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An ultra-thin double barrier enhancement mode (E-mode) AlGaN/GaN high electron mobility transistor (HEMT) with p-type buffer layer and Si 3 N 4 /graded p-AlGaN gate is proposed and investigated by Silvaco TCAD. The simulation results show that the designed HEMT can obtain a high threshold voltage over 5.0 V and large gate swing. The maximum gate leakage current is 3.11×10 -4 A/mm at 30 V gate voltage, which decreases four orders of magnitude compared to the conventional double barrier HEMTs. Due to the p-type buffer layer, the cut-off frequency for the proposed HEMT is raised over three-times compared to the conventional double barrier structure HEMT with n-type buffer layer. Meanwhile the designed HEMT exhibits high breakdown voltage and large current-gain. Moreover, the impacts of Si 3 N 4 layer thickness under gate and GaN channel layer thickness are analyzed. Both layers play significantly roles in obtaining high threshold voltage for the device by adjusting the conduction band energy of AlGaN/GaN interface quantum well.

The power conversion efficiency (PCE) of polymer solar cells (PSCs) are strongly depended on the bulk-heterojunction active layer. Here, the 1,8-diiodooctane (DIO) additives have been added into the PCDTBT: PC70BM blend PSCs. Based on the higher boiling point than host solvent ODB and better solubility of PC71BM, the device photovoltaic properties with DIO additive were changed obviously. The investigations of EQE indicate that the DIO can influence the charge recombination and transportation process, and absorption studies demonstrate that the charge carriers generation process can also be affected by DIO. The overall impact reflected on the decreased equivalent resistant. With 3% v/v DIO, the Jsc, Voc and FF are both increased. Correspondingly, a highest PCE is achieved of 6.15%, while the reference device without DIO only has a PCE of 5.23%. Hence, adding DIO solvent additive is a effective method for the photovoltaic properties improving of PCDTBT: PC70BM blend PSCs.

Impedance mismatch that degrades signal power transfer and affects communication reliability is a major obstacle for power line communications (PLC). Impedance matching techniques can be designed to effectively compensate for the impedance mismatch between PLC modems and power line networks at a specific frequency or for a given frequency band. In this paper, we discuss the tradeoffs that need to be made when designing an effective impedance matching network. We also make a comprehensive review of previous state-of-the-art PLC impedance matching techniques and provide a useful classification of each technique. Finally, we discuss important issues (concerns) and provide suggestions for research directions deserving more attention. This review provides a useful guideline for researchers and manufacturers to quickly understand impedance matching principles and facilitate the design of an effective impedance matching coupler for PLC applications.

Delay Tolerant Network (DTN) is an intermittently connected network where there is no complete path from source to destination for most of the time, and routing becomes one of the most challenging and open problems in DTN. To deal with this issue and avoid random and blindfold forwarding in Binary Spray and Wait (BSW) routing, we present the concept of CoN (Capability of Node), then propose the CoN-ASW routing algorithm, which uses the CoN to calculate the number of message copies to be forwarded and determine whether to forward messages to the encounter node. The simulation results show that the proposed algorithm can significantly improve the delivery utility while enhancing delivery rate and reduce the overhead.

In power line communication (PLC), coupling transformers are usually required for coupling, band-pass filtering and impedance matching. However, coupling transformer design involves so many parameters that it is typically an imprecise and experimental procedure. In addition, the cost and size of transformers prevent them from being an economic and compact solution for PLC couplers. This paper first analyzes a simplified, distributed parameter model of the power line, which can be used to calculate power line impedance easily and accurately. Next, a low-cost, band-pass matching coupler with compact architecture is designed to replace the coupling transformer for direct current PLC (DC-PLC), which ensures impedance matching on the basis of an accurate power line impedance instead of using an average value. Finally, simulations as well as laboratory tests are conducted under 95–125[Formula: see text]kHz (CENELEC B-band), which confirm the new coupler’s excellent band-pass filtering and impedance matching performance.

In this paper, the finite-time tracking control problem for multiple nonholonomic mobile robots in the presence of external disturbances and uncertainties is investigated. First of all, the resulting tracking error system is derived. Secondly, continuous distributed cooperative finite-time tracking control laws are designed for each mobile robot, where the communication topology among the multiple mobile robots is assumed to be a directed graph. Rigorous proof shows that the group of mobile robots converge to the desired reference trajectory in finite time. Simulation example illustrates the effectiveness of our method.

Delay Tolerant Networks (DTNs) is a mobile wireless network, in which it is difficult to establish end-to-end paths. Meanwhile, the nodes transmit message copies randomly, resulting in a high overhead of message propagation. In this paper, a Transfer Utility of Node Spray and Wait (TUoN-SNW) routing is proposed to forward the message copies dynamically, which avoid randomness of Spray and Wait routing protocol when message copies are forwarded. And in order to reduce the overhead, a Based on Transfer Utility of Node's Buffer Scheduling Strategy (BTUoN-BSP) is also applied. Simulation results show that compared with the Spray and Wait (SNW) routing, the algorithms could not only improve the delivery rate but also reduce the overhead of network obviously.

Inter-crystalline pores, cavities, and fractures created from diagenetic shrinkage of dolomite are inter-connected each other, forming fine oil-and gas-bearing reservoirs. It is hard to predict these complex fracture-cavity reservoirs because of their random distribution, different growth timing, and so on. Taking the lacustrine dolomite fracture-pore reservoir in the Lower Cretaceous Xiagou Formation in the Qingxi oilfield within the Jiuquan basin as an example, we put forward a comprehensive geophysical method to predict carbonate fractures.

In power line communication (PLC), couplers such as coupling transformers and band-pass matching coupling circuits are usually required for coupling, band-pass filtering, and impedance matching. However, the cost and size of transformers prevent them from being an economic and compact solution for PLC couplers. In addition, passive band-pass matching coupling circuits need accurate impedance matching and possibly incur power losses. In this paper, a 6th order multiple feedback (MFB) active power filter with the minimum number of components was designed for narrow-band PLC, which has high input impedance and low output impedance, allowing outstanding performance in main voltage isolation, suppressing the current-harmonics and compensating the reactive power simultaneously. Finally, simulations were conducted in the range of 95 kHz-125 kHz (CENELEC “B-band”), which confirmed that the new filter met the CENELEC requirements for transmission and disturbance levels.

Delay Tolerant Network is an emerging research field. In this network, a long period of network partition happens frequently. In this paper, we present the notion of QoN (Quality of Node) based on the differences of node activity. Then we introduce the notion of QoN to forward the number of message copies dynamically to improve the Binary Spray and Wait routing. This Protocol can avoid the blindness of the BSW routing (Binary Spray and Wait) when message copies are forwarded. The results show that QoN-BSW routing can significantly enhance delivery utility and reduce the overhead while improving the delivery probability and reducing the delay.