Search

In this article, a new electro-thermal optimization algorithm is proposed to determine the parallel power cables arrangement to obtain the maximum ampacity. The optimization procedure is based on the imperialist competitive algorithm (ICA). Electrical calculations are performed using the sub-conductors method and consideration of the skin and proximity effects. FEM thermal model and electrical calculations are coupled with optimization procedure to determine the ampacity in the optimization algorithm. Optimized arrangements are determined under sinusoidal and harmonic load currents conditions. Furthermore, the effects of different boundary conditions of the ground surface such as isothermal and convective heat flux are evaluated. The underground single conductor cables with solid bonded metallic sheaths and existing of circulating currents are considered. Cables are considered to be installed adjacent to each other in different rows above each other in flat formations. Also, the artificial bee colony (ABC) optimization algorithm is performed to validate the ICA procedure. Experimental measurement of a case study is carried out for simulation confirmation and the results show good agreement. [ABSTRACT FROM AUTHOR]

Laser wakefield acceleration (LWFA) is a plasma-based electron beam accelerator technology that can deliver electron beams with energies up to several GeVs, depending mainly on the power of the used laser system and the electron injection scheme. Here, we present the results from a GeV electron accelerator with a high reproducibility and a charge up to 30 pC using 110–120-TW laser pulses and by employing the well-established self-truncated ionization injection (STII) mechanism. These electron beams can be further used via bremsstrahlung in high-Z solid materials for the generation of gamma-rays and positron beams, therefore, composing a compact radiation source for various applications. Here, we use the Monte Carlo simulation code “Geant4” for studying the properties of those radiations. As expected, the characteristics of the generated gamma-rays and positron beams showed a strong dependence on the incident electron beam, target material, and thickness. The trend of positrons and gamma-rays energies and yield is shown for different high-Z to low-Z targets with the same areal mass density. Thicknesses of the target material in terms of its radiation length have been varied periodically in order to find the optimal thickness for obtaining the maximum energy and yield of the radiations. A trend can be seen in terms of energy spectra of the gamma-rays and positrons while increasing the thickness of the targets. The amount of radiation yields is also crucial to the choice of appropriate thickness of the target. In addition, this paper provides a brief description of the electrodynamics processes such as bremsstrahlung and electron–positron pair production initiated by LWFA electron beams. [ABSTRACT FROM AUTHOR]

By using 25–45 TW ultra-short (30 fs) laser pulses, we report on the effect of the injection gas concentration on the quality of electron beams generated by a laser-driven plasma wakefield acceleration employing the ionization-injection. For a plasma formed from helium-nitrogen gas mixture and depending on the concentration of the nitrogen gas, we could distinguish a clear trend for the quality of the generated electron beams in terms of their peak energy, energy-spread, divergence angle, and beam charge. The results clearly showed that the lower the nitrogen concentration, the better the quality (higher peak energy, smaller energy spread, and smaller emittance) of the generated electron beams. The results are in reasonable agreement with two-dimensional particle-in-cell simulations. [ABSTRACT FROM AUTHOR]

The V-I characteristic of ZnO varistor which has been obtained from experimental test, is an important parameter to model surge arrester electrical behavior. Generally, in grid voltage, this characteristic depends on temperature variations. In this paper, an improved metal oxide surge arrester electrical model has been proposed under grid voltage. Temperature effects on surge arrester performance have been considered in the proposed model. Artificial neural network has been used to determine V-I characteristic at temperature variations. Therefore, in proposed model, the V-I characteristic of each varistor has been estimated based on applied voltage and operating temperature. To validate proposed model, laboratory setup and infrared thermal camera have been arranged and experimental tests results have been compared with simulation ones. Results revealed that there has been a good agreement between simulation and experimental results. Moreover, electrical behavior of surge arrester is predictable with high precision through the proposed artificial model. [ABSTRACT FROM AUTHOR]

