A study of magnetic non-linearity and finite length effects in solid iron subjected to a travelling MMF wave

This thesis describes an experimental and analytic study of the effects of magnetic non-linearity and finite length on the loss and field distribution in solid iron due to a travelling mmf wave. In the first half of the thesis, a two-dimensional solution is developed which accounts for the effects of both magnetic non-linearity and eddy-current reaction; this solution is extended, in the second half, to a three-dimensional model. In the two-dimensional solution, new equations for loss and flux/pole are given; these equations contain the primary excitation, the machine parameters and factors describing the shape of the normal B-H curve. The solution applies to machines of any air-gap length. The conditions for maximum loss are defined, and generalised torque/frequency curves are obtained. A relationship between the peripheral component of magnetic field on the surface of the iron and the primary excitation is given. The effects of magnetic non-linearity and finite length are combined analytically by introducing an equivalent constant permeability into a linear three-dimensional analysis. The equivalent constant permeability is defined from the non-linear solution for the two-dimensional magnetic field at the axial centre of the machine to avoid iterative solutions. In the linear three-dimensional analysis, the primary excitation in the passive end-regions of the machine is set equal to zero and the secondary end faces are developed onto the air-gap surface. The analyses, and the assumptions on which they are based, were verified on an experimental machine which consists of a three-phase rotor and alternative solid iron stators, one with copper end rings, and one without copper end rings j the main dimensions of the two stators are identical. Measurements of torque, flux /pole, surface current density and radial power flow were obtained for both stators over a range of frequencies and excitations. Comparison of the measurements on the two stators enabled the individual effects of finite length and saturation to be identified, and the definition of constant equivalent permeability to be verified. The penetration of the peripheral flux into the stator with copper end rings was measured and compared with theoretical penetration curves. Agreement between measured and theoretical results was generally good.

Rough-terrain groundspeed measurement:a radar-based commercial solution

Off-highway motive plant equipment is costly in capital outlay and maintenance. To reduce these overheads and increase site safety and workrate, a technique of assessing and limiting the velocity of such equipment is required. Due to the extreme environmental conditions met on such sites, conventional velocity measurement techniques are inappropriate. Ogden Electronics Limited were formed specifically to manufacture a motive plant safety system incorporating a speed sensor and sanction unit; to date, the only such commercial unit available. However, problems plague the reliability, accuracy and mass production of this unit. This project assesses the company's exisiting product, and in conjunction with an appreciation of the company history and structure, concludes that this unit is unsuited to its intended application. Means of improving the measurement accuracy and longevity of this unit, commensurate with the company's limited resources and experience, are proposed, both for immediate retrofit and for longer term use. This information is presented in the form of a number of internal reports for the company. The off-highway environment is examined; and in conjunction with an evaluation of means of obtaining a returned signal, comparisons of processing techniques, and on-site gathering of previously unavailable data, preliminary designs for an alternative product are drafted. Theoretical aspects are covered by a literature review of ground-pointing radar, vehicular radar, and velocity measuring systems. This review establishes and collates the body of knowledge in areas previously considered unrelated. Based upon this work, a new design is proposed which is suitable for incorporation into the existing company product range. Following production engineering of the design, five units were constructed, tested and evaluated on-site. After extended field trials, this design has shown itself to possess greater accuracy, reliability and versatility than the existing sensor, at a lower unit cost.

Quantum dot-based terahertz photoconductive antennas

We present novel Terahertz (THz) emitting optically pumped Quantum Dot (QD) photoconductive (PC) materials and antenna structures on their basis both for pulsed and CW pumping regimes. Full text Quantum dot and microantenna design - Presented here are design considerations for the semiconductor materials in our novel QD-based photoconductive antenna (PCA) structures, metallic microantenna designs, and their implementation as part of a complete THz source or transceiver system. Layers of implanted QDs can be used for the photocarrier lifetime shortening mechanism[1,2]. In our research we use InAs:GaAs QD structures of varying dot layer number and distributed Bragg reflector(DBR)reflectivity range. According to the observed dependence of carrier lifetimes on QD layer periodicity [3], it is reasonable to assume that electron lifetimes can be potentially reduced down to 0.45ps in such structures. Both of these features; long excitation wavelength and short carriers lifetime predict possible feasibility of QD antennas for THz generation and detection. In general, relatively simple antenna configurations were used here, including: coplanar stripline (CPS); Hertzian-type dipoles; bow-ties for broadband and log-spiral(LS)or log-periodic(LP)‘toothed’ geometriesfor a CW operation regime. Experimental results - Several lasers are used for antenna pumping: Ti:Sapphire femtosecond laser, as well as single-[4], double-[5] wavelength, and pulsed [6] QD lasers. For detection of the THz signal different schemes and devices were used, e.g. helium-cooled bolometer, Golay cell and a second PCA for coherent THz detection in a traditional time-domain measurement scheme.Fig.1shows the typical THz output power trend from a 5 um-gap LPQD PCA pumped using a tunable QD LD with optical pump spectrum shown in (b). Summary - QD-based THz systems have been demonstrated as a feasible and highly versatile solution. The implementation of QD LDs as pump sources could be a major step towards ultra-compact, electrically controllable transceiver system that would increase the scope of data analysis due to the high pulse repetition rates of such LDs [3], allowing real-time THz TDS and data acquisition. Future steps in development of such systems now lie in the further investigation of QD-based THz PCA structures and devices, particularly with regards to their compatibilitywith QD LDs as pump sources. [1]E. U. Rafailov et al., “Fast quantum-dot saturable absorber for passive mode-locking of solid-State lasers,”Photon.Tech.Lett., IEEE, vol. 16 pp. 2439-2441(2004) [2]E. Estacio, “Strong enhancement of terahertz emission from GaAs in InAs/GaAs quantum dot structures. Appl.Phys.Lett., vol. 94 pp. 232104 (2009) [3]C. Kadow et al., “Self-assembled ErAs islands in GaAs: Growth and subpicosecond carrier dynamics,” Appl. Phys. Lett., vol. 75 pp. 3548-3550 (1999) [4]T. Kruczek, R. Leyman, D. Carnegie, N. Bazieva, G. Erbert, S. Schulz, C. Reardon, and E. U. Rafailov, “Continuous wave terahertz radiation from an InAs/GaAs quantum-dot photomixer device,” Appl. Phys. Lett., vol. 101(2012) [5]R. Leyman, D. I. Nikitichev, N. Bazieva, and E. U. Rafailov, “Multimodal spectral control of a quantum-dot diode laser for THz difference frequency generation,” Appl. Phys. Lett., vol. 99 (2011) [6]K.G. Wilcox, M. Butkus, I. Farrer, D.A. Ritchie, A. Tropper, E.U. Rafailov, “Subpicosecond quantum dot saturable absorber mode-locked semiconductor disk laser, ” Appl. Phys. Lett. Vol 94, 2511 © 2014 IEEE.

Úton a megoldásalapú gondolkodás felé – szolgálatosodási jellemzők magyarországi termelővállalatoknál (Towards solution-based thinking: characteristics of servitization at Hungarian manufacturing companies)

A cikk fő célja a magyarországi termelővállalatok szolgálatosodási folyamatának jellemzése a versenyképesség- kutatás adatainak felhasználásával. Relevanciáját az adja, hogy a nemzetközi szakirodalom a jelenséget inkább a fejlett országokban vizsgálja. A szerzők kutatásukban körüljárták, hogy a szolgálatosodás nemzetközi szakirodalom által elfogadott jellemzői mennyiben tekinthetők érvényesnek a magyarországi viszonyok közepette. A szolgálatosodást három szinten vizsgálták: stratégia, működés és pénzügyi eredményesség. Vizsgálatuk eredményei azt mutatják, hogy a nemzetközi szakirodalommal összhangban a szolgáltatások stratégiai szerepe még alacsony a magyarországi termelővállalatoknál a termelési stratégia többi versenycéljához képest. Ugyanakkor mintájukban már megtalálhatók azok a vállalatok, amelyek mind stratégiai, mind működési szinten jelentősebb hangsúlyt fektetnek a szolgáltatások nyújtására. Fontos eredmény ugyanakkor, hogy a szolgálatosodástól elvárt pénzügyi előnyök még ezeknél a vállalatoknál sem realizálódnak. _______ The main purpose of the authors is to describe the servitization process of Hungarian manufacturing companies based on data of the Competitiveness research. The relevance of this article is given by the fact that international literature analyzes this phenomenon mainly in developed countries. In the present paper they analyze to what extent characteristics of the servitization process, generally accepted in the literature, are also applicable in a developing macroenvironment, i.e. Hungary. They approach servitization from three different perspectives: strategy, operations and financial payoffs. Results of their analysis show that, in concordance with the literature, the strategic role of services at the Hungarian manufacturing companies is still lower than other manufacturing competitive priorities. However, their sample contains a number manufacturing companies that place a greater emphasis on offering services both on strategic and operational level. An important conclusion of their study is that in case of these companies financial benefits attributable to higher levels of servitization do not yet seem to materialize.

