2D atomic crystal molecular superlattices by soft plasma intercalation

Two-dimensional (2D) atomic crystal superlattices integrate diverse 2D layered materials enabling adjustable electronic and optical properties. However, tunability of the interlayer gap and interactions remain challenging. Here we report a solution based on soft oxygen plasma intercalation. 2D atomic crystal molecular superlattices (ACMSs) are produced by intercalating O2+ ions into the interlayer space using the plasma electric field. Stable molecular oxygen layer is formed by van der Waals interactions with adjacent transition metal dichalcogenide (TMD) monolayers. The resulting interlayer gap expansion can effectively isolate TMD monolayers and impart exotic properties to homo-(MoS2[O2]x) and hetero-(MoS2[O2]x/WS2[O2]x) stacked ACMSs beyond typical capacities of monolayer TMDs, such as 100 times stronger photoluminescence and 100 times higher photocurrent. Our potentially universal approach to tune interlayer stacking and interactions in 2D ACMSs may lead to exotic superlattice properties intrinsic to monolayer materials such as direct bandgap pursued for future optoelectronics.

Thermoacoustics of Can-Annular Combustors

Can-annular combustors consist of a set of independent cans, connected on the upstream side to the combustor plenum and on the downstream side to the turbine inlet, where a transition duct links the round geometry of each can with the annular segment of the turbine inlet. Each transition duct is open on the sides toward the adjacent transition ducts, so that neighboring cans are acoustically connected through a so-called cross-talk open area. This theoretical, numerical, and experimental work discusses the effect that this communication has on the thermoacoustic frequencies of the combustor. We show how this communication gives rise to axial and azimuthal modes, and that these correspond to particularly synchronized states of axial thermoacoustic oscillations in each individual can. We show that these combustors typically show clusters of thermoacoustic modes with very close frequencies and that a slight loss of rotational symmetry, e.g., a different acoustic response of certain cans, can lead to mode localization. We corroborate the predictions of azimuthal modes, clusters of eigenmodes, and mode localization with experimental evidence.

Thermoacoustics of Can-Annular Combustors

Can-annular combustors consist of a set of independent cans, connected on the upstream side to the combustor plenum, and on the downstream side to the turbine inlet, where a transition duct links the round geometry of each can with the annular segment of the turbine inlet. Each transition duct is open on the sides towards the adjacent transition ducts, so that neighbouring cans are acoustically connected through a so called cross-talk open area. This theoretical, numerical and experimental work discusses the effect that this communication has on the thermoacoustic frequencies of the combustor. We show how this communication gives rise to axial and azimuthal modes, and that these correspond to particularly synchronised states of axial thermoacoustic oscillations in each individual can. We show that these combustors typically show clusters of thermoacoustic modes with very close frequencies and that a slight loss of rotational symmetry, e.g. a different acoustic response of certain cans, can lead to mode localization. We corroborate the predictions of azimuthal modes, clusters of eigenmodes and mode localization with experimental evidence.

Availability and cost analysis of an engineering system involving subsystems in series configuration

Purpose The purpose of this paper is to evaluate various reliability measures like availability, reliability, mean time to failure and profit function. Design/methodology/approach The authors present a novel method for availability analysis of an engineering system incorporating waiting time to repair. The considered system consists of two subsystems, namely, A and B connected in series. The subsystem B has two identical units in standby arrangement. Each unit of the subsystem has two modes, i.e. normal efficiency or failed. The two standby units of the subsystem B are connected by an imperfect switching. The system is analyzed by supplementary variable technique, Laplace transformation and Gumbel-Hougaard family of copula. Findings Numerical examples with a way to highlight the important results have been appended at last. Numerical calculation shows that availability and reliability of the system is decreasing with respect to time when failure rates are fixed at different values. Finally, cost analysis of system reveals that the expected profit decreases with increase in service cost. Originality/value This paper presents a mathematical model in which an important aspect of switching has been taken into consideration, which is consistent with actual failures of switching by assuming two different types of failure between adjacent transition. It is evaluated with the help of the Gumbel-Hougaard family of copula.

Design and performance of the Yele asphalt-core rockfill dam

The planning, design, and performance of the Yele asphalt-core rockfill dam in Sichuan Province, China, are presented. The dam has a maximum height of 124.5 m, is located in a very seismic region with inclement climate, and is founded on a geologically complex foundation, partly resting on a deep and pervious alluvial overburden and partly on bedrock. With these site conditions only an embankment-type dam was considered feasible, and three different options were considered for the design of the impervious barrier: (i) earth core, (ii) concrete facing, and (iii) asphalt core. The third option was chosen. The design is based on extensive analyses and laboratory tests, and a special model test was performed to study the behavior of the connection between the narrow asphalt core and concrete plinth. An impoundment test was performed when the dam was 73 m high to test the imperviousness of the constructed core and the connections between (i) the core and plinth and (ii) the plinth and foundation cut-off wall. An extensive field monitoring program was implemented. Design predictions are compared with field performance observations of the core and its interaction with the adjacent transition zones.

Stability of Beams on Bi-Moduli Elastic Foundation

This paper adopts the newly structured δ function and displacement function. Using two adjacent transition points as two interval terminals while beams buckle makes the interval [xi−1,xi]. According to the Winkler’s beam buckling theory on elastic foundation, we present the energy solutions of beams and then the exact solutions of buckling load of simple supported beams on bi-moduli elastic foundation.