纳米层状双金属氢氧化物的制备及结构表征

采用恒定pH 12±0.2,按n(Mg2+)∶n(Al3+)∶n(OH-)∶n(CO2-3)=6∶2∶16∶1配制溶液,采用一步反应液相法,制备纳米层状双金属氢氧化物(LDH)粉体.为了获得无团聚、分散均匀的纳米粉体,探讨了溶剂置换干燥、真空干燥、常压干燥对纳米LDH粉体形成团聚的影响;用X射线衍射仪、透射电镜、红外光谱仪和元素分析仪对样品的物相、形貌、粒径和组成进行了表征.结果表明,溶剂置换干燥能够有效防止纳米粉体形成硬团聚,样品分散性好,呈针状形态,长50 nm,宽5 nm.     

在OsO_4催化作用下烯烃的立体选择性氧化反应

四氧化锇是一种贵而毒性大的试剂。本文介绍催化剂量的四氧化锇在立体选择性高的烯烃氧化反应中的应用，为四氧化锇在有机合成中的应用，开辟了新的途径。     

Alternative hydrocarbon solvents for cottonseed extraction

Hexane has been used for decades to extract edible oil from cottonseed. However, due to increased regulations affecting hexane because of the 1990 Clean Air Act and potential health risks, the oil-extraction industry urgently needs alternative hydrocarbon solvents to replace hexane. Five solvents,n-heptane, isohexane, neohexane, cyclohexane, and cylopentane, were compared with commercial hexane using a benchscale extractor. The extractions were done with a solvent to cottonseed flake ratio of 5.5 to 1 (w/w) and a miscella recycle flow rate of 36 mL/min/sq cm (9 gal/min/sq ft) at a temperature of 10 to 45°C below the boiling point of the solvent. After a 10-min single-stage extraction, commercial hexane removed 100% of the oil from the flakes at 55°C; heptane extracted 100% at 75°C and 95.9% at 55°C; isohexane extracted 93.1% at 45°C; while cyclopentane, cyclohexane, and neohexane removed 93.3, 89.4, and 89.6% at 35, 55, and 35°C, respectively. Each solvent removed gossypol from cottonseed flakes at a different rate, with cyclopentane being most and neohexane least effective. Based on the bench-scale extraction results and the availability of these candidate solvents, heptane and isohexane are the alternative hydrocarbon solvents most likely to replace hexane. Presented in part at the AOCS Annual Meeting & Expo, Atlanta, Georgia, May 1994.     

用RAP法引上技术生长KCL晶体

用RAP法(reactivo atmosphere process)处理KCl熔体,在不改变生长气氛和RAP继续处理的情况下,提拉生长KCl晶体,以解决高纯、大尺寸、生长速度快、成品率高和有较大经济效益的问题。     

Event-driven observer-based output feedback control for linear systems

This paper concerns the problem of event-driven observer-based output feedback control of linear systems. Contrary to normal sampled-data control systems, where the controller is updated periodically, in event-driven systems, it is updated only when an “event” happens, and a typical event is defined as some error signals exceeding a given threshold. Both continuous- and discrete-time event detector cases are considered. It is shown that even with the significantly reduced sampling frequency, the global uniform ultimate boundedness of the event-driven closed-loop systems can also be guaranteed. A numerical example is finally used to illustrate the effectiveness and advantages of the proposed approaches.     

Observability of linear systems with commensurate delays and unknown inputs

This paper investigates the observability analysis for linear time systems whose outputs are affected by unknown inputs. Three different definitions of observability are proposed. By introducing the Smith form and comparing the invariant factors, a sufficient condition is deduced for each proposed observability definition. Three examples are given for the purpose of highlighting the effectiveness of the proposed approach.     

VPN与负载均衡技术在黄委上游广域网中的应用

VPN(Virtual Private Network):虚拟专用网络,是一门网络新技术,为我们提供了一种通过公用网络安全地对企业内部专用网络进行远程访问的连接方式。负载均衡技术是建立在现有网络结构之上,它提供了一种廉价有效透明的方法扩展网络设备和服务器的带宽、增加吞吐量、加强网络数据处理能力、提高网络的灵活性和可用性。本文就是通过对这两种新技术概念的阐述,系统介绍了这两种新技术在黄委计算机网络中的应用。     

The factors of speeds and loads on the tribological properties of PVA‐H/HA composites

Poly (vinyl alcohol) (PVA)/Hydroxy apatite (HA) composite prepared from aqueous solution of the polymer and dimethylsulfoxide (DMSO) by freezing and thawing method are developing to repair or replace articular cartilage. In the present study, the tribological behaviors of this composite were investigated in a three‐factor, three‐level designed experiment using an improved four‐ball tester. Factors include sliding velocity, applied load, and HA content of composite. Friction coefficient of the PVA‐H/HA was found to depend significantly on load and sliding velocity, while HA content had small effects on the friction coefficient of PVA‐HA composite. We also found that wear loss of PVA‐H/HA increased sharply with the increasing loads and HA content of specimen. Increased HA content from 0.5% to 1.5% resulted in an increasing of 355% in wear loss, while increasing sliding velocity slightly decreases wear loss of specimen. We also found some correlation between friction coefficient and wear loss of specimen under the given condition. These results may be useful in the tribological design of PVA‐H/HA composite for both low wear and low friction using as artificial cartilage substitutes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

高效乙烯聚合催化剂的制备——I．催化剂的制备规律

研究了新型含镁络合物的结构、性质及其用于制备高效乙烯聚合催化剂的制备规律。结果表明：将镁、有机醇以及不与镁发生“格式反应”的卤代烷相互作用可迅速发生反应形成新型含镁络合物溶液。该络合物在溶液中可析出结晶。具有特定的化学结构．可以均匀承载于多孔硅胶的孔隙中，负载TiCl4后制备出形态良好的球形高效乙烯集合催化剂。     

Kinetics of thermo-fixation of solvent dyes and pigments in polyester fibres

The diffusion coefficient of a dye in fibres is critical to understanding the dyeing process and coloration quality of products. In this paper, the diffusion kinetics of solvent dyes in the thermosol dyeing of polyester fibres was studied by measuring K / S of the dyed polyester fabrics based on the Kubelka–Munk equation. The diffusion coefficients of two model solvent dyes were estimated with Hill's equation using the experimentally measured K / S values and were found to be in good agreement with those calculated from the traditional extraction method. Such a measurement method was applied to several other solvent dyes and pigments that have different molecular sizes and a good correlation between the measured diffusion coefficients and sizes of these dyes and pigments was found. The results indicate that it is feasible to use K / S measurement of dyed fabrics and Hill's equation to evaluate the kinetics of the thermosol dyeing process under certain conditions.