长江河口内溢油轨迹的数值模拟研究

构建了海洋与溢油模型相耦合的长江河口的溢油轨迹预报系统,海洋模型能较好模拟该海域的表层流场;溢油模型采用拉格朗日和随机游走的油粒子追踪法,可快速预测油粒子的漂移扩散轨迹和扫海面积。研究表明,大潮时溢油的油粒子的分布范围和扫海面积均比小潮时刻大,在南支溢出的油粒子会漂移到南、北港和南、北槽,对生态环境危害最大,会影响陈行和青草沙两大水库取水口,并对中华鲟和九段沙湿地保护区产生潜在的生态危害;在北支溢出的油粒子主要分布在北支水道和两岸,如果溢油点位于上段会倒灌进南支水道,将会产生较大的生态危害;在南港溢出的油粒子会漂移到南北槽,不会对两大水库和中华鲟保护区产生危害,但会对九段沙保护区造成潜在的危害;在北港溢出的油粒子则会漂移到崇明岛外海,且扩散范围很大,只对中华鲟保护区造成危害。     

Composites reinforced in three dimensions by using low magnetic fields

The orientation and distribution of reinforcing particles in artificial composites are key to enable effective reinforcement of the material in mechanically loaded directions, but remain poor if compared to the distinctive architectures present in natural structural composites such as teeth, bone, and seashells. We show that micrometer-sized reinforcing particles coated with minimal concentrations of superparamagnetic nanoparticles (0.01 to 1 volume percent) can be controlled by using ultralow magnetic fields (1 to 10 milliteslas) to produce synthetic composites with tuned three-dimensional orientation and distribution of reinforcements. A variety of structures can be achieved with this simple method, leading to composites with tailored local reinforcement, wear resistance, and shape memory effects.     

颗粒特性对矩形养殖舱中颗粒物去除效果的影响

养殖工船是拓展深远海养殖空间的新途径之一,在船载舱养过程中,如果未消化的饲料残渣和排泄物等颗粒物不能及时排出,则会对鱼类健康及其生长环境产生严重的负面影响。该文章采用FLOW-3D软件进行数值仿真计算,研究了静止状态下30万t级养殖工船养殖舱出水口数目对舱内流场特征的影响,并在此基础上探究不同粒径与密度的颗粒物在舱内的去除效果。结果表明：当总进出水流量与出水口总面积恒定时,出水口数目从1增加到4,V99%从0.244 m/s降低至0.232 m/s,V95%从0.215 m/s降低至0.203 m/s,随着出水口数目的增加,养殖舱内流速减小;以占总量95%的颗粒物排出养殖舱所需时间为评价标准,当颗粒物密度为1050 kg/m3时,粒径为1 mm的颗粒物排出需要约24 min,粒径为0.5 mm的颗粒物排出需要约45 min,粒径为0.1 mm的颗粒物排出需要约78 min,当颗粒物密度相同时,随着粒径增大,其在养殖舱内的停留时间减少;颗粒物粒径为1 mm时,密度为1100 kg/m3的颗粒物排出需要约15 min,密度为1150 kg/m3的颗粒物排出需要约11.6 min,当颗粒物粒径相同时,颗粒物密度越大,其在养殖舱流场内的停留时间越短。该研究形成了CFD数值仿真计算与数理统计有机结合的综合分析方法,为之后具有不同横摇周期和较大横摇幅值的复杂工况提供研究手段及理论依据。     

Progesterone retards postpartum involution of the rabbit myometrium

Postpartum involution of the uterus was significantly reduced in rabbits by immediate and repeated injections of progesterone. Progesterone had no effect if the injections commenced 24 hours after delivery. The decrease in concentration of progesterone that accompanies birth results in release of proteolytic and other degradative enzymes from subcellular particles; these enzymes cause the involution, and, once the enzymes are released into the cellular milieu, progesterone has no effect.     

