Aerodynamic characteristics research on wide-speed range waverider configuration

Waverider generated from a given flow field has a high lift-to-drag ratio because of attached bow shock on leading edge. However, leading edge blunt and off-design condition can make bow shock off leading edge and have unfavorable influence on aerodynamic characteristics. So these two problems have always been concerned as important engineering science issues by aeronautical engineering scientists. In this paper, through respectively using low speed and high speed waverider design principles, a wide-speed rang vehicle is designed, which can level takeoff and accelerate to hypersonic speed for cruise. In addition, sharp leading edge is blunted to alleviated aeroheating. Theoretical study and wind tunnel test show that this vehicle has good aerodynamic performance in wide-speed range of subsonic, transonic, supersonic and hypersonic speeds.

环境CO2浓度和群落密度对红桦(Betula albosinensis Burk.)幼苗碳氮吸收和分配的影响

当前大气CO2浓度升高是全球变化的主要趋势之一，CO2浓度升高还会引起全球变暖等其它环境问题，因而CO2浓度浓度升高对植物影响的研究已经成为全球变化领域的焦点。红桦是川西亚高山地区暗针叶林演替初期的先锋树种和演替后期的建群种，在群落演替过程中它对环境因子的响应决定红桦群落的演替进程。本文通过控制CO2浓度的气候室试验，研究了CO2浓度倍增环境下，不同密度水平红桦碳氮固定、分配可能发生的改变，并探讨了升高大气CO2浓度对群体内部竞争的影响。以期通过本研究明确川西亚高山地区代表性物种红桦对未来气候变化的响应，为今后采取措施应对气候变化、妥善进行森林管理提供理论依据和科学指导。主要研究结果如下： 1.升高CO2浓度对红桦幼苗生长的影响以及树皮、树干响应的不同 (1) CO2浓度升高显著促进红桦幼苗的生物量、株高、基茎的生长，同时也改变生物量在体内的分配格局，主要是增加根和主茎、减少叶在总生物量中的比重。(2)树皮和树干对升高CO2浓度的影响有差异，它们对CO2浓度升高的反应程度不同，但反应方向一致。 2.密度的副效应 (1) 增加种植密度对单株生物量、株高和基径的生长具有副效应，也降低升高CO2浓度对红桦生长的正效应。(2) 增加种植密度，显著增加红桦幼苗的群体生物量，从而使红桦群体固定更多的大气CO2气体。可见密度在决定红桦生物量及固碳能力方面具有重要意义。探索适合未来大气CO2浓度升高条件下植物生长的密度，对未来的森林经济生产、生态恢复具有重要意义。 3. 升高CO2浓度对红桦幼苗苗冠结构及冠层内部竞争的影响 (1) 冠幅、冠高、苗冠表面积和苗冠体积等树冠特征均受CO2浓度升高的影响而增加，但是受密度增加的影响而降低。(2) 单位苗冠投影面积叶片数(LDcpa)和单位苗冠体积叶片数(LDcv)均低于相应的现行CO2浓度处理，这主要是由于冠幅和冠高的快速生长所造成的。(3) LDcpa和LDcv的降低表明，红桦在升高CO2浓度的条件下，会作出积极的响应，从而缓解由于群体和个体生长的增加所引起的竞争压力的增加。 4. 升高CO2浓度对红桦幼苗养分元素吸收与分配的影响 (1) CO2浓度升高，植株各器官N、P含量降低，但单株N、P总吸收量均增加。红桦幼苗体内N、P浓度的下降是由于生物量迅速增加引起的稀释效应造成的。(2) CO2浓度升高，N、P向主茎和根的分配增加，向叶片的分配减少，主要是由于前者在总生物量中的比重增加，而后者减少了。(3) CO2浓度升高，氮磷利用效率(NUE和PUE)提高，氮磷累积速率(NAcR和PAcR)显著增加。而NUE和PUE的提高可以有效缓解CO2浓度升高后，亚高山和高山地区森林土壤中养分元素不足对森林生产力的限制。 5. 升高CO2浓度对红桦幼苗群体碳平衡的影响 (1) 升高CO2浓度对植物的光合作用、呼吸速率和生长均具有促进作用。(2) 土壤有机碳含量在实验前期迅速增加，后期积累速率下降。(3) 升高CO2浓度以后，土壤呼吸显著增强；土壤呼吸还具有明显的季节变化。(4) 红桦群体日固碳量受到升高CO2浓度的促进作用。结果(1)-(4)说明所研究群落的碳动态对现行的气候波动是敏感的；所研究群落在作为大气CO2气体的源-汇关系方面至少存在季节间的源汇飘移。(5)种植密度的升高显著增加了群体固碳量。 6. 升高CO2浓度对红桦幼苗生长后期叶片衰老的影响 升高CO2浓度有利于减缓红桦幼苗叶片生长季节末期的衰老。生长季节末期，随着CO2浓度的升高光合速率和可溶性蛋白含量均呈上升趋势，同时MDA（丙二醛）含量下降，保护酶SOD（超氧化物岐化酶）、CAT（过氧化氢酶）活性升高。由此说明，升高CO2浓度有利于减缓生长季节后期叶片的衰老，使叶片维持较高的光合速率，也从生理学的角度支持了本文及前人有关CO2浓度升高促进植物光合和生长的假说及结果。 The increased CO2 concentration is one of the most important problems among global changes. The increase of CO2 will also cause other environmental problems, such as global warming, etc. So the effects of elevated CO2 on plant have drawn sights of many scientists in the research field of global change. Red birch (Betula albosinensis) usually emerges as the pioneer species in initial stage and as constructive species in later stages of forest community succession of the dark coniferous forests in Western Sichuan, China. It’s response to elevated CO2 may determine the succession process of the community where it lives in. By controlling CO2 at the ambient and twice as the ambient level (ambient + 350 umol mol-1) using enclosed-top chambers (ETC), possible effects of elevated CO2 on carbon fixation and allocation under two plantation densities are investigated. The effects of elevated CO2 on competition within canopy of red birch seedlings are also observed in the present paper. We hope to make sure of the effects of elevated CO2 on the representative species, red birch. And so that, our results could provide a strong theoretical evidence and scientific direction for forest management and afforestation under a future, CO2 elevated world. The results are as fowllows: 1. The effects of elevated CO2 on growth and the different responses of wood and bark of red birch seedlings (1) Elevated CO2 increases the growth of seedling biomass, seedling height and basal diameter of red birch. It also changed the biomass allocation in red birch seedlings. The ratio of root and main stem to all biomass is increased and the ratio of leaf is decreased. (2) Tree bark and wood show different response degree but similar response direction to elevated CO2. 