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Loess landslides have complicated deformation mechanisms. Accurately describing the internal failure deformation of loess landslides and establishing a theoretical method of landslide instability evaluation for the prevention of subsequent landslides have become important topics in western development project construction in China. This paper presents a case study of the Zhonglou Mountain landslide in Shaanxi Province, China. Based on field investigation results, a two-dimensional stability analysis model was constructed using the finite element method. Taking the deformation characteristics of the landslide as the research basis, the distribution laws of the displacement, stress, and shear strain of this landslide were identified with the strength reduction finite element numerical simulation method. Additionally, the safety factor was evaluated under normal and storm conditions. The numerical simulation results show that the horizontal tensile stress of the landslide was mainly distributed in the middle and upper parts of the landslide under normal conditions, while the vertical tensile stress was distributed near the sliding surface. Under heavy rainfall, the sliding force increased, and the anti-sliding force and anti-sliding section decreased; the location of the maximum shear strain shifted down from the middle and upper parts of the landslide body to the area with a shear crack, and the plastic shear strain area expanded along nearly the entire the sliding surface, leading to the occurrence of a landslide. Thus, the use of anti-slide piles to stabilize the landslide was proposed and tested. Monitoring points were arranged along the sliding surface to evaluate the displacement, stress, and strain responses. The on-site observation results agreed with the modeling results. The use of anti-slide piles was demonstrated to be an effective stabilization method for the Zhonglou Mountain landslide.

The lithium–sulfur battery (LSB) attracts significant attention to meet the ever-growing energy demand for future technology because of the high theoretical specific capacity of sulfur. To achieve the goal of 500 W h kg−1, the fabrication of thick sulfur cathodes is critical. The ensuing interfacial issues between different components will become more severe because of the intrinsic drawbacks of LSBs, including the low conductivity of sulfur, volumetric variation during cycling, and the solubility of polysulfides. This review summarizes the recent development of thick sulfur cathodes from the perspective of interfacial design. First, the selection of conductive agents with high specific areas and incorporation of catalysts can provide enough electrical conduction for the electrochemical conversions at the interface of sulfur and conductive agents. Then it is essential to control the porosity and tortuosity of the cathode to increase its contact area with the electrolyte for sufficient Li ions transport. A protective layer can be introduced to avoid the side effects of dissolved polysulfides. To maintain the integrity of the cathode, the mechanical properties of the binders and their adhesion to the current collectors should be improved. Overall, interfacial design is important to achieve stable sulfur cathodes.

The high-precision patterning of metal halide perovskites (MHPs) is of paramount importance for their device application. Here, we demonstrate the femtosecond (fs)-laser-assisted formation of three-dimensional MHP nanocrystal (NC) patterns with strong blue photoluminescence (PL) inside an oxide glass. Our strategy enables the crystallization and erasing of CsPb(Cl/Br)

The three-dimensional (3D) patterning of semiconductors is potentially important for exploring new functionalities and applications in optoelectronics1,2. Here, we show that it is possible to write on demand 3D patterns of perovskite quantum dots (QDs) inside a transparent glass material using a femtosecond laser. By utilizing the inherent ionic nature and low formation energy of perovskite, highly luminescent CsPbBr3 QDs can be reversibly fabricated in situ and decomposed through femtosecond laser irradiation and thermal annealing. This pattern of writing and erasing can be repeated for many cycles, and the luminescent QDs are well protected by the inorganic glass matrix, resulting in stable perovskite QDs with potential applications such as high-capacity optical data storage, information encryption and 3D artwork. Luminescent CsPbBr3 quantum dots can be written into glass using femtosecond laser pulses and thermal annealing, and erased by further femtosecond laser irradiation. The resulting quantum dot patterns could prove useful for data storage, decoration or security purposes.

Carbon quantum dots (CQDs) with multi-color emission are synthesized through hydrothermal method by varying the ratio of citric acid (CA) and urea, the solvent (water, ethyl alcohol, and dimethylformamide), the hydrothermal temperature, and reaction time. The CQDs emit bright fluorescence which can be gradually tuned from blue to red continuously, almost covering the whole visible spectrum. The emission peaks of the CQDs shift from 450 nm to 650 nm with the surface groups and structures changing. Importantly, all solid state CQDs@SiO2 nanophosphors are successfully synthesized by reversed-phase micromulsion method. Based on these solid state phosphors, multi-color CQDs@SiO2 phosphors-based light-emitting diodes (LED) and white light-emitting diode (WLED) with a Commission Internationale de L’ Eclairage (CIE) value of (0.3497, 0.3045) are fabricated in a low-cost, environment-friendly way.

