天然产物在缓催释肥料中的应用

综述了国内外几种天然产物松香、腐殖酸、木质素、多聚糖、植物油、天然橡胶在缓／控释肥料中的应用情况，着重介绍了这几种天然产物在包膜肥料中的应用现状。     

Growth of lithium doped silver niobate single crystals and their piezoelectric properties

Lithium doped silver niobate (Ag_1−xLi_xNbO₃, 0 < x < 0.1) is one of the candidate materials for lead-free piezoelectric materials. In this study, Ag_1−xLi_xNbO₃ single crystals were successfully grown by a slow cooling method. Crystal structure was assigned to perovskite-type orthorhombic (monoclinic) phase. Dielectric properties were measured as a function of temperature. As a result, with increasing lithium contents, the phase transition at around 60 °C was shifted to lower temperature while the phase transition at around 400 °C was shifted to higher temperature. On the basis of these peak shifts, the lithium contents in Ag_1−xLi_xNbO₃ single crystals were determined. Moreover, P–E hysteresis measurement revealed that pure silver niobate crystal was weak ferroelectrics with P_r of 0.095 μC/cm² while Ag_0.9Li_0.1NbO₃ (ALN10) crystal was normal ferroelectrics with P_r of 10.68 μC/cm². About this ALN10 crystal, polling treatment was performed and finally piezoelectric properties were measured. As a result, high electromechanical coupling coefficient k₃₁ over 70% was observed.     

缓释肥在茶花上的应用研究

通过盆栽试验 ,研究了缓释肥对茶花的效应。结果表明 ,缓释肥可明显促进茶花苗木生长 ,与普通肥相比 ,生物量增加 183 %。同时 ,叶片的叶绿素含量增加 ,叶色浓绿 ,鲜艳 ,观赏性和商品价值提高。肥料氮利用率提高 ,施肥后 9个月 ,土壤中仍有较多的氮残留量。     

浅谈internet访问缓慢的原因与解决方法

随着internet的发展速度日益加快,通过使用internet电子商务业务,网上冲浪,网上游戏,资料查询变得越来越方便,internet是目前世界上最大的计算机互连网络,提供有丰富的信息和资源,使用它所提供的服务,使得企业与外界的联系变得简单、方便、准确、高效。它最大的优势之一就是使用便捷,入网用户不必具备计算机网络的专门知识,便可在网上自由翱翔在使用,在使用internet的同时,人们对internet的访问速度,下载速度要求变得越来越高,本文对影响到internet访问速度的原因及解决方法进行详细说明。     

绿色交通理念下的城市平面交叉口慢行一体化规划方法研究

慢行交通是城市规划提倡的低碳、环保的绿色交通出行方式,可实现居民的短距离出行和接驳公共交通。城市平面交叉口是城市道路交通的关键节点,本文从地面慢行系统一体化、行人过街安全岛规划、公交站台一体化等方面入手,提出城市平面交叉口慢行一体化的规划,以满足交叉口慢行交通的通行需求,实现机非分离,保障慢行者的出行安全。     

Inhibition of stress corrosion cracking of alloy AA8090 T-8171 by addition of rare earth salts

Aluminium-lithium alloys are suitable for aeronautical purposes because of their good mechanical properties and high damage tolerance. Although these alloys are less susceptible to stress corrosion cracking than conventional alloys, Al-Li-Cu-Mg alloy (8090-T8171) still experiences this problem in a NaCl + H₂O₂ solution.In this work it has been demonstrated that the addition of 10,000 ppm of CeCl₃ to the medium inhibits the stress corrosion cracking of 8090 alloy by precipitation of cerium oxides/hydroxides. The deposition of these compounds on the alloy surface decreases the pit density and slows the crack growth through the grain boundaries by hindering the anodic dissolution of T phases.     

The susceptibility of 90Cu-10Ni alloy to stress corrosion cracking in seawater polluted by sulfide ions

Electrochemical polarization measurements and slow strain rate tests (SSRT) of a 90Cu-10Ni alloy in highly sulfide polluted seawater were conducted to investigate stress-corrosion cracking (SCC) behavior. The severity of the SCC depends on the sulfide concentration in the seawater. The severity increases as the concentration increases. Because the major time in SCC is spent in the initiation process of the propagating crack, the fracture toughness has only a minor effect in the component life failed by SCC. The SCC behavior of CDA706 is strictly linked to sulfide concentration in the range of 100 to 1000 ppm. The general corrosion of Cu-Ni alloys in low (<100 ppm) and high (>100 ppm) sulfide polluted seawater increases due to the selective copper dissolution. Cyclic polarization measurements confirmed that the corrosion rate decreases slightly as the sulfide concentration increases. Pitting tendency was high in the low concentration range of sulfide and low in the high concentration range. The presence of stresses in SCC removes the protective layer as it increases during testing of the specimen or during the actual service of a component. The authors propose that film rupture occurred, and two proposed SCC mechanisms were operational, namely sulfide stress cracking associated with the anodic dissolution in the low sulfide concentration range and hydrogen embrittlement, which was dominant in the high sulfide concentration range. It was found that a synergism exists between sulfide and stress that enhances the effect of the latter.     

GEANT4 simulation of slow positron beam implantation profiles

The paper presents the positron implantation profiles, which are important for proper interpretation of data produced in slow-positron depth defect spectroscopy (VEPAS). In the paper, we compared the profiles reported in other publications and those obtained using the GEANT4 codes, which are used for the simulation of interaction of energetic particles with matter. The comparison shows that the GEANT4 codes produce profiles which match fairly well with those generated by other codes, which take into account more accurately processes at low energies when positrons interact with core electrons, valence electrons, plasmons etc. The profiles in different materials simulated for different implant energies were parameterized using two analytical formulas: the Makhovian profile and the profile proposed by Ghosh et al. [V.J. Ghosh, D.O. Welch, K.G. Lynn, in: E. Ottewite, A.H. WeissSlow (Eds.), Positron Beam Techniques for Solids and Surfaces, Jackson Hole, Wyoming, AIP Conference Proceedings, Vol. 303, New York, 1994, p. 37]. The adjustable parameters obtained are presented in Table 1 and Table 2. The total backscattering probability obtained from the GEANT4 simulations is in agreement with experimental data reported.     

毫米波行波管金刚石夹持高频结构的设计和优化

利用TWTCAD软件和美国一维螺旋线行波管大信号计算程序对金刚石夹持高频结构和氧化铍高频结构进行了模拟计算,模拟结果表明采用金刚石作为夹持材料可以大大提高高频结构的耦合阻抗和电子效率,同时在采用非均匀输出线路设计时,金刚石结构对电子效率的提高更为明显。     

DP980冷轧高强钢连续退火工艺及强韧性行为研究

采用连续退火模拟试验机研究了连续退火工艺中缓冷及过时效温度对DP980冷轧高强钢组织性能的影响规律,并利用扫描电镜、透射电镜及拉伸试验机进行了显微组织及力学性能检测。研究结果表明：缓冷温度降低有利于新生铁素体及富碳岛状马氏体的生成,且实验钢屈服强度基本不变,抗拉强度先下降后升高,伸长率逐渐上升。缓冷温度为650 ℃时,强塑积（PSE）达到最大值15.55 GPa·%。随着过时效温度的升高,实验钢抗拉强度及屈服强度略有下降,断后伸长率显著升高。工业试制HC550/980DP成品的屈服强度不小于570 MPa,抗拉强度不小于1 080 MPa,伸长率不小于7%,达到应用标准。