A new thermoplastic vulcanizate (TPVs) composed of polypropylene and fluorosilicone rubber was successfully prepared via dynamic vulcanization focusing on undersea cable and automobile applications. ...Phase morphology confirms the dispersed rubber particles in a continuous thermoplastic phase. The influence of vulcanization and post-curing time on the mechanical and dynamic properties of TPVs was investigated. Notably, the tensile strength decreased, and the compression set increased with an increase in vulcanization time. Overall, the fabricated TPVs possessed good tensile strength, elastic behavior, and thermal stability. The post-curing time effect on TPVs exhibited a good compression set and lower hardness, but tensile properties deteriorated.
In this paper, the development of compact transmission soft x-ray microscopy (XM) with sub-50 nm spatial resolution for biomedical applications is described. The compact transmission soft x-ray ...microscope operates at lambda = 2.88 nm (430 eV) and is based on a tabletop regenerative x-ray source in combination with a tandem ellipsoidal condenser mirror for sample illumination, an objective micro zone plate and a thinned back-illuminated charge coupled device to record an x-ray image. The new, compact x-ray microscope system requires the fabrication of proper x-ray optical devices in order to obtain high-quality images. For an application-oriented microscope, the alignment procedure is fully automated via computer control through a graphic user interface. In imaging studies using our compact XM system, a gold mesh image was obtained with 45 nm resolution at x580 magnification and 1 min exposure. Images of a biological sample (Coscinodiscus oculoides) were recorded.
In this study, the performance of intelligent reflecting surfaces (IRSs) with a discrete phase shift strategy is examined in multiple-antenna systems. Considering the IRS network overhead, the ...achievable rate model is newly designed to evaluate the practical IRS system performance. Finding the optimal resolution of the IRS discrete phase shifts and a corresponding phase shift vector is an NP-hard combinatorial problem with an extremely large search complexity. Recognizing the performance trade-off between the IRS passive beamforming gain and IRS signaling overheads, the incremental search method is proposed to present the optimal resolution of the IRS discrete phase shift. Moreover, two low-complexity sub-algorithms are suggested to obtain the IRS discrete phase shift vector during the incremental search algorithms. The proposed incremental search-based discrete phase shift method can efficiently obtain the optimal resolution of the IRS discrete phase shift that maximizes the overhead-aware achievable rate. Simulation results show that the discrete phase shift with the incremental search method outperforms the conventional analog phase shift by choosing the optimal resolution of the IRS discrete phase shift. Furthermore, the cumulative distribution function comparison shows the superiority of the proposed method over the entire coverage area. Specifically, it is shown that more than 20% of coverage extension can be accomplished by deploying IRS with the proposed method.
In this study, an intelligent reflecting surface (IRS)-aided space-time line code (STLC) system is examined to efficiently extend its coverage area. The IRS phase-shift values of each element can be ...designed using a semidefinite relaxation (SDR) method to maximize the received signal-to-noise ratio of the IRS-STLC systems. A unit-modulus constraint relaxation (UCR) method is proposed to reduce the computational complexity of the SDR method. The numerical results verify that the proposed UCR-based IRS can achieve comparable bit-error-rate performance to the SDR-based IRS, albeit with significantly reduced computational complexity. Owing to the proposed IRS, the coverage area can be significantly extended.
We investigated the gate bias stress effects of multilayered MoS2 field effect transistors (FETs) with a back-gated configuration. The electrical stability of the MoS2 FETs can be significantly ...influenced by the electrical stress type, relative sweep rate, and stress time in an ambient environment. Specifically, when a positive gate bias stress was applied to the MoS2 FET, the current of the device decreased and its threshold shifted in the positive gate bias direction. In contrast, with a negative gate bias stress, the current of the device increased and the threshold shifted in the negative gate bias direction. The gate bias stress effects were enhanced when a gate bias was applied for a longer time or when a slower sweep rate was used. These phenomena can be explained by the charge trapping due to the adsorption or desorption of oxygen and/or water on the MoS2 surface with a positive or negative gate bias, respectively, under an ambient environment. This study will be helpful in understanding the electrical-stress-induced instability of the MoS2-based electronic devices and will also give insight into the design of desirable devices for electronics applications.
A practically efficient resource allocation scheme is designed for multiple device-to-device cluster (D2DC) multicast communications underlay cellular networks. The transmit power and the channel are ...allocated to D2DC to maximize the sum effective throughput provided that the cellular communications maintain a certain level of quality of service. We devise a channel allocation scheme using partial information of device locations. For this, we derive the outage probability and an effective throughput of D2DC communications in approximate forms. Numerical results reveal that, when the number of D2DC receivers is large, the proposed scheme achieves the near optimal sum effective throughput, which can be obtained by using full information of device locations.
Recognizing the various and broad range of applications of unmanned aerial vehicles (UAVs) and unmanned aircraft systems (UAS) for personal, public and military applications, recent un-intentional ...malfunctions of uncontrollable UAVs or intentional attacks on them divert our attention and motivate us to devise a protection system, referred to as a counter UAV system (CUS). The CUS, also known as a counter-drone system, protects personal, commercial, public, and military facilities and areas from uncontrollable and belligerent UAVs by neutralizing or destroying them. This paper provides a comprehensive survey of the CUS to describe the key technologies of the CUS and provide sufficient information with wich to comprehend this system. The first part starts with an introduction of general UAVs and the concept of the CUS. In the second part, we provide an extensive survey of the CUS through a top-down approach: i) the platform of CUS including ground and sky platforms and related networks; ii) the architecture of the CUS consisting of sensing systems, command-and-control (C2) systems, and mitigation systems; and iii) the devices and functions with the sensors for detection-and-identification and localization-and-tracking actions and mitigators for neutralization. The last part is devoted to a survey of the CUS market with relevant challenges and future visions. From the CUS market survey, potential readers can identify the major players in a CUS industry and obtain information with which to develop the CUS industry. A broad understanding gained from the survey overall will assist with the design of a holistic CUS and inspire cross-domain research across physical layer designs in wireless communications, CUS network designs, control theory, mechanics, and computer science, to enhance counter UAV techniques further.
Abstract
We investigated the trap-mediated electronic transport properties of pentacene/molybdenum disulphide (MoS
2
) p-n heterojunction devices. We observed that the hybrid p-n heterojunctions were ...gate-tunable and were strongly affected by trap-assisted tunnelling through the van der Waals gap at the heterojunction interfaces between MoS
2
and pentacene. The pentacene/MoS
2
p-n heterojunction diodes had gate-tunable high ideality factor, which resulted from trap-mediated conduction nature of devices. From the temperature-variable current-voltage measurement, a space-charge-limited conduction and a variable range hopping conduction at a low temperature were suggested as the gate-tunable charge transport characteristics of these hybrid p-n heterojunctions. Our study provides a better understanding of the trap-mediated electronic transport properties in organic/2-dimensional material hybrid heterojunction devices.
PDF
