N2和O2冷等离子体处理对木材胶合强度的影响

采用N2、O2两种等离子体气体分别处理木材,处理功率为300 W,处理时间为5 min,将处理后的木材采用MUF胶粘合起来,测试了胶合强度,并对冷等离子体处理前后的木材表面能进行了分析。实验结果表明:经N2、O2冷等离子体处理后的木材表面的接触角明显减小,表面自由能明显增大;经冷等离子体处理后的胶合板的平均干状胶合强度和湿状强度均有明显(50%以上)增大。     

混合菌降解土壤中多环芳烃的试验研究

PAHs生物降解程度受多种因素影响。通过筛选驯化PAHs降解菌,研究混合菌对土壤中菲、芘、苯并（a）蒽、苯并（b）荧蒽、苯并（k）荧蒽、茚并（1,2,3-cd）芘的生物降解性能,并考察污染时间对土壤中PAHs降解效果的影响。结果表明,筛选的混合菌具有很强的PAHs降解能力,缩短了PAHs生物降解的半衰期,且PAHs起始降解速率较快,之后趋于平缓。27d内土壤中的菲、芘、苯并（a）蒽、苯并（b）荧蒽、苯并（k）荧蒽、茚并（1,2,3-cd）芘的平均降解率分别为98.14%、89.97%、88.47%、63.55%、65.24%、60.49%,其中菲在5d之内的降解率高于93%。污染210d的土壤中各PAHs的起始降解速率高于污染50d的土壤,因此污染时间越长,PAHs生物降解的停滞期越短。     

美国路易斯安那州铁矿石土壤薄层磐层的表征特性

Placic horizons, defined as thin, wavy, hardened layers of iron and organic matter, are rare within the United States, occurring only in Washington, Alaska, and Hawaii. While ironstone is common in many soils of the southeastern United States, it is not known to contain appreciable organic matter. As a pilot study evaluating the justification for a larger study on ironstone in Louisiana, a 40 m lateral exposure with suspected placic horizons was evaluated in Vernon Parish, Louisiana. Results of laboratory analysis show elevated levels of iron and organic matter in the suspect horizons that meet the criteria of placic horizons as defined by the Soil Survey Staff. Based on the results of this study, additional evaluation of multiple pedons with similar features is warranted. Should additional pedons demonstrate similar properties, a new great group of ‘Petrudepts’ would be needed to describe both the placic horizons in the pedon and the udic moisture regime in which they occur.     

Experiments on heat loss characteristics in a fully opened cylindrical cavity receiver

The climate has a great impact on highway bridge rubber bearings than on building rubber bearings. In order to study the change of the mechanical properties during the life of the plain chloroprene rubber bearings of highway bridge under freeze-thaw cycle condition, the plain chloroprene rubber bearings were processed 25, 50, 75, 100 times by freeze-thaw cycle in the standard freeze-thaw chamber, then the axial compression tests were carried. The changes of the performance indicators in the bearing capacity , the ultimate compressive strength, vertical stiffness, elastic modulus under different freeze-thaw cycles were analyzed comparatively. The results show that the plain chloroprene rubber bearings are more prone to brittle failure after the freeze-thaw cycle, and the failure phenomena of steel plate exposing or cracks is more serious than the phenomena of the standard specimen. With the increase of the number of freeze-thaw cycle, the ultimate bearing capacity, ultimate compressive strength and compressive elastic modulus of the plain chloroprene rubber bearings decrease. The attenuation formula and decay curve in 50 years of ultimate compressive strength and elastic modulus of compression are analyzed by least square method, the trends of change are both in line with the exponential function. The mechanical properties of plain chloroprene rubber bearings of highway bridge significantly decreased under freeze-thaw cycle condition. therefore, the temperature ranges of plain chloroprene rubber bearings of highway bridge should be strictly controlled, and some suggestions, such as increasing its minimum applicable temperature, usng the natural rubber bearings as much as possible in cold regions, have been given.     

Solving Method for Soil Spring Stiffness of Shallow Shield Tunneling

Based on complex variable theory in plane elasticity, the equivalent spring stiffness is derived from the analytical solution by means of simplifying shallow shield tunneling to semi-infinite plane with hole, which is applied to response displacement method. The performances of the analytical solution are evaluated and compared with that of the deep shield tunneling through a series of selected various tunnel depths and soil Poisson's ratios. The relation of compression and shear spring stiffness is discussed. Meanwhile, two factors affected soil spring stiffness, tunnel depth and soil Poisson's ratio, are also analyzed. It is shown that soil spring stiffness of shallow shield tunneling is different from that of deep shield tunneling, and the ratio of compression and shear spring stiffness varies along shallow shield tunneling. It is also found that the value and distribution law of soil spring stiffness of shallow shield tunneling greatly depend on tunnel depth and soil Poisson's ratio.     

Induction of parturition in the sow with a prostaglandin analogue (I.C.I. 80996)

Summary

Parturition was induced in 112 gilts and sows on day 111, 112, and 113 of gestation by means of a single intramuscular injection of 175 mcg of a prostaglandin F2α analogue (Cloprostenol, I.C.I. 80996). No side effects were detected immediately after injection and the course of the induced parturition was normal. The interval between injection and parturition was approximately 28 hours. Induction of parturition on day 113 resulted in a significant shortening of this interval as compared with day 111 and 112. The average weights of the piglets at birth and at 5 weeks were within the normal range. The percentage of stillbirths and the loss of piglets up to weaning did not differ significantly between control and experimental groups. The practical applications of induction of parturition are discussed.     

Stiffness moduli of various softwood and hardwood species determined with ultrasound

Abstract

Comprehensive data sets of the elastic constants are available for only a few European wood species. The goal of this study was to provide stiffnesses for the principal directions and planes for further selected European softwoods and hardwoods, to extend the currently existing data sets. For this purpose, a dynamic technique was chosen: the moduli were estimated on the basis of sound velocity and density measurements. The collected data may be helpful for specialists in the relevant research and practical fields, particularly when stresses and strains of structural elements have to be calculated using modelling approaches.     

竹缠绕复合管环刚度测试试验

测试了竹缠绕复合管母管的环刚度值,与母管承插连接后的环刚度值,以及母管与束节连接后的环刚度值。结果表明：DN 600管承插连接后的环刚度值为承口和插口环刚度值之和的97.3%;DN 600和DN 1 000管束节连接后环刚度值分别为束节和母管环刚度值之和的116%和107%。试验结果可为优化竹缠绕复合管的连接结构提供参考。     

渐开线齿轮重合度与双齿啮合刍议

重合度是衡量齿轮传动平稳性和承载能力的一个重要指标,可反映在啮合过程中双齿啮合的比例。本文对齿轮啮合过程进行解析,阐述齿轮的双齿啮合比概念,并解析了齿轮的双齿啮合比的计算式,介绍并纠正学生在理解双齿啮合过程时的一个误区。