ABSTRACT >To quantitatively evaluate the effect of stubble height and mulching on soil resistance to wind erosion in protected cultivated chestnut soil farmland under different wind speed conditions, tests were carried out on conservation and conventional tillage in Mongolian Plateau, China, using a mobile wind erosion wind tunnel. Chestnut soils were a soil type in fragile semi-arid ecosystems that were susceptible to desertification following wind erosion and were found mainly in Central Asia and the North American continent. The results show that soil erosion on conservation tillage was lower than conventional tillage at different wind speeds. The resistance of conservation tillage to soil wind erosion increases with increasing stubble height and cover. At a stubble height of 300 mm and 50% cover, conservation tillage's average wind erosion resistance efficiency was 74.82%, effectively preventing wind erosion of agricultural soils.

Resumo Para avaliar quantitativamente o efeito da altura do restolho e da cobertura morta na resistência do solo à erosão do vento em terras cultivadas protegidas de castanheiros sob diferentes condições de velocidade do vento, foram realizados testes de conservação e lavoura convencional no planalto da Mongólia, China, utilizando um túnel móvel de vento de erosão do vento. Os solos de castanha são um tipo de solo em ecossistemas semi-áridos frágeis que são suscetíveis à desertificação após a erosão pelo vento e são encontrados principalmente na Ásia Central e no continente norte-americano. Os resultados mostram que a erosão do solo na lavoura de conservação é menor do que a lavoura convencional em diferentes velocidades de vento. A resistência da lavoura de conservação à erosão do solo pelo vento aumenta com o aumento da altura do restolho e da cobertura. Com uma altura do restolho de 300 mm e uma cobertura de 50%, a eficiência média de resistência da lavoura de conservação à erosão pelo vento é de 74,82%, evitando efetivamente a erosão pelo vento dos solos agrícolas.

Abstract Rice protein is a protein with high nutritional value and its essential amino acids are complete. Rice protein content is related to the Nutritional value of rice powder mixture. Three-dimensional synchronous fluorescence spectroscopy combined with Parallel factor analysis (PARAFAC) and Partial least squares (PLS) was applied for Protein content in rice starch. Synchronous Fluorescence Spectroscopy were obtained at 250-400 nm (excitation) and 260-750 nm (wave-length deviation). Firstly, data of Rice starch were collected using synchronous fluorescence spectroscopy equipment and the protein content of samples were got by Dumas Nitrogen analyzer ; secondly, three improved PLS methods, including interval partial least squares (iPLS), backward interval partial least squares (biPLS) and synergy interval partial least squares (siPLS),were used to find the most informative range. Lastly, models with better predictive turbidity of fragrance vinegar using PLS was established in the whole wavelength range .The results showed that the models by siPLS method, which separated the whole spectra into 10 intervals, and combine four intervals of [1 3 4 5]had the best predictive ability, the RMSECV and RMSEP were 0.1482 and 0.1696, and the calibration and prediction correlation coefficient were 0.8513 and 0.8236. Using three-dimensional synchronous fluorescence spectroscopy for rapid detection of Protein content in rice starch was feasible.

RESUMO Para construir um modelo de simulação acoplada da erosão eólica do solo e fluxo bifásico em regiões áridas e semi-áridas, os parâmetros de contato apropriados do modelo de simulação de elementos discretos do solo são obtidos com base no teste de calibração do ângulo de repouso (AoR). O modelo de simulação acoplado foi estabelecido através da combinação da dinâmica computacional dos fluidos. O valor de resposta da velocidade do vento de iniciação da areia foi usado para verificar a precisão do modelo. Devido às características dos solos áridos e semi-áridos, este trabalho usa o modelo de contato Hertz-Mindlin com JKR no software EDEM para calibrar os parâmetros do solo com base nos testes físicos do solo, e projeta o Plackett-Burman, a subida mais íngreme, e os testes Box-Behnken de acordo com o software Design-Expert para obter a regressão de segunda ordem do AoR do solo. Com o AoR 33,52° como alvo, obtém-se a melhor combinação de parâmetros: recuperação de colisão solo-solo 0,64, coeficiente de atrito estático solo-aço 0,31, energia de superfície JKR 3,302 J m-2. Finalmente, usando parâmetros calibrados e a velocidade do vento inicial como valor de resposta, o teste de fluxo de ar e vento sólido de duas fases foi conduzido em ANSYS Fluent e EDEM, com o erro relativo entre a velocidade do vento inicial registrada pela câmera de alta velocidade no teste de túnel de vento e a velocidade do vento inicial mostrada no modelo de simulação calculada em 8,7%, e os parâmetros calibrados do solo atenderam aos requisitos da simulação acoplada. Os resultados da simulação indicam que os parâmetros de calibração do solo podem ser utilizados para modelar a erosão do vento em duas fases do solo em ambientes semi-áridos.

