From the Owens Valley Radio Observatory 40 m radio telescope, we have collected the light curves of the 15 GHz radio band for FSRQ J0153-1153, spanning from 2009 February to 2018 February. The Lomb–Scargle Periodogram method and the Weighted Wavelet Z-transform method are employed to search for the quasi-periodic oscillation (QPO) signal of these data, and the simulation method for the light curve is utilized to estimate the significance level of this QPO signal; thus through these techniques, the QPO signal of 3.7 ± 0.5 yr with a significance level of 3.68 σ is revealed for the first time. It is most likely an explanation for the QPO signal that a binary black hole system gives rise to a Newtonian-driven the precession of jet. Based on this assumption, we find that the mass of the secondary black hole in this system may be larger than the mass of the primary black hole; and we estimate the intrinsic QPO of jet precession and the QPO of companion star orbit.

The production of a large number of metal oxide semiconductor materials is more for design needs, while theoretical exploration is relatively less concerned. In this work, WO3 nanoparticles were prepared by the tungstic acid thermolysis method, and the catalysts of Pt and Ru were loaded on the surface of nanoparticles with a wet impregnation method. As expected, the sensitive responses were enhanced significantly with the additional loading of Pt, which revealed that bimetallic loading could achieve better properties with a smaller loaded amount than single metal. According to the power-law response to oxygen and H2-TPR results, the sensitization mechanism of noble metals loaded WO3 to acetone as the typical VOCs was investigated. The results showed that the sensing processes were dominated by oxygen adsorption behavior and there was no difference with the loading of Ru. Furthermore, the power-law coefficient n became smaller with Pt loading. It is proposed that oxygen adsorbates on the surface become more active due to Pt. We would like to propose further a perspective, i.e., polymetallic loading that utilizes the properties of different metals to achieve synergism.

In this work, the directional excitation of acoustic graphene plasmons (AGPs) are numerically studied using Finite Element Methods. In our proposed designs, under oblique incidences, not only AGPs are excited efficiently, but also their unidirectional propagations are successfully realized. The net power flow along one direction is also calculated to demonstrate great unidirectional net energy transporting in our proposed structure. The dependence of directionality of AGPs on the structural parameters has also been studied systematically. Due to the tunable graphene conductivity, AGPs propagation can be dynamically controlled by an externally applied bias voltage (electrostatic gating). Most importantly, based on nano-sized space between graphene and metallic gate electrodes, relatively low voltages are required to dynamically control directionally propagating AGPs. The prototype structure may find applications in ultra-confined plasmons launchers and switchers in integrated optics.

Photonic crystals (PhCs) with rough surfaces can considerably enhance the formation of electromagnetic hotspots, which significantly promote surface-enhanced Raman scattering (SERS) activity. In this study, porous silicon PhCs with rough surfaces were synthesized. Deposition of gold nanoparticles on the substrate yielded a SERS substrate with good activity and reproducibility, consequently achieving the ultratrace detection of Rhodamine 6 G (R6G), with a minimum concentration of 10(-)(15) M. The SERS activity of this substrate was simulated via finite element modeling. The experimental and theoretical results confirmed that the optical characteristics of the "black silicon," created by inducing a rough surface, and the enhancement of the effective Raman susceptibility, or the time period of the light-matter interaction owing to photonic crystals, played an important role in the enhancement of the overall SERS activity. Furthermore, we demonstrated that the rough-surface porous silicon SERS substrate could be employed to selectively detect ultratrace military explosives containing picric acid (PA) with increased sensitivity. Accordingly, the detection limits of PA and the probe molecule R6G in the Raman spectra were 0.79 nM and 0.24 fM, respectively. This study suggests that the porous silicon PhCs with rough surfaces are promising candidates for ultratrace chemical sensing.

Surface-enhanced Raman scattering sensors and optical detection devices often incorporate rough surfaces or porous Si photonic crystals to enhance optical absorption and localized surface plasmon resonances. This study reports a porous Si photonic crystal structure fabricated on the backside of a crystalline Si substrate by room-temperature electrochemical etching. Scanning electron microscopy showed that the rough surface did not affect the vertical etching rate, but influenced the porosity and pore size distribution. X-ray diffraction analysis showed broader and lower-intensity peaks from the sample prepared on the back side, indicating that the backside porous Si had strong light-scattering effects and lattice contraction, which led to greater oxidation because of its higher porosity. A reflectance of similar to 1% was obtained over a broad wavelength range (400-700 nm) and the optical reflectance suppression mechanism was analyzed. These optical characteristics showed backside porous Si photonic crystals have significant potential utility in photovoltaic and photonics applications.

We investigate the issue of how the energy consumption with some certain step sizes in human walking being least. Firstly, we establish a physical model simulating the human walking. By analyzing factors relating to energy consumption, the movement of the body can be broken down into two parts, the translational motion of the whole body and the rotational motion around a fixed point. Then we obtain that the work consists of three parts: the potential energy of raising the gravity center of body, the translation kinetic energy of the upper part of the body and the kinetic energy of the motion of the two legs. Finally, we obtain the function relationship between the work done in walking and the steps by numerical simulation.