International Journal of Modern Physics B

Terahertz (THz) focusing metasurface plays a key role in micro-focusing and micro-imaging. Most of the existing focus sets only show the number and deflection of focuses. However, few researches are concerned about the adjustment of focus intensity. Herein we designed a complementary metasurface based on a C-ring and cross-shaped composite slot structures, and the effect of structural thickness on focusing intensity and focal length were studied. We find that the angle of anomalously transmitted beam can be scanned from $17.5^{\circ }$ to $26.5^{\circ }$ when the frequency changes from 1.2 THz to 1.8 THz, while the focal length of the focusing metasurface can be linearly changed from 1000 $\mu \mathrm{\text{m}}$ to 1650 $\mu \mathrm{\text{m}}$. With increase in the thickness of the C-ring area, more interestingly, the focus intensity decreased linearly from 8.0 dB (V/m) to 4.5 dB (V/m). However, the focus intensity showed no obvious change when the thickness of the cross-shaped area was increased from 0.2 $\mu \mathrm{\text{m}}$ to 5 $\mu \mathrm{\text{m}}$. Therefore, our work would enhance the application of THz in high-resolution imaging, new THz device, and flat lens with adjustable focus intensity.

In this study, the $\alpha$-Fe₂O₃ nanowires were synthesized and decorated by ZnO nanoparticles using the hydrothermal method. The structural and morphological study of samples was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDS), High resolution transmission electron microscopy (HRTEM), and Fourier transform infrared spectroscopy (FTIR) techniques. FTIR was employed for $\alpha$-Fe₂O₃ and $\alpha$-Fe₂O₃ decorated with ZnO nanoparticles composites to verify the presence of ZnO in the composite after decorating. Furthermore, the optical properties was carried out using UV-vis spectrophotometer and photoluminescence spectra (PL) techniques. XRD analysis showed $\alpha$-Fe₂O₃ nanowires had a rhombohedral structure with a preferred crystal plane (104). In the $\alpha$-Fe₂O₃ nanowires decorated by ZnO nanoparticles, ZnO nanoparticles showed a hexagonal structure. Due to SEM images, the nanowires had an average diameter of 41 nm, and ZnO nanoparticles had a spherical shape with a maximum diameter of 70 nm. A uniform distribution was observed for both the $\alpha$-Fe₂O₃ nanowires and the $\alpha$-Fe₂O₃ nanowires decorated with ZnO nanoparticles. Furthermore, the result of bandgap energy calculation was 2.12 eV for $\alpha$-Fe₂O₃, while for $\alpha$-Fe₂O₃ nanowires decorated with ZnO nanoparticles was 3.17 eV which is near to the bandgap energy of ZnO nanoparticles. PL spectra revealed a few transitions in which the origin of these emissions would be associated to oxygen vacancies, iron vacancies, defects and band-to-band transition. The PL emission peaks of $\alpha$-Fe₂O₃ nanowires decorated with ZnO nanoparticles are similar to $\alpha$-Fe₂O₃ nanowires, but notably quenched with the ZnO nanoparticles. Based on the result of this study, it is possible to tune bandgap energy for various applications. In addition, this composite is promising candidates for solar cell photo electrodes and gas sensor applications.

In this work, a general method to manipulate the angle of reflection from an arbitrary two-dimensional (2D) surface is proposed by applying an appropriate phase discontinuity along the arbitrary surface. Three surfaces, including plane surface, parabolic surface and circular surface are taken as instances to validate this method. The results show that angle of reflection is conducted to $60^{\circ }$ for a wave incident to a plane surface at $45^{\circ }$, while $30^{\circ }$ for a wave incident to the parabolic and circular surfaces normally. This kind of manipulation of acoustic waves for arbitrary reflecting surfaces opens up an avenue for reflected wavefront modulations and associated applications such as anti-sonar technology.

In this study, we propose a novel modified Modica–Mortola (MM) equation with a phase-dependent interfacial function. The classical MM functional has a multiple-well potential and the derived classical MM equation allows multiple local minima. The MM equation has a good property compared to its counterpart vector-valued Allen–Cahn (AC) system because the MM equation consists of a single equation. In the MM equation, one phase-field can represent multiple states. However, with a constant interfacial parameter, the interfacial transition layer is getting wider as the jump across two adjacent phases is higher. To overcome this unwanted phenomenon, we propose a phase-dependent interfacial function which has smaller value if gradient of phase-field is larger. We present several computational experiments to demonstrate the superior performance of the proposed modified MM equation over the conventional MM equation.

A large number of studies have shown that the correlation of spike trains in paired neurons is a key indicator of functional connectivity. Acting as the important components of neurons, dendrites affect the generation of spike train and the transmission of signals by changing the transfer function of neurons. However, it is not clear how the intrinsic properties of dendrites influence the degree of correlation of neuronal spike trains. This paper used a biophysically-based two-compartment model to simulate the firing output of neurons that receive correlated input currents, quantify the relationship between the active and passive properties of dendrites and the pairwise spike train correlations. We found that increasing the proportion of dendritic area or the coupling conductance between two compartments increases the output correlation. It is also shown that decreasing the intracellular calcium concentration and the conductance of calcium activated outward potassium channel or increasing the conductance of sodium and potassium channel in dendritic compartment increases the output correlation. This results from the increase of the number of dendritic spikes due to changing dendritic intrinsic properties, which causes more internal current flowing into the soma from dendrites, thereby leading to an increase of somatic firing rate. Our results reveal the influence of the intrinsic characteristics of dendrites on firing output of individual neuron, which further influences the correlation between the spike trains of a pairs or population of neurons. This study is of great significance for understanding how neuronal intrinsic properties affect neural network coding.

