Linear actuators for locomotion of microrobots

University of Technology, Sydney. Faculty of Engineering.The successful development of the miniaturisation techniques for electronic components and devices has paved the way for the miniaturisation in other technological fields. In the past two decades, the research achievements in micromechatronics have spurred fast development of micro machines and micro robotic systems. Miniature or micro actuators are the critical components to make these machines more dexterous, compact and cost effective. The main purpose of this dissertation is to develop micro actuators suitable for the locomotion of an in-pipe or endoscopic microrobot. The content of the thesis covers the selection of the actuation principle, robotic system design, actuator design and prototype construction, performance analysis, and design, analysis, and implementation of the appropriate drive control system. Among different types of actuation principles, piezoelectric and electromagnetic actuators are the two major candidates for the micro robotic systems. In order to find a suitable actuation principle for the desired robotic application, a comparative study was conducted on the scaling effects, attainable energy density, and dynamic performances of both types of actuators. Through the study, it was concluded that the electromagnetic actuator is more suitable for the endoscopic microrobot. Linear actuators are the common design used for the locomotion of microrobots due to many advantages compared to their rotational counterparts. Through a thorough review and comparison of the electromagnetic linear actuator topologies, a moving-coil tubular linear actuator was chosen as the first design due to its simplest structure. Via the magnetic circuit analysis and numerical magnetic field solutions, the actuator was designed for optimum force capability, and the electromagnetic force and the machine parameters of the actuator were predicted. According to the results obtained from the magnetic field analysis, the dynamic model of the actuation system with a driving control scheme was established and used in the actuation performance analysis of the robotic system. Based on the experience achieved through the first design, a new moving-magnet tubular linear actuator was designed. The methodology developed in the design and analysis of the moving-coil linear actuator was adopted for the moving-magnet actuator design. However, the optimal design is more complicated due to the multi-pole and multi-phase structure of the moving-magnet actuator. The electromagnetic force of the actuator was analysed under the condition of different excitation methods. An enhanced parameter computation method is proposed for predicting the actuator parameters. Based on the results of magnetic field analysis, a comprehensive dynamic model of the actuator was developed. Through the coupled field-circuit analysis, this model can predict accurately the dynamic performance of the actuator. The characteristics analysis shows that the performance of the moving-magnet actuator is much better than that of the moving-coil actuator. Two prototypes of the moving-magnet tubular linear actuator with different dimensions were constructed to verify the performance and the scaling theory. Various precision machining techniques were employed during the fabrication. The performances and parameters of the two different prototypes were measured and the results agree substantially with the theory. The brushless DC drive method was chosen for the driving control of the proposed linear actuator because of the compact circuit topology and simple implementation, which are two essential factors for micro applications. A sensorless control scheme based on the back EMF was developed as physical position sensors are not permitted in such a micro system. The control scheme was then applied to the locomotion control of the proposed microrobot. The system simulation shows that the control performances of both the actuator and microrobot are satisfactory. A dSPACE prototyping system based driving control hardware was designed and implemented to experimentally verify the control design. The experimental results agree substantially with the theoretical work

Identification and Functional Characterization of Genes that Regulate Biomass Production, Floral Development, and Leaf Senescence in Populus Species using Genetic Engineering and Bioinformatics Tools

