Surface charging and flashover on insulators in vacuum

Investigations have been carried out on right cylindrical Teflon spacers in vacuum under dc stress to study the effect of cathode geometry on surface charging and flashover. Three cathode support arrangements were used. Type 1 involved a recess in the cathode into which the spacer was located, type 2 was a simple flat plate cathode, while type 3 had a raised insert on the cathode surface over which the spacer was located. In all cases the surface charge density and distribution is primarily dependent upon the magnitude of the electric stress. Using the type 1 arrangement inception for charge deposition was always ~10 kV even when the spacer had been subjected to repeated flashovers. At applied voltages higher than this the density of the charge, which was fairly uniformly distributed around the surface, was more or less proportional to the applied voltage. For the type 2 and type 3 arrangements, a distinct, uniformly distributed negative charge of ⩽20 μC/m² was always detected at low values of applied stress and at a fairly well-defined transition voltage this gave way to a distribution which was substantially uniform in the case of type 2 but quite filamentary in type 3, and both involved the deposition of positive charge     

Metal (IV) tetras (8‐hydroxyquinoline) (M = Zr,Hf) used as electroluminescent material and electron‐transport layer in OLEDs

Abstract— In this paper, we report on the utilization of zirconium (IV) tetras (8‐hydroxyquinoline), Zrq₄, and hafnium (IV) tetras (8‐hydroxyquinoline), Hfq₄, as an electroluminescent material in fluorescent organic light‐emitting diodes (OLED) and as electron transport layer (ETL) for high‐efficiency electrophosphorescent organic light‐emitting diodes (PHOLEDs). Structural studies show that the metal tetraquinolates (Mq₄) have a very low dipole moment (<0.1 D), in contrast to Alq₃ which has an estimated dipole moment of 4.7 D. Mobility measurements show that Mq₄ complexes give mobilities of (3.5 ± 0.5) × 10^?6 cm²/V‐sec, which are close to the values reported for Alq₃, i.e., (2.3–4.3) × 10^?6 cm²/V‐sec. OLEDs were prepared with the structure ITO/NPD (400 Å)/Mq_n (500 Å)/LiF/Al (NPD = 4‐4′‐bis[N‐(1‐naphthyl)‐N‐phenyl‐amino]bi phenyl, Mq_n = Alq₃, Zrq₄, Hfq₄. The Mq₄‐based OLEDs gave external efficiencies of 1.1%, while the Alq₃‐based devices of the same structure gave efficiencies of 0.7%. PHOLEDs have been fabricated with the structure ITO/NPD (500 Å)/CBP‐8% Ir(ppy)³ (250 Å)/BCP (150 Å)/Mq_n (250 Å)/LiF/Al (CBP = N,N′‐dicarbazolyl‐4‐4′‐biphenyl, Ir(ppy)³ = fac‐tris(2‐phenylpyrridine)iridium, BCP = bathocruprione). PHOLEDs with Mq₄ ETLs showed a greatly improved efficiency, when compared to Alq₃‐based PHOLEDs. The Zrq₄‐based PHOLEDs gave a peak external quantum efficiency of 14% at 0.3 mA/cm² (150 cd/m²), while the Hfq₄ based PHOLED gave a peak external quantum efficiency of 15% at 0.6 mA/cm² (300 cd/m²). Comparable PHOLEDs with an Alq₃ ETL give peak external quantum efficiencies of 8.0% at 0.5 mA/cm². The devices gave an electroluminescence (EL) spectrum consisting only of fac‐tris(2‐phenylpyrridine)iridium (Ir(ppy)³) dopant emission (CIE coordinates of 0.26, 0.66), with no Mq₄ emission observed at any bias level.     

基于静态同步补偿器的变电站中电磁辐射测试分析

安装新型FACTS设备变电站的电磁兼容环境需要重新评估，以提出足够的电磁抗扰性措施。应用电磁场天线和光纤传输等技术，对一个典型的STATCOM变电站进行了现场测试和分析，结果表明STATCOM的高频电磁辐射集中在10kHz～5MHz，STATCOM变电站的电磁兼容性要好于安装常规SVC设备的变电站。将测量数据与当前国际电工委员会的IEC61000—4系列电磁兼容标准进行了相关比较，针对基于STATCOM的电磁辐射干扰提出两项抗扰性试验的具体改进建议。初步理论分析指出，GTO阀的开关特性和STATCOM结构的杂散参数是产生高频辐射干扰(谐波以上)的主要原因。     

Influence of diglycerides on crystallisation of palm oil

Palm oil diglycerides and pure synthetic diglycerides of 1,2‐(2,3‐) and 1,3‐dipalmitoylglycerol, dioleoylglycerol and palmitoyloleoyl glycerol were added to purified triglycerides of palm oil. The crystallisation kinetics of the samples were studied by spectrophotometry, NMR analysis of the solid fat content and by X‐ray diffraction of the crystals obtained at 20°C. Palm oil diglycerides inhibited the nucleation process and retarded the crystal growth rate of palm triglycerides. The effect was less pronounced at a higher degree of supercooling. The extent of inhibition depended on the nature of the diglycerides and the concentration. © 1999 Society of Chemical Industry     

Improving maintenance efficiency and safety through a human-centric approach

This paper presents an adaptive human-machine interface (HMI) that can provide appropriate sets of digital maintenanceinformation and guidance to an operator du...     

