The article considers the problem of point control of the differential-difference equation with distributed parameters on the graph in the class of summable functions. The differential- difference system is closely related to the evolutionary differential system and moreover the properties of the differential system are preserved. This connection is established by the universal method of semi-discretization in a time variable for a differential system, which provides an effective tool in order to find conditions for unique solvability and continuity on the initial data for the differential-difference system. For this differential-difference system, a special case of the optimal control problem is studied: the problem of point control action on the controlled differential-difference system is considered by the control, concentrated at all internal nodes of the graph. At the same time, the restrictive set of permissible controls is set by the means of conditions depending on the nature of the applied tasks. In this case, the controls are concentrated at the end points of the edges adjacent to each inner node of the graph. This is a characteristic feature of the study presented, quite often used in practice when building a mechanism for managing the processes of transportation of different kinds of masses over network media. The study essentially uses the conjugate state of the system and the conjugate system for a differential-difference system — obtained ratios that determine optimal point control. The obtained results underlie the analysis of optimal control problems for differential systems with distributed parameters on the graph, which have interesting analogies with multi-phase problems of multidimensional hydrodynamics.
The self‐healing performance of epoxidized deproteinized natural rubber (EDPNR) and EDPNR/graphene oxide (GO) composites was investigated. Composites of EDPNR25 and EDPNR50 with GO contents of 0.5 and 1.0 phr were prepared by adding a GO dispersion into a EDPNR latex and the product was subsequently cast into films. Tensile strengths of the original samples and after self‐healing were used to evaluate self‐healing performance. The tensile strength of EDPNR25 after self‐healing achieved about 65% of tensile strength of original EDPNR25. The recovery of tensile strength for the composite increased to 81% for EDPNR25/GO0.5 and 105% for EDPNR25/GO1.0 for self‐healing at 25°C for 24 h. At 70°C, EDPNR25/GO0.5 and EDPNR25/GO1.0 composite achieved ~100% recovery after 24 h. On the other hand, the tensile strength recoveries of EDPNR50, EDPNR50/GO0.5, and EDPNR50/GO1.0 were relatively low (33%, 28%, and 24%, respectively) at 25°C. At 70°C, recoveries increased to 63%, 67%, and 52%, respectively. This result demonstrated that the interdiffusion of epoxidized natural rubber molecules plays a key role in the self‐healing performance rather than hydrogen bonds between GO and functional groups on EDPNR molecules.
In this study, we aimed to evaluate the effect of sulfolane (SL) as a co-solvent in conventional carbonate-based electrolytes and its compatibility with a LiMn2O4 (LMO) cathode. The amount of SL was varied from 10 to 50 vol.% in an EC-DMC mixture (1:1 vol. ratio) within a 1.0-M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. The thermal properties of the electrolytes were studied using thermogravimetric analysis (TGA). Solvent flammability was measured via self-extinguishing time (SET) and ignition time indexes while viscosity was gauged by the Ostwald method. Ionic conductivity was evaluated by electrochemical impedance spectroscopy (EIS). Electrochemical techniques such as cyclic voltammetry (CV) and galvanostatic cycling with potential limitation (GCPL) were carried out to evaluate battery performance with the selected electrolytes. The results indicated that an increasing proportion of SL leads to an enhancement of the thermal and oxidation stability of the electrolytes. At 20-vol.% SL and below, the as-synthesized electrolytes exhibited a high ionic conductivity of 7.45 mS.cm-1 (25oC) and enabled LMO to deliver a specific capacity of 103 mAh.g-1 with a capacity retention of 92% after 20 cycles at C/10 rate. Due to such favourable properties, SL can be used as a co-solvent in EC-DMC systems to enhance the safety of lithium-ion batteries under high voltage conditions.
The discourses of risk serve to organise the ways in which we understand and respond to potential harms and threats, which have become a major concern in our daily life. However, the discourses of risk have not been extensively investigated using linguistic text-based methods on the multimodal level, nor deeply examined beyond Western contexts. Grounded in the literature of risk and multimodal discourse, the aim of the study is to demonstrate Multimodal Discourse Analysis from a Systemic Functional Linguistics perspective as a potential methodology to investigate how risk discourses are constructed in and through semiotic resources in a non-Western setting. Through a case study of child helmet awareness advertisements in Vietnam, the multimodal analysis reveals a comprehensive picture of risk discourses constructed across various semiotic modes. In this analysis, the discourses of risk are constructed through a negotiation of expert knowledge and traditional values to encourage the audience to take actions and provide helmets for their children. Findings of the study demonstrate the use of Systemic Functional multimodal approach to media and communication to provide evidence for risk discourses in the Vietnamese setting, which are at odds with the current literature and can potentially be extended to other contexts.
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