Loess landslides induced by irrigation are common geological disasters in the Loess Plateau, China. Long-term watering decreases the matric suction and soil strength of loess, thus causing the frequent occurrence of landslides. Therefore, studying the strength characteristics of unsaturated loess is of great significance for knowing how such landslides occur and, a step further, preventing them. Undisturbed loess samples in Heifangtai Platform were collected to measure their soil water characteristic curves (SWCC) and a series of direct shear tests and triaxial shear tests were carried out with unsaturated loess. Moreover, the strength characteristics of the loess were discussed. The results showed that in the direct shear test, the cohesion (c) increased linearly with increasing matric suction whereas the suction internal friction angle (φb) was approximately constant. In the triaxial shear test, c increased nonlinearly with increasing matric suction. The value of φb was a constant when matric suction was 0–100 kPa, but decreased as matric suction increased within the range of 100–200 kPa. The effective stress parameter (χ) lay in the range from 0.5 to 0.8. When the matric suction was small, the shear strength calculated by Lu’s suction theory was almost the same as that obtained by Fredlund’s theory. With the increase of matric suction, the shear strength calculated by Fredlund’s theory gradually outperformed that of Lu’s suction theory. The shear strength calculated by the curve of moisture desorption was slightly larger than that of moisture absorption. The variation trends of strength parameters with matric suction under the two tests were similar. The effective internal friction angles obtained by the triaxial shear test are slightly larger than those by the direct shear test. The suction internal friction angle (φb) was approximately a constant and smaller than φ´. The φb obtained by the direct shear test was slightly larger than that obtained by the triaxial test. Lu’s theory can be used to evaluate the stability of unsaturated soils on some loess slopes with high soil moisture content.

The use of a conducting interlayer between separator and cathode is one of the most promising methods to trap lithium polysulfides (LiPSs) for enhancing the performance of lithium-sulfur (Li-S) batteries. Red phosphorus nanoparticles (RP

Graphite-like carbon nitride (g-C3N4) modified with different non-metal ions (boron and sulfur) was synthesized by directly heating a mixture of melamine and dopant with a continuous doping concentration. The effect of the doping ion and its concentration on the structural and optical properties of the samples were investigated in detail. Surprisingly, with the doping concentration increasing, an unexpected relative blue shift was determined in the photoluminescence (PL) spectra of the doped g-C3N4, showing an enhancement in the bandgap which is not in agreement with the typical red shifts in the PL spectra of no-metal ion-doped g-C3N4. To investigate this interesting variation in PL, density functional theory (DFT) has been used and a possible mechanism for the non-metal ion-modified g-C3N4 system was proposed. It is supposed that the blue shift of the non-metal ion-doped g-C3N4 could be mainly attributed to the doping-induced electronic redistribution and structural reconstruction.

Pulsed lasers operating in the mid-infrared (3-25 µm) are increasingly becoming the light source of choice for a wide range of industrial and scientific applications such as spectroscopy, biomedical research, sensing, imaging, and communication. Up to now, one of the factors limiting the mid-infrared pulsed lasers is the lack of optical switch with a capability of pulse generation, especially for those with wideband response. Here, a semiconductor material of bismuth oxyselenide (Bi2 O2 Se) with a facile processibility, constituting an ultrabroadband saturable absorber for the mid-infrared (actually from the near-infrared to mid-infrared: 0.8-5.0 µm) is exhibited. Significantly, it is found that the optical response is associated with a strong nonlinear character, showing picosecond response time and response amplitude up to ≈330.1% at 5.0 µm. Combined with facile processibility and low cost, these solution-processed Bi2 O2 Se materials may offer a scalable and printable mid-infrared optical switch to open up the long-sought parameter space which is crucial for the exploitation of compact and high-performance mid-infrared pulsed laser sources.

