An analysis of some common scanning techniques for lossless imagecoding

Though most image coding techniques use a raster scan to order pixels prior to coding, Hilbert and other scans have been proposed as having better performance due to their superior locality preserving properties. However, a general understanding of the merits of various scans has been lacking. This paper develops an approach for quantitatively analyzing the effect of pixel scan order for context-based, predictive lossless image compression and uses it to compare raster, Hilbert, random and hierarchical scans. Specifically, for a quantized-Gaussian image model and a given scan order, it shows how the encoding rate can be estimated from the frequencies with which various pixel configurations are available as previously scanned contexts, and from the corresponding conditional differential entropies. Formulas are derived for such context frequencies and entropies. Assuming an isotropic image model and contexts consisting of previously scanned adjacent pixels, it is found that the raster scan is better than the Hilbert scan which is often used in compression applications due to its locality preserving properties. The hierarchical scan is better still, though it is based on nonadjacent contexts. The random scan is the worst of the four considered. Extensions and implications of the results to lossy coding are also discussed.     

Supercritical extraction of binder containing poly(vinyl butyral) and dioctyl phthalate from barium titanate–platinum multilayer ceramic capacitors

Supercritical extraction using carbon dioxide was examined for the removal of binder from multilayer ceramic capacitors. The binder contained poly(vinyl butyral) (PVB) and dioctyl phthalate (DOP), and the dielectric and metal electrode materials were barium titanate and platinum, respectively. At 40 MPa of carbon dioxide at 95 °C, approximately 55 wt % of the binder could be removed, and this was mainly the dioctyl phthalate component. The use of entrainers such as 2-propanol, methyl isobutyl ketone, and n-hexane was seen to have negligible effect on the degree of binder removal. The dielectric constant, loss tangent, and breakdown voltage of devices processed by supercritical extraction were similar as compared to devices processed by thermal oxidation alone. Although it was not possible to extract all of the binder with supercritical carbon dioxide, removal of the DOP fraction increases the pore space in the body by a factor of two. Transport model calculations indicate this partial removal of binder mitigates the buildup of pressure in the subsequent thermal processing step and can reduce the processing time for thermal removal of the remaining binder by a factor of 25.     

钙处理对涟钢高强机械用钢夹杂物的影响

对涟钢LG600/LG700XL冶炼过程中夹杂物的衍变机理进行分析,分批次试验研究了精炼渣性能和钙处理工艺对钢液洁净度和钢中夹杂物的影响。结果表明,在钙处理工艺下,夹杂物的衍变路线为Al_2O_3→MgO-Al_2O_3→Al_2O_3-CaO,中间包钢液中的夹杂物主要是Al_2O_3-CaO和Al_2O_3-TiO_x复合氧化物。取消钙处理以后,铸坯中氧的质量分数从16×10~(-6)降低到11×10~(-6)。两种工艺下,材样中绝大部分夹杂物都是核心为铝酸盐、外层为TiN的复合夹杂,钙处理工艺下夹杂物核心是Al_2O_3-CaO-CaS,取消钙处理工艺下夹杂物核心是MgO-Al_2O_3尖晶石。两类复合夹杂物尺寸都比较小(10μm),对钢材性能的影响有限。取消钙处理以后,钢液可浇性基本保持不变,没有发生水口堵塞,说明取消精炼过程中的钙处理工艺对涟钢高强机械用钢而言是可行的。     

Sol-gel poly(ethylene glycol) stationary phase for high-resolution capillary gas chromatography

