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Based on the stochastic uncertainty of the system's operating environment, this research presents statistical inferences on the mean time to failure (MTTF) of a K-out-of-N: G non-repairable system model with switching failure under Poisson shocks. The standby component is switched to the operating component when an operating component fails, with a switching failure probability of p. The MTTF of the system is derived by using the Markov process theory and the Laplace transform for two cases where the shock threshold is a constant value or a random variable. The maximum likelihood estimator (MLE) of the MTTF is obtained, and based on this estimator, asymptotic confidence interval estimation and hypothesis testing are performed. Based on the setting of the basic parameter values, the MTTF under two different cases of the shock threshold is compared. The effect of each parameter on the MTTF is analyzed in numerical simulation. The effectiveness of the above statistical inference methods is also verified by numerical simulation.

In order to facilitate farmers to accurately identify rice leaf diseases, this study improves the original AlexNet model to identify eight kinds of rice leaf diseases. The original AlexNet model was improved by changing the original Relu activation function to Leakyrelu activation function, as well as removing the last convolution layer and changing the number of convolutional kernels of each original convolutional layer to 1/2 of the original. Finally, the output nodes of the full connection layer were reduced. The results show that the recognition rate of the improved model reaches 99.23%, significantly higher than that of the original, and so, a new idea for the identification of rice leaf diseases was put forward. In addition, this paper verifies the generalisation of the model by designing five comparative experiments with different activation functions, different dataset sizes, different optimisers, different batch sizes, and different learning rates.

Area-selective deposition (ASD) of low-kmaterials is desired in back-end-of-line processes for fabricating nanopatterns such as fully self-aligned vias. However, the high temperature and/or aggressive coreactants used in conventional low-kmaterial deposition have limited the application of the organic inhibitors used in ASD. Here, we report a strategy to selectively deposit low-kmethylene-bridged silicon oxycarbide (SiOC) thin films on metal/dielectric patterns by combining growth using molecular layer deposition (MLD) and inhibition using self-assembled monolayers (SAMs). By using bis (trichlorosilyl)-methane and water as a precursor and coreactant, respectively, SiOC thin films with a dielectric constant of 3.6–3.8 are deposited at 40 °C and at a growth rate of 1.5 Å/cycle. We demonstrate area-selective MLD of this SiOC material for up to 30 cycles (equiv. 4.5 nm) on SiO2vsCu using a dodecanethiol SAM to block growth on Cu, and up to 70 cycles (equiv. 10 nm) on SiO2vsAl using an octadecylphosphonic acid SAM to block growth on native oxide-covered Al. Positive and negative pattern transfer of SiOC films on a Cu/Al2O3pattern is exhibited as a proof of concept. Moreover, because the Cu substrates are contaminated by HCl which is generated as a byproduct in the MLD process, we develop a mild post-treatment method using ethanol to remove chlorine residues.

It has recently been shown that sulfur, a solid material in its elementary form S8, can stay in a supercooled state as liquid sulfur in an electrochemical cell. We establish that this newly discovered state could have implications for lithium–sulfur batteries. Here, through in situ studies of electrochemical sulfur generation, we show that liquid (supercooled) and solid elementary sulfur possess very different areal capacities over the same charging period. To control the physical state of sulfur, we studied its growth on two-dimensional layered materials. We found that on the basal plane, only liquid sulfur accumulates; by contrast, at the edge sites, liquid sulfur accumulates if the thickness of the two-dimensional material is small, whereas solid sulfur nucleates if the thickness is large (tens of nanometres). Correlating the sulfur states with their respective areal capacities, as well as controlling the growth of sulfur on two-dimensional materials, could provide insights for the design of future lithium–sulfur batteries.

The Mg/S battery is attractive because of its high theoretical energy density and the abundance of Mg and S on the earth. However, its development is hindered by the lack of understanding to the underlying electrochemical reaction mechanism of its charge–discharge processes. Here, using a unique in situX-ray absorption spectroscopic tool, we systematically study the reaction pathways of the Mg/S cells in Mg(HMDS)2–AlCl3electrolyte. We find that the capacity degradation is mainly due to the formation of irreversible discharge products, such as MgS and Mg3S8, through a direct electrochemical deposition or a chemical disproportionation of intermediate polysulfide. In light of the fundamental understanding, we propose to use TiS2as a catalyst to activate the irreversible reaction of low-order MgSxand MgS, which results in an increased discharging capacity up to 900 mAh·g–1and a longer cycling life.