In this paper, a three-body hybrid quantum system with the solid-state spin and topological qubit both mediated by a torsional nanomechanical resonator (NMR) is built by taking advantage of two different coupling mechanisms, the so-called strain and the magnetism, respectively. Two basic quantum manipulation (QM) schemes with respect to the quantum interface for arbitrary-state transfer and two-qubit Mølmer–Sørensen (MS) gate are also studied here. Then the efficiency for both QM processes is also systematically estimated, even under the influence of all kinds of adverse factors such as dissipation, decoherence and dephasing. This work may provide an extensible route towards a wider range of applications in quantum manipulation.

This paper constructs and simulates the interface circuit of a temperature sensor based on SMIC 0.18 $\mu$m CMOS. The simulation results show that when the power supply voltage is 1.8 V, the chopper op-amp gain is 89.44 dB, the low-frequency noise is 71.83 nV/Hz,${}^{1/2}$ and the temperature coefficient of the core temperature sensitive circuit is 1.7808 mV/${}^{\circ }$C. The sampling rate of 10-bit SAR ADC was 10 kS/s, effective bit was 9.0119, SNR was 59.3256 dB, SFDR was 68.7091 dB, and THD was −62.5859 dB. The measurement range of temperature sensor interface circuit is −50${}^{\circ }$C$\sim +125^{\circ }$C, the relative temperature measurement error is ±0.47${}^{\circ }$C, the resolution is 0.2${}^{\circ }$C/LSB, and the overall average power consumption is 434.9 $\mu$W.

Flat micro-Heat Pipe (FHP) provides an excellent solution to the heat dissipation problem of an electronic chip by the gas–liquid two-phase flow. Therefore, the liquid channels and the gas channels are part of the FHP. It determines the performance of the FHP. To this end, these channels were optimized by infiltration modification to accelerate the gas-liquid circulation. In this work, the wick underwent hydrophilic treatment by chemical corrosion and the solutions selected were KOH and (NH₄)₂S₂O₈. The shell surface undergoes hydrophobic treatment by electrodeposition with a mixture of zinc-nickel ions. The thermal transfer performance of the Hydrophilic Wick FHP (HW-FHP) and the Hydrophobic Shells FHP (HS-FHP) was analyzed. The results show that the maximum thermal power of the HW-FHP is 10.8 W, 9.1% higher than that of the Untreated FHP (UFHP). The HS-FHP is 11.9 W, 20% higher than that of the UFHP. The HW has a high capillary force, resulting in faster fluid flow. The vapor flow channels made up of the HS have a low resistance to the vapor flow. The hydrophobic surface can reduce the droplet diameter and prevent blocked vapor flow channels.

In this work, a sensitive fluorescent sensor for the detection of ciprofloxacin (CIP) was developed by wrapping the surface of CdTe quantum dots (QDs) with molecularly imprinted polymers (MIPs). The MIP@QDs were synthesized via a simple sol–gel method using 3-aminopropyltriethoxysilane (APTES) as the functional monomer and tetraethoxysilane (TEOS) as the crosslinker. The fluorescence emission of the probe was at 643 nm. Linear calibration curves were obtained in the range of 0.5–24 $\mu$M for CIP with the detection limit of 0.23 $\mu$M (S/N$=$3). The fluorescent probe was successfully applied to the determination of CIP in seawater samples with the spiked recoveries ranging from 98.2% to 110.6% and the relative standard deviation (RSD) was less than 10.7%. It is the first time that QDs with molecularly imprinted polymers (MIP@QDs) were introduced for separation and detection of CIP in seawater and obtained good specific identification ability and potential practical value.

This paper proposes a new concentration gradient generator based on the principle and flow characteristics of solution mixing in the microchannel. This concentration gradient generator works with oscillating bubbles in the microchannel, which are excited with bulk acoustic wave. The oscillating bubbles are used to mix the solution in the microchannel. The volume of each bubble is controllable individually and the number of bubbles partaken mixing is adjustable. Therefore, the mixing position of the solution and the concentration gradient in the microchannel are adjustable. Therefore, the new concentration gradient generator has the advantages of fast response and high flexibility. Simulation software COMSOL 5.5 was used to simulate the influence of the inlet flow rate, the bubble amplitude, and the number of bubbles on the mixing result. The simulation result shows that the inlet flow rate and the bubble amplitude affect the mixing width of the solution in the microchannel. The simulation result also shows that the concentration distribution with different gradient can be generated by adjusting the number of bubbles located in the solution microchannel. The simulation has an important reference for the design of the concentration gradient generator.