2. Negative effects of planting density (1) The increase of planting density showes negative effects on the individual growth of seedling biomass, seedling height and basal diameter of red birch. It also eliminates the positive effects of elevated CO2 on growth of red birch seedlings. (2) Community biomass is increased by the elevated planting density, which means that the high density red birch community could fix more CO2 than the low density one. These results show that planting density plays an important role in determining biomass and carbon fixation ability of red birch community. Thus, exploring proper planting density becomes economically important for the future, CO2 elevated word. 3. The effects of elevated CO2 on crown architecture and competition within canopy of red birch seedlings (1) Crown width, crown depth, crown surface area and crown volume are all increased under the influence of elevated CO2. (2) Leaf number per unit area of projected crown area (LDcpa) and per unit volume of crown volume (LDcv) are lower under elevated CO2. This is resulted from the stimulated growth of tree crown features. (3) The decrease of LDcpa and LDcv indicate that plants will respond forwardly to reduce the possible increase of competition resulted from stimulated growth of individual plant and collectives in conditions of elevated CO2. 4. The effects of elevated CO2 on nutrition accumulation and allocation of red birch seedlings (1) Contents of N and P decrease due to the prompt increase of biomass of plant organs caused by elevated CO2. However, their accumulations increase under elevated CO2. (2) Elevated CO2 increases the allocation of N, P to main stem but reduced its allocation to leaf for that dry weight of the former increased but the dry weight of the later decreased. (3) Using efficiencies of N, P (NUE and PUE) and their accumulation rates (NAcR and PAcR) are found to increase under elevated CO2. Soil nutrition contents are always the limiting factors for plant growth at subalpine and alpine region. The increased NUE and PUE are helpful to eliminate the nutrition limitation in this area in the future world, when CO2 concentration doubles the ambient. 5. The effects of elevated CO2 on carbon balance of red birch communities (1) Net photosynthetic rates (Pn), dark respiration rates (Rd) and growth are all stimulated by elevated CO2. (2) Content soil organic carbon increases sharply at the primary stage of experiments and then the increasing rates decrease to a low level at later stages. (3) Soil respiration rates increase significantly with the elevation of CO2 concentration. (4) The daily carbon fixations of whole community are heightened by elevated CO2. The results (1)-(4) suggest that, the community being studied are sensitive to current climate change; the studied community, as a sink of atmospheric CO2, is pool-sink alternative between seasons. (5) The carbon fixations are increased along the increase of planting densities. 6. The effects of elevated CO2 on physiological features of leaf senescences of red birch seedlings at the later stage of growing season Elevated CO2 helps to postpone the leaf senescences of red birch at the end of the growth season. CO2 enrichment increases the photosynthetic rates, contents of soluble proteins and photosynthetic pigments. And meanwhile contents of malondialdehyde (MDA) decreases and activities of superoxide dismutase (SOD) and catalase (CAT) are both increased. These results suggest that the senescences of red birch leaves are delayed by elevated CO2, which keep the photosynthetic rates at relatively high levels. Our results lend supports to hypothesis and results on stimulated photosynthetic rates and growth from both other researchers and the present paper.

