Pseudomomentum: origins and consequences

The balance of pseudomomentum is discussed and applied to simple elasticity, ideal fluids, and the mechanics of inextensible rods and sheets. A general framework is presented in which the simultaneous variation of an action with respect to position, time, and material labels yields bulk balance laws and jump conditions for momentum, energy, and pseudomomentum. The example of simple elasticity of space-filling solids is treated at length. The pseudomomentum balance in ideal fluids is shown to imply conservation of vorticity, circulation, and helicity, and a mathematical similarity is noted between the evaluation of circulation along a material loop and the J-integral of fracture mechanics. Integration of the pseudomomentum balance, making use of a prescription for singular sources derived by analogy with the continuous form of the balance, directly provides the propulsive force driving passive reconfiguration or locomotion of confined, inhomogeneous elastic rods. The conserved angular momentum and pseudomomentum are identified in the classification of conical sheets with rotational inertia or bending energy.

Abrasion performance of the scraper conveyor chute under complex working conditions

In the coal mine transportation, the scraper conveyor chute is badly worn. However, the abrasion performance has not been well documented. In this study, the chute was wear tested under a single factor using a modified pin-on-disc apparatus, including normal load, sliding distance, bulk coal characteristics (water content, gangue content), and chute material. Experiments were also carried out with a simultaneous variation of these factors. Generally speaking, the influence of coal characteristics on the chute wear was obviously higher than that of normal load and sliding distance. An improved wear predict model was obtained taking the operational parameters and bulk coal characteristics into account. The wear mechanism involved micro-ploughing, corrosion, adhesion, and fatigue peeling.

Multifunctionality of Polypyrrole Polyethyleneoxide Composites: Concurrent Sensing, Actuation and Energy Storage

In films of conducting polymers, the electrochemical reaction(s) drive the simultaneous variation of different material properties (reaction multifunctionality). Here, we present a parallel study of actuation-sensing-energy storage triple functionality of polypyrrole (PPy) blends with dodecylbenzenesulfonate (DBS-), PPy/DBS, without and with inclusion of polyethyleneoxide, PPy-PEO/DBS. The characterization of the response of both materials in aqueous solutions of four different salts indicated that all of the actuating, sensing and charge storage responses were, independent of the electrolyte, present for both materials, but stronger for the PPy-PEO/DBS films: 1.4× higher strains, 1.3× higher specific charge densities, 2.5× higher specific capacitances and increased ion-sensitivity towards the studied counterions. For both materials, the reaction energy, the material potential and the strain variations adapt to and sense the electrical and chemical (exchanged cation) conditions. The driving and the response of actuation, sensing and charge can be controlled/read, simultaneously, via just two connecting wires. Only the cooperative actuation of chemical macromolecular motors from functional cells has such chemical multifunctionality.

Development and Validation of a Simple HPLC-UV Method to Assay DEET Repellents and its Application to Different Commercial Forms

Background: N’,N’-diethyl-m-toluamide (DEET) is the most widely used repellent substance worldwide. It is formulated as aerosol, solution, lotion, gel and patches. However, the official compendia report monographs to analyze only DEET drug substance and solution. Objective: In this study an isocratic HPLC method was validated to assay DEET in lotion, gel and solution, under the same analytical conditions. Method: The method was validated according to ICH requirements and DEET detection was achieved at around 11 min, using C-18 column, a mobile phase composed by methanol, acetonitrile and water pH 4.5 (45:10:45), flow rate at 1 mL min-1 and detection at 270 nm. Results: A linear relationship was observed in the range of 2.5 to 100 µg mL-1, the method was precise (relative standard deviation < 2%) and accuracy was demonstrated by DEET recovery values ranging from 99.5 to 100.2%. The specificity was studied by a forced degradation test, where degradation products were observed after alkaline degradation and ultraviolet radiation. Appropriate resolution between DEET, degradation products and excipient peaks indicated the method specificity. Robustness was evaluated by a full factorial design, and no effect on DEET assay was observed under simultaneous variation in analytical parameters. The method was applied to assay nine marketed formulations, demonstrating its good applicability. Conclusion: The validated HPLC method was successfully applied to the quantitative analysis of DEET in lotion, gel and solution, contributing to improve the quality control and the efficacy of these formulations.

A Fractional-Order Discrete Noninvertible Map of Cubic Type: Dynamics, Control, and Synchronization

In this paper, a new fractional-order discrete noninvertible map of cubic type is presented. Firstly, the stability of the equilibrium points for the map is examined. Secondly, the dynamics of the map with two different initial conditions is studied by numerical simulation when a parameter or a derivative order is varied. A series of attractors are displayed in various forms of periodic and chaotic ones. Furthermore, bifurcations with the simultaneous variation of both a parameter and the order are also analyzed in the three-dimensional space. Interior crises are found in the map as a parameter or an order varies. Thirdly, based on the stability theory of fractional-order discrete maps, a stabilization controller is proposed to control the chaos of the map and the asymptotic convergence of the state variables is determined. Finally, the synchronization between the proposed map and a fractional-order discrete Loren map is investigated. Numerical simulations are used to verify the effectiveness of the designed synchronization controllers.

