The electrochemical redox processes in methacrylate-based polymer electrolytes II. - Study on microelectrodes

The electrochemical behaviour of ferrocene was studied in different gel polymer electrolytes based on methyl, ethyl and 2-ethoxyethyl methacrylate and compared to the liquid aprotic solution (propylene carbonate). Voltammetric and chronoamperometric measurements on microelectrodes were conducted in order to describe the qualitative as well as quantitative behaviour of ferrocene in different conditions. Heterogeneous electron-transfer rate constants and diffusion coefficients of ferrocene in polymer electrolytes were estimated to be 1.1-7.8 × 10⁻³ cm s⁻¹ and 4-13 × 10⁻⁸ cm² s⁻¹ depending on the electrolyte composition. The influence of the polymer polarity, ferrocene concentration and level of polymer cross-linkage on the kinetics of ferrocene oxidation and its transport was discussed. The electrolytes with poly(2-ethoxyethyl methacrylate) exhibit the highest ionic conductivity (2-4 × 10⁻⁴ S cm⁻¹) as well as diffusion coefficient of ferrocene (1.3 × 10⁻⁷ cm² s⁻¹) in their structure.     

Supplier evaluation and selection using Taguchi loss functions

The purchasing function directly affects the competitive ability of a firm. Purchasing managers need to periodically evaluate supplier performance in order to retain those suppliers who meet their requirement. Four attributes are frequently used as performance criteria. These attributes are quality, on-time delivery, price and service. An evaluation and selection system of suppliers using Taguchi loss functions is proposed in this paper based on these four attributes. These four attributes are transferred to the quality loss and combined to one decision variable for decision making. It is useful to make supplier evaluation and selection for promoting the competitive ability of a firm. An example of application to supplier evaluation and selection is also presented.     

聚苯醚/三烯丙基异氰酸酯体系相行为的研究

通过浊点法研究了聚苯醚／三烯丙基异氰酸酯(PPE／TALC)体系的相行为。结果表明,PPE／TAIC体系具有最高上临界温度行为,其相分离是完全可逆的。在PPE的质量分数约为60％的Berghmans点,把相图分为两个区,当PPE质量分数小于60％时,PPE／TAIC体系都具有大约50℃的玻璃化转变温度;当PPE质量分数大于60％时,在整个温度范围内是均匀的,不会出现相分离,另外还利用红外光谱研究了PPE／TAIC体系在180℃下的固化行为。     

个人健康管理系统数据库的设计与实现

个人健康管理系统能够帮助人们获得大量有价值的健康信息,为了实现一款安全、高效的个人健康管理系统,在充分考虑用户实际需求的前提下,对该系统数据库进行了设计与实现;首先对系统数据库进行了全面的需求分析,然后进行概念结构设计,形成实体联系(E-R)图,并将(E-R)图进行逻辑结构的转换,根据三范式的要求形成数据关系表,同时,在设计过程中通过牺牲一定存储空间的反范式操作,来换取更加快速的查询速度;通过上述方法,最终设计并实现了一款个人健康信息数据库;该数据库能够满足个人健康管理系统的实际开发需求,并且保证系统的查询运行效率,让用户能够更加方便,快捷的使用该系统对健康数据进行管理,达到帮助用户获得更多、更有价值的健康信息的目的。     

响应面法优化梅花鹿胎盘寡肽微胶囊包埋的研究

利用反复冻融法制备的梅花鹿胎盘寡肽颜色深,腥味重,影响了梅花鹿胎盘寡肽的食用。微胶囊技术具有遮蔽颜色、消除腥味、提高物质稳定性、增强缓释作用等优点。试验以β-环糊精为壁材,利用超声波辅助,采用冷冻干燥技术,对梅花鹿胎盘寡肽进行微胶囊化。通过响应面试验设计,确定了微胶囊包埋的最佳工艺为:壁芯比8、超声温度44℃、超声功率100 W,包埋率为69.25%。该工艺有效地掩蔽了梅花鹿胎盘寡肽的颜色,消除了腥味,保护了寡肽的生物活性、缓释作用较强。     

