Dynamic Braking of Induction Motors Using DC Injection

ABSTRACT

Dynamic braking of 3-phase induction motors through dc injection in commonly used in applications such as cranes and hoists. The paper analyses the performance of a slip ring induction motor with dc injection and derives expressions for the optimum values of injection voltage and rotor resistance. Digital computer simulation of the sequence of operations like motoring and braking is also given.     

Superparamagnetic magnetite nanoparticles for cancer cells treatment via magnetic hyperthermia: effect of natural capping agent,particle size and concentration

Journal of Materials Science: Materials in Electronics - Superparamagnetic iron oxide nanoparticles (SPMNPs) continue to emerge as one of the most potential candidates in biomedical applications....     

Conjunctive Use of Surface and Groundwater with Inter-Basin Transfer Approach: Case Study Piranshahr

Disregarding water as a key sustainable development has led to the water crisis in Iran. This problem is the biggest factor for marginalizing the planning and long-term management of water. The sustainable development policies in water resources management of IRAN require consideration of the different aspects of management that each of them demands the scientific integrated programs. Optimal use of inter-basin surface and groundwater resources and transfer of surplus water to adjacent basins are important from different aspects. The purpose of this study is to develop an efficient optimization model based on inter-basin water resources and restoration of outer-basin water resources. In the proposed model the three different objectives are as follow supplying inter-basin water demand, reducing the amount of water output of the boundary of IRAN and increasing water transfer to adjacent basins (Urmia Lake basin) are considered. In this model, water allocation is done based on consumption and resources priorities and groundwater table level constraints. In this research, the non-dominate sorting genetic algorithm is used for performing the developed model regarding the complexity and nonlinearity of the objectives and the decision variables. The optimal allocation of each water resources and water transfer to adjacent basin can be determined by using of proposed model. Optimal allocation policy presented based on optimal value and planning horizon. The results show that we can transfer considerable volume of water resources within the basin for restoration the outside basin and prevent the great flow of water by the border rivers applying the optimal operation policy.     

Crowdsourcing contests: understanding the effect of competitors’ participation history on their performance

Crowdsourcing contests have become increasingly important and prevalent with the ubiquity of the Internet. Designing efficient crowdsourcing contests is not possible without the deep understanding of the factors affecting individuals’ continuous participation and their performance. Prior studies have mainly focused on identifying the effect of task-specific, environment-specific, organisation-specific, and individual-specific factors on individuals’ performance in crowdsourcing contests. And to our knowledge, there are no or very few studies on evaluating the effect of individuals’ participation history on their performance. This paper aims to address this research gap using a data set from TopCoder. This study derives competitors’ participation history factors, such as participation frequency, participation recency, winning frequency, winning recency, tenure, and last performance to construct models depicting effects of these factors on competitors’ performance in online crowdsourcing contests. The research findings demonstrate that most of competitors’ participation history factors have significant effect on their performance. This paper also indicates that competitors’ participation frequency and winning frequency moderate the relationship between last performance and performance, and relationship between tenure and performance positively. On the other hand, individuals’ participation recency and winning recency moderate relationship between last performance and performance negatively, but have no significant effect on the relationship between tenure and performance.     

A Study of the Activated Decomposition of CO2 on the Cu Component of a Cu/ZnO/Al2O3 Catalyst

The decomposition of CO₂ over the Cu component of two ZnO/Al₂O₃ supported Cu catalysts, having different Cu areas, has been studied over the temperature range 393–513 K. The time dependence of the evolution of CO from a CO₂/He stream (10% CO₂, 101 kPa) which was dosed continuously over the catalyst showed two peak maxima, the first of which moved to shorter times on raising the temperature. The activation energy for the decomposition of CO₂ on the ZnO/Al₂O₃ supported polycrystalline copper was obtained from a plot of the logarithm of the time to the peak maximum of the first peak against the reciprocal of the dosing temperature. The value so obtained was 83±10 kJ mol^-1 (catalyst A) and 86±10 kJ mol^-1 (catalyst B) for fresh catalysts reduced in H₂ at 513 K. This value fell to 49 ±4 kJ mol^-1 (catalyst A) and 55±5 kJ mol^-1 (catalyst B) after CO reduction at 473 K of the Cu which had been oxidised by the decomposition of the CO₂. This lowering of the activation energy for the second CO₂ decomposition is considered to be due to the original morphology of the Cu not being restored by reduction in CO after the oxygen-driven reconstruction of the Cu deriving from the decomposition of the CO₂.     

