带未知干扰的模块化航天器系统相对轨道的队形控制

基于多智能体系统一致性理论,在有向拓扑结构中对模块化航天器相对轨道的队形控制问题进行研究.考虑与状态相关的未知外部干扰,在存在模块质量不确定性的情形下,基于自适应增益技术,设计仅依赖模块自身及其邻近模块信息的分布式控制算法,并通过Lyapunov稳定性方法证明闭环系统是渐近稳定的.最后在Matlab/Simulink中对6个模块组成的模块化航天器系统的队形进行仿真分析,仿真结果表明所设计的控制律是有效且可行的.     

Stabilized heteropolyacid/Nafion composite membranes for elevated temperature/low relative humidity PEFC operation

Organic/inorganic composite membranes with different inorganic heteropolyacid (HPA) additives maintain sufficient proton conductivities for atmospheric pressure elevated temperature (>100 °C) polymer electrolyte fuel cell (PEFC) operation. However, membrane and membrane electrode assembly (MEA) processing is severely curtailed because of the solubility of the HPA additives in aqueous media. Composite membranes with the HPA (phosphotungstic acid; PTA) additive rendered insoluble by ion exchanging protons with larger cations such as Cs⁺, NH₄⁺, Rb⁺ and Tl⁺ were fabricated. The additive loss in aqueous media was lowered from nearly 100% (unmodified HPA) to about 5% (modified HPA). The membranes were robust, and demonstrated low H₂ crossover currents of around 2 mA/cm² for a 28 μm thick membrane. All membranes were evaluated at high temperatures and low relative humidities in an operating fuel cell. The conductivities of the composite membranes at 120 °C and 35% relative humidity were on the order of 1.6 × 10⁻² S/cm.     

基于动态有噪网络的增量社团发现算法

在动态社会网络中,诸如垃圾邮件之类的噪声会影响网络的稳定性,导致其社团结构难以被准确发现。针对该问题,提出一种采用增量结构的社团发现算法。利用相对熵处理噪声,通过改进的增量算法发现社团结构。实验结果表明,该算法针对不同动态社会网络的发现性能均优于传统动态社团发现算法,其模块度可达到0.8左右,互信息值变化也较平稳,可有效避免噪声对算法性能的影响。     

国产SEBS流变性能评价

通过对国产SEBS(氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物)流变性能进行测试．分析不同结构、不同嵌段的S／B质量比值、不同相对分子质量、不同加工温度对SEBS产品流变性能的影响．促进用户对国产SEBS性能的了解。     

Agronomic evaluation of fertilizer products derived from Sukulu Hills phosphate rock

Partial acidulation of phosphate rock (PR) or compaction of PR with soluble P fertilizers can improve the usefulness of unreactive PR for use as P fertilizer. A greenhouse study was conducted to evaluate nonconventional phosphate fertilizers derived from a low reactive Sukulu Hills PR from Uganda. Raw PR (which contained 341.0 g kg^–1 Fe₂O₃), beneficiated or concentrate PR, partially acidulated PR (PAPR) and PR compacted with triple superphosphate (TSP) were evaluated. Compacted materials had a P ratio of PR:TSP = 50:50. PAPR materials were made by 50% acidulation with H₂SO₄. TSP was used as a reference fertilizer. Fertilizers were applied to an acidic (pH = 5.4) Hiwassee loam (clayey, kaolinitic, thermic Rhodic Kanhapludults) at rates of 0, 50, 100, 200, 300 and 400 mg P kg^–1 soil. Two successive corn (Zea mays L.) crops were grown for 6 weeks. Compacted concentrate PR + TSP and raw PR + TSP were 94.4 and 89.7% as effective as TSP, respectively, in increasing dry-matter yields for the first corn crop. PAPR from the concentrate was 54.8% as effective as TSP. Raw PR, concentrate PR and the PAPR from the raw PR were ineffective in increasing dry-matter yields. The same trends were obtained when P uptake was used to compare effectiveness. Ineffectiveness of the raw PR and its corresponding PAPR was attributed to a high Fe₂O₃ content in the raw PR. Bray I and Pi paper were found to be nearly equally suitable at estimating available P in the soils treated with responsive fertilizer materials. Mehlich 1 overestimated available P in soil treated with raw PR, concentrate PR or the PAPR from the raw PR.     

