Effects of hydrogen addition on oblique detonations in methane–air mixtures

As a low-carbon fuel, methane has been used in various engines; however, the studies on its application in hypersonic propulsion are few. Here, oblique detonation waves (ODWs) in methane–air mixtures have been simulated to facilitate methane applications in shock-induced combustion ramjets. The shortcoming of using methane in hypersonic air-breathing propulsions has been presented via examining initiation distance of ODWs. Results demonstrate that ODWs are difficult to be initiated in the methane–air mixture, and similar to normal detonations studies before, this leads to a long initiation length; therefore, methane-fueled ODW is only applicable for high flight Mach number (M₀). To broaden the M₀ regime, hydrogen has been added to methane to decrease the initiation length. An increasing in the hydrogen percentage leads to the nonlinear decrease of the initiation length, and the initiation structures also vary simultaneously. To elaborate the physical mechanism of the initiation length variation, a theoretical model of the initiation length for fuel blends has been proposed. Meanwhile, the advantages of methane fuel in ODW-based propulsion have been discussed by analyzing on the effects of hydrogen addition on the total pressure.     

Analysis and Design of Instant Message System Based on P2P

By analyzing current development conditions of mainstream Instant Message technologies and services,some detailed discussion about technical solution and formal operation deployment strategies of P2P Instant Message Services based on Internet is made.Several crucial problems of P2P Instant Message System about services management,interconnection with other instant message,security and profit-making mode are analyzed,,and how to develop P2P IM Services is proposed.     

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。     

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.     

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。     

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.     

OSGi/SIP通信中间件架构设计

根据未来家庭网络应用对3G网络的需求,提出基于开放服务网关协议/会话初化协议(OSGi/SIP)的通信中间件架构.该架构依托Android操作系统,通过套接字通信机制解决SIP网络层和OSGi应用层数据的交互问题,利用SIP的会话功能为远程用户提供交互网关应用服务.实验结果表明,该架构具有较好的通用性,适用于医疗保健监...     

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。