Study on the effect of focal position change on the expansion velocity and propagation mechanism of plasma generated by millisecond pulsed laser-induced fused silica

In this work, by controlling the positional relationship between the target and the focal point, the surface damage, shock wave phenomenon and propagation mechanism involved in the plasma generation of fused silica by millisecond pulsed laser irradiation at different focal positions were studied. Laser energy is an important experimental variable. The dynamic process of plasma was detected by optical shadow method, and the influence of surface film damage on plasma propagation and the propagation mechanism at different focal positions were discussed. The study found that the plasma induced by the pulsed laser at the focus position within 0–20 μs exploded, the micro-droplets formed around 20 μs. At the same time, a shock wave is formed by the compressed air, the micro-droplets are compressed under the action of the shock wave recoil pressure, and the micro-droplets channel phenomenon is observed in the micro-droplets. The peak velocities of plasma and combustion wave appear earlier in the pre-focus position than in the post-focus position. This research provides a reference for the field of laser processing using fused silica as the substrate.

The relationship between farm size and fertilizer use efficiency:Evidence from China

Low fertilizer use efficiency is commonly found in China’s agriculture sector. It is critical to understand the drivers of fertilizer use in order to increase fertilizer use efficiency(FUE). The purpose of this paper is to investigate the relationship between farm size and FUE based on farm-level data in China. The results suggest a positive farm size–FUE relationship. The estimated elasticities of farm size for rice, maize, wheat–maize, and rice–maize are similar, and the average elasticity of farm size is around 0.2. Statistically, a 1% increase in farm size is associated with a 0.2%increase in FUE. The positive effect of farm size on FUE is not due to the increase in yield, but the reduction in fertilizer use while keeping yield largely unchanged. The findings suggest that promoting the expansion of farm size may increase FUE, and thus reduce environmental pollution caused by fertilizer overuse.

MVCE-Net: Multi-View Region Feature and Caption Enhancement Co-Attention Network for Visual Question Answering

Visual question answering(VQA)requires a deep understanding of images and their corresponding textual questions to answer questions about images more accurately.However,existing models tend to ignore the implicit knowledge in the images and focus only on the visual information in the images,which limits the understanding depth of the image content.The images contain more than just visual objects,some images contain textual information about the scene,and slightly more complex images contain relationships between individual visual objects.Firstly,this paper proposes a model using image description for feature enhancement.This model encodes images and their descriptions separately based on the question-guided coattention mechanism.This mechanism increases the feature representation of the model,enhancing the model’s ability for reasoning.In addition,this paper improves the bottom-up attention model by obtaining two image region features.After obtaining the two visual features and the spatial position information corresponding to each feature,concatenating the two features as the final image feature can better represent an image.Finally,the obtained spatial position information is processed to enable the model to perceive the size and relative position of each object in the image.Our best single model delivers a 74.16%overall accuracy on the VQA 2.0 dataset,our model even outperforms some multi-modal pre-training models with fewer images and a shorter time.

基于最小二乘法的变位机与焊接机器人的位置关系标定

基于最小二乘法,通过相关试验求取了两者基坐标系之间的变换矩阵,实现了对变位机和焊接机器人的位置关系的标定,并验证了试验结果。结果表明,在卡盘上任取一点,将旋转变位机获得的不同位姿数据进行球面拟合,可以得到最优球面,能够精确地计算出球面半径和变位机基坐标系原点在机器人坐标系中的位置;利用获得的位姿数据可以计算出x,y,z三个的轴的单位坐标矢量,获取变位机和机器人基坐标系两者之间的转换矩阵。通过对试验结果的验证可知,利用位姿变换矩阵求取各点在机器人基坐标系中的坐标的偏差较小,符合要求。

PMS-Sorting:A New Sorting Algorithm Based on Similarity

Borda sorting algorithm is a kind of improvement algorithm based on weighted position sorting algorithm,it is mainly suitable for the high duplication of search results,for the independent search results,the effect is not very good and the computing method of relative score in Borda sorting algorithm is according to the rule of the linear regressive,but position relationship cannot fully represent the correlation changes.aimed at this drawback,the new sorting algorithm is proposed in this paper,named PMS-Sorting algorithm,firstly the position score of the returned results is standardized processing,and the similarity retrieval word string with the query results is combined into the algorithm,the similarity calculation method is also improved,through the experiment,the improved algorithm is superior to traditional sorting algorithm.

Algebraic Conditions for Classifying the Positional Relationships Between TwoConies and Their Applications

In many fields of computer science such as computer animation, computergraphics, computer aided geometric design and robotics, it is a common problem to detect thepositional relationships of several entities. Based on generalized characteristic polynomials andprojective transformations, algebraic conditions are derived for detecting the various positionalrelationships between two planar conies, namely, outer separation, exterior contact, intersection,interior contact and inclusion. Then the results are applied to detecting the positionalrelationships between a cylinder (or a cone) and a quadric. The criteria is very effective andeasier to use than other known methods.