Preparation and electrocatalytic oxidation properties of a nickel pentacyanonitrosylferrate modified carbon composite electrode by two-step sol-gel technique: improvement of the catalytic activity

The sol-gel technique was used to construct nickel pentacyanonitrosylferrate (NiPCNF) modified composite ceramic carbon electrodes (CCEs). This involves two steps: forming a CCE containing Ni powder and then immersing the electrode into a sodium pentacyanonitrosyl-ferrate solution (electroless deposition). The cyclic voltammograms of the resulting surface modified CCE under optimum conditions show a well-defined redox couple due to the [Ni^IIFe^III/II(CN)₅NO]^0/−1 system. The electrochemical properties and stability of the modified electrode were investigated by cyclic voltammetry. The apparent electron transfer rate constant (k_s) and transfer coefficient (α) were determined by cyclic voltammetry being about 1.1 s⁻¹ and 0.55, respectively. Sulfite has been chosen as a model to elucidate the electrocatalytic ability of NiPCNF-modified CCE prepared by one- or two-step sol-gel technique. The modified electrode showed excellent electrocatalytic activity toward the SO₃²⁻ electro oxidation in pH range 3-9 in comparison with CCE modified by homogeneous mixture of graphite powder, Ni(NO₃)₂ and Na₂[Fe(CN)₅NO] (one-step sol-gel technique). Sulfite was determined amperometrically at the surface of this modified electrode in pH 7. Under the optimized conditions the calibration curve is linear in the concentration range 2 μM to 2.0 mM. The detection limit (signal-to-noise is 3) and sensitivity are 0.5 μM and 13.5 nA/μM. The modified carbon ceramic electrode containing nickel pentacyanonitrosylferrate shows good repeatability, short response time, t (90%) <2 s, long-term stability (3 months), and it is renewed by simple mechanical polishing and its immersing in Na₂[Fe(CN)₅NO] solution. The advantages of the SO₃²⁻ amperometrically detector based on the nickel pentacyanonitrosylferrate-doped CCE is high sensitivity, inherent stability at wide pH range, excellent catalytic activity and less expense and simplicity of preparation. This sensor can be used as amperometric detector in chromatographic instruments.     

Jitter models for the design and test of Gbps-speed serial interconnects

We present a comprehensive analysis of jitter causes and types, and develops accurate jitter models for design and test of high-speed interconnects. The recent deployment of gigabit-per-second (Gbps) serial I/O interconnects aims at overcoming data transfer bottlenecks resulting from the limited ability to increase chip pin counts in parallel bus architectures. The traditional measure of a communication link's performance has been its associated bit error rate (BER), which is the ratio of the number of bits received in error to the total number of bits transmitted. When data rates increase, jitter magnitude and signal amplitude noise must decrease to maintain the same BER. As data rates exceed 1 Gbps, a slight increase in jitter or amplitude noise has a far greater effect on the BER.     

HSA loaded with CoFe2 O4 /MNPs as a high‐efficiency carrier for epirubicin anticancer drug delivery