The current distribution, ampacity and magnetic field of parallel power cables are calculated. The calculations are performed in both sinusoidal and harmonic current profiles. The simulations are conducted on the underground medium voltage cables with metallic sheaths. The effects of single‐point bonding and solid bonding of sheaths grounding system are evaluated. In this study, cables are installed in flat formation with three cables in each phase and the effect of different distances between cables on the parallel cables parameters is studied. Computations are conducted for all possible arrangements of parallel cables and the worst and the best arrangements from the point of balancing current division, maximum ampacity and minimum magnetic field are presented. Furthermore, the effects of placing parallel cables in one row or two rows above each other are investigated. Calculations of current distribution and magnetic field are performed using the sub‐conductors method that considers the skin and proximity effects. Finite element method thermal simulations are excited to determine the power cable ampacity in different configurations. Experimental tests on parallel cables in both single‐point bonding and solid bonding systems are carried out and the results verify the accuracy of simulations. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of metallic sheaths on alternating current (AC) losses and ampacity of power cables. The AC losses are expressed as AC/direct current (DC) resistance in power cables, which is the main factor in loss computations. With regard to the importance of harmonic contents of the currents, a comprehensive study is performed on AC/DC resistance of medium-voltage cables in the presence of harmonics. Different harmonic frequencies include triple and nontriple orders are considered. A derating factor is proposed on the basis of cable constructions. Two types of sheathed and unsheathed medium-voltage power cables are considered. Also for metallic sheathed cables, 2 types of sheath grounding are investigated. It is shown that single-point bonding and both-ends bonding of sheaths have different effects on cable ampacity in harmonic frequencies. Moreover, different conductor cross sections and distances between cables are considered, and their effects on AC/DC resistance and ampacity derating are assessed. It is shown that these factors have important effects on AC/DC resistance and thus power cable losses. Furthermore, all cases are investigated in both flat and trefoil formations that are the most popular formations in power cables. To achieve precise results, we performed this study on the basis of finite element simulation, which is an exact way to cable losses computations in each configuration. [ABSTRACT FROM AUTHOR]

This article presents an online diagnostics method to predict critical conditions in ceramic insulators. For this purpose, a variety of experimental tests have been conducted on different kinds of ceramic insulators under different environmental conditions in order to analyze their leakage current. Fast Fourier transform analysis of leakage currents shows a strong correlation between the ratio of the third to fifth harmonic amplitude regarding occurrence of critical conditions and degree of insulator ageing. Therefore, the index of the third to fifth harmonic amplitude is utilized as the detection indicator of critical conditions in ceramic insulators. An increase in the index of the third to fifth harmonic amplitude to more than one represents a critical condition in the insulators and estimates a high probability of flashover occurrence. The obtained results have also shown the viability of the index in insulators monitoring procedures. Training the proposed index to a microprocessor powered device gives ability to the system for online diagnosis of ceramic insulator qualifications, detecting critical conditions, and predicting flashover occurrence. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper presents losses distribution in power cables conductors and metallic sheaths. Losses are computed in sinusoidal and non-sinusoidal currents with considering all sequences harmonics. Two numerical methods as finite element and integral method are used to determine the distributions and also total harmonic losses. Thus skin and proximity effects of all metallic parts of cables are considered accurately. Integral method is utilized for losses calculation by considering of earth return path and eliminating it. Furthermore, IEC formulations are used for losses computations. Numerical results suggest inserting the earth return path effect on cable losses in some harmonic frequencies of currents. Power cables are assumed to be single core medium voltage type. Lead sheaths of cables are bonding together and grounded at both ends for calculation of circulating current losses. Also the effects of different distances between cables in losses calculations are assessed. For validation of integral method, finite element simulation, as proven method in accurate power cable losses computations is used. These methods are completely described in this paper. Accuracy of integral method for harmonic losses computations of conductor and sheaths is verified by finite element simulation results. Also it is shown that proximity and skin effects are considered very well by integral method even in metallic sheaths. © 2016 Wiley Periodicals, Inc. Comput Appl Eng Educ 24:692-705, 2016; View this article online at ; DOI [ABSTRACT FROM AUTHOR]