Understanding and optimizing the effects of edge states and nanoflake dimensions on the photon harvesting efficiency in ultrathin transition-metal dichalcogenide (TMD) semiconductor photoelectrodes is critical to assessing their practical viability for solar energy conversion. We present herein a novel filtration-based separation approach to systematically vary the TMD nanoflake dimensions and edge density of solution-processed large-area multiflake WSe2photocathodes. Photoelectrochemical measurements in both aqueous electrolyte (for water reduction) and a sacrificial redox system, together with a continuum-based charge transport model, reveal the role of the edge sites and the effects of the flake size on the light harvesting, charge transport, and recombination. A selective passivation technique using atomic layer deposition is developed to address detrimental recombination at flake edges. Edge-passivated WSe2films prepared with the smallest flakes (∼150 nm width, 9 nm thickness) demonstrate an internal quantum yield of 60% (similar to bulk single-crystal results). An optimized (1 sun) photocurrent density of 2.64 mA cm–2is achieved with 18-nm-thick flakes (700 nm width) despite transmitting ∼80% of the accessible photons. Overall, these results represent a new benchmark in the performance of solution-processed TMDs and suggest routes for their development into large-area low-cost solar energy conversion devices.

Lithium–sulfur batteries are promising for low-cost and high-energy storage, but their applications are still limited by poor cycling stability owing to soluble lithium polysulfide shuttling during battery operation. Avoiding shuttle effect is challenging but it is essential to avoid active material loss and prevent performance decay. Here, we use an ultrathin layer of MoS2with thickness of 10–40 nm, which is 1–2 orders of magnitude thinner than conventional interlayers, for Li–S batteries to mitigate polysulfide shuttling. The MoS2layer formed by exfoliated nanoflakes is deposited by the scalable liquid-based self-assembly method. With less than 1% of additional weight in the cathode, the MoS2interlayer with complete coverage inhibits polysulfide diffusion across the separator and therefore remarkably improves the battery performances. Reversible specific capacity reaches 1010 and 600 mA h g–1at 0.5 and 2C rates, respectively, which decay slowly over 400 cycles (0.11% per cycle). Moreover, the MoS2films with high density of catalytic active flake edges enable high areal sulfur loading up to 10 mg cm–2and areal capacity up to 9.7 mA h cm–2at a current density of 3.2 mA cm–2.

Dual pH- and light-responsive nanomicelles self-assembled from amphiphilic random poly(methacrylic acid-co-methyl methacrylate-co-7-(4-vinylbenzyloxyl)-4-methylcoumarin) (P(MAA-co-MMA-co-VM)) have been successfully prepared and employed as particulate emulsifiers to stabilize the oil/water interface. The self-assembling behavior of copolymers in a selective solvent is explored. The structural transitions of CP55 micelles based on a copolymer with 55 mol % hydrophilic methacrylic acid units are investigated by the dosage of ultraviolet irradiation and pH variation. As pH increases, the ionization of the carboxyl groups leads to the swelling of micelles. Both the size and polydispersity index of cross-linked micelles are far larger than those of un-cross-linked micelles under alkaline conditions. The comparison of the configuration of the un-cross-linked micelles and cross-linked micelles at the oil/water interface is investigated by scanning electron microscopy. The results show that the ability of swelling and conformational changing in response to external pH- and light-triggers largely affected the emulsifying performance of the particulate emulsifiers. Especially for emulsions stabilized by the cross-linked micelles, oil begins to separate out as pH elevated over 7.3 on account of the restricted conformational adjustment that resulted from the increasing interparticle cross-linking and electrostatic repulsion. The findings may be useful for challenging industrial areas where organic macromolecules and surfactants cooperate.

Ternary bulk heterojunctions with cascade-type energy-level configurations are of significant interest for further improving the power conversion efficiency (PCE) of organic solar cells. However, controlling the self-assembly in solution-processed ternary blends remains a key challenge. Herein, we leverage the ability to control the crystallinity of molecular semiconductors via a spiro linker to demonstrate a simple strategy suggested to drive the self-assembly of an ideal charge-cascade morphology. Spirobifluorene (SF) derivatives with optimized energy levels from diketopyrrolopyrrole (DPP) or perylenediimide (PDI) components, coded as SF-(DPP)4and SF-(PDI)4, are synthesized and investigated for application as ternary components in the host blend of poly(3-hexylthiophene-2,5-diyl):[6,6]phenyl-C61-butyric acid methyl ester (P3HT:PCBM). Differential scanning calorimetry and X-ray/electron diffraction studies suggest that at low loadings (up to 5 wt %) the ternary component does not perturb crystallization of the donor:acceptor host blend. In photovoltaic devices, up to 36% improvement in the PCE (from 2.5% to 3.5%) is found when 1 wt % of either SF-(DPP)4or SF-(PDI)4is added, and this is attributed to an increase in the fill factor and open-circuit voltage, while at higher loadings, the PCE decreased because of a lower short-circuit current density. A comparison of the quantum efficiency measurements [where light absorption of SF-(DPP)4was found to give up to 95% internal conversion] suggests that improvement due to enhanced light absorption or to better exciton harvesting via resonance energy transfer is unlikely. These data, together with the crystallinity results, support the inference that the SF compounds are excluded to the donor:acceptor interface by crystallization of the host blend. This conclusion is further supported by impedance spectroscopy and a longer measured charge-carrier lifetime in the ternary blend.