Thermal performance of fully wet longitudinal porous fin with temperature-dependent thermal conductivity, surface emissivity and heat transfer coefficient

Purpose The purpose of this paper is to study the thermal behaviour of a fully wet porous fin of longitudinal profile. The significance of radiative and convective heat transfer has been scrutinised along with the simultaneous variation of surface emissivity, heat transfer coefficient and thermal conductivity with temperature. The emissivity of the surface and the thermal conductivity are considered as linear functions of the local temperature between fin and the ambient. Darcy’s model was considered to formulate the heat transfer equation. According to this, the porous fin permits the flow to penetrate through it and solid–fluid interaction occurs. Design/methodology/approach Runge–Kutta–Fehlberg fourth–fifth-order method has been used to solve the reduced non-dimensionalized ordinary differential equation involving highly nonlinear terms. Findings The impact of pertinent parameters, such as convective parameter, radiative parameter, conductivity parameter, emissivity parameter, wet porous parameter, etc., on the temperature profiles were elaborated mathematically with the plotted graphs. The heat transfer from the fin enhances with the rise in convective parameter. Originality/value The wet nature of the fin enhances heat transfer and in many practical applications the parameters, such as thermal conductivity, heat transfer coefficient as well as surface emissivity, vary with temperature. Hence, the main objective of the current study is to depict the significance of simultaneous variation in surface emissivity, heat transfer coefficient and thermal conductivity with respect to temperature under natural convection and radiation condition in a totally wetted longitudinal porous fin.

Dispersion of Mechanical Properties at Nanoscale Studied by Indentation Mapping of a Fiber Reinforced Composite

The properties of a resin transfer molded sheet of strand-reinforced composite for automotive applications are investigated at the microscopic level. Three components of the composite can be identified in the bright field micrograph – glass fibers, epoxy matrix and binder. The latter having been added in manufacturing process. Accelerated Nanoindentation with 64.451 single indentation experiments is performed at room temperature to generate a mechanical property map of an area containing the 3 components. The distribution of properties, mean value and standard deviation, is determined for each component. Two locations in the composite are selected for a study of the local glass transition behavior by performing dynamic indentation experiments while simultaneous variation of the temperature of the indenter tip and sample within a micro-heating chamber.

Response of Microbial Communities and Their Metabolic Functions to Drying–Rewetting Stress in a Temperate Forest Soil

Global climate change is predicted to alter drought–precipitation patterns, which will likely affect soil microbial communities and their functions, ultimately shifting microbially-mediated biogeochemical cycles. The present study aims to investigate the simultaneous variation of microbial community compositions and functions in response to drought and following rewetting events, using a soil metaproteomics approach. For this, an established field experiment located in an Austrian forest with two levels (moderate and severe stress) of precipitation manipulation was evaluated. The results showed that fungi were more strongly influenced by drying and rewetting (DRW) than bacteria, and that there was a drastic shift in the fungal community towards a more Ascomycota-dominated community. In terms of functional responses, a larger number of proteins and a higher functional diversity were observed in both moderate and severe DRW treatments compared to the control. Furthermore, in both DRW treatments a rise in proteins assigned to “translation, ribosomal structure, and biogenesis” and “protein synthesis” suggests a boost in microbial cell growth after rewetting. We also found that the changes within intracellular functions were associated to specific phyla, indicating that responses of microbial communities to DRW primarily shifted microbial functions. Microbial communities seem to respond to different levels of DRW stress by changing their functional potential, which may feed back to biogeochemical cycles.

Sunk time fallacy with recoverable monetary costs

PurposeThe purpose of this paper is to examine the sunk-time fallacy in the context of simultaneous variations of time and money when financial expenditures are recoverable. The study compares a recoverable monetary scenario with conditions where money is either not spent or spent, but purchase and payment are decoupled.Design/methodology/approachA sample of 184 participants was utilised in three experiments. A randomised design was used, and experimental manipulations were achieved using the vignette method.FindingsThe results indicate that consumers are susceptible to sunk-time fallacy. Specifically, results suggest that there is no significant difference in sunk cost fallacy when a consumer spends only time vs when a consumer spends money and time both but money can be recovered. The sunk-time fallacy did not occur in credit card purchases. The sunk-time fallacy did not happen in temporal investments of less than a week but appeared in the temporal investments of two weeks.Research limitations/implicationsThe study indicates that sunk-time fallacy occurs after a minimum threshold of time is spent on a particular activity.Practical implicationsOnline retailers may vary the delivery period of ordered merchandise to reduce product returns. Online retailers may not deliver the merchandise too early to take advantage of the sunk-time fallacy. Bestseller products should be quickly delivered as there are lesser chances of product return. On the other hand, new products or products with mixed consumer reviews should be provided preferably with a time lag beyond a week. Managers should incentivise payments through debit card/net banking and cash-on-delivery to reduce returns by using sunk-time fallacy.Originality/valueThe study is perhaps the first one to study the sunk-time fallacy in a simultaneous variation of time and money where monetary costs can be recovered fully.