水杨酸对盐胁迫下沙冬青幼苗抗氧化酶活性及PSⅡ光化学效率的影响

濒危植物沙冬青Ammopiptanthus mongolicus为亚洲中部荒漠地区唯一的常绿阔叶灌木,具有较高的保护和园林绿化价值.为了解水杨酸对沙冬青在盐胁迫下的缓解作用,使用水培方法培养沙冬青幼苗,测定其在w=1.3%NaCl胁迫下经不同浓度水杨酸处理后的抗氧化酶活性、PSⅡ光化学效率及其他与植物抗性有关的生理指标的变化.结果表明,0.5 mmol·L~(-1)水杨酸处理下,根和茎叶鲜质量比盐胁迫组分别提高了100%和85%,总叶绿素含量达到盐胁迫组的1.3倍;而1 mmol·L~(-1)水杨酸可使根和茎叶鲜质量均提高90%,总叶绿素含量达到盐胁迫组的1.7倍.这2种浓度的水杨酸均可使叶绿素荧光参数恢复到正常对照水平.水杨酸可以显著增强超氧化物歧化酶(SOD)和过氧化物酶(POD)活性,其中1.0 mmol·L~(-1)水杨酸处理下叶片与根部SOD酶活性分别比盐胁迫组升高了54%和68%;POD酶活性则分别提高了80%和117%,均显著高于对照组与盐胁迫组.同时,水杨酸还抑制了过氧化氢酶(CAT)的活性,减少丙二醛积累,从而缓解NaCl对沙冬青的胁迫.但是水杨酸浓度过高(达到2.0 mmol·L~(-1)),沙冬青幼苗生长即受到抑制,各项生理指标均低于单纯盐胁迫下的幼苗.综合各项生理指标,水杨酸1 mmol·L~(-1)的施用效果优于0.5 mmol·L~(-1).     

高温胁迫对岷江百合幼苗耐热指数和理化特性的影响

为了探明岷江百合幼苗在高温胁迫下的生理反应,以离体扩繁的岷江百合幼苗为研究材料,对其进行了不同高温(37 ℃/30 ℃、42 ℃/37 ℃)和不同时间(0、4、8、16、32、48 h)处理,研究了高温胁迫对其耐热指数和有关生理生化指标(叶绿素、丙二醛、游离脯氨酸、可溶性蛋白含量和SOD活性)的影响.结果表明:随着温度的升高和处理时间的延长,植株的耐热指数不断下降,叶绿素含量减少,丙二醛(MDA)含量增加;42 ℃胁迫32 h后,游离脯氨酸、可溶性蛋白含量、SOD活性均达到最大值,分别比对照增加了0.66倍、1.77倍和9.78倍.但胁迫48 h后,指标显著下降,这说明,42 ℃间断胁迫48 h对植株产生了不可逆的的热伤害作用.     

模拟过载对猕猴眼压及视神经的影响

针对航天返回段过载环境可能对眼造成不利影响的问题,研究模拟过载对猕猴眼压及视神经的影响。12只猕猴分为A组和B组,每组6只。采用离心机模拟嫦娥号、阿波罗号过载曲线,A组以卧姿、B组以躺姿分别进行13 G和15 G重力模拟过载,2次过载暴露间隔24 h。于13 G过载前(基线)、13 G过载后、15 G过载前、后应用iCare手持式回弹眼压计测量眼压、离体UBM观察房角结构、HE染色观察小梁网及视神经改变。结果显示：与基线眼压相比,A组和B组13 G、15 G过载后眼压均下降(P<0.001,P<0.05),B组降低幅度小于A组;13 G与15 G过载后两组之间眼压降低幅度均有统计学意义(P<0.05)。B组有1只猕猴双眼出现眼压异常升高伴睫状充血等急性高眼压症状,离体UBM未观察到前房变浅及房角狭窄等异常,HE染色未发现小梁网异常;短暂眼压升高未发现视神经形态有明显异常变化。过载可能导致个别眼压异常升高,短暂过载对猕猴视神经未发现明显影响。     

