Modeling and control of flexible link robots

Master'sMASTER OF ENGINEERIN

Fusion Zone Microstructure Evolution of Al-Alloyed TRIP Steel in Diode Laser Welding

TRansformation Induced Plasticity (TRIP) steels are promising materials to achieve a better combination of formability and strength than conventional steels due to their unique microstructural makeup. Though welding is a vital part of auto body manufacturing, the weldability of TRIP steels has some complex and poorly understood features, which has served to retard the growth of its applications in the automotive industry. In this study, autogeneous welds were carried out on Al-alloyed TRIP steel using a 4 kW diode laser. Both fusion zone solidification behavior and subsequent austenite transformation products were investigated with optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. In terms of solidification behavior, fusion zones solidified with high temperature -ferrite as the primary phase. Fusion zone microstructure at room temperature was composed of ferrite with a skeletal morphology characteristic of solidification, and austenite decomposition products almost all having a lath morphology. Skeletal ferrite covered about 30% fusion zone area. Upper bainite laths separated by retained austenite films comprised most of the transformed microstructure, about 65% of the fused area. Lower bainite with carbide particles dispersed in an aligned way, chunk shaped retained austenite, lath martensite and twinned martensite were also occasionally observed. The Al content was considered to be for a dominant influence on fusion zone microstructure evolution

Dynamic Transformation of Nano-MoS2 in a Soil-Plant System Empowers Its Multifunctionality on Soybean Growth

Molybdenum disulfide (nano-MoS2) nanomaterials have shown great potential for biomedical and catalytic applications due to their unique enzyme-mimicking properties. However, their potential agricultural applications have been largely unexplored. A key factor prior to the application of nano-MoS2 in agriculture is understanding its behavior in a complex soil-plant system, particularly in terms of its transformation. Here, we investigate the distribution and transformation of two types of nano-MoS2 (MoS2 nanoparticles and MoS2 nanosheets) in a soil-soybean system through a combination of synchrotron radiation-based X-ray absorption near-edge spectroscopy (XANES) and single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS). We found that MoS2 nanoparticles (NPs) transform dynamically in soil and plant tissues, releasing molybdenum (Mo) and sulfur (S) that can be incorporated gradually into the key enzymes involved in nitrogen metabolism and the antioxidant system, while the rest remain intact and act as nanozymes. Notably, there is 247.9 mg/kg of organic Mo in the nodule, while there is only 49.9 mg/kg of MoS2 NPs. This study demonstrates that it is the transformation that leads to the multifunctionality of MoS2, which can improve the biological nitrogen fixation (BNF) and growth. Therefore, MoS2 NPs enable a 30% increase in yield compared to the traditional molybdenum fertilizer (Na2MoO4). Excessive transformation of MoS2 nanosheets (NS) leads to the overaccumulation of Mo and sulfate in the plant, which damages the nodule function and yield. The study highlights the importance of understanding the transformation of nanomaterials for agricultural applications in future studies.</p

Trait evaluation and trial cultivation of Dongfang No. 2, the hybrid of a male gametophyte clone of Laminaria longissima (Laminariales, Phaeophyta) and a female one of L. japonica

Direct cultivation of the first filial generation of gametophyte clones from different Laminaria species is a highly effective way of utilizing kelp heterozygous vigor (heterosis). A male gametophyte clone of L. longissima Miyabe and a female one of L. japonica Areschoug were hybridized, generating Dongfang No. 2 hybrid kelp. This hybrid kelp was used directly in trial cultivation, and its agronomical traits were evaluated. L. longissima and L. japonica are obviously different and complement each other in their morphological characteristics and ecological performances. The hybrid of their gametophyte clones, Dongfang No. 2, showed 56.8% heterozygous vigor in yield. It also showed increased yields of 41.0 and 76.4% compared to the widely used commercial kelps Variety 1 and Variety 2, respectively. In large-scale cultivation trials at different locations and in different years, Dongfang No. 2 attained significantly higher yields than Varieties 1 and 2, increasing yield by 26.4% on average over Variety 1 and by 65.0% over the other. Dongfang No. 2 has a robust holdfast and a wide, long and deep-brown uniform blade, which shows a distinct middle groove. In addition to yield, Dongfang No. 2 also demonstrates obvious heterozygous vigor in other agronomic traits. It is resistant to strong irradiance, as the two commercial varieties are, has an appropriate vegetative maturation time, and adapts well to a range of different culture conditions. The parentage analysis using AFLP of total DNA and SNP of the ITS region of ribosomal RNA transcription unit showed that Dongfang No. 2 is the real hybrid of L. japonica and L. longissima