This dissertation is comprised of four studies on different elements of Populus biotechnology and genomic science: 1) growth improvement by recombinant DNA (rDNA) modification of gibberellin (GA) metabolism; 2) gene editing using zinc-finger nucleases (ZFNs); 3) induction of floral sterility by RNA interference (RNAi) of AGAMOUS (AG) gene homologs; and 4) transcriptome analysis during natural leaf senescence. The genus Populus includes a number of environmentally and commercially important tree species. The breeding of Populus has emphasized improved stress resistance, increased wood production, and tailored wood properties for diverse uses. Genetic engineering appears to be able to complement or facilitate Populus breeding in many ways, such as imparting improved or novel traits and accelerating the breeding process. However, the efficacy of traits shown in laboratory or greenhouse trials with model plants and trees may not translate to the field in their effects or stability under plantation conditions. In addition, the scientific knowledge for advanced engineering of useful traits such as bioproduct synthesis are inadequate, and public and regulatory concerns over transgene dispersal from these plants may hinder their delivery of benefits unless such gene movement is mitigated. We conducted several studies to address these research needs. In study 1, we examined the growth and hormonal consequences of modified GA metabolism and signaling in a model poplar genotype (Populus tremula x P. alba). We tested a total eight genes (i.e., rDNA constructs), two cisgenes, four intragenes, and two transgenes, in greenhouse, and six of them under field conditions. Greenhouse studies showed that four constructs significantly increased stem volume, and two constructs significantly modified the proportion of root or shoot biomass. One of the cisgenic constructs elevated the concentrations of bioactive GA1 and its direct precursor GA20. In field, however, only one intragenic construct led to significant growth improvement. The inconsistent growth performance between greenhouse and field tests was possibly to due to cross-talk among the GA pathway and other stress response pathways, or interactions between the cis- and intragenes with similar endogenes. Our results emphasize the need for extensive field trials in evaluating the value and pleiotropic effects of GA-modifying genes and other applied biotechnology research. In study 2, we evaluated the efficiency of ZFN-induced mutagenesis in poplar organogenic systems. We created four pairs of heat-inducible ZFN systems, two targeting the floral meristem identity gene LEAFY (LFY), and two targeting the floral homeotic gene AG, into two hybrid poplar clones. Despite that over a total of 21,000 explants were transformed, we were only able to obtain 391 transgenic events. We found two of these events had 7-bp deletions in one allele of the AG2 gene. We did not observe mutations in the LFY or AG1 genes. The ZFN constructs, together with heat induction of their expression, also seemed to depress transformation rates. These results suggested a mutation rate of zero to 0.3% per explant per allele, among the lowest reported for ZFN mutagenesis in plants, and the need for further technical improvements towards efficient use of ZFNs in poplar. In study 3, we examined floral changes as a result of RNAi-induced suppression of two AG orthologues in field-grown poplar. Among a total of 34 flowering RNAi-events, 17 of them showed altered phenotypes, including altered floral organ identity, loss of floral organ determinacy, and impaired ovule and seed-hair development that was associated with the degree of AG suppression. In addition, five seedless events showed strong suppression of two SEEDSTICK (STK) paralogues. All RNAi-events appeared normal in their vegetative morphology and growth, and alterations in floral phenotypes were stable over multiple years. These results suggested that RNAi suppression of AG and STK genes appears to be a safe and effective means of genetic containment in poplar. In study 4, we examined transcriptome changes during leaf senescence in field-grown Populus trichocarpa ‘Nisqually-1’, which is the basis of the reference genome. Using monthly (from May to October) transcriptomes from three years (2012, 2015, and 2016) containing 36,007 expressed Populus gene models, we found 17,974 genes that were differentially expressed during the study period. In addition, we assigned 2015 and 2016 collections into four major developmental phases and identified 14,415 DEGs were directly related to transitions between the developmental phases. Gene ontology (GO) enrichment revealed that GOs related to catalytic activity, kinase activity, and enzyme inhibitor activity were up-regulated during leaf senescence, while those related to photosynthesis were down-regulated. A total of 881 TF genes from 54 TF families, notably bHLH, MYB, ERF, MYB-related, NAC, and WRKY family members, were active during leaf senescence. Fuzzy C-means clustering analysis sorted the differentially expressed genes into five groups based on their gene expression patterns. Two groups of genes showed constantly increasing expression during senescence, and a number of upstream sequence motifs, including five with high-confidence, were identified associated with these groups. This study provides a robust resource for investigating leaf senescence and related developmental traits such as programmed cell death and stress tolerance in perennial species. It also could inform efforts to engineer the synthesis of coproducts in leaves in association with senescence onset to mitigate its costs to net photosynthesis

Preferences and Tourism Development under Uncertainty: An Empirical Study

Using the Global Preferences Survey dataset, this paper examines the effects of six measures of preferences (altruism, negative reciprocity, patience, positive reciprocity, risk-taking, and trust) on the per capita international tourist arrivals and the per capita incoming tourist receipts. The data focus on 74 countries for the period from 1995 to 2019. The paper finds that citizens’ trust is positively related to tourism development, and its impact is statistically significant. This evidence indicates that a country with a higher level of trust in other nations’ people attracts more tourists and generates higher tourism receipts

Oxygen vacancy engineering of Bi2O3/Bi2O2CO3 heterojunctions: Implications of the interfacial charge transfer, NO adsorption and removal

Efficient enrichment of targeted gaseous pollutants and fast diffusion rates of charge carriers are essential for the photocatalytic removal of nitric oxides at ambient concentration levels. Here we demonstrate that the construction of nano-structured Bi2O3/Bi2O2CO3 heterojunctions with oxygen vacancies, increasing the photocatalytic NO removal activity, durability and selectivity for final products nitrate formation. Combining the experimental and density-functional theory calculations, it was elucidated that the presence of surface oxygen vacancies not only work as adsorption sites of low concentration NO, but also offer an intimate and integrated structure between surface defects and the light-harvesting heterojunctions, which can facilitate solar energy conversion and charge carrier transfer (more than 2 times). Control experiments with pristine Bi2O3/Bi2O2CO3 also confirmed the crucial role of surface oxygen vacancies on the improvement of NO adsorption and removal ability during the photocatalytic degradation process. We explain the enhanced removal of NO through the synergistic effect of oxygen vacancy and heterojunction, which not only guaranteed the generation of more center dot OH radicals, but also provided another route to produce hydrogen peroxide. Our findings may provide an opportunity to develop a promising catalyst for air pollution control

