A three-phase symmetrical multistage Voltage multiplier

A three-phase symmetrical Cockcroft-Walton (CW) multistage voltage multiplier (VM) is proposed. It consists of one smoothing column and six oscillating columns. The oscillating columns are connected to three-phase power through center-tap transformers. The capacitors of the smoothing column are charged six times per cycle by six oscillating columns and are discharged six times through the load, unlike the conventional symmetrical VM in which they are charged and discharged twice per cycle. The three-phase symmetrical structure completely eliminates the first five harmonic components of load-generated voltage ripple. Theoretical analysis indicates that the proposed three-phase symmetrical CW-VM has one-third the voltage ripple and voltage drop of the conventional single-phase symmetrical CW-VM. Experimental and simulation results of the proposed three-phase symmetrical CW-VM as well as of the conventional single-phase symmetrical CW-VM are presented. A comparison shows that the three-phase symmetrical CW-VM has significantly less voltage ripple, half the voltage drop, and a fourfold increase in output power over the conventional single-phase symmetrical CW-VM.     

Way forward in meeting energy challenges in Pakistan

In this review the energy potential of Pakistan from hydro, coal, wind, solar and nuclear sources has been discussed. The new projects that are being commissioned on coal, wind, solar, hydel and nuclear-based technologies have also been mentioned. The review has also explored the future prospects of the country’s energy requirements. Pakistan has potential to produce 100,000?MW of electricity from Thar coal for 20 years, 56,000?MW of hydroelectricity, 150,000?MW of wind energy and ～50,000?MW from solar sources. The coal-fired power generation is expected to 11,500?MW in period 2017–2019. The country is moving in the right direction to cater its energy needs. However, there is a need to find local and foreign investment in the country to meet high energy demands in the country in future.     

FeGaB (25 nm)/Al2O3/FeGaB(25 nm)多层薄膜结构：氧化铝(Al2O3)厚度变化对静态与动态磁性能的影响

铁镓(FeGa)薄膜与其它软磁材料相比具有较大的磁致伸缩常数,在设计集成磁性传感器芯片中具有独特的优势,本文通过采用非磁性掺杂和多层膜方法来控制这种合金薄膜的磁学与电学性能参数。我们实验发现在掺杂一定量硼(B)元素后,厚度小于30 nm的FeGa薄膜顽力可以得到显著降低,而对于较厚薄膜在插入超薄Al2 O3中间层后软磁性能可以得到同样程度显著改善,同时饱和磁化(Ms)变化可忽略。对于我们制备的FeGaB (25 nm)/Al2O3(0.5 nm)/FeGaB(25 nm)多层膜,其易轴矫顽力可以小到0.98 Oe,电阻率与50nm单层FeGaB膜相比增加了1.5倍,同时具有吉赫兹高磁导率谱。样品微结构分析表明,磁性颗粒结晶质量和物理尺寸的减小对软磁性改善起到重要作用,另外我们也讨论分析了静磁相互作用和表面形貌对磁畴运动及矫顽力的影响。本文发展的掺杂与多层膜混合方案来来增强电磁性能的方法,也可应用于其他类型的软磁材料系统。     

Effect of plasma treatment and electron beam radiations on the strength of nanofilled adhesive‐bonded joints

This investigation highlights the adhesion performance of carbon fiber‐ and glass fiber‐reinforced polyphenylene sulfide when joined by high‐performance neat epoxy adhesive and nanofilled epoxy adhesive. A significant increase in the surface energy of these materials is observed after the surface modification with atmospheric plasma treatment. An increase in surface roughness is observed after exposing the surface to plasma. Lap shear testing of untreated and plasma‐treated joints is carried out to correlate the improvement in adhesion properties with the joint strength. A considerable increase in joint strength is observed when the surfaces of these materials are modified by atmospheric pressure plasma. There is a further increase in joint strength when the composites are joined by nanofilled epoxy adhesive, and subsequent exposure to electron beam radiations results in minor increase in the joint strength. Finally, the fractured surfaces of the joints are examined and the analysis is performed. POLYM. ENG. SCI., 50:1505–1511, 2010. © 2010 Society of Plastics Engineers     