More than 40% area of the Xixian New Area is a loess deposit region, and most of the loess landform is tableland and terrace where the thickness of loess is very large. Therefore, loess collapsibility will be the most important geotechnical problem in future foundation investigation and construction. To explore loess collapsibility in the Xixian New Area, we conducted the K0 compression test, based on the collapsibility mechanism, which has different combinations of pressure (0~1.2 MPa) and water content (4%~Sat). Based on the σ-ε curve under different water content, we calculated the generalised collapse settlement and collapsibility coefficient of every water content under every pressure by subtracting the relevant curve from the saturated curve, and analysed the cross action of pressure and water on loess compressibility. The results show that the average collapsibility level of the northern Xixian New Area is self-weight collapsible level Ⅱ, with a lower limit of 14 m. Compressibility of loess is proportional to pressure and water content. Under low water content, the collapsibility coefficient δs increased while the pressure increased, but under medium and high water content, δs will reach peak with increasing pressure and after that, δs will decrease until its value is close to constant. When under the same pressure, δs decreases when water content increases. If set the additional strain 1.5% as collapse start criterion, then the initial collapse pressure Pi will linear proportional to water content. The initial collapse water content wi will increase sharply when pressure increases under low pressure, but wi will reach a constant value of 26% when pressure is larger than 200 kPa. This consequence will be meaningful for future geotechnical investigation and design in the Xixian New Area. Para estimar la colapsabilidad en Xixian se realizó el test de compresión (K0), de acuerdo con el mecanismo de colapsabilidad, con diferentes combinaciones de presión (0~1.2 MPa) y contenido de agua (4%~Sat). Basado en la curva σ-ε con diferentes contenidos de agua se calcularon los coeficientes de asentamiento y colapsabilidad a partir de substracción de la curva en condiciones de saturación y analizando los efectos de presión y contenido de agua. Los resultados muestran que el promedio de colapsabilidad por su propio peso para el área de Xixian es de nivel II, con un límite bajo de hasta 14 m. La compresibilidad de loess es proporcional a la presión y al contenido de agua. Con un bajo contenido de agua, el coeficiente de colapsabilidad (δs) se incrementó mientras la presión se aumentó; pero, con contenidos medios y altos de agua, el coeficiente de colapsabilidad alcanzó su pico con el incremento de la presión, y luego bajó para prácticamente estabilizarse. Bajo presión constante, la colapsabilidad descendió al aumentar el contenido de agua. Si se asume como criterio inicial de colapso (Pi) una deformación adicional de 1.5%, Pi es linealmente proporcional al contenido de agua. El contenido de agua inicial de colapso (wi) se incrementa drásticamente cuando la presión se eleva a baja presión, sin embargo, el contenido de agua alcanza un valor constante de 26 % cuando la presión es de más de 200 kPa. Estos resultados son significativos para la investigación geotécnica y el diseño estructural en Xixian.

In materials showing reverse saturable absorption (RSA), optical transmittance decreases at intense laser irradiation. One approach to application of these materials is to protect the sensors or human eyes from laser damage. To date, research has mainly concentrated on thin films and suspensions of graphite and its nanostructure (including nanotubes, graphene, and graphene oxides), which are mainly used as an optical limiter for nanosecond laser pulses. Moreover, thin individual pieces of semiconductor usually exhibit increased transmittance due to saturable absorption when the laser energy (Elaser ) is higher than the band gap (EB ). Here, it is shown that indirect gap semiconductor WSe2 exhibits high RSA on exposure to a femtosecond laser under Elaser > EB near band gap excitation, which is attributed to the longitudinal optical phonon-assisted anti-Stokes transition by the annihilation of phonons and the absorption of photons. An optical limiting threshold (≈21.6 mJ cm-2 ) lower than those reported for other optical-limiting materials currently for femtosecond laser at 800 nm is observed.

Controlled morphology modulation of graphene carbon nitride (g-C3N4) is successfully realized from bulk to 3D loose foam architecture via the blowing effect of a bubble, which can be controlled by heating rate. The loose foam network is comprised by spatially scaffolded few-atom-layer interconnected flakes with the large specific surface area, as supporters to prevent agglomeration and provide a pathway for electron/phonon transports. The photocatalytic performance of 3D foam strutted g-C3N4 toward RhB decomposition and hydrogen evolution is significantly enhanced with the morphology optimization while its excellent optoelectronic properties are maintained simultaneously. Herein, the ultrathin, mono-, and high-quality foam g-C3N4 interconnected flakes with controlled layer are facilely obtained through ultrasonic, thus overcoming the drawbacks of a traditional top–down approach, opening a wide horizon for diverse practical usages. Additionally, the layer control mechanism of 3D hierarchical structure has been explored by means of bubble growth kinetics analysis and the density functional theory calculations.