下一代通信技术对广播电视业务发展的影响(下)

(接上期第43页) 3 下一代通信接入对广播电视业务发展的影响 3.1 突破用户接入的瓶颈 随着宽带业务的发展,网络接入部分(最后1 km)的带宽瓶颈问题显露出来.目前,接入部分两侧都已跨入吉比特级以上的速率,如用户端广泛使用的PC,其内部传送速率已达到32 Gb/s,城域网或长途网的每波长速率也已达到2.5～10 Gb/s,两者都比接入部分高出至少3个数量级.可见,尽快打通接入部分的带宽瓶颈,各种宽带服务与应用才能开展起来,网络容量的潜力才能真正发挥.     

On the processing-structure-property relationship of ITO layers deposited on crystalline and amorphous Si

Indium-tin-oxide (ITO) antireflection coatings were deposited on crystalline Si (c-Si), amorphous hydrogenated Si (a-Si:H) and glass substrates at room temperature (RT), 160 °C and 230 °C by magnetron sputtering. The films were characterised using atomic force microscopy, transmission electron microscopy, angle resolved X-ray photoelectron spectroscopy, combined with resistance and transmittance measurements. The conductivity and refractive index as well as the morphology of the ITO films showed a significant dependence on the processing conditions. The films deposited on the two different Si substrates at higher temperatures have rougher surfaces compared to the RT ones due to the development of crystallinity and growth of columnar grains.     

PCB原型能在设计过程中增值

您如何使用原型?是否仅做系统设计中那些棘手部件的原型?您反复制造原型PCB,使之与设计保持一致吗?EDN应如何报道PCB设计?     

Effect of Cryogenic Temperature Deposition of Various Metal Contacts on Bulk Single-Crystal <Emphasis Type="Italic">n</Emphasis>-Type ZnO

The effect of cryogenic temperatures during metal deposition on the contact properties of Pd, Pt, Ti, and Ni on bulk single-crystal n-type ZnO has been investigated. Deposition at both room and low temperature produced contacts with Ohmic characteristics for Ti and Ni metallizations. By sharp contrast, both Pd and Pt contacts showed rectifying characteristics after deposition with barrier heights between 0.37 eV and 0.69 eV. Changes in contact behavior were measured on Pd to anneal temperatures of ∼300 °C, showing an increase in barrier height along with a decrease in ideality factor with increasing annealing temperature. This difference with annealing temperature is in sharp contrast to previous results for Au contacts to ZnO. There were no differences in near-surface stoichiometry for the different deposition temperatures; however, low temperature contacts demonstrated some peeling/cracking for Pt and Pd.     

Mitigating the risk of high power damage to the BT network

Optical powers used in optical telecommunications networks have increased over time with the advent of technologies such as erbium-doped fibre amplifiers, dense WDM, and fibre Raman amplifiers. Erbium fibre and Raman amplifiers with output powers up to 1 W and 2 W respectively are now available for deployment giving optical power densities of ≈ 14 000 MW/m² per Watt launched into a single mode fibre. This compares with 74 MW/m² for the surface of the sun. It is thus essential to ensure that the risk of optical damage to the fibre is understood and steps are taken to mitigate it where necessary. Research carried out by BT over the last few years has shown that fibres carrying relatively modest optical powers, as low as 200 mW for the most sensitive fibres, can be catastrophically damaged at tight fibre bends. Damage is caused by some of the optical power lost at the bend being absorbed by the fibre coating that may over time lead to a sudden increase in temperature to over 700 °C causing either the silica to kink mimicking a fibre break, or the coating to burn off at the bend leading to fibre failure on subsequent handling. This paper describes factors that increase the risk of short-term catastrophic damage at fibre bends, presents experimental results to show the variation in sensitivity between different fibres, and discusses new important theoretical results modelling the temperature rise in the fibre.     

昆钢高炉铁水脱碳实验研究

研究了不同铁矿粉氧化剂以及矿粉加入量、铁水初始成分、铁水温度等因素对铁水碳、硅、锰氧化的影响.实验表明巴西粉与滇滩矿具有较好的脱碳效果,在高炉出铁温度范围内,用巴西粉或滇滩矿加入量为2%时,可平均脱去3.3%的碳、50%的硅和30%的锰.对铁水进行氧化脱碳处理后进行冷却,没有发现片状石墨析出.     

Modeling the effects of hypoglycemia on a two-choice task in adult humans.

Objective: Previous research has demonstrated that hypoglycemia causes reaction times to be slower and more variable. Reaction time tests, however, use multiple cognitive and noncognitive processes. This study is the first to use a validated sequential sampling model (diffusion model) applied to results obtained from a simple 2-choice task in adult humans to assess the effects of hypoglycemia on the basic parameters of decision making. Method: Fourteen adult volunteers were tested on a numerosity discrimination task with and without reduced blood glucose concentrations. The results were analyzed with a model that dissects the components of processing that underlie decisions: the quality of the information on which a decision is based (drift rate), the critical amount of evidence that must be accumulated before a decision is made (boundary separation), and the time taken by nondecision processes. Results: Hypoglycemia resulted in a reduction of mean drift rate from 0.290 to 0.211, t(13) = 4.10, p