ABSTRACT To construct a coupled simulation model of soil wind erosion and two-phase flow in arid and semiarid regions, the proper contact parameters of the soil discrete element simulation model are obtained based on the angle of repose (AoR) calibration test. The coupled simulation model is established by combining computational fluid dynamics. The response value of the wind speed of sand initiation is used to verify the model’s accuracy. Due to the characteristics of arid and semiarid soils, this paper uses the Hertz-Mindlin with JKR contact model in EDEM software to calibrate the soil parameters based on soil physical tests and designs the Plackett-Burman, steepest climb, and Box-Behnken tests according to Design-Expert software to obtain the soil AoR second-order regression. With the AoR of 33.52° as the target, the best combination of parameters is obtained: soil-soil collision recovery of 0.64, soil-steel static friction coefficient of 0.31, JKR surface energy of 3.302 J m-2. Finally, by using calibrated parameters and the threshold wind velocity as the response value, the wind-sand air-solid two-phase flow test is conducted in ANSYS Fluent and EDEM, with the relative error between the starting wind speed recorded by the high-speed camera in the wind tunnel test and the threshold wind velocity shown in the simulation model calculated to be 8.7%, and the calibrated soil parameters met the requirements of the coupled simulation.

Abstract To better understand the penetration mechanism of the elliptical cross-section projectile (ECSP) into semi-infinite concrete target, penetration experiments using three types of ECSPs with different shape ratios (1, 1.25 and 1.61) and with striking velocities ranged from 550 m/s to 1050 m/s were conducted. Penetration depths, penetration trajectory and mass erosion rates of the projectile were obtained after the experiments. The experiment results show that the penetration performance and ballistic stability of the ECSP are equivalent to those of the circular cross-section projectile (CCSP). Based on the theory of complex variable function and conformal transformation, a semi-analytical model which can calculate the cavity boundary stress distribution of elliptical section cavity controlled by the displacement boundary condition was established and the model was validated by comparing the model degenerate solution with Kirsch problem results. Theoretical calculation results show that the radial stress of elliptical section cavity increases progressively from the minor axis to the major axis. In addition, a formula combining with the semi-analytical theoretical model and the local interaction theory was developed. The predicted penetration depths were compared with 30 groups of experiment data with different projectile parameters and striking velocities and coincide quite well with the corresponding experimental data. Finally, the influence of shape ratio and caliber-radius-head (CRH) on the penetration performance of projectile and the application prospect of ECSPs on hypersonic weapon platform were studied.

The novel coronavirus pneumonia (NCP) outbreak occurred in Wuhan, China at the end of 2019. Here, we report the clinical characteristics and therapeutic procedure for a case of severe NCP. The patient was started on glucocorticoids and non-invasive ventilator treatment. After treatment, the patient’s symptoms improved, and the status was confirmed as NCP negative. Our results may provide clues for the treatment of NCP.

Abstract The novel coronavirus pneumonia (NCP) outbreak occurred in Wuhan, China at the end of 2019. Here, we report the clinical characteristics and therapeutic procedure for a case of severe NCP. The patient was started on glucocorticoids and non-invasive ventilator treatment. After treatment, the patient’s symptoms improved, and the status was confirmed as NCP negative. Our results may provide clues for the treatment of NCP.

ABSTRACT Objective: To evaluate the influence of sub-minimum inhibitory concentrations (MICs) of ciprofloxacin (CIP) on biofilm formation and virulence factors of Escherichia coli clinical isolates. Methods: Sub-MICs of CIP were determined using growth curve experiments. The biofilm-forming capacity of E. coli clinical isolates and E. coli ATCC 25922 treated or untreated with sub-MICs of CIP was assessed using a crystal violet staining assay. The biofilm structure of E. coli isolate was assessed with scanning electron microscopy (SEM). The expression levels of the virulence genes fim, usp, and iron and the biofilm formation genes of the pgaABCD locus were measured using quantification RT-PCR (qRT-PCR) in E. coli isolates and E. coli ATCC 25922. Results: Based on our results, the sub-MICs of CIP were 1/4 MICs. Sub-MICs of CIP significantly inhibited biofilm formation of E. coli clinical isolates and E. coli ATCC 25922 (p < 0.01). SEM analyses indicated that the biofilm structure of the E. coli changed significantly after treatment with sub-MICs of CIP. Expression levels of the virulence genes fim, usp, and iron and the biofilm formation genes of the pgaABCD locus were also suppressed. Conclusions: The results revealed that treatment with sub-MICs of CIP for 24 h inhibited biofilm formation and reduced the expression of virulence genes and biofilm formation genes in E. coli.