Surface Features of Metallic Spherules

Metallic spherules of variable character have been recovered from Antarctic snow. Three types were recognized from their surface features: type 1, smooth, polished spherules, apparently produced by surface melting of the particles upon entry into the earth's atmosphere; type 11, spherules with a corrugated surface caused by differential hardness of internal, intersecting lamellae, but modified by superimposed pits; and type III, spherules with random, circular depressions or pits apparently resulting from impact with submicroscopic particles. Spherules of types II and III were too small to have suffered abrasion by impacts in the earth's atmosphere, and it is postulated that their surfaces may have been produced by erosion in space. Preservation of these surface details would have been possible if entry into the atmosphere took place at low velocities and low-angle trajectories.     

Transient particle acceleration associated with solar flares

Understanding how individual charged particles can be accelerated to extreme energies (10(20) electron volts), remains a foremost problem in astrophysics. Within our solar system, the active sun is capable of producing, on a short time scale, ions with energies higher than 25 gigaelectron volts. Satellite and ground-based observation over the past 30 years have greatly increased our knowledge of the properties of transient bursts of energetic particles emitted from the sun in association with solar flares, but a real understanding of the solar flare particle acceleration process requires greatly refined experimental data. On the practical side, it is also imperative that this problem be solved if man is to venture, for long periods of time, beyond the protective umbrella of Earth's magnetic field, which excludes much of the biologically damaging solar energetic particles. It is only through an understanding of the basic acceleration problem that we can expect to be able to predict the occurrence of a solar flare with lethal solar radiations. For our knowledge of these effects to advance, a new space mission dedicated to studying the high-energy aspects of solar flares at high spatial and energy resolution will be required.     

影响水泥刨花板性能的因素的研究

本文论述刨花的形态、水泥/刨花的比率及水泥的种类对水泥刨花板静曲强度、弹性模量和尺寸稳定性的影响。     

Photothermal imaging of nanometer-sized metal particles among scatterers

Ambient optical detection of labeled molecules is limited for fluorescent dyes by photobleaching and for semiconducting nanoparticles by "blinking" effects. Because nanometer-sized metal particles do not optically bleach, they may be useful optical labels if suitable detection signals can be found. We demonstrate far-field optical detection of gold colloids down to diameters of 2.5 nanometers with a photothermal method that combines high-frequency modulation and polarization interference contrast. The photothermal image is immune to the effects of scattering background, which limits particle imaging through Rayleigh scattering to diameters larger than 40 nanometers.     

西藏雅鲁藏布江中游下段沙地高山松林研究

在有种源的情况下,该区高山松不仅可以在粉粒(0.01～0.05mm)含量40％以上的阶地上生长更新,而且可以在细砂为主的阶地覆沙地和山坡覆沙地上生长,并可在沙丘移动较慢的地段天然更新。繁茂枝叶可阻挡沙丘前移,形成高7m以下的沙丘。因此高山松不仅可作为先锋固沙树种,且具有强的阻沙固沙能力。阶地高山松幼林高生长主要受自身生物节律所控制,山坡覆沙地高山松高生长已受环境因子(4月份平均气温)制约。     

Charged Particles

There was a complete absence of charged particles associated with the planet Venus at radial distances as small as 41,000 km on the sunward side of the planet. This result is taken to mean that the magnetosphere of Venus, if any, does not extend to that great a distance. The most plausible interpretation is that (MV/ME) 相似文献   

含蜡原油管道胶凝形成机理研究进展

介绍了国内外献中对含蜡原油胶凝形成机理的研究成果。研究结果表明，在含蜡原油管道中，当油温低于浊点时，易在管壁处形成一层类似固体的凝胶物质。含蜡原油管道胶凝的形成主要受热历史和剪切历史的影响，胶凝湿度随冷却速度的减小而降低，随剪切应力的增大而降低，而浊点与冷却速度和剪切应力无关。在环境湿度高于油温的情况下， 即便油温低于浊点湿度，含蜡原油也不会形成胶凝。由于胶凝具有类似固体的机械特性，因此冷却速率越快，石蜡晶体越小，越多，屈服应力也越大，胶凝屈服应力取决于蜡晶的大小和数目。     

