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The photoluminescence experiment was performed at 77 K on two types of heterostructures of In0.52Al0.48As/InP grown by molecular beam epitaxy. One type has the so-called direct interface formed with In0.52Al0.48As grown on the InP (100) substrate, and another is a double heterostructure type, i.e., InP/In0.52Al0.48As/InP, including the inverse interface formed with the InP cap. The thickness of both the as-grown InAlAs and InP layers is 2 µm. Under the excitation of 852 nm semiconductor laser, a single peak at 1.198 eV (P0) was observed for the direct interface whereas the inverse interface showed two peaks at 1.240 eV (P1) and 1.117 eV (P2). However, P2 manifests differently from P1 with two interesting features. First, it disappears when the excitation was replaced with the 532 nm laser. Second, when the cap layer of InP/In0.52Al0.48As/InP is thinned to 200 nm, P2 displays a large blueshift effect with the increase in laser intensity, but the extent of blueshift drops when the excitation is increased further into a higher power range. The phenomenon of P2 was attributed to the interface excitation-induced interplay between the luminescence with a carrier localization effect and that caused by the recombination of 2-dimensional electrons with the light-injected holes in the potential well at the interface.

Byline: Xing. Fang, Hui. Liang A 46-year-old man presented with gait disturbance, generalized stiffness, difficulty in swallowing, and bladder incontinence for the past 15 years. Consanguineous marriage was confirmed among [...]

Natural gas hydrate solid fluidization mining technology is a new hydrate mining technology, but due to the lack of combined nozzle design theory and basis, the crushing efficiency of mining tools is low. To solve this problem, the characteristics of the combined jet flow fields of nozzles with diameters from 1 mm to 4 mm and combination angles from 10° to 20° were studied in this paper by means of experiments and simulations. The results show that the maximum velocity at the merging point increases negatively linearly with increases in the combination angle and positively linearly with increase in the nozzle diameter. The position of the merging point changes little with the nozzle diameter and increases exponentially with increases in the combination angle. The effective crushing lengths of nozzles with different diameters all turn (increase first and then decrease) when the combination angle is 12.5°. The optimal combination angle for nozzles with diameter less than 4.5 mm is 12.5°, and 15° is for nozzles with diameter more than 4.5 mm. This study reveals the flow field variation mechanism for the combined nozzle and provides guidance for the design of the combined nozzles of gas hydrate combined nozzles. [ABSTRACT FROM AUTHOR]

Construction sites rely on erosion control practices to protect bare slopes and prevent soil loss. The effectiveness of certain erosion controls is often under-evaluated if they are not a part of a product evaluation program. Furthermore, erosion controls in general are not fully understood regarding how their performance can be affected by site specific variables, such as soil variations. This study used large-scale rainfall simulators to evaluate how a commonly used erosion control on construction sites, broadcasted straw mulch, performs on three common soil types in Alabama. The study at the Auburn University, Stormwater Research Facility (AU-SRF) used the industry standard testing method and three different soil types: sand, loam, and clay in accordance with ASTM D6459-19, the standard test method for testing rolled erosion control products' (RECPs) performance in protecting hillslopes from rainfall-induced erosion. As required by ASTM D6459-19, the rainfall simulators simulated a storm of varying 20 min increments of 2 in./h (5.08 cm/h), 4 in./h (10.16 cm/h), and 6 in./h (15.24 cm/h). A total of nine bare soil tests on the 4:1 test plots was performed with an average total soil loss of 1977 lb (897 kg), 236.2 lb (107 kg), and 114.2 lb (51.8 kg) for sand, loam, and clay, respectively. The average erodibility K-factor for each soil type is calculated to be 0.37 (sand), 0.043 (loam), and 0.013 (clay). Nine straw tests were performed on the 4:1 plots, with an average total soil loss of 44.31 lb (20.1 kg), 6.74 lb (3.1 kg), and 17.13 lb (7.8 kg) for sand, loam, and clay, respectively. Straw testing indicated substantial soil loss reduction with average cover management C-factor values under the revised universal soil loss equation (RUSLE) method of 0.021, 0.047, and 0.193 for sand, loam, and clay applications, respectively. This variation in C-factor across the three soil types indicates that the single C-factor, often reported by product manufacturers, is not adequate to imply performance. [ABSTRACT FROM AUTHOR]

A visible‐light‐initiated energy‐transfer enabled radical cyclization for the divergent synthesis of polycyclic γ‐sultine derivatives has been developed. The reaction provides an alternative and expeditious access to benzofused γ‐sultine frameworks, the analogues of γ‐lactones and γ‐sultones, and features good functional group compatibility, mild reaction conditions and excellent diastereoselectivity. The robustness and application potential of this method have also been successfully displayed by two gram‐scale reactions and the synthesis of polycyclic sultones. Mechanistic studies indicated the transformations through a possible energy‐transfer enabled intramolecular radical homolytic substitution or hydrogen atom transfer process mainly. [ABSTRACT FROM AUTHOR]

To achieve precise control of the symmetrical unmanned surface vehicle (USV) under strong external disturbances, we propose a disturbance estimation and conditional disturbance compensation control (CDCC) scheme. First, the differential flatness method is applied to convert the underactuated model into a fully actuated one, simplifying the controller design. Then, a nonlinear disturbance observer (NDOB) is designed to estimate the lumped disturbance. Subsequently, a continuous disturbance characterization index (CDCI) is proposed, which not only indicates whether the disturbance is beneficial to the system stability but also makes the controller switch smoothly and suppresses the chattering phenomenon greatly. Indicated by the CDCI, the proposed CDCC method can not only utilize the beneficial disturbance but also compensate for the detrimental disturbance, which improves the USV's control performance under strong external disturbances. Moreover, a trajectory-planning method is designed to generate an obstacle avoidance reference trajectory for the controller. Finally, simulations verify the feasibility of applying the proposed control method to USV. [ABSTRACT FROM AUTHOR]