Airborne array synthetic aperture radar (SAR) can achieve three-dimensional (3D) imaging of the observed scene in a single flight. Nevertheless, the imaging process of airborne array SAR is subject to various parameter errors due to unstable factors. Such errors degrade the quality of 3D imaging, particularly for the elevation imaging results, which necessitates the employment of super-resolution algorithms. The most significant error parameters include the amplitude and phase imbalances between multiple channels, as well as the phase-center positions of each channel. Owing to the coupled nature of these parameter errors, the calibration accuracy for each parameter independently is relatively sub-par, while super-resolution algorithms have strict demands for parameter precision. Addressing these challenges, this article proposes a multi-parameter calibration method for airborne array SAR based on the Newton method and the genetic algorithm. Initially, a least squares model for multi-parameter calibration is established, followed by leveraging the global optimization characteristics of genetic algorithms and the rapid convergence property of the Newton method. The genetic algorithm is utilized to locate a sub-optimal solution in proximity to the optimal one, subsequently converging swiftly to the optimal solution via the Newton method, which incorporates second-order information. This approach averts the pitfalls of local convergence due to large initial value errors, thereby enhancing the algorithm’s robustness. The proposed method effectively enhances the precision of multi-parameter calibration, which is of significant importance in ensuring the quality of 3D imaging of airborne array SAR.

Low-thrust trajectory design in the context of the three-body problem, particularly in the vicinity of liberation points, is addressed in this paper with a focus on efficiency and accuracy. The Finite Fourier series, previously successful in approximating near-coplanar low-thrust trajectories within two-body dynamics, is applied to the challenging landscape of the three-body problem, marked by instability and nonlinearity. This paper introduces a novel approach for constructing an initial guess trajectory, which combines coast arcs from periodic orbits and intermediate trajectory arcs from other natural dynamical structures. The resulting initial guess trajectory is instrumental in generating efficient initial estimates for the coefficients of the Finite Fourier series. The study encompasses the analysis of homoclinic and heteroclinic transfers in both two-dimensional and three-dimensional scenarios. The approximated trajectories derived from this methodology serve as invaluable starting points for high-fidelity optimization solvers, offering promise for enhancing the precision and efficiency of low-thrust transfers in cislunar space.

The Joule balance, which relates mechanical energy and electrical energy, was proposed by the National Institute of Metrology (NIM) to measure the Planck constant and realize the kilogram with the Planck constant based on the new definition of the kilogram. In 2019, the NIM-2 Joule balance participated in the first key comparison of kilogram realizations (CCM.M-K8.2019) with a combined relative standard uncertainty of $4.5\times 10^{-8}$ . After the first key comparison, a series of improvements on the mechanical, electrical, and alignment systems have been carried out. To improve the accuracy of the electrical measurement, the periodical calibration of the digital voltmeter (DVM) with the programmable Josephson voltage system (PJVS) was also realized. The calibration period of the DVM was reduced from five days to 3.5 h. With these improvements, the corresponding uncertainties were decreased significantly.

The centroid deviation is an important factor affecting the dynamic performance of aero-engine rotors. To measure and reduce the centroid deviation, this paper builds a measurement model of the centroid deviation of aero-engine rotors by decoupling unbalance, reveals the spatial transmission mechanism of the centroid deviation of the assembled rotors under the influence of machining errors, and proposes a measurement model of the centroid deviation of assembled rotors in the rotation axis coordinate system. The experimental results clarified that the maximum deviation of the theoretical results and the experimental results of the centroid deviation is 3.98 mu m, and the maximum centroid deviation can be reduced by 5.68 mu m. Finally, this paper analyzes the measurement results of machining errors and the influence of the centroid deviation after adjustment. The measurement and adjustment model of the centroid deviation can realize the benchmark measurement and adjustment of the centroid deviation of assembled rotors.

Ship detection in optical remote sensing images plays a vital role in numerous civil and military applications, encompassing maritime rescue, port management and sea area surveillance. However, the multi-scale and deformation characteristics of ships in remote sensing images, as well as complex scene interferences such as varying degrees of clouds, obvious shadows, and complex port facilities, pose challenges for ship detection performance. To address these problems, we propose a novel ship detection method by combining multi-scale deformation modeling and fine region highlight-based loss function. First, a visual saliency extraction network based on multiple receptive field and deformable convolution is proposed, which employs multiple receptive fields to mine the difference between the target and the background, and accurately extracts the complete features of the target through deformable convolution, thus improving the ability to distinguish the target from the complex background. Then, a customized loss function for the fine target region highlight is employed, which comprehensively considers the brightness, contrast and structural characteristics of ship targets, thus improving the classification performance in complex scenes with interferences. The experimental results on a high-quality ship dataset indicate that our method realizes state-of-the-art performance compared to eleven considered detection models.

