干粉浸渍研制玻璃纤维连续增强低密度聚乙烯带材

高强纤维增强材料因其机械性能优良，重量轻被大量用于航天、航空以及日常产品中，本文讨论了玻璃纤维增强低密度聚乙烯（LDPE）的加工及其特性，并得到如下结论：①玻纤增强LDPE带可以用连续干式粉末浸渍法生产；②带材的强度及模量主要取决于带材所含纤维量的多少。

关于倍频绿光问题的研究(英文)

采用双波片晶体的物理模型和Jones矩阵方法 ,得到了在连续多纵模腔内倍频激光器中压缩噪声的必要条件 ,推导出与Ⅱ类和Ⅰ类相位匹配方式相对应的消除和频效应的公式 ,并推广为往返Jones矩阵元所应满足的关系 ,以及相应的腔内本征矢。

水环境与冻融共同作用下混凝土力学性能研究

基于不同pH值水环境下冻融循环对混凝土断裂性能影响的研究现状和发展方向,采用加速腐蚀试验、单轴压缩试验与三点弯曲试验,对在酸碱中性溶液中浸泡、再经不同次数的冻融循环后的混凝土的断裂性能及宏观力学特性进行研究。此外,利用IPP(image-pro plus)软件对由电镜扫描获得的混凝土SEM(scanning electron microscope)图像进行分析,并对损伤劣化规律,以及微观层面混凝土腐蚀及冻害破坏机理等方面进行研究。结果表明:虽然水环境的pH值对冻融前的混凝土各力学性能影响不尽相同,但随着pH值的减小,冻融循环作用对混凝土力学性能的破坏趋于严重。不同pH值溶液浸泡后混凝土试件的内部微观劣化规律相似,损失变量与冻融循环次数存在二次函数关系。由此推导出不同p H溶液下不同冻融循环次数后的损伤变量公式。

Gas exchange of Populus euphratica leaves in a riparian zone

Riparian vegetation belts in arid regions of Central Asia are endangered to lose their ecosystem services due to intensified land use.For the development of sustained land use,management knowledge of plant performance in relation to resource supply is needed.We estimated productivity related functional traits at the edges of the habitat of Populus euphratica Oliv.Specific leaf area （SLA） and carbon/nitrogen （C/N） ratio of P.euphratica leaves growing near a former river bank and close to moving sand dunes in the Ebinur Lake National Nature Reserve in Xinjiang,Northwest China （near Kazakhstan） were determined and daily courses of CO2 net assimilation （PN）,transpiration （E）,and stomatal conductance （gs） of two consecutive seasons were measured during July-August 2007 and June-July 2008.Groundwater level was high （1.5-2.5 m below ground） throughout the years and no flooding occurred at the two tree stands.SLA was slightly lower near the desert than at the former river bank and leaves contained less N in relation to C.Highest E and gs of P.euphratica were reached in the morning before noon on both stands and a second low maximum occurred in the afternoon despite of the unchanged high levels of air to leaf water vapor pressure deficit （ALVPD）.Decline of gs in P.euphratica was followed by decrease of E.Water use efficiency （WUE） of leaves near the desert were higher in the morning and the evening,in contrast to leaves from the former river bank that maintained an almost stable level throughout the day.High light compensation points and high light saturation levels of PN indicated the characteristics of leaves well-adapted to intensive irradiation at both stands.In general,leaves of P.euphratica decreased their gs beyond 20 Pa/kPa ALVPD in order to limit water losses.Decrease of E did not occur in both stands until 40 Pa/kPa ALVPD was reached.Full stomatal closure of P.euphratica was achieved at 60 Pa/kPa ALVPD in both stands.E through the leaf surface amounted up to 30％ of the highest E rates,indicating dependence on water recharge from the ground despite of obviously closed stomata.A distinct leaf surface temperature （Tleaf） threshold of around 30℃ also existed before stomata started to close.Generally,the differences in gas exchange between both stands were small,which led to the conclusion that micro-climatic constraints to E and photosynthesis were not the major factors for declining tree density with increasing distance from the river.

High Delivery Performance Opportunistic Routing Scheme for Delay Tolerant Networks

In Delay Tolerant Networks (DTNs), establishing routing path from a source node to a destination node may not be possible, so the opportunistic routings are widely used. The energy and buffer constraints are general in DTNs composed of the mobile phones or Pads. This paper proposes a novel opportunistic routing protocol, denoted by Large Opporturioty (LAOP), for the energy and buffer constrained DTNs. The objective of LAOP is to reach many receivers of a message with a small number of transmissions. By LAOP, the sender floods a message when the number of its neighbors is not less than a threshold. We compare the delivery performance of LAOP with other four widely used Delay or Disruption Tolerant Network (DTN) routing protocols, Direct Delivery, Epidemic routing, SprayAndWait and PRoPHET and demonstrate that LAOP can improve the delivery performance and decrease the delivery latency simultaneously.

Influence of temperature and pressure during thermoforming of softwood pulp

In this study,the influence of thermoforming conditions on the resulting material properties was investigated,which aimed at developing advanced wood-fiber-based materials for the replacement of fossil plastics.Two bleached softwood pulps were studied,i.e.,northern bleached softwood Kraft pulp(NBSK)and chemi-thermomechanical softwood pulp(CTMP).The thermoforming conditions were varied between 2–100 MPa and 150–200℃,while pressing sheets of 500 g/m^(2)for 10 min to represent thin-walled packaging more closely.As our results showed,the temperature had a more pronounced effect on the CTMP substrates than on the Kraft pulp.This was explained by the greater abundance of lignin and hemicelluloses,while fibrillar dimensions and the fines content may play a role in addition.Moreover,the CTMP exhibited an optimum in terms of tensile strength at intermediate thermoforming pressure.This effect was attributed to two counteracting effects:1)Improved fiber adhesion due to enhanced densification,and 2)embrittlement caused by the loss of extensibility.High temperatures likely softened the lignin,enabling fiber collapse and a tighter packing.For the Kraft substrates,the tensile strength increased linearly with density.Both pulps showed reduced wetting at elevated thermoforming temperature and pressure,which was attributed to hornification and densification effects.Here,the effect of temperature was again more pronounced for CTMP than for the Kraft fibers.It was concluded that the thermoforming temperature and pressure strongly affected the properties of the final material.The chemical composition of the pulps will distinctly affect their response to thermoforming,which could be useful for tailoring cellulose-based replacements for packaging products.