Preparation and characterization of DLC/SiO2/Al2O3 nanofiltration membrane

High quality ceramic thin films were fabricated by thin film deposition process in semiconductor field in order to fabricate high performance carbon/SiO ₂ /Al ₂ O₃ membrane. α-Al ₂ O ₃ substrate was used as a supporting material. A severe thermal stress and rough surface for active ceramic top layer such as zeolite were observed. To overcome thermal stress, intermediate layer of SiO₂ and diamond-like carbon (DLC) thin film were used. SiO ₂ and DLC thin films on porous alumina support were deposited using plasma-enhanced chemical vapour deposition (PECVD). Homogeneous and smooth surfaces and interfaces of DLC/SiO ₂ /Al ₂ O ₃ membrane were observed by FESEM. The phases of DLC and SiO ₂ thin films were identified by X-ray diffraction pattern. Gas permeabilities of the nanofiltration membrane with DLC/SiO ₂ /Al ₂ O ₃ were observed at various annealing temperatures. Mixed gas permeability of the membrane with 1 μm-thick SiO₂ and 2 μm-thick DLC thin film annealed at 200 °C was ～18 ccm at 1018 mb back pressure.     

基于高通量计算的成形过程分析

目的介绍一种来自材料基因组计划的方法,由高通量计算、高通量实验与数据管理构成,并以45#钢为例,介绍高通量计算与高通量实验的优势。方法先以模拟软件与理论结合,预测研发方向,再设计合适高通量的实验方案,最后将所得数据建立数据库,方便管理。以45#大型钢铸锭为例,以COMSOL软件模拟3种不同钢锭成形过程,设计实验方案,记录过程参数,并记录于数据库中。结果 COMSOL软件在高通量计算中扮演重要角色,其强大的耦合功能让模拟精度更高,各项参数也较为准确。透过模拟得知,约2.9 h后,20 t钢锭凝固厚度最厚达约500 mm,此时将中间液芯挤出,可减少划痕等缺陷的产生,并将凝固过程的缺陷挤出。结论材料基因组计划在材料研发的进程中能起到较大的指导作用,因此在国家支持下国内已有多个项目开展,将此研究方法用于传统浇铸工业的步骤中具有一定的推广价值。     

nForce力量——微星K7N420 pro主板全面测试

在2004年6月4日，nVIDIA公司于中国台北举办的Computex大展上正式发布了备受期待的整合图形处理器架构——nForce.拥有128bit Twinbank内存总线、HyperTransport总线技术，双DSP架构的MCP1-D、整合的GF2MX显卡等耀眼的特性，nForce一问世就马上受到业界密切的关注。nVIDIAIV当初承诺的是在冬季的时候正式推出nForce芯片组，     

White luminescence of Ho3+/Tm3+/Yb3+-codoped CaWO4 synthesized via citrate complex route assisted by microwave irradiation

The nanocrystalline Ho³⁺/Tm³⁺/Yb³⁺ co-doped CaWO₄ upconversion (UC) phosphors were successfully synthesized by a modified citrate complex method using microwave irradiation. The citrate complex precursors were heat-treated at temperature ranging from 300 to 700 °C for 3 h. Crystallization of the Ho³⁺/Tm³⁺/Yb³⁺ co-doped CaWO₄ was detected at 400 °C, and entirely completed at 600 °C. The Ho³⁺/Tm³⁺/Yb³⁺ co-doped CaWO₄ heat-treated at 600 °C showed primarily spherical and homogeneous morphology. Under the laser excitation of 980 nm, Ho³⁺/Tm³⁺/Yb³⁺ co-doped CaWO₄ shows the bright white upconversion (UC) emission visible to the naked eye, which is composed of a blue emission at 475 nm from Tm³⁺, and green and red emissions at 543 and 651 nm respectively from Ho³⁺. The coordinates of Ho³⁺/Tm³⁺/Yb³⁺ co-doped CaWO₄ in the Commission International De'eclairage (CIE) chromaticity diagram could be controlled from a cool to a warm white color depending on the Tm³⁺ and Ho³⁺ concentrations. The UC luminescent properties on Tm³⁺ and Ho³⁺ concentrations and related mechanism based on laser pump power were discussed in detail.     

石墨表面改性对MgO-C耐火材料抗氧化性能的改善(英文)

石墨常作为传统MgO-C耐火材料的碳源。石墨在经酸化剂改性后,可在表面产生负电荷,从而增强铝相的涂覆率。从弥散度和氧化性能方面对改性后的石墨与天然石墨进行了比较。首先,将经过和未经过表面改性的石墨颗粒分别添加至酸化剂Al(NO3)3悬浮液中,并在室温下过滤,得到改性后的石墨。试验表明:改性后的石墨较天然石墨具有更好的弥散性,其Al相涂覆率得到了增强。在氧化性能方面,优化后的石墨没有Al涂层时,在900°C热处理时与空气充分氧化;而有Al涂层时,则在900°C时开始氧化,在1000°C时充分氧化,并分别变为灰色和白色。可见,由于Al涂层在石墨表面均匀覆盖,Al相涂覆率的提高增强了石墨的抗氧化性能。     

Stability and robustness of discrete event dynamic systems

In this paper, the general concepts of stability of discrete event dynamic systems are defined and investigated. We present the stability in the sense of Lyapunov with resiliency, by incorporating the Lyapunov stability concepts (Michel and Miller 1977, Passino et al. 1994) with the concept of stability in the sense of error recovery (Ozveren and Willsky 1991a). We also provide algorithms for verifying stability and obtaining the domain of attraction. Upon the proposed stability concepts, we address the issue of robust stability and stabilizability. We assume that the plant G is not known exactly but we only know that it belongs to a set of models. In robust stability, we analyse the stability of the common invariant states set of all possible plant models. Then we derive the necessary and sufficient conditions for the robust stabilizability, i.e. the existence of a supervisor which makes the uncertain system robustly stable.     