In this paper, an improved method to diagnose the critical conditions in the porcelain and glass insulators has been proposed through investigating leakage current (LC) and applied voltage signals. Hence, Fast Fourier Transform (FFT) analysis has been used to calculate the phase angle values of the applied voltage and LC signals. Analyzing phase angle difference of LC and applied voltage waveforms demonstrate a strong correlation of the phase difference between the applied voltage and LC waveforms with the insulators conditions. So, the phase difference cosine (P.D%) has been offered as a diagnostic index of porcelain and glass insulators conditions. In this case, when the P.D% value is lower than 30%, the insulators are in clean and normal conditions. On the other hand, if the P.D% is more than 30%, the insulators are in extreme conditions. Moreover, by increasing %P.D value more than 85%, the probability of the flashover occurrence in porcelain and glass insulators will be very high. The obtained experimental results validate the veracity of considering P.D% as a criterion for prediction of flashover in porcelain and glass insulators. [ABSTRACT FROM PUBLISHER]

This paper proposes an adaptive model for electro-thermal analysis of metal oxide surge arresters based on finite element method. The input of the proposed model has been derived from power loss curve using adaptive network based fuzzy inference system (ANFIS). Moreover, degradation factor has been introduced as a new index to represent operating history of metal oxide surge arrester. Therefore, applied voltage, temperature, and degradation factor have been considered as inputs in the ANFIS model to obtain accurate power loss which is of paramount importance in electro-thermal analysis. High voltage experimental setup and an oven have been prepared to acquire data for the proposed model. Degrading effect has been undertaken by measurement of the voltage-current characteristic of used and degraded varistors. The effect of assembling process, in addition, has been considered using different virgin (not degraded) varistors in experimental measurements. In addition, according to the IEC standard, the aging effect has been obtained experimentally by putting the varistor under 115 °C and continuous operating voltage for 1000 h. To validate the results of the electro-thermal model, thermal infrared camera has been used under different applied voltages. Obtained results show that the electro-thermal behavior of surge arrester is predictable with high precision through the proposed artificial model. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This study proposes a new method for modelling of metal-oxide surge arresters (MOSAs) thermal balance diagram based on power loss and heat dispersion curve. Adaptive network-based fuzzy inference system (ANFIS)- based method was offered to compute surge arrester power loss characteristic. Thermal stability (TS) of surge arrester, which is analysed by thermal balance diagram, has a great influence on their proper functions. MOSA material variation is an important factor that has an influence on its TS. Degradation factor (DF) was introduced as a new index in this study to represent material variations of MOSA. Therefore, applied voltage, temperature and DF were considered as inputs in ANFIS model to obtain accurate power loss which is a very important factor in TS characteristic. Heat dispersion curve was obtained as a main feature in the thermal balance diagram from surge arrester cooling curve. Degrading effect was considered using voltage and current measured from MOSA which are degraded by utilisation in the network. In addition, effect of assembling process has been considered by using new different varistors in experimental measurements. This study shows that the thermal balance diagram of surge arrester is predictable with a good accuracy by using artificial model. [ABSTRACT FROM AUTHOR]

Owing to the increasing electricity load demand on one hand and in order to have a reliable electric network on the other hand, constructions of new transmission lines and generation sources are extremely essential. Such expansions, however, raise the fault current level which can even exceed the maximum short-circuit level rating of the circuit breakers (CBs). High fault current, in addition to the adverse effect on the CB function, can damage other substation equipment suddenly or over the time. To this end, severity of the fault current is a key factor in the substation reliability assessment. In this context, fault current limiters (FCLs) which are employed to decline the fault current level need to be precisely modelled and their impact should be extensively studied. In this study, the effect of FCL on the failure rate of substation equipment is first investigated. A computational technique for assessing the substation reliability is accordingly devised. As the location of FCL installation in a given substation or in substations with different arrangements would not be the same, various credible configurations are incorporated here. The results show that from the perspective of reliability indices, double-bus double-breaker and one breaker and a half configurations are more suitable for FCL installation. [ABSTRACT FROM AUTHOR]