Thin-film diffractive optical elements (DOEs) have considerable potential to be used in the field of high-resolution remote sensing imaging satellites because of advantages such as a large aperture, small volume, lightness, wide tolerance range of surface shape, and easy replication. However, there are problems associated with thin-film diffraction imaging, including space variation, serious blur, and low contrast, which result in insufficient imaging quality with regard to traditional optical system requirements. To address this, a local adaptive prior-based image restoration method is proposed for thin-film diffraction imaging systems. An entire degraded image was divided into several isohalo regions based on imaging characteristics. Then, the regularization constraints were adaptively selected and updated according to the local scene prior characteristics. Additionally, the system parameters in the corresponding field of view were used as input to restore each subregion. In particular, the diffraction efficiency (DIE) was introduced into the model to remove the nondesign level background radiation. The experimental results show that the proposed algorithm can effectively improve the image quality of a thin-film diffraction imaging system, including space variation correction, clarity enhancement, and background radiation suppression. Furthermore, a DIE of less than 60% was found to significantly impact the final image products.

针对能量天平试验中力矢量加载引起悬挂系统持续摆动给测量引入系统误差的问题,提出一种同时兼顾悬挂线圈和砝码托盘的精密被动电磁阻尼器.该电磁阻尼器基于磁场的涡流效应,由金属阻尼片和永磁体组成.为了避免置于磁场中的弱磁性阻尼片给天平称重引入附加力,阻尼片由抗磁性材质和顺磁性材质按一定比例采用"铜-铝-铜"三层复合结构组合而成,复合型阻尼片在磁场中静止时受力被抵消.此外,为了避免阻尼器泄漏的强磁场磁化精密金属砝码,电磁阻尼器外设计组合式磁屏蔽罩:内部单层电工纯铁屏蔽罩和外部双层坡莫合金屏蔽罩.设计的阻尼器及其屏蔽罩进行有限元仿真分析、试验验证,结果表明,复合阻尼片静止时,固有力约为0.92μg;电磁阻尼器在称重砝码位置的外泄磁场约为5.04 μT,小于地磁场量级;阻尼器将原有悬挂系统摆动时间缩短约88.3％;设计的阻尼器总体满足能量天平试验要求.

Due to the advantages of high rotation accuracy and long life, hydrostatic air bearings are widely used in precision rotation equipment, such as machine tools and turntables. It is imperative to reasonably design the structural size of the bearing, especially as the size of the bearing in the precision turntable determines the bearing capacity of the turntable. At present, commercial CFD software is used chiefly for simulation verification for the design of air bearings. The mesh divided in the simulation calculation has a significant impact on the efficiency of the calculation and determines the accuracy of the final simulation results. Therefore, this paper takes the symmetrical multi-throttle thrust bearing in the precision turntable as the research object and compares and studies the advantages and disadvantages of sliced structured meshes, continuous structured meshes, and unstructured meshes. On this basis, simulation analysis of bearing capacity for different radial equalizing groove lengths, widths, and depths and explores the influence of the structure size of the thrust bearing on its bearing capacity. The study shows that the length and depth of the throttle groove significantly influence the bearing capacity, while the width has little influence on the bearing capacity. Therefore, under the specific cavity volume to ensure the dynamic characteristics of the bearing, the width of the throttling groove should be reduced first, and the length and depth of the throttling groove should be increased to improve the bearing capacity.

High-quality remote sensing images have wide application prospects in agroforestry investigation, target monitoring, disaster prevention, urban planning and military defense. However, remote sensing imaging links such as atmosphere, platform and optical system seriously affect the ability of image interpretation and analysis. The traditional regularized processing methods have a strong ability to improve the definition, but most of them may sacrifice texture details or introduce artifacts, because their fixed prior parameters cannot fully adapt to various kinds of scenes. To address this problem, we propose a novel fine-processing method based on the adaptive hyper-Laplacian prior for remote sensing imaging systems. The method is developed by automatically updating and optimizing the prior parameters and objective function in the iterative process based on the prior characteristics of different regions of remote sensing images. Experimentally, the proposed method can realize the fine-processing of remote sensing images, including the edge enhancement, texture detail preservation, and artifact suppression.

