Oscillation flow induced by underwater supersonic gas jets

This paper describes an experimental study on the oscillation flow characteristics of submerged supersonic gas jets issued from Laval nozzles. The flow pattern during the jet development and the jet expansion feedback phenomenon are studied using a high-speed camera and a pressure measurement system. The experimental results indicate that along the downstream distance, the jet has three flow regimes: (1) momentum jet; (2) buoyant jet; (3) plume. In the region near the nozzle exit a so-called bulge phenomenon is found. Bulging of the jet occurs many times before the more violent jet expansion feedback occurs. During the feedback process, the jet diameter can become several times that of the original one depending on the jet Mach number. The frequencies of the jet bulging and the jet expansion feedback are measured.

Research on the mechanics of underwater supersonic gas jets

An experimental research was carried out to study the fluid mechanics of underwater supersonic gas jets. High pressure air was injected into a water tank through converging-diverging nozzles (Laval nozzles). The jets were operated at different conditions of over-, full-and under-expansions. The jet sequences were visualized using a CCD camera. It was found that the injection of supersonic air jets into water is always accompanied by strong flow oscillation, which is related to the phenomenon of shock waves feedback in the gas phase. The shock wave feedback is different from the acoustic feedback when a supersonic gas jet discharges into open air, which causes screech tone. It is a process that the shock waves enclosed in the gas pocket induce a periodic pressure with large amplitude variation in the gas jet. Consequently, the periodic pressure causes the jet oscillation including the large amplitude expansion. Detailed pressure measurements were also conducted to verify the shock wave feedback phenomenon. Three kinds of measuring methods were used, i.e., pressure probe submerged in water, pressure measurements from the side and front walls of the nozzle devices respectively. The results measured by these methods are in a good agreement. They show that every oscillation of the jets causes a sudden increase of pressure and the average frequency of the shock wave feedback is about 5-10 Hz.

大熊猫“盛林1号”放归监测

大熊猫(Ailuropoda melanoleuca)是我国特有的珍稀濒危物种，国家Ⅰ级重点保护野生动物，被称为“国宝”。目前，大熊猫被局限在我国中西部的岷山、邛崃、大相岭、小相岭、凉山和秦岭6大山系中。对大熊猫的保护和研究，我国政府、保护生物学科研人员、社会各界及国际保护组织都做了大量的工作。根据全国三次大熊猫调查结果显示，大熊猫栖息地片段化现象依然存在，形成多个隔离的大熊猫小种群。尤其在小相岭、大相岭、岷山B和岷山C种群，大熊猫数量较少，且栖息地破碎，面临较大威胁。有的山系大熊猫种群数量些已低于最小可存活大熊猫种群的数量，如果不采取人工措施，这些种群的大熊猫存在灭绝的危险。 将圈养大熊猫放归野外，以补充野外大熊猫种群数量，增加其遗传多样性，复壮和扩大野生大熊猫种群，是大熊猫人工繁育的最终目标。为降低放归的风险性，在放归人工繁育大熊猫前，将救护存活的野生大熊猫先有计划放归野外，并对其进行跟踪监测，对积累大熊猫放归经验，进一步研究大熊猫野外生物学习性，丰富放归地大熊猫种群遗传多样性，为人工繁育大熊猫放归野外夯实基础，具有十分重要的意义。2005年8月8日，国家林业局和四川省人民政府联合将救护野生大熊猫“盛林1号”放归于龙溪－虹口国家级自然保护区内岷山B大熊猫种群栖息地，并进行系统监测研究。成功的积累了一些放归经验和放归大熊猫的生物学资料，为人工繁育大熊猫的放归奠定了一定基础。 2005年8月至2007年6月期间，我们采用GPS无线电项圈、粪便DNA检测和红外线自动触发相机陷阱的方法，对大熊猫“盛林１号”进行了追踪监测，获得了以下成果： 1.通过分析“盛林1号”放归后了活动趋势和采用两种贝叶斯方法，利用目前五大山系的已有微卫星遗传数据，检测“盛林１号”与五大山系的遗传关系的远近，推测其来源于邛崃山系的可能性较大。 2.收集了大量“盛林1号”野外生境选择数据。我们认为“盛林1号”放归后经历了应急期、初步稳定期、长途迁徙期三个阶段（这可能是今后放归大熊猫都必经的三个时期），并与当地大熊猫种群已发生交流。目前“盛林１号”仍在寻找适合的巢域。 3.结合过去监测数据分析，在放归区域大熊猫和羚牛尽管同域分布，但由于食性不同，对微生境选择还是有着很大差异，因此保护管理对策要有针对性。 4.“盛林1号”的放归是成功的。救护大熊猫异地放归工作应继续开展，但要改进放归后的监测技术。要改进现有对人工饲养大熊猫野化培训方法和放归方式，才能真正将人工繁殖个体放归野外。 Giant Panda (Ailuropoda melanoleuca) is an endangered species endemic to China. It was listed as National Protected I Class Species and is crowned as “National treasure” of China. The populations of Giant Panda are limited in 6 mountain system in Center-West of China, i.e. Mingshan, Mt. Qionglai, Mt. Daxiangling，Mt. Xiaoxiangling, Mt. Liangshan and Mt. Qinling. The results of the Third National Survey on Giant Panda showed that the habitats of Giant Panda is still fracted and Giant Panda population is divided into several isolated small populations. Population B from Mt. Daxiangling, Mt. Xiaoxiangling and Mt. Mingshan and Population C from Mt. Mingshan are very small with very fracted habitat and are more endangered. Several populations in those mountain systems are smaller than Minimum Viable Population of Giant Panda. It is very possible that those populations will be extinct without artificial help. The ultimate Goal of Reintroduction caged Giant Panda to wild is to increase wild population size and genetics diversity and rebuild and expand wild Giant Panda population. It is of significant to return rescued wild Giant Panda to wild and monitor their behavior before reintroduction artificial reproduced Giant Panda. It will increase our knowledge on reintroduction of Giant Panda. Aug 8th, 2005, “Shenglin 1”, a rescued wild Giant Panda was returned to Longxi-Hongkou National Nature Reservoir, which is habitat of Giant Panda Population B of Mt. Mingshan. A systematic monitor was carried out on “Shenglin 1”, and the successful return enriched our biological knowledge on Giant Panda reintroduction. It will be very help for future conservation work on reintroduce artificial reproduced Giant Panda. “Shenglin 1” was tracked with GPS collar, DNA in feces and infrared-trigged camera from Aug 2005 to Jun 2007. 1. Locomotion behavior and microsatellites comparison with Giant Panda from the 5 mountain systems indicated that “Shenglin 1” is possibly from Mt. Qionglai. 2. Habitat usage of “Shenglin 1” was studied. It was suggested that there were 3 phases after return, i.e. emergency response, preliminary stable phase and long distance locomotion, which could be a general process for other returned Giant Panda. It was indicated that there was some interaction between “Shenglin 1” and local population. “Shenglin 1” is seeking for suitable home range now. 3. Monitor data also indicated that microhabitat preference of Giant Panda and takin (Budorcas taxicolor) are different because of different diet, though they are sympatric. It was suggested that conservation management for the two species should be plan in particular. 4. The reintroduction of “Shenglin 1” is a successful case. The program of return rescued Giant Panda to other habitats is of value and should be continued. However, more improvement is needed for the monitor technique. More improvement is need for feralization and returning before we return artificial reproduced Giant Panda to wild.

