环境因素对枝孢霉菌生长特性的影响

考察了温度、pH、Fe3+质量浓度等主要环境因素对喷气燃料中特征微生物——枝孢霉菌生长的影响,为喷气燃料中枝孢霉菌的防治提供科学指导。在500 nm波长处,测定了不同浓度枝孢霉菌菌液的OD值,得出其浓度与OD值线性相关,且相关性大于99%。经生长特性试验,表明枝孢霉菌在24~40℃生命力较强,在32℃生长最为旺盛,低温和高温枝孢霉菌几乎停滞生长,高温对真菌的抑制作用更加明显;p H为3~11,随着pH增大,生长速度先加快随后减慢,最适宜生长的p H为9;Fe3+质量浓度为0~200 mg/L,随着Fe3+质量浓度增大,枝孢霉菌生长趋于旺盛,即Fe3+能促进枝孢霉菌的生长。所以,监测和控制储罐中温度和pH,减少储罐和管道腐蚀,是预防和控制喷气燃料中枝孢霉菌污染的有效措施。     

基于混料设计的快硬土壤固化材料配方优化

为探索普通硅酸盐水泥(P·O)、熟石灰(HL)、硅灰(SF)三元混料系统对固化土无侧限抗压强度的影响,综合极端顶点设计和均匀设计思想建立混料回归模型,得出了响应面图形,确定了三元混料系统的最佳配方。在该配方下,固化土7d实际抗压强度可以达到4.75MPa。通过交互作用分析揭示了混料因子间的作用规律:P·O与HL交互作用对固化土7d无侧限抗压强度影响极其显著,P·O与SF交互作用对固化土7d无侧限抗压强度影响显著。对比试验表明,该混料设计方案对提高固化土7d无侧限抗压强度有显著效果,对土壤固化剂配合比优化设计和固化土无侧限抗压强度预测具有指导意义。     

地下工程非爆破开挖机械破碎法机理及应用

针对非爆破法开挖工序中的关键问题——导向孔布置方案优化,结合非爆破施工实作流程及工艺,利用波动理论探索了破碎锤冲击破岩机理。破碎锤通过钎杆冲击导向孔产生孔间贯穿裂缝进而破岩掘进,破碎锤冲击破岩的过程是岩石被拉坏的过程,孔间岩石中的切向应力是提高破岩效率的关键因素。基于岩石断裂力学理论,总结得出导向孔间裂缝产生、扩展、贯通的判据,并依托实际工程进行验算,理论计算结果与现场试验结果吻合良好,同时提出了导向孔布置优化方案的改进建议。     

生物技术在军事领域中的应用

目前,生物技术已成为科学界公认的重要技术,甚至是主导性技术,生物技术已越来越多地涌入军事领域.文章介绍了生物技术的特点,阐述了生物技术在军事领域的主要应用,对其军事应用前景进行了分析.     

按照新修订的《党委工作条例》推进党委工作创新发展

贯彻落实新的<党委工作条例>,应当充分认清形势任务要求,按照新条例提升党委工作的起点和层次;紧紧围绕中心任务,遵循新条例聚焦党委工作的领导效能;着力强化依法办事,依据新条例规范党委工作有效运行,努力推进部队党委工作创新发展.     

牢牢把握国防和军队建设的主题和主线

牢牢把握国防和军队建设的主题和主线,充分体现了国防和军队建设又好又快发展的内在要求;对实现国防和军队建设"十二五"目标任务具有决定性意义;必须把握主题和主线,进一步推进国防和军队建设科学发展创新发展.     

积极运用网络开展思想政治教育

网络思想政治教育必须以加强基层部队政治教育网络建设、科学设置思想政治教育内容、打造思想交流互动平台、建立网络政治教育工作评价考核体系为着力点,并处理好"趋利"与"避害"、互联网与军队内部网、自我教育与网络教育、硬件建设与软件建设的关系.     

Single machine parallel batch scheduling subject to precedence constraints

We consider the single machine parallel batch scheduling problems to minimize makespan and total completion time, respectively, under precedence relations. The complexities of these two problems are reported as open in the literature. In this paper, we settle these open questions by showing that both problems are strongly NP‐hard, even when the precedence relations are chains. When the processing times of jobs are directly agreeable or inversely agreeable with the precedence relations, there is an O(n²) time algorithm to minimize the makespan. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004     

Research on the influences of confining pressure and strain rate on NEPE propellant: Experimental assessment and constitutive model

In order to study the influences of confining pressure and strain rate on the mechanical properties of the Nitrate Ester Plasticized Polyether (NEPE) propellant, uniaxial tensile tests were conducted using the self-made confining pressure system and material testing machine. The stress-strain responses of the NEPE propellant under different confining pressure conditions and strain rates were obtained and analyzed. The results show that confining pressure and strain rate have a remarkably influence on the mechanical responses of the NEPE propellant. As confining pressure increases (from 0 to 5.4 MPa), the maximum tensile stress and ultimate strain increase gradually. With the coupled effects of confining pressure and strain rate, the value of the maximum tensile stress and ultimate strain at 5.4 MPa and 0.0667 s⁻¹ is 2.03 times and 2.19 times of their values under 0 MPa and 0.00333 s⁻¹, respectively. Afterwards, the influence mechanism of confining pressure on the NEPE propellant was analyzed. Finally, based on the viscoelastic theory and continuous damage theory, a nonlinear constitutive model considering confining pressure and strain rate was developed. The damage was considered to be rate-dependent and pressure-dependent. The constitutive model was validated by comparing experimental data with predictions of the constitutive model. The whole maximum stress errors of the model predictions are lower than 4% and the corresponding strain errors are lower than 7%. The results show that confining pressure can suppress the damage initiation and evolution of the NEPE propellant and the nonlinear constitutive model can describe the mechanical responses of the NEPE propellant under various confining pressure conditions and strain rates. This research can lay a theoretical foundation for analyzing the structural integrity of propellant grain accurately under working pressure loading.     

Hypersonic impact flash characteristics of a long-rod projectile collision with a thin plate target

Impact flash occurs when objects collide at supersonic speeds and can be used for real-time damage assessment when weapons rely on kinetic energy to destroy targets.However,the mechanism of impact flash remains unclear.A series of impact flash experiments of flat-head long-rod projectiles impacting thin target plates were performed with a two-stage light gas gun.The impact flash spectra for 6061 aluminum at 1.3-3.2 km/s collision speeds were recorded with a high-speed camera,a photoelectric sensor,and a time-resolved spectrometer.The intensity of the impact flash exhibited a pulse charac-teristic with time.The intensity(I)increased with impact velocity(V0)according to I∝Vn0,where n = 4.41 for V0 ＞ 2 km/s.However,for V0 ＜ 2 km/s,n = 2.21,and the intense flash duration is an order of magnitude less than that of higher V0.When V0 ＞ 2 km/s,a continuous spectrum(thermal radiation background)was observed and increased in intensity with V0.However,for V0 ＜ 2 km/s,only atomic line spectra were detected.There was no aluminum spectral lines for V0 ＜ 2 km/s,which indicated that it had not been vaporized.The initial intense flash was emission from excited and ionized ambient gases near the impact surface,and had little relationship with shock temperature rise,indicating a new mechanism of impact flash.