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Investigating the biological function of proteins is a key aspect of protein studies. Bioinformatic methods become important for studying the biological function of proteins. In this paper, we first give the chaos game representation (CGR) of randomly-linked functional protein sequences, then propose the use of the recurrent iterated function systems (RIFS) in fractal theory to simulate the measure based on their chaos game representations. This method helps to extract some features of functional protein sequences, and furthermore the biological functions of these proteins. Then multifractal analysis of the measures based on the CGRs of randomly-linked functional protein sequences are performed. We find that the CGRs have clear fractal patterns. The numerical results show that the RIFS can simulate the measure based on the CGR very well. The relative standard error and the estimated probability matrix in the RIFS do not depend on the order to link the functional protein sequences. The estimated probability matrices in the RIFS with different biological functions are evidently different. Hence the estimated probability matrices in the RIFS can be used to characterise the difference among linked functional protein sequences with different biological functions. From the values of the Dq curves, one sees that these functional protein sequences are not completely random. The Dq of all linked functional proteins studied are multifractal-like and sufficiently smooth for the Cq (analogous to specific heat) curves to be meaningful. Furthermore, the Dq curves of the measure μ based on their CGRs for different orders to link the functional protein sequences are almost identical if q ≥ 0. Finally, the Cq curves of all linked functional proteins resemble a classical phase transition at a critical point. [ABSTRACT FROM AUTHOR]

Step-coupler waveguide-integrated Ge/Si avalanche photodetector (APD) is based on the vertical multimode interference (MMI), enhancing light scattering towards the Ge active region and creating mirror images of optical modes close to the Ge layer. However, there are two ineluctable contact angels between selectively epitaxial growth Ge and Si layers and selectively epitaxial growth Si and Si substrate, which has an effect on the coupling efficiency and the absorption of the photodetector. Therefore, step-coupled Ge/Si avalanche photodetectors with different step lengths are designed and fabricated. It is found that responsivity of APDs with step-coupler-length of is 0.51 A/W at −6 V, 21% higher than that of , which matches well with simulation absorption. The multiplication gain factor is as high as 50, and the maximum gain-bandwidth product reaches up to 376 GHz. [ABSTRACT FROM AUTHOR]

In this paper, we investigated phase modulation-based computational ghost imaging. According to the results of numerical simulations, we found that the range of the random phase affects the quality of the reconstructed image. Besides, compared with those amplitude modulation-based computational ghost imaging schemes, introducing random phase modulation into the computational ghost imaging scheme could significantly improve the spatial resolution of the reconstructed image, and also extend the field of view. [ABSTRACT FROM AUTHOR]

We investigate the close-range relative motion and control of a spacecraft approaching a tumbling target. Unlike the traditional rigid-body dynamics with translation and rotation about the center of mass (CM), the kinematic coupling between translation and rotation is taken into consideration to directly describe the motion of the spacecraft’s sensors or devices which are not coincident with the CM. Thus, a kinematically coupled 6 degrees-of-freedom (DOF) relative motion model for the instrument (feature point) is set up. To make the chaser spacecraft’s feature point track the target’s, an optimal tracking problem is defined and a control law with a feedback-feedforward structure is designed. With quasi-linearization of the nonlinear dynamical system, the feedforward term is computed from a specified constraint about the dynamical system and the reference model, and the feedback action is derived starting from the state-dependent Ricca equation (SDRE). The proposed controller is compared with an existing suboptimal tracking controller, and numerical simulations are presented to illustrate the effectiveness and superiority of the proposed method. [ABSTRACT FROM AUTHOR]

The digital measurement and processing is an important direction in the measurement and control field. The quantization error widely existing in the digital processing is always the decisive factor that restricts the development and applications of the digital technology. In this paper, we find that the stability of the digital quantization system is obviously better than the quantization resolution. The application of a border effect in the digital quantization can greatly improve the accuracy of digital processing. Its effective precision has nothing to do with the number of quantization bits, which is only related to the stability of the quantization system. The high precision measurement results obtained in the low level quantization system with high sampling rate have an important application value for the progress in the digital measurement and processing field. [ABSTRACT FROM AUTHOR]

A nonlinear controller for disturbances rejection and collision avoidance is proposed for spacecraft formation flying. The formation flying is described by a nonlinear model with the J2 perturbation and atmospheric drag. Based on the theory of the state-dependent Riccati equation (SDRE), a finite time nonlinear control law is developed for the nonlinear dynamics involved in formation flying. Then, a compensative internal mode (IM) control law is added to eliminate disturbances. These two control laws compose a finite time nonlinear tracking controller with disturbances rejection. Moreover, taking safety requirements into account, the repulsive control law is incorporated in the composite controller to perform collision avoidance manoeuvres. A numerical simulation is presented to demonstrate the effectiveness of the proposed method. Compared to the conventional control method, the proposed method provides better performance in the presence of the obstacles and external disturbances. [ABSTRACT FROM AUTHOR]

A novel see-through display with a liquid crystal lens array was proposed. A liquid crystal Fresnel lens display (LCFLD) with a holographic screen was demonstrated. The proposed display system has high efficiency, simple fabrication, and low manufacturing cost due to the absence of a polarizer and color filter. [ABSTRACT FROM AUTHOR]

A series of azobenzene liquid crystals with one or two terminal acrylate groups were synthesized and their polymers were fabricated. The azobenzene liquid crystals and their polymers achieved the photoisomerization from the liquid crystalline trans-isomer to the isotropic cis-isomer with UV irradiation. Then, the cis to trans isomerization induced by an electric field was studied, the time required for electro-isomerization was measured, the texture change and absorption variation from cis to trans form induced by the electric field were observed clearly, and the time required for electro-isomerization was much shorter than that for thermal relaxation. The influence of the polar group (fluorine), terminal acrylate group, and flexible alkyl chain on the time of electro-isomerization was studied. The results show that the compounds with polar fluorine group require shorter time for electro-isomerization and the polymerization of terminal acrylate group delays the electro-isomerization. [ABSTRACT FROM AUTHOR]