Low partial pressure chemical vapor deposition of graphene on copper

A systematic study of the Cu-catalyzed chemical vapor deposition of graphene under extremely low partial pressure is carried out. A carbon precursor supply of just P CH4∼ 0.009 mbar during the deposition favors the formation of large-area uniform monolayer graphene verified by Raman spectra. A diluted HNO 3 solution is used to remove Cu before transferring graphene onto SiO 2/Si substrates or carbon grids. The graphene can be made suspended over a ∼12 μm distance, indicating its good mechanical properties. Electron transport measurements show the graphene sheet resistance of ∼0.6 kΩ/□ at zero gate voltage. The mobilities of electrons and holes are ∼1800 cm 2/Vs at 4.2 K and ∼1200 cm 2/Vs at room temperature. © 2011 IEEE.

Modelling non-linearities in a MEMS square wave oscillator

The modelling of the non-linear behaviour of MEMS oscillators is of interest to understand the effects of non-linearities on start-up, limit cycle behaviour and performance metrics such as output frequency and phase noise. This paper proposes an approach to integrate the non-linear modelling of the resonator, transducer and sustaining amplifier in a single numerical modelling environment so that their combined effects may be investigated simultaneously. The paper validates the proposed electrical model of the resonator through open-loop frequency response measurements on an electrically addressed flexural silicon MEMS resonator driven to large motional amplitudes. A square wave oscillator is constructed by embedding the same resonator as the primary frequency determining element. Measurements of output power and output frequency of the square wave oscillator as a function of resonator bias and driving voltage are consistent with model predictions ensuring that the model captures the essential non-linear behaviour of the resonator and the sustaining amplifier in a single mathematical equation. © 2012 IEEE.

新疆额尔齐斯河水系银鲫克隆多样性研究

银鲫(Carassius auratus gibelio Bloch)由于其独特的遗传背景和繁殖方式而成为研究进化遗传学和选择育种的一个独特的模式生物。到目前为止,我们对新疆额尔齐斯河水系银鲫群体的多样性状况一直知之甚少。为了更好地了解额尔齐斯河水系银鲫群体的克隆多样性状况,本研究中,我们采集了来自新疆额尔齐斯河水系的4个鲫鱼群体。通过流式细胞术分析血细胞样品,结果证实这些鲫鱼均为三倍体银鲫。通过血清转铁蛋白电泳表型分析,我们从这些银鲫群体中鉴定出总共8个不同的克隆。在这些鉴定的克隆中,有4个克隆(克隆A

湖泊底泥中微囊藻DNA的分子检测

通过改进裂解温度和延长裂解时间并增加苯酚/氯仿洗脱次数的DNA提取方法获得南京玄武湖底泥中的DNA,通过PCR法来扩增微囊藻的16SrRNA基因．结果表明在所有采样点中均得到微囊藻基因组DNA,并且纯度较高,OD_(260)/ OD_(280)均高于1．54,最高值达到1．89．PCR的扩增结果显示所有样点的DNA都得到212 bp大小的微囊藻16SrRNA基因片断,表明这种方法可以有效的从底泥中提取微囊藻的DNA,从而为研究底泥微囊藻生理生态及其越冬、上浮、形成水华的机理提供更有利的方法．

大兴安岭阿尔山沼泽鼓藻类中国新记录

大兴安岭阿尔山是我国沼泽分布最集中的地区之一,其中鼓藻类植物十分丰富。2004年7月,2005年8月、10月和2006年5月,作者先后4次在该地区采集标本共260号,在对标本鉴定过程中,发现有中国新记录鼓藻10个分类单位,隶属于4个属,包括8种2变种:厚皮鼓藻加厚变种Cosmarium pachydermumvar.incrassatum、穿孔鼓藻C.perforatum、伸长鼓藻C.protractum、具齿角星鼓藻Staurastrum denticulatum、不等角星鼓藻S.dispar、分叉角星

Computation of transient and steady turbulent isothermal flows with an impinging rectangular jet

The computation of both transient and steady turbulent incompressible isothermal flows is studied. The flow is very complex, having streamline curvature, large vortex structures and stagnation resulting from an impinging rectangular jet. For transient computations, the standard k-ε model is adopted. For steady flows, the k-ε, high and low Reynolds number k-l and mixing length models are tried. Zonal approaches combining the above turbulence models are also investigated. None of the models are found to give satisfactory agreement with velocity measurements.