The most monitoring techniques of metal oxide surge arresters are based on harmonics analysis of resistive leakage current. Therefore, the extraction of resistive component from total leakage current is required. Up to now, several methods have been proposed for resistive leakage current extraction such as time-delay addition method. This method is only able to separate accurate resistive component under pure sinusoidal applied voltage. An improved time-delay addition method is proposed in this paper which is able to extract surge arrester resistive component under applied harmonic voltage. To accomplish this purpose, experimental tests have been performed on 20 kV surge arrester and obtained voltage and leakage current signals have been applied to the proposed and previous algorithms for resistive component extraction. In addition to investigate the ability of proposed algorithm, a typical surge arrester has been simulated in ATP-EMTP software and total leakage currents have been applied to both algorithms for resistive leakage current extraction. Results show that the proposed method is able to extract resistive component under applied harmonic voltage more accurate than previous one. Therefore, it is an improvement with respect to previous one that only works for sinusoidal voltage. [ABSTRACT FROM AUTHOR]

Metal-oxide surge arresters (MOSAs) are essential equipments for power system protection and devices from lightning and switching transient overvoltages. Therefore, their operating condition and diagnosis are very important. In this study, a multi-layer support vector machine (SVM) classifier has been used for MOSA conditions monitoring based on experimental tests. Three features are extracted based on the test results for determining surge arresters operating conditions including clean virgin, ultraviolet (UV) aged clean surface, surface contaminations after and before UV housing ageing, and degraded varistors along active column. Then, the multi-layer SVM classifier is trained with the training samples, which are extracted by the above data processing. Finally, the five fault types of surge arresters are identified by this classifier. The test results show that the classifier has an excellent performance on training speed and reliability which confirm the high applicability of introduced features for correct diagnostic of surge arresters conditions. [ABSTRACT FROM AUTHOR]

This paper proposes a new method to estimate power loss characteristics of metal oxide surge arresters. The method was used to compute surge arrester power loss curve based on adaptive network based fuzzy inference system (ANFIS) and artificial neural network (ANN). Surge arrester operating history is an important factor that bears influence on its power loss. Degradation was, in this paper, introduced as a new index to represent operating history of metal oxide surge arrester. Therefore, applied voltage, temperature and degradation factor were considered as inputs in ANFIS system and ANN models to obtain accurate power loss which is a very important factor in surge arrester thermal stability. Degrading effect was undertaken by measurement voltage and current in varistors degraded by utilization in network. The results of the two artificial models were compared. Results show that ANFIS was more accurate than ANN. This study shows that the power loss characteristics of surge arrester are to a great extent accurately predictable using proposed artificial model. [ABSTRACT FROM AUTHOR]

Metal-oxide surge arresters are one of the most important equipments for power system protection against switching and lightning over-voltages. Surge arresters leakage currents increase by the operating time. In this study, the important factors on leakage current variations such as surface contamination, ultraviolet ageing and varistor degradation have been studied. To accomplish this purpose, experimental tests have been performed on various polymer housed surge arresters. Fast Fourier transform analysis has been performed on measured leakage currents. Results show that ultraviolet radiation and varistor degradation affect resistive harmonic components, especially the third and fifth harmonics. Moreover, it is observed that surface contamination has influence on fundamental harmonic variation more than ultraviolet ageing. In addition, combination of ultraviolet radiation and pollution had more effect on leakage currents. The investigation and the discussion of the results can be used to easily analyse arresters condition leading to effective schedule maintenance. [ABSTRACT FROM AUTHOR]

ABSTRACT Analysis of electro-thermal behavior in various operating condition based on finite element method was proposed in this article. Power frequency and impulse stresses vary the operating region and temperature of surge arresters. Therefore, adaptive power loss was considered as a source in the modeling of surge arrester based on finite element method. Adaptive network based fuzzy inference system and frequency dependent model were used to model power loss in low and high current regions, respectively. To obtain accurate power loss, which is very important factor in electro-thermal analysis, applied voltage and temperature were considered as inputs in adaptive network based fuzzy inference system model. The experimental setup including impulse generator, power frequency high voltage generator and also an oven was arranged to achieve real data. Finally, the results of simulation based on proposed adaptive method were compared with the thermal infrared camera results. This study shows that the electro-thermal behavior of surge arrester is predictable with a good accuracy by using artificial model. © 2015 Wiley Periodicals, Inc. Comput Appl Eng Educ 23:910-920, 2015; View this article online at ; DOI [ABSTRACT FROM AUTHOR]