A novel urchinlike gold/platinum hybrid nanocatalyst with controlled size

In this paper, we have explored a simple and new strategy to obtain quasimonodisperse Au/Pt hybrid nanoparticles (NPS) with urchinlike morphology and controlled size and Pt shell thickness. Through changing the molar ratios of Au to Pt, the Pt shell thickness of urchinlike Au/Pt hybrid NPs could be easily controlled; through changing the size of Au NPs (the size was easily controlled from similar to 3 to similar to 70 nm via simple heating of HAuCl4-citrate aqueous solution), the size of urchinlike Au/Pt hybrid NPs could be facilely dominated. It should be noted that heating the solution (100 degrees C) was very necessary for obtaining three-dimensional (3D) urchinlike nanostructures while H2PtCl6 was added to gold NPs aqueous solution in the presence of reductant (ascorbic acid). The electrocatalytic oxygen reduction reaction (ORR, a reaction greatly pursued by scientists in view of its important application in fuel cells) and the electron-transfer reaction between hexacyanoferrate(III) ions and thiosulfate ions of urchinlike Au/Pt hybrid NPs were investigated. It is found that the as-prepared urchinlike Au/Pt hybrid NPs exhibited higher catalytic activities than that of similar to Pt NPs with similar size.

中低纬度变化磁场的暴时特征研究

Magnetic storm is a kind of severe disturbances in the whole solar-earth electromagnetic space. It has significant effects on communication, electric power, oil transport pipe and human activities in space. Therefore, magnetic storms are worth for applications systems, not only being a favorable issue for scientists. In this paper, the spatial and temporal distributions of the magnetic fields produced by the magnetosphere-ionosphere current systems during storms are studied. Four parts are included in this paper decomposion of different disturbances with different origins, topological structure of the ring current, the asymmetric characteristics of the ring current, and the statistic peculiarities of the day-to-day variability (DTD) of Sq. 1 The decomposition of magnetic disturbances at mid-low latitudes and its evolutions during storms Transient variations in the geomagnetic field recorded at mid-low latitudes mainly include the storm-time variation (Dst), solar quiet daily variation (Sq) and disturbance daily variation (SD). With the data of the geomagnetic meridian chain observatories in China, 25 storms during the period of 1997 to 1999 have been analyzed. According to the features of different variations, a method of “three-steps decomposition” is developed by using the method of Natural Orthogonal Components (NOC), Correlation Analysis and Fourier Analysis to separate those three components in turn. The results show that, the first eigenmode by the MNOC clearly describing the special distribution and temporal evolution of storm-time variation, in addition, Correlation Analysis and Fourier Analysis offer a useful method to extract the Sq and SD variations. The latitudinal shift of the Sq current focus seems to be the principal reason of the day-to-day variaitons in the daily range of Sq. The magnitude of SD reaches a maximum during the main phase, and then gradually decreases. 2 The topology structure of the ring current during storms Both the mechanism of the ring current and the geomagnetic data suggest that the central plane of the ring current is declining to the geomagnetic equator plane with a tilt angle δ. Using the H and Z component data at two stations in a meridian chain, we deduce a new parameter describing the invariable peculiarity of different storms. Then the δ angle is calculated by using the data from a meridian chain and tested with the ERC model. Finally the deduced tilt angles are used to modify Dst index. 3 The asymmetric characteristics of the ring current during storms The variations of the geomagnetic field at mid-low latitudes show a significant dawn-dusk asymmetry, resulting from the superposition of the fields from the symmetric ring current and the partial ring current. On the basis of the data from the 20°E, 30°E meridian chains and 30°N latitudinal chain, the dawn-dusk asymmetry is investigated by using three methods, namely, statistic analysis, ring current model calculation and typical event analysis. This characteristic implies the asymmetry of the spatial distribution of the ring current. In addition, during the main phase after the sudden commencement (SC), H field increases and reaches maximum around noontime, implying the effect of the Chapman-Ferraro current. 4 The statistic characteristics of the day-to-day variability and its mechanism The day-to-day variability of the geomagnetic Sq field is studied by using the magnetic data from a meridian chain of magnetometers along 120° E longitude. The method of NOC is applied to separate the Sq variation from complicated disturbances. The first eigenmode with the largest eigenvalue represents fairly well the Sq variation with a conspicuous day-to-day variability in the daily range. For the stations on the same north- or south-side of the Sq current system focus, the day-to-day variations show a positive correlation. In contrast, for the stations on the different sides of the Sq focus, they show a negative correlation, suggesting an important role of latitudinal shift of the Sq current system focus to the day-to-day variability of the Sq daily range. The Sq daily range is correlated with the magnetic indices Ap and Dst in a peculiar way: on some severe disturbed days, noticeably enhancements of the Sq are observed, implying increases of the ionospheric conductivities and/or tidal wind velocities; on other severe disturbed days, however, dramatically reduced Sq variations occur, suggesting dominant effects of the ‘disturbance dynamo’ process.

