Method to reconnoiter pulse amplitude train for phased array radar based on Hausdorff distance

This paper presents a method to estimate beam pointing of phased array radar by the pulse amplitude train, which is significant in radar electronic reconnaissance and electronic support measure. Firstly, the antenna patterns modeling of the phased array system is exploited to build the radar sweeping model and the signal propagation model. Secondly, the relationship between the variation of the radiated power and the antenna beam pointing angles in the given airspace is analyzed. Based on the above two points, the sample with obvious amplitude characteristics of the pulse amplitude train can be screened out after detecting the train peaks. Finally, the sample is matched to the subsequent pulse amplitude train based on the Hausdorff distance. The proposed methods have less prior knowledge and higher efficiency and are easier to process. By cross correlating the sample of the pulse amplitude train with the sample data of the antenna follow-up radiation, the probability of detection of the beam pointing direction becomes larger in case that the subsequent antenna beam returns to the specific position.

Parameterized time-frequency analysis to separate multi-radar signals

Multi-radar signal separation is a critical process in modern reconnaissance systems. However, the complicated battlefield is typically confronted with increasing electronic equipment and complex radar waveforms. The intercepted signal is difficult to separate with conventional parameters because of severe overlapping in both time and frequency domains. On the contrary, time-frequency analysis maps the 1D signal into a 2D time-frequency plane, which provides a better insight into the signal than traditional methods. Particularly, the parameterized time-frequency analysis (PTFA) shows great potential in processing such non stationary signals. Five procedures for the PTFA are proposed to separate the overlapped multi-radar signal, including initiation, instantaneous frequency estimation with PTFA, signal demodulation, signal separation with adaptive filter and signal recovery. The proposed method is verified with both simulated and real signals, which shows good performance in the application on multi-radar signal separation.

Modeling of Geometric Variations Within Three-Dimensional Tolerance Zones

A tolerance modeling method of geometric variations within three-dimensional(3D) tolerance domain is proposed.According to the classification method of feature variations and classes of invariance or symmetry in the new generation Geometrical Product Specifications(GPS) system,the proposed method is based on the Small Displacement Torsor(SDT) concept,and SDT is used to represent the geometric deviations between the nominal feature and the fitting feature. Furthermore,the variation zones of several kinds complex or irregular geometric features are constructed,and the corresponding tolerance modeling methods are discussed respectively. Finally,an example is presented to verify the efficiency of the presented method for modeling 3D dimensional and geometrical tolerances.The proposed modeling method based on the complete mathematical foundation conforms with the design philosophy and principle of the new generation GPS standards system.

An Optimal Sorting of Pulse Amplitude Sequence Based on the Phased Array Radar Beam Tasks

The study of phased array radar( PAR) pulse amplitude sequence characteristics is the key to understand the radar's working state and its beam's scanning manner.According to the principle of antenna pattern formation and the searching and tracking modes of beams,this paper analyzes the characteristics and differences of pulse amplitude sequence when the radar beams work in searching and tracking modes respectively.Then an optimal sorting model of pulse amplitude sequence is established based on least-squares and curve-fitting methods.This method is helpful for acquiring the current working state of the radar and recognizing its instantaneous beam pointing by sorting the pulse amplitude sequence without the necessity to estimate the antenna pattern.

Cognate pulse sorting method based on beam missions characteristics

In most multi-function phased array radar applications, multiple missions, including airspace searching and target tracking, are usually performed simultaneously by the digital beam-forming technique and the time dividing method. This paper presents a novel method to classify pulses of different missions from an interleaved pulse sequence emitted by the same radar, which is significant in radar electronic reconnaissance and electronic support measure. Firstly, two hypotheses, i.e., pulse relativity within the same mission and pulse independence among different missions, are proposed by analyzing the antenna pattern and the beam scheduling method of the phased array radar. Based on the above two hypotheses, an optimal model for pulse classification is exploited with pulse amplitude series, where the absolute-value sum of second order difference is taken as the optimal kernel to measure sequence smooth continuity. Finally, several pieces of sequences under different numbers of missions and tracking data rates are simulated for algorithm verification. The simulation results show that the long data length and the high data rate will increase classification efficiency due to the validity of the two hypotheses in sufficient pulse amplitude sequence.

