不同材料弹体超声速侵彻钢筋混凝土靶的结构破坏对比实验

设计了超声速钻地结构弹,采用203 mm口径的火炮,开展了25 kg量级弹体在1100~1300 m/s速度范围内侵彻钢筋混凝土靶的实验研究,应用数值仿真对弹体侵彻钢筋混凝土靶的过程进行了模拟计算。基于实验和仿真结果,对超声速侵彻条件下两种金属材料弹体的结构响应、质量损失等问题进行了分析。结果表明:在超声速侵彻钢筋混凝土靶的过程中,两种金属材料的弹体结构变形破坏形式主要为头部侵蚀和侧壁磨蚀,头部侵蚀量的大小与弹体壳体材料有关,高强度G50钢材料更适合用于1200 m/s速度量级的超声速侵彻环境。对出现的“径缩”现象作了初步分析,并对今后工程应用的结构弹体设计提出了指导意见。     

A novel rigid wheel for agricultural machinery applicable to paddy field with muddy soil

The working performance of agricultural machinery is largely determined by the walking performance of the wheel when driving in complex unstructured soil. However, the driving performance of existing wheels is not satisfactory for paddy field with muddy soil. The purpose of the current study is therefore to propose a novel rigid wheel for agricultural machinery which is applicable to paddy field with muddy soil. Firstly, a novel arc edge shaped wheel was designed based on the principles of mechanics on the ground. Then the driving performance of this arc edge shaped wheel was evaluated using FE modeling of interaction between rigid wheel and soil. Finally, the structure originally designed arc edge shaped wheel was improved according to FE modeling results, and this improved design was further evaluated by both FE simulation and prototype experiments. Both FE modeling and experimental results indicate that the improved arc edge shaped wheel proposed in this study has a good driving performance with regarding to wheel sinkage and soil reaction force. The proposed arc edge shaped wheel could be used as an effective component of rice harvester for paddy field with muddy soil.     

石墨炉原子吸收法测定土壤中铅、镉、钴、锑、铍

建立石墨炉原子吸收法测定土壤中铅、镉、钴、锑、铍含量的方法。优化了石墨炉原子吸收光谱法测定条件,在最佳实验条件下,采用硝酸-盐酸-氢氟酸-双氧水混合酸体系微波消解土壤样品,选用抗坏血酸-硝酸镁混合溶液为基体改进剂。铅、镉、钴、锑、铍的质量浓度在各自的范围内与吸光度成良好的线性关系,相关系数均大于0.999,各元素的检出限为0.008~0.06 μg/g。样品加标回收率为90.5%~104.0%,测定结果的相对标准偏差均小于2.5%(n=6)。该方法样品前处理简便,灵敏度高,检出限低,测定结果准确、可靠,可用于土壤中铅、镉、钴、锑、铍的测定。     

Cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction and HPLC–DAD analysis of ezetimibe and simvastatin in human plasma and urine

A new cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction (CA–HF–SLPME) followed by high‐performance liquid chromatography–diode array detection (HPLC–DAD) method was developed for simultaneous determination of ezetimibe and simvastatin in human plasma and urine samples. To prepare the CA–HF–SLPME device, the cetyl‐alcohol was immobilized into the pores of a 2.5 cm hollow fiber micro‐tube and the lumen of the micro‐tube was filled with 1‐octanol with the two ends sealed. Afterwards, the prepared device was introduced into 10 mL of the sample solution containing the analytes with agitation. Under optimized conditions, calibration curves plotted in spiked plasma and urine samples were linear in the ranges of 0.363–25/0.49–25 μg L^?1 for ezetimibe/simvastatin and 0.193–25/0.312–25 μg L^?1 for ezetimibe/simvastatin in plasma and urine samples, respectively. The limit of detection was 0.109/0.174 μg L^?1 for ezetimibe/simvastatin in plasma and 0.058/0.093 μg L^?1 for ezetimibe/simvastatin in urine. As a potential application, the proposed method was applied to determine the concentration of selected analytes in patient plasma and urine samples after medication and satisfactory results were achieved. In comparison with reference methods, the CA–HF–SLPME–HPLC–DAD method demonstrates considerable potential in the biopharmaceutical analysis of selected drugs.     

Dissipation,residue, and distribution of pyraclostrobin in banana and soil under field conditions in South China

Two independent field trials were conducted in Guangdong and Guangxi, South China, in 2013, to study the dissipation, residue levels, and distribution of pyraclostrobin in banana and soil under field conditions. Pyraclostrobin residues were determined through a quick and effective method of high-performance liquid chromatography. Results showed that the average recoveries ranged from 80.55% to 98.08%, with relative standard deviations of 3.18–7.81% at three different spiking levels for each different matrix. The quantification limit of the proposed method was 0.006 mg/kg for both banana and soil. The half-lives of pyraclostrobin in bananas were 9.09 days in Guangdong and 8.26 days in Guangxi, and both bananas exhibited a dissipation rate of 90% after 28 days. The half-lives of pyraclostrobin in soil were 11.61 days in Guangdong and 10.60 days in Guangxi, with a dissipation rate of 90% after 35 days. Although several positive banana samples (i.e., pyraclostrobin exceeding the maximum residue limits (MRL) were found, the terminal residues in banana pulp were not detectable. All the terminal residues in banana pulp were below the MRL of 0.02 mg/kg, set by the Chinese Ministry of Agriculture, indicating a negligible risk associated with the exposure to pyraclostrobin via the consumption of banana. The distribution of pyraclostrobin in soil was also investigated in two experimental sites. The pyraclostrobin in different layer soil was time dependent and did not vary between the two sites. The result also showed that pyraclostrobin could be easily transported from the top soil to the subsoil. However, the highest quantity ratio did not exceed 10% in the bottom layer (20–30 cm). The distribution assessment also revealed that no significant potential environment risk was induced by pyraclostrobin in bananas.     