Crystallisation and melting behaviour of palm kernel oil and related products by differential scanning calorimetry

Lauric oils are valuable sources for oils suitable for various food applications. They are particularly useful as cocoa butter substitutes for which steep solid fat content profiles are required. Palm kernel oil is one such fat, which upon fractionation and/or hydro‐genation provides a variety of oil fractions with different oil composition and properties. The stearins have excellent properties for confectionery fats, while the oleins can be further hydrogenated to improve their properties. This paper gives an overview of the properties of products of palm kernel oil, produced from fractionation and hydrogena‐tion. The melting and crystallisation properties from differential scanning calorimetry studies are discussed in relation to the triacylglycerols of the oils.     

Convective Drying of Ganoderma tsugae Murrill and Effect of Temperature on Basidiospores

In this study, drying of Ganoderma tsugae Murrill slices was carried out at different temperatures in a hot air circulating oven. The objectives were to investigate the drying characteristic and drying kinetics of the Ganoderma slices under constant air velocity and slice thickness. In addition, the effect of drying temperatures on the size and surface structure of Ganoderma tsugae basidiospores were studied. Using statistical analysis, a two-term model was found to fit best with the experimental data. Convective drying of Ganoderma tsugae slices at 60°C shows the minimum heat deformation to the size and surface structure of basidiospores.     

The rheological behaviour of low fat soy‐based salad dressing

Low fat soy‐based salad dressings were formulated with different oil levels (3%, 13% and 23%) and emulsifiers (whey protein concentrate, soy‐lecithin and sodium caseinate) using either blender or ultra‐turrax (UT) homogeniser. Results showed that the rheological behaviour of these samples were highly dependent on the oil content, emulsifiers and blending methods. The UT method produced samples with better viscosity and have droplet size of 2–100 μm. Samples containing higher oil level have higher viscosity, smaller droplet size, larger G′ and G″ values. All samples show a shear‐thinning effect and larger G′ than G″, indicating the elastic nature of the samples. A quantity Q(t)% was applied to estimate the elasticity and the values were found to be in the range 22.8–85.2%. G′ and G″ were found to decrease with increased temperature. However, tan δ increased slightly with temperature; the values ranged from 0.2 to 0.4 at 5 °C to 0.3–0.5 at 25 °C. Current results demonstrated that the formulated samples have good stability compared with commercial products.     

Modified RED gateways under bursty traffic

We propose modified random early detection (MRED) gateways for congestion avoidance in TCP/IP networks. MRED aims at providing better control over the burstiness level while remaining the advantages of RED. We use ns2 to simulate a series of network configurations and the numerical results demonstrate that MRED can achieve higher link utilization compared to RED without sacrificing its advantages in all simulation scenarios. The improvement becomes more significant under bursty traffic.     

Validation of respiratory inductive plethysmography using the Qualitative Diagnostic Calibration method in anaesthetized infants

The aim of this study was to compare tidal volume (VT) derived from the Qualitative Diagnostic Calibration (QDC) method (VT,QDC) with measurements from pneumotachography (VT,PN,T) in anaesthetized infants. Measurements were made during spontaneous (SV) and intermittent positive pressure (IPPV) ventilation, sighs and airway occlusions. The VT,DIF was the difference between VT,QDC and VT,PNT (%VT). The contribution of the ribcage (rc) to VT,QDC (%rc) and the thoracoabdominal phase lag were also derived. Twenty-eight infants, mean (SD) age 14.0 (6.2) months were studied. VT,QDC represented VT,PNT most closely when > or = 20 breaths were analysed. There was close agreement during SV immediately after the calibration period (95% limits of agreement (LA; QDC - PNT) -23, 3.0%). The 95% LA increased to -9.6, 10.2% after 10 min. Accuracy diminished during IPPV (95% LA -38, 31%), and sighs. During airway occlusions, when VT,PNT was zero, the 95% LA were -63, 4.1 mL x kg(-1). Mean phase lag was 36 and 2%, respectively, during SV and IPPV (p<0.05). The %rc appeared to be overestimated, being in excess of 50% in infants under 12 months. The Qualitative Diagnostic Calibration method used to estimate tidal volume in anaesthetized infants was limited by the need to analyse > or = 20 breaths and by a loss of within-subject accuracy if measurement conditions or pattern of breathing changed.