火炮机械系统可靠性强化试验方案探讨

目的尝试将可靠性强化试验理论引入其可靠性研究中,提高火炮机械系统的可靠性。方法首先分析可靠性强化试验的发展动态及其应用于机械系统的必要性,而后在对其理论依据进行分析的基础上,明确火炮机械系统可靠性强化试验研究的目的。结果依据火炮机械系统的主要失效模式,制定了包含机械工作原理分析等7个步骤的可靠性强化试验方案,详细分析了各环节的内容及作用。结论研究结果为可靠性强化试验在火炮机械系统中的应用提供一定理论支撑。     

航空结构材料环境适应性研究进展及发展方向

对航空结构材料环境适应性研究进展进行了综述,其中包括新型航空材料的环境适应性研究和环境-力学因素耦合作用对航空结构材料环境适应性的影响,最后阐述了环境适应性研究的结构化趋势,并指出了航空结构材料环境适应性研究未来将重点关注户内加速试验技术、环境适应性评价技术以及环境适应性数据的深度开发与应用,将各种科学技术和工程实践用于减缓环境对结构材料的损伤,提高装备的耐环境能力。     

EFFICACY AND COST OF AQUATIC WEED CONTROL IN SMALL PONDS'

ABSTRACT: Twenty, 0.2 hectare ponds were utilized for a four-year evaluation of three aquatic vegetation control techniques: a combination of inorganic fertilization and mechanical harvesting, aquatic herbicides, and grass carp (Ctenopharyngodon idella). Ponds used for herbicide and grass carp treatments were managed at three levels of aquatic vegetation (none, 40 and 70 percent plant occupation). Submersed vegetation was not controlled with inorganic fertilization. Vegetation levels were maintained for less than 30 days after mechanicai harvesting. Submersed macrophytes were not completely eliminated with herbicides, but the herbicide treatments utilized were effective at maintaining aquatic vegetation above 30 percent pond volume occupation. Grass carp consumed all species of submersed vegetation at the stocking densities used in this study; therefore, planned levels of submersed macrophytes were not maintained. Grass carp did not consume all floating leaf vegetation, but after four years some grass carp ponds did have lower densities of floating leaf plants. Fertilization costs were $608/hectare/year, and mechanical harvesting costs were $1979/hectare/year, resulting in a total aquatic vegetation treatment cost of $2587/hectare/ year. Herbicide costs for the different treatment levels ranged from $417/hectare/year to $1339/hectare/year over the four-year period. Grass carp were the most economical vegetation control measure tested, with costs ranging from $159/hectare/year to $248/hectare/year for the four-year study.     

Processing and Physical Properties of Plastics Made from Soy Protein Polyester Blends

Blending soy protein with polyesters using a polyvinyllactam as a compatibilizer successfully made soy protein-based plastics. The polyesters used to produce blends included polycaprolactone (PCL) and Biomax (a commercial biodegradable polyester). The blends were processed by compounding extrusion and injection molding. Blends containing soy protein/Biomax-poly(vinyl alcohol) had tensile strengths ranging from 16–22 MPa, with samples containing larger percentages of the synthetic polymer exhibiting greater strengths. Blends made from soy protein, Biomax, and PCL had tensile strengths ranging from 27–33 MPa. All the blends had high Young's moduli but demonstrated brittle characteristics as evident from their low elongations at break, ranging from 1.8–3.1%. Plastics made from soy protein/polyester blends exhibited low water absorption and had good stability under ambient conditions relative to the plastics made from soy protein alone. Blends made from soy protein flour produced plastics with the lowest water absorption.     

Effects of Storage Time on Properties of Soybean Protein-Based Plastics

Soybean protein has been considered as a potential biodegradable polymer in the manufacture of plastics. The purpose of this investigation was to characterize the effect of storage time on thermal and mechanical properties of soybean protein isolate (SPI) plastics. SPI was separated from defatted soy flour, modified with 1M or 2M urea, or plasticized with glycerol, and compression molded into plastics. Plastic made from SPI alone was used as a control. For all SPI plastics, glass transition temperatures and dynamic storage modulus increased and loss tangent decreased during storage. Excess enthalpy of relaxation of all SPI plastics had an exponential relationship with storage time, indicating a fast aging rate at the beginning of storage. All SPI plastics tended to be stiff and brittle during storage. The plastics with glycerol had the slowest aging rate and were fairly stable after 60 days, with about 8.8 MPa tensile strength and 168% strain at break. Plastics with the 2M urea-modification SPI also had a slow aging rate and became relative stable after 60 days, with about 10 MPa tensile strength and 72% elongation.     