Diffractive membrane imaging systems have been an important development trend for high-orbit satellite cameras owing to their advantages of large aperture, light weight, rapid manufacture, and low cost. However, caused by the cross-coupling effects of diffraction imaging, membrane properties, subaperture stitching, on-orbit disturbances, and other physical factors, lager-aperture space diffractive membrane imaging systems have specific and complex degradation characteristics: the modulation transfer function (MTF) and signal-to-noise ratio (SNR) have more prominent degradation and serious space-variant characteristics over fields of view, with obvious background radiation properties that seriously affect the application of imaging products. To address this problem, this study established a global information transmission model by characterizing the PSF and background radiation in a full field of view to represent the imaging law of an on-orbit system. Aiming at the inverse problem of the information transmission model, we also propose a novel image inversion restoration method for the special degradation characteristics. In particular, the effect of diffraction efficiency is introduced into the inversion restoration method to solve the background radiation problem. Moreover, we innovatively designed matrix regularization parameters to further improve the correction ability of spatial variation. When the diffraction efficiency was experimentally higher than 60% and the mean measured spatial variability was less than 0.2, the proposed method exhibited a satisfactory processing performance, and could improve multiobjective comprehensive processing, such as transfer function compensation, spatial variation correction, and background radiation removal.

The Rotating synthetic aperture (RSA) is one of the most promising novel imaging systems to meet the requirements of lightweight and high resolution for optical remote sensing satellites, especially in geostationary orbit. The point spread function (PSF) orientation relative to the observed scene, intentionally changes to measure all spatial frequency information available to a filled circular aperture having a diameter approximately equal to the length of the rectangular aperture. As with all precision optical systems, RSA is also subject to dynamic disturbances from the spacecraft/environment. If not accommodated properly in the measurement and synthesis process, the dynamic disturbances can result in significant image quality degradation. To quantify methods to reduce or eliminate the errors, we first analyze the on-orbit imaging mechanism of the RSA system theoretically and then represent the worst-case on-orbit imaging degradation characteristics.

In this paper, aiming at the feasibility of the visible and infrared large-aperture membrane diffractive optical systems in space application, we present a simulation model and fast analysis and calculation method of large-aperture diffraction optical imaging characteristics based on the two-dimensional finite difference time domain. First, we fully consider the electromagnetic field modulation characteristics of the subwavelength microstructure size of the large-aperture diffractive optical element, and establish the imaging characteristics analysis model of the subwavelength structure size diffractive optical system. Then, through vectorization programming and GPU acceleration calculation, we propose a fast simulation calculation method to solve the problem caused by vector calculation. Finally, we take a large-aperture diffractive optical system as an example and verified the imaging characteristics using the established imaging characteristics analysis method. Experimental results reveal that the proposed method can effectively characterize the imaging characteristics of the subwavelength microstructure diffractive optical system, and realize a rapid analysis of the imaging performance of diffractive optical elements.

“能量天平法”是一种基于机械电磁能量平衡的普朗克常数测量方法,该方法因存在一项由线圈特征矢量的非对准状态引起的“特征矢量对准能量误差”,其普朗克常数测量不确定度难以降低至1×10-8.为实现对准能量误差的精确补偿,针对能量天平线圈垂向运动过程中的残留水平位移的精确测量问题,提出一种基于电磁自阻尼直接垂向测量参考的差分线面式位移传感测量方法.为避免间接测量参考的调整过程引入系统误差进而导致测量精度降低,线面式位移传感器利用细丝电极作为直接垂向测量参考;设计差分式三电极电容结构用于抑制单端电容非线性特性;将另两个电极的表面形状设计为相互正对的外圆柱面,利用圆柱面在横截面内的几何形状各向同性抵消姿态倾斜对测量结果的影响,提高传感器对复杂测量条件的适应能力;采用电磁阻尼器稳定细丝电极,保证测量结果的准确性.实验结果表明,在正常工作量程范围内,差分式自阻尼位移传感器的合成扩展不确定度约为2.81 μm.

随着我国工业和科技的迅速发展,铝材需求量逐年递增,为了更好满足航空航天、海洋舰船、铝导线、医疗器械、特种装备等领域对新型高端铝合金材料的需求,稀土元素在变形铝合金的应用研究成为热点.本文作者主要综述了典型稀土元素在高端变形铝合金和铝导线中的作用,以及稀土元素在铝合金结构材料及铝导线的研究现状;同时,展望了含稀土的高端铝合金材料及铝导线的研究方向及发展趋势,为含稀土的高端铝合金的研究发展提供借鉴.