Asymmetric [4+2]-Cycloaddition of Anthracene Derivatives via Hydrazone Activation

Enantio- and diastereoselective dearomative [4+2]-cycloaddition reaction between N,N-dimethylhydrazone derived from 9-anthracenecarboxaldehyde and α,β-unsaturated aldehydes is reported. The developed strategy utilizes HOMO-rising activation of diene (via hydrazone formation) and aminocatalytic LUMO-lowering activation of dienophile (via iminium ion formation). High chemical and stereochemical efficiency have been obtained owing to the application of Jørgensen catalyst. Target cycloadducts were subjected to selected transformations aiming at unmasking the hydrazone moiety that proceeded with preservation of optical purity introduced in the organocatalytic step.     

极化SAR相干斑抑制极化白化滤波器

相干斑抑制是合成孔径雷达(SAR)图像和极化SAR图像后处理的首要问题。该文针对最优的极化相干斑抑制滤波器极化白化滤波器(PWF)仅输出一个强度图像的缺陷,对 PWF进行了改进,得到了各个极化通道的强度图像。     

Discrimination of dislocations in 4H-SiC by inclination angles of molten-alkali etched pits

Discrimination of dislocations is critical to the statistics of dislocation densities in 4H silicon carbide (4H-SiC), which are routinely used to evaluate the quality of 4H-SiC single crystals and homoepitaxial layers. In this work, we show that the inclination angles of the etch pits of molten-alkali etched 4H-SiC can be adopted to discriminate threading screw dislocations (TSDs), threading edge dislocations (TEDs) and basal plane dislocations (BPDs) in 4H-SiC. In n-type 4H-SiC, the inclination angles of the etch pits of TSDs, TEDs and BPDs in molten-alkali etched 4H-SiC are in the ranges of 27°−35°, 8°−15° and 2°−4°, respectively. In semi-insulating 4H-SiC, the inclination angles of the etch pits of TSDs and TEDs are in the ranges of 31°−34° and 21°−24°, respectively. The inclination angles of dislocation-related etch pits are independent of the etching duration, which facilitates the discrimination and statistic of dislocations in 4H-SiC. More significantly, the inclination angle of a threading mixed dislocations (TMDs) is found to consist of characteristic angles of both TEDs and TSDs. This enables to distinguish TMDs from TSDs in 4H-SiC.     

Hyperdoped silicon: Processing,properties, and devices

Hyperdoping that introduces impurities with concentrations exceeding their equilibrium solubility has been attracting great interest since the tuning of semiconductor properties increasingly relies on extreme measures. In this review we focus on hyperdoped silicon (Si) by introducing methods used for the hyperdoping of Si such as ion implantation and laser doping, discussing the electrical and optical properties of hyperdoped bulk Si, Si nanocrystals, Si nanowires and Si films, and presenting the use of hyperdoped Si for devices like infrared photodetectors and solar cells. The perspectives of the development of hyperdoped Si are also provided.     

LED‐backlit computer screens influence our biological clock and keep us more awake

Abstract— In commodity LC flat‐panel displays, the traditional CCFL backlight is being replaced more and more by LEDs. The typical spectrum of LED‐lit displays shows a significantly higher amount of blue light in the range around 464 nm. Blue light in this wavelength area suppresses the melatonin level in humans and thus effects the biological clock. Our hypothesis was that the amount of blue light reaching the human eye from a LED‐backlit display is sufficient to have a significant effect on the biological clock. The results of clinical user studies comparing the effects of LED‐ vs. CCFL‐backlit displays on humans, resulting from the emitted amount of 464‐nm light, will be presented. It was found that the LED‐backlit display causes significant suppression of melatonin, which effects the biological clock of the test persons, indicating the necessity for displays with a controllable 464‐nm emission. A technical concept for a display with such functionality will be presented.