Solution-processed semiconducting transition metal dichalcogenides are emerging as promising two-dimensional materials for photovoltaic and optoelectronic applications. Here, we have used transient absorption spectroscopy to provide unambiguous evidence and distinct signatures of photogenerated excitons and charges in solution-processed few-layer MoS2nanoflakes (10–20 layers). We find that photoexcitation above the direct energy gap results in the ultrafast generation of a mixture of free charges in direct band states and of excitons. While the excitons are rapidly trapped, the free charges are long-lived with nanosecond recombination times. The different signatures observed for these species enable the experimental extraction of the exciton binding energy, which we find to be ∼80 meV in the nanoflakes, in agreement with reported values in the bulk material. Carrier-density-dependent measurements bring new insights about the many-body interactions between free charges resulting in band gap renormalization effects in the few-layer MoS2nanoflakes.

Purpose To assess the efficacy and safety of bupivacaine compared with lidocaine in local anesthesia of nasopharynx through meta-analysis.Methods A number of medical literature data bases were searched electronically. Relevant journals and references of included studies were manually searched. Two reviewers independently performed data extraction and quality assessment.Results Four studies were included. Visual analog scale (VAS) scores, acceptable discomfort, and bleeding scores were analyzed for bupivacaine versus lidocaine. When considering the VAS scores, bupivacaine as a local anesthetic agent was better than lidocaine in controlling the pain of postoperative patients (p < 0.00001). From VAS scores of patients for transnasal fiberoptic nasopharyngolaryngoscopic examination that was performed to evaluate upper airway structures, lidocaine was found to be better at pain management in patients who underwent transnasal endoscopic examination (p < 0.00001). However, when analyzing the acceptable discomfort of patients who underwent upper gastrointestinal endoscopy, which serves as a valuable tool to evaluate upper gastrointestinal structures, the patients in the bupivacaine group demonstrated a higher acceptable discomfort than the patients in the lidocaine group (p = 0.008). With regard to the bleeding scores of the patients with nasal surgery, lidocaine was better at bleeding in postoperative patients compared with bupivacaine (p = 0.0007). These results indicated that bupivacaine showed better pain control of postoperative patients and acceptable discomfort in patients with upper gastrointestinal endoscopy. Lidocaine had a significantly increased ability the pain of patients with transnasal fiberoptic nasopharyngolaryngoscopic examination and bleeding in postoperative patients. No systemic adverse events were reported.Conclusion Bupivacaine was found to have better promotion to pain control than did lidocaine for the patients after nasal surgery. Lidocaine had a significantly increased inhibition of bleeding in these postoperative patients; however, the efficacy between bupivacaine and lidocaine was unclear for the patients who had transnasal endoscopic examinations.

We investigated the optimal operational conditions for utilizing a broadband supercontinuum (SC) source in a portable 800 nm spectral-domain (SD) endoscopic OCT system to enable high resolution, high-sensitivity, and high-speed imaging in vivo. A SC source with a 3-dB bandwidth of ∼246  nm was employed to obtain an axial resolution of ∼2.7  μm (in air) and an optimal detection sensitivity of ∼−107  dB with an imaging speed up to 35 frames/s (at 70 k A-scans/s). The performance of the SC-based SD-OCT endoscopy system was demonstrated by imaging guinea pig esophagus in vivo, achieving image quality comparable to that acquired with a broadband home-built Ti:sapphire laser.

Formal finance involves the costly acquisition of information about distant entrepreneurs, while relationship-based finance allows financiers to fund a narrow circle of close entrepreneurs without acquiring costly information. In developing economies with low capital endowments, relationship-based finance is optimal because only high-quality entrepreneurs receive funding. However, formal finance may emerge in equilibrium, and it has the only effect of shifting rents from entrepreneurs to financiers. In more-developed economies with higher capital endowments, formal finance becomes necessary to prevent funding of low-quality entrepreneurs. Nevertheless, relationship-based financing may persist in equilibrium, and low-quality close entrepreneurs are funded even when there are high-quality distant entrepreneurs.