Research Progress of STEM Education Based on Visual Bibliometric Analysis

Nowadays, science, technology, engineering, mathematics (STEM) education has been developed and implemented in many countries. To better understand the research progress in STEM education worldwide, we analyzed 1910 publications collected from the Web of Science Core Collection database. This bibliometric study was performed through software VOSviewer and CiteSpace. Results showed that the research on STEM education will remain thriving in the following years. The USA is the most active country in the research field of STEM education, and the whole world cooperated closely. The majorities of significant institutions in this field belong to the USA. International Journal of STEM Education, Journal of Science Education and Technology and Science Education are the main publications. According to the cluster results of keywords, STEM, STEM education, self-efficacy, technology constitute the knowledge base for STEM education studies. Based the analysis results of keywords and burst detection, STEM achievements, different approaches to discipline integration, educational equality, and teacher education will be the research hotspot in the future. The results give a comprehensive overview on STEM education for scholars quickly understanding the overall progress

Elementary school teachers’ attitudes towards project-based learning in China

Abstract This study analyzed the Chinese elementary school teachers’ attitudes toward project-based learning (PBL) and identified factors that may influence elementary school teachers’ attitudes. The analysis was based on a questionnaire survey of 257 elementary school teachers and interviews with 10 elementary school teachers in China. Results showed that Chinese elementary school teachers generally had positive attitudes towards PBL, but their attitudes differed based on their educational level, years of teaching, and subjects taught. Results of the regression analysis found that training, social support, resources, and availability of time all positively influenced teachers’ attitudes toward PBL. Finally, the interview data were analyzed to understand teachers’ perceptions of how they could be helped to use PBL in teaching

Data_Sheet_1_Preservice teachers’ teaching internship affects professional identity: Self-efficacy and learning engagement as mediators.docx

Preservice teachers’ professional identity is a critical factor in their motivation, effectiveness, and retention. Teaching internship can promote the transformation of professional identity and self-efficacy of preservice teachers. The internship environment also enhances students’ increasing level of learning engagement. Although much research has shown strong relationship between preservice teachers’ teaching internship and professional identity, less is known about how self-efficacy and learning engagement mediated those variables. The purpose of this study is to investigate the roles that self-efficacy and learning engagement play in the relationship between preservice teachers’ professional identities and their teaching internship experiences. The study involved 309 preservice teachers in total, and the variables were measured using questionnaires. For the data analysis, we used structural equation modeling. The study’s findings are as follows. (a) Teaching internship, professional identity, self-efficacy, and learning engagement were all significantly correlated with one another. (b) Both self-efficacy and learning engagement partially mediated the relationship between teaching internship and professional identity in a parallel manner. (c) Self-efficacy and learning engagement also sequentially mediated the relationship between teaching internship and professional identity.</p

Effect of Mo/Nb ratio variations on the microstructure and cryogenic impact toughness of NiCrMo deposited metals

Effects of varying the Mo/Nb (in weight percent) ratio in ENiCrMo-6-deposited metals on the microstructure and cryogenic impact toughness of the metals were investigated. When the Mo/Nb ratio decreased from 6.09 to 3.28, the Nb-rich phase on the grain boundaries was transformed from un-continuous precipitation to continuous precipitation, the area fraction and average size of the precipitates within the grains were significantly increased, and a eutectic-type Laves phase appeared. Although the austenitic matrix of the deposited metals indicated a ductile fracture mode, the precipitates significantly deteriorated the cryogenic impact toughness. As the average size and area fraction of the precipitates increased, the cryogenic impact value decreased significantly