An example of the use of neural computing techniques in materials science - The modelling of fatigue thresholds in Ni-base superalloys

Two adaptive numerical modelling techniques have been applied to prediction of fatigue thresholds in Ni-base superalloys. A Bayesian neural network and a neurofuzzy network have been compared, both of which have the ability to automatically adjust the network's complexity to the current dataset. In both cases, despite inevitable data restrictions, threshold values have been modelled with some degree of success. However, it is argued in this paper that the neurofuzzy modelling approach offers real benefits over the use of a classical neural network as the mathematical complexity of the relationships can be restricted to allow for the paucity of data, and the linguistic fuzzy rules produced allow assessment of the model without extensive interrogation and examination using a hypothetical dataset. The additive neurofuzzy network structure means that redundant inputs can be excluded from the model and simple sub-networks produced which represent global output trends. Both of these aspects are important for final verification and validation of the information extracted from the numerical data. In some situations neurofuzzy networks may require less data to produce a stable solution, and may be easier to verify in the light of existing physical understanding because of the production of transparent linguistic rules. © 1999 Elsevier Science S.A.

保安湖沉水植被恢复及其渔业效益

通过消除对沉水植物生长有破坏作用的草食性鱼类和杂食性鱼类，在低水位的早春选择无风浪的天气移栽水草，于 １９９４年在保安湖一个面积为 ３ ．３ｈｍ~２网栏湖汊成功地恢复了绝迹 ８个月的水草群落，秋季水草覆盖率达 ５０％，同时研究了在无鱼类摄食破坏的条件下苦草和黄丝草的生长动态．于１９９４－１９９５年在保安湖另一个面积为１３３．３ｈｍ~２土栏湖汊（即肖四海）恢复了水草群落，１９９５年秋季水草覆盖率达７０％，由于水草群落的恢复，肖四海结束了施肥投草主养四大家鱼的养殖方式，而采用了以河蟹和鳜鱼为增养殖对象的优质高

华鳈人工繁殖和早期发育的研究

1992年5月～7月分别对9组华鳈亲鱼进行的催产试验结果进行分析,并对其早期发育进行了较为详细的观察。华鳈受精卵在水温为22～33℃的条件下胚胎发育时间为54～74h,水温34℃左右时仍能正常发育;孵出时眼黑色,胸鳍基已形成,有发达的居氏管;孵出后第二天鳔即充气,第三天可以摄食并能自由在水层生活。

Structural and optical characterization of vertical GaAs/GaP core-shell nanowires grown on Si substrates

GaAs nanowires were grown on Si (111) substrates. By coating a thin GaAs buffer layer on Si surface and using a two-temperature growth, the morphology and crystal structure of GaAs nanowires were dramatically improved. The strained GaAs/GaP core-shell nanowires, based on the improved GaAs nanowires with a shell thickness of 25 nm, showed a significant shift in emission energy of 260 meV from the unstrained GaAs nanowires. © 2010 IEEE.

长江中下游江豚种群现状评价

作者根据近年在长江中下游对江豚进行考察的资料和收集到的标本,系统分析评价了长江中下游江豚的种群现状,主要结果如下:1.长江江豚上至宜昌(距河口1669公里),下至长江口,以及洞庭湖、鄱阳湖均有分布。分布型式是沿长江纵向呈集群性分布,横向呈趋岸性分布;2.长江中下游江豚种群数量估计为2700头。其数量冬季最高,夏季最低。夏季的SPUE值仅为冬季的48.7％—58.6％;3.长江中下游江豚群体以1—5头最为常见,占88％;4.理论推算长江中下游每年新产生个体为539头,年出生率为20％;5.通过分析比较长江中