复杂碎屑岩储层动、静态参数计算理论与方法研究

Reservoir characterization and reservoir modeling are two key techniques in petroleum exploration and development. They all are based on the reliable static and dynamic properties of the reservoirs, especially the static and dynamic properties of the reservoirs at each borehole. Without the static and dynamic properties of the reservoir, reservoir characterization and reservoir modeling will pass into nothingness. In fact, the static and dynamic properties of the reservoir are needed in every domain and stage of petroleum exploration & development Today, petroleum industry has reached a stage worldwide that most of the simple & large massive reservoirs have been well explored and developed. As a result, oil companies are paying more and more attention to the exploration & development of the complex & middle to small clastic reservoirs (such as low resistivity sandstone reservoirs, low or no resistivity contrast sandstone reservoirs, conglomerate reservoirs, volcanoclastic reservoirs). In the recent years, oil companies inside and outside China are focusing on the exploration and development elastic reservoirs. Most of the theories & methods being applicable for simple clastic reservoirs can not be used in complex clasic reservoirs. Some theories & methods that are not resolved in the case of simple clasic reservoirs become more impossible to be resolved in the case of complex elastic reservoirs. A set of theories & methods being applicable for computing the static and dynamic properties of the complex elastic reservoirs are developed in this paper and they have been put into practice successfully. These theories & methods are developed by integrating multi-subjects such as geology, well logging and reservoir engineering, in which geology is used as direction and modern well logging technology is used as basis and reservoir engineering is used as assistance and computer technology is used as tool. There are three outstanding breakthroughs in this paper: of the low porosity fractured and/or vuggy carbonate/igneous reservoirs too. A set of practical theories and methods of computing the static properties (such as porosity, saturation, lithology and fluid type) & dynamic properties (such as permeability and production rate) of simple clastic reservoirs have been developed with the hard efforts of many petroleum engineers and scientists in the past 70 years. However, only some of the theories & methods being applicable for simple clastic reservoirs can be used in complex clastic reservoirs after little modification because of the complexity of the complex clastic reservoirs. Most of the theories & methods being applicable for simple clastic reservoirs can not be used in complex clasic reservoirs. Some theories & methods that are not resolved in the case of simple clasic reservoirs become more impossible to be resolved in the case of complex clastic reservoirs. A set of theories & methods being applicable for computing the static and dynamic properties of the complex clastic reservoirs are developed in this paper and they have been put into practice successfully. These theories & methods are developed by integrating multi-subjects such as geology, well logging and reservoir engineering, in which geology is used as direction and modern well logging technology is used as basis and reservoir engineering is used as assistance and computer technology is used as tool. There are three outstanding breakthroughs in this paper: