RESUMO Introdução: O salto em distância é caracterizado por um alto grau de combinação de velocidade e força. Pertence ao grupo de itens de energia rápida dominados pelo condicionamento físico. Para alcançar bons resultados no salto à distância, é necessário ter bom condicionamento físico. Objetivo: A fim de explorar o efeito do treinamento composto de alongamento rápido sobre o poder explosivo dos membros inferiores dos atletas em salto à distância. Métodos: Atletas de uma determinada cidade foram selecionados como objetos de pesquisa do experimento, com um total de 100 pessoas, e foram divididos em grupos por sorteio aleatório, havia 50 pessoas no grupo controle e 50 pessoas no grupo experimental, que receberam treinamento composto de alongamento rápido. Resultados: Após a coleta das amostras independentes, efetuou-se análise estatística com Teste-T, os resultados mostraram confiança de P=0,09, superior a 0,05, indicando que não há diferença significativa no desempenho especial do salto em distância entre os dois grupos de alunos, a pontuação média dos alunos no grupo experimental foi 0,13 metros maiores que a do grupo controle. Conclusões: O rápido treinamento composto de relaxamento e contração pode melhorar efetivamente a qualidade especial nos alunos de salto em distância. Nível de evidência II; Estudos terapêuticos - investigação dos resultados do tratamento.

ABSTRACT Introduction: The long jump is characterized by a high degree of combination of speed and strength. It belongs to the group of fast power items dominated by physical conditioning. To achieve good results in long jump, it is necessary to have good physical conditioning. Objective: In order to explore the effect of compound fast stretch training on the explosive power of lower limbs of athletes in long jump. Methods: Athletes from a certain city were selected as the research objects of the experiment, with a total of 100 people, and were divided into groups by random drawing, there were 50 people in the control group and 50 people in the experimental group, who received rapid stretching compound training. Results: After collecting the independent samples, statistical analysis was performed with T-test, the results showed confidence of P=0.09, higher than 0.05, indicating that there is no significant difference in the special performance of long jump between the two groups of students, the mean score of students in the experimental group was 0.13 meters higher than the control group. Conclusions: Rapid training composed of relaxation and contraction can effectively improve the special quality in long jump students. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

RESUMEN Introducción: El salto de longitud se caracteriza por un alto grado de combinación de velocidad y fuerza. Pertenece al grupo de ítems de potencia rápida dominados por el acondicionamiento físico. Para conseguir buenos resultados en salto de longitud, es necesario tener una buena condición física. Objetivo: Explorar el efecto del entrenamiento de estiramiento rápido compuesto sobre la potencia explosiva de los miembros inferiores de los atletas en salto de longitud. Métodos: Se seleccionaron atletas de una determinada ciudad como objetos de investigación del experimento, con un total de 100 personas, y se dividieron en grupos por sorteo, había 50 personas en el grupo de control y 50 personas en el grupo experimental, que recibieron un entrenamiento de estiramiento rápido compuesto. Resultados: Después de recoger las muestras independientes, se realizó el análisis estadístico con la prueba T, los resultados mostraron una confianza de P=0,09, superior a 0,05, lo que indica que no hay diferencias significativas en el rendimiento especial de salto de longitud entre los dos grupos de alumnos, la puntuación media de los alumnos del grupo experimental fue 0,13 metros superior a la del grupo de control. Conclusiones: El entrenamiento rápido compuesto de relajación y contracción puede mejorar eficazmente la calidad especial en los alumnos de salto de longitud. Nivel de evidencia II; Estudios terapéuticos - investigación de los resultados del tratamiento.