Retention of Solar Helium and Neon in IDPs in Deep Sea Sediment

It was recently proposed that subduction of interplanetary dust particles (IDPs) contained in deep sea sediments could have introduced substantial solar helium and neon to the Earth's mantle. However, it is not certain if IDPs would retain solar noble gases during subduction. A diffusion experiment that examined He and Ne in IDPs in a magnetic separate from Pacific Ocean sediments showed that He and Ne would be lost from IDPs within 3 years at 500 degrees C, and possibly within 10(5) years at 200 degrees C, which suggests that they would be lost from subducting slabs at shallow depths.     

以Cu颗粒强化导热的木质基复合相变储热材料性能研究

  目的  高导热的填料虽然能够提升木质基复合相变储热材料的储放热速率,但存在的易团聚现象无法使其均匀分散于材料内部。本研究旨在利用溶液还原法,由内而外地在轻木基体内原位生成单分散的金属铜颗粒,为提高木质基复合相变储热材料的储放热性能探索绿色、经济的道路。  方法  首先利用酸性亚氯酸钠溶液对轻木进行脱木素处理以提高其对相变材料的封装效率。然后利用CuSO₄溶液与抗坏血酸溶液在脱木素轻木内利用溶液还原法多次循环制备单分散金属Cu颗粒,并将反应完全后的轻木利用真空浸渍法与石蜡（PW）制备具有Cu颗粒强化导热的木基复合相变储热材料。采用场发射电子显微镜（SEM）、红外光谱分析（FTIR）、X射线衍射仪（XRD）、差式扫描量热仪（DSC）、导热系数测试仪和温度巡检仪对材料的微观、结晶、化学结构及储放热性能进行评价。  结果  轻木经脱木素处理后其对石蜡的封装效率从64.9%提升至了82.6%。经过抗坏血酸对Cu2+的还原作用,在轻木基体内原位制造出了Cu。然而循环次数过少,Cu不能均匀地分布在木材基体内,而过多的循环次数则会过量地影响轻木对相变材料的封装效果;其中3次的循环次数最为合适,以此所制备的复合相变储热材料导热系数提升了1.76倍,熔融与凝固潜热分别高达143.7、142.9 J/g,同时储热与放热时间分别缩短了23.7%与32.6%,展现出了更好的温度调节潜力。  结论  利用溶液还原法能够有效地在轻木基体内均匀制备金属Cu颗粒,并且以3次循环制备的Cu颗粒强化导热的木基复合相变储热材料储放热性能较好。      

Long-Range (Casimir) Interactions

Normally, nonrelativistic electromagnetic theory with two-particle Coulombic interactions adequately determines the interaction potential of systems A and B if the systems are composed of particles with characteristic velocities much less than the speed of light. If, however, the time it takes light to travel between A and B exceeds a characteristic oscillation period of A or B, the way in which the potential function depends on the separation of the systems can be altered. Called the Casimir effect, it has only recently been confirmed, and it arises in physics, chemistry, and biology. It is the clearest physical manifestation of the fact that, even in a vacuum, electromagnetic fields cannot all vanish.     

Hubble space telescope imaging of the north polar aurora on jupiter

The first direct images of the Jovian aurora at ultraviolet wavelengths were obtained by the Hubble Space Telescope Faint Object Camera near the time of the Ulysses spacecraft encounter with Jupiter on 8 February 1992. The auroral oval is not uniformly luminous. It exhibits a brightness minimum in the vicinity of longitude 180 degrees . In the few images available, the brightest part of the oval occurs in late afternoon Jovian time. The observed oval is not concentric with calculated ovals in the O(6) model of Connerney. The size of the oval is consistent with auroral particles on field lines with magnetic L parameter >8, indicating significant migration from lo, its torus, or both, if these are their origins.     