Métodos de extração de fósforo e micronutrientes em latossolos com uso de energia ultrassônica

Assessing the soil nutrient availability to plants under lab conditions is one of the main challenges to Soil Fertility and Chemistry, due to the complex behavior and the interaction of the soil properties. Many extractant solutions associated with mechanical forms of agitation have been proposed, showing different correlations with plant growth and nutrients absorption. Using ultrasonic energy is a agitation procedure of the soil:extractant solution suspension (based on the cavitation phenomenon). It allows the establishment of relations between the amount of extracted nutrient and the ultrasonic energy level. Thus, this work aims: to evaluate the effect of cavitation intensity on the extraction of P, Zn, Cu, Mn and Fe in soil samples from five Latosols under different uses around Uberlândia and Uberaba, Minas Gerais State; to obtain extracting curves as function of ultrasonic energy levels; and to obtain an index from extracting curves to expresses the nutrient retention by the soil solid phase. A soil-solution suspension (ratio 1:10) was sonicated using a probe ultrasound equipment under different combinations of power and time: i) 30 W for 35, 70, 140 and 280 s; ii) 50 W for 21, 42, 84 and 168 s; and iii) 70 W for 15, 30, 60 and 120 s. The extractant solutions used were Mehlich-1 (for all elements), Olsen and distilled water for P. After each sonication, P concentration was quantified by molybdenum blue colorimetric method and Zn, Cu, Mn and Fe by flame atomic absorption spectrophotometry. The cavitation intensity did not affect the P extraction, only the total energy applied. The P extraction was influenced by extractant solution, decreasing as follows: Mehlich-1>Olsen>water. In cultivated Latosols, the P extraction increased linearly with ultrasonic energy, and the slope of the 1:1 linear regression reflects the P retention in the soil. The Zn and Fe extractions were influenced only by total energy applied. Mn and Cu extractions were influenced by both cavitation intensity and total ultrasonic energy. Soils containing similar amounts of P, Cu, Zn, Mn, and Fe may have a different extraction rate. Likewise, soils containing different amounts of those elements may have the same extraction rate.

PEG-based solid dispersions enhanced the solubility and dissolution of eprosartan mesylate in-vitro

Abstract - This study investigates the effect of solid dispersions prepared from of polyethylene glycol (PEG) 3350 and 6000 Da alone or combined with the non-ionic surfactant Tween 80 on the solubility and dissolution rate of a poorly soluble drug eprosartan mesylate (ESM) in attempt to improve its bioavailability following its oral administration.

INTRODUCTION

ESM is a potent anti-hypertension [1]. It has low water solubility and is classified as a Class II drug as per the Biopharmaceutical Classification Systems (BCS) leading to low and variable oral bioavailability (approximately 13%). [2]. Thus, improving ESM solubility and/or dissolution rate would eventually improve the drug bioavailability. Solid dispersion is widely used technique to improve the water solubility of poorly water-soluble drugs employing various biocompatible polymers. In this study, we aimed to enhance the solubility and dissolution of EMS employing solid dispersion (SD) formulated from two grades of poly ethylene glycol (PEG) polymers (i.e. PEG 3350 & PEG 6000 Da) either individually or in combination with Tween 80.

MATERIALS AND METHODS

ESM SDs were prepared by solvent evaporation method using either PEG 3350 or PEG 6000 at various (drug: polymer, w/w) ratios 1:1, 1:2, 1:3, 1:4, 1:5 alone or combined with Tween 80 added at fixed percentage of 0.1 of drug by weight?. Physical mixtures (PMs) of drug and carriers were also prepared at same ratios. Drug solid dispersions and physical mixtures were characterized in terms of drug content, drug dissolution using dissolution apparatus USP II and assayed using HPLC method. Drug dissolution enhancement ratio (ER %) from SD in comparison to the plain drug was calculated. Drug-polymer interactions were evaluated using Differential Scanning Calorimetry (DSC) and FT-IR.

