Micromotors powered by megahertz ultrasound, first reported about 5 years ago, have lately been considered a promising platform for a wide range of microscale applications, yet we are only at the early stage of understanding their operating mechanisms. Through carefully designed experiments, and by comparing the results to acoustic theories, we present here an in-depth study of the behaviors of particles activated by ultrasound, especially their in-plane orbiting and spinning dynamics. Experiments suggest that metallic microrods orbit in tight circles near the resonance ultrasound frequency, likely driven by localized acoustic streaming due to slightly bent particle shapes. On the other hand, particle spins around their long axes on nodal lines, where phase-mismatched orthogonal sound waves possibly produce a viscous torque. Intriguingly, such a torque spins metal-dielectric Janus microspheres back and forth in an unusual "rocking chair" fashion. Overall, our observations and analysis provide fresh and much needed insights on the interesting particle dynamics in resonating ultrasound and could help with developing more powerful and controllable micromachines with biocompatible energy sources.

An alternative approach is introduced to determine the grain size distribution directly from the shape of the line profile in X-ray diffraction from a crystalline powder.

No abstract

With the development of Internet technology, online shopping has become increasingly popular. Owing to the improvement of living standards, the quality of e-service has become one of the important criteria for online shopping, with online shopping consultation being one of the key services. At the same time, the emergence of new technologies such as Artificial Intelligent (AI) has allowed online retailers to increase the availability of non-human online shopping consultation services. Therefore, this paper investigates the service decision problem between human and non-human online shopping consultation services for online retailers in the online duopoly market. By constructing a Hotelling improvement model and applying it in a new way, considering consumer preferences for human services, this paper explores the impact of the optimal service level of human online shopping consultation services and consumers’ sensitivity to the service level of human services on online retailers’ pricing, service decisions, etc. Our research results show that consumers’ sensitivity to the service level of human online shopping consultation services has an impact on the demand and profit of online retailers. In addition, human online shopping consultation services are not always beneficial to the profitability. Furthermore, when two online retailers compete, the utility of the non-human online retailer’s service to consumers can influence the service decisions of the other online retailer.

Powder X-ray diffraction technique is a new scientific method to analyze the structure of the material, which has been applied to a variety of disciplines, such as chemistry, physics, etc. Due to the special properties of the X-ray diffraction Fourier map of each Chinese patent medicine, the geometric topology graph has the characteristic of fingerprint, and there are big differences between two peak and diffraction peak intensity. Therefore, according to the Fourier map, researchers can compare the different manufacturers and the different batches of Chinese patent medicine, to analyze whether the composition and configuration are consistent. This paper verifies the feasibility of the X-ray diffraction method for the identification of Chinese patent medicine by the above comparison, and find out the characteristic marked peaks of the Ginkgo Biloba Leaves Extract Tablets and Niuhuangjiedu tablets (pills). 粉末x射线衍射在中成药鉴定中的应用 李颖雪 1,a ，李艳坤 1,b ，赵蕾蕾 2,c 1.华北电力大学(保定) 环境科学与工程学院 中国 河北 保定 071003 2.华北电力大学(保定) 能源动力与机械工程学院 机械工程系 中国 河北 保定 071003 a 602497168@qq.com, b 309267061@qq.com, c 2773754282@qq.com 摘要：粉末 X 射线衍射技术是一种分析物质结构的新型科学方法，目前已经应用到化学、物 理等多种学科。由于每种中成药的 X 射线衍射 Fourier 图谱所具有的几何拓扑图形具有指纹特 征的专属性，两两之间的峰形和衍射峰强度存在较大的差异，因此根据得到的 Fourier 图谱， 可对比分析出不同厂家、不同批次的中成药中的成分、晶型结构是否一致。本文通过上述对 比验证了 X 射线衍射法运用于中成药鉴定可行性，并找出了银杏叶片、牛黄解毒片(丸)的 特征标记峰。 关键词：X 射线衍射法；中成药鉴定；Fourier 图谱；银杏叶片；牛黄解毒片； 1. 引言 中成药的历史由来已久，其成分复杂，常常不能以简单的化学式来表达。而不同厂家不同批 次生产的中成药的成分也有细微的差距。正是由于中成药的配方多样，有效成分不明，给中 成药的鉴定带来困难。用 X 射线衍射法鉴定中药也是近年来才出现的新方法，它的操作简单， 且测量精度很高，已经得以广泛推广。它是依据物质在经 X 射线照射后，由于其物质组成、 分子键、分子构型等的差异会产生其独有的衍射图谱来鉴定的，不会损伤物质，且具有高效