Modern Physics Letters B

Valence band anticrossing (VBAC) model is used to investigate band structure of InN${}_{1-x}$Bi${}_x$, GaN${}_{1-x}$Bi${}_x$ and AlN${}_{1-x}$Bi${}_x$ for the purpose of optimal performance group-III nitride related devices. Obvious reduction in band gap and increase in spin–orbit splitting energy are founded by doping dilute concentration of bismuth in all these III-N material. The band gap of GaN${}_{1-x}$Bi${}_x$ and AlN${}_{1-x}$Bi${}_x$ show a step change, and this can be explained by the special position relation between of Bi impurity energy level with corresponding host’s band offsets. We also show how bismuth may be used to form alloys by finding the doping region ${\mathrm{\Delta }}_{\mathrm{\text{SO}}}>E_g$ which can provide a means of suppressing non-radiative CHSH (hot-hole producing) Auger recombination and inter-valence band absorption. For InN${}_{1-x}$Bi${}_x$, bismuth concentration beyond 1.25% is found to be corresponding to the range of ${\mathrm{\Delta }}_{\mathrm{\text{SO}}}>E_g$ and it shows a continuous adjustable band gap from 0.7 eV to zero. This may make InN${}_{1-x}$Bi${}_x$ a potential candidate for near or mid-infrared optoelectronic applications.

In this paper, the symmetry analysis and similarity reduction of the (2+1)-dimensional Bogoyavlensky–Konopelchenko (B–K) equation are investigated by means of the geometric approach of an invariance group, which is equivalent to the classical Lie symmetry method. Using the extended Harrison and Estabrook’s differential forms approach, the infinitesimal generators for (2+1)-dimensional B–K equation are obtained. Firstly, the vector field associated with the Lie group of transformation is derived. Then the symmetry reduction and the corresponding explicit exact solution of (2+1)-dimensional B–K equation is obtained.

Networks with high propensity to synchronization are desired in many applications ranging from biology to engineering. In general, there are two ways to enhance the synchronizability of a network: link rewiring and/or link weighting. In this paper, we propose a new link weighting strategy based on the concept of the neighborhood subgroup. The neighborhood subgroup of a node i through node j in a network, i.e. $G^{i\to j}$, means that node u belongs to $G^{i\to j}$ if node u belongs to the first-order neighbors of j (not include i). Our proposed weighting schema used the local and global structural properties of the networks such as the node degree, betweenness centrality and closeness centrality measures. We applied the method on scale-free and Watts–Strogatz networks of different structural properties and show the good performance of the proposed weighting scheme. Furthermore, as model networks cannot capture all essential features of real-world complex networks, we considered a number of undirected and unweighted real-world networks. To the best of our knowledge, the proposed weighting strategy outperformed the previously published weighting methods by enhancing the synchronizability of these real-world networks.

In this paper, a CMOS active down-conversion mixer is presented for wideband applications. Specifically, a LO generation chain is suggested to convert AC LO signal to shaped trapezoid burst, which reduces the sinusoidal LO power level requirement by the mixer. The current-reuse technique by stacked nMOS/pMOS architecture is used to save the power consumption of the circuit. Moreover, this complementary configuration is also employed to compensate second-order nonlinearity of the circuit. Implemented in a 0.18-$\mu$m CMOS process, post-simulations show that, driven by only −10 dBm sinusoidal LO signal, the proposed inductorless mixer provides a maximal conversion gain of 15.7 dB and a noise figure (NF) of 9.1–12 dB across RF input frequency range 0.5–1.6 GHz. The IIP3 and IP1dB of 3.5 dBm and −4.8 dBm are obtained, respectively. The mixer core only consumes 3.6 mW from a 1.8-V supply.

Images taken in poor environmental conditions decrease the visibility and hidden information of digital images. Therefore, image enhancement techniques are necessary for improving the significant details of these images. An extensive review has shown that histogram-based enhancement techniques greatly suffer from over/under enhancement issues. Fuzzy-based enhancement techniques suffer from over/under saturated pixels problems. In this paper, a novel Type-II fuzzy-based image enhancement technique has been proposed for improving the visibility of images. The Type-II fuzzy logic can automatically extract the local atmospheric light and roughly eliminate the atmospheric veil in local detail enhancement. The proposed technique has been evaluated on 10 well-known weather degraded color images and is also compared with four well-known existing image enhancement techniques. The experimental results reveal that the proposed technique outperforms others regarding visible edge ratio, color gradients and number of saturated pixels.

The widely used Bouc–Wen hysteresis model can be utilized to accurately simulate the voltage–displacement curves of piezoelectric actuators. In order to identify the unknown parameters of the Bouc–Wen model, an improved artificial bee colony (IABC) algorithm is proposed in this paper. A guiding strategy for searching the current optimal position of the food source is proposed in the method, which can help balance the local search ability and global exploitation capability. And the formula for the scout bees to search for the food source is modified to increase the convergence speed. Some experiments were conducted to verify the effectiveness of the IABC algorithm. The results show that the identified hysteresis model agreed well with the actual actuator response. Moreover, the identification results were compared with the standard particle swarm optimization (PSO) method, and it can be seen that the search performance in convergence rate of the IABC algorithm is better than that of the standard PSO method.

