Abstract Multi‐needle electrospinning is a simple and general method for mass preparation of nanofiber membrane, which has great industrial potential. However, the bending instability produced in the electrospinning process makes that the deposition uniformity of the nanofiber is still a big concern, resulting in non‐uniform nanofiber membrane, which seriously affects the application of electrospun membrane in environmental filtration, new energy and medical fields. In order to improve the uniformity of nanofiber deposition in multi‐needle electrospinning, an auxiliary flow field system (AFF) is proposed, which can effectively improve the uniformity of nanofiber deposition. After image processing, the uniformity of nanofiber deposition is quantified with the index of grey distribution, and the effectiveness of this method is verified. Combined with the multi‐physical field analysis, the influence mechanism of cross‐wind field on the uniformity of fibre deposition was revealed. By optimizing the experimental parameters, the non‐uniformity of nanofiber deposition was reduced by 49.19%. Based on multi‐needle electrospinning technology, a reliable idea (AFF) and experimental basis are provided for the uniform preparation of nanofiber membrane.

Currently, the problem of air pollution is getting more and more serious, especially the pollution of tiny solid particles (PM, particulate matter) in the air, which poses a great challenge to the environment and human health. Therefore, it is particularly important to develop air filtration materials with high filtration efficiency and low resistance to meet this challenge. In this study, we propose to prepare air filtration membranes by centrifugal jet electrospinning technology, design multifactorial orthogonal coupling experiments, and investigate the effects of key process parameters of centrifugal jet electrostatic spinning, including solution concentration, airflow rate, rotational speed, and voltage, on the fiber diameter and uniformity by applying the polar analysis of variance and analysis of variance. PAN-BaTiO3 electret nanofiber filtration membranes with high efficiency and low resistance were prepared by combining the optimized process of centrifugal blowing electrospinning. Various characterization methods (tensile test, water contact angle test, surface charge test, filtration test) were used to evaluate the effect of different BaTiO3 electret contents (0%, 0.1%, 0.5%, 1%) on the comprehensive performance of the filtration membranes, and the electret filtration efficiency of the electret filtration membranes prepared by the present process reached as high as 96.56% with a pressure drop of 29 Pa.

The theoretical results indicate that iced bundled conductors experience spatial galloping due to wind-induced vibration, involving in-plane, out-of-plane, and torsional movements. To better understand the dynamic response of this behavior from an experimental perspective, an innovative experimental method has been proposed. The method can simultaneously measure the in-plane, out-of-plane, and torsional vibration signals of iced bundled conductors' galloping. A testing system was established, and the method is applied in the galloping experiment of continuous iced bundled conductors, validating some theoretical results. This paper describes the construction of a wide-aperture, low-speed wind tunnel suitable for testing the galloping of continuous iced bundled conductors. A 'cut-bury-glue' method was proposed to create a model of continuous iced bundled conductors effectively, along with a method for connecting subconductors to improve experimental precision. The tests utilized laser displacement sensors and wireless posture sensors, considering the installation and data collection characteristics of the sensors. Through signal conversion, error correction, and other technical methods, simultaneous measurement of in-plane, out-of-plane, and torsional vibration signals was achieved. The spatial galloping behavior, changing with wind speed, exhibits limited-amplitude and synchronous characteristics. The participation of different modes shows elliptical orbital motion in single-mode galloping and '8' shaped orbital motion in coupled-mode galloping. These results are consistent with previous theoretical research, offering a new approach to studying iced bundled conductors' galloping.

In recent years, surface defect detection methods based on deep learning have been widely applied to steel plate surface defect detection. By locating and classifying defects on the surface of steel plates, production efficiency can be improved. However, there is still a conflict between speed and accuracy in the defect detection process. To address this issue, we propose a high-precision, low-latency surface defect detection algorithm called the GhostConv-ECA-YOLOv5 Network (GEA-Net). The GEA-Net model can predict defect categories without compromising classification and detection accuracy. Experimental results show that our proposed improved model has higher performance compared to other comparative models, achieving a 75.6% mAP on the NEU-DET dataset.