表面活性剂及酸处理对污泥脱水性能影响的研究

研究表面活性剂和酸处理对污泥脱水性能的影响，并探讨其作用机理。对采用最优加药量的各种加药方案进行了从污泥性质到脱水行为的一系列横向比较。污泥性质的比较依据为絮体颗粒的宏观(目测)和微观(光学和电子显微镜)变化以及在结合水含量(DSC法测)方面的变化。脱水行为的比较依据为过滤脱水速率(比阻)、离心脱水速率(1800rpm-2min离心后的泥饼含固率)、脱水程度(4800rpm～45min离心后的泥饼含固率)及脱水清液的性质(目测及测定SS、COD、TP)。实验结果表明：除了表面活性剂与Fe^3 和CaO联用外，投加表面活性剂或酸处理对提高污泥脱水速率的意义不大，但却能有效提高污泥的机械脱水程度。表面活性剂的作用机理是：分散作用使污泥絮体结构分散解体，释放出原絮体内部的结合水；增溶作用可溶解有高度水合作用的ECP。酸处理的作用机理是：H^ 与污泥的结合，改变了污泥的表面电荷特性，促进了污泥絮体间进一步的絮凝；使ECP水解，降低了絮体对水的亲和力。     

Recycle of bio-waste banana and sisal fiber filled harmlessness epoxy hybrid composite for automotive roof application

Insists of polymer matrix composite is prepared by using natural fiber facilitates high tensile, flexural, and impact toughness properties. The natural fiber utilization in the polymer matrix can overcome the synthetic fiber demerits of poor compatibility, high moisture absorption, and high cost. The present research investigates developing a low-cost, environmentally eco-friendly epoxy hybrid composite using different volume percentages of chopped natural waste banana (0Vol%, 5Vol%, 10Vol%, and 15Vol%) and sisal fiber (0Vol%, 15Vol%, 10Vol%, and 5Vol%) through hand mould hot compression technique. The presence of natural waste banana and sisal fiber on tensile strength, flexural strength, and thermal adsorption properties of the epoxy hybrid composite are evaluated by ASTM test standards. The ASTM standard measured test results of epoxy hybrid composite with and without natural waste banana and sisal fiber were compared and sample three was identified by good tensile strength, flexural strength, and better thermal adsorption properties compared to all others. The sample three epoxy hybrid sample is recommended for automotive roof application.     

部分预应力混凝土梁疲劳性能及工程经济性分析

为解决那些由于早期桥梁的设计标准低或服役时间过长,导致破损、承载力不足以及老化严重的问题,对部分已建桥梁提出改扩建计划。对桥梁改扩建工程,在满足当前设计要求的基础上合理选择钢筋与混凝土等级,可以有效节约成本,体现环保理念。通过对两组共8根不同钢筋与混凝土等级组合下的PPC梁分别进行静力试验和疲劳试验研究,分析不同组合形式下试验梁的力学性能,并结合其工程造价进行全面的研究。结果表明,提高混凝土等级能有效提高试验梁的疲劳性能,并可节约成本,为改扩建桥梁工程中钢筋混凝土等级的选择提供参考依据。     

地铁车厢机械排烟和细水雾耦合灭火效果研究

采用火灾动力学软件FDS（FireDynamicSimulator）,以封闭单节地铁列车车厢为研究对象,模拟分析不同喷雾速度、排烟量以及排烟启动时刻条件下,车厢内火灾热释放速率、烟气层高度、烟气层温度的变化规律,对细水雾和机械排烟耦合作用下地铁列车车厢火灾灭火效果展升研究。结果表明,喷雾初速度较小时,细水雾动作之后启动排烟系统的灭火效果更好;喷雾初速度较大时,细水雾动作之前启动排烟系统的灭火效果更好;同样的喷雾初速度条件下,增大排烟量町以提高烟气层高度和降低烟气层温度,排烟量过大可能造成火焰区的扰动,降低细水雾的火火效果。     

生石灰强化机械通风法修复三氯乙烯污染土壤

机械通风法是一种操作简单、效果好、成本低的土壤修复技术,特别适合大型挥发性有机化合物(VOC)污染场地的土壤修复,但在环境温度低、土壤含水率高、土壤黏性大等情况下,其修复效果和修复周期会受到极大影响,且土壤中高浓度的污染物残留将严重影响场地修复目标的实现。为了解决这一问题,采用了在土壤中添加一定量生石灰的强化措施。结果表明:(1)生石灰可以显著提高机械通风法修复三氯乙烯(TCE)污染土壤的效果,缩短修复周期,降低污染物在土壤中的残留浓度。(2)生石灰对TCE的强化作用与生石灰的添加量和土壤类型有关,粉质黏土的强化效果要好于粉土和细砂,生石灰添加量越多,强化效果越好;(3)生石灰强化处理TCE的主要机制是提高土壤温度、降低土壤含水率、增加土壤通透性,促进土壤中TCE的解吸和挥发。