Improving the Tracking Performance under Nonlinear Time-Varying Constraints in Motion Control Applications: From Theoretical Servo Model to Experimental Validation

In the high-accuracy control of an AC machine, the knowledge of pure system parameters, with no deviation in drive coefficients and no disturbance or other nonlinear components, is a difficult issue for operators, even though it is occasionally nonviable. To overcome these troubles, this paper introduces a robust adaptation strategy based on pseudo fuzzy logic and sliding mode control (PFSMC) for an AC servo drive subject to uncertainties and/or external disturbance. Owing to the robustness of the SMC technique, the reduced sensitivity to uncertainties, and the enhanced resistance to disturbances from the pseudo fuzzy mechanism, this control algorithm can guarantee not only system stability but also the improvement of tracking errors in the steady state. To validate the design efficiency of PFSMC, both simulation and laboratory tests of the proposed scheme and a conventional PID scheme were performed to compare them as follows. In a computer environment, test cases with and without certainties were implemented with two controllers to visualize the comparative responses. Then, the two control methods were integrated into a real-world hardware platform to acquire practical outcomes. From these results, it can be noted that our successful approach showed a feasible, effective, and robust performance in AC drive.

Exploring strategies to prevent harm from web search

Web search, the process of seeking and finding information online, is an ubiquitous activity engrained in the lives of many individuals and much of broader society. This activity, which has brought many benefits to individuals and society, has also opened the door to many harms, such as echo chambers, loss of privacy and exposure to misinformation. Members of the information retrieval (IR) community now recognize the dangers of the search technologies commonplace in our daily lives. The upshot of this recognition are growing efforts to address these dangers by the IR community. These efforts focus heavily on system oriented solutions, but give limited focus on behavioural and cognitive biases and behaviours of the search and even less attention to interventions designed to address these biases and behaviours. As such, a theoretical framework is proposed, with behavioural and cognitive strategies as a core component of interactive Web search environments designed to minimize harm. Using the framework as the foundation, this thesis presents a number of offline and online studies to evaluate nudging , a popular intervention strategy rooted in the field of behavioural economics, and boosting , a successful intervention strategy from the cognitive sciences, as strategies to reduce risk of harm in Web search. The key takeaway from these studies being that both boosting and nudging should be considered as viable approaches for harm prevention in Web search environments, in addition to pure system and algorithmic solutions. Additional contributions of this thesis include methods of study design for the comparison of multiple paradigms that promote improved decision making, along with a set of evaluation metrics to measure the success of the IR system and user performance as they relate to the harms being prevented. Future research is needed to confirm the effectiveness of these strategies for other types of harms.

In vitro synthesis of 32 translation-factor proteins from a single template reveals impaired ribosomal processivity

The Protein synthesis Using Recombinant Elements (PURE) system enables transcription and translation of a DNA template from purified components. Therefore, the PURE system-catalyzed generation of RNAs and proteins constituting the PURE system itself represents a major challenge toward a self-replicating minimal cell. In this work, we show that all translation factors (except elongation factor Tu) and 20 aminoacyl-tRNA synthetases can be expressed in the PURE system from a single plasmid encoding 32 proteins in 30 cistrons. Cell-free synthesis of all 32 proteins is confirmed by quantitative mass spectrometry-based proteomic analysis using isotopically labeled amino acids. We find that a significant fraction of the gene products consists of proteins missing their C-terminal ends. The per-codon processivity loss that we measure lies between 1.3 × 10–3 and 13.2 × 10–3, depending on the expression conditions, the version of the PURE system, and the coding sequence. These values are 5 to 50 times higher than those measured in vivo in E. coli. With such an impaired processivity, a considerable fraction of the biosynthesis capacity of the PURE system is wasted, posing an unforeseen challenge toward the development of a self-regenerating PURE system.

