Accepted Papers
Recent catalogue
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Vol.73 No.21
2024-11-05
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Vol.73 No.20
2024-10-20
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Vol.73 No.19
2024-10-05
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Vol.73 No.18
2024-09-20
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GENERAL
2024, 73 (21): 210201.
doi: 10.7498/aps.73.20241112
Abstract +
Due to the limitation of existing experimental techniques, it is difficult to observe the evolution of microstructure in the sintering process in real time, resulting in a lack of in-depth understanding of the sintering mechanism of two-phase composite fuels. Therefore, it is greatly important to carry out theoretical simulation studies in the sintering process of composite fuels. In this work, a phase-field model of the two-phase sintering process of ceramic composite fuel is established, and the sintering process of UN-U3Si2 composite fuel is simulated by using this method. The simulation results show that during the formation of sintering neck, the surface deformation of the grains with higher surface energy is significant. The size of the final equilibrium dihedral angle formed by the two-phase double grains depends on the ratio of the grain boundary energy to the surface energy of the two phases. The phenomenon of large grains swallowing small grains does not occur between the two unequal double grains. Subsequently, the pore shrinkage and the properties of the trident grain boundary among the two-phase three grains are investigated in the sintering process. It is found that the angle of the trident grain boundary formed by the two-phase three grains deviates from 120°. The high-energy barrier at the grain boundary hinders the diffusion of the pore vacancies along the grain boundary, resulting in a slow shrinkage rate of the pore vacancies at the trident grain boundary. In addition, the simulation results of the microstructure evolution of two-phase polycrystalline sintered tissue with different volume fraction ratios show that the grain boundary diffusion plays a major role in the two-phase sintering process. The grain growth of the phase with a higher volume fraction is dominant, and there exists a hindrance to the migration of grain boundaries between two-phase grains. The phenomenon of grain migration exists between grains of the same phase.
GENERAL
2024, 73 (21): 210301.
doi: 10.7498/aps.73.20241150
Abstract +
Recently, researchers have proven that an infinite number of Charlies and a pair of Alice and Bob can share standard tripartite nonlocality and genuinely nonsignal nonlocality by violating the Mermin and NS inequalities within tripartite systems. This discovery undoubtedly provides new perspectives and potential in quantum information science. However, it should be noted that the above-mentioned conclusion is derived on the highly idealized assumption that the quantum system is perfect and free from external disturbances. In reality, the realization of this ideal state is a challenging proposition. As a fundamental aspect of quantum mechanics, the phenomenon of quantum entanglement is susceptible to the influence of external factors, such as noise, during its practical implementation. Additionally, the process of quantum measurement can introduce potential errors, which may potentially diminish or even negate the observed quantum nonlocality. In light of the above situation, we investigate whether it is possible to share the corresponding quantum nonlocality, despite the inevitable occurrence of noise and error. This paper aims to study and discuss the persistency of nonlocality in noisy three-qubit systems. Firstly, the sufficient conditions are provided for Alice and Bob to share standard tripartite nonlocality with any number of Charlies, even when measurements are noisy and the initial three-qubit system is in a maximally entangled state with noise. This finding indicates that certain standard tripartite nonlocality can persist under non-ideal conditions as long as certain conditions are met. Moreover, this article elucidates the necessary conditions for multiple independent Charlies to share genuinely nonsignal nonlocality with a pair of Alice and Bob in a non-ideal state. This implies that despite the presence of noise and errors, this type of genuinely nonsignal nonlocality can still be securely shared among multiple parties as long as specific conditions are met. This research provides a new theoretical basis for the security and feasibility of quantum communication. The comprehensive analysis presented in this paper offers insights into the behavior of triple quantum nonlocality under noiseless conditions.