含高氮化合物BTATz的CMDB推进剂特性

以新型高氮化合物3,6-双(1-氢-1,2,3,4-四唑-5-氨基)-1,2,4,5-四嗪(BTATz)取代RDX制得了BTATz-CMDB推进剂试样,获得了燃速结果,并利用TG-DTG,PDSC,单幅照相、燃烧波温度分布和熄火表面形貌及元素含量测试技术对推进剂的热分解特性及燃烧特性进行了系统研究。结果发现,BTATz的氧平衡值较低,用其取代双基推进剂中的NC和NG后,推进剂的各能量特性参量出现不同程度的降低,因此,BTATz在推进剂中的含量不宜太高。BTATz-CMDB推进剂适用于常规无溶剂成型工艺进行制造;BTATz在燃速提升方面具有突出潜力,尤其在对推进剂主放热反应催化加速的催化体系(邻苯二甲酸铅、己二酸铜和炭黑的混合物)作用下,燃速提升效果更加明显;BTATz-CMDB推进剂燃烧时的火焰符合双基系推进剂火焰的一般特征,但由于BTATz不存在类似RDX那样的熔融过程,该类推进剂燃烧产生了发散火焰束,燃烧表面由熔融状变为疏松珊瑚状,火焰强度增强;随着压强升高,燃烧表面产生发散火焰束的活性点增多,暗区迅速变薄,增加了火焰区向燃烧表面的热反馈,加速了燃烧反应;催化体系对推进剂燃烧反应的气相区影响不大,它加强了凝聚相及表面附近的放热反应,改变了推进剂燃烧表面的结构,在推进剂燃烧过程中,催化剂(新生态)在推进剂的燃烧表面富集,催化了推进剂的分解和燃烧,促进了推进剂燃速的提高。     

短期低温下稀土对麻楝幼苗生理指标的影响

用500和1 000 mg·L-1稀土溶液喷施麻楝Chukrasia tabularis幼苗,置于3 ℃低温下3和7 d后,对其生理指标进行了测定.结果表明:2种质量浓度稀土处理的麻楝幼苗叶片的相对电导率,低温处理3 d后分别比对照显著增加9%和14%,低温处理7 d后分别比对照下降4%和11%.2种质量浓度稀土处理的脯氨酸和可溶性蛋白质含量在低温处理3和7 d后增加.低温处理3 d后,500 mg·L-1稀土处理的幼苗叶片中叶绿素含量比对照和1 000 mg·L-1处理的均显著减少13%,低温处理7 d后,2种质量浓度稀土处理分别比对照显著增加11%和17%.稀土处理的幼苗叶片SOD活性在低温处理3 d后与对照接近或大于对照,低温处理7 d后比对照显著增加8%~11%.低温处理3 d后,500 mg·L-1稀土处理的丙二醛(MDA)含量比对照增加了8%,而1 000 mg·L-1稀土处理和低温7 d后的2种质量浓度稀土处理比对照减少了7%~11%.可见,500 mg·L-1稀土处理的幼苗经历低温7 d后以及1 000 mg·L-1稀土处理的幼苗经历3和7 d后均提高了抗寒性.     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis

Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection (PIND) method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising (DWD), cross-correlation analysis (CCA) and homo-filtering (HF), the method enhances the affectiv-ity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved.     

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl4 and SbCl3 and Azeotropic Drying

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using: (1) an ion-exchange hydrolysis to remove chlorine ions, and (2) isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the aid of TG-DTA, BET, XRD and TEM. After having calcined, the antimony-doped tin oxide nanopowder possesses a tetragonal rutile structure with high dispersivity, uniform particles and low hard agglomeration.     

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it at- tains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions (from 500-750 ℃).     

