Optimizing Wirelessly Powered Crowd Sensing: Trading energy for data

To overcome the limited coverage in traditional wireless sensor networks, \emph{mobile crowd sensing} (MCS) has emerged as a new sensing paradigm. To achieve longer battery lives of user devices and incentive human involvement, this paper presents a novel approach that seamlessly integrates MCS with wireless power transfer, called \emph{wirelessly powered crowd sensing} (WPCS), for supporting crowd sensing with energy consumption and offering rewards as incentives. The optimization problem is formulated to simultaneously maximize the data utility and minimize the energy consumption for service operator, by jointly controlling wireless-power allocation at the \emph{access point} (AP) as well as sensing-data size, compression ratio, and sensor-transmission duration at \emph{mobile sensor} (MS). Given the fixed compression ratios, the optimal power allocation policy is shown to have a \emph{threshold}-based structure with respect to a defined \emph{crowd-sensing priority} function for each MS. Given fixed sensing-data utilities, the compression policy achieves the optimal compression ratio. Extensive simulations are also presented to verify the efficiency of the contributed mechanisms.Comment: arXiv admin note: text overlap with arXiv:1711.0206

Impact of Supercapacitors on a Fuel-Cell-Based Triple Hybrid for Small Unmanned Aircraft

Hybrid fuel-cell-based propulsion systems have the potential to transform the use of small electric powered unmanned aircraft. Offering the possibility of greatly increased flight endurance and range over existing battery systems, hybrid systems also overcome some of the limitations inherent with fuel cell only systems such as low specific power and comparatively slow dynamic response. However, although there have been many fuel-cell/battery hybrid systems developed for unmanned aerial vehicle (UAV) propulsion, alternative power storage devices such as supercapacitors have not been adequately explored. Supercapacitors are fast acting with a high specific power and cycle lifetime, making them ideal candidates for use in a fuel cell hybrid system. This research develops and evaluates the use of hybrid fuel cell propulsion systems incorporating supercapacitors in the overall hybrid architecture. First, the performance of supercapacitors is evaluated and compared with the performance of fuel cells and batteries to enable an assessment of the strengths and weaknesses of the different energy sources. Next, the integration of supercapacitors with fuel cells is performed in a robust and efficient manner that ensures the hybrid system architecture maximises the benefits inherent in each of the power sources. A comparison is made between fuel-cell/battery, fuel-cell/supercapacitor, and fuel-cell/battery/supercapacitor hybrids for a UAV propulsion application through hardware-in-the-loop simulation. Finally, flight testing of a fuel-cell-based triple hybrid in a small UAV is performed to validate the operation and performance of the power system

Emergent phases in a compass chain with multisite interactions

We study a dimerised spin chain with biaxial magnetic interacting ions in the presence of an externally induced three-site interactions out of equilibrium. In the general case, the three-site interactions play a role in renormalizing the effective uniform magnetic field. We find that the existence of zero-energy Majorana modes is intricately related to the sign of Pfaffian of the Bogoliubov-de Gennes Hamiltonian and the relevant $Z_2$ topological invariant. In contrast, we show that an exotic spin liquid phase can emerge in the compass limit through a Berezinskii-Kosterlitz-Thouless (BKT) quantum phase transition. Such a BKT transition is characterized by a large dynamic exponent $z=4$, and the spin-liquid phase is robust under a uniform magnetic field. We find the relative entropy and the quantum discord can signal the BKT transitions. We also uncover a few differences in deriving the correlation functions for the systems with broken reflection symmetry.Comment: 12 pages, 10 figure

Tsinghua Micro/Nanosatellite Research and Its Application

With the development of Micro-lNano-technology, Micro-lNano-satellite are paid great attention and developed rapidly. Tsinghua Space Research Center( TSRC) has planed to develop their Microsatellite and Nanosatellite with the cooperation of Surrey Space Center (SSC). The Tsinghua-l Microsatellite is new generation 3-axis stabile Microsatellite in 50 Kg. It is used as technical demonstration of Microsatellite constellation for globe disaster forecast net. The main Payloads include Multi-Spectral Earth Image System (MEIS) which have a 50 meters ground resolution and the cameras will be mounted 15 degrees off Z-axis of the satellite to meet the 400 kilometre ground swath requirement, Date Transmit Experiment payload which is used to survey the radio frequencies interference and GPS receiver. The THNS-l is a Nanosatellite in 5Kg. One micro magnetometer, three micro 2-d sun sensor, a micro GPS receiver and MIMU is employed to determine the attitude of Nanosatellite. A small gravity-gradient boom is used as basic stabilization of satellite. The main payload is a micro Multi-Spectral Earth Imaging system (MEIS). Three on chip CMOS CCD Cameras providing 250 meter ground sampling in 3 spectral bands with an 75 kIn field of view capable of providing detailed information on Earth resources, land use and environmental haze pollution and etc. The other Micro-Mechanical-Electric-system (MEMS) devices are as experimental payloads also

4-Chloro-N-[4-(diethyl­amino)benzyl­idene]aniline

The asymmetric unit of the title compound, C17H19ClN2, contains two independent mol­ecules which differ by a 180° flip in the orientation of the 4-chloro­aniline unit with respect to the diethyl­amino­benzyl­idene unit [N=C—C—C = 10.0 (3) and −170.6 (2)°]. The dihedral angles between the two aromatic rings are 64.0 (1) and 66.5 (1)° in the two independent mol­ecules

Viscoelastic response of neural cells governed by the deposition of amyloid-ß peptides (Aß)

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A deep level transient spectroscopy study of electron irradiation induced deep levels in p-type 6H–SiC

1.7 MeV electron irradiation-induced deep levels in p-type 6H–SiC have been studied using deep level transient spectroscopy. Two deep hole traps are observed, which are located at EV+0.55 eV and EV+0.78 eV. They have been identified as two different defects because they have different thermal behaviors. These defects at EV+0.55 eV and EV+0.78 eV are annealed out at 500–200 °C, respectively, and are different from the main defects E1/E2, Z1/Z2 observed in electron irradiated n-type 6H–SiC. This indicates that new defects have been formed in p-type 6H–SiC during electron irradiation. ©1999 American Institute of Physics.published_or_final_versio