Drug synergy prediction plays a significant role in the medical field for inhibiting specific cancer agents. It can be developed as a pre-processing tool for therapeutic successes. Examination of different drug–drug interaction can be done by drug synergy score. It needs efficient regression-based machine learning approaches to minimize the prediction errors. Numerous machine learning techniques such as neural networks, support vector machines, random forests, LASSO, Elastic Nets, etc., have been used in the past to realize requirement as mentioned above. However, these techniques individually do not provide significant accuracy in drug synergy score. Therefore, the primary objective of this paper is to design a neuro-fuzzy-based ensembling approach. To achieve this, nine well-known machine learning techniques have been implemented by considering the drug synergy data. Based on the accuracy of each model, four techniques with high accuracy are selected to develop ensemble-based machine learning model. These models are Random forest, Fuzzy Rules Using Genetic Cooperative-Competitive Learning method (GFS.GCCL), Adaptive-Network-Based Fuzzy Inference System (ANFIS) and Dynamic Evolving Neural-Fuzzy Inference System method (DENFIS). Ensembling is achieved by evaluating the biased weighted aggregation (i.e. adding more weights to the model with a higher prediction score) of predicted data by selected models. The proposed and existing machine learning techniques have been evaluated on drug synergy score data. The comparative analysis reveals that the proposed method outperforms others in terms of accuracy, root mean square error and coefficient of correlation.

In this paper, a novel underwater unidirectional acoustic transmission (UAT) device consisting of a plate with bilateral asymmetric gratings is proposed and numerically investigated. The transmission spectra, the acoustic intensity field distributions, and the displacement field distributions are numerically calculated based on the finite element method. The transmission spectra show that the proposed device exhibits different UAT effects in three bands. The acoustic intensity field distributions demonstrate that the proposed device can realize UAT, which agree well with the transmission spectra. The mechanism is discussed by analyzing the displacement field distributions, and the UAT is attributed to the symmetric mode excited in brass plate. Furthermore, the effects of the lattice constant, the upper slit width, and the lower slit width on bands are discussed. Our design provides a good reference for designing underwater UAT devices and has potential applications in some fields, such as medical ultrasonic devices, acoustic barrier, and noise insulation.

All-optical switch is one of the key parts of optical circuit. We employ a temperature-sensitive resonator to form an optical switch. The resonator deforms under the applied light and adjusts the transmittance of the structure. To our knowledge, this is the first design of an all-optical surface plasmon polariton (SPP) switch based on the heat deformation effect.

The unsteady ground effect on a self-propelled undulatory foil is numerically investigated in this paper. The situation can be widely found in nature especially for fish swimming near the ground. In this study, frequency varies from 0.1 Hz to 2 Hz and distance from the ground varies from 0.2 L to 1 L. Under most kinematics, the ground has a negative effect on the performance of the foil. The swimming velocity slows down, power spend increases and swimming economy reduces. The higher frequency can produce a larger negative effect. Only at the low frequencies f = 0.1 Hz, 0.25 Hz and 0.5 Hz with distance of 0.2 L the velocity can be enhanced by 18%, 6%, 0.8%, respectively. The lift production is found to be increased. The link between the performance and the wake dynamics is also established by studying the vortex structures.

Based on the linear frequency modulation (LFM) of semiconductor laser, a laser ranging system is built. The ranging precision of the system is about micron dimension with the repetition frequency of 100 kHz and a distance of 1–10 m. We analyzed the ranging precision experimentally. As the bandwidth increases, the ranging precision becomes higher and higher. When the bandwidth is fixed, as the distance increases, the signal-to-noise ratio (SNR) will decrease, which reduces the precision.

Little, lightweight, low-power microelectromechanical system (MEMS) pressure switches offer a good development prospect for small, ultra-long, simple atmosphere environments. In order to realize MEMS pressure switch, it is necessary to solve one of the key technologies such as thermal robust optimization. The finite element simulation software is used to analyze the thermal behavior of the pressure switch and the deformation law of the pressure switch film under different temperature. The thermal stress releasing schemes are studied by changing the structure of fixed form and changing the thickness of the substrate, respectively. Finally, the design of the glass substrate thickness of 2.5 mm is used to ensure that the maximum equivalent stress is reduced to a quarter of the original value, only 154 MPa when the structure is in extreme temperature (80${}^{\circ }$C). The test results show that after the pressure switch is thermally optimized, the upper and lower electrodes can be reliably contacted to accommodate different operating temperature environments.

To enhance the interaction between Cu and graphene in graphene reinforced Cu matrix composites, the first principles calculation was carried out to study the adsorption of Cu atoms on graphene. P-type doping and n-type doping were formed, respectively, on vacancy-defected and Au-doped graphene based on band structure analysis, and this was verified by subsequent investigation on density of states. A computation on charge transfer confirmed that p-type doping could promote the electron transport between Cu and graphene, while n-type doping would prevent it. In addition, adsorption energy and Mulliken population analysis revealed that both vacancy defects and Au doping could improve the stability of the Cu–graphene system. The research conducted in this paper provides useful guidance for the preparation of Cu/graphene composites.

A bandpass sigma-delta modulator with the function of adjustable center-frequency is present in this paper. A method used to convert 2-order low-pass modulator to 4-order bandpass modulator is proposed to realize the design. Center-frequency that can be set to 1/6, 1/4 and 1/3 of sampling frequency is controlled according to the digital logic voltage. The bandwidth of pass-band is 200 Hz. Test results show that the average SNR is about 80 dB at different center-frequency when the sampling frequency is 64 kHz. The input signal can reach to −3 dBFs. The complexity to design a variable center-frequency bandpass modulator is greatly reduced.