A miniaturised monopole antenna for ultra-wide band applications with band-notch filter

This study presents a new miniaturised printed monopole antenna. The size of the antenna is 18 x 18 mm². First simple design rules are given to arrive at an initial design for the antenna, then the antenna parameters are optimised for utilisation in ultra wide band (UWB) applications. The performance parameters like voltage standing wave ratio (VSWR) of the single antenna as well as transmission function, group delay and the fidelity factor of a two-antenna system are calculated and measured. It is shown that the band-notched performance can be obtained from the designed antenna by introducing simple p-shape or V-shape slots in its radiating element. Good agreements between simulated and measured results are observed.     

Optimization of STM/FIM nanotip aspect ratio based on the Taguchi method

This paper presents optimization of electrochemical etching parameters to achieve the optimum aspect ratio of the scanning tunneling microscopy/field ion microscopy tungsten nanotip by using Taguchi method. The combination of optimum level of process parameters was obtained by using the analysis of signal-to-noise ratio. The level of importance of the process parameters on the nanotip aspect ratio was determined by using analysis of variance. It was found that the optimum level of process parameters are electrolyte concentration of 2 M/lit, wire immersion length of 2.5 mm, cathode tube inner diameter of 40 mm, and voltage of 3.5 V. Within the range of experiments and the process parameters in terms of impact significance were found to be electrolyte concentration, process voltage, wire immersion length, and inner diameter of cathode tube, respectively. By using the optimum level of the process parameters, the nanotip aspect ratio was enhanced by 263% in comparison to the mean value of the experimental results. The nanotip aspect ratio of up to 163:1 was obtained in the present research.     

Variation of the specific surface area and porosity of zinc oxide prepared in various atmospheres

Specific surface area and pore structure studies were carried out on zinc oxide samples prepared from zinc oxalate dihydrate by heating at 330 and 370°C and in various atmospheres of water vapour, oxygen and hydrogen. The variation of S_BET with water vapour pressure for the samples heated at 330°C was found to show a behaviour which can be compared with the Smith-Topley effect. For the samples prepared at 370°C, rapid sintering occurred, and the Smith-Topley effect was not followed in this case. Zinc oxide prepared in an oxygen atmosphere gave higher surface area values than that prepared in a hydrogen atmosphere, which is thought to be due to the oxidation of the carbon impurities on the surface. Analysis of nitrogen adsorption isotherms by the t-method revealed the existence of micropores in the sample prepared at 330°C in vacuo. The rest of the samples have wide pores.     

A least-squares support vector machine approach to predict temperature drop accompanying a given pressure drop for the natural gas production and processing systems

Precise estimation of temperature variations throughout gas production systems can enhance designing the production amenities. Routine methods for determining the temperature profiles in gas production systems are based on the gas composition and flash calculations. However, if the gas compositions are not available, the gas production system can be modelled by employing a black-oil approach, which is also a method for calculating the oil/gas resources and for modelling the gas reservoir operation. Accordingly, for black-oil models and when the natural gas compositions are not accessible, applying robust predictive tools in this research is of high interest in natural production systems. The current study places emphasis on applying the predictive model based on the least- squares support vector machine (LSSVM) to estimate precisely the proper temperature drop associated with a given pressure drop throughout the natural gas production systems based on the black-oil approach to acquire an accurate result for the temperature drop of natural gas streams. Genetic algorithm was used to optimise hyper-parameters (γ and σ²) which are embedded in the LSSVM model. Using this method is simple and it accurately determines the temperature drop through the natural gas stream with minimum uncertainty.     

灌排系统水转化模拟模型研究

受自然与人为因素综合影响,灌区水转化过程复杂多变。以湖北漳河水库灌区为例,分别从水平和垂直方向描述典型灌排系统的水转化过程,以水量平衡原理为基础,研发灌排系统边界处置、稻作区田间多层土壤、塘坝及排水沟道之间多个水转化模拟子模块,由此构建一种客观描述灌排系统边界半封闭结构及其水平输送、垂直运动与渠-田-沟-塘水转化过程的耦合模拟模型,解决了应用流域分布式水文模型求解灌区水转化过程中面临的灌区边界不确定、分层土壤简化处理等问题。利用漳河灌区谭店灌排系统2014-2015年水平衡测试观测数据对该模型进行检验,采用拉丁超立方抽样法对模型参数进行分层抽样,并利用偏相关法分析参数敏感性。通过模型计算可得,支沟率定期和验证期模拟结果的复相关系数分别为0.83、0.70,Ens系数分别为0.81、0.68,斗沟率定期和验证期模拟结果的复相关系数分别为0.79、0.68,Ens系数分别为0.73、0.62,结果表明该模型适用于灌排系统水转化过程模拟。与SWAT模型对比,对于同一研究区域,复相关系数由0.11提高到0.73,Ens系数由-0.71提高到0.70,进一步验证了该模型的先进性,为灌排系统尺度水转化模拟和机制研究提供了新方法。     

Gray-scale ultrasound: utility preoperatively and postoperatively in a patient with obstructive jaundice

We present a case of obstructing calculi of the common bile duct diagnosed by ultrasonography. Postoperatively, a sterile abscess due to bile leakage at the distal common bile duct developed, and was also diagnosed by ultrasound Ultrasonography was useful in following the course of clearing of the bile collection. Preoperative ultrasound evaluation of the jaundiced patient should be followed by postoperative sonography, especially if complications occur.     

Modification and abolition of re-entry within the His-Purkinje system in man by diphenylhydantoin

The phenomenon of macrore-entry (Re) within the His-Purkinje system (HPS) was consistently observed in 10 of 19 patients during retrograde refractory period studies. Effects of intravenous infusion of diphenylhydantoin (DPH) on Re were studied in these 10 patients 10 minutes after completion of infusion (mean plasma level equal to 17.0 microgram/ml). Diphenylhydantoin modified determinants of Re in seven patients (group I) and abolished Re in the remaining three patients (group II). In group I, DPH shortened the critical V1 V2 from 310.0 +/- 30.5 to 292.9 +/- 25.6 msec (P less than 0.025) and critical V2 H2 intervals for Re from 201.4 +/- 18.4 to 185.0 +/- 13.8 msec (P greater than 0.05). In group II, DPH abolished Re in two of three patients by precluding attainment of critical V2 H2 intervals whereas Re was abolished in the remaining one patient despite attainment of critical V2 H2 intervals (vs control). For both groups, DPH significantly shortened functional and effective refractory periods of the HPS (P less than 0.001 and less than 0.01, respectively) without significantly affecting the effective refractory period of the ventricular muscle. Diphenylhydantoin either completely abolished or significantly shortened the retrograde gap zones in the HPS. It is concluded that diphenylhydantoin significantly shortens His-Purkinje system refractoriness, abolishing Re in the patients with higher degree of improvement in refractoriness.