RESULTS AND DISCUSSION

The in vitro solubility and dissolution studies showed SDs prepared using both polymers produced a remarkable improvement (p<0.05) in comparison to the plain drug which reached around 32% (Fig. 1). The dissolution enhancement ratio was polymer type and concentration-dependent. Adding Tween 80 to the SD did not show further dissolution enhancement but reduced the required amount of the polymer to get the same dissolution enhancement. The DSC and FT-IR studies indicated that using SD resulted in transformation of drug from crystalline to amorphous form.

CONCLUSIONS

This study indicated that SDs prepared by using both polymers i.e. PEG 3350 and PEG 6000 improved the in-vitro solubility and dissolution of ESM remarkably which may result in improving the drug bioavailability in vivo.

Acknowledgments

This work is a part of MSc thesis of O.M. Ali at the Faculty of Pharmacy, Aleppo University, Syria.

REFERENCES

[1] Ruilope L, Jager B: Eprosartan for the treatment of hypertension. Expert Opin Pharmacother 2003; 4(1):107-14

[2] Tenero D, Martin D, Wilson B, Jushchyshyn J, Boike S, Lundberg, D, et al. Pharmacokinetics of intravenously and orally administered Eprosartan in healthy males: absolute bioavailability and effect of food. Biopharm Drug Dispos 1998; 19(6): 351- 6.

Evaluation of strontium-site-deficient Sr2Fe1.4Co0.1Mo0.5O6-δ-based perovskite oxides as intermediate temperature solid oxide fuel cell cathodes

In this paper strontium-site-deficient Sr₂Fe_1.4Co_0.1Mo_0.5O_6-δ-based perovskite oxides (S_xFCM) were prepared and evaluated as the cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). All samples exhibited a cubic phase structure and the lattice shrinked with increasing the Sr-deficiency as shown in XRD patterns. XPS results determined that the transition elements (Co/Fe/Mo) in S_xFCM oxides were in a mixed valence state, demonstrating the small polaron hopping conductivity mechanism existed. Among the samples, S_1.950FCM presented the lowest coefficient of thermal expansion of 15.62 × 10^-6 K^-1, the highest conductivity value of 28 S cm^-1 at 500 °C, and the lowest interfacial polarization resistance of 0.093 Ω cm² at 800 °C, respectively. Furthermore, an anode-supported single cell with a S_1.950FCM cathode was prepared, demonstrating a maximum power density of 1.16 W cm^-2 at 800 °C by using wet H₂ (3% H₂O) as the fuel and ambient air as the oxidant. These results indicate that the introduction of Sr-deficiency can dramatically improve the electrochemical performance of Sr₂Fe_1.4Co_0.1Mo_0.5O_6-δ, showing great promise as a novel cathode candidate material for IT-SOFCs.

High performance cobalt-free Cu1.4Mn1.6O4 spinel oxide as an intermediate temperature solid oxide fuel cell cathode

In this work Cu_1.4Mn_1.6O₄ (CMO) spinel oxide is prepared and evaluated as a novel cobalt-free cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). Single phase CMO powder with cubic structure is identified using XRD. XPS results confirm that mixed Cu⁺/Cu²⁺ and Mn³⁺/Mn⁴⁺ couples exist in the CMO sample, and a maximum conductivity of 78 S cm⁻¹ is achieved at 800 °C. Meanwhile, CMO oxide shows good thermal and chemical compatibility with a 10 mol% Sc₂O₃ stabilized ZrO₂ (ScSZ) electrolyte material. Impedance spectroscopy measurements reveals that CMO exhibits a low polarization resistance of 0.143 Ω cm² at 800 °C. Furthermore, a Ni-ScSZ/ScSZ/CMO single cell demonstrates a maximum power density of 1076 mW cm⁻² at 800 °C under H₂ (3% H₂O) as the fuel and ambient air as the oxidant. These results indicate that Cu_1.4Mn_1.6O₄ is a superior and promising cathode material for IT-SOFCs.

Computational solid mechanics using a vertex-based finite volume method

A number of research groups are now developing and using finite volume (FV) methods for computational solid mechanics (CSM). These methods are proving to be equivalent and in some cases superior to their finite element (FE) counterparts. In this paper we will describe a vertex-based FV method with arbitrarily structured meshes, for modelling the elasto-plastic deformation of solid materials undergoing small strains in complex geometries. Comparisons with rational FE methods will be given.