Abstract: Due to the advantages of short treatment period, no wastewater and oil produced, the CO2 laser is applied as an environment friendly thermal treatment for wood materials to improve the wood properties, such as appearance, color and wettability, among others. However, the morphological features of treated wood surface are also changed, which have negative effects on wooden product properties. To reveal the change tendency of surface roughness during laser irradiation, the common indexes of average roughness (Ra) and mean peak-to-valley height (Rz) were chosen to evaluate the surface roughness. The response surface methodology was selected to arrange the experiments and analyze the influences of laser parameters on surface roughness. The results showed that the poplar wood got rougher with the increased laser power, but the surface roughness decreased with increased feed speed and path spacing, due to the total heat absorption varied under different combination of laser parameters. The ANOVA results showed that the selected quadratic models for Ra∥, Rz∥, Ra⊥and Rz⊥were significant due to the values of probability value (“Prob>F”) less than 0,05. In this case, all the input laser parameters were also the significant model terms for variation of surface roughness. The values of correlation coefficient were very close to 1, which meant the selected quadratic models could give accurate prediction of surface roughness for laser treated wood. Therefore, it is of great significance to predict the surface roughness of the modified wood surface scientifically and to guide the selection of reasonable modification process parameters.

Abstract The silicon carbide (SiC)/metal composite armors with the composite cover on the front of the SiC plate were impacted by 12.7mm armor piercing incendiary (API) projectiles at velocities from 412.6m/s to 802.2m/s. The resulting projectile core and ceramic fragments were collected and then screened through a range of standard sieving screens. The mass distributions of fragments produced by projectile and ceramic impacting each other were obtained. The failure mechanism of the rigid-brittle core of 12.7mm API projectile after impacting SiC/metal composite armor was studied by examination of the failed core. The results show that the cumulative mass of core and ceramic fragments follow the Schuhmann distribution law. With the increase of impact velocity, the mass proportion of small core fragments increases, while for ceramic fragments, the mass proportion of fragments in different fractions does not change. The failure mechanism of the large equivalent diameter fragment ( >8mm) is tensile brittle fracture mainly. In contrast, the local plastic shear fracture exists on the fragments with an equivalent diameter of less than 2mm.

Abstract In order to study the critical ricochet velocity and critical penetration velocity of tungsten alloy rod obliquely penetrating a finite-thickness metal plate, experiment and numerical calculation of tungsten alloy rod impacting on homogeneous armor steel plate with a thickness of 30mm at an angle of 60° were carried out. Compared the experimental and numerical results with the results using models, it is found that, the results of the ricochet models proposed by Tate, Rosenberg and Steven B for semi-infinite thick plate are quite different from those of experiment and numerical calculation, so they can not be applied to the ricochet situation of finite-thickness plate. The critical penetration velocity model proposed by De Marre and Zhao are in good agreement with the numerical and experimental results, which can predict critical penetration velocity of tungsten alloy rod obliquely penetrating a finite-thickness metal plate with large impact angle. The penetration depth of the projectile under the critical ricochet velocity is about 1/3 of the thickness of the target plate, and the angle between the ejection trajectory of the fragments produced by projectile and target plate and projectile penetration trajectory is exactly 90° in the first penetration stage.

Abstract Purpose: To investigate the effects of exenatide on renal injury in streptozotocin-induced diabetic rats. Methods: Fifty SD rats were randomly divided into normal control, model, exenatide-1, exenatide-2 and exenatide-3 groups, 10 rats in each group. The diabetic nephropathy model was constructed in later 4 groups. Then, the later 3 groups were treated with 2, 4 and 8 μg/kg exenatide for 8 weeks, respectively. The serum and urine biochemical indexes and oxidative stress and inflammatory indexes in renal tissue were determined. Results: Compared to the model group, in exenatide-3 group the serum fasting plasma glucose and hemoglobin A1c levels were significantly decreased, the fasting insulin level was significantly increased, the renal index and blood urea nitrogen, serum creatinine and 24 h urine protein levels were significantly decreased, the renal tissue superoxide dismutase and glutathione peroxidase levels were significantly increased, the malondialdehyde level was significantly decreased, and the renal tissue tumor necrosis factor alpha, interleukin 6, hypersensitive C-reactive protein and chemokine (C-C motif) ligand 5 levels were significantly decreased P<0.05). Conclusions: Exenatide can mitigate the renal injury in diabetic rats. The mechanisms may be related to its resistance of oxidative stress and inflammatory response in renal tissue.