Tin‐based halide perovskite materials have been successfully employed in lead‐free perovskite solar cells, but the overall power conversion efficiencies (PCEs) have been limited by the high carrier ...concentration from the facile oxidation of Sn2+ to Sn4+. Now a chemical route is developed for fabrication of high‐quality methylammonium tin iodide perovskite (MASnI3) films: hydrazinium tin iodide (HASnI3) perovskite film is first solution‐deposited using presursors hydrazinium iodide (HAI) and tin iodide (SnI2), and then transformed into MASnI3 via a cation displacement approach. With the two‐step process, a dense and uniform MASnI3 film is obtained with large grain sizes and high crystallization. Detrimental oxidation is suppressed by the hydrazine released from the film during the transformation. With the MASnI3 as light harvester, mesoporous perovskite solar cells were prepared, and a maximum power conversion efficiency (PCE) of 7.13 % is delivered with good reproducibility.
High‐quality, pinhole‐free CH3NH3SnI3 films are achieved from pristine NH2NH3SnI3 perovskite, and the oxidation of Sn2+ to Sn4+ can be efficiently suppressed owing to the reduction agent hydrazine generated inside the films in the conversion. With the CH3NH3SnI3 film as light absorber, mesoporous MASnI3 perovskite solar cells were fabricated with a maximum PCE of 7.13 %.
Many factors that influence rockburst damage have been identified but the mechanism that drives rockburst is not fully understood. Weak planes such as faults and shears have been observed near ...excavation boundaries in many rockbursts and these structures must have played a role in these rockburst events. In this paper, the role of weak planes around tunnels in rockburst occurrence and damage was studied. A heterogeneous Abaqus2D explicit code was used to simulate dynamic rock failure in deep tunnels. Firstly, rock failure near the excavation boundary of a tunnel without any adjacent weak plane was modeled. Then a fault with different lengths, inclinations, and distances to the tunnel was added to the model and its effect on rock failure was simulated. The velocity and the released kinetic energy of failed rocks, the failure zone around the tunnel, and the deformed mesh were studied to identify stable and unstable rock failures. The simulation results showed that the presence of a fault near a tunnel could induce rockburst if the fault is positioned and oriented in such a way that it promotes high stress and low mine system stiffness. Finally, a rockburst occurred in the Jinping II drainage tunnel with an observed nearby fault was simulated. The modeling results captured the field observation of rockburst damage and confirmed that the presence of weak planes in the vicinity of deep tunnels is a necessary condition for the occurrence of rockburst. The presented methodology in this paper can be useful for rockburst anticipation and control during mining and tunneling in highly stressed grounds.
Bacteria are now generally believed to adopt two main lifestyles: planktonic individuals, or surface-attached biofilms. However, in recent years medical microbiologists started to stress that ...suspended bacterial aggregates are a major form of bacterial communities in chronic infection sites. Despite sharing many similarities with surface-attached biofilms and are thus generally defined as biofilm-like aggregates, these non-attached clumps of cells
show much smaller sizes and different formation mechanisms. Furthermore,
clinical isolates were frequently reported to be less attached to abiotic surfaces when compared to standard type strains. While this third lifestyle is starting to draw heavy attention in clinical studies, it has a long history in natural and environmental sciences. For example, marine gel particles formed by bacteria attachment to phytoplankton exopolymers have been well documented in oceans; large river and lake snows loaded with bacterial aggregates are frequently found in freshwater systems; multispecies bacterial "flocs" have long been used in wastewater treatment. This review focuses on non-attached aggregates found in a variety of natural and clinical settings, as well as some recent technical developments facilitating aggregate research. The aim is to summarise the characteristics of different types of bacterial aggregates, bridging the knowledge gap, provoking new perspectives for researchers from different fields, and highlighting the importance of more research input in this third lifestyle of bacteria closely relevant to our daily life.
Based on the concept of the representative elementary volume (REV) and the synthetic rock mass (SRM) modeling technique, a DFN–DEM multi-scale modeling approach is proposed for modeling excavation ...responses in jointed rock masses. Discrete fracture networks (DFNs) are generated using MoFrac. For a given volume of jointed rock masses, multi-scale DFN models are constructed according to the hierarchical order of fracture size. Based on the DFN models of various scales, equivalent rock mass properties are obtained using 3DEC SRM models. A tunnel excavation simulation using data from the Äspö TAS08 tunnel is conducted to demonstrate the applicability of the proposed multi-scale modeling approach. The modeling results show that it is efficient to model the mechanical response of the rock mass using the proposed approach. The proposed approach has the advantages of both equivalent continuum and discontinuum methods, with a higher degree of accuracy compared with the pure continuum approach and a less computational effort compared with the pure discontinuum approach.
A compact-size low-profile wideband circularly polarized (CP) omnidirectional antenna with reconfigurable polarizations is presented in this communication. This design is based on a low-profile ...omnidirectional CP antenna which consists of a vertically polarized microstrip patch antenna working in TM 01 /TM 02 modes and sequentially bended slots etched on the ground plane for radiating horizontally polarized electric field. The combined radiation from both the microstrip patch and the slots leads to a CP omnidirectional radiation pattern. The polarization reconfigurability is realized by introducing PIN diodes on the slots. By electronically controlling the states of the PIN diodes, the effective orientation of the slots on ground plane can be changed dynamically and the polarization of antenna can be altered between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). The proposed antenna exhibits a wide-operational bandwidth of 19.8% (2.09-2.55 GHz) with both axial ratio below 3 dB and return loss above 10 dB when radiates either LHCP or RHCP waves. Experimental results show good agreement with the simulation results. The present design has a compact size, a thickness of only 0.024λ and exhibits stable CP omnidirectional conical-beam radiation patterns within the entire operating frequency band with good circular polarization.
