues that Ovid’s epistles show how elite Roman society cared about emperor worship. Ovid received the proper set of statues of the imperial family from his friend and patron Cotta Messalinus. He reported to the Pomponius brothers regarding how Tiberius and Livia stant pariter beside the deified Augustus in his sacrum Caesaris, and about his prayers that are meant for public consumption (Price 1984, 92). At stake is his hope to return to Rome: the proper exercise of worship demonstrates not only his pietas but also how he projected imperial symbolism on the edge of the empire. Hence, he boasted how Pontus knew of his pietas as part of his metric resumé submitted to his friend and patron Pomponius Graecinus (Helzle 1989, 22-26). Together with Pliny the Younger’s foundation of a temple at Tifernum (Ep. 10.8), the literary sources offer a potential model for the foundation process of small temples such as the one found at Eretria (Schmid 2001, 113), or others as documented by Simon Price (1984) and Heidi Hänlein-Schäfer (1985).