An investigation of the electron beam yield (charge) form helium, nitrogen, and neon gas jet plasmas in a typical laser-plasma wakefield acceleration experiment is carried out. The charge measurement is made by imaging the electron beam intensity profile on a fluorescent screen into a charge coupled device which was cross-calibrated with an integrated current transformer. The dependence of electron beam charge on the laser and plasma conditions for the aforementioned gases are studied. We found that laser-driven wakefield acceleration in low Z-gas jet targets usually generates high-quality and well-collimated electron beams with modest yields at the level of 10-100 pC. On the other hand, filamentary electron beams which are observed from high-Z gases at higher densities reached much higher yields. Evidences for cluster formation were clearly observed in the nitrogen gas jet target, where we received the highest electron beam charge of ~1.7 nC. Those intense electron beams will be beneficial for the applications on the generation of bright X-rays, gamma rays radiations, and energetic positrons via the bremsstrahlung or inverse-scattering processes. [ABSTRACT FROM AUTHOR]

Metal oxide surge arresters are important equipments that apply to power system for protection against switching and lightning over-voltages. Surge arrester monitoring technique based on leakage current analysis is a conventional monitoring method. Lack of proper features and thresholds is most important limitation of this method. In this paper, new monitoring indexes for surge arrester diagnostic are proposed to determine surge arrester condition under different situations including clean condition, surface contamination and ultraviolet aging. The experimental tests have been performed on polymer surge arresters to evaluate the ability of the proposed indexes for distinguishing the operating condition of surge arresters. Results have been shown the viability of the new indexes on surge arrester monitoring procedures. The investigation and the discussion of the produced results can give good ideas the electric engineers in order to easily analyze arresters’ condition leading to effective schedule maintenance. [ABSTRACT FROM AUTHOR]

We report a laser wakefield acceleration of electron beams up to 130 MeV from laser-driven 4 mm long nitrogen gas jet. Using moderate laser intensity ( \sim 35\times 10^18~W\cdot cm^-2 ) and relatively low plasma densities ( 0.8\times 10^18~\mathrmcm^-3 -2.7\times 10^18~\mathrmcm^-3 ), we have achieved stable laser propagation and consequently stable acceleration of electron beams. We experimentally studied the dependence of the electron beam parameters on the laser beam energy. Evidence of the ionization-induced electron injection has been recognized from the characteristic long-tail beam energy spectrum, however, the majority of the electrons were contained in quasi-monoenergtic peaks. [ABSTRACT FROM PUBLISHER]

Transformers are usually designed and built for use at rated frequency and perfect sinusoidal load current. But transformer loading under non-linear load leads to harmonic power losses which cause increased operational costs and additional heating in power system components. It direct to higher losses and temperature, early exhaustion of insulation and reduction of the useful life of the transformer. The hot spot temperature is one of the main limiting factors that affect the useful life of the power transformer and its loading. This paper presents the determination of hot spot temperature and life assessment in three phases, 20/0.4 kV, 100 KVA transformer under linear and harmonic load conditions using two-dimensional model of transformer by COMSOL software. For numerical solution of above equation, finite element method (FEM) based on heat transfer theory is used. [ABSTRACT FROM AUTHOR]

We report on the generation of quasimonoenergetic electron beams by the laser wakefield acceleration of 17-50 TW, 30 fs laser pulses in pure neon gas jet. The generated beams have energies in the range 40-120 MeV and up to ~430 pC of charge. At a relatively high density, we observed multiple electron beamlets which has been interpreted by simulations to be the result of breakup of the laser pulse into multiple filaments in the plasma. Each filament drives its own wakefield and generates its own electron beamlet. [ABSTRACT FROM AUTHOR]