In this paper, a ball grid array（BGA） solder joint shearing experimental equipment is designed, and a supporting upper computer software to control the movement of the equipment is developed. Based on this equipment, the shear mechanical properties of BGA solder joints of two materials（SAC305 and Sn63Pb37） at fixed heights（60 μm）, different shear rates（0.1, 0.3, 0.5, 0.7 mm/s）, as well as shear mechanical properties at fixed shear rates（0.5 mm/s） and different shear heights（60, 80, 100, 120 μm） are studied. Experiments show that the shear strength of the solder joints of the two materials increases with the increasing of the shear rate under the condition of fixed shear height, and the shear strength of the solder joints of both materials decreases with the increasing of shear height under the condition of fixed shear rate. Experimental teaching through this equipment helps to cultivate students’ scientific thinking and improve students’ practical ability.

为了高效率、高精度的评定轴对称非球面零件,提出一种改进序列二次规划算法并结合非线性方程组牛顿迭代法来评定非球面的轮廓度误差.对于测量仪器检测时存在的设计坐标系与测量坐标系不重合的问题,使用坐标变换矩阵来消除测量坐标系存在的位置误差;针对非球面的特点,构建二元非线性方程组来表示非球面的投影点,并采用牛顿迭代法精准计算投影距离;为解决计算的复杂性,采用改进序列二次规划算法构建误差子问题求解,并利用拟牛顿法求解大规模无约束非线性问题.最后,对多种非球面镜片进行仿真和实验分析,并与最小二乘法和熵函数法对比.结果表明,所设计的算法有效提高了计算轮廓度误差过程中的数据处理效率和精度.

目的 为了提高非球面光学模具的表面质量和加工效率.方法 分析当前非球面超精密抛光方式及其特点,针对小口径非球面光学模具,提出一种小球头接触式抛光及磁流变抛光的组合加工方法,对小球头进行设计,并抛光碳化钨圆片,对比小球头接触式抛光及轴向、径向、水平方向磁极的永磁体球头的磁流变抛光的加工性能.分别对编号为1#、2#、3#等3个相同轮廓形状的碳化钨非球面模具进行单一方式抛光试验和组合加工试验.结果 通过对小球头抛光碳化钨圆片的加工性能进行分析发现,接触式抛光小球头的去除率为926.5 nm/h,表面粗糙度达到4.3961 nm;轴向、径向、水平方向磁极的永磁体小球头磁流变抛光的去除率分别为391.7、344.3、353.7 nm/h,表面粗糙度分别为1.4252、1.8776、1.8875 nm.对采用组合加工方法抛光碳化钨非球面的有效性进行验证时发现,非球面1#在单一接触式抛光60 min后表面粗糙度从8.7866 nm降至3.6932 nm;非球面2#在单一磁流变抛光60 min后表面粗糙度从8.2121 nm降至1.6745 nm;非球面3#在组合抛光方法下先进行15 min接触式抛光,再进行15 min磁流变抛光,表面粗糙度从8.5972 nm降至1.2694 nm,面形精度由175.2 nm提高到138.4 nm.结论 组合加工方法可以弥补单一抛光方法的缺陷,并能有效地提高工件的面形精度.与单一接触式抛光方法相比,组合加工方法获得的表面质量更好,抛光后表面粗糙度为1.2694 nm,远小于单一接触式抛光下的3.6932 nm;与单一磁流变抛光方法相比,组合加工方法更高效,将样件抛光到同等级别粗糙度所需时间从60 min减少至30 min.

Nanostructured components have been receiving considerable attention in recent years. One advantage is the use of near-field electrospinning (NFES) in microdevice manufacture. Multi-nozzle NFES is offered as a technique to increase the high-precision production rate of components. The deposition characteristics of the multi-nozzles were observed and analyzed based on the mutual influence of the jets under varied conditions. It was discovered that the mutual distance of deposition becomes larger with increases in working distance and nozzle spacing, but the influence of voltage is not particularly apparent. This paper discusses the results and conclusions of the experimental investigation and theoretical derivation.