Agronomical evaluation of phosphate fertilizer as a nutrient source of phosphorus for crops: Isotopic procedure

The agronomic effectiveness of P fertilizers, as sources of phosphorus for crops, was evaluated using the quantities, P_f, of phosphorus taken up byLolium perenne grown on 14 soils during greenhouse experiments in pot cultures. The P_f quantities were determined using³²P-labelled fertilizers. Data were analysed using a new concept: the Isotopic Relative Agronomic Effectiveness (IRAE). The IRAE value was defined as the ratio of the P_f quantity, taken up by a crop, of a tested fertilizer over the P_f quantity, taken up by a crop, of a fertilizer used as standard. In our experiments diammonium phosphate (DAP) was used as standard P fertilizer and two rock phosphates, the North Carolina rock phosphate (NCPR) and a calcium-iron-aluminium phosphate (Phospal), were tested. As a linear relationship between P_f(NCPR) quantities and P_f(DAP) quantities was obtained, with r² = 0.95, when the application rates increased from 15 mgP (kg soil)^–1 to 200 mgP (kg soil)^–1, it is conciuded that IRAE values for a given fertilizer, other than the standard fertilizer, could be determined with a single rate of application. As regards soil pH in the range 4.7 to 8.2 the IRAE_NCPR is related to soil pH by a curvilinear relationship: log IRAE_NCPR = –(0.44) pH + 4.05 with r² = 0.89. The average of IRAE_phospal values was 0.15 with a standard error = 7% irrespective of soil pH. Then a logarithmic relationship was obtained between IRAE values of the two tested fertilizers and their water P-solubility determined at the soil pH where they were applied.     

Incubating superphosphate in ‘dry’soil can reduce its effectiveness

Single superphosphate was incubated for six months at 25°C in soil which had been subject to one of three moisture treatments. These were: dried in a glasshouse, dried at a constant temperature of 25°C, or moist soil. Phosphorus (P) effectiveness was then compared with effectiveness of P from freshly-applied superphosphate using yields of wheat (Triticum aestivum) and triticale (×Triticosecale) tops in pot experiments.Incubation in soil which had been dried at 25°C did not decrease the effectiveness of the P. Incubation in moist soil decreased it to about 20% of the effectiveness of freshly-applied P in one case and to about 50% in the other case. Incubation in soil which had been dried in a glasshouse also decreased its effectiveness. The decrease varied with conditions, but in two cases the P was 70% as effective as freshly-applied P, and in one case only 45% as effective. Presumably sufficient moisture was present in the soil dried in the glasshouse to enable water-soluble P present in the fertilizer to react with the soil.     

A variable gap penalty function and feature weights for protein 3-D structure comparisons

We have developed a variable gap penalty function for use inthe comparison program COMPARER which aligns protein sequenceson the basis of their 3-D structures. For deletions and insertions,components are a function of structural features of individualamino acid residues (e.g. secondary structure and accessibility).We have also obtained relative weights for different featuresused in the comparison by examining the equivalent residuesin weight matrices and in alignments for pairs of 3-D structureswhere the equivalences are relatively unambiguous. We have usedthe new parameters and the varible gap penalty function in COMPARERto align protein structures in the Brookhaven Data Bank. Thevariable gap penalty function is useful especially in avoidinggaps in secondary structure elements and the new feature weightsgive improved alignments. The alignments for both azurins andplastocyanins and N- and C-terminal lobes for aspartic proteinasesare discussed     

On the importance of some surface and interface characteristics in the formation of the properties of adhesive joints

The importance of some relative surface characteristics which determines the strength of adhesive joints: specific surface of substrate , relative contact area β and specific contact area β in the adhesion interaction process were emphasised. Existing and potential methods of experimental evaluation of these characteristics were shortly analysed. The durability of the adhesive joints in water media significantly increases with growth of specific surface ^* of chemically treated substrate evaluated from the SEM micrographs. Specific surface calculated from the experimental data of hexane adsorption measurements for iron particles (particulate model of steel substrate) is more then ten times greater than respective ^* values. The relative contact area β of the Al₂O₃ particles (in wide range of ) with PE melt was in a roundabout way evaluated by experimental determination of the affect of on kinetic of peel strength formation of adhesive joints: Al₂O₃ filled PE-steel. The speculation was based on the ability of Al₂O₃ to adsorb low-molecular products of contact oxidation of PE which takes place in the process of formation of adhesive joints and determines their strength. The ability of sorption in its turn is proportional to efficient value of β. The availability of the Al₂O₃ surface was evaluated.     

激光推进用于飞行器姿轨控制的分析与仿真

激光推进成本低、可靠性高,可用作飞行器的空间推进和姿态调整。建立了考虑反馈控制和激光推进的飞行器动力学模型,模型中的操纵控制项模拟了飞行器操纵系统和激光推进产生的力、力矩。详细研究了确定操纵项的方法,使用自适应飞行控制律,给出一种通过求解线性方程组确定操纵控制项的方法。以圆形盘旋轨迹为例,进行了数值模拟,计算结果显示,激光推进下的飞行器能很好按照目标轨迹飞行,并对计算结果进行了分析。