Effect of potassium application during the floral initiation stage of plantains (Musa AAB)

All plantains given potassium produced better yields than the control. The optimal dose was 300 g K per plant and when applied to plantains at about 19/20th leaf stage (4–5 months after planting) significantly (P = 0.05) increased the bunch weight (73.9%), number of marketable fungers (33.7%) and finger weight (44.2%) per plant over the control. The efficiency of fruit set also increased by over 10% while the time of harvest from planting was reduced by over 3 months. Super-optimal K applications significantly (P = 0.05) decreased the yield of plantains. However, the efficacy of suboptimal applications improved when applied about the 20th leaf stage. Potassium applications later than 20th leaf stage (five months after planting) did not increase the bunches developed. Although super-optimal doses cold be applied during the vegetative stage at about 15th leaf stage (approximately 3 months planting) to obtain high yield, such applications are wasteful. High yield of plantains usually associated with heavy potassium application 2–3 months after planting could also be achieved by timely application of smaller quantities of potassium at 19/20th leaf stages when platains need it most for floral initiation.     

基于S／MIME的SIP安全性方案

针对会话初始协议（SIP）端到端的安全性问题,提出一种基于S／MIME的SIP签名与加密机制,并对其进行设计和实现。该安全机制将S／MIME的功能移植到SIP用户代理,实现对端到端通话中SIP消息体SDP的保护。仿真测试结果表明,该安全性方案具有较高的可行性,可保证SDP的完整性和不可抵赖性,达到了预期的安全效果。     

模糊层次分析法在开挖爆破影响因素分析及方案优选中的应用

影响爆破效果及爆破方案选择的因素很多,各因素在其中所占的比重仅以传统经验类比确定,具有较大的主观性,难以综合考虑各因素对爆破效果影响及爆破方案选择的定量研究。利用模糊数学理论,进行多目标决策,同时利用层次分析法(AHP)确定各影响因素的权重,科学合理地选择最优的爆破方案。     

电子雷管起爆法的安全技术探讨

针对我国电子雷管起爆安全技术及措施目前尚未有一个完整的标准和规程,介绍了电子雷管的结构原理,并针对隆芯1号数码电子雷管及其起爆系统进行了安全技术方面的探讨,对电子雷管起爆法在爆破工程中安全技术的制定提出了一些见解。可为使用电子雷管的爆破作业人员提供参考。     

水/乙基氯化铝引发体系对溶液法合成丁基橡胶的影响

以水/乙基氯化铝为引发体系,采用溶液法合成丁基橡胶,通过改变引发体系的配比、种类和用量,研究了该引发体系中各组分对丁基橡胶聚合反应的影响。结果表明,水作为主引发剂,决定了活性中心的数目,对聚合产物的分子量及其分布有显著影响。乙基氯化铝作为共引发剂,不仅用于与水作用产生阳离子活性中心,影响聚合反应的速率,也可消耗聚合体系中的杂质,避免副反应发生。同时,相较于倍半乙基氯化铝,乙基二氯化铝的活性较高,采用溶液法聚合不易控制,较难得到高分子量的产物。随引发体系用量增大,活性种增多,聚合物的分子量降低,产率升高。     

曹娥江钢筋混凝土双曲拱桥爆破拆除

根据长220m的曹娥江何家老桥的环境和结构特点,桥梁其它关键部位(如主拱肋顶部、桥墩横梁、直接与桥墩连接的桁架节点)与爆破主体桥墩同时进行爆破拆除,并对东面桥头桥拱处先行人工切割处理,对西面桥头处修筑支撑防护墩,以防止对正在修建的高速公路的破坏。由于对于复杂结构部位爆点、爆破参数、起爆顺序和延时时间的合理选择及预处理和安全防护措施得当,取得了良好的爆破效果。     

Critical Tractions for Initiating Adhesion Failure at Interfaces in Encapsulated Components

Determining the initiation of adhesive failure at a surface buried deep within the bulk of an epoxy is qualitatively different from measuring the propagation of an existing surface crack. Most current tests are shown to be unsuitable for assessing the critical traction at initiation. A new test geometry is presented that initiates failure away from an air interface, produces a slowly varying stress distribution near the initiation site and minimal contributions from thermal residual stresses, and enables tests with mixed modes of loading. This new geometry is used to examine temperature-dependent adhesive failure in tensile, shear, and mixed modes of loading for both smooth and rough surfaces. Some of the experimental results are unexpected. As examples, the critical traction at initiation of adhesive failure is apparently insensitive to surface roughness, and the critical normal traction is independent of temperature while the critical tangential traction tracks the shear yield stress.     

Two-dimensional Corrosion Pit Initiation and Growth Simulation Model

A two-dimensional corrosion initiation and growth model for aircraft aluminum materials is developed. The model takes into account the electro-chemical parameters as well as specific rules governing corrosion mechanisms. The simulation program is implemented in a cellular automata framework. The corrosion initiation and growth patterns obtained from simulations are compared qualitatively and quantitatively to the experimental data obtained from the Center for Materials Diagnostics at the University of Dayton Research Institute, Dayton. The results indicate that the present model effectively captures the corrosion damage process including initiation and growth. The effects of various electro-chemical parameters on the damage growth obtained from the simulation are presented and discussed. The results presented illustrate a new approach to modeling corrosion damage in aircraft aluminum materials. The simulation program is developed in a JAVA environment for ease of portability and usability.     

Crystallography and Structure–Property Relationships of 2,2″,4,4′,4″,6,6′,6″‐Octanitro‐1,1′ : 3′,1″‐Terphenyl (ONT)

An X‐ray crystallographic study of 2,2″,4,4′,4″,6,6′,6″‐octanitro‐1,1′ : 3′,1″‐terphenyl (ONT) has been carried out. The dihedral angles between benzene rings vary from 84.9° to 89.4°. Nonbinding interatomic distances of oxygen atoms inside all the nitro groups are shorter than the intermolecular contact radii for oxygen. On the basis of the DFT B3LYP/6‐31(d, p) method it was found that the difference between the X‐ray structure in the solid phase and DFT result for the gas phase is 98 kJ mol⁻¹, and the bearer of the highest initiation reactivity of the ONT molecule in the solid phase should be the nitro group at 4″‐position, in contrast to those at 4′‐ or 6′‐position that play this role in the isolated molecule. It has been stated that the nitro groups at the reaction centers of the ONT molecule are relatively well specified by their ¹⁵N NMR chemical shifts.     

Analyzing the mechanisms of fatigue crack initiation and propagation in CRH EMU brake discs

A significant number of high-speed electric multiple units’ (EMU) brake discs, manufactured from forged steel, showed thermal cracks during work and NDT. There exist three kinds of cracks on the friction surface; namely, the crackle, radial crack and circumferential crack. Macro-morphologies of the friction surface indicate that the cracks appeared in the interior and edges of the hotspots. Crack growth methods include the single crack propagation and multiple crack connectivity. A finite element analysis (FEA) was performed to determine temperature and stress distribution in the brake disc as well as to estimate stress distribution during braking. Simulation results indicate more significant residual, circumferential tensile stress on the external friction surface after emergency braking. The maximum residual circumferential tensile stress is 200 MPa after 300 km/h emergency braking. In addition, there is only the circumferential compressive stress on a section which is a certain distance from the exterior of the friction surface, and the distance depends on braking conditions. Therefore, not taking into account thickness reduction of the friction surface due to wear, it can be concluded that when the cracks run along the thickness direction to the specified distance, they will cease to run along this direction and begin propagating mainly in the direction of the radius. In addition, based on the simulation results, a measure was presented to prevent and inhibit the crack propagation.