Field emission from the structure of well-aligned TiO2/Ti nanotube arrays

Well-aligned TiO2/Ti nanotube arrays were synthesized by anodic oxidation of titanium foil in 0.5 wt.% HF in various anoclization voltages. The images of filed emission scanning electron microscopy indicate that the nanotubes structure parameters, such as diameter, wall thickness and density, can be controlled by adjusting the anoclization voltage. The peaks at 25.3 degrees and 48.0 degrees of X-ray diffraction pattern illuminate that the TiO2 nanotube arrays annealed at 500 degrees C are mainly in anatase phase. The filed emission (FE) properties of the samples were investigated. A turn-on electric field 7.8 V/mu m, a field enhancement factors approximately 870 and a highest FE current density 3.4 mA/cm(2) were obtained. The emission current (2.3 mA/cm(2) at 18.8 V/mu m) was quite stable within 480 min. The results show that the FE properties of TiO2/Ti have much relation to the structure parameters.

Synthesis and field emission of diamond-like carbon nanorods on TiO2/Ti nanotube arrays

Highly ordered TiO2/Ti nanotube arrays were fabricated by anodic oxidation method in 0.5 wt% HF. Using prepared TiO2/Ti nanotube arrays deposited Ni nanoparticles as substrate, high quality diamond-like carbon nanorods (DLCNRs) were synthesized by a conventional method of chemical vapor deposition at 750 degrees C in nitrogen atmosphere. DLCNRs were analyzed by filed emission scanning electron microscopy and Raman spectrometer. It is very interesting that DLCNRs possess pagoda shape with the length of 3-10 mu m. Raman spectra show two strong peaks about 1332 cm (1) and 1598 cm (1), indicating the formation of diamond-like carbon. The field emission measurements suggest that DLCNRs/TiO2/Ti has excellent field emission properties, a low turn-on field about 3.0 V/mu m, no evident decay at 3.4 mA/cm(2) in 480 min. (C) 2009 Elsevier B. V. All rights reserved.

