IR-sintering of ink-jet printed metal-nanoparticles on paper

Sintering of printed metal nanoparticles can be made not only by conventional heating, but also by, e.g., electrical, microwave, plasma, laser and flash lamp annealing. We demonstrate sintering by using low-cost incandescent lamps as an effective way of obtaining highly conductive contacts of two types of ink-jet printed metal-nanoparticle inks on paper; both alkanethiol protected gold nanoparticles and a commercially available silver nanoparticle ink. This low-cost roll-to-roll compatible sintering process is especially suitable on paper substrates because of the high diffuse reflectance, relatively high thermal stability and low thermal conductivity of paper. A volume resistivity of around 10 μΩ cm was achieved of the inkjetted silver nanoparticles within 15 s of exposure to an IR lamp, which corresponds to a conductivity of 10-20% of that of bulk silver. Too long exposure time and too high intensity, however, lead to darkening of the paper fibers. Both the crack formation and the coffee ring effect of the inkjet printed gold nanoparticles were, furthermore, found to be reduced on paper as compared to glass or plastic substrates.     

Evidence for long-lived, optically generated quenchers of excitons in single-walled carbon nanotubes

The nonlinear dependence of near-infrared photoluminescence (PL) emission on excitation intensity has been measured for individual nanotubes representing six different (n,m) species. Significant deviations from linearity are observed for intensities as low as ~100 W/cm(2), and an approximate inverse correlation is found between nonlinearity and PL action cross section (brightness). A model in which all PL nonlinearity arises from exciton-exciton annihilation is insufficient to account for the experimental data using realistic parameters. It is proposed that additional nonlinear quenching arises from photoinduced quenching states or species with longer lifetimes than emissive excitons. Evidence is also found for metastable photogenerated PL quenchers with lifetimes up to 20 s.     

DCT域基于块分类的不可感知加性数字水印

该文根据Watson感知模型提出了DCT域基于块分类不可感知加性水印模型。算法计算亮度块方差,将图像块分为五类,利用亮度块特征来加性控制嵌入服从正态分布随机水印序列的区域和长度,提高了水印图像的鲁棒性。在检测端可根据水印图像的统计特性确定水印的检测阀值,不使用原始图像,就可进行水印的相关检测。实验结果表明,MPEG视频水印图像质量的PSNR平均下降4.1dB,但主观视觉质量没有明显下降。     

视频服务器的磁盘I/O调度算法

讨论了视频服务器的Ｉ／Ｏ调度问题,通过对磁头移动和旋转延时间的优化,得出了双向扫描调度算法,对需要同时支持多种视频速率的异构系统。在Ｂｉ－ＳＣＡＮ算法的基础上,给出了固定数据长度和固定时间长度两种调度方案的接纳控制条件。通过模拟实验比较了这两种调度方案的性能,并提出了基于漏桶控制的ＣＤＬ调度方案。     

晚清宫廷氅衣与衬衣异同比较及其工艺释析

清宫氅衣和衬衣同属后妃便服,在浩如烟海的清宫档案里,没有后妃穿用这类便服的制度规定,因此,业内外有时将其混为一谈。笔者以所见大量故宫旧藏清宫后妃氅衣和衬衣实物资料以及文字史料为据,从氅衣与衬衣款式比较、氅衣与衬衣穿用异同、氅衣与衬衣的制作工艺等方面,释析晚清宫廷氅衣与衬衣异同,比较其工艺特点,为读者提供了较为详实的史料。     

ELISA法测定花生油中黄曲霉毒素B_1含量的不确定度分析

根据CNAS-GL06:2006《化学分析中不确定度的评估指南》中提供的方法,对ELISA法测定花生油中黄曲霉毒素B1含量过程中影响测定结果的因素进行分析,建立数学模型,对模型中的变量进行分解,确定影响每一变量的不确定度分量并进行计算,合成标准不确定度和扩展不确定度。花生油中黄曲霉毒素B1含量测定结果为(18.3±0.97)μg/kg,通过评定,影响含量测定的最主要不确定度分量为标准曲线的拟合。     

Flash sintering of 3YSZ/Al2O3-platelet composites

Preparation of 3YSZ/Al₂O₃-platelet composites always requires high temperature, long duration, and/or high pressure. Herein, 3YSZ/Al₂O₃-platelet composites are prepared at low temperature of 492°C-645°C in 30 seconds by flash sintering under the electric field of 300-800 V/cm. The influence of electric field and current limit on the densification and grain growth of composites is investigated. The onset temperature for flash sintering is determined by electric field, which is decreased with increasing the electric field. Under the constant electric field, the current limit has a great effect on the density and grain size of composite. The flash-sintered 3YSZ/Al₂O₃-platelet composites exhibit relatively high hardness and elastic modulus. Both Joule heating and defects generation are proposed to be responsible for the rapid densification in flash sintering. This work demonstrates the feasibility of employing the flash sintering to prepare ceramic composites with fine grain size.     

自动图像阈值分割算法

该文提出了一种新的图像阈值分割算法。该算法通过求取最大模糊熵准则下,灰度均值直方图的最佳模糊划分参数来确定两个模糊集A和B,图像分割阈值即选取为两个模糊集的交点。该算法用Zadth的模糊熵定义适应度函数,采用改进的遗传算法寻求最佳模糊参数。该文对遗传算法的改进包括,给出了缩短染色体码长的编码方法和性能良好的改进的单点交叉算子和均匀变异算子。实验结果表明,该算法的分割效果与二维模糊熵算法接近,而计算时间还没有用到二维模糊熵算法的一半。     

Formation of white spots in the shell of raw shrimps during frozen storage. Seasonal variation and effects of some production factors

During frozen storage of raw pink shrimps, Pandalus borealis, calcium carbonate tends to precipitate in the exoskeleton, giving the shrimps a spotted appearance. Seasonal variations in the formation of white spots and the influence of shrimp size, production time, chemical treatment, and storage temperature on white spot formation was determined. A significant effect (P=0·003) of day of catch was observed and shrimps caught in the summer period showed a greater tendency of white spot formation than shrimps caught during the rest of the year. Treatment in a sulphite, a phosphate or a phthalate solution prior to freezing retards calcium carbonate crystallisation (P<0·05) while treatment in a borax solution promotes crystallisation (P<0·05). Prolonged time from catch to chemical treatment and increased storage time increase the risk of white spot formation. Storage temperature has a significant effect on white spot formation for which process the rate at different temperatures was described by the Arrhenius equation with a high energy of activation of 90 kJ mol⁻¹. The size (age) of the shrimps did not influence white spot formation (P=0·69). From these findings it is concluded that calcium carbonate precipitation resulting in white spots in shrimp shell can be retarded or possibly prevented by short production time, appropriate chemical treatment and very low storage temperature. ©1997 SCI