Modelling and analysis of a multilevel voltage source inverter applied as a static var compensator

A multilevel PWM voltage source inverter, especially a five-level one, is introduced to obtain a static var compensator (SVC) as a large scale power source. The multilevel inverter has many advantages, such as better utilization of the switching devices, lower switching frequency at each semiconductor switch and reduced harmonics. In this paper, the SVC with five-level inverter is modelled using circuit DQ transformation and completely analysed including DC and AC characteristics. It is also pointed out that the modulation indexes depend on the values of the DC side capacitors to meet the DC side voltage balancing, Finally, through the experimental results from a 5kVA SVC, the validity of the analyses and the feasibility of the var compensation system are shown for high power applications.     

EFFECT OF FAR-INFRARED HEATER ON THE PHYSICOCHEMICAL CHARACTERISTICS OF GREEN TEA DURING PROCESSING

ABSTRACT

The green tea leaves (Camellia sinensis var. sinensis) were irradiated by a far‐infrared (FIR) heater during the roasting and drying step, resulting in three different treatments produced. Green tea was extracted by soaking the leaves in water, and the components were analyzed. FIR irradiation, combined with fryer heating during the roasting step and additionally applied after the drying step, increased total phenolic contents of green tea from 116.30 to 171.77 mg/g, and total flavanol contents from 17.54 to 24.76 mg/g, compared with the non‐irradiated control. Ascorbic acid contents also increased from 3.07 to 4.20 mg/g. The amounts of epicatechin gallate and epigallocatechin gallate were significantly increased from 2.41 to 4.59 mg/mL and 20.61 to 28.54 mg/mL, respectively, compared with the non‐irradiated control. FIR irradiation increased Nitrite Scavenging Ability of green tea at pH 3.0 and pH 4.2, while there was no significant difference at pH 6.0. Sweetness, umami and aroma of green tea were enhanced by FIR irradiation, while bitterness and astringency were decreased compared with those of the control. These results show that FIR heating during the green tea process affected the chemical properties of green tea, and the FIR heater can be applied to increase the physicochemical qualities of green tea.

PRACTICAL APPLICATIONS

Green tea, a widely consumed drink, has received much attention because of the beneficial biological effects attributable to its excellent antioxidant activity. In this article, a far‐infrared (FIR)‐heater for industrial application was used during the processing of green tea leaves, and the chemical characteristics and quality of FIR‐treated green tea were determined. FIR irradiation, combined with fryer heating during the roasting step and additionally applied after the drying step, significantly increased phenolic, flavanol, ascorbic acid, epicatechin gallate, epigallocatechin gallate contents and nitrite‐scavenging activity compared with non‐irradiated control. Sensory evaluation also showed a positive effect of FIR irradiation. The results indicated that FIR heater could be easily applied to increase the quality of green tea in the processing line.     

GROWTH INHIBITION OF CLOSTRIDIUM PERFRINGENS VEGETATIVE CELLS AND SPORES USING CHICKEN IMMUNOGLOBULIN Y

Egg yolk antibody (IgY) was isolated by the water dilution method from the egg yolk of chickens immunized with Clostridium perfringens vegetative cells and spores. Specific binding activity of IgY against C. perfringens vegetative cells and spores remained relatively high during the immunization period (up to 9 weeks). The titer of specific IgY against C. perfringens spores was 1.4-fold less than that of specific IgY against C. perfringens vegetable cells. The specific IgY powder (10 µg/mL) was found to inhibit the growth of C. perfringens vegetative cells or C. perfringens spores in a liquid medium. The difference of C. perfringens vegetative cell growth between the treatment and control groups was 8.9  ×  10⁶ colony forming units (cfu)/mL at 8 h of incubation and 9.95  ×  10⁷ cfu/mL at 24 h of incubation. Significant cfu reductions in C. perfringens spores were also observed with specific IgY powder at 24 h of incubation.

PRACTICAL APPLICATIONS

IgY antibody exerts an antimicrobial activity against pathogens by binding, immobilizing and consequently reducing or inhibiting the growth, replication or colony forming ability of pathogenic bacteria; thus, it is proved to be a viable alternative for antibiotics and preservatives. In this study, IgY against Clostridium perfringens can be used to replace chemical preservatives in food industries. Because IgY functions well at low temperature, it can be used to inhibit the growth of Clostridia which germinate in refrigerated storage conditions, thus preventing foodborne enterotoxicity caused by such bacteria. In practical applications, natural antimicrobial IgY antibody can be applied to meat products for the improvement of food safety.