Reframing research access

PurposeThe paper describes how Charles Darwin University (CDU) used a three-pronged approach to better serve its researchers: it developed a single interface for improved accessibility and discoverability of its research outputs, consolidated its corresponding policies and procedures and implemented training programs to support the new portal. This in turn made its suite of research outputs more openly accessible and better discoverable. The intention was to make CDU research compliant with the FAIR (Findable, Accessible, Interoperable and Reusable) policy statement, affirming the need to make Australia's research more visible, thereby enabling better access, better collaboration locally and internationally and researchers more accountable to their community.Design/methodology/approachThis paper uses case study methodology and a qualitative approach.FindingsCDU Library collaborated with the University’s Research Office in undertaking a series of strategies towards reframing access to its research. The partners migrated their research collections into a single, new, integrated interface; developed new policies and consolidated existing ones; and to this end, rolled out a training and educational program for the research community. The intention of the program was to introduce the Pure repository to new researchers and to train all staff to self archive and curate their own research outputs. This new streamlined approach ensured a more comprehensive and timely availability and accessibility of the University's research outputs.Originality/valueA single source of truth was established through the migration of iCDU’s research collections, ensuring data quality was maintained. At the start of this project, there were few institutions in Australia using the Pure system, and even fewer using it as their sole repository for displaying research outputs.

Reconstituted cell-free protein synthesis using in vitro transcribed tRNAs

Entire reconstitution of tRNAs for active protein production in a cell-free system brings flexibility into the genetic code engineering. It can also contribute to the field of cell-free synthetic biology, which aims to construct self-replicable artificial cells. Herein, we developed a system equipped only with in vitro transcribed tRNA (iVTtRNA) based on a reconstituted cell-free protein synthesis (PURE) system. The developed system, consisting of 21 iVTtRNAs without nucleotide modifications, is able to synthesize active proteins according to the redesigned genetic code. Manipulation of iVTtRNA composition in the system enabled genetic code rewriting. Introduction of modified nucleotides into specific iVTtRNAs demonstrated to be effective for both protein yield and decoding fidelity, where the production yield of DHFR reached about 40% of the reaction with native tRNA at 30°C. The developed system will prove useful for studying decoding processes, and may be employed in genetic code and protein engineering applications.

Cell-free synthesis of natural compounds from genomic DNA of biosynthetic gene clusters

A variety of chemicals can be produced in a living host cell via optimized and engineered biosynthetic pathways. Despite the successes, pathway engineering remains demanding and partly impossible owing to the lack of specific functions or substrates in the host cell, its sensitivity in vital physiological processes to the heterologous components, or constrained mass transfer across the membrane. In this study, we demonstrate that cell-free systems can be useful in driving the characterization and engineering of biosynthetic pathways. We show that complex multidomain proteins involved in natural compound biosynthesis can be produced from encoding DNA in vitro in a minimal complex PURE system to directly run multistep reactions. We prove the concept of this approach on the direct synthesis of indigoidine and rhabdopeptides with the in vitro produced multidomain megasynthases BpsA and KJ12ABC. The in vitro produced proteins are analyzed in detail, i.e., in yield, quality, post-translational modification and specific activity, and compared to recombinantly produced proteins. Our study highlights cell-free PURE systems as suitable setting for the rapid engineering of biosynthetic pathways.

Dynamic Interfacial Tension Behavior of Pure and Binary Surfactant System

Surfactants are very important surface-active agents in implementation of chemical enhanced oil recovery for oil-water interfacial tension and wettability alteration. However, the high adsorption of surfactant on reservoir rock reduces the efficiency of surfactant flooding. Conventionally, inorganic alkali has been introduced to reduce adsorption of surfactant, but alkali will lead to the formation of emulsion, formation damage and scaling. Therefore, lignosulfonate, a sacrificial agent has been introduced as an alternative to inorganic alkali. In this paper, the critical micelle concentration (CMC) and dynamic interfacial tension (IFT) behavior of a pure and binary system of internal olefin sulfonate (IOS) and lignosulfonate (LS) at brine-decane interfaces are determined by using a spinning drop method. The physicochemical properties of pure and binary of IOS and LS system are determined by conductivity and pH measurements. The CMC value of IOS in 3.5 wt% brine salinity is higher compared to LS due to the isomeric branched of IOS which can occupy a larger area per molecules. The dynamic interfacial tension of IOS shows the fast adsorption of surfactant molecules to the brine-decane interfaces. This is indicated by the fast equilibrium interfacial tension reached by IOS. In comparison, the LS pure system shows decreasing behavior of dynamic interfacial tension. The fast adsorption at the interfaces is only reached for higher LS concentrations. The synergy effect between IOS and LS system shows a reduction in the interfacial value with LS optimum concentration of 0.6 wt%. The drop in conductivity and pH values indicated the development of a tightly packed lamellar liquid crystalline structure. These physicochemical properties are in agreement with the dynamic interfacial tension behavior of the IOS and LS system. This study has demonstrated the significant impact of the LS addition in reducing the dynamic interfacial tension of the surfactant system.