Environmental radioactivity of soils and sediments: Egyptian sector of the Nile valley

The activity concentrations of natural ⁴⁰K, ²³²Th, and ²³⁸U in 89 soil and 84 sediment samples collected over the entire Egyptian Nile River basin including the Nile delta are reported based on the results of epithermal neutron activation analysis. The average activity concentrations of ⁴⁰K, ²³²Th, and ²³⁸U equal to 15.3?±?6.6, 15.6?±?11.1 and 220?±?31 Bq/kg, respectively, are significantly lower than those reported for the Upper Continental Crust, World Average Sediments as well as World Average Soils, suggesting the presence of a considerable portion of mafic material, most probably originating from the Ethiopian High Plateau. Their average activity concentrations are statistically the same in soil and sediments, indicating that the Nile sediments and soil material are of the same origin. The main goal of this study was not only to estimate the radiological hazards but also to show the influence of sedimentary material transportable by the Blue Nile from the Ethiopian High Plateau. The different hazard indices like the radium equivalent, gamma index, external hazard as well as the internal hazard show a low radiological exposure either on direct contact or if local mud bricks are used in the construction of dwellings.     

A preliminary approach of dynamic identification of slender buildings by neuronal networks

The study of the dynamic behavior of slender masonry structures is usually related to the preservation of the historic heritage. This study, for bell towers and industrial masonry chimneys, is particularly relevant in areas with an important seismic hazard. The analysis of the dynamic behavior of masonry structures is particularly complex due to the multiple effects that can affect the variation of its main frequencies along the seasons of the year: temperature and humidity. Moreover, these dynamic properties also vary considerably in structures built in areas where land subsidence due to the variation of the phreatic level along the year is particularly evident: the stiffness of the soil–structure interaction also varies. This paper presents a study to evaluate the possibility of detecting the variation of groundwater level based on the readings obtained using accelerometers in different positions on the structure. To do this a general case study was considered: a 3D numerical model of a bellower. The variation of the phreatic level was evaluated between 0 and −20 m, and 81 cases studies were developed modifying the rigidity of the soil–structure interaction associated to a position of the phreatic level. To simulate the dispositions of accelerometers on a real construction, 16 points of the numerical model were selected along the structure to obtain modal displacements in two orthogonal directions. Through an adjustment by using neural networks, a good correlation has been observed between the predicted position of the water table and acceleration readings obtained from the numerical model. It is possible to conclude that with a discrete register of accelerations on the tower it is possible to predict the water table depth.     

COUPLING EFFECTS OF VOID SHAPE AND VOID SIZE ON THE GROWTH OF AN ELLIPTIC VOID IN A FIBER-REINFORCED HYPER-ELASTIC THIN PLATE

The growth of a prolate or oblate elliptic micro-void in a fiber reinforced anisotropic incompressible hyper-elastic rectangular thin plate subjected to uniaxial extensions is studied within the framework of finite elasticity. Coupling effects of void shape and void size on the growth of the void are paid special attention to. The deformation function of the plate with an isolated elliptic void is given, which is expressed by two parameters to solve the differential equation. The solution is approximately obtained from the minimum potential energy principle. Deformation curves for the void with a wide range of void aspect ratios and the stress distributions on the surface of the void have been obtained by numerical computation. The growth behavior of the void and the characteristics of stress distributions on the surface of the void are captured. The combined effects of void size and void shape on the growth of the void in the thin plate are discussed. The maximum stresses for the void with different sizes and different void aspect ratios are compared.     

Symbiotic N2 Fixation and N Uptake of Yellow and White Lupines Influenced by Spontaneous Rhizobia Infection and Substrate

Abstract

By using soil as substrate, white and yellow lupines (Lupinus albus L., Lupinus luteus L.) assimilated higher N amounts than under quartz sand conditions. This was caused by spontaneous infection of lupines with wild Rhizobia strains and also by an additional N uptake from the soil. In yellow lupines without inoculation in non-sterile soil, only the additional N uptake played a role. Differences in P and K supply as the cause of different N acquisition from soil and quartz sand could be excluded. As compared with white lupines, yellow lupines inoculated with Rhizobia had a high N₂ fixation that exceeded the effect of spontaneous infections. This result as well as the positive effect of spontaneous infections with soil-borne Rhizobia on white lupines indicates insufficient effectiveness of the strains used for inoculation on this plant species.     

Nuklearpharmaka — Ihre Entwicklung,Präparation und Anwendungsmöglichkeiten

Radioaktiv markierte Präparate haben in denletzten Jahren in schnell zunehmendem Maße Eingang in die klinische Medizin gefunden. Sie sind beieiner Reihe von Indikationen schon jetzt außerordentlich wertvolle Hilfsmittel bei der Diagnose, besonders bei der Prüfung von Organfunktionen.