Suppression of collisional shifts in a strongly interacting lattice clock

Optical lattice clocks with extremely stable frequency are possible when many atoms are interrogated simultaneously, but this precision may come at the cost of systematic inaccuracy resulting from atomic interactions. Density-dependent frequency shifts can occur even in a clock that uses fermionic atoms if they are subject to inhomogeneous optical excitation. However, sufficiently strong interactions can suppress collisional shifts in lattice sites containing more than one atom. We demonstrated the effectiveness of this approach with a strontium lattice clock by reducing both the collisional frequency shift and its uncertainty to the level of 10(-17). This result eliminates the compromise between precision and accuracy in a many-particle system; both will continue to improve as the number of particles increases.     

Absorption of sunlight in the atmosphere of venus

In this report the fluxes measured by the solar flux radiometer (LSFR) of the Pioneer Venus large probe are compared with calculations for model atmospheres. If the large particles of the middle and lower clouds are assumed to be sulfur, strong, short-wavelength absorption results in a net flux profile significantly different from the LSFR net flux measurements. Models in which the smallest particles are assumed to be sulfur gave flux profiles consistent with the measurements if an additional source of absorption is included in the upper cloud. The narrowband data from 0.590 to 0.665 micrometer indicate an absorption optical depth of about 0.05 below the cloud bottom. The broadband data imply that either this absorption extends over a considerable wavelength interval (as might be the case for dust) or that a very strong absorption band lies on one side of the narrowband filter (as suggested by early Venera 11 and Venera 12 reports). Thermal balance calculations based on the measured visible fluxes indicate high surface temperature for reasonable assumptions of cloud opacity and water vapor abundance. The lapse rate becomes convective within the middle cloud. For water mixing ratios of 2.0 x 10(-4) below the clouds we find a subadiabatic region extending from the cloud bottom to altitudes near 35 kilometers.     

南堡油田海底管道砂沉积预测与模型检验

介绍了几种砂沉积预测模型,包括均匀颗粒计算模型杜兰德公式以及非均匀颗粒计算模型卡察斯基公式、舒克公式、王可钦公式。以南堡35-2油田WHPB-CEP海底混输管道为例进行砂沉积预测计算,采用激光粒度仪对积砂进行粒度分析,验证了预测结果的可靠性。按照均匀颗粒计算得砂沉积的临界流速为1．931m/s,按照非均匀颗粒计算得砂沉积的最小临界流速为0．193m／s,均大于根据实际工况条件计算得到的水相流速0．12m/s,说明海管以目前的工况运行,存在砂沉积问题。积砂粒径的平均值为178．36μm,远大于滤砂网孔径对应的粒径63μm,说明经过长期运行,滤砂网磨损,导致过滤孔径增大。提出了降低清管器卡堵风险、防止携砂过度沉积的具体方法。     

土壤环境中粘粒的分散-凝聚行为及其影响因素

本文研究了一般无机离子,重金属离子,表面活性剂和高分子化合物对土壤粘粒分散凝聚行为的影响,以期为土壤环境的保护与管理提供理论依据。结果表明i:)一般无机离子可通过对粘粒表面扩散双电层的压缩作用导致粘粒凝聚,且离子价数越高压缩作用越强i;i)重金属离子在粘粒上的专性吸附,导致其对扩散双电层的压缩作用更强i;ii)阳离子表面活性剂在较低浓度时可形成粒间疏水性表面胶束使粘粒凝聚,而在较高浓度时可形成粒内亲水性表面胶束使粘粒分散i;v)阳离子型高分子化合物在较低浓度时对粘粒的架桥作用可使粘粒凝聚,而在较高浓度时的静电斥力可使粘粒分散;v)随着pH的升高,粘粒由于表面负电荷的增加而趋于分散。以上说明:双电层的压缩、专性吸附、粒间疏水性表面胶束和架桥作用等均可使土壤粘粒凝聚,降低其稳定性。