Drug delivery is one of the most important challenges in the domain of health. Non‐toxic and biocompatible carriers are provided by human serum albumin nano‐capsule (HSA/NC) for drug delivery applications. In this study, HSA, with high loadings of drug‐modified cobalt ferrite (CoFe₂ O₄) magnetic nanoparticle (CoFe₂ O₄ /MNPs) was fabricated for epirubicin anticancer drug delivery. In the initial step, CoFe₂ O₄ /MNPs was synthesised via co‐precipitation technique and characterised by X‐ray powder diffraction, vibrating sample magnetometry, energy dispersive X‐ray analysis, scanning electron microscopy and map analysis. Furthermore, CoFe₂ O₄ /MNPs and epirubicin were loaded into HSA/NC and utilised as a novel system against breast cancer cell line (MCF‐7). IC₅₀ for free epirubicin, unloaded CoFe₂ O₄ /MNPs/HSA/NC, CoFe₂ O₄ /MNPs and epirubicin‐loaded CoFe₂ O₄ /MNPs/HSA/NC were 7.7, 2400, 840 and 430 μg/ml, respectively. The results obtained revealed high cytotoxicity effect of epirubicin‐loaded CoFe₂ O₄ /MNPs on breast cancer cell line.Inspec keywords: drug delivery systems, biomedical materials, nanoparticles, cobalt compounds, ferrites, nanomedicine, proteins, molecular biophysics, drugs, magnetic particles, nanomagnetics, nanofabrication, precipitation (physical chemistry), X‐ray diffraction, X‐ray chemical analysis, scanning electron microscopy, cancer, cellular biophysics, toxicology, magnetic hysteresisOther keywords: HSA, high‐efficiency carrier, epirubicin anticancer drug delivery, human serum albumin nanocapsule, drug‐modified cobalt ferrite magnetic nanoparticle, coprecipitation technique, X‐ray powder diffraction, vibrating sample magnetometry, energy dispersive X‐ray analysis, scanning electron microscopy, map analysis, breast cancer cell line, cytotoxicity effect, CoFe₂ O₄      

Effects of cationic CTAB and anionic SDBS surfactants on the performance of Zn–MnO2 alkaline batteries

Inhibiting properties of two kinds of surfactant, cationic cetyl trimethyl ammonium bromide (CTAB) and anionic sodium dodecyl benzene sulfonate (SDBS) with three different concentrations, in relation to zinc passivation have been explained in the primary Zn/MnO₂ alkaline batteries. Discharge performance of alkaline cell affected by utilization of surfactant in anodic gel. Therefore, electrochemical properties of anodic zinc have been investigated by cyclic voltammetry, X-ray diffraction, scanning electron microscopy (SEM) and ac impedance techniques. The results show that alkaline cell with 0.01 g l⁻¹ of anionic SDBS surfactant decreased effectively the rate of zinc-passivation reaction. Also, it exhibited ZnO morphology with smaller grain size, causing longer service life gradually, step by step.     

High‐performance immunosensor for urine albumin using hybrid architectures of ZnO nanowire/carbon nanotube

In this work, the authors reported the hybrid architecture of carbon nanotube (CNT)–zinc oxide (ZnO) nanowire as a multi‐functional probe in amperometric immunosensor for the detection of urine albumin. Low‐cost substrate such as glass is possible because of novel low‐temperature growth process of CNT/ZnO nanowires as a multi‐function electrode in this sensor. Based on Schottky like behaviour this structure exhibit excellent high current density to achieve higher performance. Measurement of urine albumin is a new way for early detection of diabetic and also low concentration of it in culture media is also considered in order to verify the conversion of stem cells to liver cells. Human albumin serum antibody is used as a selective and sensitive part. The amperometric performance of immunosensor is studied and showed excellent performance for detection of albumin in urine samples. Very high linear range (from 3.3 ng/µl to 3.3 mg/µl) with a correlation coefficient of 0.825 and low detection limit (3.3 ng/µl or 4.96 × 10⁻⁸ mol l⁻¹) are the main characteristics of this sensor. Due to the high dynamic range and sensitivity, this sensor was also used in medical diagnosis and biomedical applications.Inspec keywords: biosensors, zinc compounds, wide band gap semiconductors, nanosensors, nanowires, carbon nanotubes, amperometric sensors, II‐VI semiconductors, electrochemical electrodes, Schottky effect, current density, chemical variables measurementOther keywords: amperometric immunosensor, low‐temperature growth process, current density, multifunction electrode probe, nanowire‐carbon nanotube architectures, CNT, human albumin serum antibody detection, Schottky like behaviou, urine albumin measurement, diabetic detection, stem cell conversion, liver cell conversion, medical diagnosis, biomedical applications, ZnO‐C