A Metabolomics Profiling Study in Hand-Foot-and-Mouth Disease and Modulated Pathways of Clinical Intervention Using Liquid Chromatography/Quadrupole Time-of-Flight Mass Spectrometry

Hand-foot-and-mouth disease (HFMD), with poorly understood pathogenesis, has become a major public health threat across Asia Pacific. In order to characterize the metabolic changes of HFMD and to unravel the regulatory role of clinical intervention, we have performed a metabolomics approach in a clinical trial. In this study, metabolites profiling was performed by liquid chromatography/quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) platform from the HFMD clinical patient samples. The outcome of this study suggested that 31 endogenous metabolites were mainly involved and showed marked perturbation in HFMD patients. In addition, combination therapy intervention showed normalized tendency in HFMD patients in differential pathway. Taken together, these results indicate that metabolomics approach can be used as a complementary tool for the detection and the study of the etiology of HFMD

Resveratrol differentially modulates inflammatory responses of microglia and astrocytes

<p>Abstract</p> <p>Background</p> <p>Inflammatory responses in the CNS mediated by activated glial cells play an important role in host-defense but are also involved in the development of neurodegenerative diseases. Resveratrol is a natural polyphenolic compound that has cardioprotective, anticancer and anti-inflammatory properties. We investigated the capacity of resveratrol to protect microglia and astrocyte from inflammatory insults and explored mechanisms underlying different inhibitory effects of resveratrol on microglia and astrocytes.</p> <p>Methods</p> <p>A murine microglia cell line (N9), primary microglia, or astrocytes were stimulated by LPS with or without different concentrations of resveratrol. The expression and release of proinflammatory cytokines (TNF-α, IL-1β, IL-6, MCP-1) and iNOS/NO by the cells were measured by PCR/real-time PCR and ELISA, respectively. The phosphorylation of the MAP kinase superfamily was analyzed by western blotting, and activation of NF-κB and AP-1 was measured by luciferase reporter assay and/or electrophoretic mobility shift assay.</p> <p>Results</p> <p>We found that LPS stimulated the expression of TNF-α, IL-1β, IL-6, MCP-1 and iNOS in murine microglia and astrocytes in which MAP kinases, NF-κB and AP-1 were differentially involved. Resveratrol inhibited LPS-induced expression and release of TNF-α, IL-6, MCP-1, and iNOS/NO in both cell types with more potency in microglia, and inhibited LPS-induced expression of IL-1β in microglia but not astrocytes. Resveratrol had no effect on LPS-stimulated phosphorylation of ERK1/2 and p38 in microglia and astrocytes, but slightly inhibited LPS-stimulated phosphorylation of JNK in astrocytes. Resveratrol inhibited LPS-induced NF-κB activation in both cell types, but inhibited AP-1 activation only in microglia.</p> <p>Conclusion</p> <p>These results suggest that murine microglia and astrocytes produce proinflammatory cytokines and NO in response to LPS in a similar pattern with some differences in signaling molecules involved, and further suggest that resveratrol exerts anti-inflammatory effects in microglia and astrocytes by inhibiting different proinflammatory cytokines and key signaling molecules.</p

Metal-chelate dye-controlled organization of Cd32S14(SPh)(40)(4-) nanoclusters into three-dimensional molecular and covalent open architecture

通讯作者地址: Feng, PY (通讯作者), Univ Calif Riverside, Dept Chem, Riverside, CA 92521 USA 地址: 1. Univ Calif Riverside, Dept Chem, Riverside, CA 92521 USA 2. Calif State Univ Long Beach, Dept Chem & Biochem, Long Beach, CA 90840 USA 电子邮件地址: [email protected]

Crystalline superlattices from single-sized quantum dots

通讯作者地址: Feng, PY (通讯作者), Univ Calif Riverside, Dept Chem, Riverside, CA 92521 USA 地址: 1. Univ Calif Riverside, Dept Chem, Riverside, CA 92521 USA 2. Calif State Univ Long Beach, Dept Chem & Biochem, Long Beach, CA 90840 USA 电子邮件地址: [email protected]