GENERAL
2024, 73 (21): 210302.
doi: 10.7498/aps.73.20240804
Abstract +
Measurement basis choice is an essential step in the underwater continuous variable quantum key distribution system based on homodyne detection. However, in practice, finite bandwidth of analog-to-digital converter on the receiver’s side is limited, which can result in defects in the measurement basis choice. That is, the receiver cannot accurately modulate the corresponding phase angle on the phase modulator for measurement basis choice to implement homodyne detection. The imperfect measurement basis choice will introduce extra excess noise, which affects the security of underwater continuous variable quantum key distribution scheme. To solve this problem, we propose an underwater continuous variable quantum key distribution scheme based on imperfect measurement basis choice, and analyze the influence of imperfect measurement basis choice on the performance of underwater continuous variable quantum key distribution system in detail. The research results indicate that the extra excess noise introduced by imperfect measurement basis choice can reduce the secret key rate and maximum transmission distance of the underwater Gaussian modulated quantum key distribution, thus reducing the security of the system. In order to achieve reliable underwater continuous variable quantum key distribution, we quantitatively analyze the extra excess noise introduced by choosing the imperfect measurement basis and obtain its security limit. Besides, we also consider the influence of different seawater depths on the security limit of the proposed scheme, effectively solving the security risks caused by the imperfect measurement basis choice. Furthermore, for the proposed scheme, we consider not only its asymptotic security case but also its composable security case, and the performance curves obtained in the latter are tighter than that achieved in the former. The proposed scheme aims to promote the practical process of underwater continuous variable quantum key distribution system and provide theoretical guidance for accurately evaluating the water channel parameters in underwater communication of global quantum communication networks.
GENERAL
2024, 73 (21): 210501.
doi: 10.7498/aps.73.20241028
Abstract +
Discrete chaotic system, as a pseudo-random signal source, plays a very important role in realizing secure communication. However, many low-dimensional chaotic systems are prone to chaos degradation. Therefore, many scholars have studied the construction of high-dimensional chaotic systems. However, many existing algorithms for constructing high-dimensional chaotic systems have relatively high time complexity and relatively complex structures. To solve this problem, this paper explores an n-dimensional discrete hyperchaotic system with a simple structure. Firstly, the n-dimensional discrete hyperchaotic system is constructed by using sine function and power function and simple operations. Then, it is theoretically analyzed based on Jacobian matrix method that the system can have the positive Lyapunov exponents. Next, the algorithm time complexity, sample entropy, correlation dimension and other indexes are compared with those of the existing methods. The experimental results show that our system has a simple structure, high complexity and good algorithm time complexity. Therewith, a six-dimensional chaotic system is chosen as an example, and the phase diagram, bifurcation diagram, Lyapunov expnonents, complexity and other characteristics of the system are analyzed. The results show that the proposed system has good chaotic characteristics. Moreover, to show the application of the proposed system, we apply it to audio encryption. According to this system, we combine it with the XOR operation and true random numbers to explore a novel method of one-cipher audio encryption. Through experimental simulation, compared with some existing audio encryption algorithms, this algorithm can satisfy various statistical tests and resist various common attacks. It is also validated that the proposed system can be effectively applied to the field of audio encryption.
GENERAL
2024, 73 (21): 210502.