溯源至普朗克常数的能量天平法由于悬挂系统的初始位姿不理想,电磁力与砝码重力之间很难达到理想的平衡状态,总会不可避免地产生水平力与转矩,进而引起准直误差.立足于能量天平悬挂系统的准直误差的产生机理,结合能量天平悬挂系统的力学和电磁学特性,分析并建立悬挂系统初始位姿与寄生位移之间的数学模型,为准直误差的抑制奠定理论基础.

随着"健康深圳"的计划的实施,深圳的健康水平已成为深圳最受关注的话题之一.因此我们根据深圳市的相关数据应用BP神经网络模型,对社会公共卫生环境和个人分别进行分析.同时应用Matlab软件对我们的数据进行训练、预测.所得出的模型能有效地动态测控健康水平.

We proposed a novel inversion restoration method for the newly developing space diffractive membrane imaging system, in which specific imaging characteristics were first integrated into the degradation model. On this basis, a novel image inversion restoration model was established based on sparse regularization frames and matrixing confidence parameters. Then, an efficient solution method was proposed using an improved iterative shrinkage-thresholding algorithm. Experimentally, when the diffraction efficiency was higher than 60%, the proposed inversion restoration method exhibited a satisfactory processing performance, and could achieve multi-objective image quality improvement, including texture detail restoration, background radiation removal, and noise suppression.

In the production of plant chemical alcohol, a large amount of salty high-concentration organic waste liquid is by-produced, in which a large amount of high-value sodium tungstate and chemical heat energy are contained. Through the design of the pilot water-cooled incinerator, the operating parameters and the characteristics of alkali ash deposition of the waste incinerator were tested. The pilot incinerator is a natural-cycle steam boiler, has a full water-cooled II-type structure, with liquid slag discharge, and the furnace design has selected reasonable volumetric heat load and flue gas residence time. Combustion distribution is the core parameter affecting the combustion of waste liquid. Studies have shown that increasing the primary air rate and the excess air coefficient are beneficial to improve the combustion performance of waste liquid, increase steam production, and reduce CO and SO2 emissions in flue gas, but also increase the concentration of NO. When the excess air ratio was 1.2, and the primary air ratio was 0.65, the NO concentration in the tail flue gas was less than 10 ppm, and the SO2 concentration was zero. The TG-DTA method measured that when the alkali ash melting temperature was less than 587 °C, the alkali ash had strong adhesion in the high temperature zone of the incinerator and less deposition in the low temperature region of the tail. The alkali ash deposition rate and relative deposition rate were used to quantitatively study the characteristic of alkali ash deposition.

In the present study, the expansion characteristics of plant chemical alcohol waste liquid were experimentally studied with a vertical tube furnace system. The results showed that the droplet quality, heating temperature, and atmosphere directly influenced the droplet expansion. The droplet mass had nothing to do with the swelling volume index (SVI) but had a significant influence on the expansion time, with a larger droplet mass and longer expansion time. The heating temperature had a significant influence on the expansion characteristics of the waste liquid. As the heating temperature increased, the droplet SVI became larger with a shorter expansion time. The nitrogen atmosphere was more conducive to droplet volume expansion than the air atmosphere but had less of an effect on the expansion time. The volume of waste liquid droplets expanded more than 5 times, forming an internal porous structure, thereby increasing the comparative area and the probability of contact with oxygen to facilitate the combustion of the waste liquid.

In this paper, we present a novel wavefront sensing method for diffraction optical system based on phase diversity. Based on the physical-imaging mechanism of diffractive optical system, the wavefront characteristics of the diffraction optical system are characterized by using diffraction efficiency. On this basis, a novel modified phase diversity (PD) wavefront sensing method is established based on the blocking idea. After that, the global optimization method of corresponding method based on particle swarm optimization algorithm is proposed. Finally, some experiment results are achieved with the experiment on a membrane diffraction optical system. Experimental results indicate that the proposed algorithm performs well on both wavefront reconstruction and image restoration and is far superior to traditional methods in diffraction optical systems. The accuracy of our proposed PD method is at least two orders of magnitude higher than the traditional method. Taking the 0.01 degrees field of view for example, our modified PD method can achieve the accuracy of 2.5 x 10(-4) wavelength when the diffraction efficiency is higher than 0.6. This proposed method can be applied to improve the image quality of the diffraction optical system and further support the on-orbit application of ultra-large aperture membrane imaging technology.