旧时王谢堂前燕,飞入寻常百姓家——提升文物的“曝光度”

文物承载了我国的灿烂文明和优秀文化,具有多重观赏和研究价值。随着我国文化事业的迅速发展,进一步提升文物的＂曝光度＂,是增强民族自信,促进社会发展以及满足人们日益增长的文化精神追求的保证。本文分析了我国文物＂曝光＂存在的问题,并提出了相应的解决对策。

Nano-Level Electron Beam Lithography

The JEOL JBX-5000LS is a vector type machine.The system hardware features an ion-pumped column,a LaB 6 electron emitter,25kV and 50kV accelerating voltage,and a turbo-pumped sample chamber.The resolution,stability,stitching and overlay of this system are evaluated.The system can write complex patterns at dimensions down to 30nm.The demonstrated overlay accuracy of this system is better than 40nm.

Impact of cold indoor thermal environmental conditions on human thermal response

To explore the thermal responses under the non-thermal equilibrium cold environmental conditions,a laboratory study was conducted in climate chamber.The local skin temperatures and thermal sensation of 20 subjects were recorded at 10 min intervals for 90 min under air temperatures of 7.4,9.1,11 and 15 °C.The results show that both local skin temperatures and mean skin temperature decrease not only with the drop of ambient air temperature but also with the exposure time.Local thermal sensation and overall the thermal sensation have the similar temperature-varying and time-varying characteristics.Predicted mean vote(PMV) model cannot correctly predict the thermal sensation under non-thermal equilibrium cold environment.The correlation between local thermal sensation and local skin temperatures shows that thermal sensation is closely related to skin temperature.Skin temperature is an effective indicator of thermal sensation.A linear relationship model between overall thermal sensation and mean skin temperature,considering both ambient temperature and exposure time,was established in the non-thermal equilibrium cold environment,which makes the evaluation of thermal sensation more objective.

Effects of electron beam lithography process parameters on structure of silicon optical waveguide based on SOI

Electron beam lithography(EBL) is a key technology in the fabrication of nanoscale silicon optical waveguide. The influence of exposure dose, the main process parameter of EBL, on the structure profile of poly-methyl methacrylate(PMMA) after development was studied using a silicon on insulator(SOI) wafer with 220 nm top silicon as the substrate. The relationship between exposure dose and structure pattern width after development was analyzed according to the measurement results. The optimum exposure dose of 220 μC/cm^(2) was found to obtain a final structure consistent with the designed mask value through subsequent processes. At the same time, according to the image segmentation curve tracking technology, the contour extraction process of the dose test results was carried out, and the relationship among mask design value, exposure dose and two-dimensional roughness of boundary contour was analyzed, which can provide reference for the subsequent electron beam lithography of the same substrate material.

Femtosecond Optical Trapping of Cells:Efficiency and Viability

The femtosecond optical trapping capability and the effect of femtosecond laser pulses on cell viability were studied.The maximum lateral velocity at which the particles just failed to be trapped,together with the measured average trapping power,were used to calculate the lateral trapping force(Q-value) .The viability of the cells after femtosecond laser trapping was ascertained by vital staining.Measurement of the Q-values shows that femtosecond optical tweezers are just as effective as continuous wave optical tweezers.The experiments demonstrate that there is a critical limit for exposure time at each corresponding laser power of femtosecond optical tweezers,and femtosecond laser tweezers are safe for optical trapping at low power with short exposure time.

Exploration of computerized image processing in underexposed and overexposed X-rays of bones and joints

Objective: To study the effective computerized image processing of underexposed and overexposed X-rays of bones and joints. Methods: Ninety-nine conventional X-ray images (82 were overexposed and 17 were underexposed),scanned by an UMAX Astra 4000U Scanner, were converted into digital images on the basis of their analog images. A computerized imaging processing program consisting of five functional modules such as Contrast Stretch, Fast Flourier Transform (FFT), Image Smoothing Modules, Inverse Fast Flourier Transform (IFFT) and Nonlinear Transform performed image contrast stretch and smoothing. Three senior doctors from hospital image sections made their evaluation of all the processed images. Results: Of 82 overexposed films, 71 met the clinical requirements after image processing, and 11 were unable to be applied to clinical diagnosis, accounting for 87% and 13% respectively. Of the other 17 underexposed X-ray images, 11 met the clinical requirements while 6 were not, making a percentage of 64 and 35. Conclusion: Image contrast stretch and smoothing processing are significantly effective on conventional X-ray images which were inappropriately exposed, and can avoid more X-ray radiation caused by handling of radiological photograph again. This method can decrease hospital cost and provide acute and effective X-ray examinations for the treatment and cure for critical patients.

Comparison of two sampling methods when studying periphyton colonization in Lam Tsuen River, Hong Kong, China

We used standard periphyton samplers to examine the colonization pattern of periphytic algae on artificial substrates (glass slides) in Lam Tsuen River, Hong Kong, in dry (winter) and wet (summer) seasons. In each season, six replicated slides were retrieved randomly and replaced by new slides at weekly intervals over a period of 6 weeks. We thus obtained two batches of slides, both with a series of different exposure times (1 to 6 weeks): one batch was set up at the same time (start of the sampling) and the other was harvested at the same time (end of the sampling). Changes in taxonomic composition, species diversity (Shannon-Wiener diversity index), standing crop (in terms of cell density and cell biovolume), and abundance of the abundant algal species were monitored and compared between the two batches of slides. The succession patterns of the periphytic algae were similar between the two batches in each season, while more remarkable differences were observed between the two seasons, suggesting that either batch would be suitable for a colonization study of periphytic algae. The cell density was dominated by diatoms in both seasons, while the cell biovolume was dominated by diatoms in winter and by green algae in summer. The cell density and biovolume attributed to blue green algae was relatively small. Most of the diatom species exhibited similar colonization patterns throughout the experiment, while green algae showed different succession patterns in different seasons or sampling methods, indicating that diatoms are better bio-indicators than green algae for a periphyton colonization study. In general, the diversity indices and the standing crops reached their maximums at around week 4, and they were higher in summer than in winter.

Incipient motion of non-uniform coarse grain of bedload considering the impact of two-way exposure

The incipient motion of bedload is due to the interaction between the flow and sediment.It is stochastically correlated with the flow structure,the sediment gradation and the arrangement of grains on the bed surface.The random position of the sediment on bed can be represented by a hiding factor or an exposure degree.Based on the numerical simulation of the disturbed flow in the interstice of grains,the influence of the two-way exposure degree(the vertical exposure degree and the longitudinal exposure degree) on the coarse grain incipient motion was investigated in this work.Results show that the exposure degree varies with the position of the sediment on the bed,which influences the flow structure around the particle and the incipient motion.In this paper,the major research achievements on this phenomenon include:Firstly,a mathematical model is established for the rolling-pattern incipient motion of the coarse grain under a critical state of moment balance.The influence of the partial disturbed flow is considered.Secondly,the two-way relative-exposure-degree probability distribution functions are developed to reflect the influence of the disturbed flow and the random arrangement of sediments.Thirdly,a formula to calculate the incipient velocity is presented based on the above results,which considers the impact of the two-way exposure degree of sediment particles.