Modification of Fe/Cu Multilayers under 2-MeV Xe20+ Irradiation

Multilayers with a structure of Si/[Fe(10 nm)/CU(10 nm)](5) were deposited on Si(100) substrates and then irradiated at room temperature by using 2-MeV Xe20+. The modifications of the multilayers were characterized using a depth profile analysis of the Auger electron spectroscopy (AES) data and the evolution of crystallite structures of the multilayers were analyzed by using X-ray diffraction (XRD). The AES depth profiles indicated that de-mixing of the Fe and the Cu layers was observed at low ion fluences, but inter-mixing of the Fe and the Cu layers was found at high ion fluences and destroyed the layered structure of the multilayers. The obtained XRD patterns showed that, after irradiation by 2-MeV Xe20+ at; 2 x 10(16) ions/cm(2), the peaks of the multilayers related to a Cu-based fee solid solution and an Fe-based bee solid solution phase became visible, which implied that the inter-mixing at the Fe/Cu interface resulted in the formation of new phases. A possible mechanism of modification in the Fe/Cu multilayers induced by ion irradiation is briefly discussed.

Systematic study of the pi(-)/pi(+) ratio in heavy-ion collisions with the same neutron/proton ratio but different masses

A systematic study of the pi(-)/pi(+) ratio in heavy-ion collisions with the same neutron/proton ratio but different masses can help single out effects of the nuclear mean field on pion production. Based on simulations using the IBUU04 transport model, it is found that the pi(-)/pi(+) ratio in head-on collisions of Ca-48 + Ca-48, Sn-124 + Sn-124, and Au-197 + Au-197 at beam energies from 0.25 to 0.6 GeV/nucleon increases with increasing the system size or decreasing the beam energies. A comprehensive analysis of the dynamical isospin fractionation and the pi(-)/pi(+) ratio as well as their time evolution and spatial distributions demonstrates clearly that the pi(-)/pi(+) ratio is an effective probe of the high-density behavior of the nuclear symmetry energy.

高电荷态离子126Xeq+引起GaN表面形貌变化研究

用不同电荷态的126Xeq+离子（9≤q≤30）在室温下轰击GaN晶体表面，经原子力显微镜分析表明，当q>18，辐照区域由隆起转为显著的刻蚀.被轰击后的GaN晶体表面形貌主要取决于入射离子的电荷态.同时，样品表面形貌还与入射离子的剂量和入射角有关；在实验参数范围，与入射离子的初动能没有明显关系（180 keV≤Ek≤600 keV）.当入射离子的电荷态q=18，与样品表面法线成60°角倾斜入射和垂直表面入射时，样品的表面几乎没有变化，只是倾斜入射后有很微小的隆起；当q＜18时，样品表面膨胀隆起，粗糙度增强，倾斜入射时表面隆起比垂直入射时更明显，而且都有清晰的峰状分界区；当q＞18时，样品表面被蚀刻呈凹陷状，有明显的齿状刻痕，且侵蚀深度与离子剂量近似呈线性关系，倾斜入射时的刻蚀深度大于垂直入射时的刻蚀深度.

Rapid detection of porcine circovirus type 2 by loop-mediated isothermal amplification

A method of loop-mediated isothermal amplification (LAMP) was employed to develop a rapid and simple detection system for porcine circovirus type 2 (PCV2). The amplification could be finished in 60 min under isothermal condition at 64 degrees C by employing a set of four primers targeting the cap gene of PCV2. The LAMP assay showed higher sensitivity than the conventional PCR, with a detection limit of five copies per tube of purified PCV2 genomic DNA. No cross-reactivity was observed from the samples of other related viruses including porcine circovirus type 1 (PCV1), porcine parvovirus (PPV), porcine pseudorabies virus (PRV) and porcine reproductive and respiratory syndrome virus (PRRSV). The detection rate of PCV2 LAMP for 86 clinical samples was 96.5% and appeared greater than that of the PCR method. The LAMP assay reported can provide a rapid yet simple test of PCV2 suitable for laboratory diagnosis and pen-side detection due to ease of operation and the requirement of only a regular water bath or heat block for the reaction. (c) 2008 Elsevier B.V. All rights reserved.

Photoluminescence character of Xe ion irradiated sapphire

In the present work the photoluminescence (PL) character of sapphire implanted with 180 keV Xe and irradiated with 308 MeV Xe ions was studied. The virgin, implanted and irradiated samples were investigated by PL and Fourier transform infrared (FTIR) spectra measurements. The obtained PL spectra showed the maximum emission bands at 2.75, 3.0 and 3.26 eV for the implanted fluence of 1.0 x 10(15) ions/cm(2) and at 2.4 and 3.47 eV for the irradiated fluence of 1.0 x 10(13) ions/cm(2). The FTIR spectra showed a broaden absorption band between 460 and 630 cm(-1), indicating that strong damaged region formed in Al2O3.