A laser wakefield acceleration (LWFA) experiment is performed using 30 TW, 30 fs, and 800 nm laser pulses, focused onto pure nitrogen plasma having relatively low densities in the range of 0.8 × 1018 cm-3 to 2.7 x 1018 cm-3 . Electron beams having a low divergence of ~3 mrad (fullwidth at half-maximum) and quasi-monoenergetic peak energies of ~105 MeV are achieved over 4-mm interaction length. The total electron beam charge reached to 2 nC, however, only 1%-2% of this (tens of pC) had energies >35 MeV. We tried different conditions to optimize the electron beam acceleration; our experiment verifies that lower nitrogen plasma densities are generating electron beams with high quality in terms of divergence, charge, pointing stability, and maximum energy. In addition, if LWFA is to be widely used as a basis for compact particle accelerators in the future, therefore, from the economic and safety points of view we propose the use of nitrogen gas rather than helium or hydrogen. [ABSTRACT FROM AUTHOR]

Induction motors are widely used in industrial, commercial and residential applications. An induction motor may exposed to the unbalanced voltage in the various operating conditions. Therefore, it is vital to investigate influences of voltage unbalance on performance of induction motors. In this paper, the performance of a three-phase squirrel cage induction motor has been simulated using Finite Element Method(FEM) supplied by different unbalanced voltages with the same Voltage Unbalance Factor(VUF) as well as the same positive-sequence phase voltage components. In addition, input/output powers, losses and efficiency of the simulated motor under mentioned conditions have been studied. [ABSTRACT FROM AUTHOR]

Porcelain string insulators are widely used in high-voltage transmission lines. Calculation of potential distribution is extensively performed in the design and development of high-voltage insulators. This article applies a three-dimensional electromagnetic analysis program to calculate the potential distribution of 230-kV porcelain suspension insulators under clean and dry conditions. The effects of cross-arm length, number of units, corona ring parameters, and also effects of wind force on the potential distribution along the porcelain suspension insulators are investigated and discussed. The results are useful for analyzing the potential distribution for porcelain suspension insulators. [ABSTRACT FROM AUTHOR]

In order to restrain ferroresonance in coupling capacitor voltage transformers (CCVT), three kinds of ferroresonance suppression circuits (FSCs) have been presented The resonant type, the fast-saturation reactor type and electronic type which are connected to secondary side of CCVTs, are proposed in this paper. Frequency domain analyses, for voltage ratio magnitude, are carried out for CCVTs to obtain preferable FSC. Furthermore, using surge suppressors such as metal oxide varistors (MOV) to improve the performance of the FSCs is investigated Time domain simulations demonstrate that ferroresonance can be cleared in few cycles in presence of FSCs. In addition, to mitigate ferroresonanse in inductive transformers (VTs), we connect the damping resistor to the open-delta-arranged auxiliary winding. [ABSTRACT FROM AUTHOR]

Thermal stress due to losses and environment temperature causes degradation to paper/oil insulation systems in transformers, even at operating temperature. Experience indicates that thermal ageing of oil and paper in power transformers leads to the change of some insulation characteristics. In this paper, insulating papers immersed in oil have been acceleratory aged at 140, 150, and 160°C under laboratory conditions. Some of the oil properties, such as water content, breakdown voltage, acidity, together with the aged insulating paper properties such as electric strength, dielectric dissipation factor and tensile strength were measured and analyzed. Also, insulation system conditions under thermal stress have been evaluated by electrical/distinctive techniques like recovery voltage, polarization and depolarization currents. Correlations between these parameters have been investigated. Finally, paper tensile strength has been used as a criterion to estimation of insulating paper life time. [ABSTRACT FROM AUTHOR]