Description of the Cover Picture

The cover picture is taken from the article＂ An Optimal Sorting of Pulse Amplitude Sequence Based on the Phased Array Radar Beam Tasks＂ It shows the 3D pattern of 100 ＊ 100 phased array at elevation angle （0°, 0°）. This model is generated with MATLAB software and used to analyze the beam pointing of the antenna, and determine the normalized power by different colors. Then when the beam changes its direction continuously, the received pulse amplitude at a fixed point va- ries accordingly. In radar searching mode, by modeling and simulating the distribution variation of the power and analyzing its variation pattern at a certain coordinate point, it will help us to analyze the direction information of the radareffectively.

Tribological Behaviors of Ni_3Al Intermetallics with MoO_3 Multilayer Ribbon Crystal Prepared by Spark Plasma Sintering

This study reports that small amounts of MoO3 multilayer ribbon crystal （MOO3 MLRC） in Ni3Al intermetallics showed the decreased friction coefficients and improved wear resistance at different contact loads. Specifically, the friction coefficients （0.32-0.34） and wear rates [（2-4）× 10^-5 mm^3 N^-1 m^-1] are significantly reduced for NiaAl at 2-8 N. A possible explanation for the friction and wear reduction is that MoO3 MLRC as a multilayer material shears easily in the tribo-layer during the sliding contact, and provides low friction. In addition, this MoO3 MLRC with excellent bending strength is found to dissipate shear stress and suppress severe plastic deformation under a cyclic stress, thus drastically improving wear resistance of Ni3Al.

Gradient-induced long-range optical pulling force based on photonic band gap

Optical pulling provides a new degree of freedom in optical manipulation.It is generally believed that long-range optical pulling forces cannot be generated by the gradient of the incident field.Here,we theoretically propose and numerically demonstrate the realization of a long-range optical pulling force stemming from a self-induced gradient field in the manipulated object.In analogy to potential barriers in quantum tunnelling,we use a photonic band gap design in order to obtain the intensity gradients inside a manipulated object placed in a photonic crystal waveguide,thereby achieving a pulling force.Unlike the usual scattering-type optical pulling forces,the proposed gradient-field approach does not require precise elimination of the reflection from the manipulated objects.In particular,the Einstein-Laub formalism is applied to design this unconventional gradient force.The magnitude of the force can be enhanced by a factor of up to 50 at the optical resonance of the manipulated object in the waveguide,making it insensitive to absorption.The developed approach helps to break the limitation of scattering forces to obtain longrange optical pulling for manipulation and sorting of nanoparticles and other nano-objects.The developed principle of using the band gap to obtain a pulling force may also be applied to other types of waves,such as acoustic or water waves,which are important for numerous applications.

The Impact of New Regulations on Prevention and Control of E-Cigarettes on Adolescents in Middle Schools—A City in China,2022–2023

What is already known about this topic?To protect the health of young people from the harmful impacts of electronic cigarettes(e-cigarettes),China has enacted various policies and regulations since 2018.As of October 1,2022,the Electronic Cigarette Management Measures were put into action.They prohibited the sale of flavored e-cigarettes,permitting only those of plain tobacco flavor to be sold.What is added by this report?The illegal market for flavored e-cigarettes,often disguised as milk tea cups,cola cans,and violent bear images,continues to flourish.There is an increased need to bolster support for the prohibition of flavored e-cigarettes and enhance public awareness of associated regulations.What are the implications for public health practice?To advance the health of China’s youth,it is crucial to improve the implementation and understanding of ecigarette policies and guidelines.