A hybrid organic–inorganic compound, (pyrrolidinium)MnBr3
, distinguished from rare earth (RE)‐doped inorganic perovskites, is discovered as a new member of the ferroelectrics family, having ...excellent luminescent properties and relatively large spontaneous polarization of 6 μC cm−2, as well as a weak ferromagnetism at about 2.4 K. With a quantum yield of >28% and emission lifetime >0.1 ms, such multiferroic photoluminescence is a suitable candidate for future applications in luminescence materials, photovoltaics, and magneto‐optoelectronic devices.
Although the orbitofrontal cortex (OFC) has been studied intensely for decades, its precise functions have remained elusive. We recently hypothesized that the OFC contains a “cognitive map” of task ...space in which the current state of the task is represented, and this representation is especially critical for behavior when states are unobservable from sensory input. To test this idea, we apply pattern-classification techniques to neuroimaging data from humans performing a decision-making task with 16 states. We show that unobservable task states can be decoded from activity in OFC, and decoding accuracy is related to task performance and the occurrence of individual behavioral errors. Moreover, similarity between the neural representations of consecutive states correlates with behavioral accuracy in corresponding state transitions. These results support the idea that OFC represents a cognitive map of task space and establish the feasibility of decoding state representations in humans using non-invasive neuroimaging.
•We tested a novel theory of OFC function directly in humans with fMRI•Multivariate pattern analysis showed evidence for state encoding in OFC•Performance within and across participants was related to state encoding in OFC•The findings provide strong support for the state representation theory of OFC
Schuck et al. present evidence that orbitofrontal cortex contains an up-to-date representation of task-related information during decision making. This “state” representation might provide important input for efficient reinforcement learning and decision making elsewhere in the brain.
Based on a two-scale tessellation technique in Neper, a 3DEC-GBM modeling approach considering inter- and intra-grain contact failures is proposed to study brittle rock failure. Plane strain problems ...are solved using 3DEC to reduce computation time. A parametric study of inter- and intra-grain contact properties is conducted and a calibration procedure is suggested for determining micro-mechanical properties of granular materials. The modeling results indicate that inter- and intra-grain contact strength heterogeneity affects not only the peak strength of rock but also the microcrack spatial location and hence the fracture development path and fracture pattern.
A new Schiff base ligand, which is formed by the condensation reaction of 5-fluorosalicylaldehyde and pyrimidine-4-carbonyl hydrazide {H
2
L
Schiff
= (
E
)-
N
...-(5-fluoro-2-hydroxybenzylidene)pyrimidine-4-carbohydrazide}, was made to react with different dysprosium(
iii
) salts in an alkaline solution to assemble Dy
4
and Dy
6
cluster complexes, Dy
4
(OH)
2
(L
Schiff
)
4
(H
2
O)
2
(NO
3
)
2
·4MeCN·MeOH (
1
) and Dy
6
(CO
3
)
2
(L
Schiff
)
6
(H
2
O)
3
(MeOH)Cl
2
·5MeOH (
2
), depending on whether the anion used is nitrate or chloride. Complex
1
corresponding to the nitrate anion is a butterfly-like Dy
4
cluster complex with four different Dy(
iii
) coordination configurations of O
6
N
2
, O
8
N, O
7
N
2
and O
6
N
3
; when the anion is replaced by the chloride anion, carbon dioxide can be automatically captured from the air and converted into a carbonate bridging ligand, and the final product obtained is complex
2
, which is a triangular prism-type Dy
6
cluster complex with double μ
3
-carbonate bridging ligands. Both
1
and
2
show good zero-field SMM properties, with
U
eff
/
k
values of 116.5 K for
1
and 150.9 K for
2
.
The same Schiff base ligand was used to assemble different zero-field Dy(
iii
) cluster single-molecule magnets with a nuclei number of 4 or 6, depending on the anions.
Soil-rock mixtures (SRMs) are the main unfavorable geologic bodies in Southwest China. This paper presents a novel mesoscale computational modeling study of SRMs with concave aggregates. An efficient ...3D mesoscale SRM generation method is proposed by combining the Gilbert–Johnson–Keerthi (GJK)-based collision detection technique, the border placement algorithm and the particle position selection method. A periodic mesh is generated based on the mesh mapping technique. A numerical homogenization analysis of an SRM with a large number of elements is realized, and the estimated parameters are validated by the experimental test results. The results indicate that SRMs with concave aggregates have a higher elastic modulus than those with convex aggregates. This method is helpful for predicting the physical properties of SRMs and has promising applications in engineering.
•A novel 3D SRM mesoscale modeling method with concave particles is presented.•A collision detection technique incorporating Gilbert–Johnson–Keerthi (GJK) and convex decomposition algorithm is developed.•Numerical homogenization analysis of 3D SRM is conducted and verified by experimental results.•Parameter study indicates that SRMs with concave aggregates have higher elastic modulus than that with convex aggregates.
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