The issue of demographic transition has become a principle preoccupation of demographers during the last few decades. As explained by some scholars, the omnipresent differentials in the trends and determinants of transition warrant separate and detailed study in various regions and countries to obtain a better understanding of the issue. In this article, an attempt is made to elaborate on the recent trend of fertility and its determinants in the Islamic Republic of Iran. After providing a brief introduction to the general demographic characteristics of the country, I discuss fertility limitation in the past and Islamic views about birth control. Subsequently, I elaborate on the swings in fertility limitation in the past three decades and the determinants of those swings. [ABSTRACT FROM AUTHOR]

• Proposing comprehensive equivalent electric circuit of polluted insulator. • Considering dynamic behavior for arc parameters instead of static one. • Evaluating proposed mathematical model with experimental results for real insulators. • Comparing the proposed mathematical model with static models for the same frame of real insulators. • Analyzing leakage current behavior under various pollution and humidity. This paper presents an improved dynamic mathematical model of critical parameters for ceramic insulators based on an extended equivalent electric circuit model of a polluted insulator. The extended equivalent electric circuit model introduces a capacitance in dry band. The model proposes that the electric arc constants (n, N) of critical parameters (voltage and current) in the mathematical model are not static. These factors depend on insulator's profile, pollution intensity and thermal characteristic of insulator discharge. The dynamic values of electric arc parameters are suggested based on the analysis of the experimental data and mathematical calculation of critical voltage of the polluted insulators. The calculated critical voltage of the proposed mathematical model is compared against the experimentally measured values of the critical voltage under different operating conditions. The experimental test results validate the competency of the proposed dynamic model in an accurate performance prediction of the polluted insulators. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports an investigation into the effect of a number of operating factors on the removal of Acid Blue 92 (AB92) from an aqueous solution using hydroxyl-terminated polybutadiene (HTPB) as an adsorbent. The optimum values of adsorbent dose and pH were found to be 35mgL−1 and 6, respectively. Temperature showed a significant effect, with maximum dye removal being observed at 45°C. Stirring the solution during the treatment process resulted in significant removal improvement. The Langmuir adsorption model was used to quantify the amount of AB92 adsorbed on the surface of HTPB. FT-IR spectrometry results for HTPB, AB92, and HTPB-AB92 verified the efficiency of the treatment. Further, the adsorbent was characterized using SEM and H NMR techniques. [Copyright &y& Elsevier]

Background: The aim of this study was to evaluate respiratory problems via pulmonary function testing in cement transport workers at Incheh Borun border in northeast of Iran in 2016., Methods: The study was conducted on 358 male workers. All subjects were evaluated for respiratory symptoms via pulmonary function testing and completion of the American Thoracic Society questionnaire., Results: Mean age of workers was 34.8±12.87 yr (age range 16-79 yr). Mean duration of employment was 6.1±4.36 yr. Most workers (75.4%) were illiterate or had elementary education. In addition, 56 (15.6%) subjects were smokers. Only three individuals (0.3%) had obstructive pattern. There was a significant relationship between age of workers and frequency of respiratory problems ( P <0.05)., Conclusion: It is necessary to educate the workers about the health and safety regulations and use of personal protective equipment in workplace. In addition, periodic evaluation of respiratory function could help protect workers from developing occupational diseases., Competing Interests: Conflict of interest The authors declare that there is no conflict of interests.

We report on overall enhancement of a single-stage laser wakefield acceleration (LWFA) using the ionization injection in a mixture of 0.3% nitrogen gas in 99.7% helium gas. Upon the interaction of 30-TW, 30-fs laser pulses with a gas jet of the above gas mixture, >300 MeV electron beams were generated at a helium plasma densities of 3.3-8.5 × 10(18) cm(-3). Compared with the uncontrolled electron self-injection in pure helium gas jet, the ionization injection process due to the presence of ultra-low nitrogen concentrations appears to be self-controlled; it has led to the generation of electron beams with higher energies, higher charge, lower density threshold for trapping, and a narrower energy spread without dark current (low energy electrons) or multiple bunches. It is foreseen that further optimization of such a scheme is expected to bring the electron beam energy-spread down to 1%, making them suitable for driving ultra-compact free-electron lasers.