Fuzzy Self-tuning PID Controller for Speedtronic Governor Controlled Heavy Duty Gas Turbine Power Plants

Heavy duty gas turbine power plants may cause severe instability in grid connected operation under load fluctuations. To overcome such instability problems, an attempt has been made to develop proportional-integral-derivative controller for all the heavy duty gas turbine models with Speedtronic governor. Proportional-integral-derivative gains are tuned by Ziegler-Nichols and performance index methods and the step responses are obtained by using MATLAB/Simulink considering various droop settings. Simulation results of all the models reveal that the integral of squared error tuned proportional-integral-derivative controller provide better response. In order to improve the stability further, fuzzy self-tuning proportional-integral-derivative controller has been proposed in this article for all the heavy duty gas turbine models. On analyzing the simulation results, the proposed fuzzy self-tuning proportional-integral-derivative controller is found to be adaptive for all the heavy duty gas turbine models irrespective of the droop settings and yield better transient and steady state responses than Ziegler Nichols and Performance index methods.     

A New Distance Relaying Algorithm for Single-phase-to-ground Faults on Series-compensated Parallel Lines without the Parameter Requirement of Mutual Coupling and Series Capacitor Device

A new distance-relaying algorithm for single-phase-to-ground faults on series-compensated parallel transmission lines is proposed in this article. Fault impedance can be calculated using this algorithm without any parameters requirement of mutual coupling and series capacitor device (series capacitor/metal oxide arrestor/discharging gap). The series capacitor device is simplified as linearized impedance during faults. The parameters of mutual coupling and a series capacitor device can be used as variables in the fault loop equations. Real-time digital simulator tests show that the proposed distance-relaying algorithm can obtain more accurate results than traditional distance-relaying algorithms for series-compensated parallel transmission lines.     

Proteins and trypsin inhibitor activity of guar (Cyamopsis tetragonoloba L. Taub) seed

Proteins soluble in tris-acetate buffer (pH9.0) were fractionated by DEAE-cellulose, DEAE-Sephadex A-50 and Sephadex G-200 column chromatography. The purified proteins which contained 5–6% carbohydrate, had molecular weights of 125 900 and 22 390 amu. The high molecular weight fraction was homogeneous by polyacrylamide gel electrophoresis. Proteins extracted in phosphate buffer (0.1M , pH7.6) when subjected to Sephadex G-200 gel chromatography were resolved into three fractions, all of which showed considerable trypsin inhibitor activity. Germination for 3 days reduced the trypsin inhibitor activity of the seed by about 30%.     

Morphological and palynological assessment of taxonomically problematic genus Paspalum based on light and scanning electron microscopy

Present research work was carried out to clarify the variations among species of genus Paspalum morphologically and palynologically as this genus is taxonomically difficult due to having multiple similar morphologically overlapping characters which make it difficult to identify. Henceforth present research work was carried out to delimit taxa within the same genus by morphological and palynological tools through light microscopy (LM) and scanning electron microscopy (SEM). Both these tools are considered as the most useful taxonomic characters for taxonomically problematic genera. The results showed a lot of variations among morphological characters. In Paspalum dilatatum, the upper glume was ovate whereas in the other two species, the upper glume was elliptic. The upper glume apex found in P. dilatatum and Paspalum scrobiculatum was obtuse whereas in Paspalum distichum, upper glume apex was acute. Glume nerves showed variation in all three species. Paspalum distichum was 3 nerved, P. scrobiculatum was 5–7 nerved, and P. dilatatum was 5–9 nerved. All three species showed variation in lemma nerves. Paspalum scrobiculatum had 3 nerved lemma whereas in P. distichum 3–5 nerved and P. dilatatum 5–9 nerved lemma were present. In polar and equatorial view, pollen grains ranged from 25 (20–30) to 37.5 (30–45) μm. Paspalum distichum appeared to be the smallest in size whereas P. dilatatum was the largest. Exine thickness ranged from 0.75 (0.5–1) to 1.35 (1.2–1.5) μm. The higher value of pollen fertility was found in P. scrobiculatum as 87.69% and the lowest value was in P. distichum as 78.08%. Morphological keys were also given for correct identification.