doi: 10.7498/aps.73.20241007
Abstract +
The influences of group behavior on pedestrian evacuation under zero-visibility conditions are analyzed in depth by combining controlled experiments with modeling and simulation in this work. Initially, by experiments on pedestrian evacuation under zero-visibility conditions, typical evacuation behaviors are identified such as group behavior, auditory guidance behavior, and wall-following behavior. The pedestrians rely on auditory information to guide their companions in the process of forming groups. Pedestrian group behavior can be divided into three modes, the walking speeds of grouped pedestrians greatly depending on their spatial positions. By comparing and analyzing the walking speeds and evacuation times of pedestrians under different grouping modes, it is found that group behavior under zero-visibility condition reduces evacuation efficiency, while walking along the walls can improve evacuation efficiency. Subsequently, considering the movement characteristics of pedestrians in different group behavior modes, the influence mechanisms of auditory guidance and wall-following behavior on the evacuation process, a pedestrian evacuation model based on cellular automata under zero-visibility conditions is developed. Finally, the proposed model is validated by using experimental results, and simulations are conducted to analyze the influences of group behavior on the evacuation process under zero-visibility conditions. By comparing and analyzing the pedestrian movement trajectories and evacuation times during both the simulation and experiment, it is verified that the model can effectively reproduce the group evacuation processes of pedestrians under zero-visibility conditions. When auditory guidance errors are considered, pedestrians exhibit wandering behaviors in their movement trajectories. In the evacuation process, the greater the distance that pedestrians can perceive each other for grouping, the higher the probability of group formation is. As a result, groups are formed earlier, which will reduce the evacuation efficiency. This indicates that under zero-visibility conditions, group behavior exerts a negative influence on the evacuation process. This research lays a scientific foundation for formulating pedestrian evacuation strategies and schemes in similar scenarios.
REVIEW
2024, 73 (21): 210701.
doi: 10.7498/aps.73.20240957
Abstract +
ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
2024, 73 (21): 214201.
doi: 10.7498/aps.73.20241023
Abstract +
We introduce a class of specular and antispecular twisted Gaussian Schell-model beams, which are generated by inserting a twisted Gaussian Schell-model beam into a wavefront folding interferometer (WFI). The analytical expression for the cross-spectral density function of the beam propagating in free space is derived, and the statistical properties of the optical field are investigated in detail. The results show that the twisted effect is still maintained after the transformation, and the spectral density of the light field always rotates to 90 degrees around the axis during propagation. Furthermore, with appropriate optical field adjustment, the twist effect of the spectral degree of coherence (DOC) can be observed, but in opposite directions to the irradiance profile. We also find that the twisted phase not only controls the rotation of the field, but also effectively modulates the overall spot contour. For the far-field spectral density distribution, a larger twist effect will induce a smaller ellipticity of the beam spot. However, the intensity pattern in the central area is mainly determined by the phase difference of WFI. To be specific, the specular twisted field always has a sharp central peak during propagation, and in the antispecular case it has a central dip. Besides, the DOC distribution can be flexibly adjusted by the source coherence, the twisted phase and the phase difference of the WFI. The results of our work have important applications in the fields of free-space beam communication and particle trapping.
ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
2024, 73 (21): 214202.
doi: 10.7498/aps.73.20241026
Abstract +
Generalized parabolic beams have various optical morphologies. They can be used in different research fields, such as component design, aero-optics, and microwave wireless power transmission. Studying the near-field transmission characteristics of these beams is important for improving utilization efficiency. We develop a more accurate theoretical framework to precisely understand the propagation behaviors of complex light fields in the near-field range, especially to break through the limitations of conventional near-axis approximation. This framework fully reveals the propagation mechanism of parabolic beams and their energy transmission modes. Here, based on the principle of independent propagation and the virtual source method, a group of virtual sources are introduced to analyze generalized parabolic beams. These beams can be expanded into the superposition of infinite continuous integer Bessel beams. Then, by combining the Weber integral formula and the Fourier Bessel transform, we rigorously derive an integral expression for generalized parabolic beams during near-field propagation. This expression breaks through the limitation of the traditional paraxial approximation and contains all the key propagation parameters of the family of beams. Based on this integral expression, the intensity distribution and phase characteristics of the generalized parabolic beam along the optical axis are further calculated and analyzed to reveal its energy transfer mode and phase characteristics. By comparing the paraxial approximate solution with the nonparaxial corrected solution for generalized parabolic beams, the far-field propagation of generalized parabolic beams is found to be the same when the propagation distance is sufficiently long. Such simulation results indirectly confirm the correctness of the obtained theoretical solution. The simple paraxial approximation theory can be used conveniently to calculate the far-field propagation of generalized parabolic beams. However, large errors exist when paraxial theory is used to calculate the near-field distribution of generalized parabolic beams. Although calculating nonparaxial propagation is especially complex, the nonparaxial correction solution is necessary when generalized parabolic beams are used in near-field research. Such research results not only deepen the understanding of the propagation mechanism of generalized parabolic beams but also lay a theoretical foundation for studying the precise propagation behaviors of other complex light fields in near-field optics.
ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
Miniaturized photoacoustic/ultrasound endoscopic imaging probe for molecular imaging of deep tissues
2024, 73 (21): 214203.
doi: 10.7498/aps.73.20241076
Abstract +
Colorectal cancer is one of the leading causes of cancer-related deaths worldwide. Traditional gastrointestinal endoscopes for colorectal cancer mainly rely on optical endoscope and ultrasound endoscope. Owing to significant light scattering in tissues the optical endoscope is limited to superficial tissue imaging, while the ultrasound endoscope, despite deeper penetration, provides limited molecular imaging capabilities. In this work, we build a miniaturized handheld photoacoustic/ultrasound dual-modality endoscopic probe to address these problems. It has a small size of 8 mm, and presents the dual advantages of high penetration depth and superior molecular imaging capability, marking a significant advancement over traditional methods. Results show that this probe achieves a high lateral resolution of 345 μm for photoacoustic imaging and 185 μm for ultrasound imaging at a depth of 12 mm within tissues. It also exhibits the ability to effectively image complex structural targets, as demonstrated by the imaging of a phantom with an embedded metal mesh. Furthermore, the probe adopts an innovative pump-probe method, which effectively mitigates interference from blood and other background tissues, thereby achieving high-specificity photoacoustic molecular imaging. This ability is first confirmed by imaging the distribution of methylene blue (MB) in a phantom, and then by observing the distribution of MB in the depth of tumor in mice. This handheld photoacoustic/ultrasound endoscopic probe has the advantages of small size, high penetration depth, high spatial resolution, and superior molecular imaging ability, and is expected to become an important diagnostic tool for colorectal cancer and other gastrointestinal cancer. This study can provide strong support for early diagnosis and treatment monitoring, potentially revolutionizing the detection and management of these diseases.
ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS
2024, 73 (21): 214204.
doi: 10.7498/aps.73.20241017
Abstract +
White LEDs have the broad application prospect and market demand, while the red phosphor can greatly affect the color temperature and color rendering index of the modulated white light. In this work, a series of Li2Gd4–x Smx(MoO4)7 (x = 0.01–0.13) phosphors is prepared by the high-temperature solid phase method. The successful doping of Sm3+ into Li2Gd4(MoO4)7 is confirmed by X-ray diffractometry (XRD) and does not lead to any change in crystal structure. The samples are detected by scanning electron microscope (SEM) to have irregular blocky structures with particle size less than 20 μm. The existence of Li, Gd, Mo, O and Sm elements in the phosphor is confirmed by energy dispersive X-ray spectroscopy (EDS). The observation of X-ray photoelectron spectroscopy (XPS) shows that the activators are successfully doped into materials. Under 406 nm excitation, the emission peaks of the samples are located at 563, 598, 645 and 706 nm respectively, which are caused by the 4f-4f transition of Sm3+, and the strongest emission peak comes from 4G5/2→6H9/2 transition. It is found that optimal concentration of Sm3+ is 0.07. With the increase of Sm3+ concentration, the fluorescence lifetime decreases gradually. The temperature-dependent emission of phosphor is also studied. The emission intensity at 473 K is still 79% of that at 298 K, indicating that the sample has excellent heat resistance. The CIE chromaticity diagram shows the luminescence of the prepared phosphor is located in the orange-red region and the color purity is high (99%). Moreover, a white LED is fabricated using the optical doped phosphor, which has CIE coordinates of (0.3788, 0.3134) that are located in the circle of white light. Research shows that the Li2Gd4(MoO4)7:Sm3+ phosphor is a promising orange-red phosphor for white LEDs.
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