A sol-gel chemistry-based method was developed for the preparation of highly stable capillary gas chromatography (GC) columns with surface-bonded poly(ethylene glycol) (PEG) stationary phase. Through a single-step procedure, it concurrently provided column deactivation, stationary-phase coating, and chemical immobilization of the coated film. Sol-gel reactions were carried out within fused-silica capillaries that were filled with properly designed sol solutions containing two sol-gel precursors, two different triethoxysilyl-derivatized poly(ethylene glycol)s, two sol-gel catalysts, and a deactivation reagent. Hydrolytic polycondensation reactions led to the formation of a sol-gel coating chemically bonded to the inner walls of the capillary. A number of sol-gel coated fused-silica capillary columns were prepared using sol-gel-active PEG derivatives. These columns demonstrated many inherent advantages, the main being the strong anchoring of the coating to the capillary wall resulting from chemical bonding with the silanol groups on the fused-silica capillary inner surface. This chemical bonding yielded strongly immobilized PEG coatings with outstanding thermal stability (up to 320 degrees C). To our knowledge, such a high thermal stability has not been achieved so far on conventionally prepared PEG GC columns. Sol-gel PEG columns provided excellent chromatographic performances: high number of theoretical plates, excellent run-to-run and column-to-column reproducibility, and pronounced selectivity for a wide range of test solutes. Using n-octadecane as a test solute (k = 7.14), an efficiency value of 3200 theoretical plates/m was obtained on a 10 m x 0.25 mm i.d. fused-silica capillary column. Five sol-gel PEG columns provided RSD values of 1.09% for column efficiency (solute, n-octadecane), 1.37% for retention factor (solute, n-octadecane), and 0.9% for separation factor (for solute pair o- and p-xylene). In five replicate measurements using the same column, RSD values of less than 0.50% for the retention time and 1.36% for retention factor (k) were obtained.     

Mass transfer in packed columns: co-current operation

The theory of gas absorption accompanied by fast pseudo-m^th order reaction was used to obtain values of effective interfacial area in 10,15 and 20 cm i.d. packed columns which were operated co-currently. A variety of ceramic, metal and plastic packings were used. The range of superficial gas and liquid velocities was 50–300 cm/sec, and 0·1–3·5 cm/sec, respectively. Values of gas side mass transfer coefficients for some of the packings were also obtained. In addition some data were obtained for the counter-current mode of operation.     

Detection of drugs of abuse in saliva by surface-enhanced Raman spectroscopy (SERS)

Eighty drugs of abuse and metabolites were successfully measured by surface-enhanced Raman spectroscopy (SERS) using gold- and silver-doped sol-gels immobilized in glass capillaries. A method was developed that provided consistent detection of 50 ppb cocaine in saliva in a focused study. This general method was successfully applied to the detection of a number of additional drugs in saliva, such as amphetamine, diazepam, and methadone.     

Supercritical CO2/co-solvent extraction of porogens and surfactant templates to obtain ultralow dielectric constant films

A method of pore generation by supercritical CO₂ (SCCO₂) and co-solvent extraction for the preparation of nanohybrid film and mesoporous organosilicate thin film for ultralow dielectric constant materials is investigated. The films were treated with SCCO₂/methyl ethyl ketone-tetrahydrofuran co-solvent combination and it was found that the treatment produced dielectric constant (k) values of 2.30 for closed-pore and 1.61 for open-pore nanohybrid films; 2.14 for cetyl trimethylammonium bromide-based and 2.50 for polyethylene glycol octadecyl ether-based films. These results suggest that the SCCO₂/co-solvent treatment produces closely comparable results with thermal decomposition in terms of Fourier Transform Infrared spectroscopy data, optical constants obtained from variable angle spectroscopic ellipsometry, and k values.     

核磁共振录井技术在岩石物性分析方面的应用研究

核磁共振录井技术是利用油和水中的氢原子在磁场中具有共振并产生信号的特性,来探测和评价岩石物性。在实验样品类型、大小及钻井液浸泡对测量结果影响不大的基础上,对岩样的孔隙度、T₂截止值、渗透率、可动流体饱和度、含油饱和度、孔喉分布、润湿性、原油粘度等多个方面进行了应用研究和探讨,并阐述了所取得的认识。研究认为核磁共振录井技术实现了对岩石物性的快速测量和评价,对现场决策、完井及试油讨论具有重要的参考价值和指导意义。