超声速燃烧数值模拟中的湍流与化学反应相互作用模型

高精度数值模拟有助于理解超声速湍流燃烧中湍流与化学反应的相互作用,可为发动机燃烧室等工程应用设计提供可靠的预测模型。除直接数值模拟外,目前在湍流燃烧应用中使用的大涡模拟和雷诺平均Navier-Stokes模拟均需要借助模型模化发生在湍流小尺度上的流动与化学反应过程对湍流大尺度运动的影响。现有的湍流与化学反应相互作用模型大致可分为:火焰面类模型和概率密度函数类模型,2类模型在不同的应用中各自具有优势和局限性。此外,现有模型大都基于低马赫数燃烧,而超声速燃烧中通常会伴随快速混合、局部熄火和再着火以及激波等复杂过程,这为发展其中的湍流与化学反应相互作用模型提出了更多的挑战。     

适于低轨卫星IP网络的单核共享树组播算法(英文)

为了解决低轨卫星IP网络中现有典型源组播算法的信道资源浪费问题,本文提出了一套单核共享树组播算法,即核心群合并共享树(CCST)和加权核心群合并共享树(w-CCST)算法。CCST 算法包括动态近似中心(DAC)选核方法和核心群合并组播路径构建方法。DAC方法专为周期、规律运动的低轨卫星网络提出,不需要复杂的星上计算。在核心群合并方法中,以核节点作为初始核心群,通过核心群和剩余组成员的最短路径方法逐步扩展直至整棵组播树构建完成,从而使得组播树的树代价最小,大大提高了网络的带宽利用率和组播传输效率。w-CCST 算法中所提出的加权因子可以调整树代价和端到端传播时延之间的折衷程度,因此,可以通过调整加权因子来适度增大树代价、降低端到端传播时延以支持某些端到端时延要求苛刻的实时组播业务。最后,与低轨卫星 IP 网络中典型算法进行了性能比较,仿真结果说明,CCST 算法的平均树代价比其它算法显著降低,w-CCST 算法的平均端到端传播时延小于 CCST 算法。     

Jet Vectoring Control Using a Novel Synthetic Jet Actuator

A primary air jet vectoring control system with a novel synthetic jet actuator (SJA) is presented and simulated numerically. The results show that, in comparison with an existing traditional synthetic jet actuator, which is able to perform the duty of either “push” or “pull”, one novel synthetic jet actuator can fulfill both “push” and “pull” functions to vector the primary jet by shifting a slide block inside it. Therefore, because the new actuator possesses greater efficiency, it has potentiality to replace the existing one in various appli- cations, such as thrust vectoring and the reduction of thermal signature. Moreover, as the novel actuator can fulfill those functions that the existing one can not, it may well be expected to popularize it into more flow control systems.     

Nonlinear Adaptive Slewing Motion Control of Spacecraft Truss Driven by Synchronous V-gimbaled CMG Precession

The slewing motion control of a truss arm driven by a V-gimbaled control-moment-gyro (CMG) is a nonlinear control problem. The V-gimbaled CMG consists of a pair of gyros that must precess synchronously. The moment of inertia of the system, the angular momentum of the gyros and the external disturbances are not exactly known. With the help of feedback linearization and recursive Lyapunov design method, an adaptive nonlinear controller is designed to deal with the unknown items. Performance of the proposed controller is verified by simulation.     

An SOR Implicit Time-accurate Scheme in Calculating Unsteady Flows

A new time-accurate marching scheme for unsteady flow calculations is proposed in the present work. This method is the combination of classical Successive Over-Relaxation (SOR) iteration method and Jacobian matrix diagonally dominant splitting method of LUSGS. One advantage of this algorithm is the second-order accuracy because of no factorization error. Another advantage is the low computational cost because the Jacobian matrices and fluxes are only calculated once in each physical time step. And, the SOR algorithm has better convergence property than Gauss-Seidel. To investigate its accuracy and convergency, several unsteady flow computa- tional tests are carried out by using the proposed SOR algorithm. Roe’s FDS scheme is used to discritize the inviscid flux terms. Un- steady computational results of SOR are compared with the experiment results and those of Gauss-Seidel. Results reveal that the numerical results agree well with the experimental data and the second-order accuracy can be obtained as the Gauss-Seidel for unsteady flow computations. The impact of SOR factor is investigated for unsteady computations by using different SOR factors in this algorithm to simulate each computational test. Different numbers of inner iterations are needed to converge to the same criterion for different SOR factors and optimal choice of SOR factor can improve the computational efficiency greatly.